Atomically Precise Prediction of 2D Self‐Assembly of Weakly Bonded Nanostructures: STM Insight into Concentration‐Dependent Architectures

A joint experimental and computational study is reported on the concentration‐dependant self‐assembly of a flat C₃‐symmetric molecule on a graphite surface. As a model system a tripodal molecule, 1,3,5‐tris(pyridin‐3‐ylethynyl)benzene, has been chosen, which can adopt either C_3h or C_s symmetry when planar, as a result of pyridyl rotation along the alkynyl spacers. Density functional theory (DFT) simulations of 2D nanopatterns with different surface coverage reveal that the molecule can generate different types of self‐assembled motifs. The stability of fourteen 2D patterns and the influence of concentration are analyzed. It is found that ordered, densely packed monolayers and 2D porous networks are obtained at high and low concentrations, respectively. A concentration‐dependent scanning tunneling microscopy (STM) investigation of this molecular self‐assembly system at a solution/graphite interface reveals four supramolecular motifs, which are in perfect agreement with those predicted by simulations. Therefore, this DFT method represents a key step forward toward the atomically precise prediction of molecular self‐assembly on surfaces and at interfaces.     

High-pressure investigations of positive ion-molecule reactions in a mixtureof H2S and CH4

The positive ion-molecule reactions in the mixtures of hydrogen sulfide and methane have been examined by means of quadrupole mass spectrometer with the high-pressure ion source. The concentration of hydrogen sulfide in mixtures ranged from 10% to 90% with 10% increment. For each mixture major bimolecular ion-molecule reactions have been identified in the total pressure range from 0.7 to 33.3 Pa. The electron energy for all measurements was fixed at 300 eV and the repeller potential was maintained at 5 V. Relative intensities of ion currents for the observed ions C⁺, CH⁺, CH₂⁺, CH₃⁺, CH₄⁺, CH₅⁺, C₂H₃⁺, C₂H₄⁺, C₂H₅⁺, S⁺, HS⁺, H₂S⁺, H₃S⁺, H₃³⁴S⁺, CHS⁺, CH₃S⁺, S₂⁺, HS₂⁺ and H₂S₂⁺ were determined as a function of total gas pressure inside the ion source collision chamber, repeller potential and concentration of methane in the mixture.     

Characterisation of enzymatically oxidised lignosulfonates and their application on lignocellulosic fabrics

BACKGROUND: The ‘double function’ of laccase, from the ascomycete Myceliophthora, to depolymerise/polymerise lignin was studied in this work. A lignosulfonate (LS) compound was oxidised by enzymatic action and several techniques were applied to measure the polymeric changes obtained. This study was focused on the attachment level of the oxidised LS at the flax surface. RESULTS: Modified solutions were studied in terms of surface charge. Zeta potential values obtained showed an increase of polymerisation after several days of incubation. The change in molecular weight after LS polymerisation was detected using gel permeation chromatography. An increase of 1700 Da was achieved. Fourier transform infrared and UV‐visible spectroscopy techniques were applied and the results showed an increase of the degree of polymerisation. The colour strength of flax fabrics incubated with oxidised LS solutions was also measured and an increase of K/S (K, absorption coefficient; S, scattering coefficient) after enzymatic oxidation was observed. CONCLUSION: The oxidised lignin products obtained show good potential for use in natural surface modification of textile materials containing flavonoids. These findings have important practical implications for lignocellulosic fibre coloration, where new polymers can replace harsh chemicals in the textile industry. Copyright © 2009 Society of Chemical Industry     

A comparative performance study of common and popular task‐centric programming frameworks

Programmers today face a bewildering array of parallel programming models and tools, making it difficult to choose an appropriate one for each application. An increasingly popular programming model supporting structured parallel programming patterns in a portable and composable manner is the task‐centric programming model. In this study, we compare several popular task‐centric programming frameworks, including Cilk Plus, Threading Building Blocks, and various implementations of OpenMP 3.0. We have analyzed their performance on the Barcelona OpenMP Tasking Suite benchmark suite both on a 48‐core AMD Opteron 6172 server and a 64‐core TILEPro64 embedded many‐core processor. Our results show that the OpenMP offers the highest flexibility for programmers, and this flexibility comes to a cost. Frameworks supporting only a specific and more restrictive model, such as Cilk Plus and Threading Building Blocks, are generally more efficient both in terms of performance and energy consumption. However, Intel's implementation of OpenMP tasks performs the best and closest to the specialized run‐time systems. Copyright © 2013 John Wiley & Sons, Ltd.     

