Theoretical estimates for proton-NMR spin-lattice relaxation rates of heterometallic spin r

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Lhc——精选推荐

On LHC,Supersymmetry and Mathematics1One of the most exciting experiments of physics has just commenced at CERN.The Large Hadron Collider,LHC collides two beams of proton moving with almost the speed of light,with a center of mass energy eventually targeted to be10TeV,about5times higher energy than the highest energy currently reached at the colliders.By probing this region in energy we expect to be able to answer some of the most important questions that fundamental physics has tried to answer in the past forty years.A key missing ingredient in what is called the Standard Model of particle physics is a particle known as‘Higgs’which is predicted to exist based on electroweak symmetry breaking.Moreover all particles we know of are believed to receive their mass through their interactions with a condensate of the Higgsﬁeld.While the discovery of Higgs particle would be spectacular conﬁrmation of decades long anticipation of theoretical physicists,that may not end up being the most exciting ﬁnd of the LHC.Through astrophysical and cosmological observations we know that the matter making up the universe is made up mostly of unknown matter.Moreover,simple estimates of the energy range relevant for probing this‘dark matter’suggests that the LHC energy is roughly the right range for producing such matter.LHC may end up producing the dark matter and thus solving another puzzle of physics.The main theoretical question is what do we expect this extra matter to be?Over the past few decades,string theory, with deep links to mathematics,has emerged as a prime candidate for uniﬁcation of forces with gravity and for providing a consistent framework for a quantum theory of gravity.It is natrual to ask if string theory can make predictions for what this extra matter may be?One important symmetry of string theory at the shortest distance scale is Supersymmetry.This is a symmetry which relates bosons and fermions together.In other words,for each particle there would exist its supersymmetric partner,whose spin diﬀers by1/2,with otherwise exactly the same properties.We know that this cannot be the case at the larger length scales that we have performed experiments.For example there is no partner to electron (‘selectron’)which has the same mass and charge as the electron but that it has spin0. Thus supersymmetry,even if a true symmetry of nature at shortest distance scale,must be broken at longer distance scales.Supersymmetry has also played a key role in connecting1A version of this article appeared in CMI annual report20091modern physics with mathematics.In particular in the context of topologicalﬁeld theories initiated by Witten,the concept of supersymmetry is a key ingredient.These include a deeper understanding of Donaldson invariants for smooth4-manifolds,and a signiﬁcant impact on understanding of enumerative geometry.Thus supersymmetry is aesthetically and mathematically a very rich structure.Since we know that this symmetry is not realized at the lowest energy scales,the main question thefore for string theory would be to explore at what scale this symmetry is broken.If it is broken at a very short distance(high energy) scale,there would be no leftover imprint of it at the scale that LHC is doing its experiment. This is entirely possible,though unfortunate!However,there are good reasons to speculate that supersymmetry may play a role at the LHC.One such reason is that the uniﬁcation of forces works more naturally in this context.Another reason has to do with the‘hierarchy problem’which is why the mass of the Higgs particle is so low compared to the fundamental mass scale in physics, i.e.the Planck scale?Supersymmetry while it would not by itself explain why the scale is so diﬀerent,it would explain why it is natrual to have this small mass scale be stable against quantum corrections.This would be the case as long as supersymmetry breaking would happen at suﬃciently low energy scales.In fact,regardless of string theory,due to the above reasons,one of the most popular ideas pursued by particle theorists for models beyond the standard model has been its supersymmetric extension and its breaking at energies which leaves an imprint at the LHC energy scale.Even if one assumes that supersymmetry plays a key role at energy scales of LHC,to predict precisely what would be seen at LHC requires the knowledge of how supersymmetry is exactly broken.This involves the choice of parameters controlling this breaking which can be viewed as a choice of a point on a manifold of100+dimensions!One can make various assumptions,as particle physicists have done to narrow the region for search,but still typically the leftover region is too wide to be viewed as a deﬁnitive prediction.The one prediction that essentially all such models make is the existence of a stable dark matter which is the lightest of the supersymmetric particles.However we need to narrow down the choice of parameteres for the supersymmetry broken theory,in order to make more speciﬁc predictions for the LHC,which could thus conﬁrm/reject such theories.Atﬁrst sight string theory seems not to help too much in narrowing the search for how supersymmetry breaking may appear at low energy scales.However,with some mild assumptions(that the matter and gauge forces arise from tiny regions of internal compact-iﬁcation manifold)together with some colleagues(and in particular Jonathan Heckman)2we have made some surprisingly speciﬁc predictions.This involves the study of geometry of ellipticallyﬁbered Calabi-Yau4-folds and translating various singularity loci in terms of ing this picture we have come to the conclusion that if supersymmetry leaves an imprint on the LHC energy scale,the lighest supersymmetric particle is gravitino(super-symmetric partner of graviton)with a mass of a100times larger than that of the electron. This is too weakly interacting to observe directly.So what is important is what is the next lightest particle?In our models this particle turns out to be semi-stable(of a lifetime in the range of a second to an hour).There are two possibilities for what this next particle is:In most parameter ranges for us it turns out to be a charged particle(known as stau), which would leave a dramatic track once it leaves the LHC detectors.There is also the less likely possibility that it would be neutral(a particle known as bino)which has no direct impact on LHC but can be discovered by the missing energy using convervation of energy.Next few years may be among the most exciting times for physicists in search of fundamental laws of nature.The discovery of supersymmetry,if it happens,is not only the most exciting new discovery of a principle of physics,but it would nicely mirror the important role it has played in providing a bridge between physics and mathematics.We will have to wait a few years and see!3。

乙酸蒸汽催化重整制氢的研究进展

CHEMICAL INDUSTRY AND ENGINEERING PROGRESS 2017年第36卷第5期·1658·化工进展乙酸蒸汽催化重整制氢的研究进展王东旭1，肖显斌2，李文艳1（1华北电力大学能源动力与机械工程学院，北京 102206；2华北电力大学生物质发电成套设备国家工程实验室，北京 102206）摘要：通过生物油蒸汽重整制备氢气可以减少环境污染，降低对化石燃料的依赖，是一种极具潜力的制氢途径。

乙酸是生物油的主要成分之一，常作为模型化合物进行研究。

镍基催化剂是乙酸蒸汽重整过程中常用的催化剂，但容易因积炭失去活性，降低了制氢过程的经济性。

本文首先分析了影响乙酸蒸汽重整制氢过程的各种因素，阐述了在这一过程中镍基催化剂的积炭原理，讨论了优化镍基催化剂的方法，包括优化催化剂的预处理过程、添加助剂和选择合适的载体，最后对乙酸蒸汽重整制氢的热力学分析研究进展进行了总结。

未来应重点研究多种助剂复合使用时对镍基催化剂积炭与活性的影响，分析多种助剂的协同作用机理，得到一种高活性、高抗积炭能力的用于生物油蒸汽重整制氢的镍基催化剂。

关键词：生物油；乙酸；制氢；催化剂；热力学中图分类号：TK6 文献标志码：A 文章编号：1000–6613（2017）05–1658–08 DOI ：10.16085/j.issn.1000-6613.2017.05.014A review of literatures on catalytic steam reforming of acetic acid forhydrogen productionWANG Dongxu 1，XIAO Xianbin 2，LI Wenyan 1（1 School of Energy ，Power and Mechanical Engineering ，North China Electric Power University ，Beijing 102206，China ；2 National Engineering Laboratory for Biomass Power Generation Equipment ，North China Electric PowerUniversity ，Beijing 102206，China ）Abstract ：Hydrogen production via steam reforming of bio-oil ，a potential way to produce hydrogen ， can reduce environmental pollution and dependence on fossil fuels. Acetic acid is one of the main components of bio-oil and is often selected as a model compound. Nickel-based catalyst is widely used in the steam reforming of acetic acid ，but it deactivates fast due to the carbon deposition. In this paper ，the affecting factors for the steam reforming of acetic acid are analyzed. The coking mechanism of nickel-based catalyst in this process is illustrated. Optimization methods for nickel-baed catalyst are discussed ，including optimizing the pretreatment process ，adding promoters ，and choosing appropriate catalyst supports. Research progresses in the thermodynamics analyses for steaming reforming of acetic acid are summarized. Further studies should be focused on the effects of a combination of a variety of promoters on carbon deposition. Catalytic activity and the synergy mechanism should be analyzed to produce a novel nickel-based catalyst with high activity ，high resistance to caborn deposition for hydrogen production via steam reforming of bio-oil. Key words ：bio-oil ；acetic acid ；hydrogen production ；catalyst ；thermodynamics第一作者：王东旭（1994—），男，硕士研究生，从事生物质能利用技术研究。

