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Plant phenology regulates ecosystem functions at diverse scales but is impacted by micro and macro climatic variations, and climate change. In India, precise estimations of pheno-phase transition dates remain scarce at different spatial and temporal scales, necessitating comprehensive research efforts. This study aims to gather continuous intra-day ground data about vegetation and climate conditions using PhenoCam (optical RGB and IR images) along with meteorological sensors, at Dalma Wildlife Sanctuary (DWS), Jharkhand. To derive phenological metrics, different indices were computed from images captured by PhenoCam sensors and Satellite derived Normalized Difference Vegetation Index (NDVI). Since the PhenoCam covers diverse vegetation species in the frame, the analysis was performed over three specific subset Region of Interests (ROI): Bombax ceiba (Semal) tree, background cluster of vegetation and a sample tree. MODIS NDVI data revealed that most of the area is highly deciduous with major greening in the 1st half of April and senescence during 2nd half of March. The study found that Green Chromatic Coordinate Index (GCC) and Blue Chromatic Coordinate Index (BCC) results could reveal greening and senescence phases correctly. The timing of start of leaf flush (SOLF), end of leaf flush (EOLF) and end of leaf maturity (EOLM) estimated based on inflection point method from Pheno-Cam images are: for Semal tree: 5th April, 2nd May, 10th June, 2022; for background vegetation: 15th March, 28th March and 2nd May, 2022; and for sample tree: 15th March, 28th March and 25th April, 2022, respectively. The dates of SOLF differed in 2023 and it occurred twice for Semal and background vegetation: for Semal tree: 20th February and 3rd April 2023, and for background vegetation: 20th January and 8th March, 2023, respectively. The rate of leaf flush and rate of leaf maturity was not similar in different years as the rates were much higher in 2023 than in 2022. The temperature and rainfall during winter and spring played an important role in greening, senescence, and its sustenance. These findings revealed the micro-climatic effect on plant phenology in the Dalma Wildlife Sanctuary, as well as the importance of integrating PhenoCam and satellite data in accurate monitoring of phenological phases. [ABSTRACT FROM AUTHOR]

The present work reports the development of nanosized multiferroic filler BiFeO3 impregnated PVA based nanocomposite gel polymer electrolyte (NCGPEs) through conventional solution cast technique. The gel films have been characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray diffraction (XRD), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Electrochemical Impedance Spectroscopy (EIS) to ascertain their performance in electrochemical devices. FTIR studies confirmed complexation of salt with polymer matrix and change in morphology upon addition of BiFeO3 fillers. Enhancement in glass transition temperature with increasing filler content was observed in DSC studies. Filler inclusion increased thermal stability of the system according to TGA results. High value of ionic transference number (0.99) reveals ionic conduction. The NCGPEs sample [PVA (35): NH4CH3 COO(65)]:0.5wt%BiFeO3 exhibited highest ionic conductivity (1.05X10−3Scm−1). Charge carrier concentration seems to be responsible for high ionic conduction. CV&LSV measurement indicate the applicability of electrolyte in energy storage applications. [ABSTRACT FROM AUTHOR]

In this work, we discuss the dynamics of a spatially homogeneous and isotropic flat Friedmann-Lemaître-Robertson-Walker (FLRW) model of the Universe powered by the gravitationally induced 'adiabatic' matter creation with generalized Chaplygin gas (GCG) equation of state. In recent years, the CGC has been proposed successfully to unify the dark matter and dark energy by using an exotic equation of state p = − A / ρ α . Considering adiabatic matter creation cosmology, as developed by Prigogine et al, we examine the effect of matter creation in describing the unification with GCG by assuming the natural phenomenological matter creation rate Γ = 3 β H , where β is a constant and H is the Hubble parameter. We constrain the proposed model using a joint observational dataset of Type Ia supernovae Pantheon, H (z) and BAO with Markov-Chain Monte-Carlo (MCMC) method. In addition, we discuss the selection criterion (AIC and BIC) and stability criteria to analyze the dynamics and differences with the standard Λ CDM model. [ABSTRACT FROM AUTHOR]

Ecological corridors have been identified as an important tool in the conservation of sloth bears by providing the structural and functional connectivity between isolated habitats. We evaluated possible connectivity linking five protected habitats in Gujarat state (India). The resistance score was developed for layers impeding the movement of sloth bears using the Analytical hierarchy process (AHP). Maximum resistance was shown by areas with human–bear conflict locations followed by land use/land cover. Based on the resistance scores, we mapped six potential corridors amongst protected habitats through least-cost path corridor analysis. Our results show the two links with minimum resistance between Ratanmahal–Shoolpaneshwar and Balaram Ambaji–Jambughoda. In the latter linkage, a large Euclidean distance tends to lower the quality of the corridor. A single link identified connecting Jessore and Balaram is potentially an important path to conserve the habitat in the north. We estimated the centrality flow along with the least cost path (LCP) assessing the importance of each node representing protected habitats in developing connectivity. Analysis revealed Balaram Ambaji as an important link in developing the connectivity through all the habitats for sloth bears in Gujarat state. The present study allows conserving potential habitats with less density of sloth bears by connecting them with highly dense habitats through ecological corridors. Developing the ecological corridors once validated on ground level can lead to long-term conservation of wildlife residing across the disconnected areas in the state, this, in turn, will assist in improving the quality of habitats while promoting co-existence amongst the humans and bears. [ABSTRACT FROM AUTHOR]

