Mesoscopic Structures and Coexisting Phases in Silica Films.

Silica films represent a unique two-dimensional film system, exhibiting both crystalline and vitreous forms. While much scientific work has focused on the atomic-scale features of this film system, mesoscale structures can play an important role for understanding confined space reactions and other applications of silica films. Here, we report on mesoscale structures in silica films grown under ultrahigh vacuum and examined with scanning tunneling microscopy (STM).

Lignin nanoparticles enter the scene: A promising versatile green tool for multiple applications.

Strategies to take advantage of residual lignin from industrial processes are well regarded in the field of green chemistry and biotechnology. Quite recently, researchers transformed lignin into nanomaterials, such as nanoparticles, nanofibers, nanofilms, nanocapsules and nanotubes, attracting increasing attention from the scientific community. Lignin nanoparticles are seen as green way to use high-value renewable resources for application in different fields because recent studies have shown they are non-toxic in reasonable concentrations (both in vitro and in vivo assays), inexpensive (a waste generated in the biorefinery, for example, from the bioethanol platform) and potentially biodegradable (by fungi and bacteria in nature).

Growth and Atomic-Scale Characterization of Ultrathin Silica and Germania Films: The Crucial Role of the Metal Support.

The present review reports on the preparation and atomic-scale characterization of the thinnest possible films of the glass-forming materials silica and germania. To this end state-of-the-art surface science techniques, in particular scanning probe microscopy, and density functional theory calculations have been employed. The investigated films range from monolayer to bilayer coverage where both, the crystalline and the amorphous films, contain characteristic XO (X=Si,Ge) building blocks.

Sensing the Spin of an Individual Ce Adatom.

The magnetic moment of rare earth elements originates from electrons in the partially filled 4f orbitals. Accessing this moment electrically by scanning tunneling spectroscopy is hampered by shielding of outerlying orbitals. Here, we show that we can detect the magnetic moment of an individual Ce atom adsorbed on a Cu_{2}N ultrathin film on Cu(100) by using a sensor tip that has its apex functionalized with a Kondo screened spin system.

From Crystalline to Amorphous Germania Bilayer Films at the Atomic Scale: Preparation and Characterization.

A new two-dimensional (2D) germanium dioxide film has been prepared. The film consists of interconnected germania tetrahedral units forming a bilayer structure, weakly coupled to the supporting Pt(111) metal-substrate. Density functional theory calculations predict a stable structure of 558-membered rings for germania films, while for silica films 6-membered rings are preferred.

Upscale and characterization of lignin-modifying enzymes from Marasmiellus palmivorus VE111 in a bioreactor under parameter optimization and the effect of inducers.

Testing different pHs, dissolved oxygen concentrations and temperatures, plus the addition of inducers, to optimize ligninolytic enzyme activity, resulted in increased production of laccases, total peroxidases and manganese peroxidases on the order of 2.1-fold, 4.6-fold and 10-fold, respectively; laccases reached 6588 U/mL, total peroxidases reached 3533 U/mL and manganese peroxidase achieved 60 U/mL.

Charge Control in Model Catalysis: The Decisive Role of the Oxide-Nanoparticle Interface.

In chemistry and physics the electronic charge on a species or material is one important determinant of its properties. In the present Minireview, the essential requirements for a model catalyst system suitable to study charge control are discussed. The ideal model catalyst for this purpose consists of a material system, which comprises a single crystal metal support, covered by an epitaxially grown ultrathin oxide film, and flat, two-dimensional nanoparticles residing on this film.

Penicillium echinulatum secretome analysis reveals the fungi potential for degradation of lignocellulosic biomass.

Background: The enzymatic degradation of lignocellulosic materials by fungal enzyme systems has been extensively studied due to its effectiveness in the liberation of fermentable sugars for bioethanol production. Recently, variants of the fungus Penicillium echinulatum have been described as a great producer of cellulases and considered a promising strain for the bioethanol industry.

Results: Penicillium echinulatum, wild-type 2HH and its mutant strain S1M29, were grown on four different carbon sources: cellulose, sugar cane bagasse pretreated by steam explosion (SCB), glucose, and glycerol for 120 h.

