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1.
R.J. Deltete 《Foundations of Chemistry》2007,9(3):265-316
This is the second of a series of essays on the development and reception of Wilhelm Ostwald’s energetics. The first essay
described the chemical origins of Ostwald’s interest in the energy concept and his motivations for seeking a comprehensive
science of energy. The present essay and the next discuss his various attempts, beginning in 1891 and extending over almost
3 years, to develop a consistent and coherent energetic theory. A final essay will consider reactions to this work and Ostwald’s
replies, and will also seek to evaluate his program of research. Ostwald’s project – to reconstruct physics and chemistry
“as a pure energetics” – is worth attending to for several reasons: first, because Ostwald did ground-breaking work in chemistry
(he was awarded a Nobel Prize in 1909 for his studies in catalysis and rates of reaction); second, because an important school
of physical chemistry formed around him at Leipzig, a school that promoted his ideas; and, finally, because he was a prominent
and vigorous participant in debates at the end of the nineteenth century concerning the proper course of physical theory. 相似文献
2.
R. Wood 《Accreditation and quality assurance》1996,1(4):140-149
The European Union has prescribed strict quality standards for official food laboratories and the methods of analysis to
be used in laboratories when carrying out official food control work. These requirements, which are based on accreditation,
participation in proficiency testing schemes and using validated methods of analysis, are described in detail. The similar
approach being taken within the Codex Alimentarius Commission is also outlined. The procedures prescribed will ensure that
official food control laboratories have in place the measures to ensure that consistently reliable data can be produced.
Received: 29 November 1995 Accepted: 8 January 1996 相似文献
3.
Charles W. Bauschlicher Jr. 《Theoretical chemistry accounts》1997,96(1):11-13
The ˜c state of CH2 is found to be bent at the highest levels of theory used in this work, but the energy difference between the linear and bent
geometries is only about 10 cm−1. Improving the basis set or correlation treatment favors the linear geometry over the bent, thus it is impossible to definitively
determine if the ˜c state has a barrier in its bending potential. If there is a barrier, it is clear that it will be so small
that the ˜c state will be quasilinear.
Received: 3 September 1996 / Accepted: 23 September 1996 相似文献
4.
In this work the development of a new ultracentrifugation method is described. The preparative density gradient method (PDDG)
allows the fractionation of colloidal systems according to the density of their components. The fractions—collected separately—can
be subjected to further investigations with any appropriate physical or analytical method. The particle density of a colloidal
system is a very valuable information that can be used in many ways. Here for the first time a method is presented that could
make the access to that information much easier for laboratories throughout the world. The preparative dynamic density gradient
is performed in a preparative ultracentrifugation tube by layering heavy water under a sample that is dispersed or dissolved
in water. The water and heavy water molecules undergo a fast diffusion process finally leading to a homogeneous solvent mixture.
While reaching this equilibrium the water–heavy water concentration varies over the cell radius. Thus a density gradient is
built up. Fractions of the sample will move to the radial position where their densities are matched. They can then be collected
separately. In this work basic experiments and results that lead to the development of the PDDG will be presented. Calculations
based on basic ultracentrifugation theory confirm the described experimental findings. An example will demonstrate the problem
solving capability of this new method. 相似文献
5.
The idea behind the original quantum network (QN) model is simple enough. One joins each atom to its nearest neighbours, and
then treats electrons (though quantum mechanically of course) as though they flowed through one-dimensional wires as in an
electrical circuit obeying Kirchhoff’s Laws at every node. Here we will begin with two periodic systems: namely a single graphene
layer, which has recently been produced experimentally, and a two-dimensional sheet of boron atoms. This will be followed
by a discussion of B nanotubes, using the simplest QN model, supplemented by comparison of these results with very recent
work of other authors using density functional theory. Then the disordered quantum network (DQN) model will be treated in
some detail. First of all, the main, physically motivated, steps by which Dancz, Edwards and March passed from the DQN model
to the Boltzmann equation will be set out. They will then be related to substantial progress made on the mathematical solution
of the DQN model by a number of authors; again a substantial part of this work invoking the Boltzmann equation.
Invited paper presented at the Workshop “Graph Models of Mesoscopic Systems, Wave Guides, and Nano-Structures (AGAW03)”, Newton
Institute, Cambridge, UK, April 10–13, 2007. 相似文献
6.
