20 research outputs found
Topological Triviality of Flat Hamiltonians
Landau levels play a key role in theoretical models of the quantum Hall
effect. Each Landau level is degenerate, flat and topologically non-trivial.
Motivated by Landau levels, we study tight-binding Hamiltonians whose energy
levels are all flat. We demonstrate that in two dimensions, for such
Hamiltonians, the flat bands must be topologically trivial. To that end, we
show that the projector onto each flat band is necessarily strictly local. Our
conclusions do not need the assumption of lattice translational invariance.Comment: 7 pages, 2 figure
Scattering Expansion for Localization in One Dimension: from Disordered Wires to Quantum Walks
We present a perturbative approach to a broad class of disordered systems in
one spatial dimension. Considering a long chain of identically disordered
scatterers, we expand in the reflection strength of any individual scatterer.
This expansion accesses the full range of phase disorder from weak to strong.
We apply this expansion to several examples, including the Anderson model, a
general class of periodic-on-average-random potentials, and a two-component
discrete-time quantum walk, showing analytically in the latter case that the
localization length can depend non-monotonically on the strength of phase
disorder (whereas expanding in weak disorder yields monotonic decrease).
Returning to the general case, we extend the perturbative derivation of
single-parameter scaling to another order and obtain to all orders a particular
non-separable form for the joint probability distribution of the
log-transmission and reflection phase. Furthermore, we show that for weak local
reflection strength, a version of the scaling theory of localization holds: the
joint distribution is determined by just three parameters.Comment: 23+15 pages, 10 figures. Longer version of arXiv:2210.0799
Universal localization-delocalization transition in chirally-symmetric Floquet drives
Periodically driven systems often exhibit behavior distinct from static
systems. In single-particle, static systems, any amount of disorder generically
localizes all eigenstates in one dimension. In contrast, we show that in
topologically non-trivial, single-particle Floquet loop drives with chiral
symmetry in one dimension, a localization-delocalization transition occurs as
the time is varied within the driving period (). We find that the time-dependent localization length
diverges with a universal exponent as approaches the
midpoint of the drive:
with . We provide analytical and numerical evidence for the universality
of this exponent within the AIII symmetry class.Comment: 17 + 5 pages, 7 figure
Search and rescue at sea aided by hidden flow structures
Every year hundreds of people die at sea because of vessel and airplane
accidents. A key challenge in reducing the number of these fatalities is to
make Search and Rescue (SAR) algorithms more efficient. Here we address this
challenge by uncovering hidden TRansient Attracting Profiles (TRAPs) in
ocean-surface velocity data. Computable from a single velocity-field snapshot,
TRAPs act as short-term attractors for all floating objects. In three different
ocean field experiments, we show that TRAPs computed from measured as well as
modelled velocities attract deployed drifters and manikins emulating people
fallen in the water. TRAPs, which remain hidden to prior flow diagnostics, thus
provide critical information for hazard responses, such as SAR and oil spill
containment, and hence have the potential to save lives and limit environmental
disasters
Integrated proteomics and phosphoproteomics revealed druggable kinases in neoadjuvant chemotherapy resistant tongue cancer
Tongue squamous cell carcinoma is an aggressive oral cancer with a high incidence of metastasis and poor prognosis. Most of the oral cavity cancer patients present in clinics with locally advanced unresectable tumors. Neoadjuvant treatment is beneficial for these individuals as it reduces the tumor size aiding complete resection. However, patients develop therapy resistance to the drug regimen. In this study, we explored the differential expression of proteins and altered phosphorylation in the neoadjuvant chemotherapy resistant tongue cancer patients. We integrated the proteomic and phosphoproteomic profiles of resistant (n = 4) and sensitive cohorts (n = 4) and demonstrated the differential expression and phosphorylation of proteins in the primary tissue of the respective subject groups. We observed differential and extensive phosphorylation of keratins such as KRT10 and KRT1 between the two cohorts. Furthermore, our study revealed a kinase signature associated with neoadjuvant chemotherapy resistance. Kinases such as MAPK1, AKT1, and MAPK3 are predicted to regulate the resistance in non-responders. Pathway analysis showed enrichment of Rho GTPase signaling and hyperphosphosphorylation of proteins involved in cell motility, invasion, and drug resistance. Targeting the kinases could help with the clinical management of neoadjuvant chemotherapy-resistant tongue cancer
Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19
IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19.
Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19.
DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022).
INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days.
MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes.
RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively).
CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes.
TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570