On the commutant algebras corresponding to the permutation representations of the full collineation groups of PG(k, s) and EG(k, s), s = pr, k ⩾ 2

In this paper, the dimension t and a linear basis of the commutant algebra corresponding to the representation of the full collineation group as matrices permuting the flags (incident point-line or point-hyperplane pairs) have been determined for each one of the four geometries PG(2, s), EG(2, s), PG(k, s), and EG(k, s), s = pr, k ⩾ 3. For the four geometries, t = 6, 7, 7, and 8, respectively, and the corresponding linear bases are (I, G, B, T, BT, TB), (I, G, B, T, BT, TB, BTB), (I, G, B, T, BT, TB, S), and (I, G, B, T, BT, TB, BTB, S). I, G, B, T are the relationship matrices of James (Ann. Math. Statist. 28 (1957), 993–1082) and the matrix S was introduced by Sysoev and Shaikin (Avtomat. i Telemekh. 5 (1976), 64–73)

On the algebras of symmetries (groups of collineations) of designs from finite Desarguesian planes with applications in statistics

Decomposition into a direct sum of irreducible representations of the representation of the full collineation group of a finite Desarguesian plane, as a group of matrices permuting the flags of the plane and the simple components of the corresponding commutant algebra, have been worked out here for the projective plane PG(2, 2) and the affine plane EG(2, 3). The dimension and the components of the covariance matrix of the observations from a design derived from such a plane, which commutes with such a permutation representation of the full collineation group of the plane, are thus determined. This paper is in the spirit of earlier works by, James (1957), Mann (1960), 6. and 7., McLaren (1963), and Sysoev and Shaikan (1976). A. T. James, Ann. Math. Statist.28 (1957), 993–1002, H. B. Mann, Ann. Math. Statist.31 (1960), 1–15, E. J. Hannan, Research Report (Part. (I)), Summer Research Institute, Australian Math. Soc. and Methuen's Monographs on Applied Probability and Statistics, Supplementary Review Series in Applied Probability, Vol. 3, A. D. McLaren, Proc. Cambridge Philos. Soc.59 (1963), 431–450, and L. P. Sysoev and M. E. Shaikin, Avtomat. i Telemekh.5 (1976), 64–73

Insights into the 9 December 2019 eruption of Whakaari/White Island from analysis of TROPOMI SO₂ imagery.

From Europe PMC via Jisc Publications RouterHistory: ppub 2021-06-01, epub 2021-06-18Publication status: PublishedSmall, phreatic explosions from volcanic hydrothermal systems pose a substantial proximal hazard on volcanoes, which can be popular tourist sites, creating casualty risks in case of eruption. Volcano monitoring of gas emissions provides insights into when explosions are likely to happen and unravel processes driving eruptions. Here, we report SO2 flux and plume height data retrieved from TROPOMI satellite imagery before, during, and after the 9 December 2019 eruption of Whakaari/White Island volcano, New Zealand, which resulted in 22 fatalities and numerous injuries. We show that SO2 was detected without explosive activity on separate days before and after the explosion, and that fluxes increased from 10 to 45 kg/s ~40 min before the explosion itself. High temporal resolution gas monitoring from space can provide key insights into magmatic degassing processes globally, aiding understanding of eruption precursors and complementing ground-based monitoring

The Only Thing That Stops a Guy with a Bad Policy is a Guy with a Good Policy: An Examination of the NRA’s “National School Shield” Proposal

With the recent tragedy at Sandy Hook Elementary in Newtown, CT, the public and the government are looking for solutions to school violence. The National Rifle Association (NRA), a Second Amendment, pro-gun advocacy group, has proposed an “education and training emergency response program” called The National School Shield, which advocates the placement of armed security in schools. Although the program sounds provocative, serious questions complicate its plausibility, necessity, motive, and effectiveness. Furthermore, the potential policy and practical ramifications of encouraging armed security forces in U.S. schools are complex. The authors examined the proposal’s key elements from a public policy perspective and determined that the NRA program would be expensive in terms of both implementation and civil and/or criminal liability, would increase juvenile contact with the criminal justice system, would increase the potential for injuries and deaths from firearms, and would potentially only serve to increase profits for those invested in security industries. More potentially effective and safe policy alternatives are offered

The Carina Nebula and Gum 31 molecular complex: II. The distribution of the atomic gas revealed in unprecedented detail

We report high spatial resolution observations of the HI 21cm line in the Carina Nebula and the Gum 31 region obtained with the Australia Telescope Compact Array. The observations covered $\sim$ 12 deg$^2$ centred on $l= 287.5\deg,b = -1\deg$, achieving an angular resolution of $\sim$ 35 arcseconds. The HI map revealed complex filamentary structures across a wide range of velocities. Several "bubbles" are clearly identified in the Carina Nebula Complex, produced by the impact of the massive star clusters located in this region. An HI absorption profile obtained towards the strong extragalactic radio source PMN J1032--5917 showed the distribution of the cold component of the atomic gas along the Galactic disk, with the Sagittarius-Carina and Perseus spiral arms clearly distinguishable. Preliminary calculations of the optical depth and spin temperatures of the cold atomic gas show that the HI line is opaque ($\tau \gtrsim$ 2) at several velocities in the Sagittarius-Carina spiral arm. The spin temperature is $\sim100$ K in the regions with the highest optical depth, although this value might be lower for the saturated components. The atomic mass budget of Gum 31 is $\sim35 \%$ of the total gas mass. HI self absorption features have molecular counterparts and good spatial correlation with the regions of cold dust as traced by the infrared maps. We suggest that in Gum 31 regions of cold temperature and high density are where the atomic to molecular gas phase transition is likely to be occurring.Comment: 20 pages, 1 table, 16 Figures, Accepted for Publication in the Monthly Notices of the Royal Astronomical Society Journa

The Only Thing That Stops a Guy with a Bad Policy is a Guy with a Good Policy: An Examination of the NRA’s “National School Shield” Proposal

With the recent tragedy at Sandy Hook Elementary in Newtown, CT, the public and the government are looking for solutions to school violence. The National Rifle Association (NRA), a Second Amendment, pro-gun advocacy group, has proposed an “education and training emergency response program” called The National School Shield, which advocates the placement of armed security in schools. Although the program sounds provocative, serious questions complicate its plausibility, necessity, motive, and effectiveness. Furthermore, the potential policy and practical ramifications of encouraging armed security forces in U.S. schools are complex. The authors examined the proposal’s key elements from a public policy perspective and determined that the NRA program would be expensive in terms of both implementation and civil and/or criminal liability, would increase juvenile contact with the criminal justice system, would increase the potential for injuries and deaths from firearms, and would potentially only serve to increase profits for those invested in security industries. More potentially effective and safe policy alternatives are offered