Spectral Action for Robertson-Walker metrics

We use the Euler-Maclaurin formula and the Feynman-Kac formula to extend our previous method of computation of the spectral action based on the Poisson summation formula. We show how to compute directly the spectral action for the general case of Robertson-Walker metrics. We check the terms of the expansion up to a_6 against the known universal formulas of Gilkey and compute the expansion up to a_{10} using our direct method

Anisotropic flow at RHIC

We present the first measurement of directed flow ($v_1$) at the Relativistic Heavy Ion Collider (RHIC). $v_1$ is found to be consistent with zero at pseudorapidities $\eta$ from -1.2 to 1.2, then rises to the level of a couple of percent over the range $2.4 < |\eta| < 4$. The latter observation is similar to that from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. We studied the evolution of elliptic flow from p+p collisions through d+Au collision, and onto Au+Au collisions. Measurements of higher harmonics are presented and discussed.Comment: 6 pages, 3 figures. Proceeding for the 20th Winter Workshop on Nuclear Dynamics, Jamaic

New Challenges to Hydrodynamics from Azimuthal Anisotropy at RHIC

This paper presents $v_{4}/v_{2}^2$ ratio as a function of transverse momentum ($p_{t}$), pseudorapidity ($\eta$) and collision centrality in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). It is found that $v_{4}/v_{2}^2$ is larger than Hydrodynamic calculations, the centrality and transverse dependence of this ratio can not be fully described by Hydrodynamics, and the pseudorapidity dependence is opposite to what one expects from Hydrodynamics. The $p_{t}$ dependence of $v_{1}$ is also presented. It is found that $v_{1}(p_{t})$ for $|\eta|<1.3$ changes sign, and two possible explanations of the sign change are discussed.Comment: 4 pages, 3 figures. CIPANP 06 proceedin

Graphene as an electronic membrane

Experiments are finally revealing intricate facts about graphene which go beyond the ideal picture of relativistic Dirac fermions in pristine two dimensional (2D) space, two years after its first isolation. While observations of rippling added another dimension to the richness of the physics of graphene, scanning single electron transistor images displayed prevalent charge inhomogeneity. The importance of understanding these non-ideal aspects cannot be overstated both from the fundamental research interest since graphene is a unique arena for their interplay, and from the device applications interest since the quality control is a key to applications. We investigate the membrane aspect of graphene and its impact on the electronic properties. We show that curvature generates spatially varying electrochemical potential. Further we show that the charge inhomogeneity in turn stabilizes ripple formation.Comment: 6 pages, 11 figures. Updated version with new results about the re-hybridization of the electronic orbitals due to rippling of the graphene sheet. The re-hybridization adds the next-to-nearest neighbor hopping effect discussed in the previous version. New reference to recent STM experiments that give support to our theor

Noncommutative geometry and stochastic processes

The recent analysis on noncommutative geometry, showing quantization of the volume for the Riemannian manifold entering the geometry, can support a view of quantum mechanics as arising by a stochastic process on it. A class of stochastic processes can be devised, arising as fractional powers of an ordinary Wiener process, that reproduce in a proper way a stochastic process on a noncommutative geometry. These processes are characterized by producing complex values and so, the corresponding Fokker-Planck equation resembles the Schroedinger equation. Indeed, by a direct numerical check, one can recover the kernel of the Schroedinger equation starting by an ordinary Brownian motion. This class of stochastic processes needs a Clifford algebra to exist. In four dimensions, the full set of Dirac matrices is needed and the corresponding stochastic process in a noncommutative geometry is easily recovered as is the Dirac equation in the Klein-Gordon form being it the Fokker--Planck equation of the process.Comment: 16 pages, 2 figures. Updated a reference. A version of this paper will appear in the proceedings of GSI2017, Geometric Science of Information, November 7th to 9th, Paris (France

Hyporheic Zone Microbiome Assembly Is Linked to Dynamic Water Mixing Patterns in Snowmelt-Dominated Headwater Catchments

Terrestrial and aquatic elemental cycles are tightly linked in upland fluvial networks. Biotic and abiotic mineral weathering, microbially mediated degradation of organic matter, and anthropogenic influences all result in the movement of solutes (e.g., carbon, metals, and nutrients) through these catchments, with implications for downstream water quality. Within the river channel, the region of hyporheic mixing represents a hot spot of microbial activity, exerting significant control over solute cycling. To investigate how snowmelt-driven seasonal changes in river discharge affect microbial community assembly and carbon biogeochemistry, depth-resolved pore water samples were recovered from multiple locations around a representative meander on the East River near Crested Butte, CO, USA. Vertical temperature sensor arrays were also installed in the streambed to enable seepage flux estimates. Snowmelt-driven high river discharge led to an expanding zone of vertical hyporheic mixing and introduced dissolved oxygen into the streambed that stimulated aerobic microbial respiration. These physicochemical processes contributed to microbial communities undergoing homogenizing selection, in contrast to other ecosystems where lower permeability may limit the extent of mixing. Conversely, lower river discharge conditions led to a greater influence of upwelling groundwater within the streambed and a decrease in microbial respiration rates. Associated with these processes, microbial communities throughout the streambed exhibited increasing dissimilarity between each other, suggesting that the earlier onset of snowmelt and longer periods of base flow may lead to changes in the composition (and associated function) of streambed microbiomes, with consequent implications for the processing and export of solutes from upland catchments

