Self-Organized Formation of Hexagonal Pore Arrays in Anodic Alumina Fabrication
氧化亚铜的文献
Brush-Like Hierarchical ZnO Nanostructures:Synthesis,Photoluminescence and Gas Sensor PropertiesYuan Zhang,†,‡Jiaqiang Xu,*,†,§Qun Xiang,†Hui Li,†,‡Qingyi Pan,†and Pengcheng Xu §Department of Chemistry,College of Science,Shanghai Uni V ersity,Shanghai 200444,China,Department of Physics,College of Science,Shanghai Uni V ersity,Shanghai 200444,China,and State Key Laboratory of Transducer Technology,Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences,Shanghai 200050,ChinaRecei V ed:September 12,2008;Re V ised Manuscript Recei V ed:December 28,2008Brush-like hierarchical ZnO nanostructures assembled from initial 1D ZnO nanostructures were prepared from sequential nucleation and growth following a hydrothermal process.The morphology,structure,and optical property of hierarchical ZnO nanostructures were characterized by X-ray diffraction (XRD),field-emission scanning electron microscopy (FE-SEM),and photoluminescence (PL)studies.The FE-SEM images showed that the brush-like hierarchical ZnO nanostructures are composed of 6-fold nanorod-arrays grown on the side surface of core pared with ZnO nanowires,brush-like hierarchical ZnO nanostructures easily fabricated satisfactory ethanol sensors.The main advantages of these sensors are featured in excellent selectivity,fast response (less than 10s),high response (sensitivity),and low detection limit (with detectable ethanol concentration in ppm).1.IntroductionNanoscale materials have stimulated great interest in current materials science due to their importance in such basic scientific researches and potential technology applications as microelec-tronic devices,1chemical and biological sensors,2light-emitting displays,3catalysis,4and energy conversion and storage devices.5Previous studies indicated that the shape of nanoscale materials have a profound influence on their properties.6This has led to intensive investigation on quantum dots,7nanowires,8nano-tubes,9and self-assembled monolayers (SAMs).10In recent years,much attention has been paid to three-dimensional and hierarchical architectures that derive from the above-mentioned low dimensional nanostructures as building blocks,due to various novel applications.For example,the Lieber group has reported that core/shell coaxial silicon nanowires architectures can be employed as solar cells.1Wang reported that a novel hierarchical nanostructure based on Kevlar fibers coated with ZnO nanowires could serve as nanogenerators.11Though tremendous progress has been made in this significant field,there are still great demands on the synthesis of alternative three-dimensional and hierarchical architectures with novel or po-tential applications.Hierarchical ZnO architectures have been extensively pro-duced with gas-phase approaches.12-14With these synthetic methods,nanowire arrays,15nanohelitics,16nanopropeller,17and tower-like nanocolumns 18have been successfully prepared.However,these protocols often require high temperature and induce impurities in the final products when catalysts and templates are introduced to the reaction system.In practice,this made it difficult to obtain organic/inorganic hybrid hierarchical architectures.In addition,although the solution-based synthetic strategies are simple and effective in the production of thebuilding blocks of hierarchical nanostructures such as nanopar-ticles,19nanowires,20and nanorods,21achievement of hierarchical architectures from such techniques remains a challenge.Herein,we developed a simple nucleation and growth strategy to synthesize brush-like hierarchical ZnO nanostructures.The two step seeded-growth approach allows stepwise control and optimization of experimental conditions and provides an op-portunity for rational design and synthesis of controlled architectures in nanostructures.22-24We also investigated the effect of morphology and structure of brush-like hierarchical ZnO nanostructures on its gas sensing responses.The results show that ZnO hierarchical nanostructures display better ethanol sensing property than that of ZnO nanowires.2.Experimental SectionAll reagents employed were analytically pure and used as received from Shanghai Chemical Industrial Co.Ltd.