The Two-Nucleon 1S0 Amplitude Zero in Chiral Effective Field Theory

We present a new rearrangement of short-range interactions in the $^1S_0$ nucleon-nucleon channel within Chiral Effective Field Theory. This is intended to reproduce the amplitude zero (scattering momentum $\simeq$ 340 MeV) at leading order, and it includes subleading corrections perturbatively in a way that is consistent with renormalization-group invariance. Systematic improvement is shown at next-to-leading order, and we obtain results that fit empirical phase shifts remarkably well all the way up to the pion-production threshold. An approach in which pions have been integrated out is included, which allows us to derive analytic results that also fit phenomenology surprisingly well.Comment: 34 pages, 7 figure

Transport properties of armchair graphene nanoribbon junctions between graphene electrodes

The transmission properties of armchair graphene nanoribbon junctions between graphene electrodes are investigated by means of first-principles quantum transport calculations. First the dependence of the transmission function on the size of the nanoribbon has been studied. Two regimes are highlighted: for small applied bias transport takes place via tunneling and the length of the ribbon is the key parameter that determines the junction conductance; at higher applied bias resonant transport through HOMO and LUMO starts to play a more determinant role, and the transport properties depend on the details of the geometry (width and length) of the carbon nanoribbon. In the case of the thinnest ribbon it has been verified that a tilted geometry of the central phenyl ring is the most stable configuration. As a consequence of this rotation the conductance decreases due to the misalignment of the $pi$ orbitals between the phenyl ring and the remaining part of the junction. All the computed transmission functions have shown a negligible dependence on different saturations and reconstructions of the edges of the graphene leads, suggesting a general validity of the reported results

A standardised method for measuring in situ denitrification in shallow aquifers: numerical validation and measurements in riparian wetlands

A tracer test to examine in situ denitrification in shallow groundwater by a piezometer with a packer system used bromide as a tracer of dilution and acetylene (10%) to block the denitrification process at the nitrous oxide stage. During the test, dissolved oxygen, nitrate (NO3-), bromide (Br-), nitrous oxide (N2O) and dissolved organic carbon (DOC) were measured. To calibrate the experimental method, comparison with numerical simulations of the groundwater transfer were carried out, taking into account the environmental characteristics. The method was tested by measurements undertaken in different environmental conditions (geology, land use and hydrology) in two riparian wetlands. Denitrification rates measured by this method ranged from 5.7 10-6 g N-NO3-L-1 h-1 to 1.97 10-3 g N-NO3-L-1 h-1 The method is applicable in shallow aquifers with a permeability from 10-2 to 10-4m s-1

LIINUS/SERPIL: a design study for interferometric imaging spectroscopy at the LBT

LIINUS/SERPIL is a design study to augment LBTs interferometric beam combiner camera LINC-NIRVANA with imaging spectroscopy. The FWHM of the interferometric main beam at 1.5 micron will be about 10 mas, offering unique imaging and spectroscopic capabilities well beyond the angular resolution of current 8-10m telescopes. At 10 mas angular scale, e.g., one resolution element at the distance of the Galactic Center corresponds to the average diameter of the Pluto orbit (79 AU), hence the size of the solar system. Taking advantage of the LBT interferometric beam with an equivalent maximum diameter of 23 m, LIINUS/SERPIL is an ideal precursor instrument for (imaging) spectrographs at extremely large full aperture telescopes. LIINUS/SERPIL will be built upon the LINC-NIRVANA hardware and LIINUS/SERPIL could potentially be developed on a rather short timescale. The study investigates several concepts for the optical as well as for the mechanical design. We present the scientific promises of such an instrument together with the current status of the design study.Comment: 12 pages, SPIE conference proceeding, Orlando, 200

Wetland restoration and nitrate reduction: the example of the periurban wetland of Vitoria-Gasteiz (Basque Country, North Spain)

Changes in land use and agricultural intensification caused wetlands on the quaternary aquifer of Vitoria-Gasteiz (Basque Country) to disappear some years ago and nitrate concentration in groundwaters increased very quickly. The Basque Government recently declared the East Sector of this aquifer a Vulnerable Zone according to the 91/676/CEE European Directive. Recently, the wetlands have been restored through the closure of the main drainage ditches, the consequent elevation of the water table and the abondonment of agricultural practices near the wetlands. This is the case of the Zurbano wetland. Restoration has allowed the recovery of its biogeochemical function, which has reduced nitrate concentrations in waters. Nitrate concentrations which exceed 50 mg l–1 in groundwaters entering into the wetland are less than 10 mg l–1 at the outlet. Conditions in the wetland are conducive to the loss of nitrates: organic matter rich wetted soils, clay presence allowing a local semiconfined flow and very low hydraulic gradient. Water quality monitoring at several points around the wetland showed the processes involved in nitrate loss, although some aspects still remain unresolved. However, during storm events, the wetland effectively reduces the nitrate concentration entering the Alegria River, the most important river on the quaternary aquifer