OneNMR Probe 400-700 MHz 说明书

OneNMR Probe 400-700 MHz Technical OverviewIntroductionThe OneNMR probe represents a new class of NMR probes. This technology is the most signiﬁ cant advance in solution-state probe technology in over a decade. The OneNMR probe is not a reworked version of a broadband or indirect detection probe, but a new technology free of the performance trade-offs of those classic designs. It is see an entirely new design with performance beneﬁ ts unmatched by other probes.SensitivityThe OneNMR probe is simultaneously optimized for both high-andlow-band frequencies, and deliversthe performance advantages ofboth the classic carbon probe andthe highly sensitive proton probe ina single design. The signal/noise(S/N) speciﬁ cations for the family of 400-700 MHz OneNMR probes is shown in Table 1, with excellent sensitivity on both channels.It is understood that actual S/N performance will vary depending on how well your system is shimmed.The design and manufacturing of the OneNMR probe results in a very tight performance distribution so that all probes are very similar. The S/N results in Figure 2 were obtained using a typical 400 MHz OneNMR probe with an Agilent 400-MR magnet.The proton sensitivity data in Figure 1 is 20 % greater than the speciﬁ cation. These data illustrate one of the dangers of comparing probes on the basis of published speciﬁ cations alone. Probe speciﬁ cations for a given vendor (probe to probe) tend to be consistent, making direct within-vendor comparisons easy. However, direct comparisons between vendors are much more difﬁ cultowing to differences in methods and philosophy. When sensitivity is used as a basis for probe selection, your safest bet is a direct head-to-head comparison with the same sample (yours) and operator (you). Table 1. 400-700 MHz OneNMR Probe Sensitivity Speciﬁ cations.4005006007001H480:1730:1900:11150:10.1 % Ethybenzene Wilmad 545-pp13C225:1300:1380:1460:10.1 % Ethybenzene Wilmad 545-pp15N20:125:135:145:190 % Formamide Wilmad 535-pp31P90:1135:1170:1220:10.0485 M TPP Wilmad 535-pp19F550:1800:11050:10.05 % TFT Wilmad 535-pp Figure 1. 400 MHz OneNMR Probe High & Low Band Sensitivity (A) Proton S/N, (B) Fluorine S/N, (C) Carbon S/N.ACBThe OneNMR Probe lock sensitivityis also enhanced to provide a more stable lock and to support fast gradient shimming for increased ﬂ exibility (e.g.3 mm tubes) and greater ease-of-use.Sensitivity, while important, is just one aspect of probe performance and only part of the story. The sections which follow will introduce you to the advantages of the OneNMR probe that extend far beyond sensitivity alone.Pulse Performance and LineshapeThe 400-700 MHz OneNMR Probesprovide superior lineshape both spinning and non-spinning which means ease of shimming and well resolved spectra. The lineshape speciﬁ cations are shown in Figure 2, along with an example of the proton-decoupled 13C NMR spectrum of dioxane.The OneNMR probe’s modern design and efﬁ cient power handling leads to excellent pulse performance. The PW90 pulse widths for the 400-700 MHz OneNMR probes are listed in Table 2. These relatively short PW90’s are ideal for experiments requiring excitationor decoupling over a wide spectral window (e.g. 19F).600 MHz700 Mhz Sample1H7 µsec8 µsec9 µsec10 µsec 1 % 13C-Iodomethane 13C8 µsec10 µsec9 µsec10 µsec 1 % 13C-Iodomethane 15N14 µsec20 µsec18 µsec20 µsec90 % Formamide31P8 µsec15 µsec12 µsec15 µsec0.0485 M TPP19F8 µsec10 µsec10 µsec0.05 % TFTTable 2. 400-700 OneNMR Probes pulse performance.Figure 2. OneNMR Probe lineshape speciﬁ cations (left) and a spinning 13C dioxane example. 400-700 MHz OneNMR ProbeLineshape Speciﬁ cationsSpinning Non-spin13C1H1H50 %≤0.150.450.80.55 %≤ 1.5 5.07.00.11 %≤ 3.010.014.0Sidebands≤ 1 % 1 %13C LineshapeDecoupled Dioxane0.0850 %0.670.55 %1.400.11 %Figure 3. A comparison of spin projections (signal intensity along the z-axis of the coil) of a standard DB probe (Coil A, in red) and the OneNMR Probe (Coil B, in blue). The OneNMR Probe provides a more uniform signal than the standard DB probe.Figure 4. Relative performance of the OneNMR Probe compared to the standard DB probe. The results are given in units of time to complete the experiment.RF Hom o geneityThe OneNMR probe has excellent RF homogeneity on both channels while a dual broadband (DB) probe hasrelatively poor RF homogeneity. If you look at a spin projection comparing a standard dual broadband probe(Coil A) to the OneNMR Probe (Coil B), as shown in Figure 3, you can see that over the length of the sample, the amplitude of the signal with the OneNMR Probe is more uniform than for the standard dual broadband probe. What this means is that only the spins in the center of Coil A will be at maximum amplitude while nearly all the spins of Coil B will be at maximum amplitude. For a single pulse this difference may not be so important, but many experiments have several pulses in rapid succession. So if on the ﬁ rst pulse only 85 % of the spins line up, then on the second pulse only 85 % of 85 % line up, and so on until you very rapidly lose your signal. In contrast, with a more homogenous RF ﬁ eld, you lose less signal with each pulse and the summed signal from Coil B ends up being larger than Coil A. This is especially important when you consider that modern pulse sequences tend to incorporate more rather than fewer pulses.The standard way to look at this is by comparing the 1H 810 °/90 ° or the 13C 720 °/0 °, where the higher ratio of intensities indicates better RF homogeneity. An average 810 °/90 ° for an indirect detection probe is around 70 % whereas a standard DB probe will give you around 55 %. When we initially introduced the OneNMR Probe, both the 810 °/90 ° and the 720 °/0 ° were 78 %, and the current release is even better. Consequently, not only isCoil A = Coil B =the performance of the OneNMR Probe better than a standard DB probe in a 1D experiment, it is signiﬁ cantly better for 2D experiments as well.The advantages of good RFhomogeneity can be seen by comparing the OneNMR Probe to an indirect detection probe. The proton coil of the ID probe is closer to the sample and, as you would expect, this gives it a better signal-to-noise than the OneNMR Probe – 20 % better for a single 90 ° pulse. However the RF homogeneity (810 °/90 °) of the OneNMR probe is better than the indirect detection probe by about 9 %. This seemingly small difference in RF homogeneity has a big impact in 2D experiments with multiple pulses, such as the gHSQC-NOESY (Figure 4). The more homogenous RF ﬁ eld of the OneNMR probe compensates for the lower signal-to-noise ratio. This effect isFigure 5. OneNMR Probe advantage in 2D experiments. Three gHSQC-NOESY spectra are identically scaled using the AutoX DB Probe (left), the OneNMR Probe (middle), and the AutoX ID Probe(right). The superior RF homogeneity of the OneNMR probe compensates for the ID probe’s greater sensitivity (20 %) to yield comparable results.shown in Figure 5, where the OneNMR Probe (middle) performs almost as well as the indirect detection probe (right) in this 2D experiment. For comparison, the performance of a DB probe (left) is also shown.Superior DecouplingWhen you combine the efﬁ cient power handling, pulse performance, and RF homogeneity of the OneNMR probe, the result is outstanding decoupling performance. In real-world applications, like a 13C observe experiment, improved decoupling results in narrower lines (increased resolution) and increased sensitivity. The improved decoupling can be seen by comparing the line-widths of the OneNMR and Dual Broadband probes under identical conditions (see Figure 6).Superior decoupling leads directly to increased sensitivity. The 500 MHz 1D carbon spectra for vitamin B12 were measured under identical conditions using the ID, DB, and OneNMR probes. The results (Figure 7) show signiﬁ cant sensitivity enhancements for many peaks when using the OneNMRprobes. You would not have predicted this outcome on the basis of carbon sensitivity alone, since the Dual Broadband has a slight advantage. Once again we see that sensitivity, while important, isn’t the whole story. Because decoupling efﬁ ciency is suchan important factor in 13C performance, it is desirable to include it in any sensitivity testing. For this reason, we ﬁ nd 10 % ethylbenzene a superior (real-world) 13C sensitivity test since it is measured under proton-decoupled conditions. The ASTM standard, while important for its historical signiﬁ cance, was developed for use when decoupling efﬁ ciency was poor. Since modern NMR spectrometers exhibit excellent decoupling, the ASTM standard is no longer relevant.Figure 6. Decoupled Cholesteryl Acetate (28 ppm) resonance at 400 MHz, comparing the 20 % line-width of the (a) OneNMR Probe and (b) Dual Broadband Probe.Figure 7. Decoupled 500 MHz 1D Carbon spectra for vitamin B12 collected using an ID probe (top), DB probe (middle) and OneNMR probe (bottom).Water SuppressionThe OneNMR probe’s excellent sensitivity, pulse performance, and RF homogeneity make it an ideal probe for water suppression. The 400 MHz presaturation spectrum of 2 mMsucrose (90:10 H2O/D2O) shows a 65 Hzresidual water peak and an anomeric splitting of 85 % (Figure 8). The right-hand spectrum was acquired under automation using PURGE and 8 scans. These results show that the OneNMR probe has outstanding performance in water suppression.Salt ToleranceNMR samples interact electromagnetically with the RF coilsin the NMR probe. The magnitude of this interaction is proportional to the dielectric constant of the sample. When placed in the probe, samples with a high dielectric constant (e.g., ionic solutions) couple strongly to the RF coils, increasing the capacitance of the circuit and changing the tuning of the probe. Unless the probe is re-tuned for this new condition, the length of the90 ° pulse width can suffer dramatically. Conversely, a probe tuned appropriately for a high dielectric sample will not perform as well if the sample has a comparatively low dielectric constant (e.g., chloroform).The performance cost for runningthe NMR system in a poorly tuned state is signiﬁ cant for most standard probes, but this is not the case for the OneNMR Probe. The unique designof the OneNMR probe is very tolerant of dielectric differences, thereby eliminating the need for sampletuning for routine 1H and 13C studies. Figure 8. 2 mM sucrose (90:10 H2O/D2O) at 400 MHz: presaturation water suppression (A), anomeric splitting (B), and PURGE (C)water suppression, acquired under automation.Figure 9. Relative 13C probe performance for a chloroform sample when tuned to chloroform and200 mM salt for the (A) 500 MHz Dual Broadband Probe, and the (B) 500 MHz OneNMR Probe. Both signal-to-noise measurements were made using the pulse width and power levels calibrated for the accurately tuned sample.A Dual BroadbandPW90S/NTuned to chloroform10.75 µs 1.00Tuned to 200 mM salt15.00 µs0.59B OneNMRPW90S/NTuned to chloroform 6.95 µs 1.00Tuned to 200 mM salt7.55 µs0.94A B CThis feature allows high-quality datacollection on typical organic chemistrysamples without the cost in time, wearand tear, and complexity required toactively tune the probe for each sample.To demonstrate this effect, astandard 500 MHz, 5 mm DB probewas accurately tuned on an organicchemistry sample dissolved indeuterochloroform. Carbon spectrawere acquired to establish baselineperformance for the 90 ° pulse widthand sensitivity. An aqueous 200 mMNaCl sample was then inserted intothe probe and the system was tunedto this sample. Using this tune setting,the chloroform sample was returnedto the magnet, and the pulse widthand sensitivity data were once againcollected. The results (Figure 9) showthat a classic DB probe suffers asigniﬁ cant loss in sensitivity (39 %)and pulse performance under theseconditions. Repeating the experimentwith the OneNMR probe shows it tobe remarkably tolerant of these highsalt conditions retaining 94 % of itssensitivity with a much smaller impacton pulse width.Given the 13C performance resultspresented above and the excellent 1Hspeciﬁ cations of the OneNMR probe,one might anticipate that the protonchannel would suffer from this typeof intentionally mis-optimized tuneexperiment. This is not the case. Whenthe same worst-case set of tuningexperiments were repeated using thehigh frequency channel on the 500 MHzOneNMR probe, the performancechanges between the well-tunedprobe and the poorly tuned probe werenegligible. The proton 90 ° pulse widthincreased by 5.9 %, while the S/N ratiodecreased by only 5.3 %.The HSQC experiment is a cornerstone NMR experiment for organic chemistry. It is also one of the more challenging experiments with respect to the quality of the NMR pulses used to collectthe data. This makes it a perfect test experiment to demonstrate the ability of the OneNMR probe to yield high-quality data without the need for careful tuning adjustments.Figure 10 displays two gHSQC data sets obtained on a mixture of two alkaloids in deuterochloroform using the500 MHz OneNMR probe. These data show that running a demanding 2D experiment without tune optimization has little effect on sensitivity. In fact, comparison of the ﬁ rst increment of two adiabatic HSQC experiments with the probe tuned, versus detuned as described above, yielded a S/N change of less than 9 %.Solvent Tuning ToleranceThe ability of the OneNMR probe to accept a wide range of solvents with minimal change in probe tuning means that, for routine organic chemistry applications, the OneNMR probe can be used to collect high-quality data without adjusting the tuning circuit from sample-to-sample.The typical NMR solvents used in organic chemistry do not represent a large range of dielectric constants:benzene (ε0 2.27) is at the low end ofthe scale and water (ε0 80.1) is at thehigh end. Given this situation, one could easily tune the OneNMR probe to the middle of your working range and simply leave it there. The full range of organic NMR solvents would then be available for use without any need to retune the probe, while maintaining essentially all of the excellent performance of the OneNMR probe. This is especially useful for high throughput applications.Automatic Probe Tuning –ProTuneProTune is an advanced system forautomatic probe tuning and matchingwhich includes accessory hardware andsoftware components built into AgilentVnmrJ software.ProbeIDProbeID is a new feature which allowsthe console and software to recognizeand communicate directly with theprobe. Building this intelligence into theprobe allows you to work moreintuitively while the system does theheavy lifting. Beneﬁ ts of ProbeIDinclude ensuring that variousoperational parameters remain withinthe limits of the probe (such as RFpower and temperature). The softwarecan prevent the accidental selection ofincompatible probe ﬁ les, which canbe helpful in automation and multi-user environments.ProbeID allows the factory to storeprobe speciﬁ cations, calibrations, andprobe-test data directly on the probeitself. The probe will contain a copy ofthe factory and installation test data,tuning data, and probe ﬁ les should theyever be needed for reference or service.With ProbeID, probe-speciﬁ c dataalways remains with the probe.Figure 10. gHSQC data spectra acquired on a mixture of two alkaloids in deuterochloroform usingthe OneNMR probe. The data in the left panel were obtained with the RF coils carefully tuned to the sample. The data in the right panel were obtained on the same sample but with both the proton and carbon RF coils tuned on a sample of 200 mM NaCl in D2O. No attempt was made to compensatefor the mis-optimization of the RF pulses in the second experiment; the pulse widths, power levels, and parameterization used for each experiment were identical, and displayed at the same absolute contour level. The experiment time for each data set was less than 5 minutes.This information is subject to change without notice.© Agilent Technologies, Inc., 2012Printed in the USA, March 30, 20125990-7612ENLearn more/chem/nmr Find a local Agilent customer center /chem/contactusUSA and Canada 1-800-227-9770*****************************Europe************************Asia Paciﬁ c************************SummaryThe OneNMR probe represents an entirely new class of NMR probes, unlike the classic broadband or indirect detection probes available today. The OneNMR probe has excellent sensitivity on both channels, but this is just a small part of the performance capabilities. The probe exhibits excellent RF-homogeneity on bothchannels, excellent lineshape and pulse performance, superior decoupling, enhanced lock sensitivity, andunprecedented salt and solvent tuning tolerance. The performance beneﬁ ts of the OneNMR probe are unmatched by any other probe.。