Molecular Adsorption Changes the Quantum Structure of Oxide-Supported Gold Nanoparticles: Chemisorption versus Physisorption.

STM conductance spectroscopy and mapping has been used to analyze the impact of molecular adsorption on the quantized electronic structure of individual metal nanoparticles. For this purpose, isophorone and CO2, as prototype molecules for physisorptive and chemisorptive binding, were dosed onto monolayer Au islands grown on MgO thin films. The molecules attach exclusively to the metal-oxide boundary, while the interior of the islands remains pristine.

Phonon-mediated electron transport through CaO thin films.

Scanning tunneling microscopy has developed into a powerful tool for the characterization of conductive surfaces, for which the overlap of tip and sample wave functions determines the image contrast. On insulating layers, as the CaO thin film grown on Mo(001) investigated here, direct overlap between initial and final states is not enabled anymore and electrons are transported via hopping through the conduction-band states of the oxide. Carrier transport is accompanied by strong phonon excitations in this case, imprinting an oscillatory signature on the differential conductance spectra of the system.

Morphogenesis and production of enzymes by Penicillium echinulatum in response to different carbon sources.

The effect of different carbon sources on morphology and cellulase and xylanase production of Penicillium echinulatum was evaluated in this work. Among the six carbon sources studied, cellulose and sugar cane bagasse were the most suitable for the production of filter paper activity, endoglucanases, xylanases, and β-glucosidases. However, sucrose and glucose showed β -glucosidase activities similar to those obtained with the insoluble sources.

Scanning tunneling microscopy and spectroscopy of supported nanostructures.

Recent advances in low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) have provided new opportunities for the investigation of the local geometric, electronic, magnetic, and optical properties of nanostructures. This review focuses on the presentation and discussion of single molecules, supramolecular assemblies, and other nanostructures; all research results obtained in our laboratory. The emphasis is directed to the observation of new effects, where the properties of matter at the nanoscale differ from those at the mesoscopic or macroscopic scale: small is different.

Dynamical Coulomb blockade observed in nanosized electrical contacts.

Electrical contacts between nanoengineered systems are expected to constitute the basic building blocks of future nanoscale electronics. However, the accurate characterization and understanding of electrical contacts at the nanoscale is an experimentally challenging task. Here, we employ low-temperature scanning tunneling spectroscopy to investigate the conductance of individual nanocontacts formed between flat Pb islands and their supporting substrates.

Supramolecular self-assembly driven by electrostatic repulsion: The 1D aggregation of rubrene pentagons on Au111.

At present, organic molecules are among the best candidate "building blocks" for the construction of self-assembling nanoscale devices based on metal substrates. Control of the formation of specific patterns in the submonolayer regime is usually achieved by appropriate choice and/or functionalization of the adsorbates. The effect of this intervention, though, is limited by the typically short-range character of the bonding.

Coverage-dependent self-assembly of rubrene molecules on noble metal surfaces observed by scanning tunneling microscopy.

Coverage-dependent self-assembly of rubrene molecules on different noble metal surfaces, Au(111) and Au(100), Ag(111) and Ag(100), is presented. On Au(111), the homochiral supramolecular assemblies evolve with increasing rubrene coverage from very small structures composed of a few molecules, to honeycomb islets, and to one-dimensional chains of supramolecular pentamers. At higher coverage, the racemic mixture of molecules forms close-packed islands.

[Examples for asbestos-related findings in HRCT - criteria for the assessment of causal relationships in surveillance programmes and medical expert opinion].

The increasing use of high-resolution computed tomography in formerly asbestos-exposed workers requires valid diagnostic criteria for the findings which have to be reported as suspicious for being asbestos-related in surveillance programmes and for the assessment of causal relationships between former asbestos exposure and findings in computed tomography. The present article gives examples for asbestos-related findings in HR-CT and discusses the specificity of parenchymal and pleural changes due to asbestos fibres.

