Distribution of trace elements in waters and sediments of the Seversky Donets transboundary watershed (Kharkiv region, Eastern Ukraine)

International audienceThis paper reports on the aquatic chemistry of trace elements in terms of spatial and temporal distribution, but also pollution sources in the transboundary watershed of the Seversky Donets River (Ukraine/Russia). Bed sediments and filtered water were collected from the Udy and Lopan Rivers at sites from the river source in the Belgorod region (Russia) to rural and urban areas in the Kharkiv region (Ukraine) in May and August 2009. Priority trace elements (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn), an urban tracer (Ag) and additional metals (Co, Mo, V) and Th were measured in stream water and sediments. The low levels and variability of Th-normalized concentrations indicated the absence of geochemical anomalies in the upstream part of the rivers and suggested that these data represent a regional baseline for trace elements in bed sediments. In contrast, water and sediments within the city of Kharkiv were contaminated by Ag, Pb, Cd, Cu, Cr and Zn, which are mainly attributed to municipal wastewater inputs and urban run-off. Results of the environmental quality assessment showed that element concentrations in the sediments can be considered as potentially toxic to aquatic organisms in sites downstream of the wastewater discharges

Designing Durable Vapor-Deposited Surfaces for Reduced Hydrate Adhesion

The formation and accumulation of clathrate hydrates inside oil and gas pipelines cause severe problems in deep-sea oil/gas operations. In the present work, durable and mechanically robust bilayer poly-divinyl benzene/poly(perfluorodecylacrylate) coatings are developed using initiated chemical vapor deposition (iCVD) to reduce the adhesion strength of hydrates to underlying substrates (silicon and steel). Tetrahydrofuran (THF) dissolved in water with a wt% concentration of 0–70 is used to study the formation of hydrates and their adhesion strength. Goniometric measurements of the THF–water droplets on the substrates exhibit a reduction in advancing and receding contact angles with an increase in the THF concentration. The strength of hydrate adhesion experiences a tenfold reduction when substrates are coated with these iCVD polymers: from 1050 ± 250 kPa on bare silicon to 128 ± 100 kPa on coated silicon and from 1130 ± 185 kPa on bare steel to 153 ± 86 kPa on coated steel. The impact of subcooling temperature and time on the adhesion strength of hydrate on substrates is also studied. The results of this work suggest that the THF–water mixture repellency of a given substrate can be utilized to assess its hydrate-phobic behavior; hence, it opens a pathway for studying hydrate-phobicity.Chevron Corporation (MIT-Chevron University Partnership Program

Noble gases and radiocarbon in natural gases

In samples of pure natural gas hydrates from Hydrate Ridge, Cascadia Margin, virtually no helium and neon components are present providing evidence that the light noble gases are not incorporated into the structure of natural methane hydrates. In contrast, the hydrates contain significant amounts of argon, krypton and xenon. These gases show a distinct fractionation pattern, with the heavier ones preferentially incorporated into the gas hydrate structure. The hydrate methane is devoid of 14C indicating that there is no contribution of a recent (14C-active) organic carbon reservoir to the hydrate carbon pool. On the basis of the δ13C and δ2H signature, it appears that microbial CO2-reduction is the dominant CH4 production pathway

Equilibrium conditions for semi-clathrate hydrates formed with CO2, N2 or CH4 in the presence of tri-n-butylphosphine oxide

We measured the thermodynamic stability conditions for the N, CO, or CH semiclathrate hydrate formed from the aqueous solution of tri-n-butylphosphine oxide (TBPO) at 26 wt %, corresponding to the stoichiometric composition for TBPO·34.5HO. The measurements were performed in the temperature range 283.71-300.34 K and pressure range 0.35-19.43 MPa with the use of an isochoric equilibrium step-heating pressure-search method. The results showed that the presence of TBPO made these semiclathrate hydrates much more stable than the corresponding pure N , CO, and CH hydrates. At a given temperature, the semiclathrate hydrate of 26 wt % TBPO solution + CH was more stable than that of 26 wt % TBPO solution + CO, which in turn was more stable than that of 26 wt % TBPO solution + N. We analyzed the phase equilibrium data using the Clausius-Clapeyron equation and found that, in the pressure range 0-20 MPa, the mean dissociation enthalpies for the semiclathrate hydrate systems of 26 wt % TBPO solution + N, 26 wt % TBPO solution + CO, and 26 wt % TBPO solution + CH were 177.75, 206.23, and 159.00 kJ·mol, respectively

