Aleksandar Jokić

Chemometric estimation of post-mortem interval based on Na+ and K+ concentrations from human vitreous humour by linear least squares and artificial neural networks modelling

The subject of this paper is to determine the post-mortem interval (PMI) using the data obtained by potentiometric measurements of the electrolyte concentrations (potassium and sodium) in human vitreous humour. The data were processed by linear least squares (LLS) and artificial neural network (ANN) procedures. The LLS mathematical models have been developed as calibration models for prediction of the PMI. The quality of the models was validated by the leave one out (LOO) technique and by using an external data set. High agreement between experimental and predicted PMI values indicated the good quality of the derived models. Additionally, we analysed the influence of various factors (the cause of death, sex, differences between electrolyte concentrations in left and right eye) on the accuracy and reliability of obtained PMI. The ANN method was based on 174 forensic cases with different causes of death and known PMI ranging from 3.1–24.1 hours. The external data sets corresponding to 40 selected forensic cases were tested. Excellent correlation between experimental PMI and PMI predicted by ANN was obtained with a coefficient of correlation r2=0.9611. In comparison to the LLS regression method applied on the complete available data, the prediction of PMI with ANN was improved by1.66 hours.

Flux Improvement during Cross-flow Microfiltration of Wheat Starch Suspension using Turbulence Promoter

The objective of this study was to investigate the effects of the process variables (transmembrane pressure, flow rate, and concentration) on the permeate flux during the microfiltration of model starch suspensions, and to determine the conditions under which the use of Kenics statics mixer as a turbulence promoter is justified. A response surface methodology was used to examine the influence of the selected operating conditions on starch suspension microfiltration using a single channel ceramic membrane with 200 nm pore size. The experimental results clearly show that the improved performance of starch suspension cross-flow microfiltration can be obtained by using a Kenics static mixer, especially at lower flow rates. Compared to the operation without the turbulence promoter, the average permeate flux improvement during the filtration period ranged from 30% to 230%. As a result of the statistical analysis, the optimal conditions for starch suspension microfiltration were determined and applied to microfiltration of starch industry wastewater.

MATERIAL AND ENERGY FLOW MANAGEMENT- LIFELONG LEARNING COURSES EXPERIENCES

Material and energy flow management is among the most important factors for the economic growth of a society in harmony with nature and it will play the main role only in the area of sustainable development. The three lifelong learning courses were developed in order to introduce this concept to the industry professionals and administration at the city and regional level. The main goal was to heighten awareness of participants to this topic, as in Serbia it is relatively new approach in corporate and administrative management. The results of the courses confirmed the interest in this kind of lifelong learning courses with suggestion to join it in a single course with emphasise on the specific participant’s problems.

Optimization of the flux values in multichannel ceramic membrane microfiltration of Baker`s yeast suspension

The objective of this work was to estimate the effects of the operating parameters on the bakers yeast microfiltration through multichannel ceramic membrane. The selected parameters were transmembrane pressure, suspension feed flow, and initial suspension concentration. In order to investigate the influence and interaction effects of these parameters on the microfiltration operation, two responses have been chosen: average permeate flux and flux decline. The Box-Behnken experimental design and response surface methodology was used for result processing and process optimization. According to the obtained results, the most important parameter influencing permeate flux during microfiltration is the initial suspension concentration. The maximum average flux value was achieved at an initial concentration of 0.1 g/L, pressure around 1.25 bars and a flow rate at 16 L/h.

Membrane technology application in the framework of zero emission concept

The Zero emissions concept envisages all industrial inputs being used in final products or converted into value-added inputs for other industries or processes. In this way, industries are reorganized into clusters such that each industrys wastes / by-products are fully matched with the input requirements of another industry, and the integrated whole produces no waste of any kind. This technique is based on the well-established economic analysis tool known as the input/output approach. In the framework of the zero emission concept capture of CO2 plays an important role. CO2 can be captured and permanently stored, or it can be re-used. Carbon sequestration is a two-step process where the capture of CO2 from a gas stream is followed by its permanent storage. The capture step contributes 75% to the overall carbon sequestration process cost. For this reason, the scientific community has paid a great attention to the development of new processes for CO2 capture. Currently, there is a wide range of technologies to separate CO2 from gas streams. They are based on different physical and chemical processes including absorption, adsorption, cryogenics and membrane technology. The choice of a suitable technology depends on the characteristics of the flue gas stream and, as a consequence, on the power plant technology. As an alternative to conventional process es for CO2 separation and capture, membrane technology shows great potentiality for CO2 capture owing to its easy applicability, efficiency, flexibility, ability to maintain high CO2 pressure and to perform separations at low energy penalties. CO2-selective membranes allow separation of CO2 from different gas streams, such as: flue gas (post-combustion system), natural gas (natural gas processing) and hydrogen (pre-combustion systems) or oxygen from nitrogen (in an oxyfuel combustion system). In the framework of zero emission concept, this paper gives an overview and analysis of the types of membranes used and membrane technology application in CO2 capture from the point of cost and energy consumption.

OPTIMIZATION OF MEDIA FOR ANTIMICROBIAL COMPOUNDS PRODUCTION BY BACILLUS SUBTILIS

Bacillus subtilis is one of the most important producers of diverse antimicrobial compounds. This bacterium grows and produces antibiotics on different substrates. The increase of the antibiotics yield can be achieved by changing the conditions of cultivation and the composition of the culture media. In this study, response surface methodology was used for optimization of glycerol, sodium nitrite, and phosphate content in media for production of antibiotics effective against Staphylococcus aureus. As biosynthesis strain Bacillus subtilis ATCC 6633 was used. The developed model predicts that the maximum inhibition zone radius (38.08 mm) against Staphylococcus aureus and minimal amount of residual nutrients (glycerol 1.75 g l −1 , nitrogen 0.21 g l −1 , phosphorus 0.18 g l −1 ) are achieved, when the initial content of glycerol, sodium nitrite, and phosphate are 49.99 g l −1 , 1.00 g l −1 , and 5.00 g l −1 , respectively.

Environmental biotechnology for the treatment of waste effluents from biofuels production

Bioethanol, biodiesel and biogas represent very significant alternatives to fossil fuels in order to reduce carbon- dioxide emissions, so there is a need to develop energy efficient technologies, equipment and waste management procedures to make production profitable by reducing production costs. One way to accomplish this is to solve the problem of waste effluents by using them to obtain high-value products. All biotechnological processes are energy intensive to some extent, so saving energy becomes one of the main goals of all biotechnological processes in addition to preserving the environment and the management or reuse of waste. The availability of waste effluents from the production of biofuels, such as distillery stillage and crude glycerol, will increase over the next few years due to the growth of the biofuel industry and will provide a great possibility for the biotechnological production of high-value products.

Primena višekanalne keramičke membrane u mikrofiltraciji suspenzija skroba

This work investigates influence of different process parameters such as transmembrane pressure, flow rate and concentration of wheat starch suspension on the average permeate flux and permeate flux decline. Used membrane in all experiments was 19 channels ceramic membrane with 0.2 μm pore size. Experimental results were analyzed using response surface methodology. It is observed that the significant average permeate flux enhancement of 200% was achieved by the increase of the transmembrane pressure, while the increase of flow rate and concentration affected the increase in average permeate flux in the range of 40-100%. Permeate flux decline was almost independent of the transmembrane pressure, but the increase of the flow rate, as well as the decrease of the concentration led to decrease of permeate flux decline in the range of 20-50%.