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MARTINIČ, SANDRA. „ENERGETSKA TEKMA ZA ARKTIKO“. NOVA NEVOJAŠKA TVEGANJA/ NEW NON-MILITARY RISKS, VOLUME 2015/ ISSUE 17/3 (30.09.2015): 45–62. http://dx.doi.org/10.33179//bsv.99.svi.11.cmc.17.3.3.
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Arktika je podvržena podnebnim spremembam, ki odkrivajo njen energetski, politični in gospodarski potencial in jo spreminjajo v novi Orient. Energetski viri, ki se skrivajo pod Arktičnim oceanom, lahko podaljšajo življenjsko dobo držav, ki so odvisne od nafte. Brez razvoja držav in tehnologije, ki bi nadomestila svetovno odvisnost in vedno hitrejšo porabo nafte, ostane edina rešitev iskanje novih virov energije. Arktika ponuja možnost, a brez ustrezne vrtalne tehnologije je dostopnost do virov nemogoča. Številna vprašanja ob tem ostajajo odprta. Ali bodo geopolitični interesi krojili prihodnost Arktike in s tem akterjev? Ali so države zmožne rešiti spore miroljubno? Povečana vojaška prisotnost ne kaže na mirno prihodnost, sploh s povečano napetostjo med Rusijo in ZDA. The Arctic is subjected to climate changes, which are revealing its energy, political and economic potential, and are turning it into the new "Orient". Energy resources hidden beneath the Arctic Ocean can extend the lifespan of the countries dependent on oil. Without further development of countries and the technology to substitute global dependence and the increasingly fast oil consumption, the only solution remaining is the search for new energy resources. The Arctic offers this possibility; however with no adequate drilling technology, the access to resources is impossible. Several questions still remain open in this respect. Will the geopolitical interests shape the future of the Arctic and, consequently, the actors? Are the countries able to resolve conflicts in a peaceful manner? Increased military presence in the Arctic indicates a not so peaceful future, especially due to the increased tensions between Russia and the United States.
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Zawierucha, Krzysztof, Tobias R. Vonnahme, Miloslav Devetter, Małgorzata Kolicka, Marta Ostrowska, Sebastian Chmielewski und Jakub Z. Kosicki. „Area, depth and elevation of cryoconite holes in the Arctic do not influence Tardigrada densities“. Polish Polar Research 37, Nr. 2 (01.06.2016): 325–34. http://dx.doi.org/10.1515/popore-2016-0009.
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Abstract Water bears (Tardigrada) are known as one of the most extremophile animals in the world. They inhabit environments from the deepest parts of the oceans up to the highest mountains. One of the most extreme and still poorly studied habitats which tardigrades inhabit are cryoconite holes. We analysed the relation between area, depth, elevation and tardigrades densities in cryoconite holes on four glaciers on Spitsbergen. The mean (±SD) of cryoconite area was 1287.21±2400.8 cm2, while the depth was on average 10.8±11.2 cm, the elevation 172.6±109.66 m a.s.l., and tardigrade density 24.9±33.0 individuals per gram of wet material (n = 38). The densities of tardigrades on Hans Glacier reached values of up to 168 ind. cm3, 104 ind. g−1 wet weight, and 275 ind. g−1 dry weight. The densities of tardigrades of the three glaciers in Billefjorden were up to 82 ind. cm2, 326 ind. g−1 wet weight and 624 ind. g−1 dry weight. Surprisingly, although the model included area, depth and elevation as independent variables, it cannot explain Tardigrada density in cryoconite holes. We propose that due to the rapid melting of the glacier surface in the Arctic, the constant flushing of cryoconite sediments, and inter-hole water-sediment mixing, the functioning of these ecosystems is disrupted. We conclude that cryoconite holes are dynamic ecosystems for microinvertebrates in the Arctic.
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Gugolek, A., M. O Lorek, Z. Rotkiewicz und T. Rotkiewicz. „Effects of probiotic bacteria on the performance of arctic foxes, pathomorphology and microflora of their alimentary tracts“. Czech Journal of Animal Science 49, No. 6 (12.12.2011): 265–70. http://dx.doi.org/10.17221/4309-cjas.
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Studies on the use of Enterococcus faecium and Lactobacillus acidophilus cultures in arctic fox nutrition were performed on 80 foxes, in the period from weaning to the end of growth and fur development. Diets for the experimental animals were supplemented with 1 g of a probiotic preparation that provided the supply of each bacterial culture in the amount of 1 × 10<sup>9</sup> CFU (colony forming units) per day. The performance of the animals was estimated on the basis of their body weights, conformation and pelt quality. Histopathological examinations of the liver, kidneys and selected segments of the alimentary tract were also conducted. The results show that a mixture of Enterococcus faecium and Lactobacillus acidophilus cultures had beneficial effects on the health of artic foxes. The probiotic changed the composition of the alimentary tract microflora, which had a positive influence on the morphology of the alimentary tract mucosa and allowed to reduce morphological damage to the liver and kidneys. The good condition of foxes resulted in higher body weight gains and better parameters of conformation and pelt quality.
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Huang, Jingyin, Kasia Jankiewicz und Piotr Przytycki. „Cocompactly cubulated 2-dimensional Artin groups“. Commentarii Mathematici Helvetici 91, Nr. 3 (2016): 519–42. http://dx.doi.org/10.4171/cmh/394.
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Collins, L. E., R. Klein und D. Bai. „Development of High Strength Line Pipe for Arctic Applications“. Canadian Metallurgical Quarterly 48, Nr. 3 (September 2009): 261–70. http://dx.doi.org/10.1179/cmq.2009.48.3.261.
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Kirtsideli, Irina Yu, Dmitry Yu Vlasov, Evgeny V. Abakumov, Elena P. Barantsevich, Yuri K. Novozhilov, Viacheslav A. Krylenkov und Vladimir T. Sokolov. „Airborne fungi in arctic settlement Tiksi (Russian Arctic, coast of the Laptev Sea)“. Czech Polar Reports 7, Nr. 2 (01.06.2017): 300–310. http://dx.doi.org/10.5817/cpr2017-2-29.
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Biodiversity and number of airborne fungi isolated from indoor and outdoor air of different location in the areas of arctic settlement Tiksi (Russian Arctic) are described. Different locations (coastal areas, landscape, streets of Tiksi, abandoned empty houses, flats, public buildings) were observed. Aeromycota characterized by a significant biodiversity (50 species), but only several species were abundant. Airborne fungal spores concentration (CFU) in Tiksi locations was found low. The maximum spore concentrations were observed in air of the abandoned empty houses (inhabited in the past). Many species common for soil were observed at the samples taken at streets and abandoned buildings. Most of them are also known as inhabitants of building materials. Microfungi CFU at settlement territory was twice as high as natural territory. Phospholipase, albuminase and hemolytic activities of microfungi isolates as well as their relation to temperature were studied. Most of the tested isolates demonstrated high levels of all the tested activities. It was concluded that there is a risk of ‘‘mold’’ allergy diseases for the people especially with weakening of immunity at arctic settlement Tiksi. Main sources of the air contamination in arctic settlements and houses could be many anthropogenic substrates which were colonized by soil fungi.
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Funakura, Takeo. „On Coefficients of Artin L Functions as Dirichlet Series“. Canadian Mathematical Bulletin 33, Nr. 1 (01.03.1990): 50–54. http://dx.doi.org/10.4153/cmb-1990-008-1.
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AbstractThe paper is motivated by a result of Ankeny [1] above Dirichlet L functions in 1952. We generalize this from Dirichlet L functions to Artin L functions of relative abelian extensions, by complementing the ingenious proof of Ankeny's theorem given by Iwasaki [4]. Moreover, we characterize Dirichlet L functions in the class of all Artin L functions in terms of coefficients as Dirichlet series.
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Li, Dawei, Rong Zhang und Thomas Knutson. „Comparison of Mechanisms for Low-Frequency Variability of Summer Arctic Sea Ice in Three Coupled Models“. Journal of Climate 31, Nr. 3 (22.01.2018): 1205–26. http://dx.doi.org/10.1175/jcli-d-16-0617.1.
