1,544 research outputs found

    Astronomical, physical, and meteorological parameters for planetary atmospheres

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    A newly compiled table of astronomical, physical, and meteorological parameters for planetary atmospheres is presented. Formulae and explanatory notes for their application and a complete listing of sources are also given

    The Jovian Atmospheres

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    A conference on the atmosphere of Jupiter produced papers in the areas of thermal and ortho-para hydrogen structure, clouds and chemistry, atmospheric structure, global dynamics, synoptic features and processes, atmospheric dynamics, and future spaceflight opportunities. A session on the atmospheres of Uranus and Neptune was included, and the atmosphere of Saturn was discussed in several papers

    {\em Ab initio} Quantum Monte Carlo simulation of the warm dense electron gas in the thermodynamic limit

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    We perform \emph{ab initio} quantum Monte Carlo (QMC) simulations of the warm dense uniform electron gas in the thermodynamic limit. By combining QMC data with linear response theory we are able to remove finite-size errors from the potential energy over the entire warm dense regime, overcoming the deficiencies of the existing finite-size corrections by Brown \emph{et al.}~[PRL \textbf{110}, 146405 (2013)]. Extensive new QMC results for up to N=1000N=1000 electrons enable us to compute the potential energy VV and the exchange-correlation free energy FxcF_{xc} of the macroscopic electron gas with an unprecedented accuracy of ΔV/V,ΔFxc/Fxc103|\Delta V|/|V|, |\Delta F_{xc}|/|F|_{xc} \sim 10^{-3}. A comparison of our new data to the recent parametrization of FxcF_{xc} by Karasiev {\em et al.} [PRL {\bf 112}, 076403 (2014)] reveals significant deviations to the latter

    Identifying a sufficient core group for trachoma transmission.

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    BackgroundIn many infectious diseases, a core group of individuals plays a disproportionate role in transmission. If these individuals were effectively prevented from transmitting infection, for example with a perfect vaccine, then the disease would disappear in the remainder of the community. No vaccine has yet proven effective against the ocular strains of chlamydia that cause trachoma. However, repeated treatment with oral azithromycin may be able to prevent individuals from effectively transmitting trachoma.Methodology/principal findingsHere we assess several methods for identifying a core group for trachoma, assuming varying degrees of knowledge about the transmission process. We determine the minimal core group from a completely specified model, fitted to results from a large Ethiopian trial. We compare this benchmark to a core group that could actually be identified from information available to trachoma programs. For example, determined from the rate of return of infection in a community after mass treatments, or from the equilibrium prevalence of infection.Conclusions/significanceSufficient groups are relatively easy for programs to identify, but will likely be larger than the theoretical minimum

    Retrieval of Volcanic and Man-Made Stratospheric Aerosols from Orbital Polarimetric Measurements

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    Stratospheric aerosols that are caused by a major volcanic eruption can serve as a valuable test of global climate models, as well as severely complicate tropospheric-aerosol monitoring from space. In either case, it is highly desirable to have accurate global information on the optical thickness, size, and composition of volcanic aerosols. We report sensitivity study results, which analyze the implications of making precise multi-angle photopolarimetric measurements in a 1.378-m spectral channel residing within a strong water-vapor absorption band. We demonstrate that, under favorable conditions, such measurements would enable near-perfect retrievals of the optical thickness, effective radius, and refractive index of stratospheric aerosols. Besides enabling accurate retrievals of volcanic aerosols, such measurements can also be used to monitor man-made particulates injected in the stratosphere for geoengineering purposes

    The Annual Economic Survey of Federal Gulf Shrimp Permit Holders: Report on the Design, Implementation, and Descriptive Results for 2006

