Wallpaper Fermions and the Nonsymmorphic Dirac Insulator

Recent developments in the relationship between bulk topology and surface crystal symmetry have led to the discovery of materials whose gapless surface states are protected by crystal symmetries. In fact, there exists only a very limited set of possible surface crystal symmetries, captured by the 17 "wallpaper groups." We show that a consideration of symmetry-allowed band degeneracies in the wallpaper groups can be used to understand previous topological crystalline insulators, as well as to predict new examples. In particular, the two wallpaper groups with multiple glide lines, $pgg$ and $p4g$, allow for a new topological insulating phase, whose surface spectrum consists of only a single, fourfold-degenerate, true Dirac fermion. Like the surface state of a conventional topological insulator, the surface Dirac fermion in this "nonsymmorphic Dirac insulator" provides a theoretical exception to a fermion doubling theorem. Unlike the surface state of a conventional topological insulator, it can be gapped into topologically distinct surface regions while keeping time-reversal symmetry, allowing for networks of topological surface quantum spin Hall domain walls. We report the theoretical discovery of new topological crystalline phases in the A$_2$B$_3$ family of materials in SG 127, finding that Sr$_2$Pb$_3$ hosts this new topological surface Dirac fermion. Furthermore, (100)-strained Au$_2$Y$_3$ and Hg$_2$Sr$_3$ host related topological surface hourglass fermions. We also report the presence of this new topological hourglass phase in Ba$_5$In$_2$Sb$_6$ in SG 55. For orthorhombic space groups with two glides, we catalog all possible bulk topological phases by a consideration of the allowed non-abelian Wilson loop connectivities, and we develop topological invariants for these systems. Finally, we show how in a particular limit, these crystalline phases reduce to copies of the SSH model.Comment: Final version, 6 pg main text + 29 pg supplement, 6 + 13 figure

Li non-stoichiometry and crystal growth of untwinned 1D quantum spin system Lix Cu2 O2

Floating-zone growth of untwinned single crystal of Li_xCu_2O_2 with high Li content of x ~ 0.99 is reported. Li content of Li_xCu_2O_2 has been determined accurately through combined iodometric titration and thermogravimetric methods, which also ruled out the speculation of chemical disorder between Li and Cu ions. The morphology and physical properties of single crystals obtained from slowing-cooling (SL) and floating-zone (FZ) methods are compared. The floating-zone growth under Ar/O_2=7:1 gas mixture at 0.64 MPa produces large area of untwinned crystal with highest Li content, which has the lowest helimagnetic ordering temperature ~19K in the Li_xCu_2O_2 system.Comment: 4 pages, 3 figure

Thoracoscopic Repair of Congenital Diaphragmatic Hernia in Neonates: Lessons Learned

Abstract Purpose: We sought to characterize our recent experience with thoracoscopic congenital diaphragmatic hernia (CDH) repair and identify patient selection factors. Methods: We reviewed the medical records of full-term neonatal (<1 month of age) patients who underwent thoracoscopic CDH repair between 2004 and 2008 (n=15). We obtained data on prenatal diagnosis, characteristics of the CDH and repair, complications, and outcome. Results: All patients were stabilized preoperatively and underwent repair at an average of 5.7+/-1.3 days. Six patients were prenatally diagnosed, including the 5 inborn. Thirteen defects were left-sided. All were intubated shortly after birth and 2 required extracorporeal membrane oxygenation (ECMO). Twelve of 15 (80%) patients underwent successful thoracoscopic primary repair, including 1 of the patients who required ECMO prior to repair. Conversion to open repair occurred in 3 of 15 (20%) patients because of the need for patch closure or intraoperative instability. Among those converted to open, all had left-sided CDH defects and 3 had stomach herniation (of 5 such patients). Patients spent an average of 6.9+/-1.0 days on the ventilator following repair. The average time until full-enteral feeding was 16.7+/-2.25 days, and average length of hospital stay was 23.8+/-2.73 days. All patients survived to discharge, and average length of follow-up was 15.3+/-3.6 months. Conclusions: Thoracoscopic repair of CDH is a safe, effective strategy in patients who have undergone prior stabilization. Stomach herniation is associated with, but does not categorically predict, conversion to open repair. ECMO use prior to repair should not be an absolute contraindication to thoracoscopic repair.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78119/1/lap.2009.0129.pd

