In vitro evaluation of a novel bioreactor based on an integral oxygenator and a spirally wound nonwoven polyester matrix for hepatocyte culture as small aggregates

BACKGROUND/AIMS: The development of custom-made bioreactors for use as a bioartificial liver (BAL) is considered to be one of the last challenges on the road to successful temporary extracorporeal liver support therapy. We devised a novel bioreactor (patent pending) which allows individual perfusion of high density cultured hepatocytes with low diffusional gradients, thereby more closely resembling the conditions in the intact liver lobuli. METHODS: The bioreactor consists of a spirally wound nonwoven polyester matrix, i.e. a sheet-shaped, three-dimensional framework for hepatocyte immobilization and aggregation, and of integrated hydrophobic hollow-fiber membranes for decentralized oxygen supply and CO2 removal. Medium (plasma in vivo) was perfused through the extrafiber space and therefore in direct hepatocyte contact. Various parameters were assessed over a period of 4 days including galactose elimination, urea synthesis, lidocaine elimination, lactate/pyruvate ratios, amino acid metabolism, pH, the last day being reserved exclusively for determination of protein secretion. RESULTS: Microscopic examination of the hepatocytes revealed cytoarchitectural characteristics as found in vivo. The biochemical performance of the bioreactor remained stable over the investigated period. The urea synthesizing capacity of hepatocytes in the bioreactor was twice that of hepatocytes in monolayer cultures. Flow sensitive magnetic resonance imaging (MRI) revealed that the bioreactor construction ensured medium flow through all parts of the device irrespective of its size. CONCLUSIONS: The novel bioreactor showed encouraging efficiency. The device is easy to manufacture with scale-up to the liver mass required for possible short-term support of patients in hepatic failure.     

On the robustness of ultra-wide bandwidth signals in densemultipath environments

The results of an ultra-wide bandwidth (UWB) signal propagation experiment, using bandwidth in excess of 1 GHz, performed in a typical modern office building are presented. The robustness of the UWB signal in multipath is quantified through cumulative distribution functions of the signal quality in various locations of the building. The results show that an UWB signal does not suffer multipath fading     

Effects of industrial by-product based geopolymers on the strength development of a soft soil

Portland cement is traditionally used as a binder in ground improvement projects on soft soil foundations. The use of cement in ground improvement projects, however, is fraught with both, financial and environmental concerns due to its relatively high cost, the use of natural resources and the high carbon footprint from cement production. Attempts are being made to find alternative environmentally friendly binders with a low carbon footprint using industrial by-products such as fly ash (FA) and slag (S). Using waste by-products such as FA and S to produce geopolymer binders, as novel green cementitious materials, may provide an environmentally friendly and effective ground improvement option. In this study, the effect of adding geopolymers to a soft soil was investigated for usage in deep soil mixing (DSM) applications. The soil was a soft marine clay known as Coode Island Silt (CIS). Different combinations of FA and S with six combinations of sodium and potassium based liquid alkaline activators (L) were added to the soil to study the effects on its engineering and chemical properties. These changes were evaluated via an unconfined compression strength (UCS) test, scanning electron microscopy (SEM) imaging and energy-dispersive X-ray spectroscopy (EDS) tests. The tests were conducted after 3, 7, 14 and 28?days of curing. Based on the results, the important role of L in strength development was studied, and the combination of 30% NaOH with 70% Na₂SiO₃ was found to achieve the highest strengths. Furthermore, increasing the S content was found to result in significant improvements in strength. The excellent correlation between strength and stiffness shown in the results are expected to help in the development of relationships for strength prediction of these green binders in geotechnical applications. This study shows that FA and S based geopolymers can be used as sustainable binders in DSM projects, with significant environmental benefits.     

Investigation on thermal performance of glazed solar chimney walls

This paper reports investigation on the thermal performance of glazed solar chimney walls (GSCW) under the tropical climatic conditions of Thailand. The GSCW consisted of double glass panes with an air layer and openings located at the bottom (room side glass pane) and at the top (ambient side glass pane). A prototype of GSCW was integrated into the southern wall of a small room of 2.8 m³ volume. Its dimensions were as follows: 0.74 m height, 0.50 m width and 0.10 m air gap. The size of openings was 0.05 × 0.5 m². With a clear glass of 6 mm thickness, velocity field measurement indicated that the induced airflow rate was about 0.13–0.28 m³/s. The temperature difference between room and ambient was less than that with a single layer clear glass window. The reduction of daylight due to the double glass layer is negligible. Comparison between simulated and experimental results showed a reasonable agreement, therefore, the developed numerical model is valid and could be used as a tool for the design of GSCW.     

