261 research outputs found
Test of Lorentz Symmetry by using a 3He/129Xe Co-Magnetometer
To test Lorentz symmetry we used a 3He/129Xe co-magnetometer. We will give a
short summary of our experimental setup and the results of our latest
measurements. We obtained preliminary results for the equatorial component of
the background field interacting with the spin of the bound neutron: b_n < 3.72
x 10^(-32) GeV (95 C.L.).Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28 - July 2, 201
Limit on Lorentz and CPT violation of the bound Neutron Using a Free Precession 3He/129Xe co-magnetometer
We report on the search for Lorentz violating sidereal variations of the
frequency difference of co-located spin-species while the Earth and hence the
laboratory reference frame rotates with respect to a relic background field.
The co-magnetometer used is based on the detection of freely precessing nuclear
spins from polarized 3He and 129Xe gas samples using SQUIDs as low-noise
magnetic flux detectors. As result we can determine the limit for the
equatorial component of the background field interacting with the spin of the
bound neutron to be bn < 3.7 x 10^{-32} GeV (95 C.L.).Comment: 5 pages, 4 figure
Blood lead level and dental caries in school-age children.
The association between blood lead level and dental caries was evaluated in cross-sectional analyses of baseline data for 543 children 6-10 years old screened for enrollment in the Children's Amalgam Trial, a study designed to assess potential health effects of mercury in silver fillings. Approximately half of the children were recruited from an urban setting (Boston/Cambridge, MA, USA) and approximately half from a rural setting (Farmington, ME, USA). Mean blood lead level was significantly greater among the urban subgroup, as was the mean number of carious tooth surfaces. Blood lead level was positively associated with number of caries among urban children, even with adjustment for demographic and maternal factors and child dental practices. This association was stronger in primary than in permanent dentition and stronger for occlusal, lingual, and buccal tooth surfaces than for mesial or distal surfaces. In general, blood lead was not associated with caries in the rural subgroup. The difference between the strength of the associations in the urban and rural settings might reflect the presence of residual confounding in the former setting, the presence of greater variability in the latter setting in terms of important caries risk factors (e.g., fluoride exposure), or greater exposure misclassification in the rural setting. These findings add to the evidence supporting a weak association between children's lead exposure and caries prevalence. A biologic mechanism for lead cariogenicity has not been identified, however. Our data are also consistent with residual confounding by factors associated with both elevated lead exposure and dental caries
Zwitters: particles between quantum and classical
We describe both quantum particles and classical particles in terms of a
classical statistical ensemble, characterized by a probability distribution in
phase space. By use of a wave function in phase space both can be treated in
the same quantum formalism. The different dynamics of quantum and classical
particles resides then only from different evolution equations for the
probability distribution. Quantum particles are characterized by a specific
choice of observables and time evolution of the probability density. All
relations for a quantum particle in a potential, including interference and
tunneling, can be described in terms of the classical probability distribution.
We formulate the concept of zwitters - particles for which the time evolution
interpolates between quantum and classical particles. Experiments can test a
small parameter which quantifies possible deviations from quantum mechanics.Comment: extended discussion of possible realizations of zwitters, including
macroscopic droplets or BEC condensate
Ultra-sensitive magnetometry based on free precession of nuclear spins
We discuss the design and performance of a very sensitive low-field
magnetometer based on the detection of free spin precession of gaseous, nuclear
polarized 3He or 129Xe samples with a SQUID as magnetic flux detector. The
device will be employed to control fluctuating magnetic fields and gradients in
a new experiment searching for a permanent electric dipole moment of the
neutron as well as in a new type of 3He/129Xe clock comparison experiment which
should be sensitive to a sidereal variation of the relative spin precession
frequency. Characteristic spin precession times T_2 of up to 60h could be
measured. In combination with a signal-to-noise ratio of > 5000:1, this leads
to a sensitivity level of deltaB= 1fT after an integration time of 220s and to
deltaB= 10^(-4)fT after one day. Even in that sensitivity range, the
magnetometer performance is statistically limited, and noise sources inherent
to the magnetometer are not limiting. The reason is that free precessing 3He
(129Xe) nuclear spins are almost completely decoupled from the environment.
