Association between Surgery, Anesthesia, and Obstetric Workforce and Emergent Surgical and Obstetric Mortality among United States Hospital Referral Regions.

OBJECTIVE: To determine the association between SAO workforce and mortality from emergent surgical and obstetric conditions within US HR Rs. BACKGROUND: SAO workforce per capita has been identified as a core metric of surgical capacity by the Lancet Commission on Global Surgery, but its utility has not been assessed at the subnational level for a high-income country. METHODS: The number of practicing surgeons, anesthesiologists, and obstetricians per capita was estimated for all HRRs using the US Health Resources & Services Administration Area Health Resource File Database. Deaths due to emergent general surgical and obstetric conditions were determined from the Center for Disease Control and Prevention WONDER database. We utilized B-spline quantile regression to model the relationship between SAO workforce and emergent surgical mortality at different quantiles of mortality and calculated the expected change in mortality associated with increases in SAO workforce. RESULTS: The median SAO workforce across all HRRs was 74.2 per 100,000 population (interquartile range 33.3-241.0). All HRRs met the Lancet Commission on Global Surgery lower target of 20 SAO per 100,000, and 97.7% met the upper target of 40 per 100,000. Nearly 2.8 million Americans lived in HRRs with fewer than 40 SAO per 100,000. Increases in SAO workforce were associated with decreases in surgical mortality in HRRs with high mortality, with minimal additional decreases in mortality above 60 to 80 SAO per 100,000. CONCLUSIONS: Increasing SAO workforce capacity may reduce emergent surgical and obstetric mortality in regions with high surgical mortality but diminishing returns may be seen above 60 to 80 SAO per 100,000. Trial Registration: N/A.

Sistrunk vs modified Sistrunk procedures: Does procedure type matter?

BACKGROUND: Thyroglossal Duct Cyst (TDC) is the most common congenital neck mass in children and is surgically managed with a Sistrunk procedure. Some surgeons perform a modified Sistrunk (mSis), involving the dissection of the fistula beyond the hyoid bone without coring out the foramen cecum at the base of the tongue. We aim to evaluate surgical outcomes of children undergoing Sistrunk (Sis) or modified Sistrunk (mSis) procedures for TDC at an academic pediatric institution. MATERIALS AND METHODS: We conducted a retrospective chart review of the Children's National Medical Center database from 2004 to 2014. Basic demographic information, preoperative characteristics, postoperative complications, and recurrence were extracted for children diagnosed with TDC. We estimated descriptive statistics using Kruskal-Wallis tests and Pearson's chi-square for continuous and categorical values. RESULTS: 157 patients that underwent TDC excision were identified. Sistrunk (Sis) was performed in 52 cases (33%) and modified Sistrunk (mSis) performed in 105 (67%) cases. 84 (54%) were female and the mean age at surgery was 5.4 years (SD=4.5). Overall recurrence was detected in 8 cases (5.1%) and did not differ significantly by procedure type [2 (4%) in Sis and 6 (6%) in mSis, p = 0.616]. Post-operative complications did not differ significantly between Sis and mSis procedure: swelling [6 (12%) and 18 (17%), p = 0.481]; seroma [5 (10%) and 10 (10%), p = 1.00]; surgical site infection [3 (6%) and 8 (8%), p = 0.752]; or post-excision incision and drainage [3 (6%) and 9 (9%), p = 0.752] (respectively). CONCLUSIONS: Our findings reveal no statistical difference in recurrence rates between Sis and mSis with no risk factors for recurrence identified. Furthermore, there was no difference in post-operative complications between the groups. Both surgical procedures were associated with few complications and low recurrence.

Qualitative and quantitative analysis of stability and instability dynamics of positive lattice solitons.

We present a unified approach for qualitative and quantitative analysis of stability and instability dynamics of positive bright solitons in multidimensional focusing nonlinear media with a potential (lattice), which can be periodic, periodic with defects, quasiperiodic, single waveguide, etc. We show that when the soliton is unstable, the type of instability dynamic that develops depends on which of two stability conditions is violated. Specifically, violation of the slope condition leads to a focusing instability, whereas violation of the spectral condition leads to a drift instability. We also present a quantitative approach that allows one to predict the stability and instability strength.

Drift instability and tunneling of lattice solitons.

We derive an analytic formula for the lateral dynamics of solitons in a general inhomogeneous nonlinear media, and show that it can be valid over tens of diffraction lengths. In particular, we show that solitons centered at a lattice maximum can be "mathematically unstable" but "physically stable." We also derive an analytic upper bound for the critical velocity for tunneling, which is valid even when the standard Peierls-Nabarro potential approach fails.

Theory of magnetodynamics induced by spin torque in perpendicularly magnetized thin films.

A nonlinear model of spin-wave excitation using a point contact in a thin ferromagnetic film is introduced. Large-amplitude magnetic solitary waves are computed, which help explain recent spin-torque experiments. Numerical simulations of the fully nonlinear model predict excitation frequencies in excess of 0.2 THz for contact diameters smaller than 6 nm. Simulations also predict a saturation and redshift of the frequency at currents large enough to invert the magnetization under the point contact. The theory is approximated by a cubic complex Ginzburg-Landau type equation. The mode's nonlinear frequency shift is found by use of perturbation techniques, whose results agree with those of direct numerical simulations.

Multiple filamentation of circularly polarized beams.

We derive a new system of equations that describes the propagation of circularly polarized laser beams in a Kerr medium. Analysis and simulations of this system show that multiple filamentation is suppressed for circularly polarized beams.

Deterministic vectorial effects lead to multiple filamentation.

The standard explanation for multiple filamentation of laser pulses is that it is caused by noise in the input beam. We propose an alternative explanation that is based on deterministic vectorial (polarization) effects. We present numerical simulations in support of the vectorial-effects explanation and suggest a simple experiment for deciding whether multiple filamentation is due to vectorial effects.