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Choiński, Adam y Mariusz Ptak. "Variation in the ice cover thickness on Lake Samołęskie as a result of underground water supply". Limnological Review 12, n.º 3 (1 de marzo de 2012): 133–38. http://dx.doi.org/10.2478/v10194-012-0053-5.
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AbstractThe character of phenomena related to freezing depends on macroscale factors and mainly on thermal conditions, but local conditions can also be of great importance in shaping the course of these phenomena. Building of ice cover can be substantially different even for neighbouring lakes as a result of different individual features such as, for example, morphometric parameters. In this study the variation in the thickness of ice cover on Lake Samołęskie (29 ha) localised in western Poland, is analysed. According to measurements performed the differences in the thickness of ice cover was significant as it varied from 20 to 33 cm. A characteristic feature was that along the west bank of the lake the ice cover was thinner and its thickness increased towards the east. Analysis of the hydrogeological data revealed that this phenomenon is related to the supply of water to the lake basin by efficient water-carrying formations. The influx of water affects the bottom layer of the ice cover. This effect is aggravated by the fact that the water is supplied under elevated pressure as evidenced by the presence of a polynia of about 10 m in diameter, over the deepest (over 20 metres deep) site in the lake. The polynia is never frozen, even during the coldest winters. The specific features of the lake illustrate the influence of local geological conditions on the character of processes taking place in lakes in general.
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Dragon, Anne-Cécile, Marie-Noëlle Houssais, Christophe Herbaut y Jean-Benoît Charrassin. "A note on the intraseasonal variability in an Antarctic polynia: Prior to and after the Mertz Glacier calving". Journal of Marine Systems 130 (febrero de 2014): 46–55. http://dx.doi.org/10.1016/j.jmarsys.2013.06.006.
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Hollands, T., V. Haid, W. Dierking, R. Timmermann y L. Ebner. "Sea ice motion and open water area at the Ronne Polynia, Antarctica: Synthetic aperture radar observations versus model results". Journal of Geophysical Research: Oceans 118, n.º 4 (abril de 2013): 1940–54. http://dx.doi.org/10.1002/jgrc.20158.
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das Neves, Rogério Coutinho, Márcia Renata Mortari, Elisabeth Ferroni Schwartz, André Kipnis y Ana Paula Junqueira-Kipnis. "Antimicrobial and Antibiofilm Effects of Peptides from Venom of Social Wasp and Scorpion on Multidrug-Resistant Acinetobacter baumannii". Toxins 11, n.º 4 (10 de abril de 2019): 216. http://dx.doi.org/10.3390/toxins11040216.
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Intravascular stent infection is a rare complication with a high morbidity and high mortality; bacteria from the hospital environment form biofilms and are often multidrug-resistant (MDR). Antimicrobial peptides (AMPs) have been considered as alternatives to bacterial infection treatment. We analyzed the formation of the bacterial biofilm on the vascular stents and also tested the inhibition of this biofilm by AMPs to be used as treatment or coating. Antimicrobial activity and antibiofilm were tested with wasp (Agelaia-MPI, Polybia-MPII, Polydim-I) and scorpion (Con10 and NDBP5.8) AMPs against Acinetobacter baumannii clinical strains. A. baumannii formed a biofilm on the vascular stent. Agelaia-MPI and Polybia-MPII inhibited biofilm formation with bacterial cell wall degradation. Coating biofilms with polyethylene glycol (PEG 400) and Agelaia-MPI reduced 90% of A. baumannii adhesion on stents. The wasp AMPs Agelaia-MPI and Polybia-MPII had better action against MDR A. baumannii adherence and biofilm formation on vascular stents, preventing its formation and treating mature biofilm when compared to the other tested peptides.
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das Neves, Rogerio Coutinho, Monalisa Martins Trentini, Juliana de Castro e Silva, Karina Smidt Simon, Anamelia Lorenzetti Bocca, Luciano Paulino Silva, Marcia Renata Mortari, Andre Kipnis y Ana Paula Junqueira-Kipnis. "Antimycobacterial Activity of a New Peptide Polydim-I Isolated from Neotropical Social Wasp Polybia dimorpha". PLOS ONE 11, n.º 3 (1 de marzo de 2016): e0149729. http://dx.doi.org/10.1371/journal.pone.0149729.
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Yang, Yi, Ryo Murai, Yuka Takahashi, Airi Mori, Masaya Hane, Ken Kitajima y Chihiro Sato. "Comparative Studies of Polysialic Acids Derived from Five Different Vertebrate Brains". International Journal of Molecular Sciences 21, n.º 22 (14 de noviembre de 2020): 8593. http://dx.doi.org/10.3390/ijms21228593.
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Polysialic acid (polySia/PSA) is a linear homopolymer of sialic acid (Sia) that primarily modifies the neural cell adhesion molecule (NCAM) in mammalian brains. PolySia-NCAM not only displays an anti-adhesive function due to the hydration effect, but also possesses a molecule-retaining function via a direct binding to neurologically active molecules. The quality and quantity of polySia determine the function of polySia-NCAM and are considered to be profoundly related to the maintenance of normal brain functions. In this study, to compare the structures of polySia-NCAM in brains of five different vertebrates (mammals, birds, reptiles, amphibians, and fish), we adopted newly developed combinational methods for the analyses. The results revealed that the structural features of polySia considerably varied among different species. Interestingly, mice, as a mammal, possess eminently distinct types of polySia, in both quality and quantity, compared with those possessed by other animals. Thus, the mouse polySia is of larger quantities, of longer and more diverse chain lengths, and of a larger molecular size with higher negative charge, compared with polySia of other species. These properties might enable more advanced brain function. Additionally, it is suggested that the polySia/Sia ratio, which likely reflects the complexity of brain function, can be used as a new promising index to evaluate the intelligence of different vertebrate brains.
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Oltmann-Norden, Imke, Sebastian P. Galuska, Herbert Hildebrandt, Rudolf Geyer, Rita Gerardy-Schahn, Hildegard Geyer y Martina Mühlenhoff. "Impact of the Polysialyltransferases ST8SiaII and ST8SiaIV on Polysialic Acid Synthesis during Postnatal Mouse Brain Development". Journal of Biological Chemistry 283, n.º 3 (28 de noviembre de 2007): 1463–71. http://dx.doi.org/10.1074/jbc.m708463200.
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Polysialic acid (polySia), a post-translational modification of the neural cell adhesion molecule (NCAM), is the key regulator of NCAM-mediated functions and crucial for normal brain development, postnatal growth, and survival. Two polysialyltransferases, ST8SiaII and ST8SiaIV, mediate polySia biosynthesis. To dissect the impact of each enzyme during postnatal brain development, we monitored the developmental changes in NCAM polysialylation in wild-type, ST8SiaII-, and ST8SiaIV-deficient mice using whole brain lysates obtained at 10 time points from postnatal days 1 to 21 and from adult mice. In wild-type and ST8SiaIV-null brain, polySia biosynthesis kept pace with the rapid increase in brain weight until day 9, and nearly all NCAM was polysialylated. Thereafter, polySia dropped by ∼70% within 1 week, accompanied by the first occurrence of polySia-free NCAM-140 and NCAM-180. In ST8SiaII-null brain, polySia declined immediately after birth, leading to 60% less polySia at day 9 combined with the untimely appearance of polySia-free NCAM. Polysialyltransferase deficiency did not alter NCAM expression level or isoform pattern. In all three genotypes, NCAM-140 and NCAM-180 were expressed at constant levels from days 1 to 21 and provided the major polySia acceptors. By contrast, NCAM-120 first appeared at day 5, followed by a strong up-regulation inverse to the decrease in polySia. Together, we provide a comprehensive quantitative analysis of the developmental changes in polySia level, NCAM polysialylation status, and polysialyltransferase transcript levels and show that the predominant role of ST8SiaII during postnatal brain development is restricted to the first 15 days.
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BIGGS, NICHOLAS R. T., MIGUEL A. MORALES MAQUEDA y ANDREW J. WILLMOTT. "Polynya flux model solutions incorporating a parameterization for the collection thickness of consolidated new ice". Journal of Fluid Mechanics 408 (10 de abril de 2000): 179–204. http://dx.doi.org/10.1017/s0022112099007673.
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Previous polynya flux models have specified a constant value for the collection thickness of frazil ice, H, at the polynya edge. In certain circumstances, this approach can cause the frazil ice depth, h, within the polynya, to exceed H, a result which violates assumptions made in the formulation of the ice flux balance equations at the polynya edge. To overcome this problem, a parameterization for H is derived in terms of the depth of frazil ice arriving at the polynya edge and the component, normal to the polynya edge, of the frazil ice velocity relative to the velocity of the consolidated ice pack. Thus, H is coupled to the unknown polynya edge. Using the new parameterization for H, an analysis of the unsteady one-dimensional opening of a coastal polynya is presented. Analytical solutions are also derived, using the new parameterization for H, for steady-state two-dimensional polynyas adjacent to a semi-infinite and finite-length coastal barrier, the latter case representing a prototype island. In all cases, the solutions show close qualitative and quantitative agreement with those derived using a constant value for H. However, the steady-state two-dimensional polynya edge can, in certain circumstances, exhibit a corner at the point where the offshore equilibrium width is reached. Precise conditions for the existence of a corner are derived in terms of the orientation of the frazil ice velocity (u) and the consolidated ice velocity (U). Upper and lower bounds are also obtained for the area of the steady-state island polynya, and it is shown that over a large range of orientations of u and U, the area exceeds that associated with the island polynya with constant H. Finally, two simulations of the St. Lawrence Island Polynya are presented using the new parameterization for H, and the results are compared with the H-constant theory.
