Necdet Aslan

Low Temperature Plasma for decontamination of E. coli in milk

Raw milk is a natural, highly nutritious product and a quick and easy supplement for human dietary requirements. Elimination of bacteria in milk has been a problem for decades and new methods with regards to non-thermal applications which do not harm the chemical composition of milk, are currently under investigation. The objective of the study was to determine the potential use of a novel, Low Temperature Plasma (LTP) system for its capability of killing Escherichia coli in milk with different fat contents. The time dependent effect of atmospheric corona discharge generated with 9kV of AC power supply on E. coli ATCC 25922 dispersed in whole, semi skimmed and skimmed milk was examined. Plasma was applied at time intervals of 0, 3, 6, 9, 12, 15 and 20min. A significant 54% reduction in the population of E. coli cells after only 3min was observed regardless of the fat content of the milk. The initial pre-plasma bacterial count of 7.78 Log CFU/ml in whole milk was decreased to 3.63 Log CFU/ml after 20min of plasma application. LTP did not cause any significant change to the pH and color values of raw milk samples. No viable cells were detected after one week examination in whole milk samples and remained so over the 6week storage period. The findings of this study show that the novel LTP system tested was able to significantly reduce E. coli in milk by more than a 3 fold log reduction without significantly affecting pH or color properties.

Enhancement of thermal conductivity upon application of magnetic field to Fe3O4 nanofluids

Enhancement of thermal conductivity of fluids upon addition of nanoparticles has been previously observed. In this study, Fe3O4 magnetite particles were used and thermal conductivity enhancements both in water and in heptane with increasing volume fraction have been shown. Upon measuring thermal conductivity under externally applied magnetic field, it has been shown experimentally that thermal conductivity can be further increased even at low concentrations and low magnetic field strengths in both fluids. Theoretical calculations are presented to support the effect of magnetic field on the thermal conductivity enhancement. This enhancement is attributed to the thermomagnetic convection which due to a temperature gradient, results in a non-uniform magnetic body force resulting in more efficient thermal conductance.

Optical properties and chemical behavior of Laser-dye Coumarin-500 and the influence of atmospheric corona discharges.

Structure elucidation of Coumarin-500 Laser-dye in cyclohexane at room temperature has been studied by UV-Vis, Raman, and FTIR spectroscopic techniques. Optical properties and chemical behavior under the influence of atmospheric positive electric pulsed corona discharges were also examined. The effects of UV-Vis irradiation changed some optical parameters, such as decrease in optical density on the absorption spectrum and formation of photoproducts, due to the chromaticity removal. No significant optical changes were observed in the light absorption upon UV-irradiation but large changes in absorption spectrum were observed after positive electric corona discharge treatments, FTIR and Raman spectra in non-polar solvent are recorded and interpreted.

The Effect of Atmospheric Pressure Plasma Corona Discharge on pH, Lipid Content and DNA of Bacterial Cells

Effect of plasma corona discharges on the pH, whole cell lipids and DNA of bacteria is investigated. Results showed an increase in the acidity levels of water due to plasma reactive species which, however, were not responsible for bacterial cell death. No changes in the whole cell lipid contents were observed, while DNA after plasma treatment showed deterioration of the amplified sequences, indicating the possible occurrence of DNA degradation. In conclusion, reactive species produced by plasma discharges affects DNA, possibly contributing to cell death.

Effect of thymol on the antibacterial efficiency of plasma-treated cotton fabric

In this research, the effect of thymol on the antibacterial activity of cotton fabric when modified by low-temperature plasma was investigated. The modification consisted of plasma pre-functionalization followed by one-step wet treatment with thymol. Oxygen and nitrogen were used as the working gases in the plasma reactor. The results showed that plasma-treated samples can absorb more thymol than untreated samples. Thus, the antibacterial activity of the samples in this case, which was analyzed by the bacteria counting test, was increased considerably. Durability of the antibacterial property was also assessed. It was concluded that loading thymol on plasma-treated cotton fabric produced effective durable antibacterial textiles.

Exact Pressure Evolution Equation for Incompressible Fluids

An important aspect of computational fluid dynamics is related to the determination of the fluid pressure in isothermal incompressible fluids. In particular this concerns the construction of an exact evolution equation for the fluid pressure which replaces the Poisson equation and yields an algorithm which is a Poisson solver, i.e., it permits to time‐advance exactly the same fluid pressure without solving the Poisson equation. In fact, the incompressible Navier‐Stokes equations represent a mixture of hyperbolic and elliptic pde’s, which are extremely hard to study both analytically and numerically. This amounts to transform an elliptic type fluid equation into a suitable hyperbolic equation, a result which usually is reached only by means of an asymptotic formulation. Besides being a still unsolved mathematical problem, the issue is relevant for at least two reasons: a) the proliferation of numerical algorithms in computational fluid dynamics which reproduce the behavior of incompressible fluids only in ...

Obtaining useful properties of different materials by using magnetron sputtering

The objective of this work was to alter the surface morphology of materials such as textiles, metals, glass by using magnetron sputtering deposition in order to get new useful properties. This coating technique was chosen because it is very clean, nontoxic, and produces no chemical contamination compared to other methods, such as spraying and electroplating.1 Antibacterial properties of textiles after coating with copper, silver, and titanium were examined using the test microorganisms Escherichia coli ATCC-25922 and Staphylococcus aureus ATCC-25923 according to the standard protocol for the parallel streak method (AATCC-TM-147) and suspension test (ASTME-2149). Not only were the antibacterial properties of coated textiles investigated, but their surface wettability was studied as well. It was seen that copper coated textiles gained hydrophobic properties similar to textiles coated with silver.2 The electrical conductivity change of non-woven textiles before and after coating was also studied. A dramatic resistance decrease was observed after silver coating was done on non-woven fabric. The optical transmittance and resistivity of microscope glass slides were also studied after ITO and silver coatings. Cluster formation in the ITO coatings was observed as in previous studies.3 The reduction of sheet resistance of ITO-Ag-ITO multilayer in comparison with ITO monolayer resistance was also observed. Scanning electron microscope (SEM) images of coated surfaces were taken to examine their surface morphology.