Dye–surfactant interaction in aqueous solutions

The interaction of four ionic dyes, C.I. Mordant Black 11, C.I. Mordant Black 17, C.I. Direct Yellow 50 and C.I. Basic Blue 9, with cationic and anionic surfactants was studied by absorption spectroscopy. The dyes interact strongly with oppositely charged surfactant in the premicellar concentration range and the appropriate values of constant of dye–surfactant complex formation were estimated. In addition, the most important factor affecting the number of dye particles solubilized in the surfactant micelle was its molecular mass.     

Programmable Switched Capacitor Finite Impulse Response Filter with Circular Memory Implemented in CMOS 0.18 μm Technology

This paper presents a programmable multi-mode finite impulse response (FIR) filter implemented as switched capacitor (SC) technique in CMOS 0.18 μm technology. Intended application of the described circuit is in analog base-band filtering in GSM/WCDMA systems. The proposed filter features a regular structure that allows for elimination of some parasitic capacitances, thus significantly improving the filtering accuracy. Due to its modularity that allows for dividing the circuit into two separate sections, the circuit can be easily reconfigured to work as either infinite impulse response (IIR) or as finite impulse (FIR) filter. One of the key components that allows for this multi-mode operation is the proposed programmable and ultra low power multiphase clock circuit. The 24-taps filter for the sampling frequency of 30 MHz dissipates power of 4.5 mW from a 1.8 V supply.     

Volumetric Properties of Binary Mixtures of 2,4,6-Trimethylpyridine with 1,2-Ethanediol,Methanol, and Water,and the Association Energies of the O–H· · ·N Bonded Complexes

2,4,6-Trimethylpyridine forms 1:1 complexes with methanol, 1,2-ethanediol, and water due to the O–H· · ·N bonds. The association energy of the complexes was calculated using MP2 and DFT methods. The complexes with 1,2-ethanediol and water aggregate in the liquid phase as a result of the O–H· · ·O bonds. In spite of the higher O–H· · ·N bond energy, the aggregation of the ethanediolic complexes is less pronounced than that of the aqueous ones. That is probably caused by the weaker induction effect due to the C–C chain separating the hydroxyl groups in the diol molecule. Aggregation is impossible in the methanolic system, because of the lack of proton-donating functional groups. Differences in the hydrogen bond energy and in the ability to aggregate are manifested in the volumetric properties of the mixtures.     

Infrared transmittance model for pyrometric monitoring of surface quality of thin diamond films

The thickness and surface roughness of thin diamond films grown on quartz substrates are studied in the paper using a model of changes in the infrared transmission ratio associated with multiple constructive interference within a thin crystal film. On the other hand, the model is referred to periodic variations of the apparent temperature of the substrate measured by the two-color pyrometer. Obtained results are then compared with those of other similar studies, and the AFM measurements. Some discrepancy between the results from infrared and AFM data is explained in terms of optical absorption of the crystal, which is neglected in the transmittance model.     

Agricultural biogas plants in Poland: Investment process,economical and environmental aspects,biogas potential

The formal and legal requirements as well as the support system for building agricultural biogas plants in Poland have been presented. There are currently 24 agricultural biogas plants operating in Poland. The fermentation substrates are slurry, food waste and maize silage. It is most often mesophilic fermentation. Produced biogas is combusted in cogeneration and thus obtained electrical and thermal energy is used for the biogas plant's own needs and sold. The support system for biogas plants' operation in Poland is based on a system of certificates. In this system it is cost-effective to use waste for fermentation whilst it is not cost-effective for a biogas plant to run on maize silage. It has been calculated that in Poland the theoretical annual biogas potential for cattle slurry is 3646 million m³, for pig slurry it is 2581 million m³, for poultry manure it is 717 million m³, from maize after seed harvest it is 1044 million m³, from municipal waste biofraction it is 100 million m³ of biogas.     

