Multi-Nozzle Biopolymer Deposition for Freeform Fabrication of Tissue Constructs

Advanced freeform fabrication techniques have been recently used for the construction of tissue scaffolds because of the process repeatability and capability of high accuracy in fabrication resolution at the macro and micro scales. Among many applicable tissue scaffolding materials, polymeric materials have unique properties in terms of the biocompatibility and degradation, and have thus been widely utilized in tissue engineering applications. Hydrogels, such as alginate, has been one of the most important polymer scaffolding materials because of its biocompatibility and internal structure similarity to that of the extracellular matrix of many tissues, and its relatively moderate processing. Three-dimensional deposition has been an entreating freeform fabrication method of biopolymer and particularly hydrogel scaffolds because of its readiness to deposit fluids at ambient temperatures. This paper presents a recent development of biopolymer deposition based freeform fabrication for 3-diemnsinal tissue scaffolds. The system configuration of multi-nozzles used in the deposition of sodium alginate solutions and Poly-?- Caprolactone (PCL) are described. Studies on polymer deposition feasibility and structural formability are conducted, and the preliminary results are presented.Mechanical Engineerin

A stochastic epidemiological model and a deterministic limit for BitTorrent-like peer-to-peer file-sharing networks

In this paper, we propose a stochastic model for a file-sharing peer-to-peer network which resembles the popular BitTorrent system: large files are split into chunks and a peer can download or swap from another peer only one chunk at a time. We prove that the fluid limits of a scaled Markov model of this system are of the coagulation form, special cases of which are well-known epidemiological (SIR) models. In addition, Lyapunov stability and settling-time results are explored. We derive conditions under which the BitTorrent incentives under consideration result in shorter mean file-acquisition times for peers compared to client-server (single chunk) systems. Finally, a diffusion approximation is given and some open questions are discussed.Comment: 25 pages, 6 figure

The Pathologic Affinities of Beriberi and Scurvy

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Baseline Scotland : groundwater chemistry of the Carboniferous sedimentary aquifers of the Midland Valley

This report describes the baseline groundwater chemistry of the sedimentary aquifers of Carboniferous age in the Midland Valley of Scotland. Groundwater is an important resource in the Midland Valley, largely for agriculture, but also for industry – including food and drink processing and mineral water bottling, and for domestic use. A large but unquantified volume of groundwater is also still pumped from former mine workings, largely coal mines, in order to maintain water levels and for quality treatment. Analyses for 62 groundwater samples were interpreted for the purposes of this study. Of these, 36 samples were collected for the Baseline Scotland project between September and December 2008. These were augmented with a further 25 samples collected during separate BGS projects since 2001. The sites were chosen largely to be representative of groundwater in the area, and sources that were very poorly constructed were avoided. A small number of samples were deliberately targeted from mines, either from adits, shafts or boreholes. The data were classed in one of five different hydrogeological units (or aquifer groups): four chronostratigraphic groups, which in decreasing order of age are the Inverclyde, Strathclyde, Clackmannan and Coal Measures groups; and a fifth group incorporating waters sampled from mine discharges. An estimate of the baseline groundwater chemistry conditions in the four chronostratigraphic hydrogeological units is presented, based on a statistical summary of the chemical data, which represents values between the 10th and 90th A summary of the conclusions arising from this study follows. percentiles of the full dataset range. This statistical approach to estimating baseline compositions was complemented by selecting 11 analyses of groundwater from sources where there is little or no indication of direct contamination, including likely impact from mining. The chemistry of these samples represents the typical groundwater conditions in the four non-mine hydrogeological units in the sedimentary Carboniferous aquifers of the Midland Valley

Injectable and Spatially Patterned Microporous Annealed Particle (MAP) Hydrogels for Tissue Repair Applications.

Spatially patterned hydrogels are becoming increasingly popular in the field of regenerative medicine and tissue repair because of their ability to guide cell infiltration and migration. However, postfabrication technologies are usually required to spatially pattern a hydrogel, making these hydrogels difficult to translate into the clinic. Here, an injectable spatially patterned hydrogel is reported using hyaluronic acid (HA)-based particle hydrogels. These particle hydrogels are sequentially loaded into a syringe to form a pattern and, once injected, they maintain the pattern. The applicability of this hydrogel in a wound healing skin model, a subcutaneous implant model, as well as a stroke brain model is examined and distinct patterning in all models tested is shown. This injectable and spatially patterned hydrogel can be used to create physical or biochemical gradients. Further, this design can better match the scaffold properties within the physical location of the tissue (e.g., wound border vs wound center). This allows for better design features within the material that promote repair and regeneration

Hidden breakpoints in genome alignments

During the course of evolution, an organism's genome can undergo changes that affect the large-scale structure of the genome. These changes include gene gain, loss, duplication, chromosome fusion, fission, and rearrangement. When gene gain and loss occurs in addition to other types of rearrangement, breakpoints of rearrangement can exist that are only detectable by comparison of three or more genomes. An arbitrarily large number of these "hidden" breakpoints can exist among genomes that exhibit no rearrangements in pairwise comparisons. We present an extension of the multichromosomal breakpoint median problem to genomes that have undergone gene gain and loss. We then demonstrate that the median distance among three genomes can be used to calculate a lower bound on the number of hidden breakpoints present. We provide an implementation of this calculation including the median distance, along with some practical improvements on the time complexity of the underlying algorithm. We apply our approach to measure the abundance of hidden breakpoints in simulated data sets under a wide range of evolutionary scenarios. We demonstrate that in simulations the hidden breakpoint counts depend strongly on relative rates of inversion and gene gain/loss. Finally we apply current multiple genome aligners to the simulated genomes, and show that all aligners introduce a high degree of error in hidden breakpoint counts, and that this error grows with evolutionary distance in the simulation. Our results suggest that hidden breakpoint error may be pervasive in genome alignments.Comment: 13 pages, 4 figure

Two Cases of Anaphylactic Serum Disease Over Six Years After the Primary Injection of Horse-Serum (Yersin's Antipest Serum)

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