Size effect on the irradiation performance of coated fuel particles

Outer coatings that were as near alike as possible were applied to two different sizes of inert TRISO particles that were larger than those commonly used to fuel HTGR reactors and these particles were then irradiated in a test reactor to observe the influence of particle size on outer coating failures that resulted from irradiation-induced shrinkage of coatings onto the more stable SiC substrates over which they were applied. Outer coatings of plain pyrocarbon and of Si-alloyed pyrocarbon were used to make up two test pairs of particles with diameters of about 1050 and 1300 μm. For a fast-neutron fluence of 5.5 × 10²⁵ n/m² (E > 29 fJ) at an irradiation temperature of 1125K, failure was about twice as high in the larger 1300 μm particle of each test pair as in the smaller 1050 μm particle (16 vs 8%), with each of the coating types having roughly the same behavior. This observed size effect is somewhat greater than predicted by volume-dependent Weibull theory, which estimates failure of the larger size particles at 13% when the smaller size particles fail at a rate of 8%. However, experimental uncertainties are sufficient to account for the difference between observed size effects and those predicted by Weibull theory. The conclusion that the irradiation performance of coated particles is size dependent is reinforced by the fact that failure for regular 850 μm fueled particles in the same irradiation test was essentially zero.     

Methodology for competitive strategy development

Fighting terrorists involves taking action against a highly adaptive and cunning adversary. In this competitive situation, however, those involved may have dissimilar objectives. Given this difference of purpose, selecting an optimal strategy to achieve one's objectives can be a complex task. Techniques from decision theory, and specifically value focused thinking (VFT), are proven approaches for developing creative strategies to yield better decisions. However, these methods are focused on one decision maker choosing an optimal decision without reference to the affect the decision has on other decision makers and without reference to the affect the decisions of others have on them. On-the-other-hand, techniques especially suited for analyzing competitive situations, such as game theory, assume strategies exist without guidance on how to develop the strategies. This paper presents a methodology to bridge this gap by providing a means to develop strategies in competitive situations where the objectives of those involved are not necessarily the same.     

全球首款HDMI1.3高清声卡——华硕Xonar HDAV 1.3 Deluxe首测

作为全球首款支持HDMI 1．3a标准和可输出高清音频源码的声卡,华硕XOnar HDAV 1．3 Deluxef以下简称HDAV 1．3）自今年6月份在CeBIT展会上展示了工程样品以来就倍受全球高清玩家的关注。时隔3个多月,《微型计算机》高清实验室获得了这款产品,并抢先进行了测试。它能否让众多PC高清玩家获得完整的高清影音享受？这篇耗费近20天时间才完成的深度测试报告将说明一切!     

Adrenomedullary secretion of epinephrine is increased in mild essential hypertension

To assess whether patients with mild essential hypertension have excessive activities of the sympathoneuronal and adrenomedullary systems, we examined total body and forearm spillovers and norepinephrine and epinephrine clearances in 47 subjects with mild essential hypertension (25 men, 22 women, aged 38.1 +/- 6.7 years) and 43 normotensive subjects (19 men, 24 women, aged 36.5 +/- 5.9 years). The isotope dilution method with infusions of tritiated norepinephrine and epinephrine was used at rest and during sympathetic stimulation by lower body negative pressure at -15 and -40 mm Hg. Hypertensive subjects had a higher arterial plasma epinephrine concentration (0.20 +/- 0.01 nmol.L-1: mean +/- SE) than normotensive subjects (0.15 +/- 0.01) (P < .01). The increased arterial plasma epinephrine levels appeared to be due to a higher total body epinephrine spillover rate in the hypertensive subjects (0.23 +/- 0.02 nmol.min-1.m-2) than the normotensive subjects (0.18 +/- 0.01) (P < .05) and not to a decreased plasma clearance of epinephrine. The arterial plasma norepinephrine level, total body and forearm norepinephrine spillover rates, and plasma norepinephrine clearance were not altered in the hypertensive subjects. The responses of the catecholamine kinetic variables to lower body negative pressure were not consistently different between normotensive and hypertensive individuals. These data indicate that individuals with mild essential hypertension (1) have elevated arterial plasma epinephrine concentrations that are due to an increased total body epinephrine spillover rate, indicating an increased adrenomedullary secretion of epinephrine; (2) have no increased generalized sympathoneuronal activity and no increased forearm norepinephrine spillover; and (3) have similar responses of both the sympathoneuronal and adrenomedullary systems to sympathetic stimulation by lower body negative pressure.     

Interrelationship between the Na+/glucose cotransporter and CFTR in Caco-2 cells: relevance to cystic fibrosis

Both the Na+-dependent glucose cotransporter (SGLT1) and the cystic fibrosis transmembrane conductance regulator (CFTR) modulate Na+ and fluid movement, although in opposite directions. Yet few studies have investigated a possible interrelationship between these two transporters. By using the Caco-2 human colon carcinoma cell line, we confirmed that the activities of these transporters increased with spontaneous differentiation to the enterocytic phenotype. We showed that SGLT1 was positively regulated by Cl- and that optimal activity of CFTR was dependent on the presence of glucose. We also demonstrated that inhibition of CFTR by glibenclamide or diphenylamine-2-carboxylate did not modify the activity of SGLT1 and inhibition of SGLT1 by phlorizin did not modify the activity of CFTR, although it resulted in inhibition of glycoconjugate synthesis. These results point to positive substrate-cross regulation of SGLT1 and CFTR and suggest that NaCl and glucose are important for not only Na+ absorption and fluid movement, but also for cAMP-dependent Cl- efflux, and glycoconjugate synthesis, functions that are known to be anomalous in cystic fibrosis.     

GTPase activity of Rab5 acts as a timer for endocytic membrane fusion

The GTPase cycle is a versatile regulatory mechanism directing many cell functions, and Rab family members use it to regulate intracellular transport. Current models propose that GTP hydrolysis by Rab proteins is either required for membrane fusion or occurs afterwards to allow recycling of the protein. To measure the GTPase activity of Rab5 in endocytic membrane fusion, we engineered a mutant that preferentially binds xanthosine 5'-triphosphate (XTP),Rab5(D136N) and monitored the kinetics of [alpha(32)P]-XTP hydrolysis in situ during endosome fusion in vitro. Surprisingly, nucleotide hydrolysis occurred even in the absence of membrane fusion, indicating that membrane-bound Rab5 undergoes futile cycles of GTP(XTP) binding and hydrolysis. Nucleotide triphosphate hydrolysis by Rab5 is not conditional on membrane fusion and is reduced by its effector Rabaptin-5. Our data reveal that the GTP cycle of Rab proteins differs from that of other GTPases (for example, EF-Tu) and indicate that GTP hydrolysis acts as a timer that determines the frequency of membrane docking/fusion events.