Pulse plating of Ni–B/WC nanocomposite coating and study of its corrosion and wear resistance

The aim of this study is to investigate the impact of WC content on the properties of the Ni–B/WC nanocomposites deposited by the pulse method. It is obtained that, although by addition of WC nanoparticles to the bath in initial steps (WC 4 and 8 g?l^?1), the grain size was increased and hence mechanical and electrochemical properties got worse, but at the higher amount of WC (WC 12 g?l^?1), due to the formation of the fine and packed structures, the great corrosion and wear resistance was achieved. The corrosion resistance of the Ni–B/WC12 g?l^?1 coating is 59,967?Ω and wear weight loss is 2.1 mg?cm^?2 with the friction coefficient of 0.64.     

Mineralogy of plain Portland and blended cement pastes

The compressive strength and microstructure of blended cement was investigated in this study. The hydration products of cements were identified by means of scanning electron microscopy (SEM) and polarising microscopy (thin section). Results indicated that the blended cement required pozzolanic activity in addition to its cementing property with the addition of 30% material. Aggregations of belite grains were observed which were surrounded by alite. Blended cement exhibited high early-term strength. However, its 3d-age strength is lower than ordinary Portland cement. On the other hand, all blended cement mortars fulfil the compressive strength requirements of TS 24. Hence, it can be said that blended cement can achieve adequate early compressive strength. A reduction in the amount of CSH gel and the porosity of the matrix in mortars were found to be responsible for the poor compressive strength of the cement paste in early the age.     

Molecular architectures for electrocatalytic amplification of oligonucleotide hybridization

In this work, we describe a new platform suitable for electrocatalytic amplification of oligonucleotide hybridization based on the use of supramolecular bioconjugates incorporating ferrocene-labeled streptavidin. Our goals were aimed at designing a biosensing platform which could support highly reproducible and stable electrocatalytic amplification with maximum efficiency. The use of nonlabeled streptavidin as an underlying layer promotes a major improvement on the characteristics of the amplified electrochemical signal. In addition, the electrocatalytic current can be easily amplified by tuning the concentration of electron donor species in solution. Because of the fact that the redox labels are bioconjugated to the DNA strands, increasing the ionic strength does not lead to the loss of redox labels. More importantly, increasing the concentration of donors only involves the magnification of the signal without implying the permeation of donors (thus reducing the efficient electrocatalysis). This approach represents a major improvement on the use of electrocatalytically amplified DNA-sensing platforms, thus overcoming any possible limitation in connection with the reproducibility and reliability of this well-established method.     

Exposures to 222Rn from consumption of underground municipal water supplies in Pakistan

This paper presents the results of radon ((222)Rn) concentration measurements in municipal supply drinking water in metropolitan Lahore city of Pakistan and evaluation of consequent radiological effects. In this respect, water samples were collected in all nine municipal towns of Lahore city and analysed employing a high-resolution gamma spectrometric system. Radon concentration varied from 2.0 +/- 0.3 to 7.9 +/- 2.1 Bq l(-1). Mean value of annual effective dose for an individual consumer was assessed to be 16.5 +/- 12.8 microSv y(-1). (222)Rn mean concentration measured in this study is comparable with the reported values for drinking water determined worldwide and found to be less than the limit of 100 Bq l(-1) recommended by the World Health Organisation for public water supplies. The results of this study may be helpful in establishing background levels of radon in drinking water that could be used not only to distinguish additional contributions when a contamination event occurs but also to implement water quality standards by the concerned authorities to maintain radioactive contamination free drinking water supplies for the population.     

PB-210 concentrations in cigarettes tobaccos and radiation doses to the smokers

Cigarette smoking is a source of radiation exposure due to the concentrations of natural radionuclides in the tobacco leaves. From the health point of view, measurement of (210)Pb and (210)Po contents in cigarette tobacco is important to assess the radiological effects associated with the tobacco smoking for the smokers. In the present study, activity concentrations of (210)Pb, which is a (210)Po precursor in the (238)U-decay series, were measured in cigarette tobaccos. Samples of nine different commonly sold brands of cigarette tobaccos were analysed by employing a planar high purity germanium (HPGe) low background detector. Activity concentrations of (210)Pb were measured from its gamma peak at 47 keV. Mean activity concentration of (210)Pb was measured to be 13 +/- 4 Bq kg(-1) from all samples analysed. The annual committed effective dose for a smoker and the collective committed effective dose corresponding to annual cigarettes production were estimated to be 64 +/- 20 microSv and 0.6 x 10(2) man-Sv, respectively.     

