Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy.

We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7-δ (YBCO) enabled us to access higher temperature and energy scales for this phenomenon. The HTSC in the hybrid device exhibits emergence of a pseudogap state for T > Tc that converts into a superconducting state with a reduced gap for T < Tc. The conversion process has been reflected in Raman spectra collected from the TI. Complementary charge transport experiments revealed emergence of the proximity-induced superconducting gap in the TI and the reduced superconducting gap in the HTSC, but no signature of the pseudogap. This allowed us to conclude that Raman spectroscopy reveals formation of the pseudogap state but cannot distinguish the proximity-induced superconducting state in the TI from the superconducting state in the HTSC characterised by the reduced gap. Results of our experiments have shown that Raman spectroscopy is a complementary technique to classic charge transport experiments and is a powerful tool for investigation of the proximity-induced superconductivity in the Bi2Te3.

Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi2Te3 heterostructure studied by high resolution Brillouin spectroscopy.

The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm-1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm-1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models.

Generation of a mode in phononic crystal based on 1D/2D structures.

The modification of phononic crystals by surface structuring allows obtaining a new parameter describing the dynamics of the structure produced in this way. We have investigated the dispersion relation of surface acoustic waves propagating in a phononic material which is based on nanometer-scale surface modulation using interconnected one-dimensional array of stripes and a two-dimensional array of pillars. The influence of these two array components on the dispersion relation has been determined experimentally (Brillouin light scattering) and theoretically (Finite Element Method). The interaction of these two nanostructures supports a new mode which is not observed in independent structures of pillars and stripes. The influence of the relative position of these two nanostructures on the frequency of the new mode has been determined.

The electron-phonon interaction at deep Bi 2 Te3-semiconductor interfaces from Brillouin light scattering.

It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.

Environmental implications and applications of carbon nanomaterials in water treatment.

Carbon nanomaterials have been proposed as a basis for developing new technologies for photocatalytic oxidation and disinfection, improved membrane processes, adsorbents, and biofilm-resistant surfaces. This study details recent progress towards the development of these proposed applications. We explored the use of carbon nanomaterials such as fullerene C60, single-wall carbon nanotubes (SWCNTs), and multi-wall carbon nanotubes (MWCNTs) for a range of new technologies including, degradation of a probe organic compound by in situ generation of reactive oxygen species (ROS), new strategies for microbial disinfection, and the inhibition of biofilm development on membrane surfaces. The results show that the degradation of 2-chlorophenol by ROS produced microbial inactivation, and the mobility of the nanoparticle aggregates of the carbon nanomaterials all increased as suspensions were fractionated to enrich with smaller aggregates with sonication followed by successive membrane filtration.

Cerium oxide nanoparticles are more toxic than equimolar bulk cerium oxide in Caenorhabditis elegans.

Engineered cerium oxide nanoparticles (CeO2 NPs) are widely used in biomedical and engineering manufacturing industries. Previous research has shown the ability of CeO2 NPs to act as a redox catalyst, suggesting potential to both induce and alleviate oxidative stress in organisms. In this study, Caenorhabditis elegans and zebrafish (Danio rerio) were dosed with commercially available CeO2 NPs. Non-nano cerium oxide powder (CeO2) was used as a positive control for cerium toxicity. CeO2 NPs suspended in standard United States Environmental Protection Agency reconstituted moderately hard water, used to culture the C. elegans, quickly formed large polydisperse aggregates. Dosing solutions were renewed daily for 3 days. Exposure of wild-type nematodes resulted in dose-dependent growth inhibition detected for all 3 days (p < 0.0001). Non-nano CeO2 also caused significant growth inhibition (p < 0.0001), but the scale of inhibition was less at equivalent mass exposures compared with CeO2 NP exposure. Some metal and oxidative stress-sensitive mutant nematode strains showed mildly altered growth relative to the wild-type when dosed with 5 mg/L CeO2 NPs on days 2 and 3, thus providing weak evidence for a role for oxidative stress or metal sensitivity in CeO2 NP toxicity. Zebrafish microinjected with CeO2 NPs or CeO2 did not exhibit increased gross developmental defects compared with controls. Hyperspectral imaging showed that CeO2 NPs were ingested but not detectable inside the cells of C. elegans. Growth inhibition observed in C. elegans may be explained at least in part by a non-specific inhibition of feeding caused by CeO2 NPs aggregating around bacterial food and/or inside the gut tract.

