325 research outputs found
Bio-based electrospun fibers for wound healing
Being designated to protect other tissues, skin is the first and largest human body organ to be injured and for this reason, it is accredited with a high capacity for self-repairing. However, in the case of profound lesions or large surface loss, the natural wound healing process may be ineffective or insufficient, leading to detrimental and painful conditions that require repair adjuvants and tissue substitutes. In addition to the conventional wound care options, biodegradable polymers, both synthetic and biologic origin, are gaining increased importance for their high biocompatibility, biodegradation, and bioactive properties, such as antimicrobial, immunomodulatory, cell proliferative, and angiogenic. To create a microenvironment suitable for the healing process, a key property is the ability of a polymer to be spun into submicrometric fibers (e.g., via electrospinning), since they mimic the fibrous extracellular matrix and can support neo- tissue growth. A number of biodegradable polymers used in the biomedical sector comply with the definition of bio-based polymers (known also as biopolymers), which are recently being used in other industrial sectors for reducing the material and energy impact on the environment, as they are derived from renewable biological resources. In this review, after a description of the fundamental concepts of wound healing, with emphasis on advanced wound dressings, the recent developments of bio-based natural and synthetic electrospun structures for efficient wound healing applications are highlighted and discussed. This review aims to improve awareness on the use of bio-based polymers in medical devices
Immunomodulatory activity of electrospun polyhydroxyalkanoate fiber scaffolds incorporating olive leaf extract
Olive tree is a well-known source of polyphenols. We prepared an olive leaf extract (OLE) and characterized it via high performance liquid chromatography (HPLC) analysis. OLE was blended with different polyhydroxyalkanoates (PHAs), namely, poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) and polyhydroxybutyrate/poly(hydroxyoctanoate-co-hydroxydecanoate) (PHB/PHOHD), to produce fiber meshes via electrospinning: OLE/PHBV and OLE/ (PHB/PHOHD), respectively. An 80–90% (w/w%) release of the main polyphenols from the OLE/PHA fibers occurred in 24 h, with a burst release in the first 30 min. OLE and the produced fiber meshes were assayed using human dermal keratinocytes (HaCaT cells) to evaluate the expression of a panel of cytokines involved in the inflammatory process and innate immune response, such as the antimicrobial peptide human beta defensin 2 (HBD-2). Fibers containing OLE were able to decrease the expression of the proinflammatory cytokines at 6 h up to 24 h. All the PHA fibers allowed an early downregulation of the pro-inflammatory cytokines in 6 h, which is suggestive of a strong anti-inflammatory activity exerted by PHA fibers. Differently from pure OLE, PHB/PHOHD fibers (both with and without OLE) upregulated the expression of HBD-2. Our results showed that PHA fiber meshes are suitable in decreasing pro-inflammatory cytokines and the incorporation of OLE may enable indirect antibac-terial properties, which is essential in wound healing and tissue regeneration
Poly(Vinyl alcohol)/gelatin scaffolds allow regeneration of nasal tissues
Need for regeneration and repair of nasal tissues occurs as a consequence of several pathologies affecting the nose, including, but not limited to infective diseases, traumas and tumor resections. A platform for nasal tissue regeneration was set up using poly(vinyl alcohol)/gelatin sponges with 20%–30% (w/w) gelatin content to be used as scaffolds, for their intrinsic hydrophilic, cell adhesive and shape recovery properties. We propose mesodermal progenitor cells (MPCs) isolated from the bone marrow as a unique stem cell source for obtaining different connective tissues of the nose, including vascular tissue. Finally, epithelial cell immune response to these scaffolds was assessed in vitro in an environment containing inflammatory molecules. The results showed that mesenchymal stromal cells (MSCs) deriving from MPCs could be used to differentiate into cartilage and fibrous tissue; whereas, in combination with endothelial cells still deriving from MPCs, into pre-vascularized bone. Finally, the scaffold did not significantly alter the epithelial cell response to inflammatory insults derived from interaction with bacterial molecules
ArgoNeuT and the Neutrino-Argon Charged Current Quasi-Elastic Cross Section
ArgoNeuT, a Liquid Argon Time Projection Chamber in the NuMI beamline at
Fermilab, has recently collected thousands of neutrino and anti-neutrino events
between 0.1 and 10 GeV. The experiment will, among other things, measure the
