Tribological Characterisation of Graphene Oxide as Lubricant Additive on Hypereutectic Al-25Si/Steel Tribopair

The performance of a lubricant greatly depends on the additives it involves. However, recently used additives produce severe pollution when they are burned and exhausted. Therefore, it is necessary to develop a new generation of green additives. Graphene oxide (GO) is considered to be environmentally friendly. The scope of this study is to explore the fundamental tribological behavior of graphene, the first existing 2D material, and evaluate its performance as a lubricant additive. The friction and wear behavior of 0.5 wt% concentrations of GO particles in ethanol and SAE20W50 engine oil on a hypereutectic Al-25Si alloy disc against steel ball was studied at 5 N load. GO as an additive reduced the wear coefficient by 60–80% with 30 Hz frequency for 120 m sliding distance. The minimum value of the coefficient of friction (0.057) was found with SAE20W50 + 0.5 wt% GO. A possible explanation for these results is that the graphene layers act as a 2D nanomaterial and form a conformal protective film on the sliding contact interfaces and easily shear off due to weak Van der Waal's forces and drastically reduce the wear. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Raman spectroscopy were used for characterization of GO and wear scars

Exceptional Record of Mid-Pleistocene Vertebrates Helps Differentiate Climatic from Anthropogenic Ecosystem Perturbations

Mid-Pleistocene vertebrates in North America are scarce but important for recognizing the ecological effects of climatic change in the absence of humans. We report on a uniquely rich mid-Pleistocene vertebrate sequence from Porcupine Cave, Colorado, which records at least 127 species and the earliest appearances of 30 mammals and birds. By analyzing \u3e20,000 mammal fossils in relation to modern species and independent climatic proxies, we determined how mammal communities reacted to presumed glacial-interglacial transitions between 1,000,000 and 600,000 years ago. We conclude that climatic warming primarily affected mammals of lower trophic and size categories, in contrast to documented human impacts on higher trophic and size categories historically. Despite changes in species composition and minor changes in small-mammal species richness evident at times of climatic change, overall structural stability of mammal communities persisted \u3e600,000 years before human impacts

Kant's conception of proper science

Kant is well known for his restrictive conception of proper science. In the present paper I will try to explain why Kant adopted this conception. I will identify three core conditions which Kant thinks a proper science must satisfy: systematicity, objective grounding, and apodictic certainty. These conditions conform to conditions codified in the Classical Model of Science. Kant's infamous claim that any proper natural science must be mathematical should be understood on the basis of these conditions. In order to substantiate this reading, I will show that only in this way it can be explained why Kant thought (1) that mathematics has a particular foundational function with respect to the natural sciences and (2) as such secures their scientific status. © 2009 The Author(s)

Disrupted habenula function in major depression.

The habenula is a small, evolutionarily conserved brain structure that plays a central role in aversive processing and is hypothesised to be hyperactive in depression, contributing to the generation of symptoms such as anhedonia. However, habenula responses during aversive processing have yet to be reported in individuals with major depressive disorder (MDD). Unmedicated and currently depressed MDD patients (N=25, aged 18-52 years) and healthy volunteers (N=25, aged 19-52 years) completed a passive (Pavlovian) conditioning task with appetitive (monetary gain) and aversive (monetary loss and electric shock) outcomes during high-resolution functional magnetic resonance imaging; data were analysed using computational modelling. Arterial spin labelling was used to index resting-state perfusion and high-resolution anatomical images were used to assess habenula volume. In healthy volunteers, habenula activation increased as conditioned stimuli (CSs) became more strongly associated with electric shocks. This pattern was significantly different in MDD subjects, for whom habenula activation decreased significantly with increasing association between CSs and electric shocks. Individual differences in habenula volume were negatively associated with symptoms of anhedonia across both groups. MDD subjects exhibited abnormal negative task-related (phasic) habenula responses during primary aversive conditioning. The direction of this effect is opposite to that predicted by contemporary theoretical accounts of depression based on findings in animal models. We speculate that the negative habenula responses we observed may result in the loss of the capacity to actively avoid negative cues in MDD, which could lead to excessive negative focus

Astroglial-Kir4.1 in Lateral Habenula Drives Neuronal Bursts to Mediate Depression

International audienceEnhanced bursting activity of neurons in the lateral habenula (LHb) is essential in driving depression-like behaviours, but the cause of this increase has been unknown. Here, using a high-throughput quantitative proteomic screen, we show that an astroglial potassium channel (Kir4.1) is upregulated in the LHb in rat models of depression. Kir4.1 in the LHb shows a distinct pattern of expression on astrocytic membrane processes that wrap tightly around the neuronal soma. Electrophysiology and modelling data show that the level of Kir4.1 on astrocytes tightly regulates the degree of membrane hyperpolarization and the amount of bursting activity of LHb neurons. Astrocyte-specific gain and loss of Kir4.1 in the LHb bidirectionally regulates neuronal bursting and depression-like symptoms. Together, these results show that a glia–neuron interaction at the perisomatic space of LHb is involved in setting the neuronal firing mode in models of a major psychiatric disease. Kir4.1 in the LHb might have potential as a target for treating clinical depression