Single-photon emission from electrically driven InP quantum dots epitaxially grown on CMOS-compatible Si(001).

The heteroepitaxy of III-V semiconductors on silicon is a promising approach for making silicon a photonic platform. Mismatches in material properties, however, present a major challenge, leading to high defect densities in the epitaxial layers and adversely affecting radiative recombination processes. However, nanostructures, such as quantum dots, have been found to grow defect-free even in a suboptimal environment. Here we present the first realization of indium phosphide quantum dots on exactly oriented Si(001), grown by metal-organic vapour-phase epitaxy. We report electrically driven single-photon emission in the red spectral region, meeting the wavelength range of silicon avalanche photodiodes' highest detection efficiency.

Disruption of PF4/H multimolecular complex formation with a minimally anticoagulant heparin (ODSH).

Recent studies have shown that ultra-large complexes (ULCs) of platelet factor 4 (PF4) and heparin (H) play an essential role in the pathogenesis of heparin-induced thrombocytopenia (HIT), an immune-mediated disorder caused by PF4/H antibodies. Because antigenic PF4/H ULCs assemble through non-specific electrostatic interactions, we reasoned that disruption of charge-based interactions can modulate the immune response to antigen. We tested a minimally anticoagulant compound (2-O, 3-O desulfated heparin, ODSH) with preserved charge to disrupt PF4/H complex formation and immunogenicity. We show that ODSH disrupts complexes when added to pre-formed PF4/H ULCs and prevents ULC formation when incubated simultaneously with PF4 and UFH. In other studies, we show that excess ODSH reduces HIT antibody (Ab) binding in immunoassays and that PF4/ODSH complexes do not cross-react with HIT Abs. When ODSH and unfractionated heparin (UFH) are mixed at equimolar concentrations, we show that there is a negligible effect on amount of protamine required for heparin neutralisation and reduced immunogenicity of PF4/UFH in the presence of ODSH. Taken together, these studies suggest that ODSH can be used concurrently with UFH to disrupt PF4/H charge interactions and provides a novel strategy to reduce antibody mediated complications in HIT.

Temperature dependences of piezoelectric, elastic and dielectric constants of L-alanine crystal.

Temperature changes in the components of piezoelectric, elastic and dielectric tensors were studied in L-alanine crystals in the range 100-300 K. A jumpwise increase in the c(55) component of the elastic stiffness accompanied by maxima in damping of all face-shear modes observed at 199 K in L-alanine crystal were interpreted as a result of changes in the NH(3)(+) vibrations occurring through electron-phonon coupling. All components of the piezoelectric tensor show small anomalies in this temperature range. The components of the electromechanical coupling coefficient determined indicate that L-alanine is a weak piezoelectric.

[Mid-term results after volar plating of distal radius fractures with a newly designed locking plate]. / Mittelfristige Ergebnisse nach operativer Versorgung der distalen Radiusfraktur mit einem neuen winkelstabilen, multidirektionalen Plattensystem.

BACKGROUND: The purpose of this retrospective study was to investigate the clinical and radiographic results after operative treatment of dislocated distal radius fractures with a new self-locking volar plate system. PATIENTS AND METHODS: 67 patients (average age 61.4 years) with a dislocated distal radius fracture were treated with the ITS plate system. Clinical and radiographic evaluation was done with a mean follow-up of 9.3 months. RESULTS: The mean DASH score reached 14 points, the modified Gartland/Werley score was 6.9. There was one loss of reduction on radiographic evaluation, which yielded to a dorsal osteosynthesis. Average postoperative radial inclination was 20.5 degrees (16-29 degrees) and the volar tilt 9.3 degrees (3-15 degrees). One plate had to be removed after three months because of dislocation of a malpositioned screw. There were no cases of infection or tendon ruptures. No patient required autograft bone. CONCLUSION: This new locking plate system offers an excellent option in the treatment of dislocated distal radius fractures, especially in osteoporotic bone with a dorsal comminution.

Comparison of manufactured and black carbon nanoparticle concentrations in aquatic sediments.

