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Transmission spectroscopy1–3of exoplanets has revealed signatures of water vapour, aerosols and alkali metals in a few dozen exoplanet atmospheres4,5. However, these previous inferences with the Hubble and Spitzer Space Telescopes were hindered by the observations’ relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species—in particular the primary carbon-bearing molecules6,7. Here we report a broad-wavelength 0.5–5.5 µm atmospheric transmission spectrum of WASP-39b8, a 1,200 K, roughly Saturn-mass, Jupiter-radius exoplanet, measured with the JWST NIRSpec’s PRISM mode9as part of the JWST Transiting Exoplanet Community Early Release Science Team Program10–12. We robustly detect several chemical species at high significance, including Na (19σ), H2O (33σ), CO2(28σ) and CO (7σ). The non-detection of CH4, combined with a strong CO2feature, favours atmospheric models with a super-solar atmospheric metallicity. An unanticipated absorption feature at 4 µm is best explained by SO2(2.7σ), which could be a tracer of atmospheric photochemistry. These observations demonstrate JWST’s sensitivity to a rich diversity of exoplanet compositions and chemical processes.

The air‐sea gas transfer velocity kis frequently estimated as an empirical function of wind speed. However, it is widely recognized that kdepends on processes other than wind speed alone. The small‐eddy model, which describes periodic events of small eddies disturbing the sea surface with water from below, suggests a direct relation between kand the dissipation rate of turbulent kinetic energy ϵat the air‐sea interface. This relation has been proven both in laboratories and in the field in various freshwater and coastal environments, but to date has not been verified in open ocean conditions. Here, concurrent North Atlantic field observations of ϵand eddy covariance measurements of DMS and CO2air‐sea gas flux are presented. Using ϵmeasurements, we compare the small‐eddy model at various depths to previously published observations. Extrapolating the measured ϵprofiles to the thickness of the viscous sublayer allows us to formulate a function of kthat depends solely on the water side friction velocity u∗w, which can be inferred from direct eddy covariance measurements of the air‐side friction velocity u∗a. These field observations are generally consistent with the theoretical small‐eddy model. Utilizing a variable Schmidt number exponent in the model, rather than a constant value of 12yields improved agreement between model and observations. We related the air‐sea gas transfer velocity to the dissipation of turbulent kinetic energy at the ocean surface

Aims.We present a comparison between independent computer codes, modeling the physics and chemistry of interstellar photon dominated regions (PDRs). Our goal was to understand the mutual differences in the PDR codes and their effects on the physical and chemical structure of the model clouds, and to converge the output of different codes to a common solution.

Context.Clouds containing molecular dark matter in quantities relevant for star formation may exist in minihaloes of the type of cold dark matter included in many cosmological simulations or in the regions of some galaxies extending far beyond their currently known boundaries.

Going Off, Growing Strong is a program for Inuit youth facing widespread social, cultural, and economic change. The overarching goals of the program are to: (1) enhance resilience and wellness; (2) build social connections for the youth; and (3) transmit traditional knowledge, skills, and values to participating youth.

A one dimensional finite difference diffusion model for simulating the Boost Diffusion Oxidation (BDO) process of titanium alloys is developed and implemented as a window-based program. The program can simulate the BDO process for both constant diffusion coefficient and concentration dependent diffusion coefficient. It is found that to accurately simulate the BDO process, the concentration dependence of oxygen diffusion has to be taken into account. If the concentration dependence is taken as the Shamblen and Redden’s equation, the simulation results agree well with the experimental results.

Modeling of gyroresonant wave‐particle interactions in the radiation belts requires solving the Vlasov‐Maxwell system of equations in an inhomogenous background geomagnetic field. Previous works have employed particle‐in‐cell methods or Eulerian solvers (such as the Vlasov Hybrid Simulation code) to provide numerical solutions to the problem. In this report, we provide an alternative numerical approach by utilizing a first order finite difference upwind scheme. When coupled to the narrowband Maxwell's equations, the model reproduces linear as well as nonlinear wave growth of coherent signals. Wave growth is nonlinear growth when the wave amplitude exceeds the minimum value for phase trapping of counterstreaming particles and is linear otherwise. The model also demonstrates free‐running frequency variation for a case with a high linear growth rate. In addition, the model confirms the theoretical prediction of a stable “phase‐space hole” during the nonlinear growth process. The plasma parameters and L shell used in this study are typical of those associated with the Siple Station wave injection experiment. Model cyclotron resonant interactions using a finite difference Vlasov solverModel linear and nonlinear growth in agreement with theory and observationsClearly resolve phase‐space hole during nonlinear growth compared to PIC method

