Morphology and scaling in the noisy Burgers equation: Soliton approach to the strong coupling fixed point

The morphology and scaling properties of the noisy Burgers equation in one dimension are treated by means of a nonlinear soliton approach based on the Martin-Siggia-Rose technique. In a canonical formulation the strong coupling fixed point is accessed by means of a principle of least action in the asymptotic nonperturbative weak noise limit. The strong coupling scaling behaviour and the growth morphology are described by a gas of nonlinear soliton modes with a gapless dispersion law and a superposed gas of linear diffusive modes with a gap. The dynamic exponent is determined by the gapless soliton dispersion law, whereas the roughness exponent and a heuristic expression for the scaling function are given by the form factor in a spectral representation of the interface slope correlation function. The scaling function has the form of a Levy flight distribution.Comment: 5 pages, Revtex file, submitted to Phys. Rev. Let

High-resolution permeability determination and two-dimensional porewater flow in sandy sediment

A new, inexpensive method is proposed to measure permeability in natural sandy sediment with high spatial resolution. This methodology allows for a reconstruction of the vertical permeability anisotropy in natural sediments, with a depth resolution of a few millimeters. Thus, the possible intrusion depth of advective flow over the water-sediment interface of sandy sediments can be deduced. Shipboard measurements on five natural sandy sediment cores taken from North Sea sediments are used to demonstrate that both the direction and magnitude of the second-order permeability tensor can be calculated from direct measurements using this method. This presents a major improvement over previous methods particularly in the context of quantifying flow and reaction in permeable sediments.info:eu-repo/semantics/publishedVersio

Nitrous oxide and methane in the Atlantic Ocean between 50 degrees North and 52 degrees South: Latitudinal distribution and sea-to-air flux

We discuss nitrous oxide (N2O) and methane (CH4) distributions in 49 vertical profiles covering the upper 300 m of the water column along two 13,500 km transects between 50°N and 52°S during the Atlantic Meridional Transect (AMT) programme (AMT cruises 12 and 13). Vertical N2O profiles were amenable to analysis on the basis of common features coincident with Longhurst provinces. In contrast, CH4 showed no such pattern. The most striking feature of the latitudinal depth distributions was a well-defined “plume” of exceptionally high N2O concentrations coincident with very low levels of CH4, located between 23.5°N and 23.5°S; this feature reflects the upwelling of deep waters containing N2O derived from nitrification, as identified by an analysis of N2O, apparent oxygen utilization (AOU) and NO3-, and presumably depleted in CH4 by bacterial oxidation. Sea-to-air emissions fluxes for a region equivalent to 42% of the Atlantic Ocean surface area were in the range 0.40–0.68 Tg N2O yr-1 and 0.81–1.43 Tg CH4 yr-1. Based on contemporary estimates of the global ocean source strengths of atmospheric N2O and CH4, the Atlantic Ocean could account for 6–15% and 4–13%, respectively, of these source totals. Given that the Atlantic Ocean accounts for around 20% of the global ocean surface, on unit area basis it appears that the Atlantic may be a slightly weaker source of atmospheric N2O than other ocean regions but it could make a somewhat larger contribution to marine-derived atmospheric CH4 than previously thought

Fractional Operators, Dirichlet Averages, and Splines

Fractional differential and integral operators, Dirichlet averages, and splines of complex order are three seemingly distinct mathematical subject areas addressing different questions and employing different methodologies. It is the purpose of this paper to show that there are deep and interesting relationships between these three areas. First a brief introduction to fractional differential and integral operators defined on Lizorkin spaces is presented and some of their main properties exhibited. This particular approach has the advantage that several definitions of fractional derivatives and integrals coincide. We then introduce Dirichlet averages and extend their definition to an infinite-dimensional setting that is needed to exhibit the relationships to splines of complex order. Finally, we focus on splines of complex order and, in particular, on cardinal B-splines of complex order. The fundamental connections to fractional derivatives and integrals as well as Dirichlet averages are presented

