Photoexcitation of the potassium octacyanotungstate(IV)· 5–nitro-1,10–phenanthroline system: kinetics and mechanism of the reaction

The kinetics of thermal reactions of the photochemically-generated species [W(CN)7OH]4− and [W(CN)6–(CNH)(H2O)]2− with 5–nitro-1,10–phenanthroline (nitrophen) in basic and acidic media, respectively, were studied in buffer solutions at pH 4.2–10.6 and ionic strength 7.5×10−2kg−1 at 20°C. The quantum yield for the formation of the photoproduct was calculated and found to depend upon pH and the ligand and [W(CN)8]4− concentrations. The rate constants and quantum yields were less compared with 1,10–phenanthroline due to the electron-withdrawing inductive effect of the nitro group in nitrophen, which makes the latter a weaker ligand. The pseudo-first-order rate constant and quantum yield values in acidic media are higher than in basic media and the mechanisms of the photochemical substitution are different in the two media. This revised version was published online in June 2006 with corrections to the Cover Date.     

Adverse selection and non-take inference with coherent risk and response scoring

The authors offer a mathematical model for adverse selection by individual borrowers based on preferences for offers and the default (Bad) or non-default (Good) status of booked accounts. We define the condition for borrower risk and response when there is no adverse selection (NAS). This definition provides us with a direct comparison between the prior and posterior conditional probabilities of default by an individual borrower who Takes an offer; this allows us to obtain estimates of differential response rates for individual borrowers and the Good/Bad odds for Take, Non-Take and Accept sub-populations. Performance of different response-risk segments allows us to compare price-driven risk elasticity and price-driven response elasticity in the presence of Good or Bad adverse selections; a special case applies when the borrower's capacity to repay is not an issue. We offer limited experimental results for selected price-risk segments where action-based risk and response scores are used to estimate borrower preferences. The critical role of Non-Take inference is described.     

Photo-induced Synthesis and Characterization of Poly（methyl methacrylate） Grafted Sodium Salt of Partially Carboxymethylated Guar Gum

Photo-induced graft copolymerization of methyl methacrylate（MMA） onto sodium salt of partially carboxymethylated guar gum（Na-PCMGG, DS = 0.291） was carried out in an aqueous medium using ceric ammonium nitrate（CAN） as photoinitiator to synthesize a novel graft copolymer, Na-PCMGG-g-PMMA, which may find its potential application as a metal adsorbent. The influences of synthesis variables such as concentrations of photoinitiator（CAN）, nitric acid and monomer（MMA） as well as reaction time, temperature and amount of substrate on the grafting yields were studied and the reaction conditions for optimum photo-grafting were evaluated. At optimum concentration, the maximum values of the grafting yields achieved were G = 271.61% and GE = 63.89%. The experimental results were found to be in very good agreement with the proposed kinetic scheme. The photo-graft copolymerization of MMA onto Na-PCMGG（ DS = 0.291） was also carried out in the presence and absence of ultraviolet radiation for studying the efficiency of the photoinitiator. The influence of carboxymethyl groups introduced onto the guar gum molecules with regard to its behavior towards ultra-violet radiation induced grafting with MMA was also investigated. Photo-grafting process was confirmed and the products were characterized with the help of the spectroscopic（1H-NMR and FTIR） and SEM techniques.     

Validated HPTLC Method for Assay of Prednisolone in Tablets and Comparison with Pharmacopeial Methods

JPC – Journal of Planar Chromatography – Modern TLC - A rapid and reliable high-performance thin-layer chromatographic method has been established for analysis of prednisolone in a...     

Novel synthesis and cytotoxic activity of some chromeno[3,4-<Emphasis Type="Italic">b</Emphasis>]pyrrol-4(3H)-ones

1-Methylchromeno[3,4-b]pyrrol-4(3H)-one and 1-phenylchromeno[3,4-b]pyrrol-4(3H)-one derivatives have been synthesized by cyclization of amides obtained by condensing α-halo ketones with 3-amino-chromenones, which show cytotoxic activity against lung, colon, and breast cancer cell lines.     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

Synthesis,Characterization and Mesomorphic Properties of New Rod-like Thiophene Based Liquid Crystals

Two new mesogenic homologous series of Schiff base esters, 2-[4-(4′-n-Alkoxy benzoyloxy) benzylidenamino] 3-cyno thiophine (Series-A) and Schiff base cinnamates, 2-[4-(4′-n-alkoxy cinnamoyloxy) benzylidenamino] 3-cyano thiophene (Series-B), comprising a thiophene moiety were synthesized. Structural elucidation was carried out using elemental analysis and spectroscopic techniques such as FT-IR, ¹H-NMR and ¹³C-NMR, and mass spectrometry. The mesomorphic properties and thermal stabilities of the title compounds were studied by using differential scanning calorimetry and optical polarizing microscopy. All the derivatives are mesomorphic in nature showing the nematic phase, and the higher members of Series-A show a smectic C phase whereas Series-B exhibits only the nematic mesophase. The mesomorphic properties of the present series are compared with other structurally related compounds.     

