scholarly journals X-Rays from Wolf-Rayet Stars Observed by the Einstein Observatory

1982 ◽  
Vol 99 ◽  
pp. 589-595
Author(s):  
W. T. Sanders ◽  
J. P. Cassinelli ◽  
K. A. van der Hucht
Keyword(s):  
Mean Value ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Total Luminosity ◽  
Hydrogen Emission Lines ◽  
Flux Level ◽  
The Mean ◽  
Einstein Observatory ◽  
Thin Source

Preliminary results of three X-ray surveys are presented. Out of a sample of 20 stars, X-rays were detected from four Wolf-Rayet stars and two 08f+ stars. The detected stars have about the same mean value as 0 stars for the X-ray to total luminosity ratio, LX/L = 10−7, but exhibit a much larger variation about the mean. The spectral energy distributions are also found to be like that of 0 stars in that they do not exhibit large attenuation of X-rays softer than 1 keV. This indicates that for both the 0 stars and WR stars much of the X-ray emission is coming from hot wisps or shocks in the outer regions of the winds and not from a thin source at the base of the wind. The general spectral shape and flux level place severe restrictions on models that attribute the lack of hydrogen emission lines to extremely high temperatures of the gas in the wind.

scholarly journals The reflexion of X-rays from the ‘anti-phase nuclei’ of AuCu 3

1943 ◽  
Vol 181 (987) ◽  
pp. 360-368 ◽  
Keyword(s):  
Mean Value ◽  
X Rays ◽  
Integral Breadth ◽  
X Ray ◽  
Structure Factors ◽  
Unit Cells ◽  
The Mean

Jones & Sykes have observed that the superlattice lines in X-ray photographs of AuCu 3 , are not always as sharp as the main lines, and that the broadening depends markedly on the indices of the line. They explain these phenomena by assuming that the crystals of AuCu 3 contain many ‘anti-phase nuclei’ in which the superlattice is organized in different ways. In the present paper it is shown that the integral breadth of a reflexion from a crystal in which all the unit cells are not the same is λ J 0 /cos θ ƒ J t dt , where J t is the mean value of the product FF* of the structure factors of two unit cells separated a distance t in the hkl direction. Detailed calculations are made of the broadening to be expected from five different ways in which the nuclei can ‘change step’. Closest agreement with the observed broadening is given by a manner of ‘ changing step ’ in which the gold atoms avoid one another.

Long-period modulated superstructures in Pd-12.5 at.%Ce and Pd-15 at.%Ce alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 164-165
Author(s):  
Noriyuki Kuwano ◽  
Masaru Itakura ◽  
Kensuke Oki
Keyword(s):  
Electron Microscopy ◽  
Mean Value ◽  
Heavy Elements ◽  
Arc Furnace ◽  
X Ray ◽  
Long Period ◽  
Ultra High Purity ◽  
Heat Treated ◽  
Atomic Scattering ◽  
The Mean

Pd-Ce alloys exhibit various anomalies in physical properties due to mixed valences of Ce, and the anomalies are thought to be strongly related with the crystal structures. Since Pd and Ce are both heavy elements, relative magnitudes of (fcc-fpd) are so small compared with <f> that superlattice reflections, even if any, sometimes cannot be detected in conventional x-ray powder patterns, where fee and fpd are atomic scattering factors of Ce and Pd, and <f> the mean value in the crystal. However, superlattices in Pd-Ce alloys can be analyzed by electron microscopy, thanks to the high detectability of electron diffraction. In this work, we investigated modulated superstructures in alloys with 12.5 and 15.0 at.%Ce.Ingots of Pd-Ce alloys were prepared in an arc furnace under atmosphere of ultra high purity argon. The disc specimens cut out from the ingots were heat-treated in vacuum and electrothinned to electron transparency by a jet method.

scholarly journals An Evaluation of Cellular Neural Networks for the Automatic Identification of Cephalometric Landmarks on Digital Images

2009 ◽  
Vol 2009 ◽  
pp. 1-12 ◽  
Author(s):  
Rosalia Leonardi ◽  
Daniela Giordano ◽  
Francesco Maiorana
Keyword(s):  
Neural Networks ◽  
Cellular Neural Networks ◽  
Automatic Identification ◽  
Cephalometric Analysis ◽  
X Rays ◽  
X Ray ◽  
Automatic Location ◽  
Landmark Identification ◽  
The Mean ◽  
Analogue To Digital

Several efforts have been made to completely automate cephalometric analysis by automatic landmark search. However, accuracy obtained was worse than manual identification in every study. The analogue-to-digital conversion of X-ray has been claimed to be the main problem. Therefore the aim of this investigation was to evaluate the accuracy of the Cellular Neural Networks approach for automatic location of cephalometric landmarks on softcopy of direct digital cephalometric X-rays. Forty-one, direct-digital lateral cephalometric radiographs were obtained by a Siemens Orthophos DS Ceph and were used in this study and 10 landmarks (N, A Point, Ba, Po, Pt, B Point, Pg, PM, UIE, LIE) were the object of automatic landmark identification. The mean errors and standard deviations from the best estimate of cephalometric points were calculated for each landmark. Differences in the mean errors of automatic and manual landmarking were compared with a 1-way analysis of variance. The analyses indicated that the differences were very small, and they were found at most within 0.59 mm. Furthermore, only few of these differences were statistically significant, but differences were so small to be in most instances clinically meaningless. Therefore the use of X-ray files with respect to scanned X-ray improved landmark accuracy of automatic detection. Investigations on softcopy of digital cephalometric X-rays, to search more landmarks in order to enable a complete automatic cephalometric analysis, are strongly encouraged.

