Bioactive glass scaffolds for bone tissue engineering: state of the art and future perspectives

The repair and regeneration of large bone defects resulting from disease or trauma remains a significant clinical challenge. Bioactive glass has appealing characteristics as a scaffold material for bone tissue engineering, but the application of glass scaffolds for the repair of load-bearing bone defects is often limited by their low mechanical strength and fracture toughness. This paper provides an overview of recent developments in the fabrication and mechanical properties of bioactive glass scaffolds. The review reveals the fact that mechanical strength is not a real limiting factor in the use of bioactive glass scaffolds for bone repair, an observation not often recognized by most researchers and clinicians. Scaffolds with compressive strengths comparable to those of trabecular and cortical bones have been produced by a variety of methods. The current limitations of bioactive glass scaffolds include their low fracture toughness (low resistance to fracture) and limited mechanical reliability, which have so far received little attention. Future research directions should include the development of strong and tough bioactive glass scaffolds, and their evaluation in unloaded and load-bearing bone defects in animal models.     

The preparation of TiO2–nitrogen doped by calcination of TiO2·xH2O under ammonia atmosphere for visible light photocatalysis

The investigation on incorporating nitrogen group into titanium dioxide in order to obtain powdered visible light-active photocatalysts is presented. The industrial hydrated amorphous titanium dioxide (TiO₂·xH₂O) obtained directly from sulphate technology installation was modified by heat treatment at temperatures of 100–800 °C for 4 h in an ammonia atmosphere. The photocatalysts were characterized by UV–VIS–DR and XRD techniques. The UV–VIS–DR spectra of the modified catalysts exhibited an additional maximum in the VIS region (, ) which may be due to the presence of nitrogen in TiO₂ structure. On the basis of XRD analysis it can be supposed that the presence of nitrogen does not have any influence on the transformation temperature of anatase to rutile. The photocatalytic activity of the modified photocatalysts was determined on the basis of decomposition rate of phenol and azo-dye (Reactive Red 198) under visible light irradiation. The highest rate of phenol degradation was obtained for catalysts calcinated at 700 °C (6.55%), and the highest rate of dye decomposition was found for catalysts calcinated at 500 and 600 °C (ca. 40–45%). The nitrogen doping during calcination under ammonia atmosphere is a very promising way of preparation of photocatalysts which could have a practical application in water treatment system under broader solar light spectrum.     

Oxidized lipoproteins including HDL and their lipid peroxidation products inhibit TNF-alpha secretion by THP-1 human macrophages

It has been established that oxidized LDL (ox-LDL) modifies cytokine secretion by macrophages, for example, by reducing tumor necrosis factor alpha (TNF-(alpha) m-RNA. However, little is known about the effects of oxidized high density lipoprotein (ox-HDL). This study reports the effects of ox-HDL subfractions 2 and 3 (ox-HDL2, ox-HDL3) compared with that of ox-LDL and some products of oxidation (hydroperoxides and aldehydes) on the secretion of TNF-alpha from THP-1 human monocytes derived macrophages in vitro. HDL2, HDL3 and LDL were oxidized with 10 microM Cu++ for 12 h and/or 24 h. Native and oxidized HDL and LDL were incubated for 24 h with macrophages with or without LPS (10 ng/ml) after which TNF-alpha secretion was measured in the culture medium. Lipid hydroperoxides and apolar aldehydes were also incubated with the cells for 2 h following which the medium was replaced and TNF-alpha secretion measured after a further 22 h of incubation. An inhibition of TNF-alpha by ox-HDL2 (p < .05), ox-HDL3 (p < .05) and ox-LDL (p < .05) from THP-1 macrophages was observed in the presence and absence of LPS. This inhibition remained the same after incubation with ox-HDL 12 h and 24 h. Hydroperoxides of linoleic acid did not modify TNF-alpha secretion by cells while five out of eight aldehydes analyzed (2,4-heptadienal, hexanal, 2-nonenal, 2-octenal, 2,4-decadienal) inhibited TNF-alpha secretion (p < .05). These findings demonstrate that ox-HDL, and some of its lipid peroxidation products, plays a role in the modulation of the inflammatory response by macrophages as previously observed for ox-LDL.     

