An Improved Instability–Shear Hail Proxy for Australia

We evaluated the performance in Australia of proxies designed to identify atmospheric conditions prone to hail and severe storms. In a convection-resolving but short-duration simulation, proxies that use instability and wind shear thresholds overestimated the probability of hail occurring when compared to the estimated occurrence of surface graupel in the model, particularly in Australia’s tropical north. We used reanalysis data and the Australian Bureau of Meteorology severe storm archive to examine atmospheric conditions at times and locations when hailstorms, other storms, and no storms were reported between January 1979 and March 2021. In instability–shear space, the best discriminator between hail and no-storm times was found to vary predictably with melting-level height, allowing a new proxy to better represent latitudinal trends in atmospheric conditions. We found extra conditions that can be applied to the new proxy to efficiently reduce the number of false alarms. The new proxy outperforms the tested existing proxies for detection of hail-prone conditions in Australia

Synthesis, Structure, and Ferromagnetism of a New Oxygen Defect Pyrochlore System Lu2V2O_{7-x} (x = 0.40-0.65)

A new fcc oxygen defect pyrochlore structure system Lu2V2O_{7-x} with x = 0.40 to 0.65 was synthesized from the known fcc ferromagnetic semiconductor pyrochlore compound Lu2V2O7 which can be written as Lu2V2O6O' with two inequivalent oxygen sites O and O'. Rietveld x-ray diffraction refinements showed significant Lu-V antisite disorder for x >= 0.5. The lattice parameter versus x (including x = 0) shows a distinct maximum at x ~ 0.4. We propose that these observations can be explained if the oxygen defects are on the O' sublattice of the structure. The magnetic susceptibility versus temperature exhibits Curie-Weiss behavior above 150 K for all x, with a Curie constant C that increases with x as expected in an ionic model. However, the magnetization measurements also show that the (ferromagnetic) Weiss temperature theta and the ferromagnetic ordering temperature T_C both strongly decrease with increasing x instead of increasing as expected from C(x). The T_C decreases from 73 K for x = 0 to 21 K for x = 0.65. Furthermore, the saturation moment at a field of 5.5 T at 5 K is nearly independent of x, with the value expected for a fixed spin 1/2 per V. The latter three observations suggest that Lu2V2O_{7-x} may contain localized spin 1/2 vanadium moments in a metallic background that is induced by oxygen defect doping, instead of being a semiconductor as suggested by the C(x) dependence.Comment: 9 pages including 7 figures, 3 table

A Radar-Based Hail Climatology of Australia

In Australia, hailstorms present considerable public safety and economic risks, where they are considered the most damaging natural hazard in terms of annual insured losses. Despite these impacts, the current climatological distribution of hailfall across the continent is still comparatively poorly understood. This study aims to supplement previous national hail climatologies, such as those based on environmental proxies or satellite radiometer data, with more direct radar-based hail observations. The heterogeneous and incomplete nature of the Australian radar network complicates this task and prompts the introduction of some novel methodological elements. We introduce an empirical correction technique to account for hail reflectivity biases at C-band, derived by comparing overlapping C- and S-band observations. Furthermore, we demonstrate how object-based hail swath analysis may be used to produce resolution-invariant hail frequencies, and describe an interpolation method used to create a spatially continuous hail climatology. The Maximum Estimated Size of Hail (MESH) parameter is then applied to a mixture of over fifty operational radars in the Australian radar archive, resulting in the first nationwide, radar-based hail climatology. The spatiotemporal distribution of hailstorms is examined, including their physical characteristics, seasonal and diurnal frequency, and regional variations of such properties across the continent.Comment: Revision 1 of manuscript submitted to Monthly Weather Revie

Reconstructing annual inflows to the headwater catchments of the Murray River, Australia, using the Pacific Decadal Oscillation

The Pacific Decadal Oscillation (PDO) is a major forcing of inter-decadal to quasi-centennial variability of the hydroclimatology of the Pacific Basin. Its effects are most pronounced in the extra-tropical regions, while it modulates the El Nino Southern Oscillation (ENSO), the largest forcing of global inter-annual climate variability. PalaeoPDO indices are now available for at least the past 500 years. Here we show that the \u3e500 year PDO index of Shen et al. (2006) is highly correlated with inflows to the headwaters of Australia\u27s longest river system, the Murray-Darling. We then use the PDO to reconstruct annual inflows to the Murray River back to A.D. 1474. These show penta-decadal and quasi-centennial cycles of low inflows and a possible 500 year cycle of much greater inflow variability. Superimposed on this is the likely influence of recent anthropogenic global warming. We believe this may explain the exceptionally low inflows of the past decade, the lowest of the previous 529 years

Superconductivity in Pr2Ba4Cu7O15-delta with metallic double chains

We report superconductivity with $T_{c,onset}$=$\sim$10K in Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-\delta}$ compound possessing metallic double chains. A reduction treatment on as-sintered samples causes not only the enhanced metallic conduction but also the appearance of superconductivity accompanied by the c-axis elongation due to oxygen deficiency

Temperature-dependent spin gap and singlet ground state in BaCuSi2O6

Bulk magnetic measurements and inelastic neutron scattering were used to investigate the spin-singlet ground state and magnetic gap excitations in BaCuSi2O6, a quasi-2-dimensional antiferromagnet with a bilayer structure. The results are well described by a model based on weakly interacting antiferromagnetic dimers. A strongly temperature-dependent dispersion in the gap modes was found. We suggest that the observed excitations are analogous to magneto-excitons in light rare-earth compounds, but are an intrinsic property of a simple Heisenberg Hamiltonian for the S=1/2 magnetic bilayer.Comment: 10 pages, 4 figures, REVTeX and PS for text, PS for figures direct download: http://papillon.phy.bnl.gov/preprints/bacusio.htm

