Mesoporous Carbons for Energy-Efficient Water Splitting to Produce Pure Hydrogen at Room Temperature

Theoretical and experimental aspects of the use of mesoporous carbons in carbon-assisted water electrolysis (CAWE) to produce pure hydrogen at room temperature are presented. It is shown that the electrical energy requirements for CAWE can be as low as 20% of the energy needed for conventional water electrolysis, the extra energy coming from the electrochemical oxidation of carbon occurring at room temperature. Although CO2 is produced at the anode in this process, it is well separated from pure H2 produced at the cathode. Experimental results are reviewed for a variety of carbons with the major focus on the results obtained with carbon BP2000, which has both mesopores and micropores and a nanocarbon produced by the hydrothermal treatment of microcrystalline cellulose

A Hybrid Secure Cloud Platform Maintenance Based on Improved Attribute-Based Encryption Strategies

In the modern era, Cloud Platforms are the most needed port to maintain documents remotely with proper security norms. The concept of cloud environments is similar to the network channel. Still, the Cloud is considered the refined form of network, in which the data can easily be stored into the server without any range restrictions. The data maintained into the remote server needs a high-security feature, and the processing power of data should be high to retrieve the data back from the respective server. In the past, there were several security schemes available to protect the remote cloud server reasonably. However, the attack possibilities over the cloud platform remain; only all the researchers continuously work on this platform without any delay. This paper introduces a hybrid data security scheme called the Improved Attribute-Based Encryption Scheme (IABES). This IABES combines two powerful data security algorithms: Advanced Encryption Standard (AES) and Attribute-Based Encryption (ABE) algorithm. These two algorithms are combined to provide massive support to the proposed approach of data maintenance over the remote cloud server with high-end security norms. This hybrid data security algorithm assures the data cannot be attacked over the server by the attacker or intruder in any case because of its robustness. The essential generation process generates a credential for the users. It cannot be identified or visible to anyone as well as the generated certificates cannot be extracted even if the corresponding user forgets the credentials. The only way to get back the certification is resetting the credential. The obtained results prove the accuracy level of the proposed cypher security schemes compared with the regular cloud security management scheme, and the proposed algorithm essential generation process is unique. No one can guess or acquire it. Even the person may be the service provider or server administrator. For all, the proposed system assures data maintenance over the cloud platform with a high level of security and robustness in Quality of Service

Spatial defects nanoengineering for bipolar conductivity in MoS2

Understanding the atomistic origin of defects in two-dimensional transition metal dichalcogenides, their impact on the electronic properties, and how to control them is critical for future electronics and optoelectronics. Here, we demonstrate the integration of thermochemical scanning probe lithography (tc-SPL) with a flow-through reactive gas cell to achieve nanoscale control of defects in monolayer MoS2. The tc-SPL produced defects can present either p- or n-type doping on demand, depending on the used gasses, allowing the realization of field effect transistors, and p-n junctions with precise sub-μm spatial control, and a rectification ratio of over 104. Doping and defects formation are elucidated by means of X-Ray photoelectron spectroscopy, scanning transmission electron microscopy, and density functional theory. We find that p-type doping in HCl/H2O atmosphere is related to the rearrangement of sulfur atoms, and the formation of protruding covalent S-S bonds on the surface. Alternatively, local heating MoS2 in N2 produces n-character

Science with the Daksha High Energy Transients Mission

We present the science case for the proposed Daksha high energy transients mission. Daksha will comprise of two satellites covering the entire sky from 1~keV to $>1$~MeV. The primary objectives of the mission are to discover and characterize electromagnetic counterparts to gravitational wave source; and to study Gamma Ray Bursts (GRBs). Daksha is a versatile all-sky monitor that can address a wide variety of science cases. With its broadband spectral response, high sensitivity, and continuous all-sky coverage, it will discover fainter and rarer sources than any other existing or proposed mission. Daksha can make key strides in GRB research with polarization studies, prompt soft spectroscopy, and fine time-resolved spectral studies. Daksha will provide continuous monitoring of X-ray pulsars. It will detect magnetar outbursts and high energy counterparts to Fast Radio Bursts. Using Earth occultation to measure source fluxes, the two satellites together will obtain daily flux measurements of bright hard X-ray sources including active galactic nuclei, X-ray binaries, and slow transients like Novae. Correlation studies between the two satellites can be used to probe primordial black holes through lensing. Daksha will have a set of detectors continuously pointing towards the Sun, providing excellent hard X-ray monitoring data. Closer to home, the high sensitivity and time resolution of Daksha can be leveraged for the characterization of Terrestrial Gamma-ray Flashes.Comment: 19 pages, 7 figures. Submitted to ApJ. More details about the mission at https://www.dakshasat.in

