Evaluation of the aromatic structure of coal tar pitch by solid and solution state n.m.r.

Rapid magic angle spinning has been used to obtain sideband-free high field ¹³C n.m.r. spectra of coal tar pitches in the solid state. However, the unfavourable cross-polarization and ¹H relaxation characteristics make it difficult to accurately estimate concentrations of quaternary aromatic carbon using the dipolar dephasing method. The concentrations of bridgehead aromatic carbon in the whole pitch and toluene-insoluble fraction investigated were deduced using a combination of solid and solution state n.m.r. and elemental analyses.     

Some remarks about the estimation of the solubility parameter of low volatile compounds from gc data

Approximate solubility parameters of monomeric stationary phases can be calculated from gas chromatographic retention volumes of aliphatic saturated hydrocarbons; and some other properties, such as the molar volume and the latent heat of vaporization, by applying the regular solution model to the chromatographic process. By including data of aromatic hydrocarbons, solubility parameters of aromatic stationary phases, nearer to the experimental ones, can be obtained. The inclusion of data of olefines, however, is irrelevant. The method can be applied to low volatile compounds usable as the stationary phase in gas chromatography (GC) of hydrocarbons.     

Reconnaissance of selected PPCP compounds in Costa Rican surface waters

Eighty-six water samples were collected in early 2009 from Costa Rican surface water and coastal locations for the analysis of 34 pharmaceutical and personal care product compounds (PPCPs). Sampling sites included areas receiving treated and untreated wastewaters, and urban and rural runoff. PPCPs were analyzed using a combination of solid phase extraction and liquid chromatography tandem mass spectrometry. The five most frequently detected compounds were doxycycline (77%), sulfadimethoxine (43%), salicylic acid (41%), triclosan (34%) and caffeine (29%). Caffeine had the maximum concentration of 1.1 mg L⁻¹, possibly due to coffee bean production facilities upstream. Other compounds found in high concentrations include: doxycycline (74 μg L⁻¹), ibuprofen (37 μg L⁻¹), gemfibrozil (17 μg L⁻¹), acetominophen (13 μg L⁻¹) and ketoprofen (10 μg L⁻¹). The wastewater effluent collected from an oxidation pond had similar detection and concentrations of compounds compared to other studies reported in the literature. Waters receiving runoff from a nearby hospital showed higher concentrations than other areas for many PPCPs. Both caffeine and carbamazepine were found in low frequency compared to other studies, likely due to enhanced degradation and low usage, respectively. Overall concentrations of PPCPs in surface waters of Costa Rica are inline with currently reported occurrence data from around the world, with the exception of doxycycline.     

Chlorination of alkylbenzenes with molecular chlorine in alcoholic media

m-Xylene is chlorinated with molecular chlorine supplied at a constant flow rate, utilising short chain alcohols as solvents. Chlorinations occur as fast and clean substitution reactions, giving very high yields of monochloro derivatives. o-Xylene and p-xylene in ethanol give, however, much lower yields, similar to those of catalysed chlorinations. The behaviour of benzene, some other alkylbenzenes, and mixtures of xylenes in ethanol is also studied. In the mixtures, m-xylene is very selectively chlorinated and almost quantitatively converted into monochloro derivatives.     

Burnout and coping in human service practitioners.

Do many Spanish human service practitioners suffer from burnout? What coping strategies are used to combat work stress, and are they associated with lower burnout? Which strategies may the psychologist promote to improve organizations? With an eye toward helping organizations improve their workers' quality of work life and service delivery, 211 professionals, either child protection workers or in-home caregivers, completed an inventory on coping and another on burnout. Coping strategies alone do not preclude burnout but may help prevent worker turnover. High job and salary satisfaction, together with active coping strategies play an important role in promoting personal accomplishment. Low job and salary satisfaction and the use of passive or emotional strategies predict elevated emotional exhaustion. The results suggest some possible points of intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of Pressure Waves Generation in Gun Combustion Chambers During the Propellant Ignition Process

At certain conditions, propelling charges for artillery – either because of their low heat of combustion, a low vulnerability, or due to other reasons – require relatively high initiation thresholds. This phenomenon, combined with large gun chambers, high initial charge densities of materials with granular geometry and low porosity powder beds, give rise to delays and irregularities in the initiation times at various points of the propelling charges. These irregular behaviors or failures in the initiation cause pressure waves within the chambers of the weapons. This paper focuses on experimental studies and tests carried out on the processes taking place in the initiation of propelling charges, which can lead to pressure waves in the bore of howitzers and cannons. Pressure waves during initiation are considered to be particularly dangerous to the safety of users and weapons. The behavior of the initiator systems, the flame volume and its distribution throughout the length of the bore are analysed by means of pressure‐time diagrams, obtained from experimental shooting. The data are processed using the standard Fourier transform and the “discrete wavelet transform”, by means of the Daubechies functions. This allows to identify when these events occur during shooting and to determine some of the causes in order to achieve virtual elimination of the pressure waves.     

The estimation of the solubility parameter of low volatile compounds from gas chromatography data

By applying the regular solution model to the solution processes that take place in gas chromatography, equations are obtained, which relate the retention volume of solutes with their molar volume and latent heat of vaporization. From these equations, solubility parameters of monomeric stationary phases are obtained and their values compared with those obtained by other methods.