Study of pure and semileptonic decays of Ds meson within R-parity violating supersymmetric model

We present the comaprative study of semileptonic and leptonic decays of Ds, D±and D0meson（D →M l＋-αl-β, D → l＋αlβ, D → l＋αvα;α,β=e,μ） within the framework of R-parity violating the（ Rp） Minimal Supersymmetric Standard Model（MSSM）. The comparison shows that combination and product couplings,（λβiα λ＊ ij qor λβqkλ＊αj k）contribution to the branching fractions of the said processes（under consideration） is consistent with or comparable to the experimental measurements in most of the cases. However, some cases exist where these contributions are highly suppressed. We identify such cases in our analysis and single out the important ones suitable for exploring in the future and current experiments.     

Investigations of Viscous Dissipation in Stagnation Point Flow Past a Stretchable Riga Wall: Modern Analysis of Heat Transport

This article scrutinizes the features of viscous dissipation in the stagnation point flow past through a linearly stretched Riga wall by implementing Cattaneo-Christov heat flux model. Viscous dissipation is carried out in Cattaneo-Christov diffusion analysis for the first time in this letter. As a result of Cattaneo-Christov model, some extra terms of viscous dissipation are appeared in the energy equation. These extra terms of viscous dissipation are missing in the literature. On the utilization of suitable transformations, the equations governing the problem are reduced under the boundary layer approximation into the non-linear and dimensionless ordinary differential equations. Convergent approach is utilized to solve the dimensionless governing equations. The solution thus acquired is used to highlight the effects of emerging parameters on velocity distribution and fluid's temperature through the graphs. Features of the drag force (or skin friction co-efficient) are graphically interpreted. It is noticed that the presence of modified Hartman number helps to reduce the fluid's temperature but enhances the velocity profile. Further an enlargement in the value of thermal time relaxation parameter helps to decrease the temperature distribution.     

Searches for B0 decays to combinations of two charmless isoscalar mesons

We search for B meson decays into two-body combinations of eta, eta', omega, and phi mesons from 89 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find the branching fraction B(B0-->etaomega)=(4.0(+1.3)(-1.2)+/-0.4)x10(-6) with a significance of 4.3 sigma. For the other decay modes we set the following 90% confidence level upper limits on the branching fractions, in units of 10(-6): B(B0-->etaeta)<2.8, B(B0-->etaeta')<4.6, B(B0-->eta'eta')<10, B(B0-->eta'omega)<2.8, B(B0-->etaphi)<1.0, B(B0-->eta'phi)<4.5, and B(B0-->phiphi)<1.5.     

Evidence for the rare decay B-->K*l+l- and measurement of the B-->Kl+l- branching fraction

We present evidence for the flavor-changing neutral current decay B-->K*l+l- and a measurement of the branching fraction for the related process B-->K l+l-, where l+l- is either an epsilon+epsilon- or a mu+mu- pair. These decays are highly suppressed in the standard model, and they are sensitive to contributions from new particles in the intermediate state. The data sample comprises 123 x 10(6) Upsilon(4S)-->B(-)B decays collected with the BABAR detector at the SLAC PEP-II epsilon+epsilon- storage ring. Averaging over K(*) isospin and lepton flavor, we obtain the branching fractions B(B-->Kl+l-)=(0.65(+0.14)(-0.13)+/-0.04)x10(-6) and B(B-->K*l+l-)=(0.88(+0.33)(-0.29)+/-0.10)x10(-6), where the uncertainties are statistical and systematic, respectively. The significance of the B-->Kl+l- signal is over 8sigma, while for B-->K*l+l- it is 3.3sigma.     

Development of a stir bar sorptive extraction method coupled to solidification of floating droplets dispersive liquid–liquid microextraction based on deep eutectic solvents for the extraction of acidic pesticides from tomato samples

A stir bar sorptive extraction method coupled with deep eutectic solvent based solidification of floating organic droplets–dispersive liquid–liquid microextraction has been used for the simultaneous derivatization and extraction of some acidic pesticides in tomato samples. In this method, initially the analytes are adsorbed on a coated stir bar from tomato juice filled in a narrow tube. After extraction, the stir bar is removed and a water–miscible deep eutectic solvent is used to elute the analytes. Afterward, a derivatization agent and a water–immiscible deep eutectic solvent (as an extraction solvent) with melting point near to room temperature are added to the obtained eluant at µL–levels and the obtained mixture is rapidly injected into deionized water. Under the optimum conditions, the introduced method indicated high enhancement (1543–3353) and enrichment (2530–2999) factors, low limits of detection (7–14 ng/L) and quantification (23–47 ng/L), good linearity (r² ≥ 0.9982), and satisfactory repeatabilities (relative standard deviation ≤12% for intra– and inter–day precisions at a concentration of 100 ng/L of each analyte). Finally, the proposed method was applied in analysis of the analytes in tomato samples.     

