8,643 research outputs found
On the X-ray number of almost smooth convex bodies and of convex bodies of constant width
The X-ray numbers of some classes of convex bodies are investigated. In
particular, we give a proof of the X-ray Conjecture as well as of the
Illumination Conjecture for almost smooth convex bodies of any dimension and
for convex bodies of constant width of dimensions 3, 4, 5 and 6
CCD photometry and new models of 5 minor planets
We present new R filtered CCD observations of 5 faint and moderately faint
asteroids carried out between October, 1998 and January, 1999. The achieved
accuracy is between 0.01-0.03 mag, depending mainly on the target brightness.
The obtained sinodic periods and amplitudes:
683 Lanzia - 4.6+/-0.2 h, 0.13 mag; 725 Amanda - >3.0 h, >=0.40 mag; 852
Wladilena - 4.62+/-0.01 h, 0.32 mag (December, 1998) and 0.27 mag (January,
1999); 1627 Ivar - 4.80+/-0.01, 0.77 mag (December, 1998) and 0.92 mag
(January, 1999). The Near Earth Object 1998 PG unambiguously showed
doubly-periodic lightcurve, suggesting the possibility of a relatively fast
precession (P_1=1.3 h, P_2=5.3 h).
Collecting all data from the literature, we determined new models for 3 minor
planets. The resulting spin vectors and triaxial ellipsoids have been
calculated by an amplitude-method. Sidereal periods and senses of rotation were
calculated for two asteroids (683 and 1627) by a modified epoch-method. The
results are:
683 - lambda_p=15/195+/-25 deg, beta_p=52+/-15 deg, a/b=1.15+/-0.05,
b/c=1.05+/-0.05, P_sid=0.1964156+/-0.0000001 d, retrograde; 852 -
lambda_p=30/210+/-20 deg, beta_p=30+/-10 deg, a/b=2.3+/-0.3, b/c=1.2+/-0.2;
1627 - lambda_p=145/325+/-8 deg, beta_p=34+/-6 deg, a/b=2.0+/-0.1,
b/c=1.09+/-0.05, P_sid=0.1999154+/-0.0000003 d, retrograde. The obtained shape
of 1627 is in good agreement with radar images by Ostro et al. (1990).Comment: 8 pages, accepted for publication in Astronomy and Astrophysics
Suppl. Serie
Massive Splenic Pseudocysts : Report of 2 cases
Splenic cysts can be classified as parasitic and nonparasitic. Non parasitic cysts can be further divided into true and pseudocysts. Pseudocysts of spleen does not contain an epithelial lining. Pseudocysts of spleen are usually post traumatic and they rarely grow to a large size and most of them are asymptomatic. It can be confused with cystic lesions of spleen or pancreas or from the surrounding structures. These cases require exploration and is both diagnostic and therapeutic. Conservative measures to preserve spleen can be considered only in presence of expertise and if remnant functional splenic parenchyma is more than 25 %. Here we present two cases of giant pseudocysts who were confused with malignancy and referred to our centre and were later found to be pseudocysts of spleen. We would like to report these cases as they are rare and as diagnostic dilemmas
Baryonic contributions to the dilepton spectrum of nucleon-nucleon collisions
We study the production of dileptons in relativistic nucleon-nucleon
collisions. Additionally to the traditional dilepton production channels
(vector meson decays, meson and Delta(1232) Dalitz decays) we included in our
model as new dilepton sources the Dalitz decay of higher unflavored baryon
resonances with spin<=5/2 and mass<=2.25 GeV/c^2. The contributions of these
new channels are estimated using experimental information about the Ngamma
decays of the resonances and have large uncertainties. The obtained dilepton
spectra are compared to the experimental data by the DLS collaboration.
Predictions for the HADES detector (SIS, GSI) are also discussed. In spite of
the large uncertainties of the higher resonance Dalitz decay contributions we
are able to draw the conclusion that these contributions are negligible
compared to the other dilepton sources and do not influence the detectability
of the phi and omega vector meson peaks.Comment: 9 pages, 4 figures, version accepted for publication in Phys. Rev.
CONSIDERATION OF TWO DIMENSIONAL SURFACE ROUGHNESSES IN QUANTITATIVE XPS ANALYSIS
The effect of two dimensional surface roughnesses on the intensities of XPS peaks have
been investigated. The following models have been studied: square base pits with side walls
perpendicular to the surface in chequered position, square base pyramid shaped pits touching
each other by their edges, square base pyramids touching each other by their bottom edges, and
spheres in closest packing with a planar tangent surface. On the latter model also the effect of ion
etching has been studied. The application of the results are demonstrated on two quantitative
surface analytical problems
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