Increased Photosynthesis Offsets Costs of Allocation to Sapwood in An Arid Environment

We assessed the effect that varying patterns of biomass allocation had on growth of ponderosa pine (Pinus ponderosa) growing in the desert climate of the Great Basin and the montane climate of the eastern Sierra Nevada. Prior work established that desert trees have lower leaf:sapwood area ratios than montane trees (0.104 and 0.201 m2/cm2, respectively) and proportionally greater stem respiration. Sapwood:leaf mass ratios are also greater and increase more as a function stem diameter in desert than in montane trees. We hypothesized that this increased allocation of carbon to stem sapwood and stem respiration in large trees could decrease growth rates in the desert compared to the montane environment, in addition to any growth reduction imposed by drought on physiology and growth processes. Trees of all diameters (dbh) in the desert environment had lower relative growth rates (RGRs) than montane trees (e.g., for a 30 cm dbh tree, RGR = 0.012 vs. 0.021 kg·kg−1·yr−1, respectively). However, growth rates of desert and montane trees declined similarly with increasing dbh and did not reflect diverging sapwood:leaf mass ratios. Alternatively, we hypothesized that desert trees may increase rates of photosynthetic carbon accumulation (per unit leaf area) with diameter, thereby compensating for increased sapwood respiration. Leaf nitrogen (N) concentration and stable-carbon isotope composition (δ13C) were measured to examine size-dependent and seasonally integrated photosynthetic capacity within desert and montane environments. Nitrogen concentration was correlated with photosynthetic capacity. Leaf nitrogen (N) concentration and δ13C values were greater in the desert (e.g., in 1-yr-old needles, desert = 1.11% and −22.96‰; montane = 0.94% and −24.20‰) and differed between desert and montane trees as a function of dbh. In desert trees, leaf nitrogen concentration in 1-yr-old through 5-yr-old needles increased with dbh, and carbon isotope composition in 1-yr-old needles increased with dbh, suggesting increased photosynthetic capacity and photosynthetic rates with increasing tree size. Needle nitrogen concentration and δ13C values decreased or remained constant with dbh in montane trees. Desert trees had greater light extinction coefficients and retained fewer needle cohorts. Our results suggest that increased allocation to heterotrophic stem tissue at the expense of photosynthetic tissue does not always incur a reduction in tree growth as predicted by current models of forest productivity

Carbon in different phases ([CII], [CI], and CO) in infrared dark clouds: Cloud formation signatures and carbon gas fractions

Context: How do molecular clouds form out of the atomic phase? And what are the relative fractions of carbon in the ionized, atomic and molecular phase? These are questions at the heart of cloud and star formation. Methods: Using multiple observatories from Herschel and SOFIA to APEX and the IRAM 30m telescope, we mapped the ionized, atomic and molecular carbon ([CII]@1900GHz, [CI]@492GHz and C18O(2-1)@220GHz) at high spatial resolution (12"-25") in four young massive infrared dark clouds (IRDCs). Results: The three carbon phases were successfully mapped in all four regions, only in one source the [CII] line remained a non-detection. Both the molecular and atomic phases trace the dense structures well, with [CI] also tracing material at lower column densities. [CII] exhibits diverse morphologies in our sample, from compact to diffuse structures probing the cloud environment. In at least two out of the four regions, we find kinematic signatures strongly indicating that the dense gas filaments have formed out of a dynamically active and turbulent atomic/molecular cloud, potentially from converging gas flows. The atomic-to-molecular carbon gas mass ratios are low between 7% and 12% with the lowest values found toward the most quiescent region. In the three regions where [CII] is detected, its mass is always higher by a factor of a few than that of the atomic carbon. The ionized carbon emission depends as well on the radiation field, however, we also find strong [CII] emission in a region without significant external sources, indicating that other processes, e.g., energetic gas flows can contribute to the [CII] excitation as well.Comment: 15 pages, 18 figures, accepted by Astronomy & Astrophysics, a higher resolution version can be found at http://www.mpia.de/homes/beuther/papers.htm