Recently, high ionic conducting composite polymer electrolytes have become of great interest on account of their probable applications in various electrochemical devices, such as batteries, supercapacitors, fuel cells, solar cells, etc. The aim of the present work is to cast a stable free-standing membrane of polyvinyl alcohol (PVA)-based nanocomposite polymer electrolyte (NCPE) gel membranes using ammonium acetate salt (NH4CH3COO) and multiwall carbon nanotube (MWNT) contents for supercapacitor applications. X-ray diffraction (XRD) studies revealed improvements in the amorphous nature. The average crystal size of the MWNT-doped NCPE system was found to lie in the range of 30–70 nm). The degree of crystallinity (χc) in this case shows a decrease of up to 35 wt.% with the increase in filler concentrations. The differential scanning calorimetry (DSC) studies show better thermal response upon the addition of MWNTs. Thermo-gravimetric analysis (TGA) studies reveal that the mass of nanocomposite polymer electrolyte gel decreases continuously with the increase in the MWNT contents. Dielectric loss studies have also been used to understand the conduction process in the system. The presence of α-relaxation was evidenced during loss measurements. The source of polarizability decreases with an increase of frequency, and finally disappears due to the inertia of mobile ions. Optimum conductivity was achieved at 5.49 × 10−4 Scm−1 for 1 wt.% MWCNT-embedded NCPE gel membranes. The electrical conductivity response seems to follow the universal power law. The studies suggest the development of environmentally friendly H+ ion (proton) conducting-based supercapacitor applications. [ABSTRACT FROM AUTHOR]

In this work, we constrain the time-varying vacuum energy models in Brans-Dicke theory within the framework of a flat Friedmann-Lamaître-Robertson-Walker space-time by using the latest observational data. In the first step, the analytical solution of field equations are found by considering the two functional forms of cosmological constant, viz. power-series form: Λ = n 1 H + n 2 H 2 and power-law form: Λ ∝ a − n , where n 1 , n 2 and n are all constants, and H and a are the Hubble parameter and scale factor, respectively. Then, to test the viability of the models, the latest data sample such as Hubble H (z) data, Type Ia supernovae and baryon acoustic oscillations are used to constrain the model parameters. We apply the Markov Chain Monte Carlo (MCMC) method to find the best-fit values of the space parameters of both the models. The cosmological implications of the models are discussed by using the best-fit values of parameters. It is found that both the models are in good agreement with the datasets and are consistent with the analytical solutions. We use jerk parameter and selection criteria (AIC and BIC) to find the consistency of the proposed models with the observation as compared to Λ CDM model. Both the models explain the late-time acceleration of the Universe. [ABSTRACT FROM AUTHOR]

Flowering exhibits a significant relationship with environmental stimuli and changes. Effect of photoperiodism and vernalization have been well studied in flowering phenology; however, the effect of soil temperature on flowering is less explored which is one of the major factors of vegetation growth in alpine ecosystem. This study thus focuses on the effects of soil and air temperature on flowering response of Rhododendron arboreum Sm., a Himalayan tree species, which is also an indicator of spring initiation in high altitude regions. To monitor the flowering pattern, we employed automated phenocam, which was set up at 3356 masl in Tungnath (Indian Alpine region of Uttarakhand) for time-lapse photography of timberline ecotone. Soil and air temperature were recorded continuously at the timberline ecotone. Three years (2017 to 2020) of datasets were used for the present study. The phenocam observations displayed an interesting event in the year 2019–2020 with complete absence of flowering in R. arboreum population at Tungnath timberline ecotone. From the soil temperature data, an increase in winter (Dec–Jan, during which floral buds form) soil temperature, by > 1 °C, and no accumulation of freezing degree-days were found for the year 2019–2020. Air temperature however did not display any relationship with the failure of flowering, ruling out aerial chilling or frost injury of floral buds. From the results, a possible relationship between soil temperature and flowering can be suggested pointing towards necessary root apex vernalization stimulus in shallow rooted Rhododendrons. However, the dependency of flowering in Rhododendrons on winter soil temperature further requires continuous monitoring and more observations to make concrete inferences. [ABSTRACT FROM AUTHOR]

