The energy—momentum tensor, the trace identity and the Casimir effect

The trace identity associated with the scale transformation x^Μ → x′^Μ = e^-ρx^Μ on the Lagrangian density for the noninteracting electromagnetic field in the co-variant gauge is shown to be violated on a single plate on which the Dirichlet boundary conditionA ^Μ(t, x¹, x², x³ = -a) = 0 is imposed. It is however respected in free space, i.e. in the absence of the plate. These results reinforce our assertions in an earlier paper where the same exercise was carried out using the Lagrangian density for the free, massive, real scalar field in 2 + 1 dimensions.     

A continuous method for computing bounds in integer quadratic optimization problems

In the graph partitioning problem, as in other NP-hard problems, the problem of proving the existence of a cut of given size is easy and can be accomplished by exhibiting a solution with the correct value. On the other hand proving the non-existence of a cut better than a given value is very difficult. We consider the problem of maximizing a quadratic function x ^T Q x where Q is an n × n real symmetric matrix with x an n-dimensional vector constrained to be an element of {–1, 1} ⁿ . We had proposed a technique for obtaining upper bounds on solutions to the problem using a continuous approach in [4]. In this paper, we extend this method by using techniques of differential geometry.     

5-Phenylpyridazinones-A serendipitous route from coumarins

A new route of the ring transformation has been discovered during the reaction of 4-bromomethylcoumarins with hydrazine hydrate leading to the formation of pharmacologically important pyridazinones in a single step with very high yields. These so obtained pyridazinones have the potential for further functional group interconversions.     

Routing and Admission Control in General Topology Networks with Poisson Arrivals

Emerging high-speed networks will carry traffic for services such as video-on-demand and video teleconferencing that require resource reservation along the path on which the traffic is sent. High bandwidth-delay product of these networks prevents circuit rerouting, i.e., once a circuit is routed on a certain path, the bandwidth taken by this circuit remains unavailable for the duration (holding time) of this circuit. As a result, such networks will need effectiveroutingandadmission controlstrategies. Recently developed on-line routing and admission control strategies have logarithmic competitive ratios with respect to theadmission ratio(the fraction of admitted circuits). Such guarantees on performance are rather weak in the most interesting case where the rejection ratio of the optimum algorithm is very small or even 0. Unfortunately, these guarantees cannot be improved in the context of the considered models, making it impossible to use these models to identify algorithms that are going to perform well in practice. In this paper we develop routing and admission control strategies for a probabilistic model, where the requests for virtual circuits between any two points arrive according to a Poisson process and where the circuit holding times are exponentially distributed. Our model is close to the one that was developed to analyze and tune the (currently used) strategies for managing traffic in long-distance telephone networks. We strengthen this model by assuming that the rates of the Poisson processes (the “traffic matrix”) are unknown to the algorithm and are chosen by the adversary. Our strategy is competitive with respect to the expectedrejection ratio. More precisely, it achieves an expected rejection ratio of at mostR* + ?, whereR* is the optimum expected rejection ratio. The expectations are taken over the distribution of the request sequences, and, whereris the maximum fraction of an edge bandwidth that can be requested by a single circuit. Our result should be viewed in the context of the previous competitive routing and admission control strategies that requirer ≤ 1/log n, but are not able to formally analyze the (intuitively clear) relation betweenrand the performance achievable in realistic situations.     

Projection methods for the numerical solution of non-self-adjoint elliptic partial differential equations

We compare the relative performances of two iterative schemes based on projection techniques for the solution of large sparse nonsymmetric systems of linear equations, encountered in the numerical solution of partial differential equations. The Block–Symmetric Successive Over-Relaxation (Block-SSOR) method and the Symmetric–Kaczmarz method are derived from the simplest of projection methods, that is, the Kaczmarz method. These methods are then accelerated using the conjugate gradient method, in order to improve their convergence. We study their behavior on various test problems and comment on the conditions under which one method would be better than the other. We show that while the conjugate-gradient-accelerated Block-SSOR method is more amenable to implementation on vector and parallel computers, the conjugate-gradient accelerated Symmetric–Kaczmarz method provides a viable alternative for use on a scalar machine.     

