ASingleSitePositioningMethodBasedonTOAandDOAEstima
A Single-Site Positioning Method Based on TOA and DOA Estimation Using Virtual Stations in NLOS Environment
Rui Zhang, Weiwei Xia*, Feng Yan, Lianfeng Shen
chow that comparing with the multipath fingerprinting scheme, the proposed method has better performance in various simulation scenarios. Keywords: single-site positioning; TOA; DOA; NLOS; virtual station
I. INTRODUCTION
Wireless positioning can be defined as one of the essential modules of many commercial and government applications and services [1]. In many positioning techniques, the geometric relationship between the mobile station (MS) and the base station (BS), or the reference station, is exploited to formulate the Euclidean distance and to identify the physical location. This relationship is mainly determined by the ranging parameters, such as the received signal strength (RSS) [2], the time of arrival (TOA) [3], the time difference of arrival (TDOA) [4], and the direction of arrival (DOA) [5]. Most of the techniques are based on the classical triangulation or trilateration algorithms, using several reference sites. But recently, the single-site positioning has attracted lots of attentions, especially in the deployment cost
National Mobile Communications Research Laboratory, Southeast University, Nanjing 210096, China * The corresponding author, email: wwxia@
Received: Nov. 1, 2017 Revised: Mar. 24, 2018 Editor: Jianhua Zhang
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Abstract: This paper presents a single-site positioning method based on the joint estimation of propagation time-of-arrival (TOA) and direction-of-arrival (DOA), with the assist of virtual stations in the typical non-line-of-sight (NLOS) environment. Consider the influence of multipath noise on the positioning performance, the proposed method firstly presents a modified high-resolution estimation technique called Multipath noise Limiting Matrix Pencil (MLMP) algorithm to achieve the TOA/DOA estimations, in which the matrix pencil and matrix enhancement process are implemented to deal with the measurements from the uniform linear array (ULA) receiver. Meanwhile, the subspace dimension estimation is improved via an adaptive threshold, for enhancing the performance of high-resolution techniques in low signal-noise-ration (SNR) situation. Next the proposed method generates virtual stations utilizing the known floor plan of surrounding reflectors, and adopts a weighted Least Square (WLS) position estimator to calculate the required position, combining the TOA/DOA estimations with the location of virtual stations. Simulations are conducted to evaluate the proposed method under NLOS
航线运输驾驶员执照ATPL理论考试题库-680道题+中文翻译
A.680道英文题(后面附加有中文说明)1..Which flight conditions of a large jet airplane create the most severe flight hazard by generating wingtip vortices of the greatest strength?A.Heavy,slow,gear and flaps up.B.Heavy,slow,gear and flaps down.C.Heavy,fast,gear and flaps down.A X2..In a decision-making process,a participatory leaderA.allows each team member to have a say and to participate in team processes.B.tends to make all team decisions and controls all resources.C.may ultimately decide the team's actions,but seldom takes into consideration the team members'experience,knowledge,and preferences.A X3..The perception of color is a function of theA.cones on the retina and is diminished in dim ambient lighting.B.rods on the retina and is diminished in dim ambient lighting.C.cones on the retina and is diminished in bright lighting conditions.A X4..Hypoxia may be caused byA.fly with a head cold.B.breathing too quickly and/or too deeply for therequirements of the body.C.flying at an altitude where the partial pressure of oxygen is too low.C X5..(According to Figure 4) At Shanghai,which description is correctA.The visibility is 800 meters,the sea level pressure is 996 hPa,B.The visibility is 8 kilometers,the QNH is 999.6 hPa,C.The visibility is 8 kilometers,the sea level pressure is 999.6 hPa,C X6.At which speed will increasing the pitch attitude cause an airplane to climb?A.Low speed.B.High speed.C.Any speed.B X7..A plane,MH 160°,receive this ATC clearance: "... HOLD EAST OF THE ABC VORTAC ON THE ZERO NINER ZERO RADIAL...",What is therecommended procedure to enter the holding pattern?A.Teardrop onlyB.Direct onlyC.Parallel onlyC X8..The maximum duty time in 24 consecutive hours that a carrier may schedule a pilot in a three pilot crew (including a second-in-commander pilot) without a rest period isA.16hoursB.17 hoursC.18 hoursA X9..A person whose duties include the handing or carriage of dangerous articles and/or magnetized materials must have satisfactorily completed an established and approvedtraining program within the precedingA.6 calendar months.B.12 calendar months.C.24 calendar months.B X10..Which dispatch requirement applies to an international air carrier that isscheduled for a 10 hours IFR flight?A.No alternate airport is required if the visibility at thedestination airport is desired to be at least 4,800m.B.An alternate airport is required.C.An alternate airport is not required if the ceiling at the destination airport is at least 600m AGL.B X11..If a flight engineer becomes incapacitated duringflight,who may perform the flight engineer's duties?A.The second in command only.B.Any flight crewmember, if qualified.C.Either pilot, if they have a flight engineer certificate.B X12..(Refer to Figure 1) According to the aeronautical weather report on figure 1,the QNH for ZUUU isA.998 hPaB.1099.8 hPaC.999.8 hPaA X13..Which condition will for the formation of radiation fog?A. Moist, stable air being moved over gradually rising ground by a wind.B. A clear sky, little or no wind,and high relative humidity.C. Moist air moves over colder ground or water.B X14..If a pilot suspects that he/she is suffering the effects of hypoxia,the most appropriate remedy would bee supplement oxygen or descend immediately to a low levelB.voluntarily increase the depth of breathing to induce more oxygen into the lungsC.voluntarily increase the breathing rate to increase the oxygen uptakeA X15..For the purpose of testing the flight recorder system.A.A minimum of 1 hour of the oldest recorded data must be erased to get a valid testB.A total of 1 hour of the oldest recorded data accumulated at the time of testing may be erasedC.A total of no more than 1 hour of recorded data may be erasedB X16.What effect does the leading edge slot in the wing have on performance?A. Decrease profile drag.B. Changes the stalling angle of attack to a higher angle.C. Decelerates the upper surface boundary layer air.B X17.. Under what condition should a pilot on IFR advise ATC of minimum fuel status?A. When the fuel supply becomes less than that required for IFR.B. If the remaining fuel suggests a need for traffic or landing priority.C. If the remaining fuel precludes any undue delay.C X18.. In the Northern hemisphere, if a pilot makes along-distance flight from east to west, under which of the following conditions,A.(接正文encounter against the wind forming by air pressure system?) when the airplane is in the south of high pressure system and in the north of low pressure system.B. When the airplane is in the north of high pressure system and in the south of low pressure system.C. When the airplane is in the north of high pressure and low pressure systems .B X19.. An alternate airport for departure is requiredA.if weather conditions are below authorized landing minimums at the departure airport.B.when the weather forecast at the estimated time ofdeparture is for landing minimums only.C.when destination weather is marginal IFR.A X20.. [Refer to Figures 4-50,4-51,4-52,4-53, and 4-54.] What is the total fuel required at .80 Mach?A.22,836 pounds.B.22,420 pounds.C.22,556 pounds.B X21.. Which is a definition of V2 speed?A.Takeoff decision speed.B.Takeoff safety speed.C.Minimum takeoff speed.B X22.. What is the approximate rate unsaturated air will cool flowing upslope?A. 3℃per 1,000 feet.B. 2℃per 1,000 feet.C. 4℃per 1,000 feet.A X23. An airport approved by the Administrator for use by an air carrier certificate holder for the purpose of providing service to a community when the regular airport is notavailable is a/an:A.destination airport.B.provisional airport.C.alternate airport.B X24.. (Refer to Figure 6-7) If the en route altitude of an aircraft is FL118, what is the altitude when the aircraft operates to DAWANGZHUANG along 007oA.FL118.B.FL128.C.FL138.A X25.. Who is responsible for the issue of Series D NOTAMs?AFC.B.Area flight information center.C.Airport flight information office.C X26..What temperature condition is indicated if precipitation in the form of wet snow occurs during flight?A. the temperature is above freezing at flight altitude.B. The temperature is above freezing at higher altitudes.C. There is an inversion with colder air below.A X27.Which ground components are required to be operative fora Category II approach in addition to LOC glide slope, marker beacons, and approach lights?A.Radar and RVR.B.RCLS and REILC.HIRL, TDZL, RCLS, and RVR.C X28.If an aircraft level turns at an angle of bank of 30 degree , the load factor isA.1Gs.B.2Gs.C.1.4GsC X29.. The ATS unit must ensure that pilots are kept informed of any change in the status of airport facilities_______________.A. at their destinationsB. at their alternate aerodromesC. A and BC X30.. (Refer to Figure 6-5) If an aircraft is estimated to arrive WEIXIAN at 1300z, pilot should contact ZHENGZHOU CONTROL on the frequency ofA.122.20MHz.B.8897KHz.C.3016KHz.C X31..