Conditional VaR estimation using Pearson’s type IV distribution

This paper presents a new value at risk (VaR) estimation model for equity returns time series and tests it extensively on Stock Indices of 14 countries. Two most important stylized facts of such series are volatility clustering, and non-normality as a result of fat tails of the return distribution. While volatility clustering has been extensively studied using the GARCH model and its various extensions, the phenomenon of non-normality has not been comprehensively explored, at least in the context of VaR estimation. A combination of extreme value theory (EVT) and GARCH has been explored to analyze financial data showing non-normal behavior. This paper proposes a combination of the Pearson’s Type IV distribution and the GARCH (1, 1) approach to furnish a new method with superior predictive abilities. The approach is back tested for the entire sample as well as for a holdout sample using rolling windows.     

On the problematic rising ratio of cosmic-ray positrons at ultra-high energies

Summary The rising ratio of cosmic-ray positrons at ultra-high energies of interactions seems to have puzzled the theorists to a great extent. We have made here a somewhat successful attempt to interpret the behaviour of this ratio,R=e⁺/(e⁺+e⁻), by putting into use the main physical ideas from our two previous works. The importance and the implications of this observation have also been highlighted and emphasized in the proper background.

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Riassunto Il crescente rapporto dei positroni dei raggi cosmici ad energie ultra-alte di interazioni sembra aver non poco confuso i teorici. Qui si tenta con un certo successo di interpretare il comportamento di questo rapportoR=e⁺/(e⁺+e⁻) usando i principali concetti fisici dei nostri due precedenti lavori. L'importanza e le implicazioni di questa osservazione sono state sottolineate ed enfatizzate nell'appropriato contesto.

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Резюме Увеличивающиеся отношение позитронов космических лучей при ультравыс оких энергиях, по-видимому, представляет загадку для теоретиков. В этой статье мы предпринимает отчасти успешную попытку интерпретировать поведение этого отношенияR=e⁺/(e⁺+e⁻), используя основные физические идеи из наших двух предыдущих публикаций. Отмчаются важностя и приложения полученных результатов.

     

Zur Analyse von Eisen und-Stahl

Ohne Zusammenfassung     

The acute toxicity of tri-n-butyltin taurocholate

The acute toxicity for tri-n-butyltin taurocholate (TBT-TA), a newly synthesized organotin steroid, was determined using Long Evans rats. The organotin compound was suspended in corn oil and administered by gavage using standard techniques. The TBT-TA exhibited a taurocholic acid toxicity at 24 h and a tributyltin toxicity at three days. The LD₅₀ values were 611 and 384 mg kg^?1 respectively. The dead rats exhibited distended stomachs, enlarged cecums, and lesions in the gastrointestinal tract. The toxicity is similar to that observed with other trialkyltin compounds.     

Evaluation of finite-plasticity theories for torsion-tension members made of tresca materials

Finite-incremental Tresca and von Mises theories are developed for solid circular-section torsion-tension members subjected to proportionate and nonproportionate loading. The materials are assumed to be isotropic and even. Two Tresca theories and a von Mises theory are compared with test data obtained from torsion-tension members. Three different kinds of steels were tested; they are hot-rolled mild steel, annealed mild steel, and hot-rolled SAE 1017 steel. The fully plastic values of axial load and torque predicted by the Tresca theories agree with the experimental results; however, the deformations, in the strain-hardening region, predicted by both of the Tresca theories were greater than observed. The von Mises theory is nonconservative in predicting the fully plastic loads of torsion members and torsion-tension members and in predicting the deformations of torsion members in the strain-hardening region, but gives good correlation between predicted and experimental deformations for the torsion-tension members in the strain-hardening region.     

Aqueous-phase synthesis of PAA in PVDF membrane pores for nanoparticle synthesis and dichlorobiphenyl degradation

This paper deals with bimetallic (Fe/Pd) nanoparticle synthesis inside the membrane pores and application for catalytic dechlorination of toxic organic compounds form aqueous streams. Membranes have been used as platforms for nanoparticle synthesis in order to reduce the agglomeration, encountered in solution phase synthesis which leads to a dramatic loss of reactivity. The membrane support, polyvinylidene fluoride (PVDF) was modified by in situ polymerization of acrylic acid in aqueous phase. Subsequent steps included ion exchange with Fe²⁺, reduction to Fe⁰ with sodium borohydride and Pd deposition. Various techniques, such as STEM, EDX, FTIR and permeability measurements, were used for membrane characterization and showed that bimetallic (Fe/Pd) nanoparticles with an average size of 20–30 nm have been incorporated inside of the PAA-coated membrane pores. The Fe/Pd-modified membranes showed a high reactivity toward a model compound, 2,2′-dichlorobiphenyl and a strong dependence of degradation on Pd (hydrogenation catalyst) content. The use of convective flow substantially reduces the degradation time: 43% conversion of dichlorobiphenyl to biphenyl can be achieved in less than 40 s residence time. Another important aspect is the ability to regenerate and reuse the Fe/Pd bimetallic systems by washing with a solution of sodium borohydride, because the iron becomes inactivated (corroded) as the dechlorination reaction proceeds.     

Structure, stability and dissociation of silanitriles RSiN (R = H2B, H2N, H2P)

Structure, stability, and dissociation of H₂BSiN, H₂NSiN, H₂PSiN and their isomers H₂BNSi, H₂NNSi, H₂PNSi have been studied in detail using ab initio MP2 and CCSD(T) methods. After dissociation of H₂BNSi, H₂NNSi, H₂PNSi and their isomers, the fragmented atoms have been considered to be either in their ground state or in their valence excited state in various dissociation channels. Only allowed dissociations of these molecules are considered. Various dissociation channels of H₂BNSi, H₂NNSi, H₂PNSi and their isomers have been explored and interesting trends are observed for the dissociation of stable isomers H₂BNSi, H₂NNSi, H₂PNSi and less stable isomers H₂BSiN, H₂NSiN, H₂PSiN. The effect of substituents on their structural properties has been discussed. The potential energy surfaces for the RSiN ? RNSi isomerization reactions have been analyzed. The structural properties of these molecules agree well with the theoretical values wherever available.     

A fast, inexpensive, and safe method for residue analysis of meptyldinocap in different fruits by liquid chromatography/tandem mass spectrometry

An analytical method is reported for residue analysis of the fungicide meptyldinocap in different fruit matrixes that involves extraction with ethyl acetate, hydrolysis of the residues with ethanolamine, and determination by LC/MS/MS. The method involves extraction of 10 g sample with 10 mL ethyl acetate; evaporation of the ethyl acetate phase to dryness, and subsequent hydrolysis of the residues to 4,6-dinitro-2-(1-methylheptyl) phenol on reaction with 1% ethanolamine. The pH of this hydrolyzed product was neutralized with formic acid and analyzed by LC/MS/MS. The hydrolysis reaction followed pseudo-first-order kinetics, and the reaction product was spectroscopically confirmed as 2-(1-methylheptyl)-4,6-dinitrophenol. The method offered > 80% recoveries at an LOQ of 10 ng/g for grape and mango, 25 ng/g for pomegranate with intralaboratory Horwitz ratio < 0.5, and measurement uncertainties < 10% at LOQ levels. Considering first-order rate kinetics, activation energy, enthalpy of activation, and entropy of activation varied as solvent > mango > grape > pomegranate. Free energy of activation at 298 K was higher than at 280 K and was similar for solvent and three matrixes at both temperatures.