Oxide formation and anodic polarization behavior of thin films of amorphous and crystalline Fe---Cr---P alloys prepared by ion beam mixing

An experimental program has been conducted to determine the effect of phosphorus on the corrosion and passivation behavior of Fe---Cr---P alloys. Chemically homogeneous 60 nm films of Fe---10Cr---xP (x from 0 to 35 at.%) were prepared by multilayer evaporation followed by ion beam mixing with Kr+ ions. Films with a phosphorus content of at least 25 at.% were found to be entirely amorphous, while films with 15 at.% P consisted of both amorphous and bcc phases. Recrystallization of the amorphous phase was accomplished by heating the samples to 450[deg]C in a purified argon flow furnace.Electrochemical polarization tests in an acid solution have shown the Fe---10Cr---xP films to be more corrosion resistant than Fe---10Cr, with the corrosion resistance increasing with the amount of P present. The corrosion resistance is not significantly affected when the amorphous films are recrystallized, indicating that the behavior is chemically controlled and not a result of the amorphous structure. When examined by XPS, the phosphorus appears to enhance passivation by encouraging Cr enrichment in the oxide and by incorporating in the oxide as phosphate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29265/1/0000323.pd

Chemical and structural effects of phosphorus on the corrosion behavior of ion beam mixed Fe-Cr-P alloys

An experimental program was conducted to determine the mechanisms by which phosphorus affects the corrosion and passivation behavior of Fe-Cr-P alloys. To identify separately the effects of structure and chemistry on the corrosion behavior, thin films of Fe-10Cr-xP (0xat.%) were prepared by ion beam mixing. Films with a phosphorus content greater than approximately 20 at.% were found to be entirely amorphous. Devitrification of the amorphous phase was accomplished by heating the samples to 450 [deg]C in an inert environment.Standard polarization tests of the alloys in sulfuric acid (with and without Cl-) indicated that the films containing phosphorus were more corrosion resistant than Fe-10Cr, at both active and passive potentials. There was a monotonic relationship between the amount of phosphorus in the alloy and the corrosion resistance, with the open-circuit corrosion rate of Fe-10Cr-35P nearly four orders of magnitude lower than that of Fe-10Cr. Devitrification of the alloys had no significant effect on the corrosion rate, indicating that the primary effect of phosphorus is chemical in nature, and not structural. The passive oxides were depth-profiled using X-ray photoelectron spectroscopy, which indicated that phosphorus was a primary constituent, as phosphate. The presence of phosphate in the passive oxides reduced the overall corrosion rate directly, by suppressing anodic dissolution. The presence of phosphorus did enhance chromium enrichment in the oxide, but that was not thought to be the primary mechanism by which phosphorus increased the corrosion resistance.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30101/1/0000473.pd

Seasonal and intraspecific variability of chlorophyll fluorescence, pigmentation and growth of Pinus ponderosa subjected to elevated CO{sub 2}

Atmospheric CO{sub 2}2 is expected to double in the next century, and these increases will have substantial impact on forest ecosystems. However, the database on the effects of elevated CO{sub 2} on forests is limited, and the extent of intraspecific variability remains unknown. We are investigating the effects of elevated CO{sub 2} on the intraspecific variability of quantum yield (as measured through chlorophyll fluorescence Fv/Fm ratio) and pigmentation, and how these are correlated to variability in growth. Four-year-old Pinus ponderosa seedlings were obtained from nine different sources across California. These seedlings were grown in standard outdoor exposure chambers for sixteen months at either ambient levels of CO{sub 2}, ambient+175ppm CO{sub 2}, or ambient+350ppm CO{sub 2}. The seedlings were periodically measured for growth, pigmentation, and chlorophyll fluorescence. The results showed a variable growth response of the nine sources during all measurement periods. Increasing CO{sub 2} resulted in a decrease in Fv/Fm among sources ranging from {minus}2.1% to {minus}23.2% in February, and 3.1% to {minus}12.5% in June. The source that had the best growth throughout the study, also had a minimal reduction in quantum yield (Fv/Fm) in the presence of elevated CO{sub 2}. For the seedlings of fastest growing sources, the correspondence between total growth and chlorophyll fluorescence was strongest during the February measurement period. Our results also showed a significant reduction in pigmentation due to increased CO{sub 2}. There are at least three explanations for the different responses during each measurement periods. First, the trees could be adapting favorably to increasing CO{sub 2}. Secondly, 1993 needles could be under less physiological stress than the current year needles. Third, there is a seasonal effect dependent upon temperature or light which is influencing the Fv/Fm ratio and pigmentation

Recent changes of water discharge and sediment load in the Yellow River basin, China

