XMM-Newton Reflection Grating Spectrometer Observations of the Prototypical Starburst Galaxy M82

We present results from XMM-Newton Reflection Grating Spectrometer observations of the prototypical starburst galaxy M82. These high resolution spectra represent the best X-ray spectra to date of a starburst galaxy. A complex array of lines from species over a wide range of temperatures is seen, the most prominent being due to Lyman-alpha emission from abundant low Z elements such as N, O, Ne, Mg and Si. Emission lines from Helium-like charge states of the same elements are also seen in emission, as are strong lines from the entire Fe-L series. Further, the OVII line complex is resolved and is seen to be consistent with gas in collisional ionization equilibrium. Spectral fitting indicates emission from a large mass of gas with a differential emission measure over a range of temperatures (from 0.2 keV to 1.6 keV, peaking at 0.7 keV), and evidence for super-solar abundances of several elements is indicated. Spatial analysis of the data indicates that low energy emission is more extended to the south and east of the nucleus than to the north and west. Higher energy emission is far more centrally concentrated.Comment: 5 pages, 4 figures, MNRAS accepte

The holographic RG flow in a field theory on a curved background

As shown by Freedman, Gubser, Pilch and Warner, the RG flow in ${\cal N}=4$ super-Yang-Mills theory broken to an ${\cal N}=1$ theory by the addition of a mass term can be described in terms of a supersymmetric domain wall solution in five-dimensional ${\cal N}=8$ gauged supergravity. The FGPW flow is an example of a holographic RG flow in a field theory on a flat background. Here we put the field theory studied by Freedman, Gubser, Pilch and Warner on a curved $AdS_4$ background, and we construct the supersymmetric domain wall solution which describes the RG flow in this field theory. This solution is a curved (non Ricci flat) domain wall solution. This example demonstrates that holographic RG flows in supersymmetric field theories on a curved $AdS_4$ background can be described in terms of curved supersymmetric domain wall solutions.Comment: 14 pages, LaTe

Efficient Gravitational Wave Searches with Pulsar Timing Arrays using Hamiltonian Monte Carlo

Pulsar timing arrays (PTAs) detect low-frequency gravitational waves (GWs) by looking for correlated deviations in pulse arrival times. Current Bayesian searches use Markov Chain Monte Carlo (MCMC) methods, which struggle to sample the large number of parameters needed to model the PTA and GW signals. As the data span and number of pulsars increase, this problem will only worsen. An alternative Monte Carlo sampling method, Hamiltonian Monte Carlo (HMC), utilizes Hamiltonian dynamics to produce sample proposals informed by first-order gradients of the model likelihood. This in turn allows it to converge faster to high dimensional distributions. We implement HMC as an alternative sampling method in our search for an isotropic stochastic GW background, and show that this method produces equivalent statistical results to similar analyses run with standard MCMC techniques, while requiring 100-200 times fewer samples. We show that the speed of HMC sample generation scales as $\mathcal{O}(N_\mathrm{psr}^{5/4})$ where $N_\mathrm{psr}$ is the number of pulsars, compared to $\mathcal{O}(N_\mathrm{psr}^2)$ for MCMC methods. These factors offset the increased time required to generate a sample using HMC, demonstrating the value of adopting HMC techniques for PTAs.Comment: 9 pages, 5 figures, submitted to Physical Review

Comparative Outcomes of Autologous Chondrocyte Implantation and Osteochondral Allograft Transplantation with Patellar Realignment for Patellar Instability with Associated Cartilage Defects

