1,951 research outputs found
High Precision Laser and Microwave Spectroscopy of Antiprotonic Helium
This talk gives an overview of the recent results on the precision
spectroscopy of antiprotonic helium which was performed by the ASACUSA
collaboration at the Antiproton Decelerator of CERN. The laser spectroscopy of
energy levels of the antiproton has reached a relative accuracy of , and by comparing the experimental value for the transition
wavelengths with theoretical calculations, a CPT test on the equality of proton
and antiproton charge and mass of has been obtained. In a
recent experiment, the hyperfine structure of the state of
antiprotonic helium has been measured for the first time with an accuracy of .Comment: Invited talk at the XIVth Rencontres de Blois on Matter-Antimatter
Asymmetry, Blois, June 200
A Facility for Low-energy Antiproton and Ion Research
The future accelerator facility for beams of ions and antiprotons at
Darmstadt will provide antiproton beams of intensities that are two orders of
magnitude higher than currently available. Within the foreseen scheme,
antiprotons can be decelerated to 30 MeV. The low-energy antiproton community
has recently formed a users group to make use of this opportunity to create a
next-generation low-energy antiproton facility called FLAIR, which will be able
to provide cooled antiproton beams well below 100 keV kinetic energy. This talk
gives an overview of the layout and physics program of the proposed facility.Comment: Proceedings of the XLII Interantional Winter Meeting on Nuclear
Physics, Bormio (Italy), Janaury 25 - February 1, 200
In-beam hyperfine spectroscopy of antihydrogen, hydrogen and deuterium
The ASACUSA collaboration is developing a polarized beam of antihydrogen
atoms to precisely determine the ground-state hyperfine structure for studies
of CPT and Lorentz invariance. Using a beam of ordinary hydrogen, measurements
of both the and -transition have been performed, investigating
orientation-dependent SME coefficients. Furthermore a first hyperfine
experiment with a beam of deuterium is being prepared.Comment: 5 pages, 3 figures. Presented at the Ninth Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, May 17-26, 202
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Relationship between thoracic kyphosis and neural axis abnormalities in patients with adolescent idiopathic scoliosis.
Purpose:Previous studies have suggested an association between increased thoracic kyphosis and neural axis abnormalities in patients with adolescent idiopathic scoliosis (AIS). However, the basis for this finding is unclear, and this association has been mainly noted in retrospective studies on a non-consecutive series of patients. The purpose of this study was to assess the relationship between thoracic kyphosis and neural axis abnormalities in patients with AIS. Methods:We studied a consecutive series of AIS patients treated with spinal fusion. Thoracic kyphosis (T2 to T12) was measured from preoperative lateral radiographs. All patients underwent a spine magnetic resonance imaging (MRI) prior to surgery, and MRI reports were reviewed to determine the presence of neural axis abnormalities. Statistical analyses included descriptive statistics and chi-squared analysis. Results:This study included 210 patients with AIS. There were no significant differences in age or gender between patients with thoracic hypokyphosis (kyphosis < 20°), normal thoracic kyphosis (kyphosis 20° to 40°) and thoracic hyperkyphosis (kyphosis > 40°) (p > 0.05). Neural axis abnormalities were present in 17.9% of patients with thoracic hypokyphosis, 9.8% of patients with normal thoracic kyphosis and 13.6% of patients with thoracic hyperkyphosis (p = 0.60). There were no significant differences in rates of Chiari malformation, syrinx, intra-spinal masses and other central nervous system abnormalities between groups (p > 0.05). Conclusions:Thoracic kyphosis was not associated with neural axis abnormalities in our consecutive series of patients with AIS. Increased thoracic kyphosis may not be a reliable indicator for the presence of neural axis abnormalities in patients with AIS. Level of Evidence:IV
Pull-out strength of axially loaded steel rods bonded in glulam perpendicular to the grain
A total of 86 pull-out strength tests on glued-in steel rods with metric threads M12, M16 and M20 are reported in this paper. The rods were bonded in glulam made of Norway spruce lamellas perpendicular to the grain by means of an epoxy-type adhesive using the GSA®-system. The slenderness ratios of the rods λ calculated from the anchoring lengths ℓ with respect to the diameter of the drill hole d h (λ=ℓ/d h) varied between 7.5 and 12.5. Registered failure loads were considerably higher than design values derived from different existing approaches. The pull-out strength was found to be almost directly proportional to the surface area of the bond line. Based on this an approach to estimate the pull-out strength is suggested. Dependence between pull-out strength and anchoring length ℓ as well as slenderness ratio λ exists, whereas such dependence for the diameter of the rod was not found. The pull-out strength is influenced by the wood density. Compared to rods bonded in parallel to the grain, pull-out strength of rods with same diameter and anchoring length set perpendicular to the grain are 20-50% highe
Pull-out strength of axially loaded steel rods bonded in glulam parallel to the grain
Bonded-in steel rods are very efficient in withstanding high forces applied to timber members. Investigations of bonded-in rods started in the late eighties of the last century and several design models were published since. By comparing these approaches on base of an extensive literature review a certain degree of discrepancy and partly even contradiction can be found. The paper describes a test program which aimed to study the influence of timber density and of geometric parameters on the pull-out strength of single axially loaded steel rods. Following the GSA®-procedure, which is a well established glued-in rods joint in Switzerland, rods with metric thread were bonded in glulam made of Norway spruce lamellas using an epoxy-type adhesive. The tests showed that the influence of the timber density can be quantified by a power function of ρ with an exponent of 0.6. The parameters length of the glued zone ℓ and diameter of the hole d H can be summarized in the slenderness ratio λ = ℓ/d H, which itself is related to the mean shear strength in the anchoring zone by an exponent of approximately −1/3. In order to prevent the specimens from premature splitting, distances between the axis of the rod and the edge of the specimen of 2.3 times the diameter of the rod have been use
Polar and magnetic order in GaV4Se8
In the present work, we provide results from specific heat, magnetic
susceptibility, dielectric constant, ac conductivity, and electrical
polarization measurements performed on the lacunar spinel GaV4Se8. With
decreasing temperature, we observe a transition from the paraelectric and
paramagnetic cubic state into a polar, probably ferroelectric state at 42 K
followed by magnetic ordering at 18 K. The polar transition is likely driven by
the Jahn-Teller effect due to the degeneracy of the V4 cluster orbitals. The
excess polarization arising in the magnetic phase indicates considerable
magnetoelectric coupling. Overall, the behavior of GaV4Se8 in many respects is
similar to that of the skyrmion host GaV4S8, exhibiting a complex interplay of
orbital, spin, lattice, and polar degrees of freedom. However, its dielectric
behavior at the polar transition markedly differs from that of the Jahn-Teller
driven ferroelectric GeV4S8, which can be ascribed to the dissimilar electronic
structure of the Ge compound.Comment: 7 pages, 6 figures. Revised version according to suggestions of
referee
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