Light-induced in situ patterning of DNA-tagged biomolecules and nanoparticles

We present an in situ method for the selective manipulation of DNA-tagged nano-objects such as vesicles or gold colloids in aqueous solution, at neutral pH. The method makes use of the photosensitizer concept found in photodynamic therapy. Here, single-stranded DNA is immobilized onto a surface via the biotin/streptavidin linkage. If the streptavidin is fluorescently labeled, reactive species will be created during laser-induced photobleaching of the label. These reactive species can then completely or partly suppress the DNA hybridization and cause the removal of the streptavidin. The technique thereby enables a dynamic on–off control over surface density of immobilized DNA-tagged nano-objects. Furthermore, combining this in situ manipulation of DNA with prepatterning of single-stranded DNA in the micro and later in the nano range provides a means for the dynamic patterning required for applications in biosensing and nanotechnology.     

Broadband scattering of the solar spectrum by spherical metal nanoparticles

Metal nanoparticles offer the possibility of improved light trapping in solar cells, but careful design is required to maximise scattering and minimise parasitic absorption across the wavelength range of interest. We present an analysis of the broadband scattering and absorption characteristics of spherical metal nanoparticles, optimized for either crystalline silicon (c‐Si) or amorphous silicon (a‐Si:H) solar cells. A random two‐dimensional array of optimally sized Ag spheres can scatter over 97% of the AM1.5 spectrum from 400 to 1100 nm. Larger particles are required for c‐Si devices than a‐Si:H due to the increased spectral range, with optimum particle sizes ranging from 60 nm for a‐Si:H to 116 nm for c‐Si. Positioning the particles at the rear of the solar cell decreases absorption losses because these principally occur at short wavelengths. Increasing the refractive index of the surrounding medium beyond the optimum value, which is 1.0 for a‐Si:H and 1.6 for c‐Si, shifts absorption to longer wavelengths and decreases scattering at short wavelengths. Ag nanoparticles scatter more of the solar spectrum than Au, Cu or Al nanoparticles. Of these other metals, Al can only be considered for a‐Si:H applications due to high absorption in the near‐infrared, whereas Au and Cu can only be considered for the rear of c‐Si devices due to high absorption in the ultraviolet (UV) and visible. In general, we demonstrate the importance of considering the broadband optical properties of metal nanoparticles for photovoltaic applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Graduate Student Literature Review: Udder edema in dairy cattle—A possible emerging animal welfare issue

Physiological udder edema is a noninfectious metabolic disorder in dairy cattle, which may be present in a high percentage of dairy cows. This review summarizes the factors associated with udder edema. They include genetics, nutrition, oxidative stress, and physiological changes in freshening heifers. Udder edema negatively affects the productive life of a dairy cow. Udder support structures may be broken down due to tissue damage. Swollen teats may become sensitive, which makes attaching the milking unit more difficult. The amount of milk produced is decreased due to fluid buildup in the tissue spaces. Risk of secondary diseases, such as mastitis or udder cleft dermatitis, is also increased. All of these elements have an economic impact on the dairy farmer, in both the short term and the long term. If severe, damage could lead to early culling. Some possible methods for managing udder edema include (1) providing a separate diet for late-gestation heifers to monitor anionic salt intake, (2) selecting for either genetic lines with lower milk production or a phenotypic reduction of udder edema, and (3) ensuring that adequate exogenous antioxidants, such as vitamin E, vitamin C, carotenoids, and flavonoids, are provided in the diet to mitigate oxidative stress. In conclusion, udder edema may be an emerging issue that has the potential to seriously affect dairy cow welfare. Many of the research studies are outdated, and research with modern dairy cows is needed. The development of a scientifically validated udder edema scoring system is also needed to assess the severity of udder edema.     

The effect of increased response requirements on discriminative performance of the domestic hen in a visual acuity task

Six domestic hens were trained in a spatial discrimination task. A controlled reinforcement procedure insured that the ratio of scheduled and obtained reinforcement remained equal. Gray stimuli and gratings ranging in spatial frequency from 1 to 10 cycles per millimeter were presented in seven descending series of probes. The response requirement to the sample key was varied from fixed ratio 1 to fixed ratio 40 in seven experimental conditions. An increase in response requirements from fixed ratio 1 to fixed ratio 5 and fixed ratio 10 resulted in significantly higher accuracy at discriminable grating values. Further increases in response requirements did not consistently improve performance. Generally, response biases increased and occasionally became extreme for probes at finer gratings with increased response requirements.     

Thermal Motion and Conformational Disorder in Protein Crystal Structures: Comparison of Multi-Conformer and Time-Averaging Models

Models describing thermal motion and conformational variability in protein crystal structures were applied to the refinement of a 1.8 Å crystal structure of penicillopepsin. Three methods were tested: conventional refinement using restrained B factors, multiple-conformer refinement, and time-averaging refinement using molecular dynamics. The information content of the models was assessed by cross-validation and by estimating the phase accuracy of the model using phases obtained by multiple isomorphous replacement. The R value always decreased when using multi-conformer and time-averaging methods, as compared to conventional refinement. In contrast, the cross-validated (“free”) R value and the phase accuracy worsened for time-averaging in vacuum. Inclusion of solvent produced a slight improvement of both measures compared to conventional refinement. Multi-conformer refinements always improved both measures. An optimum was reached for simultaneous refinement of between four and eight conformers. At the resolution limit of the penicillopepsin data, multi-conformer refinement is an efficient method to describe conformational variability and thermal motion.     

Polarization fluctuation measurements on installed single-modeoptical fiber cables

Measurements are reported of the polarization fluctuation observed at 1550 nm on samples of cable that Telecom Australia has installed in its interexchange network. The rate of polarization fluctuations is found to be slow, on the order of hours. The fluctuation in the polarization angle is typically in the range of 2-10° each day, with some changes up to about 25°. The results indicate there are no significant limitations on implementing polarization control in a coherent system receiver     

Atypical chondrodysplasia: a further variant of multiple enchondromatosis with vertebral involvement?

We report the case of a child with asymmetrical enchondromatosis and vertebral involvement, who presented in utero, and postulate its relationship to similar rarely reported cases.     

EPR studies on molybdenum phosphates Mo2P4O15, NaMo3P3O16 and BaMo2P4O16 in the temperature range 300–4·2K

EPR studies of molybdenum phosphates, Mo₂P₄O₁₅, NaMo₃P₃O₁₆ and BaMo₂P₄O₁₆ in the range 300–4·2 K was carried out. Delocalization of 4d ¹ electron on a Mo⁵⁺ site in the MoO₆ octahedra occurs due to tunneling process. This gives rise to unresolved EPR lineshapes in all the cases except in Mo₂P₄O₁₅. The slight indication of hyperfine structure in Mo₂P₄O₁₅ is due to less feasibility of delocalization of the 4d ¹ electron, as MoO₆ octahedron is connected through a PO₄ group to only three octahedra as compared with higher numbers in the case of others. The negative g-shift is observed in all the cases due to positive sign of the spin-orbit coupling constant. The decreasing trend in g_iso-values in Mo₂P₄O₁₅ and NaMo₃P₃O₁₆ with decreasing temperature is observed, whereas in BaMo₂P₄O₁₆ the g_iso-value increases with decreasing temperature.     

Network management for automated banking

The Postipankki Bank in Finland has installed a network monitoring and control system to keep watch on the network linking its central data centre and six remote processing centres; in total, a configuration of 2000 terminals. The criteria on which the network was selected are discussed, and the improvements obtained in availability of information on network utilization and fault monitoring are described.