Controlled ex-vivo plasma hydrolysis of valaciclovir to acyclovir demonstration using tandem mass spectrometry.

Plasma estimation of valaciclovir, an antiviral drug, is challenging due to both in-vivo and ex-vivo hydrolysis to active metabolite acyclovir. A simultaneous method is described involving the solid-phase ion-exchange extraction procedure requiring 100 μL of plasma volume, a reverse-phase Lichrosphere RP Select B (125 × 6 mm, 5 μm) column and isocratic mobile phase to achieve the desired chromatographic separation. ESI-MS/MS multiple reaction monitoring in positive polarity, detected mass pairs for valaciclovir (m/z 325.

Rainfall, household crowding, and acute respiratory infections in the tropics.

SUMMARYAcute respiratory infections (ARI) are the leading cause of death worldwide in children aged <5 years, and understanding contributing factors to their seasonality is important for targeting and implementing prevention strategies. In tropical climates, ARI typically peak during the pre-rainy and rainy seasons. One hypothesis is that rainfall leads to more time spent indoors, thus increasing exposure to other people and in turn increasing the risk of ARI.

Malaria epidemiology along Indo-Bangladesh border in Tripura State, India.

Malaria epidemiological surveys were conducted in 16 villages along the Indo-Bangladesh border in Tripura, northeastern India. Insecticide resistance among malaria vectors and chloroquine resistance in the parasite were also studied along with monitoring of vector density using light traps. The epidemiological data indicated that malaria incidence was highest during June-July and lowest during November.

Nonawakening following general anaesthesia after ventriculo-peritoneal shunt surgery: An acute presentation of intracerebral haemorrhage.

Emergence from general anaesthesia has been a process characterized by large individual variability. Delayed emergence from anaesthesia remains a major cause of concern both for anaesthesiologist and surgeon. The principal factor for delayed awakening from anaesthesia is assumed to be the medications and anaesthetic agents used in the perioperative period.

Selective suppression of two-photon fluorescence in laser scanning microscopy by ultrafast pulse-train excitation.

Selective excitation of a particular fluorophore in the presence of others demands clever design of the optical field interacting with the molecules. We describe the use of 20- to 50-GHz pulse-train excitation leading to two-photon absorption, followed by successive one-photon stimulated emission as a potential technique in the context of controlling two-photon molecular fluorescence, with applications in microscopy.

Bioequivalence of venlafaxine modified-release capsule revisited with an innovative approach using experimental and predictive models.

Background: To evaluate the venlafaxine:O-desmethyl venlafaxine (active metabolite) in vivo formation ratio (MR) in three independent bioequivalence (BE) studies consisting of single-dosed (under fasted and fed conditions) and multiple-dosed clinical trials on healthy subjects. The pooled data pharmacokinetic (PK) analysis demonstrates a model to conduct enantiomer/racemate/active metabolite bioanalysis for regulatory submission of bioavailability/bioequivalence (BA/BE) studies using an interesting MR concept.

Results: BE was established for all three studies.

Probing intermolecular interaction through thermal-lens spectroscopy.

Binary liquid mixtures are studied using femtosecond pump-probe thermal-lens (TL) spectroscopy. Changes in the measured TL signals as a function of relative concentration of binary mixtures show that these result from a combined effect of physical and molecular properties of the constituent binary liquids. The experimental TL values deviate from the ones calculated from phenomenological equations.

Rational design for variability minimization in bioanalytical method validation: illustration with LC-MS/MS assay method for terbinafine estimation in human plasma.

Terbinafine, a widely used antifungal drug, is a challenging molecule for quantitative bioanalysis due to certain factors contributing assay variability. Despite previous attempts at human plasma determination of terbinafine, exhaustive stability of the drug or an internal standard was lacking. Internal standard stability with negligible variation throughout the analysis is an indicator of a reliable bioanalytical method as the majority of LC-MS/MS assays are based on analyte/IS response ratios for quantitation.

Stability-indicating validation of acitretin and isoacitretin in human plasma by LC-ESI-MS/MS bioanalytical method and its application to pharmacokinetic analysis.

LC- ESI- MS/MS simultaneous bioanalytical method was developed to determine acitretin and its metabolite isoacitretin in human plasma using acitretin-d3 used as the internal standard for both analytes. The compounds were extracted using protein precipitation coupled with liquid-liquid extraction with flash freezing technique. Negative mass transitions (m/z) of acitretin, isoacitretin and acitretin-d3 were detected in multiple reactions monitoring (MRM) mode at 325.

Towards Stable Trapping of Single Macromolecules in Solution.

The implementation of high instantaneous peak power of a femtosecond laser pulse at moderate time-averaged power (~10 mW) to trap latex nanoparticles, which is otherwise impossible with continuous wave illumination at similar power level, has recently been shown [De, A. K., Roy, D.

A new two-pulse synthesis model for digital volume pulse signal analysis.

Analysis of digital volume pulse (DVP) signal measured by photoplethysmograph (PPG) technique is a low cost non-invasive method of obtaining vital information related to arterial conditions. In this paper, we present a new two-pulse synthesis (TPS) model for deriving arterial parameters, useful for noninvasive assessment of human vascular health. The model is based on the use of Rayleigh function.

Spectroscopic and theoretical insights into the origin of fullerene-calix[4]pyrrole interaction.

The present paper reports, for the first time, supramolecular interaction of meso-octamethyl calix[4]pyrrole (1) with fullerenes C(60) and C(70) in solutions having varying polarity (e.g., toluene, 1,2-dichlorobenzene and benzonitrile and chloroform).

