Biodegradable zinc-based materials with a polymer coating designed for biomedical applications

Over the last decades, biodegradable metals have gained popularity for biomedical applications due to their ability to assist in tissue healing. These materials degrade in vivo, while the corrosion products formed are either absorbed or excreted by the body, and no further surgical intervention is required for removal. Intensive research has been carried out mainly on degradable biomaterials based on Mg and Fe. In recent years, zinc-based degradable biomaterials have been explored by the biomedical community for their intrinsic physiological relevance, desirable biocompatibility, intermediate degradation rate, tuneable mechanical properties and pro-regeneration properties. Since pure Zn does not exhibit sufficient mechanical properties for orthopedic applications, various Zn alloys with better properties are being developed. In this work, the combined effect of minor Fe addition to Zn and a polyethyleneglycol (PEG) coating on the surface morphology, degradation, cytotoxicity and mechanical properties of Zn-based materials was studied. There are several studies regarding the influence of the production of Zn alloys, but the effect of polymer coating on the properties of Zn-based materials has not been reported yet. A positive effect of Fe addition and polymer coating on the degradation rate and mechanical properties was observed. However, a reduction in biocompatibility was also detected.     

Structural investigation of bismuth borate glass ceramics containing gadolinium ions by X-ray diffraction and FTIR spectroscopy

X-ray diffraction and FTIR spectroscopy measurements have been employed to investigate the xGd₂O₃ · (100 − x)[2Bi₂O₃ · B₂O₃] glass ceramics system, with 0  ≤ x ≤ 20 mol%. Heat treatment of glass samples at 625 °C for 24 h led to the formation of two crystalline phases. One crystalline phase is for the sample without gadolinium ions which belongs to the cubic system and another one is for the sample containing 20 mol% Gd₂O₃ which is orthorhombic with two unit cell parameters very close to each other. Between x = 0 mol% and x = 20 mol% there is a mixture of these crystalline phases. FTIR spectroscopy data suggest that the gadolinium ions play the network modifier role in the studied glasses. These data show that the glass structure consists of the BiO₃, BiO₆, BO₃, and BO₄ structural units, and the conversion among these units mainly depends on the Gd₂O₃ content.     

Condensation of a Quasi-one Dimensional Gas Within a Single Wall Carbon Nanotube

Gases adsorbed within carbon nanotubes display novel phases associated with reduced dimensionality. A quasi-one dimensional (1D) environment is realized for sufficiently small tube radii such that adsorbed atoms are constrained to move along the nanotube axis. We show that, in this quasi-1D regime, a condensation transition arises from adsorption-induced tube expansion.     

Structural and electronic properties of tellurite glasses

The structural properties of some tellurite glasses were investigated by FT-IR spectroscopy, density measurements, and quantum chemical calculations. Main results reveal that the ratio TeO₄/TeO₃ is found to decrease in the order V₂O₅ > B₂O₃ > P₂O₅. For borate–tellurate glasses, the Van Hove singularities corresponding to Te 5s orbital-derived states are cleft suggesting that there are strong tellurium–oxygen interactions. On the other hand, a strong effect of TeO₂ on the vitreous B₂O₃ network is also demonstrated by FT-IR spectrum. This effect yields the apparition of small peaks in the region ranges between 800 and 1600 cm⁻¹ and probably the partial crystallization of the sample. Its spectral features are due to the B–O bond stretching of [BO₄] and [BO₃] structural units. The quantum chemical data obtained by us show that phosphate–tellurite and vanado–tellurate glasses can behave as semiconductors, whereas borate–tellurite glasses as insulators because the gap between the valence and conduction bands is >3 eV.     

A Data Mining Approach for Detecting Higher-Level Clones in Software

Code clones are similar program structures recurring in variant forms in software system(s). Several techniques have been proposed to detect similar code fragments in software, so-called simple clones. Identification and subsequent unification of simple clones is beneficial in software maintenance. Even further gains can be obtained by elevating the level of code clone analysis. We observed that recurring patterns of simple clones often indicate the presence of interesting higher-level similarities that we call structural clones. Structural clones show a bigger picture of similarity situation than simple clones alone. Being logical groups of simple clones, structural clones alleviate the problem of huge number of clones typically reported by simple clone detection tools, a problem that is often dealt with postdetection visualization techniques. Detection of structural clones can help in understanding the design of the system for better maintenance and in reengineering for reuse, among other uses. In this paper, we propose a technique to detect some useful types of structural clones. The novelty of our approach includes the formulation of the structural clone concept and the application of data mining techniques to detect these higher-level similarities. We describe a tool called Clone Miner that implements our proposed technique. We assess the usefulness and scalability of the proposed techniques via several case studies. We discuss various usage scenarios to demonstrate in what ways the knowledge of structural clones adds value to the analysis based on simple clones alone.     

The influence of phosphorous pentoxide on the phase composition and formation of Portland clinker

The influence of phosphorous pentoxide (P₂O₅) on the phase composition and formation of Portland clinker was studied in laboratory conditions. Phosphorous pentoxide in the form of calcium phosphate was added to common cement-making raw meal in graded quantities up to 5 wt.%. The raw meal properties were studied by thermal analysis. The development of clinker formation by burning for periods ranging from 20 s to 30 min in a special semi-automatic oven with a manipulator was followed using light optical microscopy. The phase composition of clinkers burnt to equilibrium was quantified by the optical point counting method. The entry of P₂O₅ into clinker minerals was determined by electron microprobe analyses. The laboratory tests show that at 0.7 wt.% of P₂O₅ in the clinker the alite (Ca₃SiO₅) content decreases and belite (Ca₂SiO₄) content increases. At a P₂O₅ content of 4.5 wt.% alite formation was totally blocked and the resulting clinker contained free lime in equilibrium with belite.     

N-doped carbon nanotubes for liquid-phase CC bond hydrogenation

The introduction of foreign elements inside the channel of carbon nanotubes could lead to a significant modification of the intrinsic properties of these nanomaterials. Nitrogen atoms entering in the graphene sheets as substitute of carbon could modify in a large extend the acido-basic properties and also adsorption of the nanotube itself. Depending on the synthesis conditions, i.e. nature of the N-source, temperature and C-to-N atomic ratio, various N-doped carbon nanotubes can be synthesized with different surface properties. The aim of the present work is to report the synthesis of N-doped CNTs using a common nitrogen source precursor namely ammonia (NH₃) with C₂H₆ as carbon source. The as-synthesized N-CNTs were subsequently employed as catalyst support in the liquid-phase hydrogenation of cinnamaldehyde using palladium as an active phase.     

Polymer-derived microcellular SiOC foams with magnetic functionality

SiOC microcellular ceramic foams possessing soft-ferromagnetic properties were produced from a pre-ceramic polymer, poly-methyl-methacrylate microbeads (PMMA) (used as sacrificial pore formers) and iron silicide micro-powders (as functional filler). The interactions between the matrix and the filler were studied as a function of the amount of powders introduced and the pyrolysis temperature. Magnetic and mechanical properties were also investigated.