426 research outputs found
Direct limit of matrix ordered spaces
In this paper we initiate the study of ordered f-bimodules as the inductive limit of matrix ordered spaces
Synthesis of possible room temperature superconductor LK-99:PbCu(PO)O
The quest for room-temperature superconductors has been teasing scientists
and physicists, since its inception in 1911 itself. Several assertions have
already been made about room temperature superconductivity but were never
verified or reproduced across the labs. The cuprates were the earliest high
transition temperature superconductors, and it seems that copper has done the
magic once again. Last week, a Korean group synthesized a Lead Apatite-based
compound LK-99, showing a T of above 400K. The signatures of
superconductivity in the compound are very promising, in terms of resistivity
(R = 0) and diamagnetism at T. Although, the heat capacity (C) did not
show the obvious transition at T. Inspired by the interesting claims of
above room temperature superconductivity in LK-99, in this article, we report
the synthesis of polycrystalline samples of LK-99, by following the same heat
treatment as reported in [1,2] by the two-step precursor method. The phase is
confirmed through X-ray diffraction (XRD) measurements, performed after each
heat treatment. The room temperature diamagnetism is not evidenced by the
levitation of a permanent magnet over the sample or vice versa. Further
measurements for the confirmation of bulk superconductivity on variously
synthesized samples are underway. Our results on the present LK-99 sample,
being synthesized at 925C, as of now do not approve the appearance of
bulk superconductivity at room temperature. Further studies with different heat
treatments are though, yet underway.Comment: Short Commun.: 8pages Text + Figs: Comments/suggestion Welcom
Topological Superconductor Sn4Au: A first principle study
Topological semimetals such as Weyl or Dirac semimetal with superconductivity
have emerged as a new class of topological materials to realize and study
Majorana Fermion in its intrinsic form. This article reports the Density
Functional Theory (DFT) calculated bulk electronic band structure of recently
discovered topological superconductor candidate Sn4Au. This study is further
extended to the calculation of Z2 invariants. The Fermi surfaces corresponding
to the bands which are responsible for non-trivial band topology along with the
surface states are also mapped. The complete study suggests that Sn4Au is a
topological semimetal. On Sn4Au, it is the first report in the literature
showing the non-trivial band topology based on first-principle calculations.Comment: 19 Pages Text + Figs: SUST - Special issue: Superconductivity
Research in Indi
Weak Antilocalization and topological edge states in PdSn
Here we report, the successful synthesis of single crystals of topological
semimetal (TSM) candidate, PdSn using the self-grown route. The synthesized
crystal is well characterized through X-ray diffraction (XRD), field emission
scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy
(XPS). Detailed Rietveld analysis of the powder XRD pattern of PdSn
confirmed the same to crystallize in the Aea2 space group instead of reported
Ccce. A large magnetoresistance (MR) along with Subnikov-de Haas oscillations
have been observed in magnetotransport measurements at 2K. The presence of a
weak antilocalization (WAL) effect in synthesized PdSn crystal is confirmed
and analyzed using Hikami Larkin Nagaoka (HLN) formalism, being applied on
magnetoconductivity of the same at the low magnetic field. An extended Kohler
rule is implemented on MR data, to determine the role of the scattering process
and temperature-dependent carrier density on transport phenomenon in PdSn.
