Grain boundary engineering with gold nanoparticles

We investigated high-T C grain boundary Josephson junctions with and without incorporated gold nanoparticles. Pulsed laser deposition was used for the deposition of YBa 2 Cu 3 O 7−δ thin films on SrTiO 3 bicrystal substrates with different grain boundary angles. During the deposition process, single-crystalline nanoparticles self-assembled from a thin gold layer which was sputtered on the substrate before the YBCO deposition. The interaction between nanoparticles and thin film growth significantly influences the quality of the YBCO films [1]. The critical current density and the critical temperature of the superconducting films can be increased in a defined manner. Furthermore, the nanoparticles influence the growth conditions in the region of the grain boundary and thus the properties of the later patterned Josephson junctions. The comparison between Josephson junctions with and without nanoparticles on the same substrate shows a reduction of the critical current I C and an increase of the normal state resistance RN for all investigated types of grain boundaries in the areas with gold nanoparticles. In some cases we even found an increase of the resulting I C R N product. We present the influence of light irradiation on the properties of the Josephson junctions

Development of a sensitive method to extract and detect low numbers of Cryptosporidium oocysts from adult cattle faecal samples:results from the MRC ALL97 clinical trial

AbstractCryptosporidium transmission studies to date have concluded that adult cattle are not a significant source of oocysts contributing to clinical cryptosporidiosis in calves on farm. However current methods of sample processing have been optimised for calf faecal samples and may be less sensitive when used on adult samples due to lower numbers of oocysts and larger size of samples. A modified and novel method of oocyst extraction and concentration was developed and applied in an experiment involving spiking adult cattle faecal samples with known concentrations of Cryptosporidium oocysts. The results showed an increased sensitivity of detection from 100oocysts/g of faecal sample using conventional protocols to 5oocysts/g using the newly developed method. As it is important to be able to accurately assess the contribution of adult ruminants to the transmission of Cryptosporidium, both on farm and in the environment, the development of the techniques described here is likely to make an important contribution to Cryptosporidium transmission studies in future and in subsequent control strategies aimed at the reduction of Cryptosporidium infection in calves on farm

Coherent nonlinear optical spectroscopy of single quantum dot excited states

We report a coherent nonlinear optical signature of the excited states of two quantum dots. By comparing the nonlinear spectra with the linear photoluminescence excitation spectrum, a clear identification of excited states is possible. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70297/2/APPLAB-84-11-1928-1.pd

Measurement of relaxation between polarization eigenstates in single quantum dots

Low temperature relaxation of excitons between polarization eigenstates in single interface fluctuation quantum dots is studied using copolarized and cross-polarized transient differential transmission spectroscopy. The measured spin relaxation times are on the order of ∼100 ps. Such a spin relaxation time is longer than the reported times for thin quantum wells, but considerably shorter than the predicted times for interface fluctuation quantum dots. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70166/2/APPLAB-81-22-4251-1.pd

Single quantum dot states measured by optical modulation spectroscopy

Using optical modulation spectroscopy, we report the direct observation of absorption lines from excitons localized in GaAs single quantum dot potentials. The data provide a measurement of the linewidth, resonance energy, and oscillator strength of the transitions, and show that states which decay primarily by nonradiative processes can be directly probed using this technique. The experiments establish this technique for the characterization of single quantum dot transitions, thereby complementing luminescence studies. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70527/2/APPLAB-75-19-2933-1.pd

Wavelength modulation spectroscopy of single quantum dots

We demonstrate that external cavity diode lasers with large mode-hop-free tuning ranges (up to 80 GHz) together with wavelength modulation spectroscopy can be used to study excitonic transitions in semiconductor nanostructures. Such transitions are characterized by homogeneous linewidths typically on the order of a few GHz. Wavelength modulation spectroscopy offers a high signal-to-noise method for the determination of resonance line shapes. We have used this technique to accurately measure dipole moments and dephasing rates of single semiconductor quantum dot eigenstates. These measurements are important for the use of quantum dots in semiconductor cavities and quantum logic gates, and for an improved understanding of the physics of exciton confinement. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70029/2/APPLAB-80-11-1876-1.pd

Selection of Neospora caninum antigens stimulating bovine CD4+ve T cell responses through immuno-potency screening and proteomic approaches

