Molecular theory of underdamped dielectric relaxation: understanding collective effects in dipolar liquids

A molecular theory of underdamped dielectric relaxation of a dense dipolar liquid is presented. This theory properly takes into account the collective effects that are present (due to strong intermolecular correlations) in a dipolar liquid. For small rigid molecules, the theory again leads to a three-variable description which, however, is somewhat different from the traditional version. In particular, two of the three parameters are collective in nature and are determined by the orientational pair correlation function. A detailed comparison between the theory and the computer simulation results of Neria and Nitzan is performed and an excellent agreement is obtained without the use of any adjustable or free parameter - the calculation is fully microscopic. The theory can also provide a systematic description of the Poley absorption often observed in dipolar liquids in the high-frequency regime.

Functions Of Cytochrome-C In Regulation Of Electron-Transfer And Protein Folding

Cytochrome c, a "mobile electron carrier" of the mitochondrial respiratory chain, also occurs in detectable amounts in the cytosol, and can receive electrons from cytochromes present in endoplasmic reticulum and plasma membranes as well as from superoxide and ascorbate. The pigment was found to dissociate from mitochondrial membranes in liver and kidney when rats were subjected to heat exposure and starvation, respectively. Treating cytochrome c with hydroxylamine gives a partially deaminated product with altered redox properties; decreased stimulation of respiration by deficient mitochondria, increased reduction by superoxide, and complete loss of reducibility by plasma membranes. Mitochondria isolated from brown adipose tissue of cold-exposed rats are found to be sub-saturated with cytochrome c. The ability of cytochrome c to reactivate reduced ribonuclease is now reinterpreted as a molecular chaperone role for the hemoprotein.

Gradient solid electrolytes for thermodynamic measurements: System Na2CO3-Na2SO4

The thermodynamic properties of Na2CO3-Na2SO4 solid solution with hexagonal structure have been measured in the temperature range of 873 to 1073 K, using a composite-gradient solid electrolyte. The cell used can be represented as The composite-gradient solid electrolyte consisted of pure Na2CO3 at one extremity and the solid solution under study at the other, with variation in composition across the electrolyte. A CO2 + O2 + Ar gas mixture was used to fix the chemical potential of sodium at each electrode. The Nernstian response of the cell to changes in partial pressures of CO2 and O2 at the electrodes has been demonstrated. The activity of Na2CO3 in the solid solution was measured by two techniques. In the first method, the electromotive force (emf) of the cell was measured with the same CO2 + O2 + Ar mixture at both electrodes. The resultant emf is directly related to the activity of Na2CO3 at the solid solution electrode. By the second approach, the activity was calculated from the difference in compositions Of CO2 + O2 + Ar mixtures at the two electrodes required to produce a null emf. Both methods gave identical results. The second method is more suitable for gradient solid electrolytes that exhibit significant electronic conduction. The activity of Na2CO3 exhibits positive deviation from Raoult's law. The excess Gibbs' energy of mixing of the solid solution can be represented using a subregular solution model such as the following: DELTAG(E) = X(1 - X)[6500(+/-200)X + 3320(+/-80)(1 - X)J mol-1 where X is the mole fraction of Na2CO3. By combining this information with the phase diagram, mixing properties of the liquid phase are obtained.

Chance constrained uncertain classification via robust optimization

This paper studies the problem of constructing robust classifiers when the training is plagued with uncertainty. The problem is posed as a Chance-Constrained Program (CCP) which ensures that the uncertain data points are classified correctly with high probability. Unfortunately such a CCP turns out to be intractable. The key novelty is in employing Bernstein bounding schemes to relax the CCP as a convex second order cone program whose solution is guaranteed to satisfy the probabilistic constraint. Prior to this work, only the Chebyshev based relaxations were exploited in learning algorithms. Bernstein bounds employ richer partial information and hence can be far less conservative than Chebyshev bounds. Due to this efficient modeling of uncertainty, the resulting classifiers achieve higher classification margins and hence better generalization. Methodologies for classifying uncertain test data points and error measures for evaluating classifiers robust to uncertain data are discussed. Experimental results on synthetic and real-world datasets show that the proposed classifiers are better equipped to handle data uncertainty and outperform state-of-the-art in many cases.

Structure of N-tert-butyloxycarbonyl-[alpha]-aminoisobutyryl-DL-pipecolyl-[alpha]-aminoisobutyric acid methyl ester

C20H35N3O6 (Boc-Aib-DL-Pip-Aib-OMe, Boc = tert-butyloxycarbonyl, Aib = alpha-aminoisobutyric acid, Pip = pipecolic acid, OMe = methoxy), M(r) = 413.5, monoclinic, P2(1)/c, a = 18.055 (3), b = 15.048 (3), c = 17.173 (3) angstrom, beta = 91.7 (1)-degrees, V = 4663.8 (9) angstrom3, Z = 8, D(m) = 1.16, D(x) = 1.178 Mg m-3, lambda(Mo Kalpha) = 0.71069 angstrom, mu = 0.081 mm-1, F(000) = 1792, T = 297 K. The final R value for 4925 [I greater-than-or-equal-to 3sigma(I)] reflections is 0.065 (wR = 0.067). The peptide backbone of the two independent molecules in the asymmetric unit is folded at the -Aib-Pip- sequence to form a type-I (I') beta-bend stabilized by a 1 <-- 4 intramolecular N-H...O=C hydrogen bond between the Aib(3) peptide N-H and Boc urethane C=O groups.

