Atmospheric dynamical mechanisms have been prevalently used to explain the characteristics of the summer monsoon intraseasonal oscillation (MISO), which dictates the wet and dry spells of the monsoon ...rainfall. Recent studies show that ocean–atmosphere coupling has a vital role in simulating the observed amplitude and relationship between precipitation and sea surface temperature (SST) at the intraseasonal scale. However it is not clear whether this role is simply ‘passive’ response to the atmospheric forcing alone, or ‘active’ in modulating the northward propagation of MISO, and also whether the extent to which it modulates is considerably noteworthy. Using coupled NCEP–Climate Forecast System (CFSv2) model and its atmospheric component the Global Forecast System (GFS), we investigate the relative role of the atmospheric dynamics and the ocean–atmosphere coupling in the initiation, maintenance, and northward propagation of MISO. Three numerical simulations are performed including (1) CFSv2 coupled with high frequency interactive SST, the GFS forced with both (2) observed monthly SST (interpolated to daily) and (3) daily SST obtained from the CFSv2 simulations. Both CFSv2 and GFS simulate MISO of slightly higher period (~60 days) than observations (~45 days) and have reasonable seasonal rainfall over India. While MISO simulated by CFSv2 has realistic northward propagation, both the GFS model experiments show standing mode of MISO over India with no northward propagation of convection from the equator. The improvement in northward propagation in CFSv2, therefore, may not be due to improvement of the model physics in the atmospheric component alone. Our analysis indicates that even with the presence of conducive vertical wind shear, the absence of meridional humidity gradient and moistening of the atmosphere column north of convection hinders the northward movement of convection in GFS. This moistening mechanism works only in the presence of an ‘active’ ocean. In CFSv2, the lead-lag relationship between the atmospheric fluxes, SST and convection are maintained, while such lead-lag is unrealistic in the uncoupled simulations. This leads to the conclusion that high frequent and interactive ocean–atmosphere coupling is a necessary and crucial condition for reproducing the realistic northward propagation of MISO in this particular model.
Using spectral line observations of HNCO, N2H+, and HNC, we investigate the kinematics of dense gas in the central ∼250 pc of the Galaxy. We present scouse (Semi-automated multi-COmponent Universal ...Spectral-line fitting Engine), a line-fitting algorithm designed to analyse large volumes of spectral line data efficiently and systematically. Unlike techniques which do not account for complex line profiles, scouse accurately describes the {l, b, v
LSR} distribution of Central Molecular Zone (CMZ) gas, which is asymmetric about Sgr A* in both position and velocity. Velocity dispersions range from 2.6 km s−1 < σ < 53.1 km s−1. A median dispersion of 9.8 km s−1, translates to a Mach number,
$\mathcal {M}_{\rm 3D}\ge 28$
. The gas is distributed throughout several ‘streams’, with projected lengths ∼100–250 pc. We link the streams to individual clouds and sub-regions, including Sgr C, the 20 and 50 km s−1 clouds, the dust ridge, and Sgr B2. Shell-like emission features can be explained by the projection of independent molecular clouds in Sgr C and the newly identified conical profile of Sgr B2 in {l, b, v
LSR} space. These features have previously invoked supernova-driven shells and cloud–cloud collisions as explanations. We instead caution against structure identification in velocity-integrated emission maps. Three geometries describing the 3D structure of the CMZ are investigated: (i) two spiral arms; (ii) a closed elliptical orbit; (iii) an open stream. While two spiral arms and an open stream qualitatively reproduce the gas distribution, the most recent parametrization of the closed elliptical orbit does not. Finally, we discuss how proper motion measurements of masers can distinguish between these geometries, and suggest that this effort should be focused on the 20 km s−1 and 50 km s−1 clouds and Sgr C.