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Abstract In this study the mechanisms for low-frequency variability of summer Arctic sea ice are analyzed using long control simulations from three coupled models (GFDL CM2.1, GFDL CM3, and NCAR CESM). Despite different Arctic sea ice mean states, there are many robust features in the response of low-frequency summer Arctic sea ice variability to the three key predictors (Atlantic and Pacific oceanic heat transport into the Arctic and the Arctic dipole) across all three models. In all three models, an enhanced Atlantic (Pacific) heat transport into the Arctic induces summer Arctic sea ice decline and surface warming, especially over the Atlantic (Pacific) sector of the Arctic. A positive phase of the Arctic dipole induces summer Arctic sea ice decline and surface warming on the Pacific side, and opposite changes on the Atlantic side. There is robust Bjerknes compensation at low frequency, so the northward atmospheric heat transport provides a negative feedback to summer Arctic sea ice variations. The influence of the Arctic dipole on summer Arctic sea ice extent is more (less) effective in simulations with less (excessive) climatological summer sea ice in the Atlantic sector. The response of Arctic sea ice thickness to the three key predictors is stronger in models that have thicker climatological Arctic sea ice.
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Ritchie, J. C., K. A. Hadden und K. Gajewski. „Modern pollen spectra from lakes in arctic western Canada“. Canadian Journal of Botany 65, Nr. 8 (01.08.1987): 1605–13. http://dx.doi.org/10.1139/b87-220.
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Fifty-four samples of modern sediment from Banks Island and the Melville–Horton region of the Northwest Territories illustrate the major features of pollen deposition from the high to low arctic. Modern pollen deposition in the high arctic of Banks Island is characterized by up to 14% windblown tree pollen. Indicator taxa of the high and mid arctic include Oxyria (<5–23%), Saxifragaceae, Saxifraga oppositifolia, and Cruciferae (all up to 8%) and Dryas (up to 3%). Arboreal pollen increases to 60% in low-arctic and subarctic samples. Pollen concentration decreases from between 3 500 and 20 000 in the low arctic to less than 5 000 grains/cm3 in the high and mid arctic. Pollen spectra from the Late Glacial of northwestern Canada differ from those of the modern high and mid arctic not only by the absence of trees and shrubs but also in the relative proportions of Artemisia and of such indicator taxa as Oxyria and Saxifragaceae.
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Perlis, Robert. „On the Analytic Determination of the Trace Form“. Canadian Mathematical Bulletin 28, Nr. 4 (01.12.1985): 422–30. http://dx.doi.org/10.4153/cmb-1985-051-2.
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AbstractThe Dedekind zeta function of an algebraic number field E determines the rational equivalence class of the trace form of E. The Hasse symbols of the trace form are related to the local Artin root numbers of the zeta function by formulas of Serre and Deligne. This is used to settle the question of which families of complex numbers appear as the local Artin root numbers of a continuous real representation of the absolute Galois group of ℚ.
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Rush, David E. „Artin Rings with Two-Generated Ideals“. Canadian Mathematical Bulletin 35, Nr. 1 (01.03.1992): 133–35. http://dx.doi.org/10.4153/cmb-1992-019-3.
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AbstractIt is shown that each commutative Artin local ring having each of its ideals generated by two elements is the homomorphic image of a one-dimensional local complete intersection ring which also has each of its ideals generated by two elements. It is indicated how this can be applied to show that the property that each ideal is projective over its endomorphism ring does not pass to homomorphic images, and in determining the commutative group rings with the two-generator property.
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Wong, Peng-Jie. „On critical values of twisted Artin $L$-functions“. Czechoslovak Mathematical Journal 67, Nr. 2 (28.03.2017): 551–55. http://dx.doi.org/10.21136/cmj.2017.0134-16.
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Fichou, Goulwen, Ronan Quarez und Masahiro Shiota. „Artin Approximation Compatible with a Change of Variables“. Canadian Mathematical Bulletin 59, Nr. 4 (01.12.2016): 760–68. http://dx.doi.org/10.4153/cmb-2016-034-1.
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AbstractWe propose a version of the classical Artin approximation that allows us to perturb the variables of the approximated solution. Namely, it is possible to approximate a formal solution of a Nash equation by a Nash solution in a compatible way with a given Nash change of variables. This result is closely related to the so-called nested Artin approximation and becomes false in the analytic setting. We provide local and global versions of this approximation in real and complex geometry together with an application to the Right-Left equivalence of Nash maps.
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Najdet Nasret Coran, Ali, Prof Dr Hayri Sever und Dr Murad Ahmed Mohammed Amin. „Acoustic data classification using random forest algorithm and feed forward neural network“. International Journal of Engineering & Technology 9, Nr. 2 (01.07.2020): 582. http://dx.doi.org/10.14419/ijet.v9i2.30815.
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Speaker identification systems are designed to recognize the speaker or set of speakers according to their acoustic analysis. Many approach-es are made to perform the acoustic analysis in the speech signal, the general description of those systems is time and frequency domain analysis. In this paper, acoustic information is extracted from the speech signals using MFCC and Fundamental Frequency methods combi-nation. The results are classified using two different algorithms such as Random-forest and Feed Forward Neural Network. The FFNN classifier integration with the acoustic model resulted a recognition accuracy of 91.4 %. The CMU ARCTIC Database is referred in this work.
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Tyson, W. R., R. Bouchard, L. Malik, M. Tomin und J. McCallum. „Steel Selection for Arctic Ships: Effects of Elevated Loading Rate on Toughness“. Canadian Metallurgical Quarterly 32, Nr. 3 (Juli 1993): 261–65. http://dx.doi.org/10.1179/cmq.1993.32.3.261.
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de Bernardis, P., und S. Masi. „Precision CMB measurements with long-duration stratospheric balloons: activities in the Arctic“. Proceedings of the International Astronomical Union 8, S288 (August 2012): 208–13. http://dx.doi.org/10.1017/s1743921312016894.
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AbstractWe report on the activities preparing long duration stratospheric flights, suitable for CMB (Cosmic Microwave Background) measurements, in the Arctic region. We focus on pathfinder flights, and on two forthcoming experiments to be flown from Longyearbyen (Svalbard islands): the OLIMPO Sunyaev-Zeldovich spectrometer, and the Large-Scale Polarization Explorer (LSPE).
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Wang, Chao, und Xiaoyan Yang. „(Strongly) Gorenstein injective modules over upper triangular matrix Artin algebras“. Czechoslovak Mathematical Journal 67, Nr. 4 (01.03.2017): 1031–48. http://dx.doi.org/10.21136/cmj.2017.0346-16.
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Ariya, P. A., F. Domine, G. Kos, M. Amyot, V. Côté, H. Vali, T. Lauzier et al. „Snow - a photobiochemical exchange platform for volatile and semi-volatile organic compounds with the atmosphere“. Environmental Chemistry 8, Nr. 1 (2011): 62. http://dx.doi.org/10.1071/en10056.
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Environmental context Recent research has been directed towards the exchange of microorganisms and chemical compounds between snow and air. We investigate how microorganisms and chemical species in snow from the Arctic and temperate regions are transferred to the atmosphere and altered by the sun's energy. Results suggest that snow photo-biochemical reactions, in addition to physical‐chemical reactions, should be considered in describing organic matter in air–snow exchanges, and in investigations of climate change. AbstractField and laboratory studies of organic compounds in snow (12 species; concentrations ≤17 µg L–1) were conducted and microorganisms in snow and aerosols at urban and Arctic sites were investigated (snow: total bacteria count ≤40000 colony forming units per millilitre (CFU mL–1), fungi ≤400 CFU mL–1; air: bacteria ≤2.2 × 107 CFU m–3, fungi ≤84 CFU m–3). Bio-organic material is transferred between snow and air and influence on snow-air exchange processes is demonstrated. Volatile organic compounds in snow are released into the air upon melting. In vitro photochemistry indicated an increase of ≤60 µg L–1 for 1,3- and 1,4-dimethylbenzenes. Bacillus cereus was identified and observed in snow and air with ice-nucleating being P. syringae absent. As a result snow photobiochemical reactions should be considered in describing organic matter air–snow exchanges, and the investigation of climate change.
