4,370 research outputs found
Inferences Drawn from a Risk Assessment Compared Directly with a Randomized Trial of a Home Drinking Water Intervention
Risk assessments and intervention trials have been used by the U.S. Environmental Protection Agency to estimate drinking water health risks. Seldom are both methods used concurrently. Between 2001 and 2003, illness data from a trial were collected simultaneously with exposure data, providing a unique opportunity to compare direct risk estimates of waterborne disease from the intervention trial with indirect estimates from a risk assessment. Comparing the group with water treatment (active) with that without water treatment (sham), the estimated annual attributable disease rate (cases per 10,000 persons per year) from the trial provided no evidence of a significantly elevated drinking water risk [attributable risk = −365 cases/year, sham minus active; 95% confidence interval (CI), −2,555 to 1,825]. The predicted mean rate of disease per 10,000 persons per person-year from the risk assessment was 13.9 (2.5, 97.5 percentiles: 1.6, 37.7) assuming 4 log removal due to viral disinfection and 5.5 (2.5, 97.5 percentiles: 1.4, 19.2) assuming 6 log removal. Risk assessments are important under conditions of low risk when estimates are difficult to attain from trials. In particular, this assessment pointed toward the importance of attaining site-specific treatment data and the clear need for a better understanding of viral removal by disinfection. Trials provide direct risk estimates, and the upper confidence limit estimates, even if not statistically significant, are informative about possible upper estimates of likely risk. These differences suggest that conclusions about waterborne disease risk may be strengthened by the joint use of these two approaches
Colliding Hadrons as Cosmic Membranes and Possible Signatures of Lost Momentum
We argue that in the TeV-gravity scenario high energy hadrons colliding on
the 3-brane embedded in D=4+n-dimensional spacetime, with n dimensions smaller
than the hadron size, can be considered as cosmic membranes. In the
5-dimensional case these cosmic membranes produce effects similar to cosmic
strings in the 4-dimensional world. We calculate the corrections to the eikonal
approximation for the gravitational scattering of partons due to the presence
of effective hadron cosmic membranes. Cosmic membranes dominate the momentum
lost in the longitudinal direction for colliding particles that opens new
channels for particle decays.Comment: 15 pages, Late
The effect of the systemic inflammatory response on plasma vitamin 25 (OH) D concentrations adjusted for albumin
<b>Aim</b><p></p>
To examine the relationship between plasma 25(OH)D, CRP and albumin concentrations in two patient cohorts.<p></p>
<b>Methods</b><p></p>
5327 patients referred for nutritional assessment and 117 patients with critical illness were examined. Plasma 25 (OH) D concentrations were measured using standard methods. Intra and between assay imprecision was <10%.<p></p>
<b>Result</b><p></p>
In the large cohort, plasma 25 (OH) D was significantly associated with CRP (rs = −0.113, p<0.001) and albumin (rs = 0.192, p<0.001). 3711 patients had CRP concentrations ≤10 mg/L; with decreasing albumin concentrations ≥35, 25–34 and <25 g/l, median concentrations of 25 (OH) D were significantly lower from 35 to 28 to 14 nmol/l (p<0.001). This decrease was significant when albumin concentrations were reduced between 25–34 g/L (p<0.001) and when albumin <25 g/L (p<0.001). 1271 patients had CRP concentrations between 11–80 mg/L; with decreasing albumin concentrations ≥35, 25–34 and <25 g/l, median concentrations of 25 (OH) D were significantly lower from 31 to 24 to 19 nmol/l (p<0.001). This decrease was significant when albumin concentration were 25–34 g/L (p<0.001) and when albumin <25 g/L (p<0.001). 345 patients had CRP concentrations >80 mg/L; with decreasing albumin concentrations ≥35, 25–34 and <25 g/l, median concentrations of 25 (OH) D were not significantly altered varying from 19 to 23 to 23 nmol/l. Similar relationships were also obtained in the cohort of patients with critical illness.<p></p>
<b>Conclusion</b><p></p>
Plasma concentrations of 25(OH) D were independently associated with both CRP and albumin and consistent with the systemic inflammatory response as a major confounding factor in determining vitamin D status.<p></p>
Adaptive memory: Stereotype activation is not enough
Studies have shown that survival processing leads to superior memorability. The aim of the present study was to examine whether this survival recall advantage might result from stereotype activation. To test this hypothesis, we conducted a pilot study and two experiments in which participants were primed with stereotypes (Experiment 1, professor and elderly person; Experiment 2, survival-stereotype). In Experiment 1, 120 undergraduates were randomly assigned to a survival, professor stereotype, elderly person stereotype, or moving scenario and rated words for their relevance to the imagined scenario. In Experiment 2, 75 undergraduates were given a survival, survival-stereotype (based on our pilot study), or moving scenario. Both experiments showed that survival processing leads to a greater recall advantage over the stereotype groups and control group. These data indicate that the mere activation of stereotypes cannot explain the survival recall advantage