(Shanghai,China)unless otherwise mentioned.2.1.Synthesis.The strategies to fabricate the brush-like hierarchical ZnO nanostructures are summarized as follows.First,the ZnO nanowires with a uniform shape were synthesized as described elsewhere,25which was used as the initial material to grow hierarchical ZnO nanostructures.Subsequently,a saturated solution of Zn(OH)42-was prepared by dissolving excess ZnO in 10mL of NaOH solution (5mol/L)for growing hierarchical ZnO nanostructures.Third,the ZnO nanowires (0.05g)were uniformly suspended in deionized water (37mL)in an ultrasonic bath.The suspension was mixed with the Zn(OH)42-saturated solution (3mL).After the mixture was transferred into a Teflon-lined autoclave (50mL),it was kept at 100°C for 10h.Finally,upon the hydrothermal treatment a white precipitate was formed,which was washed thoroughly with ethanol and distilled water in sequence,and dried at 60°C under vacuum for 6h.2.2.Characterization.The initial ZnO seeds were character-ized by transmission electron microscopy (TEM,JEM-200CX,using an accelerating voltage of 160kV).The morphology of*Corresponding author.Tel:+862166134728.Fax:+862166134725.E-mail:xujiaqiang@.†Department of Chemistry,Shanghai University.‡Department of Physics,Shanghai University.§Chinese Academy of Sciences.J.Phys.Chem.C 2009,113,3430–3435343010.1021/jp8092258CCC:$40.75 2009American Chemical SocietyPublished on Web 02/06/2009hierarchical ZnO nanostructures was observed by field emission scanning electron microscopy (FE-SEM,JSM-6700F).The crystal phase of as-synthesized products was identified by powder X-ray diffraction (XRD)analysis using a D/max 2550V diffractometer with Cu K R radiation (λ) 1.54056Å)(Rigaku,Tokyo,Japan),and the XRD data were collected at a scanning rate of 0.02deg s -1for 2θin a range from 10°to 70°.2.3.Photoluminescence (PL)Measurement.Room tem-perature PL measurements were performed on a Hitachi RF-5301PC spectrofluophotometer using the 350nm Xe laser line as the excitation source.2.4.Gas Sensor Fabrication and Response Test.The ZnO powder was mixed with Terpineol and ground in an agate mortar to form a paste.The resulting paste was coated on an alumina tube-like substrate on which a pair of Au electrodes had been printed previously,followed by drying at 100°C for about 2h and subsequent annealing at 600°C for about 2h.Finally,a small Ni -Cr alloy coil was inserted into the tube as a heater,which provided the working temperature of the gas sensor.The schematic drawing of the as-fabricated gas sensor is shown in Figure 1.In order to improve the long-term stability,the sensors were kept at the working temperature for several days.A stationary state gas distribution method was used for testing gas response (Air humidity:47%).In the measurement of electric circuit for gas sensors (Figure 2),a load resistor (Load resistor value:470k Ω)was connected in series with a gas sensor.The circuit voltage was set at 10V,and the output voltage (V out )was the terminal voltage of the load resistor.The working temperature of a sensor was adjusted through varying the heating voltage.The resistance of a sensor in air or test gas was measured by monitoring V out .The test was operated in a measuring system of HW-30A (Hanwei Electronics Co.Ltd.,P.R.China).Detect-ing gases,such as C 2H 5OH,were injected into a test chamber and mixed with air.The gas response of the sensor in this paper was defined as S )R a /R g (reducing gases)or S )R g /R a (oxidizing gases),where R a and R g were the resistance in air and test gas,respectively.The response or recovery time was expressed as the time taken for the sensor output to reach 90%of its saturation after applying or switching off the gas in a step function.3.Results and Discussion3.1.Structure and Morphology.In the XRD pattern of the as-synthesized products (Figure 3),all of the peaks were well indexed to hexagonal wurtzite ZnO (JCPDS No.36-1451,a )0.3249nm,c )0.5205nm)with high crystallization.No characteristic peaks were observed for impurities.The FE-SEM images of hierarchical ZnO nanostructures (Figure 4)were observed at low and medium magnifications,respectively.From the low magnification image (Figure 4a),the secondary nanorods self-organized into very regular arrays,which mimic brush-like hierarchical nanostructures.These nanorod arrays that grew onto one common central nucleus could also be revealed from the protrudent brush-like structures (Figure 4a).The medium magnification (Figure 4b)clearly indicated that these secondary nanorod arrays were brush-like 6-fold symmetry.MorecarefulFigure 1.Sketch of the gassensor.Figure 2.Measuring electric circuit of the gassensor.Figure 3.XRD pattern of the brush-like hierarchical ZnOnanostructures.Figure 4.FE-SEM images of the brush-like hierarchical ZnO nanostructures:(a)at low magnification and (b)at medium magnification.Brush-Like Hierarchical ZnO Nanostructures J.Phys.Chem.C,Vol.113,No.9,20093431observation of the morphology of hierarchical nanostructures indicated that the nanorod arrays grew on the side surface of core nanowire.The reason for nanorod arrays to grow into 6-fold symmetry may arise from the hexagonal symmetry of the major core.26The central stems provide its six prismatic crystal planes/facets as growth platforms for branching of multipod units.The synthesis of 6-fold ZnO nanostructures have been reported;17,26-28however,the solution-based