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1.
Zhonghua Jie He He Hu Xi Za Zhi ; 46(6): 558-564, 2023 Jun 12.
Artigo em Chinês | MEDLINE | ID: mdl-37278169

RESUMO

Objective: To describe the clinical characteristics, diagnosis, genetic features and treatment of hereditary pulmonary hypertension complicated with suspected hereditary hemorrhagic telangiectasia (HHT). Methods: Firstly, we summarized and analyzed the clinical data of two cases of suspected HHT admitted to the Department of Pulmonary and Critical Care Medicine, the Second Xiangya Hospital, Central South University. Secondly, the genes of peripheral blood of patients and their families were completely sequenced and sanger sequencing was performed to verify the variation sites, and then the mRNA deletion caused by the variation was further verified. Thirdly, "HHT" "FPAH" and "BMPR2 gene variation" were used as keywords,and the related literatures of Wanfang database and PubMed database from January 2000 to November 2021 were searched and reviewed. Results: We found two patients in a family from Yiyang, Hunan province, who had symptoms of hemoptysis or pulmonary hypertension without epistaxis or other clinical features of HHT. However, both patients had pulmonary vascular abnormalities and pulmonary hypertension in their lungs. We found that BMPR2 gene variation (NM_001204.7:c.1128+1G>T) was positive and ENG, ACVRL1 and SMAD4 genes were negative. Family analysis and Sanger verification were carried out on 16 individuals in 4 generations of the family (7 of whom were found to carry the mutant gene), and then transcriptional level mRNA sequencing further confirmed that the variation resulted in the deletion of exon 8 and exon 9, and amino acid sequence estimation revealed that the amino acids of the protein from 323 to 425 were deleted. We thought that the incomplete translation of BMPR2 gene could lead to BMPRⅡ dysfunction. Therefore, it was diagnosed as hereditary pulmonary hypertension with suspected HHT. Both patients were suggested to reduce the pulmonary artery pressure, and at the same time, the whole-body imaging examination should be performed to screen other arteriovenous malformations, and the annual cardiac color Doppler ultrasound should be reviewed to evaluate the changes of pulmonary artery pressure. Conclusions: Hereditary pulmonary hypertension (HPAH) is a group of diseases with increasing pulmonary vascular resistance caused by genetic factors, including familial PAH and simple PAH. Variation in the BMPR2 gene is an important pathogenic factor of HPAH. Therefore, we should pay attention to the inquiry of family history when we clinically encounter young patients with pulmonary hypertension. If the cause is unknown, genetic testing is recommended. HHT is a rare autosomal dominant genetic disease. The possibility of this disease should be considered in clinical manifestations such as familial pulmonary vascular abnormality, pulmonary hypertension and recurrent epistaxis. There is no effective specific treatment for HPAH and HHT, which are treated symptomatically (including blood pressure reduction and hemostasis, etc.). It is suggested for these patients that pulmonary artery pressure should be dynamically monitored and have genetic counseling before giving birth.


Assuntos
Hipertensão Pulmonar , Telangiectasia Hemorrágica Hereditária , Gravidez , Humanos , Feminino , Hipertensão Pulmonar/diagnóstico , Epistaxe/complicações , Telangiectasia Hemorrágica Hereditária/genética , Telangiectasia Hemorrágica Hereditária/complicações , Telangiectasia Hemorrágica Hereditária/diagnóstico , Pulmão/patologia , Mutação , Receptores de Proteínas Morfogenéticas Ósseas Tipo II/genética , Receptores de Activinas Tipo II/genética
2.
Public Health ; 221: 23-30, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37356324