Electrical properties of the DGEBA/PANI-Ag composites

The metallopolymer polyaniline-silver (PANI-Ag) was synthesized and used as conductive filler in crosslinked diglycidyl ether of bisphenol A (DGEBA) epoxy network. The hybrid organic/inorganic PANI-Ag powders were successfully synthesized via in situ chemical oxidation of polyaniline-emeraldine base (PANI-EB) by the capped Ag⁺ on the polyaniline-emeraldine base (PANI-EB) surface. The UV–Vis and FT-IR spectra confirmed the pernigraniline structure (PN) of PANI in the hybrid PANI-Ag. The PANI-Ag dispersion in epoxidic matrix was analyzed by optical microscopy (OM). The images analysis from OM showed that the particle agglomerate size of the metallopolymer increased with increasing PANI-Ag concentration in the DGEBA composite, owing to the aggregation effect. The dc conductivity and impedance spectroscopy of the DGEBA/PANI-Ag composite was measured at different PANI-Ag concentrations in the DGEBA network. The electrical dc conductivity of the PANI-Ag was 35.1 S cm⁻¹ and was dependent of the PANI-Ag concentration in DGEBA matrix. The real and imaginary part of impedance complex measurements indicates a strong interfacial polarization at low frequency for both PANI-Ag and DGEBA/PANI-Ag, respectively. The imaginary part of impedance complex Im(Z) data decrease with the PANI-Ag hybrid concentration in the frequencies range of 10²–10⁶ Hz. The dependence of the Im(Z) on the frequency exhibited a relaxation process in both, PANI-Ag and DGEBA/PANI-Ag composite with 10 phr of PANI-Ag powder.     

An Overlooked Hepcidin–Cadmium Connection

Hepcidin (DTHFPICIFCCGCCHRSKCGMCCKT), an iron-regulatory hormone, is a 25-amino-acid peptide with four intramolecular disulfide bonds circulating in blood. Its hormonal activity is indirect and consists of marking ferroportin-1 (an iron exporter) for degradation. Hepcidin biosynthesis involves the N-terminally extended precursors prepro-hepcidin and pro-hepcidin, processed by peptidases to the final 25-peptide form. A sequence-specific formation of disulfide bonds and export of the oxidized peptide to the bloodstream follows. In this study we considered the fact that prior to export, reduced hepcidin may function as an octathiol ligand bearing some resemblance to the N-terminal part of the α-domain of metallothioneins. Consequently, we studied its ability to bind Zn(II) and Cd(II) ions using the original peptide and a model for prohepcidin extended N-terminally with a stretch of five arginine residues (5R-hepcidin). We found that both form equivalent mononuclear complexes with two Zn(II) or Cd(II) ions saturating all eight Cys residues. The average affinity at pH 7.4, determined from pH-metric spectroscopic titrations, is 10^10.1 M⁻¹ for Zn(II) ions; Cd(II) ions bind with affinities of 10^15.2 M⁻¹ and 10^14.1 M⁻¹. Using mass spectrometry and 5R-hepcidin we demonstrated that hepcidin can compete for Cd(II) ions with metallothionein-2, a cellular cadmium target. This study enabled us to conclude that hepcidin binds Zn(II) and Cd(II) sufficiently strongly to participate in zinc physiology and cadmium toxicity under intracellular conditions.     

