Yonghe Zhang , http://www.amhuilin.com For a long time,the ionic and the covalent nature have been considered as the isolated or falsedichotomy properties, and no quantitative correlations between the two. The ionocovalent theory changed the old antagonistic qualitative relations of theionic-versus-covalent dichotomy of bond nature. The ionic energy I(Z*,n*,I z ) is harmonized with covalent environment C(r c , r c -1 , n*r c -1 ) to form anunified new quantitative Ionocovalency (potential energy) continuum scale: IC =. I(Z*,n*,I z ) I (Z*,n*,I z ) It indicated that a compound consists of both the ionic nature and the covalent nature of its relative content components of the composition. In this scale, the ionicand the covalent are inverse sequence; the larger ionocovalency, the stronger the covalent, the weaker the ionic, vice versa. Ionocovalent Bond Parameters, Functions and Scales . Fig.1 Covalent radium156 pm of LiF is smaller than that of Li Fig.2 The electrostatic forces between Hydrogen atom A (A1 and A2) and Hydrogen tom B（B1 and B2) are not always the same. It should be noted that, so called “pure ionic bond” and pure covalent bond do not exist, as shown in Figure 1 , the covalent radius of 156pm of the most typical pure Ionic compounds LiF due to the covalent bond orbital overlap is smaller than the covalent radius of 252pm of Li atoms. And the so called “pure covalent bond” also actually not exists. As Hydrogen molecule, Figure 2 shows that in the actual molecule, due to the conjugation effect, steric hindrance conjugation effect, steric hindrance effects and adjacent group electronegativity effects, the same kind of bond length could be some differences and there could be some part of the ionic nature. The electrostatic forces between atom A (A1 and A2) and tom B（B1 and B2) are not always the same. The Metal bond is a non-localized covalent bond, and the hydrogen bond is not part of the chemical bond, only the intermolecular force. Thus, the ionocovalent bond is binary chemical bond and the pure ionic and the pure covalent are the two extremes of the ionocovalent scale at the end of each side . Zhang, Y. Ionocovalency andApplications 1. Ionocovalency Model and Orbital Hybrid Scales. Int. J. Mol. Sci. 2010, 11, 4381-4406. IC-Model Full-Text Zhang, YH. Ionocovalent Theory , J.Am. Huilin. Ins. 2011, 5, 1-11 Zhang,Y. Electronegativities of Elements in ValenceStates and Their ... 1 Electronegativities of elements invalence states, Inorg. Chem., 1982, 21 (11), pp 3886–3889 . Lower, S. Chemical bonds: covalentor ionic or what? . In Chem1 Virtual Textbook
https://snf.stanford.edu/SNF/equipment/chemical-vapor-deposition/pecvd/STS%20PECVD STS PECVD, sts The STS is a plasma-enhanced chemical vapor deposition system which is used for low temperature (350°C) deposition of oxide, nitride, and oxynitride. (STS also manufactures a deep RIE etching system which is available here at SNF. Click here for more information.) Features: * Low temperature PECVD (350°C) of silicon dioxide, silicon nitride, and oxynitride. * Large deposition electrode: up to 5 - 3", 4 - 4" wafers or a single 6" wafer can be accomodated. * Programmable dual frequency operation for precise stress control. Contents Picture and Location Background Process Capabilities Cleanliness Standard Performance of the Tool Contact List and How to Become a User Contact List Training to Become a Tool User Operating Procedures Process Monitoring and Machine Qualification Tool Qualification Run: On Jan. 2010 ran a nitride test using both high and low frequencies for total time of 10 minutes. Average thickness 944 angstroms. Dep. rate 94 A/min. Nitride etch rate using 6:1 134A/min. Machine Status States Process Monitoring Results: Ran four wafers ran through Low Frequency and four through High Frequency oxide. Average results for each wafer listed below. Picture and Location The tool is located at B5 on the Lab Map. Background Process Capabilities Cleanliness Standard The sts deposition system is in the " Gold Equipment Group ". Materials control policies are governed by equipment groups; for the description of this policy, click here . For equipment compatibility with specific materials, click here . Performance of the Tool What the Tool CAN do Item A. What the Tool CANNOT do Item A. Process Monitoring Contact List and How to Become a User Contact List The following people make up the Tool Quality Circle: Process Staff: Jeannie Perez Maintenance: Jim Hayden Super-Users: Training to Become a Tool User Operating Procedures Special Notes: This system is Gold contaminated. The PECVD STS deposition tool is mainly used for depositing of silicon nitride film. A mix-frequency program is available for this process. A low frequency program is available for the silicon dioxide process. The system is equipped with 13.56 MHz and 187.5 kHz frequencies. The temperature of the system is always kept at 350 degrees. Therefore, only the materials that are stable at this temperature are allowed in the STS deposition system. Please make sure you wear only latex gloves when you are working with this system. Don’t wear any vinyl gloves. Use only clean metal tweezers. You can process 4 of 4" wafers at a time (in the center of the wafer platen). With prior approval from staff, additional training is required for special processing of wafers coming out of the STS PEVCD with clean (non-contaminated) wafers. Separate