Relaxation of Fermionic Excitations in a Strongly Attractive Fermi Gas in an Optical Lattice

We theoretically study the relaxation of high energy single particle excitations into molecules in a system of attractive fermions in an optical lattice, both in the superfluid and the normal phase. In a system characterized by an interaction scale $U$ and a tunneling rate $t$, we show that the relaxation rate scales as $\sim Ct\exp(-\alpha U^2/t^2)$ in the large $U/t$ limit. We obtain explicit expressions for the exponent $\alpha$, both in the low temperature superfluid phase and the high temperature phase with pairing but no coherence between the molecules. We find that the relaxation rate decreases both with temperature and deviation of the fermion density from half-filling. We show that quasiparticle and phase degrees of freedom are effectively decoupled within experimental timescales allowing for observation of ordered states even at high total energy of the system.Comment: 5 pages, 3 figure

Magnetism and d-wave superconductivity on the half-filled square lattice with frustration

The role of frustration and interaction strength on the half-filled Hubbard model is studied on the square lattice with nearest and next-nearest neighbour hoppings t and t' using the Variational Cluster Approximation (VCA). At half-filling, we find two phases with long-range antiferromagnetic (AF) order: the usual Neel phase, stable at small frustration t'/t, and the so-called collinear (or super-antiferromagnet) phase with ordering wave-vector $(\pi,0)$ or $(0,\pi)$, stable for large frustration. These are separated by a phase with no detectable long-range magnetic order. We also find the d-wave superconducting (SC) phase ($d_{x^2-y^2}$), which is favoured by frustration if it is not too large. Intriguingly, there is a broad region of coexistence where both AF and SC order parameters have non-zero values. In addition, the physics of the metal-insulator transition in the normal state is analyzed. The results obtained with the help of the VCA method are compared with the large-U expansion of the Hubbard model and known results for the frustrated J1-J2 Heisenberg model. These results are relevant for pressure studies of undoped parents of the high-temperature superconductors: we predict that an insulator to d-wave SC transition may appear under pressure.Comment: 12 pages, 10 figure

A null mutation of the neuronal sodium channel NaV1.6 disrupts action potential propagation and excitation‐contraction coupling in the mouse heart

Evidence supports the expression of brain‐type sodium channels in the heart. Their functional role, however, remains controversial. We used global NaV1.6‐null mice to test the hypothesis that NaV1.6 contributes to the maintenance of propagation in the myocardium and to excitation‐contraction (EC) coupling. We demonstrated expression of transcripts encoding full‐length NaV1.6 in isolated ventricular myocytes and confirmed the striated pattern of NaV1.6 fluorescence in myocytes. On the ECG, the PR and QRS intervals were prolonged in the null mice, and the Ca2+ transients were longer in the null cells. Under patch clamping, at holding potential (HP) = –120 mV, the peak INa was similar in both phenotypes. However, at HP = –70 mV, the peak INa was smaller in the nulls. In optical mapping, at 4 mM [K+]o, 17 null hearts showed slight (7%) reduction of ventricular conduction velocity (CV) compared to 16 wild‐type hearts. At 12 mM [K+]o, CV was 25% slower in a subset of 9 null vs. 9 wild‐type hearts. These results highlight the importance of neuronal sodium channels in the heart, whereby NaV1.6 participates in EC coupling, and represents an intrinsic depolarizing reserve that contributes to excitation.—Noujaim, S. F., Kaur, K., Milstein, M., Jones, J. M., Furspan, P., Jiang, D., Auerbach, D. S., Herron, T., Meisler, M. H., Jalife, J. A null mutation of the neuronal sodium channel NaV1.6 disrupts action potential propagation and excitation‐contraction coupling in the mouse heart. FASEB J. 26, 63–72 (2012). www.fasebj.orgPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154524/1/fsb2fj10179770.pd

Francisella tularensis subsp. novicida isolated from a human in Arizona

<p>Abstract</p> <p>Background</p> <p><it>Francisella tularensis </it>is the etiologic agent of tularemia and is classified as a select agent by the Centers for Disease Control and Prevention. Currently four known subspecies of <it>F. tularensis </it>that differ in virulence and geographical distribution are recognized:<it>tularensis </it>(type A), <it>holarctica </it>(type B), <it>mediasiatica</it>, and <it>novicida</it>. Because of the Select Agent status and differences in virulence and geographical location, the molecular analysis of any clinical case of tularemia is of particular interest. We analyzed an unusual <it>Francisella </it>clinical isolate from a human infection in Arizona using multiple DNA-based approaches.</p> <p>Findings</p> <p>We report that the isolate is <it>F. tularensis </it>subsp. <it>novicida</it>, a subspecies that is rarely isolated.</p> <p>Conclusion</p> <p>The rarity of this <it>novicida </it>subspecies in clinical settings makes each case study important for our understanding of its role in disease and its genetic relationship with other <it>F. tularensis </it>subspecies.</p

HOW THE GROWING GAP IN LIFE EXPECTANCY MAY AFFECT RETIREMENT BENEFITS AND REFORMS.