The Yellow River basin contributes approximately 6% of the sediment load from all river systems globally, and the annual runoff directly supports 12% of the Chinese population. As a result, describing and understanding recent variations of water discharge and sediment load under global change scenarios are of considerable importance. The present study considers the annual hydrologic series of the water discharge and sediment load of the Yellow River basin obtained from 15 gauging stations (10 mainstream, 5 tributaries). The Mann-Kendall test method was adopted to detect both gradual and abrupt change of hydrological series since the 1950s. With the exception of the area draining to the Upper Tangnaihai station, results indicate that both water discharge and sediment load have decreased significantly (p<0.05). The declining trend is greater with distance downstream, and drainage area has a significant positive effect on the rate of decline. It is suggested that the abrupt change of the water discharge from the late 1980s to the early 1990s arose from human extraction, and that the abrupt change in sediment load was linked to disturbance from reservoir construction.Geography, PhysicalGeosciences, MultidisciplinarySCI(E)43ARTICLE4541-5613

Mood Modulates Auditory Laterality of Hemodynamic Mismatch Responses during Dichotic Listening

Hemodynamic mismatch responses can be elicited by deviant stimuli in a sequence of standard stimuli even during cognitive demanding tasks. Emotional context is known to modulate lateralized processing. Right-hemispheric negative emotion processing may bias attention to the right and enhance processing of right-ear stimuli. The present study examined the influence of induced mood on lateralized pre-attentive auditory processing of dichotic stimuli using functional magnetic resonance imaging (fMRI). Faces expressing emotions (sad/happy/neutral) were presented in a blocked design while a dichotic oddball sequence with consonant-vowel (CV) syllables in an event-related design was simultaneously administered. Twenty healthy participants were instructed to feel the emotion perceived on the images and to ignore the syllables. Deviant sounds reliably activated bilateral auditory cortices and confirmed attention effects by modulation of visual activity. Sad mood induction activated visual, limbic and right prefrontal areas. A lateralization effect of emotion-attention interaction was reflected in a stronger response to right-ear deviants in the right auditory cortex during sad mood. This imbalance of resources may be a neurophysiological correlate of laterality in sad mood and depression. Conceivably, the compensatory right-hemispheric enhancement of resources elicits increased ipsilateral processing

Enhanced Memory for Scenes Presented at Behaviorally Relevant Points in Time

What determines whether a scene is remembered or forgotten? Our results show how visual scenes are encoded into memory at behaviorally relevant points in time

The Human Affectome

Over the last decades, the interdisciplinary field of the affective sciences has seen proliferation rather than integration of theoretical perspectives. This is due to differences in metaphysical and mechanistic assumptions about human affective phenomena (what they are and how they work) which, shaped by academic motivations and values, have determined the affective constructs and operationalizations. An assumption on the purpose of affective phenomena can be used as a teleological principle to guide the construction of a common set of metaphysical and mechanistic assumptions—a framework for human affective research. In this capstone paper for the special issue “Towards an Integrated Understanding of the Human Affectome”, we gather the tiered purpose of human affective phenomena to synthesize assumptions that account for human affective phenomena collectively. This teleologically-grounded framework offers a principled agenda and launchpad for both organizing existing perspectives and generating new ones. Ultimately, we hope Human Affectome brings us a step closer to not only an integrated understanding of human affective phenomena, but an integrated field for affective research

Elucidating Poor Decision-Making in a Rat Gambling Task

Although poor decision-making is a hallmark of psychiatric conditions such as attention deficit/hyperactivity disorder, pathological gambling or substance abuse, a fraction of healthy individuals exhibit similar poor decision-making performances in everyday life and specific laboratory tasks such as the Iowa Gambling Task. These particular individuals may provide information on risk factors or common endophenotypes of these mental disorders. In a rodent version of the Iowa gambling task – the Rat Gambling Task (RGT), we identified a population of poor decision makers, and assessed how these rats scored for several behavioral traits relevant to executive disorders: risk taking, reward seeking, behavioral inflexibility, and several aspects of impulsivity. First, we found that poor decision-making could not be well predicted by single behavioral and cognitive characteristics when considered separately. By contrast, a combination of independent traits in the same individual, namely risk taking, reward seeking, behavioral inflexibility, as well as motor impulsivity, was highly predictive of poor decision-making. Second, using a reinforcement-learning model of the RGT, we confirmed that only the combination of extreme scores on these traits could induce maladaptive decision-making. Third, the model suggested that a combination of these behavioral traits results in an inaccurate representation of rewards and penalties and inefficient learning of the environment. Poor decision-making appears as a consequence of the over-valuation of high-reward-high-risk options in the task. Such a specific psychological profile could greatly impair clinically healthy individuals in decision-making tasks and may predispose to mental disorders with similar symptoms