Optical design of type-I x-ray telescopes and itsapplication to STAR-X

2020 ◽

Vol 500 (3) ◽

pp. 2958-2968

Author(s):

Grant Merz ◽

Zach Meisel

Keyword(s):

Light Curve ◽

Nuclear Reaction ◽

Nuclear Physics ◽

Thermal Structure ◽

Reaction Rates ◽

High Mass ◽

Type I ◽

Model Calculations ◽

X Ray ◽

Lower Temperature

ABSTRACT The thermal structure of accreting neutron stars is affected by the presence of urca nuclei in the neutron star crust. Nuclear isobars harbouring urca nuclides can be produced in the ashes of Type I X-ray bursts, but the details of their production have not yet been explored. Using the code MESA, we investigate urca nuclide production in a one-dimensional model of Type I X-ray bursts using astrophysical conditions thought to resemble the source GS 1826-24. We find that high-mass (A ≥ 55) urca nuclei are primarily produced late in the X-ray burst, during hydrogen-burning freeze-out that corresponds to the tail of the burst light curve. The ∼0.4–0.6 GK temperature relevant for the nucleosynthesis of these urca nuclides is much lower than the ∼1 GK temperature most relevant for X-ray burst light curve impacts by nuclear reaction rates involving high-mass nuclides. The latter temperature is often assumed for nuclear physics studies. Therefore, our findings alter the excitation energy range of interest in compound nuclei for nuclear physics studies of urca nuclide production. We demonstrate that for some cases this will need to be considered in planning for nuclear physics experiments. Additionally, we show that the lower temperature range for urca nuclide production explains why variations of some nuclear reaction rates in model calculations impacts the burst light curve but not local features of the burst ashes.

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The study of multipeaked type-I X-ray bursts in the neutron star low-mass X-ray binary 4U 1636 − 536 with RXTE

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3539 ◽

2020 ◽

Vol 501 (1) ◽

pp. 168-178

Author(s):

Chen Li ◽

Guobao Zhang ◽

Mariano Méndez ◽

Jiancheng Wang ◽

Ming Lyu

Keyword(s):

Neutron Star ◽

Flux Ratio ◽

Light Curves ◽

Type I ◽

X Ray ◽

Soft State ◽

Peak Flux ◽

Low Mass ◽

Two Peaks ◽

Second Peak

ABSTRACT We have found and analysed 16 multipeaked type-I bursts from the neutron-star low-mass X-ray binary 4U 1636 − 53 with the Rossi X-ray Timing Explorer (RXTE). One of the bursts is a rare quadruple-peaked burst that was not previously reported. All 16 bursts show a multipeaked structure not only in the X-ray light curves but also in the bolometric light curves. Most of the multipeaked bursts appear in observations during the transition from the hard to the soft state in the colour–colour diagram. We find an anticorrelation between the second peak flux and the separation time between two peaks. We also find that in the double-peaked bursts the peak-flux ratio and the temperature of the thermal component in the pre-burst spectra are correlated. This indicates that the double-peaked structure in the light curve of the bursts may be affected by enhanced accretion rate in the disc, or increased temperature of the neutron star.

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Latitudinal Shear Instabilities during Type I X‐Ray Bursts

The Astrophysical Journal ◽

10.1086/431731 ◽

2005 ◽

Vol 630 (1) ◽

pp. 441-453 ◽

Cited By ~ 16

Author(s):

Andrew Cumming

Keyword(s):

Type I ◽

X Ray ◽

Shear Instabilities

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A new model for packing of type-I collagen molecules in the native fibril

Bioscience Reports ◽

10.1007/bf01114803 ◽

1981 ◽

Vol 1 (10) ◽

pp. 801-810 ◽

Cited By ~ 49

Author(s):

Karl A. Piez ◽

Benes L. Trus

Keyword(s):

Type I Collagen ◽

Hexagonal Lattice ◽

Three Dimensional ◽

Equatorial Region ◽

Type I ◽

X Ray Diffraction ◽

X Ray ◽

Left Handed ◽

Crystal Model ◽

Collagen Molecules

A specific fibril model is presented consisting of bundles of five-stranded microfibrils, which are usually disordered (except axially) but under lateral compression become ordered. The features are as follows (where D = 234 residues or 67 nm): (1) D-staggered collagen molecules 4.5 D long in the helical microfibril have a left-handed supercoil with a pitch of 400–700 residues, but microfibrils need not have helical symmetry. (2) Straight-tilted 0.5-D overlap regions on a near-hexagonal lattice contribute the discrete x-ray diffraction reflections arising from lateral order, while the gap regions remain disordered. (3) The overlap regions are equivalent, but are crystallographically distinguished by systematic displacements from the near-hexagonal lattice. (4) The unit cell is the same as in a recently proposed three-dimensional crystal model, and calculated intensities in the equatorial region of the x-ray diffraction pattern agree with observed values.

