Biomechanical properties of early keratoconus: Suppressed deformation signal wave

Purpose

To examine the diagnostic validity of different corneal biomechanical parameters for the detection of early keratoconus

Biogenic amines formation in Streptococcus thermophilus isolated from home-made natural yogurt

Twelve different biogenic amines formation in 58 isolates of Streptococcus thermophilus from home-made natural yogurt were investigated in histidine (HDB) and lysine decarboxylase broth (LDB). All S. thermophilus isolates had an ability to produce twelve different biogenic amines in HDB and LDB. Most of the S. thermophilus isolates formed low amounts of histamine (1–50 mg/L) from histidine. Apart from one isolate, S. thermophilus produced tyramine at low (47 isolates) and medium (10 isolates) levels. The amount of each specific biogenic amine produced by S. thermophilus was generally lower than 100 mg L⁻¹. Also, the presence of hdcA gene was investigated using PCR technique and relation between gene and histamine production was conducted in S. thermophilus isolates. This study showed that most of the S. thermophilus isolates have the ability to form biogenic amines, especially histamine, and tyramine, which is an important consideration when selecting strains as starter cultures.     

Equivalence of the Lagrange interpolator for uniformly sampled signals and the scaled binomially windowed shifted sinc function

The maximally flat (MF) fractional delay (FD) filter which is in fact a Lagrange interpolator for uniformly sampled signals, has previously been shown to be equal to the scaled binomially windowed shifted version of the sinc function; the ideal interpolation kernel for band-limited signals. In this paper, another proof for this equivalence is presented. Unlike its counterparts available in the literature, the proof given here is neither strictly algebraic, nor deploys the explicit coefficient formulas of the MFFD filter. It follows a frequency domain approach based on the definition of this filter instead, and aims to provide more insight into the corresponding equivalence.     

Effect of P2O5, B2O3 and PbO on the sinterability of β.quartz solid solution and gahnite glass-ceramics

The effect of P₂O₅, B₂O₃ and PbO additives on the sintering and crystallization behaviour of .quartz solid solution and gahnite glass-ceramics were investigated. According to our results, only the addition of PbO to glasses produces sinterable glass-ceramics containing .quartz solid solution gahnite as the sole crystalline phases, respectively. The nucleation mechanism of the glasses were determined by the Ozawa equation and their activation energy for crystallization were determined by the modified form of the Kissinger, Matusita and Marotta equations. The results indicate that the better sinterability of the lead bearing .q._ss glass-ceramic than the lead free one could be explained by changes of bulk to surface nucleation and increase of its activation energy for crystallization. At the other hand, it could not be observed any differences between the nucleation mechanism and the activation energy for crystallization of the lead bearing and lead free gahnite glass-ceramics. Then the differences in sinterability of the two glass-ceramics could not be explained by comparison of theirs activation energy for crystallization.     

Microfluidic Synthesis of Ultrasmall Chitosan/Graphene Quantum Dots Particles for Intranasal Delivery in Alzheimer's Disease Treatment

Nanoparticles (NPs) based therapies for Alzheimer's disease (AD) attract interest due to their ability to pass across or bypass the blood-brain barrier. Chitosan (CS) NPs or graphene quantum dots (GQDs) are promising drug carriers with excellent physicochemical and electrical properties. The current study proposes the combination of CS and GQDs in ultrasmall NP form not as drug carriers but as theranostic agents for AD. The microfluidic-based synthesis of the CS/GQD NPs with optimized characteristics makes them ideal for transcellular transfer and brain targeting after intranasal (IN) delivery. The NPs have the ability to enter the cytoplasm of C6 glioma cells in vitro and show dose and time-dependent effects on the viability of the cells. IN administration of the NPs to streptozotocin (STZ) induced AD-like models lead to a significant number of entrances of the treated rats to the target arm in the radial arm water maze (RAWM) test. It shows the positive effect of the NPs on the memory recovery of the treated rats. The NPs are detectable in the brain via in vivo bioimaging due to GQDs as diagnostic markers. The noncytotoxic NPs localize in the myelinated axons of hippocampal neurons. They do not affect the clearance of amyloid β (Aβ) plaques at intercellular space. Moreover, they showed no positive impact on the enhancement of MAP2 and NeuN expression as markers of neural regeneration. The memory improvement in treated AD rats may be due to neuroprotection via the anti-inflammation effect and regulation of the brain tissue microenvironment that needs to be studied.     