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    This technical memorandum documents the design, implementation, data preparation, and descriptive results for the 2006 Annual Economic Survey of Federal Gulf Shrimp Permit Holders. The data collection was designed by the NOAA Fisheries Southeast Fisheries Science Center Social Science Research Group to track the financial and economic status and performance by vessels holding a federal moratorium permit for harvesting shrimp in the Gulf of Mexico. A two page, self-administered mail survey collected total annual costs broken out into seven categories and auxiliary economic data. In May 2007, 580 vessels were randomly selected, stratified by state, from a preliminary population of 1,709 vessels with federal permits to shrimp in offshore waters of the Gulf of Mexico. The survey was implemented during the rest of 2007. After many reminder and verification phone calls, 509 surveys were deemed complete, for an ineligibility-adjusted response rate of 90.7%. The linking of each individual vessel’s cost data to its revenue data from a different data collection was imperfect, and hence the final number of observations used in the analyses is 484. Based on various measures and tests of validity throughout the technical memorandum, the quality of the data is high. The results are presented in a standardized table format, linking vessel characteristics and operations to simple balance sheet, cash flow, and income statements. In the text, results are discussed for the total fleet, the Gulf shrimp fleet, the active Gulf shrimp fleet, and the inactive Gulf shrimp fleet. Additional results for shrimp vessels grouped by state, by vessel characteristics, by landings volume, and by ownership structure are available in the appendices. The general conclusion of this report is that the financial and economic situation is bleak for the average vessels in most of the categories that were evaluated. With few exceptions, cash flow for the average vessel is positive while the net revenue from operations and the “profit” are negative. With negative net revenue from operations, the economic return for average shrimp vessels is less than zero. Only with the help of government payments does the average owner just about break even. In the short-term, this will discourage any new investments in the industry. The financial situation in 2006, especially if it endures over multiple years, also is economically unsustainable for the average established business. Vessels in the active and inactive Gulf shrimp fleet are, on average, 69 feet long, weigh 105 gross tons, are powered by 505 hp motor(s), and are 23 years old. Three-quarters of the vessels have steel hulls and 59% use a freezer for refrigeration. The average market value of these vessels was 175,149in2006,aboutahundredthousanddollarslessthantheaverageoriginalpurchaseprice.Theoutstandingloansaveraged175,149 in 2006, about a hundred-thousand dollars less than the average original purchase price. The outstanding loans averaged 91,955, leading to an average owner equity of 83,194.Basedonthesample,85owneroperated.Onaverage,thesevesselsburned52,931gallonsoffuel,landed101,268poundsofshrimp,andreceived83,194. Based on the sample, 85% of the federally permitted Gulf shrimp fleet was actively shrimping in 2006. Of these 386 active Gulf shrimp vessels, just under half (46%) were owner-operated. On average, these vessels burned 52,931 gallons of fuel, landed 101,268 pounds of shrimp, and received 2.47 per pound of shrimp. Non-shrimp landings added less than 1% to cash flow, indicating that the federal Gulf shrimp fishery is very specialized. The average total cash outflow was 243,415ofwhich243,415 of which 108,775 was due to fuel expenses alone. The expenses for hired crew and captains were on average 54,866whichindicatestheimportanceoftheindustryasasourceofwageincome.Theresultingaveragenetcashflowis54,866 which indicates the importance of the industry as a source of wage income. The resulting average net cash flow is 16,225 but has a large standard deviation. For the population of active Gulf shrimp vessels we can state with 95% certainty that the average net cash flow was between 9,500and9,500 and 23,000 in 2006. The median net cash flow was 11,843.BasedontheincomestatementforactiveGulfshrimpvessels,theaveragefixedcostsaccountedforjustunderaquarterofoperatingexpenses(23.1Theaveragelaborcontribution(ascaptain)ofanowneroperatorisestimatedatabout11,843. Based on the income statement for active Gulf shrimp vessels, the average fixed costs accounted for just under a quarter of operating expenses (23.1%), labor costs for just over a quarter (25.3%), and the non-labor variable costs for just over half (51.6%). The fuel costs alone accounted for 42.9% of total operating expenses in 2006. It should be noted that the labor cost category in the income statement includes both the actual cash payments to hired labor and an estimate of the opportunity cost of owner-operators’ time spent as captain. The average labor contribution (as captain) of an owner-operator is estimated at about 19,800. The average net revenue from operations is negative 7,429,andisstatisticallydifferentandlessthanzeroinspiteofalargestandarddeviation.TheeconomicreturntoGulfshrimpingisnegative47,429, and is statistically different and less than zero in spite of a large standard deviation. The economic return to Gulf shrimping is negative 4%. Including non-operating activities, foremost an average government payment of 13,662, leads to an average loss before taxes of 907forthevesselowners.Theconfidenceintervalofthisvaluestraddleszero,sowecannotreject,with95TheaverageinactiveGulfshrimpvesselisgenerallyofasmallerscalethantheaverageactivevessel.Inactivevesselsarephysicallysmaller,arevaluedmuchlower,andarelessdependentonloans.Fixedcostsaccountfornearlythreequartersofthetotaloperatingexpensesof907 for the vessel owners. The confidence interval of this value straddles zero, so we cannot reject, with 95% certainty, that the population average is zero. The average inactive Gulf shrimp vessel is generally of a smaller scale than the average active vessel. Inactive vessels are physically smaller, are valued much lower, and are less dependent on loans. Fixed costs account for nearly three quarters of the total operating expenses of 11,926, and only 6% of these vessels have hull insurance. With an average net cash flow of negative 7,537,theinactiveGulfshrimpfleethasamajorliquidityproblem.Onaverage,netrevenuefromoperationsisnegative7,537, the inactive Gulf shrimp fleet has a major liquidity problem. On average, net revenue from operations is negative 11,396, which amounts to a negative 15% economic return, and owners lose 9,381ontheirvesselsbeforetaxes.Tosustainsuchlossesandespeciallytosurvivethenegativecashflow,manyoftheownersmustbesubsidizingtheirshrimpvesselswiththehelpofotherincomeorwealthsourcesoraredrawingdowntheirequity.ActiveGulfshrimpvesselsinallstatesbutTexasexhibitednegativereturns.TheAlabamaandMississippifleetshavethehighestassets(vesselvalues),onaverage,yettheygeneratezerocashflowandnegative9,381 on their vessels before taxes. To sustain such losses and especially to survive the negative cash flow, many of the owners must be subsidizing their shrimp vessels with the help of other income or wealth sources or are drawing down their equity. Active Gulf shrimp vessels in all states but Texas exhibited negative returns. The Alabama and Mississippi fleets have the highest assets (vessel values), on average, yet they generate zero cash flow and negative 32,224 net revenue from operations. Due to their high (loan) leverage ratio the negative 11% economic return is amplified into a negative 21% return on equity. In contrast, for Texas vessels, which actually have the highest leverage ratio among the states, a 1% economic return is amplified into a 13% return on equity. From a financial perspective, the average Florida and Louisiana vessels conform roughly to the overall average of the active Gulf shrimp fleet. It should be noted that these results are averages and hence hide the variation that clearly exists within all fleets and all categories. Although the financial situation for the average vessel is bleak, some vessels are profitable. (PDF contains 101 pages

