THE DENSITY DISTRIBUTION IN TURBULENT BISTABLE FLOWS

International Nuclear Information System (INIS)

Gazol, Adriana; Kim, Jongsoo

2013-01-01

We numerically study the volume density probability distribution function (n-PDF) and the column density probability distribution function (Σ-PDF) resulting from thermally bistable turbulent flows. We analyze three-dimensional hydrodynamic models in periodic boxes of 100 pc by side, where turbulence is driven in the Fourier space at a wavenumber corresponding to 50 pc. At low densities (n ∼ –3 ), the n-PDF is well described by a lognormal distribution for an average local Mach number ranging from ∼0.2 to ∼5.5. As a consequence of the nonlinear development of thermal instability (TI), the logarithmic variance of the distribution of the diffuse gas increases with M faster than in the well-known isothermal case. The average local Mach number for the dense gas (n ∼> 7.1 cm –3 ) goes from ∼1.1 to ∼16.9 and the shape of the high-density zone of the n-PDF changes from a power law at low Mach numbers to a lognormal at high M values. In the latter case, the width of the distribution is smaller than in the isothermal case and grows slower with M. At high column densities, the Σ-PDF is well described by a lognormal for all of the Mach numbers we consider and, due to the presence of TI, the width of the distribution is systematically larger than in the isothermal case but follows a qualitatively similar behavior as M increases. Although a relationship between the width of the distribution and M can be found for each one of the cases mentioned above, these relations are different from those of the isothermal case.

10% low density corn-oil emulsion oral contrast agent for abdominal computed tomography

International Nuclear Information System (INIS)

Choi, Sun Kyou; Chon, Dong Kwon; Han, Young Min; Kim, Chong Soo; Sohn, Myung Hee; Song, Ho Young; Choi, Ki Chul

1990-01-01

CT of the gastrointestinal tract is commonly performed after administration of a high-density diluted iodinated oral contrast material. However, because if inadequate mixing of the contrast material with the gastrointestinal contents, pseudotumor and poor mucosal visualization are frequently shown on abdominal CT. To overcome these problem, 10% corn oil emulsion (COE) is tested as an alternative oral contrast agent in 40 patients. We analyse patients tolerance, gastric mucosal visualization and discrimination of pancreas from the duodenal C-loop to 10% COE in 40 patients compared with those obtained from 35 patients, who was received high-density diluted iodinated oral contrast agent (gastrografin). The results are as follows : 1. Patients' tolerance to 10% COE is similar to that to conventional oral contrast agent. 2. Image of the gastric mucosa from patients receiving 10% COE is superior to that receiving oral contrast agent. 3. The discrimination between pancreatic head from duodenal C-loop is better in patients receiving 10% COE than in patients receiving conventional oral contrast agent. 4. In patients receiving 10% COE, differentiation of cystic masses from intestinal loops is sometimes difficult. The results of this study indicate that 10% COE may be useful oral contrast agent for optimal visualization of gastric mucosa and pancreatico-duodenal discrimination on abdominal CT

Radiologic diagnosis of gastro-oesophageal reflux. Comparison of barium and low-density contrast medium

Energy Technology Data Exchange (ETDEWEB)

Fransson, S.G.; Soekjer, H.; Johansson, K.E.; Tibbling, L.

It has been proposed that the high density of ordinary barium suspension may complicate the radiologic diagnosis of gastro-oesophageal reflux. For this reason P-contrast was developed (Ferring AB); a contrast medium with the same density as water (1 g/cm/sup 3/). A comparison of P-contrast and barium (Mixobar Ventrikel 400 mg/ml) was performed in 82 patients. All patients were examined with both contrast media and the findings were compared with those at reflux test at manometry, endoscopy and 24-hour pH monitoring. Another 40 patients and 15 symptom-free controls were examined with two different amounts of barium, 100 ml and 200 ml, to study if the radiologic diagnosis of reflux varied with the volume of contrast medium administered. P-contrast was found to have no advantages over barium for the diagnosis of gastro-oesophageal reflux. The outcome of the radiologic examination was not influenced by the different volumes of barium used.

Development of a new high density (HD) barium meal (Falibaryt HD) for double contrast investigation of the stomach

International Nuclear Information System (INIS)

Dietze, R.

1986-01-01

During the development of a new double contrast barium meal barium sulfate preparations with various densities, additives and particle size distributions were tested. Phantoms made of leather, rubber and the opened stomachs of cows and pigs were used. A HD bariumsulfate suspension (200 - 250% W/V) of low viscosity and suitable grain size spectrum containing additives improving the adherence (e.g. natrium citrate) showed the best quality parameters for an optimal imaging of the fine mucosal relief. (author)

Noncontact 3-D Speckle Contrast Diffuse Correlation Tomography of Tissue Blood Flow Distribution.

Science.gov (United States)

Huang, Chong; Irwin, Daniel; Zhao, Mingjun; Shang, Yu; Agochukwu, Nneamaka; Wong, Lesley; Yu, Guoqiang

2017-10-01

Recent advancements in near-infrared diffuse correlation techniques and instrumentation have opened the path for versatile deep tissue microvasculature blood flow imaging systems. Despite this progress there remains a need for a completely noncontact, noninvasive device with high translatability from small/testing (animal) to large/target (human) subjects with trivial application on both. Accordingly, we discuss our newly developed setup which meets this demand, termed noncontact speckle contrast diffuse correlation tomography (nc_scDCT). The nc_scDCT provides fast, continuous, portable, noninvasive, and inexpensive acquisition of 3-D tomographic deep (up to 10 mm) tissue blood flow distributions with straightforward design and customization. The features presented include a finite-element-method implementation for incorporating complex tissue boundaries, fully noncontact hardware for avoiding tissue compression and interactions, rapid data collection with a diffuse speckle contrast method, reflectance-based design promoting experimental translation, extensibility to related techniques, and robust adjustable source and detector patterns and density for high resolution measurement with flexible regions of interest enabling unique application-specific setups. Validation is shown in the detection and characterization of both high and low contrasts in flow relative to the background using tissue phantoms with a pump-connected tube (high) and phantom spheres (low). Furthermore, in vivo validation of extracting spatiotemporal 3-D blood flow distributions and hyperemic response during forearm cuff occlusion is demonstrated. Finally, the success of instrument feasibility in clinical use is examined through the intraoperative imaging of mastectomy skin flap.

Regions of low density in the contrast-enhanced pituitary gland: normal and pathologic processes

International Nuclear Information System (INIS)

Chambers, E.F.; Turski, P.A.; LaMasters, D.; Newton, T.H.

1982-01-01

The incidence of low-density regions in the contrast-enhanced pituitary gland and the possible causes of these regions were investigated by a retrospective review of computed tomographic (CT) scans of the head in 50 patients and autopsy specimens of the pituitary in 100 other patients. It was found that focal areas of low density within the contrast enhanced pituitary gland can be caused by various normal and pathologic conditions such as pituitary microadenomas, pars intermedia cysts, foci of metastasis, infarcts, epidermoid cysts, and abscesses. Although most focal low-density regions probably represent pituitary microadenomas, careful clinical correlation is needed to establish a diagnosis

ON THE ORIGIN OF THE HIGH COLUMN DENSITY TURNOVER IN THE H I COLUMN DENSITY DISTRIBUTION

International Nuclear Information System (INIS)

Erkal, Denis; Gnedin, Nickolay Y.; Kravtsov, Andrey V.

2012-01-01

We study the high column density regime of the H I column density distribution function and argue that there are two distinct features: a turnover at N H I ≈ 10 21 cm –2 , which is present at both z = 0 and z ≈ 3, and a lack of systems above N H I ≈ 10 22 cm –2 at z = 0. Using observations of the column density distribution, we argue that the H I-H 2 transition does not cause the turnover at N H I ≈ 10 21 cm –2 but can plausibly explain the turnover at N H I ∼> 10 22 cm –2 . We compute the H I column density distribution of individual galaxies in the THINGS sample and show that the turnover column density depends only weakly on metallicity. Furthermore, we show that the column density distribution of galaxies, corrected for inclination, is insensitive to the resolution of the H I map or to averaging in radial shells. Our results indicate that the similarity of H I column density distributions at z = 3 and 0 is due to the similarity of the maximum H I surface densities of high-z and low-z disks, set presumably by universal processes that shape properties of the gaseous disks of galaxies. Using fully cosmological simulations, we explore other candidate physical mechanisms that could produce a turnover in the column density distribution. We show that while turbulence within giant molecular clouds cannot affect the damped Lyα column density distribution, stellar feedback can affect it significantly if the feedback is sufficiently effective in removing gas from the central 2-3 kpc of high-redshift galaxies. Finally, we argue that it is meaningful to compare column densities averaged over ∼ kpc scales with those estimated from quasar spectra that probe sub-pc scales due to the steep power spectrum of H I column density fluctuations observed in nearby galaxies.

The video densitometric analysis of the radiographic density and contrast

International Nuclear Information System (INIS)

Yoo, Young Sun; Lee, Sang Rae

1992-01-01

Generally the patient's absorb dose and readability of radiograms are affected by the exposure time and kVp of which are related with the radiographic density and contrast. The investigator carried studies to know the adequate level of exposure time and kVp to obtain the better readability of radiograms. In these studies dried human mandible with each other by video densitometry among various combination sets of the exposure time, such as, 5, 6, 8, 12, 15, 19, 24, 30, 38, 48 and 60, and varing level of kVp, such as 60, 65, 70, 80 and 90 respectively. The obtained results were as follows: 1. As exposure time and kVp were increased, radiographic density of radiograms was increased. 2. The subject contrast was increased where aluminum step wedge was thin and reduced in the reversed condition. As the thin aluminum step wedge, subject contrast was increased at the condition of lower kilovoltage than that of higher kilovoltage. 3. In the case of non-contrast was increased in the lower kilovoltage with the longer exposure time and the higher kiovoltage with the shorter exposure time. 4. At the condition of short exposure time, bitter readability of each reading item was obtained with the increment of the kilovoltage but at the opposite condition increasing exposure time worsened readability of radiograms.Since X-ray machine in the current dental clinics is fixed between the range of 60-70 kVp and 10 mA, good radiograms can be obtained by varied exposure time. But according to the conclusion of these studies, better radiograms can be obtained by using filtered high kVp and then the absorb dose to patient and exposure time can be reduced.

Effects of growth temperature and arsenic pressure on size distribution and density of InAs quantum dots on Si (001)

International Nuclear Information System (INIS)

Zhao, Z.M.; Hul'ko, O.; Kim, H.J.; Liu, J.; Shi, B.; Xie, Y.H.

2005-01-01

InAs self-assembled quantum dots (QDs) were grown on Si (001) substrates via molecular beam epitaxy. The size distribution and density of InAs QDs grown under different conditions were studied using plan-view transmission electron microscopy. Dot density was shown to strongly depend on arsenic beam equivalent pressure (BEP) ranging from 2.8x10 -5 to 1.2x10 -3 Pa. In contrast, dot density was nearly independent of substrate temperature from 295 to 410 deg. C under constant arsenic BEP, while broadening of size distribution was observed with increasing temperature. The mechanism accounting for some of the main features of the experimental observations is discussed. Finally, InAs quantum dots with optimized narrow size distribution and high density were grown at low arsenic BEP of 7.2 x10 -5 Pa and low temperature of 250 deg. C followed by annealing at arsenic BEP of 1.9 x10 -4 Pa and temperature of 410 deg. C

Density Distribution Sunflower Plots

Directory of Open Access Journals (Sweden)

William D. Dupont

2003-01-01

Full Text Available Density distribution sunflower plots are used to display high-density bivariate data. They are useful for data where a conventional scatter plot is difficult to read due to overstriking of the plot symbol. The x-y plane is subdivided into a lattice of regular hexagonal bins of width w specified by the user. The user also specifies the values of l, d, and k that affect the plot as follows. Individual observations are plotted when there are less than l observations per bin as in a conventional scatter plot. Each bin with from l to d observations contains a light sunflower. Other bins contain a dark sunflower. In a light sunflower each petal represents one observation. In a dark sunflower, each petal represents k observations. (A dark sunflower with p petals represents between /2-pk k and /2+pk k observations. The user can control the sizes and colors of the sunflowers. By selecting appropriate colors and sizes for the light and dark sunflowers, plots can be obtained that give both the overall sense of the data density distribution as well as the number of data points in any given region. The use of this graphic is illustrated with data from the Framingham Heart Study. A documented Stata program, called sunflower, is available to draw these graphs. It can be downloaded from the Statistical Software Components archive at http://ideas.repec.org/c/boc/bocode/s430201.html . (Journal of Statistical Software 2003; 8 (3: 1-5. Posted at http://www.jstatsoft.org/index.php?vol=8 .

Ring-like spatial distribution of laser accelerated protons in the ultra-high-contrast TNSA-regime

Science.gov (United States)

Becker, G. A.; Tietze, S.; Keppler, S.; Reislöhner, J.; Bin, J. H.; Bock, L.; Brack, F.-E.; Hein, J.; Hellwing, M.; Hilz, P.; Hornung, M.; Kessler, A.; Kraft, S. D.; Kuschel, S.; Liebetrau, H.; Ma, W.; Polz, J.; Schlenvoigt, H.-P.; Schorcht, F.; Schwab, M. B.; Seidel, A.; Zeil, K.; Schramm, U.; Zepf, M.; Schreiber, J.; Rykovanov, S.; Kaluza, M. C.

2018-05-01

The spatial distribution of protons accelerated from submicron-thick plastic foil targets using multi-terawatt, frequency-doubled laser pulses with ultra-high temporal contrast has been investigated experimentally. A very stable, ring-like beam profile of the accelerated protons, oriented around the target’s normal direction has been observed. The ring’s opening angle has been found to decrease with increasing foil thicknesses. Two-dimensional particle-in-cell simulations reproduce our results indicating that the ring is formed during the expansion of the proton density distribution into the vacuum as described by the mechanism of target-normal sheath acceleration. Here—in addition to the longitudinal electric fields responsible for the forward acceleration of the protons—a lateral charge separation leads to transverse field components accelerating the protons in the lateral direction.

Number and density discrimination rely on a common metric: Similar psychophysical effects of size, contrast, and divided attention.

Science.gov (United States)

Tibber, Marc S; Greenwood, John A; Dakin, Steven C

2012-06-04

While observers are adept at judging the density of elements (e.g., in a random-dot image), it has recently been proposed that they also have an independent visual sense of number. To test the independence of number and density discrimination, we examined the effects of manipulating stimulus structure (patch size, element size, contrast, and contrast-polarity) and available attentional resources on both judgments. Five observers made a series of two-alternative, forced-choice discriminations based on the relative numerosity/density of two simultaneously presented patches containing 16-1,024 Gaussian blobs. Mismatches of patch size and element size (across reference and test) led to bias and reduced sensitivity in both tasks, whereas manipulations of contrast and contrast-polarity had varied effects on observers, implying differing strategies. Nonetheless, the effects reported were consistent across density and number judgments, the only exception being when luminance cues were made available. Finally, density and number judgment were similarly impaired by attentional load in a dual-task experiment. These results are consistent with a common underlying metric to density and number judgments, with the caveat that additional cues may be exploited when they are available.

Millimeter-wave Line Ratios and Sub-beam Volume Density Distributions

Energy Technology Data Exchange (ETDEWEB)

Leroy, Adam K.; Gallagher, Molly [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Usero, Antonio [Observatorio Astronmico Nacional (IGN), C/Alfonso XII, 3, E-28014 Madrid (Spain); Schruba, Andreas [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße 1, D-85748 Garching (Germany); Bigiel, Frank [Institute für theoretische Astrophysik, Zentrum für Astronomie der Universität Heidelberg, Albert-Ueberle Str. 2, D-69120 Heidelberg (Germany); Kruijssen, J. M. Diederik; Schinnerer, Eva [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Kepley, Amanda [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Blanc, Guillermo A. [Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); Bolatto, Alberto D. [Department of Astronomy, Laboratory for Millimeter-wave Astronomy, and Joint Space Institute, University of Maryland, College Park, MD 20742 (United States); Cormier, Diane; Jiménez-Donaire, Maria J. [Max Planck Institute für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Hughes, Annie [CNRS, IRAP, 9 av. du Colonel Roche, BP 44346, F-31028 Toulouse cedex 4 (France); Rosolowsky, Erik [Department of Physics, University of Alberta, Edmonton, AB (Canada)

2017-02-01

We explore the use of mm-wave emission line ratios to trace molecular gas density when observations integrate over a wide range of volume densities within a single telescope beam. For observations targeting external galaxies, this case is unavoidable. Using a framework similar to that of Krumholz and Thompson, we model emission for a set of common extragalactic lines from lognormal and power law density distributions. We consider the median density of gas that produces emission and the ability to predict density variations from observed line ratios. We emphasize line ratio variations because these do not require us to know the absolute abundance of our tracers. Patterns of line ratio variations have the potential to illuminate the high-end shape of the density distribution, and to capture changes in the dense gas fraction and median volume density. Our results with and without a high-density power law tail differ appreciably; we highlight better knowledge of the probability density function (PDF) shape as an important area. We also show the implications of sub-beam density distributions for isotopologue studies targeting dense gas tracers. Differential excitation often implies a significant correction to the naive case. We provide tabulated versions of many of our results, which can be used to interpret changes in mm-wave line ratios in terms of adjustments to the underlying density distributions.

Density Distribution of Liquid Argon in Nano-channel Poiseuille Flows

Science.gov (United States)

She, Jiangwei; Wang, Yuyi; Zhou, Zhe-Wei

2017-11-01

The density layering parallel to the boundaries of liquid has been measured in many experiments and also observed in molecular dynamics (MD) simulations. In this study, a detail and systematic investigation of density distribution in nano-scale Poiseuille flows is carried out. Through analyzing the difference of density distribution curves obtained under different conditions, the influence of interaction parameters, configuration form of solid wall and temperature on the layering are investigated. The internal mechanism is also explored in this paper. The detail description of the density distribution results and simulation algorithm is given. National natural science foundation (A020405).

Evaluation of changes in vertebral body density following administration of contrast medium during routine CT examination

International Nuclear Information System (INIS)

Janicek, M.; Bruna, J.; Stenhova, H.

1984-01-01

The possibility is discussed of depicting changes in the density of spongiosis of the vertebral body in normal patients after intravenous administration of a bolus of 40 ml 60% Diazetrizoate in the course of a routine CT examination. The average increase in density immediately after the administration of the contrast medium is 12 H (8%), in the course of 10 minutes is reduced to 5 H (4%) against the initial values in native examination. These average changes are statistically significant, in individual patients, however, the increase in density following the administration of a contrast medium fluctuates considerably (from 0.7% to 10%). Only systematic comparison with various pathological conditions will make it possible to assess the possibilities of the evaluation of the structure of the vertebral body in routine CT with the administration of a contrast medium into the blood flow. (author)

A Comprehensive Survey of Pelagic Megafauna: Their Distribution, Densities, and Taxonomic Richness in the Tropical Southwest Indian Ocean

Directory of Open Access Journals (Sweden)

Sophie Laran

2017-05-01

Full Text Available The distribution and density of pelagic megafauna (marine mammals, seabirds, elasmobranches, and sea turtles are important indicators of marine biodiversity, reflecting the condition of the underlying ecosystems. A dedicated aerial survey was conducted in the tropical Southwest Indian Ocean to map their distribution, the taxonomic diversity, and to estimate their densities to serve as a baseline for the area. This large survey across three ecological sub-regions revealed contrasting spatial distributions: maps of taxonomic richness of marine mammals and seabirds revealed different “hotspots” in the area. Densities were estimated for eight cetacean taxa with small and large Delphininae, or small Globicephalinae dominating, and for seven seabird taxa, with terns and noddies dominating. At the community level, the Southwest Indian Ocean megafauna was structured by the marine environment with strong differences between the Mozambique Channel and the Mascarene Islands, or between shelf and slope/oceanic habitats. Our results illustrate how multi-taxa aerial surveys are relevant and cost-effective monitoring tools for marine megafauna, allowing a community-wide approach.

Central depression of nuclear charge density distribution

International Nuclear Information System (INIS)

Chu Yanyun; Ren Zhongzhou; Wang Zaijun; Dong Tiekuang

2010-01-01

The center-depressed nuclear charge distributions are investigated with the parametrized distribution and the relativistic mean-field theory, and their corresponding charge form factors are worked out with the phase shift analysis method. The central depression of nuclear charge distribution of 46 Ar and 44 S is supported by the relativistic mean-field calculation. According to the calculation, the valence protons in 46 Ar and 44 S prefer to occupy the 1d 3/2 state rather than the 2s 1/2 state, which is different from that in the less neutron-rich argon and sulfur isotopes. As a result, the central proton densities of 46 Ar and 44 S are highly depressed, and so are their central charge densities. The charge form factors of some argon and sulfur isotopes are presented, and the minima of the charge form factors shift upward and inward when the central nuclear charge distributions are more depressed. Besides, the effect of the central depression on the charge form factors is studied with a parametrized distribution, when the root-mean-square charge radii remain constant.

10 CFR 960.5-2-1 - Population density and distribution.

Science.gov (United States)

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general region...

Distributions of the ion temperature, ion pressure, and electron density over the current sheet surface

International Nuclear Information System (INIS)

Kyrie, N. P.; Markov, V. S.; Frank, A. G.; Vasilkov, D. G.; Voronova, E. V.

2016-01-01

The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampère force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampère force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampère force is counterbalanced by the pressure gradient.

Distributions of the ion temperature, ion pressure, and electron density over the current sheet surface

Energy Technology Data Exchange (ETDEWEB)

Kyrie, N. P., E-mail: kyrie@fpl.gpi.ru; Markov, V. S., E-mail: natalya.kyrie@yandex.ru; Frank, A. G.; Vasilkov, D. G.; Voronova, E. V. [Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)

2016-06-15

The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampère force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampère force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampère force is counterbalanced by the pressure gradient.

MDCT appearance of the appendix: how does the low-density barium sulfate oral contrast agent affect it?

Science.gov (United States)

Yaghmai, Vahid; Aghaei-Lasboo, Anahita; Brandwein, Warren M; Tochetto, Sandra; Mafi, John N; Miller, Frank H; Nikolaidis, Paul

2011-01-01

We compared the effect of low-density barium sulfate neutral oral contrast agent on the diameter of normal appendix and its luminal content versus that of water on multidetector-row CT. CT scans of 24 patients who had been imaged on two separate occasions for the evaluation of pancreatic pathology, once with water and subsequently with low-density barium sulfate as the neutral oral contrast agent were evaluated (total of 48 scans). Studies were randomized and reviewed in consensus on a workstation in the stack mode by two radiologists blinded to the type of oral contrast. The appendix was measured at baseline and 10 days later to obtain an average diameter. Results of the water and low-density barium sulfate groups were compared using paired t test. Contents of the appendiceal lumen were also noted (gas, fluid, mixed, and collapsed appendix). The average diameter of the appendix for scans obtained with water and low-density barium sulfate was 4.09 ± 0.87 mm (median, 4.22 mm; range, 2.50-5.65 mm) and 4.13 ± 0.93 mm (median, 4 mm, range, 2.2-5.65 mm), respectively. This difference was not statistically significant (P = 0.69). There was no statistically significant difference in the appendiceal content when water or low-density barium sulfate were used as oral contrast (χ (2) = 4.25, P = 0.89). Low-density barium sulfate does not affect appendiceal content or diameter and, therefore, should not adversely affect evaluation of the appendix on multidetector row CT.

Central depression of the charge density distributions in lead isotopes

International Nuclear Information System (INIS)

Haddad, S.

2008-01-01

The central-depression parameters is determined by fitting the charge density distributions in lead isotopes to a three-parameter Fermi distribution. The central-depression parameter increases with the number of neutrons due to the isovector coupling channel of the nuclear interaction and its dependency on density. (author)

Central depression of the charge density distributions in lead isotopes

International Nuclear Information System (INIS)

Haddad, S.

2007-01-01

The central-depression parameter is determined by fitting the charge density distributions in lead isotopes to a three-parameter Fermi distribution. The central-depression parameter increases with the number of neutrons due to the isovector coupling channel of the nuclear interaction and its dependency on density. (author)

Non-invasive prediction of hemodynamically significant coronary artery stenoses by contrast density difference in coronary CT angiography

Energy Technology Data Exchange (ETDEWEB)

Hell, Michaela M., E-mail: michaela.hell@uk-erlangen.de [Department of Cardiology, University of Erlangen (Germany); Dey, Damini [Department of Biomedical Sciences, Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Taper Building, Room A238, 8700 Beverly Boulevard, Los Angeles, CA 90048 (United States); Marwan, Mohamed; Achenbach, Stephan; Schmid, Jasmin; Schuhbaeck, Annika [Department of Cardiology, University of Erlangen (Germany)

2015-08-15

Highlights: • Overestimation of coronary lesions by coronary computed tomography angiography and subsequent unnecessary invasive coronary angiography and revascularization is a concern. • Differences in plaque characteristics and contrast density difference between hemodynamically significant and non-significant stenoses, as defined by invasive fractional flow reserve, were assessed. • At a threshold of ≥24%, contrast density difference predicted hemodynamically significant lesions with a specificity of 75%, sensitivity of 33%, PPV of 35% and NPV of 73%. • The determination of contrast density difference required less time than transluminal attenuation gradient measurement. - Abstract: Objectives: Coronary computed tomography angiography (CTA) allows the detection of obstructive coronary artery disease. However, its ability to predict the hemodynamic significance of stenoses is limited. We assessed differences in plaque characteristics and contrast density difference between hemodynamically significant and non-significant stenoses, as defined by invasive fractional flow reserve (FFR). Methods: Lesion characteristics of 59 consecutive patients (72 lesions) in whom invasive FFR was performed in at least one coronary artery with moderate to high-grade stenoses in coronary CTA were evaluated by two experienced readers. Coronary CTA data sets were acquired on a second-generation dual-source CT scanner using retrospectively ECG-gated spiral acquisition or prospectively ECG-triggered axial acquisition mode. Plaque volume and composition (non-calcified, calcified), remodeling index as well as contrast density difference (defined as the percentage decline in luminal CT attenuation/cross-sectional area over the lesion) were assessed using a semi-automatic software tool (Autoplaq). Additionally, the transluminal attenuation gradient (defined as the linear regression coefficient between intraluminal CT attenuation and length from the ostium) was determined

Juvenile Penaeid Shrimp Density, Spatial Distribution and Size ...

African Journals Online (AJOL)

The effects of habitat characteristics (mangrove creek, sandflat, mudflat and seagrass meadow) water salinity, temperature, and depth on the density, spatial distribution and size distribution of juveniles of five commercially important penaied shrimp species (Metapenaus monoceros, M. stebbingi, Fenneropenaeus indicus, ...

Noninvasive visualization of in vivo release and intratumoral distribution of surrogate MR contrast agent using the dual MR contrast technique.

Science.gov (United States)

Onuki, Yoshinori; Jacobs, Igor; Artemov, Dmitri; Kato, Yoshinori

2010-09-01

A direct evaluation of the in vivo release profile of drugs from carriers is a clinical demand in drug delivery systems, because drug release characterized in vitro correlates poorly with in vivo release. The purpose of this study is to demonstrate the in vivo applicability of the dual MR contrast technique as a useful tool for noninvasive monitoring of the stability and the release profile of drug carriers, by visualizing in vivo release of the encapsulated surrogate MR contrast agent from carriers and its subsequent intratumoral distribution profile. The important aspect of this technique is that it incorporates both positive and negative contrast agents within a single carrier. GdDTPA, superparamagnetic iron oxide nanoparticles, and 5-fluorouracil were encapsulated in nano- and microspheres composed of poly(D,L-lactide-co-glycolide), which was used as a model carrier. In vivo studies were performed with orthotopic xenograft of human breast cancer. The MR-based technique demonstrated here has enabled visualization of the delivery of carriers, and release and intratumoral distribution of the encapsulated positive contrast agent. This study demonstrated proof-of-principle results for the noninvasive monitoring of in vivo release and distribution profiles of MR contrast agents, and thus, this technique will make a great contribution to the field. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Subchondral bone density distribution of the talus in clinically normal Labrador Retrievers.

Science.gov (United States)

Dingemanse, W; Müller-Gerbl, M; Jonkers, I; Vander Sloten, J; van Bree, H; Gielen, I

2016-03-15

Bones continually adapt their morphology to their load bearing function. At the level of the subchondral bone, the density distribution is highly correlated with the loading distribution of the joint. Therefore, subchondral bone density distribution can be used to study joint biomechanics non-invasively. In addition physiological and pathological joint loading is an important aspect of orthopaedic disease, and research focusing on joint biomechanics will benefit veterinary orthopaedics. This study was conducted to evaluate density distribution in the subchondral bone of the canine talus, as a parameter reflecting the long-term joint loading in the tarsocrural joint. Two main density maxima were found, one proximally on the medial trochlear ridge and one distally on the lateral trochlear ridge. All joints showed very similar density distribution patterns and no significant differences were found in the localisation of the density maxima between left and right limbs and between dogs. Based on the density distribution the lateral trochlear ridge is most likely subjected to highest loads within the tarsocrural joint. The joint loading distribution is very similar between dogs of the same breed. In addition, the joint loading distribution supports previous suggestions of the important role of biomechanics in the development of OC lesions in the tarsus. Important benefits of computed tomographic osteoabsorptiometry (CTOAM), i.e. the possibility of in vivo imaging and temporal evaluation, make this technique a valuable addition to the field of veterinary orthopaedic research.

Spatial distribution of limited resources and local density regulation in juvenile Atlantic salmon.

Science.gov (United States)

Finstad, Anders G; Einum, Sigurd; Ugedal, Ola; Forseth, Torbjørn

2009-01-01

1. Spatial heterogeneity of resources may influence competition among individuals and thus have a fundamental role in shaping population dynamics and carrying capacity. In the present study, we identify shelter opportunities as a limiting resource for juvenile Atlantic salmon (Salmo salar L.). Experimental and field studies are combined in order to demonstrate how the spatial distribution of shelters may influence population dynamics on both within and among population scales. 2. In closed experimental streams, fish performance scaled negatively with decreasing shelter availability and increasing densities. In contrast, the fish in open stream channels dispersed according to shelter availability and performance of fish remaining in the streams did not depend on initial density or shelters. 3. The field study confirmed that spatial variation in densities of 1-year-old juveniles was governed both by initial recruit density and shelter availability. Strength of density-dependent population regulation, measured as carrying capacity, increased with decreasing number of shelters. 4. Nine rivers were surveyed for spatial variation in shelter availability and increased shelter heterogeneity tended to decrease maximum observed population size (measured using catch statistics of adult salmon as a proxy). 5. Our studies highlight the importance of small-scale within-population spatial structure in population dynamics and demonstrate that not only the absolute amount of limiting resources but also their spatial arrangement can be an important factor influencing population carrying capacity.

Uncovering the Density of Matter from Multiplicity Distribution

International Nuclear Information System (INIS)

Bialas, A.

2010-01-01

Multiplicity distributions in the form of superposition of Poisson distributions which are observed in multiparticle production are interpreted as reflection of a two-step nature of this process: the creation and evolution of the strongly interacting fluid, followed by its uncorrelated decay into observed hadrons. A method to uncover the density of the fluid from the observed multiplicity distribution is described. (author)

Influence of Contrast Media on Bone Mineral Density (BMD) Measurements from Routine Contrast-Enhanced MDCT Datasets using a Phantom-less BMD Measurement Tool.

Science.gov (United States)

Toelly, Andrea; Bardach, Constanze; Weber, Michael; Gong, Rui; Lai, Yanbo; Wang, Pei; Guo, Yulin; Kirschke, Jan; Baum, Thomas; Gruber, Michael

2017-06-01

Aim  To evaluate the differences in phantom-less bone mineral density (BMD) measurements in contrast-enhanced routine MDCT scans at different contrast phases, and to develop an algorithm for calculating a reliable BMD value. Materials and Methods  112 postmenopausal women from the age of 40 to 77 years (mean age: 57.31 years; SD 9.61) who underwent a clinically indicated MDCT scan, consisting of an unenhanced, an arterial, and a venous phase, were included. A retrospective analysis of the BMD values of the Th12 to L4 vertebrae in each phase was performed using a commercially available phantom-less measurement tool. Results  The mean BMD value in the unenhanced MDCT scans was 79.76 mg/cm³ (SD 31.20), in the arterial phase it was 85.09 mg/cm³ (SD 31.61), and in the venous phase it was 86.18 mg/cm³ (SD 31.30). A significant difference (p Influence of Contrast Media on Bone Mineral Density (BMD) Measurements from Routine Contrast-Enhanced MDCT Datasets using a Phantom-less BMD Measurement Tool. Fortschr Röntgenstr 2017; 189: 537 - 543. © Georg Thieme Verlag KG Stuttgart · New York.

Extraction of density distributions and particle locations from hologram images

International Nuclear Information System (INIS)

Ikeda, Koh; Okamoto, Koji; Kato, Fumitake; Shimizu, Isao.

1996-01-01

In this study, the simultaneous measurement technique for three-dimensional density and three-dimensional velocity distributions was evaluated. The Holographic Particle Image Velocimetry (HPIV) was the technique to record the three-dimensional position of the tracer particle on the hologram. In the hologram, the interferogram between reference beam and particle scattering were recorded. When there were density distributions in the interrogation region, the plane optical wave may be modulated because of the difference of the refraction indices. Then, both of the plane wave modulated by density and the spherical wave by particle scatter were interfered with the reference beam, being recorded on the hologram. With reconstructing the hologram, the both of the modulated plane wave and spherical wave were reconstructed. Since the plane wave and spherical wave had low and high frequency, respectively, the plane wave was reconstructed with the low-pass filter, resulting in the information of the density distributions to be obtained. With the high-pass filter, the particle three-dimensional positions was determined, i.e., the same procedure with the original HPIV technique. In the experiment, a jet of carbon-dioxide into air with mist were measured. Both mist particle position and the fringe shift caused by the density distribution were well observed, showing the effectiveness of the proposed technique. (author)

Estimation of current density distribution under electrodes for external defibrillation

Directory of Open Access Journals (Sweden)

Papazov Sava P

2002-12-01

Full Text Available Abstract Background Transthoracic defibrillation is the most common life-saving technique for the restoration of the heart rhythm of cardiac arrest victims. The procedure requires adequate application of large electrodes on the patient chest, to ensure low-resistance electrical contact. The current density distribution under the electrodes is non-uniform, leading to muscle contraction and pain, or risks of burning. The recent introduction of automatic external defibrillators and even wearable defibrillators, presents new demanding requirements for the structure of electrodes. Method and Results Using the pseudo-elliptic differential equation of Laplace type with appropriate boundary conditions and applying finite element method modeling, electrodes of various shapes and structure were studied. The non-uniformity of the current density distribution was shown to be moderately improved by adding a low resistivity layer between the metal and tissue and by a ring around the electrode perimeter. The inclusion of openings in long-term wearable electrodes additionally disturbs the current density profile. However, a number of small-size perforations may result in acceptable current density distribution. Conclusion The current density distribution non-uniformity of circular electrodes is about 30% less than that of square-shaped electrodes. The use of an interface layer of intermediate resistivity, comparable to that of the underlying tissues, and a high-resistivity perimeter ring, can further improve the distribution. The inclusion of skin aeration openings disturbs the current paths, but an appropriate selection of number and size provides a reasonable compromise.

Intravenous contrast injection significantly affects bone mineral density measured on CT

Energy Technology Data Exchange (ETDEWEB)

Pompe, Esther; Willemink, Martin J.; Dijkhuis, Gawein R.; Verhaar, Harald J.J.; Hoesein, Firdaus A.A.M.; Jong, Pim A. de [University Medical Center Utrecht, Department of Radiology and Internal Medicine-Geriatrics, Postbus 85500, Postbox: E.03.511, GA, Utrecht (Netherlands)

2014-09-05

The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. One hundred and fifty-two patients (99 without and 53 with malignant neoplasm) who underwent both unenhanced and two contrast-enhanced (arterial and portal venous phase) abdominal CT examinations in a single session between June 2011 and July 2013 were included. BMD was evaluated on the three examinations as CT-attenuation values in Hounsfield Units (HU) in the first lumbar vertebra (L1). CT-attenuation values were significantly higher in both contrast-enhanced phases, compared to the unenhanced phase (p < 0.01). In patients without malignancies, mean ± standard deviation (SD) HU-values increased from 128.8 ± 48.6 HU for the unenhanced phase to 142.3 ± 47.2 HU for the arterial phase and 147.0 ± 47.4 HU for the portal phase (p < 0.01). In patients with malignancies, HU-values increased from 112.1 ± 38.1 HU to 126.2 ± 38.4 HU and 130.1 ± 37.3 HU (p < 0.02), respectively. With different thresholds to define osteoporosis, measurements in the arterial and portal phase resulted in 7-25 % false negatives. Our study showed that intravenous contrast injection substantially affects BMD-assessment on CT and taking this into account may improve routine assessment of low BMD in nonquantitative CT. (orig.)

Intravenous contrast injection significantly affects bone mineral density measured on CT

International Nuclear Information System (INIS)

Pompe, Esther; Willemink, Martin J.; Dijkhuis, Gawein R.; Verhaar, Harald J.J.; Hoesein, Firdaus A.A.M.; Jong, Pim A. de

2015-01-01

The objective is to evaluate the effect of intravenous contrast media on bone mineral density (BMD) assessment by comparing unenhanced and contrast-enhanced computed tomography (CT) examinations performed for other indications. One hundred and fifty-two patients (99 without and 53 with malignant neoplasm) who underwent both unenhanced and two contrast-enhanced (arterial and portal venous phase) abdominal CT examinations in a single session between June 2011 and July 2013 were included. BMD was evaluated on the three examinations as CT-attenuation values in Hounsfield Units (HU) in the first lumbar vertebra (L1). CT-attenuation values were significantly higher in both contrast-enhanced phases, compared to the unenhanced phase (p < 0.01). In patients without malignancies, mean ± standard deviation (SD) HU-values increased from 128.8 ± 48.6 HU for the unenhanced phase to 142.3 ± 47.2 HU for the arterial phase and 147.0 ± 47.4 HU for the portal phase (p < 0.01). In patients with malignancies, HU-values increased from 112.1 ± 38.1 HU to 126.2 ± 38.4 HU and 130.1 ± 37.3 HU (p < 0.02), respectively. With different thresholds to define osteoporosis, measurements in the arterial and portal phase resulted in 7-25 % false negatives. Our study showed that intravenous contrast injection substantially affects BMD-assessment on CT and taking this into account may improve routine assessment of low BMD in nonquantitative CT. (orig.)

A method to describe inelastic gamma field distribution in neutron gamma density logging.

Science.gov (United States)

Zhang, Feng; Zhang, Quanying; Liu, Juntao; Wang, Xinguang; Wu, He; Jia, Wenbao; Ti, Yongzhou; Qiu, Fei; Zhang, Xiaoyang

2017-11-01

Pulsed neutron gamma density logging (NGD) is of great significance for radioprotection and density measurement in LWD, however, the current methods have difficulty in quantitative calculation and single factor analysis for the inelastic gamma field distribution. In order to clarify the NGD mechanism, a new method is developed to describe the inelastic gamma field distribution. Based on the fast-neutron scattering and gamma attenuation, the inelastic gamma field distribution is characterized by the inelastic scattering cross section, fast-neutron scattering free path, formation density and other parameters. And the contribution of formation parameters on the field distribution is quantitatively analyzed. The results shows the contribution of density attenuation is opposite to that of inelastic scattering cross section and fast-neutron scattering free path. And as the detector-spacing increases, the density attenuation gradually plays a dominant role in the gamma field distribution, which means large detector-spacing is more favorable for the density measurement. Besides, the relationship of density sensitivity and detector spacing was studied according to this gamma field distribution, therefore, the spacing of near and far gamma ray detector is determined. The research provides theoretical guidance for the tool parameter design and density determination of pulsed neutron gamma density logging technique. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spin Density Distribution in Open-Shell Transition Metal Systems: A Comparative Post-Hartree-Fock, Density Functional Theory, and Quantum Monte Carlo Study of the CuCl2 Molecule.

Science.gov (United States)

Caffarel, Michel; Giner, Emmanuel; Scemama, Anthony; Ramírez-Solís, Alejandro

2014-12-09

We present a comparative study of the spatial distribution of the spin density of the ground state of CuCl2 using Density Functional Theory (DFT), quantum Monte Carlo (QMC), and post-Hartree-Fock wave function theory (WFT). A number of studies have shown that an accurate description of the electronic structure of the lowest-lying states of this molecule is particularly challenging due to the interplay between the strong dynamical correlation effects in the 3d shell and the delocalization of the 3d hole over the chlorine atoms. More generally, this problem is representative of the difficulties encountered when studying open-shell metal-containing molecular systems. Here, it is shown that qualitatively different results for the spin density distribution are obtained from the various quantum-mechanical approaches. At the DFT level, the spin density distribution is found to be very dependent on the functional employed. At the QMC level, Fixed-Node Diffusion Monte Carlo (FN-DMC) results are strongly dependent on the nodal structure of the trial wave function. Regarding wave function methods, most approaches not including a very high amount of dynamic correlation effects lead to a much too high localization of the spin density on the copper atom, in sharp contrast with DFT. To shed some light on these conflicting results Full CI-type (FCI) calculations using the 6-31G basis set and based on a selection process of the most important determinants, the so-called CIPSI approach (Configuration Interaction with Perturbative Selection done Iteratively) are performed. Quite remarkably, it is found that for this 63-electron molecule and a full CI space including about 10(18) determinants, the FCI limit can almost be reached. Putting all results together, a natural and coherent picture for the spin distribution is proposed.

Experimental validation of the Wigner distributions theory of phase-contrast imaging

International Nuclear Information System (INIS)

Donnelly, Edwin F.; Price, Ronald R.; Pickens, David R.

2005-01-01

Recently, a new theory of phase-contrast imaging has been proposed by Wu and Liu [Med. Phys. 31, 2378-2384 (2004)]. This theory, based upon Wigner distributions, provides a much stronger foundation for the evaluation of phase-contrast imaging systems than did the prior theories based upon Fresnel-Kirchhoff diffraction theory. In this paper, we compare results of measurements made in our laboratory of phase contrast for different geometries and tube voltages to the predictions of the Wu and Liu model. In our previous publications, we have used an empirical measurement (the edge enhancement index) to parametrize the degree of phase-contrast effects in an image. While the Wu and Liu model itself does not predict image contrast, it does measure the degree of phase contrast that the system can image for a given spatial frequency. We have found that our previously published experimental results relating phase-contrast effects to geometry and x-ray tube voltage are consistent with the predictions of the Wu and Liu model

Bulk density and porosity distributions in a compost pile

NARCIS (Netherlands)

Ginkel, van J.T.; Raats, P.A.C.; Haneghem, van I.A.

1999-01-01

This paper mainly deals with the description of the initial distribution of bulk density and porosity at the moment a compost pile is built or rebuilt. A relationship between bulk density and vertical position in a pile is deduced from theoretical and empirical considerations. Formulae to calculate

Modeling of branching density and branching distribution in low-density polyethylene polymerization

NARCIS (Netherlands)

Kim, D.M.; Iedema, P.D.

2008-01-01

Low-density polyethylene (ldPE) is a general purpose polymer with various applications. By this reason, many publications can be found on the ldPE polymerization modeling. However, scission reaction and branching distribution are only recently considered in the modeling studies due to difficulties

Extraction of density distributions and particle locations from hologram images

Energy Technology Data Exchange (ETDEWEB)

Okamoto, Koji; Ikeda, Koh; Madarame, Haruki [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab.

1996-10-01

In this study, the simultaneous measurement technique for three-dimensional density and three-dimensional velocity distributions was evaluated. The Holographic Particle Image Velocimetry (HPIV) was the technique to record the three-dimensional position of the tracer particle on the hologram. When there were density distributions in the interrogation region, the plane optical wave may be modulated because of the difference of the refraction indices. Then, both of the plane wave modulated by density and the spherical wave by particle scatter were interfered with the reference beam, being recorded on the hologram. With reconstructing the hologram, the both of the modulated plane wave and spherical wave were reconstructed. Since the plane wave and spherical wave had low and high frequency, respectively, the two information could be separated using low-pass and high-pass filter. In the experiment, a jet of carbon-dioxide into air with mist were measured. Both mist particle position and the fringe shift caused by the density distribution were well observed, showing the effectiveness of the proposed technique. (author)

Coulomb displacement energies and neutron density distributions

International Nuclear Information System (INIS)

Shlomo, S.

1979-01-01

We present a short review of the present status of the theory of Coulomb displacement energies, ΔEsub(c), discussing the Okamoto-Nolem-Schiffer anomaly and its solution. We emphasize, in particular, that contrary to previous hopes, ΔEsub(c) does not determine rsub(ex), the root-mean square (rms) radius of the excess (valence) neutron density distribution. Instead, ΔEsub(c) is very sensitive to the value of Δr = rsub(n) - rsub(p), the difference between the rms radii of the density distributions of all neutrons and all protons. For neutron rich nuclei, such as 48 Ca and 208 Pb, a value of Δr = 0.1 fm is found to be consistent with ΔEsub(c). This value of Δr, which is considerably smaller than that (of 0.2 - 0.3 fm) predicted by some common Hartree-Fock calculations, seems to be confirmed by very recent experimental results. (orig.)

Influence of a diffuse distribution of nucleon density on the effective moments of inertia of fissioning nuclei

International Nuclear Information System (INIS)

Adeev, G.; Trunova, T.

1982-01-01

The effective moments of inertia of pre-actinide nuclei with 73< or =Z< or =85 are calculated in the droplet model. In contrast to studies carried out previously, the influence of the diffuseness of the nuclear surface and the nonuniformity of the distribution of nucleon density was taken into account both in calculation of the saddle-point configurations and directly in calculation of the effective moments of inertia of the fissioning nuclei. The results are compared with the moments of inertia calculated in the liquid-drop model and with experimental data

Fabrication Flaw Density and Distribution in Weld Repairs

International Nuclear Information System (INIS)

Doctor, Steven R.

2009-01-01

The Pacific Northwest National Laboratory (PNNL) is developing a generalized flaw distribution for the population of nuclear reactor pressure vessels and for piping welds in the U. S. operating reactors. The purpose of the generalized flaw distribution is to predict component-specific flaw densities. The estimates of fabrication flaws are intended for use in fracture mechanics structural integrity assessments. Structural integrity assessments, such as estimating the frequency of loss-of-coolant accidents, are performed by computer codes that require, as input, accurate estimates of flaw densities. Welds from four different cancelled reactor pressure vessels and a collection of archived pipes have been studied to develop empirical estimates of fabrication flaw densities. This paper describes the fabrication flaw distribution and characterization in the repair weld metal of vessels and piping. This work indicates that large flaws occur in these repairs which are complex in composition and sometimes include cracks on the ends of the repair cavities. Parametric analysis using an exponential fit is performed on the data. Construction records where available were reviewed. It is difficult to make conclusions due to the limited number of construction records reviewed. However, the records reviewed to date show a significant change in repair frequency over the years when the components in this study were fabricated. A description of repair flaw morphology is provided with a discussion of fracture mechanics significance.

A two-population sporadic meteoroid bulk density distribution and its implications for environment models

Science.gov (United States)

Moorhead, Althea V.; Blaauw, Rhiannon C.; Moser, Danielle E.; Campbell-Brown, Margaret D.; Brown, Peter G.; Cooke, William J.

2017-12-01

The bulk density of a meteoroid affects its dynamics in space, its ablation in the atmosphere, and the damage it does to spacecraft and lunar or planetary surfaces. Meteoroid bulk densities are also notoriously difficult to measure, and we are typically forced to assume a density or attempt to measure it via a proxy. In this paper, we construct a density distribution for sporadic meteoroids based on existing density measurements. We considered two possible proxies for density: the KB parameter introduced by Ceplecha and Tisserand parameter, TJ. Although KB is frequently cited as a proxy for meteoroid material properties, we find that it is poorly correlated with ablation-model-derived densities. We therefore follow the example of Kikwaya et al. in associating density with the Tisserand parameter. We fit two density distributions to meteoroids originating from Halley-type comets (TJ 2); the resulting two-population density distribution is the most detailed sporadic meteoroid density distribution justified by the available data. Finally, we discuss the implications for meteoroid environment models and spacecraft risk assessments. We find that correcting for density increases the fraction of meteoroid-induced spacecraft damage produced by the helion/antihelion source.

Variation in sensitivity, absorption and density of the central rod distribution with eccentricity.

Science.gov (United States)

Tornow, R P; Stilling, R

1998-01-01

To assess the human rod photopigment distribution and sensitivity with high spatial resolution within the central +/-15 degrees and to compare the results of pigment absorption, sensitivity and rod density distribution (number of rods per square degree). Rod photopigment density distribution was measured with imaging densitometry using a modified Rodenstock scanning laser ophthalmoscope. Dark-adapted sensitivity profiles were measured with green stimuli (17' arc diameter, 1 degrees spacing) using a T ubingen manual perimeter. Sensitivity profiles were plotted on a linear scale and rod photopigment optical density distribution profiles were converted to absorption profiles of the rod photopigment layer. Both the absorption profile of the rod photopigment and the linear sensitivity profile for green stimuli show a minimum at the foveal center and increase steeply with eccentricity. The variation with eccentricity corresponds to the rod density distribution. Rod photopigment absorption profiles, retinal sensitivity profiles, and the rod density distribution are linearly related within the central +/-15 degrees. This is in agreement with theoretical considerations. Both methods, imaging retinal densitometry using a scanning laser ophthalmoscope and dark-adapted perimetry with small green stimuli, are useful for assessing the central rod distribution and sensitivity. However, at present, both methods have limitations. Suggestions for improving the reliability of both methods are given.

Estimation of current density distribution of PAFC by analysis of cell exhaust gas

Energy Technology Data Exchange (ETDEWEB)

Kato, S.; Seya, A. [Fuji Electric Co., Ltd., Ichihara-shi (Japan); Asano, A. [Fuji Electric Corporate, Ltd., Yokosuka-shi (Japan)

1996-12-31

To estimate distributions of Current densities, voltages, gas concentrations, etc., in phosphoric acid fuel cell (PAFC) stacks, is very important for getting fuel cells with higher quality. In this work, we leave developed a numerical simulation tool to map out the distribution in a PAFC stack. And especially to Study Current density distribution in the reaction area of the cell, we analyzed gas composition in several positions inside a gas outlet manifold of the PAFC stack. Comparing these measured data with calculated data, the current density distribution in a cell plane calculated by the simulation, was certified.

Study of optimal X-ray exposure conditions in consideration of bone mineral density. Relation between bone mineral density and image contrast

International Nuclear Information System (INIS)

Kondo, Yuji

2003-01-01

Bone mineral density (BMD) increases through infancy and adolescence, reaching a maximum at 20-30 years of age. Thereafter, BMD gradually decreases with age in both sexes. The image contrast of radiographs of bones varies with the change in BMD owing to the changes in the X-ray absorption of bone. The image contrast of bone generally is higher in the young adult than in the older adult. To examine the relation between BMD and image visibility, we carried out the following experiments. We measured the image contrast of radiographs of a lumbar vertebra phantom in which BMD was equivalent to the average BMD for each developmental period. We examined image visibility at various levels of imaging contrast using the Howlett chart. The results indicated that differences in BMD affect the image contrast of radiographs, and, consequently, image visibility. It was also found that image visibility in the young adult was higher than that in the older adult. The findings showed that, in digital radiography of young adults with high BMD, X-ray exposure can be decreased according the ratio of improvement in image visibility. (author)

Relation between size of contrast meter and radiographic density difference for radiographic test aluminium welds

International Nuclear Information System (INIS)

Senda, Tomio; Hirayama, Kazuo; Masaoka, Naotoshi; Fujita, Minoru.

1977-01-01

The influence of contrast meter with difference surface area (5.0 mm x 5.0 mm, 10.0 mm x 10.0 mm, 15.0 mm x 15.0 mm, 30.0 mm x 30.0 mm) and separated type on radiographic density difference (Δ D) were investigated for radiographic test of aluminum welds. It was found that the effect of scattered radiation on contrast meter represented highest at test specimen thickness of 20 mm, and Δ D was constant as the size was increased from 10.0 mm x 10.0 mm to 15.0 mm x 15.0 mm for aluminum contrast meter. For this reason, a proposal of the contrast meter with 10.0 mm x 10.0 mm (surface area) has made to replace (15.0 mm x 15 mm) at amendment of JIS Z 3105. (auth.)

THE 'TRUE' COLUMN DENSITY DISTRIBUTION IN STAR-FORMING MOLECULAR CLOUDS

International Nuclear Information System (INIS)

Goodman, Alyssa A.; Pineda, Jaime E.; Schnee, Scott L.

2009-01-01

We use the COMPLETE Survey's observations of the Perseus star-forming region to assess and intercompare the three methods used for measuring column density in molecular clouds: near-infrared (NIR) extinction mapping; thermal emission mapping in the far-IR; and mapping the intensity of CO isotopologues. Overall, the structures shown by all three tracers are morphologically similar, but important differences exist among the tracers. We find that the dust-based measures (NIR extinction and thermal emission) give similar, log-normal, distributions for the full (∼20 pc scale) Perseus region, once careful calibration corrections are made. We also compare dust- and gas-based column density distributions for physically meaningful subregions of Perseus, and we find significant variations in the distributions for those (smaller, ∼few pc scale) regions. Even though we have used 12 CO data to estimate excitation temperatures, and we have corrected for opacity, the 13 CO maps seem unable to give column distributions that consistently resemble those from dust measures. We have edited out the effects of the shell around the B-star HD 278942 from the column density distribution comparisons. In that shell's interior and in the parts where it overlaps the molecular cloud, there appears to be a dearth of 13 CO, which is likely due either to 13 CO not yet having had time to form in this young structure and/or destruction of 13 CO in the molecular cloud by the HD 278942's wind and/or radiation. We conclude that the use of either dust or gas measures of column density without extreme attention to calibration (e.g., of thermal emission zero-levels) and artifacts (e.g., the shell) is more perilous than even experts might normally admit. And, the use of 13 CO data to trace total column density in detail, even after proper calibration, is unavoidably limited in utility due to threshold, depletion, and opacity effects. If one's main aim is to map column density (rather than temperature

Inversion of gravity and gravity gradiometry data for density contrast surfaces using Cauchy-type integrals

DEFF Research Database (Denmark)

Zhdanov, Michael; Cai, Hongzhu

2014-01-01

We introduce a new method of modeling and inversion of potential field data generated by a density contrast surface. Our method is based on 3D Cauchy-type integral representation of the potential fields. Traditionally, potential fields are calculated using volume integrals of the domains occupied...

Wigner Function of Density Operator for Negative Binomial Distribution

International Nuclear Information System (INIS)

Xu Xinglei; Li Hongqi

2008-01-01

By using the technique of integration within an ordered product (IWOP) of operator we derive Wigner function of density operator for negative binomial distribution of radiation field in the mixed state case, then we derive the Wigner function of squeezed number state, which yields negative binomial distribution by virtue of the entangled state representation and the entangled Wigner operator

Device for measuring neutron-flux distribution density

International Nuclear Information System (INIS)

Rozenbljum, N.D.; Mitelman, M.G.; Kononovich, A.A.; Kirsanov, V.S.; Zagadkin, V.A.

1977-01-01

An arrangement is described for measuring the distribution of neutron flux density over the height of a nuclear reactor core and which may be used for monitoring energy release or for detecting deviations of neutron flux from an optimal level so that subsequent balance can be achieved. It avoids mutual interference of detectors. Full constructional details are given. (UK)

Investigating the impact of uneven magnetic flux density distribution on core loss estimation

DEFF Research Database (Denmark)

Niroumand, Farideh Javidi; Nymand, Morten; Wang, Yiren

2017-01-01

is calculated according to an effective flux density value and the macroscopic dimensions of the cores. However, the flux distribution in the core can alter by core shapes and/or operating conditions due to nonlinear material properties. This paper studies the element-wise estimation of the loss in magnetic......There are several approaches for loss estimation in magnetic cores, and all these approaches highly rely on accurate information about flux density distribution in the cores. It is often assumed that the magnetic flux density evenly distributes throughout the core and the overall core loss...

Three-dimensional lithospheric density distribution of China and surrounding regions

Directory of Open Access Journals (Sweden)

Chuantao Li

2014-01-01

Full Text Available In this paper, we analyze lithospheric density distribution of China and surrounding regions on the basis of 30′ × 30′ gravity data and 1° × 1° P-wave velocity data. Firstly, we used the empirical equation between the density and the P-wave velocity difference as the base of the initial model of the Asian lithospheric density. Secondly, we calculated the gravity anomaly, caused by the Moho discontinuity and the sedimentary layer discontinuity, by the Parker formula. Thirdly, the gravity anomaly of the spherical harmonics with 2–40 order for the anomalous body below the lithosphere is calculated based on the model of EGM96. Finally, by using Algebra Reconstruction Techniques (ART, the inversion of 30′ × 30′ residual lithospheric Bouguer gravity anomaly caused by the lithosphere yields a rather detailed structural model. The results show that the lithospheric density distribution of China and surrounding regions has a certain connection with the tectonic structure. The density is relatively high in the Philippine Sea plate, Japan Sea, the Indian plate, the Kazakhstan shield and the Western Siberia plain, whereas the Tibetan Plateau has low-density characteristics. The minimum value of density lies in the north of Philippines, in the Taiwan province and in the Ryukyu island arc.

