Picosecond electric-field-induced threshold switching in phase-change materials

Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag$_4$In$_3$Sb$_{67}$Te$_{26}$. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on sub-picosecond time-scales - faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.Comment: 6 pages manuscript with 3 figures and 8 pages supplementary materia

Critical behavior of the dimerized Si(001) surface: A continuous order-disorder phase transition in the 2D Ising universality class

The critical behavior of the order-disorder phase transition in the buckled dimer structure of the Si(001) surface is investigated both theoretically by means of first-principles calculations and experimentally by spot profile analysis low-energy electron diffraction (SPA-LEED). We use density functional theory (DFT) with three different functionals commonly used for Si to determine the coupling constants of an effective lattice Hamiltonian describing the dimer interactions. Experimentally, the phase transition from the low-temperature $c(4 {\times} 2)$- to the high-temperature $p(2 {\times} 1)$-reconstructed surface is followed through the intensity and width of the superstructure spots within the temperature range of 78-400 K. Near the critical temperature $T_\mathrm{c} = 190.6$ K, we observe universal critical behavior of spot intensities and correlation lengths which falls into the universality class of the two-dimensional (2D) Ising model. From the ratio of correlation lengths along and across the dimer rows we determine effective nearest-neighbor couplings of an anisotropic 2D Ising model, $J_\parallel = (-24.9 \pm 0.9_\mathrm{stat} \pm 1.3_\mathrm{sys})$ meV and $J_\perp = (-0.8 \pm 0.1_\mathrm{stat})$ meV. We find that the experimentally determined coupling constants of the Ising model can be reconciled with those of the more complex lattice Hamiltonian from DFT when the critical behavior is of primary interest. The anisotropy of the interactions derived from the experimental data via the 2D Ising model is best matched by DFT calculations using the PBEsol functional. The trends in the calculated anisotropy are consistent with the surface stress anisotropy predicted by the DFT functionals, pointing towards the role of surface stress reduction as a driving force for establishing the $c(4 {\times} 2)$-reconstructed ground state

Sequential Kibble-Zurek dynamics in the anisotropic Ising model of the Si(001) surface

As a simplified description of the non-equilibrium dynamics of buckled dimers on the Si(001) surface, we consider the anisotropic 2D Ising model and study the freezing of spatial correlations during a cooling quench across the critical point. The dependence of the frozen correlation lengths $\xi_\|$ and $\xi_\perp$ on the cooling rate obtained numerically matches the Kibble-Zurek scaling quite well. However, we also find that the ratio $\xi_\|/\xi_\perp$ of their frozen values deviates significantly from the ratio in equilibrium. Supported by analytical arguments, we explain this difference by the fact that the deviation from equilibrium in the weakly coupled direction occurs earlier than in the strongly coupled direction.Comment: 4+2+1 pages, 3 figure

The Transcriptome of Compatible and Incompatible Interactions of Potato (Solanum tuberosum) with Phytophthora infestans Revealed by DeepSAGE Analysis

Late blight, caused by the oomycete Phytophthora infestans, is the most important disease of potato (Solanum tuberosum). Understanding the molecular basis of resistance and susceptibility to late blight is therefore highly relevant for developing resistant cultivars, either by marker-assissted selection or by transgenic approaches. Specific P. infestans races having the Avr1 effector gene trigger a hypersensitive resistance response in potato plants carrying the R1 resistance gene (incompatible interaction) and cause disease in plants lacking R1 (compatible interaction). The transcriptomes of the compatible and incompatible interaction were captured by DeepSAGE analysis of 44 biological samples comprising five genotypes, differing only by the presence or absence of the R1 transgene, three infection time points and three biological replicates. 30.859 unique 21 base pair sequence tags were obtained, one third of which did not match any known potato transcript sequence. Two third of the tags were expressed at low frequency (<10 tag counts/million). 20.470 unitags matched to approximately twelve thousand potato transcribed genes. Tag frequencies were compared between compatible and incompatible interactions over the infection time course and between compatible and incompatible genotypes. Transcriptional changes were more numerous in compatible than in incompatible interactions. In contrast to incompatible interactions, transcriptional changes in the compatible interaction were observed predominantly for multigene families encoding defense response genes and genes functional in photosynthesis and CO2 fixation. Numerous transcriptional differences were also observed between near isogenic genotypes prior to infection with P. infestans. Our DeepSAGE transcriptome analysis uncovered novel candidate genes for plant host pathogen interactions, examples of which are discussed with respect to possible function

Ten papers for teachers of evidence-based medicine and health care: Sicily workshop 2019