That makes this type of magnetometer in particular attractive for precision
field measurements where a long-term stability is required
Dosimetric precision of an ion beam tracking system
<p>Abstract</p> <p>Background</p> <p>Scanned ion beam therapy of intra-fractionally moving tumors requires motion mitigation. GSI proposed beam tracking and performed several experimental studies to analyse the dosimetric precision of the system for scanned carbon beams.</p> <p>Methods</p> <p>A beam tracking system has been developed and integrated in the scanned carbon ion beam therapy unit at GSI. The system adapts pencil beam positions and beam energy according to target motion.</p> <p>Motion compensation performance of the beam tracking system was assessed by measurements with radiographic films, a range telescope, a 3D array of 24 ionization chambers, and cell samples for biological dosimetry. Measurements were performed for stationary detectors and moving detectors using the beam tracking system.</p> <p>Results</p> <p>All detector systems showed comparable data for a moving setup when using beam tracking and the corresponding stationary setup. Within the target volume the mean relative differences of ionization chamber measurements were 0.3% (1.5% standard deviation, 3.7% maximum). Film responses demonstrated preserved lateral dose gradients. Measurements with the range telescope showed agreement of Bragg peak depth under motion induced range variations. Cell survival experiments showed a mean relative difference of -5% (-3%) between measurements and calculations within the target volume for beam tracking (stationary) measurements.</p> <p>Conclusions</p> <p>The beam tracking system has been successfully integrated. Full functionality has been validated dosimetrically in experiments with several detector types including biological cell systems.</p
Development of a duodenal gallstone ileus with gastric outlet obstruction (Bouveret syndrome) four months after successful treatment of symptomatic gallstone disease with cholecystitis and cholangitis: a case report
<p>Abstract</p> <p>Introduction</p> <p>Cases of gallstone ileus account for 1% to 4% of all instances of mechanical bowel obstruction. The majority of obstructing gallstones are located in the terminal ileum. Less than 10% of impacted gallstones are located in the duodenum. A gastric outlet obstruction secondary to a gallstone ileus is known as Bouveret syndrome. Gallstones usually enter the bowel through a biliary enteral fistula. Little is known about the formation of such fistulae in the course of gallstone disease.</p> <p>Case presentation</p> <p>We report the case of a 72-year-old Caucasian woman born in Germany with a gastric outlet obstruction due to a gallstone ileus (Bouveret syndrome), with a large gallstone impacted in the third part of the duodenum. Diagnostic investigations of our patient included plain abdominal films, gastroscopy and abdominal computed tomography, which showed a biliary enteric fistula between the gallbladder and the duodenal bulb. Our patient was successfully treated by laparotomy, duodenotomy, extraction of the stone, cholecystectomy, and resection of the fistula in a one-stage surgical approach. Histopathological examination showed chronic and acute cholecystitis, with perforated ulceration of the duodenal wall and acute purulent inflammation of the surrounding fatty tissue. Four months prior to developing a gallstone ileus our patient had been hospitalized for cholecystitis, a large gallstone in the gallbladder, cholangitis and a small obstructing gallstone in the common biliary duct. She had been treated with endoscopic retrograde cholangiopancreatography, endoscopic biliary sphincterotomy, balloon extraction of the common biliary duct gallstone, and intravenous antibiotics. At the time of her first presentation, abdominal ultrasound and endoscopic examination (including esophagogastroduodenoscopy and endoscopic retrograde cholangiopancreatography) had not shown any evidence of a biliary enteral fistula. In the four months preceding the gallstone ileus our patient had been asymptomatic.</p> <p>Conclusion</p> <p>In patients known to have gallstone disease presenting with symptoms of ileus, the differential diagnosis of a gallstone ileus should be considered even in the absence of preceding symptoms related to the gallbladder disease. Gallstones large enough to cause intestinal obstruction usually enter the bowel by a biliary enteral fistula. During the formation of such a fistula, patients can be asymptomatic.</p
Structural study of GaSb/AlSb strained-layer superlattice
Owing to the lattice mismatch between GaSb and AlSb, a superlattice consisting of alternating layers of these materials will be strained. We have carried out ion-channeling measurements by backscattering of 1.76-MeV He ions, and present an experimental procedure and a data-analysis technique to measure the difference in strain between the two individual layers of the superlattice. The data analysis is based on computer simulations of channeling, the accuracy of which is supported by the many fine details of the experiments reproduced in the simulations. X-ray rocking-curve analysis yielded detailed profiles of strains in directions perpendicular and parallel to the surface. The x-ray value for the strain present at an unirradiated spot on the crystal is in excellent agreement with the value calculated by elasticity theory. In the bombarded region, the values of strain are less than the value calculated by elasticity theory. It appears that bombardment by the He ions reduced the strain by 50% and created lateral inhomogeneities in the crystal structure
FDG-PET/CT in infections: the imaging method of choice?
[No abstract available
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