scholarly journals Measurement of the 236U(n,f) cross section at fast neutron energies with Micromegas Detectors

2020 ◽  
Vol 239 ◽  
pp. 05001
Author(s):  
M. Diakaki ◽  
V. Michalopoulou ◽  
A. Tsinganis ◽  
A. Axiotis ◽  
A. Kalamara ◽  
...  
Keyword(s):  
Cross Section ◽  
Energy Deposition ◽  
Rutherford Backscattering Spectrometry ◽  
The Other ◽  
Alpha Spectroscopy ◽  
Active Volume ◽  
Experimental Procedure ◽  
Fission Fragments ◽  
National Centre ◽  
Actinide Targets

In the present work, the measurement of the 236U(n,f) cross section was performed, with reference to the 238U(n,f) reaction. The measurements took place at the neutron beam facility of the National Centre for Scientific Research "Demokritos" (Greece) and the quasi-monoenergetic neutron beams were produced via the 2H(d,n)3He reaction in the energy range 4–10 MeV. Five actinide targets (two 236U, two 238U and one 235U) and the corresponding Micromegas detectors for the detection of the fission fragments were used. Detailed Monte Carlo simulations were performed, on one hand for the study of the neutron flux and energy distribution at the position of each target, and on the other hand for the study of the energy deposition of the fission fragments in the active volume of the detector. The mass and homogeneity of the actinide targets were experimentally determined via alpha spectroscopy and the Rutherford Backscattering Spectrometry, respectively. The experimental procedure, the analysis, the methodology implemented to correct for the presence of parasitic neutrons and the cross section results will be presented and discussed.

scholarly journals Measurement of the 236U(n,f) cross-section between 4 and 10 MeV with Micromegas detectors

2019 ◽  
Vol 26 ◽  
pp. 172
Author(s):  
V. Michalopoulou ◽  
M. Diakaki ◽  
A. Stamatopoulos ◽  
A. Kalamara ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Cross Section ◽  
Neutron Beam ◽  
Fission Chamber ◽  
Monoenergetic Neutron ◽  
Fission Fragments ◽  
National Centre ◽  
First Results ◽  
Reference Samples

In this work, the measurement of the 236U(n,f) cross-section is presented, in the energy range 4 – 10 MeV, with the use of quasi-monoenergetic neutron beams produced via the 2H(d,n)3He reaction. The measurements took place at the neutron beam facility of the National Centre for Scientific Research ‘Demokritos’. The detection of the fission fragments was achieved with Micromegas detectors placed in a fission chamber, containing both the 236U targets and the reference samples, namely 238U and 235U. The analysis of the experimental data, as well as the first results will be presented.

scholarly journals Measurement of the 236U(n,f) cross-section between 4 and 10 MeV with Micromegas detectors

2019 ◽  
Vol 26 ◽  
Author(s):  
V. Michalopoulou ◽  
M. Diakaki ◽  
A. Stamatopoulos ◽  
A. Kalamara ◽  
M. Kokkoris ◽  
...  
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Cross Section ◽  
Neutron Beam ◽  
Fission Chamber ◽  
Monoenergetic Neutron ◽  
Fission Fragments ◽  
National Centre ◽  
First Results ◽  
Reference Samples

In this work, the measurement of the 236U(n,f) cross-section is presented, in the energy range 4 – 10 MeV, with the use of quasi-monoenergetic neutron beams produced via the 2H(d,n)3He reaction. The measurements took place at the neutron beam facility of the National Centre for Scientific Research ‘Demokritos’. The detection of the fission fragments was achieved with Micromegas detectors placed in a fission chamber, containing both the 236U targets and the reference samples, namely 238U and 235U. The analysis of the experimental data, as well as the first results will be presented.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Electron Irradiation Effects in Polyoxymethylene Crystals Grown Inside Trioxane Crystals

1971 ◽  
Vol 29 ◽  
pp. 78-79
Author(s):  
J. P. Colson ◽  
D. H. Reneker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Detailed Examination ◽  
The Other ◽  
Electron Micrograph ◽  
Irradiation Effects ◽  
Threefold Axis ◽  
Typical Sample ◽  
Polymer Crystals ◽  
Chain Axis