Reinvestigation of the charge density distribution in arc discharge fusion system

Energy Technology Data Exchange (ETDEWEB)

Sheng, Lin Horng; Yee, Lee Kim; Nan, Phua Yeong; Thung, Yong Yun; Khok, Yong Thian; Rahman, Faidz Abd [Centre of Photonics and Advance Material, Universiti Tunku Abdul Rahman Kuala Lumpur (Malaysia)

2015-04-24

A continual arc discharge system has been setup and the light intensity of arc discharge has been profiled. The mathematical model of local energy density distribution in arc discharge fusion has been simulated which is in good qualitative agreement with light intensity profile of arc discharge in the experiments. Eventually, the local energy density distribution of arc discharge system is able to be precisely manipulated to act as heat source in the fabrication of fused fiber devices.

Reinvestigation of the charge density distribution in arc discharge fusion system

International Nuclear Information System (INIS)

Sheng, Lin Horng; Yee, Lee Kim; Nan, Phua Yeong; Thung, Yong Yun; Khok, Yong Thian; Rahman, Faidz Abd

2015-01-01

A continual arc discharge system has been setup and the light intensity of arc discharge has been profiled. The mathematical model of local energy density distribution in arc discharge fusion has been simulated which is in good qualitative agreement with light intensity profile of arc discharge in the experiments. Eventually, the local energy density distribution of arc discharge system is able to be precisely manipulated to act as heat source in the fabrication of fused fiber devices

X-ray electron density distribution of GaAs

International Nuclear Information System (INIS)

Pietsch, U.

1986-01-01

Using ten X-ray structure amplitudes of strong reflections and nine weak reflections both, the valence electron and the difference electron density distribution of GaAs, are calculated. The experimental data are corrected for anomalous dispersion using a bond charge model. The calculated plots are compared with up to now published band structure-based and semiempirically calculated density plots. Taking into account the experimental data of germanium, measured on the same absolute scale, the difference density between GaAs and Ge is calculated. This exhibits the charge transfer between both the f.c.c.-sublattices as well as both, the shift and the decrease of the bond charge, quite closely connected to the theoretical results published by Baur et al. (author)

Low density contrast agents for x-ray phase contrast imaging: the use of ambient air for x-ray angiography of excised murine liver tissue

International Nuclear Information System (INIS)

Laperle, Christopher M; Wintermeyer, Philip; Derdak, Zoltan; Wands, Jack R; Hamilton, Theron J; Walker, Evan J; Diebold, Gerald; Rose-Petruck, Christoph; Shi, Daxin; Anastasio, Mark A

2008-01-01

We report a new preparative method for providing contrast through reduction in electron density that is uniquely suited for propagation-based differential x-ray phase contrast imaging. The method, which results in an air or fluid filled vasculature, makes possible visualization of the smallest microvessels, roughly down to 15 μm, in an excised murine liver, while preserving the tissue for subsequent histological workup. We show the utility of spatial frequency filtering for increasing the visibility of minute features characteristic of phase contrast imaging, and the capability of tomographic reconstruction to reveal microvessel structure and three-dimensional visualization of the sample. The effect of water evaporation from livers during x-ray imaging on the visibility of blood vessels is delineated. The deformed vascular tree in a cancerous murine liver is imaged.

Fish species composition, density-distribution patterns, and impingement during upwelling

International Nuclear Information System (INIS)

Spigarelli, S.A.; Sharma, R.K.

1975-01-01

The effects of cooling system intakes and discharges on Lake Michigan fishes are highly dependent on inshore species composition and spatial distribution which, in turn, are affected by natural hydrological conditions. Significant (5 to 10 C) short-term decreases in water temperature (due to upwelling) could cause cold shock in fish equilibrated to either ambient or plume temperatures; substantial changes in distribution due to avoidance or attraction responses; and resultant changes in susceptibility to impingement. The objectives of this study are to characterize the changes in fish species composition, density, and thermal distribution as a result of natural upwellings, and to relate these factors to intake and discharge effects. Day and night sampling was conducted in ambient (reference) and thermal plume waters near the Zion Nuclear Plant on four occasions between 17 July and 11 September 1975. Density-distribution patterns and species composition of fish were determined by means of gill nets, bottom trawls, seines, and a sonic fish locater

A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams

Energy Technology Data Exchange (ETDEWEB)

Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Koch, J. A.; Haugh, M. J.; Romano, E.; Lee, J. J.; Huffman, E.; Weber, F. A. [National Security Technologies, LLC, Livermore, California 94550 (United States); Bowers, J. W. [National Security Technologies, LLC, Livermore, California 94550 (United States); University of California at Berkeley, Berkeley, California 94720 (United States); Benedetti, L. R.; Wilson, M.; Prisbrey, S. T.; Wehrenberg, C. E.; Baumann, T. F.; Lenhardt, J. M.; Cook, A.; Arsenlis, A.; Park, H.-S.; Remington, B. A. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2016-07-15

A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ∼10.3% accuracy with ∼30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX–6 (C{sub 20}H{sub 30}) aerogel are discussed in this manuscript.

The use of dilute calogen[reg] as a fat density oral contrast medium in upper abdominal computed tomography, compared with the use of water and positive oral contrast media

International Nuclear Information System (INIS)

Ramsay, Duncan W.; Markham, Derrian H.; Morgan, Bruno; Rodgers, Peter M.; Liddicoat, Amanda J.

2001-01-01

AIM: Oral contrast media are commonly given prior to computed tomography (CT) examination of the upper abdomen. Although positive oral contrast media are normally used, there is increasing interest in using negative agents such as water and less commonly fat density products. The aim of this study was to compare a positive oral contrast medium, water, and a diluted emulsion of arachis oil (Calogen[reg], a fat density food supplement) for assessment of the upper abdomen. MATERIALS AND METHODS: Seventy-one patients referred for upper abdominal CT were randomized to receive either 500 ml water, 2% sodium diatrizoate or a dilute suspension of Calogen[reg]. The CT images were scored independently by three radiologists. Distension and anatomical identification was assessed for the stomach, duodenum and jejunum; with anatomical identification recorded for the pancreas, retroperitoneum, liver, gallbladder and spleen. RESULTS: Dilute Calogen[reg] produced a significant improvement (P < 0.01) in distension and anatomical visualization of the stomach and proximal duodenum. Only minimal differences were demonstrated between the three contrast media for visualization of more distal small bowel or identification of the other upper abdominal viscera. Significantly more artifacts were caused by positive contrast media than with the Calogen[reg] mixture. CONCLUSION: A dilute suspension of Calogen[reg] as an oral contrast medium is recommended when disease is suspected within the stomach or proximal duodenum. Ramsay, D.W. et al. (2001)

The force distribution probability function for simple fluids by density functional theory.

Science.gov (United States)

Rickayzen, G; Heyes, D M

2013-02-28

Classical density functional theory (DFT) is used to derive a formula for the probability density distribution function, P(F), and probability distribution function, W(F), for simple fluids, where F is the net force on a particle. The final formula for P(F) ∝ exp(-AF(2)), where A depends on the fluid density, the temperature, and the Fourier transform of the pair potential. The form of the DFT theory used is only applicable to bounded potential fluids. When combined with the hypernetted chain closure of the Ornstein-Zernike equation, the DFT theory for W(F) agrees with molecular dynamics computer simulations for the Gaussian and bounded soft sphere at high density. The Gaussian form for P(F) is still accurate at lower densities (but not too low density) for the two potentials, but with a smaller value for the constant, A, than that predicted by the DFT theory.

Dynamics of the spatial electron density distribution of EUV-induced plasmas

Science.gov (United States)

van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Banine, V. Y.

2015-11-01

We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure.

Dynamics of the spatial electron density distribution of EUV-induced plasmas

International Nuclear Information System (INIS)

Van der Horst, R M; Beckers, J; Banine, V Y; Osorio, E A

2015-01-01

We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure. (fast track communication)

Effects of the distribution density of a biomass combined heat and power plant network on heat utilisation efficiency in village-town systems.

Science.gov (United States)

Zhang, Yifei; Kang, Jian

2017-11-01

The building of biomass combined heat and power (CHP) plants is an effective means of developing biomass energy because they can satisfy demands for winter heating and electricity consumption. The purpose of this study was to analyse the effect of the distribution density of a biomass CHP plant network on heat utilisation efficiency in a village-town system. The distribution density is determined based on the heat transmission threshold, and the heat utilisation efficiency is determined based on the heat demand distribution, heat output efficiency, and heat transmission loss. The objective of this study was to ascertain the optimal value for the heat transmission threshold using a multi-scheme comparison based on an analysis of these factors. To this end, a model of a biomass CHP plant network was built using geographic information system tools to simulate and generate three planning schemes with different heat transmission thresholds (6, 8, and 10 km) according to the heat demand distribution. The heat utilisation efficiencies of these planning schemes were then compared by calculating the gross power, heat output efficiency, and heat transmission loss of the biomass CHP plant for each scenario. This multi-scheme comparison yielded the following results: when the heat transmission threshold was low, the distribution density of the biomass CHP plant network was high and the biomass CHP plants tended to be relatively small. In contrast, when the heat transmission threshold was high, the distribution density of the network was low and the biomass CHP plants tended to be relatively large. When the heat transmission threshold was 8 km, the distribution density of the biomass CHP plant network was optimised for efficient heat utilisation. To promote the development of renewable energy sources, a planning scheme for a biomass CHP plant network that maximises heat utilisation efficiency can be obtained using the optimal heat transmission threshold and the nonlinearity

Chemical bonding and charge density distribution analysis of ...

Indian Academy of Sciences (India)

tice and the electron density distributions in the unit cell of the samples were investigated. Structural ... titanium and oxygen ions and predominant ionic nature between barium and oxygen ions. Average grain sizes ... trations (at <1%) is responsible for the formation of .... indicated by dots and calculated powder patterns are.

Probabilities of filaments in a Poissonian distribution of points -I

International Nuclear Information System (INIS)

Betancort-Rijo, J.

1989-01-01

Statistical techniques are devised to assess the likelihood of a Poisson sample of points in two and three dimensions, containing specific filamentary structures. For that purpose, the expression of Otto et al (1986. Astrophys. J., 304) for the probability density of clumps in a Poissonian distribution of points is generalized for any value of the density contrast. A way of counting filaments differing from that of Otto et al. is proposed, because at low density contrast the filaments counted by Otto et al. are distributed in a clumpy fashion, each clump of filaments corresponding to a distinct observed filament. (author)

The effect of electrodeposition process parameters on the current density distribution in an electrochemical cell

Directory of Open Access Journals (Sweden)

R. M. STEVANOVIC

2001-02-01

Full Text Available Cell voltage – current density dependences for a model electrochemical cell of fixed geometry were calculated for different electrolyte conductivities, Tafel slopes and cathodic exchange current densities. The ratio between the current density at the part of the cathode nearest to the anode and the one furthest away were taken as a measure for the estimation of the current density distribution. The calculations reveal that increasing the conductivity of the electrolyte, as well as increasing the cathodic Tafel slope should both improve the current density distribution. Also, the distribution should be better under total activation control or total diffusion control rather than at mixed activation-diffusion-Ohmic control of the deposition process. On the contrary, changes in the exchange current density should not affect it. These results, being in agreement with common knowledge about the influence of different parameters on the current distribution in an electrochemical cell, demonstrate that a quick estimation of the current distribution can be performed by a simple comparison of the current density at the point of the cathode closest to anode with that at furthest point.

Calculation of flux density distribution on irradiation field of electron accelerator

International Nuclear Information System (INIS)

Tanaka, Ryuichi

1977-03-01

The simple equation of flux density distribution in the irradiation field of an ordinary electron accelerator is a function of the physical parameters concerning electron irradiation. Calculation is based on the mean square scattering angle derived from a simple multiple scattering theory, with the correction factors of air scattering, beam scanning and number transmission coefficient. The flux density distribution was measured by charge absorption in a graphite target set in the air. For the calculated mean square scattering angles of 0.089-0.29, the values of calculation agree with those by experiment within about 10% except at large scattering angles. The method is applicable to dose evaluation of ordinary electron accelerators and design of various irradiators for radiation chemical reaction. Applicability of the simple multiple scattering theory in calculation of the scattered flux density and periodical variation of the flux density of scanning beam are also described. (auth.)

Correlation Between Contrast Time-Density Time on Digital Subtraction Angiography and Flow: An in Vitro Study.

Science.gov (United States)

Brunozzi, Denise; Shakur, Sophia F; Ismail, Rahim; Linninger, Andreas; Hsu, Chih-Yang; Charbel, Fady T; Alaraj, Ali

2018-02-01

Digital subtraction angiography (DSA) provides an excellent anatomic characterization of cerebral vasculature, but hemodynamic assessment is often qualitative and subjective. Various clinical algorithms have been produced to semiquantify flow from the data obtained from DSA, but few have tested them against reliable flow values. An arched flow model was created and injected with contrast material. Seventeen injections were acquired in anterior-posterior and lateral DSA projections, and 4 injections were acquired in oblique projection. Image intensity change over the angiogram cycle of each DSA run was analyzed through a custom MATLAB code. Time-density plots obtained were divided into 3 components (time-density times, TDTs): TDT 10%-100% (time needed for contrast material to change image intensity from 10% to 100%), TDT 100%-10% (time needed for contrast material to change image intensity from 100% to 10%), and TDT 25%-25% (time needed for contrast material to change from 25% image intensity to 25%). Time-density index (TDI) was defined as model cross-sectional area to TDT ratio, and it was measured against different flow rates. TDI 10%-100% , TDI 100%-10% , and TDI 25%-25% all correlated significantly with flow (P < 0.001). TDI 10%-100% , TDI 100%-10% , and TDI 25%-25% showed, respectively, a correlation coefficient of 0.91, 0.91, and 0.97 in the anterior-posterior DSA projections (P < 0.001). In the lateral DSA projection, TDI 100%-10% showed a weaker correlation (r = 0.57; P = 0.03). Also in the oblique DSA projection, TDIs correlated significantly with flow. TDI on DSA correlates significantly with flow. Although in vitro studies might overlook conditions that occur in patients, this method appears to correlate with the flow and could offer a semiquantitative method to evaluate the cerebral blood flow. Copyright © 2017 Elsevier Inc. All rights reserved.

Properties of medium-density fiberboard produced in an oil-heated laboratory press

Science.gov (United States)

O. Suchsland; G.E. Woodson

1976-01-01

Medium-density fiberboards from pressurized double-disk refined fibers have a close correlation between layer density and layer dynamic modulus of elasticity. Density distribution over the thickness was readily controlled by manipulating platen temperature and applied pressure. Thus, overall modulus of elasticity could be adjusted. In contrast to modulus of elasticity...

Differential controls on soil carbon density and mineralization among contrasting forest types in a temperate forest ecosystem

Science.gov (United States)

You, Ye-Ming; Wang, Juan; Sun, Xiao-Lu; Tang, Zuo-Xin; Zhou, Zhi-Yong; Sun, Osbert Jianxin

2016-01-01

Understanding the controls on soil carbon dynamics is crucial for modeling responses of ecosystem carbon balance to global change, yet few studies provide explicit knowledge on the direct and indirect effects of forest stands on soil carbon via microbial processes. We investigated tree species, soil, and site factors in relation to soil carbon density and mineralization in a temperate forest of central China. We found that soil microbial biomass and community structure, extracellular enzyme activities, and most of the site factors studied varied significantly across contrasting forest types, and that the associations between activities of soil extracellular enzymes and microbial community structure appeared to be weak and inconsistent across forest types, implicating complex mechanisms in the microbial regulation of soil carbon metabolism in relation to tree species. Overall, variations in soil carbon density and mineralization are predominantly accounted for by shared effects of tree species, soil, microclimate, and microbial traits rather than the individual effects of the four categories of factors. Our findings point to differential controls on soil carbon density and mineralization among contrasting forest types and highlight the challenge to incorporate microbial processes for constraining soil carbon dynamics in global carbon cycle models. PMID:26925871

Curve fitting of the corporate recovery rates: the comparison of Beta distribution estimation and kernel density estimation.

Science.gov (United States)

Chen, Rongda; Wang, Ze

2013-01-01

Recovery rate is essential to the estimation of the portfolio's loss and economic capital. Neglecting the randomness of the distribution of recovery rate may underestimate the risk. The study introduces two kinds of models of distribution, Beta distribution estimation and kernel density distribution estimation, to simulate the distribution of recovery rates of corporate loans and bonds. As is known, models based on Beta distribution are common in daily usage, such as CreditMetrics by J.P. Morgan, Portfolio Manager by KMV and Losscalc by Moody's. However, it has a fatal defect that it can't fit the bimodal or multimodal distributions such as recovery rates of corporate loans and bonds as Moody's new data show. In order to overcome this flaw, the kernel density estimation is introduced and we compare the simulation results by histogram, Beta distribution estimation and kernel density estimation to reach the conclusion that the Gaussian kernel density distribution really better imitates the distribution of the bimodal or multimodal data samples of corporate loans and bonds. Finally, a Chi-square test of the Gaussian kernel density estimation proves that it can fit the curve of recovery rates of loans and bonds. So using the kernel density distribution to precisely delineate the bimodal recovery rates of bonds is optimal in credit risk management.

Crack problem in superconducting cylinder with exponential distribution of critical-current density

Science.gov (United States)

Zhao, Yufeng; Xu, Chi; Shi, Liang

2018-04-01

The general problem of a center crack in a long cylindrical superconductor with inhomogeneous critical-current distribution is studied based on the extended Bean model for zero-field cooling (ZFC) and field cooling (FC) magnetization processes, in which the inhomogeneous parameter η is introduced for characterizing the critical-current density distribution in inhomogeneous superconductor. The effect of the inhomogeneous parameter η on both the magnetic field distribution and the variations of the normalized stress intensity factors is also obtained based on the plane strain approach and J-integral theory. The numerical results indicate that the exponential distribution of critical-current density will lead a larger trapped field inside the inhomogeneous superconductor and cause the center of the cylinder to fracture more easily. In addition, it is worth pointing out that the nonlinear field distribution is unique to the Bean model by comparing the curve shapes of the magnetization loop with homogeneous and inhomogeneous critical-current distribution.

A measurement of the turbulence-driven density distribution in a non-star-forming molecular cloud

Energy Technology Data Exchange (ETDEWEB)

Ginsburg, Adam; Darling, Jeremy [CASA, University of Colorado, 389-UCB, Boulder, CO 80309 (United States); Federrath, Christoph, E-mail: Adam.G.Ginsburg@gmail.com [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800 (Australia)

2013-12-10

Molecular clouds are supersonically turbulent. This turbulence governs the initial mass function and the star formation rate. In order to understand the details of star formation, it is therefore essential to understand the properties of turbulence, in particular the probability distribution of density in turbulent clouds. We present H{sub 2}CO volume density measurements of a non-star-forming cloud along the line of sight toward W49A. We use these measurements in conjunction with total mass estimates from {sup 13}CO to infer the shape of the density probability distribution function. This method is complementary to measurements of turbulence via the column density distribution and should be applicable to any molecular cloud with detected CO. We show that turbulence in this cloud is probably compressively driven, with a compressive-to-total Mach number ratio b=M{sub C}/M>0.4. We measure the standard deviation of the density distribution, constraining it to the range 1.5 < σ {sub s} < 1.9, assuming that the density is lognormally distributed. This measurement represents an essential input into star formation laws. The method of averaging over different excitation conditions to produce a model of emission from a turbulent cloud is generally applicable to optically thin line observations.

Control of plasma density distribution via wireless power transfer in an inductively coupled plasma

International Nuclear Information System (INIS)

Lee, Hee-Jin; Lee, Hyo-Chang; Kim, Young-Cheol; Chung, Chin-Wook

2013-01-01

With an enlargement of the wafer size, development of large-area plasma sources and control of plasma density distribution are required. To control the spatial distribution of the plasma density, wireless power transfer is applied to an inductively coupled plasma for the first time. An inner powered antenna and an outer resonant coil connected to a variable capacitor are placed on the top of the chamber. As the self-resonance frequency ω r of the resonant coil is adjusted, the power transfer rate from the inner powered coil to the outer resonant coil is changed and the dramatic evolution of the plasma density profile is measured. As ω r of the outer resonant coil changes from the non-resonant condition (where ω r is not the driving angular frequency ω rf ) to the resonant condition (where ω r = ω rf ), the plasma density profile evolves from a convex shape with maximal plasma density at the radial center into a concave shape with maximal plasma density in the vicinity of the resonant antenna coil. This result shows that the plasma density distribution can be successfully controlled via wireless resonance power transfer. (fast track communication)

Curve fitting of the corporate recovery rates: the comparison of Beta distribution estimation and kernel density estimation.

Directory of Open Access Journals (Sweden)

Rongda Chen

Full Text Available Recovery rate is essential to the estimation of the portfolio's loss and economic capital. Neglecting the randomness of the distribution of recovery rate may underestimate the risk. The study introduces two kinds of models of distribution, Beta distribution estimation and kernel density distribution estimation, to simulate the distribution of recovery rates of corporate loans and bonds. As is known, models based on Beta distribution are common in daily usage, such as CreditMetrics by J.P. Morgan, Portfolio Manager by KMV and Losscalc by Moody's. However, it has a fatal defect that it can't fit the bimodal or multimodal distributions such as recovery rates of corporate loans and bonds as Moody's new data show. In order to overcome this flaw, the kernel density estimation is introduced and we compare the simulation results by histogram, Beta distribution estimation and kernel density estimation to reach the conclusion that the Gaussian kernel density distribution really better imitates the distribution of the bimodal or multimodal data samples of corporate loans and bonds. Finally, a Chi-square test of the Gaussian kernel density estimation proves that it can fit the curve of recovery rates of loans and bonds. So using the kernel density distribution to precisely delineate the bimodal recovery rates of bonds is optimal in credit risk management.

Curve Fitting of the Corporate Recovery Rates: The Comparison of Beta Distribution Estimation and Kernel Density Estimation

Science.gov (United States)

Chen, Rongda; Wang, Ze

2013-01-01

Recovery rate is essential to the estimation of the portfolio’s loss and economic capital. Neglecting the randomness of the distribution of recovery rate may underestimate the risk. The study introduces two kinds of models of distribution, Beta distribution estimation and kernel density distribution estimation, to simulate the distribution of recovery rates of corporate loans and bonds. As is known, models based on Beta distribution are common in daily usage, such as CreditMetrics by J.P. Morgan, Portfolio Manager by KMV and Losscalc by Moody’s. However, it has a fatal defect that it can’t fit the bimodal or multimodal distributions such as recovery rates of corporate loans and bonds as Moody’s new data show. In order to overcome this flaw, the kernel density estimation is introduced and we compare the simulation results by histogram, Beta distribution estimation and kernel density estimation to reach the conclusion that the Gaussian kernel density distribution really better imitates the distribution of the bimodal or multimodal data samples of corporate loans and bonds. Finally, a Chi-square test of the Gaussian kernel density estimation proves that it can fit the curve of recovery rates of loans and bonds. So using the kernel density distribution to precisely delineate the bimodal recovery rates of bonds is optimal in credit risk management. PMID:23874558

Determination of protein and solvent volumes in protein crystals from contrast variation data

Energy Technology Data Exchange (ETDEWEB)

Badger, J. [Brandeis Univ., Waltham, MA (United States)

1994-12-31

By varying the relative values of protein and solvent scattering densities in a crystal, it is possible to obtain information on the shape and dimensions of protein molecular envelopes. Neutron diffraction methods are ideally suited to these contrast variation experiments because H/D exchange leads to large differential changes in the protein and solvent scattering densities and is structurally non-perturbing. Low resolution structure factors have been measured from cubic insulin crystals with differing H/D contents. Structure factors calculated from a simple binary density model, in which uniform scattering densities represent the protein and solvent volumes in the crystals, were compared with these data. The contrast variation differences in the sets of measured structure factors were found to be accurately fitted by this simple model. Trial applications to two problems in crystal structure determination illustrate how this fact may be exploited. (1) A translation function that employs contrast variation data gave a sharp minimum within 1-9{Angstrom} of the correctly positioned insulin molecule and is relatively insensitive to errors in the atomic model. (2) An ab initio phasing method for the contrast variation data, based on analyzing histograms of the density distributions in trial maps, was found to recover the correct molecular envelope.

Wood density variations of Norway spruce (Picea abies (L. Karst. under contrasting climate conditions in southwestern Germany

Directory of Open Access Journals (Sweden)

Marieke van der Maaten-Theunissen

2013-05-01

Full Text Available We analyzed inter-annual variations in ring width and maximumwood density of Norway spruce (Picea abies (L. Karst. at different altitudes in Baden-Württemberg, southwestern Germany, to determine the climate response of these parameters under contrasting climate conditions. In addition, we compared maximum, average and minimum wood density between sites. Bootstrapped correlation coefficients of ring width and maximum wood density with monthly temperature and precipitation, revealed a different climate sensitivity of both parameters. Ring width showed strong correlations with climate variables in the previous year and in the first half of the growingseason. Further, a negative relationship with summer temperature was observed at the low-altitude sites. Maximum wood density correlated best with temperature during the growing season, whereby strongest correlations were found between September temperature and maximum wood density at the high-altitude sites. Observed differences in maximum, average and minimum wood density are suggested to relate to the local climate; with lower temperature and higher water availability having a negative effect on wood density.

Wood density variations of Norway spruce (Picea abies (L. Karst. under contrasting climate conditions in southwestern Germany

Directory of Open Access Journals (Sweden)

Marieke van der Maaten-Theunissen

2013-07-01

Full Text Available We analyzed inter-annual variations in ring width and maximum wood density of Norway spruce (Picea abies (L. Karst. at different altitudes in Baden-Württemberg, southwestern Germany, to determine the climate response of these parameters under contrasting climate conditions. In addition, we compared maximum, average and minimum wood density between sites. Bootstrapped correlation coefficients of ring width and maximum wood density with monthly temperature and precipitation, revealed a different climate sensitivity of both parameters. Ring width showed strong correlations with climate variables in the previous year and in the first half of the growing season. Further, a negative relationship with summer temperature was observed at the low-altitude sites. Maximum wood density correlated best with temperature during the growing season, whereby strongest correlations were found between September temperature and maximum wood density at the high-altitude sites. Observed differences in maximum, average and minimum wood density are suggested to relate to the local climate; with lower temperatures and higher water availability having a negative effect on wood density. 

Electron density distribution in ferromagnetic nickel: A γ -ray diffraction study

Science.gov (United States)

Jauch, W.; Reehuis, M.

2008-12-01

High-accuracy single-crystal structure factors, complete up to sinθ/λ=1.9Å-1 , have been measured from ferromagnetic nickel at 295 K using 316.5-keV gamma radiation. The experimental uncertainty of the structure factors is of the order of 10 millielectrons per atom for all data. A detailed description of the electron density distribution is presented in terms of a multipolar atomic deformation model. Achievement of a reliable Debye-Waller factor is of vital importance in this context. The charge asphericity is due to an excess eg orbital occupancy of 43.4(2)%. The 3d shell in the metal is contracted by 2.07(5)% relative to the free atom. The results are discussed and compared with earlier experimental and theoretical works. In contrast to bcc Cr and Fe, solid-state effects are less pronounced in fcc Ni. Clear disentanglement between the 3d and 4s valence electrons could be accomplished for the first time. The general expectation that the number of 3d electrons in the metal should be increased as compared to the atom was confirmed in the case of iron by combining spin and charge-density data. In the case of nickel, it is rejected as revealed by the γ -ray data alone. Only with the d8 configuration, consistency is achieved between observed and refined mosaic widths of the sample crystal. A 3d8 configuration implies that the majority-spin d band cannot be full. Strong support is lent to a localized atomic character of the valence electrons.

Density, distribution, and orientation of water molecules inside and outside carbon nanotubes.

Science.gov (United States)

Thomas, J A; McGaughey, A J H

2008-02-28

The behavior of water molecules inside and outside 1.1, 2.8, 6.9, and 10.4 nm diameter armchair carbon nanotubes (CNTs) is predicted using molecular dynamics simulations. The effects of CNT diameter on mass density, molecular distribution, and molecular orientation are identified for both the confined and unconfined fluids. Within 1 nm of the CNT surface, unconfined water molecules assume a spatially varying density profile. The molecules distribute nonuniformly around the carbon surface and have preferred orientations. The behavior of the unconfined water molecules is invariant with CNT diameter. The behavior of the confined water, however, can be correlated to tube diameter. Inside the 10.4 nm CNT, the molecular behavior is indistinguishable from that of the unconfined fluid. Within the smaller CNTs, surface curvature effects reduce the equilibrium water density and force water molecules away from the surface. This effect changes both the molecular distribution and preferred molecular orientations.

The electron density and temperature distributions predicted by bow shock models of Herbig-Haro objects

International Nuclear Information System (INIS)

Noriega-Crespo, A.; Bohm, K.H.; Raga, A.C.

1990-01-01

The observable spatial electron density and temperature distributions for series of simple bow shock models, which are of special interest in the study of Herbig-Haro (H-H) objects are computed. The spatial electron density and temperature distributions are derived from forbidden line ratios. It should be possible to use these results to recognize whether an observed electron density or temperature distribution can be attributed to a bow shock, as is the case in some Herbig-Haro objects. As an example, the empirical and predicted distributions for H-H 1 are compared. The predicted electron temperature distributions give the correct temperature range and they show very good diagnostic possibilities if the forbidden O III (4959 + 5007)/4363 wavelength ratio is used. 44 refs

Electron density distribution in Si and Ge using multipole, maximum ...

Indian Academy of Sciences (India)

Si and Ge has been studied using multipole, maximum entropy method (MEM) and ... and electron density distribution using the currently available versatile ..... data should be subjected to maximum possible utility for the characterization of.

Synthesis of ultrasound contrast agents: characteristics and size distribution analysis (secondary publication)

Energy Technology Data Exchange (ETDEWEB)

Lee, Hak Jong [Program in Nano Science and Technology, Dept. of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Seoul (Korea, Republic of); Yoon, Tae Jong [Dept. of Radiology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam (Korea, Republic of); Yoon, Young Il [Dept. of Applied Bioscience, CHA University, Pocheon (Korea, Republic of)

2017-10-15

The purpose of this study was to establish a method for ultrasound (US) contrast agent synthesis and to evaluate the characteristics of the synthesized US contrast agent. A US contrast agent, composed of liposome and sulfur hexafluoride (SF6), was synthesized by dissolving 21 μmol 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC, C40H80NO8P), 9 μmol cholesterol, and 1.9 μmol of dihexadecylphosphate (DCP, [CH3(CH2)15O]2P(O)OH) in chloroform. After evaporation in a warm water bath and drying for 12-24 hours, the contrast agent was synthesized using the sonication process by the addition of a buffer and SF6 gas. The size distribution of the bubbles was analyzed using dynamic light scattering measurement methods. The degradation curve was evaluated by assessing the change in the number of contrast agent bubbles using light microscopy immediately, 12, 24, 36, 48, 60, 72, and 84 hours after synthesis. The echogenicity of the synthesized microbubbles was compared with commercially available microbubbles (SonoVue, Bracco). contrast agent was synthesized successfully using an evaporation-drying-sonication method. Most bubbles had a mean diameter of 154.2 nm and showed marked degradation 24 hours after synthesis. Although no statistically significant differences were observed between SonoVue and the synthesized contrast agent, a difference in echogenicity was observed between the synthesized contrast agent and saline (P<0.01). We successfully synthesized a US contrast agent using an evaporation-dryingsonication method. These results may help future research in the fields of anticancer drug delivery, gene delivery, targeted molecular imaging, and targeted therapy.

Synthesis of ultrasound contrast agents: characteristics and size distribution analysis (secondary publication)

International Nuclear Information System (INIS)

Lee, Hak Jong; Yoon, Tae Jong; Yoon, Young Il

2017-01-01

The purpose of this study was to establish a method for ultrasound (US) contrast agent synthesis and to evaluate the characteristics of the synthesized US contrast agent. A US contrast agent, composed of liposome and sulfur hexafluoride (SF6), was synthesized by dissolving 21 μmol 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine (DPPC, C40H80NO8P), 9 μmol cholesterol, and 1.9 μmol of dihexadecylphosphate (DCP, [CH3(CH2)15O]2P(O)OH) in chloroform. After evaporation in a warm water bath and drying for 12-24 hours, the contrast agent was synthesized using the sonication process by the addition of a buffer and SF6 gas. The size distribution of the bubbles was analyzed using dynamic light scattering measurement methods. The degradation curve was evaluated by assessing the change in the number of contrast agent bubbles using light microscopy immediately, 12, 24, 36, 48, 60, 72, and 84 hours after synthesis. The echogenicity of the synthesized microbubbles was compared with commercially available microbubbles (SonoVue, Bracco). contrast agent was synthesized successfully using an evaporation-drying-sonication method. Most bubbles had a mean diameter of 154.2 nm and showed marked degradation 24 hours after synthesis. Although no statistically significant differences were observed between SonoVue and the synthesized contrast agent, a difference in echogenicity was observed between the synthesized contrast agent and saline (P<0.01). We successfully synthesized a US contrast agent using an evaporation-dryingsonication method. These results may help future research in the fields of anticancer drug delivery, gene delivery, targeted molecular imaging, and targeted therapy

Estimation of dislocations density and distribution of dislocations during ECAP-Conform process

Science.gov (United States)

Derakhshan, Jaber Fakhimi; Parsa, Mohammad Habibi; Ayati, Vahid; Jafarian, Hamidreza

2018-01-01

Dislocation density of coarse grain aluminum AA1100 alloy (140 µm) that was severely deformed by Equal Channel Angular Pressing-Conform (ECAP-Conform) are studied at various stages of the process by electron backscattering diffraction (EBSD) method. The geometrically necessary dislocations (GNDs) density and statistically stored dislocations (SSDs) densities were estimate. Then the total dislocations densities are calculated and the dislocation distributions are presented as the contour maps. Estimated average dislocations density for annealed of about 2×1012 m-2 increases to 4×1013 m-2 at the middle of the groove (135° from the entrance), and they reach to 6.4×1013 m-2 at the end of groove just before ECAP region. Calculated average dislocations density for one pass severely deformed Al sample reached to 6.2×1014 m-2. At micrometer scale the behavior of metals especially mechanical properties largely depend on the dislocation density and dislocation distribution. So, yield stresses at different conditions were estimated based on the calculated dislocation densities. Then estimated yield stresses were compared with experimental results and good agreements were found. Although grain size of material did not clearly change, yield stress shown intensive increase due to the development of cell structure. A considerable increase in dislocations density in this process is a good justification for forming subgrains and cell structures during process which it can be reason of increasing in yield stress.

The Influence of Orthographic Neighborhood Density and Word Frequency on Visual Word Recognition: Insights from RT Distributional Analyses

Directory of Open Access Journals (Sweden)

Stephen Wee Hun eLim

2016-03-01

Full Text Available The effects of orthographic neighborhood density and word frequency in visual word recognition were investigated using distributional analyses of response latencies in visual lexical decision. Main effects of density and frequency were observed in mean latencies. Distributional analyses, in addition, revealed a density x frequency interaction: for low-frequency words, density effects were mediated predominantly by distributional shifting whereas for high-frequency words, density effects were absent except at the slower RTs, implicating distributional skewing. The present findings suggest that density effects in low-frequency words reflect processes involved in early lexical access, while the effects observed in high-frequency words reflect late postlexical checking processes.

Calculation of the magnetic flux density distribution in type-II superconductors with finite thickness and well-defined geometry

International Nuclear Information System (INIS)

Forkl, A.; Kronmueller, H.

1995-01-01

The distribution of the critical current density j c (r) in hard type-II superconductors depends strongly on their sample geometry. Rules are given for the construction of j c (r). Samples with homogeneous thickness are divided into cakelike regions with a unique current direction. The spatial magnetic flux density distribution and the magnetic polarization of such a cakelike unit cell with homogeneous current density are calculated analytically. The magnetic polarization and magnetic flux density distribution of a superconductor in the mixed state is then given by an adequate superposition of the unit cell solutions. The theoretical results show good agreement with magneto-optically determined magnetic flux density distributions of a quadratic thin superconducting YBa 2 Cu 3 O 7-x film. The current density distribution is discussed for several sample geometries

Student Difficulties in Learning Density: A Distributed Cognition Perspective

Science.gov (United States)

Xu, Lihua; Clarke, David

2012-08-01

Density has been reported as one of the most difficult concepts for secondary school students (e.g. Smith et al. 1997). Discussion about the difficulties of learning this concept has been largely focused on the complexity of the concept itself or student misconceptions. Few, if any, have investigated how the concept of density was constituted in classroom interactions, and what consequences these interactions have for individual students' conceptual understanding. This paper reports a detailed analysis of two lessons on density in a 7th Grade Australian science classroom, employing the theory of Distributed Cognition (Hollan et al. 1999; Hutchins 1995). The analysis demonstrated that student understanding of density was shaped strongly by the public classroom discussion on the density of two metal blocks. It also revealed the ambiguities associated with the teacher demonstration and the student practical work. These ambiguities contributed to student difficulties with the concept of density identified in this classroom. The results of this study suggest that deliberate effort is needed to establish shared understanding not only about the purpose of the activities, but also about the meaning of scientific language and the utility of tools. It also suggests the importance of appropriate employment of instructional resources in order to facilitate student scientific understanding.

A density distribution algorithm for bone incorporating local orthotropy, modal analysis and theories of cellular solids.

Science.gov (United States)

Impelluso, Thomas J

2003-06-01

An algorithm for bone remodeling is presented which allows for both a redistribution of density and a continuous change of principal material directions for the orthotropic material properties of bone. It employs a modal analysis to add density for growth and a local effective strain based analysis to redistribute density. General re-distribution functions are presented. The model utilizes theories of cellular solids to relate density and strength. The code predicts the same general density distributions and local orthotropy as observed in reality.

Crust-mantle density distribution in the eastern Qinghai-Tibet Plateau revealed by satellite-derived gravity gradients

Science.gov (United States)

LI, Honglei; Fang, Jian; Braitenberg, Carla; Wang, Xinsheng

2015-04-01

As the highest, largest and most active plateau on Earth, the Qinghai-Tibet Plateau has a complex crust-mantle structure, especially in its eastern part. In response to the subduction of the lithospheric mantle of the Indian plate, large-scale crustal motion occurs in this area. Despite the many previous studies, geodynamic processes at depth remain unclear. Knowledge of crust and upper mantle density distribution allows a better definition of the deeper geological structure and thus provides critically needed information for understanding of the underlying geodynamic processes. With an unprecedented precision of 1-2 mGal and a spatial resolution better than 100 km, GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission products can be used to constrain the crust-mantle density distribution. Here we used GOCE gravitational gradients at an altitude of 10km after reducing the effects of terrain, sediment thickness variations, and Moho undulations to image the density structures of eastern Tibet up to 200 km depths. We inverted the residual satellite gravitational gradients using a least square approach. The initial density model for the inversion is based on seismic velocities from the tomography. The model is composed of rectangular blocks, having a uniform density, with widths of about 100 km and variable thickness and depths. The thickness of the rectangular cells changes from10 to 60km in accordance with the seismic model. Our results reveal some large-scale, structurally controlled density variations at depths. The lithospheric root defined by higher-density contrast features from southwest to northeast, with shallowing in the central part: base of lithosphere reaches a depth of180 km, less than 100km, and 200 km underneath the Lhasa, Songpan-Ganzi, and Ordos crustal blocks, respectively. However, these depth values only represent a first-order parameterization because they depend on model discretization inherited from the original seismic

EVOLUTION OF DARK MATTER PHASE-SPACE DENSITY DISTRIBUTIONS IN EQUAL-MASS HALO MERGERS

International Nuclear Information System (INIS)

Vass, Ileana M.; Kazanzidis, Stelios; Valluri, Monica; Kravtsov, Andrey V.

2009-01-01

We use dissipationless N-body simulations to investigate the evolution of the true coarse-grained phase-space density distribution f(x, v) in equal-mass mergers between dark matter (DM) halos. The halo models are constructed with various asymptotic power-law indices ρ ∝ r -γ ranging from steep cusps to core-like profiles and we employ the phase-space density estimator 'EnBid' developed by Sharma and Steinmetz to compute f(x, v). The adopted force resolution allows robust phase-space density profile estimates in the inner ∼1% of the virial radii of the simulated systems. We confirm that merger events result in a decrease of the coarse-grained phase-space density in accordance with expectations from Mixing Theorems for collisionless systems. We demonstrate that binary mergers between identical DM halos produce remnants that retain excellent memories of the inner slopes and overall shapes of the phase-space density distribution of their progenitors. The robustness of the phase-space density profiles holds for a range of orbital energies, and a variety of encounter configurations including sequences of several consecutive merger events, designed to mimic hierarchical merging, and collisions occurring at different cosmological epochs. If the progenitor halos are constructed with appreciably different asymptotic power-law indices, we find that the inner slope and overall shape of the phase-space density distribution of the remnant are substantially closer to that of the initial system with the steepest central density cusp. These results explicitly demonstrate that mixing is incomplete in equal-mass mergers between DM halos, as it does not erase memory of the progenitor properties. Our results also confirm the recent analytical predictions of Dehnen regarding the preservation of merging self-gravitating central density cusps.

Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

Science.gov (United States)

Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

1976-01-01

Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

Dust Density Distribution and Imaging Analysis of Different Ice Lines in Protoplanetary Disks

Energy Technology Data Exchange (ETDEWEB)

Pinilla, P. [Department of Astronomy/Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Pohl, A. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Stammler, S. M.; Birnstiel, T., E-mail: pinilla@email.arizona.edu [University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, D-81679 Münich (Germany)

2017-08-10

Recent high angular resolution observations of protoplanetary disks at different wavelengths have revealed several kinds of structures, including multiple bright and dark rings. Embedded planets are the most used explanation for such structures, but there are alternative models capable of shaping the dust in rings as it has been observed. We assume a disk around a Herbig star and investigate the effect that ice lines have on the dust evolution, following the growth, fragmentation, and dynamics of multiple dust size particles, covering from 1 μ m to 2 m sized objects. We use simplified prescriptions of the fragmentation velocity threshold, which is assumed to change radially at the location of one, two, or three ice lines. We assume changes at the radial location of main volatiles, specifically H{sub 2}O, CO{sub 2}, and NH{sub 3}. Radiative transfer calculations are done using the resulting dust density distributions in order to compare with current multiwavelength observations. We find that the structures in the dust density profiles and radial intensities at different wavelengths strongly depend on the disk viscosity. A clear gap of emission can be formed between ice lines and be surrounded by ring-like structures, in particular between the H{sub 2}O and CO{sub 2} (or CO). The gaps are expected to be shallower and narrower at millimeter emission than at near-infrared, opposite to model predictions of particle trapping. In our models, the total gas surface density is not expected to show strong variations, in contrast to other gap-forming scenarios such as embedded giant planets or radial variations of the disk viscosity.

Predicting moisture content and density distribution of Scots pine by microwave scanning of sawn timber

International Nuclear Information System (INIS)

Johansson, J.; Hagman, O.; Fjellner, B.A.

2003-01-01

This study was carried out to investigate the possibility of calibrating a prediction model for the moisture content and density distribution of Scots pine (Pinus sylvestris) using microwave sensors. The material was initially of green moisture content and was thereafter dried in several steps to zero moisture content. At each step, all the pieces were weighed, scanned with a microwave sensor (Satimo 9,4GHz), and computed tomography (CT)-scanned with a medical CT scanner (Siemens Somatom AR.T.). The output variables from the microwave sensor were used as predictors, and CT images that correlated with known moisture content were used as response variables. Multivariate models to predict average moisture content and density were calibrated using the partial least squares (PLS) regression. The models for average moisture content and density were applied at the pixel level, and the distribution was visualized. The results show that it is possible to predict both moisture content distribution and density distribution with high accuracy using microwave sensors. (author)

Distributed Noise Generation for Density Estimation Based Clustering without Trusted Third Party

Science.gov (United States)

Su, Chunhua; Bao, Feng; Zhou, Jianying; Takagi, Tsuyoshi; Sakurai, Kouichi

The rapid growth of the Internet provides people with tremendous opportunities for data collection, knowledge discovery and cooperative computation. However, it also brings the problem of sensitive information leakage. Both individuals and enterprises may suffer from the massive data collection and the information retrieval by distrusted parties. In this paper, we propose a privacy-preserving protocol for the distributed kernel density estimation-based clustering. Our scheme applies random data perturbation (RDP) technique and the verifiable secret sharing to solve the security problem of distributed kernel density estimation in [4] which assumed a mediate party to help in the computation.

Ion distributions, exclusion coefficients, and separation factors of electrolytes in a charged cylindrical nanopore: a partially perturbative density functional theory study.

Science.gov (United States)

Peng, Bo; Yu, Yang-Xin

2009-10-07

The structural and thermodynamic properties for charge symmetric and asymmetric electrolytes as well as mixed electrolyte system inside a charged cylindrical nanopore are investigated using a partially perturbative density functional theory. The electrolytes are treated in the restricted primitive model and the internal surface of the cylindrical nanopore is considered to have a uniform charge density. The proposed theory is directly applicable to the arbitrary mixed electrolyte solution containing ions with the equal diameter and different valences. Large amount of simulation data for ion density distributions, separation factors, and exclusion coefficients are used to determine the range of validity of the partially perturbative density functional theory for monovalent and multivalent counterion systems. The proposed theory is found to be in good agreement with the simulations for both mono- and multivalent counterion systems. In contrast, the classical Poisson-Boltzmann equation only provides reasonable descriptions of monovalent counterion system at low bulk density, and is qualitatively and quantitatively wrong in the prediction for the multivalent counterion systems due to its neglect of the strong interionic correlations in these systems. The proposed density functional theory has also been applied to an electrolyte absorbed into a pore that is a model of the filter of a physiological calcium channel.

Effects of drive current rise-time and initial load density distribution on Z-pinch characteristics

Institute of Scientific and Technical Information of China (English)

Duan Yao-Yong; Guo Yong-Hui; Wang Wen-Sheng; Qiu Ai-Ci

2005-01-01

A two-dimensional, three-temperature radiation magneto-hydrodynamics model is applied to the investigation of evolutional trends in x-ray radiation power, energy, peak plasma temperature and density as functions of drive current rise-time and initial load density distribution by using the typical experimental parameters of tungsten wire-array Z-pinch on the Qiangguang-Ⅰ generator. The numerical results show that as the drive current rise-time is shortened, x-ray radiation peak power, energy, peak plasma density and peak ion temperature increase approximately linearly, but among them the x-ray radiation peak power increases more quickly. As the initial plasma density distribution in the radial direction becomes gradually flattened, the peak radiation power and the peak ion-temperature almost exponentially increase, while the radiation energy and the peak plasma density change only a little. The main effect of shortening drive current rise-time is to enhance compression of plasma, and the effect of flattening initial load density distribution in the radial direction is to raise the plasma temperature. Both of the approaches elevate the x-ray peak radiation power.

Individual variation in cone photoreceptor density in house sparrows: implications for between-individual differences in visual resolution and chromatic contrast.

Science.gov (United States)

Ensminger, Amanda L; Fernández-Juricic, Esteban

2014-01-01

Between-individual variation has been documented in a wide variety of taxa, especially for behavioral characteristics; however, intra-population variation in sensory systems has not received similar attention in wild animals. We measured a key trait of the visual system, the density of retinal cone photoreceptors, in a wild population of house sparrows (Passer domesticus). We tested whether individuals differed from each other in cone densities given within-individual variation across the retina and across eyes. We further tested whether the existing variation could lead to individual differences in two aspects of perception: visual resolution and chromatic contrast. We found consistent between-individual variation in the densities of all five types of avian cones, involved in chromatic and achromatic vision. Using perceptual modeling, we found that this degree of variation translated into significant between-individual differences in visual resolution and the chromatic contrast of a plumage signal that has been associated with mate choice and agonistic interactions. However, there was no evidence for a relationship between individual visual resolution and chromatic contrast. The implication is that some birds may have the sensory potential to perform "better" in certain visual tasks, but not necessarily in both resolution and contrast simultaneously. Overall, our findings (a) highlight the need to consider multiple individuals when characterizing sensory traits of a species, and (b) provide some mechanistic basis for between-individual variation in different behaviors (i.e., animal personalities) and for testing the predictions of several widely accepted hypotheses (e.g., honest signaling).

Surface flux density distribution characteristics of bulk high-T c superconductor in external magnetic field

International Nuclear Information System (INIS)

Nishikawa, H.; Torii, S.; Yuasa, K.

2005-01-01

This paper describes the measured results of the two-dimensional flux density distribution of a YBCO bulk under applied AC magnetic fields with various frequency. Melt-processed oxide superconductors have been developed in order to obtain strong pinning forces. Various electric mechanical systems or magnetic levitation systems use those superconductors. The major problem is that cracks occur because the bulk superconductors are brittle. The bulk may break in magnetizing process after cracks make superconducting state instable. The trapped flux density and the permanent current characteristics of bulk superconductors have been analyzed, so as to examine the magnetizing processes or superconducting states of the bulk. In those studies, the two-dimensional surface flux density distributions of the bulk in static fields are discussed. On the other hand, the distributions in dynamic fields are little discussed. We attempted to examine the states of the bulk in the dynamic fields, and made a unique experimental device which has movable sensors synchronized with AC applied fields. As a result, the two-dimensional distributions in the dynamic fields are acquired by recombining the one-dimensional distributions. The dynamic states of the flux of the bulk and the influences of directions of cracks are observed from the distributions. In addition, a new method for measuring two-dimensional flux density distribution under dynamic magnetic fields is suggested

Evaluation of contrast in duplicated radiographs

International Nuclear Information System (INIS)

Thunthy, K.H.; Weinberg, R.

1982-01-01

This investigation evaluated changes in the contrast of duplicated radiographs made at different ultraviolet light exposures. Increasing ultraviolet light exposure had different effects on the duplicates of originals of different background densities. When correctly exposed, a duplicate radiograph enhanced contrast. When originals had the same contrast but different background densities, their duplicates did not have the same contrast. It was not possible to duplicate accurately all the different contrasts measured on an original. It was possible, however, to produce duplicates with all contrasts greater than those of the original

Probing ultrafast dynamics of solid-density plasma generated by high-contrast intense laser pulses

Science.gov (United States)

Jana, Kamalesh; Blackman, David R.; Shaikh, Moniruzzaman; Lad, Amit D.; Sarkar, Deep; Dey, Indranuj; Robinson, Alex P. L.; Pasley, John; Ravindra Kumar, G.

2018-01-01

We present ultrafast dynamics of solid-density plasma created by high-contrast (picosecond contrast ˜10-9), high-intensity (˜4 × 1018 W/cm2) laser pulses using time-resolved pump-probe Doppler spectrometry. Experiments show a rapid rise in blue-shift at early time delay (2-4.3 ps) followed by a rapid fall (4.3-8.3 ps) and then a slow rise in blue-shift at later time delays (>8.3 ps). Simulations show that the early-time observations, specifically the absence of any red-shifting of the reflected probe, can only be reproduced if the front surface is unperturbed by the laser pre-pulse at the moment that the high intensity pulse arrives. A flexible diagnostic which is capable of diagnosing the presence of low-levels of pre-plasma formation would be useful for potential applications in laser-produced proton and ion production, such as cancer therapy and security imaging.

Carbon density and distribution of six Chinese temperate forests

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

Quantifying forest carbon(C) storage and distribution is important for forest C cycling studies and terrestrial ecosystem modeling.Forest inventory and allometric approaches were used to measure C density and allocation in six representative temperate forests of similar stand age(42-59 years old) and growing under the same climate in northeastern China.The forests were an aspen-birch forest,a hardwood forest,a Korean pine plantation,a Dahurian larch plantation,a mixed deciduous forest,and a Mongolian oak forest.There were no significant differences in the C densities of ecosystem components(except for detritus) although the six forests had varying vegetation compositions and site conditions.However,the differences were significant when the C pools were normalized against stand basal area.The total ecosystem C density varied from 186.9 tC hm-2 to 349.2 tC hm-2 across the forests.The C densities of vegetation,detritus,and soil ranged from 86.3-122.7 tC hm-2,6.5-10.5 tC hm-2,and 93.7-220.1 tC hm-2,respectively,which accounted for 39.7% ± 7.1%(mean ± SD),3.3% ± 1.1%,and 57.0% ± 7.9% of the total C densities,respectively.The overstory C pool accounted for > 99% of the total vegetation C pool.The foliage biomass,small root(diameter < 5mm) biomass,root-shoot ratio,and small root to foliage biomass ratio varied from 2.08-4.72 tC hm-2,0.95-3.24 tC hm-2,22.0%-28.3%,and 34.5%-122.2%,respectively.The Korean pine plantation had the lowest foliage production efficiency(total biomass/foliage biomass:22.6 g g-1) among the six forests,while the Dahurian larch plantation had the highest small root production efficiency(total biomass/small root biomass:124.7 g g-1).The small root C density decreased with soil depth for all forests except for the Mongolian oak forest,in which the small roots tended to be vertically distributed downwards.The C density of coarse woody debris was significantly less in the two plantations than in the four naturally regenerated forests.The variability

The influence of density distribution on the stability of beams

International Nuclear Information System (INIS)

Guy, F.W.; Lapostolle, P.M.; Wangler, T.P.

1987-01-01

We examine the effect of various density distributions in four-dimensional phase space and their projections in real and velocity space on the stability of continuous beams in alternating-gradient transport lines using particle-following computer simulations. We discuss the susceptibility of three different distributions (Kapchinskii-Vladimirskii, bicylinder, and thermal) to third- and higher-order mode instabilities. These distributions are all uniform in real space, but their velocity distributions are different; they also react differently to structure resonances. Velocity distributions of high-current beams tend to evolve to a peaked Gaussian-like form. Is there a specific velocity distribution that is stable and, therefore, the preferred injection distribution for minimizing emittance growth? Forced smoothness or uniformity in real space is necessary for setting up particle simulations of high-current beams so that spurious charge-redistribution emittance growth can be avoided. Is forced smoothness also desirable in four dimensions for continuous beams and possibly in six dimensions for bunched beams? We consider these and related questions

Effects of edge contrast on redback salamander distribution in even-aged northern hardwoods

Science.gov (United States)

Richard M. DeGraaf; Mariko. Yamasaki

2002-01-01

Terrestrial salamanders are sensitive to forest disturbance associated with even-aged management. We studied the distribution of redback salamanders (Plethodon cinereus) for 4 yr at edges between even-aged northern hardwood stands along three replicate transects in each of three edge contrast types: regeneration/mature, sapling/mature, and...

Distribution of temperature coefficient density for muons in the atmosphere

Directory of Open Access Journals (Sweden)

Kuzmenko V.S.

2017-12-01

Full Text Available To date, several dozens of new muon detectors have been built. When studying cosmic-ray intensity variations with these detectors, located deep in the atmosphere, it is necessary to calculate all characteristics, including the distribution of temperature coefficient density for muons in the atmosphere, taking into account their specific geometry. For this purpose, we calculate the density of temperature coefficients of muon intensity in the atmosphere at various zenith angles of detection at sea level and at various depths underground for different absorption ranges of primary protons and pions in the atmosphere.

Vessel Wall Inflammation of Takayasu Arteritis Detected by Contrast-Enhanced Magnetic Resonance Imaging: Association with Disease Distribution and Activity.

Directory of Open Access Journals (Sweden)

Yoko Kato

Full Text Available The assessment of the distribution and activity of vessel wall inflammation is clinically important in patients with Takayasu arteritis. Magnetic resonance imaging (MRI is a useful tool, but the clinical utility of late gadolinium enhancement (LGE in Takayasu arteritis has yet to be determined. The aim of the present study was to evaluate the utility of LGE in assessing vessel wall inflammation and disease activity in Takayasu arteritis.We enrolled 49 patients with Takayasu arteritis who had undergone 1.5 T MRI. Patients were divided into Active (n = 19 and Inactive disease (n = 30 groups. The distribution of vessel wall inflammation using angiography and LGE was assessed by qualitative analysis. In 79% and 63% of patients in Active and Inactive groups, respectively, greater distribution of vessel wall inflammation was observed with LGE than with conventional angiography. MRI values of pre- and post-contrast signal-to-noise ratios (SNR, SNR increment (post-SNR minus pre-SNR, pre- and post-contrast contrast-to-noise ratios (CNR, and CNR increment (post-CNR minus pre-CNR were evaluated at arterial wall sites with the highest signal intensity using quantitative analysis of post-contrast LGE images. No statistically significant differences in MRI parameters were observed between Active and Inactive groups. Contrast-enhanced MRI was unable to accurately detect active disease.Contrast-enhanced MRI has utility in detecting the distribution of vessel wall inflammation but has less utility in assessing disease activity in Takayasu arteritis.

