2,101 research outputs found
The broad emission-line region: the confluence of the outer accretion disc with the inner edge of the dusty torus
(Abridged) We investigate the observational characteristics of BLR geometries
in which the BLR clouds bridge the gap, both in distance and scale height,
between the outer accretion disc and the hot dust, forming an effective surface
of a "bowl". The gas dynamics are dominated by gravity, and we include the
effects of transverse Doppler shift, gravitational redshift and scale-height
dependent macro-turbulence. Our simple model reproduces many of the phenomena
observed in broad emission-line variability studies, including (i) the absence
of response in the core of the optical recombination lines on short timescales,
(ii) the enhanced red-wing response on short timescales, (iii) differences
between the measured delays for the HILs and LILs, and (iv) identifies
turbulence as a means of producing Lorentzian profiles (esp. for LILs) in low
inclination systems, and for suppressing significant continuum--emission-line
delays between the line wings and line core (esp. in LILs). A key motivation of
this work was to reveal the physical underpinnings of the reported measurements
of SMBH masses and their uncertainties. We find that SMBH masses derived from
measurements of the fwhm of the mean and rms profiles show the closest
correspondence between the emission lines in a single object, even though the
emission line fwhm is a more biased mass indicator with respect to inclination.
The predicted large discrepancies in the SMBH mass estimates between emission
lines at low inclination, as derived using the line dispersion, we suggest may
be used as a means of identifying near face-on systems. Our general results do
not depend on specific choices in the simplifying assumptions, but are in fact
generic properties of BLR geometries with axial symmetry that span a
substantial range in radially-increasing scale height supported by turbulence,
which then merge into the inner dusty TOR.Comment: 29 pages, 23 figures and 1 tabl
Test results of collision warning systems on off-highway dump trucks: phase 2
"This report summarizes ongoing research at the National Institute for Occupational Safety and Health, Spokane Research Laboratory, in which collision warning systems for surface mining dump trucks are being evaluated. Common accidents involve these large trucks running over smaller vehicles or pedestrian workers. Collision warning systems currently use one of several methods, including radar, radio-frequency-signal detection, or ultrasonic signals, to detect and warn of the presence of an object or person in the blind spots of the mining equipment. Most available systems have not been tested on large off-highway dump trucks. This report evaluates several systems on two sizes of trucks, a 50-ton-capacity truck commonly used in quarries and construction and a 240-ton-capacity truck commonly used in open-pit mines. Tests were conducted to determine false alarm rates, alarm effectiveness, and reliable detection zones for a person and a pickup truck. The results indicate that radar and radiofrequency identification systems show promise for this application and that several of the improved systems are ready for extensive field tests. However, challenges still exist in applying these technologies to large trucks." - NIOSH-2"February 2001."Also available via the World Wide Web as an Acrobat .pdf file (6.17 MB, 27 p.).Includes bibliographical references (p. 21)
Quantum rainbow scattering at tunable velocities
Elastic scattering cross sections are measured for lithium atoms colliding
with rare gas atoms and SF6 molecules at tunable relative velocities down to
~50 m/s. Our scattering apparatus combines a velocity-tunable molecular beam
with a magneto-optic trap that provides an ultracold cloud of lithium atoms as
a scattering target. Comparison with theory reveals the quantum nature of the
collision dynamics in the studied regime, including both rainbows as well as
orbiting resonances
Electronic bulk and domain wall properties in B-site doped hexagonal ErMnO
Acceptor and donor doping is a standard for tailoring semiconductors. More
recently, doping was adapted to optimize the behavior at ferroelectric domain
walls. In contrast to more than a century of research on semiconductors, the
impact of chemical substitutions on the local electronic response at domain
walls is largely unexplored. Here, the hexagonal manganite ErMnO is donor
doped with Ti. Density functional theory calculations show that
Ti goes to the B-site, replacing Mn. Scanning probe microscopy
measurements confirm the robustness of the ferroelectric domain template. The
electronic transport at both macro- and nanoscopic length scales is
characterized. The measurements demonstrate the intrinsic nature of emergent
domain wall currents and point towards Poole-Frenkel conductance as the
dominant transport mechanism. Aside from the new insight into the electronic
properties of hexagonal manganites, B-site doping adds an additional degree of
freedom for tuning the domain wall functionality
Two-Spinon and Orbital Excitations of the Spin-Peierls System TiOCl
We combine high-resolution resonant inelastic x-ray scattering with cluster
calculations utilizing a recently derived effective magnetic scattering
operator to analyze the polarization, excitation energy, and momentum dependent
excitation spectrum of the low-dimensional quantum magnet TiOCl in the range
expected for orbital and magnetic excitations (0 - 2.5 eV). Ti 3d orbital
excitations yield complete information on the temperature-dependent
