The increment of heat capacity at the glass transition for semi-crystalline poly(ethylene terephthalate) (PET) observed by
temperature-modulated differential scanning calorimetry (TMDSC) shows significant deviations from a simple crystalline/amorphous
two-phase model. Introduction of a rigid amorphous fraction, which is non-crystalline but which also does not participate
in the normal glass transition, allows a much better description of the transition behaviour in semi-crystalline PET. Certain
questions arise such as what is the rigid amorphous fraction and over what temperature range do these rigid amorphous segments
devitrify? These TMDSC results show that the rigid amorphous component may be treated as an interphase between amorphous and
crystalline phases. This interphase does not exhibit a separate glass transition temperature at temperatures above the normal
Tg. The suggestion is made that the glass transition of the rigid amorphous component occurs continually between the glass transition
temperature of the amorphous phase and up to about 135C for this particular sample of PET.
Both melatonin and leptin show a circadian variation in circulating levels and participate in energy metabolism. An interrelationship between these two hormones has thus been proposed. In addition, melatonin has been shown to be capable of influencing circulating leptin concentration. However, whether melatonin will increase or decrease leptin production is still uncertain. This study was undertaken to examine the effect of melatonin on leptin production using male C57BL/6 adult mice treated with or without daily melatonin supplements (10 μg/mL) in drinking water for 1 month. In addition,
experiments using adipose tissue fragments derived from epididymal fat pads of adult mice incubated with or without melatonin (1 nM) administration were also conducted. The results showed that melatonin-supplemented mice had significantly higher plasma leptin levels than control mice. However, melatonin incubation did not cause any marked changes in the amount of leptin secreted from adipose tissue fragments. Our findings from this study indicate that melatonin does not affect leptin secretion via mouse adipose tissue. Nevertheless, melatonin could still influence leptinemia indirectly via regulatory effects in intact animals.
This paper presents a rapid and quantitative radiochemical separation method for the Pu, Am and Cm isotopes with an anion
exchange resin and a TRU resin. After the Pu isotopes were purified with an anion exchange resin method and the Am and Cm
isotopes were purified with the TRU resin method, micro-coprecipitation method was applied for an alpha-source preparation.
The activity concentrations and activity ratios for the Pu, Am and Cm isotopes in a radioactive sample were measured by radiation
counting methods such as an alpha-spectrometry and a liquid scintillation counting as well as by a mass spectroscopic method
such as a thermal ionization mass spectrometry.
Zinc (Zn) has the potential of regulating the action of thiazolidinedione (TZD), an anti-diabetic drug. Since some diabetic patients cannot achieve optimal glycemic control when receiving TZD, we investigated if Zn deficiency affects TZD’s efficacy in glucose metabolism. Diabetic mice were fed diets containing 3 or 30 mg/kg Zn for 6 weeks. Thereafter, all mice were oral gavaged with 2,4-thiazolidinedione. Our results showed that blood glucose values at fasting and during the glucose tolerance test were significantly higher in low-Zn mice than those of adequate-Zn mice. Thus, low Zn intake may attenuate TZD’s efficacy on reducing diabetic hyperglycemia.
Authors:M. Song, D. Hourston, M. Reading, H. Pollock, and A. Hammiche
A modulated-temperature differential scanning calorimetry (M-TDSC) method for the analysis of interphases in multi-component
polymer materials has been developed further. As examples, interphases in a polybutadiene-natural rubber (50:50 by mass) blend,
a poly(methyl methacrylate)-poly(vinyl acetate) (50:50 by mass) structured latex film, a polyepichlorohydrinpoly(vinyl acetate)
bilayer film, and polystyrene-polyurethane (40:60 by mass) and poly(ethyl methacrylate)-polyurethane (60:40 by mass) interpenetrating
polymer networks were investigated. The mass fraction of interphase and its composition can be calculated quantitatively.
