Backscattered intensity from model atmospheric ice crystals in the millimeter-wave range

The effectiveness of modeling atmospheric ice crystals of varying aspect ratios as clusters of spheres is investigated by calculation of the backscattered intensity in the millimeter-wave range by the transition matrix approach. Both single crystals and dispersions with a few choices of the orientational distribution are considered. Our calculations reproduce the features of the backscattered intensity that are due to the overall symmetry of the crystals and yield results in agreement with analogous calculations performed by other authors within the framework of the discrete dipole approximation.     

Zeolitization of pumice in ash-sodium salt solutions

Lipari pumice has selectively been transformed into zeolites in $\text{NaOH}\text{NaCl}$ media. The influence of NaOH concentration and residence time on the degree of zeolitization are discussed.     

Optical properties of a dispersion of randomly oriented identical aggregates of spheres deposited on a plane surface

Our previous theory for calculating the scattering pattern from a single aggregate of spheres deposited on a dielectric substrate is extended to deal with a dispersion of identical aggregates onto the substrate with a random distribution of their orientations. To this end the definition of the transition matrix of an aggregate is generalized to take account of the presence of the substrate; then the transformation properties under rotation of the newly defined transition matrix are used to perform analytically the required orientational averages. When the patterns calculated with this theory are compared with the calculations for a single aggregate, it can easily be seen that the features that reveal the anisotropy of the scatterers are not canceled by the averaging procedure.     

Resonance suppression in the extinction spectrum of single and aggregated hemispheres on a reflecting surface

The extinction spectrum from single and aggregated hemispheres whose flat faces lie on a reflecting surface is calculated, and some of the expected resonances are found to disappear for specific choices of the direction and the polarization of the incident wave. This resonance-suppressing effect is fully explained for the case of single hemispheres, whereas for the case of aggregated hemispheres the guidelines for its explanation are given.     

Body mass and growth of overwintering brown trout in relation to stream habitat complexity

In winter, juvenile salmonids hide within the substrate during the day and emerge to feed on drifting invertebrates at night. In channelized streams, where the streambed heterogeneity has been artificially reduced, suitable microhabitats (low‐flow refugia) may be in short supply. Therefore, restoration of stream habitat by enhancement structures might improve the overwintering conditions of juvenile salmonids. We used a set of artificial streams to test whether individually‐marked juvenile brown trout of two age‐classes (age‐0 and age‐1 trout) loose mass during the winter differently in channelized and semi‐natural streams. Fish of both age‐classes lost mass early in the winter (November to January), but age‐0 fish in the channelized streams lost more of their initial mass than did the restored‐stream fish (ca. 10% vs. 2.5% on average, respectively). They then exhibited zero‐growth in both treatments in late winter (January to April), and by early spring (May), the channelized‐stream fish had completely caught up for their greater initial mass loss. In control tanks where the fish were fed continuously, age‐0 trout exhibited zero‐growth from November to January, then gaining mass constantly through the rest of the experiment. Significant time*treatment interaction was also detected for age‐1 trout, but all differences were caused by the faster growth of fish in the control tanks, whereas the two channel treatments did not differ significantly. The shortage of suitable sheltering sites in the channelized streams apparently intensified competition and caused greater initial mass loss in age‐0 trout. Furthermore, growth compensation exhibited by juvenile trout may have negative impacts on the long‐term fitness of individuals. Therefore, by increasing the amount of sheltering sites, in‐stream restoration may have potential to enhance the overwintering success of juvenile salmonids. Copyright © 2010 John Wiley & Sons, Ltd.     

A new methodology in the study of PVAc‐based adhesive formulations

The role of the main components of a PVAc‐based wood adhesive formulation in the formation and performance of the adhesive joint was investigated. A new analytical methodology was applied to carry out the chemical separation and characterization of the adhesive components present in the bond line. By using extraction techniques on the wet and dry glues it was possible to observe the variation in the solubility of the adhesive components, for different glue formulations. The swollen‐state NMR technique proved to be a very useful tool to characterize the insoluble parts present in the adhesive films. These findings, when put into relation to some specific properties of the adhesive joints, contribute to the understanding of the mechanisms involved in the adhesion process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Real-time polymerase chain reaction-based identification of bacteria in milk samples from bovine clinical mastitis with no growth in conventional culturing

In more than 30% of milk samples from clinical and subclinical bovine mastitis, bacteria fail to grow even after 48 h of conventional culture. The “no-growth” samples are problematic for mastitis laboratories, veterinarians, and dairy producers. This study provides the first investigation of the bacteriological etiology of such samples, using a real-time PCR-based commercial reagent kit. The assay targets the DNA of the 11 most common bacterial species or groups in mastitis and the staphylococcal blaZ gene (responsible for penicillin resistance) and can identify and quantify bacterial cells even if dead or growth-inhibited. A study was made of 79 mastitic milk samples with no-growth bacteria in conventional culture, originating from cows with clinical mastitis. Of the 79 samples, 34 (43%) were positive for 1 (32 samples) or 2 (2 samples) of the target bacteria. The positive findings included 11 Staphylococcus spp. (staphylococci other than Staphylococcus aureus), 10 Streptococcus uberis, 2 Streptococcus dysgalactiae, 6 Corynebacterium bovis, 3 Staph. aureus, 1 Escherichia coli, 1 Enterococcus, and 1 Arcanobacterium pyogenes. The positive samples contained as many as 10³ to 10⁷ bacterial genome copies per milliliter of milk. This study demonstrates that in nearly half of the clinical mastitis cases in which conventional culture failed to detect bacteria, mastitis pathogens were still present, often in substantial quantities. The clearly elevated N-acetyl-β-d-glucosaminidase activity values of the milk samples, together with clinical signs of the infected cows and quarters, confirmed the diagnosis of clinical mastitis and indicated that real-time, PCR-based bacterial findings are able to reveal bacteriological etiology. We conclude that all common mastitis bacteria can occur in large quantities in clinical mastitis samples that exhibit no growth in conventional culture, and that the real-time PCR assay is a useful tool for bacteriological diagnosis of such milk samples. Low bacterial concentration is commonly speculated to explain the no-growth milk samples. This hypothesis is not supported by the results of the current study.     

Effect of an electrostatic field on the optical properties of a cloud of dielectric particles

The optical properties of a cloud of anisotropic dielectric particles when the orientational distribution is made nonrandom by interaction with an electrostatic field are studied. Since the interaction energy is determined by the polarizability of the particles, a general expression for the polarizability of nonspherical particles is worked out. In particular, we investigated the response to the electrostatic field of two different dispersions whose component particles are built as clusters of four identical spheres. Although in one cloud the clusters were shaped as linear chains, and in the other cloud the clusters were shaped as squares, the optical properties of both dispersions as a function of the static field are rather similar. There are, however, noticeable ranges of size within which the optical response of the two kinds of particles is substantially different.