Effect of different surface treatments on the shear bond strength of resin cement to zirconia ceramic and metal alloy*

The bonding of resin cement to ceramic materials plays an important role in dentistry. The purpose of this study is to evaluate the effects of various surface treatments on the shear bond strength (SBS) of zirconia ceramic and metal alloy. A total of 60 specimens were prepared from Y-TZP ceramic and metal alloy. The specimens were divided into three subgroups (n = 10) that received different surface treatments for each material. An Er:YAG laser (ER), a femtosecond laser (FS), and air-borne particle abrasion (A) were employed as surface treatments. One specimen from each group was analyzed using a scanning electron microscope (SEM) at 500 x magnification after surface treatments. The self-adhesive resin cement was then bonded to the treated surfaces using a Teflon mold. The specimens were thermocycled for 5,000 cycles at 5–55 °C, and then the SBS test was performed. Kruskal–Wallis and Mann–Whitney U tests were used to determine the differences between the groups (p = 0.05), and failure modes were evaluated for each specimen. Statistical analyses revealed significant differences between the surface treatment methods. The mean SBS values of the air-borne particle-abraded groups were higher than those of the other groups. The femtosecond-irradiated groups of each material showed significantly higher SBS values than the Er:YAG-irradiated groups (p < 0.05). Within the limitations of this study, air-borne particle abrasion and the femtosecond laser were more effective than Er:YAG laser treatment.     

Utilization of waste polyethylene terephthalate as a reducing agent in the reduction of iron ore composite pellets

The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies have been conducted to recycle and eliminate waste plastics. The potential for recycling waste plastics in the iron and steel industry has been underestimated; the high C and H contents of plastics may make them suitable as alternative reductants in the reduction process of iron ore. This study aims to substitute plastic wastes for coal in reduction melting process and to investigate their performance during reduction at high temperature. We used a common type of waste plastic, polyethylene terephthalate （PET）, because of its high carbon and hydrogen contents. Composite pellets containing PET wastes, coke, and magnetite iron ore were reduced at selected temperatures of 1400 and 1450℃ for reduction time from 2 to 10 min to investigate the reduction melting behavior of these pellets. The results showed that an increased temperature and reduction time increased the reduction ratio of the pellets. The optimum experimental conditions for obtaining metallic iron （iron nuggets） were reduction at 1450℃ for 10 min using composite pellets containing 60% PET and 40% coke.     

Direction‐Based Modified Particle Filter for Vehicle Tracking

This research proposes a modified particle filter to increase the accuracy of vehicle tracking in a noisy and occluded medium. In our proposed method for vehicle tracking, the direction angle of a target vehicle is calculated. The angular difference between the motion direction of the target vehicle and each particle of the particle filter is observed. Particles are filtered and weighted depending on their angular distance to the motion direction. Those particles moving in a direction similar to that of the target vehicle are assigned larger weights; this, in turn, increases their probability in a given likelihood function (part of the process of estimation of a target's state parameters). The proposed method is compared against a condensation algorithm. Our results show that the proposed method improves the stability of a particle filter tracker and decreases the particle consumption.     

Understanding the potential for adoption of high-iron varieties of pearl millet in Maharashtra,India: what explains their popularity?

Pearl millet is one of the most important food staples of poorer populations in the drylands of India. To better understand the potential market for high-iron, pearl millet hybrids, we explored factors associated with growing pearl millet, and those that influence whether farmers grow major (popular) hybrids, as compared with minor cultivars in the State of Maharashtra. We tested the relationships among cultivar choice, seed source, and information sources. The data confirm that pearl millet is more likely to be grown by poorer households in drier, drought-prone areas. Scheduled castes are more likely to grow popular hybrids, and less likely to grow minor cultivars, but are no less likely to acquire seed from commercial vendors than less privileged people. Farmers who ascribe more importance to consumption attributes are more likely to grow minor than popular hybrids. De facto, popular pearl millet varieties are likely to reach less privileged farmers. To attain adoption potential, popular hybrids could be targeted for iron enrichment, and commercial marketing strategies should be pursued with diversified public and private sector partnerships.     

Comparison of restorative materials and surface alterations after prebiotic and probiotic beverages: A nanoindentation and SEM study

The purpose was to investigate the surface characteristics of various resin-based materials by immersing in probiotic beverages. A total of 420 disc-shaped samples (5 mm × 2 mm) were prepared from resin-based composites. Samples were divided into four groups and immersed for 10 min/day for 1 month in either a probiotic sachet, kefir, kombucha, or artificial saliva (control). Surface roughness was measured at baseline and 1 month. One sample of each of the tested materials was examined under nanoindentation to evaluate the reduced elasticity modulus and nanohardness scores. Scanning electron microscopy (SEM) was used to compare surface differences. Data were analyzed statistically using one-way ANOVA test and the significance was set at p < .05. The lowest roughness scores were observed in Z250, Estelite Bulk Fill, and HRi ENA in most of the test groups. Among conventional composites, Z250 group had the highest nanohardness and elasticity modulus scores. Among bulk-fill composites, Estelite Bulk Fill Flow had the lowest surface roughness after immersion in probiotic beverages and the highest nanohardness values. Reveal HD, as a bulk-fill group showed higher surface roughness and considerably lower nanohardness and elasticity modulus scores. Maximum height levels of samples were recorded. SEM images revealed voids and microcracks on the surfaces of test materials. Dentists may prefer Z250 as microhybrid and Estelite Bulk Fill Flow as bulk-fill composites for the restorations of patients who consume gut-friendly drinks regularly. When there are various types of materials, nanoindentation is a useful method for evaluating surface alterations and sensible comparisons.     