The interaction between coherent whistler mode waves and energetic radiation belt electrons can result in pitch angle scattering of electrons into the bounce loss cone and subsequent precipitation. In studying the effects of VLF transmitter signals on particle precipitation, past modeling efforts have focused on the computation of diffusion coefficients for a Fokker‐Planck model. In contrast, to capture the nonlinear effects of large‐amplitude coherent waves, we evaluate particle precipitation using a Vlasov‐Liouville (VL) model which computes the phase space particle distribution function directly using a characteristic‐based solution of the Vlasov equation. Previous work has shown that in the case of large‐amplitude coherent waves, phase trapping can significantly perturb resonant particles from their adiabatic paths. We evaluate the importance of phase trapping over a range of wave amplitudes (up to 200 pT); the percentage of particles that precipitate after being phase trapped is computed over a phase space grid in the loss cone. The results demonstrate that phase trapping contributes significantly to precipitation when a large‐amplitude wave (>100 pT) is present. Additionally, linear theory can be valid over a broad range of amplitudes and the relative accuracy of linear theory in calculating the precipitated flux depends strongly on the initial particle distribution. Additionally, we demonstrate the ability of the VL model to calculate the time evolution of the precipitated flux due to short‐duration whistler mode pulses. The physical parameters used in this study are typical of those associated with the Siple Station wave injection experiment. Developed numerical model of precipitationEvaluate effect of particle phase trapping on precipitationCompare nonlinear precipitation model to linear theory

AbstractThe lack of an immediate-release sedative (i.e., one for which no postsedation holding or withdrawal period is required) jeopardizes fish and fisheries research and poses considerable risk to those involved in aquatic resource management and the operation of public hatcheries and commercial fish farms. Carbon dioxide may be used as an immediate-release sedative, but it is slow-acting and difficult to apply uniformly and effectively. Tricaine methanesulfonate (MS-222) is easier to apply but requires a 21-d withdrawal period. The lack of an immediate-release sedative approved by the U.S. Food and Drug Administration (FDA) is a consequence of numerous factors, including the complexities of the approval process, the substantial human and monetary resources involved, and the specialized nature of the work. Efforts are currently underway to demonstrate the safety and effectiveness of benzocaine- and eugenol-based products as immediate-release sedatives. However, pursuing approvals within the current framework will consume an exorbitant amount of public and private resources and will take years to complete, even though both compounds are “generally recognized as safe” for certain applications by the FDA. We recommend using risk management–based approaches to increase the efficiency of the drug approval process and the availability of safe and effective drugs, including immediate-release sedatives, for use in the fisheries and aquaculture disciplines.Received March 29, 2012; accepted September 14, 2012

The lack of an immediate-release sedative (i.e., one for which no postsedation holding or withdrawal period is required) jeopardizes fish and fisheries research and poses considerable risk to those involved in aquatic resource management and the operation of public hatcheries and commercial fish farms. Carbon dioxide may be used as an immediate-release sedative, but it is slow-acting and difficult to apply uniformly and effectively. Tricaine methanesulfonate (MS-222) is easier to apply but requires a 21-d withdrawal period. The lack of an immediate-release sedative approved by the U.S. Food and Drug Administration (FDA) is a consequence of numerous factors, including the complexities of the approval process, the substantial human and monetary resources involved, and the specialized nature of the work. Efforts are currently underway to demonstrate the safety and effectiveness of benzocaine- and eugenol-based products as immediate-release sedatives. However, pursuing approvals within the current framework will consume an exorbitant amount of public and private resources and will take years to complete, even though both compounds are “generally recognized as safe” for certain applications by the FDA. We recommend using risk management–based approaches to increase the efficiency of the drug approval process and the availability of safe and effective drugs, including immediate-release sedatives, for use in the fisheries and aquaculture disciplines.

