Multiscale change-point segmentation: beyond step functions.

Modern multiscale type segmentation methods are known to detect multiple change-points with high statistical accuracy, while allowing for fast computation. Underpinning (minimax) estimation theory has been developed mainly for models that assume the signal as a piecewise constant function. In this paper, for a large collection of multiscale segmentation methods (including various existing procedures), such theory will be extended to certain function classes beyond step functions in a nonparametric regression setting. This extends the interpretation of such methods on the one hand and on the other hand reveals these methods as robust to deviation from piecewise constant functions. Our main finding is the adaptation over nonlinear approximation classes for a universal thresholding, which includes bounded variation functions, and (piecewise) Holder functions of smoothness order 0 < alpha <= 1 as special cases. From this we derive statistical guarantees on feature detection in terms of jumps and modes. Another key finding is that these multiscale segmentation methods perform nearly (up to a log-factor) as well as the oracle piecewise constant segmentation estimator (with known jump locations), and the best piecewise constant approximants of the (unknown) true signal. Theoretical findings are examined by various numerical simulations

Simultaneous epidemic development of scald and net blotch on single leaf layers of a spring barley crop

Background and objectives Two pathogens growing on the same leaf compete for the same resources, i.e. space and plant nutrients. This may lead to density dependent disease development. The pathogens may also influence each other directly such that the influence of one on the other is more complex than a simple function of the area of the other pathogen. Different interaction types are, for example, competition, mutualism and exploitation. The importance of such interactions for epidemics of simultaneously occurring pathogens has received little attention. The objective of this study is to investigate the simultaneous epidemic development of Rhynchosporium secalis (causing scald) and Drechslera teres (causing net blotch) on spring barley under field conditions. Materials and methods The field trial was performed with artificial inoculation of R. secalis and D. teres on three spring barley varieties differing in their susceptibility towards the pathogens. The pathogens were inoculated in three combinations: only one was inoculated, they were inoculated together, the second pathogen was inoculated 26 days after the first. A non-inoculated treatment was included. The trial had three replications. Nine plants were harvested from each plot five times during the season. Leaves were dried and disease severity and senescence observed. Only leaves with < 50 % senescence were included in the analysis. Whole-plant disease severity over time was calculated as average of disease severity on leaves weighted by leaf area. Disease development per leaf layer was evaluated by fitting an exponential model to severity data over time for each leaf layer per variety, treatment and replicate. Association between scald and net blotch severity on individual leaves was analysed using Kendall’s tau. Results and discussion Net blotch developed on all leaf layers and reached whole-plant disease severities up to 15%. Scald did not develop on upper leaf layers and whole-plant severity was less than 2%. Disease severity curves at whole-plant level showed no effect of inoculating the other pathogen. The analysis of the growth rate of each disease per leaf layer showed a significant effect of variety and leaf layer within variety but no effect of treatment. However, we observed significant negative associations between the diseases on individual leaves for several combinations of leaf layer and variety. These results show that the individual leaf approach can provide new information and underline the importance of considering interactions between pathogens in the field. Acknowledgement This work was funded by the DARCOF II project BAR-O

Net blotch severity is best assessed at early grain filling with respect to its effect on grain weight of spring barley

Appropriate disease assessment methods and parameters reflecting whole-season disease severity levels in field plots remain important issues in studies related to plant disease epidemiology, disease resistance of crop cultivars, and disease-induced yield losses. Such methods and parameters should be yield-related to ensure relevance. Net blotch severity was determined over time in inoculated and non-inoculated field plots of three spring barley varieties by whole plot assessments and by assessments of individual leaves of single main tillers. Disease severity measures such as the area-under-disease-progress-curve, mean and maximum severity as well as severity levels at specific growth stages (GS) were derived from the data. Their relation to thousand grain weight (TGW) and their inter-correlations were examined by means of general linear model (GLM) and factor analyses (FA), respectively. All parameters of net blotch severity were significantly negatively correlated with TGW. Disease parameters derived from whole-plot assessments gave a slightly better explanation of TGW than parameters derived by assessing single main tillers. Net blotch severity at GS 70 (beginning of grain filling) of whole plot assessments yielded the highest adjusted R-squared (0.43) while the adjusted R-squared values resulting from using the same parameter of assessments of the upper three, four or all leaves of single tillers were between 0.34 and 0.35. Also, the residuals of TGW of GLM’s using disease covariates from whole-plot assessments and variety effects as independent variables exhibited less pattern related to other sources of variation than residuals of the corresponding models that used single-tiller-based disease covariates. FA revealed that all disease parameters were highly inter-correlated and co-varied along the 1 principal component axis. The results indicate that disease assessments at GS 70 are appropriate to reflect whole-season severity levels of net blotch. In this respect, the time consuming single-tiller method is in this respect not superior to the simpler whole-plot method. However, assessing individual leaf layers of single tillers allows to observe the epidemic development and thus to examine the dynamics of epidemics in much greater detail than assessing whole-plots. This showed, for example, how much each leaf layer contributed at any given time to the total disease and revealed that a substantial fraction of the total disease is being removed during the course of an epidemic by senescence of diseased lower leaves. This level of detail in examining the dynamics of epidemics cannot be achieved by the whole-plot method

