This work presents and discusses the antiwear behaviour of nanoparticle suspensions in a polyalphaolefin (PAO 6). CuO, ZnO and ZrO2 nanoparticles were separately dispersed at 0.5%, 1.0% and 2.0%wt. ...in PAO 6 using an ultrasonic probe for 2 min. AW properties were obtained using a TE53SLIM tribometer with a block-on-ring configuration. Tests were made under a load of 165 N, sliding speed of 2 m/s and a total distance of 3.066 m. Wear surfaces were analysed by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) after wear tests. The study led to the following conclusions: all nanoparticle suspensions exhibited reductions in friction and wear compared to the base oil; the suspensions with 0.5% of ZnO and ZrO2 had the best general tribological behaviour, exhibiting high friction and wear reduction values even at low deposition levels on the wear surface; CuO suspensions showed the highest friction coefficient and lowest wear per nanoparticle content of 2%; and the antiwear mechanism of nanoparticulate additive was produced by tribo-sintering.
Sleep Spindles: Mechanisms and Functions Fernandez, Laura M J; Lüthi, Anita
Physiological reviews,
2020-Apr-01, 2020-04-01, 20200401, Letnik:
100, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Sleep spindles are burstlike signals in the electroencephalogram (EEG) of the sleeping mammalian brain and electrical surface correlates of neuronal oscillations in thalamus. As one of the most ...inheritable sleep EEG signatures, sleep spindles probably reflect the strength and malleability of thalamocortical circuits that underlie individual cognitive profiles. We review the characteristics, organization, regulation, and origins of sleep spindles and their implication in non-rapid-eye-movement sleep (NREMS) and its functions, focusing on human and rodent. Spatially, sleep spindle-related neuronal activity appears on scales ranging from small thalamic circuits to functional cortical areas, and generates a cortical state favoring intracortical plasticity while limiting cortical output. Temporally, sleep spindles are discrete events, part of a continuous power band, and elements grouped on an infraslow time scale over which NREMS alternates between continuity and fragility. We synthesize diverse and seemingly unlinked functions of sleep spindles for sleep architecture, sensory processing, synaptic plasticity, memory formation, and cognitive abilities into a unifying sleep spindle concept, according to which sleep spindles
) generate neural conditions of large-scale functional connectivity and plasticity that outlast their appearance as discrete EEG events,
) appear preferentially in thalamic circuits engaged in learning and attention-based experience during wakefulness, and
) enable a selective reactivation and routing of wake-instated neuronal traces between brain areas such as hippocampus and cortex. Their fine spatiotemporal organization reflects NREMS as a physiological state coordinated over brain and body and may indicate, if not anticipate and ultimately differentiate, pathologies in sleep and neurodevelopmental, -degenerative, and -psychiatric conditions.
The nature of inter-group relations among prehistoric hunter-gatherers remains disputed, with arguments in favour and against the existence of warfare before the development of sedentary societies. ...Here we report on a case of inter-group violence towards a group of hunter-gatherers from Nataruk, west of Lake Turkana, which during the late Pleistocene/early Holocene period extended about 30 km beyond its present-day shore. Ten of the twelve articulated skeletons found at Nataruk show evidence of having died violently at the edge of a lagoon, into which some of the bodies fell. The remains from Nataruk are unique, preserved by the particular conditions of the lagoon with no evidence of deliberate burial. They offer a rare glimpse into the life and death of past foraging people, and evidence that warfare was part of the repertoire of inter-group relations among prehistoric hunter-gatherers.
Structural damage assessment is critical after disasters but remains a challenge. Many studies have explored the potential of remote sensing data, but limitations of vertical data persist. Oblique ...imagery has been identified as more useful, though the multi-angle imagery also adds a new dimension of complexity. This paper addresses damage assessment based on multi-perspective, overlapping, very high resolution oblique images obtained with unmanned aerial vehicles (UAVs). 3-D point-cloud assessment for the entire building is combined with detailed object-based image analysis (OBIA) of façades and roofs. This research focuses not on automatic damage assessment, but on creating a methodology that supports the often ambiguous classification of intermediate damage levels, aiming at producing comprehensive per-building damage scores. We identify completely damaged structures in the 3-D point cloud, and for all other cases provide the OBIA-based damage indicators to be used as auxiliary information by damage analysts. The results demonstrate the usability of the 3-D point-cloud data to identify major damage features. Also the UAV-derived and OBIA-processed oblique images are shown to be a suitable basis for the identification of detailed damage features on façades and roofs. Finally, we also demonstrate the possibility of aggregating the multi-perspective damage information at building level.
The cost analysis of a real facility for the production of high value microalgae biomass is presented. The facility is based on ten 3m3 tubular photobioreactors operated in continuous mode for ...2years, data of Scenedesmus almeriensis productivity but also of nutrients and power consumption from this facility being used. The yield of the facility was close to maximum expected for the location of Almería, the annual production capacity being 3.8t/year (90t/ha·year) and the photosynthetic efficiency being 3.6%. The production cost was 69 €/kg. Economic analysis shows that labor and depreciation are the major factors contributing to this cost. Simplification of the technology and scale-up to a production capacity of 200t/year allows to reduce the production cost up to 12.6 €/kg. Moreover, to reduce the microalgae production cost to approaches the energy or commodities markets it is necessary to reduce the photobioreactor cost (by simplifying its design or materials used), use waste water and flue gases, and reduce the power consumption and labor required for the production step. It can be concluded that although it has been reported that production of biofuels from microalgae is relatively close to being economically feasible, data here reported demonstrated that to achieve it by using the current production technologies, it is necessary to substantially reduce their costs and to operate them near their optimum values.
