Standing and traveling waves in a model of periodically modulated one-dimensional waveguide arrays.

In the present work we study coherent structures in a one-dimensional discrete nonlinear Schrödinger lattice in which the coupling between waveguides is periodically modulated. Numerical experiments with single-site initial conditions show that, depending on the power, the system exhibits two fundamentally different behaviors. At low power, initial conditions with intensity concentrated in a single site give rise to transport, with the energy moving unidirectionally along the lattice, whereas high-power initial conditions yield stationary solutions. We explain these two behaviors, as well as the nature of the transition between the two regimes, by analyzing a simpler model where the couplings between waveguides are given by step functions. For the original model, we numerically construct both stationary and moving coherent structures, which are solutions reproducing themselves exactly after an integer multiple of the coupling period. For the stationary solutions, which are true periodic orbits, we use Floquet analysis to determine the parameter regime for which they are spectrally stable. Typically, the traveling solutions are characterized by having small-amplitude oscillatory tails, although we identify a set of parameters for which these tails disappear. These parameters turn out to be independent of the lattice size, and our simulations suggest that for these parameters, numerically exact traveling solutions are stable.

Floquet solitons in square lattices: Existence, stability, and dynamics.

In the present work, we revisit a recently proposed and experimentally realized topological two-dimensional lattice with periodically time-dependent interactions. We identify the fundamental solitons, previously observed in experiments and direct numerical simulations, as exact, exponentially localized, periodic in time solutions. This is done for a variety of phase-shift angles of the central nodes upon an oscillation period of the coupling strength. Subsequently, we perform a systematic Floquet stability analysis of the relevant structures. We analyze both their point and their continuous spectrum and find that the solutions are generically stable, aside from the possible emergence of complex quartets due to the collision of bands of continuous spectrum. The relevant instabilities become weaker as the lattice size gets larger. Finally, we also consider multisoliton analogs of these Floquet states, inspired by the corresponding discrete nonlinear Schrödinger (DNLS) lattice. When exciting initially multiple sites in phase, we find that the solutions reflect the instability of their DNLS multi-soliton counterparts, while for configurations with multiple excited sites in alternating phases, the Floquet states are spectrally stable, again analogously to their DNLS counterparts.

High molecular weight kininogen contributes to early mortality and kidney dysfunction in a mouse model of sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) is characterized by chronic hemolytic anemia, vaso-occlusive crises, chronic inflammation, and activation of coagulation. The clinical complications such as painful crisis, stroke, pulmonary hypertension, nephropathy and venous thromboembolism lead to cumulative organ damage and premature death. High molecular weight kininogen (HK) is a central cofactor for the kallikrein-kinin and intrinsic coagulation pathways, which contributes to both coagulation and inflammation. OBJECTIVE: We hypothesize that HK contributes to the hypercoagulable and pro-inflammatory state that causes end-organ damage and early mortality in sickle mice. METHODS: We evaluated the role of HK in the Townes mouse model of SCD. RESULTS/CONCLUSIONS: We found elevated plasma levels of cleaved HK in sickle patients compared to healthy controls, suggesting ongoing HK activation in SCD. We used bone marrow transplantation to generate wild type and sickle cell mice on a HK-deficient background. We found that short-term HK deficiency attenuated thrombin generation and inflammation in sickle mice at steady state, which was independent of bradykinin signaling. Moreover, long-term HK deficiency attenuates kidney injury, reduces chronic inflammation, and ultimately improves survival of sickle mice.

Novel approach to uterine artery pseudoaneurysm embolization for delayed post-partum hemorrhage.

Uterine artery pseudoaneurysms (UAP) are a rare cause of post-partum hemorrhage. Conservative management is discouraged due to the risk of spontaneous hemorrhage. Intra-arterial embolization is highly successful (>90%) and offers definitive treatment. We present the case of a 27-year-old woman with significant delayed post-partum hemorrhage after cesarean section who was found to have a UAP on imaging. Her tortuous vascular anatomy and spasmodic aneurysmal neck presented technical challenges to embolization with traditional material, such as gel foam and coils. Intra-arterial thrombin was then employed with good technical and clinical outcome. To our knowledge, this is the first case describing the use of intra-arterial thrombin in the treatment of UAP. Given its success in this case, we argue that intra-arterial thrombin should be considered a viable alternative for embolization of UAP when more traditional techniques fail.

Computed tomography scan versus upper gastrointestinal fluoroscopy for diagnosis of staple line leak following bariatric surgery.

BACKGROUND: The best radiographic modality to diagnose staple line leaks following bariatric surgery remains controversial. Two common studies used are upper gastrointestinal (UGI) fluoroscopy and computed tomography (CT). This study sought to determine the better modality in detecting clinically significant postoperative leaks. METHODS: This retrospective review was performed of patients undergoing imaging for suspected staple line leaks following bariatric surgery. These studies were reinterpreted by 2 radiologists who were blinded to the original findings. RESULTS: Six hundred nineteen radiographic "leak tests" were selectively performed following bariatric procedures at our institution between January 2005 and December 2011. CT was found to have a sensitivity of 95% (95% confidence interval [CI] 81.8 to 99.1) and a specificity of 100% (95% CI 93.1 to 100) in diagnosing postoperative leaks, while UGI demonstrated a sensitivity of 79.4% (95% CI 61.6 to 90.0) and a specificity of 95% (95% CI 85.2 to 98.7). CONCLUSION: CT is a superior modality compared with UGI for detecting staple line leaks following bariatric surgery.