Influence of weak organic acids and salts on the denaturation characteristics of intramuscular connective tissue. A differential scanning calorimetry study

Intramuscular connective tissue obtained from Longissimus dorsi muscle of a 4-year-old beef carcass was treated with NaCl solutions of 2, 4, and 6% (w/v), and CaCl₂ solutions of 50, 100, and 150 mM, and citric and lactic acid solutions of 0.5, 1.0, and 1.5% for three different marinating periods (24, 46, and 72 h). Changes in denaturation characteristics were investigated using differential scanning calorimetry and it was found that the denaturation onset temperature (T_o) and the denaturation peak temperature (T_p) increased as the NaCl concentration increased but decreased as the CaCl₂ concentration increased, irrespective of marinating time. Lactic and citric acid decreased T_o to about 39°C, from over 60°C breaking the structure of fibrils.     

Surface combustion microengines based on photocatalytic oxidations of hydrocarbons at room temperature

The concept of a surface combustion microengine that is fuelled by volatile hydrocarbons at room temperature is demonstrated on a microcantilever covered with a thin layer of titanium oxide (TiO(2)). Exposing this microengine to ultraviolet (UV) radiation and hydrocarbon vapor produces controlled bending of the microcantilever as a result of differential stress produced by photocatalytic oxidation of organic molecules on the TiO(2) coating. Compared to the motion generated solely by UV radiation or hydrocarbon adsorption, the unique photocatalytic-mechanical effects in the presence of UV and hydrocarbon produce more work and exhibit fast response. The surface combustion based microengines would require less maintenance in minimally controlled field environment and could be potentially used in construction of miniature movable machines, conversion of solar and chemical energy to mechanical work, when extended to a large array of microcantilevers. We believe such microengines can be fuelled by a variety of molecules or mixtures due to the generally favorable photocatalytic reactivity of TiO(2), thus potentially offering a broad approach for mechanical work generation from multiple energy sources.     

Nanorod heterostructures showing photoinduced charge separation

Size- and shape-dependent property modifications of semiconductor nanocrystals have been a subject of intense interest because of their potential for future engineering devices. The bandgap and related optical-property tuning of these materials are mainly governed by the nature of their band edges. In addition, fusing one type of nanocrystal over another enables further control of material properties that are dependent on the relative alignments of their energy levels. On a molecular scale, the synthesis of supramolecular compounds has inspired advances in theories for photoinduced charge transfer. Heterostructured nanocrystals potentially provide a nanoscale analog of such systems. A method for preparing heterostructured nanocrystals of complex morphologies showing photoinduced charge separation is presented. It is shown that the energy and lifetime of the charge-transfer photoluminescence band can be tuned by changing the relative alignment of band edges in CdSe/CdTe heterostructure nanorods. The long-lived charge transfer states in these type II semiconductors may make them attractive for photovoltaic applications.     

Enhanced surface-excitonic emission in ZnO/Al(2)O(3) core-shell nanowires

We report the influence of an Al(2)O(3) shell on the photoluminescence emission of ZnO nanowires. At room temperature, the spectrum of the core-shell nanowires shows a strong reduction of the relative intensity of the green defect emission with respect to the near-band-edge emission. At 5?K an increase of the relative intensity of the surface exciton band with respect to the donor-bound exciton emission is observed. Annealing the core-shell nanowires at 500?°C does not increase the green defect luminescence at 5?K. We propose a model explaining the spectral changes.     

Passive Q switching of a solar-pumped Nd:YAG laser

Passive Q switching is a preferable choice for switching the Q factor of a solar-pumped laser because it requires neither a driver nor an electrical power supply. The superior thermal characteristics and durability of Cr(4+):YAG single crystals as passive Q switches for lamp and diode-pumped high-power lasers has been demonstrated. Here we report on an average power of 37 W and a switching efficiency of 80% obtained by use of a solar-pumped Nd:YAG laser Q switched by a Cr(4+):YAG saturable absorber. Concentration of the pumping solar energy on the laser crystal was obtained with a three-stage concentrator, composed of 12 heliostats, a three-dimensional compound parabolic concentrator (CPC) and a two-dimensional CPC. The water-cooled passive Q switch also served as the laser rear mirror. Repetition rates of as much as 50 kHz, at pulse durations between 190 and 310 ns (FWHM) were achieved. From the experimental results, the saturated single-pass power absorption of the Cr(4+):YAG device was estimated as 3 ? 1%.     

