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Microstructural Modification and High-Temperature Grain Stability of Aluminum in an Aluminum-Titanium Friction Stir Weld with Zinc Interlayer
No full textIn dissimilar friction stir welding (FSW), the presence of a third interlayer material can have a positive influence on local ternary chemical reactions due to complex mechanical mixing in the weld nugget. This leads to a reduction and distribution of intermetallic compounds as fine particles in the weld nugget. These fine particles can provide high-temperature grain stability. In the present investigation, a zinc (Zn) interlayer was used during the FSW of aluminum (Al) with titanium (Ti). X-ray computed tomography results revealed the occurrence of mechanical mixing of Zn with both Al and Ti. To understand the nature of the weld nugget at high temperatures, heat treatment of the weld was carried out at 500 degrees C for 60min. The detailed mechanisms leading to the superior grain stability of Al in the weld nugget were investigated. The improvement in grain stability of Al may open up a new area of research and development to produce new materials with high-temperature grain stability
Enhancement of the Nuclear Spin Noise Signal Using Wavelet Transform
No full textSpin noise spectroscopy has attracted considerable attention recently owing partly to intrinsic interest in the phenomenon and partly to its significant application potential. Here, we address the inherent problem of low sensitivity of nuclear spin noise and examine the utility of wavelet transform to mitigate this problem by distinguishing real peaks from the noise contaminated data. Suppression of the random circuit noise and the consequent enhancement of the correlated nuclear spin noise signal have been demonstrated with discrete wavelet transform. Spectra of both H-1 and C-13 nuclear spins have been considered and significant signal enhancements in both the cases have been observed. A detailed analysis of several possible wavelet, thresholding and decomposition solutions have been made to obtain the optimum condition for signal enhancement. It is observed that the application of wavelet transform leaves the spin noise signal line shape essentially unchanged, which is an advantage for several applications involving spin noise spectra
Development and studies of low capacity adsorption refrigeration systems based on silica gel-water and activated carbon-R134a pairs
No full textAdsorption Refrigeration Systems (ARS) are gaining considerable importance in view of their applications in several areas and in particular to transport industries. The refrigerants used in these systems are also quite acceptable from the points of view of Global warming and Ozone depletion. In our efforts to develop such refrigeration systems for transport vehicles, a sub-atmospheric Silicagel-Water ARS (SWARS) and a positive pressure Activated Carbon / R134a ARS (ACRARS) have been designed, fabricated and experimentally studied to evaluate their performances. A lumped parameter simulation model has been used to describe the dynamic behavior of these systems. The rate of adsorption / desorption of the refrigerants in both cases are assumed to be governed by the Linear Drive Force (LDF) model. The amount of refrigerants in adsorbent at equilibrium conditions are assumed to be described by the equations for modified Freundlich and Dubinin-Astakhov models for SWARS and ACRARS respectively. The simulation models are numerically solved by finite difference method with the simulation programs coded in MATLAB. The simulation results are found to be in good agreement with experimental results in both cases. A two-bed Silicagel-water adsorption refrigeration system has been built and it is well known that the refrigeration is produced at the evaporator. If the refrigeration power is not used to cool an external heat load (for example, by allowing the circulation of water through the heat exchanger coil embedded in the evaporator), the evaporator reaches the lowest temperature. This is the no-load condition at which the refrigeration power produced by the system is zero. When the evaporator temperature is higher than this lowest temperature, a finite refrigeration power is produced which increases with increasing evaporator temperature. The above Silicagel-water system reaches the lowest temperature of 5.3 degrees C at no load conditions and produces a refrigeration power of 284 +/- 9W at 18 degrees C, which refers to the average temperature (T-avg) of the flowing water through the heat exchanger coil within the evaporator. An experimental COP of 0.52 has been measured for this system. On the other hand, the simulation model predicts a refrigeration power of 325W at 18 degrees C with a COP of 0.55. Using Activated Carbon - R134a pair, a four bed adsorption refrigeration system has been designed and developed. The refrigeration system is designed such that it can be operated in three different configurations and they are: (A) A single bed (i.e. all four beds arranged in parallel), (B) A twin bed, (i.e. the four beds get grouped in two pairs and undergo the opposite processes of the adsorption cycle and (C) Four independent beds each undergoing the different processes of the adsorption cycle. The measured lowest temperatures under no-load conditions are 14.5 degrees C, 13.3 degrees C and 11.9 degrees C for configurations A, B and C