tools needed for this procedure. To find out about the status of the system, check the run sheet filled out before you. Please make sure that you fill out a run sheet while you are running a process on the STS. Stand by mode: Make sure the Ar to the pump key is open (up). This key is the black toggle key located in the right hand side of the system. If the Ar Purge key is left off for a long time while you are not running any process, the chamber will get oil back fill from the pump. This will contaminate the chamber as well as your wafer. To clean this contamination the O2 descum program should be run prior to any process. Make sure that lights to the RF power supplies are on (green). Start up, Loading the wafer deposit: Enable the STS on Coral. The keyboard on the STS will not work if the system is not enabled. Switch off the Ar purge key (switch down) Use the keys on the keyboard to select (F3) "vent" from the menu. Pause for at least 5second before Selecting "open valve" (F1). DOS software is old and slow to respond. This will start venting the chamber. Make sure you hear the sound of valve opening. A message" venting the chamber, please wait" will appear on the screen. Check the process chamber lid seal. Wait until the seal is opened and there is a gap between the lid and the base of the chamber. This will take 2 -5 minutes. While pressing the two blue buttons located under the chamber on the panel to lift the lid all the way up. This should rise slowly so that you do not release any particles. Make sure there are no particles on the wafer platen. You can use the N2 gun located next to the system to remove the particles. Please make sure that the N2 gun is aimed downward to avoid any particle trapping in the shower head. Locate wafers in the center of the platen. Please note that the wafers start to move on the platen, when the pump down starts. So please load your wafers accordingly surrounding your samples with pieces so they don't move to an edge during pump down. Select "close valve" (F1) to close the lid While pushing in both blue buttons until the lid is completely down, and the computer screen will has changed showing the Mimic or Text page. Only at this time you may use a slow pump if desired by turning the black knob under the chamber in the direction of the line, waiting approximately five minutes. Close by turning the knob perpendicular to the line. Using the arrow keys selecting the desired recipe, then press enter . This will start the pump down of the system. This will take about 5 minutes. Wait until the pump down is complete. Select "Deposit" (F1) to start the process. Unloading the wafer, shut down: When the process step is completed, the program will go to the next step, which is "16 hours Warm down". This step is the last step of all processes, which will perform a N2 purge to the chamber for 16 hours to protect the chamber from any pump oil back fill. You should abort this step to end the program. To abort this step select "Abort " ( F1) Wait until the purging of the gas lines is complete and system is in the standby mode (this usually takes about 5 minutes for the silicon nitride process) Then select "vent" (F3) Select "Open the vent valve" (F1) Using the two blue buttons in front of the hardware, pressing both buttons until the Lid is completely up before releasing. Unload your wafer Select "Close Lid" (F1) Using the two blue buttons in front of the hardware, wait until the Lid is completely down before releasing. If no wafers are loaded in the chamber, it is not necessary to use the slow pump knob at this time. Select desired recipe using the arrow keys and then enter. This will start to pump down the chamber. Wait until the pump down is complete (takes about 2-5 minutes). Once you see the four F1, F2, F3, F4 on the screen. Turn on the Ar Purge key (key up) Disable the system on Coral. Modifying a program: Select "Main Menu" (F6). This only work if the F1, F2, F3, F4 on the bottom of the screen. Change the level from operator to service level by: In front of the command, type in" level", then enter Will ask for a password, leave blank and press enter Type in "setup" Using the arrow keys select load/save and then enter Select "load process" then enter Select the desired program, then enter Select Dep. Def’N, then enter, you'll have five options. Select "modify step" then enter. This will show three steps of the process which are: 15 min. warm up, Mix Freq. Nit., and 16 h warm down. Using arrow keys, highlight the 2 nd step "Mix Freq. Nit.", then enter Highlight "R.F. info.", then enter Select "Low RF setting", enter Select "Process Time", enter Enter the desired process time as: hh:mm:ss, enter Push "Esc" key 3 times. Highlight " Load/Save" Select "Save", enter Enter the file name. Please note that each user will have only one program. It will warn you about over writting your file. Answer yes. Push any key first then "Esc" key 2 times. Then there will be a message "Do you want to quit now?" Answer: yes "Y" then enter. This will take you to the main menu screen Select "Text page" (F8). This will take you to the text page. Select "new process" (F2) Select the desired program from the list Choose "deposit" (F1) Loading a new program: The procedure for loading a new program without opening the chamber to air is as follows: Select "new process" (F2) Select the desired program from the list. This will