A three-dimensional particle tracking model for colloid transport in porous media was developed that predicts colloid retention in porous media in the presence of an energy barrier via two ...mechanisms: (1) wedging of colloids within grain to grain contacts; (2) retention of colloids (without attachment) in flow stagnation zones. The model integrates forces experienced by colloids during transport in porous media, i.e., fluid drag, gravity, diffusion, and colloid−surface Derjaguin−Landau−Verwey−Overbeek interac tions. The model was implemented for a fluid flow field that explicitly represented grain to grain contacts. The model utilized a variable time stepping routine to allow finer time steps in zones of rapid change in fluid velocity and colloid−surface interaction forces. Wedging was favored by colloid:collector ratios greater than about 0.005, with this threshold ratio increasing with decreasing fluid velocity. Retention in flow stagnation zones was demonstrated for colloid:collector ratios less than about 0.005, with this threshold decreasing with increasing fluid velocity. Both wedging and retention in flow stagnation zones were sensitive to colloid−surface interaction forces (energy barrier height and secondary energy minimum depth). The model provides a mechanistic basis for colloid retention in the presence of an energy barrier via processes that were recently hypothesized to explain experimental observations.
At a time of growing concern over the rising costs and long-term environmental impacts of the use of fossil fuels and nuclear energy, wind energy has become an increasingly important sector of the ...electrical power industry, largely because it has been promoted as being emission-free and is supported by government subsidies and tax credits. However, large numbers of bats are killed at utility-scale wind energy facilities, especially along forested ridgetops in the eastern United States. These fatalities raise important concerns about cumulative impacts of proposed wind energy development on bat populations. This paper summarizes evidence of bat fatalities at wind energy facilities in the US, makes projections of cumulative fatalities of bats in the Mid-Atlantic Highlands, identifies research needs, and proposes hypotheses to better inform researchers, developers, decision makers, and other stakeholders, and to help minimize adverse effects of wind energy development.
Nutrition and its role in human evolution James, W. P. T.; Johnson, R. J.; Speakman, J. R. ...
Journal of internal medicine,
20/May , Letnik:
285, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Our understanding of human evolution has improved rapidly over recent decades, facilitated by large‐scale cataloguing of genomic variability amongst both modern and archaic humans. It seems clear ...that the evolution of the ancestors of chimpanzees and hominins separated 7–9 million years ago with some migration out of Africa by the earlier hominins; Homo sapiens slowly emerged as climate change resulted in drier, less forested African conditions. The African populations expanded and evolved in many different conditions with slow mutation and selection rates in the human genome, but with much more rapid mutation occurring in mitochondrial DNA. We now have evidence stretching back 300 000 years of humans in their current form, but there are clearly four very different large African language groups that correlate with population DNA differences. Then, about 50 000–100 000 years ago a small subset of modern humans also migrated out of Africa resulting in a persistent signature of more limited genetic diversity amongst non‐African populations. Hybridization with archaic hominins occurred around this time such that all non‐African modern humans possess some Neanderthal ancestry and Melanesian populations additionally possess some Denisovan ancestry. Human populations both within and outside Africa also adapted to diverse aspects of their local environment including altitude, climate, UV exposure, diet and pathogens, in some cases leaving clear signatures of patterns of genetic variation. Notable examples include haemoglobin changes conferring resistance to malaria, other immune changes and the skin adaptations favouring the synthesis of vitamin D. As humans migrated across Eurasia, further major mitochondrial changes occurred with some interbreeding with ancient hominins and the development of alcohol intolerance. More recently, an ability to retain lactase persistence into adulthood has evolved rapidly under the environmental stimulus of pastoralism with the ability to husband lactating ruminants. Increased amylase copy numbers seem to relate to the availability of starchy foods, whereas the capacity to desaturase and elongate monounsaturated fatty acids in different societies seems to be influenced by whether there is a lack of supply of readily available dietary sources of long‐chain polyunsaturated fatty acids. The process of human evolution includes genetic drift and adaptation to local environments, in part through changes in mitochondrial and nuclear DNA. These genetic changes may underlie susceptibilities to some modern human pathologies including folate‐responsive neural tube defects, diabetes, other age‐related pathologies and mental health disorders.