How Accurate is Qcbed ? -- the Case of Rutile (TiO2)

2001 ◽  
Vol 7 (S2) ◽  
pp. 368-369
Author(s):  
B. Jiang ◽  
J. Friis ◽  
J.C.H. Spence
Keyword(s):  
Systematic Errors ◽  
Mean Value ◽  
Order Structure ◽  
Data Sets ◽  
X Ray ◽  
Silicon Crystals ◽  
Structure Factors ◽  
The Mean ◽  
Mott Formula ◽  
Better Than

An accuracy of better than 1% is needed to measure the changes in charge density due to bonding. Here we report an accuracy up to 0.025% (random error) obtained in rutile crystal structure factors measurement by QCBED. This error is the standard deviation in the mean value obtained from ten data sets. Systematic errors may be present. Figure 1 gives an example of the (200) refinement results. Table 1 lists several low order structure factor refinement results. The accuracy of the measured electron structure factors was 0.1-0.2% but after conversion to x-ray structure factors, the accuracy for low orders improved due to the Mott formula [1] For (110) and (101) reflections, the accuracy in x-ray structure factors became 0.025% and 0.048% respectively. This accuracy is equivalent to that of the X-ray single crystal Pendellosung method on silicon crystals [2].The experiments were done on a Leo 912 Omega TEM.

Isoelastic Cementless Total Hip Replacement in Rheumatoid Arthritis. Long-Term Results

1992 ◽  
Vol 2 (2) ◽  
pp. 43-46
Author(s):  
U. Fusco ◽  
R. Capelli ◽  
A. Avai ◽  
M. Gerundini ◽  
L. Colombini ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Hip Replacement ◽  
The Other ◽  
Long Term Results ◽  
X Rays ◽  
X Ray ◽  
The Mean ◽  
Cementless Total Hip Replacement

Between 1980 and 1987 we have implanted 46 isoelastic cementless THR in 40 patients affected with rheumatoid arthritis. We have reviewed 38 hips clinically and by X-ray. The mean follow-up was 8,5 years. Harris hip scores ranged from 30.6 preoperatively to 73,4 post-operatively when reviewed. While on the other hand Merle D'Aubigné hip scores ranged from 7,06 pre-operatively to 15,59 post-operatively. All patients have been satisfied, and X-rays showed an improvement for both Charnely and Gruen X-ray score.

Ulnar Variance in Kienböck’s Disease

1986 ◽  
Vol 11 (2) ◽  
pp. 258-260
Author(s):  
S. S. KRISTENSEN ◽  
E. THOMASSEN ◽  
F. CHRISTENSEN
Keyword(s):  
Bone Formation ◽  
Mean Value ◽  
Observation Time ◽  
Ulnar Variance ◽  
X Rays ◽  
Lunate Bone ◽  
Kienböck’S Disease ◽  
Kienböck's Disease ◽  
The Mean ◽  
Kienbock’S Disease

Forty four patients with forty seven wrists suffering from Kienböck’s disease were re-examined. The mean observation time was 20.5 years. In all forty seven wrists the treatment had been immobilization. Using a standard X-ray projection, and a reliable method of ulnar variance measuring, the ulnar variance was determined by three observers independently. Comparing the result with the ulnar variance in normal wrists we found the so-called “ulnar minus variant” overrepresented in patients with Kienböck’s disease. However, comparing X-rays taken at the time of diagnosis with X-rays at re-examination, we found in eight out of forty seven wrists that a subchondral bone formation in the distal radius opposite the lunate bone had taken place. This bone formation will tend to enhance the negative value of ulnar variance measurements, and suggests an explanation of the overrepresentation of “ulnar minus variants” in Kienböck’s disease. Excluding these eight wrists from the material and comparing the mean ulnar variance value in the remaining thirty nine wrists with the mean value in normal wrists no statistical difference was shown. Based on these observations it seems unlikely that the “ulnar minus variant” has any bearing on the cause of Kienböck’s disease.

scholarly journals A NuSTAR view of powerful γ-ray loud blazars

2019 ◽  
Vol 627 ◽  
pp. A72 ◽  
Author(s):  
G. Ghisellini ◽  
M. Perri ◽  
L. Costamante ◽  
G. Tagliaferri ◽  
T. Sbarrato ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Peak Frequency ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Γ Ray ◽  
The Universe ◽  
Jet Power

We observed three blazars at z >  2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them we were able to study the source in different states, and investigate the main cause of the different observed spectral energy distribution. We then collected all blazars at redshifts greater than 2 observed by NuSTAR, and confirm that these hard and luminous X-ray blazars are among the most powerful persistent sources in the Universe. We confirm the relation between the jet power and the disk luminosity, extending it at the high-energy end.

