Tribological characteristics of nitrogen (N+) implanted iron

The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure ion sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (25 C), a dry air atmosphere, a load of 1/2 kg (4.9 N), sliding velocities of 0.043 to 0.078 m/sec (15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a U.S.P. mineral oil and nitrogen ion implantation doses of 5x10 to the 15th power and 5x10 to the 17th power ions/sq cm. No differences in wear rates were observed in the low dose experiments. In the high dose experiments, small reductions in initial (40 percent) and steady state (20 percent) wear rates were observed for nitrogen implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose. Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 0.8 microns. Similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed

Spin properties of dense near-surface ensembles of nitrogen-vacancy centres in diamond

We present a study of the spin properties of dense layers of near-surface nitrogen-vacancy (NV) centres in diamond created by nitrogen ion implantation. The optically detected magnetic resonance contrast and linewidth, spin coherence time, and spin relaxation time, are measured as a function of implantation energy, dose, annealing temperature and surface treatment. To track the presence of damage and surface-related spin defects, we perform in situ electron spin resonance spectroscopy through both double electron-electron resonance and cross-relaxation spectroscopy on the NV centres. We find that, for the energy ($4-30$~keV) and dose ($5\times10^{11}-10^{13}$~ions/cm$^2$) ranges considered, the NV spin properties are mainly governed by the dose via residual implantation-induced paramagnetic defects, but that the resulting magnetic sensitivity is essentially independent of both dose and energy. We then show that the magnetic sensitivity is significantly improved by high-temperature annealing at $\geq1100^\circ$C. Moreover, the spin properties are not significantly affected by oxygen annealing, apart from the spin relaxation time, which is dramatically decreased. Finally, the average NV depth is determined by nuclear magnetic resonance measurements, giving $\approx10$-17~nm at 4-6 keV implantation energy. This study sheds light on the optimal conditions to create dense layers of near-surface NV centres for high-sensitivity sensing and imaging applications.Comment: 12 pages, 7 figure

Friction wear and auger analysis of iron implanted with 1.5-MeV nitrogen ions

The effect of implantation of 1.5-MeV nitrogen ions on the friction and wear characteristics of pure iron sliding against steel was studied in a pin-on disk apparatus. An implantation dose of 5 x 10 to the 17th power ions/sq cm was used. Small reductions in initial and steady-state wear rates were observed for nitrogen-implanted iron riders as compared with unimplanted controls. Auger electron spectroscopy revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 15 at. % at a depth of 8 x 10 to the -7th m. A similar analysis within the wear scar of an implanted rider after 20 microns of wear yielded only background nitrogen concentration, thus giving no evidence for diffusion of nitrogen beyond the implanted range

Silicon on sapphire for ion implantation studies

Van der Pauw or bridge samples are ultrasonically cut from silicon on sapphire wafers. Contact pad regions are implanted with moderately heavy dose of ions. Ion of interest is implanted into sample; and, before being annealed in vacuum, sample is sealed with sputtered layer of silicon dioxide. Nickel or aluminum is sputtered onto contact pad areas and is sintered in nitrogen atmosphere

Compositon of Tantalum Nitride Thin Films Grown by Low-Energy Nitrogen Implantation: A Factor Analysis Study of the Ta 4f XPS Core Level

Tantalum nitride thin films have been grown by in situ nitrogen implantation of metallic tantalum at room temperature over the energy range of 0.5-5keV. X-ray photoelectron spectroscopy (XPS) and Factor Analysis (FA) have been used to characterise the chemical composition of the films. The number of the different Ta-N phases formed during nitrogen implantation, as well as their spectral shape and concentrations, have been obtained using principal component analysis (PCA) and iterative target transformation factor analysis (ITTFA), without any prior assumptions. According to FA results, the composition of the tantalum nitride films depends on both the ion dose and ion energy, and is mainly formed by a mixture of metallic tantalum, beta-TaN0.05, gamma-Ta2N and cubic/hexagonal TaN phases.Comment: 24 pages, 5 figures submitted to Applied Physics

Association between Outdoor Air Pollution and Childhood Leukemia: A Systematic Review and Dose-Response Meta-Analysis.

