Dissolution kinetics of ulexite in acetic acid solutions

Ulexite is an important boron mineral used for the production of boron compounds. The aims of this study are to examine the dissolution kinetics of ulexite in acetic acid solutions, and to present an alternative process to produce boric acid. In order to investigate the dissolution kinetics of ulexite in acetic acid solutions, the concentration of solution, reaction temperature, solid-to-liquid ratio, and particle size were selected as experimental parameters. It was determined that the dissolution rate of ulexite increased with increasing solution concentration and temperature and decreasing particle size and solid-to-liquid ratio. The activation energy of the process was found to be 55.8 kJ/mol.     

The study of MIG weldability of heat-treated aluminum alloys

In this article, Metal Inert Gas (MIG) weldability of commercially received and aged samples of 6061-T₆ and 7075-T₆₅₁ aluminum alloys was investigated. The welding joints were prepared in ten different combinations. Microstructure, microhardness, EDX, energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were used in order to evaluate the effect of aged heat treatment on the performance of welded joints. In addition, the mechanical properties of welding joints were characterized using the tensile and microhardness tests. In conclusion, it was shown that prewelding aging heat treatment improves the mechanical properties of welding joints.     

XANES analysis of calcium and sodium phosphates and silicates and hydroxyapatite–Bioglass®45S5 co-sintered bioceramics

Bioglass®45S5 was co-sintered with hydroxyapatite at 1200 °C. When small amounts (< 5 wt.%) of Bioglass®45S5 was added it behaved as a sintering aid and also enhanced the decomposition of hydroxyapatite to β-tricalcium phosphate. However when 10 wt.% and 25 wt.% Bioglass®45S5 was used it resulted in the formation of Ca₅(PO₄)₂SiO₄ and Na₃Ca₆(PO₄)₅ in an amorphous silicate matrix respectively. These chemistries show improved bioactivity compared to hydroxyapatite and are the subject of this study. The structure of several crystalline calcium and sodium phosphates and silicates as well as the co-sintered hydroxyapatite–Bioglass®45S5 bioceramics were examined using XANES spectroscopy. The nature of the crystalline and amorphous phases were studied using silicon (Si) and phosphorus (P) K- and L_2,3-edge and calcium (Ca) K-edge XANES.Si L_2,3-edge spectra of sintered bioceramic compositions indicates that the primary silicates present in these compositions are sodium silicates in the amorphous state. From Si K-edge spectra, it is shown that the silicates are in a similar structural environment in all the sintered bioceramic compositions with 4-fold coordination.Using P L_2,3-edge it is clearly shown that there is no evidence of sodium phosphate present in the sintered bioceramic compositions. In the P K-edge spectra, the post-edge shoulder peak at around 2155 eV indicates that this shoulder to be more defined for calcium phosphate compounds with decreasing solubility and increasing thermodynamic stability. This shoulder peak is more noticeable in hydroxyapatite and β-TCP indicating greater stability of the phosphate phase. The only spectra that does not show a noticeable peak is the composition with Na₃Ca₆(PO₄)₅ in a silicate matrix indicating that it is more soluble compared to the other compositions.     

Survival and predictors of disability in Turkish MS patients. Turkish Multiple Sclerosis Study Group (TUMSSG)

OBJECTIVE: To examine the natural history, survival, and prognostic factors in a sample of Turkish MS patients. METHOD: This multicenter study included 1,259 definite MS patients diagnosed according to the criteria of Poser et al. Actuarial analysis of selected disability levels of 3, 6, 8, and 10 achieved with the Expanded Disability Status Scale (EDSS); a multivariate Cox regression analysis for prognostic factors related to time to reach EDSS > or = 6; and Pearson's correlation coefficient for individual factors were performed. RESULTS: The survival (+/- SE) at 15 years from onset was 94.6 +/- 2.9%, and at 25 years was 89.0 +/- 5.8%. The disability reached by 15 years was EDSS > or = 3 in 66.4%, EDSS > or = 6 in 41.2%, EDSS > or = 8 in 10.5%, and EDSS = 10 in 5.4%. The most significant unfavorable prognostic factors were progressive course (relative risk [RR], 3.73; CI, 2.71 to 5.13) and sphincter symptoms at onset (RR, 1.86; CI, 1.23 to 2.82), followed by male sex, motor symptoms at onset, and a high attack frequency within the first 5 years. Primary progressive disease was correlated positively with male sex (r = 0.0895, p = 0.001), older age (r = 0.1807, p = 0.000), and motor (r = 0.1433, p = 0.000) or sphincter symptoms (r = 0.1001, p = 0.000) at onset, unlike relapsing-remitting and secondary progressive disease. CONCLUSIONS: Although a slightly better prognosis is observed in the Turkish MS population, early prognostic factors are similar to most of the previous Western series. Primary progressive disease, mostly seen in older men with motor and sphincter involvement at onset, has a worse prognosis and may represent a distinct behavioral variant of MS.     

Metallurgical and Corrosion Properties of Explosively Welded Ti6Al4V/Low Carbon Steel Clad

Titanium alloy (Ti6Al4V) and Iow carbon steel (LCS) were joined by explosive welding method using different ratios of explosive. Some metallurgical properties of joined samples were investigated. Joined samples were examined by means of optical microscope, scanning electron microscope (SEM) and tensile-shearing tests. Bending, tensile, hardness and corrosion behaviour of the samples were investigated. Separation was not occurred on the joining interface after tensile-shearing and bending tests. It is seen that hardness of both plates were increased with increasing explosive.It is found that increasing explosive ratio leads to an increase in corrosion. It is also found that corrosion rate was high at the beginning of the experiment but the rate of the corrosion decreased subsequently during the experiment.     

