3,947 research outputs found

    (Non-)Decoupled Supersymmetric Field Theories

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    We study some consequences of coupling supersymmetric theories to (super)gravity. To linear order, the couplings are determined by the energy-momentum supermultiplet. At higher orders, the couplings are determined by contact terms in correlation functions of the energy-momentum supermultiplet. We focus on the couplings of one particular field in the supergravity multiplet, the auxiliary field MM. We discuss its linear and quadratic (seagull) couplings in various supersymmetric theories. In analogy to the local renormalization group formalism, we provide a prescription for how to fix the quadratic couplings. They generally arise at two-loops in perturbation theory. We check our prescription by explicitly computing these couplings in several examples such as mass-deformed N{\cal N} = 4 and in the Coulomb phase of some theories. These couplings affect the Lagrangians of rigid supersymmetric theories in curved space. In addition, our analysis leads to a transparent derivation of the phenomenon known as Anomaly Mediation. In contrast to previous approaches, we obtain both the gaugino and scalar masses of Anomaly Mediation by relying just on classical, minimal supergravity and a manifestly local and supersymmetric Wilsonian point of view. Our discussion naturally incorporates the connection between Anomaly Mediation and supersymmetric AdS4AdS_4 Lagrangians. This note can be read without prior familiarity with Anomaly Mediated Supersymmetry Breaking (AMSB).Comment: 35 pages, 3 figure

    Structural analysis and design of floating wind turbine systems

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    Thesis (S.M. in Mechanical Engineering and Naval Architecture and Marine Engineering)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 139-140).As oil supply rates approach potential maximums and the global detrimental effects of carbon emitting energy technology are becoming more comprehensively understood, the world is searching for environmentally benign energy technology which can be reliably and economically harvested. Deep water offshore wind is a vast, reliable and potentially economical energy source which remains globally untapped. In order to harvest this resource, potential floating turbine systems must be analyzed and designed for economic production and deployment, reliable operation, and adequate service life. The Laboratory of Ship and Platform Flow (LSPF) has created trusted hydrodynamic modeling software used to perform a Pareto Optimization which resulted in an optimized Floating Wind Turbine (FWT) design which is a Tension Leg Platform (TLP); hereto called MIT TLP-1. This thesis details the structural design aspects of Floating Wind Turbines (FWT) in a rationally based optimization approach for incorporation into existing LSPF hydrodynamic optimization approaches. A steel structural design is created based on the geometry and loading of the MIT TLP-1 for a 10m significant wave height. The design is based on similar system analysis, classic linear structural theory, American Bureau of Shipping rules and American Petroleum Institute recommended practices. The design is verified using Finite Element Analysis (FEA). The results of this work show that the MIT TLP-1 design is technically feasible from a structural integrity, performance and producibility standpoint.by Joshua Di Pietro.S.M.in Mechanical Engineering and Naval Architecture and Marine Engineerin

    On Over-Squashing in Message Passing Neural Networks: The Impact of Width, Depth, and Topology

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    Message Passing Neural Networks (MPNNs) are instances of Graph Neural Networks that leverage the graph to send messages over the edges. This inductive bias leads to a phenomenon known as over-squashing, where a node feature is insensitive to information contained at distant nodes. Despite recent methods introduced to mitigate this issue, an understanding of the causes for over-squashing and of possible solutions are lacking. In this theoretical work, we prove that: (i) Neural network width can mitigate over-squashing, but at the cost of making the whole network more sensitive; (ii) Conversely, depth cannot help mitigate over-squashing: increasing the number of layers leads to over-squashing being dominated by vanishing gradients; (iii) The graph topology plays the greatest role, since over-squashing occurs between nodes at high commute (access) time. Our analysis provides a unified framework to study different recent methods introduced to cope with over-squashing and serves as a justification for a class of methods that fall under `graph rewiring'.Comment: Accepted to ICML23; 21 page

    The role of the cognitive control system in recovery from bilingual aphasia: a multiple single-case fMRI study

