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Second Transition (second + transition)

Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

Prospective prediction of children's smoking transitions: role of parents' and older siblings' smoking

ADDICTION, Issue 1 2006
Jonathan B. Bricker
ABSTRACT Aims To use a novel social epidemic probability model to investigate longitudinally the extent to which parents' and older siblings' smoking predict children's smoking transitions. Design Parents' and older siblings' smoking status was assessed when children were in 3rd grade (baseline). Three smoking transitions were assessed over the period of child/adolescent smoking acquisition (up to 12th grade): (1) transition from never smoking to trying smoking, (2) transition from trying to monthly smoking and (3) transition from monthly to daily smoking. Setting Forty Washington State school districts participating in the long term Hutchinson Smoking Prevention Project (HSPP). Participants and measurements Participants were the 5520 families for whom data on both parents' and older siblings' baseline smoking status, as well as on children's smoking transitions, were available. Findings The probability that a smoking parent influenced their child to make the first transition to trying smoking was 32% (95% CI: 27%, 36%); to make the second transition from trying to monthly smoking, 15% (95% CI: 10%, 19%); and to make the third transition from monthly to daily smoking, 28% (95% CI: 21%, 34%). The probability that an older sibling influenced a child to make the first transition to trying smoking was 29% (95% CI: 17%, 39%); to make the second transition from trying to monthly smoking, 0% (95% CI: 0%, 8%); and to make the third transition from monthly to daily smoking, 20% (95% CI: 4%, 33%). Conclusions In contrast to previous research, the results provide new evidence suggesting that family smoking influences both initiation and escalation of children's smoking. Results also quantify, in terms of probabilities, the importance of parents' and older siblings' smoking on children's three major smoking transitions. Parents' smoking, as well as older siblings' smoking, are important behaviors to target in preventing adolescents from making smoking transitions. [source]

Use of associating polymers as multifunctional thickeners: studies of Their structure in aqueous solutions via nmr, qels, fluorescence, And rheology measurements

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 5 2007
Katsunori Yoshida
The solution properties of an associating polymer were studied by NMR, quasi-elastic light scattering (QELS), fluorescence, and rheology measurements. An associative thickening (AT) polymer was designed having a nonionic poly(ethylene oxide) backbone with long alkyl chains at both ends to achieve high viscosity even at relatively high salt concentrations and over a wide pH range. This study focuses on the associative state of the polymer in aqueous solutions at various polymer concentrations. In a fluorescence probe study using pyrene a spectral change in the I3/I1 ratio was observed for pyrene at a polymer concentration (Cp) of 3 x 10 -4%, indicating an apparent critical concentration (cmc) of the amphiphilic polymer. The viscosity, self-diffusion coefficient (Dsel), and hydrodynamic size (Rh) distribution measurements at various Cp all suggest that there is a second transition at Cp, 0.4%. Although we observed the discontinuity in viscosity, Dsel, and Rh at Cp, 0.4%, no changes in the relaxation times (T1 and T2) were recognized for either the alkyl chain or the ethylene oxide moiety of the polymer at C p= 0.1,1%. These data suggest that there are no structural changes or phase transitions at Cp, 0.4%, but that intermicellar networks are presumably formed by bridging of the end alkyl groups of the polymer, which is driven by hydrophobic forces. Because the polymer forms networks by hydrophobic interaction and the polymer itself is nonionic, the viscosity of the polymer solution was influenced very little by either the addition of salt or a pH change, as would be expected. The dynamic viscoelastic study revealed that the polymer solution exhibits a single mode Maxwell type relaxation behavior with a terminal relaxation time of about 0.61 s, which imparts a unique flow appearance to the polymer solutions. The time course measurements of the dynamic elastic modulus of the stratum corneum revealed that the polymer has excellent potential for skin softening. It was concluded that the associative thickening polymer not only is a useful thickener with a salt and pH tolerance but also has beneficial skincare effects. [source]

Glass transition behaviour of fructose

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2004
Vinh Truong
Summary The glass transition temperature and the second transition (the endothermic change between the glass transition and melting temperatures) of fructose were studied. The thermal history strongly affected both transitions of fructose. Storage for 10 days at 22 °C increased the dynamic glass transition temperature from 16 to 25 °C and decreased the second transition of fructose from 110 to 98 °C in the first differential scanning calorimetric (DSC) scan. The amplitude of the second transition increased slightly with storage time and reached 260% of the first transition for vacuum oven dried samples. The effect of thermal history on the glass transition temperature of fructose can be removed by scanning the sample in a DSC to 130 °C. The effects of water content, glucose and sucrose on the two transitions were also investigated. [source]

A-Site and B-Site Order in (Na1/2La1/2)(Mg1/3Nb2/3)O3 Perovskite

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2004
Rachel Tarvin
(Na1/2La1/2)(Mg1/3Nb2/3)O3 undergoes a series of phase transitions that involve cation order on the A- and B-sites of the parent perovskite structure. At high temperatures both sites contain a random distribution of cations; below 1275°C a ,111, layering of Mg and Nb leads to the formation of a 1:2 ordered structure with a monoclinic supercell. A second transition was observed at 925°C, where the Na and La cations order onto alternate A-site positions along the ,001, direction of the parent subcell. By quenching samples from above 1275°C to preserve the disorder on the B-site, a fourth variant of this compound was obtained by inducing A-site order through a subsequent anneal at 900°C. Although the changes in structure do not produce significant alterations in the relative permittivity (,r, 35), they do have a significant effect on the value of the temperature coefficient of the capacitance. [source]

Influence of Sn doping upon the phase change characteristics of Ge2Sb2Te5

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2004
K. Wang
Abstract The influence of Sn doping upon the phase change characteristics of Ge2Sb2Te5 alloys has been investigated using four-point-probe electrical resistance measurements, grazing incidence X-ray diffraction (XRD), X-ray reflectometry (XRR) and variable incident angle spectroscopic ellipsometry (VASE), a static tester and atomic force microscopy (AFM). For a Ge2Sb2Te5 alloy doped with 4% Sn, two transition temperatures are observed in the temperature dependent sheet resistance measurements at 125 °C and 250 °C, respectively. The evolution of structures upon annealing, investigated by XRD, reveals that the first transition is caused by the crystallization of the amorphous film to a NaCl-type structure, while the second transition is related to the transition to a hexagonal structure. The density values of 6.02 ± 0.05 g cm,3, 6.38 ± 0.05 gcm,3 and 6.42 ± 0.05 gcm,3 are measured by XRR for the film in the amorphous, NaCl-type and hexagonal structure, respectively. Ultra-fast crystallization, which is correlated with a single NaCl-structure phase and the reduced activation barrier, is demonstrated. Sufficient optical contrast is exhibited and can be correlated with the density change upon crystallization. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]