Globally, the treelines at higher elevations in mountains are reported to be advancing up-slope in response to recent climate warming. However, little is known about the treeline advancement in the Himalaya due to paucity of baseline vegetation data with which to compare, thus making their assessment and monitoring challenging. To fill this knowledge gap, the present study documented floristic and functional diversity of two treeline ecotone sites in Kashmir Himalaya. At each site, we conducted field sampling by laying five 20-m2 plots, with one at the highest limit (T0 plot), two plots below and two above the treeline and two nested subplots of 5-m2 for shrubs and five 1-m2 for herbs in each plot. We recorded 97 plant species belonging to 33 families from the two sites. We observed a considerable difference in species composition and distribution along the treeline ecotone. Majority of the species reported were perennial herbs. We observed a significant association of growth forms with the particular plots along the treeline ecotone. At both the sites, we recorded highest species richness at the T0 plot which was correlated well with the functional traits, thus indicating convergence of floristic and functional diversity at this transition zone. Interestingly, the T0 plot at both the sites showed maximum overlap of species with the plots above and below the treeline. In an era of climate warming, our study provides crucial baseline data that will facilitate assessment and monitoring of the Himalayan treelines. [ABSTRACT FROM AUTHOR]

In this paper, we study Friedmann cosmology with time-varying vacuum energy density in the context of Brans–Dicke theory. We consider an isotropic and homogeneous flat space, filled with a matter-dominated perfect fluid and a dynamical cosmological term Λ (t) , obeying the equation of state of the vacuum. As the exact nature of a possible time-varying vacuum is yet to be found, we explore Λ (t) given by the phenomenological law Λ (t) = λ + σ H , where λ and σ are positive constants. We solve the model and then focus on two different cases Λ H 1 and Λ H 2 by assuming Λ = λ and Λ = σ H , respectively. Notice that Λ H 1 is the analog of the standard Λ CDM, but within the Brans–Dicke cosmology. We find the analytical solution of the main cosmological functions such as the Hubble parameter, the scale factor, deceleration and equation of state parameters for these models. In order to test the viability of the cosmological scenarios, we perform two sets of joint observational analyses of the recent Type Ia supernova data (Pantheon), observational measurements of Hubble parameter data, Baryon acoustic oscillation/Cosmic microwave background data and Local Hubble constant for each model. For the sake of comparison, the same data analysis is performed for the Λ CDM model. Each model shows a transition from decelerated phase to accelerated phase and can be viewed as an effective quintessence behavior. Using the model selection criteria AIC and BIC to distinguish from existing dark energy models, we find that the Brans–Dicke analog of the Λ -cosmology (i.e. our model Λ H 1 ) performs at a level comparable to the standard Λ CDM, whereas Λ H 2 is less favoured. [ABSTRACT FROM AUTHOR]

In this paper, we study the validity of the generalized second law of thermodynamics by applying Bekestein–Hawking (BH) entropy and Barrow entropy for the horizon entropy, respectively in the viscous holographic Ricci dark energy (HRDE) model. The background is a spatially flat Friedmann–Robertson–Walker universe filled with pressureless dark matter and viscous HRDE. The bulk viscous coefficient is assumed to be ζ = ζ 0 + ζ 1 H . In first step, we find the analytical solution of the field equations of viscous HRDE model. We use the observational data from SNe, OHD and BAO/CMB in order to extract the constraints on viscous HRDE model. In second step, we calculate the entropy time-variation for each fluid component and for the apparent horizon itself. In BH entropy case, the sum of the entropy of the fluids (viscous HRDE and dark matter) enclosed by the apparent horizon plus the entropy of the horizon itself is non-decreasing function of time which shows that the generalized second law of thermodynamics is valid. It also satisfies the convexity condition which shows that the model approaches a stable equilibrium thermal state. However, in the case of Barrow entropy, the generalized second law of thermodynamics may be violated as it depends on the universe evolution. Finally, we examine the generalized second law of thermodynamics of viscous HRDE model by taking into account the Casimir effect and find that it is valid throughout the evolution of the universe. [ABSTRACT FROM AUTHOR]

The domesticated silkworm, Bombyx mori is not only an economically important insect but also a suitable model for the study of insect immunity and molecular genetics. The silk of B. mori is composed of mainly sericin and fibroin proteins, but few other proteins are found associated with silk. Seroin proteins are the silk-associated proteins, which play a crucial role in the protection of silk from microbes. Seroin proteins have been shown to inhibit the growth of Bombyx mori nuclear polyhedrosis virus (BmNPV) in B. mori, but the mechanism of action and their regulation is not known. Here to get insight into the mechanism, in vitro incubation of seroin proteins with BmNPV budded virions prior to infection was carried out. Subsequently, infection was done using these budded virions that resulted in suppression of virus proliferation in B. mori larvae. On the other hand, the microRNA-mediated regulation of Seroin2 in BmN cells of B. mori was studied. MicroRNAs (miRNAs) are the class of small non-coding RNAs that regulate several vital biological processes through post-transcriptional gene regulation. Target sites for host-encoded miRNAs on mRNA of Seroin2 were predicted using RNAhybrid software. Bmo-miR-71 and bmo-miR-252 were found to have target sites on the mRNA of Seroin2. Ectopic overexpression of bmo-miR-71 and bmo-miR-252 in the BmN cells resulted in the significant downregulation of Seroin2 expression at the transcript level, as determined by RT-qPCR. These results indicate that seroin proteins' direct interaction with BmNPV may decrease its infectivity and Seroin2 is plausibly under the regulation of host miRNAs. [ABSTRACT FROM AUTHOR]

