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Relations between mercury fractions and microbial community components in seawater under the presence and absence of probable phosphorus limitation conditions

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Journal of Environmental Sciences 2019年第1期31卷 145-162页

作者： igor ?ivkovi? Vesna Fajon Jo?e Kotnik Yaroslav Shlyapnikov Kristina Obu Vazner Ermira Begu Stefanija ?estanovi? Danijela ?anti? Ana Vrdoljak Slaven Jozi? Mladen ?oli? Jelena Lu?i? Jere Ve?a Grozdan Ku?pili? Marin Ordulj Frano Mati? Branka Grbec Natalia Bojani? ?ivana Nin?evi? Gladan Milena Horvat Department of Environmental Sciences Jo?ef Stefan Institute Jo?ef Stefan International Postgraduate School Ecological Engineering Institute Maribor 2000 Slovenia Laboratory of Marine Microbiology Institute of Oceanography and FisheriesSplit 21000 Croatia Laboratory of Chemical Oceanography and Sedimentology of the Sea Institute of Oceanography and FisheriesSplit 21000 Croatia Laboratory of Chemical Oceanography and Sedimentology of the Sea Institute of Oceanography and Fisheries Department of Marine Studies University of SplitSplit 21000 Croatia Laboratory of Physical Oceanography Institute of Oceanography and FisheriesSplit 21000 Croatia Laboratory of Plankton and Shellfish Toxicity Institute of Oceanography and FisheriesSplit 21000 Croatia

Microbial transformations of toxic monomethylmercury(MMHg) and dissolved gaseous mercury(DGM) at the lower levels of the marine food web are not well understood, especially in oligotrophic and phosphorus-limited seas. To examine the effects of probable phosphorus limitation(~PP-limitation) on relations between mercury(Hg) fractions and microorganisms, we determined the total mercury(THg), total methylated mercury(MeHg), DGM, and microbiological and chemical parameters in the Central Adriatic Sea. Using statistical analysis, we assessed the potential microbial effects on Hg transformations and bioaccumulation. Only in the absence of ~PP-limitation conditions(^(NO–P)P-limitation) is MeHg significantly related to most chemical and microbial parameters, indicating metabolism-dependent Hg transformations.The heterotrophic activity of low nucleic acid bacteria(abundant in oligotrophic regions)seems responsible for most of Hg methylation under ^(NO–P)P-limitation. Under these conditions,DGM is strongly related to microbial fractions and chlorophyll a, indicating biological DGM production, which is probably not metabolically induced, as most of these relations are also observed underPP-limitation. MMHg biomagnification was observed through an increased bioaccumulation factor from microseston to mesozooplankton. Our results indicate that Hgtransformations and uptake might be enhanced under ^(NO–P)P-limitation conditions, emphasizing their impact on the transfer of Hg to higher trophic levels.

关键词： Mercury speciation Methylmercury Probable phosphorus limitation Microbial community

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Improvement of the software for modeling the dynamics of epidemics and developing a user-friendly interface

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Infectious Disease Modelling 2023年第3期8卷 806-821页

作者： igor Nesteruk Institute of Hydromechanics National Academy of Sciences of UkraineKyivUkraine igor Sikorsky Kyiv Polytechnic Institute KyivUkraine

