Keck Echellette Spectrograph and Imager Observations of Metal-poor Damped Lyα Systems

We present the first results from a survey of SDSS quasars selected for strong H I damped Lyα (DLA) absorption with corresponding low equivalent width absorption from strong low-ion transitions (e.g., C II λ1334 and Si II λ1260). These metal-poor DLA candidates were selected from the SDSS fifth release quasar spectroscopic database, and comprise a large new sample for probing low-metallicity galaxies. Medium-resolution echellette spectra from the Keck Echellette Spectrograph and Imager spectrograph for an initial sample of 35 systems were obtained to explore the metal-poor tail of the DLA distribution and to investigate the nucleosynthetic patterns at these metallicities. We have estimated saturation corrections for the moderately underresolved spectra, and systems with very narrow Doppler parameters (b ≤ 5 km s^(–1)) will likely have underestimated abundances. For those systems with Doppler parameters b > 5 km s^(–1), we have measured low-metallicity DLA gas with [X/H] < –2.4 for at least one of C, O, Si, or Fe. Assuming non-saturated components, we estimate that several DLA systems have [X/H] < –2.8, including five DLA systems with both low equivalent widths and low metallicity in transitions of both C II and O I. All of the measured DLA metallicities, however, exceed or are consistent with a metallicity of at least 1/1000 of solar, regardless of the effects of saturation in our spectra. Our results indicate that the metal-poor tail of galaxies at z ~ 3 drops exponentially at [X/H] ≾ –3. If the distribution of metallicity is Gaussian, the probability of identifying interstellar medium gas with lower abundance is extremely small, and our results suggest that DLA systems with [X/H] < –4.0 are extremely rare, and could comprise only 8 × 10^(–7) of DLA systems. The relative abundances of species within these low-metallicity DLA systems are compared with stellar nucleosynthesis models, and are consistent with stars having masses of 30 M_⊙ < M * < 100 M_⊙. The observed ratio of [C/O] for values of [O/H] < –2.5 exceeds values seen in moderate metallicity DLA systems, and also exceeds theoretical nucleosynthesis predictions for higher mass Population III stars. We also have observed a correlation between the column density N(C IV) with [Si/H] metallicity, suggestive of a trend between mass of the DLA system and its metallicity

Pragmatic Rigor: Principles and Criteria for Conducting and Evaluating Practitioner Scholarship

Practitioner scholarship is a promising avenue for addressing the gap between academic research and practice. To advance the objective of publishing the findings of practitioner scholarship, we develop the concept of pragmatic rigor, which is intended to complement but not replace scientific rigor. We propose four principles of pragmatic rigor: relevance, actionability, comprehensibility, and ethical reasoning. For each principle, we develop associated criteria for conducting and evaluating practical research. Pragmatic principles are relevant to the research process, from choice of topic to final evaluation by journal reviewers. We believe that applying these principles can advance the practical value of studies and help to bridge the gap between scholars and practitioners

Incidence of surgical site infection following mastectomy with and without immediate reconstruction using private insurer claims data

OBJECTIVE: The National Healthcare Safety Network classifies breast operations as clean procedures with an expected 1–2% surgical site infection (SSI) incidence. We assessed differences in SSI incidence following mastectomy with and without immediate reconstruction in a large, geographically diverse population. DESIGN: Retrospective cohort study. PATIENTS: Commercially-insured women aged 18–64 years with ICD-9-CM procedure or CPT-4 codes for mastectomy from 1/1/2004–12/31/2011. METHODS: Incident SSIs within 180 days after surgery were identified by ICD-9-CM diagnosis codes. The incidence of SSI after mastectomy +/− immediate reconstruction was compared by the chi-square test. RESULTS: From 2004–2011, 18,696 mastectomy procedures among 18,085 women were identified, with immediate reconstruction in 10,836 (58%) procedures. The 180-day incidence of SSI following mastectomy with or without reconstruction was 8.1% (1,520/18,696). Forty-nine percent of SSIs were identified within 30 days post-mastectomy, 24.5% between 31–60 days, 10.5% between 61–90 days, and 15.7% between 91–180 days. The incidence of SSI was 5.0% (395/7,860) after mastectomy-only, 10.3% (848/8,217) after mastectomy plus implant, 10.7% (207/1,942) after mastectomy plus flap, and 10.3% (70/677) after mastectomy plus flap and implant (p<0.001). The SSI risk was higher after bilateral compared with unilateral mastectomy with (11.4% vs. 9.4%, p=0.001) and without (6.1% vs. 4.7%, p=0.021) immediate reconstruction. CONCLUSIONS: SSI incidence was two-fold higher after mastectomy with immediate reconstruction than after mastectomy alone. Only 49% of SSIs were coded within 30 days after operation. Our results suggest stratification by procedure type will facilitate comparison of SSI rates after breast operations between facilities