C13-NMR

C CH H3C C C CH3 73.6 84.7 67.0 H3C CH2 CH2 CH2 CH C 67.4 82.8 29.9 17.4 12.9 21.2 HC C OCH 2CH3 H3C C C OCH 3 28.0 88.4 23.9 89.4 H3C CH2
13C NMR谱图
1.C7H14O
Saturated carbon - sp3 electronegativity effects
40 - 80
35 - 80 25 - 65
Unsaturated carbon - sp2
C C=C
C
Alkyne carbons - sp
65 - 90
100 - 150 110 - 175
Aromatic ring carbons C=O C=O 200
化学位移规律：烷烃
碳数n >4 端甲基 C=13-14
C>CH> CH2 >CH3
邻碳上取代基增多C 越大
取代烷烃:
H 3C 13.9
C H2 22.8
C H2 34.7
C H2
C H3
化学位移规律：烯烃
C C
C=100-150（成对出现）端碳=CH2 110；邻碳上取代基增多C越大：
香豆精反转门去偶与宽带去偶谱20015010050rch30range830155520604080358025656590100150110175155185185220saturatedcarbonsp3noelectronegativityeffectsrch2rr3chr4ccocclcbrsaturatedcarbonsp3electronegativityeffectsunsaturatedcarbonsp2ccccalkynecarbonssparomaticringcarbonscoco200acidsamidesestersanhydridesaldehydesketones150100500correlationchartfor13cchemicalshiftsppm应该熟记的c13nmr位移位移应该熟记的approximate13cchemicalshiftrangesforselectedtypesofcarbonppmrch3r2ch2r3chcicbrcclcnco830155520600402565358030654080cccccn6590100150110140110175oorcorrcohorcnh2oorchrcr1551851551851852201propanolhoch2ch2ch3cbaprotondecoupled200150100500protondecoupled13cspectrumof1propanol225mhz22dimethylbutane22bromocyclohexanecyclohexanoltoluenecyclohexenecyclohexanone12dichlorobenzene12baabcclccl13dichlorobenzene13accldbclsolventad影响化学位移因素杂化轨道电子短失正碳位移250330ppm孤电子对有未享用的孤电子对该碳向低场移约50ppm位移增加50ppm影响化学位移因素电负性共轭效应氢键会导致碳电子密度降低构型因素顺式一般在高场低位移弛豫13c的弛豫要比1h慢很多1h的t常在1011秒而13c常大于1s

