A europium chelate for quantitative point-of-care immunoassays using direct surface measurement

New labels and assay techniques are needed to improve the sensitivity and quantitativeness of point-of-care immunotesting while sustaining the rapidity and ease of use of the assays. We synthesized a novel, intrinsically fluorescent nonadentate europium chelate with two chromophores and hydrophilic alpha-galactose side groups. The chelate is highly fluorescent, soluble in water, and provides effective shielding of Eu from water. The performance of the nonadentate chelate was compared with a heptadentate chelate in a dry reagent immunoassay for human chorionic gonadotropin (hCG). After 15-min incubation and washing, time-resolved fluorescence was measured directly from a wet or dried well surface. Contrary to the heptadentate label, the effect of aqueous quenching on the nonadentate label was found to be insignificant, with calculated analytical detection limits (background + 3 SD) of 0.9 and 0.7 IU/L hCG for wet and dry measurements, respectively, and a linear range up to 5000 IU/L. The CVs for the new label were <8% at the cutoff of 25 IU/L and above in both whole blood and plasma. The novel nonadentate label facilitates short turnaround times and simple instrumentation due to the absence of all signal development steps, at the same time retaining an excellent immunoassay performance.     

Methodology for calculating turn-off transient of photoconductive circuit elements in picosecond optoelectronics

A methodology for calculating the transient following sudden removal of photon or mass-particle excitation is developed for semiconductor devices in which high hole-electron recombination rates, rather than short transit times, yield picosecond response time. We suggest the name photoconductive circuit element (PCE) for these optoelectronic transducers to emphasize their potential application to diverse circuit and system functions. The device consists of a nearly intrinsic active region that contains extremely high concentrations of deep-level states acting as recombination centers. Regions of semiconductors highly doped with shallow donor or acceptor atoms connected to metallic contacts border this active region. In calculating the turnoff transient, we set forth criteria that define nearly ideal ohmic-contact systems and the quasi-neutrality regime of the intrinsic region. If these criteria are met, the turn-off transient becomes a problem in photoconductive decay. For incremental variations in the electron and hole quasi-Fermi voltages much less than the thermal voltage, two characteristic times, assigned to each recombination-center energy level, rather than a single lifetime, describe electron-hole recombination. A computer algorithm accounting for incremental variations within suitably small time intervals then enables calculation of observables that may vary by many orders of magnitude, InP:Fe photoconductive circuit elements containing eight different Fe concentrations, excited by 780 and 600 nm laser-light pulses and 6 MeV electron pulses, showed a (1/e)-fall-time versus Fe-concentration in general accord with results calculated by the methodology. The capture cross sections and the energy distribution of the recombination-center energy levels receive attention. The InP:Fe transducers showed (1/e)-fall-times in the sub- 100-ps regime.     

Diurnal variation in subsidiary reaction time in a long-term driving task

Traffic accidents show a marked diurnal rhythm, which is a seldom investigated phenomenon. One possible background factor examined in the present study is the biological circadian rhythm. Eight subjects drove for 3 hr, beginning at 0300, 0900, 1500 and 2100. During each session a subsidiary reaction time task was used as an indirect measure of driving performance. Critical confounding factors, such as lighting conditions, traffic intensity, amount of sleep preceding the session and temperature in the car were considered. The results showed that there were small differences in the level of performance among the four sessions. However, differences in the rate of performance deterioration were not observed. From these results it was concluded that biological rhythm as a single variable has only a minor influence on this type of performance. Consequently the diurnal rhythm of traffic accidents must be attributed to other factors such as long hours of driving and/or sleep deprivation which culminate during the morning hours.     

Dependence of reproducing gap null on head geometry

The spatial frequency response of reproduce heads with infinite depth, but finite pole length, is determined to very good accuracy by superposition of conformal map solutions for simpler geometries. This approach yields closed form approximations of the frequency response which are accurate to better than 7% for any head length-to-gap length ratio and any spatial frequency. In particular, the effect of this ratio on the location of the first gap null in the frequency response spectrum is explored for narrow pole length heads. The results lead to design considerations for extending the useful frequency range of thin film reproduce heads.     

Tyrosine-derived polycarbonate membrane in treating mandibular bone defects. An experimental study.

