Search results for "bone"
showing 10 items of 2629 documents
Efecto de la temperatura sobre el crecimiento, desarrollo y supervivencia de pollos de carbonero común Parus major en un entorno de cambio climático
2016
En una población aviar, la supervivencia en el nido viene determinada por la interacción de factores bióticos y abióticos, entre los cuales la temperatura ambiental puede jugar un papel crucial sobre el devenir de los polluelos. Asimismo, la condición de los pollos en el momento de abandonar el nido (determinada por todos aquellos factores que afectan a su desarrollo previo) y el momento en que éste se produce, son dos de los aspectos más influyentes sobre la supervivencia durante el primer año de vida, periodo marcado por una alta tasa de mortalidad. En esta Tesis Doctoral se analizan algunos de los factores que pueden afectar al crecimiento, desarrollo y supervivencia de los pollos de car…
Stability and marginal bone loss in implants placed using piezoelectric osteotomy versus conventional drilling: systematic review and meta-analysis.
2021
Background The main objective of this systematic review was to compare primary and secondary implant stability between placement with piezoelectric osteotomy and conventional drilling, comparing marginal bone losses as a secondary objective. Material and Methods An electronic search was conducted using PubMed (MEDLINE), Scopus, and Cochrane Library (Wiley) databases, besides a manual search. Results A total of 153 articles were retrieved, 39 from Pubmed, 44 from Scopus, and 70 from the Cochrane Library. After removing duplicates, 112 articles (1 from the manual search) were screened, and 9 were finally selected for qualitative and statistical analyses. Conclusions Piezoelectric surgery is a…
Detection of poly(methylmethacrylate) wear particles in capsule tissue surrounding endoprotheses by pyrolysis gas chromatography
1982
Pyrolysis gas chromatography (PGC) is used to detect polymer wear particles in capsule tissue surrounding endoprotheses implanted with poly(methylmethacrylate) as bone cement. The method allows the detection of the polymer incorporated in tissue even in the range of 1 weight%.
Prediction of the retention in reversed-phase liquid chromatography using solute-mobile phase-stationary phase polarity parameters.
2002
Abstract A previously reported algorithm, based on the equation: log k=( log k) 0 +p(P N m −P N s ) , that relates the retention in reversed-phase liquid chromatography with solute (p), mobile phase (PmN) and stationary phase (PsN) relative polarity parameters, is improved. The retention data reported by several authors for different sets of compounds, eluted with acetonitrile–water and methanol–water mixtures, are used to test the algorithm and elaborate a database of p values. The methodology is successfully applied to predict the retention using PmN values calculated as PmN=1.00−(2.13ϕ)/(1+1.42ϕ) for acetonitrile–water and PmN=1.00−(1.33ϕ)/(1+0.47ϕ) for methanol–water, ϕ being the organi…
Collagen overglycosylation: a biochemical feature that may contribute to bone quality.
2005
Skeletal ability to resist mechanical stress is determined by bone amount and quality, which relies on macro- and micro-architecture, turnover, bone matrix, and mineralisation; the role of collagen has not been clearly elucidated. Numerous post-translational steps are involved in collagen type I biosynthesis, including residue hydroxylation and glycosylation catalysed by enzymes that work until the protein folds forming the triple helix; therefore, folding rate regulates these processes. Overglycosylated hydroxylysines are poor substrates for epsilon-amino group deamination which initiates cross-link formation. Three clinical conditions associated with fractures may relate collagen overglyc…
Bio-inspired Resorbable Calcium Phosphate-Polymer Nanocomposites for Bone Healing Devices with Controlled Drug Release
2011
In orthopedic research, increasing attention is being paid to bioresorbable composite materials as an attractive alternative to permanent metal bone healing devices. Typical composites consist of a biodegradable polyester matrix loaded with bioactive calcium phosphate ceramic particles (tricalcium phosphate, TCP or hydroxyapatite, HA) added to improve the biological response and mechanical properties of the neat polymer. The mechanical behavior of such particle-reinforced composites, however, falls far short of the expected performance in high-load bearing situations. Replicating some features of nacre—a strong and tough natural nanocomposite with a very high content of brittle inorganic ph…
Influence of the position of two dehydro-amino acids residues in the oligopeptide sequence on the binding ability towards Cu(II) ions
2005
Abstract Studies on the binding ability of bis-dehydro-hexa- and pentapeptides have shown that the hexapeptides bind Cu+2 with similar efficacy as pentapeptides. The increase of distance between two dehydro-amino acid residues in the peptide backbone has no impact on the efficacy in metal ion binding. The type of isomeration [(Z) or (E)] has an influence on the coordination of the metal ion only to the first amide nitrogen.
Structure of bottle brush polymers on surfaces: weak versus strong adsorption.
2011
Large-scale Monte Carlo simulations are presented for a coarse-grained model of cylindrical molecular brushes adsorbed on a flat structureless substrate, varying both the chain length N of the side chains and the backbone chain length N(b). For the case of good solvent conditions, both the cases of weak adsorption (only 10 to 15% of the monomers being bound to the surface) and strong adsorption (~40% of the monomers being bound to the surface, forcing the bottle brush into an almost 2D conformation) are studied. We focus on the scaling of the total linear dimensions of the cylindrical brush with both chain lengths N and N(b), demonstrating a crossover from rod-like behavior (for not very la…
Conformational studies of bottle-brush polymers absorbed on a flat solid surface.
2010
The adsorption of a bottle-brush polymer end-grafted with one chain end of its backbone to a flat substrate surface is studied by Monte Carlo simulation of a coarse-grained model, that previously has been characterized in the bulk, assuming a dilute solution under good solvent conditions. Applying the bond fluctuation model on the simple cubic lattice, we vary the backbone chain length $N_b$ from $N_b=67$ to $N_b = 259$ effective monomeric units, the side chain length $N$ from N=6 to N=48, and the grafting density $\sigma=1$, i.e., parameters that correspond well to the experimentally accessible range. When the adsorption energy strength $\epsilon$ is varied, we find that the adsorption tra…
Inorganic Polymers: Morphogenic Inorganic Biopolymers for Rapid Prototyping Chain
2013
In recent years, considerable progress has been achieved towards the development of customized scaffold materials, in particular for bone tissue engineering and repair, by the introduction of rapid prototyping or solid freeform fabrication techniques. These new fabrication techniques allow to overcome many problems associated with conventional bone implants, such as inadequate external morphology and internal architecture, porosity and interconnectivity, and low reproducibility. However, the applicability of these new techniques is still hampered by the fact that high processing temperature or a postsintering is often required to increase the mechanical stability of the generated scaffold, …