Scale-Free Networks in International Trade

The paper analyzes the network structure of international trade. Adapting a network approach developed in the physical sciences, we propose that international trade functions like a scale-free network. For each commodity group we calculate a characteristic parameter which reflects the structure of its trading network. We then insert this variable into an expanded gravity model to explore the effect of the network structure on the value of bilateral trade. The estimation suggests that, inter alia, globalization has reduced the value of trade per product group.Networks, International trade, Gravity model

Tunneling Spectroscopy and Vortex Imaging in Boron-Doped Diamond

We present the first scanning tunneling spectroscopy study of single-crystalline boron doped diamond. The measurements were performed below 100 mK with a low temperature scanning tunneling microscope. The tunneling density of states displays a clear superconducting gap. The temperature evolution of the order parameter follows the weak coupling BCS law with $\Delta(0)/k_B T_c \simeq 1.74$. Vortex imaging at low magnetic field also reveals localized states inside the vortex core that are unexpected for such a dirty superconductor.Comment: 4 pages, 4 figures, replaced with revised versio

The surfing effect in the interaction of electromagnetic and gravitational waves. Limits on the speed of gravitational waves

In the current work we investigate the propagation of electromagnetic waves in the field of gravitational waves. Starting with simple case of an electromagnetic wave travelling in the field of a plane monochromatic gravitational wave we introduce the concept of surfing effect and analyze its physical consequences. We then generalize these results to an arbitrary gravitational wave field. We show that, due to the transverse nature of gravitational waves, the surfing effect leads to significant observable consequences only if the velocity of gravitational waves deviates from speed of light. This fact can help to place an upper limit on the deviation of gravitational wave velocity from speed of light. The micro-arcsecond resolution promised by the upcoming precision interferometry experiments allow to place stringent upper limits on $\epsilon = (v_{gw}-c)/c$ as a function of the energy density parameter for gravitational waves $\Omega_{gw}$. For $\Omega_{gw} \approx 10^{-10}$ this limit amounts to $\epsilon\lesssim 2\cdot 10^{-2}$

Retrospective Review of Fluoroscopic Swallowing Studies and Outcomes at an Academic Health Center

Introduction: Aspiration is often associated with underlying medical conditions and can cause pneumonia or death. Aspiration risk can be assessed via video fluoroscopic swallowing study (VFSS) or barium swallow (BaSw). We aimed to assess the diagnoses and clinical course of patients who were evaluated for potential aspiration through VFSS or BaSw to determine if there is a degree of aspiration that increases the risk of developing pneumonia and/or death. Methods: We conducted a retrospective chart review of 374 patients in TJUH who were evaluated via VFSS or BaSw from January 1 to June 30, 2017. We recorded the degree and contents of aspiration, the underlying diagnoses, and evidence of subsequent pneumonia. We then collected data for any future admissions concerning for pneumonia. Results: Of the 374 patients, 165 had swallowing studies positive for laryngeal penetration or aspiration. Of the 165 patients, 78 patients (47.2%) had evidence of clinical and radiological pneumonia, and 18 of those 78 patients (23.1%) died. We found that 61 of 165 exhibited laryngeal penetration. Of those 61, 23 patients (37.7%) showed clinical and radiological signs of pneumonia, and 7 of the 23 (30.4%) died of aspiration pneumonia. Discussion: The incidence of pneumonia was considerable in persons with an abnormal swallow and the mortality rate was substantial. Minimally abnormal swallows with laryngeal penetration, but no true aspiration, still had serious consequences. While the incidence of pneumonia was lower (37.7%), there was a substanitial mortality rate (30.4%)