Semi-empirical mass formula-液滴模型

A graphical representation of the semi-empirical binding energy formula. The binding energy per nucleon in MeV (highest numbers in dark red, in excess of 8.5 MeV per nucleon) is plotted for various nuclides as a function of Z , the atomic number (on the y-axis), vs. N ,the neutron number (on the x-axis). The highest numbers are seen for Z = 26 (iron).Semi-empirical mass formulaFrom Wikipedia, the free encyclopediaIn nuclear physics, the semi-empirical mass formula (SEMF ) (sometimes also called Weizsäcker's formula , or the Bethe-Weizsäcker formula , or the Bethe-Weizsäcker mass formula to distinguish it from the Bethe–Weizsäcker process) is used to approximate the mass and various other properties of an atomic nucleus. As the name suggests, it is based partly on theory and partly on empiricalmeasurements. The theory is based on the liquid drop model proposed by George Gamow, which can account for most of the terms in the formula and gives rough estimates for the values of thecoefficients. It was first formulated in 1935 by German physicist Carl Friedrich von Weizsäcker, and although refinements have been made to the coefficients over the years, the structure of the formula remains the same today.[1][2]The SEMF gives a good approximation for atomic masses and several other effects, but does not explain the appearance of magic numbers of protons and neutrons, and the extra binding-energy and measure of stability that are associated with these numbers of nucleons.Contents1 The liquid drop model andits analysis2 The formula3 Terms3.1 Volume term3.2 Surface term3.3 Coulomb term3.4 Asymmetry term3.5 Pairing term4 Calculating thecoefficients5 Examples for consequencesof the formula6 Notes7 References8 External linksThe liquid drop modeland its analysisThe liquid drop model in nuclearphysics treats the nucleus as a dropof incompressible nuclear fluid. Itwas first proposed by George Gamowand then developed by Niels Bohr andJohn Archibald Wheeler. The fluid is made of nucleons (protons and neutrons), which are held together by the strong nuclear force. This is a crude model that does not explain all the properties of the nucleus, but does explain the spherical shape of most nuclei. It also helps to predict the nuclear binding energy.Mathematical analysis of the theory delivers an equation which attempts to predict the binding energy of a nucleus in terms of the numbers of protons and neutrons it contains. This equation has five terms on its right hand side. These correspond to the cohesive binding of all the nucleons by the strong nuclear force, the electrostatic mutual repulsion of the protons, a surface energy term, an asymmetry term (derivable from the protons and neutrons occupying independent quantum momentum states) and a pairing term (partly derivable from the protons and neutrons occupying independent quantum spinstates).If we consider the sum of the following five types of energies, then the picture of a nucleus as a drop of incompressible liquid roughly accounts for the observed variation of binding energy of the nucleus:Volume energy. When an assembly of nucleons of the same size is packed together into the smallest volume, each interior nucleon has a certain number of other nucleons in contact with it. So, this nuclear energy is proportional to the volume.Surface energy. A nucleon at the surface of a nucleus interacts with fewer other nucleons than one in the interior of the nucleus and hence its binding energy is less. This surface energy term takes that into account and is therefore negative and is proportional to the surface area.Coulomb Energy. The electric repulsion between each pair of protons in a nucleus contributes toward decreasing its binding energy.Asymmetry energy (also called Pauli Energy). An energy associated with the Pauli exclusion principle. Were it not for the Coulomb energy, the most stable form of nuclear matter would have the same number of neutrons as protons, since unequal numbers of neutrons and protons imply filling higher energylevels for one type of particle, while leaving lower energy levels vacant for the other type.Pairing energy. An energy which is a correction term that arises from the tendency of proton pairs and neutron pairs to occur. An even number of particles is more stable than an odd number.The formulaIn the following formulae, let A be the total number of nucleons, Z the number of protons, and N the number of neutrons.The mass of an atomic nucleus is given bywhere and are the rest mass of a proton and a neutron, respectively, and is the bindingenergy of the nucleus. The semi-empirical mass formula states that the binding energy will take the following form:Each of the terms in this formula has a theoretical basis, as will be explained below.TermsVolume termThe term is known as the volume term. The volume of the nucleus is proportional to A, so this term is proportional to the volume, hence the name.The basis for this term is the strong nuclear force. The strong force affects both protons and neutrons, and as expected, this term is independent of Z. Because the number of pairs that can be takenfrom A particles is , one might expect a term proportional to . However, the strong forcehas a very limited range, and a given nucleon may only interact strongly with its nearest neighbors and next nearest neighbors. Therefore, the number of pairs of particles that actually interact is roughly proportional to A, giving the volume term its form.The coefficient is smaller than the binding energy of the nucleons to their neighbours , whichis of order of 40 MeV. This is because the larger the number of nucleons in the nucleus, the larger their kinetic energy is, due to the Pauli exclusion principle. If one treats the nucleus as a Fermiball of nucleons, with equal numbers of protons and neutrons, then the total kinetic energy is, with the Fermi energy which is estimated as 28 MeV. Thus the expected value of in this model is , not far from the measured value.Surface termThe term is known as the surface term. This term, also based on the strong force, is a correction to the volume term.The volume term suggests that each nucleon interacts with a constant number of nucleons, independent of A. While this is very nearly true for nucleons deep within the nucleus, those nucleons on the surface of the nucleus have fewer nearest neighbors, justifying this correction. This can also be thought of as a surface tension term, and indeed a similar mechanism creates surface tension in liquids.If the volume of the nucleus is proportional to A, then the radius should be proportional to and the surface area to . This explains why the surface term is proportional to . It can also be deduced that should have a similar order of magnitude as .Coulomb termThe term or is known as the Coulomb or electrostatic term.The basis for this term is the electrostatic repulsion between protons. To a very rough approximation, the nucleus can be considered a sphere of uniform charge density. The potential energy of such a charge distribution can be shown to bewhere Q is the total charge and R is the radius of the sphere. Identifying Q with , and noting as above that the radius is proportional to , we get close to the form of the Coulomb term. However, because electrostatic repulsion will only exist for more than one proton, becomes . Thevalue of can be approximately calculated using the equation above:Empirical nuclear radius:Quantum charge integers:Integration by substitution:Potential energy of charge distribution:Electrostatic Coulomb constant:The value of using the fine structure constant:where is the fine structure constant and is the radius of a nucleus, giving to be approximately 1.25 femtometers. is the proton Compton radius and the proton mass. This givesan approximate theoretical value of 0.691 MeV, not far from the measured value.Asymmetry termThe term or isknown as the asymmetry term. Note that as, the parenthesized expression can berewritten as . The form isused to keep the dependence on A explicit, as willbe important for a number of uses of the formula.The theoretical justification for this term ismore complex. The Pauli exclusion principle statesthat no two fermions can occupy exactly the samequantum state in an atom. At a given energy level,there are only finitely many quantum statesavailable for particles. What this means in thenucleus is that as more particles are "added",these particles must occupy higher energy levels,increasing the total energy of the nucleus (anddecreasing the binding energy). Note that thiseffect is not based on any of the fundamentalforces (gravitational, electromagnetic, etc.), only the Pauli exclusion principle.Protons and neutrons, being distinct types of particles, occupy different quantum states. One can think of two different "pools" of states, one for protons and one for neutrons. Now, for example, if there are significantly more neutrons than protons in a nucleus, some of the neutrons will be higher in energy than the available states in the proton pool. If we could move some particles from the neutron pool to the proton pool, in other words change some neutrons into protons, we would significantly decrease the energy. The imbalance between the number of protons and neutrons causes the energy to be higher than it needs to be, for a given number of nucleons. This is the basis for the asymmetry term. The actual form of the asymmetry term can again be derived by modelling the nucleus as a Fermi ball of protons and neutrons. Its total kinetic energy iswhere , are the numbers of protons and neutrons and , are their Fermi energies. Sincethe latter are proportional to and , respectively, one getsfor some constant C.The leading expansion in the difference is thenAt the zeroth order expansion the kinetic energy is just the Fermi energy multipliedby . Thus we getThe first term contributes to the volume term in the semi-empirical mass formula, and the second term is minus the asymmetry term (remember the kinetic energy contributes to the total binding energy with a negative sign).is 38 MeV, so calculating from the equation above, we get only half the measured value. The discrepancy is explained by our model not being accurate: nucleons in fact interact with each other, and are not spread evenly across the nucleus. For example, in the shell model, a proton and a neutron with overlapping wavefunctions will have a greater strong interaction between them and stronger binding energy. This makes it energetically favourable (i.e. having lower energy) for protons and neutrons to have the same quantum numbers (other than isospin), and thus increase the energy cost of asymmetry between them.One can also understand the asymmetry term intuitively, as follows. It should be dependent on the absolute difference , and the form is simple and differentiable, which is important for certain applications of the formula. In addition, small differences between Z and N do not have a high energy cost. The A in the denominator reflects the fact that a given difference is lesssignificant for larger values of A.Pairing termThe term is known as the pairing term (possibly also known as the pairwise interaction). This term captures the effect of spin-coupling. It is given by:[3]whereDue to Pauli exclusion principle the nucleus would have a lower energy if the number of protons with spin up were equal to the number of protons with spin down. This is also true for neutrons. Only if both Z and N are even can both protons and neutrons have equal numbers of spin up and spin down particles. This is a similar effect to the asymmetry term.The factor is not easily explained theoretically. The Fermi ball calculation we have used above, based on the liquid drop model but neglecting interactions, will give an dependence, as in the asymmetry term. This means that the actual effect for large nuclei will be larger than expected by that model. This should be explained by the interactions between nucleons; For example, in the shell model, two protons with the same quantum numbers (other than spin) will have completely overlapping wavefunctions and will thus have greater strong interaction between them and stronger binding energy. This makes it energetically favourable (i.e. having lower energy) for protons to pair in pairs of opposite spin. The same is true for neutrons.Calculating the coefficientsThe coefficients are calculated by fitting to experimentally measured masses of nuclei. Their values can vary depending on how they are fitted to the data. Several examples are as shown below, with units of megaelectronvolts.Least-squares fit Wapstra[4]Rohlf[5]15.814.115.7518.31317.80.7140.5950.71123.21923.712n/a n/a(even-even)n/a-33.5+11.18(odd-odd)n/a+33.5-11.18(even-odd)n/a00The semi-empirical mass formula provides a good fit to heavier nuclei, and a poor fit to very light nuclei, especially 4He. This is because the formula does not consider the internal shell structure of the nucleus. For light nuclei, it is usually better to use a model that takes this structure into account.Examples for consequences of the formulaBy maximizing B(A,Z) with respect to Z, we find the number of protons Z of the stable nucleus of atomic weight A.[citation needed] We getThis is roughly A/2 for light nuclei, but for heavy nuclei there is an even better agreement with nature.By substituting the above value of Z back into B one obtains the binding energy as a function of the atomic weight, B(A). Maximizing B(A)/A with respect to A gives the nucleus which is most strongly bound, i.e. most stable. The value we get is A = 63 (copper), close to the measured values of A = 62 (nickel) and A = 58 (iron).Notes1. ^ von Weizsäcker, C. F. (1935). "Zur Theorie der Kernmassen". Zeitschrift für Physik (in German) 96 (7–8):431–458. Bibcode:1935ZPhy...96..431W (/abs/1935ZPhy...96..431W).doi:10.1007/BF01337700 (/10.1007%2FBF01337700).2. ^ Bailey, D. "Semi-empirical Nuclear Mass Formula"(http://www.upscale.utoronto.ca/GeneralInterest/DBailey/SubAtomic/Lectures/LectF25/Lect25.htm). PHY357: Strings & Binding Energy. University of Toronto. Retrieved 2011-03-31.3. ^ Krane, K. (1988). Introductory Nuclear Physics. John Wiley & Sons. p. 68. ISBN 0-471-85914-1.4. ^ Wapstra, A. H. (1958). "Atomic Masses of Nuclides". External Properties of Atomic Nuclei. Springer. pp. 1–37. doi:10.1007/978-3-642-45901-6_1 (/10.1007%2F978-3-642-45901-6_1). ISBN 978-3-642-45902-3.5. ^ Rohlf, J. W. (1994). Modern Physics from α to Z0. John Wiley & Sons. ISBN 978-0471572701.ReferencesFreedman, R.; Young, H. (2004). Sears and Zemanskey's University Physics with Modern Physics (11th ed.). pp. 1633–1634. ISBN 0-8053-8768-4.Liverhant, S. E. (1960). Elementary Introduction to Nuclear Reactor Physics. John Wiley & Sons.p. 58-62. LCCN 60011725 (/60011725).Choppin, G.; Liljenzin, J.-O.; Rydberg, J. (2002). "Nuclear Mass and Stability"(http://jol.liljenzin.se/KAPITEL/CH03NY3.PDF). Radiochemistry and Nuclear Chemistry(http://jol.liljenzin.se/BOOK-3.HTM) (3rd ed.). Butterworth-Heinemann. pp. 41–57. ISBN 978-0-7506-7463-8.External linksNuclear liquid drop model (/hbase/nuclear/liqdrop.html)The semi-empirical mass formula (http://www.phy.uct.ac.za/courses/phy300w/np/ch1/node22.html) Liquid drop model (/hbase/nuclear/liqdrop.html) in thehyperphysics (/HBASE/hframe.html) online reference at Georgia State University.Liquid drop model with parameter fit(http://www.phys.jyu.fi/research/gamma/publications/akthesis/node4.html) from First Observations of Excited States in the Neutron Deficient Nuclei 160,161W and 159Ta, Alex Keenan, PhD thesis, University of Liverpool, 1999 (HTML version(http://www.phys.jyu.fi/research/gamma/publications/akthesis/thesis.html)).Retrieved from "/w/index.php?title=Semi-empirical_mass_formula&oldid=595734949" Categories: Nuclear physics Nuclear chemistry Subatomic particles Radiochemistry Mass This page was last modified on 16 February 2014 at 14:54.Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy.Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.。

