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1.
Nat Commun ; 13(1): 6410, 2022 10 27.
Artículo en Inglés | MEDLINE | ID: mdl-36302781

RESUMEN

Low-lying island nations like Indonesia are vulnerable to sea level Height EXtremes (HEXs). When compounded by marine heatwaves, HEXs have larger ecological and societal impact. Here we combine observations with model simulations, to investigate the HEXs and Compound Height-Heat Extremes (CHHEXs) along the Indian Ocean coast of Indonesia in recent decades. We find that anthropogenic sea level rise combined with decadal climate variability causes increased occurrence of HEXs during 2010-2017. Both HEXs and CHHEXs are driven by equatorial westerly and longshore northwesterly wind anomalies. For most HEXs, which occur during December-March, downwelling favorable northwest monsoon winds are enhanced but enhanced vertical mixing limits surface warming. For most CHHEXs, wind anomalies associated with a negative Indian Ocean Dipole (IOD) and co-occurring La Niña weaken the southeasterlies and cooling from coastal upwelling during May-June and November-December. Our findings emphasize the important interplay between anthropogenic warming and climate variability in affecting regional extremes.


Asunto(s)
El Niño Oscilación del Sur , Viento , Estaciones del Año , Indonesia , Océano Índico
2.
West Afr J Med ; 38(9): 851-858, 2021 09 30.
Artículo en Inglés | MEDLINE | ID: mdl-34676741

RESUMEN

BACKGROUND: Body temperature is an important vital sign in clinical practice which can be measured via electronic contact thermometers and infrared non-contact thermometers. OBJECTIVE: To compare temperature readings taken by non contact infrared thermometer with the conventional digital axillary, rectal and oral temperature readings as well as the influence of environmental temperature on noncontact infrared thermometer readings. METHODOLOGY: A prospective study carried out in the Paediatric outpatient clinic of the Rivers State University Teaching Hospital, Nigeria from September 2020 to December 2020. Infrared noncontact forehead and jugular temperatures along with contact axillary, oral and rectal temperatures at a recorded atmospheric temperature and pressure were measured. Data collected was analysed. RESULTS: A total of 247 children aged 1month to 16 years were enrolled, the mean differences of the temperature pairs of contact and non-contact thermometry ranged from 0.45 - 0.77°C (1.64, -1.81°C) 95% LoA. The highest mean difference was found between infrared forehead and axillary [MD; 0.45(1.64,-0.73°C) 95%LoA] temperatures. There was a significant positive correlation between the mean difference of infrared forehead/ rectal temperature and atmospheric temperature (r = 0 .211 p = 0.029). Linear regression model showed that infrared forehead temperature of 37.1°C was equivalent to rectal temperature of 38°C and axillary of 37.4°C which is the standard cut off for fever. Infrared jugular of 37.2°C was equivalent to rectal of 38°C and axillary temperature of 37.4°C was equivalent to infrared jugular of 37.03°C all at a mean atmospheric temperature of 28.3±1.8°C. CONCLUSION: The mean difference by which infrared noncontact thermometry predicts core temperatures may differ based on atmospheric temperature. Infrared non-contact forehead thermometer reading of 37.1°C could be considered as the fever cut off for non-contact forehead thermometry in Nigeria in regions where the mean atmospheric temperature is 28.3±1.8°C.