Complex mechanical loading and inflammation in intervertebral disc degeneration

Introduction Intervertebral disc (IVD) degeneration is the cause of around half of all low back pain cases in young adults, however the initiating and risk factors are poorly understood, limiting development of personalized therapies. [1] Although the effects of pro-inflammatory cytokines and mechanical loading has been investigated within the IVD, [2] it is unknown how IVD response to complex mechanical loading is affected by the presence of cytokines. Thus, we aimed to investigate the combined effects of dynamic compression and torsion with catabolic cytokine interleukin 1 beta (IL-1β) and inhibitory cytokine interleukin 1 receptor antagonist (IL-1Ra), on bovine IVDs using ex vivo culture, magnetic resonance imaging (MRI), and finite element (FE) modeling. Methods Whole bovine IVDs obtained within 3-4 hours portmortem from a local abattoir were isolated and the IVDs cultured in a customized two degrees-of-freedom bioreactor applying diurnal dynamic compression (0.1- 0.5 MPa) and torsion (6°) under normal (HG DMEM), catabolic (10 ng/ml IL-1β) and inhibitory (10 ng/ml IL1Ra) media conditions for one week. Static compression (0.1 MPa) under the same media conditions were used as a control. Before and after culture, the IVDs were imaged using 3T MRI, which was used to create subjectspecific FE models. Downstream analyses included height measurement, qPCR, glycosaminoglycan (GAG) quantification, and cell metabolic activity. For statistical analysis (when n>3), nonparametric distribution was assumed and a Kruskal–Wallis test then Dunn’s multiple comparisons test were performed, and a P < 0.05 considered statistically significant. Results Following one week of culture, IVD height decreased in all conditions (Figure 1a & b), however, this disc height decreases was less pronounced within IVDs stimulated with IL-1Ra. Cellular metabolic activity in the nucleus pulposus (NP) decreased in all conditions, but the difference was only significant in IVDs stimulated with IL-1β and complex dynamic loading (Figure 1c). Similarly, the GAG content decreased in the NP of all conditions, but was not significant. Gene expression of anabolic genes, i.e. collagen type II (COL II) decreased (Figure 1e), while expression of catabolic genes, i.e. matrix metalloproteinase 3 (MMP3) increased in the NP tissue for all conditions except in control static IVDs and in IL-1Ra stimulated IVDs, respectively (Figure 1d). Introduction Intervertebral disc (IVD) degeneration is the cause of around half of all low back pain cases in young adults, however the initiating and risk factors are poorly understood, limiting development of personalized therapies. [1] Although the effects of pro-inflammatory cytokines and mechanical loading has been investigated within the IVD, [2] it is unknown how IVD response to complex mechanical loading is affected by the presence of cytokines. Thus, we aimed to investigate the combined effects of dynamic compression and torsion with catabolic cytokine interleukin 1 beta (IL-1β) and inhibitory cytokine interleukin 1 receptor antagonist (IL-1Ra), on bovine IVDs using ex vivo culture, magnetic resonance imaging (MRI), and finite element (FE) modeling. Methods Whole bovine IVDs obtained within 3-4 hours portmortem from a local abattoir were isolated and the IVDs cultured in a customized two degrees-of-freedom bioreactor applying diurnal dynamic compression (0.1- 0.5 MPa) and torsion (6°) under normal (HG DMEM), catabolic (10 ng/ml IL-1β) and inhibitory (10 ng/ml IL1Ra) media conditions for one week. Static compression (0.1 MPa) under the same media conditions were used as a control. Before and after culture, the IVDs were imaged using 3T MRI, which was used to create subjectspecific FE models. Downstream analyses included height measurement, qPCR, glycosaminoglycan (GAG) quantification, and cell metabolic activity. For statistical analysis (when n>3), nonparametric distribution was assumed and a Kruskal–Wallis test then Dunn’s multiple comparisons test were performed, and a P < 0.05 considered statistically significant. Results Following one week of culture, IVD height decreased in all conditions (Figure 1a & b), however, this disc height decreases was less pronounced within IVDs stimulated with IL-1Ra. Cellular metabolic activity in the nucleus pulposus (NP) decreased in all conditions, but the difference was only significant in IVDs stimulated with IL-1β and complex dynamic loading (Figure 1c). Similarly, the GAG content decreased in the NP of all conditions, but was not significant. Gene expression of anabolic genes, i.e. collagen type II (COL II) decreased (Figure 1e), while expression of catabolic genes, i.e. matrix metalloproteinase 3 (MMP3) increased in the NP tissue for all conditions except in control static IVDs and in IL-1Ra stimulated IVDs, respectively (Figure 1d). Introduction Intervertebral disc (IVD) degeneration is the cause of around half of all low back pain cases in young adults, however the initiating and risk factors are poorly understood, limiting development of personalized therapies. [1] Although the effects of pro-inflammatory cytokines and mechanical loading has been investigated within the IVD, [2] it is unknown how IVD response to complex mechanical loading is affected by the presence of cytokines. Thus, we aimed to investigate the combined effects of dynamic compression and torsion with catabolic cytokine interleukin 1 beta (IL-1β) and inhibitory cytokine interleukin 1 receptor antagonist (IL-1Ra), on bovine IVDs using ex vivo culture, magnetic resonance imaging (MRI), and finite element (FE) modeling. Methods Whole bovine IVDs obtained within 3-4 hours portmortem from a local abattoir were isolated and the IVDs cultured in a customized two degrees-of-freedom bioreactor applying diurnal dynamic compression (0.1- 0.5 MPa) and torsion (6°) under normal (HG DMEM), catabolic (10 ng/ml IL-1β) and inhibitory (10 ng/ml IL1Ra) media conditions for one week. Static compression (0.1 MPa) under the same media conditions were used as a control. Before and after culture, the IVDs were imaged using 3T MRI, which was used to create subjectspecific FE models. Downstream analyses included height measurement, qPCR, glycosaminoglycan (GAG) quantification, and cell metabolic activity. For statistical analysis (when n>3), nonparametric distribution was assumed and a Kruskal–Wallis test then Dunn’s multiple comparisons test were performed, and a P <0.05 considered statistically significant. Results Following one week of culture, IVD height decreased in all conditions (Figure 1a & b), however, this disc height decreases was less pronounced within IVDs stimulated with IL-1Ra. Cellular metabolic activity in the nucleus pulposus (NP) decreased in all conditions, but the difference was only significant in IVDs stimulated with IL-1β and complex dynamic loading (Figure 1c). Similarly, the GAG content decreased in the NP of all conditions, but was not significant. Gene expression of anabolic genes, i.e. collagen type II (COL II) decreased (Figure 1e), while expression of catabolic genes, i.e. matrix metalloproteinase 3 (MMP3) increased in the NP tissue for all conditions except in control static IVDs and in IL-1Ra stimulated IVDs, respectively (Figure 1d).Discussion We hypothesized that catabolic cytokines, i.e. IL-1β, in the microenvironment of the IVD are sufficient to negatively alter the cellular response to complex loading, leading to further downstream degeneration. However, markers of degeneration were found in all conditions, which could indicate that loading was supraphysiological and catabolic alone. This will be investigated further using subject-specific FE models developed from the MRI images. Additionally, short half-lives of cytokines could have prevented them from diffusing through the IVD effectively, thus limiting the cellular response. This will be further investigated using immunohistochemistry and ELISA. Nevertheless, the results convey that static or complex dynamic loading is sufficient to induce catabolism with or without cytokine stimulation. References 1. Baumgartner L et al., J. Int J Mol Sci. 2021; 22(2):703. 2. Walter BA et al., PLOS ONE. 2015; 10(3): e0118358.5

