Energy transfer kinetics of the np5(n + 1)p excited states of Ne and Kr

Energy transfer rate constants for Ne(2p(5)3p) and Kr(4p(5)5p) atoms colliding with ground state rare gas atoms (Rg) have been measured. In part, this study is motivated by the possibility of using excited rare gas atoms as the active species in optically pumped laser systems. Rg(np(5)(n + 1)s) metastable states may be produced using low-power electrical discharges. The potential then exits for optical pumping and laser action on the np(5)(n + 1)p ? np(5)(n + 1)s transitions. Knowledge of the rate constants for collisional energy transfer and deactivation of the np(5)(n + 1)p states is required to evaluate the laser potential for various Rg + buffer gas combinations. In the present study we have characterized energy transfer processes for Ne (2p(5)3p) + He for the six lowest energy states of the multiplet. Rate constants for state-to-state transfer have been determined. Deactivation of the lowest energy level of Kr (4p(5)5p) by He, Ne, and Kr has also been characterized. Initial results suggest that Kr (4p(5)5p) + Ne mixtures may be the best suited for optically pumped laser applications.     

Influence of ion size on the stability of chloroplumbates containing PbCl<Stack><Subscript>5</Subscript><Superscript>−</Superscript></Stack> or PbCl<Stack><Subscript>6</Subscript><Superscript>2−</Superscript></Stack>

The enthalpies of formation of PbCl₄, PbCl₅⁻ and PbCl₆²⁻, originating from quantum mechanics, have enabled the thermodynamic behaviour of these ions with respect to Cl-detachment to be assessed. The stability of salts containing PbCl₅⁻ and PbCl₆²⁻ as a function of the dimensions of these anions and complementary cations was studied using an approach combining the Kapustinskii-Yatsimirskii equation with basic thermochemical relationships. It was found that hexachloroplumbates of monovalent metal cations will not dissociate into metal chlorides and PbCl₄, provided the complementary cations are suitably large in size. Hexachloroplumbates of divalent metal cations have not yet been synthesised since no known metal cations attain the requisite large size. Such salts will not dissociate if the divalent metal cations are able to complex suitably large electron-donating ligands. The pentachloroplumbates of both monovalent and divalent metal cations are unstable, since no known metal cations have appropriately large ionic radii. The approach adopted appears to be useful for the examination of the thermal behaviour, stability and reactivity of chloroplumbates.     

An ab initio study of the proton affinities of some heteroatomic rings: Imidazole,oxazole, and thiazole

The proton affinities of imidazole, oxazole, and thiazole rings, relevant to the binding of lexitropsins that contain these rings to the minor groove of DNA, are calculated using ab initio (Hartree–Fock) calculations. It is found that the proton affinities decrease in the order imidazole, oxazole, thiazole and that a methyl group substituent increases the proton affinity of imidazole, while a peptidic group decreases it.     

Protonation and hydrogenation of triosmium clusters containing the bridging diphosphine ligands Ph2P(CH2nPPh2 (n = 1 to 4)

Members of the series of bridging diphosphine clusters [Os₃(CO)₁₀(diphos)] where diphos = Ph₂P(CH_2nPPh₂ [dppm (n = 1), dppe (n = 2), dppp (n = 3), or dppb (n = 4)] show interesting differences in their reactivity towards H⁺ and H₂. Protonation leads to [Os₃(μ-H)(CO)₁₀(diphos)]⁺ with the hydrides bridging the same osmium atoms as the diphos ligand when diphos is dppe, dppp, or dppb, whereas the hydride and dppm bridge different edges in [Os₃9μ-H)(CO)₁₀(dppm)]⁺. Hydrogenation of the 1,2-diphos compounds leads to [Os₃(μ-H)₂(CO)₈(diphos)] (diphos = dppm, dppe, dppp) in good to excellent yield but the dppb analogue could not be made. Geometric and electronic factors affecting the ability to incorporate hydride ligands in these clusters are discussed.     

Improvement of Seed Germination Rate,Agronomic Traits,Enzymatic Activity and Nutritional Composition of Bread Wheat (Triticum aestivum) Using Low-Frequency Glow Discharge Plasma

Plasma Chemistry and Plasma Processing - Plasma agriculture is an emerging field. In this report, we studied the effect of medium pressure (~?10&nbsp;torr) low-frequency...     