Evaluation of population density and distribution criteria in nuclear power plant siting

International Nuclear Information System (INIS)

Young, M.

1994-06-01

The NRC has proposed revisions to 10 CFR 100 which include the codification of nuclear reactor site population density limits to 500 people per square mile, at the siting stage, averaged over any radial distance out to 30 miles, and 1,000 people per square mile within the 40-year lifetime of a nuclear plant. This study examined whether there are less restrictive alternative population density and/or distribution criteria which would provide equivalent or better protection to human health in the unlikely event of a nuclear accident. This study did not attempt to directly address the issue of actual population density limits because there are no US risk standards established for the evaluation of population density limits. Calculations were performed using source terms for both a current generation light water reactor (LWR) and an advanced light water reactor (ALWR) design. The results of this study suggest that measures which address the distribution of the population density, including emergency response conditions, could result in lower average individual risks to the public than the proposed guidelines that require controlling average population density. Studies also indicate that an exclusion zone size, determined by emergency response conditions and reactor design (power level and safety features), would better serve to protect public health than a rigid standard applied to all sites

The energy density distribution of an ideal gas and Bernoulli’s equations

Science.gov (United States)

Santos, Leonardo S. F.

2018-05-01

This work discusses the energy density distribution in an ideal gas and the consequences of Bernoulli’s equation and the corresponding relation for compressible fluids. The aim of this work is to study how Bernoulli’s equation determines the energy flow in a fluid, although Bernoulli’s equation does not describe the energy density itself. The model from molecular dynamic considerations that describes an ideal gas at rest with uniform density is modified to explore the gas in motion with non-uniform density and gravitational effects. The difference between the component of the speed of a particle that is parallel to the gas speed and the gas speed itself is called ‘parallel random speed’. The pressure from the ‘parallel random speed’ is denominated as parallel pressure. The modified model predicts that the energy density is the sum of kinetic and potential gravitational energy densities plus two terms with static and parallel pressures. The application of Bernoulli’s equation and the corresponding relation for compressible fluids in the energy density expression has resulted in two new formulations. For incompressible and compressible gas, the energy density expressions are written as a function of stagnation, static and parallel pressures, without any dependence on kinetic or gravitational potential energy densities. These expressions of the energy density are the main contributions of this work. When the parallel pressure was uniform, the energy density distribution for incompressible approximation and compressible gas did not converge to zero for the limit of null static pressure. This result is rather unusual because the temperature tends to zero for null pressure. When the gas was considered incompressible and the parallel pressure was equal to static pressure, the energy density maintained this unusual behaviour with small pressures. If the parallel pressure was equal to static pressure, the energy density converged to zero for the limit of the

Density and energy distribution of epithermal secondary electrons in a plasma with fast charged particles

International Nuclear Information System (INIS)

Jayakumar, R.; Fleischmann, H.H.

1989-01-01

The production of intermediate energy secondary electrons in plasmas through collisions with fast charged particles is investigated. The density and the distribution of the secondary electrons are obtained by calculating the generation, slow down and diffusion rates, using basic Rutherford collision cross sections. It is shown that the total density of secondaries is much smaller than the fast particle density and that the energy distribution has roughly a 1/√E dependence. The higher generation secondary populations are also obtained. (orig.)

HI column density distribution function at z=0 : Connection to damped Ly alpha statistics

NARCIS (Netherlands)

Zwaan, Martin; Verheijen, MAW; Briggs, FH

We present a measurement of the HI column density distribution function f(N-HI) at the present epoch for column densities > 10(20) cm(-2). These high column densities compare to those measured in damped Ly alpha lines seen in absorption against background quasars. Although observationally rare, it

On the link between column density distribution and density scaling relation in star formation regions

Science.gov (United States)

Veltchev, Todor; Donkov, Sava; Stanchev, Orlin

2017-07-01

We present a method to derive the density scaling relation ∝ L^{-α} in regions of star formation or in their turbulent vicinities from straightforward binning of the column-density distribution (N-pdf). The outcome of the method is studied for three types of N-pdf: power law (7/5≤α≤5/3), lognormal (0.7≲α≲1.4) and combination of lognormals. In the last case, the method of Stanchev et al. (2015) was also applied for comparison and a very weak (or close to zero) correlation was found. We conclude that the considered `binning approach' reflects rather the local morphology of the N-pdf with no reference to the physical conditions in a considered region. The rough consistency of the derived slopes with the widely adopted Larson's (1981) value α˜1.1 is suggested to support claims that the density-size relation in molecular clouds is indeed an artifact of the observed N-pdf.

Performance of 12 DIR algorithms in low-contrast regions for mass and density conserving deformation

International Nuclear Information System (INIS)

Yeo, U. J.; Supple, J. R.; Franich, R. D.; Taylor, M. L.; Smith, R.; Kron, T.

2013-01-01

Purpose: Deformable image registration (DIR) has become a key tool for adaptive radiotherapy to account for inter- and intrafraction organ deformation. Of contemporary interest, the application to deformable dose accumulation requires accurate deformation even in low contrast regions where dose gradients may exist within near-uniform tissues. One expects high-contrast features to generally be deformed more accurately by DIR algorithms. The authors systematically assess the accuracy of 12 DIR algorithms and quantitatively examine, in particular, low-contrast regions, where accuracy has not previously been established.Methods: This work investigates DIR algorithms in three dimensions using deformable gel (DEFGEL) [U. J. Yeo, M. L. Taylor, L. Dunn, R. L. Smith, T. Kron, and R. D. Franich, “A novel methodology for 3D deformable dosimetry,” Med. Phys. 39, 2203–2213 (2012)], for application to mass- and density-conserving deformations. CT images of DEFGEL phantoms with 16 fiducial markers (FMs) implanted were acquired in deformed and undeformed states for three different representative deformation geometries. Nonrigid image registration was performed using 12 common algorithms in the public domain. The optimum parameter setup was identified for each algorithm and each was tested for deformation accuracy in three scenarios: (I) original images of the DEFGEL with 16 FMs; (II) images with eight of the FMs mathematically erased; and (III) images with all FMs mathematically erased. The deformation vector fields obtained for scenarios II and III were then applied to the original images containing all 16 FMs. The locations of the FMs estimated by the algorithms were compared to actual locations determined by CT imaging. The accuracy of the algorithms was assessed by evaluation of three-dimensional vectors between true marker locations and predicted marker locations.Results: The mean magnitude of 16 error vectors per sample ranged from 0.3 to 3.7, 1.0 to 6.3, and 1.3 to 7

Evaluation for the models of neutron diffusion theory in terms of power density distributions of the HTTR

International Nuclear Information System (INIS)

Takamatsu, Kuniyoshi; Shimakawa, Satoshi; Nojiri, Naoki; Fujimoto, Nozomu

2003-10-01

In the case of evaluations for the highest temperature of the fuels in the HTTR, it is very important to expect the power density distributions accurately; therefore, it is necessary to improve the analytical model with the neutron diffusion and the burn-up theory. The power density distributions are analyzed in terms of two models, the one mixing the fuels and the burnable poisons homogeneously and the other modeling them heterogeneously. Moreover these analytical power density distributions are compared with the ones derived from the gross gamma-ray measurements and the Monte Carlo calculational code with continuous energy. As a result the homogeneous mixed model isn't enough to expect the power density distributions of the core in the axial direction; on the other hand, the heterogeneous model improves the accuracy. (author)

Polar observations of electron density distribution in the Earth’s magnetosphere. 2. Density profiles

Directory of Open Access Journals (Sweden)

H. Laakso

2002-11-01

Full Text Available Using spacecraft potential measurements of the Polar electric field experiment, we investigate electron density variations of key plasma regions within the magnetosphere, including the polar cap, cusp, trough, plasmapause, and auroral zone. The statistical results were presented in the first part of this study, and the present paper reports detailed structures revealed by individual satellite passes. The high-altitude (> 3 RE polar cap is generally one of the most tenuous regions in the magnetosphere, but surprisingly, the polar cap boundary does not appear as a steep density decline. At low altitudes (1 RE in summer, the polar densities are very high, several 100 cm-3 , and interestingly, the density peaks at the central polar cap. On the noonside of the polar cap, the cusp appears as a dense, 1–3° wide region. A typical cusp density above 4 RE distance is between several 10 cm-3 and a few 100 cm-3 . On some occasions the cusp is crossed multiple times in a single pass, simultaneously with the occurrence of IMF excursions, as the cusp can instantly shift its position under varying solar wind conditions, similar to the magnetopause. On the nightside, the auroral zone is not always detected as a simple density cavity. Cavities are observed but their locations, strengths, and sizes vary. Also, the electric field perturbations do not necessarily overlap with the cavities: there are cavities with no field disturbances, as well as electric field disturbances observed with no clear cavitation. In the inner magnetosphere, the density distributions clearly show that the plasmapause and trough densities are well correlated with geomagnetic activity. Data from individual orbits near noon and midnight demonstrate that at the beginning of geomagnetic disturbances, the retreat speed of the plasmapause can be one L-shell per hour, while during quiet intervals the plasmapause can expand anti-earthward at the same speed. For the trough region, it is found

Field line distribution of density at L=4.8 inferred from observations by CLUSTER

Directory of Open Access Journals (Sweden)

S. Schäfer

2009-02-01

Full Text Available For two events observed by the CLUSTER spacecraft, the field line distribution of mass density ρ was inferred from Alfvén wave harmonic frequencies and compared to the electron density ne from plasma wave data and the oxygen density nO+ from the ion composition experiment. In one case, the average ion mass M≈ρ/ne was about 5 amu (28 October 2002, while in the other it was about 3 amu (10 September 2002. Both events occurred when the CLUSTER 1 (C1 spacecraft was in the plasmatrough. Nevertheless, the electron density ne was significantly lower for the first event (ne=8 cm−3 than for the second event (ne=22 cm−3, and this seems to be the main difference leading to a different value of M. For the first event (28 October 2002, we were able to measure the Alfvén wave frequencies for eight harmonics with unprecedented precision, so that the error in the inferred mass density is probably dominated by factors other than the uncertainty in frequency (e.g., magnetic field model and theoretical wave equation. This field line distribution (at L=4.8 was very flat for magnetic latitude |MLAT|≲20° but very steeply increasing with respect to |MLAT| for |MLAT|≳40°. The total variation in ρ was about four orders of magnitude, with values at large |MLAT| roughly consistent with ionospheric values. For the second event (10 September 2002, there was a small local maximum in mass density near the magnetic equator. The inferred mass density decreases to a minimum 23% lower than the equatorial value at |MLAT|=15.5°, and then steeply increases as one moves along the field line toward the ionosphere. For this event we were also able to examine the spatial dependence of the electron density using measurements of ne from all four CLUSTER spacecraft. Our analysis indicates that the density varies with L at L~5 roughly like L−4, and that ne is also locally peaked at the magnetic equator, but with a smaller peak. The value of ne reaches a density minimum

Isovector coupling channel and central properties of the charge density distribution in heavy spherical nuclei

International Nuclear Information System (INIS)

Haddad, S.

2010-01-01

The influence of the isovector coupling channel on the central depression parameter and the central value of the charge density distribution in heavy spherical nuclei was studied. The isovector coupling channel leads to about 50% increase of the central depression parameter, and weakens the dependency of both central depression parameter and the central density on the asymmetry, impressively contributing to the semibubble form of the charge density distribution in heavy nuclei, and increasing the probability of larger nuclei with higher proton numbers and higher neutron-to-proton ratios stable. (author)

Subchondral bone density distribution in the human femoral head

Energy Technology Data Exchange (ETDEWEB)

Wright, David A.; Meguid, Michael; Lubovsky, Omri; Whyne, Cari M. [Sunnybrook Research Institute, Orthopaedic Biomechanics Laboratory, Toronto, Ontario (Canada)

2012-06-15

This study aims to quantitatively characterize the distribution of subchondral bone density across the human femoral head using a computed tomography derived measurement of bone density and a common reference coordinate system. Femoral head surfaces were created bilaterally for 30 patients (14 males, 16 females, mean age 67.2 years) through semi-automatic segmentation of reconstructed CT data and used to map bone density, by shrinking them into the subchondral bone and averaging the greyscale values (linearly related to bone density) within 5 mm of the articular surface. Density maps were then oriented with the center of the head at the origin, the femoral mechanical axis (FMA) aligned with the vertical, and the posterior condylar axis (PCA) aligned with the horizontal. Twelve regions were created by dividing the density maps into three concentric rings at increments of 30 from the horizontal, then splitting into four quadrants along the anterior-posterior and medial-lateral axes. Mean values for each region were compared using repeated measures ANOVA and a Bonferroni post hoc test, and side-to-side correlations were analyzed using a Pearson's correlation. The regions representing the medial side of the femoral head's superior portion were found to have significantly higher densities compared to other regions (p < 0.05). Significant side-to-side correlations were found for all regions (r {sup 2} = 0.81 to r {sup 2} = 0.16), with strong correlations for the highest density regions. Side-to-side differences in measured bone density were seen for two regions in the anterio-lateral portion of the femoral head (p < 0.05). The high correlation found between the left and right sides indicates that this tool may be useful for understanding 'normal' density patterns in hips affected by unilateral pathologies such as avascular necrosis, fracture, developmental dysplasia of the hip, Perthes disease, and slipped capital femoral head epiphysis. (orig.)

Determining the temperature and density distribution from a Z-pinch radiation source

International Nuclear Information System (INIS)

Matuska, W.; Lee, H.

1997-01-01

High temperature radiation sources exceeding one hundred eV can be produced via z-pinches using currently available pulsed power. The usual approach to compare the z-pinch simulation and experimental data is to convert the radiation output at the source, whose temperature and density distributions are computed from the 2-D MHD code, into simulated data such as a spectrometer reading. This conversion process involves a radiation transfer calculation through the axially symmetric source, assuming local thermodynamic equilibrium (LTE), and folding the radiation that reaches the detector with the frequency-dependent response function. In this paper the authors propose a different approach by which they can determine the temperature and density distributions of the radiation source directly from the spatially resolved spectral data. This unfolding process is reliable and unambiguous for the ideal case where LTE holds and the source is axially symmetric. In reality, imperfect LTE and axial symmetry will introduce inaccuracies into the unfolded distributions. The authors use a parameter optimization routine to find the temperature and density distributions that best fit the data. They know from their past experience that the radiation source resulting from the implosion of a thin foil does not exhibit good axial symmetry. However, recent experiments carried out at Sandia National Laboratory using multiple wire arrays were very promising to achieve reasonably good symmetry. For these experiments the method will provide a valuable diagnostic tool

Towards the Moho depth and Moho density contrast along with their uncertainties from seismic and satellite gravity observations

Science.gov (United States)

Abrehdary, M.; Sjöberg, L. E.; Bagherbandi, M.; Sampietro, D.

2017-12-01

We present a combined method for estimating a new global Moho model named KTH15C, containing Moho depth and Moho density contrast (or shortly Moho parameters), from a combination of global models of gravity (GOCO05S), topography (DTM2006) and seismic information (CRUST1.0 and MDN07) to a resolution of 1° × 1° based on a solution of Vening Meinesz-Moritz' inverse problem of isostasy. This paper also aims modelling of the observation standard errors propagated from the Vening Meinesz-Moritz and CRUST1.0 models in estimating the uncertainty of the final Moho model. The numerical results yield Moho depths ranging from 6.5 to 70.3 km, and the estimated Moho density contrasts ranging from 21 to 650 kg/m3, respectively. Moreover, test computations display that in most areas estimated uncertainties in the parameters are less than 3 km and 50 kg/m3, respectively, but they reach to more significant values under Gulf of Mexico, Chile, Eastern Mediterranean, Timor sea and parts of polar regions. Comparing the Moho depths estimated by KTH15C and those derived by KTH11C, GEMMA2012C, CRUST1.0, KTH14C, CRUST14 and GEMMA1.0 models shows that KTH15C agree fairly well with CRUST1.0 but rather poor with other models. The Moho density contrasts estimated by KTH15C and those of the KTH11C, KTH14C and VMM model agree to 112, 31 and 61 kg/m3 in RMS. The regional numerical studies show that the RMS differences between KTH15C and Moho depths from seismic information yields fits of 2 to 4 km in South and North America, Africa, Europe, Asia, Australia and Antarctica, respectively.

Three-dimensional dose distribution in contrast-enhanced digital mammography using Gafchromic XR-QA2 films: Feasibility study

International Nuclear Information System (INIS)

Hwang, Yi-Shuan; Lin, Yu-Ying; Cheung, Yun-Chung; Tsai, Hui-Yu

2014-01-01

This study was aimed to establish three-dimensional dose distributions for contrast-enhanced digital mammography (CEDM) using self-developed Gafchromic XR-QA2 films. Dose calibration and distribution evaluations were performed on a full-field digital mammography unit with dual energy (DE) contrast-enhanced option. Strategy for dose calibration of films in the DE mode was based on the data obtained from common target/filter/kVp combinations used clinically and the dose response model modified from Rampado's model. Dose derived from films were also verified by measured data from an ionization chamber. The average difference of dose was 8.9% in the dose range for clinical uses. Three-dimensional dose distributions were estimated using triangular acrylic phantom equipped with the mammography system. Five pieces of film sheets were separately placed between the acrylic slabs to evaluate the dose distribution at different depths. After normalizing the dose in each pixel to the maximum dose at the top-center position of the acrylic, normalized dose distribution for transverse, coronal and sagittal planes, could thus be obtained. The depth dose distribution evaluated in this study may further serve as a reference for evaluating the patient glandular dose at different depths based on the entrance exposure information. - Highlights: • CEDM techniques can enhance contrast uptake areas and suppress background tissue. • Dose for the dual-energy acquisition is about 20% higher than standard mode. • A new method is proposed to estimate the 3D dose distribution in dual-energy CEDM. • Depth of normalized dose ratio of 0.5 is less than but near 1 cm in the DE mode

Suction/inspiration against resistance or standardized Mueller maneuver: a new breathing technique to improve contrast density within the pulmonary artery: a pilot CT study

Energy Technology Data Exchange (ETDEWEB)

Gutzeit, Andreas [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Hirslanden Hospital St. Anna, Institute of Radiology and Nuclear Medicine, Clinical Research Unit, Lucerne (Switzerland); Kantonsspital Winterthur, Department of Radiology, Winterthur (Switzerland); Froehlich, Johannes M.; Weymarn, Constantin von; Goyen, Matthias [Hirslanden Hospital St. Anna, Institute of Radiology and Nuclear Medicine, Clinical Research Unit, Lucerne (Switzerland); Waelti, Stephan [Cantonal Hospital St. Gallen, Department of Radiology and Nuclear Medicine, St. Gallen (Switzerland); Roos, Justus E. [Duke University Medical Center, Department of Radiology, Durham, NC (United States); Meissnitzer, Matthias; Hergan, Klaus [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Czell, David [Cantonal Hospital Winterthur, Department of Neurology, Winterthur (Switzerland); Reischauer, Carolin [Paracelsus Medical University Salzburg, Department of Radiology, Salzburg (Austria); Hirslanden Hospital St. Anna, Institute of Radiology and Nuclear Medicine, Clinical Research Unit, Lucerne (Switzerland)

2015-11-15

Our aim was to prospectively investigate whether the recently introduced suction/inspiration against resistance breathing method leads to higher computed tomography (CT) contrast density in the pulmonary artery compared to standard breathing. The present study was approved by the Medical Ethics committee and all subjects gave written informed consent. Fifteen patients, each without suspicious lung emboli, were randomly assigned to four different groups with different breathing maneuvers (suction against resistance, Valsalva, inspiration, expiration) during routine CT. Contrast enhancement in the central and peripheral sections of the pulmonary artery were measured and compared with one another. Peripheral enhancement during suction yielded increased mean densities of 138.14 Hounsfield units (HU) (p = 0.001), compared to Valsalva and a mean density of 67.97 HU superior to inspiration (p = 0.075). Finally, suction in comparison to expiration resulted in a mean increase of 30.51 HU (p = 0.42). Central parts of pulmonary arteries presented significantly increased enhancement values (95.74 HU) for suction versus the Valsalva technique (p = 0.020), while all other mean densities were in favour of suction (versus inspiration: p = 0.201; versus expiration: p = 0.790) without reaching significance. Suction/Inspiration against resistance is a promising technique to improve contrast density within pulmonary vessels, especially in the peripheral parts, in comparison to other breathing maneuvers. (orig.)

Correlation of double-contrast high-density barium enema, colonoscopy, and histology in children with special attention to disparities

International Nuclear Information System (INIS)

Stringer, D.A.; Sherman, P.M.; Jakowenko, N.

1986-01-01

Colonscopic and double-contrast high-density barium enema (DCBE) findings were correlated in 68 patients (39 boys and 29 girls) aged 6 months to 18 years (mean 11.6 years) evaluated over a 24-month period. There was excellent correlation in 53 patients (78.0%) and good correlation in another 3 (4.4%) who had identical diagnoses and only slightly differing extent of disease reported. In 2 of these, DCBE showed more extensive disease, confirmed histologically in 1. Distal colitis seen on colonoscopy as reddening and neovascularity was missed on DCBE in 6 patients. Colonoscopy and DEBE failed to show a polyp in 1 patient each. One patient who had a normal DCBE and colonoscopy demonstrated a histological abnormality, and 1 patient with an abnormality on histology and DCBE was normal on colonscopy. A disparity resulted from the time between procedures in 1 patient and observer error in another. This high correlation is far better than any previously reported in children, supporting the use of high-density barium sulfate and double-contrast barium enemas in pediatric patients. (orig.)

High density, uniformly distributed W/UO2 for use in Nuclear Thermal Propulsion

Science.gov (United States)

Tucker, Dennis S.; Barnes, Marvin W.; Hone, Lance; Cook, Steven

2017-04-01

An inexpensive, quick method has been developed to obtain uniform distributions of UO2 particles in a tungsten matrix utilizing 0.5 wt percent low density polyethylene. Powders were sintered in a Spark Plasma Sintering (SPS) furnace at 1600 °C, 1700 °C, 1750 °C, 1800 °C and 1850 °C using a modified sintering profile. This resulted in a uniform distribution of UO2 particles in a tungsten matrix with high densities, reaching 99.46% of theoretical for the sample sintered at 1850 °C. The powder process is described and the results of this study are given below.

Matter density distributions and elastic form factors of some two ...

Indian Academy of Sciences (India)

Ahmed N Abdullah

2017-08-31

Aug 31, 2017 ... include the proton, neutron and matter density distributions, the corresponding rms radii, the binding energy per nucleon and the charge form ... the nuclear structure models based on the experimental data for stable nuclei ... Most exotic nuclei are so short lived that they cannot be used as targets at rest.

Verification of the high density after contrast enhancement in the 2nd week in cerebroischemic lesion

Energy Technology Data Exchange (ETDEWEB)

Shibata, T; Kanno, T; Sano, H; Katada, Kazuhiro; Futimoto, K [Fujita Gakuen Univ., Toyoake, Aichi (Japan). School of Medicine

1978-12-01

To determine the indication, it is necessary to make clear the relation among the Stage (time and course), the Strength, the Pathogenesis, and the Effects of the operation in these diseases (SSPE relation). In this report, we focused on the High Density of CT after the contrast enhancement in the cases of ischemic lesions (the High Density was named ''Ribbon H. D.''). Seventeen cases of Ribbon H. D. in fresh infarctions were verified concerning the time of the appearance of the H. D., the features of its location and nature, and the histological findings. The results were as follows: The Ribbon H. D. appeared in the early stage of infarctions, and had its peak density at the end of the 2nd week after the onset. The Ribbon H. D. was mostly located along the cortical line, showing a ribbon-like band. The Ribbon H. D. did not appear in the sharply demarcated coagulation necrosis in the early stage or in the defined Low Density (L. D.) in the late stage of infarctions. Although the Ribbon H. D. shows the extravasation of contrast media, it does not necessarily show the existence of the hemorrhagic infarction. Some part of the Ribbon H. D. changes to a well-defined L. D. and the rest of the part becomes relative isodensity in the late stage. This change corresponds to the change in the incomplete necrosis which is afterwards divided into a resolution with a cystic cavity and the glial replacement in the late stage. In conclusion, it is possible to understand that the Ribbon H. D. corresponds to the lesion of an incomplete necrosis, with neovascularization, in the early stage of infarctions. Therefore, in addition to the present indication of a by-pass operation (TIA, RIND), this incomplete necrosis (Ribbon H. D.), its surrounding area and just before the appearance of the Ribbon H. D. might be another indication of the operation.

Regional absolute conductivity reconstruction using projected current density in MREIT

International Nuclear Information System (INIS)

Sajib, Saurav Z K; Kim, Hyung Joong; Woo, Eung Je; Kwon, Oh In

2012-01-01

Magnetic resonance electrical impedance tomography (MREIT) is a non-invasive technique for imaging the internal conductivity distribution in tissue within an MRI scanner, utilizing the magnetic flux density, which is introduced when a current is injected into the tissue from external electrodes. This magnetic flux alters the MRI signal, so that appropriate reconstruction can provide a map of the additional z-component of the magnetic field (B z ) as well as the internal current density distribution that created it. To extract the internal electrical properties of the subject, including the conductivity and/or the current density distribution, MREIT techniques use the relationship between the external injection current and the z-component of the magnetic flux density B = (B x , B y , B z ). The tissue studied typically contains defective regions, regions with a low MRI signal and/or low MRI signal-to-noise-ratio, due to the low density of nuclear magnetic resonance spins, short T 2 or T* 2 relaxation times, as well as regions with very low electrical conductivity, through which very little current traverses. These defective regions provide noisy B z data, which can severely degrade the overall reconstructed conductivity distribution. Injecting two independent currents through surface electrodes, this paper proposes a new direct method to reconstruct a regional absolute isotropic conductivity distribution in a region of interest (ROI) while avoiding the defective regions. First, the proposed method reconstructs the contrast of conductivity using the transversal J-substitution algorithm, which blocks the propagation of severe accumulated noise from the defective region to the ROI. Second, the proposed method reconstructs the regional projected current density using the relationships between the internal current density, which stems from a current injection on the surface, and the measured B z data. Combining the contrast conductivity distribution in the entire imaging

Fractal-based exponential distribution of urban density and self-affine fractal forms of cities

International Nuclear Information System (INIS)

Chen Yanguang; Feng Jian

2012-01-01

Highlights: ► The model of urban population density differs from the common exponential function. ► Fractal landscape influences the exponential distribution of urban density. ► The exponential distribution of urban population suggests a self-affine fractal. ► Urban space can be divided into three layers with scaling and non-scaling regions. ► The dimension of urban form with characteristic scale can be treated as 2. - Abstract: Urban population density always follows the exponential distribution and can be described with Clark’s model. Because of this, the spatial distribution of urban population used to be regarded as non-fractal pattern. However, Clark’s model differs from the exponential function in mathematics because that urban population is distributed on the fractal support of landform and land-use form. By using mathematical transform and empirical evidence, we argue that there are self-affine scaling relations and local power laws behind the exponential distribution of urban density. The scale parameter of Clark’s model indicating the characteristic radius of cities is not a real constant, but depends on the urban field we defined. So the exponential model suggests local fractal structure with two kinds of fractal parameters. The parameters can be used to characterize urban space filling, spatial correlation, self-affine properties, and self-organized evolution. The case study of the city of Hangzhou, China, is employed to verify the theoretical inference. Based on the empirical analysis, a three-ring model of cities is presented and a city is conceptually divided into three layers from core to periphery. The scaling region and non-scaling region appear alternately in the city. This model may be helpful for future urban studies and city planning.

Disk-galaxy density distribution from orbital speeds using Newton's law

OpenAIRE

Nicholson, Kenneth F.

2000-01-01

Given the dimensions (including thickness) of an axisymmetric galaxy, Newton's law is used in integral form to find the density distributions required to match a wide range of orbital speed profiles. Newton's law is not modified and no dark matter halos are required. The speed distributiions can have extreme shapes if they are reasonably smooth. Several examples are given.

Changes of the electron density distribution during MHD activity in CHS

International Nuclear Information System (INIS)

Soltwisch, H.; Tanaka, K.

2000-09-01

Density oscillations induced by MHD activities were observed in NBI heated plasmas on CHS by using an HCN laser interferometer. The accompanied changes of the density profiles were also observed. The oscillations are composition of m=0 sawteeth like crash and m=2 sinusoidal oscillations as a post courser of the crash. Possible models of the oscillation structure are examined in order to explain experimental data of the interferometer. Rotating plasma core, which is hollow profile and keeps constant elongation of the flux surface can explain amplitude and phase distribution of the sinusoidal oscillation. (author)

Modeling Bubble Flow and Current Density Distribution in an Alkaline Electrolysis Cell

Directory of Open Access Journals (Sweden)

Ravichandra S. Jupudi

2009-12-01

Full Text Available The effect of bubbles on the current density distribution over the electrodes of an alkaline electrolyzer cell is studied using a two-dimensional computational fluid dynamics model. Model includes Eulerian-Eulerian two-phase flow methodology to model the multiphase flow of Hydrogen and Oxygen with water and the behavior of each phase is accounted for using first principle. Hydrogen/Oxygen evolution, flow field and current density distribution are incorporated in the model to account for the complicated physics involved in the process. Fluent 6.2 is used to solve two-phase flow and electrochemistry is incorporated using UDF (User Defined Function feature of Fluent. Model is validated with mesh refinement study and by comparison with experimental measurements. Model is found to replicate the effect of cell voltage and inter-electrode gap (distance between the electrodes on current density accurately. Further, model is found to capture the existence of optimum cell height. The validated model is expected to be a very useful tool in the design and optimization of alkaline electrolyzer cells.

Estimating large carnivore populations at global scale based on spatial predictions of density and distribution – Application to the jaguar (Panthera onca)

Science.gov (United States)

Robinson, Hugh S.; Abarca, Maria; Zeller, Katherine A.; Velasquez, Grisel; Paemelaere, Evi A. D.; Goldberg, Joshua F.; Payan, Esteban; Hoogesteijn, Rafael; Boede, Ernesto O.; Schmidt, Krzysztof; Lampo, Margarita; Viloria, Ángel L.; Carreño, Rafael; Robinson, Nathaniel; Lukacs, Paul M.; Nowak, J. Joshua; Salom-Pérez, Roberto; Castañeda, Franklin; Boron, Valeria; Quigley, Howard

2018-01-01

Broad scale population estimates of declining species are desired for conservation efforts. However, for many secretive species including large carnivores, such estimates are often difficult. Based on published density estimates obtained through camera trapping, presence/absence data, and globally available predictive variables derived from satellite imagery, we modelled density and occurrence of a large carnivore, the jaguar, across the species’ entire range. We then combined these models in a hierarchical framework to estimate the total population. Our models indicate that potential jaguar density is best predicted by measures of primary productivity, with the highest densities in the most productive tropical habitats and a clear declining gradient with distance from the equator. Jaguar distribution, in contrast, is determined by the combined effects of human impacts and environmental factors: probability of jaguar occurrence increased with forest cover, mean temperature, and annual precipitation and declined with increases in human foot print index and human density. Probability of occurrence was also significantly higher for protected areas than outside of them. We estimated the world’s jaguar population at 173,000 (95% CI: 138,000–208,000) individuals, mostly concentrated in the Amazon Basin; elsewhere, populations tend to be small and fragmented. The high number of jaguars results from the large total area still occupied (almost 9 million km2) and low human densities (conservation actions. PMID:29579129

Fast Radio Bursts’ Recipes for the Distributions of Dispersion Measures, Flux Densities, and Fluences

Science.gov (United States)

Niino, Yuu

2018-05-01

We investigate how the statistical properties of dispersion measure (DM) and apparent flux density/fluence of (nonrepeating) fast radio bursts (FRBs) are determined by unknown cosmic rate density history [ρ FRB(z)] and luminosity function (LF) of the transient events. We predict the distributions of DMs, flux densities, and fluences of FRBs taking account of the variation of the receiver efficiency within its beam, using analytical models of ρ FRB(z) and LF. Comparing the predictions with the observations, we show that the cumulative distribution of apparent fluences suggests that FRBs originate at cosmological distances and ρ FRB increases with redshift resembling the cosmic star formation history (CSFH). We also show that an LF model with a bright-end cutoff at log10 L ν (erg s‑1 Hz‑1) ∼ 34 are favored to reproduce the observed DM distribution if ρ FRB(z) ∝ CSFH, although the statistical significance of the constraints obtained with the current size of the observed sample is not high. Finally, we find that the correlation between DM and flux density of FRBs is potentially a powerful tool to distinguish whether FRBs are at cosmological distances or in the local universe more robustly with future observations.

Incident energy and target dependence of interaction cross sections and density distribution of neutron drip-line nuclei

International Nuclear Information System (INIS)

Shimoura, S.

1992-01-01

The relation between nuclear density distribution and interaction cross section is discussed in terms of Glauber model. Based on the model, density distribution of neutron drip-line nucleus 11 Be and 11 Li is determined experimentally from incident energy dependence of interaction cross sections of 11 Be and 11 Li on light targets. The obtained distributions have long tails corresponding to neutron halos of loosely bound neutrons. (Author)

In vitro experiments for the development of a high density (HD) barium sulfate contrast medium

International Nuclear Information System (INIS)

Klein, J.

1986-01-01

In vitro experiments with the high-density (HD) barium meal Falibaryt HD are described. Several charges of BaSO 4 were tested together with certain additives influencing dispersion, stability of the suspension, flowability, surface tension etc. Particle size spectra were measured by the manufacturer, VEB Fahlberg-List. With a simple PVC test plate containing several grooves simulating small details (areae gastricae) the diagnostic capabilities of the HD contrast medium were evaluated in an in vitro test. The developed barium meal Falibaryt HD is in its physical and chemical parameters comparable with Prontobario-HD, one of the best HD barium meals. (author)

Enhancement of image contrast in linacgram through image processing

International Nuclear Information System (INIS)

Suh, Hyun Suk; Shin, Hyun Kyo; Lee, Re Na

2000-01-01

Conventional radiation therapy portal images gives low contrast images. The purpose of this study was to enhance image contrast of a linacgram by developing a low--cost image processing method. Chest linacgram was obtained by irradiating humanoid phantom and scanned using Diagnostic-Pro scanner for image processing. Several types of scan method were used in scanning. These include optical density scan, histogram equalized scan, linear histogram based scan, linear histogram independent scan, linear optical density scan, logarithmic scan, and power square root scan. The histogram distribution of the scanned images were plotted and the ranges of the gray scale were compared among various scan types. The scanned images were then transformed to the gray window by pallette fitting method and the contrast of the reprocessed portal images were evaluated for image improvement. Portal images of patients were also taken at various anatomic sites and the images were processed by Gray Scale Expansion (GSE) method. The patient images were analyzed to examine the feasibility of using the GSE technique in clinic. The histogram distribution showed that minimum and maximum gray scale ranges of 3192 and 21940 were obtained when the image was scanned using logarithmic method and square root method, respectively. Out of 256 gray scale, only 7 to 30% of the steps were used. After expanding the gray scale to full range, contrast of the portal images were improved. Experiment performed with patient image showed that improved identification of organs were achieved by GSE in portal images of knee joint, head and neck, lung, and pelvis. Phantom study demonstrated that the GSE technique improved image contrast of a linacgram. This indicates that the decrease in image quality resulting from the dual exposure, could be improved by expanding the gray scale. As a result, the improved technique will make it possible to compare the digitally reconstructed radiographs (DRR) and simulation image for

Discerning the neutron density distribution of 208Pb from nucleon elastic scattering

International Nuclear Information System (INIS)

Karataglidis, S.; Amos, K.; University of Melbourne, VIC; Brown, B.A.; Deb, P.K.

2001-01-01

We seek a measure of the neutron density of 208 Pb from analyses of intermediate energy nucleon elastic scattering. The pertinent model for such analyses is based on coordinate space nonlocal optical potentials obtained from model nuclear ground state densities. As a calibration of the use of Skyrme-Hartree-Fock models the elastic scattering from 40 Cawas considered as well. Those potentials give predictions of integral observables and of angular distributions which show sensitivity to the neutron density. When compared with experiment, and correlated with analyses of electron scattering data, the results suggest that 208 Pb has a neutron skin thickness ∼ 0.17 fm

Surface flux density distribution characteristics of bulk high-Tc superconductor in external magnetic field

International Nuclear Information System (INIS)

Torii, S.; Yuasa, K.

2004-01-01

Various magnetic levitation systems using oxide superconductors are developed as strong pinning forces are obtained in melt-processed bulk. However, the trapped flux of superconductor is moved by flux creep and fluctuating magnetic field. Therefore, to examine the internal condition of superconductor, the authors measure the dynamic surface flux density distribution of YBCO bulk. Flux density measurement system has a structure with the air-core coil and the Hall sensors. Ten Hall sensors are arranged in series. The YBCO bulk, which has 25 mm diameter and 13 mm thickness, is field cooled by liquid nitrogen. After that, magnetic field is changed by the air-core coil. This paper describes about the measured results of flux density distribution of YBCO bulk in the various frequencies of air-core coils currents

Surface flux density distribution characteristics of bulk high- Tc superconductor in external magnetic field

Science.gov (United States)

Torii, S.; Yuasa, K.

2004-10-01

Various magnetic levitation systems using oxide superconductors are developed as strong pinning forces are obtained in melt-processed bulk. However, the trapped flux of superconductor is moved by flux creep and fluctuating magnetic field. Therefore, to examine the internal condition of superconductor, the authors measure the dynamic surface flux density distribution of YBCO bulk. Flux density measurement system has a structure with the air-core coil and the Hall sensors. Ten Hall sensors are arranged in series. The YBCO bulk, which has 25 mm diameter and 13 mm thickness, is field cooled by liquid nitrogen. After that, magnetic field is changed by the air-core coil. This paper describes about the measured results of flux density distribution of YBCO bulk in the various frequencies of air-core coils currents.

Molecular dynamics equation designed for realizing arbitrary density: Application to sampling method utilizing the Tsallis generalized distribution

International Nuclear Information System (INIS)

Fukuda, Ikuo; Nakamura, Haruki

2010-01-01

Several molecular dynamics techniques applying the Tsallis generalized distribution are presented. We have developed a deterministic dynamics to generate an arbitrary smooth density function ρ. It creates a measure-preserving flow with respect to the measure ρdω and realizes the density ρ under the assumption of the ergodicity. It can thus be used to investigate physical systems that obey such distribution density. Using this technique, the Tsallis distribution density based on a full energy function form along with the Tsallis index q ≥ 1 can be created. From the fact that an effective support of the Tsallis distribution in the phase space is broad, compared with that of the conventional Boltzmann-Gibbs (BG) distribution, and the fact that the corresponding energy-surface deformation does not change energy minimum points, the dynamics enhances the physical state sampling, in particular for a rugged energy surface spanned by a complicated system. Other feature of the Tsallis distribution is that it provides more degree of the nonlinearity, compared with the case of the BG distribution, in the deterministic dynamics equation, which is very useful to effectively gain the ergodicity of the dynamical system constructed according to the scheme. Combining such methods with the reconstruction technique of the BG distribution, we can obtain the information consistent with the BG ensemble and create the corresponding free energy surface. We demonstrate several sampling results obtained from the systems typical for benchmark tests in MD and from biomolecular systems.

Disk-galaxy density distribution from orbital speeds using Newton's law, version 1.1

OpenAIRE

Nicholson, Kenneth F.

2000-01-01

Given the dimensions(including thickness) of an axisymmetric galaxy, Newton's law is used in integral form to find the density distributions required to match a wide range of orbital speed profiles. Newton's law is not modified and no dark-matter halos are required. The speed distributions can have extreme shapes if they are reasonably smooth. Several examples are given.

Density contrast indicators in cosmological dust models

Indian Academy of Sciences (India)

contrast, which may or may not be monotonically increasing with time. We also find that monotonic- ity seems to be related to the initial conditions of the model, which may be of potential interest in connection with debates regarding gravitational entropy and the arrow of time. 1. Introduction. An important question in ...

A verification of the high density after contrast enhancement in the 2nd week in cerebroischemic lesion

International Nuclear Information System (INIS)

Shibata, Taichiro; Kanno, Tetsuo; Sano, Hirotoshi; Katada, Kazuhiro; Fujimoto, Kazuo

1978-01-01

To determine the indication, it is necessary to make clear the relation among the Stage (time and course), the Strength, the Pathogenesis, and the Effects of the operation in these diseases (SSPE relation). In this report, we focused on the High Density of CT after the contrast enhancement in the cases of ischemic lesions (the High Density was named ''Ribbon H. D.''). Seventeen cases of Ribbon H. D. in fresh infarctions were verified concerning the time of the appearance of the H. D., the features of its location and nature, and the histological findings. The results were as follows: The Ribbon H. D. appeared in the early stage of infarctions, and had its peak density at the end of the 2nd week after the onset. The Ribbon H. D. was mostly located along the cortical line, showing a ribbon-like band. The Ribbon H. D. did not appear in the sharply demarcated coagulation necrosis in the early stage or in the defined Low Density (L. D.) in the late stage of infarctions. Although the Ribbon H. D. shows the extravasation of contrast media, it does not necessarily show the existence of the hemorrhagic infarction. Some part of the Ribbon H. D. changes to a well-defined L. D. and the rest of the part becomes relative isodensity in the late stage. This change corresponds to the change in the incomplete necrosis which is afterwards divided into a resolution with a cystic cavity and the glial replacement in the late stage. In conclusion, it is possible to understand that the Ribbon H. D. corresponds to the lesion of an incomplete necrosis, with neovascularization, in the early stage of infarctions. Therefore, in addition to the present indication of a by-pass operation (TIA, RIND), this incomplete necrosis (Ribbon H. D.), its surrounding area and just before the appearance of the Ribbon H. D. might be another indication of the operation. (author)

Contrast-enhanced radiotherapy: feasibility and characteristics of the physical absorbed dose distribution for deep-seated tumors

Energy Technology Data Exchange (ETDEWEB)

Garnica-Garza, H M [Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional Unidad Monterrey, Via del Conocimiento 201 Parque de Investigacion e Innovacion Tecnologica, Apodaca NL C.P. 66600 (Mexico)], E-mail: hgarnica@cinvestav.mx

2009-09-21

Radiotherapy using kilovoltage x-rays in conjunction with contrast agents incorporated into the tumor, gold nanoparticles in particular, could represent a potential alternative to current techniques based on high-energy linear accelerators. In this paper, using the voxelized Zubal phantom in conjunction with the Monte Carlo code PENELOPE to model a prostate cancer treatment, it is shown that in combination with a 360 deg. arc delivery technique, tumoricidal doses of radiation can be delivered to deep-seated tumors while still providing acceptable doses to the skin and other organs at risk for gold concentrations in the tumor within the range of 7-10 mg-Au per gram of tissue. Under these conditions and using a x-ray beam with 90% of the fluence within the range of 80-200 keV, a 72 Gy physical absorbed dose to the prostate can be delivered, while keeping the rectal wall, bladder, skin and femoral heads below 65 Gy, 55 Gy, 40 Gy and 30 Gy, respectively. However, it is also shown that non-uniformities in the contrast agent concentration lead to a severe degradation of the dose distribution and that, therefore, techniques to locally quantify the presence of the contrast agent would be necessary in order to determine the incident x-ray fluence that best reproduces the dosimetry obtained under conditions of uniform contrast agent distribution.

Contrast enhanced cartilage imaging: Comparison of ionic and non-ionic contrast agents

International Nuclear Information System (INIS)

Wiener, Edzard; Woertler, Klaus; Weirich, Gregor; Rummeny, Ernst J.; Settles, Marcus

2007-01-01

Our objective was to compare relaxation effects, dynamics and spatial distributions of ionic and non-ionic contrast agents in articular cartilage at concentrations typically used for direct MR arthrography at 1.5 T. Dynamic MR-studies over 11 h were performed in 15 bovine patella specimens. For each of the contrast agents gadopentetate dimeglumine, gadobenate dimeglumine, gadoteridol and mangafodipir trinatrium three patellae were placed in 2.5 mmol/L contrast solution. Simultaneous measurements of T 1 and T 2 were performed every 30 min using a high-spatial-resolution 'MIX'-sequence. T 1 , T 2 and ΔR 1 , ΔR 2 profile plots across cartilage thickness were calculated to demonstrate the spatial and temporal distributions. The charge is one of the main factors which controls the amount of the contrast media diffusing into intact cartilage, but independent of the charge, the spatial distribution across cartilage thickness remains highly inhomogeneous even after 11 h of diffusion. The absolute ΔR 2 -effect in cartilage is at least as large as the ΔR 1 -effect for all contrast agents. Maximum changes were 5-12 s -1 for ΔR 1 and 8-15 s -1 for ΔR 2 . This study indicates that for morphologically intact cartilage only the amount of contrast agents within cartilage is determined by the charge but not the spatial distribution across cartilage thickness. In addition, ΔR 2 can be considered for quantification of contrast agent concentrations, since it is of the same magnitude and less time consuming to measure than ΔR 1

Statistical tests for whether a given set of independent, identically distributed draws comes from a specified probability density.

Science.gov (United States)

Tygert, Mark

2010-09-21

We discuss several tests for determining whether a given set of independent and identically distributed (i.i.d.) draws does not come from a specified probability density function. The most commonly used are Kolmogorov-Smirnov tests, particularly Kuiper's variant, which focus on discrepancies between the cumulative distribution function for the specified probability density and the empirical cumulative distribution function for the given set of i.i.d. draws. Unfortunately, variations in the probability density function often get smoothed over in the cumulative distribution function, making it difficult to detect discrepancies in regions where the probability density is small in comparison with its values in surrounding regions. We discuss tests without this deficiency, complementing the classical methods. The tests of the present paper are based on the plain fact that it is unlikely to draw a random number whose probability is small, provided that the draw is taken from the same distribution used in calculating the probability (thus, if we draw a random number whose probability is small, then we can be confident that we did not draw the number from the same distribution used in calculating the probability).

Testing DARKexp against energy and density distributions of Millennium-II halos

Energy Technology Data Exchange (ETDEWEB)

Nolting, Chris; Williams, Liliya L.R. [School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN, 55454 (United States); Boylan-Kolchin, Michael [Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX, 78712 (United States); Hjorth, Jens, E-mail: nolting@astro.umn.edu, E-mail: llrw@astro.umn.edu, E-mail: mbk@astro.as.utexas.edu, E-mail: jens@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Copenhagen, DK-2100 Denmark (Denmark)

2016-09-01

We test the DARKexp model for relaxed, self-gravitating, collisionless systems against equilibrium dark matter halos from the Millennium-II simulation. While limited tests of DARKexp against simulations and observations have been carried out elsewhere, this is the first time the testing is done with a large sample of simulated halos spanning a factor of ∼ 50 in mass, and using independent fits to density and energy distributions. We show that DARKexp, a one shape parameter family, provides very good fits to the shapes of density profiles, ρ( r ), and differential energy distributions, N ( E ), of individual simulated halos. The best fit shape parameter φ{sub 0} obtained from the two types of fits are correlated, though with scatter. Our most important conclusions come from ρ( r ) and N ( E ) that have been averaged over many halos. These show that the bulk of the deviations between DARKexp and individual Millennium-II halos come from halo-to-halo fluctuations, likely driven by substructure, and other density perturbations. The average ρ( r ) and N ( E ) are quite smooth and follow DARKexp very closely. The only deviation that remains after averaging is small, and located at most bound energies for N ( E ) and smallest radii for ρ( r ). Since the deviation is confined to 3–4 smoothing lengths, and is larger for low mass halos, it is likely due to numerical resolution effects.

The interaction between the spatial distribution of resource patches and population density: consequences for intraspecific growth and morphology.

Science.gov (United States)

Jacobson, Bailey; Grant, James W A; Peres-Neto, Pedro R

2015-07-01

How individuals within a population distribute themselves across resource patches of varying quality has been an important focus of ecological theory. The ideal free distribution predicts equal fitness amongst individuals in a 1 : 1 ratio with resources, whereas resource defence theory predicts different degrees of monopolization (fitness variance) as a function of temporal and spatial resource clumping and population density. One overlooked landscape characteristic is the spatial distribution of resource patches, altering the equitability of resource accessibility and thereby the effective number of competitors. While much work has investigated the influence of morphology on competitive ability for different resource types, less is known regarding the phenotypic characteristics conferring relative ability for a single resource type, particularly when exploitative competition predominates. Here we used young-of-the-year rainbow trout (Oncorhynchus mykiss) to test whether and how the spatial distribution of resource patches and population density interact to influence the level and variance of individual growth, as well as if functional morphology relates to competitive ability. Feeding trials were conducted within stream channels under three spatial distributions of nine resource patches (distributed, semi-clumped and clumped) at two density levels (9 and 27 individuals). Average trial growth was greater in high-density treatments with no effect of resource distribution. Within-trial growth variance had opposite patterns across resource distributions. Here, variance decreased at low-population, but increased at high-population densities as patches became increasingly clumped as the result of changes in the levels of interference vs. exploitative competition. Within-trial growth was related to both pre- and post-trial morphology where competitive individuals were those with traits associated with swimming capacity and efficiency: larger heads/bodies/caudal fins

Characterization of intraventricular and intracerebral hematomas in non-contrast CT.

Science.gov (United States)

Nowinski, Wieslaw L; Gomolka, Ryszard S; Qian, Guoyu; Gupta, Varsha; Ullman, Natalie L; Hanley, Daniel F

2014-06-01

Characterization of hematomas is essential in scan reading, manual delineation, and designing automatic segmentation algorithms. Our purpose is to characterize the distribution of intraventricular (IVH) and intracerebral hematomas (ICH) in NCCT scans, study their relationship to gray matter (GM), and to introduce a new tool for quantitative hematoma delineation. We used 289 serial retrospective scans of 51 patients. Hematomas were manually delineated in a two-stage process. Hematoma contours generated in the first stage were quantified and enhanced in the second stage. Delineation was based on new quantitative rules and hematoma profiling, and assisted by a dedicated tool superimposing quantitative information on scans with 3D hematoma display. The tool provides: density maps (40-85HU), contrast maps (8/15HU), mean horizontal/vertical contrasts for hematoma contours, and hematoma contours below a specified mean contrast (8HU). White matter (WM) and GM were segmented automatically. IVH/ICH on serial NCCT is characterized by 59.0HU mean, 60.0HU median, 11.6HU standard deviation, 23.9HU mean contrast, -0.99HU/day slope, and -0.24 skewness (changing over time from negative to positive). Its 0.1(st)-99.9(th) percentile range corresponds to 25-88HU range. WM and GM are highly correlated (R (2)=0.88; phematoma density distributions is at 55.6±5.8HU with the corresponding GM/hematoma percentiles of 88(th)/40(th). Objective characterization of IVH/ICH and stating the rules quantitatively will aid raters to delineate hematomas more robustly and facilitate designing algorithms for automatic hematoma segmentation. Our two-stage process is general and potentially applicable to delineate other pathologies on various modalities more robustly and quantitatively.

One-dimensional contrast modulations in [001] high-resolution reverse images of Bi2Sr2(Cu1-xNdx)Cu2O8+δ ceramics

International Nuclear Information System (INIS)

Onozuka, T.

1993-01-01

The one-dimensional contrast modulation along the b axis of [001] high-resolution reverse images of the compounds Bi 2 Sr 2 (Ca 1-x Nd x )Cu 2 O 8+δ (x=0.05+0.1n; n=1, 2, 6 and 7) is examined closely using the density distribution recorded from a wide area of the negative film by microphotometric densitometry. Three typical short units of the density distribution, of lengths 4.5b 0 , 5b 0 and 4b 0 , characterized by twin peaks or a single maximum peak with subpeaks in the middle of the unit, are discerned. The density distributions of the three units and the contrast modulations of their images are reproduced well by computer simulations, using three structure models modulated with longitudinal displacement waves along the b axis of the metal atoms. The one-dimensional contrast modulation is attributed to sinusoidal changes in the effective scattering amplitudes for the [001] electron beam of the metal-atom chains along the c axis. The results of the simulation are applied to investigation of the (2, 1) 5 and (3, 1) 4 modulation modes in the modulated structure. (orig.)

Marine litter distribution and density in European seas, from the shelves to deep basins.

Science.gov (United States)

Pham, Christopher K; Ramirez-Llodra, Eva; Alt, Claudia H S; Amaro, Teresa; Bergmann, Melanie; Canals, Miquel; Company, Joan B; Davies, Jaime; Duineveld, Gerard; Galgani, François; Howell, Kerry L; Huvenne, Veerle A I; Isidro, Eduardo; Jones, Daniel O B; Lastras, Galderic; Morato, Telmo; Gomes-Pereira, José Nuno; Purser, Autun; Stewart, Heather; Tojeira, Inês; Tubau, Xavier; Van Rooij, David; Tyler, Paul A

2014-01-01

Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets) was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments.

Predação de larvas de pacu (Piaractus mesopotamicus, Holmberg por copépodes ciclopóides (Mesocyclops longisetus, Thiébaud em diferentes densidades e ambientes e com diferentes contrastes visuais Predation of pacu (Piaractus mesopotamicus, Holmberg larvae by cyclopoid copepods (Mesocyclops longisetus, Thiébaud at different densities in environments with different visual contrast

Directory of Open Access Journals (Sweden)

Carmino Hayashi

2001-05-01

Full Text Available O objetivo do presente trabalho foi avaliar a influência da densidade de copépodes ciclopóides (Mesocyclops longisetus na predação de larvas de pacu (Piaractus mesopotamicus em ambientes com diferentes contrastes visuais. Foram utilizadas 360 larvas de pacu (Lt = 5,77±0,23 mm e Wt = 6,57 mg, distribuídas em 24 aquários (1-L de vidro transparente, em um delineamento em blocos casualizados com oito tratamentos e três repetições, que constaram de 0, 10, 20 e 30 copépodes/L, em aquários com paredes sem revestimento ou com paredes revestidas de plástico escuro. Realizou-se a contagem, a cada uma hora, das larvas mortas e em seguida elas eram retiradas com uma pipeta. Observou-se um aumento linear nas taxas de predação (p Influence of density of cyclopoid copepods (Mesocyclops longisetus on pacu larvae (Piaractus mesopotamicus predation in environments with different visual contrast is provided. Three hundred and sixty larvae (Lt: 5.77±0.23 mm and Wt: 6.57 mg were distributed in 24 one-liter light-color-lined aquaria, in a entirely randomized design, with eight treatments and three replications, with densities 0, 10, 20 and 30 copepods/L. Similar densities were used and distributed in aquaria with dark plastic lined interior. Dead larvae were counted hourly and removed with a pipette. After three hours from the start of experiment a linear increase in predation rate (p th to the 9th observation, with smaller survival values of pacu larvae in light-colored aquaria. It may be concluded that increase in copepod density and absence of lining on walls of aquaria favor higher predation rates of copepods on pacu larvae

Correlations Between the Gradient of Contrast Density, Evaluated by Cardio CT, and Functional Significance of Coronary Artery Stenosis

Directory of Open Access Journals (Sweden)

Orzan Marius

2016-06-01

Full Text Available Background: Assessment of the hemodynamic significance of a coronary artery stenosis is a challenging task, being extremely important for the establishment of indication for revascularization in atherosclerotic coronary artery stenosis. The aim of this study was to evaluate the role of a new marker reflecting the functional significance of a coronary artery stenosis, represented by the attenuation degree of contrast density along the stenosis by Coronary CT.

Investigating the effect of tablet thickness and punch curvature on density distribution using finite elements method.

Science.gov (United States)

Diarra, Harona; Mazel, Vincent; Busignies, Virginie; Tchoreloff, Pierre

2015-09-30

Finite elements method was used to study the influence of tablet thickness and punch curvature on the density distribution inside convex faced (CF) tablets. The modeling of the process was conducted on 2 pharmaceutical excipients (anhydrous calcium phosphate and microcrystalline cellulose) by using Drucker-Prager Cap model in Abaqus(®) software. The parameters of the model were obtained from experimental tests. Several punch shapes based on industrial standards were used. A flat-faced (FF) punch and 3 convex faced (CF) punches (8R11, 8R8 and 8R6) with a diameter of 8mm were chosen. Different tablet thicknesses were studied at a constant compression force. The simulation of the compaction of CF tablets with increasing thicknesses showed an important change on the density distribution inside the tablet. For smaller thicknesses, low density zones are located toward the center. The density is not uniform inside CF tablets and the center of the 2 faces appears with low density whereas the distribution inside FF tablets is almost independent of the tablet thickness. These results showed that FF and CF tablets, even obtained at the same compression force, do not have the same density at the center of the compact. As a consequence differences in tensile strength, as measured by diametral compression, are expected. This was confirmed by experimental tests. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of a sampling strategy and sample size calculation to estimate the distribution of mammographic breast density in Korean women.

Science.gov (United States)

Jun, Jae Kwan; Kim, Mi Jin; Choi, Kui Son; Suh, Mina; Jung, Kyu-Won

2012-01-01

Mammographic breast density is a known risk factor for breast cancer. To conduct a survey to estimate the distribution of mammographic breast density in Korean women, appropriate sampling strategies for representative and efficient sampling design were evaluated through simulation. Using the target population from the National Cancer Screening Programme (NCSP) for breast cancer in 2009, we verified the distribution estimate by repeating the simulation 1,000 times using stratified random sampling to investigate the distribution of breast density of 1,340,362 women. According to the simulation results, using a sampling design stratifying the nation into three groups (metropolitan, urban, and rural), with a total sample size of 4,000, we estimated the distribution of breast density in Korean women at a level of 0.01% tolerance. Based on the results of our study, a nationwide survey for estimating the distribution of mammographic breast density among Korean women can be conducted efficiently.

