Boric acid nanotubes, nanotips, nanorods, microtubes, and microtips

Thin films containing boron, carbon, and oxygen were synthesized by plasma-enhanced chemical vapor deposition (PE-CVD). When the thin films were exposed to humid atmosphere, nano- or micro-scale boric acid structures were observed to grow spontaneously. Depending on the relative humidity, temperature, and exposure time to the humid atmosphere, these boric acid structures were either nanotubes, nanotips, nanorods, microtubes, or microtips. X-ray photoelectron spectroscopy (XPS) studies on the thin film surface suggested that the thin films contained B2O3, BCO2, and C-C clusters. The relative amounts of boron, carbon, and oxygen in the thin films were about 41.3, 14, and 43.9% respectively. Secondary ion mass spectrometry (SIMS) results indicated that the elemental distribution of boron, carbon, and oxygen in the thin films was rather homogeneous. X-ray diffraction (XRD) was used to study the time evolution of these boric acid structures at 23 degreesC and 45 +/- 3% relative humidity. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the structures showed that the boric acid tubes and tips had a hollow structure, whereas the boric acid rods were solid. The boric acid structures dehydrated into similarly shaped amorphous structures in a vacuum. In-situ X-ray diffraction studies in a vacuum showed that at 23 degreesC and 45 +/- 3% relative humidity (at one atmosphere pressure), the dissociation rate law of the boric acid structures at 250 and 500 mTorr was [-ln(1 -alpha)](1/2) = kt; whereas at 1000 mTorr, the dissociation rate law was [-ln(1 - alpha)] = kt, where a, k, and t were the fraction of decomposed reactant, the reaction rate constant, and the time, respectively

Epitaxial stabilization of orthorhombic cuprous oxide films on MgO(110)

Continuous epitaxial films of cuprous oxide (Cu2O) have been formed by the thermal oxidation of 1.5-mum-thick Cu metal films deposited on MgO(110) substrates. These films melted at 1118 degreesC in air, in agreement with equilibrium phase diagrams. Upon cooling from the liquid, a highly crystalline, epitaxial, 2.5-mum-thick Cu2O film was formed. X-ray diffraction spectroscopy revealed that the Cu2O film crystal structure was orthorhombically distorted from the bulk cubic crystal structure. High-resolution transmission electron microscopy showed that the film is coherent, and energy dispersive x-ray spectroscopy showed that interdiffusion is limited to the interface. These results suggest that a new epitaxially stabilized phase of Cu2O has been formed

Large second harmonic response in ZnO thin films

The second-order susceptibilities in the ZnO films have been studied systemically. In very thin films, we observe an enhancement of second-order susceptibilities, which is larger than that of single-crystal ZnO. It was also observed that the second-order susceptibilities for ZnO films depend on the thickness but not on the film growth technique used (reactive sputtering or plasma-enhanced chemical vapor deposition). We suggest a mechanism to explain the reduction in the second-order susceptibilities of the thicker films. (C) 2002 American Institute of Physics

Multi-scale order in amorphous transparent oxide thin films

Nominally diffraction amorphous materials represent a pervasive challenge in establishing classical structure-property relationships. This stems from the difficulty in defining the structure of nominally amorphous materials and experimentally differentiating the short-range (10 Å) and medium-range (10 to 30 Å) order as a function of process parameters which are important due to their influence on physical, chemical, or transport properties. Herein, we report on the determination of short- and medium-range order in nominally amorphous zinc and tin co-substituted indium oxide In 1.4Zn 0.3Sn 0.3O 3 (a-ZITO) thin films grown by pulsed laser deposition. These thin films are being explored as transparent conductors that exhibit changes in transport properties depending on deposition temperature while remaining diffraction amorphous. Reduced density function (RDF) analysis from electron diffraction accompanied by density functional theory molecular dynamics simulation of a liquid quench suggests ordering at short range. Scanning transmission fluctuation electron microscopy (STFEM) indicates the presence of ordered ZITO regions at medium range. For a-ZITO films grown at different temperatures, RDF analysis showed no significant change in the short range order. However, STFEM revealed notable structural (and symmetry) differences at medium range. The existence of this type of multi-scale local order in amorphous ZITO thin films highlights the importance of a combined approach to unravel the structures of nominally amorphous materials and to understand structure-properties correlations. © 2012 American Institute of Physics

613 cases of splenic rupture without risk factors or previously diagnosed disease: a systematic review

Background Rupture of the spleen in the absence of trauma or previously diagnosed disease is largely ignored in the emergency literature and is often not documented as such in journals from other fields. We have conducted a systematic review of the literature to highlight the surprisingly frequent occurrence of this phenomenon and to document the diversity of diseases that can present in this fashion. Methods Systematic review of English and French language publications catalogued in Pubmed, Embase and CINAHL between 1950 and 2011. Results We found 613 cases of splenic rupture meeting the criteria above, 327 of which occurred as the presenting complaint of an underlying disease and 112 of which occurred following a medical procedure. Rupture appeared to occur spontaneously in histologically normal (but not necessarily normal size) spleens in 35 cases and after minor trauma in 23 cases. Medications were implicated in 47 cases, a splenic or adjacent anatomical abnormality in 31 cases and pregnancy or its complications in 38 cases. The most common associated diseases were infectious (n = 143), haematologic (n = 84) and non-haematologic neoplasms (n = 48). Amyloidosis (n = 24), internal trauma such as cough or vomiting (n = 17) and rheumatologic diseases (n = 10) are less frequently reported. Colonoscopy (n = 87) was the procedure reported most frequently as a cause of rupture. The anatomic abnormalities associated with rupture include splenic cysts (n = 6), infarction (n = 6) and hamartomata (n = 5). Medications associated with rupture include anticoagulants (n = 21), thrombolytics (n = 13) and recombinant G-CSF (n = 10). Other causes or associations reported very infrequently include other endoscopy, pulmonary, cardiac or abdominal surgery, hysterectomy, peliosis, empyema, remote pancreato-renal transplant, thrombosed splenic vein, hemangiomata, pancreatic pseudocysts, splenic artery aneurysm, cholesterol embolism, splenic granuloma, congenital diaphragmatic hernia, rib exostosis, pancreatitis, Gaucher's disease, Wilson's disease, pheochromocytoma, afibrinogenemia and ruptured ectopic pregnancy. Conclusions Emergency physicians should be attuned to the fact that rupture of the spleen can occur in the absence of major trauma or previously diagnosed splenic disease. The occurrence of such a rupture is likely to be the manifesting complaint of an underlying disease. Furthermore, colonoscopy should be more widely documented as a cause of splenic rupture