Ionization and population transfer in lithium Rydberg states with ultrashort chirped laser pulses

We present a theoretical study of dynamics of Rydberg states of lithium using ultra short chirped laser pulse having a Gaussian envelope. The population transfer probabilities are calculated of different Rydberg states on chirped laser factors. The calculations are performed by direct numerical integration of Schr?dinger equation using fourth order Runge-Kutta method. The behavior of dynamics of Rydberg states for these factors is of great significance. These results are of potential interest in coherent quantum control, quantum computation and in many physical and chemical processes.     

Estimation of effective Debye temperature from sound velocity of N-(p-n-alkoxybenzylidene)-p-n-alkylanilines, (nO.m) liquid crystalline compounds

The ratio of specific heats (γ), Poisson's ratio (σ), effective Debye temperature (θ_D) collision factor (S_m), etc., are estimated in different LC phases of N-(p-n-alkoxybenzylidene)-p-n-alkylanilines, (nO.m's) liquid crystalline compounds using the density and sound velocity data. The variation of these parameters in different mesomorphic phases with the chain length is studied. The effective Debye temperature (θ_D), the collision factor (S_m) exhibits a similar variation with the alkyl chain length. Further, the space filling factor (r_fm) estimated using Kittel's formula is constant for all the materials irrespective of the phase with a value of 0.416. The molecular radius shows an increment of 0.074, 0.072 and 0.068 ? per CH₂ group in isotropic, nematic and smectic-A phases respectively in 5O.m series. Further, the specific heat ratio (γ) value is found to be lower in isotropic phase than in liquid crystalline phases. The data is compared with the body of the data in the literature.     

Using Gas Modifiers to Significantly Improve Sensitivity and Selectivity in a Cylindrical FAIMS Device

Recent reports describing enhanced performance when using gas additives in a DMS device (planar electrodes) have indicated that comparable benefits are not attainable using FAIMS (cylindrical electrodes), owing to the non-homogeneous electric fields within the analyzer region. In this study, a FAIMS system (having cylindrical electrodes) was modified to allow for controlled delivery of gas additives. An experiment was carried out that illustrates the important distinction between gas modifiers present as unregulated contaminants and modifiers added in a controlled manner. The effect of contamination was simulated by adjusting the ESI needle position to promote incomplete desolvation, thereby permitting ESI solvent vapor into the FAIMS analyzer region, causing signal instability and irreproducible CV values. However, by actively controlling the delivery of the gas modifier, reproducible CV spectra were obtained. The effects of adding different gas modifiers were examined using 15 positive ions having mass-to-charge (m/z) values between 90 and 734. Significant improvements in peak capacity and increases in ion transmission were readily attained by adding acetonitrile vapor, even at trace levels (≤0.1%). Increases in signal intensity were greatest for the low m/z ions; for the six lowest molecular weight species, signal intensities increased by ～10- to over 100-fold compared with using nitrogen without gas additives, resulting in equivalent or better signal intensities compared with ESI without FAIMS. These results confirm that analytical benefits derived from the addition of gas modifiers reported with a uniform electric field (DMS) also are observed using a non-homogenous electric field (FAIMS) in the analyser region.

Simulation and experimental studies of a vibro-impact capsule system driven by an external magnetic field

This paper studies the electromagnetic field used for driving a vibro-impact capsule prototype for small bowel endoscopy. Mathematical models of the electromagnetic field and the capsule system are introduced, and analytical solution of the magnetic force applied on the capsule is derived and verified by experiment. The impact force between the inner mass of the capsule and the capsule body is also compared via numerical simulation and experimental testing. By comparing the capsule’s progressions under different control parameters (e.g. the excitation frequency and duty cycle), the merits of using the vibro-impact propulsion are revealed. Based on the experimental results, the optimised speed of the prototype can achieve up to 3.85 mm/s. It is therefore that the potential feasibility of using the external electromagnetic field for propelling the vibro-impact capsule system is validated.