These interphases do not exhibit clear separate glass transition temperatures, but occur continually between the glass transition
temperatures of the constituent polymers.
Authors:D. Hourston, M. Song, H. Pollock, and A. Hammiche
Modulated-temperature differential scanning calorimetry was used to measure the glass transition temperature,Tg, the heat capacity relaxation in the glassy state and the increment of heat capacity, δCp, in the glass transition region for several polymers. The differential of heat capacity with respect to temperature was used
to analyseTg and δCp simply and accurately. These measurements are not affected by complex thermal histories.
Authors:Y. Park, B. Song, M. Chowdhury, and K. Jee
A neutron induced prompt γ -ray spectrometry (NIPS) facility has been developed at the Nuclear Chemistry Research Division,
of the Korea Atomic Energy Research Institute (KAERI) with the aim of analyzing the major components of various elements in
aqueous samples. The facility is equipped with a 252Cf neutron source and a γ-γ coincidence setup with two n-type coaxial HPGe detectors based on NIM spectrometric modules in
association with data acquisition and spectral analysis systems. The development of the system, its set-up and the calibration
of detection efficiency up to 8 MeV using a set of radionuclides and the (n,γ) reactions of chlorine are described in the
The thermal decompositions of dehydrated or anhydrous bivalent transition metal (Mn, Fe, Co, Ni, Cu, Zn, Cd) and alkali rare
metal (Mg, Ca, Sr, Ba) methanesulfonates were studied by TG/DTG, IR and XRD techniques in dynamic Air at 250–850 °C. The initial
decomposition temperatures were calculated from TG curves for each compound, which show the onsets of mass loss of methanesulfonates
were above 400 °C. For transition metal methanesulfonates, the pyrolysis products at 850 °C were metal oxides. For alkali
rare metal methanesulfonates, the pyrolysis products at 850 °C of Sr and Ba methanesulfonates were sulphates, while those
of Mg and Ca methanesulfonate were mixtures of sulphate and oxide.
Authors:M Wang, Y Song, JS Baker, G Fekete, and Y Gu
Background and aims
Sedentary lifestyles have recently been identified as potential mechanism for obesity and associated metabolic diseases linked to ill health. The aim of this study was to investigate the effects of standing and sitting–standing positional changes on energy cost and consequently interrupting sedentary sitting time while working.
A total of 26 healthy male volunteers performed normal typing and editing work for 100 min under three conditions. The conditions included sustained sitting, sustained standing, and sitting–standing alternation every 20 min using a sit–stand desk. Respiratory parameters measured included minute ventilation (VE), oxygen consumption (VO2), and energy expenditure (EE). Measurements were recorded using a calibrated Cosmed K4b2 portable gas analysis system.
The mean value for VE was the highest in the standing position (VE = 13.33 ± 0.71), followed by sitting–standing alternation (VE = 12.04 ± 0.62). Both were significantly different from sitting (VE = 10.59 ± 0.69). The maximum VE and EE for standing (VE = 14.81 ± 0.43 and EE = 1.84 ± 0.10) and sitting–standing alternation (VE = 14.80 ± 0.40 and EE = 1.93 ± 0.08) were significantly higher than that of sitting (VE = 12.15 ± 0.42 and EE = 1.67 ± 0.07). No significant differences were observed in the mean VO2 among the three conditions. However, the maximum VO2 for both standing (VO2 = 5.40 ± 0.20) and sitting–standing alternation (VO2 = 5.14 ± 0.17) had shown to be significantly higher than sitting (VO2 = 4.50 ± 0.18). There were no significant differences observed in the mean EE levels between sitting (EE = 1.43 ± 0.07) and sitting–standing alternation (EE = 1.55 ± 0.08). However, the mean EE while standing (EE = 1.62 ± 0.09) significantly increased compared to sitting.
The findings of this study indicate that sitting–standing alternations may be implemented as an effective intervention to interrupt prolonged sitting while working.