The challenges humanity is facing due to the Covid-19 pandemic require timely and accurate forecasting of the dynamics of various epidemics to minimize the negative consequences for public health and the economy.One can use a variety of well-known and new mathematical models,taking into account a huge number of factors.However,complex models contain a large number of unknown parameters,the values of which must be determined using a limited number of observations,e.g.,the daily datasets for the accumulated number of cases.Successful experience in modeling the COVID-19 pandemic has shown that it is possible to apply the simplest SIR model,which contains 4 unknown parameters.Application of the original algo-rithm of the model parameter identification for the first waves of the COVID-19 pandemic in China,South Korea,Austria,Italy,Germany,France,Spain has shown its high accuracy in pre-dicting their duration and number of diseases.To simulate different epidemic waves and take into account the incompleteness of statistical data,the generalized SIR model and algorithms for determining the values of its parameters were proposed.The interference of the previous waves,changes in testing levels,quarantine or social behavior require constant monitoring of the epidemic dynamics and performing SIR simulations as often as possible with the use of a user-friendly interface.Such tool will allow predicting the dynamics of any epidemic using the data on the number of diseases over a limited period(e.g.,14 days).It will be possible to predict the daily number of new cases for the country as a whole or for its separate region,to estimate the number of carriers of the infection and the probability of facing such a carrier,as well as to estimate the number of deaths.Results of three SIR simulations of the COVID-19 epidemic wave in Japan in the summer of 2022 are presented and discussed.The predicted accumulated and daily numbers of cases agree with the results of observations,especially for the simulation based on the datasets correspo

关键词： COVID-19 pandemic Epidemic waves Epidemic dynamics in Japan Mathematical modeling of infection diseases SIR model Parameter identification Statistical methods

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Shapes of the fastest fish and optimal underwater and floating hulls

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Theoretical & Applied Mechanics Letters 2022年第6期12卷 403-408页

作者： igor Nesteruk Institute of Hydromechanics National Academy of Sciences of UkraineNational Technical University of Ukraine“Igor Sikorsky Kyiv Polytechnic Institute”Ukraine

A streamlined shape of the best swimmers removes the boundary-layer separation and ensures a laminar flow pattern.The fastest fish have a very sharp convex nose(rostrum),the purpose of which remains unclear.The bodies of revolution similar to their shapes are analyzed in steady underwater and floating motion.The sources and sinks were located on the axis of symmetry and above the water surface to estimate the pressure on the body and the vertical velocities on the water surface.It was shown that the flow patterns on a special shaped body with concave nose has no stagnation points and ensure small values of the water surface elevation.These fact allow diminishing the maximum pressure on the surface and wave drag.Special shapes with the sharp concave nose and negative pressure gradients on their surface could be parts of the low drag underwater and floating hulls.

关键词： Drag reduction Wave drag Ship hulls optimization Unseparated shapes Water locomotion

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Central Asia—A Global Model for the Formation of Epigenetic Deposits in a Platform Sedimentary Cover

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Journal of Earth Science 2022年第2期33卷 278-288页

作者： igor Pechenkin Vladislav Petrov FSBI All-Russian Scientific-Research Institute of Mineral Resources MoscowRussia Institute of Geology of Ore Deposits Petrography Mineralogy and Geochemistry RAS MoscowRussia

Metallogenic specialization of sedimentary cover in Central Asia is determined by its tectonic setting that governs the hydrodynamic regime(exfiltrational or infiltrational)and as a consequence,the hydrogeochemical zonality(type of water and its gaseous and microcomponent composition).Hydrodynamic conditions(distribution of recharge and discharge areas)determine the direction of stratal water flow and location of mineralization resulted from the change in geochemical,thermodynamic,lithological,structural and other conditions.The exfiltrational regime suggests a dependence of the epigenetic mineralization upon the distribution and degree of preservation of hydrocarbon occurrences.Often,hydrocarbon matter serves as a reducing barrier and ore-concentrating factor during the formation of polymineral concentrations related to stratal oxidation zone.The supergene epigenetic ore-forming processes are induced by the interaction between the Earth’s sedimentary cover and hydrosphere.Sedimentary rocks themselves commonly serve as a source of ore materials.The ore deposition zones on geochemical barriers and ore material source are often located significantly apart from each other.The trend of these processes is determined by the position of ore-bearing depressions in large tectonic blocks.