Agilent The OneNMR Probe for Metabolomics 说明书

Advantage Statement: Collecting high-qualitymetabolomics data requires good probe performance in a wide variety of areas. Historically, no single probe design could deliver all the necessary specificationssimultaneously, leading to significant compromise on some facet of the experimental results.By combining excellent lineshape performance, superior B1 field homogeneity, and outstanding salt tolerance into a single NMR probehead, the revolutionary Varian OneNMR™ Probe is better suited to the demanding task of metabolomic analysis than any conventional probe design.Solvent SuppressionFor many years, presaturation has been the default solvent suppression technique used by most spectroscopists. While there are many published techniques that can outperform presaturation in efficiency, selectivity, etc., the simplicity and robustness of presaturation typically makes it the method of choice. With the introduction of the OneNMR Probe, however, Varian opens the way for routine use of a recently published solvent suppression technique known as ”Presaturation Utilizing Relaxation Gradients,” or PURGE.1As shown in Figure 1, the PURGE technique involves hard rotations interspersed with short periods of gentle presaturation excitation (i.e., ~8-12 Hz decoupling fields) and gradient pulses. The result is very efficient and robust solvent suppression, excellent frequency selectivity, and no baseline perturbations outside of the suppression window. Importantly, this pulse sequence element is equally as trivial to implement as standard presaturation, with the only requirement being calibration of the 90° pulse width.In practice, using the PURGE sequence with the OneNMR Probe delivers very high quality solvent suppression, as can be seen in Figures 2 and 3.Figure 1. The PURGE solvent suppression method as implemented in a 1D proton NMR pulse sequence.Figure 2. The PURGE solvent suppression method as applied on a 2 mM sucrose standard sample in 90% H 2O/10% D 2O.Solvent suppression without a narrow suppression band leads to attenuation of those signals with resonance frequencies near the solvent peak. As compared to a simple presaturation experiment, PURGE delivers suppression with a high degree of frequency specificity due to the lower irradiation power required for efficient performance (See Figure 4).1Figure 3. The PURGE solvent suppression method as applied to a sampleof white wine in 90% H2O/10% D2O with phosphate buffer.Figure 4. Comparison of the suppression window afforded using presaturation (52 Hz field, bottom) and PURGE (11 Hz field, top). The nominal suppression window observed for the PURGE method would allow accurate integration of resonances with no more than a 125 Hz offset from the saturation frequency.The only drawback to the routine use of PURGE solvent suppression lies in the fact that a full 720° of spin rotation is applied to all spins in the sample prior to the beginning of the excitation pulse. Inhomogeneity in the B1field during rotation engenders loss in signal intensity. As shown in Figure 5, the OneNMR Probe has superiorB1field homogeneity retaining 78% of the initial signal intensity after 810° of spin rotation. Hence, PURGE solvent suppression remains a viable solvent suppression technique in the OneNMR Probe.Figure 5. Proton Spin Nutation Experiment for the OneNMR Probe. Thisdata set demonstrates the excellent B1 field homogeneity observedfor the OneNMR Probe. The signal observed after 810° of spin rotation retains 78% of the intensity observed for a 90° pulse. Deuterium SensitivitySpectroscopists often don’t consider the sensitivity of the lock coil when choosing a probe, but this simple performance criterion can be critical in metabolomics applications. The OneNMR Probe delivers outstanding performance on the deuterium channel (see Figure 6). Figure 6. Deuterium signal-to-noise measurement for the OneNMRProbe as measured on CDCl3. At a value of greater than 7200-to-1, this spectrum demonstrates performance that is more than double that typically seen for a standard inverse detection probe.In those situations where minimum dilution of ananalyte with D2O is desirable, the OneNMR Probe allows automated locking and shimming with confidence onsamples containing as little as 2% D2O (see Figure 7).SI-1849 11/08 Printed in U.S.A.Chromatography • Spectroscopy • Mass Spectrometry • Magnetic Resonance Spectroscopy and Imaging • X-Ray Crystallography • Dissolution • Consumables • Data Systems • VacuumVarian and the Varian logo are trademarks or registered trademarks of Varian, Inc. in the U.S. and other countries.© 2008 Varian, Inc.Varian, Inc.North America: 800.926.3000, 925.939.2400 Europe The Netherlands: 31.118.67.1000 Asia Pacific Australia: 613.9560.7133 Latin America Brazil: 55.11.3238.0400Other sales offices and dealers throughout the world _ check our Web site.Figure 7. Proton Spectrum of urine collected using the OneNMR™ Probe. This sample contained only 2% D 2O, yet completely automated locking and shimming operations executed flawlessly.Salt ToleranceBiological NMR samples are commonly prepared in buffer solutions for data collection and biological fluids are often intrinsically of high ionic strength. A highly dielectric sample strongly couples to the receiver coil, therebylowering the “Quality Factor” of the system and adversely impacting the sensitivity of the probe.The classic indirect detection (ID) probe is currently the ‘standard’ probe configuration used for most metabolomics work. When compared with the OneNMR Probe, however, the performance of the ID probe suffers proportionally as the concentration of salt in the sample increases. (SeeTable 1.)OneNMR ProbeInverse Detection Probe91.2%78.5%Table 1. Relative signal-to-noise retention for 2 mM sucrose in 250 mM NaCl solution as compared to a salt-free reference sample.The unique design of the OneNMR Probe minimizes the effect of “lossy” samples and allows high quality spectra to be obtained with a minimum of instrument time (see Figure 8).Figure 8. HSQC Spectrum of 2 mM sucrose in 90% H 2O/10% D 2O containing 300 mM sodium chloride. These data were collected in 72 minutes of acquisition time.ConclusionsThe OneNMR Probe was intended to provide thehighest level of performance for metabolomic analysis. The outstanding lineshape and B 1 field homogeneity combine to afford world-class solvent suppression. The excellent sensitivity of the deuterium channel allows the preparation of biological samples with an absolute minimum of dilution with D 2O. Finally, the salt tolerant design yields the best sensitivity available in a warm probe for biological fluid analysis.These features make the OneNMR probe a superior tool for metabolomics research.1PURGE: Presaturation Utilizing Relaxation Gradients Simpson and Brown, J. Magn. Reson., 175 (2005),pp. 340-346。