In situdating of monazite grains preserved as inclusions within foliations defining FIAs (foliation inflection/intersection axes preserved within porphyroblasts) contained within garnet, staurolite, andalusite and cordierite porphyroblasts provides a chronology of ages that matches the FIA succession for the Big Thompson region of the northern Colorado Rocky Mountains. FIA sets 1, 2 and 3 trending NE–SW, E–W and SE–NW were formed at 1760.5 ± 9.7, 1719.7 ± 6.4 and 1674 ± 11 Ma, respectively. For three samples where garnet first grew during just one of each of these FIAs, the intersection of Ca, Mg, and Fe isopleths in their cores indicate that these rocks never got above 4 kbars throughout the Colorado Orogeny. Furthermore, they remained around approximately the same depth for ~250 million years to the onset of the younger Berthoud Orogeny at 1415 ± 16 Ma when the pressure decreased slightly as porphyroblasts formed with inclusion trails preserving FIA set 4 trending NNE–SSW. No porphyroblast growth occurred during the intervening ~250 million years of quiescence, even though the PT did not change over this period. This confirms microstructural evidence gathered over the past 25 years that crenulation deformation at the scale of a porphyroblast is required for reactions to re-initiate and enable further growth.

It is now well documented that Arctic climates and ecosystems are changing at some of the fastest rates on planet Earth. These changes are significant for all Arctic biodiversity, and they are a great challenge for cooperative management boards of Canada's Arctic national parks, those legislated to maintain or improve the ecological integrity of all national parks. Owing to the inherent complexity of natural ecosystems, it is not at all clear how, nor how rapidly, these ongoing changes will affect park biodiversity and impact the traditional land-based lifestyles of Indigenous park cooperative management partners. In this context, this paper reviews and integrates recent research carried out in Canadian Arctic national parks: (1) geophysical– a reduction in glacial area and volume, active layer thickening, warming soil temperatures, and terrain instability; (2) vegetation– widespread but ecosystem-specific increases in NDVI ‘greenness’, plant biomass, shrub and herb coverage, and growing season lengths; and (3) wildlife– complex changes in small mammals and ungulate populations, very negative effects on some polar bear populations, and relatively stable mammalian predator and raptor populations at this time. This work provides a partial snapshot of ongoing and evolving ecological effects of climate change in Arctic national parks, and provides a strong foundation for prioritising future research and monitoring efforts. These evolving changes also undermine the historical paradigm of place-based conservation and necessitate a new approach for managing protected areas that involves acceptance of ongoing transformational change and adoption of a risk-based, forward looking paradigm in a changing world. It is proposed that Arctic national parks are ideal locations to focus Arctic science, especially as a component of a strategic, coordinated, and pan-Arctic approach to Arctic research that makes the most effective use of limited resources in the vast areas of Canada's north.

The article reports on the events of the 2011 Best Warrior Competition held in Fort Lee, Virginia on October 3 to 7, 2011. The Best Warrior Competition is a sergeant major of the Army-directed event held to show who possesses the best core skills and attributes that are essential for battlefield success. On its tenth year, the event tests critical and adaptive thinking, tactics and techniques, and resilience of the participating twenty-six experienced soldiers from ages 19 to 33.

Das Verschleißverhalten nichtrostender Stählekann durch eine Anreicherung der Randschicht mit Stickstoff und/oder Kohlenstoff, d. h. die Bildung von expandiertem Austenit, verbessert werden. Zur Vermeidung einer Verschlechterung ihrer exzellenten Korrosionsbeständigkeit muss die Behandlungstemperatur niedrig genug sein, um eine Ausscheidung des gelösten Chroms als Chromnitrid oder -carbid zu vermeiden. In den letzten zwanzig Jahren wurden zur Erzielung einer kombinierten Verbesserung des Verschleiß-, Korrosionsund Ermüdungsverhaltens umfangreiche Forschungs- und Entwicklungsarbeiten durchgeführt. Dieser Beitrag gibt einen Überblick über die Struktur und die Eigenschaften von austenitischen und austenitisch-ferritischen nichtrostenden Stählen nach einer thermochemischen Behandlung bei tiefen Temperaturen mit industriell angewendeten Technologien.

