Quantitative Susceptibility Imaging of Tissue Microstructure Using Ultra-High Field MRI

This thesis has used ultra-high field (UHF) magnetic resonance imaging (MRI) to investigate the fundamental relationships between tissue microstructure and such susceptibility-based contrast parameters as the apparent transverse relaxation rate (R2*), the local Larmor frequency shift (LFS) and quantitative volume magnetic susceptibility (QS). The interaction of magnetic fields with biological tissues results in shifts in the LFS which can be used to distinguish underlying cellular architecture. The LFS is also linked to the relaxation properties of tissues in a gradient echo MRI sequence. Equally relevant, histological analysis has identified iron and myelin as two major sources of the LFS. As a result, computation of LFS and the associated volume magnetic susceptibility from MRI phase data may serve as a significant method for in vivo monitoring of changes in iron and myelin associated with normal, healthy aging, as well as neurological disease processes. In this research, the cellular level underpinnings of the R2* and LFS signals were examined in a model rat brain system using 9.4 T MRI. The study was carried out using biophysical modeling and correlation with quantitative histology. For the first time, multiple biophysical modeling schemes were compared in both gray and white matter of excised rat brain tissue. Suprisingly, R2* dependence on tissue orientation has not been fully understood. Accordingly, scaling relations were derived for calculating the reversible, mesoscopic magnetic field component, R2\u27, of the apparent transverse relaxation rate from the orientation dependence in gray and white matter. Our results demonstrate that the orientation dependence of R2* and LFS in both white and cortical gray matter has a sinusoidal dependence on tissue orientation and a linear dependence on the volume fraction of myelin in the tissue. A susceptibility processing pipeline was also developed and applied to the calculation of phase-combined LFS and QS maps. The processing pipeline was subsequently used to monitor myelin and iron changes in multiple sclerosis (MS) patients compared to healthy, age and gender-matched controls. With the use of QS and R2* mapping, evidence of statistically significant increases in iron deposition in sub-cortical gray matter, as well as myelin degeneration along the white matter skeleton, were identified in MS patients. The magnetic susceptibility-based MRI methods were then employed as potential clinical biomarkers for disease severity monitoring of MS. It was demonstrated that the combined use of R2* and QS, obtained from multi-echo gradient echo MRI, could serve as an improved metric for monitoring both gray and white matter changes in early MS

Torsion free groups with indecomposable holonomy group I

We study the torsion free generalized crystallographic groups with the indecomposable holonomy group which is isomorphic to either a cyclic group of order ${p^s}$ or a direct product of two cyclic groups of order ${p}$.Comment: 22 pages, AMS-Te

Инженерно-геологическая характеристика долины реки Припять в пределах Республики Беларусь

The features of formation and spatial differentiation of engineering-geological conditions are considered. Genetic types of soil strata are identified as followed: alluvial, lake and marsh, water-glacial, moraine. Based on the analysis of physical and mechanical properties of soils, the assessment of their use as a basement for engineering structures was conducted. It is advised to use within the Pripyat River valley loamy, sandy and sandy sediments of different genesis as natural foundations for buildings the structures. It is noted that the widespread in this area marsh sediments are extremely undesirable to use as natural foundations.Рассмотрены особенности формирования и пространственной дифференциации инженерногеологических условий, выделены генетические типы грунтовых толщ: аллювиальные, озерные и болотные, водно-ледниковые, моренные. Проанализированы физико-механические свойства грунтов и дана оценка их использования как оснований инженерных сооружений. Определено, что в пределах речной долины Припяти целесообразно в качестве естественных оснований зданий и сооружений использовать суглинистые, супесчаные и песчаные отложения различного генезиса, а широко распространенные на изучаемой территории болотные отложения использовать в качестве естественных оснований крайне нежелательно

Synthesis of Capped AIIBVI Nanoparticles for Fluorescent Biomarkers

The conditions for growing CdS nanoparticles suitable for the visualization of biological tissues were theoretically studied and experimentally checked. The optimal ranges for pH values and precursors’ concentrations were determined. The applicability of the mercaptoethanol-capped nanoparticles for in vitro luminescence visualization of several cellular forms in histological specimens of human placenta has been prove

Retardation of nanoparticles growth by doping

The process of doping of CdS nanoparticles with Mn during colloidal synthesis is analyzed by EPR and optical studies. Analysis of EPR results demonstrated that Mn2+ ions are successfully incorporated into the nanoparticles and occupy the crystal sites both in the bulk of a NP and near the surface of a NP. Optical absorption measurements revealed the retardation of absorption edge shift during the growth for Mn-doped CdS NPs as compared to the undoped CdS NPs. It was concluded that the presence of Mn in the solution leads to the inhibition of NPs growth

Corrosion monitoring of transit gasmain pipelines

Розроблено та експериментально перевірено методику вивчення деформації та руйнування трубопровідних систем, встановлено закономірності корозійно-механічної деградації трубопроводів в основних типах ґрунтових електролітів. Для забезпечення безпеки транзитних трубопроводів розроблено та розпочато реалізацію комплексного методу корозійного моніторингу.Developed and experimentally verified a methodology study of deformation and destruction of pipeline systems, established patterns of corrosion-mechanical degradation of pipelines in the major soil types of electrolytes. To ensure the safety of transit pipelines developed and begun implementation of a comprehensive method of corrosion monitoring

Influence of parameters of delayed asphalt coking process on yield and quality of liquid and solid-phase products

Paper studies the effect of excess pressure during delayed coking of asphalt, obtained by propane deasphaltization of tar, on yield and physical and chemical properties of hydrocarbon fuels' components and solid-phase product – petroleum coke. Asphalt was coked at a temperature of 500 °C and excess pressure of 0.15-0.35 MPa in a laboratory unit for delayed coking of periodic action. Physical and chemical properties of raw materials and components of light (gasoline), medium (light gasoil), and heavy (heavy gasoil) distillates obtained during experimental study were determined: density, viscosity, coking ability, sulfur content, iodine number, pour points, flash points, fluidity loss and fractional composition. Quantitative group hydrocarbon and microelement compositions and properties of obtained samples of petroleum coke (humidity, ash content, volatiles' yield, sulfur content, etc.) were also studied. Comparative assessment of their quality is given in accordance with requirements of GOST 22898-78 “Low-sulfur petroleum coke. Specifications”. In addition, patterns of changes in excess coking pressure on yield and quality indicators of distillate products and petroleum coke were revealed. With an increase in excess pressure of coking process from 0.15 to 0.35 MPa, content of paraffin-naphthenic hydrocarbons in light and heavy gasoils of delayed coking  decreases. Common pattern in asphalt coking is an increase in yield of coke and hydrocarbon gas with an increase in excess pressure from 0.15 to 0.35 MPa