907 research outputs found

    Development of a ROT22 - DATAMAP interface

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    This report (Contract NAS2-10331- Mod 10), outlines the development and validation of an interface between the three-dimensional transonic analysis program ROT22 and the Data from Aeromechanics Test and Analytics-Management and Analysis Package (DATAMAP). After development of the interface, the validation is carried out as follows. First, the DATAMAP program is used to analyze a portion of the Tip Aerodynamics and Acoustics Test (TAAT) data. Specifically, records 2872 and 2873 are analyzed at an azimuth of 90 deg, and record 2806 is analyzed at 60 deg. Trim conditions for these flight conditions are then calculated using the Bell performance prediction program ARAM45. Equivalent shaft, pitch, and twist angles are calculated from ARAM45 results and used as input to the ROT22 program. The interface uses the ROT22 results and creates DATAMAP information files from which the surface pressure contours and sectional pressure coefficients are plotted. Twist angles input to ROT22 program are then iteratively modified in the tip region until the computed pressure coefficients closely match the measurements. In all cases studied, the location of the shock is well predicted. However, the negative pressure coefficients were underpredicted. This could be accounted for by blade vortex interaction effects

    Cellular automaton model of precipitation/dissolution coupled with solute transport

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    Precipitation/dissolution reactions coupled with solute transport are modelled as a cellular automaton in which solute molecules perform a random walk on a regular lattice and react according to a local probabilistic rule. Stationary solid particles dissolve with a certain probability and, provided solid is already present or the solution is saturated, solute particles have a probability to precipitate. In our simulation of the dissolution of a solid block inside uniformly flowing water we obtain solid precipitation downstream from the original solid edge, in contrast to the standard reaction-transport equations. The observed effect is the result of fluctuations in solute density and diminishes when we average over a larger ensemble. The additional precipitation of solid is accompanied by a substantial reduction in the relatively small solute concentration. The model is appropriate for the study of the r\^ole of intrinsic fluctuations in the presence of reaction thresholds and can be employed to investigate porosity changes associated with the carbonation of cement.Comment: LaTeX file, 13 pages. To appear in Journal of Statistical Physics (Proceedings of Lattice Gas'94, June 1994, Princeton). Figures available from author. Requests may be submitted by E-mail ([email protected]) or ordinary mail (Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland

    Effects of aerodynamic interaction between main and tail rotors on helicopter hover performance and noise

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    A model test was conducted to determine the effects of aerodynamic interaction between main rotor, tail rotor, and vertical fin on helicopter performance and noise in hover out of ground effect. The experimental data were obtained from hover tests performed with a .151 scale Model 222 main rotor, tail rotor and vertical fin. Of primary interest was the effect of location of the tail rotor with respect to the main rotor. Penalties on main rotor power due to interaction with the tail rotor ranged up to 3% depending upon tail rotor location and orientation. Penalties on tail rotor power due to fin blockage alone ranged up to 10% for pusher tail rotors and up to 50% for tractor tail rotors. The main rotor wake had only a second order effect on these tail rotor/fin interactions. Design charts are presented showing the penalties on main rotor power as a function of the relative location of the tail rotor

    Surface Modification of Porous Polyethylene Implants with an Albumin-Based Nanocarrier-Release System

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    Background: Porous polyethylene (PPE) implants are used for the reconstruction of tissue defects but have a risk of rejection in case of insufficient ingrowth into the host tissue. Various growth factors can promote implant ingrowth, yet a long-term gradient is a prerequisite for the mediation of these effects. As modification of the implant surface with nanocarriers may facilitate a long-term gradient by sustained factor release, implants modified with crosslinked albumin nanocarriers were evaluated in vivo. Methods: Nanocarriers from murine serum albumin (MSA) were prepared by an inverse miniemulsion technique encapsulating either a low-or high-molar mass fluorescent cargo. PPE implants were subsequently coated with these nanocarriers. In control cohorts, the implant was coated with the homologue non-encapsulated cargo substance by dip coating. Implants were consequently analyzed in vivo using repetitive fluorescence microscopy utilizing the dorsal skinfold chamber in mice for ten days post implantation. Results: Implant-modification with MSA nanocarri-ers significantly prolonged the presence of the encapsulated small molecules while macromolecules were detectable during the investigated timeframe regardless of the form of application. Conclusions: Surface modification of PPE implants with MSA nanocarriers results in the alternation of release kinetics especially when small molecular substances are used and therefore allows a prolonged factor release for the promotion of implant integration.</p