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Volodin, Evgenii M. „The nature of 60-year oscillations of the Arctic climate according to the data of the INM RAS climate model“. Russian Journal of Numerical Analysis and Mathematical Modelling 33, Nr. 6 (19.12.2018): 359–66. http://dx.doi.org/10.1515/rnam-2018-0031.
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Abstract Using the data of pre-industrial experiment with the INM-CM5 climate model for the period of 1200 years, we study the mechanism of natural oscillations of Arctic climate with the period of about 60 years. It is shown that for a quarter of the period prior to the Arctic warming there is a flow of Atlantic water into the Arctic ocean (AO) being more intense than usual, the salinity and density are less than usual near the coast and shelf border. As the result of advection of Atlantic water after Arctic warming, the water near the coast and shelf border becomes more salty and heavy, which leads to a weakening of the flow of Atlantic water and the change of oscillation phase. The conclusions are confirmed by calculations of the generation of anomalies of temperature, salinity, and velocity of currents by different terms, as well as estimation of the contribution of various components to the change of oscillation phase.
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Okon, James S., und J. Paul Vicknair. „A Gorenstein Ring with Larger Dilworth Number than Sperner Number“. Canadian Mathematical Bulletin 43, Nr. 1 (01.03.2000): 100–104. http://dx.doi.org/10.4153/cmb-2000-015-2.
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AbstractA counterexample is given to a conjecture of Ikeda by finding a class of Gorenstein rings of embedding dimension 3 with larger Dilworth number than Sperner number. The Dilworth number of is computed when A is an unramified principal Artin local ring.
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Nesteruk, V. I. „On the Kolyvagin's formula, the Tate pairing associated to an isogeny, the local Artin map and the Hilberts symbol“. Carpathian Mathematical Publications 5, Nr. 1 (20.06.2013): 94–101. http://dx.doi.org/10.15330/cmp.5.1.94-101.
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A proof of nondegeneracy of the Tate pairing and Kolyvagin's formula for elliptic curves with good reductions over an $n$-dimensional $(n\leq 3)$ pseudolocal field, the Tate pairing associated to an isogeny between abelian varieties over pseudolocal field and an $n$-dimensional $(n\leq 3)$ pseudolocal field, and the relations of local Artin map and of the Hilbert symbol for an $n$-dimensional $(n\leq 3)$ general local field is given.
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Brigham, R. J., M. McLean, V. S. Donepudi, S. Santyr, L. Malik und A. Garner. „Evaluation of Weld-Zone Corrosion of Shipbuilding Steel Plates for Use in the Arctic Environment“. Canadian Metallurgical Quarterly 27, Nr. 4 (Oktober 1988): 311–21. http://dx.doi.org/10.1179/cmq.1988.27.4.311.
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Krylov, Artem A., Ivan V. Egorov, Sergey A. Kovachev, Dmitry A. Ilinskiy, Oleg Yu Ganzha, Georgy K. Timashkevich, Konstantin A. Roginskiy et al. „Ocean-Bottom Seismographs Based on Broadband MET Sensors: Architecture and Deployment Case Study in the Arctic“. Sensors 21, Nr. 12 (09.06.2021): 3979. http://dx.doi.org/10.3390/s21123979.
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The Arctic seas are now of particular interest due to their prospects in terms of hydrocarbon extraction, development of marine transport routes, etc. Thus, various geohazards, including those related to seismicity, require detailed studies, especially by instrumental methods. This paper is devoted to the ocean-bottom seismographs (OBS) based on broadband molecular–electronic transfer (MET) sensors and a deployment case study in the Laptev Sea. The purpose of the study is to introduce the architecture of several modifications of OBS and to demonstrate their applicability in solving different tasks in the framework of seismic hazard assessment for the Arctic seas. To do this, we used the first results of several pilot deployments of the OBS developed by Shirshov Institute of Oceanology of the Russian Academy of Sciences (IO RAS) and IP Ilyinskiy A.D. in the Laptev Sea that took place in 2018–2020. We highlighted various seismological applications of OBS based on broadband MET sensors CME-4311 (60 s) and CME-4111 (120 s), including the analysis of ambient seismic noise, registering the signals of large remote earthquakes and weak local microearthquakes, and the instrumental approach of the site response assessment. The main characteristics of the broadband MET sensors and OBS architectures turned out to be suitable for obtaining high-quality OBS records under the Arctic conditions to solve seismological problems. In addition, the obtained case study results showed the prospects in a broader context, such as the possible influence of the seismotectonic factor on the bottom-up thawing of subsea permafrost and massive methane release, probably from decaying hydrates and deep geological sources. The described OBS will be actively used in further Arctic expeditions.
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Stasiak, K., B. Janicki und J. Glogowski. „Determination of sperm acrosin activity in the arctic fox (Alopex lagopus L.) – using method developed for human spermatozoa“. Polish Journal of Veterinary Sciences 15, Nr. 4 (01.12.2012): 799–800. http://dx.doi.org/10.2478/v10181-012-0121-4.
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Abstract The aim of the study was to adapt a method to determine acrosin activity of human spermatozoa to arctic fox (Alopex lagopus L.) spermatozoa. We modified this method by reducing sperm count per sample from 1÷10 × 106 to 25÷200 × 103, incubation time from 180 minutes to 60 minutes, and Triton X-100 concentration in the reaction mixture from 0.01% to 0.005% per 100 cm3. It has also confirmed that arctic fox seminal plasma is rich in proteinases and their inhibitors. To completely abolish the inhibitory effect of seminal plasma on acrosin activity it is recommended to wash the spermatozoa four times. Benzamidine served an inhibitor of acrosin activity.
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Stasiak, K., und B. Janicki. „Effect of age and breeding season on sperm acrosin activity in the arctic fox (Alopex lagopus L.)“. Polish Journal of Veterinary Sciences 17, Nr. 1 (01.03.2014): 177–79. http://dx.doi.org/10.2478/pjvs-2014-0025.
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Abstract The objective of this study was to determine the effect of age and reproductive season on selected properties of semen from the arctic fox, Alopex lagopus L. The experiment used 40 ejaculates collected manually from 6 animals (3 foxes aged one year and 3 foxes older than three years). Statistically less semen (0.39 cm3) was collected from the young compared to the older animals, and the ejaculates obtained were characterized by higher concentration of spermatozoa (195.04 x 106/cm3). In turn, sperm acrosomal extracts from the older animals contained statistically more acrosin (6,4 mU/106 spermatozoa). In the sperm acrosomal extracts prepared during the first semen sampling, the mean acrosin activity did not exceed 2.3 mU/million spermatozoa. At subsequent semen sampling dates, the activity of the analysed enzyme increased to reach 7.72mU/million spermatozoa. In the extracts obtained from the semen collected at the end of the breeding season of arctic foxes, the acrosin activity again reached a value obtained at the beginning of the season.
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Volodin, Evgeny, und Andrey Gritsun. „Simulation of observed climate changes in 1850–2014 with climate model INM-CM5“. Earth System Dynamics 9, Nr. 4 (25.10.2018): 1235–42. http://dx.doi.org/10.5194/esd-9-1235-2018.
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Abstract. Climate changes observed in 1850–2014 are modeled and studied on the basis of seven historical runs with the climate model INM-CM5 under the scenario proposed for the Coupled Model Intercomparison Project Phase 6 (CMIP6). In all runs global mean surface temperature rises by 0.8 K at the end of the experiment (2014) in agreement with the observations. Periods of fast warming in 1920–1940 and 1980–2000 as well as its slowdown in 1950–1975 and 2000–2014 are correctly reproduced by the ensemble mean. The notable change here with respect to the CMIP5 results is the correct reproduction of the slowdown in global warming in 2000–2014 that we attribute to a change in ocean heat uptake and a more accurate description of the total solar irradiance in the CMIP6 protocol. The model is able to reproduce the correct behavior of global mean temperature in 1980–2014 despite incorrect phases of the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation indices in the majority of experiments. The Arctic sea ice loss in recent decades is reasonably close to the observations in just one model run; the model underestimates Arctic sea ice loss by a factor of 2.5. The spatial pattern of the model mean surface temperature trend during the last 30 years looks close to the one for the ERA-Interim reanalysis. The model correctly estimates the magnitude of stratospheric cooling.
