Kinetics of Topological Stone-Wales Defect Formation in Single Walled Carbon

Topological Stone-Wales defect in carbon nanotubes plays a central role in plastic deformation, chemical functionalization, and superstructure formation. Here, we systematically investigate the formation kinetics of such defects within density functional approach coupled with the transition state theory. We find that both the formation and activation energies depend critically on the nanotube chairality, diameter, and defect orientation. The microscopic origin of the observed dependence is explained with curvature induced rehybridization in nanotube. Surprisingly, the kinetic barrier follows an empirical Br{\o}nsted-Evans-Polanyi type correlation with the corresponding formation energy, and can be understood in terms of overlap between energy-coordinate parabolas representing the structures with and without the defect. Further, we propose a possible route to substantially decrease the kinetic activation barrier. Such accelerated rates of defect formation are desirable in many novel electronic, mechanical and chemical applications, and also facilitate the formation of three-dimensional nanotube superstructures.Comment: 10 pages, Supporting information, The Journal of Physical Chemistry C (2015

Development of a semi automated dual feed unit to produce FGM coatings using the HVOF thermal spray process

The application of functionally graded materials (FGMs) is quite difficult, but thermal spray processes like Plasma spray have demonstrated their unique potential in producing graded deposits, where researchers have used twin powder feed systems to mix different proportions of powders. FGMs vary in composition and/or microstructure from one boundary (substrate) to another (top service surface), and innovative characteristics result from the gradient from metals to ceramics or non-metallic to metals. The present study investigates an innovative modification of a high velocity oxy-fuel (HVOF) thermal spray process to produce functionally graded thick coatings. In order to deposit thick coatings, certain problems have to be overcome. Graded coatings enable gradual variation of the coating composition and/or microstructure, which offers the possibility of reducing residual stress build-up with in coatings. In order to spray such a coating, modification to a commercial powder feed hopper was required to enable it to deposit two powders simultaneously which allows deposition of different layers of coating with changing chemical compositions, without interruption to the spraying process. Various concepts for this modification were identified and one design was selected, having been validated through use of a process model, developed using ANSYS Flotran finite element analysis. In the current research the mixing of different proportions of powders were controlled by a computer using LabVIEW software and hardware, which allowed the control and repeat-ability of the micro structure when producing functionally graded coatings

LABORATORY EVALUATION OF EFFICACY OF THREE DIATOMACEOUS EARTH FORMULATIONS AGAINST TRIBOLIUM CASTANEUM HERBST (COLEOPTERA: TENEBRIONIDAE) IN STORED WHEAT

Laboratory experiments were conducted to evaluate three DE formulations - Protect-It, DiaFil 610 and Celite 209 at dose rates 500, 750 and 1000 mg/kg of wheat, against the red flour beetle Tribolium castaneum Herbst under ambient laboratory conditions (26 - 32°C and 48 - 65% r.h.). Mortality of exposed adults increased with increase in dose and exposure period; however consistency was notable only after 7days of exposure. With all DE formulations, mortality was low on grains treated at 500 and 750 mg/kg after 3 and 7 days of exposure. Protect-It was highly effectives at 1000 mg/kg causing 100% adult mortality after 3 days of exposure. Similarly, all the three DE formulations caused complete adult mortality on grains treated at 750 and 1000 mg/kg after 14 days of exposure. In addition, at these dose rates complete progeny suppression was recorded except on grain treated with DiaFil 610 at 750 mg/kg. The findings of this study have demonstrated that the efficacy of the three DE formulations to control T. castaneum and as potential alternative to synthetic insecticides

Evaluation of poultry processing practices, related public health laws and diseases of chickens at slaughter: A pilot study in Kaduna state

Poultry processing procedures and environment are integral to the quality and safety of meat derived from poultry. The existing practices used in the slaughter and processing of poultry and the disposition of poultry workers towards poultry inspection in four major live bird markets in Kaduna were evaluated using structured questionnaires administered to 30 marketers, 51 processors, 19 marketers/processors and each market manager respectively. Background public health regulations related to poultry production and processing as provided within the Meat Law (1968), Food and Drug Act (1974) and Animal Diseases (Control) Act (1988) were also assessed for gaps that could compromise quality and safety of poultry products in Nigeria. The diseases detectable at postmortem inspection of 1000 poultry carcasses processed in these live bird markets were documented. Live bird market workers were all males mainly between 20-39 years of age and had secondary school education (64%). Majority (51%) consist of poultry processors, largely ignorant of public health laws. Up to 95% and 74% of the workers will welcome routine ante-mortem and post mortem inspection respectively. Lesions related to Newcastle disease had the highest frequency of occurrence (41.6%) amongst inspected birds. Existing laws have made provisions to ensure that animal production and processing are coordinated for the benefits and health of the general populace. Laws evaluated have gaps that could compromise various stages of quality assurance along the poultry value chain, lack specificity in terms of addressing specific issues of poultry hygiene and did not adequately empower the veterinary services to enforce measures that will ensure safe poultry products. Hence, the revised Animal Disease Control Edict and Meat Hygiene Act should be passed into law, Nigerian live poultry market workforce needs training on poultry processing precautionary public health measures, and the use of protective clothing should be made mandatory. Keywords: Inspection, Legislation, Poultry, Processing, Public healt

Investigating the Effect of Varying Tubing Air Concentration during the Descaling of Petroleum Production Tubing using Multiple High-Pressure Nozzles

