Femtosecond laser microstructuring of monolithic zirconia: Effects of laser parameters on resin bond strength

This study aimed to investigate the effects of different femtosecond (fs) laser treatment protocols on the surface roughness (Ra) and shear bond strength (SBS) of resin cement to zirconia. A total of 110 zirconia specimens were divided into 11 subgroups according to the surface treatment: Control (C), airborne-particle abrasion (APA), laser irradiation applying 400 mW, 600 mW, and 800 mW of 90 fs laser pulses with 1, 5, and 10 repetitions (Fs_(400/1), Fs_(400/5), Fs_(400/10), Fs_(600/1), Fs_(600/5), Fs_(600/10), Fs_(800/1), Fs_(800/5), and Fs_{(800/10) )}, respectively). Ra values were measured using a profilometer, and topographical changes were evaluated under a scanning electron microscope. X-ray diffraction analyses were performed to determine the crystallographic changes. Self-adhesive resin cement was bonded to zirconia specimens, and SBS tests were conducted. C and Fs_(800/10) groups exhibited the lowest and the highest Ra and SBS values, respectively. Regardless of the fs laser power, application of five and 10 repetitions resulted in higher Ra values than air-abrasion. Fs_(400/10), Fs_(600/5), Fs_(600/10), Fs_(800/5), and Fs_(800/10) groups showed higher SBS values than the APA group (p < .05), while SBS of other laser groups did not differ from the APA group (p > .05). Fs laser treatment protocols used in this study may be promising for zirconia-resin bonding. However, the effects of these treatments on the mechanical properties of zirconia need evaluation.     

Chitotriosidase as a novel biomarker of early atherosclerosis in hemodialysis patients

Introduction: Increasing evidence suggests that inflammation and increased macrophage activity have a central role in pathogenesis of atherosclerosis. It is shown that chitotriosidase (CHIT‐1) is a marker of macrophage activity in atherosclerotic plaque, and is found associated with severity of atherosclerotic lesion. There is no data about CHIT‐1 activity of hemodialysis patients in the literature. Thus, we hypothesized that in hemodialysis patients, CHIT‐1 levels might be a novel biomarker in early atherosclerosis. Methods: Forty‐five hemodialysis patients were included in the study (age: 61.93 ± 13.34). Intima media thickness (IMT) was evaluated with high‐resolution B‐mode ultrasonography. Biomarker levels were measured in serum of patients. Findings: We found positive correlation among IMT, age (R: 0.426, P: 0.004) and, CHIT‐1 value (R: 0.462, P: 0.001) in spearman correlation analysis. When age, CRP, creatinine, P, Alb, CHIT‐1 were chosen as measures that can effect IMT in multiple regression model, IMT level was related with CHIT‐1 (Beta: 0,396, P: 0.012) and age (Beta: 0,313 P: 0,048) independently. Discussion: In conclusion, this is the first report showing that serum CHIT‐1 level was related independently with carotid IMT in hemodialysis patients. This biomarker might have an unknown role in the development of atherosclerosis during uremia.     

A new polyimide film for VLSI and its electrical characterization

Multilevel structures consisting of alternating metal and dielectric layers are necessary to achieve interconnection in high density or VLSI (very large scale integration) circuits using either MOS or bipolar technology. Polyimide is one of the excellent high temperature heat-resistant polymers in organic materials and has good planarization capability and electrical insulating properties. In this work, following the synthesis of DAPDS (4,4'-bis (3-aminophenoxy)diphenyl sulfone), by nucleophilic aromatic substitution of 4,4'-dichlorodiphenyl sulfone with m-aminophenol, DAPDS/pyromellitic dianhydride based soluble and processable fully imidized polyimide was synthesized successfully by using solution imidization technique. Using this specific polyimide, a metal-polyimide-silicon MIS (metal polyimide silicon) structure was manufactured. Electrical properties of the MIS capacitance have been examined. The planarizing and patterning characteristics and electrical characteristics such as current vs. voltage, breakdown field strength, permittivity and capacitance vs. voltage for quasi-static and high frequency measurements are discussed. The results are compared with conventional dielectric films used in integrated circuit fabrication     

Atomic and electronic properties of realizable size single-crystal GaN nanotubes by first principles