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Griffies, Stephen M., Michael Winton, Leo J. Donner, Larry W. Horowitz, Stephanie M. Downes, Riccardo Farneti, Anand Gnanadesikan et al. „The GFDL CM3 Coupled Climate Model: Characteristics of the Ocean and Sea Ice Simulations“. Journal of Climate 24, Nr. 13 (01.07.2011): 3520–44. http://dx.doi.org/10.1175/2011jcli3964.1.
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Abstract This paper documents time mean simulation characteristics from the ocean and sea ice components in a new coupled climate model developed at the NOAA Geophysical Fluid Dynamics Laboratory (GFDL). The GFDL Climate Model version 3 (CM3) is formulated with effectively the same ocean and sea ice components as the earlier CM2.1 yet with extensive developments made to the atmosphere and land model components. Both CM2.1 and CM3 show stable mean climate indices, such as large-scale circulation and sea surface temperatures (SSTs). There are notable improvements in the CM3 climate simulation relative to CM2.1, including a modified SST bias pattern and reduced biases in the Arctic sea ice cover. The authors anticipate SST differences between CM2.1 and CM3 in lower latitudes through analysis of the atmospheric fluxes at the ocean surface in corresponding Atmospheric Model Intercomparison Project (AMIP) simulations. In contrast, SST changes in the high latitudes are dominated by ocean and sea ice effects absent in AMIP simulations. The ocean interior simulation in CM3 is generally warmer than in CM2.1, which adversely impacts the interior biases.
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Corbett, JJ, JJ Winebrake und EH Green. „An assessment of technologies for reducing regional short-lived climate forcers emitted by ships with implications for Arctic shipping“. Carbon Management 1, Nr. 2 (Dezember 2010): 207–25. http://dx.doi.org/10.4155/cmt.10.27.
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Kudo, A., J. Zheng, R. Yamada, G. Tao, T. Sasaki und M. Sugahara. „Global transport rates and future prediction of hazardous materials: Pu and Cs – from Nagasaki to Canadian Arctic“. Water Science and Technology 42, Nr. 7-8 (01.10.2000): 163–69. http://dx.doi.org/10.2166/wst.2000.0565.
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A historical man-made global pollution of hazardous materials occurred at Nagasaki, Japan on August 9, 1945 detonation of a plutonium (10–15 kg) atomic bomb. Recent advancements in analytical technology made it possible for artificial radionuclides released from the nuclear explosion to be detected in the Arctic ice core layer of 1945. The fission product, 137Cs (23.4 g or 7.44×1013 Bq), and unexpended fission material, 239+240Pu (8.8–13.8 kg or 2.22–3.49×1013 Bq), originating from the Nagasaki A-bomb were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada. The deposition rates were 20 mBq/cm2 for 137Cs and 0.16 mBq/cm2 for 239+240Pu, originating from Nagasaki. Assuming the radionuclides, excluding the amount deposited as local fallout, are deposited evenly throughout the northern hemisphere, a rate of 67% of the expected amount of 137Cs arrived at the Arctic while 1.1% of 239+240Pu reached the Arctic. The results suggest that different transport mechanisms exist for these two hazardous contaminants in the global transport system. A non-reactive rare gas, such as neon and argon, can spread evenly throughout northern hemisphere, including Ellesmere island at the Canadian Arctic, while a reactive gas, sulfur dioxide (SO2) will not reach the ice cap. The measured global transport rates of 137Cs and 239+240Pu were 67% and 1.1%, respectively. These measured rates were for the historical man-made hazardous materials and probably obtained for the longest distance of global transport over 10,000 km. Assuming there was a consistency in climate for the next 10,000 years, the chronological anthropogenic deposits, mainly of 239+240Pu, could be detected in the ice layer between 97–98 m from the snow surface at 11,999 AD on the Agassiz ice cap. Even if there were no improvements in the radioactive analytical method used, the ice layers for the 1945–1980 period could still be easily identified with the present analytical technology. Hopefully this study will find a way to use our generation's artefacts for the benefit of our future descendants.
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Ram Murty, M., und S. Srinivasan. „Some Remarks on Artin's Conjecture“. Canadian Mathematical Bulletin 30, Nr. 1 (01.03.1987): 80–85. http://dx.doi.org/10.4153/cmb-1987-012-5.
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AbstractIt is a classical conjecture of E. Artin that any integer a > 1 which is not a perfect square generates the co-prime residue classes (mod ρ) for infinitely many primes ρ. Let E be the set of a > 1, a not a perfect square, for which Artin's conjecture is false. Set E(x) = card(e ∊ E: e ≤ x). We prove that E(x) = 0(log6 x) and that the number of prime numbers in E is at most 6.
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Mortazavi, R., S. Attiya und P. A. Ariya. „A next generation sequencing of Arctic bacteria in snow and frost flowers: identification, abundance and freezing nucleation“. Atmospheric Chemistry and Physics Discussions 14, Nr. 23 (19.12.2014): 32093–131. http://dx.doi.org/10.5194/acpd-14-32093-2014.
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Abstract. During the spring of 2009, as part of the Ocean–Atmosphere–Sea Ice–Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the conventional culture-based PCR identification approach, we deployed a state-of-the-art genomic Next Generation Sequencing (NGS) technique to examine diverse bacterial communities in Arctic samples. 11–18 known phyla or candidate divisions were identified with the great majority of sequences (12.3–83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes and Cyanobacteria. At the genus level, 101–245 different genera were detected. The highest number of cultivable bacteria in cultured samples was observed in frost flowers (FF) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU mL−1, respectively; and for cultivable fungi 5 ± 1 CFU mL−1 in windpack (WP) and blowing snow (BS). Complementary morphology and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolate ranged from −20.3 ± 1.5 to −15.7 ± 5.6 °C, and for melted samples from 9.5 ± 1.0 to 18.4 ± 0.1 °C. An isolate belonging to the Bacillus species (96% similarity) had ice nucleation activity of −6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed a seemingly diverse community of bacteria exists in the Arctic with many originating from distinct ecological environments, and we discuss the potential impact of microbial snow in the freezing and melting process of the snowpack in the Arctic.
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Mortazavi, R., S. Attiya und P. A. Ariya. „Arctic microbial and next-generation sequencing approach for bacteria in snow and frost flowers: selected identification, abundance and freezing nucleation“. Atmospheric Chemistry and Physics 15, Nr. 11 (05.06.2015): 6183–204. http://dx.doi.org/10.5194/acp-15-6183-2015.
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Abstract. During the spring of 2009, as part of the Ocean–Atmosphere–Sea Ice–Snowpack (OASIS) campaign in Barrow, Alaska, USA, we examined the identity, population diversity, freezing nucleation ability of the microbial communities of five different snow types and frost flowers. In addition to the culturing and gene-sequence-based identification approach, we utilized a state-of-the-art genomic next-generation sequencing (NGS) technique to examine the diversity of bacterial communities in Arctic samples. Known phyla or candidate divisions were detected (11–18) with the majority of sequences (12.3–83.1%) belonging to one of the five major phyla: Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Cyanobacteria. The number of genera detected ranged from, 101–245. The highest number of cultivable bacteria was observed in frost flowers (FFs) and accumulated snow (AS) with 325 ± 35 and 314 ± 142 CFU m L−1, respectively; and for cultivable fungi 5 ± 1 CFU m L−1 in windpack (WP) and blowing snow (BS). Morphology/elemental composition and ice-nucleating abilities of the identified taxa were obtained using high resolution electron microscopy with energy-dispersive X-ray spectroscopy and ice nucleation cold-plate, respectively. Freezing point temperatures for bacterial isolates ranged from −20.3 ± 1.5 to −15.7 ± 5.6 °C, and for melted snow samples from −9.5 ± 1.0 to −18.4 ± 0.1 °C. An isolate belonging to the genus Bacillus (96% similarity) had ice nucleation activity of −6.8 ± 0.2 °C. Comparison with Montreal urban snow, revealed that a seemingly diverse community of bacteria exists in the Arctic with some taxa possibly originating from distinct ecological environments. We discuss the potential impact of snow microorganisms in the freezing and melting process of the snowpack in the Arctic.