Mid-infrared optical parametric amplifier using silicon nanophotonic waveguides
All-optical signal processing is envisioned as an approach to dramatically
decrease power consumption and speed up performance of next-generation optical
telecommunications networks. Nonlinear optical effects, such as four-wave
mixing (FWM) and parametric gain, have long been explored to realize
all-optical functions in glass fibers. An alternative approach is to employ
nanoscale engineering of silicon waveguides to enhance the optical
nonlinearities by up to five orders of magnitude, enabling integrated
chip-scale all-optical signal processing. Previously, strong two-photon
absorption (TPA) of the telecom-band pump has been a fundamental and
unavoidable obstacle, limiting parametric gain to values on the order of a few
dB. Here we demonstrate a silicon nanophotonic optical parametric amplifier
exhibiting gain as large as 25.4 dB, by operating the pump in the mid-IR near
one-half the band-gap energy (E~0.55eV, lambda~2200nm), at which parasitic
TPA-related absorption vanishes. This gain is high enough to compensate all
insertion losses, resulting in 13 dB net off-chip amplification. Furthermore,
dispersion engineering dramatically increases the gain bandwidth to more than
220 nm, all realized using an ultra-compact 4 mm silicon chip. Beyond its
significant relevance to all-optical signal processing, the broadband
parametric gain also facilitates the simultaneous generation of multiple
on-chip mid-IR sources through cascaded FWM, covering a 500 nm spectral range.
Together, these results provide a foundation for the construction of
silicon-based room-temperature mid-IR light sources including tunable
chip-scale parametric oscillators, optical frequency combs, and supercontinuum
generators
Steam reforming on transition-metal carbides from density-functional theory
A screening study of the steam reforming reaction (CH_4 + H_2O -> CO + 3H_2)
on early transition-metal carbides (TMC's) is performed by means of
density-functional theory calculations. The set of considered surfaces includes
the alpha-Mo_2C(100) surfaces, the low-index (111) and (100) surfaces of TiC,
VC, and delta-MoC, and the oxygenated alpha-Mo_2C(100) and TMC(111) surfaces.
It is found that carbides provide a wide spectrum of reactivities towards the
steam reforming reaction, from too reactive via suitable to too inert. The
reactivity is discussed in terms of the electronic structure of the clean
surfaces. Two surfaces, the delta-MoC(100) and the oxygen passivated
alpha-Mo_2C(100) surfaces, are identified as promising steam reforming
catalysts. These findings suggest that carbides provide a playground for
reactivity tuning, comparable to the one for pure metals.Comment: 6 pages, 4 figure
Spectral Line-by-Line Pulse Shaping of an On-Chip Microresonator Frequency Comb
We report, for the first time to the best of our knowledge, spectral phase
characterization and line-by-line pulse shaping of an optical frequency comb
generated by nonlinear wave mixing in a microring resonator. Through
programmable pulse shaping the comb is compressed into a train of
near-transform-limited pulses of \approx 300 fs duration (intensity full width
half maximum) at 595 GHz repetition rate. An additional, simple example of
optical arbitrary waveform generation is presented. The ability to characterize
and then stably compress the frequency comb provides new data on the stability
of the spectral phase and suggests that random relative frequency shifts due to
uncorrelated variations of frequency dependent phase are at or below the 100
microHertz level.Comment: 18 pages, 4 figure
Aharonov-Bohm interferences from local deformations in graphene
One of the most interesting aspects of graphene is the tied relation between
structural and electronic properties. The observation of ripples in the
graphene samples both free standing and on a substrate has given rise to a very
active investigation around the membrane-like properties of graphene and the
origin of the ripples remains as one of the most interesting open problems in
the system. The interplay of structural and electronic properties is
successfully described by the modelling of curvature and elastic deformations
by fictitious gauge fields that have become an ex- perimental reality after the
suggestion that Landau levels can form associated to strain in graphene and the
subsequent experimental confirmation. Here we propose a device to detect
microstresses in graphene based on a scanning-tunneling-microscopy setup able
to measure Aharonov-Bohm inter- ferences at the nanometer scale. The
interferences to be observed in the local density of states are created by the
fictitious magnetic field associated to elastic deformations of the sample.Comment: Some bugs fixe
- …