Universality in the one-dimensional chain of phase-coupled oscillators

We apply a recently developed renormalization group (RG) method to study synchronization in a one-dimensional chain of phase-coupled oscillators in the regime of weak randomness. The RG predicts how oscillators with randomly distributed frequencies and couplings form frequency-synchronized clusters. Although the RG was originally intended for strong randomness, i.e. for distributions with long tails, we find good agreement with numerical simulations even in the regime of weak randomness. We use the RG flow to derive how the correlation length scales with the width of the coupling distribution in the limit of large coupling. This leads to the identification of a universality class of distributions with the same critical exponent $\nu$. We also find universal scaling for small coupling. Finally, we show that the RG flow is characterized by a universal approach to the unsynchronized fixed point, which provides physical insight into low-frequency clusters.Comment: 14 pages, 10 figure

Renormalization Group Approach to Oscillator Synchronization

We develop a renormalization group method to investigate synchronization clusters in a one-dimensional chain of nearest-neighbor coupled phase oscillators. The method is best suited for chains with strong disorder in the intrinsic frequencies and coupling strengths. The results are compared with numerical simulations of the chain dynamics and good agreement in several characteristics is found. We apply the renormalization group and simulations to Lorentzian distributions of intrinsic frequencies and couplings and investigate the statistics of the resultant cluster sizes and frequencies, as well as the dependence of the characteristic cluster length upon parameters of these Lorentzian distributions.Comment: 13 pages, 7 figures: 8 figure files in *.eps format and one *.tex fil

Hereditary thrombotic thrombocytopenic purpura and COVID-19: Impacts of vaccination and infection in this rare disease.

Introduction Severe COVID-19 is associated with an important increase of von Willebrand factor and mild lowering of ADAMTS13 activity that may, in the presence of a strong inflammatory reaction, increase the risk of acute thrombotic thrombocytopenic purpura (TTP). Although acute episodes of immune-mediated TTP associated with COVID-19 or SARS-CoV-2 vaccination have been reported, data about clinical evolution of hereditary TTP (hTTP) during the pandemic are scarce. Method We conducted a survey among adult patients of the International Hereditary TTP Registry about SARS-CoV-2 vaccination, COVID-19, and occurrence of acute hTTP episodes. Results Of 122 adult hTTP patients invited to participate, 86 (70.5%) responded. Sixty-five had been vaccinated (75.6%), of which 14 had received in addition a booster, resulting in 139 individual vaccine shots. Although vaccinations in patients on plasma prophylaxis were done within 1 week of the last plasma infusion, all 23 patients treated with plasma on demand were vaccinated without prior plasma infusions. One patient on uninterrupted weekly plasma infusions presented within 3 days from his second vaccination with neurological symptoms and computed tomography scan 9 days later showed subacute ischemic/hemorrhagic frontal lobe infarction. A second male patient developed acute myocarditis after his second dose of mRNA-1273 vaccine. Twelve (14%) patients had COVID-19, associated with an acute hTTP episode in three of them: one patient had a transient ischemic attack, one a stroke, and a pregnant woman was hospitalized to intensify plasma treatment. Discussion The risk of an acute episode triggered by COVID-19 seems higher than following vaccination in hTTP patients, who can be safely vaccinated against SARS-CoV-2

Lumenato protects normal human dermal fibroblasts from neutrophil-induced collagen-3 damage in co-cultures.

Collagen is the major structural protein in the extracellular matrix of skin produced by fibroblasts. UV exposure results in infiltration of neutrophils within the epidermis and dermis, inducing collagen damage and contributing to the process of photo-aging. Collagen-3 is an integral structural component with collagen-1, and is an important regulator of collagen-1 fibrillogenesis. Addition of neutrophils activated with TNFα to normal human dermal fibroblast cultures, but not their supernatant, caused significant collagen-3 damage. To study whether Lumenato can protect from collagen-3 damage, it was added to co-cultures of Normal human dermal fibroblasts and neutrophils activated with TNFα. Lumenato prevented collagen-3 damage induced by activated neutrophils in a dose-dependent manner in the co-cultures. Lumenato also induced a low rate of collagen-3 synthesis in a dose-dependent manner detected by pro-collagen-3 secretion, but did not affect fibroblast cell number. Although Lumenato inhibited MMP-8, MMP-9, and elastase secreted from neutrophils, its main effect was in inhibiting both NADPH oxidase-producing superoxides and MPO activity-producing halides in a dose-dependent manner that correlated with protection from collagen-3 damage. In conclusion, the results suggest that Lumenato induces low levels of collagen-3 that may contribute for skin health and is very effective in defending the co-cultures from collagen-3 damage by inhibiting free radicals secreted from neutrophils, thus, indicating Lumenato's possible potential for skin protection

Potassium Level Variation Following Packed Cell Transfusion in Critically Ill Adult Patients—How Alert Should We Be?

One of the most clinically important effects following the administration of packed cell transfusion (PCT) is hyperkalemia, which can cause severe life-threatening cardiac arrhythmias. This retrospective population-based cohort study included adults hospitalized between January 2007 and December 2019 in a general intensive care unit for 24 h or more, with normal levels of serum potassium on admission. We assessed changes in serum potassium levels after administration of one unit of packed cells and sought to identify clinical parameters that may affect these changes. We applied adjusted linear mixed models to assess changes in serum potassium. The mean increase in serum potassium was 0.09 mEq/L (C.U 0.04–0.14, p-value < 0.001) among the 366 patients who were treated with a single PCT compared to those not treated with PCT. Increased serum potassium levels were also found in patients who required mechanical ventilation, and to a lesser degree in those treated with vasopressors. Hypertension, the occurrence of a cerebrovascular accident, and increased creatinine levels were all associated with reduced serum potassium levels. Due to the small rise in serum potassium levels following PCT, we do not suggest any particular follow-up measures for critically ill patients who receive PCT