Leprosy tests: diagnostic problems (apropos of 2 cases)

Two cases of reactional leprosy leading to wrong diagnosis are reported. The first one concerns a reversal reaction predominantly neuritic, initially taken for polyarthritis. The second one concerns an erythema nodosum leprosum with extensive cutaneous necrosis (Lucio's phenomenon or ulcerative lazarine leprosy). Main aspects and mechanisms of leprosy reactional states are reviewed. It is emphasized that errors or delays in diagnosis are often caused by failing to recognize cutaneous or neuritic symptoms.     

Faceted and vertically aligned GaN nanorod arrays fabricated without catalysts or lithography

Monocrystalline, vertically aligned and faceted GaN nanorods with controlled diameter have been synthesized by selective organometallic vapor phase epitaxy (OMVPE) onto GaN exposed at the bottom of pores in silicon dioxide templates patterned by reactive ion etching through self-organized porous anodic alumina films. This process is free of foreign catalysts, and the nanorod diameter control is achieved without the need for low-throughput nanolithographic techniques. The use of conventional OMVPE growth conditions allows for the straightforward adaptation of conventional doping and heterostructure growth as will be necessary for the fabrication of nanorod-based strain-relaxed electrically pumped lasers and light-emitting diodes.     

Sensitivity of space-borne SAR data to forest parameters over sloping terrain. Theory and experiment

Recently, SAR data proved to be useful for the retrieval of forest biomass. However, the effects of terrain slope must be addressed towards the generalization of biomass retrieval for varied forest and environmental conditions. To this aim, we developed experimental and theoretical approaches allowing the study of multi-frequency/multi-polarization forest backscatter of a given forest type, as a function of forest parameters and SAR local incidence angle over the relief. The experimental results showed that the sensitivity of SAR data to biomass was similar to that obtained over a flat terrain, only if the backscatter data were calibrated for slope effects. Moreover, the backscatter must also be corrected for its angular decrease, which can be removed using a simple angular model developed under assumptions of theoretical equations. The highest correlation of corrected backscatter with forest parameters related to aboveground biomass (such as stand age and bole volume) was achieved at L-HV 55° (R ²     

Directed self-assembly of quantum structures by nanomechanical stamping using probe tips

We demonstrate that nanomechanically stamped substrates can be used as templates to pattern and direct the self-assembly of epitaxial quantum structures such as quantum dots. Diamond probe tips are used to indent or stamp the surface of GaAs(100) to create nanoscale volumes of dislocation-mediated deformation, which alter the growth surface strain. These strained sites act to bias nucleation, hence allowing for selective growth of InAs quantum dots. Patterns of quantum dots are observed to form above the underlying nanostamped template. The strain state of the patterned structures is characterized by micro-Raman spectroscopy. The potential of using nanoprobe tips as a quantum dot nanofabrication technology are discussed.     

Peeling force spectroscopy: exposing the adhesive nanomechanics of one-dimensional nanostructures

The physics of adhesion and stiction of one-dimensional nanostructures such as nanotubes, nanowires, and biopolymers on different material substrates is of great interest for the study of biological adhesion and the development of nanoelectronics and nanocomposites. Here, we combine theoretical models and a new mode in the atomic force microscope to investigate quantitatively the physics of nanomechanical peeling of carbon nanotubes and nanocoils on different substrates. We demonstrate that when an initially straight nanotube is peeled from a surface, small perturbations can trigger sudden transitions between different geometric configurations of the nanotube with vastly different interfacial energies. This opens up the possibility of quantitative comparison and control of adhesion between nanotubes or nanowires on different substrates.     

Preparation of high-surface-area carbon nanoparticle/graphene composites

A method has been developed for synthesizing high-surface-area carbon nanoparticle/graphene composites. Functionalized carbon nanoparticles were anchored to the graphene planes and function as spacers to prevent the restacking of graphene sheets during drying. The composite has a layered structure in which functionalized carbon nanoparticles are sandwiched between graphene stacks. This layering leads to a porous structure with a specific surface area as high as 1256 m²/g. Such a structure provides easy access to both sides of the graphene for either gas or liquid species and allows their fast transfer. A specific capacitance as high as 324.6 F/g at a current density of 0.3 A/g was achieved using the composites in a supercapacitor.     

Die Bestimmung der isosteren Adsorptionswärme von n-Butan an den Zeolithen NaX und NaY

Isosteric Heat of Adsorption of n-Butane on Zeolites NaX and NaY Using the technique of measuring isosteres the equilibria of adsorption of n-butane on zeolites NaX and NaY were investigated. From the isosteres the heats of adsorption were calculated. Although the differences between the enthalpies are small the zeolithe with higher electrostatic field in the cavity always shows larger heats of adsorption. These differences are explained assuming an adsorption of the n-butane molecules at (or near) Na⁺-cations in SIII position (which are found only in NaX-zeolites).     

Characterization of surface roughness of Pt Schottky contacts on quaternary n-Al0.08In0.08Ga0.84N thin film assessed by atomic force microscopy and fractal analysis

The purpose of this study was to analyze surface topography of Pt Schottky contacts on quaternary n-Al_0.08In_0.08Ga_0.84N thin film. To understand how the effect of temperature changes the layers surface, the surface topography was characterized through atomic force microscopy (AFM) and fractal analysis. Pt Schottky contacts grown on nanostructure Al_0.08In_0.08Ga_0.84N thin film grown by molecular beam epitaxy technique on sapphire substrate at annealing temperatures range of 300–500 °C were used. AFM analysis was performed in contact mode, on square areas of 10 × 10 μm², by using a Nanosurf Easyscan 2 AFM system. Detailed surface characterization of the surface topography was obtained using statistical parameters of 3D surface roughness, according with ISO 25178-2: 2012, provided by the AFM software. The results revealed that the high quality Schottky contact with the Schottky barrier heights and ideality factor of 0.76 and 1.03 respectively can be obtained under 30 min annealing at 400 °C in N₂ ambience. The surface roughness of Pt Schottky contacts on quaternary n-Al_0.08In_0.08Ga_0.84N thin film revealed a fractal structure at nanometer scale. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. AFM and fractal analysis are accurate tools that may assist manufacturers in developing Pt Schottky contacts on quaternary n-Al_0.08In_0.08Ga_0.84N thin film with optimal surface characteristics and provides different yet complementary information to that offered by traditional surface statistical parameters.