approach to this structure is rarely disclosed.Under hydrothermal conditions,heteronucleation can take place,and the interfacial energy between crystal nuclei and substrates is usually smaller than that between crystal nuclei and solutions.22Therefore,the secondary rod-like branches can grow on the wire-like ZnO central core.3.2.Impact of the Reaction Conditions on the Growth of ZnO Hierarchical Nanostructures.Our studies suggest that the morphology of ZnO seeds and the concentration of OH -ion in the reaction system are the key factors for the formation of ZnO hierarchical nanostructures.First,ZnO nanostructures with different morphology were used as seeds for the nucleation and growth process.In the synthesis of brush-like ZnO hierarchical nanostructures,high aspect ratio (height/width)ZnO nanowires were used as seeds.These ZnO nanowires have typical diameters of 80-100nm and lengths up to 10µm (Figure 5).In order to study the effect of the seeds morphology on the growth of brush-like ZnO hierarchical nanostructures,a lower aspect ratio of ZnO nanorods (200nm diameter,aspect ratio <5,Figure 6a)was used as substitute seeds in this seeding growth method.When nanorods were used as seeds for further crystal growth,shorter and thicker rod-like ZnO nanostructures were obtained (Figure 6b).Second,the brush-like ZnO hierarchical nanostructures could only be obtained under an optimized concentration (5M)of OH -ion.The morphologies of the as-obtained products varied remarkably with changes in the OH -ion concentration.When the OH -ion concentration dropped to 3M,only a few disorder secondary nanorods grew on each common central nucleus (Figure 7a).As the OH -ion concentration increased to 15M,the secondary rod-like branches structures and the brush-like hierarchical nanostructures became shorter than those at lower concentrations because of the dissolve effect of NaOH (Figure 7b).When the OH -ion concentration increased to 20M,the amount of sub-branch nanorods also increased,and chrysan-themum-like microstructures could be obtained (Figure 7c).It is worth mentioning that these secondary rod-like crystals have a relatively planar bottom at high OH -ion concentration.We noted that the concentration of NaOH (i.e.,the concentra-tion of OH -)was crucial to the formation of Zn(OH)42-precursor.The growth of ZnO did not proceed at low concentra-tion of OH -because no Zn(OH)2was formed in the solution.Accordingly,only a few disordered sub-branch nanorods grew on each common central nucleus.With an increase of OH -concentration,the nucleation of ZnO was accelerated leading to more nanorods growing on the central nucleus.When the concentration of OH -was further increased,the growth of sub-branch nanorods was impeded,29and the average aspect ratio of ZnO nanorods was decreased.However,when excess NaOH was employed,it became not only a source of hydroxyl ions to form ZnO,but a capping agent.30ZnO crystal is a polar solid with a positive polar plane (0001)rich in Zn and a negativepolar plane (0001j )rich in O.31At a high OH -concentration,OH -ions are preferably adsorbed on the (0001)plane of ZnO,29,32and the growth of the ZnO nanocrystallite along the c axis is partially suppressed.It suggests that the OH -ion could act as a surface termination reagent,thus impeding the growth of crystal face (0001).29Accordingly,the secondary rod-like crystals have a flat face.Previous studies indicated that surfactants could control the morphology in the solution phase process.33-36We synthesized the ZnO hierarchical nanostructures V ia a surfactant-free route.But,do surfactants have a positive effect on the morphology of the products?Taking a typical surfactant CTAB (cetyltrimethy-lammonium bromide)as example,when CTAB was introduced into the reaction system,the morphology of the as-obtained products was ZnO microsphere consisting of nanorods(FigureFigure 5.TEM image of the ZnO nanowireseeds.Figure 6.TEM images of the ZnO samples:(a)the initial ZnO nanorods seeds and (b)the secondary crystals from the initial ZnO nanorods.3432J.Phys.Chem.C,Vol.113,No.9,2009Zhang et al.7d).The ability of CTAB to form diversified shapes of microparticles has been exploited extensively.37-41Due to the coulomb force action between [Zn(OH)42-]and CTAB,they interact to form complexes,which are adsorbed on the circum-ference of the ZnO nuclei.42Upon the formation of globules,the zinc complex dissociated to form rod-like nanostructures with the assistance of CTAB,43,44leading to the nanorod-assembled microsphere.In addition,the hydrothermal temperature (100-120°C)and hydrothermal time (10-15h)made no obvious difference in the morphology of ZnO hierarchical nanostructures.3.3.Optical Properties Measurement.The photolumines-cence spectrum of the secondary brush-shaped nanostructures was measured using Xe laser (350nm)as