We describe a
3
He magnetometer capable to measure high magnetic fields (
B
> 0.1 T) with a relative accuracy of better than 10
-12
. Our approach is based on the measurement of the free induction ...decay of gaseous, nuclear spin polarized
3
He following a resonant radio frequency pulse excitation. The measurement sensitivity can be attributed to the long coherent spin precession time T
2
∗
being of order minutes which is achieved for spherical sample cells in the regime of “motional narrowing” where the disturbing influence of field inhomogeneities is strongly suppressed. The
3
He gas is spin polarized in situ using a new, non-standard variant of the metastability exchange optical pumping. We show that miniaturization helps to increase T
2
∗
further and that the measurement sensitivity is not significantly affected by temporal field fluctuations of order 10
-4
.
Metastability exchange optical pumping (MEOP) is experimentally investigated in
3
He at 4.7 T, at room temperature and for gas pressures ranging from 1 to 267 mbar. The 2
3
S-2
3
P transition at 1083 ...nm is used for optical pumping and for detection of the laser-induced orientation of
3
He atoms in the rf discharge plasma. The collisional broadening rate is measured (12.0 ± 0.4 MHz mbar
−1
FHWM) and taken into account for accurate absorption-based measurements of both nuclear polarization in the ground state and atom number density in the metastable 2
3
S state. The results lay the ground for a comprehensive assessment of the efficiency of MEOP, by comparison with achievements at lower field (1 mT–2 T) over an extended range of operating conditions. Stronger hyperfine decoupling in the optically pumped 2
3
S state is observed to systematically lead to slower build-up of
3
He orientation in the ground state, as expected. The nuclear polarizations obtained at 4.7 T still decrease at high pressure but in a less dramatic way than observed at 2 T in the same sealed glass cells. To date, thanks to the linear increase in gas density, they correspond to the highest nuclear magnetizations achieved by MEOP in pure
3
He gas. The improved efficiency puts less demanding requirements for compression stages in polarized gas production systems and makes high-field MEOP particularly attractive for magnetic resonance imaging of the lungs, for instance.
High magnetic fields (> 1 T) are measured by NMR magnetometers with un-rivaled precision if the precessing spin sample provides long coherence times. The longest coherence times are found in diluted ...\({}^{3}\)He samples, which can be hyperpolarized for sufficient signal strength. In order to have minimal influence on the homogeneity and value of the measured magnetic field the optimal container for the \({}^{3}\)He should be a perfect sphere. A fused silica sphere with an inner diameter of 8 mm and an outer diameter of 12 mm was made from two hemispheres by diffusion bonding leaving only a small hole for cleaning and evacuation. This hole was closed in vacuum by a CO\({}_{2}\) laser and the inner volume was filled with a few mbars of \({}^3\)He via wall permeation. NMR-measurements on such a sample had coherence times of 5 min. While the hemispheres were produced with < 1 \(\mu\)m deviation from sphericity, the bonding left a step of ca. 50 \(\mu\)m at maximum. The influence of such a mismatch, its orientation and materials in the direct vicinity of the sample are analyzed by FEM-simulations and discussed in view of coherence times and absolute fields.
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages ...119-131).
The climate of North America reflects the natural variability of global atmospheric circulation, and is impacted by two primary anthropogenic forcings: increasing concentrations of greenhouse gases (GHG) and Land Use/Land Cover Change (LULC). The objective of this thesis is to quantify the relative impacts that these two anthropogenic forcings have had on summer climate over North America in the course of the 20th century. Simulations are conducted spanning the full 20th century over the United States to the east of the Rocky Mountains, and analysis of model simulations and observations is carried out with a focus on the Midwestern United States. This region has exhibited significant changes in climate from the early to late 20th century, and has been impacted not only by increasing GHG concentrations but by rapid and extensive agricultural LULC changes. These land use changes can be broken into three components: expansion of agriculture, expansion of irrigated cropland, and agricultural intensification in the form of linear productivity gains for corn and soybean. The simulations in this thesis use a modified version of the MIT Regional Climate Model (MRCM). New input data sets are used in order to represent contemporaneous and evolving lateral and surface boundary conditions. Studies in the past have shown a link between LULC changes and regional/local climate change, and in particular cropland-influenced climatic change in regions with high agricultural intensity. This thesis adopts an approach involving the application of long-term simulations of historic LULC evolution in conjunction with appropriate scenarios of GHG concentrations. Two sets of simulations are run using either ERA20C or CERA20C 20th century reanalysis data from the European Centre for Medium-Range Weather Forecasting. The simulations are conducted from 1900 or 1901 to 2005 based on data availability, at 30 km resolution on 18 vertical pressure levels. Analysis of changes from 1920-1949 to 1970-1999 show that in most cases, the regional climate impacts from vegetation development in the study area over this period outweigh the impacts from greenhouse gases, but in all variables except temperature, the combined impacts of LULC and GHG alone are not adequate to reproduce the observed climate changes. The analysis of background conditions points to the potentially strong impact of internal variability, and the strong influence that the assumed boundary conditions based on reanalysis data can impose on model results.
by Catherine Anna Nikiel.
