469 research outputs found
Estudio in vitro de la actividad citotóxica de resinas dentales tipo BIS-GMA
Las resinas composites se emplean desde hace varias décadas en distintas aplicaciones
estomatológicas, volviéndose indispensables para lograr una alta calidad en los servicios modernos.
Uno de los monómeros acrílicos más utilizados en estos materiales poliméricos de recubrimiento
es el 2-bis-[p-(2-hidroxi-3-metacriloxipropoxi) fenil] propano, conocido comúnmente como Bis-
GMA. El conocimiento de las interacciones de estos materiales con el sistema biológico es de vital
importancia debido al uso tan difundido de los mismos en la práctica clínica. El comportamiento de
una célula viva en contacto con un material extraño es un problema esencial en las aplicaciones
biomédicas de polímeros sintéticos. Los ensayos in vitro son sistemas muy útiles para la evaluación
de los efectos biológicos de los biomateriales.
En el laboratorio de Inmunofarmacología del INOR se llevó a cabo la evaluación de la
toxicidad de dos resinas dentales tipo Bis-GMA producidas por el Centro de Biomateriales de la
Universidad de La Habana: el Obtudent Fotocurado (FC), resina fotopolimerizable para restauraciones
dentales y el Cubridem Autocurado (AC), sellante dental para fosas y fisuras. Este estudio
forma parte de las evaluaciones preclínicas biológicas de biomateriales y equipos médicos
implantables que se lleva a cabo en Cuba a través de la Red Funcional de Implantología del
Ministerio de Salud Pública. Se aplicó el método de citotoxicidad in vitro descrito por Stanley para
la evaluación toxicológica de materiales dentales. Ambos composites resultaron citotóxicos para
la línea de fibroblastos L929, lo que se corresponde con lo descrito en la literatura para este tipo
de material. Su citotoxicidad se encontró en el rango de la de los análogos comerciales evaluados.Peer Reviewe
A 3-D in vitro co-culture model of mammary gland involution.
Involution is a process whereby the mammary gland undergoes extensive tissue remodelling involving exquisitely coordinated cell death, extracellular matrix degradation and adipose tissue regeneration following the weaning of offspring. These processes are mediated in part through Jak/Stat signalling pathways, which can be deregulated in breast cancer. Synthetic in vitro analogues of the breast could become important tools for studying tumorigenic processes, or as personalized drug discovery platforms and predictors of therapeutic response. Ideally, such models should support 3D neo-tissue formation, so as to recapitulate physiological organ function, and be compatible with high-throughput screening methodologies. We have combined cell lines of epithelial, stromal and immunological origin within engineered porous collagen/hyaluronic acid matrices, demonstrating 3D-specific molecular signatures. Furthermore seeded cells form mammary-like branched tissues, with lobuloalveolar structures that undergo inducible involution phenotypes reminiscent of the native gland under hormonal/cytokine regulation. We confirm that autophagy is mediated within differentiated mammary epithelial cells in a Stat-dependent manner at early time points following the removal of a prolactin stimulus (H/WD). In addition, epithelial cells express markers of an M2 macrophage lineage under H/WD, a process that is attenuated with the introduction of the monocyte/macrophage cell line RAW 264.7. Thus, such 3D models are suitable platforms for studying cell-cell interactions and cell death mechanisms in relation to cancer.This is the accepted manuscript. The final version is available from RSC at http://pubs.rsc.org/en/content/articlehtml/2014/ib/c3ib40257f
Phase Transitions in a Forest-Fire Model
We investigate a forest-fire model with the density of empty sites as control
parameter. The model exhibits three phases, separated by one first-order phase
transition and one 'mixed' phase transition which shows critical behavior on
only one side and hysteresis. The critical behavior is found to be that of the
self-organized critical forest-fire model [B. Drossel and F. Schwabl, Phys.
Rev. Lett. 69, 1629 (1992)], whereas in the adjacent phase one finds the spiral
waves of the Bak et al. forest-fire model [P. Bak, K. Chen and C. Tang, Phys.