     

Synthesis of 3-(arylamino)-5-bromo-2-phenyl-2,3-dihydro-2λ5-benzo[d][1,2]-oxaphosphol-2-oxides

An efficient synthesis of cis-3-(arylamino)-5-bromo-2-phenyl-2,3-dihydro-2λ⁵-benzo[d][1,2]-oxaphosphol-2-oxides 4a–h is described involving a three-component reaction of dichlorophenylphosphine (2), 5-bromosalicylaldehyde (1), and different substituted aromatic primary amines (3) in anhydrous benzene. The product structures were characterized by IR and NMR spectral data.     

Simultaneous Quantification of Aliskiren, Valsartan and Sitagliptin by LC with Fluorescence Detection: Evidence of Pharmacokinetic Interaction in Rats

A sensitive, precise and simple LC method for the simultaneous quantification of aliskiren, valsartan and sitagliptin in rat plasma has been developed and validated. The chromatographic separation was achieved on a C₁₈ column (250 mm × 4.6 mm, 5 μm) maintained at room temperature, using isocratic elution with acetonitrile/20 mM ammonium acetate buffer (35:65, v/v), pH adjusted to 4.85 with glacial acetic acid, and detected using a fluorescence detector. Liquid–liquid extraction of the aliskiren, valsartan and sitagliptin from the rat plasma with t-butyl methyl ether resulted in their high recoveries. LC calibration curves based on the extracts from the rat plasma were linear in the range of 25–2,000 ng mL^?1 for aliskiren and sitagliptin and 50–4,000 ng mL^?1 for valsartan. The limits of quantification were 25 ng mL^?1 for aliskiren and sitagliptin and 50 ng mL^?1 for valsartan. The precision and accuracy of the method were well within the generally accepted criteria for biomedical analysis. The described method was successfully applied to study the pharmacokinetics of aliskiren, valsartan and sitagliptin following oral administration, individually as well as in combination in Sprague–Dawley rats. The results of the study implied the occurrence of pharmacokinetic interaction upon the co-administration of these three drugs.     

Stereocontrolled Oxidative Additions upon 1,4-Dihydropyridines: Synthesis of Hexahydrofuro[2,3-b]pyridine and Hexahydropyrano[2,3-b]pyridine Derivatives

trans-α-Alkoxy-β-halotetrahydropyridines are synthesized in a very efficient single step by stereocontrolled N-halosuccinimide (NXS)–promoted alcohol addition to the enamine group in N-alkyl-1,4-dihydropyridines. These compounds are cyclized using sodium cyanoborohydride in the presence of 2,2′-azobis(2-methylpropionitrile), azabisisobutyronitrile (AIBN) (cat.), and tributylstannane (cat.), affording hexahydrofuro[2,3-b]pyridine and hexahydropyrano[2,3-b]pyridine derivatives. The cyclized product undergoes ring-opening reaction by a nucleophile in the presence of Lewis acid to afford highly functionalized tetrahydropyridines.     

System reduction using factor division algorithm and eigen spectrum analysis

A mixed method is proposed which combines the factor division algorithm with the eigen spectrum analysis for deriving reduced order models of high-order linear time invariant systems. Pole centroid and system stiffness of both original and reduced order systems remain same in this method. The proposed method guarantees stability of the reduced model if the original high-order system is stable and is comparable in quality with the other well known existing methods of order reduction. The method is illustrated by four numerical examples including one example of a multivariable system.     

Studies on pyrimidine derivatives. Michael addition of β-nitrostyrenes to substituted 6-aminouracils

A series of 5-(2-nitro-l-phenyl)ethyluracils were obtained when β-nitrostyrenes were reacted with 1,3-di-methyl-6-substituted uracil derivatives, instead of cyclic compounds. The structures of the compounds 5, 6 , and 7 were proved by spectroscopic methods and their mass fragmentation patterns are discussed.     

Trimethylsilyl cyanide addition to aldimines and its application in the synthesis of (S)-phenylglycine methyl ester

The addition of TMSCN to a variety of arylaldimines (Strecker reaction) in the presence of LiClO₄ or BF₃·Et₂O in acetonitrile has been studied. The reaction provided the addition products in very high yields. The method has been successfully utilized for the synthesis of (S)-phenylglycine methyl ester.