The Indian summer monsoon of 2013 covered the entire country by 16 June, one month earlier than its normal date. Around that period, heavy rainfall was experienced in the north Indian state of ...Uttarakhand, which is situated on the southern slope of Himalayan Ranges. The heavy rainfall and associated landslides caused serious damages and claimed many lives. This study investigates the scientific rationale behind the incidence of the extreme rainfall event in the backdrop of large scale monsoon environment. It is found that a monsoonal low pressure system that provided increased low level convergence and abundant moisture, and a midlatitude westerly trough that generated strong upper level divergence, interacted with each other and helped monsoon to cover the entire country and facilitated the occurrence of the heavy rainfall event in the orographic region. The study also examines the skill of an ensemble prediction system (EPS) in predicting the Uttarakhand event on extended range time scale. The EPS is implemented on both high (T382) and low (T126) resolution versions of the coupled general circulation model CFSv2. Although the models predicted the event 10–12 days in advance, they failed to predict the midlatitude influence on the event. Possible reasons for the same are also discussed. In both resolutions of the model, the event was triggered by the generation and northwestward movement of a low pressure system developed over the Bay of Bengal. The study advocates the usefulness of high resolution models in predicting extreme events.
The combined influence of tropical Indian Ocean (TIO) and Pacific Ocean (TPO) sea surface temperature (SST) anomalies on Indian summer monsoon rainfall (ISMR) variability is studied in the context of ...mid-1970s regime shift. The rainfall pattern on the various stages of monsoon during the developing and decaying summer of El Niño is emphasized. Analysis reveals that ISMR anomalies during El Niño developing summer in epoch-1 (1950–1979) are mainly driven by El Niño forcing throughout the season, whereas TIO SST exhibits only a passive influence. On the other hand in epoch-2 (1980–2009) ISMR does not show any significant relation with Pacific during the onset phase of monsoon whereas withdrawal phase is strongly influenced by El Niño. Again the eastern Indian Ocean cooling and westward shift in northwest Pacific (NWP) cyclonic circulation during epoch-2 have strong positive influence on the rainfall over the central and eastern India during the matured phase of monsoon. ISMR in the El Niño decaying summer does not show any significant anomalies in epoch-1 as both Pacific and Indian Ocean warming dissipate by the summer. On the other hand in epoch-2 ISMR anomalies are significant and display strong variability throughout the season. In the onset phase of monsoon, central and east India experience strong negative precipitation anomalies due to westward extension of persistent NWP anticyclone (forced by persisting Indian Ocean warming). The persistent TIO warming induces positive precipitation anomalies in the withdrawal phase of monsoon by changing the atmospheric circulation and modulating the water vapour flux. Moisture budget analysis unravels the dominant processes responsible for the differences between the two epochs. The moisture convergence and moisture advection are very weak (strong) over Indian land mass during epoch-1 (epoch-2) in El Niño decaying summer. The changing moisture availability and convergence play important role in explaining the weakening of ENSO monsoon relation in the recent years. The local TIO SST forcing and NWP circulation are prominent forcing factors for the interannual variability of ISMR during epoch-2.
Water bodies are being poisoned by a variety of organic and inorganic pollutants in the modern era of industrial civilization. To solve this vital issue, various scientists and researchers have come ...up with an eco-friendly method of photocatalysis which is a promising strategy for the removal of organic pollutants especially organic dyes from wastewater. In the present work, we report the enhanced photocatalytic activity of graphene oxide (GO) nanosheets synthesized via a simple, cost-effective, and eco-friendly method. The photocatalytic ability to degrade Malachite green (MG) and Congo red (CR) was investigated as such dyes are primary chemical pollutants in the textile industry. To optimize the conditions for the best performance, experimental variables such as contact time, dye solution concentration, catalyst dose, and pH were adjusted. The present investigation reveals that GO synthesized by the novel route is an extremely efficient photocatalyst for the degradation of MG and CR and observed 100% degradation of MG in 60 min and 85% degradation of CR in 90 min under UV irradiation. The present investigation explores the potential of graphene oxide-based composite materials for future energy and environmental remediation.
ZnO/ITO/ZnO/ITO/ZnO five layer thin films are fabricated by pulsed laser deposition on quartz substrate kept at a substrate temperature (
T
s) 873
K at a background oxygen pressure (
pO
2) of 0.05
...mbar for different deposition duration for ZnO layers (5, 10, 15 and 20
min) while keeping a constant deposition time for ITO layers. The structural, optical and electrical properties of the as-deposited thin films have been investigated by GIXRD, AFM, UV–visible spectra, photoluminescence spectra and temperature-dependent electrical resistivity measurements (10–300
K) using four-probe technique. XRD patterns of the films show a polycrystalline nature. From the AFM images, the average grain size and mean surface roughness are estimated and the particles are densely packed in the film. A high transmittance is observed for all the films in the visible and IR region. The PL spectra show that the emission is in the UV and visible region due to the near band edge and deep level transitions of ZnO. The electrical resistivity of all the films are calculated and are very low compared to the reported values of as deposited ZnO thin films. The co-existence of very high transmittance in the visible region and very low dc resistivity enables these films suitable for optoelectronic device fabrications. The structural, optical and electrical studies reveal that ITO buffer layers improve the crystalline quality, optical and electrical properties of ZnO multilayered thin films.
