4,495 research outputs found
Millennial Variability in an Idealized Ocean Model: Predicting the AMOC Regime Shifts
No full textA salient feature of paleorecords of the last glacial interval in the North Atlantic is pronounced millennial variability, commonly known as Dansgaard–Oeschger events. It is believed that these events are related to variations in the Atlantic meridional overturning circulation and heat transport. Here, the authors formulate a new low-order model, based on the Howard–Malkus loop representation of ocean circulation, capable of reproducing millennial variability and its chaotic dynamics realistically. It is shown that even in this chaotic model changes in the state of the meridional overturning circulation are predictable. Accordingly, the authors define two predictive indices which give accurate predictions for the time the circulation should remain in the on phase and then stay in the subsequent off phase. These indices depend mainly on ocean stratification and describe the linear growth of small perturbations in the system. Thus, monitoring particular indices of the ocean state could help predict a potential shutdown of the overturning circulation
E. S. Fedorov Promoting the Russian-German Scientific Interrelationship
No full textAt the dawn of crystal structure analysis, the close personal contact between researchers in Russia and Germany, well documented in the “Zeitschrift für Krystallographie und Mineralogie”, contributed significantly to the evolution of our present knowledge of the crystalline state. The impact of the Russian crystallographer E. S. Fedorov upon German scientists such as A. Schoenflies and P. Groth and the effect of these contacts for Fedorov are highlighted hundred years after the death of the latter. A creative exchange of ideas paved the way for the analysis of crystal structures with the aid of X-ray diffraction
Psettina multisquamea Fedorov & Foroshchuk 1988
No full textPsettina multisquamea Fedorov & Foroshchuk, 1988 (Fig. 8) Vopr. Ikhtiol., 28 (4): 532, figs. 1, 2. Current status: Psettina multisquamea Fedorov & Foroshchuk, 1988 Holotype: ZIN 45661 female, Indian Ocean, Saya de Malha Bank, 11 o 27′S, 61 o 35′E, 134 m, FV «Yel’sk», tr. 348, 03.01.1978, collector V.P.Foroshchuk. Paratype: ZIN 45662 (1) male, same data as that for the holotype.Published as part of Voronina, Elena P. & Volkova, Galina A., 2019, Annotated catalogue of type specimens of flatfishes (Osteichthyes: Pleuronectiformes) in the Zoological Institute, St. Petersburg, Russia, pp. 253-282 in Zootaxa 4695 (3) on pages 261-262, DOI: 10.11646/zootaxa.4695.3.2, http://zenodo.org/record/353256
Numerical solution of boundary value problems for second-order linear ordinary differential equations with a small parameter multiplying the highest derivative
No full textAn optimal numerical method for a singularly perturbed boundary value problem with a small parameter multiplying the higher order derivative
No full textA method for solving a class of one-dimensional boundary value problems for the reaction–diffusion equation with a small parameter multiplying the higher order derivative is proposed. The method is optimal in the sense that its approximation error is equal (up to a constant) to the lower esti-
mate of the n-width of the compact set consisting of weak (generalized) solutions to problems in the
class
The Leading, Interdecadal Eigenmode of the Atlantic Meridional Overturning Circulation in a Realistic Ocean Model
No full textVariations in the strength of the Atlantic meridional overturning circulation (AMOC) are a major potential source of decadal and longer climate variability in the Atlantic. This study analyzes continuous integrations of tangent linear and adjoint versions of an ocean general circulation model [Océan Parallélisé (OPA)] and rigorously shows the existence of a weakly damped oscillatory eigenmode of the AMOC centered in the North Atlantic Ocean and controlled solely by linearized ocean dynamics. In this particular GCM, the mode period is roughly 24 years, its e-folding decay time scale is 40 years, and it is the least-damped oscillatory mode in the system. Its mechanism is related to the westward propagation of large-scale temperature anomalies in the northern Atlantic in the latitudinal band between 30° and 60°N. The westward propagation results from a competition among mean eastward zonal advection, equivalent anomalous westward advection caused by the mean meridional temperature gradient, and westward propagation typical of long baroclinic Rossby waves. The zonal structure of temperature anomalies alternates between a dipole (corresponding to an anomalous AMOC) and anomalies of one sign (yielding no changes in the AMOC). Further, it is shown that the system is nonnormal, which implies that the structure of the least-damped eigenmode of the tangent linear model is different from that of the adjoint model. The “adjoint” mode describes the sensitivity of the system (i.e., it gives the most efficient patterns for exciting the leading eigenmode). An idealized model is formulated to highlight the role of the background meridional temperature gradient in the North Atlantic for the mode mechanism and the system nonnormality.<br/
Comment on 'The Imbert-Fedorov shift of paraxial light beams'
No full textHere I argue that Liu and Li [B.-Y. Liu, C.-F. Li, Opt. Commun. 281 (2008) 3427] reproduce calculations of the Imbert-Fedorov transverse shift previously made in a number of other works. However, it has recently been shown that these results are not valid for standard uniformly polarized beams. The corrected values of the Imbert-Fedorov shift were derived in papers [K.Y. Bliokh, Y.P. Bliokh, Phys. Rev. Lett. 96 (2006) 073903; Phys. Rev. E 75 (2007) 066609] and confirmed by recent measurements [O. Hosten, P. Kwiat, Science 319 (2008) 787] with a great accuracy
Prof. S.P. Fedorov — founder of urology in Russia (150th anniversary of the birthday)
No full textThis article presents the important scientific achievements of S.P. Fedorov as a urologist. S.P. Fedorov is the author of over 120 scientific papers. It was noted that in 1892 he was the first in Russia to prepare and use cholera antitoxin for the treatment of patients, then tetanus toxin and antitoxin, found that antitoxin protects against tetanus if it is administered simultaneously with the toxin. Abroad S.P. Fedorov studied the system of aseptic mode of operation from K. Schimmelbush, and L. Casper studied the method of cystoscopy and catheterization of the ureters and other endoscopic methods that appeared at that time. It was shown that S.P. Fedorov developed new surgeries — in situ pyelotomy, subcapsular nephrectomy, and new surgical instruments were proposed. He is rightly called the father of Russian urology. The circumstance is analyzed that the main direction of S.P. Fedorov's scientific activity was the problems of surgery of the urinary and biliary tracts. He summarized the extensive experience of the surgeon in the Atlas of Cystoscopy and Rectoscopy (1911), the Surgery of the Kidneys and Ureters (1923-1925), and others. Galpernom edition of the surgical journal «New Surgical Archive», essentially the first Soviet surgical journal, created in the difficult years of the Civil War and post-war devastation. He was the editor of the 1st edition of the BME, together with S.S. Girgolavom and A.V. Martynov was the editor of the multivolume Guide to Practical Surgery. S.P. Fedorov created a major domestic surgical school, from which dozens of specialists, heads of surgical departments of medical universities in various cities of the USSR graduated. The name of S.P. Fedorov was given to the department of hospital surgery of the Military Medical Academy. S.M. Kirov. It is noted that he was the first of the Soviet surgeons to be awarded the Order of Lenin (1933)
Solar Theory of Climate Change
No full textThe article presents an interview of the journal “Environmantal Earth and Energy Study” deputy editor-in-chief K. Degtyarev with the senior researcher of Laboratory for Geo-ecology ot the Northern Territories at Geographical Faculty of Lomonosov Moscow State University, PhD Valery Fedorov. The topic under discussion is theories and causes of global climate change. The author believes that the climate is changing, primarily due to natural causes, and puts forward a theory, which he called the Solar Theory of Climate Change (STCC)
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