Newspaper archives : a knowledge asset

This paper deals with Newspaper Content as a source of knowledge and how Times Archives of the Times Group has converted the 166-year span of socio-political content of “The Times of India” and the 43 year economic and business barometer “The Economic Times” into an easily accessible Archive. The value of this Archive as a Knowledge Asset lies in its potential of being recalled, researched, reused and re-expressed by the various ventures of the Group. This paper describes the process of Microfilm Archiving and Digital Archiving of a Newspaper. The advantages and disadvantages of both have been discussed

Effect of Dirac Spinons on ARPES signatures of Herbertsmithe

The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To solidify evidence for its existence, we address the question of what will be the Angle Resolved Photoemission Spectroscopy (ARPES) signatures of single crystal samples of Herbertsmithite assuming it is described by the Dirac spin liquid state. In particular, we show that the electron spectral function will have a linear in energy dependence near specific wave vectors and that this dependence is expected even after fluctuations to the mean field values are taken into account. Observation of this unique signature in ARPES will provide very strong evidence for the existence of spinons in greater than one dimension.Comment: 10 page

Boson features in STM spectra of cuprate superconductors: Weak-coupling phenomenology

We derive the shape of the high-energy features due to a weakly coupled boson in cuprate superconductors, as seen experimentally in Bi_2 Sr_2 Ca_1 Cu_2 O_8+x (BSCCO) by Lee et al. [Nature (London) 442, 546 (2006)]. A simplified model is used of d-wave Bogoliubov quasiparticles coupled to Einstein oscillators with a momentum-independent electron-boson coupling and an analytic fitting form is derived, which allows us (a) to extract the boson mode's frequency and (b) to estimate the electron-boson coupling strength. We further calculate the maximum possible superconducting gap due to an Einstein oscillator with the extracted electron-boson coupling strength, which is found to be less than 0.2 times of the observed gap indicating at the observed boson's non-dominant role in the superconductivity's mechanism. The extracted momentum-independent electron-boson coupling parameter (that we show a posteriori to indeed be in the weak-coupling regime) is then to be interpreted as an (band-structure detail dependent weighted) average over the Brillouin zone of the actual momentum-dependent electron-boson coupling in BSCCO.Comment: 6.5 page

N\'eel to valence-bond solid transition on the honeycomb lattice: Evidence for deconfined criticality

We study a spin-1/2 SU(2) model on the honeycomb lattice with nearest-neighbor antiferromagnetic exchange $J$ that favors N\'eel order, and competing 6-spin interactions $Q$ which favor a valence bond solid (VBS) state in which the bond-energies order at the "columnar" wavevector ${\mathbf K} = (2\pi/3,-2\pi/3)$. We present quantum Monte-Carlo evidence for a direct continuous quantum phase transition between N\'eel and VBS states, with exponents and logarithmic violations of scaling consistent with those at analogous deconfined critical points on the square lattice. Although this strongly suggests a description in terms of deconfined criticality, the measured three-fold anisotropy of the phase of the VBS order parameter shows unusual near-marginal behaviour at the critical point.Comment: published version with extensive T > 0 data; author list rearranged to reflect these new result

Sign-problem-free Monte Carlo simulation of certain frustrated quantum magnets

We introduce a Quantum Monte Carlo (QMC) method which efficiently simulates in a sign-problem-free way a broad class of frustrated $S=1/2$ models with competing antiferromagnetic interactions. Our scheme uses the basis of total spin eigenstates of clusters of spins to avoid the severe sign problem faced by other QMC methods. We also flag important limitations of the new method, and comment on possibilities for further progress.Comment: 6 pages + appendix with supplemental informatio

