The role of cracks in the nonlinear interaction of a P-wave with an S-wave

Cracks play a key role in our ability to produce oil and gas, from micro-scalecracks that enable permeability in tight formations to faults and fractures that compartmentalize reservoirs; our ability to sense and understand them remotely is thus of key importance. We explore the role that cracks play in the nonlinear interaction of propagating waves. We present a laboratory experiment in which a strong S-wave slightly changes the velocity of a lower amplitude P-wave, and use a rock sample with aligned fractures to demonstrate that this signal is strongly dependent on fracture orientation. We build on the linear slip theory to show that the propagating S-wave is indeed able to open the cracks that the P-wave velocity will be most sensitive to. This gives firm, direct evidence that cracks are a controlling factor in the nonlinear elastic properties of rocks, and opens up the possibility of using such signals to remotely map fracture orientations

Analytical approach to electromagnetic processes in loosely bound nuclei: application to 8B

In this paper we develop an analytical model in order to study electromagnetic processes involving loosely bound neutron--rich and proton--rich nuclei. We construct a model wave function, to describe loosely bound few--body systems, having the correct behaviour both at large and small distances. The continuum states are approximated by regular Coulomb functions. As a test case we consider the two--body Coulomb dissociation of 8B and, the inverse, radiative capture reaction. The difference between using a pure two--body model and the results obtained when incorporating many--body effects, is investigated. We conclude that the interpretation of experimental data is highly model dependent and stress the importance of measuring few--body channels.Comment: Accepted for publication in Physics Letters B. Added a comparison with a potential model calculation in Fig.

Experience gained at the Ural Turbine Works with retrofitting steam turbine units for thermal power stations

Examples of projects on retrofitting, modernizing, and renovating steam turbine units at thermal power stations implemented with participation of the Ural Turbine Works are given. Advanced construction and layout solutions were used in implementing these projects both on the territory of Russia and abroad. © 2013 Pleiades Publishing, Ltd

Steam turbines produced by the Ural Turbine Works for combined-cycle plants

The most interesting and innovative solutions adopted in the projects of steam turbines for combined-cycle plants with capacities from 115 to 900 MW are pointed out. The development of some ideas and components from the first projects to subsequent ones is shown. © 2013 Pleiades Publishing, Ltd

The effect of crack orientation on the nonlinear interaction of a P wave with an S wave

Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presence and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal

ПАРАТИРЕОИДЭКТОМИЯ У КРЫС С ИСПОЛЬЗОВАНИЕМ МИКРОХИРУРГИЧЕСКОЙ ТЕХНИКИ И МЕДИЦИНСКОГО КЛЕЯ «СУЛЬФАКРИЛАТ»