In this paper, we present the bulk viscous phenomena to mimic new holographic dark energy behavior in modified f(R, T) gravity. We assume the bulk viscosity coefficient, ζ in the form of ζ = ζ 0 + ζ 1 H , where ζ 0 , ζ 1 are positive constants and H is the Hubble parameter. We obtain the exact solution of the scale factor and classify all the possible scenarios (deceleration, acceleration and their transition) of the evolution of the Universe. It is observed that the model transits from the decelerated phase to accelerated phase in early or late time depending on the values of viscous terms. For large values of viscous terms, the model always accelerates throughout the evolution. Furthermore, we also analyze two diagnostic parameters, statefinder r , s and Om to discriminate our model with the other existing dark energy models. The evolutions of these diagnostics are shown in r - s , r - q and Om − z planes. It is found that the behavior of trajectories in different planes depends on the bulk viscous coefficients. A small combination of ζ 0 and ζ 1 gives the quintessence-like behavior, whereas a large combination gives Chaplygin gas-like model. However, the model approaches the ΛCDM model in the late time evolution of the Universe. The value of the effective equation of state parameter comes to be − 0.9745 which is very close to the observational data. The entropy and generalized second law of thermodynamics are valid under certain constraints. The analysis shows that the dark energy phenomena may be explained in the presence of bulk viscosity in the modified theory of gravity. [ABSTRACT FROM AUTHOR]

In this paper, we consider a holographic dark energy model driven by the gravitationally induced adiabatic matter creation with constant creation rate. It is assumed that the present accelerating stage is a consequence of the negative pressure describing the irreversible process of gravitational matter creation. Exact solutions are obtained to discuss the evolution of the universe. We obtain the best-fit values of the model parameters through MCMC method by the use of EMCEE python package on latest observational data. With the best-fit values, it is found that the universe shows transition from decelerated phase to accelerated phase. We carry out the diagnostic analysis to distinguish our model with other standard dark energy models. We also discuss the cosmography analysis of our model. We analyse the model by applying Akaike information criterion (AIC) and Bayesian information criterion (BIC) based on the penalization associated to the number of parameters. The results show that the model behaves quintessence like and approaches to Λ CDM model in late time. [ABSTRACT FROM AUTHOR]

The changes in natural ecosystems provide opportunity to increase vegetation carbon sink capacity and thereby contribute to mitigation of climate change impacts. The Indian tropics and the large ecological variation within the country afford the advantage of diverse niches and offer opportunities to reveal the role of biotic factors at different levels of organization from populations to ecosystems. The last 4 decades of research and development in the Indian space science community has been primarily application driven in response to the government space programme for national development. The expenditure in R&D over next 5 year suggest that scientific research is higher on the country's agenda. The Indo-UK Terrestrial Carbon Group (IUTCG) comprising both Indian and UK scientists, funded jointly by the Department of Science and Technology, India and the Department of Business, Innovation and Skills organised a workshop to explore ways in which Earth observation data can be effectively utilised in mitigating the impacts of climate change through vegetation management. Effective integration of field observations, collected through various monitoring networks, and satellite sensor data has been proposed to provide country-wide monitoring. [ABSTRACT FROM AUTHOR]

We study the matter creation cosmology as an alternative theory to explain the dark energy phenomena. We discuss the matter-dominated Universe in a flat Friedmann-Robertson-Walker line element by adopting the thermodynamics of open systems, in which the matter creation irreversible processes may take place at a cosmological scale. We propose a new form of the matter creation rate, Γ = 3 α H 0 + 3 β H + 3 γ a ¨ a ˙ , which generalizes some of the previous models in the literature. Exact solutions of the field equations are found and discussed the evolution of the Universe. Constraints on the model parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the Supernova distance modulus data, observational measurements of Hubble parameter, Baryon acoustic oscillation data. The trajectories of the evolution of the scale factor, deceleration parameter and equation of state parameter are plotted by using best-fit values of the parameters. It is observed that the model shows accelerating behavior and behaves quintessence like ( ω > - 1 ). The age of the Universe is obtained which is in good agreement with Λ CDM model. We examine the model using two independent diagnostic parameters, namely statefinder and Om . We apply Akaike information criterion (AIC) and Bayesian information criterion (BIC) to discriminate the model based on the penalization associated to the number of parameters. The analysis shows that the model has close resemblance to the Λ C D M cosmology. We also discuss the thermodynamics of the model and find that the model satisfies the generalized second law of thermodynamics with certain constraints. [ABSTRACT FROM AUTHOR]

