JMASM 32: Multiple Imputation of Missing Multilevel, Longitudinal Data: A Case When Practical Considerations Trump Best Practices?

A pedagogical tool is presented for applied researchers dealing with incomplete multilevel, longitudinal data. It explains why such data pose special challenges regarding missingness. Syntax created to perform a multiply-imputed growth modeling procedure in Stata Version 11 (StataCorp, 2009) is also described

Raman spectroscopy of ion irradiated SiC: chemical defects, strain, annealing, and oxidation

Raman spectroscopy has been used to identify defective bonding in neon and silicon ion irradiated single crystals of 6H-SiC. Observable differences exist in the C-C bonding region corresponding to different defect structures for neon and silicon ion implantations. Raman spectra of ion irradiated SiC show less tensile strain than neutron irradiations, explained by a residual compressive stress caused by the swelling constrained by the undamaged substrate. Evidence of oxidation during high temperature ion implantation is observed as C-O and Si-O Raman signals. Annealing irradiated SiC while acquiring Raman spectra shows rapid recovery of Si-C bonding, but not a complete recovery of the unirradiated structure. Annealing irradiated SiC causes surface oxidation where unirradiated SiC does not oxidise. Comparisons are made to the apparent radiation resistance of diamond and silicon which have similar crystal structures, but are monatomic, leading to the suggestion that chemical defects are responsible for increased radiation damage in SiC.Comment: 24 pages, 8 figure

Winter 1968

Massachusetts Turf and Lawn Grass CouncilBetter Turf Through Research and Education Contents: Trees and Shrubs on the Golf Course (page 3) Human Safety in the Use of Agricultural Chemicals by Irma West, M.D. (7) Temporary Soil Sterilants (10) Environmental Influence on Bentgrass Treated with Silvex by Lloyd M. Callahan, Ralph E. Engel, and Richard D. Illnicki (12) Soil Production by Floyd Hilliker (18) Editorial (20) Phosphorus Study (20

Runoff- and erosion-driven transport of cattle slurry:linking molecular tracers to hydrological processes

The addition of cattle slurry to agricultural land is a widespread practise, but if not correctly managed it can pose a contamination risk to aquatic ecosystems. The transport of inorganic and organic components of cattle slurry to watercourses is a major concern, yet little is known about the physical transport mechanisms and associated fluxes and timings of contamination threats. Therefore, the aim of the study was to ascertain the importance of flow pathway partitioning in the transport (fluxes and timing) of dissolved and particulate slurry-derived compounds with implications for off-site contamination. A series of rainfall–runoff and erosion experiments were carried out using the TRACE (Test Rig for Advancing Connectivity Experiments) experimental hillslope facility. The experiments allowed the quantification of the impact of changing slope gradient and rainfall intensity on nutrient transport from cattle slurry applied to the hillslope, via surface, subsurface, and vertical percolated flow pathways, as well as particulate transport from erosion. The dissolved components were traced using a combination of ammonium (NH₄⁺) and fluorescence analysis, while the particulate fraction was traced using organic biomarkers, 5<i>β</i>-stanols. Results showed that rainfall events which produced flashy hydrological responses, resulting in large quantities of surface runoff, were likely to move sediment and also flush dissolved components of slurry-derived material from the slope, increasing the contamination risk. Rainfall events which produced slower hydrological responses were dominated by vertical percolated flows removing less sediment-associated material, but produced leachate which could contaminate deeper soil layers, and potentially groundwater, over a more prolonged period. Overall, this research provides new insights into the partitioning of slurry-derived material when applied to an unvegetated slope and the transport mechanisms by which contamination risks are created

Learning to Swim: What Influences Success?

Swimming and water safety skills are important life skills, particularly in Australia, where aquatic activities are regularly enjoyed. Little research has been undertaken exploring children’s swimming and water safety skills, what level they can achieve, and what factors impact their ability to learn these skills. This study explores children aged 5-12 years who participated in the Australian Capital Territory Primary Schools Swim and Survive Program, 2009-2011. Children who were more likely to achieve higher levels were older, were female, attended private school, swam at least once a fortnight, had a swimming pool at home, or visited a public swimming pool. Those who were less likely were Aboriginal or Torres Strait Islander, had a negative experience, and swam less than once a fortnight

Overprinting orogenic events, ductile extrusion and strain partitioning during Caledonian transpression, NW Mainland Shetland