(according to figure 2), the forcasting visibility at ZSSS is____A. 5000 m between 00Z-05Z, and 3000 m at other timeB. 5000 m between 00Z-09ZC. 5000 m between 00Z-05Z, 5000 m above at other timeA X32. By regulation, who shall provide the pilot in command of a domestic or flag air carrier airplane information concerning weather, and irregularities of facilities and services?A.The aircraft dispatcher.B.Air route traffic control center.C.Director of operations.A X33.. If the wind direction measured by the weather station is 270°,the optimum takeoff and landing direction is .A.from east to westB.from west to eastC.from north to southA X34.What characteristic should exist if an airplane is loaded tothe rear of its CG range?A.Sluggish in aileron control.B.Sluggish in rudder controlC.Unstable about the lateral axisC X35. Which is a definition of the term "crewmember"?A.Only a pilot, flight engineer, or flight navigator assigned to duty in an aircraft during flight time.B.A person assigned to perform duty in an aircraft during flight time.C.Any person assigned to duty in an aircraft during flight except a pilot or flight engineer.B X36.. The most important restriction to the operation of turbojet or turboprop engines isA.Limiting compressor speed.B.Limiting Turbine Inlet Temperature (TIT).C.Limiting torque.B X37. If it becomes necessary to shut down one engine on a domestic air carrier three-engine turbojet airplane, thepilot in commandA. must land at the nearest suitable airport, in point of time,at which a safe landing can be made.B. may continue to the planned destination if approved by the company aircraft dispatcher.C. may continue to the planned destination if this is considered as safe as landing at the nearest suitable airport.C X38. In a 24-hour consecutive period, what is the maximum time, excluding briefing and debriefing, that an airline transport pilot may instruct other pilots in air transportationservice?A.6 hours.B.8 hours. 2C.10 hours.B X39.. [Refer to Figures 4-46, 4-47 and 4-48.] What is the ETE from Chicago Midway Airport to Greater Buffalo Intl?A.2 hours 12 minutes.B.2 hours 15 minutes.C.2 hours 18 minutes.A X40.. You should advise ATC of minimum fuel status when your fuel supply has reached a state where, upon reaching your destination, you cannot accept any undue delay.A. This will ensure your priority handling by ATC.B. ATC will consider this action as if you had declared an emergency.C. If your remaining usable fuel supply suggests the need for traffic priority to ensure a safe landing, declare an emergency due to low fuel and report fuel remaining in minutes.C X41.. (Refer to Figure 7) In this chart, ISOL EMBD CB 340/XXX meansA. Some places have CBs, CBs with little or no separationB. Isolated cumulonimbus embedded in layers of other clouds, the top of the cumulonimbus is 34000 feet, the base is unknownC. The airplane is embedded in layers of clouds, the top of the cumulonimbus is 34000 feet, the base is unknownB X42.Within what frequency range dies the localizer transmitter of the ILS operate?A.108.10 to 118.10 MHZB.108.10 to 111.95 MHZC.108.10 to 117.95 MHZ.B X43..Which of the following characteristics heatthunderstorm?A.It moves with the weather system.B.It covers small area and is isolated with openingsC. It strengthens at night and weakens in the day on landB X44.. What is the time limitation for filing flight application?A.At least before 1500 Beijing Time prior to the departure date.B.At least before 1700 Beijing Time prior to the departure date.C.At least before 1200 Beijing Time prior to the departure date.A X45.What is the purpose of an elevator trim tab?A.Provide horizontal balance as airspeed is increased toallow hands-off flight.B.Adjust the speed tail load for different airspeeds in flight allowing neutral control forces.C.Modify the downward tail load for various airspeeds inflight eliminating flight-control pressures.C X47.．Hypoxia is always accompanied byA. dizzinessB.a degradation in the performance of a pilotC.vomitingB X48.The "runway hold position" sign denotesA.An area protected for an aircraft approaching a runwayB.An entrance to runway from a taxiwayC.Intersecting runwaysC X49.. An alternate airport must be listed in the dispatch and flight release for all international operation air carrier flights longer thanA.7 hours.B.8 hours.C.6 hours.C X50.．Carbon monoxide is dangerous becauseA.it displace oxygen from the blood's red cellsB.it is highly acidic and attacks the lining of the lungsC.it displaces oxygen from the lungs causing suffocationA X51.. In flight, pilots find forane clouds consisting of cloud bar and cloud band with flat floor and piled clouds on the top of some clouds. The descriptive cloud should be.A. cumulus congestusB. cumulostratusC. towering cloudsC X52.. What condition produces the most frequent type ofground-or surface-based temperature inversion?A. The movement of colder air under warm air or the movement of warm air over cold air.B. Widespread sinking of air within a thick layer aloft resulting in heating by compression.C. Terrestrial radiation on a clear, relatively calm night.C X53.．What is a symptom of carbon monoxide poisoning?A.Rapid, shallow breathing.B.Pain and cramping of the hands and feet.C.Dizziness.C X54.．Hypoxia is the result of which of these conditions?A.Insufficient oxygen reaching the brain.B.Excessive carbon dioxide in the bloodstream.C.Limited oxygen reaching the heart muscles.A X55.Which "rule-of-thumb" may be used to approximate therate of descent required for a 3 glide path?A.5times groundspeed in knots.B. 8times groundspeed in knots.C.10 times groundspeed in knots.A X56.A pilot of a high-performance airplane should be aware that flying a steeper-than-normal VASI glide slope angle may result inA. A hard landing.B. Increased landing rollout.C. Landing short of the runway threshold.B X57. A domestic air carrier airplane lands at an intermediate airport at 1815Z. The latest time it may depart without a specific authorization from an aircraft dispatcher isA.1945Z.B.1915Z.C.1845Z.B X58.. An aircraft that encounters a headwind of 45knots, withina microburst, may expect a total shear across the microburst ofA. 40 knotsB. 80 knotsC. 90 knotsC X59.．Which of the following is not the tip for good SA management during the flight?A.Resolve discrepancies- contradictory data or personal conflicts.B.Fixation-focusing on any one thing to the exclusion of everything else.C.Monitor and evaluate current status relative to our plan.B X60.. If the landing minimums for a NDB approach shown on the IAP chart are visibility 2,000m and MDA 120m, which minimums apply when you actually divert to this airport?A.Visibility 2,800m and MDA 180m.B.Visibility 3,600m and MDA 240m.C.Visibility 2,000m and MDA 120m.C X61. A pilot flight crewmember, other than pilot in command, must have received a proficiency check or line-oriented simulator training within the precedingA.6 calendar months.B.12 calendar months.C.24 calendar months.C X62.. (Refer to Figure 6-1) Which approach lighting is available for VOR/DME Rwy 36R?A.HIALS.B.HIALS with PAPI.C.PAPI.B X63.Holding position signs haveA.White inscriptions on a red backgroundB.Red inscriptions on a white backgroundC.Yellow inscriptions on a red backgroundA X64.．A common source of human error is the false hypothesis. Under certain conditions this is more or less likely than at other times. From the following list, select the situation least likely toA.(续正文，result in a person arriving at a falsehypothesis)when expectancy of an event is highB.after a period of intense concentrationC.during normal operationC X65..Which airplane performance characteristics should berecognized during takeoff when encountering a tailwind shear that increases in intensity?A. loss of, or diminished, airspeed performanceB. decreased takeoff distanceC. increased climb performance immediately after takeoffA X66.Which airplanes are required to be equipped with a ground proximity warning glide slope deviation alerting system?A.All turbine powered airplanesB.Passenger -carrying turbine-powered airplanes onlyrge turbine-powered airplanes onlyA X67..During the life cycle of a thunderstorm, which stage is characterized predominately by downdrafts?A. cumulusB. dissipatingC. matureB X68.When are outboard ailerons normally used?A.Low-speed flight only.B.High-speed flight only.C.Low-speed and high-speed flight.A X69.. What does the throttle opening of aturbo-charged-reciprocating engine control?A.Supercharger gear ratio.B.Exhaust gas discharge.C.The desired manifold pressure.C X70.During an en route descent in a fixed-thrust andfixed-pitch attitude configuration, both the ram air input and drain hole of the pilot system become completely blocked by ice. What airspeed indication can be expected?A.Increase in indicated airspeed.B.Decrease in indicated airspeed.C.Indicated airspeed remains at the value prior to icingB X71. An applicant who is taking a practical test for a type rating to be added to a commercial pilot certificate, in an approved simulator, isA.required to have a first-class medical certificate.B.required to have a second-class medical certificate.C.not required to have a medical certificate.C X72..If the aircraft enters the strong downdraft burst, where is the aircraft expected to meet the strongest downdraft?A. in the center of strong downdraft burstB. when it enters the strong downdraft burstC. when leaves the strong downdraft burstA X73.. It should be reported without ATC request thatA. When unable to climb at a rate of at least 500 feet per minute.B. When unable to descend at a rate of at least 1000 feet per minute.C. When unable to climb or descend at a rate of at least 600 feet per minute.A X74.. [Refer to Figure 4-28.] How much will landing distance be reduced by using 15o of flaps rather than 0o flaps at a landing weight of 115,000 pounds?A.500 feet.B.800 feet.C.2,700 feet.B X75.．