Diversity of mycorrhizal plant species and arbuscular mycorrhizal fungi in evergreen forest, deciduous forest and grassland ecosystems of Southern Chile

In the Valdivian rainforest region of the Southern Chilean Andes three main ecosystems are found: Primary evergreen forests, secondary deciduous forests, and grassland areas. The secondary forest and the grasslands are habitually the result of the clearance of the primary forest some 60 years ago. The secondary forest consists mainly of the deciduous tree species Nothofagus alpina; forest management practices such as crown thinning and clearance of the understorey are applied to the secondary forest to improve its economic value. The grasslands are used by extensive cattle grazing. Soils in this region are acid Andosols with high organic matter content, high exchangeable aluminum and low levels of available phosphorus. The main objective of this study was to investigate the diversity of arbuscular mycorrhizal (AM) plant species and of arbuscular mycorrhizal fungi (AMF) in these three ecosystems. The highest diversity with 53 plant species was found in the evergreen forest with 77.4% of them AM, while in the grassland 91% of the 22 plant species were AM. The deciduous forest had 11 plant species only and the lowest proportion of AM plant species (55%). Thirty-nine AM fungal species were found in total, of which most are being reported for the first time from Southern Chile. Thirteen fungal species were of the Acaulospora genus, 10 of Glomus, 4 species each of Scutellospora and Archaeospora, 3 species each of Pacispora and Entrophospora, and one species each of Paraglomus and Diversispora. AMF species were more abundant in the grassland (29 spp.) than in the evergreen forest (20 spp.) which is likely related to a higher relative proportion of AM plant species in the grassland. Four AMF species were present in all the ecosystems, and 15 species were apparently quite specific as they were only found in one of the ecosystems. Noteworthy was the lack of Paraglomus and Scutellospora spp. in any of the forest ecosystems, and the relatively higher presence of Entrophospora spores in those ecosystems. It was concluded that the diversity of the AMF species in the ecosystems is strongly influenced by the proportion of AM plant species in each ecosystem and that their diversity is not related to soil chemical properties

Temperature dependence of the diffuse scattering fine structure in equiatomic CuAu

The temperature dependence of the diffuse scattering fine structure from disordered equiatomic CuAu was studied using {\it in situ} x-ray scattering. In contrast to Cu$_3$Au the diffuse peak splitting in CuAu was found to be relatively insensitive to temperature. Consequently, no evidence for a divergence of the antiphase length-scale at the transition temperature was found. At all temperatures studied the peak splitting is smaller than the value corresponding to the CuAuII modulated phase. An extended Ginzburg-Landau approach is used to explain the temperature dependence of the diffuse peak profiles in the ordering and modulation directions. The estimated mean-field instability point is considerably lower than is the case for Cu$_3$Au.Comment: 4 pages, 5 figure

The RMS Charge Radius of the Proton and Zemach Moments

On the basis of recent precise measurements of the electric form factor of the proton, the Zemach moments, needed as input parameters for the determination of the proton rms radius from the measurement of the Lamb shift in muonic hydrogen, are calculated. It turns out that the new moments give an uncertainty as large as the presently stated error of the recent Lamb shift measurement of Pohl et al.. De Rujula's idea of a large Zemach moment in order to reconcile the five standard deviation discrepancy between the muonic Lamb shift determination and the result of electronic experiments is shown to be in clear contradiction with experiment. Alternative explanations are touched upon.Comment: 6 pages, 4 figures, final version includes discussion of systematic and numerical error

The Three Pillars of Natural Product Dereplication. Alkaloids from the Bulbs of Urceolina peruviana (C. Presl) J.F. Macbr. as a Preliminary Test Case

The role and importance of the identification of natural products are discussed in the perspective of the study of secondary metabolites. The rapid identification of already reported compounds, or structural dereplication, is recognized as a key element in natural product chemistry. The biological taxonomy of metabolite producing organisms, the knowledge of metabolite molecular structures, and the availability of metabolite spectroscopic signatures are considered as the three pillars of structural dereplication. The role and the construction of databases is illustrated by references to the KNApSAcK, UNPD, CSEARCH, and COCONUT databases, and by the importance of calculated taxonomic and spectroscopic data as substitutes for missing or lost original ones. Two NMR-based tools, the PNMRNP database that derives from UNPD, and KnapsackSearch, a database generator that provides taxonomically focused libraries of compounds, are proposed to the community of natural product chemists. The study of the alkaloids from Urceolina peruviana, a plant from the Andes used in traditional medicine for antibacterial and anticancer actions, has given the opportunity to test different approaches to dereplication, favoring the use of publicly available data sources

Near-earth cosmic ray decreases associated with remote coronal mass ejections

Galactic cosmic ray (GCR) flux is modulated by both particle drift patterns and solar wind structures on a range of timescales. Over solar cycles, GCR flux varies as a function of the total open solar magnetic flux and the latitudinal extent of the heliospheric current sheet. Over hours, drops of a few percent in near-Earth GCR flux (Forbush decreases, FDs) are well known to be associated with the near-Earth passage of solar wind structures resulting from corotating interaction regions (CIRs) and transient coronal mass ejections (CMEs). We report on four FDs seen at ground-based neutron monitors which cannot be immediately associated with significant structures in the local solar wind. Similarly, there are significant near-Earth structures which do not produce any corresponding GCR variation. Three of the FDs are during the STEREO era, enabling in situ and remote observations from three well-separated heliospheric locations. Extremely large CMEs passed the STEREO-A spacecraft, which was behind the West limb of the Sun, approximately 2–3 days before each near- Earth FD. Solar wind simulations suggest that the CMEs combined with pre-existing CIRs, enhancing the pre-existing barriers to GCR propagation. Thus these observations provide strong evidence for the modulation of GCR flux by remote solar wind structures

