Argon and krypton ion-induced changes in permalloy thin films

The effects of 75-keV Ar and 100-keV Kr ion irradiations of 72-nm thin DC-sputtered permalloy (Ni₈₁Fe₁₉) films on Si(100) wafers were studied at fluences of up to 10¹⁶ ions/cm². The changes of the structural and magnetic properties were measured via X-ray diffraction, Rutherford backscattering spectroscopy, and magneto-optical Kerr effect. The irradiations increase the lattice constant and improve the crystallinity of the samples. They induce also strong changes of the magnetic polarisation and the coercive field for increasing ion fluence. The hysteresis loops suggest that, with increasing ion fluence, the reversal of the magnetisation changes gradually from rotation-dominated in the as-deposited films to domain-wall-motion dominated at the highest ion fluences. The results are compared with those obtained for Ni-, Cr-and Xe-ion irradiated permalloy films.     

Assay of bradykinin-related peptides in human body fluids using capillary electrophoresis with laser-induced fluorescence detection

A CE with LIF detection was developed for separation and determination of bradykinin (BK)-related peptides, such as BK, kallidin (Kal), and neurokinin A (NKA). BK-related peptides were derivatized with FITC prior to CE-LIF analysis. Sodium borate 10 mmol/L at pH 9.5 was selected as derivatization media in order to get the high efficiency. Three peptides were baseline-separated within 10 min by using 110 mmol/L sodium borate-sodium hydroxide solution at pH 10.0 as the running buffer. Concentration detection limits (S/N = 3) for BK, Kal, and NKA were 0.08, 0.5, and 0.2 nmol/L, respectively. Meanwhile we have also developed a simple, quick, and sensitive large-volume sample stacking (LVSS) technique for CE-LIF detection of BK, Kal, and NKA. By using this stacking technique, the detection limits (S/N = 3) for BK, Kal, and NKA were 0.02, 0.05, and 0.04 nmol/L, respectively. This method has been applied to the assay of human saliva and cerebrospinal fluid with satisfactory results.     

Fluid and plastic flow dynamics of the critical state for a strongly pinned 2D superconductor

The frequency of the Raman active A_1g radial breathing mode has been widely used as a tool to estimate the distribution of diameters of single wall carbon nanotubes (SWNT). However, the relation between frequency and diameter is not straightforward and results are model-dependent. Because most of the experiments are performed on bundles and not on isolated tubes, the model should especially take into account the van der Waals intertube interactions. Here, we use a pair-potential approach to account for such interactions and we derive a nonlinear relation between the SWNT diameter and the frequency of the A_1g radial breathing modes. We demonstrate a good agreement between calculations and the diameters derived from diffraction experiments on the same samples. Received 22 December 1999 and Received in final form 17 July 2000     

The Relationship of Glutathione-S-Transferase and Multi-Drug Resistance-Related Protein 1 in Nitric Oxide (NO) Transport and Storage

Nitric oxide is a diatomic gas that has traditionally been viewed, particularly in the context of chemical fields, as a toxic, pungent gas that is the product of ammonia oxidation. However, nitric oxide has been associated with many biological roles including cell signaling, macrophage cytotoxicity, and vasodilation. More recently, a model for nitric oxide trafficking has been proposed where nitric oxide is regulated in the form of dinitrosyl-dithiol-iron-complexes, which are much less toxic and have a significantly greater half-life than free nitric oxide. Our laboratory has previously examined this hypothesis in tumor cells and has demonstrated that dinitrosyl-dithiol-iron-complexes are transported and stored by multi-drug resistance-related protein 1 and glutathione-S-transferase P1. A crystal structure of a dinitrosyl-dithiol-iron complex with glutathione-S-transferase P1 has been solved that demonstrates that a tyrosine residue in glutathione-S-transferase P1 is responsible for binding dinitrosyl-dithiol-iron-complexes. Considering the roles of nitric oxide in vasodilation and many other processes, a physiological model of nitric oxide transport and storage would be valuable in understanding nitric oxide physiology and pathophysiology.     

