6,019 research outputs found
An Emergence Trap for Aquatic Insects
Excerpt: The identification of organisms is a prerequisite to developing water quality criteria for aquatic life. Identification is necessary because differences in water quality requirements are specific and may be different for closely allied species. The taxonomy of various species, particularly those associated with the aquatic environment, is much more detailed and better known for adults than for immature instars. To facilitate correlation of adult and larval forms, a trap was needed to collect the emerging adults from the various streams
Modified bubble level senses pitch and roll angles over wide range
Bubble level sensor with fiber-optic field flattener is simple, rugged, small, and impervious to temperature and vibration effects. Pitch angles from -15 deg to +40 deg and roll angles of +30 deg are determined within 0.5 deg
Epitaxial Growth of an n-type Ferromagnetic Semiconductor CdCr2Se4 on GaAs(001) and GaP(001)
We report the epitaxial growth of CdCr2Se4, an n-type ferromagnetic
semiconductor, on both GaAs and GaP(001) substrates, and describe the
structural, magnetic and electronic properties. Magnetometry data confirm
ferromagnetic order with a Curie temperature of 130 K, as in the bulk material.
The magnetization exhibits hysteretic behavior with significant remanence, and
an in-plane easy axis with a coercive field of ~125 Oe. Temperature dependent
transport data show that the films are semiconducting in character and n-type
as grown, with room temperature carrier concentrations of n ~ 1 x 10^18 cm-3.Comment: 12 pages, 3 figure
Comparison of cattail (Typha sp.) occurrence on a photo-interpreted map versus a satellite data map
A comparison between a 1985 photo-interpreted vegetation map
and a vegetation map made from classified 1987 satellite data of
the Loxahatchee National Wildlife Refuge showed that 81% of
samples taken in areas occupied by cattail (Typha sp.) on the
photo-interpreted map corresponded with cattail on the satellite
data map.(5 page document
Innervation Patterns of Harp Seal (Pagophilus groenlandicus) Vibrissal Sensory Systems
Vibrissae, or whiskers, are largest among pinnipeds and are specialized hairs that potentially evolved to serve sensory, thermoregulatory or protective functions. Behavioral data from pinniped and rodent vibrissa studies indicate that functional differences exist between medial microvibrissae and lateral macrovibrissae. However, comparative data are lacking, and current pinniped studies only focus on the largest ventrolateral macrovibrissae. Consequently, we investigated the medial-to-lateral innervation and microanatomy of harp seal (Pagophilus groenlandicus) vibrissal Follicle-Sinus Complexes (F-SCs). F-SCs were sectioned either longitudinally or in cross-section. Sections remained unstained or were stained with a modified Bodian silver stain (innervation) or Masson’s trichrome stain (microanatomy). Harp seals possessed 88-105 F-SCs and each exhibited a tripartite blood organization system. Hair shafts were more circular medially but became more elliptical laterally. Medial F-SCs had more symmetrical dermal capsule thicknesses and distributions of major branches of the deep vibrissal nerve, but these symmetries diminished as F-SCs became more lateral. Medial-to-lateral axon counts ranged from 550 ± 97.4 axons/F-SC (medial) to 1632 ± 173.2 axons/F-SC (lateral). Overall, axon counts averaged 1221 ± 422.3 axons/F-SC (n=146 cross-sections), indicating a total of 117,235 axons/snout. Lateral F-SCs alone possessed a mean of 1533 ± 192.9 axons (n=82 cross-sections), which is similar to counts reported in other pinniped vibrissal innervation studies. These data suggest that conventional studies that only examine lateral vibrissae overestimate total innervation by ~20%. Moreover, we counted axon bundles with and without silver staining (n=834) and determined that unstained sections yielded more accurate and ~10% greater axon counts. Consequently, conventional analyses are likely only overestimating innervation by ~10% overall. The relationship between axon count and F-SC surface area was non-linear (p<<0.01; n=24 cross-sections), presumably from mechanoreceptors reaching carrying capacity, and axon densities were consistent across the snout. Presumptive Merkel-Neurite complexes and lanceolate endings were observed at the glassy membrane and outer root sheath interface. Our data agree well with behavioral research on pinnipeds and rodents that documents functional compartmentalization between micro-(medial) and macrovibrissae (lateral). Furthermore, our results support that vibrissal innervation variation observed among extant mammals initially diverged as a result of phylogeny and then environment (i.e., terrestrial, semi-aquatic, fully aquatic)
The relationship between biophysical variables and halocarbon distributions in the waters of the Amundsen and Ross Seas, Antarctica
Little is known regarding the distribution of volatile halogenated organic compounds (halocarbons) in Antarctic waters and their relation to biophysical variables. During the austral summer (December to January) in 2007-08 halocarbon and pigment concentrations were measured in the Amundsen (100-130 degrees W) and Ross Sea (158 degrees W-160 degrees E). In addition, halocarbons were determined in air, snow and sea ice. The distribution of halocarbons was influenced to a large extent by sea ice, and to a much lesser extent by pelagic biota. Concentrations of naturally produced halocarbons were elevated in the surface mixed layer in ice covered areas compared to open waters in polynyas and in the bottom waters of the Ross Sea. Higher concentrations of halocarbons were also found in sea ice brine compared to the surface waters. Incubations of snow revealed an additional source of halocarbons. The distribution of halocarbons also varied considerably between the Amundsen and Ross Seas, mainly due to the different oceanographic settings. For iodinated compounds, weak correlations were found with the presence of pigments indicative of Phaeocystis, mainly in the Ross Sea. Surface waters of the Amundsen and Ross Seas are a sink for bromoform (saturation anomalies, SA, -83 to 11%), whereas sea ice was found to be both a source and sink (SA -61-97%). In contrast, both surface waters and sea ice were found to be a source of chloroiodomethane (SA -6-1 200% and 91-22 000 resp.). Consequently, polar waters can have a substantial impact on global halocarbon budgets and need to be included in large-scale assessments. (C) 2012 Elsevier B.V. All rights reserved
Doubly heavy quark baryon spectroscopy and semileptonic decay
Working in the framework of a nonrelativistic quark model we evaluate the
spectra and semileptonic decay widths for the ground state of doubly heavy
and baryons. We solve the three-body problem using a variational
ansatz made possible by the constraints imposed by heavy quark spin symmetry.
In order to check the dependence of our resultson the inter-quark interaction
we have used five different quarkquark potentials which include Coulomb and
hyperfine terms coming fromone-gluon exchange, plus a confining term. Our
results for the spectra are in good agreement with a previous calculation done
using a Faddeev approach. For the semileptonic decay our results for the total
decay widths are in a good agreement with the ones obtained within a
relativistic quark model in the quark-diquark approximation.Comment: Talk given at the IVth International Conference on Quarks an Nuclear
Physics (QNP06), Madrid, June 5th-10th 200
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