Floating macro-litter along the Mediterranean French coast: Composition, density, distribution and overlap with cetacean range.

Science.gov (United States)

Di-Méglio, Nathalie; Campana, Ilaria

2017-05-15

This study investigated the composition, density and distribution of floating macro-litter along the Liguro-Provençal basin with respect to cetaceans presence. Survey transects were performed in summer between 2006 and 2015 from sailing vessels with simultaneous cetaceans observations. During 5171km travelled, 1993 floating items were recorded, widespread in the whole study area. Plastics was the predominant category, with bags/packaging always representing >45% of total items. Overall mean density (14.98 items/km 2 ) was stable with significant increase reported only in 2010-2011; monthly analysis showed lower litter densities in July-September, suggesting possible seasonal patterns. Kernel density estimation for plastics revealed ubiquitous distribution rather than high accumulation areas, mainly due to the circulation dynamics of this area. The presence range of cetaceans (259 sightings, 6 species) corresponded by ~50% with plastic distribution, indicating high potential of interaction, especially in the eastern part of the area, but effective risks for marine species might be underrepresented. Copyright © 2017 Elsevier Ltd. All rights reserved.

Numerical Calculation of Distribution of Induced Carge Density on Planar Confined Surfaces

International Nuclear Information System (INIS)

Bolotov, V.; Druzhchenko, R.; Karazin, V.; Lominadze, J.; Kharadze, F.

2007-01-01

The calculation method of distribution of induced charge density on planar surfaces, including fractal structures of Sierpinski carpet type, is propesed. The calculation scheme is based on the fact that simply connected conducting surface of arbitrary geometry is an equipotential surface. (author)

Determining integral density distribution in the mach reflection of shock waves

Science.gov (United States)

Shevchenko, A. M.; Golubev, M. P.; Pavlov, A. A.; Pavlov, Al. A.; Khotyanovsky, D. V.; Shmakov, A. S.

2017-05-01

We present a method for and results of determination of the field of integral density in the structure of flow corresponding to the Mach interaction of shock waves at Mach number M = 3. The optical diagnostics of flow was performed using an interference technique based on self-adjusting Zernike filters (SA-AVT method). Numerical simulations were carried out using the CFS3D program package for solving the Euler and Navier-Stokes equations. Quantitative data on the distribution of integral density on the path of probing radiation in one direction of 3D flow transillumination in the region of Mach interaction of shock waves were obtained for the first time.

The Density Functional Theory of Flies: Predicting distributions of interacting active organisms

Science.gov (United States)

Kinkhabwala, Yunus; Valderrama, Juan; Cohen, Itai; Arias, Tomas

On October 2nd, 2016, 52 people were crushed in a stampede when a crowd panicked at a religious gathering in Ethiopia. The ability to predict the state of a crowd and whether it is susceptible to such transitions could help prevent such catastrophes. While current techniques such as agent based models can predict transitions in emergent behaviors of crowds, the assumptions used to describe the agents are often ad hoc and the simulations are computationally expensive making their application to real-time crowd prediction challenging. Here, we pursue an orthogonal approach and ask whether a reduced set of variables, such as the local densities, are sufficient to describe the state of a crowd. Inspired by the theoretical framework of Density Functional Theory, we have developed a system that uses only measurements of local densities to extract two independent crowd behavior functions: (1) preferences for locations and (2) interactions between individuals. With these two functions, we have accurately predicted how a model system of walking Drosophila melanogaster distributes itself in an arbitrary 2D environment. In addition, this density-based approach measures properties of the crowd from only observations of the crowd itself without any knowledge of the detailed interactions and thus it can make predictions about the resulting distributions of these flies in arbitrary environments, in real-time. This research was supported in part by ARO W911NF-16-1-0433.

Multipole lenses with implicit poles and with harmonic distribution of current density in a coil

International Nuclear Information System (INIS)

Skachkov, V.S.

1984-01-01

General theory of the multipole lense with implicit poles is presented. The thickness of lense coil is finite. Current density distribution in the coil cross section is harmonic in the azimuth direction and arbitrary in the radial one. The calculation of yoke contribution in the lence field is given. Two particular lense variants differing from each other in the method of current density radial distribution are considered and necessary calculated relations for the lense with and without yoke ar presented. A comparative analysis of physical and technological peculiarities of these lenses is performed

Determination of power density distribution of fuel assemblies for research reactor by directly measuring the strontium-91 activities

International Nuclear Information System (INIS)

Yuan, Liq-Ji

1987-01-01

This work described the investigations of reactor core power peaking and three dimensional power density distribution of present core configuration of Tsing Hua Open-pool reactor (THOR). An experimental program, based on non-destructive fuel gamma scanning of 91 Sr activities, provides the data of fission density distribution for individual fuel pin of four-rod TRIGA-LEU cluster or for MTR-type fuel assembly. The informations are essentially important for the safety of reactor operation and for fuel management especially for the mixed loading with three different types of fuel at present. The relative power peaking values and the power density distribution for present core are discussed. (author)

Founder takes all: density-dependent processes structure biodiversity.

Science.gov (United States)

Waters, Jonathan M; Fraser, Ceridwen I; Hewitt, Godfrey M

2013-02-01

Density-dependent processes play a key role in the spatial structuring of biodiversity. Specifically, interrelated demographic processes, such as gene surfing, high-density blocking, and competitive exclusion, can generate striking geographic contrasts in the distributions of genes and species. Here, we propose that well-studied evolutionary and ecological biogeographic patterns of postglacial recolonization, progressive island colonization, microbial sectoring, and even the 'Out of Africa' pattern of human expansion, are fundamentally similar, underpinned by a 'founder takes all' density-dependent principle. Additionally, we hypothesize that older historic constraints of density-dependent processes are seen today in the dramatic biogeographic shifts that occur in response to human-mediated extinction events, whereby surviving lineages rapidly expand their ranges to replace extinct sister taxa. Copyright © 2012 Elsevier Ltd. All rights reserved.

Controlling the Laser Guide Star power density distribution at Sodium layer by combining Pre-correction and Beam-shaping

Science.gov (United States)

Huang, Jian; Wei, Kai; Jin, Kai; Li, Min; Zhang, YuDong

2018-06-01

The Sodium laser guide star (LGS) plays a key role in modern astronomical Adaptive Optics Systems (AOSs). The spot size and photon return of the Sodium LGS depend strongly on the laser power density distribution at the Sodium layer and thus affect the performance of the AOS. The power density distribution is degraded by turbulence in the uplink path, launch system aberrations, the beam quality of the laser, and so forth. Even without any aberrations, the TE00 Gaussian type is still not the optimal power density distribution to obtain the best balance between the measurement error and temporal error. To optimize and control the LGS power density distribution at the Sodium layer to an expected distribution type, a method that combines pre-correction and beam-shaping is proposed. A typical result shows that under strong turbulence (Fried parameter (r0) of 5 cm) and for a quasi-continuous wave Sodium laser (power (P) of 15 W), in the best case, our method can effectively optimize the distribution from the Gaussian type to the "top-hat" type and enhance the photon return flux of the Sodium LGS; at the same time, the total error of the AOS is decreased by 36% with our technique for a high power laser and poor seeing.

Comparison in electron density distribution of tokamak plasma between ruby-laser scattering and milli-meter wave interferometric measurements

International Nuclear Information System (INIS)

Matoba, Tohru; Funahashi, Akimasa; Itagaki, Tokiyoshi; Takahashi, Koki; Kumagai, Katsuaki

1976-08-01

The electron density in JFT-2 tokamak has been measured by two methods, i.e. Thomson scattering of ruby-laser light and interferometry of millimeter wave. Two-dimensional distribution of the scattered light intensities were obtained by scattering measurement; absolute calibration was made by normalizing the scattered intensities with the averaged density determined from interferometric measurement. The horizontal density distributions in laser scattering were compared with those in from the averaged densities measured with a 4-mm interferometer through inverse-transformation. Agreement is good between the two measurements, except where they give erroneous data because of irreproducibility of the discharge. (auth.)

Visualizing measurement for 3D smooth density distributions by means of linear programming

International Nuclear Information System (INIS)

Tayama, Norio; Yang, Xue-dong

1994-01-01

This paper is concerned with a theoretical possibility of a new visualizing measurement method based on an optimum 3D reconstruction from a few selected projections. A theory of optimum 3D reconstruction by a linear programming is discussed, utilizing a few projections for sampled 3D smooth-density-distribution model which satisfies the condition of the 3D sampling theorem. First by use of the sampling theorem, it is shown that we can set up simultaneous simple equations which corresponds to the case of the parallel beams. Then we solve the simultaneous simple equations by means of linear programming algorithm, and we can get an optimum 3D density distribution images with minimum error in the reconstruction. The results of computer simulation with the algorithm are presented. (author)

A distributed current stimulator ASIC for high density neural stimulation.

Science.gov (United States)

Jeong Hoan Park; Chaebin Kim; Seung-Hee Ahn; Tae Mok Gwon; Joonsoo Jeong; Sang Beom Jun; Sung June Kim

2016-08-01

This paper presents a novel distributed neural stimulator scheme. Instead of a single stimulator ASIC in the package, multiple ASICs are embedded at each electrode site for stimulation with a high density electrode array. This distributed architecture enables the simplification of wiring between electrodes and stimulator ASIC that otherwise could become too complex as the number of electrode increases. The individual ASIC chip is designed to have a shared data bus that independently controls multiple stimulating channels. Therefore, the number of metal lines is determined by the distributed ASICs, not by the channel number. The function of current steering is also implemented within each ASIC in order to increase the effective number of channels via pseudo channel stimulation. Therefore, the chip area can be used more efficiently. The designed chip was fabricated with area of 0.3 mm2 using 0.18 μm BCDMOS process, and the bench-top test was also conducted to validate chip performance.

Influences of radiation and leaf area vertical distribution on the growth of Chinese fir young plantation with different densities

International Nuclear Information System (INIS)

Wang Lili

1990-01-01

A study on the radiation and leaf area vertical distribution in relation to the growth of 8-year-old Chinese fir plantations of 5 densities was conducted. The leaf area vertical distribution and LAI were closely related to stem density. The crown form varies from conic to cylindric with the increase of stem density. The LAI rises at first and then declines with the increase of density. The extinction of radiation sharpened when the crown density increased. The extinction leveled at the depth of 3/4 forest heights from the tops of forest canopies. Calculating the extinction coefficients by means of accumulated leaf area index separately for each crown layer can minimize the errors caused by the irregularity of leaf distribution. Four indices, i.e., absorption of radiation, LAI,biomass of individual tree and averaged annual increment of biomass were used to have a comprehensive evaluation on the growth of Chinese fir of 5 densities. The results showed that the plantation with a stem density of 2m × 1 m was the best one among the 5 young plantations

Measurements and predictions of the air distribution systems in high compute density (Internet) data centers

Energy Technology Data Exchange (ETDEWEB)

Cho, Jinkyun [HIMEC (Hanil Mechanical Electrical Consultants) Ltd., Seoul 150-103 (Korea); Department of Architectural Engineering, Yonsei University, Seoul 120-749 (Korea); Lim, Taesub; Kim, Byungseon Sean [Department of Architectural Engineering, Yonsei University, Seoul 120-749 (Korea)

2009-10-15

When equipment power density increases, a critical goal of a data center cooling system is to separate the equipment exhaust air from the equipment intake air in order to prevent the IT server from overheating. Cooling systems for data centers are primarily differentiated according to the way they distribute air. The six combinations of flooded and locally ducted air distribution make up the vast majority of all installations, except fully ducted air distribution methods. Once the air distribution system (ADS) is selected, there are other elements that must be integrated into the system design. In this research, the design parameters and IT environmental aspects of the cooling system were studied with a high heat density data center. CFD simulation analysis was carried out in order to compare the heat removal efficiencies of various air distribution systems. The IT environment of an actual operating data center is measured to validate a model for predicting the effect of different air distribution systems. A method for planning and design of the appropriate air distribution system is described. IT professionals versed in precision air distribution mechanisms, components, and configurations can work more effectively with mechanical engineers to ensure the specification and design of optimized cooling solutions. (author)

Method of measuring the current density distribution and emittance of pulsed electron beams

International Nuclear Information System (INIS)

Schilling, H.B.

1979-07-01

This method of current density measurement employs an array of many Faraday cups, each cup being terminated by an integrating capacitor. The voltages of the capacitors are subsequently displayed on a scope, thus giving the complete current density distribution with one shot. In the case of emittance measurements, a moveable small-diameter aperture is inserted at some distance in front of the cup array. Typical results with a two-cathode, two-energy electron source are presented. (orig.)

Marine litter distribution and density in European seas, from the shelves to deep basins.

Directory of Open Access Journals (Sweden)

Christopher K Pham

Full Text Available Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments.

Asymptotic Behavior of the Stock Price Distribution Density and Implied Volatility in Stochastic Volatility Models

International Nuclear Information System (INIS)

Gulisashvili, Archil; Stein, Elias M.

2010-01-01

We study the asymptotic behavior of distribution densities arising in stock price models with stochastic volatility. The main objects of our interest in the present paper are the density of time averages of the squared volatility process and the density of the stock price process in the Stein-Stein and the Heston model. We find explicit formulas for leading terms in asymptotic expansions of these densities and give error estimates. As an application of our results, sharp asymptotic formulas for the implied volatility in the Stein-Stein and the Heston model are obtained.

High density, uniformly distributed W/UO{sub 2} for use in Nuclear Thermal Propulsion

Energy Technology Data Exchange (ETDEWEB)

Tucker, Dennis S., E-mail: dr.dennis.tucker@nasa.gov [EM32, MSFC, Al 35812 (United States); Barnes, Marvin W. [EM32, MSFC, Al 35812 (United States); Hone, Lance; Cook, Steven [Center for Space Nuclear Research, Idaho Falls, ID 83401 (United States)

2017-04-01

An inexpensive, quick method has been developed to obtain uniform distributions of UO{sub 2} particles in a tungsten matrix utilizing 0.5 wt percent low density polyethylene. Powders were sintered in a Spark Plasma Sintering (SPS) furnace at 1600 °C, 1700 °C, 1750 °C, 1800 °C and 1850 °C using a modified sintering profile. This resulted in a uniform distribution of UO{sub 2} particles in a tungsten matrix with high densities, reaching 99.46% of theoretical for the sample sintered at 1850 °C. The powder process is described and the results of this study are given below.

Distributed material density and anisotropy for optimized eigenfrequency of 2D continua

DEFF Research Database (Denmark)

Pedersen, Pauli; Pedersen, Niels Leergaard

2015-01-01

A practical approach to optimize a continuum/structural eigenfrequency is presented, including design of the distribution of material anisotropy. This is often termed free material optimization (FMO). An important aspect is the separation of the overall material distribution from the local design...... with respect to material density and from this values of the element OC. Each factor of this expression has a physical interpretation. Stated alternatively, the optimization problem of material distribution is converted into a problem of determining a design of uniform OC values. The constitutive matrices...... are described by non-dimensional matrices with unity norms of trace and Frobenius, and thus this part of the optimized design has no influence on the mass distribution. Gradients of eigenfrequency with respect to the components of these non-dimensional constitutive matrices are therefore simplified...

Vertical Distribution of Soil Organic Carbon Density in Relation to Land Use/Cover, Altitude and Slope Aspect in the Eastern Himalayas

Directory of Open Access Journals (Sweden)

Tshering Dorji

2014-10-01

Full Text Available In-depth understanding about the vertical distribution of soil organic carbon (SOC density is crucial for carbon (C accounting, C budgeting and designing appropriate C sequestration strategies. We examined the vertical distribution of SOC density under different land use/land cover (LULC types, altitudinal zones and aspect directions in a montane ecosystem of Bhutan. Sampling sites were located using conditioned Latin hypercube sampling (cLHS scheme. Soils were sampled based on genetic horizons. An equal-area spline function was fitted to interpolate the target values to predetermined depths. Linear mixed model was fitted followed by mean separation tests. The results show some significant effects of LULC, altitudinal zone and slope aspect on the vertical distribution of SOC density in the profiles. Based on the proportion of mean SOC density in the first 20 cm relative to the cumulative mean SOC density in the top meter, the SOC density under agricultural lands (34% was more homogeneously distributed down the profiles than forests (39%, grasslands (59% and shrublands (43%. Similarly, the SOC density under 3500–4000 m zone (35% was more uniformly distributed compared to 3000–3500 m zone (43% and 1769–2500 m and 2500–3000 m zones (41% each. Under different aspect directions, the north and east-facing slopes (38% each had more uniform distribution of SOC density than south (40% and west-facing slopes (49%.

Density distribution of {sup 14}Be from reaction cross-section measurements

Energy Technology Data Exchange (ETDEWEB)

Moriguchi, T. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Ozawa, A., E-mail: ozawa@tac.tsukuba.ac.jp [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Ishimoto, S. [High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Abe, Y. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Fukuda, M. [Department of Physics, Osaka University, Osaka 560-0043 (Japan); Hachiuma, I. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Ishibashi, Y.; Ito, Y. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Kuboki, T. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Lantz, M. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Nagae, D. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Namihira, K. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Nishimura, D. [Department of Physics, Osaka University, Osaka 560-0043 (Japan); Ohtsubo, T. [Department of Physics, Niigata University, Niigata 950-2181 (Japan); Ooishi, H. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Suda, T. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Suzuki, H. [Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Suzuki, T. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Takechi, M.; Tanaka, K. [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); and others

2014-09-15

We measured the reaction cross sections of the two-neutron halo nucleus {sup 14}Be with proton and carbon targets at about 41 and 76 MeV/nucleon. Based on a Glauber model calculation, we deduced the matter density distribution of {sup 14}Be in which previously measured interaction cross sections at relativistic energies were also included. An s-wave dominance in {sup 14}Be has been confirmed, although the halo tail of {sup 14}Be is not distributed as much as that of {sup 11}Li. Significant mixing of the p-wave in addition to the s- and d-wave is also suggested.

Assessing different parameters estimation methods of Weibull distribution to compute wind power density

International Nuclear Information System (INIS)

Mohammadi, Kasra; Alavi, Omid; Mostafaeipour, Ali; Goudarzi, Navid; Jalilvand, Mahdi

2016-01-01

Highlights: • Effectiveness of six numerical methods is evaluated to determine wind power density. • More appropriate method for computing the daily wind power density is estimated. • Four windy stations located in the south part of Alberta, Canada namely is investigated. • The more appropriate parameters estimation method was not identical among all examined stations. - Abstract: In this study, the effectiveness of six numerical methods is evaluated to determine the shape (k) and scale (c) parameters of Weibull distribution function for the purpose of calculating the wind power density. The selected methods are graphical method (GP), empirical method of Justus (EMJ), empirical method of Lysen (EML), energy pattern factor method (EPF), maximum likelihood method (ML) and modified maximum likelihood method (MML). The purpose of this study is to identify the more appropriate method for computing the wind power density in four stations distributed in Alberta province of Canada namely Edmonton City Center Awos, Grande Prairie A, Lethbridge A and Waterton Park Gate. To provide a complete analysis, the evaluations are performed on both daily and monthly scales. The results indicate that the precision of computed wind power density values change when different parameters estimation methods are used to determine the k and c parameters. Four methods of EMJ, EML, EPF and ML present very favorable efficiency while the GP method shows weak ability for all stations. However, it is found that the more effective method is not similar among stations owing to the difference in the wind characteristics.

Linearized image reconstruction method for ultrasound modulated electrical impedance tomography based on power density distribution

International Nuclear Information System (INIS)

Song, Xizi; Xu, Yanbin; Dong, Feng

2017-01-01

Electrical resistance tomography (ERT) is a promising measurement technique with important industrial and clinical applications. However, with limited effective measurements, it suffers from poor spatial resolution due to the ill-posedness of the inverse problem. Recently, there has been an increasing research interest in hybrid imaging techniques, utilizing couplings of physical modalities, because these techniques obtain much more effective measurement information and promise high resolution. Ultrasound modulated electrical impedance tomography (UMEIT) is one of the newly developed hybrid imaging techniques, which combines electric and acoustic modalities. A linearized image reconstruction method based on power density is proposed for UMEIT. The interior data, power density distribution, is adopted to reconstruct the conductivity distribution with the proposed image reconstruction method. At the same time, relating the power density change to the change in conductivity, the Jacobian matrix is employed to make the nonlinear problem into a linear one. The analytic formulation of this Jacobian matrix is derived and its effectiveness is also verified. In addition, different excitation patterns are tested and analyzed, and opposite excitation provides the best performance with the proposed method. Also, multiple power density distributions are combined to implement image reconstruction. Finally, image reconstruction is implemented with the linear back-projection (LBP) algorithm. Compared with ERT, with the proposed image reconstruction method, UMEIT can produce reconstructed images with higher quality and better quantitative evaluation results. (paper)

Laser ultrasonics for bulk-density distribution measurement on green ceramic tiles

Science.gov (United States)

Revel, G. M.; Cavuto, A.; Pandarese, G.

2016-10-01

In this paper a Laser Ultrasonics (LUT) system is developed and applied to measure bulk density distribution of green ceramic tiles, which are porous materials with low heat conductivity. Bulk density of green ceramic bodies is a fundamental parameter to be kept under control in the industrial production of ceramic tiles. The LUT system proposed is based on a Nd:YAG pulsed laser for excitation and an air-coupled electro-capacitive transducer for detection. The paper reports experimental apparent bulk-density measurements on white ceramic bodies after a calibration procedures. The performances observed are better than those previously achieved by authors using air-coupled ultrasonic probes for both emission and detection, allowing to reduce average uncertainty down to about ±6 kg/m3 (±0.3%), thanks to the increase in excitation efficiency and lateral resolution, while maintaining potential flexibility for on-line application. The laser ultrasonic procedure proposed is available for both on-line and off-line application. In this last case it is possible to obtain bulk density maps with high spatial resolution by a 2D scan without interrupting the production process.

Fractal dimension of the topological charge density distribution in SU(2) lattice gluodynamics

International Nuclear Information System (INIS)

Buividovich, P.V.; Kalaydzhyan, T.; Polikarpov, M.I.

2011-11-01

We study the effect of cooling on the spatial distribution of the topological charge density in quenched SU(2) lattice gauge theory with overlap fermions. We show that as the gauge field configurations are cooled, the Hausdorff dimension of regions where the topological charge is localized gradually changes from d=2/3 towards the total space dimension. Hence the cooling procedure destroys some of the essential properties of the topological charge distribution. (orig.)

Fractal dimension of the topological charge density distribution in SU(2) lattice gluodynamics

Energy Technology Data Exchange (ETDEWEB)

Buividovich, P.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Kalaydzhyan, T. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation); Polikarpov, M.I. [Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation)

2011-11-15

We study the effect of cooling on the spatial distribution of the topological charge density in quenched SU(2) lattice gauge theory with overlap fermions. We show that as the gauge field configurations are cooled, the Hausdorff dimension of regions where the topological charge is localized gradually changes from d=2/3 towards the total space dimension. Hence the cooling procedure destroys some of the essential properties of the topological charge distribution. (orig.)

A method to measure the suprathermal density distribution by electron cyclotron emission

International Nuclear Information System (INIS)

Tutter, M.

1986-05-01

Electron cyclotron emission spectra of suprathermal electrons in a thermal main plasma are calculated. It is shown that for direction of observation oblique to the magnetic field, which decays in direction to the receiver, one may obtain information on the spatial density distribution of the suprathermal electrons from those spectra. (orig.)

Ventilatory protective strategies during thoracic surgery: effects of alveolar recruitment maneuver and low-tidal volume ventilation on lung density distribution.

Science.gov (United States)

Kozian, Alf; Schilling, Thomas; Schütze, Hartmut; Senturk, Mert; Hachenberg, Thomas; Hedenstierna, Göran

2011-05-01

The increased tidal volume (V(T)) applied to the ventilated lung during one-lung ventilation (OLV) enhances cyclic alveolar recruitment and mechanical stress. It is unknown whether alveolar recruitment maneuvers (ARMs) and reduced V(T) may influence tidal recruitment and lung density. Therefore, the effects of ARM and OLV with different V(T) on pulmonary gas/tissue distribution are examined. Eight anesthetized piglets were mechanically ventilated (V(T) = 10 ml/kg). A defined ARM was applied to the whole lung (40 cm H(2)O for 10 s). Spiral computed tomographic lung scans were acquired before and after ARM. Thereafter, the lungs were separated with an endobronchial blocker. The pigs were randomized to receive OLV in the dependent lung with a V(T) of either 5 or 10 ml/kg. Computed tomography was repeated during and after OLV. The voxels were categorized by density intervals (i.e., atelectasis, poorly aerated, normally aerated, or overaerated). Tidal recruitment was defined as the addition of gas to collapsed lung regions. The dependent lung contained atelectatic (56 ± 10 ml), poorly aerated (183 ± 10 ml), and normally aerated (187 ± 29 ml) regions before ARM. After ARM, lung volume and aeration increased (426 ± 35 vs. 526 ± 69 ml). Respiratory compliance enhanced, and tidal recruitment decreased (95% vs. 79% of the whole end-expiratory lung volume). OLV with 10 ml/kg further increased aeration (atelectasis, 15 ± 2 ml; poorly aerated, 94 ± 24 ml; normally aerated, 580 ± 98 ml) and tidal recruitment (81% of the dependent lung). OLV with 5 ml/kg did not affect tidal recruitment or lung density distribution. (Data are given as mean ± SD.) The ARM improves aeration and respiratory mechanics. In contrast to OLV with high V(T), OLV with reduced V(T) does not reinforce tidal recruitment, indicating decreased mechanical stress.

Applications of energy loss contrast STIM

International Nuclear Information System (INIS)

Bench, G.; Saint, A.; Legge, G.J.F.; Cholewa, M.

1992-01-01

Scanning Transmission Ion Microscopy (STIM) with energy loss contrast is a quantitative imaging technique. A focussed MeV ion microbeam is scanned over the sample and measured energy losses of residual ions at each beam location are used to provide the contrast in the image. The technique is highly efficient as almost every ion carries useful information from which quantitative data can be obtained. The high efficiency of data collection at present necessitates the use of small beam currents. Therefore small apertures can be used and fine spatial resolution can be achieved. High efficiency also makes it possible to collect large data sets for high definition imaging with a small radiation dose. Owing to the simple relationship between energy loss and areal density, STIM with energy loss contrast can provide a quantitative image that can be used to obtain areal density information on the sample. These areal density maps can be used not only to provide a high resolution image of the sample but also to normalise Particle Induced Xray Emission (PIXE) data. The small radiation dose required to form these areal density maps also allows one to use STIM with energy loss contrast to quantitatively monitor ion beam induced specimen changes caused by higher doses and dose rates used in other microanalytical techniques. STIM with energy loss contrast also provides the possibility of stereo imaging and ion microtomography. STIM has also been used in conjunction with channeling to explore transmission channeling in thin crystals. This paper will discuss these applications of STIM with energy loss contrast and look at further developments from them

Cell wall microstructure, pore size distribution and absolute density of hemp shiv

Science.gov (United States)

Jiang, Y.; Lawrence, M.; Ansell, M. P.; Hussain, A.

2018-04-01

This paper, for the first time, fully characterizes the intrinsic physical parameters of hemp shiv including cell wall microstructure, pore size distribution and absolute density. Scanning electron microscopy revealed microstructural features similar to hardwoods. Confocal microscopy revealed three major layers in the cell wall: middle lamella, primary cell wall and secondary cell wall. Computed tomography improved the visualization of pore shape and pore connectivity in three dimensions. Mercury intrusion porosimetry (MIP) showed that the average accessible porosity was 76.67 ± 2.03% and pore size classes could be distinguished into micropores (3-10 nm) and macropores (0.1-1 µm and 20-80 µm). The absolute density was evaluated by helium pycnometry, MIP and Archimedes' methods. The results show that these methods can lead to misinterpretation of absolute density. The MIP method showed a realistic absolute density (1.45 g cm-3) consistent with the density of the known constituents, including lignin, cellulose and hemi-cellulose. However, helium pycnometry and Archimedes' methods gave falsely low values owing to 10% of the volume being inaccessible pores, which require sample pretreatment in order to be filled by liquid or gas. This indicates that the determination of the cell wall density is strongly dependent on sample geometry and preparation.

On the Distribution of Ion Density Depletion Along Magnetic Field Lines as Deduced Using C-NOFS

Science.gov (United States)

Dao, E.; Kelley, M. C.; Hysell, D. L.; Retterer, J. M.; Su, Y.-J.; Pfaff, Robert F.; Roddy, P. A.; Ballenthin, J. O.

2012-01-01

To investigate ion density depletion along magnetic field lines, we compare in situ-measured ion density fluctuations as seen from C/NOFS and compare them to the field-line-integrated depletion of the whole bubble as inferred from electric field measurements. Results show that, within C/NOFS' range, local measurement of the normalized density depletion, (Delta)n/n(sub 0), near the apex may be far less than at other points on the same field line. We argue that the distribution of (Delta)n/n(sub 0) is a weighted distribution concentrated at latitudes of the Appleton anomalies and becomes more heavily weighted the closer the field-aligned bubble rises to the peak of the anomalies. A three-dimensional simulation of an ionospheric bubble verifies our arguments.

A three-dimensional dose-distribution estimation system using computerized image reconstruction

International Nuclear Information System (INIS)

Nishijima, Akihiko; Kidoya, Eiji; Komuro, Hiroyuki; Tanaka, Masato; Asada, Naoki.

1990-01-01

In radiotherapy planning, three dimensional (3-D) estimation of dose distribution has been very troublesome and time-consuming. To solve this problem, a simple and fast 3-D dose distribution image using a computer and Charged Couple Device (CCD) camera was developed. A series of X-ray films inserted in the phantom using a linear accelerator unit was exposed. The degree of film density was degitized with a CCD camera and a minicomputer (VAX 11-750). After that these results were compared with the present depth dose obtained by a JARP type dosimeter, with a dose error being less than 2%. The 3-D dose distribution image could accurately depict the density changes created by aluminum and air put into the phantom. The contrast resolution of the CCD camera seemed to be superior to the convention densitometer in the low-to-intermediate contrast range. In conclusion, our method seem to be very fast and simple for obtaining 3-D dose distribution images and is very effective when compared with the conventional method. (author)

Demographic determinants of risk, colon distribution and density scores of diverticular disease.

Science.gov (United States)

Golder, Mark; Ster, Irina Chis; Babu, Pratusha; Sharma, Amita; Bayat, Muhammad; Farah, Abdulkadir

2011-02-28

To investigate associations between ethnicity, age and sex and the risk, colon distribution and density scores of diverticular disease (DD). Barium enemas were examined in 1000 patients: 410 male, 590 female; 760 whites, 62 Asians, 44 black africans (BAs), and 134 other blacks (OBs). Risks and diverticula density of left-sided DD (LSDD) and right-sided-component DD (RSCDD = right-sided DD + right and left DD + Pan-DD) were compared using logistic regression. Four hundred and forty-seven patients had DD (322 LSDD and 125 RSCDD). Adjusted risks: (1) LSDD: each year increase in age increased the odds by 6% (95% CI: 5-8, SE: 0.8%, P colonic DD might be more common and has higher diverticula density in the west than previously reported. BAs appear predisposed to DD, whereas other ethnic differences appear conserved following migration.

Tomographic reconstruction of the time-averaged density distribution in two-phase flow

International Nuclear Information System (INIS)

Fincke, J.R.

1982-01-01

The technique of reconstructive tomography has been applied to the measurement of time-average density and density distribution in a two-phase flow field. The technique of reconstructive tomography provides a model-independent method of obtaining flow-field density information. A tomographic densitometer system for the measurement of two-phase flow has two unique problems: a limited number of data values and a correspondingly coarse reconstruction grid. These problems were studied both experimentally through the use of prototype hardware on a 3-in. pipe, and analytically through computer generation of simulated data. The prototype data were taken on phantoms constructed of all Plexiglas and Plexiglas laminated with wood and polyurethane foam. Reconstructions obtained from prototype data are compared with reconstructions from the simulated data. Also presented are some representative results in a horizontal air/water flow

THE STELLAR NUMBER DENSITY DISTRIBUTION IN THE LOCAL SOLAR NEIGHBORHOOD IS NORTH-SOUTH ASYMMETRIC

Energy Technology Data Exchange (ETDEWEB)

Yanny, Brian [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Gardner, Susan [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States)

2013-11-10

We study the number density distribution of a sample of K and M dwarf stars, matched north and south of the Galactic plane within a distance of 2 kpc from the Sun, using observations from the Ninth Data Release of the Sloan Digital Sky Survey. We determine distances using the photometric parallax method, and in this context systematic effects exist which could potentially impact the determination of the number density profile with height from the Galactic plane—and ultimately affect a number density north-south asymmetry. They include: (1) the calibration of the various photometric parallax relations, (2) the ability to separate dwarfs from giants in our sample, (3) the role of stellar population differences such as age and metallicity, (4) the ability to determine the offset of the Sun from the Galactic plane, and (5) the correction for reddening from dust in the Galactic plane, though our stars are at high Galactic latitudes. We find the various analyzed systematic effects to have a negligible impact on our observed asymmetry, and using a new and larger sample of stars we confirm and refine the earlier discovery of Widrow et al. of a significant Galactic north-south asymmetry in the stellar number density distribution.

THE STELLAR NUMBER DENSITY DISTRIBUTION IN THE LOCAL SOLAR NEIGHBORHOOD IS NORTH-SOUTH ASYMMETRIC

Energy Technology Data Exchange (ETDEWEB)

Yanny, Brian; Gardner, Susan

2013-10-17

We study the number density distribution of a sample of K and M dwarf stars, matched North and South of the Galactic plane within a distance of 2 kpc from the sun, using observations from the Ninth Data Release of the Sloan Digital Sky Survey. We determine distances using the photometric parallax method, and in this context systematic effects exist which could potentially impact the determination of the number density profile with height from the Galactic plane --- and ultimately affect a number density North-South asymmetry. They include: (i) the calibration of the various photometric parallax relations, (ii) the ability to separate dwarfs from giants in our sample, (iii) the role of stellar population differences such as age and metallicity, (iv) the ability to determine the offset of the sun from the Galactic plane, and (v) the correction for reddening from dust in the Galactic plane, though our stars are at high Galactic latitudes. We find the various analyzed systematic effects to have a negligible impact on our observed asymmetry, and using a new and larger sample of stars we confirm and refine the earlier discovery of Widrow et al. of a significant Galactic North-South asymmetry in the stellar number density distribution.

CO2 laser imaging heterodyne and phase contrast interferometer for density profile and fluctuation measurements in LHD

International Nuclear Information System (INIS)

Tanaka, K.; Michael, C.; Akiyama, T.; Kawahata, K.; Ito, Y.; Vyacheslavov, L.N.; Sanin, A.L.; Okajima, S.

2007-01-01

A CO 2 laser heterodyne imaging interferometer (CO 2 HI) and a CO 2 laser phase contrast imaging interferometer (CO 2 PCI) were installed in LHD. The purpose of CO 2 HI is to measure electron density profile at high density (>1x10 20 m -3 ), where the existing far infrared laser (wavelength 118.9 μm) interferometer suffers from fringe jump due to the reduction of signal intensity caused by refraction. In the beginning of 10th LHD experimental campaign (2006-2007), sixty three three of CO 2 HI with 10 channels of YAG HI for vibration compensation, and in the later of 10th LHD experimental campaign. Eighty one channels CO 2 HI and 15 channels YAG HI became available. The purpose of CO 2 PCI is to measure turbulent fluctuation, which can contribute to the energy and particle transport. In order to get local fluctuation information, magnetic shear technique was applied with use of 48 (6 by 8) channel two dimensional detector. (author)

Unpolarized and polarized parton densities in term of Fermi-Dirac distributions

International Nuclear Information System (INIS)

Bourrely, C.

1996-01-01

A description of quark parton densities of the proton in terms of Fermi-Dirac distributions parametrized with very few parameters is given. It allows a fair description of the NMC, BCDMS, SLAC and HERA data on F 2 p (x,Q 2 ) in a broad range of x and Q 2 . With some simple assumptions unpolarized and polarized quark parton distributions are related which lead to a fair description of the spin-dependent structure functions xg 1 p (x,Q 2 ) and xg 1 n (x,Q 2 ). Finally, several predictions are presented for lepton pair and gauge boson production in pp collisions at energies accessible in the future at RHIC. (author)

Experimental Infection of Taenia saginata eggs in Bali Cattle: Distribution and Density of Cysticercus bovis

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Nyoman Sadra Dharmawan

2009-12-01

Full Text Available The objective of this study was to observe the development, distribution, and infection density ofTaenia saginata metacestodes in Bali cattle. Three Bali cattle were experimentally infected with T. saginataeggs which were collected from taeniasis patients. The experimental animal was inoculated with : i1000,00 T. saginata; ii 500,000 eggs; and iii 1,000,000 eggs, respectivelly 100,000 (cattle 1, 500,000(cattle 2, and 1,000,000 (cattle 3 T. saginata eggs, respectively. To observe the development of cysticerci,all cattle were slaughtered at 24 weeks post infection. To observe their distribution and density, slicingwas done to the cattle?s tissues. The study results showed that cysts were found distributed to all muscletissues and some visceral organs such as heart, diaphragm, lungs, and kidney of the cattle infected with100,000 and 500,000 T. saginata eggs. Density of the cyst was in the range of 11 to 95 cysts per 100 gramsof tissue. The highest density was noted in the heart (58/100 grams and in diaphragm (55/100 grams.This study has confirmed that T. saginata eggs derived from taeniasis patient in Bali, if infected to Balicattle can develop and spread to all muscle tissues and some visceral organs. From this study it wasconcluded that it is necessary to include the heart in the meat inspection at slaughter house for possibilityof T. saginata cyst infection.$?

Density and radioactivity distribution of respirable range human serum albumin aerosol

International Nuclear Information System (INIS)

Raghunath, B.; Somasundaram, S.; Soni, P.S.

1988-01-01

Dry human serum albumin (HSA) aerosol in the respirable size range was generated using the BARC nebulizer. The aerosol was sampled using Lovelace Aerosol Particle Separator (LAPS) and the density of HSA was determined. Labelling of HSA with 99m TcO 4 - was done, both in HSA solution and with dry denatured HSA particles, to study the distribution of radioactivity in both cases. The results are discussed. (author)

Asymmetric Velocity Distributions from Halo Density Profiles in the Eddington Approach

International Nuclear Information System (INIS)

Vergados, J. D.

2015-01-01

We show how to obtain the energy distribution f(E) in our vicinity starting from WIMP density profiles in a self-consistent way by employing the Eddington approach and adding reasonable angular momentum dependent terms in the expression of the energy. We then show how we can obtain the velocity dispersions and the asymmetry parameter β in terms of the parameters describing the angular momentum dependence. From this expression, for f(E), we proceed to construct an axially symmetric WIMP a velocity distribution, which, for a gravitationally bound system, automatically has a velocity upper bound and is characterized by the same asymmetriy β. This approach is tested and clarified by constructing analytic expressions in a simple model, with adequate structure. We then show how such velocity distributions can be used in determining the event rates, including modulation, in both the standard and the directional WIMP searches.

Finite difference applied to the reconstruction method of the nuclear power density distribution

International Nuclear Information System (INIS)

Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S.

2016-01-01

Highlights: • A method for reconstruction of the power density distribution is presented. • The method uses discretization by finite differences of 2D neutrons diffusion equation. • The discretization is performed homogeneous meshes with dimensions of a fuel cell. • The discretization is combined with flux distributions on the four node surfaces. • The maximum errors in reconstruction occur in the peripheral water region. - Abstract: In this reconstruction method the two-dimensional (2D) neutron diffusion equation is discretized by finite differences, employed to two energy groups (2G) and meshes with fuel-pin cell dimensions. The Nodal Expansion Method (NEM) makes use of surface discontinuity factors of the node and provides for reconstruction method the effective multiplication factor of the problem and the four surface average fluxes in homogeneous nodes with size of a fuel assembly (FA). The reconstruction process combines the discretized 2D diffusion equation by finite differences with fluxes distribution on four surfaces of the nodes. These distributions are obtained for each surfaces from a fourth order one-dimensional (1D) polynomial expansion with five coefficients to be determined. The conditions necessary for coefficients determination are three average fluxes on consecutive surfaces of the three nodes and two fluxes in corners between these three surface fluxes. Corner fluxes of the node are determined using a third order 1D polynomial expansion with four coefficients. This reconstruction method uses heterogeneous nuclear parameters directly providing the heterogeneous neutron flux distribution and the detailed nuclear power density distribution within the FAs. The results obtained with this method has good accuracy and efficiency when compared with reference values.

Surface flux density distribution characteristics of bulk high-T{sub c} superconductor in external magnetic field

Energy Technology Data Exchange (ETDEWEB)

Torii, S.; Yuasa, K

2004-10-01

Various magnetic levitation systems using oxide superconductors are developed as strong pinning forces are obtained in melt-processed bulk. However, the trapped flux of superconductor is moved by flux creep and fluctuating magnetic field. Therefore, to examine the internal condition of superconductor, the authors measure the dynamic surface flux density distribution of YBCO bulk. Flux density measurement system has a structure with the air-core coil and the Hall sensors. Ten Hall sensors are arranged in series. The YBCO bulk, which has 25 mm diameter and 13 mm thickness, is field cooled by liquid nitrogen. After that, magnetic field is changed by the air-core coil. This paper describes about the measured results of flux density distribution of YBCO bulk in the various frequencies of air-core coils currents.

A mathematical model of the current density distribution in electrochemical cells - AUTHORS’ REVIEW

Directory of Open Access Journals (Sweden)

PREDRAG M. ŽIVKOVIĆ

2011-06-01

Full Text Available An approach based on the equations of electrochemical kinetics for the estimation of the current density distribution in electrochemical cells is presented. This approach was employed for a theoretical explanation of the phenomena of the edge and corner effects. The effects of the geometry of the system, the kinetic parameters of the cathode reactions and the resistivity of the solution are also discussed. A procedure for a complete analysis of the current distribution in electrochemical cells is presented.

[Carbon density distribution characteristics and influencing factors in aerially seeded Pinus massoniana plantations].

Science.gov (United States)

Pan, Ping; Han, Tian Yi; OuYang, Xun Zhi; Liu, Yuan Qiu; Zang, Hao; Ning, Jin Kui; Yang, Yang

2017-12-01

The distribution characteristics of carbon density under aerially seeded Pinus massoniana plantations in Ganzhou City of Jiangxi Province were studied. Total 15 factors, including site, stand, understory vegetation, litter and so on were selected to establish a relationship model between stand carbon density and influencing factors, and the main influencing factors were also screened. The results showed that the average carbon density was 98.29 t·hm -2 at stand level with soil layer (49.58 t·hm -2 ) > tree layer (45.25 t·hm -2 ) > understory vegetation layer (2.23 t·hm -2 ) > litter layer (1.23 t·hm -2 ). Significantly positive correlations were found among the tree, litter and soil layers, but not among the other layers. The main factors were tree density, avera-ge diameter at breast height (DBH), soil thickness, slope position, stand age and canopy density to affect carbon density in aerially seeded P. massoniana plantations. The partial correlation coefficients of the six main factors ranged from 0.331 to 0.434 with significance by t test. The multiple correlation coefficient of quantitative model I reached 0.796 with significance by F test (F=9.28). For stand density, the best tree density and canopy density were 1500-2100 plants·hm -2 and 0.4-0.7, respectively. The moderate density was helpful to improve ecosystem carbon sequestration. The carbon density increased with increasing stand age, DBH and soil thickness, and was higher in lower than middle and upper slope positions.

Comparative study of pneumocystography, positive contrast cystography and double contrast cystography in dogs

International Nuclear Information System (INIS)

Thibaut, J.; Parada, E.; Vargas, L.; Deppe, R.; Born, R.

1997-01-01

In order to compare three radiographic techniques: pneumocystography, positive contrast cystography and double contrast cystography, three series of 24 radiographs each in lateral and ventrodorsal projections were made. Six healthy adult male dogs with weight ranging between 7 and 16 kg were used. Food was withheld for 24 hours and two enemas were made before the series of radiographs were taken. Dogs were anaesthetized with sodium thiopental (20 mg/kg i.v.). The contrast medium was introduced through a urethral catheter. Pneumocystography was performed in the first series introducing air (10 ml/kg) in the bladder. Positive contrast cystography was performed in the second series introducing Hypaque M-60% diluted, contributing 100 mg of iodine per ml (10 ml/kg). In the double contrast cystography Hypaque M-60% diluted (10 ml) was introduced, in concentration of 150 mg of iodine per ml. Then air was introduced (10 ml/kg) through a catheter. Plates were taken in both projections at 1 and 10 minutes for each technique. The radiographic plates of each series were analized comparing the characteristics of radiographic density, outline and size. In neumocystography, positive contrast and double contrast cystography, the radiographic density was predominantly low, high and intermediate, respectively. The radiographic outline was mainly regular for the three techniques. With respect to bladder size, there was a decrease of height and an increase of length and width at 10 minutes. Comparing these three radiographic techniques, it can be concluded that the one that best outlines the bladder mucosa is double contrast. Pneumocystography provides the best image for opaque structures and cystography best shows the position of the urinary bladder [es

Spectral triangulation molecular contrast optical coherence tomography with indocyanine green as the contrast agent

OpenAIRE

Yang, Changhuei; McGuckin, Laura E. L.; Simon, John D.; Choma, Michael A.; Applegate, Brian E.; Izatt, Joseph A.

2004-01-01

We report a new molecular contrast optical coherence tomography (MCOCT) implementation that profiles the contrast agent distribution in a sample by measuring the agent's spectral differential absorption. The method, spectra triangulation MCOCT, can effectively suppress contributions from spectrally dependent scatterings from the sample without a priori knowledge of the scattering properties. We demonstrate molecular imaging with this new MCOCT modality by mapping the distribution of indocyani...

Solar corona electron density distribution

International Nuclear Information System (INIS)

Esposito, P.B.; Edenhofer, P.; Lueneburg, E.

1980-01-01

Three and one-half months of single-frequency (f= 0 2.2 x 10 9 Hz) time delay data (earth-to-spacecraft and return signal travel time) were acquired from the Helios 2 spacecraft around the time of its solar occupation (May 16, 1976). Following the determination of the spacecraft trajectory the excess time delay due to the integrated effect of free electrons along the signal's ray path could be separated and modeled. An average solar corona, equatorial, electron density profile, during solar minimum, was deduced from time delay measurements acquired within 5--60 solar radii (R/sub S/) of the sun. As a point of reference, at 10 R/sub S/ from the sun we find an average electron density of 4500 el cm -3 . However, there appears to be an asymmtry in the electron density as the ray path moved from the west (preoccultation) to east (post-occulation) solar limb. This may be related to the fact that during entry into occulation the heliographic latitude of the ray path (at closes approach to the sun) was about 6 0 , whereas during exit it became -7 0 . The Helios electron density model is compared with similar models deduced from a variety of different experimental techniques. Within 5--20 R/sub S/ of the sun the models separate according to solar minimum or maximum conditions; however, anomalies are evident

Generalized image contrast enhancement technique based on the Heinemann contrast discrimination model

Science.gov (United States)

Liu, Hong; Nodine, Calvin F.

1996-07-01

This paper presents a generalized image contrast enhancement technique, which equalizes the perceived brightness distribution based on the Heinemann contrast discrimination model. It is based on the mathematically proven existence of a unique solution to a nonlinear equation, and is formulated with easily tunable parameters. The model uses a two-step log-log representation of luminance contrast between targets and surround in a luminous background setting. The algorithm consists of two nonlinear gray scale mapping functions that have seven parameters, two of which are adjustable Heinemann constants. Another parameter is the background gray level. The remaining four parameters are nonlinear functions of the gray-level distribution of the given image, and can be uniquely determined once the previous three are set. Tests have been carried out to demonstrate the effectiveness of the algorithm for increasing the overall contrast of radiology images. The traditional histogram equalization can be reinterpreted as an image enhancement technique based on the knowledge of human contrast perception. In fact, it is a special case of the proposed algorithm.

Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps

International Nuclear Information System (INIS)

Clerkin, L.; Kirk, D.; Manera, M.; Lahav, O.; Abdalla, F.

2016-01-01

It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence (κWL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the counts-in-cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey Science Verification data over 139 deg"2. We test whether the underlying density contrast is well described by a lognormal distribution for the galaxies, the convergence and their joint PDF. We confirm that the galaxy density contrast distribution is well modelled by a lognormal PDF convolved with Poisson noise at angular scales from 10 to 40 arcmin (corresponding to physical scales of 3–10 Mpc). We note that as κWL is a weighted sum of the mass fluctuations along the line of sight, its PDF is expected to be only approximately lognormal. We find that the κWL distribution is well modelled by a lognormal PDF convolved with Gaussian shape noise at scales between 10 and 20 arcmin, with a best-fitting χ"2/dof of 1.11 compared to 1.84 for a Gaussian model, corresponding to p-values 0.35 and 0.07, respectively, at a scale of 10 arcmin. Above 20 arcmin a simple Gaussian model is sufficient. The joint PDF is also reasonably fitted by a bivariate lognormal. As a consistency check, we compare the variances derived from the lognormal modelling with those directly measured via CiC. Lastly, our methods are validated against maps from the MICE Grand Challenge N-body simulation.

Study of α-crystallin structure by small-angle neutron scattering with contrast variation

International Nuclear Information System (INIS)

Krivandin, A.V.; Muranov, K.O.; Polyanskij, N.B.; Ostrovskij, M.A.; Murugova, T.N.; Kuklin, A.I.; Aksenov, V.L.

2010-01-01

The structure of the oligomeric protein α-crystallin from the bovine eye lens has been investigated by small-angle neutron scattering (SANS) by the contrast variation method (volume fraction of D 2 O was 0, 23, 68 and 90%). Experiments were carried out on YuMO spectrometer (IBR-2 reactor, JINR). From the SANS curves the match point for α-crystallin (43% D 2 O) and its average scattering length density at this point (2.4·10 10 cm -2 ) have been obtained. The radius of gyration and distance distribution functions for α-crystallin have been calculated as well. On the basis of these calculations it was concluded that α-crystallin has a homogeneous distribution of the scattering density in domains inaccessible for water penetration and all parts of this protein undergo a uniform deuteration. The latter indicates that all α-crystallin subunits have an equal accessibility for water and presumably for some other low molecular weight substances. These conclusions on the α-crystallin structure (a homogeneous distribution of the scattering density and an equal accessibility of all subunits for low molecular weight substances) should be taken into account in the time of elaboration of α-crystallin quaternary structure models

Extensive variation in the density and distribution of DNA polymorphism in sorghum genomes.

Directory of Open Access Journals (Sweden)

Joseph Evans

Full Text Available Sorghum genotypes currently used for grain production in the United States were developed from African landraces that were imported starting in the mid-to-late 19(th century. Farmers and plant breeders selected genotypes for grain production with reduced plant height, early flowering, increased grain yield, adaptation to drought, and improved resistance to lodging, diseases and pests. DNA polymorphisms that distinguish three historically important grain sorghum genotypes, BTx623, BTx642 and Tx7000, were characterized by genome sequencing, genotyping by sequencing, genetic mapping, and pedigree-based haplotype analysis. The distribution and density of DNA polymorphisms in the sequenced genomes varied widely, in part because the lines were derived through breeding and selection from diverse Kafir, Durra, and Caudatum race accessions. Genomic DNA spanning dw1 (SBI-09 and dw3 (SBI-07 had identical haplotypes due to selection for reduced height. Lower SNP density in genes located in pericentromeric regions compared with genes located in euchromatic regions is consistent with background selection in these regions of low recombination. SNP density was higher in euchromatic DNA and varied >100-fold in contiguous intervals that spanned up to 300 Kbp. The localized variation in DNA polymorphism density occurred throughout euchromatic regions where recombination is elevated, however, polymorphism density was not correlated with gene density or DNA methylation. Overall, sorghum chromosomes contain distal euchromatic regions characterized by extensive, localized variation in DNA polymorphism density, and large pericentromeric regions of low gene density, diversity, and recombination.

Effect of contrast on treatment planning system dose calculations in the lung

International Nuclear Information System (INIS)

Lees, J.; Holloway, L.; Fuller, M.; Forstner, D.

2004-01-01

Full text: Contrast-enhanced x-ray computed tomography is utilised in the planning of radiotherapy lung treatments to allow greater accuracy in defining tumour volume and nodal areas. The use of contrast results in increased density in the region of the tumour and may result in an overall increased density in the lung volume. It is possible that this change in density may affect the accuracy of any dose calculations based on this CT data. As yet, the effect of the contrast agent on the calculations performed by the treatment planning computer is unclear. Ideally, a study would be undertaken using pre- and post- contrast patient data, however this may be considered unethical as an extra CT scan would be required. For this reason, the following study was undertaken to assess the possible impact in a simulated environment. The object of this study was to explore the effect of the contrast agent upon the isodose curves and the monitor units calculated by the treatment planning system. Two investigations were made. Initially, pre- and post-contrast images were acquired using an anthropomorphic phantom. Contrast-enhancement was simulated by replacing cylindrical sections of the lung with lengths of drinking straw containing contrast agent. The effect of increased density in the tumour volume was considered in this comparison. Secondly, block density corrections were used in an existing patient dataset to simulate an increase in lung density and compared with the original dataset. In the two investigations, a treatment was generated using both datasets. Fields were placed on the non contrast-enhanced scan, and then transferred onto the contrast-enhanced scan. The numbers of monitor units calculated in each of the plans were compared, as were the resulting isodose curves. In the first investigation, the relative electron density in the contrast-enhanced scan varied between 0.523 and 1.705 within the tumour volume. This resulted from the presence of undiluted contrast agent

Pressure dependence of electron density distribution and d-p-π hybridization in titanate perovskite ferroelectrics

Science.gov (United States)

Yamanaka, Takamitsu; Nakamoto, Yuki; Ahart, Muhtar; Mao, Ho-kwang

2018-04-01

Electron density distributions of PbTi O3 , BaTi O3 , and SrTi O3 were determined by synchrotron x-ray powder diffraction up to 55 GPa at 300 K and ab initio quantum chemical molecular orbital (MO) calculations, together with a combination of maximum entropy method calculations. The intensity profiles of Bragg peaks reveal split atoms in both ferroelectric PbTi O3 and BaTi O3 , reflecting the two possible positions occupied by the Ti atom. The experimentally obtained atomic structure factor was used for the determination of the deformation in electron density and the d-p-π hybridization between dx z (and dy z) of Ti and px (and py) of O in the Ti-O bond. Ab initio MO calculations proved the change of the molecular orbital coupling and of Mulliken charges with a structure transformation. The Mulliken charge of Ti in the Ti O6 octahedron increased in the ionicity with increasing pressure in the cubic phase. The bonding nature is changed with a decrease in the hybridization of the Ti-O bond and the localization of the electron density with increasing pressure. The hybridization decreases with pressure and disappears in the cubic paraelectric phase, which has a much more localized electron density distribution.

Analytical method for reconstruction pin to pin of the nuclear power density distribution

International Nuclear Information System (INIS)

Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S.

2013-01-01

An accurate and efficient method for reconstructing pin to pin of the nuclear power density distribution, involving the analytical solution of the diffusion equation for two-dimensional neutron energy groups in homogeneous nodes, is presented. The boundary conditions used for analytic as solution are the four currents or fluxes on the surface of the node, which are obtained by Nodal Expansion Method (known as NEM) and four fluxes at the vertices of a node calculated using the finite difference method. The analytical solution found is the homogeneous distribution of neutron flux. Detailed distributions pin to pin inside a fuel assembly are estimated by the product of homogeneous flux distribution by local heterogeneous form function. Furthermore, the form functions of flux and power are used. The results obtained with this method have a good accuracy when compared with reference values. (author)

Analytical method for reconstruction pin to pin of the nuclear power density distribution

Energy Technology Data Exchange (ETDEWEB)

Pessoa, Paulo O.; Silva, Fernando C.; Martinez, Aquilino S., E-mail: ppessoa@con.ufrj.br, E-mail: fernando@con.ufrj.br, E-mail: aquilino@imp.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)

2013-07-01

An accurate and efficient method for reconstructing pin to pin of the nuclear power density distribution, involving the analytical solution of the diffusion equation for two-dimensional neutron energy groups in homogeneous nodes, is presented. The boundary conditions used for analytic as solution are the four currents or fluxes on the surface of the node, which are obtained by Nodal Expansion Method (known as NEM) and four fluxes at the vertices of a node calculated using the finite difference method. The analytical solution found is the homogeneous distribution of neutron flux. Detailed distributions pin to pin inside a fuel assembly are estimated by the product of homogeneous flux distribution by local heterogeneous form function. Furthermore, the form functions of flux and power are used. The results obtained with this method have a good accuracy when compared with reference values. (author)

Vegetation in Bangalore's Slums: Composition, Species Distribution, Density, Diversity, and History

Science.gov (United States)

Gopal, Divya; Nagendra, Harini; Manthey, Michael

2015-06-01

There is widespread acknowledgement of the need for biodiversity and greening to be part of urban sustainability efforts. Yet we know little about greenery in the context of urban poverty, particularly in slums, which constitute a significant challenge for inclusive development in many rapidly growing cities. We assessed the composition, density, diversity, and species distribution of vegetation in 44 slums of Bangalore, India, comparing these to published studies on vegetation diversity in other land-use categories. Most trees were native to the region, as compared to other land-use categories such as parks and streets which are dominated by introduced species. Of the most frequently encountered tree species, Moringa oleifera and Cocos nucifera are important for food, while Ficus religiosa plays a critical cultural and religious role. Tree density and diversity were much lower in slums compared to richer residential neighborhoods. There are also differences in species preferences, with most plant (herb, shrub and vines) species in slums having economic, food, medicinal, or cultural use, while the species planted in richer residential areas are largely ornamental. Historic development has had an impact on species distribution, with older slums having larger sized tree species, while recent slums were dominated by smaller sized tree species with greater economic and food use. Extensive focus on planting trees and plant species with utility value is required in these congested neighborhoods, to provide livelihood support.