Abstract: Argument about shear on foliations began in the mid 19th century and continues to the present day. It results from varying interpretations of what takes place during the development of different types of foliations ranging from slaty cleavages through differentiated crenulation cleavages, schistosity and gneissosity to mylonites. Computer modelling, quantitative microstructural work and monazite dating have provided a unique solution through access to the history of foliation development preserved by porphyroblasts. All foliations involve shear in their development and most can be used to derive a shear sense. The shear sense obtained is consistent between foliation types and accords with recent computer modelling of these structures preserved within porphyroblasts relative to those in the matrix. The asymmetry of curving foliation into a locally developing new one allows determination of the shear sense along the latter foliation in most rocks. The problem of shear on fold limbs and parallelism of foliation and the flattening plane of the strain ellipse is resolved through the partitioning of shearing and shortening components of deformation into zones that anastomose around ellipsoidal domains lying parallel to the XY plane. Conflicts in shear sense occur if multiple reuse or reactivation of foliations is not recognized and allowed for but are readily resolved if taken into account.

Although orogenesis commonly lasts 100 million years, a maximum of three foliations are usually preserved within any outcrop. They record little of the total history due to the effects of preferential partitioning of progressive shearing along S0. Such reactivation eventually destroys or rotates multiple successive foliations into parallelism with any layering that is present. Plate motion subjects a collisional orogen to spatially partitioned, episodic, but non-stop deformation. The bulk forces operating are horizontal and intermittently vertical (associated with gravitational load due to crustal thickening) forming sub-vertical and sub-horizontal foliations. These orientations are preserved in the strain shadows of anything competent that hinders reactivation of the compositional layering. Deformation partitioning results in portions of rock remaining unaffected for many events. Gravitational collapse of over-thickened orogen cores leads to significant extrusion in orogen rims and a dominance of sub-horizontal foliations in the latter and episodically continues throughout orogenesis. Reactivation causes decrenulation and/or rotation of foliations into parallelism with S0, destroying evidence that multiple sub-vertical and sub-horizontal foliations have developed except where preserved as inclusion trails in porphyroblasts and multiply truncated foliations in mylonites. However, the same processes operate in both the cores of orogens and ductile portions of their margins.

The article presents various construction projects of the U.S. Army Team. The exterior of all the buildings in the Phase 1 of the Aberdeen Proving Ground, Maryland campus has been completed in the spring of 2009. A ground breaking ceremony was headed by Lieutenant General Jack C. Stultz, chief of the Army Reserve, and Army Reserve Command Sergeant Major Leon Caffie at Fort Bragg, North Carolina on December 8, 2008. The Armed Forces Reserve Center of Fort Hamilton in New York is under construction as of July 2009 and is set to finish by 2011.

The ever-increasing demands for combined properties in modern machinery operating under ever more severe conditions have been the driver for the rapid developments of many advances surface engineering technologies. Designers thus have many surface engineering technologies to select from in the design of components. However, it also presents challenges to designers to select an optimal surface engineering process for a specific application. To this end, a contact mechanics model has been developed based on modern theories of multilayered surface contact, taking into account the multilayered structure, real surface roughness and friction effects. With this model, the performance of surface engineered components can be successfully predicted. In this paper, the development of Hertz contact theory is first reviewed, the Birmingham multilayered real rough surface contact mechanical model is discussed and a number of major steps towards designing dynamically loaded surface engineered components are demonstrated by case studies.

