Large zero-field cooled exchange-bias in bulk Mn2PtGa

We report a large exchange-bias (EB) effect after zero-field cooling the new tetragonal Heusler compound Mn2PtGa from the paramagnetic state. The first-principle calculation and the magnetic measurements reveal that Mn2PtGa orders ferrimagnetically with some ferromagnetic (FM) inclusions. We show that ferrimagnetic (FI) ordering is essential to isothermally induce the exchange anisotropy needed for the zero-field cooled (ZFC) EB during the virgin magnetization process. The complex magnetic behavior at low temperatures is characterized by the coexistence of a field induced irreversible magnetic behavior and a spin-glass-like phase. The field induced irreversibility originates from an unusual first-order FI to antiferromagnetic transition, whereas, the spin-glass like state forms due to the existence of anti-site disorder intrinsic to the material.Comment: 5 pages, 4 figures, supplementary material included in a separate file; accepted for publication in PR

GIS BASED MORPHOMETRIC CHARACTERISTICS OF KADAVANAR RIVER BASIN IN TAMIL NADU, INDIA

The Remote Sensing and GIS technique is an effective tool for analyzing the morphological characteristics of a river basin. The geographical location of Kadavanar river basin between latitudes 10° 52' 34.70"N and 10° 10' 57.59"N, and longitudes 77° 37' 48.14"E and 78° 13' 27.69"E, and one of the contributors to Cauvery river. The study focused on the river basin linear, areal, and relief aspects of morphometric characteristics. The study concentrated on the morphometric parameters and evolution of the stream order (U), stream length (Lu), bifurcation ratio (Rb), drainage density (Dd), stream frequency (Fs), drainage texture (Rt), elongation ratio (Re), circularity ratio (Rc), form factor (Rf), basin relief (Bh), relief ratio (Rh) and ruggedness number (Rn). The Kadavanar basin has a six-order of the drainage system, with a total of 841 stream networks, of which are 653 in the first-order, 143 in the second-order, 34 in the third-order, 8 in the fourth-order, 2 in the fifth-order stream, and 1 in the sixth-order stream according to morphometric study. The first order of the stream has a longer overall length, which decreases as the stream order increases. The average bifurcation ratio is 3.80, signifying that there were more structural disruptions due to geological influence. There has observed a low drainage density of the value of 0.91 km/km2. It indicates that the river basin has a dense vegetation cover and is highly permeable. The basin morphometric study revealed that it has a slight risk of soil erosion and flood of the basin, indicating that surface runoff of the upland region of the river basin is significantly infiltration gently downstream of the basin, contributing to the groundwater potentiality of the region. Further study of Remote Sensing and GIS techniques is more effective in developing an appropriate natural resource for the groundwater management system of the region

Effect of La Doping on Microstructure and Critical Current Density of MgB2

In the present study, La-doped MgB_2 superconductors with different doping level (Mg1-xLaxB2; x=0.00, 0.01, 0.03 & 0.05) have been synthesized by solid-state reaction route at ambient pressure. Effect of La doping have been investigated in relation to microstructural characteristics and superconducting properties, particularly intragrain critical current density (Jc). The microstructural characteristics of the as synthesized Mg(La)B2 compounds were studied employing transmission electron microscopic (TEM) technique. The TEM investigations reveal inclusion of LaB6 nanoparticles within the MgB2 grains which provide effective flux pinning centres. The evaluation of intragrain Jc through magnetic measurements on the fine powdered version of the as synthesized samples reveal that Jc of the samples change significantly with the doping level. The optimum result on Jc is obtained for Mg0.97La0.03B2 at 5K, the Jc reaches ~1.4x107A/cm2 in self field, ~2.1 x 106A/cm2 at 1T, ~2.5 x 105A/cm2 at 2.5T and ~1.8 x 104 A/cm2 at 4.5T. The highest value of intragrain Jc in Mg0.97La0.03B2 superconductor has been attributed to the inclusion of LaB6 nanoparticles which are capable of providing effective flux pinning centres

Comparative study on Haemodynamic response to extubation: Attenuation with Lignocaine, Esmolol, Propofol

Background: Endotracheal extubation is an unpredictable and tricky part of anaesthetic management. Elevation in blood pressure and heart rate due to extubation are brief but may have detrimental effects. Hence there should be an effective means of attenuating sympathetic responses to tracheal extubation. Many strategies have been advocated to minimize these hemodynamic adverse responses. Among the recommended procedures i.v. lignocaine, fentanyl and esmolol appear to fulfil the above mentioned criteria.Methods: This prospective randomized study was done on 90 patients to evaluate haemodynamic effects of intravenous Propofol, Lignocaine, Esmolol given two minutes prior to extubation.Results: Heart rate, Systolic, Diastolic and Mean blood pressure decreased significantly to Esmolol 1.5mg/kg and propofol 0.5 mg/kg 2 minutes prior to extubation. With lignocaine there was an initial rise in blood pressure. Lignocaine, Esmolol and Propofol were able to attenuate cough and strain of extubation in > 90% of the patients.Regarding Esmolol, our study coincided with similar studies done by different authors but we found that esmolol in doses of 1.5mg/kg showed better results to control haemodynamic response during extubation.  Sedation score was a little high in Propofol group. Extubation scoring was good with all the three drugs.Conclusions: Esmolol IV is preferred for attenuation of haemodynamic responses when compared with IV propofol 0.5 mg/kg and IV lignocaine (2%) 1 mg/kg as the attenuation effect is elicited immediately.

