IV.3. Bioreactors in tissue engineering.

IV.3. Bioreactors in tissue engineering

Osteoblast response to rest periods during bioreactor culture of collagen-glycosaminoglycan scaffolds.

Flow perfusion bioreactors have been shown to enhance fluid transport and improve cell viability throughout tissue-engineered bone constructs. Furthermore, osteoblasts have been shown to be stimulated by flow during bioreactor culture, although the optimum flow regime to promote an osteogenic response has yet to be found. One problem is that bone cells lose their ability to respond to stimulation; however, mechanosensitivity can be restored by introducing resting periods between bouts of loading. The aim of this study was to analyze the effect of rest-insertion on the response of osteoblasts seeded on collagen-glycosaminoglycan scaffolds in a flow perfusion bioreactor over culture periods up to 14 days. Short-term rests of 5, 10, or 15 s and long-term rests of 7 h were incorporated into stimulation patterns. Cell distribution was enhanced in all flow groups, whereas static culture controls exhibited encapsulation. Cyclooxygenase-2 expression and prostaglandin E(2) levels increased significantly because of bioreactor culture over static controls. Osteopontin expression was significantly higher for the rest-inserted groups than the static control group or steady-flow group. These results indicate that the insertion of resting periods during flow enhances cellular distribution and osteogenic responses on collagen-glycosaminoglycan constructs cultured in a flow perfusion bioreactor

Stimulation of osteoblasts using rest periods during bioreactor culture on collagen-glycosaminoglycan scaffolds.

Osteoblasts respond to mechanical signals which play a key role in the formation of bone however, after extended periods of stimulation they become desensitised. Mechanosensitivity has been shown to be restored by the introduction of resting periods between loadings. The aim of this study was to analyse the effect of rest periods on the response of osteoblast-like cells seeded on collagen-glycosaminoglycan (CG) scaffolds in a flow perfusion bioreactor up to 14 days. Short (10 s) and long (7 h) term rests were incorporated into stimulation patterns. Constructs cultured in the bioreactor had a more homogenous cell distribution albeit with lower cell numbers than the static group. Osteopontin expression was significantly higher on the rest-inserted group than on the steady flow and static control. These results indicate that the insertion of short term rests during flow improves cellular distribution and osteogenic responses on CG constructs cultured in a flow perfusion bioreactor

Parental experiences of end of life care decision-making for children with life-limiting conditions in the paediatric intensive care unit: a qualitative interview study

Objectives To provide an in-depth insight into the experience and perceptions of bereaved parents who have experienced end of life care decision-making for children with life-limiting or life-threatening conditions in the paediatric intensive care unit (PICU). Design An in-depth qualitative interview study with a sample of parents of children with life-limiting or life-threatening conditions who had died in PICU within the previous 12 months. A thematic analysis was conducted on the interview transcripts. Setting A PICU in a large National Health Service (NHS) tertiary children’s hospital in the West Midlands, UK. Participants 17 parents of 11 children who had died in the PICU. Results Five interconnected themes were identified related to end of life care decision-making:(1) parents have significant knowledge and experiences that influence the decision-making process.(2) Trusted relationships with healthcare professionals are key to supporting parents making end of life decisions.(3) Verbal and non-verbal communication with healthcare professionals impacts on the family experience.(4) Engaging with end of life care decision-making can be emotionally overwhelming, but becomes possible if parents reach a ‘place of acceptance’.(5) Families perceive benefits to receiving end of life care for their child in a PICU. Conclusions and implications The death of a child is an intensely emotional experience for all involved. This study adds to the limited evidence base related to parental experiences of end of life care decision-making and provides findings that have international relevance, particularly related to place of care and introduction of end of life care discussions. The expertise and previous experience of parents is highly relevant and should be acknowledged. End of life care decision-making is a complex and nuanced process; the information needs and preferences of each family are individual and need to be understood by the professionals involved in their care

