2,042 research outputs found

    A deep convolutional neural network for real-time full profile analysis of big powder diffraction data

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    We present Parameter Quantification Network (PQ-Net), a regression deep convolutional neural network providing quantitative analysis of powder X-ray diffraction patterns from multi-phase systems. The network is tested against simulated and experimental datasets of increasing complexity with the last one being an X-ray diffraction computed tomography dataset of a multi-phase Ni-Pd/CeO2-ZrO2/Al2O3 catalytic material system consisting of ca. 20,000 diffraction patterns. It is shown that the network predicts accurate scale factor, lattice parameter and crystallite size maps for all phases, which are comparable to those obtained through full profile analysis using the Rietveld method, also providing a reliable uncertainty measure on the results. The main advantage of PQ-Net is its ability to yield these results orders of magnitude faster showing its potential as a tool for real-time diffraction data analysis during in situ/operando experiments

    Building nonparametric nn-body force fields using Gaussian process regression

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    Constructing a classical potential suited to simulate a given atomic system is a remarkably difficult task. This chapter presents a framework under which this problem can be tackled, based on the Bayesian construction of nonparametric force fields of a given order using Gaussian process (GP) priors. The formalism of GP regression is first reviewed, particularly in relation to its application in learning local atomic energies and forces. For accurate regression it is fundamental to incorporate prior knowledge into the GP kernel function. To this end, this chapter details how properties of smoothness, invariance and interaction order of a force field can be encoded into corresponding kernel properties. A range of kernels is then proposed, possessing all the required properties and an adjustable parameter nn governing the interaction order modelled. The order nn best suited to describe a given system can be found automatically within the Bayesian framework by maximisation of the marginal likelihood. The procedure is first tested on a toy model of known interaction and later applied to two real materials described at the DFT level of accuracy. The models automatically selected for the two materials were found to be in agreement with physical intuition. More in general, it was found that lower order (simpler) models should be chosen when the data are not sufficient to resolve more complex interactions. Low nn GPs can be further sped up by orders of magnitude by constructing the corresponding tabulated force field, here named "MFF".Comment: 31 pages, 11 figures, book chapte

    Modulation of N-methyl-N-nitrosourea induced mammary tumors in Sprague–Dawley rats by combination of lysine, proline, arginine, ascorbic acid and green tea extract

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    INTRODUCTION: The limited ability of current treatments to control metastasis and the proposed antitumor properties of specific nutrients prompted us to examine the effect of a specific formulation (nutrient supplement [NS]) of lysine, proline, arginine, ascorbic acid, and green tea extract in vivo on the development of N-methyl-N-nitrosourea (MNU)-induced mammary tumors in rats. METHODS: A single intraperitoneal dose of MNU was injected into each of 20 female Sprague–Dawley rats (aged 50 days) to induce tumors. Two weeks after MNU treatment, a time by which the animals had recovered from MNU-induced toxicity, the rats were divided into two groups. Rats in group 1 (n = 10) were fed Purina chow diet, whereas those in group 2 (n = 10) were fed the same diet supplemented with 0.5% NS. After a further 24 weeks, the rats were killed and tumors were excised and processed. RESULTS: NS reduced the incidence of MNU-induced mammary tumors and the number of tumors by 68.4%, and the tumor burden by 60.5%. The inhibitory effect of NS was also reflected by decreased tumor weight; the tumor weights per rat and per group were decreased by 41% and 78%, respectively. In addition, 30% of the control rats developed ulcerated tumors, in contrast to 10% in the nutrient supplemented rats. CONCLUSION: These findings suggest that the specific formulation of lysine, proline, arginine, ascorbic acid, and green tea extract tested significantly reduces the incidence and growth of MNU-induced mammary tumors, and therefore has strong potential as a useful therapeutic regimen for inhibiting breast cancer development

    Epidermolysa bullosa in Danish Hereford calves is caused by a deletion in LAMC2 gene

