2,106 research outputs found
The Effects of Different Intensity of Thinning on the Development in Scots Pine (Pinus sylvestris L.) Stands in Kazakh Uplands
The search for more accurate methods of predicting the growth and development of forest stands became the most urgent task set for foresters of Kazakhstan to determine the permissible interventions in the natural course of the life of plantings, provide high durability and resilience in forests. The aim of the study was to identify the effects of diameter and density of Scots pine stands of Kazakh Uplands on their growth and productivity and the related productivity of single plantation stands taking into account the conditions of growth and development of internal factors as well as further study of the methodology for assessing the forestry cost-effectiveness and improvement thinning. To achieve this aim, effects of varied felling intensities on Scots pine stands were studied. The most common two forest types in upland Scots pine forests were chosen as permanent sample plots; the dead pine-lichen and moss pine-grass. The results showed that improvement thinning of moderate and severe intensity which are more profitable should be done in Scots pine forests of Kazakh Upland as well as carrying out such thinning increases the yield of the larger logs and increases the value of the left stand
Thermochemical stability of low-iron, manganese-enriched olivine in astrophysical environments
Low-iron, manganese-enriched (LIME) olivine grains are found in cometary samples returned by the Stardust mission from comet 81P/Wild 2. Similar grains are found in primitive meteoritic clasts and unequilibrated meteorite matrix. LIME olivine is thermodynamically stable in a vapor of solar composition at high temperature at total pressures of a millibar to a microbar, but enrichment of solar composition vapor in a dust of chondritic composition causes the FeO/MnO ratio of olivine to increase. The compositions of LIME olivines in primitive materials indicate oxygen fugacities close to those of a very reducing vapor of solar composition. The compositional zoning of LIME olivines in amoeboid olivine aggregates is consistent with equilibration with nebular vapor in the stability field of olivine, without re-equilibration at lower temperatures. A similar history is likely for LIME olivines found in comet samples and in interplanetary dust particles. LIME olivine is not likely to persist in nebular conditions in which silicate liquids are stable
Condensation of Rocky Material in Astrophysical Environments
Volatility-dependent fractionation of the rock-forming elements at high
temperatures is an early, widespread process during formation of the earliest
solids in protoplanetary disks. Equilibrium condensation calculations allow
prediction of the identities and compositions of mineral and liquid phases
coexisting with gas under presumed bulk chemical, pressure and temperature
conditions. A graphical survey of such results is presented for systems of
solar and non-solar bulk composition. Chemical equilibrium was approached to
varying degrees in the local regions where meteoritic chondrules, Ca-Al-rich
inclusions, matrix and other components formed. Early, repeated vapor-solid
cycling and homogenization, followed by hierarchical accretion in dust-rich
regions, is hypothesized for meteoritic inclusions. Disequilibrium chemical
effects appear to have been common at all temperatures, but increasingly so in
less refractory meteoritic components. Work is needed to better model
high-temperature solid solutions, indicators of these processes.Comment: 43 pages, 4 color plates, 2 figure
Condensation Calculations in Planetary Science and Cosmochemistry
Cool a piece of the Sun to 1000 K at one millibar pressure to yield a mineral
assemblage consistent with those found in the most primitive meteorites. This
is an equilibrium or fractional condensation experiment simulated by
calculations using equations of state for hundreds of gaseous molecules,
condensed mineral solids, and silicate liquids, the products of a century of
experimental measurements and theoretical studies. Such calculations have
revolutionized our understanding of the chemistry of the cosmos.
The mid-20th Century realization that meteorites are fossil records of the
early Solar System made chemistry central to understanding planetary origins.
Thus "condensation", the distribution of elements and isotopes between vapor
and condensed solids and/or liquids at or approaching chemical equilibrium,
deeply informs discussion of how meteor/comet compositions bear on planets.
Condensation calculations have been applied to disks around young stars, to
the mineral "rain" of mineral grains expected to form in cool dwarf star
atmospheres, to the expanding envelopes of giant stars, to the vapor plumes
that form in planetary impacts, and to the chemically and isotopically distinct
"shells" computed and observed to exist in supernovae. As with all
sophisticated calculations, there are inherent caveats, subtleties, and
computational difficulties.
