Biodegradation of low‐density polyethylene/thermoplastic starch foams before and after electron beam irradiation

Foamy low‐density polyethylene/plasticized starch (LDPE/PLST) blends at different compositions were produced in the presence of azodicarbonamide (ACA) compound as foaming agent. The LDPE/PLST blends before and after electron beam irradiation were investigated in terms of mechanical properties, bulk density, and structure morphology. Moreover, the biodegradability of these materials was evaluated by the soil burial test for 2 months, in which the buried sheets were also examined by scanning electron microscopy (SEM). The results showed that the increase of PLST content from 24 to 30% was accompanied by a decrease in the yield and break stresses of 10 and 20% for the unirradiated blends without the foaming agent, respectively. Further decrease in these mechanical parameters was observed after the foaming process. The bulk density, void fraction, cell size measurements as well as the examination by SEM illustrate clearly the cell growth of the foam structure. The soil burial test and SEM micrographs indicate the growth of microorganisms overall the blend sheets and that the blend was completely damaged after two months of burying. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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.     

Comparison of an Eigenvector Music Method with Classical FFT and Model Based AR Methods in the Analysis of Mitral Valve Doppler Signals

Abstract

Mitral valve stenosis is an important heart condition that develops when the mitral valve fails to open as wide as it should. In this study, we have performed Eigenvector based Music, FFT based Welch, and AR based Burg methods of Doppler signals real clinical data from patients with mitral valve stenosis and healthy volunteers. Using these methods, we have not only utilized power spectral density distribution graphs, but also facilitated Doppler sonograms and estimation of SBI to obtain medical information about mitral stenosis and determination of spectral broadening in the presence of mitral stenosis. In conclusion, this research has shown that frequency level of maximum power spectral density is distinctive and there is an advantage in using the EIG‐Music over the FFT‐Welch and AR‐Burg for the determination of SBI. Using the Music method among them, the calculation of SBI may help determine mitral valve stenosis.     

Polymer Membrane Electrodes for Sensitive Potentiometric Determination of β-blockers

ABSTRACT

The construction of PVC matrix-type β-blockers (sotalol, carvedilol, and betaxolol) ion selective electrodes and their use for direct potentiometry of their respective species are described. The proposed sensors are based on the complex ion associates of β-blockers with tungstophosphate (TP) and Ammonium Reineckate (Rein) ionophoris in poly vinyl chloride membrane (PVC) with Dioctylphthalate (DOP) plasticizer. The four electrodes (Beta-TP), (Sota-TP), (Carve-TP), and (Cave-Rein) show stable potential response with near Nernstian slope of 50.8, 33.7, 32.35, and 33 mv per decade, range of concentration 10?2–10?7 M β-blockers. Selectivity coefficients data obtained for 11 different organic and inorganic ions are presented. The electrodes have fast response time (30 and 40 s) and were used over wide range of pH 4.5–8.5. Validation of the method according to the quality assurance standers shows suitability of proposed sensors for use in the quality control assessment of these drugs. The results obtained for the determination of β-blockers with the proposed electrodes show average recoveries of 100.78% and a mean standard deviation of ±1.2. The nominal are obtained. The data agree well with those obtained by standard methods.     

Evaluation of surface topography changes in three NiTi file systems using rotary and reciprocal motion: An atomic force microscopy study

Aim: To evaluate the surface topography changes in three nickel‐titanium (NiTi) file systems using either rotary or reciprocal motion using atomic force microscopy (AFM), and to determine the effect of scanning area on the AFM results in this study. Methodology: Five points on a F2 Protaper file, R25 Reciproc file, and a Primary file from WaveOne systems were scanned preoperatively in 1 × 1 and 5 × 5 µm² with an AFM device that can scan an intact (not sectioned) file. One standardized resin block was used for each instrument, according to the manufacturer's recommendations. Points were re‐scanned postoperatively using the same AFM and settings. Root‐mean‐square (RMS) and roughness average (Ra) values were obtained. The preoperative and postoperative surface topographies were compared separately in terms of RMS and Ra values. The surface topography change scores were analyzed using Kruskal–Wallis and Mann–Whitney U tests using a 0.10 significance level. Results: There were no significant differences preoperatively among the NiTi file systems in 1 × 1 or 5 × 5 µm² areas. Postoperatively, the WaveOne Primary had more surface irregularities (significant for 5 × 5 µm² scan in Ra evaluation). Conclusions: Three‐dimensional AFM images of instrument surfaces showed topographic irregularities preoperatively and postoperatively. AFM results differ depending on the scanning area and file used. Microsc. Res. Tech. 77:177–182, 2014. © 2013 Wiley Periodicals, Inc.     

The microstructure of buccal cavity and alimentary canal of Siganus rivulatus: Scanning electron microscope study

The microstructure of the oral cavity and alimentary canal of herbivorous fish Siganus rivulatus collected from the Red Sea were investigated by using scanning electron microscope (SEM). The results showed that S. rivulatus has three types of teeth, tri‐cusped, bi‐cusped, and papilliform. A taste bud (Type I) was recorded in the oropharyngeal cavity. Characteristic styles of microridges on the cell's surface inside the buccal cavity were recorded. Also, the distribution of the mucous cells in the lining of the mouth cavity, alimentary canal was observed. Mucosal folds along the distinct parts of alimentary canal, showed characteristic pattern which was complex in the intestinal mucosa. The results concluded that there are characteristic microstructures according to feeding habitat compared with other bony fishes.     

Quality assessment of surface and groundwater in Solaklı Basin (Trabzon, Turkey)

The paper reports a study of the surface and ground water in Solakl? Basin, Trabzon, from an assessment of 33 sampling points. Many of the parameters analysed are only marginally acceptable as potable water, even though the samples were collected during the wet season. The highest concentrations of contaminants were found downstream of the centres of population. The results indicate regular monitoring is required and some measures should be taken to protect the limited resources.