Gorenstein Projective Modules Over Triangular Matrix Rings

We study totally acyclic complexes of projective modules over triangular matrix rings and then use it to classify Gorenstein projective modules over such rings. We also use this classification to obtain some information concerning Cohen-Macaulay finite and virtually Gorenstein triangular matrix artin algebras.Comment: This paper is now accepted for publication in the Algebra Colloquiu

Topological Photonics

Topology is revolutionizing photonics, bringing with it new theoretical discoveries and a wealth of potential applications. This field was inspired by the discovery of topological insulators, in which interfacial electrons transport without dissipation even in the presence of impurities. Similarly, new optical mirrors of different wave-vector space topologies have been constructed to support new states of light propagating at their interfaces. These novel waveguides allow light to flow around large imperfections without back-reflection. The present review explains the underlying principles and highlights the major findings in photonic crystals, coupled resonators, metamaterials and quasicrystals.Comment: progress and review of an emerging field, 12 pages, 6 figures and 1 tabl

Gauge fields for ultracold atoms in optical superlattices

We present a scheme that produces a strong U(1)-like gauge field on cold atoms confined in a two-dimensional square optical lattice. Our proposal relies on two essential features, a long-lived metastable excited state that exists for alkaline-earth or Ytterbium atoms, and an optical superlattice. As in the proposal by Jaksch and Zoller [New Journal of Physics 5, 56 (2003)], laser-assisted tunneling between adjacent sites creates an effective magnetic field. In the tight-binding approximation, the atomic motion is described by the Harper Hamiltonian, with a flux across each lattice plaquette that can realistically take any value between 0 and $\pi$. We show how to take advantage of the superlattice to ensure that each plaquette acquires the same phase, thus simulating a uniform magnetic field. We discuss the observable consequences of the artificial gauge field on non-interacting bosonic and fermionic gases. We also outline how the scheme can be generalized to non-Abelian gauge fields

Rapidly Rotating Fermions in an Anisotropic Trap

We consider a cold gas of non-interacting fermions in a two dimensional harmonic trap with two different trapping frequencies $\omega_x \leq \omega_y$, and discuss the effect of rotation on the density profile. Depending on the rotation frequency $\Omega$ and the trap anisotropy $\omega_y/\omega_x$, the density profile assumes two qualitatively different shapes. For small anisotropy ($\omega_y/\omega_x \ll \sqrt{1+4 \Omega^2/\omega_x^2}$), the density consists of elliptical plateaus of constant density, corresponding to Landau levels and is well described by a two dimensional local density approximation. For large anisotropy ($\omega_y/\omega_x \gg \sqrt{1+4 \Omega^2/\omega_x^2}$), the density profile is Gaussian in the strong confining direction and semicircular with prominent Friedel oscillations in the weak direction. In this regime, a one dimensional local density approximation is well suited to describe the system. The crossover between the two regimes is smooth where the step structure between the Landau level edges turn into Friedel oscillations. Increasing the temperature causes the step structure or the Friedel oscillations to wash out leaving a Boltzmann gas density profile.Comment: 14 pages, 7 figure

Survivors of Congenital Diaphragmatic Hernia Repair Face Barriers to Long-Term Follow-Up Care

BACKGROUND: Congenital diaphragmatic hernia (CDH) carries high morbidity and mortality, and survivors commonly have neurodevelopmental, gastrointestinal, and pulmonary sequela requiring multidisciplinary care well beyond repair. We predict that following hospitalization for repair, CDH survivors face many barriers to receiving future medical care. METHODS: A retrospective review was conducted of all living CDH patients between ages 0 to 12 years who underwent repair at Riley Hospital for Children (RHC) from 2010 through 2019. Follow-up status with specialty providers was reviewed, and all eligible families were contacted to complete a survey regarding various aspects of their child's care, including functional status, quality of life, and barriers to care. Bivariate analysis was applied to patient data (P < 0.05 was significant) and survey responses were analyzed qualitatively. RESULTS: After exclusions, 70 survivors were contacted. Thirty-three (47%) were deemed lost to follow up to specialist providers, and were similar to those who maintained follow-up with respect to defect severity type (A-D, P = 0.57), ECMO use (P = 0.35), number of affected organ systems (P = 0.36), and number of providers following after discharge (P = 0.33). Seventeen (24%) families completed the survey, of whom eight (47%) were deemed lost to follow up to specialist providers. Families reported distance and time constraints, access to CDH-specific information and care, access to CDH-specific resources, and access to healthcare as significant barriers to care. All respondents were interested in a multidisciplinary CDH clinic. CONCLUSIONS: CDH survivors require multidisciplinary care beyond initial repair, but attrition to follow-up after discharge is high. A multidisciplinary CDH clinic may address caregivers' perceived barriers