International standards for brucellosis prevention and management

Summary International standards are a crucial element in brucellosis prevention and management. They allow policy-makers, scientists, epidemiologists, laboratories and trade entities to have a common vocabulary for communication and understanding of the disease. These standards cover the entire spectrum of activities from surveillance, testing, prophylaxis, transport and trade to policy development, research and reporting. Developing, adhering to and monitoring standards increases both the effectiveness and effi ciency of prevention and management programmes. Creating standards with the input of all stakeholders ensures that the standards do not adversely affect the requirements of any of the multiple parties involved. The World Organisation for Animal Health (OIE), in conjunction with its Member Countries, and through its standing and ad hoc committees plus expert input, has taken a key leadership role in developing and reviewing brucellosis standards. These standards are used to harmonise testing, prevention processes, vaccines and reporting, to support trade and to protect human and animal health

Portable performance on heterogeneous architectures

Trends in both consumer and high performance computing are bringing not only more cores, but also increased heterogeneity among the computational resources within a single machine. In many machines, one of the greatest computational resources is now their graphics coprocessors (GPUs), not just their primary CPUs. But GPU programming and memory models differ dramatically from conventional CPUs, and the relative performance characteristics of the different processors vary widely between machines. Different processors within a system often perform best with different algorithms and memory usage patterns, and achieving the best overall performance may require mapping portions of programs across all types of resources in the machine. To address the problem of efficiently programming machines with increasingly heterogeneous computational resources, we propose a programming model in which the best mapping of programs to processors and memories is determined empirically. Programs define choices in how their individual algorithms may work, and the compiler generates further choices in how they can map to CPU and GPU processors and memory systems. These choices are given to an empirical autotuning framework that allows the space of possible implementations to be searched at installation time. The rich choice space allows the autotuner to construct poly-algorithms that combine many different algorithmic techniques, using both the CPU and the GPU, to obtain better performance than any one technique alone. Experimental results show that algorithmic changes, and the varied use of both CPUs and GPUs, are necessary to obtain up to a 16.5x speedup over using a single program configuration for all architectures.United States. Dept. of Energy (Award DE-SC0005288)United States. Defense Advanced Research Projects Agency (Award HR0011-10-9-0009)National Science Foundation (U.S.) (Award CCF-0632997

Anisotropic Spin Diffusion in Trapped Boltzmann Gases

Recent experiments in a mixture of two hyperfine states of trapped Bose gases show behavior analogous to a spin-1/2 system, including transverse spin waves and other familiar Leggett-Rice-type effects. We have derived the kinetic equations applicable to these systems, including the spin dependence of interparticle interactions in the collision integral, and have solved for spin-wave frequencies and longitudinal and transverse diffusion constants in the Boltzmann limit. We find that, while the transverse and longitudinal collision times for trapped Fermi gases are identical, the Bose gas shows diffusion anisotropy. Moreover, the lack of spin isotropy in the interactions leads to the non-conservation of transverse spin, which in turn has novel effects on the hydrodynamic modes.Comment: 10 pages, 4 figures; submitted to PR

'The Brick' is not a brick : A comprehensive study of the structure and dynamics of the Central Molecular Zone cloud G0.253+0.016