Paul F. van Hutten Georges Hadziioannou 《Monatshefte für Chemie / Chemical Monthly》2001,18(10):129-139
Organic opto-electronic devices comprise one or more organic layers and the electrodes. The interfaces between these very different components play a crucial role to the performance of the devices. In donor–acceptor composites for photovoltaics, the electronic processes occurring at the interface will benefit from a particular interface morphology on the 10–100 nanometer level; this is demonstrated for composites of oligophenylenevinylene and C60. Phase separation on such a scale may be achieved naturally in diblock copolymers. The synthesis of an OPV–C60 diblock copolymer is described. 相似文献
7.
Paul F. van Hutten Georges Hadziioannou 《Monatshefte für Chemie / Chemical Monthly》2001,132(1):129-139
Summary. Organic opto-electronic devices comprise one or more organic layers and the electrodes. The interfaces between these very
different components play a crucial role to the performance of the devices. In donor–acceptor composites for photovoltaics,
the electronic processes occurring at the interface will benefit from a particular interface morphology on the 10–100 nanometer
level; this is demonstrated for composites of oligophenylenevinylene and C60. Phase separation on such a scale may be achieved naturally in diblock copolymers. The synthesis of an OPV–C60 diblock copolymer is described.
Received June 23, 2000. Accepted (revised) July 18, 2000 相似文献
8.
Daniel G. Cummings James D. Sommers Mary L. Adamic Marcos Jimenez Jeffrey J. Giglio Kevin P. Carney Karl Grimm 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):923-928
A radioactive 137Cs source has been analyzed for the radioactive parent 137Cs and stable decay daughter 137Ba. The ratio of the daughter to parent atoms is used to estimate the date when Cs was purified prior to source encapsulation
(an “age” since purification). The isotopes were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) after chemical
separation. In addition, Ba was analyzed by isotope dilution ICP-MS (ID-ICP-MS). A detailed error analysis of the mass spectrometric
work has been undertaken to identify areas of improvement, as well as quantifying the effect the errors have on the “age”
determined. This paper reports an uncertainty analysis to identifying areas of improvement and alternative techniques that
may reduce the uncertainties. In particular, work on isotope dilution using ICP-MS for the “age” determination of sealed sources
is presented. The results will be compared to the original work done using external standards to calibrate the ICP-MS instrument. 相似文献
9.
Low-spin/high-spin energy splittings for Fe(II) transition-metal complexes – particularly in weak ligand fields – cannot
be well described by density functional methods. Different density functionals yield results which differ by up to 1 eV in
transition-metal complexes with sulfur-rich first coordination spheres. We attribute this failure to the fact that the high-spin
state is systematically favoured in Hartree–Fock-type theories, because Fermi correlation is included in the exact exchange,
while Coulomb correlation is not. We thus expect that the admixture of exact exchange to a given density functional will heavily
influence the energy splitting between states of different multiplicity. We demonstrate that the energy splitting depends
linearly on the coefficient of exact exchange admixture. This remarkable result is found for all the Fe(II)–S complexes studied.
From this observation we conclude in connection with experimental results that Becke's 20% admixture should be reduced to
about 15% if meaningful energetics are sought for transition-metal compounds. We rationalize that this reduction by 5% will
not affect the quality of the hybrid functional since we arrive at a slightly modified functional, which lies between the
pure density functional and the hybrid density functional, which both give good results for “standard” systems.
Received: 13 July 2001 / Accepted: 31 August 2001 / Published online: 16 November 2001 相似文献
10.
Robert J. Deltete 《Foundations of Chemistry》2008,10(3):187-221
This is the third of a series of essays on the development and reception of Wilhelm Ostwald’s energetics. The first essay
described the chemical origins of Ostwald’s interest in the energy concept and his motivations for seeking a comprehensive
science of energy. The second essay and the present one discuss his various attempts, beginning in 1891 and extending over
almost 3 years, to develop a consistent and coherent energetic theory. A final essay will consider reactions to this work
and Ostwald’s replies, and will also seek to evaluate his program of research. Ostwald’s project—to reconstruct physics and
chemistry “as a pure energetics”—is worth attending to for several reasons: first, because Ostwald did ground-breaking work
in chemistry (he was awarded a Nobel Prize in 1909 for his studies in catalysis and rates of reaction); second, because an
important school of physical chemistry formed around him at Leipzig, a school that promoted his ideas; and, finally, because
he was a prominent and vigorous participant in debates at the end of the nineteenth century concerning the proper course of
physical theory.
