Electron transport in Ga-rich InxGa1-xN alloys

WOS: 000249810900060Resistivity and Hall effect measurements on n-type undoped Ga-rich InxGa1-xN (0.06 <= x <= 0.135) alloys grown by metal-organic vapour phase epitaxy (MOVPE) technique are carried out as a function of temperature (15-350K). Within the experimental error, the electron concentration in InxGa1-xN alloys is independent of temperature while the resistivity decreases as the temperature increases. Therefore, 1nxGai_x1V (0.06 <= x <= 0.135) alloys are considered in the metallic phase near the Mott transition. It has been shown that the temperature-dependent metallic conductivity can be well explained by the Mott model that takes into account electron-electron interactions and weak localization effects

HT breakdown of Mn-bearing elbaite from the Anjanabonoina pegmatite, Madagascar

The thermal behavior of a gem-quality purplish-red Mn-bearing elbaite from the Anjanabonoina pegmatite, Madagascar, with composition X(Na0.41□0.35Ca0.24)Σ1.00 Y(Al1.81Li1.00Fe3+ 0.04Mn3+ 0.02Mn2+ 0.12Ti0.004)Σ3.00 ZAl6[T(Si5.60B0.40)Σ6.00O18](BO3)3(OH)3 W[(OH)0.50F0.13O0.37]Σ1.00 was investigated using both in situ High-Temperature X-Ray powder diffraction (HT-pXRD) and ex situ X-Ray single-crystal diffraction (SC-XRD) on two single crystals previously heated in the air up to 750 and 850 °C. The first occurrence of mullite diffraction peaks allowed us to constrain the breakdown temperature of Mnbearing elbaite at ambient pressure, at 825 °C. The breakdown products from the HT-pXRD experiments were cooled down to ambient temperature and identified via pXRD, represented by B-mullite and γ-LiAlSi2O6. A thermally induced oxidation of Mn2+ to Mn3+ was observed with both in-situ and ex-situ techniques; it started at 470 °C and is assumed to be counterbalanced by deprotonation, according to the equation: Mn2+ + (OH)– → Mn3+ + O2– + 1/2H2. At temperatures higher than 752 °C, a partial disorder between the Y and Z sites is observed from unit-cell parameters and mean bond distances, possibly caused by the inter-site exchange mechanism YLi + ZAl → ZLi + YAl

Dietary Nitrate: Effects on the health of weaning pigs and Antimicrobial activity on seven probiotic Bifidobacterium spp. strains

The potential role of nitrite as an antimicrobial substance in the stomach may be of some importance in the ecology of the gastrointestinal tract and in host physiology. It has been shown that nitrite, under the acidic conditions of the stomach, may kill gut pathogens like Salmonella enteritidis, Escherichia coli, Salmonella typhimurium, and Yersinia enterocolitica, whereas acid alone has only a bacteriostatic effect. An in vivo study was conducted in order to assess the effects of dietary nitrate on microbiota and on the health of the gut (particularly in the stomach and small intestine). 96 weaning pigs were fed a diet containing high nitrate levels (15 mg and 150 mg) and then challenged with Salmonella enterica serovar typhimurium. Differences in composition of the gut microbiota were assessed by analysing samples from the pigs: To date analysis of 48 pigs has been completed.. Preliminary results demonstrated no effect on the population densities of microbial groups either from the challenge or from nitrate intake. However, increasing the time from challenge decreased either the counts of LAB in the stomach and jejunum or of clostridia in the stomach. Bifidobacteria also decreased in the stomach contents as nitrate supplementation increased. Supplementing the feedstuff with high dietary nitrate intake and then challenging with Salmonella did not affect the gastric pH or the degree of ulceration in the pigs. The synergistic bactericidal effects of pH, nitrite and thiocyanate on seven probiotic Bifidobacterium spp. strains were also investigated in an in vitro study. The results of the in vitro study demonstrated that an inhibitory effect exists on the seven probiotic bifidobacteria investigated with an exposure longer than 2 hours and pH values < 5.0. Addition of thiocyanate also increased the susceptibility of the tested strains. In this in vitro study, the most resistant strains at all conditions were B. animalis subsp. lactis Ra 18 and P32 and B. choerinum Su 877, Su 837 and Su 891

