Hopping Conduction in Uniaxially Stressed Si:B near the Insulator-Metal Transition

Using uniaxial stress to tune the critical density near that of the sample, we have studied in detail the low-temperature conductivity of p-type Si:B in the insulating phase very near the metal-insulator transition. For all values of temperature and stress, the conductivity collapses onto a single universal scaling curve. For large values of the argument, the scaling function is well fit by the exponentially activated form associated with variable range hopping when electron-electron interactions cause a soft Coulomb gap in the density of states at the Fermi energy. The temperature dependence of the prefactor, corresponding to the T-dependence of the critical curve, has been determined reliably for this system, and is proportional to the square-root of T. We show explicitly that nevlecting the prefactor leads to substantial errors in the determination of the scaling parameters and the critical exponents derived from them. The conductivity is not consistent with Mott variable-range hopping in the critical region nor does it obey this form for any range of the parameters. Instead, for smaller argument of the scaling function, the conductivity of Si:B is well fit by an exponential form with exponent 0.31 related to the critical exponents of the system at the metal- insulator transition.Comment: 13 pages, 6 figure

Absence of Conventional Spin-Glass Transition in the Ising Dipolar System LiHo_xY_{1-x}F_4

The magnetic properties of single crystals of LiHo_xY_{1-x}F_4 with x=16.5% and x=4.5% were recorded down to 35 mK using a micro-SQUID magnetometer. While this system is considered as the archetypal quantum spin glass, the detailed analysis of our magnetization data indicates the absence of a phase transition, not only in a transverse applied magnetic field, but also without field. A zero-Kelvin phase transition is also unlikely, as the magnetization seems to follow a non-critical exponential dependence on the temperature. Our analysis thus unmasks the true, short-ranged nature of the magnetic properties of the LiHo_xY_{1-x}F_4 system, validating recent theoretical investigations suggesting the lack of phase transition in this system.Comment: 5 pages, 4 figure

Night sky at the Indian Astronomical Observatory during 2000-2008

We present an analysis of the optical night sky brightness and extinction coefficient measurements in UBVRI at the Indian Astronomical Observatory (IAO), Hanle, during the period 2003-2008. They are obtained from an analysis of CCD images acquired at the 2 m Himalayan Chandra Telescope at IAO. Night sky brightness was estimated using 210 HFOSC images obtained on 47 nights and covering the declining phase of solar activity cycle-23. The zenith corrected values of the moonless night sky brightness in mag/square arcsecs are 22.14(U), 22.42(B), 21.28(V), 20.54(R) and 18.86(I) band. This shows that IAO is a dark site for optical observations. No clear dependency of sky brightness with solar activity is found. Extinction values at IAO are derived from an analysis of 1325 images over 58 nights. They are found to be 0.36 in U-band, 0.21 in B-band, 0.12 in V-band, 0.09 in R-band and 0.05 in I-band. On average, extinction during the summer months is slightly larger than that during the winter months. No clear evidence for a correlation between extinction in all bands and the average night time wind speed is found. Also presented here is the low resolution moonless optical night sky spectrum for IAO covering the wavelength range 3000-9300 \AA. Hanle region thus has the required characteristics of a good astronomical site in terms of night sky brightness and extinction, and could be a natural candidate site for any future large aperture Indian optical-infrared telescope(s).Comment: 18 pages, 7 figures, uses basi.cls, accepted for publication in Bulletin of the Astronomical Society of Indi

Present Scenario of Fog Computing and Hopes for Future Research

According to the forecast that billions of devices will get connected to the Internet by 2020. All these devices will produce a huge amount of data that will have to be handled rapidly and in a feasible manner. It will become a challenge for real-time applications to handle this huge data while considering security issues as well as time constraints. The main highlights of cloud computing are on-demand service and scalability; therefore the data generated from IoT devices are generally handled in cloud infrastructure. Though, dealing with IoT application requests on the cloud exclusively is not a proficient result for some IoT applications particularly time-sensitive ones. These issues can be settled by utilizing another idea called, Fog computing. Fog computing has become one of the major fields of research from both academia and industry perspectives. The ongoing research commitments on few issues in fog computing are figuring out in this paper. At long last, this paper also highlights some open issues in fog with IoT, which will determine the future research direction for implementing Fog computing paradigm

Conductivity of Metallic Si:B near the Metal-Insulator Transition: Comparison between Unstressed and Uniaxially Stressed Samples

The low-temperature dc conductivities of barely metallic samples of p-type Si:B are compared for a series of samples with different dopant concentrations, n, in the absence of stress (cubic symmetry), and for a single sample driven from the metallic into the insulating phase by uniaxial compression, S. For all values of temperature and stress, the conductivity of the stressed sample collapses onto a single universal scaling curve. The scaling fit indicates that the conductivity of si:B is proportional to the square-root of T in the critical range. Our data yield a critical conductivity exponent of 1.6, considerably larger than the value reported in earlier experiments where the transition was crossed by varying the dopant concentration. The larger exponent is based on data in a narrow range of stress near the critical value within which scaling holds. We show explicitly that the temperature dependences of the conductivity of stressed and unstressed Si:B are different, suggesting that a direct comparison of the critical behavior and critical exponents for stress- tuned and concentration-tuned transitions may not be warranted

Water poverty in the northeastern hill region (India): potential alleviation through multiple-use water systems: cross-learnings from Nepal Hills

Water poverty index / Construction / Multiple use / Water storage / Farming systems / Villages / Social aspects / Drip irrigation / India / Nepal / Nagaland / Mon district / Lampong Sheanghah

A study on commercial cultivation and storage of water chestnut (Trapa natans L.) under wetland ecosystem of North Bihar, India

Water chestnut is an excellent economical and medicinal winter crop from fresh water ecosystem. It is well known for its nutrient content including protein and antioxidants. Different water chestnut germplasm viz. Green Spineless, Green Spine, Red Spineless and Red Spine were studied at wetland ecosystem of North Bihar in India under Research Centre on Makhana, Darbhanga, during 2016-17. Under wetland ecosystem, Green Spineless variety of water chestnut produced large quality nut (24.42 g) followed by Red Spineless (23.11 g). Regarding yield, Green Spineless gave rise to the maximum yield of 12.24 t/ha. The Red Spineless variety exhibited the maximum TSS of 9.60B followed by Green Spineless (9.20B). Water chestnut beetle (Galerucella birmanica Jacoby.) was dangerous pest under wet land ecosystem as compared to aphid.  Green colored varieties were resistant to beetle and aphid. Different approaches had been made to enhance the shelf life of water chestnut variety Red Spineless as it was sweetest and attractive in colour among trial varieties. The results revealed that poly packaging with 5% perforation and stored in refrigerator for 40C (T1) increased storage life up to 14.0days as compared to open ambient (T4) (4.72 days) maintaining  fair market acceptability. This treatment (T1) also improved the TSS content of the fruit to 9.80B by slow and gradual PLW about 21.15 % during two weeks of storage. From our present study it may be concluded that irrespective of color, spineless varieties of water chestnut were promising under wetland ecosystem of North Bihar on account of their yield potential and nut quality

Predator Harvesting in Systems with One Predator and Two Prey Habitats

Harvesting of the predator in systems consisting of one predator and two preys where the preys live in two different habitats is considered. It is assumed that the prey species have resources in abundance and the predator specie is able to switch to the most abundant prey specie. We consider two types of predator harvesting. One is when we harvest a fixed amount of predators (constant harvest quota) and the other is when we harvest a fixed percentage of the predators (constant harvest effort). Stability analysis is carried out and hypothetical cases are used to support our analysis