In this second in a series of three papers on wall relaxation of 3He-spins we discuss relaxation in metal-coated glass cells in terms of hyperfine coupling to paramagnetic conduction electrons at the ...Fermi surface. This scales with the square of the work function of the coating and thereby also with its He-adsorption energy. In this sense we investigate coatings with particularly low work function and adsorption energy, namely Cs and Cs-suboxides. Although we observe a suppression of relaxation rates by two orders of magnitude as compared to bare Pyrex and fused silica walls, their temperature dependence still shows the same Arrhenius dependence as observed for bare substrates, instead of a T 3/2 dependence expected for a metallic surface. From this finding we conclude that, on one hand, the surface coverage is not complete and, on the other hand, the relaxation at the alkali surface itself is extremely slow. This finding is supported, too, by a semi-empirical estimate based on measured relaxation rates at ordinary metal surfaces, rescaled then with the respective dependence on adsorption energy.
The Brookhaven muon storage ring magnet Danby, G.T.; Addessi, L.; Armoza, Z. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2001, Letnik:
457, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The muon g-2 experiment at Brookhaven National Laboratory has the goal of determining the muon anomalous
g-value
a
μ
(=(g−2)/2)
to the very high precision of 0.35 parts per million and thus requires ...a storage ring magnet with great stability and homogeniety. A superferric storage ring with a radius of 7.11 m and a magnetic field of 1.45 T has been constructed in which the field quality is largely determined by the iron, and the excitation is provided by superconducting coils operating at a current of 5200 A. The storage ring has been constructed with maximum attention to azimuthal symmetry and to tight mechanical tolerances and with many features to allow obtaining a homogenous magnetic field. The fabrication of the storage ring, its cryogenics and quench protection systems, and its initial testing and operation are described.
We construct real polarizable Hodge structures on the reduced leafwise cohomology of Kahler-Riemann foliations by complex manifolds. As in the classical case one obtains a hard Lefschetz theorem for ...this cohomology. Serre's Kahlerin analogue of the Weil conjectures carries over as well. Generalizing a construction of Looijenga and Lunts one obtains possibly infinite-dimensional Lie algebras attached to Kahler-Riemann foliations. Finally using (\mathfrak g, K)-cohomology we discuss a class of examples obtained by dividing a product of symmetric spaces by a cocompact lattice and considering the foliations coming from the factors. PUBLICATION ABSTRACT
We introduce a frequency-domain terahertz (THz) spectrometer based on a comb locked frequency synthesizer which combines > 3 THz scanning range at rates > 0.3 THz/s. We demonstrate kHz frequency ...resolution in THz precision spectroscopy of ultrahigh-Q whispering-gallery mode resonators.
The Gly 972 Arg variant in the insulin receptor substrate-1 (IRS-1) gene may interact with the pathogenesis of common insulin-resistance disorders raising the hypothesis that the mutation may ...predispose to type 2 diabetes. We examined the codon 972 variant in 144 non-diabetic first degree relatives of patients with type 2 diabetes (FDR), who underwent extensive phenotyping: Glucose tolerance was determined by an oral glucose load, insulin sensitivity by euglycaemic-hyperinsulinaemic glucose clamp (glucose metabolic clearance rate, MCR) and body composition by bioelectrical impedance. 20 (14%) of the FDR showed the Gly 972 Arg variant in heterozygous form, 2 (1.3%) probands were homozygous. Carriers of the polymorphism did not differ in MCR independent of body weight and total body fat. The polymorphism does not seem to determine clamp-derived insulin sensitivity. Despite identical fasting plasma glucose, carriers of the polymorphism showed a slightly lower fasting serum insulin and lower insulin response to an oral glucose load but higher glucose concentrations. In an obese subgroup (BMI > 25) the polymorphism did not show a higher frequency and was not associated with lower insulin sensitivity. In the investigated group of young, healthy relatives of type 2 diabetes patients, the frequency of the mutation corresponded to that of a diabetic population. In summary our data show that the polymorphism is not suitable to predict insulin resistance.
We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized 3Helium (3He→). Single-breath, single-bolus ...visualization of 3He→ administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure pO2(t). We model the dynamics of hyperpolarization in the lung by rate equations. Based hereupon, a double acquisition technique is presented to separate depolarization by RF pulses and oxygen induced relaxation. It permits the determination of pO2 with a high accuracy of up to 3% with simultaneous flip angle calibration using no additional input parameters. The time course of pO2 during short periods of breathholding is found to be linear in a pig as well as in a human volunteer. We also measured the wall relaxation time in the lung and deduced a lower limit of 4.3 min.
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