Generation and orientation of organoxenon molecule H–Xe–CCH in the gas phase

We report on the first observation of the organoxenon HXeCCH molecule in the gas phase. This molecule has been prepared in a molecular beam experiment by 193 nm photolysis of an acetylene molecule on Xen clusters (¯n ≈ 390). Subsequently the molecule has been oriented via the pseudofirst-order Stark effect in a strong electric field of the polarized laser light combined with the weak electrostatic field in the extraction region of a time-of-flight spectrometer. The experimental evidence for the oriented molecule has been provided by measurements of its photodissociation. For comparison, photolysis of C₂H₂ on Arn clusters (¯n ≈ 280) has been measured. Here the analogous rare gas molecule HArCCH could not be generated. The interpretation of our experimental findings has been supported by ab initio calculations. In addition, the experiment together with the calculations reveals information on the photochemistry of the HXeCCH molecule. The 193 nm radiation excites the molecule predominantly into the 2¹∑⁺ state, which cannot dissociate the Xe-H bond directly, but the system evolves along the Xe-C coordinate to a conical intersection of a slightly non-linear configuration with the dissociative 1¹∏ state, which then dissociates the Xe-H bond

Adapting SAM for CDF

The CDF and D0 experiments probe the high-energy frontier and as they do so have accumulated hundreds of Terabytes of data on the way to petabytes of data over the next two years. The experiments have made a commitment to use the developing Grid based on the SAM system to handle these data. The D0 SAM has been extended for use in CDF as common patterns of design emerged to meet the similar requirements of these experiments. The process by which the merger was achieved is explained with particular emphasis on lessons learned concerning the database design patterns plus realization of the use cases.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, pdf format, TUAT00

Effect of Biodiversity Changes in Disease Risk: Exploring Disease Emergence in a Plant-Virus System

The effect of biodiversity on the ability of parasites to infect their host and cause disease (i.e. disease risk) is a major question in pathology, which is central to understand the emergence of infectious diseases, and to develop strategies for their management. Two hypotheses, which can be considered as extremes of a continuum, relate biodiversity to disease risk: One states that biodiversity is positively correlated with disease risk (Amplification Effect), and the second predicts a negative correlation between biodiversity and disease risk (Dilution Effect). Which of them applies better to different host-parasite systems is still a source of debate, due to limited experimental or empirical data. This is especially the case for viral diseases of plants. To address this subject, we have monitored for three years the prevalence of several viruses, and virus-associated symptoms, in populations of wild pepper (chiltepin) under different levels of human management. For each population, we also measured the habitat species diversity, host plant genetic diversity and host plant density. Results indicate that disease and infection risk increased with the level of human management, which was associated with decreased species diversity and host genetic diversity, and with increased host plant density. Importantly, species diversity of the habitat was the primary predictor of disease risk for wild chiltepin populations. This changed in managed populations where host genetic diversity was the primary predictor. Host density was generally a poorer predictor of disease and infection risk. These results support the dilution effect hypothesis, and underline the relevance of different ecological factors in determining disease/infection risk in host plant populations under different levels of anthropic influence. These results are relevant for managing plant diseases and for establishing conservation policies for endangered plant species

Fermilab Main Injector Beam Position Monitor Upgrade

An upgrade of the Beam Position Monitor (BPM) signal processing and data acquisition system for the Fermilab Main Injector is described. The Main Injector is a fast cycling synchrotron that accelerates protons or antiprotons from 8 to 150 GeV. Each Main Injector cycle can have a totally different magnet ramp, RF frequency configuration, beam bunch structure, and injection/extraction pattern from the previous cycle. The new BPM system provides the capabilities and flexibility required by the dynamic and complex machine operations. The system offers measurement capability in the 2.5 MHz and 53 MHz channels to detect the range of bunch structures for protons and antiprotons in both wideband (turn-by-turn) and narrowband (closed-orbit) modes. The new BPM read-out system is based on the digital receiver concept and is highly configurable, allowing the signal processing of nearly all Main Injector beam conditions, including the detection of individual batches. An overview of the BPM system in the Main Injector operating environment, some technology details and first beam measurements are presented