    Safety of overlapping inpatient orthopaedic surgery: A multicenter study

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    BackgroundAlthough overlapping surgery is used to maximize efficiency, more empirical data are needed to guide patient safety. We conducted a retrospective cohort study to evaluate the safety of overlapping inpatient orthopaedic surgery, as judged by the occurrence of perioperative complications.MethodsAll inpatient orthopaedic surgical procedures performed at 5 academic institutions from January 1, 2015, to December 31, 2015, were included. Overlapping surgery was defined as 2 skin incisions open simultaneously for 1 surgeon. In comparing patients who underwent overlapping surgery with those who underwent non-overlapping surgery, the primary outcome was the occurrence of a perioperative complication within 30 days of the surgical procedure, and secondary outcomes included all-cause 30-day readmission, length of stay, and mortality. To determine if there was an association between overlapping surgery and a perioperative complication, we tested for non-inferiority of overlapping surgery, assuming a null hypothesis of an increased risk of 50%. We used an inverse probability of treatment weighted regression model adjusted for institution, procedure type, demographic characteristics (age, sex, race, comorbidities), admission type, admission severity of illness, and clustering by surgeon.ResultsAmong 14,135 cases, the frequency of overlapping surgery was 40%. The frequencies of perioperative complications were 1% in the overlapping surgery group and 2% in the non-overlapping surgery group. The overlapping surgery group was non-inferior to the non-overlapping surgery group (odds ratio [OR], 0.61 [90% confidence interval (CI), 0.45 to 0.83]; p < 0.001), with reduced odds of perioperative complications (OR, 0.61 [95% CI, 0.43 to 0.88]; p = 0.009). For secondary outcomes, there was a significantly lower chance of all-cause 30-day readmission in the overlapping surgery group (OR, 0.67 [95% CI, 0.52 to 0.87]; p = 0.003) and shorter length of stay (e, 0.94 [95% CI, 0.89 to 0.99]; p = 0.012). There was no difference in mortality.ConclusionsOur results suggest that overlapping inpatient orthopaedic surgery does not introduce additional perioperative risk for the complications that we evaluated. The suitability of this practice should be determined by individual surgeons on a case-by-case basis with appropriate informed consent.Level of evidenceTherapeutic Level III. See Instructions for Authors for a complete description of levels of evidence
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