In this paper, we show that concentrations of manufactured carbon-based nanoparticles (MCNPs) in aquatic sediments will be negligible compared to levels of black carbon nanoparticles (BCNPs). This is concluded from model calculations accounting for MCNP sedimentation fluxes, removal rates due to aggregation or degradation, and MCNP burial in deeper sediment layers. The resultant steady state MCNP levels are compared with BCNP levels calculated from soot levels in sediments and weight fractions of nanosized fractions of these soot particles. MCNP/BCNP ratios range from 10(-7) to 10(-4) (w:w). This suggests that the often acclaimed effect of MCNPs on organic pollutant binding and bioavailability will likely be below the level of detection if natural BCNPs are present, even if binding to MCNP is one to two orders of magnitude stronger than to BCNPs. Furthermore, exposure and toxic effects of MCNPs in sediments and soils will be negligible compared to that of BCNPs.

Nanomaterials as possible contaminants: the fullerene example.

An assessment of the potential risks posed by nanomaterials will require case-by-case evaluations of the processes controlling exposure and hazards such as toxicity. Factors that control fullerene transport and transformation in aqueous environments and their relationship to toxicity are discussed. Natural organic matter is observed to either increase or decrease nanoparticle stability while trends in reactive oxygen generation run counter to proposed mechanisms of possible fullerene toxicity.

Responsible development of nanotechnologies for water and wastewater treatment.

Emerging technologies, including nanotechnologies, affect the social, economic, and environmental dimensions of our world, often in ways that are entirely unanticipated. There is considerable effort underway to explore uses of nanomaterials in applications such as membrane separations, catalysis, adsorption, and analysis with the goal of better protecting environmental quality. Along with the growth of a nanochemistry industry there is also the need to consider impacts of nanomaterials on environment and human health.

Processes of particle deposition in membrane operation and fabrication.

The processes that control particle deposition on surfaces that are of interest in understanding operational aspects of membrane filtration, also hold significance in controlling the morphology of particle deposits as intermediate steps in membrane fabrication. This paper summarizes processes controlling particle deposit morphology. The implications of these processes for understanding membrane fouling by particles and in fabricating membranes are then considered.

Fullerol-sensitized production of reactive oxygen species in aqueous solution.

The relative production rate of reactive oxygen in aqueous solution sensitized by fullerol (a polyhydroxylated, water-soluble form of the fullerene C60) was measured and compared to known reactive oxygen sensitizers using an oxygen consumption method. The solutions were irradiated by polychromatic visible and ultraviolet light. Reactive oxygen species were generated under both visible and ultraviolet light sources. The greatest rates of oxygen consumption were observed at acidic pH. We show for the first time evidence of both singlet oxygen and superoxide production by fullerol under both UV and polychromatic light sources.

Long term behavioural outcome after neonatal arterial switch operation for transposition of the great arteries.

AIMS: To evaluate behavioural outcome and quality of life in children aged 8-14 years after neonatal arterial switch operation for transposition of the great arteries. METHODS: Sixty children operated as neonates with combined deep hypothermic circulatory arrest and low flow cardiopulmonary bypass were evaluated at age 7.9-14.3 years by the Child Behaviour Checklist (CBCL) and the Inventory for the Assessment of the Quality of Life in Children and Adolescents (IQCL). RESULTS: Parent reported behavioural outcome on all CBCL problem and competence scores was worse, whereas quality of life on self reported IQCL scores was not reduced compared to the normal population. On multivariate analysis, severe preoperative hypoxia was related to parent reported social problems; peri- and postoperative cardiocirculatory insufficiency was associated with internalizing, externalizing, attention, and total behavioural problems. Reduced expressive language was associated with total behavioural problems, and poor academic achievement was related to parent reported deficits in school performance. Impaired neurological status and reduced endurance capacity both predicted self reported stress by illness. CONCLUSIONS: The neonatal arterial switch operation with combined circulatory arrest and low flow bypass is associated with parent reported long term behavioural impairment, but not with self reported general reduction in quality of life. This discrepancy may be a result of different perception of illness. In our experience, increased risk of long term psychosocial maladjustment after neonatal corrective cardiac surgery is related to the presence of neurological impairment and reduced endurance capacity.

Solid-phase synthesis of a nonpeptide RGD mimetic library: new selective alphavbeta3 integrin antagonists.