专业英语--天然药化方面

紫外-可见（UV-VIS）吸收光谱electromagnetic spectrum 电磁谱spectrum 光谱,波谱,谱spectra(复数)spectral 光谱的spectroscopy 光谱学,光谱研究spectroscopic 分光镜的spectroscope分光器，分光镜Infrared 红外visible light 可见光Wave numbers 波数proportional to energy 能量成正比Red light 红外线low-energy end 低能量的末端violet light 紫射线high-energy end 高能量的末端nanometers (nm) 纳米deci(分) centi(厘) milli(毫) micro(微) nano(纳)ultraviolet (UV) spectrum 紫外谱conjugated diene 共轭二烯absorption maxima 最大吸收峰UV spectra 紫外光谱absorption peak 吸收峰Wavelength 波长absorbance A 吸收值Aconcentration in solution 溶液的浓度path length 厚度molar absorptivity 摩尔吸收系数literature reference 参考文献literature citation 参考文献structural information 结构信息红外光谱nmr spectroscopy：核磁共振光谱nuclear magnetic resonance spectroscopy infrared (ir) spectroscopy：红外光谱structure determination：结构鉴定organic compounds：有机化合物unknown compound：未知化合物spectroscopic methods：光谱（仪器）方法functional groups：官能团molecule：分子molecular:分子的molecular weight（M.W.) 分子量Infrared radiation：红外辐射electromagnetic spectrum: 电磁波Microwaves：微波wave number：波数micrometer(μm)：微米reciprocal centimeters (cm-1)：厘high-energy end：高能量端low-energy end：低能量端electromagnetic radiation：电磁波辐射vibrational energy states：振动能级状态photon：光子lowest vibrational state ：最低的振动能级状态ground vibrational state：基态stretching modes：伸缩振动bending modes：弯曲振动methylene ：亚甲基fingerprints：指纹，指印snowflakes：雪花superposability：相似性，重合superposable：可重合的, 可叠合的，可置于上面的hexane:己烷absorption peaks：吸收峰carbon-hydrogen stretching vibrations：碳-氢伸缩振动bending vibrations：弯曲振动physical state：物理状态solid，liquid，gas：固、液、气neat sample：纯样品sodium chloride：氯化钠disk：片,圆板,圆盘,圆盘状物thin film：薄膜carbon tetrachloride：四氯化碳chloroform：氯仿potassium bromide：溴化钾thin wafer：薄片structure determination : 结构鉴定vibrations characteristic: 振动特征functional groups：官能团fingerprint region：指纹区pattern of peaks：峰形frequencies：频率wave numbers：波数organic compounds：有机化合物质谱MASS SPECTROMETRYMass spectrometry: 质谱spectrometry n. [物]光谱测定法,度谱术spectrometric adj. [物]光谱测定的,分光光谱仪的spectrometer n. [物]分光计molecule：分子bombarded ：轰击high-energy electrons ：高能量电子electron-volts：电子伏特collides with ：碰撞molecule : 分子electron ：电子cation radical ：正离子ionize : vt. 使离子化，vi. 电离ionization : n. 离子化, 电离electron impact ：电子轰击molecular ion ：分子离子fragment ion :碎片离子positively charged ：带正电荷odd number of electrons ：奇数电子，不成对电子odd : 奇数even：偶数mass ：n. 质量, 块, 大多数, 大量molecular ion : 分子离子dissociating ：裂解，分离，游离fragments ：n. 碎片, 断片, 片段fragmental adj. 破片的, 断片的fragmentation n. 分裂, 破碎cation radical ：正离子neutral fragment ：中性碎片positively charged one ：正离子，带正电荷fragmentations：断裂，分裂, 破碎Ionization and fragmentation：电离和裂解particle：粒子electron-impact mass spectrometer：电子轰击质谱分光仪bombarded with ：轰击molecular ion: 分子离子fragment ions：碎片离子analyzer tube：分析器magnet ：n. 磁体, 磁铁, 磁场magnetic : adj. 磁的,有磁性的,有吸引力的magnetically : adv. 有磁力地, 有魅力地deflects：v. (使)偏斜, (使)偏转deflect from : 使...从...偏斜, 使...从...转变方向deflected :偏离的original trajectory : 起始轨道original adj. 最初的, 原始的, 独创的, 新颖的n. 原物, 原作trajectory：n. [物](射线的) 轨道, 弹道, 轨线circular path ：环形轨迹radius：n. 半径, 范围, 辐射光线, 有效航程,mass/charge ratio (m/z)：质量/电荷比，质/荷比magnetic field strength ：磁场强度analyzer：分析仪，分析器narrow slit ：狭缝detector：检测器scan：扫描positive ions : 正离子mass spectrum：质谱图computerized data handling systems：计算机数据处理系统bar graphs ：棒状图bar : n. 条, 棒, 横木, 酒吧间, 栅, 障碍物vt. 禁止, 阻挡, 妨碍, 把门关住, 除...之外graph : n. 图表, 曲线图relative intensity：相对丰度benzene：苯PROTON NUCLEAR MAGNETIC RESONANCE (1H-NMR) HOW CHEMICAL SHIFT IS MEASUREDshielding : 屏蔽proton : n. [核]质子chemical shifts：化学位移standard substance：标准物质tetramethylsilane (CH3)4Si ，TMS) ：四甲基硅烷coincides with：与...一致, 与...相符frequency：频率hertz：n. 赫, 赫兹(频率单位：周/秒); (Hz)赫兹downfield：低场magnetic field strength：磁场强度60-MHz: 60 兆周nmr spectrum: 核磁共振光谱chloroform (CHCl3)：氯仿signal due to the proton：氢信号downfield from：比…低场chemical shifts (δ)：化学位移parts per million (ppm)：百万分之几chemical shift for the proton：氢化学位移Nuclear magnetic resonance spectra：核磁共振光谱nuclear magnetic resonance：核磁共振nuclear magnetic resonance spectroscopy：核磁共振(光谱)分析parts per million (ppm)：百万分之几zero point：零点field strength：场强度nmr spectrometer：核磁共振仪nuclear spin：核自旋nuclear adj. [核]核子的, 原子能的, 核的, 中心的nuclear resonance：核共振irrespective of：adj. 不顾的, 不考虑的, 无关的magnetic field strength：磁场强度signal due to the proton：氢信号carbon：碳hydrogen：氢oxygen：氧nitrogen: 氮PATTERNS OF SPIN-SPIN SPLITTING. THE ETHYL GROUPsplitting : 裂分nmr spectra：核磁共振谱structure determination ：结构鉴定ethyl group：乙基nmr spectrum：核磁共振光谱ethyl bromide：溴乙烷ethyl：n. [化]乙基, 乙烷基bromide ：n. [化]溴化物bromide chloride ：一氯化溴electronegative atom or group : 电负性的原子或基团electronegative：adj. 负电的, 带负电bromine：溴ethyl bromide ：溴乙烷triplet-quartet pattern ：三重-四重峰系统triplet ：n. 三重峰, 三个一组, 三份quartet: n. 四重峰, 四重奏, 四重唱methylene：亚甲基methyl：甲基coupling with ：与…偶合coupling : n. 联结, 接合, 耦合vicinal coupling：邻位偶合adjacent：adj. 邻近的, 接近的Multiplet: 多重峰Singlet : 单峰Doublet ：双峰Triplet ：三重峰Quartet ：四重峰Pentet ：五重峰Hextet ：六重峰Heptet ：七重峰CARBON-13 NUCLEAR MAGNETIC RESONANCE.――THE SENSITIVITY PROBLEMcarbon n. [化]碳(元素符号C), (一张)复写纸carbon paper复写纸Magnetic resonance spectroscopy 核磁共振谱Nuclei n. [nucleus的复数] 核心、中心、细胞核nuclear [核]核子的, 原子能的, 核的, 中心的isotope n. [化]同位素isotopic adj. 同位素的nuclear spins ：核自旋skeleton n. 骨架, 骨骼, 基干, 纲要, 万能钥匙substituent n. 取代adj. 取代的substitute n. 代用品, 代替者, 替代品v. 代替, 替换, 替代substitute A for B 用A替Bsubstituted 取代的, 代替的substituted aromatic 取代的芳香化合物substituted benzene 取代苯苯的同系物structure determination 结构鉴定isotopic form of carbon 碳的同位素nuclear spin 核自旋sensitivity 灵敏度nmr spectrometer 核磁共振仪Tune vt. 调音, 调整, 拨收, 收听n. 曲调, 调子, 和谐, 合调13C magnetic resonance 13C核磁共振background noise 背景噪音13C nmr (cmr) spectroscopy 13C核磁共振光谱routine technique 常规技术organic structure determination 有机结构鉴定nmr spectrometers 核磁共振仪sensitivity-enhancing 提高灵敏度strategy n. 策略, 军略, 计划random n. 随意, 任意adj. 任意的, 随便的, 胡乱的regardless of 不管, 不顾Scanned v. 扫描, 细看,审视,浏览n. 扫描signal-to-noise ratio 信噪比值solution to n. 解答, 解决办法, 溶解, 溶液from low field to high field 从低场到高场pulse n. 脉搏, 脉冲radiofrequency 射频higher spin state 高能级自旋态excited nuclei 被激发的核relax to their lower energy state 弛豫到低能级态Fourier Transform 傅立叶变换/转换(FT) nmr spectrometers 傅立叶变换核磁共振仪FT nmr 傅立叶变换核磁共振13C nmr 13C核磁共振SUMMARY1H Nuclear magnetic resonance spectroscopy 氢核磁共振光谱external magnetic field 外界磁场nuclear spin 核自旋proton质子flip vt. 掷, 弹, 轻击,抽打, vi. 