load the program to the system Select "deposit" (F1) Cleaning the Chamber: The total thickness of the film deposited in the chamber including predep. steps should not exceed 4.5 micron. A seven steps cleaning procedure is required for cleaning of the STS chamber as follows: Run program "Etchbak3". This program which takes about 2 1/2 hours, cleans the walls and the platen of the chamber using CF4 gas and O2. Vent the system and lift the lid. Then use folded clean wipe soaked with IPA to wipe the upper part of the wall then lower part of the wall and quartz window. Then clean the o-ring. Use the N2 gun to remove all the particle from the platen and under the platen. The last part that you need to wipe is under the hot platen. Please make sure that during the wipe don’t touch the shower head or the hot platen. Also don’t squeeze any IPA on the hot platen. Run the o2descum recipe. This recipe is set for 15 minutes. Run oxpredep recipe. This will coat the chamber with 1 micron of silicon dioxide. This recipe is set for 30 minutes Repeat step 2 of the cleaning procedure, exactly the same way with soaked clean wipes. Run the o2descum recipe, time is set for 15 minutes. Run the silicon nitride recipe for the thickness of 0.25 micron only if the next user is going to deposit nitride. This will take about 26 minutes. The purpose of this step is seasoning the chamber with the process that you are interested to run after cleaning procedure. When the cleaning procedure is completed the chamber will be coated with a total thickness of 1.25 micron. So please add this thickness to the film thickness that you get on the first run after cleaning and record it in the run sheet. If nitride wasn't needed or deposited the total thickness will be recorded on the log sheet as 1.0 um. last updated 9/20/11 JP Process Monitoring and Machine Qualification Tool Qualification Run: November 2012, STS is up for high frequency Nitride ONLY. RMS (Roughness) for SiNx is 0.49 nm (1000A) 350C. November 2012 STS is up for high frequency Oxide ONLY. RMS (Roughness) for SiOx is 0.381 nm (1000A) 350C. 20:1 ER 523A/min Unable to do dual frequency nitride at this time. Four test wafers; Oxide deposition rate 348A/min, 352A/min, 354A/min, 360A/min, index of reflection 1.46. Nitride deposition rate 96A/min, 96A/min, 95A/min. Etch rate in BOE 6:1 156A/min. Index of refraction 2.05. Nitride is tensile, 428.5 MPa _____________________________________________________________________________________________________________________________ On Jan. 2010 ran a nitride test using both high and low frequencies for total time of 10 minutes. Average thickness 944 angstroms. Dep. rate 94 A/min. Nitride etch rate using 6:1 134A/min. Frequency Procedure Responsibility Recommendation to users with critical processes: Before committing wafers, you should always verify by running a process test. Machine Status States Red : Unable to use Yellow : Some restrictions or problem. Green : Able to use equipment under normal conditions. Process Monitoring Results: Ran four wafers ran through Low Frequency and four through High Frequency oxide. Average results for each wafer listed below. Low Frequency test wafers High Frequency test wafers B 357 A /min *6:1 BOE 1566 A/min 394 A/min *6:1 BOE 2269 A/min R 362 A/min 6:1 BOE 1327 A/min 405 A/min 6:1 BOE 2643 A/min F 364 A/min *20:1 BOE 379 A/min 415 A/min *20:1 BOE 596 A/min L 368 A/min 20:1 BOE 454 A/min 397 A/min 20:1 BOE 593 A/min Etche Rates with an Asterisk indicate that the etch test was repeated.
美国气象学会的Charney奖是为了纪念气象大师J. Charney教授而设立的美国气象学会最高奖，主要表彰世界范围内取得杰出成就的大气科学家。2013年度的Charney奖授予给了美国麻省理工学院的气象学家Alan Plumb教授，以表彰他在大气动力学，地球物理流体力学等研究领域所取得的独特贡献。Plumb教授最著名的工作是提出了三维EP通量表达式，现被广泛应用。到目前为止，他培养的学生和发表的论文都不算多。Plumb教授现为英国皇家学会会员(相当于我的院士，但在他的简历中没这方面的信息）。 见他的网页： http://www-eaps.mit.edu/~rap/ THE JULE G. CHARNEY AWARD Raymond Alan Plumb For fundamental contributions to the understanding of geophysical fluid dynamics, stratospheric dynamics, chemical transport, and the general circulation of the atmosphere and oceans。
E1 reaction-induced synthesis of hydrophilic oxide nanoparticles in non-hydrophilic solvent DOI: 10.1039/C2NR32255B Nanoscale , 2012, 4 , 6284-6288 DOI: 10.1039/C2NR32255B Received 12 Aug 2012, Accepted 03 Sep 2012 First published on the web 06 Sep 2012 Abstract In this paper, tert-amyl alcohol was employed to directly react with metal chlorides to prepare oxide nanoparticles. Some typical metal oxide or hydroxides with different morphologies, such as TiO2 nanoparticles, TiO2 nanorods, FeOOH nanowires, Fe2O3 nanoparticles, SnO2 nanoparticles, can be easily fabricated through such some simple chemical reactions. E1 reaction was found to play the leading role in the synthesis of metal oxides attributed to better stability of tertiary carbocations in tert-amyl alcohol and the strong interaction of metal chlorides with hydroxyl groups that result in the easy dissociation of carbon-oxygen bonds in tert-amyl alcohol. SN1 reaction can also happen in certain reactions due to nucleophilic substitution of chloride ions for hydroxyl groups. As-prepared metal oxides show good compatibility with aqueous system while they were synthesized in non-hydrophilic solvent probably attributed to specific E1 reaction mechanism involving the generation of water, and can be directly incorporated into aqueous soluble polymer, such as PVA, to exhibit many promising applications.
