New applications for ultrasonic sensors in process industries

Today, sophisticated instruments and algorithms used for process control allow the efficient production of substances with the quality guaranteed to the customer. However, production and management techniques are changing. This article aims to analyze trends resulting from those changes from the point of view of ultrasonic sensors. The focus will be on plant asset management. One part of plant asset management is maintenance management. Its goal is cost saving by avoiding unexpected shutdowns of single components or the complete plant. However, new maintenance concepts like condition-based or predictive maintenance require reliable methods of condition monitoring. This article will discuss these new applications for ultrasonic sensors. A new ultrasonic measurement based on acoustic emission analyses for condition monitoring of high pressure process pumps is introduced and economic benefits for the user are discussed.     

Costing communication standards in information systems using a minimum cut approach

On a very abstract level, an information system consists of a set of system elements which communicate with each other. Communication is an unproductive operation, so the time needed to communicate data should be kept as short as possible and, to put it in monetary terms, the opportunity costs for communication should be kept small. Now, communicating data is more than just transmitting it; it consists in large parts of converting data structures that are used by one system element into data structures that are used by another system element. Such conversion can be avoided, if the system elements, use a common standard of data structures. Since establishing a standard at a system element incurs standardization costs, a decision-maker has to check, if the cost savings gained by standardized communication outweigh the costs for installing the standard. In a recent paper by Buxmann et al¹, it is claimed that this so-called standardization problem is an NP-hard optimization problem without giving a formal proof for it. We will demonstrate that this claim is not true, but in fact the standardization problem can be solved in polynomial time by solving a minimum cut problem.     

Mode of heavy meromyosin adsorption and motor function correlated with surface hydrophobicity and charge

The in vitro motility assay is valuable for fundamental studies of actomyosin function and has recently been combined with nanostructuring techniques for the development of nanotechnological applications. However, the limited understanding of the interaction mechanisms between myosin motor fragments (heavy meromyosin, HMM) and artificial surfaces hampers the development as well as the interpretation of fundamental studies. Here we elucidate the HMM-surface interaction mechanisms for a range of negatively charged surfaces (silanized glass and SiO2), which is relevant both to nanotechnology and fundamental studies. The results show that the HMM-propelled actin filament sliding speed (after a single injection of HMM, 120 microg/mL) increased with the contact angle of the surfaces (in the range of 20-80 degrees). However, quartz crystal microbalance (QCM) studies suggested a reduction in the adsorption of HMM (with coupled water) under these conditions. This result and actin filament binding data, together with previous measurements of the HMM density (Sundberg, M.; Balaz, M.; Bunk, R.; Rosengren-Holmberg, J. P.; Montelius, L.; Nicholls, I. A.; Omling, P.; T?gerud, S.; M?nsson, A. Langmuir 2006, 22, 7302-7312. Balaz, M.; Sundberg, M.; Persson, M.; Kvassman, J.; M?nsson, A. Biochemistry 2007, 46, 7233-7251), are consistent with (1) an HMM monolayer and (2) different HMM configurations at different contact angles of the surface. More specifically, the QCM and in vitro motility assay data are consistent with a model where the molecules are adsorbed either via their flexible C-terminal tail part (HMMC) or via their positively charged N-terminal motor domain (HMMN) without other surface contact points. Measurements of zeta potentials suggest that an increased contact angle is correlated with a reduced negative charge of the surfaces. As a consequence, the HMMC configuration would be the dominant configuration at high contact angles but would be supplemented with electrostatically adsorbed HMM molecules (HMMN configuration) at low contact angles. This would explain the higher initial HMM adsorption (from probability arguments) under the latter conditions. Furthermore, because the HMMN mode would have no actin binding it would also account for the lower sliding velocity at low contact angles. The results are compared to previous studies of the microtubule-kinesin system and are also discussed in relation to fundamental studies of actomyosin and nanotechnological developments and applications.     

Contact angle measurements by confocal microscopy for non-destructive microscale surface characterization

Contact angle measurements are of great importance in surface characterization but the practical use has often been limited to macroscopic dimensions (millimeters). Therefore, we have developed a confocal microscopy method that allows non-destructive measurements of both low (<30 degrees ) and high (30 degrees -90 degrees ) contact angles. Low contact angles were measured by reconstructing the drop profile from the interference patterns in droplets condensed from atmospheric humidity. At higher contact angles water droplets with a small amount of fluorescein were sprayed onto the surfaces and 3D-image stacks were recorded and used to extract the contact angle. Suitable drop sizes were between a few up to about 50 mum radius, using a 40x magnification objective. Using drops >10 micrometers radius for microcontact angle measurements a good correlation was obtained between measured micro- and macrocontact angles. After microcontact angle measurements the surfaces were rinsed and heavy meromyosin motor fragments were adsorbed to the surface. Importantly, the sensitive actin propelling function of these motor proteins was not affected by the previous contact angle measurements using fluorescent droplets. This suggests that the methodology should be suitable for non-destructive characterization of different parts of micropatterned surfaces being developed for biological assays.     