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Monfort, Patrick, Serge Demers und Maurice Levasseur. „Bacterial dynamics in first year sea ice and underlying seawater of Saroma-ko Lagoon (Sea of Okhotsk, Japan) and Resolute Passage (High Canadian Arctic): Inhibitory effects of ice algae on bacterial dynamics“. Canadian Journal of Microbiology 46, Nr. 7 (01.07.2000): 623–32. http://dx.doi.org/10.1139/w00-024.
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The seasonal development of bacterial abundance in first year bottom ice and underlying seawater were studied at Saroma-ko Lagoon in Hokkaido, Japan, and at Resolute Passage in the High Canadian Arctic during the algal bloom in spring 1992. The aim of this study was to evaluate whether the high algal concentrations reached during the bloom of ice algae have inhibitory effects on bacterial dynamics. Bacterial abundance (measured as total cell count and colony-forming units CFU) increased with the increase of the algal biomass up to 500 µg Chla·L-1in both locations. Culturable fraction (measured as the percentage of CFU counts versus the total cell counts) was between 7% and 22% at Saroma-ko, and approximately 0.08% at Resolute Passage. When algal biomass exceeded 500 µg of Chla·L-1, both bacterial abundance and culturable fraction decreased significantly. There was a maximum threshold of algal biomass (between 500 and 800 µg of Chla·L-1) after which bacterial dynamics become negatively coupled to the algal biomass. These results suggest that bactericidal and/or bacteriostatic compounds from these extremely high algal concentrations could explain the decrease in bacterial abundance and culturability in bottom ice observed after the ice algae bloom.Key words: bacteria, culturability, algae, inhibitory effects, sea ice, Arctic.
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Powers, Linda, Walther R. Ellis und Christopher R. Lloyd. „Real-time in situ detection and quantification of bacteria in the Arctic environment“. Journal of Innovative Optical Health Sciences 07, Nr. 02 (März 2014): 1350038. http://dx.doi.org/10.1142/s1793545813500387.
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At present, there are no methods that determine the total microbial load on an abiotic substrate in real time. The utility of such a capability ranges from sterilization and medical diagnostics to the search for new microorganisms in the environment and study of their ecological niches. We report the development of a hand-held, fluorescence detection device and demonstrate its applicability to the field detection of Arctic bacteria. This technology is based on the early pioneering work of Britton Chance which elucidated the intrinsic fluorescence of a number of metabolites and protein cofactors in cells, including reduced pyridine nucleotides, cytochromes and flavins. A PDA controls the device (fluorescence excitation and data collection) and processes the multiwavelength signals to yield bacterial cell counts, including estimates of live cells, dead cells and endospores. Unlike existing methods for cell counting, this method requires no sample contact or addition of reagents. The use of this technology is demonstrated with in situ measurements of two sub-glacial microbial communities at sites in Palander and colonized surface rocks in the Bockfjord Volcanic Complex during AMASE 2008 (Arctic Mars Analog Svalbard Expedition). The total bacterial load on the interrogated sample surfaces ranged from < 20 cells/cm2 to > 109 cells/cm2.
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Shafaat, Hannah S., und Adrian Ponce. „Applications of a Rapid Endospore Viability Assay for Monitoring UV Inactivation and Characterizing Arctic Ice Cores“. Applied and Environmental Microbiology 72, Nr. 10 (Oktober 2006): 6808–14. http://dx.doi.org/10.1128/aem.00255-06.
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ABSTRACT We have developed a rapid endospore viability assay (EVA) in which endospore germination serves as an indicator for viability and applied it to (i) monitor UV inactivation of endospores as a function of dose and (ii) determine the proportion of viable endospores in arctic ice cores (Greenland Ice Sheet Project 2 [GISP2] cores; 94 m). EVA is based on the detection of dipicolinic acid (DPA), which is released from endospores during germination. DPA concentrations were determined using the terbium ion (Tb3+)-DPA luminescence assay, and germination was induced by l-alanine addition. The concentrations of germinable endospores were determined by comparison to a standard curve. Parallel EVA and phase-contrast microscopy experiments to determine the percentage of germinable spores yielded comparable results (54.3% ± 3.8% and 48.9% ± 4.5%, respectively), while only 27.8% ± 7.6% of spores produced CFU. EVA was applied to monitor the inactivation of spore suspensions as a function of UV dose, yielding reproducible correlations between EVA and CFU inactivation data. The 90% inactivation doses were 2,773 J/m2, 3,947 J/m2, and 1,322 J/m2 for EVA, phase-contrast microscopy, and CFU reduction, respectively. Finally, EVA was applied to quantify germinable and total endospore concentrations in two GISP2 ice cores. The first ice core contained 295 ± 19 germinable spores/ml and 369 ± 36 total spores/ml (i.e., the percentage of germinable endospores was 79.9% ± 9.3%), and the second core contained 131 ± 4 germinable spores/ml and 162 ± 17 total spores/ml (i.e., the percentage of germinable endospores was 80.9% ± 8.8%), whereas only 2 CFU/ml were detected by culturing.
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Mogo, S., V. E. Cachorro, J. F. Lopez, E. Montilla, B. Torres, E. Rodríguez, Y. Bennouna und A. M. de Frutos. „In situ measurements of aerosols optical properties and number size distributions in a subarctic coastal region of Norway“. Atmospheric Chemistry and Physics Discussions 11, Nr. 12 (13.12.2011): 32921–64. http://dx.doi.org/10.5194/acpd-11-32921-2011.
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Abstract. In situ measurements of aerosol optical properties were made in the summer of 2008 at the ALOMAR station facility (69°16 N, 16°00 E), located at a rural site in the north of the island of Andøya (Vesterålen archipelago), approximately 300 km north of the Arctic Circle. The extended three-month campaign was part of the POLARCAT Project (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) of the International Polar Year (IPY-2007-2008). Its goal was to characterize the aerosols of this sub-Arctic area, which are frequently transported to the Arctic region. The ambient light-scattering coefficient, σs (550 nm), at ALOMAR had a measured hourly mean value of 5.41 Mm−1 (StD = 3.55 Mm−1), and the light-absorption coefficient, σa (550 nm), had a measured hourly mean value of 0.40 Mm−1 (StD = 0.27 Mm−1). The scattering/absorption Ångström exponents, αs,a, are used for a detailed analysis of the variations of the spectral shape of σs,a. Whereas αs demonstrates the presence of two particle sizes corresponding to two types of aerosols, the αa demonstrates only one type of absorbing aerosol particles. Values of αa above 1 were not observed. The single-scattering albedo, ω0, ranged from 0.62 to 0.99 (mean = 0.91, StD = 0.05), and the relationships of this property to the absorption/scattering coefficients and the Ångström exponents are presented. The concentration of the particles was monitored using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer (APS) and an ultrafine condensation particle counter (UCPC). The shape of the median size distribution of the particles in the submicrometer fraction was bimodal, and the submicrometer, micrometer and total concentrations presented hourly mean values of 1277 cm3 (StD = 1563 cm3), 1 cm3 (StD = 1 cm3) and 2463 cm3 (StD = 4251 cm3), respectively. The modal correlations were investigated, and the concentration of particles sized between 30 and 100 nm (Aitken mode) are presented as a function of the concentration of the particles sized between 100 and 390 nm (accumulation mode). The optical and the microphysical parameters are related to each other, and the results are presented. The origins and pathways of air masses were examined by computing the back-trajectories in a trajectory model (HYSPLIT). Six geographical sectors were defined to classify the air masses, and, based on the sector classification, the linkage between the air mass origin and the optical parameters was established. Aerosol size distributions were also evaluated in relation to the air masses. The relationships between the air mass origins and other parameters, especially those related to the single scattering albedo, allow us to describe two characteristic situations: northern and western air masses, which had predominantly marine aerosols, presented lower optical parameter values, indicating predominantly coarser and non-absorbent particles; and eastern and southern air masses, in which continental aerosols were predominant, presented higher values for all optical parameters, indicating the presence of smaller absorbent particles.