CONTEXTE: La température corporelle est un signe vital important dans la pratique clinique qui peut être mesurée à l'aide de thermomètres électroniques à contact et de thermomètres infrarouges sans contact. OBJECTIF: Comparer les lectures de température prises par un thermomètre infrarouge sans contact avec les lectures de température axillaire, rectale et buccale numériques conventionnelles, ainsi que l'influence de la température ambiante sur les lectures de thermomètre infrarouge sans contact. MÉTHODOLOGIE: Une étude prospective réalisée dans la clinique pédiatrique ambulatoire du Rivers State University Teaching Hospital, au Nigéria, de septembre 2020 à décembre 2020. Températures infrarouges sans contact du front et de la jugulaire ainsi que des températures axillaire, orale et rectale de contact à une température et une pression atmosphériques enregistrées ont été mesurés. Les données recueillies ont été analysées. RÉSULTATS: Un total de 247 enfants âgés de 1 mois à 16 ans ont été inclus, les différences moyennes des paires de températures de la thermométrie avec contact et sans contact variaient de 0,45 à 0,77°C (1,64, -1,81°C) 95 % LoA. La différence moyenne la plus élevée a été trouvée entre l'infrarouge frontal et axillaire [MD; 0,45 (1,64,-0,73°C) 95 % LoA]. Il y avait une corrélation positive significative entre la différence moyenne de la température infrarouge frontale/rectale et la température atmosphérique (r = 0,211 p = 0,029). Le modèle de régression linéaire a montré que la température frontale infrarouge de 37,1 °C était équivalente à la température rectale de 38 °C et axillaire de 37,4 °C, qui est la valeur seuil standard pour la fièvre. L'infrarouge jugulaire de 37,2°C équivalait à une température rectale de 38°C et la température axillaire de 37,4°C équivalait à l'infrarouge jugulaire de 37,03°C, le tout à une température atmosphérique moyenne de 28,3±1,8°C. CONCLUSION: La différence moyenne par laquelle la thermométrie infrarouge sans contact prédit les températures centrales peut différer en fonction de la température atmosphérique. La lecture du thermomètre frontal infrarouge sans contact de 37,1 °C pourrait être considérée comme le seuil de fièvre pour la thermométrie frontale sans contact au Nigeria dans les régions où la température atmosphérique moyenne est de 28,3 ± 1,8 °C. Mots clés: Thermomètre sans contact, température rectale, température axillaire, buccale, front, jugulaire, température atmosphérique.


Asunto(s)
Temperatura Corporal , Termómetros , Niño , Fiebre/diagnóstico , Humanos , Estudios Prospectivos , Temperatura
3.
Clin Transl Oncol ; 23(4): 783-787, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32789774

RESUMEN

PURPOSE: The mechanisms of brain metastasis are incompletely understood. Circulating tumor cells travel to the right heart and through the pulmonary circulation, where they may become lung metastases, and can circulate further to the left heart and brain. In patients who develop brain metastases without lung involvement, we hypothesized that cancer cells may travel directly from the right atrium to left atrium via a patent foramen ovale (PFO), akin to paradoxical embolism. If the prevalence of PFO is greater in these individuals compared to the general population (20-30%), PFO may play a role in brain metastasis, and prophylactic closure may provide benefit. Accordingly, we investigated the prevalence of PFO in patients with brain metastases without prior lung involvement. METHODS: We prospectively identified patients with brain metastases from a non-lung primary cancer with no preceding or concurrent lung involvement. Nine eligible participants underwent a transcranial Doppler study with intravenous agitated saline to assess for PFO. RESULTS: Among nine participants, primary cancers were breast (n = 6), upper gastrointestinal (n = 2), and thyroid (n = 1). A positive bubble study was identified in 2/9 (22.2%) participants: one female with breast cancer and one male with duodenal adenocarcinoma. No participants developed lung metastases on subsequent chest imaging. CONCLUSION: In this prospective pilot study, we found a similar prevalence of PFO in patients who developed brain metastases without preceding lung involvement compared to estimates for the general population. Through a larger study is needed, the development of brain metastases in these individuals may primarily reflect tumor-specific biological factors diecting metastasis organotropism.


Asunto(s)
Neoplasias Encefálicas/secundario , Foramen Oval Permeable/epidemiología , Adenocarcinoma/secundario , Adulto , Anciano , Anciano de 80 o más Años , Neoplasias de la Mama/patología , Circulación Cerebrovascular/fisiología , Neoplasias Duodenales/patología , Neoplasias Esofágicas/patología , Femenino , Foramen Oval Permeable/complicaciones , Foramen Oval Permeable/diagnóstico por imagen , Foramen Oval Permeable/patología , Neoplasias Gastrointestinales/patología , Humanos , Masculino , Persona de Mediana Edad , Proyectos Piloto , Prevalencia , Estudios Prospectivos , Circulación Pulmonar/fisiología , Flujo Sanguíneo Regional/fisiología , Solución Salina/administración & dosificación , Cáncer Papilar Tiroideo/secundario , Neoplasias de la Tiroides/patología , Ultrasonografía Doppler Transcraneal , Maniobra de Valsalva
4.
Proc Natl Acad Sci U S A ; 117(31): 18355-18358, 2020 08 04.
Artículo en Inglés | MEDLINE | ID: mdl-32690712

