14,999 research outputs found
Effects of drinking-water filtration on Cryptosporidium Seroepidemiology, Scotland
Continuous exposure to low levels of Cryptosporidium oocysts is associated with production of protective antibodies. We investigated prevalence of antibodies against the 27-kDa Cryptosporidium oocyst antigen among blood donors in 2 areas of Scotland supplied by drinking water from different sources with different filtration standards: Glasgow (not filtered) and Dundee (filtered). During 2006ā2009, seroprevalence and risk factor data were collected; this period includes 2007, when enhanced filtration was introduced to the Glasgow supply. A serologic response to the 27-kDa antigen was found for ā75% of donors in the 2 cohorts combined. Mixed regression modeling indicated a 32% step-change reduction in seroprevalence of antibodies against Cryptosporidium among persons in the Glasgow area, which was associated with introduction of enhanced filtration treatment. Removal of Cryptosporidium oocysts from water reduces the risk for waterborne exposure, sporadic infections, and outbreaks. Paradoxically, however, oocyst removal might lower immunity and increase the risk for infection from other sources
HOLLYWOOD:The political economy and global citation of an emblematic language object
The HOLLYWOOD sign is arguably the world's most famous language object. Emblematic of prestige and cultural capital, the sign can be found not just in Los Angeles, but in citations all over the world. Beginning with the history of its valorization, HOLLYWOOD is shown to emanate symbolic value through a set of enregistered semiotic features. Drawing upon a set of globally sourced citations of HOLLYWOOD, the circulation and stratified bundling of size, emplacement, alignment, typeface, and color indicates how the citation of language objects is mediated by political economy. A process of diffuse citation is further observed, in which the quotation of language features is not overt, but the source of emanation is still tangible, revealing HOLLYWOOD as the source of a global linguistic-semiotic register. As this register circulates in citations overt and diffuse, language objects are revealed as key sites for the reproduction of commodity values. (The Hollywood sign, language object, citation, enregisterment, global emblems, recontexualization)
Was Adam Smith an individualist?
Smith is generally regarded as an individualist without qualification. This article argues that his predominantly individualist policy prescription is rooted in a more complex philosophy. He sees nature, including human nature, as a vast machine supervised by God and designed to maximize human happiness. Human weaknesses, as well as strengths, display the wisdom of God and play their part in this scheme. While Smith pays lip-service to justice, it is really social order that preoccupies him, and, within that, the defence of property. Individuals are valued as bearers of property. As persons, individuals are deceived by nature into acting in a socially beneficial way. In different ways Smith systematically denies the autonomy of the individual with respect to the whole of which he or she is part. For Smith, individual liberty is not the end, but the means, of sustaining social order and property
Characterization of a temperature-sensitive DNA ligase from Escherichia coli
DNA ligases are essential enzymes in cells due to their ability to join DNA strand breaks formed during DNA replication. Several temperature-sensitive mutant strains of Escherichia coli, including strain GR501, have been described which can be complemented by functional DNA ligases. Here, it is shown that the ligA251 mutation in E. coli GR501 strain is a cytosine to thymine transition at base 43, which results in a substitution of leucine by phenylalanine at residue 15. The protein product of this gene (LigA251) is accumulated to a similar level at permissive and non-permissive temperatures. Compared to wild-type LigA, at 20 Ā°C purified LigA251 has 20-fold lower ligation activity in vitro, and its activity is reduced further at 42 Ā°C, resulting in 60-fold lower ligation activity than wild-type LigA. It is proposed that the mutation in LigA251 affects the structure of the N-terminal region of LigA. The resulting decrease in DNA ligase activity at the non-permissive temperature is likely to occur as the result of a conformational change that reduces the rate of adenylation of the ligase
Coagulation and fragmentation processes with evolving size and shape profiles : a semigroup approach
We investigate a class of bivariate coagulation-fragmentation equations. These equations describe the evolution of a system of particles that are characterised not only by a discrete size variable but also by a shape variable which can be either discrete or continuous. Existence and uniqueness of strong solutions to the associated abstract Cauchy problems are established by using the theory of substochastic semigroups of operators
The impact of intraoperative adverse events on orthopaedic surgery residents
Background: The goal of this study was to quantify the impact of intraoperative adverse events on orthopaedics residents to better understand how these occurrences affect resident training. Additionally, the study identified the emotional toll of adverse events on trainees and barriers to reporting.Methods: An anonymous 26 question web-based survey was adapted from the Boston intraoperative adverse events surgeonsā attitude study (BISA) survey to be applicable to orthopaedic residents. The survey was sent to orthopaedic residency program coordinators listed in the Council of Orthopaedic Residency Directors (CORD) database. The coordinators then distributed the survey to each programās residents and fellows.Results: 77 orthopaedic residents and fellows completed the survey. Almost all (84.4%) reported having been involved in an IAE during their training, and the majority (80.6%) experienced emotional distress as a result. 50.7% of respondents have never been involved in discussions with patients or their family regarding a complication during their training.Conclusions: The majority of residents have experienced emotional distress following an intraoperative adverse event, but residents are not routinely involved in subsequent discussions with patients and families following complications. This represents a significant area for improvement in both supporting and training surgical residents
