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1.
Time, structure, and fluctuations 总被引:1,自引:0,他引:1
Prigogine I 《Science (New York, N.Y.)》1978,201(4358):777-785
Fundamental conceptual problems that arise from the macroscopic and microscopic aspects of the second law of thermodynamics are considered. It is shown that nonequilibrium may become a source of order and that irreversible processes may lead to a new type of dynamic states of matter called "dissipative structures." The thermodynamic theory of such structures is outlined. A microscopic definition of irreversible processes is given, and a transformation theory is developed that allows one to introduce nonunitary equations of motion that explicitly display irreversibility and approach to thermodynamic equilibrium. The work of the group at the University of Brussels in these fields is briefly reviewed. In this new development of theoretical chemistry and physics, it is likely that thermodynamic concepts will play an ever-increasing role. 相似文献
2.
作为Maxwell-Boltzmann统计法(以下简称M-B统计法)的经典应用导出Maxwell速度分布律,只要求近独立子系处于热动平衡即可,至于系统是单原子分子或多原子分子其形式具有协变性,且重力场条件F=O并非必要(F为重力场中单位质量的粒子所受的力)。但由Boltzmann积分微分方程导出Maxwell速度分布律时,重力场条件F=O是必不可少的。用两种方法导出同一结果(从下面的推导可知两种方法本身是正确无误的),所需重力场条件又有上述之不同,似乎出现了一对矛盾。通过椎证分析,上述不同并非矛盾,只是一佯谬。 相似文献
3.
A basic thermodynamic cycle for the production of mechanical power from materials that may be made to contract forcibly and reversibly is described. The cycle differs from existing mechanical power cycles which generally employ expanding fluid as working substances. A "contraction turbine" operating on this cycle has been devised, which has collagen fiber as its working substance and salt solution as fuel and produces mechanical work directly from chemical free energy. Direct conversion of chemical to mechanical energy is routinely effected in muscle but not in usual man-made engines. 相似文献
4.
Lam RT Belenguer A Roberts SL Naumann C Jarrosson T Otto S Sanders JK 《Science (New York, N.Y.)》2005,308(5722):667-669
Directed chemical synthesis can produce a vast range of molecular structures, but the intended product must be known at the outset. In contrast, evolution in nature can lead to efficient receptors and catalysts whose structures defy prediction. To access such unpredictable structures, we prepared dynamic combinatorial libraries in which reversibly binding building blocks assemble around a receptor target. We selected for an acetylcholine receptor by adding the neurotransmitter to solutions of dipeptide hydrazones [proline-phenylalanine or proline-(cyclohexyl)alanine], which reversibly combine through hydrazone linkages. At thermodynamic equilibrium, the dominant receptor structure was an elaborate [2]-catenane consisting of two interlocked macrocyclic trimers. This complex receptor with a 100 nM affinity for acetylcholine could be isolated on a preparative scale in 67% yield. 相似文献
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Kubo R 《Science (New York, N.Y.)》1986,233(4761):330-334
This article is a personal reflection of the branch of nonequilibrium statistical mechanics called the linear response theory that has as its heart the fluctuation-dissipation thereom, which states that irreversible processes ip nonequilibrium are necessarily related to thermal fluctuations in equilibrium. Its origi lies in the Einstein relation for the diffusion constant and the mobility of a Brownian particle. The short history of the fluctuation-dissipation theorem is described. Then the linear response theory is brifly summarized and the meaning of stochastization is considered. The Langevin equation approach and its extensions are reviewed. 相似文献
7.
Individual polymers at thermal equilibrium were exposed to an elongational flow producing a high strain rate, and their dynamics were recorded with video fluorescence microscopy. The flow was turned on suddenly so that the entire evolution of molecular conformation could be observed without initial perturbations. The rate of stretching of individual molecules is highly variable and depends on the molecular conformation that develops during stretching. This variability is due to a dependence of the dynamics on the initial, random equilibrium conformation of the polymer coil. The increasing appearance at high strain rates of slowly unraveling hairpin folds is an example of nonergodic dynamics, which can occur when a statistical mechanical system is subjected to nonadiabatic, or "sudden," external forces. 相似文献
8.