Environmental context. Dimethylsulfide (DMS) is recognised as a potentially significant climate-forcing gas, owing to its role in particle and cloud formation in the marine atmosphere, where it is the dominant source of acidity. Ammonia, the dominant naturally occurring base in the atmosphere, plays an important role in neutralising particles formed from DMS oxidation products and may even enhance the formation rate of new particles. A biogeochemical coupling has previously been proposed between DMS and ammonia fluxes from the ocean to the atmosphere, in the form of coproduction of the two gases in seawater. We revise this suggestion by introducing the concept of ‘co-emission' of the gases, where DMS emission controls the rate of emission of ammonia from the ocean by acidifying the atmosphere.Abstract. A strong correlation between aerosol ammonium and non-sea salt sulfate is commonly observed in the remote marine boundary layer. It has been suggested that this relationship implies a biogeochemical linkage between the nitrogen (N) and sulfur (S) cycles at the cellular biochemical level in phytoplankton in the ocean, or a linkage in the atmosphere (see P. S. Liss and J. N. Galloway, Interactions of C, N, P and S biogeochemical cycles and global change(Springer, 1993), and P. K. Quinn et al. in J. Geophys. Res. – Atmos.1990, 95). We argue that an oceanic linkage is unlikely and draw on mechanistic and observational evidence to make the argument that the atmospheric connection is based on simple physical chemistry. Drawing on an established analogous concept in terrestrial trace gas biogeochemistry, we propose that any emission of dimethylsulfide (DMS) from the ocean will indirectly influence the flux of NH3from the ocean, through the neutralisation of acidic DMS oxidation products and consequent lowering of the partial pressure of NH3in the atmosphere. We present a simple numerical model to investigate this hypothesised phenomenon, using a parameterisation of the rate and thermodynamics of gas-to-particle conversion of NHxand explicitly modelled ocean–atmosphere NH3exchange. The model indicates that emission of acidic sulfur to the atmosphere (e.g. as a product of DMS oxidation) may enhance the marine emission of NH3. It also suggests that the ratio of ammonium to non-sea salt sulfate in the aerosol phase is strongly dependent on seawater pH, temperature and wind speed – factors that control the ocean–atmosphere ammonia flux. Therefore, it is not necessary to invoke a stoichiometric link between production rates of DMS and ammonia in the ocean to explain a given ammonium to non-sea salt sulfate ratio in the aerosol. We speculate that this mechanism, which can provide a continuous resupply of ammonia to the atmosphere, may be involved in a series of biogeochemical-climate feedbacks.

Hepatitis C virus (HCV) infection may be associated with neurocognitive deficits. The Hemophilia Growth and Development Study enrolled HIV-infected and HIV-uninfected patients and a group of nonhemophiliac siblings. After controlling for multiple factors, HCV monoinfection was not associated with deficits in adaptive behavior, intelligence, or attention/concentration.

Evidence for intramolecular photoinduced electron transfer (ET) in synthetic systems consisting of a triphenylamine-perylenediimide donor-acceptor dendrimer or a triphenylamine-peryleneimide dendrimer at the ensemble and single-molecule (SM) level is presented. Moreover, for the first time a direct observation of the forward as well as the backward ET step is made in a single emitting entity. Fluctuations in the values of the rate constants for forward and backward ET were observed, induced by the local environment as well as by conformational changes of the dendrimer itself. The results obtained in a weakly coupled system can also be extended to a strongly coupled donor-acceptor system based on peryleneimide and penta-phenylene.

The inherent poor tribological behaviour of austenitic stainless steels has been a barrier to their wider application under corrosion wear conditions. Therefore, researchers have long dreamt of developing new technologies to enhance the wear resistance of stainless steel surfaces without loss of their attractive ‘stainless’ characteristics. For example, the discovery of low temperature plasma nitriding in the mid 1980s allowed a new phase with a high hardness and good corrosion resistance to be produced on austenitic stainless steel surfaces. Since then much research and development has aimed to combine improvements in wear, corrosion and fatigue properties. This has been demonstrated by various low temperature surface alloying processes (including plasma, ion beam, gaseous and salt bath methods) and increasing numbers of academic publications, reflecting rapidly expanding niche markets in the food, chemical, nuclear and medical sectors. In this paper, the historical evolution and development of low temperature thermochemical surface alloying processes are overviewed. The research and development of low temperature surface alloying of austenitic stainless steels in an attempt to combine improvements in wear, corrosion and fatigue properties are also assessed. Finally, new directions and key areas for future development are identified and discussed.

A low temperature plasma carburising process has been developed to engineer the surfaces of austenitic stainless steels to achieve combined improvements in wear and corrosion resistance. Previous studies have investigated the chemical, mechanical and structural characteristics of this carburised layer produced on AISI 316 steel at temperatures between 400° C and 600° C. The present paper focuses on the thermal stability of this carbon S phase layer. The investigation included isothermal annealing of the S phase layer as well as microstructure and property characterisation of the specimens. The results show that the S phase is metastable. When thermally annealed at certain temperatures for long enough, the carbon S phase decomposes into chromium carbides. Correspondingly, the hardness and corrosion resistance also varied. A preliminary isothermal transformation diagram has been constructed, which provides a basic guideline for the application of low temperature plasma carburised 316 austenitic stainless steel.