This study investigates the impact of initial injection conditions on colloid transport and retention in porous media. Employing both uniform and flux‐weighted distributions for the initial colloid ...locations, the research explores diverse flow scenarios, ranging from simple Poiseuille flow to more complex geometries. The results underscore the pivotal role the injection mode plays on the shape of colloid retention profiles (RPs), particularly those that display anomalous non‐exponential decay with distance. Broadly, uniform injection yields multi‐exponential profiles, while flux‐weighted injection can lead to nonmonotonic profiles in certain conditions. The study identifies preferential flow paths as a key factor in producing nonmonotonic RPs. Notably, variations in fluid velocity, colloid size, and ionic strength affect attachment rates near the inlet but do not significantly alter the qualitative transition between multi‐exponential and nonmonotonic profiles. The study emphasizes that the chosen injection mode dictates retention profile shapes, highlighting its crucial role in porous media colloid transport. These insights provide a possible partial explanation of previously observed anomalous transport behaviors, urging consideration of injection conditions in interpretations of experiments, where they can be difficult to accurately control and measure with high precision.
Key Points
The study finds that initial injection conditions strongly influence colloid transport and retention profiles
Different injection methods lead to varied retention patterns, revealing insights into anomalous transport in porous media
The findings underscore the importance of injection conditions in experimental design to better understand colloid transport behavior
A record fuel hot-spot pressure P_{hs}=56±7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the ...60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ∼60% of the value required for ignition A. Bose et al., Phys. Rev. E 93, 011201(R) (2016), similar to indirect-drive implosions R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015), and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.
•Habitat change is a major driver of species distribution and persistence.•We measured habitat loss over 22years for 5 subpopulations of woodland caribou.•Habitat loss was dramatic, correlating ...strongly with population decline.
Habitat change is a major driver of species distribution and persistence, but there have been few recorded extinction events for terrestrial mammals across Canada. Currently, we are observing the decline, extirpation, and perhaps extinction of several evolutionarily significant units of woodland caribou (Rangifer tarandus caribou), an iconic and cultural keystone species. We used an extensive set of caribou locations (5 subpopulations, 102 animals, 270,808GPS-collar locations) collected over 11years within the Central Mountain Designatable Unit to develop species distribution models that quantified avoidance by caribou of anthropogenic and natural disturbance features. Those empirical relationships allowed us to measure the loss of habitat over a 22-year period and correlate habitat change with measured population decline. The disturbance responses for caribou were complex and varied by season and subpopulation. We modelled a zone of influence for roads (1.75km), seismic and pipelines (2.5km), oil and gas features (4.25km), cutblocks (5.5km), burns (8.0km), and coal mines (3.0km). When the distribution models for each subpopulation were applied to the respective seasonal ranges, we measured a maximum loss in high-quality habitat of 65.9%. The reduction in habitat was strongly correlated with the annual multiplicative growth rate of 5 subpopulations of caribou. At current rates of habitat loss and population decline, these caribou, a significant component of Canada’s biodiversity, are unlikely to persist. Although the factors leading to extinction are complex, the cumulative impacts of industrial development are a correlative if not causative factor.
The aim of this investigation was to determine whether murine models of inflammatory, neuropathic and cancer pain are each characterized by a unique set of neurochemical changes in the spinal cord ...and sensory neurons. All models were generated in C3H/HeJ mice and hyperalgesia and allodynia behaviorally characterized. A variety of neurochemical markers that have been implicated in the generation and maintenance of chronic pain were then examined in spinal cord and primary afferent neurons.
Three days after injection of complete Freund’s adjuvant into the hindpaw (a model of persistent inflammatory pain) increases in substance P, calcitonin gene-related peptide, protein kinase Cγ, and substance P receptor were observed in the spinal cord. Following sciatic nerve transection or L5 spinal nerve ligation (a model of persistent neuropathic pain) significant decreases in substance P and calcitonin gene-related peptide and increases in galanin and neuropeptide Y were observed in both primary afferent neurons and the spinal cord. In contrast, in a model of cancer pain induced by injection of osteolytic sarcoma cells into the femur, there were no detectable changes in any of these markers in either primary afferent neurons or the spinal cord. However, in this cancer-pain model, changes including massive astrocyte hypertrophy without neuronal loss, increase in the neuronal expression of c-Fos, and increase in the number of dynorphin-immunoreactive neurons were observed in the spinal cord, ipsilateral to the limb with cancer.
These results indicate that a unique set of neurochemical changes occur with inflammatory, neuropathic and cancer pain in C3H/HeJ mice and further suggest that cancer induces a unique persistent pain state. Determining whether these neurochemical changes are involved in the generation and maintenance of each type of persistent pain may provide insight into the mechanisms that underlie each of these pain states.
Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in ...response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community responses to temperature, factors that can influence the apparent temperature sensitivity of breakdown and the relative proportion of C lost to the atmosphere vs. stored or transported downstream. Here, we synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity, as measured by the activation energy (Ea, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which Ea could be calculated. Higher values of Ea were correlated with lower‐quality litter, but these correlations were influenced by a single, N‐fixing genus (Alnus). Ea values converged when genera were classified into three breakdown rate categories, potentially due to continual water availability in streams and rivers modulating the influence of leaf chemistry on breakdown. Across all data representing 85 plant genera, the Ea was 0.34 ± 0.04 eV, or approximately half the value (0.65 eV) predicted by metabolic theory. Our results indicate that average breakdown rates may increase by 5–21% with a 1–4 °C rise in water temperature, rather than a 10–45% increase expected, according to metabolic theory. Differential warming of tropical and temperate biomes could result in a similar proportional increase in breakdown rates, despite variation in Ea values for these regions (0.75 ± 0.13 eV and 0.27 ± 0.05 eV, respectively). The relative proportions of gaseous C loss and organic matter transport downstream should not change with rising temperature given that Ea values for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale.
Warmer water enhances decomposition of organic matter in streams and rivers, but it is unclear if climate change will result in more carbon emitted to the atmosphere or transported to the ocean. We assembled over 1000 published data points on leaf litter breakdown in streams and rivers globally to assess how rates of breakdown will change with elevated temperature. Across 85 plant genera, we found that rates may increase only half as much as expected should water temperature rise by 1–4 °C. Among 12 plant genera for which temperature sensitivity could be calculated individually, higher sensitivity was correlated with lower quality litter. Similarity in the temperature sensitivity of breakdown mediated by microbes alone or microbes plus detritivores suggests the relative proportions of carbon converted to gas or transported as smaller particles will not change with elevated temperature.
The demand for spatial climate data in digital form has risen dramatically in recent years. In response to this need, a variety of statistical techniques have been used to facilitate the production ...of GIS-compatible climate maps. However, observational data are often too sparse and unrepresentative to directly support the creation of high-quality climate maps and data sets that truly represent the current state of knowledge. An effective approach is to use the wealth of expert knowledge on the spatial patterns of climate and their relationships with geographic features, termed 'geospatial climatology', to help enhance, control, and parameterize a statistical technique. Described here is a dynamic knowledge-based framework that allows for the effective accumulation, application, and refinement of climatic knowledge, as expressed in a statistical regression model known as PRISM (parameter-elevation regressions on independent slopes model). The ultimate goal is to develop an expert system capable of reproducing the process a knowledgeable climatologist would use to create high-quality climate maps, with the added benefits of consistency and repeatability. However, knowledge must first be accumulated and evaluated through an ongoing process of model application; development of knowledge prototypes, parameters and parameter settings; testing; evaluation; and modification. This paper describes the current state of a knowledge-based framework for climate mapping and presents specific algorithms from PRISM to demonstrate how this framework is applied and refined to accommodate difficult climate mapping situations. A weighted climate-elevation regression function acknowledges the dominant influence of elevation on climate. Climate stations are assigned weights that account for other climatically important factors besides elevation. Aspect and topographic exposure, which affect climate at a variety of scales, from hill slope to windward and leeward sides of mountain ranges, are simulated by dividing the terrain into topographic facets. A coastal proximity measure is used to account for sharp climatic gradients near coastlines. A 2-layer model structure divides the atmosphere into a lower boundary layer and an upper free atmosphere layer, allowing the simulation of temperature inversions, as well as mid-slope precipitation maxima. The effectiveness of various terrain configurations at producing orographic precipitation enhancement is also estimated. Climate mapping examples are presented.
Stroke is a leading cause of death and disability worldwide. Imaging plays a critical role in evaluating patients suspected of acute stroke and transient ischemic attack, especially before initiating ...treatment. Over the past few decades, major advances have occurred in stroke imaging and treatment, including Food and Drug Administration approval of recanalization therapies for the treatment of acute ischemic stroke. A wide variety of imaging techniques has become available to assess vascular lesions and brain tissue status in acute stroke patients. However, the practical challenge for physicians is to understand the multiple facets of these imaging techniques, including which imaging techniques to implement and how to optimally use them, given available resources at their local institution. Important considerations include constraints of time, cost, access to imaging modalities, preferences of treating physicians, availability of expertise, and availability of endovascular therapy. The choice of which imaging techniques to employ is impacted by both the time urgency for evaluation of patients and the complexity of the literature on acute stroke imaging. Ideally, imaging algorithms should incorporate techniques that provide optimal benefit for improved patient outcomes without delaying treatment.
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