Influence of free charge carrier density on the magnetic behavior of (Zn,Co)O thin film studied by Field Effect modulation of magnetotransport.

The origin of (ferro)magnetic ordering in transition metal doped ZnO is a still open question. For applications it is fundamental to establish if it arises from magnetically ordered impurity clusters embedded into the semiconducting matrix or if it originates from ordering of magnetic ions dilute into the host lattice. In this latter case, a reciprocal effect of the magnetic exchange on the charge carriers is expected, offering many possibilities for spintronics applications. In this paper we report on the relationship between magnetic properties and free charge density investigated by using Zinc oxide based field effect transistors, in which the charge carrier density is modulated by more than 4 order of magnitude, from 1016 to 1020 e-/cm3. The magnetotransport properties are employed to probe the magnetic status of the channel both in pure and cobalt doped zinc oxide transistors. We find that it is widely possible to control the magnetic scattering rates by field effect. We believe that this finding is a consequence of the modulation of magnetization and carrier spin polarization by the electric field. The observed effects can be explained by the change in size of bound magnetic polarons that induces a percolation magnetic ordering in the sample.

Controlling the spin of co atoms on pt(111) by hydrogen adsorption.

We investigate the effect of H adsorption on the magnetic properties of individual Co atoms on Pt(111) with scanning tunneling microscopy. For pristine Co atoms, we detect no inelastic features in the tunnel spectra. Conversely, CoH and CoH2 show a number of low-energy vibrational features in their differential conductance identified by isotope substitution. Only the fcc-adsorbed species present conductance steps of magnetic origin, with a field splitting identifying their effective spin as Seff=2 for CoH and 3/2 for CoH2. The exposure to H2 and desorption through tunnel electrons allow the reversible control of the spin in half-integer steps. Because of the presence of the surface, the hydrogen-induced spin increase is opposite to the spin sequence of CoHn molecules in the gas phase.

Electronic states of moiré modulated Cu films.

We examined by low-energy electron diffraction and scanning tunneling microscopy the surface of thin Cu films on Pt(111). The Cu/Pt lattice mismatch induces a moiré modulation for films from 3 to about 10 ML thickness. We used angle-resolved photoemission spectroscopy to examine the effects of this structural modulation on the electronic states of the system. A series of hexagonal- and trigonal-like constant energy contours is found in the proximity of the Cu(111) zone boundaries. These electronic patterns are generated by Cu sp-quantum well state replicas, originating from multiple points of the reciprocal lattice associated with the moiré superstructure. Layer-dependent strain relaxation and hybridization with the substrate bands concur to determine the dispersion and energy position of the Cu Shockley surface state.

FISH-based analysis of 10- and 25-kV soft X-ray-induced DNA damage in 184A1 human mammary epithelial cells.

Over the past years, several in vitro studies have been performed on DNA damage induced by soft X-rays, especially in the energy range below 50 keV. Radiation effects originating from such low-energy photons are relevant in the context of medical diagnostics, for example, mammography, or of accidental exposure to scattered radiation. The present study was initiated to investigate the X-ray energy-dependent induction of stable and unstable chromosomal aberrations in the human mammary epithelial cell line 184A1. Three colour fluorescence in situ hybridisation was applied to identify chromosomal damage in chromosomes 1, 8 and 17, induced by 10-kV or 25-kV soft X-rays as well as by 200-kV X-rays as a reference quality. The overall results confirm the X-ray energy dependencies published for human lymphocytes showing increasing chromosomal aberration frequencies and higher aberration complexity with decreasing X-ray energy and increasing dose. Comparing the obtained dose dependencies, ratios of 0.84 ± 0.09 and 1.22 ± 0.18 were revealed for stable translocations induced by 25- and 10-kV X-rays, respectively, using 200-kV X-rays as reference. Moreover, the analysis of the minimum number of breaks required to form the visible chromosomal damage resulted in similar ratios of 0.93 ± 0.07 for 25-kV X-rays and 1.25 ± 0.10 for 10-kV X-rays relative to 200-kV X-rays. In addition, non-DNA-proportional contributions of chromosomes 8 and 17 to the whole DNA damage and deviations from the expected 1:1 ratio of translocations and dicentrics were observed for cell line 184A1.

Application of an equilibrium-based model for diffusion barrier charcoal canisters in a small volume non-steady state radon chamber.