Nine wild Iberian provenances of Castanea sativa Mill. grouped in two gene pools, North Iberian Peninsula and Mediterranean, were evaluated for several adaptive traits in two provenance-progeny ...trials with the aim of evaluating the role of natural selection in shaping adaptive variation and increasing our understanding of the genetic structure of this species, as well as reporting complete information on the genetic variation among and within the studied populations. An annual growth rhythm experiment was evaluated during the first 3 years after establishment for phenology, growth, stem form and survival, and a periodic drought-stress experiment was evaluated for dry weight, growth, survival and other related drought traits in both well-watered and drought-stress treatments. The high genetic variability reported in both trials is largely due to the genetic variation among populations. The significant differences reported between quantitative genetic and neutral marker differentiation indicated the local adaptation of these populations through directional selection, mainly for phenology, growth and biomass allocation. A clinal variation among populations was determined through correlations of phenology with latitude and xerothermic index of the provenances, showing that central and southern Mediterranean populations had earlier phenology than northern populations and that drought played a relevant role in this differentiation. The significant correlation between phenological traits and the ancestry values in the Mediterranean gene pool supported the different pattern of behavior between both gene pools and also indicated the existence of two ecotypes: xeric and mesophytic ecotypes, corresponding to Mediterranean and North Iberian gene pools, respectively. The results obtained in the drought-stress experiment confirmed that, in general terms, xeric populations showed a greater adaptability to drought, with more developed root systems and higher survival than northern populations. Moreover, the genetic variability observed within populations indicated the potential response capacity of Iberian C. sativa populations to undergo fast adaptive evolution.
Because of their physico-chemical inherent properties, mangrove sediments may act as a sink for pollutants coming from catchments. The main objective of this study was to assess the distribution of ...some trace metals in the tissues of various mangrove plants developing downstream highly weathered ferralsols, taking into account metals partitioning in the sediment. In New Caledonia, mangroves act as a buffer between open-cast mines and the world's largest lagoon. As a result of the erosion of lateritic soils, Ni and Fe concentrations in the sediment were substantially higher than the world average. Whatever the mangrove stand and despite low bioaccumulation and translocations factors, Fe and Ni were also the most abundant metals in the different plant tissues. This low bioaccumulation may be explained by: i) the low availability of metals, which were mainly present in the form of oxides or sulfur minerals, and ii) the root systems acting as barriers towards the transfer of metals to the plant. Conversely, Cu and Zn metals had a greater mobility in the plant, and were characterized by high bioconcentration and translocation factors compared to the other metals. Cu and Zn were also more mobile in the sediment as a result of their association with organic matter. Whatever the metal, a strong decrease of trace metal stock was observed from the landside to the seaside of the mangrove, probably as a result of the increased reactivity of the sediment due to OM enrichment. This reactivity lead to higher dissolution of bearing phases, and thus to the export of dissolved trace metals trough the tidal action. Cu and Zn were the less concerned by the phenomenon probably as a result of higher plant uptake and their restitution to the sediment with litter fall in stands where tidal flushing is limited.
Display omitted
•Unusual high concentrations of Fe and Ni were measured in mangrove tissues.•Bioconcentration and translocation factors of Fe, Ni, Co and Mn were low.•Low bioavailability can result from metal association with refractory bearing phase.•Cu and Zn have greater mobility in mangrove sediments and plants.•Metals stocks decreased towards the sea as a result of more reactive substrate.
Eccentric strength training alters muscle architecture, but it is also an important factor for the prevention of hamstring injuries. The purpose was to determine the architectural adaptations of the ...biceps femoris long head (BFlh) after eccentric strength training with nordic hamstring exercise (NHE), followed by a subsequent detraining period. The participants in this intervention (n=23) completed a period of 13 weeks consisting of a first week of control and prior training, followed by 8 weeks of eccentric strength training with NHE, and concluding with a 4‐week period of detraining. The architectural characteristics of the BFlh were measured at rest using two‐dimensional ultrasound before (M1—week 1) and after (M2—week 9) the eccentric strength training, and at the end of the detraining period (M3—week 13). The muscle fascicle length significantly increased (t=−7.73, d=2.28, P<.001) in M2 compared to M1, as well as the muscle thickness (t=−5.23, d=1.54, P<.001), while the pennation angle presented a significant decrease (t=7.81, d=2.3, P<.001). The muscle fascicle length decreased significantly (t=6.07, d=1.79, P<.001) in M3 compared to M2, while the pennation angle showed a significant increase (t=−4.63, d=1.36, P<.001). The results provide evidence that NHE may cause alterations in the architectural conditions of the BFlh and may have practical implications for injury prevention and rehabilitation programs.
Diabetes refers to a group of metabolic diseases characterized by impaired insulin signalling and high blood glucose. A growing body of epidemiological evidence links diabetes to several types of ...cancer but the underlying molecular mechanisms are poorly understood. The signalling cascade connecting insulin and FOXO proteins provides a compelling example for a conserved pathway at the interface between insulin signalling and cancer. FOXOs are transcription factors that orchestrate programs of gene expression known to control a variety of processes in response to cellular stress. Genes regulated by this family of proteins are involved in the regulation of cellular energy production, oxidative stress resistance and cell viability and proliferation. Accordingly, FOXO factors have been shown to play an important role in the suppression of tumour growth and in the regulation of metabolic homeostasis. There is emerging evidence that deregulation of FOXO factors might account for the association between insulin resistance‐related metabolic disorders and cancer.
PDF
