254 research outputs found
Increased traffic exposure and negative birth outcomes: a prospective cohort in Australia
Background: Pregnant women exposed to traffic pollution have an increased risk of negative birth outcomes. We aimed to investigate the size of this risk using a prospective cohort of 970 mothers and newborns in Logan, Queensland. ----- ----- Methods: We examined two measures of traffic: distance to nearest road and number of roads around the home. To examine the effect of distance we used the number of roads around the home in radii from 50 to 500 metres. We examined three road types: freeways, highways and main roads.----- ----- Results: There were no associations with distance to road. A greater number of freeways and main roads around the home were associated with a shorter gestation time. There were no negative impacts on birth weight, birth length or head circumference after adjusting for gestation. The negative effects on gestation were largely due to main roads within 400 metres of the home. For every 10 extra main roads within 400 metres of the home, gestation time was reduced by 1.1% (95% CI: -1.7, -0.5; p-value = 0.001).----- ----- Conclusions: Our results add weight to the association between exposure to traffic and reduced gestation time. This effect may be due to the chemical toxins in traffic pollutants, or because of disturbed sleep due to traffic noise
An Improved Neutron Electric Dipole Moment Experiment
A new measurement of the neutron EDM, using Ramsey's method of separated
oscillatory fields, is in preparation at the new high intensity source of
ultra-cold neutrons (UCN) at the Paul Scherrer Institute, Villigen, Switzerland
(PSI). The existence of a non-zero nEDM would violate both parity and time
reversal symmetry and, given the CPT theorem, might lead to a discovery of new
CP violating mechanisms. Already the current upper limit for the nEDM
(|d_n|<2.9E-26 e.cm) constrains some extensions of the Standard Model.
The new experiment aims at a two orders of magnitude reduction of the
experimental uncertainty, to be achieved mainly by (1) the higher UCN flux
provided by the new PSI source, (2) better magnetic field control with improved
magnetometry and (3) a double chamber configuration with opposite electric
field directions.
The first stage of the experiment will use an upgrade of the RAL/Sussex/ILL
group's apparatus (which has produced the current best result) moved from
Institut Laue-Langevin to PSI. The final accuracy will be achieved in a further
step with a new spectrometer, presently in the design phase.Comment: Flavor Physics & CP Violation Conference, Taipei, 200
An Improved Search for the Neutron Electric Dipole Moment
A permanent electric dipole moment of fundamental spin-1/2 particles violates
both parity (P) and time re- versal (T) symmetry, and hence, also charge-parity
(CP) symmetry since there is no sign of CPT-violation. The search for a neutron
electric dipole moment (nEDM) probes CP violation within and beyond the Stan-
dard Model. The experiment, set up at the Paul Scherrer Institute (PSI), an
improved, upgraded version of the apparatus which provided the current best
experimental limit, dn < 2.9E-26 ecm (90% C.L.), by the RAL/Sussex/ILL
collaboration: Baker et al., Phys. Rev. Lett. 97, 131801 (2006). In the next
two years we aim to improve the sensitivity of the apparatus to sigma(dn) =
2.6E-27 ecm corresponding to an upper limit of dn < 5E-27 ecm (95% C.L.), in
case for a null result. In parallel the collaboration works on the design of a
new apparatus to further increase the sensitivity to sigma(dn) = 2.6E-28 ecm.Comment: APS Division for particles and fields, Conference Proceedings, Two
figure
Athena: Advanced air launched space booster
The infrastructure for routine, reliable, and inexpensive access of space is a goal that has been actively pursued over the past 50 years, but has yet not been realized. Current launch systems utilize ground launching facilities which require the booster vehicle to plow up through the dense lower atmosphere before reaching space. An air launched system on the other hand has the advantage of being launched from a carrier aircraft above this dense portion of the atmosphere and hence can be smaller and lighter compared to its ground based counterpart. The goal of last year's Aerospace Engineering Course 483 (AE 483) was to design a 227,272 kg (500,000 lb.) air launched space booster which would beat the customer's launch cost on existing launch vehicles by at least 50 percent. While the cost analysis conducted by the class showed that this goal could be met, the cost and size of the carrier aircraft make it appear dubious that any private company would be willing to invest in such a project. To avoid this potential pitfall, this year's AE 483 class was to design as large an air launched space booster as possible which can be launched from an existing or modification to an existing aircraft. An initial estimate of the weight of the booster is 136,363 kg (300,000 lb.) to 159,091 kg (350,000 lb.)