BackgroundA causal link between outdoor air pollution and childhood leukemia has been proposed, but some older studies suffer from methodological drawbacks. To the best of our knowledge, no systematic reviews have summarized the most recently published evidence and no analyses have examined the dose-response relation.ObjectiveWe investigated the extent to which outdoor air pollution, especially as resulting from traffic-related contaminants, affects the risk of childhood leukemia.MethodsWe searched all case-control and cohort studies that have investigated the risk of childhood leukemia in relation to exposure either to motorized traffic and related contaminants, based on various traffic-related metrics (number of vehicles in the closest roads, road density, and distance from major roads), or to measured or modeled levels of air contaminants such as benzene, nitrogen dioxide, 1,3-butadiene, and particulate matter. We carried out a meta-analysis of all eligible studies, including nine studies published since the last systematic review and, when possible, we fit a dose-response curve using a restricted cubic spline regression model.ResultsWe found 29 studies eligible to be included in our review. In the dose-response analysis, we found little association between disease risk and traffic indicators near the child's residence for most of the exposure range, with an indication of a possible excess risk only at the highest levels. In contrast, benzene exposure was positively and approximately linearly associated with risk of childhood leukemia, particularly for acute myeloid leukemia, among children under 6 y of age, and when exposure assessment at the time of diagnosis was used. Exposure to nitrogen dioxide showed little association with leukemia risk except at the highest levels.DiscussionOverall, the epidemiologic literature appears to support an association between benzene and childhood leukemia risk, with no indication of any threshold effect. A role for other measured and unmeasured pollutants from motorized traffic is also possible. https://doi.org/10.1289/EHP4381

Differences in Crop Growth Rate , Chlorophyll Content Index and Nitrate Reductase in Source N of Sweet Corn

A research to assess the interaction of nitrogen sources and doses of N in the growth and production as well as physiological effects of corn plants has been conducted in the Faculty of Animal and Agricultural Sciences, Diponegoro University, Indonesia. The research uses two sources of nitrogen namely NO3- (potassium nitrate) and NH4+ (ammonium sulfate), and doses of N (0, 50, 100 and 150 kg N/ha). The results showed that the dose of N fertilizer significantly effected on plant height, CCI, NR, CGR and weight of corn cobs. The interaction between the source of N and the dose of fertilizer N significantly effected on CCI, NR, and CGR, however, it had no significant effect on plant height and weight of corn cobs. The dose of N as much as 150 kg per ha resulted in plant height, CCI, NR, CGR and the highest cobs, respectively 82.33cm, 2.43, 84.3 umol, 18.87 g/day and 3538.2 g per plot. Keywords: sweet corn, chlorophyll content index, NR, CGR, cornco

A single weekly Kt/Vurea target for peritoneal dialysis patients does not provide an equal dialysis dose for all

Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.Dialysis adequacy is traditionally based on urea clearance, adjusted for total body volume (Kt/Vurea), and clinical guidelines recommend a Kt/Vurea target for peritoneal dialysis. We wished to determine whether adjusting dialysis dose by resting and total energy expenditure would alter the delivered dialysis dose. The resting and total energy expenditures were determined by equations based on doubly labeled isotopic water studies and adjusted Kturea for resting energy expenditure and total energy expenditure in 148 peritoneal dialysis patients (mean age, 60.6 years; 97 male [65.5%]; 54 diabetic [36.5%]). The mean resting energy expenditure was 1534 kcal/d, and the total energy expenditure was 1974 kcal/day. Using a weekly target Kt/V of 1.7, Kt was calculated using V measured by bioimpedance and the significantly associated (r = 0.67) Watson equation for total body water. Adjusting Kt for resting energy expenditure showed a reduced delivered dialysis dose (ml/kcal per day) for women versus men (5.5 vs. 6.2), age under versus over 65 years (5.6 vs. 6.4), weight 80 kg (5.8 vs. 6.1), low versus high comorbidity (5.9 vs. 6.2), all of which were significant. Adjusting for the total energy expenditure showed significantly reduced dosing for those employed versus not employed (4.3 vs. 4.8), a low versus high frailty score (4.5 vs. 5.0) and nondiabetic versus diabetic (4.6 vs. 4.9). Thus, the current paradigm for a single target Kt/Vurea for all peritoneal dialysis patients does not take into account energy expenditure and metabolic rate and may lead to lowered dialysis delivery for the younger, more active female patient.Peer reviewedFinal Accepted Versio