Vekselvirkning mellem plantesygdomme påvirker sygdomsudviklingen

Sygdomme i planter kan være forårsaget af mange forskellige mikroorganismer, og ofte vil der i en enkelt afgrøde og på én plante være flere arter tilstede samtidigt. På trods af denne erfaring har der været tradition for at forske i sygdomme enkeltvis, og betydningen på det totale sygdomsniveau af vekselvirkninger mellem de enkelte patogener er kun blevet studeret i begrænset omfang. Her beskrives vekselvirkningen mellem sygdommene bladplet og skoldplet på byg i markforsøg

Testing for lack of fit in inverse regression - with applications to photonic imaging.

Regression; Problems; Lack-of-fit; Applications;

Optical bistability involving planar metamaterial with broken structural symmetry

We report on a bistable light transmission through a planar metamaterial composed of a metal pattern of weakly asymmetric elements placed on a nonlinear substrate. Such structure bears the Fano-like sharp resonance response of a trapped-mode excitation. The feedback required for bistability is provided by the coupling between the strong antiphased trapped-mode-resonance currents excited on the metal elements and the intensity of inner field in the nonlinear substrate.Comment: 4 pages, 4 figure

Age validation of quillback rockfish (Sebastes maliger) using bomb radiocarbon

Rockfishes (Sebastes spp.) support one of the most economically important f isheries of the Pacific Northwest and it is essential for sustainable management that age estimation procedures be validated for these species. Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon (14C) signal in the ocean environment that scientists have identified as a useful tracer and chronological marker in natural systems. In this study, we first demonstrated that fewer samples are necessary for age validation using the bomb-generated 14C signal by emphasizing the utility of the time-specific marker created by the initial rise of bomb-14C. Second, the bomb-generated 14C signal retained in fish otoliths was used to validate the age and age estimation method of the quillback rockfish (Sebastes maliger) in the waters of southeast Alaska. Radiocarbon values from the first year’s growth of quillback rockfish otoliths were plotted against estimated birth year to produce a 14C time series spanning 1950 to 1985. The initial rise in bomb-14C from prebomb levels (~ –90‰) occurred in 1959 [±1 year] and 14C levels rose relatively rapidly to peak Δ14C values in 1967 (+105.4‰) and subsequently declined through the end of the time series in 1985 (+15.4‰). The agreement between the year of initial rise of 14C levels from the quillback rockfish time series and the chronology determined for the waters of southeast Alaska from yelloweye rockfish (S. ruberrimus) otoliths validated the aging method for the quillback rockfish. The concordance of the entire quillback rockfish 14C time series with the yelloweye rockfish time series demonstrated the effectiveness of this age validation technique, confirmed the longevity of the quillback rockfish up to a minimum of 43 years, and strongly confirms higher age estimates of u

Critical dynamics of ballistic and Brownian particles in a heterogeneous environment

The dynamic properties of a classical tracer particle in a random, disordered medium are investigated close to the localization transition. For Lorentz models obeying Newtonian and diffusive motion at the microscale, we have performed large-scale computer simulations, demonstrating that universality holds at long times in the immediate vicinity of the transition. The scaling function describing the crossover from anomalous transport to diffusive motion is found to vary extremely slowly and spans at least 5 decades in time. To extract the scaling function, one has to allow for the leading universal corrections to scaling. Our findings suggest that apparent power laws with varying exponents generically occur and dominate experimentally accessible time windows as soon as the heterogeneities cover a decade in length scale. We extract the divergent length scales, quantify the spatial heterogeneities in terms of the non-Gaussian parameter, and corroborate our results by a thorough finite-size analysis.Comment: 14 page

Multimodality in Aerodynamic Wing Design Optimization

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143093/1/6.2017-3753.pd

MSL Entry, Descent, and Landing Instrumentation: Return on Investment

On Aug 5, 2012 the Mars Science Laboratory (MSL) Entry, Descent, and Landing Instrumentation (MEDLI) suite on MSL entry vehicle heatshield suc-cessfully returned surface pressure and in-depth temperature data.1,2 The MEDLI data has given scientists and engineers an unprecedented ability to reconstruct entry environment, atmospheric density, and flight trajectory, and flight validation of predic-tions vehicle aerodynamics and thermal protection system (TPS) performance. This presentation will dis-cuss key findings from MEDLI, some of which are being applied to improve definition of aerothermal environment and TPS sizing margins for existing NASA entry missions. The postflight analysis has shown that a significant thermal protection mass saving upon redesign is possible for an MSL-class vehicle. The success of MEDLI has also demonstrated and qualified robust flight instrumentation technologies at very low risk to the mission. The potential benefits of MEDLI to planetary exploration and sample return missions, as well as to exploration class missions to Mars will be presented