The influence of oxygen ambient annealing conditions on the quality of Al/SiO2/n-type 4H-SiC MOS structure

The effect of reoxidation process in O₂ on the electrical properties of metal-oxide-semiconductor (MOS) capacitors fabricated on n-type 4H-SiC (0 0 0 1) is investigated. All samples were oxidized in wet oxygen at temperature of 1175 °C. Reoxidation process was carried out on four of the five samples. Samples were annealed at temperature of 700 °C and 800 °C for different process times. The reoxidation process in oxygen improves the quality of the dielectric layer and the interface of Al/SiO₂/n-type 4H-SiC MOS structure. The best quality of the SiO₂/SiC interface can be achieved for the MOS structure annealed in O₂ at higher temperature (800 °C) for longer time. However, higher and more uniformly distributed values of breakdown voltage were obtained for MOS structures reoxidized at temperature of 700 °C.     

Thermal characterization of screen printed conductive pastes for RFID antennas

Thermal resistance is an essential aspect of electronic circuits designing. It leads to unexpected changes in electronic components during their work. In this study, new materials for screen printed RFID tag's antennas were characterized in terms of their resistance to thermal exposure. Polymer materials containing silver flakes, silver nanopowder, carbon nanotubes or conductive polymer PEDOT:PSS were elaborated and used for antenna printing on flexible materials. In order to verify their long term susceptibility to damages caused by the changing environmental conditions, the temperature cycling test was used in three different temperature ranges: +65 °C, −12 °C, −40 °C/+85 °C (3 h in each temp., dwell time 1 h). The highest durability to thermal exposure exhibited the paste with carbon nanotubes dispersed in poly(methyl methacrylate) PMMA and the lowest one – the paste with conductive polymer PEDOT:PSS.     

Technology of ZnO nanofibers based devices

In the presented work, the possibility of fabrication of ZnO single- and multi-nanofiber structures using a standard microelectronic device technology were studied. An innovative fabrication step, namely, selective wet chemical nanofibers etching through a photoresist mask, was used to define the active area, along with mesa etch in the Si/SiO₂ substrate. Test structures in the configuration of a resistor and Schottky diode with chemically active electrospun ZnO nanofibers were prepared. The Ti/Au ohmic and Pt Schottky contacts were fabricated using a lift-off photolithography process. Optical and scanning electron microscopy studies were done to characterize ZnO nanofibers and topography of contacts. The measurements made for electrical characterization showed linear I–V dependence and saturation of the current for single ZnO nanofiber structures.     

Thermal properties of high-power diode lasers investigated by means of high resolution thermography

In the present work, thermal effects in high-power diode lasers are investigated by means of high resolution thermography. Thermal properties of the devices emitting in the 650 nm and 808 nm wavelength ranges are compared. The different versions of the heterostructure design are analyzed. The results show a lowering of active region temperature for diode lasers with asymmetric heterostructure scheme with reduced quantum well distance from the heterostructure surface (and the heat sink). Optimization of technological processes allowed for the improvement of the device performance, e.g. reduction of solder non-uniformities and local defect sites at the mirrors which was visualized by the thermography.     

Carbon nanofibers produced from modified electrospun PAN/hydroxyapatite precursors as scaffolds for bone tissue engineering

In the current study we have proposed a method to obtain a carbon/HAp bioactive nanofibrous scaffold. The modified carbon nanofibrous nonwoven' fabrics were obtained by the use of electrospinning and subsequent stabilization and carbonization processes. The modified with HAp powder nanofibrous PAN nonwovens were thermally stabilized using a multi-stage process in the temperature ranging from 100 °C to 300 °C in an oxidative environment and then carbonized at 1000 °C in argon atmosphere. The changes of properties of composite precursor membranes taking place during stabilization and carbonization processes were investigated using the methods of: DSC, TGA, FTIR, SEM, EDX, WAXD and mechanical tests. Bioactivity was determined by assessing the formation of crystalline apatite on the surface of membranes upon immersion in Simulated Body Fluid (SBF). The FTIR, SEM and WAXD investigation clearly prove that hydroxyapatite added to the electrospinning solution was present also in composites nanofibrous nonwovens after stabilization and carbonization process. It was found that due to HAp addition: the significant decrease of fibers average diameter occurs and that the average pore size for modified membranes is smaller than for the unmodified one. On the other hand it was shown that the ceramic additive protects fibers from mass reduction during the stabilization treatment. Finally a drastic increase of mineralization activity of nCF/HAp scaffolds as compared to their nCF counterparts has been proved.