5,368 research outputs found
Serological evidence of exposure to Rickettsia felis and Rickettsia typhi in Australian veterinarians
BACKGROUND: Rickettsia felis and Rickettsia typhi are emerging arthropod-borne zoonoses causing fever and flu-like symptoms. Seroprevalence and risk factors associated with exposure to these organisms was explored in Australian veterinarians. METHODS: One hundred and thirty-one veterinarians from across Australia were recruited to participate in a cross-sectional survey. Veterinarians provided a single blood sample and answered a questionnaire on potential risk factors influencing their exposure to R. felis and R. typhi. Indirect microimmunofluorescence antibody testing (IFAT) was used to identify evidence of serological exposure of the participants to R. felis and R. typhi. Results were analyzed and a logistical regression model performed to predict risk factors associated with seropositivity. RESULTS: In total, 16.0% of participants were seropositive to R. felis, 4.6% to R. typhi and 35.1% seropositive to both, where cross-reactivity of the IFAT between R. felis and R. typhi precluded a definitive diagnosis. Veterinarians residing within the south-eastern states of Victoria and Tasmania were at a higher risk of exposure to R. felis or generalised R. felis or R. typhi exposure. Older veterinarians and those that recommended flea treatment to their clients were found to be significantly protected from exposure. CONCLUSIONS: The high exposure to R. felis amongst veterinary professionals suggests that flea-borne spotted fever is an important cause of undifferentiated fever conditions that may not be adequately recognized in Australia
Resonant x-ray scattering study on multiferroic BiMnO3
Resonant x-ray scattering is performed near the Mn K-absorption edge for an
epitaxial thin film of BiMnO3. The azimuthal angle dependence of the resonant
(003) peak (in monoclinic indices) is measured with different photon
polarizations; for the channel a 3-fold symmetric oscillation
is observed in the intensity variation, while the scattering
intensity remains constant. These features are accounted for in terms of the
peculiar ordering of the manganese 3d orbitals in BiMnO3. It is demonstrated
that the resonant peak persists up to 770 K with an anomaly around 440 K; these
high and low temperatures coincide with the structural transition temperatures,
seen in bulk, with and without a symmetry change, respectively. A possible
relationship of the orbital order with the ferroelectricity of the system is
discussed.Comment: 14 pages, 4 figure
Superclustering at Redshift Z=0.54
We present strong evidence for the existence of a supercluster at a redshift
of z=0.54 in the direction of Selected Area 68. From the distribution of
galaxies with spectroscopic redshifts we find that there is a large
over-density of galaxies (a factor of four over the number expected in an
unclustered universe) within the redshift range 0.530 < z < 0.555. By
considering the spatial distribution of galaxies within this redshift range
(using spectroscopic and photometric redshifts) we show that the galaxies in
SA68 form a linear structure passing from the South-West of the survey field
through to the North-East (with a position angle of approximately 35 deg East
of North). This position angle is coincident with the positions of the X-ray
clusters CL0016+16, RX J0018.3+1618 and a new X-ray cluster, RX J0018.8+1602,
centered near the radio source 54W084. All three of these sources are at a
redshift of approximately z=0.54 and have position angles, derived from their
X-ray photon distributions, consistent with that measured for the supercluster.
Assuming a redshift of 0.54 for the distribution of galaxies and a FWHM
dispersion in redshift of 0.020 this represents a coherent structure with a
radial extent of 31 Mpc, transverse dimension of 12 Mpc, and a thickness of
approximately 4 Mpc. The detection of this possible supercluster demonstrates
the power of using X-ray observations, combined with multicolor observations,
to map the large scale distribution of galaxies at intermediate redshifts.Comment: 12 pages, 3 figures, Latex, aaspp4.sty, accepted for publication in
Ap J Letters. Figure 3 and followup observations can be found at
http://tarkus.pha.jhu.edu/~ajc/papers/supercluster
Faint HI 21-cm Emission Line Wings at Forbidden-Velocities
We present the results of a search for faint HI 21-cm emission line wings at
velocities forbidden by Galactic rotation in the Galactic plane using the
Leiden/Dwingeloo HI Survey data and the HI Southern Galactic Plane Survey data.
These ``forbidden-velocity wings (FVWs)'' appear as protruding excessive
emission in comparison with their surroundings in limited (< 2 deg) spatial
regions over velocity extent more than ~20 km/s in large-scale (l-v) diagrams.