excitation source.We also measured the PL spectrum of the initial nanowires for comparison (Figure 8).Strong emission at ∼389nm was observed for both structures.In addition,we observed that the green emission intensity at ∼558nm for the brush-shaped nanostructures is stronger than that of the initial nanowires.The green emission peak is commonly referred to singly ionized oxygen vacancy in ZnO resulting from the radiative recombina-tion of a photogenerated hole with an electron occupying theoxygen vacancy.15,45The stronger green light emission intensity suggests that there is a greater fraction of oxygen vacancies in the brush-shaped nanostructures.Defects at metal oxide surfaces are believed to significantly influence a variety of surface properties,including chemical adsorption reactivity,46,47such as heterogeneous catalysis,cor-rosion inhibition and gas sensing.The influence of the intrinsic defects on the ZnO surface chemistry and the effects of chemisorption have been addressed by theoretical calculation and experimental data.47-50Moreover,the mechanism of the oxygen vacancies induced gas sensing enhancement properties of ZnO has been explained.51A large quantity of oxygen vacancy results in high adsorptions of oxygen,and in turn enhances the chance of interaction with testing gases.3.4.Gas Sensing Properties.The gas sensing properties of low dimensional ZnO nanostructures (nanoparticles,nanowires,nanorods)have been widely investigated by many research groups;52-55however,the influence of hierarchical ZnO mor-phology on their gas sensing performance has scarcely been investigated.In this paper,we also studied the ethanol gas-sensing properties of ZnO hierarchical nanostructures,and discussed the effect of morphology on the gas sensing responses.Eight typical reducing gases (CH 4,H 2,NH 3,i -C 4H 10,HCHO,CO,C 6H 6,and C 2H 5OH)and two typical oxidizing gases (NO 2and Cl 2)were selected as target gases to investigate the gas response at an optimal operating temperature of 265°C,where the concentration of all the tested gases was 50ppm.The gas sensor based on the ZnO hierarchical nanostructures (Figure 9)showed good selectivity to ethanol with little interference against other gases.ZnO is a very common ethanol sensing material.56-58The ethanol sensing mechanism of the ZnO sensors has also been reported in our previous studies.59However,only few studies indicate that ZnO has higher gas response to ethanol than other commonly used gases.58Most metal oxide semiconductor gas sensors are based on the conductance change arising fromtheFigure 7.The FE-SEM images of the secondary ZnO nanostructures obtained under different conditions a)3M NaOH,b)15M NaOH,c)20M NaOH,d)1gCTAB.Figure 8.Photoluminescence spectra of different ZnO samples (a)brush-like hierarchical nanostructures and (b)nanowires.Brush-Like Hierarchical ZnO Nanostructures J.Phys.Chem.C,Vol.113,No.9,20093433reactions between the oxygen ions and the detecting gas molecules adsorbed on the active surface.60,61We found that the electron donating effect of the testing gas molecule is an important factor in the explanation of this phenomenon (In the several forms of oxygen adsorbates,the O -is more active form of adsorbed oxygen.).For example,the typical testing gas sensing reactions are expressed as follows:CO +O -f CO 2+e -(1)H 2+O -f H 2O +e -(2)HCHO +2O -f H 2O +CO 2+2e -(3)Catalytic oxidation of ethanol gas is known through two different routes depending on the acid or base properties of catalyst surface,i.e.,a dehydrogenation route through CH 3CHO intermediate (on the basic surface)and a dehydration route through a C 2H 4intermediate (on the acidic surface).61,62Since ZnO is a basic oxide,dehydrogenation is favored,providing CH 3CHO as the major which undergoes subsequent oxidation to form CO 2and H 2O.C 2H 5OH f CH 3CHO +H 2(4)CH 3CHO(ad)+5O -(ad)f 2CO 2+2H 2O +5e -(5)According to these equations,the electron donating effect of ethanol is stronger than that of the other gases.Therefore,the gas response of ethanol is higher than that of the other gases at the equivalent concentration.However,owing to the complicated reactivity of some gas molecules on the ZnO surface,the electron donating effect is not the only influential factor on gas response.Other factors (such as reaction of testing gases and sensing material,humidity,temperature,and some additional external fluctuating factor)may exist and compete against each other.Interestingly,the response of brush-like hierarchical nano-structures (Figure 9)is greater than that of initial ZnO nanowires.This observation is general to all the gases examined herein.The gas sensing response enhancement can be attributed to more active centers that are obtained from the enhanced oxygen vacancy defects on the brush-shaped nanostructures.Besides,the formation of initial