Design of an antibacterial gelatin based on a covalent protein–protein coupling

An antibacterial peptide (AMP), i.e., nisin, was covalently bound to gelatin through a protein–protein coupling. Various reaction conditions were tested to study and optimize parameters of grafting e.g., orientation and density of AMP, which could impact the final antibacterial activity of the modified biopolymer. Modification was investigated by Fourier transform infrared (FT‐IR) spectroscopy and zeta potential. The antibacterial activity of the nisin‐enriched gelatin was evaluated against two staphylococci bacterial strains, i.e., Staphylococus epidermidis and Staphylococcus aureus. A higher activity was found for gelatin modified at pH = 7.4 revealing an influence of the nisin orientation on the protein antibacterial property. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41825.     

Studies of Work ‘in the Wild’

Computer Supported Cooperative Work (CSCW) -     

Robust dual-quantisation multibit sigma-delta modulator

A new dual-quantisation sigma-delta modulator is proposed, which introduces an additional feedback path in the input of the second integrator. In this way, unlike other dual-quantisation architectures, larger signal-to-noise ratios can be obtained by means of aggressive noise-shaping, like in a conventional multibit modulator. The proposed modulator is also shown to be more robust against non-idealities than other dual-quantisation architectures.     

Nasopharyngeal colonization in Costa Rican children during the first year of life

BACKGROUND: The establishment of the nasopharyngeal flora was followed in Costa Rican children from birth to 1 year of age. METHODS: Nasopharyngeal cultures were obtained at 1 (n = 413), 3 (n = 393), 6 (n = 376) and 12 months (n = 356) of age from children representative of the population in the Puriscal district. Weekly cultures were obtained from a subcohort of these children (n = 101). Mother-infant diads (n = 95) and preschool children (n = 208) attending day-care centers were also studied. RESULTS: The estimated proportion of colonized children in the population differed markedly depending on the frequency of culture. Quarterly cultures showed a slow increase in carrier rates from 3.9% for Haemophilus influenzae, 3.1% for Streptococcus pneumoniae and 6.5% for Moraxella catarrhalis at 1 month of age to 10.1% carrying H. influenzae and 19.4% carrying S. pneumoniae by the end of the first year. By quarterly culture the proportion of children colonized at least once was 36% for S. pneumoniae, 26% for H. influenzae and 28% for M. catarrhalis. In contrast weekly sampling showed that 95 to 100% of the children were colonized at least once during the first year of life with H. influenzae, S. pneumoniae or M. catarrhalis. Nasopharyngeal carriage of H. influenzae, S. pneumoniae and M. catarrhalis was low in the mothers, and very few mother-infant pairs carried identical bacteria at the same time. In contrast carrier rates were high in the siblings attending day care (H. influenzae 27.9%, S. pneumoniae 39.4%, both organisms 26.6%). Infants with siblings had significantly higher bacterial carriage at all ages than infants without siblings. CONCLUSIONS: Quarterly nasopharyngeal cultures showed that Costa Rican infants acquire their nasopharyngeal flora at a rate comparable with that for infants in developed countries and that siblings are an important source of the bacteria. Weekly samplings showed that virtually all children were colonized at least once during the first year of life.     

Wavelength-switchable fiber laser using acoustic waves

We report a wavelength-switchable fiber ring laser that includes a Bragg grating-based acoustooptic superlattice modulator. Wavelength switching of the laser emission is achieved by controlling the peak reflectivity of the different reflection bands that appear on both sides of the Bragg wavelength when a longitudinal acoustic wave propagates along the grating.     

Polarization control in a vertical cavity surface emitting laser submitted to optical feedback

We study experimentally and theoretically two polarization effects in a vertical cavity surface emitting laser submitted to optical feedback. In a first experiment, we obtain flips between two linearly polarized laser modes up to a frequency of 50 MHz using an external cavity with a polarizer. In a second experiment, polarization self modulation is demonstrated up to a frequency of 2.6 GHz, using a quarter wave plate instead. Numerical calculations, based on a four levels model for the active medium, show a good agreement with the experiments.     

Steady flow of a power-law fluid past a cylinder

Summary Considered in this paper is the two-dimensional steady flow of a power-law fluid past a stationary circular cylinder. The governing nonlinear equations, expressed in terms of a stream function and vorticity, were solved by finite differences for Reynolds numbers (based on the radius of the cylinder)R=5,20, 40 for various power-law indices,n. Parameters such as the drag coefficient, separation angle, wake length and critical Reynolds number are presented and contrasted with those of a Newtonian fluid (n=1) to illustrate the non-Newtonian effects. For a given-Reynolds number a consistent behaviour withn was observed in the parameters for the ranges considered. The results obtained for the Newtonian case agree well with documented results.     

Analysis of integrated optical waveguide mirrors

A new method is presented to analyze reflection losses of integrated mirrors, taking into account the exact guided mode profile and assuming that this profile remains unchanged up to the reflecting plane. The fraction of the reflected light coupled to one of the guided modes of the output waveguide is calculated, taking into account the mirror reflection coefficient. The influence of both translation and tilt of the reflecting plane is investigated. The method applies for every guided mode and any reflection angles. Numerical calculations are derived for a 90° optical corner mirror     

Influence of Missing Values on the Prediction of a Stationary Time Series

Abstract. The influence of missing observations on the linear prediction of a stationary time series is investigated. Simple bounds for the prediction error variance and asymptotic behaviours for short and long‐memory processes respectively are presented.