Evidence That the Anomalous Emission from CaF2:Yb2+ Is Not Described by the Impurity Trapped Exciton Model.

Yb-substituted CaF2 exhibits an anomalous red-shifted luminescence after UV excitation, attributed to the relaxation of impurity trapped excitons (ITE). CaF2:Yb is the archetype system for this model, in which the Yb2+ ions can be excited into a long-lived (ms) exciton state. Upon de-excitation, the emission intensity should be proportional to the Yb2+ concentration, but that could not be checked when this model was first proposed. Using the X-ray absorption near edge structure (XANES) technique, we determine the fractions of Yb2+ and Yb3+ for low Yb concentrations, 0.01% to 0.1%, and thus determine the net concentration of Yb2+. A comparison with luminescence data shows that the intensity is not proportional to the Yb2+ concentration, and only a fraction of Yb2+ ions contributes to the anomalous luminescence. This is inconsistent with the ITE model and illustrates the importance of checking the dependence of the emission intensity on the Yb2+ concentration.

Structure and magnetism in LaCoO3.

The temperature dependence of the hexagonal lattice parameter c of single crystal LaCoO3(LCO) with H = 0 and 800 Oe, as well as LCO bulk powders with H = 0, was measured using high-resolution x-ray scattering near the transition temperature To ≈35 K. The change of c(T) is well characterized by a power law in T − To for T>To and by a temperature independent constant for T

Local vibrations and negative thermal expansion in ZrW2O8.

We present an x-ray pair distribution function (XPDF) analysis and extended x-ray absorption fine structure (EXAFS) data for ZrW2O8 (10-500 K) with a focus on the stiffness of the Zr-O-W linkage. The XPDF is highly sensitive to W-Zr and W-W correlations, but much less so to O-O or W-O correlations. The Zr-W peak in the XPDF data has a weak temperature dependence and, hence, this linkage is relatively stiff and does not permit bending of the Zr-O-W link. We propose that the low energy vibrational modes that lead to negative thermal expansion involve correlated rotations of ZrO6 octahedra that produce large <111> translations of the WO4 tetrahedra, rather than a transverse motion of O atoms that imply a flexible Zr-O-W linkage.

Lead is not off center in PbTe: the importance of r-space phase information in extended x-ray absorption fine structure spectroscopy.

PbTe is a well-known thermoelectric material. Recent x-ray total scattering studies suggest that Pb moves off center along 100 in PbTe, by ∼0.2 Å at 300 K, producing a split Pb-Te pair distribution. We present an extended x-ray absorption fine structure spectroscopy (EXAFS) study of PbTe (and Tl doped PbTe) to determine if Pb or Te is off center. EXAFS provides sensitive r- or k-space phase information which can differentiate between a split peak for the Pb-Te distribution (indicative of off-center Pb) and a thermally broadened peak. We find no evidence for a split peak for Pb-Te or Te-Pb. At 300 K, the vibration amplitude for Pb-Te (or Te-Pb) is large; this thermally induced disorder is indicative of weak bonds, and the large disorder is consistent with the low thermal conductivity at 300 K. We also find evidence of an anharmonic potential for the nearest Pb-Te bonds, consistent with the overall anharmonicity found for the phonon modes. This effect is modeled by a "skew" factor (C3) which significantly improves the fit of the Pb-Te and Te-Pb peaks for the high temperature EXAFS data; C3 becomes significant above approximately 150-200 K. The consequences of these results will be discussed.

Evolution of magnetic oxygen states in Sr-doped LaCoO3.

Magnetism in La(1-x)Sr(x)CoO(3) as a function of doping is investigated with x-ray absorption spectroscopy and x-ray magnetic circular dicrhoism at the O K edge, and corresponding first principles electronic structure calculations. For small x, the spectra are consistent with the formation of ferromagnetic clusters occurring within a nonmagnetic insulating matrix. Sr-induced, magnetic O-hole states form just above E(F) and grow with increasing Sr doping. Density functional calculations for x=0 yield a nonmagnetic ground state with the observed rhombohedral distortion and indicates that doping introduces holes at the Fermi level in magnetic states with significant O 2p and Co t(2g) character for the undistorted pseudocubic structure. Supercell calculations show stronger magnetism on oxygen atoms having more Sr neighbors.

Spin-orbital short-range order on a honeycomb-based lattice.