RESUMEN

Extensive empirical evidence suggests that there is a maximal number of people with whom an individual can maintain stable social relationships (the Dunbar number). We argue that this arises as a consequence of a natural phase transition in the dynamic self-organization among N individuals within a social system. We present the calculated size dependence of the scaling properties of complex social network models to argue that this collective behavior is an enhanced form of collective intelligence. Direct calculation establishes that the complexity of social networks as measured by their scaling behavior is nonmonotonic, peaking around 150, thereby providing a theoretical basis for the value of the Dunbar number. Thus, we establish a theory-based bridge spanning the gap between sociology and psychology.


Asunto(s)
Modelos Teóricos , Conducta Social , Red Social , Algoritmos , Procesos de Grupo , Humanos , Relaciones Interpersonales
5.
Epidemiol Psychiatr Sci ; 29: e38, 2019 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-31142398

RESUMEN

AIMS: Human trafficking is a crime and a human rights violation that involves various and simultaneous traumatic events (sexual and physical violence, coercion). Yet, it is unknown how the patterning of violence and coercion affects the mental health of female and male trafficking survivors. METHODS: We conducted a cross-sectional study using a sample of 1015 female and male survivors of trafficking who received post-trafficking assistance services in Cambodia, Thailand or Vietnam. We assessed symptoms of anxiety and depression with the Hopkins Symptoms Checklist and symptoms of post-traumatic stress disorder (PTSD) with the Harvard Trauma Questionnaire. Violence was measured with questions from the World Health Organization International Study on Women's Health. Latent class analysis (LCA) was used to identify distinct patterns of violence and coercion in females and males. Novel multi-step mixture modelling techniques were employed to assess the association of the emergent classes with anxiety, depression and PTSD in females and males. RESULTS: LCA identified two distinct classes of violence and coercion experiences in females (class I: severe sexual and physical violence and coercion (20%); class II: sexual violence and coercion (80%)) and males (class I: severe physical violence and coercion (41%); class II: personal coercion (59%)). Females in class I had a two-fold increase in the odds of anxiety (OR = 2.10; 95% CI: 1.57-2.81) and PTSD (OR = 2.07; 95% CI: 1.03-4.17) compared with females in class II, but differences in the prevalence of anxiety, depression and PTSD were not significant when comparing males in class I to class II. CONCLUSIONS: Specific patterns of violence and coercion provide a more in-depth understanding of the role of gender in the experience of violence and coercion and its association with mental health in survivors of trafficking. This information could be useful to target comprehensive mental health services for female and male trafficking survivors.


Asunto(s)
Ansiedad/psicología , Coerción , Víctimas de Crimen/psicología , Depresión/psicología , Trata de Personas/psicología , Trastornos por Estrés Postraumático/psicología , Violencia/psicología , Adolescente , Adulto , Ansiedad/epidemiología , Cambodia/epidemiología , Niño , Víctimas de Crimen/estadística & datos numéricos , Depresión/epidemiología , Femenino , Trata de Personas/estadística & datos numéricos , Humanos , Análisis de Clases Latentes , Masculino , Salud Mental , Delitos Sexuales/psicología , Delitos Sexuales/estadística & datos numéricos , Trastornos por Estrés Postraumático/epidemiología , Sobrevivientes , Tailandia/epidemiología , Vietnam/epidemiología , Violencia/estadística & datos numéricos
6.
BMC Public Health ; 19(1): 90, 2019 Jan 19.
Artículo en Inglés | MEDLINE | ID: mdl-30660198