Radon in indoor air is often measured using activated charcoal in canisters. These are generally calibrated using large, humidity- and temperature-controlled radon chambers capable of maintaining a constant radon concentration over several days. Reliable and reproducible chambers are expensive and may be difficult to create and maintain. This study characterizes a small radon chamber in which Rn gas is allowed to build up over a period of several days for use in charcoal canister calibration and educational demonstrations, as well as various radon experiments using charcoal canisters. Predictive models have been developed that accurately describe radon gas kinetics in the charcoal canisters. Three models are available for kinetics in the small chamber with and without radon-adsorbing charcoal canisters. Presented here are both theoretical and semi-empirical applications of this equilibrium-based model of radon adsorption as applied to canisters in the small chamber. Several charcoal canister experiments in the small chamber with an equilibrium-based model of radon adsorption applied are reported. Results show that it is necessary to include a continuous radon monitor in the chamber during canister exposures, as the radon removal rate is highly variable. Furthermore, the presence of the canisters significantly decreases the amount of radon in the small chamber, especially when several canisters are present. It was found that canister response in the small chamber is largely consistent with the equilibrium-based model for both applications, with average errors of 1% for the theoretical application and -4% for the semi-empirical approach.

An equilibrium-based model for measuring environmental radon using charcoal canisters.

Radon in indoor air is often measured using canisters of activated charcoal that function by adsorbing radon gas. The use of a diffusion barrier charcoal canister (DBCC) minimizes the effects of environmental humidity and extends the useful exposure time by several days. Many DBCC protocols model charcoal canisters as simple integrating detectors, which introduces errors due to the fact that radon uptake changes over the exposure period. Errors are compensated for by calculating a calibration factor that is nonlinear with respect to exposure time. This study involves the development and testing of an equilibrium-based model and corresponding measurement protocol that treats the charcoal canisters as a system coming into equilibrium with the surrounding radon environment. This model applies to both constant and temporally varying radon concentration situations, which was essential, as efforts are currently underway using a temporally varying radon chamber. It was found that the DBCCs equilibrate following the relationship E = (1 - e) where E is a measure of how close the DBCC is to equilibrium, t is exposure time, and q is the equilibration constant. This equilibration constant was empirically determined to be 0.019 h. The proposed model was tested in a blind test as well as compared with the currently accepted U.S. Environmental Protection Agency (U.S. EPA) model. Comparisons between the two methods showed a slight decrease in measurement error when using the equilibrium-based method as compared to the U.S. EPA method.

High resolution in situ magneto-optic Kerr effect and scanning tunneling microscopy setup with all optical components in UHV.

A surface magneto-optic Kerr effect (MOKE) setup fully integrated in an ultrahigh vacuum chamber is presented. The system has been designed to combine in situ MOKE and scanning tunneling microscopy. Magnetic fields up to 0.3 T can be applied at any angle in the transverse plane allowing the study of in-plane and out-of-plane magnetization. The setup performance is demonstrated for a continuous film of 0.9 monolayers (ML) Co/Rh(111) with in-plane easy axis and for a superlattice of nanometric double layer Co islands on Au(11,12,12) with out-of-plane easy axis. For Co/Au(11,12,12) we demonstrate that the magnetic anisotropy energies deduced from thermally induced magnetization reversal and from applying a torque onto the magnetization by turning the field are the same. For the presented setup we establish a coverage detection limit of 0.5 ML for transverse and 0.1 ML for polar MOKE. For island superlattices with the density of Co/Au(11,12,12), the latter limit corresponds to islands composed of about 50 atoms. The detection limit can be further reduced when optimizing the MOKE setup for either one of the two Kerr configurations.

Linkage disequilibrium under genetic hitchhiking in finite populations.

The model of genetic hitchhiking predicts a reduction in sequence diversity at a neutral locus closely linked to a beneficial allele. In addition, it has been shown that the same process results in a specific pattern of correlations (linkage disequilibrium) between neutral polymorphisms along the chromosome at the time of fixation of the beneficial allele. During the hitchhiking event, linkage disequilibrium on either side of the beneficial allele is built up whereas it is destroyed across the selected site. We derive explicit formulas for the expectation of the covariance measure D and standardized linkage disequilibrium sigma 2D between a pair of polymorphic sites. For our analysis we use the approximation of a star-like genealogy at the selected site. The resulting expressions are approximately correct in the limit of large selection coefficients. Using simulations we show that the resulting pattern of linkage disequilibrium is quickly-i.e., in <0.1N generations-destroyed after the fixation of the beneficial allele for moderately distant neutral loci, where N is the diploid population size.

