Note: Autoignition Temperature of Selected Polymers at Elevated Oxygen Pressure and Their Heat of Combustion

Autoignition temperature and heat of combustion are two important parameters in determining the oxygen compatibility of materials. This study investigates the autoignition temperature of 32 polymers at an elevated oxygen pressure of 10.3 MPa and reports their heat of combustion. © 1996 by John Wiley & Sons, Ltd.     

An investigation of scotopic threshold-versus-illuminance curves for the analysis of color-matching data

Stiles developed a method for estimating whether rod-photoreceptor activity contributed to color-matching data. This method requires knowledge of the rod threshold at the illuminance levels of lights being viewed. Stiles suggested that the Aguilar and Stiles scotopic threshold-versus-illuminance (TVI) curve could serve as a convenient approximation of the rod threshold. Stiles' method was intended for use in color-matching experiments where the stimuli are presented side by side, but, in the Aguilar and Stiles experiment, detection thresholds were measured for temporally pulsed lights. This study compares rod-sensitivity with detection and side-by-side adjustment tasks. The illumination level of the test and background light was kept below the absolute threshold of the short-wavelength sensitive cones, because there is evidence that cone signals may interact with the scotopic TVI function. The threshold data fell mainly within the range of the Aguilar and Stiles observers. There were two notable deviations from the Aguilar and Stiles curve: (1) consistent with previous reports, the scotopic TVI function had a slope shallower than the Aguilar and Stiles curve when measured with a short-wavelength background; (2) thresholds measured from a dark surround with a spatial adjustment task were higher than the Aguilar and Stiles thresholds even though the slopes were the same. © 1996 John Wiley & Sons, Inc.     

Residual stress and electrical properties of Pb(Zr0.52,Ti0.48)O3 thin films RF sputtered directly on Cu foils

Polycrystalline Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films between 250 and 1000 nm thick were deposited on Cu foils via RF magnetron sputtering. Samples were crystallized ex situ between 550°C and 750°C in a low oxygen partial pressure atmosphere, pO₂, in order to avoid oxidation of the substrate. These were compared to films made on more common Pt/TiO_x/SiO₂/Si substrates also crystallized under low pO₂ conditions. The mismatch of the coefficients of thermal expansion for Cu and PZT caused large compressive residual stresses to develop in the films, whereas films on Pt‐Si experienced more moderate tensile stresses. Stress was measured using the sin²ψ method. In addition to mechanical implications, i.e., film cracking and delamination, the effect of residual stress on electrical properties is discussed. Dielectric constants of PZT were lower on Cu than on Pt/TiO_x/SiO₂/Si. This could be due either to a dead layer effect or to the residual stress imposed by the substrate. The remanent polarizations for films on Cu were between 18 and 41 μC/cm², while coercive fields were between 37 and 54kV/cm. Rayleigh analysis was used to describe the role of defects affecting domain wall mobility, as they act as pinning centers and decrease the extrinsic polarization response.     

Biodistribution of single and aggregated gold nanoparticles exposed to the human lung epithelial tissue barrier at the air-liquid interface

Background

The lung represents the primary entry route for airborne particles into the human body. Most studies addressed possible adverse effects using single (nano)particles, but aerosolic nanoparticles (NPs) tend to aggregate and form structures of several hundreds nm in diameter, changing the physico-chemical properties and interaction with cells. Our aim was to investigate how aggregation might affect the biodistribution; cellular uptake and translocation over time of aerosolized NPs at the air-blood barrier interface using a multicellular lung system.

Results

Model gold nanoparticles (AuNPs) were engineered and well characterized to compare single NPs with aggregated NPs with hydrodynamic diameter of 32 and 106 nm, respectively. Exposures were performed by aerosolization of the particles onto the air-liquid interface of a three dimensional (3D) lung model. Particle deposition, cellular uptake and translocation kinetics of single and aggregated AuNPs were determined for various concentrations, (30, 60, 150 and 300 ng/cm²) and time points (4, 24 and 48 h) using transmission electron microscopy and inductively coupled plasma optical emission spectroscopy. No apparent harmful effect for single and aggregated AuNPs was observed by lactate dehydrogenase assay, nor pro-inflammation response by tumor necrosis factor α assessment. The cell layer integrity was also not impaired. The bio-distribution revealed that majority of the AuNPs, single or aggregated, were inside the cells, and only a minor fraction, less than 5%, was found on the basolateral side. No significant difference was observed in the translocation rate. However, aggregated AuNPs showed a significantly faster cellular uptake than single AuNPs at the first time point, i.e. 4 h.

Conclusions

Our studies revealed that aggregated AuNPs showed significantly faster cellular uptake than single AuNPs at the first time point, i.e. 4 h, but the uptake rate was similar at later time points. In addition, aggregation did not affect translocation rate across the lung barrier model since similar translocation rates were observed for single as well as aggregated AuNPs.