cross section of the neutrino and anti-neutrino Charged Current Quasi-Elastic
interaction and analyze the vertex activity associated with such events. These
topics are discussed along with ArgoNeuT's automated reconstruction software,
currently capable of fully reconstructing the muon and finding the event vertex
in neutrino interactions.Comment: 6 pages, 4 figures, presented at the International Nuclear Physics
Conference, Vancouver, Canada, July 4-9, 2010, to be published in Journal of
Physics: Conference Series (JPCS
Universidad en América Latina, transdisciplina y redes de investigación colaborativas
The higher education system distributes its core functions in multiple areas, but without a doubt, they are recognized and important within the academic world some such as teaching, research, extension, the social projection, the development of talent, among others according to the strategic definitions and priorities of the education, science, technology and innovation system in each country. Currently, is rethinks approach to these activities from updated outlooks, subject to realities and emerging issues of context, prioritizing processes pooled between researchers and transdisciplinary networks. In the last two decades, research in Latin America has been organized around networks cooperative and innovative, that is, in order to promote the achievement of theoretical results or in practice, this being an important dynamic axis in the production of knowledge. In this context, are inserted needs of development social, economic, political, to the know popular and to the production scientific, that not only presented from them different looks of knowledge and experiences, but also from several logical of interpretation, unveiling so, them practices socializing that must be addressed taking into account their differences and contradictions to be exceeded of way inclusive, global and plural. It is essential then, a science to the service of the society and in collaboration among peers, to boost relations solidary, plural, with collective learning, indigenous and interdisciplinary. The present dissertation aims to reveal the university practice from collaborative, interdisciplinary, research through the work of networks of research and academic. The method facilitates the literature review and constructive perspective enables the necessary dialogic between groups of researchers and complex networks. It is concluded that evidence of some experiences of research networks, privilege complex action from different realities and joint solutions.El sistema de educación superior distribuye sus funciones medulares en múltiples áreas, pero sin lugar a dudas, son reconocidas e importantes dentro del mundo académico algunas como la docencia, la investigación, la extensión, la proyección social, el desarrollo de talento, entre otras, según las definiciones estratégicas y prioridades del sistema de educación, ciencia, tecnología e innovación establecidas en cada país. En la actualidad, se replantea el abordaje de estas actividades desde perspectivas actualizadas, sujetas a realidades y problemas emergentes del contexto, priorizando procesos mancomunados entre investigadores y redes transdisciplinarias. En las últimas dos décadas, la investigación en América Latina se ha organizado en torno a redes científicas, cooperativas e innovadoras, esto es, con el fin de favorecer la consecución de resultados teóricos o en la praxis, siendo este un importante eje dinamizador en la producción del conocimiento. En este contexto, se insertan necesidades de desarrollo social, económico, político, al saber popular y a la producción científica, que no solo presentan desde las diversas miradas de conocimiento y experiencias, sino también desde varias lógicas de interpretación, develando así, las prácticas socializadoras que deben ser abordadas teniendo en cuenta sus diferencias y contradicciones para ser superadas de manera incluyente, global y plural. Es indispensable entonces, una ciencia para el servicio de las sociedades y en colaboración entre pares, para impulsar relaciones solidarias, plurales, con aprendizajes colectivos, autóctonos y transdisciplinares. La presente disertación, tiene como objetivo develar la práctica universitaria desde la investigación colaborativa, transdisciplinaria, a través del trabajo de redes de investigación y académicas. El método facilita la revisión bibliográfica y la perspectiva constructiva permite establecer la dialógica necesaria entre grupos de investigadores y redes complejas. Se concluye que la evidencia de algunas experiencias de redes de investigación, privilegian la acción compleja desde realidades diversas y soluciones conjuntas
Energy-Spread Preservation and High Efficiency in a Plasma-Wakefield Accelerator
