Fast inactivation in Shaker K+ channels. Properties of ionic and gating currents.

Fast inactivating Shaker H4 potassium channels and nonconducting pore mutant Shaker H4 W434F channels have been used to correlate the installation and recovery of the fast inactivation of ionic current with changes in the kinetics of gating current known as "charge immobilization" (Armstrong, C.M., and F. Bezanilla. 1977. J. Gen. Physiol. 70:567-590.). Shaker H4 W434F gating currents are very similar to those of the conducting clone recorded in potassium-free solutions. This mutant channel allows the recording of the total gating charge return, even when returning from potentials that would largely inactivate conducting channels. As the depolarizing potential increased, the OFF gating currents decay phase at -90 mV return potential changed from a single fast component to at least two components, the slower requiring approximately 200 ms for a full charge return. The charge immobilization onset and the ionic current decay have an identical time course. The recoveries of gating current (Shaker H4 W434F) and ionic current (Shaker H4) in 2 mM external potassium have at least two components. Both recoveries are similar at -120 and -90 mV. In contrast, at higher potentials (-70 and -50 mV), the gating charge recovers significantly more slowly than the ionic current. A model with a single inactivated state cannot account for all our data, which strongly support the existence of "parallel" inactivated states. In this model, a fraction of the charge can be recovered upon repolarization while the channel pore is occupied by the NH2-terminus region

Reversals in nature and the nature of reversals

The asymmetric shape of reversals of the Earth's magnetic field indicates a possible connection with relaxation oscillations as they were early discussed by van der Pol. A simple mean-field dynamo model with a spherically symmetric $\alpha$ coefficient is analysed with view on this similarity, and a comparison of the time series and the phase space trajectories with those of paleomagnetic measurements is carried out. For highly supercritical dynamos a very good agreement with the data is achieved. Deviations of numerical reversal sequences from Poisson statistics are analysed and compared with paleomagnetic data. The role of the inner core is discussed in a spectral theoretical context and arguments and numerical evidence is compiled that the growth of the inner core might be important for the long term changes of the reversal rate and the occurrence of superchrons.Comment: 24 pages, 12 figure

THE UTILIZATION OF THORIUM-232 IN ADVANCED PWR – FROM SMALL TO BIG REACTORS

Since the beginning of Nuclear Energy Development, thorium was considered as a potential fuel, mainly due to the potential to produce fissile 233U. Several Th/U fuel cycles, using thermal and fast reactors were proposed and are still under investigation. However, the technical feasibility to use thorium was made in PWR; the USA PWR Indian Point Reactor was the first to utilize a core load with (Th0-0.9./U1-0.1)O2, with highly enriched U (93 w/0), achieving a maximum burn up of 32 MWD/kg HM. Also the last core of the Shipping port PWR (shutdown in 1982) was ThO2 and (Th/U)O2, operating as a Light Water Breeder Reactor (Seed- Blanket Concept) during 1200 effective full power days of operation (60 MWD/kg HM). More recently, many researchers turned their attention to Th fuel cycles in PWRs aiming at reducing the generation of minor actinide waste, at improving the nuclear power sustainability and at better fuel utilization. These studies were interested in assessing the feasibility of using 233U-Th fuels in PWR without worrying about how to obtain the initial 233U fuel load or the transition from an uranium to a thorium core in the current nuclear power plants. In this paper a review of the recent initiatives to utilize mixed oxide of U-Th in PWR is going to be provided, with an emphasis in two types of Advanced Reactors, the first a Small Modular Reactor (SMR); and the second a Generation III Advanced PWR (APWR). For the SMR, we use as criteria the fact that the core is designed to stand for a complete cycle, without the need to be refueled, but they need to be strongly poisoned at the beginning of life. So, since thorium can be used as a poison and a fertile fuel it could be a good option to be used as mixed oxide with uranium, and so we could reduce the burnable poison and have an extended burnup cycle. For the APWR, we use as criterion that the transition from the current UO2 APWR core to one with mixed U/Th fuels should be such that minimum changes occur on its current core design and operational parameters. Thus, one could consider the following requirements in this study: produce important amounts of 233U (maximization) for future 233U/Th cores; keep the current fuel assembly geometry, i.e., fuel rod diameter and pitch and meet the current thermal-hydraulic limits such as maximum center line fuel rod temperature and maximum linear power density; keep the current fuel cycle length of 18 months. As case studies, for the SMR, we used the Korean SMART reactor (the first integrated PWR to receive design certification), and for the APWR we used the Westinghouse AP 1000, due to its commercial success, with units being constructed in the USA and China. For both reactors we used a parametric study using homogeneous and heterogeneous fuel assemblies keeping the same geometry as the original UO2 core, and just changing the pellet material for (U-Th) O2. All the calculations were made by Monte Carlo codes. The results for both reactors show the feasibility to utilize thorium and satisfying the criterium imposed, even with advantages such as an extended discharge burn up, reducing the burn up poison, and a lower linear power density. As conclusion, we notice that the utilization of thorium in small or big PWR could be done successfully, without needing any changes in the current Nuclear Power Plants