RESUMO

OBJECTIVES: This study aimed to project future temperature-associated mortality risk and additional deaths among Taiwan's elderly (aged >65 years) population. STUDY DESIGN: This study investigated retrospective temperature-mortality risk associations and future mortality projections. METHODS: A distributed lag non-linear model and random effect meta-analyses were employed to assess the risk of daily temperature-associated deaths in all-cause, circulatory, and respiratory diseases. Using the statistical downscaling temperature projections of the Representative Concentration Pathways (RCPs; i.e. RCP2.6, RCP6.0 and RCP8.5), future risk of mortalities were projected among the elderly for 2030-2039, 2060-2069 and 2090-2099, with a 30%, 40% and 50% expected increase in elderly population proportions, respectively. RESULTS: The baseline analysis from 2005 to 2018 identified that Taiwan's population is more vulnerable to cold effects than heat, with the highest cold-related mortality risk being attributed to circulatory diseases, followed by all-cause and respiratory diseases. However, future projections suggest a declining trend in cold-related mortalities and a significant rise in heat-related mortalities under different RCP scenarios. Heat-attributable mortalities under the RCP8.5 scenario by 2090-2099 would account for almost 170,360, 36,557 and 29,386 additional annual deaths among the elderly due to all-cause, circulatory and respiratory diseases, respectively. Heat-attributable all-cause mortalities among the elderly would increase by 3%, 11% and 30% under RCP2.6, RCP6.0 and RCP8.5, respectively, by 2090-2099. CONCLUSIONS: The findings of this study provide predictions on future temperature-related mortality among the elderly in a developed, ageing society with a hot and humid climate. The results from this study can guide public health interventions and policies for climate change and ageing society-associated health risks.


Assuntos
Temperatura Alta , Doenças Respiratórias , Idoso , Humanos , Temperatura , Estudos Retrospectivos , Envelhecimento , Mudança Climática , Mortalidade
3.
Zhonghua Jie He He Hu Xi Za Zhi ; 46(1): 51-55, 2023 Jan 12.
Artigo em Chinês | MEDLINE | ID: mdl-36617929

RESUMO

We reported the manifestations, auxiliary examination, and treatment courses of a case of scimitar syndrome with pulmonary sequestration containing carcinoma. The clinical characteristics of scimitar syndrome with pulmonary sequestration, pulmonary sequestration containing carcinoma were summarized based on the data of this case and the related literatures before January 2022. Scimitar syndrome can coexist with ipsilateral pulmonary sequestration. Because sequestered lung tissue has a risk of malignant transformation, a cancer screening test is useful for early diagnosis and timely treatment.


Assuntos
Sequestro Broncopulmonar , Carcinoma , Neoplasias Pulmonares , Veias Pulmonares , Síndrome de Cimitarra , Humanos , Sequestro Broncopulmonar/complicações , Síndrome de Cimitarra/complicações , Pulmão , Neoplasias Pulmonares/complicações , Carcinoma/complicações
4.
Eur Rev Med Pharmacol Sci ; 24(16): 8359-8366, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32894542

RESUMO

OBJECTIVE: Primary gallbladder carcinoma (GBC) is one of the most common biliary malignancies in the gastrointestinal tract. In this work, we examined the roles of circular-mitochondrial translation optimization 1 (circ-MTO1) in GBC tissues and patient plasma. PATIENTS AND METHODS: Circ-MTO1 expression in GBC tissues and patient plasma was evaluated by quantitative Real Time-PCR (qRT-PCR). The relationships between circ-MTO1 expression and the pathological characteristics of GBC were analyzed. Kaplan-Meier survival curve was applied to calculate overall survival (OS) and progression-free survival (PFS) in GBC patients with different circ-MTO1 expression. The univariate COX regression curve analysis method was employed to analyze the potential relationships between high circ-MTO1 expression and OS and PFS. At last, we assessed the diagnostic value of the circ-MTO1 level in GBC patient plasma. RESULTS: Circ-MTO1 expression was significantly upregulated in tumor tissues and plasma in GBC patients. In addition, circ-MTO1 expression was associated with clinical-pathological characteristics in GBC. High circ-MTO1 expression served as an independent prognostic factor for poor OS and PFS in GBC patients. Moreover, upregulated plasma circ-MTO1 level was significantly associated with tumor development. CONCLUSIONS: Circ-MTO1 is a potential early diagnostic and prognostic biomarker for patients with gallbladder cancer. Thus, our present work might provide a new understanding of the diagnosis and treatment of GBC.


Assuntos
Biomarcadores Tumorais/genética , Neoplasias da Vesícula Biliar/genética , RNA Circular/genética , Feminino , Neoplasias da Vesícula Biliar/diagnóstico , Humanos , Masculino , Pessoa de Meia-Idade
6.
J R Army Med Corps ; 164(6): 399-404, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30012664