Molecular Genetic Approaches to Disease of Neural Development

This study utilized novel genetic techniques in order to find causative gene mutations that underlie diseases of neural development. Our laboratory has collected 175 cases of malformations of cortical development (MCD) from the United States and Europe. Four of these cases are the focus of this manuscript: two familial cases of infantile neuroaxonal dystrophy (INAD), a familial case of hereditary spastic paraparesis (HSP), and a sporadic case of Greig cephalopolysyndactyly (GCPS) and cerebral cavernous malformations (CCMs). The techniques utilized to study the affected patients include microarray-based single nucleotide polymorphism (SNP) genotyping and copy number variation (CNV) analysis, both of which are powerful tools in the hunt for disease-causing gene mutations. In the familial cases of INAD, we report two novel mutations in the PLA2G6 gene, previously shown to cause INAD when mutated. In the familial case of HSP, we demonstrate linkage to the SPG11 locus on chromosome 15q. Finally, in the sporadic case of GCPS and CCM, we published the first report on this novel syndrome along with a genetic analysis that demonstrates a microdeletion on chromosome 7p, resulting in heterozygous loss of both the GLI3 and CCM2 genes. The three studies presented in this manuscript demonstrate the utility of SNP genotyping and CNV analysis in revealing the genetic mutations that underlie diseases of neural development

Radar and environment-based hail damage estimates using machine learning

Large hail events are typically infrequent, with significant time gaps between occurrences at specific locations. However, when these events do happen, they can cause rapid and substantial economic losses within a matter of minutes. Therefore, it is crucial to have the ability to accurately observe and understand hail phenomena to improve the mitigation of this impact. While in situ observations are accurate, they are limited in number for an individual storm. Weather radars, on the other hand, provide a larger observation footprint, but current radar-derived hail size estimates exhibit low accuracy due to horizontal advection of hailstones as they fall, the variability of hail size distributions (HSDs), complex scattering and attenuation, and mixed hydrometeor types. In this paper, we propose a new radar-derived hail product developed using a large dataset of hail damage insurance claims and radar observations. We use these datasets coupled with environmental information to calculate a hail damage estimate (HDE) using a deep neural network approach aiming to quantify hail impact, with a critical success index of 0.88 and a coefficient of determination against observed damage of 0.79. Furthermore, we compared HDE to a popular hail size product (MESH), allowing us to identify meteorological conditions that are associated with biases on MESH. Environments with relatively low specific humidity, high CAPE and CIN, low wind speeds aloft, and southerly winds at the ground are associated with a negative MESH bias, potentially due to differences in HSD, hail hardness, or mixed hydrometeors. In contrast, environments with low CAPE, high CIN, and relatively high specific humidity aloft are associated with a positive MESH bias.</p

Hole depletion and localization due to disorder in insulating PrBa2Cu3O7-d: a Compton scattering study

The (mostly) insulating behaviour of PrBa2Cu3O7-d is still unexplained and even more interesting since the occasional appearance of superconductivity in this material. Since YBa2Cu3O7-d is nominally iso-structural and always superconducting, we have measured the electron momentum density in these materials. We find that they differ in a striking way, the wavefunction coherence length in PrBa2Cu3O7-d being strongly suppressed. We conclude that Pr on Ba-site substitution disorder is responsible for the metal-insulator transition. Preliminary efforts at growth with a method to prevent disorder yield 90K superconducting PrBa2Cu3O7-d crystallites.Comment: 4 pages, 3 figures, revised version submitted to PR

Group A Streptococcus M1T1 Intracellular Infection of Primary Tonsil Epithelial Cells Dampens Levels of Secreted IL-8 Through the Action of SpyCEP.

Streptococcus pyogenes (Group A Streptococcus; GAS) commonly causes pharyngitis in children and adults, with severe invasive disease and immune sequelae being an infrequent consequence. The ability of GAS to invade the host and establish infection likely involves subversion of host immune defenses. However, the signaling pathways and innate immune responses of epithelial cells to GAS are not well-understood. In this study, we utilized RNAseq to characterize the inflammatory responses of primary human tonsil epithelial (TEpi) cells to infection with the laboratory-adapted M6 strain JRS4 and the M1T1 clinical isolate 5448. Both strains induced the expression of genes encoding a wide range of inflammatory mediators, including IL-8. Pathway analysis revealed differentially expressed genes between mock and JRS4- or 5448-infected TEpi cells were enriched in transcription factor networks that regulate IL-8 expression, such as AP-1, ATF-2, and NFAT. While JRS4 infection resulted in high levels of secreted IL-8, 5448 infection did not, suggesting that 5448 may post-transcriptionally dampen IL-8 production. Infection with 5448ΔcepA, an isogenic mutant lacking the IL-8 protease SpyCEP, resulted in IL-8 secretion levels comparable to JRS4 infection. Complementation of 5448ΔcepA and JRS4 with a plasmid encoding 5448-derived SpyCEP significantly reduced IL-8 secretion by TEpi cells. Our results suggest that intracellular infection with the pathogenic GAS M1T1 clone induces a strong pro-inflammatory response in primary tonsil epithelial cells, but modulates this host response by selectively degrading the neutrophil-recruiting chemokine IL-8 to benefit infection