We studied the diameter and wall thickness dependent atomic and electronic properties of practical size single-crystal GaN nanotubes using first principle calculations. Single-crystal GaN nanotubes are similar to the hexagonal GaN nanowires, grown in the [0001] direction with [10-10] facets, except there is an axial hexagonal void in them. We first demonstrated that the atomic and electronic properties of these tubes are mainly determined by the thickness of their wurtzite walls; and their diameters have negligible effects. Then, considering the individual walls of GaN nanotubes in two-dimensional slab calculations we examine the bond distances, formation energy, band gap, effective electron mass and the evolution of electronic density of the states as a function of thickness for unsaturated and hydrogen-saturated slabs of GaN. Calculations revealed that the unsaturated dangling bonds at the surfaces induce defect states in the band gap region of unsaturated tubes. Therefore, regardless of diameter and wall thickness, their band gaps are always smaller than that of the bulk GaN. However, the band gaps of the hydrogen-saturated tubes are found to be amplified with respect to bulk GaN. The amplification in the band gaps as a function of wall thickness in the range of 5.6-16.9 A and 16.9-28.1 A scales with a factor of 1/d(0.9281) and 1/d(1.769), respectively. Our results show that, regardless of diameter, hydrogen saturated single-crystal GaN tubes with the wall thickness as small as 28.1 A would be stable and they would have a noticeably larger band gap with respect to the band gap of bulk GaN.     

An effective polydopamine coating to improve stability and bioactivity of carvacrol-loaded zein nanoparticles

In this study, a simple and facile method was used to fabricate carvacrol-loaded zein nanoparticles (CLZNPs), and CLZNPs were coated with different concentrations (0.25, 0.5 and 1 mg mL⁻¹) of polydopamine (PDA) to fabricate CLZPNPs. Dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses showed that CLNPs and CLZPNPs possessed spherical shapes with smooth surfaces in the sizes of 562 and 725 nm and were highly stable possessing high encapsulation efficiency (81.3%). The antioxidant activity of CLZPNPs (ranging from 70.97% to 89.84%) was higher than that (51.42%) of CLZNPs. PDA had a significant effect to increase the antioxidant activity of the CLZNPs. The thermal stability of the particles was influenced by a temperature change from 30 °C to 70 °C. While 1 CLZPNP sample possessed the highest retention rate of carvacrol, the uncoated CLZNPs had the lowest retention value at all temperatures. The antibacterial effect of CLZNPs could be remarkably increased by their coating with PDA at different concentrations (0.25, 0.5 and 1 mg mL⁻¹), reaching the level of 100% inhibition of Salmonella typhimurium, Pseudomonas aeruginosa and Staphylococcus aureus. As a result, coating the carvacrol-loaded nanoparticles (CLZNPs) with PDA enabled us to fabricate highly stable CLZPNPs possessing improved stability and bioactivity. The results of this study suggest that the fabricated nanoformulation would find an application in food packaging technology to increase the storage stability of the products and control various foodborne bacterial pathogens.     

Pullulan/poly(N-vinylimidazole) cryogel: An efficient adsorbent for methyl orange

Pullulan/poly(N-vinylimidazole) (PNVI) hybrid cryogels were synthesized under free radical polymerization and chemical crosslinking conditions in an alkaline, aqueous solution of pullulan (PUL), N-vinylimidazole (NVI), ammonium persulfate and epicholorohydrin (ECH) at −18°C. PUL and PNVI cryogels alone were also synthesized under similar conditions. Optimum cryogel formation conditions were determined by considering product yields and gel fractions of the samples. The products were characterized by elemental analysis, FTIR-ATR spectrometry, Thermal gravimetric analysis, and scanning electron microscopy (SEM) analyses. It has been found that PUL/PNVI hybrid samples bear improved physicochemical properties compared to ECH crosslinked PUL and PNVI samples alone. They act as hydrogels in aqueous medium reaching equilibrium swelling capacity values of the order of 600%. Dried PUL/PNVI cryogels show higher thermal stability than the dried cryogels of the parent polymers and maintain their physical integrity over a prolonged time period. Macroporous morphology was revealed by SEM analysis. Having 54.2 mg/g maximum equilibrium adsorption capacity in 200 ppm methyl orange solution and maintaining 95% of its adsorption capacity at the end of seven consecutive adsorption/desorption cycles, PUL/PNVI cryogel proved to be an efficient and durable dye adsorbent using methyl orange as the model compound in aqueous solution.     

Physical,thermal, optical,structural and nuclear radiation shielding properties of Sm2O3 reinforced borotellurite glasses

To observe direct effect of samarium (III) oxide reinforcement on physical, thermal, optical, structural and nuclear radiation attenuation properties, a broad-range experimental and numerical investigations were performed with a group of novel borotellurite glasses. FTIR spectra of powdered samples were taken at 250-4000 cm^-1. The transmittance and absorption characteristics, optical band gaps, and Urbach energies were measured. The glass transition temperatures, crystallization temperatures and melting temperature values of the samples were determined. Nuclear radiation shielding properties have been determined for gamma-ray, neutrons and heavy charged particles. The lowest transmittance and highest absorbance were reported for the TBVS1.5 sample with highest Sm₂O₃ additive. In addition, obtained results from the nuclear radiation shielding calculations have showed that TBVS1.5 sample has superior nuclear radiation shielding properties against gamma-ray, neutron and heavy charged particles. The increasing Sm2O3 additive has visibly improved the nuclear radiation attenuation properties by keeping other material properties within usable limits.