Frustrated magnetic materials, in which local conditions for energy minimization are incompatible because of the lattice structure, can remain disordered to the lowest temperatures. Such is the case for Ba(3)CuSb(2)O(9), which is magnetically anisotropic at the atomic scale but curiously isotropic on mesoscopic length and time scales. We find that the frustration of Wannier's Ising model on the triangular lattice is imprinted in a nanostructured honeycomb lattice of Cu(2+) ions that resists a coherent static Jahn-Teller distortion. The resulting two-dimensional random-bond spin-1/2 system on the honeycomb lattice has a broad spectrum of spin-dimer-like excitations and low-energy spin degrees of freedom that retain overall hexagonal symmetry.

Homicide-suicide in the United States, 1968-1975.

This paper describes for the first time the epidemiology of homicide-suicide events in the whole of the United States using archival data. From 1968 to 1975, there were 2215 homicide-suicide events out of 123,467 homicides. The mean rate of homicide-suicide events was 0.134 per 100,000 per year. The murderers in these events differ from the typical murderer and the typical suicide in socio-demographic characteristics. Details of the characteristics of this population may be valuable for understanding the circumstances of homicide-suicide events and planning preventive measures.

Mean ages of homicide victims and victims of homicide-suicide.

Using Riedel and Zahn's 1994 reformatted version of an FBI database, the mean age of homicide victims in 2,175 homicide-suicides (4,350 deaths) was compared with that of all other victims of homicides reported for the USA from 1968 to 1975. The overall mean age of homicide victims in homicide-suicides was 1 yr. greater than for victims of homicides not followed by suicides, whereas the mean age for both male and female homicide-suicide victims was, respectively, 3 yr. less and greater than the other homicide victims. The mean age of Black homicide victims of homicide-suicides was 2.4 yr. less than that for Black victims of other homicides, whereas the means for Black and White male homicide victims in homicide-suicides were, respectively, about 4 and 5 yr. less than for victims of other homicides. Also, the mean age of White female homicide victims in homicide-suicides was more than two years greater than for female victims of homicides not followed by suicides. When both sex and race were considered, the mean age for those killed in homicide-suicides relative to those killed in homicides not followed by suicides may represent subpopulations with different mean ages of victims.

Use of age-adjusted rates of suicide in time series studies in Israel.

Durkheim's modified theory of suicide was examined to explore how consistent it was in predicting Israeli rates of suicide from 1965 to 1997 when using age-adjusted rates rather than crude ones. In this time-series study, Israeli male and female rates of suicide increased and decreased, respectively, between 1965 and 1997. Conforming to Durkheim's modified theory, the Israeli male rate of suicide was lower in years when rates of marriage and birth are higher, while rates of suicide are higher in years when rates of divorce are higher, the opposite to that of Israeli women. The corrected regression coefficients suggest that the Israeli female rate of suicide remained lower in years when rate of divorce is higher, again the opposite suggested by Durkheim's modified theory. These results may indicate that divorce affects the mental health of Israeli women as suggested by their lower rate of suicide. Perhaps the "multiple roles held by Israeli females creates suicidogenic stress" and divorce provides some sense of stress relief, mentally speaking. The results were not as consistent with predictions suggested by Durkheim's modified theory of suicide as were rates from the United States for the same period nor were they consistent with rates based on "crude" suicide data. Thus, using age-adjusted rates of suicide had an influence on the prediction of the Israeli rate of suicide during this period.

Comment on Zekeri (2007).

Zekeri's comments (2007) on Bridges and Kunselman's work (2005) were not sufficiently grounded in sociological theory, the calculation of the "rates of potential years of life lost" (PYLL) was modified but unreported, and the use of PYLL, despite limitations as a measure of premature mortality "was not justified." The theoretical framework, however, consisted of "environmental" and "social group" statements which gave a specific means for grounding "premature mortality" in sociological theory, and findings were consistent with Lester's social deviancy theory of suicide (1989). How the "rates of PYLL" were calculated, i.e., by the Canadian government is misinterpreted, although Allard, et al. (2004) provided justification for the use of age-standardized rates of PYLL in their 2005 study.

Local structure of La1-xSrxCoO3 determined from EXAFS and neutron pair distribution function studies.

The combined local structure techniques, extended x-ray absorption fine structure and neutron pair distribution function analysis, have been used for temperatures 4< or =T< or =330 K to rule out a large Jahn-Teller (JT) distortion of the Co-O bond in La1-xSrxCoO3 for a significant fraction of Co sites (x< or =0.35), indicating few, if any, JT-active, singly occupied e_{g} Co sites exist.

Social integration and suicide in the Western Pacific Islands.

In the Western Pacific Islands, the rate of suicide was more common in those islands with faster growing populations, but not among the islands with larger total populations or with greater population densities. This offers partial support for some of the propositions of Durkheim and Lester.

Body Mass Index, suicide, and homicide among inhabitants of the Caribbean Islands.

