Morphology of ferromagnetic sol–gel submicron silica powders doped with iron and nickel particles

The sol–gel submicron spherical silica particles were obtained with the modified Stöber method using methanol. Iron and nickel dopants produced by the exploding wire method were introduced to the SiO₂ powders during the sol–gel process. The electron microscopy and laser diffraction particle size analyzer studies showed that the hybrid powders agglomerated easily in ethanol. The difference of ζ-potential in pure water between the pure silica (− 46.8 mV), the Fe-doped (− 39.7 mV) and the Ni-doped silica (− 41.5 mV) proved that doping changes the surface properties. The SEM studies confirmed that the Ni-particles could attach to the surface of the silica shells. With TEM it has been found that the differently sized Ni-particles may be encapsulated in silica shells, form clusters within silica or they may remain separate if they were larger than the silica particles. The saturation magnetization of the ferromagnetic hybrid powders was 0.81 emu/g (Fe-doped) and 0.51 emu/g (Ni-doped), while the hysteresis of magnetization revealed that the magnetic particles may have close to a single domain structure. The magnetization values and the X-ray studies confirmed that some Fe-oxides of the initial doping powder remained in the hybrid powder, while the Ni applied was nearly totally metallic.     

Optical and electrical properties of crystalline indium tin oxide thin film deposited by vacuum evaporation technique

Indium tin oxide (ITO) thin film was deposited on glass substrate by means of vacuum evaporation technique and annealed at 200 °C, 300 °C and 400 °C in air for 1 h. The characterization and properties of the deposited film samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-VIS-NIR spectroscopy techniques. From the XRD patterns, it was found that the deposited thin film was of crystalline at an annealing temperature of 400 °C. The crystalline phase was indexed as cubic structure with lattice constant and crystallite size of 0.511 nm and 40 nm, respectively. The SEM images showed that the films exhibited uniform surface morphology with well-defined spherical grains. The optical transmittance of ITO thin film annealed at 400 °C was improved from 44% to 84% in the wavelength range from 250 nm to 2 100 nm and an optical band gap was measured as 3.86 eV. Hall effect measurement was used to measure the resistivity and conductivity of the prepared film.     

Hybrid composites of jute and man-made cellulose fibers with polypropylene by injection moulding

A number of hybrid composites was made with jute, mercerised jute, and high tenacity man-made cellulose tyre cord yarn Cordenka of dissimilar ratios by a pultrusion process and subsequent injection moulding. Composites of jute, mercerised jute, and Cordenka were also made in order to compare the properties. The matrix material was a polypropylene/ethylene block copolymer (PP), and a maleic acid anhydride grafted PP (MAPP) was used as a coupling agent. The overall fiber contain was 25%. Mechanical properties such as tensile and bending strength, tensile and bending modulus, Charpy impact strength, and heat distortion temperature (HDT) were determined. High strength (>70 MPa) and excellent impact properties (>80 kJ/m²) were achieved with pure Cordenka reinforcement. Partial substitution of jute instead of Cordenka leads to enhance stiffness properties of the composite as well as increased heat distortion temperature (HDT) values above 105 °C for all the tested compositions (25%, 50%, 75%, and 100% jute) and for an overall fiber load of 25%. On the other hand, impact strength decreases with increasing jute fraction down to 22 kJ/m² for pure jute. A good property balance is achieved for a composite with 25 wt.% jute and 75 wt.% Cordenka, maintaining impact strength of 79 kJ/m². Mercerisation of the jute fibers gave moderate improvements in the composite properties. Very good fiber (both jute and Cordenka) matrix adhesion was observed by SEM.     

Developing stable optical fiber refractometers using PMDI with two-parallel Fabry–Perots

The paper presents a new approach to developing an optical fiber refractometer. The objective of the study is to come up with a relatively inexpensive but reliable optical refractometer that can be used to measure the change of refractive index in a resolution of 10⁻⁵ and to work in a dynamic range up to 6×10⁻³ at a DC frequency of up to 100 Hz. It is known that the phase modulations of optical fiber sensors are very sensitive to external disturbances, especially to the effects of thermal drifts or vibrations. A cancellation technique to compensate the effect of variation on a PZT stack is proposed in this paper to stabilize the system. Two parallel Fabry–Perot sensing cavities corresponding to two path-matching cavities for read-out systems are employed to form path-matching differential interferometries (PMDI). One Fabry–Perot cavity is used as sensing head, and the other as reference sensor. As a result, the experimental data show that the change of refractive index of a so designed sensing system can be kept in at the level of 10⁻⁴ without any serious variations even for a 3-h long-term monitoring. Accordingly, the proposed new system can be easily implemented and used as a long-term monitoring system in a medical care environment.     