A previous article sought to signpost papers that were considered helpful when starting on the journey of practicing evidence-based medicine (EBM). The lead author was invited to run a workshop at the Eighth Conference of the International Society for Evidence-Based Health Care run in collaboration with the Gruppo Italiano per la Medicina Basata sulle Evidenze from 6 November to 9 November 2019. The aim of the workshop was to challenge a group of teachers and educators to consider useful papers for the teaching of EBM/evidence-based healthcare (EBHC). The second aim was to start a database of such studies. The third aim was to share learning and foster discussion from the workshop through journal publication. EBM and EBHC are used interchangeably throughout this article

Defining the Critical Hurdles in Cancer Immunotherapy

ABSTRACT: Scientific discoveries that provide strong evidence of antitumor effects in preclinical models often encounter significant delays before being tested in patients with cancer. While some of these delays have a scientific basis, others do not. We need to do better. Innovative strategies need to move into early stage clinical trials as quickly as it is safe, and if successful, these therapies should efficiently obtain regulatory approval and widespread clinical application. In late 2009 and 2010 the Society for Immunotherapy of Cancer (SITC), convened an "Immunotherapy Summit" with representatives from immunotherapy organizations representing Europe, Japan, China and North America to discuss collaborations to improve development and delivery of cancer immunotherapy. One of the concepts raised by SITC and defined as critical by all parties was the need to identify hurdles that impede effective translation of cancer immunotherapy. With consensus on these hurdles, international working groups could be developed to make recommendations vetted by the participating organizations. These recommendations could then be considered by regulatory bodies, governmental and private funding agencies, pharmaceutical companies and academic institutions to facilitate changes necessary to accelerate clinical translation of novel immune-based cancer therapies. The critical hurdles identified by representatives of the collaborating organizations, now organized as the World Immunotherapy Council, are presented and discussed in this report. Some of the identified hurdles impede all investigators, others hinder investigators only in certain regions or institutions or are more relevant to specific types of immunotherapy or first-in-humans studies. Each of these hurdles can significantly delay clinical translation of promising advances in immunotherapy yet be overcome to improve outcomes of patients with cancer

Defining the critical hurdles in cancer immunotherapy

Scientific discoveries that provide strong evidence of antitumor effects in preclinical models often encounter significant delays before being tested in patients with cancer. While some of these delays have a scientific basis, others do not. We need to do better. Innovative strategies need to move into early stage clinical trials as quickly as it is safe, and if successful, these therapies should efficiently obtain regulatory approval and widespread clinical application. In late 2009 and 2010 the Society for Immunotherapy of Cancer (SITC), convened an "Immunotherapy Summit" with representatives from immunotherapy organizations representing Europe, Japan, China and North America to discuss collaborations to improve development and delivery of cancer immunotherapy. One of the concepts raised by SITC and defined as critical by all parties was the need to identify hurdles that impede effective translation of cancer immunotherapy. With consensus on these hurdles, international working groups could be developed to make recommendations vetted by the participating organizations. These recommendations could then be considered by regulatory bodies, governmental and private funding agencies, pharmaceutical companies and academic institutions to facilitate changes necessary to accelerate clinical translation of novel immune-based cancer therapies. The critical hurdles identified by representatives of the collaborating organizations, now organized as the World Immunotherapy Council, are presented and discussed in this report. Some of the identified hurdles impede all investigators; others hinder investigators only in certain regions or institutions or are more relevant to specific types of immunotherapy or first-in-humans studies. Each of these hurdles can significantly delay clinical translation of promising advances in immunotherapy yet if overcome, have the potential to improve outcomes of patients with cancer

Matter manipulation with extreme terahertz light: Progress in the enabling THz technology

Terahertz (THz) light has proven to be a fine tool to probe and control quasi-particles and collective excitations in solids, to drive phase transitions and associated changes in material properties, and to study rotations and vibrations in molecular systems. In contrast to visible light, which usually carries excessive photon energy for collective excitations in condensed matter systems, THz light allows for direct coupling to low-energy (meV scale) excitations of interest, The development of light sources of strong-field few-cycle THz pulses in the 2000s opened the door to controlled manipulation of reactions and processes. Such THz pulses can drive new dynamic states of matter, in which materials exhibit properties entirely different from that of the equilibrium. In this review, we first systematically analyze known studies on matter manipulation with strong-field few-cycle THz light and outline some anticipated new results. We focus on how properties of materials can be manipulated by driving the dynamics of different excitations and how molecules and particles can be controlled in useful ways by extreme THz light. Around 200 studies are examined, most of which were done during the last five years. Secondly, we discuss available and proposed sources of strong-field few-cycle THz pulses and their state-of-the-art operation parameters. Finally, we review current approaches to guiding, focusing, reshaping and diagnostics of THz pulses. (C) 2019 The Author(s). Published by Elsevier B.V