Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 85
Filtrar
1.
J Egypt Public Health Assoc ; 99(1): 11, 2024 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-38797806

RESUMO

BACKGROUND: Internet addiction is increasing among adolescents worldwide. There is a lack of research assessing internet addiction and factors contributing to it among adolescents in Jeddah city. The current study aimed to assess the rate of internet addiction among adolescents in Jeddah, Saudi Arabia, and the potential factors associated with it. METHODS: A cross-sectional online survey, hosted by SurveyMonkey, was used to capture data on internet use from 462 adolescents aged 12-18 years between March and May 2022. Young's Internet Addiction Scale was used to assess the degree of internet addiction as perceived by adolescents. Multiple linear regression analysis was used to identify possible predictors of internet addiction among adolescents in Jeddah. RESULTS: The mean age of the participants was 15.5 ± 1.9 years. The majority were females (75%) from public schools (63%), spent an average of six hours on the internet daily, owned smartphones (98%), accessed the internet via a smartphone (94%), and used the internet for socializing (82%). Internet addiction mean score was 39.20 ± 15.20 out of 100. More than two-thirds of the participants had mild to moderate levels of internet addiction (68%). Significant predictors contributing to internet addiction were using the internet for socialization and playing online games. The more hours spent on the internet daily, the more the internet addiction was (p ≤ 0.05). CONCLUSIONS: The internet addiction rate is high among school adolescents in Jeddah. The majority of high school adolescents had mild to moderate levels of internet addiction. Interventional multidisciplinary programs are needed to mitigate the factors that influence internet addiction.

2.
Hum Mol Genet ; 33(4): 374-385, 2024 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-37934784

RESUMO

Genome-wide association studies have contributed extensively to the discovery of disease-associated common variants. However, the genetic contribution to complex traits is still largely difficult to interpret. We report a genome-wide association study of 2394 cases and 2393 controls for age-related macular degeneration (AMD) via whole-genome sequencing, with 46.9 million genetic variants. Our study reveals significant single-variant association signals at four loci and independent gene-based signals in CFH, C2, C3, and NRTN. Using data from the Exome Aggregation Consortium (ExAC) for a gene-based test, we demonstrate an enrichment of predicted rare loss-of-function variants in CFH, CFI, and an as-yet unreported gene in AMD, ORMDL2. Our method of using a large variant list without individual-level genotypes as an external reference provides a flexible and convenient approach to leverage the publicly available variant datasets to augment the search for rare variant associations, which can explain additional disease risk in AMD.


Assuntos
Estudo de Associação Genômica Ampla , Degeneração Macular , Humanos , Estudo de Associação Genômica Ampla/métodos , Degeneração Macular/genética , Genótipo , Testes Genéticos , Sequenciamento Completo do Genoma , Polimorfismo de Nucleotídeo Único/genética , Predisposição Genética para Doença , Fator H do Complemento/genética
3.
Cureus ; 15(11): e48257, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-38054146

RESUMO

Pyosalpinx is the collection of pus in the fallopian tube. Pyosalpinx usually follows pelvic inflammatory disease, sexually transmitted disease, or rarely non-sexually transmitted infection. This is the first-ever report of bilateral pyosalpinx due to intrauterine device in situ for the past 16 years, which presented as appendicitis. Pyosalpinx should be considered in female patients with lower abdominal pain.

4.
J Oncol Pharm Pract ; 29(6): 1467-1479, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37559370

RESUMO

OBJECTIVE: Chemotherapy is the mainstay for triple-negative breast cancer (TNBC) patients. Over the years, the use of chemotherapy for these patients has demonstrated many adversities, including toxicity and resistance, which suggested the need to develop novel alternative therapeutic options, such as poly(ADP-ribose) polymerase inhibitors (PARPi). Herein, we provide an overview on PARPi, mechanisms of action and the role of biomarkers in PARPi sensitivity trials, clinical advances in PARPi therapy for TNBC patients based on the most recent studies and findings of clinical trials, and challenges that prevent PARP inhibitors from achieving high efficacy such as resistance and overlapping toxicities with other chemotherapies. DATA SOURCES: Searching for relevant articles was done using PubMed and Cochrane Library databases by using the keywords including TNBC; chemotherapy; PARPi; BRCA; homologous recombination repair (HRR). Studies had to be published in full-text in English in order to be considered. DATA SUMMARY: Although PARPi have been used in the treatment of local/metastatic breast malignancies that are HER2 negative and has a germline BRCA mutation, several questions are still to be answered in order to maximize the clinical benefit of PARP inhibitors in TNBC treatment, such as questions related to the optimal use in the neoadjuvant and metastatic settings as well as the best combinations with various chemotherapies. CONCLUSIONS: PARPi are emerging treatment options for patients with gBRCA1/2 mutations. Determining patients that are most likely to benefit from PARPi and identifying the optimal treatment combinations with high efficacy and fewer side effects are currently ongoing.

