5,632 research outputs found

    The Descending Path

    Get PDF

    The Climb

    Get PDF

    Extended flight evaluation of a near-term pitch active control system

    Get PDF
    Fuel savings can be achieved by moving the center of gravity of an aircraft aft which reduces the static stability margin and consequently the trim drag. However, flying qualities of an aircraft with relaxed static stability can be significantly degraded. The flying qualities can be restored by using a pitch active control system (PACS). This report documents the work accomplished during a follow-on program (see NASA CR-165951 for initial program report) to perform extended flight tests of a near-term PACS. The program included flying qualities analyses, piloted flight simulation tests, aircraft preparation and flight tests to demonstrate that the near-term PACS provided good flying qualities within the linear static stability envelope to a negative 3% static stability margin

    On the Rates of Type Ia Supernovae in Dwarf and Giant Hosts with ROTSE-IIIb

    Get PDF
    We present a sample of 23 spectroscopically confirmed Type Ia supernovae that were discovered in the background of galaxy clusters targeted by ROTSE-IIIb and use up to 18 of these to determine the local (z = 0.05) volumetric rate. Since our survey is flux limited and thus biased against fainter objects, the pseudo-absolute magnitude distribution (pAMD) of SNeIa in a given volume is an important concern, especially the relative frequency of high to low-luminosity SNeIa. We find that the pAMD derived from the volume limited Lick Observatory Supernova Search (LOSS) sample is incompatible with the distribution of SNeIa in a volume limited (z<0.12) sub sample of the SDSS-II. The LOSS sample requires far more low-luminosity SNeIa than the SDSS-II can accommodate. Even though LOSS and SDSS-II have sampled different SNeIa populations, their volumetric rates are surprisingly similar. Using the same model pAMD adopted in the SDSS-II SNeIa rate calculation and excluding two high-luminosity SNeIa from our sample, we derive a rate that is marginally higher than previous low-redshift determinations. With our full sample and the LOSS pAMD our rate is more than double the canonical value. We also find that 5 of our 18 SNeIa are hosted by very low-luminosity (M_B > -16) galaxies, whereas only 1 out 79 nearby SDSS-II SNeIa have such faint hosts. It is possible that previous works have under-counted either low luminosity SNeIa, SNeIa in low luminosity hosts, or peculiar SNeIa (sometimes explicitly), and the total SNeIa rate may be higher than the canonical value.Comment: 18 pages; accepted for publication in The Astronomical Journa

    Increasing Doses of Intraoperative Hydromorphone Do Not Reduce Postoperative Pain

    Get PDF
    Introduction: • Intermediate and long acting opioids are given intraoperatively to reduce pain during emergence from anesthesia. • Recent evidence suggests that intraoperative opioids have inconsistent effects on nociception and pain in the immediate postoperative period. • Multiple potent, short-acting opioids such as remifentanil, sufentanil and fentanyl have been shown to produce dose-related increases in pain scores and opioid consumption in the immediate postoperative recovery period. • Intraoperative doses of longer acting opioids such as morphine and methadone6 have been shown to reduce pain scores and narcotic requirements in the immediate postoperative period. • Hydromorphone is an intermediate duration narcotic which is commonly used intraoperatively but has not been studied for its potential to reduce pain in the immediate postoperative period

    A case series of premenstrual disorders presenting to the UK's National Female Hormone Clinic

    Get PDF
    Aims and method We aimed to describe the clinical characteristics of female patients presenting with premenstrual disorders to a tertiary service in the UK. We conducted a retrospective case-note review of referrals to the National Female Hormone Clinic from April 2014 to August 2020. Based on clinical assessment, we determined whether the patient met criteria for premenstrual dysphoric disorder or premenstrual exacerbation of an underlying psychiatric disorder. Results Of 146 patients seen in clinic for premenstrual disorders, an ICD-10 psychiatric diagnosis was made in 130 (89.0%); a minority 16 (11.0%) did not have a psychiatric diagnosis. Following assessment, 94 patients (64.4%) met criteria for premenstrual dysphoric disorder and 67 (45.6%) had exacerbation of a psychiatric disorder. Clinical implications Patients presenting to this specialist service had complex psychiatric comorbidity; almost half presented with exacerbation of a psychiatric disorder

    Density functional theory and DFT+U study of transition metal porphines adsorbed on Au(111) surfaces and effects of applied electric fields

    Full text link
    We apply Density Functional Theory (DFT) and the DFT+U technique to study the adsorption of transition metal porphine molecules on atomistically flat Au(111) surfaces. DFT calculations using the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional correctly predict the palladium porphine (PdP) low-spin ground state. PdP is found to adsorb preferentially on gold in a flat geometry, not in an edgewise geometry, in qualitative agreement with experiments on substituted porphyrins. It exhibits no covalent bonding to Au(111), and the binding energy is a small fraction of an eV. The DFT+U technique, parameterized to B3LYP predicted spin state ordering of the Mn d-electrons, is found to be crucial for reproducing the correct magnetic moment and geometry of the isolated manganese porphine (MnP) molecule. Adsorption of Mn(II)P on Au(111) substantially alters the Mn ion spin state. Its interaction with the gold substrate is stronger and more site-specific than PdP. The binding can be partially reversed by applying an electric potential, which leads to significant changes in the electronic and magnetic properties of adsorbed MnP, and ~ 0.1 Angstrom, changes in the Mn-nitrogen distances within the porphine macrocycle. We conjecture that this DFT+U approach may be a useful general method for modeling first row transition metal ion complexes in a condensed-matter setting.Comment: 14 pages, 6 figure

    Time-series Analysis of Clusters in City Size Distributions

    Get PDF
    Complex systems, such as urban systems, emerge unpredictably without the influence of central control as a result of adaptive behavior by their component, interacting agents. This paper analyses city size distributions, by decade, from the south-western region of the United States for the years 1890–1990. It determines if the distributions were clustered and documents changes in the pattern of clusters over time. Clusters were determined utilizing a kernel density estimator and cluster analysis. The data were clustered as determined by both methods. The analyses identified 4–7 clusters of cities in each of the decades analysed. Cities cluster into size classes, suggesting variability in growth rates at different scales
    • …
    corecore