Lett. A 147, 297 (1990)]. In the third phase one observes clustering of trees
with the fire burning at the edges of the clusters. The relation between the
density distribution in the spiral state and the percolation threshold is
explained and the implications for stationary states with spiral waves in
arbitrary excitable systems are discussed. Furthermore, we comment on the
possibility of mapping self-organized critical systems onto 'ordinary' critical
systems.Comment: 30 pages RevTeX, 9 PostScript figures (Figs. 1,2,4 are of reduced
quality), to appear in Phys. Rev.
Nuclear Attenuation of high energy two-hadron system in the string model
Nuclear attenuation of the two-hadron system is considered in the string
model. The two-scale model and its improved version with two different choices
of constituent formation time and sets of parameters obtained earlier for the
single hadron attenuation, are used to describe available experimental data for
the -dependence of subleading hadron, whereas satisfactory agreement with
the experimental data has been observed. A model prediction for
-dependence of the nuclear attenuation of the two-hadron system is also
presented.Comment: 8 page
Quasiperiodic Patterns in Boundary-Modulated Excitable Waves
We investigate the impact of the domain shape on wave propagation in
excitable media. Channelled domains with sinusoidal boundaries are considered.
Trains of fronts generated periodically at an extreme of the channel are found
to adopt a quasiperiodic spatial configuration stroboscopically frozen in time.
The phenomenon is studied in a model for the photo-sensitive
Belousov-Zabotinsky reaction, but we give a theoretical derivation of the
spatial return maps prescribing the height and position of the successive
fronts that is valid for arbitrary excitable reaction-diffusion systems.Comment: 4 pages (figures included
Detecting the (Quasi-)Two-Body Decays of Leptons in Short-Baseline Neutrino Oscillation Experiments
Novel detector schemes are proposed for the short-baseline neutrino
experiments of next generation, aimed at exploring the large-
domain of \omutau oscillations in the appearance mode. These schemes emphasize
good spectrometry for charged particles and for electromagnetic showers and
efficient reconstruction of \ypi_gg decays. The basic elements are a sequence
of relatively thin emulsion targets, immersed in magnetic field and
interspersed with electronic trackers, and a fine-grained electromagnetic
calorimeter built of lead glass. These elements act as an integral whole in
reconstructing the electromagnetic showers. This conceptual scheme shows good
performance in identifying the (quasi-)two-body decays by their
characteristic kinematics and in selecting the electronic decays of the .Comment: 34 pages, 8 figure
Application of a laser induced fluorescence model to the numerical simulation of detonation waves in hydrogen-oxygen-diluent mixtures
A laser-induced-fluorescence model has been implemented and used to post-process detonation wave numerical simulation results to allow a direct comparison with previous experimental visualizations of detonations in hydrogen–oxygen–diluent mixtures. The model is first applied to steady one-dimensional simulation results obtained with detailed chemistry. The effects on the fluorescence intensity of the model parameters are examined to explore the dominant processes. The dominant interference process in the experiments carried out to date is the absorption of incident laser light by the high concentration of OH in and behind the reaction zone. The model is then applied to unsteady two-dimensional simulation results obtained with reduced chemical schemes to obtain synthetic PLIF image. The results demonstrate good qualitative agreement between the experimental and calculated laser-induced-fluorescence intensities. The model limitations and the experimental uncertainties are discussed together with a critical evaluation of the modeling approach
Observation of a baryon resonance with positive strangeness in K+ collisions with Xe nuclei
The status of our investigation of low-energy Xe collisions in the Xenon
bubble chamber DIANA is reported. In the charge-exchange reaction the spectrum of effective mass shows a resonant enhancement
with MeV/c and ^24.4\sigma$. The mass and width of the
observed resonance are consistent with expectations for the lightest member of
the anti-decuplet of exotic pentaquark baryons, as predicted in the framework
of the chiral soliton model.Comment: 9 pages, 4 figure
Comparison of Radiation Damage in Lead Tungstate Crystals under Pion and Gamma Irradiation
Studies of the radiation hardness of lead tungstate crystals produced by the
Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of
Ceramics in China have been carried out at IHEP, Protvino. The crystals were
irradiated by a 40-GeV pion beam. After full recovery, the same crystals were
irradiated using a -ray source. The dose rate profiles along
the crystal length were observed to be quite similar. We compare the effects of
the two types of radiation on the crystals light output.Comment: 10 pages, 8 figures, Latex 2e, 28.04.04 - minor grammatical change
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