Diffusion characteristics of large molecules assessed by proton MRS on a whole-body MR system.

Methods for examinations of diffusion of large molecules of the size of fatty acids or triglycerides were developed for whole body MR units. Samples of aliphatic molecules were examined to study the influence of chain length. Feasibility under in vivo conditions was tested on lard samples at 37 degrees C and on human subjects Three stimulated echo sequences with maximum b-values of 2000 s/mm(2), 20000 s/mm(2), and 80000 s/mm(2) were used to assess a wide range of mobility. Sequence timing was optimized to minimize relaxation losses of fatty tissue. Apparent diffusion coefficients (ADC) were determined from five spectra with different diffusion weighting. In-vitro experiments were performed on butanol, decanol, and oleic acid to study the influence of chain length. In vivo conditions were mimicked using lard at 37 degrees C representing a composition of substances of various chain lengths. Subcutaneous fat and tibial bone marrow were studied in three healthy volunteers. ADC of muscular lipids of the lower leg was determined in two subjects. ADC values of pure aliphatic substances were in the range between 3.2 x 10(-5) mm(2)/s for oleic acid and 37.8 x 10(-5) mm(2)/s for butanol. In vivo investigations revealed ADC values of 1.11-1.24 x 10(-5) mm(2)/s for tibial bone marrow and 1.21-2.05 x 10(-5) mm(2)/s for subcutaneous fat. Diffusion coefficients of extra- and intramyocellular lipids were 1.83-3.65 x 10(-5) mm(2)/s and 2.22-3.60 x 10(-5) mm(2)/s, respectively. The proposed technique enables determination of ADC values of relatively large molecules and of lipid tissue compartments under in vivo conditions. Diffusion properties in several human lipid compartments are reported for the first time. Incoherent voxel motion influences the in vivo results to an unknown degree because of high motion sensitivity. In vitro experiments revealed ADC values depending on the chain length of the substances, indicating a residual dependence of measured ADC's on sequence timing.

Blockade of the CD28 and CD40 pathways result in the acceptance of pig and rat islet xenografts but not rat cardiac grafts in mice.

Previously, we demonstrated that combination CTLA4-Fc and anti-CD40L mAb treatment results in tolerance to concordant, cellular islet xenografts. The aim of this study was to determine its effectiveness in a model of fetal pig pancreas (FPP) xenotransplantation. Survival of FPP fragment grafts were compared to the survival of rat islet or cardiac xenografts following short term CTLA4-Fc and anti-CD40L mAb treatment. Rat islet and FPP fragment grafts survived long-term. However, rat cardiac grafts were rejected by 52-91 days. Both rat islet and FPP grafts showed similar histology with intact islet structures and adjacent 'nests' of lymphocytes. Concordant vascularised rat hearts showed extensive polymorphonuclear infiltrate, concentric vasculitis and a perivascular infiltrate predominantly of CD8+ T cells. This suggests that this therapy is effective for prolonging islet xenografts and demonstrates that the cellular mechanism of rejection for vascularised and non-vascularised xenografts are different.

[Needle biopsy vs. conventional surgical biopsy - biochemical analysis of various prognostic factors]. / Vergleich der biochemischen Analyse verschiedener Prognosefaktoren zwischen Stanzbiopsie und intraoperativ gewonnenem Tumormaterial beim Mammakarzinom.

OBJECTIVE: In which way is the biochemical analysis of fine needle biopsy comparable to the biochemical analysis of conventional surgical biopsy samples in the examination of prognosis factors in mammary carcinomas. MATERIAL AND METHODS: Conventional surgical biopsy and fine needle biopsy were performed on 63 mammary carcinomas. The results from the biochemical analysis of tissue samples, from each form of biopsy, with respect to estradiol and progesterone receptor, UPA and PAI-1, as well as Kathepsin D and the EGF receptor, were compared and statistically analyzed. RESULTS: When compared to conventional tissue biopsy samples, the sensitivity and specificity of the measured prognosis factors in fine needle biopsy tissue were variable for each parameter, but fell within the statistically safe margin of 86 to 100%. CONCLUSIONS: The biochemical analysis of the prognosis factors found in fine needle biopsy samples showed that fine needle biopsy is a viable alternative to intraoperative conventional surgical biopsy.

