4,336 research outputs found
A novel, mitogen-activated nuclear kinase is related to a Drosophila developmental regulator
Although the ultimate targets of many signal transduction pathways are nuclear transcription factors, the vast majority of known protein kinases are cytosolic. Here, we report on a novel human kinase that is present exclusively in the nucleus. Kinase activity is increased upon cellular proliferation and is markedly elevated in patients with acute and chronic lymphocytic leukemias. We have identified a human gene that encodes this nuclear kinase and find that it is closely related to Drosophila female sterile homeotic (fsh), a developmental regulator with no known biochemical activity. Collectively, these results suggest that this nuclear kinase is a component of a signal transduction pathway that plays a role in Drosophila development and human growth control
A depth-encoding PET detector module with improved spatial sampling
Proceeding of: 1998 IEEE Nuclear Science Symposium and Medical Imaging Conference, Toronto, Ont., 08 - 14 Nov. 1998Detector modules in small ring diameter PET scanners
must possess depth-of-interaction (DOI) encoding, increased
spatial sampling, high sensitivity and the ability to handle high
photon input rates without excessive pulse pileup or random
coincidences. We created such a module by optically
coupling an entrance array of individual LGSO crystals to an
exit array of individual GSO (and other) crystals that was, in
turn, optically and directly coupled to a miniature PSPMT.
DO1 was determined for each event by delayed charge
integration (DCI), a technique that exploits differences in light
decay time between GSO and LGSO.
Spatial sampling in 3D was increased by introducing a half
crystal pitch spatial offset between the entrance and exit arrays
in both the X and Y directions. Position detection accuracy in
both the LGSO and GSO layers, and the accuracy of DO1
assignment of events to either layer was high. These results
suggest that this combination of scintillators and
acquisition/processing methods may be particularly useful in
the design of high performance, small ring diameter PET
scanners for small animal imagingPublicad
Resolution uniformity and sensitivity of the NIH ATLAS small animal PET scanner: comparison to simulated LSO scanners without depth-of-interaction capability
Proceeding of: 2001 Nuclear Science Symposium and Medical Imaging Conference, november 4-10, 2001, San Diego, CaliforniaPET scanners designed to image animals the size of rats and mice should possess simultaneously high and uniform spatial resolution and high sensitivity. ATLAS (Advanced Technology Laboratory Animal Scanner), an 11.8 cm diameter aperture, 2 cm axial field-of-view ring-type research scanner seeks these goals by surrounding the animal with eighteen 15 mm deep, LGSO (7 mm) / GSO (8 mm) phoswich detector modules.
A Monte Carlo simulation was used to compare the variation of resolution across the field-of-view and the absolute central point source sensitivity (ACS) of ATLAS to similar systems comprised only of LSO arrays of different depths with no depth-of-interaction (DOI) capability. For ATLAS radial spatial resolution deteriorated by 27% from the center to 3 cm off-axis. Scanners comprised of 15 mm deep, 10 mm deep and 7 mm deep LSO crystals deteriorated by 100%, 51%, and 20% respectively, over the same distance. Simulated ACS (absorbed energies > 250 keV) for ATLAS was 2.0% and
for the 15 mm, 10 mm deep and 7 mm deep LSO scanners 2.4%, 1.5%, and 0.9%, respectively.
Radial resolution loss 3 cm off-axis and ACS measured for the actual ATLAS scanner were similar to the values obtained by simulation (27% resolution loss, 1.8% ACS). The phoswich design thus achieves good resolution uniformity over a 6 cm FOV while preserving sensitivity compared to equivalent non-DOI LSO scanners with a range of crystal depths.Publicad
An inexpensive phantom for evaluating gated blood pool data acquisition/processing systems at heart rates above 400/min
Proceeding of: 1998 IEEE Nuclear Science Symposium and Medical Imaging Conference, Toronto, Ont., 08 - 14 Nov. 1998Equilibrium gated blood pool imaging of the heart is a
common diagnostic procedure for visualizing cardiac function
in human subjects. Recently, this procedure has been modified
to evaluate cardiac function in mice. However, the high heart
rates encountered in these animals (often greater than 400
beatdmin) can confound R-wave trigger devices, acquisition
systems and image processing software containing default
conditions tailored specifically to the lower heart rates of
human subjects. In order to determine whether data acquisition
and processing components of a commercial or self-generated
gated blood pool imaging procedure are performing properly,
input of known timing and imaging signals that mimic those
generated during high heart rate gated blood pool imaging is
required. Here, we describe an inexpensive phantom that is
suitable for initial evaluation of an unknown system or for
ongoing QC of a previously verified system.Publicad
Metaphase and Interphase Cytogenetics with Alu-PCR-amplified Yeast Artificial Chromosome Clones Containing the BCR Gene and the Protooncogenes c-raf-1, c-fms, and c-erbB-21
A human yeast artificial chromosome (YAC) library was screened by polymerase chain reaction with oligonucleotide primers defined for DNA sequences of the BCR gene and the protooncogenes c-raf-1, c-fms, and c-erB-2. Alu-PCR-generated human DNA sequences were obtained from the respective YAC clones and used for fluorescence in situ hybridization experiments under suppression conditions. After chromosomal in situ suppression hybridization to GTG-banded human prometaphase chromosomes, seven of nine initially isolated YAC clones yielded strong signals exclusively in the chromosome bands containing the respective genes. Two clones yielded additional signals on other chromosomes and were excluded from further tests. The band-specific YACs were successfully applied to visualize specific structural chromosome aberrations in peripheral blood cells from patients with myelodysplasia exhibiting del(5)(q13q34), chronic myeloid leukemia and acute lymphocytic leukemia with t(9;22)(q34;q11), acute promyelocytic leukemia (M3) with t(15;17)(q22;q21), and in a cell line established from a proband with the constitutional translocation t(3;8)(p14.2;q24). In addition to the analysis of metaphase spreads, we demonstrate the particular usefulness of these YAC clones in combination with whole chromosome painting to analyze specific chromosome aberrations directly in the interphase nucleus
D-instanton partition functions
Duality arguments are used to determine D-instanton contributions to certain
effective interaction terms of type II supergravity theories in various
dimensions. This leads to exact expressions for the partition functions of the
finite N D-instanton matrix model in d=4 and 6 dimensions that generalize our
previous expression for the case d=10. These results are consistent with the
fact that the Witten index of the T-dual D-particle process should only be
non-vanishing for d=10.Comment: 20 pages, harvmac, typos corrected, reference adde
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