7,777 research outputs found

    Impact hazard protection efficiency by a small kinetic impactor

    Get PDF
    In this paper the ability of a small kinetic impactor spacecraft to mitigate an Earth-threatening asteroid is assessed by means of a novel measure of efficiency. This measure estimates the probability of a space system to deflect a single randomly-generated Earth-impacting object to a safe distance from the Earth. This represents a measure of efficiency that is not biased by the orbital parameters of a test-case object. A vast number of virtual Earth-impacting scenarios are investigated by homogenously distributing in orbital space a grid of 17,518 Earth impacting trajectories. The relative frequency of each trajectory is estimated by means Opik’s theory and Bottke’s near Earth objects model. A design of the entire mitigation mission is performed and the largest deflected asteroid computed for each impacting trajectory. The minimum detectable asteroid can also be estimated by an asteroid survey model. The results show that current technology would likely suffice against discovered airburst and local damage threats, whereas larger space systems would be necessary to reliably tackle impact hazard from larger threats. For example, it is shown that only 1,000 kg kinetic impactor would suffice to mitigate the impact threat of 27.1% of objects posing similar threat than that posed by Apophis

    The metaphysics of Machian frame-dragging

    Get PDF
    The paper investigates the kind of dependence relation that best portrays Machian frame-dragging in general relativity. The question is tricky because frame-dragging relates local inertial frames to distant distributions of matter in a time-independent way, thus establishing some sort of non-local link between the two. For this reason, a plain causal interpretation of frame-dragging faces huge challenges. The paper will shed light on the issue by using a generalized structural equation model analysis in terms of manipulationist counterfactuals recently applied in the context of metaphysical enquiry by Schaffer (2016) and Wilson (2017). The verdict of the analysis will be that frame-dragging is best understood in terms of a novel type of dependence relation that is half-way between causation and grounding

    Benefit-cost methodology study with example application of the use of wind generators

    Get PDF
    An example application for cost-benefit methodology is presented for the use of wind generators. The approach adopted for the example application consisted of the following activities: (1) surveying of the available wind data and wind power system information, (2) developing models which quantitatively described wind distributions, wind power systems, and cost-benefit differences between conventional systems and wind power systems, and (3) applying the cost-benefit methodology to compare a conventional electrical energy generation system with systems which included wind power generators. Wind speed distribution data were obtained from sites throughout the contiguous United States and were used to compute plant factor contours shown on an annual and seasonal basis. Plant factor values (ratio of average output power to rated power) are found to be as high as 0.6 (on an annual average basis) in portions of the central U. S. and in sections of the New England coastal area. Two types of wind power systems were selected for the application of the cost-benefit methodology. A cost-benefit model was designed and implemented on a computer to establish a practical tool for studying the relative costs and benefits of wind power systems under a variety of conditions and to efficiently and effectively perform associated sensitivity analyses

    STATUS OF COMPOUND DRC-1339 REGISTRATIONS

    Get PDF
    Compound DRC-1339 is a restricted-use, slow-acting avicide that is registered to control a number of avian pests. It is unique because of its selective high toxicity to most pest birds, low-to-moderate toxicity to most mammals and predatory birds, and lack of known secondary hazards when used on baits. The most widely known product containing DRC- 1339 is Purina Mills’ Starlicide Complete®, a pelleted bait used to control blackbirds and starlings in feedlots. Other DRC- 1339 registrations are held by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA/APHIS), for the use of nonpelletized baits at feedlots and for the control of gulls in or near their nesting colonies. Over 20 State Special Local Need 24(c) registrations have also been issued to APHIS for special DRC-1339 uses. To consolidate these registrations, APHIS has submitted data to amend its feedlot registration for blackbirds and starlings, and applied for three registrations for control of 1) raven and crow depredations on livestock and for wildlife protection, 2) pigeons in and around structures, and 3) blackbirds, starlings, and crows at preroosting staging areas. Because most of the submitted data were collected in the 1960s and 1970s, none of it was produced under the Environmental Protection Agency\u27s (EPA) Good Laboratory Practices (GLP) regulations; therefore, new data will probably be needed to support these registrations. Future data needs and procedures for collecting valid information for DRC-1339 are suggested

    Gaze following in ungulates: Domesticated and non-domesticated species follow the gaze of both human and conspecifics in an experimental context

