88 research outputs found
Limits on the ultra-bright Fast Radio Burst population from the CHIME Pathfinder
We present results from a new incoherent-beam Fast Radio Burst (FRB) search
on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Pathfinder. Its
large instantaneous field of view (FoV) and relative thermal insensitivity
allow us to probe the ultra-bright tail of the FRB distribution, and to test a
recent claim that this distribution's slope, , is quite small. A 256-input incoherent beamformer was
deployed on the CHIME Pathfinder for this purpose. If the FRB distribution were
described by a single power-law with , we would expect an FRB
detection every few days, making this the fastest survey on sky at present. We
collected 1268 hours of data, amounting to one of the largest exposures of any
FRB survey, with over 2.4\,\,10\,deg\,hrs. Having seen no
bursts, we have constrained the rate of extremely bright events to
\,sky\,day above \,220 Jy\,ms
for between 1.3 and 100\,ms, at 400--800\,MHz. The non-detection also
allows us to rule out with 95 confidence, after
marginalizing over uncertainties in the GBT rate at 700--900\,MHz, though we
show that for a cosmological population and a large dynamic range in flux
density, is brightness-dependent. Since FRBs now extend to large
enough distances that non-Euclidean effects are significant, there is still
expected to be a dearth of faint events and relative excess of bright events.
Nevertheless we have constrained the allowed number of ultra-intense FRBs.
While this does not have significant implications for deeper, large-FoV surveys
like full CHIME and APERTIF, it does have important consequences for other
wide-field, small dish experiments
280 GHz Focal Plane Unit Design and Characterization for the SPIDER-2 Suborbital Polarimeter
We describe the construction and characterization of the 280 GHz bolometric
focal plane units (FPUs) to be deployed on the second flight of the
balloon-borne SPIDER instrument. These FPUs are vital to SPIDER's primary
science goal of detecting or placing an upper limit on the amplitude of the
primordial gravitational wave signature in the cosmic microwave background
(CMB) by constraining the B-mode contamination in the CMB from Galactic dust
emission. Each 280 GHz focal plane contains a 16 x 16 grid of corrugated
silicon feedhorns coupled to an array of aluminum-manganese transition-edge
sensor (TES) bolometers fabricated on 150 mm diameter substrates. In total, the
three 280 GHz FPUs contain 1,530 polarization sensitive bolometers (765 spatial
pixels) optimized for the low loading environment in flight and read out by
time-division SQUID multiplexing. In this paper we describe the mechanical,
thermal, and magnetic shielding architecture of the focal planes and present
cryogenic measurements which characterize yield and the uniformity of several
bolometer parameters. The assembled FPUs have high yields, with one array as
high as 95% including defects from wiring and readout. We demonstrate high
uniformity in device parameters, finding the median saturation power for each
TES array to be ~3 pW at 300 mK with a less than 6% variation across each array
at one standard deviation. These focal planes will be deployed alongside the 95
and 150 GHz telescopes in the SPIDER-2 instrument, slated to fly from McMurdo
Station in Antarctica in December 2018
The effect of uncertain material properties on free vibrations of thin periodic plates
Impact of IL-28B polymorphisms on pegylated interferon plus ribavirin treatment response in children and adolescents infected with HCV genotypes 1 and 4
IL-28B polymorphisms are predictors of response to therapy in adults infected with hepatitis C. We do not know whether they are markers of response to therapy in children and adolescents. The aim of this study was to determine whether single-nucleotide polymorphisms (SNPs) in the IL-28B gene could influence the probability of response to therapy compared with other known baseline prognostic factors and correlate with clinical findings in pediatric patients infected with hepatitis C virus (HCV) genotypes 1 or 4. We determined three SNPs of IL-28B (rs12979860, rs12980275, and rs8099917) in 82 patients with chronic HCV infection treated with pegylated interferon alpha and ribavirin (peg-IFNα/RBV). Treatment response and clinical data were analyzed. Overall, sustained virological response (SVR) was achieved by 45 % of patients infected with difficult-to-treat HCV genotypes 1 and 4. Except for IL-28B polymorphisms, there was no association of SVR with any other clinical data. IL-28B rs12979860 CC [odds ratio (OR), 6.81; p = 0.001] and rs8099917 TT (OR, 3.14; p = 0.013) genotypes were associated with higher SVR rates. IL-28B rs12980275 was not significantly associated with SVR ( p = 0.058). Only the distribution between CC and CT-TT genotypes of rs12979860 significantly differentiated patients achieving early virological response (EVR) (OR, 10.0; p = 0.011). Children with the rs12979860 CC genotype had significantly higher baseline viral load compared with CT-TT patients ( p = 0.010). In children and adolescents chronically infected with HCV genotypes 1 and 4, IL-28B rs12979860 and rs8099917 polymorphisms were the only predictors of response to peg-IFN/RBV
Quantification of endogenous levels of IAA, IAAsp and IBA in micro-propagated shoots of hybrid chestnut pre-treated with IBA
Endogenous levels of indole-3-acetic acid (IAA),
indole-3-acetylaspartic acid (IAAsp) and indole-3-butyric
