No abstract

The rational design of nano- and micrometer-sized particles with tailor-made optical properties for biological, diagnostic, and photonic applications requires tools to characterize the signal-relevant properties of these typically scattering bead suspensions. This includes methods for the preferably nondestructive quantification of the number of fluorophores per particle and the measurement of absolute fluorescence quantum yields and absorption coefficients of suspensions of fluorescent beads for material performance optimization and comparison. Here, as a first proof-of-concept, we present the first time determination of the number of dye molecules per bead using nondestructive quantitative ((19)F) NMR spectroscopy and 1000 nm-sized carboxylated polystyrene particles loaded with varying concentrations of the laser dye coumarin 153 containing a CF(3) group. Additionally, the signal-relevant optical properties of these dye-loaded particles were determined in aqueous suspension in comparison to the free dye in solvents of different polarity with a custom-built integrating sphere setup that enables spectrally resolved measurements of emission, transmission, and reflectance as well absolute fluorescence quantum yields. These measurements present an important step toward absolute brightness values and quantitative fluorescence analysis with particle systems that can be exploited, for example, for optical imaging techniques and different fluorescence assays as well as for the metrological traceability of fluorescence methods.

Nutritional and physical factors which influence the germination of akinetes of Nodularia spumigena (Cyanobacteriaceae) were examined. Low concentrations of phosphorus (<0.9 ,M) were required for germination. Nitrate had no effect, but ammonia, at concentrations of >45 ,uM, inhibited germination. Salinities of >209o were inhibitory to germination. Optimum temperatures were 22°C or greater. Germination did not take place in the dark, but only very low light intensities (0.5 microeinstein m-2 s-') were necessary to initiate germination. Red light (620 to 665 nm) was required. More than 24 h of continuous exposure to light was necessary for any significant germination to occur. The conditions for germination corresponded with conditions in the Peel-Harvey Estuary, Western Australia, 2 to 3 weeks before large summer Nodularia blooms.

Variations in nitrogen fixation (acetylene reduction) by Nodularia spumigena blooms in the Peel-Harvey estuarine system were examined with respect to spatial (sampling station location, and depth) and temporal (seasonal and diurnal) distribution. The annual contributions of nitrogen fixation by the blooms to the nitrogen budget of the estuary were estimated to range from 309 to 713t. Contributions by nitrogen fixation were similar to the riverine inputs in the Harvey Estuary, but lower in the Peel Inlet.The Harvey Estuary had higher biomass and total fixation rates (to 0.4 nmol C2H2 *ml-l -h-l), but the heterocyst nitrogen fixation rates were greater in the Peel Inlet (to 9x 10e4 nmol CzHz. heterocyst-l *h-l). Nitrogen fixation decreased with depth in response to light, though other factors also appeared to be involved. The rates of fixation decreased concurrently with increasing bloom age, total soluble inorganic nitrogen and salinities. Maximum daily fixation rates occurred in the early morning.

The synthesis, characterization, self-assembly, and gel formation of poly(γ-benzyl-l-glutamate) (PBLG) in a molecular weight range from ca. 7,000–100,000 g/mol and with narrow molecular weight distribution are described. The PBLG is synthesized by the nickel-mediated ring-opening polymerization and is characterized by size-exclusion chromatography coupled with multiple-angle laser light scattering, NMR, and Fourier transform infrared spectroscopy. The self-assembly and thermoreversible gel formation in the helicogenic solvent toluene is investigated by transmission electron microscopy, atomic force microscopy, small-angle X-ray scattering, and synchrotron powder X-ray diffraction. At concentrations significantly below the minimum gelation concentration, spherical aggregates are observed. At higher concentrations, gels are formed, which show a 3D network structure composed of nanofibers. The proposed self-assembly mechanism is based on a distorted hexagonal packing of PBLG helices parallel to the axis of the nanofiber. The gel network forms due to branching and rejoining of bundles of PBLG nanofibers. The network exhibits uniform domains with a length of 200 ± 42 nm composed of densely packed PBLG helices.Electronic supplementary materialThe online version of this article (doi:10.1007/s00396-012-2866-9) contains supplementary material, which is available to authorized users.

Windrow composting represents an effective method to reduce the environmental burden of Cl. difficile associated with biosolids.

Our data emphasize the need for standardized criteria, including elastic stains, to reliably detect vascular invasion in CRC. Doing so, however, the prognostic impact of venous invasion in stage I and II CRC may be lower as previously anticipated.

Right colon diverticulitis, representing 1-3.6% of cases of diverticular disease is an uncommon cause of right lower quadrant pain. Its presentation is difficult to distinguish from acute appendicitis. Patients are between 35 and 50 years old, have a history of 2-3 days of abdominal pain and few gastrointestinal symptoms. The diagnosis is best confirmed by computed tomography and colonoscopy. Conservative treatment is justified in uncomplicated disease, whereas perforations, abcesses and inflammatory tumors require resection. We describe the cases of six patients treated at our institution from 1991 to 1996. Presentation, geographic variations, diagnostic procedures and management are discussed.