A method for the definition of integrity constraints in object-oriented conceptual modeling languages

We propose a new method that eases the definition of integrity constraints in object-oriented conceptual modeling languages. The essence of the method is to represent constraints by special operations that we call constraint operations. The formal specification of these operations is the definition of the corresponding constraints. The method allows the specialization of constraints and the definition of exceptions. The main application of the method is for static constraints. However, a variant of it can also be applied for creation-time and deletion-time constraints, two particular classes of temporal constraints. The method can be adapted to any object-oriented language, and we show its adaptation to the UML. We also show that our method has several advantages over existing methods.     

Microstructure of (Fe0.2Co0.8)0.8(Fe2.38Co0.62O4): A Magnetic Oxidation Resistant Composite Formed by Coprecipitation

The metal–ferrite composite (Fe_0.2Co_0.8)_0.8(Fe_2.38Co_0.62O₄) has been studied by X-ray diffractometry measurements and high-resolution transmission electron microscopy. Spinel ferrite occurs in highly crystalline domains 100–150 nm in size, and the iron–cobalt alloy occurs in smaller and less-crystalline domains (10–20 nm). Both phases are heterogeneous in composition. The metal is embedded in the spinel phase, located near the edges, and overlaid by a poorly crystallized layer or misshapen regions containing small spinel crystals and amorphous phases. By annealing under vacuum up to 800°C, the misshapen regions disappear and the size of the metallic regions increases. The concentration of iron in the metallic regions decreases and their structure changes to face-centered cubic, while the spinel becomes enriched in iron.     

Detecting evoked potentials with SVD- and ICA-based statistical models.

In the functional diagnostics of human sensor systems, the analysis of stimulus responses embedded in an electroencephalogram (EEG), e.g. evoked potentials (EPs), is of high relevance for an objective electrophysiological assessment. The aim of this work is to detect weak EPs from highly contaminated signal traces. In principle this can be done using methods of spatiotemporal signal processing, which simultaneously increase the weak SNR (signal-to-noise ratio). However, methods based on any a priori knowledge of spatial or temporal properties as well as the propagation speed and direction are not applicable. Models with adjustable signal properties similar to real cortical activity are necessary for the development and evaluation of new methods of spatiotemporal signal processing. A model is needed which can be used in forward- and inverse-projection calculations. This study aims to develop a signal generator of the background EEG activity with embedded EPs of fully adjustable signal parameters. The study also compares the results of modeled signal analysis by known methods for signal decomposition, SVD (singular value decomposition) and ICA (independent component analysis).     

Use of bipartite graphs as a notation for data bases

Studies on computing systems making use of data bases have produced various notations to represent “schemata” of relations between data. These notations use graphs both as a tool to describe features relevant to applications and as an effective method of teaching. However, a critical limit may be the fact that they handle in different ways the concepts relevant to data and those relevant to programs. As a matter of fact, the ways of handling concepts relevant to programs are often unsuitable. For example, note that an answer to easy requests may require fairly complex programs. This paper introduces a uniform notation both for data-base schemata and for a class of application programs. This is accomplished by associating a suitable interpretation with bipartite graphs.     

The phenomena of the interaction of Nd3+-glass laser light with 6H13 alloy steel

The variation in the physical and chemical structure of the 6H13 alloy steel irradiated by laser light have been investigated. The phenomena of the capillary waves within the power density range (4.3×10⁹<P<13.8×10⁹) watt/m² have been observed and the hydrodynamic parameters of alloy steel have been determinated. The nature of the laser light interaction with metal is discussed in electronmicroscopy and X-rays analysis terms.     

Cognitive–behavioral stress management decreases dysphoric mood and herpes simplex virus-Type 2 antibody titers in symptomatic HIV-seropositive gay men.

This study tested the effects of a 10-week group cognitive–behavioral stress management (CBSM) intervention on mood and immunologic parameters in HIV-seropositive gay men whose disease had progressed to a symptomatic stage. Men were randomized to either CBSM or a modified waiting-list control group. The CBSM intervention significantly decreased self-reported dysphoria, anxiety, and total distress. Individuals who practiced relaxation more consistently had significantly greater drops in dysphoria. The intervention also decreased herpes simplex virus-Type 2 (HSV-2) immunoglobulin G antibody titers. The control group showed no significant changes in either mood or antibody titers. Individual difference analyses revealed that decreases in dysphoria significantly predicted lower HSV-2 antibody titers by the end of the 10-week period. Neither group displayed changes in HSV-Type I antibody titers or in CD4+ or CD8+ cell numbers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)