Leptospirosis as a cause of fever in urban Bangladesh.

We tested paired sera from 584 febrile persons in an low-income urban community in Bangladesh for evidence of Leptospira infection. A total of 8.4% of the persons met criteria for definite or probable infection.

Bactericidal effects of silver plus titanium dioxide-coated endotracheal tubes on Pseudomonas aeruginosa and Staphylococcus aureus.

Purpose: Ventilator-associated pneumonia (VAP) is a nosocomial infection resulting in significant morbidity and mortality. Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S.

Polarization induced control of single and two-photon fluorescence.

Modulation of two-photon absorption, two-photon fluorescence (TPF), as well as single-photon fluorescence (SPF), is shown through incident laser polarization for different fluorescent dyes. TPF intensity increases as the polarization changes from circular to linear irrespective of the dye, though the intensity and wavelength dependent studies of two-photon polarization ratio for any particular dye (e.g.

Synthesis, structure, and two-photon absorption studies of a phosphorus-based tris hydrazone ligand (S)P[N(Me)N=CH-C6H3-2-OH-4-N(CH2CH3)2]3 and its metal complexes.

A phosphorus-supported multidentate ligand (S)P[N(Me)N=CH-C(6)H(3)-2-OH-4-N(CH (2)CH(3))(2)](3) (1) has been used to prepare mononuclear complexes LM [M = Fe (2) Co (3)] and trinuclear complexes L(2)M(3) [M = Mn (4), Ni (5), Zn (6), Mg (7), Cd (8)]. In both 2 and 3 the ligand binds the metal ion in a facial coordination mode utilizing three imino nitrogen (3N) and three phenolic oxygen (3O) atoms. The molecular structures of L(2)Mn(3), L(2)Ni(3), L(2)Zn(3), L(2)Mg(3), and L(2)Cd(3) (4-8) are similar; two trihydrazone ligands are involved in coordination to hold the three metal ions in a linear fashion.

Influenza is a major contributor to childhood pneumonia in a tropical developing country.

Background: Pneumonia is the leading cause of child mortality worldwide. The role of influenza in childhood pneumonia in tropical developing countries is poorly understood. We undertook population-based surveillance among low-income urban preschool children to determine its role in childhood pneumonia.

Fluorescence advantages with microscopic spatiotemporal control.

We present a clever design concept of using femtosecond laser pulses in microscopy by selective excitation or de-excitation of one fluorophore over the other overlapping one. Using either a simple pair of femtosecond pulses with variable delay or using a train of laser pulses at 20-50 Giga-Hertz excitation, we show controlled fluorescence excitation or suppression of one of the fluorophores with respect to the other through wave-packet interference, an effect that prevails even after the fluorophore coherence timescale. Such an approach can be used both under the single-photon excitation as well as in the multi-photon excitation conditions resulting in effective higher spatial resolution.

Applying genetic algorithm optimization to a folded geometry acousto-optic modulated spatial pulse shaper.

A folded geometry acousto-optic modulator spatial pulse shaper has been designed for shaping individual pulses from a high power amplified laser. The design preserves the capability of computer programmable amplitude and phase modulation of femtosecond laser pulses. An additional application of genetic algorithm optimization approach for compressing a stretched pulse is also demonstrated for such a pulse shaper.

Ultrafast pulse-pair control in multiphoton fluorescence laser-scanning microscopy.

In multiphoton fluorescence laser-scanning microscopy, ultrafast laser pulses [i.e., light pulses having pulse width View Article and Find Full Text PDF

Probing the ultrafast solution dynamics of a cyanine dye in an organic solvent interfaced with water.

Dependence of ultrafast dynamics on the excited state evolution and ground state recovery of a cyanine dye (IR125) in dichloromethane (DCM) solvent interfaced with neat water is presented. We use degenerate pump-probe transient absorption spectroscopy to show that the excited-state dynamics of the dye molecule is strongly dependent on the position of the measurements from bulk DCM solution to the solution near the water layer. The decay component of the transient corresponding to the excited state lifetime increases from bulk DCM solution to its interface with water.

Solvent effect on two-photon absorption and fluorescence of rhodamine dyes.

For a series of rhodamine dyes, two-photon absorption (TPA) and two-photon fluorescence (TPF) have been performed in different solvents. Solvent-dependent TPA spectra of these dyes were measured with open aperture z-scan method and compared to their respective single-photon spectra at equivalent energies. In the TPA spectra, relative peak intensities and positions are highly solvent dependent, which could be a result of vibronic couplings that depend on solvent environment.

Room temperature reversible hydrogen storage in polyaniline (PANI) nanofibers.

We report for the first time the reversible hydrogen storage behavior at room temperature in polyaniline nanofibers. The rate of hydrogen sorption during the initial run was very rapid and an extended plateau pressure of about 30 bars was obtained from the pressure-composition isotherm profiles of these polyaniline nanofibers. The reversible cycling capacity of approximately 3-4 wt% was demonstrated at room temperature and has been attributed to the unique nanofibrous microstructural and surface properties.

Evidence for a layer-dependent Ehrlich-Schwöbel barrier in organic thin film growth.

We report direct experimental evidence for a layer-dependent step-edge barrier in organic thin film growth, investigating di-indenoperylene on SiO_{2} as an archetypical system. In particular, we show that a noticeable Ehrlich-Schwöbel effect emerges only beyond the 3rd molecular layer, accompanied by mass step-upward diffusion. We further disclose that this thickness dependence of the interlayer transport is directly related to molecular reorientations during the first stages of the growth.