United States Department of the Army

About: United States Department of the Army is a government organization based out in Arlington, Virginia, United States. It is known for research contribution in the topics: Poison control & Population. The organization has 32668 authors who have published 42453 publications receiving 947075 citations. The organization is also known as: DA & U.S. Department of the Army.

One Thousand Centuries of Climatic Record from Camp Century on the Greenland Ice Sheet

Abstract: A correlation of time with depth has been evaluated for the Camp Century, Greenland, 1390 meter deep ice core. Oxygen isotopes in approximately 1600 samples throughout the core have been analyzed. Long-term variations in the isotopic composition of the ice reflect the climatic changes during the past nearly 100,000 years. Climatic oscillations with periods of 120, 940, and 13,000 years are observed.

Eight-band k ⋅ p model of strained zinc-blende crystals

Abstract: Second-order L\"owdin perturbation theory is used to calculate the interaction matrices for an eight-band k\ensuremath{\cdot}p model (near the \ensuremath{\Gamma} point) of zinc-blende crystals under a uniform strain. The model treats the ${\mathrm{\ensuremath{\Gamma}}}_{6}$ conduction bands, ${\mathrm{\ensuremath{\Gamma}}}_{8}$ valence bands, and ${\mathrm{\ensuremath{\Gamma}}}_{7}$ spin-orbit split-off bands. The model includes strain interactions arising from both the orbital and spin-orbit terms of the Hamiltonian. In addition to the usual Pikus-Bir deformation-potential constants, a, b, and d, which describe the coupling of the valence band to strain, two new deformation-potential constants arise, a' and b', which describe the coupling of the conduction band to strain. The constant a' couples the conduction band to hydrostatic deformations and the constant b', which results from a lack of inversion symmetry, couples the conduction band to shear deformations. The strain also introduces a k-dependent conduction-band--valence-band mixing that is linear in strain, in wave vector, and in the momentum matrix element between the conduction and valence bands. In the absence of strain, the eight-band Kane model is recovered. Under a finite strain, in the limit of a large conduction-band--valence-band gap and large spin-orbit splitting, the four-band Luttinger model with strain is recovered.

Epidemiology of Inapparent and Symptomatic Acute Dengue Virus Infection: A Prospective Study of Primary School Children in Kamphaeng Phet, Thailand

Abstract: Dengue viruses are a major cause of morbidity in tropical and subtropical regions of the world. Knowledge about the epidemiology and host determinants of inapparent and severe dengue virus infections is limited. In this paper, the authors report findings from the first 3 years of a prospective study of dengue virus transmission and disease severity conducted in a cohort of 2,119 elementary school children in northern Thailand. A total of 717,106 person-school days were observed from 1998 to 2000. The incidence of inapparent and of symptomatic dengue virus infection was 4.3% and 3.6% in 1998, 3.2% and 3.3% in 1999, and 1.4% and 0.8% in 2000, respectively. Symptomatic dengue virus infection was responsible for 3.2%, 7.1%, and 1.1% of acute-illness school absences in 1998, 1999, and 2000, respectively. The early symptom complex of acute dengue virus infection is protean and difficult to distinguish from other causes of febrile childhood illnesses. The authors' results illustrate the spatial and temporal diversity of dengue virus infection and the burden of dengue disease in schoolchildren in Thailand. Their findings increase understanding of dengue virus transmission and disease severity in a well-defined cohort population and offer a study design in which to test the efficacy of potential dengue vaccines.

Effects of hot and cold temperature exposure on performance: a meta-analytic review

Abstract: A meta-analysis to mathematically summarize the effect of hot and cold temperature exposure on performance was completed. The results from 515 effect sizes calculated from 22 original studies suggest that hot and cold temperatures negatively impact performance on a wide range of cognitive-related tasks. More specifically, hot temperatures of 90°F (32.22°C) Web Bulb Globe Temperature Index or above and cold temperatures of 50°F (10°C) or less resulted in the greatest decrement in performance in comparison to neutral temperature conditions (14.88% decrement and 13.91% decrement, respectively). Furthermore, the duration of exposure to the experimental temperature, the duration of exposure to the experimental temperature prior to the task onset, the type of task and the duration of the task had differential effects on performance. The current results indicate that hot and cold temperature exposure have a negative impact on performance and that other variables (e.g., length of exposure to the temperature or task duration) may modify this relationship.