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Substrate effects in high gain, low operating voltage SnSe2 photoconductor
No full textHigh gain photoconductive devices find wide spread applications in low intensity light detection. Ultra-thin layered materials have recently drawn a lot of attention from researchers in this regard. However, in general, a large operating voltage is required to obtain large responsivity in these devices. In addition, the characteristics are often confounded by substrate induced trap effects. Here we report multi-layer SnSe2 based photoconductive devices using two different structures: (1) SiO2 substrate supported inter-digitated electrode (IDE), and (2) suspended channel. The IDE device exhibits a responsivity of approximate to 10(3) A W-1 and approximate to 8.66 x 10(4) A W-1 at operating voltages of 1 mV and 100 mV, respectively-a superior low voltage performance over existing literature on planar 2D structures. However, the responsivity reduces by more than two orders of magnitude, while the transient response improves for the suspended device-providing insights into the critical role played by the channel-substrate interface in the gain mechanism. The results, on one hand, are promising for highly sensitive photoconductive applications consuming ultra-low power, and on the other hand, show a generic methodology that could be applied to other layered material based photoconductive devices as well for extracting the intrinsic behavior
Microheterogeneity in imidazolium and piperidinium cation-based ionic liquids: 1D and 2D NMR studies
No full textExistence of microheterogeneity of imidazolium and piperidinium cation-based ionic liquids (ILs) containing PF6 and NTf2 anions has been investigated by 1D and 2D NMR spectroscopy. 2D NMR (especially NOESY and HOESY) has been employed for studying the interactions present between cation and anion as well as the intermolecular interaction among cations. HOESY spectrum shows that fluorine of anion (PF6- and NTf2-) significantly interacts with proton of the cations. Combined results of HOESY and NOESY for imidazolium IL indicate that the PF6- and imidazolium cation are distributed in organized manner, resulting a heterogeneous environment in liquid state. We have also observed existence of heterogeneous environment for piperidinium cation-based ILs which is different from imidazolium ILs. It appears that existence of microheterogeneity in IL is ubiquitous and therefore open up the ILs field to revisit. Copyright (C) 2017 John Wiley & Sons, Ltd
A new cryptic, rupicolous species of Hemidactylus Oken, 1817 (Squamata: Gekkonidae) from Meghamalai, Tamil Nadu, India
No full textA distinct new gecko of the genus Hemidactylus is described from the Meghamalai massif in Tamil Nadu, India. This large sized (average SVL 88.2 +/- 16.0 to at least 112.2 mm), cryptic, rock-dwelling species is superficially similar to its tuberculate South Asian congeners of comparable size, but can be distinguished from them in having 17-19 longitudinal rows of fairly regularly arranged, strongly keeled, striated tubercles with the two most medial parasagittal rows smaller, flatter, strongly keeled and rounded, increasing in size laterally and becoming strongly conical at the flanks; 8-10 and 10-12 subdigital lamellae under the first and fourth digits respectively of both manus and pes; 17-22 femoral pores on each side separated medially by a diastema of 10-11 poreless scales; 11-15 supralabials and 9-14 infralabials. Molecular data supports the distinctiveness of this species and helps ascertain its phylogenetic position within the larger Indian Hemidactylus clade
Influence of secondary compression on undrained strength of soft kaolinites
No full textSoft kaolinite deposits of marine origin are encountered as foundation soils in many parts of the world. The well-developed flocculated structure of kaolinite-bearing marine deposits is amenable to alterations from leaching of pore solution salts, loss of overburden, and secondary compression. Secondary compression causes densification of microstructure that may impact the viscous resistance, soil stiffness, and undrained shear strength of kaolinite-bearing marine deposits. This study examines the influence of secondary compression on viscous resistance and constrained stress-strain modulus of soft kaolinites prepared in synthetic seawater and sodium chloride solutions. The impact of secondary compression on undrained shear strength is interpreted from changes in microstructure, percent monovalent cation concentration, viscous resistance, and constrained stress-strain modulus. Kaolinite specimens experience reduction in void space during secondary compression. Breakdown of edge-face (E-F) and edge-edge (E-E) contacts of kaolinite particles during secondary compression and creation of interlocking zones is observed from scanning electron micrograph studies. Breakdown of E-F and E-E contacts is considered responsible for reduction in constrained stress-strain modulus during secondary compression. Concomitant, creation of interlocking zones at particle contacts increases the viscous resistance of microstructure that enhances the undrained shear strength of soft kaolinites
Lack of thermal energy in superbubbles: hint of cosmic rays?