相似文献
Robert J. DelteteEmail: |
11.
Petra J. van Koningsbruggen Matthias Grunert Peter Weinberger 《Monatshefte für Chemie / Chemical Monthly》2003,134(2):183-198
Summary. The structures of linear chain Fe(II) spin-crossover compounds of α,β- and α,ω-bis (tetrazol-1-yl)alkane type ligands are
described in relation to their magnetic properties. The first threefold interlocked 3-D catenane Fe(II) spin-transition system,
[μ-tris(1,4-bis(tetrazol-1-yl)butane-N1,N1′) iron(II)] bis(perchlorate), will be discussed. An analysis is made among the
structures and the cooperativity of the spin-crossover behaviour of polynuclear Fe(II) spin-transition materials.
Corresponding author. E-mail: koning@iacgu7.chemie.uni-mainz.de
Received April 8, 2002; accepted April 18, 2002 相似文献
12.
采用密度泛函理论方法,对Cs以不同覆盖度吸附在石墨烯表面时系统的结构稳定性和场发射性能进行了研究.计算结果表明单原子Cs吸附在石墨烯表面的碳六元环的中心位置时系统的能量最低.随着Cs的覆盖度增加,碱金属Cs与石墨烯之间的吸附作用逐渐增强,(4×4)R 0°和(2×2)R 0°结构是稳定的.由于碱金属Cs的修饰作用,Cs/石墨烯体系的功函明显下降,且随着碱金属Cs的覆盖度增大,系统的功函逐渐减小.态密度的计算结果表明功函的下降主要与Cs和石墨烯之间的电子转移有关.随着覆盖度的增大,石墨烯的电子态逐渐向低能方向移动,系统的费米能级升高并导致材料的功函下降. 相似文献
13.
A method is described for the substoichiometric determination of traces of palladium by neutron activation analysis involving
the extraction of palladium with isonitrosoacetophenone. The sensitivity of the method is 0.005 μg of Pd. With 200 mg of silver
alloy containing 0.0005% palladium, the average of three determinations of Pd is 0.98 μg, which varies between 1.07 μg and
0.91 μg at 95% confidence limit. The time required for radiochemical purification and counting of the sample does not exceed
12 minutes.
Part of this work was presented at the International Conference on Modern Trends Activation Analysis, held in Gaithersburg,
Maryland, USA, October 7–11, 1968. 相似文献
14.
采用密度泛函理论方法,对Cs以不同覆盖度吸附在石墨烯表面时系统的结构稳定性和场发射性能进行了研究。计算结果表明单原子Cs吸附在石墨烯表面的碳六元环的中心位置时系统的能量最低。随着Cs的覆盖度增加,碱金属Cs与石墨烯之间的吸附作用逐渐增强,(4×4)R 0°和(2×2)R 0°结构是稳定的。由于碱金属Cs的修饰作用,Cs/石墨烯体系的功函明显下降,且随着碱金属Cs的覆盖度增大,系统的功函逐渐减小。态密度的计算结果表明功函的下降主要与Cs和石墨烯之间的电子转移有关。随着覆盖度的增大,石墨烯的电子态逐渐向低能方向移动,系统的费米能级升高并导致材料的功函下降。 相似文献
15.
J. D. Baker C. A. McGrath T. S. Hill R. Reifarth F. Tovesson 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(2):555-560
The Advanced Fuel Cycle Initiative (AFCI) and the Generation IV Reactor Initiative have demonstrated a lack of detailed neutron
cross sections for certain “minor” actinides. For some closed-fuel-cycle reactor designs more than 50% of reactivity will,
at some point, be derived from “minor” actinides that currently have poorly known or in some cases not measured (n,γ) and
(n,f) cross sections. Using a combination of resurrected techniques and new developments, we have made a series of targets
including highly enriched 239Pu, 240Pu, and 242Pu. Thus far, we have electrodeposited these actinide targets. The chemical purification and electodeposition techniques will
be described. 相似文献
16.