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Hane, Masaya, Mizuki Sumida, Ken Kitajima y Chihiro Sato. "Structural and functional impairments of polysialic acid (polySia)-neural cell adhesion molecule (NCAM) synthesized by a mutated polysialyltransferase of a schizophrenic patient". Pure and Applied Chemistry 84, n.º 9 (24 de junio de 2012): 1895–906. http://dx.doi.org/10.1351/pac-con-11-12-10.
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Polysialic acid (polySia) is a homopolymer of sialic acid with a degree of polymerization (DP) of 8–400. When present on neural cell adhesion molecule (NCAM), polySia has anti-adhesive effects on cell–cell interactions owing to its bulky polyanionic nature, and is involved in the regulation of neurogenesis and neuronal functions. Recently, we demonstrated that polySia functions not only as an anti-cell adhesion molecule, but also as a reservoir scaffold for brain-derived neurotrophic factor (BDNF) and fibroblast growth factor 2 (FGF2), which are biologically active molecules in neurogenesis. To understand the significance of polySia structure in the reservoir function, we focused on polySia-NCAM biosynthesized by mutated polysialyltransferase (ST8SiaII or STX) that was reported in a schizophrenia patient. The polySia-NCAM biosynthesized by mutant ST8SiaII/STX contained less polySia with shorter chain length and exhibited impaired reservoir function for BDNF and FGF2 as compared with that synthesized by wild-type (wt) ST8SiaII/STX. Our findings suggest that the quantity and quality of polySia on NCAM are important for normal neuronal functioning.
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Lourido, Gilcélia Melo, Thiago Mahlmann V. Lopes, Alexandre Somavilla y Karla Francini G. Guerra. "Social wasps as biological control agents against Diaphania hyalinata (Linnaeus, 1767) (Lepidoptera, Crambidae), a cucumber pest in Amazonas, Brazil". Sociobiology 66, n.º 4 (30 de diciembre de 2019): 610. http://dx.doi.org/10.13102/sociobiology.v66i4.3576.
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Diaphania hyalinata (Lepidoptera: Crambidae), popularly known as “melonworm moth”, is considered a main pest of the cucumber, and depending on the intensity of infestation, the damage can reach 100%. Herein, we report the predation of D. hyalinata larvae by seven social wasp species: Brachygastra lecheguana, Polybia dimidiata, Polybia ignobilis, Polybia liliacea, Protopolybia minutissima, Synoeca surinama and Synoeca virginea, and predation of D. hyalinata pupae by Polybia liliacea. We suggest that Polybia liliacea, should be considered as a potential biological control for cucumbers, due to its high index of captured prey and intense foraging activity.
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Mori, Airi, Yi Yang, Yuka Takahashi, Masaya Hane, Ken Kitajima y Chihiro Sato. "Combinational Analyses with Multiple Methods Reveal the Existence of Several Forms of Polysialylated Neural Cell Adhesion Molecule in Mouse Developing Brains". International Journal of Molecular Sciences 21, n.º 16 (16 de agosto de 2020): 5892. http://dx.doi.org/10.3390/ijms21165892.
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Polysialic acid (polySia/PSA) is an anionic glycan polymer of sialic acid, and it mostly modifies the neural cell adhesion molecule (NCAM) in mammalian brains. Quality and quantity of the polySia of the polySia–NCAM is spatio-temporally regulated in normal brain development and functions, and their impairments are reported to be related to diseases, such as psychiatric disorders and cancers. Therefore, precise understanding of the state of polySia–NCAM structure would lead to the diagnosis of diseases for which their suitable evaluation methods are necessary. In this study, to develop these evaluation methods, structures of polySia–NCAM from mouse brains at six different developmental stages were analyzed by several conventional and newly developed methods. Integrated results of these experiments clearly demonstrated the existence of different types of polySia–NCAMs in developing brains. In addition, combinational analyses were shown to be useful for precise understanding of the quantity and quality of polySia, which can provide criteria for the diagnosis of diseases.
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Kühnle, Andrea, Thomas Lütteke, Kim Bornhöfft y Sebastian Galuska. "Polysialic Acid Modulates the Binding of External Lactoferrin in Neutrophil Extracellular Traps". Biology 8, n.º 2 (28 de marzo de 2019): 20. http://dx.doi.org/10.3390/biology8020020.
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Neutrophil extracellular traps (NETs) are formed by neutrophils during inflammation. Among other things, these DNA constructs consist of antimicrobial proteins such as lactoferrin and histones. With these properties, NETs capture and destroy invading microorganisms. The carbohydrate polysialic acid (polySia) interacts with both lactoferrin and histones. Previous experiments demonstrated that, in humans, lactoferrin inhibits the release of NET and that this effect is supported by polySia. In this study, we examined the interplay of lactoferrin and polySia in already-formed NETs from bovine neutrophils. The binding of polySia was considered to occur at the lactoferricin (LFcin)-containing domain of lactoferrin. The interaction with the peptide LFcin was studied in more detail using groups of defined polySia chain lengths, which suggested a chain-length-dependent interaction mechanism with LFcin. The LFcin domain of lactoferrin was found to interact with DNA. Therefore, the possibility that polySia influences the integration of lactoferrin into the DNA-structures of NETs was tested by isolating bovine neutrophils and inducing NETosis. Experiments with NET fibers saturated with lactoferrin demonstrated that polySia initiates the incorporation of external lactoferrin in already-loaded NETs. Thus, polySia may modulate the constituents of NET.
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Goswami, Surbhi, Shubham Parashar, Vandita Dwivedi, Asif Shajahan y Srinivasa-Gopalan Sampathkumar. "Chemical and biological methods for probing the structure and functions of polysialic acids". Emerging Topics in Life Sciences 2, n.º 3 (11 de septiembre de 2018): 363–76. http://dx.doi.org/10.1042/etls20180008.
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Owing to its poly-anionic charge and large hydrodynamic volume, polysialic acid (polySia) attached to neural cell adhesion molecule regulates axon–axon and axon–substratum interactions and signalling, particularly, in the development of the central nervous system (CNS). Expression of polySia is spatiotemporally regulated by the action of two polysialyl transferases, namely ST8SiaII and ST8SiaIV. PolySia expression peaks during late embryonic and early post-natal period and maintained at a steady state in adulthood in neurogenic niche of the brain. Aberrant polySia expression is associated with neurological disorders and brain tumours. Investigations on the structure and functions, over the past four decades, have shed light on the physiology of polySia. This review focuses on the biological, biochemical, and chemical tools available for polySia engineering. Genetic knockouts, endo-neuraminidases that cleave polySia, antibodies, exogenous expression, and neuroblastoma cells have provided deep insights into the ability of polySia to guide migration of neuronal precursors in neonatal brain development, neuronal clustering, axonal pathway guidance, and axonal targeting. Advent of metabolic sialic acid engineering using ManNAc analogues has enabled reversible and dose-dependent modulation polySia in vitro and ex vivo. In vivo, ManNAc analogues readily engineer the sialoglycans in peripheral tissues, but show no effect in the brain. A recently developed carbohydrate-neuroactive hybrid strategy enables a non-invasive access to the brain in living animals across the blood–brain barrier. A combination of recent advances in CNS drugs and imaging with ManNAc analogues for polySia modulation would pave novel avenues for understanding intricacies of brain development and tackling the challenges of neurological disorders.
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Kawaguchi, Yusuke, Sohey Nihashi, Humio Mitsudera y Kay I. Ohshima. "Formation Mechanism of Huge Coastal Polynyas and Its Application to Okhotsk Northwestern Polynya". Journal of Physical Oceanography 40, n.º 11 (1 de noviembre de 2010): 2451–65. http://dx.doi.org/10.1175/2010jpo4304.1.
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Abstract This paper investigates the formation mechanism of broad coastal polynyas beyond 100 km in offshore width. It is known that two regimes for wind-driven polynya opening exist: one is a convergent regime at the polynya edge in which inner frazil ice catches up with outer consolidated ice, whereas the other is a divergent regime in which the consolidated ice drifts offshore faster than the frazil ice at the edge. In this study, the authors focus on the latter, divergent polynya-edge regime. Because in the divergent regime the polynya possibly evolves without bound, they consider a thermal growth for inner frazil ice to find a finite solution of offshore width. Then, the authors investigate responses of the polynya opening for various wind angles ϕ from the offshore direction from the viewpoint of the polynya-edge regimes. At first, the authors estimate the deviation angle and wind factor for the frazil and consolidated ice based on each momentum balance, because sea ice motion driven by wind varies depending on the ice thickness due to relative effect of the Coriolis force. It was found that, when the surface wind deviates leftward about 10° or greater from offshore, the divergent regime at the polynya edge generates a great polynya evolution. Otherwise, the convergent regime takes place yielding small offshore extent. These theoretical results were verified for the Okhotsk northwestern polynya using thin-ice-thickness data derived from Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) and the Japanese 25-year Reanalysis (JRA-25) surface wind. The data show that the polynya development distinctively changes at ϕ ∼ 0°, and the largest width is shown in the leftward wind angle of ϕ = 0°–30°. This clear relationship between the surface wind angle and the offshore extent of polynya nicely supports the theory.