Beam energy distribution influences on density modulation efficiency in seeded free-electron lasers

Directory of Open Access Journals (Sweden)

Guanglei Wang

2015-06-01

Full Text Available The beam energy spread at the entrance of an undulator system is of paramount importance for efficient density modulation in high-gain seeded free-electron lasers (FELs. In this paper, the dependences of high harmonic bunching efficiency in high-gain harmonic generation (HGHG, echo-enabled harmonic generation (EEHG and phase-merging enhanced harmonic generation (PEHG schemes on the electron beam energy spread distribution are studied. Theoretical investigations and multidimensional numerical simulations are applied to the cases of uniform and saddle beam energy distributions and compared to a traditional Gaussian distribution. It shows that the uniform and saddle electron energy distributions significantly enhance the bunching performance of HGHG FELs, while they almost have no influence on EEHG and PEHG schemes. A further start-to-end simulation example demonstrated that, with the saddle distribution of sliced beam energy spread controlled by a laser heater, the 30th harmonic can be directly generated by a single-stage HGHG scheme for a soft x-ray FEL facility.

Distribution of the Current Density in Electrolyte of the Pem Fuel Cell

Directory of Open Access Journals (Sweden)

Eugeniusz Kurgan

2004-01-01

Full Text Available In this paper water management in proton exchange membrane (PEM fuel cell is considered. Firt mass convervation law for water is applied. Next proton transport is described by the Nernst-Planck equation and liqid water convection velocity is eliminated by the Schlogl equation. Electro-osmotic drag coefficient is related to hydrogen index and experimentally determined swelling coefficient. Three partial differential equations for molar water concentration Cw, electric potential ϕ and water pressure Pw are formulated. Current density vector i is derived from proton flux expression. These equations together with adequate boundary conditions were solved using finite element method. The distribution of electric potential and current density in function of geometrical parametres is investigated. At the end some illustrative example is given.

Random distribution of background charge density for numerical simulation of discharge inception

International Nuclear Information System (INIS)

Grange, F.; Loiseau, J.F.; Spyrou, N.

1998-01-01

The models of electric streamers based on a uniform background density of electrons may appear not to be physical, as the number of electrons in the small active region located in the vicinity of the electrode tip under regular conditions can be less than one. To avoid this, the electron background is modelled by a random density distribution such that, after a certain time lag, at least one electron is present in the grid close to the point electrode. The modelling performed shows that the streamer inception is not very sensitive to the initial location of the charged particles; the ionizing front, however, may be delayed by several tens of nanoseconds, depending on the way the electron has to drift before reaching the anode. (J.U.)

The measurement of density distribution of bentonite buffer extruded into fractures

International Nuclear Information System (INIS)

Matsumoto, Kazuhiro; Tanai, Kenji

2008-01-01

For the geological disposal of the high-level radioactive waste, it is important to develop the model to evaluate the long-term stability of the engineered barrier system. The increase in the reliability of the evaluation model may reduce the uncertainty of the safety assessment. In this study, the density distribution of the bentonite buffer extruded into the artificial fractures was measured by using a X-ray CT scanner to promote understanding of the extrusion phenomenon of the bentonite into fractures. (author)

A comparison of shock-cloud and wind-cloud interactions: effect of increased cloud density contrast on cloud evolution

Science.gov (United States)

Goldsmith, K. J. A.; Pittard, J. M.

2018-05-01

The similarities, or otherwise, of a shock or wind interacting with a cloud of density contrast χ = 10 were explored in a previous paper. Here, we investigate such interactions with clouds of higher density contrast. We compare the adiabatic hydrodynamic interaction of a Mach 10 shock with a spherical cloud of χ = 103 with that of a cloud embedded in a wind with identical parameters to the post-shock flow. We find that initially there are only minor morphological differences between the shock-cloud and wind-cloud interactions, compared to when χ = 10. However, once the transmitted shock exits the cloud, the development of a turbulent wake and fragmentation of the cloud differs between the two simulations. On increasing the wind Mach number, we note the development of a thin, smooth tail of cloud material, which is then disrupted by the fragmentation of the cloud core and subsequent `mass-loading' of the flow. We find that the normalized cloud mixing time (tmix) is shorter at higher χ. However, a strong Mach number dependence on tmix and the normalized cloud drag time, t_{drag}^' }, is not observed. Mach-number-dependent values of tmix and t_{drag}^' } from comparable shock-cloud interactions converge towards the Mach-number-independent time-scales of the wind-cloud simulations. We find that high χ clouds can be accelerated up to 80-90 per cent of the wind velocity and travel large distances before being significantly mixed. However, complete mixing is not achieved in our simulations and at late times the flow remains perturbed.

Can pre-operative contrast-enhanced dynamic MR imaging for prostate cancer predict microvessel density in prostatectomy specimens?

Energy Technology Data Exchange (ETDEWEB)

Schlemmer, Heinz-Peter [Department of Oncological Diagnostics and Therapy, German Cancer Research Center, University Hospital Mannheim, Ruprecht Karls University, Heidelberg (Germany); Department of Diagnostic Radiology, University Hospital Tuebingen, Hoppe-Seyler-Strasse 3, 72076, Tuebingen (Germany); Merkle, Jonas; Kaick, Gerhard van [Department of Oncological Diagnostics and Therapy, German Cancer Research Center, University Hospital Mannheim, Ruprecht Karls University, Heidelberg (Germany); Grobholz, Rainer [Department of Pathology, University Hospital Mannheim, Ruprecht Karls University, Heidelberg (Germany); Jaeger, Tim; Michel, Maurice Stephan [Department of Urology, University Hospital Mannheim, Ruprecht Karls University, Heidelberg (Germany); Werner, Axel; Rabe, Jan [Department of Diagnostic Radiology, University Hospital Mannheim, Ruprecht Karls University, Heidelberg (Germany)

2004-02-01

The aim of this study was to correlate quantitative dynamic contrast-enhanced MRI (DCE MRI) parameters with microvessel density (MVD) in prostate carcinoma. Twenty-eight patients with biopsy-proven prostate carcinoma were examined by endorectal MRI including multiplanar T2- and T1-weighted spin-echo and dynamic T1-weighted turbo-FLASH MRI during and after intravenous Gd-DTPA administration. Microvessels were stained on surgical specimens using a CD31 monoclonal antibody. The MVD was quantified in hot spots by counting (MVC) and determining the area fraction by morphometry (MVAF). The DCE MRI data were analyzed using an open pharmacokinetic two-compartment model. In corresponding anatomic locations the time shift ({delta}t) between the beginning of signal enhancement of cancer and adjacent normal prostatic tissue, the degree of contrast enhancement and the contrast exchange rate constant (k{sub 21}) were calculated. The MVC and MVAF were elevated in carcinoma (p<0.001 and p=0.002, respectively) and correlated to k{sub 21} (r=0.62, p<0.001 and r=0.80, p<0.001, respectively). k{sub 21}-values of carcinoma were significantly higher compared with normal peripheral but not central zone tissue. {delta}t was longer in high compared with low-grade tumors (p=0.025). The DCE MRI can provide important information about individual MVD in prostate cancer, which may be helpful for guiding biopsy and assessing individual prognosis. (orig.)

Synthesis of Laboratory Ultrasound Contrast Agents

Directory of Open Access Journals (Sweden)

Jaemin Oh

2013-10-01

Full Text Available Ultrasound Contrast Agents (UCAs were developed to maximize reflection contrast so that organs can be seen clearly in ultrasound imaging. UCAs increase the signal to noise ratio (SNR by linear and non-linear mechanisms and thus help more accurately visualize the internal organs and blood vessels. However, the UCAs on the market are not only expensive, but are also not optimized for use in various therapeutic research applications such as ultrasound-aided drug delivery. The UCAs fabricated in this study utilize conventional lipid and albumin for shell formation and perfluorobutane as the internal gas. The shape and density of the UCA bubbles were verified by optical microscopy and Cryo SEM, and compared to those of the commercially available UCAs, Definity® and Sonovue®. The size distribution and characteristics of the reflected signal were also analyzed using a particle size analyzer and ultrasound imaging equipment. Our experiments indicate that UCAs composed of spherical microbubbles, the majority of which were smaller than 1 um, were successfully synthesized. Microbubbles 10 um or larger were also identified when different shell characteristics and filters were used. These laboratory UCAs can be used for research in both diagnoses and therapies.

Radial power density distribution of MOX fuel rods in the HBWR

International Nuclear Information System (INIS)

Koo, Yang Hyun; Joo, Hyung Kook; Lee, Byung Ho; Sohn, Dong Seong

1999-07-01

Two MOX fuel rods, which ar being fabricated in the Paul Scherrer Institute (PSI), Switzerland in cooperation with the Korea Atomic Energy Research Institute (KAERI), are going to be irradiated in the HBWR (Halden Boiling Water Reactor) from the beginning of 2000 in the framework of OECD Halden Reactor Programme (HRP) together with a reference MOX fuel rod supplied by the BNFL. Since fuel temperature, which is influenced by radial power distribution, is a basic property in analyzing fuel behavior, it is required to consider radial power distribution in the HBWR. A subroutine FACTOR H BWR that calculates radial power density distribution for three MOX fuel rods have been developed subroutine FACTOR H BWR gives good agreement with the physics calculation except slight underprediction in the central part and a little overprediction at the outer part of the pellet. The subroutine will be incorporated into a computer code COSMOS and used to analyze the in-reactor behavior of the three MOX fuel rods during the Halden irradiation test. (author). 5 refs., 3 tabs., 24 figs

Application of reconstructive tomography to the measurement of density distribution in two-phase flow

International Nuclear Information System (INIS)

Fincke, J.R.; Berggren, M.J.; Johnson, S.A.

1980-01-01

The technique of reconstructive tomography has been applied to the measurement of average density and density distribution in multiphase flows. The technique of reconstructive tomography provides a model independent method of obtaining flow field density information. The unique features of interest in application of a practical tomographic densitometer system are the limited number of data values and the correspondingly coarse reconstruction grid (0.5 by 0.5 cm). These features were studied both experimentally, through the use of prototype hardware on a 3-in. pipe, and analytically, through computer generation of simulated data. Prototypical data were taken on phantoms constructed of Plexiglas and laminated Plexiglas, wood, and polyurethane foam. Reconstructions obtained from prototype data were compared with reconstructions from the simulated data

Numerical simulation of the temperature, electron density, and electric field distributions near the ionospheric reflection height after turn-on of a powerful HF wave

International Nuclear Information System (INIS)

Muldrew, D.B.

1986-01-01

The time variation of the electron temperature profile in the ionosphere following turn-on of a powerful 1-s HF pulse is determined numerically from the energy balance equation. Using this and the equations of motion and continuity for a plasma, the effect of heating and the pondermotive force of a powerful HF wave on the electron density and electric field distributions are determined by numerical simulation. The temperature variation and ponderomotive force modify the density distribution, and this new density distribution, in turn, modifies the electric field distribution of the HF wave. The density deviations grow for a few hundred milliseconds after HF turn-on and then begin to fluctuate in time. At all heights the wave number of the density deviations is approximately twice the wave number of the HF wave. For electric fields near reflection of about 6.0 V/m, the electric field distribution becomes complicated, apparently depending on Bragg scattering of the HF wave from the density deviations. Density impulses propagate away (up and down) from electric field maxima, at the ion thermal velocity, at both turn-on and turn-off of the HF wave

Studies of the pressure dependence of the charge density distribution in cerium phosphide by the maximum-entropy method

CERN Document Server

Ishimatsu, N; Takata, M; Nishibori, E; Sakata, M; Hayashi, J; Shirotani, I; Shimomura, O

2002-01-01

The physical properties relating to 4f electrons in cerium phosphide, especially the temperature dependence and the isomorphous transition that occurs at around 10 GPa, were studied by means of x-ray powder diffraction and charge density distribution maps derived by the maximum-entropy method. The compressibility of CeP was exactly determined using a helium pressure medium and the anomaly that indicated the isomorphous transition was observed in the compressibility. We also discuss the anisotropic charge density distribution of Ce ions and its temperature dependence.

Effects of low-dose simvastatin on the distribution of plasma cholesterol and oxidized low-density lipoprotein in three ultra-centrifugally separated low-density lipoprotein subfractions: 12- month, open-label trial.

Science.gov (United States)

Homma, Yasuhiko; Michishita, Ichiro; Hayashi, Hiroshi; Shigematsu, Hiroshi

2010-10-27

The effects of statins on the distribution of oxidized LDL in plasma LDL subfractions have not been well defined. Effects of 12-month treatment with low-dose simvastatin on the distribution of cholesterol and oxidized LDL in 3 ultracentrifugally separated plasma LDL subfractions were compared in patients with hypercholesterolemia. Simvastatin was administered to 30 hypercholesterolemic subjects for 12 months at an initial dose of 5 mg/day, which was increased to 20 mg/day via 10mg/day to decrease plasma LDL-cholesterol (C) lower than 130 mg/dL. Simvastatin dose was fixed after 3 months of treatment. The amounts of cholesterol and oxidized LDL in 3 ultracentrifugally separated plasma LDL subfractions were compared between 0 and 12 months of treatment. The distribution of ox-LDL skewed to denser LDL fractions, compared with cholesterol in plasma LDL subfractions. Plasma cholesterol in low-density LDL, medium-density LDL and high-density LDL decreased significantly by 31%, 30%, and 25%, respectively (pLDL was decreased from 70 U/L to 56 U/L in medium-density LDL (p=0.042). Oxidized LDL in low-density LDL and high-density LDL did not change significantly after 12 months of treatment. Treatment with low-dose simvastatin decreased plasma cholesterol in 3 LDL subfractions and oxidized LDL in medium-density LDL. The decrease of oxidized LDL seemed to be not due to the decrease of cholesterol in plasma LDL subfractions because the decreasing patterns of cholesterol and ox-LDL were different in 3 LDL subfractions.

Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

KAUST Repository

Carney, Randy P.; Kim, Jin Young; Qian, Huifeng; Jin, Rongchao; Mehenni, Hakim; Stellacci, Francesco; Bakr, Osman

2011-01-01

Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (?P) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. 2011 Macmillan Publishers Limited. All rights reserved.

Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

KAUST Repository

Carney, Randy P.

2011-06-07

Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (?P) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. 2011 Macmillan Publishers Limited. All rights reserved.

Density and distribution of nitrifying guilds in rapid sand filters for drinking water production: Dominance of Nitrospira spp

DEFF Research Database (Denmark)

Tatari, Karolina; Musovic, Sanin; Gülay, Arda

2017-01-01

distribution of these guilds, filter material was sampled at four drinking water treatment plants (DWTPs) in parallel filters of the pre- and after-filtration stages at different locations and depths. The target guilds were quantified by qPCR targeting 16S rRNA and amoA genes. Total bacterial densities......We investigated the density and distribution of total bacteria, canonical Ammonia Oxidizing Bacteria (AOB) (Nitrosomonas plus Nitrosospira), Ammonia Oxidizing Archaea (AOA), as well as Nitrobacter and Nitrospira in rapid sand filters used for groundwater treatment. To investigate the spatial...

Current density and catalyst-coated membrane resistance distribution of hydro-formed metallic bipolar plate fuel cell short stack with 250 cm2 active area

Science.gov (United States)

Haase, S.; Moser, M.; Hirschfeld, J. A.; Jozwiak, K.

2016-01-01

An automotive fuel cell with an active area of 250 cm2 is investigated in a 4-cell short stack with a current and temperature distribution device next to the bipolar plate with 560 current and 140 temperature segments. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this current scan shunt module. The applied fuel cell consists of bipolar plates constructed of 75-μm-thick, welded stainless-steel foils and a graphitic coating. The electrical conductivities of the bipolar plate and gas diffusion layer assembly are determined ex-situ with this module with a 6% deviation in in-plane conductivity. The current density distribution is evaluated up to 2.4 A cm-2. The entire cell's investigated volumetric power density is 4.7 kW l-1, and its gravimetric power density is 4.3 kW kg-1 at an average cell voltage of 0.5 V. The current density distribution is determined without influencing the operating cell. In addition, the current density distribution in the catalyst-coated membrane and its effective resistivity distribution with a finite volume discretisation of Ohm's law are evaluated. The deviation between the current density distributions in the catalyst-coated membrane and the bipolar plate is determined.

Relations between the matter density and layer thickness radial distributions in spherically symmetric objects: for high energy nuclear physics and astrophysics use

International Nuclear Information System (INIS)

Zielinska, M.; Zawislawski, Z.; Strugalska-Gola, E.; Strugalski, Z.

1991-01-01

It is shown how it is possible to transform known data on radial distribution of the matter layer thickness to unknown radial distribution of the matter density inside spherically symmetric objects. Appropriate formulas and testing of them are presented. An application of the method for the radial distribution of the matter density inside a target nucleus is discussed as an example. 2 refs.; 2 figs

Probability densities and Lévy densities

DEFF Research Database (Denmark)

Barndorff-Nielsen, Ole Eiler

For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated.......For positive Lévy processes (i.e. subordinators) formulae are derived that express the probability density or the distribution function in terms of power series in time t. The applicability of the results to finance and to turbulence is briefly indicated....

Assessing distributions of two invasive species of contrasting habits in future climate.

Science.gov (United States)

Panda, Rajendra Mohan; Behera, Mukunda Dev; Roy, Partha Sarathi

2018-05-01

Understanding the impact of climate change on species invasion is crucial for sustainable biodiversity conservation. Through this study, we try to answer how species differing in phenological cycles, specifically Cassia tora and Lantana camara, differ in the manner in which they invade new regions in India in the future climate. Since both species occupy identical niches, exploring their invasive potential in different climate change scenarios will offer critical insights into invasion and inform ecosystem management. We use three modelling protocols (i.e., maximum entropy, generalised linear model and generalised additive model) to predict the current distribution. Projections are made for both moderate (A1B) and extreme (A2) IPCC (Intergovernmental Panel on Climate Change) scenarios for the year 2050 and 2100. The study reveals that the distributions of C. tora (annual) and L. camara (perennial) would depend on the precipitation of the warmest quarter and moisture availability. C. tora may demonstrate physiological tolerance to the mean diurnal temperature range and L. camara to the solar radiation. C. tora may invade central India, while L. camara may invade the Western Himalaya, parts of the Eastern Himalaya and the Western Ghats. The distribution ranges of both species could shift in the northern and north-eastern directions in India, owing to changes in moisture availability. The possible alterations in precipitation regimes could lead to water stress, which might have cascading effects on species invasion. L. camara might adapt to climate change better compared with C. tora. This comparative analysis of the future distributions of two invasive plants with contrasting habits demonstrates that temporal complementarity would prevail over the competition. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multishot echo-planar MREIT for fast imaging of conductivity, current density, and electric field distributions.

Science.gov (United States)

Chauhan, Munish; Vidya Shankar, Rohini; Ashok Kumar, Neeta; Kodibagkar, Vikram D; Sadleir, Rosalind

2018-01-01

Magnetic resonance electrical impedance tomography (MREIT) sequences typically use conventional spin or gradient echo-based acquisition methods for reconstruction of conductivity and current density maps. Use of MREIT in functional and electroporation studies requires higher temporal resolution and faster sequences. Here, single and multishot echo planar imaging (EPI) based MREIT sequences were evaluated to see whether high-quality MREIT phase data could be obtained for rapid reconstruction of current density, conductivity, and electric fields. A gel phantom with an insulating inclusion was used as a test object. Ghost artifact, geometric distortion, and MREIT correction algorithms were applied to the data. The EPI-MREIT-derived phase-projected current density and conductivity images were compared with simulations and spin-echo images as a function of EPI shot number. Good agreement among measures in simulated, spin echo, and EPI data was achieved. Current density errors were stable and below 9% as the shot number decreased from 64 to 2, but increased for single-shot images. Conductivity reconstruction relative contrast ratios were stable as the shot number decreased. The derived electric fields also agreed with the simulated data. The EPI methods can be combined successfully with MREIT reconstruction algorithms to achieve fast imaging of current density, conductivity, and electric field. Magn Reson Med 79:71-82, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Understanding spatial connectivity of individuals with non-uniform population density.

Science.gov (United States)

Wang, Pu; González, Marta C

2009-08-28

We construct a two-dimensional geometric graph connecting individuals placed in space within a given contact distance. The individuals are distributed using a measured country's density of population. We observe that while large clusters (group of individuals connected) emerge within some regions, they are trapped in detached urban areas owing to the low population density of the regions bordering them. To understand the emergence of a giant cluster that connects the entire population, we compare the empirical geometric graph with the one generated by placing the same number of individuals randomly in space. We find that, for small contact distances, the empirical distribution of population dominates the growth of connected components, but no critical percolation transition is observed in contrast to the graph generated by a random distribution of population. Our results show that contact distances from real-world situations as for WIFI and Bluetooth connections drop in a zone where a fully connected cluster is not observed, hinting that human mobility must play a crucial role in contact-based diseases and wireless viruses' large-scale spreading.

Centrality dependence of the pseudorapidity density distribution for charged particles in Pb-Pb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV

CERN Document Server

Abbas, Ehab; Adam, Jaroslav; Adamova, Dagmar; Adare, Andrew Marshall; Aggarwal, Madan; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agocs, Andras Gabor; Agostinelli, Andrea; Ahammed, Zubayer; Ahmad, Arshad; Ahmad, Nazeer; Ahn, Sang Un; Ahn, Sul-Ah; Aimo, Ilaria; Ajaz, Muhammad; Akindinov, Alexander; Aleksandrov, Dmitry; Alessandro, Bruno; Alici, Andrea; Alkin, Anton; Almaraz Avina, Erick Jonathan; Alme, Johan; Alt, Torsten; Altini, Valerio; Altinpinar, Sedat; Altsybeev, Igor; Andrei, Cristian; Andronic, Anton; Anguelov, Venelin; Anielski, Jonas; Anson, Christopher Daniel; Anticic, Tome; Antinori, Federico; Antonioli, Pietro; Aphecetche, Laurent Bernard; Appelshauser, Harald; Arbor, Nicolas; Arcelli, Silvia; Arend, Andreas; Armesto, Nestor; Arnaldi, Roberta; Aronsson, Tomas Robert; Arsene, Ionut Cristian; Arslandok, Mesut; Asryan, Andzhey; Augustinus, Andre; Averbeck, Ralf Peter; Awes, Terry; Aysto, Juha Heikki; Azmi, Mohd Danish; Bach, Matthias Jakob; Badala, Angela; Baek, Yong Wook; Bailhache, Raphaelle Marie; Bala, Renu; Baldisseri, Alberto; Baltasar Dos Santos Pedrosa, Fernando; Ban, Jaroslav; Baral, Rama Chandra; Barbera, Roberto; Barile, Francesco; Barnafoldi, Gergely Gabor; Barnby, Lee Stuart; Barret, Valerie; Bartke, Jerzy Gustaw; Basile, Maurizio; Bastid, Nicole; Basu, Sumit; Bathen, Bastian; Batigne, Guillaume; Batyunya, Boris; Batzing, Paul Christoph; Baumann, Christoph Heinrich; Bearden, Ian Gardner; Beck, Hans; Behera, Nirbhay Kumar; Belikov, Iouri; Bellini, Francesca; Bellwied, Rene; Belmont-Moreno, Ernesto; Bencedi, Gyula; Beole, Stefania; Berceanu, Ionela; Bercuci, Alexandru; Berdnikov, Yaroslav; Berenyi, Daniel; Bergognon, Anais Annick Erica; Bertens, Redmer Alexander; Berzano, Dario; Betev, Latchezar; Bhasin, Anju; Bhati, Ashok Kumar; Bhom, Jihyun; Bianchi, Nicola; Bianchi, Livio; Bianchin, Chiara; Bielcik, Jaroslav; Bielcikova, Jana; Bilandzic, Ante; Bjelogrlic, Sandro; Blanco, F; Blanco, Francesco; Blau, Dmitry; Blume, Christoph; Boccioli, Marco; Boettger, Stefan; Bogdanov, Alexey; Boggild, Hans; Bogolyubsky, Mikhail; Boldizsar, Laszlo; Bombara, Marek; Book, Julian; Borel, Herve; Borissov, Alexander; Bossu, Francesco; Botje, Michiel; Botta, Elena; Braidot, Ermes; Braun-Munzinger, Peter; Bregant, Marco; Breitner, Timo Gunther; Broker, Theo Alexander; Browning, Tyler Allen; Broz, Michal; Brun, Rene; Bruna, Elena; Bruno, Giuseppe Eugenio; Budnikov, Dmitry; Buesching, Henner; Bufalino, Stefania; Buncic, Predrag; Busch, Oliver; Buthelezi, Edith Zinhle; Caffarri, Davide; Cai, Xu; Caines, Helen Louise; Calvo Villar, Ernesto; Camerini, Paolo; Canoa Roman, Veronica; Cara Romeo, Giovanni; Carena, Francesco; Carena, Wisla; Carlin Filho, Nelson; Carminati, Federico; Casanova Diaz, Amaya Ofelia; Castillo Castellanos, Javier Ernesto; Castillo Hernandez, Juan Francisco; Casula, Ester Anna Rita; Catanescu, Vasile; Cavicchioli, Costanza; Ceballos Sanchez, Cesar; Cepila, Jan; Cerello, Piergiorgio; Chang, Beomsu; Chapeland, Sylvain; Charvet, Jean-Luc Fernand; Chattopadhyay, Subhasis; Chattopadhyay, Sukalyan; Cherney, Michael Gerard; Cheshkov, Cvetan; Cheynis, Brigitte; Chibante Barroso, Vasco Miguel; Chinellato, David; Chochula, Peter; Chojnacki, Marek; Choudhury, Subikash; Christakoglou, Panagiotis; Christensen, Christian Holm; Christiansen, Peter; Chujo, Tatsuya; Chung, Suh-Urk; Cicalo, Corrado; Cifarelli, Luisa; Cindolo, Federico; Cleymans, Jean Willy Andre; Colamaria, Fabio; Colella, Domenico; Collu, Alberto; Conesa Balbastre, Gustavo; Conesa del Valle, Zaida; Connors, Megan Elizabeth; Contin, Giacomo; Contreras, Jesus Guillermo; Cormier, Thomas Michael; Corrales Morales, Yasser; Cortese, Pietro; Cortes Maldonado, Ismael; Cosentino, Mauro Rogerio; Costa, Filippo; Cotallo, Manuel Enrique; Crescio, Elisabetta; Crochet, Philippe; Cruz Alaniz, Emilia; Cruz Albino, Rigoberto; Cuautle, Eleazar; Cunqueiro, Leticia; Dainese, Andrea; Dalsgaard, Hans Hjersing; Dang, Ruina; Danu, Andrea; Das, Kushal; Das, Indranil; Das, Supriya; Das, Debasish; Dash, Ajay Kumar; Dash, Sadhana; De, Sudipan; de Barros, Gabriel; De Caro, Annalisa; de Cataldo, Giacinto; de Cuveland, Jan; De Falco, Alessandro; De Gruttola, Daniele; Delagrange, Hugues; Deloff, Andrzej; De Marco, Nora; Denes, Ervin; De Pasquale, Salvatore; Deppman, Airton; D'Erasmo, Ginevra; de Rooij, Raoul Stefan; Diaz Corchero, Miguel Angel; Di Bari, Domenico; Dietel, Thomas; Di Giglio, Carmelo; Di Liberto, Sergio; Di Mauro, Antonio; Di Nezza, Pasquale; Divia, Roberto; Djuvsland, Oeystein; Dobrin, Alexandru Florin; Dobrowolski, Tadeusz Antoni; Donigus, Benjamin; Dordic, Olja; Driga, Olga; Dubey, Anand Kumar; Dubla, Andrea; Ducroux, Laurent; Dupieux, Pascal; Dutta Majumdar, AK; Elia, Domenico; Emschermann, David Philip; Engel, Heiko; Erazmus, Barbara; Erdal, Hege Austrheim; Eschweiler, Dominic; Espagnon, Bruno; Estienne, Magali Danielle; Esumi, Shinichi; Evans, David; Evdokimov, Sergey; Eyyubova, Gyulnara; Fabris, Daniela; Faivre, Julien; Falchieri, Davide; Fantoni, Alessandra; Fasel, Markus; Fehlker, Dominik; Feldkamp, Linus; Felea, Daniel; Feliciello, Alessandro; Fenton-Olsen, Bo; Feofilov, Grigory; Fernandez Tellez, Arturo; Ferretti, Alessandro; Festanti, Andrea; Figiel, Jan; Figueredo, Marcel; Filchagin, Sergey; Finogeev, Dmitry; Fionda, Fiorella; Fiore, Enrichetta Maria; Floratos, Emmanuel; Floris, Michele; Foertsch, Siegfried Valentin; Foka, Panagiota; Fokin, Sergey; Fragiacomo, Enrico; Francescon, Andrea; Frankenfeld, Ulrich Michael; Fuchs, Ulrich; Furget, Christophe; Fusco Girard, Mario; Gaardhoje, Jens Joergen; Gagliardi, Martino; Gago, Alberto; Gallio, Mauro; Gangadharan, Dhevan Raja; Ganoti, Paraskevi; Garabatos, Jose; Garcia-Solis, Edmundo; Gargiulo, Corrado; Garishvili, Irakli; Gerhard, Jochen; Germain, Marie; Geuna, Claudio; Gheata, Andrei George; Gheata, Mihaela; Ghidini, Bruno; Ghosh, Premomoy; Gianotti, Paola; Girard, Martin Robert; Giubellino, Paolo; Gladysz-Dziadus, Ewa; Glassel, Peter; Gomez, Ramon; Gonzalez Ferreiro, Elena; Gonzalez-Trueba, Laura Helena; Gonzalez-Zamora, Pedro; Gorbunov, Sergey; Goswami, Ankita; Gotovac, Sven; Graczykowski, Lukasz Kamil; Grajcarek, Robert; Grelli, Alessandro; Grigoras, Alina Gabriela; Grigoras, Costin; Grigoriev, Vladislav; Grigoryan, Ara; Grigoryan, Smbat; Grinyov, Boris; Grion, Nevio; Gros, Philippe; Grosse-Oetringhaus, Jan Fiete; Grossiord, Jean-Yves; Grosso, Raffaele; Guber, Fedor; Guernane, Rachid; Guerzoni, Barbara; Guilbaud, Maxime Rene Joseph; Gulbrandsen, Kristjan Herlache; Gulkanyan, Hrant; Gunji, Taku; Gupta, Ramni; Gupta, Anik; Haake, Rudiger; Haaland, Oystein Senneset; Hadjidakis, Cynthia Marie; Haiduc, Maria; Hamagaki, Hideki; Hamar, Gergoe; Han, Byounghee; Hanratty, Luke David; Hansen, Alexander; Harmanova, Zuzana; Harris, John William; Hartig, Matthias; Harton, Austin; Hatzifotiadou, Despoina; Hayashi, Shinichi; Hayrapetyan, Arsen; Heckel, Stefan Thomas; Heide, Markus Ansgar; Helstrup, Haavard; Herghelegiu, Andrei Ionut; Herrera Corral, Gerardo Antonio; Herrmann, Norbert; Hess, Benjamin Andreas; Hetland, Kristin Fanebust; Hicks, Bernard; Hippolyte, Boris; Hori, Yasuto; Hristov, Peter Zahariev; Hrivnacova, Ivana; Huang, Meidana; Humanic, Thomas; Hwang, Dae Sung; Ichou, Raphaelle; Ilkaev, Radiy; Ilkiv, Iryna; Inaba, Motoi; Incani, Elisa; Innocenti, Pier Giorgio; Innocenti, Gian Michele; Ippolitov, Mikhail; Irfan, Muhammad; Ivan, Cristian George; Ivanov, Vladimir; Ivanov, Andrey; Ivanov, Marian; Ivanytskyi, Oleksii; Jacholkowski, Adam Wlodzimierz; Jacobs, Peter; Jahnke, Cristiane; Jang, Haeng Jin; Janik, Malgorzata Anna; Jayarathna, Sandun; Jena, Satyajit; Jha, Deeptanshu Manu; Jimenez Bustamante, Raul Tonatiuh; Jones, Peter Graham; Jung, Hyung Taik; Jusko, Anton; Kaidalov, Alexei; Kalcher, Sebastian; Kalinak, Peter; Kalliokoski, Tuomo Esa Aukusti; Kalweit, Alexander Philipp; Kang, Ju Hwan; Kaplin, Vladimir; Kar, Somnath; Karasu Uysal, Ayben; Karavichev, Oleg; Karavicheva, Tatiana; Karpechev, Evgeny; Kazantsev, Andrey; Kebschull, Udo Wolfgang; Keidel, Ralf; Ketzer, Bernhard Franz; Khan, Kamal Hussain; Khan, Mohisin Mohammed; Khan, Palash; Khan, Shuaib Ahmad; Khanzadeev, Alexei; Kharlov, Yury; Kileng, Bjarte; Kim, Minwoo; Kim, Se Yong; Kim, Beomkyu; Kim, Taesoo; Kim, Dong Jo; Kim, Do Won; Kim, Jonghyun; Kim, Jin Sook; Kim, Mimae; Kirsch, Stefan; Kisel, Ivan; Kiselev, Sergey; Kisiel, Adam Ryszard; Klay, Jennifer Lynn; Klein, Jochen; Klein-Bosing, Christian; Kliemant, Michael; Kluge, Alexander; Knichel, Michael Linus; Knospe, Anders Garritt; Kohler, Markus; Kollegger, Thorsten; Kolojvari, Anatoly; Kompaniets, Mikhail; Kondratiev, Valery; Kondratyeva, Natalia; Konevskih, Artem; Kovalenko, Vladimir; Kowalski, Marek; Kox, Serge; Koyithatta Meethaleveedu, Greeshma; Kral, Jiri; Kralik, Ivan; Kramer, Frederick; Kravcakova, Adela; Krelina, Michal; Kretz, Matthias; Krivda, Marian; Krizek, Filip; Krus, Miroslav; Kryshen, Evgeny; Krzewicki, Mikolaj; Kucera, Vit; Kucheriaev, Yury; Kugathasan, Thanushan; Kuhn, Christian Claude; Kuijer, Paul; Kulakov, Igor; Kumar, Jitendra; Kurashvili, Podist; Kurepin, A; Kurepin, AB; Kuryakin, Alexey; Kushpil, Svetlana; Kushpil, Vasily; Kvaerno, Henning; Kweon, Min Jung; Kwon, Youngil; Ladron de Guevara, Pedro; Lakomov, Igor; Langoy, Rune; La Pointe, Sarah Louise; Lara, Camilo Ernesto; Lardeux, Antoine Xavier; La Rocca, Paola; Lea, Ramona; Lechman, Mateusz; Lee, Sung Chul; Lee, Graham Richard; Legrand, Iosif; Lehnert, Joerg Walter; Lemmon, Roy Crawford; Lenhardt, Matthieu Laurent; Lenti, Vito; Leon, Hermes; Leoncino, Marco; Leon Monzon, Ildefonso; Levai, Peter; Li, Shuang; Lien, Jorgen; Lietava, Roman; Lindal, Svein; Lindenstruth, Volker; Lippmann, Christian; Lisa, Michael Annan; Ljunggren, Hans Martin; Lodato, Davide Francesco; Loenne, Per-Ivar; Loggins, Vera; Loginov, Vitaly; Lohner, Daniel; Loizides, Constantinos; Loo, Kai Krister; Lopez, Xavier Bernard; Lopez Torres, Ernesto; Lovhoiden, Gunnar; Lu, Xianguo; Luettig, Philipp; Lunardon, Marcello; Luo, Jiebin; Luparello, Grazia; Luzzi, Cinzia; Ma, Ke; Ma, Rongrong; Madagodahettige-Don, Dilan Minthaka; Maevskaya, Alla; Mager, Magnus; Mahapatra, Durga Prasad; Maire, Antonin; Malaev, Mikhail; Maldonado Cervantes, Ivonne Alicia; Malinina, Ludmila; Mal'Kevich, Dmitry; Malzacher, Peter; Mamonov, Alexander; Manceau, Loic Henri Antoine; Mangotra, Lalit Kumar; Manko, Vladislav; Manso, Franck; Manzari, Vito; Mao, Yaxian; Marchisone, Massimiliano; Mares, Jiri; Margagliotti, Giacomo Vito; Margotti, Anselmo; Marin, Ana Maria; Markert, Christina; Marquard, Marco; Martashvili, Irakli; Martin, Nicole Alice; Martinengo, Paolo; Martinez, Mario Ivan; Martinez Garcia, Gines; Martynov, Yevgen; Mas, Alexis Jean-Michel; Masciocchi, Silvia; Masera, Massimo; Masoni, Alberto; Massacrier, Laure Marie; Mastroserio, Annalisa; Matyja, Adam Tomasz; Mayer, Christoph; Mazer, Joel; Mazzoni, Alessandra Maria; Meddi, Franco; Menchaca-Rocha, Arturo Alejandro; Mercado Perez, Jorge; Meres, Michal; Miake, Yasuo; Mikhaylov, Konstantin; Milano, Leonardo; Milosevic, Jovan; Mischke, Andre; Mishra, Aditya Nath; Miskowiec, Dariusz; Mitu, Ciprian Mihai; Mizuno, Sanshiro; Mlynarz, Jocelyn; Mohanty, Bedangadas; Molnar, Levente; Montano Zetina, Luis Manuel; Monteno, Marco; Montes, Esther; Moon, Taebong; Morando, Maurizio; Moreira De Godoy, Denise Aparecida; Moretto, Sandra; Morreale, Astrid; Morsch, Andreas; Muccifora, Valeria; Mudnic, Eugen; Muhuri, Sanjib; Mukherjee, Maitreyee; Muller, Hans; Munhoz, Marcelo; Murray, Sean; Musa, Luciano; Musinsky, Jan; Nandi, Basanta Kumar; Nania, Rosario; Nappi, Eugenio; Nattrass, Christine; Nayak, Tapan Kumar; Nazarenko, Sergey; Nedosekin, Alexander; Nicassio, Maria; Niculescu, Mihai; Nielsen, Borge Svane; Niida, Takafumi; Nikolaev, Sergey; Nikolic, Vedran; Nikulin, Sergey; Nikulin, Vladimir; Nilsen, Bjorn Steven; Nilsson, Mads Stormo; Noferini, Francesco; Nomokonov, Petr; Nooren, Gerardus; Nyanin, Alexandre; Nyatha, Anitha; Nygaard, Casper; Nystrand, Joakim Ingemar; Ochirov, Alexander; Oeschler, Helmut Oskar; Oh, Saehanseul; Oh, Sun Kun; Oleniacz, Janusz; Oliveira Da Silva, Antonio Carlos; Oppedisano, Chiara; Ortiz Velasquez, Antonio; Oskarsson, Anders Nils Erik; Ostrowski, Piotr Krystian; Otwinowski, Jacek Tomasz; Oyama, Ken; Ozawa, Kyoichiro; Pachmayer, Yvonne Chiara; Pachr, Milos; Padilla, Fatima; Pagano, Paola; Paic, Guy; Painke, Florian; Pajares, Carlos; Pal, Susanta Kumar; Palaha, Arvinder Singh; Palmeri, Armando; Papikyan, Vardanush; Pappalardo, Giuseppe; Park, Woo Jin; Passfeld, Annika; Patalakha, Dmitri Ivanovich; Paticchio, Vincenzo; Paul, Biswarup; Pavlinov, Alexei; Pawlak, Tomasz Jan; Peitzmann, Thomas; Pereira Da Costa, Hugo Denis Antonio; Pereira De Oliveira Filho, Elienos; Peresunko, Dmitri; Perez Lara, Carlos Eugenio; Perrino, Davide; Peryt, Wiktor Stanislaw; Pesci, Alessandro; Pestov, Yury; Petracek, Vojtech; Petran, Michal; Petris, Mariana; Petrov, Plamen Rumenov; Petrovici, Mihai; Petta, Catia; Piano, Stefano; Pikna, Miroslav; Pillot, Philippe; Pinazza, Ombretta; Pinsky, Lawrence; Pitz, Nora; Piyarathna, Danthasinghe; Planinic, Mirko; Ploskon, Mateusz Andrzej; Pluta, Jan Marian; Pocheptsov, Timur; Pochybova, Sona; Podesta Lerma, Pedro Luis Manuel; Poghosyan, Martin; Polak, Karel; Polichtchouk, Boris; Poljak, Nikola; Pop, Amalia; Porteboeuf-Houssais, Sarah; Pospisil, Vladimir; Potukuchi, Baba; Prasad, Sidharth Kumar; Preghenella, Roberto; Prino, Francesco; Pruneau, Claude Andre; Pshenichnov, Igor; Puddu, Giovanna; Punin, Valery; Putis, Marian; Putschke, Jorn Henning; Qvigstad, Henrik; Rachevski, Alexandre; Rademakers, Alphonse; Raiha, Tomi Samuli; Rak, Jan; Rakotozafindrabe, Andry Malala; Ramello, Luciano; Raniwala, Sudhir; Raniwala, Rashmi; Rasanen, Sami Sakari; Rascanu, Bogdan Theodor; Rathee, Deepika; Rauch, Wolfgang; Read, Kenneth Francis; Real, Jean-Sebastien; Redlich, Krzysztof; Reed, Rosi Jan; Rehman, Attiq Ur; Reichelt, Patrick; Reicher, Martijn; Renfordt, Rainer Arno Ernst; Reolon, Anna Rita; Reshetin, Andrey; Rettig, Felix Vincenz; Revol, Jean-Pierre; Reygers, Klaus Johannes; Riccati, Lodovico; Ricci, Renato Angelo; Richert, Tuva; Richter, Matthias Rudolph; Riedler, Petra; Riegler, Werner; Riggi, Francesco; Rodriguez Cahuantzi, Mario; Rodriguez Manso, Alis; Roed, Ketil; Rogochaya, Elena; Rohr, David; Rohrich, Dieter; Romita, Rosa; Ronchetti, Federico; Rosnet, Philippe; Rossegger, Stefan; Rossi, Andrea; Roy, Pradip Kumar; Roy, Christelle Sophie; Rubio Montero, Antonio Juan; Rui, Rinaldo; Russo, Riccardo; Ryabinkin, Evgeny; Rybicki, Andrzej; Sadovsky, Sergey; Safarik, Karel; Sahoo, Raghunath; Sahu, Pradip Kumar; Saini, Jogender; Sakaguchi, Hiroaki; Sakai, Shingo; Sakata, Dosatsu; Salgado, Carlos Albert; Salzwedel, Jai; Sambyal, Sanjeev Singh; Samsonov, Vladimir; Sanchez Castro, Xitzel; Sandor, Ladislav; Sandoval, Andres; Sano, Masato; Santagati, Gianluca; Santoro, Romualdo; Sarkamo, Juho Jaako; Sarkar, Debojit; Scapparone, Eugenio; Scarlassara, Fernando; Scharenberg, Rolf Paul; Schiaua, Claudiu Cornel; Schicker, Rainer Martin; Schmidt, Hans Rudolf; Schmidt, Christian Joachim; Schuchmann, Simone; Schukraft, Jurgen; Schuster, Tim; Schutz, Yves Roland; Schwarz, Kilian Eberhard; Schweda, Kai Oliver; Scioli, Gilda; Scomparin, Enrico; Scott, Rebecca; Scott, Patrick Aaron; Segato, Gianfranco; Selyuzhenkov, Ilya; Senyukov, Serhiy; Seo, Jeewon; Serci, Sergio; Serradilla, Eulogio; Sevcenco, Adrian; Shabetai, Alexandre; Shabratova, Galina; Shahoyan, Ruben; Sharma, Natasha; Sharma, Satish; Sharma, Rohni; Shigaki, Kenta; Shtejer, Katherin; Sibiriak, Yury; Sicking, Eva; Siddhanta, Sabyasachi; Siemiarczuk, Teodor; Silvermyr, David Olle Rickard; Silvestre, Catherine; Simatovic, Goran; Simonetti, Giuseppe; Singaraju, Rama Narayana; Singh, Ranbir; Singha, Subhash; Singhal, Vikas; Sinha, Bikash; Sinha, Tinku; Sitar, Branislav; Sitta, Mario; Skaali, Bernhard; Skjerdal, Kyrre; Smakal, Radek; Smirnov, Nikolai; Snellings, Raimond; Sogaard, Carsten; Soltz, Ron Ariel; Song, Myunggeun; Song, Jihye; Soos, Csaba; Soramel, Francesca; Sputowska, Iwona; Spyropoulou-Stassinaki, Martha; Srivastava, Brijesh Kumar; Stachel, Johanna; Stan, Ionel; Stefanek, Grzegorz; Steinpreis, Matthew; Stenlund, Evert Anders; Steyn, Gideon Francois; Stiller, Johannes Hendrik; Stocco, Diego; Stolpovskiy, Mikhail; Strmen, Peter; Suaide, Alexandre Alarcon do Passo; Subieta Vasquez, Martin Alfonso; Sugitate, Toru; Suire, Christophe Pierre; Sultanov, Rishat; Sumbera, Michal; Susa, Tatjana; Symons, Timothy; Szanto de Toledo, Alejandro; Szarka, Imrich; Szczepankiewicz, Adam; Szymanski, Maciej; Takahashi, Jun; Tangaro, Marco-Antonio; Tapia Takaki, Daniel Jesus; Tarantola Peloni, Attilio; Tarazona Martinez, Alfonso; Tauro, Arturo; Tejeda Munoz, Guillermo; Telesca, Adriana; Ter-Minasyan, Astkhik; Terrevoli, Cristina; Thader, Jochen Mathias; Thomas, Deepa; Tieulent, Raphael Noel; Timmins, Anthony; Tlusty, David; Toia, Alberica; Torii, Hisayuki; Toscano, Luca; Trubnikov, Victor; Truesdale, David Christopher; Trzaska, Wladyslaw Henryk; Tsuji, Tomoya; Tumkin, Alexandr; Turrisi, Rosario; Tveter, Trine Spedstad; Ulery, Jason Glyndwr; Ullaland, Kjetil; Ulrich, Jochen; Uras, Antonio; Urciuoli, Guido Marie; Usai, Gianluca; Vajzer, Michal; Vala, Martin; Valencia Palomo, Lizardo; Vande Vyvre, Pierre; Van Hoorne, Jacobus Willem; van Leeuwen, Marco; Vannucci, Luigi; Vargas, Aurora Diozcora; Varma, Raghava; Vasileiou, Maria; Vasiliev, Andrey; Vechernin, Vladimir; Veldhoen, Misha; Venaruzzo, Massimo; Vercellin, Ermanno; Vergara, Sergio; Vernet, Renaud; Verweij, Marta; Vickovic, Linda; Viesti, Giuseppe; Viinikainen, Jussi; Vilakazi, Zabulon; Villalobos Baillie, Orlando; Vinogradov, Yury; Vinogradov, Leonid; Vinogradov, Alexander; Virgili, Tiziano; Viyogi, Yogendra; Vodopianov, Alexander; Volkl, Martin Andreas; Voloshin, Sergey; Voloshin, Kirill; Volpe, Giacomo; von Haller, Barthelemy; Vorobyev, Ivan; Vranic, Danilo; Vrlakova, Janka; Vulpescu, Bogdan; Vyushin, Alexey; Wagner, Boris; Wagner, Vladimir; Wan, Renzhuo; Wang, Yaping; Wang, Mengliang; Wang, Yifei; Watanabe, Kengo; Weber, Michael; Wessels, Johannes; Westerhoff, Uwe; Wiechula, Jens; Wikne, Jon; Wilde, Martin Rudolf; Wilk, Grzegorz Andrzej; Williams, Crispin; Windelband, Bernd Stefan; Xaplanteris Karampatsos, Leonidas; Yaldo, Chris G; Yamaguchi, Yorito; Yang, Shiming; Yang, Ping; Yang, Hongyan; Yasnopolsky, Stanislav; Yi, JunGyu; Yin, Zhongbao; Yoo, In-Kwon; Yoon, Jongik; Yu, Weilin; Yuan, Xianbao; Yushmanov, Igor; Zaccolo, Valentina; Zach, Cenek; Zampolli, Chiara; Zaporozhets, Sergey; Zarochentsev, Andrey; Zavada, Petr; Zaviyalov, Nikolai; Zbroszczyk, Hanna Paulina; Zelnicek, Pierre; Zgura, Sorin Ion; Zhalov, Mikhail; Zhang, Haitao; Zhang, Xiaoming; Zhang, Yonghong; Zhou, Daicui; Zhou, Fengchu; Zhou, You; Zhu, Hongsheng; Zhu, Jianlin; Zhu, Xiangrong; Zhu, Jianhui; Zichichi, Antonino; Zimmermann, Alice; Zinovjev, Gennady; Zoccarato, Yannick Denis; Zynovyev, Mykhaylo; Zyzak, Maksym

2013-11-04

We present the first wide-range measurement of the charged-particle pseudorapidity density distribution, for different centralities (the 0-5%, 5-10%, 10-20%, and 20-30% most central events) in Pb-Pb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV at the LHC. The measurement is performed using the full coverage of the ALICE detectors, -5.0 < $\\eta$ < 5.5, and employing a special analysis technique based on collisions arising from LHC ' satellite' bunches. We present the pseudorapidity density as a function of the number of participating nucleons as well as an extrapolation to the total number of produced charged particles ($N_{ch}$ = 17165 +/- 772 for the 0-5% most central collisions). From the measured d$N_{ch}$/d$\\eta$ distribution we derive the rapidity density distribution, d$N_{ch}$/dy, under simple assumptions. The rapidity density distribution is found to be significantly wider than the predictions of the Landau model, which reproduce data well at RHIC energies. We assess the validity of longitudinal sca...

Density distribution function of a self-gravitating isothermal compressible turbulent fluid in the context of molecular clouds ensembles

Science.gov (United States)

Donkov, Sava; Stefanov, Ivan Z.

2018-03-01

We have set ourselves the task of obtaining the probability distribution function of the mass density of a self-gravitating isothermal compressible turbulent fluid from its physics. We have done this in the context of a new notion: the molecular clouds ensemble. We have applied a new approach that takes into account the fractal nature of the fluid. Using the medium equations, under the assumption of steady state, we show that the total energy per unit mass is an invariant with respect to the fractal scales. As a next step we obtain a non-linear integral equation for the dimensionless scale Q which is the third root of the integral of the probability distribution function. It is solved approximately up to the leading-order term in the series expansion. We obtain two solutions. They are power-law distributions with different slopes: the first one is -1.5 at low densities, corresponding to an equilibrium between all energies at a given scale, and the second one is -2 at high densities, corresponding to a free fall at small scales.

Nonlinear electron-density distribution around point defects in simple metals. I. Formulation

International Nuclear Information System (INIS)

Gupta, A.K.; Jena, P.; Singwi, K.S.

1978-01-01

Modification, which is exact in the limit of long wavelength, of the nonlinear theory of Sjoelander and Stott of electron distribution around point defects is given. This modification consists in writing a nonlinear integral equations for the Fourier transform γ 12 (q) of the induced charge density surrounding the point defect, which includes a term involving the density derivative of γ 12 (q). A generalization of the Pauli-Feynman coupling-constant-integration method, together with the Kohn-Sham formalism, is used to exactly determine the coefficient of this derivative term in the long-wavelength limit. The theory is then used to calculate electron-density profiles around a vacancy, an eight-atom void, and a point ion. The results are compared with those of (i) a linear theory, (ii) Sjoelander-Stott theory, and (iii) a fully self-consistent calculation based on the density-functional formalism of Kohn and Sham. It is found that in the case of a vacancy, the results of the present theory are in very good agreement with those based on Kohn-Sham formalism, whereas in the case of a singular attractive potential of a proton, the results are quite poor in the vicinity of the proton, but much better for larger distances. A critical discussion of the theory vis a vis the Kohn-Sham formalism is also given. Some applications of the theory are pointed out

The correlation function for density perturbations in an expanding universe. IV - The evolution of the correlation function. [galaxy distribution

Science.gov (United States)

Mcclelland, J.; Silk, J.

1979-01-01

The evolution of the two-point correlation function for the large-scale distribution of galaxies in an expanding universe is studied on the assumption that the perturbation densities lie in a Gaussian distribution centered on any given mass scale. The perturbations are evolved according to the Friedmann equation, and the correlation function for the resulting distribution of perturbations at the present epoch is calculated. It is found that: (1) the computed correlation function gives a satisfactory fit to the observed function in cosmological models with a density parameter (Omega) of approximately unity, provided that a certain free parameter is suitably adjusted; (2) the power-law slope in the nonlinear regime reflects the initial fluctuation spectrum, provided that the density profile of individual perturbations declines more rapidly than the -2.4 power of distance; and (3) both positive and negative contributions to the correlation function are predicted for cosmological models with Omega less than unity.

A STATISTICAL STUDY OF THE MASS AND DENSITY STRUCTURE OF INFRARED DARK CLOUDS

International Nuclear Information System (INIS)

Peretto, N.; Fuller, G. A.

2010-01-01

How and when the mass distribution of stars in the Galaxy is set is one of the main issues of modern astronomy. Here, we present a statistical study of mass and density distributions of infrared dark clouds (IRDCs) and fragments within them. These regions are pristine molecular gas structures and progenitors of stars and so provide insights into the initial conditions of star formation. This study makes use of an IRDC catalog, the largest sample of IRDC column density maps to date, containing a total of ∼11,000 IRDCs with column densities exceeding N H 2 = 1x10 22 cm -2 and over 50,000 single-peaked IRDC fragments. The large number of objects constitutes an important strength of this study, allowing a detailed analysis of the completeness of the sample and so statistically robust conclusions. Using a statistical approach to assigning distances to clouds, the mass and density distributions of the clouds and the fragments within them are constructed. The mass distributions show a steepening of the slope when switching from IRDCs to fragments, in agreement with previous results of similar structures. IRDCs and fragments are divided into unbound/bound objects by assuming Larson's relation and calculating their virial parameter. IRDCs are mostly gravitationally bound, while a significant fraction of the fragments are not. The density distribution of gravitationally unbound fragments shows a steep characteristic slope such as ΔN/Δlog(n) ∝ n -4.0±0.5 , rather independent of the range of fragment mass. However, the incompleteness limit at a number density of ∼10 3 cm -3 does not allow us to exclude a potential lognormal density distribution. In contrast, gravitationally bound fragments show a characteristic density peak at n ≅ 10 4 cm -3 but the shape of the density distributions changes with the range of fragment masses. An explanation for this could be the differential dynamical evolution of the fragment density with respect to their mass as more massive

A study on current density distribution reproduction by bounded-eigenfunction expansion for a tokamak plasma

International Nuclear Information System (INIS)

Kurihara, Kenichi

1997-11-01

Plasma current density distribution is one of the most important controlled variables to determine plasma performance of energy confinement and stability in a tokamak. However, its reproduction by using magnetic measurements solely is recognized to yield an ill-posed problem. A method to presume the formulas giving profiles of plasma pressure and current has been adopted to regularize the ill-posedness, and hence it has been reported the current density distribution can be reproduced as a solution of Grad-Shafranov equation within a certain accuracy. In order to investigate its strict reproducibility from magnetic measurements in this inverse problem, a new method of 'bounded-eigenfunction expansion' is introduced, and it was found that the reproducibility directly corresponds to the independence of a series of the special function. The results from various investigations in an aspect of applied mathematics concerning this inverse problem are presented in detail. (author)

Influence of the potential well and the potential barrier on the density distribution of confined-model fluids

CERN Document Server

Lee, B H; Lee, C H; Seong Baek Seok

2000-01-01

A density functional perturbative approximation, which is based on the density functional expansion of the one-particle direct correlation function of model fluids with respect to the bulk density, has been employed to investigate the influence of the potential well and the potential barrier on the density behavior of confined-model fluids. The mean spherical approximation has been used to calculate the two-particle direct correlation function of the model fluids. At lower densities, the density distributions are strongly affected by the barrier height and the well depth of the model potential, the contribution from the short-range repulsive part being especially important. However, the effects of the barrier height and the well depth of the model potential decrease with increasing bulk density. The calculated results also show that in the region where the effect of the wall-fluid interaction is relatively weak, the square-barrier part of the model potential leads to a nonuniformity in the density distributio...