Further, the non-trivial band topology and presence of edge states are shown
through density functional theory (DFT) based theoretical calculations. All
calculations are performed considering the Aea2 space group symmetry. The
calculated Z2 invariants suggest the presence of weak topological insulating
properties in PdSn. Clear evidence of topological edge states at the
point is visible in calculated edge state spectra. This is the first
report on PdSn, showing the presence of SdH oscillation in magneto
transport measurement.Comment: 26 PAGES TEXT + FIGS. REVISED J. APPL. PHYS. 202
Dynamic classification using case-specific training cohorts outperforms static gene expression signatures in breast cancer
The molecular diversity of breast cancer makes it impossible to identify prognostic markers that are applicable to all breast cancers. To overcome limitations of previous multigene prognostic classifiers, we propose a new dynamic predictor: instead of using a single universal training cohort and an identical list of informative genes to predict the prognosis of new cases, a case-specific predictor is developed for each test case. Gene expression data from 3,534 breast cancers with clinical annotation including relapse-free survival is analyzed. For each test case, we select a case-specific training subset including only molecularly similar cases and a case-specific predictor is generated. This method yields different training sets and different predictors for each new patient. The model performance was assessed in leave-one-out validation and also in 325 independent cases. Prognostic discrimination was high for all cases (n = 3,534, HR = 3.68, p = 1.67 E-56). The dynamic predictor showed higher overall accuracy (0.68) than genomic surrogates for Oncotype DX (0.64), Genomic Grade Index (0.61) or MammaPrint (0.47). The dynamic predictor was also effective in triple-negative cancers (n = 427, HR = 3.08, p = 0.0093) where the above classifiers all failed. Validation in independent patients yielded similar classification power (HR = 3.57). The dynamic classifier is available online at http://www.recurrenceonline.com/?q=Re_training. In summary, we developed a new method to make personalized prognostic prediction using case-specific training cohorts. The dynamic predictors outperform static models developed from single historical training cohorts and they also predict well in triple-negative cancers
Detailed structural and topological analysis of SnBi2Te4 single crystal
We report herein the successful synthesis of the topological material
SnBi2Te4 in single-crystal form. Phase purity and unidirectional growth are
evident from X-ray diffraction (XRD) patterns acquired from a powdered sample
and a crystal flake. The crystalline morphology has also been visualized by
acquiring a field-emission scanning electron microscope (FESEM) image. The
crystal has been thoroughly characterized by means of Raman spectroscopy and X
ray photoelectron spectroscopy (XPS) measurements. The topological properties
of SnBi2Te4 have been probed through magneto-transport measurements. SnBi2Te4
has been found to exhibit a small but non-saturating magneto-resistance (MR) up
to 12 T. The low-field magnetoconductivity (MC) of SnBi2Te4 at 2 K can be well
explained through the Hikami Larkin Nagaoka (HLN) formalism, which confirms the
presence of a weak anti-localization (WAL) effect in its crystal. Moreover, the
non-trivial topological character has been evidenced through first-principles
calculations using density functional theory (DFT), with and without spin-orbit
coupling (SOC) protocols. A significant change in the bulk electronic band
structure is observed upon the inclusion of SOC parameters, signifying the
topological properties of SnBi2Te4. Its topological non-trivial character has
also been verified through the calculation of Z2 invariants and the surface
states spectrum in the (111) plane.Comment: 24 Pages TEXT + Figs: J. Phys. Chem. Solid
Drastic suppression of CDW (charge density wave) by Pd addition in TiSe2
TiSe2 is a known Topological semimetal (TSM) having both the semi-metallic
and topological characters simultaneously and the Charge density wave (CDW) at
below 200K. In the current short article, we study the impact of Pd addition on
the CDW character of TiSe2 and the possible induction of superconductivity at
low temperatures. Bulk samples of TiSe2 and Pd0.1TiSe2 are synthesized by
solid-state reaction route, which is further characterized by powder X-ray
diffraction (PXRD) and field emission scanning electron microscopy (FESEM),
respectively, for their structural and micro-structural details. The
vibrational modes of both samples are being analyzed by Raman spectroscopy,
showing the occurrence of both A1g and Eg modes. CDW of pure TiSe2 seen at
around 200K in electrical transport measurements, in terms of sharp
semi-metallic to metallic transition peak with hysteresis in cooling/warming
cycles is not seen in Pd0.1TiSe2, and rather a near metallic transport is seen
down to 2K. Although superconductivity is not seen down to 2K, the CDW
transition is seemingly completely suppressed in Pd0.1TiSe2. Pd addition in
TiSe2 suppresses CDW drastically. Trials are underway to induce
superconductivity in Pd-added TiSe2. Density functional theory (DFT)
calculations show primary evidence of suppression of CDW by adding Pd in TiSe2
due to an increase in the density of states.Comment: 11 Pages Text + Figs: Accepted J. Sup. Novel Ma
Home sweet home: a critical comment on Saunders and Williams
While accepting the need for research which focuses on the social meaning of the home, this article takes issue with some of Saunders’ and Williams’ formulations for a research programme — in particular, the emphasis given to physical and design features of the home at the expense of an understanding of more fundamental gender and generational relations within the home. It attempts to uncover the assumptions lying behind those formulations, to clarify some of the conceptual confusions, and to point out some of the serious theoretical difficulties which such formulations have to resolve. It argues that theoretical advance in this area does not have to depend upon the adoption of a Weberian perspective, but must be situated within a broader theory of the production and maintenance of ideology, and this theory must be explicitly linked with theories of power and kinship. In particular, it is emphasised that power relations within the home, associated mainly with gender and age differences, need to be investigated in greater depth if the social significance of the home is to be properly understood
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