Energy storage is one of the highest priority challenges in transitioning to a low-carbon economy. Fluctuating, intermittent primary renewable sources such as wind and solar require low-carbon ...storage options to enable effective load matching, ensuring security of supply. Chemical storage is one such option, with low or zero carbon fuels such as hydrogen, alcohols and ammonia having been proposed. Ammonia provides zero-carbon hydrogen storage whilst offering liquefaction at relatively low pressures and atmospheric temperatures, enabling ease of transportation in a pre-existing infrastructure. Ammonia can also be used directly as a fuel in power plants such as gas turbines to avoid complete conversion back to hydrogen. It is a relatively unreactive fuel, and so it is of interest to explore the potential utilisation of ammonia/hydrogen mixtures. Hence, the goal of this paper is to provide a first assessment of the suitability of a chosen 70%NH330%H2 (%vol) blend for utilisation within a gas turbine environment, based on primary combustion diagnostics including combustion stability – via OH chemiluminescence - and emissions (NOx and NH3). An established optical generic swirl-burner enabled studies of the influence of equivalence ratio (φ > 1), ambient temperature (<484 ± 10 K) and bypass air, with a focus on NOx reduction, one of the main challenges for ammonia combustion. A numerical GT cycle model is developed alongside the experimental investigation. The results demonstrate that the blend has considerable potential as a fuel substitute with reasonable combustion stability and significant reduction of emissions for the cases without bypass air, due to increased chemical reactivity of unburned ammonia. However, emissions are still above those recommended for gas turbine cycles, with a theoretical cycle that still produces low efficiencies compared to DLN methane, highlighting the requirement for new injection techniques to reduce NOx/unburned NH3 in the flue gases whilst ensuring increased power outputs.
•Ammonia can become a new energy vector for large-scale power generation.•Ammonia/Hydrogen blends can be created by cracking small amounts of NH3.•Current research shows stable flames with 70:30 NH3/H2 blends.•High inlet air temperatures increase NOx and OH reactivity, reducing flame size.•Current gas turbines will be inefficient using solely these blends.
Fossil apes and human evolution Almécija, Sergio; Hammond, Ashley S; Thompson, Nathan E ...
Science (American Association for the Advancement of Science),
05/2021, Letnik:
372, Številka:
6542
Journal Article
Recenzirano
Odprti dostop
Humans diverged from apes (chimpanzees, specifically) toward the end of the Miocene ~9.3 million to 6.5 million years ago. Understanding the origins of the human lineage (hominins) requires ...reconstructing the morphology, behavior, and environment of the chimpanzee-human last common ancestor. Modern hominoids (that is, humans and apes) share multiple features (for example, an orthograde body plan facilitating upright positional behaviors). However, the fossil record indicates that living hominoids constitute narrow representatives of an ancient radiation of more widely distributed, diverse species, none of which exhibit the entire suite of locomotor adaptations present in the extant relatives. Hence, some modern ape similarities might have evolved in parallel in response to similar selection pressures. Current evidence suggests that hominins originated in Africa from Miocene ape ancestors unlike any living species.
Mutations in mitochondrial DNA (mtDNA) accumulate in tissues of mammalian species and have been hypothesized to contribute to aging. We show that mice expressing a proofreading-deficient version of ...the mitochondrial DNA polymerase g (POLG) accumulate mtDNA mutations and display features of accelerated aging. Accumulation of mtDNA mutations was not associated with increased markers of oxidative stress or a defect in cellular proliferation, but was correlated with the induction of apoptotic markers, particularly in tissues characterized by rapid cellular turnover. The levels of apoptotic markers were also found to increase during aging in normal mice. Thus, accumulation of mtDNA mutations that promote apoptosis may be a central mechanism driving mammalian aging.