nanorod/secondary nanorods junctions may be an additional reason for the response enhancement.These junctions are considered as the active sites that canenhance the response of the gas sensors.63Moreover,the nanorod arrays could increase the numbers of the gas channels leading to more effective surface areas (defined as the areas which can contact with the gas).The enhancement in gas response of the brush-like hierarchi-cal nanostructures with the increase of ethanol concentration was observed (Figure 10)in a range of 5-50ppm.The gas response of brush-like hierarchical nanostructures was so high that even if the concentration of ethanol decreased to 5ppm,the gas response increased by 3.0times.In addition,the brush-like hierarchical ZnO nanostructures had very high responses to ethanol,showing a promise as ethanol-sensing materials.The dynamic response of brush-like hierarchical ZnO nanostructures to 10,30,and 50ppm ethanol (Figure 11)displayed impressive response and recovery properties for the brush-like hierarchical ZnO nanostructure-based sensors.All the response time and the recovery time of the sensors at the ethanol concentration of 10,30,and 50ppm were less than 10s.The SEM image (Figure 12)of brush-like hierarchical ZnO nanostructure after sintering at 600°C for 2h suggested that the brush-like hierarchical nanostructures were kept well.The heat treatment did not affect the morphology and sizes of these hierarchical nanostructures,which demonstrated a high stability of the brush-like hierarchical ZnO nanostructures.The structural stability may be in favor of the long-term stability of sensors suitable for practical applications.4.ConclusionIn this paper,we developed a simple hydrothermal route to synthesize brush-like hierarchical ZnO nanostructures under mild conditions.Our results showed that a soft chemical route is promising for rational and structural design of the nanoscale materials.The photoluminescence and gas sensing properties of brush-like hierarchical ZnO nanostructures were studied.The photoluminescence spectrum suggested higher oxygen vacancy defects on the brush-shaped nanostructures thannanowires,Figure 9.Responses of the brush-like hierarchical ZnO nanostructures and the ZnO nanowires to various gases (The concentration of all gases was 50ppm).Figure 10.Relationship between gas response of the brush-like hierarchical ZnO nanostructures and ethanolconcentration.Figure 11.Response of sensor based on brush-like hierarchical ZnO nanostructures to 10,30,and 50ppm ethanol.3434J.Phys.Chem.C,Vol.113,No.9,2009Zhang et al.which combined with special ZnO morphology were able to generate more active centers so as to enhance the gas response.The gas sensing measurements showed that the brush-like hierarchical ZnO nanostructures could serve excellent ethanol sensors.Acknowledgment.We appreciate the financial support of Shanghai NSF (No.07ER14039)and Leading Academic Discipline Project of Shanghai Municipal Education Commis-sion (No.J50102).We also thank the Analysis and Research Center at Shanghai University for sample characterization.References and Notes(1)Lauhon,L.J.;Gudiksen,M.S.;Wang,C.L.;Lieber,C.M.Nature 2002,420,57.(2)Modi,A.;Koratkar,N.;Lass,E.;Wei,B.Q.;Ajayan,P.M.Nature 2003,424,171.(3)Banerjee,D.;Jo,S.H.;Ren,Z.F.Ad V .Mater.2004,16,2028.(4)Bansal,V.;Jani,H.;Du Plessis,J.;Coloe,P.J.;Bhargava,S.K.Ad V .Mater.2008,20,717.(5)Arico, A.S.;Bruce,P.;Scrosati, B.;Tarascon,J.M.;Van 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英国的景观介绍英语作文
英国的景观介绍英语作文英文回答：The United Kingdom is renowned for its breathtaking landscape, a tapestry of rolling hills, lush meadows, sparkling rivers, and dramatic coastlines. Varying from region to region, its scenery is as diverse as its people, offering a kaleidoscope of natural beauty to explore.England, the largest country in the UK, boasts iconic landmarks such as the rolling Cotswolds, an enchanting region of honey-colored villages nestled amidst gentle slopes and tranquil valleys. In contrast, the rugged Pennines offer a more exhilarating landscape, with heather-clad moors, steep valleys, and cascading waterfalls. The Lake District, a haven for outdoor enthusiasts, is renowned for its pristine lakes, towering mountains, and picturesque villages.Venturing to the north, Scotland's untamed beautycaptivates the imagination. The Scottish Highlands, a landof towering peaks, shimmering lochs, and ancient forests, provide an unrivaled wilderness experience. The Isle of Skye, with its dramatic cliffs and breathtaking sunsets, is a testament to the country's rugged allure.Wales, the land of dragons and song, offers a rich tapestry of landscapes. Snowdonia National Park, with its rugged mountains, shimmering lakes, and enchanting valleys, is a haven for hikers and nature lovers. The Brecon Beacons, a range of rolling