Partial splenectomy in children: Long-term reoperative outcomes

PURPOSE: Partial, or subtotal, splenectomy (PS) has become an accepted alternative to total splenectomy (TS) for management of hematologic disorders in children, but little is known about its long-term outcomes. Here, we present our institutional experience with partial splenectomy, to determine rate of subsequent TS or cholecystectomy and identify if any factors affected this need. METHODS: All patients who underwent partial splenectomy at a single tertiary children's hospital were retrospectively reviewed from 2002 through 2019 after IRB approval. Primary outcome of interest was rate of reoperation to completion splenectomy (CS) and rate of cholecystectomy. Secondary outcome were positive predictor(s) for these subsequent procedures. RESULTS: Twenty-four patients underwent PS, at median age 6.0 years, with preoperative spleen size of 12.7 cm by ultrasound. At median follow up time of 8.0 years, 29% of all patients and 24% of hereditary spherocytosis (HS) patients underwent completion splenectomy at median 34 months and 45 months, respectively. Amongst HS patients who did not have a cholecystectomy with or prior to PS, 39% underwent a delayed cholecystectomy following PS. There were no significant differences in age at index procedure, preoperative splenic volume, weight of splenic specimen removed, transfusion requirements, preoperative or postoperative hematologic parameters (including hemoglobin, hematocrit, total bilirubin, and reticulocyte count) amongst patients of all diagnoses and HS only who underwent PS alone compared to those who went on to CS. There were no cases of OPSS or deaths. CONCLUSION: Partial splenectomy is a safe alternative to total splenectomy in children with hematologic disease with theoretical decreased susceptibility to OPSS. However, families should be counseled of a 29% chance of reoperation to completion splenectomy, and, in HS patients, a 39% chance of delayed cholecystectomy if not performed prior to or with PS. Further studies are needed to understand predictors of these outcomes

Traumatic abdominal wall hernias in children: A case for early exploration

Purpose Traumatic abdominal wall hernia (TAWH) is a rare consequence of blunt abdominal trauma (BAT). We examined a series of patients suffering TAWH to evaluate its frequency, rate of associated concurrent intraabdominal injuries (CAI) and correlation with CT, management and outcomes. Methods A Level 1 pediatric trauma center trauma registry was queried for children less than 18 years old suffering TAWH from BAT between 2009 and 2019. Results 9370 patients were admitted after BAT. TAWH was observed in 11 children, at incidence 0.1%. Eight children (73%) were male, at mean age 10 years, and mean ISS of 16. Six cases (55%) were because of MVC, three (27%) impaled by a handlebar or pole, and two (18%) dragged under large machinery. Seven (64%) had a CAI requiring operative or interventional management. Patients with CAI were similar to those without other injury, with 20% and 50% CT scan sensitivity and specificity for detection of associated injury, respectively. Five patients had immediate hernia repair with laparotomy for repair of intraabdominal injury, three had delayed repair, two have asymptomatic unrepaired TAWH, and one resolved spontaneously. Conclusions Children with TAWH have high rates of CAI requiring operative repair. CT scans have low sensitivity and specificity for detecting associated injuries. A high suspicion of injury and low threshold for exploration must be maintained in TAWH cases

Topological states in photonic systems

Optics played a key role in the discovery of geometric phase. It now joins the journey of exploring topological physics, bringing bosonic topological states that equip us with the ability to make perfect photonic devices using imperfect interfaces.National Science Foundation (U.S.) (DMR-1419807)United States. Department of Energy (DE-SC0001299

Topologically-protected refraction of robust kink states in valley photonic crystals

Recently discovered valley photonic crystals (VPCs) mimic many of the unusual properties of two-dimensional gapped valleytronic materials such as bilayer graphene or MoS2. Of the utmost interest to optical communications is their ability to support topologically protected chiral edge (kink) states at the internal domain wall between two VPCs with spectrally overlapping bandgap zones and opposite half-integer valley-Chern indices. We experimentally demonstrate the robustness of the kink states in VPCs that support degenerate transverse-electric-like (TE) and transverse-magnetic-like (TM) topological phases, thus enabling polarization multiplexing in a single topological waveguide. The propagation direction of the kink states is locked to the valleys of the reverse Brave lattice and, therefore, cannot be reversed in the absence of inter-valley scattering. At the intersection between the internal domain wall and the external edge separating the VPCs from free space, the kink states are shown to exhibit >97% out-coupling efficiency into directional free-space beams. This constitutes the first experimental demonstration of meron-like valley-projected topological phases with half-integer valley-Chern indices.Comment: 19 pages, 4 figure