Doping Molecular Monolayers: Effects on Electrical Transport Through Alkyl Chains on Silicon

n‐Si/C_nH_{2n + 1}/Hg junctions (n = 12, 14, 16 and 18) can be prepared with sufficient quality to assure that the transport characteristics are not anymore dominated by defects in the molecular monolayers. With such organic monolayers we can, using electron, UV and X‐ray irradiation, alter the charge transport through the molecular junctions on n‐ as well as on p‐type Si. Remarkably, the quality of the self‐assembled molecular monolayers following irradiation remains sufficiently high to provide the same very good protection of Si from oxidation in ambient atmosphere as provided by the pristine films. Combining spectroscopic (UV photoemission spectroscopy (UPS), X‐ray photoelectron spectroscopy (XPS), Auger, near edge‐X‐ray absorption fine structure (NEXAFS)) and electrical transport measurements, we show that irradiation induces defects in the alkyl films, most likely C?C bonds and C? C crosslinks, and that the density of defects can be controlled by irradiation dose. These altered intra‐ and intermolecular bonds introduce new electronic states in the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of the alkyl chains and, in the process, dope the organic film. We demonstrate an enhancement of 1–2 orders of magnitude in current. This change is clearly distinguishable from the previous observed difference between transport through high quality and defective monolayers. A detailed analysis of the electrical transport at different temperatures shows that the dopants modify the transport mechanism from tunnelling to hopping. This study suggests a way to extend significantly the use of monolayers in molecular electronics.     

Standpunkte, Praktiken und Kenntnisstand zur Ferkelkastration in Europa (PIGCAS) – Projektziele und erste Ergebnisse

Most of the male piglets in the EU are castrated. According to the current EU legislation, surgical castration can be performed without anaesthesia up to the age of 7 days. A report of the European Food Safety Authority (EFSA) on the welfare aspects in relation to the castration of pigs has underlined the need for further research. As a follow up, the EU has launched a two-year project (Specific Support Action PIGCAS) within the 6^th EU Framework Programme, starting in January 2007. “PIGCAS” is the acronym for “Attitudes, practices and state of the art regarding piglet castration in Europe”. The main objectives are: [A] to collect information on the attitudes of the various stakeholders (consumer groups, NGOs and industry stakeholders); [B] to collect information on the extent of the practice of castration of piglets (male or female) within the EU and the conditions under which castration is performed; [C] to evaluate research work and other sources of information, in order to examine surgical castration without anaesthesia and its possible alternatives from different perspectives and derive research priorities; and [D] to integrate the collected information and evaluation in a report providing support for EU policy in the field of research and legislation. Preliminary results are now available on objectives [A] and [B]. When referring to the alternatives to surgical castration, one has to distinguish between short-term and long-term solutions. Surgical castration with anaesthesia was mentioned by most of the stakeholders as a short-term alternative. Genetic control of boar taint and sperm sexing to select only females for pork production are considered as long-term alternatives. Current practices of castration and levels of acceptability vary substantially between and within countries and regions. The current research focuses on practical methods for acute and postoperative pain alleviation and analyses the complex consequences of raising entire males or immunocastrated boars. Considering the different dimensions (attitudes, extent of practice, animal welfare, pork quality and economy) of importance, it is intended to propose to the EU short and long-term strategies to handle this problem.

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Eingegangen: 26. Februar 2008; angenommen: 29. Februar 2008     

Deliqueszenz und Effloreszenz hygroskopischer Salzpartikeln in Partikel‐Wand‐ und Partikel‐Partikel‐Kontakten

In case of dust separation with surface filters, adhesive bonds at particle‐wall and particle‐particle contacts are of great importance. The deliquescence and efflorescence of hygroscopic salt particles can significantly influence the adhesive bonds at particle contacts with such salt particles. Therefore, to investigate these phenomena, various types of particle contacts were produced by the separation of aerosols on filtering collectors and subsequently observed in the chamber of an environmental SEM during the moisture‐induced deliquescence and efflorescence.     

Lebenszyklusbetrachtungen als Grundlage für die Nachhaltigkeitsbewertung von Straßenbrücken

Lebenszyklusbetrachtungen spielen bei der Bewertung der Nachhaltigkeit von Bauwerken eine besondere Rolle. Sie fokussieren nicht nur auf die einmaligen Umweltwirkungen und die Investitionskosten bei der Herstellung von Bauwerken, sondern ermöglichen die ganzheitliche Beurteilung der fortlaufend anfallenden ökologischen und ökonomischen Wirkungen. Mit der Untersuchung von zwei Autobahnbrücken und zwei Überführungsbauwerken wird das Ziel verfolgt, einen einheitlichen Durchschnittswert für die ökologischen und die ökonomischen Wirkungen von Brückenbauwerken zu definieren. Der Beitrag befasst sich mit der Festlegung derartiger Referenzwerte und stellt erste Lösungsansätze zur Berücksichtigung des Recyclingpotentials von Materialien vor. Life cycle considerations as a base for assessment of the sustainability of road bridges. Life cycle considerations are important for the assessment of the sustainability of constructions. Taking the life cycle into account it is not only possible to determine single environmental impacts and investment costs arising during the construction of buildings, but also to assess the consecutive ecological and economical impacts. The aim of this study was to define a consistent average value for ecological as well as economical impacts of road bridges by evaluating two viaducts and two overcrossings. This article deals with the determination of those reference values and presents an approach how to deal with the recycling potential of materials within the life cycle assessment.     

