A direct numerical simulation method for complex modulus of particle dispersions

We report an extension of the smoothed profile method (SPM)[Y. Nakayama, K. Kim, and R. Yamamoto, Eur. Phys. J. E {\bf 26}, 361(2008)], a direct numerical simulation method for calculating the complex modulus of the dispersion of particles, in which we introduce a temporally oscillatory external force into the system. The validity of the method was examined by evaluating the storage $G'(\omega)$ and loss $G"(\omega)$ moduli of a system composed of identical spherical particles dispersed in an incompressible Newtonian host fluid at volume fractions of $\Phi=0$, 0.41, and 0.51. The moduli were evaluated at several frequencies of shear flow; the shear flow used here has a zigzag profile, as is consistent with the usual periodic boundary conditions

Investigation of Surface Magnetic Noise by Shallow Spins in Diamond

We present measurements of spin relaxation times (T1, T1ρ, T2) on very shallow (≲5  nm) nitrogen-vacancy centers in high-purity diamond single crystals. We find a reduction of spin relaxation times up to 30 times compared to bulk values, indicating the presence of ubiquitous magnetic impurities associated with the surface. Our measurements yield a density of 0.01–0.1μB/nm2 and a characteristic correlation time of 0.28(3) ns of surface states, with little variation between samples and chemical surface terminations. A low temperature measurement further confirms that fluctuations are thermally activated. The data support the atomistic picture where impurities are associated with the top carbon layers, and not with terminating surface atoms or adsorbate molecules. The low spin density implies that the presence of A single surface impurity is sufficient to cause spin relaxation of a shallow nitrogen-vacancy center

Self-similar shear-thickening behavior in CTAB/NaSal surfactant solutions

The effect of salt concentration Cs on the critical shear rate required for the onset of shear thickening and apparent relaxation time of the shear-thickened phase, has been investigated systematically for dilute CTAB/NaSal solutions. Experimental data suggest a self-similar behavior of the critical shear rate and relaxation time as functions of Cs. Specifically, the former ~ Cs^(-6) whereas the latter ~ Cs^(6) such that an effective Weissenberg number for the onset of the shear thickened phase is only weakly dependent on Cs. A procedure has been developed to collapse the apparent shear viscosity versus shear rate data obtained for various values of Cs into a single master curve. The effect of Cs on the elastic modulus and mesh size of the shear-induced gel phase for different surfactant concentrations is discussed. Experiments performed using different flow cells (Couette and cone-and-plate) show that the critical shear rate, relaxation time and the maximum viscosity attained are geometry-independent. The elastic modulus of the gel phase inferred indirectly by employing simplified hydrodynamic instability analysis of a sheared gel-fluid interface is in qualitative agreement with that predicted for an entangled phase of living polymers. A qualitative mechanism that combines the effect of Cs on average micelle length and Debye parameter with shear-induced configurational changes of rod-like micelles is proposed to rationalize the self-similarity of SIS formation.Comment: 27 pages, 17 figure

Could clazosentan, first approved in Japan, improve neurological prognosis after subarachnoid hemorrhage in combination with modified water-electrolyte management?

An aneurysmal subarachnoid hemorrhage (aSAH) is a devastating event associated with a high mortality and morbidity rate. Though numerous medications are used to prevent cerebral vasospasm and vasospasm-related cerebral infarction after aSAH, no effective pharmacological treatment has been established. Clazosentan, a highly selective endothelin receptor type A antagonist, was approved for use in Japan in April 2022 based on results of two pivotal randomized, placebo-controlled phase 3 studies (JapicCTI-163369, JapicCTI-163368). These studies indicated that clazosentan significantly reduced the incidence of vasospasm-related morbidity and all-cause mortality after aneurysm coiling and clipping. Clazosentan is thus expected to become a “game changer” for improving the neurological prognosis after aSAH. However, other reports indicate that even when clazosentan or nimodipine are administered for prophylaxis against delayed neurological decline, patients treated with increased colloid administration or hypertonic saline (3% sodium chloride) load exhibit poor functional outcome and higher mortality, suggesting that extra fluid and sodium derived from prophylactic colloid administration contribute to negative outcomes after aSAH. Pharmacological treatments such as clazosentan in addition to perioperative management involving delivery of less water and sodium might be crucial for achieving better outcomes than conventional therapy. Based on a literature review, we present here the future perspectives regarding clazosentan and the necessity for modifying management of the water-electrolyte balance by focusing on endothelin-1 and blood–brain barrier disruption