The evolution of the upright posture and gait—a review and a new synthesis

During the last century, approximately 30 hypotheses have been constructed to explain the evolution of the human upright posture and locomotion. The most important and recent ones are discussed here. Meanwhile, it has been established that all main hypotheses published until the last decade of the past century are outdated, at least with respect to some of their main ideas: Firstly, they were focused on only one cause for the evolution of bipedality, whereas the evolutionary process was much more complex. Secondly, they were all placed into a savannah scenario. During the 1990s, the fossil record allowed the reconstruction of emerging bipedalism more precisely in a forested habitat (e.g., as reported by Clarke and Tobias (Science 269:521–524, 1995) and WoldeGabriel et al. (Nature 412:175–178, 2001)). Moreover, the fossil remains revealed increasing evidence that this part of human evolution took place in a more humid environment than previously assumed. The Amphibian Generalist Theory, presented first in the year 2000, suggests that bipedalism began in a wooded habitat. The forests were not far from a shore, where our early ancestor, along with its arboreal habits, walked and waded in shallow water finding rich food with little investment. In contrast to all other theories, wading behaviour not only triggers an upright posture, but also forces the individual to maintain this position and to walk bipedally. So far, this is the only scenario suitable to overcome the considerable anatomical and functional threshold from quadrupedalism to bipedalism. This is consistent with paleoanthropological findings and with functional anatomy as well as with energetic calculations, and not least, with evolutionary psychology. The new synthesis presented here is able to harmonise many of the hitherto competing theories

Comparison of Mammalian Species Richness and Community Structure in Historic and Mid-Pleistocene Times in the Colorado Rocky Mountains

Volume: 56, Supplement IStart Page: 50End Page: 6

Vertebrate Natural History Laboratory and Field Syllabus – Integrative Biology 104LF

The primary objective of the laboratory and field work in this course is to aid the student in making personal, first-hand observations on the biology of living vertebrate animals in their natural environments. Containing a variety of habitats and ecological formations, such as coniferous forest, oak-bay woodland, chaparral, grassland, fresh-water marsh, lakes, and stream banks, East Bay Regional Parks support a rich variety of vertebrate species and are easily accessible. We will emphasize the behavior, adaptations, and way of life of Bay Area vertebrate species in an effort to understand their natural history, their interactions, and the ecosystems of which they are a part. Attention is given to techniques of field study, species identification, ecologic niches, foraging behavior, food habits, predator-prey relationships, habitat selection, competition within and among species, geographic distribution, and interactions between humans and vertebrate animals as they relate to conservation and human welfare. Although different species may be present in other areas, it should be realized that the techniques and principles of vertebrate natural history learned by the study of local animals will have broad geographic application

Vertebrate Natural History Laboratory and Field Syllabus – Integrative Biology 104LF

The primary objective of the laboratory and field work in this course is to aid the student in making personal, first-hand observations on the biology of living vertebrate animals in their natural environments. Containing a variety of habitats and ecological formations, such as coniferous forest, oak-bay woodland, chaparral, grassland, fresh-water marsh, lakes, and stream banks, East Bay Regional Parks support a rich variety of vertebrate species and are easily accessible. We will emphasize the behavior, adaptations, and way of life of Bay Area vertebrate species in an effort to understand their natural history, their interactions, and the ecosystems of which they are a part. Attention is given to techniques of field study, species identification, ecologic niches, foraging behavior, food habits, predator-prey relationships, habitat selection, competition within and among species, geographic distribution, and interactions between humans and vertebrate animals as they relate to conservation and human welfare. Although different species may be present in other areas, it should be realized that the techniques and principles of vertebrate natural history learned by the study of local animals will have broad geographic application

A report on late Quaternary vertebrate fossil assemblages from the eastern San Francisco Bay region, California

Here we report on vertebrate fossil assemblages from two late Quaternary localities in the eastern San Francisco Bay region, Pacheco 1 and Pacheco 2. At least six species of extinct mammalian megaherbivores are known from Pacheco 1. The probable occurrence of Megalonyx jeffersonii suggests a late Pleistocene age for the assemblage. Pacheco 2 has yielded a minimum of 20 species of mammals, and provides the first unambiguous Quaternary fossil record of Urocyon, Procyon, Antrozous, Eptesicus, Lasiurus, Sorex ornatus, Tamias, and Microtus longicaudus from the San Francisco Bay region. While a radiocarbon date of 405 ± 45 RCYBP has been obtained for a single bone sample from Pacheco 2, the possibility that much of the assemblage is considerably older than this date is suggested by (1) the substantial loss of collagen in all other samples for which radiocarbon dating was unsuccessfully attempted and (2) the occurrence of Microtus longicaudus approximately 160 km to the west of, and 600 m lower in elevation than, its present range limit. The taphonomic data and limited stratigraphic information for the two localities suggest deposition of bones within a riparian system. Multiple lines of evidence including the taxonomic composition and the relative abundance of skeletal elements point to the original accumulation of most, if not all, of the small vertebrate remains at Pacheco 2 by owls. Based on taxonomic composition, Pacheco 1 appears to have been located in a mosaic of grassland and woodland habitats, and Pacheco 2 in moist woodland with dense underbrush and a body of freshwater