Opportunities,Challenges and Pitfalls of Using Cannabidiol as an Adjuvant Drug in COVID-19 †

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection may lead to coronavirus disease 2019 (COVID-19) which, in turn, may be associated with multiple organ dysfunction. In this review, we present advantages and disadvantages of cannabidiol (CBD), a non-intoxicating phytocannabinoid from the cannabis plant, as a potential agent for the treatment of COVID-19. CBD has been shown to downregulate proteins responsible for viral entry and to inhibit SARS-CoV-2 replication. Preclinical studies have demonstrated its effectiveness against diseases of the respiratory system as well as its cardioprotective, nephroprotective, hepatoprotective, neuroprotective and anti-convulsant properties, that is, effects that may be beneficial for COVID-19. Only the latter two properties have been demonstrated in clinical studies, which also revealed anxiolytic and antinociceptive effects of CBD (given alone or together with Δ⁹-tetrahydrocannabinol), which may be important for an adjuvant treatment to improve the quality of life in patients with COVID-19 and to limit post-traumatic stress symptoms. However, one should be aware of side effects of CBD (which are rarely serious), drug interactions (also extending to drugs acting against COVID-19) and the proper route of its administration (vaping may be dangerous). Clearly, further clinical studies are necessary to prove the suitability of CBD for the treatment of COVID-19.     

Tribological research on the development of White Etching Cracks (WECs)

The aim of the presented research activities was to identify mechanical, thermal, and chemical factors possibly linked to the formation of WECs (White Etching Cracks). By means of a systematic variation of various influencing parameters, the significance of each of those was investigated. It is hoped that, once the parameters promoting WECs have been identified, the physical and chemical mechanisms responsible for WEC can be thoroughly understood in the near future. This would allow to prevent costly premature bearing failures, e.?g. given in wind turbines.Four research centers in Kaiserslautern, Münster and Hannover (Institute of Machine Elements, Gears and Transmissions (MEGT), Technische Universität Kaiserslautern, Materials Testing Group (AWP), Technische Universität Kaiserslautern, Institute of Physics, Westfälische Wilhelms-Universität Münster, and Institute for Machine Design and Tribology (IMKT), Leibniz University Hannover) provide their expertise and laboratory facilities for this purpose.At IMKT full bearing investigations with cylindrical roller thrust bearings and model tests with a special ring-roller-ring tribometer were performed under varied test conditions. In a theoretical work package, the stresses induced to the bearing surface were simulated.At “Physikalisches Institut” in Münster surfaces of the bearing washers (and rolling elements) were analysed applying Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) to determine the actual respective chemical composition of the tribofilms.At MEGT component tests were carried out on a three-axis dynamic test rig with radially loaded cylindrical roller bearings. The internal bearing dynamics and, above all, the associated distribution of frictional energy were analysed by means of multi-body simulation.The AWP concentrated on synthesized multi-axial dynamic stresses aimed at mirroring the stresses in a rolling contact apllied on laboratory test specimens to investigate crack initiation and growth in depth.     

Die diskontinuierliche Zentrifuge als Betriebssystem in der Chemischen Industrie

Discontinuous centrifuges as operating systems in the chemical industry . Centrifuges are machines with rotors as working spaces in which the relative concentrations in mixtures of substances can be modified. Batch operating centrifuges are particularly suitable for this purpose when high demand on quality are made with regard to separation and purity of the substances separated or when the material parameters are subject to variation. The construction permits optimum adaptation to all operating parameters. The structural components for basic and additional functions have achieved a high standard of technical maturity and some have be specified in proven DIN standards. Centrifuges are particularly suitable for use as components of combined mechanical-thermal demoisturing plants. The technology of the drive systems of centrifuges and the control systems for conducting the process and for safety purposes utilize advanced hydraulics, pneumatics and electronics. Numerous materials of construction are available, including highly corrosion-resistant metals and alloys and those bearing a corrosion-resistant protective layer. The choice and utilization of a particular structural form are determined by the specific operational behaviour on filling, washing of the filter cake residual moisture content attainable, output of solids, demoisturizing capacity, industrial hygiene aspects of sealing during demoisturization and on output, optimum arrangement of the centrifuge in the overall plant, as well as costs of acquisition, installation and operation. Safety features are of particular importance in view of the large amount of energy stored and the possibility of operating with flammable liquids. On the basis of systematic analyses of the sources of danger, constructive measures and systems have been developed for the avoidance of explosion and fire which ensure safe operation of centrifuges.     

Flow-Sheeting-Programme für die Prozeßsimulation

Flowsheeting systems for process simulation. Simulation of process plants with flowsheeting systems has been state of the art in chemical plant design and in the chemical industry for many years. Modern computers now permit steady state simulation of complex chemical plants with sufficient accuracy. This paper outlines the different approaches to steady state process simulation, names the advantages and disadvantages, and gives an outlook on further developments. Process optimization, process integration, and process synthesis will be discussed. The integration of different programs, e.g. the connection between flowsheeting systems and computer-aided design (CAD) will be described. An advance in user friendliness will be reached by latest developments in the field of personal computers and workstations and by database management systems.     

Sensortechnik in der Chemie – Status und Trend

Sensor technology in the chemical process industries – status and trends . Sensor technology is used in chemical process industries to provide information on product and process properties. The computerized handling of this information has altered the requirements for sensor systems. New production methods and the automation of existing processes lead to new tasks for sensor systems. The advancement of sensor technology is proceeding on a broad front and in small steps, also exploiting the potential of microelectronics. Model-based measuring methods utilizing a priori knowledge about the process may substantially increase the information gain.