Severe slugging phenomenon and a novel method for its mitigation based on the Surface Jet Pump technology

Master's thesis in Offshore technology : industrial asset managementThe present thesis is focused on the problem of severe slugging and ways to mitigate it. Severe slugging is an oscillatory multiphase flow regime characterized by high variations in production rates occurring in offshore pipeline-riser systems. Chapter 1 provides basic notions related to multiphase flow, which are essential for understanding of the rest of the thesis. Chapter 2 gives a thorough description of the severe slugging occurrence mechanism and preconditions as well as introduces different types of the phenomenon. Special attention is given to the effect of mass transfer and how it alters the flow regime’s behavior. Detrimental effects of severe slugging are discussed and some examples are provided. Chapter 3, making a significant part of the thesis, provides its reader with carefully gathered data concerning severe slugging alleviation and mitigation methods published from 1973 to 2015, both conventional and purely speculative methods are discussed. Examples, where possible, are given. Chapter 4 considers modeling of severe slugging in a vertical riser with aids of the multiphase simulation program OLGA. A constructed study case is considered and described with some of the mitigation techniques implemented and tested. Chapter 5 evaluates a novel severe slugging mitigation method proposed by Caltec Ltd. UK. The method assumes pipeline system depressurization by installation of a Surface Jet Pump on the production platform. The chapter gives the method description and verifies its feasibility using a simulation model within OLGA. The thesis ends with Conclusions and Recommendations for further work and self-evaluation

Molecular mechanisms of peripheral nerve regeneration: emerging roles of microRNAs

MicroRNAs are small non-coding RNAs that suppress gene expression through target mRNA degradation or translation repression. Recent studies suggest that miRNA plays an important role in multiple physiological and pathological processes in the nervous system. In this review article, we described what is currently known about the mechanisms in peripheral nerve regeneration on cellular and molecular levels. Recently, changes in microRNA expression profiles have been detected in different injury models, and emerging evidence strongly indicates that these changes promote neurons to survive by shifting their physiology from maintaining structure and supporting synaptic transmission towards a regenerative phenotype. We reviewed the putative mechanisms involved in miRNA mediated post-transcriptional regulation and pointed out several areas where future research is necessary to advance our understanding of how targeting miRNA machinery can be used as a therapeutic approach for treating nerve injuries

MicroRNA-431 regulates axon regeneration in mature sensory neurons by targeting the Wnt antagonist

MicroRNAs (miRNAs) are small, non-coding RNAs that function as key post-transcriptional regulators in neural development, brain function, and neurological diseases. Growing evidence indicates that miRNAs are also important mediators of nerve regeneration, however, the affected signaling mechanisms are not clearly understood. In the present study, we show that nerve injury-induced miR-431 stimulates regenerative axon growth by silencing Kremen1, an antagonist of Wnt/beta-catenin signaling. Both the gain-of-function of miR-431 and knockdown of Kremen1 significantly enhance axon outgrowth in murine dorsal root ganglion neuronal cultures. Using cross-linking with AGO-2 immunoprecipitation, and 3′-untranslated region (UTR) luciferase reporter assay we demonstrate miR-431 direct interaction on the 3′-UTR of Kremen1 mRNA. Together, our results identify miR-431 as an important regulator of axonal regeneration and a promising therapeutic target

Size effects in multiferroic BiFeO3 nanodots: A first-principles-based study

An effective Hamiltonian scheme is developed to investigate structural and magnetic properties of BiFeO3 nanodots under short-circuit-like electrical boundary conditions. Various striking effects are discovered. Examples include (a) scaling laws involving the inverse of the dots' size for the magnetic and electric transition temperatures; (b) the washing out of some structural phases present in the bulk via size effects; (c) the possibility of tailoring the difference between the Neel and Curie temperatures, by playing with the size and electrical boundary conditions; and (d) an universal critical thickness of the order of 1.6 nm below which the dots do not possess any long-range ordering for the electrical and magnetic dipoles, as well as, for the oxygen octahedral tiltings.Comment: 3 figure

Special Aspects of DC Air Plasma Torch’s Operating Modes under Turbulent Flow Conditions

The article is dedicated to the analysis of plasma flow turbulization processes inside DC air plasma torches. The influence of plasma torch’s arc current and plasma gas flow rate on plasma flow turbulization inside the torch channel is described. Also, measurements of voltage fluctuation due to motion of point of arc attachment are presented in the article. The mathematical model for the analysis of arc processes inside and outside of plasma torches is developed

Pharmaceutical Impact of the Different Ionization States of a Weakly Basic Drug within a Living Organism

