The search for extraterrestrial intelligence: Telecommunications technology

Efforts to discover evidence of intelligent extraterrestrial life have become not only feasible, but respectable. Fledgling observational projects have begun that will use state-of-the-art hardware to develop sophisticated receiving and data processing systems. The rationale behind the Search for Extraterrestrial Intelligence, the manner in which the program is taking shape, and the implications for telecommunications are described. It is concluded that the breadth of technological development required for the detection of signals from galactic brethren has particular relevance for the future of telecommunications in Earth oriented uses

Migrant Farmworkers\u27 Perceptions of Pesticide Risk Exposure in Adams County, Pennsylvania: A Cultural Risk Assessment

Agricultural exceptionalism, a system in which regular labor laws and standards do not apply to farm labor, makes migrant farmworkers particularly vulnerable populations—economically, socially, and in terms of environmental health. To address inequities inherent in migrant farmworker margin­aliza­tion, studies advocate for actively engaging the migrant farmworker population in the conversation surrounding these issues. We conducted 40 semi­structured interviews with migrant farmworkers in Adams County, Pennsylvania, to understand pesti­cide risk exposure perceptions and practices. We employed the Health Belief Model as our cultural risk assessment frame, using it in combination with technical risk assessment, which uses government calculations (from the Environmental Protection Agency) to quantify pesticide risk exposure. We used mixed methods analyses (quantitative and qualitative) to compare and understand farmworker demographics, perceived risk, perceived control, and risk behavior. Results show that demo­graphics —e.g., age, education, visa status—are important factors in risk perception. They also confirm observations present in many earlier studies. While trainings and educational materials are valuable to help build awareness of risk, a systemic lack of control over their circumstances make it hard for migrant farmworkers to engage in safe behavior. Results also highlight the limitations of technical risk assessment. Such calculations, however, rarely account for risk perceptions and experiences of farm­workers themselves. Acknowledging the voices of migrant farmworkers is an essential first step in rebalancing inequities of power in our food systems, and cultural risk assessment can help frame recommendations that target different stake­holders across the pesticide regulatory spectrum to ensure migrant farmworker needs and safety

A simultaneous XMM-Newton and BeppoSAX observation of the archetypal Broad Line Seyfert 1 galaxy NGC 5548

We report the spectral analysis of a long XMM-Newton observation of the well-studied, moderate luminosity Broad Line Seyfert 1 galaxy NGC 5548. The source was at an historically average brightness and we find the hard (3-10 keV) spectrum can be well fitted by a power law of photon index gamma ~ 1.75, together with reflection. The only feature in the hard X-ray spectrum is a narrow emission line near 6.4 keV, with an equivalent width of ~ 60 eV. The energy and strength of this line is consistent with fluorescence from `neutral' iron distant from the central continuum source. We find no evidence for a broad Fe K line, with an upper limit well below previous reports, suggesting the inner accretion disc is now absent or highly ionised. The addition of simultaneous BeppoSAX data allows the analysis to be extended to 200 keV, yielding important constraints on the total reflection. Extrapolation of the hard X-ray power law down to 0.3 keV shows a clear `soft excess' below ~ 0.7 keV. After due allowance for the effects of a complex warm absorber, measured with the XMM-Newton RGS, we find the soft excess is better described as a smooth upward curvature in the continuum flux below ~ 2 keV. The soft excess can be modelled either by Comptonised thermal emission or by enhanced reflection from the surface of a highly ionised disc.Comment: 9 pages, 11 figures, accepted by MNRAS; minor changes to text and figure

Complex X-ray spectral variability in Mkn 421 observed with XMM-Newton

The bright blazar Mkn 421 has been observed four times for uninterrupted durations of ~ 9 - 13 hr during the performance verification and calibration phases of the XMM-Newton mission. The source was strongly variable in all epochs, with variability amplitudes that generally increased to higher energy bands. Although the detailed relationship between soft (0.1 - 0.75 keV) and hard (2 - 10 keV) band differed from one epoch to the next, in no case was there any evidence for a measurable interband lag, with robust upper limits of $| \tau | < 0.08$ hr in the best-correlated light curves. This is in conflict with previous claims of both hard and soft lags of ~1 hr in this and other blazars. However, previous observations suffered a repeated 1.6 hr feature induced by the low-Earth orbital period, a feature that is not present in the uninterrupted XMM-Newton data. The new upper limit on $|\tau|$ leads to a lower limit on the magnetic field strength and Doppler factor of B \delta^{1/3} \gs 4.7 G, mildly out of line with the predictions from a variety of homogeneous synchrotron self-Compton emission models in the literature of $B \delta^{1/3} = 0.2 - 0.8$ G. Time-dependent spectral fitting was performed on all epochs, and no detectable spectral hysteresis was seen. We note however that the source exhibited significantly different spectral evolutionary behavior from one epoch to the next, with the strongest correlations in the first and last and an actual divergance between soft and hard X-ray bands in the third. This indicates that the range of spectral variability behavior in Mkn 421 is not fully described in these short snippets; significantly longer uninterrupted light curves are required, and can be obtained with XMM-Newton.Comment: 21 pages, 4 figures, accepted for ApJ, scheduled for August 1, 200