Selective radiography with etched track detectors

A new technique of selective enhancement and evaluation of radiographic images in etched track detectors was developed. It is based on the image processing of individual image element units – etched tracks – by a track analysis system. A selective radiograph is obtained on the basis of the assessment of the size and optical properties of individual tracks. The computer-generated image, in addition to its selectivity, which enables, for instance, multi-elemental analysis from an autoradiograph, also offers a contrast enhancement for better visual observation and/or evaluation. The applicability of the technique is illustrated by selective imaging of ¹⁰B distribution in a whole body samples of a tumour-bearing mouse.     

A projection-based method for motion-compensated noise suppression

The diagnostic value of medical images significantly depends on the signal-to-noise ratio (SNR). Especially in fluoroscopic tomography, the SNR is limited by the radiation dose (Computer Tomography), or by the suitable acquisition techniques (Magnetic Resonance Imaging). The purpose of this paper is to introduce a projection-based method for the motion-compensated SNR enhancement applied in Radon space. It is based on a projection-based motion estimation with subsequent motion-compensated, edge-preserving filtering of the measured projections. The effect of temporal filtering as well as spatial filtering will be presented. In contrast to the recently introduced image-based approach, this method allows a very efficient computational implementation, likely to be used in real time imaging. It will be shown that a significant increase of the SNR can be achieved without introducing additional motion artifacts or blurring in the reconstructed images. The proposed technique has the potential to be used for SNR enhancement in low-dose fluoroscopy applications in CT as well as for SNR improvements in MR fluoroscopy using projection reconstruction based techniques.     

The role of the ohmic contact on the efficiency of gallium arsenide radiation detectors

It has recently been found that in gallium arsenide radiation detectors injecting ohmic contacts impede charge collection efficiency to get 100%, since breakdown occurs as soon as the electric field reaches the contact itself. In the present contribution, this phenomenon is investigated by comparing two sets of ohmic contacts realized by different technological procedures. While the overall defective state results to be nearly the same for both contacts, their performance significantly differs. Deep level junction spectroscopy shows that the defects are the same in both sets whilst there is much difference in density between a few of them.     

Serum polychlorinated biphenyls: Quantitation and identification of source of exposure by the SIMCA pattern recognition method

Luotamo, M., Aitio, A. and Wold, S., 1988. Serum polychlorinated biphenyls: quantitation and identification of source of exposure by the SIMCA pattern recognition method. Chemometrics and Intelligent Laboratory Systems, 4: 171–181.Serum specimens from persons exposed continuously at work, or for a short period of time in a capacitor accident, as well as from persons exposed through diet only, were analyzed for polychlorinated biphenyls (PCBs) using capillary column chromatography with electron capture (EC) detection, and quantitation either by the isomer specific EC response, or by a generalized pattern recognition method (partial least squares projection to latent structures), both with three different PCB standard sets. The different exposure groups were effectively identified. In the quantitative analysis, the correlation between isomer specific and PLS quantitation was excellent in every case, but the level of PCB obtained was not similar, i.e., the regression lines between different quantitation methods had slopes and intercepts clearly different from 1 and 0 respectively. This is mainly due to differences in the pattern of PCB in blood of people at different exposure situations.     

Distribution of naturally occurring radionuclides in soils of the southern districts of Bangladesh

The activity concentrations of naturally occurring radioactive materials in soil samples of an elevated radiation background area of nine southern districts of Bangladesh were determined using gamma-ray spectrometry with an aim of evaluating the environmental radioactivity. The outdoor and indoor external effective dose rates and the radiation hazard indices from the soil activity were evaluated with an aim of minimising the harmful effects of ionising radiation to the population of the area concerned. The activity of (137)Cs was measured and observed in some of the locations.     

Kinetic analysis of biohydrogen production from anaerobically treated POME in bioreactor under optimized condition

In this study, the biohydrogen production from POME was performed under mesophillic conditions by mixed culture in a 2 L bioreactor using the optimized conditions obtained previously. The effect of controlling pH initially or throughout the fermentation was also examined. The fermentation performance was monitored by comparing P, R_m, λ, and P_s in both systems. In this present study, the reactor system showed higher hydrogen production potential values with the utilization of pH control. Hydrogen production potential was increased two folds when the reactor system was equipped with pH control rather than just fixed the initial pH at 5.8. The biohydrogen production under controlled pH occurred after 7 h fermentation resulting in maximum Ps and Rm of 1.32 L/L POME and 0.144 L/L.h, respectively.