hills and cascading waterfalls, provides a contrastingly gentler experience.Northern Ireland, the UK's smallest country, boasts a landscape of enchanting beauty. The Giant's Causeway, a formation of hexagonal basalt columns, is a geological marvel that attracts visitors from around the globe. The Mourne Mountains, with their dramatic peaks and glacial valleys, offer stunning views of the surrounding countryside.The UK's landscape has inspired countless artists,writers, and poets throughout history. William Wordsworth, the Romantic poet, immortalized the beauty of the Lake District in his works, while J.M.W. Turner's paintings captured the dramatic landscapes of Scotland and Wales.Exploring the UK's landscape is a journey of discovery, a chance to immerse oneself in the beauty of nature and experience the rich heritage that has shaped the country. From the rolling hills of England to the rugged mountainsof Scotland, the UK's landscape is a testament to the diversity and beauty that the British Isles have to offer.中文回答：英国以其迷人的景观而闻名，它是一幅由连绵起伏的丘陵、郁郁葱葱的草地、波光粼粼的河流和壮丽的海岸线组成的挂毯。
原位杂交的英语
原位杂交的英语Here is an English essay on the topic of in-situ hybridization, with a word count exceeding 1,000 words.In-situ hybridization is a powerful molecular biology technique that allows researchers to visualize and localize specific nucleic acid sequences within intact cells or tissue sections. This technique has become an indispensable tool in various fields of biology, including genetics, developmental biology, and pathology. In-situ hybridization enables researchers to gain valuable insights into the spatial and temporal expression patterns of genes, providing a deeper understanding of biological processes and disease mechanisms.One of the key advantages of in-situ hybridization is its ability to preserve the natural context of the target molecules. Unlike traditional molecular techniques that often require the extraction and purification of nucleic acids, in-situ hybridization allows the detection of target sequences within the intact cellular or tissue environment. This preserves the spatial relationships between different cell types and the overall tissue architecture, enabling researchers to study the distribution and localization of specificgenes or transcripts in their native context.The fundamental principle of in-situ hybridization is the hybridization of a labeled, single-stranded nucleic acid probe to its complementary sequence within the target cells or tissues. The probe is typically a short, synthetic oligonucleotide or a complementary DNA (cDNA) fragment that is labeled with a reporter molecule, such as a fluorescent dye, a radioactive isotope, or an enzyme-conjugated label. When the labeled probe binds to its target sequence, the reporter molecule can be detected using various imaging techniques, allowing the visualization and localization of the target nucleic acid.In-situ hybridization can be performed on a variety of sample types, including fixed and paraffin-embedded tissue sections, frozen tissue sections, cell cultures, and whole-mount preparations. The choice of sample preparation method depends on the specific research question, the target molecule, and the desired level of resolution.One of the most widely used in-situ hybridization techniques is fluorescence in-situ hybridization (FISH). In FISH, the labeled probe is detected using fluorescent dyes, and the signal is visualized using fluorescence microscopy. FISH allows for the simultaneous detection of multiple target sequences by using probes labeled with different fluorescent dyes. This technique has been extensively used in cytogenetics, cancer research, and the study of chromosomalaberrations.Another variant of in-situ hybridization is chromogenic in-situ hybridization (CISH), where the labeled probe is detected using an enzyme-catalyzed chromogenic reaction. The resulting colored precipitate can be visualized using a standard light microscope, making CISH a more widely accessible and cost-effective technique compared to FISH.In addition to the traditional in-situ hybridization methods, recent advancements in technology have led to the development of novel techniques that enhance the sensitivity, specificity, and resolution of target detection. For example, single-molecule FISH (smFISH) allows the visualization of individual mRNA molecules within cells, providing unprecedented insights into the spatial and temporal dynamics of gene expression.The applications of in-situ hybridization are diverse and span various fields of biology and medicine. In developmental biology, in-situ hybridization has been instrumental in elucidating the spatiotemporal patterns of gene expression during embryonic development, enabling researchers to better understand the complex regulatory networks that govern tissue patterning