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TiO_(2)/WO_(3)heterogeneous structures prepared by electrospinning and sintering steps:Characterization and analysis of the impedance variation to humidity

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Journal of Advanced Ceramics 2019年第2期8卷 238-246页

作者： Evando S.ARAuJO victor n.S.LEAO Research Group on Electrospinning and nanotechnology Applications(GPEA-nano) Department of Materials ScienceUniversidade Federal do Vale do Sao Francisco

Relative humidity(RH) is a critical environmental variable for transportation and storage of products and for the quality guarantee of several other production processes and services. Heterogeneous structures prepared from the selective semiconductor oxides may improve the sensitivity to humidity due to the better electronic and surface properties, when compared to pristine oxides. This work shows an alternative fabrication route for producing titanium dioxide/tungsten trioxide(TiO2/WO3) heterogeneous structures(by electrospinning and sintering) for potential application on the RH detection. The microstructural properties of the materials were analyzed by scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDS), X-ray diffraction, and Raman spectroscopy. The electrical characterization of the structures was performed by electrical impedance spectroscopy in RH range of 10%–100%. Results indicated a p-to n-type conduction transition at around 30%–40% RH for all tested settings. The analysis of the impedance signature to humidity showed that the amount of fiber layers on the electrode and working temperature are important parameters to improve the humidity sensing of the TiO2/WO3 systems.

关键词： electrospinning heterogeneous structures preparation relative humidity semiconductors

Brain-derived neurotrophic factor signaling in the neuromuscular junction during developmental axonal competition and synapse elimination

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neural Regeneration Research 2025年第2期20卷 394-401页

作者： Josep Tomàs Víctor Cilleros-Mañé Laia Just-Borràs Marta Balanyà-Segura Aleksandra Polishchuk Laura nadal Marta Tomàs Carolina Silvera-Simón Manel M.Santafé Maria A.Lanuza Unitat d’Histologia i neurobiologia(UHneurob) Facultat de Medicina i Ciències de la SalutUniversitat Rovira i VirgiliReusSpain

During the development of the nervous system,there is an overproduction of neurons and *** competition between neighboring nerve endings and synapses performing different activity levels leads to their elimination or *** have extensively studied the involvement of the brain-derived neurotrophic factor-Tropomyosin-related kinase B receptor neurotrophic retrograde pathway,at the neuromuscular junction,in the axonal development and synapse elimination process versus the synapse *** purpose of this review is to describe the neurotrophic influence on developmental synapse elimination,in relation to other molecular pathways that we and others have found to regulate this *** particular,we summarize our published results based on transmitter release analysis and axonal counts to show the different involvement of the presynaptic acetylcholine muscarinic autoreceptors,coupled to downstream serine-threonine protein kinases A and C(PKA and PKC)and voltage-gated calcium channels,at different nerve endings in developmental *** dynamic changes that occur simultaneously in several nerve terminals and synapses converge across a postsynaptic site,influence each other,and require careful studies to individualize the mechanisms of specific *** describe an activity-dependent balance(related to the extent of transmitter release)between the presynaptic muscarinic subtypes and the neurotrophin-mediated TrkB/p75nTR pathways that can influence the timing and fate of the competitive interactions between the different axon *** downstream displacement of the PKA/PKC activity ratio to lower values,both in competing nerve terminals and at postsynaptic sites,plays a relevant role in controlling the elimination of supernumerary ***,calcium entry through L-and P/Q-subtypes of voltage-gated calcium channels(both channels are present,together with the n-type channel in developing nerve terminals)contributes to red

关键词： acetylcholine release adenosine receptors axonal competition brain-derived neurotrophic factor calcium channels motor end-plate muscarinic acetylcholine receptors postnatal synapse elimination serine kinases tropomyosin-related kinase receptorB

Resilience by design:How nature,nurture,environment,and microbiome mitigate stress and allostatic load

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World Journal of Psychiatry 2023年第5期13卷 144-159页

作者： Souhad Chbeir victor Carrión Department of Psychiatry and Behavioral Sciences School of MedicineStanford UniversityStanfordCA 94305United States

Resilience to psychological stress is defined as adaption to challenging life experiences and not the absence of adverse life *** of resilience include personality traits,genetic/epigenetic modifications of genes involved in the stress response,cognitive and behavioral flexibility,secure attachment with a caregiver,social and community support systems,nutrition and exercise,and alignment of circadian rhythm to the natural light/dark ***,resilience is a dynamic and flexible process that continually evolves by the intersection of different domains in human’s life;biological,social,and *** objective of this minireview is to summarize the existing knowledge about the multitude factors and molecular alterations that result from resilience to stress *** the multiple contributing factors in building resilience,we set out a goal to identify which factors were most supportive of a causal role by the current *** focused on resilience-related molecular alterations resulting from mind-body homeostasis in connection with psychosocial and environmental *** conclude that there is no one causal factor that differentiates a resilient person from a vulnerable ***,building resilience requires an intricate network of positive experiences and a healthy lifestyle that contribute to a balanced mind-body ***,a holistic approach must be adopted in future research on stress response to address the multiple elements that promote resilience and prevent illnesses and psychopathology related to stress allostatic load.