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Dmitrenko, I., J. A. Hölemann, K. Tyshko, V. Churun, S. Kirillov y H. Kassens. "The Laptev Sea flaw polynya, Russian Arctic: effects on the mesoscale hydrography". Annals of Glaciology 33 (2001): 373–76. http://dx.doi.org/10.3189/172756401781818455.
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AbstractA detailed analysis of hydrographic data from a period of 20 years (1980−99) has shown that the persistent presence of a flaw polynya influences mesoscale hydrography of the Laptev Sea, Russian Arctic. Based on these data, the interannual variability of surface water salinity within the polynya has been estimated. As the salinity increase in the surface water layer is mainly caused by the formation of new ice within the polynya, the average ice-production rate of the polynya was calculated. The results indicate an ice production of 3−4 m per season. A further aim of this study was to calculate the probability that the convective mixing in the polynya penetrates to the sea-floor. It is demonstrated that the probability is maximal in the flaw-polynya area, but does not exceed 20% in the eastern and 70% in the western part of the polynya as a result of strong vertical density stratification from river runoff, especially in the eastern Laptev Sea. Additional studies of water circulation in the marginal zone of the flaw polynya were carried out during field observations in April-May 1999. On the basis of conductivity-temperature-depth and current measurements we deduce that high current velocities (62 cm s-1) recorded in surface waters near the fast-ice edge are caused by a convectively driven circulation system under the polynya. Our measurements indicate that these high-velocity currents are part of a cellular circulation, which results from the rejection of brine during intensive ice formation in the polynya. The observed azimuthal alignment of the crystalline structure of sea ice is also, most probably, the consequence of this quasi-stationary cellular circulation.
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Walkington, I. A. y A. J. Willmott. "A Coupled Coastal Polynya–Atmospheric Boundary Layer Model". Journal of Physical Oceanography 36, n.º 5 (1 de mayo de 2006): 897–913. http://dx.doi.org/10.1175/jpo2901.1.
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Abstract This paper formulates and presents opening solutions of a one-dimensional coastal polynya flux model in which frazil ice is characterized by its depth and concentration. In comparison with polynya flux models in which variable frazil ice concentration is absent, this model is found to predict a smaller heat flux to the atmosphere. Consequently the model in this paper exhibits a wider steady-state polynya and longer opening times when compared with models in which ice concentration is neglected. The aforementioned polynya flux model is then coupled to a lower-atmosphere boundary layer model, and it is demonstrated that the polynya opening time and the steady-state width are significantly altered in the coupled, as compared with the decoupled, system. In essence, the heating of the lower atmosphere above the evolving polynya in the coupled system reduces the sensible heat flux between the ocean and atmosphere, thereby reducing the frazil ice production rate and hence leading to longer polynya opening time and wider steady-state width. This phenomenon is particularly noticeable when the potential temperature of the atmosphere at the coast is only slightly below the freezing point. In addition, a cutoff atmospheric wind speed is shown to exist, above which a steady-state polynya can never be obtained. Solutions calculated by the two models, using parameters representative of the St. Lawrence Island polynya, show that the new models contain substantial predictive capability.
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Liao, Si-Ming, Bo Lu, Xue-Hui Liu, Zhi-Long Lu, Shi-Jie Liang, Dong Chen, Frederic A. Troy, Ri-Bo Huang y Guo-Ping Zhou. "Molecular Interactions of the Polysialytransferase Domain (PSTD) in ST8Sia IV with CMP-Sialic Acid and Polysialic Acid Required for Polysialylation of the Neural Cell Adhesion Molecule Proteins: An NMR Study". International Journal of Molecular Sciences 21, n.º 5 (26 de febrero de 2020): 1590. http://dx.doi.org/10.3390/ijms21051590.
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Polysialic acid (polySia) is an unusual glycan that posttranslational modifies neural cell adhesion molecule (NCAM) proteins in mammalian cells. The up-regulated expression of polySia-NCAM is associated with tumor progression in many metastatic human cancers and in neurocognitive processes. Two members of the ST8Sia family of α2,8-polysialyltransferases (polySTs), ST8Sia II (STX) and ST8Sia IV (PST) both catalyze synthesis of polySia when activated cytidine monophosphate(CMP)-Sialic acid (CMP-Sia) is translocate into the lumen of the Golgi apparatus. Two key polybasic domains in the polySTs, the polybasic region (PBR) and the polysialyltransferase domain (PSTD) areessential forpolysialylation of the NCAM proteins. However, the precise molecular details to describe the interactions required for polysialylation remain unknown. In this study, we hypothesize that PSTD interacts with both CMP-Sia and polySia to catalyze polysialylation of the NCAM proteins. To test this hypothesis, we synthesized a 35-amino acid-PSTD peptide derived from the ST8Sia IV gene sequence and used it to study its interaction with CMP-Sia, and polySia. Our results showed for the PSTD-CMP-Sia interaction, the largest chemical-shift perturbations (CSP) were in amino acid residues V251 to A254 in the short H1 helix, located near the N-terminus of PSTD. However, larger CSP values for the PSTD-polySia interaction were observed in amino acid residues R259 to T270 in the long H2 helix. These differences suggest that CMP-Sia preferentially binds to the domain between the short H1 helix and the longer H2 helix. In contrast, polySia was principally bound to the long H2 helix of PSTD. For the PSTD-polySia interaction, a significant decrease in peak intensity was observed in the 20 amino acid residues located between the N-and C-termini of the long H2 helix in PSTD, suggesting a slower motion in these residues when polySia bound to PSTD. Specific features of the interactions between PSTD-CMP-Sia, and PSTD-polySia were further confirmed by comparing their 800 MHz-derived HSQC spectra with that of PSTD-Sia, PSTD-TriSia (DP 3) and PSTD-polySia. Based on the interactions between PSTD-CMP-Sia, PSTD-polySia, PBR-NCAM and PSTD-PBR, these findingsprovide a greater understanding of the molecular mechanisms underlying polySia-NCAM polysialylation, and thus provides a new perspective for translational pharmacological applications and development by targeting the two polysialyltransferases.
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Bartling, Bastian, Johanna S. Rehfeld, Daniel Boßmann, Ingo de Vries, Jörg Fohrer, Frank Lammers, Thomas Scheper y Sascha Beutel. "Determination of the Structural Integrity and Stability of Polysialic Acid during Alkaline and Thermal Treatment". Molecules 25, n.º 1 (31 de diciembre de 2019): 165. http://dx.doi.org/10.3390/molecules25010165.
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Polysialic acid (polySia) is a linear homopolymer of varying chain lengths that exists mostly on the outer cell membrane surface of certain bacteria, such as Escherichia coli (E. coli) K1. PolySia, with an average degree of polymerization of 20 (polySia avDP20), possesses material properties that can be used for therapeutic applications to treat inflammatory neurodegenerative diseases. The fermentation of E. coli K1 enables the large-scale production of endogenous long-chain polySia (DP ≈ 130) (LC polySia), from which polySia avDP20 can be manufactured using thermal hydrolysis. To ensure adequate biopharmaceutical quality of the product, the removal of byproducts and contaminants, such as endotoxins, is essential. Recent studies have revealed that the long-term incubation in alkaline sodium hydroxide (NaOH) solutions reduces the endotoxin content down to 3 EU (endotoxin units) per mg, which is in the range of pharmaceutical applications. In this study, we analyzed interferences in the intramolecular structure of polySia caused by harsh NaOH treatment or thermal hydrolysis. Nuclear magnetic resonance (NMR) spectroscopy revealed that neither the incubation in an alkaline solution nor the thermal hydrolysis induced any chemical modification. In addition, HPLC analysis with a preceding 1,2-diamino-4,5-methylenedioxybenzene (DMB) derivatization demonstrated that the alkaline treatment did not induce any hydrolytic effects to reduce the maximum polymer length and that the controlled thermal hydrolysis reduced the maximum chain length effectively, while cost-effective incubation in alkaline solutions had no adverse effects on LC polySia. Therefore, both methods guarantee the production of high-purity, low-molecular-weight polySia without alterations in the structure, which is a prerequisite for the submission of a marketing authorization application as a medicinal product. However, a specific synthesis of low-molecular-weight polySia with defined chain lengths is only possible to a limited extent.
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Takizawa, Takatoshi, Kay I. Ohshima, Ushio Shcki, Toshiyuki Kawamura y Hiroyuki Enomoto. "Temperature structure and characteristics appearing on SSM/I images of the Cosmonaut Sea, Antarctica". Annals of Glaciology 20 (1994): 298–306. http://dx.doi.org/10.3189/172756494794587537.
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Water-temperature structure in the Cosmonaut Sea at 60 68° S, 35 65° E in 1987–92 shows that cold water with a temperature below -1.5°C was present in the coastal region. The Circumpolar Deep Water with a temperature higher than 1.0°C was found below about 150m depth from northeast to northwest of the cold water area. The SSM/I images in 1987–91 indicate that polynya activities were intensive in 1988 and the typical Cosmonaut Polynya was observed; due to weaker activities, the small and sporadic Cosmonaut Polynya formed in 1987, 1989, 1990 and 1991. A coastal polynya was frequently observed every year at about 66° S, 50–60° E. A train of polynyas to the east of Cosmonaut Polynya often appeared. It is considered that the Atmospheric Convergence Line and Antarctic Divergence Region are responsible for polynya activities in the Cosmonaut Sea.