Taxon abundance, diversity, co-occurrence and network analysis of the ruminal microbiota in response to dietary changes in dairy cows

We thank Mari Talvisilta and the staff in the metabolism unit at Natural Resources Institute Finland for technical support, care of experimental animals and assistance in sample collection. We thank Paula Lidauer for ruminal cannulation surgeries, Richard Hill from Aberystwyth University, UK for performing qPCR and Aurélie Bonin from Laboratoire d'Ecologie Alpine, CNRS, France for preparing archaea amplicon libraries for sequencing. Kevin J. Shingfield passed away before the submission of the final version of this manuscript. Ilma Tapio accepts responsibility for the integrity and validity of the data collected and analyzed. Funding: Study was funded by the Finnish Ministry of Agriculture and Forestry as part of the GreenDairy Project (Developing Genetic and Nutritional Tools to Mitigate the Environmental Impact of Milk Production; Project No. 2908234). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Measurement of the resonant and CP components in B¯ 0 → J=ψπþπ− decays

The resonant structure of the reaction B¯0→J/ψπ+π− is studied using data from 3  fb−1 of integrated luminosity collected by the LHCb experiment, one third at 7 TeV center-of-mass energy and the remainder at 8 TeV. The invariant mass of the π+π− pair and three decay angular distributions are used to determine the fractions of the resonant and nonresonant components. Six interfering π+π− states, ρ(770), f0(500), f2(1270), ρ(1450), ω(782) and ρ(1700), are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative charge parity fractions of each of the resonant final states are determined. The f0(980) meson is not seen and the upper limit on its presence, compared with the observed f0(500) rate, is inconsistent with a model where these scalar mesons are formed from two quarks and two antiquarks (tetraquarks) at the eight standard deviation level. In the qq¯ model, the absolute value of the mixing angle between the f0(980) and the f0(500) scalar mesons is limited to be less than 17° at 90% confidence level

Measurement of CP asymmetry in D 0 → K - K + and D 0 → π - π decays

Time-integrated CP asymmetries in D 0 decays to the final states K - K + and π - π + are measured using proton-proton collisions corresponding to 3fb-1 of integrated luminosity collected at centre-of-mass energies of 7 TeV and 8 TeV. The D 0 mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in CP asymmetries between the two final states is measured to be Δ ACP = ACP (K- K +) ACP (π- π+) = (+ 0.14 ± 0.16 (stat) ± 0.08 (syst)) %. A measurement of A CP (K - K +) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D decays. It is found to be ACP (K- K+) = (- 0.06 ± 0.15 (stat) ± 0.10 (syst)) %, where the correlation coefficient between ΔA CP and A CP (K - K +) is ρ = 0.28. By combining these results, the CP asymmetry in the D 0 → π - π + channel is A CP (π - π +) = (-0.20 ± 0.19 (stat) ± 0.10 (syst))%

Measurement of the Xi(-)(b) and Omega(-)(b) baryon lifetimes

Using a data sample of pp collisions corresponding to an integrated luminosity of 3 fb−1, the Ξ−b and Ω−b baryons are reconstructed in the Ξ−b → J/ψΞ− and Ω−b → J/ψΩ− decay modes and their lifetimes measured to be τ(Ξ−b) = 1.55+0.10−0.09 (stat) ± 0.03 (syst) ps, τ(Ω−b) = 1.54+0.26−0.21 (stat) ± 0.05 (syst) ps. These are the most precise determinations to date. Both measurements are in good agreement with previous experimental results and with theoretical predictions