Kinetics of semicarbazide and nitrofurazone in chicken eggs and egg powders

The accumulation, depletion and partitioning of semicarbazide (SEM) and its parent compound nitrofurazone (NFZ) in eggs were studied using hens fed NFZ at therapeutic and sub-therapeutic levels. Dietary NFZ correlated strongly with NFZ and total SEM in eggs, while 28% of observed SEM was present in the form of parent NFZ. Depletion half-life in eggs was 2.4 days for SEM and 1.1 days for NFZ. NFZ accumulated preferentially in yolk (57-63%) as opposed to albumen, while 71-80% of SEM was found in yolk. In whole egg, 29% of SEM was present as tissue-bound residues compared with 80% in breast muscle. Whilst NFZ and SEM were partly degraded by pasteurization and spray drying, sufficient NFZ remained to suggest it might be detectable in egg powders when SEM is observed at low microg kg(-1) concentrations. NFZ was detectable in whole eggs during ingestion of only 0.1% of the therapeutic NFZ dose, making detection of intact NFZ in eggs a feasible means to prove conclusively the administration of this banned compound.     

Cyclic perturbation of lowland river channels and ecological response

Certain lowland streams have experienced prehistorical and historical cycles of aggradation, occlusion, degradation, headward incision, and renewed aggradation. Historical cycles appear to be related to human activities. A case study is presented of the Yalobusha River in Mississippi with emphasis on the effects of blockage and removal on aquatic habitats and fish. The adjacent Skuna River, which was channelized and unblocked, was used in space for time substitution to infer effects of blockage removal on the Yalobusha. Variables describing physical aquatic habitat and fish were sampled from three groups of river reaches: unblocked channelized, channelized and blocked, and naturally sinuous. Fish collections were used to compute six indicators of ecological integrity. At baseflow, mean water depths were an order of magnitude lower in the unblocked channelized stream than for the others. In‐channel aquatic habitat volume per unit valley length was 5, 85, and 283 m³/m for the channelized, blocked channelized, and natural reaches, respectively. Mean values for all six ecological indicators were lowest for the channelized group. Species richness was greatest for the channelized blocked reach. The ecological indicators displayed gradients in response to the range of observed physical conditions. Management of corridors susceptible to the cycle described above should involve a blend of measures designed to conserve higher quality habitats.     

Experimental demonstration of a silicon carbide IMPATT oscillator

Silicon carbide (SiC) is an excellent material for high-power and high-frequency applications because of its high critical field, high electron saturation velocity, and high thermal conductivity. In this letter, we report the first experimental demonstration of microwave oscillation in 4H-SiC impact-ionization-avalanche-transit-time (IMPATT) diodes. The prototype devices are single-drift diodes with a high-low doping profile. DC characteristics exhibit hard, sustainable avalanche breakdown, as required for IMPATT operation. Microwave testing is performed in a reduced-height waveguide cavity. Oscillations are observed at 7.75 GHz at a power level of 1 mW     

Implications of fossil fuel constraints on economic growth and global warming

Energy Security and Global Warming are analysed as 21st century sustainability threats.     

Critical Behavior in the Low-Energy Spin Fluctuations in High-Tc Superconductors

We study the spin fluctuations of pure and Zn-substituted La_{2 – x} Sr _x CuO₄ using the muon spin relaxation technique. Superconductivity is found to coexist with low-frequency spin fluctuations over a large region of the superconducting phase diagram. The characteristic temperature of spin fluctuations detected by SR decreases with increasing x and vanishes above a critical doping x _c 0.19. This value of x _c coincides with the doping at which the normal state pseudogap extrapolates to zero. These results are discussed in terms of a quantum transition that separates the superconducting phase diagram of high-temperature superconductors into two distinct ground states.     

Gel protein capillary extraction apparatus. electronic protein transfer

A gel protein capillary extraction apparatus is developed and demonstrated for its rapid and effective transfer of SDS-protein complexes from polyacrylamide gel to a fused-silica capillary. The small dimensions of capillary columns permit the application of high voltages for achieving rapid and effective transfer of gel proteins. Furthermore, the fused-silica capillaries are internally coated with polyacrylamide for the elimination of electroosmotic pumping and protein adsorption onto the capillary wall. The extracted proteins are present in a highly concentrated solution plug as the result of field amplification and sample stacking during the extraction process. Three model proteins, including cytochrome c (14 kDa), ovalbumin (45 kDa), and beta-galactosidase (116 kDa), are visualized using coomassie blue staining and electrophoretically extracted from the gels with protein loading as low as 50 ng. The SDS-cytochrome c complexes extracted from a 50-ng protein loading are concentrated in a 30-nL solution plug inside the capillary with an estimated concentration of 0. 1 mg/mL or 10(-5) M. The capillary format allows the straightforward integration of a miniaturized trypsin-membrane reactor for on-line proteolytic digestion and ESI-MS analysis for protein/peptide identification.     

Bringing forth worlds

Kress encourages us to understand writing as “transformative engagement in the world,” and his emphasis on the materiality of modes draws our attention to the multiple possibilities offered by different materials and sensory channels. Writing involves the transformation of all aspects of the resources for meaning; thus writing is always an ethical act, and the worlds that different cultures and communities bring forth through their semiotic work offer different possibilities of being.     

Development and Application of a Phosphorus Model for a Shallow Oxbow Lake

A three-dimensional numerical model was developed for simulating the phosphorus concentration in shallow lakes. In this model, the computational domain was divided into two parts: the water column and the bed sediment layer. The processes of mineralization, settling, adsorption, desorption, bed release (diffusion), growth, and death of phytoplankton were taken into account, and the concentration of organic phosphorus, phosphate, and related water quality constituents was simulated. The concentrations of adsorbed (particulate) and dissolved phosphate due to adsorption-desorption were calculated using two formulas derived based on the Langmuir equation. The release rate of phosphorus from the bed sediment layer was calculated by considering the effects of the concentration gradient across the water-sediment interface, pH, temperature, dissolved oxygen concentration, and flow conditions. The adsorption and desorption of phosphate from sediment particles, as well as its release from bed sediment, were verified using laboratory experimental data. The model was calibrated and applied to Deep Hollow Lake in the Mississippi alluvial plain. The simulated trends and magnitudes of phosphorus concentration were compared with field observations. The simulation results show that there are strong interactions between sediment-related processes and phosphorus concentration.     

Driving on Mars with RSVP

The rover sequencing and visualization program (RSVP) suite of tools has been a critical factor in the success of the Mars exploration rover (MER) missions. It would be impossible to prepare the large command loads each sol without the capabilities that it possesses. It has proven to be robust and easy to use and capable of answering key questions about sequence validity and constraints. Certainly, training is required to use RSVP, but this is primarily in the general area of command sequencing and rover operations. Once these concepts are understood, RSVP feels natural for building sequences. RSVP has met its prime requirements of supporting rapid assimilation and understanding of the terrain and operational constraints, rapid sequence generation and validation, and production of documentation and archival products. This can be seen in the very limited number of sols lost due to errors in the command sequences. The success of the MER mission and the tremendous amount of science data collected attest to the capability of RSVP.