关键词： stress load alignment

Formation of diffuse and spark discharges between two needle electrodes with the scattering of particles

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Plasma Science and Technology 2024年第9期26卷 32-39页

作者： victor F TARASEnKO Dmitry V BELOPLOTOV Alexei n PAnCHEnKO Dmitry A SOROKIn Institute of High Current Electronics Siberian BranchRussian Academy of SciencesTomsk 634055Russia national Research Tomsk State University Tomsk 634050Russia

The development of a nanosecond discharge in a pin-to-pin gap filled with air at atmospheric pressure has been studied with high temporal and spatial resolutions from a breakdown start to the spark *** and negative nanosecond voltage pulses with an amplitude of tens of kilovolts were ***-resolved images of the discharge development were taken with a fourchannel Intensified Charge Coupled Device(ICCD)*** minimum delay between the camera channels could be as short as≈0.1 *** made it possible to study the gap breakdown process with subnanosecond *** was observed that a wide-diameter streamer develops from the high-voltage pointed *** ionization processes near the grounded pin electrode started when the streamer crossed half of the *** bridging the gap by the streamer,a diffuse discharge was *** development of spark leaders from bright spots on the surface of the pointed electrodes was observed at the next *** was found that the rate of development of the spark leader is an order of magnitude lower than that of the wide-diameter *** thin luminous tracks were observed against the background of a discharge plasma *** has been established that the tracks are adjacent to brightly glowing spots on the electrodes and are associated with the flight of small particles.

关键词： needle electrodes short voltage pulses atmospheric air streamer breakdown diffuse and spark discharges scattering metal particles

Long-term changes in the plant ecology of an African savanna landscape and the implications for ecosystem theory and conservation management

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Ecological Processes 2021年第1期10卷 213-224页

作者： David Western victor n.Mose David Maitumo Caroline Mburu African Conservation Centre P.O.Box 15289-00509NairobiKeny

Background:Studies of the African savannas have used national parks to test ecological theories of natural ecosystems,including equilibrium,non-equilibrium,complex adaptive systems,and the role of top-down and bottom-up physical and biotic *** such studies have excluded the impact of pastoralists in shaping grassland ecosystems and,over the last half century,the growing human impact on the world’s *** mounting human impact calls for selecting indicators and integrated monitoring methods able to track ecosystem changes and the role of natural and human *** study draws on five decades of monitoring the Amboseli landscape in southern Kenya to document the declining role of natural agencies in shaping plant ecology with rising human ***:We show that plant diversity and productivity have declined,biomass turnover has increased in response to a downsizing of mean plant size,and that ecological resilience has declined with the rising probability of extreme shortfalls in pasture *** signature of rainfall and physical agencies in driving ecosystem properties has decreased sharply with growing human *** compare the Amboseli findings to the long-term studies of Kruger and Serengeti national parks to show that the human influence,whether by design or default,is increasingly shaping the ecology of savanna *** look at the findings in the larger perspective of human impact on African grasslands and the world rangelands,in general,and discuss the implications for ecosystem theory and conservation policy and ***:The Amboseli study shows the value of using long-term integrated ecological monitoring to track the spatial and temporal changes in the species composition,structure,and function of rangeland ecosystems and the role of natural and human agencies in the process of *** study echoes the widespread changes underway across African savannas and world’s rangelands,concluding that some level

关键词： Savannas Plants Human dominance Macroecology Conservation

Phasor-domain Dynamic Model of Asymmetric Current Injection Controller for Converter-interfaced Generator

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Journal of Modern Power Systems and Clean Energy 2021年第6期9卷 1269-1278页

作者： victor A.F.Almeida Glauco n.Taranto José M.T.Marinho Electrical Engineering Department of the Federal University of Rio de Janeiro(COPPE/UFRJ) Petrobras S.A.

This paper presents a controller model of asymmetric current injection for converter-interfaced generators suitable for root-mean-square(RMS)phasor-domain,fundamentalfrequency,three-phase,and dynamic simulation *** effectiveness of the proposed controller is assessed with simulations in test systems with high percentage of converter-interfaced *** simulations focus on the operation of protection relays that use negative-sequence quantities in their directional *** paper also presents and compares two strategies to limit reactive negative-sequence currents,and active and reactive positive-sequence currents.A tutorial test system and a regional system part of the actual Brazilian Interconnected Power System are used to assess the correctness of the proposed controller in three-phase fundamental-frequency RMS dynamic simulations.