Ultrafast spectroscopy was used to study vibrational energy transfer between vibrational reporter groups on different parts of a molecule in a liquid. When OH stretching vibrations of different alcohols were excited by mid-infrared laser pulses, vibrational energy was observed to move through intervening CH2 or CH groups, taking steps up and down in energy, ending up at terminal CH3 groups. For each additional CH2 group in the path between OH and CH3, the time for vibrational energy transfer increased by about 0.4 picosecond. 相似文献
9.
Because of the high temperatures prevailing in the lower atmosphere of Venus, its chemistry is dominated by the tendency toward thermodynamic equilibrium. From the atomic composition deduced spectroscopically, the thermodynamic equilibrium composition of the atmosphere of Venus is computed, and the following conclusions drawn. (i) There can be no free carbon, hydrocarbons, formaldehyde, or any other organic molecule present in more than trace amounts. (ii) The original atomic composition of the atmosphere must have included much larger quantities of hydrogen and a carbon/oxygen ratio = 0.5. (This ratio is now almost precisely 0.5.) (iii) The present atomic proportions of the atmosphere of Venus are so unique that an evolutionary mechanism involving two independent processes seems necessary, as follows. Water, originally present in large quantities, has been photodissociated in the upper atmosphere, and the resulting atomic hydrogen has been lost in space. The resulting excess oxygen has been very effectively bound to the surface materials. (iv) There must be some weathering process, for example, violent wind erosion, to disturb and expose a sufficient quantity of reduced surface material to react with the oxygen produced by photodissociation. 相似文献
10.
We report a method for controllably attaching an arbitrary number of charge dopant atoms directly to a single, isolated molecule. Charge-donating K atoms adsorbed on a silver surface were reversibly attached to a C60 molecule by moving it over K atoms with a scanning tunneling microscope tip. Spectroscopic measurements reveal that each attached K atom donates a constant amount of charge (approximately 0.6 electron charge) to the C60 host, thereby enabling its molecular electronic structure to be precisely and reversibly tuned. 相似文献
11.
Hammer NI Shin JW Headrick JM Diken EG Roscioli JR Weddle GH Johnson MA 《Science (New York, N.Y.)》2004,306(5696):675-679
The arrangement of water molecules around a hydrated electron has eluded explanation for more than 40 years. Here we report sharp vibrational bands for small gas-phase water cluster anions, (H2O)(4-6)- and (D2O)(4-6)-. Analysis of these bands reveals a detailed picture of the diffuse electron-binding site. The electron is closely associated with a single water molecule attached to the supporting network through a double H-bond acceptor motif. The local OH stretching bands of this molecule are dramatically distorted in the pentamer and smaller clusters because the excited vibrational levels are strongly coupled to the electron continuum. The vibration-to-electronic energy transfer rates, as revealed by line shape analysis, are mode-specific and remarkably fast, with the symmetric stretching mode surviving for less than 10 vibrational periods [50 fs in (H2O)4-]. 相似文献
12.
陈清硕 《扬州大学学报(农业与生命科学版)》1986,(1)
在统计力学中,熵是混乱度的度量。它一方面与土壤信息出现概率有关,一方面和土壤热力学系统中的自由能有关。土壤信息在约定前提下出现概率可反映土壤整体肥力水平,土壤热力学熵则更直接地反映了土壤系统的作功能力,是高度综合的土壤肥力指标。土壤系统耗散结构从热力学机率大的状态过渡到机率小的状态,是一个不断输入能量和获得信息的过程,为土壤肥力研究另辟蹊径。 相似文献
13.
Oya T Enoki T Grosberg AY Masamune S Sakiyama T Takeoka Y Tanaka K Wang G Yilmaz Y Feld MS Dasari R Tanaka T 《Science (New York, N.Y.)》1999,286(5444):1543-1545
A general approach is presented for creating polymer gels that can recognize and capture a target molecule by multiple-point interaction and that can reversibly change their affinity to the target by more than one order of magnitude. The polymers consist of majority monomers that make the gel reversibly swell and shrink and minority monomers that constitute multiple-point adsorption centers for the target molecule. Multiple-point interaction is experimentally proven by power laws found between the affinity and the concentration of the adsorbing monomers within the gels. 相似文献
14.
