RF Studies for Ultrahigh Field MRI RF Coils and Arrays

Over the past few decades, different research groups have worked on different facets of Ultra-High Field (UHF) Magnetic Resonance Imaging (MRI); these developments culminated with the FDA approval of the first clinical 7 Tesla (T) MR scanner, Siemens MAGNETOM Terra in late-2017. MRI is still the preferred non-invasive multi-modal imaging technique for visualization of structural and functional correlates in-vivo and clinical diagnosis. Key issues with UHF MRI are in homogeneities in electric and magnetic fields as the size of imaged object becomes comparable with or larger than the radiofrequency (RF) wavelength. This inherent electromagnetic field inhomogeneity and elevated RF power deposition associated with UHF human imaging can have detrimental effects on the quality and safety in high field MRI. To address these challenges, the research work presented in this study 1) evaluated different cylindrical loop receive (Rx) array geometry to establish their effect on the transmit (Tx) coil RF fields. 2) performed detailed analysis, phantom and in-vivo, comparing the performance of the Tic Tac Toe (TTT) coil with a 16-element Transverse Electromagnetic (TEM) coil using multiple anatomical head models and in-vivo. The abovementioned areas of research included: Rx geometry model extraction from CAD models, and development of multiple anatomically detailed models and evaluation of MR coils simulations using full wave Maxwell's equations. Furthermore, an important part of the thesis work was bench marking of transmit coil performance for efficient and safe use in-vivo. The transmit arrays were tested for reproducibility, reliability and safe usage across multiple studies. Finite Difference Time Domain simulations of the Tx and composite of five head models were used to optimize parameters, to obtain homogenous whole brain excitation with low RF absorption or specific absorption rate (SAR)

A case report on penicillin/co-trimoxazole induced Jarisch Herxheimer reaction in secondary syphilis with human immunodeficiency virus

The Jarisch-Herxheimer reaction (JHR) typically occurs after the initiation of antibiotic treatment in syphilis. Although JHR was identified and looked at over many years, the prevention and management of JHR remain unclear. Previous reports have described the occurrence of JHR due to antibiotic treatment in syphilis, we presented a case of a young man with recurrence of JHR in syphilis, first due to penicillin which later was worsened due to co-trimoxazole

Bott--Kitaev periodic table and index theory

We consider topological insulators and superconductors with discrete symmetries and clarify the relevant index theory behind the periodic table proposed by Kitaev. An effective Hamiltonian determines the analytical index, which can be computed by a topological index. We focus on the spatial dimensions one, two and three, and only consider the bulk theory. In two dimensions, the $\mathbb{Z}$-valued invariants are given by the first Chern number. Meanwhile, $\mathbb{Z}_2$-valued invariants can be computed by the odd topological index and its variations. The Bott-Kitaev periodic table is well-known in the physics literature, we organize the topological invariants in the framework of KR-theory.Comment: 37 page

Restriction fragment length polymorphism of Mycobacterium tuberculosis strains from various regions of India, using direct repeat probe

Intraspecies differentiation was studied on 68 M. tuberculosis strains obtained from 6 states of India by restriction fragment length polymorphism (RFLP) using a direct repeat probe (DR probe) hybridised with Alu I digest of DNA. Most strains showed polymorphism based patterns that comprised between 2 to 7 bands and were grouped into 26 RFLP types. Of the 11 strains tested from Amritsar, 8 were RFLP type 5; the remaining 3 were of type 11 and were exclusively confined to this region. The strains from other regions were more heterogeneous. We confirm that DR-associated RFLP can be an excellent tool for the differentiation of M. tuberculosis strains. Depending on their geographical origin, these strains can be differentiated to a large extent by DR fingerprinting

Generation of energetic negative ions from clusters using intense laser fields

Intense laser fields are known to induce strong ionization in atoms. In nanoclusters, ionization is only stronger, resulting in very high charge densities that lead to Coulomb explosion and emission of accelerated highly charged ions. In such a strongly ionized system, it is neither conceivable nor intuitive that energetic negative ions can originate. Here we demonstrate that in a dense cluster ensemble, where atomic species of positive electron affinity are used, it is indeed possible to generate negative ions with energy and ion yield approaching that of positive ions. It is shown that the process behind such a strong charge reduction is extraneous to the ionization dynamics of single clusters within the focal volume. Normal and well-known charge transfer reactions are insufficient to explain the observations. Our analysis reveals the formation of a manifold of Rydberg excited clusters around the focal volume that facilitate orders of magnitudes more efficient electron transfer. This phenomenon, which involves an active role of laser-heated electrons, comprehensively explains the formation of copious accelerated negative ions from the nano-cluster plasma

Evaluation of ELISA as a diagnostic test in pulmonary tuberculosis

The reproducibility and ability of ELISA to discriminate patients with active disease from those infected were investigated.. The results obtained on 60 sputum-positive adult tuberculous patients and 60 adult control subjects showed groupwise discrimination. The anti-PPD antibodies (Ig G class) were significantly elevated in tuberculous patients as compared with control subjects. But because of the large day-to-day variation and considerable overlap in the distribution of antibody levels in tuberculous and control subjects, it is not possible to use ELISA as a diagnostic tool for adult pulmonary tuberculosis