RESUMO

INTRODUCTION: Betel nut chewing may cause obesity, neurohormonal activation and inflammation, possibly impairing exercise performances. METHODS: We examined the cross-sectional association in 4388 military male adults aged 18-50 years from the cardiorespiratory fitness in armed forces study in Taiwan between 2013 and 2014. The status of betel nut chewing was classified as current and former/never based on each participant's response to a questionnaire. Physical fitness was evaluated by three basic exercise tests including 3000 m running, 2 min sit-ups and 2 min push-ups. Multiple logistic regression for the best 10% and the worst 10% performers in each exercise, and linear regression were used to determine the relationship. RESULTS: There were 564 current chewers and 3824 non-current chewers for the analysis. The linear regression shows that current betel nut chewing was positively correlated with 3000 m running duration (r=0.37, p=0.042) after adjusting for age, service specialty, body mass index, exercise frequency and alcohol intake. In addition, the logistic regression shows that as compared with non-current chewers, current chewers had lower odds of being the top 10% performers in 2 min push-ups and higher odds of being the bottom 10% performers in 2 min sit-ups (ORs and 95% CIs: 0.71 (0.50 to 0.99) and 1.32 (1.00 to 1.75), respectively). However, the associations between betel nut chewing and physical fitness were all insignificant after further adjusting for current smoking. CONCLUSIONS: Our findings suggest that the impairment of physical fitness associated with betel nut chewing of military young men might be mainly mediated or moderated by the coexisted cigarette smoking.


Assuntos
Areca , Desempenho Atlético , Mastigação , Militares , Adolescente , Adulto , Fumar Cigarros/efeitos adversos , Fumar Cigarros/epidemiologia , Estudos de Coortes , Estudos Transversais , Exercício Físico , Teste de Esforço , Humanos , Modelos Lineares , Masculino , Pessoa de Meia-Idade , Aptidão Física , Taiwan/epidemiologia , Adulto Jovem
8.
Opt Lett ; 43(6): 1219-1221, 2018 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-29543255

RESUMO

The Nd3+-doped Bi4Ge3O12 (BGO) single-crystal fiber (SCF) was successfully grown by the micro-pulling-down method with the resistance heating system. The fluorescence spectrum and transmission spectrum of the Nd:BGO SCF were measured. Excited by a continuous-wave 808-nm laser diode, a fluorescence peak around 1064 nm was observed. At an absorbed pump power of 15.25 W, the Nd:BGO SCF laser delivered a power of 3.37 W with a slope efficiency of 31.2%.

9.
Br J Dermatol ; 178(1): 124-131, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28815560

RESUMO

BACKGROUND: Indigo naturalis and its refined formulation, Lindioil, are effective in treating psoriatic symptoms topically. Indirubin is the active ingredient in indigo naturalis. OBJECTIVES: To determine the efficacy and safety of different concentrations of indirubin in Lindioil ointment for treating psoriasis. METHODS: In this randomized, double-blind trial, adult patients presenting with chronic plaque psoriasis for > 1 year and with < 20% of the body surface area (BSA) affected were randomized to apply Lindioil ointment containing 200, 100, 50 or 10 µg g-1 of indirubin twice daily for 8 weeks followed by an additional 12-week safety/extension period. The primary end point was the mean percentage change in Psoriasis Area and Severity Index (PASI) score along with the proportion of participants achieving 75% and 90% reductions in PASI scores (PASI 75 and PASI 90, respectively) from baseline to week 8. RESULTS: The results from week 8 revealed that the 200 µg g-1 group had the greatest reduction in PASI score [69·2%, 95% confidence interval (CI) 55·5-82·8], followed by the 100 µg g-1 group (63·1%, 95% CI 52·8-73·5), the 10 µg g-1 group (53·4%, 95% CI 42·8-64·0) and the 50 µg g-1 group (50·3%, 95% CI 37·4-63·2), with a between-group comparison of P = 0·0445. The group with the highest proportion of the patients achieving PASI 75 (57%, P = 0·0474) and PASI 90 (30%, P = 0·0098) was the 200 µg g-1 group. No severe treatment-related adverse events were reported during the 20-week evaluation. CONCLUSIONS: An amount of 200 µg g-1 of indirubin in Lindioil ointment is the most effective concentration studied so far for treating psoriasis topically, and is safe.