and organ formation.In the field of cancer research, in-situ hybridization has become a valuable tool for the detection and localization of specific genetic alterations, such as chromosomal rearrangements, gene amplifications, and viral integrations. This information can aid in the diagnosis, prognosis, and targeted treatment of various types of cancer.In the field of neuroscience, in-situ hybridization has been used to map the expression of neurotransmitter receptors, ion channels, and other key molecules within the complex architecture of the brain. This has led to a better understanding of the functional organization of the nervous system and the pathological changes associated with neurological disorders.Furthermore, in-situ hybridization has found applications in the study of infectious diseases, where it can be used to detect and localize the presence of viral or bacterial nucleic acids within infected tissues. This information can be crucial for the diagnosis, monitoring, and development of targeted therapies for infectious diseases.Despite its numerous advantages, in-situ hybridization also faces some challenges and limitations. The sensitivity and specificity of the technique can be influenced by factors such as probe design, sample preparation, and the abundance of the target sequence. Additionally, the interpretation of in-situ hybridization results can be complex,particularly in cases where the spatial distribution of the target molecule is not straightforward.To address these challenges, researchers have continued to refine and improve in-situ hybridization techniques. Advancements in probe design, signal amplification strategies, and image analysis algorithms have helped to enhance the sensitivity, specificity, and quantitative capabilities of in-situ hybridization. Furthermore, the integration of in-situ hybridization with other imaging modalities, such as electron microscopy and super-resolution microscopy, has enabled the visualization of target molecules at unprecedented spatial resolutions.In conclusion, in-situ hybridization is a versatile and powerful technique that has become an indispensable tool in modern biology and medicine. By allowing the visualization and localization of specific nucleic acid sequences within their natural cellular and tissue context, in-situ hybridization has provided researchers with invaluable insights into the complex mechanisms that govern biological processes and disease pathogenesis. As technology continues to evolve, the future of in-situ hybridization promises even greater advancements in our understanding of the fundamental principles of life.。
分子生物学名词解释
AAbundance(mRNA丰度)：指每个细胞中mRNA分子的数目。
AbundantmRNA(高丰度mRNA)：由少量不同种类mRNA组成，每一种在细胞中出现大量拷贝。
Acceptorsplicingsite(受体剪切位点)：内含子右末端和相邻外显子左末端的边界。
Acentricfragment(无着丝粒片段)：(由打断产生的)染色体无着丝粒片段缺少中心粒，从而在细胞分化中被丢失。
Activesite(活性位点)：蛋白质上一个底物结合的有限区域。
Allele(等位基因)：在染色体上占据给定位点基因的不同形式。
Allelicexclusion(等位基因排斥)：形容在特殊淋巴细胞中只有一个等位基因来表达编码的免疫球蛋白质。
Allostericcontrol(别构调控)：指蛋白质一个位点上的反应能够影响另一个位点活性的能力。
Alu-equivalentfamily(Alu相当序列基因)：哺乳动物基因组上一组序列，它们与人类Alu家族相关。
Alufamily(Alu家族)：人类基因组中一系列分散的相关序列，每个约300bp长。
每个成员其两端有Alu切割位点(名字的由来)。
α-Amanitin(鹅膏覃碱)：是来自毒蘑菇Amanitaphalloides二环八肽，能抑制真核RNA聚合酶，特别是聚合酶II转录。
Ambercodon(琥珀密码子)：核苷酸三联体UAG，引起蛋白质合成终止的三个密码子之一。
Ambermutation(琥珀突变)：指代表蛋白质中氨基酸密码子占据的位点上突变成琥珀密码子的任何DNA改变。
Ambersuppressors(琥珀抑制子)：编码tRNA的基因突变使其反密码子被改变，从而能识别UAG密码子和之前的密码子。
Aminoacyl-tRNA(氨酰-tRNA)：是携带氨基酸的转运RNA，共价连接位在氨基酸的NH2基团和tRNA终止碱基的3￠或者2￠－OH基团上。
Aminoacyl-tRNAsynthetases(氨酰-tRNA合成酶)：催化氨基酸与tRNA3￠或者2￠－OH基团共价连接的酶。
不同结构六边形斑图演化过程光谱特性
不同结构六边形斑图演化过程光谱特性冯建宇;董丽芳;魏领燕;郝芳;杜天;崔义乾【摘要】采用发射光谱法，研究了水电极介质阻挡放电中具有相同对称性的3种不同结构的六边形斑图演化过程的光谱特性。
实验结果表明，随着外加电压的增加，放电首先形成六边形点阵斑图，然后是空心六边形斑图，最后是蜂窝六边形斑图。
利用氩原子696.5 nm(2P2→1S5)谱线的展宽、氩原子763.2 nm(2P6→1S5)与772.1 nm(2P2→1S3)两条谱线强度比法和氮分子第二正带系( C3Πu→B3Πg )的发射谱线，研究上述3种斑图的电子密度、电子激发温度及分子振动温度。
结果发现，随着外加电压的升高，六边形点阵斑图、空心六边形斑图和蜂窝六边形斑图的电子密度逐渐减小，而电子激发温度和分子振动温度逐渐增加。
等离子体状态的改变直接影响着斑图的自组织。
%The spectral characteristics of different kinds of hexagon pattern with the same symmetry in evolutionary process were studied in dielectric barrier discharge by optical emission spectrum. It is found that the discharge undergoes hexagon superlattice pattern, hollow hexagon pattern and hon-eycomb pattern with the increasing ofthe applied voltage. The electronic density, electron excitation temperature and molecular vibration temperature of the three kinds of patterns were investigated by the broadening of spectral line 696. 5 nm, the relative intensity ratio method of spectral lines of ArⅠ763. 2 nm (2P6→1S5) and Ar Ⅰ772. 1 nm (2P2→1S3) and the emission spectra of nitrogen band of second positive system ( C3Πu→B3Πg ) , respectively. The results showthat the electronic density of the hexagon superlattice pattern, hollow hexagon pattern and honeycomb pattern gradually decreases, while theelectron excitation temperature and molecular vibration temperature ofthe three kinds of patterns gradually increase with the applied voltage increasing. It is found that the change of the plasma state has effect on the self-organization of the pattern.【期刊名称】《发光学报》【年(卷),期】2016(037)009【总页数】6页(P1076-1081)【关键词】介质阻挡放电;斑图;发射光谱;电子密度;电子激发温度;分子振动温度【作者】冯建宇;董丽芳;魏领燕;郝芳;杜天;崔义乾【作者单位】河北大学物理科学与技术学院，河北保定 071002;河北大学物理科学与技术学院，河北保定 071002;河北大学物理科学与技术学院，河北保定071002;河北大学物理科学与技术学院，河北保定 071002;河北大学物理科学与技术学院，河北保定 071002;河北大学物理科学与技术学院，河北保定 071002【正文语种】中文【中图分类】O461介质阻挡放电(DBD)是一种典型的非平衡态交流气体放电，已经成为低温等离子体的一个重要的研究领域[1-4]。