Carbon nanofibers (CNF) were dispersed into an epoxy resin using a combination of ultrasonication and mechanical mixing. The electronic transport properties of the resulting composites were ...investigated by means of impedance spectroscopy. It was found that a very low critical weight fraction (
p
c
=
0.064
wt%) which may be taken to correspond to the formation of a tunneling conductive network inside the matrix. The insulator-to-conductor transition region spanned about one order of magnitude from 0.1 to 1
wt%. Far from the transition, the conductivity increased by two orders of magnitude. This increase and the low value of the conductivity were explained in terms of the presence of an epoxy film at the contact between CNF. A simple model based on the CNF–CNF contact network inside the matrix was proposed in order to evaluate the thickness of that film.
Variation in natural gas composition, alongside the potential for H2 enrichment, creates the potential for significant changes to premixed flame behaviour. To strengthen fundamental understanding of ...lean multi-component alternative fuel blends, an outwardly propagating spherical flame was employed to measure the flame speeds and Markstein lengths of C1C4 hydrocarbons, alongside precisely mixed blends of CH4/C2H6, CH4/C3H8 and CH4/H2. Theoretical relationships between Markstein length and Lewis Number are explored alongside effective Lewis number formulations. Under lean conditions, equal volumetric additions of H2 and C3H8 (30% vol.) to CH4 resulted in similar augmentation of burning velocity, however, opposite susceptibility to preferential diffusional instability was noted. At a fixed equivalence ratio of 0.65, limited changes in composition provide a marked change in the premixed flame response with the addition of C2H6 and C3H8 to CH4. For lean CH4/H2 mixtures, a diffusional based Lewis Number formulation yielded a favourable correlation, whilst a heat-release model resulted in better agreement for lean CH4/C3H8 blends. Modelling work suggests that measured enhancement of lean CH4 flames upon H2 or C3H8 is strongly correlated to changes in volumetric heat release rates and production of H radicals. Furthermore, a systematic analysis of the flame speed enhancement effects (thermal, kinetic, diffusive) of H2 and C3H8 addition to methane was undertaken. Augmented flame propagation of CH4/H2 and CH4/C3H8 was demonstrated to be principally an Arrhenius effect, predominantly through reduction of associated activation energy. Finally, plausible short-term variations in composition with hydrogen-enriched multi-component natural gas flames were investigated experimentally and numerically. At the leanest conditions, small variations in CH4:C3H8 content at a fixed H2 fraction resulted in discernible changes in stretch related behaviour, a reflection of the thermo-diffusive behaviour of each fuel's response.
The aim of this study was to assess the impact of adding assistants in nursing to acute care hospital ward nurse staffing on adverse patient outcomes using administrative health data.
Logistic ...regression modelling was used with linked administrative health data to examine the association between seven adverse patient outcomes and use of assistants in nursing utilising a pre-test/post-test design. Outcomes included were in-hospital 30-day mortality, failure to rescue, urinary tract infection, pressure injury, pneumonia, sepsis and falls with injury.
Eleven acute care metropolitan hospitals in Western Australia.
Patients were retained in the dataset if they spent any time on a medical, surgical or rehabilitation ward during their admission and excluded if they only spent time on other ward types, as the outcomes used in this study are only validated for these patient populations. There were 256,302 patient records in the total sample with 125,762 in the pre-test period (2006–2007) and 130,540 in the post-test period (2009–2010).
The results showed three significant increases in observed to expected adverse outcomes on the assistant in nursing wards (failure to rescue, urinary tract infection, falls with injury), with one significant decrease (mortality). On the non-assistant in nursing wards there was one significant decrease (pneumonia) in the observed to expected adverse outcomes and one significant increase (falls with injury). Post-test analysis showed that spending time on assistant in nursing wards was a significant predictor for urinary tract infection and pneumonia. For every 10% of extra time patients spent on assistant in nursing wards they had a 1% increase in the odds of developing a urinary tract infection and a 2% increase in the odds of developing pneumonia.
The results suggest that the introduction of assistants in nursing into ward staffing in an additive role should be done under a protocol which clearly defines their role, scope of practice, and working relationship with registered nurses, and the impact on patient care should be monitored.
