5,183 research outputs found
The Lesser Role of Shear in Star Formation: Insight from the Galactic Ring Survey
We analyse the role played by shear in regulating star formation in the
Galaxy on the scale of individual molecular clouds. The clouds are selected
from the 13^CO J=1-0 line of the Galactic Ring Survey. For each cloud, we
estimate the shear parameter which describes the ability of density
perturbations to grow within the cloud. We find that for almost all molecular
clouds considered, there is no evidence that shear is playing a significant
role in opposing the effects of self-gravity. We also find that the shear
parameter of the clouds does not depend on their position in the Galaxy.
Furthermore, we find no correlations between the shear parameter of the clouds
with several indicators of their star formation activity. No significant
correlation is found between the shear parameter and the star formation
efficiency of the clouds which is measured using the ratio of the massive young
stellar objects luminosities, measured in the Red MSX survey, to the cloud
mass. There are also no significant correlations between the shear parameter
and the fraction of their mass that is found in denser clumps which is a proxy
for their clump formation efficiency, nor with their level of fragmentation
expressed in the number of clumps per unit mass. Our results strongly suggest
that shear is playing only a minor role in affecting the rates and efficiencies
at which molecular clouds convert their gas into dense cores and thereafter
into stars.Comment: Accepted to ApJ. 30 pages, 11 figures. Content substantially enlarged
and includes quantitative correlations between the SFE of molecular clouds
and their shear parameters. Some references correcte
Electric vehicle battery performance investigation based on real world current harmonics
Electric vehicle (EV) powertrains consist of power electronic components as well as electric machines to manage the energy flow between different powertrain subsystems and to deliver the necessary torque and power requirements at the wheels. These power subsystems can generate undesired electrical harmonics on the direct current (DC) bus of the powertrain. This may lead to the on-board battery being subjected to DC current superposed with undesirable high- and low- frequency current oscillations, known as ripples. From real-world measurements, significant current harmonics perturbations within the range of 50 Hz to 4 kHz have been observed on the high voltage DC bus of the EV. In the limited literature, investigations into the impact of these harmonics on the degradation of battery systems have been conducted. In these studies, the battery systems were supplied by superposed current signals i.e., DC superposed by a single frequency alternating current (AC). None of these studies considered applying the entire spectrum of the ripple current measured in the real-world scenario, which is focused on in this research. The preliminary results indicate that there is no difference concerning capacity fade or impedance rise between the cells subjected to just DC current and those subjected additionally to a superposed AC ripple current
A framework of indicators to measure project circularity in construction circular economy.
The construction circular economy (CE) literature lacks a holistic framework for systematic assessment of project 'circularity', thereby impeding industry restructuring and full transition to CE. The proposed 'project life-cycle assessment circularity indicators and themes' (PLACIT) framework supports thematic circularity ratings in construction projects using 12 circularity indicators (CIs), representing high-level requirements of CE, grouped into five themes relevant to project life-cycle stages. This helps identify areas of good practice and those requiring circularity improvements. A systematic literature review, structured in line with PLACIT, revealed an increasing association between CE and 'constructability' but varying engagement with CIs. The predominant engagement with indicators within the industry's comfort zone indicates supply-push practices focusing on aspirational CE design solutions and CE management, missing opportunities from engaging with more demand-pull indicators – for example, reduced material inputs – and embedding circular materials in design practices. Full transition to CE will require engaging with a wide range of indicators throughout the whole project life cycle in a more complex network. Moreover, PLACIT has potentials to set clear boundaries between 'sustainability' and CE concepts, currently ill defined in the literature. Future research (Association for Project Management supported) will seek to validate PLACIT using expert feedback and use circularity ratings to support decision making in construction
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Internal Consistency and Convergent Validity of the Inventory of Hyperacusis Symptoms.
