Magnetic domain walls in constrained geometries

Magnetic domain walls have been studied in micrometer-sized Fe20Ni80 elements containing geometrical constrictions by spin-polarized scanning electron microscopy and numerical simulations. By controlling the constriction dimensions, the wall width can be tailored and the wall type modified. In particular, the width of a 180 degree Neel wall can be strongly reduced or increased by the constriction geometry compared with the wall in unconstrained systems.Comment: 4 pages, 6 figure

Regulation of MMP-9 by p53 in first trimester cytotrophoblastic cells

BACKGROUND The matrix metalloproteinase (MMP) family is known to play a key role in tissue remodelling during embryonic development and in pathological conditions, such as cardiovascular disease, arthritis and cancer metastasis. It has been shown previously that p53 regulates positively or negatively the expression of different MMPs. Because of p53 overexpression in trophoblastic cells, and its potential role in regulating MMP-2 and MMP-9 expression in different cell lines, we hypothesized that the expression of MMP-9 could also be regulated by p53 in first trimester cytotrophoblasts (CTB). METHODS and RESULTS Transfection experiments in CTB demonstrated that wild-type p53 down-regulates the −670 (P < 0.001) but not the −531 and −90 human MMP-9 promoter/CAT reporter plasmid activity, whereas p53 mutants partially lost this repressive activity. However, endogenous p53 is not able to regulate MMP-9 expression in CTB. The presence of high molecular weight complexes of p53 in CTB suggests a potential mechanism of inactivation of p53 transcriptional activity towards MMPs in these cells. CONCLUSIONS Although p53 is mutated in trophoblast, it is functionally incompetent towards MMPs in these cell

Direct observation of domain-wall configurations transformed by spin currents

Direct observations of current-induced domain-wall propagation by spin-polarized scanning electron microscopy are reported. Current pulses move head-to-head as well as tail-to-tail walls in sub-micrometer Fe_{20}Ni_{80} wires in the direction of the electron flow, and a decay of the wall velocity with the number of injected current pulses is observed. High-resolution images of the domain walls reveal that the wall spin structure is transformed from a vortex to a transverse configuration with subsequent pulse injections. The change in spin structure is directly correlated with the decay of the velocity.Comment: 5 pages, 3 figure

GRP78 as a marker of pre-eclampsia: an exploratory study

Although the exact mechanisms that lead to shallow invasion or defective trophoblastic differentiation in pre-eclampsia are still unknown, it is widely admitted that the etiology of pre-eclampsia is a defect in trophoblast invasion of the uterine spiral arteries. We have previously observed that the status of a chaperone protein, glucose regulated protein 78 (GRP78) is associated with the invasive properties of cytotrophoblastic cells; we therefore hypothesized that circulating GRP78 could serve as a diagnostic tool in pre-eclampsia. In a prospective case-control study, we quantified GRP78 autoantibodies, complexes of GRP78 with autoantibodies and GRP78 (C-term fragment, N-term fragment and full-length GRP78) by ELISA. Plasma from women diagnosed with pre-eclampsia (n = 16), from women during the first trimester of pregnancy who subsequently developed pre-eclampsia (n = 10) and from healthy pregnant women (controls, n = 58 at term, n = 26 at first trimester) were analysed and compared. We observed no significant difference between pre-eclamptic and healthy pregnant women for autoantibodies-GRP78 complexes or total GRP78 at both first trimester and at delivery. In contrast, the ratio of C-terminal GRP78 over full length GRP78 was significantly different in plasma of pre-eclamptic patients as compared with controls both during first trimester (P < 0.004) and at term (P < 0.0001). Our findings suggest that circulating C-terminal GRP78 reflect the invasive properties of cells, and could be used as a predictive marker for pre-eclampsia early in pregnanc

Fluctuation-Response Relations for Multi-Time Correlations

We show that time-correlation functions of arbitrary order for any random variable in a statistical dynamical system can be calculated as higher-order response functions of the mean history of the variable. The response is to a ``control term'' added as a modification to the master equation for statistical distributions. The proof of the relations is based upon a variational characterization of the generating functional of the time-correlations. The same fluctuation-response relations are preserved within moment-closures for the statistical dynamical system, when these are constructed via the variational Rayleigh-Ritz procedure. For the 2-time correlations of the moment-variables themselves, the fluctuation-response relation is equivalent to an ``Onsager regression hypothesis'' for the small fluctuations. For correlations of higher-order, there is a new effect in addition to such linear propagation of fluctuations present instantaneously: the dynamical generation of correlations by nonlinear interaction of fluctuations. In general, we discuss some physical and mathematical aspects of the {\it Ans\"{a}tze} required for an accurate calculation of the time correlations. We also comment briefly upon the computational use of these relations, which is well-suited for automatic differentiation tools. An example will be given of a simple closure for turbulent energy decay, which illustrates the numerical application of the relations.Comment: 28 pages, 1 figure, submitted to Phys. Rev.