No full textUsing analytic methods and 1D two-fluid simulations, we study the effect of cosmic rays (CRs) on the dynamics of interstellar superbubbles (ISBs) driven by multiple supernovae (SNe)/stellar winds in OB associations. In addition to CR advection and diffusion, our models include thermal conduction and radiative cooling. We find that CR injection at the reverse shock or within a central wind-driving region can affect the thermal profiles of ISBs and hence their X-ray properties. Even if a small fraction (10-20 per cent) of the total mechanical power is injected into CRs, a significant fraction of the ram pressure at the reverse shock can be transferred to CRs. The energy transfer becomes efficient if (1) the reverse shock gas Mach number exceeds a critical value (M-th greater than or similar to 12) and (2) the CR acceleration time-scale tau(acc) similar to k(cr)/v(2) is shorter than the dynamical time, where k(cr) is a CR diffusion coefficient and v is the upstream velocity. We show that CR affected bubbles can exhibit a volume-averaged hot gas temperature 1-5 x 10(6) K, lower by a factor of 2 -10 than without CRs. Thus, CRs can potentially solve the long-standing problem of the observed low ISB temperatures
Geocell reinforcement for performance improvement of vertical plate anchors in sand
No full textIn this paper influence of geocell reinforcement on performance of vertical plate anchors is studied. A series of model tests were carried out in a test bed-cum-loading frame assembly. The anchor used was a steel plate of size 100 mm x 100 mm. With geocell reinforcement the anchor could sustain deformations as high as 60-70% of its height when the load carrying capacity was increased by four fold. The optimum length, width, and height of geocell mattress giving maximum performance improvement are found to be 5, 3 and 2.8 times the anchor height respectively. For adequate performance improvement size of geocell pocket opening should be close to the anchor size. The load dispersion angle that depicts the rigidity of the geocell mattress tends to increase with increase in its width, height and reduction in pocket size. A numerical study using fast Lagrangian analysis of continua was carried out. The agreement between observed and computed results is found to be reasonably good
A nano-catalytic approach for C-B bond formation reactions
No full textHerein, we present a chronological survey of the metal/metal oxide nanoparticle-catalysed borylation reactions. Transition metal-catalysed borylation is considered to be one of the most efficient methods for the synthesis of organoboron derivatives. Considering chemical and pharmaceutical processes, the major drawbacks of homogeneous catalysis are metal contamination in products and inability to recover catalysts for reuse, which limit its application industrially, in biomolecules, and materials science. The use of nanoparticles as heterogeneous catalysts is a current topic of research to overcome these limitations. This review gives an overview of the metal nanoparticle-catalysed borylation reactions and also discusses the reaction mechanisms
Sustainable use of termite activity in agro-ecosystems with reference to earthworms. A review
No full textSustainable agriculture and agro-ecology justify the need to study and understand the role played by ecological processes, and soil biodiversity in particular, in agro-ecosystem functioning. A large number of studies have focused on earthworms in temperate and humid tropical ecosystems and have demonstrated their importance for improving soil biological, physical, and chemical properties in agro-ecosystems. Their ``success'' is so essential that earthworms are widely considered key species and relevant indicators of soil health in temperate ecosystems. In arid and sub-arid ecosystems, the role of ``soil engineer'' is usually attributed to termites, and especially fungus-growing termites in Africa and Asia. However, despite this recognition, significant effort is spent eradicating them in plantations because of their pest status. In this review, we discuss the status of termites (''pests'' vs. ``soil engineers'') and question whether termites play similar roles to earthworms in arid-and sub-arid agroecosystems, with a focus on their influence on nutrient cycling and water dynamics. We argue that the dream of controlling natural interactions and ridding plantations of termites remains a costly legacy of the green revolution. We review the agricultural practices that have been used to reduce termite damage in plantations by restoring refuges to predators or by reorienting termite foraging activity towards organic amendments. Then, we show that the stimulation of termite activity can be used to improve key ecological functions in agroecosystems, such as increasing water availability to plants or producing fertility hot-spots. Finally, we suggest that more research on how termites can be used for improving ecosystem services, as is actually done with earthworms in temperate and humid tropical countries, could lead to a paradigm shift in our understanding of the impact of termites in tropical agro-ecosytems
Extraction and bioactive profile of the compounds produced by Rhodococcus sp. VLD-10 (vol 6, 261, 2016)
No full textNew insights into microstructural evolution of epitaxial Ni-Mn-Ga films on MgO (100) substrate by high-resolution X-ray diffraction and orientation imaging investigations
No full textIn this work, a detailed investigation has been performed on hetero-epitaxial growth and microstructural evolution in highly oriented Ni-Mn-Ga (1 0 0) films grown on MgO (1 0 0) substrate using high-resolution X-ray diffraction and orientation imaging microscopy. Mosaicity of the films has been analysed in terms of tilt angle, twist angle, lateral and vertical coherence length and threading dislocation densities by performing rocking curve measurements and reciprocal space mapping. Density of edge dislocations is found to be an order of magnitude higher than the density of screw dislocations, irrespective of film thickness. X-ray pole figure measurements have revealed an orientation relationship of || 0 0 1](MgO) between the film and substrate. Microstructure predicted by X-ray diffraction is in agreement with that obtained from electron microscopy and atomic force microscopy. The evolution of microstructure in the film with increasing thickness has been explained vis-a-vis dislocation generation and growth mechanisms. Orientation imaging microscopy observations indicate evolutionary growth of film by overgrowth mechanism. Decrease in coercivity with film thickness has been explained as an interplay between stress field developed due to crystal defects and magnetic domain pinning due to surface roughness