crystal-field splitting. In the spin-Peierls phase we observe a dispersive
two-spinon excitation and estimate the inter- and intra-dimer magnetic exchange
coupling from a comparison to cluster calculations
Mechanism for the reactions of sulfides with hypochlorous acid and N âchlorosulfonâamides: Formation of solvated chlorosulfonium cation and λ 4 âsulfane intermediates
Ordering of the pyrochlore Ising model with the long-range RKKY interaction
The ordering of the Ising model on a pyrochlore lattice interacting via the
long-range RKKY interaction, which models a metallic pyrochlore magnet such as
Pr_2Ir_2O_7, is studied by Monte Carlo simulations. Depending on the parameter
k_F representing the Fermi wavevector, the model exhibits rich ordering
behaviors
Reference Data for the Ruff Figural Fluency Test Stratified by Age and Educational Level
The Ruff Figural Fluency Test (RFFT) was developed to avoid the difficulties that were encountered in earlier tests of figural fluency. Although the test characteristics of the RFFT seem to be good and it is a valuable addition to neuropsychological assessments, reference data are still scarce. To this aim, we required 2,404 community dwelling persons in Groningen, the Netherlands to perform the RFFT. All 1,651 persons with a complete RFFT and known educational level formed the reference sample. Their age ranged from 35 to 82 years and their educational level from primary school to university grade. Ninety-six percent of the persons were of Western European descent. All tests were analyzed by two independent examiners and subsequently three measures were calculated: number of unique designs, number of perseverative errors and error ratio. The main finding was that performance on the RFFT was dependent on age and educational level. This was not only observed in older persons but also in young and middle-aged persons. Reference data for the three RFFT measures are presented in groups of five years of age ranging from 35â39 years to 75 years or older
Qualitative exploration of perceived benefits of care and barriers influencing HIV care in trans Nzoia, Kenya
Background: Substantial efforts have been made to ensure people living with HIV (PLHIV) are linked to and retained in care but many challenges deter care utilization. We report perceived benefits of seeking HIV care and barriers to HIV care that were identified through a formative assessment conducted to advise the development of an alternative care model to deliver antiretroviral treatment therapy (ART) in Trans Nzoia County, Kenya.
Methods: Data were collected in 2015 through key informant interviews (KIIs), in-depth interviews (IDIs), and focus group discussions (FGDs). The study involved 55 participants of whom 53% were female. Ten KIIs provided community contextual information and viewpoints on the HIV epidemic in Trans Nzoia County while 20 PLHIV (10 male and 10 female) participated in IDIs. Twenty-five individuals living with HIV participated in four FGDs - two groups for men and two for women. Key informants were purposively selected, while every third patient above 18 years at the Kitale HIV Clinic was invited to share their HIV care experience through IDIs or FGDs. Trained research assistants moderated all sessions and audio recordings were transcribed and analyzed thematically.
Results: Findings showed that PLHIV in Trans Nzoia County used both conventional and complementary alternative care for HIV; however, public health facilities were preferred. Popular perceived benefits of adopting care were relief from symptoms and the chance to live longer. Benefits of care uptake included weight gain, renewed energy, and positive behavior change. Individual-level barriers to HIV care included lack of money and food, use of alternative care, negative side effects of ART, denial, and disclosure difficulties. At the community level, stigma, limited social support for conventional HIV treatment, and poor means of transport were reported. The health system barriers were limited supplies and staff, long distance to conventional HIV care, and unprofessional providers.
Conclusions: Diverse individual, community and health system barriers continue to affect HIV care-seeking efforts in Kenya. Appreciation of context and lived experiences allows for development of realistic care models
Spectral, mineralogical, and geochemical variations across Home Plate, Gusev Crater, Mars indicate high and low temperature alteration
Over the last ~ 3 years in Gusev Crater, Mars, the Spirit rover observed coherent variations in color, mineralogy, and geochemistry across Home Plate, an ~ 80 m-diameter outcrop of basaltic tephra. Observations of Home Plate from orbit and from the summit of Husband Hill reveal clear differences in visible/near-infrared (VNIR) colors between its eastern and western regions that are consistent with mineralogical compositions indicated by Mössbauer spectrometer (MB) and by Miniature Thermal Emission Spectrometer (Mini-TES). Pyroxene and magnetite dominate the east side, while olivine, nanophase Fe oxide (npOx) and glass are more abundant on the western side. Alpha Particle X-Ray Spectrometer (APXS) observations reveal that eastern Home Plate has higher Si/Mg, Al, Zn, Ni, and K, while Cl and Br are higher in the west. We propose that these variations are the result of two distinct alteration regimes that may or may not be temporally related: a localized, higher temperature recrystallization and alteration of the east side of Home Plate and lower temperature alteration of the western side that produced npOx
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