639 research outputs found
Auto and cross correlation of phases of the whole-sky CMB and foreground maps from the 1-year WMAP data
The issue of non-Gaussianity is not only related to distinguishing the
theories of the origin of primordial fluctuations, but also crucial for the
determination of cosmological parameters in the framework of inflation
paradigm. We present an advenced method for testing non-Gaussianity on the
whole-sky CMB anisotropies. This method is based on the Kuiper's statistic to
probe the two-dimensional uniformity on a periodic mapping square associating
phases: return mapping of phases of the derived CMB (similar to auto
correlation) and cross correlations between phases of the derived CMB and
foregrounds. Since phases reflect morphology, detection of cross correlation of
phases signifies the contamination of foreground signals in the derived CMB
map. The advantage of this method is that one can cross check the auto and
cross correlation of phases of the derived CMB and foregrounds, and mark off
those multipoles in which the non-Gaussianity results from the foreground
contaminations. We apply this statistic on the derived signals from the 1-year
WMAP data. The auto-correlations of phases from the ILC map shows the
significance above 95% CL against the random phase hypothesis on 17 spherical
harmonic multipoles, among which some have pronounced cross correlations with
the foreground maps. We conclude that most of the non-Gaussianity found in the
derived CMB maps are from foreground contaminations, except, among others, l=6.
With this method we are better equipped to approach the issue of
non-Gaussianity of primordial origin for the upcoming PLANCK mission.Comment: 2 figures added: new representation of reconstructed (from 1D Fourier
composition) DT distribution for each multipole number el
Secure neighborhood creation in wireless ad hoc networks using hop count discrepancies
A fundamental requirement for nodes in ad hoc and sensor networks is the ability to correctly determine their neighborhood. Many applications, protocols, and network wide functions rely on correct neighborhood discovery. Malicious nodes that taint neighborhood information using wormholes can significantly disrupt the operation of ad hoc networks. Protocols that depend only on cryptographic techniques (e.g, authentication and encryption) may not be able to detect or prevent such attacks. In this paper we propose SECUND, a protocol for creating a SECUre NeighborhooD, that makes use of discrepancies in routing hop count information to detect "true" neighbors and remove those links to nodes that appear to be neighbors, but are not really neighbors. SECUND is simple, localized and needs no special hardware, localization, or synchronization. We evaluate SECUND using simulations and demonstrate its effectiveness in the presence of multiple and multi-ended wormholes. Lastly, we present approaches to improve the efficiency of the SECUND process. © Springer Science+Business Media, LLC 2010
Experimental verification of strong rotational dependence of fluorescence and predissociation yield in the bâÂčΠᔀ(v = 1) level of ÂčâŽNâ
New, rotationally resolved fluorescence-excitation spectra confirm coupled-channel SchroÌdinger-equation predictions of strong rotational dependence of the fluorescence and predissociation yields in the b(v = 1) level of ÂčâŽNâ.This work was supported by the National Science Foundation
grant AST-0906158 and the Australian Research Council
grants DP0558962, DP0773050, and LX0882438
Acoustic Energy and Momentum in a Moving Medium
By exploiting the mathematical analogy between the propagation of sound in a
non-homogeneous potential flow and the propagation of a scalar field in a
background gravitational field, various wave ``energy'' and wave ``momentum''
conservation laws are established in a systematic manner. In particular the
acoustic energy conservation law due to Blokhintsev appears as the result of
the conservation of a mixed co- and contravariant energy-momentum tensor, while
the exchange of relative energy between the wave and the mean flow mediated by
the radiation stress tensor, first noted by Longuet-Higgins and Stewart in the
context of ocean waves, appears as the covariant conservation of the doubly
contravariant form of the same energy-momentum tensor.Comment: 25 Pages, Late
Decrease in seroprevalence of Hepatitis A after the implementation of nationwide disposable tableware use in Taiwan
<p>Abstract</p> <p>Background</p> <p>Taiwan is an endemic area of viral hepatitis, including hepatitis A, which is transmitted mainly from the fecal-oral route. In order to reduce the transmission through food intake, the government implemented a policy of nationwide disposal tableware use in public eating places in 1982. We conducted a study to estimate the seroprevalence of Hepatitis A in a group of workers in Taiwan in 2005, determine the risk factors, and compare seroprevalence to published estimates in Taiwan to evaluate changes in the seroprevalence after the implementation of the nationwide disposal tableware use.</p> <p>Methods</p> <p>We recruited workers of an industrial park during their annual health examinations in 2005 and measured their anti-hepatitis A virus IgG titer using microparticle enzyme immunoassay. We compared the seroprevalence across different birth cohorts within the study population and also analyzed data from previous studies.</p> <p>Results</p> <p>The overall sero-positive rate was 22.0% in the 11,777 participants. The rate was much lower among those who were covered by the program since birth (born after 1982) in comparison with those who were not (2.7% vs. 25.3%, p < 0.001). From the analyses of data from pervious studies, we found the age-specific rates were similar in cohorts born in or after 1982 across studies conducted in different time periods but decreased with the calendar year in cohorts born before 1982. In particular, the age-specific seroprevalence dropped to less than one third in a three-year period among those who were born around 1982.</p> <p>Conclusions</p> <p>Data from both the current and previous studies in different time periods supported the effectiveness of disposal tableware in preventing the transmission of hepatitis A.</p
Using Web Search Query Data to Monitor Dengue Epidemics: A New Model for Neglected Tropical Disease Surveillance
A variety of obstacles, including bureaucracy and lack of resources, delay detection and reporting of dengue and exist in many countries where the disease is a major public health threat. Surveillance efforts have turned to modern data sources such as Internet usage data. People often seek health-related information online and it has been found that the frequency of, for example, influenza-related web searches as a whole rises as the number of people sick with influenza rises. Tools have been developed to help track influenza epidemics by finding patterns in certain web search activity. However, few have evaluated whether this approach would also be effective for other diseases, especially those that affect many people, that have severe consequences, or for which there is no vaccine. In this study, we found that aggregated, anonymized Google search query data were also capable of tracking dengue activity in Bolivia, Brazil, India, Indonesia and Singapore. Whereas traditional dengue data from official sources are often not available until after a long delay, web search query data is available for analysis within a day. Therefore, because it could potentially provide earlier warnings, these data represent a valuable complement to traditional dengue surveillance
Author Correction: Cross-ancestry genome-wide association analysis of corneal thickness strengthens link between complex and Mendelian eye diseases.
Emmanuelle Souzeau, who contributed to analysis of data, was inadvertently omitted from the author list in the originally published version of this Article. This has now been corrected in both the PDF and HTML versions of the Article
Spectral theory of Taylor vortices
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46192/1/205_2004_Article_BF00252461.pd
Nasopharyngeal Carcinoma Metastatic to the Mandible
Nasopharyngeal carcinoma (NPC) is one of the most common malignancies in the head and neck region, especially
among those of Chinese origin. NPC has multifactorial aetiologies including genetic susceptibility, consumption of
food with high salt content, and the EpsteinâBarr virus. The primary tumour usually arises from the lateral walls of the
nasopharynx and is characterized by a rich sub-mucosal lymphatic structure, often leading to cervical lymph node metastasis.
Distant metastasis has been recognized to be a major cause of treatment failure in patients with nasopharyngeal carcinoma.
Bone, liver and lung are the most frequent sites of NPC metastases
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