1,591 research outputs found
Inertia compensation while scanning screw threads on coordinate-measuring machines
Usage of scanning coordinate-measuring machines for inspection of screw
threads has become a common practice nowadays. Compared to touch trigger
probing, scanning capabilities allow to speed up measuring process while still
maintaining high accuracy. However, in some cases accuracy drasticaly depends
on the scanning speed. In this paper a compensation method is proposed allowing
to reduce the influence of some dynamic effects while scanning screw threads on
coordinate-measuring machines
Analysis of RR Lyrae Stars in the Northern Sky Variability Survey
We use data from the Northern Sky Variability Survey (NSVS), obtained from
the first generation Robotic Optical Transient Search Experiment (ROTSE-I), to
identify and study RR Lyrae variable stars in the solar neighborhood. We
initially identified 1197 RRab (RR0) candidate stars brighter than the ROTSE
median magnitude V = 14. Periods, amplitudes, and mean V magnitudes are
determined for a subset of 1188 RRab stars with well defined light curves.
Metallicities are determined for 589 stars by the Fourier parameter method and
by the relationship between period, amplitude, and [Fe/H]. We comment upon the
difficulties of clearly classifying RRc (RR1) variables in the NSVS dataset.
Distances to the RRab stars are calculated using an adopted
luminosity-metallicity relation with corrections for interstellar extinction.
The 589 RRab stars in our final sample are used to study the properties of the
RRab population within 5 kpc of the Sun. The Bailey diagram of period versus
amplitude shows that the largest component of this sample belongs to Oosterhoff
type I. Metal-rich ([Fe/H] > -1) RRab stars appear to be associated with the
Galactic disk. Our metal-rich RRab sample may include a thin disk as well as a
thick disk population, although the uncertainties are too large to establish
this. There is some evidence among the metal-rich RRab stars for a decline in
scale height with increasing [Fe/H], as was found by Layden (1995). The
distribution of RRab stars with -1 < [Fe/H] < -1.25 indicates that within this
metallicity range the RRab stars are a mixture of stars belonging to halo and
disk populations.Comment: 68 pages, 26 figures, 9 tables, accepted to A
Spatial Variability in the Ratio of Interstellar Atomic Deuterium to Hydrogen. I. Observations toward delta Orionis by the Interstellar Medium Absorption Profile Spectrograph
Studies of the abundances of deuterium in different astrophysical sites are
of fundamental importance to answering the question about how much deuterium
was produced during big bang nucleosynthesis and what fraction of it was
destroyed later. With this in mind, we used the Interstellar Medium Absorption
Profile Spectrograph (IMAPS) on the ORFEUS-SPAS II mission to observe at a
wavelength resolution of 4 km/s (FWHM) the L-delta and L-epsilon absorption
features produced by interstellar atomic deuterium in the spectrum of delta Ori
A. A chi-square analysis indicated that 0.96 < N(D I)< 1.45e15 cm^{-2} at a 90%
level of confidence, and the gas is at a temperature of about 6000K. To obtain
an accurate value of N(H I) needed for a determination of the atomic ratio of D
to H, we measured the L-alpha absorption features in 57 spectra of delta Ori in
the IUE archive. From our measurement of N(H I)= 1.56e20 cm^{-2}, we found that
N(D I)/N(H I)= 7.4(+1.9,-1.3)e-6 (90% confidence). Our result for D/H contrasts
with the more general finding along other lines of sight that D/H is
approximately 1.5e-5. The underabundance of D toward delta Ori A is not
accompanied by an overabundance of N or O relative to H, as one might expect if
the gas were subjected to more stellar processing than usual.Comment: 37 pages, 6 figures. Submitted to the Astrophysical Journa
Microlensing optical depth toward the Galactic Bulge using bright sources from OGLE-II
We present a measurement of the microlensing optical depth toward the
Galactic Bulge based on 4 years of the OGLE-II survey using Red Clump Giant
(RCG). Using 32 events we find tau=2.55_{-0.46}^{+0.57}* 10^{-6} at
(l,b)=(1.16, -2.75). Taking into account the measured gradient along the
Galactic latitude b, tau = [ (4.48+/- 2.37) + (0.78+/- 0.84)* b]* 10^{-6}, this
value is consistent with previous measurements using RCG sources and recent
theoretical predictions. We determine the microlensing parameters and select
events using a model light curve with the flux blending. We find that ~38% of
the OGLE-II events which appear to have RCG sources are actually due to much
fainter stars blended with a bright companion. We show explicitly that model
