Synthesis of solid state fluorescent quino[2,3-b]carbazoles via copper(II) triflate-catalyzed heteroannulation: application to detection of TNT

New analogues of solid state fluorescent quino[2,3-b]carbazoles have been synthesized from heteroannulation of quinoline alkynylaldehyde and indole. Their preliminary photophysical properties are studied and application as chemosensory material for detection of trinitrotoluene is explored.     

Thermal Studies on Ammonium Uranates

Ammonium uranates are important intermediates in the preparation of nuclear fuel UO₂. These can generally be prepared through two different routes: heterogeneous (conventional) and homogeneous methods of precipitation. In the conventional method, ammonium hydroxide, gaseous ammonia and ammonium carbonate are the precipitating agents. In the homogeneous method, urea hydrolysis is used to generate in situ ammonia needed for precipitation. For the present studies, ammonium hydroxide is used for the conventional and urea for the homogeneous methods of precipitation. The uranates, thusprepared, are characterized by thermogravimetry (TG), differential thermogravimetry (DTG)and differential thermal analysis (DTA). Thermally the numbers of decomposition steps are identical for both uranates but the temperatures of the decomposition and mass losses vary. The intermediate and final oxides are identified by X-ray diffractometry (XRD). This revised version was published online in July 2006 with corrections to the Cover Date.     

LC‐MS/MS‐ESI method for simultaneous quantitation of metformin and repaglinidie in rat plasma and its application to pharmacokinetic study in rats

A highly sensitive and specific LC‐MS/MS‐ESI method has been developed for simultaneous quantification of metformin (MFN) and repaglinide (RGN) in rat plasma (50 μL) using phenacetin as an internal standard (IS). Simple protein precipitation was used to extract MFN and RGN from rat plasma. The chromatographic resolution of MFN, RGN and IS was achieved with a mobile phase consisting of 0.2% formic acid in water–acetonitrile (1:1, v/v) with a time program flow gradient on a Chromolith RP‐18e column. The total chromatographic run time was 3.5 min and the elution of MFN, RGN and IS occurred at 1.64, 2.21 and 2.15 min, respectively. A linear response function was established for the range of concentrations 0.855–394 and 0.021–21.7 ng/mL for MFN and RGN, respectively. The intra‐ and inter‐day precision values for MFN and RGN met the acceptance as per FDA guidelines. MFN and RGN were stable in battery of stability studies viz., bench‐top, auto‐sampler and freeze–thaw cycles. The developed assay was applied to a pharmacokinetic study in rats. Copyright © 2012 John Wiley & Sons, Ltd.     

Stability analysis of the Rayleigh–Bénard convection for a fluid with temperature and pressure dependent viscosity

The classical problem of thermal-convection involving the classical Navier–Stokes fluid with a constant or temperature dependent viscosity, within the context of the Oberbeck–Boussinesq approximation, is one of the most intensely studied problems in fluid mechanics. In this paper, we study thermal-convection in a fluid with a viscosity that depends on both the temperature and pressure, within the context of a generalization of the Oberbeck–Boussinesq approximation. Assuming that the viscosity is an analytic function of the temperature and pressure we study the linear as well as the non-linear stability of the problem of Rayleigh–Bénard convection. We show that the principle of exchange of stability holds and the Rayleigh numbers for the linear and non-linear stability coincide.     

Ultrasonic Investigations in Ternary Mixtures Containing Water, 2-Butoxyethanol and <Emphasis Type="Italic">t</Emphasis>-Butanol at 298.15 K

Ultrasonic speeds in, and isentropic compressibilities of, aqueous solutions of water + 2-butoxyethanol (2BE)+t-butanol have been determined at 298.15 K. The concentrations of t-butanol at which the ultrasonic speed becomes maximum and isentropic compressibility becomes minimum are found to decrease with increases in the concentration of 2BE, x _2BE, in the cosolvent (aqueous 2BE). This behavior indicates that the aqueous ternary solutions are less structured than aqueous t-butanol. In the presence of 2-butoxyethanol, enhancement in the hydrogen bonded structure of water due to hydrophobic hydration between t-butanol and water molecules decreases as the concentration of x _2BE in the cosolvent increases. When x _2BE>0.2, the ternary solution behaves like a normal liquid. This behavior is also very well reflected in the concentration dependence of the excess ultrasonic speed and excess isentropic compressibility. The optimum concentrations of t-butanol, ($x_{\mathrm{t}\mbox{-}\mathrm{B}}$x_{\mathrm{t}\mbox{-}\mathrm{B}})_opt, at which extrema in ultrasonic speed, isentropic compressibility, excess ultrasonic speed and excess isentropic compressibility are observed decrease with increase in x _2BE in the cosolvent. The results are explained as being due to a reduction in the strength of hydrophobic interactions responsible for enhancement in the structure of water in aqueous t-butanol in the presence 2BE. Beyond (x_t-Bx_{\mathrm{t}\mbox{-}\mathrm{B}})_opt, the hydrogen bonded network of water collapses and water, 2-butoxyethanol and t-butanol molecules interact with each other as normal liquid molecules.     