Measurement of natural radioactivity in bottled drinking water in Pakistan and consequent dose estimates

Natural radioactivity was determined in 11 different brands of commonly sold bottled drinking water in the federal capital Islamabad and Rawalpindi city of Pakistan using gamma spectrometry technique. Mean concentrations of 226Ra, 232Th and (40)K were found to be 11.3 +/- 2.3, 5.2 +/- 0.4 and 140.9 +/- 30.6 mBq l(-1), respectively. The annual cumulative effective doses due to all three natural radionuclides for different age groups of 1-5 y, 5-10 y, 10-15 y and adults (>or=18 y) were estimated to be 4.0, 3.4, 3.1 and 4.1 microSv y(-1), respectively. Among the three natural radionuclides, annual effective doses for all age groups from 226Ra were significant. Children in the age group of 1-5 y appeared to be at risk with respect to the annual effective doses from 226Ra as compared to the other age groups. Results obtained in this study are compared with the reported values from other countries of the world and it was observed that measured activity concentrations of three natural radionuclides in the bottled drinking water were lower than these values. Annual estimated effective doses for all four age groups from the intake of natural radionuclides in bottled drinking water were also found below the World Health Organisation (WHO) recommended limit of 0.1 mSv y(-1) as well as the average radiation dose of 0.29 mSv y(-1) received per head worldwide due to ingestion of natural radionuclides assessed by UNSCEAR (2000).     

Evaluation of adhesion strength,flammability, and degradation of HBCD‐containing polyurethane adhesives

In this work, moisture curable flame retardant HTPB‐based polyurethane adhesives were synthesized. The influence of HBCD (Hexabromocyclododecane) as flame retardant on adhesion, degradation and change in flammability of synthesized HTPB‐based polyurethane has been studied. Relationship between phase separation in hard and soft domains and adhesion has also been investigated. FTIR analysis was used to determine phase separation in synthesized adhesives. Lap shear test was used to determine adhesion properties of adhesives applied on aluminum and glass substrates. Thermal Gravimetry analysis and Limited Oxygen Index (LOI) tests were carried out on flame retardant adhesives to evaluate effect of HBCD on degradation and flammability. Addition of HBCD to adhesives leads to reduction of thermal stability and lap shear strength for all substrates, in spite of flame retardant adhesives show higher LOI value. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of silica fume and steel fibers on some properties of high-strength concrete

The main disadvantage of high-strength concrete is its highly brittle behavior and this can beovercome by adding fibers to the concrete. This would also improve some other mechanical properties of high-strength concrete such as tensile strength and compressive strength. These properties are not very well established for high-strength steel-fiber reinforced concrete (HSFRC) yet. In this study the influence of silica fume on the properties of HSFRC were investigated by using silica fume of two different percentages and three different hooked-end fibers namely, 30/0.50, 60/0.80 and 50/0.60 length/diameter (mm/mm). Fibers were added to concrete in three different volume percentages of 0.5, 1.0 and 2.0 by volume of concrete. The results indicated that there is a linear function between splitting tensile strength (F_splt) and volume percentage of fibers (V_f) [i.e. F_plt = A(V_f) + B, where A and B are correlation coefficients] as well as between splitting tensile strength (F_splt) and compressive strength (F_c) of plain series A concrete [i.e. F_splt = C (√F_c) + D, where C and D are correlation coefficients]. These relations can describe the development of splitting tensile strength of HSFRC containing no silica fume, 5% silica fume and 10% silica fume by weight of cement. On the other hand, although silica fume has an effect on compressive strength, volume percentage and aspect ratio of steel fibers has little effect.     

Identification of monocot flora using pollen features through scanning electron microscopy

Pollen used to track structural and functional evolution in plants as well as to investigate the problems relative to plant classification. Pollen characters including ornamentation, shape, apertural pattern, pollen symmetry, colpus length, width, and margins used to detect the similarities and dissimilarities between genera and also species of the same genus. In this study pollen features of 20 monocot species belonging to 15 genera of the Amaryllidaceae, Asparagaceae, Iridaceae, Ixioliriaceae, Liliaceae, and Xanthorrhoeaceae were studied using scanning electron microscopy (SEM) and light microscopy (LM). In this study two species that is Zephyranthes citrina and Tulbaghia violacea were reported for the first time from Pakistan. Pollen grains were visualized with LM. Non‐acetolyzed and acetolyzed pollen were examined using SEM. A taxonomic key was developed to highlight the variation in pollen features in order to make their systematic application for correct species identification.