1,161 research outputs found

    Прогнозирование прочности стальных труб, поврежденных водной коррозией

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    Показана возможность прогноза долговечности поврежденных стальных труб. Вследствие электрохимического взаимодействия металла и воды образуются щелеобразные коррозионные дефекты, которые являются концентраторами напряжений и приводят к локальному перенапряжению материала и разрушению труб. Долговечность труб рассчитывается по скорости роста коррозионных дефектов и степени концентрации напряжений. С повышением температуры скорость электрохимической коррозии увеличивается, что приводит к снижению долговечности труб.Показана можливість прогнозування довговічності пошкоджених сталевих водопровідних труб. Внаслідок електрохімічної взаємодії металу і води виникають щілиноподібні корозійні дефекти, що є концентраторами напружень і зумовлюють локальну перенапругу матеріалу та руйнування труб. Довговічність труб розраховується по швидкості росту корозійних дефектів і ефективності концентрації напружень. Із підвищенням температури швидкість електрохімічної корозії збільшується, що призводить до зниження довговічності труб.We have demonstrated a possibility of predicting service life of damaged steel pipes. The electrochemical interaction of the metal and water causes initiation of crack-like corrosive defects, which, being stress concentrators, induce local overstressing of the material and destruction of pipes. One can calculate the durability of a pipe from the corrosion crack-growth rate and the degree of the stress concentration. An increase in temperature accelerates electrochemical corrosion, which results in the reduction of life of water pipes

    Phase variation controls expression of Salmonella lipopolysaccharide modification genes by a DNA methylation-dependent mechanism

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    The O-antigen of Salmonella lipopolysaccharide is a major antigenic determinant and its chemical composition forms the basis for Salmonella serotyping. Modifications of the O-antigen that can affect the serotype include those carried out by the products of glycosyltransferase operons (gtr), which are present on specific Salmonella and phage genomes. Here we show that expression of the gtr genes encoded by phage P22 that confers the O1 serotype is under the control of phase variation. This phase variation occurs by a novel epigenetic mechanism requiring OxyR in conjunction with the DNA methyltransferase Dam. OxyR is an activator or a repressor of the system depending on which of its two binding sites in the gtr regulatory region is occupied. Binding is decreased by methylation at Dam target sequences in either site, and this confers heritability of the expression state to the system. Most Salmonella gtr operons share the key regulatory elements that are identified here as essential for this epigenetic phase variation

    Protective effect of budesonide/formoterol compared with formoterol, salbutamol and placebo on repeated provocations with inhaled AMP in patients with asthma: a randomised, double-blind, cross-over study

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    <p>Abstract</p> <p>Background</p> <p>The budesonide/formoterol combination is successfully used for fast relief of asthma symptoms in addition to its use as maintenance therapy. The temporarily increased corticosteroid dose during increasing inhaler use for symptom relief is likely to suppress any temporary increase in airway inflammation and may mitigate or prevent asthma exacerbations. The relative contribution of the budesonide and formoterol components to the improved asthma control is unclear.</p> <p>Methods</p> <p>The acute protective effect of inhaled budesonide was tested in a model of temporarily increased airway inflammation with repeated indirect airway challenges, mimicking an acute asthma exacerbation. A randomised, double-blind, cross-over study design was used. Asthmatic patients (n = 17, mean FEV<sub>1 </sub>95% of predicted) who previously demonstrated a ≥30% fall in forced expiratory volume in 1 second (FEV<sub>1</sub>) after inhaling adenosine 5'-monophosphate (AMP), were challenged on four consecutive test days, with the same dose of AMP (at 09:00, 12:00 and 16:00 hours). Within 1 minute of the maximal AMP-induced bronchoconstriction at 09:00 hours, the patients inhaled one dose of either budesonide/formoterol (160/4.5 μg), formoterol (4.5 μg), salbutamol (2 × 100 μg) or placebo. The protective effects of the randomised treatments were assessed by serial lung function measurements over the test day.</p> <p>Results</p> <p>In the AMP provocations at 3 and 7 hours after inhalation, the budesonide/formoterol combination provided a greater protective effect against AMP-induced bronchoconstriction compared with formoterol alone, salbutamol and placebo. In addition all three active treatments significantly increased FEV<sub>1 </sub>within 3 minutes of administration, at a time when inhaled AMP had induced the 30% fall in FEV<sub>1</sub>.</p> <p>Conclusions</p> <p>A single dose of budesonide/formoterol provided a greater protective effect against inhaled AMP-induced bronchoconstriction than formoterol alone, both at 3 and at 7 hours after inhalation. The acute protection against subsequent bronchoconstrictor stimuli such as inhaled AMP and the rapid reversal of airway obstruction supports the use of budesonide/formoterol for both relief and prevention in the treatment of asthma.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov number NCT00272753</p

    The effects of upper body exercise on the physical capacity of people with a spinal cord injury: a systematic review