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    Aphasia in bilingual patients is a therapeutic challenge since both languages can be impacted by the same lesion. Language control has been suggested to play an important role in the recovery of first (L1) and second (L2) language in bilingual aphasia following stroke. To test this hypothesis, we collected behavioral measures of language production (general aphasia evaluation and picture naming) in each language and language control (linguistic and nonlinguistic switching tasks), as well as fMRI during a naming task at one and four months following stroke in five bilingual patients suffering from poststroke aphasia. We further applied dynamic causal modelling (DCM) analyses to the connections between language and control brain areas. Three patients showed parallel recovery in language production, one patient improved in L1, and one improved in L2 only. Language-control functions improved in two patients. Consistent with the dynamic view of language recovery, DCM analyses showed a higher connectedness between language and control areas in the language with the better recovery. Moreover, similar degrees of connectedness between language and control areas were found in the patients who recovered in both languages. Our data suggest that engagement of the interconnected language-control network is crucial in the recovery of languages

    anamorphic projection analogical digital algorithms

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    The study presents the first results of a wider research project dealing with the theme of "anamorphosis", a specific technique of geometric projection of a shape on a surface. Here we investigate how new digital techniques make it possible to simplify the anamorphic applications even in cases of projections on complex surfaces. After a short excursus of the most famous historical and contemporary applications, we propose several possible approaches for managing the geometry of anamorphic curves both in the field of descriptive geometry (by using interactive tools such as Cabri and GeoGebra) and during the complex surfaces realization process, from concept design to manufacture, through CNC systems (by adopting generative procedural algorithms elaborated in Grasshopper)

    Serum miR-502: A potential biomarker in the diagnosis of concussion in a pilot study of patients with normal structural brain imaging

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    Establishing a diagnosis of concussion within the context of competitive sport is frequently difficult due to the heterogeneity of presentation. Over the years, many endogenous proteins, including the recent Food and Drug Administration approved for mild-to-moderate traumatic brain injury, glial fibrillary acid protein and ubiquitin carboxy-terminal hydrolase, have been studied as potential biomarkers for the diagnosis of mild traumatic brain injury. Recently, a new class of potential biomarkers, the microRNAs, has shown promise as indicators of traumatic brain injury. In this pilot study, we have analysed the ability of pre-validated serum microRNAs (mi-425-5p and miR-502) to diagnose concussion, in cases without structural pathology. Their performance has been assessed alongside a set of identified protein biomarkers for traumatic brain injury in cohort of 41 concussed athletes. Athletes with a confirmed concussion underwent blood sampling after 48 h from concussion along with magnetic resonance imaging. Serum mi-425-5p and miR-502 were analysed by quantitative reverse transcription polymerase chain reaction, and digital immunoassay was used to determine serum concentrations of ubiquitin carboxy-terminal hydrolase, glial fibrillary acid protein, neurofilament light and Tau. Results were matched with 15 healthy volunteers. No structural/haemorrhagic pathology was identified. Protein biomarkers demonstrated variability among groups reflecting previous performance in the literature. Neurofilament light was the only marker to positively correlate with symptoms reported and SCAT5 scores. Despite the sub optimal timing of sampling beyond the optimal window for many of the protein biomarkers measured, miR-502 was significantly downregulated at all time points within a week form concussion ictus, showing a diagnostic sensitivity in cases beyond 48 h and without structural pathology

    Prevalence of Posterior Shoulder Subluxation in Children With Neonatal Brachial Plexus Palsy After Early Full Passive Range of Motion Exercises

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    BackgroundChildren with neonatal brachial plexus palsy (NBPP) are often prescribed shoulder range of motion (ROM) exercises; however, the extent and timing of exercise implementation remains controversial in the context of shoulder joint integrity. The association of ROM exercises to delayed posterior shoulder subluxation (PSS) is unknown.ObjectiveTo determine prevalence of PSS in children with NBPP who began full passive ROM exercises before 6 months of age, and characteristics associated with development or absence of PSS in children.DesignCrossâ sectional study.SettingTertiary care NBPP referral center.ParticipantsFortyâ six children with NBPP, aged 24â 57 months, who began full ROM exercises before 6 months of age.MethodsOne radiologist conducted bilateral shoulder ultrasound (US) on each child to evaluate for PSS. One occupational therapist evaluated each child clinically for PSS using defined parameters without knowledge of US results.Main Outcome MeasuresBy US, 20% of children had PSS; 46% had PSS by clinical examination. Shoulder active ROM limitations and history of shoulder surgery were associated with presence of PSS. Extent of NBPP was not associated with PSS.ResultsNine of 46 children (20%) met US criteria for PSS; α angle was 58° ± 21° (mean ± standard deviation [SD]). Twentyâ one children (46%) met clinical criteria. Mean age at examination was 35 ± 10 months. Shoulder active ROM (P â ¤ .004) was associated with PSS, whereas passive ROM was not (P â ¥ .08). History of secondary shoulder surgery and primary nerve graft repair were associated with PSS (P = .04). Extent of NBPP by Narakas classification was not associated with PSS (P = .48).ConclusionsEarly use of fullâ arc passive ROM home exercise program is not associated with increased prevalence of PSS in children with NBPP compared to prevalence of PSS in published literature. We suggest careful clinical examination, based on defined criteria, provides a reasonable screening examination for evaluating PSS that can be confirmed by noninvasive US.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147125/1/pmr21235.pd