Pancreatic islet xenograft tolerance after short-term costimulation blockade is associated with increased CD4+ T cell apoptosis but not immune deviation.

BACKGROUND: Our purpose was to determine if short-term inhibition of the CD40/CD40L and CD28/B7 costimulatory pathways was capable of inducing specific unresponsiveness to pancreatic islet xenografts and to ascertain the mechanism of tolerance induction. METHODS: Diabetic B6AF1 mice were transplanted with Wistar or DA rat islets and were treated short term with CTLA4-Fc and anti-CD40L mAb (MR1). RESULTS: Coadministration of CTLA4-Fc with MR1, resulted in indefinite rat islet xenograft survival in mice. Tolerance was species but not strain specific as long-term surviving recipients rejected third party BALB/c islet allografts but accepted a second rat islet xenograft from the same or different donor strain. Tolerance induction was associated with a large leukocyte infiltrate that did not exhibit features of immune deviation as intragraft T cell-specific cytokine gene expression was globally reduced. In particular, interleukin-4 gene expression was markedly suppressed. There was a complete inhibition of anti-donor IgG, IgG1, and IgM antibody in the serum of CTLA4-Fc/MR1- treated animals. Tolerance induction was associated with increased CD4+ T cell apoptosis as there was an increased proportion of annexin-V staining and Fas expressing CD4+ T cells and a decrease in CD4+ T cell Bcl-2 expression in the grafts and draining lymph nodes of CTLA4-Fc/MR1-treated recipients. CONCLUSION: Combined costimulatory blockade was capable of producing tolerance to pancreatic islet xenografts. The induction of this tolerant state was associated with increased T cell apoptosis, whereas the maintenance phase of tolerance was associated with the accumulation of a large number of inactive lymphocytes within the graft.

IL-10/Fc inhibits macrophage function and prolongs pancreatic islet xenograft survival.

BACKGROUND: Xenograft rejection is a complex response in which macrophages and other effector cells are activated by CD4+ T cells. Initiation and regulation of this response is in part mediated by cytokines. In this study we test the hypothesis that xenograft destruction is an interleukin- (IL) 10 responsive, macrophage-mediated event. METHODS: To study the effect of the systemic administration of IL-10 on pancreatic islet xenograft rejection, a fusion protein of IL-10/Fc was used. This immunoligand possesses the bioavailability of IL-10 and the long circulating t1/2 in vivo, characteristic of Ig. Wistar rat islets were transplanted into C57BL6 mice. IL-10/Fc was administered either immediately before transplantation or in the posttransplant period. RESULTS: Both therapeutic protocols prolonged xenograft survival. Macrophage effector function was reduced in IL-10/Fc-treated mice, with a reduced macrophage infiltrate, reduced IL-12 and tumor necrosis factor-alpha gene expression and reduced serum NO2- levels. Although the number of T cells infiltrating islet grafts was not reduced, T cell effector function was inhibited in IL-10/Fc-treated animals with reduced interferon-gamma and IL-4 gene expression, reduced anti-donor cytotoxicity by recipient splenocytes and reduced anti-donor IgG1 antibody production. Ultimate rejection of the xenografts appears to be mediated by a CD4+ T cell dependent mechanism probably as a result of inadequate inhibition of IL-12 production by macrophages. CONCLUSION: IL-10/Fc prolonged rat pancreatic islet xenograft survival by inhibiting macrophage mediated immune responses. The effectiveness of this agent when administered pretransplant suggests it may have a role as an induction agent with potential clinical application.

The cytokine and histological response in islet xenograft rejection is dependent upon species combination.

BACKGROUND: Islet xenografts have clinical potential, may avoid hyperacute rejection, and therefore are a good place to examine the cellular xenograft immune response. The aim of this study was to examine the cellular, humoral, and cytokine response in islet xenograft rejection and to determine the difference in the immune response with a different donor species. METHODS: Two islet xenograft models (DA rat islets to B6AF1 mouse and canine islets to B6AF1 mouse) and a mouse syngeneic control model were examined histologically and by a semiquantitative polymerase chain reaction method. RESULTS: There was significant up-regulation of all intragraft cytokines tested (interleukin [IL]-2, IL-4, IL-5, IL-10, and interferon-gamma) in both xenograft models compared with the controls. However, the dog islet grafts had higher levels of IL-4 and IL-5 gene expression than the rat islet grafts, which, conversely, had higher levels of interferon-gamma gene expression. These differences correlated with the histological and anti-donor antibody production differences between the two models. The dog to mouse model had an intense eosinophilic infiltrate and an early up-regulation of anti-donor antibody, whereas there was little eosinophilic infiltrate and a delayed anti-donor antibody up-regulation in the rat to mouse model. CONCLUSIONS: The mouse used different mechanisms to reject the rat and canine islets, suggesting that the immune response in islet xenograft rejection may be dependent on the species combination. It may not be possible to characterize the cellular xenograft rejection response in a bipolar manner as has been the case with humoral rejection response. Caution therefore needs to be taken before extrapolating the cellular immune responses seen in animal models to the clinical setting.