Cylindrical anisotropic α2\alpha^{2} dynamos

We explore the influence of geometry variations on the structure and the time-dependence of the magnetic field that is induced by kinematic $\alpha^{2}$ dynamos in a finite cylinder. The dynamo action is due to an anisotropic $\alpha$ effect which can be derived from an underlying columnar flow. The investigated geometry variations concern, in particular, the aspect ratio of height to radius of the cylinder, and the thickness of the annular space to which the columnar flow is restricted. Motivated by the quest for laboratory dynamos which exhibit Earth-like features, we start with modifications of the Karlsruhe dynamo facility. Its dynamo action is reasonably described by an $\alpha^{2}$ mechanism with anisotropic $\alpha$ tensor. We find a critical aspect ratio below which the dominant magnetic field structure changes from an equatorial dipole to an axial dipole. Similar results are found for $\alpha^{2}$ dynamos working in an annular space when a radial dependence of $\alpha$ is assumed. Finally, we study the effect of varying aspect ratios of dynamos with an $\alpha$ tensor depending both on radial and axial coordinates. In this case only dominant equatorial dipoles are found and most of the solutions are oscillatory, contrary to all previous cases where the resulting fields are steady.Comment: 15 pages, 8 figure

IDENTIFIKASI MUTASI GEN FOLLICLE STIMULATING HORMONE (FSH) PADA ITIK PITALAH SUMATERA BARAT

The purpose of this study was to identify Follicle Stimulating Hormone (FSH) gene mutation of West Sumatera Pitalah ducks. This study used blood samples from 50 Pitalah ducks (5 males and 45 females). Extraction blood samples was analized by Kit from iNtRON Biotechnology and amplification of DNA extraction used the primer with fragmen target 318 bp. Sequencing was analized by 1st Base Singapore and this product was analized by Dnastar. Based on the result of the study is identify Follicle Stimulating Hormone (FSH) gene mutation of West Sumatera Pitalah ducks. Key Words: FSH, Gene, Mutation, Pitalah Duck, Sequensin

Asymmetric polarity reversals, bimodal field distribution, and coherence resonance in a spherically symmetric mean-field dynamo model

Using a mean-field dynamo model with a spherically symmetric helical turbulence parameter alpha which is dynamically quenched and disturbed by additional noise, the basic features of geomagnetic polarity reversals are shown to be generic consequences of the dynamo action in the vicinity of exceptional points of the spectrum. This simple paradigmatic model yields long periods of constant polarity which are interrupted by self-accelerating field decays leading to asymmetric polarity reversals. It shows the recently discovered bimodal field distribution, and it gives a natural explanation of the correlation between polarity persistence time and field strength. In addition, we find typical features of coherence resonance in the dependence of the persistence time on the noise.Comment: 5 pages, 7 figure

Body condition score (BCS) and metabolic status of shelter dogs

A group of 147 shelter dogs were weighted and assigned a body condition score (BCS) using a 9 point scale system, in order to evaluate the prevalence of obesity in the kennel. More than 60% of the animals showed a BCS³6 (overweight and obese) and this condition was mainly attributed to an excess of carbohydrates and fat in the diet. In 67/147 dogs, a blood sample was drawn and the effects of BCS, age and time spent in the shelter were evaluated on biochemical parameters. Obese dogs showed significantly higher levels of triglycerides (P<0.01), while increasing BCS determined only an increasing non significant trend on cholesterol values. Age influenced creatinine (P<0.05) and the oldest dogs scoring BCS³6 registered significant higher NEFA (P<0.05) and CK (P=0.01) levels. Time spent in the shelter did not affect any parameter. The dogs' metabolic condition reflects the need of taking more care of the quality of feed administered in the shelters to avoid the negative health effects caused by chronic obesity