Limits of small functors

For a small category K enriched over a suitable monoidal category V, the free completion of K under colimits is the presheaf category [K*,V]. If K is large, its free completion under colimits is the V-category PK of small presheaves on K, where a presheaf is small if it is a left Kan extension of some presheaf with small domain. We study the existence of limits and of monoidal closed structures on PK.Comment: 17 page

Food-grade Pickering stabilisation of foams by in situ hydrophobisation of calcium carbonate particles

© 2016 Elsevier Ltd The aim of this study was to investigate the possibility of stabilising foam bubbles in water by adsorption of calcium carbonate (CaCO 3 ) particles. Because CaCO 3 is hydrophilic and not surface-active, particles were hydrophobised in situ with several emulsifiers. The used emulsifiers were food-grade and negatively charged at the pH employed. The effect of particle addition on foamability and foam stability of solutions containing either β-lactoglobulin, sodium caseinate, Quillaja, sodium dodecanoate (SD) or sodium stearoyl-2-lactylate (SSL) was studied. It was found that the ability of the emulsifiers to induce surface activity such that the particles are able to adsorb to the air-water interface is related to their structure. The structure needs to consist of a well-defined hydrophobic part and a charged part. Large emulsifiers with a complex structure, such as β-lactoglobulin, sodium caseinate and Quillaja, were able to partially hydrophobise the particles but were not able to act synergistically with the particles to increase the foam stability. Low molecular weight emulsifiers, however, consisting of a single tail with one charged group, such as SD and SSL, adsorbed at the particle surface rendering the particles partially hydrophobic such that they adsorb to the air-water interface. In a subsequent investigation, the pH was changed to a value typical for food products (pH 6–7) and the addition of milk salts on the foamability and foam stability was assessed. Based on these results, the use of food-grade CaCO 3 particles hydrophobised in situ with food-grade surfactants (SD or SSL) to prepare ultra-stable aqueous foams is demonstrated

Multi-walled microchannels: free-standing porous silicon membranes for use in µTAS

Electrochemically formed porous silicon (PS) can be released from the bulk silicon substrate by underetching at increased current density. Using this technique, two types of channels containing free-standing layers of PS were constructed, which were failed multi-walled microchannels (MW µCs). They can be used in devices like microsieves, microbatteries, and porous electrodes. Two types of MWµC were made: the 'conventional' version, consisting of two or more coaxially constructed microchannels separated by a suspended PS membrane, and the buried variety, where a PS membrane is suspended halfway in an etched cavity surrounded by silicon nitride walls. The latter is more robust. The pore size of the PS was measured using transmission electron microscopy and field emission gun scanning electron microscopy (FEGSEM) and found to be of the order of 7 n

Enhanced 2-categories and limits for lax morphisms

We study limits in 2-categories whose objects are categories with extra structure and whose morphisms are functors preserving the structure only up to a coherent comparison map, which may or may not be required to be invertible. This is done using the framework of 2-monads. In order to characterize the limits which exist in this context, we need to consider also the functors which do strictly preserve the extra structure. We show how such a 2-category of weak morphisms which is "enhanced", by specifying which of these weak morphisms are actually strict, can be thought of as category enriched over a particular base cartesian closed category F. We give a complete characterization, in terms of F-enriched category theory, of the limits which exist in such 2-categories of categories with extra structure.Comment: 77 pages; v2 minor changes only, to appear in Advance

We \u27ll never Let Our Old Flag Fall

https://digitalcommons.library.umaine.edu/mmb-vp/2635/thumbnail.jp

A colimit decomposition for homotopy algebras in Cat

Badzioch showed that in the category of simplicial sets each homotopy algebra of a Lawvere theory is weakly equivalent to a strict algebra. In seeking to extend this result to other contexts Rosicky observed a key point to be that each homotopy colimit in simplicial sets admits a decomposition into a homotopy sifted colimit of finite coproducts, and asked the author whether a similar decomposition holds in the 2-category of categories Cat. Our purpose in the present paper is to show that this is the case.Comment: Some notation changed; small amount of exposition added in intr

Sprouty1 regulates reversible quiescence of a self-renewing adult muscle stem cell pool during regeneration.