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Ignition latitude and the shape of Type I X-ray bursts

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2007.12558.x ◽

2007 ◽

Vol 383 (1) ◽

pp. 387-398 ◽

Cited By ~ 26

Author(s):

Immanuel Maurer ◽

Anna L. Watts

Keyword(s):

Type I ◽

X Ray

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The Effect of Different Methods to Pretreat Reed Pulp on the Crystallinity of Microcrystalline Cellulose

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1056.12 ◽

2014 ◽

Vol 1056 ◽

pp. 12-15 ◽

Cited By ~ 1

Author(s):

Wen Long Zhang ◽

Wen Long Zhao ◽

Ya Jie Dai

Keyword(s):

Crystallite Size ◽

Microcrystalline Cellulose ◽

Average Crystallite Size ◽

Comprehensive Analysis ◽

Raw Material ◽

Type I ◽

X Ray Diffraction ◽

X Ray ◽

Dimethyl Acetamide ◽

Crystal Type

Reed Pulp was Raw Material that Pretreated by Four Methods {ultrasonic, Microwave, N, N-Dimethyl Acetamide (DMAc) and Tetrahydrofuran (THF)}. Reed Microcrystalline Cellulose (MCC) was Prepared by the Dilute Hydrochloric Acid Hydrolysis from Pretreated Reed Pulp. the Influences of Pretreatment Methods on Crystalline Type, Crystallinity and Crystallite Size of MCC were Investigated by X-Ray Diffraction (XRD). the Results Showed that the Crystallinity of MCC with Four Pretreatment Methods was 68.45%, 62.28%, 63.21% and 69.56%, Respectively. the Average Crystallite Size of MCC Prepared by Hydrolysis after Pretreated by Dmac was the Largest. whereas, the Crystal Type of MCC was Not Changed, it was still the Cellulose Type I. Comprehensive Analysis Indicated that the Effects of MCC Prepared by Hydrolysis after Pretreated by Ultrasonic were the Best.

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Entropy estimation of the fragments of chest X-ray images

Кибернетика и программирование ◽

10.25136/2644-5522.2021.1.31676 ◽

2021 ◽

pp. 20-26

Author(s):

Aleksei Aleksandrovich Rumyantsev ◽

Farkhad Mansurovich Bikmuratov ◽

Nikolai Pavlovich Pashin

Keyword(s):

Neural Network ◽

Neural Networks ◽

Binary Classification ◽

Statistical Characteristics ◽

Type I ◽

Deep Convolutional Neural Networks ◽

Preliminary Calculation ◽

X Ray ◽

The Matrix ◽

Chest X Ray

The subject of this research is medical chest X-ray images. After fundamental pre-processing, the accumulated database of such images can be used for training deep convolutional neural networks that have become one of the most significant innovations in recent years. The trained network carries out preliminary binary classification of the incoming images and serve as an assistant to the radiotherapist. For this purpose, it is necessary to train the neural network to carefully minimize type I and type II errors. Possible approach towards improving the effectiveness of application of neural networks, by the criteria of reducing computational complexity and quality of image classification, is the auxiliary approaches: image pre-processing and preliminary calculation of entropy of the fragments. The article provides the algorithm for X-ray image pre-processing, its fragmentation, and calculation of the entropy of separate fragments. In the course of pre-processing, the region of lungs and spine is selected, which comprises approximately 30-40% of the entire image. Then the image is divided into the matrix of fragments, calculating the entropy of separate fragments in accordance with Shannon’s formula based pm the analysis of individual pixels. Determination of the rate of occurrence of each of the 255 colors allows calculating the total entropy. The use of entropy for detecting pathologies is based on the assumption that its values differ for separate fragments and overall picture of its distribution between the images with the norm and pathologies. The article analyzes the statistical values: standard deviation of error, dispersion. A fully connected neural network is used for determining the patterns in distribution of entropy and its statistical characteristics on various fragments of the chest X-ray image.

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