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.     

Investigation of third-order nonlinear optical properties of conjugated benzodioxal derivatives

An investigation of third-order nonlinear optical characterization of newly synthesized conjugated benzodioxal derivatives has been done by using nanosecond Z-scan technique at 532 nm. The molecules demonstrate self-defocusing effect with intensity dependent refractive index (n₂) of the order of 10⁻¹⁴ cm²/W. The measured molecular TPA cross-section is ranging from 2.47 ×10⁻⁴⁷ cm⁴ s/photon to 6.00 cm⁴ s/photon. Their input-output curves indicate that there is a clear optical power limiting behavior with the limiting threshold in the range 125-181 μJ. The main factor to exhibit the observed nonlinearity in these molecules is the presence of charge donor and acceptor groups. The increased conjugation length increases the nonlinear refraction and increased electron density enhances the nonlinear absorption. The molecules exhibit good nonlinear optical properties, comparable to those of regular azoaromatic compounds. Therefore, the molecules investigated here are promising candidates for optical power limiting devices.     

In silico exploratory study using structure–activity relationship models and metabolic information for prediction of mutagenicity based on the Ames test and rodent micronucleus assay

The mutagenic potential of chemicals is a cause of growing concern, due to the possible impact on human health. In this paper we have developed a knowledge-based approach, combining information from structure–activity relationship (SAR) and metabolic triggers generated from the metabolic fate of chemicals in biological systems for prediction of mutagenicity in vitro based on the Ames test and in vivo based on the rodent micronucleus assay. In the first part of the work, a model was developed, which comprises newly generated SAR rules and a set of metabolic triggers. These SAR rules and metabolic triggers were further externally validated to predict mutagenicity in vitro, with metabolic triggers being used only to predict mutagenicity of chemicals, which were predicted unknown, by SARpy. Hence, this model has a higher accuracy than the SAR model, with an accuracy of 89% for the training set and 75% for the external validation set. Subsequently, the results of the second part of this work enlist a set of metabolic triggers for prediction of mutagenicity in vivo, based on the rodent micronucleus assay. Finally, the results of the third part enlist a list of metabolic triggers to find similarities and differences in the mutagenic response of chemicals in vitro and in vivo.     

Simultaneous determination of alkali,alkaline earth and transition metal elements in uranium and thorium based nuclear fuel materials by single column ion chromatography

A single-column ion chromatography (SCIC) for the simultaneous determination of alkali, alkaline earth and transition metal elements in UO₂, ThO₂ powders and sintered (Th, U) O₂ pellet is described in this paper. Metrosep cation 1-2 analytical column containing poly butadiene-maleic acid (PBDMA) coated silica has been applied to the ion chromatographic separation of 12 cations (copper, lithium, sodium, ammonium, nickel, potassium, zinc, cobalt, manganese, magnesium, calcium and strontium) using an isocratic elution with tartaric acid and oxalic acid as mobile phase with non-suppressed conductivity detection. Mobile phase composition was optimized to 1 mM tartaric acid and 0.75 mM oxalic acid for the baseline separation of 12 cations. The calibration plots were linear in the range of 0.05–40 mg L⁻¹ with regression coefficients better than 0.998. The relative standard deviations (RSDs) of the retention time, peak area and peak height were less than 1, 2.8 and 3.0%, respectively. The recoveries of the spiked samples for the cations were 94–110%. The method developed was validated by comparison with certified standards of UO₂ and ThO₂ powders.