Electrical, Thermal and Spectroscopic Characterization of Bulk Bi2Se3 Topological Insulator

We report electrical (angular magneto-resistance, and Hall), thermal (heat capacity) and spectroscopic (Raman, x-ray photo electron, angle resolved photo electron) characterization of bulk Bi2Se3 topological insulator, which is being is grown by self flux method through solid state reaction from high temperature (950C) melt and slow cooling (2C/hour) of constituent elements. Bi2Se3 exhibited metallic behaviour down to 5K. Magneto transport measurements revealed linear up to 400% and 30% MR at 5K under 14 Tesla field in perpendicular and parallel field direction respectively. We noticed that the magneto-resistance (MR) of Bi2Se3 is very sensitive to the angle of applied field. MR is maximum when the field is normal to the sample surface, while it is minimum when the field is parallel. Hall coefficient (RH) is seen nearly invariant with negative carrier sign down to 5K albeit having near periodic oscillations above 100K. Heat capacity (Cp) versus temperature plot is seen without any phase transitions down to 5K and is well fitted (Cp = gammaT + betaT3) at low temperature with calculated Debye temperature (ThetaD) value of 105.5K. Clear Raman peaks are seen at 72, 131 and 177 cm-1 corresponding to A1g1, Eg2 and A1g2 respectively. Though, two distinct asymmetric characteristic peak shapes are seen for Bi 4f7/2 and Bi 4f5/2, the Se 3d region is found to be broad displaying the overlapping of spin - orbit components of the same. Angle-resolved photoemission spectroscopy (ARPES) data of Bi2Se3 revealed distinctly the bulk conduction bands (BCB), surface state (SS), Dirac point (DP) and bulk valence bands (BVB) and 3D bulk conduction signatures are clearly seen. Summarily, host of physical properties for as grown Bi2Se3 crystal are reported here.Comment: 6 Pages Text + Figs; Comments Suggestions welcom

Superconductivity at 5.5 K in Nb2PdSe5 compound

We report superconductivity in as synthesized Nb2PdSe5, which is similar to recently discovered Nb2PdS5 compound having very high upper critical field, clearly above the Pauli paramagnetic limit [Sci. Rep. 3, 1446 (2013)]. A bulk polycrystalline Nb2PdSe5 sample is synthesized by solid state reaction route in phase pure structure. The structural characterization has been done by X ray diffraction, followed by Rietveld refinements, which revealed that Nb2PdSe5 sample is crystallized in monoclinic structure with in space group C2/m. Structural analysis revealed the formation of sharing of one dimensional PdSe2 chains. Electrical and magnetic measurements confirmed superconductivity in Nb2PdSe5 compound at 5.5K. Detailed magneto-resistance results, exhibited the value of upper critical field to be around 8.2Tesla. The estimated Hc2(0) is within Pauli Paramagnetic limit, which is unlike the Nb2PdS5.Comment: 13 pages text + Fig

Analysis on DV-Hop Algorithm and its variants by considering threshold

Wireless Sensor networks is a network of lowpriced, small sized and energy constraint sensor nodes where each sensor node is programmed to sense the events and send it to the Base station using multi-hop communication. In almost all applications of Wireless Sensor Networks, event detection information is required along with the location of the event. Thus, to find the location of event, node localization plays an important role. Many researchers have put tremendous efforts in designing localization algorithms. In the literature, it is confirmed that DV-Hop algorithm and its variants are the most suitable range-free based algorithms for node localization, due to its cost effectiveness, simplicity and feasibility for medium to large scale networks, but these algorithms consume very high energy. The DV-Hop algorithm works in three phases. The first phase allows all the nodes to get their distance from few localized nodes called anchors in terms of hop. The hop is the count of neighboring nodes between two nodes. Then in second phase, the anchor nodes find out their approximate distances from every node. The third phase computes the location of node using the information obtained from first two phases and by applying trilateration method. The high energy is consumed due to transmission of large number of packets in the first two phases by anchor nodes. In order to reduce communication overhead of the first two phase of DV-Hop, an improved DV-Hop is proposed that considers only k-hop transmission of the anchor packet which reduces the communication overheads to the large extent. Simulation experiments and results prove that the proposed method reduces the energy consumption by approximately 50% compare to the traditional DV-Hop algorithm

Assessment of optical, mechanical and nonlinear properties of potassium acid phthalate single crystal: a potential candidate for optoelectronic applications