The time of useful consciousness(TUC) is affected by many factors, such as flight altitude, climbing rate, pilot'sactivity level, pilot'sA.(续正文，health, and whether the pilot smoking or not. Thestatement is )rightB.wrongA X76. (Refer to Figure 2-12) what is the runway distance remaining at "A" for a nighttime takeoff on runway 9?A.1,000 feetB.2,000 feetC.2,500 feetB X77.. Maximum range performance of a turbojet aircraft is obtained by which procedure as aircraft weight reduces?A.Increasing speed or altitude.B.Increasing altitude or decreasing speed.C.Increasing speed or decreasing altitude.B X78..Which type of weather conditions are covered in the Convective SIGMETA. Embedded thunderstorms, severe turbulenceB. Cumulonimbus clouds, light turbulenceC. severe icing, surface visibility lower than 5000 metersA X79. When a pilot plans a flight using NDB NAVAIDS. Which rule applies?A.The airplane must have sufficient fuel to proceed. by means of VOR NAVIDS, to a suitable airport and land.B.The pilot must be able to return to the departure airport using other navigation radios.C.The airplane must have sufficient fuel to proceed, by means of VOR NAVAIDS, to a suitable airport and complete an instrument approach by use of the remaining airplane radio system.C X80.. What is an area identified by the term "clearway"?A.centrally located about the extended centerline and under airport authorities, which does not contain obstructions and can be considered when calculating takeoff performance.B.An area, at least the same width as the runway, capable of supporting an airplane during a normal takeoff.C.An area beyond the takeoff runway, which is able to support the airplane, for use in decelerating the airplane during an aborted takeoff.A X81. A crewmember who has served as second-in-command on a particular type airplane (e.g., B737-300), may serve aspilot-in-command upon completing which training program?A.Upgrade training.B.Recurrent training.C.Initial training.A X82.. Which points should be report to ATC without request?A. when leaving the final approach fix outbound.B. when leaving an assigned holding fix.C. when leaving the final approach fix outbound, or when leaving an assigned holding fix.C X83.. What is the correct symbol for minimum unstick speed?A.VMU.B.VMD.C.VFC.A X84.．The two different types of light sensitive elements on the retina are classified asA.rods which are sensitive to color and cones which work best in dim light.B.cones which are sensitive to color and rods which work best in dim light.C.rods and cones both of which are responsible for color vision.B X85.(Refer to Figures 2-4 and 2-5)To which aircraft position does HSI presentation "A" correspond?A.9and6B.9 onlyC.6 onlyA X86.．Which of the following is the clue of SA weaken or loss during the flight?A.Fixation-focusing on any one thing to the exclusion of everything else.B.Adhere to standard operating procedures.C.Meet expected checkpoint on flight plan or profile-ETA, fuel burn, etC．as far as possible.A X87..Which type clouds are indicative of very strong turbulence?A. nimbostratus.B. Standing lenticular.C. Cirrocumulus.B X88.. What effect will an increase in altitude have upon the available equivalent shaft horsepower (ESHP) of a turboprop engine?A.Lower air density and engine mass flow will cause a decrease in power.B.Higher propeller efficiency will cause an increase in usable power (ESHP) and thrust.C.Power will remain the same but propeller efficiency will decrease.A X89.. You can't enter tower controlled airspace under IFR weather conditions unless you have filed an IFR flight plan andA.slowed down to the final approach IAS.B.received an ATC clearance.C.climbed to the appropriate altitude.B X90.. Series C NOTAMs of Class 2 must be disseminated to domestic area flight information center NOTAMs officeA.25 days ago.B.15 days ago.C.7 days ago.B X91..(according to figure 2), at ZBAA, the max predicting wind speed is___.A. 17 m/sB. 8 m/sC. 6 m/sA X92.. [Refer to Figure 4-28.] What is the ground roll when landing with 5o of flaps at a landing weight of 142,500 pounds?A.1,750 feet.B.2,100 feet.C.2,500 feet.C X93.．Which of the following is not normally a symptom of hypoxia?A.increased visual fieldB.An increase in breathing rateC.Sleepiness or frequent yawningA X94.. (Refer to Figure 6-3) The true direction of Rwy 35 at PUDONG isA.342o.B.347o.C.352o.A X95.. What effect would a change in air density have ongas-turbine-engine performance?A.As air density decreases, thrust increases.B.As air density increases, thrust increases.C.As air density increases, thrust decreases.B X96. When is DME required for an instrument flight?A.At or above 24000 feet MSL if VOR navigational equipment is requiredB.In terminal radar service areasC.Above 12,500 feet MSLA X97. . (Refer to Figure 6-2) Which approach lighting isavailable for ILS/DME Rwy 36L?A.HIALS with PAPI.B.HIALS.C.PAPI.A X98.. (According to Figure 1) which station reports the max wind speedA.ZSSSB.ZUUUC.ZWWWC X99.What is a characteristic of longitudinal instability?A.Pitch oscillations becoming progressively greater.B.Bank oscillations becoming progressively greater.C.Aircraft constantly tries pitch down.A X100.. (Refer to Figure 6-3, 6-4) What distance is available for takeoff on Rwy 17 at PUDONG?A.12,093 feet.B.12,097 feet.C.13,123 feet.C X101..Crew resource management is a process using allavailable information and resources, i.e. equipment, procedures and people, to achieve a safe andA.(续正文，efficient flight operation. The statement is)rightB.wrongA X102.. [Refer to Figure 4-41.] What is the approximate landing weight for Operating Conditions below? WEIGHT (START TO ALT): 87,000,DISTANCE (NM): 370,WIND COMPONENT: 60HW,HOLDINGTIME AT ALT (MIN): 15A.80,850 pounds.B.85,700 pounds.C.77,600 pounds.A X103.．(Refer to Figure 1) What weather condition is reported at Urumchi (ZWWW)A. Strong wind with showerB. Snow and rainC. Strong west wind and blowing snowC X104.. [Refer to Figure 4-28 and 4-29.] What approach speed and landing distance will be needed when landing at a weight of 140,000 pounds with 15o of flaps?A.123 knots and 3,050 feet.B.138 knots and 3,050 feet.C.153 knots and 2,050 feet.B X105.If a required instrument on a multiengine airplane becomes inoperative, which document dictates whether the flight may continue en route?A. An approved Minimum Equipment list for the airplane.B. Original dispatch release.C. Certificate holder's manual.C X106.. [Refer to Figure 4-34.] What are the recommended IAS and EPR settings for holding under Operating Conditionsbelow? ,ALTITUDE: 30,000,WEIGHT (*1000): 92.5,ENGINES OPERATING: 2,HOLDING TIME (MIN): 10A.221 knots and 1.83 EPR.B.210 knots and 1.69 EPR.C.217 knots and 1.81 EPR.B X107.. How often is SNOWTAM broadcast to distant centers?A.Hourly.B.One hour and a half a time.C.30 minutes a time.A X108..When light passes through the lens it is brought to focus at the back of the eyeball on theA.retinaB.corneaC.irisA X109..When is the course deviation indicator (CDI) considered to have a full-scale deflection?A.When the CDI deflects from full-scale left to full-scale tight, or vice versa.B.When the CDI deflects from the center of the scale tofull-scale left or right.C.When the CDI deflects from half-scale left to half-scale right, or vice versa.B X110.．Effective CRM has some characteristics, which of the following is right description about it?A.CRM is a process using all available information and resources, i.e. equipment, procedures and people, to achieve a safe and efficient flight operation.B.CRM can be blended into all forms of aircrew trainingC.A and BC X111.. [Refer to Figure 4-25.] What is the maximum landing weight which will permit stopping 1,500 feet short of the end of a 4,950-foot dry runway with reversers and spoilers inoperative?A.119,000 pounds.B.136,000 pounds.C.139,000 pounds.C X112. Who is required to submit a written report on a deviation that occurs during an emergency?A. Person who found the emergency.B. Person who heard the emergency.C. Pilot in command.C X113..Northwest wing can be presented as .A. 200°or NWB. 315°or NWC. 135°or SEB X114..What characterizes a transient compressor stall?A.Loud, steady roar accompanied by heavy shuddering.B.Sudden loss of thrust accompanied by a loud whine.C.Intermittent "bang," as backfires and flow reversals take place.C X115..Which of the following is not the way of increasing MCRIT in jet transport designsA. give the wing a lower camberB. increase wing sweep.C.add slatsC X116Under what condition is VMC the highest?A.Gross weight is at the maximum allowable value.B.CG is at the most rearward allowable position.C.CG is at the most forward allowable position.。
晶体结构缺陷的类型
二 按缺陷产生旳原因分类
晶体缺陷
辐照缺陷 杂质缺陷
电荷缺陷 热缺陷 非化学计量缺陷
1. 热缺陷
定义:热缺陷亦称为本征缺陷，是指由热起伏旳原因所产生 旳空位或间隙质点（原子或离子）。
类型:弗仑克尔缺陷（Frenkel defect）和肖特基缺陷 （Schottky defect）
T E 热起伏(涨落) 原子脱离其平衡位置
面缺陷旳取向及分布与材料旳断裂韧性有关。
面缺陷－晶界
晶界示意图
亚晶界示意图
晶界: 晶界是两相邻晶粒间旳过渡界面。因为相邻晶粒 间彼此位向各不相同，故晶界处旳原子排列与晶内不同， 它们因同步受到相邻两侧晶粒不同位向旳综合影响，而做 无规则排列或近似于两者取向旳折衷位置旳排列，这就形 成了晶体中旳主要旳面缺陷。
-"extra" atoms positioned between atomic sites.
