Contrasting Effect of Additives on Photoinduced Reactions of SmI2

The work described herein compares the effect of additives (HMPA, methanol, ethylene glycol, pinacol, N-methylethanolamine) on thermal and photochemical reactions of samarium diiodide (SmI₂). In thermal reactions, additives that coordinate to SmI₂ induce a significant increase in reaction rate. In photochemical reactions, the presence of an electronegative atom with a highly localized negative charge on the substrate leads to a rate deceleration. In order to benefit from the columbic interaction with the positively charged samarium cation, these substrates react preferentially by an inner sphere reduction mechanism. The addition of ligands prevents this close interaction causing rate retardation. Furthermore, studies demonstrate that excited state quenching of Sm^II by ethylene glycol and other additives indicate that it is unlikely to be the major cause for the observed rate retardation. This effect provides a simple diagnostic tool to distinguish between an inner and an outer sphere reduction mechanism.     

A Synthesis of the 4-Alkylamino-2,4-Dideoxy-l-threo-pentopyranose Components of the Calicheamicins and Esperamicins

Abstract

A general synthetic approach to enantiomerically pure 4-substituted 2,4-dideoxypentopyranosides has been developed which provides access to the 4-alkylamino-2,4-dideoxy-L-threo-pentopyranose components of the calicheamicins and esperamicins.     

Origin of the insulating state in NaCuO2

We study the electronic structure of NaCuO₂ by analysing experimental core level photoemission and X-ray absorption spectra using a cluster as well as an Anderson impurity Hamiltonianincluding the band structure of the oxygen sublattice. We show that the X-ray absorption results unambiguously establish a negative value of the charge transfer energy, Δ. Further, mean-field calculations for the edge-shared one-dimensional CuO₂ lattice of NaCuO₂ within the multiband Hubbard Hamiltonian show that the origin of the insulating nature lies in the band structure rather than in the correlation effects. LMTO-ASA band structure calculations suggest that NaCuO₂ is an insulator with a gap of around 1 eV.     

Axially Symmetric Bianchi Type-I Model with Massless Scalar Field and Cosmic Strings in Barber’s Self-Creation Cosmology

Axially symmetric Bianchi type-I space time is considered in the presence of massless scalar field and cosmic strings in Barber’s (Gen. Relativ. Gravit. 14:117, 1982) self-creation theory with two conditions (i) A=B ⁿ and (ii) ε+λ=0. Some physical and kinematical properties of the model, thus obtained, are also discussed.     

String Cloud and Domain Walls with Quark Matter in <Emphasis Type="Italic">n</Emphasis>-Dimensional Kaluza-Klein Cosmological Model

We have obtained Kaluza-Klein cosmological solutions in n-dimensions for quark matter coupled with the string cloud and domain walls in general relativity. Some properties of the models, thus obtained, are also studied.     

Comparison between a high-resolution single-stage Orbitrap and a triple quadrupole mass spectrometer for quantitative analyses of drugs

The capabilities of a high-resolution (HR), accurate mass spectrometer (Exactive-MS) operating in full scan MS mode was investigated for the quantitative LC/MS analysis of drugs in patients' plasma samples. A mass resolution of 50,000 (FWHM) at m/z 200 and a mass extracted window of 5?ppm around the theoretical m/z of each analyte were used to construct chromatograms for quantitation. The quantitative performance of the Exactive-MS was compared with that of a triple quadrupole mass spectrometer (TQ-MS), TSQ Quantum Discovery or Quantum Ultra, operating in the conventional selected reaction monitoring (SRM) mode. The study consisted of 17 therapeutic drugs including 8 antifungal agents (anidulafungin, caspofungin, fluconazole, itraconazole, hydroxyitraconazole posaconazole, voriconazole and voriconazole-N-oxide), 4 immunosuppressants (ciclosporine, everolimus, sirolimus and tacrolimus) and 5 protein kinase inhibitors (dasatinib, imatinib, nilotinib, sorafenib and sunitinib). The quantitative results obtained with HR-MS acquisition show comparable detection specificity, assay precision, accuracy, linearity and sensitivity to SRM acquisition. Importantly, HR-MS offers several benefits over TQ-MS technology: absence of SRM optimization, time saving when changing the analysis from one MS to another, more complete information of what is in the samples and easier troubleshooting. Our work demonstrates that U/HPLC coupled to Exactive HR-MS delivers comparable results to TQ-MS in routine quantitative drug analyses. Considering the advantages of HR-MS, these results suggest that, in the near future, there should be a shift in how routine quantitative analyses of small molecules, particularly for therapeutic drugs, are performed.     

String Cosmology in Brans–Dicke Theory for Kasner Type Metric

For a string Bianchi type-I metric of Kasner form in Brans–Dicke theory of gravity, it is not possible to describe an anisotropic physical model of the universe.