The principle of microscopic reversibility in organic chemistry - a critique

The principle of microscopic reversibility is one of the few generalising principles used in organic chemistry which have their roots in the fundamental laws of thermodynamics. It has, therefore, been highly popular. However, although the principle has some important uses, its general application is not without pitfalls. The principle is easy to misunderstand and to misapply: indeed, some of its formulations are semantically dubious. The principle is most dangerous when used as a charm, for it is more subtle than some of its formulations suggest. But above all, the principle may not be used for deducing or disproving the mechanism of a reaction, except when the mechanism in the reverse direction is known independently. For, such use is, perhaps, the deadliest misapplication.

A polynomial bound on the number of light cycles in an undirected graph

Let G be an undirected graph with a positive real weight on each edge. It is shown that the number of minimum-weight cycles of G is bounded above by a polynomial in the number of edges of G. A similar bound holds if we wish to count the number of cycles with weight at most a constant multiple of the minimum weight of a cycle of G.

Solution grafting of maleic anhydride onto polyethylene and compatibilization of polyetylene-nylon blends

Maleic anhydride (MAH) has been grafted onto high density polyethylene (HDPE) with benzoyl peroxide (BOP) initiator in toluene solution. Maximum degree of grafting (12%) without crosslinking has been obtained using MAH/HDPE and BOP/HDPE weight ratios of 1.0 and 0.15 respectively, at 110 degrees C. The HDPE-g-MAH compatibilizer is found to drastically reduce the dispersed phase size and also to produce homogeneous blends for relatively low concentrations of dispersed phase in HDPE/nylon blends. Addition of this compatibilizer results in increase of tensile strength and modulus with increasing nylon content of HDPE/nylon blends, while the opposite is found for the blends without any added compatibilizer.

Scheduling expression trees for delayed-load architectures

In this paper we consider the problem of scheduling expression trees on delayed-load architectures. The problem tackled here takes root from the one considered in [Proceedings of the ACM SIGPLAN '91 Conf. on Programming Language Design and Implementation, 1991. p. 256] in which the leaves of the expression trees all refer to memory locations. A generalization of this involves the situation in which the trees may contain register variables, with the registers being used only at the leaves. Solutions to this generalization are given in [ACM Trans. Prog. Lang. Syst. 17 (1995) 740, Microproc. Microprog. 40 (1994) 577]. This paper considers the most general case in which the registers are reusable. This problem is tackled in [Comput. Lang, 21 (1995) 49] which gives an approximate solution to the problem under certain assumptions about the contiguity of the evaluation order: Here we propose an optimal solution (which may involve even a non-contiguous evaluation of the tree). The schedule generated by the algorithm given in this paper is optimal in the sense that it is an interlock-free schedule which uses the minimum number of registers required. An extension to the algorithm incorporates spilling. The problem as stated in this paper is an instruction scheduling problem. However, the problem could also be rephrased as an operations research problem with a difference in terminology. (C) 2002 Elsevier Science B.V. All rights reserved.

Dicopper(II) complexes showing DNA hydrolase activity and monomeric adduct formation with bis(4-nitrophenyl)phosphate

Ferromagnetic dicopper(II) complexes [Cu(2)(mu-O(2)CCH(3))(mu-OH)(L)(2)(mu-L(1))](PF(6))(2), where L = 1,10-phenanthroline (phen), L(1) = H(2)O in 1 and L = dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), L(1) = CH(3)CN in 2, are prepared and structurally characterized. Crystals of 1 and 2 belong to the monoclinic space group of P2(1)/n and P2(1)/m, respectively. The copper(II) centers display distorted square-pyramidal geometry having a phenanthroline base and two oxygen atoms of the bridging hydroxo and acetate group in the basal plane. The fifth coordination site has weak axially bound bridging solvent molecule H(2)O in 1 and CH(3)CN in 2. The Cu center dot center dot center dot Cu distances are 3.034 and 3.046 angstrom in 1 and 2, respectively. The complexes show efficient hydrolytic cleavage of supercoiled pUC19 DNA as evidenced from the mechanistic studies that include T4 DNA ligase experiments. The binuclear complexes form monomeric copper(II) adducts [Cu(L)(2)(BNPP)](PF(6)) (L = phen, 3; dpq, 4) with bis(4-nitrophenyl)phosphate (BNPP) as a model phosphodiester. The crystal structures of 3 and 4 reveal distorted trigonal bipyramidal geometry in which BNPP binds through the oxygen atom of the phosphate. The kinetic data of the DNA cleavage reactions of the binuclear complexes under pseudo- and true-Michaelis-Menten conditions indicate remarkable enhancement in the DNA hydrolysis rate in comparison to the control data. (C) 2011 Elsevier B.V. All rights reserved.

Ion-Acoustic Solitary Waves in Multicomponent Plasmas with Negative Ions

By using the perturbation technique, a Kortewege-de-Vries (K-dV) equation for a multicomponent plasma with negative ions and isothermal electrons has been derived. We have discussed the stationary solutions of K-dV equation and it has shown that in the presece of multiple ions, the amplitude of solitons exhibits interesting behaviour, especiallY when the negative ions are present.

Bounds on Probability of Error in Decision Feedback Equalizers

Evaluation of the probability of error in decision feedback equalizers is difficult due to the presence of a hard limiter in the feedback path. This paper derives the upper and lower bounds on the probability of a single error and multiple error patterns. The bounds are fairly tight. The bounds can also be used to select proper tap gains of the equalizer.