A 3.6 km thick stack of mid-crustal deformed Precambrian rocks is associated with the North Roe Nappe (NRN) and Walls Boundary Fault in the northernmost Scottish Caledonides on NW Mainland Shetland. The greenschist- to amphibolite-facies rocks display unusually complex and heterogeneous combinations of coaxial and non-coaxial transpressional deformation. Previously published isotopic dating, together with new detailed field mapping and microstructural characterisation show that the NRN preserves a record of Neoarchaean, Neoproterozoic (Knoydartian) and Ordovician-Silurian (Caledonian) overprinting deformation and metamorphism. Neoarchaean events in the Uyea Gneiss Complex located in its footwall are reworked by younger events in the overlying nappe pile. The main ductile fabrics were formed during Caledonian top-to-the W/NW thrusting and top-to-the N sinistral shearing, with subordinate regions of top- to-the E extensional and NNE-SSW dextral shearing. In lower parts of the NRN, these different kinematic domains are texturally indistinguishable and overprinting relationships are absent. At higher levels, top-to-the-W/NW thrust-related fabrics are consistently overprinted by top-to-the-N/NE sinistral shearing. The highly partitioned transpressional deformation shows similarities with equivalent rocks of the Moine Nappe in NW Scotland

Efficient quantum algorithms for simulating sparse Hamiltonians

We present an efficient quantum algorithm for simulating the evolution of a sparse Hamiltonian H for a given time t in terms of a procedure for computing the matrix entries of H. In particular, when H acts on n qubits, has at most a constant number of nonzero entries in each row/column, and |H| is bounded by a constant, we may select any positive integer $k$ such that the simulation requires O((\log^*n)t^{1+1/2k}) accesses to matrix entries of H. We show that the temporal scaling cannot be significantly improved beyond this, because sublinear time scaling is not possible.Comment: 9 pages, 2 figures, substantial revision

The subduction experiment : cruise report R/V Knorr : cruise number 138 leg XV : subduction 3 mooring recovery cruise, 13-30 June 1993

Subduction is the mechanism by which water masses formed in the mixed layer and near the surface of the ocean find their way into the upper thermocline. The subduction process and its underlying mechanisms were studied though a combination of Eulerian and Langrangian measurements of velocity, measurements of tracer distributions and hydrographic properties and modeling. An array of five surface moorings carrying meteorological and oceanographic instrumentation were deployed for a period of two years beginning in June 1991 as part of an Office of Naval Research (ONR) funded Subduction experiment. Three eight month deployments were planned. The moorings were deployed at 18°N 34°W, 18°N 22°W, 25.5°N 29°W, 33°N 22°W and 33°N 34°W. A Vector Averaging Wind Recorder (VAWR) and an Improved Meteorological Recorder (IMET) collected wind speed and wind direction, sea surface temperature, air temperature, short wave radiation, barometric pressure and relative humidity. The IMET also measured precipitation. The moorings were heavily instrumented below the surface with Vector Measuring Current Meters (VMCM) and single point temperature recorders. Expendable bathythermograph (XBT) data were collected and meteorological observations were made while transmitting between mooring locations. This report describes the work that took place during R/V Knorr cruise number 138 leg XV which was the fourth scheduled Subduction mooring cruise. During this cruise the moorings previously deployed for a third and final eight month period were recovered. This report includes a description of the moorings and instrumentation that were recovered, has information about the underway measurements (XBT and meteorological observations) that were made including plots of the data, and presents a chronology of the cruise events.Funding provided by the Office of Naval Research under Contract No. N00014-90-J-1490

Schumacher's quantum data compression as a quantum computation

An explicit algorithm for performing Schumacher's noiseless compression of quantum bits is given. This algorithm is based on a combinatorial expression for a particular bijection among binary strings. The algorithm, which adheres to the rules of reversible programming, is expressed in a high-level pseudocode language. It is implemented using $O(n^3)$ two- and three-bit primitive reversible operations, where $n$ is the length of the qubit strings to be compressed. Also, the algorithm makes use of $O(n)$ auxiliary qubits; however, space-saving techniques based on those proposed by Bennett are developed which reduce this workspace to $O(\sqrt{n})$ while increasing the running time by less than a factor of two.Comment: 37 pages, no figure

Premarital sex and schooling transitions in four sub-Saharan African countries

Using data from the 2004 National Survey of Adolescents conducted in Burkina Faso, Ghana, Malawi, and Uganda, this Population Council working paper investigates the timing of two key transitions in adolescence—school exit and premarital sex—among those who remain enrolled in school at the beginning of adolescence (age 12). Girls appear more vulnerable to dropout once they become sexually mature and once they engage in premarital sex. While girls were found to be less likely than boys, at any given age and controlling for other covariates, to have had premarital sex (except in Ghana), school enrollment and the timing of school entry were not consistent factors explaining gender differences. Results indicate that the negative consequences for schooling associated with sexual maturation and premarital sex appear to be greater for adolescents in these four countries, especially for girls, than the consequences of leaving school early for the likelihood of premarital sex. Future studies that collect more-detailed information on the educational environment should help clarify the associations between school experiences and sexual behavior among young people in sub-Saharan Africa