Insights on long-term ecosystem changes from stable isotopes in historical squid beaks

Background - Assessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023. Results - We detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii's trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century. Conclusions - Our results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids' increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems

Improved W boson mass measurement with the D0 detector

We have measured the W boson mass using the D0 detector and a data sample of 82 pb^-1 from the Tevatron collider. This measurement used W -> e nu decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such 'edge' electrons have not been used in any previous D0 analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous D0 W boson mass measurements, we obtain M_W = 80.483 +/- 0.084 GeV. The 8% improvement from the previous D0 measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.Comment: submitted to Phys. Rev. D; 20 pages, 18 figures, 9 table

Search for mSUGRA in single-electron events with jets and large missing transverse energy in ppbar collisions at center of mass energy of 1.8 TeV

We describe a search for evidence of minimal supergravity (mSUGRA) in 92.7 pb^(-1) of data collected with the D{\O}detector at the Fermilab Tevatron ppbar collider at center of mass energy of 1.8 TeV. Events with a single electron, four or more jets, and large missing transverse energy were used in this search. The major backgrounds are from W+jets, misidentified multijet, ttbar, and WW production. We observe no excess above the expected number of background events in our data. A new limit in terms of mSUGRA model parameters is obtained.Comment: 24 pages, 17 figures; submitted to PRD; FERMILAB-Pub-02/074-

Study of vertical milling machine layout in terms of rigidity

© 2020 Published under licence by IOP Publishing Ltd. The paper explores the signs of static elastic deformation when operating milling machines. The research is concerned with the issue of simulation of a machine-device-tool-workpiece system for preliminary evaluation of elastic deformation on treatment in order to eliminate rejects. Linear and angular deformations were defined. Total rigidity of a milling machine depends not only on its inherent stiffness and contact rigidity of its components, but also on geometrical characteristics of manufacturing system layout. These characteristics could be evaluated through axes of rigidity. Errors in surface machining depend on both tool deflection and workpiece distortion. That is why it is necessary to analyze workpiece and tool load-deformation curve separately. Especially that their rigidity is determined by different layouts of bearing system. Main deformation values are defined and vectors of axes of rigidity are created. Using the results of the analysis it is possible to select a cutting pattern or change manufacturing system layout so that the resultant of cutting forces comes closer to highest rigidity axis, which reduces elastic deformations and improves working accuracy

Reduction of Static Elastic Displacements During Processing on Vertical Milling Machines

This article focuses on improving the accuracy of processing on milling machines of complex parts, such as dies and molds. One of the important factors affecting machining accuracy is static elastic displacement. This article discusses the reduction of static elastic displacements due to the use of a spatial geometric factor called the stiffness axis. Methods for determining the axes of rigidity in the working space of a vertical milling machine through the use of finite element modeling are considered. A mathematical model is proposed that relates static elastic displacements along the normal vector to the treated surface with the angle of the resultant cutting forces relative to the axis of stiffness. Using this mathematical model, we studied the change in static elastic displacements with a change in cutting conditions, and as a result, with a change in the values of the cutting forces and the location of the resultant cutting forces relative to the stiffness axes. By solving the problem of optimization of the proposed mathematical model, cutting modes were defined to allow the equal cutting force to approach the axis of maximum rigidity, and as a result, to reduce static elastic movements. The adequacy of the developed mathematical model was tested experimentally

Evaluation of the Harmonic Locus of the Milling Technological System Based on the Analysis of the Vibro-Acoustic Signal

© 2020, Springer Nature Switzerland AG. The article deals with the use of acoustic signals of noise caused by vibrations of the technological system, consisting of technological equipment, tools and blanks, in order to obtain the harmonic locus of the dynamic system of equipment. Vibrations are one of the factors that prevent productivity increase in milling machines. Therefore, vibrations prevent the efficient use of such machines. For effective use of technological systems, it is necessary to determine experimentally the amplitude-phase frequency response. The analysis of vibroacoustic signals is the easiest way to obtain such a characteristic experimentally. The article gives the principles of mathematical processing of vibroacoustic signals, which allows obtaining the required characteristics. The experimental part is presented, which describes the acquisition of signals during the processing of the workpiece on the machine and obtaining its amplitude phase-frequency characteristics. The practical application of this technique for the analysis of the dynamic stability of the technological system and for the selection of optimal cutting conditions is considered

Springtail (Hexapoda: Collembola) functional group composition varies between different biotopes in Russian rice growing systems

