Gravitational Microlensing by Globular Clusters

Stars in globular clusters can act either as sources for MACHOs (Massive Astrophysical Compact Halo Objects) located along the line of sight or as lenses for more distant background stars. Although the expected rate of microlensing events is small, such observations can lead to very useful results. In particular, one could get information on the shape of the galactic halo along different lines of sight, allowing to better constrain its total dark matter content. Moreover, on can also infer the total dark matter content of globular clusters, which is presently not well known. To this latter purpose, we analyse the microlensing events towards the galactic bulge, which lie close to the three globular clusters NGC 6522, NGC 6528 and NGC 6540. We find evidence that some microlensing events are indeed due to MACHOs located in the globular clusters, suggesting, therefore, that these clusters contain a significant amount of dark matter.Comment: 15 pages, 10 figures included. Accepted for publication in A &

Defect propagation in one-, two-, and three-dimensional compounds doped by magnetic atoms

Inelastic neutron scattering experiments were performed to study manganese(II) dimer excitations in the diluted one-, two-, and three-dimensional compounds CsMn(x)Mg(1-x)Br(3), K(2)Mn(x)Zn(1-x)F(4), and KMn(x)Zn(1-x)F(3) (x<0.10), respectively. The transitions from the ground-state singlet to the excited triplet, split into a doublet and a singlet due to the single-ion anisotropy, exhibit remarkable fine structures. These unusual features are attributed to local structural inhomogeneities induced by the dopant Mn atoms which act like lattice defects. Statistical models support the theoretically predicted decay of atomic displacements according to 1/r**2, 1/r, and constant (for three-, two-, and one-dimensional compounds, respectively) where r denotes the distance of the displaced atoms from the defect. The observed fine structures allow a direct determination of the local exchange interactions J, and the local intradimer distances R can be derived through the linear law dJ/dR.Comment: 22 pages, 5 figures, 2 table

The barocaloric effect: A Spin-off of the Discovery of High-Temperature Superconductivity

Some key results obtained in joint research projects with Alex M\"uller are summarized, concentrating on the invention of the barocaloric effect and its application for cooling as well as on important findings in the field of high-temperature superconductivity resulting from neutron scattering experiments.Comment: 26 pages, 9 figure

Comparative activity of the penem antibiotic Sch 34343 against Gram-negative and Gram-positive bacteria with special reference to multiresistant strains

A new penem antibiotic, Sch 34343, was shown to be active against a large number of Gram-positive bacteria. The drug inhibited penicillinase-positive and -negative staphylococci equally well, being five times more active than cefamandole and ten times more active than methiallin. Most methicillin-rcsistant staphylococci were inhibited by concentrations between 0.25 and 4 mg/1, but a small group of highly resistant strains were observed. Sch 34343 was eight times less active than ampicillin and penicillin G, but as active as piperacilhn against enterococci. The drug showed excellent activity against various streptococci. Sch 34343 was as bactericidal as flucloxacillin, ampicillin and penicillin G against staphylococci, enterococci and streptococci, respectively, in killing kinetic tests Enterobacteriaceae susceptible to third-generation cephalosporins were approximately five times less susceptible to Sch 34343, but MICs were far below the susceptibility breakpoint Sch 34343 was equally active against Citrobacter and Enterobacter strains that were highly resistant to third-generation cephalosporins and to aztreonam. Together with thienamycin, this drug seems to be a good alternative for the treatment of infections caused by bacteria resistant to third-generation cephalosporins and to aztreona

Long-term evaluation of patients with free tissue transfer to the lower leg in terms of functional, socioeconomic, and esthetic aspects

A retrospective, quantitative, long-term evaluation of patients with a free flap transfer to the lower extremity was carried out with respect to functional, socioeconomic, and esthetic outcome. The study included 57 patients who were examined by questionnaire filled out by both an examiner and the patients themselves. Indications for the free flaps were acute trauma or osteomyelitis and unstable scars arising from a previous trauma to the lower leg. The flap success rate was 94.7%. The period between the operation and evaluation was at least 3years. A local, flap-specific functional impairment was found in 17 patients (30%) and a general impairment of the lower extremity in 56% of the subjects. With respect to the socioeconomic outcome more than two-thirds of the patients returned to their previous occupation with no restrictions; approximately 20% of subjects had to switch to a less strenuous job. Although from the viewpoint of the examiner the esthetic appearance was satisfactory in 44 free flaps (77%), the majority of the patients were conscious of pigmental, textural, or contour changes which produced a subjective esthetic compromise in 56% of cases. In conclusion, despite a considerably high rate of local functional impairment the majority of patients (89%) were satisfied and judged the application of a free flap as having been beneficial in preventing a loss in socioeconomic status. The high rate of esthetic problems demonstrates the importance of including esthetic considerations in designing the free flap, in particular with regard to (a) meticulously tailoring the flap, (b) aiming at a homogeneous skin surface, and (c) thoroughly shaping the affected lower extremit

Natural methicillin resistance in comparison with that selected by in-vitro drug exposure in Staphylococcus aureus

Methicillin resistant staphylococci selected during serial passage in increasing concentrations of methicillin were compared with an isogenic methicillin resistant strain carrying the methicillin resistance determinant (mec) found in clinical isolates of Staphylococcus aureus. Selection for methicillin resistance was followed by changes in the binding characteristic of penicillin binding proteins (PBPs) 2 and 4. There was no immunological nor genetic relationship between the mec-determined low affinity PBP2′ and the PBPs of the in-vitro selected mutants. The Tn551 insertion Ω2003, which inactivates mec determined methicillin resistance, but which is not linked to mec, also partially reduced in-vitro selected methicillin resistance. This suggests that this methicillin resistance controlling factor contributes at least partially to methicillin resistance selected in vitr

Evidence for competition between the superconducting and the pseudogap state in (BiPb)_2(SrLa)_2CuO_{6+\delta} from muon-spin rotation experiments

The in-plane magnetic penetration depth \lambda_{ab} in optimally doped (BiPb)_2(SrLa)_2CuO_{6+\delta} (OP Bi2201) was studied by means of muon-spin rotation. The measurements of \lambda_{ab}^{-2}(T) are inconsistent with a simple model of a d-wave order parameter and a uniform quasiparticle weight around the Fermi surface. The data are well described assuming the angular gap symmetry obtained in ARPES experiments [Phys. Rev. Lett {\bf 98}, 267004 (2007)], where it was shown that the superconducting gap in OP Bi2201 exists only in segments of the Fermi surface near the nodes. We find that the remaining parts of the Fermi surface, which are strongly affected by the pseudogap state, do not contribute significantly to the superconducting condensate. Our data provide evidence that high temperature superconductivity and pseudogap behavior in cuprates are competing phenomena.Comment: 5 pages, 3 figure