Catálogo de publicaciones - revistas

<jats:title>Constraining symmetry</jats:title> <jats:p> Most superconductors have only one transition point, and below a certain temperature, their electrical resistance drops to zero. In very rare cases, another superconducting transition appears at a lower temperature. By measuring its specific heat, Hayes <jats:italic>et al</jats:italic> . reveal that this two-step superconductivity occurs in the compound uranium ditelluride. Complementary optical measurements indicated the breaking of time reversal symmetry, constraining the possible symmetries of the order parameter in this material. —JS </jats:p>

<jats:title>Boridene: a 2D boride</jats:title> <jats:p> A range of two-dimensional (2D) materials, including graphene and hexagonal boron nitride, have been synthesized and studied because of the unusual properties that occur when one dimension becomes very small. MXenes are a family of materials made of layers of inorganic transition metal carbides and nitrides that are a few atoms thick and are manufactured by selective etching. Attempts to make similar boridene materials have been challenging because of the reactive nature of boride phases and because the parent materials tend to dissolve rather than selectively etch. Zhou <jats:italic>et al</jats:italic> . synthesized boridene in the form of single-layer 2D molybdenum boride sheets by selective etching in aqueous hydrofluoric acid to produce sheets with ordered metal vacancies, opening up an additional family of materials for study. —MSL </jats:p>

<jats:p>Little is known about woolly mammoth (<jats:italic>Mammuthus primigenius</jats:italic>) mobility and range. Here we use high temporal resolution sequential analyses of strontium isotope ratios along an entire 1.7-meter-long tusk to reconstruct the movements of an Arctic woolly mammoth that lived 17,100 years ago, during the last ice age. We use an isotope-guided random walk approach to compare the tusk’s strontium and oxygen isotope profiles to isotopic maps. Our modeling reveals patterns of movement across a geographically extensive range during the animal’s ~28-year life span that varied with life stages. Maintenance of this level of mobility by megafaunal species such as mammoth would have been increasingly difficult as the ice age ended and the environment changed at high latitudes.</jats:p>

<jats:p>Total daily energy expenditure (“total expenditure”) reflects daily energy needs and is a critical variable in human health and physiology, but its trajectory over the life course is poorly studied. We analyzed a large, diverse database of total expenditure measured by the doubly labeled water method for males and females aged 8 days to 95 years. Total expenditure increased with fat-free mass in a power-law manner, with four distinct life stages. Fat-free mass–adjusted expenditure accelerates rapidly in neonates to ~50% above adult values at ~1 year; declines slowly to adult levels by ~20 years; remains stable in adulthood (20 to 60 years), even during pregnancy; then declines in older adults. These changes shed light on human development and aging and should help shape nutrition and health strategies across the life span.</jats:p>

<jats:title>Gut bugs and systemic disease risk</jats:title> <jats:p> What people eat has an immediate selective effect on the microbial populations resident in the gut. A high-fat diet is associated with the occurrence of microbes that catabolize choline and the accumulation of trimethylamine <jats:italic>N</jats:italic> -oxide (TMAO) in the bloodstream, a contributing factor for heart disease. Yoo <jats:italic>et al</jats:italic> . explored the microbial organisms and pathways that convert choline into TMAO in mice. Although gene clusters for choline metabolism are found widely among the microbiota, it is only the facultative anaerobes that become abundant in hosts on a high-fat diet. A high-fat diet impairs mitochondrial uptake of oxygen into host enterocytes and elevates nitrate in the mucus, which in turn weakens healthy anaerobic gut function. Facultative anaerobes such as the pathobiont <jats:italic>Escherichia coli</jats:italic> become dominant, which leads to an overall increase in the amount of choline catabolized into the precursor for TMAO. Whether this pathway plays a role in heart disease remains unclear. —CA </jats:p>

<jats:title>Defenses against SARS-CoV-2 variants</jats:title> <jats:p> Our key defense against the COVID-19 pandemic is neutralizing antibodies against the SARS-CoV-2 virus elicited by natural infection or vaccination. Recent emerging viral variants have raised concern because of their potential to escape antibody neutralization. Wang <jats:italic>et al</jats:italic> . identified four antibodies from early-outbreak convalescent donors that are potent against 23 variants, including variants of concern, and characterized their binding to the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Yuan <jats:italic>et al</jats:italic> . examined the impact of emerging mutations in the receptor-binding domain of the spike protein on binding to the host receptor ACE2 and to a range of antibodies. These studies may be helpful for developing more broadly effective vaccines and therapeutic antibodies. —VV </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>

<jats:title>Waters of high Asia</jats:title> <jats:p> How the rivers of the Himalaya-Karakoram region of Asia respond to climate change is critical for the billion-plus people who depend on the water that they provide. In a review, Azam <jats:italic>et al</jats:italic> . discuss recent progress in understanding the importance of glacier and snow melt in the hydrological budget there, which is driven largely by advances in remote sensing and modeling. Observational data remain sparse and challenging to collect. —HJS </jats:p>