Addition of Synthetic Biomaterials to Deproteinized Bovine Bone Mineral (DBBM) for Bone Augmentation—A Preclinical In Vivo Study

(1) Aim: To investigate the effect of synthetic bone substitutes, α-tricalcium phosphate (α-TCP) or bi-layered biphasic calcium-phosphate (BBCP) combined with deproteinized bovine bone mineral (DBBM), on bone formation. (2) Methods: Thirty critical size defects were randomly treated with the following five different treatment modalities: (1) negative control (NC, empty), (2) DBBM, (3) α-TCP + DBBM (1:1), (4) BBCP 3%HA/97%α-TCP + DBBM (1:1), and (5) BBCP 6%HA/94%α-TCP + DBBM (1:1). The samples, at four weeks post-surgery, were investigated by micro-CT and histological analysis. (3) Results: A similar level of new bone formation was demonstrated in the DBBM with α-TCP bone substitute groups when compared to the negative control by histomorphometry. DBBM alone showed significantly lower new bone area than the negative control (p = 0.0252). In contrast to DBBM, the micro-CT analysis revealed resorption of the α-TCP + DBBM, BBCP 3%HA/97%α-TCP + DBBM and BBCP 6%HA/94%α-TCP + DBBM, as evidenced by a decrease of material density (p = 0.0083, p = 0.0050 and p = 0.0191, respectively), without changing their volume. (4) Conclusions: New bone formation was evident in all defects augmented with biomaterials, proving the osteoconductive properties of the tested material combinations. There was little impact of the HA coating degree on α-TCP in bone augmentation potential and material resorption for four weeks when mixed with DBBM.     

Investigation of surface and near-surface effects on hydrogen desorption kinetics of MgH2

Desorption of hydrogen atoms from the (110) surface of rutile magnesium hydride (MgH₂) was investigated using density functional theory (DFT) and pseudopotential method. System was represented by (110) (2×2) slab MgH₂ supercell with 12 atomic layers along the z-axis. The H-desorption was modeled by the successive release of the four two-fold bonded H atoms from the (110) surface of MgH₂. Dependence of the H-desorption energy on number and configuration of remaining surface hydrogen atoms has been determined. The features of the H atoms diffusion from the bulk towards the surface have been investigated, too. The results suggest that decrease in number of surface H atoms generally lowers the H-desorption energy in each desorption step and that both the H–H and the Mg–H interatomic interactions strongly influence the H-desorption process. The hydrogen vacancy formation energy in the first three sub-surface layers also exhibits a pronounced dependence on concentration. These findings lead to the conclusion that tendency of the MgH₂ (110) surface to preserve a maximum possible surface H concentration in its most stable configuration is the limiting factor for the H-desorption kinetics. In principle, the obtained results allow us to determine preferred paths of surface and sub-surface H-diffusion for a wide range of H concentrations and the principle features of the MgH₂ dehydrogenation process, at least for the H-rich region. Being rather comprehensive, the approach is applicable for other metal hydrides, as well.     

Facteur de couplage phase-amplitude des diodes lasers avec absorbant saturable

The phase-amplitude coupling factor (α-factor) is one of the fundamental parameters of semiconductor lasers. We show that this factor can be evaluated by time-resolved spectroscopic measurements in pulsed regime. Experiments are carried out with injectionseeded single-mode GaAs lasers whose active stripe includes regions of saturable absorption made by ion implantation. We show that the measured pulse downchirp is proportional to pulse energy. The downchirp amplitude is found to approach four laser cavity intermode spacings at the highest energies. Correspondingly, the ±-values can be five times higher than those reported to date in litterature. High a-values are confirmed in pulse compression experiments. Several mechanisms are proposed to interprete these new results.     

Determination of As(III) and As(V) in oilseeds by chronopotentiometric stripping analysis: development of a method

Chronopotentiometric stripping analysis (CSA) was used for selective determination of As(III) and As(V) in different oilseeds. After the optimization of experimental parameters an appropriate procedure for sample pretreatment was developed. A detection limit of 2 microg/dm3 for As(III) was obtained with an electrolysis time of 600 s. This method was used for arsenic determination in sunflower, pumpkin, and flax seed, as well as for soy flakes and almond.     

Application of the Cascade-Correlation network to the classification of circularly scanned images

This paper describes an application of the Cascade-Correlation (CC) network to pattern recognition. The pattern recognition task was to simulate an automatic vision inspection system that had to properly classify five different objects. The feature vectors were extracted from 2D images of circularly scanned images and used as inputs for a neural network that was then trained to classify an unknown presented object. The results show that the CC network is viable tool in pattern recognition tasks. It is able to classify partially occluded objects with high accuracy, and to considerably improve classification of noisy images based on simple histogram trimming preprocessing.     

