Effects of Growth Rates and Compositions on Dendrite Arm Spacings in Directionally Solidified Al-Zn Alloys

Dendritic spacing can affect microsegregation profiles and also the formation of secondary phases within interdendritic regions, which influences the mechanical properties of cast structures. To understand dendritic spacings, it is important to understand the effects of growth rate and composition on primary dendrite arm spacing (λ ₁) and secondary dendrite arm spacing (λ ₂). In this study, aluminum alloys with concentrations of (1, 3, and 5 wt pct) Zn were directionally solidified upwards using a Bridgman-type directional solidification apparatus under a constant temperature gradient (10.3 K/mm), resulting in a wide range of growth rates (8.3–165.0 μm/s). Microstructural parameters, λ ₁ and λ ₂ were measured and expressed as functions of growth rate and composition using a linear regression analysis method. The values of λ ₁ and λ ₂ decreased with increasing growth rates. However, the values of λ ₁ increased with increasing concentration of Zn in the Al-Zn alloy, but the values of λ ₂ decreased systematically with an increased Zn concentration. In addition, a transition from a cellular to a dendritic structure was observed at a relatively low growth rate (16.5 μm/s) in this study of binary alloys. The experimental results were compared with predictive theoretical models as well as experimental works for dendritic spacing.     

Thermal Characteristics in a Tube With Loose-Fit Perforated Twisted Tapes

Enhanced heat transfer and pressure loss in a tube with loose-fit perforated twisted tapes were experimentally investigated. The effects of the twist ratio and the hole diameter ratio were also described. A constant twisted tape width of 52 mm, which is lower than the tube inside diameter of 56 mm, was used in order to reduce excessive pressure drops associated with full-width twisted tape elements. The tests were conducted using the tapes with three different ratios of pitch length of twisted tape to inner diameter of tube (twist ratios = 2, 2.5, 3) and three different ratios of hole to inner diameter (diameter ratios = 0.0714, 0.107, 0.143) in a range of Reynolds number 4860 to 24,130 under uniform heat flux conditions. The experimental findings revealed that the Nusselt number, friction factor, and thermal performance factor increase with decreasing twist ratio and hole diameter ratio. The maximum value of thermal performance factor of 1.27 was achieved for the case at a twist ratio of 2 and a hole diameter ratio of 0.0714. Eventually, the experimental results of Nusselt number, friction factor and thermal performance factor were correlated, and the deviations determined for Nusselt number, friction factor, and thermal performance factor were within ±7%, ±8%, and ±6%, respectively.     

High‐performance liquid chromatography of some natural dyes: analysis of plant extracts and dyed textiles

In this study, wool fibre samples were mordanted by means of 25% alum mordant solution. The mordanted wool samples were dyed in 50%Reseda luteola L. (weld), 20%Rhamnus petiolaris Boiss (buckthorn) and 50%Datisca cannabina L. (bastard hemp) dyebaths. A reverse‐phase high‐performance liquid chromatography with diode‐array detection method was utilised for the identification of dyes in the dyed wool samples and the plant extracts. The extraction of dyes was carried out with a hydrogen chloride/methanol/water (2:1:1; v/v/v) mixture.     

In Vitro Models for Studying Secondary Plant Metabolite Digestion and Bioaccessibility

There is an increased interest in secondary plant metabolites, such as polyphenols and carotenoids, due to their proposed health benefits. Much attention has focused on their bioavailability, a prerequisite for further physiological functions. As human studies are time consuming, costly, and restricted by ethical concerns, in vitro models for investigating the effects of digestion on these compounds have been developed and employed to predict their release from the food matrix, bioaccessibility, and assess changes in their profiles prior to absorption. Most typically, models simulate digestion in the oral cavity, the stomach, the small intestine, and, occasionally, the large intestine. A plethora of models have been reported, the choice mostly driven by the type of phytochemical studied, whether the purpose is screening or studying under close physiological conditions, and the availability of the model systems. Unfortunately, the diversity of model conditions has hampered the ability to compare results across different studies. For example, there is substantial variability in the time of digestion, concentrations of salts, enzymes, and bile acids used, pH, the inclusion of various digestion stages; and whether chosen conditions are static (with fixed concentrations of enzymes, bile salts, digesta, and so on) or dynamic (varying concentrations of these constituents). This review presents an overview of models that have been employed to study the digestion of both lipophilic and hydrophilic phytochemicals, comparing digestive conditions in vitro and in vivo and, finally, suggests a set of parameters for static models that resemble physiological conditions.     

Some properties and potential applications of the Na- and Ca-bentonites of ordu (N.E. Turkey)

Ca- and Na-bentonites formed throughout the Eastern Black Sea were distinguished on the basis of their mineralogical, chemical, and physical properties. The properties of the Na- and Ca-bentonites were studied using X-ray diffraction, chemical analyses and a series of physical testing methods. Montmorillonite is the major mineral in both bentonites. Except for montmorillonite, the Ca-bentonites (CAB) contain opal-CT, minor amounts of quartz, feldspar and biotite, and (rarely) pyrite and calcite. The Na-bentonites (NAB) contain smectite (montmorillonite) and small amounts of opal-CT, quartz, and feldspar. In the natural state, the chemical and physical properties including cation exchange capacity, viscosity, swelling index, gelling strength and pH of the NAB are higher than the CAB. Surface area and brightness of the CAB are unusually high compared to the NAB. Their bleaching properties are generally similar. The specific surface area and filtration loss of CAB are higher than in NAB. The natural bentonites could be used in paper coating and filling, paint, pharmaceuticals, and as cosmetics and filtering agents after the removal of non-clay minerals and after making some processes/modifications.     

