Finitely Generated Nil but Not Nilpotent Evolution Algebra

To use evolution algebras to model population dynamics that both allow extinction and introduction of certain gametes in finite generations, nilpotency must be built into the algebraic structures of these algebras with the entire algebras not to be nilpotent if the populations are assumed to evolve for a long period of time. To adequately address this need, evolution algebras over rings with nilpotent elements must be considered instead of evolution algebras over fields. This paper develops some criteria, which are computational in nature, about the nilpotency of these algebras, and shows how to construct finitely generated evolution algebras which are nil but not nilpotent

Evaluation of reconstructed sea surface temperatures based on U37k′ from sediment surface samples of the North Pacific

The alkenone unsaturation index (Uk'37) as proxy for sea surface temperature (SST) is an important tool in paleoclimatology for reconstructing past ocean temperature variability. Typically, Uk'37 recorded in marine surface sediments shows a linear correlation with modern mean annual SST. However, in high-latitude oceanic regions, such as the subpolar Pacific, Uk'37-based SSTs do overestimate the mean annual temperature by up to 6 °C, potentially leading to obscured paleoclimatic information drawn from stratigraphic Uk'37-records. The reason for this “warm bias” is still not well understood. Here, we present a compilation of 97 sediment surface samples from Multicores collected in the Bering Sea, the Okhotsk Sea and the North Pacific to evaluate the alkenone-temperature proxy against observational data from the North Pacific. Sediment surface samples were analysed for alkenones and the derived Uk'37-indices converted to water temperatures using different calibration equations established in the literature. Uk'37-based SSTs were then compared to instrumental SST data, as well as modern alkenone flux data from sediment traps in the North Pacific. Our results confirm that most Uk'37-based SSTs from the subpolar Pacific are 2–6 °C too warm compared to instrumental mean annual SSTs for calibrations applied. However, with an uncertainty at the level of ±1.5 °C or less reconstructed SSTs fit quite well to modern autumn temperatures north of the Subarctic Front (SAF), when maximum export flux of alkenones to the seafloor is indicated by sediment trap data. South of the SAF, reconstructed SSTs largely mimic the modern mean annual SST signal with an uncertainty of ±1.5 °C or less, which is likely due to the attenuation of seasonality and longer growth season of coccolithophorids according to sediment trap data. Our study further demonstrates that Uk'37, when seasonality in alkenone production and export are known and considered, is able to provide reasonable estimates of SSTs in modern high-latitude ocean settings. We conduct a case study using available alkenone time-series derived from a sediment core collected from the south-western Okhotsk Sea to better understand the potential effect of seasonality in alkenone production on stratigraphic Uk'37-record in the subpolar Pacific. The case study from the Okhotsk Sea indicates that even a small shift in seasonality may lead to strongly biased SSTs with broader regional implications for paleoclimate reconstructions in high-latitude ocean settings

Scalable generation of large-scale unstructured meshes by a novel domain decomposition approach

© 2018 Elsevier Ltd A parallel algorithm is proposed for scalable generation of large-scale tetrahedral meshes. The key innovation is the use of a mesh-simplification based domain decomposition approach. This approach works on a background mesh with both its surface and its interior elements much larger than the final elements desired, and decomposes the domain into subdomains containing no undesirable geometric features in the inter-domain interfaces. In this way, the most time-consuming part of domain decomposition can be efficiently parallelized, and other sequential parts consume reasonably limited computing time since they treat a very coarse background mesh. Meanwhile, the subsequent parallel procedures of mesh generation and improvement are most efficient because they can treat individual subdomains without compromising element quality. Compared with published state-of-the-art parallel algorithms, the developed parallel algorithm can reduce the clock time required by the creation of one billion elements on 512 computer cores from roughly half an hour to less than 4 minutes

Development of Knowledge Integration Model for E-Maintenance

Abstract: In recent years, e-maintenance provides the opportunity for a new maintenance generation. Knowledge is one of core e-maintenance resources. To improve the efficiency of knowledge management and so as to improve the quality of e-maintenance work, a knowledge integration model for e-maintenance was proposed. The proposed model was made up of the relationships among role knowledge, task knowledge and equipment knowledge, to achieve the integration of maintenance business and knowledge resources. This study involved the following tasks: (1) developed the key components of the proposed model, including e-maintenance federation ontology, emaintenance knowledge space and knowledge integration network; (2) designed the construction procedures for the proposed model; (3) presented an example to illustrate the application of the proposed model. Results of this study can improve the level of knowledge management for e-maintenance

