Surface conservation laws at microscopically diffuse interfaces

In studies of interfaces with dynamic chemical composition, bulk and interfacial quantities are often coupled via surface conservation laws of excess surface quantities. While this approach is easily justified for microscopically sharp interfaces, its applicability in the context of microscopically diffuse interfaces is less theoretically well-established. Furthermore, surface conservation laws (and interfacial models in general) are often derived phenomenologically rather than systematically. In this article, we first provide a mathematically rigorous justification for surface conservation laws at diffuse interfaces based on an asymptotic analysis of transport processes in the boundary layer and derive general formulae for the surface and normal fluxes that appear in surface conservation laws. Next, we use nonequilibrium thermodynamics to formulate surface conservation laws in terms of chemical potentials and provide a method for systematically deriving the structure of the interfacial layer. Finally, we derive surface conservation laws for a few examples from diffusive and electrochemical transport.     

Are Laws of Nature and Scientific Theories Peculiar in Chemistry? Scrutinizing Mendeleev's Discovery

The problem of the peculiarcharacter of chemical laws and theories is a central topic in philosophy of chemistry. Oneof the most characteristic and, at the sametime, most puzzling examples in discussions onchemical laws and theories is Mendeleev'speriodic law. This law seems to be essentiallydifferent in its nature from the exact laws ofclassical physics, the latter being usuallyregarded as a paradigm of science byphilosophers. In this paper the main argumentsconcerning the peculiar character of chemicallaws and theories are examined. The laws ofchemistry are natural laws to the same extentas are the laws of physics. The law discoveredby Mendeleev is a normal law of nature. It isnot a law of physics, nevertheless, it is exactin the same philosophical sense as are the lawsof physics. The periodic system of chemicalelements was established by constructing anidealized system of idealized elements. Thefundamental idealization substantiated byexperimental chemistry was the chemicalelement as a place in the periodicsystem.     

Rheological characterisation of bis-urea based viscoelastic solutions in an apolar solvent

The rheological properties of hydrogen bonded reversible aggregates in apolar solvent have been investigated. The zero shear viscosity, the plateau modulus and the terminal viscoelastic relaxation time exhibit power laws dependencies with the concentration that have been compared with the behaviours expected for reversible polymers. It appears that the dynamics originate from scission/recombination mechanisms. Moreover, the growth of the aggregates with concentration follows the laws observed and predicted for worm-like micelles at low concentrations allowing the length of the aggregates to be estimated 500 nm at 3 g L(-1). However, at the highest concentrations investigated, deviations from the power laws suggest the presence of some intrinsic chain stopper poisons in the solutions.     

Excess thermodynamic quantities in binary systems of non electrolytes.: Different ways of calculating excess compressibilities.

Recent work involved the evaluation of ideal and excess quantities for a wide-ranging set of thermodynamic variables. A literature search revealed that unjustifiable assumptions are frequently made in establishing the expressions of ideal mixing laws, giving rise to erroneous values of corresponding quantities.A large number of such approximate laws have been proposed to estimate “excess” isothermal and isentropic compressibility. The knowledge of rigorous ideal mixing laws allows the difference between pseudo-excess and exact excess compressibility to be evaluated. This provides us with an excellent tool for recalculating exact excess quantities from erroneous data likely to be found in the literature. The amplitude of the various differences has been illustrated using examples taken from among the properties of the water—acetonitrile system.     

Energy trapping in mixed molecular crystals

We obtain numerically decay laws due to trapping on strongly-disordered two- and three-dimensional lattices, on which the migration proceeds through long-range dipolar steps. We find that the analytical decay laws for ordered lattices extend smoothly to disordered structures and that long-range steps override percolative effects.     

Scaling laws for charge transfer in multiply bridged donor/acceptor molecules in a dissipative environment

The ability of multiple spatial pathways to sum coherently and facilitate charge transfer is examined theoretically. The role of multiple spatial pathways in mediating charge transfer has been invoked several times in the recent literature while discussing charge transfer in proteins, while multiple spatial pathways are known to contribute to charge transport in metal-molecule-metal junctions. We look at scaling laws for charge transfer in donor-bridge-acceptor (D-B-A) molecules and show that these scaling laws change significantly when environment-induced dephasing is included. In some cases, D-B-A systems are expected to show no enhancement in the rate of charge transfer with the addition of multiple degenerate pathways. The origins of these different scaling laws are investigated by looking at which Liouville space pathways are active in different dephasing regimes.     

