2,694 research outputs found
Calculation of Optimal Geometrical Magnification and Spatial Resolution of Betatron Tomograph
One of the perspective directions of development of non-destructive testing is the method of computed tomography. Computed tomography really enhances the ability of X-ray inspection, from thin and simple to thick and complex parts. There are many factors that influence the performance of computed tomography, the main parameters for computed tomography scanners and also scanner based on betatron, are geometric magnification and spatial resolution. Calculations of these parameters for the betatron tomograph are shown in this paper
The Selection of Computed Tomography Scanning Schemes for Lengthy Symmetric Objects
The article describes the basic computed tomography scan schemes for lengthy symmetric objects: continuous (discrete) rotation with a discrete linear movement; continuous (discrete) rotation with discrete linear movement to acquire 2D projection; continuous (discrete) linear movement with discrete rotation to acquire one–dimensional projection and continuous (discrete) rotation to acquire of 2D projection. The general method to calculate the scanning time is discussed in detail. It should be extracted the comparison principle to select a scanning scheme. This is because data are the same for all scanning schemes: the maximum energy of the X–ray radiation; the power of X–ray radiation source; the angle of the X-ray cone beam; the transverse dimension of a single detector; specified resolution and the maximum time, which is need to form one point of the original image and complies the number of registered photons). It demonstrates the possibilities of the above proposed method to compare the scanning schemes. Scanning object was a cylindrical object with the mass thickness is 4 g/cm2, the effective atomic number is 15 and length is 1300 mm. It analyzes data of scanning time and concludes about the efficiency of scanning schemes. It examines the productivity of all schemes and selects the effective one
Deep Hubble Space Telescope/ACS Observations of I Zw 18: a Young Galaxy in Formation
We present V and I photometry of the resolved stars in the most
metal-deficient blue compact dwarf galaxy known, I Zw 18 (Zsun/50), using
Hubble Space Telescope/Advanced Camera for Surveys (ACS) images, the deepest
ones ever obtained for this galaxy. The resulting I vs. V-I color-magnitude
diagram (CMD) reaches limiting magnitudes V=I=29 mag. It reveals a young
stellar population of blue main-sequence (MS) stars (age <30 Myr) and blue and
red supergiants (10 Myr<age<100 Myr), but also an older evolved population of
asymptotic giant branch (AGB) stars (100 Myr<age<500 Myr). We derive a distance
to I Zw 18 in the range 12.6 Mpc - 15 Mpc from the brightness of its AGB stars,
with preferred values in the higher range. The red giant branch (RGB) stars are
conspicuous by their absence, although, for a distance of I Zw 18 <15 Mpc, our
imaging data go ~ 1-2 mag below the tip of the RGB. Thus, the most evolved
stars in the galaxy are not older than 500 Myr and I Zw 18 is a bona fide young
galaxy. Several star formation episodes can be inferred from the CMDs of the
main body and the C component. There have been respectively three and two
episodes in these two parts, separated by periods of ~ 100-200 Myr. In the main
body, the younger MS and massive post-MS stars are distributed over a larger
area than the older AGB stars, suggesting that I Zw 18 is still forming from
the inside out. In the C component, different star formation episodes are
spatially distinct, with stellar population ages decreasing from the northwest
to the southeast, also suggesting the ongoing build-up of a young galaxy.Comment: 29 pages, 13 Postscript figures, accepted for publication in the
Astrophysical Journa
The Oxygen Abundance of Nearby Galaxies from Sloan Digital Sky Survey Spectra
We have derived the oxygen abundance for a sample of nearby galaxies in the
Data Release 5 of the Sloan Digital Sky Survey (SDSS) which possess at least
two independent spectra of one or several HII regions with a detected
[OIII]4363 auroral line. Since, for nearby galaxies, the [OII]3727 nebular line
is out of the observed wavelength range, we propose a method to derive (O/H)_ff
abundances using the classic Te method coupled with the ff relation. (O/H)_7325
abundances have also been determined, based on the [OII]7320,7330 line
intensities, and using a small modification of the standard Te method. The
(O/H)_ff and (O/H)_7325 abundances have been derived with both the one- and
two-dimensional t_2 - t_3 relations. It was found that the (O/H)_ff abundances
derived with the parametric two-dimensional t_2 - t_3 relation are most
reliable. Oxygen abundances have been determined in 29 nearby galaxies, based
on 84 individual abundance determinations in HII regions. Because of our
selection methods, the metallicity of our galaxies lies in the narrow range 8.2
