Transient engine simulation program. NERVA program

IBM 7094 transient engine simulation program for NERV

Systematics in the Pb^(208)-Th^(232), Pb^(207)-U^(235), and Pb^(206)-U^(238) Systems

In a study of cogenetic zircons it was found that the measured Pb^(208)/Th^(232) and Pb^(207)/U^(235) ratios formed a linear array in the corresponding coupled Pb-U-Th evolution diagram, which has an upper intersection on the concordia curve at the same time point as that determined by the Pb^(206)/U^(238), Pb^(207)/U^(235) array. Although the U-Pb data lie in the accessible region for nonfractionating daughter loss, the Th-Pb results lie outside the corresponding region. The zircon concentrates analyzed were shown to be multiphase assemblages with variable U and Th contents and variable Th/U ratios, even within single crystals. The zircons contain local domains of high radioactivity which appear to be highly discordant. A relationship between discordance and the average concentration of U and Th in a sample is given. The degree of discordance increases with the concentration of U and Th and with the increasing Th/U ratio, causing preferential loss of Pb^(208) and the departure from the region accessible to a single phase without fractionation. The theoretical aspects of the (equation image) diagram from the viewpoint of single-phase and multiphase assemblages are discussed, and it is shown that the variability of the Th/U ratio is of fundamental importance in understanding the evolution of the Th-U-Pb system. The existence of these systematics in nature may provide an additional independent dating system and a further means of studying transport from natural systems

Polar coronal holes during the past solar cycle: Ulysses observations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95040/1/jgra20853.pd

Kinetic properties of heavy solar wind ions from Ulysses‐SWICS

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95282/1/grl20935.pd

Rapid Dynamics of Polyomavirus Type BK in Renal Transplant Recipients

BackgroundPolyomavirus type BK-associated nephropathy (PVAN) is an emerging cause of early renal transplant failure. No specific antiviral treatment has been established. Current interventions rely on improving immune functions by reducing immunosuppression. In patients with PVAN, a high BK virus (BKV) load is detectable in plasma. However, the relationship between BKV replication and disease is not well understood MethodsIn a retrospective analysis of BKV plasma load in renal transplant recipients undergoing allograft nephrectomy (n=3) or changes in immunosuppressive regimen (n=12), we calculated viral clearance rates and generation times and estimated the loss of BKV-infected renal cells ResultsAfter nephrectomy, BKV clearance was fast (viral half-life [t 1/2], 1-2 h) or moderately fast (t 1/2, 20-38 h), depending on the sampling density, but it was independent of continued immunosuppressive regimens. After changing immunosuppressive regimens, BKV was cleared with a t 1/2 of 6 h-17 days. Using the basic reproductive ratio, the efficacies of intervention ranged from 7% to 83% (mean, 28%; median, 22%) ConclusionThe results emphasize that high-level BKV replication is a major pathogenetic factor that may have implications for genome rearrangements, immune evasion, and antiviral resistanc

Oxygen flux in the solar wind: Ulysses observations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94605/1/grl27577.pd

2. Genotypes of merozoite surface protein 2 of Plasmodium falciparum in Tanzania

The merozoite surface protein 2 (MSP2) of Plasmodium falciparum is extremely polymorphic: 82 different msp2 alleles were found in 4 studies of molecular epidemiology conducted in Tanzania. This diversity renders msp2 suitable as a marker gene for the genotyping of P. falciparum infections. Amplification of msp2 by the polymerase chain reaction (PCR), and subsequent restriction digests of the PCR product (PCR-restriction fragment length polymorphism genotyping), has proved to be an informative tool for enumerating multiple concurrent infections in a blood sample, and distinguishing individual alleles. Depending on the specific questions asked in a genotyping study, analytical techniques of different degrees of complexity are employed. The restriction fragments resulting from a single HinfI digest generally allow the enumeration of multiple concurrent infections and the determination of their allelic families. When a restriction pattern is too complex to be resolved, owing to the high number of concurrent infections, or due to the appearance of previously undescribed alleles, one or more additional digests (DdeI, RsaI, ScrfI) may be necessary. To determine individual alleles unequivocally, in particular in longitudinal studies, when several consecutive samples need to be compared with each other, a more detailed analysis involving all 3 additional digests is applied. The methodological experience and results gained in 4 epidemiological field studies involving msp2 genotyping are summarized. We also provide the HinfI restriction patterns and some nucleotide sequences of the alleles found so far in our studies in Tanzani

Variations in solar wind fractionation as seen by ACE/SWICS over a solar cycle and the implications for Genesis Mission results

We use ACE/SWICS elemental composition data to compare the variations in solar wind fractionation as measured by SWICS during the last solar maximum (1999-2001), the solar minimum (2006-2009) and the period in which the Genesis spacecraft was collecting solar wind (late 2001 - early 2004). We differentiate our analysis in terms of solar wind regimes (i.e. originating from interstream or coronal hole flows, or coronal mass ejecta). Abundances are normalized to the low-FIP ion magnesium to uncover correlations that are not apparent when normalizing to high-FIP ions. We find that relative to magnesium, the other low-FIP elements are measurably fractionated, but the degree of fractionation does not vary significantly over the solar cycle. For the high-FIP ions, variation in fractionation over the solar cycle is significant: greatest for Ne/Mg and C/Mg, less so for O/Mg, and the least for He/Mg. When abundance ratios are examined as a function of solar wind speed, we find a strong correlation, with the remarkable observation that the degree of fractionation follows a mass-dependent trend. We discuss the implications for correcting the Genesis sample return results to photospheric abundances.Comment: Accepted for publication in Ap

A Unified Picture of the FIP and Inverse FIP Effects

We discuss models for coronal abundance anomalies observed in the coronae of the sun and other late-type stars following a scenario first introduced by Schwadron, Fisk & Zurbuchen of the interaction of waves at loop footpoints with the partially neutral gas. Instead of considering wave heating of ions in this location, we explore the effects on the upper chromospheric plasma of the wave ponderomotive forces. These can arise as upward propagating waves from the chromosphere transmit or reflect upon reaching the chromosphere-corona boundary, and are in large part determined by the properties of the coronal loop above. Our scenario has the advantage that for realistic wave energy densities, both positive and negative changes in the abundance of ionized species compared to neutrals can result, allowing both FIP and Inverse FIP effects to come out of the model. We discuss how variations in model parameters can account for essentially all of the abundance anomalies observed in solar spectra. Expected variations with stellar spectral type are also qualitatively consistent with observations of the FIP effect in stellar coronae.Comment: 25 pages, 4 figures, submitted to Ap