Visualizing Atomic-Scale Negative Differential Resistance in Bilayer Graphene

We investigate the atomic-scale tunneling characteristics of bilayer graphene on silicon carbide using the scanning tunneling microscopy. The high-resolution tunneling spectroscopy reveals an unexpected negative differential resistance (NDR) at the Dirac energy, which spatially varies within the single unit cell of bilayer graphene. The origin of NDR is explained by two near-gap van Hove singularities emerging in the electronic spectrum of bilayer graphene under a transverse electric field, which are strongly localized on two sublattices in different layers. Furthermore, defects near the tunneling contact are found to strongly impact on NDR through the electron interference. Our result provides an atomic-level understanding of quantum tunneling in bilayer graphene, and constitutes a useful step towards graphene-based tunneling devices. DOI: 10.1103/PhysRevLett.110.036804X11109sciescopu

Efficacy of chest X-rays after drain removal in adult and pediatric patients undergoing cardiac and thoracic surgery: A systematic review.

BACKGROUND: Chest X-rays are routinely obtained after the removal of chest drains in patients undergoing cardiac and thoracic surgical procedures. However, a lack of guidelines and evidence could question the practice. Routine chest X-rays increase exposure to ionizing radiation, increase health-care costs, and lead to overutilisation of available resources. This review aims to explore the evidence in the literature regarding the routine use of chest X-rays following the removal of chest drains. MATERIALS & METHOD: A systematic literature search was conducted in PubMed, Medline via Ovid, Cochrane central register of control trials (CENTRAL), and ClinicalTrials. gov without any limit on the publication year. The references of the included studies are manually screened to identify potentially eligible studies. RESULTS: A total of 375 studies were retrieved through the search and 18 studies were included in the review. Incidence of pneumothorax remains less than 10% across adult cardiac, and pediatric cardiac and thoracic surgical populations. The incidence may be as high as 50% in adult thoracic surgical patients. However, the reintervention rate remains less than 2% across the populations. Development of respiratory and cardiovascular symptoms can adequately guide for a chest X-ray following the drain removal. As an alternative, bedside ultrasound can be used to detect pneumothorax in the thorax after the removal of a chest drain without the need for ionizing radiation. CONCLUSION: A routine chest X-ray following chest drain removal in adult and pediatric patients undergoing cardiac and thoracic surgery is not necessary. It can be omitted without compromising patient safety. Obtaining a chest X-ray should be clinically guided. Alternatively, bedside ultrasound can be used for the same purpose without the need for radiation exposure

PRESENT STATUS OF THE POHANG LIGHT-SOURCE

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Accretion Processes for General Spherically Symmetric Compact Objects

We investigate the accretion process for different spherically symmetric space-time geometries for a static fluid. We analyse this procedure using the most general black hole metric ansatz. After that, we examine the accretion process for specific spherically symmetric metrics obtaining the velocity of the sound during the process and the critical speed of the flow of the fluid around the black hole. In addition, we study the behaviour of the rate of change of the mass for each chosen metric for a barotropic fluid.Comment: 10 pages, 15 figures, v2 accepted for publication in 'European Physical Journal C

Advanced load-shift system: an experimental validation of the ac-dc converter as shunt active power filter

This paper presents a load-shift system with advanced functionalities to interface the power grid (PG). When compared with the conventional approach, an advanced load-shift system (aLSS) permits the compensation of power quality (PQ) problems for the grid-side, namely problems related to current harmonics, current imbalance, and power factor. The proposed aLSS is composed by a bidirectional ac-dc converter to interface the PG and by a bidirectional dc-dc converter to interface an energy storage system (ESS). Since the main innovation is related with the PG interface, the focus of this work is on the analysis of the ac-dc converter, which is based on a three-phase four-leg converter. A theoretical study and the details concerning the control algorithm are presented and discussed along the paper. A laboratory prototype of the proposed aLSS was developed and the details of implementation are described in the paper. Experimental results obtained with the developed prototype prove that the aLSS contributes for the technology progress in this area, validating a new concept of operation concerning the PQ on the PG side.This work has been supported by FCT – Fundação para a Ciência e Tecnologia with-in the Project Scope: UID/CEC/00319/2019. This work has been supported by the FCT Project QUALITY4POWER PTDC/EEI-EEE/28813/2017, and by the FCT Project newERA4GRIDs PTDC/EEI-EEE/30283/2017