Despite the continued research effort on erosion behaviour of multiple flat fan nozzles in removing different types of scale deposits from petroleum production tubing, effect of chamber air concentration and nozzles configuration is yet to be given detail consideration. This study, therefore, considers the utilization of multiple high-pressure sprays at different chamber air concentration to enhance the rate of scale removal from petroleum production tubing. Additionally, options of altering chamber air/water ratio and header configurations for more effective scale removal were explored. So also, the relationship of nozzle header arrangement towards the removal of paraffin of different stages of deposition in petroleum production tubing have been studied. Consequently, theselection of chamber air concentration and header configuration (nozzles arrangement) for effective scale removal was found to be governed by the shape and type of the scale deposit. More so, the descaling capacity increases with decrease in number of nozzlesdue to pressure drop effect irrespective of the type or shape of the scale deposit. This novel descaling experiment of utilising 10 MPa injection pressure from 25 mm jetting position averagely removes hollow paraffin deposits that ranges from 44 to 280 g and 34 to 89g of solid shaped paraffin as a result of altering nozzles configuration. Correspondingly, an average removal difference ranging from 48 to 270 g of hollow shaped and 35 to 218 g of solid shaped paraffin depositwas recorded as a result of compressing the chamber pressure by 0.2 MPa and subsequently suctioning it by -0.008 MPa respectively

CPT violation and B-meson oscillations

Recent evidence for anomalous CP violation in B-meson oscillations can be interpreted as resulting from CPT violation. This yields the first sensitivity to CPT violation in the B_s^0 system, with the relevant coefficient for CPT violation constrained at the level of parts in 10^{12}.Comment: 4 pages two-column REVTeX; Rapid Communications, Physical Review D, in pres

Investigating the Impact of Non-Hydrodynamically Connected Descaling Parameters in the Removal of Different Stages of Paraffin Deposits Using Multiple Nozzles in Petroleum Production Tubing

Despite the continued research efforts in understanding the erosional behaviors of multiple flat fan nozzles in the removal of different types of scale deposits from petroleum production tubing. The non-hydrodynamically connected descaling parameters such as stand-off distance, nozzle arrangement and chamber pressure have not been duly considered up to date. This research utilizes 3-flat fan high-pressure nozzles at a high injection pressure of 10 MPa to remove paraffin deposits at different growth stages from petroleum production tubing to evaluate the effects of the descaling parameters on scale removal. A stand-off distance of 25 mm, 50 mm and 75 mm; nozzle arrangement in novel orientations (triangle, diagonal & right-angle) involving 7-nozzles header and chamber pressures (in compression – 0.2 MPa and vacuum -8.0 x10-3 MPa) were utilized as the varying non-hydrodynamically connected parameters. Generally, the selection of both nozzle arrangement and chamber air concentration was found to be governed by the type and shape of the deposit in question while the scale removal capability was found to be reduced with an increase in stand-off distance due to poor jet contact. An average hollow shaped paraffin removal of 276 g, 259 g and 226 g were recorded at ambient condition across the respective stand-off distance of the three respective nozzles arrangements. While the introduction of 0.2 MPa compressed air significantly increased the respective removal of the early stage paraffin deposition to 342 g, 299 g and 277 g respectively. Also, more hollow shaped removal improvement of 366 g, 320 g and 288 g were achieved after suctioning the chamber by -0.008 MPa, while simultaneously pumping water at 10 MPa. The case of solid shaped paraffin signifying complete tubing blockage was not effective at ambient condition, with average paraffin removal of 99 g, 126 g and 112 g respectively. However, the introduction of compressed chamber air registered the best solid paraffin removal results of 235 g, 286 g and 256 g respectively. Whereas the suction operation recorded an average removal of 229 g, 270 g and 250 g of paraffin across the respective jet positions and nozzle configurations. This result provides a practical approach to the removal of organic scales deposits at varying descaling conditions of injection pressure, standoff distance and nozzle arrangement

Is Investment-Cash flow Sensitivity a Good Measure of Financing Constraints? New Evidence from Indian Business Group Firms

Several studies use the investment - cash flow sensitivity as a measure of financing constraints while some others disagree.The source of this disparity lies mostly in differences in opinion regarding the segregation of severely financially constrained firms from less constrained ones.We examine this controversy by analyzing firms affiliated to business groups that are subject to less financing constraints relative to independent firms.Our results show strong investment - cash flow sensitivities for both group and non-group firms, but no significant difference between them.The finding is robust to alternative investment models and estimation techniques.We investigate this finding further by analyzing the influence of various firm-specific characteristics like size, age, leverage and ownership structure.We continue to observe that less financially constrained firms do not exhibit a significantly lower sensitivity of investment to cash flow.The results of the study thus provide new and compelling evidence demonstrating the inability of investment cash flow sensitivity to be a good measure of a firm's financing constraint.

Emergence of noncollinear magnetic ordering in small magnetic clusters: Mnn_n and As@Mnn_n

Using first-principles density functional calculations, we have studied the magnetic ordering in pure Mn$_n$ ($n=2-$10, 13, 15, 19) and As@Mn$_n$ ($n=1-$10) clusters. Although, for both pure and doped manganese clusters, there exists many collinear and noncollinear isomers close in energy, the smaller clusters with $n\leqslant$5 have collinear magnetic ground state and the emergence of noncollinear ground states is seen for $n\geqslant$6 clusters. Due to strong $p-d$ hybridization in As@Mn$_n$ clusters, the binding energy is substantially enhanced and the magnetic moment is reduced compared to the corresponding pure Mn$_n$ clusters.Comment: 10 Pages and 5 Figure