Kurzschlußvorgänge in mehrfach gespeisten,vermaschten Netzen

Zusammenfassung Die Darstellung des Kurzschlusses erfolgte durch Überlagerung der Spannung am Kurzschlußort mit einer Überlagerungsspannung, die ihrerseits wieder in einheitlicher, für die Zeiten vor und nach dem Kurzschlußeintritt geltender Form durch ein Fourier-Integral dargestellt wurde. Aus diesem Überlagerungsspannungsintegral wurden die Überlagerungsstromintegrale abgeleitet unter Verwendung der Stromgleichungen für die einzelnen Teile der untersuchten Anordnungen bzw. der entsprechenden Ersatzwiderstände, deren Aufbau aus den Ersatzwiderständen der Schaltelemente der Anordnungen in allgemeiner Form behandelt wurde. Die Auswertung der Stromintegrale wurde sodann ebenfalls in allgemeiner Form vorgenommen, wobei ein Näherungsverfahren zu grundsätzlicher Anwendung kam, das eine erhebliche Vereinfachung der Rechnung mit sich brachte, ohne daß praktisch eine Einbuße an Genauigkeit auftrat.Zur Erläuterung der gewonnenen allgemeinen Rechenvorschriften wurden einige typische Beispiele behandelt, deren Ergebnisse als Charakteristikum der beim Kurzschluß in vermaschten, mehrfach gespeisten Netzen auftretenden Ausgleichsvorgängen die Tatsache erkennen lassen, daß der Ausgleichsstrom aus mehreren Wechselstromund Gleichstromgliedern besteht, die verschiedene Zeitkonstanten besitzen und sich auf die einzelnen Teile der Anordnung in verschiedener Weise vcrteilen. Im besonderen ergibt sich, daß die Zahl der Wechselstromglieder gleich der Zahl der nicht mehr zusammenfaßbaren Generatoren, und die Zahl der Gleichstromglieder gleich der Zahl der vom Kurzschlußort ausgehenden Stromwege mit verschiedenem Verhältnis von Selbstinduktion zu ohmschem Widerstand plus der Zahl der nicht mehr zusammenfaßbaren Kapazitäten ist. Ferner zeigt sich, daß sich die Stromglieder nicht notwendigerweise sämtlich addieren müssen, sondern daß sie auch teilweise in Opposition stehen können, so daß an manchen Stellen der Fall eintreten kann, daß der Gesamt-Wechselstromanteil oder -Gleichstromanteil anfänglich nur wenig abnimmt, konstant bleibt oder sogar anschwillt.Bemerkenswert ist ferner das Ergebnis, daß beim zweipoligen Kurzschluß im allgemeinen die gesunde Phase nur am Kurzschlußort frei von Überlagerungsströmen ist, während in den übrigen Teilen der Anordnungen auch in dieser Phase ein Überlagerungsstrom fließt, der jedoch ohne Stoßerscheinung von Null auf seinen Endwert anwächst.Dissertation des Verfassers, T. H. Berlin, Fakultät für Maschinenwesen.     

The Detectability of the Viral RNA in Blood and Cerebrospinal Fluid of Patients with Tick-Borne Encephalitis

Background: The detection rate of viral RNA in tick-borne encephalitis (TBE) is low and variable between studies, and its diagnostic/prognostic potential is not well defined. We attempted to detect RNA of TBE virus (TBEV) in body fluids of TBE patients. Methods: We studied 98 adults and 12 children with TBEV infection, stratified by the disease phase and presentation. EDTA blood and cerebrospinal fluid (CSF) samples were obtained upon hospital admission. RNA was extracted from freshly obtained plasma, concentrated leukocyte-enriched CSF, and whole blood samples, and real time PCR was performed with a Rotor-Gene Q thermocycler. Results: TBEV RNA was detected in (1) plasma of one (of the two studied) adult patients with an abortive infection, (2) plasma of two (of the two studied) adults in the peripheral phase of TBE, and (3) plasma and blood of an adult in the neurologic phase of TBE presenting as meningoencephalomyelitis. No CSF samples were TBEV RNA-positive. Conclusions: The detection of TBEV RNA in blood might be diagnostic in the peripheral phase of TBE. The lack of TBEV RNA in the CSF cellular fraction speaks against TBEV influx into the central nervous system with infiltrating leukocytes and is consistent with a relatively low intrathecal viral burden.