Cell mediated immune response in South India pulmonary tuberculosis patients

Ninety-two untreated pulmonary tuberculosis (TB) patients and sixty two non-tuberculous (non-TB) controls drawn from the same socio-economic strata were studied for their delayed hypersensitivity (DH), cell mediated immunity (CMI) and bacillary-load. There was no correlation between bacillary load and response in parameters of CMI, namely, lymphocyte transformation test (LTT) and leucocyte migration inhibition test (LMI). Migration Index (MI) in LMI did not correlate with DH in TB patients. There was no significant difference in the mean values of MI between TB and non-TB control patients. Response of lymphocytes to mitogens and percentage of T-rosetting cells also did not differ between TB and non-TB control patients. On the contrary, differences were found in the two groups of patients with regard to lymphocyte response to PPD antigen and mean B-cell percentage. While, among non-TB patients. high Mantoux reactors had significantly higher LTT response to PPD compared to low Mantoux reactors: no such difference was observed among TB patients. The mean B-Cell percentage was significantly higher in TB patients than in non-TB controls. The relevance of these differences in relation to tuberculosis in discussed

Dual optimization method of radiofrequency and quasistatic field simulations for reduction of eddy currents generated on 7T radiofrequency coil shielding.

PURPOSE: To optimize the design of radiofrequency (RF) shielding of transmit coils at 7T and reduce eddy currents generated on the RF shielding when imaging with rapid gradient waveforms. METHODS: One set of a four-element, 2 × 2 Tic-Tac-Toe head coil structure was selected and constructed to study eddy currents on the RF coil shielding. The generated eddy currents were quantitatively studied in the time and frequency domains. The RF characteristics were studied using the finite difference time domain method. Five different kinds of RF shielding were tested on a 7T MRI scanner with phantoms and in vivo human subjects. RESULTS: The eddy current simulation method was verified by the measurement results. Eddy currents induced by solid/intact and simple-structured slotted RF shielding significantly distorted the gradient fields. Echo-planar images, B1+ maps, and S matrix measurements verified that the proposed slot pattern suppressed the eddy currents while maintaining the RF characteristics of the transmit coil. CONCLUSION: The presented dual-optimization method could be used to design RF shielding and reduce the gradient field-induced eddy currents while maintaining the RF characteristics of the transmit coil

Production of Lovastatin using Liquid Cheese Whey by Fusarium nectrioides (MH173849), an Endophytic Fungi Isolated from Euphorbia hirta

Lovastatin is a naturally produced 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase enzyme inhibitor- used for treating hypercholesterolemia. It was the first statin drug which was approved by the United States Food and Drug Administration (USFDA). In the current study, endophytic fungus Fusarium nectrioides (MH173849) isolated from Euphorbia hirta L. was used for the production of lovastatin. Four different culture media indicated as M1, M2, M3 and M4 were used for the initial production of lovastatin. Liquid cheese whey was used as nitrogen source. Growth morphology of fungi was investigated using Scanning Electron Microscopy analysis. Also, parameters like temperature, pH, inoculum size, incubation time, and RPM were optimized for the obtaining highest lovastatin production. Among the four media, M4 was found to produce the maximum concentration of lovastatin. Parameters such as temperature of 28°C, pH 6, RPM – 180 rpm and inoculum size of 5 x107 spores/mL were optimal for the production of lovastatin by F. nectrioides (MH173849)

Drivers of vaccine hesitancy among vulnerable populations in India: a cross-sectional multi-state study

ObjectivesIndia’s Covid-19 vaccination campaign engaged frontline workers (FLWs) to encourage vaccination among vulnerable segments of society. The FLWs report encountering a variety of barriers to vaccination and are often unsuccessful despite multiple visits to the same person. This cross-sectional study aims to pinpoint which of these barriers drive vaccine hesitancy among these segments, to help streamline vaccine communication, including FLW training, to better safeguard the population.MethodsTrained field enumerators contacted 893 individuals from five states across India and collected self-reported assessments of fifteen vaccination barriers (identified through discussions with FLWs), current vaccination status and future vaccination intentions, and covariates (demographics/comorbidities). Factor analysis of the fifteen barriers yielded two factors, one relating to fear of vaccine adverse effects and a second focused on peripheral concerns regarding the vaccine. The covariates significantly associated with current vaccination status were combined under a latent class regime to yield three cluster types (health access, financial strength, and demographics). The primary analysis examined the effect of the two barrier factors, the covariate clusters, and comorbidity, on current vaccination status and future vaccine intentions.ResultsFear of vaccine adverse effects was the primary driver of vaccine hesitancy; peripheral concerns frequently mentioned by the FLWs had no impact. Although cluster membership and the presence of comorbidities predicted vaccine uptake, neither of them materially altered the effect of fear of vaccine adverse effects with the following exception: fear of adverse effects was not associated with vaccination status among young Muslim men.ConclusionSubject to limitations, these results indicate that interventions to decrease vaccine hesitancy should focus primarily on fear associated with vaccines rather than spend resources trying to address peripheral concerns