A Search for Ultra-High Energy Counterparts to Gamma-Ray Bursts

A small air shower array operating over many years has been used to search for ultra-high energy (UHE) gamma radiation ($\geq 50$ TeV) associated with gamma-ray bursts (GRBs) detected by the BATSE instrument on the Compton Gamma-Ray Observatory (CGRO). Upper limits for a one minute interval after each burst are presented for seven GRBs located with zenith angles $\theta < 20^{\circ}$. A $4.3\sigma$ excess over background was observed between 10 and 20 minutes following the onset of a GRB on 11 May 1991. The confidence level that this is due to a real effect and not a background fluctuation is 99.8\%. If this effect is real then cosmological models are excluded for this burst because of absorption of UHE gamma rays by the intergalactic radiation fields.Comment: 4 pages LaTeX with one postscript figure. This version does not use kluwer.sty and will allow automatic postscript generatio

What's the point of knowing how?

Why is it useful to talk and think about knowledge-how? Using Edward Craig’s discussion of the function of the concepts of knowledge and knowledge-how as a jumping off point, this paper argues that considering this question can offer us new angles on the debate about knowledge-how. We consider two candidate functions for the concept of knowledge-how: pooling capacities, and mutual reliance. Craig makes the case for pooling capacities, which connects knowledge-how to our need to pool practical capacities. I argue that the evidence is much more equivocal. My suggested diagnosis is that the concept of knowledge-how plays both functions, meaning that the concept of knowledge-how is inconsistent, and that the debate about knowledge-how is at least partly a metalinguistic negotiation. In closing, I suggest a way to revise the philosophical concept of knowledge how

CARMA Large Area Star Formation Survey: Observational Analysis of Filaments in the Serpens South Molecular Cloud

We present the N2H+(J=1-0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey (CLASSy). The observations cover 250 square arcminutes and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km/s, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N2H+ emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two or three quasi-parallel N2H+ filaments comprise a single observed dust continuum filament. The difference between the dust and gas filament widths casts doubt on Herschel ability to resolve the Serpens South filaments. Some molecular filaments show velocity gradients along their major axis, and two are characterized by a steep velocity gradient in the direction perpendicular to the filament axis. The observed velocity gradient along one of these filaments was previously postulated as evidence for mass infall toward the central cluster, but these kind of gradients can be interpreted as projection of large-scale turbulence.Comment: 12 pages, 4 figures, published in ApJL (July 2014

The Algebraic Bethe Ansatz and Tensor Networks

We describe the Algebraic Bethe Ansatz for the spin-1/2 XXX and XXZ Heisenberg chains with open and periodic boundary conditions in terms of tensor networks. These Bethe eigenstates have the structure of Matrix Product States with a conserved number of down-spins. The tensor network formulation suggestes possible extensions of the Algebraic Bethe Ansatz to two dimensions

Implementation of Lean Principles in a Food Manufacturing Company

Lean is a powerful tool, which can bring significant benefit to manufacturing industries by creating value through reduction of waste. Although the lean concept has become very popular in mass production industries such as the automotive industry, more recently the concept has been adopted in different batch processing industries and service sectors. The application of lean tools into the food processing industry has not received the same level of attention compared to the traditional manufacturing industries. The paper focuses on implementation of lean tools in a food manufacturing company in UK. The company produces diverse ranges of meat-free and dairy-free food products such as vegetable burgers, sausages, cutlets etc., and supply to the major supermarket chains in UK. In general, the typical manufacturing cycle includes raw material preparation, cooking, mixing, forming into a desired shape, coating with a crumb mixture, and frying. Finally, the products are frozen and then packaged. First, lean tools and lean practices in food manufacturing industries have been briefly presented. The implementation of lean into the company started with reviewing the products, manufacturing processes, technical facilities, and process flow charts. Key areas have been identified to achieve tangible benefits by implementing lean tools such as waste elimination, 5S, single minute exchanges of dies (SMED), Andon system, visual management, work standardisation etc. The results have been presented in the form of a case study. The paper concludes that lean tools can be successfully implemented in a food manufacturing company to improve production efficiency, to improve product quality, and to reduce production cost by reducing waste and adding value. The information presented will be of interest to general food manufacturers and in particular to frozen food manufacturers