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Perng, Jau-Woei, Tung-Li Hsieh und Cheng-Yan Guo. „A Novel Dentary Bone Conduction Device Equipped with Laser Communication in DSP“. Sensors 21, Nr. 12 (20.06.2021): 4229. http://dx.doi.org/10.3390/s21124229.
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In this study, we designed a dentary bone conduction system that transmits and receives audio by laser. The main objective of this research was to propose a complete hardware design method, including a laser audio transmitter and receiver and digital signal processor (DSP) based digital signal processing system. We also present a digital filter algorithm that can run on a DSP in real time. This experiment used the CMU ARCTIC databases’ human-voice reading audio as the standard audio. We used a piezoelectric sensor to measure the vibration signal of the bone conduction transducer (BCT) and separately calculated the signal-to-noise ratio (SNR) of the digitally filtered audio output and the unfiltered audio output using DSP. The SNR of the former was twice that of the latter, and the BCT output quality significantly improved. From the results, we can conclude that the dentary bone conduction system integrated with a DSP digital filter enhances sound quality.
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Langlands, Robert P. „Un nouveau point de repère dans la théorie des formes automorphes“. Canadian Mathematical Bulletin 50, Nr. 2 (01.06.2007): 243–67. http://dx.doi.org/10.4153/cmb-2007-026-4.
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Ceux qui connaissent l’auteur et ses écrits, comme par exemple [L1] et [L2], savent que la notion de fonctorialité et les conjectures rattachées à celle-ci ont été introduites —en suivant ce que Artin avait fait pour un ensemble plus restreint de fonctions— pour aborder le problème de la prolongation analytique générale des fonctions L-automorphes. Ils savent en plus que je suis d’avis que seules les méthodes basées sur la formule des traces pourront aller au fond des problèmes. Il n’en reste pas moins que malgré de récents progrès importants sur le lemme fondamental et la formule des traces nous sommes bien loin de notre but.
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Sands, Jonathan W. „L-functions for Quadratic Characters and Annihilation of Motivic Cohomology Groups“. Canadian Mathematical Bulletin 58, Nr. 3 (01.09.2015): 620–31. http://dx.doi.org/10.4153/cmb-2014-072-3.
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AbstractLet n be a positive even integer, and let F be a totally real number field and L be an abelian Galois extension which is totally real or CM. Fix a finite set S of primes of F containing the infinite primes and all those which ramify in L, and let SL denote the primes of L lying above those in S. Then OSL denotes the ring of SL-integers of L. Suppose that ψ is a quadratic character of the Galois group of L over F. Under the assumption of the motivic Lichtenbaum conjecture, we obtain a nontrivial annihilator of the motivic cohomology group from the lead term of the Taylor series for the S-modified Artin L-function .
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Lee, Ki-Seung. „Voice Conversion Using a Perceptual Criterion“. Applied Sciences 10, Nr. 8 (22.04.2020): 2884. http://dx.doi.org/10.3390/app10082884.
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In voice conversion (VC), it is highly desirable to obtain transformed speech signals that are perceptually close to a target speaker’s voice. To this end, a perceptually meaningful criterion where the human auditory system was taken into consideration in measuring the distances between the converted and the target voices was adopted in the proposed VC scheme. The conversion rules for the features associated with the spectral envelope and the pitch modification factor were jointly constructed so that perceptual distance measurement was minimized. This minimization problem was solved using a deep neural network (DNN) framework where input features and target features were derived from source speech signals and time-aligned version of target speech signals, respectively. The validation tests were carried out for the CMU ARCTIC database to evaluate the effectiveness of the proposed method, especially in terms of perceptual quality. The experimental results showed that the proposed method yielded perceptually preferred results compared with independent conversion using conventional mean-square error (MSE) criterion. The maximum improvement in perceptual evaluation of speech quality (PESQ) was 0.312, compared with the conventional VC method.
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Miller, Kimberley, Chun-Ta Lai, Randy Dahlgren und David Lipson. „Anaerobic Methane Oxidation in High-Arctic Alaskan Peatlands as a Significant Control on Net CH4 Fluxes“. Soil Systems 3, Nr. 1 (09.01.2019): 7. http://dx.doi.org/10.3390/soilsystems3010007.
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Terrestrial consumption of the potent greenhouse gas methane (CH4) is a critical aspect of the future climate, as CH4 concentrations in the atmosphere are projected to play an increasingly important role in global climate forcing. Anaerobic oxidation of methane (AOM) has only recently been considered a relevant control on methane fluxes from terrestrial systems. We performed in vitro anoxic incubations of intact peat from Utqiaġvik (Barrow), Alaska using stable isotope tracers. Our results showed an average potential AOM rate of 15.0 nmol cm3 h−1, surpassing the average rate of gross CH4 production (6.0 nmol cm3 h−1). AOM and CH4 production rates were positively correlated. While CH4 production was insensitive to additions of Fe(III), there was a depth:Fe(III) interaction in the kinetic reaction rate constant for AOM, suggestive of stimulation by Fe(III), particularly in shallow soils (<10 cm). We estimate AOM would consume 25–34% of CH4 produced under ambient conditions. Soil genetic surveys showed phylogenetic links between soil microbes and known anaerobic methanotrophs in ANME groups 2 and 3. These results suggest a prevalent role of AOM to net CH4 fluxes from Arctic peatland ecosystems, and a probable link with Fe(III)-reduction.
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Weigel, R., C. M. Volk, K. Kandler, E. Hösen, G. Günther, B. Vogel, J. U. Grooß, S. Khaykin, G. V. Belyaev und S. Borrmann. „Enhancements of the refractory submicron aerosol fraction in the Arctic polar vortex: feature or exception?“ Atmospheric Chemistry and Physics 14, Nr. 22 (25.11.2014): 12319–42. http://dx.doi.org/10.5194/acp-14-12319-2014.
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Abstract. In situ measurements with a four-channel stratospheric condensation particle counter (CPC) were conducted at up to 20 km altitude on board the aircraft M-55 Geophysica from Kiruna, Sweden, in January through March (EUPLEX 2003, RECONCILE 2010) and in December (ESSenCe 2011). During all campaigns air masses from the upper stratosphere and mesosphere were subsiding inside the Arctic winter vortex, thus initializing a transport of refractory aerosol into the lower stratosphere (Θ < 500 K). The strength and extent of this downward transport varied between the years depending on the dynamical evolution of the vortex. Inside the vortex and at potential temperatures Θ ≥ 450 K around 11 submicron particles per cm3 were generally detected. Up to 8 of these 11 particles per cm3 were found to contain thermo-stable (at 250 °C) residuals with diameters of 10 nm to about 1 μm. Particle mixing ratios (150 mg−1) and fractions of non-volatile particles (75% of totally detected particles) exhibited highest values in air masses having the lowest content of nitrous oxide (70 nmol mol−1 of N2O). This indicates that refractory aerosol originates from the upper stratosphere or the mesosphere. Derived from the mixing ratio of the simultaneously measured long-lived tracer N2O, an empirical index serves to differentiate probed air masses according to their origin: inside the vortex, the vortex edge region, or outside the vortex. Previously observed high fractions of refractory submicron aerosol in the 2003 Arctic vortex were ascribed to unusually strong subsidence during that winter. However, measurements under perturbed vortex conditions in 2010 and during early winter in December 2011 revealed similarly high values. Thus, the abundance of refractory aerosol in the lower stratosphere within the Arctic vortices appears to be a regular feature rather than the exception. During December, the import from aloft into the lower stratosphere appears to be developing; thereafter the abundance of refractory aerosol inside the vortex reaches its highest levels in March. The correlations of refractory aerosol with N2O suggest that, apart from mean subsidence, diabatic dispersion inside the vortex significantly contributes to the transport of particles to the Arctic lower stratosphere. A measurement-based estimate of the total mass of refractory aerosol inside the vortex is provided for each campaign. Based on the derived increase of particle mass in the lower stratospheric vortex (100–67 hPa pressure altitude) by a factor of 4.5 between early and late winter, we estimate the total mass of mesospheric particles deposited over the winter 2009/2010 in the entire Arctic vortex to range between 77 × 103 and 375 × 106 kg. This estimate is compared with the expected atmospheric influx of meteoritic material (110 ± 55 × 103 kg per day). Such estimates at present still hold considerable uncertainties, which are discussed in this article. Nevertheless, the results enable placing constraints on the shape of the so far unknown size distribution of refractory aerosol within the vortex.