Stoichometry and Stability of Molecular Clatrates

Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Управління капіталом у контексті забезпечення конкурентних переваг суб’єкта підприємницької діяльності роздрібної торгівлі

It has been proved that capital is a resource that is accumulated and is involved in the processes of reproduction and growth of value through mutual conversion of its various types, which are invested in the creation of assets, which is the total amount of financial resources of enterprises. It has been demonstrated that it is possible to determine the most rational ratio of capital indicators calculated on the basis of factors of influence, risks and practical experience that brings the target capital structure as close as possible to its optimal value. Given that the capital structure affects the market value of the enterprise through the price of capital, the concept of capital structure is studied in the same theoretical complex with the concepts of capital value and market value of the enterprise. The analysis has demonstrated that the first stage of optimizing the financial structure of enterprise’s capital as a specific object of anti-crisis retail business allows to determine the presence or absence of capital volume for a particular business entity. If the answer is positive, the optimization of the ratio of all sources of capital is carried out within this volume. If the available amount of capital is insufficient, it is necessary to find out whether the company has the opportunity to expand it and the sources to accomplish it. The second stage – assessing the capital structure by the criterion of financial stability – is carried out by comparing the actual values of the ratio of the current assets of business entities in retail trade in equity with the “normal” value, where its minimum level is 0.1. The capital structure is assessed during the third stage from the standpoint of the value of capital. Appropriate calculations are made by using the weighted average cost of capital of a business entity. The capital structure is evaluated during the fourth stage in terms of its efficiency. The basis for assessing the structure of capital by the criterion of its effectiveness is the calculation of the effect of financial leverage in previous periods and determining the impact of individual factors (return on assets, weighted average cost of debt, share of debt and equity) on this effect by using the method of chain substitutions regarding the weighted average cost of borrowed capital adjusted for the net operating result of the investment, the value of leased fixed assets, the amount of rent, as well as the share of financial loans, trade payables and long-term credit in the form of leased fixed assets in total borrowed capital. Finally, the target-oriented capital structure is formed during the fifth stage, taking into account the obtained results of optimization according to all the criteria and features of the components of capital and the factors that affect them. The fulfillment of this stage requires a thorough development of specific measures that should allow to form the necessary capital structure of the business entity in retail.Проанализированы общие особенности формирования и функционирования предпринимательского капитала. Рассмотрены основные этапы оптимизации финансовой структуры капитала предприятий как специфического объекта антикризисной предпринимательской деятельности розничной торговли. Охарактеризованы основные этапы оптимизации финансового потенциала как ключевого звена, приводящего вектор движения предпринимательской деятельности. Раскрыты основные элементы как минимизации затрат при реализации превентивных антикризисных мер, так и возможности противостоять конкурентным вызовам путем обновления системы производства. Показано, что практические пути реализации антикризисных мер являются приоритетными и решающими для определения степени жизнеспособности и перспектив развития субъекта, направленных на прирост его рыночной стоимости и наращивание финансовых резервов, которые позволят в будущем усилить защитные свойства.Проаналізовано загальні особливості формування та функціонування підприємницького капіталу. Обґрунтовано основні етапи оптимізації фінансової структури капіталу підприємств як специфічного об’єкта антикризової підприємницької діяльності роздрібної торгівлі. Надано характеристику фінансового потенціалу як ключової ланки, що зумовлює вектор руху підприємницької діяльності. Визначено основні елементи як мінімізації витрат під час реалізації превентивних антикризових заходів, так і можливості протистояти конкурентним викликам шляхом оновлення системи виробництва. Доведено, що практичні шляхи реалізації антикризових заходів є пріоритетними і вирішальними для визначення ступеня життєздатності та перспектив розвитку суб’єкта, спрямованих на зростання його ринкової вартості, зміцнення фінансової потужності та нарощування фінансових резервів, які дозволять у майбутньому посилити захисні властивості