Results from the ALEPH experiment at LEP 2

High energy data from LEP are used to make precise measurements of parameters of the standard model, and to search for physics beyond it. W pairs are studied, enabling a number of independent measurements of the W mass and studies of W decays. Limits are presented for the masses of neutral and charged Higgs particles, while searches for supersymmetric particles have allowed significant regions of SUSY parameter space to be excluded. Lower limits on the masses of neutralinos, charginos, sleptons and squarks are presented, and supergravity and $R$-parity violating models are investigated

Risk and protective factors for meningococcal disease in adolescents: matched cohort study

Objective: To examine biological and social risk factors for meningococcal disease in adolescents. Design: Prospective, population based, matched cohort study with controls matched for age and sex in 1:1 matching. Controls were sought from the general practitioner. Setting: Six contiguous regions of England, which represent some 65% of the country’s population. Participants: 15-19 year olds with meningococcal disease recruited at hospital admission in six regions (representing 65% of the population of England) from January 1999 to June 2000, and their matched controls. Methods: Blood samples and pernasal and throat swabs were taken from case patients at admission to hospital and from cases and matched controls at interview. Data on potential risk factors were gathered by confidential interview. Data were analysed by using univariate and multivariate conditional logistic regression. Results: 144 case control pairs were recruited (74 male (51%); median age 17.6). 114 cases (79%) were confirmed microbiologically. Significant independent risk factors for meningococcal disease were history of preceding illness (matched odds ratio 2.9, 95% confidence interval 1.4 to 5.9), intimate kissing with multiple partners (3.7, 1.7 to 8.1), being a university student (3.4, 1.2 to 10) and preterm birth (3.7, 1.0 to 13.5). Religious observance (0.09, 0.02 to 0.6) and meningococcal vaccination (0.12, 0.04 to 0.4) were associated with protection. Conclusions: Activities and events increasing risk for meningococcal disease in adolescence are different from in childhood. Students are at higher risk. Altering personal behaviours could moderate the risk. However, the development of further effective meningococcal vaccines remains a key public health priority

Self-contained Kondo effect in single molecules

Kondo coupling of f and conduction electrons is a common feature of f-electron intermetallics. Similar effects should occur in carbon ring systems(metallocenes). Evidence for Kondo coupling in Ce(C8H8)2 (cerocene) and the ytterbocene Cp*2Yb(bipy) is reported from magnetic susceptibility and L_III-edge x-ray absorption spectroscopy. These well-defined systems provide a new way to study the Kondo effect on the nanoscale, should generate insight into the Anderson Lattice problem, and indicate the importance of this often-ignored contribution to bonding in organometallics.Comment: 4 pages, 5 figures (eps

Direct Observation of High-Temperature Polaronic Behavior In Colossal Magnetoresistive Manganites

The temperature dependence of the electronic and atomic structure of the colossal magnetoresistive oxides $La_{1-x}Sr_{x}MnO_{3}$ (x = 0.3, 0.4) has been studied using core and valence level photoemission, x-ray absorption and emission, and extended x-ray absorption fine structure spectroscopy. A dramatic and reversible change of the electronic structure is observed on crossing the Curie temperature, including charge localization and spin moment increase of Mn, together with Jahn-Teller distortions, both signatures of polaron formation. Our data are also consistent with a phase-separation scenario.Comment: 5 pages, 4 figures, revte

Quantifying structural damage from self-irradiation in a plutonium superconductor

The 18.5 K superconductor PuCoGa5 has many unusual properties, including those due to damage induced by self-irradiation. The superconducting transition temperature decreases sharply with time, suggesting a radiation-induced Frenkel defect concentration much larger than predicted by current radiation damage theories. Extended x-ray absorption fine-structure measurements demonstrate that while the local crystal structure in fresh material is well ordered, aged material is disordered much more strongly than expected from simple defects, consistent with strong disorder throughout the damage cascade region. These data highlight the potential impact of local lattice distortions relative to defects on the properties of irradiated materials and underscore the need for more atomic-resolution structural comparisons between radiation damage experiments and theory.Comment: 7 pages, 5 figures, to be published in PR

Immune Reconstitution After Gene Therapy Approaches in Patients With X-Linked Severe Combined Immunodeficiency Disease

