Does stability of relativistic dissipative fluid dynamics imply causality?

We investigate the causality and stability of relativistic dissipative fluid dynamics in the absence of conserved charges. We perform a linear stability analysis in the rest frame of the fluid and find that the equations of relativistic dissipative fluid dynamics are always stable. We then perform a linear stability analysis in a Lorentz-boosted frame. Provided that the ratio of the relaxation time for the shear stress tensor, $\tau_\pi$, to the sound attenuation length, $\Gamma_s = 4\eta/3(\varepsilon+P)$, fulfills a certain asymptotic causality condition, the equations of motion give rise to stable solutions. Although the group velocity associated with perturbations may exceed the velocity of light in a certain finite range of wavenumbers, we demonstrate that this does not violate causality, as long as the asymptotic causality condition is fulfilled. Finally, we compute the characteristic velocities and show that they remain below the velocity of light if the ratio $\tau_\pi/\Gamma_s$ fulfills the asymptotic causality condition.Comment: 30 pages, 10 figures

Complex Relationship of Body Mass Index with Mortality in Patients with Critical Limb Ischemia Undergoing Endovascular Treatment

ObjectiveTo investigate the relationship between body mass index (BMI) and long-term outcomes of patients with CLI after endovascular treatment (EVT).DesignRetrospective multicenter study.Subjects1088 consecutive patients (1306 limbs, mean age 72 ± 10 years) with CLI who underwent EVT for isolated infrapopliteal artery lesions were evaluated. These subjects were identified in the J-BEAT III registry.MethodsThe patients were divided into groups based on BMI <18.5 kg/m2 (underweight, n = 188; 219 limbs), 18.5 to 24.9 kg/m2 (normal weight, n = 718; 868 limbs), and >25.0 kg/m2 (overweight/obese, n = 182; 219 limbs). The endpoints were overall survival and freedom from major adverse limb events (MALE).ResultsThe median follow up period was 1.5 years (range: 1 month–8.7 years). The 3 year overall survival rates were 33.3%, 61.2%, and 69.8% in underweight, normal, and overweight/obese patients, respectively. The survival rate was significantly lower in underweight patients and significantly higher in overweight/obese patients compared with patients of normal weight (both p < .0001). The 3 year rates of freedom from MALE did not differ significantly among the three groups (36.4%, 45.4%, and 52.3%, respectively, p = .32). Age, BMI <18.5 kg/m2, heart failure, aortic valve stenosis, renal failure, triglyceride levels, serum albumin <3.0 g/dL, anticoagulant treatment, non-ambulatory status, and Rutherford 6 classification all were significantly associated with overall survival.ConclusionsBMI has a complex correlation with mortality in patients with CLI after EVT for isolated infrapopliteal artery lesions. Underweight patients with CLI have an extremely poor prognosis. Such patients have many other factors associated with mortality, but low BMI was identified as an independent predictor of a poor prognosis in patients with CLI. Similarly, normal weight patients had a small but significant increase in mortality compared with overweight/obese patients

Validation of pressure gradient and peripheral fractional flow reserve measured by a pressure wire for diagnosis of iliofemoral artery disease with intermediate stenosis

Naotaka Murata,1 Hideaki Aihara,2 Yoshimitsu Soga,1 Yusuke Tomoi,1 Seiichi Hiramori,1 Yohei Kobayashi,1 Kei Ichihashi,1 Nobuhiro Tanaka3 1Department of Cardiology, Kokura Memorial Hospital, Kitakyushu, 2Department of Cardiology, Tsukuba Medical Center Hospital, Ibaraki, 3Department of Cardiology, Tokyo Medical University, Tokyo, Japan Objective: To examine the pressure gradient and peripheral fractional flow reserve (pFFR) measured by a pressure wire as indicators of hemodynamic significance in iliofemoral angiographic intermediate stenosis. Background: The utility of pressure measurements using a pressure wire with vasodilators is unclear in cases with intermediate iliofemoral stenosis. Methods: The mean pressure gradient (MPG) and mean pressure ratio (MPR) were measured at baseline and after injection of isosorbide dinitrate in 23 lesions with angiographically intermediate iliofemoral stenosis. Patients with complex lesions, infrapopliteal artery lesions, chronic total occlusion, and surgical bypass grafts were excluded. Hyperemic MPR was considered equivalent to pFFR. Changes in parameters in response to vasodilators were assessed and correlations of peak systolic velocity ratio (PSVR) with hyperemic MPG and pFFR were examined using duplex ultrasound. Results: After injection of isosorbide dinitrate, hyperemic MPG increased significantly (from 9.0&plusmn;5.7 to 16.3&plusmn;6.2 mmHg; P&lt;0.05) and hyperemic MPR (pFFR) decreased significantly (from 0.92&plusmn;0.06 to 0.81&plusmn;0.07; P&lt;0.05). PSVR was significantly correlated with hyperemic MPG (R=0.52; P&lt;0.05) and pFFR (R=&ndash;0.50; P&lt;0.05). The optimal cut-off value of pFFR as an indicator of significant hemodynamic stenosis (PSVR &gt;2.5) was 0.85 (area under the curve 0.72; sensitivity 94%; specificity 50%, P&lt;0.05). Conclusion: pFFR measured using a pressure wire is reliable for prediction of hemodynamic significance in iliofemoral intermediate stenosis. Keywords: endovascular therapy, peripheral artery disease, pressure measurements, hyperemia, vasodilators, hemodynamics&nbsp

Abscisic Acid Acts as a Regulator of Molecular Trafficking through Plasmodesmata in the Moss Physcomitrella patens

In multi-cellular organisms, cell-to-cell communication is crucial for adapting to changes in the surrounding environment. In plants, plasmodesmata (PD) provide a unique pathway for cell-to-cell communication. PD interconnect most cells and generate a cytoplasmic continuum, allowing the trafficking of various micro- and macromolecules between cells. This molecular trafficking through PD is dynamically regulated by altering PD permeability dependent on environmental changes, thereby leading to an appropriate response to various stresses; however, how PD permeability is dynamically regulated is still largely unknown. Moreover, studies on the regulation of PD permeability have been conducted primarily in a limited number of angiosperms. Here, we studied the regulation of PD permeability in the moss Physcomitrella patens and report that molecular trafficking through PD is rapidly and reversibly restricted by abscisic acid (ABA). Since ABA plays a key role in various stress responses in the moss, PD permeability can be controlled by ABA to adapt to surrounding environmental changes. This ABA-dependent restriction of PD trafficking correlates with a reduction in PD pore size. Furthermore, we also found that the rate of macromolecular trafficking is higher in an ABA-synthesis defective mutant, suggesting that the endogenous level of ABA is also important for PD-mediated macromolecular trafficking. Thus, our study provides compelling evidence that P. patens exploits ABA as one of the key regulators of PD function