Synthesis,spectral, thermal,and antibacterial investigation of mixed ligand complexes of oxovanadium(IV)

Novel mononuclear mixed-ligand oxovanadium(IV) complex [VO(PMFP)(Bipy)]ClO₄ was prepared by the condensation of VOSO₄ · 5H₂O with ligands 1-phenyl-3-methyl-4-formyl-2-pyrazolin-5one (PMFP) and 2,2′-bipyridyl (Bipy). The corresponding Schiff bases were prepared by the condensation of [VO(PMFP)(Bipy)]ClO₄ with ethylenediamine, ethanolamine, and glycine. All the compounds have been characterized by elemental analysis, magnetic susceptibility, X-ray crystallography, conductometry measurement, ¹H NMR, FT-IR, ESR, electronic spectra, and mass spectrometry. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of the oxovanadium(IV) complexes. Thermal stability, kinetic order, heat capacity, and activation energy of thermal degradation of these complexes were determined by TGA and DSC. The presence of one coordinate water molecule is suggested from the IR and TGA studies. Hamiltonian and bonding parameters were found from ESR spectra, indicating that the metal-ligand bonding is partial covalent. Antibacterial screening is reported for the ligand and complexes of oxovanadium(IV). The text was submitted by the authors in English.     

Synthetic mimics of antimicrobial peptides with immunomodulatory responses

A new series of aryl-based synthetic mimics of antimicrobial peptides (SMAMPs) with antimicrobial activity and selectivity have been developed via systematic tuning of the aromatic groups and charge. The addition of a pendant aromatic group improved the antimicrobial activity against Gram-negative bacteria, while the addition of charge improved the selectivity. SMAMP 4 with six charges and a naphthalene central ring demonstrated a selectivity of 200 against both Staphylococcus aureus and Escherichia coli , compared with a selectivity of 8 for the peptide MSI-78. In addition to the direct antimicrobial activity, SMAMP 4 exhibited specific immunomodulatory activities in macrophages both in the presence and in the absence of lipopolysaccharide, a TLR agonist. SMAMP 4 also induced the production of a neutrophil chemoattractant, murine KC, in mouse primary cells. This is the first nonpeptidic SMAMP demonstrating both good antimicrobial and immunomodulatory activities.     

Fracto-mechanoluminescence and mechanics of fracture of solids

The present paper explores the correlation between fracto-mechanoluminescence and fracture of solids and thereby provides a clear understanding of the physics of fracto-mechanoluminescence. When a fluorescent or non-photoluminescent crystal is fractured impulsively by dropping a load on it, then initially the mechanoluminescence (ML) intensity increases linearly with time, attains a maximum value I_m at a particular time t_m and later on it decreases exponentially with time. However, when a phosphorescent crystal is fractured impulsively by dropping a load on it, then initially the ML intensity increases linearly with time, attains a maximum value I_m at a particular time t_m and later on it decreases initially at a fast rate and then at a slow rate. For low impact velocity the value of t_m is constant, however, for higher impact velocity t_m decreases logarithmally with the increasing impact velocity. Whereas the peak ML intensity I_m increases linearly with the impact velocity, the total ML intensity I_T, initially increases linearly with the impact velocity and then it tends to attain a saturation value for higher values of the impact velocity. The value of t_m increases logarithmally with the thickness of crystals, I_m increases linearly with the area of cross-section of crystals and I_T increases linearly with the volume of crystals. Generally, the ML of non-irradiated crystals decreases with increasing temperature of crystals. Depending on the prevailing conditions the ML spectra consist of either gas discharge spectra or solid state luminescence spectra or combination of the both. On the basis of the rate of generation of cracks and the rate of creation of new surface area of crystals, expressions are derived for the ML intensity and they are found to explain satisfactorily the temporal, spectral, thermal, crystal-size, impact velocity, surface area, and other characteristics of ML. The present investigation may be useful in designing of damage sensors, fracture sensors, ML-based safety management monitoring system, fuse-system for army warheads, milling machine, etc. The present study may be helpful in understanding the processes involved in earthquakes, earthquake lights and mine-failure as they basically involve fracture of solids.