The effect of merger and consolidation activities on the efficiency of electricity distribution regions in Turkey

International Nuclear Information System (INIS)

Çelen, Aydın

2013-01-01

In this study, we analyze the efficiency performances of Turkish electricity distribution companies throughout 2002 and 2009 in the stochastic frontier analysis (SFA) framework. Our more specific goal is to measure how the efficiency performances of the electricity distribution regions were affected by the mergers between distribution regions occurred in 2005. The results demonstrate that efficiencies of the companies serving to mostly the residential customers are higher than those of other companies. However, the positive impact of residential customers on the efficiencies decreased significantly following the mergers between electricity distribution companies. In contrast, the positive impact of higher customer density on efficiency also decreased, but insignificantly following the restructuring activities in the market in 2005. Our study also witnesses that the positive impact of the mergers on the efficiencies decreases as the proportion of sales to residential customers in regions increases. In contrast, the restructuring activities of 2005 increased equally the efficiencies of the companies serving in the regions with higher and lower customer densities. - Highlights: • We analyze efficiency performances of Turkish electricity distribution companies. • The efficiencies of companies serving to mostly residential customers are higher. • Positive impact of residential customers on the efficiencies dropped after mergers. • Positive impact of customer density also decreased, but insignificantly. • Positive impact of mergers on efficiency decreases as sales to residents increase

Application of image processing to STEM tomography of low-contrast materials

International Nuclear Information System (INIS)

Ortalan, V.; Herrera, M.; Morgan, D.G.; Browning, N.D.

2009-01-01

In this study, the effect of various image-processing techniques on the visibility of tomographic reconstructions is investigated for a low-contrast material system of non-uniform thickness containing complex features such as grain boundaries and nanoparticles. Starting with a tilt series of high-angle annular dark-field (HAADF) images from an area of Dy-doped YBa 2 Cu 3 O 7-x -coated superconductor obtained using a scanning transmission electron microscope, various image-processing techniques were applied. These can be classified as edge detection, contrast-enhancing methods for non-uniform thickness and image sharpening. Although the processing methods violate the projection criterion for tomographic reconstruction, they were found, at least in this case, to enhance contrast and define the correct shape and size of structural features with minimal artifacts. Enhancing the visibility of structural features in this way allows the spatial distribution of the nanoparticles, their size, number density and location relative to each other and grain boundaries to be determined, which are essential to understand the flux-pinning characteristics of these materials.

Contrast-enhanced voiding urosonography phantom study: intravenous iodinated and gadolinium-based contrast agents may cause false-negative results in assessment of vesicoureteral reflux in children

International Nuclear Information System (INIS)

Veldhoen, Simon; Sauer, Alexander; Gassenmaier, Tobias; Petritsch, Bernhard; Herz, Stefan; Blanke, Philipp; Bley, Thorsten A.; Wirth, Clemens; Derlin, Thorsten

2015-01-01

Contrast-enhanced voiding urosonography (ce-VUS) is commonly requested simultaneously to other diagnostic imaging necessitating intravenous contrast agents. To date there is limited knowldedge about intravesical interactions between different types of contrast agents. To assess the effect of excreted intravenous iodinated and gadolinium-based contrast agents on the intravesical distribution of ultrasound contrast within contrast-enhanced voiding urosonography. Iodinated (iomeprol, iopamidol) and gadolinium-based (gadoterate meglumine) contrast agents were diluted to bladder concentration and injected into balloons filled with saline solution. CT scans were performed to assess the contrast distribution in these phantoms. Regions of interest were placed at the top and bottom side of each balloon and Hounsfield units (HU) were measured. Three other balloons were filled with saline solution and contrast media likewise. The ultrasound contrast agent sulphur hexafluoride was added and its distribution was assessed using sonography. MDCT scans showed a separation of two liquid layers in all bladder phantoms with the contrast layers located at the bottom and the saline solution at the top. Significant differences of the HU measurements at the top and bottom side were observed (P < 0.001-0.007). Following injection of ultrasound contrast agent, US showed its distribution exclusively among the saline solution. False-negative results of contrast-enhanced voiding urosonography may occur if it is performed shortly after imaging procedures requiring intravenous contrast. (orig.)

Contrasting cue-density effects in causal and prediction judgments.

Science.gov (United States)

Vadillo, Miguel A; Musca, Serban C; Blanco, Fernando; Matute, Helena

2011-02-01

Many theories of contingency learning assume (either explicitly or implicitly) that predicting whether an outcome will occur should be easier than making a causal judgment. Previous research suggests that outcome predictions would depart from normative standards less often than causal judgments, which is consistent with the idea that the latter are based on more numerous and complex processes. However, only indirect evidence exists for this view. The experiment presented here specifically addresses this issue by allowing for a fair comparison of causal judgments and outcome predictions, both collected at the same stage with identical rating scales. Cue density, a parameter known to affect judgments, is manipulated in a contingency learning paradigm. The results show that, if anything, the cue-density bias is stronger in outcome predictions than in causal judgments. These results contradict key assumptions of many influential theories of contingency learning.

Using regional bird density distribution models to evaluate protected area networks and inform conservation planning

Science.gov (United States)

John D. Alexander; Jaime L. Stephens; Sam Veloz; Leo Salas; Josée S. Rousseau; C. John Ralph; Daniel A. Sarr

2017-01-01

As data about populations of indicator species become available, proactive strategies that improve representation of biological diversity within protected area networks should consider finer-scaled evaluations, especially in regions identified as important through course-scale analyses. We use density distribution models derived from a robust regional bird...

Properties of conventional contrast media

International Nuclear Information System (INIS)

Muetzel, W.

1981-01-01

A comprehensive overview is given of the properties of contrast media currently used in computed tomography (CT). The chemical structure of the compounds and the physicochemical properties derived therefrom are described. Emphasis is placed on the importance of the physicochemical properties of contrast media for tolerance and the pharmacokinetic behavior of compounds in the body. An outline is given of the basic ideas governing rational use of contrast media in CT, which result from complex, time-dependent distribution of contrast media in different tissue spaces. (Auth.)

Radial power density distribution of MOX fuel rods in the IFA-651

Energy Technology Data Exchange (ETDEWEB)

Lee, Byung Ho; Koo, Yang Hyun; Joo, Hyung Kook; Cheon, Jin Sik; Oh, Je Yong; Sohn, Dong Seong [Korea Atomic Energy Research Institute, Taejeon (Korea)

2002-04-01

Two MOX fuel rods, which were fabricated in the Paul Scherrer Institute (PSI), Switzerland in cooperation with Korea Atomic Energy Research Institute, have been irradiated in the HBWR from June, 2000 in the framework of OECD-HRP together with a reference MOX fuel rod supplied by the BNFL. Since fuel temperature, which is influenced by radial power distribution, is basic in analyzing fuel behavior, it is required to consider radial power distribution in the HBWR. A subroutine FACTOR{sub H}BWR that calculates radial power density distribution for three MOX fuel rods has been developed based on neutron physics results and DEPRESS program. The developed subroutine FACTOR{sub H}BWR gives good agreement with the physics calculation except slight under-prediction at the outer part of the pellet above the burnup of 20 MWd/kgHM. The subroutine will be incorporated into a computer code COSMOS and used to analyze the in-reactor behavior of the three MOX fuel rods during the Halden irradiation test. 24 figs., 4 tabs. (Author)

Conservation implications of brown hyaena (Parahyaena brunnea population densities and distribution across landscapes in Botswana

Directory of Open Access Journals (Sweden)

Christiaan W. Winterbach

2017-05-01

Full Text Available The brown hyaena (Parahyaena brunnea is endemic to southern Africa. The largest population of this near-threatened species occurs in Botswana, but limited data were available to assess distribution and density. Our objectives were to use a stratified approach to collate available data and to collect more data to assess brown hyaena distribution and density across land uses in Botswana. We conducted surveys using track counts, camera traps and questionnaires and collated our results and available data to estimate the brown hyaena population based on the stratification of Botswana for large carnivores. Brown hyaenas occur over 533 050 km² (92% of Botswana. Our density estimates ranged from 0 brown hyaenas/100 km² in strata of northern Botswana to 2.94 (2.16–3.71 brown hyaenas/100 km² in the southern stratum of the Central Kalahari Game Reserve. We made assumptions regarding densities in strata that lacked data, using the best references available. We estimated the brown hyaena population in Botswana as 4642 (3133–5993 animals, with 6.8% of the population in the Northern Conservation Zone, 73.1% in the Southern Conservation Zone, 2.0% in the smaller conservation zones and 18.1% in the agricultural zones. The similar densities of brown hyaenas in the Central Kalahari Game Reserve and the Ghanzi farms highlight the potential of agricultural areas in Botswana to conserve this species. The conservation of brown hyaenas in the agricultural landscape of Botswana is critical for the long-term conservation of the species; these areas provide important links between populations in South Africa, Namibia and Zimbabwe. Conservation implications: Botswana contains the core of the brown hyaena population in southern Africa, and conflict mitigation on agricultural land is crucial to maintaining connectivity among the range countries.

Display characterization by eye: contrast ratio and discrimination throughout the grayscale

Science.gov (United States)

Gille, Jennifer; Arend, Larry; Larimer, James O.

2004-06-01

We have measured the ability of observers to estimate the contrast ratio (maximum white luminance / minimum black or gray) of various displays and to assess luminous discrimination over the tonescale of the display. This was done using only the computer itself and easily-distributed devices such as neutral density filters. The ultimate goal of this work is to see how much of the characterization of a display can be performed by the ordinary user in situ, in a manner that takes advantage of the unique abilities of the human visual system and measures visually important aspects of the display. We discuss the relationship among contrast ratio, tone scale, display transfer function and room lighting. These results may contribute to the development of applications that allow optimization of displays for the situated viewer / display system without instrumentation and without indirect inferences from laboratory to workplace.

Spherical electron momentum density distribution and Bayesian analysis of the renormalization parameter in Li metal

International Nuclear Information System (INIS)

Dobrzynski, Ludwik

2000-01-01

The Bayesian analysis of the spherical part of the electron momentum density was carried out with the goal of finding the best estimation of the spherically averaged renormalization parameter, z , quantifying the discontinuity in the electron momentum density distribution in Li metal. Three models parametrizing the electron momentum density were considered and nuisance parameters integrated out. The analysis show that the most likely value of z following from the data of Sakurai et al is in the range of 0.45-0.50, while 0.55 is obtained for the data of Schuelke et al . In the maximum entropy reconstruction of the spherical part of the electron momentum density three different algorithms were used. It is shown that all of them produce essentially the same results. The paper shows that the accurate Compton scattering experiments are capable of bringing information on this very important Fermiological aspect of the electron gas in a metal. (author)

Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

KAUST Repository

Kalaroni, S.

2016-04-12

A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the Singular Evolutive Interpolated Kalman (SEIK) filter, the ensemble variant of the Singular Evolutive Extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in-situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depth-distributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α.

Data assimilation of depth-distributed satellite chlorophyll-α in two Mediterranean contrasting sites

KAUST Repository

Kalaroni, S.; Tsiaras, K.; Petihakis, G.; Hoteit, Ibrahim; Economou-Amilli, A.; G.Triantafyllou

2016-01-01

A new approach for processing the remote sensing chlorophyll-α (Chl-α) before assimilating into an ecosystem model is applied in two contrasting, regarding productivity and nutrients availability, Mediterranean sites: the DYFAMED and POSEIDON E1-M3A fixed point open ocean observatories. The new approach derives optically weighted depth-distributed Chl-α profiles from satellite data based on the model simulated Chl-α vertical distribution and light attenuation coefficient. We use the 1D version of the operational ecological 3D POSEIDON model, based on the European Regional Seas Ecosystem Model (ERSEM). The required hydrodynamic properties are obtained (off-line) from the POSEIDON operational 3D hydrodynamic Mediterranean basin scale model. The data assimilation scheme is the Singular Evolutive Interpolated Kalman (SEIK) filter, the ensemble variant of the Singular Evolutive Extended Kalman (SEEK) filter. The performance of the proposed assimilation approach was evaluated against the Chl-α satellite data and the seasonal averages of available in-situ data for nitrate, phosphate and Chl-α. An improvement of the model simulated near-surface and subsurface maximum Chl-α concentrations is obtained, especially at the DYFAMED site. Model nitrate is improved with assimilation, particularly with the new approach assimilating depth-distributed Chl-α, while model phosphate is slightly worse after assimilation. Additional sensitivity experiments were performed, showing a better performance of the new approach under different scenarios of model Chl-α deviation from pseudo-observations of surface Chl-α.

MRI contrast agent concentration and tumor interstitial fluid pressure.

Science.gov (United States)

Liu, L J; Schlesinger, M

2016-10-07

The present work describes the relationship between tumor interstitial fluid pressure (TIFP) and the concentration of contrast agent for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). We predict the spatial distribution of TIFP based on that of contrast agent concentration. We also discuss the cases for estimating tumor interstitial volume fraction (void fraction or porosity of porous medium), ve, and contrast volume transfer constant, K(trans), by measuring the ratio of contrast agent concentration in tissue to that in plasma. A linear fluid velocity distribution may reflect a quadratic function of TIFP distribution and lead to a practical method for TIFP estimation. To calculate TIFP, the parameters or variables should preferably be measured along the direction of the linear fluid velocity (this is in the same direction as the gray value distribution of the image, which is also linear). This method may simplify the calculation for estimating TIFP. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Plasma Diagnostics in High Density Reactors

International Nuclear Information System (INIS)

Daltrini, A. M.; Moshkalyov, S.; Monteiro, M. J. R.; Machida, M.; Kostryukov, A.; Besseler, E.; Biasotto, C.; Diniz, J. A.

2006-01-01

Langmuir electric probes and optical emission spectroscopy diagnostics were developed for applications in high density plasmas. These diagnostics were employed in two plasma sources: an electron cyclotron resonance (ECR) plasma and an RF driven inductively coupled plasma (ICP) plasma. Langmuir probes were tested using a number of probing dimensions, probe tip materials, circuits for probe bias and filters. Then, the results were compared with the optical spectroscopy measurements. With these diagnostics, analyses of various plasma processes were performed in both reactors. For example, it has been shown that species like NH radicals generated in gas phase can have critical impact on films deposited by ECR plasmas. In the ICP source, plasmas in atomic and molecular gases were shown to have different spatial distributions, likely due to nonlocal electron heating. The low-to-high density transitions in the ICP plasma were also studied. The role of metastables is shown to be significant in Ar plasmas, in contrast to plasmas with additions of molecular gases

An analytical solution for stationary distribution of photon density in traveling-wave and reflective SOAs

International Nuclear Information System (INIS)

Totović, A R; Crnjanski, J V; Krstić, M M; Gvozdić, D M

2014-01-01

In this paper, we analyze two semiconductor optical amplifier (SOA) structures, traveling-wave and reflective, with the active region made of the bulk material. The model is based on the stationary traveling-wave equations for forward and backward propagating photon densities of the signal and the amplified spontaneous emission, along with the stationary carrier rate equation. We start by introducing linear approximation of the carrier density spatial distribution, which enables us to find solutions for the photon densities in a closed analytical form. An analytical approach ensures a low computational resource occupation and an easy analysis of the parameters influencing the SOA’s response. The comparison of the analytical and numerical results shows high agreement for a wide range of the input optical powers and bias currents. (paper)

The virialization density of peaks with general density profiles under spherical collapse

OpenAIRE

Rubin, Douglas; Loeb, Abraham

2013-01-01

We calculate the non-linear virialization density, $\\Delta_c$, of halos under spherical collapse from peaks with an arbitrary initial and final density profile. This is in contrast to the standard calculation of $\\Delta_c$ which assumes top-hat profiles. Given our formalism, the non-linear halo density can be calculated once the shape of the initial peak's density profile and the shape of the virialized halo's profile are provided. We solve for $\\Delta_c$ for halos in an Einstein de-Sitter an...

Current distribution and enhancement of the engineering critical current density in multifilament Bi-2223 tapes

DEFF Research Database (Denmark)

Wang, W.G.; Jensen, M.B.; Kindl, B.

2000-01-01

The spatial distribution of the critical current density (Jc) and engineering critical current density (Je) along the tape width direction was studied by a cutting technique on Bi-2223 multifilamentary tapes. In general, an increase of Jc towards the centre of the tape was measured. We attribute...... microstructure with a great amount of secondary phases. Local variation of Jc was measured within the centre segment of the tape. This indicates the influence of other factors on Jc, such as filament shape, connectivity of the filaments, and sausaging. Enhancement of Je has been pursued in which average Je of 12...

Self-similar structure in the distribution and density of the partition function zeros

International Nuclear Information System (INIS)

Huang, M.-C.; Luo, Y.-P.; Liaw, T.-M.

2003-01-01

Based on the knowledge of the partition function zeros for the cell-decorated triangular Ising model, we analyze the similar structures contained in the distribution pattern and density function of the zeros. The two own the same symmetries, and the arising of the similar structure in the road toward the infinite decoration-level is exhibited explicitly. The distinct features of the formation of the self-similar structure revealed from this model may be quite general

An x-ray backlit Talbot-Lau deflectometer for high-energy-density electron density diagnostics

Science.gov (United States)

Valdivia, M. P.; Stutman, D.; Stoeckl, C.; Theobald, W.; Mileham, C.; Begishev, I. A.; Bromage, J.; Regan, S. P.

2016-02-01

X-ray phase-contrast techniques can measure electron density gradients in high-energy-density plasmas through refraction induced phase shifts. An 8 keV Talbot-Lau interferometer consisting of free standing ultrathin gratings was deployed at an ultra-short, high-intensity laser system using K-shell emission from a 1-30 J, 8 ps laser pulse focused on thin Cu foil targets. Grating survival was demonstrated for 30 J, 8 ps laser pulses. The first x-ray deflectometry images obtained under laser backlighting showed up to 25% image contrast and thus enabled detection of electron areal density gradients with a maximum value of 8.1 ± 0.5 × 1023 cm-3 in a low-Z millimeter sized sample. An electron density profile was obtained from refraction measurements with an error of x-ray source-size, similar to conventional radiography.

Micro-Scale Distribution of CA4+ in Ex Vivo Human Articular Cartilage Detected with Contrast-Enhanced Micro-Computed Tomography Imaging

Science.gov (United States)

Karhula, Sakari S.; Finnilä, Mikko A.; Freedman, Jonathan D.; Kauppinen, Sami; Valkealahti, Maarit; Lehenkari, Petri; Pritzker, Kenneth P. H.; Nieminen, Heikki J.; Snyder, Brian D.; Grinstaff, Mark W.; Saarakkala, Simo

2017-08-01

Contrast-enhanced micro-computed tomography (CEµCT) with cationic and anionic contrast agents reveals glycosaminoglycan (GAG) content and distribution in articular cartilage (AC). The advantage of using cationic stains (e.g. CA4+) compared to anionic stains (e.g. Hexabrix®), is that it distributes proportionally with GAGs, while anionic stain distribution in AC is inversely proportional to the GAG content. To date, studies using cationic stains have been conducted with sufficient resolution to study its distributions on the macro-scale, but with insufficient resolution to study its distributions on the micro-scale. Therefore, it is not known whether the cationic contrast agents accumulate in extra/pericellular matrix and if they interact with chondrocytes. The insufficient resolution has also prevented to answer the question whether CA4+ accumulation in chondrons could lead to an erroneous quantification of GAG distribution with low-resolution µCT setups. In this study, we use high-resolution µCT to investigate whether CA4+ accumulates in chondrocytes, and further, to determine whether it affects the low-resolution ex vivo µCT studies of CA4+ stained human AC with varying degree of osteoarthritis. Human osteochondral samples were immersed in three different concentrations of CA4+ (3 mgI/ml, 6mgI/ml, and 24 mgI/ml) and imaged with high-resolution µCT at several timepoints. Different uptake diffusion profiles of CA4+ were observed between the segmented chondrons and the rest of the tissue. While the X-ray -detected CA4+ concentration in chondrons was greater than in the rest of the AC, its contribution to the uptake into the whole tissue was negligible and in line with macro-scale GAG content detected from histology. The efficient uptake of CA4+ into chondrons and surrounding territorial matrix can be explained by the micro-scale distribution of GAG content. CA4+ uptake in chondrons occurred regardless of the progression stage of osteoarthritis in the samples

Micro-Scale Distribution of CA4+ in Ex vivo Human Articular Cartilage Detected with Contrast-Enhanced Micro-Computed Tomography Imaging

Directory of Open Access Journals (Sweden)

Sakari S. Karhula

2017-08-01

Full Text Available Contrast-enhanced micro-computed tomography (CEμCT with cationic and anionic contrast agents reveals glycosaminoglycan (GAG content and distribution in articular cartilage (AC. The advantage of using cationic stains (e.g., CA4+ compared to anionic stains (e.g., Hexabrix®, is that it distributes proportionally with GAGs, while anionic stain distribution in AC is inversely proportional to the GAG content. To date, studies using cationic stains have been conducted with sufficient resolution to study its distributions on the macro-scale, but with insufficient resolution to study its distributions on the micro-scale. Therefore, it is not known whether the cationic contrast agents accumulate in extra/pericellular matrix and if they interact with chondrocytes. The insufficient resolution has also prevented to answer the question whether CA4+ accumulation in chondrons could lead to an erroneous quantification of GAG distribution with low-resolution μCT setups. In this study, we use high-resolution μCT to investigate whether CA4+ accumulates in chondrocytes, and further, to determine whether it affects the low-resolution ex vivo μCT studies of CA4+ stained human AC with varying degree of osteoarthritis. Human osteochondral samples were immersed in three different concentrations of CA4+ (3 mgI/ml, 6 mgI/ml, and 24 mgI/ml and imaged with high-resolution μCT at several timepoints. Different uptake diffusion profiles of CA4+ were observed between the segmented chondrons and the rest of the tissue. While the X-ray -detected CA4+ concentration in chondrons was greater than in the rest of the AC, its contribution to the uptake into the whole tissue was negligible and in line with macro-scale GAG content detected from histology. The efficient uptake of CA4+ into chondrons and surrounding territorial matrix can be explained by the micro-scale distribution of GAG content. CA4+ uptake in chondrons occurred regardless of the progression stage of osteoarthritis

Analytical results for the time-dependent current density distribution of expanding ultracold gases after a sudden change of the confining potential

Science.gov (United States)

Boumaza, R.; Bencheikh, K.

2017-12-01

Using the so-called operator product expansion to lowest order, we extend the work in Campbell et al (2015 Phys. Rev. Lett 114 125302) by deriving a simple analytical expression for the long-time asymptotic one-body reduced density matrix during free expansion for a one-dimensional system of bosons with large atom number interacting through a repulsive delta potential initially confined by a potential well. This density matrix allows direct access to the momentum distribution and also to the mass current density. For initially confining power-law potentials we give explicit expressions, in the limits of very weak and very strong interaction, for the current density distributions during the free expansion. In the second part of the work we consider the expansion of ultracold gas from a confining harmonic trap to another harmonic trap with a different frequency. For the case of a quantum impenetrable gas of bosons (a Tonks-Girardeau gas) with a given atom number, we present an exact analytical expression for the mass current distribution (mass transport) after release from one harmonic trap to another harmonic trap. It is shown that, for a harmonically quenched Tonks-Girardeau gas, the current distribution is a suitable collective observable and under the weak quench regime, it exhibits oscillations at the same frequencies as those recently predicted for the peak momentum distribution in the breathing mode. The analysis is extended to other possible quenched systems.

Examination of the constancy of the medium optical density of conventional chest radiographs

International Nuclear Information System (INIS)

Stieve, F.E.; Rupp, N.; Niederhofer, F.; Gfirtner, H.

2002-01-01

Purpose: To determine whether the medium optical density of conventional chest radiographs is constant. Materials and Methods: 47 PA chest radiographs were digitized to measure the optical density and its dynamic range of normal and pathologically altered lungs. Results: For constant exposure factors and a correctly positioned region of interest, the medium optical density deviates only minimal despite differences in AP chest diameter, entry dose and dynamic range, and is largely independent of the pathologic pulmonary findings. Conclusion: Digitization of the radiograph enables the determination of the physical parameters used to operate the imaging system, such as medium optical density, image contrast, image latitude and density distribution, in accordance to the guidelines of the German Medical Association. If the region of interest encompasses the clinically relevant region of the lung, the measured value of the optical density corresponds with only minor variation to the average value of the entire lung region. (orig.) [de

Quantitative comparison of cities : Distribution of street and building types based on density and centrality measures

NARCIS (Netherlands)

Berghauser Pont, M.Y.; Stavroulaki, G.; Lopes Gil, J.A.; Marcus, L.; Serra, M; Hausleitner, B.; Olsson, J.; Abshirini, E.; Dhanani, A.

2017-01-01

It has been argued that different urban configurations-planned vs. organic, treelike vs. grid like-perform differently when it comes to the intensity and distribution of pedestrian flows, built density and land uses. However, definitions of urban configurations are often rather abstract,

A coupled diffusion-fluid pressure model to predict cell density distribution for cells encapsulated in a porous hydrogel scaffold under mechanical loading.

Science.gov (United States)

Zhao, Feihu; Vaughan, Ted J; Mc Garrigle, Myles J; McNamara, Laoise M

2017-10-01

Tissue formation within tissue engineering (TE) scaffolds is preceded by growth of the cells throughout the scaffold volume and attachment of cells to the scaffold substrate. It is known that mechanical stimulation, in the form of fluid perfusion or mechanical strain, enhances cell differentiation and overall tissue formation. However, due to the complex multi-physics environment of cells within TE scaffolds, cell transport under mechanical stimulation is not fully understood. Therefore, in this study, we have developed a coupled multiphysics model to predict cell density distribution in a TE scaffold. In this model, cell transport is modelled as a thermal conduction process, which is driven by the pore fluid pressure under applied loading. As a case study, the model is investigated to predict the cell density patterns of pre-osteoblasts MC3T3-e1 cells under a range of different loading regimes, to obtain an understanding of desirable mechanical stimulation that will enhance cell density distribution within TE scaffolds. The results of this study have demonstrated that fluid perfusion can result in a higher cell density in the scaffold region closed to the outlet, while cell density distribution under mechanical compression was similar with static condition. More importantly, the study provides a novel computational approach to predict cell distribution in TE scaffolds under mechanical loading. Copyright © 2017 Elsevier Ltd. All rights reserved.

The molecular electron density distribution meeting place of X-ray diffraction and quantum chemistry intermediate - between theory and experiment

NARCIS (Netherlands)

Feil, D.; Feil, Dirk

1992-01-01

Quantum chemistry and the concepts used daily in chemistry are increasingly growing apart. Among the concepts that are able to bridge the gap between theory and experimental practice, electron density distribution has an important place. The study of this distribution has led to new developments in

Contrasting the surface ocean distribution of bromoform and methyl iodide; implications for boundary layer physics, chemistry and climate

Energy Technology Data Exchange (ETDEWEB)

Palmer, C J, E-mail: carl.j.palmer@gmail.co [Department of Oceanography, University of Cape Town, 7701 (South Africa)

2010-08-15

Bromoform and methyl iodide are both methane-like hydrocarbons with a halogen atom replacing one or more of the hydrogen atoms. Both of these compounds occur naturally in the environment as a result of their production from seaweed and kelp. They are of interest to climate science as a result of their catalytic destruction of boundary layer ozone (a potent greenhouse gas) and, specifically for methyl iodide, the proposed role in the formation of new cloud condensation nuclei with implications for climate. In this paper, the currently available data on the distribution of bromoform and methyl iodide are analysed and contrasted to show that the concentrations of bromoform and methyl iodide do not correlate, that, in contrast to bromoform, the parameterization of sea surface methyl iodide concentrations demands only the sea surface temperature, and that the pelagic distribution of methyl iodide appears to follow the solar zenith angle. These three observations together suggest that, while the pelagic source of bromoform is mostly biogenic, the source of methyl iodide is photochemical. This has implications for the understanding of planetary boundary layer chemistry and potential organohalogen mediated feedbacks to climate.

Contrasting the surface ocean distribution of bromoform and methyl iodide; implications for boundary layer physics, chemistry and climate

International Nuclear Information System (INIS)

Palmer, C J

2010-01-01

Bromoform and methyl iodide are both methane-like hydrocarbons with a halogen atom replacing one or more of the hydrogen atoms. Both of these compounds occur naturally in the environment as a result of their production from seaweed and kelp. They are of interest to climate science as a result of their catalytic destruction of boundary layer ozone (a potent greenhouse gas) and, specifically for methyl iodide, the proposed role in the formation of new cloud condensation nuclei with implications for climate. In this paper, the currently available data on the distribution of bromoform and methyl iodide are analysed and contrasted to show that the concentrations of bromoform and methyl iodide do not correlate, that, in contrast to bromoform, the parameterization of sea surface methyl iodide concentrations demands only the sea surface temperature, and that the pelagic distribution of methyl iodide appears to follow the solar zenith angle. These three observations together suggest that, while the pelagic source of bromoform is mostly biogenic, the source of methyl iodide is photochemical. This has implications for the understanding of planetary boundary layer chemistry and potential organohalogen mediated feedbacks to climate.

Preliminary research on dual-energy X-ray phase-contrast imaging

Science.gov (United States)

Han, Hua-Jie; Wang, Sheng-Hao; Gao, Kun; Wang, Zhi-Li; Zhang, Can; Yang, Meng; Zhang, Kai; Zhu, Pei-Ping

2016-04-01

Dual-energy X-ray absorptiometry (DEXA) has been widely applied to measure the bone mineral density (BMD) and soft-tissue composition of the human body. However, the use of DEXA is greatly limited for low-Z materials such as soft tissues due to their weak absorption, while X-ray phase-contrast imaging (XPCI) shows significantly improved contrast in comparison with the conventional standard absorption-based X-ray imaging for soft tissues. In this paper, we propose a novel X-ray phase-contrast method to measure the area density of low-Z materials, including a single-energy method and a dual-energy method. The single-energy method is for the area density calculation of one low-Z material, while the dual-energy method aims to calculate the area densities of two low-Z materials simultaneously. Comparing the experimental and simulation results with the theoretical ones, the new method proves to have the potential to replace DEXA in area density measurement. The new method sets the prerequisites for a future precise and low-dose area density calculation method for low-Z materials. Supported by Major State Basic Research Development Program (2012CB825800), Science Fund for Creative Research Groups (11321503) and National Natural Science Foundation of China (11179004, 10979055, 11205189, 11205157)

3D CT cerebral angiography technique using a 320-detector machine with a time–density curve and low contrast medium volume: Comparison with fixed time delay technique

International Nuclear Information System (INIS)

Das, K.; Biswas, S.; Roughley, S.; Bhojak, M.; Niven, S.

2014-01-01

Aim: To describe a cerebral computed tomography angiography (CTA) technique using a 320-detector CT machine and a small contrast medium volume (35 ml, 15 ml for test bolus). Also, to compare the quality of these images with that of the images acquired using a larger contrast medium volume (90 or 120 ml) and a fixed time delay (FTD) of 18 s using a 16-detector CT machine. Materials and methods: Cerebral CTA images were acquired using a 320-detector machine by synchronizing the scanning time with the time of peak enhancement as determined from the time–density curve (TDC) using a test bolus dose. The quality of CTA images acquired using this technique was compared with that obtained using a FTD of 18 s (by 16-detector CT), retrospectively. Average densities in four different intracranial arteries, overall opacification of arteries, and the degree of venous contamination were graded and compared. Results: Thirty-eight patients were scanned using the TDC technique and 40 patients using the FTD technique. The arterial densities achieved by the TDC technique were higher (significant for supraclinoid and basilar arteries, p < 0.05). The proportion of images deemed as having “good” arterial opacification was 95% for TDC and 90% for FTD. The degree of venous contamination was significantly higher in images produced by the FTD technique (p < 0.001%). Conclusion: Good diagnostic quality CTA images with significant reduction of venous contamination can be achieved with a low contrast medium dose using a 320-detector machine by coupling the time of data acquisition with the time of peak enhancement

Direct calculation of unambiguous electron-density distributions of Langmuir-Blodgett films normal to the membrane plane

International Nuclear Information System (INIS)

Frieling, M. von; Bradaczek, H.

1990-01-01

In regard to X-ray diffraction, Langmuir-Blodgett (LB) films consisting of lipid bilayers represent a 'one-dimensional crystal' with a very small number of unit cells in the direction of stacking. Such bounded systems yield X-ray diffraction diagrams which, in certain respects, contain more information than those of the conventional effectively infinite single crystals. This additional information consists of the profiles of the broadened reflections and their dislocation from the reciprocal-lattice points. These profiles are specific for each different structure and hence enable the direct calculation of unambiguous electron-density distributions from a single set of intensity data. At first, the Q function (the generalized Patterson function), i.e. the distance statistics of the structure sought after is calculated from the intensity data. Thereafter, the unambiguous convolution square root of the Q function must be determined, which is identical to the unknown electron-density distribution. For this purpose two mathematically completely different methods were established and compared. They were applied to diffraction patterns of Langmuir-Blodgett films of simple synthetic lipids with characteristic molecular subunits and showed identical results within the experimental resolution. This verifies the structures and the methods to calculate them. Furthermore, all features of the simple structures were compatible with the expectations. All one-dimensional electron-density distributions showed the common features of lipid bilayers. The characteristic molecular subunits can be recognized and reveal some interesting details. In general, they yield information about orientation, conformation and localization of molecular subunits and membrane components. (orig.)

Temporal and spatial effects of ablation plume on number density distribution of droplets in an aerosol measured by laser-induced breakdown

International Nuclear Information System (INIS)

Yashiro, H.; Kakehata, M.

2013-01-01

We proposed and experimentally demonstrated a novel method of evaluating the number density of droplets in an aerosol by laser-induced breakdown. The number density of droplets is evaluated from the volume in which the laser intensity exceeds the breakdown threshold intensity for droplets, and the number of droplets in this volume, which is evaluated by the experimentally observed breakdown probability. This measurement method requires a large number of laser shots for not only precise measurement but also highly temporally and spatially resolved density distribution in aerosol. Laser ablation plumes ejected from liquid droplets generated by breakdown disturb the density around the measurement points. Therefore, the recovery time of the density determines the maximum repetition rate of the probe laser irradiating a fixed point. The expansion range of the ablation plume determines the minimum distance at which the measurement points are unaffected by a neighboring breakdown when multiple laser beams are simultaneously irradiated. These laser irradiation procedures enable the measurement of the number density distribution of droplets in an aerosol at a large number of points within a short measurement time.

Temporal and spatial effects of ablation plume on number density distribution of droplets in an aerosol measured by laser-induced breakdown

Energy Technology Data Exchange (ETDEWEB)

Yashiro, H.; Kakehata, M. [Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

2013-05-07

We proposed and experimentally demonstrated a novel method of evaluating the number density of droplets in an aerosol by laser-induced breakdown. The number density of droplets is evaluated from the volume in which the laser intensity exceeds the breakdown threshold intensity for droplets, and the number of droplets in this volume, which is evaluated by the experimentally observed breakdown probability. This measurement method requires a large number of laser shots for not only precise measurement but also highly temporally and spatially resolved density distribution in aerosol. Laser ablation plumes ejected from liquid droplets generated by breakdown disturb the density around the measurement points. Therefore, the recovery time of the density determines the maximum repetition rate of the probe laser irradiating a fixed point. The expansion range of the ablation plume determines the minimum distance at which the measurement points are unaffected by a neighboring breakdown when multiple laser beams are simultaneously irradiated. These laser irradiation procedures enable the measurement of the number density distribution of droplets in an aerosol at a large number of points within a short measurement time.

Density and spatial distribution of Parkia biglobosa pattern in Benin under climate change

Directory of Open Access Journals (Sweden)

Fafunkè Titilayo Dotchamou

2016-06-01

Full Text Available Parkia biglobosa is an indigenous species which, traditionally contributes to the resilience of the agricultural production system in terms of food security, source of income, poverty reduction and ecosystem stability. Therefore, it is important to improve knowledge on its density, current and future spatial distribution. The main objective of this study is to evaluate the tree density, the climate change effects on the spatial distribution of the species in the future for better conservation. The modeling of the current and future geographical distribution of the species is based on the principle of Maximum Entropy (MaxEnt on a total of 286 occurrence points from field work and Global Biodiversity Information Facility GBIF-Data Portal-(www.gbif.org. Two climatic models (HadGEM2_ES and Csiro_mk3_6_0 have been used under two scenarios RCP 2.6 and RCP 8.5 for the projection of the species distribution at the horizon 2050. The correlation analyses and Jackknife test have helped to identify seven variables which are less correlated (r < 0.80 with highest modeling participation. The soil, annual precipitation (BIO12 and temperature (diurnal average Deviation are the variables which have mostly contributed to performance of the models. Currently, 53% of national territory, spread from north to south is very suitable to the cultivation of P. biglobosa. The scenarios have predicted at the horizon 2050, a loss of the habitats which are currently very suitable for the cultivation and conservation of P. biglobosa, to the benefit of moderate and weak habitats. 51% and 57% are the highest proportion of this lost which will be registered with HadGEM2_ES model under two scenarios. These results revealed that the suitable habitat of the species is threatened by climate change in Benin. In order to limit damage such as decreased productivity, extinction of species, some appropriate solutions must be found.

Density distribution of currents induced inside the brain in the head part of the human model exposed to power frequency electric field

Energy Technology Data Exchange (ETDEWEB)

Chiba, Atsuo [Yongo National Collage of Technology (Japan); Isaka, Katsuo [University of Tokushima (Japan)

1999-07-01

The health effect of the weak current induced in the human body as a result of the interaction between human body and power frequency electric fields has been investigated. However, the current density inside the head part tissues of the human body exposed to the electric fields has rarely been discussed. In this paper, the finite element method is applied to the analysis of the current density distribution of the head part composed of scalp, skull, cerebrospinal liquid and brain tissues. The basic characteristics of the current density distributions of the brain in the asymmetrical human model have been made clear. (author)

Abnormal myocardial capillary density in apical hypertrophic cardiomyopathy can be assessed by myocardial contrast echocardiography

International Nuclear Information System (INIS)

Moon, Jeonggeun; Cho, In-Jeong; Shim, Chi-Young; Ha, Jong-Won; Jang, Yangsoo; Chung, Namsik; Rim, Se-Joong

2010-01-01

Myocardial ischemia and dysfunction can occur in hypertrophic cardiomyopathy (HCM) because of the high muscle-to-blood ratio, even without significant coronary artery disease. Microbubbles reside only in the intravascular space and myocardial video-intensity during systole results mostly from microbubbles within capillaries. The hypothesis explored in the present study was that an abnormal capillary density in apical HCM (ApHCM) can be demonstrated using myocardial contrast echocardiography (MCE). The 56 patients were investigated (31 males, age 58±9 years; 33 ApHCM, 9 hypertensive left ventricular hypertrophy [LVH], 14 controls). MCE was performed with low-mechanical-index power modulation imaging. Tissue Doppler imaging to assess myocardial contractile function was obtained at the mitral annulus (S'), and 99m Tc-MIBI single photon emission computed tomography (SPECT) was also performed. All ApHCM patients exhibited perfusion defects at the hypertrophied segments in the systolic phase during MCE, whereas SPECT showed normal or rather increased perfusion at those sites. The cyclic variation of video-intensity was exaggerated in ApHCM when compared with the LVH or control group (% of [systolic video-intensity]/[diastolic video-intensity]: 33.0±12.3%, 88.3±19.2% and 79.4±13.9%, respectively [P<0.05]). Concurrently, MCE cyclic variation and perfusion defect size were related to decreased S' (P<0.05 for all). A perfusion defect at the hypertrophied segment, representing abnormal myocardial capillary density, was observed in ApHCM patients during MCE. The extent of MCE cyclic variation and the perfusion defect size both correlate with decreased myocardial contractile property in ApHCM. (author)

Contrasting water strategies of two Mediterranean shrubs of limited distribution: uncertain future under a drier climate.

Science.gov (United States)

Lázaro-Nogal, Ana; Forner, Alicia; Traveset, Anna; Valladares, Fernando

2013-12-01

Plants have evolved different strategies to cope with drought, involving alternative ecophysiologies and different levels of plasticity. These strategies are critical for species of limited distribution, which are especially vulnerable to the current rates of rapid environmental change. The aim of this study was to assess the water strategy of two species with limited distribution, Cneorum tricoccon L. and Rhamnus ludovici-salvatoris Chodat., and evaluate their interpopulation variability along an aridity gradient to estimate their vulnerability to a drier climate. We measured different ecophysiological traits influenced by drought--stomatal conductance, maximum photochemical efficiency of photosynthesis II, carbon isotope ratio and chlorophyll concentration--in two climatically contrasting years, before and during summer drought. Both species were vulnerable to drought at the aridity limit of the gradient, but showed contrasting water strategies: while C. tricoccon was consistent in its water conservation strategy across the aridity gradient, R. ludovici-salvatoris was not, displaying higher and more variable stomatal conductances and being able to increase water-use efficiency at the most xeric sites. Changes in length and intensity of drought events may favor one species' strategy to the detriment of the other: C. tricoccon is more vulnerable to chronic and prolonged droughts, whereas short but acute droughts might have a stronger effect on R. ludovici-salvatoris. In those communities where these two species coexist, such different strategies might lead to changes in community structure under climate change scenarios, with unknown cascade effects on ecosystem functioning.

Measurements of the initial density distribution of gas puff liners by using Rayleigh scattering

Energy Technology Data Exchange (ETDEWEB)

Kalinin, Yu G; Shashkov, A Yu [Kurchatov Institute, Moscow (Russian Federation)

1997-12-31

Rayleigh scattering of a laser beam in a gas jet is proposed for the measurements of initial density distribution of gas-puff liners. The scattering method has several advantages when compared with interferometry. In particular, it provides information on the local gas density, it is more sensitive, and the output data can be absolutely calibrated. Theoretical background of the method is briefly discussed in the paper and the optical setup used in real experiments is described. Imaging of the scattering object make it possible to detect detailed profiles of the investigated gas jet, as illustrated by several examples taken from the experiment. In some cases even the gas jet stratification has been observed. (J.U.). 1 tab., 3 figs., 1 ref.

T1 weighted brain images at 7 Tesla unbiased for Proton Density, T2* contrast and RF coil receive B1 sensitivity with simultaneous vessel visualization.

Science.gov (United States)

Van de Moortele, Pierre-François; Auerbach, Edwards J; Olman, Cheryl; Yacoub, Essa; Uğurbil, Kâmil; Moeller, Steen

2009-06-01

At high magnetic field, MR images exhibit large, undesirable signal intensity variations commonly referred to as "intensity field bias". Such inhomogeneities mostly originate from heterogeneous RF coil B(1) profiles and, with no appropriate correction, are further pronounced when utilizing rooted sum of square reconstruction with receive coil arrays. These artifacts can significantly alter whole brain high resolution T(1)-weighted (T(1)w) images that are extensively utilized for clinical diagnosis, for gray/white matter segmentation as well as for coregistration with functional time series. In T(1) weighted 3D-MPRAGE sequences, it is possible to preserve a bulk amount of T(1) contrast through space by using adiabatic inversion RF pulses that are insensitive to transmit B(1) variations above a minimum threshold. However, large intensity variations persist in the images, which are significantly more difficult to address at very high field where RF coil B(1) profiles become more heterogeneous. Another characteristic of T(1)w MPRAGE sequences is their intrinsic sensitivity to Proton Density and T(2)(*) contrast, which cannot be removed with post-processing algorithms utilized to correct for receive coil sensitivity. In this paper, we demonstrate a simple technique capable of producing normalized, high resolution T(1)w 3D-MPRAGE images that are devoid of receive coil sensitivity, Proton Density and T(2)(*) contrast. These images, which are suitable for routinely obtaining whole brain tissue segmentation at 7 T, provide higher T(1) contrast specificity than standard MPRAGE acquisitions. Our results show that removing the Proton Density component can help in identifying small brain structures and that T(2)(*) induced artifacts can be removed from the images. The resulting unbiased T(1)w images can also be used to generate Maximum Intensity Projection angiograms, without additional data acquisition, that are inherently registered with T(1)w structural images. In addition

T1 weighted Brain Images at 7 Tesla Unbiased for Proton Density, T2* contrast and RF Coil Receive B1 Sensitivity with Simultaneous Vessel Visualization

Science.gov (United States)

Van de Moortele, Pierre-François; Auerbach, Edwards J.; Olman, Cheryl; Yacoub, Essa; Uğurbil, Kâmil; Moeller, Steen

2009-01-01

At high magnetic field, MR images exhibit large, undesirable signal intensity variations commonly referred to as “intensity field bias”. Such inhomogeneities mostly originate from heterogeneous RF coil B1 profiles and, with no appropriate correction, are further pronounced when utilizing rooted sum of square reconstruction with receive coil arrays. These artifacts can significantly alter whole brain high resolution T1-weighted (T1w) images that are extensively utilized for clinical diagnosis, for gray/white matter segmentation as well as for coregistration with functional time series. In T1 weighted 3D-MPRAGE sequences, it is possible to preserve a bulk amount of T1 contrast through space by using adiabatic inversion RF pulses that are insensitive to transmit B1 variations above a minimum threshold. However, large intensity variations persist in the images, which are significantly more difficult to address at very high field where RF coil B1 profiles become more heterogeneous. Another characteristic of T1w MPRAGE sequences is their intrinsic sensitivity to Proton Density and T2* contrast, which cannot be removed with post-processing algorithms utilized to correct for receive coil sensitivity. In this paper, we demonstrate a simple technique capable of producing normalized, high resolution T1w 3D-MPRAGE images that are devoid of receive coil sensitivity, Proton Density and T2* contrast. These images, which are suitable for routinely obtaining whole brain tissue segmentation at 7 Tesla, provide higher T1 contrast specificity than standard MPRAGE acquisitions. Our results show that removing the Proton Density component can help identifying small brain structures and that T2* induced artifacts can be removed from the images. The resulting unbiased T1w images can also be used to generate Maximum Intensity Projection angiograms, without additional data acquisition, that are inherently registered with T1w structural images. In addition, we introduce a simple technique

Effect of gravity on density distributions and orthopositronium annihilation rates in ethane and methane near the critical point

International Nuclear Information System (INIS)

Sharma, S.C.; Kafle, S.R.S.

1983-01-01

The effect of gravity on density distributions has been studied in ethane and methane near their critical points using the linear-model parametric equation of state. The results obtained from this study are used to further understand the sensitivity of orthopositronium annihilation rates to density fluctuations in molecular gases. It is shown that the influence of gravity is too small to account for the recently observed dependence of orthopositronium annihilation rates on the density of ethane gas at 306.4 K. However, a significant variation in local density vs height is calculated at temperatures closer to the gas--liquid critical point. The density and temperature dependencies of the annihilation rates of orthopositronium atoms, recently observed in ethane and methane gases, are discussed in terms of the findings of this study

Interaction cross section of 11Li + d reaction and the determination of nucleon density distribution in 11Li

International Nuclear Information System (INIS)

Tanihata, I.; Yoshida, K.; Suzuki, T.

1992-01-01

Interaction cross sections for 11 Li beams have been measured using p, d, and C targets at 800A and 400A MeV. The density distribution of the 11 Li nucleus has been determined, for the first time, combining interaction cross sections with various targets and energies. It was confirmed that only the distributions with long tails describe the observed data. (author)

Mathematical modeling of current density distribution in composite cathode of solid oxide fuel cells. Paper no. IGEC-1-099

International Nuclear Information System (INIS)

Kenney, B.; Karan, K.

2005-01-01

Cathodes processes in a solid oxide fuel cell (SOFC) are thought to dominate the overall electrochemical losses. One strategy for minimizing the cathode electrochemical losses in a state-of-the-art SOFC that utilize lanthanum-strontium-manganate (LSM) electrocatalyst and yttria-stabilized-zirconia (YSZ) electrolyte is to utilize composite cathodes comprising a mixture of LSM and YSZ. Composite cathodes improve performance by extending the active reaction zone from electrolyte-electrode interface to throughout the electrode. In this study, a two-dimensional composite cathode model was developed to assess cathode performance in terms of current density distributions. The model results indicate that geometric and microstructural parameters strongly influence current density distribution. In addition electrode composition affects magnitude and distribution of current. An optimum composition for equal-sized LSM/YSZ is 40 vol% LSM and 60 vol% YSZ at 900 o C. (author)

Comparison of positive and negative enteral contrast agents for MR imaging of the abdomen

International Nuclear Information System (INIS)

Kaminsky, S.; Langer, M.

1994-01-01

Following oral administration of a buffered gadopentetate-dimeglumine solution (Magnevist enteral R , 1 mmol/l, 6-17 ml/kg) T 1 -, proton-density- and T 2 -weighted spin-echo images of abdominal and retroperitoneal lesions were acquired (0.5 T). Gadopentetate is a signal-enhancing, positive MR contrast agent, intraluminar air served as a model of a signal-free, negative agent. In 21 patients contrast/noise ratios of gadopentetate and air versus lesions and fat were compared quantitatively (t-test). In T 1 - and T 2 -weighted images contrast/noise ratios of gadopentetate versus lesions were significantly higher than those of air. In proton-density images there was no significant difference. In T 1 - and proton-density images contrast/noise ratios of air versus abdominal fat were significantly higher than those of gadopentetate, in T 2 -weighted images gadopentetate had a significantly higher contrast/noise ratio than air. Signal-enhancing positive contrast agents seem advantageous over signal-free negative enteral MR contrast agents. (orig.) [de

Spatial distribution of ozone density in pulsed corona discharges observed by two-dimensional laser absorption method

Energy Technology Data Exchange (ETDEWEB)

Ono, Ryo; Oda, Tetsuji [Department of Electrical Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656 (Japan)

2004-03-07

The spatial distribution of ozone density is measured in pulsed corona discharges with a 40 {mu}m spatial resolution using a two-dimensional laser absorption method. Discharge occurs in a 13 mm point-to-plane gap in dry air with a pulse duration of 100 ns. The result shows that the ozone density increases for about 100 {mu}s after the discharge pulse. The rate coefficient of the ozone-producing reaction, O + O{sub 2} + M {yields} O{sub 3} + M, is estimated to be 3.5 x 10{sup -34} cm{sup 6} s{sup -1}. It is observed that ozone is mostly distributed in the secondary-streamer channel. This suggests that most of the ozone is produced by the secondary streamer, not the primary streamer. After the discharge pulse, ozone diffuses into the background from the secondary-streamer channel. The diffusion coefficient of ozone is estimated to be approximately 0.1 to 0.2 cm{sup 2} s{sup -1}.

Spatial distribution of ozone density in pulsed corona discharges observed by two-dimensional laser absorption method

International Nuclear Information System (INIS)

Ono, Ryo; Oda, Tetsuji

2004-01-01

The spatial distribution of ozone density is measured in pulsed corona discharges with a 40 μm spatial resolution using a two-dimensional laser absorption method. Discharge occurs in a 13 mm point-to-plane gap in dry air with a pulse duration of 100 ns. The result shows that the ozone density increases for about 100 μs after the discharge pulse. The rate coefficient of the ozone-producing reaction, O + O 2 + M → O 3 + M, is estimated to be 3.5 x 10 -34 cm 6 s -1 . It is observed that ozone is mostly distributed in the secondary-streamer channel. This suggests that most of the ozone is produced by the secondary streamer, not the primary streamer. After the discharge pulse, ozone diffuses into the background from the secondary-streamer channel. The diffusion coefficient of ozone is estimated to be approximately 0.1 to 0.2 cm 2 s -1

Generalized image contrast enhancement technique based on Heinemann contrast discrimination model

Science.gov (United States)

Liu, Hong; Nodine, Calvin F.

1994-03-01

This paper presents a generalized image contrast enhancement technique which equalizes perceived brightness based on the Heinemann contrast discrimination model. This is a modified algorithm which presents an improvement over the previous study by Mokrane in its mathematically proven existence of a unique solution and in its easily tunable parameterization. The model uses a log-log representation of contrast luminosity between targets and the surround in a fixed luminosity background setting. The algorithm consists of two nonlinear gray-scale mapping functions which have seven parameters, two of which are adjustable Heinemann constants. Another parameter is the background gray level. The remaining four parameters are nonlinear functions of gray scale distribution of the image, and can be uniquely determined once the previous three are given. Tests have been carried out to examine the effectiveness of the algorithm for increasing the overall contrast of images. It can be demonstrated that the generalized algorithm provides better contrast enhancement than histogram equalization. In fact, the histogram equalization technique is a special case of the proposed mapping.

Post double-contrast sigmoid flush: An adjuvant technique in imaging diverticular disease

International Nuclear Information System (INIS)

Lappas, J.C.; Maglinte, D.D.T.; Kopecky, K.K.; Cockerill, E.M.; Lehman, G.A.

1987-01-01

In a prospective study, the effect of a low-density contrast medium infusion was evaluated as an adjunct to high-density double-contrast medium sigmoid imaging. Following a double-contrast medium barium enema (DCBE), 52 consecutive patients with sigmoid diverticulosis received an additional 500-700-mL enema with either water or a 1.5%CT barium suspension. Rectosigmoid films were evaluated for luminal distention, visualization of the interhaustral space, definition of diverticula, and interpretation of polypoid defects. While double-contrast medium views were excellent in 21%, improvement in multiple factors by water or 1.5% barium flush resulted in improved sigmoid images in 65% and 73% of patients, respectively. Polyps may be confirmed and artifactual defects confidently excluded. Sigmoid flush, particularly with low-density barium, is a simple adjunct to DCBE that improves visualization of the diverticular sigmoid

Production of Transverse Controllable Laser Density Distribution in Fermilab/NICADD Photoinjector

CERN Document Server

Li, Jianliang; Tikhoplav, Rodion

2005-01-01

The Fermilab/NICADD photoinjector laboratory consist of a photoemission electron source based on an L band rf-gun. The CsTe photocathode is illuminated by an ultrashort UV laser. The transport line from the laser to the photocathode was recently upgraded to allow imaging of an object plane located ~20 m from the photocathode. This upgrade allows the generation of transverse laser distributions with controlled nonuniformity, yielding the production of an electron beam with various transverse densities patterns. Measuring the evolution of the artificial pattern on the electron bunch provides information that can be used to benchmark numerical simulations and investigate the impact of space charge. Preliminary data on these investigations are presented in the present paper.

Urban particle size distributions during two contrasting dust events originating from Taklimakan and Gobi Deserts

International Nuclear Information System (INIS)

Zhao, Suping; Yu, Ye; Xia, Dunsheng; Yin, Daiying; He, Jianjun; Liu, Na; Li, Fang

2015-01-01

The dust origins of the two events were identified using HYSPLIT trajectory model and MODIS and CALIPSO satellite data to understand the particle size distribution during two contrasting dust events originated from Taklimakan and Gobi deserts. The supermicron particles significantly increased during the dust events. The dust event from Gobi desert affected significantly on the particles larger than 2.5 μm, while that from Taklimakan desert impacted obviously on the particles in 1.0–2.5 μm. It is found that the particle size distributions and their modal parameters such as VMD (volume median diameter) have significant difference for varying dust origins. The dust from Taklimakan desert was finer than that from Gobi desert also probably due to other influencing factors such as mixing between dust and urban emissions. Our findings illustrated the capacity of combining in situ, satellite data and trajectory model to characterize large-scale dust plumes with a variety of aerosol parameters. - Highlights: • Dust particle size distributions had large differences for varying origins. • Dust originating from Taklimakan Desert was finer than that from Gobi Desert. • Effect of dust on the supermicron particles was obvious. • PM_1_0 concentrations increased by a factor of 3.4–25.6 during the dust event. - Dust particle size distributions had large differences for varying origins, which may be also related to other factors such as mixing between dust and urban emissions.

Penetration and distribution of gadolinium-based contrast agents into the cerebrospinal fluid in healthy rats: a potential pathway of entry into the brain tissue.

Science.gov (United States)

Jost, Gregor; Frenzel, Thomas; Lohrke, Jessica; Lenhard, Diana Constanze; Naganawa, Shinji; Pietsch, Hubertus

2017-07-01

Signal hyperintensity on unenhanced MRI in certain brain regions has been reported after multiple administrations of some, but not all, gadolinium-based contrast agents (GBCAs). One potential initial pathway of GBCA entry into the brain, infiltration from blood into the cerebrospinal fluid (CSF), was systematically evaluated in this preclinical study. GBCA infiltration and distribution in the CSF were investigated in healthy rats using repeated fluid-attenuated MRI up to 4 h after high-dose (1.8 mmol/kg) administration of six marketed and one experimental GBCA. Additionally, gadolinium measurements in CSF, blood and brain tissue samples (after 24 h) were performed using inductively coupled plasma mass spectrometry. Enhanced MRI signals in the CSF spaces with similar distribution kinetics were observed for all GBCAs. No substantial differences in the gadolinium concentrations among the marketed GBCAs were found in the CSF, blood or brain tissue. After 4.5 h, the concentration in the CSF was clearly higher than in blood but was almost completely cleared and lower than the brain tissue concentration after 24 h. In contrast to the brain signal hyperintensities, no differences in penetration and distribution into the CSF of healthy rats exist among the marketed GBCAs. • Gadolinium-based contrast agents can cross the blood-CSF barrier. • Fluid-attenuated MRI shows GBCA distribution with CSF flow. • GBCA structure and physicochemical properties do not impact CSF penetration and distribution. • GBCA clearance from CSF was almost complete within 24 h in rats. • CSF is a potential pathway of GBCA entry into the brain.

