Zero-point vacancies in quantum solids

A Jastrow wave function (JWF) and a shadow wave function (SWF) describe a quantum solid with Bose--Einstein condensate; i.e. a supersolid. It is known that both JWF and SWF describe a quantum solid with also a finite equilibrium concentration of vacancies x_v. We outline a route for estimating x_v by exploiting the existing formal equivalence between the absolute square of the ground state wave function and the Boltzmann weight of a classical solid. We compute x_v for the quantum solids described by JWF and SWF employing very accurate numerical techniques. For JWF we find a very small value for the zero point vacancy concentration, x_v=(1.4\pm0.1) x 10^-6. For SWF, which presently gives the best variational description of solid 4He, we find the significantly larger value x_v=(1.4\pm0.1) x 10^-3 at a density close to melting. We also study two and three vacancies. We find that there is a strong short range attraction but the vacancies do not form a bound state.Comment: 19 pages, submitted to J. Low Temp. Phy

Effects of 59Fe, 65Zn and of three soil types on dry matter yield, chemical composition and nitrogen fixation in Phaseolus vulgaris L. cv. carioca

The aim of this work was to study in greenhouse conditions the effects of two levels of iron and zinc on yield and chemical composition of common bean (Phaseolus vulgaris L.) and on atmospheric nitrogen fixation, in three soils, classified as Terra Roxa Estruturada (TRE), Latossol Vermelho Escuro (LVE), and Podzolico Vermelho Amarelo (PVA). The coefficient of utilization of these micronutrients by this crop and its distribution in above-ground parts and roots were also assessed. The rates for iron were 1.5 and 3.0 ppm, and for zinc, 2.5 and 5.0 ppm. It was applied 7.5 µCi of 59Fe/kg of soil with the lower rate of the stable iron, and 5.0 and 10.0 µCi of Zn/kg of soil in the pots corresponding to the lower and higher rate of the stable zinc, respectively. The plants were harveste at the age of 60 days and nitrogen, phosphorus, potassium, iron and zinc contents were determined. Immediately after harvest, symbiotic nitrogen fixation was assessed, using the acetylene reduction method. The detection of 59Fe and 65zn radioactivity were carried out on nitric percloric extract, by gamma ray spectrometry. The behavior of common bean presented high variation among the three soils, for all the variables. There was no influence of treatments of iron and zinc on dry matter of above ground part and root and also on the weight and number of nodules. The rate of 3.0 ppm of iron decreased the capacity of nodules to fix atmospheric nitrogen in relation to rate of 1.5 ppm, while the rate of 5.0 ppm of zinc increased this capacity, in relation to the rate of 2.5 ppm. There was significative effect of treatments on nitrogen, potassium and zinc contents in above ground part and on nitrogen and zinc contents in the root. The absorption of zinc from the fertilizer and the percentagem of zinc in the plant derived from fertilizer were diretly influenced by rate of zinc The higher coefficient of utilization of zinc from the fertilizer was 4.0%.No presente trabalho, conduzido em casa de vegetação, procuramos estudar os efeitos dos micronutrientes ferro e zinco na produção de materia seca, composição química do feijoeiro (Phaseolus vulgaris L.) e na fixação do nitrogênio atmosférico, em três solos, classificados como Terra Roxa Estruturada (TRE), Latossol Vermelho Escuro (LVE) e Podzólico Vermelho Amarelo (PVA). Procuramos também determinar os índices de aproveitamento destes micronutrientes pelo feijoeiro e sua distribuição na parte aérea e na raiz. O delineamento experimental foi um fatorial 3x7, sendo três solos e sete tratamentos por solo, com três repetições. Nos tratamentos, foram utilizados duas doses de ferro e duas doses de zinco em separado ou combinando as doses menores e maiores destes micronutrientes (Fe1Zn1, Fe2Zn2). As doses de ferro foram 1,5 e 3,0 ppm e as de zinco foram 2,5 e 5,0 ppm. Foram aplicados 7,5 µCi de 59Fe/kg de solo nos vasos correspondentes à dose menor de ferro e 5,0 e 10,0 µCi de 65Zn/kg de solo nos vasos correspondentes respectivamente à dose menor e maior de zinco. Todos os tratamentos receberam uma adubação básica. O comportamento do feijoeiro apresentou grande variação entre os três tipos de solos, para todas as variáveis. Não houve influência dos tratamentos de ferro e zinco na produção de parte aérea e raiz e nem no peso e numero dos nodulos. A dose de 3,0 ppm de ferro diminuiu a capacidade dos nódulos de fixarem nitrogênio atmosférico em relação à dose de 1,5 ppm enquanto que a dose de 5,0 ppm de zinco aumentou esta capacidade, em relação à dose de 2,5 ppm. Houve um efeito significativo dos tratamentos na concentração de nitrogênio, potássio, ferro e zinco na parte aérea e na concentração de nitrogênio, e zinco na raiz. A absorção de zinco dos fertilizantes e a percentagem do zinco na planta proveniente do adubo foram influenciadas diretamente pelas doses de zinco. O maior coeficiente de aproveitamento do zinco do adubo foi de 4,0%