distortion of planes
selfinterstitiallids
Two outcomes if impurity (B) added to host (A):
• Solid solution of B in A (i.e., random dist. of point defects)
OR
Substitutional alloy (e.g., Cu in Ni)
Interstitial alloy (e.g., C in Fe)
Impurities in Ceramics
本章主要内容：
§2.1 晶体构造缺陷旳类型 §2. 2 点缺陷 §2.3 线缺陷 §2.4 面缺陷 §2.5 固溶体 §2.6 非化学计量化合物
星站差分gps在远海打桩定位中的应用
文章编号：1009-4539(2019) 12-0147-06.其他•星站差分GPS在远海打桩定位中的应用陈士清(中国铁建港航局集团有限公司广东珠海519000)摘要：目前海上风电已由近岸向远海方向发展。
常规的GPS-RTK技术虽然定位精度能够达到厘米级，但却无法满足超过其信号覆盖范围以外区域。
星站差分G P S既具有接近传统R T K测量定位精度高的优点，又具有全球性、全天候、连续性和实用性的特点，不需要架设基准站，单机即可作业，工作范围广，效率高。
本文介绍了星站差分的基本原理和OmniSTAR技术的四种服务达到的精度，简述采用OmniSTAR技术对现有打桩船测量定位系统进行技术改进，最后通过海上测风塔桩基工程实例，介绍了星站差分G P S在远海施工测量中的应用。
关键词：星站差分G P S-R T K远海定位O m n iS T A R测风塔中图分类号：U445.551 文献标识码：A DOI：10.3969/j. issn. 1009-4539.2019. 12.034Application of Satellite-station Differential GPS in Far-sea Piling PositionChen Shiqing(CRCC Harbour & Channel Engineering Bureau Group Co. Ltd., Zhuhai Guangdong 519000, China)Abstract：At present, the wind farm has developed from the near shore to the distant sea. Conventional GPS-RTK technologycan achieve centimeter-level positioning accuracy, but it can not satisfy the area beyond its signal coverage. The differentialGPS of satellite-station has the advantages of high positioning accuracy close to traditional RTK measurement, and has thecharacteristics of global, all-weather, continuity and practicability. It does not need to set up a base station, it can be operatedon a single machine with a wide working range and high efficiency. The article introduced the basic principle of the satellite-station difference and the accuracy of the four services of the OmniSTAR technology, and briefly described the technicalimprovement of the existing positioning system of piling boat by using OmniSTAR technology. Finally, the application ofsatellite-station differential GPS in offshore engineering survey was introduced through an example of offshore anemometertower pile foundation engineering.K ey words：satellite-station difference；GPS-RTK；far se a；1引言风能作为一种可再生的无污染的优质能源，越 来越受到世界许多国家的重视。
翻译
Unit 12. 出席晚宴的客人对那个美国人威严的语气感到有点意外。
The guests at the dinner party were slightly surprised at the commanding tone of the American.4. 当全部乘客都向出口处(exit) 走去时，他却独自留在座位上，好像不愿意离开这架飞机似的。
While all the other passengers made for the exit, he alone remained in his seat as if unwilling to leave the plane.6. 南希虽然很想参加辩论，但腼腆得不敢开口。
While she felt like joining in the argument, Nancy was too shy to open her mouth.8. 猎人一看见有只狐狸从树丛中出现并向他设下(lay) 的陷阱(trap) 方向跑去，脸上顿时闪出了兴奋的表情。
The hunter’s face lit up with excitement as soon as he saw a fox emerge from among the bushes and run in the direction of / make for the trap he had laid.Unit 22) 这些青年科学家通过现场观察，获得了研究工作所需的第一手资料。
By making on-the-spot observations, the young scientists obtained first-hand information they needed in their research work.4) 委员会成员在新机场最佳选址(location) 这一问题上持有不同意见。
The committee members have conflicting opinions as to the best location of the new airport.6) 我们产品质量的稳步提高在很大程度上是由于设备有所改进。
Strong-Coupling Theory of High Temperature Superconductivity
INTRODUCTION
The seminal work by Bardeen, Cooper and Schrieffer (BCS)[1] extended further by Eliashberg [2] to the intermediate coupling regime solved one of the major scientific problems of Condensed Matter Physics in the last century. While the BCS theory provides a qualitatively correct description of some novel superconductors like magnesium diboride and doped fullerenes, if the phonon dressing of carriers (i.e. polaron formation) is properly taken into account, high-temperature superconductivity (HTS) of cuprates represents a challenge to the conventional theory. Here I discuss a multi-polaron approach to the problem based on our extension of the BCS theory to the strong-coupling regime [3]. Attractive electron correlations, prerequisite to any HTS, are caused by an almost unretarded electron-phonon (e-ph) interaction sufficient to overcome the direct Coulomb repulsion in this regime. Low energy physics is that of small polarons and bipolarons (real-space electron (hole) pairs dressed by phonons). They are itinerant quasiparticles existing in the Bloch states at temperatures below the characteristic phonon frequency. Since there is almost no retardation (i.e. no Tolmachev-Morel-Anderson logarithm) reducing the Coulomb repulsion, e-ph interactions should be relatively strong to overcome the direct Coulomb repulsion, so carriers must be polaronic to form pairs in novel superconductors. I identify the Fr¨ ohlich electron-phonon interaction as the most essential for pairing in superconducting cuprates. Many experimental observations have been satisfactorily understood in the framework of the bipolaron theory [3] providing evidence for a novel state of electronic matter in layered cuprates, which is a charged Bose-liquid of small mobile bipolarons. Here the band structure and essential interactions in oxide superconductors are discussed
Positioning Crenarchaeal tRNA-Introns
P ositioning Crenarchaeal tRNA ositioning Crenarchaeal tRNA--Introns IntronsSmarajit Das (a), Zhumur Ghosh (a), Jayprokas Chakrabarti (a, b, *),Bibekanand Mallick (a) and Satyabrata Sahoo (a)(a) Computational Biology Group (CBG) (a) Computational Biology Group (CBG)Theory DepartmentIndian Association for the Cultivation of ScienceCalcutta 700032 India(b)(b) Biogyan Biogyan BiogyanBF 286, Salt LakeCalcutta 700064 India* * Author for correspondence Author for correspondence Author for correspondenceTelephone: +91-33-24734971, ext. 281(Off.)Fax: +91-33-24732805E-mail : tpjc@iacs.res.in ; biogyan@AbstractAbstractBackground: Introns play a key role in deciphering tRNA genes .Their positions Backgroundhave to be fixed consistent with the conserved sequence motifs in tRNA . The bulge-helix-bulge secondary structures at the exon-intron boundaries need careful attention .Results: We precisely position a noncanonical intron in the odd second copy of ResultstRNA Asp(GTC) gene in the newly sequenced crenarchaea Sulfolobus acidocaldarius. The uniform assortment of some features from normal aspartate tDNA and some from those corresponding to unnatural amino acids conduce us to conjecture it to be a novel tRNA gene – probably coding for a modified aspartate residue. Further we reposition intron in tRNA His(GUG) gene in Pyrobaculum aerophilum. We argue this intron repositioning enhances the structural stability of the tRNA, retaining all its archaeal-tRNA-signatures. The bulge-helix-bulge motifs at the exon-intron boundaries are re-analyzed and found to support our conjectures.Conclusions: We conclude Sulfolobus acidocaldarius contains a new tRNA form for Conclusionssome nonstandard amino acid derived from aspartate . The histidine tRNA in Pyrobaculum aerophilum has its intron located at an altogether different position .Keywords: Crenarchaea; tRNA; nonstandard amino acid; intron; pyrrolysine tRNA; Keywords:bulge-helix-bulge motifBackgroundBackgroundArchaeal tRNA genes (tDNAs) have been a subject of our recent work [1]. While working on crenarchaeal cytoplasmic tDNAs we find the need to define new introns and reposition some existing (NCBI annotated) ones to improve the secondary structure [2. In the newly sequenced crenarchaea Sulfolobus acidocaldarius we identify a second copy of aspartate tRNA gene with curiously odd attributes. We define a noncanonical intron (NCI) in its acceptor (A-arm). The interpretation of this tRNA is delicately balanced. It could be the aspartate tRNA gene or it could correspond to some unnatural amino acid. Sifting through the evidences and comparing with the pyrrolysine tRNA we opt for the nonstandard amino acid choice. In addition to this, the present study establishes an in-silico approach to reposition intron in the histidine tDNA in P. aerophilum and argues in favor of this new intron position over the old one.Archaeal tDNA introns are located mostly in anticodon (AC) loop between tRNA positions 37/38. These are the canonical introns (CI). Archaeal tDNAs also have introns at positions other than canonical. These noncanonical introns in archaeal tDNAs were observed in 1987 [3]. Presence of introns in tDNAs at canonical position is detected by the algorithm tRNAscan-SE [4]. But detecting the noncanonical introns could be difficult. This is due to the lack of prior knowledge regarding their lengths and exact locations. A structural deviation in the secondary structure of the tRNA from the standard one hints towards improper positioning of the intron. For instance, in the NCBI-annotated crenarchaeal genome of P. aerophilum, tRNA Gly(CCC) gene ranges between 663679 and 663772 , with a 19 base long CI. ButMarck and Grosjean records the above-mentioned sequence range to be tRNA Met(CAU) gene with a 20 base long NCI between 29/30 [5]. Although the sequence range carries signatures of both these possibilities, the BHB structural motif appears to favour the second possibility over the first. Again, the conflict between tRNA Ser(GCT) and tRNA Met(CAU) has been addressed by Marck and Grosjean for this species. These amusing anomalies led us to re-investigate crenarchaeal genomes for precise positioning of the introns.Archaeal splicing endonucleases recognize and cleave a conserved secondary structure motif called the bulge-helix-bulge (BHB) that appears at the intron-exon boundaries. Archaeal splicing machinery cleaves introns at variable positions in pre-tRNAs within the BHB motif [6]. Splicing of introns hence is a RNA-protein interaction which requires mutual recognition of complementary tertiary structures. The conformation of the BHB motif is more important for archaeal endonuclease recognition than its sequence [7].From the time when the triplet nature of the genetic code was revealed there have been speculations that some of the sixty-four codons encode a few of the rare amino acids found in proteins [8]. The great majority of the nonstandard amino acids are created by chemical modifications of standard amino acids. Some of these may be a post translational modification, but a few are directly specified by the genetic code as in the case of selenocysteine (TGA) [9, 10] or pyrrolysine (TAG). Methanosarcina barkeri genome revealed the presence of pyrrolysine tRNA gene. Both the selenocysteine and pyrrolysine systems use tRNAs that are first charged by standard amino acids (serine and lysine respectively) and are then modified into non-standard derivatives (selenocysteine and pyrrolysine). Selenocystiene pathwayis widespread in all kingdoms of life. But pyrrolysine is restricted to certain archaea and eubacteria [11]. The NCI defined odd-second-copy of tRNA Asp has interesting structural similarities with pyrrolysine tRNA.For the present work all tDNAs of crenarchaeal genomes were investigated. Our conclusions agreed with what is known in all but two cases. In the odd-second-copy of pre-tRNA Asp of Sulfolobus acidocaldarius DSM 639 (NC_007181), we define a new NCI in A-arm. This unnatural tRNA is speculated to perform the function of coding modified form of Aspartate