OBJECTIVES: The aim was to assess the internal consistency and convergent and discriminant validity of a new questionnaire for hyperacusis, the Inventory of Hyperacusis Symptoms (IHS; Greenberg & Carlos 2018), using a clinical population. DESIGN: This was a retrospective study. Data were gathered from the records of 100 consecutive patients who sought help for tinnitus and/or hyperacusis from an audiology clinic in the United Kingdom. The average age of the patients was 55 years (SD = 13 years). Audiological measures were the pure-tone average threshold (PTA) and uncomfortable loudness levels (ULL). Questionnaires administered were: IHS, Tinnitus Handicap Inventory (THI), Hyperacusis Questionnaire (HQ), Insomnia Severity Index, Generalized Anxiety Disorder, and Patient Health Questionnaire-9. RESULTS: Cronbach's alpha for the 25-item IHS questionnaire was 0.96. Neither the total IHS score nor scores for any of its five subscales were correlated with the PTA of the better or worse ear. This supports the discriminant validity of the IHS, as hyperacusis is thought to be independent of the PTA. There were moderately strong correlations between IHS total scores and scores for the HQ, Tinnitus Handicap Inventory, Generalized Anxiety Disorder, and Patient Health Questionnaire-9, with r = 0.58, 0.58, 0.61, 0.54, respectively. Thus, although IHS scores may reflect hyperacusis itself, they may also reflect the coexistence of tinnitus, anxiety, and depression. The total score on the IHS was significantly different between patients with and without hyperacusis (as diagnosed based on ULLs or HQ scores). Using the HQ score as a reference, the area under the receiver operating characteristic for the IHS was 0.80 (95% confidence interval = 0.71 to 0.89) and the cutoff point of the IHS with highest overall accuracy was 56/100. The corresponding sensitivity and specificity were 74% and 82%. CONCLUSIONS: The IHS has good internal consistency and reasonably high convergent validity, as indicated by the relationship of IHS scores to HQ scores and ULLs, but IHS scores may also partly reflect the co-occurrence of tinnitus, anxiety, and depression. We propose an IHS cutoff score of 56 instead of 69 for diagnosing hyperacusis
Quantitative Methods for Optimizing Patient Outcomes in Liver Transplantation
Liver transplantation continues to be the gold standard for treating patients
with end-stage liver diseases. However, despite the huge success of liver
transplantation in improving patient outcomes, long term graft survival
continues to be a major problem. The current clinical practice in the
management of liver transplant patients is centered around immunosuppressive
multidrug regimens. Current research has been focusing on phenotypic
personalized medicine as a novel approach in the optimization of
immunosuppression, a regressional math modeling focusing on individual patient
dose and response using specific markers like transaminases. A prospective area
of study includes the development of a mechanistic computational math modeling
for optimizing immunosuppression to improve patient outcomes and increase
long-term graft survival by exploring the intricate immune/drug interactions to
help us further our understanding and management of medical problems like
transplants, autoimmunity, and cancer therapy. Thus, by increasing long-term
graft survival, the need for redo transplants will decrease, which will free up
organs and potentially help with the organ shortage problem promoting equity
and equal opportunity for transplants, as well as decreasing the medical costs
associated with additional testing and hospital admissions. Although long-term
graft survival remains challenging, computational and quantitative methods have
led to significant improvements. In this article, we review recent advances and
remaining opportunities. We focus on the following topics: donor organ
availability and allocation with a focus on equity, monitoring of patient and
graft health, and optimization of immunosuppression dosing.Comment: 2 figures, including a graphical abstrac
Transcutaneous auricular vagus nerve stimulation with concurrent upper limb repetitive task practice for poststroke motor recovery: A pilot study.
Invasive vagus nerve stimulation (VNS) has the potential to enhance the effects of physiotherapy for upper limb motor recovery after stroke. Noninvasive, transcutaneous auricular branch VNS (taVNS) may have similar benefits, but this has not been evaluated in stroke recovery. We sought to determine the feasibility of taVNS delivered alongside upper limb repetitive task-specific practice after stroke and its effects on a range of outcome measures evaluating limb function. Thirteen participants at more than 3 months postischemic stroke with residual upper limb dysfunction were recruited from the community of Sheffield, United Kingdom (October-December 2016). Participants underwent 18 × 1-hour sessions over 6 weeks in which they made 30-50 repetitions of 8-10 arm movements concurrently with taVNS (NEMOS; Cerbomed, Erlangen, Germany, 25 Hz, .1-millisecond pulse width) at maximum tolerated intensity (mA). An electrocardiogram and rehabilitation outcome scores were obtained at each visit. Qualitative interviews determined the acceptability of taVNS to participants. Median time after stroke was 1.16 years, and baseline median/interquartile range upper limb Fugl-Meyer (UFM) score was 63 (54.5-99.5). Participants attended 92% of the planned treatment sessions. Three participants reported side effects, mainly fatigue, but all performed mean of more than 300 arm repetitions per session with no serious adverse events. There was a significant change in the UFM score with a mean increase per participant of 17.1 points (standard deviation 7.8). taVNS is feasible and well-tolerated alongside upper limb repetitive movements in poststroke rehabilitation. The motor improvements observed justify a phase 2 trial in patients with residual arm weakness. [Abstract copyright: Copyright © 2018 National Stroke Association. Published by Elsevier Inc. All rights reserved.
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