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Takizawa, Takatoshi, Kay I. Ohshima, Ushio Shcki, Toshiyuki Kawamura y Hiroyuki Enomoto. "Temperature structure and characteristics appearing on SSM/I images of the Cosmonaut Sea, Antarctica". Annals of Glaciology 20 (1994): 298–306. http://dx.doi.org/10.1017/s0260305500016608.
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Water-temperature structure in the Cosmonaut Sea at 60 68° S, 35 65° E in 1987–92 shows that cold water with a temperature below -1.5°C was present in the coastal region. The Circumpolar Deep Water with a temperature higher than 1.0°C was found below about 150m depth from northeast to northwest of the cold water area. The SSM/I images in 1987–91 indicate that polynya activities were intensive in 1988 and the typical Cosmonaut Polynya was observed; due to weaker activities, the small and sporadic Cosmonaut Polynya formed in 1987, 1989, 1990 and 1991. A coastal polynya was frequently observed every year at about 66° S, 50–60° E. A train of polynyas to the east of Cosmonaut Polynya often appeared. It is considered that the Atmospheric Convergence Line and Antarctic Divergence Region are responsible for polynya activities in the Cosmonaut Sea.
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Nihashi, Sohey, Naoto Ebuchi, Yasushi Fukamachi y Shuhei Takahashi. "Characteristics of sea ice in the Okhotsk coastal polynyas revealed by satellites, ice-profiling sonar and digital camera observations". Annals of Glaciology 52, n.º 57 (2011): 133–39. http://dx.doi.org/10.3189/172756411795931624.
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AbstractThe characteristics of ice in the Okhotsk coastal polynyas are examined. A map of AMSR-E thin-ice thickness in the northwest shelf region shows that most of the coastal polynya area is covered by thin ice with a thickness of 0.1 m. the thickness increases sharply at the edge of the polynya. From comparisons with QuikSCAT backscatter, the thin-ice area corresponds well with the low-backscatter area during almost all the coastal polynya period. A comparison with ice thickness measured by an ice-profiling sonar in the coastal polynya region of northeastern Sakhalin shows a similar relationship, with the backscatter tending to be low when the ice is thin. the averaged backscatter of thin (≤0.1 m) ice is –19.6±2.8 dB (horizontal polarization). the backscatter of thin ice is considered to be mainly determined by the surface roughness because volume scattering of thin ice is low due to the dielectric properties associated with the high salinity. the results of this study suggest that the coastal polynya is covered with grease ice/nilas whose surface is almost mirror smooth. This is confirmed by a comparison with photographs taken at the coastal polynya region near Magadan, Russia. At the outer edge of the coastal polynya, a region of relatively high backscatter (>–16 dB) exists, probably because it has a rougher ice surface than the polynya area. This suggests that ice motion in this area may be convergent.
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Hachem, Nadim E., Luisa Humpfle, Peter Simon, Miriam Kaese, Birgit Weinhold, Juliane Günther, Sebastian P. Galuska y Ralf Middendorff. "The Loss of Polysialic Acid Impairs the Contractile Phenotype of Peritubular Smooth Muscle Cells in the Postnatal Testis". Cells 10, n.º 6 (29 de mayo de 2021): 1347. http://dx.doi.org/10.3390/cells10061347.
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In the testis, the germinal epithelium of seminiferous tubules is surrounded by contractile peritubular cells, which are involved in sperm transport. Interestingly, in postnatal testis, polysialic acid (polySia), which is also an essential player for the development of the brain, was observed around the tubules. Western blotting revealed a massive decrease of polySia from postnatal day 1 towards puberty, together with a fundamental reduction of the net-like intertubular polySia. Using polysialyltransferase knockout mice, we investigated the consequences of the loss of polySia in the postnatal testis. Compared to postnatal wild-type animals, polySia knockouts showed slightly reduced smooth muscle actin (SMA) immunostaining of peritubular smooth muscle cells (SMCs), while calponin, marking more differentiated SMCs, dramatically decreased. In contrast, testicular SMA and calponin immunostaining remained unchanged in vascular SMCs in all genotypes. In addition, the cGMP-dependent protein kinase PKG I, a key enzyme of SMC relaxation, was nearly undetectable in the peritubular SMCs. Cell proliferation in the peritubular layer increased significantly in the knockouts, as shown by proliferating cell nuclear anti (PCNA) staining. Taken together, in postnatal testis, the absence of polySia resulted in an impaired differentiation of peritubular, but not vascular, SMCs to a more synthetic phenotype. Thus, polySia might influence the maintenance of a differentiated phenotype of non-vascular SMCs.
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Rogers, Christopher K., Gregory A. Lawrence y Paul F. Hamblin. "Thermal impact of artificial circulation on an ice-covered mid-latitude lake". Canadian Journal of Civil Engineering 23, n.º 5 (1 de octubre de 1996): 1081–91. http://dx.doi.org/10.1139/l96-915.
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We measured the impact of an artificial circulation device designed to maintain a polynya in an otherwise ice-covered lake. Field observations revealed that the presence of the polynya causes a substantial reduction in average lake temperature when compared with a nearby lake left in its natural state. We extended a numerical model of the heat budget of a small ice-covered lake to incorporate the effects of the artificial circulation device. The model showed that during the cooling period the average heat lost from turbulent heat transfer between water and ice was three times that lost across the polynya surface. Lake temperature, polynya size, and snow depth were well represented by the model; however, there were discrepancies between early winter ice thickness predictions and observations. Key words: polynya, artificial circulation, radial jet, ice-covered lake, heat budget, numerical simulation.
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Gordon, Arnold L., Martin Visbeck y Josefino C. Comiso. "A Possible Link between the Weddell Polynya and the Southern Annular Mode*". Journal of Climate 20, n.º 11 (1 de junio de 2007): 2558–71. http://dx.doi.org/10.1175/jcli4046.1.
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Abstract Shortly after the advent of the first imaging passive microwave sensor on board a research satellite an anomalous climate feature was observed within the Weddell Sea. During the years 1974–1976, a 250 × 103 km2 area within the seasonal sea ice cover was virtually free of winter sea ice. This feature, the Weddell Polynya, was created as sea ice formation was inhibited by ocean convection that injected relatively warm deep water into the surface layer. Though smaller, less persistent polynyas associated with topographically induced upwelling at Maud Rise frequently form in the area, there has not been a reoccurrence of the Weddell Polynya since 1976. Archived observations of the surface layer salinity within the Weddell gyre suggest that the Weddell Polynya may have been induced by a prolonged period of negative Southern Annular Mode (SAM). During negative SAM the Weddell Sea experiences colder and drier atmospheric conditions, making for a saltier surface layer with reduced pycnocline stability. This condition enables Maud Rise upwelling to trigger sustained deep-reaching convection associated with the polynya. Since the late 1970s SAM has been close to neutral or in a positive state, resulting in warmer, wetter conditions over the Weddell Sea, forestalling repeat of the Weddell Polynya. A contributing factor to the Weddell Polynya initiation may have been a La Niña condition, which is associated with increased winter sea ice formation in the polynya area. If the surface layer is made sufficiently salty due to a prolonged negative SAM period, perhaps aided by La Niña, then Maud Rise upwelling meets with positive feedback, triggering convection, and a winter persistent Weddell Polynya.
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Herdina, Anita, Gabriela Bitencourt, Rocco Di Mare y Bruno Corrêa Barbosa. "Polybia (Myrapetra) scutellaris (Hymenoptera: Vespidae) foraging on flies at carcasses of Rattus norvegicus (Rodentia: Muridae)". Sociobiology 63, n.º 1 (29 de abril de 2016): 728. http://dx.doi.org/10.13102/sociobiology.v63i1.937.
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Social wasps stand out due to their role in the trophic balance of the ecosystems. These insects can get nutrients by preying on other insects, such as Lepidoptera, Diptera, Hymenoptera and the decomposing remains of vertebrates. Some species, such as Polybia scutellaris, can also use pollen and nectar stored in their nests to produce honey. Some studies lay emphasis on the prey captured by social wasps, showing that predation, in some conditions, is directed to Lepidoptera larvae, such as for Polybia occidentalis, Polybia paulista and Polybia ignobilis. Other species like P. scutellaris focus on flies of the Tabanidae, Syrphidae, Muscidae and Anthomyiidae families. There are few studies with social wasps that feed on animal carcasses; this way, our study aims to report the predation on individuals of the Sarcophagidae family, which use Rattus norvegicus carcasses as a food source, by the social wasp Polybia scutellari
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Abd El-Wahed, Aida, Nermeen Yosri, Hanem H. Sakr, Ming Du, Ahmed F. M. Algethami, Chao Zhao, Ahmed H. Abdelazeem et al. "Wasp Venom Biochemical Components and Their Potential in Biological Applications and Nanotechnological Interventions". Toxins 13, n.º 3 (12 de marzo de 2021): 206. http://dx.doi.org/10.3390/toxins13030206.
