Single Photon Source with Individualized Single Photon Certifications

As currently implemented, single-photon sources cannot be made to produce single photons with high probability, while simultaneously suppressing the probability of yielding two or more photons. Because of this, single photon sources cannot really produce single photons on demand. We describe a multiplexed system that allows the probabilities of producing one and more photons to be adjusted independently, enabling a much better approximation of a source of single photons on demand. The scheme uses a heralded photon source based on parametric downconversion, but by effectively breaking the trigger detector area into multiple regions, we are able to extract more information about a heralded photon than is possible with a conventional arrangement. This scheme allows photons to be produced along with a quantitative ``certification'' that they are single photons. Some of the single-photon certifications can be significantly better than what is possible with conventional downconversion sources (using a unified trigger detector region), as well as being better than faint laser sources. With such a source of more tightly certified single photons, it should be possible to improve the maximum secure bit rate possible over a quantum cryptographic link. We present an analysis of the relative merits of this method over the conventional arrangement.Comment: 11 pages, 5 figures, SPIE Free-Space Laser Communication and Laser Imaging II. To appear in the proceeding of SPIE Free-Space Laser Communication and Laser Imaging II, vol 482

A Study of the School Lunch Situation In Houston County Texas

The development of the physical health of children has come to be regarded as an important part of education. A better understanding of the relation of diet to disease has resulted in studies of the food habits and health habits of children with a view to improving them. Through studies made by doctors and dietitians, it has been found that health depends to a very large extent on correct eating habits, and that children must have food in proper quantities and of the right kind. Physical health is essential to the development of mental and moral health, which make for effective living, growth and development. Therefore it is very necessary that children form correct eating habits while they are young

Lymphotoxins and cytomegalovirus cooperatively induce interferon-beta, establishing host-virus détente

Tumor necrosis factor (TNF)-related cytokines regulate cell death and survival and provide strong selective pressures for viruses, such as cytomegalovirus (CMV), to evolve counterstrategies in order to persist in immune-competent hosts. Signaling by the lymphotoxin (LT)-β receptor or TNF receptor-1, but not Fas or TRAIL receptors, inhibits the cytopathicity and replication of human CMV by a nonapoptotic, reversible process that requires nuclear factor κB (NF-κB)-dependent induction of interferon-β (IFN-β). Efficient induction of IFN-β requires virus infection and LT signaling, demonstrating the need for both host and viral factors in the curtailment of viral replication without cellular elimination. LTα-deficient mice and LTβR-Fc transgenic mice were profoundly susceptible to murine CMV infection. Together, these results reveal an essential and conserved role for LTs in establishing host defense to CMV

Fusing Information in a 3D Chart-of-the-Future Display

The Data Visualization Research Lab at the Center for Coastal and Ocean Mapping is investigating how three-dimensional navigational displays can most effectively be constructed. This effort is progressing along multiple paths and is implemented in the GeoNav3D system, a 3D chart-of-the-future research prototype. We present two lines of investigation here. First, we explore how tide, depth, and planning information can be combined (fused) into a single view, in order to give the user a more realistic picture of effective water depths. In the GeoNav3D system, 3D shaded bathymetry, coded for color depth, is used to display navigable areas. As in ENC displays, different colors are used to easily identify areas that are safe, areas where under-keel clearance is minimal, and areas where depths are too shallow. Real-time or model-generated tide information is taken into account in dynamically color-coding the depths. One advantage to using a continuous bathymetric model, versus discrete depth areas, is that the model can be continuously adjusted for water level. This concept is also extended for planning purposes by displaying the color-coded depths along a proposed corridor at the expected time of reaching each point. In our second line of investigation, we explore mechanisms for linking information from multiple 3D views into a coherent whole. In GeoNav3D, it is possible to create a variety of plan and perspective views, and these views can be attached to moving reference frames. This provides not only semi-static views such as from-the-bridge and under-keel along-track profile views, but also more dynamic, interactive views. These views are linked through visual devices that allow the fusion of information from among the views. We present several such devices and show how they highlight relevant details and help to minimize user confusion. Investigation into the utility of various linked views for aiding realsituation decision-making is ongoin

Point Process Algorithm: A New Bayesian Approach for Planet Signal Extraction with the Terrestrial Planet Finder

The capability of the Terrestrial Planet Finder Interferometer (TPF-I) for planetary signal extraction, including both detection and spectral characterization, can be optimized by taking proper account of instrumental characteristics and astrophysical prior information. We have developed the Point Process Algorithm (PPA), a Bayesian technique for extracting planetary signals using the sine-chopped outputs of a dual nulling interferometer. It is so-called because it represents the system being observed as a set of points in a suitably-defined state space, thus providing a natural way of incorporating our prior knowledge of the compact nature of the targets of interest. It can also incorporate the spatial covariance of the exozodi as prior information which could help mitigate against false detections. Data at multiple wavelengths are used simultaneously, taking into account possible spectral variations of the planetary signals. Input parameters include the RMS measurement noise and the a priori probability of the presence of a planet. The output can be represented as an image of the intensity distribution on the sky, optimized for the detection of point sources. Previous approaches by others to the problem of planet detection for TPF-I have relied on the potentially non-robust identification of peaks in a "dirty" image, usually a correlation map. Tests with synthetic data suggest that the PPA provides greater sensitivity to faint sources than does the standard approach (correlation map + CLEAN), and will be a useful tool for optimizing the design of TPF-I.Comment: 17 pages, 6 figures. AJ in press (scheduled for Nov 2006

The frequency of item writing flaws in multiple-choice questions used in high stakes nursing assessments

Multiple-choice questions are a common assessment method in nursing examinations. Few nurse educators, however, have formal preparation in constructing multiple-choice questions. Consequently, questions used in baccalaureate nursing assessments often contain item-writing flaws, or violations to accepted item-writing guidelines. In one nursing department, 2770 MCQs were collected from tests and examinations administered over a five-year period from 2001 to 2005. Questions were evaluated for 19 frequently occurring item-writing flaws, for cognitive level, for question source, and for the distribution of correct answers. Results show that almost half (46.2%) of the questions contained violations of item-writing guidelines and over 90% were written at low cognitive levels. Only a small proportion of questions were teacher generated (14.1%), while 36.2% were taken from testbanks and almost half (49.4%) had no source identified. MCQs written at a lower cognitive level were significantly more likely to contain item-writing flaws. While there was no relationship between the source of the question and item-writing flaws, teachergenerated questions were more likely to be written at higher cognitive levels (p < 0.001). Correct answers were evenly distributed across all four options and no bias was noted in the placement of correct options. Further training in item-writing is recommended for all faculty members who are responsible for developing tests. Pre-test review and quality assessment is also recommended to reduce the occurrence of item-writing flaws and to improve the quality of test questions. © 2006 Elsevier Ltd. All rights reserved.postprin