Older Americans have experienced dramatic gains in life expectancy in recent decades, but an emerging literature reveals that these gains are accumulating mostly to those at the top of the income distribution. We explore how growing inequality in life expectancy affects lifetime benefits from Social Security, Medicare, and other programs and how this phenomenon interacts with possible program reforms. We first project that life expectancy at age 50 for males in the two highest income quintiles will rise by 7 to 8 years between the 1930 and 1960 birth cohorts, but that the two lowest income quintiles will experience little to no increase over that time period. This divergence in life expectancy will cause the gap between average lifetime program benefits received by men in the highest and lowest quintiles to widen by $130,000 (in$2009) over this period. Finally we simulate the effect of Social Security reforms such as raising the normal retirement age and changing the benefit formula to see whether they mitigate or enhance the reduced progressivity resulting from the widening gap in life expectancy

Genomic islands from five strains of Burkholderia pseudomallei

<p>Abstract</p> <p>Background</p> <p><it>Burkholderia pseudomallei </it>is the etiologic agent of melioidosis, a significant cause of morbidity and mortality where this infection is endemic. Genomic differences among strains of <it>B. pseudomallei </it>are predicted to be one of the major causes of the diverse clinical manifestations observed among patients with melioidosis. The purpose of this study was to examine the role of genomic islands (GIs) as sources of genomic diversity in this species.</p> <p>Results</p> <p>We found that genomic islands (GIs) vary greatly among <it>B. pseudomallei </it>strains. We identified 71 distinct GIs from the genome sequences of five reference strains of <it>B. pseudomallei</it>: K96243, 1710b, 1106a, MSHR668, and MSHR305. The genomic positions of these GIs are not random, as many of them are associated with tRNA gene loci. In particular, the 3' end sequences of tRNA genes are predicted to be involved in the integration of GIs. We propose the term "tRNA-mediated site-specific recombination" (tRNA-SSR) for this mechanism. In addition, we provide a GI nomenclature that is based upon integration hotspots identified here or previously described.</p> <p>Conclusion</p> <p>Our data suggest that acquisition of GIs is one of the major sources of genomic diversity within <it>B. pseudomallei </it>and the molecular mechanisms that facilitate horizontally-acquired GIs are common across multiple strains of <it>B. pseudomallei</it>. The differential presence of the 71 GIs across multiple strains demonstrates the importance of these mobile elements for shaping the genetic composition of individual strains and populations within this bacterial species.</p

Tertiary-Treated Municipal Wastewater is a Significant Point Source of Antibiotic Resistance Genes Into Duluth-Superior Harbor

In this study, the impact of tertiary-treated municipal wastewater on the quantity of several antibiotic resistance determinants in Duluth-Superior Harbor was investigated by collecting surface water and sediment samples from 13 locations in Duluth-Superior Harbor, the St. Louis River, and Lake Superior. Quantitative PCR (qPCR) was used to target three different genes encoding resistance to tetracycline (tet(A), tet(X), and tet(W)), the gene encoding the integrase of class 1 integrons (intI1), and total bacterial abundance (16S rRNA genes) as well as total and human fecal contamination levels (16S rRNA genes specific to the genus Bacteroides). The quantities of tet(A), tet(X), tet(W), intI1, total Bacteroides, and human-specific Bacteroides were typically 20-fold higher in the tertiary-treated wastewater than in nearby surface water samples. In contrast, the quantities of these genes in the St. Louis River and Lake Superior were typically below detection. Analysis of sequences of tet(W) gene fragments from four different samples collected throughout the study site supported the conclusion that tertiary-treated municipal wastewater is a point source of resistance genes into Duluth-Superior Harbor. This study demonstrates that the discharge of exceptionally treated municipal wastewater can have a statistically significant effect on the quantities of antibiotic resistance genes in otherwise pristine surface waters

Differences in the Quality of Pediatric Resuscitative Care Across a Spectrum of Emergency Departments