residue. In pre-tRNA His gene of Pyrobaculum aerophilum (NC_003364) we propose new splicing position for the intron.Results Results and and and D D Discussions:iscussions:iscussions: Positioning Introns Positioning IntronsSulfolobus acidocaldariusSulfolobus acidocaldarius Structural peculiarities of odd the odd tRNA Asp (GTC) gene: This gene lies between (427581..427656) . We define an NCI of length 6 lying between 3/4. Amongst the identity elements of archaeal aspartate tRNA gene [1], G34, U35, C36 and G6:C67 are present in this tRNA. But curiously A73 instead of G73. Amongst the conserved base pairs G26:U44 and U54:A58 are present. But again curiously G8:U14 rather than U8:A14 of normal Asp tRNA. Deviations also include the absence of the 16th and the 17th nucleotides and remarkably also of the normally conserved G19. Additionally in D-loop 15C and 18C instead of 15G and 18G. The BHB of the newly-defined NCI in A-arm has h // bh / L motif (h // is the helix formed by base pairing between the sequence atctt upstream of the tRNA gene and the exonic sequence tgggg between 12-16 of the unspliced tRNA). The splice sites are marked by arrows in fig 1a.Note that NCBI annotated gene between (427588-427653) has an anomalous tRNA-secondary structure with just 3 base-pairs in A-arm. There is further an extra base again in A-arm.Similarities Similarities with tRNA pyrrolysine with tRNA pyrrolysinewith tRNA pyrrolysine: The M. barkeri genome has a tRNA Pyl gene [10] coding for the 22nd amino acid Pyrrolysine. Some of the secondary structural features of it match with this odd aspartate tRNA gene of S. acidocaldarius . In both the tRNAs the 16th , the 17th and the19th bases are absent. U35 and N36 (here N does not include U) are important identifying features of pyrrolysine tRNAs. Remarkably these are there in this odd aspartate tRNA. The characteristic peculiarities of this odd tRNA Asp and its resemblance with tRNA Pyl of M. barkeri are marked in fig 2.New Intron New Intron Splice Splice Splice--Site in P.aerophilum :tRNA His gene :gene : Using our tRNA-gene identification routine we identified it between c(21869..21775). We define an NCI of 16 bases lying at 43/44. The conserved C50:G64, G29:C41 of archaeal tRNA His are consistently there in this tRNA. The key element for proper aminoacylation C73, unique to tRNA His , is also present here. G26:A44 and G31:C39 too match well with all other crenarchaeal histidinyl tRNAs[1]. In addition for the newly defined NCI we have checked the hallmark of a proper intron - the BHB. At the exon-intron boundary we find h e bh /L motif with splicing positions marked by arrows in fig 1b. The 4bp long exonic helix (h e ) is followed by a bulge (b). In this bulge lies the 3/ as well as the 5/ splice sites. It is followed by another helix (h /), followed by a loop (L) [h / is sometimes purely intronic. Again, intron-exon portions sometimes shuffled together within the same helix].Note the same region of the genome is annotated in NCBI to be histidine tRNA gene with a canonical intron of 13 bases. Now, with this definition of canonical intron,31:39 base pair is absent. This is very unusual. Again the short V-arm is composed of four to five bases in all tDNAs. The exceptions are tDNA Ser and tDNA Leu(these have long V-arms) [12, 5]. Importantly, G26:G44 and the three extra bases between 43 and 49 distorts the tRNA secondary structure from that of other crenarchaeal tRNA His(GUG).Precise positioning of the NCI, as done here, removes the extra bases between 43 and 49, generates proper base pairing at 31-39 and at 26-44. These improve the structure of the resulting tRNA..Conclusions::ConclusionsThe great majority of the nonstandard amino acids are created by chemical modifications of standard amino acids. These may be post translational modifications, or else directly specified by the genetic code as is the case with selenocysteine (TGA) or pyrrolysine (TAG). Selenocysteine and pyrrolysine tRNAs are first charged with serine and lysine, chemically modified thereafter [8, 10]. This implies that these tRNAs contain certain features of normal tRNAs as well as some special features for the modification of the attached amino acid. The secondary features of the odd aspartate tRNA gene of S. acidocaldarius have certain features of archaeal tRNA Asp gene. G34, U35 and C36 along with G73 are the major identity elements of aspartate tRNA [1, 13]. All the identity elements except the base at 73rd are present in this tRNA Asp. The normal purine base G73 is replaced by another purine A73 for this odd one. In addition to these deviations from the normal aspartate tRNA, certain key similarities with pyrrolysine (corresponding to modified lysine residue) lead us to the ansatz that it is a tRNA for an unnatural amino acid , perhaps , of a modified aspartate residue.Further we re-positioned intron in tRNA His from P. aerophilum. Precise fixing of intron splice site restructure the anticodon base pairing including the 3D- one between 26:44. The hallmark of intron-exon boundaries is the presence of a sequence capable of folding into the characteristic bulge-helix-bulge (BHB). A consistent BHB in this establishes our intron positioning.Methodology : Methodology : Bioinformatic Bioinformatic Bioinformatic Input InputInputThe tRNA search programs tRNAscan-SE [4] and ARAGORN key on primary sequence patterns and/or secondary structures specific to tRNAs. But a few loop- holes exist .This has to do with the inability of these existing algorithms to identify tRNA genes if it harbours noncanonical introns, specially if these are in A-stem, T-loop and AC-stem. Although unusually located introns in tDNA were observed in 1987 [3], insilico identification of tDNAs harbouring these continues to be a challenge. Some tRNAs are misidentified or missed altogether. We studied [1] about one thousand archaeal tRNAs. From the data we developed and fine-tuned our procedure to annotate CI as well as NCI containing tRNA genes from genomes. The salient features of our procedure to locate introns are the followings: (i) Introns are considered anywhere in tRNA gene, but required to harbour the BHB motif for splicing out during tRNA maturation. (ii) After the introns are spliced out the resulting tRNA has to generate the regular cloverleaf structure. (iii) There are some exclusive crenarchaeal tRNA specific identity features. The features considered in the search are G7:C66, U55, U54:A58, G52:C62 and G53:C61. These are considered as conserved for all crenarchaea.(iv) The constraints of lengths of stems of A-arm, D arm, AC arm and T arm are 7,3, 5 and 5 base pair respectively.(v) Base positions optionally occupied in D-loop are 16,17, 17a, 19, 20a and 20b, (vi) an extra arm or V arm is considered for type II tRNAs; its length constrained to maximum of 21 bases.Once we find a candidate tRNA we sift through our data [1] to position the introns with proper BHB at the intron-exon boundaries. This has to be done consistent with all conserved sequence features. Identification of tRNA depends on these conserved bases and base-pairs.Authors Authors’’ contribut contributions ions ionsSD and ZG analyzed the BHB motifs at the exon-intron boundaries ; SD,ZG,JC and BM conceived and implemented the main ideas presented here . SS developed the necessary softwares . The work was drafted by ZG and JC .Acknowledgements Acknowledgements : : :We acknowledge useful discussions and critical comments from Dhananjay Bhattacharyya.References:References:[1] Mallick B, Chakrabarti J, Sahoo S, Ghosh Z, Das S: Identity Elements of Archaeal tRNA Archaeal tRNA. DNA Research 2005 (article in press).[2] Cannone J J , Subramanian S, Schnare MN, Collett JR, D'Souza LM, Du Y , Feng B, Lin N , Madabusi LV, M üller K, Pande N , Shang Z , Yu N and Gutell RR: The Comparative RNA Web (CRW) Site: an online database of comparative The Comparative RNA Web (CRW) Site: an online database of comparative sequence and structure information for ribosomal, int sequence and structure information for ribosomal, intron, and other RNAs ron, and other RNAs ron, and other RNAs. BMC Bioinformatics 2002, 3:2.[3] Wich G, Leinfelder W, Böck A: Genes for stable RNA in the thermophile signal.Thermoproteus tenax: introns and transcription signal. EMBO J. 1987, 6:6: 523-528.[4] Lowe TM , Eddy SR: tRNAscan tRNAscan--SE:SE: f A program for or improved detection of transfer RNA genes in genomic sequence transfer RNA genes in genomic sequence. Nucleic Acids Res. 1997, 252525: 955-964. [5] Marck C , Grosjean H: intron Identification of BHB splicing motifs in intron--containing tRNAs from 18 archaea: evolutionary implicationsimplications. RNA 2003, 9:9: 1516-1531.[6] Li H, Trotta CR , Abelson J: Crystal structure and evolution of a transfer RNA splicing enzyme RNA splicing enzyme. Science 1998, 280280280: 279-284. [7] Lykke-Andersen J , Garrett RA: Structural characteristics of the stable RNA Structural characteristics of the stable RNA introns of archaeal hyperthermophiles and introns of archaeal hyperthermophiles and their splicing junctions. their splicing junctions. their splicing junctions. J. Mol. Biol. 1994, 243243243: 846-855. [8] Atkins JF , Gesteland R: The 22The 22nd Amino acid Amino acid. Science 2002, 296296296: :: 1409-1410.[9] Lescure A, Gautheret D, Carbon P , Krol A: Novel selenoproteins identified in Novel selenoproteins identified in silico and in vivo by using a co silico and in vivo by using a conserved RNA structural motif nserved RNA structural motif nserved RNA structural motif. J Biol Chem. 1999, 274:274: 38147- 38154. [10] Rajbhandary UL: Once there were twenty Once there were twenty Once there were twenty. Pro. Natl. Acad. Sci. USA 1997, 94:94: 11761-11763. [11]Théobald-Dietrich A, Frugier M, Giege R, Rudinger-Thirion J: Atypical pyrro archaeal tRNA pyrrolysine EF lysine transcript behaves towards EF--Tu as a typical elongator tRNA.elongator tRNA. Nucleic Acids Res. 2004, 323232: 1091-1096. [12] Marck C, Grosjean H: tRNomics: Analysis of tRNA genes from 50 genomes tRNomics: Analysis of tRNA genes from 50 genomes anticodon of Eukarya, Archaea, and Bacteria reveals anticodon--strategies sparing strategies anddomain domain--specific features specific features. RNA 2002, 88: 1189-1232. [13]Becker HD, Giegé R, Kern D: Identity of prokaryotic and eukaryotic aspartyl tRNA(Asp) for aminoacylation by aspartyl--tRNA synthetase from Thermus thermophilus thermophilus. Biochemistry 1996, 35:35:35: 7447-7458.Intron 3/4 Intron 3/4 Figure 1a a Figure 1Intron 43/44Intron 43/44Intron 43/44Figure Figure Figure 1b 1b 1bFigure 2 Figure 2Figure 2Figure LegendsFigure LegendsFigure 1:Figure 1NCIs denotes start position of noncanonical intron.NCIe denotes end position of noncanonical intron.h/ is sometimes purely intronic and sometimes intron-exon portion shuffled together within the same helix.Figure 1a: Unusual tRNA Asp with the BHB structure of the intron in the A-arm.h// is the helix formed by base pairing between the sequence atctt upstream of the tRNA gene and the exonic sequence tgggg between 12-16 of the unspliced tRNA.b denotes bulge. h/ here is purely intronic.Bases 2-15 of the unspliced tRNA are replaced within conventional cloverleaf scheme by asterisks and are drawn in an alternative 2D structure that fits the splicing motif (h//bh/L) requirement.Figure 1b: tRNA His with the BHB structure of the intron between 43/44.h e denotes exonic helix. b denotes bulge. h/ here is purely intronic.Bases 40-52 are replaced within conventional cloverleaf scheme by asterisks and are drawn in an alternative 2D structure that fits the splicing motif (h e bh/L) requirement.Figure 2: Cloverleaf structure of the odd tRNA Asp showing similarity with tRNA Pyl and deviation from normal archaeal tRNA structure.The conserved bases of aspartate tRNA are boxed. The empty circles and circled bases are non-canonical (those which deviates from universal features) archaeal tRNA features. The asterisk marked bases match with pyrrolysine tRNA of M. barkeri.。