关键词： Central Asia Kyzyl Kum Bukantau ore-forming systems epigenetic ore deposit geology

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Risk Assessment of a Stochastic Service System

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Journal of Systems Science and Systems Engineering 2020年第5期29卷 537-554页

作者： igor Lazov Faculty of Informatics European University Skopje1000 SkopjeMacedonia

A stochastic service system of finite size M is comprised of identical service facilities,including or not a waiting queue,which simultaneously treats N customers,N∈{0,1,…,M}.Depending on the concepts of system information z.and system entropy S=£(f),we promote a risk assessment procedure.By definition,the system entropy is the uncertainty associated with the system,and the system expected loss is the risk associated with the system.Thus,accepting the system information as loss function,we can identify risk and uncertainty,associated with the system,using the entropy as risk function.Further,we differ risk of the system(i.e.,risk observed by an outside observer),risk observed by an arriving customer,and risk observed by a departing customer,giving a separate expression for each one.Then,these risks are compared with each other,when the system has the same average number E(N)of customers seen by any viewpoint.The three risk types(together with the three customer means)allow us to distinguish two systems obeying the same probability distribution.This approach enables system operators to choose suitable values for system utilization and size,in view of the three risks ratio.The developed procedure is applied to the information linear system,Erlang loss system,single-server queueing system with discouraged arrivals,Binomial system and Engset loss system.

关键词： Absolute and relative risk uncertainty system information and entropy system utilization stochastic service system

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Output feedback control with disturbancecompensation in nonlinear MIMO systems undermeasurement noises

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Journal of Control and Decision 2022年第1期9卷 35-44页

作者： igor Furtat Pavel Gushchin Institute for Problems of Mechanical Engineering of the Russian Academy of Sciences(IPME RAS) St.-PetersburgRussia

A novel output feedback control law with disturbance compensation for nonlinear multiinputmulti-output (MIMO) time-invariant systems under measurement noises is proposed. Thedesigned control law, based on the noise and disturbance estimations, ensures the accuracy insteady state depending on the disturbance, only one component of noise vector and its firstderivatives. Therefore, the proposed algorithm is efficient under noises with large magnitudes.Sufficient conditions in terms of linear matrix inequalities (LMIs) provide a practical exponentialstability of the closed-loop system. The simulations illustrate an efficiency of the proposedmethod compared with some existing ones.

关键词： Nonlinear system disturbance measurement noise compensation S-procedure LMI

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New solutions for old challenges in glaucoma treatment:is taurine an option to consider?

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Neural Regeneration Research 2021年第5期16卷 967-971页

作者： igor Iezhitsa Renu Agarwal School of Medicine International Medical UniversityKuala LumpurMalaysia Volgograd State Medical University Research Centre for Innovative MedicinesVolgogradRussian Federation

Glaucoma is a range of progressive optic neuropathies characterized by progressive retinal ganglion cell loss and visual field defects.It is recognized as a leading cause of irreversible blindness affecting more than 70 million people worldwide.Currently,reduction of intraocular pressure,a widely recognized risk factor for glaucoma development,is the only pharmacological strategy for slowing down retinal ganglion cell loss and disease progression.However,retinal ganglion cell death and visual field loss have been observed in normotensive glaucoma,suggesting that the disease process is partially independent of intraocular pressure.Taurine is one of the agents that have attracted attention of researchers recently.Taurine has been shown to be involved in multiple cellular functions,including a central role as a neurotransmitter,as a trophic factor in the central nervous system development,as an osmolyte,as a neuromodulator,and as a neuroprotectant.It also plays a role in the maintenance of the structural integrity of the membranes and in the regulation of calcium transport and homeostasis.Taurine is known to prevent N-methyl-D-aspartic acid-induced excitotoxic injury to retinal ganglion cells.A recently published study clearly demonstrated that taurine prevents retinal neuronal apoptosis both in vivo and in vitro.Protective effect of taurine may be attributed to direct inhibition of apoptosis,an activation of brain derived neurotrophic factor-related neuroprotective mechanisms and reduction of retinal oxidative and nitrosative stresses.Further studies are needed to fully explore the potential of taurine as a neuroprotective agent,so that it can be applied in clinical practice,particularly for the treatment of glaucoma.The objective of current review was to summarize recent evidence on neuroprotective properties of taurine in glaucoma.