Satellite cells are skeletal muscle stem cells capable of self-renewal and differentiation after transplantation, but whether they contribute to endogenous muscle fiber repair has been unclear. The transcription factor Pax7 marks satellite cells and is critical for establishing the adult satellite cell pool. By using a lineage tracing approach, we show that after injury, quiescent adult Pax7(+) cells enter the cell cycle; a subpopulation returns to quiescence to replenish the satellite cell compartment, while others contribute to muscle fiber formation. We demonstrate that Sprouty1 (Spry1), a receptor tyrosine kinase signaling inhibitor, is expressed in quiescent Pax7(+) satellite cells in uninjured muscle, downregulated in proliferating myogenic cells after injury, and reinduced as Pax7(+) cells re-enter quiescence. We show that Spry1 is required for the return to quiescence and homeostasis of the satellite cell pool during repair. Our results therefore define a role for Spry1 in adult muscle stem cell biology and tissue repair

Transition to professional social work practice: The first three years

This article presents the findings of a longitudinal research project that followed the employ-ment outcomes of one cohort of Bachelor of Social Work graduates for three years. Prior to graduation, students receive professional preparation that develops their ability to critically engage with theory and practice. Following graduation, newly qualified social workers require quality induction, supervision and other workload management strategies to support the transition to social work practice. The development of this study was fuelled by political criticism of social work education. Additionally, there was a desire to track the employment outcomes of the graduates and understand what supported their transition to competent professional practice. The findings fit within a five-year longitudinal research project that follows three separate graduate cohorts each for three years to seek and compare participants’ experiences for their first three years post-qualification. An anonymous, semi-structured, on-line survey was used to provide both quantitative and qualitative data. By the second year of practice, these respond-ents were taking on the workload of an experienced social work practitioner with widely varied levels of support. By the end of their third year in practice, they reported that they had found little opportunity to apply their critical analytical academic skills to consider the wider social system in practice. Further, the graduates’ confidence in their cultural competencies also gradually decreased over the three-year period

Mechanisms of enhanced non-viral gene delivery to human mesenchymal stem cells induced by glucocorticoid priming

Background: Because of unique roles in wound healing, trophic tissue support, immunomodulation, differentiation ability, and immune privileged status, human mesenchymal stem cells (hMSCs), which can be easily derived from many adult tissues (e.g. bone marrow (BMSCs) and adipose tissue (AMSCs)), are under intense study for the applications of cell and gene therapeutics, as well as tissue engineering and regenerative medicine1. Genetic modification of hMSCs could allow for targeted delivery of transgenic therapeutic factors or genetically-guided differentiation. Non-viral gene delivery (i.e. cationic polymer- and lipid-mediated) is safer and more flexible than immunogenic and mutagenic viral vectors2, but it is less effective, especially in hMSCs (i.e. maximum 10-30% transfection)3. As part of an approach to understand molecular mechanisms of non-viral gene delivery4 and ‘prime’ cells to be more receptive to transfection5, our lab recently demonstrated that transgene expression from lipofected hMSCs can be increased about 10-fold by priming cells, 30 mins before plasmid DNA (pDNA) transfection, with 100 nM dexamethasone (DEX), a glucocorticoid (Gc) drug, relative to EtOH vehicle control (VC)6. This work investigates the mechanisms by which Gc priming enhances non-viral gene delivery, which are currently unknown. Studies provide insights into the biological processes of Gc priming and transfection to inform future gene delivery technologies, and characterize a simple protocol to significantly enhance non-viral gene delivery of therapeutic transgenes for future clinical applications. Please click Additional Files below to see the full abstract