Matrices for tissue engineering-scaffold structure for a bioartificial liver support system

Gillnets are a widely used fishing gear in Kenya’s artisanal fisheries, yet their mesh sizes are inadequately monitored or regulated. This study evaluated the impacts of gillnets of seven stretched-mesh sizes, through comparative analysis of species-related metrics and catch per unit effort (CPUE), to inform Kenya’s small-scale fisheries regulations. Data were collected from June 2014 to May 2015. Three mesh-size groups were identified from catch composition data using non-metric multidimensional scaling and comprised small (1.3, 5.1 and 7.6 cm), medium (10.2 and 15.2 cm) and large (20.3 and 25.4 cm) mesh. The dominant species (and their mean lengths) that were caught in the small, medium and large mesh sizes, respectively, were whitespotted rabbitfish Siganus sutor (21.7 cm [SD 5.3]), mackerel tuna Euthynnus affinis (40.8 cm [SD 9.1]) and honeycomb stingray Himantura uarnak (87.3 cm [SD 37.4]). Values of length at first capture (L 50) for S. sutor and E. affinis caught with the small and medium mesh sizes were below length at maturity (L m). Catches of juveniles were proportionately high in the small meshes (61.3–74.2%) and lower in the medium (38.3–50.9%) and large (9.1–36.2%) mesh sizes. Catches with small mesh tended to be species categorised as Least Concern on the IUCN Red List, in contrast to catches with large mesh which tended to be Near Threatened or Vulnerable species. Biomass CPUE differed between mesh-size groups, with the small sizes recording low CPUE. The medium sizes caught mid- to high-trophic-level species with high-income returns, displayed moderate CPUE, and had the lowest juvenile retention and capture of threatened species. Medium mesh sizes are therefore recommended for artisanal fisheries, given low trade-offs between ecological impact and fishery returns.

Mathematical models were used to generate numerical results by (1) combining the growth and mortality curves of a hypothetical lake whitefish (Coregonus clupeaformis) population to yield a length-frequency distribution, (2) calculating the number of fish caught by different mesh sizes and at different rates of exploitation by means of a gill-net selectivity model, and (3) subtracting the fish caught from the unexploited population. Assumptions on some population parameters and the choice of gill-net selectivity curves were verified against field data from the James Bay area. Results indicate that the use of a mix of mesh sizes (76.2-127 mm) is more compatible with the natural population structure than the use of one large mesh size alone, provided that the fishing intensity is controlled. These findings suggest a change in management policy from primarily regulating the mesh size to regulating the fishing intensity.

Size selectivity and catch efficiency of four codends were tested and compared for mantis shrimp (Oratosquilla oratoria) in demersal trawl fisheries of the South China Sea (SCS). These codends were differing in mesh shapes, diamond mesh (T0) and diamond-mesh turned 90° (T90) with mesh sizes of 30 and 35 mm, respectively. The results demonstrated that the T0 codend with a lower mesh size, 30 mm, presented poorer selective properties for the target species, while size selectivity would be significantly improved with the mesh size increasing to 35 mm, or substituting the T0 codend with the T90 codend. For the T90 codend with a larger mesh size, 35 mm, the size selectivity was the highest, whereas the loss of the legal individuals was also significantly considerable. Considering the trade-off between releasing undersized individuals and maintaining the legal ones, the T0 codend with 35-mm mesh size or the T90 codend with 30-mm mesh size might be a better choice to target mantis shrimp in demersal trawl fisheries of the SCS.

Genetically modified Bacillus thuringiensis Berliner (Bt) maize (Zea mays L.) expressing Cry toxins against various target pests is now grown on more than 16 million hectares worldwide, but its potential effects on the soil ecosystem need to be further investigated. In an 8-month field study, we investigated the effects of Bt maize expressing the Cry1Ab protein on both the soil community and maize residue decomposition. We used litterbags with three different mesh sizes (20, 125, and 5,000 μm) to investigate potential effects of different soil organism groups on the decomposition processes. Litterbags were incorporated into the soil in fall into a field that had previously been planted with non-Bt maize and subsamples were removed monthly. The dry weight of the remaining residue was measured for all bags. Bt and non-Bt maize decomposed similarly in large mesh bags, which allowed the whole soil organism community to enter and interact with each other. In contrast, Bt maize decomposed significantly faster than non-Bt maize at some sample dates in winter in bags with small and medium mesh sizes. At the end of the experiment in late spring, however, there was no significant difference in the amount of maize plant residues remaining for any of these three mesh sizes. Additionally, soil organisms from bags with the largest mesh size were identified. The most frequent taxa extracted were collembolans (Isotomidae, Tullbergiidae, Entomobryidae), mites (Gamasina, Oribatida), and annelids (Enchytraeidae). Three of these taxa were extracted in higher numbers from non-Bt than Bt residue (Tullbergiidae, Gamasina, Enchytraeidae), while there was no difference in the number of individuals extracted for the remaining three taxa. Our results do not show major changes in the decomposition of Bt maize residue and in the composition of the soil organism community. However, further studies are needed that assess the impact of the continuous release of Cry1Ab via root exudates and plant biomass on the soil ecosystem.