Abstract Background: Articular cartilage pathology can stem from a spectrum of etiologies including osteochondritis dissecans, avascular necrosis, degenerative joint disease, and injury resulting from recurrent instability of the patella. Hypothesis/Purpose: The purpose of this study was to identify differences in clinical and functional outcomes in patients treated with either ACI or OCA transplantation for chondral defects with concomitant MPFL reconstruction and tibia tubercle osteotomy. Study Design: Retrospective Cohort Study Methods: A retrospective review identified patients who underwent autologous chondrocyte implantation (ACI) or osteochondral allograft (OCA) transplantation with concomitant medial patellofemoral ligament (MPFL) reconstruction and tibia tubercle osteotomy (TTO). Outcome measures included the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS JR), International Knee Documentation Committee (IKDC) evaluation, and Short Form Health Survey (SF-12) physical scores, all collected a minimum of 2 years after surgery. Defect location, size, complications, and rate of subsequent surgery were determined. Results: Eighteen patients (11 ACI and 7 OCA) were included in this study to analyze clinical and functional outcomes following surgical correction of 23 chondral defects (ACI n=12, OCA n=10). Defects had comparable baseline characteristics in each group including size measured during index arthroscopy (3.34 cm2 vs 4.03 cm2, P = .351), Outerbridge classification (54.8% grade 4 vs 60.0% grade 4, P = 1.000), and AMADEUS score (47.1 vs 58.6, P = .298). Postoperative outcomes were comparable including revision rate (15.4% vs 10.0%, P=1.000) and 2-year IKDC scores (74.2 vs 51.2, P = .077). However, ACI did have significantly higher 2-year KOOS JR (85.1 vs 63.7, P = .031) and SF-12 scores (54.1 vs 42.6, P = .007) compared to OCA. Conclusion: ACI or OCA transplantation for chondral defects with concomitant MPFL reconstruction and TTO can be safely performed in an outpatient setting with functional and clinical outcomes being comparable. Functional scores including KOOS JR and SF-12 were shown to be significantly higher at 2-year follow-up in the ACI cohort, however, postoperative IKDC scores, rates of revisions, and clinical evaluations were comparable between cohorts

The Effect of Graft Selection on Patients’ Subjective Readiness to Return to Sport After ACL Reconstruction

Background: Patients who undergo ACL reconstruction with allografts may have an easier functional recovery compared to autograft patients. This is due to decreased donor site morbidity and less muscle atrophy compared to autograft patients. This “easier” recovery may be perceived by patients and may result in a subjective earlier readiness for return to sports. Hypothesis/Purpose: To determine if there is a difference in perceived readiness to return to sport (RTS) in the first year postoperative period between individuals who undergo ACL reconstruction utilizing bone-patellar tendon-bone (BTB) autografts or allografts. Study Design: Prospective Cohort Study, Level II Methods: This was a prospective, observational cohort study for patients aged 14-25 years old undergoing primary ACL reconstruction done either with BTB autograft or allograft. Patients completed questionnaires postoperatively evaluating their perceived ability to perform various activities, and their responses were used to compare subjective ability to RTS. Results: Fifty-nine patients were included in the study. Sixteen patients underwent ACL reconstruction with allograft while 43 patients received autograft. At 3 months those who received autograft reported higher perceived ability to cut (P = .003). At 6-months, patients who received allograft reconstruction reported higher perceived ability to run (P = .033), cut (P = .048), and decelerate (P = .008) as well as a higher overall perceived ability to RTS (P = .032). At all other times, there was no significant difference between cohorts’ subjective readiness to perform activities. Conclusion The results of this study indicate that at times within the first year of recovery following ACL reconstruction, patients who receive allografts and autografts may have significantly different perceived ability to perform activities or RTS. However, while present at various times throughout the first year of recovery, any difference in perceived ability to perform activities or in overall RTS is no longer present at 12 months. This study does not implicate a subjective difference in ability to return to sport or ability to perform sport-like activities between autograft or allograft as being associated with an increased risk for re-injury in the first year following surgery. Key Terms: knee ligament, ACL, allograft, imaging, general sports traum

Dense mapping of MYH9 localizes the strongest kidney disease associations to the region of introns 13 to 15

Admixture mapping recently identified MYH9 as a susceptibility gene for idiopathic focal segmental glomerulosclerosis (FSGS), HIV-associated nephropathy (HIVAN) and end-stage kidney disease attributed to hypertension (H-ESKD) in African Americans (AA). MYH9 encodes the heavy chain of non-muscle myosin IIA, a cellular motor involved in motility. A haplotype and its tagging SNPs spanning introns 12–23 were most strongly associated with kidney disease (OR 2–7; P < 10−8, recessive). To narrow the region of association and identify potential causal variation, we performed a dense-mapping study using 79 MYH9 SNPs in AA populations with FSGS, HIVAN and H-ESKD (typed for a subset of 46 SNPs), for a total of 2496 cases and controls. The strongest associations were for correlated SNPs rs5750250, rs2413396 and rs5750248 in introns 13, 14 and 15, a region of 5.6 kb. Rs5750250 showed OR 5.0, 8.0 and 2.8; P = 2 × 10−17, 2 × 10−10 and 3 × 10−22, respectively, for FSGS, HIVAN and H-ESKD; OR 5.7; P = 9 × 10−27 for combined FSGS and HIVAN, recessive. An independent association was observed for rs11912763 in intron 33. Neither the highly associated SNPs nor the results of resequencing MYH9 in 40 HIVAN or FSGS cases and controls revealed non-synonymous changes that could account for the disease associations. Rs2413396 and one of the highly associated SNPs in intron 23, rs4821480, are predicted splicing motif modifiers. Rs5750250 combined with rs11912763 had receiver operator characteristic (ROC) C statistics of 0.80, 0.73 and 0.65 for HIVAN, FSGS and H-ESKD, respectively, allowing prediction of genetic risk by typing two SNPs

