Kinetic Roughening in Slow Combustion of Paper

Results of experiments on the dynamics and kinetic roughening of one-dimensional slow-combustion fronts in three grades of paper are reported. Extensive averaging of the data allows a detailed analysis of the spatial and temporal development of the interface fluctuations. The asymptotic scaling properties, on long length and time scales, are well described by the Kardar-Parisi-Zhang (KPZ) equation with short-range, uncorrelated noise. To obtain a more detailed picture of the strong-coupling fixed point, characteristic of the KPZ universality class, universal amplitude ratios, and the universal coupling constant are computed from the data and found to be in good agreement with theory. Below the spatial and temporal scales at which a cross-over takes place to the standard KPZ behavior, the fronts display higher apparent exponents and apparent multiscaling. In this regime the interface velocities are spatially and temporally correlated, and the distribution of the magnitudes of the effective noise has a power-law tail. The relation of the observed short-range behavior and the noise as determined from the local velocity fluctuations is discussed.Comment: RevTeX v3.1, 13 pages, 12 Postscript figures (uses epsf.sty), 3 tables; submitted to Phys. Rev.

Effect of a columnar defect on the shape of slow-combustion fronts

We report experimental results for the behavior of slow-combustion fronts in the presence of a columnar defect with excess or reduced driving, and compare them with those of mean-field theory. We also compare them with simulation results for an analogous problem of driven flow of particles with hard-core repulsion (ASEP) and a single defect bond with a different hopping probability. The difference in the shape of the front profiles for excess vs. reduced driving in the defect, clearly demonstrates the existence of a KPZ-type of nonlinear term in the effective evolution equation for the slow-combustion fronts. We also find that slow-combustion fronts display a faceted form for large enough excess driving, and that there is a corresponding increase then in the average front speed. This increase in the average front speed disappears at a non-zero excess driving in agreement with the simulated behavior of the ASEP model.Comment: 7 pages, 7 figure

Proficiency Test on soil improver maturity tests

Evira and Proftest SYKE carried out this proficiency test in November-December 2012 for sample phytotoxicity and aerobic biological activity by determining the effect of soil improver samples on germination and root growth of cress, sample CO2-production or oxygen uptake and sample dry weight and organic matter content. In total 11 laboratories took part in this test. Sample material was soil improver (S1) and soil improver and peat based growing medium (S2). Standard methods were used to determinate the properties from the samples, except for CO2 evolution rate analysis for which no standard exist. The robust means of the reported results by the participants were used as the assigned values for measurements. The evaluation of performance was based on the z scores which were calculated using the standard deviation for proficiency assessment. z scores were not calculated for CO2 (S2), CO2 production per bottle, and root length index (RI; S1), oxygen consumption (Oc) and oxygen uptake rate (OUR). In total, 91 % of the results were satisfactory when the deviations of 4-80 % from the as-signed values were accepted. It seems further guidance in some of the methods is needed. According to the results many laboratories have good practices and manage these analyses well. Other laboratories still need more experience. In future rounds of proficiency tests also pretreatment practices will be taken into account

Scaling and Noise in Slow Combustion of Paper

We present results of high resolution experiments on kinetic roughening of slow combustion fronts in paper, focusing on short length and time scales. Using three different grades of paper, we find that the combustion fronts show apparent spatial and temporal multiscaling at short scales. The scaling exponents decrease as a function of the order of the corresponding correlation functions. The noise affecting the fronts reveals short range temporal and spatial correlations, and non-Gaussian noise amplitudes. Our results imply that the overall behavior of slow combustion fronts cannot be explained by standard theories of kinetic roughening.Peer reviewe

Analysis of Frankia populations in three soils devoid of actinorhizal plants

Frankia populations were analyzed in three soils devoid of actinorhizal plants but containing monocultures of birch (Betula pendula Roth), pine (Pinus sylvestris L.) or spruce (Picea abies (L.) Karsten). Bioassays using seedlings of Alnus incana as capture plants resulted in nodulation capacities of 3160±7, 2267±13, and 2747±6 nodulation units g−1 of these soils, respectively. Comparative sequence analysis of an actinomycetes-specific insertion in domain III of the 23S rRNA allowed a grouping of isolates obtained from nodules of the capture plants into three distinct groups of the Alnus host infection group. This separation was confirmed by the analysis of genomic fingerprints of the isolates generated by rep-PCR fingerprinting with the BOX primer. Genomic fingerprints also demonstrated that all isolates differed from each other. The isolates accounted for a significant proportion of the Frankia population in root nodules of the capture plants as shown by in situ hybridization with specific probes. However, only those Frankia strains isolated from soil of the birch stand via Alnus seemed to represent the total Frankia population in root nodules. Nodules induced after inoculation with soil from the pine or spruce stand also contained Frankia populations which were not isolated during this study and which could not be identified by in situ hybridization. Depending upon whether the soil originated from a birch, pine or spruce stand, different Frankia populations were found in the nodules of the capture plants. Because a nested PCR on nucleic acids extracted from these different soils did not indicate differences in the diversity of the total Frankia populations, it was concluded that Frankia populations in nodules of the capture plants represent the fraction of physiologically active, infecting frankiae in the soils rather than the total Frankia populatio

Temporal and Spatial Persistence of Combustion Fronts in Paper

The spatial and temporal persistence, or first-return distributions are measured for slow-combustion fronts in paper. The stationary temporal and (perhaps less convincingly) spatial persistence exponents agree with the predictions based on the front dynamics, which asymptotically belongs to the Kardar-Parisi-Zhang universality class. The stationary short-range and the transient behavior of the fronts are non-Markovian, and the observed persistence properties thus do not agree with the predictions based on Markovian theory. This deviation is a consequence of additional time and length scales, related to the crossovers to the asymptotic coarse-grained behavior.Peer reviewe

Comment on: Kinetic Roughening in Slow Combustion of Paper

We comment on a recent Letter by Maunuksela et al. [Phys. Rev. Lett. 79, 1515 (1997)].Comment: 1 page, 1 figure, http://polymer.bu.edu/~hmakse/Home.htm

Kinetic Roughening in Slow Combustion of Paper

We present results from an experimental study on the kinetic roughening of slow combustion fronts in paper sheets. The sheets were positioned inside a combustion chamber and ignited from the top to minimize convection effects. The emerging fronts were videotaped and digitized to obtain their time-dependent heights. The data were analyzed by calculating two-point correlation functions in the saturated regime. Both the growth and roughening exponents were determined and found consistent with the Kardar-Parisi-Zhang equation, in agreement with recent theoretical work.Peer reviewe