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R L Withers

Publications and source records attributed to R L Withers.

6 recordsLinked to original sources
PubMed2002

Missing the target: a comparison of buyback and fatality related guns.

OBJECTIVES: To determine whether the firearms recovered in buyback programs in a large urban community are the types most closely associated with firearm fatalities in the same geographic area. METHODS: The type, caliber, and manufacturer of 941 handguns recovered in Milwaukee County 1994-96 buyback programs were compared with 369 homicide related and 125 suicide related handguns used in Milwaukee during 1994-97. RESULTS: Buyback handguns differed substantially from those used in homicide and suicide. One third of buyback handguns were semiautomatic pistols versus two thirds of homicide related handguns (p<0.001) and 40% of suicide related handguns (p=NS). Over 75% of buyback handguns were small caliber compared with 24% of homicide and 32% of suicide handguns (p<0.001). The top two manufacturers of buyback handguns represented 30% of these guns but only 5% of fatality related handguns (p<0.001). Companies currently out of business manufactured 15% of buyback handguns versus 7% of fatality related handguns (p<0.001). CONCLUSIONS: Handguns recovered in buyback programs are not the types most commonly linked to firearm homicides and suicides. Although buyback programs may increase awareness of firearm violence, limited resources for firearm injury prevention may be better spent in other ways.

Accident Prevention↗
PubMed2001

Ab initio structure determination of BiPb2VO6 from powder diffraction data.

The crystal structure of BiPb2VO6 has been determined from powder diffraction data using a combination of direct methods and the novel approach of applying simulated annealing methods simultaneously to X-ray and neutron data; BiPb2VO6 is a polar, noncentrosymmetric, second harmonic generation active material and its crystal structure is one of the more complex to be solved ab initio from powder diffraction data.

Journal Article↗
PubMed2001

Intergrowth polytypoids as modulated structures: a superspace description of the Sr(n)(Nb,Ti)(n)O(3n + 2) compound series.

A new, unified superspace approach to the structural characterization of the perovskite-related Sr(n)(Nb,Ti)(n)O(3n + 2) compound series, strontium niobium/titanium oxide, is presented. To a first approximation, the structure of any member of this compound series can be described in terms of the stacking of (110)-bounded perovskite slabs, the number of atomic layers in a single perovskite slab varying systematically with composition. The various composition-dependent layer-stacking sequences can be interpreted in terms of the structural modulation of a common underlying average structure. The average interlayer separation distance is directly related to the average structure periodicity along the layer stacking direction, while an inherent modulation thereof is produced by the presence of different types of layers (particularly vacant layers) along this stacking direction. The fundamental atomic modulation is therefore occupational and can be described by means of crenel (step-like) functions which define occupational atomic domains in the superspace, similarly to what occurs for quasicrystals. While in a standard crystallographic approach, one must describe each structure (in particular the space group and cell parameters) separately for each composition, the proposed superspace model is essentially common to the whole compound series. The superspace symmetry group is unique, while the primary modulation wavevector and the width of some occupation domains vary linearly with composition. For each rational composition, the corresponding conventional three-dimensional space group can be derived from the common superspace group. The resultant possible three-dimensional space groups are in agreement with all the symmetries reported for members of the series. The symmetry-breaking phase transitions with temperature observed in many compounds can be explained in terms of a change in superspace group, again in common for the whole compound series. Inclusion of the incommensurate phases, present in many compounds of the series, lifts the analysis into a five-dimensional superspace. The various four-dimensional superspace groups reported for this incommensurate phase at different compositions are shown to be predictable from a proposed five-dimensional superspace group apparently common to the whole compound series. A comparison with the scarce number of refined structures in this system and the homologous (Nb,Ca)(6)Ti(6)O(20) compound demonstrates the suitability of the proposed formalism.

Journal Article↗
PubMed2000

Towards a unified description of the AMOB2O5 (A=K, Rb, Cs, Tl; M=Nb, Ta) family of compounds.

Single-crystal X-ray diffraction data (Mo Kalpha radiation) are used to re-refine the structure of RbNbOB2O5, rubidium niobium oxo pyroborate. The structure is refined as an incommensurate modulated structure with superspace group symmetry Pmn2(1)(0,0.4,0)s and lattice parameters a = 7.406 (2), b = 3.939 (2) and c = 9.475 (2) A. Refinement on 3242 unique reflections converged to R = 0.031, while a previous conventional superstructure refinement led to R = 0.090. This lowering of the R factor goes hand-in-hand with a substantial reduction in the number of refined parameters. The refinement strongly suggests that the structure is effectively incommensurately modulated, despite an apparently rational magnitude of the primary modulation wave-vector and overlap of satellite reflections.

Journal Article↗
PubMedDate not supplied

Public health: a successful paradigm applied to firearm injuries.

Firearm injuries are a major contributor to injury mortality and morbidity in the United States and account for substantial loss of productive years of life. A public health approach to injury reduction, and particularly firearm injury prevention, has promise because it emphasizes prevention rather than reaction, it utilizes a scientific approach to policies and programs, it brings an integrative, multi-disciplinary approach to the effort, and it emphasizes the role of communities in solving health problems. The new Firearm Injury Center at the Medical College of Wisconsin exemplifies the public health approach to this vexing problem.

Health Policy↗