Correlated decay of triplet excitations in the Shastry-Sutherland compound SrCu2_2(BO3_3)2_2

The temperature dependence of the gapped triplet excitations (triplons) in the 2D Shastry-Sutherland quantum magnet SrCu$_2$(BO$_3$)$_2$ is studied by means of inelastic neutron scattering. The excitation amplitude rapidly decreases as a function of temperature while the integrated spectral weight can be explained by an isolated dimer model up to 10~K. Analyzing this anomalous spectral line-shape in terms of damped harmonic oscillators shows that the observed damping is due to a two-component process: one component remains sharp and resolution limited while the second broadens. We explain the underlying mechanism through a simple yet quantitatively accurate model of correlated decay of triplons: an excited triplon is long-lived if no thermally populated triplons are near-by but decays quickly if there are. The phenomenon is a direct consequence of frustration induced triplon localization in the Shastry--Sutherland lattice.Comment: 5 pages, 4 figure

Spin density wave induced disordering of the vortex lattice in superconducting La2−x_{2-x}Srx_xCuO4_4

We use small angle neutron scattering to study the superconducting vortex lattice in La$_{2-x}$Sr$_x$CuO$_4$ as a function of doping and magnetic field. We show that near optimally doping the vortex lattice coordination and the superconducting coherence length $\xi$ are controlled by a van-Hove singularity crossing the Fermi level near the Brillouin zone boundary. The vortex lattice properties change dramatically as a spin-density-wave instability is approached upon underdoping. The Bragg glass paradigm provides a good description of this regime and suggests that SDW order acts as a novel source of disorder on the vortex lattice.Comment: Accepted in Phys. Rev.

The Disk and Extraplanar Environment of NGC 247

The stellar content of the spiral galaxy NGC 247 is investigated. The main sequence turn-off (MSTO) in the inner 12 kpc of the disk corresponds to an age of 6 Myr. A mean star formation rate (SFR) of 0.1 solar masses per year during the past 16 Myr is computed from star counts. The color of the red supergiant plume does not change with radius, suggesting that the mean metallicity of young stars does not vary by more than 0.1 dex. The number of bright main sequence stars per local stellar mass density climbs towards larger radii out to a distance of 12 kpc; the scale lengths that characterize the radial distributions of young and old stars in the disk thus differ. The density of bright main sequence stars with respect to projected HI mass gradually drops with increasing radius. The population of very young stars disappears in the outer disk; the MSTO at galactocentric radii between 12 and 15 kpc corresponds to 16 Myr, while between 15 and 18 kpc the age is > 40 Myr. Red giant branch (RGB) stars are resolved at a projected minor axis galactocentric distance of 12 kpc. There is a broad spread in metallicity among the RGB stars, with a mean [M/H] = -1.2. The RGB-tip occurs at i' = 24.5 +/- 0.1, indicating that the distance modulus is 27.9 +/- 0.1. Luminous AGB stars with an age 3 Gyr are also seen in this field.Comment: Includes 16 eps figures; to appear in the Astrophysical Journa

Practice Characteristics and Job Satisfaction of Private Practice and Academic Surgeons

IMPORTANCE: Private practice and academic surgery careers vary significantly in their daily routine, compensation schemes, and definition of productivity. Data are needed regarding the practice characteristics and job satisfaction of these career paths for surgeons and trainees to make informed career decisions and to identify modifiable factors that may be associated with the health of the surgical workforce. OBJECTIVE: To obtain and compare the differences in practice characteristics and career satisfaction measures between academic and private practice surgeons. DESIGN, SETTING, AND PARTICIPANTS: In this cross-sectional survey performed from June 4 to August 1, 2018, an online survey accommodating smartphone, tablet, and desktop formats was distributed by email to 25 748 surgeons who were actively practicing fellows of the American College of Surgeons; had completed a general surgery residency or categorical fellowship in plastic, cardiothoracic, or vascular surgery; and had an active email address on file. MAIN OUTCOMES AND MEASURES: Demographic, training, and current practice characteristics were obtained, and satisfaction measures were measured on a 5-point Likert scale and compared by surgeon type. Nonresponse weights adjusted for respondent sex, age, and presence of subspecialty training between respondents and the total surveyed American College of Surgeons population. RESULTS: There were 3807 responses (15% response rate) from surgeons: 1735 academic surgeons (1390 men [80%]; median age, 53 years [interquartile range (IQR), 44-61 years]) and 1464 private practice surgeons (1276 men [87%]; median age, 56 years [IQR, 48-62 years]); 589 surgeons who reported being neither an academic surgeon nor a private practice surgeon and 19 surgeons who did not respond to questions on their practice type were excluded. Academic surgeons reported working a median of 59 hours weekly (IQR, 38-65 hours) compared with 57 hours weekly (IQR, 45-65 hours) for private practice surgeons. Academic surgeons reported more weekly hours performing nonclinical work than did private practice surgeons (24 hours [IQR, 14-38 hours] vs 9 hours [IQR, 4-17 hours]; P < .001). Academic surgeons were more likely than private practice surgeons to be satisfied with their career as a surgeon (1448 of 1706 [85%] vs 1109 of 1420 [78%]; P < .001) and their financial compensation (997 of 1703 [59%] vs 546 of 1416 [39%]; P < .001). Academic surgeons were less likely than private practice surgeons to feel that competition with other surgeons is a threat to financial security (341 of 1705 [20%] vs 559 of 1422 [39%]; P < .001) and less likely to feel that malpractice experience has decreased job satisfaction (534 of 1703 [31%] vs 686 of 1413 [49%]; P < .001). CONCLUSIONS AND RELEVANCE: This study suggests that, although overall surgeon satisfaction was high, academic surgeons reported higher career satisfaction on several measures when compared with private practice surgeons. Advocacy for private practice surgeons is important to encourage career longevity and sustain US surgeon workforce needs

