Ultrathin catalyst-free InAs nanowires on silicon with distinct 1D sub-band transport properties.

Ultrathin InAs nanowires (NW) with a one-dimensional (1D) sub-band structure are promising materials for advanced quantum-electronic devices, where dimensions in the sub-30 nm diameter limit together with post-CMOS integration scenarios on Si are much desired. Here, we demonstrate two site-selective synthesis methods that achieve epitaxial, high aspect ratio InAs NWs on Si with ultrathin diameters below 20 nm. The first approach exploits direct vapor-solid growth to tune the NW diameter by interwire spacing, mask opening size and growth time. The second scheme explores a unique reverse-reaction growth by which the sidewalls of InAs NWs are thermally decomposed under controlled arsenic flux and annealing time. Interesting kinetically limited dependencies between interwire spacing and thinning dynamics are found, yielding diameters as low as 12 nm for sparse NW arrays. We clearly verify the 1D sub-band structure in ultrathin NWs by pronounced conductance steps in low-temperature transport measurements using back-gated NW-field effect transistors. Correlated simulations reveal single- and double degenerate conductance steps, which highlight the rotational hexagonal symmetry and reproduce the experimental traces in the diffusive 1D transport limit. Modelling under the realistic back-gate configuration further evidences regimes that lead to asymmetric carrier distribution and breakdown of the degeneracy depending on the gate bias.

Tuning structure and mechanical properties of Ta-C coatings by N-alloying and vacancy population.

Tailoring mechanical properties of transition metal carbides by substituting carbon with nitrogen atoms is a highly interesting approach, as thereby the bonding state changes towards a more metallic like character and thus ductility can be increased. Based on ab initio calculations we could prove experimentally, that up to a nitrogen content of about 68% on the non-metallic sublattice, Ta-C-N crystals prevail a face centered cubic structure for sputter deposited thin films. The cubic structure is partly stabilized by non-metallic as well as Ta vacancies - the latter are decisive for nitrogen rich compositions. With increasing nitrogen content, the originally super-hard fcc-TaC0.71 thin films soften from 40 GPa to 26 GPa for TaC0.33N0.67, accompanied by a decrease of the indentation modulus. With increasing nitrogen on the non-metallic sublattice (hence, decreasing C) the damage tolerance of Ta-C based coatings increases, when characterized after the Pugh and Pettifor criteria. Consequently, varying the non-metallic sublattice population allows for an effective tuning and designing of intrinsic coating properties.

Tuning Lasing Emission toward Long Wavelengths in GaAs-(In,Al)GaAs Core-Multishell Nanowires.

Semiconductor nanowire (NW) lasers are attractive as integrated on-chip coherent light sources with strong potential for applications in optical communication and sensing. Realizing lasers from individual bulk-type NWs with emission tunable from the near-infrared to the telecommunications spectral region is, however, challenging and requires low-dimensional active gain regions with an adjustable band gap and quantum confinement. Here, we demonstrate lasing from GaAs-(InGaAs/AlGaAs) core-shell NWs with multiple InGaAs quantum wells (QW) and lasing wavelengths tunable from ∼0.8 to ∼1.1 µm. Our investigation emphasizes particularly the critical interplay between QW design, growth kinetics, and the control of InGaAs composition in the active region needed for effective tuning of the lasing wavelength. A low shell growth temperature and GaAs interlayers at the QW/barrier interfaces enable In molar fractions up to ∼25% without plastic strain relaxation or alloy intermixing in the QWs. Correlated scanning transmission electron microscopy, atom probe tomography, and confocal PL spectroscopy analyses illustrate the high sensitivity of the optically pumped lasing characteristics on microscopic properties, providing useful guidelines for other III-V-based NW laser systems.

Modulation of the atopy patch test reaction by topical corticosteroids and tar.