Thermopower and thermal conductivity in the Weyl semimetal NbP

The Weyl semimetal NbP exhibits an extremely large magnetoresistance (MR) and an ultra-high mobility. The large MR originates from a combination of the nearly perfect compensation between electron- and hole-type charge carriers and the high mobility, which is relevant to the topological band structure. In this work we report on temperature- and field-dependent thermopower and thermal conductivity experiments on NbP. Additionally, we carried out complementary heat capacity, magnetization, and electrical resistivity measurements. We found a giant adiabatic magnetothermopower with a maximum of 800 $\mu$V/K at 50 K in a field of 9 T. Such large effects have been observed rarely in bulk materials. We suggest that the origin of this effect might be related to the high charge-carrier mobility. We further observe pronounced quantum oscillations in both thermal conductivity and thermopower. The obtained frequencies compare well with our heat capacity and magnetization data.Comment: 6 pages, 3 figure

Development of 0.2C-CrMnMoV Ultra High Strength Steel

A study was carried out to develop a low alloy ultra high strength steel by induction melting and thermomechanical treatment (TMT) containing alloying elements like carbon, manganese, molybdenum, chromium and vanadium. A base alloy was prepared with 0.24%C, 1.16% Mn, 0.23% Si, 5.61% Cr, 0.42%V, 1.01% Mo, 0.026%S and 0.032%P. It showed tensile strength of 1467 MPa, yield strength of about 1180 MPa, impact strength of 6.3J and elongation of 5.9% in as-tempered condition. Other alloy was prepared by addition of 0.054% titanium with the base composition. It displayed tensile strength, yield strength, impact toughness and % elongation of 1615 MPa, 1240 MPa, 8.2J and 6.15%, respectively. The optical, SEM and TEM microstructures confirmed that the base alloy and the titanium alloy consisted with tempered lath martensites. The remaining part of the ingot was further processed by the thermomechanical treatment. The ingots were rolled in two passes, initially at 950 C and subsequently at 850 C followed by immediate cooling in oil. The TMT plates of the base alloy confirmed the tensile strength of 1755 MPa, yield strength in excess of 1460 MPa and impact strength of 9.1J. The titanium added TMT plate displayed tensile strength of 1860 MPa, yield strength of 1580 MPa and impact strength of 10.1J. Microstructures of titanium added alloy consisted finer lath martensite and precipitates of titanium carbides/carbonitrides. It was observed that the addition of titanium significantly improved the mechanical properties of 0.2C-Cr Mn Mo V alloys and the mechanical properties were also improved significantly by thermomechanical treatment

An Intelligent Gain based Ant Colony Optimisation Method for Path Planning of Unmanned Ground Vehicles

 In many of the military applications, path planning is one of the crucial decision-making strategies in an unmanned autonomous system. Many intelligent approaches to pathfinding and generation have been derived in the past decade. Energy reduction (cost and time) during pathfinding is a herculean task. Optimal path planning not only means the shortest path but also finding one in the minimised cost and time. In this paper, an intelligent gain based ant colony optimisation and gain based green-ant (GG-Ant) have been proposed with an efficient path and least computation time than the recent state-of-the-art intelligent techniques. Simulation has been done under different conditions and results outperform the existing ant colony optimisation (ACO) and green-ant techniques with respect to the computation time and path length

Strong correlation between mobility and magnetoresistance in Weyl and Dirac semimetals

The discovery of Weyl and Dirac fermions in solid systems is a recent major breakthrough in the field of condensed matter physics. These materials exhibit extraordinary properties in terms of carrier mobility and magnetoresistance (MR). These two quantities are highly dependent in the Weyl semimetal transition monopnictide family, i.e. NbP, TaP, NbAs, and TaAs. Furthermore, the gathered mobility and MR (or slope of MR) at 2 K in 9 T of other well-known Weyl and Dirac semimetals follow a relation similar to the right turn symbol, i.e. the MR increases rapidly with mobility; thereafter it begins to saturate after reaching a value of 10(3). This suggests a nonlinear dependency. Nevertheless, for materials possessing high carrier mobility, it is valid to expect high MR

Nonclassical properties of states engineered by superpositions of quantum operations on classical states

We consider an experimentally realizable scheme for manipulating quantum states using a general superposition of products of field annihilation ($\hat{a}$) and creation ($\hat{a}^\dag$) operators of the type ($s \hat{a}\hat{a}^\dag+ t \hat{a}^\dag \hat{a}$), with $s^2 + t^2 = 1$. Such an operation, when applied on states with classical features, is shown to introduce strong nonclassicality. We quantify the generated degree of nonclassicality by the negative volume of Wigner distribution in the phase space and investigate two other observable nonclassical features, sub-Poissonian statistics and squeezing. We find that the operation introduces negativity in the Wigner distribution of an input coherent state and changes the Gaussianity of an input thermal state. This provides the possibility of engineering quantum states with specific nonclassical features.Comment: 19 pages, IOPclass(iopart.cls

Recovering missing slices of the discrete fourier transform using ghosts

The discrete Fourier transform (DFT) underpins the solution to many inverse problems commonly possessing missing or unmeasured frequency information. This incomplete coverage of the Fourier space always produces systematic artifacts called Ghosts. In this paper, a fast and exact method for deconvolving cyclic artifacts caused by missing slices of the DFT using redundant image regions is presented. The slices discussed here originate from the exact partitioning of the Discrete Fourier Transform (DFT) space, under the projective Discrete Radon Transform, called the discrete Fourier slice theorem. The method has a computational complexity of O(n\log-{2}n) (for an n=N\times N image) and is constructed from a new cyclic theory of Ghosts. This theory is also shown to unify several aspects of work done on Ghosts over the past three decades. This paper concludes with an application to fast, exact, non-iterative image reconstruction from a highly asymmetric set of rational angle projections that give rise to sets of sparse slices within the DFT