Moderate phosphorus additions consistently affect community composition of arbuscular mycorrhizal fungi in tropical montane forests in southern Ecuador

Summary: Anthropogenic atmospheric deposition can increase nutrient supply in the most remoteecosystems, potentially affecting soil biodiversity. Arbuscular mycorrhizal fungal (AMF) com-munities rapidly respond to simulated soil eutrophication in tropical forests. Yet the limitedspatio-temporal extent of such manipulations, together with the often unrealistically high fer-tilization rates employed, impedes generalization of such responses. We sequenced mixed root AMF communities within a seven year-long fully factorial nitro-gen (N) and phosphorus (P) addition experiment, replicated at three tropical montane forestsin southern Ecuador with differing environmental characteristics. We hypothesized: strongshifts in community composition and species richness after long-term fertilization, site- andclade-specific responses to N vs P additions depending on local soil fertility and clade life his-tory traits respectively. Fertilization consistently shifted AMF community composition across sites, but only reducedrichness of Glomeraceae. Compositional changes were mainly driven by increases in P supplywhile richness reductions were observed only after combined N and P additions. We conclude that moderate increases of N and P exert a mild but consistent effect on tropi-cal AMF communities. To predict the consequences of these shifts, current results need to besupplemented with experiments that characterize local species-specific AMF functionalit

The relative importance of ecological drivers of arbuscularmycorrhizal fungal distribution varies with taxon phylogeneticresolution

The phylogenetic depth at which arbuscular mycorrhizal (AM) fungi harbor a coherent eco-logical niche is unknown, which has consequences for operational taxonomic unit (OTU)delineation from sequence data and the study of their biogeography. We tested how changes in AM fungi community composition across habitats (beta diver-sity) vary with OTU phylogenetic resolution. We inferred exact sequence variants (ESVs) toresolve phylotypes at resolutions finer than provided by traditional sequence clustering andanalyzed beta diversity profiles up to order-level sequence clusters. At the ESV level, we detected the environmental predictors revealed with traditional OTUsor at higher genetic distances. However, the correlation between environmental predictorsand community turnover steeply increased at a genetic distance ofc. 0.03 substitutions persite. Furthermore, we observed a turnover of either closely or distantly related taxa (respec-tively at or above 0.03 substitutions per site) along different environmental gradients. This study suggests that different axes of AM fungal ecological niche are conserved at dif-ferent phylogenetic depths. Delineating AM fungal phylotypes using DNA sequences shouldscreen different phylogenetic resolutions to better elucidate the factors that shape communi-ties and predict the fate of AM symbioses in a changing environment

Use of quinolones in bull semen extenders to reduce sperm deoxyribonucleic acid damage

Cryopreserved sperm samples from Holstein bulls (n = 20) were examined for bacterial presence and Sperm DNA Fragmentation (SDF) dynamics. SDF was assessed after thawing (T0) and at 4, 24 and 48 h of incubation (37°C) and the rate of SDF (r-SDF), as an estimator of the DNA degradation over time, was calculated. Two groups of bulls were identified based on the presence or absence of bacteria: One group (n = 10) had a readily detectable bacterial presence, while the other group (n = 10) had an undetectable bacterial presence. Differences in the SDF at T0 were not observed between these two groups. However, statistically different results were found after 24 h of incubation at 37°C (Kaplan-Meier estimator; Log- Rank Matel-Cox, p0.05) were not detected between the control and the quinolone treated sample for those samples without bacteria. However, differences (p<0.000) in SDF were observed for quinolone treated samples that previously presented bacteria. Incubation of sealed straws showed that bacterial contamination occurred prior to cryopreservation. These results call attention to three points: (1) sperm samples were in contact with bacteria before cryopreservation; (2) the r-SDF can be directly correlated with bacterial presence but this effect remains cryptic after thawing and (3) the r-SDF can be reduced by treating the semen samples with an adequate antibiotic such as quinolones, a finding not previously reported in the scientific literature, but important in terms of reproductionThis work was supported by the Ministry of Education and Science, Spain (Grant BFU2010-16738/BFI

Pre-multisymplectic constraint algorithm for field theories

We present a geometric algorithm for obtaining consistent solutions to systems of partial differential equations, mainly arising from singular covariant first-order classical field theories. This algorithm gives an intrinsic description of all the constraint submanifolds. The field equations are stated geometrically, either representing their solutions by integrable connections or, what is equivalent, by certain kinds of integrable m-vector fields. First, we consider the problem of finding connections or multivector fields solutions to the field equations in a general framework: a pre-multisymplectic fibre bundle (which will be identified with the first-order jet bundle and the multimomentum bundle when Lagrangian and Hamiltonian field theories are considered). Then, the problem is stated and solved in a linear context, and a pointwise application of the results leads to the algorithm for the general case. In a second step, the integrability of the solutions is also studied. Finally, the method is applied to Lagrangian and Hamiltonian field theories and, for the former, the problem of finding holonomic solutions is also analized.Comment: 30 pp. Presented in the International Workshop on Geometric Methods in Modern Physics (Firenze, April 2005

