Microfluidics structures for probing the dynamic behaviour of filamentous fungi

Although filamentous fungi live in physically and chemically complex natural environments that require optimal survival strategies, both at colony and individual cell level, their growth dynamics are usually studied on homogenous media. This study proposes a new research methodology based on the purposeful design, fabrication and operation of microfluidics structures to examine the temporal and spatial responses of filamentous fungi. Two model fungal strains, the wild type of Neurospora crassa – a commonly used model organisms – and the ro-1 mutant strain of this species impaired in hyphal growth and morphology, have been chosen to demonstrate the potential of this new methodology. Time-lapse observations of both species show that filamentous fungi respond rapidly to the physically microstructured environment without any detectable temporal or spatial adjustment period. Despite their genetic differences, and consequently different growth behaviour, both strains present efficient space-search strategies enabling them to solve the microsized networks successfully and in similar periods, thus demonstrating that the space-searching algorithms are robust and mutation-independent. Additionally, the use of the proposed methodology could put in evidence new biological mechanisms responsible for the apical extension of filamentous fungi, beyond the classical theory based on the central role of Spitzenkörper.     

Identifikation NSO-heterocyclischer Prioritärsubstanzen zur Erkundung und Überwachung Teeröl-kontaminierter Standorte

The German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV) requires the monitoring of NSO-heterocyclic hydrocarbons without specifying the extent of such analysis. An assessment procedure for the identification of NSO-heterocyclic priority substances was thus created within the “KORA” project (“Natural Attenuation: Retention and Degradation Processes Reducing Contaminations in Groundwater and Soil”) funded by the German Federal Ministry of Education and Research (BMBF). This assessment includes physicochemical properties, biodegradability, toxicity, and groundwater propagation of these substances at creosote-contaminated sites. In addition to unsubstituted compounds, the derived list of 20 priority NSO-heterocycles also contains substituted derivatives as well as relevant transformation products.     

Polymerization in magnetic field: XVIII. Influence of surfactant nature on the synthesis and thermal properties of poly(methyl methacrylate) and poly[(methyl methacrylate)‐co‐(epoxypropyl methacrylate)]

BACKGROUND: The possibility to use β‐cyclodextrin as biodegradable tensioactive and an electromagnetic field in order to improve the kinetic parameters of radical emulsion polymerization is of interest. Thus, the influence of different surfactants—sodium lauryl sulfate (SLS) and β‐cyclodextrin (CD)—on the pathway of emulsion polymerization of methyl methacrylate (MMA) and emulsion copolymerization of MMA with 2,3‐epoxypropyl methacrylate (GMA) performed with or without the presence of a continuous electromagnetic field (MF) was studied. RESULTS: The presence of the MF leads to a considerable increase of the conversion during the first part of the reaction if the classic surfactant (SLS) is used. The reactions performed without MF and with CD exhibit a decrease of the conversion and of the polymerization rate as compared with the variants using SLS. The swelling rate and the maximum degree of swelling vary with the surfactant nature and with the reaction conditions and MF presence. Data from thermogravimetry and differential scanning calorimetry evidence the dependences between the polymer characteristics and the preparation conditions. CONCLUSION: This research underlines the coupling possibilities of the influence of a MF—growth of the reaction rate and conversion explained through radical pairs mechanism—with a combination of the ‘cage’ effect and ‘conformational control’ afforded by CD. The presence of MF and CD during the syntheses leads to an increase of T_g and an increase of PMMA and P(MMA‐co‐GMA) thermal stability. Copyright © 2007 Society of Chemical Industry     

Optimization Problems Related to Zigzag Pocket Machining

A fundamental problem of manufacturing is to produce mechanical parts from billets by clearing areas within specified boundaries from the material. Based on a graph-theoretical formulation, the algorithmic handling of one particular machining problem—``zigzag pocket machining'—is investigated. We present a linear-time algorithm that ensures that every region of the pocket is machined exactly once, while attempting to minimize the number of tool retractions required. This problem is shown to be -hard for pockets with holes. Our algorithm is provably good in the sense that the machining path generated for a pocket with h holes requires at most 5 . . . OPT + 6 . . . h retractions, where OPT is the (unknown) minimum number of retractions required by any algorithm. The algorithm has been implemented, and practical tests for pockets without holes suggest that one can expect an approximation factor of about 1.5 for practical examples, rather than the factor 5 as proved by our analysis. Received July 3, 1997; revised September 7, 1997.     

External Calibration of SIR-B Imagery with Area-Extended and Point Targets

Data takes on two ascending orbits of the Shuttle Imaging Radar-B (SIR-B) over an agricultural test site in west-central Illinois were used to establish end-to-end transfer functions for conversion of the digital numbers on the 8-bit image to values of the radar backscattering coefficient ?0 (m2/m2) in dB. The transfer function for each data take was defined by the SIR-B response to an array of six calibrated point targets of known radar cross section (transponders) and to a large number of area-extended targets also with known radar cross section as measured by externally calibrated, truck-mounted scatterometers. The radar cross section of each transponder at the SIR-B center frequency was measured on an antenna range as a function of the local angle of incidence. Two truck-mounted scatterometers observed 20-80 agricultural fields daily at 1.6 GHz with HH-polarization and at azimuth viewing angles and incidence angles equivalent to those of the SIR-B. The form of the transfer function is completely defined by the SIR-B receiver and the incoherent averaging procedure incorporated into production of the standard SIR-B image product. Assuming that the processing properly accounts for the antenna gain, all transfer function coefficients are known except for the thermal noise power and a system " constant" that has been shown to vary as a function of uncommanded changes in the effective SIR-B transmit power.