Identifying ferroresonance initiation for a range of initial conditions and parameters

The paper presents an experimental and numerical investigation carried out on a ferroresonant circuit in order to determine to what extent the initiation of ferroresonance depends on initial conditions and phase shift. The range of voltage source values at which the initiation of ferroresonance depends on initial conditions and phase shift is named as a possible ferroresonant range, and is determined numerically and experimentally.     

Free convection heat transfer from a horizontal fin attached cylinder between confined nearly adiabatic walls

Steady state two-dimensional free convection heat transfer from a horizontal, isothermal fin attached cylinder, located between nearly two adiabatic walls is studied experimentally using a Mach–Zehnder interferometer. Effects of the walls inclination angel (θ) on heat transfer from the cylinder is investigated for Rayleigh number ranging from 1000 to 15,500. Two cylinders with different diameters of D = 10 and 20 mm are used to cover wide Rayleigh range. Results indicate that, heat transfer phenomena differ for different Rayleigh number. For Rayleigh numbers lower than 5500, heat transfer rate from cylinder surface is lower than the heat transfer from a single cylinder. In this range by the use of walls, heat transfer from the cylinder decreases slightly and walls’ inclination does not change heat transfer rate from the cylinder surface. For Rayleigh number ranging from 5500 to 15,500, amount of heat transfer from the cylinder surface is less than that of a single cylinder. However, by adding nearly adiabatic walls to experimental model heat transfer mechanism differs and chimney effect between fin and walls increases the heat transfer rate from the cylinder surface. By increasing the walls inclination angel from 0° to 20°, the chimney effect between walls and fin diminishes and heat transfer rate from the cylinder surface is approaching to the heat transfer rate of fin attached cylinder without adiabatic walls.     

Effect of mercerization and gamma irradiation on the dyeing behaviour of cotton using stilbene based direct dye

The dyeing behaviour of mercerized and gamma irradiated cotton fabric using stilbene based direct dye has been investigated. The fabric was treated with different concentrations of alkali to optimize the mercerization. The optimum mercerized cotton fabric was irradiated to absorbed doses of 2, 4, 6, 8 and 10 kGy using Cs-137 gamma irradiator. Dyeing was performed using irradiated and un-irradiated cotton with dye solutions. The dyeing parameters such as temperature, time of dyeing, pH of dyeing solutions and salt concentration were optimized. The colour strength values of dyed fabrics were evaluated by comparing irradiated and un-irradiated cotton in CIE Lab system using Spectra flash SF650. Methods suggested by International Standard Organization (ISO) were employed to study the effect of gamma irradiation on the colourfastness properties of dyed fabric. It was found that mercerized and irradiated cotton have not only improved the colour strength but enhanced the rating of fastness properties also.     

Synthesis of highly functionalized biaryls by condensation of 2-fluoro-1,3-bis(silyloxy) 1,3-dienes with 3-cyanochromones and subsequent domino "retro-Michael/aldol/fragmentation"

The Me(3)SiOTf-mediated condensation of 1-ethoxy-2-fluoro-1,3-bis(trimethylsilyloxy) 1,3-dienes with 3-cyanochromones afforded 3-cyano-2-(4-ethoxy-3-fluoro-2,4-dioxobutyl)chroman-4-ones. Their reaction with triethylamine afforded fluorinated azaxanthones or biaryls. The product distribution depends on the structure of the diene. The formation of the biaryls can be explained by an unprecedented domino "retro-Michael/aldol/fragmentation" reaction.     

Separation mechanism of chiral impurities, ephedrine and pseudoephedrine, found in amphetamine-type substances using achiral modifiers in the gas phase

A new mechanism is proposed that describes the gas-phase separation of chiral molecules found in amphetamine-type substances (ATS) by the use of high-resolution ion mobility spectrometry (IMS). Straight-chain achiral alcohols of increasing carbon chain length, from methanol to n-octanol, are used as drift gas modifiers in IMS to highlight the mechanism proposed for gas-phase separations of these chiral molecules. The results suggest the possibility of using these achiral modifiers to separate the chiral molecules (R,S) and (S,R)-ephedrine and (S,S) and (R,R)-pseudoephedrine which contain an internal hydroxyl group at the first chiral center and an amino group at the other chiral center. Ionization was achieved with an electrospray source, the ions were introduced into an IMS with a resolving power of 80, and the resulting ion clusters were characterized with a coupled quadrupole mass spectrometer detector. A complementary computational study conducted at the density functional B3LYP/6-31g level of theory for the electronic structure of the analyte–modifier clusters was also performed, and showed either “bridged” or “independent” binding. The combined experimental and simulation data support the proposed mechanism for gas-phase chiral separations using achiral modifiers in the gas phase, thus enhancing the potential to conduct fast chiral separations with relative ease and efficiency.     

Measurement of radionuclides and absorbed dose rates in soil samples of Peshawar, Pakistan, using gamma ray spectrometry

The analysis of gamma-emitting radionuclides in nature, i.e. (226)Ra, (232)Th, (40)K and (137)Cs, has been carried out in soil samples collected from Peshawar University Campus and surrounding areas using a high purity germanium detector coupled with a computer-based high-resolution multichannel analyser. The activity concentrations in soil ranged from 30.20±0.65 to 61.90±0.95, 50.10±0.54 to 102.80±1.04, 373.60±4.56 to 1082±11.38 and 9.50±0.11 to 46.60±0.42?Bq?kg(-1) for (226)Ra, (232)Th, (40)K and (137)Cs, with a mean value of 45±7.70, 67±12.50, 878±180 and 19±9.20?Bq?kg(-1), respectively. The radium equivalent activity, internal and external hazard indices have mean values of 203.40±29.40?Bq?kg(-1), 0.56 and 0.68, respectively. The mean values of outdoor and indoor absorbed dose rates in air and the annual effective dose equivalents were found to be 106.50 and 128?nGy?h(-1) and 0.19 and 0.54?mSv?y(-1), respectively. In the present study, (40)K was the major radionuclide present in soil samples. The presence of (137)Cs indicates that this area also received some fallout from the nuclear accident of the Chernobyl power plant in 1986. The activity concentrations of radionuclides found in soil samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the public.     

