Determination of polycyclic aromatic hydrocarbons in smoked pork by effect-directed bioassay with confirmation by chemical analysis

Polycyclic aromatic hydrocarbons (PAHs) are generated during smoke curing and other heating treatments of food and represent a large class of chemical pollutants including a number of carcinogens. At present, PAHs are frequently detected by costly and time-consuming chemical analysis. Effect-directed in vitro cell-based bioassays of contaminants can offer a rapid, sensitive, and relatively inexpensive alternative for screening of contaminants in comparison to instrumental analysis. They enable estimation of total biological activity of all compounds acting through the same mode of binding. The aryl hydrocarbon receptor as a binding site plays an important role in PAH-induced carcinogenesis. The in vitro chemical-activated luciferase expression assay (using conditions to detect PAH) was investigated for its applicability for effect-directed analysis of PAH levels in smoked meat. There was an intra-assay variability of 0 to 15% and a mean coefficient of variation of 25% (3 to 50%) for the cleanup and bioassay analysis of the smoked pork samples. There was a correlation between the total responses of the bioassay and the individual amounts of the PAHs with a high molecular weight. The comparison of 2,3,7,8-tetrachlorodibenzo-p-dioxin and benzo[k]fluoranthene used as standard in the in vitro chemical-activated luciferase expression assay resulted in benzo[k]fluoranthene being able to be used as an alternative, nontoxic standard in the bioassay. This bioassay is an applicable effect-directed functional prescreening method for the analysis of PAHs in smoked meat and appears to have potential in being used for food control in the future.     

Styrene-Butadiene Polytelomers for Pressure-Sensitive Applications

Novel styrene-butadiene polymer latex compositions and their utility for pressure-sensitive and other adhesive applications are described. These compositions, termed polytelomers, are based on the concept of synthesising sequentially a low glass transition temperature, high molecular weight (polymeric) fraction, followed by a high glass transition, low molecular weight (telomeric) fraction, in an attempt to simulate the compounding of elastomeric adhesives. Some of the described compositions can exhibit multiphase morphology, having discrete styrene-rich domains surrounded by butadiene rich phase, both of these phases being embedded in a “honeycomb” carboxyl-rich phase. The compositions were characterized by dynamic mechanical spectroscopy and by electron transmission microscopy, as well as by molecular weight distribution and glass transition temperature range data. Examples of adhesive applications are also given.     

Photoconductivity of polymeric dibenz [b,i] 1,4,8,11-tetraaza [14] annulenato (μ-pyrazin)iron(II) [Fetaa(pyz)]n

Summary Results of experiments on dark- and photoconductivity of polymeric dibenz[b,i] 1,4,8,11-tetraaza[14]annulenato(-pyrazin) iron(II) [Fetaa(pyz)]_n are described. By studying the dependence of photoconductivity on electric field, intensity and wavelength it is shown that photogeneration of charge carriers occurred at short wavelengths by an Onsager mechanism and in the near-infrared region by a photoinjection process from the electrodes.Dedicated to Prof. Dr. G. Manecke on the occasion of his 70th birthdayThe authors would like to thank the Volkswagen Foundation for financial support.     

Role of Plant Volatiles in Host Plant Recognition by <Emphasis Type="Italic">Listronotus maculicollis</Emphasis> (Coleoptera: Curculionidae)

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is an economically important pest of short cut turfgrass. Annual bluegrass, Poa annua L., is the most preferred and suitable host for ABW oviposition, larval survival and development. We investigated the involvement of grass volatiles in ABW host plant preference under laboratory and field conditions. First, ovipositional and feeding preferences of ABW adults were studied in a sensory deprivation experiment. Clear evidence of involvement of olfaction in host recognition by ABW was demonstrated. Poa annua was preferred for oviposition over three bentgrasses, Agrostis spp., but weevils with blocked antennae did not exhibit significant preferences. ABW behavioral responses to volatiles emitted by Agrostis spp. and P. annua were examined in Y-tube olfactometer assays. Poa annua was attractive to ABW females and preferred to Agrostis spp. cultivars in Y-tube assays. Headspace volatiles emitted by P. annua and four cultivars of Agrostis stolonifera L. and two each of A. capillaris L. and A. canina L. were extracted, identified and compared. No P. annua specific volatiles were found, but Agrostis spp. tended to have larger quantities of terpenoids than P. annua. (Z)-3-hexenyl acetate, phenyl ethyl alcohol and their combination were the most attractive compounds to ABW females in laboratory Y-tube assays. The combination of these compounds as a trap bait in field experiments attracted adults during the spring migration, but was ineffective once the adults were on the short-mown turfgrass. Hence, their usefulness for monitoring weevil populations needs further investigation.     

