Quantum diffusion of the positive muon in the superconducting state of Al

We report low temperature studies of muon diffusion and trapping in Al doped with Li impurities. The trapping rate at Li and the deduced muon diffusion rate increase more rapidly with decreasing temperature in the superconducting state compared with the normal state. The temperature dependence of the quantum diffusion rate in the superconducting state is close to that predicted by the Kondo theory.     

A strategy for ranking environmentally occurring chemicals. Part VI. QSARs for the mutagenic effects of halogenated aliphatics.

A strategy for the systematic analysis and priority ranking of environmental chemicals has been applied to a class of 58 halogenated aliphatic hydrocarbons. A training set of ten compounds representing this class, was selected by statistical design. The training set compounds were then subjected to biological testing in the Salmonella typhimurium reverse mutation assay (Ames test). The measured biological data, recorded as dose-response curves, were analyzed to determine the mutagenic potency (slope of the initial portion) and the mutagen dose (MD 50) required to increase the number of revertants above the background by 50%. For each compound, four mutagenic potency estimates and four MD 50 values were determined, all originating from the tester strains TA 100 and TA 1535 with and without metabolic activation. The obtained responses were analyzed with multivariate techniques to give QSAR models relating the mutagenic potency data to the physico-chemical properties of the compounds. Finally, the derived QSARs were used to predict the mutagenic potencies and the MD 50S for the non-tested compounds in the class.     

Hyperfine fields at Ce in GdAl2 and DyAl2

The local fields at¹⁴⁰Ce in the cubic intermetallic compounds GdAl₂ and DyAl₂ have been measured with the DPAC method. At our lowest temperatures we obtainB _eff (30K)=54(2) T for GdAl₂ andB _eff(12.5K)=27(1) T for DyAl₂ which are considerably lower than the hyperfine field of the free Ce³⁺ ion (183 T). The (Ce)GdAl₂ field is quantitatively explained by a cubic crystal field splitting of 4f states but for DyAl₂ additional effects are discussed.     

Baryon-antibaryon bound states and annihilation

In order to gain some insight into the problem of the widths of quasi-nuclear levels in the $\text{B}\text{B}$ systems, we investigate a simple multichannel model for the influence of decay channels on a bound state. The shift and width of a bound-state level is found to depend strongly not only on the range of the annihilation and the $\text{B}\text{B}$ wave function at small distances but also on the position of the level relative to the thresholds. We point out a new mechanism through which a level in the vicinity of open thresholds can remain narrow even for strong coupling to the decay channels.     

An investigation of the spatial resolution requirements for two-point correlation measurements using LDV

The spatial resolution requirements for accurate two-point correlation measurements at small separations are investigated. Practical guidelines in terms of characteristic measuring volume sizes and estimated Kolmogorov length scales are given. Sample measurements of two-point one-component longitudinal correlations on the centerline of a turbulent jet are presented.Financial support from NUTEK, the Swedish National Board for Industrial and Technical Development, is acknowledged.     

The Auger electron spectrum of carbon suboxide (C3O2)

The high resolution KLL Auger electron spectrum of carbon suboxide (C₃O₂) in gas form, has been recorded. Assignments, assisted by intensity and energy calculations, are proposed for the peaks in the spectrum. A comparison is made with the oxygen Auger spectrum of CO. The ground state energy of the doubly charged C₃O₂ ion is found to be 29.7 eV.     

Analysis of the Look-Locker T(1) mapping sequence in dynamic contrast uptake studies: simulation and in vivo validation

An alternative to the pulse sequences at present used in dynamic contrast uptake MRI is the dynamic LL-EPI T(1) mapping method. This method generates T(1) estimates in a few seconds, thereby allowing dynamic studies. A particular advantage of the LL-EPI technique is that it provides the opportunity to generate spatial and temporal information about the paramagnetic contrast agent concentration independently of the inflow rate. This paper illustrates, by computer simulations, the accuracy of the estimated 1/T(1) value when using the LL-EPI technique in situations that are not supported by the model. The simulated situations not supported by the model are those in which the longitudinal and transversal relaxation rates change during the T(1) mapping. The most critical moment occurs during a bolus passage of contrast agent when the concentration gradient is large. The computer simulations of the LL-EPI T(1) mapping method in non-supported situations show that in normal perfused capillary tissue the error in the estimated 1/T(1) value is within the absolute error of 0.1 s(-1) in most simulated situations, although in a typical vessel the simulations do indicate that the stated absolute error tolerance of 0.5 s(-1) is exceeded relatively easily. However, this transgression can be rectified by a non-bolus injection of the contrast agent media.