Effect of aligned carbon nanotubes on electrical conductivity behaviour in polycarbonate matrix

This article reports effects of alignment of embedded carbon nanotubes in a polycarbonate polymer matrix under magnetic, direct and alternating current electric fields on the electrical properties of the resulting nanocomposites. Composites consisting of different quantities of carbon nanotubes in a polycarbonate matrix have been prepared using a solution casting technique. The effects of field strength and nanotube concentration on the resulted network structure and conductivity of the composites were studied by in situ optical microscopy, transmission electron microscopy and four-point probe technique. The results showed that the composites prepared in the presence of field had better conductivity than those of as-prepared composites. It was also concluded that the application of alternating current electric field and magnetic field in this system led to the formation of relatively continuing networks while direct current electric field only prevented agglomeration of the carbon nanotubes in the polycarbonate matrix and created relatively uniform distribution of nanotubes in the matrix.     

Application of multivariate statistical analyses in the differentiation between two phosphate ores from the Nuba Mountains,Sudan

In previously published research, uranium abundance and major and trace element content were determined in phosphate ore samples from the Kurun and Uro areas of the Nuba Mountains in Sudan. The current work aims to characterise and differentiate between the phosphate ores from these two areas by subjecting the obtained geochemical data to quantitative and qualitative statistical analyses. Multivariate statistical analyses and correlation studies show several geochemical differences in the occurrence of uranium in Kurun and Uro phosphate ores. Uranium in Uro phosphate ore shows a higher degree of mobility coefficient of variability (CV%?=?91) than that in Kurun phosphate ore (CV%?=?48). Kurun and Uro phosphate ores are found to be good sources of titanium and strontium. The average concentrations of Ti and Sr in Uro phosphate ore are 4880 and 2780?mg?kg^–1, respectively. The corresponding values in Kurun phosphate ore are 7300 and 2630?mg?kg^–1, respectively. A cluster analysis of trace elements demonstrates that both Ti and Sr, which are the most abundant trace elements, appear in individual groups or in sub-groups. Uranium behaves in the same manner in both phosphate ores in that it associates in groups containing all the transition metals except for the most abundant trace element, titanium.     

THE AMINO ACIDS CONTENT OF SOME IRAQI DATES

SUMMARY –Amino acid content and nutritive value of three varieties of Iraqi dates was studied. Protein of the date was acid hydrolyzed for 24 hr and the amino acid content determined in a Phoenix automatic analyzer. The protein content on a fresh weight basis was 1.96% for Zahdi, 1.89% for Hillawi and 2.38% for Sayer. The following amino acids were present in these varieties: lysine, histidine, arginine, aspartic acid, threonine, glutamic acid, serine, prolin, glycine, alanine, cystine, valine, methionine, isoleucine, leucine, tyrosine and phenylalanine. Glutamic acid was present in highest concentration and Sayer variety contained more amino acids than Hillawi and Zahdi. Tryptophan and half-cystine may have been destroyed during acid hydrolysis.     

Logarithmic analogue-digital converter based on a non-linear analogue-to-digital converter

The paper describes a non-linear analogue-to-digital converter (NL-ADC) whose output is proportional to the natural logarithm of the input voltage. It is based on Maclaurin's series of the natural logarithm function. The design is based on voltage-to-frequency conversion (VFC) and a decimal rate multiplier (DRM). The NL-ADC introduces four digital numbers proportional to the first, second, third and fourth powers of the input DC signal. These numbers are digitally added and subtracted according to the first four terms of Maclaurin's series. A microprocessor-controlled hybrid computer with efficient analogue devices is used in the circuit design and implementation.     

Influence of the concentration of carbon nanotubes on electrical conductivity of magnetically aligned MWCNT–polypyrrole composites

The goal of this work is to study the effect of high magnetic pulses on electrical property of carbon nanotube–polypyrrole (CNT–PPy) composites with different CNT concentrations. CNT–PPy composites are produced in fractions of 1, 5 and 9 wt%. During the polymerization process, the CNTs are homogeneously dispersed throughout the polymer matrix in an ultrasonic bath. Nanocomposite rods are prepared. After exposure to 30 magnetic pulses, the resistivity of the rods is measured. The surface conductivity of thin tablets of composites is studied by 4-probe technique. The magnitude of the pulsed magnetic field is 10 Tesla with time duration of 1.5 ms. The results show that after applying 30 magnetic pulses, the electrical resistivity of the composites decreases depending on the concentration of CNTs in the composites. The orientation of CNTs is probed by atomic force microscopy (AFM) technique. AFM images approved alignment of CNT–polymer fibres in the magnetic field. We found that the enhancement in the electrical properties of CNT–PPy composites is due to rearrangement and alignment of CNTs in a high magnetic field. The stability of nano-composites is studied by Fourier transform infrared spectroscopy.