651 research outputs found

    Computing, Symbols and Math

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    Efficient Generic Quotients Using Exact Arithmetic

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    The usual formulation of efficient division uses Newton iteration to compute an inverse in a related domain where multiplicative inverses exist. On one hand, Newton iteration allows quotients to be calculated using an efficient multiplication method. On the other hand, working in another domain is not always desirable and can lead to a library structure where arithmetic domains are interdependent. This paper uses the concept of a whole shifted inverse and modified Newton iteration to compute quotients efficiently without leaving the original domain. The iteration is generic to domains having a suitable shift operation, such as integers or polynomials with coefficients that do not necessarily commute

    Efficient Quotients of Non-Commutative Polynomials

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    It is shown how to compute quotients efficiently in non-commutative univariate polynomial rings. This expands on earlier work where generic efficient quotients were introduced with a primary focus on commutative domains. Asymptotically fast algorithms are given for left and right quotients when the polynomial variable commutes with coefficients. These algorithms are based on the concept of the ``whole shifted inverse'', which is a specialized quotient where the dividend is a power of the polynomial variable. When the variable does not commute with coefficients, that is for skew polynomials, left and right whole shifted inverses are defined and the left whole shifted inverse may be used to compute the right quotient, although not with asymptotically fast complexity. Examples are shown of polynomials with matrix coefficients and differential operators and a proof-of-concept Maple implementation is given

    Enhanced recovery after surgery

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    Enhanced Recovery or Fast Track Recovery after Surgery protocols (ERAS) have significantly changed perioperative care following colorectal surgery and are promoted as reducing the stress response to surgery. The present systematic review aimed to examine the impact on the magnitude of the systemic inflammatory response (SIR) for each ERAS component following colorectal surgery using objective markers such as C-reactive protein (CRP) and interleukin-6 (IL-6). A literature search was performed of the US National Library of Medicine (MEDLINE), EMBASE, PubMed, and the Cochrane Database of Systematic Reviews using appropriate keywords and subject headings to February 2015. Included studies had to assess the impact of the selected ERAS component on the SIR using either CRP or IL-6. Nineteen studies, including 1898 patients, were included. Fourteen studies (1246 patients) examined the impact of laparoscopic surgery on the postoperative markers of SIR. Ten of these studies (1040 patients) reported that laparoscopic surgery reduced postoperative CRP. One study (53 patients) reported reduced postoperative CRP using opioid-minimising analgesia. One study (142 patients) reported no change in postoperative CRP following preoperative carbohydrate loading. Two studies (108 patients) reported conflicting results with respect to the impact of goal-directed fluid therapy on postoperative IL-6. No studies examined the effect of other ERAS components, including mechanical bowel preparation, antibiotic prophylaxis, thromboprophylaxis, and avoidance of nasogastric tubes and peritoneal drains on markers of the postoperative SIR following colorectal surgery. The present systematic review shows that, with the exception of laparoscopic surgery, objective evidence of the effect of individual components of ERAS protocols in reducing the stress response following colorectal surgery is limited

    Correcting for Beam Aberrations in a Beam-Waveguide Antenna

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    A method for correcting the aim of a beam-waveguide microwave antenna compensates for the beam aberration that occurs during radio tracking of a target that has a component of velocity transverse to the line of sight from the tracking station. The method was devised primarily for use in tracking of distant target spacecraft by large terrestrial beam-waveguide antennas of NASA's Deep Space Network (DSN). The method should also be adaptable to tracking, by other beam-waveguide antennas, of targets that move with large transverse velocities at large distances from the antennas

    Clinicopathological determinants of an elevated systemic inflammatory response following elective potentially curative resection for colorectal cancer