Time-dependent and site-dependent morphological changes in rupture-prone arteries : ovariectomized rat intracranial aneurysm model

OBJECTIVE The pathogenesis of intracranial aneurysm rupture remains unclear. Because it is difficult to study the time course of human aneurysms and most unruptured aneurysms are stable, animal models are used to investigate the characteristics of intracranial aneurysms. The authors have newly established a rat intracranial aneurysm rupture model that features site-specific ruptured and unruptured aneurysms. In the present study the authors examined the time course of changes in the vascular morphology to clarify the mechanisms leading to rupture. METHODS Ten-week-old female Sprague-Dawley rats were subjected to hemodynamic changes, hypertension, and ovariectomy. Morphological changes in rupture-prone intracranial arteries were examined under a scanning electron microscope and the association with vascular degradation molecules was investigated. RESULTS At 2–6 weeks after aneurysm induction, morphological changes and rupture were mainly observed at the posterior cerebral artery; at 7–12 weeks they were seen at the anterior Willis circle including the anterior communicating artery. No aneurysms at the anterior cerebral artery–olfactory artery bifurcation ruptured, suggesting that the inception of morphological changes is site dependent. On week 6, the messenger RNA level of matrix metalloproteinase–9, interleukin-1β, and the ratio of matrix metalloproteinase–9 to the tissue inhibitor of metalloproteinase–2 was significantly higher at the posterior cerebral artery, but not at the anterior communicating artery, of rats with aneurysms than in sham-operated rats. These findings suggest that aneurysm rupture is attributable to significant morphological changes and an increase in degradation molecules. CONCLUSIONS Time-dependent and site-dependent morphological changes and the level of degradation molecules may be indicative of the vulnerability of aneurysms to rupture

Progression to In-Hospital Ischemic Stroke

Background and Purpose: Little attention has been paid to the pathogenesis of in-hospital stroke, despite poor outcomes and a longer time from stroke onset to treatment. We studied the pathophysiology and biomarkers for detecting patients who progress to in-hospital ischemic stroke (IHS). Methods: Seventy-nine patients with IHS were sequentially recruited in the period 2011–2017. Their characteristics, care, and outcomes were compared with 933 patients who had an out-of-hospital ischemic stroke (OHS) using a prospectively collected database of the Tokushima University Stroke Registry. Results: Active cancer and coronary artery disease were more prevalent in patients with IHS than in those with OHS (53.2 and 27.8% vs. 2.0 and 10.9%, respectively; p < 0.001), the median onset-to-evaluation time was longer (300 vs. 240 min; p = 0.015), and the undetermined etiology was significantly higher (36.7 vs. 2.4%; p < 0.001). Although there was no significant difference in stroke severity at onset between the groups, patients with IHS had higher modified Rankin Scale (mRS) scores (3–6) at discharge (67.1 vs. 50.3%; p = 0.004) and rates of death during hospitalization (16.5 vs. 2.9%; p < 0.001). D-dimer (5.8 vs. 0.8 µg/mL; p < 0.001) and fibrinogen (532 vs. 430 mg/dL; p = 0.014) plasma levels at the time of onset were significantly higher in patients with IHS after propensity score matching. Multivariate logistic regression analysis revealed that active cancer (odds ratio [OR] 2.30; 95% confidence interval [CI] 1.26–4.20), prestroke mRS scores 3–5 (OR 6.78; 95% CI 3.96–11.61), female sex (OR 1.57; 95% CI 1.19–2.08), and age ≥75 years (OR 2.36; 95% CI 1.80–3.08) were associated with poor outcomes. Conclusions: Patients with IHS had poorer outcomes than those with OHS because of a higher prevalence of active cancer and functional dependence before stroke onset. Elevated plasma levels of D-dimer and fibrinogen, especially with active cancer, can help identify patients who are at a higher risk of progression to IHS

Self-assembly in solution of a reversible comb-shaped supramolecular polymer

We report a single step synthesis of a polyisobutene with a bis-urea moiety in the middle of the chain. In low polarity solvents, this polymer self-assembles by hydrogen bonding to form a combshaped polymer with a central hydrogen bonded backbone and polyisobutene arms. The comb backbone can be reversibly broken, and consequently, its length can be tuned by changing the solvent, the concentration or the temperature. Moreover, we have proved that the bulkiness of the side-chains have a strong influence on both the self-assembly pattern and the length of the backbone. Finally, the density of arms can be reduced, by simply mixing with a low molar mass bis-urea