    Risk factors for chronic postsurgical pain in visceral surgery: a matched case-control analysis.

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    PURPOSE Chronic postsurgical pain (CPSP) after abdominal visceral surgery is an underestimated long-term complication with relevant impact on health-related quality of life and socioeconomic costs. Early identification of affected patients is important. We aim to identify the incidence and risk factors for CPSP in this patient population. METHODS Retrospective case-control matched analysis including all patients diagnosed with CPSP after visceral surgery in our institution between 2016 and 2019. One-to-two case-control matching was based on operation category (HPB, upper-GI, colorectal, transplantation, bariatric, hernia and others) and date of surgery. Potential risk factors for CPSP were identified using conditional multivariate logistic regression. RESULTS Among a cohort of 3730 patients, 176 (4.7%) were diagnosed with CPSP during the study period and matched to a sample of 352 control patients. Independent risk factors for CPSP were age under 55 years (OR 2.64, CI 1.51-4.61), preexisting chronic pain of any origin (OR 3.42, CI 1.75-6.67), previous abdominal surgery (OR 1.99, CI 1.11-3.57), acute postoperative pain (OR 1.29, CI 1.16-1.44), postoperative use of non-steroidal anti-inflammatory drugs (OR 3.73, OR 1.61-8.65), opioid use on discharge (OR 3.78, CI 2.10-6.80) and length of stay over 3 days (OR 2.60, CI 1.22-5.53). Preoperative Pregabalin intake was protective (OR 0.02, CI 0.002-0.21). CONCLUSION The incidence of CPSP is high and associated with specific risk factors, some of them modifiable. Special attention should be given to sufficient treatment of preexisting chronic pain and acute postoperative pain

    Safety and feasibility of outpatient surgery in benign prostatic hyperplasia: a systematic review and meta-analysis

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    Purpose: Most of endourological procedures along the urinary tract have been widely practiced as outpatient operations, including surgery for BPH. This systematic review and meta-analysis was conducted to assess safety and feasibility of outpatient surgery for patients suffering from symptomatic BPH candidate for endoscopic disobstruction. Materials and methods: PubMed, Web of Science, Cochrane, and Embase were searched up until March 30, 2020. MINORS tool was utilized to assess the quality of included studies and a pooled measure of failure or event rate (FR, ER) estimate was calculated. Further sensitivity analysis, subgroup analysis, and meta-regression were conducted to investigate contribution of moderators to heterogeneity. Results: Twenty studies with a total of 1626 patients treated according to outpatient criteria for endoscopic BPH surgery were included. In total, 18 studies reporting data on immediate hospital readmission and/or inability to discharge after endoscopic procedure presented FR estimates ranging from 1.7% to 51.1%. Pooled FR estimate was 7.8% (95% confidence interval [CI]: 5.2%-10.3%); Heterogeneity: Q=76.85; d.f.=17, p<.001; I2= 75.12%. Subgroup analysis according to surgical technique revealed difference among the three approaches with pooled FR of 3% (95%CI: 1%-4.9%), 7.1% (95%CI: 3.9-10.4) and 11.8% (95%CI: 7-16.7%) for TURP, Green-light and HoLEP respectively (p<.001). At meta-regression analysis, none of the retrieved covariates were able to significantly influence the cumulative outcomes reported. ER for postoperative complications and early outpatient visit showed a pooled estimate of 18.6% (95%CI: 13.2%-23.9%) and 7.7% (95%CI: 4.3%-11%) respectively. Conclusions: Our analysis revealed how transurethral procedures for BPH on an outpatient setting are overall reliable and safe. Of note, there were significant outcome differences between groups with regard of type of surgical procedure, perioperative prostate volume and discharge protocol suggesting the need for further prospective analysis to better elucidate the best strategy in such outpatient conduct
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