关键词： apoptosis excitotoxicity glaucoma oxidative and nitrosative stresses retinal neuroprotection taurine

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Arteriovenous malformations:the newest Sonic hedgehog game in the postnatal brain

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Neural Regeneration Research 2021年第5期16卷 996-998页

作者： igor Giarretta Roberto Pola Department of Translational Medicine and Surgery Fondazione Policlinico Universitario A.Gemelli IRCCSUniversitàCattolica del Sacro CuoreSchool of MedicineRomeItaly Department of Cardiovascular Sciences Fondazione Policlinico Universitario A.Gemelli IRCCSUniversitàCattolica del Sacro CuoreSchool of MedicineRomeItaly

The morphogen Sonic hedgehog(Shh)is crucial for the embryonic development of the central nervous system,but is also an important player in the postnatal brain,with activities that range from the modulation of self-renewal and specification of neural stem cells to the regulation of neural regeneration after injury.Active Shh signaling occurs also in molecular subclasses of brain tumors,such as medulloblastoma and adult glioma.

关键词： Shh neural venous

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Analytical model of 2D leakoff in waterflood-induced fractures

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1713-1733页

作者： igor Reznikov Dimitry Chuprakov Ilmir Bekerov Schlumberger Moscow Research MoscowRussia

Waterflood-induced fractures,also known as self-induced fractures,spontaneously form at injection wells during waterflooding.These fractures propagate long distances through rock,allowing injected fluids to travel far away from a well,both within and outside the flooding layer.Essentially,the me-chanics of waterflood-induced fracture propagation is similar to that of hydraulic fractures,which are intentionally created for reservoir stimulation.Fracturing models developed for hydraulic fractures can also be applied to waterflood-induced fractures.However,waterflood-induced fractures are typically pumped with much larger volumes of water or brine and grow much longer in time.As a result,fluid leakoff from waterflood fractures into the formation is more extensive and two-dimensional(2D),a characteristic that is often ignored in a majority of modern fracturing simulators,making their appli-cation to waterflood fractures unreliable.In this work,we revisit the problem of leakoff for long-growing waterflood-induced fractures and develop a new analytical model for fluid leakoff that provides improved predictions of fracture geometry and can be easily implemented in fracturing simulators.We incorporate the developed solution into the classical Perkins-Kern-Nordgren(PKN)model of fracture growth,which shows that the choice of the Carter or a 2D leakoff model greatly impacts fracture ge-ometry at large time.The conducted parametric study shows while a toughness-dominated regime af-fects fracture evolution,most of fracture lifetime occurs in a viscosity-and-leakoff-dominated regime.We also develop an asymptotic solution for a leakoff profile in the limiting case of 2D leakoff domination(~~M and~~K).Finally,we study 3D fracture growth and out-of-zone injection with three layers and a complex structure of zones.The study shows that ignoring the 2D leakoff during simulation results in a significant overestimation of fracture geometry predictions.The present work,thus,plays an important role in improving waterflood fracture model

关键词： Waterflooding Leakoff Analytical model Hydraulic fracturing Two-dimensional flow

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On character sums with determinants

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Science China Mathematics 2023年第12期66卷 2693-2714页

作者： Etienne Fouvry igor E.Shparlinski CNRS Laboratoire de Mathématiques d'OrsayUniversité Paris-SaclayOrsay 91405France School of Mathematics and Statistics University of New South WalesSydneyNSW 2052Australia

We estimate weighted character sums with determinants ad-bc of 2×2 matrices modulo a prime p with entries a,b,c and d vary ing over the interval [1,N].Our goal is to obtain non-trivial bounds for values of N as small as possible.In particular,we achieve this goal,with a power saving,for N≥p^(1/8+ε) with any fixed ε>0,which is very likely to be the best possible unless the celebrated Burgess bound is improved,By other techniques,we also treat more general sums but sometimes for larger values of N.

关键词： character sum determinant Burgess bound

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