S phase layers produced on AISI 316 stainless steel by low temperature plasma nitriding and plasma carburising were examined in order to investigate their mechanical and chemical properties. Cylindrical disc specimens were used for testing hardness, pin on disc wear and electrochemical corrosion. Toroidal specimens were used for the fatigue and fretting fatigue tests. Both plasma nitriding and carburising processes created S phase layers on the surface of AISI 316 and greatly improved the steel's tribological properties. SEM showed that more precipitation of nitrogen occurred in the plasma nitrided specimens and GDS revealed that the nitrogen in the nitriding specimens did not penetrate as far into the substrate as the carbon in the carburising specimens. This is due to the nitrogen bonding easily with chromium in the surface layer which obstructs the diffusion of nitrogen into the substrate. The hardness tests showed that the nitriding layer was harder than the carburised layer but was more brittle and did not extend far into the substrate whereas the hardness of the carburised layer reduced gradually to a depth of 10 μm. The nitrided layer did better in the abrasion tests whereas the carburising layer performed better in the fatigue tests. The importance of these discoveries is discussed.

Photoinduced electronic energy transfer (EET) and electron transfer (PET) have been investigated in a multichromophoric system 2, that comprises zinc porphyrin (ZnP), dimethoxynaphthalene, and [60]fullerene (C60) chromophores separated by norbornylogous bridge sections of six and five bond lengths, respectively. In toluene as solvent, EET from ZnP to C60 occurs in folded and extended conformations of the molecule with rate constants of 1.3 × 10¹⁰ and 8.1 × 10⁸ s^-1, respectively. Evidence is presented for the existence of a third collapsed conformation of 2 which can undergo PET with a rate constant of 1.1 × 10¹² s^-1. In benzonitrile solvent, PET can also occur in the folded and extended geometries leading to a charge separated lifetime of 460 ns. The mechanisms for the unusually complex solvent and conformationally dependent excited-state processes in this molecule are discussed.

Dry rolling-sliding wear tests have been carried out in the present work to investigate the tribological behavior of the novel surface engineered layers produced on AISI 316 austenitic stainless steel by the low-temperature, plasma-carburizing technique. Three carburized layers with varying thickness, ranging from 15 to 40 μm, have been tested using the Amsler configuration. The results show that the carburized layers can prevent surface plastic deformation and improve the wear resistance of the steel during the early stage of the wear process. However, subsurface plastic deformation occurs beneath the layer, leading to the catastrophic failure of the layer and a transition in the wear rate after a limited duration of testing. The thickest layer tested produces the best wear performance under the present rolling-sliding test conditions.

Active screen plasma nitriding (ASPN) is an emerging surface engineering technology that offers many advantages over the conventional dc plasma nitriding (DCPN). In this work, samples of a low alloy steel 722M 24 were AS plasma nitrided with various gas compositions and using different active screen setups. Normal dc plasma nitriding was also performed under similar conditions for comparison. The nitrided samples were characterised with a variety of analytical techniques, including optical microscopy and SEM for morphological and structural examination, XRD for phase identification, and microhardness testing for surface hardness and hardness profile measurements. It has been shown that ASPN can achieve a similar nitriding effect as the normal DCPN but without the common problems associated with dc nitriding such as the arcing surface damage, the edging effect, and the hollow cathode effect. The mechanism of nitrogen mass transfer in AS plasma nitriding has been investigated, and a modified sputtering deposition model has been used to explain the AS plasma nitriding experimental results.

Abstract: Recently, a thermal oxidation (TO) technique has been successfully developed and applied to the titanium alloy Ti-6Al-4V. This TO technique produces a thin, hard, rutile-based, wear-resistant coating on the surface of the titanium alloy, thus significantly improving the tribological properties of the titanium alloy. In the present investigation, the same principle has been applied to the α+β high-strength titanium alloy Timet 550. A series of TO treatments have been carried out in air within the temperature range of 600 °C to 650 °C. This developed a rutile-based coating which greatly improved the tribological properties of Timet 550. Systematic characterization of the TO-treated surface was carried out using glow-discharge optical emission spectroscopy (GDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution scanning electron microscopy (HR-SEM) techniques. Ball-on-disc friction testing was used to show the improvement in tribological properties for Timet 550 when TO treated. The sliding wear resistance of the TO treatment was investigated using an Amsler wear tester, utilizing a counterformal block-on-wheel configuration; the TO-treated Timet 550 was run against a carburized S156 steel with splash oil lubrication. It was found that the wear resistance of the TO-treated Timet 550 was greatly improved.

