Preparation and characterization of poly(lactic‐co‐glycolic acid) microparticles containing DNA molecules encoding a malaria vaccine candidate

BACKGROUND: A novel ultrasonic atomization approach for the formulation of biodegradable poly(lactic‐co‐glycolic acid) (PLGA) microparticles of a malaria DNA vaccine is presented. A 40 kHz ultrasonic atomization device was used to create the microparticles from a feedstock containing 5 volumes of 0.5% w/v PLGA in acetone and 1 volume of condensed DNA which was fed at a flow rate of 18 ml h^?1. The plasmid DNA vectors encoding a malaria protein were condensed with a cationic polymer before atomization. RESULTS: High levels of gene expression in vitro were observed in COS‐7 cells transfected with condensed DNA at a nitrogen to phosphate (N/P) ratio of 10. At this N/P ratio, the condensed DNA exhibited a monodispersed nanoparticle size (Z‐average diameter of 60.8 nm) and a highly positive zeta potential of 38.8 mV. The microparticle formulations of malaria DNA vaccine were quality assessed and it was shown that the microparticles displayed high encapsulation efficiencies between 82–96% and a narrow size distribution in the range of 0.8–1.9 µm. In vitro release profile revealed that approximately 82% of the DNA was released within 30 days via a predominantly diffusion controlled mass transfer system. CONCLUSIONS: This ultrasonic atomization technique showed excellent particle size reproducibility and displayed potential as an industrially viable approach for the formulation of controlled release particles. Copyright © 2009 Society of Chemical Industry     

The formation of well-oriented dense ZnO film using MOCVD

For utilization of ZnO in optoelectronics, the large-area heteroepitaxy of ZnO is needed. However the lattice mismatch and anisotropy of ZnO prevent the successful heteroepitaxy of ZnO film through the conventional slow growth approach. This paper demonstrates an unconventional approach of dense ZnO film formation by high growth rate deposition using metal-organic chemical vapor deposition. The mechanism of the formation of well-oriented and dense ZnO film with large grains is illustrated in terms of dimethylzinc flow rate, oxygen flow rate, and VI/II ratio.     

Wideband wavelength tunable modelocked fibre laser over 1557-1607nm

An electronically wavelength tunable modelocked fibre laser operating over a 50 nm range using an all-fibre acousto-optic tunable filter is presented. The tuning range is 1557-1607 nm, for a 70 m long erbium-doped fibre (EDF) with a 270 ppm concentration     

Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide

BACKGROUND: Nitric oxide (NO) is released by activated macrophages, neutrophils, and stimulated bronchial epithelial cells. Exhaled NO has been shown to be increased in patients with asthma and has been put forward as a marker of airways inflammation. However, we have found that exhaled NO is not raised in patients with cystic fibrosis, even during infective pulmonary exacerbation. One reason for this may be that excess airway secretions may prevent diffusion of gaseous NO into the airway lumen. We hypothesised that exhaled NO may not reflect total NO production in chronically suppurative airways and investigated nitrite as another marker of NO production. METHODS: Breath condensate nitrite concentration and exhaled NO levels were measured in 21 clinically stable patients with cystic fibrosis of mean age 26 years and mean FEV1 57% and 12 healthy normal volunteers of mean age 31 years. Breath condensate was collected with a validated method which excluded saliva and nasal air contamination and nitrite levels were measured using the Griess reaction. Exhaled NO was measured using a sensitive chemiluminescence analyser (LR2000) at an exhalation rate of 250 ml/s. Fourteen patients with cystic fibrosis had circulating plasma leucocyte levels and differential analysis performed on the day of breath collection. RESULTS: Nitrite levels were significantly higher in patients with cystic fibrosis than in normal subjects (median 1.93 microM compared with 0.33 microM). This correlated positively with circulating plasma leucocytes and neutrophils (r = 0.6). In contrast, exhaled NO values were not significantly different from the normal range (median 3.8 ppb vs 4.4 ppb). There was no correlation between breath condensate nitrite and lung function and between breath condensate nitrite and exhaled NO. CONCLUSIONS: Nitrite levels in breath condensate were raised in stable patients with cystic fibrosis in contrast to exhaled NO. This suggests that nitrite levels may be a more useful measure of NO production and possibly airways inflammation in suppurative airways and that exhaled NO may not reflect total NO production.     