Comparing rapid methods for detecting Listeria in seafood and environmental samples using the most probably number (MPN) technique

The standard Bacteriological Analytical Manual (BAM) protocol for detecting Listeria in food and on environmental surfaces takes about 96 h. Some studies indicate that rapid methods, which produce results within 48 h, may be as sensitive and accurate as the culture protocol. As they only give presence/absence results, it can be difficult to compare the accuracy of results generated. We used the Most Probable Number (MPN) technique to evaluate the performance and detection limits of six rapid kits for detecting Listeria in seafood and on an environmental surface compared with the standard protocol. Three seafood products and an environmental surface were inoculated with similar known cell concentrations of Listeria and analyzed according to the manufacturers' instructions. The MPN was estimated using the MPN-BAM spreadsheet. For the seafood products no differences were observed among the rapid kits and efficiency was similar to the BAM method. On the environmental surface the BAM protocol had a higher recovery rate (sensitivity) than any of the rapid kits tested. Clearview™, Reveal®, TECRA® and VIDAS® LDUO detected the cells but only at high concentrations (> 10² CFU/10 cm²). Two kits (VIP™ and Petrifilm™) failed to detect 10⁴ CFU/10 cm². The MPN method was a useful tool for comparing the results generated by these presence/absence test kits. There remains a need to develop a rapid and sensitive method for detecting Listeria in environmental samples that performs as well as the BAM protocol, since none of the rapid tests used in this study achieved a satisfactory result.     

Stiffness of free-standing thermal barrier coating top coats measured by bending tests

Free-standing miniature beam specimens of thermal barrier coating (TBC) top coats were prepared by metal dissolution from high pressure turbine blades coated with TBC by electron beam physical vapour deposition (EBPVD) and thermally cycled to 1150 °C for various times. The beams comprised the yttria stabilized zirconia (YSZ) TBC and the thermally grown oxide (TGO) and their effective elastic modulus was measured using a miniaturized three-point bending test. The measured effective modulus was typically in the range of 10–22 GPa, with large specimen-to-specimen variations. The modulus increased with thermal exposure of the coated blades up to 85 cycles, but decreased for a larger number of cycles. The Young’s modulus of the YSZ layer alone was derived from the effective modulus of the composite beams (YSZ and TGO) by taking into account the contribution of the TGO. The derived Young’s modulus of the YSZ was in the range 5–10 GPa, and was verified independently by TGO residual stress measurement. Significant inelastic deformation was found to occur during the bending test when a relatively high load was applied and is speculated to be due to micro-fractures between columns in the YSZ. Specimens prepared from the concave part of the turbine blade were found to be approximately four times stiffer than those taken from a flat part of the blade, indicating that the modulus of the TBC is strongly dependent on the microstructure of the YSZ coating.     

MIMO Diversity in the Presence of Double Scattering

The potential benefits of multiple-antenna systems may be limited by two types of channel degradations-rank deficiency and spatial fading correlation of the channel. In this paper, we assess the effects of these degradations on the diversity performance of multiple-input multiple-output (MIMO) systems, with an emphasis on orthogonal space-time block codes (OSTBC), in terms of the symbol error probability (SEP), the effective fading figure (EFF), and the capacity at low signal-to-noise ratio (SNR). In particular, we consider a general family of MIMO channels known as double-scattering channels-i.e., Rayleigh product MIMO channels-which encompasses a variety of propagation environments from independent and identically distributed (i.i.d.) Rayleigh to degenerate keyhole or pinhole cases by embracing both rank-deficient and spatial correlation effects. It is shown that a MIMO system with transmit and receive antennas achieves the diversity of order in a double-scattering channel with effective scatterers. We also quantify the combined effect of the spatial correlation and the lack of scattering richness on the EFF and the low-SNR capacity in terms of the correlation figures of transmit, receive, and scatterer correlation matrices. We further show the monotonicity properties of these performance measures with respect to the strength of spatial correlation, characterized by the eigenvalue majorization relations of the correlation matrices.     

Frequency noise measurement of diode-pumped Nd:YAG ring lasers

The combined frequency noise spectrum of two lightwave Model 120-01A nonplanar ring oscillator lasers was measured by first heterodyne detecting the IF signal and then measuring the IF frequency noise using an RF frequency discriminator. The results indicated the presence of a 1/f² noise component in the power spectral density of the frequency fluctuations between 1 Hz and 1 kHz. After incorporating this 1/f² into the analysis of the optical phase tracking loop, the measured phase error variance closely matches the theoretical predictions     

Atypical case of Smith-Lemli-Opitz syndrome: implications for diagnosis

Anti-GQ1b antibodies were assayed by an enzyme-linked immunosorbent assay in sera from patients with non-neurological disorders (N = 20), and with various neurological disorders (N = 59), including nine cases of Miller Fisher syndrome, 16 cases of Guillain-Barré syndrome and one case of acute post-infectious ophthalmoparesis. Such antibodies were found in most cases (8 out of 9) of Miller Fisher syndrome, and at very high titres, in one case of Guillain-Barré syndrome characterised by an initial ophthalmoparesis, and in the case of isolated post-infectious ophthalmoparesis. The latter was characterised by a long-lasting occurrence of these antibodies. Anti-GQ1b antibodies are specific for an immune-mediated neuropathy of the cranial, especially oculomotor, nerves.