Effect of nitrogen on the antibacterial behavior of oxynitride glasses

The main drawback of bioglasses is their restricted use in load bearing applications and the consequent need to develop stronger glassy materials. This has led to the consideration of oxynitride glasses for numerous biomedical applications. This paper investigated two different types of glasses at a constant cationic ratio, with and without nitrogen (a N containing and a N-free glass composition) to better understand the effect of N on the biological properties of glasses. The results revealed that the addition of N increased the glass transition temperature, isoelectric point (IEP) and slightly increased wettability. Moreover, compared to N including glass, N-free glass exhibited better anti-bacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), two key bacteria that infect implants. In summary, these in vitro results indicated that amine functional groups existing in N containing glasses which are missing in N-free glasses, caused a slight difference in wetting behavior and a more obvious change in isoelectric point and in bacterial response. N-free glasses exhibited better inhibitory results both against E. coli and S. aureus compared to N including glass suggesting that oxygen rich glasses should be further studied for their novel antibacterial properties.     

The survival of E. coli O157:H7, S. Typhimurium and L. monocytogenes in black carrot (Daucus carota) juice

In this study the survival and growth patterns of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in various concentrations of black carrot juice were investigated during incubation period at 4 °C and 37 °C for 7 days. Several parameters, such as juice concentration (%), pH, incubation temperature (°C) and time (days) were found effective on the survival of pathogens tested. Although L. monocytogenes has been found to be the less resistant microorganism to the variable conditions, there were only ca. 1 and 2 log reductions in the number of the cells in the juice samples incubated at 4 °C for 2 and 7 days, respectively. Incubating at low temperature (4 °C) enhanced the survival of test microorganisms.     

Predictive modeling of human operators using parametric and neuro-fuzzy models by means of computer-based identification experiment

Driving a car and piloting an airplane are the most common examples for manual control of complicated processes. Human operators are known to be nonlinear, adaptive, time varying and intelligent controllers. In some cases, the human operator may or may not be well trained or an expert, showing different dynamics from operator to operator as in driving example. Therefore, it is very difficult to obtain mathematical models of human operators in a human-in-the-loop-manual control tasks. The goal of this research is to find a simple dynamic model for the prediction of the human operator actions in a manual control system. A computer-based experiment has been designed using the system identification theory to collect data from human operators. The autoregressive with exogenous inputs (ARX), as a parametric model and the adaptive-network-based fuzzy inference system (ANFIS), as an intelligent modeling approach that has the advantages of both neural networks and fuzzy logic, have been investigated and compared for simple and fast implementation to predict the response of human operators. ANFIS, having only 32 rules, provided much better prediction results than ARX model.     

Antimicrobial Effect of Ozone on Cariogenic Microorganisms In Vitro

The aim of this study was to examine the antibacterial effect of ozone on cariogenic microorganisms. Streptococcus salivarius, Streptococcus mutans, Lactobacillus acidophilus, Lactobacillus casei and Actinomyces viscosus were used to test the antimicrobial activity of ozone. The microorganisms were exposed to power levels 2, 3, or 4 of an ozone device for 20, 40, 60, or 120 s. CFU numbers of bacteria were counted after the ozone application; as a result, the number of bacterial cells was decreased. The bacterial cells were also evaluated with a fluorescence microscope. This analysis revealed that some bacterial cells were killed instantaneously in ozone. The electron microscopic analysis showed no difference in surface morphology between bacteria to which ozone had been applied and those to which it had not.     

Predictive human operator model to be utilized as a controller using linear,neuro-fuzzy and fuzzy-ARX modeling techniques

Modeling human operator's behavior as a controller in a closed-loop control system recently finds applications in areas such as training of inexperienced operators by expert operator's model or developing warning systems for drivers by observing the driver model parameter variations. In this research, first, an experimental setup has been developed for collecting data from human operators as they controlled a nonlinear system. Appropriate reference signals and scenarios were designed according to the system identification and human operator modeling theory, to collect data from subjects. Different modeling schemes, namely ARX models as linear approach, and adaptive-network-based fuzzy inference system (ANFIS) as intelligent modeling approach have been evaluated. A hybrid modeling method, fuzzy-ARX (F-ARX) model, has been developed and its performance was found to be better in terms of predicting human operator's control actions as well as replacing the operator as a stand-alone controller. It has been concluded that F-ARX models can be a good alternative for modeling the human operator.     

Prediction of manually controlled vessels’ position and course navigating in narrow waterways using Artificial Neural Networks

Despite modern navigation devices, there are still some problems for navigating of vessels in narrow waterways because of geographical structures and various disturbances. In this study, a guidance and an early warning method by means of predicting three-minute-ahead position of a vessel, especially in the turning points, has been developed for navigating in narrow waterways. The Istanbul Strait has been specifically studied as a model. Since operators in Vessel Traffic Services (VTS) can watch only straight bearing of vessels on VTS panels but especially for turning regions, they have to foresee a risk on time which may result in a disaster. The objective of this study is to predict the future coordinates of a manually controlled vessel using Artificial Neural Networks (ANN).Artificial Neural Networks have been trained by using position and speed data collected from vessels which navigated manually in the Strait. Three-minute-ahead position of vessels has been predicted by using the trained ANN. Some on-line experiments have been done in Istanbul VTS centre and it has been observed that the method satisfied the goal in especially turning points of the Strait. Hence the proposed method could be utilized for warning system by VTS operators and guidance system by vessel crew.     

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.     

A comparative study of silicon nitride and SiAlON ceramics against E. coli

In recent decades, due to some limitations from alumina (Al₂O₃) and zirconia (ZrO₂), silicon nitride (Si₃N₄) has been investigated as a novel bioceramic material, mainly in situations where a bone replacement is required. Si₃N₄ ceramics and its derivative form, SiAlON, possess advantages in orthopedics due to their mechanical properties and biologically acceptable chemistry, which accelerates bone repair. However, biological applications require additional properties, enabling stronger chemical bonding to the surrounding tissue for better fixation and the prevention of bacteria biofilm formation. Therefore, two commercial Si₃N₄ and SiAlON ceramics were investigated in this study and compared to each other according to their material properties (like wetting angles and surface chemistry) and their antibacterial behaviors using E. coli. Results provided evidence of a 15% reduction in E. coli colonization after just 24 h on Si₃N₄ compared to SiAlON which is impressive considering no antibiotics were used. Further, a mechanism of action is provided. In this manner, this study provides evidence that Si₃N₄ should be further studied for a wide range of antibacterial orthopedic, or other suitable biomaterial applications.     

Chitosan‐based wet‐spun scaffolds for bioactive agent delivery

Use of scaffolds both as supporting materials at defect site and delivery vehicles for bioactive agents is a commonly employed strategy to aid in tissue repair and regeneration. In this study, fibrous meshes of chitosan were prepared by wet spinning and coated with alginate. BSA as a model protein and gentamicin as a model antibiotic were incorporated into the scaffolds in multiple loading models and their release kinetics were studied. The effects of structural form of scaffold and properties of bioactive agents on release profiles were evaluated. Our results suggest that, designed scaffolds are potential candidates for tissue engineering with the feature of controlled bioactive agent delivery. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3759–3769, 2013