Human femur fracture by mechanical compression: Towards the repeatability of bone fracture acquisition.

The increase in life expectancy combined with greater bone fragility over the years is causing a rise in the bone fracture cases. Femur fractures are the most important due to their high mortality rate. This multidisciplinary work is carried out in this context and focuses on the experimental reproduction of human femur fractures by compression. We describe a sequence of steps supervised by orthopaedic surgeons for the correct arrangement of specimens on the system set up to perform the experiment. The device applies force by compression until the human bone is fractured. All tests performed have been monitored and evaluated from different knowledge perspectives. The results obtained have demonstrated the repeatability of the fracture type in a controlled environment as well as identifying the main features involved in this process. In addition, the fractured bones have been digitized to analyze the fracture zone to recreate and evaluate future simulations.

A platelet derived growth factor delivery system for bone regeneration.

platelet derived growth factor (PDGF) was formulated in a calcium phosphate/biodegradable polymer system for local and controlled delivery to enhance bone regeneration. Implants with a porosity of 67 %, composed of hydroxyapatite, PLGA microspheres and Pluronic(®), were obtained by compression. An increase in porosity with time was expected due to Pluronic(®) dissolution and PLGA microsphere degradation. In vivo PDGF release and tissue distribution were monitored after system implantation into femurs of rabbits using (125)I-PDGF. Most of the PDGF was released within approximately 5 days and remained located around the implantation site with negligible systemic exposure. Compared with the reference groups, an important enhancement of bone regeneration was found with doses of 600 and 1,200 ng of PDGF, although no histological differences were observed between the two doses. In conclusion, the elaborated system exhibited good biocompatibility and offered a physiologically relevant PDGF profile that enhances bone formation compared to the non-treated bone defect.

A new approach to the ferritin iron core growth: influence of the H/L ratio on the core shape.

An electron microscopy study, in combination with modeling and image simulation, of four different reconstituted ferritin samples: recombinant human H and L homopolymers, and H and L heteropolymers of native L-subunit-rich horse spleen and H-subunit-rich human heart ferritins, points out the existence of a correlation between iron core shape and protein shell.

From synthetic to natural nanoparticles: monitoring the biodegradation of SPIO (P904) into ferritin by electron microscopy.

A strong focus on Superparamagnetic Iron Oxide Nanoparticles (SPIOs) has been appreciated recently especially for their use in Magnetic Resonance Imaging (MRI). However, some questions are being raised over these particles due to their long-term toxicity related to the production of toxic free iron during their biodegradation. Here we show by Electron Microscopy how SPIOs (P904) (Guerbet, Paris) are degraded after they are taken up by macrophages, so that iron from the SPIO core is progressively incorporated into the iron-storing protein ferritin (a nontoxic form of iron).

Fibrous MnO2 nanoparticles with (2 x 2) tunnel structures. Catalytic activity in the total oxidation of volatile organic compounds.

Manganese oxides having 2 x 2 tunnel structures (cryptomelanes) have been synthesized by a milling method in order to test their efficiency as catalysts for the abatement of volatile organic compounds, using toluene as probe molecule. These materials present excellent textural properties, arising from the nanofiber morphology and were active for toluene total oxidation. DRIFTS of the adsorbed phase allow proposing the role of lattice oxygen in the catalytic reaction.

3 D characterization of gold nanoparticles supported on heavy metal oxide catalysts by HAADF-STEM electron tomography.

Living on the edge: Three-dimensional reconstructions from electron tomography data recorded from Au/Ce(0.50)Tb(0.12)Zr(0.38)O(2-x) catalysts show that gold nanoparticles (see picture; yellow) are preferentially located on stepped facets and nanocrystal boundaries. An epitaxial relationship between the metal and support plays a key role in the structural stabilization of the gold nanoparticles.

A novel catalyst for synthesis of styrene: carbon nanofibers immobilized on activated carbon.

Carbon NanoFibers (CNFs) with hierarchically structure have been immobilized onto Activated Carbon (AC) by impregnation with an aqueous solution of Fe(CH3COO)2, reduction and subsequent chemical vapor decomposition of ethylene. The morphology of the CNFs can be modulated by adjusting the pH of the Fe(CH3COO)2 solution used for impregnating the AC. A stable yield of 35% in the oxidative dehydrogenation of ethylbenzene to styrene was obtained at a temperature of 673 K, around 200 K lower than the current industrial process. The immobilized CNFs on AC catalysts combine the catalytic properties of the carbon nanofibers and the suprastructure of the AC host. The final material is an easy to handle active catalyst, with an open structure of immobilized CNFs avoiding the pressure drop problem, which is typically observed for fine powder forms of CNFs. The immobilized CNFs on AC are attractive for gas-phase fixed-bed industrial applications.