RESUMEN

BACKGROUND: Globally, diarrhea is a leading cause of child morbidity and mortality. Although latrines are integral for reducing enteric pathogen transmission, several studies have shown no evidence that latrine ownership improved child health. There are a number of explanations for these results. One explanation is that latrine access does not equate to latrine use. Latrine use, however, is difficult to accurately ascertain, as defecation behavior is often stigmatized. To address this measurement issue, we measure latrine use as a latent variable, indicated by a suite of psychosocial variables. METHODS: We administered a survey of 16 defecation-related psychosocial questions to 251 individuals living in rural Ecuador. We applied latent class analysis (LCA) to these data to model the probability of latrine use as a latent variable. To account for uncertainty in predicted latent class membership, we used a pseudo-class approach to impute five different probabilities of latrine use for each respondent. Via regression modeling, we tested the association between household sanitation and each imputed latrine use variable. RESULTS: The optimal model presented strong evidence of two latent classes (entropy = 0.86): consistent users (78%) and inconsistent users (22%), predicted by 5 of our 16 psychosocial variables. There was no evidence of an association between the probability of latrine use, predicted from the LCA, and household access to basic sanitation (OR = 1.1, 95% CI = 0.6-2.1). This suggests that home access to a sanitation facility may not ensure the use of the facility for every family member at all times. CONCLUSION: Effective implementation and evaluation of sanitation programs requires accurate measurement of latrine use. Psychosocial variables, such as norms, perceptions, and attitudes may provide robust proxy-measures. Future longitudinal studies will help to strengthen the use of these surrogate measures, as many of these factors may be subject to secular trends. Additionally, subgroup analyses will elucidate how our  proxy indicators of latrine defecation vary by individual-level characteristics.


Asunto(s)
Análisis de Clases Latentes , Propiedad/estadística & datos numéricos , Saneamiento/estadística & datos numéricos , Cuartos de Baño/estadística & datos numéricos , Adulto , Niño , Salud Infantil/estadística & datos numéricos , Defecación , Ecuador , Composición Familiar , Femenino , Humanos , Masculino , Probabilidad , Población Rural/estadística & datos numéricos , Estereotipo , Encuestas y Cuestionarios , Adulto Joven
8.
HIV Med ; 19 Suppl 1: 5-10, 2018 02.
Artículo en Inglés | MEDLINE | ID: mdl-29488707

RESUMEN

OBJECTIVES: The objective of the article is to provide an overview of the results of the HepHIV 2017 Conference organized by the HIV in Europe initiative under the Maltese EU Presidency in January 2017. METHODS: A thourough review of all conference presentations (oral and poster presentations) was performed to retrieve the key outcomes of the conference. RESULTS: The key result from the conference was a call to action summarising key priorities in HIV and viral hepatitis testing and linkage to care. This included improving monitoring of viral hepatitis and HIV, mixing testing strategies and ensuring policy support. The important contribution and outcomes of EU funded projects OptTEST and EuroHIVEdat was highlighted. CONCLUSION: An integrated approach to earlier testing and linkage to care across diseases is needed in Europe and the HepHIV conferences create an important forum to reach this aim.


Asunto(s)
Infecciones por VIH/complicaciones , Infecciones por VIH/diagnóstico , Prioridades en Salud , Hepatitis Viral Humana/complicaciones , Hepatitis Viral Humana/diagnóstico , Investigación , Diagnóstico Precoz , Unión Europea , Humanos
9.
Addict Behav ; 79: 17-23, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29241081

RESUMEN

OBJECTIVES: We used two waves of National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) data and examined whether the misuse of prescription tranquilizers or sedatives at Wave 1 was associated with either continued misuse, tranquilizer/sedative use disorder, or other substance use disorder (SUD) at Wave 2. METHODS: Prospective data were analyzed from structured diagnostic interviews using the Alcohol Use disorders and Associated Disabilities Interview Schedule: DSM-IV Version (AUDADIS-DSM-IV). A nationally representative sample of 34,653 of U.S. adults, 18years or older at Wave 1 (2001-2002), were re-interviewed at Wave 2 (2004-2005). After applying the survey weights, the sample represented a population that was 52% female, 71% White, 12% Hispanic, 11% African American, 4% Asian and 2% Native American or other. RESULTS: An estimated 79% of adults who engaged in tranquilizer or sedative misuse at Wave 1 had stopped using these drugs at Wave 2. Only a small percentage (4.3%) of misusers at Wave 1 had a tranquilizer or sedative use disorder at Wave 2. However, 45% (45.0%) of misusers at Wave 1 had at least one other SUD at Wave 2. Among those in remission from a sedative or tranquilizer use disorder at Wave 1, 4.8% had a tranquilizer or sedative use disorder while 34.7% had at least one other SUD at Wave 2. CONCLUSIONS: Most adults who engaged in the misuse of prescription tranquilizers or sedatives ceased using within 3years; however, their prior misuse was associated with higher prevalence of having a SUD three years later.