     

The effect of beta-alanine supplementation on neuromuscular fatigue in elderly (55–92 Years): a double-blind randomized study

Background

Ageing is associated with a significant reduction in skeletal muscle carnosine which has been linked with a reduction in the buffering capacity of muscle and in theory, may increase the rate of fatigue during exercise. Supplementing beta-alanine has been shown to significantly increase skeletal muscle carnosine. The purpose of this study, therefore, was to examine the effects of ninety days of beta-alanine supplementation on the physical working capacity at the fatigue threshold (PWC_FT) in elderly men and women.

Methods

Using a double-blind placebo controlled design, twenty-six men (n = 9) and women (n = 17) (age ± SD = 72.8 ± 11.1 yrs) were randomly assigned to either beta-alanine (BA: 800 mg × 3 per day; n = 12; CarnoSyn?) or Placebo (PL; n = 14) group. Before (pre) and after (post) the supplementation period, participants performed a discontinuous cycle ergometry test to determine the PWC_FT.

Results

Significant increases in PWC_FT (28.6%) from pre- to post-supplementation were found for the BA treatment group (p < 0.05), but no change was observed with PL treatment. These findings suggest that ninety days of BA supplementation may increase physical working capacity by delaying the onset of neuromuscular fatigue in elderly men and women.

Conclusion

We suggest that BA supplementation, by improving intracellular pH control, improves muscle endurance in the elderly. This, we believe, could have importance in the prevention of falls, and the maintenance of health and independent living in elderly men and women.     

Changing perceptions of hunger on a high nutrient density diet

Background  

People overeat because their hunger directs them to consume more calories than they require. The purpose of this study was to analyze the changes in experience and perception of hunger before and after participants shifted from their previous usual diet to a high nutrient density diet.     

Nondestructive NMR determination of oil composition in transformed canola seeds

Magic-angle spinning (MAS) ¹³C nuclear magnetic resonance (NMR) spectroscopy is a convenient method for nondestructive, quantitative characterization of seed oil composition. We describe results for intact hybrid and transformed canola seeds. The MAS ¹³C NMR technique complements and agrees with gas chromatography results. The spectral resolution approaches that of neat, liquid oils. MAS ¹³C NMR data allow quantitative analysis of major oil components, including saturates and oleic, linoleic, and linolenic acyl chains. ¹³C NMR directly and quantitatively elucidates, triglyceride regiochemistry and acyl chain cis-trans isomers that cannot be quickly detected by other methods. MAS ¹³C NMR can serve as the primary method for development of near-infrared seed oil calibrations. These NMR methods are nondestructive and attractive for plant-breeding programs or other studies (e.g., functional genomics) where loss of seed viability is inconvenient.     

A new energy future for South Africa: The political ecology of South African renewable energy

Renewable energy remains a contested topic in South Africa. This paper argues that South Africa can build on the momentum surrounding its introduction of a feed-in tariff by enacting policies that may, if given adequate funding and political effort, allow the country to be a world leader in renewable energy. Given a variety of renewable energy policy options for moving forward, a majority of stakeholders consulted in this study strongly prefer the development of a renewable energy manufacturing cluster, in which government develops coordinated policy mechanisms that attract renewable energy manufacturers, over three other policies suggested by the authors. Interviews with key informants that play critical roles in this decision-making process suggest that there are reasons to remain cautiously optimistic about the country's renewable energy future while cognizant of the challenges that must still be overcome. Opportunities for a low carbon renewable energy transition in South Africa include the prevalence of broad stakeholder consultation, facilitated by civil society, and an innovative policy development context. Significant impediments also exist, however, and include pervasive social issues such as poverty and political inertia, along with the ongoing difficulties facing renewable energy technologies in reaching grid parity with inexpensive and abundant South African coal.     

XRD study of the grain growth in CdTe films annealed at different temperatures

The CdTe thin films electrodeposited on stainless steel substrates were annealed in air at various temperatures and time durations in order to investigate the influence of post-deposition heat treatments on the grain growth of the films. The recrystallization process at lower annealing temperature is different from that of the high-temperature annealing. The annealing at lower temperature promotes better grain growth by maintaining the preference for the (1 1 1) plane. In general the grain size increases due to annealing and the recrystallization happens in three phases. The grain growth exponent is a function of temperature and time. In the beginning of the annealing, irrespective of the annealing temperatures the grain growth obeys the ideal parabolic law and for longer annealing times it deviates from the ideal case.     

减小电感尺寸,设计纤薄的PFC电源段

功率因数校正（PFC）电路嵌在交流线路与主电源之间,从交流线路汲入正弦电流,从而提供恒定直流电压。这中间段一般是升压转换器,电感是系统中体积最大且昂贵的元器件之一。在对成本和尺寸敏感的应用中,必须将电感的尺寸和成本降至最低。