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Stable gravastars： Guilfoyle＇s electrically charged solutions

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Chinese Physics C 2018年第11期42卷 120-130页

作者： ayan banerjee J.R. Villanueva Phongpichit Channuie Kimet Jusufi Department of Mathematics Jadavpur University Kolkata-700032 India Instituto de Fisica y Astronomia Facultad de Ciencias Universidad de Valparaiso Gran Bretana 1111 Valparaiso Chile School of Science Walailak University Nakhon Si Thammarat 80160 Thailand Physics Department State University of Tetovo Ilinden Street nn 1200 Macedonia

Compelling alternatives to black holes, namely, gravitational vacuum stars （gravastars）, which are multilayered compact objects, have been proposed to avoid a number of theoretical problems associated with event horizons and singularities. In this work, we construct a spherically symmetric thin-shell charged gravastar model where the vacuum phase transition between the de Sitter interior and the external Reissner-Nordstrom spacetime （RN） are matched at a junction surface, by using the cut-and-paste procedure. Gravastar solutions are found among the Guilfoyle exact solutions where the gravitational potential We and the electric potential field Ф obey a particular relation in a simple form a（b-εФ）^2＋b1, where a, b and bl are arbitrary constants. The simplest ansatz of Guilfoyle＇s solution is implemented by the following assumption： that the total energy density 8πρm＋Q^2/r^4 is constant, where Q（r） is the electric charge up to a certain radius r. We show that, for certain ranges of the parameters, we can avoid the horizon formation, which allows us to study the linearized spherically symmetric radial perturbations around static equilibrium solutions. To lend our solution theoretical support, we also analyze the physical and geometrical properties of gravastar configurations.

关键词： gravastar Guilfoyle exact solutions stability analysis

Charged quark stars in f(R,T)gravity

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Chinese Physics C 2022年第11期46卷 308-317页

作者： Juan M.Z.Pretel Takol Tangphati ayan banerjee Anirudh Pradhan Centro Brasileiro de Pesquisas Físicas Rua Dr.Xavier Sigaud150 URCARio de Janeiro CEP 22290-180RJBrazil Theoretical and Computational Physics Group Theoretical and Computational Science Center(TaCS)Faculty of ScienceKing Mongkut’s University of Technology Thonburi126 Prachauthid Rd.Bangkok 10140Thailand Astrophysics and Cosmology Research Unit School of MathematicsStatistics and Computer ScienceUniversity of KwaZulu-NatalPrivate Bag X54001Durban 4000South Africa Centre for Cosmology Astrophysics and Space ScienceGLA UniversityMathura-281406Uttar PradeshIndia

Recent advances in nuclear theory and new astrophysical observations have led to the need for specific theoretical models applicable to dense-matter physics *** chromodynamics(QCD)predicts the existence of non-nucleonic degrees of freedom at high densities in neutron-star matter,such as quark *** a confining quark matter model,which consists of homogeneous,neutral 3-flavor interacting quark matter with O(m_(s)^(4))corrections,we examine the structure of compact stars composed of a charged perfect fluid in the context of f(R,T)*** system of differential equations describing the structure of charged compact stars has been derived and numerically solved for a gravity model with f(R,T)=R+2β*** simplicity,we assumed that the charge density is proportional to the energy density,namely,ρ_(ch)=αρ.It is demonstrated that the matter-geometry coupling constant β and charge parameter α affect the total gravitational mass and the radius of the star.

关键词： charged stars f(R T)gravity

Spectral analysis of χ class data of GRS 1915+105 using TCAF solution

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Research in Astronomy and Astrophysics 2020年第12期20卷 347-356页

作者： Anuvab banerjee ayan Bhattacharjee Dipak Debnath Sandip K.Chakrabarti S.N.Bose National Centre for Basic Sciences Block-JDSector-3Salt LakeKolkata700106India Indian Centre for Space Physics 43 ChalantikaGaria St.Rd.Kolkata700084India

The class variable source GRS 1915+105 exhibits a wide range of time variabilities on timescales of a few seconds to a few days. Depending on the count rates in different energy bands and the nature of the conventional color-color diagram, the variabilities were classified into sixteen classes that were later sequenced in ascending order of Comptonization Efficiency(CE), which is the ratio of power-law and blackbody photons. However, CE estimation is based on an empirical model which does not provide us with a comprehensive picture regarding accretion flow dynamics around the central source. In reality, the accretion flow is comprised of two components: the high angular momentum Keplerian flow in the form of a radiatively efficient disk and a low angular momentum radiatively inefficient sub-Keplerian halo enveloping the disk. These two components contribute differently to the overall flux due to the differences in their radiative efficiencies. Therefore, it is necessary to analyze the spectral behaviors and time variabilities in terms of accretion rates. In χ class, X-ray flux is steady with no significant variation, however various χsubclasses are observed at different X-ray fluxes and variations of count rates across different χ subclasses must be linked to the variation of flow parameters such as the accretion rates, be it the Keplerian disk rate and/or the low angular momentum halo rate. This motivated us to analyze the spectra of the χ class data implementing the physical Two Component Advective Flow(TCAF) solution which directly extracts these two rates from spectral fits. We find that in the χ2,4 classes, which are reportedly devoid of significant outflows, the spectra could be fitted well applying the TCAF solution alone. In the χ1,3 classes, which are always linked with outflows, a cutoff power-law model is needed in addition to the TCAF *** the same time, the normalization required by this model along with the variation of photon index and exponent