5.
Micromachines (Basel) ; 14(4)2023 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-37421113

RESUMO

This paper presents a finger-actuated micropump with a consistent flow rate and no backflow. The fluid dynamics in interstitial fluid (ISF) extraction microfluidics are studied through analytical, simulation, and experimental methods. Head losses, pressure drop, diodocity, hydrogel swelling, criteria for hydrogel absorption, and consistency flow rate are examined in order to access microfluidic performance. In terms of consistency, the experimental result revealed that after 20 s of duty cycles with full deformation on the flexible diaphragm, the output pressure became uniform and the flow rate remained at nearly constant levels of 2.2 µL/min. The flow rate discrepancy between the experimental and predicted flow rates is around 22%. In terms of diodicity, when the serpentine microchannel and hydrogel-assisted reservoir are added to the microfluidic system integration, the diodicity increases by 2% (Di = 1.48) and 34% (Di = 1.96), respectively, compared to when the Tesla integration (Di = 1.45) is used alone. A visual and experimentally weighted analysis finds no signs of backflow. These significant flow characteristics demonstrate their potential usage in many low-cost and portable microfluidic applications.

6.
J Infect Dev Ctries ; 17(2): 218-225, 2023 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-36897903

RESUMO

INTRODUCTION: Many people worldwide attempt to lose weight or adopt strategies to control it. Some have resorted to the consumption of commercialized diet pills to achieve this goal. Multiple brands exist without clearly indicating their mechanism of action or adverse effects on human health. This study aims to determine the antibacterial effect of commercial diet pills on members of the intestinal microbiota. METHODOLOGY: Commercialized diet pills were bought from a pharmacy in the North of Lebanon. Broth microdilution test was performed to determine the Minimum Inhibitory Concentrations (MICs) of the aqueous suspension against forty-two isolates distributed into four Enterobacterales species. MIC of the digested form was determined against six different strains. GC-MS analysis was performed to elucidate the components of the diet pill compared to the manufacturer's list. RESULTS: Broth microdilution results revealed that MICs of the diet pill aqueous suspension ranged from 3.9x103-9.76x102 µg/mL for Escherichia coli, Enterobacter spp., and Proteus spp. For Klebsiella species, MIC of carbapenem-resistant isolates reached 1.95x103 µg/mL. The digested form had a significantly lower antibacterial effect compared to the aqueous suspension. GC-MS analysis results corresponded with the list of ingredients provided by the manufacturer. CONCLUSIONS: The results showed significant antibacterial activity of a commercial diet pill on different members of the human intestinal microbiota regardless of their resistance profile. Further work is needed to elucidate the antibacterial effect of the digested components to accurately understand their effect on the intestinal microflora and thus on human health.


Assuntos
Antibacterianos , Carbapenêmicos , Humanos , Antibacterianos/farmacologia , Testes de Sensibilidade Microbiana , Carbapenêmicos/farmacologia , Klebsiella , Dieta
7.
Cureus ; 15(12): e50626, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-38226090