In this paper, the dissipative mechanism (bulk viscosity and matter creation) is introduced to describe the effects of cosmic non-perfect fluid on the Ricci dark energy (RDE) model. We consider matter creation and bulk viscosity as two independent irreversible processes. Assuming suitable forms of the bulk viscous coefficient and matter creation rate, we find the exact solution of the field equations. We carry out fitting analysis on the cosmological parameters in the model by using Type Ia supernovae data, observational Hubble data and baryon acoustic oscillation (BAO) data with cosmic microwave background. We plot the trajectory of cosmological parameters with the best-fit values of model parameters and discuss all possible (deceleration, acceleration and their transitions) evolutions of the model. The current values of deceleration parameter and equation of state parameter are found to be q 0 = - 0.362 and ω eff = - 0.575 , respectively. The age of the Universe is found to be t 0 ≃ 13.397 Gyr, which is very close to the Λ CDM model. We further discuss the geometrical diagnostic parameters such as statefinder and Om to distinguish the model with Λ CDM model. Finally, we discuss the behaviour of energy conditions for our model and find that the model satisfies the null energy condition (NEC), weak energy condition (WEC) and dominant energy condition (DEC) while it violates strong energy condition (SEC). [ABSTRACT FROM AUTHOR]

We explore a matter-dominated model with bulk viscosity in Brans-Dicke theory to interpret the observed cosmic accelerating expansion phenomena. We obtain the exact solution of the field equations by taking constant bulk viscous coefficient (which potentially could explain the present accelerated expansion of the Universe) and Brans-Dicke scalar field proportional to some power of the scale factor. The model is studied statistically using the available astronomical data and then compare using the tools taken from information criterion. Using the best-fit values of model parameters we find that the model shows transition from decelerated phase to accelerated phase. The effective equation of state parameter is within the quintessence region (− 1 ≤ ω < 0 ). Thus, the model shows quintessence behavior and approaches to Λ CDM model in late time. It does not cross the phantom divide line and hence it is free from big-rip singularity. The viscous model also alleviates the age problem. We discuss two diagnostic parameters, namely statefinder and O m (z) and compare the model with the existing models by plotting the trajectories. We also apply Akaike information criterion (AIC) and Bayesian information criterion (BIC) to discriminate the viscous model based on the penalization associated to the number of parameters. The analyses based on the AIC indicates that there is less support for the viscous model when compared to the Λ CDM model, while those based on the BIC indicates that there is strong evidence against it in favor of the Λ CDM model. [ABSTRACT FROM AUTHOR]

Globally, treeline in mountain landscapes is reported to be sensitive to projected warming by climate change. Betula utilis (Himalayan birch), a principal tree species defining the natural treeline in Himalayas, is a potential indicator species to track the signal of climate change. The present study models the ensemble distribution of B. utilis using Biomod2 package for present and future (RCP's 2.6–8.5 covering 2050 and 2070). The final ensemble model obtained had AUC = 0.886 and TSS = 0.655, thus indicating robustness of the model. We assessed change in the habitat suitability, area expansion and contraction based on ensemble model using SDM Toolbox. The highly suitable area for B. utilis is predicted to shift towards the eastern parts of Himalayas in future, with suitability declining towards the western part of Himalayas. The study, to our best knowledge, for the first time used Ecospat package to assess niche dynamics (i.e. overlap, similarity and equivalency) of B. utilis, which predicted the climatic niche of this treeline species is moderately shifting in future scenarios. Further, the PCA analysis indicated that significant variation (33.45% on PC1 and 24.63% on PC2) exists in the climatic conditions between current and future scenarios. The similarity and equivalency test revealed that B. utilis niche is similar but not identical between current and future climate change scenarios. Hopefully, the results from the present study will contribute significantly in understanding the impacts of climate change in Himalayas with wide implications for scientifically-informed adaptation and mitigation strategies. [ABSTRACT FROM AUTHOR]

The present work reports development of bismuth iron oxide (BFO)-doped PVA:(NH4 CH3COO) nanocomposite gel polymer electrolyte (NCGPE) films. XRD profiles revealed enhancement in the amorphous behavior of composite gel electrolyte upon incorporation of BFO as filler particles. I-t measurements exhibit ionic charge transport. The ionic conductivity of the electrolytes has been evaluated from impedance spectroscopy, and the highest value at room temperature have been found to be 1.05 × 10−3 S cm−1 for the composite gel samples containing 0.5 wt% filler concentration. The temperature dependence of ionic conductivity exhibits a combination of Arrhenius and Vogel-Tamman-Fulcher (VTF) behavior. Charge carrier density has been also evaluated from the dielectric response of the electrolyte films. Cyclic voltammetry of the films reveals a wide electrochemical window (− 2.54 to +2.89 V) with good cyclic response to suggest its applicability for battery applications. [ABSTRACT FROM AUTHOR]

The holographic Ricci dark energy (HRDE) model is studied with bulk viscosity in modified f(R, T) gravity theory. We consider a universe filled with bulk viscous HRDE and pressureless dark matter. We obtain exact solutions and study the evolution of the scale factor and deceleration parameter and their transition from decelerated to accelerated expansion of the universe. The bulk viscosity coefficient is assumed to be constant. The behaviors concerning the cosmic expansion depend on the coupling parameter of f(R, T) and bulk viscous term. We apply two geometric diagnostics, the statefinder {r, s} and Om(z), to discriminate HRDE model from the ΛCDM model. We plot the evolution trajectories in the statefinder plane and Om(z) plane. We find that the viscous HRDE model behaves like quintessence at small values of the bulk-viscous term and like a Chaplygin gas at large values of the bulk-viscous term. However, the model approaches ΛCDM at late times of the evolution of the universe. We explore the obvious violation of energy-momentum conservation in f(R, T) gravity and provide a thermodynamic interpretation of extra terms generated by the nonminimal geometry-matter coupling describing particle production. We observe that the current acceleration of our universe is well explained with bulk viscosity. [ABSTRACT FROM AUTHOR]