Thermal behavior of schorl up to breakdown temperature at room pressure

Schorl is one of the most widespread tourmaline compositions in the world, known from many different geological settings. Its role as boron and water carrier has been moderately investigated together with its stability field. In this study, the richest schorl in Fe2+ content was investigated to constraint its breakdown temperature at room pressure through in situ powder X-Ray Diffraction (in situ pXRD), its breakdown products and the coupled thermally induced dehydrogenation-dehydrogenation process experienced approaching the breakdown conditions. Schorl turned out to begin its breakdown at 850 °C with the first appearance of hematite, followed by a dominant B-mullite phase. The breakdown reaction of schorl can be expressed as follows: 2NaFe2+3Al6(BO3)3Si6O18(OH)=3Fe2O3+4/3Al9Si2BO19+(Na- Si- B-rich) glass+4H2O.The breakdown process is completed at 950 °C, when no trace of residual tourmaline is found. Annealing the schorl at 450 °C in air was enough to set the Fe oxidation out, counterbalanced by the deprotonation reaction: (Fe2+)+(OH)- → (Fe3+)+ (O2-)+1/2H2(g)

In vivo estimation of target registration errors during augmented reality laparoscopic surgery

PURPOSE: Successful use of augmented reality for laparoscopic surgery requires that the surgeon has a thorough understanding of the likely accuracy of any overlay. Whilst the accuracy of such systems can be estimated in the laboratory, it is difficult to extend such methods to the in vivo clinical setting. Herein we describe a novel method that enables the surgeon to estimate in vivo errors during use. We show that the method enables quantitative evaluation of in vivo data gathered with the SmartLiver image guidance system. METHODS: The SmartLiver system utilises an intuitive display to enable the surgeon to compare the positions of landmarks visible in both a projected model and in the live video stream. From this the surgeon can estimate the system accuracy when using the system to locate subsurface targets not visible in the live video. Visible landmarks may be either point or line features. We test the validity of the algorithm using an anatomically representative liver phantom, applying simulated perturbations to achieve clinically realistic overlay errors. We then apply the algorithm to in vivo data. RESULTS: The phantom results show that using projected errors of surface features provides a reliable predictor of subsurface target registration error for a representative human liver shape. Applying the algorithm to in vivo data gathered with the SmartLiver image-guided surgery system shows that the system is capable of accuracies around 12 mm; however, achieving this reliably remains a significant challenge. CONCLUSION: We present an in vivo quantitative evaluation of the SmartLiver image-guided surgery system, together with a validation of the evaluation algorithm. This is the first quantitative in vivo analysis of an augmented reality system for laparoscopic surgery

Reconstructing 3D x-ray CT images of polymer gel dosimeters using the zero-scan method

In this study x-ray CT has been used to produce a 3D image of an irradiated PAGAT gel sample, with noise-reduction achieved using the ‘zero-scan’ method. The gel was repeatedly CT scanned and a linear fit to the varying Hounsfield unit of each pixel in the 3D volume was evaluated across the repeated scans, allowing a zero-scan extrapolation of the image to be obtained. To minimise heating of the CT scanner’s x-ray tube, this study used a large slice thickness (1 cm), to provide image slices across the irradiated region of the gel, and a relatively small number of CT scans (63), to extrapolate the zero-scan image. The resulting set of transverse images shows reduced noise compared to images from the initial CT scan of the gel, without being degraded by the additional radiation dose delivered to the gel during the repeated scanning. The full, 3D image of the gel has a low spatial resolution in the longitudinal direction, due to the selected scan parameters. Nonetheless, important features of the dose distribution are apparent in the 3D x-ray CT scan of the gel. The results of this study demonstrate that the zero-scan extrapolation method can be applied to the reconstruction of multiple x-ray CT slices, to provide useful 2D and 3D images of irradiated dosimetry gels