RESUMO

Introduction B vitamins help generate energy within cells. A significant portion of populations in developed countries suffer a deficiency in one or more B vitamins. This study assesses the use of vitamin B supplements and their effects. Methodology This cross-sectional study was conducted using public participants in Saudi Arabia. Participants from all over Saudi Arabia were recruited through self-conducted surveys to study the effects of using vitamin B supplements on appetite, BMI, energy, and sleep, and to identify any side effects in participants. Inclusion criteria included age (18 years or older) and use of vitamin B supplements. Children, pregnant women, adults who had never used vitamin B, and those not willing to participate in the study were excluded. Results In total, 1,521 adults were recruited. Most of the participants were young Saudi Females. While taking vitamin B supplements, a minority of participants complained of mild gastrointestinal upset, but a significant proportion experienced no side effects. In this study, a significant proportion of participants experienced an increase in appetite, which was associated with a significant increase in BMI after taking vitamin B supplements. This study also explored increases in energy, which were significant and associated with significant increases in sleeping time. Male participants in the present study noticed a significant increase in erectile dysfunction (ED). Conclusions This study found significant effects of vitamin B supplements on BMI, appetite, energy, and sleep, as well as an increase in ED in male participants. More studies are needed to further explore these findings.

8.
Forensic Sci Int ; 340: 111469, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36162300

RESUMO

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) started in December 2019. An immediate prevention approach for the outbreak is the development of a vaccination program. Despite a growing number of publications showing the effectiveness of vaccination in preventing SARS-CoV-2 outbreak and reducing the mortality rate, substantial fatal adverse effects were reported after vaccination. Confirmation of the causal relationship of death is required to reimburse under the national vaccination program and could provide a reference for the selection of vaccination. However, a lack of guidelines in the laboratory study and autopsy approach hampered the investigation of post-vaccination death. In this paper, we performed a systematic electronic search on scientific articles related to severe Covid-19 vaccination adverse effects and approaches in identifying the severe side effects using PubMed and Cochrane libraries. A summary on the onset, biochemistry changes and histopathological analyzes of major lethally side effects post-vaccination were discussed. Ultimately, a checklist is suggested to improve the quality of investigation.


Assuntos
COVID-19 , SARS-CoV-2 , Humanos , Autopsia , COVID-19/prevenção & controle , Vacinas contra COVID-19/efeitos adversos , Vacinação
9.
Ann Med Surg (Lond) ; 78: 103823, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35734708

RESUMO

Background: In an effort to increase donor safety in living donor liver transplantation, the utilization of vascular staplers for the division of the right portal and hepatic veins in patients undergoing right lobe liver donation for living donor liver transplantation (LDLT) was implemented. In here we report our experience with vascular staplers in patients undergoing LDLT and evaluate the subsequent feasibility and safety for donors. Material and methods: 17 cases of living donor liver transplant were retrospectively analyzed. The right portal vein was transected directly at the bifurcation of the main portal vein, the right hepatic vein was resected directly at the wall of the inferior vena cava using a vascular stapler device. Results: We registered a complication rate of 41.2% (7 donors). According to the Clavien-Dindo classification, grade II and grade III complications were each observed in 5.9% and grade IIIb complications in 29.4%, whereas catastrophic bleeding, complications with residual disability or the necessity of re-laparatomy did not occur. Upon 6 weeks, all donors were able to return to their previous occupation in fully recovered condition. Conclusions: The utilization of vascular staplers in donors during open LDLT presents an encouraging alternative to manual over-sewing of vascular stumps. Apart from its timesaving aspect, the technique reduces the potential risk of life-threatening clamp slippage with subsequent uncontrolled blood loss.

10.
PLoS One ; 17(1): e0262570, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35085307

RESUMO

This study proposes SVM based Random Subspace (RS) ensemble classifier to discriminate different Power Quality Events (PQEs) in a photovoltaic (PV) connected Microgrid (MG) model. The MG model is developed and simulated with the presence of different PQEs (voltage and harmonic related signals and distinctive transients) in both on-grid and off-grid modes of MG network, respectively. In the pre-stage of classification, the features are extracted from numerous PQE signals by Discrete Wavelet Transform (DWT) analysis, and the extracted features are used to learn the classifiers at the final stage. In this study, first three Kernel types of SVM classifiers (Linear, Quadratic, and Cubic) are used to predict the different PQEs. Among the results that Cubic kernel SVM classifier offers higher accuracy and better performance than other kernel types (Linear and Quadradic). Further, to enhance the accuracy of SVM classifiers, a SVM based RS ensemble model is proposed and its effectiveness is verified with the results of kernel based SVM classifiers under the standard test condition (STC) and varying solar irradiance of PV in real time. From the final results, it can be concluded that the proposed method is more robust and offers superior performance with higher accuracy of classification than kernel based SVM classifiers.