Effect of riblets on the streaky structures excited by free stream tip vortices in boundary layer

In this study, experimental investigations were made regarding the effect of riblets on the streak instability in boundary layer. The streak instability is now regarded as a major source of the self-regeneration mechanism for the hairpin type coherent structures in turbulent boundary layer flow. Thus, it is important to control the instability to suppress the drag-inducing vortical structure in terms of drag reduction. Toward enhancing the measurement accuracy and spatial resolution, an enlarged version of riblets was applied to a streak which was artificially induced by a microwing in a laminar boundary layer. It is found that the riblets have attenuation effect on the streak instability, i.e., to reduce the spanwise velocity gradient of the quasi-streamwise streak in boundary layer.     

Evaluation of a recombinant 27-kDa outer membrane protein of Coxiella burnetii as an immunodiagnostic reagent

The 27-kDa outer membrane protein from eight strains of Coxiella burnetii was expressed in the pET-21c protein expression system. Two fusion proteins with molecular masses of 30 and 32 kDa were evident in all eight of the recombinants by SDS-PAGE and immunoblotting. A protein having an approximate size of 30 kDa was purified from the Escherichia coli lysates by one-step affinity purification. The utility of the purified recombinant protein in ELISA was also evaluated by testing its reactivity with human sera and comparing this reactivity with that of Nine Mile phase II antigen. All of the 40 IF-positive serum samples were ELISA-positive for both the Nine Mile phase II and recombinant antigens, and negative serum controls were negative for both antigens. These results suggest that ELISA with the 27-kDa recombinant antigen is a sensitive and specific method for detecting anti-C. burnetii antibodies in human sera.     

Picosecond mid-IR laser induced surface damage on Gallium Phosphate (GaP) and Calcium Fluoride(CaF<Subscript>2</Subscript>)

Picosecond mid-IR USPL induced surface damage on a Gallium Phosphate (GaP) and Calcium Fluoride (CaF₂) is reported. A semiconductor GaP and a dielectric material CaF₂, that are transparent over3–10μm, were exposed to one picosecond mid-IR light (4.7μm) to investigate laser-induced surface morphological changes on the target The initiation of damage along the polishing scratch line of GaP and the random location of damage digs on the CaF₂ suggests that the mid-IR picosecond laser-induced damage on targets started from intrinsic surface defects. Multiple pulse irradiations produced periodic corrugated surface structures (ripples) perpendicular to the polarization of light on both GaP and CaF₂. In terms of the orientation and the spacing between ripples, observed ripples have common features with previously reported ripples.     

Estimating Travel Times of Field Engineers

BT's Work Manager platform uses a dynamic scheduler to plan the daily jobs of field engineers. In order to produce reliable schedules, Work Manager requires accurate estimates about the time an engineer spends on travelling from one job location to the next (inter-job time) and how much time is required to complete a job. We have developed a generic platform called Intelligent Travel Time Estimation and Management System (ITEMS) that we have used to derive a specialised version for modelling the behaviour of BT's mobile workforce. This travel time estimation system (TTE) receives job data every night and learns a new estimation model on a daily basis. When a new estimation model significantly differs from the currently used model, the new estimation model is automatically uploaded into Work Manager. The estimation algorithm has been used in a loosely coupled trial for about two years. Currently, we are undertaking trials of TTE — a tightly coupled Web-based system that fully automates the learning and management of estimation models, providing a graphical user interface that displays rich detail about the travel patterns of BT's mobile workforce. During the trial period we have observed that using TTE can quickly improve the accuracy of travel time estimates by up to 10%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Charging effect of Si nanocrystals in gate oxide near gate on MOS capacitance

MOS structure with Si nanocrystals embedded in the gate oxide close to the gate has a much larger capacitance compared to a similar MOS structure without the nanocrystals. However, charge trapping in the nanocrystals reduces the capacitance dramatically, and after most of the nanocrystals are charged up the capacitance is much smaller than that of the MOS structure without nanocrystals. An equivalent-capacitance model is proposed to explain the phenomena observed.