Erbium alloyed AlN thin films: Structural, piezoelectric and magnetic properties

This research was undertaken to determine the effect of Erbium in Erbium-alloyed AlN thin films on their structural, piezoelectric and magnetic properties. For this purpose, Erbium-alloyed AlN thin films with Er concentration of 0, 1, 3 and 4 atomic percent were deposited on (001) p-type Si substrates by reactive magnetron sputtering. The samples were characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and Variable Angle Spectroscopic Ellipsometry (VASE). XRD measurements showed that Er alloying leads to preferential c-axis film deposition with a decrease in grain size and an increase in the lattice constant. XPS analysis was used to determine the Er concentration and its possible chemical state. VASE measurements were used to determine the thickness and refractive indices of the thin films. Refractive indices were used as metric to determine the structural order of polycrystalline thin films. Piezoelectric measurements showed that Er alloying results in the higher magnitude of the piezoelectric coefficient d33. Values of as high as 15.0 pm/V is measured for AlN:Er whereas the maximum value obtained for pure AlN thin films is 6.9 pm/V.;In order to determine the electronic state of Er in AlN:Er thin films, magnetization (M) of the samples was measured as a function of temperature (2 K to 300 K) and magnetic field (H) up to 90 kOe at select temperatures. In particular, the focus was to determine whether Er in AlN:Er is present as Er metal, Er2O3 or Er3+ substituting for Al3+. For this purpose, a detailed investigation of the magnetic properties of Er metal sample and a powder sample of Er2O 3 was also carried out for comparison purposes. Analysis of the results from these investigations showed that Er in AlN:Er is present as Er 3+ substituting for Al3+ in concentrations which are in good agreement with those determined from XPS. Lattice expansion of AlN:Er compared to AlN observed in XRD measurements is hence attributed to larger size Er3+ replacing Al3+.;New results obtained from the analysis of M vs. H data in Er2O 3 showed the presence of two magnetic-field induced transitions below its Neel temperature TN ∼ 3.3 K. Measurements of magnetization (M) vs. magnetic field (H) at 2 K show a transition at HSF ∼ 15 kOe which is interpreted in terms of spin flop transition and a second observed transition at Hsp ∼ 31 kOe represents field-aligned ferromagnetism in Er2O 3. This interpretation is confirmed by theoretical analysis. Magnetic field dependence of the Neel temperature TN is determined and it is observed to follow the equation TN(H) = TN(0) - D1H2 expected for antiferromagnets. From the temperature dependence of magnetic susceptibility of Er2O3 above TN and its fit to the Curie-Weiss law, the molecular field model is used to determine the nearest neighbor (nn) and next nearest neighbor (nnn) exchange constants J1 = -0.57 K and J2 = -3.38 K respectively. The determined values of J 1 and J2 are then used to calculate the magnetic field strength for field-induced ferromagnetic transition and it agrees very well with experimental value of 31 kOe.;The major conclusions from this research are that Erbium in Erbium alloyed AlN thin films is present as Er3+ substituting for Al 3+ thereby increasing its lattice constant, preferentially ordering the thin films and significantly enhancing the piezoelectric coefficient. For the related compound of Er2O3, two new magnetic-field induced transitions and associated magnitudes of exchange parameters are reported

Prevalence of drug-resistant pulmonary tuberculosis in India: systematic review and meta-analysis

Abstract Background Drug-resistant pulmonary tuberculosis (DR-TB) is a significant public health issue that considerably deters the ongoing TB control efforts in India. The purpose of this review was to investigate the prevalence of DR-TB and understand the regional variation in resistance pattern across India from 1995 to 2015, based on a large body of published epidemiological studies. Methods A systematic review of published studies reporting prevalence of DR-TB from biomedical databases (PubMed and IndMed) was conducted. Meta-analysis was performed using random effects model and the pooled prevalence estimate (95% confidence interval [CI]) of DR-TB, multidrug resistant (MDR-) TB, pre-extensively drug-resistant (pre-XDR) TB and XDR-TB were calculated across two study periods (decade 1: 1995 to 2005; decade 2: 2006 to 2015), countrywide and in different regions. Heterogeneity in this meta-analysis was assessed using I2 statistic. Results A total of 75 of 635 screened studies that fulfilled the inclusion criteria were selected. Over 40% of 45,076 isolates suspected for resistance to any first-line anti-TB drugs tested positive. Comparative analysis revealed a worsening trend in DR-TB between the two study decades (decade 1: 37.7% [95% CI = 29.0; 46.4], n = 25 vs decade 2: 46.1% [95% CI = 39.0; 53.2], n = 36). The pooled estimate of MDR-TB resistance was higher in previously treated patients (decade 1: 29.8% [95% CI = 20.7; 39.0], n = 13; decade 2: 35.8% [95% CI = 29.2; 42.4], n = 24) as compared with the newly diagnosed cases (decade 1: 4.1% [95% CI = 2.7; 5.6], n = 13; decade 2: 5.6% [95% CI = 3.8; 7.4], n = 17). Overall, studies from Western states of India reported highest prevalence of DR-TB (57.8% [95% CI = 37.4; 78.2], n = 6) and MDR-TB (39.9% [95% CI = 21.7; 58.0], n = 6) during decade 2. Prevalence of pre-XDR TB was 7.9% (95% CI = 4.4; 11.4, n = 5) with resistance to fluoroquinolone (66.3% [95% CI = 58.2; 74.4], n = 5) being the highest. The prevalence of XDR-TB was 1.9% (95% CI = 1.2; 2.6, n = 14) over the 20-year period. Conclusion The alarming increase in the trend of anti-TB drug resistance in India warrants the need for a structured nationwide surveillance to assist the National TB Control Program in strengthening treatment strategies for improved outcomes