Doubled haploid ramets via embryogenesis of haploid tissue cultures

Tissue culture in the oil palm business is generally concerned with the multiplication (clonal production) of dura, pisifera and tenera palms. These are all normal diploids (2n=2x=36). Sumatra Bioscience has pioneered haploid tissue culture of oil palm (n=x=18). Haploid oil palm is the first step in producing doubled haploid palms which in turn provide parental lines for F1 hybrid production. Chromosome doubling is known to occur during embryogenesis in other haploid cultures, e.g. barley anther culture. Haploid tissue cultures in oil palm were therefore set up to investigate and exploit spontaneous chromosome doubling during embryogenesis. Flow cytometry of embryogenic tissue showed the presence of both haploid (n) and doubled haploid (2n) cells indicating spontaneous doubling. Completely doubled haploid ramets were regenerated suggesting that doubling occurred during the first mitoses of embryogenesis. This is the first report of doubled haploid production in oil palm via haploid tissue culture. The method provides a means of producing a range of doubled haploids in oil palm from the 1,000 plus haploids available at Sumatra Bioscience, in addition the method also produced doubled haploid (and haploid) clones. 1

Tradeoff between short-term and long-term adaptation in a changing environment

We investigate the competition dynamics of two microbial or viral strains that live in an environment that switches periodically between two states. One of the strains is adapted to the long-term environment, but pays a short-term cost, while the other is adapted to the short-term environment and pays a cost in the long term. We explore the tradeoff between these alternative strategies in extensive numerical simulations, and present a simple analytic model that can predict the outcome of these competitions as a function of the mutation rate and the time scale of the environmental changes. Our model is relevant for arboviruses, which alternate between different host species on a regular basis.Comment: 9 pages, 3 figures, PRE in pres

Improved Quantification of Important Beer Quality Parameters based on Non-linear Calibration Methods applied to FT-MIR Spectra

During the production process of beer, it is of utmost importance to guarantee a high consistency of the beer quality. For instance, the bitterness is an essential quality parameter which has to be controlled within the specifications already at the beginning of the production process in the unfermented beer (wort) as well as in final products such as beer and beer mix beverages. Nowadays, analytical techniques for quality control in beer production are mainly based on manual supervision, i.e. samples are taken from the process and analyzed in the laboratory. This typically requires significant lab technicians efforts for only a small fraction of samples to be analyzed, which leads to significant costs for beer breweries and companies. Fourier transform mid-infrared (FT-MIR) spectroscopy was used in combination with non-linear multivariate calibration techniques to overcome (i) the time consuming off-line analyses in beer production and (ii) already known limitations of standard linear chemometric methods , like partial least squares (PLS), for important quality parameters [1][2] such as bitterness, citric acid, total acids, free amino nitrogen, final attenuation or foam stability. The calibration models are established with enhanced non-linear techniques based (i) on a new piece-wise linear version of PLS by employing fuzzy rules for local partitioning the latent variable space and (ii) on extensions of support vector regression variants (ε-PLSSVR and ν-PLSSVR), for overcoming high computation times in high-dimensional problems and time-intensive and inappropriate settings of the kernel parameters. Furthermore, we introduce a new model selection scheme based on bagged ensembles in order to improve robustness and thus predictive quality of the final models. The approaches are tested on real-world calibration data sets for wort and beer mix beverages, and successfully compared to linear methods, as showing a clear out-performance in most cases and being able to meet the model quality requirements defined by the experts at the beer company

Optical and X-ray Spectroscopy of 1E 0449.4-1823: Demise of the original type 2 QSO

New optical spectra of the original narrow-line quasar 1E 0449.4-1823 show that it now has broad emission lines of considerable strength, eliminating it as a "type 2 QSO" candidate. We suggest that the behavior of 1E 0449.4-1823 is the same as that of some Seyfert 1.8 and 1.9 galaxies, in which Goodrich attributed long-term variations of their broad Balmer lines to dynamical motions of obscuring material located in or around the broad-line region. The optical continuum and broad emission-line regions of 1E 0449.4-1823 may still be partly covered in our line of sight, which would explain its large forbidden-line equivalent widths and flat alpha_ox relative to other low-redshift QSOs. Also present are apparent absorption features in the broad Balmer lines and in Mg II, which may be related to the past obscuration and current emergence of the broad-line region. However, it is difficult to distinguish absorption from broad emission-line peaks that are displaced in velocity; we consider the latter a plausible competing interpretation of these peculiar line profiles. An ASCA X-ray spectrum of 1E 0449.4-1823 can be fitted with a power-law of Gamma = 1.63, intrinsic N_H < 9 x 10^20 cm-2, and no Fe Kalpha line emission. Its 2-10 keV luminosity is 6.7 x 10^44 ergs/s. With regard to the still hypothetical type 2 QSOs, we argue that there is little evidence for the existence of any among X-ray selected samples.Comment: to appear in ApJ July 1, 1998 (vol. 501). 23 pages including figures. Uses LaTeX macro aasms4.st