    Get PDF
    Gaze following is the ability to use others’ gaze to obtain information about the environment (e.g., food location, predators, and social interactions). As such, it may be highly adaptive in a variety of socio-ecological contexts, and thus be widespread across animal taxa. To date, gaze following has been mostly studied in primates, and partially in birds, but little is known on the gaze following abilities of other taxa and, especially, on the evolutionary pressures that led to their emergence. In this study, we used an experimental approach to test gaze following skills in a still understudied taxon, ungulates. Across four species (i.e., domestic goats and lamas, and non-domestic guanacos and mouflons), we assessed the individual ability to spontaneously follow the gaze of both conspecifics and human experimenters in different conditions. In line with our predictions, species followed the model’s gaze both with human and conspecific models, but more likely with the latter. Except for guanacos, all species showed gaze following significantly more in the experimental conditions (than in the control ones). Despite the relative low number of study subjects, our study provides the first experimental evidence of gaze following skills in non-domesticated ungulates, and contributes to understanding how gaze following skills are distributed in another taxon—an essential endeavor to identify the evolutionary pressures leading to the emergence of gaze following skills across taxa

    Drain Versus No Drain in Open Mesh Repair for Incisional Hernia, Results of a Prospective Randomized Controlled Trial.

    Get PDF
    Open mesh repair of incisional hernia is associated with different local complications, particularly bleeding and seroma formation. Traditionally, drains have been placed perioperatively to prevent these complications, despite the lack of scientific evidence or expert consensus. We formulated the hypothesis that the absence of drainage would reduce number of patients presenting collections or complications. The present study aimed to compare postoperative complication rates after open mesh repair for incisional hernia with or without prophylactic wound drainage. Prospective randomized study using standardized surgical technique and drain placement. The primary endpoint was the evaluation of residual fluid collection with ultrasound on postoperative day 30. Other complications, subdivided into medical and surgical, were analyzed as secondary endpoints. There were 144 patients randomized (70 with drain, 74 without drain). No difference was identified between both groups for fluid collection at 30 days (60.3% vs. 62%, p = 0.844). However, less surgical complications were identified in the drain group (21.7% vs. 42.7%, p = 0.007), with a lower wound dehiscence rate (1.5% vs. 9.3%, p = 0.041). Prophylactic drainage in open incisional hernia repair does not objectively reduce the rate of postoperative fluid collections. Therefore, our results do not support the use of routine drainage in incisional hernia repair. Trial registration on clinicaltrials.gov (NCT00478348)

    Monte-Carlo simulation with FLUKA for liquid and solid targets

    Get PDF
    Introduction Monte-Carlo simulations can be used to assess isotope production on small medical cyclotrons. These simulations calculate the particle interactions with electric and magnetic fields, as well as the nuclear reactions. The results can be used to predict both yields and isotopic contaminations and can aid in the optimum design of target material and target geometry [1,2]. FLUKA is a general-purpose tool widely used in many applications from accelerator shielding to target design, calorimetry, activation, dosimetry, detector design, neutrino physics, or radiotherapy [3,4]. In this work, we applied the Monte-Carlo code FLUKA to determine the accuracy of predicting yields of various isotopes as compared to experimental yields. Material and Methods The proton beam collimation system, as well as the liquid and solid target of the TR13 cyclotron at TRIUMF, has been modeled in FLUKA. The proton beam parameters were initially taken from the cyclotron design specifications and were optimized against experimental measurements from the TR13. Data from irradiations of different targets and with different beam currents were collected in order to account for average behavior, see FIG. 1. Yields for a pencil proton beam as well as a beam spread out in direction and energy have been calculated and have been compared to experimental results obtained with the TR13. Results and Conclusion The reactions listed in TABLE 1 were assessed. For most reactions a good agreement was found in the comparison between experimental and simulated saturation yield. TABLE 1 only shows the yields simulated with a proton beam with a spread in both direction and energy. In most cases, the simulated yield is slightly larger or comparable. Only the calculated yield for 55Co was significantly lower by a factor of 4.2. This is still a good agreement considering that FLUKA was originally a high-energy physics code. It may indicate that the FLUKA internal cross-section calculation for this isotope production needs some optimization. In summary, we conclude that FLUKA can be used as a tool for the prediction of isotope production as well as for target design
    corecore