Random Fields from Quenched Disorder in an Archetype for Correlated Electrons: the Parallel Spin Stripe Phase of La1.6−x_{1.6-x}Nd0.4_{0.4}Srx_xCuO4_4 at the 1/8 Anomaly

The parallel stripe phase is remarkable both in its own right, and in relation to the other phases it co-exists with. Its inhomogeneous nature makes such states susceptible to random fields from quenched magnetic vacancies. We argue this is the case by introducing low concentrations of nonmagnetic Zn impurities (0-10%) into La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$ (Nd-LSCO) with $x$ = 0.125 in single crystal form, well below the percolation threshold of $\sim$ 41% for two-dimensional (2D) square lattice. Elastic neutron scattering measurements on these crystals show clear magnetic quasi-Bragg peaks at all Zn dopings. While all the Zn-doped crystals display order parameters that merge into each other and the background at $\sim$ 68 K, the temperature dependence of the order parameter as a function of Zn concentration is drastically different. This result is consistent with meandering charge stripes within the parallel stripe phase, which are pinned in the presence of quenched magnetic vacancies. In turn it implies vacancies that preferentially occupy sites within the charge stripes, and hence that can be very effective at disrupting superconductivity in Nd-LSCO ($x$ = 0.125), and, by extension, in all systems exhibiting parallel stripes

The Isolation and Partial Characterization of Two Novel Sphingolipids from Neurospora crassa: Di(Inositolphosphoryl)ceramide and [(gal)_3glu]ceramide

Neurospora crassa strains labeled uniformly with ^(32)P_i and [^3H]inositol exhibit at least six phospholipid components containing ^3H when separated by paper chromatography. One of the major components is phosphatidylinositol. Other components, which account for 40 to 60% of the lipid-extractable ^3H in various strains, are stable to mild alkaline methanolysis and appear to be sphingolipids with equivalent amounts of inositol and phosphorus. The major phosphosphingolipid was purified by means of differential solubility and by column chromatography on porous silica beads. This substance contains equivalent amounts of hydroxysphinganine and hydroxytetracosanoic acid and 2 eq each of myoinositol, phosphorus, and sodium. Alkaline degradation yielded 2 eq of inositol monophosphate and periodate degradation gave a C-15 fragment. The elemental composition of this compound also fits the formulation, (inositol-P)_2-ceramide. A [^3H]inositol pulse-chase experiment carried out with an inositol-requiring mutant in exponential growth shows labeled inositol accumulating in the sphingolipid accompanied by decreased labeling in phosphatidylinositol and the acid-soluble fraction. These changes also occur when the chase is carried out during inositol starvation suggesting that degradation of phosphatidylinositol and formation of sphingolipid occurs in the absence of growth. A neutral glycosphingolipid was also obtained as a by-product of the phospholipid purification. This substance is provisionally formulated as the ceramide tetrahexoside: [(gal)_3glu]-N-hydroxytetracosonyl-hydroxysphinganine

A Small-molecule Inhibitor Directed against the Chemokine Receptor CXCR4 Prevents its Use as an HIV-1 Coreceptor

The chemokine receptor CXCR4 is the major coreceptor used for cellular entry by T cell– tropic human immunodeficiency virus (HIV)-1 strains, whereas CCR5 is used by macrophage (M)-tropic strains. Here we show that a small-molecule inhibitor, ALX40-4C, inhibits HIV-1 envelope (Env)-mediated membrane fusion and viral entry directly at the level of coreceptor use. ALX40-4C inhibited HIV-1 use of the coreceptor CXCR4 by T- and dual-tropic HIV-1 strains, whereas use of CCR5 by M- and dual-tropic strains was not inhibited. Dual-tropic viruses capable of using both CXCR4 and CCR5 were inhibited by ALX40-4C only when cells expressed CXCR4 alone. ALX40-4C blocked stromal-derived factor (SDF)-1α–mediated activation of CXCR4 and binding of the monoclonal antibody 12G5 to cells expressing CXCR4. Overlap of the ALX40-4C binding site with that of 12G5 and SDF implicates direct blocking of Env interactions, rather than downregulation of receptor, as the mechanism of inhibition. Thus, ALX40-4C represents a small-molecule inhibitor of HIV-1 infection that acts directly against a chemokine receptor at the level of Env-mediated membrane fusion

Cardiac evaluation of hospitalized children with 2019 coronavirus (COVID-19) infection at a single large quaternary center

Background: Cardiac complications of serious SARS-CoV-2 infections, especially Multisystem Inflammatory Syndrome of Children (MIS-C) are well described, however current studies have not considered pediatric patients hospitalized with no cardiac concerns. We established a protocol for cardiac evaluation of all admitted COVID-19 patients three weeks post-discharge, irrespective of cardiac concerns. We assessed cardiovascular outcomes and hypothesized that patients with absent cardiac concerns are at lower risk for cardiac abnormalities. Methods: This was a retrospective study of 160 patients admitted for COVID-19 (excluding MIS-C) between March 2020 and September 2021 with subsequent echocardiogram(s) performed at our center. Patients were divided into 4 subgroups: Group 1 included patients with absent cardiac concerns, admitted to acute care (1a) and intensive care unit (ICU) (1 b). Group 2 included patients with cardiac concerns, admitted to acute care (2a) and ICU (2 b). Groups were compared based on clinical endpoints and echocardiographic measurements, including tissue Doppler imaging (TDI) assessment of diastolic function (z-score of septal Mitral E/TDI E′ and lateral E/TDI E′). Chi-squared, Fisher's exact, and Kruskal-Wallis tests were used. Results: Traditional cardiac abnormalities varied significantly between the groups; with Group 2 b having the most (n = 8, 21%), but still found in Group 1a (n = 2, 3%) and Group 1 b (n = 1, 5%). No patients in Group 1 demonstrated abnormal systolic function, compared to Group 2a (n = 1, 3%) and Group 2 b (n = 3, 9%, p = 0.07). When including TDI assessment of diastolic function, the total incidence of abnormalities found on echocardiogram was increased in all groups. Conclusion: Cardiac abnormalities were found in pediatric patients admitted with COVID-19, even those without apparent cardiovascular concerns. The risk was greatest in ICU-admitted patients with cardiac concerns. The clinical significance of diastolic function assessment in these patients remains unknown. Further studies are needed to assess long-term cardiovascular sequelae of children with COVID-19, irrespective of cardiac concerns