< 12 + log (O/H) < 8.4. The radial distribution of oxygen abundances in the
disk of the spiral galaxy NGC 4490 is determined for the first time.Comment: 39 pages, 10 figures, 4 tables, accepted for publication in the
Astrophysical Journa
Pseudo-Hermiticity and some consequences of a generalized quantum condition
We exploit the hidden symmetry structure of a recently proposed non-Hermitian
Hamiltonian and of its Hermitian equivalent one. This sheds new light on the
pseudo-Hermitian character of the former and allows access to a generalized
quantum condition. Special cases lead to hyperbolic and Morse-like potentials
in the framework of a coordinate-dependent mass model.Comment: 10 pages, no figur
On subgroups in division rings of type
Let be a division ring with center . We say that is a {\em
division ring of type } if for every two elements the division
subring is a finite dimensional vector space over . In this paper
we investigate multiplicative subgroups in such a ring.Comment: 10 pages, 0 figure
Immunodeficiency in Pancreatic Adenocarcinoma with Diabetes Revealed by Comparative Genomics
Purpose: Pancreatic adenocarcinomas (PAAD) often are not diagnosed until their late stages, leaving no effective treatments. Currently, immunotherapy provides a promising treatment option against this malignancy. However, a set of immunotherapy agents benefit patients with many types of cancer, but not PAAD. Sharing the origin in the same organ, diabetes and PAAD tend to occur concurrently. We aimed to identify the impact of diabetes on immunotherapy of PAAD by conducting a comparative genomics analysis.Experimental Design: We analyzed level 3 PAAD genomics data (RNAseq, miRNAseq, DNA methylation, somatic copy number, and somatic mutation) from The Cancer Genome Atlas (TCGA) and Firehose. The differential molecular profiles in PAAD with/out diabetes were performed by the differential gene expression, pathway analysis, epigenetic regulation, somatic copy-number alteration, and somatic gene mutation.Results: Differential gene expression analysis revealed a strong enrichment of immunogenic signature genes in diabetic individuals, including PD-1 and CTLA4, that were currently targetable for immunotherapy. Pathway analysis further implied that diabetic individuals were defective in immune modulation genes. Somatic copy-number aberration (SCNA) analysis showed a higher frequency of amplification and deletion occurred in the cohort without diabetes. Integrative analysis revealed strong association between differential gene expression, and epigenetic regulations, however, seemed not affected by SCNAs. Importantly, our somatic mutation analysis showed that the occurrence of diabetes in PAAD was associated with a large set of gene mutations encoding genes participating in immune modulation.Conclusions: Our analysis reveals the impact of diabetes on immunodeficiency in PAAD patients and provides novel insights into new therapeutic opportunities
WaveCNV: allele-specific copy number alterations in primary tumors and xenograft models from next-generation sequencing.
MotivationCopy number variations (CNVs) are a major source of genomic variability and are especially significant in cancer. Until recently microarray technologies have been used to characterize CNVs in genomes. However, advances in next-generation sequencing technology offer significant opportunities to deduce copy number directly from genome sequencing data. Unfortunately cancer genomes differ from normal genomes in several aspects that make them far less amenable to copy number detection. For example, cancer genomes are often aneuploid and an admixture of diploid/non-tumor cell fractions. Also patient-derived xenograft models can be laden with mouse contamination that strongly affects accurate assignment of copy number. Hence, there is a need to develop analytical tools that can take into account cancer-specific parameters for detecting CNVs directly from genome sequencing data.ResultsWe have developed WaveCNV, a software package to identify copy number alterations by detecting breakpoints of CNVs using translation-invariant discrete wavelet transforms and assign digitized copy numbers to each event using next-generation sequencing data. We also assign alleles specifying the chromosomal ratio following duplication/loss. We verified copy number calls using both microarray (correlation coefficient 0.97) and quantitative polymerase chain reaction (correlation coefficient 0.94) and found them to be highly concordant. We demonstrate its utility in pancreatic primary and xenograft sequencing data.Availability and implementationSource code and executables are available at https://github.com/WaveCNV. The segmentation algorithm is implemented in MATLAB, and copy number assignment is implemented [email protected] informationSupplementary data are available at Bioinformatics online
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