16,984 research outputs found
The Standard Cosmological Model and CMB Anisotropies
This is a course on cosmic microwave background (CMB) anisotropies in the
standard cosmological model, designed for beginning graduate students and
advanced undergraduates. ``Standard cosmological model'' in this context means
a Universe dominated by some form of cold dark matter (CDM) with adiabatic
perturbations generated at some initial epoch, e.g., Inflation, and left to
evolve under gravity alone (which distinguishes it from defect models). The
course is primarily theoretical and concerned with the physics of CMB
anisotropies in this context and their relation to structure formation. Brief
presentations of the uniform Big Bang model and of the observed large--scale
structure of the Universe are given. The bulk of the course then focuses on the
evolution of small perturbations to the uniform model and on the generation of
temperature anisotropies in the CMB. The theoretical development is performed
in the (pseudo--)Newtonian gauge because it aids intuitive understanding by
providing a quick reference to classical (Newtonian) concepts. The fundamental
goal of the course is not to arrive at a highly exact nor exhaustive
calculation of the anisotropies, but rather to a good understanding of the
basic physics that goes into such calculations.Comment: Course given at the International School of Space Science: 3K
Cosmology, held in L'Aquila, Italy, September 1998. 44 pages with 4 figure
Microwave dosimeter - A concept
Dosimeter determines time-integrated radiation dosage to which an individual is exposed. Integration is measured chemically in proportion to radiation detected. Wearer receives an exposure measurement representing an average of the dose over the entire body
Measuring cluster masses with CMB lensing: a statistical approach
We present a method for measuring the masses of galaxy clusters using the
imprint of their gravitational lensing signal on the cosmic microwave
background (CMB) temperature anisotropies. The method first reconstructs the
projected gravitational potential with a quadratic estimator and then applies a
matched filter to extract cluster mass. The approach is well-suited for
statistical analyses that bin clusters according to other mass proxies. We find
that current experiments, such as Planck, the South Pole Telescope and the
Atacama Cosmology Telescope, can practically implement such a statistical
methodology, and that future experiments will reach sensitivities sufficient
for individual measurements of massive systems. As illustration, we use
simulations of Planck observations to demonstrate that it is possible to
constrain the mass scale of a set of 62 massive clusters with prior information
from X-ray observations, similar to the published Planck ESZ-XMM sample. We
examine the effect of the thermal (tSZ) and kinetic (kSZ) Sunyaev-Zeldovich
(SZ) signals, finding that the impact of the kSZ remains small in this context.
The stronger tSZ signal, however, must be actively removed from the CMB maps by
component separation techniques prior to reconstruction of the gravitational
potential. Our study of two such methods highlights the importance of broad
frequency coverage for this purpose. A companion paper presents application to
the Planck data on the ESZ-XMM sample.Comment: 9 pages, 5 figures, version accepted for publication in A&
Metabolic simulation chamber
Metabolic simulation combustion chamber was developed as subsystem for breathing metabolic simulator. Entire system is used for evaluation of life support and resuscitation equipment. Metabolism subsystem simulates a human by consuming oxygen and producing carbon dioxide. Basic function is to simulate human metabolic range from rest to hard work
Point Source Confusion in SZ Cluster Surveys
We examine the effect of point source confusion on cluster detection in
Sunyaev-Zel'dovich (SZ) surveys. A filter matched to the spatial and spectral
characteristics of the SZ signal optimally extracts clusters from the
astrophysical backgrounds. We calculate the expected confusion (point source
and primary cosmic microwave background [CMB]) noise through this filter and
quantify its effect on the detection threshold for both single and multiple
frequency surveys. Extrapolating current radio counts, we estimate that
confusion from sources below 100 microJy limits single-frequency surveys to
1-sigma detection thresholds of Y 3.10^{-6} arcmin^2 at 30 GHz and Y 10^{-5}
arcmin^2 at 15 GHz (for unresolved clusters in a 2 arcmin beam); these numbers
are highly uncertain, and an extrapolation with flatter counts leads to much
lower confusion limits. Bolometer surveys must contend with an important
population of infrared point sources. We find that a three-band matched filter
with 1 arcminute resolution (in each band) efficiently reduces confusion, but
does not eliminate it: residual point source and CMB fluctuations contribute
significantly the total filter noise. In this light, we find that a 3-band
filter with a low-frequency channel (e.g, 90+150+220 GHz) extracts clusters
more effectively than one with a high frequency channel (e.g, 150+220+300 GHz).Comment: Accepted for publication in Astronomy & Astrophysics; Updated grant
information in acknowledgement
‘The intoxicated co-witness: How alcohol and discussion affect eyewitness memory reports.
Intoxicated witnesses are routinely encountered by law enforcement officers (Evans, Schreiber Compo & Russano, 2009). Such witnesses may have discussed details of the crime with each other prior to having their statement taken (Skagerberg & Wright, 2008). In order to understand the consequences of co-witness discussion on intoxicated witnesses, three studies were conducted investigating the effect of intoxication on misinformation when (a) the source of misinformation is a written statement from a seemingly intoxicated source in an online study; (b) when two intoxicated dyad partners engage in a face to face discussion in a laboratory based, alcohol administration study; and (c) when an intoxicated person encounters post event information from a sober video witness in the field.
The results suggest that intoxication does not influence the tendency to report misinformation. This is consistent when the source of misinformation is perceived to be intoxicated and the recipient is sober, both co-witnesses are intoxicated, or the recipient of misinformation is intoxicated whilst the source is sober. Intoxication also does not influence source monitoring ability. That is, both sober and intoxicated participants are equally able to identify the source of their memory recall. The results also add to the current literature on the effect of intoxication on eyewitness memory at an individual level. They demonstrate that at moderate doses, whilst accuracy is not impaired, intoxication may reduce the completeness of recall and the confidence a witness has in their memory. At higher doses however, in addition to the detrimental effects of alcohol on confidence and completeness, accuracy is also impaired.
The findings have implications for the criminal justice system given that intoxicated witnesses usually complete their evidential interview at a later date when sober (Crossland, Kneller & Wilcock, 2018). Witnesses who were intoxicated at the time of the crime and who engaged in co-witness discussion are no more prone than their sober counterparts to report co-witness information and are equally able to identify the source of the information that they report. Additionally, an intoxicated witness may report fewer details, and the accuracy of their statement may be influenced by their degree of intoxication. As such, breathalysing witnesses at the scene of the crime should be encouraged in order to understand the likely effect intoxication will have on their testimony
Temperature and humidity control of simulated human breath
Subsystem was developed for breathing metabolic simulator which adjusts temperature and humidity of air to levels of human exhaled breath. Temperature-humidity subsystem is described, consisting of aluminum enclosure with 400 watt heat sheet glued to bottom, vertical separators, inlet connection, and check valve
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