Evidence for Rapid Iron K_alpha Line Flux Variability in MCG--6-30-15

This paper employs direct spectral fitting of individual orbital data in order to measure rapid X-ray iron K_alpha line and continuum spectral slope variations in Seyfert 1 galaxies with unprecedented temporal resolution. Application of this technique to a long RXTE observation of MCG--6-30-15 indicates that the line flux does vary on short (~1d) timescales, but that these variations are not correlated with changes in the continuum flux or slope. These rapid variations indicate that the line does indeed originate close to the black hole, confirming predictions based on its very broad profile. However, the lack of a correlation with the continuum presents problems for models in which the line variations are driven by those in the continuum, modified only by light-travel time effects. Instead, it may be that the line responds according to a physical process with a different time scale, such as ionization instabilities in the disk, or perhaps that the geometry and physical picture is more complex than implied by the simplest disk-corona models. These data also indicate that the slope of the underlying power-law continuum (Gamma) shows strong variability and is tightly correlated with the continuum flux in the sense that the spectrum steepens as the source brightens. All of these results have been checked with extensive simulations, which also indicated that a spurious correlation between Gamma and Compton reflection fraction (R) will result if these quantities are measured from the same spectra. This casts serious doubts on previous claims of such a Gamma-R correlation.Comment: Accepted for publication in Ap

ASSESSMENT OF LUNG CANCER RISK REDUCTION BEFORE AND AFTER ADOPTION OF A RADON RESISTANT NEW CONSTRUCTION (RRNC) BUILDING CODE STANDARD IN AMITY TOWNSHIP, PA

Radon 222 (222Rn) is an element found in the soil surrounding many homes in the United States. It is formed during the natural radioactive decay of uranium. Radon gas moves into homes through cracks or holes in the foundation and can then be inhaled by the home residents. Inhaled radon is the second leading cause of lung cancer after smoking and is the leading cause in non-smokers. Radon-Resistant New Construction (RRNC) reduces residential radon exposure and reduces the risk of developing lung cancer. Several townships and municipalities in Pennsylvania have adopted ordinances that require new houses to be built using RRNC. To evaluate the effectiveness of RRNC in reducing radon-related lung cancer risk, residential radon concentrations were compared in homes with and without RRNC in a Pennsylvania township that has adopted the RRNC statue into their building codes. This study utilizes a risk-based decision framework to assess the lung cancer risk reduction in Amity Township, PA after adoption of a RRNC standard. The work primarily uses data on residential radon measurements that have been compiled by the Pennsylvania Department of Environmental Protection (PADEP). These measurements are reported to the PADEP by certified testers and homeowners. The results from the initial analysis on the radon concentrations will be used in a peer-reviewed lung cancer risk model to examine the reduction in risk for residents of RRNC homes versus non-RRNC homes. This work also uses publicly available measurable characteristics of health indicators such as lung cancer incidence and mortality collected from and/or about Amity Township, PA. Because the smoking rates were not available down to the township level, the smoking rates of Berks County, PA (where Amity Township is located) will be utilized. The health and economic benefits of adopting an RRNC standard will also be reviewed as part of the decision process

Effect of Acid Adaptation on the Thermal Inactivation of Listeria monocytogenes in Heating Menstrua Having Various Combinations of pH and Water Activities

The impact of prior growth and food matrix conditions on thermal resistance of &lt;i&gt;L. monocytogenes&lt;/i&gt;, a causative agent of the foodborne illness listeriosis, was evaluated in this study. In an initial study ( Main Study #1), acid induced and non-induced cells of thirteen strains of &lt;i&gt;Listeria monocytogenes&lt;/i&gt; were placed into two heating menstrua: pH 3.0, water activity (Aw) 0.987 and pH 7.0, Aw 0.970. In twelve out of twenty-six combinations, non-induced cells were more heat resistant than induced cells. &lt;i&gt;L. monocytogenes&lt;/i&gt; strain #201, in a follow-up study ( Main Study #2) using a factorial design to test additional combinations of water activity and pH heating menstrua, non-acid-induced cells generally were more heat resistant than acid-induced cells although the acid-induced cells showed greater thermal resistance in the heating menstrua having the lowest pH values. An increase in thermal resistance could lead to underestimation of treatments necessary to eliminate potential contamination by &lt;i&gt;L. monocytogenes&lt;/i&gt;

Telecommunications systems design techniques handbook

Handbook presents design and analysis of tracking, telemetry, and command functions utilized in these systems with particular emphasis on deep-space telecommunications. Antenna requirements are also discussed. Handbook provides number of tables outlining various performance criteria. Block diagrams and performance charts are also presented