acid (IBA) were measured during the first 8 d of in vitro
rooting of rootstock from the chestnut âM3â hybrid by high
performance liquid chromatography (HPLC). Rooting was
induced either by dipping the basal ends of the shoots into a
4.92-mM IBA solution for 1 min or by sub-culturing the
shoots on solid rooting medium supplemented with 14.8-
ÎŒM IBA for 5 d. For root development, the induced shoots
were transferred to auxin-free solid medium. Auxins were
measured in the apical and basal parts of the shoots by
means of HPLC. Endogenous levels of IAA and IAAsp
were found to be greater in IBA-treated shoots than in
control shoots. In extracts of the basal parts of the shoots,
the concentration of free IAA showed a significant peak 2 d
after either root inductive method and a subsequent gradual
decrease for the remainder of the time course. The
concentration of IAAsp peaked at day 6 in extracts of the
basal parts of shoots induced with 14.8-ÎŒM IBA for 5 d,
whereas shoots induced by dipping showed an initial
increase until day 2 and then remained stable. In extracts
from basal shoot portions induced by dipping, IBA
concentration showed a transient peak at day 1 and a plateau between day 2 and 4, in contrast to the profile of
shoots induced on auxin-containing medium, which
showed a significant reduction between 4 and 6 d after
transferred to auxin-free medium. All quantified auxins
remained at a relatively low level, virtually constant, in
extracts from apical shoot portions, as well as in extracts
from control non-rooting shoots. In conclusion, the natural
auxin IAA is the signal responsible for root induction,
although it is driven by exogenous IBA independently of
the adding conditions
Contamination of rural surface and ground water by endosulfan in farming areas of the Western Cape, South Africa
BACKGROUND: In South Africa there is little data on environmental pollution of rural water sources by agrochemicals. METHODS: This study investigated pesticide contamination of ground and surface water in three intensive agricultural areas in the Western Cape: the Hex River Valley, Grabouw and Piketberg. Monitoring for endosulfan and chlorpyrifos at low levels was conducted as well as screening for other pesticides. RESULTS: The quantification limit for endosulfan was 0.1 Όg/L. Endosulfan was found to be widespread in ground water, surface water and drinking water. The contamination was mostly at low levels, but regularly exceeded the European Drinking Water Standard of 0.1 Όg/L. The two most contaminated sites were a sub-surface drain in the Hex River Valley and a dam in Grabouw, with 0.83 ± 1.0 Όg/L (n = 21) and 3.16 ± 3.5 Όg/L (n = 13) average endosulfan levels respectively. Other pesticides including chlorpyrifos, azinphos-methyl, fenarimol, iprodione, deltamethrin, penconazole and prothiofos were detected. Endosulfan was most frequently detected in Grabouw (69%) followed by Hex River (46%) and Piketberg (39%). Detections were more frequent in surface water (47%) than in groundwater (32%) and coincided with irrigation, and to a lesser extent, to spraying and trigger rains. Total dietary endosulfan intake calculated from levels found in drinking water did not exceed the Joint WHO/FAO Meeting on Pesticide Residues (JMPR) criteria. CONCLUSION: The study has shown the need for monitoring of pesticide contamination in surface and groundwater, and the development of drinking water quality standards for specific pesticides in South Africa
Understanding Lecturers' Perceptions of Workplace Fear: An Interpretive Study in the Cypriot Higher Education Context
This chapter explores how Cypriot lecturers perceive and experience fear while being at work. Drawing on the lens of interpretive inquiry, data were collected through interviews with 19 lecturers. Analysis focused on experiences of workplace fear offering rich insights into characteristics of fear, eliciting events, and coping ways. Findings help to unveil the specific events that lead to fear in the Cypriot universities, and the ways lecturers manage their fearful experiences. The study contributes to the study of discrete emotions, by empirically examining fearâs own storyline through the workersâ own perspectives, within a specific context
Nitrogen distribution and ammonia release from the overlying water and sediments of Poyang Lake, China
Occurrence of Cyanazine Compounds in Groundwater: Degradates More Prevalent Than the Parent Compound
Recent Advances in Nanoporous Anodic Alumina: Principles, Engineering, and Applications
The development of aluminum anodization technology features many stages. With the story stretching for almost a century, rather straightforwardâfrom current perspectiveâtechnology, raised into an iconic nanofabrication technique. The intrinsic properties of alumina porous structures constitute the vast utility in distinct fields. Nanoporous anodic alumina can be a starting point for: Templates, photonic structures, membranes, drug delivery platforms or nanoparticles, and more. Current state of the art would not be possible without decades of consecutive findings, during which, step by step, the technique was more understood. This review aims at providing an update regarding recent discoveriesâimprovements in the fabrication technology, a deeper understanding of the process, and a practical application of the materialâproviding a narrative supported with a proper background
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