Relativity accommodates superluminal mean velocities

Contrary to a widespread belief, measures of velocity can yield a value larger than $c$, the instantaneous light speed in vacuum, without contradicting Einstein's relativity. Nevertheless, the effect turns out to be too small to explain the recently claimed superluminal velocity by the OPERA collaboration. Several other general relativistic effects acting on the OPERA neutrinos are also analyzed. All of them are unable to explain the OPERA result.Comment: 5 pages; Latex source, 2 eps figures (expanded discussion, a few typos corrected, some refs. added

Nitrogen fertilizer value of digestates from anaerobic digestion of animal manures and crops

After anaerobic digestion (AD) of manures for biogas production the concentration of ammonium-N is increased and the concentration of decomposable carbon in manure is decreased. That implies that the first year fertilizer value of the manure can be increased by the treatment. However, pH is also increased by AD thereby increasing the risk of ammonia losses while the lowered dry matter content on the other hand improves the manure infiltration in soil and reduces the risk of ammonia loss. Therefore the effects of AD on plant N availability can be expected to interact with the manure application method used. In stockless organic farming it has been suggested that nitrogen utilization can be improved by using anaerobic digestion of plant-based green manures, but the information about such manures is scarce. We have compared nitrogen fertilizer values of 1) pig and cattle slurries before and after AD and 2) digested plant-based manures. Mineral fertilizer replacement values (MFRV) were determined after direct injection to barley and oats crops and after surface-banding in a winter wheat crop. The manures were digested in continuously fed pilot digesters at thermophilic conditions (ca. 50°C). The manures were applied to small framed plots and grain yields and N uptake were compared to plots receiving increasing amounts of mineral N fertilizer. The three tested plant-based manures derived from crops of either grass clover, yellow lupine or a triticale-winter vetch mixture. The MFRV of total N in two different injected cattle slurries increased from 58-75% to 69-82% after AD. The MFRV of cattle slurry after surface-banding in winter wheat was much lower: 30-37% for untreated slurry and 38-49% after AD. The low availability after surface-banding can be ascribed to high ammonia volatilization. The MFRV of injected pig slurry was high and similar with and without AD: 89-91%. After surface banding of pig slurry MFRV was 75% for untreated and 87% for digested pig slurry. The plant-based manures contained a high proportion of ammonium-N (59-68% of total N) after AD and the MFRVs of total manure N were comparable to the digested cattle slurries: 73-77% after injection, but only 43-57% after surface-banding of the manure. The influence of AD of manure on N turnover in soil has also been evaluated in a soil incubation study with some of the same manures, and the differences between untreated and digested manures were more distinct in this incubation study than the observed differences in fertilizer value. We conclude that the potential plant availability of pig and cattle slurry can be increased by 10-15% points after AD. However, after surface-banding of digested manures rich in fibers, such as cattle and plant-based manures, significant ammonia loss can be expected resulting in relative poor N utilization

Grain Characteristics, Chemical Composition, and Functional Properties of Rye (Secale cereale L.) As Influenced by Genotype and Harvest Year

Grain characteristic, chemical composition, and functional properties of rye were measured in 19 different cultivars grown in one location in up to 3 years. The cultivars included 8 adapted hybrids, 7 adapted population cultivars, and 4 nonadapted population cultivars. The results showed a significant influence of both harvest year and genotype on grain characteristics, chemical composition, and functional properties of the grain. Multivariate data analysis confirmed that the variations in the data were explained by yearly and genotype differences. Calculations of variance components showed that the variations in plant height, harvest yield, and protein content were mainly due to genotype differences and to a lesser extent to differences among harvest years. The kernel weight, hardness index, and content of dietary fiber components, however, were more strongly influenced by the harvest year than by the genotype. Differences in starch properties measured by falling number (FN), amylograph peak viscosity, and temperature at peak viscosity were more strongly influenced by harvest year. The water absorption was strongly influenced by genotype effects, compared to yearly differences. FN and amylograph peak temperature were positively correlated (r = 0.94). No correlation was found between the water absorption and the relative proportion of water-extractable arabinoxylan (AX) compared to the total AX content. However, the degree of ferulic acid cross-linking showed a negative correlation (r = -0.70) with the water absorption

Cosmogenic Neutrinos Through the GRAND Lens Unveil the Nature of Cosmic Accelerators

The sources of cosmic rays with energies above 55 EeV are still mysterious. A guaranteed associated flux of ultra high energy neutrinos known as the cosmogenic neutrino flux will be measured by next generation radio facilities, such as the proposed Giant Radio Array for Neutrino Detection (GRAND). By using the orthogonal information provided by the cosmogenic neutrino flux, we here determine the prospects of GRAND to constrain the source redshift evolution and the chemical composition of the cosmic ray sources. If the redshift evolution is known, independently on GRAND's energy resolution, GRAND with 200,000 antennas will constrain the proton/iron fraction to the $\sim5-10\%$ level after one year of data taking; on the other hand, if hints on the average source composition are given, GRAND will measure the redshift evolution of the sources to a $\sim 10\%$ uncertainty. However, the foreseen configuration of GRAND alone will not be able to break the degeneracy between redshift evolution of the sources and their composition. Our findings underline the discriminating potential of next generation radio array detectors and motivate further efforts in this direction.Comment: 18 pages, 6 figures, 1 table, comments welcome; clarifying comments added, matches published versio