Assuntos
Centrais Elétricas , Energia Solar , Algoritmos , Redes Neurais de Computação , Máquina de Vetores de Suporte , Análise de Ondaletas
11.
J Pediatr Adolesc Gynecol ; 35(2): 192-195, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34687904

RESUMO

BACKGROUND: Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a congenital disorder characterized by underdevelopment of the uterus and vagina. CASE: A 4-year-old girl was declared dead on arrival to the hospital with a history of chronic constipation since birth. Postmortem examination showed Müllerian remnants attached to abnormal fibrous tissue. The fibrous tissue extended from the descending colon to the rectum and connected to a urinary bladder duplication cyst. The fibrous tissue formed into a constricted band around the rectum. The cause of death was Streptococcus pyogenes sepsis with intestinal obstruction secondary to the rectal fibrotic band and urinary bladder duplication cyst. SUMMARY AND CONCLUSION: MRKH syndrome is a rare congenital disorder, and the malformations rarely cause death. We describe the features of abnormal fibrous tissue and urinary bladder duplication cyst in a patient with MRKH syndrome.


Assuntos
Transtornos 46, XX do Desenvolvimento Sexual , Anormalidades Congênitas , Obstrução Intestinal , Transtornos 46, XX do Desenvolvimento Sexual/complicações , Criança , Pré-Escolar , Feminino , Humanos , Obstrução Intestinal/etiologia , Obstrução Intestinal/cirurgia , Ductos Paramesonéfricos/anormalidades , Vagina/anormalidades
12.
Biomarkers ; 27(1): 22-34, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34882051

RESUMO

OBJECTIVE: A new breakthrough development in cancer treatment is chimeric antigen receptor (CAR)-T cell therapy. In this review, we focussed on its efficacy & safety in prostate cancer, obstacles impeding its clinical use, and some strategies trying to overcome them. METHODS: Searching for relevant articles was done using the PubMed and Cochrane Library databases. Studies had to be published in full-text in English in order to be considered. RESULTS: Many factors can limit optimal CAR-T cell outcomes, including the hostile Prostate microenvironment, age, comorbidities, and tumour grade. The adverse effects of the therapy, particularly the cytokine release syndrome, are a major source of worry after treatment administration. Attempts to alter gamma/delta T-cells and NK cells with CAR, on the other hand, have demonstrated higher effectiveness and safety than conventional CAR-T cells. CONCLUSION: To improve the use of immunotherapies, a greater understanding of the prostate cancer microenvironment is required. Concerning toxicity, more research is needed to find the most specific and highly expressed prostate antigens. Furthermore, discovering predictive biomarkers for toxicities, as well as choosing the correct patient for therapy, might decrease immune-related side effects and achieve a greater response.


Assuntos
Neoplasias da Próstata , Receptores de Antígenos Quiméricos , Humanos , Imunoterapia , Imunoterapia Adotiva/efeitos adversos , Masculino , Neoplasias da Próstata/patologia , Neoplasias da Próstata/terapia , Linfócitos T , Microambiente Tumoral
13.
PLoS One ; 16(8): e0256050, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34383821

RESUMO

This study presents a nature-inspired, and metaheuristic-based Marine predator algorithm (MPA) for solving the optimal power flow (OPF) problem. The significant insight of MPA is the widespread foraging strategy called the Levy walk and Brownian movements in ocean predators, including the optimal encounter rate policy in biological interaction among predators and prey which make the method to solve the real-world engineering problems of OPF. The OPF problem has been extensively used in power system operation, planning, and management over a long time. In this work, the MPA is analyzed to solve the single-objective OPF problem considering the fuel cost, real and reactive power loss, voltage deviation, and voltage stability enhancement index as objective functions. The proposed method is tested on IEEE 30-bus test system and the obtained results by the proposed method are compared with recent literature studies. The acquired results demonstrate that the proposed method is quite competitive among the nature-inspired optimization techniques reported in the literature.