The Implementation of Optimization Methods for Contrast Enhancement

The performances of the multivariate techniques are directly related to the variable selection process, which is time consuming and requires resources for testing each possible parameter to achieve the best results. Therefore, optimization methods for variable selection process have been proposed in the literature to find the optimal solution in short time by using less system resources. Contrast enhancement is the one of the most important and the parameter dependent image enhancement technique. In this study, two optimization methods are employed for the variable selection for the contrast enhancement technique. Particle swarm optimization (PSO) and artificial bee colony (ABC) optimization methods are implemented to the histogram stretching technique in parameter selection process. The results of the optimized histogram stretching technique are compared with one of the parameter independent contrast enhancement technique; histogram equalization. The results show that the performance of the optimized histogram stretching is better not only in distorted images but also in original images. Histogram equalization degraded the original images while the optimized histogram stretching has no effect due to being an adaptive solution.     

Smartphone based sperm counting - an alternative way to the visual assessment technique in sperm concentration analysis

Sperm Counting is the first phase of the infertility diagnosis. Computer Aided Sperm Analysis (CASA) and Visual Assessment (VA) are two evaluation techniques employed in analyses. VA is carried out by observing sperm on counting chambers. Therefore, diagnosis strongly depends on the skills and experiences. CASA isolates the human factor by utilizing the computer based techniques. However, it is more costly than VA and requires exhausted parameter settings. In this study, we present a novel approach that uses smartphone and computer for sperm counting analysis. Smartphone is used to obtain images similar to VA technique. Then, sample videos are transferred to the computer side where we developed the Computerized Sperm Counting Software (CSCS) to count the sperm using counting chambers and eliminate human effects. CSCS consists of four modules: (1) Data Acquisition and Organization, (2) Regions of Interest (ROI) detection, (3) Motile/Immotile Sperm Detection, (4) Counting. Smartphone based data acquisition provided less costly design contrary to CASA systems. ROI extraction was realized by a combinational approach of line detection and segmentation methods. Background and Foreground extractions were employed in immotile and motile sperm detection process, respectively. Additionally, active contour was implemented to enhance the segmentation of immotile sperm. As the final step, detected sperms were counted by pixel based blob analysis. According to experimental results, the proposed smartphone based sperm concentration analysis can be adapted in laboratories due to its modularity, functionality, accuracy and cost when compare to CASA and VA based sperm counting analysis.

     

Investigation of the Microstructural,Mechanical and Corrosion Properties of Grade A Ship Steel-Duplex Stainless Steel Composites Produced <Emphasis Type="Italic">via</Emphasis> Explosive Welding

Grade A ship-building steel-AISI 2304 duplex stainless steel composite plates were manufactured via explosive welding. The AISI 2304 plates were used to clad the Grade A plates. Optical microscopy studies were conducted on the joining interface for characterization of the manufactured composite plates. Notch impact, tensile-shear, microhardness, bending and twisting tests were carried out to determine the mechanical properties of the composites. In addition, the surfaces of fractured samples were examined by scanning electron microscopy (SEM), and neutral salt spray (NSS) and potentiodynamic polarization tests were performed to examine corrosion behavior. Near the explosion zone, the interface was completely flat, but became wavy as the distance from the explosion zone increased. The notch impact tests indicated that the impact strength of the composites decreased with increasing distance from the explosion zone. The SEM studies detected brittle behavior below the impact transition temperature and ductile behavior above this temperature. Microhardness tests revealed that the hardness values increased with increasing distance from the explosion zone and mechanical tests showed that no visible cracking or separation had occurred on the joining interface. The NSS and potentiodynamic polarization tests determined that the AISI 2304 exhibited higher corrosion resistance than the Grade A steel.     

Dissolution of ulexite in ammonium carbonate solutions

The dissolution of ulexite in ammonium carbonate solutions is investigated. The effect of concentration, particle size, stirring speed, and reaction temperature is examined. It is found that the dissolution rate increases with increasing concentration and reaction temperature, and with decreasing particle size. No effect of stirring speed was observed on the conversion. It is determined that the dissolution rate fits to the first order pseudo-homogeneous reaction model.     

Paroxysmal dyskinesias: clinical features and classification

We studied 46 patients with paroxysmal dyskinesia and classified them according to phenomenology, duration of attacks, and etiology. There were 13 patients, 7 females, who had paroxysmal kinesigenic dyskinesia (PKD), 10 with attacks lasting 5 minutes or less (short lasting) and 3 with attacks lasting longer than 5 minutes (long lasting). Twenty-six patients, 18 females, had paroxysmal nonkinesigenic dyskinesia (PNKD), 9 with short-lasting and 17 with long-lasting PNKD. Five patients, 3 females, had paroxysmal exertion-induced dyskinesia (PED), 3 with short-lasting PED and the other 2 with long-lasting PED. In addition, there was 1 patient with paroxysmal hypnogenic dyskinesia (PHD) and 1 with paroxysmal superior oblique myokymia. Only 2 patients, 1 with PKD and 1 with PHD, had family history of paroxysmal dyskinesias. No specific cause could be identified in 21 patients; in the other 23 patients the etiologies included the following: psychogenic (9 patients), cerebrovascular diseases (4), multiple sclerosis (2), encephalitis (2), cerebral trauma (2), peripheral trauma (2), migraine (1), and kernicterus (1). Nine of 10 (90%) patients with PKD improved with medications, mostly anticonvulsants, compared with only 7 of 19 (37%) with PNKD. This new classification, based chiefly on precipitating events, allowed appropriate categorization of the attacks in all our patients with paroxysmal dyskinesias.