Despite intensive study, many aspects of the evolutionary history of great apes and humans (Hominidae) are not well understood. In particular, the phylogenetic relationships of many fossil taxa ...remain poorly resolved. This study aims to provide an updated hypothesis of phylogenetic relationships for Middle-Late Miocene fossil apes, focusing on those taxa typically considered to be great apes. The character matrix compiled here samples 274 characters from the skull, dentition, and postcranium. Multiple iterations were performed to examine the effects of ingroup taxon selection, outgroup constraints, treatment of continuous data, character partitions (craniodental, postcranial), and missing data. Parsimony and Bayesian methods were used to infer phylogenetic relationships. Most European hominoids (Hispanopithecus, Rudapithecus, Dryopithecus, Pierolapithecus) are recovered as stem hominids, not more closely related to orangutans or to African apes and humans (Homininae), whereas Ouranopithecus, Graecopithecus, and Nakalipithecus are inferred to be members of the hominine clade. Asian fossil hominoids, with the exception of Lufengpithecus hudienensis, are recovered as part of the orangutan clade (Ponginae). Results suggest that Kenyapithecus and Griphopithecus are possible stem hominids, whereas Equatorius and Nacholapithecus are consistently recovered as stem hominoids. Oreopithecus and Samburupithecus are not recovered as hominids. Results of Bayesian analyses differ from those of parsimony analyses. Craniodental and postcranial character partitions are incongruent in the placement of hylobatids, which is interpreted as evidence that hylobatids and hominids independently evolved adaptations to suspensory positional behaviors. An understanding of phylogenetic relationships is necessary to address many of the questions asked in paleoanthropology. Thus, the updated hypothesis of phylogenetic relationships presented here can be used to gain a better understanding of important morphological transitions that took place during hominid evolution, ancestral morphotypes at key nodes, and the biogeography of the clade.
Aging is the most significant risk factor for a range of diseases, including many cancers, neurodegeneration, cardiovascular disease, and diabetes. Caloric restriction (CR) without malnutrition ...delays aging in diverse species, and therefore offers unique insights into age-related disease vulnerability. Previous studies suggest that there are shared mechanisms of disease resistance associated with delayed aging, however quantitative support is lacking. We therefore sought to identify a common response to CR in diverse tissues and species and determine whether this signature would reflect health status independent of aging. We analyzed gene expression datasets from eight tissues of mice subjected to CR and identified a common transcriptional signature that includes functional categories of mitochondrial energy metabolism, inflammation and ribosomal structure. This signature is detected in flies, rats, and rhesus monkeys on CR, indicating aspects of CR that are evolutionarily conserved. Detection of the signature in mouse genetic models of slowed aging indicates that it is not unique to CR but rather a common aspect of extended longevity. Mice lacking the NAD-dependent deacetylase SIRT3 fail to induce mitochondrial and anti-inflammatory elements of the signature in response to CR, suggesting a potential mechanism involving SIRT3. The inverse of this transcriptional signature is detected with consumption of a high fat diet, obesity and metabolic disease, and is reversed in response to interventions that decrease disease risk. We propose that this evolutionarily conserved, tissue-independent, transcriptional signature of delayed aging and reduced disease vulnerability is a promising target for developing therapies for age-related diseases.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this work, multiwall carbon nanotubes (MWCNTs) have been used as a network of sensors to predict the failure region and to monitor the degradation of mechanical properties in laminated composites ...subjected to tensile and cyclic fatigue loadings. This is achieved by measuring the electrical resistance change in the semi-conductive MWCNT-fiber glass–epoxy polymer matrix composites. By partitioning the tensile and fatigue samples with electrically conductive probes, it is shown that with both increasing tensile load and number of cycles different resistance changes are detected in different regions and failure happens in the part in which higher resistance change was detected. In cyclic loading, when compared to strain gauge readings, resistance change measurements show more sensitivity in identifying the crack location, which gives this technique a good potential for monitoring damage during fatigue.
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