Yin Y, Zhang YL, Liu XH, Zhu GW, Qin BQ, Shi ZQ, Feng LQ. Temporal and spatial variations of chemical oxygen demand in Lake Taihu, China, from 2005 to 2009. Hydrobiologia , 2011, 665: 129–141. Temporal and spatial variations of chemical oxygen demand in Lake Taihu, China, .pdf
CONTENTS OF “CHEMICAL SUPPRESSION OF DUST” Chemical Suppression of Dust . By prof WU CHAO. Changsha: Central South University Press, 2003.6 ISBN 7-81061-652-8 Forward Chapter I Introduction Dust and dust suppression techniques Review of chemical dust suppressants Research and development of chemical dust suppressants An outlook on chemical dust suppression techniques References Chapter II Properties of dust and their measurement Dust particle and definitions Shape and structure of dust Agglomeration of dust Adhesion of dust Density of dust Specific surface area of dust Electrostatic charge of dust Wettability of dust Electro-chemical characteristics of dust Measuring particle size distribution and concentration of dust References Chapter III Fundamental principles of chemical dust suppression—surface chemistry Surface tension and surface free energy Basis of surface thermodynamics The liquid meniscus Measurements of surface tension Phenomena of wetting Contact angle and Young’s equation Wetting of capillary systems Contact angle on practical solid surface Measurements of contact angle Wetting of liquid on solid surface References Chapter IV Basic components of chemical dust suppressants--surfactants Surfactants and their classification Anionic surfactants Cationic surfactants Amphoteric surfactants Non-ionic surfactants High molecular surfactants Characteristics of aqueous solution of surfactants Relationship between the solubility of surfactants and temperature Variation of surface tension with time Adsorption of surfactants on solid surface References Chapter V Chemical dust suppressants of wetting type Dust suppression mechanism in spraying system with wetting agents Dust suppression behaviors of coal dust wetting agents and affecting factors Dust suppression behaviors and principles of coal dust wetting agents with sulfate addition Dust suppression behaviors of silica dust wetting agents Behaviors of silica dust wetting by inorganic salt solution References Chapter VI Dust suppression with organic chemical substances of binding type Emulsification of emulsifier Solubilization of emulsifier Hydrophile-lipophile balance of emulsifier Foaming and de-foaming of emulsifier Asphalt as basic composition of dust suppressant Emulsified asphalt Formulations and applications of emulsified asphalt liquid Dust suppressing behaviors of tar emulsified liquid with low concentration Technology and practice of dust suppression with tar emulsified liquid for low grade roadways References Chapter VII Dust binding and dirt stabilization with stabilizing materials Dust binding and dirt stabilization with complexes of halides, lime and water glass Dust binding and dirt stabilization by penetrating the chloride and water glass solutions with aiding penetration agents Dirt stabilization with broken stone for roadways Dirt stabilization with complexes of grave and crushed stone for roadways Maintenance of grave and crushed stone roadways Dust binding and dirt stabilization by blending dirt with lime on roadways Other soil stabilization methods for binding dust and stabilizing dirt Dust binding and dirt stabilization with industrial wastes Mechanical characteristics of binding layers by macadam, grave and other materials References Chapter VIII Chemical dust suppressants of strong hygroscopy Resins of super water absorbents and their applications Method of preparing super water absorbing resins by homogeneous liquid system synthesis Method of preparing super water absorbing resins by heterogeneous system synthesis Solid-phase method and other special methods of preparing super water absorbing resins Dust suppression behaviors of starch-linked sodium polyacrylate resin Dust suppression behaviors of sodium polyacrylate resin gel Dust suppression mechanism of super water absorbing resins Dust suppression