8,277 research outputs found
An analysis of legal highs: do they contain what it says on the tin?
In recent years the availability of so called legal highs over the internet has hugely increased. Numerous online legal high retailers market a broad variety of products
which are advertised as research chemicals, bath salts or plant food although clearly intended for human consumption as recreational drug replacements. No guidelines exist as to what is sold and in what purity. Consumers are led to believe that purchased goods are entirely legal.
In this study several legal high products were purchased and analysed for their content. The powdered products were screened with ATR-FTIR followed by GC-MS analysis of methanol extracts. Spectra were compared to reference standards and the NIST library.
Results showed that 6 out of 7 products did not contain the advertised active ingredient. Moreover, five samples contained the controlled substances benzylpiperazine and 1-[3-(trifluoromethyl)phenyl]piperazine combined with
caffeine
Initial Plant Growth in Sand Mine Spoil Amended with Peat Moss and Fertilizer Under Greenhouse Conditions: Potential Species for Use in Reclamation
The Great Lakes Basin exhibits the largest collection of freshwater sand dunes in the world. Sand dunes are ecologically important and support a unique assemblage of flora and fauna. Sand dunes are also economically valuable. However, when sand dunes are mined, soil quality is drastically reduced. Therefore, soil quality improvements followed by revegetation maybe necessary for successful reclamation. This study evaluates the germination and initial growth of 2 legume species, sundial lupine (Lupinus perennis) and Illinois bundleflower (Desmanthus illinoensis), and 2 warm-season grass species, Indian grass (Sorghastrum nutans) and little bluestem (Schizachyrium scoparium), in the presence of 2 soil amendments (inorganic fertilizer and sphagnum peat moss) added to spoil from a local sand mine. We sowed species in pots and propagated them under greenhouse conditions. Results indicate that sundial lupine and Illinois bundleflower exhibited the greatest germination and growth among species. Peat moss had the greatest overall impact on germination and growth while the addition of fertilizer positively affected initial growth. Based on these results, sundial lupine is recognized as a primary candidate for sand mine reclamation, while Illinois bundleflower is also recommended as an appropriate species for revegetation efforts. We recommend using soil amendments that are functionally equivalent to peat in increasing soil water holding capacity. We further suggest that fertilization may be accomplished by including legumes in plant species mixes used for revegetation. Results presented here may help to identify appropriate species and soil amendments for the reclamation of former sand mines or restoration of freshwater sand dunes
Deep Extragalactic X-ray Surveys
Deep surveys of the cosmic X-ray background are reviewed in the context of
observational progress enabled by the Chandra X-ray Observatory and the X-ray
Multi-Mirror Mission-Newton. The sources found by deep surveys are described
along with their redshift and luminosity distributions, and the effectiveness
of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key
results from deep surveys are highlighted including (1) measurements of AGN
evolution and the growth of supermassive black holes, (2) constraints on the
demography and physics of high-redshift AGN, (3) the X-ray AGN content of
infrared and submillimeter galaxies, and (4) X-ray emission from distant
starburst and normal galaxies. We also describe some outstanding problems and
future prospects for deep extragalactic X-ray surveys.Comment: 32 pages; Annu. Rev. Astron. Astrophys., Volume 43 (2005); updated to
match accepted versio
Three Applications of the String-Inspired Technique to Quantum Electrodynamics
We discuss the following recent applications of the ``string-inspired''
worldline technique to calculations in quantum electrodynamics: i) Photon
splitting in a constant magnetic field, ii) The two-loop Euler-Heisenberg
Lagrangian, iii) A progress report on a recalculation of the three-loop QED
beta -- function.Comment: 10 pages, uuencoded Postscript-File, talk given by C. Schubert at the
Zeuthen Workshop on Elementary Particle Theory: QCD and QED in Higher Orders,
Rheinsberg, Germany, 21-26 Apr 199
Harpacticoida (Crustacea, Copepoda) across a longitudinal transect of the Vema Fracture Zone and along a depth gradient in the Puerto Rico trench