Curved BPS domain walls and RG flow in five dimensions

We determine, in the context of five-dimensional ${\cal N}=2$ gauged supergravity with vector and hypermultiplets, the conditions under which curved (non Ricci flat) supersymmetric domain wall solutions may exist. These curved BPS domain wall solutions may, in general, be supported by non-constant vector and hyper scalar fields. We establish our results by a careful analysis of the BPS equations as well as of the associated integrability conditions and the equations of motion. We construct an example of a curved BPS solution in a gauged supergravity model with one hypermultiplet. We also discuss the dual description of curved BPS domain walls in terms of RG flows.Comment: 18 pages, LaTeX, 5 figures; added reference

Curved BPS domain wall solutions in four-dimensional N=2 supergravity

We construct four-dimensional domain wall solutions of N=2 gauged supergravity coupled to vector and to hypermultiplets. The gauged supergravity theories that we consider are obtained by performing two types of Abelian gauging. In both cases we find that the behaviour of the scalar fields belonging to the vector multiplets is governed by the so-called attractor equations known from the study of BPS black hole solutions in ungauged N=2 supergravity theories. The scalar fields belonging to the hypermultiplets, on the other hand, are either constant or exhibit a run-away behaviour. These domain wall solutions preserve 1/2 of supersymmetry and they are, in general, curved. We briefly comment on the amount of supersymmetry preserved by domain wall solutions in gauged supergravity theories obtained by more general gaugings.Comment: 18 pages, latex, no figures, final version for Nuclear Physics B (typos corrected plus minor changes

Mice Deficient in Ribosomal Protein S6 Phosphorylation Suffer from Muscle Weakness that Reflects a Growth Defect and Energy Deficit

BACKGROUND: Mice, whose ribosomal protein S6 cannot be phosphorylated due to replacement of all five phosphorylatable serine residues by alanines (rpS6(P-/-)), are viable and fertile. However, phenotypic characterization of these mice and embryo fibroblasts derived from them, has established the role of these modifications in the regulation of the size of several cell types, as well as pancreatic beta-cell function and glucose homeostasis. A relatively passive behavior of these mice has raised the possibility that they suffer from muscle weakness, which has, indeed, been confirmed by a variety of physical performance tests. METHODOLOGY/PRINCIPAL FINDINGS: A large variety of experimental methodologies, including morphometric measurements of histological preparations, high throughput proteomic analysis, positron emission tomography (PET) and numerous biochemical assays, were used in an attempt to establish the mechanism underlying the relative weakness of rpS6(P-/-) muscles. Collectively, these experiments have demonstrated that the physical inferiority appears to result from two defects: a) a decrease in total muscle mass that reflects impaired growth, rather than aberrant differentiation of myofibers, as well as a diminished abundance of contractile proteins; and b) a reduced content of ATP and phosphocreatine, two readily available energy sources. The abundance of three mitochondrial proteins has been shown to diminish in the knockin mouse. However, the apparent energy deficiency in this genotype does not result from a lower mitochondrial mass or compromised activity of enzymes of the oxidative phosphorylation, nor does it reflect a decline in insulin-dependent glucose uptake, or diminution in storage of glycogen or triacylglycerol (TG) in the muscle. CONCLUSIONS/SIGNIFICANCE: This study establishes rpS6 phosphorylation as a determinant of muscle strength through its role in regulation of myofiber growth and energy content. Interestingly, a similar role has been assigned for ribosomal protein S6 kinase 1, even though it regulates myoblast growth in an rpS6 phosphorylation-independent fashion