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    Introduction: The postoperative systemic inflammatory response (SIR) is related to both long- and short-term outcomes following surgery for colorectal cancer. However, it is not clear which clinicopathological factors are associated with the magnitude of the postoperative SIR. The present study was designed to determine the clinicopathological determinants of the postoperative systemic inflammatory response following colorectal cancer resection. Methods: Patients with a histologically proven diagnosis of colorectal cancer who underwent elective, potentially curative resection during a period from 1999 to 2013 were included in the study (n = 752). Clinicopathological data and the postoperative SIR, as evidenced by postoperative Glasgow Prognostic Score (poGPS), were recorded in a prospectively maintained database. Results: The majority of patients were aged 65 years or older, male, were overweight or obese, and had an open resection. After adjustment for year of operation, a high day 3 poGPS was independently associated with American Society of Anesthesiologists (ASA) grade (hazard ratio [HR] 1.96; confidence interval [CI] 1.25–3.09; p = 0.003), body mass index (BMI) (HR 1.60; CI 1.07–2.38; p = 0.001), mGPS (HR 2.03; CI 1.35–3.03; p = 0.001), and tumour site (HR 2.99; CI 1.56–5.71; p < 0.001). After adjustment for year of operation, a high day 4 poGPS was independently associated with ASA grade (HR 1.65; CI 1.06–2.57; p = 0.028), mGPS (HR 1.81; CI 1.22–2.68; p = 0.003), NLR (HR 0.50; CI 0.26–0.95; p = 0.034), and tumour site (HR 2.90; CI 1.49–5.65; p = 0.002). Conclusions: ASA grade, BMI, mGPS, and tumour site were consistently associated with the magnitude of the postoperative systemic inflammatory response, evidenced by a high poGPS on days 3 and 4, in patients undergoing elective potentially curative resection for colorectal cancer

    Violence risk identification, assessment, and management practices in inpatient psychiatry

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    Serious mental illness is a major risk factor for violence. Research suggests that many committed psychiatric inpatients have perpetrated violence before, during, and after hospitalization. Despite the prevalence and implications of violence among committed psychiatric patients, the responsibility of health care professionals to identify, assess and manage violence risk, and the development of identification and assessment tools to assist health care professionals in discharging their responsibility, little is actually known about what practices are being used to identify, assess, and manage violence in inpatient psychiatry units. The purpose of this study is to obtain a better understanding of violence risk identification, assessment, and management practices used by inpatient psychiatric units. Specifically, this study involved semistructured interviews with key informants from 13 inpatient psychiatry units in the largest health region in Western Canada. Every inpatient psychiatry unit that was invited to take part in this study agreed to participate. Data were analyzed using frequency and content analysis. The analysis revealed limited use of formal identification and assessment instruments for violence and diversity with respect to strategies used to manage violence. These findings have implications for highlighting promising practices that are currently being used, and identifying potential areas for future improvement

    Development of the mammalian liver and ventral pancreas is dependent on GATA4

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    <p>Abstract</p> <p>Background</p> <p>In the mouse, the parenchyma of both the liver and ventral pancreas is specified from adjacent domains of the ventral foregut endoderm. GATA4, a zinc finger transcription factor, is strongly expressed in these endodermal domains and molecular analyses have implicated GATA4 in potentiating liver gene expression during the onset of hepatogenesis. We therefore hypothesized that GATA4 has an integral role in controlling the early stages of pancreatic and liver development.</p> <p>Results</p> <p>To determine whether GATA4 contributes to development of either the pancreas or liver we characterized the formation of pancreatic and hepatic tissues in embryos derived from <it>Gata4</it><sup>-/- </sup>ES cells by tetraploid embryo complementation. In the absence of GATA4, development of the liver and ventral pancreas was disrupted. At embryonic day (E) 9.5, the liver bud failed to expand although, contrary to expectations, the hepatic endoderm was able to form a pseudo-stratified epithelial liver bud that expressed hepatic genes. Moreover, as we had shown previously, the embryos lacked septum transversum mesenchyme suggesting that liver defects may be cell non-autonomous. Analyses of pancreatic development revealed a complete absence of the ventral but not the dorsal pancreas in <it>Gata4</it><sup>-/- </sup>embryos. Moreover, <it>Gata6</it><sup>-/- </sup>embryos displayed a similar, although less dramatic phenotype, suggesting a critical role for multiple GATA factors at the earliest stages of ventral pancreas development.</p> <p>Conclusion</p> <p>This study defines integral roles for GATA factors in controlling early development of the mammalian liver and pancreas.</p
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