Energy-efficient plasma-wakefield acceleration of particle bunches with low energy spread is a promising path to realizing compact free-electron lasers and particle colliders. High efficiency and low energy spread can be achieved simultaneously by strong beam loading of plasma wakefields when accelerating bunches with carefully tailored current profiles [M. Tzoufras et al., Phys. Rev. Lett. 101, 145002 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.145002]. We experimentally demonstrate such optimal beam loading in a nonlinear electron-driven plasma accelerator. Bunches with an initial energy of 1 GeV were accelerated by 45 MeV with an energy-transfer efficiency of (42±4)% at a gradient of 1.3 GV/m while preserving per-mille energy spreads with full charge coupling, demonstrating wakefield flattening at the few-percent level
The FLASHForward Facility at DESY
The FLASHForward project at DESY is a pioneering plasma-wakefield
acceleration experiment that aims to produce, in a few centimetres of ionised
hydrogen, beams with energy of order GeV that are of quality sufficient to be
used in a free-electron laser. The plasma wave will be driven by high-current
density electron beams from the FLASH linear accelerator and will explore both
external and internal witness-beam injection techniques. The plasma is created
by ionising a gas in a gas cell with a multi-TW laser system, which can also be
used to provide optical diagnostics of the plasma and electron beams due to the
<30 fs synchronisation between the laser and the driving electron beam. The
operation parameters of the experiment are discussed, as well as the scientific
program.Comment: 19 pages, 9 figure
Possible Origin of Fermion Chirality and Gut Structure From Extra Dimensions
The fundamental chiral nature of the observed quarks and leptons and the
emergence of the gauge group itself are most puzzling aspects of the standard
model. Starting from general considerations of topological properties of gauge
field configurations in higher space-time dimensions, it is shown that the
existence of non-trivial structures in ten dimensions would determine a class
of models corresponding to a grand unified GUT structure with complex fermion
representations with respect to . The
discussion is carried out within the framework of string theories with
characteristic energy scales below the Planck mass. Avoidance of topological
obstructions upon continuous deformation of field configurations leads to
global chiral symmetry breaking of the underlying fundamental theory, imposes
rigorous restrictions on the structure of the vacuum and space-time itself and
determines uniquely the gauge structure and matter content.Comment: final version to appear in Phys. Rev.
Cosmological anti-deSitter space-times and time-dependent AdS/CFT correspondence
We study classes of five-dimensional cosmological solutions with negative
curvature, which are obtained from static solutions by an exchange of a spatial
and temporal coordinate, and in some cases by an analytic continuation. Such
solutions provide a suitable laboratory to address the time-dependent AdS/CFT
correspondence. For a specific example we address in detail the calculation of
the boundary stress-energy and the Wilson line and find disagreement with the
standard AdS/CFT correspondence. We trace these discrepancies to the
time-dependent effects, such as particle creation, which we further study for
specific backgrounds. We also identify specific time-dependent backgrounds that
reproduce the correct conformal anomaly. For such backgrounds the calculation
of the Wilson line in the adiabatic approximation indicates only a Coulomb
repulsion.Comment: LaTeX file, 47 pages, discussion is extended, version to appear in
PR
A high transformer ratio scheme for PITZ PWFA experiments
In the field of plasma wakefield acceleration (PWFA) sig-nificant progress has been made throughout the recent years.However, an important issue in building plasma based ac-celerators that provide particle bunches suitable for userapplications will be a high transformer ratio, i.e. the ra-tio between maximum accelerating field in the witness andmaximum decelerating fields in the driver bunch. The trans-former ratio for symmetrical bunches in an overdense plasmais naturally limited to 2. Theory and simulations show thatthis limit can be exceeded using asymmetrical bunches. Ex-perimentally this was proven in RF-structures, but not inPWFA. To study transformer ratios above this limit in thelinear regime of a plasma wake, an experimental schemetailored to the unique capabilities of the Photoinjector TestFacility at DESY Zeuthen site (PITZ), a 25-MeV electronaccelerator, is being investigated. The numerical simula-tions of beam transport and plasma wakefields, as well aspreparatory studies on the photocathode laser system andplasma sources are presented
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