Segmentation, Target Marketing, and Positioning
Market Targeting
– The act of evaluating and selecting one or more segments to serve
Market Positioning
– Occupying a specific place in the minds of customers within target markets – Differentiating your product/service from those of competitors
COMPETITOR POSITIONING AGAINST ANOTHER PRODUCT CLASS OR VIS-A-VIS THE COMPETITION
Undifferentiated (TotalMarket) – One marketing mix for all segments
Differentiated (Multisegment) – Different marketing mixes for different segments – Full Market Coverage Concentrated (Niche) – One marketing mix for one segment
travelers. Greater variety of ethnic food offerings.
Trends in Segmentation and Target Marketing (Continued)
Increased supply of cruises and special-
Positioning
The objective of positioning is to create a
【市场营销英文版】12.Positioning_and_Competition
Positionห้องสมุดไป่ตู้ng
To be branded, a product must be differentiated.
Five dimensions of product differentiation: 1.Product 2.Services 3.Personnel 4.Channel 5.Image
Positioning
Product, areas which can be differentiated: •Form •Features •Conformance •Durability •Reliability •Reparability •Style •Design •Quality
Positioning
Category Membership类目成员: a product’s inclusion in a category. Who defines categories and determines a product’s membership? Answer: the customers.
Positioning
Positioning
Positioning, a definition:
The act of designing a product and its image to occupy a distinct place in the mind of the target customer(s). A good brand positioning clarifies the essence of the brand, what goals that it will help the consumer achieve, and how it helps achieve them in its own unique way. The result of a good positioning is the creation of a “customer focused value proposition”.
10篇英语阅读-带翻译题目答案版
OneYou must have been troubled by when to say "I love you" because it is one of the greatest puzzles in our life.What if you say it first and your partner doesn‟ t love you back? or if they do say. it but you don‟t feel they mean it? Being the first to declare your love can be nerver racking(紧张）and risky and can leave you feeling as vulnerable as a turtle with no shell. But is the person who says it first really in a position of weakness? Doesn‟ t it pay to hold back, play it cool and wait until the oth er half has shown their hand fast?A really good relationship should be about being fair and being equal," says psychologist Sidney Crown. "But love is seldom equal. " All. relationships go through power struggles but, he says, if a love imbalance contin ues for years, the rot will set in. "That feeling of ‟ I‟ ve always loved you more‟ may be subverted(颠覆，破坏) for a time, but it never goes away completely and it often emerges in squabbling(大声争吵). " In love, at least, the silent, withholding type is not always the most powerful. "The strongest one in a relationship is often the person who feels confident enough to talk about their feelings," says educational psychologist Ingrid Collins. Psychosexual therapist Paula Hall agrees. "The one with the upper hand i s often the person who takes the initiative. In fact, the person who says ‟ I love you‟ first may also be the one who says ‟ I‟ m bored with you‟ first. " Hall believes that much depends on how "I love you" is said and the motivation of the person saying i t. "Is it said when they‟ re drunk? Is it said. before their partner files off on holiday, and what it really means is ‟ Please don‟ t be unfaithful to me‟ ? By saying ‟ I love you‟, they really saying‟ Do you love me?‟ If so, wouldn‟t it just be more hone st to say mat.Collins agrees that intention is everything. "It‟s not what is said, but how it‟ s said. What it comes down to is the sincerity of the speaker.”51. What is the main idea of this passage?[ A ] The importance of "I love you"[ B ] The meaning of "I love you"[ C ] The time of saying "I love you".[ D ] The place of saying. "I love you"52. In the first sentence the author means that[ A ] it is easy to say "I love you"[ B ] it is hard to say "I love you"[ C ] we have many troubles in our life[ D ] people usually do not know when to say "I love you"53. According to the expert, a good relationship should be[ A ] fair and equal[ B ] fair and kind[ C ] powerful and equal[ D] confident and fair54. In the third paragraph, the phrase "with the upper hand" means[ A ] being low in spirit[ B ] having only one hand[ C ] being active[ D ] being passive55. What is the most important for you to consider when somebody say "I love you"to you?[ A ] The intention.[ B ] The place.[ C ] The time.[ D ] The determination.Text 2 参考译文你一定曾经为何时说“我爱你”而烦恼过，因为这是我们生活中的一大难题。
Endoscopic Ultrasound-Guided Fine Needle Aspiration
Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNA) is currently performed on a routine basis at many endoscopic centers and it is evident that this procedure has a major impact on the therapeutic management of patients by obtaining a definite tissue diagnosis from lesions outlined by endosonography. The reported yield of EUS-FNA is about 90-95%, with an overall sensitivity and specificity of 90% and 100%,respectively. Moreover, even minute lesions down to a size of 5 mm may be imaged and consequently biopsied. This Review describes the technique of EUS-FNA in detail, based on a literature review and the authors' extensive experience with this method. The endoscopes and needle systems available on the market are presented in detail. The biopsy procedure is carefully explained, as well as the preparation of the cytologysmears. Finally, the limitations and complications of the procedure are reviewed in brief, stressing the low rate of complications (below 1-2%), most of them being minor and self-limiting. Currently endosonography hasstrengthened its position as a diagnostic and staging method, especially after establishing the method of FNA biopsy. Thus, EUS-FNA is very useful to establish an initial tissue diagnosis of malignancy, but also toaccurately stage the patients preoperatively, influencing the decision-making process and reducing the morbidity and mortality that accompanies inappropriate surgical interventions in patients with advanced cancer.The development of endoscopic ultrasound scanning (EUS) began in the early 1980s with mechanical radial scanning transducers.[1] In spite of an excellent imaging resolution the method did not gain widespread popularity until the development of EUS-guided fine needle aspiration biopsy (EUS-FNA).[2] EUS-FNA is at present performed on a routine basis at many endoscopic centers and it is evident that this procedure has a major impact on the therapeutic management of patients by obtaining a definite tissue diagnosis from lesions outlined by endosonography.[3,4]It is obvious that EUS-FNA is not at all limited to gastroenterology, as the gastrointestinal tract traverses through anatomical regions related to other medical specialties such as pulmonology, thoracic surgery, internalmedicine, oncology, urology, gynecology and endocrinology.[5] There is also considerable evidence that EUS-FNA in experienced hands can replace many other far more invasive and risky diagnostic procedures, such as mediastinoscopy, diagnostic laparoscopy and even laparotomy or thoracotomy.[6,7] However, the technique is not easy to master and considerable energy and effort has to be invested before the practitioner reaches an acceptable success rate. This is reported in the literature to be about 90-95%, with an overall sensitivity and specificity of 90% and 100%, respectively.[8-14] Even minute lesions down to a size of 5 mm may be imaged and consequently biopsied (Fig. 1). Moreover, contrary to what should be expected, the size of the lesions (small ≤25 mm or large >25 mm) does not necessarily influence the overall diagnostic yield, sensitivity, specificity or accuracy of the method.[15] Consequently, the accuracy of the method is variable in the literature between 85 and 95%, even in the cases where other alternative biopsy techniques have failed.[8-15]Endoscopic Ultrasound-Guided Fine Needle Aspiration Biopsy: Equipment and TechniquePeter Vilmann, Adrian S ăftoiu J Gastroenterol Hepatol. 2006;21(11):1646-1655.Multiple-use needle system type 'Hancke–Vilmann' by Medi-Globe.The aim of the present review is to describe the technique of EUS-FNA in detail, based on a literature review and our extensive experience with this method.Different electronic linear scanning endoscopes are commercially available for EUS-FNA ( ). Some of these devices have an elevator that should facilitate the positioning of the needle. When deciding which endoscope to choose, several factors need consideration, including use of elevator, stiffness/flexibility and lengths of the distal part of the endoscope, diameter of the distal end of the endoscope, diameter of the working channel and last, but not least, the quality of the ultrasonic image. The final decision relies on a compromise between these options.In the early 1990s, special biopsy equipment was developed by one of the authors (P.V.) and Søren Hancke, and this gave the final breakthrough for the EUS-guided biopsy method.[2,8] All other biopsy equipment for EUS-FNA that is available on the market at present has the same construction principles, so that the procedure of EUS-FNA can be explained based on the original construction of the Hancke-Vilmann needle system (GIP-Medizin Technik, now Medi-Globe).