Gegenwart P Westerkamp T Krellner C Tokiwa Y Paschen S Geibel C Steglich F Abrahams E Si Q 《Science (New York, N.Y.)》2007,315(5814):969-971
We report thermodynamic measurements in a magnetic-field-driven quantum critical point of a heavy fermion metal, YbRh2Si2. The data provide evidence for an energy scale in the equilibrium excitation spectrum that is in addition to the one expected from the slow fluctuations of the order parameter. Both energy scales approach zero as the quantum critical point is reached, thereby providing evidence for a new class of quantum criticality. 相似文献
15.
MANWELL C 《Science (New York, N.Y.)》1960,132(3426):550-551
In contrast to hemerythrin from five different species of sipunculid worms, ecardine brachiopod Lingula hemerythrin has an oxygen equilibrium which is reversibly altered by pH changes, both the oxygen affinity (Bohr effect) and the interactions between oxygen-binding centers being a function of pH. The significance of these phenomena is discussed in view of the phylogenetic distribution of hemerythrin and the function of respiratory pigments. 相似文献
16.
The CUO molecule, formed from the reaction of laser-ablated U atoms with CO in a noble gas, exhibits very different stretching frequencies in a solid argon matrix [804.3 and 852.5 wave numbers (cm(-1))] than in a solid neon matrix (872.2 and 1047.3 cm(-1)). Related experiments in a matrix consisting of 1% argon in neon suggest that the argon atoms are interacting directly with the CUO molecule. Relativistic density functional calculations predict that CUO can bind directly to one argon atom (U-Ar = 3.16 angstroms; binding energy = 3.2 kilocalories per mole), accompanied by a change in the ground state from a singlet to a triplet. Our experimental and theoretical results also suggest that multiple argon atoms can bind to a single CUO molecule. 相似文献
17.
Molecular crowding on the cell surface 总被引:6,自引:0,他引:6
Strong steric interactions among proteins on crowded living cell surfaces were revealed by measurements of the equilibrium spatial distributions of proteins in applied potential gradients. The fraction of accessible surface occupied by mobile surface proteins can be accurately represented by including steric exclusion in the statistical thermodynamic analysis of the data. The analyses revealed enhanced, concentration-dependent activity coefficients, implying unanticipated thermodynamic activity even at typical cell surface receptor concentrations. 相似文献
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Kim N Huang SN Williams JS Li YC Clark AB Cho JE Kunkel TA Pommier Y Jinks-Robertson S 《Science (New York, N.Y.)》2011,332(6037):1561-1564
The ribonuclease (RNase) H class of enzymes degrades the RNA component of RNA:DNA hybrids and is important in nucleic acid metabolism. RNase H2 is specialized to remove single ribonucleotides [ribonucleoside monophosphates (rNMPs)] from duplex DNA, and its absence in budding yeast has been associated with the accumulation of deletions within short tandem repeats. Here, we demonstrate that rNMP-associated deletion formation requires the activity of Top1, a topoisomerase that relaxes supercoils by reversibly nicking duplex DNA. The reported studies extend the role of Top1 to include the processing of rNMPs in genomic DNA into irreversible single-strand breaks, an activity that can have distinct mutagenic consequences and may be relevant to human disease. 相似文献
20.
Wong KL Pawin G Kwon KY Lin X Jiao T Solanki U Fawcett RH Bartels L Stolbov S Rahman TS 《Science (New York, N.Y.)》2007,315(5817):1391-1393
We found that anthraquinone diffuses along a straight line across a flat, highly symmetric Cu111 surface. It can also reversibly attach one or two CO2 molecules as "cargo" and act as a "molecule carrier," thereby transforming the diffusive behavior of the CO2 molecules from isotropic to linear. Density functional theory calculations indicated a substrate-mediated attraction of approximately 0.12 electron volt (eV). Scanning tunneling microscopy revealed individual steps of the molecular complex on its diffusion pathway, with increases of approximately 0.03 and approximately 0.02 eV in the diffusion barrier upon attachment of the first and second CO2 molecule, respectively. 相似文献