Assuntos
Algoritmos , Organismos Aquáticos/fisiologia , Fontes de Energia Elétrica/normas , Biologia Marinha , Modelos Biológicos , Comportamento Predatório , Animais , Eletricidade , Comportamento Alimentar , Movimento
14.
Exp Clin Transplant ; 19(8): 826-831, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33952180

RESUMO

OBJECTIVES: Early hepatic artery thrombosis is a serious complication that may follow living donor liver transplant. Acute graft loss and patient morbidity and mortality are possible consequences. The therapeutic algorithm includes surgical or interventional revascularization, conservative approaches, or retransplantation. MATERIALS AND METHODS: Among 155 patients who underwent living donor liver transplant at our transplant center from 2004 to 2020, there were 5 who developed hepatic artery thrombosis. From our 13- year experience, we herein present their demographic and clinical characteristics, radiological imaging findings, perioperative courses, and the postoperative follow-up. RESULTS: All patients displayed advanced liver disease with a Child-Pugh score of C and a mean Model for End-Stage Liver Disease score of 32. Underlying causes for end-stage liver disease included hepatitis B and C infection and cryptogenic liver cirrhosis. The mean patient age was 49 years; 2 patients were female. Living donor liver transplant was performed with donor tissue from immediate kin, according to Jordanian allocation rules. The diagnosis of hepatic artery thrombosis was made by Doppler ultrasonography and confirmed via computed tomography. After surgical revision of the anastomosis, our first patient experienced thrombotic recurrence. All patients received interventional catheterization with local thrombolysis and subsequently developed rethrombosis. Despite prevalent thrombosis, 4 patients achieved long-term survival without further deterioration of liver function. Cumulative 1-year, 5-year, and 10-year survival rates were 80%, 80%, and 60%, respectively. Spontaneous recanalization of the hepatic artery was observed in 1 patient. CONCLUSIONS: Favorable long-term outcomes are achievable in patients with persistent hepatic artery thrombosis. When retransplant is not feasible and interventional approaches fail, conservative treatment with careful observation of liver function should be implemented. Attentive observation of collateral circulation toward the liver, distal of the thrombosis, may be beneficial to both graft and patient survival.


Assuntos
Doença Hepática Terminal , Transplante de Fígado , Trombose , Doença Hepática Terminal/etiologia , Feminino , Artéria Hepática/diagnóstico por imagem , Artéria Hepática/cirurgia , Humanos , Jordânia/epidemiologia , Transplante de Fígado/métodos , Doadores Vivos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Índice de Gravidade de Doença , Trombose/diagnóstico por imagem , Trombose/etiologia , Trombose/terapia , Resultado do Tratamento
15.
Exp Clin Transplant ; 18(7): 796-802, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33349208

RESUMO

OBJECTIVES: Budd-Chiari syndrome is an infrequent, but potentially fatal, hepatic condition with the clinical manifestation of obstructed venous drainage. This may lead to progressive hepatic congestion, portal hypertension, and, ultimately, liver failure. If medical, interventional, and surgical approaches are not effective, liver transplant offers a rescue modality. The primary objective of this study was to report the perioperative and, above all, the vascular challenges associated with living donor liver transplant in patients with Budd-Chiari syndrome. MATERIALS AND METHODS: We retrospectively reviewed demographic and clinical characteristics of 6 patients with Budd-Chiari syndrome who underwent living donor liver transplant at our transplant center from April 2004 to July 2020. We also evaluated all data regarding perioperative course, surgical outcome, and the postoperative follow-up period. RESULTS: All patients displayed advanced liver disease with a Child-Pugh score C. The mean calculated Model for End-Stage Liver Disease score was 32. The causes of Budd-Chiari syndrome were factor V Leiden thrombophilia in 1 patient, myeloproliferative disorder in 3 patients, antiphospholipid antibody syndrome in 1 patient, and a protein C deficiency in 1 patient. The mean age of patients was 40 years. One of the 6 patients was female. All patients had living donor liver transplant from immediate kin according to Jordanian allocation rules. The mean graft-to-recipient weight ratio was 0.9, and the median follow-up period was 89 months. Cumulative 1-, 3-, and 5-year-survival rates were 84%, 67%, and 67%, respectively. CONCLUSIONS: Good survival rates are achievable with living donor liver transplant for patients with advanced Budd-Chiari syndrome, particularly by means of posterior cavoplasty for enlargement of the cava orifice. Therefore, in countries with insufficient deceased donor programs, such as Jordan, living donor liver transplant may be a lifesaving therapeutic possibility.