Assuntos
Fármacos Dermatológicos/administração & dosagem , Medicamentos de Ervas Chinesas/administração & dosagem , Psoríase/tratamento farmacológico , Adulto , Fármacos Dermatológicos/efeitos adversos , Fármacos Dermatológicos/análise , Relação Dose-Resposta a Droga , Método Duplo-Cego , Esquema de Medicação , Medicamentos de Ervas Chinesas/química , Feminino , Humanos , Indóis/administração & dosagem , Indóis/efeitos adversos , Indóis/análise , Masculino , Pomadas , Resultado do Tratamento
10.
QJM ; 110(10): 649-655, 2017 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-28482057

RESUMO

BACKGROUND: Sleep-related movement disorders (SRMD) have been shown to increase the risk of cardiovascular diseases. However, the relationship between SRMD and stroke remains unclear. AIM: To explore the relationship between SRMD and stroke in the general population. DESIGN: Two cohorts of patients with SRMD and without SRMD were followed up for the occurrence of hemorrhagic and ischemic stroke. METHODS: The study cohort enrolled 604 patients who were initially diagnosed as SRMD between 2000 and 2005. 2,416 age- and sex-matched patients without prior stroke were selected as the comparison cohort. A Cox-proportional hazard regression analysis was performed for multivariate adjustment. RESULTS: Patients with SRMD had a higher risk for developing all-cause stroke [adjusted hazard ratio (HR) = 2.29, 95% confidence interval (CI) = 1.42-3.80]. Patients of below 45 years old had the greatest stroke risk (HR = 4.03, 95% CI = 3.11-5.62), followed by patients aged ≥65 years (HR = 2.64, 95% CI = 1.12-3.44) and 45-64 years (HR = 1.07, 95% CI = 1.02-1.71). The age-stratified analysis suggested that the increased risk of hemorrhagic stroke was more significant than ischemic stroke among all age groups. Furthermore, males with SRMD were at greater risk to develop all-cause stroke (HR = 2.98, 95% CI = 1.74-4.50) than that of females (HR = 1.94, 95% CI = 1.01-3.77). CONCLUSIONS: Patients with SRMD were found to have an increased risk of all-cause stroke along with a higher possibility of hemorrhagic stroke over ischemic stroke.


Assuntos
Hemorragias Intracranianas/epidemiologia , Transtornos dos Movimentos/complicações , Transtornos do Sono-Vigília/complicações , Acidente Vascular Cerebral/epidemiologia , Adulto , Distribuição por Idade , Idoso , Feminino , Humanos , Hemorragias Intracranianas/etiologia , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Programas Nacionais de Saúde , Modelos de Riscos Proporcionais , Fatores de Risco , Distribuição por Sexo , Acidente Vascular Cerebral/etiologia , Taiwan/epidemiologia
11.
Acta Physiol (Oxf) ; 220(4): 432-445, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-27875022

RESUMO

AIM: Atrial fibrosis plays a pivotal role in the pathophysiology of heart failure (HF). The left atrium (LA) experiences greater fibrosis than the right atrium (RA) during HF. It is not clear whether LA cardiac fibroblasts contain distinctive activities that predispose LA to fibrosis. METHODS: LA and RA fibrosis were evaluated in healthy and isoproterenol-induced HF Sprague Dawley rats. Rat LA and RA primary isolated fibroblasts were subjected to proliferation assay, oxidative stress assay, cell migration analysis, collagen measurement, cytokine array and Western blot. RESULTS: Healthy rat LA and RA had a similar extent of collagen deposition. HF significantly increased fibrosis to a greater severity in LA than in RA. Compared to isolated RA fibroblasts, the in vitro experiments showed that isolated LA fibroblasts had higher oxidative stress and exhibited higher collagen, transforming growth factor-ß1, connective tissue growth factor production and less vascular endothelial growth factor (VEGF) production, but had similar migration, myofibroblast differentiation and proliferation activities. VEGF significantly increased the collagen production ability of LA fibroblasts, but not RA fibroblasts. LA fibroblasts had more phosphorylated ERK1/2 and P38 expression. ERK inhibitor (PD98059, 50 µmol L-1 ) significantly attenuated collagen production and increased VEGF production in RA fibroblasts but not in LA fibroblasts. P38 inhibitor (SB203580, 30 µmol L-1 ) significantly attenuated collagen production in LA fibroblasts but not in RA fibroblasts. P38 inhibitor also significantly increased VEGF production in RA and LA fibroblasts. CONCLUSIONS: Differences in profibrotic activity between LA and RA fibroblasts may be caused by different responses to mitogen-activated protein kinase signalling.