Asunto(s)
Hipnóticos y Sedantes , Mal Uso de Medicamentos de Venta con Receta/estadística & datos numéricos , Trastornos Relacionados con Sustancias/epidemiología , Tranquilizantes , Adolescente , Adulto , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Prevalencia , Estados Unidos/epidemiología , Adulto Joven
10.
Oncogene ; 36(43): 6049-6058, 2017 10 26.
Artículo en Inglés | MEDLINE | ID: mdl-28759044

RESUMEN

Glioblastomas represent the most aggressive glioma grade and are associated with a poor patient prognosis. The current standard of care, consisting of surgery, radiation and chemotherapy, only results in a median survival of 14 months, underscoring the importance of developing effective new therapeutic strategies. Among the challenges in treating glioblastomas are primary resistance and the rapid emergence of recurrent disease, which can result from tumor cell-intrinsic mechanisms in addition to tumor microenvironment (TME)-mediated extrinsic resistance. Using a PDGF-B-driven proneural glioma mouse model, we assessed a panel of tyrosine kinase inhibitors with different selectivity profiles. We found that PLX3397, an inhibitor of colony stimulating factor-1 receptor (CSF-1R), blocks glioma progression, markedly suppresses tumor cell proliferation and reduces tumor grade. By contrast, the multi-targeted tyrosine kinase inhibitors dovitinib and vatalanib, which directly target tumor cells, exert minimal anti-tumoral effects in vivo, despite killing glioma cells in vitro, suggesting a TME-mediated resistance mechanism may be involved. Interestingly, PLX3397 interferes with tumor-mediated education of macrophages and consequently restores the sensitivity of glioma cells to tyrosine kinase inhibitors in vivo in preclinical combination trials. Our findings thus demonstrate that microenvironmental alteration by CSF-1R blockade renders tumor cells more susceptible to receptor tyrosine kinase inhibition in a preclinical glioblastoma model, which may have important translational relevance.


Asunto(s)
Resistencia a Antineoplásicos/genética , Glioma/tratamiento farmacológico , Receptores de Factor Estimulante de Colonias de Granulocitos y Macrófagos/genética , Aminopiridinas/administración & dosificación , Animales , Becaplermina , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Modelos Animales de Enfermedad , Glioma/genética , Glioma/patología , Humanos , Ratones , Inhibidores de Proteínas Quinasas/administración & dosificación , Proteínas Proto-Oncogénicas c-sis/genética , Pirroles/administración & dosificación , Microambiente Tumoral/efectos de los fármacos
11.
Mol Cell Neurosci ; 80: 123-133, 2017 04.
Artículo en Inglés | MEDLINE | ID: mdl-28286294

RESUMEN

An important hallmark of various neurodegenerative disorders is the proliferation and activation of microglial cells, the resident immune cells of the central nervous system (CNS). Mice that lack multifunctional protein-2 (MFP2), the key enzyme in peroxisomal ß-oxidation, develop excessive microgliosis that positively correlates with behavioral deficits whereas no neuronal loss occurs. However, the precise contribution of neuroinflammation to the fatal neuropathology of MFP2 deficiency remains largely unknown. Here, we first attempted to suppress the inflammatory response by administering various anti-inflammatory drugs but they failed to reduce microgliosis. Subsequently, Mfp2-/- mice were treated with the selective colony-stimulating factor 1 receptor (CSF1R) inhibitor PLX5622 as microglial proliferation and survival is dependent on CSF1R signaling. This resulted in the elimination of >95% of microglia from control mice but only 70% of the expanded microglial population from Mfp2-/- mice. Despite microglial diminution in Mfp2-/- brain, inflammatory markers remained unaltered and residual microglia persisted in a reactive state. CSF1R inhibition did not prevent neuronal dysfunction, cognitive decline and clinical deterioration of Mfp2-/- mice. Collectively, the unaltered inflammatory profile despite suppressed microgliosis concurrent with persevering clinical decline strengthens our hypothesis that neuroinflammation importantly contributes to the Mfp2-/- phenotype.