[2]A stiff steel needle for fine needle aspiration biopsy is the 'core' of this biopsy instrument. The needle is manipulated by a handle piston in the biopsy handle (Fig. 1). The handle piston can be locked and unlocked by means of a button (or screw) to avoid advancement of the needle during introduction and withdrawal of the biopsy assembly (Fig. 2).When the needle is completely retracted inside the sheath, it can be fixed to avoid accidental forward movement of the needle tip. The image shows the stylet with the unprotected needle, when the needle piston is unlocked. This may of course damage the working channel during introduction of the needle assembly.The needle is supported by a stable metal spiral sheath that is firmly connected to the handle. The handle can be firmly connected to the endoscope using a Luer-lock. When the handle is screwed on the Luer-lock connection of the endoscope, the metal spiral extends 4-5 mm out of the distal outlet of the working channel, so that the needle cannot damage the instrument channel of the endoscope.Inside the needle, there is a stylet that has, in its original version, a rounded tip to avoid perforation of the spiral and damage of the working channel leading to very expensive repairs of the equipment. Nowadays the needle is also available with an optional beveled stylet.Different multiple-use or disposable EUS-FNA needles are also available ( ). However, many examiners still use the conventional biopsy equipment that provides—due to the pure metal component structure—a high stability and guide precision, as this may have advantages with regards to the biopsy of hard tumors (Fig. 3). The needles have different sheath designs (either made of metal rings with and without Teflon coating, or sheaths made entirely of Teflon or other plastic types), as well as different sizes. Some needles have in addition the possibility for adjustment of the length of the needle sheath according to the variable length of the endoscope working channel (Fig. 4). Different laser treated needle tips are also available for an enhanced ultrasonic needle visualization (Fig. 5). However, according to the authors' experience, no major difference in needle monitoring and visualization exists between the different designs but rather a variance in how they look on the ultrasonic image. Only a small study with insufficient number of patients assessed comparatively two commercially available needles, with no statistically significant differences detected in the handling or characteristics of needles.[16]Conventional multiple-use needle system by Olympus with a reusable hard metal sheet that can be reloaded with sterile fine aspiration needles.New Sono-tip II single-use needle system by Medi-Globe with adjustable length of the needle sheath according to the variable length of the endoscope working channel.'Echo-Tip' single use system by Wilson Cook, with laser treated needle tip for enhanced ultrasonic needle visualization.Recently, nitinol instead of stainless steel needles have been made available in order to avoid bending of the needle. However, experience with this needle system is at present limited, as this development has only recently been released. An automatic spring-loaded biopsy system (Power Shot, Olympus) is also on the market; it has a metal spring that can forcefully 'shoot' the needle out up to 3 cm (depth adjustable) (Fig. 6). Only a single histological Trucut needle (Quick-Core, Wilson Cook) with a spring loaded shot mechanism is at present available (Fig. 7). Two preliminary studies assessed comparatively the Trucut biopsy with EUS-FNA biopsy concerning both the specimen adequacy and diagnostic accuracy.[17,18] The results showed that the diagnosis accuracy was not significantly different; however, the safety profile of the Trucut needle seems modest and further prospective studies are necessary.'Echo-Tip' single use system by Wilson Cook, with laser treated needle tip for enhanced ultrasonic needle visualization.'Quick-Core' spring-loaded histological Trucut needle by Wilson Cook.The endoscope must also be carefully selected to fit closely with the type of needle. EUS-FNA biopsies with large channel endoscopes can be done safely. However, the ultrasonic control of the needle during biopsy is more difficult with standard needle systems due to a size difference between the needle sheath and the working channel. There is a tendency to lose the ultrasonic sight of the needle due to a 'floppy' needle sheath, unsupported by the endoscope working channel. This tendency may be reduced by using the elevator, which holds the sheath in a firm position. However, needles with an extended sheath size that fit better into the working channel of the endoscope should be preferred.In most cases, EUS-FNA can safely be performed as an outpatient procedure. Laboratory tests are only necessary in selected patients, such as those on anticoagulants or with known or potential bleeding disorders. As with all endoscopic procedures the patient should be fasted for at least 4-6 h. It is recommended that the examination is performed with a typical sedation used for endoscopy. Drugs generally used include midazolam and phentanyl in carefully titrated dosages. Propofol administered by an anesthesiologist is also a valid option.Before EUS-FNA biopsy is begun, it is advisable to consider several issues. First, the right indications should be fulfilled and the patient's safety should be considered. It is advisable for the inexperienced not to begin with the most difficult biopsies. Contrary to what might be expected, the stomach wall is the most difficult tobiopsy as the wall tends to move considerably together with the needle. Also, several of the indications in this location are submucosal tumors that are difficult to diagnose by fine needle aspiration (i.e. gastrointestinal stromal tumors and leiomyomas).[19] Based on our experience, a difficulty level in increasing order is shown in . Therefore, it is our advice to begin with a biopsy of a large mediastinal tumor suspect for lung cancer, which in most cases is very easy to target and where the diagnosis is easy to obtain (Fig. 8).[20](a) Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNA) of a large mediastinal tumor. The needle (arrowheads) should be clearly visible during the entire biopsy procedure. (b) Cytology demonstrated atypical cells with hypertrophic, pleomorphic nuclei, in a background of erythrocytes (modified Giemsa, original magnification ×20).A cooperative patient is an important condition for a complication-free performance of the biopsy. Sudden movements have to be avoided to prevent injuries. Of course, the biopsy must no be performed if a vessel is interposed between the transducer and the target lesion. To exclude this, color or power Doppler techniques are very useful.At first, the transducer has to be brought into a stable position in front of the targeted lesion. As the angle between the needle and the transducer is quite small, it is advantageous to position the lesion cranial in the image, adjacent to the transducer, by using the up-down wheel of the scope before introducing the needle. The metal spiral is then introduced into the biopsy channel observing carefully that the needle piston is securely locked and the needle is completely retracted. The spiral is inserted entirely and the handle with the Luer-lock is firmly screwed onto the biopsy channel.To ensure that the sheath is protecting the entire length of the working channel of the endoscope two methods can be used: (i) by using the optic of the endoscope, it can be observed that the sheath is extending from the distal end in a secure distance of 3-5 mm; or (ii) by controlling the position of the sheath guided by ultrasound. The needle should only be moved forward when the handle is firmly screwed onto the biopsy channel and the sheath is visible at the distal end. This is to avoid damage to the working channel by unintended disconnection of the Luer-lock connection during biopsy.While monitoring the needle ultrasonically (Fig. 9), the examiner must try to keep a very firm and stable contact between the transducer and the inner surface of the gastrointestinal tract. Straightening of the endoscope should be done especially when puncturing the pancreatic head (as in the endoscopic retrograde cholangiopancreatography [ERCP] position), because these tumors are often very hard to biopsy.Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNA) of a 10 mm lymph node (arrows) situated between the aorta and the emergence of the left subclavian artery. Complete monitoring of the needle tip (arrowheads) is important to avoid puncturing of the vascular structures.Once the position is carefully adjusted, the needle with the attached stylet should be advanced until the biopsy direction can be estimated and the target can be reached easily. There is no doubt that an elevator is an advantage when very deep lesions have to be reached. However, it has to be taken into account that the needle with stylet is stiff and the activation of the elevator causes considerably strain to the sheath, the biopsy needle and the stylet. Additionally, the flexion makes it more difficult to move the needle forward and backward during the biopsy procedure. In most cases, it is possible to adjust the direction of the biopsy needle insertion very precisely with the conventional endoscopic handle control buttons.The next step is determined by the nature of the stylet, either round or sharp (beveled). The round type leads to significantly less damages of the instrument channel and should be preferred by the inexperienced practitioner. When performing a biopsy using a beveled stylet advancement of the needle into a lesion can be performed directly after advancing the needle. When choosing a round type of stylet, it has to be retracted a fewmillimeters (as it normally extends beyond the needle tip by 1-2 mm) before performing the actual penetration through the gut wall. Upon retracting the stylet, the needle tip is exposed and can freely penetrate the tissue. It is often unavoidable that a few cells from the gut wall (esophageal, gastric or duodenal mucosa) appear in the cytological material. Consequently, it is very important to inform the cytologist precisely about the method and the route of the biopsy.With the stylet retracted but still inside the needle, the biopsy needle is now moved forward into the lesion under full real-time ultrasound control. Complete monitoring of the needle tip is important whenever possible (Fig. 9). There are a few cases where a 'punch' technique is the only way to penetrate a hard lesion. When puncturing hard tumors, a bending of the needle is sometimes observed; this may create problems with the monitoring of the needle tip and may potentially cause injury to surrounding structures and especially vessels. If severe bending of the needle is experienced, a new needle should be chosen for a repeat biopsy. There is also a tendency created by the needle advancement to push the transducer apart from the mucosa thereby losing the ultrasonic image. The loss of ultrasonic needle monitoring may be avoided by inflating the balloon immediately after initial mucosal contact with the needle.After penetration into the middle of a lesion, the stylet is completely removed. Upon reaching the optimal needle position in the middle of the lesion, a 10 mL syringe with a locking device is firmly screwed on the needle, pulling the syringe piston to create a low pressure (Fig. 10). The syringe piston is locked in this position for permanent suction. The needle is now moved to and fro 5-10 times inside the lesion under complete ultrasonic control. If considerable resistance is experienced when using the elevator during the biopsy, try to neutralize the elevator as soon as the needle tip is in the middle of the lesion. With the needle tip still in the lesion, suction is slowly released and the needle safely retracted inside the needle sheath and locked in a secure position. The complete needle assembly is now removed by disconnection from the inlet of the endoscope.A needle system firmly attached to the biopsy inlet of the endoscope. A syringe with suction is mounted during the aspiration biopsy.If several lesions are present during EUS examination, a decision should be made on how many of these lesions, which lesion and in which order these lesions should be biopsied. A careful consideration incorporating knowledge of the TNM stage grouping of each disease is mandatory. It is obvious that a lesion suspected to be a distant metastasis should be biopsied before local lymph nodes and last the primary lesion, in successive order, if the same needle is to be used. If this is not done a potential false positive upstaging of the disease may occur. If another distant lesion is detected after an initial biopsy, a completely new needle should be used.In the absence of an on-site cytopathologist, a decision should be made on the number of passes used for the diagnosis. It is currently agreed that the aspiration site (primary tumor, lymph node, metastasis, ascites) can be used to direct the number of passes.