Theoretical Treatment of a Cathodic Stripping Mechanism of an Insoluble Salt Coupled with a Chemical Reaction in Conditions of Square Wave Voltammetry. Application to 6‐Mercaptopurine‐9‐D‐Riboside in the Presence of Ni(II)

Cathodic stripping mechanism of an insoluble salt coupled with a homogenous chemical reaction is considered both theoretically and experimentally under conditions of square‐wave voltammetry. For the mercury electrode in aqueous solution, the electrode reaction is described as L(aq)+Hg(l)=HgL(s)+2e^?, where L(aq) is the reactive ligand that forms a sparingly soluble compound HgL(s). The electrode reaction is coupled with a homogenous, first‐order chemical reaction, A(aq)=L(aq). Theoretical predictions are confirmed by experiments with 6‐mercaptopurine‐9‐D‐riboside in the presence of nickel(II) ions.     

Development of a new microextraction method based on a dynamic single drop in a narrow-bore tube: application in extraction and preconcentration of some organic pollutants in well water and grape juice samples

A novel sample preparation technique, the microextraction method based on a dynamic single drop in a narrow-bore tube, coupled with gas chromatography-flame ionization detection (GC-FID) is presented in this paper. The most important features of this method are simplicity and high enrichment factors. In this method, a microdrop of an extraction solvent assisted by an air bubble was repeatedly passed through a narrow-bore closed end tube containing aqueous sample. It has been successfully used for the analysis of some pesticides as model analytes in aqueous samples. Parameters affecting the method's performance such as selection of extraction solvent type and volume, number of extractions, volume of aqueous sample (tube length), and salt effect were studied and optimized. Under the optimal conditions, the enrichment factors (EFs) for triazole pesticides were in the range of 141-214 and the limits of detection (LODs) were between 2 and 112 μg L⁻¹. The relative standard deviations (C = 1000 μg L⁻¹, n = 6) were obtained in the range of 2.9-4.5%. The recoveries obtained for the spiked well water and grape juice samples were between 71 and 106%. Low cost, relatively short sample preparation time and less solvent consumption are other advantages of the proposed method.     

Elimination of man-made radionuclides from natural waters by applying a standard coagulation-flocculation process

We studied the effectiveness of potable water treatment processes that consist of the stages of coagulation-flocculation-decantation, using iron-based coagulants, in eliminating gamma-emitting man-made radioisotopes of cesium, strontium, and americium from two natural waters with different degrees of mineralization. The resulting decontamination was found to depend on the chemical behavior of each of the radionuclides considered, on the pH at which the process of coagulation is carried out, and on the concentration of the other stable cations present. This revised version was published online in July 2006 with corrections to the Cover Date.     

A simple and rapid dispersive liquid-liquid microextraction method followed by GC-FID for determination of N-methylpyrrolidine in cefepime

A simple, rapid and efficient sample preparation technique, dispersive liquid-liquid microextraction, coupled with gas chromatography-flame ionization detection has been developed to determine N-methylpyrrolidine in cefepime. The effect of various experimental factors on the preparation procedure, such as the nature and volume of extraction and disperser solvents, extraction time, the nature of buffer and its pH, and salt effect, was investigated, optimized and the following results were obtained: extraction solvent, chloroform; dispersive solvent and solvent for dissolving cefepime, a mixture of methanol/water (88:12, v/v); salting out agent, NaCl; and buffer, carbonate/bicarbonate (C=0.5?M, pH=12). The optimized conditions were applied to the real sample (cefepime) for the extraction and determination of N-methylpyrrolidine. The calibration graph is linear from 0.02 to 850?mg/L with the square of correlation coefficient 0.999. LOD and LOQ are 6.4 and 21.2?μg/L in solution, respectively, and 0.2 (2×10(-5) ) and 0.6 (6×10(-5) ) μg/g (%, w/w) in cefepime powder, respectively, using sample size 50?mg. Repeatability of the method is good and RSD% for six repeated experiments (C=170?mg/L) is 6.35%.     

Role of cetyltrimethylammonium bromide (cationic surfactant) on the tryptophan–MnO4 reaction

Upon addition of permanganate to a solution of tryptophan (Trp), yellow-brown color species appears within the time of mixing of tryptophan in absence and presence of cetyltrimethylammonium bromide (CTAB), which was stable for some days. Spectroscopic and kinetic evidences suggest the formation of water-soluble colloidal MnO₂ as the most stable reduction product of MnO₄⁻. Carbon dioxide and ammonia are not formed as the oxidation products. Carbon–carbon double bond of indole moiety of Trp is responsible for the fast reduction of permanganate. Cetyltrimethylammonium bromide catalyses the permanganate oxidation of Trp with a rate enhancement of ca. 200-fold. Sub- and postmicellar catalytic effect of CTAB ascribed to the association/incorporation/solubilization of both reactants (MnO₄⁻ and Trp) with the CTAB aggregates and into the Stern layer of cationic micelles. Quantitative kinetic analysis of the rate constant–[CTAB] data has been performed on the basis of modified pseudo-phase model of the micelles. A comparison was made of the oxidation rates of different amino acids by permanganate. The order of the effectiveness was as follows: tryptophan  tyrosine  phenylalanine.