Neospora caninum is recognised worldwide as a major cause of bovine infectious abortion. There is a real need to develop effective strategies to control infection during pregnancy which may lead to either abortion or congenital transmission. Due to the intracellular nature of the parasite, cell-mediated immune (CMI) responses involving CD4+ve, CD8+ve, γ/δ TCR+ve T cells and NK cells, as well as production of IFN-γ, are thought to be important for protective immunity. In this study we applied a combination of proteomic and immunological approaches to identify antigens of N. caninum that are recognized by CD4+ve T cell lines derived from infected cattle. Initially, N. caninum tachyzoite Water Soluble Antigens (NcWSA) were fractionated by size-exclusion HPLC and then screened for immune-potency using CD4+ve T cell lines. LC-ESI-MS/MS (liquid chromatography electrospray ionisation tandem mass spectrometry) was employed to catalogue and identify the proteins comprising three immunologically selected fractions and led to the identification of six N. caninum target proteins as well as sixteen functional orthologues of Toxoplasma gondii. This approach allows the screening of biologically reactive antigenic fractions by the immune cells responsible for protection (such as bovine CD4+ve cells) and the subsequent identification of the stimulating components using tandem mass spectrometry

Molecular analysis of two novel missense mutations in the GDF5 proregion that reduce protein activity and are associated with brachydactyly type C

Growth and differentiation factor 5 (GDF5) plays a central role in bone and cartilage development by regulating the proliferation and differentiation of chondrogenic tissue. GDF5 is synthesized as a preproprotein. The biological function of the proregion comprising 354 residues is undefined. We identified two families with a heterozygosity for the novel missense mutations p.T201P or p.L263P located in the proregion of GDF5. The patients presented with dominant brachydactyly type C characterized by the shortening of skeletal elements in the distal extremities. Both mutations gave rise to decreased biological activity in in vitro analyses. The variants reduced the GDF5-induced activation of SMAD signaling by the GDF5 receptors BMPR1A and BMPR1B. Ectopic expression in micromass cultures yielded relatively low protein levels of the variants and showed diminished chondrogenic activity as compared to wild-type GDF5. Interestingly, stimulation of micromass cells with recombinant human proGDF5(T201P) and proGDF5(L263P) revealed their reduced chondrogenic potential compared to the wild-type protein. Limited proteolysis of the mutant recombinant proproteins resulted in a fragment pattern profoundly different from wild-type proGDF5. Modeling of a part of the GDF5 proregion into the known three-dimensional structure of TGFbeta1 latency-associated peptide revealed that the homologous positions of both mutations are conserved regions that may be important for the folding of the mature protein or the assembly of dimeric protein complexes. We hypothesize that the missense mutations p.T201P and p.L263P interfere with the protein structure and thereby reduce the amount of fully processed, biologically active GDF5, finally causing the clinical loss of function phenotype

Manipulation of the Spin Memory of Electrons in n-GaAs

We report on the optical manipulation of the electron spin relaxation time in a GaAs based heterostructure. Experimental and theoretical study shows that the average electron spin relaxes through hyperfine interaction with the lattice nuclei, and that the rate can be controlled by the electron-electron interactions. This time has been changed from 300 ns down to 5 ns by variation of the laser frequency. This modification originates in the optically induced depletion of n-GaAs layer

Characterization of the immune cell response in the placentas from cattle following experimental inoculation with Neospora caninum throughout pregnancy

Trabajo presentado al 2nd International Meeting on Apicomplexan Parasites in Farm Animals (Kusadasi, Turquía, 31 octubre al 2 noviembre, 2013).Despite Neospora caninum (NC) being a major cause of bovine abortion worldwide, its pathogenesis is not completely understood. Evidence of immune mediated placental pathology has been reported as being responsible for compromising pregnancy probably due to the adverse effect of an exacerbated Th1 response at the maternal-foetal interface. Different clinical outcomes are known to follow experimental infections at different stages of gestation, with foetal death being the most common finding during early gestation infections, and the birth of live congenitally infected calves upon infection at mid or late gestation. The aim of our studies was to characterise placental immune responses following experimental infection during pregnancy. Cows were infected with NC tachyzoites at day 70, 140 and 210 of pregnancy and culled at 14, 28, 42 and 56 days post inoculation. Placentomes were examined by immunohistochemistry using antibodies against macrophages, T-cells (CD3, CD4, CD8, ¿¿TCR), NK and B cells and by in situ hybridization to characterize cytokine expression (IL-12, IFN-¿, TNF-¿ and IL-4). Inflammation was mainly characterised by the presence of CD3+, CD4+ and ¿¿ T-cells during the three time points. In early gestation inflammation was generally moderate to severe and mainly characterized by infiltration of IL-12, IFN-¿ and TNF-¿ expressing cells. This infiltration was more pronounced in the samples of placentome collected from dams carrying a dead foetus or one that had aborted, compared with the mothers carrying live foetuses at the time of sampling. In contrast, the infiltration of CD3+, CD4+, CD8+ and ¿¿ T-cells and Th1 cytokine expressing-cells was less evident following NC infection at mid gestation and scarce during infection at late gestation. These findings may partially explain the milder clinical outcome observed when animals are infected with NC at mid or late gestation.Peer Reviewe