Steps on Rutile TiO2(110): Active Sites for Water and Methanol Dissociation

We present a detailed investigation of the structure and activity of extended defects namely monoatomic steps on (1x1)-TiO2(110). Specifically, the two most stable and step edges are considered. Employing an automated genetic algorithm that samples a large number of candidates for each step edge, more stable, reconstructed structures were found for the step edge, while the bulk truncated structures were recovered for the step edge. We demonstrate how oxygen vacancies along these defects have lower formation energies than on flat terraces and how water and methanol molecules adsorb dissociatively on reduced step edges. Our findings are in agreement with earlier experimental results and indicate an important contribution from step edges to the reactivity of the TiO2(110) surface

Multimode optomechanical system in the quantum regime

We realise a simple and robust optomechanical system with a multitude of long-lived ($Q>10^7$) mechanical modes in a phononic-bandgap shielded membrane resonator. An optical mode of a compact Fabry-Perot resonator detects these modes' motion with a measurement rate ($96~\mathrm{kHz}$) that exceeds the mechanical decoherence rates already at moderate cryogenic temperatures ($10\,\mathrm{K}$). Reaching this quantum regime entails, i.~a., quantum measurement backaction exceeding thermal forces, and thus detectable optomechanical quantum correlations. In particular, we observe ponderomotive squeezing of the output light mediated by a multitude of mechanical resonator modes, with quantum noise suppression up to -2.4 dB (-3.6 dB if corrected for detection losses) and bandwidths $\lesssim 90\,\mathrm{ kHz}$. The multi-mode nature of the employed membrane and Fabry-Perot resonators lends itself to hybrid entanglement schemes involving multiple electromagnetic, mechanical, and spin degrees of freedom.Comment: 19 pages, 9 figure

Elementary analysis of the special relativistic combination of velocities, Wigner rotation, and Thomas precession

The purpose of this paper is to provide an elementary introduction to the qualitative and quantitative results of velocity combination in special relativity, including the Wigner rotation and Thomas precession. We utilize only the most familiar tools of special relativity, in arguments presented at three differing levels: (1) utterly elementary, which will suit a first course in relativity; (2) intermediate, to suit a second course; and (3) advanced, to suit higher level students. We then give a summary of useful results, and suggest further reading in this often obscure field.Comment: V1: 25 pages, 6 figures; V2: 22 pages, 5 figures. The revised version is shortened and the arguments streamlined. Minor changes in notation and figures. This version matches the published versio

The Building the Bridge survey for z=3 Ly-alpha emitting galaxies I: method and first results

We present the first results of an observational programme at the ESO Very Large Telescope aimed at detecting a large sample of high-redshift galaxies fainter than the current spectroscopic limit of R=25.5 for Lyman-Break galaxies. In this paper, we describe the results of deep narrow and broad-band imaging and subsequent follow-up multi-object spectroscopy of faint high-redshift galaxies in the fields of the BRI1346-0322 and Q2138-4427. These QSOs have intervening absorbers, at redshifts z=2.85 and z=3.15 respectively, for which redshifted Ly-alpha emission falls within less than a few AA from the central wavelengths of existing VLT (~60 AA wide) narrow-band filters. We selected 37 and 27 candidate emission-line galaxies in the two fields respectively. About 85% of the candidates have R-band magnitudes fainter than R=25.5. The first spectroscopic follow-up of a sub-sample of the candidates resulted in 41 confirmed candidates and 4 foreground galaxies (three [OII] emitters and one CIV emitter). The confirmation rate is 82% and 68% in the field of BRI1346-0322 and Q2138-4427 respectively. In addition, we serendipitously detect a number of other emission-line sources on some of the slitlets not used for candidates. Of these, 9 are also most likely Ly-alpha emitters with redshifts ranging from 1.98 to 3.47. The redshift distribution of confirmed candidates in the field of BRI1346-0322 is consistent with being drawn from a uniform distribution weighted by the filter response curve, whereas the galaxies in the field of Q2138-4427 have redshifts clustering very close to the redshift of the damped Ly-alpha absorber. This latter fact indicates the existence of a large `pancake'-like structure confirming the earlier suggestions of Francis & Hewitt (1993).Comment: 12 pages, 10 figures, to appear in the Astronomy & Astrophysics main journal. A full resolution version of the paper can be found at : http://astro.ifa.au.dk/~jfynbo/papers/bridge.ps.g