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Masson-Delmotte, V., P. Braconnot, G. Hoffmann, J. Jouzel, M. Kageyama, A. Landais, Q. Lejeune et al. „Sensitivity of interglacial Greenland temperature and δ<sup>18</sup>O: ice core data, orbital and increased CO<sub>2</sub> climate simulations“. Climate of the Past 7, Nr. 3 (29.09.2011): 1041–59. http://dx.doi.org/10.5194/cp-7-1041-2011.
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Abstract. The sensitivity of interglacial Greenland temperature to orbital and CO2 forcing is investigated using the NorthGRIP ice core data and coupled ocean-atmosphere IPSL-CM4 model simulations. These simulations were conducted in response to different interglacial orbital configurations, and to increased CO2 concentrations. These different forcings cause very distinct simulated seasonal and latitudinal temperature and water cycle changes, limiting the analogies between the last interglacial and future climate. However, the IPSL-CM4 model shows similar magnitudes of Arctic summer warming and climate feedbacks in response to 2 × CO2 and orbital forcing of the last interglacial period (126 000 years ago). The IPSL-CM4 model produces a remarkably linear relationship between TOA incoming summer solar radiation and simulated changes in summer and annual mean central Greenland temperature. This contrasts with the stable isotope record from the Greenland ice cores, showing a multi-millennial lagged response to summer insolation. During the early part of interglacials, the observed lags may be explained by ice sheet-ocean feedbacks linked with changes in ice sheet elevation and the impact of meltwater on ocean circulation, as investigated with sensitivity studies. A quantitative comparison between ice core data and climate simulations requires stability of the stable isotope – temperature relationship to be explored. Atmospheric simulations including water stable isotopes have been conducted with the LMDZiso model under different boundary conditions. This set of simulations allows calculation of a temporal Greenland isotope-temperature slope (0.3–0.4‰ per °C) during warmer-than-present Arctic climates, in response to increased CO2, increased ocean temperature and orbital forcing. This temporal slope appears half as large as the modern spatial gradient and is consistent with other ice core estimates. It may, however, be model-dependent, as indicated by preliminary comparison with other models. This suggests that further simulations and detailed inter-model comparisons are also likely to be of benefit. Comparisons with Greenland ice core stable isotope data reveals that IPSL-CM4/LMDZiso simulations strongly underestimate the amplitude of the ice core signal during the last interglacial, which could reach +8–10 °C at fixed-elevation. While the model-data mismatch may result from missing positive feedbacks (e.g. vegetation), it could also be explained by a reduced elevation of the central Greenland ice sheet surface by 300–400 m.
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Pokhotelov, D., P. T. Jayachandran, C. N. Mitchell und M. H. Denton. „High-latitude ionospheric response to co-rotating interaction region- and coronal mass ejection-driven geomagnetic storms revealed by GPS tomography and ionosondes“. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 466, Nr. 2123 (05.05.2010): 3391–408. http://dx.doi.org/10.1098/rspa.2010.0080.
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Positive ionospheric anomalies induced in the polar cap region by co-rotating interaction region (CIR)- and coronal mass ejection (CME)-driven geomagnetic storms are analysed using four-dimensional tomographic reconstructions of the ionospheric plasma density based on measurements of the total electron content along ray paths of GPS signals. The results of GPS tomography are compared with ground-based observations of F region plasma density by digital ionosondes located in the Canadian Arctic. It is demonstrated that CIR- and CME-driven storms can produce large-scale polar cap anomalies of similar morphology in the form of the tongue of ionization (TOI) that appears on the poleward edge of the mid-latitude dayside storm-enhanced densities in positive ionospheric storms. The CIR-driven event of 14–16 October 2002 was able to produce ionospheric anomalies (TOI) comparable to those produced by the CME-driven storms of greater Dst magnitude. From the comparison of tomographic reconstructions and ionosonde data with solar wind measurements, it appears that the formation of large-scale polar cap anomalies is controlled by the orientation of the interplanetary magnetic field (IMF) with the TOI forming during the periods of extended southward IMF under conditions of high solar wind velocity.
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Garlitska, L. А., E. S. Chertoprud, D. A. Portnova und A. I. Azovsky. „Benthic Harpacticoida of the Cara sea: species composition and bathymetric distribution“. Океанология 59, Nr. 4 (17.09.2019): 600–611. http://dx.doi.org/10.31857/s0030-1574594600-611.
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Data on benthic harpacticoid copepods from the Voronin Trench (central part of the Kara Sea) are reported for the first time. Harpacticoids accounted for 1–25% of total meiofauna, their abundance varied from 6 to 102 ind/10 cm2 and decreased with depth. Totally, 42 nominal species have been found, 15 species are new for the Kara Sea, and at least eight species are new for science. Several species are first records for the Arctic waters (Cylindronannopus bispinosus, Haloschizopera clotensis, H. bathyalis, Metauntemannia pseudomagniceps, Mesocletdemus duosetosus, M. parabodini, Proameira echinipes, Cletodes tuberculatus). Ameiridae, Argestidae, Pseudotachidiidae, Miraciidae and Ectinosomatidae are the most species-rich families. Joint analysis with data on shallow-water stations (Yenisei Gulf, southern Kara Sea) revealed three assemblages occupying different habitats. The assemblage inhabiting shallow silts (20–62 m in depth) was the poorest one, the shallow sands were more species-rich, while the deepest stations (92–698 m) was the richest one. The latter assemblage had the composition of families typical for the deep-sea areas. The known fauna of the Kara Sea includes 82 harpacticoid species, most of which have been also reported from north Atlantic and/or western Arctic waters.
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Li, Danni, Jeffrey Misialek, Clifford Jack, Michelle Mielke, David Knopman, Rebecca Gottesman, Tom Mosley und Alvaro Alonso. „Plasma Metabolites Associated with Brain MRI Measures of Neurodegeneration in Older Adults in the Atherosclerosis Risk in Communities–Neurocognitive Study (ARIC-NCS)“. International Journal of Molecular Sciences 20, Nr. 7 (09.04.2019): 1744. http://dx.doi.org/10.3390/ijms20071744.
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Background: Plasma metabolites are associated with cognitive and physical function in the elderly. Because cerebral small vessel disease (SVD) and neurodegeneration are common causes of cognitive and physical function decline, the primary objective of this study was to investigate the associations of six plasma metabolites (two plasma phosphatidylcholines [PCs]: PC aa C36:5 and PC aa 36:6 and four sphingomyelins [SMs]: SM C26:0, SM [OH] C22:1, SM [OH] C22:2, SM [OH] C24:1) with magnetic resonance imaging (MRI) features of cerebral SVD and neurodegeneration in older adults. Methods: This study included 238 older adults in the Atherosclerosis Risk in Communities study at the fifth exam. Multiple linear regression was used to assess the association of each metabolite (log-transformed) in separate models with MRI measures except lacunar infarcts, for which binary logistic regression was used. Results: Higher concentrations of plasma PC aa C36:5 had adverse associations with MRI features of cerebral SVD (odds ratio of 1.69 [95% confidence interval: 1.01, 2.83] with lacunar infarct, and beta of 0.16 log [cm3] [0.02, 0.30] with log [White Matter Hyperintensities (WMH) volume]) while higher concentrations of 3 plasma SM (OH)s were associated with higher total brain volume (beta of 12.0 cm3 [5.5, 18.6], 11.8 cm3 [5.0, 18.6], and 7.3 cm3 [1.2, 13.5] for SM [OH] C22:1, SM [OH] C22:2, and SM [OH] C24:1, respectively). Conclusions: This study identified associations between certain plasma metabolites and brain MRI measures of SVD and neurodegeneration in older adults, particularly higher SM (OH) concentrations with higher total brain volume.