Importance: The quality of pediatric resuscitative care delivered across the spectrum of emergency departments (EDs) in the United States is poorly described. In a recent study, more than 4000 EDs completed the Pediatric Readiness Survey (PRS); however, the correlation of PRS scores with the quality of simulated or real patient care has not been described. Objective: To measure and compare the quality of resuscitative care delivered to simulated pediatric patients across a spectrum of EDs and to examine the correlation of PRS scores with quality measures. Design, Setting, and Participants: This prospective multicenter cohort study evaluated 58 interprofessional teams in their native pediatric or general ED resuscitation bays caring for a series of 3 simulated critically ill patients (sepsis, seizure, and cardiac arrest). Main Outcomes and Measures: A composite quality score (CQS) was measured as the sum of 4 domains: (1) adherence to sepsis guidelines, (2) adherence to cardiac arrest guidelines, (3) performance on seizure resuscitation, and (4) teamwork. Pediatric Readiness Survey scores and health care professional demographics were collected as independent data. Correlations were explored between CQS and individual domain scores with PRS. Results: Overall, 58 teams from 30 hospitals participated (8 pediatric EDs [PEDs], 22 general EDs [GEDs]). The mean CQS was 71 (95% CI, 68-75); PEDs had a higher mean CQS (82; 95% CI, 79-85) vs GEDs (66; 95% CI, 63-69) and outperformed GEDs in all domains. However, when using generalized estimating equations to estimate CQS controlling for clustering of the data, PED status did not explain a higher CQS (beta = 4.28; 95% CI, -4.58 to 13.13) while the log of pediatric patient volume did explain a higher CQS (beta = 9.57; 95% CI, 2.64-16.49). The correlation of CQS to PRS was moderate (r = 0.51; P \u3c .001). The correlation was weak for cardiac arrest (r = 0.24; P = .07), weak for sepsis (rho = 0.45; P \u3c .001) and seizure (rho = 0.43; P = .001), and strong for teamwork (rho = 0.71; P \u3c .001). Conclusions and Relevance: This multicenter study noted significant differences in the quality of simulated pediatric resuscitative care across a spectrum of EDs. The CQS was higher in PEDs compared with GEDs. However, when controlling for pediatric patient volume and other variables in a multivariable model, PED status does not explain a higher CQS while pediatric patient volume does. The correlation of the PRS was moderate for simulation-based measures of quality

Community-based in situ simulation: bringing simulation to the masses

Simulation-based methods are regularly used to train inter-professional groups of healthcare providers at academic medical centers (AMC). These techniques are used less frequently in community hospitals. Bringing in-situ simulation (ISS) from AMCs to community sites is an approach that holds promise for addressing this disparity. This type of programming allows academic center faculty to freely share their expertise with community site providers. By creating meaningful partnerships community-based ISS facilitates the communication of best practices, distribution of up to date policies, and education/training. It also provides an opportunity for system testing at the community sites. In this article, we illustrate the process of implementing an outreach ISS program at community sites by presenting four exemplar programs. Using these exemplars as a springboard for discussion, we outline key lessons learned discuss barriers we encountered, and provide a framework that can be used to create similar simulation programs and partnerships. It is our hope that this discussion will serve as a foundation for those wishing to implement community-based, outreach ISS

Signal Transduction Pathways in the Pentameric Ligand-Gated Ion Channels

The mechanisms of allosteric action within pentameric ligand-gated ion channels (pLGICs) remain to be determined. Using crystallography, site-directed mutagenesis, and two-electrode voltage clamp measurements, we identified two functionally relevant sites in the extracellular (EC) domain of the bacterial pLGIC from Gloeobacter violaceus (GLIC). One site is at the C-loop region, where the NQN mutation (D91N, E177Q, and D178N) eliminated inter-subunit salt bridges in the open-channel GLIC structure and thereby shifted the channel activation to a higher agonist concentration. The other site is below the C-loop, where binding of the anesthetic ketamine inhibited GLIC currents in a concentration dependent manner. To understand how a perturbation signal in the EC domain, either resulting from the NQN mutation or ketamine binding, is transduced to the channel gate, we have used the Perturbation-based Markovian Transmission (PMT) model to determine dynamic responses of the GLIC channel and signaling pathways upon initial perturbations in the EC domain of GLIC. Despite the existence of many possible routes for the initial perturbation signal to reach the channel gate, the PMT model in combination with Yen's algorithm revealed that perturbation signals with the highest probability flow travel either via the β1-β2 loop or through pre-TM1. The β1-β2 loop occurs in either intra- or inter-subunit pathways, while pre-TM1 occurs exclusively in inter-subunit pathways. Residues involved in both types of pathways are well supported by previous experimental data on nAChR. The direct coupling between pre-TM1 and TM2 of the adjacent subunit adds new insight into the allosteric signaling mechanism in pLGICs. © 2013 Mowrey et al