[Recommendations for reporting benign asbestos-related findings in chest X-ray and CT to the accident insurances].

Asbestos-related diseases still play an important role in occupational medicine. The detection of benign asbestos-related diseases is one condition for the compensation of asbestos-related lung cancer in Germany. Due to the increasing use of computed tomography, asbestos-related diseases are more frequently detected in the early stages.

[Digital radiography in chest imaging of occupational and environmental lung diseases].

The classification of pneumoconiosis according to ILO standard - comparing a X-ray of the lung with ILO radiographs - is well established in Germany. The extension of digital imaging is a challenging task in occupational medicine as well as in pneumology. Technical requirements are not known sufficiently and the necessary equipment is not well distributed.

Melting of two-dimensional adatom superlattices stabilized by long-range electronic interactions.

The melting transition of Ce adatom superlattices stabilized by long-range substrate-mediated electronic interactions on Cu(111) and Ag(111) noble metal surfaces has been investigated by low-temperature scanning tunneling microscopy, density functional theory calculations, and kinetic Monte Carlo simulations. Intriguingly, owing to the interaction between Ce adatoms and substrate, these superlattices undergo two-dimensional melting to a liquid without transition through the hexatic phase. The crucial parameters for this direct solid to liquid transition are identified.

Reduction of the superconducting gap of ultrathin Pb islands grown on Si(111).

The energy gap Delta of superconducting Pb islands grown on Si(111) was probed in situ between 5 and 60 monolayers by low-temperature scanning tunneling spectroscopy. Delta was found to decrease from its bulk value as a function of inverse island thickness. Corresponding T_{c} values, estimated using bulk gap-to-T_{c} ratio, are in quantitative agreement with ex situ magnetic susceptibility measurements, however, in strong contrast to previous scanning probe results.

Three-dimensional chirality transfer in rubrene multilayer islands on Au(111).

The growth of rubrene (C(42)H(28), 5,6,11,12-tetraphenylnaphthacene) multilayer islands up to a thickness of six layers on a Au(111) surface has been investigated by scanning tunneling microscopy. The molecules self-organize in parallel twin rows, forming mirror domains of defined local structural chirality. Each layer is composed of twin-row domains of the same structural handedness rotated by 120 degrees with respect to each other.

Plasmon enhanced luminescence from fullerene molecules excited by local electron tunneling.

Tunneling electrons from a scanning tunneling microscope (STM) induce luminescence from C(60) and C(70) molecules forming fullerene nanocrystals grown on ultrathin NaCl films on Au(111). Intramolecular fluorescence and phosphorescence associated with the transitions between the lowest electronic excited state and ground state of C(70) molecules are identified, leading to unambiguous chemical recognition on the nanoscale. Moreover we demonstrate that the molecular luminescence is selectively enhanced by localized surface plasmons in the STM tip-sample gap.

Spectroscopic manifestations of the Kondo effect on single adatoms.

The present topical review focuses on recent advances concerning an intriguing phenomenon in condensed matter physics, the scattering of conduction electrons at the localized spin of a magnetic impurity: the Kondo effect. Spectroscopic signatures of this effect have been observed in the past by high-resolution photoemission which, however, has the drawback of averaging over a typical surface area of 1 mm(2). By combining the atomic-scale spatial resolution of the scanning tunneling microscope (STM) with an energy resolution of a few tens of µeV achievable nowadays in scanning tunneling spectroscopy (STS), and by exposing the magnetic adatom to external magnetic fields, our understanding of the interaction of a single magnetic impurity with the conduction electrons of the nonmagnetic host has been considerably deepened.

Dose-response relationships between occupational exposure to potash, diesel exhaust and nitrogen oxides and lung function: cross-sectional and longitudinal study in two salt mines.

Objective: Several studies have shown that underground salt miners may have an increased incidence of chest symptoms and sometimes decreased lung function. Miners of two salt mines were investigated to evaluate relationships between the lung function and the workplace exposure. The effect of nitrogen monoxide (NO) and nitrogen dioxide (NO(2)) was investigated in view of the recent debate on European occupational exposure limits.