Lifetime embrittlement of reactor core materials

Over a core lifetime, the reactor materials Zircaloy-2, Zircaloy-4, and hafnium may become embrittled due to the absorption of corrosion- generated hydrogen and to neutron irradiation damage. Results are presented on the effects of fast fluence on the fracture toughness of wrought Zircaloy-2, Zircaloy-4, and hafnium; Zircaloy-4 to hafnium butt welds; and hydrogen precharged beta treated and weld metal Zircaloy-4 for fluences up to a maximum of approximately 150 x 10{sup 24} n/M{sup 2} (> 1 Mev). While Zircaloy-4 did not exhibit a decrement in K{sub IC} due to irradiation, hafnium and butt welds between hafnium and Zircaloy-4 are susceptible to embrittlement with irradiation. The embrittlement can be attributed to irradiation strengthening, which promotes cleavage fracture in hafnium and hafnium-Zircaloy welds, and, in part, to the lower chemical potential of hydrogen in Zircaloy-4 compared to hafnium, which causes hydrogen, over time, to drift from the hafnium end toward the Zircaloy-4 end and to precipitate at the interface between the weld and base-metal interface. Neutron radiation apparently affects the fracture toughness of Zircaloy-2, Zircaloy-4, and hafnium in different ways. Possible explanations for these differences are suggested. It was found that Zircaloy-4 is preferred over Zircaloy-2 in hafnium-to- Zircaloy butt-weld applications due to its absence of a radiation- induced reduction in K{sub IC} plus its lower hydrogen absorption characteristics compared with Zircaloy-2

Synapse efficiency diverges due to synaptic pruning following over-growth

In the development of the brain, it is known that synapses are pruned following over-growth. This pruning following over-growth seems to be a universal phenomenon that occurs in almost all areas -- visual cortex, motor area, association area, and so on. It has been shown numerically that the synapse efficiency is increased by systematic deletion. We discuss the synapse efficiency to evaluate the effect of pruning following over-growth, and analytically show that the synapse efficiency diverges as O(log c) at the limit where connecting rate c is extremely small. Under a fixed synapse number criterion, the optimal connecting rate, which maximize memory performance, exists.Comment: 15 pages, 16 figure

Light-cone QCD Sum Rules for the Λ\Lambda Baryon Electromagnetic Form Factors and its magnetic moment

We present the light-cone QCD sum rules up to twist 6 for the electromagnetic form factors of the $\Lambda$ baryon. To estimate the magnetic moment of the baryon, the magnetic form factor is fitted by the dipole formula. The numerical value of our estimation is $\mu_\Lambda=-(0.64\pm0.04)\mu_N$, which is in accordance with the experimental data and the existing theoretical results. We find that it is twist 4 but not the leading twist distribution amplitudes that dominate the results.Comment: 13 page, 7 figures, accepted for publication in Euro. Phys. J.

Spatio-temporal gait analysis in children with cerebral palsy using, foot-worn inertial sensors.

A child's natural gait pattern may be affected by the gait laboratory environment. Wearable devices using body-worn sensors have been developed for gait analysis. The purpose of this study was to validate and explore the use of foot-worn inertial sensors for the measurement of selected spatio-temporal parameters, based on the 3D foot trajectory, in independently walking children with cerebral palsy (CP). We performed a case control study with 14 children with CP aged 6-15 years old and 15 age-matched controls. Accuracy and precision of the foot-worn device were measured using an optical motion capture system as the reference system. Mean accuracy±precision for both groups was 3.4±4.6cm for stride length, 4.3±4.2cm/s for speed and 0.5±2.9° for strike angle. Longer stance and shorter swing phases with an increase in double support were observed in children with CP (p=0.001). Stride length, speed and peak angular velocity during swing were decreased in paretic limbs, with significant differences in strike and lift-off angles. Children with cerebral palsy showed significantly higher inter-stride variability (measured by their coefficient of variation) for speed, stride length, swing and stance. During turning trajectories speed and stride length decreased significantly (p<0.01) for both groups, whereas stance increased significantly (p<0.01) in CP children only. Foot-worn inertial sensors allowed us to analyze gait spatiotemporal data outside a laboratory environment with good accuracy and precision and congruent results with what is known of gait variations during linear walking in children with CP

Treatment with the platelet-activating factor antagonist TCV-309 in patients with severe systemic inflammatory response syndrome: a prospective, multi-center, double-blind, randomized phase II trial.

Treatment with the platelet-activating factor antagonist TCV-309 in patients with severe systemic inflammatory response syndrome: a prospective, multi-center, double-blind, randomized phase II trial. Froon AM, Greve JW, Buurman WA, van der Linden CJ, Langemeijer HJ, Ulrich C, Bourgeois M. Academic Hospital Maastricht, The Netherlands. In a prospective randomized, double-blind, placebo-controlled clinical study, the safety and efficacy of the platelet-activating factor antagonist TCV-309 in the treatment of systemic inflammatory response syndrome was studied. In total 29 patients were treated with 1.0 mg/kg TCV-309 twice daily during 7 days or with placebo. Study parameters were as follows: adverse events, 28 and 56 day all cause mortality, multi-organ failure scores, and the inflammatory mediators tumor necrosis factor, interleukin 6, interleukin 8, and soluble E-selectin. There was no difference in number and severity of adverse events between TCV-309- and placebo-treated patients. Day 28 and day 56 mortality was similar in both groups (day 56: 7/12 TCV-309 vs. 9/16 placebo, NS). Pulmonary and hematological failure scores improved significantly in TCV-309-treated patients (p < .05). There was no difference in inflammatory mediator levels between TCV-309- and placebo-treated patients. Treatment with TCV-309 appears to be safe in patients with systemic inflammatory response syndrome and does improve organ failure significantly. Publication Types: Clinical Trial Clinical Trial, Phase II Multicenter Study Randomized Controlled Tria

Ocorrência de Listeria monocytogenes em queijo artesanal tipo coalho comercializado na cidade de Manaus-AM, Brasil Occurrence of Listeria monocytogenes in handmade type cheese coagulum marketed in the city of Manaus-Amazonas, Brazil

A ocorrência de Listeria sp. em queijo artesanal tipo coalho comercializado na cidade de Manaus foi estudada. No período de março a maio de 1998 foram coletadas 58 amostras do produto em feiras e mercados localizados em seis zonas da cidade de Manaus. Em duas amostras de queijo foram identificadas duas espécies de Listeria: L. monocytogenes e L. innocua. A primeira espécie é reconhecidamente patogênica para o ser humano. Os resultados apresentados demonstraram haver risco de transmissão de enfermidades pelo consumo de queijos processados sem os devidos cuidados de higiene.<br>The occurrence of Listeria sp. in cheese craft type coagulum marketed in the city of Manaus was studied. In the period of March to May of 1998 58 samples of the product were collected at fairs and located markets in six areas of the city. In two cheese samples we identified two species of Listeria: L. monocytogenes and L. innocua. The first species was found fobe pathogenic for the human being. The results demonstrated there to be risk of transmission of illnesses from the consumption of cheeses processed without the due hygiene care