New Evidence for Efficient Collisionless Heating of Electrons at the Reverse Shock of a Young Supernova Remnant
Although collisionless shocks are ubiquitous in astrophysics, certain key
aspects of them are not well understood. In particular, the process known as
collisionless electron heating, whereby electrons are rapidly energized at the
shock front, is one of the main open issues in shock physics. Here we present
the first clear evidence for efficient collisionless electron heating at the
reverse shock of Tycho's supernova remnant (SNR), revealed by Fe-K diagnostics
using high-quality X-ray data obtained by the Suzaku satellite. We detect
K-beta (3p->1s) fluorescence emission from low-ionization Fe ejecta excited by
energetic thermal electrons at the reverse shock front, which peaks at a
smaller radius than Fe K-alpha (2p->1s) emission dominated by a relatively
highly-ionized component. Comparison with our hydrodynamical simulations
implies instantaneous electron heating to a temperature 1000 times higher than
expected from Coulomb collisions alone. The unique environment of the reverse
shock, which is propagating with a high Mach number into rarefied ejecta with a
low magnetic field strength, puts strong constraints on the physical mechanism
responsible for this heating, and favors a cross-shock potential created by
charge deflection at the shock front. Our sensitive observation also reveals
that the reverse shock radius of this SNR is about 10% smaller than the
previous measurement using the Fe K-alpha morphology from the Chandra
observations. Since strong Fe K-beta fluorescence is expected only from
low-ionization plasma where Fe ions still have many 3p electrons, this feature
is key to diagnosing the plasma state and distribution of the immediate
postshock ejecta in a young SNR.Comment: 7 pages, 9 figures, resubmitted to ApJ with minor changes following
the referee repor
Cues, context, and long-term memory: the role of the retrosplenial cortex in spatial cognition
Spatial navigation requires representations of landmarks and other navigation cues. The retrosplenial cortex (RSC) is anatomically positioned between limbic areas important for memory formation, such as the hippocampus and the anterior thalamus, and cortical regions along the dorsal stream known to contribute importantly to long-term spatial representation, such as the posterior parietal cortex. Damage to the RSC severely impairs allocentric representations of the environment, including the ability to derive navigational information from landmarks. The specific deficits seen in tests of human and rodent navigation suggest that the RSC supports allocentric representation by processing the stable features of the environment and the spatial relationships among them. In addition to spatial cognition, the RSC plays a key role in contextual and episodic memory. The RSC also contributes importantly to the acquisition and consolidation of long-term spatial and contextual memory through its interactions with the hippocampus. Within this framework, the RSC plays a dual role as part of the feedforward network providing sensory and mnemonic input to the hippocampus and as a target of the hippocampal-dependent systems consolidation of long-term memory
Machine learning the relationship between Debye temperature and superconducting transition temperature
Recently a relationship between the Debye temperature and the
superconducting transition temperature of conventional superconductors
has been proposed [npj Quantum Materials , 59 (2018)]. The
relationship indicates that for phonon-mediated BCS
superconductors, with being a pre-factor of order . In order to
verify this bound, we train machine learning (ML) models with 10,330 samples in
the Materials Project database to predict . By applying our ML models
to 9,860 known superconductors in the NIMS SuperCon database, we find that the
conventional superconductors in the database indeed follow the proposed bound.
We also perform first-principles phonon calculations for HS and
LaH at 200 GPa. The calculation results indicate that these
high-pressure hydrides essentially saturate the bound of versus
.Comment: 10 pages, 5 figure
Candidate Type II Quasars at 2 < z < 4.3 in the Sloan Digital Sky Survey III
At low redshifts, dust-obscured quasars often have strong yet narrow
permitted lines in the rest-frame optical and ultraviolet, excited by the
central active nucleus, earning the designation Type II quasars. We present a
sample of 145 candidate Type II quasars at redshifts between 2 and 4.3,
encompassing the epoch at which quasar activity peaked in the universe. These
objects, selected from the quasar sample of the Baryon Oscillation
Spectroscopic Survey of the Sloan Digital Sky Survey III, are characterized by
weak continuum in the rest-frame ultraviolet (typical continuum magnitude of i
\approx 22) and strong lines of CIV and Ly \alpha, with Full Width at Half
Maximum less than 2000 kms-1. The continuum magnitudes correspond to an
absolute magnitude of -23 or brighter at redshift 3, too bright to be due
exclusively to the host galaxies of these objects. Roughly one third of the
objects are detected in the shorter-wavelength bands of the WISE survey; the
spectral energy distributions (SEDs) of these objects appear to be intermediate
between classic Type I and Type II quasars seen at lower redshift. Five objects
are detected at rest frame 6\mu m by Spitzer, implying bolometric luminosities
of several times 10^46 erg s-1. We have obtained polarization measurements for
two objects; they are roughly 3% polarized. We suggest that these objects are
luminous quasars, with modest dust extinction (A_V ~ 0.5 mag), whose
ultraviolet continuum also includes a substantial scattering contribution.
Alternatively, the line of sight to the central engines of these objects may be
partially obscured by optically thick material.Comment: 26 pages, 13 figures, 10 tables, 4 machine readable tables. Accepted
for publication in MNRA
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