نتایج جستجو برای: crystallization
تعداد نتایج: 23168 فیلتر نتایج به سال:
The amorphous-to-microcrystalline phase transition of Ge in Pb/Ge multilayer geometry has been investigated as a function of layer thicknesses with the use of high-temperature x-raydiA'raction techniques. During crystallization, the modulation structure is destroyed and the Pb texture improves. In addition, the crystallization temperature decreases with decreasing amorphous Ge thickness and inc...
Dielectric spectra of the polyester poly(propylene succinate) were measured upon crystallization. For this model aliphatic polyester the alpha and beta relaxations appear simultaneously and are well resolved in the experimental frequency window. During isothermal crystallization, this fact allows one to use the beta relaxation to characterize the crystalline structural development while the alp...
We report that an electron beam focused for high resolution imaging rapidly initiates observable crystallization of amorphous Me-Si-C films. For 200-keV electron irradiation of Nb-Si-C and Zr-Si-C films, crystallization is observed at doses of ~2.8*10 and ~4.7*10 e /nm, respectively. The crystallization process is driven by atomic displacement events, rather than heating from the electron beam ...
The kinetics of the initial stage of crystallization of one-component gas hydrates in aqueous solutions are analyzed. The temporal evolution of the volume of hydrate crystallized and the moles of gas consumed are determined. Expressions are derived for the supersaturation dependence of the hydrate crystallite growth rate and the induction time in hydrate crystallization. These expressions are u...
Amorphous films of the anticonvulsant drug carbamazepine are easily accessible by various methods, while the crystallization into specific polymorphs represents a challenging and time-consuming task. In this work, the crystallization of drop cast carbamazepine at silica surfaces is investigated by atomic force microscopy and both in situ and ex situ grazing incidence X-ray diffraction. The pris...
We evaluated the crystallization of calcium oxalate (CaOx) in undiluted urine, collected 3 hours after intake of a test meal by healthy males. In two experiments in vitro, either the total citrate concentration was increased (urine A) or the pH was elevated (urine B). In addition, in three clinical trials, the bioequivalence of orally taken potassium citrate (PC) and potassium-sodium citrate (P...
When crystallization screening is conducted many outcomes are observed but typically the only trial recorded in the literature is the condition that yielded the crystal(s) used for subsequent diffraction studies. The initial hit that was optimized and the results of all the other trials are lost. These missing results contain information that would be useful for an improved general understandin...
INTRODUCTION Crystallization of actives in skin following topical application was suggested by studies in the 1950s and 1960s but is poorly understood. In contrast, the problem of crystallization of actives on skin and in transdermal formulations has been known for many years. AREAS COVERED With respect to crystallization in skin, this review describes early reports of a skin 'reservoir' and ...
The failure of multi-step experimental procedures to yield diffraction-quality crystals is a major bottleneck in protein structure determination. Accordingly, several bioinformatics methods have been successfully developed and employed to select crystallizable proteins. Unfortunately, the majority of existing in silico methods only allow the prediction of crystallization propensity, seldom enab...
The presence of a metastable fluid-fluid critical point is thought to dramatically influence the crystallization pathway, increasing the nucleation rate by many orders of magnitude over the predictions of classical nucleation theory. We use molecular dynamics simulations to study the kinetics of crystallization in the vicinity of this metastable critical point and throughout the metastable flui...
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