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Wasps, members of the order Hymenoptera, are distributed in different parts of the world, including Brazil, Thailand, Japan, Korea, and Argentina. The lifestyles of the wasps are solitary and social. Social wasps use venom as a defensive measure to protect their colonies, whereas solitary wasps use their venom to capture prey. Chemically, wasp venom possesses a wide variety of enzymes, proteins, peptides, volatile compounds, and bioactive constituents, which include phospholipase A2, antigen 5, mastoparan, and decoralin. The bioactive constituents have anticancer, antimicrobial, and anti-inflammatory effects. However, the limited quantities of wasp venom and the scarcity of advanced strategies for the synthesis of wasp venom’s bioactive compounds remain a challenge facing the effective usage of wasp venom. Solid-phase peptide synthesis is currently used to prepare wasp venom peptides and their analogs such as mastoparan, anoplin, decoralin, polybia-CP, and polydim-I. The goal of the current review is to highlight the medicinal value of the wasp venom compounds, as well as limitations and possibilities. Wasp venom could be a potential and novel natural source to develop innovative pharmaceuticals and new agents for drug discovery.
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Gordon, Arnold L. "Southern Ocean polynya". Nature Climate Change 4, n.º 4 (26 de marzo de 2014): 249–50. http://dx.doi.org/10.1038/nclimate2179.
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Morales Maqueda, Miguel A., A. J. Willmott y I. A. Walkington. "The opening of wind-driven polynyas". Journal of Fluid Mechanics 746 (31 de marzo de 2014): 236–72. http://dx.doi.org/10.1017/jfm.2014.118.
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AbstractThe opening of wind-driven coastal polynyas has often been investigated using idealised flux models. Polynya flux models postulate that the boundary separating the region of thin ice adjacent to the coast within the polynya from the thicker ice piling up downstream is a mathematical shock. To conserve mass, any divergence of the ice flux across the shock translates into a change in the shock’s position or, in other words, a change in the width of the thin-ice region of the polynya. Polynya flux models are physically incomplete in that, while they conserve ice mass, they do not conserve linear momentum. In this paper, we investigate the improvements that can be achieved in the simulation of polynyas by imposing conservation of momentum as well as mass. We start by adopting a mathematically solid formulation of the ice mass and momentum balances throughout the polynya region, from the coast to the pack ice. Hydrostatic and plastic versions of the ice internal forces are used in the model. Two different approaches are then explored. We first postulate the existence of a shock at the seaward edge of the thin-ice region of the polynya and derive jump conditions for the conservation of ice mass and momentum at the shock which are consistent with the continuous model physics. Polynyas simulated by this mass- and momentum-conserving shock model always reach a steady state if the polynya forcing is uniform in space and constant in time. This is also true for all polynya flux models presented previously in the literature, but the location of the steady-state polynya edge and the time required to reach it can greatly differ between shock formulations and more simplistic flux ones. We next relax the assumption that a shock exists and let the boundary between thin ice and piling up ice emerge naturally as part of the full solution of the continuous model equations. Polynyas simulated in this way are very different from those simulated by either shock or flux models. Most notably, we find that steady-state polynya solutions are not always attainable in the continuous model. We determine under which conditions this is so and explain how such unsteady solutions come about. We also show that, in those cases when a steady-state solution exists in the continuous model, the steady-state polynya width is considerably larger than in the shock model, and the time required to attain it is accordingly longer. The occurrence of such significant differences between the polynya solutions calculated with flux and shock models, on the one hand, and with more sophisticated continuous formulations, on the other hand, suggests that the former are, at best, incomplete, and should be used with caution.
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Kern, Stefan, Gunnar Spreen, Lars Kaleschke, Sara De La Rosa y Georg Heygster. "Polynya Signature Simulation Method polynya area in comparison to AMSR-E 89GHz sea-ice concentrations in the Ross Sea and off the Adélie Coast, Antarctica, for 2002–05: first results". Annals of Glaciology 46 (2007): 409–18. http://dx.doi.org/10.3189/172756407782871585.
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AbstractThe Polynya Signature Simulation Method (PSSM) is applied to Special Sensor Microwave/Imager observations from different Defense Meteorological Satellite Program spacecraft for 2002–05 to analyze the polynya area in the Ross Sea (Ross Ice Shelf polynya (RISP) and Terra Nova Bay polynya (TNBP)) and off the Adélie Coast (Mertz Glacier polynya (MGP)), Antarctica, on a sub-daily scale. The RISP and the MGP exhibit similar average total polynya areas. Major area changes (>10000km2; TNPB: >2000km2) occur over a range of 2–3 to 20 days in all regions. Sub-daily area changes are largest for the MGP (5800km2) and smallest for the TNBP (800km2), underlining the persistence of the forcing of the latter. ARTIST sea-ice (ASI) algorithm concentration maps obtained using 89 GHz Advanced Microwave Scanning Radiometer (AMSR-E) data are compared to PSSM maps, yielding convincing agreement in the average, similarly detailed winter polynya distribution. Average ASI algorithm ice concentrations take values of 25–40% and 65–80% for the PSSM open-water and thin-ice class, respectively. The discrepancy with expected values (0% and 100%) can be explained by the different spatial resolution and frequency used by the methods. A new land mask and a mask to flag icebergs are introduced. Comparison of PSSM maps with thermal ice thickness based on AVHRR infrared temperature and ECMWF ERA-40 data suggests an upper thickness limit for the PSSM thin-ice class of 20–25 cm.
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Krumpen, Thomas, Sascha Willmes, Miguel Angel Morales Maqueda, Christian Haas, Jens A. Hölemann, Rüdiger Gerdes y David Schröder. "Evaluation of a polynya flux model by means of thermal infrared satellite estimates". Annals of Glaciology 52, n.º 57 (2011): 52–60. http://dx.doi.org/10.3189/172756411795931615.
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AbstractWe test the ability of a two-dimensional flux model to simulate polynya events with narrow open-water zones by comparing model results to ice-thickness and ice-production estimates derived from thermal infrared Moderate Resolution Imaging Spectroradiometer (MODIS) observations in conjunction with an atmospheric dataset. Given a polynya boundary and an atmospheric dataset, the model correctly reproduces the shape of an 11 day long event, using only a few simple conservation laws. Ice production is slightly overestimated by the model, owing to an underestimated ice thickness. We achieved best model results with the consolidation thickness parameterization developed by Biggs and others (2000). Observed regional discrepancies between model and satellite estimates might be a consequence of the missing representation of the dynamic of the thin-ice thickening (e.g. rafting). We conclude that this simplified polynya model is a valuable tool for studying polynya dynamics and estimating associated fluxes of single polynya events.
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Kühnle, Andrea, Christina E. Galuska, Kristina Zlatina y Sebastian P. Galuska. "The Bovine Antimicrobial Peptide Lactoferricin Interacts with Polysialic Acid without Loss of Its Antimicrobial Activity against Escherichia coli". Animals 10, n.º 1 (18 de diciembre de 2019): 1. http://dx.doi.org/10.3390/ani10010001.
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The lactoferrin-derived peptide lactoferricin (LFcin) belongs to the family of antimicrobial peptides, and its bovine form has already been successfully applied to counteract enterohemorrhagic Escherichia coli (EHEC) infection. Recently, it was described that LFcin interacts with the sugar polymer polysialic acid (polySia) and that the binding of lactoferrin to polySia is mediated by LFcin, included in the N-terminal domain of lactoferrin. For this reason, the impact of polySia on the antimicrobial activity of bovine LFcin was investigated. Initially, the interaction of LFcin was characterized in more detail by native agarose gel electrophoresis, demonstrating that a chain length of 10 sialic acid residues was necessary to bind LFcin, whereas approximately twice-as-long chains were needed to detect binding of lactoferrin. Remarkably, the binding of polySia showed, independently of the chain length, no impact on the antimicrobial effects of LFcin. Thus, LFcin binds polySia without loss of its protective activity as an antimicrobial peptide.
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Wang, Kairong, Jiexi Yan, Ru Chen, Wen Dang, Bangzhi Zhang, Wei Zhang, Jingjing Song y Rui Wang. "Membrane-Active Action Mode of Polybia-CP, a Novel Antimicrobial Peptide Isolated from the Venom of Polybia paulista". Antimicrobial Agents and Chemotherapy 56, n.º 6 (26 de marzo de 2012): 3318–23. http://dx.doi.org/10.1128/aac.05995-11.
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ABSTRACTThe extensive use of antibiotics in medicine, the food industry, and agriculture has resulted in the frequent emergence of multidrug-resistant bacteria, which creates an urgent need for new antibiotics. It is now widely recognized that antimicrobial peptides (AMPs) could play a promising role in fighting multidrug-resistant bacteria. Antimicrobial peptide polybia-CP was purified from the venom of the social waspPolybia paulista. In this study, we synthesized polybia-CP and studied its action mode of antibacterial activity. Our results revealed that polybia-CP has potent antibacterial activity against both Gram-positive and Gram-negative bacteria. The results from both the real bacterial membrane and thein vitromodel membrane showed that polybia-CP is membrane active and that its action target is the membrane of bacteria. It is difficult for bacteria to develop resistance to polybia-CP, which may thus offer a new strategy for defending against resistant bacteria in medicine and the food and farming industries.
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Smedsrud, Lars H., W. Paul Budgell, Alastair D. Jenkins y Bjørn Ådlandsvik. "Fine-scale sea-ice modelling of the Storfjorden polynya, Svalbard". Annals of Glaciology 44 (2006): 73–79. http://dx.doi.org/10.3189/172756406781811295.
