In developing advanced wear-resistant coatings for tribologically extreme highly loaded applications such as high speed metal cutting a critical requirement is to investigate their behaviour at ...elevated temperature since the cutting process generates frictional heat which can raise the temperature in the cutting zone to 700–900°C or more. High temperature micro-tribological tests provide severe tests for coatings that can simulate high contact pressure sliding/abrasive contacts at elevated temperature. In this study ramped load micro-scratch tests and repetitive micro-scratch tests were performed at 25 and 500°C on commercial monolayer coatings (AlCrN, TiAlN and AlTiN) deposited on cemented carbide cutting tool inserts. AlCrN exhibited the highest critical load for film failure in front of the moving scratch probe at both temperatures but it was prone to an unloading failure behind the moving probe. Scanning electron microscopy showed significant chipping outside the scratch track which was more extensive for AlCrN at both room and elevated temperature. Chipping was more localised on TiAlN although this coating showed the lowest critical loads at both test temperatures. EDX analysis of scratch tracks after coating failure showed tribo-oxidation of the cemented carbide substrate. AlTiN showed improved scratch resistance at higher temperature. The von Mises, tensile and shear stresses acting on the coating and substrate sides of the interface were evaluated analytically to determine the main stresses acting on the interface. At 1N there are high stresses near the coating-substrate interface. Repetitive scratch tests at this load can be considered as a sub-critical load micro-scale wear test which is more sensitive to adhesion differences than the ramped load scratch test. The analytical modelling showed that a dramatic improvement in the performance of AlTiN in the 1N test at 500°C could be explained by the stress distribution in contact resulting in a change in yield location due to the high temperature mechanical properties. The increase in critical load with temperature on AlTiN and AlCrN is primarily a result of the changing stress distribution in the highly loaded sliding contact rather than an improvement in adhesion strength.
•Wear behaviour of hard nitride coatings in repetitive micro-scratch tests was highly temperature-sensitive.•The wear mechanism in repetitive scratch tests depends on whether plastic flow starts in coating or substrate.•Differences in scratch critical load with temperature are due to changing stress distributions not adhesion.
A comprehensive study of the mechanical properties of TiAlN and AlCrN coated cutting tools has been performed at room and elevated temperatures (up to 500 °C) using Micro Material's NanoTest Platform ...System. Micro-mechanical properties have been measured such as microhardness, elastic modulus, H/E ratio, microhardness dissipation parameter (MDP), critical load values (
L
c1—first crack event;
L
c2—load of dramatic coating failure) during scratch testing; a scratch crack propagation resistance parameter, CPR
s
=
L
c1(
L
c2
−
L
c1) as well as nano-impact fracture resistance. Cutting tool life was studied under end milling conditions of the structural AISI 1040 steel.
A correlation between CPR
s was found with H/E ratio and MDP values. These parameters could be used to characterize the fracture toughness of the coatings. It was shown that mechanical characteristics such as H/E ratio, MDP and CPR
s as well as nano-impact fracture resistance can be used to assess the resistance to adhesive-fatigue wear that is typical for end milling conditions.
It was found that the microhardness of the coating and the H/E ratio reduces with rising temperature while the MDP value grows.
The data obtained during quick laboratory nanohardness, nanoscratch as well as nano-impact fatigue testing can be used to rank the coatings studied and in some cases predict the relative life of a coated tool.
We study the physical conditions, elemental abundances, and kinematics of the high-velocity clouds (HVCs) along the sight lines toward active galaxies HE 0226-4110 and PG 0953+414 using Hubble Space ...Telescope Space Telescope Imaging Spectrograph and Far Ultraviolet Spectroscopic Explorer data. No 21 cm H I emission is detected in these clouds, but our observations reveal multiple components of HVC absorption in lines of H I, C II, C III, C IV, O VI, Si II, Si III, and Si IV in both directions. We investigate whether photoionization by the extragalactic background radiation or by escaping Milky Way radiation can explain the observed ionization pattern. We find that photoionization is a good explanation for the C II, C III, Si II, and Si III features but not for the O VI or C IV associated with the HVCs, suggesting that two principal phases exist: a warm (T - 10 super(4) K), photoionized phase and a hotter (T = 1-3 x 10 super(5) K), collisionally ionized phase; the broader line widths of the high ions are consistent with this multiphase hypothesis. The warm HVCs toward HE 0226-4110 have high levels of ionization (97%-99%) and metallicities (Z/H between -0.9 and -0.4) close to those in the Magellanic Stream, which lies 11 away on the sky at similar velocities. These HVCs may well be stripped fragments of the Stream that have been ionized by the pervading radiation field; they have thermal pressures that would place them close to equilibrium in a fully ionized 10 super(6) K Galactic corona with n sub(H) = 4-9 x 10 super(-5) cm super(-3) at 50 kpc. The warm HVCs seen at -146 and 125 km s super(-1) toward PG 0953+414 have Z/H = -0.6 c 0.2 and -0.8 c 0.2, respectively, suggesting they are not formed from purely Galactic material. A minisurvey of the hot, collisionally ionized HVC components seen here and in five other sight lines finds that in 11/12 cases, the high ions have kinematics and ionic ratios that are consistent with an origin in conductive interfaces, where energy flows into the HVCs from a hot surrounding medium and produces O VI- and C IV-bearing boundary layers. However, the broad absorption wing on the O VI profile toward PG 0953+414 is not completely explained by the interface scenario. This feature may be tracing the outflow of hot gas into the Milky Way halo as part of a Galactic fountain or wind.