Polyoxymethylene (POM) crystals grow inside trioxane crystals which have been irradiated and heated to a temperature slightly below their melting point. Figure 1 shows a low magnification electron micrograph of a group of such POM crystals. Detailed examination at higher magnification showed that three distinct types of POM crystals grew in a typical sample. The three types of POM crystals were distinguished by the direction that the polymer chain axis in each crystal made with respect to the threefold axis of the trioxane crystal. These polyoxymethylene crystals were described previously.At low magnifications the three types of polymer crystals appeared as slender rods. One type had a hexagonal cross section and the other two types had rectangular cross sections, that is, they were ribbonlike.

scholarly journals Experimental Procedure Used To Determine The Flexural Rigidity For Composite Sandwich Bars With Various Thickness Values

2015 ◽  
Vol 67 (1) ◽  
pp. 7-12
Author(s):  
Cosmin Mihai Miriţoiu
Keyword(s):  
Carbon Fiber ◽  
Flexural Rigidity ◽  
Free Vibrations ◽  
The Other ◽  
Honeycomb Core ◽  
Experimental Procedure ◽  
Composite Sandwich

Abstract In this paper there is presented an experimental procedure used to determine the flexural rigidity for composite sandwich bars with polypropylene honeycomb core with various thickness values: 1, 1,5 and 2 cm. The composite bars will be reinforced with one layer of carbon fiber. The width value of the composite bars will be of 6 cm. In order to obtain the flexural rigidity the composite bars will be clamped at one end and left free at the other. An accelerometer will be placed at the free end used to record the free vibrations of these bars. The simplifying assumption of “bar” will be used in this research, so I have chosen several free lengths for the bars: 29, 32 and 35 cm. The eigenfrequency of the first eigenmode will be used to determine the flexural rigidity of the bars.

Effective, Shortened Drying of Agar-Gelcasting Al2O3 Tube Through Immersing in Acetone

2021 ◽  
Author(s):  
Ramnaree Kaemkit ◽  
Supawan Vichaphund ◽  
Anukorn Phureungrat ◽  
Methee Promsawat ◽  
Suksawat Sirijarukul ◽  
...  
Keyword(s):  
Cross Section ◽  
Concentration Gradient ◽  
Water Concentration ◽  
Drying Shrinkage ◽  
The Other ◽  
Air Drying ◽  
Al2o3 Tube ◽  
Acetone Water ◽  
Porous Microstructure ◽  
Glass Tubes

Abstract A liquid drying agent, i.e. acetone, was employed for allowing the faster drying of Al2O3 tubes fabricated by agar gelcasting than the conventional air drying. The mixture of Al2O3 slurry and agar solution was separately prepared and then mixed prior to molding out of a set of warmed glass tubes. After the mixture transformed into gelled tube, the gelled tube was demolded and then immersed in acetone at different periods of time from 0 to 50 h. The immersed periods of 50 h led to the acetone replacement for water being inside of the gelling tube by 74 wt.% and then shortened the drying period to be 25 min. On the other hand, the conventional air drying spent 420 min drying completely. After drying, the immersed tubes possessed spherical cross section; whereas, no immersed tubes showed the deformation of cross section. The shortened drying was in line with the smaller drying shrinkage (4.7%), broader pore-size distribution and higher porous microstructure, comparing to the conventional air drying. The mechanism of acetone replacement for water was attributed to the acetone-water concentration gradient creating their inter-diffusion.

The Defect Structure of BaTiO3 Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
L.A. Wills ◽  
B.W. Wessels
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Defect Structure ◽  
Oxygen Vacancies ◽  
Vacuum Annealing ◽  
Deep Level ◽  
Energy Levels ◽  
The Other ◽  
Optical Cross Section ◽  
Impurity Defects

AbstractThe defect structure of BaTiO3 thin films grown on (100) Si was examined using transient photocapacitance spectroscopy. The concentration, optical cross section and associated energy levels of both native and impurity defects in as-grown and annealed BaTiO3 films were evaluated. Deep level defects withpeak energies of Ev+1.8, Ev+2.4, Ev+2.7, Ev+3.0-3.1 and Ev+3.2-3.3 eV were observed in the as-grown films. Upon vacuum annealing, the concentration of the traps at Ev+3.0 and Ev+3.2 eV increased while the concentration of the traps at Ev+ 1.8 and Ev+2.4 eV decreased. The levels at Ev+3.0-3.1 and Ev+3.2-3.3 eV are attributed to oxygen vacancies. The other levels are tentatively ascribed to Fe and Fe related defects.