Makoto Misono 《Catalysis Surveys from Asia》2008,12(3):184-187
A big research project, 2002–2008, on environmental chemical technology has successfully been completed. The project aimed
at creation of scientific and technological basis for innovative chemical technologies for the conservation of the environment.
The outline of the project will briefly be described with some major achievements. 相似文献
17.
Jürgen Vogt Rolf-Horst Flagmeyer Johannes Heitmann Dietmar Lehmann Tilo Reinert Steffen Jankuhn Daniel Spemann Wolfgang Tröger Tilman Butz 《Mikrochimica acta》2000,133(1-4):105-111
The high-energy ion nanoprobe LIPSION at the University of Leipzig has been operational since October 1998. The ultrastable
single ended 3.5 MV SINLETRONTM accelerator supplies the H+ or He+ ion beam. A magnetic scanning system moves the focused beam across the sample. At present, a resolution of 150 nm in the
low current mode and 300 nm at 5 pA could be achieved.
The UHV grade experimental chamber is equipped with electron-, energy dispersive X-ray-, and particle detectors. They can
be used simultaneously to analyse the sample by means of PIXE (particle induced X-ray emission), RBS (Rutherford backscattering)
and in the case of thin samples STIM (scanning transmission ion microscopy).
A goniometer allows the application of channeling measurements in single crystals in combination with these methods.
The detection limits depend on the elements to be analysed and range from (1000⋯1) μg/g relative and (1⋯0.01) pg absolute.
The analysis is nondestructive, but the sample has to be vacuum resistant. Applications of the nanoprobe in the field of semiconductor
research, biomedicine, and archaeology will be described. 相似文献
18.
F. Ditrói S. Takács F. Tárkányi E. Corniani R. W. Smith M. Jech T. Wopelka 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):1147-1152
In the present work we demonstrate the development of a thin layer activation (TLA) method to be able to measure micrometer
wear or less by using radioactive tracing. In order to activate very swallow depths we decreased the bombarding energy to
the “linear” region of the cross-section curve. The disadvantage of the method is that the wear curve will be “linear” near
to the surface instead of “constant” as is the case with the usual (high energy) TLA. The advantage is that the activity of
the sample will be much lower and it is concentrated in the swallower studied depth. The other possible method is irradiation
under small angle (15 to 30° or even grazing incidence), which also causes a near-surface concentration of the activity produced.
Both methods are demonstrated with the most suitable nuclear reactions and some commonly used industrial materials. 相似文献
19.
Matthew Hudelson 《Journal of mathematical chemistry》2010,47(1):219-228
We expand on the work of Hosoya to describe a generalization of continued fractions called “tree expressions.” Each rooted
tree will be shown to correspond to a unique tree expression which can be evaluated as a rational number (not necessarily
in lowest terms) whose numerator is equal to the Hosoya index of the entire tree and whose denominator is equal to the tree
with the root deleted. In the development, we use Z(G) to define a natural candidate ζ(G, v) for a “vertex topological index” which is a value applied to each vertex of a graph, rather than a value assigned to the
graph overall. Finally, we generalize the notion of tree expression to “labeled tree expressions” that correspond to labeled
trees and show that such expressions can be evaluated as quotients of determinants of matrices that resemble adjacency matrices. 相似文献
20.
Boris N. Afanasyev Yulia P. Akulova Maria M. Kotlyar 《Journal of Solid State Electrochemistry》1997,1(1):68-76
The function Δ(ΔG
A
0), which is the difference of Gibbs energies characterizing surface-active substance (surfactant, SAS) adsorption at metal/solution
and air/solution surfaces, has been introduced. The equation connecting the function Δ(ΔG
A
0) with SAS ionization potential has been obtained using the elementary theory of donor-acceptor interactions. Published experimental
data on SAS adsorption at mercury, bismuth and gold have been used for Δ(ΔG
A
0) calculation. The dependence of Δ(ΔG
A
0) on ionization potentials can be described by an equation derived in this work. It has been demonstrated that the value of
the hydrophilicity of gold is much higher than the values for mercury and bismuth. The lifetime of SAS molecules at a metal
surface has been estimated. The question of the possibility of theoretica
l estimation of standard energies ΔG
A
0 characterizing SAS adsorption at a metal/solution surface has been discussed.
Received: 9 December 1996 / Accepted: 13 January 1997 相似文献