fits without blending result in similar tau estimates through partial
cancellation of contributions from higher detection efficiency, underestimated
time-scales and larger number of selected events. This approach, however, leads
to biased time-scale distributions and event rates. Consequently, microlensing
studies should carefully consider source confusion effects even for bright
stars.Comment: 49 pages and 18 figures, ApJ in press, the value changed due to the
systematic correctio
Gravitational Microlensing as a probe of the Electron Scattering Region in Q2237+0305
Recent observations have provided strong evidence for the presence of an
Electron Scattering Region (ESR) within the central regions of AGNs. This is
responsible for reprocessing emission from the accretion disk into polarised
radiation. The geometry of this scattering region is, however, poorly
constrained. In this paper, we consider the influence of gravitational
microlensing on polarised emission from the ESR in the quadruply imaged quasar,
Q2237+0305, demonstrating how correlated features in the resultant light curve
variations can determine both the size and orientation of the scattering
region. This signal is due to differential magnification between
perpendicularly polarised views of the ESR, and is clearest for a small ESR
width and a large ESR radius. Cross- and auto-correlation measures appear to be
independent of lens image shear and convergence parameters, making it ideal to
investigate ESR features. As with many microlensing experiments, the time-scale
for variability, being of order decades to centuries, is impractically long.
However, with a polarization filter oriented appropriately with respect to the
path that the quasar takes across the caustic structure, the ESR diameter and
radius can be estimated from the auto- and cross-correlation of polarized light
curves on much shorter time-scales.Comment: 11 pages, 12 figures, 1 table, accepted for MNRA
Gamma-Ray Burst at the extreme: "the naked-eye burst" GRB 080319B
On 19 March 2008, the northern sky was the stage of a spectacular optical
transient that for a few seconds remained visible to the naked eye. The
transient was associated with GRB 080319B, a gamma-ray burst at a luminosity
distance of about 6 Gpc (standard cosmology), making it the most luminous
optical object ever recorded by human kind. We present comprehensive sky
monitoring and multi-color optical follow-up observations of GRB 080319B
collected by the RAPTOR telescope network covering the development of the
explosion and the afterglow before, during, and after the burst. The extremely
bright prompt optical emission revealed features that are normally not
detectable. The optical and gamma-ray variability during the explosion are
correlated, but the optical flux is much greater than can be reconciled with
single emission mechanism and a flat gamma-ray spectrum. This extreme optical
behavior is best understood as synchrotron self-Compton model (SSC). After a
gradual onset of the gamma-ray emission, there is an abrupt rise of the prompt
optical flux suggesting that variable self-absorption dominates the early
optical light curve. Our simultaneous multi-color optical light curves
following the flash show spectral evolution consistent with a rapidly decaying
red component due to large angle emission and the emergence of a blue forward
shock component from interaction with the surrounding environment. While
providing little support for the reverse shock that dominates the early
afterglow, these observations strengthen the case for the universal role of the
SSC mechanism in generating gamma-ray bursts.Comment: accepted for publication in Ap
Intravaginal brachytherapy for patients with endometrial cancer after surgery-review of technical developments
The use of intravaginal brachytherapy as a post-operative procedure to reduce the incidence of reccurence of carcinoma of the endometrium is well known. We analysed 3 differents methods of intravaginal brachytherapy: conventional brachytherapy Ra-226, LDR after-loading technic Cez 137 and HDR after-loading brachytherapy lrydium 192. In the period 1953–1986 in Gynaecological Radiotherapy Department in Poznań, brachytherapy with vaginal applicators containing 30 mg radium, filtrated by 2 mm Pb, were used after total hysterectomy. The given dose was 3000 mgh in 100 hours of one insertion. Since 1986 Caesium 137 in one oblong applicator has been used to fill the vagina. Usualy four sources were employed and treatment time was about 24 hours. On the basis of the radiological verification in two planes, the doses were calculated at 0,5 cm from the applicator surface and at the contact point of the contrast image of the Foley catheter placed in the bladder neck. Dose in the rectum was calculated at the distance shown by a marker situated in the rectum. The patients were treated to the total dose of 30 Gy. From 1995 HDR after-loading inreasingly replaced LDR after-loading in intravaginal brachytherapy. With iridium 192 the overall dose was applied in three fractions-each 6 Gy calculated at 0,5 cm from the surface of the oblong applicator. Complications were graded with EORTC\RTOG criteria
