12 research outputs found
Learning structure in nested logit models
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 67-68).This work is about developing an estimation procedure for nested logit models that optimizes over the nesting structure in addition to the model parameters. Current estimation practices require an a priori specification of a nesting structure. We formulate the problem of learning an optimal nesting structure as a mixed integer nonlinear programming (MINLP) optimization problem and solve it using a variant of the linear outer approximation algorithm. We demonstrate that it is indeed possible to recover the nesting structure directly from the data by applying our method to synthetic and real datasets.by Youssef Medhat Aboutaleb.S.M. in TransportationS.M.S.M.inTransportation Massachusetts Institute of Technology, Department of Civil and Environmental EngineeringS.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc
Solar Water Heaters and its Applications; a Narrative Review
No full text
This article was published at the 2nd International Conference on the Application of Materials and Advanced Manufacturing in Industries and only its abstract is available for pulic access.
The full paper can be requested by contacting the author at ([email protected]) .
Abstract
With increasing environmental problems, depletion of fossil fuel resources, increasing world population and concomitant increase in demand for renewable energy, much attention has been given to solar energy, which has the greatest potential among renewable energies. The use of solar energy to heat water consumption in buildings is an old technology, but optimized and promising. This article will describe solar thermal systems in detail. Next, the components used to manufacture a solar water heater were reviewed. Furthermore, the solar collectors, which are the heart of these systems, were specially studied and their types were classified. Finally, a number of practical methods and ideas for increasing the performance of solar water heaters that have been studied in recent years were reviewed.</p
Berberine confers neuroprotection in coping with focal cerebral ischemia by targeting inflammatory cytokines
No full textScope: Existing research indicates that anti-inflammatory and antioxidant properties of berberine play major roles in coping with oxidative stress in neurodegenerative diseases, but it is not known if this isoquinoline alkaloid affects inflammatory cytokines such as interleukin 10 in focal cerebral ischemia. Methods and results: Male Wistar rats (10 weeks old) were treated with 40 mg/kg concentration of berberine 1 h after focal cerebral ischemia and the anti-inflammatory properties of berberine were evaluated by immunohistochemical analysis, water content measure and behavioral tests. Evaluation of infarct volume was performed by TTC staining. Immunohistochemistry and behavioral assessment indicated recovery in treatment group compared to only ischemia group. The infarct volume decreased in treatment group compared to ischemia group. Berberine administration significantly decreased brain edema and contributed to the restoration of motor function. Moreover, berberine potently contributed to neuroprotection in motor area through downregulation of pro-inflammatory cytokines and upregulation of anti-inflammatory cytokines. Conclusions: These findings confirm the validity of berberine as a potent anti-inflammatory agent in treatment of ischemic stroke. © 2017 The Author
Comparison of two specimen retrieval techniques in laparoscopic sleeve gastrectomy: what is the role of endobag?
No full textModulation of autophagy as the target of mesenchymal stem cells-derived conditioned medium in rat model of myocardial ischemia/reperfusion injury
No full textHuman amniotic membrane mesenchymal stem cells-derived conditioned medium (hAM-MSCs-CM) has positive effects against myocardial ischemia/reperfusion (MI/R) injury. However, it needs further investigations how hAM-MSCs-CM leads to the cell survival under MI/R via modulation of autophagy. The purpose of this study is investigating the effects of hAM-MSCs-CM in a rat model of MI/R injury by focusing on the role of autophagy as one of its possible mechanisms. Male Wistar rats (44 rats, 175�200 g) were randomly divided into four groups: Sham, MI/R, culture media-receiving and conditioned medium-receiving. MI/R was induced by 30 min of left anterior descending coronary artery ligation. After 15 min reperfusion, culture media or hAM-MSCs-CM (150 μl) were injected intramyocardially. At the end of the experiment, CK-MB, autophagy markers, phosphorylated and total forms of mTOR and ULK1, cardiac function and fibrosis were measured. hAM-MSCs-CM significantly decreased CK-MB levels (P < 0.0001), and also the mRNA levels of Beclin1 (P < 0.0001), LC3 (P = 0.012) and p62 (P = 0.003). In addition, hAM-MSCs-CM significantly reduced Beclin1, LC3II/LC3I and p62 protein levels (P < 0.0001), and increased p-mTOR/mTOR (P = 0.022) and p-ULK1/ULK1 (P < 0.0001) expressions. Moreover, hAM-MSCs-CM improved cardiac function and decreased fibrosis (P < 0.0001). This study showed cardioprotective effects of hAM-MSCs-CM against MI/R injury through modulation of autophagy via mTOR/ULK1 pathway. Based on these findings, it can be concluded that hAM-MSCs-CM can be offered as an attractive candidate for attenuation of MI/R injury in future, but needs further investigations. © 2021, The Author(s), under exclusive licence to Springer Nature B.V
Preconditioning With Morphine Protects Hippocampal CA1 Neurons Against Ischemia/Reperfusion Injury via the Activation of the mTOR Pathway
No full textIn the present study, we examined the role of mammalian target of rapamycin (mTOR) to reveal the neuroprotective effects of chronic morphine preconditioning on the hippocampus following ischemia/reperfusion (I/R) injury. Morphine was administrated for 5 days twice a day before I/R injury induction. The role of mTOR was evaluated by the injection of rapamycin (5 mg/kg, ip) before I/R injury. The passive avoidance test was used to evaluate memory. Neuronal density and apoptosis were measured in the CA1 region, 72 hours after the induction of I/R injury. The expressions of mTOR and phosphorylated mTOR (p-mTOR) and superoxide dismutase (SOD) activity were determined 24 hours after I/R injury induction. Chronic morphine treatment attenuated the apoptosis and neuronal loss in the hippocampus, which led to improvement in memory (PThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
First measurements of energetic protons in Mega Amp Spherical Tokamak Upgrade (MAST-U).
