602 research outputs found
De groei van de Middeleeuwse handel in vis: archeologische opgravingen te Quoygrew (Orkney, Schotland) = Excavations at Quoygrew (Orkney, Scotland) and the growth of the mediaeval fish trade
The metal finds and their implications
Major interdisciplinary study of metal artefacts from major Norse site in Orkney
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Studies of defects and surfaces by channeling
Uses of channeling to study defects and surfaces are reviewed briefly with emphasis on ways in which they are currently evolving. Consideration is first given to normalization of yields for channeling directions to the yield for a random direction, this normalization being important to the accuracy of both defect and surface studies. The discussion of atom location concentrates on the use that can be made of quantitative calculations of flux peaking. The treatment of surfaces includes accurate determination of the area of the surface peak as well as basic ways of extracting from experiments information on the positions of surface atoms
Functional and genetic evidence that nucleoside transport is highly conserved in Leishmania species: Implications for pyrimidine-based chemotherapy
Leishmania pyrimidine salvage is replete with opportunities for therapeutic intervention with enzyme inhibitors or antimetabolites. Their uptake into cells depends upon specific transporters; therefore it is essential to establish whether various Leishmania species possess similar pyrimidine transporters capable of drug uptake. Here, we report a comprehensive characterization of pyrimidine transport in L. major and L. mexicana. In both species, two transporters for uridine/adenosine were detected, one of which also transported uracil and the antimetabolites 5-fluoruracil (5-FU) and 5F,2′deoxyuridine (5F,2′dUrd), and was designated uridine-uracil transporter 1 (UUT1); the other transporter mediated uptake of adenosine, uridine, 5F,2′dUrd and thymidine and was designated Nucleoside Transporter 1 (NT1). To verify the reported L. donovani model of two NT1-like genes encoding uridine/adenosine transporters, and an NT2 gene encoding an inosine transporter, we cloned the corresponding L. major and L. mexicana genes, expressing each in T. brucei. Consistent with the L. donovani reports, the NT1-like genes of either species mediated the adenosine-sensitive uptake of [3H]-uridine but not of [3H]-inosine. Conversely, the NT2-like genes mediated uptake of [3H]-inosine but not [3H]-uridine. Among pyrimidine antimetabolites tested, 5-FU and 5F,2′dUrd were the most effective antileishmanials; resistance to both analogs was induced in L. major and L. mexicana. In each case it was found that the resistant cells had lost the transport capacity for the inducing drug. Metabolomics analysis found that the mechanism of action of 5-FU and 5F-2′dUrd was similar in both Leishmania species, with major changes in deoxynucleotide metabolism. We conclude that the pyrimidine salvage system is highly conserved in Leishmania species - essential information for the development of pyrimidine-based chemotherapy
Association of FCGR3A and FCGR3B haplotypes with rheumatoid arthritis and primary Sjögren's syndrome [POSTER PRESENTATION]
Background
Rheumatoid arthritis (RA) is an autoimmune disease that is thought to arise from a complex interaction between multiple genetic factors and environmental triggers. We have previously demonstrated an association between a Fc gamma receptor (FcγR) haplotype and RA in a cross-sectional cohort of RA patients. We have sought to confirm this association in an inception cohort of RA patients and matched controls. We also extended our study to investigate a second autoanti-body associated rheumatic disease, primary Sjögren's syndrome (PSS).
Methods
The FCGR3A-158F/V and FCGR3B-NA1/NA2 functional polymorphisms were examined for association in an inception cohort of RA patients (n = 448), and a well-characterised PSS cohort (n = 83) from the United Kingdom. Pairwise disequilibrium coefficients (D') were calculated in 267 Blood Service healthy controls. The EHPlus program was used to estimate haplotype frequencies for patients and controls and to determine whether significant linkage disequilibrium was present. A likelihood ratio test is performed to test for differences between the haplotype frequencies in cases and controls. A permutation procedure implemented in this program enabled 1000 permutations to be performed on all haplotype associations to assess significance.