behaviors of solid halide References Chapter IX Chemical wet scrubbers for dust cleaning Spray towers with chemical wetting agents Centrifugal scrubbers with chemical wetting agents Pond type scrubbers with chemical wetting agents Porous scrubbers with chemical foaming agents Mechanical scrubbers with chemical wetting agents Venturi scrubbers with chemical wetting agents High efficient dust scrubbers with foaming and wetting agents for continuous miners in underground mine Micro droplet formation of wetting agent Liquid for dust scrubbers Dewatering devices for chemical wet scrubbers Sewage treatment and corrosion protection of chemical wet scrubbers References Appendix ： List of English-Chinese Names Acknowledgement 《化学抑尘》目录 吴超 著 . 化学抑尘 . 长沙 : 中南大学出版社 , 2003.6 ISBN 7-81061-652-8 前言 第一章 概论 粉尘与化学抑尘技术 化学抑尘剂成果综述 化学抑尘剂的研制方法 化学抑尘技术的展望 参考文献 第二章 粉尘的性质与测定 粉尘粒子的粒度 粉尘 粒子 的形状与结构 粉尘的凝集 粉尘的粘附 粉尘的密度 粉尘的 比表面积 粉尘的 静电荷 粉尘的可湿性 粉尘的电化学特性 粉尘的粒径分布与浓度的测定方法 参考文献 第三章 化学抑尘的基本原理——表面化学 表面张力与表面自由能 表面热力学基础 弯曲液面 表面张力的测定 润湿现象 接触角和杨氏方程 毛细管体系的润湿 非理想固体表面上的接触角 接触角的测定 固体表面的润湿 参考文献 第四章 化学抑尘剂的基本组分——表面活性剂 表面活性剂及其分类 阴离子表面活性剂 阳离子表面活性剂 两性表面活性剂 非离子表面活性剂 高分子表面活性剂 表面活性剂水溶液的特性 表面活性剂的溶解度与温度的关系 表面张力随时间的变化 表面活性剂在固体表面的吸附 参考文献 第五章 湿润型化学抑尘剂 湿润剂喷雾系统的抑尘机制 煤尘湿润剂的抑尘性能及其影响因素 煤尘湿润剂添加硫酸盐的抑尘性能及其原理 硅尘湿润剂的抑尘性能 无机盐溶液湿润硅尘的性能 参考文献 第六章 粘结型有机化学材料抑尘 乳化剂的乳化作用 乳化剂的增溶作用 乳化剂的亲水 - 亲油平衡 乳化剂的起泡和消泡作用 石油沥青抑尘材料 乳化沥青 沥青乳化液的配方及应用 渣油 - 水系乳化液的抑尘性能 渣油乳化液抑制低等级公路扬尘的工艺与实践 参考文献 第七章 稳定土材料固土抑尘 卤化物与 CaO 、水玻璃的复合物固土抑尘 氯化钙、水玻璃溶液和助渗剂的复合物固土抑尘 碎石路面固土抑尘 级配砾（碎）石路面固土抑尘 碎（砾）石路面的养护 石灰土基层固土抑尘 其它稳定土方法固土抑尘 工业废渣固土抑尘 碎、砾石和稳定土层面的力学特性 参考文献 第八章 吸水型化学抑尘剂 超强吸水树脂及其应用概述 液相均相系合成吸水树脂的方法 非均相系合成吸水树脂的方法 固相法和其它特殊合成吸水树脂的方法 淀粉接枝聚丙烯酸钠抑尘树脂的抑尘性能 聚丙烯酸钠抑尘溶胶的抑尘性能 高倍吸水树脂的抑尘机理 固体卤化物的抑尘性能 参考文献 第九章 化学湿式除尘器 应用化学湿润剂的喷淋塔 应用化学湿润剂的离心式洗涤器 应用化学湿润剂的水池式洗涤器 应用化学发泡剂的多孔洗涤器 应用化学湿润剂的机械洗涤器 应用 化学湿润剂的文丘里洗涤器 应用发泡剂和湿润剂的地下连续采矿机高效除尘器 化学湿式除尘器洗涤液的微粒化 化学湿式除尘器的脱液装置 化学湿式除尘器的污水处理及 防腐蚀 参考文献 附录 ：中英文人名对照 后记
Professor Chuan He http://he-group.uchicago.edu/index.html Chang group http://www.cchem.berkeley.edu/cjcgrp/index.html Ming Xian http://organic.wsu.edu/faculty/xian Professor W. E. Moerner http://www.stanford.edu/group/moerner/members.html Prof. Dr. Engin U. Akkaya http://www.fen.bilkent.edu.tr/~eua/publications.html Tetsuo Nagano http://www.f.u-tokyo.ac.jp/~tlong/en/publications-2012.html Dr. Belinda Heyne http://www.ucalgary.ca/chem/pages/heyne
从“化学物质”想起的 在我国，甚至其他一些国家，公众一说“化学物质”（ Chemical substances ），第一反应一定是“有毒”，“污染”，“致癌”，反正不是好东西。 看一看Wikipedia, the free encyclopedia， 什么是“化学物质”（ Chemical substances ）： In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. They can be solids, liquids or gases. 看一看Wikipedia, the free encyclopedia对药品（drug）的定义： In pharmacology, a drug is a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being. 看一看《中华人民共和国药品管理法》第一百零二条关于药品的定义： 药品是指用于预防、治疗、诊断人的疾病，有目的地调节人的生理机能并规定有适应症或者功能主治、用法和用量的 物质 ，包括中药材、中药饮片、中成药、化学原料药及其制剂、抗生素、生化药品、放射性药品、血清、疫苗、血液制品和诊断药品等。 看一看中国国家基本药物目录 第一部分 化学药品 和生物制品，205种 第二部分中成药，102种 看一看WHO Model List of Essential Medicines（世界卫生组织基本医药目录），全部是 化学药品 。http://www.who.int/medicines/publications/essentialmedicines/en/index.html 对比这些，不难有所感悟。
http://www.mdbbs.org/thread-5696-1-1.html 简单的第一性原理介绍 什么是第一性原理计算(What are first principles calculations?) 1。What are first principles calculations? A material is simply a collection of atoms that are bound by chemical reactions. Chemical reactions, in turn, are simply interactions between electrons . These interactions are described by the laws of quantum physics. This means that all material properties (chemical, mechanical, electrical, magnetic, optical, thermal,…) can, in principle, be predicted from nothing more than the atomic number and mass of the atomic species involved , with the aid of quantum physics. This is precisely what first principles calculations attempt to do. One of the joys of first principles calculations is that a few atomic numbers make abstract quantum concepts come to life in the form of quantitatively accurate, experimentally verifiable predictions- for quantities ranging from the Young modulus of diamond to the absorption spectra of conjugated polymers . 2。