A controlled study of deflazacort in the treatment of idiopathic nephrotic syndrome.

Forty patients with steroid-dependent idiopathic nephrotic syndrome (INS), a mean follow-up of 5.5 years, and a mean number of relapses of ten were blindly assigned to either deflazacort (DFZ) (n = 20) or prednisone (PDN) (n = 20) according to a ratio of equivalence of DFZ/ PDN = 0.8. This treatment was given for 1 year. The number of relapses was significantly lower in patients receiving DFZ. After 1 year, 12 remained in remission with DFZ compared with 2 with PDN. Growth velocity was not different in the two groups. Bone mineral content, assessed by quantitative computed tomography of L1 L2 vertebrae, decreased after 1 year by 6% in the DFZ group versus 12% in the PDN group (NS). The mean body weight increase of +3.9 +/- 4.1 kg in the PDN group was higher than that of the DFZ group, +1.7 +/- 2.8 kg (P = 0.06). Cushingoid symptoms tended to be less after 12 months in the DFZ group. In conclusion, this study shows that DFZ was more effective than PDN in limiting relapses in steroid-dependent INS, and that cushingoid symptoms, weight gain, and decrease in bone mineral content tended to be less marked with this drug than with PDN.

[Value of cyclosporine in the treatment of the recurrence of nephrosis after renal transplantation]. / Intérêt de la ciclosporine dans le traitement des récidives de néphrose après transplantation rénale.

From May 1992 to December 1994, 14 children with end stage renal failure secondary to steroid-resistant idiopathic nephrotic syndrome received a cadaver kidney graft. Immediate recurrence of the nephrotic syndrome occurred in four patients. In the four patients, a complete remission was observed shortly after the start of intravenous cyclosporin; two children received in addition methylprednisolone pulses for secondary rejection. Two children were still protein-free 9 and 15 months after transplantation. In the third patient, proteinuria relapsed after 9 months of complete remission and persisted in spite of the reintroduction of intravenous cyclosporin. The fourth graft was lost at 3.5 month from irreversible rejection. The creatinine clearance of the 3 functioning grafts was respectively: 73, 76 and 92 ml/mn/1.73 m2 16, 10 and 15 months after transplantation. Intravenous cyclosporin started shortly after the recurrence, maintaining blood levels between 200 and 300 ng/ml, may induce a remission in recurrent nephrotic syndrome after renal transplantation in childhood.

Craniosynostosis and kidney malformation in a case of Hennekam syndrome.

Hennekam syndrome is a rare autosomal recessive syndrome which was described for the first time in 1989. Here, we present a girl with intestinal lymphangiectasia, severe lymphedema of limbs, seizures, mild mental retardation, and facial anomalies consistent with the diagnosis of Hennekam syndrome. In addition, she had an ectopic kidney and craniosynostosis of the coronal suture, 2 manifestations not previously reported in this syndrome. While the molecular basis of Hennekam syndrome remains, as yet, unknown, this report illustrates its variable clinical expression.

Effect of Viscum album L. on rapidly proliferating amniotic fluid cells. Sister chromatid exchange frequency and proliferation index.

Amniotic fluid cells (AFC) from 10 women undergoing amniocentesis were investigated. The 5-bromo-2'-deoxyuridine-induced sister chromatid exchange (SCE) frequency of AFC remained stable after the addition of a therapeutical concentration of Viscum album L. preparation Iscador P but decreased significantly after administration of high drug doses. As the proliferation index remained stable, even at extremely high drug concentrations, this effect could not be ascribed to a reduction of proliferation. No indications of cytogenetic damage or effects of mutagenicity were seen after the addition of Viscum album L. preparation P.