25,123 research outputs found
Discovery of A New Faint Radio SNR G108.2-0.6
A new faint and large shell-type radio Supernova Remnant (SNR) G108.2-0.6 has
been discovered in the Canadian Galactic Plane Survey (CGPS). The SNR shows an
elliptical shell-type structure at 1420 MHz, and has a 408-1420 MHz TT-plot
spectral index of =-0.50.1 (S),
typical of a shell-type SNR. The remnant's flux density at 1420 MHz is
6.60.7 Jy, and at 408 MHz is 11.51.2 Jy. Both of these are corrected
for compact sources. An integrated spectral index of 0.13 is
determined. This new SNR has among the lowest surface brightness of any known
remnant (=2.4 W m Hz
sr). 21 cm Stokes Q and U CGPS data (plus preliminary Effelsberg Q and U
maps) show some suggestive features that correlate with total power. \ion{H}{i}
observations show structures associated with G108.20.6 in the radial
velocity range 53 to 58 km s, and indicate it is located in the
Perseus arm shock at a distance of 3.20.6 kpc. At this distance the
diameter of G108.20.6 is 58 pc. IRAS maps (12, 25, 60 and 100\mu m) of the
new SNR show rich infrared emission surrounding G108.20.6.Comment: 10 pages, 6 figs, accepted by A&
Water-resource records of Brevard County, Florida
The U. S. Geological Survey made a comprehensive
investigation of the water resources of Brevard County
from 1954 to 1958. The purposes of this investigation were:
(1) to determine the occurrence and chemical quality of
water in the streams and lakes, (2) to determine the location
and the thickness of aquifers, and (3) to determine the
occurrence and chemical quality of the ground water. During
the period from 1933 to 1954, water records were collected
from a few stream-gaging stations and a few observation
wells. The purpose of this report is to present basic data
collected during these investigations. (Document has 188 pages.
Clonal mixing in the soldier-producing aphid <i>Pemphigus spyrothecae</i> (Hemiptera: Aphididae)
Illuminating the genetic relationships within soldier-producing aphid colonies is an essential element of any attempt to explain the evolution of the altruistic soldier caste. Pemphigus spyrothecae is a soldier-producing aphid that induces galls on the leaf petioles of its host (trees of the genus Populus). At least a quarter of the aphids within the clonally produced gall population are morphologically and behaviourally distinct first-instar soldiers that defend the gall population from predation. Using field trapping and microsatellites, we investigated the degree of clonal mixing within natural gall populations. Field trapping in the UK showed that all the migrants of P. spyrothecae and of two other Pemphigus species were wingless first-instar soldiers. The average degree of mixing estimated from trapping P. spyrothecae migrants was 0.68% (range = 0–15%). Microsatellite genotyping of 277 aphids from 13 galls collected in Italy revealed an average mixing level of 10.4% (range = 0–59%). Six galls contained more than one clone (range = 2–5 clones). Non-kin aphids were not restricted to the soldier caste but were evenly distributed across instars. An additional gall, from which 527 occupants were genotyped, contained 12 non-kin aphids distributed among nine clones, showing that clonal diversity can be high even when mixing is very low. These observations suggest that although soldiers migrate regularly and can moult and reproduce within foreign galls, clonal mixing in this species is generally low and is unlikely to provide a barrier to the evolution of investment by the aphid clones in an altruistic soldier caste
Bond Strength of an Amorphous Calcium Phosphate–Containing Orthodontic Adhesive
Objective: To determine whether an amorphous calcium phosphate (ACP)-containing adhesive has an acceptable level of shear bond strength to be used as an orthodontic adhesive.
Materials and Methods: Sixty extracted premolars were randomly divided into three groups for orthodontic bonding. Group 1 used a composite resin adhesive (Transbond XT), group 2 was bonded with an ACP-containing adhesive (Aegis Ortho), and group 3 used a resin-modified glass ionomer (Fuji Ortho LC). All bonded teeth were stored in distilled water at 37°C for 40 ± 2 hours prior to debonding. Shear bond strength and adhesive remnant index (ARI) were recorded for each specimen.
Results: The mean shear bond strengths for the three test groups were: group 1 (15.2 ± 3.6 MPa), group 2 (6.6 ± 1.5 MPa), and group 3 (8.3 ± 2.8 MPa). A one-way analysis of variance showed a significant difference in bond strengths between the groups. A post hoc Tukey test showed group 1 to be significantly (P \u3c .001) greater than groups 2 and 3. A Kruskal-Wallis test and a Mann-Whitney U-test showed groups 1 and 3 exhibited lower ARI scores than group 2, but a majority of specimens in each group had greater than 50% of the cement removed along with the bracket during debonding.
Conclusions: The ACP-containing adhesive demonstrated a low, but satisfactory bond strength needed to function as an orthodontic adhesive
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