    Entrepreneurs’ age, institutions, and social value creation goals: a multi-country study

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    This study explores the relationship between an entrepreneur's age and his/her social value creation goals. Building on the lifespan developmental psychology literature and institutional theory, we hypothesize a U-shaped relationship between entrepreneurs’ age and their choice to create social value through their ventures, such that younger and older entrepreneurs create more social value with their businesses while middle age entrepreneurs are relatively more economically and less socially oriented with their ventures. We further hypothesize that the quality of a country’s formal institutions in terms of economic, social, and political freedom steepen the U-shaped relationship between entrepreneurs’ age and their choice to pursue social value creation as supportive institutional environments allow entrepreneurs to follow their age-based preferences. We confirm our predictions using multilevel mixed-effects linear regressions on a sample of over 15,000 entrepreneurs (aged between 18 and 64 years) in 45 countries from Global Entrepreneurship Monitor data. The findings are robust to several alternative specifications. Based on our findings, we discuss implications for theory and practice, and we propose future research directions

    An All-Sky 2MASS Mosaic Constructed on the TeraGrid

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    The Montage mosaic engine supplies on-request image mosaic services for the NVO astronomical community. A companion paper describes scientific applications of Montage. This paper describes one application in detail: the generation at SDSC of a mosaic of the 2MASS All-sky Image Atlas on the NSF TeraGrid. The goals of the project are: to provide a value-added 2MASS product that combines overlapping images to improve sensitivity; to demonstrate applicability of computing at-scale to astronomical missions and surveys, especially projects such as LSST; and to demonstrate the utility of the NVO Hyperatlas format. The numerical processing of an 8 TB, 32-bit survey to produce a 64-bit, 20 TB output atlas presented multiple scalability and operational challenges. An MPI Python module, MYMPI, was used to manage the alternately sequential and parallel steps of the Montage process. This allowed us to parallelize all steps of the mosaic process: that of many, sequential steps executing simultaneously for independent mosaics and that of a single MPI parallel job executing on many CPUs for a single mosaic. The Storage Resource Broker (SRB) was used to archive the output results in the Hyperatlas. The 2MASS mosaics are now being assessed for scientific quality. Around 130,000 CPU-hours were used to complete the mosaics. The output consists of 1734 plates spanning 6◦ for each of 3 bands. Each of the 5202 mosaics is roughly 4 GB in size, and each has been tiled into a 12×12 array of 26 MB files for ease of handling. The total size is about 20 TB in 750,000 tiles

    Socioeconomic Equity in the Receipt of In-Hospital Care and Outcomes in Australian Acute Coronary Syndrome Patients: The CONCORDANCE Registry

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    Background: Socioeconomic status (SES) is a social determinant of both health and receipt of health care services, but its impact is under-studied in acute coronary syndrome (ACS). The aim of this study was to examine the influence of SES on in-hospital care, and clinical events for patients presenting with an ACS to public hospitals in Australia. Methods: Data from 9064 ACS patient records were collected from 41 public hospitals nationwide from 2009 as part of the Cooperative National Registry of Acute Coronary Syndrome Care (CONCORDANCE) registry. For this analysis, we divided the cohort into four socioeconomic groups (based on postcode of usual residence) and compared the in-hospital care provided and clinical outcomes before and after adjustment for both patient clinical characteristics and hospital clustering. Results: Patients were divided into four SES groups (from the most to the least disadvantaged: 2042 (23%) vs. 2104 (23%) vs. 1994 (22%) vs. 2968 (32%)). Following adjustments for patient characteristics, there were no differences in the odds of receiving coronary angiogram, revascularisation, prescription of recommended medication, or referral to cardiac rehabilitation across the SES groups (p = 0.06, 0.69, 0.89 and 0.79, respectively). After adjustment for clinical characteristics, no associations were observed for in-hospital and cumulative death (p = 0.62 and p = 0.71, respectively). However, the most disadvantaged group were 37% more likely to have a major adverse cardiovascular event (MACE) than the least disadvantaged group (OR (95% CI): 1.37 (1.1, 1.71), p = 0.02) driven by incidence of in-hospital heart failure. Conclusions: Although there may be gaps in the delivery of care, this delivery of care does not differ by patient's SES. It is an encouraging affirmation that all patients in Australian public hospitals receive equal in-hospital care, and the likelihood of death is comparable between the SES groups

