Development of mathematical models to control the technological properties of cement slurries

Oil and gas producing enterprises are making increasingly high demands on well casing quality, including the actual process of injection and displacement of cement slurry, taking into account requirements for the annular cement level, eliminating possible hydraulic fracturing, with developing a hydraulic cementing program. It is necessary to prevent deep invasion of cement slurry filtrate into the formation to exclude bridging of productive layers. It is impossible to fulfill all these requirements at the same time without application of modifying additives; complex cement compositions are being developed and applied more often. Furthermore, need to adjust cement slurries recipes appears for almost every particular well. In order to select and justify cement slurries recipes and their prompt adjustment, taking into account requirements of well construction project, as well as geological and technical conditions for cementing casing strings, mathematical models of the main technological properties of cement slurries for cementing production casing strings in the Perm Region were developed. Analysis of the effect of polycarboxylic plasticizer (Pl) and a filtration reducer (fluid loss additive) based on hydroxyethyl cellulose (FR) on plastic viscosity (V), spreadability (S) and filtration (F) of cement slurries is conducted. Development of mathematical models is performed according to more than 90 measurements

Effect of C-terminal His-tag and Purification Routine on the Activity and Structure of the Metalloenzyme, L-alanyl-d-glutamate Peptidase of the Bacteriophage T5

In this work, we studied the effect of the C-terminally attached poly-histidine tag (His-tag), as well as the peculiarities of the protein purification procedure by the immobilized metal affinity chromatography (IMAC) on the activity and structure of the metalloenzyme, l-alanyl-d-glutamate peptidase of bacteriophage T5 (EndoT5), whose zinc binding site and catalytic aspartate are located near the C-terminus. By itself, His-tag did not have a significant effect on either activity or folding of the polypeptide chain, nor on the binding of zinc and calcium ions to the protein. However, the His-tagged EndoT5 samples had low shelf-life, with storage of these samples resulting in an increased propensity for protein self-association and decreased enzymatic activity of EndoT5. Furthermore, disastrous effects on the activity of the enzyme were exerted by the presence of imidazole and nickel ions accompanying metal chelate chromatography. The activity of the protein can be restored by thorough washing off of these low molecular impurities via the prolonged dialysis of the His-tagged EndoT5 samples at the specifically elaborated conditions

Компенсация высших гармоник и токов нейтральных проводников в трехфазных четырехпроводных сетях

Load unbalance and modern office equipment result in a significant neutral current in three-phase four-wire low-voltage power systems. This paper considers a new configuration of hybrid power filter for power quality management in three-phase four-wire low voltage power systems. The proposed hybrid filter is composed of a single-phase power converter and a three-phase passive filter connected in series. The hybrid filter can be operated in both passive and hybrid mode. The compensating performance of the filter is confirmed with computer simulation using MATLAB software. Analysis and simulation proved that the hybrid filter is an effective solution for neutral current mitigationСовременное офисное оборудование и несимметрия нагрузок являются основной причиной увеличения токов нейтральных проводников в трехфазных четырехпроводных сетях низкого напряжения. В статье рассмотрена новая конфигурация силового гибридного фильтра для управления качеством электроэнергии в трехфазных четырехпроводных сетях. Предложенный гибридный фильтр образован последовательным соединением трехфазного пассивного фильтра, настроенного на частоту доминирующей третьей гармоники, и однофазного инвертора. Фильтр может работать как в пассивном, так и в гибридном режиме. Компенсационные характеристики предложенного фильтра проанализированы с помощью моделирования в MATLAB. Анализ показал, что предложенный гибридный фильтр является эффективным средством ослабления гармоник и токов нейтральных проводнико

Компенсация высших гармоник и токов нейтральных проводников в трехфазных четырехпроводных сетях

Load unbalance and modern office equipment result in a significant neutral current in three-phase four-wire low-voltage power systems. This paper considers a new configuration of hybrid power filter for power quality management in three-phase four-wire low voltage power systems. The proposed hybrid filter is composed of a single-phase power converter and a three-phase passive filter connected in series. The hybrid filter can be operated in both passive and hybrid mode. The compensating performance of the filter is confirmed with computer simulation using MATLAB software. Analysis and simulation proved that the hybrid filter is an effective solution for neutral current mitigationСовременное офисное оборудование и несимметрия нагрузок являются основной причиной увеличения токов нейтральных проводников в трехфазных четырехпроводных сетях низкого напряжения. В статье рассмотрена новая конфигурация силового гибридного фильтра для управления качеством электроэнергии в трехфазных четырехпроводных сетях. Предложенный гибридный фильтр образован последовательным соединением трехфазного пассивного фильтра, настроенного на частоту доминирующей третьей гармоники, и однофазного инвертора. Фильтр может работать как в пассивном, так и в гибридном режиме. Компенсационные характеристики предложенного фильтра проанализированы с помощью моделирования в MATLAB. Анализ показал, что предложенный гибридный фильтр является эффективным средством ослабления гармоник и токов нейтральных проводнико

Molecularly Smooth Single-Crystalline Films of Thiophene–Phenylene Co-Oligomers Grown at the Gas–Liquid Interface

Single crystals of thiophene–phenelyne co-oligomers (TPCOs) have previously shown their potential for organic optoelectronics. Here we report on solution growth of large-area thin single-crystalline films of TPCOs at the gas–liquid interface by using solvent–antisolvent crystallization, isothermal slow solvent evaporation, and isochoric cooling. The studied co-oligomers contain identical conjugated core (5,5′-diphyenyl-2,2′-bithiophene) and different terminal substituents, fluorine, trimethylsilyl, or trifluoromethyl. The fabricated films are molecularly smooth over areas larger than 10 × 10 μm², which is of high importance for organic field-effect devices. The low-defect structure of the TPCO crystals is suggested from the monoexponential kinetics of the PL decay measured in a wide dynamic range (up to four decades) and from low crystal mosaicity assessed by microfocus X-ray diffraction. The TPCO crystal structure is solved using a combination of X-ray and electron diffraction. The terminal substituents affect the crystal structure of TPCOs, bringing about the formation of a noncentrosymmetric crystal lattice with a crystal symmetry <i>Cc</i> for the bulkiest trimethylsilyl terminal groups, which is unusual for linear conjugated oligomers. Comparing the different crystal growth techniques, it is concluded that the solvent–antisolvent crystallization is the most robust for fabrication of single-crystalline TPCOs films. The possible nucleation and crystallization mechanisms operating at the gas–solution interface are discussed