Type-IV DCT, DST, and MDCT algorithms with reduced numbers of arithmetic operations
We present algorithms for the type-IV discrete cosine transform (DCT-IV) and
discrete sine transform (DST-IV), as well as for the modified discrete cosine
transform (MDCT) and its inverse, that achieve a lower count of real
multiplications and additions than previously published algorithms, without
sacrificing numerical accuracy. Asymptotically, the operation count is reduced
from ~2NlogN to ~(17/9)NlogN for a power-of-two transform size N, and the exact
count is strictly lowered for all N > 4. These results are derived by
considering the DCT to be a special case of a DFT of length 8N, with certain
symmetries, and then pruning redundant operations from a recent improved fast
Fourier transform algorithm (based on a recursive rescaling of the
conjugate-pair split radix algorithm). The improved algorithms for DST-IV and
MDCT follow immediately from the improved count for the DCT-IV.Comment: 11 page
Type-II/III DCT/DST algorithms with reduced number of arithmetic operations
We present algorithms for the discrete cosine transform (DCT) and discrete
sine transform (DST), of types II and III, that achieve a lower count of real
multiplications and additions than previously published algorithms, without
sacrificing numerical accuracy. Asymptotically, the operation count is reduced
from ~ 2N log_2 N to ~ (17/9) N log_2 N for a power-of-two transform size N.
Furthermore, we show that a further N multiplications may be saved by a certain
rescaling of the inputs or outputs, generalizing a well-known technique for N=8
by Arai et al. These results are derived by considering the DCT to be a special
case of a DFT of length 4N, with certain symmetries, and then pruning redundant
operations from a recent improved fast Fourier transform algorithm (based on a
recursive rescaling of the conjugate-pair split radix algorithm). The improved
algorithms for DCT-III, DST-II, and DST-III follow immediately from the
improved count for the DCT-II.Comment: 9 page
Diffuse reflection of ultracold neutrons from low-roughness surfaces
We report a measurement of the reflection of ultracold neutrons from flat, large-area plates of different Fermi potential materials with low surface roughness. The results were used to test two diffuse reflection models, the well-known Lambert model and the micro-roughness model which is based on wave scattering. The Lambert model fails to reproduce the diffuse reflection data. The surface roughness b and correlation length w , obtained by fitting the micro-roughness model to the data are in the range 1 b 3 nm and 10 w 120 nm, in qualitative agreement with independent measurements using atomic force microscop
Alzheimer's early detection in post-acute COVID-19 syndrome: a systematic review and expert consensus on preclinical assessments.
The risk of developing Alzheimer's disease (AD) in older adults increasingly is being discussed in the literature on Post-Acute COVID-19 Syndrome (PACS). Remote digital Assessments for Preclinical AD (RAPAs) are becoming more important in screening for early AD, and should always be available for PACS patients, especially for patients at risk of AD. This systematic review examines the potential for using RAPA to identify impairments in PACS patients, scrutinizes the supporting evidence, and describes the recommendations of experts regarding their use.
We conducted a thorough search using the PubMed and Embase databases. Systematic reviews (with or without meta-analysis), narrative reviews, and observational studies that assessed patients with PACS on specific RAPAs were included. The RAPAs that were identified looked for impairments in olfactory, eye-tracking, graphical, speech and language, central auditory, or spatial navigation abilities. The recommendations' final grades were determined by evaluating the strength of the evidence and by having a consensus discussion about the results of the Delphi rounds among an international Delphi consensus panel called IMPACT, sponsored by the French National Research Agency. The consensus panel included 11 international experts from France, Switzerland, and Canada.
Based on the available evidence, olfaction is the most long-lasting impairment found in PACS patients. However, while olfaction is the most prevalent impairment, expert consensus statements recommend that AD olfactory screening should not be used on patients with a history of PACS at this point in time. Experts recommend that olfactory screenings can only be recommended once those under study have reported full recovery. This is particularly important for the deployment of the olfactory identification subdimension. The expert assessment that more long-term studies are needed after a period of full recovery, suggests that this consensus statement requires an update in a few years.
Based on available evidence, olfaction could be long-lasting in PACS patients. However, according to expert consensus statements, AD olfactory screening is not recommended for patients with a history of PACS until complete recovery has been confirmed in the literature, particularly for the identification sub-dimension. This consensus statement may require an update in a few years
Gravitational depolarization of ultracold neutrons: comparison with data
We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin-depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data
Effective one-dimensionality of AC hopping conduction in the extreme disorder limit
It is argued that in the limit of extreme disorder AC hopping is dominated by
"percolation paths". Modelling a percolation path as a one-dimensional path
with a sharp jump rate cut-off leads to an expression for the universal AC
conductivity, that fits computer simulations in two and three dimensions better
than the effective medium approximation.Comment: 6 postscript figure
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