Convection-reaction equation based magnetic resonance electrical properties tomography (cr-MREPT)

Cataloged from PDF version of article.Images of electrical conductivity and permittivity of tissues may be used for diagnostic purposes as well as for estimating local specific absorption rate distributions. Magnetic resonance electrical properties tomography (MREPT) aims at noninvasively obtaining conductivity and permittivity images at radio-frequency frequencies of magnetic resonance imaging systems. MREPT algorithms are based on measuring the B1 field which is perturbed by the electrical properties of the imaged object. In this study, the relation between the electrical properties and the measured B1 field is formulated for the first time as a well-known convection-reaction equation. The suggested novel algorithm, called “cr-MREPT,” is based on the solution of this equation on a triangular mesh, and in contrast to previously proposed algorithms, it is applicable in practice not only for regions where electrical properties are relatively constant but also for regions where they vary. The convective field of the convection-reaction equation depends on the spatial derivatives of the B1 field, and in the regions where its magnitude is low, a spot-like artifact is observed in the reconstructed electrical properties images. For eliminating this artifact, two different methods are developed, namely “constrained cr-MREPT” and “double-excitation cr-MREPT.” Successful reconstructions are obtained using noisy and noise-free simulated data, and experimental data from phantoms

Measurement of the Nitric Oxide Altitude Distribution in the Mid-Latitude Mesosphere

A simple rocket-borne system has been developed for deriving nitric oxide concentration in the mesosphere from measurements of resonantly scattered solar ultraviolet radiation in the NOg ammbaa nd near 2150 •. The NO signal is extracted from a background of Rayleigh-scattered light by a direct measurement of this scattered light by use of an NO absorption cell. This system was utilized to measure the NO concentration above White Sands, New Mexico, in the altitude range from 69 to 101 km. The derived NO profile shows a concentration of about 3 x 10 7 cm-3 at 67 and 100 km with a deep valley (more than an order of magnitude less) at about 84 km. Comparison with model calculations indicates that the time constant for NO chemistry is smaller than or comparable with that for transpor

International Nonregimes: A Research Agenda1

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146934/1/j.1468-2486.2007.00672.x.pd

Origins of the Ambient Solar Wind: Implications for Space Weather

The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress -- in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue connected with a 2016 ISSI workshop on "The Scientific Foundations of Space Weather." 44 pages, 9 figure

Association between the choice of the conditioning regimen and outcomes of allogeneic hematopoietic cell transplantation for myelofibrosis

Allogeneic hematopoietic cell transplantation (allo-HCT) remains the only curative treatment for myelofibrosis. However, the optimal conditioning regimen either with reduced intensity conditioning (RIC) or myeloablative conditioning (MAC) is not well known. Using the Center for International Blood and Marrow Transplant Research database, we identified adults aged ≥18 years with myelofibrosis undergoing allo-HCT between 2008-2019 and analyzed the outcomes separately in the RIC and MAC cohorts based on the conditioning regimens used. Among 872 eligible patients, 493 underwent allo-HCT using RIC (Fludarabine/busulfan=166, Fludarabine/melphalan=327) and 379 using MAC (Fludarabine/busulfan=247, Busulfan/cyclophosphamide=132). In multivariable analysis with RIC, Fludarabine/melphalan was associated with inferior overall survival (HR 1.80, 95% CI 1.15-2.81, p=0.009), higher early non-relapse mortality (HR 1.81, 95% CI 1.12-2.91, p=0.01) and higher acute graft versus host disease (GVHD) (grade II-IV- HR 1.45, 95% CI 1.03-2.03, p=0.03; grade III-IV HR 2.21, 95%CI 1.28-3.83, p=0.004) compared to Fludarabine/busulfan. In the MAC setting, Busulfan/cyclophosphamide was associated with a higher acute GVHD (grade II-IV HR 2.33, 95% CI 1.67-3.25, p\u3c0.001; grade III-IV HR 2.31, 95% CI 1.52-3.52, p\u3c0.001) and inferior GVHD-free relapse-free survival (GRFS) (HR 1.94, 95% CI 1.49-2.53, p\u3c0.001) as compared to Fludarabine/busulfan. Hence, our study suggests that Fludarabine/busulfan is associated with better outcomes in RIC (better overall survival, lower early non-relapse mortality, lower acute GVHD) and MAC (lower acute GVHD and better GRFS) in myelofibrosis

