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31.
32.
The effect of hydrogen on ZnO while annealing at 1370 K under oxygen-poor conditions with excess Zn vapor or Ti metal is studied.
ZnO turns red only when hydrogen is present in a complex with oxygen vacancies. A practical method is described to remove
hydrogen from ZnO in a sealed ampoule and to bind it to Ti metal. Hydrogen coupled to an oxygen vacancy is the simplest defect
to explain the observations. The coloration is reversible at 1370 K by adding or removing hydrogen, consistent with an activation
energy >1.5 eV. In red ZnO Hall data show a shallow donor level around 45 meV. 相似文献
33.
Raji Soundararajan Kelvin G. Lynn Salah Awadallah Csaba Szeles Su-Huai Wei 《Journal of Electronic Materials》2006,35(6):1333-1340
We have studied the defect levels in as grown and post growth processed cadmium telluride (CdTe) using thermoelectric effect
spectroscopy (TEES) and thermally stimulated current (TSC) techniques. We have extracted the thermal energy (Eth) and trapping cross section (σth) for the defect levels using the initial rise and variable heating rate methods. We have identified 10 different defect levels
in the crystals. Thermal ionization energy values obtained experimentally were compared to theoretical values of the transition-energy
levels of intrinsic and extrinsic defects and defect complexes in CdTe determined by first-principles band-structure calculations.
On the basis of this comparison, we have associated the observed ionization levels with various native defects and impurity
complexes. 相似文献
34.
Blake N. Johnson Karen Z. Lancaster Gehua Zhen Junyun He Maneesh K. Gupta Yong Lin Kong Esteban A. Engel Kellin D. Krick Alex Ju Fanben Meng Lynn W. Enquist Xiaofeng Jia Michael C. McAlpine 《Advanced functional materials》2015,25(39):6205-6217
A 3D printing methodology for the design, optimization, and fabrication of a custom nerve repair technology for the regeneration of complex peripheral nerve injuries containing bifurcating sensory and motor nerve pathways is introduced. The custom scaffolds are deterministically fabricated via a microextrusion printing principle using 3D models, which are reverse engineered from patient anatomies by 3D scanning. The bifurcating pathways are augmented with 3D printed biomimetic physical cues (microgrooves) and path‐specific biochemical cues (spatially controlled multicomponent gradients). In vitro studies reveal that 3D printed physical and biochemical cues provide axonal guidance and chemotractant/chemokinetic functionality. In vivo studies examining the regeneration of bifurcated injuries across a 10 mm complex nerve gap in rats showed that the 3D printed scaffolds achieved successful regeneration of complex nerve injuries, resulting in enhanced functional return of the regenerated nerve. This approach suggests the potential of 3D printing toward advancing tissue regeneration in terms of: (1) the customization of scaffold geometries to match inherent tissue anatomies; (2) the integration of biomanufacturing approaches with computational modeling for design, analysis, and optimization; and (3) the enhancement of device properties with spatially controlled physical and biochemical functionalities, all enabled by the same 3D printing process. 相似文献
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The pre- and postnatal findings of a fetus with a de novo del(13)(pter-->q21:) and an occipital encephalocoele are described. Maternal serum alpha-fetoprotein (AFP) screening at 19 weeks' gestation demonstrated a high level of 2.5 multiples of the median (MOM) and ultrasonography at 27 weeks' gestation showed severe intrauterine growth retardation, cardiomegaly, an occipital encephalocoele, and a calvarial defect. Genetic amniocentesis revealed a karyotype of 46,XX,del(13)(pter-->q21:). The proband postnatally displayed additional abnormalities such as microphthalmia, hypertelorism, large low-set ears, and micrognathia. We discuss the association of central nervous system (CNS) malformations with 13q deletions and emphasize that pregnancies with neural tube defects warrant cytogenetic analysis, especially when additional fetal abnormalities and neonatal dysmorphism are observed. 相似文献
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M Tymianski RA Willinsky CH Tator D Mikulis KG TerBrugge L Markson 《Canadian Metallurgical Quarterly》1994,35(5):974-7; discussion 977
A highly vascular petroclival meningioma supplied by tentorial branches of the internal carotid artery was embolized by temporary balloon occlusion of the parent vessel distal to the tumor, followed by obliteration of the tumor vascularity with polyvinyl alcohol particles. Subsequently, in vivo proton spectroscopy showed necrosis of a large portion of the tumor and helped determine the timing of surgery. Both innovative techniques considerably facilitated the subsequent radical excision of the tumor with no neurological morbidity. 相似文献