BACKGROUND: Pharmacologic studies in atopic eczema (AE) are difficult to standardize. Patients with AE differ in the stage of their skin disease (acute, subacute, chronic). OBJECTIVE: This study was designed to assess macroscopic and microscopic effects of pretreatment with topical glucocortico-steroids (GCSs) and tar on the atopy patch test (APT) reaction in patients with atopic eczema. METHODS: Nonlesional skin of the back of patients with AE (n = 6) was treated for 3 weeks at 3 different sites with triamcin-olonacetonide 0.1% in cetamacrogol ointment (GCSs), pix liquida 10% in cetamacrogol ointment (tar), and cetamacrogol ointment (vehicle), respectively. APTs were performed, and biopsy specimens were taken from all these sites (time = 0 and 24 hours) for immunohistochemical analysis. RESULTS: Treatment with both GCSs and tar was able to reduce the macroscopic outcome of the APT reaction. Furthermore, both treatment modalities had an almost equally inhibiting effect on the influx of T cells, eosinophils, and CD1(+), RFD1(+), IFN-gamma(+), and IL-4(+) cells, as well as on the percentage of vessels expressing the adhesion molecules vascular cell adhesion molecule 1 and E-selectin in response to epicutaneous aeroallergen challenge. CONCLUSION: Although both treatments significantly reduced the various cellular constituents of allergic inflammation, all cell types remained present. In addition, this study shows that the APT can be used to evaluate the effect of topical anti-inflammatory treatments on allergic inflammation in patients with AE.

Attraction of adult Rhagoletis indifferens (Diptera: Tephritidae) to unbaited and odor-baited red spheres and yellow rectangles.

Five sizes of red spheres (4, 6, 8, 10, and 12 cm diameter) and 2 orientations of yellow rectangles (vertical and V) were evaluated as unbaited sticky-coated traps for western cherry fruit flies, Rhagoletis indifferens Curran, in unmanaged cherry trees in Washington and Oregon. Red spheres that were 10 cm in diameter attracted more flies than red spheres that were 8 or 12 cm in diameter and significantly more flies than 4- or 6-cm spheres and yellow rectangles of either orientation. In a 2nd test, red spheres (10 cm diameter) baited with ammonium carbonate alone or ammonium carbonate plus putrescine attracted significantly more R. indifferens than similar spheres baited with ammonium acetate alone, putrescine alone, 3-methyl-1-butanol alone, or combinations of these substances. In a 3rd test, vertical yellow rectangles baited with ammonium carbonate alone attracted numerically more R. indifferens than any of the aforementioned substances alone or in combination. We discuss the potential value of 10-cm red spheres baited with ammonium carbonate for monitoring and direct control of R. indifferens.

Transformation of the structure of collagen. A time-resolved analysis of mechanochemical processes using synchrotron radiation.

Mechanochemically induced molecular transformations of collagen fibres were analysed using time-resolved small-angle diffraction spectra and histomechanical measurements. In particular, the influence of aqueous and methanolic perchlorate solutions was examined. According to a transformation continuing from the periphery towards the centre, the macroscopic contraction that is completed less than five minutes after incubation with perchlorate is caused by peripherally transformed fibrils only, whereas the centrally situated fibrils first undergo an accordion-like folding, but after more than 20 minutes are transformed similarly. The triple-helical transformation is preceded by a structure-breaking effect on structural water that can be monitored in time-resolved diffraction spectra. The combined loss of meridional low-angle reflections and cross-striated fibrils in micrographs is irreversible. By dialysis of colloidally dissolved collagen against a solution of ATP, however, segment-long spacing aggregates are obtained. Under isometric conditions, an instantaneous transformation of intermittent regions leads to an increase in the long period of adjacent, still structured regions of the same fibril that is correlated with a delayed increase in tension in the fibre. Increase of tension under isometric conditions as well as the flow-properties of a fibre relaxed in perchlorate are interpreted in terms of the parallel sliding of subunits of varying lengths, which has been demonstrated by diffraction analysis.

[Preliminary physiological and psychological results under various electroclimatic conditions (author's transl)]. / Physiologische und psychologische Erstresultate unter verschiedenen elektroklimatischen Bedingungen.