The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient and sampled for detailed vegetation analysis using multi summit approach as per Global observation research initiative in alpine environments (GLORIA). Species richness, diversity, and evenness among four summits as well as the interaction between environmental variables with plant communities were assessed. Monthly mean soil temperature was calculated using data retrieved from geo-precision temperature logger in order to identify the trend of soil temperature among different season and altitudinal gradient and its implications to plant communities. Soil samples were analyzed from each summit by collecting randomized composite soil samples. The indirect non-metric multidimensional scaling (NMDS) and direct canonical correspondence analysis (CCA) tools of ordination techniques to determine the linkage between plant species from various sample summits and biotic/abiotic environmental gradients were used in the present study. The results of the study demonstrated increase in species richness as soil temperature increases, the ecotone representing summits were found most warm summits followed by highest species richness. Annual soil temperature increased by 1.43°C at timberline ecotone. Whereas, at upper alpine zone the soil temperature increased by 0.810C from year 2015 to 2016. Sørensen’s similarity index was found to be increased between subalpine and upper alpine zone with increase in the presence of subalpine plant species at upper alpine zone. Both the ordination tools separate the subalpine summit and their respective vegetation from summits representing timberline ecotone and upper alpine zone. Soil pH, altitude, soil cation exchange capacity were found as the key abiotic drivers for distribution of plant species. [ABSTRACT FROM AUTHOR]

We consider a spatially homogeneous and totally anisotropic Bianchi-I space-time with perfect fluid (dark matter and standard visible matter) and anisotropic dark energy, which has dynamical energy density. The two sources are assumed to interact minimally and therefore their energy momentum tensors are conserved separately. Using suitable physical assumptions, the field equations are solved exactly. Various dark energy models are studied and it is found that quintessence model is suitable for describing the present evolution of the universe. The geometrical and kinematical features of the models and the behavior of the anisotropy of the dark energy, are examined in detail. [ABSTRACT FROM AUTHOR]

Exact solutions of the field equations for a Bianchi type-I space-time, filled with a viscous fluid and cosmological constant, are obtained. We utilize the constancy of deceleration parameter to get singular and non-singular solutions. We investigate a number of solutions with constant and time-varying cosmological constant together with a linear relation between shear viscosity and expansion scalar. Due to dissipative processes, the mean anisotropy and shear of the model tend to zero at a faster rate. [ABSTRACT FROM AUTHOR]

In this paper we present a spatially homogeneous locally-rotationally-symmetric (LRS) Bianchi type-V cosmological model with perfect fluid and heat flow. A general approach is introduced to solve Einstein's field equations using a law of variation for the mean Hubble parameter, which is related to average scale factor of the model that yields a constant value for the deceleration parameter. Exact solutions that correspond to singular and non-singular models are found with heat flow. The physical constraints on the solution and, in particular, the thermodynamical laws that govern such solutions are discussed in some detail. [ABSTRACT FROM AUTHOR]

In this paper we consider a locally-rotationally-symmetric (LRS) Bianchi type-V perfect fluid model with variable cosmological ‘constant’ representing the energy density of vacuum. The field equations are solved with and without heat conduction by using a variation law for the mean Hubble parameter, which is related to the average scale factor of the metric and yields a constant value of the deceleration parameter. A constant value of deceleration parameter generates power-law form of average scale factor which is used to find the exact solutions with and without heat conduction with decaying vacuum density. The solutions presented here satisfy all the necessary conditions for the physically acceptability. The thermodynamical relations in decaying vacuum fluid model are also studied in detail. [ABSTRACT FROM AUTHOR]

We consider Einstein’s field equations with variable gravitational and cosmological “constants” for a spatially homogeneous and anisotropic Bianchi-I space-time. A law of variation for the Hubble parameter, which is related to the average scale factor and yields a constant value of the deceleration parameter, is assumed to solve the field equations. The gravitational constant is allowed to follow a power-law form. We find that a time-increasing gravitational constant is suitable for describing the present evolution of universe. The solutions reveal the dynamics of a universe, which expands forever. The physical interpretation of the solutions is discussed in detail. [ABSTRACT FROM AUTHOR]

The paper presents a spatially homogeneous and anisotropic Bianchi type-I cosmological model consisting of a dissipative fluid. The field equations are solved explicitly by using a law of variation for mean Hubble parameter, which is related to average scale factor and yields a constant value for deceleration parameter. We find that the constant value of deceleration parameter describes the different phases of the evolution of universe. A barotropic equation of state ( p= γ ρ) together with a linear relation between shear viscosity and expansion scalar, is assumed. It is found that the viscosity plays a key role in the process of the isotropization of the universe. The presence of viscous term does not change the fundamental nature of initial singularity. The thermodynamical properties of the solutions are studied and the entropy distribution is also given explicitly. [ABSTRACT FROM AUTHOR]