Transitions to valence-bond solid order in a honeycomb lattice antiferromagnet

We use Quantum Monte-Carlo methods to study the ground state phase diagram of a S=1/2 honeycomb lattice magnet in which a nearest-neighbor antiferromagnetic exchange J (favoring N\'eel order) competes with two different multi-spin interaction terms: a six-spin interaction Q_3 that favors columnar valence-bond solid (VBS) order, and a four-spin interaction Q_2 that favors staggered VBS order. For Q_3 ~ Q_2 >> J, we establish that the competition between the two different VBS orders stabilizes N\'eel order in a large swathe of the phase diagram even when J is the smallest energy-scale in the Hamiltonian. When Q_3 >> (Q_2,J) (Q_2 >> (Q_3,J)), this model exhibits at zero temperature phase transition from the N\'eel state to a columnar (staggered) VBS state. We establish that the N\'eel-columnar VBS transition is continuous for all values of Q_2, and that critical properties along the entire phase boundary are well-characterized by critical exponents and amplitudes of the non-compact CP^1 (NCCP^1) theory of deconfined criticality, similar to what is observed on a square lattice. However, a surprising three-fold anisotropy of the phase of the VBS order parameter at criticality, whose presence was recently noted at the Q_2=0 deconfined critical point, is seen to persist all along this phase boundary. We use a classical analogy to explore this by studying the critical point of a three-dimensional XY model with a four-fold anisotropy field which is known to be weakly irrelevant at the three-dimensional XY critical point. In this case, we again find that the critical anisotropy appears to saturate to a nonzero value over the range of sizes accessible to our simulations.Comment: 14 page

Fatiguing Effects of Indirect Vibration Stimulation in Upper Limb Muscles- pre, post and during Isometric Contractions Superimposed on Upper Limb Vibration

© 2019 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/ , which permits unrestricted use, provided the original author and source are credited.Whole-body vibration and upper limb vibration (ULV) continue to gain popularity as exercise intervention for rehabilitation and sports applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. We investigated the effects of ULV stimulation superimposed on fatiguing isometric contractions using a purpose developed upper limb stimulation device. Thirteen healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions (V) and isometric contractions alone Control (C). Both Vibration (V) and Control (C) exercises were performed at 80% of the maximum voluntary contractions. The stimulation used was 30 Hz frequency of 0.4 mm amplitude. Surface-electromyographic (EMG) activity of the Biceps Brachii, Triceps Brachii and Flexor Carpi Radialis were measured. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels. All muscles displayed significantly higher reduction in MEFs and a corresponding significant increase in EMGrms with the V than the Control, during fatiguing contractions (p < 0.05). Post vibration, all muscles showed higher levels of MEFs after recovery compared to the control. Our results show that near-maximal isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment.Peer reviewedFinal Published versio

Ageing performance of biodegradable PLA for durable applications

The durability of 2 commercially available injection mold grades and one extrusion grade of polylactic acid (PLA) was assessed. Here, the materials were exposed to elevated temperatures/humidity for a period of several weeks. Moisture absorption, molecular weight change, mechanical properties, crystallinity changes, and microscopic imaging were all monitored at regular intervals throughout the course of the combined heat and humidity ageing study. The conditions for the ageing study were set at 60°C and 45% relative humidity and all three PLA grades showed a significant increase in crystallinity and conversely reduced mechanical performance over the 68-day ageing period. Microscopic images of the materials suggested that surface degradation was not dominant. It is known that the moisture absorption of PLA which is revealed by weight gain is usually low for PLA, but the amount absorbed is sufficient to induce bulk degradation, and the mechanical performance was reduced over the ageing period. All materials exhibited a loss in molecular weight over time. The molecular weight at any given time was reflective of the starting molecular weight and thus the extrusion grade PLA showed better mechanical performance than the injection mold grades at any given time. This behavior was satisfactorily modeled using an acid-catalyzed hydrolysis model. Interestingly the higher molecular weight PLA exhibited slower degradation kinetics as compared to the lower molecular weight injection molding grades. This study showed that commercially available PLA resins are not suitable for use in applications that require long sustained durability in environmental conditions such as these where high temperature and humidity are encountered for any appreciable amount of time