关键词： X-Rays:binaries stars:individual(GRS 1915+105) stars:black holes accretion,accretion disks ISM:jets and outflows radiation:dynamics

Six Newly Discovered Eclipsing Binary Systems in the TESS field

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Research in Astronomy and Astrophysics 2023年第3期23卷 143-154页

作者： Burak Ulas Vildan ayan Department of Space Sciences and Technologies Faculty of Sciences?anakkale Onsekiz Mart UniversityTerzioglu CampusTR 17100CanakkaleTurkey

We present the first detailed investigation of six eclipsing binary systems in the TESS *** TESS light curves of the targets are analyzed by determining the initial effective temperatures via SED *** absolute parameters are derived and the systems are compared to well-known binaries of the same *** show that CD-58791,CD-621257 and TYC 9356-355-1 are detached binary ***-54942 and UCAC4136-007295 are contact binaries while TYC 8508-1413-1 is a semidetached system.

关键词： TESS absolute field

Hydrogeochemical characteristics and its role in controlling arsenic mobilization in a shallow aquifer

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Acta Geochimica 2021年第6期40卷 912-925页

作者： ayan Das Abhijit Mandal Department of Chemistry University of KalyaniKalyaniWest BengalIndia Department of General Science and Humanities GKCIETMaldaWest BengalIndia

The relevance of groundwater hydrogeochemistry to explain the occurrence and distribution of arsenic in groundwater is of great *** insightful discussions on the control of shallow groundwater(<50 m)hydrogeochemistry in arsenic mobilization are known to be a viable tool to explain the arsenic menace in shallow *** present investigation emphasizes the hydrogeochemical driver and/or control over the reductive dissolution of Fe-bearing host minerals and thereby releasing arsenic into the shallow groundwater of the study *** study suggests that hydrogeochemical evolution is mainly governed by carbonate minerals dissolution,silicate weathering,and competitive ion-exchange processes in the shallow aquifers(<50 m).The present study also indicates the prevalence of carbonate minerals dissolution over silicate *** emergence of Cl^(-)concentration in the shallow groundwater founds the possibilities of anthropogenic inputs into the shallow aquifers(<50 m).The reducing environment in shallow aquifers(<50 m)of the study area is evident in the reductive dissolution of Febearing shallow aquifer minerals which absorb arsenic in the solid phase and mobilize arsenic onto shallow *** study opted for many statistical approaches to delineate the correlation among major and minor ionic constituents of the groundwater which are very helpful to understand the comprehensive mechanism of arsenic mobilization into shallow groundwater.

关键词： Arsenic mobilization Groundwater hydrogeochemistry Aquifer sediments Shallow aquifers Redox environment

A Comprehensive View on the Progress of Organoid Research with an Emphasis on its Relevance to Disease Characterization

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Biomedical and Environmental Sciences 2023年第10期36卷 959-971页

作者： Chandra KISHORE Vaishali Ji Saurav Mallik ayan MUKHERJI Namrata TOMAR Soumen Kumar Pati LI Ai Min Sinthia Roy banerjee Soumadip GHOSH Raza Ali NAQVI University of California Irvine Medical CenterOrangeCA 92868USA Department of Botany J.D.Women’s CollegeBailey RoadPatna-800023India Harvard T.H.Chan School of Public Health BostonMA 02115USA Department of Information Technology Haldia Institute of TechnologyHaldiaWest BengalIndia Medical College of Wisconsin MilwaukeeWI 53226USA Department of Bioinformatics Maulana Abul Kalam Azad University of TechnologyNadiaWest BengalIndia Center for Precision Health School of Biomedical InformaticsThe University of Texas Health Science Center at HoustonHoustonTX 77030USA School of Computer Science and Engineering Xi’an University of TechnologyXi'an 710048ShaanxiChina Department of Information Technology Guru Nanak Institute of TechnologyKolkataWest BengalIndia Department of Computer Science and Engineering Sister Nivedita UniversityKolkataWest BengalIndia Center for Precision Health School of Biomedical InformaticsUniversity of IllinoisChicago60612USA

INTRODUCTION Organoids are primary tissue or stem cells derived cell aggregates that have the capacity for self-organization,self-renewal,and the capacity to mimic cellular and tissue level *** can overcome the shortc... 详细信息

