Recognition and analysis of local structure in polycrystalline configurations

A method is described for obtaining information about the local order existing in monoatomic model solids or real materials based on their atomistic configurations. An efficient algorithmic implementation is provided. The shape of the polyhedra formed by ‘relevant’ neighbors of each atom enter a pattern recognition method to resolve the type of the (usually non-ideal) crystal structure to which atoms surrounded by their relevant neighbors belong: hexagonal close-packed, face-centered cubic or body-centered cubic. Further, this approach allows for the analysis of icosahedral structure which preferably occurs in amorphous solids. Results of a molecular dynamics computer simulation illustrate how this method can be applied to contribute to an understanding of the mechanical and structural properties of solids (i) undergoing a steady shear stress and (ii) upon increasing temperature.     

Serum response of Escherichia coli strains causing dyspepsia and urinary tract infection: relation to alpha-hemolysin production and O type

A total of 109 alpha-hemolytic and 104 nonhemolytic Escherichia coli isolates from children with dyspepsia and urinary tract infections were investigated for resistance to the bactericidal activity of human serum. A significantly higher proportion of serum resistance was found in alpha-hemolytic E. coli isolates than in nonhemolytic isolates (P < 0.01). An association between the titer of alpha-hemolysin produced and serum resistance was found.     

VOC Emissions after Building Renovations: Traditional and Less Common Indoor Air Contaminants,Potential Sources,and Reported Health Complaints

Abstract Volatile organic compounds (VOCs) were measured in the air of 51 renovated rooms in Schleswig-Holstein. The buildings examined were of different types – private flats, schools, kindergartens, office buildings – the only common characteristic being that they had all been renovated within the last two years. Among the dominating substances in the 46/51 complaint cases were well-known substances such as alkylbenzenes or monoterpenes at high concentrations but also less common substances, i.e. those which have only recently been reported as indoor air contaminants, for example phenoxyethanol, 2-(2-butoxyethoxy)-ethylacetate (butyldiglycolacetate) or longifolene (Mohr, 1994) at remarkable concentrations. A tentative investigation was made to identify the simultaneous occurrences of the different substances, especially the uncommon ones with their potential sources, as well as health impairments. Finally, VOC emissions from two carpet glues, suspected during the investigations of playing a role as a potential source of the less common substances, were carefully measured under test chamber conditions. This additional laboratory experiment was made to verify the tendency shown in the field study that modern ecological building materials contain less volatile and less common substances but with increased indoor persistence, that could partially account for the increasing number of complaints in relation to the SBS phenomenon.     

Detection of infrequent and multiple K-ras mutations in human tumors and tumor-adjacent tissues

A sensitive method was developed and applied to examine the distribution of K-ras gene mutations in histologically differing areas of lung tissues obtained from lung cancer patients. This method, which combines polymerase chain reaction (PCR), mutation allele enrichment (MAE), and denaturing gradient gel electrophoresis (DGGE), allows detection of one K-ras mutant allele present in 10(4) to 10(5) wild-type alleles. It was applied to analyze mutations in codon 12 of the K-ras gene in 43 tissue sites microdissected from paraffin-embedded sections obtained from 8 archival cases of lung cancer, all previously shown to have codon 12 K-ras mutations by direct sequencing. In four cases, mutations were detected only in the tumor, while in the other four cases, the same mutations were also found in tissues adjacent to tumors, using the MAE + DGGE method. No mutations were detected among normal-appearing cells in areas distant from the tumors in any of the cases studied. These findings demonstrate that K-ras mutations can be detected at low frequencies in normal-appearing cells from tissues adjacent to the tumor in some lung cancer cases. In addition, this approach also allowed detection of multiple mutations in colorectal tissues obtained from colorectal cancer patients. Thus, the MAE + DGGE method may be applicable to study of K-ras mutations in premalignant or morphologically suspicious lesions in bronchial mucosa or other types of human cancer.     

25th Anniversary Article: A Soft Future: From Robots and Sensor Skin to Energy Harvesters

Scientists are exploring elastic and soft forms of robots, electronic skin and energy harvesters, dreaming to mimic nature and to enable novel applications in wide fields, from consumer and mobile appliances to biomedical systems, sports and healthcare. All conceivable classes of materials with a wide range of mechanical, physical and chemical properties are employed, from liquids and gels to organic and inorganic solids. Functionalities never seen before are achieved. In this review we discuss soft robots which allow actuation with several degrees of freedom. We show that different actuation mechanisms lead to similar actuators, capable of complex and smooth movements in 3d space. We introduce latest research examples in sensor skin development and discuss ultraflexible electronic circuits, light emitting diodes and solar cells as examples. Additional functionalities of sensor skin, such as visual sensors inspired by animal eyes, camouflage, self‐cleaning and healing and on‐skin energy storage and generation are briefly reviewed. Finally, we discuss a paradigm change in energy harvesting, away from hard energy generators to soft ones based on dielectric elastomers. Such systems are shown to work with high energy of conversion, making them potentially interesting for harvesting mechanical energy from human gait, winds and ocean waves.     

Floc-based sequential partial nitritation and anammox at full scale with contrasting N2O emissions

New Activated Sludge (NAS^®) is a hybrid, floc-based nitrogen removal process without carbon addition, based on the control of sludge retention times (SRT) and dissolved oxygen (DO) levels. The aim of this study was to examine the performance of a retrofitted four-stage NAS^® plant, including on-line measurements of greenhouse gas emissions (N₂O and CH₄). The plant treated anaerobically digested industrial wastewater, containing 264 mg N L⁻¹, 1154 mg chemical oxygen demand (COD) L⁻¹ and an inorganic carbon alkalinity of 34 meq L⁻¹. The batch-fed partial nitritation step received an overall nitrogen loading rate of 0.18-0.22 kg N m⁻³ d⁻¹, thereby oxidized nitrogen to nitrite (45-47%) and some nitrate (13-15%), but also to N₂O (5.1-6.6%). This was achieved at a SRT of 1.7 d and DO around 1.0 mg O₂ L⁻¹. Subsequently, anammox, denitrification and nitrification compartments were followed by a final settler, at an overall SRT of 46 d. None of the latter three reactors emitted N₂O. In the anammox step, 0.26 kg N m⁻³ d⁻¹ was removed, with an estimated contribution of 71% by the genus Kuenenia, which constituted 3.1% of the biomass. Overall, a nitrogen removal efficiency of 95% was obtained, yielding a dischargeable effluent. Retrofitting floc-based nitrification/denitrification with carbon addition to NAS^® allowed to save 40% of the operational wastewater treatment costs. Yet, a decrease of the N₂O emissions by about 50% is necessary in order to obtain a CO₂ neutral footprint. The impact of emitted CH₄ was 20 times lower.