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    OBJECTIVE: To describe the effects of upper body training on the physical capacity of people with a spinal cord injury. DATA SOURCES: The databases of PubMed, CINAHL, Sport Discus and Cochrane were searched from 1970 to May 2006. REVIEW METHODS: The keywords 'spinal cord injury', 'paraplegia', 'tetraplegia' and 'quadriplegia' were used in combination with 'training'. The methodological quality of the included articles (both randomized controlled trials and controlled clinical trials) was assessed with the modified 'van Tulder et al.' checklist. Studies were described with respect to population, test design, training protocol and mode of training. The training effects on physical capacity, reflected by peak power output (PO(peak)) and oxygen uptake (VO(2peak)), were summarized. RESULTS: Twenty-five studies were included with a mean score of 8.8 out of 17 items on the quality checklist. The methodological quality was quite low, mostly because of the absence of randomized controlled trials. Therefore no meta-analysis was possible. In the 14 articles of acceptable quality the mean (SD) increase in VO( 2peak) and PO(peak,) following a period of training, was 17.6 (11.2)% and 26.1 (15.6)%, respectively. CONCLUSIONS: Due to the overall low quality of studies it is not possible to draw definitive conclusions on training effects for different lesion groups or training modes. The results of the relatively few studies with an acceptable quality seem to support the view that upper body exercise may increase the physical capacity of people with spinal cord injury. The magnitude of improvement in PO( peak) and VO(2peak), however, varies considerably among studie

    The Parallel Persistent Memory Model

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    We consider a parallel computational model that consists of PP processors, each with a fast local ephemeral memory of limited size, and sharing a large persistent memory. The model allows for each processor to fault with bounded probability, and possibly restart. On faulting all processor state and local ephemeral memory are lost, but the persistent memory remains. This model is motivated by upcoming non-volatile memories that are as fast as existing random access memory, are accessible at the granularity of cache lines, and have the capability of surviving power outages. It is further motivated by the observation that in large parallel systems, failure of processors and their caches is not unusual. Within the model we develop a framework for developing locality efficient parallel algorithms that are resilient to failures. There are several challenges, including the need to recover from failures, the desire to do this in an asynchronous setting (i.e., not blocking other processors when one fails), and the need for synchronization primitives that are robust to failures. We describe approaches to solve these challenges based on breaking computations into what we call capsules, which have certain properties, and developing a work-stealing scheduler that functions properly within the context of failures. The scheduler guarantees a time bound of O(W/PA+D(P/PA)log1/fW)O(W/P_A + D(P/P_A) \lceil\log_{1/f} W\rceil) in expectation, where WW and DD are the work and depth of the computation (in the absence of failures), PAP_A is the average number of processors available during the computation, and f1/2f \le 1/2 is the probability that a capsule fails. Within the model and using the proposed methods, we develop efficient algorithms for parallel sorting and other primitives.Comment: This paper is the full version of a paper at SPAA 2018 with the same nam

    Barriers and facilitators perceived by healthcare professionals for implementing lifestyle interventions in patients with osteoarthritis:a scoping review

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    OBJECTIVE: To provide an overview of barriers and facilitators that healthcare professionals (HCPs) perceive regarding the implementation of lifestyle interventions (LIs) in patients with hip and/or knee osteoarthritis (OA). DESIGN: Scoping review. DATA SOURCES: The databases PubMed, Embase, CINAHL, PsycINFO and the Cochrane Library were searched from inception up to January 2021. ELIGIBILITY CRITERIA: Primary research articles with a quantitative, qualitative or mixed-methods design were eligible for inclusion if they reported: (1) perceptions of primary and/or secondary HCPs (population); (2) on implementing LIs with physical activity and/or weight management as key components (concept) and (3) on conservative management of hip and/or knee OA (context). Articles not published in English, German or Dutch were excluded. DATA EXTRACTION AND SYNTHESIS: Barriers and facilitators were extracted by two researchers independently. Subsequently, the extracted factors were linked to a framework based on the Tailored Implementation for Chronic Diseases checklist. RESULTS: Thirty-six articles were included. In total, 809 factors were extracted and subdivided into nine domains. The extracted barriers were mostly related to non-optimal interdisciplinary collaboration, patients’ negative attitude towards LIs, patients’ low health literacy and HCPs’ lack of knowledge and skills around LIs or promoting behavioural change. The extracted facilitators were mostly related to good interdisciplinary collaboration, a positive perception of HCPs’ own role in implementing LIs, the content or structure of LIs and HCPs’ positive attitude towards LIs. CONCLUSIONS: Multiple individual and environmental factors influence the implementation of LIs by HCPs in patients with hip and/or knee OA. The resulting overview of barriers and facilitators can guide future research on the implementation of LIs within OA care. To investigate whether factor frequency is related to the relevance of each domain, further research should assess the relative importance of the identified factors involving all relevant disciplines of primary and secondary HCPs. PROSPERO REGISTRATION NUMBER: CRD42019129348

    Shoulder load during synchronous handcycling and handrim wheelchair propulsion in persons with paraplegia

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    Objective: To compare the shoulder load during handcycling and wheelchair propulsion under similar conditions of external power in persons with spinal cord injury. Design: Cross-sectional. Subjects: Eight men with spinal cord injury. Methods: Kinetics and kinematics were measured during handbike and wheelchair propulsion at 25, 35, 45 and 55 W on a treadmill. Shoulder load (glenohumeral contact forces, relative muscle forces) was calculated with the Delft Shoulder and Elbow Model. Results: At all power output levels, glenohumeral contact forces were significantly lower during handcycling compared with wheelchair propulsion (p < 0.001). At 55 W, the mean glenohumeral contact force was 345 N for handcycling, whereas it was 585 N for wheelchair propulsion. Also, relative muscle forces were lower during handcycling. The largest differences between handbike and wheelchair propulsion were found in the supraspinatus (4.5% vs. 20.7%), infraspinatus (3.7% vs. 16.5%) and biceps (5.0% vs. 17.7%). Conclusion: Due to continuous force application in handcycling, shoulder load was lower compared with wheelchair propulsion. Furthermore, muscles that are prone to overuse injuries were less stressed during handcycling. Therefore, handcycling may be a good alternative for outdoor mobility and may help prevent overuse injuries of the shoulder complex. © 2012 The Authors
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