A redox-gated slow-fast-stop molecular rotor

A pentiptycene-derived p-phenylenediamine mimics a molecular double-rotor system that displays redox-dependent rotation rates for the amino rotors about the pentiptycene-amine C-N bond. The rotation is accelerated in the radical cation state but stopped in the di(radical cation) state. Electronic interplay of the two rotors is also discussed.     

Thermodynamic characterization of the biocompatible ionic liquid effects on protein model compounds and their functional groups

The stability of proteins under co-solvent conditions is dependant on the nature of the co-solvent; the co-solvent can alter a protein's properties and structural effects through bimolecular interactions between its functional groups and co-solvent particles. Ionic liquids (ILs) represent a rather diverse class of co-solvents that are combinations of different ions, which are liquids at or close to room temperature. To quantify the bimolecular interactions of protein functional groups with biocompatible ILs, we report the systematic and quantitative apparent transfer free energies (ΔG'(tr)) of a homologous series of cyclic dipeptides (CDs) from water to aqueous solutions of ILs through solubility measurements, as a function of IL concentration at 25 °C under atmospheric pressure. The materials investigated in the present work included the CDs of cyclo(Gly-Gly), cyclo(Ala-Gly), cyclo(Ala-Ala), cyclo(Leu-Ala), and cyclo(Val-Val). The ILs used such as diethylammonium acetate ([Et(2)NH][CH(3)COO], DEAA), triethylammonium acetate ([Et(3)NH][CH(3)COO], TEAA), diethylammonium dihydogen phosphate ([Et(3)NH][H(2)PO(4)], DEAP), triethylammonium dihydogen phosphate ([Et(3)NH][H(2)PO(4)], TEAP), diethylammonium sulfate ([Et(3)NH][HSO(4)], DEAS) and triethylammonium sulfate ([Et(3)NH][HSO(4)], TEAS). We observed positive values of ΔG'(tr) for CDs from water to ILs, indicating that interactions between ILs and CDs are unfavourable, which leads to stabilization of the native structure of CDs. The experimental results were further used for estimating the transfer free energies (Δg'(tr)) of the peptide bond (-CONH-), the peptide backbone unit (-CH(2)C=ONH-), and various functional groups from water to IL solutions. Our results explicitly elucidate that a series of all ammonium ILs act as stabilizers for tested model compounds through the exclusion of ILs from CDs surface.     

Remote-Raman spectroscopic study of minerals under supercritical CO2 relevant to Venus exploration

The authors have utilized a recently developed compact Raman spectrometer equipped with an 85 mm focal length (f/1.8) Nikon camera lens and a custom mini-ICCD detector at the University of Hawaii for measuring remote Raman spectra of minerals under supercritical CO(2) (Venus chamber, ～102 atm pressure and 423 K) excited with a pulsed 532 nm laser beam of 6 mJ/pulse and 10 Hz. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10× beam expander to a 1mm spot on minerals located at 2m inside a Venus chamber, it is possible to measure the remote Raman spectra of anhydrous sulfates, carbonates, and silicate minerals relevant to Venus exploration during daytime or nighttime with 10s integration time. The remote Raman spectra of gypsum, anhydrite, barite, dolomite and siderite contain fingerprint Raman lines along with the Fermi resonance doublet of CO(2). Raman spectra of gypsum revealed dehydration of the mineral with time under supercritical CO(2) at 423 K. Fingerprint Raman lines of olivine, diopside, wollastonite and α-quartz can easily be identified in the spectra of these respective minerals under supercritical CO(2). The results of the present study show that time-resolved remote Raman spectroscopy with a compact Raman spectrometer of moderate resolution equipped with a gated intensified CCD detector and low power laser source could be a potential tool for exploring Venus surface mineralogy both during daytime and nighttime from a lander.     

A classification of homogeneous operators in the Cowen–Douglas class

An explicit construction of all the homogeneous holomorphic Hermitian vector bundles over the unit disc D is given. It is shown that every such vector bundle is a direct sum of irreducible ones. Among these irreducible homogeneous holomorphic Hermitian vector bundles over D, the ones corresponding to operators in the Cowen–Douglas class Bn(D) are identified. The classification of homogeneous operators in Bn(D) is completed using an explicit realization of these operators. We also show how the homogeneous operators in Bn(D) split into similarity classes.     

Identification of a company’s suitability for the adoption of cloud computing and modelling its corresponding Return on Investment

Internet has become pervasive in our daily life and cloud computing is the newest offering as service over the ubiquitous Web. Cloud computing has been considered as a much hyped phenomenon in the IT and business world promising to deliver a host of benefits. Companies need to look beyond this hype and seriously consider the real value of incorporating the Cloud in their own businesses. This paper is aimed at helping companies analyze several characteristics of their own business as well as pre-existing IT resources to identify their favorability in the migration to the Cloud Architecture. A general Return on Investment (ROI) model has also been developed here taking into consideration various intangible impacts of Cloud Computing, apart from the cost. The analysis presented herein provides a much broader perspective and insight into Cloud Computing to its prospective adopters.     