关键词： functions. overcome shortcomings

Long-term effects of metformin use in gestational diabetes mellitus on offspring health

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World Journal of Diabetes 2021年第11期12卷 1812-1817页

作者： ayan Roy Jayaprakash Sahoo Department of Endocrinology and Metabolism All India Institute of Medical SciencesJodhpur 342005RajasthanIndia Department of Endocrinology Jawaharlal Institute of Postgraduate Medical Education and ResearchPuducherry 605006India

Metformin is the first-line drug for the treatment of type 2 diabetes mellitus,but its role in gestational diabetes mellitus(GDM)management is not *** evidence suggests a certain beneficial effect of metformin in the treatment of GDM,but a high treatment failure rate leads to the initiation of additional medications,such as ***,since metformin crosses the placental barrier and reaches a significant level in the fetus,it is likely to influence the fetal metabolic *** evidence indicates the long-term safety in children exposed to metformin in utero except for mild adverse anthropometric *** follow-up of metformin-exposed offspring is warranted from the clinician’s point of view.

关键词： Anthropometry Fetal Gestational diabetes mellitus Long-term Metformin Offspring

Predicting and Curing Depression Using Long Short Term Memory and Global Vector

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Computers, Materials & Continua 2023年第3期74卷 5837-5852页

作者： ayan Kumar Abdul Quadir Md J.Christy Jackson Celestine Iwendi School of Computer Science and Engineering Vellore Institute of TechnologyChennai600127India School of Creative Technologies University of BoltonBoltonUK

In today’s world, there are many people suffering from mentalhealth problems such as depression and anxiety. If these conditions are notidentified and treated early, they can get worse quickly and have far-reachingnegative effects. Unfortunately, many people suffering from these conditions,especially depression and hypertension, are unaware of their existence until theconditions become chronic. Thus, this paper proposes a novel approach usingBi-directional Long Short-Term Memory (Bi-LSTM) algorithm and GlobalVector (GloVe) algorithm for the prediction and treatment of these *** and fitness bands can be equipped with these algorithms whichcan share data with a variety of IoT devices and smart systems to betterunderstand and analyze the user’s condition. We compared the accuracy andloss of the training dataset and the validation dataset of the two modelsnamely, Bi-LSTM without a global vector layer and with a global vector *** was observed that the model of Bi-LSTM without a global vector layer hadan accuracy of 83%,while Bi-LSTMwith a global vector layer had an accuracyof 86% with a precision of 86.4%, and an F1 score of 0.861. In addition toproviding basic therapies for the treatment of identified cases, our model alsohelps prevent the deterioration of associated conditions, making our methoda real-world solution.

关键词： Emotion dynamics depression heart rate internet of things global vector long short term memory machine learning sentiment analysis

Effects of stand types on recreational preferences of society in the Sub-Alpine Zone,northern Turkey

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Journal of Mountain Science 2022年第11期19卷 3246-3256页

作者： Tuğrul VAROL Halil BarışÖZEL Ferhat KARA İlkimÇAVUŞKARA Sezgin ayan Bartın University Faculty of ForestryDepartment of Forest EngineeringBartın 74100Turkey Kastamonu University Faculty of ForestryDepartment of Forest EngineeringKastamonu 37150Turkey Kastamonu-Ilgaz Mountain National Park Directorate Kastamonu 37100Turkey

The main objective of this study was to examine how different stand types influenced the tendency of visitors for varying recreational activities(i.e.,hiking,trekking,camping and hunting)from 1993 to 2018 in the surrounding areas of Uluyayla Natural Recreation Site in Bart1n,northern Turkey.A total of 627 visitors were selected on a voluntary basis,and questioned in the form of *** of the participants were in the age of 21-40 years old,and they were mostly(62.4%)*** of the participants(82.7%)lived in cities,while 62.8%of them were tourists when visiting the *** determining the preferences of the visitors regarding the stand types for different recreational activities,several images of each stand were shared with them,and they were asked which stand type they would prefer for a given recreation activity(i.e.,hiking,tracking,camping and hunting).A range of options from 1 to 5 in Likert's scale was used in evaluating the given *** degree of positive and negative effects was examined via trend *** was found that stand type had influence on the preferences of visitors regarding the recreational *** general,unmanaged and moderately treated stands were more preferred by visitors for the recreational purposes,compared to the previously managed *** the other hand,visitors'preference for the activities were different during two periods(i.e.,1993-2005 and 2006-2018).For each recreational activity,there was an increasing trend from 1993 to *** had been a continuous increase for hunting since 1996,and for trekking and camping after *** increases between 1993-1996 and 1996-1999 were likely due to the increasing awareness of the society as a result of the training and consciousness raising activities for nature *** demand on the recreational activities continuously increased in unmanaged and moderately treated stands,while no significant changes were examined in the previously managed *** st

关键词： Camping Hunting National Park Recreation Subalpine Silviculture