988 resultados para Library storage centers -- Catalonia


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Experiments were conducted to investigate physiological mechanisms of solid matrix priming (SMP) on germination enhancement of loblolly pine (Pinus taeda) seeds. During SMP, osmotic potential in the embryo decreased by 0.65 MPa, concentration of crystalloid proteins decreased to 62% and concentrations of buffer soluble proteins and free amino acids increased by 22% and by 166%, respectively. Observations under an electron microscope demonstrated protein bodies in the embryo were mobilized. Inhibitor analysis indicated thiol protease was the dominant enzyme among endopiptidases to degrade the reserved proteins. A fragment of thiol protease was cloned from the primed seed embryos and it has high identities to those thiol proteases responsive to water stress. RNA get blot analysis showed a 1.5 kb thiol protease gene was up-regulated by SMP. Treatment with E64, a thiol protease inhibitor, negated SMP effects on germination performance, water potentials and protein profiles. Based on the experimental results, reserve protein mobilization induced by SMP in the embryo before radicle emergence might be one of the mechanisms to enhance germination in loblolly pine seeds.

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Primary aldosteronism (PA) is a common form of endocrine hypertension previously believed to account for less than 1% of hypertensive patients. Hypokalemia was considered a prerequisite for pursuing diagnostic tests for PA. Recent studies applying the plasma aldosterone/plasma renin activity ratio (ARR) as a screening test have reported a higher prevalence. This study is a retrospective evaluation of the diagnosis of PA from clinical centers in five continents before and after the widespread use of the ARR as a screening test. The application of this strategy to a greater number of hypertensives led to a 5- to 15-fold increase in the identification of patients affected by PA. Only a small proportion of patients ( between 9 and 37%) were hypokalemic. The annual detection rate of aldosterone-producing adenoma (APA) increased in all centers ( by 1.3-6.3 times) after the wide application of ARR. Aldosterone-producing adenomas constituted a much higher proportion of patients with PA in the four centers that employed adrenal venous sampling ( 28 - 50%) than in the center that did not (9%). In conclusion, the wide use of the ARR as a screening test in hypertensive patients led to a marked increase in the detection rate of PA. Copyright © 2004 by The Endocrine Society

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Multi-layer hydrogen storage thin films with Mg and MmNi(3.5)(CoAlMn)(1.5) (here Mm denotes La-rich mischmetal) as alternative layers were prepared by direct current magnetron sputtering. Transmission electron microscopy investigation shows that the microstructure of the MmNi(3.5)(CoAlMn)(1.5) and Mg layers are significantly different although their deposition conditions are the same. The MmNi(3.5)(CoAlMn)(1.5) layer is composed of two regions: one is an amorphous region approximately 4 nm thick at the bottom of the layer and the other is a nanocrystalline region on top of the amorphous region. The Mg layer is also composed of two regions: one is a randomly orientated nanocrystalline region 50 nm thick at the bottom of the layer and the other is a columnar crystallite region on top of the nanocrystalline region. These Mg columnar crystallites have their [001] directions parallel to the growth direction and the average lateral size of these columnar crystallites is about 100 nm. A growth mechanism of the multi-layer thin films is discussed based on the experiment results. Wiley-Liss, Inc.

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Hydrogen adsorption in alkali-doped carbon materials is investigated theoretically. Our calculations show that hydrogen molecules can be physically adsorbed on alkali-doped graphite at 0 K but such an adsorption is thermodynamically unfavourable. The binding energy of hydrogen adsorption decreases significantly with the increase in temperature and becomes nearly zero at ambient temperature. We suggest that it may be unlikely to observe any hydrogen uptake in alkali-doped carbon materials at or above ambient temperature in the TGA (thermogravimetric) system, the previously reported hydrogen uptake in alkali-doped carbon materials was caused by either uncyclable chemisorbed hydrogen on the defects of carbon (defects were produced by repeated heat treatment) and/or moisture adsorption. (C) 2004 Elsevier Ltd. All rights reserved.