用指轻弹, 抽打nucleus核shielded屏蔽molecule 分子chemical shifts 化学位移1H nmr spectrum 氢核磁共振波谱chemical shift nonequivalent protons 化学位移不等价质子integrated areas 积分面积splitting pattern 裂分图形adjacent 邻近的, 接近的13C Nuclear magnetic resonance spectroscopy碳核磁共振光谱signal enhancement 提高信号强度13C nmr spectra 碳核磁共振光谱carbon signals 碳信号singlets 单峰off-resonance decoupling 偏共振去偶multiplets 多重峰bonded hydrogens 键合的氢Infrared spectroscopy 红外光谱molecular structure 分子结构transitions 跃迁vibrational energy levels 振动能级electromagnetic radiation 电磁波辐射functional groups 官能团absorption 吸收frequencies 频率Ultraviolet-visible spectroscopy紫外-可见吸收光谱Transitions 跃迁electronic energy levels电子能级uv-vis spectroscopy 紫外-可见吸收光谱absorption peaks 吸收峰conjugated π-electron systems共轭π-电子系统Mass spectrometry 质谱ionized 电离，使离子化electron impact 电子轰击dissociates 裂解, 分裂fragments 碎片Positive ions正离子mass/charge ratio 质荷比deduce 推论, 推断，演绎出chromatographic 结晶，晶体reacted 起反应phenolic 酚的hydroxyl 羟基acridone 吖啶酮skeleton 骨架chelated 螯合的hydroxyl 羟基protons 质子resonances 共振aromatic 芬芳的substituted 取代的，代替的pyran ring 吡喃环carbonyl 羰基cross-peaks 相关峰Angular 角的acridone吖啶酮aromatic 芬芳的dihydro 两氢的chelated 螯合的hydroxyl signal 羟基信号correlations 相关性dihydro 二氢的Wavenumbers are directly proportional to energy,so visible light is approximately 10 times more energetic than infrared radiation. Red light is the low-energy end of the visible region, violet light the high-energy end.There are no additional absorption maxima beyond 280nm. So that portion of the spectrum has been omitted. As is typical of most UV spectra, the absorption peak is rather broad. The wavelength at which absorption is a maximum is referred to as the λmax of the sample.The absorbance A of a sample is proportional to its concentration in solution and the path length through which the beam of ultraviolet radiation passes.Prior to the introduction of nmr spectroscopy, infrared (ir) spectroscopy was the instrumental method most often applied to structure determination of organic compounds. While nmr spectroscopy is，in general, more revealing of the structure of an unknown compound，IR still retains an important place in the chemist’s inventory of spectroscopic methods be cause of its usefulness in identifying the presence of certain functional groups within a molecule.Infrared radiation comprises the portion of the electromagnetic spectrum (Figure 14.1) in which the wavelengths range from approximately 10-4 to 10-6 m.Absorption of a photon of infrared radiation excites a molecule from its lowest, or ground, vibrational state to a higher one.These vibrations include stretching and bending modes of the type illustrated for a methylene group in Figure 14.24.The peaks at 1460, 1380 and 725 cm-1 are due to various bending vibrations.It does not depend on the selective absorption of particular frequencies of electromagnetic radiation but rather examines what happens to a molecule，when it is bombarded with high-energy electrons.Electrons this energetic not only bring about the ionization of a molecule but impart a large amount of energy to the molecular ion. The molecular ion dissipates this excess energy by dissociating into smaller fragments.The sample is bombarded with 70eV electrons and the resulting positively charged ions (the molecular ion as well as fragment ions) are directed into an analyzer tube surrounded by a magnet.The protons of TMS are more shielded than those of almost all organic compounds. In a solution containing TMS. All the relevant signals appear to the left of the TMS peak.Peak positions are measured in frequency units (hertz) downfield from the TMS peak.Nuclear magnetic resonance spectra are recorded on chart paper that is calibrated in both parts per million (ppm) and hertz. And both are referred to the TMS peak as the zero point. When reporting chemical shifts in frequency units (hertz) the field strength of the instrument must be specified. A 60-MHz nmr spectrometer separates the energy of nuclear spin states only 60 percent as much as does a 100-MHz spectrometer.It tells us how many protons are vicinal to a proton responsible for a particular signal.The peaks are too weak to be detected and are lost in the background noise. This hampered the development of 13C nmr (cmr) spectroscopy as a routine techniquefor organic structure determination until a new generation of nmr spectrometers incorporating special sensitivity-enhancing features became available in the 1970s.The strategy behind sensitivity enhancement is based on the fact that background noise is random but the signals of a particular sample, even though they may be weak, always appear at the same chemical shift regardless of how many times the spectrum is scanned.In the HMBC spectrum (Fig. 1), the proton at δ5.29 showed cross-peaks with carbon signals at C-12a (δ141.5), C-12b (δ96.7), and C-4a (δ158.8). This finding clearly indicatedcommon-used Chinese materia medica常用中药材品种整理和质量研究traditional Chinese patent medicines and preparations 中成药和中药制剂益胃生津，滋阴清热benefit the stomach, promote the production of body fluid and remove the excessive heat①Strengthen the study of medicinal plant resources 加强药用植物基源研究cyclohexane-chloroform-ethyl acetate-formic acid 环己烷氯仿乙酸乙酯甲酸ursolic acid 熊果酸nmr spectroscopy（nuclear magnetic resonance spectroscopy）：核磁共振光谱conservation of germplasm of the rare and endangered medicinal plants 珍稀濒危药用植物的种质资源保护②Carry out the researches on specific biology of medicinal plantsspecific adj. 种的，明确的，特殊的，具有特效的n. 特效药，详情，特性③Map out GAP (Good Agriculturing Practice) in medicinal cultivationmap out 规划seed quality standards 种子的质量标准processing rules and regulations 加工方法及规范④Established standards of quality control and renew methodologycriteria 标准protocol 草案foreign matter杂质⑤Apply modern comprehensive multidisciplinary studies on Chinese medicinal plantscomprehensive：综合的，广泛的multidisciplinary：多学科⑥Establish information systems in modern research of Chinese medicinal herbsEthnobotany 人类植物学Ethnopharmacology民族药理学Ethno- 民族，种族semi-colonial and semi-feudal nation/半殖民半封建的国家constraint and devastation/ 压迫与毁坏the inheritance and development of Chinese troditional medicine ……/继承和发扬many difficult and complicated diseases 疑难杂症Strengthening basic researches on Chinese Medicinal Plants and its relations to realizing物基础研究及其与中药现代化的关系Traditional Chinese Medicine (TCM) 中药养心安神：clear heart-fire and remove restlessnessRhizomes short and stout, sometimes with remains of a stem at the apex.根状茎短,粗壮,有时是一杆的顶端。