Local chemistry has yet to be consistently integrated into dynamical
astrophysical simulations so that effects like the blocking of radiation by
grains, absorption and reemission of light by grains, and buffering of heat by
grain evaporation/condensation feed back into the physics at each node of a
gridded calculation over time. A deeper integration of thermochemistry with
physical models makes the prospect of a general protoplanetary disk model as
hopeful now as a general circulation model for global climate was in the early
1970's.Comment: Review for Oxford Encyclopedi
Bayesian Analysis for Food-Safety Risk Assessment: Evaluation of Dose-Response Functions within WinBUGS
The interferon-stimulated gene IFITM3 restricts West Nile virus infection and pathogenesis
The interferon-induced transmembrane protein (IFITM) family of proteins inhibit infection of several different enveloped viruses in cell culture by virtue of their ability to restrict entry and fusion from late endosomes. As few studies have evaluated the importance of Ifitm3 in vivo in restricting viral pathogenesis, we investigated its significance as an antiviral gene against West Nile virus (WNV), an encephalitic flavivirus, in cells and mice. Ifitm3(−/−) mice were more vulnerable to lethal WNV infection, and this was associated with greater virus accumulation in peripheral organs and central nervous system tissues. As no difference in viral burden in the brain or spinal cord was observed after direct intracranial inoculation, Ifitm3 likely functions as an antiviral protein in nonneuronal cells. Consistent with this, Ifitm3(−/−) fibroblasts but not dendritic cells resulted in higher yields of WNV in multistep growth analyses. Moreover, transcomplementation experiments showed that Ifitm3 inhibited WNV infection independently of Ifitm1, Ifitm2, Ifitm5, and Ifitm6. Beyond a direct effect on viral infection in cells, analysis of the immune response in WNV-infected Ifitm3(−/−) mice showed decreases in the total number of B cells, CD4(+) T cells, and antigen-specific CD8(+) T cells. Finally, bone marrow chimera experiments demonstrated that Ifitm3 functioned in both radioresistant and radiosensitive cells, as higher levels of WNV were observed in the brain only when Ifitm3 was absent from both compartments. Our analyses suggest that Ifitm3 restricts WNV pathogenesis likely through multiple mechanisms, including the direct control of infection in subsets of cells. IMPORTANCE As part of the mammalian host response to viral infections, hundreds of interferon-stimulated genes (ISGs) are induced. The inhibitory activity of individual ISGs varies depending on the specific cell type and viral pathogen. Among ISGs, the genes encoding interferon-induced transmembrane protein (IFITM) have been reported to inhibit multiple families of viruses in cell culture. However, few reports have evaluated the impact of IFITM genes on viral pathogenesis in vivo. In this study, we characterized the antiviral activity of Ifitm3 against West Nile virus (WNV), an encephalitic flavivirus, using mice with a targeted gene deletion of Ifitm3. Based on extensive virological and immunological analyses, we determined that Ifitm3 protects mice from WNV-induced mortality by restricting virus accumulation in peripheral organs and, subsequently, in central nervous system tissues. Our data suggest that Ifitm3 restricts WNV pathogenesis by multiple mechanisms and functions in part by controlling infection in different cell types
Alcohol Interventions for Trauma Patients Treated in Emergency Departments and Hospitals: A Cost Benefit Analysis
Summarizes a study of whether screening for problem drinking and interventions to reduce alcohol intake in hospital trauma centers reduce the direct cost of injury-related health care. Compares the costs of injury recidivism with and without intervention
Mineral Processing by Short Circuits in Protoplanetary Disks
Meteoritic chondrules were formed in the early solar system by brief heating
of silicate dust to melting temperatures. Some highly refractory grains (Type B
calcium-aluminum-rich inclusions, CAIs) also show signs of transient heating. A
similar process may occur in other protoplanetary disks, as evidenced by
observations of spectra characteristic of crystalline silicates. One possible
environment for this process is the turbulent magnetohydrodynamic flow thought
to drive accretion in these disks. Such flows generally form thin current
sheets, which are sites of magnetic reconnection, and dissipate the magnetic
fields amplified by a disk dynamo. We suggest that it is possible to heat
precursor grains for chondrules and other high-temperature minerals in current
sheets that have been concentrated by our recently described short-circuit
instability. We extend our work on this process by including the effects of
radiative cooling, taking into account the temperature dependence of the
opacity; and by examining current sheet geometry in three-dimensional, global
models of magnetorotational instability. We find that temperatures above 1600 K
can be reached for favorable parameters that match the ideal global models.
This mechanism could provide an efficient means of tapping the gravitational
potential energy of the protoplanetary disk to heat grains strongly enough to
form high-temperature minerals. The volume-filling nature of turbulent magnetic
reconnection is compatible with constraints from chondrule-matrix
complementarity, chondrule-chondrule complementarity, the occurrence of igneous
rims, and compound chondrules. The same short-circuit mechanism may perform
other high-temperature mineral processing in protoplanetary disks such as the
production of crystalline silicates and CAIs.Comment: 6 pages, 3 figures, ApJL published versio
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