Correlation coefficients between different methods of expressing bacterial quantification using real time PCR

The applications of conventional culture-dependent assays to quantify bacteria populations are limited by their dependence on the inconsistent success of the different culture-steps involved. In addition, some bacteria can be pathogenic or a source of endotoxins and pose a health risk to the researchers. Bacterial quantification based on the real-time PCR method can overcome the above-mentioned problems. However, the quantification of bacteria using this approach is commonly expressed as absolute quantities even though the composition of samples (like those of digesta) can vary widely; thus, the final results may be affected if the samples are not properly homogenized, especially when multiple samples are to be pooled together before DNA extraction. The objective of this study was to determine the correlation coefficients between four different methods of expressing the output data of real-time PCR-based bacterial quantification. The four methods were: (i) the common absolute method expressed as the cell number of specific bacteria per gram of digesta; (ii) the Livak and Schmittgen, ΔΔCt method; (iii) the Pfaffl equation; and (iv) a simple relative method based on the ratio of cell number of specific bacteria to the total bacterial cells. Because of the effect on total bacteria population in the results obtained using ΔCt-based methods (ΔΔCt and Pfaffl), these methods lack the acceptable consistency to be used as valid and reliable methods in real-time PCR-based bacterial quantification studies. On the other hand, because of the variable compositions of digesta samples, a simple ratio of cell number of specific bacteria to the corresponding total bacterial cells of the same sample can be a more accurate method to quantify the population.     

A coupled Thermal‐mechanical FE Model of Flow Localization during the Hot Torsion Test

The hot torsion test (HTT) has been extensively used to analyse and physically model the flow behaviour and microstructure evolution of materials and alloys during hot deformation processes. The geometry of the specimen is a key factor for obtaining reliable results. In the present work, a thermo‐rigid viscoplastic FE code, THORAX.FOR, was developed to describe the interaction of thermal‐mechanical conditions and geometries of the HTT specimens. This was used to recommend the conditions for avoiding flow localization during HTT of API‐X70 microalloyed steel. The simulation results show how an inappropriate choice of both test specimen geometry and twist rate of deformation could lead to a significant temperature raise in the middle of the gauge section and temperature gradient in the radial and longitudinal direction of the specimen. This consequently causes flow localization during the test. Therefore, assumptions of isothermal forming conditions or uniform strain softening may not be valid in many test scenarios. These assumptions could introduce significant errors in the post results of the test such as flow curve and interpretation of microstructure evolution. Recommendations on proper specimen geometry for a specified strain rate will be given to avoid flow localization during the hot torsion test.     

Ultrasonic assisted dry grinding of 42CrMo4

In recent years, many cooling lubricants are classified as health hazards, while their end-of-life treatment poses numerous ecological threats. Dry machining is a solution for greener production and also is a favorable process from an economical point of view. However, compared to other machining processes, conventional grinding has a low material removal rate and involves high specific energy. A major part of the specific energy in grinding is changed to heat that makes harmful effect on surface quality. Therefore, in conventional dry grinding, as there are no cutting fluids to transfer the heat from the contact zone, the temperature of workpiece surface and grinding wheel surface will be increased resulted to thermal damage and poor surface integrity, increasing of wheel wear and inefficient grinding compared to conventional grinding. To make a step forward to pure dry grinding and to eliminate the negative environmental impact of the cutting fluids, a new technique called ultrasonic assisted dry grinding has been used. The advantages of ultrasonic assisted grinding were proved mostly for the brittle material. Our investigations show the improvement on the surface roughness, considerable reduction of the normal grinding force, and thermal damage in case of using ultrasonic assisted dry grinding compared to conventional dry grinding for a soft material, 42CrMo4. A decrease of up to 60% of normal grinding forces has been achieved.     

Lasing in a three-dimensional photonic crystal of the liquid crystal blue phase II

Photonic-bandgap materials, with periodicity in one, two or three dimensions, offer control of spontaneous emission and photon localization. Low-threshold lasing has been demonstrated in two-dimensional photonic-bandgap materials, both with distributed feedback and defect modes. Liquid crystals with chiral constituents exhibit mesophases with modulated ground states. Helical cholesterics are one-dimensional, whereas blue phases are three-dimensional self-assembled photonic-bandgap structures. Although mirrorless lasing was predicted and observed in one-dimensional helical cholesteric materials and chiral ferroelectric smectic materials, it is of great interest to probe light confinement in three dimensions. Here, we report the first observations of lasing in three-dimensional photonic crystals, in the cholesteric blue phase II. Our results show that distributed feedback is realized in three dimensions, resulting in almost diffraction-limited lasing with significantly lower thresholds than in one dimension. In addition to mirrorless lasing, these self-assembled soft photonic-bandgap materials may also be useful for waveguiding, switching and sensing applications.     

Performance of ANFIS Coupled with PSO in Manufacturing Superior Wear Resistant Aluminum Matrix Nano Composites

In this study, ANFIS was combined with PSO in order to optimize the parameters in pressure assisted semi solid processing of A360 aluminum matrix nano composites. ANFIS was utilized to calculate the objective function, which was later minimized using PSO. Combination of EMS semi solid processing and pressure assistance during solidification resulted in improvement of microstructural features and tribological properties. Globular grain structure was formed in the pressure assisted EMS parts. Tribological properties were investigated using pin on disk. It was noted that wear properties of EMS parts were benefited from the refinement of the primary α-Al phase and uniform distribution of the particles. EMS composites showed higher hardness than conventional cast parts, consequently there was a lower real area of contact and therefore lower wear rate. Moreover, hard dispersoid made the virgin alloy plastically constrained and improved their wear resistance.     

Gas holdup in two phase gas–liquid and three phase gas–liquid–solid production and transportation

The gas holdup is an important parameter that is needed for design and development of surface facilities and transportation pipelines in the field of petroleum engineering. There is no general model for prediction of this parameter in different systems and under different conditions. As a result, development of accurate and general models for prediction of this parameter in various situations is of great importance. This study presents new experimental gas holdup data in the kerosene+CO₂ and kerosene+N₂ systems. The experimental data were measured by using a bubble column setup. Moreover, a computer-based model namely PSO-ANFIS model is also developed for prediction of the gas holdup in different systems. A total of 818 experimental gas holdup data in various systems were utilized including the newly measured experimental data in the present work as well as experimental data from several published works in the literature. Results showed that the developed PSO-ANFIS model is accurate for prediction of experimental data with an R² value of 0.998 and average absolute relative deviation (AARD%) of 3.4%.