Operational Variants of the Minimum Mean Squared Error Estimator in Linear Regression Models with Non-Spherical Disturbances

There is a good deal of literature that investigates the properties of various operational variants of Theil's (1971, Principles of Econometrics, Wiley, New York) minimum mean squared error estimator. It is interesting that virtually all of the existing analysis to date is based on the premise that the model's disturbances are i.i.d., an assumption which is not satisfied in many practical situations. In this paper, we consider a model with non-spherical errors and derive the asymptotic distribution, bias and mean squared error of a general class of feasible minimum mean squared error estimators. A Monte-Carlo experiment is conducted to examine the performance of this class of estimators in finite samples.     

Velogenic Newcastle Disease Virus as an Oncolytic Virotherapeutics: In Vitro Characterization

Cancer is one of the killer diseases in humans and needs alternate curative measures despite recent improvement in modern treatment modalities. Oncolytic virotherapy seems to be a promising nonconventional way to treat cancers. Newcastle disease virus (NDV), a poultry virus, is nonpathogenic to human and domestic animals and has a long history of being used in oncotherapy research in several preclinical studies. The ability of NDV to successfully infect and destroy cancer cells is dependent on the strain and the pathotype of the virus. Adaptation of viruses to heterologous hosts without losing its replicative and oncolytic potential is prerequisite for use as cancer virotherapeutics. In the present study, velogenic NDV was adapted for replication in HeLa cells, and its cytotoxic potential was evaluated by observing morphological, biochemical, and nuclear landmarks of apoptosis. Our results indicated that the NDV-induced apoptosis in HeLa cells was dependent on upregulation of TNF-related apoptosis-inducing ligand (TRAIL) and caspases activation. Different determinants of apoptosis evaluated in the present study indicated that this strain could be a promising candidate for cancer therapy in future.     

Perspectives on the synthesis of organic carbamates

In this review, various kinds of synthetic methodologies for the synthesis of organic carbamates employing diversity of reagents and catalytic systems have been reviewed, from the beginning to the recent reports (covering till December 2010).

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Equation of state of Al for compressed and expanded states from first-principles calculations

Results of theoretical calculations of equation of state and critical temperature of Al are presented using a three-term EOS model. In this model cold (0 K) term is calculated from first-principles method near normal conditions. Cold curve is extrapolated to ultrahigh pressures using Thomas– Fermi–Dirac model and to expanded states using a soft sphere function. Electron thermal term is calculated using Thomas–Fermi statistical model. Ion-thermal term is calculated using the modified Cowan model. In expanded state, the adjustable parameters of the modified Cowan model are tuned using quantum molecular dynamics (QMD) results. In compressed state, P−ρ$P-\rho$ and U_s−U_p$U_{\mathrm{s}}-U_{\mathrm{p}}$ Hugoniots derived using our results show good agreement with the reported experimental results. In expanded state, the estimated critical temperature shows good agreement with the reported results and pressure versus internal energy along isochores show reasonably good agreement with the reported experimental results.     

An improved stereoselective total synthesis of (R)-rugulactone

A novel route for the stereoselective total synthesis of (R)-rugulactone 1 has been developed, starting from substituted epoxide 4 and 3-phenylpropionaldehyde 5 employing Julia-Kocienski olefination as a key step to construct E-configured α,β-unsaturated keto-group. The overall yield of the synthesized rugulactone is 19.94% and is better than the reported methods.     

Sterol Glycosyltransferases—The Enzymes That Modify Sterols

Sterols are important components of cell membranes, hormones, signalling molecules and defense-related biotic and abiotic chemicals. Sterol glycosyltransferases (SGTs) are enzymes involved in sterol modifications and play an important role in metabolic plasticity during adaptive responses. The enzymes are classified as a subset of family 1 glycosyltransferases due to the presence of a signature motif in their primary sequence. These enzymes follow a compulsory order sequential mechanism forming a ternary complex. The diverse applications of sterol glycosides, like cytotoxic and apoptotic activity, anticancer activity, medicinal values, anti-stress roles and anti-insect and antibacterial properties, draws attention towards their synthesis mechanisms. Many secondary metabolites are derived from sterol pathways, which are important in defense mechanisms against pathogens. SGTs in plants are involved in changed sensitivity to stress hormones and their agrochemical analogs and changed tolerance to biotic and abiotic stresses. SGTs that glycosylate steroidal hormones, such as brassinosteroids, function as growth and development regulators in plants. In terms of metabolic roles, it can be said that SGTs occupy important position in plant metabolism and may offer future tools for crop improvement.     

Silver(I) catalyzed oxidation of thiocarboxylic acids into the corresponding disulfides and synthesis of some new Ag(I) complexes of thiophene-2-thiocarboxylate

Aromatic thiocarboxylic acids in presence of a base on treatment with silver nitrate under ambient conditions were oxidized to the corresponding disulfides. The reactions were found to be catalyzed by Ag⁺ ions. The catalytic oxidation is paralleled by the Ag(SCOAr) complex formation reaction which could be considerably subsided by adjustment of the reaction conditions. Attempts to use [Ag(PPh₃)₂]⁺ or [Ag(PPh₃)]⁺ ion as the catalyst were unsuccessful as these resulted in the formation of the corresponding thiocarboxylate complexes. The products, ArCOSSCOAr (1, 2), [Ag(SCOAr)(PPh₃)₂] (3, 4) and [Ag(SCOAr)(PPh₃)]₄ (5) (Ar = C₆H₅, C₄H₃S) were characterized by single crystal X-ray analysis. Compounds 3 and 4 are monomeric while 5 is a cyclic tetramer in the crystalline phase.     

Quantum chemical and experimental studies on the structure and vibrational spectra of substituted 2-pyranones

A systematic study on the structural characteristics of the 2-pyranone ring containing molecules with bromine, nitrile, and amide substituents at the C-3 position in the ring is conducted in the electronic ground (S ₀) state by DFT calculations using the B3LYP/6-311++G** method. The geometrical structure of the bromine substituted compound, which shows potent hepatoprotective activity, is studied both in the ground (S ₀) and first excited singlet (S ₁) states using RHF/6-311++G** and CIS/6-311++G** methods respectively. The molecules are found to exist in two isomeric forms gauche and trans that have the enthalpy difference of less than 3.32 kcal/mol; the latter is the preferred orientation in the gaseous phase. The S ₁ state is a ¹(π,π*) state that arises π-electron transfer from the region of a double bond in the pyranone ring to the region of the internuclear bond connecting the 2-pyranone and benzene rings. A complete vibrational analysis is conducted for the 3-bromo-6-(4-chlorophenyl)-4-thiomethyl-2H-pyran-2-one molecule based on the experimental infrared spectra in the 50–4000 cm⁻¹ region and DFT/6- 311++G** computations of vibrational frequencies for the gauche and trans isomeric forms. Spectral assignments based on the potential energy distribution along the internal coordinates confirm the nonplanar structure of the molecule.     

Delta Shock Wave Solution of the Riemann Problem for the Non-homogeneous Modified Chaplygin Gasdynamics

The motivation of the present study is to derive the solution of the Riemann problem for modified Chaplygin gas equations in the presence of constant external force. The analysis leads to the fact that in some special circumstances delta shock appears in the solution of the Riemann problem. Also, the Rankine–Hugoniot relations for delta shock wave which are utilized to determine the strength, position and propagation speed of the delta shocks have been derived. Delta shock wave solution to the Riemann problem for the modified Chaplygin gas equation is obtained. It is found that the external force term, appearing in the governing equations, influences the Riemann solution for the modified Chaplygin gas equation.