Assessment of right ventricular (RV) function remains challenging because of complex RV chamber geometry and a paucity of easily derived and objective functional methods.
Visual 2-dimensional ...echocardiographic estimates of RV ejection fraction (EF), tricuspid annular plane systolic excursion, Doppler tissue imaging, and myocardial performance index (MPI) were compared with biplanar Simpson's rule RV EF in 101 consecutive patients. Data were analyzed using simple linear regression and receiver operating characteristic curves.
RV EF was significantly correlated with tricuspid annular plane systolic excursion (r = 0.48, P <.0001), Doppler tissue imaging peak systolic velocity (r = 0.45, P <.0001), and MPI (r = -0.38, P =.006). Using a Simpson's RV EF < 50%, the sensitivity, specificity, and positive and negative predictive values of tricuspid annular plane systolic excursion < 1.5 cm were 59%, 94%, 71%, and 89%; of Doppler tissue imaging peak systolic velocity < 10 cm/s were 59%, 92%, 67%, and 89%; and of MPI < 0.40 were 100%, 35%, 29%, and 100%, respectively. The area under the receiver operating characteristic curves was similar for the 3 indices.
Measurements of tricuspid annular motion are easy to obtain, correlate with Simpson's RV EF, and have a high specificity and negative predictive value for detecting abnormal RV systolic function; and the MPI, although not specific, has high sensitivity and negative predictive value for detecting abnormal RV systolic function.
Positive affect elicited in a mother toward her newborn infant may be one of the most powerful and evolutionarily preserved forms of positive affect in the emotional landscape of human behavior. This ...study examined the neurobiology of this form of positive emotion and in so doing, sought to overcome the difficulty of eliciting robust positive affect in response to visual stimuli in the physiological laboratory. Six primiparous human mothers with no indications of postpartum depression brought their infants into the laboratory for a photo shoot. Approximately 6 weeks later, they viewed photographs of their infant, another infant, and adult faces during acquisition of functional magnetic resonance images (fMRI). Mothers exhibited bilateral activation of the orbitofrontal cortex (OFC) while viewing pictures of their own versus unfamiliar infants. While in the scanner, mothers rated their mood more positively for pictures of their own infants than for unfamiliar infants, adults, or at baseline. The orbitofrontal activation correlated positively with pleasant mood ratings. In contrast, areas of visual cortex that also discriminated between own and unfamiliar infants were unrelated to mood ratings. These data implicate the orbitofrontal cortex in a mother's affective responses to her infant, a form of positive emotion that has received scant attention in prior human neurobiological studies. Furthermore, individual variations in orbitofrontal activation to infant stimuli may reflect an important dimension of maternal attachment.
We present Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope observations of high-, intermediate-, and low-ion absorption in high- velocity cloud (HVC) Complex C along the lines of ...sight toward five active galaxies. Our purpose is to investigate the idea that Complex C is surrounded by an envelope of highly ionized material, arising from the interaction between the cloud and a hot surrounding medium. We measure column densities of high-velocity high-ion absorption and compare the kinematics of low-, intermediate-, and high- ionization gas along the five sight lines. We find that in all five cases, the H I and O VI high-velocity components are centered within 20 km s super(-1) of one another, with an average displacement of image = 3 plus or minus 12 km s super(-1). In those directions where the H I emission extends to more negative velocities (the so- called high-velocity ridge), so does the O VI absorption. The kinematics of Si II is also similar to that of O VI, with image = 0 plus or minus 15 km s super(-1). We compare our high-ion column density ratios to the predictions of various models, adjusted to account for both recent updates to the solar elemental abundances and relative elemental abundance ratios in Complex C. Along the PG 1259+593 sight line, we measure N(Si image)/N(O image) = 0.10 plus or minus 0.02, N(C image)/N(O image) = 0.35image, and N(N image)/N(O image) < 0.07 (3 capital sigma ). These ratios are inconsistent with collisional ionization equilibrium at one kinetic temperature. Photoionization by the extragalactic background is ruled out as the source of the high ions since the path lengths required would make HVCs unreasonably large; photoionization by radiation from the disk of the Galaxy also appears unlikely since the emerging photons are not energetic enough to produce O VI. By themselves, ionic ratios are insufficient to discriminate between various ionization models, but by considering the absorption kinematics as well, we consider the most likely origin for the highly ionized high-velocity gas to be at the conductive or turbulent interfaces between the neutral/warm ionized components of Complex C and a surrounding hot medium. The presence of interfaces on the surface of HVCs provides indirect evidence for the existence of a hot medium in which the HVCs are immersed. This medium could be a hot (T > ~ 10 super(6) K) extended Galactic corona or hot gas in the Local Group.