No full textFirst proton production rates from the d(d,p)t reaction in the Mega Amp Spherical Tokamak Upgrade (MAST-U) are measured. The data were taken during the MAST-U experimental campaign with an upgraded version of the proton detector (PD) previously used in MAST. The new detector array consists of three collimated silicon surface barrier detectors with a depletion depth of 300 μm and a collimated 120 μm thick diamond detector, mounted on the MAST-U reciprocating probe arm. This array measures the energies of unconfined energetic 3 MeV protons and 1 MeV tritons mainly produced by beam-thermal DD reactions during neutral beam injection heating. Diamond detectors have the potential to be uniquely suited to detect charged fusion products as they promise to be much more radiation resistant and much less sensitive to temperature variations compared to silicon-based detectors. Using silicon and diamond-based detectors simultaneously allowed us to directly compare the performance of these two detector types. PD particle rates measured during different plasma scenarios are presented and compared to neutron rates measured using the neutron camera upgrade and TRANSP predictions. [Abstract copyright: © 2024 Author(s). Published under an exclusive license by AIP Publishing.
Overview of physics results from MAST upgrade towards core-pedestal-exhaust integration
No full text© 2024 Crown copyright, UK Atomic Energy Authority & The Author(s). Published by IOP Publishing Ltd on behalf of the IAEA. All rights reserved. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence...Recent results from MAST Upgrade are presented, emphasising understanding the capabilities of this new device and deepening understanding of key physics issues for the operation of ITER and the design of future fusion power plants. The impact of MHD instabilities on fast ion confinement have been studied, including the first observation of fast ion losses correlated with Compressional and Global Alfvén Eigenmodes. High-performance plasma scenarios have been developed by tailoring the early plasma current ramp phase to avoid internal reconnection events, resulting in a more monotonic q profile with low central shear. The impact of m/n = 3/2, 2/1 and 1/1 modes on thermal plasma confinement and rotation profiles has been quantified, and scenarios optimised to avoid them have transiently reached values of normalised beta approaching 4.2. In pedestal and ELM physics, a maximum pedestal top temperature of ∼350 eV has been achieved, exceeding the value achieved on MAST at similar heating power. Mitigation of type-I ELMs with n = 1 RMPs has been observed. Studies of plasma exhaust have concentrated on comparing conventional and Super-X divertor configurations, while X-point target, X-divertor and snowflake configurations have been developed and studied in parallel. In L-mode discharges, the separatrix density required to detach the outer divertors is approximately a factor 2 lower in the Super-X than the conventional configuration, in agreement with simulations. Detailed analysis of spectroscopy data from studies of the Super-X configuration reveal the importance of including plasma-molecule interactions and D2 Fulcher band emission to properly quantify the rates of ionisation, plasma-molecule interactions and volumetric recombination processes governing divertor detachment. In H-mode with conventional and Super-X configurations, the outer divertors are attached in the former and detached in the latter with no impact on core or pedestal confinement
Overview of physics results from MAST upgrade towards core-pedestal-exhaust integration
No full textPublisher Copyright: © 2024 Crown copyright, UK Atomic Energy Authority & The Author(s).Recent results from MAST Upgrade are presented, emphasising understanding the capabilities of this new device and deepening understanding of key physics issues for the operation of ITER and the design of future fusion power plants. The impact of MHD instabilities on fast ion confinement have been studied, including the first observation of fast ion losses correlated with Compressional and Global Alfvén Eigenmodes. High-performance plasma scenarios have been developed by tailoring the early plasma current ramp phase to avoid internal reconnection events, resulting in a more monotonic q profile with low central shear. The impact of m/n = 3/2, 2/1 and 1/1 modes on thermal plasma confinement and rotation profiles has been quantified, and scenarios optimised to avoid them have transiently reached values of normalised beta approaching 4.2. In pedestal and ELM physics, a maximum pedestal top temperature of ∼350 eV has been achieved, exceeding the value achieved on MAST at similar heating power. Mitigation of type-I ELMs with n = 1 RMPs has been observed. Studies of plasma exhaust have concentrated on comparing conventional and Super-X divertor configurations, while X-point target, X-divertor and snowflake configurations have been developed and studied in parallel. In L-mode discharges, the separatrix density required to detach the outer divertors is approximately a factor 2 lower in the Super-X than the conventional configuration, in agreement with simulations. Detailed analysis of spectroscopy data from studies of the Super-X configuration reveal the importance of including plasma-molecule interactions and D2 Fulcher band emission to properly quantify the rates of ionisation, plasma-molecule interactions and volumetric recombination processes governing divertor detachment. In H-mode with conventional and Super-X configurations, the outer divertors are attached in the former and detached in the latter with no impact on core or pedestal confinement.Peer reviewe
SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study
No full textBackground: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling.
Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty.
Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year.
Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population