Fluorescence-based tracing of transplanted intestinal epithelial cells using confocal laser endomicroscopy

BACKGROUND: Intestinal stem cell transplantation has been shown to promote mucosal healing and to engender fully functional epithelium in experimental colitis. Hence, stem cell therapies may provide an innovative approach to accomplish mucosal healing in patients with debilitating conditions such as inflammatory bowel disease. However, an approach to label and trace transplanted cells, in order to assess engraftment efficiency and to monitor wound healing, is a key hurdle to overcome prior to initiating human studies. Genetic engineering is commonly employed in animal studies, but may be problematic in humans due to potential off-target and long-term adverse effects. METHODS: We investigated the applicability of a panel of fluorescent dyes and nanoparticles to label intestinal organoids for visualization using the clinically approved imaging modality, confocal laser endomicroscopy (CLE). Staining homogeneity, durability, cell viability, differentiation capacity, and organoid forming efficiency were evaluated, together with visualization of labeled organoids in vitro and ex vivo using CLE. RESULTS: 5-Chloromethylfluorescein diacetate (CMFDA) proved to be suitable as it efficiently stained all organoids without transfer to unstained organoids in co-cultures. No noticeable adverse effects on viability, organoid growth, or stem cell differentiation capacity were observed, although single-cell reseeding revealed a dose-dependent reduction in organoid forming efficiency. Labeled organoids were easily identified in vitro using CLE for a duration of at least 3 days and could additionally be detected ex vivo following transplantation into murine experimental colitis. CONCLUSIONS: It is highly feasible to use fluorescent dye-based labeling in combination with CLE to trace intestinal organoids following transplantation to confirm implantation at the intestinal target site