Quantitative imaging of cation adsorption site densities in undisturbed soil

Science.gov (United States)

Keck, Hannes; Strobel, Bjarne W.; Gustafsson, Jon-Petter; Koestel, John

2017-04-01

The vast majority of present soil system models assume a homogeneous distribution and accessibility of cation adsorption sites (CAS) within soil structural units like e.g. soil horizons. This is however in conflict with several recent studies finding that CAS in soils are not uniformly but patchily distributed at and below the cm-scale. It is likely that the small-scale distribution of CAS has significant impact on the performance of these models. However, systematic approaches to map CAS densities in undisturbed soil with 3-D resolution that could lead to respective model improvements are still lacking. We therefore investigated the 3-D distribution of the CAS in undisturbed soils using X-ray scanning and barium ions as a contrast agent. We appraised the validity of the approach by comparing X-ray image-derived cation exchange coefficients (CEC) with ones obtained using the ammonium acetate method. In the process, we evaluated whether there were larger CAS concentrations at aggregate and biopore boundaries as it is often hypothesized. We sampled eight small soil cores (approx. 10 ccm) from different locations with contrasting soil texture and organic matter contents. The samples were first saturated with a potassium chloride solution (0.1 mol per liter), whereupon a 3-D X-ray image was taken. Then, the potassium chloride solution was flushed out with a barium chloride solution (0.3 mol per liter) with barium replacing the potassium from the CAS due to its larger exchange affinity. After X-ray images as well as electrical conductivity in the effluent indicated that the entire sample had been saturated with the barium chloride, the sample was again rinsed using the potassium chloride solution. When the rinsing was complete a final 3-D X-ray image was acquired. The difference images between final and initial 3-D X-ray images were interpreted as depicting the adsorbed barium as the density of barium exceeds the one of potassium by more than 2 times. The X-ray image

Refractive index contrast in porous silicon multilayers

Energy Technology Data Exchange (ETDEWEB)

Nava, R.; Mora, M.B. de la; Tagueena-Martinez, J. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Rio, J.A. del [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Centro Morelense de Innovacion y Transferencia Tecnologica, Consejo de Ciencia y Tecnologia del Estado de Morelos (Mexico)

2009-07-15

Two of the most important properties of a porous silicon multilayer for photonic applications are flat interfaces and a relative large refractive index contrast between layers in the optical wavelength range. In this work, we studied the effect of the current density and HF electrolyte concentration on the refractive index of porous silicon. With the purpose of increasing the refractive index contrast in a multilayer, the refractive index of porous silicon produced at low current was studied in detail. The current density applied to produce the low porosity layers was limited in order to keep the electrolyte flow through the multilayer structure and to avoid deformation of layer interfaces. We found that an electrolyte composed of hydrofluoric acid, ethanol and glycerin in a ratio of 3:7:1 gives a refractive index contrast around 1.3/2.8 at 600 nm. Several multilayer structures with this refractive index contrast were fabricated, such as dielectric Bragg mirrors and microcavities. Reflectance spectra of the structures show the photonic quality of porous silicon multilayers produced under these electrochemical conditions. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Topology of charge density of flucytosine and related molecules and characteristics of their bond charge distributions.

Science.gov (United States)

Murgich, Juan; Franco, Héctor J; San-Blas, Gioconda

2006-08-24

The molecular charge distribution of flucytosine (4-amino-5-fluoro-2-pyrimidone), uracil, 5-fluorouracil, and thymine was studied by means of density functional theory calculations (DFT). The resulting distributions were analyzed by means of the atoms in molecules (AIM) theory. Bonds were characterized through vectors formed with the charge density value, its Laplacian, and the bond ellipticity calculated at the bond critical point (BCP). Within each set of C=O, C-H, and N-H bonds, these vectors showed little dispersion. C-C bonds formed three different subsets, one with a significant degree of double bonding, a second corresponding to single bonds with a finite ellipticity produced by hyperconjugation, and a third one formed by a pure single bond. In N-C bonds, a decrease in bond length (an increase in double bond character) was not reflected as an increase in their ellipticity, as in all C-C bonds studied. It was also found that substitution influenced the N-C, C-O, and C-C bond ellipticity much more than density and its Laplacian at the BCP. The Laplacian of charge density pointed to the existence of both bonding and nonbonding maxima in the valence shell charge concentration of N, O, and F, while only bonding ones were found for the C atoms. The nonbonding maxima related to the sites for electrophilic attack and H bonding in O and N, while sites of nucleophilic attack were suggested by the holes in the valence shell of the C atoms of the carbonyl groups.

Difference in distribution of membrane proteins between low- and high-density secretory granules in parotid acinar cells

International Nuclear Information System (INIS)

Fujita-Yoshigaki, Junko; Katsumata, Osamu; Matsuki, Miwako; Yoshigaki, Tomoyoshi; Furuyama, Shunsuke; Sugiya, Hiroshi

2006-01-01

Secretory granules (SGs) are considered to be generated as immature granules and to mature by condensation of their contents. In this study, SGs of parotid gland were separated into low-, medium-, and high-density granule fractions by Percoll-density gradient centrifugation, since it was proposed that the density corresponds to the degree of maturation. The observation with electron microscopy showed that granules in the three fractions were very similar. The average diameter of high-density granules was a little but significantly larger than that of low-density granules. Although the three fractions contained amylase, suggesting that they are all SGs, distribution of membrane proteins was markedly different. Syntaxin6 and VAMP4 were localized in the low-density granule fraction, while VAMP2 was concentrated in the high-density granule fraction. Immunoprecipitation with anti-syntaxin6 antibody caused coprecipitation of VAMP2 from the medium-density granule fraction without solubilization, but not from Triton X-100-solubilized fraction, while VAMP4 was coprecipitated from both fractions. Therefore, VAMP2 is present on the same granules, but is separated from syntaxin6 and VAMP4, which are expected to be removed from immature granules. These results suggest that the medium-density granules are intermediates from low- to high-density granules, and that the membrane components of SGs dynamically change by budding and fusion during maturation

A analytical comparison of different estimators for the density distribution of the catalyst in a experimental riser by a gammametric technique

International Nuclear Information System (INIS)

Lima, Emerson Alexandre de Oliveira; Dantas Carlos C.; Melo, Silvio de Barros; Santos, Valdemir Alexandre dos

2005-01-01

In this paper, we solve the following questions: what will be the estimate of the r = r (x, y, z) function format? Which method would describe the density distribution function more precisely? Which is the best estimator? Also, once the ρ=ρ(x, y, z) format and the approximation technique is defined, comes the experimental arrangement and pass length configuration, which are the next problems to be solved. Finding the best parameter estimation for the ρ=ρ(x, y, z) function according to the C pass lengths and their spatial configuration. The latter is required to define the ρ=ρ(x, y, z) function resolution and the mechanical scanning movements of the arrangement. Such definitions will be implemented for an automate arrangement, by a computational program, to further development of the reconstruction of catalyst density distribution on experimental risers.. The precision evaluation was finally compared to the arrangement geometry that yields the best pass length spatial configuration. The results are shown in graphics for the two known density distributions. As a conclusion, the parameters for an automate arrangement design, are given under the required precision for the catalyst distribution reconstruction. (author)

Density, distribution, and activity of the ocelot Leopardus pardalis (Carnivora: Felidae) in Southeast Mexican rainforests.

Science.gov (United States)

Pérez-Irineo, Gabriela; Santos-Moreno, Antonio

2014-12-01

The ocelot Leopardus pardalis is of particular significance in terrestrial communities due to its ecological role within the group of small-sized felids and as a mesopredator. However, despite the reduction of ocelot habitat in Southeast Mexico, there are still very few ecological studies. This research aimed to contribute with some ecological aspects of the species in this region. For this, 29 camera trap stations were established in a rain forest in Los Chimalapas (an area of 22 km2) during a two years period (March 2011-June, 2013), in Oaxaca state, Southeast Mexico. Data allowed the estimation of the population density, activity pattern, sex ratio, residence time, and spatial distribution. Population density was calculated using Capture-Recapture Models for demographically open populations; besides, circular techniques were used to determine if nocturnal and diurnal activity varied significantly over the seasons, and Multiple Discriminant Analysis was used to determine which of the selected environmental variables best explained ocelot abundance in the region. A total of 103 ocelot records were obtained, with a total sampling effort of 8,529 trap-days. Density of 22-38 individuals/100 km2 was estimated. Ocelot population had a high proportion of transient individuals in the zone (55%), and the sex ratio was statistically equal to 1:1. Ocelot activity was more frequent at night (1:00-6:00h), but it also exhibited diurnal activity throughout the study period. Ocelot spatial distribution was positively affected by the proximity to the village as well as by the amount of prey. The ocelot population here appears to be stable, with a density similar to other regions in Central and South America, which could be attributed to the diversity of prey species and a low degree of disturbance in Los Chimalapas.

Current density distribution mapping in PEM fuel cells as an instrument for operational measurements

Energy Technology Data Exchange (ETDEWEB)

Geske, M.; Heuer, M.; Heideck, G.; Styczynski, Z. A. [Otto-von-Guericke University Magdeburg, Chair Electric Power Networks and Renewable Energy Sources, Magdeburg (Germany)

2010-07-01

A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC). Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board was chosen for the development of the new system. This type of system consists of a sensor, a special electronic device and the control and visualization PC. For the acquisition of the current density distribution values, a sensor device was designed and installed within a multilayer printed circuit board with integrated shunt resistors. Varying shunt values can be taken into consideration with a newly developed and evaluated calibration method. The sensor device was integrated in a PEM fuel cell stack to prove the functionality of the whole measurement system. A software application was implemented to visualize and save the measurement values. Its functionality was verified by operational measurements within a PEMFC system. Measurement accuracy and possible negative reactions of the sensor device during PEMFC operation are discussed in detail in this paper. The developed system enables operational measurements for different operating phases of PEM fuel cells. Additionally, this can be seen as a basis for new opportunities of optimization for fuel cell design and operation modes. (author)

Current Density Distribution Mapping in PEM Fuel Cells as An Instrument for Operational Measurements

Directory of Open Access Journals (Sweden)

Martin Geske

2010-04-01

Full Text Available A newly developed measurement system for current density distribution mapping has enabled a new approach for operational measurements in proton exchange membrane fuel cells (PEMFC. Taking into account previously constructed measurement systems, a method based on a multi layer printed circuit board was chosen for the development of the new system. This type of system consists of a sensor, a special electronic device and the control and visualization PC. For the acquisition of the current density distribution values, a sensor device was designed and installed within a multilayer printed circuit board with integrated shunt resistors. Varying shunt values can be taken into consideration with a newly developed and evaluated calibration method. The sensor device was integrated in a PEM fuel cell stack to prove the functionality of the whole measurement system. A software application was implemented to visualize and save the measurement values. Its functionality was verified by operational measurements within a PEMFC system. Measurement accuracy and possible negative reactions of the sensor device during PEMFC operation are discussed in detail in this paper. The developed system enables operational measurements for different operating phases of PEM fuel cells. Additionally, this can be seen as a basis for new opportunities of optimization for fuel cell design and operation modes.

Imaging of current density distributions with a Nb weak-link scanning nano-SQUID microscope

Science.gov (United States)

Shibata, Yusuke; Nomura, Shintaro; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Ishiguro, Ryosuke; Takayanagi, Hideaki

2015-10-01

Superconducting quantum interference devices (SQUIDs) are accepted as one of the highest magnetic field sensitive probes. There are increasing demands to image local magnetic fields to explore spin properties and current density distributions in a two-dimensional layer of semiconductors or superconductors. Nano-SQUIDs have recently attracting much interest for high spatial resolution measurements in nanometer-scale samples. Whereas weak-link Dayem Josephson junction nano-SQUIDs are suitable to miniaturization, hysteresis in current-voltage (I-V) characteristics that is often observed in Dayem Josephson junction is not desirable for a scanning microscope. Here we report on our development of a weak-link nano-SQUIDs scanning microscope with small hysteresis in I-V curve and on reconstructions of two-dimensional current density vector in two-dimensional electron gas from measured magnetic field.

Relative power density distribution calculations of the Kori unit 1 pressurized water reactor with full-scope explicit modeling of monte carlo simulation

International Nuclear Information System (INIS)

Kim, J. O.; Kim, J. K.

1997-01-01

Relative power density distributions of the Kori unit 1 pressurized water reactor calculated by Monte Carlo modeling with the MCNP code. The Kori unit 1 core is modeled on a three-dimensional representation of the one-eighth of the reactor in-vessel component with reflective boundaries at 0 and 45 degrees. The axial core model is based on half core symmetry and is divided into four axial segments. Fission reaction density in each rod is calculated by following 100 cycles with 5,000 test neutrons in each cycle after starting with a localized neutron source and ten noncontributing settle cycles. Relative assembly power distributions are calculated from fission reaction densities of rods in assembly. After 100 cycle calculations, the system coverages to a κ value of 1.00039 ≥ 0.00084. Relative assembly power distribution is nearly the same with that of the Kori unit 1 FSAR. Applicability of the full-scope Monte Carlo simulation in the power distribution calculation is examined by the relative root mean square error of 2.159%. (author)

Primordial inhomogeneities in the expanding universe. I - Density and velocity distributions of galaxies in the vicinities of rich clusters

Science.gov (United States)

Silk, J.; Wilson, M. L.

1979-01-01

The density profiles and Hubble flow deviations in the vicinities of rich galaxy clusters are derived for a variety of models of initial density and velocity perturbations at the recombination epoch. The galaxy correlation function, measured with respect to the Abell clusters, is used to normalize the theoretical models. The angular scales of the required primordial inhomogeneities are calculated. It is found that the resulting density profiles around rich clusters are surprisingly insensitive to the shape of the initial perturbations and also to the cosmological density parameter, Omega. However, it is shown that the distribution of galaxy radial velocities can provide a possible means of deriving Omega.

Effect of heterogeneous distribution of crosslink density on physical properties of radiation vulcanized NR (Natural Rubber) latex film

International Nuclear Information System (INIS)

Keizo Makuuchi; Fumio Yoshii; Miura, H.; Murakami, K.

1996-01-01

Thus a study has been carried out to investigate the effect of particle to particle variation in crosslink density on physical properties of radiation vulcanized NR latex film. NR latex was irradiated in small bottle by γ rays without vulcanization accelerator to provide latex rubber particles having homogeneous distribution of crosslink density. The doses were 30, 50, 100, 250, 300, 400, 500 and 600 kGy. Weight swelling ratio, gel fraction, tensile strength and elongation at break of the latex film from the mixed latex were measured. The vulcanization dose of this latex was 250 kGy. Then the two different latexes were mixed in a such way to adjust the average dose of 250 kGy to prepare a latex consisting of rubber particles having heterogeneous distribution of crosslink density. Tensile strength of the latex film was depressed by mixing. The reduction increased with increasing the decrease of gel fraction by mixing. However the reduction was not serious when the dose difference of two latexes was less than 200 kGy

3D analysis of synaptic vesicle density and distribution after acute foot-shock stress by using serial section transmission electron microscopy

DEFF Research Database (Denmark)

Khanmohammadi, M; Darkner, S; Nava, N

2017-01-01

was employed to compare two groups of male rats: (1) rats subjected to foot-shock stress and (2) rats with sham stress as control group. Two-dimensional (2D) density measures are common in microscopic images and are estimated by following a 2D path in-section. However, this method ignores the slant...... in comparison to the 2D measures. Our results showed that acute foot-shock stress exposure significantly affected both the spatial distribution and density of the synaptic vesicles within the presynaptic terminal.......Behavioural stress has shown to strongly affect neurotransmission within the neocortex. In this study, we analysed the effect of an acute stress model on density and distribution of neurotransmitter-containing vesicles within medial prefrontal cortex. Serial section transmission electron microscopy...

Time-dependent density functional theory (TD-DFT) coupled with reference interaction site model self-consistent field explicitly including spatial electron density distribution (RISM-SCF-SEDD)

Energy Technology Data Exchange (ETDEWEB)

Yokogawa, D., E-mail: d.yokogawa@chem.nagoya-u.ac.jp [Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8602 (Japan)

2016-09-07

Theoretical approach to design bright bio-imaging molecules is one of the most progressing ones. However, because of the system size and computational accuracy, the number of theoretical studies is limited to our knowledge. To overcome the difficulties, we developed a new method based on reference interaction site model self-consistent field explicitly including spatial electron density distribution and time-dependent density functional theory. We applied it to the calculation of indole and 5-cyanoindole at ground and excited states in gas and solution phases. The changes in the optimized geometries were clearly explained with resonance structures and the Stokes shift was correctly reproduced.

54 relative density and distribution of tantalus monkey

African Journals Online (AJOL)

Tersor

RANGES OF SAMBISA GAME RESERVE. M. Modu*, A. A. ... density and he found a negative relationship with minimum density. .... analysis. A comprehensive computer software .... a large effect on the abundance and ranging ecology of ...

Contrast-enhanced MRI of the lung

International Nuclear Information System (INIS)

Kauczor, Hans-Ulrich; Kreitner, Karl-Friedrich

2000-01-01

The lung has long been neglected by MR imaging. This is due to unique intrinsic difficulties: (1) signal loss due to cardiac pulsation and respiration; (2) susceptibility artifacts caused by multiple air-tissue interfaces; (3) low proton density. There are many MR strategies to overcome these problems. They consist of breath-hold imaging, respiratory and cardiac gating procedures, use of short repetition and echo times, increase of the relaxivity of existing spins by administration of intravenous contrast agents, and enrichment of spin density by hyperpolarized noble gases or oxygen. Improvements in scanner performance and frequent use of contrast media have increased the interest in MR imaging and MR angiography of the lung. They can be used on a routine basis for the following indications: characterization of pulmonary nodules, staging of bronchogenic carcinoma, in particular assessment of chest wall invasion; evaluation of inflammatory activity in interstitial lung disease; acute pulmonary embolism, chronic thromboembolic pulmonary hypertension, vascular involvement in malignant disease; vascular abnormalities. Future perspectives include perfusion imaging using extracellular or intravascular (blood pool) contrast agents and ventilation imaging using inhalation of hyperpolarized noble gases, of paramagnetic oxygen or of aerosolized contrast agents. These techniques represent new approaches to functional lung imaging. The combination of visualization of morphology and functional assessment of ventilation and perfusion is unequalled by any other technique

Quantitation of MRI sensitivity to quasi-monodisperse microbubble contrast agents for spatially resolved manometry.

Science.gov (United States)

Bencsik, Martin; Al-Rwaili, Amgad; Morris, Robert; Fairhurst, David J; Mundell, Victoria; Cave, Gareth; McKendry, Jonathan; Evans, Stephen

2013-11-01

The direct in-vivo measurement of fluid pressure cannot be achieved with MRI unless it is done with the contribution of a contrast agent. No such contrast agents are currently available commercially, whilst those demonstrated previously only produced qualitative results due to their broad size distribution. Our aim is to quantitate then model the MR sensitivity to the presence of quasi-monodisperse microbubble populations. Lipid stabilised microbubble populations with mean radius 1.2 ± 0.8 μm have been produced by mechanical agitation. Contrast agents with increasing volume fraction of bubbles up to 4% were formed and the contribution the bubbles bring to the relaxation rate was quantitated. A periodic pressure change was also continuously applied to the same contrast agent, until MR signal changes were only due to bubble radius change and not due to a change in bubble density. The MR data compared favourably with the prediction of an improved numerical simulation. An excellent MR sensitivity of 23 % bar(-1) has been demonstrated. This work opens up the possibility of generating microbubble preparations tailored to specific applications with optimised MR sensitivity, in particular MRI based in-vivo manometry. Copyright © 2012 Wiley Periodicals, Inc.

Quantitative contrast-enhanced mammography for contrast medium kinetics studies

Science.gov (United States)

Arvanitis, C. D.; Speller, R.

2009-10-01

Quantitative contrast-enhanced mammography, based on a dual-energy approach, aims to extract quantitative and temporal information of the tumour enhancement after administration of iodinated vascular contrast media. Simulations using analytical expressions and optimization of critical parameters essential for the development of quantitative contrast-enhanced mammography are presented. The procedure has been experimentally evaluated using a tissue-equivalent phantom and an amorphous silicon active matrix flat panel imager. The x-ray beams were produced by a tungsten target tube and spectrally shaped using readily available materials. Measurement of iodine projected thickness in mg cm-2 has been performed. The effect of beam hardening does not introduce nonlinearities in the measurement of iodine projected thickness for values of thicknesses found in clinical investigations. However, scattered radiation introduces significant deviations from slope equal to unity when compared with the actual iodine projected thickness. Scatter correction before the analysis of the dual-energy images provides accurate iodine projected thickness measurements. At 10% of the exposure used in clinical mammography, signal-to-noise ratios in excess of 5 were achieved for iodine projected thicknesses less than 3 mg cm-2 within a 4 cm thick phantom. For the extraction of temporal information, a limited number of low-dose images were used with the phantom incorporating a flow of iodinated contrast medium. The results suggest that spatial and temporal information of iodinated contrast media can be used to indirectly measure the tumour microvessel density and determine its uptake and washout from breast tumours. The proposed method can significantly improve tumour detection in dense breasts. Its application to perform in situ x-ray biopsy and assessment of the oncolytic effect of anticancer agents is foreseeable.

Measurements of transient electron density distributions by femtosecond X-ray diffraction

International Nuclear Information System (INIS)

Freyer, Benjamin

2013-01-01

This thesis concerns measurements of transient charge density maps by femtosecond X-ray diffraction. Different X-ray diffraction methods will be considered, particularly with regard to their application in femtosecond X-ray diffraction. The rotation method is commonly used in stationary X-ray diffraction. In the work in hand an X-ray diffraction experiment is demonstrated, which combines the method with ultrafast X-ray pulses. This experiment is the first implementation which makes use of the rotation method to map transient intensities of a multitude of Bragg reflections. As a prototype material Bismuth is used, which previously was studied frequently by femtosecond X-ray diffraction by measuring Bragg reflections successively. The experimental results of the present work are compared with the literature data. In the second part a powder-diffraction experiment will be presented, which is used to study the dynamics of the electron-density distribution on ultrafast time scales. The experiment investigates a transition metal complex after photoexcitation of the metal to ligand charge transfer state. Besides expected results, i. e. the change of the bond length between the metal and the ligand and the transfer of electronic charge from the metal to the ligand, a strong contribution of the anion to the charge transfer was found. Furthermore, the charge transfer has predominantly a cooperative character. That is, the excitation of a single complex causes an alteration of the charge density of several neighboring units. The results show that more than 30 transition-metal complexes and 60 anions contribute to the charge transfer. This collective response is a consequence of the strong coulomb interactions of the densely packed ions.

Energy sprawl, land taking and distributed generation: towards a multi-layered density

International Nuclear Information System (INIS)

Moroni, Stefano; Antoniucci, Valentina; Bisello, Adriano

2016-01-01

The transition from fossil fuels to renewable resources is highly desirable to reduce air pollution, and improve energy efficiency and security. Many observers are concerned, however, that the diffusion of systems based on renewable resources may give rise to energy sprawl, i.e. an increasing occupation of available land to build new energy facilities of this kind. These critics foresee a transition from the traditional fossil-fuel systems, towards a renewable resource system likewise based on large power stations and extensive energy grids. A different approach can be taken to reduce the risk of energy sprawl, and this will happen if the focus is as much on renewable sources as on the introduction of distributed renewable energy systems based on micro plants (photovoltaic panels on the roofs of buildings, micro wind turbines, etc.) and on multiple micro-grids. Policy makers could foster local energy enterprises by: introducing new enabling rules; making more room for contractual communities; simplifying the compliance process; proposing monetary incentives and tax cuts. We conclude that the diffusion of innovation in this field will lead not to an energy sprawl but to a new energy system characterized by a multi-layered density: a combination of technology, organization, and physical development. - Highlights: • Energy sprawl is not a necessary consequence of the transition to renewable sources. • A polycentric, distributed renewable energy system reduces land consumption. • This polycentric model is founded on building-related renewable energy production and micro-grids. • Enabling rules, simplified compliance, and tax cuts can foster this result. • The concept of multi-layered density is proposed as a new framework for interpreting this scenario.

Quantitative evaluation of contrast agent uptake in standard fat-suppressed dynamic contrast-enhanced MRI examinations of the breast.

Science.gov (United States)

Kousi, Evanthia; Smith, Joely; Ledger, Araminta E; Scurr, Erica; Allen, Steven; Wilson, Robin M; O'Flynn, Elizabeth; Pope, Romney J E; Leach, Martin O; Schmidt, Maria A

2018-01-01

To propose a method to quantify T 1 and contrast agent uptake in breast dynamic contrast-enhanced (DCE) examinations undertaken with standard clinical fat-suppressed MRI sequences and to demonstrate the proposed approach by comparing the enhancement characteristics of lobular and ductal carcinomas. A standard fat-suppressed DCE of the breast was performed at 1.5 T (Siemens Aera), followed by the acquisition of a proton density (PD)-weighted sequence, also fat suppressed. Both sequences were characterized with test objects (T 1 ranging from 30 ms to 2,400 ms) and calibration curves were obtained to enable T 1 calculation. The reproducibility and accuracy of the calibration curves were also investigated. Healthy volunteers and patients were scanned with Ethics Committee approval. The effect of B 0 field inhomogeneity was assessed in test objects and healthy volunteers. The T 1 of breast tumors was calculated at different time points (pre-, peak-, and post-contrast agent administration) for 20 patients, pre-treatment (10 lobular and 10 ductal carcinomas) and the two cancer types were compared (Wilcoxon rank-sum test). The calibration curves proved to be highly reproducible (coefficient of variation under 10%). T 1 measurements were affected by B 0 field inhomogeneity, but frequency shifts below 50 Hz introduced only 3% change to fat-suppressed T 1 measurements of breast parenchyma in volunteers. The values of T 1 measured pre-, peak-, and post-contrast agent administration demonstrated that the dynamic range of the DCE sequence was correct, that is, image intensity is approximately directly proportional to 1/T 1 for that range. Significant differences were identified in the width of the distributions of the post-contrast T 1 values between lobular and ductal carcinomas (P contrast T 1 values, potentially related to their infiltrative growth pattern. This work has demonstrated the feasibility of fat-suppressed T 1 measurements as a tool for clinical studies. The

Study of Different Tissue Density Effects on the Dose Distribution of a 103Pd Brachytherapy Source Model MED3633

Directory of Open Access Journals (Sweden)

Ali Asghar Mowlavi

2010-09-01

Full Text Available Introduction: Clinical application of encapsulated radioactive brachytherapy sources has a major role in cancer treatment. In the present research, the effects of different tissue densities on the dose distribution of a 103Pd brachytherapy source in a spherical phantom of 50 cm radius have been studied. Material and Methods: As is well known, absorbed dose in tissue depends to its density, but this difference is not clear in measurements. Therefore, we applied the MCNP code to evaluate the effect of density on the dose distribution. 103Pd brachytherapy sources are used to treat prostate, breast and other cancers. Results: Absorbed dose has been calculated and presented around a source placed in the center of the phantom for different tissue densities. Also, we derived anisotropy and radial dose functions and compared our Monte Carlo results with experimental results of Rivard and Li et al. for F(1, θ and g(r in 1.040 g/cm3 tissue. Conclusion: The results of this study show that relative dose variations around the source center are very considerable at different densities, because of the presence of a photoabsorber (Au-Cu alloy in the source core. Dose variation exceeds 80% at the point (Z = 2.4 mm, Y = 0 mm. Computed values of anisotropy and radial dose functions are in good agreement with the experimental results of Rivard and Li et al.

Approximation of the breast height diameter distribution of two-cohort stands by mixture models III Kernel density estimators vs mixture models

Science.gov (United States)

Rafal Podlaski; Francis A. Roesch

2014-01-01

Two-component mixtures of either the Weibull distribution or the gamma distribution and the kernel density estimator were used for describing the diameter at breast height (dbh) empirical distributions of two-cohort stands. The data consisted of study plots from the Å wietokrzyski National Park (central Poland) and areas close to and including the North Carolina section...

Nuclear density distributions of 40,42,44,48Ca from elastic scattering of 104 MeV alpha particles

International Nuclear Information System (INIS)

Gils, H.J.; Friedman, E.; Majka, Z.

1979-12-01

The elastic scattering of 104 MeV α particles from 40 , 42 , 44 , 48 Ca has been analyzed by a single folding model with a density dependent effective interaction. Nuclear density distributions have been extracted using various descriptions including Fourier-Bessel series which distinctly reduces the model dependence of the results and enables realistic estimates of errors. Differences of the density shapes of the Ca-isotopes are well determined showing evidence for a neutron skin in 48 Ca. The resulting root mean square radii are compared to the results obtained from other methods. The sensitivity and limitations of various methods are discussed. (orig.) 891 KBE/orig. 892 BRE

Nanocrystal core high-density lipoproteins: a multimodality contrast agent platform

NARCIS (Netherlands)

Cormode, David P.; Skajaa, Torjus; van Schooneveld, Matti M.; Koole, Rolf; Jarzyna, Peter; Lobatto, Mark E.; Calcagno, Claudia; Barazza, Alessandra; Gordon, Ronald E.; Zanzonico, Pat; Fisher, Edward A.; Fayad, Zahi A.; Mulder, Willem J. M.

2008-01-01

High density lipoprotein (HDL) is an important natural nanoparticle that may be modified for biomedical imaging purposes. Here we developed a novel technique to create unique multimodality HDL mimicking nanoparticles by incorporation of gold, iron oxide, or quantum dot nanocrystals for computed

Enhanced renal image contrast by ethanol fixation in phase-contrast X-ray computed tomography.

Science.gov (United States)

Shirai, Ryota; Kunii, Takuya; Yoneyama, Akio; Ooizumi, Takahito; Maruyama, Hiroko; Lwin, Thet Thet; Hyodo, Kazuyuki; Takeda, Tohoru

2014-07-01

Phase-contrast X-ray imaging using a crystal X-ray interferometer can depict the fine structures of biological objects without the use of a contrast agent. To obtain higher image contrast, fixation techniques have been examined with 100% ethanol and the commonly used 10% formalin, since ethanol causes increased density differences against background due to its physical properties and greater dehydration of soft tissue. Histological comparison was also performed. A phase-contrast X-ray system was used, fitted with a two-crystal X-ray interferometer at 35 keV X-ray energy. Fine structures, including cortex, tubules in the medulla, and the vessels of ethanol-fixed kidney could be visualized more clearly than that of formalin-fixed tissues. In the optical microscopic images, shrinkage of soft tissue and decreased luminal space were observed in ethanol-fixed kidney; and this change was significantly shown in the cortex and outer stripe of the outer medulla. The ethanol fixation technique enhances image contrast by approximately 2.7-3.2 times in the cortex and the outer stripe of the outer medulla; the effect of shrinkage and the physical effect of ethanol cause an increment of approximately 78% and 22%, respectively. Thus, the ethanol-fixation technique enables the image contrast to be enhanced in phase-contrast X-ray imaging.

Density, size and distribution of stomata in 35 rainforest trees species in Central Amazonia

OpenAIRE

Miguel Angelo Branco Camargo; Ricardo Antonio Marenco

2011-01-01

Stomata are turgor-operated valves that control water loss and CO2 uptake during photosynthesis, and thereby water relation and plant biomass accumulation is closely related to stomatal functioning. The aims of this work were to document how stomata are distributed on the leaf surface and to determine if there is any significant variation in stomatal characteristics among Amazonian tree species, and finally to study the relationship between stomatal density (S D) and tree height. Thirty five ...

Density, size and distribution of stomata in 35 rainforest tree species in Central Amazonia

OpenAIRE

Camargo, Miguel Angelo Branco; Marenco, Ricardo Antonio

2011-01-01

Stomata are turgor-operated valves that control water loss and CO2 uptake during photosynthesis, and thereby water relation and plant biomass accumulation is closely related to stomatal functioning. The aims of this work were to document how stomata are distributed on the leaf surface and to determine if there is any significant variation in stomatal characteristics among Amazonian tree species, and finally to study the relationship between stomatal density (S D) and tree height. Thirty five ...

Hadronic multiplicity distributions: the negative binomial and its alternatives

International Nuclear Information System (INIS)

Carruthers, P.

1986-01-01

We review properties of the negative binomial distribution, along with its many possible statistical or dynamical origins. Considering the relation of the multiplicity distribution to the density matrix for Boson systems, we re-introduce the partially coherent laser distribution, which allows for coherent as well as incoherent hadronic emission from the k fundamental cells, and provides equally good phenomenological fits to existing data. The broadening of non-single diffractive hadron-hadron distributions can be equally well due to the decrease of coherent with increasing energy as to the large (and rapidly decreasing) values of k deduced from negative binomial fits. Similarly the narrowness of e + -e - multiplicity distribution is due to nearly coherent (therefore nearly Poissonian) emission from a small number of jets, in contrast to the negative binomial with enormous values of k. 31 refs

Hadronic multiplicity distributions: the negative binomial and its alternatives

International Nuclear Information System (INIS)

Carruthers, P.

1986-01-01

We review properties of the negative binomial distribution, along with its many possible statistical or dynamical origins. Considering the relation of the multiplicity distribution to the density matrix for boson systems, we re-introduce the partially coherent laser distribution, which allows for coherent as well as incoherent hadronic emission from the k fundamental cells, and provides equally good phenomenological fits to existing data. The broadening of non-single diffractive hadron-hadron distributions can be equally well due to the decrease of coherence with increasing energy as to the large (and rapidly decreasing) values of k deduced from negative binomial fits. Similarly the narrowness of e + -e - multiplicity distribution is due to nearly coherent (therefore nearly Poissonian) emission from a small number of jets, in contrast to the negative binomial with enormous values of k. 31 refs

Limitations in accurate electron density studies

International Nuclear Information System (INIS)

Wal, R. van der.

1982-01-01

Most of X-ray diffraction studies are devoted to the determination of three-dimensional crystal structures from the electron density distributions. In these cases the density distributions are described by the independent atom model (IAM model), which consists of a superposition of spherically averaged free atom densities, which are smeared by thermal vibrations. During the last few decades studies have been made into the deviations of the density distribution from the IAM model, which enables a study of the chemical binding between atoms. The total density can be described using pseudo-atom multipole models as a superposition of aspherical pseudo-atom densities. A fundamental problem is that the separation of this density into an IAM and a deformation part is not unique. This thesis considers the problem and besides deformation densities from X-ray diffraction also considers the corresponding deformation electric field and deformation potential. (C.F.)

Asymptotically Constant-Risk Predictive Densities When the Distributions of Data and Target Variables Are Different

Directory of Open Access Journals (Sweden)

Keisuke Yano

2014-05-01

Full Text Available We investigate the asymptotic construction of constant-risk Bayesian predictive densities under the Kullback–Leibler risk when the distributions of data and target variables are different and have a common unknown parameter. It is known that the Kullback–Leibler risk is asymptotically equal to a trace of the product of two matrices: the inverse of the Fisher information matrix for the data and the Fisher information matrix for the target variables. We assume that the trace has a unique maximum point with respect to the parameter. We construct asymptotically constant-risk Bayesian predictive densities using a prior depending on the sample size. Further, we apply the theory to the subminimax estimator problem and the prediction based on the binary regression model.

X-ray electron charge density distribution in silicon

International Nuclear Information System (INIS)

Pietsch, U.

1986-01-01

During the last two years new highly accurate X-ray structure amplitudes for silicon have been published. Also the scattering phases of some 'forbidden' reflections have been determined using the X-ray three-beam case. This allows the construction of most precise valence and difference electron density plots and the comparison with those calculated on the basis of the Aldret-Hart X-ray pendelloesung data or theoretically. The density plots are discussed in details of both, the bond and the atomic site. The contributions of various Fourier components and the influence of different temperature factors on the difference density are studied. (author)

Exogenous contrast agents for thermoacoustic imaging: An investigation into the underlying sources of contrast

International Nuclear Information System (INIS)

Ogunlade, Olumide; Beard, Paul

2015-01-01

Purpose: Thermoacoustic imaging at microwave excitation frequencies is limited by the low differential contrast exhibited by high water content tissues. To overcome this, exogenous thermoacoustic contrast agents based on gadolinium compounds, iron oxide, and single wall carbon nanotubes have previously been suggested and investigated. However, these previous studies did not fully characterize the electric, magnetic, and thermodynamic properties of these agents thus precluding identification of the underlying sources of contrast. To address this, measurements of the complex permittivity, complex permeability, DC conductivity, and Grüneisen parameter have been made. These measurements allowed the origins of the contrast provided by each substance to be identified. Methods: The electric and magnetic properties of the contrast agents were characterized at 3 GHz using two rectangular waveguide cavities. The DC conductivity was measured separately using a conductivity meter. Thermoacoustic signals were then acquired and compared to those generated in water. Finally, 3D electromagnetic simulations were used to decouple the different contributions to the absorbed power density. Results: It was found that the gadolinium compounds provided appreciable electric contrast but not originating from the gadolinium itself. The contrast was either due to dissociation of the gadolinium salt which increased ionic conductivity or its nondissociated polar fraction which increased dielectric polarization loss or a combination of both. In addition, very high concentrations were required to achieve appreciable contrast, to the extent that the Grüneisen parameter increased significantly and became a source of contrast. Iron oxide particles were found to produce low but measurable dielectric contrast due to dielectric polarization loss, but this is attributed to the coating of the particles not the iron oxide. Single wall carbon nanotubes did not provide measurable contrast of any type

Exogenous contrast agents for thermoacoustic imaging: An investigation into the underlying sources of contrast

Energy Technology Data Exchange (ETDEWEB)

Ogunlade, Olumide, E-mail: o.ogunlade@ucl.ac.uk; Beard, Paul [Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT (United Kingdom)

2015-01-15

Purpose: Thermoacoustic imaging at microwave excitation frequencies is limited by the low differential contrast exhibited by high water content tissues. To overcome this, exogenous thermoacoustic contrast agents based on gadolinium compounds, iron oxide, and single wall carbon nanotubes have previously been suggested and investigated. However, these previous studies did not fully characterize the electric, magnetic, and thermodynamic properties of these agents thus precluding identification of the underlying sources of contrast. To address this, measurements of the complex permittivity, complex permeability, DC conductivity, and Grüneisen parameter have been made. These measurements allowed the origins of the contrast provided by each substance to be identified. Methods: The electric and magnetic properties of the contrast agents were characterized at 3 GHz using two rectangular waveguide cavities. The DC conductivity was measured separately using a conductivity meter. Thermoacoustic signals were then acquired and compared to those generated in water. Finally, 3D electromagnetic simulations were used to decouple the different contributions to the absorbed power density. Results: It was found that the gadolinium compounds provided appreciable electric contrast but not originating from the gadolinium itself. The contrast was either due to dissociation of the gadolinium salt which increased ionic conductivity or its nondissociated polar fraction which increased dielectric polarization loss or a combination of both. In addition, very high concentrations were required to achieve appreciable contrast, to the extent that the Grüneisen parameter increased significantly and became a source of contrast. Iron oxide particles were found to produce low but measurable dielectric contrast due to dielectric polarization loss, but this is attributed to the coating of the particles not the iron oxide. Single wall carbon nanotubes did not provide measurable contrast of any type

Quantitative investigation of the edge enhancement in in-line phase contrast projections and tomosynthesis provided by distributing microbubbles on the interface between two tissues: a phantom study

Science.gov (United States)

Wu, Di; Donovan Wong, Molly; Li, Yuhua; Fajardo, Laurie; Zheng, Bin; Wu, Xizeng; Liu, Hong

2017-12-01

The objective of this study was to quantitatively investigate the ability to distribute microbubbles along the interface between two tissues, in an effort to improve the edge and/or boundary features in phase contrast imaging. The experiments were conducted by employing a custom designed tissue simulating phantom, which also simulated a clinical condition where the ligand-targeted microbubbles are self-aggregated on the endothelium of blood vessels surrounding malignant cells. Four different concentrations of microbubble suspensions were injected into the phantom: 0%, 0.1%, 0.2%, and 0.4%. A time delay of 5 min was implemented before image acquisition to allow the microbubbles to become distributed at the interface between the acrylic and the cavity simulating a blood vessel segment. For comparison purposes, images were acquired using three system configurations for both projection and tomosynthesis imaging with a fixed radiation dose delivery: conventional low-energy contact mode, low-energy in-line phase contrast and high-energy in-line phase contrast. The resultant images illustrate the edge feature enhancements in the in-line phase contrast imaging mode when the microbubble concentration is extremely low. The quantitative edge-enhancement-to-noise ratio calculations not only agree with the direct image observations, but also indicate that the edge feature enhancement can be improved by increasing the microbubble concentration. In addition, high-energy in-line phase contrast imaging provided better performance in detecting low-concentration microbubble distributions.

Comparative study of pneumocystography, positive contrast cystography and double contrast cystography in dogs; Estudio comparativo entre la neumocistografia, la cistografia de contraste positivo y la cistografia de doble contraste en perros

Energy Technology Data Exchange (ETDEWEB)

Thibaut, J.; Parada, E. [Universidad Austral de Chile, Valdivia (Chile); Vargas, L.; Deppe, R.; Born, R.

1997-07-01

In order to compare three radiographic techniques: pneumocystography, positive contrast cystography and double contrast cystography, three series of 24 radiographs each in lateral and ventrodorsal projections were made. Six healthy adult male dogs with weight ranging between 7 and 16 kg were used. Food was withheld for 24 hours and two enemas were made before the series of radiographs were taken. Dogs were anaesthetized with sodium thiopental (20 mg/kg i.v.). The contrast medium was introduced through a urethral catheter. Pneumocystography was performed in the first series introducing air (10 ml/kg) in the bladder. Positive contrast cystography was performed in the second series introducing Hypaque M-60% diluted, contributing 100 mg of iodine per ml (10 ml/kg). In the double contrast cystography Hypaque M-60% diluted (10 ml) was introduced, in concentration of 150 mg of iodine per ml. Then air was introduced (10 ml/kg) through a catheter. Plates were taken in both projections at 1 and 10 minutes for each technique. The radiographic plates of each series were analized comparing the characteristics of radiographic density, outline and size. In neumocystography, positive contrast and double contrast cystography, the radiographic density was predominantly low, high and intermediate, respectively. The radiographic outline was mainly regular for the three techniques. With respect to bladder size, there was a decrease of height and an increase of length and width at 10 minutes. Comparing these three radiographic techniques, it can be concluded that the one that best outlines the bladder mucosa is double contrast. Pneumocystography provides the best image for opaque structures and cystography best shows the position of the urinary bladder [Spanish] Se tomaron 3 series de 24 radiografias cada una, en proyeccion lateral y ventrodorsal. Se trabajo en cada serie con 6 perros machos clinicamente sanos 5 con un peso que vario entre los 7 y 16 kg. Previo a cada serie se efectuo

SU-F-T-664: The Efficacy of Gold Nanoparticles as Contrast Agents in Mice

Energy Technology Data Exchange (ETDEWEB)

Yuan, Y; Zhang, Y; Sajo, E [University of Massachusetts Lowell, Lowell, MA (United States); Yasmin-Karim, S; Karve, A [Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA (United States); Ngwa, W [University of Massachusetts Lowell, Lowell, MA (United States); Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA (United States)

2016-06-15

Purpose: Micro-Computed Tomography (micro-CT) has been widely used as a non-invasive, high-resolution imaging modality in preclinical research. However, tumors cannot be well distinguished, since their density are similar to those of surrounding tissues, and the tumors’ natural contrast is very low. The benefits of using Gold Nanoparticles (AuNPs) as a promising high atomic weight contrast agent have been published in recent years. The aim of this study is to investigate the efficacy of AuNPs as contrast agents using different energy x-rays. Methods: The left flank of an immune-compromised athymic nude mouse was implanted with subcutaneous xenograft model of human lung cancer line, A549 cells (from ATCC). After 14 days, this mouse was imaged with dual energy cone-beam micro-CT. The selected energies were 45 kVp and 65 kVp. 10µg AuNPs (200 µg/ml concentration) approximately 12 nm in size were injected subcutaneously into the tumor. The mouse was imaged 0, 3 and 24 hours post-injection. During scanning, this mouse was anesthetized. All projection raw data have been optimized and then images were reconstructed with the FDK Algorithm. Results: Based on images, at 0 hour, AuNPs provided obvious contrast no matter which energy selected, 45 kVp or 65 kVp; and using 45 kVp X-ray, AuNps showed greater contrast. After 3 hours or evenand longer, AuNPs distributed throughout the whole body of mouse, and they were not shown clearly shown in the images. Conclusion: In this study, we investigated the efficacy of AuNPs as image contrast agents at different energies with dual-energy micro-CT, using 200µg/mL of AuNPs. Sufficiently high concentrations of AuNPs are needed to be able to track intratumoral distribution. Images showed good contrast immediately following the administration of the agent but results were poor after 3 hours.

POPULATION STRUCTURE AND SPATIAL DISTRIBUTION OF Ceratozamia mexicana BRONGN. (ZAMIACEAE IN PRESERVED AND DISTURBED ENVIRONMENTS

Directory of Open Access Journals (Sweden)

Andrés Rivera-Fernández

2012-11-01

Full Text Available Vegetal populations are affected by biotic and abiotic factors that influence the regeneration processes. The aims of this study were to know the population structure of Ceratozamia mexicana under two contrasting conditions (conserved site and disturbed site, and to determine if the sexual structure, the population density and the spatial distribution of C. mexicana are modified by effect of disturbance. Eight plots of 25 m2 within each site (conserved and disturbed were used. The structure and spatial distribution of the sites were determined. Methods included analysis of variance, spatial distribution indexes, and climatic and edaphic factors determined by conventional methods for their comparison. The conserved site showed a demographic structure of an inverted "J", while the disturbed site varied slightly with more discontinuous distribution. Population density was 0.78 individuals/m2 in the conserved site and 0.26 individuals/m2 in the disturbed site. Spatial distribution for all development stages of the plant was random, with the exception of the seedling stage, which was aggregated. Results showed that perturbation decreases the density of plants and removes reproductive individuals, which threatens the persistence of the population.

Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

Energy Technology Data Exchange (ETDEWEB)

Kemp, Gregory Elijah [The Ohio State Univ., Columbus, OH (United States)

2013-01-01

Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic

Gravity Spectra from the Density Distribution of Earth's Uppermost 435 km

Science.gov (United States)

Sebera, Josef; Haagmans, Roger; Floberghagen, Rune; Ebbing, Jörg

2018-03-01

The Earth masses reside in a near-hydrostatic equilibrium, while the deviations are, for example, manifested in the geoid, which is nowadays well determined by satellite gravimetry. Recent progress in estimating the density distribution of the Earth allows us to examine individual Earth layers and to directly see how the sum approaches the observed anomalous gravitational field. This study evaluates contributions from the crust and the upper mantle taken from the LITHO1.0 model and quantifies the gravitational spectra of the density structure to the depth of 435 km. This is done without isostatic adjustments to see what can be revealed with models like LITHO1.0 alone. At the resolution of 290 km (spherical harmonic degree 70), the crustal contribution starts to dominate over the upper mantle and at about 150 km (degree 130) the upper mantle contribution is nearly negligible. At the spatial resolution behavior is driven by the crust, the mantle lid and the asthenosphere. The LITHO1.0 model was furthermore referenced by adding deeper Earth layers from ak135, and the gravity signal of the merged model was then compared with the observed satellite-only model GOCO05s. The largest differences are found over the tectonothermal cold and old (such as cratonic), and over warm and young areas (such as oceanic ridges). The misfit encountered comes from the mantle lid where a velocity-density relation helped to reduce the RMS error by 40%. Global residuals are also provided in terms of the gravitational gradients as they provide better spatial localization than gravity, and there is strong observational support from ESA's satellite gradiometry mission GOCE down to the spatial resolution of 80-90 km.

Evaluation of liver parenchyma and perfusion using dynamic contrast-enhanced computed tomography and contrast-enhanced ultrasonography in captive green iguanas (Iguana iguana) under general anesthesia.

Science.gov (United States)

Nardini, Giordano; Di Girolamo, Nicola; Leopardi, Stefania; Paganelli, Irene; Zaghini, Anna; Origgi, Francesco C; Vignoli, Massimo

2014-05-13

Contrast-enhanced diagnostic imaging techniques are considered useful in veterinary and human medicine to evaluate liver perfusion and focal hepatic lesions. Although hepatic diseases are a common occurrence in reptile medicine, there is no reference to the use of contrast-enhanced ultrasound (CEUS) and contrast-enhanced computed tomography (CECT) to evaluate the liver in lizards. Therefore, the aim of this study was to evaluate the pattern of change in echogenicity and attenuation of the liver in green iguanas (Iguana iguana) after administration of specific contrast media. An increase in liver echogenicity and density was evident during CEUS and CECT, respectively. In CEUS, the mean ± SD (median; range) peak enhancement was 19.9% ± 7.5 (18.3; 11.7-34.6). Time to peak enhancement was 134.0 ± 125.1 (68.4; 59.6-364.5) seconds. During CECT, first visualization of the contrast medium was at 3.6 ± 0.5 (4; 3-4) seconds in the aorta, 10.7 ± 2.2 (10.5; 7-14) seconds in the hepatic arteries, and 15 ± 4.5 (14.5; 10-24) seconds in the liver parenchyma. Time to peak was 14.1 ± 3.4 (13; 11-21) and 31 ± 9.6 (29; 23-45) seconds in the aorta and the liver parenchyma, respectively. CEUS and dynamic CECT are practical means to determine liver hemodynamics in green iguanas. Distribution of contrast medium in iguana differed from mammals. Specific reference ranges of hepatic perfusion for diagnostic evaluation of the liver in iguanas are necessary since the use of mammalian references may lead the clinician to formulate incorrect diagnostic suspicions.

Experimental Electron Density Distribution in Two Cocrystals of Betaines with p-Hydroxybenzoic Acid

Directory of Open Access Journals (Sweden)

Agata Owczarzak

2018-03-01

Full Text Available Experimental determination of electron density distribution in crystals by means of high-resolution X-ray diffraction allows, among others, for studying the details of intra- and inter-molecular interactions. In case of co-crystals, this method may help in finding the conditions of creating such species. The results of such analysis for two co-crystals containing betaines, namely trigonelline (TRG: nicotinic acid N-methylbetaine, IUPAC name: 1-methylpyridinium-3-carboxylate and N-methylpiperidine betaine (MPB: 1-methylpiperidinium-1-yl-carboxylate with p-hydroxybenzoic acid (HBA are reported. TRG-HBA crystallizes as a hydrate. For both of the co-crystals, high-quality diffraction data were collected up to sinθ/λ = 1.13 Å−1. Hansen-Coppens multipolar model was then applied for modelling the electron density distribution and Atoms-In-Molecules approach was used for detailed analysis of interactions in crystals. A number of intermolecular interactions was identified, ranging from strong O-H···O hydrogen bonds through C-H···O to C-H···π and π···π interactions. Correlations between the geometrical characteristics of the contacts and the features of their critical points were analyzed in detail. Atomic charges show that in zwitterionic species there are regions of opposite charges, rather than charges that are localized on certain atoms. In case of MPB-HBA, a significant charge transfer between the components of co-crystal (0.5 e was found, as opposed to TRG-HBA, where all of the components are almost neutral.

Comparison of the image quality of intravenous urograms using low-osmolar contrast media

International Nuclear Information System (INIS)

Kaye, B.; Howard, J.; Foord, K.D.; Cumberland, D.C.

1988-01-01

Almost equivalent, intravenous iodine doses of the three new low-osmolar contrast media, ioxaglate (Hexabrix), iopamidol (Niopam) and iohexol (Omnipaque) have been compared for image quality on the intravenous urogram. Generally good radiographic images were obtained. Iohexol gave better results for the nephrogram and pelvicalyceal distension compared with the other contrast media, but only the nephrogram results were statistically significant. Pyelographic density and ureteric distension and density were similar with all three contrast media. In patients where low-osmolality contrast media need to be used for intravenous urography, we suggest that iohexol gives the best radiographic images. Other factors, such as cost and the relative incidence of side-effects of the low-osmolar contrast media also need to be taken into consideration. (author)

Lesion Contrast Enhancement in Medical Ultrasound Imaging

DEFF Research Database (Denmark)

Stetson, Paul F.; Sommer, F.G.; Macovski, A.

1997-01-01

Methods for improving the contrast-to-noise ratio (CNR) of low-contrast lesions in medical ultrasound imaging are described. Differences in the frequency spectra and amplitude distributions of the lesion and its surroundings can be used to increase the CNR of the lesion relative to the background...

Measurement of the relative power density distribution of the IPEN/MB-01 reactor, using a fuel rod gamma scanning technique

International Nuclear Information System (INIS)

Carneiro, Alvaro Luiz Guimaraes

1996-01-01

This work presents a measurement methodology for determination of radial and axial relative power density distribution of the IPEN/MB-01 Reactor core by means of the fuel rod gamma scanning. The methodology is based on the proportionality between gamma activity emitted by the radioactive decay of the fission products and power density. The scanning technique consists of counting gamma radiation above 0,6 MeV along the active area of the fuel rod, getting a distribution profile. The experimental results will be used as a benchmark for qualification and to establish possible deviations for the calculational methodology currently used at IPEN. The comparison of the calculated and measured results showed good agreement. (author)

Study on the uptake and distribution of gadolinium based contrast agents in biological samples using laser ablation with inductively coupled plasma mass spectroscopy

International Nuclear Information System (INIS)

Lingott, Jana

2016-01-01

Gadolinium based contrast agents are used for magnetic resonance imaging. After their excretion by medicated patients they reach surface water passing waste water treatment plants where they are not removed sufficiently. The behavior of the contrast agents in the environment and the interaction with organisms was investigated in this work due to the toxicity of the free Gd 3+ ion and the associated risks, such as accumulation in the human food chain. In this work, the two elemental analytical imaging methods laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and synchrotron radiation X-ray fluorescence analysis (SRXRF) have been used to investigate the uptake, distribution, and excretion of Gd-based contrast agents by various biological systems. Both methods were analytically characterized and compared for this application. The detection limits of gadolinium were determined under optimized conditions by LA-ICP-MS and SRXRF. With calibration by remains of dried elemental standard droplets detection limits of 0.78 pg absolute amount of gadolinium (LA-ICP-MS), respectively 89 pg (SRXRF) were reached. Based on filamentous algae as water plants the uptake and the excretion of Gd-based contrast agents were revealed. The dependence on concentration of the contrast agent in the exposition solution and the independence of temporal uptake within one to seven days were studied for duckweed. By LA-ICP-MS gadolinium was quantified in a leaf of cress plant. The verification of the results was performed by SRXRF and ICP-MS after digestion. Furthermore, the uptake and distribution of Gd-based contrast agents in higher organisms (water flea) were observed. The exact location of gadolinium was resolved by three-dimensional μ-computed tomography by the comparison of an exposed with a Gd-free water flea. In all studies, gadolinium was detected in the investigated exposed model organisms. It can be concluded that the contrast agents were taken from the environment.

Matter density distribution in atomic nuclei as illuminated by high energy hadrons

International Nuclear Information System (INIS)

Strugalski, Z.

1991-01-01

The method is proposed for the intranuclear matter density distribution study by means of high energy strongly interacting probes. The newly recognized process - the passage of hadrons through atomic nuclei - is employed as the physical basis of the operational principle of the method; the passage is accompanied by the nucleon emission from the target nuclei. It seems that the hadronic projectile sees a definite number of nucleons at a definite impact parameter, in passing through the target nucleus, but the number of the protons among the nucleus seen fluctuates according the binomial formula; in average, this number corresponds to the neutron-proton ratio (A-Z0/Z. 21 refs.; 4 figs.; 1 tab

Measuring device for the spatial neutron density distribution within a nuclear reactor

International Nuclear Information System (INIS)

Fracke, A.; Wachtler, H.

1974-01-01

A solid probe in a pneumatic tube is lead from the core to a measuring device outside the pressure vessel and reversely, in order to measure the local neutron density distribution inside a reactor core. The activiable solid probe is in the form of a steel spiral spring with densely open coils and semi-spherical end pieces. A good curve negotiating characteristic of the measuring probe and defined duration times are secured in the reactor core. Furthermore, the interior of the spiral can be filled with a lubricating medium, e.g. molybdenum sulphite, so that a better sliding of the measuring probe into the tubes of the pneumatic tube is ensured. (DG) [de

Post-double-contrast sigmoid flush: An adjuvant technique in imaging diverticular disease

International Nuclear Information System (INIS)

Lappas, J.C.; Maglinte, D.D.T.; Kopecky, K.K.; Cockerill, E.M.; Lehman, G.A.