Magnetic interactions in the monoclinic ludwigite Cu FeO BO

The system Cu₂FeO₂BO₃ is an oxyborate belonging to the family of the ludwigites. In this paper we present AC susceptibility, magnetization measurements and M?ssbauer spectroscopy on this material which allows for a complete characterization of its complex magnetic behavior. We find an hierarchy of interactions which clearly defines three regimes with decreasing temperature. These are associated with, the freezing of the Fe moments, the antiferromagnetic ordering of the Cu sub-lattice and finally the coupling between both systems. Received 25 September 1998     

DFT investigation of the geometrical and electronic structures of (X = B, N and Si) clusters

Geometrical and electronic structures of C₃₅X fullerenes with , N and Si as substitutional dopants have been studied. Three non-equivalent sites in the D_6h structure of C₃₆ have been considered for the substitution. We have found that the dopant has a strong tendency to substitute at sites where the carbon atom contributes significantly to the frontier orbitals of C₃₆ and has the weakest interaction with its nearest-neighbor atoms. The relative stability of C₃₅Si and C₃₅B (C₃₅N) has been investigated and high chemical reactivity of C₃₅Si has been predicted. Received 8 July 1999 and Received in final form 4 October 1999     

Optical transmittance spectroscopy of concentric-shell fullerenes layers produced by carbon ion implantation

Concentric-shell fullerenes, also called carbon onions, produced by carbon ion implantation into silver thin films, and subsequently deposited on a silica substrate, were studied by optical transmission spectroscopy in the wavelength range 0.2 - 1.2 μm. In this interval, the strongest absorption is due to the π-plasmon of sp²-like carbon. The position of the plasmon absorption band clearly evolved from 265 nm at low fluence to 230 nm at high implantation fluences. A simulation of the optical spectra based on dielectric models of the concentric-shell fullerenes layer allowed us to identify the first peak as due to disordered graphite and the latter to the carbon onions. The concentration of residual graphite and the filling fraction of the carbon onions produced at high fluences could be estimated by fitting the optical spectra with computed transmittance curves. Received 13 July 2000     

Pressure assisted evolution of defects in silicon

The effect of enhanced hydrostatic pressure following heat treatment on the evolution of point defects in neutron‐irradiated Czochralski‐grown silicon is investigated using infrared spectroscopy. The behavior of oxygen‐related defects, particularly of the VO and the VO₂ centers, is mainly studied using samples subjected to heat treatment under hydrostatic pressure. It is observed that (1) pressure accelerates the annealing process of the VO defects and enhances the growth of the VO₂ complexes and (2) the VO₂ concentration is larger than expected from the corresponding decay of the VO defects. The faster decay of the VO defects is attributed to a pressure‐induced decrease of their migration energy. The larger VO₂ concentration is also discussed. One possible explanation is that pressure stimulates an additional mechanism for the formation of the VO₂ defects, which involves the reaction of oxygen dimers with vacancies. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hierarchical Classification of Event-Related Potentials for the Recognition of Gender Differences in the Attention Task

Research on the functioning of human cognition has been a crucial problem studied for years. Electroencephalography (EEG) classification methods may serve as a precious tool for understanding the temporal dynamics of human brain activity, and the purpose of such an approach is to increase the statistical power of the differences between conditions that are too weak to be detected using standard EEG methods. Following that line of research, in this paper, we focus on recognizing gender differences in the functioning of the human brain in the attention task. For that purpose, we gathered, analyzed, and finally classified event-related potentials (ERPs). We propose a hierarchical approach, in which the electrophysiological signal preprocessing is combined with the classification method, enriched with a segmentation step, which creates a full line of electrophysiological signal classification during an attention task. This approach allowed us to detect differences between men and women in the P3 waveform, an ERP component related to attention, which were not observed using standard ERP analysis. The results provide evidence for the high effectiveness of the proposed method, which outperformed a traditional statistical analysis approach. This is a step towards understanding neuronal differences between men’s and women’s brains during cognition, aiming to reduce the misdiagnosis and adverse side effects in underrepresented women groups in health and biomedical research.     

Effective interactions of colloids on nematic films

The elastic and capillary interactions between a pair of colloidal particles trapped on top of a nematic film are studied theoretically for large separations d. The elastic interaction is repulsive and of quadrupolar type, varying as d^-5. For macroscopically thick films, the capillary interaction is likewise repulsive and proportional to d^-5 as a consequence of mechanical isolation of the system comprised of the colloids and the interface. A finite film thickness introduces a nonvanishing force on the system (exerted by the substrate supporting the film) leading to logarithmically varying capillary attractions. However, their strength turns out to be too small to be of importance for the recently observed pattern formation of colloidal droplets on nematic films.