Modeling the spread of an infectious disease with bacteria and carriers in the environment

An SIS model with immigration for the spread of an infectious disease with bacteria and carriers in the environment is proposed and analyzed. It is assumed that susceptibles get infected directly by infectives as well as by their contacts with bacteria discharged by infectives in the environment. The growth rate of density of bacteria is assumed to be proportional to the density of infectives and decreases naturally as well as by bacterial interactions with susceptibles and carriers. The carrier population density is considered to follow the logistic model and grows due to conducive human population density related factors. It is assumed further that the number of bacteria transported by carriers to susceptibles is proportional to densities of both bacteria and carriers. The model study shows that the spread of the infectious disease increases due to growth of bacteria and carriers in the environment and disease becomes more endemic due to immigration.     

A DFT study on the magnetostructural property of ferromagnetic heteroverdazyl diradicals with phenylene coupler

We have theoretically designed five different m-phenylene coupled high-spin bis-heteroverdazyl diradicals and their analogous p-phenylene coupled low-spin positional isomers. The geometry-based aromaticity index, harmonic oscillator model of aromaticity (HOMA) values for both the couplers (local HOMA), and the whole diradicals (global HOMA) have been calculated for all the diradicals. We also qualitatively relate these HOMA values with the intramolecular magnetic exchange coupling constants (J), calculated using a broken symmetry approach within unrestricted density functional theory framework. Structural aromaticity index HOMA of linkage specific benzene rings in our designed diradical systems shows that the aromatic character depends on the planarity of the molecule and it controls the sign and magnitude of J. The predicted J values are explained on the basis of spin polarization maps, average dihedral angles, and magnetic orbitals. The effect of the spin leakage phenomenon on magnetic exchange coupling constant and that on HOMA values of certain phosphaverdazyl systems has been explicitly discussed. In addition, a similar comparison is made between the calculated exchange coupling constants and corresponding HOMA values. The main novelty of this work stands on the consideration of the aromatic behavior by means of the geometrical index HOMA. We also estimate another aromaticity index, nucleus independent chemical shift (NICS) values for the phenylene coupler in each diradical to measure aromaticity and compare its value with that of HOMA. The ground state stabilities of these diradicals have also been compared.     

Determination of low atomic number elements at trace levels in uranium matrix using vacuum chamber total reflection X-ray fluorescence

Determinations of low atomic number elements Na, Mg and Al present at trace concentrations in uranium matrix were made by vacuum chamber total reflection X-ray fluorescence spectrometer for the first time. For this purpose, synthetic samples of uranium with known amounts of these low atomic number elements were prepared by mixing different volumes of their solutions with U solution of high purity. The concentrations of these elements in the samples were in the range of 100–300 μg/g with respect to uranium and 10–20 μg/mL in the solutions. Major matrix uranium was separated by solvent extraction with 30% solution of tri-n-butyl phosphate in dodecane. After the solvent extraction, aqueous phase containing trace elements was mixed with Sc internal standard and the samples were analyzed by vacuum chamber total reflection X-ray fluorescence spectrometer having a Cr Kα excitation source. The total reflection X-ray fluorescence results obtained, after blank corrections, indicated an average deviation of 14% from the calculated concentrations of these low atomic number elements on the basis of their preparation. However, the total reflection X-ray fluorescence determined concentration of Mg was exceptionally lower than the calculated concentration in two samples. These studies have shown that vacuum chamber total reflection X-ray fluorescence is a promising technique for the determination of low atomic number elements in uranium matrix after its separation.     

Energy dispersive X-Ray fluorescence determination of thorium in phosphoric acid solutions

Energy dispersive X-ray fluorescence studies on determination of thorium (in the range of 7 to 137 mg/mL) in phosphoric acid solutions obtained by dissolution of thoria in autoclave were made. Fixed amounts of Y internal standard solutions, after dilution with equal amount of phosphoric acid, were added to the calibration as well as sample solutions. Solution aliquots of approximately 2–5 µL were deposited on thick absorbent sheets to absorb the solutions and the sheets were presented for energy dispersive X-ray fluorescence measurements. A calibration plot was made between intensity ratios (Th Lα/Y Kα) against respective amounts of thorium in the calibration solutions. Thorium amounts in phosphoric acid samples were determined using their energy dispersive X-ray fluorescence spectra and the above calibration plot. The energy dispersive X-ray fluorescence results, thus obtained, were compared with the corresponding gamma ray spectrometry results and were found to be within average deviation of 2.6% from the respective gamma ray spectrometry values. The average precision obtained in energy dispersive X-ray fluorescence determinations was found to be 4% (1σ). The energy dispersive X-ray fluorescence method has an advantage over gamma ray spectrometry for thorium determination as the amount of sample required and measurement time is far less compared to that required in gamma ray spectrometry.     

Pharmacognostical specification and validated high-performance thin-layer chromatographic method for the estimation of quercetin in Phoenix sylvestris root

JPC – Journal of Planar Chromatography – Modern TLC - The present study was aimed to assess the scientific appraisal of Phoenix sylvestris in the course of pharmacognostical properties...