Assuntos
Síndrome de Budd-Chiari/cirurgia , Transplante de Fígado , Doadores Vivos , Adulto , Idoso , Síndrome de Budd-Chiari/diagnóstico , Síndrome de Budd-Chiari/mortalidade , Feminino , Sobrevivência de Enxerto , Hospitais Universitários , Humanos , Jordânia , Transplante de Fígado/efeitos adversos , Transplante de Fígado/mortalidade , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Fatores de Tempo , Resultado do Tratamento , Adulto Jovem
16.
PLoS One ; 15(11): e0241927, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33180779

RESUMO

This study analyzes the performance of two PV modules, amorphous silicon (a-Si) and crystalline silicon (c-Si) and predicts energy yield, which can be seen as facilitation to achieve the target of 35% reduction of greenhouse gases emission by 2030. Malaysia Energy Commission recommends crystalline PV modules for net energy metering (NEM), but the climate regime is a concern for output power and efficiency. Based on rainfall and irradiance data, this study aims to categorize the climate of peninsular Malaysia into rainy and dry seasons; and then the performance of the two modules are evaluated under the dry season. A new mathematical model is developed to predict energy yield and the results are validated through experimental and systematic error analysis. The parameters are collected using a self-developed ZigBeePRO-based wireless system with the rate of 3 samples/min over a period of five days. The results unveil that efficiency is inversely proportional to the irradiance due to negative temperature coefficient for crystalline modules. For this phenomenon, efficiency of c-Si (9.8%) is found always higher than a-Si (3.5%). However, a-Si shows better shadow tolerance compared to c-Si, observed from a lesser decrease rate in efficiency of the former with the increase in irradiance. Due to better spectrum response and temperature coefficient, a-Si shows greater performance on output power efficiency (OPE), performance ratio (PR), and yield factor. From the regression analysis, it is found that the coefficient of determination (R2) is between 0.7179 and 0.9611. The energy from the proposed model indicates that a-Si yields 15.07% higher kWh than c-Si when luminance for recorded days is 70% medium and 30% high. This study is important to determine the highest percentage of energy yield and to get faster NEM payback period, where as of now, there is no such model to indicate seasonal energy yield in Malaysia.


Assuntos
Gases de Efeito Estufa/química , Silício/química , Malásia , Modelos Teóricos , Estações do Ano , Temperatura
17.
PLoS One ; 15(10): e0240368, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33035254

RESUMO

This study presents an investigation on the effect of shield placement for mitigation of transient voltage in a 33/11 kV, 30 MVA transformer due to Standard Switching Impulse (SSI) and Oscillating Switching Impulse (OSI) surges. Generally, the winding and insulation in transformers could experience severe voltage stress due to the external impulses i.e. switching events. Hence, it is important to examine the voltage stress and identify the mitigation action i.e. shield placements in order to reduce the adverse effect to the transformer windings. First, the resistances, inductances, and capacitances (RLC) were calculated for disc type transformer in order to develop the winding RLC equivalent circuit. The SSI and OSI transient voltage waveforms were applied to the High Voltage (HV) winding whereby the transient voltages were simulated for each disc. The resulting voltage stresses were mitigated through different configurations of electrostatic shield placements. The resonant oscillations generated due to switching surges were analysed through initial voltage distribution. The analyses on the transient voltages of the transformer winding and standard error of the slope (SEb) reveal that the location of shield placement has a significant effect on the resonant switching voltages. The increment of the shield number in the windings does not guarantee optimize mitigation of the resonant switching transient voltages. It is found that the voltage stress along the windings is linear once a floating shield is placed between the HV and Low Voltage (LV) windings of the disc-type transformer under the SSI and OSI waveforms. These findings could assist the manufacturers with appropriate technical basis for mitigation of the transformer winding against the external transient switching overvoltage surges.