Universal scaling laws of diffusion: application to liquid metals

This work focuses on the universal scaling laws, which relate scaled diffusivity to excess entropy in fluids and their mixtures. The derivation of the new scaling law for diffusivity proposed recently [A. Samanta, Sk. M. Ali, and S. K. Ghosh, Phys. Rev. Lett. 92, 145901 (2004)] is discussed in details highlighting the nature of approximations involved. Also the applicability of the scaling law is extended to a new class of liquids, viz., liquid metals. The results calculated based on the scaling laws are shown to be in very good agreement with the simulation results for liquid Rb and Cs metals along the liquid-vapor coexistence curve corresponding to a wide variation of temperature and density. The new universal scaling law discussed here is superior to the earlier empirically proposed scaling laws and provides a very simple route to calculate a dynamical quantity such as diffusivity from an equilibrium property such as the radial distribution function.     

Power laws for the establishment of a stationary concentration in a binary solution droplet growing in a vapor-gas medium

The kinetic laws are found for establishing a stationary concentration in solution droplets growing under diffusion and free-molecular regimes in a vapor-gas medium composed of two condensing vapors and a passive gas. Parameters of these laws are related to the thermodynamic and kinetic characteristics of condensing substances. Original Russian Text ? F.M. Kuni, A.A. Lezova, 2009, published in Kolloidnyi Zhurnal, 2009, Vol. 71, No. 4, pp. 563–565.     

Pyrolysis of polyaromatic heterocyclics

The oxidative and thermal degradation of some polyaromatic heterocyclics in air and helium has been studied by dynamic thermogravimetry to 1400°C. Decomposition characteristics are the result of polymer structure, molecular weight, and method of preparation. Decomposition in air follows first-order rate laws, while degradation under inert conditions does not appear to follow simple rate laws. The activation energies for the decomposition in air are between 30 and 35 kcal./mole for most polymers investigated. Carbonaceous polymer residues at 1400°C. are present in varying quantities.     

Evaluation of membrane fouling models based on bench-scale experiments: A comparison between constant flowrate blocking laws and artificial neural network (ANNs) model

Both the blocking laws and ANNs models have been used frequently in membrane filtration process in recent years. However, specially applying these models in constant flowrate condition with synthetic surface water is rare case. Further, there has no literature been found to compare the performance of purely mathematic and mechanical model (blocking laws) with the so-called “black-box” ANNs model. In this study, the performance of both blocking laws and ANNs model is evaluated. The dominant fouling mechanisms in specific experimental period also is identified based on the individual model fitting performance.     

Transport de charges électriques par convection d'un liquide diélectrique dans une conduite cylindrique métallique

We first recal the laws of turbulent-laminar flow in a circular cylindrical tube. Introducing these laws into the diffusion-convection equations with migration, we can calculate the electrical charge transport by convection of a dielectric liquid in a cylindrical tube.     

Prior statistical distributions implied by dynamical threshold laws for molecular collisions

Dynamical threshold laws imply a particular translational energy dependence of the prior distribution function used in surprisal theory. The microcanonical prior distribution is not compatible with collinear and coplanar threshold laws but is compatible with three-dimensional dynamics.     

Analyse theorique des lois cinetiques couramment utilisees en thermoanalyse pour l'etude des reactions Solide-Gaz

Many authors use kinetic laws for the thermal analysis study of heterogeneous reactions which are essentially thermal decompositions. The authors carry out the theoretical analysis of six diffusion laws and show that only three of them are theoretically valid, because only these take into account all the relevant parameters. The definition of the word “diffusion” is discussed, and it is shown that the diffusion phenomena which often appear at the end of certain decompositions, cannot represent what really happens in the solid.     

On the Nature of Nonequilibrium Power-Law Distributions (the Zipf and Guetenberg—Richter Laws)

The empirical Zipf and Guetenberg-Richter power laws are much less informative than it is usually believed. These laws do not reflect the real microdynamics contained in the time series of dynamical variables measured to analyze the evolution of complex systems.     

Scaling tests of late stages of spinodal decomposition in PC/PMMA blends

Time-resolved light scattering studies were undertaken to elucidate the kinetics of phase separation in polycarbonate (PC)/polymethyl methacrylate (PMMA) blends. The 40:60 PC/PMMA blend undergoes thermally induced phase separation through spinodal decomposition. Temperature jump experiments were carried out from a single-phase to a two-phase temperature region. The general trend of spinodal decomposition in this blend system is nonlinear in character and obeys the power laws. The time evolution of scattering curves was analyzed in accordance with dynamical scaling laws for self-similarity and the shape of scaled structure functions.     