Asunto(s)
Antiinflamatorios/uso terapéutico , Encefalitis , Gliosis/etiología , Proteína-2 Multifuncional Peroxisomal/deficiencia , Estimulación Acústica , Análisis de Varianza , Animales , Antiinflamatorios/farmacología , Antígenos de Diferenciación/metabolismo , Reacción de Prevención/efectos de los fármacos , Reacción de Prevención/fisiología , Proteínas de Unión al Calcio/metabolismo , Modelos Animales de Enfermedad , Encefalitis/complicaciones , Encefalitis/genética , Encefalitis/patología , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Potenciales Evocados Auditivos del Tronco Encefálico/genética , Conducta Exploratoria/efectos de los fármacos , Conducta Exploratoria/fisiología , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas de Microfilamentos/metabolismo , Fuerza Muscular/efectos de los fármacos , Fuerza Muscular/genética , Proteína-2 Multifuncional Peroxisomal/genética , Índice de Severidad de la Enfermedad
12.
Rev Sci Instrum ; 86(11): 113705, 2015 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-26628142

RESUMEN

In situ characterization of micro- and nanoscale defects in polycrystalline thin-film materials is required to elucidate the physics governing defect formation and evolution during photovoltaic device fabrication and operation. X-ray fluorescence spectromicroscopy is particularly well-suited to study defects in compound semiconductors, as it has a large information depth appropriate to study thick and complex materials, is sensitive to trace amounts of atomic species, and provides quantitative elemental information, non-destructively. Current in situ methods using this technique typically require extensive sample preparation. In this work, we design and build an in situ temperature stage to study defect kinetics in thin-film solar cells under actual processing conditions, requiring minimal sample preparation. Careful selection of construction materials also enables controlled non-oxidizing atmospheres inside the sample chamber such as H2Se and H2S. Temperature ramp rates of up to 300 °C/min are achieved, with a maximum sample temperature of 600 °C. As a case study, we use the stage for synchrotron X-ray fluorescence spectromicroscopy of CuIn(x)Ga(1-x)Se2 (CIGS) thin-films and demonstrate predictable sample thermal drift for temperatures 25-400 °C, allowing features on the order of the resolution of the measurement technique (125 nm) to be tracked while heating. The stage enables previously unattainable in situ studies of nanoscale defect kinetics under industrially relevant processing conditions, allowing a deeper understanding of the relationship between material processing parameters, materials properties, and device performance.

14.
Artículo en Inglés | MEDLINE | ID: mdl-25679682

RESUMEN

We study a nonlinear Langevin equation describing the dynamic variable X(t), the mean field (order parameter) of a finite size complex network at criticality. The conditions under which the autocorrelation function of X shows any direct connection with criticality are discussed. We find that if the network is prepared in a state far from equilibrium, X(0)=1, the autocorrelation function is characterized by evident signs of critical slowing down as well as by significant aging effects, while the preparation X(0)=0 does not generate evident signs of criticality on X(t), in spite of the fact that the same initial state makes the fluctuating variable η(t)≡sgn(X(t)) yield significant aging effects. These latter effects arise because the dynamics of η(t) are directly dependent on crucial events, namely the re-crossings of the origin, which undergo a significant aging process with the preparation X(0)=0. The time scale dominated by temporal complexity, aging, and ergodicity breakdown of η(t) is properly evaluated by adopting the method of stochastic linearization which is used to explain the exponential-like behavior of the equilibrium autocorrelation function of X(t).

15.
Phys Rev E Stat Nonlin Soft Matter Phys ; 90(5-1): 052815, 2014 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-25493842

RESUMEN

We consider a dual model of decision making, in which an individual forms its opinion based on contrasting mechanisms of imitation and rational calculation. The decision-making model (DMM) implements imitating behavior by means of a network of coupled two-state master equations that undergoes a phase transition at a critical value of a control parameter. The evolutionary spatial game, being a generalization of the prisoner's dilemma game, is used to determine in objective fashion the cooperative or anticooperative strategy adopted by individuals. Interactions between two sources of dynamics increases the domain of initial states attracted to phase transition dynamics beyond that of the DMM network in isolation. Additionally, on average the influence of the DMM on the game increases the final observed fraction of cooperators in the system.