Density-dependent habitat selection has implications for fisheries management and for the recovery of depleted fish populations. According to ideal free distribution theory, populations contract into ...areas of highest habitat suitability as their abundance decreases. This can increase their vulnerability to fishing and predation. We detected density-dependent habitat selection by juvenile Atlantic cod (Gadus morhua) (ages 1 and 2) in the North Sea and compared the observed distributionabundance relationships with those predicted from a model based on ideal free distribution theory and knowledge of optimal temperatures for growth, where temperature was used as a measure of suitability. As predicted by the model, in years when stock size was low, the catches were largely confined to regions with near-optimal bottom temperatures. Conversely, when population size was high, catches were spread across a larger area including regions with suboptimal temperatures. The spatial extent of optimal habitat appears to have decreased from 1977 to 2002, reflecting a gradual warming of the North Sea. The combined negative effects of increased temperature on recruitment rates and the reduced availability of optimal habitat may have increased the vulnerability of the cod population to fishing mortality.
An approach to enlarge preformed colloidal Au nanoparticles in solution based on the Au colloidal surface-catalyzed reduction of Au3+ by NH2OH (“seeding”) has been adapted to 12-nm-diameter colloidal ...Au nanoparticles immobilized in monolayers and multilayers. Bulk characterization of the ensuing films was carried out by atomic absorption, UV−vis−near-IR optical spectroscopy, cyclic voltammetry, and dc resistance measurements. Exposure of a 12-nm-diameter Au colloid monolayer on organosilane-modified glass surfaces to NH2OH/Au3+ leads to rapid particle growth and coalescence: after roughly 5−10 min, the optical and electrical properties closely resemble that of conductive Au thin films prepared by evaporation. Evolution of the nanometer-scale architecture was followed using atomic force microscopy (AFM), surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), and field emission scanning electron microscopy (FE-SEM), leading to the following key findings: (i) Seeding of surface-confined colloidal Au leads to a very different distribution in particle size/shape than seeding with identical particles in solution. (ii) Au3+/NH2OH-mediated growth of surface-confined colloidal Au is highly dependent on particle coverage, with different particle densities in monolayers leading to distinct film architectures that are easily detected by FE-SEM and SPR.
To measure the column densities of interstellar and intergalactic gas clouds using absorption-line spectroscopy, the apparent optical depth (AOD) technique of Savage & Sembach can be used instead of ...a curve-of-growth analysis or profile fit. We show that the AOD technique, while an excellent tool when applied to data with good signal-to-noise ratio (S/N), will likely overestimate the true column densities when applied to data with low S/N. This overestimation results from the nonlinear relationship between the flux falling on a given detector pixel and the apparent optical depth in that pixel. We use Monte Carlo techniques to investigate the amplitude of this overestimation when working with data from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Space Telescope Imaging Spectrograph (STIS), for a range of values of S/N, line depth, line width, and rebinning. AOD measurements of optimally sampled, resolved lines are accurate to within 10% for FUSE LiF and STIS E140M data with S/N 7 per resolution element.
To describe the amount and nature of violence exposure and examine the relationship between violence exposure and distress symptoms among children in foster care.
Violence exposure and distress ...symptoms were evaluated in interviews, conducted between July 1996 and March 1998, of 300 children from Los Angeles County living in out-of-home placement.
Interviews were successfully completed in 91% of eligible children. The majority of children (85%) reported having been a witness to violence, and 51% had been a victim of violence during their lifetime. Of these youths, 54% and 41%, respectively, reported having been exposed to such violence in the past 6 months. Girls, victims of assaultive violence and weapon related violence, and those reporting exposure to mild violence were more likely (p < .05) to have higher levels of distress symptoms than those without such characteristics, after age was controlled for.
Children in foster care continue to have high levels of violence exposure, even after removal from their biological parents' home. The relationship between violence exposure and distress symptoms underscores the need for clinicians to inquire about multiple forms of violence exposure among children living in out-of-home placement.
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