The solid-phase synthesis of a low molecular weight RGD mimetic library is described. Activities of the compounds in inhibiting the interaction of ligands, vitronectin and fibrinogen, with isolated immobilized integrins alphavbeta3 and alphaIIbbeta3 were determined in a screening assay. Highly active and selective nonpeptide alphavbeta3 integrin antagonists with regard to orally bioavailability were developed, based on the aza-glycine containing lead compound 1. An important variation is the substitution of the aspartic amide of 1 by an aromatic residue. Furthermore, different guanidine mimetics have been incorporated to improve the pharmacokinetic profile. Exchange of the beta-amino acid NH by a methylene moiety in one set of RGD mimetics leads to the azacarba analogue compounds representing a novel peptidomimetic approach, which should increase the metabolic stability.

Application of strontium isotopes for tracing landfill leachate plumes in groundwater.

We are evaluating strontium isotopes as alternative tracers of landfill leachate in groundwater. The municipal landfill studied here is located in southeastern France. This landfill has no bottom liner, and wastes are placed directly on the ground. Based on the evaluation of chloride concentration, the plume extends a maximum of 4,600 m. Strontium isotopic composition characterizes two sources: natural groundwater (87Sr/86Sr = 0.708175) and landfill leachate contamination (87Sr/86Sr = 0.708457). The evolution of mixing ratios obtained with strontium reveals a second source of groundwater contamination: fertilizers (87Sr/ 86Sr = 0.707859). These results suggestthat isotopic signatures can be used to provide useful information on sources of groundwater contamination where conventional water quality parameters may yield ambiguous results.

Synthesis and biological evaluation of integrin antagonists containing trans- and cis-2,5-disubstituted THF rings.

The synthesis of a series of RGD mimetics is described. All compounds consist of a central 2,5-disubstituted tetrahydrofuran core, a variable linker to a guanidino group, and a beta-amino alanine unit to mimic the carboxylic acid. Three types of linkers were investigated: a simple four-atom methylene chain (type A, compounds 14, 15, 16, and 17), a four-atom methylene chain with an additional chiral center, and a nitrogen substituent (type B, compounds 38, 39, and 40), and an amide linker of different length with an additional chiral center (type C, compounds 59, 60, 61, and 62). A variety of compounds were tested as potential integrin antagonists in a receptor binding assay (alphaIIbbeta3, alphavbeta3, and alphavbeta5). The relative and absolute configuration of the chiral centers at the THF ring had a pronounced effect on the binding activity and selectivity. Compound 14 proved to be a selective inhibitor of alphaIIbbeta3 (IC50=20nM), whereas compound 40 exhibited high activity for binding of alphaIIbbeta3 (IC50=67nM) and alphavbeta3 (IC50=52nM).

[Ranking of 20 MHz sonography of malignant melanoma and pigmented lesions in routine diagnosis]. / Stellenwert der 20-MHz-Sonographie des malignen Melanoms und pigmentierter Läsionen in der Routinediagnostik.

PURPOSE: Eleven dermatology clinics from all over Germany took part in our multicenter prospective study with the aim of evaluating 20 MHz sonography in the preoperative diagnosis of malignant melanomas and other pigmented skin tumours. It was to be assessed how effective sonographic measurement of thickness would compare to histology and the clinical palpation of tumour thickness and also the significance of differential diagnosis in sonography of malignant melanomas. METHOD: The prospective multicenter study proceed as follows. To the end of August 1997 264 patients with a primary malignant melanoma and 417 patients with benign skin tumours were examined via 20 MHz sonography. Two different examiners estimated the clinical thickness of the tumour by palpation. The tumour was then excised and examined for postoperative correlation with the histology sections. RESULTS: The final results showed good correlation between the histological and sonographic estimation of tumour thickness (r = 0.97). Estimation of tumour thickness by palpation showed no correlation with the histology (r = 0.59). Most of the benign (44%) and malignant tumours (38.7%) were spindle shaped. There was no significant difference between the benign and malignant tumour groups in relation to the sonographic presented shapes or echo signs. No different diagnosis could be made. CONCLUSION: The technique of high frequency sonography in relation to preoperative diagnosis of malignant melanomas has high priority. In contrast to clinical estimation of tumour thickness, sonography provided a good correlation to histology. The effectiveness of sonography with regard to the valence of the skin tumours is limited and there is no possibility of differentiating between malignant and benign tumours from the morphological face value. Hence, there is a demand for developing a 150 MHz apparatus which will be able to supply evidence regarding the valence of skin tumours.