How do we do first principles calculations? Solving the Schrouml;dinger equation by brute mathematical force is extremely demanding computationally and not practical for all but tiny systems. Instead, we use a combination of two physical approximations : 1. We use density functional theory (DFT) , for which Prof. Walter Kohn was awarded the 1998 Nobel prize in chemistry . DFT maps the original many-electron problem into an equivalent single-electron problem. It does so by lumping all the many-body quantum phenomena (such as Pauli’s exclusion principle and electron correlation) into a single additive “exchange-correlation” potential , which is a functional of the charge density alone . In principle, this mapping is exact. In practice, the exact functional is unknown and people use approximate forms for the functional , usually (but not always) derived from properties of a uniform electron gas . 2. We use first principles pseudopotential theory . The periodic table tells us that chemical reactivity is governed by valence electrons, with core electrons being chemically inert . Pseudopotentials make use of this basic fact by replacing the inert core electrons with an effective potential . This reduces, sometimes drastically, the number of electrons we need to solve for. Even more importantly, this results in much smoother wave functions for the remaining valence electrons , making the problem much easier to solve numerically. For the calculation of excited state properties (notably optical ones), we have to move beyond DFT , which is a ground state theory . Our favorite tool is time-dependent DFT –an extension of the original method. Doesn’t the use of physical approximations mean that we’re not really doing first principles work? No! Our approximations are systematic. All “hidden parameters” within them are determined objectively from theoretical results for properties of the electron gas (DFT) or the isolated atom (pseudopotentials), and not by fitting experiments. 百度的解释： 第一性原理通常是跟计算联系在一起的，是指在进行计算的时候除了告诉 程序 你所使用的 原子 和他们的位置外，没有其他的实验的，经验的或者半经验的参量，且具有很好的移植性。作为评价事物的依据，第一性原理和经验 参数 是两个极端。第一性原理是某些硬性规定或推演得出的结论，而经验参数则是通过大量实例得出的规律性的数据，这些数据可以来自第一性原理(称为理论统计数据)，也可以来自实验(称为实验统计数据)。 但是就某个特定的问题，第一性原理和经验参数没有明显的界限，必须特别界定。如果某些原理或数据来源于第一性原理，但推演过程中加入了一些 假设 (这些假设当然是很有说服力的)，那么这些原理或数据就称为“半经验的”。 其他解释： 第一性原理，英文First Principle，是一个计算 物理 或计算 化学 专业名词，广义的第一性原理计算指的是一切基于量子力学原理的计算。 我们知道物质由 分子 组成，分子由原子组成，原子由原子核和电子组成。量子力学计算就是根据原子核和电子的 相互作用 原理去计算分子 结构 和分子 能量 （或离子），然后就能计算物质的各种性质。 从 头算（ab initio） 是狭义的第一性原理计算 ，它是指 不使用经验参数，只用电子质量，光速，质子中子质量等少数实验数据去做量子计算。但是这个计算很慢，所以就加入一些 经验参数 ，可以大大加快计算速度，当然也会不可避免的牺牲计算 结果 精度 。 那为什么使用“第一性原理”这个字眼呢？据说这是来源于“第一推动力”这个宗教词汇。第一推动力是牛顿创立的，因为牛顿第一定律说明了物质在不受外力的作用下保持静止或匀速直线运动。如果宇宙诞生之初万事万物应该是静止的，后来却都在运动，是怎么动起来的呢？牛顿相信这是由于上帝推了一把，并且牛顿晚年致力于神学研究。现代科学认为宇宙起源于大爆炸，那么大爆炸也是有原因的吧。所有这些说不清的东西，都归结为宇宙“第一推动力”问题。 科学不相信上帝，我们不清楚“第一推动力”问题只是因为我们科学知识不完善。第一推动一定由某种原理决定。这个可以成为“第一原理”。爱因斯坦晚年致力与“大统一场理论”研究，也是希望找到统概一切物理定律的“第一原理”，可惜，这是当时科学水平所不能及的。现在也远没有答案。 但是为什么称量子力学计算为 第一性原理计算 ？大概是因为 这种计算能够从根本上计算出来分子结构和物质的性质，这样的理论很接近于反映宇宙本质的原理，就称为第一原理了 。 广义的第一原理包括两大类 ，以 Hartree-Fork自洽场计算为基础的ab initio从头算 ，和 密度泛函理论（DFT）计算 。也有人主张，ab initio专指从头算，而第一性原理和所谓量子化学计算特指密度泛函理论计算。
TWEEN 20 is a polyoxyethylene sorbitol ester, with a calculated molecular weight of 1,225 daltons, assuming 20 ethylene oxide units, 1 sorbitol, and 1 lauric acid as the primary fatty acid. http://www.sigmaaldrich.com/sigma/product%20information%20sheet/p5927pis.pdf TWEEN 80 is a polyethylene sorbitol ester, with a calculated molecular weight of 1,310 daltons, assuming 20 ethylene oxide units, 1 sorbitol, and 1 oleic acid as the primary fatty acid. http://www.sigmaaldrich.com/sigma/product%20information%20sheet/p4780pis.pdf They could be called tween A and tween B. So your question was like asking why are eggs called eggs but apples called apples? I assume tween 20 was delevloped 1st and the 20 did relate to the 20 EO's reacted but then they developed a new related compound and simply called it tween 80. The 80 meaning nothing but being different to 20. What annoyed me was the pointless question you've asked here and on other forums when you could have found all the info you wanted from doing some googling yourself.
