Spin dynamics and spin freezing behavior in the two-dimensional antiferromagnet NiGa2_{2}S4_{4} revealed by Ga-NMR, NQR and μ\muSR measurements

We have performed $^{69,71}$Ga nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) and muon spin rotation/resonance on the quasi two-dimensional antiferromagnet (AFM) NiGa$_2$S$_4$, in order to investigate its spin dynamics and magnetic state at low temperatures. Although there exists only one crystallographic site for Ga in NiGa$_2$S$_4$, we found two distinct Ga signals by NMR and NQR. The origin of the two Ga signals is not fully understood, but possibly due to stacking faults along the c axis which induce additional broad Ga NMR and NQR signals with different local symmetries. We found the novel spin freezing occurring at $T_{\rm f}$, at which the specific heat shows a maximum, from a clear divergent behavior of the nuclear spin-lattice relaxation rate $1/T_{1}$ and nuclear spin-spin relaxation rate $1/T_{2}$ measured by Ga-NQR as well as the muon spin relaxation rate $\lambda$. The main sharp NQR peaks exhibit a stronger tendency of divergence, compared with the weak broader spectral peaks, indicating that the spin freezing is intrinsic in NiGa$_2$S$_4$. The behavior of these relaxation rates strongly suggests that the Ni spin fluctuations slow down towards $T_{\rm f}$, and the temperature range of the divergence is anomalously wider than that in a conventional magnetic ordering. A broad structureless spectrum and multi-component $T_1$ were observed below 2 K, indicating that a static magnetic state with incommensurate magnetic correlations or inhomogeneously distributed moments is realized at low temperatures. However, the wide temperature region between 2 K and $T_{\rm f}$, where the NQR signal was not observed, suggests that the Ni spins do not freeze immediately below $T_{\rm f}$, but keep fluctuating down to 2 K with the MHz frequency range.Comment: 14 pages, 14 figures. To appear in Phys. Rev.

Risk Prediction for Acute Kidney Injury in Acute Medical Admissions in the UK

Background Acute Kidney Injury (AKI) is associated with adverse outcomes; identifying patients who are at risk of developing AKI in hospital may lead to targeted prevention. This approach is advocated in national guidelines but is not well studied in acutely unwell medical patients. We therefore aimed to undertake a UK-wide study in acute medical units (AMUs) with the following aims: to define the proportion of acutely unwell medical patients who develop hospital-acquired AKI (hAKI); to determine risk factors associated with the development of hAKI; and to assess the feasibility of using these risk factors to develop an AKI risk prediction score. Methods In September 2016, a prospective multicentre cohort study across 72 UK AMUs was undertaken. Data were collected from all patients who presented over a 24-hour period. Chronic dialysis, community-acquired AKI (cAKI) and those with fewer than two creatinine measurements were subsequently excluded. The primary outcome was the development of h-AKI. Results 2,446 individuals were admitted to the AMUs of the 72 participating centres. 384 patients (16%) sustained AKI of whom 287 (75%) were cAKI and 97 (25%) were hAKI. After exclusions, 1,235 participants remained in whom chronic kidney disease (OR 3.08, 95% CI 1.96-4.83), diuretic prescription (OR 2.33, 95% CI 1.5-3.65), a lower haemoglobin concentration and an elevated serum bilirubin were independently associated with development of hAKI. Multivariable model discrimination was moderate (c-statistic 0.75), and this did not support the development of a robust clinical risk prediction score. Mortality was higher in those with hAKI (adjusted OR 5.22; 95% CI 2.23-12.20). Conclusion AKI in AMUs is common and associated with worse outcomes, with the majority of cases community acquired. The smaller proportion of hAKI cases, only moderate discrimination of prognostic risk factor modelling and the resource implications of widespread application of an AKI clinical risk score across all AMU admissions suggests that this approach is not currently justified. More targeted risk assessment or automated methods of calculating individual risk may be more appropriate alternatives