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Elliott, Kyle H., Gail K. Davoren und Anthony J. Gaston. „The influence of buoyancy and drag on the dive behaviour of an Arctic seabird, the Thick-billed Murre“. Canadian Journal of Zoology 85, Nr. 3 (Februar 2007): 352–61. http://dx.doi.org/10.1139/z07-012.
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We used time–depth recorders to investigate the behaviour of free-ranging Thick-billed Murres ( Uria lomvia L., 1758) after attaching positively (n = 9), negatively (n = 10), or neutrally (n = 9) buoyant handicaps and increasing cross-sectional area by 3% (2.8 cm2; n = 8) or 6% (5.6 cm2; n = 6). When buoyancy was altered or drag increased, murres reduced dive depth and duration, suggesting that murres do not manipulate dive depth to obtain neutral buoyancy during the bottom phase. Ascent rate increased as the bird surfaced and mean ascent rate increased for deeper dives, presumably reflecting steeper dive angles and greater buoyancy during deep dives. For short dives (<150 s), preceding surface pauses were better correlated with dive depth and duration than succeeding surface pauses (surface pauses were “anticipatory”), suggesting that murres control inhalation rates based on anticipated dive depth and duration. Murres reduced ascent rate near the surface, possibly to reduce the risk of decompression sickness. Neutrally buoyant recorders attached to the legs had no effect on chick feeding frequencies or adult mass loss, suggesting that this attachment method may have the least effect on the foraging behaviour of alcids.
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Wilhelm, Roland C., Thomas D. Niederberger, Charles Greer und Lyle G. Whyte. „Microbial diversity of active layer and permafrost in an acidic wetland from the Canadian High Arctic“. Canadian Journal of Microbiology 57, Nr. 4 (April 2011): 303–15. http://dx.doi.org/10.1139/w11-004.
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The abundance and structure of archaeal and bacterial communities from the active layer and the associated permafrost of a moderately acidic (pH < 5.0) High Arctic wetland (Axel Heiberg Island, Nunavut, Canada) were investigated using culture- and molecular-based methods. Aerobic viable cell counts from the active layer were ∼100-fold greater than those from the permafrost (2.5 × 105 CFU·(g soil dry mass)–1); however, a greater diversity of isolates were cultured from permafrost, as determined by 16S rRNA gene sequencing. Isolates from both layers demonstrated growth characteristics of a psychrotolerant, halotolerant, and acidotolerant community. Archaea constituted 0.1% of the total 16S rRNA gene copy number and, in the 16S rRNA gene clone library, predominantly (71% and 95%) consisted of Crenarchaeota related to Group I. 1b. In contrast, bacterial communities were diverse (Shannon’s diversity index, H = ∼4), with Acidobacteria constituting the largest division of active layer clones (30%) and Actinobacteria most abundant in permafrost (28%). Direct comparisons of 16S rRNA gene sequence data highlighted significant differences between the bacterial communities of each layer, with the greatest differences occurring within Actinobacteria. Comparisons of 16S rRNA gene sequences with those from other Arctic permafrost and cold-temperature wetlands revealed commonly occurring taxa within the phyla Chloroflexi, Acidobacteria, and Actinobacteria (families Intrasporangiaceae and Rubrobacteraceae).
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Stasiak, K., J. Glogowski, W. Demianowicz, R. Kowalski, A. Nowak-Tkaczyk und B. Janicki. „Use of biochemical markers to evaluate the quality of fresh and cryopreserved semen from the arctic fox (Vulpes lagopus)“. Polish Journal of Veterinary Sciences 17, Nr. 3 (01.09.2014): 427–32. http://dx.doi.org/10.2478/pjvs-2014-0061.
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Abstract The aim of this study was to use biochemical markers to evaluate the quality of fresh and cryopreserved semen from the arctic fox (Vulpes lagopus). Twenty-three manually collected ejaculates were analysed for the main indicators of semen quality (sperm concentration and ejaculate volume). Sperm motility and percentage of morphologically normal and abnormal spermatozoa were determined according to the stage of cryopreservation (fresh - measurement A; equilibrated - measurement B; frozen/thawed - measurement C). Furthermore, the seminal plasma and supernatants were analysed after equilibration and freeze/thawing for the activity of the enzymes alkaline phosphatase (ALP), acid phosphatase (AcP), lactate dehydrogenase (LDH) and aspartate aminotransferase (AspAT), and for the activity of acrosin inhibitors (AP). The mean concentration of sperm was 625.1 million/cm3, and ejaculate volume averaged 1.6 cm3. Seminal plasma was characterized by the highest activity of alkaline phosphatase (3.43×103 U/l) and lowest activity of acrosin inhibitors (4.55×103 U/l). After equilibration, the supernatants showed the highest activity of acid phosphatase (94.9 U/l) and after freeze-thawing, they showed a high activity of lactate dehydrogenase (535.8 U/l) and aspartate aminotransferase (577.1 U/l), which indicates that these proteins had leaked from spermatozoa into the extracellular medium during the biotechnique of semen cryopreservation. In addition, several significant relationships were found between some indicators of semen quality and plasma and/or supernatant enzyme activity.
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Westervelt, Daniel M., Nora R. Mascioli, Arlene M. Fiore, Andrew J. Conley, Jean-François Lamarque, Drew T. Shindell, Greg Faluvegi, Michael Previdi, Gustavo Correa und Larry W. Horowitz. „Local and remote mean and extreme temperature response to regional aerosol emissions reductions“. Atmospheric Chemistry and Physics 20, Nr. 5 (12.03.2020): 3009–27. http://dx.doi.org/10.5194/acp-20-3009-2020.
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Abstract. The climatic implications of regional aerosol and precursor emissions reductions implemented to protect human health are poorly understood. We investigate the mean and extreme temperature response to regional changes in aerosol emissions using three coupled chemistry–climate models: NOAA GFDL CM3, NCAR CESM1, and NASA GISS-E2. Our approach contrasts a long present-day control simulation from each model (up to 400 years with perpetual year 2000 or 2005 emissions) with 14 individual aerosol emissions perturbation simulations (160–240 years each). We perturb emissions of sulfur dioxide (SO2) and/or carbonaceous aerosol within six world regions and assess the statistical significance of mean and extreme temperature responses relative to internal variability determined by the control simulation and across the models. In all models, the global mean surface temperature response (perturbation minus control) to SO2 and/or carbonaceous aerosol is mostly positive (warming) and statistically significant and ranges from +0.17 K (Europe SO2) to −0.06 K (US BC). The warming response to SO2 reductions is strongest in the US and Europe perturbation simulations, both globally and regionally, with Arctic warming up to 1 K due to a removal of European anthropogenic SO2 emissions alone; however, even emissions from regions remote to the Arctic, such as SO2 from India, significantly warm the Arctic by up to 0.5 K. Arctic warming is the most robust response across each model and several aerosol emissions perturbations. The temperature response in the Northern Hemisphere midlatitudes is most sensitive to emissions perturbations within that region. In the tropics, however, the temperature response to emissions perturbations is roughly the same in magnitude as emissions perturbations either within or outside of the tropics. We find that climate sensitivity to regional aerosol perturbations ranges from 0.5 to 1.0 K (W m−2)−1 depending on the region and aerosol composition and is larger than the climate sensitivity to a doubling of CO2 in two of three models. We update previous estimates of regional temperature potential (RTP), a metric for estimating the regional temperature responses to a regional emissions perturbation that can facilitate assessment of climate impacts with integrated assessment models without requiring computationally demanding coupled climate model simulations. These calculations indicate a robust regional response to aerosol forcing within the Northern Hemisphere midlatitudes, regardless of where the aerosol forcing is located longitudinally. We show that regional aerosol perturbations can significantly increase extreme temperatures on the regional scale. Except in the Arctic in the summer, extreme temperature responses largely mirror mean temperature responses to regional aerosol perturbations through a shift of the temperature distributions and are mostly dominated by local rather than remote aerosol forcing.