A good optical quality semi-organic single crystal of Potassium Acid Phthalate (KAP) was harvested from aqueous solution by using slow evaporation solution growth technique (SEST) at ambient condition. The defect free single crystal of KAP was analyzed by different instrumentation techniques, for checking its compatibility for different applications. Its unit cell dimensions and phase purity was examined by powder X-ray diffraction (PXRD) and found that it crystallizes in orthorhombic with non-centrosymmetric in nature. The quality of the grown ingot was assessed by high resolution X-ray diffraction (HRXRD) technique and found that, the crystalline quality is better with less grain boundaries. Its optical properties were scrutinized by UV-vis., photoluminescence (PL) and time resolved photoluminescence (TRPL) measurements respectively. The mechanical stability of the grown crystal was tested by Vickers microhardness method and found that the grown crystal shows indentation size effect (ISE) which was explained using different theoretical models. Its third order nonlinear optical properties were studied by Z-scan measurement by using Ti:Sapphire laser as a source and determined its nonlinear absorption coefficient (beta) and it was found that the KAP crystal is one of the preferable choices for optical limiting applications

Investigation of charge carrier dynamics in Ti3C2Tx MXene for ultrafast photonics applications

The rapid advancement of nanomaterials has paved the way for various technological breakthroughs, and MXenes, in particular, have gained substantial attention due to their unique properties such as high conductivity, broad-spectrum absorption strength, and tunable band gap. This article presents the impact of the process parameters on the structural and optical properties of Ti3C2Tx MXene for application in ultrafast dynamics. XRD along with Raman spectroscopy studies, confirmed the synthesis of a single phase from their MAX phase Ti3AlC2. The complete etching of Al and increase in the interplanar distance is also observed on centrifugation at very high speed. The ultrafast transient absorption spectroscopy used to understand the effect of centrifuge speed on the charge carrier dynamics and ultrafast spectrum of MXene displayed that the carrier lifetime is critically influenced by rotation per minute (rpm) e.g. faster decay lifetime at 10k rpm than 7k rpm. The electronic relaxation probed using the time-resolved photoluminescence (TRPL) technique exhibits an average decay time of 5.13 ns and 5.35 ns at the 7k and 10k rpm, respectively, which confirms that the optical properties of the MXene are strongly affected by the centrifuge speed. The synthesized MXene at 10k rpm typically suggests that radiative processes due to longer decay lifetime and experiences fewer nonradiative losses, resulting in enhanced luminescence properties.Comment: 21 pages , 6 figure

High risk of tuberculosis during infliximab therapy despite tuberculosis screening in inflammatory bowel disease patients in India

Background/Aims The data on the risk of tuberculosis (TB) reactivation with infliximab (IFX) in patients with inflammatory bowel disease (IBD) from TB endemic countries, like India, is limited. The risk of TB reactivation on IFX and its predictors in patients with IBD was assessed. Methods This retrospective review included consecutive patients with IBD who received IFX, and were on follow-up from January 2005 to November 2017. The data was recorded on age/disease duration, indications for IFX, screening for latent tuberculosis (LTB) before IFX, response to IFX, incidence and duration when TB developed after IFX, and type of TB (pulmonary [PTB]/extra-pulmonary [EPTB]/disseminated). Results Of 69 patients (22 ulcerative colitis/47 Crohn’s disease; mean age, 35.6±14.5 years; 50.7% males; median follow-up duration after IFX, 19 months [interquartile range, 5.5–48.7 months]), primary non-response at 8 weeks and secondary loss of response at 26 and 52 weeks were seen in 14.5%, 6% and 15% patients respectively. Prior to IFX, all patients were screened for LTB, 8 (11.6%) developed active TB (disseminated, 62.5%; EPTB, 25%; PTB, 12.5%) after a median of 19 weeks (interquartile range, 14.0–84.5 weeks) of IFX. Of these 8 patients’ none had LTB, even when 7 of 8 were additionally screened with contrast-enhanced chest tomography. Though not statistically significant, more patients with Crohn’s disease than ulcerative colitis (14.9% vs. 4.5%, P=0.21), and those with past history of TB (25% vs. 9.8%, P=0.21), developed TB. Age, gender, disease duration, or extraintestinal manifestations could not predict TB reactivation. Conclusions There is an extremely high rate of TB with IFX in Indian patients with IBD. Current screening techniques are ineffective and it is difficult to predict TB after IFX

Deep phenotyping and genomic data from a nationally representative study on dementia in India

The Harmonized Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India (LASI-DAD) is a nationally representative in-depth study of cognitive aging and dementia. We present a publicly available dataset of harmonized cognitive measures of 4,096 adults 60 years of age and older in India, collected across 18 states and union territories. Blood samples were obtained to carry out whole blood and serum-based assays. Results are included in a venous blood specimen datafile that can be linked to the Harmonized LASI-DAD dataset. A global screening array of 960 LASI-DAD respondents is also publicly available for download, in addition to neuroimaging data on 137 LASI-DAD participants. Altogether, these datasets provide comprehensive information on older adults in India that allow researchers to further understand risk factors associated with cognitive impairment and dementia.Peer reviewe

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]