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.In this paper we provide a comprehensive description of the internal dynamics of G0.253+0.016 (a.k.a. 'the Brick'); one of the most massive and dense molecular clouds in the Galaxy to lack signatures of widespread star formation. As a potential host to a future generation of high-mass stars, understanding largely quiescent molecular clouds like G0.253+0.016 is of critical importance. In this paper, we reanalyse Atacama Large Millimeter Array cycle 0 HNCO $J=4(0,4)-3(0,3)$ data at 3 mm, using two new pieces of software which we make available to the community. First, scousepy, a Python implementation of the spectral line fitting algorithm scouse. Secondly, acorns (Agglomerative Clustering for ORganising Nested Structures), a hierarchical n-dimensional clustering algorithm designed for use with discrete spectroscopic data. Together, these tools provide an unbiased measurement of the line of sight velocity dispersion in this cloud, $\sigma_{v_{los}, {\rm 1D}}=4.4\pm2.1$ kms$^{-1}$, which is somewhat larger than predicted by velocity dispersion-size relations for the Central Molecular Zone (CMZ). The dispersion of centroid velocities in the plane of the sky are comparable, yielding $\sigma_{v_{los}, {\rm 1D}}/\sigma_{v_{pos}, {\rm 1D}}\sim1.2\pm0.3$. This isotropy may indicate that the line-of-sight extent of the cloud is approximately equivalent to that in the plane of the sky. Combining our kinematic decomposition with radiative transfer modelling we conclude that G0.253+0.016 is not a single, coherent, and centrally-condensed molecular cloud; 'the Brick' is not a \emph{brick}. Instead, G0.253+0.016 is a dynamically complex and hierarchically-structured molecular cloud whose morphology is consistent with the influence of the orbital dynamics and shear in the CMZ.Peer reviewedFinal Accepted Versio

Existence of Heavy Fermions in the Antiferromagnetic Phase of CeIn3

We report the pressure-dependent optical conductivity spectra of a heavy fermion (HF) compound CeIn3 below the Neel temperature of 10 K to investigate the existence of the HF state in the antiferromagnetic (AFM) phase. The peak due to the interband transition in the hybridization gap between the conduction band and nearly localized 4f states (c-f hybridization) appears at the photon energy of about 20 meV not only in the HF regime but also in the AFM regime. Both the energy and intensity of the c-f hybridization peak continuously increase with the application of pressure from the AFM to the HF regime. This result suggests that the c-f hybridization, as well as the heavy fermions, exists even in the AFM phase of CeIn3.Comment: 5 pages, 3 figure

SuperTriplets: a triplet-based supertree approach to phylogenomics

Motivation: Phylogenetic tree-building methods use molecular data to represent the evolutionary history of genes and taxa. A recurrent problem is to reconcile the various phylogenies built from different genomic sequences into a single one. This task is generally conducted by a two-step approach whereby a binary representation of the initial trees is first inferred and then a maximum parsimony (MP) analysis is performed on it. This binary representation uses a decomposition of all source trees that is usually based on clades, but that can also be based on triplets or quartets. The relative performances of these representations have been discussed but are difficult to assess since both are limited to relatively small datasets

Abnormal structural connectivity in the brain networks of children with hydrocephalus

Increased intracranial pressure and ventriculomegaly in children with hydrocephalus are known to have adverse effects on white matter structure. This study seeks to investigate the impact of hydrocephalus on topological features of brain networks in children. The goal was to investigate structural network connectivity, at both global and regional levels, in the brains in children with hydrocephalus using graph theory analysis and diffusion tensor tractography. Three groups of children were included in the study (29 normally developing controls, 9 preoperative hydrocephalus patients, and 17 postoperative hydrocephalus patients). Graph theory analysis was applied to calculate the global network measures including small-worldness, normalized clustering coefficients, normalized characteristic path length, global efficiency, and modularity. Abnormalities in regional network parameters, including nodal degree, local efficiency, clustering coefficient, and betweenness centrality, were also compared between the two patients groups (separately) and the controls using two tailed t-test at significance level of p < 0.05 (corrected for multiple comparison). Children with hydrocephalus in both the preoperative and postoperative groups were found to have significantly lower small-worldness and lower normalized clustering coefficient than controls. Children with hydrocephalus in the postoperative group were also found to have significantly lower normalized characteristic path length and lower modularity. At regional level, significant group differences (or differences at trend level) in regional network measures were found between hydrocephalus patients and the controls in a series of brain regions including the medial occipital gyrus, medial frontal gyrus, thalamus, cingulate gyrus, lingual gyrus, rectal gyrus, caudate, cuneus, and insular. Our data showed that structural connectivity analysis using graph theory and diffusion tensor tractography is sensitive to detect abnormalities of brain network connectivity associated with hydrocephalus at both global and regional levels, thus providing a new avenue for potential diagnosis and prognosis tool for children with hydrocephalus