Persistent starspot signals on M dwarfs: multi-wavelength Doppler observations with the Habitable-zone Planet Finder and Keck/HIRES

Young, rapidly-rotating M dwarfs exhibit prominent starspots, which create quasiperiodic signals in their photometric and Doppler spectroscopic measurements. The periodic Doppler signals can mimic radial velocity (RV) changes expected from orbiting exoplanets. Exoplanets can be distinguished from activity-induced false positives by the chromaticity and long-term incoherence of starspot signals, but these qualities are poorly constrained for fully-convective M stars. Coherent photometric starspot signals on M dwarfs may persist for hundreds of rotations, and the wavelength dependence of starspot RV signals may not be consistent between stars due to differences in their magnetic fields and active regions. We obtained precise multi-wavelength RVs of four rapidly-rotating M dwarfs (AD Leo, G 227-22, GJ 1245B, GJ 3959) using the near-infrared (NIR) Habitable-zone Planet Finder, and the optical Keck/HIRES spectrometer. Our RVs are complemented by photometry from Kepler, TESS, and the Las Cumbres Observatory (LCO) network of telescopes. We found that all four stars exhibit large spot-induced Doppler signals at their rotation periods, and investigated the longevity and optical-to-NIR chromaticity for these signals. The phase curves remain coherent much longer than is typical for Sunlike stars. Their chromaticity varies, and one star (GJ 3959) exhibits optical and NIR RV modulation consistent in both phase and amplitude. In general, though, we find that the NIR amplitudes are lower than their optical counterparts. We conclude that starspot modulation for rapidly-rotating M stars frequently remains coherent for hundreds of stellar rotations, and gives rise to Doppler signals that, due to this coherence, may be mistaken for exoplanets.Comment: Accepted for publication in the Astrophysical Journa

MEMS-Based Communications Systems for Space-Based Applications

As user demand for higher capacity and flexibility in communications satellites increases, new ways to cope with the inherent limitations posed by the prohibitive mass and power consumption, needed to satisfy those requirements, are under investigation. Recent studies suggest that while new satellite architectures are necessary to enable multi-user, multi-data rate, multi-location satellite links, these new architectures will inevitably increase power consumption, and in turn, spacecraft mass, to such an extent that their successful implementation will demand novel lightweight/low power hardware approaches. In this paper, following a brief introduction to the fundamentals of communications satellites, we address the impact of micro-electro-mechanical systems (MEMS) technology, in particular micro-electro-mechanical (MEM) switches to mitigate the above mentioned problems and show that low-loss/wide bandwidth MEM switches will go a long way towards enabling higher capacity and flexibility space-based communications systems

Holographic Brownian Motion in Magnetic Environments

Using the gauge/gravity correspondence, we study the dynamics of a heavy quark in two strongly-coupled systems at finite temperature: Super-Yang-Mills in the presence of a magnetic field and non-commutative Super-Yang-Mills. In the former, our results agree qualitatively with the expected behavior from weakly-coupled theories. In the latter, we propose a Langevin equation that accounts for the effects of non-commutativity and we find new interesting features. The equation resembles the structure of Brownian motion in the presence of a magnetic field and implies that the fluctuations along non-commutative directions are correlated. Moreover, our results show that the viscosity is smaller than the commutative case and that the diffusion properties of the quark are unaffected by non-commutativity. Finally, we compute the random force autocorrelator and verify that the fluctuation-dissipation theorem holds in the presence of non-commutativity.Comment: 34 pages. v2: typos corrected. v3: title and abstract slightly modified in order to better reflect the contents of the paper; footnote 3 and one reference were also added; version accepted for publication in JHE

iPSCORE: A Resource of 222 iPSC Lines Enabling Functional Characterization of Genetic Variation across a Variety of Cell Types.

Large-scale collections of induced pluripotent stem cells (iPSCs) could serve as powerful model systems for examining how genetic variation affects biology and disease. Here we describe the iPSCORE resource: a collection of systematically derived and characterized iPSC lines from 222 ethnically diverse individuals that allows for both familial and association-based genetic studies. iPSCORE lines are pluripotent with high genomic integrity (no or low numbers of somatic copy-number variants) as determined using high-throughput RNA-sequencing and genotyping arrays, respectively. Using iPSCs from a family of individuals, we show that iPSC-derived cardiomyocytes demonstrate gene expression patterns that cluster by genetic background, and can be used to examine variants associated with physiological and disease phenotypes. The iPSCORE collection contains representative individuals for risk and non-risk alleles for&nbsp;95% of SNPs associated with human phenotypes through genome-wide association studies. Our study demonstrates the utility of iPSCORE for examining how genetic variants influence molecular and physiological traits in iPSCs and derived cell lines