Improved radiative corrections and proton charge form factor from the Rosenbluth separation technique

We investigate whether the apparent discrepancy between proton electric form factor from measurements using the Rosenbluth separation technique and polarization transfer method is due to the standard approximations employed in radiative correction procedures. Inaccuracies due to both the peaking approximation and the soft-photon approximation have been removed in our simulation approach. In contrast to results from (e,e'p) experiments, we find them in this case to be too small to explain the discrepancy.Comment: 6 pages, 3 figure

Similarities in the immunoglobulin response and V(H )gene usage in rhesus monkeys and humans exposed to porcine hepatocytes

BACKGROUND: The use of porcine cells and organs as a source of xenografts for human patients would vastly increase the donor pool; however, both humans and Old World primates vigorously reject pig tissues due to xenoantibodies that react with the polysaccharide galactose α (1,3) galactose (αGal) present on the surface of many porcine cells. We previously examined the xenoantibody response in patients exposed to porcine hepatocytes via treatment(s) with bioartficial liver devices (BALs), composed of porcine cells in a support matrix. We determined that xenoantibodies in BAL-treated patients are predominantly directed at porcine αGal carbohydrate epitopes, and are encoded by a small number of germline heavy chain variable region (V(H)) immunoglobulin genes. The studies described in this manuscript were designed to identify whether the xenoantibody responses and the IgV(H )genes encoding antibodies to porcine hepatocytes in non-human primates used as preclinical models are similar to those in humans. Adult non-immunosuppressed rhesus monkeys (Macaca mulatta) were injected intra-portally with porcine hepatocytes or heterotopically transplanted with a porcine liver lobe. Peripheral blood leukocytes and serum were obtained prior to and at multiple time points after exposure, and the immune response was characterized, using ELISA to evaluate the levels and specificities of circulating xenoantibodies, and the production of cDNA libraries to determine the genes used by B cells to encode those antibodies. RESULTS: Xenoantibodies produced following exposure to isolated hepatocytes and solid organ liver grafts were predominantly encoded by genes in the V(H)3 family, with a minor contribution from the V(H)4 family. Immunoglobulin heavy-chain gene (V(H)) cDNA library screening and gene sequencing of IgM libraries identified the genes as most closely-related to the IGHV3-11 and IGHV4-59 germline progenitors. One of the genes most similar to IGHV3-11, V(H)3-11(cyno), has not been previously identified, and encodes xenoantibodies at later time points post-transplant. Sequencing of IgG clones revealed increased usage of the monkey germline progenitor most similar to human IGHV3-11 and the onset of mutations. CONCLUSION: The small number of IGV(H )genes encoding xenoantibodies to porcine hepatocytes in non-human primates and humans is highly conserved. Rhesus monkeys are an appropriate preclinical model for testing novel reagents such as those developed using structure-based drug design to target and deplete antibodies to porcine xenografts

Proton polarizability and the Lamb shift in muonic hydrogen

The proton structure and proton polarizability corrections to the Lamb shift of electronic hydrogen and muonic hydrogen were evaluated on the basis of modern experimental data on deep inelastic structure functions. Numerical value of proton polarizability contribution to (2P-2S) Lamb shift is equal to 4.4 GHz.Comment: 8 pages, LaTeX2.09, 2 figures, uses linedraw.st

Quasielastic 12C(e,e'p) Reaction at High Momentum Transfer

We measured the 12C(e,e'p) cross section as a function of missing energy in parallel kinematics for (q,w) = (970 MeV/c, 330 MeV) and (990 MeV/c, 475 MeV). At w=475 MeV, at the maximum of the quasielastic peak, there is a large continuum (E_m > 50 MeV) cross section extending out to the deepest missing energy measured, amounting to almost 50% of the measured cross section. The ratio of data to DWIA calculation is 0.4 for both the p- and s-shells. At w=330 MeV, well below the maximum of the quasielastic peak, the continuum cross section is much smaller and the ratio of data to DWIA calculation is 0.85 for the p-shell and 1.0 for the s-shell. We infer that one or more mechanisms that increase with $\omega$ transform some of the single-nucleon-knockout into multinucleon knockout, decreasing the valence knockout cross section and increasing the continuum cross section.Comment: 14 pages, 7 figures, Revtex (multicol, prc and aps styles), to appear in Phys Rev

Nuclear structure corrections in the energy spectra of electronic and muonic deuterium

The one-loop nuclear structure corrections of order (Z alpha)^5 to the Lamb shift and hyperfine splitting of the deuterium are calculated. The contribution of the deuteron structure effects to the isotope shift (ep)-(ed), (mu p)-(mu d) in the interval (1S - 2S) is obtained on the basis of modern experimental data on the deuteron electromagnetic form factors. The comparison with the similar contributions to the Lamb shift for electronic and muonic hydrogen shows, that the relative contribution due to the nucleus structure increases when passing from the hydrogen to the deuterium.Comment: Talk presented at the Conference "Physics of Fundamental Interactions" of the Nuclear Physics Section of the Physics Department of RAS, ITEP, Moscow, 2-6 December, 2002; 8 pages, REVTE