Low temperature plasma nitriding and carburising are well known as methods for improving tribological properties without deterioration of corrosion properties of austenitic stainless steels. ‘S phase’ is a key alloyed layer, achieved from these two plasma thermochemical processes, referred as nitrogen and carbon S phase, respectively. The present work has been focused on full characterisation of the mechanical and chemical properties of carbon and nitrogen S phase on austenitic stainless steel AISI 316 produced during low temperature plasma processes with different process parameters. A series of theoretical, experimental, and analytical studies have been conducted in order to lay the necessary foundations for fully realising application potential of these processes in various stress and environmental conditions.

The potential of fretting fatigue strength enhancement by a duplex surface engineering process involving shot peening of plasma nitrided steel, termed duplex SP/PN, is demonstrated. Specimens of 709M40 steel were individually plasma nitrided, shot peened, or duplex SP/PN treated. Fretting fatigue properties of the surface engineered specimens were evaluated. Surface roughness, residual stress, and hardening effect following the various surface treatments were examined and compared. It has been found that the duplex treatment can significantly improve the fretting fatigue strength of the investigated low alloy steel. Under the present testing conditions, the duplex SP/PN treatment increased the fretting fatigue strength (at 107cycles) of 709M40 steel by more than 70% relative to the nitrided, 120% to the shot peened, and 500% to the untreated steel. The improvement has been explained in terms of the significantly increased surface hardness and compressive residual stress in the near surface region following the duplex SP/PN treatment. By analysing the stress distributions in a shot peened surface, the influence of surface roughness on fretting fatigue strength is also discussed.

Ultrahigh molecular weight polyethylene (UHMWPE) samples were implanted with 46 and 80 keV nitrogen ions up to a fluence of 1017ions cm−2. The modified surface layers were studied by XPS, Fourier transform infrared spectroscopy (FTIR), Rutherford backscattering spectrometry, elastic recoil detection analysis and dynamic ultra‐microhardness measurements.

Ultrahigh molecular weight polyethylene (UHMWPE) samples were implanted with 46 and 80 keV nitrogen ions up to a fluence of 10¹⁷ ions cm⁻². The modified surface layers were studied by XPS, Fourier transform infrared spectroscopy (FTIR), Rutherford backscattering spectrometry, elastic recoil detection analysis and dynamic ultra-microhardness measurements. By XPS at relatively low fluences (~10¹⁵ ions cm⁻²) the dominant N 1s peak component was detected at ~400 eV, which was attributed to C–N-type bonds. With increasing fluence the share of component at ~398.5 eV, assigned to C–N-type bonds, increased significantly. Changes in the FTIR spectra reflected dehydrogenation (creation of trans-vinylene groups) and oxidation (creation of carbonyl groups). Rutherford backscattering spectrometry allowed the depth profiles of the elements to be obtained. In each case, the thickness of the oxygen-containing layer proved to be greater than that of the nitrogen-containing layer. Elastic recoil detection analysis revealed the formation of a layer with a characteristically graded hydrogen depletion. The thickness of this layer was greater than the projected range of the nitrogen ions. Significant improvement in the surface hardness was observed for the ion-implanted UHMWPE in the whole range of indentation depth studied. Copyright © 2000 John Wiley & Sons, Ltd.

The main aim of this work is to evaluate the effects of the plasma nitriding process on AISI M2 tool steel. In previous work, treatment time and temperature were varied to identify the treatment conditions for good wear behaviour. In the present work, the treatment time was fixed while temperature and gas pressure were varied. Samples were characterised by glow discharge optical spectroscopy, scanning electron microscopy, X‐ray diffraction, surface microhardness and wear test. The specimens nitrided at 400 and 900 Pa showed the best wear performance, which is possibly due to reduction of the friction coefficient and the low adhesive wear observed. Samples processed at 200 Pa showed spalling during the wear test, indicating a brittle surface.