Analysis for polynuclear aromatic hydrocarbons in working atmospheres by computerized gas chromatography-mass spectrometry

Polynuclear aromatic hydrocarbons in particulate matter from working atmospheres have been analyzed by a glass capillary gas chromatography—mass spectrometer—computer system which has high separation efficiency and is capable of separating and identifying these complex mixtures. More than one hundred polynuclear aromatic hydrocarbons have been identified in samples from a coke plant and an aluminum smelter, including both pure polycyclic aromatic hydrocarbons and compounds where a CH-group is substituted with the hetero atoms oxygen, nitrogen, or sulfur. The occurrence of polynuclear aromatic hydrocarbons in working atmospheres is compared to that in ambient air and emissions from other sources.     

New synthetic approach to 8-allyltheophylline

Summary The synthesis of 8-allyltheophylline (8) from 5,6-diamino-1,3-dimethyluracil (1) and 3-butenoic acid byTraube's methodvia 6-amino-5-(3-butenoylamino)-1,3-dimethyluracil (2) failed because an attempted alkaline cyclization of the intermediate2 afforded (E)-8-(1-propenyl)-theophylline (3) under rearrangement of the terminal C=C bond. Therefore, the cyclodehydratation of 6-(3-butenylamino)-5-nitroso-1,3-dimethyluracil (7), available from 6-chloro-1,3-dimethyluracil (5)via 6-(3-butenylamino) derivative6 has to be used for obtaining the required product8.

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Ein neuer synthetischer Zugang zu 8-Allyltheophyllin

Zusammenfassung 8-Allyltheophyllin (8) kann nicht mittels derTraube-Synthese aus 5,6-Diamino-1,3-dimethyluracil und 3-Butensäurevia 6-Amino-5-(3-butenoylamino)-1,3-dimethyluracil (2) hergestellt werden, wei bei der alkalischen Cyclisierung des Zwischenproduktes2 Umlagerung der terminalen C=C-Doppelbindung unter Bildung von (E)-8-(1-Propenyl)theophyllin (3) erfolgt. Zur Darstellung der Verbindung8 muss man daher die Dehydratationscyclisierung von 6-(3-Butenylamino)-5-nitroso-1,3-dimethyluracil (7) anwenden. Letzteres ist aus 6-Chloro-1,3-dimethyluracil über das 6-(3-Butenylamino)-Derivat6 zugänglich.

     

Fluorescence decay time of single semiconductor nanocrystals

We present fluorescence decay measurements of single ZnS covered CdSe nanocrystals. It is shown that the fluorescence decay time is fluctuating during the investigation leading to a multiexponential decay even for a single nanocrystal. In combination with measurements of the fluorescence blinking behavior we find that a high fluorescence intensity is correlated with a long fluorescence decay time. This is consistent with a model of fluctuating nonradiative decay channels leading to variable dynamic quenching processes of the excited state.     

Proton ordering in cubic ice and hexagonal ice; a potential new ice phase--XIc

Ordinary water ice forms under ambient conditions and has two polytypes, hexagonal ice (Ih) and cubic ice (Ic). From a careful comparison of proton ordering arrangements in Ih and Ic using periodic density functional theory (DFT) and diffusion Monte Carlo (DMC) approaches, we find that the most stable arrangement of water molecules in cubic ice is isoenergetic with that of the proton ordered form of hexagonal ice (known as ice XI). We denote this potential new polytype of ice XI as XIc and discuss a possible route for preparing ice XIc.     

Diffusion dynamics of motor-driven transport: gradient production and self-organization of surfaces

The interaction between cytoskeletal filaments (e.g., actin filaments) and molecular motors (e.g., myosin) is the basis for many aspects of cell motility and organization of the cell interior. In the in vitro motility assay (IVMA), cytoskeletal filaments are observed while being propelled by molecular motors adsorbed to artificial surfaces (e.g., in studies of motor function). Here we integrate ideas that cytoskeletal filaments may be used as nanoscale templates in nanopatterning with a novel approach for the production of surface gradients of biomolecules and nanoscale topographical features. The production of such gradients is challenging but of increasing interest (e.g., in cell biology). First, we show that myosin-induced actin filament sliding in the IVMA can be approximately described as persistent random motion with a diffusion coefficient (D) given by a relationship analogous to the Einstein equation (D = kT/gamma). In this relationship, the thermal energy (kT) and the drag coefficient (gamma) are substituted by a parameter related to the free-energy transduction by actomyosin and the actomyosin dissociation rate constant, respectively. We then demonstrate how the persistent random motion of actin filaments can be exploited in conceptually novel methods for the production of actin filament density gradients of predictable shapes. Because of regularly spaced binding sites (e.g., lysines and cysteines) the actin filaments act as suitable nanoscale scaffolds for other biomolecules (tested for fibronectin) or nanoparticles. This forms the basis for secondary chemical and topographical gradients with implications for cell biological studies and biosensing.