    A systematic review of school-based sexual health interventions to prevent STI/HIV in sub-Saharan Africa

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    Background The HIV/AIDS epidemic remains of global significance and there is a need to target (a) the adolescent age-groups in which most new infections occur; and (b) sub-Saharan Africa where the greatest burden of the epidemic lies. A focused systematic review of school-based sexual health interventions in sub-Saharan Africa to prevent HIV/AIDS and Sexually Transmitted Infections (STI) in this age group was therefore conducted. Methods Searches were conducted in Medline, Embase, Cinahl and PsychINFO according to agreed a priori criteria for studies published between 1986 and 2006. Further searches were conducted in UNAIDS and WHO (World Health Organization) websites, and 'Google'. Relevant journals were hand-searched and references cited in identified articles were followed up. Data extraction and quality assessment was carried out on studies selected for full text appraisal, and results were analysed and presented in narrative format. Results Some 1,020 possible titles and abstracts were found, 23 full text articles were critically appraised, and 12 articles (10 studies) reviewed, reflecting the paucity of published studies conducted relative to the magnitude of the HIV epidemic in sub-Saharan Africa. Knowledge and attitude-related outcomes were the most associated with statistically significant change. Behavioural intentions were more difficult to change and actual behaviour change was least likely to occur. Behaviour change in favour of abstinence and condom use appeared to be greatly influenced by pre-intervention sexual history. Conclusion There is a great need in sub-Saharan Africa for well-evaluated and effective school-based sexual health interventions

    Intervention in acute coronary syndromes:do patients undergo intervention on the basis of their risk characteristics? The Global Registry of Acute Coronary Events (GRACE)

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    OBJECTIVE: To determine whether revascularisation is more likely to be performed in higher-risk patients and whether the findings are influenced by hospitals adopting more or less aggressive revascularisation strategies. METHODS: GRACE (Global Registry of Acute Coronary Events) is a multinational, observational cohort study. This study involved 24,189 patients enrolled at 73 hospitals with on-site angiographic facilities. RESULTS: Overall, 32.5% of patients with a non-ST elevation acute coronary syndrome (ACS) underwent percutaneous coronary intervention (PCI; 53.7% in ST segment elevation myocardial infarction (STEMI)) and 7.2% underwent coronary artery bypass grafting (CABG; 4.0% in STEMI). The cumulative rate of in-hospital death rose correspondingly with the GRACE risk score (variables: age, Killip class, systolic blood pressure, ST segment deviation, cardiac arrest at admission, serum creatinine, raised cardiac markers, heart rate), from 1.2% in low-risk to 3.3% in medium-risk and 13.0% in high-risk patients (c statistic = 0.83). PCI procedures were more likely to be performed in low- (40% non-STEMI, 60% STEMI) than medium- (35%, 54%) or high-risk patients (25%, 41%). No such gradient was apparent for patients undergoing CABG. These findings were seen in STEMI and non-ST elevation ACS, in all geographical regions and irrespective of whether hospitals adopted low (4.2-33.7%, n = 7210 observations), medium (35.7-51.4%, n = 7913 observations) or high rates (52.6-77.0%, n = 8942 observations) of intervention. CONCLUSIONS: A risk-averse strategy to angiography appears to be widely adopted. Proceeding to PCI relates to referral practice and angiographic findings rather than the patient\u27s risk status. Systematic and accurate risk stratification may allow higher-risk patients to be selected for revascularisation procedures, in contrast to current international practice
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