Hematopoietic Cell Transplantation Outcomes in Monosomal Karyotype Myeloid Malignancies

The presence of monosomal karyotype (MK+) in acute myeloid leukemia (AML) is associated with dismal outcomes. We evaluated the impact of MK+ in AML (MK+AML, N=240) and in myelodysplastic syndrome (MK+MDS, N=221) on hematopoietic cell transplantation (HCT) outcomes compared to other cytogenetically defined groups (AML, N=3,360; MDS, N=1,373) as reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) from 1998 to 2011. MK+AML was associated with higher disease relapse (hazard ratio [HR] 1.98, p<0.01), similar transplant related mortality (TRM, HR 1.01, p=0.9) and worse survival (HR 1.67, p<0.01) compared to other cytogenetically defined AML. Among patients with MDS, MK+MDS was associated with higher disease relapse (HR 2.39, p<0.01), higher TRM (HR 1.80, p<0.01) and worse survival (HR 2.02, p<0.01). Subset analyses comparing chromosome 7 abnormalities (del7/7q) with or without MK+ demonstrated higher mortality for MK+ disease in for both AML (HR 1.72, p<0.01) and MDS (HR1.79, p<0.01). The strong negative impact of MK+ in myeloid malignancies was observed in all age groups and using either myeloablative or reduced intensity conditioning regimens. Alternative approaches to mitigate disease relapse in this population are needed

The Mutational Landscape in Chronic Myelomonocytic Leukemia and Its Impact on Allogeneic Hematopoietic Cell Transplantation Outcomes: A Center for Blood and Marrow Transplantation Research (CIBMTR) Analysis

Somatic mutations are recognized as an important prognostic factor in chronic myelomonocytic leukemia (CMML). However, limited data are available regarding their impact on outcomes after allogeneic hematopoietic cell transplantation (HCT). In this registry analysis conducted in collaboration with the Center for International Blood and Marrow Transplantation Registry database/sample repository, we identified 313 adult patients with CMML (median age: 64 years, range, 28- 77) who underwent allogeneic HCT during 2001-2017 and had an available biospecimen in the form of a peripheral blood sample obtained prior to the start of conditioning. In multivariate analysis, a CMML-specific prognostic scoring system (CPSS) score of intermediate-2 (HR=1.46, P=0.049) or high (HR=3.22, P=0.0004) correlated significantly with overall survival. When the molecularly informed CPSS-Mol prognostic model was applied, a high CPSS-Mol score (HR=2 P=0.0079) correlated significantly with overall survival. The most common somatic mutations were in ASXL1 (62%), TET2 (35%), KRAS/NRAS (33% combined), and SRSF2 (31%). DNMT3A and TP53 mutations were associated with decreased overall survival (HR=1.70 [95% CI: 1.11-2.60], P=0.0147 and HR=2.72 [95% CI: 1.37-5.39], P=0.0042, respectively) while DNMT3A, JAK2, and TP53 mutations were associated with decreased disease-free survival (HR=1.66 [95% CI: 1.11-2.49], P=0.0138, HR=1.79 [95% CI: 1.06-3.03], P=0.0293, and HR=2.94 [95% CI: 1.50-5.79], P=0.0018, respectively). The only mutation associated with increased relapse was TP53 (HR=2.94, P=0.0201). Nonetheless, the impact of TP53 mutations specifically should be interpreted cautiously given their rarity in CMML. We calculated the goodness of fit measured by Harrell\u27s C-index for both the CPSS and CPSS-Mol, which were very similar. In summary, via registry data we have determined the mutational landscape in patients with CMML who underwent allogeneic HCT, and demonstrated an association between CPSS-Mol and transplant outcomes although without major improvement in the risk prediction beyond that provided by the CPSS

Introduction to the special issue on the statistical mechanics of climate

We introduce the special issue on the Statistical Mechanics of Climate by presenting an informal discussion of some theoretical aspects of climate dynamics that make it a topic of great interest for mathematicians and theoretical physicists. In particular, we briefly discuss its nonequilibrium and multiscale properties, the relationship between natural climate variability and climate change, the different regimes of climate response to perturbations, and critical transitions