NATURE CHEMICAL BIOLOGY December 2010 Volume 6 Number 12, pp 845 - 921 Visit Nature Chemical Biology online to browse the journal. Now available at http://links.ealert.nature.com/ctt?kn=60m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Please note that you need to be a subscriber to enjoy full text access to Nature Chemical Biology online. To purchase a subscription, please visit: http://links.ealert.nature.com/ctt?kn=24m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Alternatively, to recommend a subscription to your library, please visit http://links.ealert.nature.com/ctt?kn=138m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 =========================== ADVERTISEMENT =========================== Do you need to understand small molecule protein interactions? 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Follow us on Twitter: http://links.ealert.nature.com/ctt?kn=31m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 ===================================================================== ---------------------- EDITORIAL ---------------------- Contemplating chemical biology p845 doi:10.1038/nchembio.465 In this special issue, Nature Chemical Biology takes a look at the past, present and future of chemical biology. http://links.ealert.nature.com/ctt?kn=68m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 ---------------------- SPECIAL FEATURE ---------------------- A decade of chemical biology pp847 - 854 Mirella Bucci, Catherine Goodman and Terry L Sheppard doi:10.1038/nchembio.489 With insights from a panel of experts, the Nature Chemical Biology editors examine the evolution and current era of chemical biology. http://links.ealert.nature.com/ctt?kn=63m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 ---------------------- COMMENTARIES ---------------------- Grand Challenge Commentary: Informative diagnostics for personalized medicine pp857 - 859 Ryan C Bailey doi:10.1038/nchembio.488 Some of the most celebrated triumphs of chemical biology are molecularly targeted therapeutics to combat human disease. However, a grand challenge looms as informative diagnostic strategies must be developed to realize the full impact of these promising pharmaceutical agents. http://links.ealert.nature.com/ctt?kn=64m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: Transforming biosynthesis into an information science pp859 - 861 Travis S Bayer doi:10.1038/nchembio.487 Engineering biosynthetic pathways to natural products is a challenging endeavor that promises to provide new therapeutics and tools to manipulate biology. Information-guided design strategies and tools could unlock the creativity of a wide spectrum of scientists and engineers by decoupling expertise from implementation. http://links.ealert.nature.com/ctt?kn=61m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: Accessing new chemical space for 'undruggable' targets pp861 - 863 Sivaraman Dandapani and Lisa A Marcaurelle doi:10.1038/nchembio.479 The synthesis and biological annotation of small molecules from underexplored chemical space will play a central role in the development of drugs for challenging targets currently being identified in frontier areas of biological research such as human genetics. http://links.ealert.nature.com/ctt?kn=62m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: RNA epigenetics? pp863 - 865 Chuan He doi:10.1038/nchembio.482 Post-transcriptional RNA modifications can be dynamic and might have functions beyond fine-tuning the structure and function of RNA. Understanding these RNA modification pathways and their functions may allow researchers to identify new layers of gene regulation at the RNA level. http://links.ealert.nature.com/ctt?kn=65m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: The chemistry of a dynamic genome pp866 - 868 Rahul M Kohli doi:10.1038/nchembio.471 In the postsequencing era, chemical biology is uniquely situated to investigate genomic DNA alterations arising through epigenetic modifications, genetic rearrangements or active mutation. These transformations significantly expand nature's diversity and may profoundly alter our view of DNA's coding potential. http://links.ealert.nature.com/ctt?kn=66m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: Beyond discovery: probes that see, grab and poke pp868 - 870 Joshua A Kritzer doi:10.1038/nchembio.469 Chemical biology is now able to discover molecules that manipulate virtually any biological target or process. It remains a grand challenge to leverage these molecules into useful probes that can be used to address unsolved problems in biology. http://links.ealert.nature.com/ctt?kn=85m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: Synthetic immunology to engineer human immunity pp871 - 872 David A Spiegel doi:10.1038/nchembio.477 Rationally designing new strategies to control the human immune response stands as a key challenge for the scientific community. Chemical biologists have the opportunity to address specific issues in this area that have important implications for both basic science and clinical medicine. http://links.ealert.nature.com/ctt?kn=75m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: Exploiting single-cell variation for new antibiotics pp873 - 875 Erick Strauss doi:10.1038/nchembio.483 Variations between single members of a bacterial population can lead to antibiotic resistance that is not gene based. The future of effective infectious disease management might depend on a better understanding of this phenomenon and the potential to manipulate both it and microbial population dynamics in general. http://links.ealert.nature.com/ctt?kn=73m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: Chassis cells for industrial biochemical production pp875 - 877 Claudia E Vickers, Lars M Blank and Jens O Kromer doi:10.1038/nchembio.484 Hyper-performing whole-cell catalysts are required for the renewable and sustainable production of petrochemical replacements. Chassis cells self-replicating minimal machines that can be tailored for the production of specific chemicals will provide the starting point for designing these hyper-performing 'turbo cells'. http://links.ealert.nature.com/ctt?kn=79m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Grand Challenge Commentary: Chemical transdifferentiation and regenerative medicine pp877 - 879 Bridget K Wagner doi:10.1038/nchembio.472 The ability to alter cell identity with small molecules represents a powerful approach to restore biological function lost because of cellular deficiency. Developing this capability through advances in chemical biology could have an enormous impact on human