Assuntos
Colágeno/biossíntese , Fibroblastos/metabolismo , Átrios do Coração/metabolismo , Átrios do Coração/patologia , Insuficiência Cardíaca/patologia , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Transdução de Sinais , Animais , Fibrose/metabolismo , Insuficiência Cardíaca/metabolismo , Masculino , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/fisiologia
12.
J Zool (1987) ; 299(2): 106-115, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27453637

RESUMO

Social monogamy is a mating strategy rarely employed by mammalian species. Laboratory studies in socially monogamous prairie voles (Microtus ochrogaster) demonstrate that oxytocin and vasopressin act within the mesolimbic dopamine pathway to facilitate pair-bond formation. Species differences in oxytocin receptor (OTR) and vasopressin 1a receptor (V1aR) distribution in this pathway are associated with species differences in mating strategy. Here we characterize the neuroanatomical distribution of OTR and V1aR binding sites in naturally occurring populations of Taiwan voles (M. kikuchii), which purportedly display social monogamy. Live trapping was conducted at two sites in 2009-2010 and receptor autoradiography for OTR and V1aR was performed on brains from 24 animals. OTR binding in two brain regions where OTR signaling regulates pair-bonding were directly compared with that of prairie voles. Our results show that like prairie voles, Taiwan voles exhibit OTR in the prefrontal cortex, insular cortex, claustrum, nucleus accumbens, caudate-putamen, dorsal lateral septal nucleus, central amygdala, and ventromedial hypothalamus. Unlike prairie voles, Taiwan voles exhibit OTR binding in the CA3 pathway of the hippocampus, as well as the indusium griseum, which has only previously been documented in tuco-tucos (Ctenomys haigi, C. sociabilis), Syrian hamsters (Mesocricetus auratus) and naked mole-rats (Heterocephalus glaber). V1aR binding was present in the ventral pallidum, lateral septum, nucleus basalis, bed nucleus of the stria terminalis, hippocampus, medial amygdala, and anterior, ventromedial and dorsomedial hypothalamus. Marked individual differences in V1aR binding were noted in the cingulate cortex and several thalamic nuclei, remarkably similar to prairie voles. While pharmacological studies are needed to determine whether oxytocin and vasopressin are involved in pair-bond formation in this species, our results lay a foundation for future investigations into the role of these neuropeptides in Taiwan vole social behavior.

13.
J Nanosci Nanotechnol ; 14(5): 3398-402, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24734558

RESUMO

Here we report our findings on the removal of metallic single-walled carbon nanotubes using an aqueous two-phase system. The aqueous two-phase system contained as received carbon nanotubes, polyethylene glycol, dextran, N-methylpyrrolidone, cetyltrimethylammonium bromide, and water which phase separated into top and bottom phases. The top phase was dominated by polyethylene glycol whereas the bottom phase was dominated by dextran. The dextran-rich phase contained more semiconducting species while metallic species was more abundant in the polyethylene glycol rich-phase. It was found via Fourier-Transform Infrared Spectroscopy that cetyltrimethylammonium bromide only present in the dextran-rich phase. A selectivity mechanism is tentatively proposed and discussed.

14.
Genet Mol Res ; 13(1): 1251-62, 2014 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-24634182

RESUMO

This study investigated the induced immune tolerance of autoantigen dendritic cells (imDCs) in homogenic lupus mice to support the use of dendritic cell treatment against autoimmune diseases, such as systemic lupus erythematosus. A lupus mouse was used to model based on in vitro cell culture. An immunohistochemistry assay was used to assess CD8(+), CD4(+) cell ratio in mouse spleen cells. The ratio of CD4(+)CD25(+) cells in mouse spleen lymphocytes was detected by flow cytometry, whereas the kidney was directly measured by immunofluorescence. After the injection of mouse antigen loaded bone marrow-derived antigen imDCs with a homogenetic background, mouse nucleoprotein immune with a homogenetic background was carried out. The results were compared against the simple mouse nucleoprotein immune model with a homogenic background. The 24-h urine protein, serum antinuclear antibody and anti-ds-DNA antibodies of the simple mouse model were lower compared to group S1. The CD4(+)CD25(+) cell percentage of spleen was higher in the simple mouse model compared to group S1. In the spleen, the number of lymphocyte CD8(+) cells declined, whereas the number of CD4(+) cells increased. In conclusion, after autoantigen uptake, imDCs are able to induce immune tolerance to the antigen by reinfusion, which appears to prevent or mitigate systemic lupus erythematosus-like illness.


