Noxious and other bad weeds of Iowa

Within the past 15 years weeds have come to be recognized as the cause of one of the most important losses suffered by American farmers. Experiment station and extension workers, farmers, weed commissioners, insurance companies and farm credit agencies, chambers of commerce and others either directly or indirectly dependent on agriculture have become aroused by the menace of an increased dissemination of noxious weeds. In Iowa weeds cause a loss of many millions of dollars annually. They crowd out desirable crops, rob them of plant food and moisture, act as hosts for insects and disease-producing organisms of crops, poison or injure livestock, depreciate land values and cause extra labor in cultivation; thus they increase the cost of food production

Our Iowa Weed Laws

If all of us were good stewards of our land, we wouldn\u27t need weed laws. But experience has shown that we do need them, and the state legislature has provided them. Here\u27s how they work

Non-Equilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind \textit{(Invited Review)}

We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of high-energy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modelling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for detection of these non-equilibrium phenomena in various spectral ranges.Comment: Solar Physics, accepte

Interactions of Uranium and Neptunium With Cementitious Materials Studied by XAFS

We have investigated the interaction of U(VI) and Np(V) actinide ions with cementitious materials that are relevant to nuclear waste repositories using X-Ray Absorption Fine Structure (XAFS) Spectroscopy. The actinide ions were individually loaded onto untreated as well as hydrothermally treated cements. The mixtures were then equilibrated at varying pH's for a period of approximately 6 months. In all cases uranium was introduced in the form of aqueous uranyl ion, UO{sub 2}{sup 2+}, and was observed to remain in this form based on the Near Edge (XANES) spectra. The uranium samples show evidence of interactions with both treated and untreated cements at all pH's, with uranyl interacting with the cement mineral phases (i.e., SiO{sub 2}) through an inner-sphere mechanism where oxygen atoms in the equatorial plane of the uranyl ion are shared with the mineral surface. In contact with the hydrothermally treated cement, the uranyl ions are also observed to form oligomeric species, proving that hydrothermal treatment of the concrete has a significant effect on the structural bonding characteristics of uranyl on the concrete. Neptunium was introduced as the neptunyl ion, NpO{sub 2}{sup +}, and was observed to undergo a reduction from Np(V) to Np(IV). Percent reduction was calculated from both component analysis of the XANES region and by curve fitting to the EXAFS region. Results from both methods were in good agreement and showed ca. 15% of Np(V) is reduced to Np(IV) in the fresh sample. In comparison, the other samples showed higher reduction rates of between 40% and 65%. Reduction was thus observed to occur over a relatively slow time scale based on XAFS data collected from a ''fresh'' sample (aged for 1 month). No Np-Np interactions were observed in the EXAFS spectra which makes surface precipitation of Np{sup 4+} phases an unlikely mechanism for sorption

Bright X-ray flares in Orion young stars from COUP: evidence for star-disk magnetic fields?

We have analyzed a number of intense X-ray flares observed in the Chandra Orion Ultradeep Project (COUP), a 13 days observation of the Orion Nebula Cluster (ONC). Analysis of the flare decay allows to determine the size, peak density and magnetic field of the flaring structure. A total of 32 events (the most powerful 1% of COUP flares), have sufficient statistics for the analysis. A broad range of decay times (from 10 to 400 ks) are present in the sample. Peak flare temperatures are often very high, with half of the flares in the sample showing temperatures in excess of 100 MK. Significant sustained heating is present in the majority of the flares. The magnetic structures which are found, are in a number of cases very long, with semi-lengths up to 10^12 cm, implying the presence of magnetic fields of hundreds of G extending to comparable distance from the stellar photosphere. These very large sizes for the flaring structures ($ >> R_*) are not found in more evolved stars, where, almost invariably, the same type of analysis results in structures with L <= R_*. As the majority of young stars in the ONC are surrounded by disks, we speculate that the large magnetic structures which confine the flaring plasma are actually the same type of structures which channel the plasma in the magnetospheric accretion paradigm, connecting the star's photosphere with the accretion disk.Comment: Accepted to ApJS, COUP special issu

Relationship between dielectric properties and critical behavior of the electric birefringence in binary liquid mixtures

We present experimental results on the critical exponent ψEKE describing the divergence of the Kerr constant of binary liquid mixtures near the critical consolute point. We show that the measured value of ψEKE agrees with the theoretical prediction only if the measurement is performed with a mixture of two liquids presenting a small mismatch in the dielectric constant, and that the measured ψEKE grows as the dielectric constant mismatch increases. Such findings are consistent with a recent model which assumes that the elongation of critical fluctations along the direction of the electric field can become so strong that fluctuations in the direction perpendicular to the electric field may cross over from Ising to mean-field behavior

Cytotoxic polyfunctionality maturation of cytomegalovirus-pp65-specific CD4 + and CD8 + T-cell responses in older adults positively correlates with response size

Cytomegalovirus (CMV) infection is one of the most common persistent viral infections in humans worldwide and is epidemiologically associated with many adverse health consequences during aging. Previous studies yielded conflicting results regarding whether large, CMV-specific T-cell expansions maintain their function during human aging. In the current study, we examined the in vitro CMV-pp65-reactive T-cell response by comprehensively studying five effector functions (i.e., interleukin-2, tumor necrosis factor-α, interferon-γ, perforin, and CD107a expression) in 76 seropositive individuals aged 70 years or older. Two data-driven, polyfunctionality panels (IL-2-associated and cytotoxicity-associated) derived from effector function co-expression patterns were used to analyze the results. We found that, CMV-pp65-reactive CD8 + and CD4 + T cells contained similar polyfunctional subsets, and the level of polyfunctionality was related to the size of antigen-specific response. In both CD8 + and CD4 + cells, polyfunctional cells with high cytotoxic potential accounted for a larger proportion of the total response as the total response size increased. Notably, a higher serum CMV-IgG level was positively associated with a larger T-cell response size and a higher level of cytotoxic polyfunctionality. These findings indicate that CMV-pp65-specific CD4 + and CD8 + T cell undergo simultaneous cytotoxic polyfunctionality maturation during aging

UV-induced ligand exchange in MHC class I protein crystals

High-throughput structure determination of protein−ligand complexes is central in drug development and structural proteomics. To facilitate such high-throughput structure determination we designed an induced replacement strategy. Crystals of a protein complex bound to a photosensitive ligand are exposed to UV light, inducing the departure of the bound ligand, allowing a new ligand to soak in. We exemplify the approach for a class of protein complexes that is especially recalcitrant to high-throughput strategies: the MHC class I proteins. We developed a UV-sensitive, “conditional”, peptide ligand whose UV-induced cleavage in the crystals leads to the exchange of the low-affinity lytic fragments for full-length peptides introduced in the crystallant solution. This “in crystallo” exchange is monitored by the loss of seleno-methionine anomalous diffraction signal of the conditional peptide compared to the signal of labeled MHC β2m subunit. This method has the potential to facilitate high-throughput crystallography in various protein families