Summary The aim of this work is to develop a simplified, though rigorously based thermogravimetric analysis (TG) method to estimate intrinsic reactivity parameters (activation energy, E, and pre-exponential factor, A) for the oxidation in air of engineering carbonaceous materials. To achieve this aim, a modified Coats-Redfern method for analysing linear curves has been devised. The new method assumes first-order reaction kinetics with respect to carbon, and uses a statistical criterion to estimate an ‘optimum’ heating rate. For the oxidation in air of a model carbon, an optimum rate of 27 K min-1 was determined, at which E=125.8 kJ mol-1. This is in good agreement with activation energies obtained using established, though more limited model-free or isoconversional methods.
of experimental techniques are employed to characterize physical and thermal
properties of poly(lactic acid), PLA. To characterize PLA in terms of molecular
mass and molecular mass distribution, size exclusion chromatography was used.
The value of the specific refractive index increment was measured by differential
refractometry. The thermal properties of semicrystalline PLA were measured
by standard and temperature-modulated differential scanning calorimetry. The
thermal stability of PLA was monitored by measuring the changes of mass using
thermogravimetric analysis. The mechanical properties of amorphous PLA were
measured by dynamic mechanical analysis and the results were discussed and
compared with DSC in the glass transition region.
Authors:Christopher J. Hammond, Corey E. Pilver, Loreen Rugle, Marvin A. Steinberg, Linda C. Mayes, Robert T. Malison, Suchitra Krishnan-Sarin, Rani A. Hoff, and Marc N. Potenza MD, PhD
Background and aims
Gambling is common in adolescents and at-risk and problem/pathological gambling (ARPG) is associated with adverse measures of health and functioning in this population. Although ARPG commonly co-occurs with marijuana use, little is known how marijuana use influences the relationship between problem-gambling severity and health- and gambling-related measures.
Survey data from 2,252 Connecticut high school students were analyzed using chi-square and logistic regression analyses.
ARPG was found more frequently in adolescents with lifetime marijuana use than in adolescents denying marijuana use. Marijuana use was associated with more severe and a higher frequency of gambling-related behaviors and different motivations for gambling. Multiple health/functioning impairments were differentially associated with problem-gambling severity amongst adolescents with and without marijuana use. Significant marijuana-use-by-problem-gambling-severity-group interactions were observed for low-average grades (OR = 0.39, 95% CI = [0.20, 0.77]), cigarette smoking (OR = 0.38, 95% CI = [0.17, 0.83]), current alcohol use (OR = 0.36, 95% CI = [0.14, 0.91]), and gambling with friends (OR = 0.47, 95% CI = [0.28, 0.77]). In all cases, weaker associations between problem-gambling severity and health/functioning correlates were observed in the marijuana-use group as compared to the marijuana-non-use group.
Some academic, substance use, and social factors related to problem-gambling severity may be partially accounted for by a relationship with marijuana use. Identifying specific factors that underlie the relationships between specific attitudes and behaviors with gambling problems and marijuana use may help improve intervention strategies.