Sintering of β.q.ss. and gahnite glass-ceramic/silicon carbide composites

The sintering of β.quartz solid solution, β.q._ss., and gahnite glass-ceramic/particulate SiC composites has been studied by two different sintering procedures. In one procedure, the composites were fired above the melting point of the crystalline phase, identified by DTA, at a very high heating rate (800 °C min⁻¹) in air, nitrogen and argon atmospheres, for 1–6 min. It was found that the reduction of ZnO constituent of the glass by SiC particles gives rise to Zn, CO, and SiO gaseous products preventing complete densification of composites. In the other procedure, sintering was done at about crystallization peak temperature of the glass phase, employing a low heating rate (40 °C min⁻¹) in air for 60 min. In this case, the circumferential tensile stress in the glass-ceramic matrix phase, caused by the presence of incompressible SiC particles, retards the densification of the composites. The maximum amount of SiC particles yielding a reasonably dense composite was found to be 9 vol.%.     

Sintering, crystallization and mechanical properties of a gel-cast cordierite glass-ceramic body

Gel-cast bodies based on cordierite glass-ceramics were prepared by sintering route. Effect of monomer and cross-linker values as well as sintering temperatures on bending strength of dried and sintered bodies were investigated. While the bending strength of dried gel-cast bodies was increased with the percentage of the polymers, bending strength of sintered bodies was changed conversely with them. Therefore, it was concluded that the least amount of monomer acrylamid (3 wt.%) and moderate amount of cross-linker (∼0.75 wt.%) guarantees the required dried and fired bending strengths. The optimum sintering temperature was about 1270 °C and specimens that was fired at this temperature showed a maximum bending strength of about 200 MPa.     

Effect of potassium sorbate and sodium benzoate on microbial population and fermentation of black olives

Black olive fermentation characteristics and diffusion of preservatives into olives were evaluated in brines containing 500 ppm potassium sorbate, 1000 ppm sodium benzoate, 500 ppm sodium benzoate + 250 ppm potassium sorbate and no preservative (control). Changes in brine pH, acidity and microbial population (lactic acid bacteria, yeasts, moulds) were followed during fermentation and storage. Results indicated that K‐sorbate when used at 500 ppm concentration in black olive fermentation had a slight stimulatory effect on the growth of lactic acid bacteria. The yeast counts of brines containing 500 ppm K‐sorbate and 1000 ppm Na‐benzoate were lower than for the brine containing 250 ppm K‐sorbate + 500 ppm Na‐benzoate and for the control with no preservative, while mould growth was completely inhibited in all treatments during fermentation. Mould counts stayed below the detection limit (<10 cfu g⁻¹) during 214 days of vacuum‐packaged storage. Yeast counts showed a progressive decline within 28 days of storage and then stayed relatively constant in all treatments thereafter. The level of yeast population was higher in the control sample than in the sample containing both preservatives during storage. The diffusion of Na‐benzoate and K‐sorbate into the olives after equilibrium was 64% and 80% during fermentation respectively. © 1999 Society of Chemical Industry     

Effect of addition of titanium on structural,mechanical and biological properties of 45S5 glass-ceramic

The purpose of the present study was to evaluate the effect of addition of titanium on the structural, mechanical, and biological properties of sol-gel derived 45S5 bioactive glass-ceramic. For the synthesis of 45S5 glass ceramics, 5 and 10?mol% titanium were added to replace calcium named as Ti5 and Ti10, respectively. The structure of glass-ceramic was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS). The ability of glass-ceramics to form hydroxyapatite (HA) was also evaluated using XRD, FTIR and FE-SEM/EDS following immersion in the simulated body fluid (SBF) for 1, 7 and 14 days. The ion release potential was also evaluated during the afore-mentioned immersion periods. Furthermore, the cell viability and alkaline phosphatase (ALP) activity of osteoblast-like cells exposed to the dissolved products of glass-ceramics were evaluated. The effect of addition of titanium on the mechanical properties was evaluated by measuring the compressive strength. Despite the slower rate of HA formation in Ti-containing groups during the first day of immersion, all groups showed similar results after 14 days. The addition of titanium to 45S5 bioactive glass-ceramic decreased the silicon and sodium ion release. Ti5 showed the highest level of cell viability and ALP activity. The compressive strength of 45S5 glass-ceramic significantly increased following addition of titanium, and Ti10 showed the highest value. In conclusion, the findings of this study support the synthesis of 45S5 glass-ceramic modified by addition of 5?mol% titanium ions due to improved mechanical and biological properties along with the ability to control solubility and ion release profile.