Results
There was significant linkage disequilibrium between FCGR3A and FCGR3B (D' = -0.445, P = 0.001). There was no significant difference in the FCGR3A or FCGR3B allele or genotype frequencies in the RA or PSS patients compared with controls. However, there was a significant difference in the FCGR3A-FCGR3B haplotype distributions with increased homozygosity for the FCGR3A-FCGR3B 158V-NA2 haplotype in both our inception RA cohort (odds ratio = 2.15, 95% confidence interval = 1.1–4.2 P = 0.027) and PSS (odds ratio = 2.83, 95% confidence interval = 1.0–8.2, P = 0.047) compared with controls. The reference group for these analyses comprised individuals who did not possess a copy of the FCGR3A-FCGR3B 158V-NA2 haplotype.
Conclusions
We have confirmed our original findings of association between the FCGR3A-FCGR3B 158V-NA2 haplotype and RA in a new inception cohort of RA patients. This suggests that there may be an RA-susceptibility gene at this locus. The significant increased frequency of an identical haplotype in PSS suggests the FcÎłR genetic locus may contribute to the pathogenesis of diverse autoantibody-mediated rheumatic diseases
Three-Body approach to the K^- d Scattering Length in Particle Basis
We report on the first calculation of the scattering length A_{K^-d} based on
a relativistic three-body approach where the two-body input amplitudes coupled
to the Kbar N channels have been obtained with the chiral SU(3) constraint, but
with isospin symmetry breaking effects taken into account. Results are compared
with a recent calculation applying a similar set of two-body amplitudes,based
on the fixed center approximation, considered as a good approximation for a
loosely bound target, and for which we find significant deviations from the
exact three-body results. Effects of the hyperon-nucleon interaction, and
deuteron -wave component are also evaluated.Comment: 5 pages, Submitted to Phys. Rev.
The Grover algorithm with large nuclear spins in semiconductors
We show a possible way to implement the Grover algorithm in large nuclear
spins 1/2<I<9/2 in semiconductors. The Grover sequence is performed by means of
multiphoton transitions that distribute the spin amplitude between the nuclear
spin states. They are distinguishable due to the quadrupolar splitting, which
makes the nuclear spin levels non-equidistant. We introduce a generalized
rotating frame for an effective Hamiltonian that governs the non-perturbative
time evolution of the nuclear spin states for arbitrary spin lengths I. The
larger the quadrupolar splitting, the better the agreement between our
approximative method using the generalized rotating frame and exact numerical
calculations.Comment: 11 pages, 18 EPS figures, REVTe
A Theory of Ferroelectric Phase Transition in SrTiO induced by Isotope Replacement
A theory to describe the dielectric anomalies and the ferroelectric phase
transition induced by oxygen isotope replacement in SrTiO is developed. The
proposed model gives consistent explanation between apparently contradictory
experimental results on macroscopic dielectric measurements versus microscopic
lattice dynamical measurements by neutron scattering studies. The essential
feature is described by a 3-state quantum order-disorder system characterizing
the degenerated excited states in addition to the ground state of TiO
cluster. The effect of isotope replacement is taken into account through the
tunneling frequency between the excited states. The dielectric properties are
analyzed by the mean field approximation (MFA), which gives qualitative
agreements with experimental results throughout full range of the isotope
concentration.The phase diagram in the temperature-tunneling
frequencycoordinate is studied by a QMC method to confirm the qualitative
validity of the MFA analysis.Comment: 26 pages, 8 figure
Effect of quantum fluctuations on structural phase transitions in SrTiO_3 and BaTiO_3
Using path-integral Monte Carol simulations and an ab initio effective
Hamiltonian, we study the effects of quantum fluctuations on structural phase
transitions in the cubic perovskite compounds SrTiO3 and BaTiO3. We find
quantum fluctuations affect ferroelectric (FE) transitions more strongly than
antiferrodistortive (AFD) ones, even though the effective mass of a single FE
local mode is larger. For SrTiO3 we find that the quantum fluctuations suppress
the FE transition completely, and reduce the AFD transition temperature from
130K to 110K. For BaTiO3, quantum fluctuations do not affect the order of the
transition, but do reduce the transition temperature by 35-50 K. The
implications of the calculations are discussed.Comment: Revtex (preprint style, 14 pages) + 2 postscript figures. A version
in two-column article style with embedded figures is available at
http://electron.rutgers.edu/~dhv/preprints/index.html#wz_qs
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