米伊林十万个为什么固体的水读后感
米伊林十万个为什么固体的水读后感英文回答："Miyelin Ten Thousand Whys: Solid Water" is a fascinating book that delves into the many mysteries and wonders of solid water, also known as ice. The author, Miyelin, takes readers on a journey through the scientific explanations and practical applications of this unique form of water.One of the most intriguing aspects of solid water isits ability to float. As Miyelin explains, this is due to the arrangement of water molecules in an ice crystal lattice. Unlike most substances, water expands when it freezes, causing its density to decrease. This decrease in density allows ice to float on top of liquid water, whichis crucial for the survival of aquatic life during winter months. This phenomenon is beautifully captured in the saying "as solid as a rock, but floats like a boat."Another interesting topic explored in the book is the various forms and structures that solid water can take. Miyelin describes how different factors such as temperature and pressure can influence the formation of different types of ice, from the hexagonal crystals of snowflakes to the dense ice found in glaciers. This diversity in ice formations is not only visually stunning but also plays a vital role in shaping our planet's landscapes.Furthermore, Miyelin delves into the practical applications of solid water. From ice sculptures to ice cubes, solid water has been utilized by humans in various ways. The author also discusses the importance of ice in industries such as refrigeration and ice cream production. Additionally, Miyelin explains how scientists are exploring the potential of ice as a renewable energy source, as it can store large amounts of energy when it melts.Reading "Miyelin Ten Thousand Whys: Solid Water" has not only deepened my understanding of the science behind solid water but also sparked my curiosity about the world around me. It has made me appreciate the beauty andcomplexity of something as seemingly simple as ice. This book has reminded me of the saying "every cloud has asilver lining," as it highlights the hidden wonders thatcan be found in everyday phenomena.中文回答：《米伊林十万个为什么固体的水》是一本迷人的书籍，深入探讨了固体水（也称为冰）的许多奥秘和奇迹。
英文作文英国旅游景点推荐
英文作文英国旅游景点推荐1. Stonehenge。
If you're into ancient mysteries and awe-inspiring landscapes, Stonehenge is a must-visit. This iconic prehistoric monument in Wiltshire will leave you wondering about its purpose and the people who built it. The massive stone circles standing tall against the backdrop of the English countryside create a surreal atmosphere that is truly captivating.2. Buckingham Palace。
For a taste of British royalty, head to Buckingham Palace in the heart of London. Watching the Changing of the Guard ceremony is a sight to behold, with the impeccably dressed guards marching in perfect synchronization. You might even catch a glimpse of the Queen herself if you're lucky!3. The Lake District。
If you're a nature lover, the Lake District in northwest England is a paradise waiting to be explored. With its picturesque lakes, rolling hills, and charming villages, this region offers endless opportunities for hiking, boating, and simply immersing yourself in the tranquility of nature. Don't forget to pack your camera to capture the stunning landscapes!4. The Tower of London。
钛及钛合金阳极氧化着色工艺及其电源的研究
即阳极氯化膜凝有多孔性和强吸附性，封闭处理提高了篡抗污性、防护性、绝缘性和瓣磨程。
３，２瑰疆对铁合金鬻援氧纯遘罄薛影噙翳测钛合鑫ＴＣｌ０绒健羞爨瞧压与襞氆貘频篷鼹关系懿表３。
２：各瞧基下ＴＣＩＯ麓极氧化着色膜颜色图如图３．１：表３。
２ＴＣＩＯ麓位着色窀压与羲色貘颜色豹关系Ｔａｂ．３．２Ｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎａｎｏｄｅｖｏｌｔａｇｅａｎｄｌｈｅｃｏｌｏｒｏｆｏｘｉｄｉｚａｔｉｏｎｆｉｌｍ——＋。
‘４“～…氧化电压（Ｖ）１０２０３０４０５０６０７０８０９０１００１１０紫深淡红玫蓝黄淡灰氧化膜颜色蓝嬷蓝黄瑰紫绿缀绿罄彦彦氆省色红色聋彦岂謦３。
ｉ氧诧瞧压与氧纯簇羧色对照瀚Ｆｉｇ．３．１Ｃｏｒｒｅｓｐｏｎｄｉｎｇｐｉｃｔｕｒｅｏｆｏｘｉｄｉｚｉｎｇｖｏｌｔａｇｅｗｉｔｈｆｉｌｍｃｏｌｏｒ表３．３钛及钛合盒氧纯满色电艇精度与着色膜颜色色羞的关系Ｔａｂ．３．３Ｔｈｅｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｔｈｅｃｏｌｏｒｄｉｆｆｅｒｅｎｃｅｏｆｏｘｉｄｉｚａｔｉｏｎｆｉｌｍａｎｄａｎｏｄｅｖｏｌｔａｇｅｐｒｅｃｉｓｉｏｎ塑垦塑蓬！垒！照董堕ｌ３８：２５一－８４．．００～－２１９５．：７５３２５００７５５１８．４７一４．～２５．…１。
嘶粼ｉ：瓣‘：嬲；豫。
ｓ不同氧化电压精度下所得氧化膜色差数据如表３．３所示；从袭３．３可以看出，采用各种电压精度的电源进行阳极氧化所获得的氧化膜的颜色是有靛异的，图３．２列出了电压精度程０。
０７Ｖ，０。
０５Ｖ，０．０４Ｖ瓣瓣毪差效暴；淡３．３中，鞭投氧亿簇颜夔色差随电源电压精度的提高两下降，当氧化电压为３０±Ｏ．０５Ｖ时，氧化膜色差值为５．７ｌ。
（ａ）ｏ．０７Ｖ电压精度（ｂ）ｏ．０５Ｖ电源精度（ｃ）０．０４Ｖ电源精艘图３．２不同电源糟度阳极氧化膜色差效果图Ｆｉｇ．３，２Ｔｈｅｃｏｌｏｒｄｉｆｆｅｒｅｎｃｅｐｉｃｔｕｒｅｏｆａｎｏｄｅｆｉｌｍｏｘｉｄｉｚｅｄｂｙｄｉｆｆｅｒｅｎｔｖｏｌｔａｇｅｐｒｅｃｉｓｉｏｎ对照图３．２可以看出直观上，阳极氧化电压精度在０．０５Ｖ时，所得到的氧化膜颟色色簇爆肉眼已较难分辨。