S.M.
High-grade serous ovarian carcinoma (HGSOC) is the most frequent histological type of ovarian cancer and the one with worst prognosis. Unfortunately, the majority of established ovarian cancer cell ...lines which are used in the research have unclear histological origin and probably do not represent HGSOC. Thus, new and reliable models of HGSOC are needed. Ascitic fluid from a patient with recurrent HGSOC was used to establish a stable cancer cell line. Cells were characterized by cytogenetic karyotyping and short tandem repeat (STR) profiling. New generation sequencing was applied to test for hot-spot mutations in 50 cancer-associated genes and fluorescence in situ hybridization (FISH) analysis was used to check for
status. Cells were analyzed for expression of several marker genes/proteins by reverse-transcription polymerase chain reaction (RT-PCR), fluorescence-activated cell sorting (FACS), and immunocytochemistry (ICC). Functional tests were performed to compare OVPA8 cells with five commercially available and frequently used ovarian cancer cell lines: SKOV3, A2780, OVCAR3, ES2, and OAW42. Our newly-established OVPA8 cell line shows morphologic and genetic features consistent with HGSOC, such as epithelial morphology, multiple chromosomal aberrations,
mutation,
mutation, and loss of one copy of
. The OVPA8 line has a stable STR profile. Cells are positive for EpCAM, CK19, and CD44; they have relatively low plating efficiency/ability to form spheroids, a low migration rate, and intermediate invasiveness in matrigel, as compared to other ovarian cancer lines. OVPA8 is sensitive to paclitaxel and resistant to cisplatin. We also tested two FGFR inhibitors; OVPA8 cells were resistant to AZD4547 (AstraZeneca, London, UK), but sensitive to the new inhibitor CPL304-110-01 (Celon Pharma, Łomianki/Kiełpin, Poland). We have established and characterized a novel cell line, OVPA8, which can be a valuable preclinical model for studies on high-grade serous ovarian cancer.
Human protein Yin Yang 1 (YY1) controls the transcription of hundreds of genes both positively and negatively through interactions with a wide range of partner proteins. Results presented here from ...proteolytic sensitivity, calorimetry, circular dichroism, fluorescence, NMR, size-exclusion chromatography, SELEX, and EMSA show that purified YY1 forms dimers via its disordered N-terminal region with strong zinc-ion concentration dependence. The YY1 dimer is shown to bind tandem repeats of a canonical recognition DNA sequence with high affinity, and analysis of human YY1 regulatory sites shows that many contain repeats of its recognition elements. YY1 dimerization may compete with partner protein interactions, making control by zinc ion concentration a previously unrecognized factor affecting YY1 gene regulation. Indeed, YY1 is known to be important in many pathogenic processes, including neoplasia, in which zinc ion concentrations are altered. The present results incentivize studies in vivo or in vitro that explore the role of zinc ion concentration in YY1-mediated gene expression.
Display omitted
•YY1 binds selectively zinc ions to its intrinsically-disordered N-terminal domain.•Zinc binding leads to conformational changes in the YY1 protein.•Zinc binding leads to YY1 protein dimerization.•Zinc controls operator affinity of YY1 by mediating dimerization via its N-terminal region.
Traditional voice evaluations, including imaging techniques, auditory-perceptual ratings, and acoustic and aerodynamic analyses, fail to assess the global handicap that a patient experiences as a ...result of a voice disorder. The Voice Handicap Index (VHI) is currently one of the most widely used and psychometrically robust instruments for measuring voice disability. The aim of the study is to translate and validate a Polish version of the VHI. The original English-language version of VHI-30 was translated into Polish. We enrolled 188 subjects-123 patients (91 women and 32 men) with voice disorders and 65 controls (53 women and 12 men) without voice disorders. Results obtained by the patients were significantly higher than those obtained by the controls on the Emotional subscale (
= 519.0;
< 0.001), Functional (
= 829.0;
< 0.001), Physical (
= 331.0;
< 0.001), and the global score (
= 390.0;
< 0.001). There were statistically significant negative correlations between maximum phonation time and global score (
= -0.31;
< 0.01) as well as all three subscales. Shimmer and Smoothed Amplitude Perturbation Quotient were correlated positively with the global score (
= 0.22;
< 0.05;
= 0.25;
< 0.01, respectively) and with all three subscales. There were also statistically significant correlations between VHI scores and auditory perceptual evaluation. In the patient group, there was excellent internal consistency (α = 0.97) and strong test-retest reliability (intraclass correlation = 0.94). The cut-off value equal to 17 points was estimated. The Polish VHI showed excellent internal consistency, good test-retest reproducibility, and clinical validity. It is a useful tool for evaluating the voice disability perceived by a patient.
PDF