Improved Adhesion, Growth and Maturation of Vascular Smooth Muscle Cells on Polyethylene Grafted with Bioactive Molecules and Carbon Particles

High-density polyethylene (PE) foils were modified by an Ar⁺ plasma discharge and subsequent grafting with biomolecules, namely glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C) or BSA and C (BSA + C). As revealed by atomic force microscopy (AFM), goniometry and Rutherford Backscattering Spectroscopy (RBS), the surface chemical structure and surface morphology of PE changed dramatically after plasma treatment. The contact angle decreased for the samples treated by plasma, mainly in relation to the formation of oxygen structures during plasma irradiation. A further decrease in the contact angle was obvious after glycine and PEG grafting. The increase in oxygen concentration after glycine and PEG grafting proved that the two molecules were chemically linked to the plasma-activated surface. Plasma treatment led to ablation of the PE surface layer, thus the surface morphology was changed and the surface roughness was increased. The materials were then seeded with vascular smooth muscle cells (VSMC) derived from rat aorta and incubated in a DMEM medium with fetal bovine serum. Generally, the cells adhered and grew better on modified rather than on unmodified PE samples. Immunofluorescence showed that focal adhesion plaques containing talin, vinculin and paxillin were most apparent in cells on PE grafted with PEG or BSA + C, and the fibres containing α-actin, β-actin or SM1 and SM2 myosins were thicker, more numerous and more brightly stained in the cells on all modified PE samples than on pristine PE. An enzyme-linked immunosorbent assay (ELISA) revealed increased concentrations of focal adhesion proteins talin and vinculin and also a cytoskeletal protein β-actin in cells on PE modified with BSA + C. A contractile protein α-actin was increased in cells on PE grafted with PEG or Gly. These results showed that PE activated with plasma and subsequently grafted with bioactive molecules and colloidal C particles, especially with PEG and BSA + C, promotes the adhesion, proliferation and phenotypic maturation of VSMC.     

Solids flow pattern in gas-flowing solids-fixed bed contactors. Part I: Experimental

An experimental investigation of the solids flow pattern in gas-flowing solids-fixed bed contactors is presented. The apparatus and procedures for determining the dynamic and static solids holdups, solids residence time distribution and the extent and rate of the exchange between particles in the static and dynamic solids holdup are described in detail.Experiments were performed in a bench scale system, containing a column (diameter ) packed with glass beads of 16 mm in diameter packed up to the height of 0.8 m. Tracer experiments with a step input in flowing solids phase were used for determining the residence time distribution and exchange between particles. Fine solids (spheres with mean diameter of ) of two different colors (all other properties being the same) were used in the tracer experiments to determine the residence time distribution and the exchange between static and dynamic solids holdup. In both types of experiments, the response curves have been obtained via color analysis of digital photos. All experiments have been repeated at different operating conditions, with a broad variation of solids mass flux and gas velocity, and reproducibility at set conditions was checked.The obtained experimental results are discussed and the observed important characteristics of the solids flow pattern are outlined. The effects of the solids flux and gas velocity on the solids flow pattern are presented and analyzed.     

The effect of composition of a polymeric coating on the biofilm formation of bacteria and filamentous fungi

Functionality of polymeric coating, especially in terms of anti-corrosive properties and stability, can be negatively influenced by formation of either bacterial or fungal biofilm on its surface. Herein, the epoxy-ester resin based polymeric coating was filled with pigments (natural silicon dioxide diatomite, natural wollastonite, tungstate and molybdate). Pigments was modified by conducting polymers (polyaniline phosphate, polypyrrole phosphate, poly(p-phenylenediamine) phosphate and ZnFe₂O₄). Impact of modified pigments on the surface energy and formation of biofilm were tested. The use of various biofilm forming species of both the bacteria and fungi filled a knowledge gap about their behavior on polymeric coatings.     

System performance analysis of cooperative multihop relaying network applying approximation to dual‐hop relaying network

In this paper, the closed‐form expressions for outage probability, channel capacity, and average symbol error probability are derived for amplify‐and‐forward multihop relay network. Based on approximation of multihop relay by dual‐hop relay systems, the analytical expressions are obtained for the case when maximal ratio combining technique is employed at each relay while destination node uses selection combining technique. The impact of system and channel parameters on the system performances is investigated, and numerical results are graphically presented. The derived analytical expressions are verified by numerical simulation.