Gauged Flavor Group with Left-Right Symmetry

We construct an anomaly-free extension of the left-right symmetric model, where the maximal flavor group is gauged and anomaly cancellation is guaranteed by adding new vectorlike fermion states. We address the question of the lowest allowed flavor symmetry scale consistent with data. Because of the mechanism recently pointed out by Grinstein et al. tree-level flavor changing neutral currents turn out to play a very weak constraining role. The same occurs, in our model, for electroweak precision observables. The main constraint turns out to come from WR-mediated flavor changing neutral current box diagrams, primarily K - Kbar mixing. In the case where discrete parity symmetry is present at the TeV scale, this constraint implies lower bounds on the mass of vectorlike fermions and flavor bosons of 5 and 10 TeV respectively. However, these limits are weakened under the condition that only SU(2)_R x U(1)_{B-L} is restored at the TeV scale, but not parity. For example, assuming the SU(2) gauge couplings in the ratio gR/gL approx 0.7 allows the above limits to go down by half for both vectorlike fermions and flavor bosons. Our model provides a framework for accommodating neutrino masses and, in the parity symmetric case, provides a solution to the strong CP problem. The bound on the lepton flavor gauging scale is somewhat stronger, because of Big Bang Nucleosynthesis constraints. We argue, however, that the applicability of these constraints depends on the mechanism at work for the generation of neutrino masses.Comment: 1+23 pages, 1 table, 5 figures. v3: some more textual fixes (main change: discussion of Lepton Flavor Violating observables rephrased). Matches journal versio

The use of social media in different phases of the new product development process: a systematic literature review

Using social media is high on the list of priorities for many firms looking to enhance their innovation performance in the different phases of the new product development (NPD) process. Mirroring this rising practical importance of using social media for NPD, scholars have presented a diverse range of perspectives and underscored the need for a systematic literature review. Accordingly, this study reviews 110 papers from 2002 to 2023, to synthesize the use of social media across three phases: discovery, development, and launch. Our analysis identifies nine NPD objectives that social media addresses and discusses challenges encountered. Building on this analysis, we develop an organizing framework to guide practitioners on how to adopt social media to achieve better NPD performance and propose directions for future research.</jats:p

Intrathecal injection of human umbilical cord blood-derived mesenchymal stem cells for the treatment of basilar artery dissection: a case report

<p>Abstract</p> <p>Introduction</p> <p>Basilar artery dissection is a rare occurrence, and is significantly associated with morbidity and mortality. To the best of our knowledge, we report the first case of basilar artery dissection treated with mesenchymal stem cells.</p> <p>Case presentation</p> <p>We present the case of a 17-year-old Korean man who was diagnosed with basilar artery dissection. Infarction of the bilateral pons, midbrain and right superior cerebellum due to his basilar artery dissection was partially recanalized by intrathecal injection of human umbilical cord blood-derived mesenchymal stem cells. No immunosuppressants were given to our patient, and human leukocyte antigen alloantibodies were not detected after cell therapy.</p> <p>Conclusions</p> <p>This case indicates that intrathecal injections of mesenchymal stem cells can be used in the treatment of basilar artery dissection.</p

Neutrino masses from new generations

We reconsider the possibility that Majorana masses for the three known neutrinos are generated radiatively by the presence of a fourth generation and one right-handed neutrino with Yukawa couplings and a Majorana mass term. We find that the observed light neutrino mass hierarchy is not compatible with low energy universality bounds in this minimal scenario, but all present data can be accommodated with five generations and two right-handed neutrinos. Within this framework, we explore the parameter space regions which are currently allowed and could lead to observable effects in neutrinoless double beta decay, $\mu - e$ conversion in nuclei and $\mu \rightarrow e \gamma$ experiments. We also discuss the detection prospects at LHC.Comment: 28 pages, 4 figures. Version to be published. Some typos corrected. Improved figures 3 and

Single to Double Hump Transition in the Equilibrium Distribution Function of Relativistic Particles

We unveil a transition from single peaked to bimodal velocity distribution in a relativistic fluid under increasing temperature, in contrast with a non-relativistic gas, where only a monotonic broadening of the bell-shaped distribution is observed. Such transition results from the interplay between the raise in thermal energy and the constraint of maximum velocity imposed by the speed of light. We study the Bose-Einstein, the Fermi-Dirac, and the Maxwell-J\"uttner distributions, all exhibiting the same qualitative behavior. We characterize the nature of the transition in the framework of critical phenomena and show that it is either continuous or discontinuous, depending on the group velocity. We analyze the transition in one, two, and three dimensions, with special emphasis on two-dimensions, for which a possible experiment in graphene, based on the measurement of the Johnson-Nyquist noise, is proposed.Comment: 5 pages, 5 figure