Reliability and Criterion Validity of the Assess2Perform Bar Sensei

The Assess2Perform Bar Sensei is a device used to measure barbell velocity for velocity-based training that has not yet been validated. The purpose of this study was to determine criterion validity and reliability of the Assess2Perform Bar Sensei in barbell back squats by comparing it against the GymAware PowerTool, a previously validated instrument. Sixteen injury-free, resistance-trained subjects (eleven males and five females) were recruited. Subjects were tested for their back squat one repetition maximum (1RM). Then, on two separate days, subjects performed two sets of three repetitions at loads of 45%, 60% and 75% 1RM. The GymAware PowerTool and Bar Sensei were attached to the barbell in similar locations for concurrent collection of mean concentric velocity (MCV) and peak concentric velocity (PCV). The Bar Sensei and PowerTool showed generally fair to poor agreement for MCV and PCV when subjects lifted 45% of 1RM (intraclass correlation;ICC 0.4–0.59), and they showed poor agreement when subjects lifted 60% and 75% of 1RM (ICC 0.3–0.4). Inter-repetition/within-set reliability for the Bar Sensei ranged between ICC = 0.273–0.451 for MCV and PCV compared to the far more reliable PowerTool (ICC = 0.651–0.793). Currently, the Bar Sensei is not a reliable or valid tool for measuring barbell velocity in back squats

Quantum spin pumping with adiabatically modulated magnetic barrier's

A quantum pump device involving magnetic barriers produced by the deposition of ferro magnetic stripes on hetero-structure's is investigated. The device for dc- transport does not provide spin-polarized currents, but in the adiabatic regime, when one modulates two independent parameters of this device, spin-up and spin-down electrons are driven in opposite directions, with the net result being that a finite net spin current is transported with negligible charge current. We also analyze our proposed device for inelastic-scattering and spin-orbit scattering. Strong spin-orbit scattering and more so inelastic scattering have a somewhat detrimental effect on spin/charge ratio especially in the strong pumping regime. Further we show our pump to be almost noiseless, implying an optimal quantum spin pump.Comment: 14 pages, 9 figures. Manuscript revised with additional new material on spin-orbit scattering and inelastic scattering. Further new additions on noiseless pumping and analytical results with distinction between weak and strong pumping regimes. Accepted for publication in Physical Review

GluN2A NMDA Receptor Enhancement Improves Brain Oscillations, Synchrony, and Cognitive Functions in Dravet Syndrome and Alzheimer's Disease Models.

NMDA receptors (NMDARs) play subunit-specific roles in synaptic function and are implicated in neuropsychiatric and neurodegenerative disorders. However, the in vivo consequences and therapeutic potential of pharmacologically enhancing NMDAR function via allosteric modulation are largely unknown. We examine the in vivo effects of GNE-0723, a positive allosteric modulator of GluN2A-subunit-containing NMDARs, on brain network and cognitive functions in mouse models of Dravet syndrome (DS) and Alzheimer's disease (AD). GNE-0723 use dependently potentiates synaptic NMDA receptor currents and reduces brain oscillation power with a predominant effect on low-frequency (12-20 Hz) oscillations. Interestingly, DS and AD mouse models display aberrant low-frequency oscillatory power that is tightly correlated with network hypersynchrony. GNE-0723 treatment reduces aberrant low-frequency oscillations and epileptiform discharges and improves cognitive functions in DS and AD mouse models. GluN2A-subunit-containing NMDAR enhancers may have therapeutic benefits in brain disorders with network hypersynchrony and cognitive impairments

Pair-breaking quantum phase transition in superconducting nanowires

A quantum phase transition (QPT) between distinct ground states of matter is a wide-spread phenomenon in nature, yet there are only a few experimentally accessible systems where the microscopic mechanism of the transition can be tested and understood. These cases are unique and form the experimentally established foundation for our understanding of quantum critical phenomena. Here we report the discovery that a magnetic-field-driven QPT in superconducting nanowires - a prototypical 1d-system - can be fully explained by the critical theory of pair-breaking transitions characterized by a correlation length exponent $\nu \approx 1$ and dynamic critical exponent $z \approx 2$. We find that in the quantum critical regime, the electrical conductivity is in agreement with a theoretically predicted scaling function and, moreover, that the theory quantitatively describes the dependence of conductivity on the critical temperature, field magnitude and orientation, nanowire cross sectional area, and microscopic parameters of the nanowire material. At the critical field, the conductivity follows a $T^{(d-2)/z}$ dependence predicted by phenomenological scaling theories and more recently obtained within a holographic framework. Our work uncovers the microscopic processes governing the transition: The pair-breaking effect of the magnetic field on interacting Cooper pairs overdamped by their coupling to electronic degrees of freedom. It also reveals the universal character of continuous quantum phase transitions.Comment: 22 pages, 5 figure