The Computational Metaphor and Cognitive Psychology

The past three decades have witnessed a remarkable growth of research interest in the mind. This trend has been acclaimed as the ‘cognitive revolution’ in psychology. At the heart of this revolution lies the claim that the mind is a computational system. The purpose of this paper is both to elucidate this claim and to evaluate its implications for cognitive psychology. The nature and scope of cognitive psychology and cognitive science are outlined, the principal assumptions underlying the information processing approach to cognition are summarised and the nature of artificial intelligence and its relationship to cognitive science are explored. The ‘computational metaphor’ of mind is examined and both the theoretical and methodological issues which it raises for cognitive psychology are considered. Finally, the nature and significance of ‘connectionism’— the latest paradigm in cognitive science—are briefly reviewed.17/12/2013. SB

Hydrodynamics of DNA confined in nanoslits and nanochannels

Modeling the dynamics of a confined, semi exible polymer is a challenging problem, owing to the complicated interplay between the configurations of the chain, which are strongly affected by the length scale for the confinement relative to the persistence length of the chain, and the polymer-wall hydrodynamic interactions. At the same time, understanding these dynamics are crucial to the advancement of emerging genomic technologies that use confinement to stretch out DNA and “read” a genomic signature. In this mini-review, we begin by considering what is known experimentally and theoretically about the friction of a wormlike chain such as DNA confined in a slit or a channel. We then discuss how to estimate the friction coefficient of such a chain, either with dynamic simulations or via Monte Carlo sampling and the Kirk-wood pre-averaging approximation. We then review our recent work on computing the diffusivity of DNA in nanoslits and nanochannels, and conclude with some promising avenues for future work and caveats about our approach

Safety and efficacy of non-steroidal anti-inflammatory drugs to reduce ileus after colorectal surgery

Background: Ileus is common after elective colorectal surgery, and is associated with increased adverse events and prolonged hospital stay. The aim was to assess the role of non-steroidal anti-inflammatory drugs (NSAIDs) for reducing ileus after surgery. Methods: A prospective multicentre cohort study was delivered by an international, student- and trainee-led collaborative group. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The primary outcome was time to gastrointestinal recovery, measured using a composite measure of bowel function and tolerance to oral intake. The impact of NSAIDs was explored using Cox regression analyses, including the results of a centre-specific survey of compliance to enhanced recovery principles. Secondary safety outcomes included anastomotic leak rate and acute kidney injury. Results: A total of 4164 patients were included, with a median age of 68 (i.q.r. 57\u201375) years (54\ub79 per cent men). Some 1153 (27\ub77 per cent) received NSAIDs on postoperative days 1\u20133, of whom 1061 (92\ub70 per cent) received non-selective cyclo-oxygenase inhibitors. After adjustment for baseline differences, the mean time to gastrointestinal recovery did not differ significantly between patients who received NSAIDs and those who did not (4\ub76 versus 4\ub78 days; hazard ratio 1\ub704, 95 per cent c.i. 0\ub796 to 1\ub712; P = 0\ub7360). There were no significant differences in anastomotic leak rate (5\ub74 versus 4\ub76 per cent; P = 0\ub7349) or acute kidney injury (14\ub73 versus 13\ub78 per cent; P = 0\ub7666) between the groups. Significantly fewer patients receiving NSAIDs required strong opioid analgesia (35\ub73 versus 56\ub77 per cent; P < 0\ub7001). Conclusion: NSAIDs did not reduce the time for gastrointestinal recovery after colorectal surgery, but they were safe and associated with reduced postoperative opioid requirement