基于蒙特卡罗的脑血氧检测光源—探测器最优距离研究

第 22卷第 12期2023年 12月Vol.22 No.12Dec.2023软件导刊Software Guide基于蒙特卡罗的脑血氧检测光源—探测器最优距离研究曹焱1，邢志明1，赵斌1，董祥美1，史以珏2，高秀敏1（1.上海理工大学光电信息与计算机工程学院，上海 200093；2.上海交通大学医学院附属瑞金医院，上海 200025）摘要：为提高近红外光谱技术的脑血氧检测装置测量精度，需要选择最优的光源—探测器（SD）距离。

传统的脑血氧检测装置，其传感器探头部分的SD距离是固定的，且在选择SD距离时没有经过研究，多根据经验进行选择，因而会造成实际使用中测量结果的不准确。

根据光在头部组织中的传输特性，选定一组颅脑组织的特性参数，利用蒙特卡罗方法对5层颅脑组织模型进行仿真，研究光在头部组织中的传输特性，根据光子传输路径分析光子在组织中传输的最大可达深度和散射传输距离。

通过分析有效深度比（EDR）和灰质层信息比（GMLIR），选择出适合此组选定颅脑参数的一组最优距离SD=1cm和SD=3.5cm。

与传统检测装置相比，通过优化光源—探测器之间的距离，为脑血氧检测装置的传感器设计及装置测量精度优化提供了一个新思路。

关键词：脑血氧检测；光源—探测器距离；传感器；蒙特卡罗方法；组织模型DOI：10.11907/rjdk.222496开放科学（资源服务）标识码（OSID）：中图分类号：TH776；R318 文献标识码：A文章编号：1672-7800（2023）012-0117-07Study on the Optimal Distance of Light Source-Detector for CerebralBlood Oxygen Detection Based on Monte CarloCAO Yan1， XING Zhiming1， ZHAO Bin1， DONG Xiangmei1， SHI Yijue2， GAO Xiumin1（1.School of Optical-electrical and Computer Engineering， University of Shanghai for Science and Technology， Shanghai 200093，China；2.Ruijin Hospital， Shanghai Jiaotong University School of Medicine， Shanghai 200025，China）Abstract：To improve the measurement accuracy of cerebral oximetry devices using near-infrared spectroscopy， it is necessary to select the optimal source-detector （SD） distance. Conventional cerebral oximetry devices with a fixed SD distance for the sensor probe part are mostly se‐lected based on experience and without specific theoretical studies， which can cause inaccurate measurement results in actual use. According to the transmission characteristics of light in the head tissue， a set of characteristic parameters of cranial tissues is selected， and the five-layer cranial brain tissue model is simulated using Monte Carlo method to study the transmission characteristics of light in the head tissue， and the maximum reachable depth and scattered transmission distance of photon transmission in the tissue are analyzed according to the transmission path of photons. By analyzing the effective depth ratio （EDR） and gray matter layer information ratio （GMLIR）， a set of optimal distances SD= 1 cm and SD=3.5 cm are selected to fit this group of selected cranial parameters. Compared with the traditional detection device， by optimizing the distance between the light source-detector， it will provide a new idea for the sensor design of the cerebral blood oxygen detection device and the measurement accuracy improvement of the device.Key Words：cerebral blood oxygen detection； light source-detector distance； sensor； Monte Carlo method； tissue model收稿日期：2022-12-16基金项目：国家重点研发计划项目（2018YFC1313803）作者简介：曹焱（1997-），男，上海理工大学光电信息与计算机工程学院硕士研究生，研究方向为光电检测；邢志明（1992-），男，上海理工大学光电信息与计算机工程学院博士研究生，研究方向为智能控制与检测；赵斌（1997-），男，上海理工大学光电信息与计算机工程学院硕士研究生，研究方向为光谱共聚焦检测；董祥美（1977-），女，博士，上海理工大学光电信息与计算机工程学院副教授、硕士生导师，研究方向为矢量光场调控；史以珏（1941-），女，博士，上海交通大学医学院附属瑞金医院主任医师、硕士生导师，研究方向为心身疾病、抑郁症等；高秀敏（1978-），男，博士，上海理工大学光电信息与计算机工程学院教授、博士生导师，研究方向为仪器仪表、智能传感技术、精密测量等。

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from the original chromium-chromium exchange whereas it remains practically unchanged for the other paramagnetic ions [15].
In a second step (Sec. 3) we investigate the principle structure of the proton spin-lattice relaxation rate T1−1 as a function of the applied magnetic ﬁeld strength at low temperatures. This quantity can be probed by Nuclear Magnetic Resonance (NMR). NMR has shown to be a powerful tool to investigate the local spin dynamics in magnetic molecules especially in the vicinity of level crossings [20,21,22]. The relaxation rate T1−1 is expected to increase drastically whenever two levels approach each other due to possible resonant energy exchange with the surrounding protons. In contrast to this expectation it appears that CuCr7 and NiCr7 show an unexpectedly reduced relaxation rate at certain level crossings which should experimentally be observable.
In accord with these investigations it was anticipated that spin rings, which host an odd number of spins or spins of diﬀerent size, would show complementary quantum eﬀects that would be interesting on their own. Odd membered rings for instance would violate the presuppositions for the theorems of Lieb, Schultz, and Mattis [8,9,6] and thus possess non-trivial ground states as well as low-lying excited states [10] with quantum numbers and degeneracies that diﬀer from those of their bipartite, i.e. even-membered counterparts. The N´eel-like local magnetization which in even-membered rings results from a superposition of the singlet ground
arXiv:cond-mat/0504658v2 [cond-mat.mtrl-sci] 22 Aug 2005
Journal of Magnetism and Magnetic Materials 0 (2008) 1–0
/locate/jmmm
Theoretical estimates for proton-NMR spin-lattice relaxation rates of heterometallic spin rings
The article closes with a summary and an outlook in Sec. 5.
2. Heisenberg Hamiltonian
The Hamilton operator of the isotropic Heisenberg model for heterometallic MCr7 wheels is given by
PACS: 75.10.-b; 75.10.Jm; 75.50.Ee
Keywords: Heisenberg model; Molecular magnets; Spin rings; Antiferromagnetism
1. Introduction
Among magnetic molecules spin rings constitute a rich subgroup of highly symmetric species of various sizes which are comprising a large variety of paramagnetic ions [1,2,3,4]. The investigation of these regular structures led to a deeper understanding especially of antiferromagnetically coupled spin systems. One of the ﬁndings is the discovery and conﬁrmation of rotational bands, see e.g. [5,6,7].
In this article we reexamine earlier susceptibility measurements [15] by means of complete diagonalization (Sec. 2) in the framework of an isotropic Heisenberg model. Our results agree with ﬁrst estimates given in Ref. [15] with the noticeable diﬀerence that we ﬁnd that the exchange parameters of the iron ion to its neighboring chromium ions in the FeCr7 wheel is
Mohammed Allalen and Ju¨rgen Schnack ∗
Universit¨at Osnabru¨ck, Fachbereich Physik, D-49069 Osnabru¨ck, Germany
Abstract
Heterometallic molecular chromium wheels are fascinating new magnetic materials. We reexamine the available experimental susceptibility data on MCr7 wheels in terms of a simple isotropic Heisenberg Hamiltonian for M=Fe, Ni, Cu, and Zn and ﬁnd in that FeCr7 needs to be described with an iron-chromium exchange that is diﬀerent from all other cases. In a second step we model the behavior of the proton spin lattice relaxation rate as a function of applied magnetic ﬁeld for low temperatures as it is measured in Nuclear Magnetic Resonance (NMR) experiments. It appears that CuCr7 and NiCr7 show an unexpectedly reduced relaxation rate at certain level crossings. c 2008 Elsevier B.V. All rights reserved.
0304-8853/08/$ - see frontmatter c 2008 Elsevier B.V. All rights reserved.
Mohammed Allalen and Ju¨rgen Schnack / Journal of Magnetism and Magnetic Materials 0 (2008) 1–0
In the case of spin ring systems comprising ions of diﬀerent chemical elements the breakthrough was already achieved with the synthesis of heterometallic MCr7 wheels [15], where one of the chromium ions of the original Cr8 ring [4,16,17,18] is replaced by another element M=Mn, Fe, Co, Ni, Cu, Zn, and Cd. The possibility of a systematic study has initiated ﬁrst investigations on these compounds as there are susceptibility measurements [15] as well as neutron scattering on MnCr7, ZnCr7, and NiCr7 wheels [19].