This study was designed to evaluate the suitability of a novel bioabsorbable material in treating bone defects. A poly(desaminotyrosyl-tyrosine-ethyl ester carbonate) (PDTE carbonate) membrane (thickness 0.2-0.3 mm) was implanted into the mandibular angle of 20 New Zealand White rabbits to cover a through-and-through defect (12 x 6 mm). In group 1, the defects were left unfilled but covered with membrane and in group 2 the defects were filled with bioactive glass mesh and covered with membrane, too. Controls were left uncovered and unfilled. The animals were followed for 6, 12, 24 and 52 weeks, respectively. The material was evaluated by qualitative analysis of histological reactions and newly formed bone.We found that PDTE carbonate elicited a modest foreign body reaction in the tissues, which was uniform throughout the study. New bone formation was seen in all samples after six weeks. Group 1 had more new bone formation until 24 weeks and after this the difference settled. Based on findings of this study it was concluded that PDTE carbonate membranes have good biocompatibility and are sufficient to enhance bone growth without additional supportive matrix.     

Relationships between probabilistic Boolean networks and dynamic Bayesian networks as models of gene regulatory networks

A significant amount of attention has recently been focused on modeling of gene regulatory networks. Two frequently used large-scale modeling frameworks are Bayesian networks (BNs) and Boolean networks, the latter one being a special case of its recent stochastic extension, probabilistic Boolean networks (PBNs). PBN is a promising model class that generalizes the standard rule-based interactions of Boolean networks into the stochastic setting. Dynamic Bayesian networks (DBNs) is a general and versatile model class that is able to represent complex temporal stochastic processes and has also been proposed as a model for gene regulatory systems. In this paper, we concentrate on these two model classes and demonstrate that PBNs and a certain subclass of DBNs can represent the same joint probability distribution over their common variables. The major benefit of introducing the relationships between the models is that it opens up the possibility of applying the standard tools of DBNs to PBNs and vice versa. Hence, the standard learning tools of DBNs can be applied in the context of PBNs, and the inference methods give a natural way of handling the missing values in PBNs which are often present in gene expression measurements. Conversely, the tools for controlling the stationary behavior of the networks, tools for projecting networks onto sub-networks, and efficient learning schemes can be used for DBNs. In other words, the introduced relationships between the models extend the collection of analysis tools for both model classes.     

Effect of Oat Bran Fractions on Extrudates Made of Defatted Oats

Food and Bioprocess Technology - Oats are rich in dietary fibre (DF) especially in β-glucan which has several health-promoting effects. Oats are not commonly used in extruded snacks because...     

Quantitative NIR chemical imaging in heritage science

Until recently, applications of spectral imaging in heritage science mostly focused on qualitative examination of artworks. This is partly due to the complexity of artworks and partly due to the lack of appropriate standard materials. With the recent advance of NIR imaging spectrometers, the interval 1000-2500 nm became available for exploration, enabling us to extract quantitative chemical information from artworks. In this contribution, the development of 2D NIR quantitative chemical maps of heritage objects is discussed along with presentation of the first quantitative image. Further case studies include semiquantitative mapping of plasticiser distribution in a plastic object and identification of historic plastic materials. In the NIR imaging studies discussed, sets of 256 spatially registered images were collected at different wavelengths in the NIR region of 1000-2500 nm. The data was analyzed as a spectral cube, both as a stack of wavelength-resolved images and as a series of spectra, one per each sample pixel, using multivariate analysis. This approach is only possible using well-characterized reference sample collections, as quantitative imaging applications need to be developed, thus enabling spatial maps of damaged and degraded areas to be visualized to a level of chemical detail previously not possible. Such quantitative chemical mapping of vulnerable areas of heritage objects is invaluable, as it enables damage to historic objects to be quantitatively visualized.     

Simulation of hydrogen deflagration and detonation in a BWR reactor building

A systematic study was carried out to investigate the hydrogen behaviour in a BWR reactor building during a severe accident. BWR core contains a large amount of Zircaloy and the containment is relatively small. Because containment leakage cannot be totally excluded, hydrogen can build up in the reactor building, where the atmosphere is normal air. The objective of the work was to investigate, whether hydrogen can form flammable and detonable mixtures in the reactor building, evaluate the possibility of onset of detonation and assess the pressure loads under detonation conditions. The safety concern is, whether the hydrogen in the reactor building can detonate and whether the external detonation can jeopardize the containment integrity. The analysis indicated that the possibility of flame acceleration and deflagration-to-detonation transition (DDT) in the reactor building could not be ruled out in case of a 20 mm² leakage from the containment. The detonation analyses indicated that maximum pressure spike of about 7 MPa was observed in the reactor building room selected for the analysis.