Evolution of Fields in a Second Order Phase Transition

We analyse the evolution of scalar and gauge fields during a second order phase transition using a Langevin equation approach. We show that topological defects formed during the phase transition are stable to thermal fluctuations. Our method allows the field evolution to be followed throughout the phase transition, for both expanding and non-expanding Universes. The results verify the Kibble mechanism for defect formation during phase transitions.Comment: 12 pages of text plus 17 diagrams available on request, DAMTP 94-8

Strong Decays of Strange Quarkonia

In this paper we evaluate strong decay amplitudes and partial widths of strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give numerical results for all energetically allowed open-flavor two-body decay modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and 1F multiplets, comprising strong decays of a total of 43 resonances into 525 two-body modes, with 891 numerically evaluated amplitudes. This set of resonances includes all strange qqbar states with allowed strong decays expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical results for all amplitudes present in each decay mode. We also discuss the status of the associated experimental candidates, and note which states and decay modes would be especially interesting for future experimental study at hadronic, e+e- and photoproduction facilities. These results should also be useful in distinguishing conventional quark model mesons from exotica such as glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table

First Observation of the Σc∗+\Sigma_{c}^{*+} Baryon and a New Measurement of the Σc+\Sigma_{c}^{+} Mass

Using data recorded with the CLEO II and CLEO II.V detector configurations at the Cornell Electron Storage Rings, we report the first observation and mass measurement of the $\Sigma_c^{*+}$ charmed baryon, and an updated measurement of the mass of the $\Sigma_c^+$ baryon. We find $M(\Sigma_c^{*+})-M(\Lambda_c^+)$= 231.0 +- 1.1 +- 2.0 MeV, and $M(\Sigma_c^{+})-M(\Lambda_c^+)$= 166.4 +- 0.2 +- 0.3 MeV, where the errors are statistical and systematic respectively.Comment: 8 pages postscript, also available through http://w4.lns.cornell.edu/public/CLN

Large-scale unit commitment under uncertainty: an updated literature survey

The Unit Commitment problem in energy management aims at finding the optimal production schedule of a set of generation units, while meeting various system-wide constraints. It has always been a large-scale, non-convex, difficult problem, especially in view of the fact that, due to operational requirements, it has to be solved in an unreasonably small time for its size. Recently, growing renewable energy shares have strongly increased the level of uncertainty in the system, making the (ideal) Unit Commitment model a large-scale, non-convex and uncertain (stochastic, robust, chance-constrained) program. We provide a survey of the literature on methods for the Uncertain Unit Commitment problem, in all its variants. We start with a review of the main contributions on solution methods for the deterministic versions of the problem, focussing on those based on mathematical programming techniques that are more relevant for the uncertain versions of the problem. We then present and categorize the approaches to the latter, while providing entry points to the relevant literature on optimization under uncertainty. This is an updated version of the paper "Large-scale Unit Commitment under uncertainty: a literature survey" that appeared in 4OR 13(2), 115--171 (2015); this version has over 170 more citations, most of which appeared in the last three years, proving how fast the literature on uncertain Unit Commitment evolves, and therefore the interest in this subject

Advanced Materials to Enhance Central Nervous System Tissue Modeling and Cell Therapy

The progressively deeper understanding of mechanisms underlying stem cell fate decisions has enabled parallel advances in basic biology-such as the generation of organoid models that can further ones basic understanding of human development and disease-and in clinical translation-including stem cell based therapies to treat human disease. Both of these applications rely on tight control of the stem cell microenvironment to properly modulate cell fate, and materials that can be engineered to interface with cells in a controlled and tunable manner have therefore emerged as valuable tools for guiding stem cell growth and differentiation. With a focus on the central nervous system (CNS), a broad range of material solutions that have been engineered to overcome various hurdles in constructing advanced organoid models and developing effective stem cell therapeutics is reviewed. Finally, regulatory aspects of combined material-cell approaches for CNS therapies are considered

Hydrogel-based milliwell arrays for standardized and scalable retinal organoid cultures.

The development of improved methods to culture retinal organoids is relevant for the investigation of mechanisms of retinal development under pathophysiological conditions, for screening of neuroprotective compounds, and for providing a cellular source for clinical transplantation. We report a tissue-engineering approach to accelerate and standardize the production of retinal organoids by culturing mouse embryonic stem cells (mESC) in optimal physico-chemical microenvironments. Arrayed round-bottom milliwells composed of biomimetic hydrogels, combined with an optimized medium formulation, promoted the rapid generation of retina-like tissue from mESC aggregates in a highly efficient and stereotypical manner: ∼93% of the aggregates contained retinal organoid structures. 26 day-old retinal organoids were composed of ∼80% of photoreceptors, of which ∼22% are GNAT2-positive cones, an important and rare sensory cell type that is difficult to study in rodent models. The compartmentalization of retinal organoids into predefined locations on a two-dimensional array not only allowed us to derive almost all aggregates into retinal organoids, but also to reliably capture the dynamics of individual organoids, an advantageous requirement for high-throughput experimentation. Our improved retinal organoid culture system should be useful for applications that require scalability and single-organoid traceability

Homeostatic mini-intestines through scaffold-guided organoid morphogenesis.

Epithelial organoids, such as those derived from stem cells of the intestine, have great potential for modelling tissue and disease biology <sup>1-4</sup> . However, the approaches that are used at present to derive these organoids in three-dimensional matrices <sup>5,6</sup> result in stochastically developing tissues with a closed, cystic architecture that restricts lifespan and size, limits experimental manipulation and prohibits homeostasis. Here, by using tissue engineering and the intrinsic self-organization properties of cells, we induce intestinal stem cells to form tube-shaped epithelia with an accessible lumen and a similar spatial arrangement of crypt- and villus-like domains to that in vivo. When connected to an external pumping system, the mini-gut tubes are perfusable; this allows the continuous removal of dead cells to prolong tissue lifespan by several weeks, and also enables the tubes to be colonized with microorganisms for modelling host-microorganism interactions. The mini-intestines include rare, specialized cell types that are seldom found in conventional organoids. They retain key physiological hallmarks of the intestine and have a notable capacity to regenerate. Our concept for extrinsically guiding the self-organization of stem cells into functional organoids-on-a-chip is broadly applicable and will enable the attainment of more physiologically relevant organoid shapes, sizes and functions