Transparent, conductive graphene electrodes for dye-sensitized solar cells

Transparent, conductive, and ultrathin graphene films, as an alternative to the ubiquitously employed metal oxides window electrodes for solid-state dye-sensitized solar cells, are demonstrated. These graphene films are fabricated from exfoliated graphite oxide, followed by thermal reduction. The obtained films exhibit a high conductivity of 550 S/cm and a transparency of more than 70% over 1000-3000 nm. Furthermore, they show high chemical and thermal stabilities as well as an ultrasmooth surface with tunable wettability.     

Fast electrical lysis of cells for capillary electrophoresis

In the past decade, capillary electrophoresis has demonstrated increasing utility for the quantitative analysis of single cells. New applications for the analysis of dynamic cellular properties demand sampling methods with sufficient temporal resolution to accurately measure these processes. In particular, intracellular signaling pathways involving many enzymes can be modulated on subsecond time scales. We have developed a technique to rapidly lyse an adherent mammalian cell using a single electrical pulse followed by efficient loading of the cellular contents into a capillary. Microfabricated electrodes were designed to create a maximum voltage drop across the flattened cell's plasma membrane at a minimum interelectrode voltage. The influence of the interelectrode distance, pulse duration, and pulse strength on the rate of cell lysis was determined. The ability to rapidly lyse a cell and collect and separate the cellular contents was demonstrated by loading cells with Oregon Green and two isomers of carboxyfluorescein. All three fluorophores were detected with a separation efficiency comparable to that of standards. Parallel comparison of electrical lysis to that produced by a laser-based lysis system revealed that the sampling efficiencies of the two techniques were comparable. Rapid cell lysis by an electrical pulse may increase the application of capillary electrophoresis to the study of cellular dynamics requiring fast sampling times.     

Optical and magneto-optical properties of copper-nickel compound metal island films

The optical properties of copper Cu-Ni compound metal island (CMI) films composed of nanoclusters of an alloy of Cu and Ni have been experimentally investigated. The spectral characteristics of the Cu-Ni CMI films are intermediate between those of conventional Cu and Ni island films in visible and near-IR regions. In addition, the magneto-optic effect has been observed in the Cu-Ni CMI films. It is also shown that the Faraday rotation in the Cu-Ni CMI films can easily be controlled by selection of the mixture ratio of Cu and Ni.     

Radioactivity concentrations in soil and dose assessment for Samsun City Centre, Turkey

In this study, natural gamma radioactivity levels were determined in the soil samples of the Samsun city centre by using the gamma ray spectrometry method. The analysis carried out with the high-purity germanium gamma spectrometry system has shown that average activity concentrations of (238)U, (232)Th, (40)K and (137)Cs were 19±2, 22±4, 521±23 and 15±1 Bq kg(-1), respectively. From the gamma analysis of soil samples, the average value of the absorbed gamma dose rates in air and the average value of the external annual effective dose rates were calculated as 45±4 nGy h(-1) and 55±5 μSv y(-1), respectively. The external hazard index has also been calculated and it has been found that the radiation hazard in Samsun is insignificant.     

空气密度和湿度对雷电击距的影响

长距离高压输电线路贯穿不同海拔区域,而不同海拔区域的天气条件变化很大。采用电荷模拟方法对雷击水平导线进行建模,探讨了天气条件（空气密度和湿度）对雷电击距的影响,并导出了用于计算天气条件对接地水平导线击距影响的表达式。