V2:Performance of the solid deuterium ultra-cold neutron source at the pulsed reactor TRIGA Mainz

The performance of the solid deuterium ultra-cold neutron source at the pulsed reactor TRIGA Mainz with a maximum peak energy of 10 MJ is described. The solid deuterium converter with a volume of V=160 cm3 (8 mol), which is exposed to a thermal neutron fluence of 4.5x10^13 n/cm2, delivers up to 550 000 UCN per pulse outside of the biological shield at the experimental area. UCN densities of ~ 10/cm3 are obtained in stainless steel bottles of V ~ 10 L resulting in a storage efficiency of ~20%. The measured UCN yields compare well with the predictions from a Monte Carlo simulation developed to model the source and to optimize its performance for the upcoming upgrade of the TRIGA Mainz into a user facility for UCN physics.Comment: 23 pages, 8 figure

Complete analysis of the B-cell response to a protein antigen, from in vivo germinal centre formation to 3-D modelling of affinity maturation

Somatic hypermutation of immunoglobulin variable region genes occurs within germinal centres (GCs) and is the process responsible for affinity maturation of antibodies during an immune response. Previous studies have focused almost exclusively on the immune response to haptens, which may be unrepresentative of epitopes on protein antigens. In this study, we have exploited a model system that uses transgenic B and CD4<sup>+</sup> T cells specific for hen egg lysozyme (HEL) and a chicken ovalbumin peptide, respectively, to investigate a tightly synchronized immune response to protein antigens of widely differing affinities, thus allowing us to track many facets of the development of an antibody response at the antigen-specific B cell level in an integrated system <i>in</i> <i>vivo</i>. Somatic hypermutation of immunoglobulin variable genes was analysed in clones of transgenic B cells proliferating in individual GCs in response to HEL or the cross-reactive low-affinity antigen, duck egg lysozyme (DEL). Molecular modelling of the antibody–antigen interface demonstrates that recurring mutations in the antigen-binding site, selected in GCs, enhance interactions of the antibody with DEL. The effects of these mutations on affinity maturation are demonstrated by a shift of transgenic serum antibodies towards higher affinity for DEL in DEL-cOVA immunized mice. The results show that B cells with high affinity antigen receptors can revise their specificity by somatic hypermutation and antigen selection in response to a low-affinity, cross-reactive antigen. These observations shed further light on the nature of the immune response to pathogens and autoimmunity and demonstrate the utility of this novel model for studies of the mechanisms of somatic hypermutation

Optimality of mutation and selection in germinal centers

The population dynamics theory of B cells in a typical germinal center could play an important role in revealing how affinity maturation is achieved. However, the existing models encountered some conflicts with experiments. To resolve these conflicts, we present a coarse-grained model to calculate the B cell population development in affinity maturation, which allows a comprehensive analysis of its parameter space to look for optimal values of mutation rate, selection strength, and initial antibody-antigen binding level that maximize the affinity improvement. With these optimized parameters, the model is compatible with the experimental observations such as the ~100-fold affinity improvements, the number of mutations, the hypermutation rate, and the "all or none" phenomenon. Moreover, we study the reasons behind the optimal parameters. The optimal mutation rate, in agreement with the hypermutation rate in vivo, results from a tradeoff between accumulating enough beneficial mutations and avoiding too many deleterious or lethal mutations. The optimal selection strength evolves as a balance between the need for affinity improvement and the requirement to pass the population bottleneck. These findings point to the conclusion that germinal centers have been optimized by evolution to generate strong affinity antibodies effectively and rapidly. In addition, we study the enhancement of affinity improvement due to B cell migration between germinal centers. These results could enhance our understandings to the functions of germinal centers.Comment: 5 figures in main text, and 4 figures in Supplementary Informatio

Successful reduced-intensity SCT from unrelated cord blood in three patients with X-linked SCID

We describe three males with X-linked SCID (X-SCID) who were successfully treated by reduced-intensity SCT from unrelated cord blood (CB). Mean age at transplant was 5.7 months (range, 3–9 months). Pre-transplant conditioning for all patients consisted of fludarabine (FLU) (30 mg/m2 per day) from day −7 to day −2 (total dose 180 mg/m2) and BU 4 mg/kg per day from day −3 to day −2 (total dose 8 mg/kg). All CB units were serologically matched at HLA-A, B and DR loci. Although two patients had suffered from fungal or bacterial pneumonia before transplantation, there were no other infectious complications during transplantation. All patients engrafted and achieved 100% donor chimerism. We also confirmed full donor chimerism of both T and B cells. Only one patient developed acute GVHD grade III, which was resolved by increasing the dose of oral corticosteroid. None of the patients has developed chronic GVHD during follow up for 21–77 months. None of the patient received i.v. Ig replacement post transplant, or showed delay in psychomotor development. Reduced-intensity conditioning consisting of FLU and BU and transplantation from unrelated CB was an effective and safe treatment for these patients with X-SCID

Extrauterine abdominal pregnancy

This case report describes an extrauterine abdominal pregnancy in a 38-year-old G2/P1 Caucasian woman who delivered a healthy preterm boy at 35 0/7 weeks of gestation

Effects of A- and B-site (co-)acceptor doping on the structure and proton conductivity of LaNbO4

B-site and A- and B-site co-doped lanthanum niobates, La(1-x)DA(x)Nb(1-y)DB(y)O(4-delta), where D-A stands for Ca or Ba and D-B for Ga, Ge or In (x = 0 or 0.01; y = 0.01), have been synthesized via the solid-state route. Essentially single-phase materials were obtained after 10 h at 1500 degrees C with monoclinic Fergusonite structure at room temperature. The unit cell volume increases slightly with the presence of the acceptor. The electrical conductivity of the materials, characterized as a function of the temperature from 300 degrees C to 900 degrees C under wet reducing conditions with AC impedance spectroscopy, was dominated by protons. The maximum conductivity of 4.1 . 10(-4) S . cm(-1) at 900 degrees C was obtained for La0.99Ca0.01Nb0.99Ga0.01O4-delta, which is a factor of similar to 2.5 lower than the highest conductivity reported for the A-site Ca-doped LaNbO4. Based on a semi-quantitative evaluation it was shown that the hydration of the B-site and A- and B-site co-doped LaNbO4, is slightly more exothermic and that the proton mobility has higher activation enthalpies than Ca-doped LaNbO4. This is accounted for by a stronger association between the acceptor and the proton for B-site than for A-site doping. (c) 2011 Elsevier B.V. All rights reserved

Experimental study of thermodynamic properties and phase equilibria in Na2CO3–K2CO3 system

Sodium and potassium carbonates and their mixtures are important for different applications, e.g. for latent thermal energy storage, die-casting processes and molten carbonate fuel cells. In this work the phase diagram and thermodynamic properties of Na2CO3–K2CO3 system were studied by differential thermal analysis, differential scanning calorimetry and high temperature X-ray diffraction. Three carbonate mixtures (56, 25 and 75 mol% of Na2CO3) have solid-solid transition in a wide temperature range between 648 K and 823 K. The high temperature XRD analysis has shown that this transition is a continuous process of changing of the unit cell volume without structural changing of the hexagonal lattice. This phenomenon has also been observed on the measured heat capacity curves. The obtained experimental results were compared with calculations performed using the previous thermodynamic datasets. The comparison of these results shows that further thermochemical assessment of this system needs to be performed to achieve better agreement with the available experimental data