883 research outputs found
Recommended from our members
Biologic surveys for the Sandia National Laboratories, Coyote Canyon Test Complex, Kirtland Air Force Base, Albuquerque, New Mexico
This report provides results of a comprehensive biologic survey performed in Coyote Canyon Test Complex (CCTC), Sandia National Laboratories (SNL), Bernalillo County, New Mexico, which was conducted during the spring and summer of 1992 and 1993. CCTC is sited on land owned by the Department of Energy (DOE) and Kirtland Air Force Base and managed by SNL. The survey covered 3,760 acres of land, most of which is rarely disturbed by CCTC operations. Absence of grazing by livestock and possibly native ungulates, and relative to the general condition of private range lands throughout New Mexico, and relative to other grazing lands in central New Mexico. Widely dispersed, low intensity use by SNL as well as prohibition of grazing has probably contributed to abundance of special status species such as grama grass cactus within the CCTC area. This report evaluates threatened and endangered species found in the area, as well as comprehensive assessment of biologic habitats. Included are analyses of potential impacts and mitigative measures designed to reduce or eliminate potential impacts. Included is a summary of CCTC program and testing activities
Probing the time dependence of dark energy
A new method to investigate a possible time-dependence of the dark energy
equation of state is proposed. We apply this methodology to two of the most
recent data sets of type Ia supernova (Union2 and SDSS) and the baryon acoustic
oscillation peak at . For some combinations of these data, we show
that there is a clear departure from the standard CDM model at
intermediary redshifts, although a non-evolving dark energy component () cannot be ruled out by these data. The approach developed here may be
useful to probe a possible evolving dark energy component when applied to
upcoming observational data.Comment: 6 pages, 3 figures, LaTe
Pion Content of the Nucleon as seen in the NA51 Drell-Yan experiment
In a recent CERN Drell-Yan experiment the NA51 group found a strong asymmetry
of and densities in the proton at . We interpret
this result as a decisive confirmation of the pion-induced sea in the nucleon.Comment: 10 pages + 3 figures, Preprint KFA-IKP(TH)-1994-14 .tex file. After
\enddocument a uu-encodeded Postscript file comprising the figures is
appende
Recommended from our members
Surface modification of mineral dust particles by sulphuric acid processing: Implications for ice nucleation abilities
The ability of coated mineral dust particles to act as ice nuclei (IN) was investigated at LACIS (Leipzig Aerosol Cloud Interaction Simulator) during the FROST1- and FROST2-campaigns (Freezing of dust). Sulphuric acid was condensed on the particles which afterwards were optionally humidified, treated with ammonia vapour and/or heat. By means of aerosol mass spectrometry we found evidence that processing of mineral dust particles with sulphuric acid leads to surface modifications of the particles. These surface modifications are most likely responsible for the observed reduction of the IN activation of the particles. The observed particle mass spectra suggest that different treatments lead to different chemical reactions on the particle surface. Possible chemical reaction pathways and products are suggested and the implications on the IN efficiency of the treated dust particles are discussed
Meson Cloud of the Nucleon in Polarized Semi-Inclusive Deep-Inelastic Scattering
We investigate the possibility of identifying an explicit pionic component of
the nucleon through measurements of polarized baryon fragments
produced in deep-inelastic leptoproduction off polarized protons, which may
help to identify the physical mechanism responsible for the breaking of the
Gottfried sum rule. The pion-exchange model predicts highly correlated
polarizations of the and target proton, in marked contrast with
the competing diquark fragmentation process. Measurement of asymmetries in
polarized production may also reveal the presence of a kaon cloud in
the nucleon.Comment: 23 pages REVTeX, 7 uuencoded figures, accepted for publication in
Zeit. Phys.
Sampling effects on the quantification of sodium content in infant formula using laser induced breakdown spectroscopy (LIBS)
Laser-induced breakdown spectroscopy (LIBS) was employed to predict the sodium content of infant formula (IF) over the range 0.5–4 mg Na g−1. Calibration models were built using partial least squares regression (PLS), correlating the LIBS spectral data with reference Na content quantified by atomic absorption spectroscopy (AAS). The main aim of this study was to demonstrate the ability of LIBS as a rapid tool for quantifying sodium in IF, but also to explore strategies concerning the acquisition and pre-processing of LIBS spectra. A range of different pre-processing techniques, measuring depths (repetition of laser shots) and accumulations were conducted and evaluated in terms of PLS performance. The best calibration model was developed using the third-layer spectra normalised by the H I 656.29 nm emission line, yielding a coefficient of determination (R2) of 0.93, and root-mean-square errors (RMSE) of 0.37 and 0.13 mg g−1 for cross-validation and validation, respectively
Hadron Production in Heavy Ion Collisions
We review hadron production in heavy ion collisions with emphasis on pion and
kaon production at energies below 2 AGeV and on partonic collectivity at RHIC
energies.Comment: 31 pages, 26 figures, accepted for publication in Landolt-Boernstein
Volume 1-23
Dust Devil Tracks
Dust devils that leave dark- or light-toned tracks are common on Mars and they can also be found on the Earth’s surface. Dust devil tracks (hereinafter DDTs) are ephemeral surface features with mostly sub-annual lifetimes. Regarding their size, DDT widths can range between ∼1 m and ∼1 km, depending on the diameter of dust devil that created the track, and DDT lengths range from a few tens of meters to several kilometers, limited by the duration and horizontal ground speed of dust devils. DDTs can be classified into three main types based on their morphology and albedo in contrast to their surroundings; all are found on both planets: (a) dark continuous DDTs, (b) dark cycloidal DDTs, and (c) bright DDTs. Dark continuous DDTs are the most common type on Mars. They are characterized by their relatively homogenous and continuous low albedo surface tracks. Based on terrestrial and martian in situ studies, these DDTs most likely form when surficial dust layers are removed to expose larger-grained substrate material (coarse sands of ≥500 μm in diameter). The exposure of larger-grained materials changes the photometric properties of the surface; hence leading to lower albedo tracks because grain size is photometrically inversely proportional to the surface reflectance. However, although not observed so far, compositional differences (i.e., color differences) might also lead to albedo contrasts when dust is removed to expose substrate materials with mineralogical differences. For dark continuous DDTs, albedo drop measurements are around 2.5 % in the wavelength range of 550–850 nm on Mars and around 0.5 % in the wavelength range from 300–1100 nm on Earth. The removal of an equivalent layer thickness around 1 μm is sufficient for the formation of visible dark continuous DDTs on Mars and Earth. The next type of DDTs, dark cycloidal DDTs, are characterized by their low albedo pattern of overlapping scallops. Terrestrial in situ studies imply that they are formed when sand-sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic albedo changes that affect large-scale weather patterns
- …