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AbstractA polynya appears regularly in Storfjorden on the east side of the Svalbard archipelago. It is mainly forced by offshore winds and contributes around 10% of the brine water produced on Arctic shelves. We have applied a regional ocean model (ROMS), including a sea-ice model, on a fine grid (2 km) to simulate a full year of sea-ice growth and decay starting on 1 August 1999. This allows us to reproduce some key processes of the polynya opening and closing events during January–April 2000. The polynya remains open as long as the offshore winds exist, and reaches a width along the direction of the wind of 10–20 km. We suggest using a mean sea-ice thickness of <0.3m as the polynya criterion, as our simulations show varying strength in the horizontal gradients in sea-ice concentration and thickness. Results show a general freeze-up during December and January, with a mean polynya area during February–April within the fjord of 33 by 50 km, being 13% of the total fjord area. Some model results including sea-ice cover and drift speed can be partially validated using satellite imagery and field data, but in general are new measurements from the polynya interior needed to further improve the modelling of solid- and grease-ice processes.
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Ludwig, Valentin, Gunnar Spreen, Christian Haas, Larysa Istomina, Frank Kauker y Dmitrii Murashkin. "The 2018 North Greenland polynya observed by a newly introduced merged optical and passive microwave sea-ice concentration dataset". Cryosphere 13, n.º 7 (29 de julio de 2019): 2051–73. http://dx.doi.org/10.5194/tc-13-2051-2019.
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Abstract. Observations of sea-ice concentration are available from satellites year-round and almost weather-independently using passive microwave radiometers at resolutions down to 5 km. Thermal infrared radiometers provide data with a resolution of 1 km but only under cloud-free conditions. We use the best of the two satellite measurements and merge thermal infrared and passive microwave sea-ice concentrations. This yields a merged sea-ice concentration product combining the gap-free spatial coverage of the passive microwave sea-ice concentration and the 1 km resolution of the thermal infrared sea-ice concentration. The benefit of the merged product is demonstrated by observations of a polynya which opened north of Greenland in February 2018. We find that the merged sea-ice concentration product resolves leads at sea-ice concentrations between 60 % and 90 %. They are not resolved by the coarser passive microwave sea-ice concentration product. The benefit of the merged product is most pronounced during the formation of the polynya. Next, the environmental conditions during the polynya event are analysed. The polynya was caused by unusual southerly winds during which the sea ice drifted northward instead of southward as usual. The daily displacement was 50 % stronger than normal. The polynya was associated with a warm-air intrusion caused by a high-pressure system over the Eurasian Arctic. Surface air temperatures were slightly below 0 ∘C and thus more than 20 ∘C higher than normal. Two estimates of thermodynamic sea-ice growth yield sea-ice thicknesses of 60 and 65 cm at the end of March in the area opened by the polynya. This differed from airborne sea-ice thickness measurements, indicating that sea-ice growth processes in the polynya are complicated by rafting and ridging. A sea-ice volume of 33 km3 was produced thermodynamically.
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Steffen, Konrad. "Ice Conditions of an Arctic Polynya: North Water in Winter". Journal of Glaciology 32, n.º 112 (1986): 383–90. http://dx.doi.org/10.1017/s0022143000012089.
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AbstractThe surface condition of the North Water was investigated during two winters (i.e. the three polynyas: Smith Sound polynya, Lady Ann Strait polynya, and Barrow Strait polynya). Since no detailed information was available on ice conditions and the extent of open water during winter, radiometric temperature measurements of the sea surface had to be taken along a flight line of 2650 km from an altitude of 300 m. From November to March 1978-79 and 1980-81, 14 remote-sensing flights were carried out. On the basis of the radiometric measurements, the following ice types were identified: ice-free, dark nilas, light nilas, grey ice, grey-white ice, and white ice. A comparison between the thermal and the visual ice classification (the latter being based on grey tones of the aerial images) showed a deviation of 3%. The analysis showed that in November, December, and January more than 50% of the Smith Sound polynya was covered by young ice, nilas, and ice-free, whereas in February and March white ice was dominant. Moreover, it was found that the two polynyas in Smith Sound and Lady Ann Strait were much smaller than previously believed. In Barrow Strait, a semi-permanent polynya was observed in the winter of 1980-81. The occurrence of polynyas in Barrow Strait seems to be connected with the location of the fast-ice edge. On the basis of the calculated ice-type distribution and heat-flux rates for different ice types, an energy loss of 178 W m-2was found on the surface of the Smith Sound polynya due to open water and thin ice for the winter months November to March. Compared with other ice-covered sea surfaces in the Arctic, the heat release by the sea-water in the Smith Sound polynya is about 100 W m-2larger.
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Steffen, Konrad. "Ice Conditions of an Arctic Polynya: North Water in Winter". Journal of Glaciology 32, n.º 112 (1986): 383–90. http://dx.doi.org/10.3189/s0022143000012089.
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AbstractThe surface condition of the North Water was investigated during two winters (i.e. the three polynyas: Smith Sound polynya, Lady Ann Strait polynya, and Barrow Strait polynya). Since no detailed information was available on ice conditions and the extent of open water during winter, radiometric temperature measurements of the sea surface had to be taken along a flight line of 2650 km from an altitude of 300 m. From November to March 1978-79 and 1980-81, 14 remote-sensing flights were carried out. On the basis of the radiometric measurements, the following ice types were identified: ice-free, dark nilas, light nilas, grey ice, grey-white ice, and white ice. A comparison between the thermal and the visual ice classification (the latter being based on grey tones of the aerial images) showed a deviation of 3%. The analysis showed that in November, December, and January more than 50% of the Smith Sound polynya was covered by young ice, nilas, and ice-free, whereas in February and March white ice was dominant. Moreover, it was found that the two polynyas in Smith Sound and Lady Ann Strait were much smaller than previously believed. In Barrow Strait, a semi-permanent polynya was observed in the winter of 1980-81. The occurrence of polynyas in Barrow Strait seems to be connected with the location of the fast-ice edge. On the basis of the calculated ice-type distribution and heat-flux rates for different ice types, an energy loss of 178 W m-2 was found on the surface of the Smith Sound polynya due to open water and thin ice for the winter months November to March. Compared with other ice-covered sea surfaces in the Arctic, the heat release by the sea-water in the Smith Sound polynya is about 100 W m-2 larger.
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Fewou, Simon Ngamli, Iris Röckle, Herbert Hildebrandt y Matthias Eckhardt. "Transgenic overexpression of polysialyltransferase ST8SiaIV under the control of a neuron-specific promoter does not affect brain development but impairs exploratory behavior". Glycobiology 29, n.º 9 (30 de mayo de 2019): 657–68. http://dx.doi.org/10.1093/glycob/cwz040.
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Abstract A large body of the literature has demonstrated that the polysialic acid (polySia) modification of the neural cell adhesion molecule (NCAM) is a key regulator of cellular interactions during brain development, maintenance and plasticity. To properly fulfill these functions, polySia concentration has to be carefully controlled. This is done by the regulation of the expression of the two polySia-synthesizing enzymes ST8SiaII and ST8SiaIV. From this point of view we and others have demonstrated that downregulation of ST8SiaIV during oligodendrocyte differentiation is a prerequisite for efficient myelin formation and maintenance. Here, we addressed the question whether the prevention of polySia downregulation in neurons affects brain and particularly myelin development and functioning. For this purpose, we developed transgenic (tg) mouse lines overexpressing the polysialyltransferase ST8SiaIV in neurons. tg expression of ST8SiaIV prevented the postnatal downregulation of polySia, and most of the polySias in the forebrain and brain stem of adult tg mice were associated with NCAM-140 and NCAM-180 isoforms. Structural examination of the brain revealed no overt abnormalities of axons and myelin. In addition, ultrastructural and western blot analyses indicated normal myelin development. However, behavioral studies revealed reduced rearing activity, a measure for exploratory behavior, while parameters of motor activity were not affected in tg mice. Taken together, these results suggest that a persisting presence of polySia in neurons has no major effect on brain structure, myelination and myelin maintenance, but causes mild behavioral changes.
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Wilchinsky, Alexander V. y Daniel L. Feltham. "Generation of a Buoyancy-Driven Coastal Current by an Antarctic Polynya". Journal of Physical Oceanography 38, n.º 5 (1 de mayo de 2008): 1011–32. http://dx.doi.org/10.1175/2007jpo3831.1.
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Abstract Descent and spreading of high salinity water generated by salt rejection during sea ice formation in an Antarctic coastal polynya is studied using a hydrostatic, primitive equation three-dimensional ocean model called the Proudman Oceanographic Laboratory Coastal Ocean Modeling System (POLCOMS). The shape of the polynya is assumed to be a rectangle 100 km long and 30 km wide, and the salinity flux into the polynya at its surface is constant. The model has been run at high horizontal spatial resolution (500 m), and numerical simulations reveal a buoyancy-driven coastal current. The coastal current is a robust feature and appears in a range of simulations designed to investigate the influence of a sloping bottom, variable bottom drag, variable vertical turbulent diffusivities, higher salinity flux, and an offshore position of the polynya. It is shown that bottom drag is the main factor determining the current width. This coastal current has not been produced with other numerical models of polynyas, which may be because these models were run at coarser resolutions. The coastal current becomes unstable upstream of its front when the polynya is adjacent to the coast. When the polynya is situated offshore, an unstable current is produced from its outset owing to the capture of cyclonic eddies. The effect of a coastal protrusion and a canyon on the current motion is investigated. In particular, due to the convex shape of the coastal protrusion, the current sheds a dipolar eddy.