A spatially homogeneous locally-rotationally-symmetric (LRS) Bianchi type-V cosmological model is considered with a perfect fluid in general relativity. We present two types of cosmologies (power-law and exponential forms- by using a law of variation for the mean Hubble parameter that yields a constant value for the deceleration parameter. We discuss the physical properties of the non-flat and flat models in each cosmology. Exact solutions that correspond to singular and non-singular models are presented. In a generic situation, models can be interpolated between different phases of the Universe. We find that a constant value for the deceleration parameter is reasonable for a description of different phases of the Universe. We arrive at the conclusion that the Universe decelerates when the value of the deceleration parameter is positive whereas it accelerates when the value is negative. The dynamical behaviours of the solutions and kinematical parameters like expansion, shear and the anisotropy parameter are discussed in detail in each section. Exact expressions for look-back time, luminosity distance and event horizon vs. redshift are derived and their significances are discussed in some detail. It has been observed that the solutions are compatible with the results of recent observations. [ABSTRACT FROM AUTHOR]

In this paper we discuss the variation law for Hubble's parameter with average scale factor in a spatially homogeneous and anisotropic Bianchi type-V space-time model, which yields constant value of the deceleration parameter. We derive two laws of variation of the average scale factor with cosmic time, one is of power-law type and the other is of exponential form. Exact solutions of Einstein field equations with perfect fluid and heat conduction are obtained for Bianchi type-V space-time in these two types of cosmologies. In the cosmology with the power-law, the solutions correspond to a cosmological model which starts expanding from the singular state with positive deceleration parameter. In the case of exponential cosmology, we present an accelerating non-singular model of the Universe. We find that the constant value of deceleration parameter is reasonable for the present day Universe and gives an appropriate description of evolution of Universe. We have also discussed different types of physical and kinematical behaviour of the models in these two types of cosmologies. [ABSTRACT FROM AUTHOR]

We present Bianchi type-I cosmological models in the presence of generalized Chaplygin gas and perfect fluid for early and late time epochs. Exact solutions of Einstein’s field equations for this model are obtained. The general solutions of gravitational field equations are expressed in an exact parametric form, with average scale factor as parameter. In the limiting cases of small and large values of the average scale factor, the solutions of the field equations are expressed in exact analytic forms. Moreover, this model predicts that the expansion of Universe is accelerating for the late times. The physical and geometrical properties of the corresponding cosmological models are discussed. [ABSTRACT FROM AUTHOR]

The variation law for generalized mean Hubble’s parameter is discussed in a spatially homogeneous and anisotropic Bianchi type V space-time with perfect fluid along with heat-conduction. The variation law for Hubble’s parameter, that yields a constant value of deceleration parameter, generates two types of solutions for the average scale factor, one is of power-law type and other one of exponential form. Using these two forms of the average scale factor, exact solutions of Einstein field equations with a perfect fluid and heat conduction are presented for a Bianchi type V space-time, which represent expanding singular and non-singular cosmological models. We find that the constant value of deceleration parameter is reasonable for the present day universe. The physical and geometrical properties of the models are also discussed in detail. [ABSTRACT FROM AUTHOR]

A spatially homogeneous and anisotropic Bianchi type-I perfect fluid model is considered with variable cosmological constant. Einstein’s field equations are solved by using a law of variation for mean Hubble’s parameter, which is related to average scale factor and that yields a constant value of deceleration parameter. An exact and singular Bianchi-I model is presented, where the cosmological constant remains positive and decreases with the cosmic time. It is found that the solutions are consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the model is carried out. [ABSTRACT FROM AUTHOR]

We consider the flat Robertson–Walker model in scalar-tensor theory proposed by Lau and Prokhovnik. In this model, the field equations are solved by using “gamma-law” form of equation of state p=( γ−1) ρ, where the adiabatic parameter ‘gamma’ ( γ) varies continuously as the universe expands. Our aim is to study how the adiabatic parameter γ should vary so that in the course of its evolution the universe goes through a transition from an inflationary to a radiation-dominated phase. A unified one parameter function of γ has been considered to describe the two early phases of evolution of universe. The solutions show the power-law expansion and cosmological constant is found to be positive and decreasing function of cosmic time. The solutions are compatible with the Dirac’s large number hypothesis. The deceleration parameter has been presented in a unified manner in terms of scale factor, which describes the inflation of the model. The nature of singularity and the physical properties have been discussed in details. [ABSTRACT FROM AUTHOR]