Provenance Discrimination of Siliciclastic Sediments in the Western Sea of Japan over the Past 30 kyr: Evidence from Major, Trace Elements, and Pb Isotopes

AbstractThe Sea of Japan (JS), a unique marginal sea without any large river influxes in the western Pacific, provides ample information about the evolution of sea level, East Asian monsoons (EAM), sea ice activity, and ocean currents in geological time. However, insufficient investigation in the western JS limits our knowledge of East Asian climate change. This study utilizes major and trace elements and Pb isotopes of fine siliciclastic components (<63 μm) of core LV53-18-2 and determines the provenances using statistical methods and discrimination diagrams. The results show that the terrigenous debris of LV53-18-2 was mainly composed of aeolian dust from northeast China, ice-rafted debris (IRD), and volcanic materials from the Far East coast over the last 30 kyr. During the late last glacial period, sea ice activity carried weakly weathered IRD to the study area. Meanwhile, the strengthened East Asian winter monsoon (EAWM) brought dust from northeast China to the study site owing to the cold climate and enlarged sandy land. During the late last deglacial period to early Holocene (15-8 kyr), ascending boreal summer insolation drove the intense melting of sea ice. This led to the deposition of large amounts of weakly weathered IRD and remarkably influenced the chemical composition of the core. After 8 kyr, the global sea level rose to -15 m below the modern sea level and opened the Tatar Strait. Consequently, freshwater supplied by the Amur River entered the JS and gave birth to the Liman Cold Current (LCC), which transported more mafic materials from the Kema terrane upstream

The relationship between habitat factors and the nutrient contents of wild Allium victorialis L. in the Changbai Mountains

Allium victorialis L. (Family: Liliaceae) is an herb with nutritional and medicinal properties. In Jilin Province, China, A. victorialis is mainly distributed in the Changbai Mountains and grows in various habitat conditions. However, the relationship between habitat factors and the nutritional quality of A. victorialis in the Changbai Mountains has not yet been examined. We assessed the nutritional quality of five A. victorialis populations growing in five different habitats in the Changbai Mountains and analyzed the relationship between nutritional quality and habitat factors. Allium victorialis populations in this region were primarily found in the undergrowth at elevations above 500 m and within specific ranges of air temperature, air relative humidity, soil temperature, and soil water content. Among the habitat factors investigated, canopy density significantly affected several nutritional components of A. victorialis; however, elevation had a significant effect only on the total flavonoid content, and the vitamin C content was not strongly associated with the main habitat factors in this study. During germplasm selection and artificial cultivation, it is important to simulate the growth conditions of the original habitat. Our results provide useful information for site selection and environmental condition optimization for the artificial cultivation of A. victorialis

Contra-Directional Expression of Serum Homocysteine and Uric Acid as Important Biomarkers of Multiple System Atrophy Severity: A Cross-Sectional Study

Aims. There is evidence suggesting that inflammatory responses play a critical role in the pathogenesis of multiple system atrophy (MSA). Whether inflammatory mediators can be used as reliable biomarkers to detect the severity and progression of MSA remains largely unknown. Methods. We performed a cross-sectional study that included 47 patients with MSA and 50 healthy age-matched controls. Serum levels of homocysteine (Hcy), uric acid (UA) and C-reactive protein (CRP) were measured. These levels positively correlated with the severity of MSA, based on both motor and non-motor symptoms (NMS). Several scales were used to rate the severity of MSA, including the Unified multiple system atrophy rating scale (UMSARS), Parkinson’s disease sleep scale (PDSS), Non-motor Symptoms Scale (NMSS), the Schwab & England Activities of Daily Living Scale (ADL), Webster Scale, modified Hoehn and Yahr staging scale (H&Y), and the Mini-Mental State Examination (MMSE). Receiver Operating Characteristic (ROC) curves was applied to map the diagnostic accuracy of MSA against healthy subjects. Results. Compared with healthy subjects, we found that serum Hcy was higher, UA was lower, and CRP levels were unchanged in MSA patients. These findings were especially prominent in male patients. No significant differences of serum Hcy and UA were observed between patients of MSA and PD. Interestingly, there was a significant correlation between Hcy levels and MSA severity such as movement dysfunction, declined cognition, and cardiovascular symptoms. Additionally, the ROC curve for the combination of Hcy and UA (AUC 0.736) showed potential diagnostic value in discriminating MSA from healthy subjects. Conclusions. Our findings suggest that the inflammatory mediators Hcy and UA may play important roles in the pathogenesis of MSA. The measurement of serum Hcy and UA levels could then be a useful tool to accurately distinguish MSA from healthy subjects

Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

The deep-ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO2 levels on millennial timescales is poorly constrained. An increase in the respired CO2 concentration in the glacial deep-ocean due to biological pump generally corresponds to deoxygenation in the ocean interior. This link thus offers a chance to study oceanic ventilation and coeval export productivity based on redox-controlled sedimentary geochemical parameters. Here, we investigate a suite of geochemical proxies in a sediment core from the Okinawa Trough to understand sedimentary oxygenation variations in the subtropical North Pacific over the last 50 000 years (50 ka). Our results suggest that enhanced mid-depth western subtropical North Pacific (WSTNP) sedimentary oxygenation occurred during cold intervals and after 8.5 ka, while oxygenation decreased during the Bölling-Alleröd (B/A) and Preboreal. The enhanced oxygenation during cold spells is linked to the North Pacific IntermediateWater (NPIW), while interglacial increase after 8.5 ka is linked to an intensification of the Kuroshio Current due to strengthened northeast tradewinds over the tropics. The enhanced formation of the NPIW during Heinrich Stadial 1 (HS1) was likely driven by the perturbation of sea ice formation and sea surface salinity oscillations in the high-latitude North Pacific. The diminished sedimentary oxygenation during the B/A due to a decreased NPIW formation and enhanced export production, indicates an expansion of the oxygen minimum zone in the North Pacific and enhanced CO2 sequestration at mid-depth waters, along with the termination of atmospheric CO2 concentration increase. We attribute the millennial-scale changes to an intensified NPIW and enhanced abyss flushing during deglacial cold and warm intervals, respectively, closely related to variations in North Atlantic Deep Water formation

Climate-Driven Changes in High-Intensity Wildfire on Orbital Timescales in Eurasia since 320 ka

AbstractWildfire is an integral part of the Earth’s climate system and plays an important role in shaping terrestrial ecosystems and biodiversity, atmospheric chemistry, regional climate, and the carbon cycle in the Earth’s history. However, the lack of high-resolution records of long wildfires limits our understanding of the natural variability, long-term trends of wildfire activity, and the reasons behind the changes in wildfire on orbital timescales. Here, a 320 ka long high-resolution wildfire record from the subarctic North Pacific is reconstructed with black carbon (BC), including its two subtypes char and soot. A 7-day-long back trajectory simulation analysis reveals the higher frequency of trajectories comes from Siberia. Our data show that continuous incidence of wildfire on a continental scale over the last 320 ka was higher during glacial periods than during the interglacial periods. The increase in wildfire frequency during glacial periods is ascribed to less precipitation. Contrasting patterns of wildfire incidence between marine isotope stages 2 and 6 may be ascribed to different fuel availability, which is related to contrasting configurations of the Northern Hemisphere ice sheet between glacial periods. A significant periodicity of 23 ka of our wildfire record suggests the precession of the Earth’s orbit pace wildfire development. The tight coupling of intensified wildfire and enhanced nutrient utilization efficiency suggests a nontrivial role of fire in the climate system

Mineralogical study of surface sediments in the western Arctic Ocean and their implications for material sources

Mineralogical analysis was performed on bulk sediments of 79 surface samples using X-ray diffraction. The analytical results, combined with data on ocean currents and the regional geological background, were used to investigate the mineral sources. Mineral assemblages in sediments and their distribution in the study area indicate that the material sources are complex. (1) Feldspar is abundant in the sediments of the middle Chukchi Sea near the Bering Strait, originating from sediments in the Anadyr River carried by the Anadyr Current. Sediments deposited on the western side of the Chukchi Sea are rich in feldspar. Compared with other areas, sediments in this region are rich in hornblende transported from volcanic and sedimentary rocks in Siberia by the Anadyr Stream and the Siberian Coastal Current. Sediments in the eastern Chukchi Sea are rich in quartz sourced from sediments of the Yukon and Kuskokwim rivers carried by the Alaska Coastal Current. Sediments in the northern Chukchi Sea are rich in quartz and carbonates from the Mackenzie River sediments. (2) Sediments of the southern and central Canada Basin contain little calcite and dolomite, mainly due to the small impact of the Beaufort Gyre carrying carbonates from the Canadian Arctic Islands. Compared with other areas, the mica content in the region is high, implying that the Laptev Sea is the main sediment source for the southern and central Canada Basin. In the other deep sea areas, calcite and dolomite levels are high caused by the input of large amounts of sediment carried by the Beaufort Gyre from the Canadian Arctic Islands (Banks and Victoria). The Siberian Laptev Sea also provides small amounts of sediment for this region. Furthermore, the Atlantic mid-water contributes some fi ne-grained material to the entire deep western Arctic Ocean