Before the start of a research project which was to stretch over a period of several years, characteristics of the control space were to be defined. Therefore the influence of spherics and 50 Hz-alternating fields in the unscreened control space were studied.--Pupils (Foster children) were the test subjects. Each test subject was subjected to the conditions of the control space as well as the testing space.--Two classes of parameters were studied. Blood sugar, blood pressure and pulse rate were recorded as physiological dimensions. Short-term memory, powers of concentration as well as the subjective well-being were the psychological parameters.--As to the parameters examined, no significant difference between testing and control space conditions was recorded. In order to examine whether the climatic factors of the control space have an antagonistic effect on the variables in question, their influence was studied separately in two further investigations. In order to clarify this problem, spherics-impulses in the 10 Khz range were given in screened space ("Vorversuch 2"/preliminary experiment 2), then--in, "Vorversuch 3"/preliminary experiment 3 - a 50 Hz-alternating field was applied. For each of the climatic factors under examination the influence on each single parameter was negative. The assumption of an antagonistic effect which would hinder the definition of standard spatial conditions was thereby shown to be incorrect.

[On the determination of changes in the large periodic structure of collagen (author's transl)]. / Uber die Bestimmung von Langperioden-Anderungen am Kollagen.

Changes in the large periodic structure of collagen were investigated with the aid of synchrotron radiation. Following results were obtained: 1) Macroscopic extension results in elastic deformation of the elements which are determinant for the structure. 2) The increase of the large period is not proportional to the macroscopic stress. 3) The interpretation of these facts requires a mechanical coupling between the structural units. Up to extensions of 4% this coupling is produced by means of a viscoelastic matrix. 4) In all probability the polypeptide helices are deformed in an inhomogeneous mode. The results were set against measurements on human tendon and on artificially crosslinked collagen. The relations between the mechanical behaviour and the change of the large period were compared with the properties of a mathematical model.

[Trace elements in several organs and mechanical properties of collagen under the influence of D-penicillamin (author's transl)]. / Der einfluss von D-Penicillamin auf den Gehalt einiger Organe an Spurenelementen sowie auf die mechanischen Eigenschaften von Kollagen.

The content of trace elements in several organs of rats under the influence of D-penicillamine (D-PA) was investigated by the neutronactivation-analysis. It could be shown an diminution of Cu, and Co under D-PA-treatment, the content of Fe, Mn, Rb and Zn was not influenced. The investigated organs didn't show any submicroscopic alterations under D-PA. On isolated collagen fibrils of tail tendon was seen a significantly diminuition of E-moduls. In accordance with Siegel the principal effect of D-PA is thought to block the synthesis of functional groups from Schiff-base crosslink precursors but not to inhibit lysyloxidase by loss of Cu-ions of connective tissue. The thermostability of D-PA influenced fibrils is changed in stretched state only and will be due to the lack of crosslink Schiff-bases; where as the shrinking point of not stretched fibrils shows only aging dependent changes.

[Disordered fibrillar structure in ruptured tendons (author's transl)]. / Fibrilläre Gefügestörung bei Sehnenruptur.

Areas of disordered fibrillar structure similar to kinking deformities have been observed in specimens from ruptured tendons. It seems possible to compare this phenomenon with experimentally produced deformations. The significance for the pathomechanics of tendon rupture is discussed.

[Kinking deformities in collagen (author's transl)]. / Knickdeformationen an Kollagen.

The affect of stretch on collagen was investigated. Alterations of mechanical dimensions and thermostability of fibrils were measured and changes in fine structure determined by x-ray diffraction and electronmicroscopy. Collagen underwent changes both in tensile strength and fine structure following stretch beyond the physiological range. The severity of these changes depended both on the degree of stretch and the cross-link density of the collagen Fibrils either became split into bundles consisting of subfibrillar units or showed circumscribed kinking deformities. The mechanism producing kinking was investigated. It is possible that a connection exists between fibrillar kinking and tendon rupture.

[Structure and mechanical properties of dermatosparactic collagen (author's transl)]. / Struktur und mechanische Eigenschaften dermatosparaktischen Kollagens.

Dermatosparactic calf-tail-tendon-collagen was investigated by mechanical measurements, electron microscopy and x-ray diffraction. We suppose, that the tensile strength decrease of the fibres is due to the irregular aggregation of subfibrils to fibrils. The x-ray diagram of the fibre is not influenced by state of disorder. Cyclic extension of dermatosparactic collagen leads to a higher increase in tensile strength than in the case of normal calf tendon. The effect might be due to the increase of fibril- and area-density resulting in an augmentation of crosslinks.