Calibration laws based on multiple linear regression applied to matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry

Operation of any mass spectrometer requires implementation of mass calibration laws to translate experimentally measured physical quantities into a m/z range. While internal calibration in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) offers several attractive features, including exposure of calibrant and analyte ions to identical experimental conditions (e.g. space charge), external calibration affords simpler pulse sequences and higher throughput. The automatic gain control method used in hybrid linear trap quadrupole (LTQ) FT-ICR-MS to consistently obtain the same ion population is not readily amenable to matrix-assisted laser desorption/ionization (MALDI) FT-ICR-MS, due to the heterogeneous nature and poor spot-to-spot reproducibility of MALDI. This can be compensated for by taking external calibration laws into account that consider magnetic and electric fields, as well as relative and total ion abundances. Herein, an evaluation of external mass calibration laws applied to MALDI-FT-ICR-MS is performed to achieve higher mass measurement accuracy (MMA).     

Development of agribiotechnology and biosafety regulations used to assess safety of genetically modified crops in Bangladesh

Bangladesh is on the verge of adopting genetically modified (GM) crops for commercial cultivation and consumption as feed and food. Most of the laboratories are engaged in tissue culture and molecular characterization on plants, whereas some have started living modified organism research with shortages of trained manpower, infrastructure, and funding. Nutritionally improved Golden Rice, biotech brinjal, and late blight-resistant potato are in contained trials in a greenhouse, and potato ring spot virus-resistant papaya is in the process of approval for a field trial. The government has taken some initiative in support of GM organism research, which include the formation of a Biotechnology Department in all institutes and the formation of the apex body, the National Task Force Committee on Biotechnology of Bangladesh under the chairpersonship of the Prime Minister. Biosafety policy guidelines and related aspects of biotechnology issues have been approved, and the laws are in the process of being promulgated. Being a party to the Cartagena Protocol, proper biosafety measures are regulated by the appropriate authority as stated. Although there are no laws made yet directly for biosafety of GM crops/foods, the relevant laws on agriculture, medicine, food, import, trade, environment, etc. may suffice and explain the situation.     

Note Concerning the Concepts of Reaction Numbers,Independent Reactions and Resistant Groups in Chemical Thermodynamics and Kinetics

A linear algebraic characterization for sets of independent reactions, independent reaction numbers, conservation laws and resistant groups for both equilibrium and kinetic systems is suggested. Basing on the ranks of two stochiometric matrices N and M, these concepts are discussed and formulas given for setting up of independent sets of equilibrium and kinetic equations. The difference in the definition of independent reaction numbers for these two types of systems is pointed out. A brief consideration is devoted to the transformations of equilibrium and kinetic equations induced by transformation from one set of linearly independent reactions to another. Finally the conservation laws are formulated as chemical invariants within the N, M framework.     

Identification of the elastic properties of an artificial capsule membrane with the compression test: effect of thickness

The mechanical properties of a capsule membrane are evaluated by means of a compression experiment between two parallel plates. Since large deformations of the membrane are involved, the choice of the wall material constitutive law is essential. In this paper, we explore different classical laws to describe the behavior of the membrane and evaluate also the limit of application of the thin shell approximation. A numerical study of the compression process is performed using Abaqus software and an inverse method is used to identify the material constants of the constitutive laws. The comparison between the model predictions and experimental measurements on capsules with serum albumin-alginate membranes, indicates that the thin shell approximation is valid only for thickness to radius ratios up to 5% and that thick membranes obey non linear elastomer type constitutive laws. The Young modulus of the membrane material is found to increase non-linearly with membrane thickness, thus indicating that fabrication of thicker serum albumin-alginate walls results in capsules stiffer than expected.     

Mathematical functions for the analysis of luminescence decays with underlying distributions: 2. Becquerel (compressed hyperbola) and related decay functions

The Becquerel (compressed hyperbola) decay law is analyzed in detail and shown to be an interesting approach for the analysis of complex luminescence decays. A decay function unifying the modified Kohlrausch and Becquerel decay laws is also introduced. It is proposed that the analysis of luminescence decays with a sum of Becquerel functions is a powerful alternative to the usual sum of exponentials. It is also shown that some complex decay laws can be written as a sum of an infinite number of exponentials and have for this reason an infinite but discrete spectrum of rate constants.