scholarly journals I Like Vegetables: A Touch-and-Feel Board Book by L. Siminovich

2011 ◽  
Vol 1 (1) ◽  
Author(s):  
Kim Frail
Keyword(s):  
Cross Section ◽  
Public Services ◽  
Picture Book ◽  
The Other ◽  
Learning Method ◽  
University Of Alberta ◽  
Young Readers ◽  
Dinner Table ◽  
Wood Grain ◽  
The University

Siminovich, Lorena. I Like Vegetables: A Touch-and-Feel Board Book. Somerville: Candlewick Press, 2011. Print.“I Like Vegetables” is a dream come true for any nutritionally conscience parent, children’s librarian or teacher. The brightly hued collage illustrations are intriguingly textured with patterns and “touch & feel” inlays. Silky peas and rough-skinned carrots invite young readers to learn about vegetables. The layout is quite clever as it leverages contrast and comparison as a learning method. On one side of the page vegetables are depicted as they would appear growing in the garden while on the other side they are in the home being prepared for the dinner table. In addition, the nature side of the page illustrates the concept of opposites. For example, there are “tall” and “short” cornstalks. Orange carrot roots are “below” the ground, while the feathery green tops are “above”. The indoor side of the page features close-ups of vegetables against a wood-grain background that evokes a cutting board. Here children get a different perspective on the harvested veggies. We see shelled peas, open cornhusks and a cross-section of a pumpkin. The concluding series of images features an “empty” gardener’s basket next to a basket “full” of colourful vegetables on a blue and white gingham picnic tablecloth inlay.  This is primarily a picture book with only the names of the vegetables and the two opposing concepts appearing on each page. The typeset is Helvetica and is large and easy to read.  It is a sturdy board book and the inlays could not be easily ripped out or damaged. It is therefore a welcome addition to any toddler’s library. Other titles in the “I Like” series by Siminovich include: “I Like Toys “, “I Like Bugs” and “I Like Fruit”. “I Like Vegetables” is sure to engage children from ages 1-3. Highly recommended: 4 out of 4 stars Reviewer: Kim FrailKim is a Public Services Librarian at the H.T. Coutts Education Library at the University of Alberta. Children’s literature is a big part of her world at work and at home. She also enjoys gardening, renovating and keeping up with her two-year old. 

scholarly journals OBSERVATIONS ON THE FINE STRUCTURE OF THE DEVELOPING SPERMATID IN THE DOMESTIC CHICKEN

1962 ◽  
Vol 14 (2) ◽  
pp. 193-205 ◽  
Author(s):  
Toshio Nagano
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Cross Section ◽  
Neck Region ◽  
Structural Features ◽  
Dense Granule ◽  
Domestic Chicken ◽  
The Other ◽  
Dense Structure ◽  
Distal Centriole

The kinetic apparatus, the acrosome and associated structures, and the manchette of the spermatid of the domestic chicken have been studied with the electron microscope. The basic structural features of the two centrioles do not change during spermiogenesis, but there is a change in orientation and length. The proximal centriole is situated in a groove at the edge of the nucleus and oriented normal to the long axis of the nucleus and at right angles to the elongate distal centriole. The tail filaments appear to originate from the distal centriole. The plasma membrane is invaginated along the tail filaments. A dense structure which appears at the deep reflection of the plasma membrane is identified as the ring. The fine structure of the ring has no resemblance to that of a centriole and there is no evidence that it is derived from or related to the centrioles. The tail of the spermatid contains nine peripheral pairs and one central pair of tubular filaments. The two members of each pair of peripheral filaments differ in density and in shape: one is dense and circular, and the other is light and semilunar in cross-section. The dense filaments have processes. A manchette consisting of fine tubules appears in the cytoplasm of the older spermatid along the nucleus, neck region, and proximal segment of the tail. The acrosome is spherical in young spermatids and becomes crescentic and, finally, U-shaped as spermiogenesis proceeds. A dense granule is observed in the cytoplasm between acrosome and nucleus. This granule later becomes a dense rod which is interpreted as the perforatorium.

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