[21-23] Consequently, 3-6 passes should be made for pancreatic masses, 2-3 for lymph nodes or liver metastases and one for ascites or pleural fluid.Under normal conditions after FNA biopsy, it is recommended to expel the biopsy material by air with the syringe immediately onto the prepared specimen slides. Another method that can be recommended at EUS-FNA is to re-introduce the stylet into the needle and move it slowly forward. This creates a high pressure in the needle and the material can be expelled carefully and controlled droplet by droplet onto the specimen slides. The decisive advantage of this method is that numerous same quality specimens can be prepared, whereas, when using the expelling by air method, a risk of uncontrollable expelling of the material may occur. This controlled technique represents an important advantage, especially regarding the fact that immunohistochemical stains are often necessary and are becoming more and more important. Using this method, it is easy to identify cylinders that can be processed with histological examinations. The technique of smearing should be discussed with the cytopathologist. Personally we smear the material with a second specimen slide that is placed smoothly on top of the first one and retracted, whereby a second specimen is obtained.The further procedure—especially the fixation—should also be discussed with the cytopathologist. Generally, the specimen can be air-dried and fixed later; however, some cytopathologists recommend immediate fixation and coloring of the smear. There is some evidence in the literature that it is preferable to have an attending cytopathologist in the examination room for an immediate evaluation of the specimen.[21-23] Upon applying a ready-to-use staining liquid it is possible to assess and evaluate the sufficiency of the specimen after only a few minutes. However, according to the experience of the authors this is not absolutely necessary if it has been observed that the ultrasonic monitoring of the needle during the biopsy is optimal and that the macroscopic appearance of the material seems to contain minute tissue fragments.Different stains are used for air-dried and alcohol-fixed smears, the most common being modified Giemsa, Diff-Quik and Papanicolau stains, respectively. In addition liquid preservation of the aspirated material (PreservCyt) followed by ThinPrep slides can be used, although the accuracy of this split sample technique may be inferior to that of conventional smears.[24] When additional material is available, a microhistological cylinder (cell block) can be prepared, formalin-fixed and used for immunohistochemical studies, with a possible increase in diagnostic accuracy.[25-27] However, despite of the excellent immunohistochemical possibilities, the diagnostic benefit of a histological specimen should not be overrated.Flow cytometry and immunocytochemistry may increase the diagnostic yield of EUS-FNA used for the diagnosis of lymphoma.[28] Molecular and/or genetic techniques are increasingly used for the analysis of the material aspirated during EUS-FNA. Although not ready for daily clinical practice, they may provide supplemental information in addition to conventional cytology.[29] Quantitative analysis of mutant K-ras gene may also enhance the diagnostic accuracy of conventional cytology, for the differential diagnosis of pancreatic cancer and focal chronic pancreatitis.[30,31] Comprehensive genetic analysis through PCR was reported to be possible for EUS-FNA biopsy specimens, enabling an assessment of the biological characteristics of pancreatic cancer before treatment.[32]The increased use of EUS-FNA biopsy is certainly due to the fact that it is considered a low-complication method. A multicenter study by Wiersema and Vilmann[33] showed that the complication rate was about 2%, with the majority being minor complications. Thus, non-fatal complications occurred at a rate of 0.5% (95% confidence interval, 0.1%−0.8%) in solid lesions as compared with 14% (95% confidence interval, 6-21%) in cystic lesions. Other studies, as well as a recent American Society of Gastrointestinal Endoscopy (ASGE) guideline, reported the same complication rate of 1-2% for EUS-FNA, mostly with no severe or fatal incidents.[34,35]Minor biopsy point bleedings are clinically insignificant, although they occur in as many as 4% of cases.[36] Heavier bleedings are rare, but they may occur due to shearing of the mucosa by the needle and due to injury of adjacent vessels when examining restless patients. Two episodes of clinically significant bleedings were described after EUS-FNA of pancreatic lesions, with one resulting in death.[37] Acute extraluminal hemorrhage at the site of the EUS-FNA is also rare, with a reported frequency of 1.3%, but no clinically recognizable consequences.[38] Acute intracystic hemorrhage can also rarely occur during EUS-FNA of cystic pancreatic lesions, without serious consequences, except a possible transient increase in abdominal pain.[39]The infection rate is also remarkably low and antibiotic prophylaxis is usually not necessary after biopsy of solid lesions. EUS-FNA is usually not associated with the occurrence of bacteremia and infectious complications, as recent studies could not find any statistically significant increase in the rate of bacteremia after the biopsy.[40-42] Moreover, none of the patients that developed bacteremia manifested clinical signs of symptoms of infection.EUS-FNA of mediastinal cysts is, however, associated with an increased risk of bacterial or fungal infection, which can lead to life-threatening mediastinitis.[43-45] Biopsy of pancreatic pseudocysts or cystic tumors (Fig. 11) is also an exception and antibiotic prophylaxis is preferable to use due to a relatively high infection risk.[13,33,35] However, data concerning EUS-guided pancreatic cyst aspiration are conflicting, as two recent studies, including a large number of patients, found a low complication rate (1.2% and 2.2%, respectively) similar to that reported for solid pancreatic lesions.[34,46](a) Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNA) of a cystic pancreatic tumor (blue arrows), with good visualization of the needle (red arrowheads) during EUS-FNA of the solid part. Power Doppler is used to avoid significant vessels. (b) Cytology demonstrated a clump of atypical cells with hypertrophic, pleomorphic nuclei (modified Giemsa, original magnification ×20).Mild or moderate acute pancreatitis has been described, especially when EUS-FNA biopsy of the pancreas is performed in patients with benign pancreatic diseases.[13,34,37,47-49] The rate of self-limiting acute pancreatitis was 1% after EUS-FNA biopsy performed in patients with suspected pancreatic cancer.[48] A large retrospective multicenter study also established that EUS-FNA is infrequently associated with acute pancreatitis after biopsyTumor cell seeding has always been a matter of discussion and concern; however, 'hard facts' supporting this potential risk are not available yet. To the best of our knowledge, only two case presentations suspected seeding or dissemination after EUS-FNA biopsy.[50,51] Moreover, EUS-FNA has a decreased risk of peritoneal contamination with malignancy as compared with computed tomography-guided FNA (2.2% vs 16.3%).[52] In any case, it is not recommended that the needle penetrate through malignant tissue to reach a suspicious lesion. An example of this may be a patient with gastric or esophageal cancer and a suspicious lymph node adjacent to the primary tumor (Fig. 12).Round-oval, hypoechoic, peritumoral lymph node (arrowheads), situated near a T3 gastric tumor (arrows). Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNA) of the lymph node for confirmation of malignancy should not be done, as the needle would pass through the tumor tissue in the stomach.Further refinements of the EUS-FNA procedure were described in recent articles, strengthening the position of EUS-FNA as a state-of-the-art technique with an important clinical impact. Thus, the accuracy of the cytological assessment was enhanced by different approaches that included the presence of a cytopathologist in the examination room[22,53-55] or the possibility of mailing the results to an expert cytopathologist.[56] Furthermore, the on-site evaluation of slides obtained by EUS-FNA helps in obtaining samples for advanced studies such as immunohistochemical analysis, flow cytometry or genetic analysis, which may enhance the diagnostic accuracy of the procedure.[57] Improvement of the EUS-FNA technique included the use of different types of suction,[58,59] as well as a recently proposed system of high negative pressure suction.[60]Despite the rapid technological development of other imaging methods, endosonography has strengthened its position as a diagnostic and staging method especially after establishing the method of FNA biopsy. EUS-FNA is very useful to establish tissue diagnosis of malignancy in patients without previous diagnosis, but also to accurately stage the disease preoperatively, influencing the decision-making process and reducing the morbidity and mortality that accompanies inappropriate surgical interventions in patients with advanced cancer. Therefore, it is even more important to utilize its superior diagnostic advantage and the low-complication rate by standardization and training programs in order to further implement the method in gastroenterology practice.The biopsy procedure: tips and tricksPreparationBefore introducing the needle, check biopsy equipment with check list:。