It is well-recognized that solid tumors are genomically, anatomically, and physiologically heterogeneous. In general, more heterogeneous tumors have poorer outcomes, likely due to the increased ...probability of harboring therapy-resistant cells and regions. It is hypothesized that the genomic and physiologic heterogeneity are related, because physiologically distinct regions will exert variable selection pressures leading to the outgrowth of clones with variable genomic/proteomic profiles. To investigate this, methods must be in place to interrogate and define, at the microscopic scale, the cytotypes that exist within physiologically distinct subregions ("habitats") that are present at mesoscopic scales. MRI provides a noninvasive approach to interrogate physiologically distinct local environments, due to the biophysical principles that govern MRI signal generation. Here, we interrogate different physiologic parameters, such as perfusion, cell density, and edema, using multiparametric MRI (mpMRI). Signals from six different acquisition schema were combined voxel-by-voxel into four clusters identified using a Gaussian mixture model. These were compared with histologic and IHC characterizations of sections that were coregistered using MRI-guided 3D printed tumor molds. Specifically, we identified a specific set of MRI parameters to classify viable-normoxic, viable-hypoxic, nonviable-hypoxic, and nonviable-normoxic tissue types within orthotopic 4T1 and MDA-MB-231 breast tumors. This is the first coregistered study to show that mpMRI can be used to define physiologically distinct tumor habitats within breast tumor models. SIGNIFICANCE: This study demonstrates that noninvasive imaging metrics can be used to distinguish subregions within heterogeneous tumors with histopathologic correlation.
In recent years, enormous attention has been paid to environmental contamination, especially human exposure to dyes because of their extensive use in industries including textiles, paper, plastics, ...tannery paints etc. These dyes impart colour to water and thereby impede light penetration which can eventually degrade the water quality and thus inhibits the photosynthetic activity in aquatic organisms. Due to the favourable reaction conditions, high rate of degradation and wide application area. Photocatalysis is a viable approach for addressing such environmental issues. In the present study, we have successfully synthesized an efficient photocatalyst based on copper oxide/graphene oxide (CuO/GO) nanocomposites in a short period of time through a cost-effective and environment-friendly method. A new area of bioremediation has been made possible by the enhanced ability of these nanocomposites to absorb light and improved heterogeneous catalytic efficiency. Various techniques such as UV–VIS spectroscopy, XRD, FTIR, SEM EDX and HR-TEM have been used to characterize the nanocomposites. The photocatalytic activity of the nanocomposites has been investigated using Malachite Green (MG) dyes as a model for water contaminants. The effect of time, dye concentration, photocatalyst dosage, and pH value on the efficiency of the photocatalyst and the photodegradation kinetics has been analysed in detail. The results indicate that the CuO/GO nanocomposites have the potential to function as an effective and versatile photocatalyst for the degradation of MG.
Graphical Abstract
It is highly desirable to develop an electrochemical double-layer supercapacitor with high energy and power densities, improved stability and other performance parameters. This goal can only be ...achieved by improving the structural and electrochemical properties of the electrodes, choosing an electrolyte with improved ionic conductivity and reducing the contact resistance of the current collector and their correlated effects. Here we investigated the effect of the current collector on the electrochemical performance of a supercapacitor by choosing different current collectors with activated carbon. Furthermore, we investigated their performance by determining their physicochemical properties via x-ray diffraction, atomic force microscopy, scanning electron microscopy and FTIR spectroscopy. Additionally, electrochemical performance was ascertained using cyclic voltammetry, galvanostatic discharge measurements and impedance spectroscopy of the fabricated supercapacitors. The results show that a supercapacitor with a printed circuit board copper clad can improve the total electrochemical performance of the device. Thus, we fabricated a supercapacitor with a high specific capacitance of 166 F/g and energy density of 23 Wh/kg. The supercapacitor was found to be the choice for use in energy storage applications.
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