The aim of this study was the investigation of abundance, composition and biodiversity of benthic deep-sea Harpacticoida (Crustacea, Copepoda) in the Verna Fracture Zone (VFZ) and Puerto Rico trench. The study revealed a clear East-West gradient in total abundance of Harpacticoida with a westward decrease in abundances in the VFZ and significant differences in the community composition in the Eastern (East Verna) and Western Atlantic basin (West Verna) on family and genus level. The Puerto Rico trench and its upper slope did not only differ in abundance, but were distinct with respect to community composition on family and genus level. Thus, the upper slope might be considered as an ecotone, a transition zone where a rapid distinction of species composition occurs. In our study fiarea, 837 adult harpacticoid specimens could be assigned to 16 families and 1 subfamily. The most abundant families found were Ameiridae Boeck, 1865, Pseudotachidiidae Lang, 1936 and Ectinosomatidae Sars, 1903. Genera and species were investigated within selected families (Argestidae Por, 1986, Cletodidae T. Scott, 1905, Canthocamptidae Brady, 1880 and Zosimeidae Seifried, 2003) where 11 genera, and 73 species could be discriminated. Within the selected families, the genera Zosime Boeck, 1873 and Mesocletades Sars, 1909 were dominant. In the study area, a high number of singletons was detected, which might be endemic to the respective region. Furthermore, a low total number of species in the trench was observed which was attributed to frequent disturbances in the dynamic environment of the Puerto Rico trench (e.g. turbidites or seismic activity) and high adaptability of specialists and opportunists to these disturbances
Chaotic and regular motion around generalized Kalnajs discs
The motion of test particles in the gravitational fields generated by the
first four members of the infinite family of generalized Kalnajs discs, is
studied. In first instance, we analyze the stability of circular orbits under
radial and vertical perturbations and describe the behavior of general
equatorial orbits and so we find that radial stability and vertical instability
dominate such disc models. Then we study bounded axially symmetric orbits by
using the Poincare surfaces of section and Lyapunov characteristic numbers and
find chaos in the case of disc-crossing orbits and completely regular motion in
other cases
Formation of the Black Hole in Nova Scorpii
Israelian et al. (1999) showed that the stellar companion of the black-hole
binary Nova Sco is polluted with material ejected in the supernova that
accompanied the formation of the black-hole primary. Here we systematically
investigate the implications of these observations for the black-hole formation
process. Using a variety of supernova models, including both standard as well
as hypernova models (for different helium-star masses, explosion energies, and
explosion geometries) and a simple model for the evolution of the binary and
the pollution of the secondary, we show that most of the observed abundance
anomalies can be explained for a large range of model parameters (apart from
the abundance of Ti). The best models are obtained for He star masses of 10 to
16 Msun, where spherical hypernova models are generally favoured over standard
supernova ones. Aspherical hypernova models also produce acceptable fits,
provided there is extensive lateral mixing. All models require substantial
fallback and that the fallback material either reached the orbit of the
secondary or was mixed efficiently with material that escaped. The black hole
therefore formed in a two-step process, where the initial mass of the collapsed
remnant was increased substantially by matter that fell back after the initial
collapse. This may help to explain the high observed space velocity of Nova Sco
either because of a neutrino-induced kick (if a neutron star was formed first)
or by asymmetric mass ejection in an asymmetric supernova explosion.Comment: 16 pages, 3 Figures, 4 Tables. submitted to Ap
Supervisory Control Synthesis of Discrete-Event Systems using Coordination Scheme
Supervisory control of discrete-event systems with a global safety
specification and with only local supervisors is a difficult problem. For
global specifications the equivalent conditions for local control synthesis to
equal global control synthesis may not be met. This paper formulates and solves
a control synthesis problem for a generator with a global specification and
with a combination of a coordinator and local controllers. Conditional
controllability is proven to be an equivalent condition for the existence of
such a coordinated controller. A procedure to compute the least restrictive
solution is also provided in this paper and conditions are stated under which
the result of our procedure coincides with the supremal controllable
sublanguage.Comment: 29 pages, 11 figure
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