Riparian alder fens — source or sink for nutrients and dissolved organic carbon? — 2. Major sources and sinks

Hepatocyte differentiation of mesenchymal stem cells

Angiogenesis plays an essential role in many pathological processes such as tumor growth, wound healing, and keloid development. Low oxygen level is the main driving stimulus for angiogenesis. In an animal tissue, the oxygen level is mainly determined by three effects—the oxygen delivery through blood flow in a refined vessel network, the oxygen diffusion from blood to tissue, and the oxygen consumption in cells. Evaluation of the oxygen field is usually the bottleneck in large scale modeling and simulation of angiogenesis and related physiological processes. In this work, a fast numerical method is developed for the simulation of oxygen supply in tissue with a large-scale complex vessel network. This method employs an implicit finite-difference scheme to compute the oxygen field. By virtue of an oxygen source distribution technique from vessel center lines to mesh points and a corresponding post-processing technique that eliminate the local numerical error induced by source distribution, square mesh with relatively large mesh sizes can be applied while sufficient numerical accuracy is maintained. The new method has computational complexity which is slightly higher than linear with respect to the number of mesh points and has a convergence order which is slightly lower than second order with respect to the mesh size. With this new method, accurate evaluation of the oxygen field in a fully vascularized tissue on the scale of centimeter becomes possible.

At present, fatigue design of welded structures is primarily based on a nominal stress or hot spot stress approach with a series of classified weld S-N curves. Although well accepted by major industries, the nominal stress based fatigue design approach is cumbersome in terms of securing a series of S-N curves corresponding to each class of joint types and loading modes. The hot spot stress based fatigue design has a difficulty of finding a proper stress through the global model, the midium size model, and the detail model of ship structure. Also, it is difficult to link proper displacements within three different mesh size models. Recently, the structural stress is proposed as a mesh-size insensitive structural stress definition that gives a stress state at weld toe with relatively large mesh size. However, this method requires an experimental validation in obtaining the fatigue strength of weldments. Therefore, in this study, a series of experiment is performed for various sizes of weldments.

Nanostructured hydrogels based on "smart" polymer conjugates of poloxamers and protein molecules were developed in order to form stimulus-responsive materials with bioactive properties for 3-D cell culture. Functionalized Pluronic F127 was covalently attached to a fibrinopeptide backbone and cross-linked into a structurally versatile and mechanically stable polymer network endowed with bioactivity and temperature-responsive structural features. Small angle X-ray scattering and transmission electron microscopy combined with rheology were used to characterize the structural and mechanical features of this biosynthetic conjugate, both in solution and in hydrogel form. The temperature at which the chemical cross-linking of F127-fibrinopeptide conjugates was initiated had a profound influence on the mechanical properties of the thermo-responsive hydrogel. The analysis of the scattering data revealed modification in the structure of the protein backbone resulting from increases in ambient temperature, whereas the structure of the polymer was not affected by ambient temperature. The hydrogel cross-linking temperature also had a major influence on the modulus of the hydrogel, which was rationally correlated to the molecular structure of the polymer network. The hydrogel structure exhibited a small mesh size when cross-linked at low temperatures and a larger mesh size when cross-linked at higher temperatures. The mesh size was nicely correlated to the mechanical properties of the hydrogels at the respective cross-linking temperatures. The schematic charts that model this material's behavior help to illustrate the relationship that exists between the molecular structure, the cross-linking temperature, and the temperature-responsive features for this class of protein-polymer conjugates. The precise control over structural and mechanical properties that can be achieved with this bioactive hydrogel material is essential in designing a tissue-engineering scaffold for clinical applications.

Gel microstructure regulates proliferation and differentiation of MC3T3-E1 cells encapsulated in alginate beads

The study explores the impacts of varying gillnet mesh size and fishing level on yield per recruit (Y/R), escapement spawning stock (ESS) and mega‐spawners (MS) of three widely distributed freshwater fishery target species. Y/R is maximised when the optimal length of capture (Lcap) is above the size of maturity (L50). However, the unimodal shape of gillnet selectivity results in lower impacts to ESS and MS with both smaller and larger mesh sizes. Under conditions of moderate exploitation, the fraction of MS was significantly larger if small meshed gillnets were used. This is due to the relatively smaller cumulative vulnerability from small mesh sizes through time, as they target a smaller size range of fish, which also grow more quickly through the vulnerable window due to higher growth rates. Therefore, unlike trawls and beach seines, which select all size classes beyond the minimum length of capture (Lc), small meshed gillnets are not necessarily destructive and may rather promote sustained production by allowing a higher proportion of the spawning biomass to remain in the stock. The work also helps to explain the observation of sustained fish production in many developing countries despite the persistent use of gillnets of small mesh size that target small, under‐sized individuals.

In order to prepare spherical salbutamol sulfate particles of adjustable size, a Nano Spray Dryer B-90 was employed. A 33 full-factorial design was used to investigate the influence of process parameters (mesh size, feed concentration, and drying air temperature) on particle size (median size and width of the particle size distribution), amount of product produced per time, and product yield. The median particle size was significantly influenced by all three factors of the statistical design. Within the design space studied, particle sizes of 1.0 to 6.4 µm were obtained. The width of the particle size distribution (span) increased with increasing mesh sizes. All particles with a particle size greater than 2.4 µm showed a bimodal particle size distribution. Generally, larger mesh sizes as well as higher concentrations led to an increase in the amount of product prepared per time. The corresponding values observed were from 0.4 to 75.8 mg/min. The product yield was independent of the process parameters studied. All products were amorphous after spray drying and were stable up to a relative humidity of 60% at a temperature of 25°C.

Simulation of hydrogen mitigation in catalytic recombiner. Part-II: Formulation of a CFD model

A note on mesh selection and sampling efficiency in benthic studies

Feeding during the development of Eurasian perch (Perca fluviatilis) larvae was studied in situ in cylindrical cages. Initially perch larvae were maintained in cages, 0.2 mm of mesh size. The initial stocking density was 7 000 larvae per cage. Fish were fed with Zooplankton and after 17 days were transplanted to cages with a larger mesh size (1.2 mm). Development was observed for additional 17 days. Larval survival was about 25% and 65% for the initial and secondary rearing, respectively. Perch larvae ate initially rotifers and later ate nauplii and copepodites. Cladocera was the dominant food item in the diet of perch at the conclusion of our observations.