health. http://links.ealert.nature.com/ctt?kn=77m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 ---------------------- NEWS AND VIEWS ---------------------- Chaperones: A story of thrift unfolds pp880 - 881 Francois Baneyx and Brent L Nannenga doi:10.1038/nchembio.468 Although members of the Hsp70-DnaK family of heat shock proteins are involved in nearly all aspects of cell physiology, some mechanistic details of their mode of action remain obscure. A new substrate helps establish DnaK as an unfoldase that requires as little as five ATP molecules to drive the refolding of one protein. http://links.ealert.nature.com/ctt?kn=93m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Molecular probes: Getting lucky in the lysosome pp881 - 883 Ethan D Goddard-Borger, Tom Wennekes and Stephen G Withers doi:10.1038/nchembio.470 Conjugation of a known, mechanism-based glycosidase inhibitor to sensitive fluorophores yielded unexpectedly potent and selective probes for quantifying active lysosomal glucocerebrosidase. These conjugates could prove to be invaluable tools for diagnosing and studying Gaucher disease. http://links.ealert.nature.com/ctt?kn=92m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Glycobiology: Cellulose squeezes through pp883 - 884 Anne Endler, Clara Sanchez-Rodriguez and Staffan Persson doi:10.1038/nchembio.480 The glucose-based polymer cellulose is of great biological and economical importance; however, little is known about how cellulose is synthesized. Now, structural estimates of one of the cellulose-synthesizing subunits in the bacterium Acetobacter xylinum help to explain the extrusion of the newly synthesized glucan chains. http://links.ealert.nature.com/ctt?kn=97m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Imaging: Visualizing a neuronal handshake pp885 - 886 Atsushi Miyawaki doi:10.1038/nchembio.486 A new method to monitor interactions between cell surface proteins reveals that interaction of the neuronal cell surface adhesion proteins neurexin and neuroligin is increased at synapses during a stimulus or developmental activity. This increased activity-dependent surface density of neurexin-neuroligin complexes is subsequently required for maturation of synapses. http://links.ealert.nature.com/ctt?kn=95m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 ---------------------- BRIEF COMMUNICATION ---------------------- Small-molecule inactivation of HIV-1 NCp7 by repetitive intracellular acyl transfer pp887 - 889 Lisa M Miller Jenkins et al. doi:10.1038/nchembio.456 The antiviral S-acyl-2-mercaptobenzamide thioester ejects an essential coordinated zinc ion from and induces aggregation and dysfunction of the HIV-1 nucleocapsid protein NCp7 via repetitive intracellular enzymatic acyl transfers, dependent on acetyl-CoA. Abstract: http://links.ealert.nature.com/ctt?kn=90m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Article: http://links.ealert.nature.com/ctt?kn=112m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 ---------------------- ARTICLES ---------------------- Microscopic rotary mechanism of ion translocation in the Fo complex of ATP synthases pp891 - 899 Denys Pogoryelov et al. doi:10.1038/nchembio.457 Free-energy molecular dynamics simulations and high-resolution structural analysis of the c-ring of the F1Fo ATPase rotary motor, which mediates ion translocation, suggest conformational flexibility and reversible ion binding in the c-subunits, in an environment mimicking the a-subunit. Abstract: http://links.ealert.nature.com/ctt?kn=111m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Article: http://links.ealert.nature.com/ctt?kn=109m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Inhibitors of protein disulfide isomerase suppress apoptosis induced by misfolded proteins pp900 - 906 Benjamin G Hoffstrom et al. doi:10.1038/nchembio.467 Expression of a Huntington's-disease variant of huntingtin protein causes accumulation of the chaperone protein disulfide isomerase. This protein is the target of compounds obtained from screening for those that can alleviate cell death promoted by the mutant huntingtin, and represents a new connection between protein misfolding and cell death. Abstract: http://links.ealert.nature.com/ctt?kn=108m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Article: http://links.ealert.nature.com/ctt?kn=107m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Ultrasensitive in situ visualization of active glucocerebrosidase molecules pp907 - 913 Martin D Witte et al. doi:10.1038/nchembio.466 Fluorescent high-affinity activity-based probes used to monitor the activity and presence of active glucocerebrosidase in vitro and in vivo help in understanding Gaucher disease and its treatment with pharmacological chaperones. Abstract: http://links.ealert.nature.com/ctt?kn=106m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Article: http://links.ealert.nature.com/ctt?kn=117m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 The kinetic parameters and energy cost of the Hsp70 chaperone as a polypeptide unfoldase pp914 - 920 Sandeep K Sharma et al. doi:10.1038/nchembio.455 Protein chaperones help misfolded proteins reach their native state, but the necessarily unstable substrates have complicated the analysis of chaperone function. A stable misfolded luciferase substrate now allows the determination of traditional enzyme parameters for the DnaK system, demonstrating that five cycles of unfolding and release are needed for one successful refolding event. Abstract: http://links.ealert.nature.com/ctt?kn=116m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Article: http://links.ealert.nature.com/ctt?kn=115m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 ---------------------- ERRATUM ---------------------- Research Highlights p921 doi:10.1038/nchembio1210-921 http://links.ealert.nature.com/ctt?kn=114m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 =========================== ADVERTISEMENT =========================== FREE ARTICLES FROM SciBX CANCER Treating brain cancer with laminin-targeting nanoconjugates http://links.ealert.nature.com/ctt?kn=57m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 Targeting bromodomains in cancer http://links.ealert.nature.com/ctt?kn=55m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 INFECTIOUS DISEASE Treating HCV infection with DGAT1 inibitors http://links.ealert.nature.com/ctt?kn=53m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0 GET ACCESS TO MORE THAN 40 FREE ARTICLES from the SciBX Cover Story Archive http://links.ealert.nature.com/ctt?kn=1m=35989779r=NDU1MzI2NDE1NgS2b=2j=ODY5MDI0MDMS1mt=1rt=0
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