TEM study of the surface morphology of extracted ZrO2-Al2O3 fibres

The surface morphology and microstructure of a series of melt extracted ZrO₂-Al₂O₃ based fibres (ZA, ZAT and ZAS) have been imaged at the nanometre scale by transmission electron microscopy (TEM) using an advanced Pt/C replica technique. Growth characteristics of ZrO₂, Al₂O₃ and other crystalline phases formed upon heating up to 1550 °C are illustrated and described. Several grain morphologies including spherical and polygonal grains, as well as grains with rounded plate-like growth were observed indicating different active growth mechanisms. ZrO₂ particles on the surface of the fibres were almost spherical with some facetting and rounding of corners. These grains were very fine (< 50 nm) in the ZA and ZAS fibres while they were several microns in size in the ZAT fibres. Al₂O₃ grains were generally much larger (up to several microns) and exhibited two distinct growth morphologies of layered and rhombohedral type. Different grain morphologies of the ZA and ZAS fibres have been correlated to the phases identified by X-ray diffraction.     

Quality traits of wild boar mould-ripened salami manufactured with different selections of meat and fat tissue, and with and without bacterial starter cultures

Quality traits of wild boar mould-ripened salami were assessed in eight batches produced from two different assortments of meat (hind leg vs. shoulder), fat tissue (backfat from domestic pigs vs. fat tissue from wild boar), and with and without addition of a commercial bacterial starter culture. Chemical composition of finished products (day 35) were in compliance with national food codex. Batches produced with a bacterial starter culture were generally preferred by taste panels, had significantly lower concentrations of TBARS (<1.5 mgmalondialdehyde/kg) and peroxide values (POVs) and lower concentrations of cadaverine (<50 mg/kg), histamine (<10 mg/kg) and putrescine (<60 mg/kg). TBARS and POVs were inversely related to sensory preference scores (r(2)=0.84 and 0.88). Batches produced from shoulder muscles contained significantly higher concentrations of cadaverine, histamine and putrescine. TBARS were highest in batches manufactured with fat tissue from wild boars. These findings should be considered when guides to good practice for the manufacture of game meat products are developed.     

Bending buckling behavior of perfect and defective single-walled carbon nanotubes via a structural mechanics model

A structural mechanics model is employed for the investigation of the bending buckling behavior of perfect and defective single-walled carbon nanotubes (SWCNTs). The effects of different types of defects (vacancies and Stone–Wales defects) at various locations on the critical bending buckling moments and curvatures are also studied for zigzag and armchair nanotubes with various aspect ratios (length/diameter). The locations of defects are along the length of the nanotube and around the circumference. Moreover, the results of this structural mechanics model are compared with a finite element model. The simple continuum model, especially, could be adopted to predict the critical buckling moments and curvatures of SWCNTs with large aspect ratio. Finally, the results of the present structural model are compared with those from molecular dynamics (MD) simulation, and there is good agreement between our model and the MD model.     

Influence of calcinated and non calcinated nanobioglass particles on hardness and bioactivity of sol�Cgel-derived TiO2�CSiO2 nano composite coatings on stainless steel substrates

Thick films of calcinated and non calcinated nanobioglass (NBG)-titania composite coatings were prepared on stainless steel substrates by alkoxide sol-gel process. Dip-coating method was used for the films preparation. The morphology, structure and composition of the nano composite films were evaluated using environmental scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscope. The SEM investigation results showed that prepared thick NBG-titania films are smooth and free of macrocracking, fracture or flaking. The grain size of these films was uniform and nano scale (50-60 nm) which confirmed with TEM. Also FTIR confirmed the presence of Si-O-Si bands on the calcinated NBG-titania films. The hardness of the prepared films (TiO(2)-calcinated NBG and TiO(2)-Non calcinated NBG) was compared by using micro hardness test method. The results verified that the presence of calcinated NBG particles in NBG-titania composite enhanced gradually the mechanical data of the prepared films. The in vitro bioactivity of these films was discussed based on the analysis of the variations of Ca and P concentrations in the simulated body fluid (SBF) and their surface morphologies against immersion time. Surface morphology and Si-O-Si bands were found to be of great importance with respect to the bioactivity of the studied films. The results showed that calcinated NBG-titania films have better bioactivity than non calcinated NBG-titania films.     

Improved surface bioactivity of stainless steel substrates using osteocalcin mimetic peptide

Although stainless steel has a good biocompatibility for most clinical cases, the higher tissue response (bone bonding property) is required in orthopedic field. In this study, to improve bone-bonding ability of stainless steel substrates, a specific sequence of osteocalcin mimetic peptide is used as bioactive coating material to biochemically modify the surface of metallic samples. This sequence consists of thirteen amino acids present in the first helix of osteocalcin is synthesized in amidic form and physically adsorbed on the surface of 316LS (316 low carbon surgical grade) stainless steel substrates. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to characterize the surface of peptide coated and uncoated substrates. The bioactivity and bone bonding ability of coated and uncoated substrates are assessed by level of hydroxyapatite formation, using transmission electron microscopy (TEM), energy-dispersive x-ray (EDS), and scanning electron microscopy (SEM). The pre-osteoblast cell attachment and proliferation are also evaluated by MTT assay. The results show that the surface of coated sample is homogenously covered by the peptide and display a rougher surface relative to uncoated sample. TEM images reveal the formation of plate-like hydroxyapatite crystals in the presence of the peptide and an amorphous calcium phosphate phase without the peptide. Pre-osteoblast cells proliferation is significantly higher on the surface of peptide coated substrate, while cell attachment remains unaffected by the peptide coatings. Pre-osteoblast cells also demonstrate a higher degree of spreading on the surface of coated sample. It is believed that osteocalcin mimetic peptide improve surface bioactivity and promote hydroxyapatite crystal formation may lead to increased mineralization and bone formation on the surface of metallic biomedical devices.     

Nonparametric spectral analysis of wideband spectrum with missing data via sample-and-hold interpolation and deconvolution

Spectral estimation of data sequences with randomly missing samples is considered in this paper. A nonparametric missing-data method is proposed based on interpolation followed by a deconvolution procedure. Sample-and-hold interpolation is considered here. The method is based on the analytic expression of the autocorrelation function of the interpolated data as a linear function of the autocorrelation function of the data to be estimated. Bias and standard deviation of both autocorrelation function and power spectral density are detailed for simulated data based on Monte Carlo analysis. The method is also compared with a fuzzy slotting technique with local normalization and weighting algorithm. Based on the results of these simulations, it is concluded that the performance of the proposed method is better than those of the slotting technique.     

Topographic distribution of visual evoked potentials in optic neuropathy

INTRODUCTION: Digital treatment of electrical signals coming from the central nervous system on stimulation of the optic nerve path offers an objective method for evaluation of visual evoked potentials (VEP) shown graphically on a cerebral map. OBJECTIVE: To evaluate the topographical distribution of VEP in cases of optic neuropathy adding this parameter to the usual parameters of latency and amplitude. MATERIAL AND METHODS: We studied 35 patients with suspected optic neuropathy and normal findings on basic ophthalmological examination, in whom VEP and VEP mapping (VEPM) was done. RESULTS: In 26% of the cases there was no response for evaluation with the usual VEP recording techniques, whilst in those with VEPM this percentage was reduced to 11.5%. In the other cases there was a potential with characteristic distribution in the occipital areas and a maximally positive dipole posteriorly. CONCLUSION: VEPM is an objective method for evaluation of the visual pathway offering better discrimination than the usual VEP in more severe cases of neuropathy.