Denitrification bioreactor trial in the Russell River catchment of the Wet Tropics: final report

Dissolved inorganic nitrogen (DIN) in runoff from agricultural land is considered to have a significant detrimental impact on the Great Barrier Reef (GBR). Losses of DIN to runoff can be reduced by good agricultural practices, but they cannot be eliminated entirely in the Wet Tropics due to the need for adequate nitrogen supply to crops, the high solubility of DIN, particularly nitrate, and high rainfall. Thus, it is inevitable that DIN concentrations are higher in runoff from agricultural land than from forested areas. Some of this DIN is removed from the water as it moves through aquifers, creeks, rivers, and wetlands on its way to the sea, through the process of microbial denitrification. Denitrification involves the conversion of nitrate and nitrite (NOx-N) to dinitrogen (N2) gas, which is lost to the atmosphere. Denitrification requires NOx-N, organic matter, and low oxygen concentration. Wetlands provide these conditions, so DIN concentrations decline in water moving through them. Similarly, denitrifying bioreactors are designed to treat water by passing it through a porous organic material, typically woodchips. The woodchips provide organic matter for the microorganisms, which in turn lower the oxygen concentration, providing ideal conditions for denitrification. Denitrifying bioreactors are now widely used to remove the NOx-N component of DIN from agricultural runoff water elsewhere, but they have not yet been evaluated in the Wet Tropics. The Wet Tropics pose a challenge for efficacy due to the large volumes of water moving through the landscape. The objective of this project was “to establish the effectiveness of denitrifying bioreactors as a remediation technology for excess DIN in agricultural runoff within the Babinda Swamp Drainage Area (BSDA) of the Russell catchment”. The Russell River exports a disproportionate amount of DIN to the GBR lagoon because of the high rainfall and high proportion of agriculture, mostly sugarcane, in its catchment

Modelling unseen flow pathways of water and contaminants in the Wet Tropics: the role of alluvial palaeochannels

Nutrients from agriculture in catchments draining to the Great Barrier Reef (GBR) are a stressor of this important ecosystem. Current GBR catchment models do not mechanistically link movement of nutrients from paddocks to rivers. An understanding of these water and nutrient flow pathways is crucial in any attempt to model and manage the GBR catchments. Conduits of water transport include surface drains and subsurface features such as palaeochannels. Palaeochannels are a common feature in alluvial landscapes, representing old river or stream beds that are often filled with coarse in-fill material which make them ideal water storage zones and conduits of water movement, either by recharging surrounding ground water (GW) or exchanging water with surface drainage networks (e.g., Keen et al., 2007, Owen & Dahlin, 2010, McLachlan et al., 2017). Their presence results in heterogeneity of soil and aquifer properties, which need to be accounted for in any attempt to assess water and nutrient transport in these flat agricultural landscapes

Physical mapping integrated with syntenic analysis to characterize the gene space of the long arm of wheat chromosome 1A

Background: Bread wheat (Triticum aestivum L.) is one of the most important crops worldwide and its production faces pressing challenges, the solution of which demands genome information. However, the large, highly repetitive hexaploid wheat genome has been considered intractable to standard sequencing approaches. Therefore the International Wheat Genome Sequencing Consortium (IWGSC) proposes to map and sequence the genome on a chromosome-by-chromosome basis. Methodology/Principal Findings: We have constructed a physical map of the long arm of bread wheat chromosome 1A using chromosome-specific BAC libraries by High Information Content Fingerprinting (HICF). Two alternative methods (FPC and LTC) were used to assemble the fingerprints into a high-resolution physical map of the chromosome arm. A total of 365 molecular markers were added to the map, in addition to 1122 putative unique transcripts that were identified by microarray hybridization. The final map consists of 1180 FPC based or 583 LTC based contigs. Conclusions/Significance: The physical map presented here marks an important step forward in mapping of hexaploid bread wheat. The map is orders of magnitude more detailed than previously available maps of this chromosome, and the assignment of over a thousand putative expressed gene sequences to specific map locations will greatly assist future functional studies. This map will be an essential tool for future sequencing of and positional cloning within chromosome 1A