Assuntos
Autoantígenos/imunologia , Células Dendríticas/transplante , Lúpus Eritematoso Sistêmico/terapia , Baço/imunologia , Animais , Contagem de Linfócito CD4 , Células Cultivadas , Células Dendríticas/imunologia , Modelos Animais de Doenças , Lúpus Eritematoso Sistêmico/imunologia , Lúpus Eritematoso Sistêmico/patologia , Camundongos , Camundongos Endogâmicos BALB C , Tolerância ao Transplante
15.
Epidemiol Infect ; 141(12): 2663-70, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23461984

RESUMO

The relationship between sexually transmitted infections (STIs) and prostate cancer (PC) remains inconclusive. Moreover, all such studies to date have been conducted in Western populations. This study aimed to investigate the risk of PC following STI using a population-based matched-cohort design in Taiwan. The study cohort comprised 1055 patients with STIs, and 10 550 randomly selected subjects were used as a comparison cohort. Cox proportional hazards regression analysis revealed that the hazard ratio for PC during the 5-year follow-up period for patients with a STI was 1.95 (95% confidence interval 1.18-3.23), that of comparison subjects after adjusting for urbanization level, geographical region, monthly income, hypertension, diabetes, hyperlipidaemia, obesity, chronic prostatitis, history of vasectomy, tobacco use disorder, and alcohol abuse. We concluded that the risk of PC was higher for men who were diagnosed with a STI in an Asian population.


Assuntos
Neoplasias da Próstata/epidemiologia , Infecções Sexualmente Transmissíveis/complicações , Adulto , Idoso , Idoso de 80 Anos ou mais , Povo Asiático , Estudos de Coortes , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Medição de Risco , Taiwan/epidemiologia
16.
Phys Rev E Stat Nonlin Soft Matter Phys ; 76(4 Pt 1): 041913, 2007 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17995032

RESUMO

The predator-prey-type ecosystem is investigated, taking into account the time-delay effect of the prey population on the predator population, as well as random variations in the birth rate of the prey and the death rate of the predators. The stochastic averaging procedure is applied to obtain the probability distributions of the predator and prey populations at the state of statistical stationarity. It is found that two system parameters, quantifying the effects of prey self-competition and the time delay, respectively, play the most important roles. Results are also obtained from Monte Carlo simulations to compare with the analytical results.


Assuntos
Biofísica/métodos , Ecossistema , Animais , Meio Ambiente , Cadeia Alimentar , Modelos Estatísticos , Método de Monte Carlo , Dinâmica Populacional , Comportamento Predatório , Probabilidade , Processos Estocásticos , Fatores de Tempo
18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 70(4 Pt 1): 041910, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15600438

RESUMO

A stochastic Lotka-Volterra-type model for the interaction between the preys and the predators in a random environment is investigated. A self-competition mechanism within the prey population itself is also included. The effect of a random environment is modeled as random variations in the birth rate of the preys and the death rate of the predators. The stochastic averaging procedure of Stratonovich and Khasminskii is applied to obtain the probability distributions of the system state variables at the state of statistical stationarity. Asymptotic behaviors of the system variables are discussed, and the mean transition time from an initial state to a critical state is obtained. Effects on the ecosystem behaviors of the self-competition term, of the random variation in the prey birth rate, and of the random variation in the predator death rate are investigated.


Assuntos
Evolução Biológica , Ecossistema , Modelos Biológicos , Dinâmica Populacional , Comportamento Predatório/fisiologia , Animais , Coeficiente de Natalidade , Simulação por Computador , Humanos , Modelos Estatísticos , Seleção Genética , Processos Estocásticos , Análise de Sobrevida
19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 70(2 Pt 2): 027104, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15447620

RESUMO

The transient behavior of a Brownian motor is investigated for more detailed particle transport occurring therein. The asymmetric nature of the time-dependent mean particle velocity is examined during the transition between two different levels of thermal noise. The possibility of current inversion is also investigated. It is found that the detailed shape of the asymmetric potential is crucial for such an inversion to occur.

20.
Naturwissenschaften ; 89(5): 187-200, 2002 May.
Artigo em Inglês | MEDLINE | ID: mdl-12135084

RESUMO

A brief introduction is first given of the history of the technical field of random vibration, tracing back to the works of physicists since the beginning of the twentieth century. This is then followed by an account of more recent developments, with emphasis on nonlinear and quasi-nonlinear systems, and on analytical solutions for the associated Fokker-Planck equation and the generalized Pontryagin equation. The governing equation of a quasi-nonlinear system is linear, but with one or more randomly varying coefficients. The techniques for finding exact probability solutions, approximate probability solutions, conditions for motion stability, and the failure probability and statistics of a system are discussed.

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