16.
Phys Life Rev ; 10(3): 391-3, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23993639
17.
Biol Cybern ; 103(2): 167-74, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-20517616

RESUMEN

Inverse power-law behavior is known to be characteristic of adaptation, learning, and memory. Herein, we propose a phenomenological model of forgetting based on renewal theory that introduces a new psychophysical concept, chipping; discrete events that chip away at chunks of memory and thereby produce forgetting. The neural mechanism producing these chips is the 1/f-noise that is generically produced in complex neuronal networks.


Asunto(s)
Memoria , Humanos , Aprendizaje , Modelos Psicológicos
18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 81(3 Pt 1): 031909, 2010 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-20365772

RESUMEN

In recent studies a number of research groups have determined that human electroencephalograms (EEG) have scaling properties. In particular, a crossover between two regions with different scaling exponents has been reported. Herein we study the time evolution of diffusion entropy to elucidate the scaling of EEG time series. For a cohort of 20 awake healthy volunteers with closed eyes, we find that the diffusion entropy of EEG increments (obtained from EEG waveforms by differencing) exhibits three features: short-time growth, an alpha wave related oscillation whose amplitude gradually decays in time, and asymptotic saturation which is achieved after approximately 1 s. This analysis suggests a linear, stochastic Ornstein-Uhlenbeck Langevin equation with a quasiperiodic forcing (whose frequency and/or amplitude may vary in time) as the model for the underlying dynamics. This model captures the salient properties of EEG dynamics. In particular, both the experimental and simulated EEG time series exhibit short-time scaling which is broken by a strong periodic component, such as alpha waves. The saturation of EEG diffusion entropy precludes the existence of asymptotic scaling. We find that the crossover between two scaling regions seen in detrended fluctuation analysis (DFA) of EEG increments does not originate from the underlying dynamics but is merely an artifact of the algorithm. This artifact is rooted in the failure of the "trend plus signal" paradigm of DFA.


Asunto(s)
Potenciales de Acción/fisiología , Relojes Biológicos/fisiología , Encéfalo/fisiología , Diagnóstico por Computador/métodos , Electroencefalografía/métodos , Modelos Neurológicos , Red Nerviosa/fisiología , Simulación por Computador , Entropía , Humanos
19.
Water Sci Technol ; 60(5): 1249-55, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19717912

RESUMEN

Past irrigation research in Marlborough showed that reducing irrigation on grapes by up to 60% would not have any impact on yield, but that the timing of the irrigation might be important for maintenance of yields. A research trial was set up with Sauvignon blanc grapes planted in containers; periods of water stress were applied for three weeks at different times of the growing season. During the three years of the trial the post-flowering (PO-F) period was consistently most sensitive to water stress. At harvest time, the crop yields for the PO-F water-stressed vines were 55%, 72% and 90% of control yields for the three consecutive years, and the bunch weights were 59%, 84% and 95%. Berry weights for the PO-F water-stressed vines were 87%, 96% and 73% of the control values, although the second-year difference was not significant. In two years out of three, there was a trend for PO-F and pre-veraison (PR-V) water-stressed vines to have the lowest berry soluble solids contents ( degrees Brix), indicating a delay in maturity. We suggest that to use irrigation sustainably, it is safe to reduce water applications for most of the season, but that immediately after flowering, any water stress should be avoided. During the period leading up to veraison, some mild water stress can be applied.


Asunto(s)
Agricultura/métodos , Deshidratación , Frutas/anatomía & histología , Frutas/crecimiento & desarrollo , Estrés Fisiológico/efectos de los fármacos , Vitis/anatomía & histología , Vitis/crecimiento & desarrollo , Agua/farmacología , Flores/crecimiento & desarrollo , Frutas/efectos de los fármacos , Lluvia , Suelo , Factores de Tiempo , Vitis/efectos de los fármacos
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