2,074 research outputs found
Method of Monte Carlo grid for data analysis
This paper presents an analysis procedure for experimental data using
theoretical functions generated by Monte Carlo. Applying the classical
chi-square fitting procedure for some multiparameter systems is extremely
difficult due to a lack of an analytical expression for the theoretical
functions describing the system. The proposed algorithm is based on the least
square method using a grid of Monte Carlo generated functions each
corresponding to definite values of the minimization parameters. It is used for
the E742 experiment (TRIUMF, Vancouver, Canada) data analysis with the aim to
extract muonic atom scattering parameters on solid hydrogen.Comment: 16 pages, 10 figures, submitted to NI
A Search for Optical Variability of Type 2 Quasars in SDSS Stripe 82
Hundreds of Type 2 quasars have been identified in Sloan Digital Sky Survey
(SDSS) data, and there is substantial evidence that they are generally galaxies
with highly obscured central engines, in accord with unified models for active
galactic nuclei (AGNs). A straightforward expectation of unified models is that
highly obscured Type 2 AGNs should show little or no optical variability on
timescales of days to years. As a test of this prediction, we have carried out
a search for variability in Type 2 quasars in SDSS Stripe 82 using
difference-imaging photometry. Starting with the Type 2 AGN catalogs of
Zakamska et al. (2003) and Reyes et al. (2008), we find evidence of significant
g-band variability in 17 out of 173 objects for which light curves could be
measured from the Stripe 82 data. To determine the nature of this variability,
we obtained new Keck spectropolarimetry observations for seven of these
variable AGNs. The Keck data show that these objects have low continuum
polarizations (p<~1% in most cases) and all seven have broad H-alpha and/or
MgII emission lines in their total (unpolarized) spectra, indicating that they
should actually be classified as Type 1 AGNs. We conclude that the primary
reason variability is found in the SDSS-selected Type 2 AGN samples is that
these samples contain a small fraction of Type 1 AGNs as contaminants, and it
is not necessary to invoke more exotic possible explanations such as a
population of "naked" or unobscured Type 2 quasars. Aside from misclassified
Type 1 objects, the Type 2 quasars do not generally show detectable optical
variability over the duration of the Stripe 82 survey.Comment: 14 pages, 8 figures. Accepted for publication in A
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
Monte Carlo Fitting Of Data From Muon Catalyzed Fusion Experiments In Solid Hydrogen
Applying the classical chi-square fitting procedure for multiparameter systems is in somecases extremely difficult due to the lack of an analytical expression for the theoretical functionsdescribing the system. This paper presents an analysis procedure for experimental datausing theoretical functions generated by Monte Carlo method, each corresponding to definitevalues of the minimization parameters. It was applied for the E742 experiment (TRIUMF,Vancouver, Canada) data analysis with the aim to analyze data from Muon Catalyzed Fusionexperiments (extraction muonic atom scattering parameters and parameters of pd fusion inpdμ molecule)
Exploring the Variable Sky with LINEAR. I. Photometric Recalibration with the Sloan Digital Sky Survey
We describe photometric recalibration of data obtained by the asteroid survey LINEAR. Although LINEAR was designed for astrometric discovery of moving objects, the data set described here contains over 5 billion photometric measurements for about 25 million objects, mostly stars. We use Sloan Digital Sky Survey (SDSS) data from the overlapping ~10,000 deg^2 of sky to recalibrate LINEAR photometry and achieve errors of 0.03 mag for sources not limited by photon statistics with errors of 0.2 mag at r ~ 18. With its 200 observations per object on average, LINEAR data provide time domain information for the brightest four magnitudes of the SDSS survey. At the same time, LINEAR extends the deepest similar wide-area variability survey, the Northern Sky Variability Survey, by 3 mag. We briefly discuss the properties of about 7000 visually confirmed periodic variables, dominated by roughly equal fractions of RR Lyrae stars and eclipsing binary stars, and analyze their distribution in optical and infrared color-color diagrams. The LINEAR data set is publicly available from the SkyDOT Web site
Osseointegration of hydroxyapatite coatings doped with silver nanoparticles: scanning electron microscopy studies on a rabbit model
Background: Modern joint arthroplasties rely on osseointegration of metal components through bone ingrowth into hydroxyapatite (HA) layers. However, such surfaces are prone to colonisation by bacteria and formation of biofilms. Application of silver nanoparticles (SNs) to hydroxyapatite coatings could reduce the risk of infection; however, little is known about how this would affect the process of bone ingrowth. This study examined osseointegration of conventional and SN doped HA coatings in a rabbit model.
Materials and methods: In this study, 12 cylindrical implants coated with conven- tional and SN doped HA were implanted into New Zealand white rabbit femora, with each animal receiving both types of implants. After 12 weeks, rabbits were sacrificed, their femora were harvested and implants removed during pull-out testing. Retrieved samples were dehydrated, sputter coated and observed using a scanning electron microscope (SEM) to verify bony ingrowth and retention of SNs.
Results: The percentage of implant in direct contact with bone was measured in cross-sections of implants. The SEM analysis demonstrated that osseointegration of the SN doped coatings was similar to the conventional HA samples. A similar morphology of newly formed trabecular bone was observed in both implants, with silver doped HA-coated implants retaining multiple nanoparticles in areas which were not overgrown by bone. Analysis of the bone-implant contact area revealed comparable results for both types of coatings. These finding indicated that SN doped HA coatings are characterised by good osseointegrative properties.
Conclusions: Since SNs were found in areas not covered by mineralised bone, it is assumed that the antimicrobial properties of the modified coating may be retained for 12 weeks after implantation. Additional studies are required to fine--tune the composition of HA coatings with SNs, to ensure optimal osseointegrative and antimicrobial properties.
The first appearance of sympathetic ganglia in human embryos at stage 13
The primordia of the sympathetic trunk ganglia were traced on serial sections
of 10 embryos at stage 13 (32 postovulatory days). It was found that in all
embryos, these primordia were present in the thoracic level T4 to T9 and they
appeared as scattered aggregates of cells lying dorsally and laterally to the
dorsal aortae
White communicating rami in human embryos at the end of the fifth week
White communicating rami were traced in 8 human embryos of developmental
stages 14 and 15 (aged 33 and 36 postovulatory days, respectively). In
embryos at stage 14 the white communicating rami were found in the spinal
nerves T1 to T9. In embryos at stage 15 the white communicating rami were
present at the spinal cord levels T1 to L3. (Folia Morphol 2010; 69, 2: 75-77
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