Electrochemical synthesis of ZnO coatings from water–isopropanol mixed baths: control over oriented crystallization

Electroreduction of an aqueous solution of a soluble Zn salt results in the deposition of ZnO crystallites with hexagonal columnar morphology. The crystallites grow with their long axes normal to the substrate resulting in adherent coatings with a strong c-axis orientation. This phenomenon is on account of the polarity of the 001 crystal face combined with the high dielectric constant of water. When the dielectric constant of the solvent is changed by making a mixture of water and isopropanol, there is a change in the direction of orientation of the coating. The switch takes place in the sequence [001] → [102], [103] → unoriented → [100], [110] as the isopropanol concentration is raised in a step-wise manner to 60% (v/v). The switch in orientation is caused by the tilt of the long axes of the hexagonal columns of ZnO with respect to the normal to the substrate. Above 60% isopropanol concentration, ZnO deposition is suppressed. This work demonstrates solution-mediated control over oriented crystallization.     

Analysis of the allergenic proteins in black tiger prawn (Penaeus monodon) and characterization of the major allergen tropomyosin using mass spectrometry

Crustaceans are the third most prevalent cause of food‐induced anaphylaxis after peanuts and tree nuts. The severity of the allergenic proteins depends mainly on the amino acid sequence that induces production of IgE antibodies. In black tiger prawn (Penaeus monodon), the crude protein extract was profiled and its allergenic potency was examined against patient's sera. Proteins having strong immunoreactivity with patient's IgE were characterized using peptide mass fingerprinting (PMF). Tropomyosin (TM) (33 kDa), myosin light chain (20 kDa), and arginine kinase (40 kDa) were identified as allergenic proteins. Tropomyosin, the most abundant and potent allergen, was purified using ion‐exchange chromatography for de novo sequencing experiments. Using bottom up tandem mass spectrometry, the full amino acid sequence was achieved by a combination of matrix‐assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) tandem mass spectrometry (QqToF). Myosin light chain and arginine kinase were also characterized, and their related peptides were de novo sequenced using the same approach. The immunological reactivity of the crude prawn extracts and purified TM samples were analyzed using a large number of patients' sera. A signature peptide was assigned for the TM protein for future quantification work of black tiger prawn TM levels in different matrices (i.e. water, air, food) in the seafood industry. Copyright © 2010 John Wiley & Sons, Ltd.     

Polytype Transformations in the SO42– Containing Layered Double Hydroxides of Zinc with Aluminum and Chromium: The Metal Hydroxide Layer as a Structural Synthon

Solid–solid inter‐polytype transformations are observed during the thermal dehydration of sulfate‐containing layered double hydroxides (LDHs). The metal hydroxide layer behaves as a “structural synthon” and the interconversion of polytypes of rhombohedral and hexagonal symmetries takes place by rigid translations of successive layers by (± 1/3, ± 2/3) relative to one another in the ab plane. These translations are selected among the many possible, as they preserve the coincidence of the symmetry elements of the individual layers and thereby conserve the threefold symmetry of the crystal across the inter‐polytype conversions. As a result, these transformations are enthalpically not expensive. These translations are facilitated at near ambient temperatures (30–60 °C) by the reversible dehydration of the LDH, which involves the deinsertion/insertion of water molecules within the restricted space of the interlayer region.     

Layered double hydroxides as potential chromate scavengers

The LDH of Ni with Fe, having the formula Ni(1-x)Fe(x)(OH)2(A(n-))(x/n)yH2O (A = NO3-, Cl-; x = 0.25, 0.33), scavenges CrO4(2-) ions from solution throughout the concentration range examined (0.00625-0.25 N). The CrO4(2-) uptake capacity is independent of the anion in the starting LDH but is higher when x = 0.25 (3.60 meq g(-1)) as compared to x = 0.33 (2.40 meq g(-1)). These values are higher than those observed for control compounds beta-Ni(OH)2 (1.86 meq g(-1)) and FeO(OH) (1.26 meq g(-1)), which do not have any interlayer chemistry, showing that chromate uptake takes place by its incorporation in the interlayer region by a stoichiometric anion-exchange reaction, rather than by adsorption. Nevertheless, the interaction between the LDH and the chromate ions is weak. The weak interaction is due to the mismatch between the symmetry of the chromate ions and the symmetry of the interlayer site, which introduces turbostratic disorder in the chromate-intercalated LDHs. The chromate ions can be completely leached out by soaking the LDH in a sodium carbonate solution.