Assuntos
Fontes de Energia Elétrica , Algoritmos , Simulação por Computador , Capacitância Elétrica , Impedância Elétrica , Desenho de Equipamento , Eletricidade Estática
18.
PLoS One ; 15(8): e0236409, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853253

RESUMO

This paper proposes an alternative approach to extract transformer's winding parameters of resistance (R), inductance (L), capacitance (C) and conductance (G) based on Finite Element Method (FEM). The capacitance and conductance were computed based on Fast Multiple Method (FMM) and Method of Moment (MoM) through quasi-electrostatics approach. The AC resistances and inductances were computed based on MoM through quasi-magnetostatics approach. Maxwell's equations were used to compute the DC resistances and inductances. Based on the FEM computed parameters, the frequency response of the winding was obtained through the Bode plot function. The simulated frequency response by FEM model was compared with the simulated frequency response based on the Multi-conductor Transmission Line (MTL) model and the measured frequency response of a 33/11 kV, 30 MVA transformer. The statistical indices such as Root Mean Square Error (RMSE) and Absolute Sum of Logarithmic Error (ASLE) were used to analyze the performance of the proposed FEM model. It is found that the simulated frequency response by FEM model is quite close to measured frequency response at low and mid frequency regions as compared to simulated frequency response by MTL model based on RMSE and ASLE analysis.


Assuntos
Capacitância Elétrica , Fontes de Energia Elétrica , Análise de Elementos Finitos , Simulação por Computador , Condutividade Elétrica , Eletricidade Estática
19.
PLoS One ; 15(8): e0235668, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32776932

RESUMO

In this paper, a novel, effective meta-heuristic, population-based Hybrid Firefly Particle Swarm Optimization (HFPSO) algorithm is applied to solve different non-linear and convex optimal power flow (OPF) problems. The HFPSO algorithm is a hybridization of the Firefly Optimization (FFO) and the Particle Swarm Optimization (PSO) technique, to enhance the exploration, exploitation strategies, and to speed up the convergence rate. In this work, five objective functions of OPF problems are studied to prove the strength of the proposed method: total generation cost minimization, voltage profile improvement, voltage stability enhancement, the transmission lines active power loss reductions, and the transmission lines reactive power loss reductions. The particular fitness function is chosen as a single objective based on control parameters. The proposed HFPSO technique is coded using MATLAB software and its effectiveness is tested on the standard IEEE 30-bus test system. The obtained results of the proposed algorithm are compared to simulated results of the original Particle Swarm Optimization (PSO) method and the present state-of-the-art optimization techniques. The comparison of optimum solutions reveals that the recommended method can generate optimum, feasible, global solutions with fast convergence and can also deal with the challenges and complexities of various OPF problems.


Assuntos
Algoritmos , Eletricidade , Dinâmica não Linear , Simulação por Computador , Centrais Elétricas , Software
20.
Hum Mol Genet ; 29(12): 2022-2034, 2020 07 29.
Artigo em Inglês | MEDLINE | ID: mdl-32246154

RESUMO

Genome-wide association studies (GWAS) have identified 52 independent variants at 34 genetic loci that are associated with age-related macular degeneration (AMD), the most common cause of incurable vision loss in the elderly worldwide. However, causal genes at the majority of these loci remain unknown. In this study, we performed whole exome sequencing of 264 individuals from 63 multiplex families with AMD and analyzed the data for rare protein-altering variants in candidate target genes at AMD-associated loci. Rare coding variants were identified in the CFH, PUS7, RXFP2, PHF12 and TACC2 genes in three or more families. In addition, we detected rare coding variants in the C9, SPEF2 and BCAR1 genes, which were previously suggested as likely causative genes at respective AMD susceptibility loci. Identification of rare variants in the CFH and C9 genes in our study validated previous reports of rare variants in complement pathway genes in AMD. We then extended our exome-wide analysis and identified rare protein-altering variants in 13 genes outside the AMD-GWAS loci in three or more families. Two of these genes, SCN10A and KIR2DL4, are of interest because variants in these genes also showed association with AMD in case-control cohorts, albeit not at the level of genome-wide significance. Our study presents the first large-scale, exome-wide analysis of rare variants in AMD. Further independent replications and molecular investigation of candidate target genes, reported here, would assist in gaining novel insights into mechanisms underlying AMD pathogenesis.


Assuntos
Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Degeneração Macular/genética , Canal de Sódio Disparado por Voltagem NAV1.8/genética , Receptores KIR2DL4/genética , Idoso , Idoso de 80 Anos ou mais , Exoma/genética , Humanos , Degeneração Macular/patologia , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único/genética , Sequenciamento do Exoma
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...