Star-galaxy separation in the AKARI NEP Deep Field
Context: It is crucial to develop a method for classifying objects detected
in deep surveys at infrared wavelengths. We specifically need a method to
separate galaxies from stars using only the infrared information to study the
properties of galaxies, e.g., to estimate the angular correlation function,
without introducing any additional bias. Aims. We aim to separate stars and
galaxies in the data from the AKARI North Ecliptic Pole (NEP) Deep survey
collected in nine AKARI / IRC bands from 2 to 24 {\mu}m that cover the near-
and mid-infrared wavelengths (hereafter NIR and MIR). We plan to estimate the
correlation function for NIR and MIR galaxies from a sample selected according
to our criteria in future research. Methods: We used support vector machines
(SVM) to study the distribution of stars and galaxies in the AKARIs multicolor
space. We defined the training samples of these objects by calculating their
infrared stellarity parameter (sgc). We created the most efficient classifier
and then tested it on the whole sample. We confirmed the developed separation
with auxiliary optical data obtained by the Subaru telescope and by creating
Euclidean normalized number count plots. Results: We obtain a 90% accuracy in
pinpointing galaxies and 98% accuracy for stars in infrared multicolor space
with the infrared SVM classifier. The source counts and comparison with the
optical data (with a consistency of 65% for selecting stars and 96% for
galaxies) confirm that our star/galaxy separation methods are reliable.
Conclusions: The infrared classifier derived with the SVM method based on
infrared sgc- selected training samples proves to be very efficient and
accurate in selecting stars and galaxies in deep surveys at infrared
wavelengths carried out without any previous target object selection.Comment: 8 pages, 8 figure
Typology of the antegonial notch in the human mandible
Background: Surgical treatment for serious malocclusions and fractures of the organ of mastication is a golden standard in medicine. Procedures performed on the mandible require detailed knowledge of the anatomy of the organ. Antegonial notching constitutes a serious technical challenge for surgeons. Therefore, a detailed anatomical description of this structure, which is the subject of this paper, is essential.
Materials and methods: We analysed 251 human Caucasian mandibles of identified sex and took measurements of all sections describing the mandibular antegonial notch. Depending on the proportion between sections we classified the shape of the antegonial notch into three types. The surface area of the notch was calculated. We analysed the dimorphic and bilateral differences for each of the three types of notch. We used variance analysis for the assessment of statistical difference.
Results: The analysis revealed that in both men and women, regardless of body side, the type 3 antegonial notch was the most frequent. Type 3 occurred with a frequency of between 38% in men on the right side and 55.9% in women on the left side of the body. Type 1 was the least frequent. Dimorphic differences in the presence of individual types of antegonial notch were statistically significant only for the left side of the body. The symmetrical type (type 2) occurred more frequently in men (by 11%) than in women. Type 3 was found more frequently in women (by 10%) than in men. Bilateral differences in men were revealed for the frequencies of types 1 and 3. On the right side type 1 was more frequent (by 8%), and on the left side type 3 was also more frequent (by 8%). The greatest surface area was found for the asymmetrical posterior type (type 1). The smallest surface area was found for the asymmetrical anterior type 3. This difference was statistically significant with respect to the surface area of types 1 and type 2 and found for both sexes for both sides of the body. However, no statistically significant differences were found between the surface areas of types 1 or 2.
Conclusions: Knowledge of the preangular notch anatomy can be useful for surgeons during reconstructive and plastic procedures on the body of the mandible
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