Background: One of the main difficulties in assessing the effectiveness of etiologic treatment of hypoparathyroidism is absence of its standardized model. Objective: The aim of the study was to develop a method of hypoparathyroidism modeling. Methods: Controlled nonrandomized study was performed on female Wistar rats aged 10 month. Group 1 (n =14) was performed with destruction of parathyroid glands with electrocoagulation; group 2 (n =12) — parathyroidectomy by the developed method. In 3 and 14 days after the surgery the levels of ionized calcium, parathyroid hormone, number of white blood cells, blood leukocyte formula, indicators of immunological tests, histological examination of organs in the area of operations were performed. Statistical analysis was performed using the nonparametric Mann–Whitney-Wilcoxon test. Results: Selection of animals by sex and age criteria, angular skin incision, use of the operating microscope, microsurgical techniques, extirpation of parathyroid glands via resection of thyroid gland with the closure of the wound defect glue appeared to be the distinctive features of the developed method. In 14 days the group 2 showed decrease in ionized calcium (p =0.016), PTH (p =0.094), leucocytes (p =0.004), PI (р =0.003), spontaneous NBT test (р =0,004), induced NBT test (р =0.003) compared with group 1. Histological examination in the group 2 revealed no changes in thyroid gland, thin connective tissue capsule, cavity with a small amount of glue, however, there were determined foci of necrosis with perifocal inflammation in the group 1. Conclusion: Combination of several techniques allowed to simulate metabolic disorders with persistent hypocalcemia as well as lack of mortality in early postoperative period. Одной из сложностей в оценке эффективности этиотропного лечения послеоперационного гипопаратиреоза является отсутствие его стандартизированной общепринятой модели. Цель исследования: разработать способ моделирования гипопаратиреоза, включающий паратиреоидэктомию с использованием микрохирургической техники и визуальным контролем объема удаляемой ткани, минимальной травматизацией щитовидной железы и применением нового клея у крыс, с оценкой эффективности предложенных приемов. Методы: контролируемое нерандомизированное исследование выполнено на крысах-самках линии Wistar десятимесячного возраста. В группе 1 (n =14) выполняли разрушение околощитовидных желез при помощи электрокоагуляции, в группе 2 (n =12) – паратиреоидэктомию разработанным способом. Через 3 и 14 сут после операции исследовали содержание ионизированного кальция, паратиреоидного гормона в сыворотке крови, подсчитывали число лейкоцитов, лейкоцитарную формулу, показатели иммунологических тестов первого уровня в венозной крови, гистологические изменения тканей в области операции. При статистическом анализе использовали непараметрические тесты Манна–Уитни, Вилкоксона. Результаты: отличительными приемами разработанного способа явились отбор животных по полу и возрасту, формирование косынкообразного кожного лоскута при доступе, использование операционного микроскопа и микрохирургической техники, экстирпация околощитовидных желез путем резекции ткани щитовидной железы с закрытием раневого дефекта клеем. Через 14 сут в группе 2 по сравнению с группой 1 зафиксировано снижение концентрации ионизированного кальция (p =0,016), паратиреоидного гормона (p =0,094),уменьшение общего числа лейкоцитов (p =0,004), фагоцитарного индекса (р =0,003), ответа в спонтанном. (р =0,004) и индуцированном тесте восстановления нитросинего тетразолия (р =0,003). В области операции в группе 2 определялась щитовидная железа с сохраненными фолликулами, формировалась «тонкая» соединительнотканная капсула, полость с небольшим количеством клея, при этом в группе 1 определялись очаги некроза с перифокальным воспалением. Заключение: сочетание нескольких приемов позволило смоделировать метаболические нарушения при гипопаратиреозе со стойкой гипокальциемией, отсутствием летальности в раннем послеоперационном периоде.

Polymeric drift control adjuvants for agricultural spraying

The movement of a pesticide or herbicide to an off-target site during agricultural spraying can cause injury to wildlife, plants and contamination of surface water. This phenomenon is known as spray drift and can be controlled by spraying during favorable environmental conditions, and by using low drift nozzles and drift control adjuvants (DCAs). Polymeric DCAs are the most common type of DCA and function by increasing the droplet size produced during spraying. There are, however, two main drawbacks of polymeric DCAs; they are prone to mechanical degradation during spraying which reduces their performance and they can produce oversized drops which reduces the efficacy of the spray. In this trend article, existing DCA technology is reviewed including the mechanism through which they function. This then provides a platform for the discussion of novel polymeric architectures which have currently not been applied in DCA formulations

Thermo-oxidative degradation of additive free polyethylene. Part I. Analysis of chemical modifications at molecular and macromolecular scales

The effects of thermal oxidation on the molecular and macromolecular structures of additive free PE were investigated between 100°C and 140°C in air in order to tentatively establish non-empirical structure/property relationships. In the first part, the changes in POOH concentration were assessed by three different analytical methods: iodometry, modulated differential scanning calorimetry, and Fourier transform infrared (FTIR) spectrophotometry after SO2 treatment. All these methods provided very similar results until the end of the induction period, after which iodometry overestimated strongly POOH concentration because it titrates also other chemical species formed at high conversion ratios, namely double bonds. In parallel, the changes in carbonyl group concentration were determined by FTIR spectrophotometry after NH3 treatment. As the accumulation kinetics of ketones, aldehydes, and carboxylic acids were closely interrelated, the question of their actual formation mechanisms in the current thermal oxidation mechanistic scheme was raised. An alternative reaction pathway was proposed for the bimolecular decomposition of POOH. In the second part, the corresponding changes in weight and number average molecular masses were monitored by high temperature gel permeation chromatography equipped with a triple detection technology. As both quantities decreased dramatically from the beginning of exposure and their ratio Mw/Mn tends toward the asymptotic value of 2 and it was concluded that a "pure" chain scission process operated. Finally, as the number of chain scissions perfectly correlates, the concentration sum of aldehydes and their oxidation products (i.e., carboxylic acids), it was also concluded that these carbonyl groups result exclusively from the β scission of alkoxy radicals