Their high-velocities imply that there should be some dynamical phenomena
associated. We have identified 87 FVWs. We present their catalog, and discuss
their distribution and statistical properties. We found that 85% of FVWs are
not coincident with known supernova remnants (SNRs), galaxies, or high-velocity
clouds. Their natures are currently unknown. We suspect that many of them are
fast-moving HI shells and filaments associated with the oldest SNRs that are
essentially invisible except via their HI line emission. We discuss other
possible origins.Comment: 41 pages, 14 figures, to be published in apj
The Asymptotic Giant Branch and the Tip of the Red Giant Branch as Probes of Star Formation History: The Nearby Dwarf Irregular Galaxy KKH 98
We investigate the utility of the asymptotic giant branch (AGB) and the red
giant branch (RGB) as probes of the star formation history (SFH) of the nearby
(D=2.5 Mpc) dwarf irregular galaxy, KKH 98. Near-infrared (IR) Keck Laser Guide
Star Adaptive Optics (AO) images resolve 592 IR bright stars reaching over 1
magnitude below the Tip of the Red Giant Branch. Significantly deeper optical
(F475W and F814W) Hubble Space Telescope images of the same field contain over
2500 stars, reaching to the Red Clump and the Main Sequence turn-off for 0.5
Gyr old populations. Compared to the optical color magnitude diagram (CMD), the
near-IR CMD shows significantly tighter AGB sequences, providing a good probe
of the intermediate age (0.5 - 5 Gyr) populations. We match observed CMDs with
stellar evolution models to recover the SFH of KKH 98. On average, the galaxy
has experienced relatively constant low-level star formation (5 x 10^-4 Mo
yr^-1) for much of cosmic time. Except for the youngest main sequence
populations (age < 0.1 Gyr), which are typically fainter than the AO data flux
limit, the SFH estimated from the the 592 IR bright stars is a reasonable match
to that derived from the much larger optical data set. Differences between the
optical and IR derived SFHs for 0.1 - 1 Gyr populations suggest that current
stellar evolution models may be over-producing the AGB by as much as a factor
of three in this galaxy. At the depth of the AO data, the IR luminous stars are
not crowded. Therefore these techniques can potentially be used to determine
the stellar populations of galaxies at significantly further distances.Comment: 15 pages, 14 figs, accepted for publication in Ap
On the Nature of the Strong Emission-Line Galaxies in Cluster Cl 0024+1654: Are Some the Progenitors of Low Mass Spheroidals?
We present new size, line ratio, and velocity width measurements for six
strong emission-line galaxies in the galaxy cluster, Cl 0024+1654, at redshift
z~0.4. The velocity widths from Keck spectra are all narrow (30<sigma<120
km/s), with three profiles showing double peaks. Four galaxies have low masses
(M<10^{10} Mo). Whereas three galaxies were previously reported to be possible
AGNs, none exhibit AGN-like emission line ratios or velocity widths. Two or
three appear as very blue spirals with the remainder more akin to luminous H-II
galaxies undergoing a strong burst of star formation. We propose that after the
burst subsides, these galaxies will transform into quiescent dwarfs, and are
thus progenitors of some cluster spheroidals (We adopt the nomenclature
suggested by Kormendy & Bender (1994), i.e., low-density, dwarf ellipsoidal
galaxies like NGC 205 are called `spheroidals' instead of `dwarf ellipticals')
seen today.Comment: 14 pages + 2 figures + 1 table, LaTeX, Acc. for publ. in ApJL also
available at http://www.ucolick.org/~deep/papers/papers.htm
Case-based reasoning approach to estimating the strength of sustainable concrete
Continuing from previous studies of sustainable concrete containing environmentally friendly materials and existing modeling approach to predicting concrete properties, this study developed an estimation methodology to predicting the strength of sustainable concrete using an advanced case-based reasoning approach. It was conducted in two steps: (i) establishment of a case database and (ii) development of an advanced case-based reasoning model. Through the experimental studies, a total of 144 observations for concrete compressive strength and tensile strength were established to develop the estimation model. As a result, the prediction accuracy of the A-CBR model (i.e., 95.214% for compressive strength and 92.448% for tensile strength) performed superior to other conventional methodologies (e.g., basic case-based reasoning and artificial neural network models). The developed methodology provides an alternative approach in predicting concrete properties and could be further extended to the future research area in durability of sustainable concrete
Event-triggered proportional-derivative control for nonlinear network systems with a novel event-triggering scheme: Differential of triggered state consideration
This article proposes event-triggered proportional-derivative control for a class of nonlinear network control systems. For derivative action of the proposed proportional-derivative control, a novel event-triggering scheme is devised together with the control that considers a differential of a triggered state. The class of the nonlinear network systems is represented as a Lur'e system to consider various nonlinear cases. Time varying transmission delay is considered which can be defined by lower and upper delay bounds. The proposed proportional-derivative control is designed by Lyapunov-Krasovskii stability analysis, and the design condition is presented by linear matrix inequalities. The proposed event-triggered proportional-derivative control and event-triggering condition are verified with numerical simulation. ? 2017 The Author(s).111Ysciescopu
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