respectively as against the predictions of the simulations which are 13.3 degrees C, 12.5 degrees C & 11.4 degrees C. The experimentally measured refrigeration powers are 430 +/- 13W, 556 +/- 17W and 657 +/- 20W at the T-avg temperature of 28.5 degrees C for configurations A, B and C respectively. On the other hand, the refrigeration powers predicted by simulation are 450W, 582W and 690W for the respective configurations. The measured COP values are 0.5, 0.65 and 0.70 for configurations A, B and C respectively as against those predicted by simulation which are 0.54, 0.67 and 0.73 respectively. It is observed that the experimental results are reasonably in good agreement with those predicted by the simulations. The highlight of the present work is that the Activated Carbon - R134a Adsorption Refrigeration System produces continuous refrigeration power which can be very useful for practical applications. Efforts are now underway to adopt this refrigeration system for cooling of truck cabins
Protein kinases orchestrate cell cycle regulators in differentiating BeWo choriocarcinoma cells
No full textChoriocarcinoma, a trophoblastic neoplasia, occurs in women as an incidence of abnormal pregnancy. BeWo choriocarcinoma cells derived from the abnormal placentation are a suitable model system to study the factors associated with differentiation, invasion and other cellular events as an alternative to clinical samples. Many protein kinases orchestrate the complex events of cell cycle and in case of malignancy such regulators are found to be mutated. In the present study, BeWo cells treated with forskolin (Fo) and phorbol 12-myristate 13-acetate (PMA) were used to study the role of PKA (protein kinase A) and PKC (protein kinase C), respectively, on the expression pattern of differentiation-related genes, membrane markers, PKC isoforms and cell cycle regulators. The effect of Fo and PMA on the cell proliferation was assessed. Progressive induction of alkaline phosphatase level and formation of multinucleated differentiated cells were observed in the cells treated with Fo. Exposure of cells to Fo and PMA induced the mRNA transcripts of -hCG, -hCG and endoglin and down-regulates E-cadherin at mRNA and protein levels. Synergistic levels of both up- and down-regulated genes/proteins were observed when cells were treated with the combination of Fo and PMA. The mRNA levels of cyclin D1, cyclin E1, p21, Rb, p53, caspase-3 and caspase-8 decreased gradually during differentiation. Fo significantly inhibited the protein levels of PCNA, Rb, PKC- and PMA stimulated mRNA expression of PKC-epsilon and PKC-. Further, failure in the activation of essential components of the cell cycle machinery caused G2/M phase arrest in differentiating BeWo cells
Cortical Electrocorticogram (ECoG) Is a Local Signal
No full textElectrocorticogram (ECoG), obtained by low-pass filtering the brain signal recorded from a macroelectrode placed on the cortex, is extensively used to find the seizure focus in drug-resistant epilepsy and is of growing importance in cognitive and brain-machine-interfacing studies. To accurately estimate the epileptogenic cortex or to make inferences about cognitive processes, it is important to determine the ``spatial spread'' of ECoG (i.e., the extent of cortical tissue that contributes to its activity). However, the ECoG spread is currently unknown; even the spread of local field potential (LFP) obtained from microelectrodes is debated, with estimates ranging from a few hundred micrometers to several millimeters. Spatial spread can be estimated by measuring the receptive field (RF) and multiplying by the cortical magnification factor, but this method overestimates the spread because RF size gets inflated due to several factors. This issue can be partially addressed using a model that compares the RFs of two measures, such as LFP and multi-unit activity (MUA). To use this approach for ECoG, we designed a customized array containing both microelectrodes and ECoG electrodes to simultaneously map MUA, LFP, and ECoG RFs from the primary visual cortex of awake monkeys (three female Macaca radiata). The spatial spread of ECoG was surprisingly local (diameter similar to 3 mm), only 3 times that of the LFP. Similar results were obtained using a model to simulate ECoG as a sum of LFPs of varying electrode sizes. Our results further validate the use of ECoG in clinical and basic cognitive research
Analysis of L-Band SAR Data for Soil Moisture Estimations over Agricultural Areas in the Tropics
No full textThe main objective of this study is to analyze the potential use of L-band radar data for the estimation of soil moisture over tropical agricultural areas under dense vegetation cover conditions. Ten radar images were acquired using the Phased Array Synthetic Aperture Radar/Advanced Land Observing Satellite (PALSAR/ALOS)-2 sensor over the Berambadi watershed (south India), between June and October of 2018. Simultaneous ground measurements of soil moisture, soil roughness, and leaf area index (LAI) were also recorded. The sensitivity of PALSAR observations to variations in soil moisture has been reported by several authors, and is confirmed in the present study, even for the case of very dense crops. The radar signals are simulated using five different radar backscattering models (physical and semi-empirical), over bare soil, and over areas with various types of crop cover (turmeric, marigold, and sorghum). When the semi-empirical water cloud model (WCM) is parameterized as a function of the LAI, to account for the vegetation's contribution to the backscattered signal, it can provide relatively accurate estimations of soil moisture in turmeric and marigold fields, but has certain limitations when applied to sorghum fields. Observed limitations highlight the need to expand the analysis beyond the LAI by including additional vegetation parameters in order to take into account volume scattering in the L-band backscattered radar signal for accurate soil moisture estimation