关键词： Converter-interfaced generator three-phase model power system protection negative-sequence current injection negative-sequence current protection unbalanced fault three-phase root-mean-square(RMS)dynamic simulation

Influence of biomass burning on ozone levels in the Megalopolis of Central Mexico during the COVID-19 lockdown

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Journal of Environmental Sciences 2024年第9期143卷 99-115页

作者： victor Almanza Luis Gerardo Ruiz-Suárez Ricardo Torres-Jardón Agustín García-Reynoso Iván Y.Hernández-Paniagua Institute for Atmospheric Sciences and Climate Change National Autonomous University of MexicoCoyoacan 04510Mexico CityMexico

The massive reductions in anthropogenic emissions resulting from the COVID-19 lockdown provided a unique opportunity to evaluate the effect of mitigation measures aiming to abate air *** Mexico,the total lockdown period took place during the dry-hot season when biomass burning activity is ***,we investigate the role of biomass burning emissions on regional ozone levels in the Megalopolis of Central *** studied period covers the lockdown phases 2 and 3,and the first month of the new *** applied a factor separation technique and process analysis to estimate the pure and synergistic contributions of emission reductions under lockdown and that from biomass burning to daily ozone maximum concentrations in 7 metropolitan areas of different states in the *** results revealed that biomass burning plumes likely masked the effect of massive reductions from mobile emissions,impacted the PBL development during phase 3 and favored transition and mixed nO_(x)-limited and VOC-limited regional *** contributed to increased ozone production in the middle to lower PBL by changing the regional background levels which potentially could bias high ozone production efficiency *** the Megalopolis contribution to economic and societal development at national scale,our study suggests that ozone mitigation measures during the dry-hot season targeting mainly mobile emissions will likely be offset by biomass burning plumes.A regional and synergic policy aiming to control biomass burning would help to reduce the occurrence of high ozone levels in Central Mexico with the co-benefit of tackling short-lived climate pollutants.

关键词： COVID-19 Mexico Megalopolis Ozone Factor Separation Process Analysis

Improved shape hardening function for bounding surface model for cohesive soils

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第4期6卷 328-337页

作者： Andrés nieto-Leal victor n.Kaliakin Department of Civil & Environmental Engineering University of Delaware Newark DE 19716 USA Department of Civil Engineering Universidad Militar Nueva Granada Bogotá Colombia

A shape hardening function is developed that improves the predictive capabilities of the generalized bounding surface model for cohesive soils, especially when applied to overconsolidated specimens. This improvement is realized without any changes to the simple elliptical shape of the bounding surface, and actually reduces the number of parameters associated with the model by one.

关键词： Constitutive model Bounding surface plasticity Shape hardening function Clay

Efficiency and productivity analysis of vegetable farming within root and tuber-based systems in the humid tropics of Cameroon

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Journal of Integrative Agriculture 2017年第8期16卷 1865-1873页

作者： Ajapnwa Akamin Jean-Claude Bidogeza Jules Rene Minkoua n victor Afari-Sefa Faculty of Economics and Management University of Yaounde IIP.O.Box 18 Soa YaoundeCameroon Liaison Office Cameroon West and Central AfricaWorld Vegetable CenterP.O.Box 2008 Messa YaoundeCameroon Samanko Research Station West and Central AfricaWorld Vegetable CenterP.O.Box 320 BemakoMali

The study analyzes the technical efficiency of vegetable farmers in root and tuber-based farming systems within selected sites of the humid tropics of Cameroon. Multistage sampling was used to collect primary data from a cross-section of vegetable farmers drawn from eight selected sites in Santa sub division, northwest region of Cameroon. Stochastic frontier analysis was used to estimate the technical efficiency of vegetable farmer and to examine its determinants. The results showed that farmyard manure was the most productive factor input, followed by farm equipment and labor. The mean technical efficiency level was 67%, revealing production shortfalls and indicating possibilities of significantly increasing production with the current input Jevels. Female, as well as more educated farmers were found to be significantly more efficient than their counterparts. The results also showed that farmers become less technical efficient as farm sizes become larger. Our study findings suggest that smallholder farmers＇ access to manure, farm implements, and increased women participation in vegetable farming, will produce huge payoffs in vegetable production efficiency in Cameroon.

关键词： technical efficiency vegetable productivity farming systems intensification crop diversification stochasticfrontier analysis