In Situ Observation of the Oxygen Nucleation in Silicon with X-Ray Single Crystal Diffraction

2011 ◽  
Vol 178-179 ◽  
pp. 353-359 ◽  
Author(s):  
Johannes Will ◽  
Alexander Gröschel ◽  
Christoph Bergmann ◽  
Andreas Magerl
Keyword(s):  
Single Crystal ◽  
Waller Factor ◽  
Dynamical Theory ◽  
Mean Value ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Float Zone ◽  
Debye Waller Factor ◽  
The Mean

The measurement of Pendellösungs oscillations was used to observe the time dependent nucleation of oxygen in a Czochralski grown single crystal at 750°C. It is shown, that the theoretical approach of the statistical dynamical theory describes the data well. Within the framework of this theory it is possible to determine the static Debye-Waller-factor as a function of the annealing time by evaluating the mean value of the Bragg intensity and the period length. The temperature influence on the Pendellösungs distance was corrected for by measurement of a Float-zone sample at the same temperature.

The Utility of Preoperative Magnetic Resonance Imaging for Determining the Flexibility of Sagittal Imbalance

Neurosurgery ◽  
2017 ◽  
Vol 83 (3) ◽  
pp. 465-470
Author(s):  
Akshay Sharma ◽  
Sina Pourtaheri ◽  
Jason Savage ◽  
Iain Kalfas ◽  
Thomas E Mroz ◽  
...  
Keyword(s):  
Lumbar Lordosis ◽  
Surgical Planning ◽  
Pelvic Incidence ◽  
Sagittal Imbalance ◽  
X Rays ◽  
Resonance Imaging ◽  
Patient Counseling ◽  
X Ray ◽  
Preoperative Magnetic Resonance ◽  
The Mean

Abstract BACKGROUND Scoliosis X-rays are the gold standard for assessing preoperative lumbar lordosis; however, particularly for flexible lumbar deformities, it is difficult to predict from these images the extent of correction required, as standing radiographs cannot predict the thoracolumbar alignment after intraoperative positioning. OBJECTIVE To determine the utility of preoperative MRI in surgical planning for patients with flexible sagittal imbalance. METHODS We identified 138 patients with sagittal imbalance. Radiographic parameters including pelvic incidence and lumbar lordosis were obtained from images preoperatively. RESULTS The mean difference was 2.9° between the lumbar lordosis measured on supine MRI as compared to the intraoperative X-rays, as opposed to 5.53° between standing X-rays and intraoperative X-ray. In patients with flexible deformities (n = 24), the lumbar lordosis on MRI measured a discrepancy of 3.08°, as compared to a discrepancy of 11.46° when measured with standing X-ray. CONCLUSION MRI adequately determined which sagittal deformities were flexible. Furthermore, with flexible sagittal deformities, lumbar lordosis measured on MRI more accurately predicted the intraoperative lumbar lordosis than that measured on standing X-ray. The ability to preoperatively predict intraoperative lumbar lordosis with positioning helps with surgical planning and patient counseling regarding expectations and risks of surgery.

scholarly journals New Spectral Observations of the Variable Galaxy Kaz 163

2013 ◽  
Vol 9 (S304) ◽  
pp. 39-40
Author(s):  
Emilia L. Karapetyan
Keyword(s):  
Elliptical Galaxy ◽  
Short Wave ◽  
Mean Value ◽  
Emission Lines ◽  
Byurakan Astrophysical Observatory ◽  
X Ray ◽  
Long Wave ◽  
The Galaxy ◽  
The Mean ◽  
Active Processes

AbstractKaz 163 is a close double galaxy. Its southern component S is compact, with a very blue nucleus, in which heated active processes take place. From time to time gas formations are ejected from it, which behave themselves like emission components around the main emission lines Hα and Hβ, around both from their long-wave and short-wave sides. This paper presents the spectral data of new observations, which were carried out with the 2.6m telescope at the Byurakan Astrophysical Observatory in September 2011. During the former observation in October 1981, lines [NII] λλ 6584,6548 were not visible in the spectrum of the component S. In 2001 they were already visible on the spectrum, and on the spectrum obtained in 2011 they already surpassed the intensity of Hα. The magnitude of the component S is also changing: its nucleus is very blue and its U-B = −0m.63. In the soft X-ray spectral range (0.1–2 keV) the flux of the radiation changed by 45% during 55,000 sec, and in the hard one (2–10keV) it changed up to 3.4 times. Photoindices Γ for the soft and hard ranges in the spectrum of galaxy S, unlike other objects, do not so much differ from each other. The mean value for the first interval is approximately 2.5 and is equal −2.0 for the second one. On the histogram of redshifts Kaz 163 corresponds to the first big peak of the distribution. It is concluded that the component S of the galaxy Kaz 163 is a NLS1 galaxy, with the development of their evolution, is in the preliminary stage. Component N is a normal elliptical galaxy with no activity.

Sign in / Sign up

Export Citation Format

Share Document