The effect of bulk viscosity on the early evolution of Universe for a spatially homogeneous and isotropic Robertson-Walker model is considered. Einstein's field equations are solved by using `gamma-law' equation of state p = (γ-1)p where the adiabatic parameter gamma (γ) depends on the scale factor of the model. The 'gamma' function is defined in such a way that it describes a unified solution of early evolution of the Universe for inflationary and radiation-dominated phases. The fluid has only bulk viscous term and the coeffient of bulk viscosity is taken to be proportional to some power function of the energy density. The complete general solutions have been given through three cases. For flat space, power-law as well as exponential solutions are found. The problem of how the introduction of viscosity affects the appearance of singularity, is briefly discussed in particular solutions. The deceleration parameter has a freedom to vary with the scale factor of the model, which describes the accelerating expansion of the Universe. [ABSTRACT FROM AUTHOR]

In this paper, a spatially homogeneous and anisotropic Bianchi type-I space-time filled with perfect fluid is investigated within the framework of a scalar-tensor theory proposed by Saez and Ballester. Two different physically viable models of the universe are obtained by using a special law of variation for Hubble’s parameter that yields a constant value of deceleration parameter. One of the models is found to generalize a model recently investigated by Reddy et al. (Astrophys. Space Sci. 306:171, ). The Einstein’s field equations are solved exactly and the solutions are found to be consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the models is carried out. [ABSTRACT FROM AUTHOR]

The law of variation for the generalized mean Hubble’s parameter in the case of a spatially homogeneous and anisotropic Bianchi type-V space-time metric that yields a constant value of deceleration parameter, is presented. The variation for Hubble’s parameter generates two types of solutions for the average scale factor one is of power-law type and second is of the exponential form. Using these two forms, Einstein’s field equations for perfect fluid Bianchi type-V models are solved separately that correspond to singular and non-singular models respectively. We find that the constant value of deceleration parameter is reasonable for description of the present day universe. We also find that the universe decelerates for positive value of deceleration parameter where as it accelerates for negative one. The behaviors of observationally important parameters such as expansion scalar, mean anisotropic parameter and shear scalar are discussed. Exact expressions for look-back time, luminosity distance and event horizon versus redshift are derived and their significances are discussed in detail. It has been observed that the solutions are compatible with the results of recent observations. [ABSTRACT FROM AUTHOR]

A special law of variation for Hubble’s parameter is presented in a spatially homogeneous and anisotropic Bianchi type-I space-time that yields a constant value of deceleration parameter. Using the law of variation for Hubble’s parameter, exact solutions of Einstein’s field equations are obtained for Bianchi-I space-time filled with perfect fluid in two different cases where the universe exhibits power-law and exponential expansion. It is found that the solutions are consistent with the recent observations of type Ia supernovae. A detailed study of physical and kinematical properties of the models is carried out. [ABSTRACT FROM AUTHOR]

The properties of locally rotationally symmetric Bianchi type-II perfect fluid space-times are analyzed in Barber’s second self-creation theory by using a special law of variation for Hubble’s parameter that yields a constant value of deceleration parameter. By assuming the equation of state p= γ ρ, many new solutions are obtained for different era—Zel’dovich, radiation, vacuum and vacuum energy dominated. The solutions with power-law and exponential expansion are discussed. A detailed study of geometrical and physical parameters is carried out. The nature of singularity is also clarified in each case. [ABSTRACT FROM AUTHOR]

Einstein's field equations are considered for a locally rotationally symmetric Bianchi Type-II space--time in the presence of a massless scalar field with a scalar potential. Exact solutions of scale factors and other physical parameters are obtained by using a special law of variation for Hubble's parameter that yields a constant value of deceleration parameter. To get inflationary solutions, a flat region is considered in which the scalar potential is constant. Power-law and exponential cases are studied and in both solutions there is an anisotropic expansion of the cosmic fluid, but the fluid has vanishing vorticity. A detailed study of geometrical and kinematical properties of solutions has been carried out. [ABSTRACT FROM AUTHOR]

Two bis(bipyridine) polymeric metal nitrate complexes with 4,4’-bipyridine of simple formula like [M(bipy)2](NO3)2⋅ xH2O (where M=Co, Ni and Cu; x=4, 2 and 0, respectively) have been prepared and characterized. Their thermal decomposition has been undertaken using simultaneous TG-DTG-DTA and DSC in nitrogen atmosphere and non-isothermal TG in air atmosphere. Isothermal TG has been performed at decomposition temperature range of the complexes to evaluate the kinetics of decomposition by applying model-fitting as well as isoconversional method. Possible mechanistic pathways have also been proposed for the thermolysis. Ignition delay measurements have been carried out to investigate the response of these complexes under the condition of rapid heating. [ABSTRACT FROM AUTHOR]

Einstein field equations are considered in zero-curvature Robertson–Walker (R–W) cosmology with perfect fluid source and time-dependent gravitational and cosmological “constants.” Exact solutions of the field equations are obtained by using the ’gamma-law' equation of state p = (γ − 1)ρ in which γ varies continuously with cosmological time. The functional form of γ ( R) is used to analyze a wide range of cosmological solutions at early universe for two phases in cosmic history: inflationary phase and Radiation-dominated phase. The corresponding physical interpretations of the cosmological solutions are also discussed. [ABSTRACT FROM AUTHOR]