Highly sensitive method for the determination of adenosine by LC-MS/MS-ESI: method validation and scope of application to a pharmacokinetic/pharmacodynamic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of adenosine in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electro‐spray ionization in the positive‐ion mode. The assay procedure involves extraction of adenosine and phenacetin (internal standard, IS) from rat plasma with a simple protein precipitation extraction process. The method was validated using rat plasma with extinguished adenosine endogenous levels. Chromatographic separation was achieved using a binary gradient using mobile phase A (acetonitrile) and B (0.2% formic acid in water) at a flow rate of 0.50 mL/min on an Atlantis dC₁₈ column with a total run time of 4.0 min. The MS/MS ion transitions monitored were 268 → 136 for adenosine and 180 → 110 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.48 ng/mL and the linearity range extended from 0.48 to 1210 ng/mL. The intra‐ and inter‐day precisions were in the ranges 2.32–12.7 and 4.01–9.40%, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

<Emphasis Type="Italic">Brugia malayi</Emphasis> Thioredoxin Peroxidase as a Potential Vaccine Candidate Antigen for Lymphatic Filariasis

Attempts were made to evaluate the protective efficacy of Brugia malayi thioredoxin peroxidase (BmTPX) in a mouse model. Mice immunized with a protein vaccine containing rBmTPX developed higher titres (1:5,000/1:10,000) of anti-BmTPX antibodies, compared with the mice immunized with the alum control. There was a higher level of cellular proliferative response in mice immunized with BmTPX compared with the alum control (p?<?0.05), which was associated with a Th2-type of response. In order to compare the prophylactic efficacy of BmTPX in natural infection, we evaluated the human immune responses to these antigens in endemic normals (EN) and infected individuals (microfilaraemic and chronic pathology). Results showed that EN subjects carry BmTPX-specific IgG1 and IgG3 circulating antibodies against natural exposure to filariasis. Peripheral blood mononuclear cells from EN subjects responded strongly to rBmTPX by proliferating, as well as by secreting interferon (IFN)-γ (Th1) and IL-5 (Th2), a mixed type of response to rBmTPX. In the case of infected individuals, there was no IFN-γ or IL-5 response. Thus, there was a clear dichotomy in the cytokine production by infected versus EN individuals. Our findings suggest that BmTPX may be a suitable antigen candidate for lymphatic filariasis, but a further study is still required.     

Fusion and sorting of two parallel trains of droplets using a railroad-like channel network and guiding tracks

We propose a robust droplet fusion and sorting method for two parallel trains of droplets that is relatively insensitive to frequency and phase mismatch. Conventional methods of droplet fusion require an extremely precise control of aqueous/oil flows for perfect frequency matching between two trains of droplets. In this work, by combining our previous two methods (i.e., droplet synchronization using railroad-like channels and manipulation of shape-dependent droplets using guiding tracks), we realized an error-free droplet fusion/sorting device for the two parallel trains of droplets. If droplet pairs are synchronized through a railroad-like channel, they are electrically fused and the fused droplets transit to a middle guiding track to flow in a middle channel; otherwise non-synchronized non-fused droplets will be discarded into the side waste channels by flowing through their own guiding tracks. The simple droplet synchronization, fusion, and sorting technology will have widespread application in droplet-based chemical or biological experiments, where two trains of the chemically or biologically treated or pre-formed droplets yield a train of 100% one-to-one fused droplets at the desired outlet channel by sorting all the non-synchronized non-fused droplets into waste outlets.     

Effect of annealing on the electronic parameters of Au/poly(ethylmethacrylate)/n-InP Schottky diode with organic interlayer

A thin poly(ethylmethacrylate) (PEMA) layer is deposited on n-InP as an interlayer for electronic modification of Au/n-InP Schottky structure. The electrical properties of Au/PEMA/n-InP Schottky diode have been investigated by current–voltage (I–V) and capacitance–voltage (C–V) measurements at different annealing temperatures. Experimental results show that Au/PEMA/n-InP structure exhibit a good rectifying behavior. An effective barrier height as high as 0.83 eV (I–V) and 1.09 eV (C–V) is achieved for the Au/PEMA/n-InP Schottky structure after annealing at 150 °C compared to the as-deposited and annealed at 100 and 200 °C. Modified Norde's functions and Cheung method are also employed to calculate the barrier height, series resistance and ideality factors. Results show that the barrier height increases upon annealing at 150 °C and then slightly decreases after annealing at 200 °C. The PEMA layer increases the effective barrier height of the structure as this layer creates a physical barrier between the Au metal and the n-InP. Terman's method is used to determine the interface state density and it is found to be 5.141 × 10¹² and 4.660 × 10¹² cm^?2 eV^?1 for the as-deposited and 200 °C annealed Au/PEMA/n-InP Schottky diodes. Finally, it is observed that the Schottky diode parameters change with increasing annealing temperature.     

Photoluminescence electron-transfer quenching of rhenium(I) rectangles with amines

Electron-transfer (ET) reactions from aromatic amines to excited states of rhenium(I)-based molecular rectangles [{Re(CO)3(mu-bpy)Br}{Re(CO)3(mu-L)Br}]2 (bpy = 4,4'-bipyridine, L = 4,4'-dipyridylacetylene (dpa), I; L = 4,4'-dipyridylbutadiyne (dpb), II; and L = 1,4-bis(4'-pyridylethynyl)benzene (bpeb), III) were investigated in a dichloromethane solution using luminescence quenching techniques. Direct evidence for the ET reaction was obtained from the detection of the amine cation radical in this system using time-resolved transient absorption spectroscopy. The values of the luminescence quenching rate constants, kq, of the 3MLCT excited state of Re(I) rectangles with amines were found to be higher than those for the monomeric Re(I) complexes and other Re(I)-based metallacyclophanes. The observed kq values were correlated well with the driving force (Delta G degrees) for the ET reactions. In addition, a semiclassical theory of ET was successfully applied to the photoluminescence quenching of Re(I) rectangles with amines.