Safety of hospital discharge before return of bowel function after elective colorectal surgery

© 2020 BJS Society Ltd Published by John Wiley & Sons LtdBackground: Ileus is common after colorectal surgery and is associated with an increased risk of postoperative complications. Identifying features of normal bowel recovery and the appropriateness for hospital discharge is challenging. This study explored the safety of hospital discharge before the return of bowel function. Methods: A prospective, multicentre cohort study was undertaken across an international collaborative network. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The main outcome of interest was readmission to hospital within 30 days of surgery. The impact of discharge timing according to the return of bowel function was explored using multivariable regression analysis. Other outcomes were postoperative complications within 30 days of surgery, measured using the Clavien–Dindo classification system. Results: A total of 3288 patients were included in the analysis, of whom 301 (9·2 per cent) were discharged before the return of bowel function. The median duration of hospital stay for patients discharged before and after return of bowel function was 5 (i.q.r. 4–7) and 7 (6–8) days respectively (P < 0·001). There were no significant differences in rates of readmission between these groups (6·6 versus 8·0 per cent; P = 0·499), and this remained the case after multivariable adjustment for baseline differences (odds ratio 0·90, 95 per cent c.i. 0·55 to 1·46; P = 0·659). Rates of postoperative complications were also similar in those discharged before versus after return of bowel function (minor: 34·7 versus 39·5 per cent; major 3·3 versus 3·4 per cent; P = 0·110). Conclusion: Discharge before return of bowel function after elective colorectal surgery appears to be safe in appropriately selected patients

Safety of hospital discharge before return of bowel function after elective colorectal surgery

Background: Ileus is common after colorectal surgery and is associated with an increased risk of postoperative complications. Identifying features of normal bowel recovery and the appropriateness for hospital discharge is challenging. This study explored the safety of hospital discharge before the return of bowel function. Methods: A prospective, multicentre cohort study was undertaken across an international collaborative network. Adult patients undergoing elective colorectal resection between January and April 2018 were included. The main outcome of interest was readmission to hospital within 30 days of surgery. The impact of discharge timing according to the return of bowel function was explored using multivariable regression analysis. Other outcomes were postoperative complications within 30 days of surgery, measured using the Clavien\u2013Dindo classification system. Results: A total of 3288 patients were included in the analysis, of whom 301 (9\ub72 per cent) were discharged before the return of bowel function. The median duration of hospital stay for patients discharged before and after return of bowel function was 5 (i.q.r. 4\u20137) and 7 (6\u20138) days respectively (P &lt; 0\ub7001). There were no significant differences in rates of readmission between these groups (6\ub76 versus 8\ub70 per cent; P = 0\ub7499), and this remained the case after multivariable adjustment for baseline differences (odds ratio 0\ub790, 95 per cent c.i. 0\ub755 to 1\ub746; P = 0\ub7659). Rates of postoperative complications were also similar in those discharged before versus after return of bowel function (minor: 34\ub77 versus 39\ub75 per cent; major 3\ub73 versus 3\ub74 per cent; P = 0\ub7110). Conclusion: Discharge before return of bowel function after elective colorectal surgery appears to be safe in appropriately selected patients