Micellar and salt effects on the interaction of [Cu(II)‐Gly‐Gly]+ with ninhydrin

The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the kinetics of interaction of copper dipeptide complex [Cu(II)‐Gly‐Gly]⁺ with ninhydrin has been studied spectrophotometrically at 70°C and pH 5.0. The reaction follows first‐ and fractional‐order kinetics, respectively, in complex and ninhydrin. The reaction is catalyzed by CTAB micelles, and the maximum rate enhancement is about twofold. The results obtained in the micellar medium are treated quantitatively in terms of the kinetic pseudophase and Piszkiewicz models. The rate constants (k_obs or k_Ψ), micellar‐binding constants (k_S for [Cu(II)‐Gly‐Gly]⁺, k_N for ninhydrin), and index of cooperativity (n) have been evaluated. A mechanism is proposed in accordance with the experimental results. The influence of different inorganic (NaCl, NaBr, Na₂SO₄) and organic (NaBenz, NaSal) salts on the reaction rate has also been seen, and it is found that tightly bound/incorporated counterions are the most effective. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 556–564, 2007     

Single machine scheduling with time-dependent linear deterioration and rate-modifying maintenance

We study single machine scheduling problems with linear time-dependent deterioration effects and maintenance activities. Maintenance periods (MPs) are included into the schedule, so that the machine, that gets worse during the processing, can be restored to a better state. We deal with a job-independent version of the deterioration effects, that is, all jobs share a common deterioration rate. However, we introduce a novel extension to such models and allow the deterioration rates to change after every MP. We study several versions of this generalized problem and design a range of polynomial-time solution algorithms that enable the decision-maker to determine possible sequences of jobs and MPs in the schedule, so that the makespan objective can be minimized. We show that all problems reduce to a linear assignment problem with a product matrix and can be solved by methods very similar to those used for solving problems with positional effects.     

Micellar effects on the rates of the condensation reaction between copper(II)‐histidine complex and ninhydrin

The kinetics of formation of N‐diketohydrindylidenehistidinatocopper(II) complex has been investigated in the presence of cationic cetyltrimethylammonium bromide (CTAB) surfactant in aqueous medium (pH = 5.0). Similarly in aqueous solution, the reaction followed irreversible first‐order kinetics with respect to [Ninhydrin]. Although the reaction mechanism remained unaltered by micelles, a typical k_ψ‐[CTAB] profile was observed, that is, with a progressive increase in [CTAB], the reaction rate increased, reached a maximum value, and then decreased. The results are treated quantitatively in terms of the kinetic pseudo‐phase model. Activation parameters were also evaluated and a large decrease in ΔS^# shows the formation of a well‐structured activated complex. It was found that anionic sodium dodecyl sulphate (SDS) and non‐ionic Triton X‐100 (TX‐100) surfactants have no effect on the reaction. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 729–736, 1999     

Kinetics of interaction of Histidine and Histidine Methyl Ester with Ninhydrin in micellar media

Kinetics of the interaction of histidine and histidine methyl ester with ninhydrin under varying concentrations of reactants, anionic (sodium dodecyl sulphate, SDS), cationic (cetyltrimethylammonium bromide, CTAB) and non‐ionic (Triton X‐100, TX‐100) micelles have been carried out. Rate of the reaction was found to be independent of the initial concentration of histidine (and histidine methyl ester) but was dependent on [Ninhydrin]. The SDS micelles had no effect on the rate of the reaction. In the presence of the CTAB micelles a small enhancement in the rate was observed. The rate − [CTAB] profile showed that the increase in [CTAB] increased the rate up to a maximum value and a further increase had a decreasing effect on the rate. The rate was enhanced by TX‐100 also but, unlike CTAB micelles, TX‐100 possessed a curve without peak for the rate − [TX‐100] profile. The following rate equation was obeyed by the reaction in CTAB and TX‐100 micelles: Values of k_w, k_m, and K_S were evaluated and are reported herein. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 103–111, 1999     

Simplifying sample preparation using fabric phase sorptive extraction technique for the determination of benzodiazepines in blood serum by high‐performance liquid chromatography

Fabric phase sorptive extraction (FPSE), a recently introduced novel sample preparation technology, has been evaluated for the extraction of benzodiazepines from human blood serum. FPSE utilizes a flexible fabric surface as the substrate platform for creating sol‐gel hybrid organic‐inorganic sorbent coatings. FPSE media can be introduced directly into the sample containing the target analyte(s), requiring no need for prior sample pretreatment or clean‐up. Benzodiazepines were selected as model analytes because they represent one of the most widely used therapeutic drugs in psychiatry and are also amongst the most frequently encountered drugs in forensic toxicology. The chromatographic separation of target analytes was performed on a LiChroCART‐LiChrospher®100 RP‐18e (5 µm, 250 × 4 mm) analytical column, operated at room temperature. Ternary gradient elution was applied with a mobile phase that consisted of acetonitrile, methanol and ammonium acetate (0.05 M), which was delivered at a flow rate of 1.0 mL/min. Diode array detection was performed with monitoring at 240 nm. FPSE was performed using cellulose fabric extraction media coated with sol‐gel poly(ethylene glycol) (sol‐gel PEG). Absolute recovery values in the equilibrium state for the examined benzodiazepines were found to be 27% for bromazepam, 63% for lorazepam, 42 % for diazepam and 39% for alprazolam. Copyright © 2015 John Wiley & Sons, Ltd.