Elman's recurrent neural network applications to condition monitoring in nuclear power plant and rotating machinery

The purpose of this study is to show the capability of recurrent neural nets (RNN) for condition monitoring and diagnosis in nuclear power plant systems and rotating machinery. In the first application, the study addresses the use of RNN for detecting anomalies introduced from the simulated power operation of a high-temperature gas cooled nuclear reactor. In the second, it is used to detect the motor bearing damage using a coherence function approach, which is defined between the motor current and vibration signals, for induction motors. Hence, the high performance of Elman's RNN was shown by means of two different applications.     

Molten‐Salt‐Assisted Self‐Assembly (MASA)‐Synthesis of Mesoporous Metal Titanate‐Titania,Metal Sulfide‐Titania,and Metal Selenide‐Titania Thin Films

New synthetic strategies are needed for the assembly of porous metal titanates and metal chalcogenite‐titania thin films for various energy applications. Here, a new synthetic approach is introduced in which two solvents and two surfactants are used. Both surfactants are necessary to accommodate the desired amount of salt species in the hydrophilic domains of the mesophase. The process is called a molten‐salt‐assisted self‐assembly (MASA) because the salt species are in the molten phase and act as a solvent to assemble the ingredients into a mesostructure and they react with titania to form mesoporous metal titanates during the annealing step. The mesoporous metal titanate (meso‐Zn₂TiO₄ and meso‐CdTiO₃) thin films are reacted under H₂S or H₂Se gas at room temperature to yield high quality transparent mesoporous metal chalcogenides. The H₂Se reaction produces rutile and brookite titania phases together with nanocrystalline metal selenides and H₂S reaction of meso‐CdTiO₃ yields nanocrystalline anatase and CdS in the spatially confined pore walls. Two different metal salts (zinc nitrate hexahydrate and cadmium nitrate tetrahydrate) are tested to demonstrate the generality of the new assembly process. The meso‐TiO₂‐CdSe film shows photoactivity under sunlight.     

Constituents,Oxidant-Antioxidant Profile,and Antimicrobial Capacity of the Essential Oil Obtained from Ferulago Sandrasica Peşmen and Quézel

Chemical constituents, total phenolic content, total oxidant status, total antioxidant status, lipid hydroperoxides, total free –SH levels, and antimicrobial activity of essential oil obtained from the Ferulago sandrasica (Umbelliferae) were investigated. The essential oil was obtained by hydrodistillation using a Clevenger-type apparatus. The chemical constituents were analyzed by gas chromatography‐mass spectrometry. The main components of the essential oil were ocimene (30.5%), carene-δ-3 (27.4%), and α-pinene (17.8). The antimicrobial activity was tested by a disc diffusion method against E. coli MC 400, E. coli ATCC 25922, E. coli 0157 H7, E. colaecea ATCC 23355, E. feacalis ATCC 19433, P. aeruginosa NRRL B-2679, S. aureus ATCC 25923, B. nischenoformis NRRL B-1001, S. aureus ATCC 33862, B. cereus NRRL B-3711, B. subtilis NRRL B-209, M. luteus NRRL B-1013, L. monocytogenes ATCC 7644, B. subtulis ATCC 6633.     

Rheological and Sensory Properties of Spray Dried Pekmez Mixtures with Wheat Starch-Gum

Pekmez, known also as grape molasses, was spray dried in the laboratory-type pilot drying unit to obtain pekmez powder. The flow characteristics of diluted pekmez powder (DPP), wheat starch (WS), and some hydrocolloids (locust bean gum, LBG; gum tragacanth, GT, and guar gum, GG) systems in double- or triple-mixed combinations were studied. The empirical power law model fitted the apparent viscosity-rotational speed data. DPP-gum and WS-gum mixed solutions exhibited a shear-thinning behaviour at 21°C with flow behaviour index (n) values of 0.88 ≤ n ≤ 0.94 and 0.17 ≤ n ≤ 0.32, respectively. WS-gum mixed solutions showed high shear-thinning behaviour with the highest consistency index (k = 49.93–214.24 Pa sⁿ). However, DPP-WS and DPP-WS-gum mixed solutions at the same temperature exhibited the shear-thickening behaviour with flow behaviour index (n) values of 1.02 ≤ n ≤ 1.07.     

Evaluation of the effects of different remineralizing agents on Streptococcus mutans biofilm adhesion

The aim of the study was to compare the effects of different remineralization methods that are well established in clinical and daily use on S. mutans biofilm adhesion. In this study 72 human third molars were used. From each tooth two pieces of 4?mm x 7?mm enamel blocks were acquired. The samples were divided into 6 groups in which include 10 samples per time period (24h and 48?h) and for each remineralization method; control, flouride, ozone, CPP-ACP, arginine, novamin. After remineralization procedures, enamel surfaces were covered with saliva. 10⁵ CFU/mL of active S. mutans culture were inoculated onto the samples. S. mutans colonies were counted with Plate Count Agar (PCA) decimal dilution method. Micromorphologic effects of different remineralization methods were observed by Scanning Electron Microscopy (SEM). The most S. mutans biofilm formation for both time periods was observed in the control group whereas the less biofilm adhesion was showed in the arginine group. There were no statistically significant differences among remineralization agents (p?>?0.05). In the control group there was statistical difference between 24?h and 48?h (p?<?0.005) but in the other study groups there were no significant difference between the time periods (p?>?0.05). Remineralization agents did not significant differ on S. mutans biofilm adhesion.