Adhesion forces between protein layers studied by means of atomic force microscopy.

Adhesion forces between different protein layers adsorbed on different substrates in aqueous media have been measured by means of an atomic force microscope using the colloid probe technique. The effects of the loading force, the salt concentration and pH of the medium, and the electrolyte type on the strength, the pull-off distance, and the separation energy of such adhesion forces have been analyzed in depth. Two very different proteins (bovine serum albumin and apoferritin) and two dissimilar substrates (silica and polystyrene) were used in the experiments. The results clearly point out a very important contribution of the electrostatic interactions in the adhesion between protein layers.

Existence of hydration forces in the interaction between apoferritin molecules adsorbed on silica surfaces.

The atomic force microscope, together with the colloid probe technique, has become a very useful instrument to measure interaction forces between two surfaces. Its potential has been exploited in this work to study the interaction between protein (apoferritin) layers adsorbed on silica surfaces and to analyze the effect of the medium conditions (pH, salt concentration, salt type) on such interactions. It has been observed that the interaction at low salt concentrations is dominated by electrical double layer (at large distances) and steric forces (at short distances), the latter being due to compression of the protein layers. The DLVO theory fits these experimental data quite well. However, a non-DLVO repulsive interaction, prior to contact of the protein layers, is observed at high salt concentration above the isoelectric point of the protein. This behavior could be explained if the presence of hydration forces in the system is assumed. The inclusion of a hydration term in the DLVO theory (extended DLVO theory) gives rise to a better agreement between the theoretical fits and the experimental results. These results seem to suggest that the hydration forces play a very important role in the stability of the proteins in the physiological media.

Hydration forces between silica surfaces: experimental data and predictions from different theories.

Silica is a very interesting system that has been thoroughly studied in the last decades. One of the most outstanding characteristics of silica suspensions is their stability in solutions at high salt concentrations. In addition to that, measurements of direct-interaction forces between silica surfaces, obtained by different authors by means of surface force apparatus or atomic force microscope (AFM), reveal the existence of a strong repulsive interaction at short distances (below 2 nm) that decays exponentially. These results cannot be explained in terms of the classical Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory, which only considers two types of forces: the electrical double-layer repulsion and the London-van der Waals attraction. Although there is a controversy about the origin of the short-range repulsive force, the existence of a structured layer of water molecules at the silica surface is the most accepted explanation for it. The overlap of structured water layers of different surfaces leads to repulsive forces, which are known as hydration forces. This assumption is based on the very hydrophilic nature of silica. Different theories have been developed in order to reproduce the exponentially decaying behavior (as a function of the separation distance) of the hydration forces. Different mechanisms for the formation of the structured water layer around the silica surfaces are considered by each theory. By the aid of an AFM and the colloid probe technique, the interaction forces between silica surfaces have been measured directly at different pH values and salt concentrations. The results confirm the presence of the short-range repulsion at any experimental condition (even at high salt concentration). A comparison between the experimental data and theoretical fits obtained from different theories has been performed in order to elucidate the nature of this non-DLVO repulsive force.

[Judicial claims for medical malpractice]. / Las reclamaciones judiciales por mala práxis médica.

BACKGROUND: Physicians' legal liability regarding malpractice has reached a previously unknown importance in Spain. This paper brings forward some statistical data on judicial claims presented by patients and their relatives. METHODS: The whole of resolutions of the First and Second Court of the Supreme Court were collected between 1870 and 1992. In Madrid, the number of lawsuits in proceedings were obtained from a sample of the Courts at the Plaza de Castilla in April 1990, and figures on legal complaints, accusations and demands were obtained through consultations at the Medical College. RESULTS: The great majority of verdicts, both in Civil and Penal Jurisprudence, correspond to the last 13 years. In Madrid, the average of penal cases in proceedings was 3.8 per Court, and an appreciable increase of claims can be noticed, with an annual rate of about 0.4 per 100 physicians. CONCLUSIONS: Appealing to Justice in order to accuse a practitioner for presumed malpractice is no longer an unusual event. Various reasons contribute in this respect. However, other reasons exist to consider the Spanish situation very far from the level in the United States of America.