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Cheon, Woo Geun, Young-Gyu Park, J. R. Toggweiler y Sang-Ki Lee. "The Relationship of Weddell Polynya and Open-Ocean Deep Convection to the Southern Hemisphere Westerlies". Journal of Physical Oceanography 44, n.º 2 (1 de febrero de 2014): 694–713. http://dx.doi.org/10.1175/jpo-d-13-0112.1.
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Abstract The Weddell Polynya of the mid-1970s is simulated in an energy balance model (EBM) sea ice–ocean coupled general circulation model (GCM) with an abrupt 20% increase in the intensity of Southern Hemisphere (SH) westerlies. This small upshift of applied wind stress is viewed as a stand in for the stronger zonal winds that developed in the mid-1970s following a long interval of relatively weak zonal winds between 1954 and 1972. Following the strengthening of the westerlies in this model, the cyclonic Weddell gyre intensifies, raising relatively warm Weddell Sea Deep Water to the surface. The raised warm water then melts sea ice or prevents it from forming to produce the Weddell Polynya. Within the polynya, large heat loss to the air causes surface water to become cold and sink to the bottom via open-ocean deep convection. Thus, the underlying layers cool down, the warm water supply to the surface eventually stops, and the polynya cannot be maintained anymore. During the 100-yr-long model simulation, two Weddell Polynya events are observed. The second one occurs a few years after the first one disappears; it is much weaker and persists for less time than the first one because the underlying layer is cooler. Based on these model simulations, the authors hypothesize that the Weddell Polynya and open-ocean deep convection were responses to the stronger SH westerlies that followed a prolonged weak phase of the southern annular mode.
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Preußer, Andreas, Günther Heinemann, Sascha Willmes y Stephan Paul. "Circumpolar polynya regions and ice production in the Arctic: results from MODIS thermal infrared imagery from 2002/2003 to 2014/2015 with a regional focus on the Laptev Sea". Cryosphere 10, n.º 6 (15 de diciembre de 2016): 3021–42. http://dx.doi.org/10.5194/tc-10-3021-2016.
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Abstract. High-resolution MODIS thermal infrared satellite data are used to infer spatial and temporal characteristics of 17 prominent coastal polynya regions over the entire Arctic basin. Thin-ice thickness (TIT) distributions (≤ 20 cm) are calculated from MODIS ice-surface temperatures, combined with ECMWF ERA-Interim atmospheric reanalysis data in an energy balance model for 13 winter seasons (2002/2003 to 2014/2015; November to March). From all available MODIS swath data, daily thin-ice thickness composites are computed in order to derive quantities such as polynya area and total thermodynamic (i.e., potential) ice production. A gap-filling approach is applied to account for cloud and data gaps in the MODIS composites. All polynya regions combined cover an average thin-ice area of 226.6 ± 36.1 × 103 km2 in winter. This allows for an average total winter-accumulated ice production of about 1811 ± 293 km3, whereby the Kara Sea region, the North Water polynya (both 15 %), polynyas on the western side of Novaya Zemlya (20 %), as well as scattered smaller polynyas in the Canadian Arctic Archipelago (all combined 12 %) are the main contributors. Other well-known sites of polynya formation (Laptev Sea, Chukchi Sea) show smaller contributions and range between 2 and 5 %. We notice distinct differences to earlier studies on pan-Arctic polynya characteristics, originating in some part from the use of high-resolution MODIS data, as the capability to resolve small-scale (> 2 km) polynyas and also large leads are increased. Despite the short record of 13 winter seasons, positive trends in ice production are detected for several regions of the eastern Arctic (most significantly in the Laptev Sea region with an increase of 6.8 km3 yr−1) and the North Water polynya, while other polynyas in the western Arctic show a more pronounced variability with varying trends. We emphasize the role of the Laptev Sea polynyas as being a major influence on Transpolar Drift characteristics through a distinct relation between increasing ice production and ice area export. Overall, our study presents a spatially highly accurate characterization of circumpolar polynya dynamics and ice production, which should be valuable for future modeling efforts of atmosphere–ice–ocean interactions in the Arctic.
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Ito, Masato, Kay I. Ohshima, Yasushi Fukamachi, Daisuke Simizu, Katsushi Iwamoto, Yoshimasa Matsumura, Andrew R. Mahoney y Hajo Eicken. "Observations of supercooled water and frazil ice formation in an Arctic coastal polynya from moorings and satellite imagery". Annals of Glaciology 56, n.º 69 (2015): 307–14. http://dx.doi.org/10.3189/2015aog69a839.
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AbstractFormation of supercooled water and frazil ice was studied in the Chukchi Sea coastal polynya off Barrow, Alaska, USA, in winter 2009/10, using moored salinity/temperature sensors and Ice Profiling Sonar (IPS) data along with satellite data. Oceanographic data from two moorings revealed episodic events of potential supercooling at 30–40m depth, including the possibility of in situ supercooling, while the polynya was open. We identified frazil ice-like signals in the IPS data down to 5–15 m depth, associated with large heat loss and windy, turbulent conditions in an active polynya. This likely represents the first IPS observation of frazil ice in the marine environment. On the day of the maximum signal of frazil ice, spaceborne synthetic aperture radar shows streaks of high backscatter within the polynya, indicating active frazil ice formation just downwind of the mooring sites. In addition, the longer-term potential supercooling that persisted for 1–3 weeks occurred twice despite the absence of polynya activity at the mooring sites. These events occurred during periods dominated by the northeastward current. A series of coastal polynyas had formed southwest of the mooring sites prior to these events. Thus, the water masses with potential supercooling were likely advected from these polynyas.
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Lenman, Annasara, A. Manuel Liaci, Yan Liu, Lars Frängsmyr, Martin Frank, Bärbel S. Blaum, Wengang Chai et al. "Polysialic acid is a cellular receptor for human adenovirus 52". Proceedings of the National Academy of Sciences 115, n.º 18 (19 de abril de 2018): E4264—E4273. http://dx.doi.org/10.1073/pnas.1716900115.
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Human adenovirus 52 (HAdV-52) is one of only three known HAdVs equipped with both a long and a short fiber protein. While the long fiber binds to the coxsackie and adenovirus receptor, the function of the short fiber in the virus life cycle is poorly understood. Here, we show, by glycan microarray analysis and cellular studies, that the short fiber knob (SFK) of HAdV-52 recognizes long chains of α-2,8-linked polysialic acid (polySia), a large posttranslational modification of selected carrier proteins, and that HAdV-52 can use polySia as a receptor on target cells. X-ray crystallography, NMR, molecular dynamics simulation, and structure-guided mutagenesis of the SFK reveal that the nonreducing, terminal sialic acid of polySia engages the protein with direct contacts, and that specificity for polySia is achieved through subtle, transient electrostatic interactions with additional sialic acid residues. In this study, we present a previously unrecognized role for polySia as a cellular receptor for a human viral pathogen. Our detailed analysis of the determinants of specificity for this interaction has general implications for protein–carbohydrate interactions, particularly concerning highly charged glycan structures, and provides interesting dimensions on the biology and evolution of members ofHuman mastadenovirus G.
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Santos, Gilberto M. M., Jucelho D. da Cruz, Carlos C. Bichara Filho, Oton M. Marques y Cândida M. L. Aguiar. "Utilização de frutos de cactos (Cactaceae) como recurso alimentar por vespas sociais (Hymenoptera, Vespidae, Polistinae) em uma área de caatinga (Ipirá, Bahia, Brasil)". Revista Brasileira de Zoologia 24, n.º 4 (diciembre de 2007): 1052–56. http://dx.doi.org/10.1590/s0101-81752007000400023.
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Este estudo teve por objetivo identificar as espécies utilizadas como recurso alimentar e descrever os padrões locais de utilização de frutos de cactos como recurso alimentar por vespas sociais em uma área de Caatinga. Novecentos e oito indivíduos de nove espécies de vespas foram capturados visitando seis espécies de cactáceas. Cereus jamacaru DC. e Pilosocereus catingicola (Gurke) Byles & G.D foram as cactáceas mais utilizadas por vespas sociais, tanto em número de espécies quanto de indivíduos. Polybia paulista von Ihering, 1896, Polybia ignobilis (Haliday, 1836), Polistes versicolor (Olivier, 1791), Polistes simillimus Zikán, 1951, Polistes billardieri Fabricius, 1804, Polistes canadensis (Linnaeus, 1758), Polybia occidentalis (Olivier, 1791) e Polybia sericea (Olivier, 1705) apresentaram as maiores amplitudes de nicho trófico. As maiores sobreposições no nicho trófico foram observadas entre Mischocyttarus lanei Zikán, 1949 e Polistes simillimus Zikán, 1951 (0,83). Os altos níveis de sobreposição de nichos observados são explicados em função do comportamento generalista das vespas sociais, bem como da exploração intensiva de poucas espécies de cactáceas.
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Zanowski, Hannah, Robert Hallberg y Jorge L. Sarmiento. "Abyssal Ocean Warming and Salinification after Weddell Polynyas in the GFDL CM2G Coupled Climate Model". Journal of Physical Oceanography 45, n.º 11 (noviembre de 2015): 2755–72. http://dx.doi.org/10.1175/jpo-d-15-0109.1.