Canonical Analysis of Condensation in Factorised Steady States

We study the phenomenon of real space condensation in the steady state of a class of mass transport models where the steady state factorises. The grand canonical ensemble may be used to derive the criterion for the occurrence of a condensation transition but does not shed light on the nature of the condensate. Here, within the canonical ensemble, we analyse the condensation transition and the structure of the condensate, determining the precise shape and the size of the condensate in the condensed phase. We find two distinct condensate regimes: one where the condensate is gaussian distributed and the particle number fluctuations scale normally as L ^1/2 where L is the system size, and a second regime where the particle number fluctuations become anomalously large and the condensate peak is non-gaussian. Our results are asymptotically exact and can also be interpreted within the framework of sums of random variables. We further analyse two additional cases: one where the condensation transition is somewhat different from the usual second order phase transition and one where there is no true condensation transition but instead a pseudocondensate appears at superextensive densities. PACS numbers: 05.40.-a, 02.50.Ey, 64.60.-i.     

Synergistic Effects of Drought Stress and Photoperiods on Phenology and Secondary Metabolism of Silybum marianum

Silybum marianum is an important medicinal plant of the family Asteraceae, well known for its set of bioactive isomeric mixture of secondary metabolites “silymarin”, primarily acting as a hepato-protective agent. Abiotic stress augments plant secondary metabolism in different plant tissues to withstand harsh environmental fluctuations. In the current study, our aim was to induce drought stress in vitro on S. marianum under the influence of different photoperiod treatments to study the effects, with respect to variations in secondary metabolic profile and plant growth and development. S. marianum was extremely vulnerable to different levels of mannitol-induced drought stress. Water deficiency inhibited root induction completely and retarded plant growth was observed; however, phytochemical analysis revealed enhanced accumulation of total phenolic content (TPC), total flavonoid content (TFC), and total protein content along with several antioxidative enzymes. Secondary metabolic content was positively regulated with increasing degree of drought stress. A dependent correlation of seed germination frequency at mild drought stress and antioxidative activities was established with 2 weeks dark?+?2 weeks 16/8 h photoperiod treatment, respectively, whereas a positive correlation existed for TPC and TFC when 4 weeks 16/8 h photoperiod treatment was applied. The effects of drought stress are discussed in relation to phenology, seed germination frequency, biomass build up, antioxidative potential, and secondary metabolites accumulation.     

Extrathermodynamic relations in the binding of charged and neutral substrates to sulfobutylether-β-CDs (SBE-β-CDs) and a 2-hydroxypropyl-β-CD (HP-β-CD)

The thermodynamics of binding of various neutral, cationic and anionic substrates to β-cyclodextrin, a hydroxylpropyl-β-cyclodextrin (HP_4M-β-CD) and three sulfobutyl-β-cyclodextrins with varying degrees of total substitution (SBE_1M-β-CD, SBE_7M-β-CD, and SBE_12M-β-CD) were determined by estimating binding constants, using a UV spectrophotometric technique, and temperature variation. linear free energy relation (LFER) plots and enthalpy–entropy Compensation (EEC) plots provided insight into the mechanisms of complexation as did carbon T ₁ relaxation times using NMR. LFER plots for charged molecules with HP_4M-β-CD deviate from the neutral substrates suggesting differences in interaction modes. LFER plots for SBE_7M-β-CD show that cationic substrates surprisingly fall within the same linear relationship for neutral substrates while anionic substrates deviate. The EEC plots for HP_4M-β-CD show the largest loss of motion and degree of desolvation upon complexation. The interaction with SBE_1M-β-CD was similar to that for β-CD. SBE_7M-β-CD, and SBE_12M-β-CD EEC plots are similar with the least loss of motion upon complex formation, suggesting a more organized and less flexible structure. This is supported by the T ₁ relaxation times for SBE_1M-β-CD, SBE_7M-β-CD, and SBE_12M-β-CD, which show a critical distance at which the mobility of the side chain is reduced to form an extended cavity. No such evidence was seen with HP_4M-β-CD, although the effect of varying of hydroxypropyl substitution was not studied.     

Advanced vapor recognition materials for selective and fast responsive surface acoustic wave sensors: A review

The necessity of selectively detecting various organic vapors is primitive not only with respect to regular environmental and industrial hazard monitoring, but also in detecting explosives to combat terrorism and for defense applications. Today, the huge arsenal of micro-sensors has revolutionized the traditional methods of analysis by, e.g. replacing expensive laboratory equipment, and has made the remote screening of atmospheric threats possible. Surface acoustic wave (SAW) sensors – based on piezoelectric crystal resonators – are extremely sensitive to even very small perturbations in the external atmosphere, because the energy associated with the acoustic waves is confined to the crystal surface. Combined with suitably designed molecular recognition materials SAW devices could develop into highly selective and fast responsive miniaturized sensors, which are capable of continuously monitoring a specific organic gas, preferably in the sub-ppm regime. For this purpose, different types of recognition layers ranging from nanostructured metal oxides and carbons to pristine or molecularly imprinted polymers and self-assembled monolayers have been applied in the past decade. We present a critical review of the recent developments in nano- and micro-engineered synthetic recognition materials predominantly used for SAW-based organic vapor sensors. Besides highlighting their potential to realize real-time vapor sensing, their limitations and future perspectives are also discussed.