Search for associated production of a Higgs boson and a single top quark in proton-proton collisions at root s=13 TeV
No full textA search is presented for the production of a Higgs boson in association with a single top quark, based on data collected in 2016 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV, which corresponds to an integrated luminosity of 35.9 fb(-1). The production cross section for this process is highly sensitive to the absolute values of the top quark Yukawa coupling, y(t); the Higgs boson coupling to vector bosons, g(HVV); and, uniquely, their relative sign. Analyses using multilepton signatures, targeting H -> WW, H -> tau tau, and H -> ZZ decay modes, and signatures with a single lepton and a b (b) over bar pair, targeting the H -> b (b) over bar decay, are combined with a reinterpretation of a measurement in the H -> gamma gamma channel to constrain y(t). For a standard model-like value of g(HVV), the data favor positive values of y(t) and exclude values of y(t) below about -0.9y(t)(SM)
Search for supersymmetry in events with a photon, jets, b-jets, and missing transverse momentum in proton-proton collisions at 13TeV
No full textA search for supersymmetry is presented based on events with at least one photon, jets, and large missing transverse momentum produced in proton-proton collisions at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 35.9 fb -1 and were recorded at the LHC with the CMS detector in 2016. The analysis characterizes signal-like events by categorizing the data into various signal regions based on the number of jets, the number of b-tagged jets, and the missing transverse momentum. No significant excess of events is observed with respect to the expectations from standard model processes. Limits are placed on the gluino and top squark pair production cross sections using several simplified models of supersymmetric particle production with gauge-mediated supersymmetry breaking. Depending on the model and the mass of the nextto-lightest supersymmetric particle, the production of gluinos with masses as large as 2120 GeV and the production of top squarks with masses as large as 1230 GeV are excluded at 95% confidence level
Functional insights into the role of C-terminal disordered domain of Sesbania mosaic virus RNA-dependent RNA polymerase and the coat protein in viral replication in vivo
No full textThe C-terminal disordered domain of sesbania mosaic virus (SeMV) RNA-dependent RNA polymerase (RdRp) interacts with the viral protein P10. The functional significance of this interaction in viral replication was examined by a comparative analysis of genomic and sub-genomic RNA levels (obtained by quantitative real time PCR) in the total RNA extracted from Cyamopsis plants agro-infiltrated with wild-type or mutant forms of SeMV infectious cDNA (icDNA). The sgRNA copy numbers were found to be significantly higher than those of gRNA in the wild-type icDNA transfected plants. Transfection of a mutant icDNA expressing an RdRp lacking the Cterminal disordered domain led to a drastic reduction in the copy numbers of both forms of viral RNA. This could be due to the loss of interaction between the disordered domain of RdRp and P10 and possibly other viral/host proteins that might be required for the assembly of viral replicase. The C-terminal disordered domain also harbours the motif E which is essential for the catalytic function of RdRp. Mutation of the conserved tyrosine within this motif in the full length icDNA resulted in complete inhibition of progeny RNA synthesis in the transfected plants confirming the importance of motif E in the polymerase function in vivo. The role of coat protein (CP) in viral infection was also investigated by agro-infiltration of a CP start codon mutant icDNA which suggested that CP is essential for the encapsidation of viral progeny RNAs at later stages of infection
Residual-Based Grid Adaptation for Meshless LSFD-U Solver
No full textThe Paper projects the meshless LSFD-U methodology as a Cartesian grid method. A point distribution obtained from a Cartesian grid is employed in a solution update, leading to an automated computational fluid dynamics process for point adaptation. An estimate of the local truncation error obtained as a higher-order residual is employed for effecting a solution-based point adaptation. Asalient aspect of this methodology is the definition of a local length scale derived from an estimate of the truncation error, which not only provides a criterion for local refinement or coarsening but also can help in evolving an automatic termination criterion for the adaptive cycle. Toward point adaptation for flows with discontinuities, a hybrid adaptive strategy employing both the error estimator and indicator is employed. Results presented demonstrate the efficacy of the proposed methodology