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AbstractThe role of Weddell Sea polynyas in establishing deep-ocean properties is explored in the NOAA Geophysical Fluid Dynamics Laboratory’s (GFDL) coupled climate model CM2G. Using statistical composite analysis of over 30 polynya events that occur in a 2000-yr-long preindustrial control run, the temperature, salinity, and water mass changes associated with the composite event are quantified. For the time period following the composite polynya cessation, termed the “recovery,” warming between 0.002° and 0.019°C decade−1 occurs below 4200 m in the Southern Ocean basins. Temperature and salinity changes are strongest in the Southern Ocean and the South Atlantic near the polynya formation region. Comparison of the model results with abyssal temperature observations reveals that the 1970s Weddell Polynya recovery could account for 10% ± 8% of the recent warming in the abyssal Southern Ocean. For individual Southern Ocean basins, this percentage is as little as 6% ± 11% or as much as 34% ± 13%.
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Shen, Xiaoyi, Chang-Qing Ke, Bin Cheng, Wentao Xia, Mengmeng Li, Xuening Yu y Haili Li. "Thinner Sea Ice Contribution to the Remarkable Polynya Formation North of Greenland in August 2018". Advances in Atmospheric Sciences 38, n.º 9 (24 de junio de 2021): 1474–85. http://dx.doi.org/10.1007/s00376-021-0136-9.
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AbstractIn August 2018, a remarkable polynya was observed off the north coast of Greenland, a perennial ice zone where thick sea ice cover persists. In order to investigate the formation process of this polynya, satellite observations, a coupled ice-ocean model, ocean profiling data, and atmosphere reanalysis data were applied. We found that the thinnest sea ice cover in August since 1978 (mean value of 1.1 m, compared to the average value of 2.8 m during 1978−2017) and the modest southerly wind caused by a positive North Atlantic Oscillation (mean value of 0.82, compared to the climatological value of −0.02) were responsible for the formation and maintenance of this polynya. The opening mechanism of this polynya differs from the one formed in February 2018 in the same area caused by persistent anomalously high wind. Sea ice drift patterns have become more responsive to the atmospheric forcing due to thinning of sea ice cover in this region.
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Starr, Christopher K. "First observations of a social wasp preying on termite workers". Sociobiology 64, n.º 2 (21 de septiembre de 2017): 225. http://dx.doi.org/10.13102/sociobiology.v64i2.1559.
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The social wasp Polybia quadricincta is observed preying opportunistically on workers of the termite Nasutitermes corniger in Trinidad, West Indies. Several Polybia spp. and other social wasps are known to prey on winged reproductive, but this appears to be the first report of any preying on workers.
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Dumont, Dany, Yves Gratton y Todd E. Arbetter. "Modeling Wind-Driven Circulation and Landfast Ice-Edge Processes during Polynya Events in Northern Baffin Bay". Journal of Physical Oceanography 40, n.º 6 (1 de junio de 2010): 1356–72. http://dx.doi.org/10.1175/2010jpo4292.1.
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Abstract A high-resolution sea ice–ocean numerical model of the North Water polynya has been developed to study the wind-driven circulation during polynya events. An idealized three-layer stratified ocean is used to initialize the model to characterize the baroclinic response to realistic wind and ice conditions. The model general circulation pattern is mainly forced by an along-channel sea level gradient between the Arctic Ocean and Baffin Bay, which determines the magnitude of the southward Baffin Current, and by an across-channel sea level gradient in Baffin Bay, which drives the northward West Greenland Current (WGC). These two currents are found to be anticorrelated to each other in the Smith Sound area. During strong northerly wind events, occurring quite frequently in the winter–spring period in the polynya, nutrient-rich Baffin Bay waters transported by the WGC are forced toward the Greenland shelf, coinciding with upwelling events along the Greenland coast. Whenever an ice bridge is present (i.e., the polynya exists and is substantially open), upwelling also occurs at the landfast ice edge. In such cases, the total upwelling area is increased by an amount that depends on the form of the ice bridge but could easily double during certain years. The baroclinic circulation associated with the upwelling response includes the formation of a cyclonic eddy attached to the ice edge that is generated during strong northerly wind events. Primary production estimations reveal that upwelling during polynya events plays a significant role in the early spring phytoplankton bloom, suggesting that the disappearance of the polynya as a result of climate change may have profound implications for the entire ecosystem.
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Massom, R. A., K. L. Hill, V. I. Lytle, A. P. Worby, M. J. Paget y I. Allison. "Effects of regional fast-ice and iceberg distributions on the behaviour of the Mertz Glacier polynya, East Antarctica". Annals of Glaciology 33 (2001): 391–98. http://dx.doi.org/10.3189/172756401781818518.
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AbstractAn observational account of research carried out in July-August 1999 shows that grounded iceberg and related fast-ice distributions, and periodic "break-outs" of fast ice (in winter as well as at other times), have an important impact on the size and behaviour of the Mertz Glacier polynya, East Antarctica, and a smaller polynya to the east. Analysis of satellite and in situ data shows that a semi-constant "stream" of thick broken-out fast ice and other large floes from the east extends westwards from north of the glacier terminus to form a compact barrier to the net west-northwesterly export of ice formed in the polynya. An annual fast-ice promontory to the west further narrows the outlet path. As a result of this and high ice-production rates, the polynya periodically "back-fills", significantly reducing the open-water area present. Intervening "flush-outs" by synoptic storm events clear the polynya region to some extent before it back-fills again. This cycle continued from mid-March until early October in 1999, when a significant change in the regional ice drift occurred. A preliminary comparison with data from 1998 indicates that the timing and magnitude of the processes may vary interannually. Similar morphological features were also observed in 1963 (on a declassified photoreconnaissance satellite image).
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Geyer, F., I. Fer y L. H. Smedsrud. "Structure and forcing of the overflow at the Storfjorden sill and its connection to the Arctic coastal polynya in Storfjorden". Ocean Science 6, n.º 1 (22 de marzo de 2010): 401–11. http://dx.doi.org/10.5194/os-6-401-2010.
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Abstract. Storfjorden (Svalbard) is a sill-fjord with an active polynya and exemplifies the dense water formation process over the Arctic shelves. Here we report on our simulations of Storfjorden covering the freezing season of 1999–2000 using an eddy-permitting 3-D ocean circulation model with a fully coupled dynamic and thermodynamic sea-ice model. The model results in the polynya region and of the dense water plume flowing over the sill crest are compared to observations. The connections of the overflow at the sill to the dense water production at the polynya and to the local wind forcing are investigated. Both the overflow and the polynya dynamics are found to be sensitive to wind forcing. In response to freezing and brine rejection over the polynya, the buoyancy forcing initiates an abrupt positive density anomaly. While the ocean integrates the buoyancy forcing over several polynya events (about 25 days), the wind forcing dominates the overflow response at the sill at weather scale. In the model, the density excess is diluted in the basin and leads to a gradual build-up of dense water behind the sill. The overflow transport is typically inferred from observations using a single current profiler at the sill crest. Despite the significant variability of the plume width, we show that a constant overflow width of 15 km produces realistic estimates of the overflow volume transport. Another difficulty in monitoring the overflow is measuring the plume thickness in the absence of hydrographic profiles. Volume flux estimates assuming a constant plume width and the thickness inferred from velocity profiles explain 58% of the modelled overflow volume flux variance and agrees to within 10% when averaged over the overflow season.
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Geyer, F., I. Fer y L. H. Smedsrud. "Structure and forcing of the overflow at the Storfjorden sill and its connection to the Arctic coastal polynya in Storfjorden". Ocean Science Discussions 7, n.º 1 (5 de enero de 2010): 17–49. http://dx.doi.org/10.5194/osd-7-17-2010.
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Abstract. The formation of deep and intermediate waters in the Arctic Ocean is primarily due to high salinity shelf waters sinking down the continental slopes. Storfjorden (Svalbard) is a sill-fjord with an active polynya and exemplifies the dense water formation process over the Arctic shelves. Here we report on our simulations of Storfjorden covering the freezing season of 1999–2000 using an eddy-permitting 3-D ocean circulation model with a fully coupled dynamic and thermodynamic sea-ice model. The model results in the polynya region and of the dense water plume flowing over the sill crest are compared to observations. The connections of the overflow at the sill to the dense water production at the polynya and to the local wind forcing are investigated. Both the overflow and the polynya dynamics are found to be sensitive to wind forcing. In response to freezing and brine rejection over the polynya, the buoyancy forcing initiates an abrupt positive density anomaly. While the ocean integrates the buoyancy forcing over several polynya events (about 25 days), the wind forcing dominates the overflow response at the sill at weather scale. In the model, the density excess is diluted in the basin and leads to a gradual build-up of dense water behind the sill. The overflow transport is typically inferred from observations using a single current profiler at the sill crest. Despite the significant variability of the plume width, we show that a constant overflow width of 15 km produces realistic estimates of the overflow volume transport. Another difficulty in monitoring the overflow is measuring the plume thickness in the absence of hydrographic profiles. Volume flux estimates assuming a constant plume width and the thickness inferred from velocity profiles explain 58% of the modelled overflow volume flux variance and agrees to within 10% when averaged over the overflow season.