Perceptions of Gender Disparities in Access to Surgical Care in Malawi: A Community Based Survey

Background Gender disparities in surgical care exist but have been minimally studied, particularly in low- and middle-income countries. This study explored perceptions and gender differences in health-seeking behavior and attitudes toward surgical care in Malawi among community members.MethodsA survey tool was administered to adults ≥18 years old at a central hospital, district hospital, and two marketplaces in Malawi from June 2018 to December 2018. Responses from men and women were compared using chi-squared tests. Results Four hundred eighty-five adults participated in the survey, 244 (50.3%) men and 241 (49.7%) women. Women were more likely to state that fear of surgery might prevent them from seeking surgical care (29.1% of men, 43.6% of women, P = .0009). Both genders reported long wait times, medicine/physician shortages, and lack of information about when surgery is needed as potential barriers to seeking surgical care. More men stated that medical preference should be given to sons (17.1% of men, 9.3% of women, P = .01). Men were more likely to report that men should have the final word about household decisions (28.7% of men vs 19.5% of women, P < .0001) and were more likely to spend money independently (68.7% of married men, 37.5% of married women, P < .0001). Few participants reported believing gender equality had been achieved (61% of men and 66.8% of women). Conclusions A multi-pronged approach is needed to reduce gender disparities in surgical care in Malawi, including addressing paternalistic societal norms, education, and improving health infrastructure

Incorporation of DPP6a and DPP6K Variants in Ternary Kv4 Channel Complex Reconstitutes Properties of A-type K Current in Rat Cerebellar Granule Cells

Dipeptidyl peptidase-like protein 6 (DPP6) proteins co-assemble with Kv4 channel α-subunits and Kv channel-interacting proteins (KChIPs) to form channel protein complexes underlying neuronal somatodendritic A-type potassium current (ISA). DPP6 proteins are expressed as N-terminal variants (DPP6a, DPP6K, DPP6S, DPP6L) that result from alternative mRNA initiation and exhibit overlapping expression patterns. Here, we study the role DPP6 variants play in shaping the functional properties of ISA found in cerebellar granule (CG) cells using quantitative RT-PCR and voltage-clamp recordings of whole-cell currents from reconstituted channel complexes and native ISA channels. Differential expression of DPP6 variants was detected in rat CG cells, with DPP6K (41±3%)>DPP6a (33±3%)>>DPP6S (18±2%)>DPP6L (8±3%). To better understand how DPP6 variants shape native neuronal ISA, we focused on studying interactions between the two dominant variants, DPP6K and DPP6a. Although previous studies did not identify unique functional effects of DPP6K, we find that the unique N-terminus of DPP6K modulates the effects of KChIP proteins, slowing recovery and producing a negative shift in the steady-state inactivation curve. By contrast, DPP6a uses its distinct N-terminus to directly confer rapid N-type inactivation independently of KChIP3a. When DPP6a and DPP6K are co-expressed in ratios similar to those found in CG cells, their distinct effects compete in modulating channel function. The more rapid inactivation from DPP6a dominates during strong depolarization; however, DPP6K produces a negative shift in the steady-state inactivation curve and introduces a slow phase of recovery from inactivation. A direct comparison to the native CG cell ISA shows that these mixed effects are present in the native channels. Our results support the hypothesis that the precise expression and co-assembly of different auxiliary subunit variants are important factors in shaping the ISA functional properties in specific neuronal populations

Dynamic Changes in the MicroRNA Expression Profile Reveal Multiple Regulatory Mechanisms in the Spinal Nerve Ligation Model of Neuropathic Pain

Neuropathic pain resulting from nerve lesions or dysfunction represents one of the most challenging neurological diseases to treat. A better understanding of the molecular mechanisms responsible for causing these maladaptive responses can help develop novel therapeutic strategies and biomarkers for neuropathic pain. We performed a miRNA expression profiling study of dorsal root ganglion (DRG) tissue from rats four weeks post spinal nerve ligation (SNL), a model of neuropathic pain. TaqMan low density arrays identified 63 miRNAs whose level of expression was significantly altered following SNL surgery. Of these, 59 were downregulated and the ipsilateral L4 DRG, not the injured L5 DRG, showed the most significant downregulation suggesting that miRNA changes in the uninjured afferents may underlie the development and maintenance of neuropathic pain. TargetScan was used to predict mRNA targets for these miRNAs and it was found that the transcripts with multiple predicted target sites belong to neurologically important pathways. By employing different bioinformatic approaches we identified neurite remodeling as a significantly regulated biological pathway, and some of these predictions were confirmed by siRNA knockdown for genes that regulate neurite growth in differentiated Neuro2A cells. In vitro validation for predicted target sites in the 3′-UTR of voltage-gated sodium channel Scn11a, alpha 2/delta1 subunit of voltage-dependent Ca-channel, and purinergic receptor P2rx ligand-gated ion channel 4 using luciferase reporter assays showed that identified miRNAs modulated gene expression significantly. Our results suggest the potential for miRNAs to play a direct role in neuropathic pain