Fatigue Strength of Trolley Bridge Stringers Made of ASTM A7 Steel

Nineteen S15×42 (in U.S. units) stringers from a trolley bridge made of ASTM A7 carbon steel were tested in constant-amplitude fatigue. The bridge was built in 1900 and was abandoned in 1958. In 1985, the stringers were removed from the bridge and were tested in the laboratory. The test results showed that uniform corrosion and pitting reduced the fatigue strength of the stringers from Category A to Category D. The fatigue strength was reduced more by pitting than by uniform corrosion.     

Identifying the Effects of Soil and Climate Types on Seasonal Variation of Pavement Roughness Using MML Inference

Pavement roughness is a common measure of pavement distress and one regularly measured by road authorities. While permanent pavement deterioration that equates to increased roughness is commonly modeled, cyclical or seasonal variations are often not included. While these variations may be small, they may be important when alternate pavements are compared directly for performance. We propose that seasonal variation may be described by partitioning the data into groups that are modeled as a segmentation problem. We developed a minimum message length (MML) segmentation tree (MMLST) criterion for partitioning and segmentation of the data. We performed simulated comparisons comparing common segmentation criterion (MMLST, maximum likelihood, Akaike information criterion, and Bayesian information criterion) and conclude that MMLST is the preferred criterion. MMLST assists in answering the following questions. First, is the observed segmentation pattern due to seasonal variation or merely random scatter? Second, given evidence of seasonal variation, what type of segmentation pattern should model these trends? Furthermore, does the interaction of climatic and soil conditions appear to affect this variation?     

Fatigue Strength of Repaired Prestressed Composite Beams

Composite steel-concrete bridges constitute a major portion of the national bridge inventory. Many of these structures are approaching or have passed their service lives and are in need of repair and rehabilitation. External prestressing by means of high-strength bars or cables attached to the steel beams has been used as an effective technique for upgrading the load carrying capacity of composite steel-concrete girders. While several researchers have investigated the static behavior of prestressed composite beams, few have reported on the fatigue strength of this structural system. The writers present the results of the experimental and analytical study of ten composite girders that were prestressed with seven-wire strands and then fatigue tested to failure. Three methods of extending the fatigue life of cracks were then explored: (1) drilling a hole at the crack tip and installing a high-strength bolt; (2) splicing the web at the cracked section; and (3) increasing the prestressing force of the tendon. The efficacy of the three methods is compared.     

Interferometric generation of parametrically shaped polarization pulses

We demonstrate the capabilities of the recently introduced interferometric parallel pulse shaper setup and present a method for fully tailoring the three-dimensional electrical field of femtosecond laser pulses. The possibility of producing parametric polarization pulses with arbitrary orientations and ellipticities in time is demonstrated with a selection of example pulses.     

Grating-coupling of surface plasmons onto metallic tips: a nanoconfined light source

We describe and demonstrate a new nanometer-scale broadband light source. It is based on the grating-coupled excitation of surface plasmon polaritons (SPPs) on the shaft of a sharp conical metal taper with a tip radius of few tens of nanometers. Far-field excitation of linear nanoslit gratings results in the resonant generation of SPPs traveling over more than 10 mum to the tip apex and converging to an intense radiative local light spot. Such nanofabricated tips are expected to find various applications in nanospectroscopy, overcoming problems with background illumination in apertureless microscopy.