Chrome and cobalt-based novel electrolyte systems for redox flow batteries

In the present work, novel redox ion-pairs (as cobalt and chromium) have been used in aqueous medium for the first time in the literature as electrolyte component of redox flow battery system. The electrochemical performance of the Co(II) and Cr(III) redox species as anolyte and catholyte was investigated by cyclic charge-discharge tests, respectively. Electrochemical behaviors of Cr(III) solutions in sulfuric acid solution were determined by using differential pulse voltammetry, electrochemical impedance spectroscopy and cyclic voltammetry via a typical three-electrode system. Morphological analyses of surface of pencil graphite electrode, which was used as anode in differential pulse voltammetric analysis, were done by scanning electron microscopy. Discharge capacity of the battery system consisting of 1.0 M Cr(III) as anolyte (negative electrolyte) and 1.0 M of Co(II) as catholyte (positive electrolyte) in 4.0 M of sulfuric acid was determined as 682.5 mAh (1.4 Ah L⁻¹) with 4 mA cm⁻² charge current density and 0.4 mA cm⁻² discharge current density. Voltage efficiency, energy efficiency and coulombic efficiency of the battery were 70.1%, 53.8% and 57.2%, respectively. The discharge cell potential of the battery was also determined as 1.40 V.     

Importance of acetic acid bacteria in food industry

Acetic acid bacteria (AAB) comprise a group of gram-negative or gram-variable, ellipsoidal to rod-shaped cells that have an obligate aerobic metabolism with oxygen as the terminal electron acceptor. In the first classification of AAB, two main genera were determined as Acetobacter and Gluconobacter, but nowadays twelve genera are recognized and accommodated to the family Acetobacteraceae, the Alphaproteobacteria: Acetobacter, Gluconobacter, Acidomonas, Gluconacetobacter, Asaia, Kozakia, Swaminathania, Saccharibacter, Neoasaia, Granulibacter, Tanticharoenia and Ameyamaea. Isolation, purification, identification and preservation of AAB are very difficult. Phenotypic methods based on physiological abilitiesies have been used for identification of AAB by using various media. These phenotypic properties have now been complemented or replaced by molecular techniques, which are DNA and RNA based techniques.AAB are widespread in nature on various plants (fruits, cereals, herbs, etc.). They are important microorganisms in food industry because of their ability to oxidize many types of sugars and alcohols to organic acids as end products during fermentation process. The best known industrial application of AAB is vinegar production. This group of bacteria is also used in cellulose and sorbose production. On the other hand, the oxidizing ability of AAB could have spoilage effect in some products such as in wine. The aim of the present review is to introduce the importance of AAB in food industry by showing their current taxonomy, enumeration, isolation and identification methods, isolation sources and beneficial effects in food production systems.     

Physical and Adsorptive Characterization of Precipitated Magnesium Silicate from Rice Hull Ash Silica

Precipitation of magnesium silicate from sodium silicate and MgCl₂ and MgSO₄ solutions was investigated at four different reactant feed rates and two temperatures (25 °C and 50 °C). Sodium silicate solutions were produced from rice hull ash silica. The final product was characterized by scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis/differential thermal analysis, crystal size distribution, and filtration rate measurements. Physical characteristics of the studied magnesium silicates were determined by the Brauner‐Emmett‐Teller method and their adsorption capacities were compared to commercial magnesium silicate (Florisil). The adsorption was spontaneous and endothermic. The best fit of the kinetic results was achieved by a pseudo‐second‐order equation. The equilibrium data were found to be well represented by the Freundlich isotherm equation.     

APPLICATION OF X-RAY CT IMAGING AS AN ALTERNATIVE TOOL FOR CLOUD POINT DETERMINATION

ABSTRACT

This study explains the use of X-Ray CT (computerized tomography’) as an alternative tool for cloud point determination of crude oils and dark fuel oils by showing the results for artificially prepared transparent oils. The technique is fully computerized and data gathering and analysis are achieved by taking the advantage of the processing of the CT images. In the study, the cloud points of diesel oil samples containing 5%, 10% and 15 % additional wax were determined with this new technique. Results show that the cloud points determined with this technique and the standardized ASTM D-3117 method are very close. This encourages the use of the proposed technique to determine the cloud point of transparent distillate fuels and dark fuel oils and crude oils, whose cloud points can not be determined easily and accurately.     

Response to thermal cycling of CAPVD (Al,Cr)N-coated hot work tool steel

The principle failure mechanism in thixoforming dies is thermal fatigue as the mechanical loading on the tooling is modest owing to a mushy feedstock. X32CrMoV33 hot work tool steel samples coated with (Al,Cr)N via Cathodic Arc Physical Vapour Deposition were submitted to thermal cycling under conditions which approximate thixoforming of steels. The PVD AlCrN coating provides adequate protection against oxidation of the hot work tool samples, shown to be one of the predominant mechanisms leading to thermal fatigue cracking. However, it does not last very long due to the extensive softening of the tool steel substrate and the thermal expansion mismatch between the hot work tool steel and the nitride coating.