21 research outputs found
A Solvable Model for Discrete Time Crystal Enforced by Nonsymmorphic Dynamical Symmetry
Discrete time crystal is a class of nonequilibrium quantum systems exhibiting
subharmonic responses to external periodic driving. Here we propose a class of
discrete time crystals enforced by nonsymmorphic dynamical symmetry. We start
with a system with nonsymmorphic dynamical symmetry, in which the instantaneous
eigenstates become M\"obius twisted, hence doubling the period of the
instantaneous state. The exact solution of the time-dependent Schr\"odinger
equation shows that the system spontaneously exhibits a period extension
without undergoing quantum superposition states for a series of specifc
evolution frequencies or in the limit of long evolution period. Moreover, in
such case the system gains a {\pi} Berry phase after two periods' evolution.
Finally, we show that the subharmonic response is stable even when many-body
interactions are introduced, indicating a DTC phase in the thermodynamic limit.Comment: 5 pages, 4 figure
Half-Quantized Hall Effect at the Parity-Invariant Fermi Surface
Condensed matter realization of a single Dirac cone of fermions in two
dimensions is a long-standing issue. Here we report the discovery of a single
gapless Dirac cone of half-quantized Hall conductance in a magnetically-doped
topological insulator heterostructure. It demonstrates that the Hall
conductance is half-quantized in the unit e^{2}/h when the parity symmetry is
invariant near the Fermi surface. The gapless Dirac point is stable and
protected by the local parity symmetry and the topologically nontrivial band
structure of the topological insulator. The one-half Hall conductance observed
in a recent experiment [Mogi et al, Nat. Phys. 18, 390 (2022)] is attributed to
the existence of the gapless Dirac cone. The results suggest a condensed matter
realization of a topological phase with a one-half topological invariant.Comment: 6 pages with 4 figure
Tubeless video-assisted thoracic surgery for pulmonary ground-glass nodules: expert consensus and protocol (Guangzhou)
Impact of cardiac arrest centers on the survival of patients with nontraumatic out‐of‐hospital cardiac arrest : a systematic review and meta‐analysis
Background
The role of cardiac arrest centers (CACs) in out‐of‐hospital cardiac arrest care systems is continuously evolving. Interpretation of existing literature is limited by heterogeneity in CAC characteristics and types of patients transported to CACs. This study assesses the impact of CACs on survival in out‐of‐hospital cardiac arrest according to varying definitions of CAC and prespecified subgroups.
Methods and Results
Electronic databases were searched from inception to March 9, 2021 for relevant studies. Centers were considered CACs if self‐declared by study authors and capable of relevant interventions. Main outcomes were survival and neurologically favorable survival at hospital discharge or 30 days. Meta‐analyses were performed for adjusted odds ratio (aOR) and crude odds ratios. Thirty‐six studies were analyzed. Survival with favorable neurological outcome significantly improved with treatment at CACs (aOR, 1.85 [95% CI, 1.52–2.26]), even when including high‐volume centers (aOR, 1.50 [95% CI, 1.18–1.91]) or including improved‐care centers (aOR, 2.13 [95% CI, 1.75–2.59]) as CACs. Survival significantly increased with treatment at CACs (aOR, 1.92 [95% CI, 1.59–2.32]), even when including high‐volume centers (aOR, 1.74 [95% CI, 1.38–2.18]) or when including improved‐care centers (aOR, 1.97 [95% CI, 1.71–2.26]) as CACs. The treatment effect was more pronounced among patients with shockable rhythm ( P =0.006) and without prehospital return of spontaneous circulation ( P =0.005). Conclusions were robust to sensitivity analyses, with no publication bias detected.
Conclusions
Care at CACs was associated with improved survival and neurological outcomes for patients with nontraumatic out‐of‐hospital cardiac arrest regardless of varying CAC definitions. Patients with shockable rhythms and those without prehospital return of spontaneous circulation benefited more from CACs. Evidence for bypassing hospitals or interhospital transfer remains inconclusive
Pan-cancer analysis of whole genomes
Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe
Ave Maria
Ave Maria is a tamil art film produced by 3.1 Productions, as part as an undergraduate Final Year Project (FYP) in the Wee Kim Wee School of Communication and Information (WKWSCI), Nanyang Technological University (NTU). It is created by Andrea Flavia William, Ang Cai Wen, Corin Too Jia Hui and Kuang Zi Ling under the supervision of Mr. Daniel Heng. This report provides a detailed account from conceptualisation to post-production and seeks to address the motivations and creative decisions that were taken in order to create this film. It also highlights the obstacles faced and solutions taken to overcome it.Bachelor of Communication Studie
Ave Maria
Ave Maria is a tamil art film produced by 3.1 Productions, as part as an undergraduate Final Year Project (FYP) in the Wee Kim Wee School of Communication and Information (WKWSCI), Nanyang Technological University (NTU). It is created by Andrea Flavia William, Ang Cai Wen, Corin Too Jia Hui and Kuang Zi Ling under the supervision of Mr. Daniel Heng. This report provides a detailed account from conceptualisation to post-production and seeks to address the motivations and creative decisions that were taken in order to create this film. It also highlights the obstacles faced and solutions taken to overcome it.Bachelor of Communication Studie