A first update on mapping the human genetic architecture of COVID-19

peer reviewe

Discovery of an ultra-quantum spin liquid

Quantum fluctuations are expected to lead to highly entangled spin-liquid states in some two-dimensional spin-1/2 compounds. We have synthesized and measured thermodynamic properties and muon relaxation rates in two related such compounds, one of which is the least disordered of this kind synthesized hitherto and reveals intrinsic properties of a class of spin-liquids. Its measured properties can all be simply characterized by scale invariant time-dependent fluctuations with a single parameter. The specific heat divided by temperature and muon relaxation rates are both temperature independent at low temperatures, followed by a logarithmic decrease with increasing temperature. Even more remarkably, $\sim$57\% of the magnetic entropy is missing down to temperatures of \textit{O}(10$^{-3}$) the exchange energy, independent of magnetic field up to $g\mu_BH > k_BT$. This is evidence that quantum fluctuations lead either to a gigantic specific heat peak from topological singlet excitations below such temperatures, or to an extensively degenerate topological singlet ground state. These results reveal an ultra-quantum state of matter

Immune response by nasal delivery of hepatitis B surface antigen and codelivery of a CpG ODN in alginate coated chitosan nanoparticles

Alginate coated chitosan nanoparticles were previously developed with the aim of protecting the antigen, adsorbed on the surface of those chitosan nanoparticles, from enzymatic degradation at mucosal surfaces. In this work, this new delivery system was loaded with the recombinant hepatitis B surface antigen (HBsAg) and applied to mice by the intranasal route. Adjuvant effect of the delivery system was studied by measuring anti-HBsAg IgG in serum, anti-HBsAg sIgA in faeces extracts or nasal and vaginal secretions and interferon-[gamma] production in supernatants of the spleen cells. The mice were primed with 10 [mu]g of the vaccine associated or not with nanoparticles and associated or not with 10 [mu]g CpG oligodeoxynucleotide (ODN) followed by two sequential boosts at three week intervals. The association of HBsAg with the alginate coated chitosan nanoparticles, administered intranasally to the mice, gave rise to the humoral mucosal immune response. Humoral systemic immune response was not induced by the HBsAg loaded nanoparticles alone. The generation of Th1-biased antigen-specific systemic antibodies, however, was observed when HBsAg loaded nanoparticles were applied together with a second adjuvant, the immunopotentiator, CpG ODN. Moreover, all intranasally vaccinated groups showed higher interferon-[gamma] production when compared to naïve mice.http://www.sciencedirect.com/science/article/B6T6C-4RR1NPN-2/1/beaa4e06ecb340a5a293ef1fd3b4c86

Mapping the human genetic architecture of COVID-19

The genetic make-up of an individual contributes to the susceptibility and response to viral infection. Although environmental, clinical and social factors have a role in the chance of exposure to SARS-CoV-2 and the severity of COVID-191,2, host genetics may also be important. Identifying host-specific genetic factors may reveal biological mechanisms of therapeutic relevance and clarify causal relationships of modifiable environmental risk factors for SARS-CoV-2 infection and outcomes. We formed a global network of researchers to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity. Here we describe the results of three genome-wide association meta-analyses that consist of up to 49,562 patients with COVID-19 from 46 studies across 19 countries. We report 13 genome-wide significant loci that are associated with SARS-CoV-2 infection or severe manifestations of COVID-19. Several of these loci correspond to previously documented associations to lung or autoimmune and inflammatory diseases3–7. They also represent potentially actionable mechanisms in response to infection. Mendelian randomization analyses support a causal role for smoking and body-mass index for severe COVID-19 although not for type II diabetes. The identification of novel host genetic factors associated with COVID-19 was made possible by the community of human genetics researchers coming together to prioritize the sharing of data, results, resources and analytical frameworks. This working model of international collaboration underscores what is possible for future genetic discoveries in emerging pandemics, or indeed for any complex human disease