1987-01-01

The sigmoid colon is the most difficult colonic segment to examine radiographically, especially when it is involved by diverticular disease. In a prospective study, infusion of a low-density contrast agent was evaluated as an adjuvant technique to high-density double-contrast sigmoid imaging. After a double-contrast barium enema, 52 consecutive patients with sigmoid diverticulosis received an additional 500-ml enema either with water or with a 1.5% CT barium suspension. Rectosigmoid films were compared and evaluated for luminal distention, visualization of the interhaustral space, definition of diverticula, and display of polypoid defects. Sigmoid flush, particularly with the 1.5% CT barium suspension, is a simple adjunct to the double-contrast examination that improves visualization of the diverticular sigmoid and increases diagnostic specificity

Angiogenesis and dynamic contrast enhanced MRI of benign and malignant breast lesions: preliminary results

International Nuclear Information System (INIS)

Liu Peifang; Bao Runxian; Niu Yun; Yu Yong

2002-01-01

Objective: To determine whether dynamic contrast enhanced MRI features of early-phase enhancement rate, enhancement amplitude, and signal intensity (SI) time course are associated with the microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression of malignant and benign breast lesions. Methods: Thirty-eight patients with histopathologically verified breast lesions underwent dynamic contrast enhanced MRI. SI changes during dynamic scanning were assessed quantitatively. Early-phase enhancement rate and enhancement amplitude were calculated. Time-SI curves of the lesions were obtained and classified according to their shapes as type I (which was steady enhancement to the end of the dynamic data acquisition at 7.5 min), type II (plateau of SI after avid initial contrast enhancement), or type III (washout of SI after avid initial contrast enhancement). the mean MVD and VEGF expression of the lesions were measured with immuno-histochemical staining method in all the histologic specimens by pathologists without the knowledge of the results of the MR examination. The relationships among dynamic contrast enhanced MRI features, MVD, and VEGF expression of benign and malignant breast lesions were analyzed. Results: Histology revealed 21 malignancies and 17 benign lesions. The mean MVD and VEGF expression for 21 malignant lesions were statistically higher than the mean MVD and VEGF expression for 17 benign lesions. High VEGF expression of benign and malignant breast lesions showed an association with increased MVD. Among all 38 lesions, greater (> 60%) MR early-phase enhancement rate and time-SI curve type II and III showed an association with increased MVD and higher VEGF expression level. All the differences mentioned above showed statistical significance except that the difference between VEGF expression and the distribution of curve types had no statistical significance. No significant relationships were observed between the mean of enhancement

Distribution Analysis of the Local Critical Temperature and Current Density in YBCO Coated Conductors using Low-temperature Scanning Laser and Hall Probe Microscopy

International Nuclear Information System (INIS)

Park, S. K.; Cho, B. R.; Park, H. Y.; Ri, H. C.

2011-01-01

Distribution of the local critical temperature and current density in YBCO coated conductors were analyzed using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared YBCO coated conductors of various bridge types to study the spatial distribution of the critical temperature and the current density in single and multi bridges. LTSLHPM system was modified for detailed linescan or two-dimensional scan both scanning laser and scanning Hall probe method simultaneously. We analyzed the local critical temperature of single and multi bridges from series of several linescans of scanning laser microscopy. We also investigated local current density and hysteresis curve of single bridge from experimental results of scanning Hall probe microscopy.

Effects of distribution density and cell dimension of 3D vegetation model on canopy NDVI simulation base on DART

Science.gov (United States)

Tao, Zhu; Shi, Runhe; Zeng, Yuyan; Gao, Wei

2017-09-01

The 3D model is an important part of simulated remote sensing for earth observation. Regarding the small-scale spatial extent of DART software, both the details of the model itself and the number of models of the distribution have an important impact on the scene canopy Normalized Difference Vegetation Index (NDVI).Taking the phragmitesaustralis in the Yangtze Estuary as an example, this paper studied the effect of the P.australias model on the canopy NDVI, based on the previous studies of the model precision, mainly from the cell dimension of the DART software and the density distribution of the P.australias model in the scene, As well as the choice of the density of the P.australiass model under the cost of computer running time in the actual simulation. The DART Cell dimensions and the density of the scene model were set by using the optimal precision model from the existing research results. The simulation results of NDVI with different model densities under different cell dimensions were analyzed by error analysis. By studying the relationship between relative error, absolute error and time costs, we have mastered the density selection method of P.australias model in the simulation of small-scale spatial scale scene. Experiments showed that the number of P.australias in the simulated scene need not be the same as those in the real environment due to the difference between the 3D model and the real scenarios. The best simulation results could be obtained by keeping the density ratio of about 40 trees per square meter, simultaneously, of the visual effects.

Size and spatial distribution of micropores in SBA-15 using CM-SANS

International Nuclear Information System (INIS)

Pollock, Rachel A.; Walsh, Brenna R.; Fry, Jason A.; Ghampson, Tyrone; Centikol, Ozgul; Melnichenko, Yuri B.; Kaiser, Helmut; Pynn, Roger; Frederick, Brian G.

2011-01-01

Diffraction intensity analysis of small-angle neutron scattering measurements of dry SBA-15 have been combined with nonlocal density functional theory (NLDFT) analysis of nitrogen desorption isotherms to characterize the micropore, secondary mesopore, and primary mesopore structure. The radial dependence of the scattering length density, which is sensitive to isolated surface hydroxyls, can only be modeled if the NLDFT pore size distribution is distributed relatively uniformly throughout the silica framework, not localized in a 'corona' around the primary mesopores. Contrast matching-small angle neutron scattering (CM-SANS) measurements, using water, decane, tributylamine, cyclohexane, and isooctane as direct probes of the size of micropores indicate that the smallest pores in SBA-15 have diameter between 5.7 and 6.2 (angstrom). Correlation of the minimum pore size with the onset of the micropore size distribution provides direct evidence that the shape of the smallest micropores is cylinderlike, which is consistent with their being due to unraveling of the polymer template.

Contrast-to-noise ratio optimization for a prototype phase-contrast computed tomography scanner

International Nuclear Information System (INIS)

Müller, Mark; Yaroshenko, Andre; Velroyen, Astrid; Tapfer, Arne; Bech, Martin; Pauwels, Bart; Bruyndonckx, Peter; Sasov, Alexander; Pfeiffer, Franz

2015-01-01

In the field of biomedical X-ray imaging, novel techniques, such as phase-contrast and dark-field imaging, have the potential to enhance the contrast and provide complementary structural information about a specimen. In this paper, a first prototype of a preclinical X-ray phase-contrast CT scanner based on a Talbot-Lau interferometer is characterized. We present a study of the contrast-to-noise ratios for attenuation and phase-contrast images acquired with the prototype scanner. The shown results are based on a series of projection images and tomographic data sets of a plastic phantom in phase and attenuation-contrast recorded with varying acquisition settings. Subsequently, the signal and noise distribution of different regions in the phantom were determined. We present a novel method for estimation of contrast-to-noise ratios for projection images based on the cylindrical geometry of the phantom. Analytical functions, representing the expected signal in phase and attenuation-contrast for a circular object, are fitted to individual line profiles of the projection data. The free parameter of the fit function is used to estimate the contrast and the goodness of the fit is determined to assess the noise in the respective signal. The results depict the dependence of the contrast-to-noise ratios on the applied source voltages, the number of steps of the phase stepping routine, and the exposure times for an individual step. Moreover, the influence of the number of projection angles on the image quality of CT slices is investigated. Finally, the implications for future imaging purposes with the scanner are discussed

Evaluation of articular cartilage degeneration with contrast-enhanced magnetic resonance imaging

International Nuclear Information System (INIS)

Fujioka, Mikihiro

1994-01-01

The evaluation of glycosaminoglycan (GAG) concentration is important in the clinical diagnosis of articular cartilage degeneration. Glycosaminoglycan provides a large number of fixed negative charges. When manganese ion (Mn 2+ ) is administered to the cartilage matrix, this cation diffuses into the matrix and accumulates in accordance with the distribution of fixed negative charges owing to the electrostatic interaction. The accumulation of Mn 2+ causes a shortening of the relaxation times, resulting in high signal intensity in the MR image, when a T 1 -weighted image is obtained. The present study applied this new method to the articular cartilage to evaluate the degree of the cartilage degeneration. Small pieces of articular cartilage were dissected from the knee joints of young chickens. Experimentally degenerated articular cartilage was obtained by treating the specimen with various concentrations of papain solution. Then specimens were soaked in manganese solution until they obtained equilibrium and served for MR microimaging. The fixed charge density (FCD), the concentration of Mn 2+ and Na + , T 1 and T 2 relaxation times were also measured. In degenerated cartilage, lower accumulation of Mn 2+ due to lower GAG density caused a lower than normal signal intensity. Thus, administration of Mn 2+ enhances the biochemical change in the cartilage matrix in terms of differences in the relaxation time. The actual signal intensity on MRI of each specimen corresponded to the theoretical signal intensity, which was calculated from the FCD. It was concluded that MR images taken with contrast enhancement by Mn 2+ give direct visual information about the GAG density in the articular cartilage. MRI with cationic contrast agent could develop into a new method for early non-invasive diagnosis of cartilage dysfunction and degeneration. (author)

Pulse sequences for contrast-enhanced magnetic resonance imaging

International Nuclear Information System (INIS)

Graves, Martin J.

2007-01-01

The theory and application of magnetic resonance imaging (MRI) pulse sequences following the administration of an exogenous contrast agent are discussed. Pulse sequences are categorised according to the contrast agent mechanism: changes in proton density, relaxivity, magnetic susceptibility and resonant frequency shift. Applications in morphological imaging, magnetic resonance angiography, dynamic imaging and cell labelling are described. The importance of optimising the pulse sequence for each application is emphasised

Study on density distribution and diffusion of deuterons in mono- and polycrystalline Ni absorbers using the nuclear reaction method

International Nuclear Information System (INIS)

Heintze, V.

1976-01-01

Irradiation experiments with cooled poly- and monocrystalline Ni absorbers are reported on. A very complex irradiation apparatus was set up, and a nuclear physics method was tested which enables an alignment of low-index crystal directions of monocrystalline absorbers in the target chamber with an exactness of at least 0.1 0 with regard to the ion beam. The nuclear reaction technique for the D(d,p)T reaction was developed far enough to enable a non-destructive determination of deuteron density distributions by analyzing proton spectra of this reaction. At low incorporation doses, there was no dose dependence of density distributions in monocrystalline Ni samples. Profile changes interpreted by a 'blurring' of the incident angle α due to an arching of the surface were only observed at doses Qsub(w) approximately > 3 x 10 18 deuterons/cm 2 . Furthermore, in polycrystalline Ni absorbers, there was a dependence of deuteron distributions on the angle between the beam and the absorber surface, which may be interpreted as a picture of a certain deposition, probability of single ions. In monocrystalline absorbers, range distributions for each of the low-index crystal directions were measured and compared with similar profiles of the polycrystalline absorber which had been measured at the same incident angle α. (orig.) [de

Parity dependence of the nuclear level density at high excitation

International Nuclear Information System (INIS)

Rao, B.V.; Agrawal, H.M.

1995-01-01

The basic underlying assumption ρ(l+1, J)=ρ(l, J) in the level density function ρ(U, J, π) has been checked on the basis of high quality data available on individual resonance parameters (E 0 , Γ n , J π ) for s- and p-wave neutrons in contrast to the earlier analysis where information about p-wave resonance parameters was meagre. The missing level estimator based on the partial integration over a Porter-Thomas distribution of neutron reduced widths and the Dyson-Mehta Δ 3 statistic for the level spacing have been used to ascertain that the s- and p-wave resonance level spacings D(0) and D(1) are not in error because of spurious and missing levels. The present work does not validate the tacit assumption ρ(l+1, J)=ρ(l, J) and confirms that the level density depends upon parity at high excitation. The possible implications of the parity dependence of the level density on the results of statistical model calculations of nuclear reaction cross sections as well as on pre-compound emission have been emphasized. (orig.)

Codimension two branes and distributional curvature

International Nuclear Information System (INIS)

Traschen, Jennie

2009-01-01

In general relativity, there is a well-developed formalism for working with the approximation that a gravitational source is concentrated on a shell, or codimension one surface. In contrast, there are obstacles to concentrating sources on surfaces that have a higher codimension, for example, a string in a spacetime with a dimension greater than or equal to four. Here it is shown that, by giving up some of the generality of the codimension one case, curvature can be concentrated on submanifolds that have codimension two. A class of metrics is identified such that (1) the scalar curvature and Ricci densities exist as distributions with support on a codimension two submanifold, and (2) using the Einstein equation, the distributional curvature corresponds to a concentrated stress-energy with equation of state p = -ρ, where p is the isotropic pressure tangent to the submanifold, and ρ is the energy density. This is the appropriate stress-energy to describe a self-gravitating brane that is governed by an area action, or a braneworld deSitter cosmology. The possibility of having a different equation of state arise from a wider class of metrics is discussed.

Contrast enhanced CT-scans are not comparable to non-enhanced scans in emphysema quantification

International Nuclear Information System (INIS)

Heussel, C.P.; Kappes, J.; Hantusch, R.; Hartlieb, S.; Weinheimer, O.; Kauczor, H.-U.; Eberhardt, R.

2010-01-01

Systemic, interventional and surgical treatments have gone new ways in treatment of emphysema. For longitudinal therapy monitoring and as end-points for clinical trials, quantification of the disease is necessary. Sensitive, easy to measure, as well as stable and reproducible parameters have to be characterized. One parameter that might affect emphysema quantification is IV contrast enhancement, which might also be indicated. Whether or not the contrast enhanced scan is also suited for emphysema quantification or an additional scan is necessary, a retrospective analysis of 12 adult patients undergoing clinically indicated both, a non-enhanced and enhanced thin section MSCT within a week (median 0 days, range 0-4 days) was done. The in-house YACTA software was used for automatic quantification of lung and emphysema volume, emphysema index, mean lung density, and 5th, 10th, 15th percentile. After IV contrast administration, the median CT derived lung volume decreased mild by 1.1%, while median emphysema volume decreased by relevant 11%. This results in a decrease of median emphysema index by 9%. The median lung density (15th percentile) increased after contrast application by 18 HU (9 HU). CT quantification delivers emphysema values that are clearly affected by IV contrast application. The detected changes after contrast application show the results of higher density in the lung parenchyma. Therefore the amount of quantified emphysema is reduced and the lung density increased after contrast enhancement. In longitudinal analyses, non-enhanced scans should be the reference, while enhanced scans cannot be used.

Identical metabolic rate and thermal conductance in Rock Sandpiper (Calidris ptilocnemis) subspecies with contrasting nonbreeding life histories

Science.gov (United States)

Ruthrauff, Daniel R.; Dekinga, Anne; Gill, Robert E.; Piersma, Theunis

2013-01-01

Closely related species or subspecies can exhibit metabolic differences that reflect site-specific environmental conditions. Whether such differences represent fixed traits or flexible adjustments to local conditions, however, is difficult to predict across taxa. The nominate race of Rock Sandpiper (Calidris ptilocnemis) exhibits the most northerly nonbreeding distribution of any shorebird in the North Pacific, being common during winter in cold, dark locations as far north as upper Cook Inlet, Alaska (61°N). By contrast, the tschuktschorum subspecies migrates to sites ranging from about 59°N to more benign locations as far south as ~37°N. These distributional extremes exert contrasting energetic demands, and we measured common metabolic parameters in the two subspecies held under identical laboratory conditions to determine whether differences in these parameters are reflected by their nonbreeding life histories. Basal metabolic rate and thermal conductance did not differ between subspecies, and the subspecies had a similar metabolic response to temperatures below their thermoneutral zone. Relatively low thermal conductance values may, however, reflect intrinsic metabolic adaptations to northerly latitudes. In the absence of differences in basic metabolic parameters, the two subspecies’ nonbreeding distributions will likely be more strongly influenced by adaptations to regional variation in ecological factors such as prey density, prey quality, and foraging habitat.

Distribution of electron density and magnetocapacitance in the regime of the fractional quantum Hall effect

Science.gov (United States)

Pikus, F. G.; Efros, A. L.

1993-06-01

A two-dimensional electron liquid (TDEL), subjected to a smooth random potential, is studied in the regime of the fractional quantum Hall effect. An analytical theory of the nonlinear screening is presented for the case when the fractional gap is much less than the magnitude of the unscreened random potential. In this ``narrow-gap approximation'' (NGA), we calculate the electron density distribution function, the fraction of the TDEL which is in the incompressible state, and the thermodynamic density of states. The magnetocapacitance is calculated to compare with the recent experiments. The NGA is found to be not accurate enough to describe the data. The results for larger fractional gaps are obtained by computer modeling. To fit the recent experimental data we have also taken into account the anyon-anyon interaction in the vicinity of a fractional singularity.

Effects of Habitual Physical Activity and Fitness on Tibial Cortical Bone Mass, Structure and Mass Distribution in Pre-pubertal Boys and Girls: The Look Study.

Science.gov (United States)

Duckham, Rachel L; Rantalainen, Timo; Ducher, Gaele; Hill, Briony; Telford, Richard D; Telford, Rohan M; Daly, Robin M

2016-07-01

Targeted weight-bearing activities during the pre-pubertal years can improve cortical bone mass, structure and distribution, but less is known about the influence of habitual physical activity (PA) and fitness. This study examined the effects of contrasting habitual PA and fitness levels on cortical bone density, geometry and mass distribution in pre-pubertal children. Boys (n = 241) and girls (n = 245) aged 7-9 years had a pQCT scan to measure tibial mid-shaft total, cortical and medullary area, cortical thickness, density, polar strength strain index (SSIpolar) and the mass/density distribution through the bone cortex (radial distribution divided into endo-, mid- and pericortical regions) and around the centre of mass (polar distribution). Four contrasting PA and fitness groups (inactive-unfit, inactive-fit, active-unfit, active-fit) were generated based on daily step counts (pedometer, 7-days) and fitness levels (20-m shuttle test and vertical jump) for boys and girls separately. Active-fit boys had 7.3-7.7 % greater cortical area and thickness compared to inactive-unfit boys (P girls, but active-fit girls had 6.1 % (P girls, which was likely due to their 6.7 % (P active-fit girls. Higher levels of habitual PA-fitness were associated with small regional-specific gains in 66 % tibial cortical bone mass in pre-pubertal children, particularly boys.

Biodiversity and the Lotka-Volterra theory of species interactions: open systems and the distribution of logarithmic densities.

Science.gov (United States)

Wilson, William G; Lundberg, Per

2004-09-22

Theoretical interest in the distributions of species abundances observed in ecological communities has focused recently on the results of models that assume all species are identical in their interactions with one another, and rely upon immigration and speciation to promote coexistence. Here we examine a one-trophic level system with generalized species interactions, including species-specific intraspecific and interspecific interaction strengths, and density-independent immigration from a regional species pool. Comparisons between results from numerical integrations and an approximate analytic calculation for random communities demonstrate good agreement, and both approaches yield abundance distributions of nearly arbitrary shape, including bimodality for intermediate immigration rates.

CT colonography: Diagnostic role of contrast enhancement of benign polyps and colorectal carcinoma

International Nuclear Information System (INIS)

Stoinova, V.; Nedevska, M.

2006-01-01

Full text: The aim of this study was to compare pre- and postcontrast CT attenuation values of benign colorectal polyps and carcinoma lesions detected by CT colonography, and to investigate whether contrast enhancement of these lesions can be potentially used for differentiation from residual fluid and feces. We retrospectively reviewed CT colonographic dataset of 120 patients. 35 benign polyps and 22 colorectal carcinomas were included in our study. All lesions were confirmed by colonoscopic biopsy or surgery. The difference in attenuation value between precontrast and postcontrast studies of polyps was statistically significant; the same was true for colorectal cancers. In the precontrast phase no statistically significant difference was observed between stool, polyps and cancers. The mean attenuation value of solid fecal residuals was 37 HU before and after contrast enhancement. Residual fluid do not take up contrast and the density does not change in the contrast-enhanced phase. The difference between postcontrast density of polyps and cancers with respect to density of stools and residual fluid was significant. The use of contrast medium could be helpful in CT colonography for discriminating polypoid benign lesions and colorectal cancer from fecal and fluid residuals

EVIDENCE FOR A ∼300 MEGAPARSEC SCALE UNDER-DENSITY IN THE LOCAL GALAXY DISTRIBUTION

Energy Technology Data Exchange (ETDEWEB)

Keenan, R. C. [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Barger, A. J. [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Cowie, L. L. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

2013-09-20

stellar mass density as a function of distance follows a similar trend. Assuming that luminous matter traces the underlying dark matter distribution, this implies that the local mass density of the universe may be lower than the global mass density on a scale and amplitude sufficient to introduce significant biases into the determination of basic cosmological observables. An under-density of roughly this scale and amplitude could resolve the apparent tension between direct measurements of the Hubble constant and those inferred by Planck.

A phase contrast interferometer on DIII-D

International Nuclear Information System (INIS)

Coda, S.; Porkolab, M.; Carlstrom, T.N.

1992-04-01

A novel imaging diagnostic has recently become operational on the DIII-D tokamak for the study of density fluctuations at the outer edge of the plasma. The phase contrast imaging approach overcomes the limitations of conventional scattering techniques in the spectral range of interest for transport-related phenomena, by allowing detection of long wavelength modes (up to 7.6 cm) with excellent spatial resolution (5 mm) in the radial direction. Additional motivation for the diagnostic is provided by wave-plasma interactions during heating and current drive experiments in the Ion Cyclotron range of frequencies. Density perturbations of 4 x 10 7 cm -3 with a 1 MHz bandwidth can be resolved. The diagnostic employs a 7.6 cm diameter CO 2 laser beam launched vertically across the plasma edge. An image of the plasma is then created on a 16-element detector array: the detector signals are directly proportional to the density fluctuations integrated along each chord. Wavelengths and correlation lengths can be inferred from the spatial mapping. The phase contrast method and its application to DIII-D are described and tests and first plasma data are presented

Spin theory of the density functional: reduced matrices and density functions

International Nuclear Information System (INIS)

Pavlov, R.; Delchev, Y.; Pavlova, K.; Maruani, J.

1993-01-01

Expressions for the reduced matrices and density functions of N-fermion systems of arbitrary order s (1<=s<=N) are derived within the frame of rigorous spin approach to the density functional theory (DFT). Using the local-scale transformation method and taking into account the particle spin it is shown that the reduced matrices and density functions are functionals of the total one-fermion density. Similar dependence is found for the distribution density of s-particle aggregates. Generalization and applicability of DFT to the case of s-particle ensembles and aggregates is discussed. 14 refs

The analysis of the contrast enhanced lesions on cerebro-vascular diseases

International Nuclear Information System (INIS)

Terada, Tomoaki; Nishiguchi, Takashi; Hyoutani, Genhachi; Miyamoto, Kazuki; Komai, Norihiko

1989-01-01

The contrast enhancement of cerebro-vascular diseases on CT is thought to be due to the increase of the cerebral blood volume (CBV) and/or the disruption of the blood brain barrier (BBB). However, it is difficult to differentiate these two conditions only by contrast enhanced CT. We employed dynamic CT (DCT) to analyse these lesions with respect to the patterns of time-density curve and peak height (PH) of the curve upon the theoretical basis that flattening of the latter part of the time-density curve reflected the degree of BBB disruption and PH reflected the CBV. In all cases of hypertensive intracerebral hemorrhage (11 cases), the contrast enhanced lesion around the hematoma showed marked BBB disruption according to the results of DCT. In 11 cases of cerebral infarction, patterns of BBB disruption and CBV varied at the contrast enhanced lesions according to the result of DCT. However, all contrast enhanced lesions with increased PH were associated with hemorrhagic infarction. Thus, the precise analysis of DCT provides appropriate therapeutic schedules by predicting the occurrence of hemorrhagic infarction. (author)

Application of phase contrast imaging to mammography

International Nuclear Information System (INIS)

Tohyama, Keiko; Yamada, Katsuhiko; Katafuchi, Tetsuro; Matsuo, Satoru; Morishita, Junji

2005-01-01

Phase contrast images were obtained experimentally by using a customized mammography unit with a nominal focal spot size of 100 μm and variable source-to-image distances of up to 1.5 m. The purpose of this study was to examine the applicability and potential usefulness of phase contrast imaging for mammography. A mammography phantom (ACR156 RMI phantom) was imaged, and its visibility was examined. The optical density of the phantom images was adjusted to approximately 1.3 for both the contact and phase contrast images. Forty-one observers (18 medical doctors and 23 radiological technologists) participated in visual evaluation of the images. Results showed that, in comparison with the images of contact mammography, the phantom images of phase contrast imaging demonstrated statistically significantly superior visibility for fibers, clustered micro-calcifications, and masses. Therefore, phase contrast imaging obtained by using the customized mammography unit would be useful for improving diagnostic accuracy in mammography. (author)

In-Line Phase-Contrast X-ray Imaging and Tomography for Materials Science.

Science.gov (United States)

Mayo, Sheridan C; Stevenson, Andrew W; Wilkins, Stephen W

2012-05-24

X-ray phase-contrast imaging and tomography make use of the refraction of X-rays by the sample in image formation. This provides considerable additional information in the image compared to conventional X-ray imaging methods, which rely solely on X-ray absorption by the sample. Phase-contrast imaging highlights edges and internal boundaries of a sample and is thus complementary to absorption contrast, which is more sensitive to the bulk of the sample. Phase-contrast can also be used to image low-density materials, which do not absorb X-rays sufficiently to form a conventional X-ray image. In the context of materials science, X-ray phase-contrast imaging and tomography have particular value in the 2D and 3D characterization of low-density materials, the detection of cracks and voids and the analysis of composites and multiphase materials where the different components have similar X-ray attenuation coefficients. Here we review the use of phase-contrast imaging and tomography for a wide variety of materials science characterization problems using both synchrotron and laboratory sources and further demonstrate the particular benefits of phase contrast in the laboratory setting with a series of case studies.

Moments expansion densities for quantifying financial risk

OpenAIRE

Ñíguez, T.M.; Perote, J.

2017-01-01

We propose a novel semi-nonparametric distribution that is feasibly parameterized to represent the non-Gaussianities of the asset return distributions. Our Moments Expansion (ME) density presents gains in simplicity attributable to its innovative polynomials, which are defined by the difference between the nth power of the random variable and the nth moment of the density used as the basis. We show that the Gram-Charlier distribution is a particular case of the ME-type of densities. The latte...

Influence of macular pigment optical density spatial distribution on intraocular scatter.

Science.gov (United States)

Putnam, Christopher M; Bland, Pauline J; Bassi, Carl J

This study evaluated the summed measures of macular pigment optical density (MPOD) spatial distribution and their effects on intraocular scatter using a commercially available device (C-Quant, Oculus, USA). A customized heterochromatic flicker photometer (cHFP) device was used to measure MPOD spatial distribution across the central 16° using a 1° stimulus. MPOD was calculated as a discrete measure and summed measures across the central 1°, 3.3°, 10° and 16° diameters. Intraocular scatter was determined as a mean of 5 trials in which reliability and repeatability measures were met using the C-Quant. MPOD spatial distribution maps were constructed and the effects of both discrete and summed values on intraocular scatter were examined. Spatial mapping identified mean values for discrete MPOD [0.32 (s.d.=0.08)], MPOD summed across central 1° [0.37 (s.d.=0.11)], MPOD summed across central 3.3° [0.85 (s.d.=0.20)], MPOD summed across central 10° [1.60 (s.d.=0.35)] and MPOD summed across central 16° [1.78 (s.d.=0.39)]. Mean intraocular scatter was 0.83 (s.d.=0.16) log units. While there were consistent trends for an inverse relationship between MPOD and scatter, these relationships were not statistically significant. Correlations between the highest and lowest quartiles of MPOD within the central 1° were near significance. While there was an overall trend of decreased intraocular forward scatter with increased MPOD consistent with selective short wavelength visible light attenuation, neither discrete nor summed values of MPOD significantly influence intraocular scatter as measured by the C-Quant device. Published by Elsevier España, S.L.U.

Contrast-enhanced color Doppler US in breast cancer: Tumoral vascularity correlated with angiogenesis

Energy Technology Data Exchange (ETDEWEB)

Kim, Eun A; Yoon, Kwon Ha; Yun, Ki Jung; Lee, Kwang Man; Park, Ki Han; Juhng, Seon Kwan; Won, Jong Jin [Wonkwang University School of Medicine, Seoul (Korea, Republic of)

2000-12-15

To evaluate the effects of contrast-enhanced color Doppler ultrasonography (CDUS) on the depiction of vascularity and flow pattern in breast cancer and to determine the relationship between tumoral vascularity and angiogenesis. Twenty-one patients with breast cancer were prospectively evaluated with CDUS before and after injection of the contrast agent (SH U 508A, 2.5g, 300 mg/ml ). The tumoral vascularity was expressed as percentage of color Doppler area, which was measured quantitatively by a computerized program (Ultrasonic Imaging Tool; Soongsil University, Seoul, Korea). The flow pattern (four-patterns; spotty, linear, branching, marginal) of the vascularity was analyzed. After surgery, tumor angiogenesis was assessed by microvessel density. The relationship between the vascularity on CDUS and microvessel density was statistically analyzed. At unenhanced CDUS, tumoral flow signals were detected in 12 lesions (48%); at contrast-enhanced CDUS, 18 lesions (86%). All These 18 lesions showed increased signals, compared with those at unenhanced CDUS. The percentage color Doppler area was 1.86 {+-} 0.48% at unenhanced CDUS and 5.23 {+-} 1.18% at contrast-enhanced CDUS. The flow patterns before contrast injection were spotty pattern in 11 tumors and linear pattern in one; after contrast injection, spotty in 8, linear in 4, branching in 5, and marginal in one. The tumoral vascularity at contrast-enhanced CDUS showed no significant correlation with microvessel density. Contrast-enhanced CDUS seems to be a valuable tool in the depiction of vascularity and characterization of flow pattern in breast cancer. However, tumoral vascularity on CDUS may not reflect tumoral angiogenesis.

CT of hepatocellular carcinoma. Analysis of contrast-enhanced CT using CT arteriography

Energy Technology Data Exchange (ETDEWEB)

Nakamura, H; Tanaka, T; Hori, S; Tokunaga, K; Yoshioka, H [Osaka Univ. (Japan). Faculty of Medicine

1981-02-01

Although changes in the CT appearance resulting from contrast enhancement (CE) for hepatocellular carcinoma have been considered in association with vascularity of tumors, no detailed studies have yet been made. We analyzed changes in the CT appearance following CE by comparing with hepatic arteriogram and CT arteriogram (CTA) performed during intraarterial infusion of contrast medium. When tumors showing low density in the plain CT were enhanced by contrast, the results were variable, ranging from intensification of the low density to replacement by high density, and the results were classified into L/sub 0/ to L/sub 3/ according to vascularity of tumors. The results after CE could also be classified into I/sub 0/ to I/sub 3/ when tumors showed isodensity in the plain CT. There was a correlation between vascularity presumed from CE and vascularity by CTA. It may be concluded that tumor vascularity could be estimated by the findings of CE which might indicate a possibility of qualitative diagnosis of tumors.

Distribution characteristics of terrestrial heat flow density in Jiyang depression of Shengli Oilfield, East China

Institute of Scientific and Technical Information of China (English)

GONG; Yuling; WANG; Liangshu; LIU; Shaowen; LI; Cheng; HAN

2004-01-01

Based on the geo-temperature data of 13 systematically continuous temperature log curves and 700 testing oil boreholes in Jiyang depression, Shengli Oilfield, and the measured thermal conductivities of 47 rock samples, the terrestrial heat flow densities of 114 boreholes of Jiyang depression and its surrounding areas are determined, including 13 of those data derived from systemically continuous temperature logging. The results show that Jiyang depression has a relatively high background heat flow with an average value (65.8 ± 5.4) mW/m2. The lateral variation of heat flow in basin has negative correlation with basement depth. Moreover, heat flow of uplift areas with shallower basement is high, so are those of regions with volcanic rocks, and those of depression areas with deep basement are relatively low. The heat flow densities of different structural units of Jiyang depression can be summarized as follows: The average heat flow value of Zhanhua sag is (67.4 ± 5.3) mW/m2, higher than that of the whole basin, that of Dongying sag is (66.0 ± 6.1) mW/m2, and that of Chezhen sag is (65.1 ± 3.7) mW/m2. It is apparent that these latter two values are approximate to the average value of the whole Jiyang depression,while the average value of Huimin sag is (63.6±5.0) mW/m2, lower than that of the whole basin. In fact, the basement depth and the distribution framework of uplift and depression areas are all controlled by the process of lithosphere extension. In addition, the distribution of volcanic rocks in basin is also relatively close to this extension geodynamic process. In summary, the distribution characteristics of terrestrial heat flow of Jiyang depression is determined by the Cenozoic tectono-thermal events of this region.

Performance assessment of density functional methods with Gaussian and Slater basis sets using 7σ orbital momentum distributions of N2O

Science.gov (United States)

Wang, Feng; Pang, Wenning; Duffy, Patrick

2012-12-01

Performance of a number of commonly used density functional methods in chemistry (B3LYP, Bhandh, BP86, PW91, VWN, LB94, PBe0, SAOP and X3LYP and the Hartree-Fock (HF) method) has been assessed using orbital momentum distributions of the 7σ orbital of nitrous oxide (NNO), which models electron behaviour in a chemically significant region. The density functional methods are combined with a number of Gaussian basis sets (Pople's 6-31G*, 6-311G**, DGauss TZVP and Dunning's aug-cc-pVTZ as well as even-tempered Slater basis sets, namely, et-DZPp, et-QZ3P, et-QZ+5P and et-pVQZ). Orbital momentum distributions of the 7σ orbital in the ground electronic state of NNO, which are obtained from a Fourier transform into momentum space from single point electronic calculations employing the above models, are compared with experimental measurement of the same orbital from electron momentum spectroscopy (EMS). The present study reveals information on performance of (a) the density functional methods, (b) Gaussian and Slater basis sets, (c) combinations of the density functional methods and basis sets, that is, the models, (d) orbital momentum distributions, rather than a group of specific molecular properties and (e) the entire region of chemical significance of the orbital. It is found that discrepancies of this orbital between the measured and the calculated occur in the small momentum region (i.e. large r region). In general, Slater basis sets achieve better overall performance than the Gaussian basis sets. Performance of the Gaussian basis sets varies noticeably when combining with different Vxc functionals, but Dunning's augcc-pVTZ basis set achieves the best performance for the momentum distributions of this orbital. The overall performance of the B3LYP and BP86 models is similar to newer models such as X3LYP and SAOP. The present study also demonstrates that the combinations of the density functional methods and the basis sets indeed make a difference in the quality of the

Molecular weight​/branching distribution modeling of low-​density-​polyethylene accounting for topological scission and combination termination in continuous stirred tank reactor

NARCIS (Netherlands)

Yaghini, N.; Iedema, P.D.

2014-01-01

We present a comprehensive model to predict the molecular weight distribution (MWD),(1) and branching distribution of low-density polyethylene (IdPE),(2) for free radical polymerization system in a continuous stirred tank reactor (CSTR).(3) The model accounts for branching, by branching moment or

Does interference competition with wolves limit the distribution and abundance of coyotes?

Science.gov (United States)

Berger, Kim Murray; Gese, Eric M

2007-11-01

Interference competition with wolves Canis lupus is hypothesized to limit the distribution and abundance of coyotes Canis latrans, and the extirpation of wolves is often invoked to explain the expansion in coyote range throughout much of North America. We used spatial, seasonal and temporal heterogeneity in wolf distribution and abundance to test the hypothesis that interference competition with wolves limits the distribution and abundance of coyotes. From August 2001 to August 2004, we gathered data on cause-specific mortality and survival rates of coyotes captured at wolf-free and wolf-abundant sites in Grand Teton National Park (GTNP), Wyoming, USA, to determine whether mortality due to wolves is sufficient to reduce coyote densities. We examined whether spatial segregation limits the local distribution of coyotes by evaluating home-range overlap between resident coyotes and wolves, and by contrasting dispersal rates of transient coyotes captured in wolf-free and wolf-abundant areas. Finally, we analysed data on population densities of both species at three study areas across the Greater Yellowstone Ecosystem (GYE) to determine whether an inverse relationship exists between coyote and wolf densities. Although coyotes were the numerically dominant predator, across the GYE, densities varied spatially and temporally in accordance with wolf abundance. Mean coyote densities were 33% lower at wolf-abundant sites in GTNP, and densities declined 39% in Yellowstone National Park following wolf reintroduction. A strong negative relationship between coyote and wolf densities (beta = -3.988, P wolves limits coyote populations. Overall mortality of coyotes resulting from wolf predation was low, but wolves were responsible for 56% of transient coyote deaths (n = 5). In addition, dispersal rates of transient coyotes captured at wolf-abundant sites were 117% higher than for transients captured in wolf-free areas. Our results support the hypothesis that coyote abundance is

Current density distribution during disruptions and sawteeth in a simple model of plasma current in a tokamak

International Nuclear Information System (INIS)

Stefanovskii, A. M.

2011-01-01

The processes that are likely to accompany discharge disruptions and sawteeth in a tokamak are considered in a simple plasma current model. The redistribution of the current density in plasma is supposed to be primarily governed by the onset of the MHD-instability-driven turbulent plasma mixing in a finite region of the current column. For different disruption conditions, the variation in the total plasma current (the appearance of a characteristic spike) is also calculated. It is found that the numerical shape and amplitude of the total current spikes during disruptions approximately coincide with those measured in some tokamak experiments. Under the assumptions adopted in the model, the physical mechanism for the formation of the spikes is determined. The mechanism is attributed to the diffusion of the negative current density at the column edge into the zero-conductivity region. The numerical current density distributions in the plasma during the sawteeth differ from the literature data.

Penetration and distribution of gadolinium-based contrast agents into the cerebrospinal fluid in healthy rats: a potential pathway of entry into the brain tissue

Energy Technology Data Exchange (ETDEWEB)

Jost, Gregor; Frenzel, Thomas; Lohrke, Jessica; Pietsch, Hubertus [MR and CT Contrast Media Research, Bayer Pharma AG, Berlin (Germany); Lenhard, Diana Constanze [Charite, Institute of Vegetative Physiology, Berlin (Germany); Naganawa, Shinji [Nagoya University Graduate School of Medicine, Department of Radiology, Nagoya (Japan)

2017-07-15

Signal hyperintensity on unenhanced MRI in certain brain regions has been reported after multiple administrations of some, but not all, gadolinium-based contrast agents (GBCAs). One potential initial pathway of GBCA entry into the brain, infiltration from blood into the cerebrospinal fluid (CSF), was systematically evaluated in this preclinical study. GBCA infiltration and distribution in the CSF were investigated in healthy rats using repeated fluid-attenuated MRI up to 4 h after high-dose (1.8 mmol/kg) administration of six marketed and one experimental GBCA. Additionally, gadolinium measurements in CSF, blood and brain tissue samples (after 24 h) were performed using inductively coupled plasma mass spectrometry. Enhanced MRI signals in the CSF spaces with similar distribution kinetics were observed for all GBCAs. No substantial differences in the gadolinium concentrations among the marketed GBCAs were found in the CSF, blood or brain tissue. After 4.5 h, the concentration in the CSF was clearly higher than in blood but was almost completely cleared and lower than the brain tissue concentration after 24 h. In contrast to the brain signal hyperintensities, no differences in penetration and distribution into the CSF of healthy rats exist among the marketed GBCAs. (orig.)

Penetration and distribution of gadolinium-based contrast agents into the cerebrospinal fluid in healthy rats: a potential pathway of entry into the brain tissue

International Nuclear Information System (INIS)

Jost, Gregor; Frenzel, Thomas; Lohrke, Jessica; Pietsch, Hubertus; Lenhard, Diana Constanze; Naganawa, Shinji

2017-01-01

Signal hyperintensity on unenhanced MRI in certain brain regions has been reported after multiple administrations of some, but not all, gadolinium-based contrast agents (GBCAs). One potential initial pathway of GBCA entry into the brain, infiltration from blood into the cerebrospinal fluid (CSF), was systematically evaluated in this preclinical study. GBCA infiltration and distribution in the CSF were investigated in healthy rats using repeated fluid-attenuated MRI up to 4 h after high-dose (1.8 mmol/kg) administration of six marketed and one experimental GBCA. Additionally, gadolinium measurements in CSF, blood and brain tissue samples (after 24 h) were performed using inductively coupled plasma mass spectrometry. Enhanced MRI signals in the CSF spaces with similar distribution kinetics were observed for all GBCAs. No substantial differences in the gadolinium concentrations among the marketed GBCAs were found in the CSF, blood or brain tissue. After 4.5 h, the concentration in the CSF was clearly higher than in blood but was almost completely cleared and lower than the brain tissue concentration after 24 h. In contrast to the brain signal hyperintensities, no differences in penetration and distribution into the CSF of healthy rats exist among the marketed GBCAs. (orig.)

Effects of emission layer doping on the spatial distribution of charge and host recombination rate density in organic light emitting devices: A numerical study

Science.gov (United States)

Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo; Peng, Yingquan

2013-12-01

Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs.

Effects of emission layer doping on the spatial distribution of charge and host recombination rate density in organic light emitting devices: A numerical study

Energy Technology Data Exchange (ETDEWEB)

Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo [Institute of Microelectronics, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Peng, Yingquan, E-mail: yqpeng@lzu.edu.cn [Institute of Microelectronics, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2013-12-28

Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs.

Effects of emission layer doping on the spatial distribution of charge and host recombination rate density in organic light emitting devices: A numerical study

International Nuclear Information System (INIS)

Li, Yanli; Zhou, Maoqing; Zheng, Tingcai; Yao, Bo; Peng, Yingquan

2013-01-01

Based on drift-diffusion theory, a numerical model of the doping of a single energy level trap in the emission layer of an organic light emitting device (OLED) was developed, and the effects of doping of this single energy level trap on the distribution of the charge density, the recombination rate density, and the electric field in single- and double-layer OLEDs were studied numerically. The results show that by doping the n-type (p-type) emission layer with single energy electron (hole) traps, the distribution of the recombination rate density can be tuned and shifted, which is useful for improvement of the device performance by reduced electrode quenching or for realization of desirable special functions, e.g., emission spectrum tuning in multiple dye-doped white OLEDs

CT of the pancreas with a fat-density oral contrast medium

International Nuclear Information System (INIS)

Raptopoulos, V.; Davidoff, A.; Davis, M.A.; Coolbaugh, B.L.; Smith, E.H.

1987-01-01

Visualization of the head of the pancreas on CT was evaluated in three groups, each consisting of 100 patients without pancreatic pathology who received a fat-density oral preparation. The corn oil emulsion was tolerated well by the patients and allowed consistently superior discrimination of the head of the pancreas from the duodenal C-loop as compared to the other two control groups. A score was developed for the CT discrimination of duodenum from pancreas. The average score for corn oil emulsion was .94, as opposed to .74 for the high-density agents and .76 for patients who did not receive any oral preparation. Until further experience is acquired, the authors do not recommend the use of corn oil in patients thought to have pancreatic pseudocysts or abscesses. In addition, the use of fat-containing oral agents may be contraindicated in patients with acute pancreatitis. For routine CT evaluation of the pancreas and upper abdomen, the authors consider corn oil emulsion superior to the other oral regimens

Contrast settling in cerebral aneurysm angiography

International Nuclear Information System (INIS)

Wang Zhijie; Hoffmann, Kenneth R; Guterman, Lee R; Wang Zhou; Rudin, Stephen; Meng Hui

2005-01-01

During angiography, blood flow is visualized with a radiopaque contrast agent, which is denser than blood. In complex vasculature, such as cerebral saccular aneurysms, the density difference may produce an appreciable gravity effect, where the contrast material separates from blood and settles along the gravity direction. Although contrast settling has been occasionally reported before, the fluid mechanics behind it have not been explored. Furthermore, the severity of contrast settling in cerebral aneurysms varies significantly from case to case. Therefore, a better understanding of the physical principles behind this phenomenon is needed to evaluate contrast settling in clinical angiography. In this study, flow in two identical groups of sidewall aneurysm models with varying parent-vessel curvature was examined by angiography. Intravascular stents were deployed into one group of the models. To detect contrast settling, we used lateral view angiography. Time-intensity curves were analysed from the angiographic data, and a computational fluid dynamic analysis was conducted. Results showed that contrast settling was strongly related to the local flow dynamics. We used the Froude number, a ratio of flow inertia to gravity force, to characterize the significance of gravity force. An aneurysm with a larger vessel curvature experienced higher flow, which resulted in a larger Froude number and, thus, less gravitational settling. Addition of a stent reduced the aneurysmal flow, thereby increasing the contrast settling. We found that contrast settling resulted in an elevated washout tail in the time-intensity curve. However, this signature is not unique to contrast settling. To determine whether contrast settling is present, a lateral view should be obtained in addition to the anteroposterior (AP) view routinely used clinically so as to rule out contrast settling and hence to enable a valid time-intensity curve analysis of blood flow in the aneurysm

Density and distribution of Patella ferruginea in a Marine Protected Area (western Sardinia, Italy: Constraint analysis for population conservation

Directory of Open Access Journals (Sweden)

S. COPPA

2012-04-01

Full Text Available The endemic limpet Patella ferruginea is the most endangered invertebrate of the Mediterranean Sea. Our study examined a population of P. ferruginea in the Marine Protected Area of Penisola del Sinis - Isola di Mal di Ventre (western Sardinia, Italy. During the summer 2009, we carried out a systematic census of P. ferruginea along a 8114 m georeferenced perimeter of coast in the no take-no entry zone to assess its density, spatial distribution, and morphometric characteristics. Our aim was to provide a detailed map of the distribution of P. ferruginea and to investigate the effects of accessibility, wave exposure and slope of the coast on its occurrence. Patella ferrugineashowed the lowest mean density ever reported (0.02 ind/m and a unimodal population structure characterised by fewer females and juveniles. Accessibility had a major negative effect on the occurrence of P. ferruginea. Exposure was also an important factor in influencing its density, size composition and specimen position within the mesolittoral, while the slope had little influence. Morphometric analysis showed the dominance of the Rouxi form, while the Lamarcki form was confined to exposed sites. Our results demonstrate a highly endangered population of P. ferruginea and suggest that human pressure represents the main risk factor.

Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

International Nuclear Information System (INIS)

Duverger, James Elber; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

2014-01-01

Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction–diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh–Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation. (paper)

Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

Science.gov (United States)

Elber Duverger, James; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

2014-11-01

Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction-diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh-Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation.

Macular pigment optical density spatial distribution measured in a subject with oculocutaneous albinism.

Science.gov (United States)

Putnam, Christopher M; Bland, Pauline J

2014-01-01

Previous studies of macular pigment optical density (MPOD) distribution in individuals with oculocutaneous albinism (OCA) have primarily used objective measurement techniques including fundus reflectometry and autofluorescence. We report here on a subject with OCA and their corresponding MPOD distribution assessed through heterochromatic flicker photometry (HFP). A subject with a history of OCA presented with an ocular history including strabismus surgery of the LE with persistent amblyopia and mild, latent nystagmus. Best corrected visual acuity was 20/25- RE and 20/40- LE. Spectral domain optical coherence tomography (SD-OCT) and fundus photography were also obtained. Evaluation of MPOD spatial distribution up to 8 degrees eccentricity from the fovea was performed using HFP. SD-OCT indicated a persistence of multiple inner retinal layers within the foveal region in the RE and LE including symmetric foveal thickening consistent with foveal hypoplasia. Fundus photography showed mild retinal pigmented epithelial (RPE) hypopigmentation and a poorly demarcated macula. OriginPro 9 was used to plot MPOD spatial distribution of the subject and a 33-subject sample. The OCA subject demonstrated a foveal MPOD of 0.10 with undetectable levels at 6 degrees eccentricity. The study sample showed a mean foveal MPOD of 0.34 and mean 6 degree eccentricity values of 0.03. Consistent with previous macular pigment (MP) studies of OCA, overall MPOD is reduced in our subject. Mild phenotypic expression of OCA with high functional visual acuity may represent a Henle fiber layer amenable to additional MP deposition. Further study of MP supplementation in OCA patients is warranted. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Deviations from the Boltzmann distribution in vibrationally excited gas flows

International Nuclear Information System (INIS)

Offenhaeuser, F.; Frohn, A.

1986-01-01

A new model for the exchange of vibrational energy in one-dimensional flows of CO 2 -H 2 O-N 2 -O 2 -He gas mixtures is presented. In contrast to previous models, the assumption of local Boltzmann distributions for the vibrational degrees of freedom is not required. This generalization was achieved by the assumption that the molecules are harmonic oscillators with one or more degrees of freedom represented by finite numbers of energy levels. The population densities of these energy levels are coupled by a set of rate equations. It is shown that in some cases of molecular gas flow the Boltzmann distribution for the vibrational degrees of freedom may be disturbed. 12 references

Experimental study of the density distribution of the particles of the material in screw installation

Directory of Open Access Journals (Sweden)

Demidov S. F.

2017-02-01

Full Text Available the experimental studies of density distribution of the particles of a mixture of wheat, oats, rye to feed pigs by infrared heating at the time of stay and temperature at the exit of the installation. The purpose of the work is to study the quality of treatment of the product with the settings with the screw and the screw with installed round jumper on the pen of the screw. Screw installations with infrared emitters of selected wavelength give the opportunity for intense and continuous heat treatment process. The authors used the optimal parameters of the process with the screw and the screw with installed round jumper on the pen of the screw. The parameters of screw installation during the study were the following: the number of revolutions of the screw was 10 rpm, density of heat flux was 12 kW/m2, output capacity – 250 kg/h.

Density, distribution, and genetic structure of grizzly bears in the Cabinet-Yaak Ecosystem

Science.gov (United States)

Macleod, Amy C.; Boyd, Kristina L.; Boulanger, John; Royle, J. Andrew; Kasworm, Wayne F.; Paetkau, David; Proctor, Michael F.; Annis, Kim; Graves, Tabitha A.

2016-01-01

The conservation status of the 2 threatened grizzly bear (Ursus arctos) populations in the Cabinet-Yaak Ecosystem (CYE) of northern Montana and Idaho had remained unchanged since designation in 1975; however, the current demographic status of these populations was uncertain. No rigorous data on population density and distribution or analysis of recent population genetic structure were available to measure the effectiveness of conservation efforts. We used genetic detection data from hair corral, bear rub, and opportunistic sampling in traditional and spatial capture–recapture models to generate estimates of abundance and density of grizzly bears in the CYE. We calculated mean bear residency on our sampling grid from telemetry data using Huggins and Pledger models to estimate the average number of bears present and to correct our superpopulation estimates for lack of geographic closure. Estimated grizzly bear abundance (all sex and age classes) in the CYE in 2012 was 48–50 bears, approximately half the population recovery goal. Grizzly bear density in the CYE (4.3–4.5 grizzly bears/1,000 km2) was among the lowest of interior North American populations. The sizes of the Cabinet (n = 22–24) and Yaak (n = 18–22) populations were similar. Spatial models produced similar estimates of abundance and density with comparable precision without requiring radio-telemetry data to address assumptions of geographic closure. The 2 populations in the CYE were demographically and reproductively isolated from each other and the Cabinet population was highly inbred. With parentage analysis, we documented natural migrants to the Cabinet and Yaak populations by bears born to parents in the Selkirk and Northern Continental Divide populations. These events supported data from other sources suggesting that the expansion of neighboring populations may eventually help sustain the CYE populations. However, the small size, isolation, and inbreeding documented by this study

Toward the Prediction of Water Exchange Rates in Magnetic Resonance Imaging Contrast Agents: A Density Functional Theory Study.

Science.gov (United States)

Regueiro-Figueroa, Martín; Platas-Iglesias, Carlos

2015-06-18

We present a theoretical investigation of Gd-Owater bonds in different complexes relevant as contrast agents in magnetic resonance imaging (MRI). The analysis of the Ln-Owater distances, electron density (ρBCP), and electron localization function (ELF) at the bond critical points of [Ln(DOTA)(H2O)](-) and [Ln(DTPA-BMA)(H2O)] indicates that the strength of the Ln-Owater bonds follows the order DTPA-BMA > DOTA (M isomer) > DOTA (m isomer). The ELF values decrease along the 4f period as the Ln-Owater bonds get shorter, in line with the labile capping bond phenomenon. Extension of these calculations to other Gd(3+) complexes allowed us to correlate the experimentally observed water exchange rates and the calculated ρBCP and ELF values. The water exchange reaction becomes faster as the Gd-Owater bonds are weakened, which is reflected in longer bond distances and lower values of ρBCP and ELF. DKH2 calculations show that the two coordinated water molecules may also have significantly different (17)O hyperfine coupling constants (HFCCs).

On density forecast evaluation

NARCIS (Netherlands)

Diks, C.

2008-01-01

Traditionally, probability integral transforms (PITs) have been popular means for evaluating density forecasts. For an ideal density forecast, the PITs should be uniformly distributed on the unit interval and independent. However, this is only a necessary condition, and not a sufficient one, as

Habitat structure and body size distributions: Cross-ecosystem comparison for taxa with determinate and indeterminate growth

Science.gov (United States)

Nash, Kirsty L.; Allen, Craig R.; Barichievy, Chris; Nystrom, Magnus; Sundstrom, Shana M.; Graham, Nicholas A.J.

2014-01-01

Habitat structure across multiple spatial and temporal scales has been proposed as a key driver of body size distributions for associated communities. Thus, understanding the relationship between habitat and body size is fundamental to developing predictions regarding the influence of habitat change on animal communities. Much of the work assessing the relationship between habitat structure and body size distributions has focused on terrestrial taxa with determinate growth, and has primarily analysed discontinuities (gaps) in the distribution of species mean sizes (species size relationships or SSRs). The suitability of this approach for taxa with indeterminate growth has yet to be determined. We provide a cross-ecosystem comparison of bird (determinate growth) and fish (indeterminate growth) body mass distributions using four independent data sets. We evaluate three size distribution indices: SSRs, species size–density relationships (SSDRs) and individual size–density relationships (ISDRs), and two types of analysis: looking for either discontinuities or abundance patterns and multi-modality in the distributions. To assess the respective suitability of these three indices and two analytical approaches for understanding habitat–size relationships in different ecosystems, we compare their ability to differentiate bird or fish communities found within contrasting habitat conditions. All three indices of body size distribution are useful for examining the relationship between cross-scale patterns of habitat structure and size for species with determinate growth, such as birds. In contrast, for species with indeterminate growth such as fish, the relationship between habitat structure and body size may be masked when using mean summary metrics, and thus individual-level data (ISDRs) are more useful. Furthermore, ISDRs, which have traditionally been used to study aquatic systems, present a potentially useful common currency for comparing body size distributions

Using the phase-space imager to analyze partially coherent imaging systems: bright-field, phase contrast, differential interference contrast, differential phase contrast, and spiral phase contrast

Science.gov (United States)

Mehta, Shalin B.; Sheppard, Colin J. R.

2010-05-01

Various methods that use large illumination aperture (i.e. partially coherent illumination) have been developed for making transparent (i.e. phase) specimens visible. These methods were developed to provide qualitative contrast rather than quantitative measurement-coherent illumination has been relied upon for quantitative phase analysis. Partially coherent illumination has some important advantages over coherent illumination and can be used for measurement of the specimen's phase distribution. However, quantitative analysis and image computation in partially coherent systems have not been explored fully due to the lack of a general, physically insightful and computationally efficient model of image formation. We have developed a phase-space model that satisfies these requirements. In this paper, we employ this model (called the phase-space imager) to elucidate five different partially coherent systems mentioned in the title. We compute images of an optical fiber under these systems and verify some of them with experimental images. These results and simulated images of a general phase profile are used to compare the contrast and the resolution of the imaging systems. We show that, for quantitative phase imaging of a thin specimen with matched illumination, differential phase contrast offers linear transfer of specimen information to the image. We also show that the edge enhancement properties of spiral phase contrast are compromised significantly as the coherence of illumination is reduced. The results demonstrate that the phase-space imager model provides a useful framework for analysis, calibration, and design of partially coherent imaging methods.

Probing topological relations between high-density and low-density regions of 2MASS with hexagon cells

Energy Technology Data Exchange (ETDEWEB)

Wu, Yongfeng [American Physical Society, San Diego, CA (United States); Xiao, Weike, E-mail: yongfeng.wu@maine.edu [Department of Astronautics Engineering, Harbin Institute of Technology, P.O. Box 345, Heilongjiang Province 150001 (China)

2014-02-01

We introduced a new two-dimensional (2D) hexagon technique for probing the topological structure of the universe in which we mapped regions of the sky with high and low galaxy densities onto a 2D lattice of hexagonal unit cells. We defined filled cells as corresponding to high-density regions and empty cells as corresponding to low-density regions. The numbers of filled cells and empty cells were kept the same by controlling the size of the cells. By analyzing the six sides of each hexagon, we could obtain and compare the statistical topological properties of high-density and low-density regions of the universe in order to have a better understanding of the evolution of the universe. We applied this hexagonal method to Two Micron All Sky Survey data and discovered significant topological differences between the high-density and low-density regions. Both regions had significant (>5σ) topological shifts from both the binomial distribution and the random distribution.