To test the hypothesis that the more overweight and obese a nation, as measured by Body Mass Index, the greater the risk of suicide; mean scores of Body Mass Index for males and females over 15 years of age in 11 Caribbean Islands were not associated with either male or female rates of suicide or homicide with one exception, i.e., when controlling for gross domestic product per capita, mean Body Mass Indices for males were significantly and negatively associated with male rate of homicide.

Universal relationship between magnetization and changes in the local structure of La1-xCaxMnO3: evidence for magnetic dimers.

We present extensive x-ray absorption fine structure measurements on La(1-x)Ca(x)MnO(3) as a function of the B field (to 11 T) and Ca concentration, chi(21%-45%). These results reveal local structure changes (associated with polaron formation) that depend only on the magnetization for a given sample, irrespective of whether the magnetization is achieved through a decrease in temperature or an applied magnetic field. Furthermore, the relationship between local structure and magnetization depends on the hole doping. A model is proposed in which a filamentary magnetization initially develops via the aggregation of pairs of Mn atoms involving a hole and an electron site. These pairs have little distortion and it is likely that they form at temperature T(*) above T(c).

Seasonal changes in suicide in the United States, 1971 to 2000.

The seasonality of suicides in the USA increased from the 1970s to the 1990s. A significant proportion of suicide variation due to the seasonal component has been reported. Noted increments in seasonal rhythms in the latter part of the 1980s and 1990s seem to support those of Warren, et al. but contradict the conclusions of diminishing drawn by Hakko, et al., Rhimer, et al., and Yip, et al.

Correlations for alcohol use, abuse, and treatment with suicide and homicide across 21 nations.

In this study which followed Lester's work of 1998 and 2001 for 27 nations of the world, membership in Alcoholics Anonymous, but not alcohol consumption or cirrhosis mortality as measures of alcohol use, abuse, and treatment, correlated with homicide but not suicide rates. Changes in Alcoholics Anonymous membership were not associated with changes in age-adjusted rates of homicide or suicide.

Local distortion induced metal-to-insulator phase transition in PrRu4P12.

Extended x-ray absorption fine structure (EXAFS) experiments have been carried out on PrRu(4)P(12) and PrOs(4)P(12) to study the metal-to-insulator (MI) phase transition in PrRu(4)P(12). No Pr displacement was observed across the MI transition temperature from the EXAFS data. Instead, our EXAFS data clearly show that a Ru displacement is associated with this MI transition. The very high Debye temperature for the Ru-P bond (Theta(D) = 690 K) suggests that a slight rotation/displacement of relatively rigid RuP(6) octahedra leads to this small Ru displacement, which accompanies the MI transition at 62 K in PrRu(4)P(12).

Premature mortality due to suicide, homicide, and motor vehicle accidents in health service delivery areas: comparison of status Indians in British Columbia, Canada, with all other residents.

From each of 15 health regions, potential years of life lost (PYLL) before age 75 for Status Indians is compared for select causes of death with all other residents. Mortality data from 1991 to 2001 for rates of PYLL (standardized to the 1991 population) are from tables of the British Columbia Vital Statistics Agency and First Nations and Inuit Health Branch in 2002. PYLL rate differences and rate ratios were compared for two groups with significance of the former indicated by the 95% confidence interval. Overall, the rates of PYLL for suicide, homicide, and deaths due to motor vehicle accidents were about 224%, 340%, and 248% higher among Status Indians than all other residents. Rates of PYLL for homicide and deaths from motor vehicle accidents among Status Indian women exceeded those of other residents who were men. For suicide, Status Indian men ranked first and all other male residents of British Columbia ranked second.

Gun control law (Bill C-17), suicide, and homicide in Canada.

Canadian Bill C-17 was implemented in 1991 to restrict the use of firearms, providing a chance to investigate the effect of firearm control laws in the use of firearms for suicide and homicide. Following Lester and Leenaars' comprehensive studies, the present study examined the use of firearms for suicide and homicide during the period prior to the bill and during the period after the passing of Bill C-17 to assess the association of the bill with rates of suicide and homicide by method. Analysis showed a significant decrease after passage of Bill C-17 in the rates of suicides and homicides involving firearms and the percentage of suicides using firearms. The analysis provides support for the position that restricting the availability of firearms as a lethal means of committing suicide and homicide may help reduce the numbers of suicides and homicides.

Use of the same and a longer time series to replicate David Lester's study of suicide and birth rates in Canada.

This is a replication of Lester's work (2000) using the time series 1970-1990 to study associations between age-standardized rates of suicide and crude birth rates in the 10 Canadian provinces were also examined between 1961 and 1999.