Antibiotic-free antibacterial hydrogels for wound healing applications

Over the past decades, bacterial cellulose (BC) has attracted great interest as a wound dressing thanks to its innate hydrogel-like structure and high biocompatibility. However, the lack of antibacterial features of cellulose poses some limitations to its use, especially in the context of increasing antimicrobial resistance. In this work, various strategies were explored for the development of novel BC-based wound healing devices that can efficiently inhibit bacterial proliferation. First, the production of BC by fermentation of Gluconacetobacter xylinus and its purification from the biomass were optimised. The material was characterised with respect to its morphological, chemical and mechanical properties. The introduction of antibacterial functional groups was then investigated by ring-opening reaction of two epoxides with the hydroxyl groups of glucose in wet basic conditions. Biological tests evidenced that the functionalisation caused a decrease in the bacterial cell count of about 50% for Staphylococcus aureus and Escherichia coli in the first 24 hours, whereas cell viability of over 90% was observed for keratinocytes for up to 6 days. An alternative method for the modification of bacterial cellulose was also studied to improve the antibacterial efficiency. The functionalisation was carried out in anhydrous conditions in two steps, i.e. acrylation by Schotten-Baumann reaction and thiol-ene Michael type addition. Once again, the material was chemically and mechanically characterised, and biological studies were carried out: >99% reduction in the bacterial cell count was observed for both S. aureus and E. coli, with high cytocompatibility towards keratinocytes at all time-points. Finally, the fabrication of Cu-chitosan/BC composites was investigated. SEM images showed no evident phase separation between the polymers, whereas mechanical assays evidenced an increase in the tensile strength and elastic modulus as compared to plain chitosan. An optimal copper concentration threshold was then identified that ensures low cytotoxicity towards keratinocytes and antibacterial activity upon direct contact of over 90% for both S. aureus and E. coli. Overall, the materials developed showed promising results in terms of biological performance to tackle the ever-growing problem of antimicrobial resistance

Smart random walkers: the cost of knowing the path

In this work we study the problem of targeting signals in networks using entropy information measurements to quantify the cost of targeting. We introduce a penalization rule that imposes a restriction to the long paths and therefore focus the signal to the target. By this scheme we go continuously from fully random walkers to walkers biased to the target. We found that the optimal degree of penalization is mainly determined by the topology of the network. By analyzing several examples, we have found that a small amount of penalization reduces considerably the typical walk length, and from this we conclude that a network can be efficiently navigated with restricted information.Comment: 9 pages, 11 figure

Integrable discretizations of the spin Ruijsenaars-Schneider models

Integrable discretizations are introduced for the rational and hyperbolic spin Ruijsenaars--Schneider models. These discrete dynamical systems are demonstrated to belong to the same integrable hierarchies as their continuous--time counterparts. Explicit solutions are obtained for arbitrary flows of the hierarchies, including the discrete time ones.Comment: LaTeX fil

Memory and long-range correlations in chess games

In this paper we report the existence of long-range memory in the opening moves of a chronologically ordered set of chess games using an extensive chess database. We used two mapping rules to build discrete time series and analyzed them using two methods for detecting long-range correlations; rescaled range analysis and detrented fluctuation analysis. We found that long-range memory is related to the level of the players. When the database is filtered according to player levels we found differences in the persistence of the different subsets. For high level players, correlations are stronger at long time scales; whereas in intermediate and low level players they reach the maximum value at shorter time scales. This can be interpreted as a signature of the different strategies used by players with different levels of expertise. These results are robust against the assignation rules and the method employed in the analysis of the time series.Comment: 12 pages, 5 figures. Published in Physica

Construction Curriculum Developed for Continuation Schools

This paper will discuss a curriculum, an introduction to construction fundamentals, that was built for continuation schools. A continuation school is a school for at-risk youth in which it provides programs of empowering, inspiration and outlet. Five modules were created that focus on different sections of the construction industry. These modules consist of Site Safety, Untroduction to Basic Math, Introduction to Power Tools, Introduction to Construction Drawings, and Basic Employable Skills. Each module will consist of a ten-question quiz and presentation. Two homework assignments were also created. One homework assignment for site safety which requires students to identify if the provided image looks safe or not and to explain why. The second homework assignment for the employable skills module which requires students to create a well-organized resume. Through these modules students will have the ability to learn from different sections of the construction industry and apply the learning objectives. Students will be provided a perspective of the construction industry and be inspired to pursue a career/future within this sector. Even if the students do not decide to go into the construction industry, they will still basic construction skills and professionalism

Innovation and Nested Preferential Growth in Chess Playing Behavior

Complexity develops via the incorporation of innovative properties. Chess is one of the most complex strategy games, where expert contenders exercise decision making by imitating old games or introducing innovations. In this work, we study innovation in chess by analyzing how different move sequences are played at the population level. It is found that the probability of exploring a new or innovative move decreases as a power law with the frequency of the preceding move sequence. Chess players also exploit already known move sequences according to their frequencies, following a preferential growth mechanism. Furthermore, innovation in chess exhibits Heaps' law suggesting similarities with the process of vocabulary growth. We propose a robust generative mechanism based on nested Yule-Simon preferential growth processes that reproduces the empirical observations. These results, supporting the self-similar nature of innovations in chess are important in the context of decision making in a competitive scenario, and extend the scope of relevant findings recently discovered regarding the emergence of Zipf's law in chess.Comment: 8 pages, 4 figures, accepted for publication in Europhysics Letters (EPL

Isogrid design handbook

Handbook has been published which presents information needed for design of isogrid triangular integral-stiffened structures. It develops equations, methods, and graphs to handle wide variety of loadings, materials, and geometry. Handbook is divided into seven sections. Handbook may be used by marine and civil engineers and by students and designers without access to computers