© 2020 Elsevier Masson SAS Regular flooding during rice cultivation adversely affects soil animals in agroecosystems and may disrupt ecological functions that they deliver. Alternation of upland crops and flooded rice potentially has a positive effect on soil fauna. However, this aspect has not yet been studied outside the tropics. We focused on the influence of interannual crop rotation accompanied by long periods of paddy drainage in Russian rice growing systems on the total abundance, species richness and abundance of functional groups of springtails (Hexapoda: Collembola) with respect to their vertical stratification. In three rice-growing regions of Russia (Krasnodarsky Krai, the Republic of Kalmykia and Primorsky Krai), we collected soil in four different biotope types: flooded rice paddies, drained paddies seeded with upland crops, paddy bunds and a control of semi-natural grasslands. We found that the total abundance and total species richness of Collembola were consistently higher in upland crops (21100 ± 12700 ind. m−2; 4 ± 0.7 species plot−1) than that in flooded rice (340 ± 190; 1 ± 0.4, respectively) across all regions. The abundance of euedaphic springtails in upland crops and flooded rice paddies (700 ± 350 and 150 ± 150 ind. m−2, respectively) remained significantly lower than that in bunds or control grassland sites (5600 ± 1900 and 6100 ± 2100, respectively). In contrast, the abundance of epiedaphic springtails was higher in upland crops (18900 ± 12500 ind. m−2) than that in flooded rice paddies (170 ± 100) but did not differ from that in control grasslands and bunds. We conclude that interannual alternation of flooded rice and upland crops in Russian rice paddies implies opportunities for soil microarthropods to rebuild their diversity and functional group composition before the next period of flooding mainly due to quicker dispersing surface-dwelling species

Fauna of Freshwater Harpacticoida (Copepoda) in the Lena River Delta

Abstract: The first description/overview of the freshwater copepod fauna of the order Harpacticoida from the Lena River delta is presented. Various habitats and regions were studied. As a result, we identified 18 species belonging to two families: Canthocamptidae and Harpacticidae. Eight of the identified species are new to the study area; five species belonging to the genera Bryocamptus, Canthocamptus, Moraria, and Maraenobiotus, presumably represent new species for science. We provide brief ecological descriptions of the species identified in the Lena River delta and analyze their differences from the typical populations. The harpacticoid fauna of the Lena delta consists of three main components including Palaearctic species, Holarctic species, and species with “Beringian” distribution patterns. We provide a morphological description of Bryocamptus umiatensis Wilson 1958. This species is quite similar to Bryocamptus jejuensis Lee and Chang 2016, recently described from Korea. The main character distinguishing these species is the ornamentation of the anal operculum. This character in our region reveals considerable interpopulation variations. We also provide an identification key to the freshwater Canthocamptidae of the Lena delta

Actual fecundity of the Arctic squid Gonatus fabricii (Cephalopoda) based on the examination of a rarely encountered spent female

Gonatus fabricii (Lichtenstein, 1818) is an ecologically important squid that spends its entire life cycle within the Arctic where it is the most abundant cephalopod. Due to the rarity of mature and reproducing females, it is unknown how many eggs females spawn (actual fecundity). Among 47,000 specimens studied between 2005 and 2019 one spent, degenerated and gelatinous female with a mantle length of 230 mm was caught in West Greenland in 2019. Examination allowed the first detailed description of fecundity and spawning pattern in the species. Oocyte development shows that the most considerable maturation of mid-vitellogenic oocytes to late vitellogenic and then to ripe stages occurs immediately after the first ripe oocytes appear in the ovary. There were no ripe oocytes in the ovary or oviducts. The ovary contained an estimated 6561 oocytes and 2551 post-ovulatory follicles and hence the total fecundity was 9112. This specimen of G. fabricii realised 28.0% of its potential fecundity which is comparable to Berryteuthis magister, which also belongs to Gonatidae, and lower than in the majority of studied deep-sea squids (including other gonatids). Spent females may provide clues as to where the major spawning areas of this abundant but poorly known squid are located

Functional morphology and ecology of the Arctic pogonophore Nereilinum murmanicum Ivanov, 1961 (Siboglinidae, Annelida)

This article deals with the external and internal morphology in the adult stages of Nereilinum murmanicum Ivanov, 1961, a widespread species of Siboglinidae in the Barents Sea. Since Siboglinidae is currently a taxon within the phylum Annelida, we revised the commonly held view of the body segmentation pattern typical of the species and provided the first des­cription of its opisthosoma. Furthermore, the postannular region and trophosome were structurally analyzed using histology and electron microscopy. The endodermal origin of the trophosome was suggested from its structure and position. The juvenile and larval stages of the species were described. The early larvae were found to resemble the trochophores in Annelida. The late larvae look like the late metatrochophora in Annelida and lack parapodia. The juvenile specimens retain no larval traits and are morphologically comparable to the adult stages. New data on the ecology of the species were obtained: it appears to also inhabit deeper water layers. The boundaries of its range in the Barents Sea were expanded and specified. The abundance distribution of the species in the Barents Sea (30–40 ind/m2 for the major part of the sea, up to 72–113 ind/ m2 for certain areas of the sea in particular years) was considered