Clofazimine (CFZ), an oral FDA-approved antibiotic for over 40 years, has been used effectively against leprosy and multi-drug resistant tuberculosis (MDR-TB). Due to its atypical pharmacokinetic parameters, orally administered CFZ free base is associated with extensive intracellular bioaccumulation of the solid drug, primarily in tissue macrophages, in a form of crystal-like drug inclusions (CLDIs) that chemically and structurally resemble CFZ hydrochloride salt (CFZ-HCl) crystals. These biocrystals are biocompatible, stable, long-lived, relatively non-toxic, and have anti-inflammatory properties. In this dissertation, I hypothesized that CFZ-HCl is a more therapeutically efficacious form of CFZ compared to CFZ free base that could be potentially used in the repurposing CFZ for other indications. To test this hypothesis, first, I established the physicochemical parameters of CFZ (e.g. pHmax, apparent pKa, CFZ-HCl aqueous solubility, CFZ free base intrinsic solubility, Ksp, etc.) that allowed me to understand the different ionization states of CFZ and their relationship to the drug’s physicochemical, pharmacokinetic, and pharmacodynamic properties. In fact, these physicochemical parameters explained the thermodynamic mechanism of differential stabilization and accumulation of the HCl salt form of CFZ in macrophage lysosomes. Based on this mechanism, I developed a specific buffer system that mimics the macrophage intralysosomal microenvironment, which ultimately helped me to determine that CFZ free base is associated with the major side effect from CFZ treatment, drug-induced skin pigmentation, that results from its partitioning into subcutaneous fat layer of the skin. Next, I developed a biomimetic formulation of CFZ drug biocrystals, micronized CFZ-HCl salt crystals, and investigated its stability in macrophages in vitro and in vivo. As a result, I determined that macrophages internalize and stabilize CFZ-HCl microcrystals, just as well as CLDIs, without any detectable toxicological effects. Furthermore, no skin pigmentation was observed when an equivalent total amount of CFZ-HCl to the total oral dose that causes maximal skin pigmentation was administered. Thus, parenteral biomimetic formulations of CFZ-HCl could be instrumental in avoiding the pigmentation side effect of oral CFZ therapy. Finally, I explored the inflammatory status and efficacy of my formulation of CFZ-HCl salt microcrystals in gouty arthritis under local administration in vivo, utilizing an FDA-recognized rat model. As a result, local injection of CFZ-HCl microcrystals led to the recruitment of macrophages to the site of action, a pro-inflammatory response, and did not facilitate the dissolution and clearance of monosodium urate (MSU) crystals from the joint, the main source of inflammation, by lowering the local pH of the synovium. Even though the results of this study suggested that my formulation is not suitable for gouty arthritis, further investigation is required to determine efficacy and anti-inflammatory action of my formulation in MDR-TB and other potential new indications. Overall, this dissertation augments the understanding of drug distribution and mechanism of action by effectively demonstrating how it is possible to distinguish the differential contribution of different ionization states of a drug (e.g. CFZ) to the drug’s efficacy and toxicity properties. Furthermore, this dissertation has advanced the rational design of formulations, in terms of being the first to develop a biomimetic form of a small molecule drug and demonstrating how the role of macrophages in determining the stability of biomimetic formulations can be probed.PHDPharmaceutical SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/149961/1/murashov_1.pd

Analysis of Electromagnetic Processes Inside the Arc Interrupting System of a High-current Circuit Breaker

Description of electromagnetic processes inside an arc interrupting system of high-current circuit breaker is presented in article. Non-stationary mathematical model of the circuit-breaker operation (short-circuit currents mode) is developed. The main regularities of the displacement of the electric arc inside an arc chute are established. The influence of the movable contact position on the conditions for the displacement of the electric arc is presented. Also, the influence of the arc chute material on the motion and interrupting of an electric arc (alternating and direct currents) is established

Information-Theoretical Technique for Optimizing Segmentation Quality

In this paper, a problem of image segmentation quality is considered. The problem of segmentation quality is viewed as selecting the best segmentation from a set of images generated by segmentation algorithm at different parameter values. A technique for selecting the best segmented image is proposed. Information redundancy measure is used as a criterion for optimizing segmentation quality. It is shown that proposed method for constructing the redundancy measure gives the extremal properties. Computing experiment confirmed that the segmented image corresponding to a minimum of redundancy measure produces the suitable dissimilarity when compared with the original image. The segmented image which was selected using the proposed criterion, gives the highest similarity with the ground-truth segmentations, available in the database.The research was supported in part by the Russian Foundation for Basic Research (grants No 15-07-09324 and No 15-0104671)