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    BACKGROUND Heritable forms of epidermolysis bullosa (EB) constitute a heterogeneous group of skin disorders of genetic aetiology that are characterised by skin and mucous membrane blistering and ulceration in response to even minor trauma. Here we report the occurrence of EB in three Danish Hereford cattle from one herd. RESULTS Two of the animals were necropsied and showed oral mucosal blistering, skin ulcerations and partly loss of horn on the claws. Lesions were histologically characterized by subepidermal blisters and ulcers. Analysis of the family tree indicated that inbreeding and the transmission of a single recessive mutation from a common ancestor could be causative. We performed whole genome sequencing of one affected calf and searched all coding DNA variants. Thereby, we detected a homozygous 2.4 kb deletion encompassing the first exon of the LAMC2 gene, encoding for laminin gamma 2 protein. This loss of function mutation completely removes the start codon of this gene and is therefore predicted to be completely disruptive. The deletion co-segregates with the EB phenotype in the family and absent in normal cattle of various breeds. Verifying the homozygous private variants present in candidate genes allowed us to quickly identify the causative mutation and contribute to the final diagnosis of junctional EB in Hereford cattle. CONCLUSIONS Our investigation confirms the known role of laminin gamma 2 in EB aetiology and shows the importance of whole genome sequencing in the analysis of rare diseases in livestock

    Machine-learning of atomic-scale properties based on physical principles

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    We briefly summarize the kernel regression approach, as used recently in materials modelling, to fitting functions, particularly potential energy surfaces, and highlight how the linear algebra framework can be used to both predict and train from linear functionals of the potential energy, such as the total energy and atomic forces. We then give a detailed account of the Smooth Overlap of Atomic Positions (SOAP) representation and kernel, showing how it arises from an abstract representation of smooth atomic densities, and how it is related to several popular density-based representations of atomic structure. We also discuss recent generalisations that allow fine control of correlations between different atomic species, prediction and fitting of tensorial properties, and also how to construct structural kernels---applicable to comparing entire molecules or periodic systems---that go beyond an additive combination of local environments

    Hypoglycaemia following upper gastrointestinal surgery: case report and review of the literature

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    <p>Abstract</p> <p>Background</p> <p>Hyperinsulinemic hypoglycemia is relatively recently recognized in persons undergoing bariatric surgery although knowledge and experience with this condition may not be commensurate with the number of such procedures being performed globally. This paper presents a novel case as an example of how such patients may present and how they may be investigated.</p> <p>Case Presentation</p> <p>A 69-year-old man was assessed 3 months post-fundoplication surgery for postprandial hypoglycaemia with neuroglycopenia that became progressively severe. A 72-h fast failed to show hypoglycaemia. During a clinic visit, the patient became confused and had a low plasma glucose, high plasma insulin, and high plasma C-peptide; symptoms were relieved with glucose. No tumours were visualized on CT, MRI, or endoscopic ultrasound. A total body Indium111-octreotide scan was negative. Selective arterial calcium stimulation showed a high insulin gradient in the splenic and superior mesenteric arteries, suggesting diffuse pancreatic beta cell hyperplasia. The patient declined pancreatic resection and recurrent symptomatic hypoglycaemia was successfully prevented with low dose octreotide.</p> <p>Conclusions</p> <p>Although increasingly recognized following bariatric surgery, this is the first reported development of NIPHS (non-insulinoma pancreatogenous hypoglycemia syndrome) following fundoplication surgery, as well as the first documented use of octreotide in post-operative NIPHS. Medical management may be an alternative to surgery for patients with this rare condition.</p

    A rare case of small bowel volvulus after jenjunoileal bariatric bypass requiring emergency surgery: a case report

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    <p>Abstract</p> <p>Introduction</p> <p>Bariatric surgery is on the increase throughout the world. Jejunoileal bypass bariatric procedures have fallen out of favor in western surgical centers due to the high rate of associated complications. They are, however, performed routinely in other centers and as a consequence of health tourism, management of complications related to these procedures may still be encountered.</p> <p>Case presentation</p> <p>We describe a rare case of small bowel obstruction in a 45-year-old British Caucasian woman, secondary to a volvulus of the jejunoileal anastomosis following bariatric bypass surgery. The pre-operative diagnosis was confirmed by radiology. We describe a successful surgical technique for this rare complication.</p> <p>Conclusions</p> <p>Bariatric surgery may be complicated by bowel obstruction. Early imaging is vital for diagnosis and effective management. The use of our surgical technique provides a simple and effective approach for the successful management of this bariatric complication.</p
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