X-linked severe immunodeficiency disease (SCID-X1) is an inherited, rare, and life-threating disease. The genetic origin is a defect in the interleukin 2 receptor γ chain (IL2RG) gene and patients are classically characterized by absence of T and NK cells, as well as presence of partially-functional B cells. Without any treatment the disease is usually lethal during the first year of life. The treatment of choice for these patients is hematopoietic stem cell transplantation, with an excellent survival rate (>90%) if an HLA-matched sibling donor is available. However, when alternative donors are used, the success and survival rates are often lower. Gene therapy has been developed as an alternative treatment initially using γ-retroviral vectors to correct the defective γ chain in the absence of pre-conditioning treatment. The results were highly promising in SCID-X1 infants, showing long-term T-cell recovery and clinical benefit, although NK and B cell recovery was less robust. However, some infants developed T-cell acute lymphoblastic leukemia after the gene therapy, due to vector-mediated insertional mutagenesis. Consequently, considerable efforts have been made to develop safer vectors. The most recent clinical trials using lentiviral vectors together with a low-dose pre-conditioning regimen have demonstrated excellent sustained T cell recovery, but also B and NK cells, in both children and adults. This review provides an overview about the different gene therapy approaches used over the last 20 years to treat SCID-X1 patients, particularly focusing on lymphoid immune reconstitution, as well as the developments that have improved the process and outcomes

Studies on the Occurrence and Elemental Composition of Bacteria in Freshwater Plankton

The occurrence and cation content of bacteria in a eutrophic freshwater lake (Rostherne Mere, Cheshire, UK) were investigated over a one year sampling period in relation to cation changes in the lake surface water and phytoplankton. Scanning electron microscope examination of trawl-net and filtered samples demonstrated bacterial association with Anabaena, Aphanizomenon and diatoms. Direct counts of associated and unassociated bacteria showed that increases in bacterial population relate to population decline of major algal constituents. Spectrophotometric determination of selected cation levels in the lake water demonstrated wide fluctuations throughout the sampling period, with elevated levels of transition metals before and at the end of Summer stratification. Zn and Pb also showed increased levels in relation to episodic events. Mass fractions of spectrophotometrically-determined selected cations (Fe, Cu, Zn and Pb) in phytoplankton also varied considerably during the sampling period, with major increases apparently following peaks in water level. X-ray microanalysis of whole, unassociated bacterial eel ls demonstrated high levels of soluble and bound cations, including K, Ca, Fe, Cu, Ni, Zn and Pb. Changes in the cation levels of bacteria did not follow a similar pattern to the general phytoplankton - probably due to differences in uptake or adsorption or to cycling of bacterial cells in the water column

The effect of the annealing temperature on the local distortion of La0.67_{0.67}Ca0.33_{0.33}MnO3_3 thin films

Mn $K$-edge fluorescence data are presented for thin film samples (3000~\AA) of Colossal Magnetoresistive (CMR) La$_{0.67}$Ca$_{0.33}$MnO$_3$: as-deposited, and post-annealed at 1000 K and 1200 K. The local distortion is analyzed in terms of three contributions: static, phonon, and an extra, temperature-dependent, polaron term. The polaron distortion is very small for the as-deposited sample and increases with the annealing temperature. In contrast, the static distortion in the samples decreases with the annealing temperature. Although the local structure of the as-deposited sample shows very little temperature dependence, the change in resistivity with temperature is the largest of these three thin film samples. The as-deposited sample also has the highest magnetoresistance (MR), which indicates some other mechanism may also contribute to the transport properties of CMR samples. We also discuss the relationship between local distortion and the magnetization of the sample.Comment: 11 pages of Preprint format, 8 figures in one tar fil

The debris disk - terrestrial planet connection

The eccentric orbits of the known extrasolar giant planets provide evidence that most planet-forming environments undergo violent dynamical instabilities. Here, we numerically simulate the impact of giant planet instabilities on planetary systems as a whole. We find that populations of inner rocky and outer icy bodies are both shaped by the giant planet dynamics and are naturally correlated. Strong instabilities -- those with very eccentric surviving giant planets -- completely clear out their inner and outer regions. In contrast, systems with stable or low-mass giant planets form terrestrial planets in their inner regions and outer icy bodies produce dust that is observable as debris disks at mid-infrared wavelengths. Fifteen to twenty percent of old stars are observed to have bright debris disks (at wavelengths of ~70 microns) and we predict that these signpost dynamically calm environments that should contain terrestrial planets.Comment: Contribution to proceedings of IAU 276: Astrophysics of Planetary System

Experimental investigation of a coherent quantum measurement of the degree of polarization of a single mode light beam

A novel method for the direct measurement of the degree of polarization is described. It is one of the first practical implementations of a coherent quantum measurement, the projection on the singlet state. Our first results demonstrate the successful operation of the method. However, due to the nonlinear crystals used presently, its application is limited to spectral widths larger than ~8nm.Comment: 23 pages, 9 figures, submitted to Journal of Modern Optic