A smart end-effector for assembly of space truss structures

A unique facility, the Automated Structures Research Laboratory, is being used to investigate robotic assembly of truss structures. A special-purpose end-effector is used to assemble structural elements into an eight meter diameter structure. To expand the capabilities of the facility to include construction of structures with curved surfaces from straight structural elements of different lengths, a new end-effector has been designed and fabricated. This end-effector contains an integrated microprocessor to monitor actuator operations through sensor feedback. This paper provides an overview of the automated assembly tasks required by this end-effector and a description of the new end-effector's hardware and control software

The motion of two masses coupled to a massive spring

We discuss the classical motion of a spring of arbitrary mass coupled to two arbitrary massive blocks attached at its ends. A general approach to the problem is presented and some general results are obtained. Examples for which a simple elastic function can be inferred are discussed and the normal modes and normal frequencies obtained. An approximation procedure to the evaluation of the normel frequencies in the case of uniform elastic function and mass density is also discussed.Comment: Standard Latex file plus three eps figure

Key habitat features facilitate the presence of Barred Owls in developed landscapes

As urbanization continues to transform landscapes, it is imperative to find ways to conserve biodiversity within fragmented habitats. Forest interior dwelling birds are particularly vulnerable to development pressures because they require large tracts of forest to support their life cycles. Although Barred Owls (Strix varia) are frequently described as an obligate mature forest species, they have been found in urbanized landscapes. To determine if certain habitat characteristics, such as mature trees, facilitate the presence of Barred Owls in developed regions, we modeled Barred Owl occupancy probability along a development gradient in the Piedmont region of the southeastern United States. We surveyed for owls by broadcasting conspecific calls to solicit response and by passively recording at survey sites using autonomous recording units. Detection/nondetection data were collected during the breeding season and analyzed within an occupancy framework to investigate patterns of habitat association in our region, while allowing for imperfect detection of owls. Average tree height was the best predictor of Barred Owl occupancy across a development gradient, regardless of forest coverage. We did not find Barred Owl occupancy to decline with increasing impervious surface density. Our research implies that developed landscapes containing mature urban trees can support breeding populations of Barred Owls

Cloning of the Complete Gene for Carcinoembryonic Antigen

Carcinoembryonic antigen (CEA) is a widely used tumor marker, especially in the surveillance of colonic cancer patients. Although CEA is also present in some normal tissues, it is apparently expressed at higher levels in tumorous tissues than in corresponding normal tissues. As a first step toward analyzing the regulation of expression of CEA at the transcriptional level, we have isolated and characterized a cosmid clone (cosCEA1), which contains the entire coding region of the CEA gene. A close correlation exists between the exon and deduced immunoglobulin-like domain borders. We have determined a cluster of transcriptional starts for CEA and the closely related nonspecific cross-reacting antigen (NCA) gene and have sequenced their putative promoters. Regions of sequence homology are found as far as approximately 500 nucleotides upstream from the translational starts of these genes, but farther upstream they diverge completely. In both cases we were unable to find classic TATA or CAAT boxes at their expected positions. To characterize the CEA and NCA promoters, we carried out transient transfection assays with promoter-indicator gene constructs in the CEA-producing adenocarcinoma cell line SW403, as well as in nonproducing HeLa cells. A CEA gene promoter construct, containing approximately 400 nucleotides upstream from the translational start, showed nine times higher activity in the SW403 than in the HeLa cell line. This indicates that cis-acting sequences which convey cell type-specific expression of the CEA gene are contained within this region

Controlling the cold collision shift in high precision atomic interferometry

We present here a new method based on a transfer of population by adiabatic passage that allows to prepare cold atomic samples with a well defined ratio of atomic density and atom number. This method is used to perform a measurement of the cold collision frequency shift in a laser cooled cesium clock at the percent level, which makes the evaluation of the cesium fountains accuracy at the $10^{-16}$ level realistic. With an improved set-up, the adiabatic passage would allow measurements of atom number-dependent phase shifts at the $10^{-3}$ level in high precision experiments.Comment: 4 pages, 3 figures, 2 table

Benefits of joint LIGO -- Virgo coincidence searches for burst and inspiral signals

We examine the benefits of performing a joint LIGO--Virgo search for transient signals. We do this by adding burst and inspiral signals to 24 hours of simulated detector data. We find significant advantages to performing a joint coincidence analysis, above either a LIGO only or Virgo only search. These include an increased detection efficiency, at a fixed false alarm rate, to both burst and inspiral events and an ability to reconstruct the sky location of a signal.Comment: 11 pages 8 figures, Amaldi 6 proceeding

A First Comparison Between LIGO and Virgo Inspiral Search Pipelines

This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed.Comment: GWDAW-9 proceeding

Uso do programa livre R na estratificação dos municípios produtores de pêssego no Rio Grande do Sul.

Informações precisas e atualizadas sobre a produção agrícola brasileira são importantes e estratégicas, tanto do ponto de vista econômico quanto em relação à segurança alimentar. A previsão oficial de safras no Brasil ainda é realizada de forma subjetiva, mas existe um esforço da Companhia Nacional de Abastecimento (Conab) para o aperfeiçoamento metodológico do atual sistema de previsão. Este trabalho pretende contribuir para esse propósito, apresentando um método de estratificação eficiente para fins de estimação de área plantada, informação fundamental para a previsão de safras. Foi utilizando o pacote computacional estatístico R, software livre e de código aberto. Como exemplo de aplicação, foi elaborado um algoritmo para estratificação dos municípios do Rio Grande do Sul, para estimação da área plantada com o pessegueiro no estado. Foi aplicado um método hierárquico de agrupamento, utilizando a função HCLUST do programa R, que resultou na formação de oito estratos sendo um deles o ?estrato certo?, onde todos os municípios serão amostrados

A first comparison of search methods for gravitational wave bursts using LIGO and Virgo simulated data

We present a comparative study of 6 search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The data's spectra were chosen to follow the design sensitivity of the two 4km LIGO interferometers and the 3km Virgo interferometer. The searches were applied on replicas of the data sets to which 8 different signals were injected. Three figures of merit were employed in this analysis: (a) Receiver Operator Characteristic curves, (b) necessary signal to noise ratios for the searches to achieve 50 percent and 90 percent efficiencies, and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.Comment: GWDAW9 proceeding