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We consider truncated SVD (or spectral cut-off, projection) estimators for a prototypical statistical inverse problem in dimension D. Since calculating the singular value decomposition (SVD) only for the largest singular values is much less costly than the full SVD, our aim is to select a data-driven truncation level (m) over cap is an element of {1, . . . , D} only based on the knowledge of the first (m) over cap singular values and vectors. We analyse in detail whether sequential early stopping rules of this type can preserve statistical optimality. Information-constrained lower bounds and matching upper bounds for a residual based stopping rule are provided, which give a clear picture in which situation optimal sequential adaptation is feasible. Finally, a hybrid two-step approach is proposed which allows for classical oracle inequalities while considerably reducing numerical complexity.
We consider a statistical inverse learning (also called inverse regression) problem, where we observe the image of a function f through a linear operator A at i.i.d. random design points X-i , superposed with an additive noise. The distribution of the design points is unknown and can be very general. We analyze simultaneously the direct (estimation of Af) and the inverse (estimation of f) learning problems. In this general framework, we obtain strong and weak minimax optimal rates of convergence (as the number of observations n grows large) for a large class of spectral regularization methods over regularity classes defined through appropriate source conditions. This improves on or completes previous results obtained in related settings. The optimality of the obtained rates is shown not only in the exponent in n but also in the explicit dependency of the constant factor in the variance of the noise and the radius of the source condition set.
Exploring Change
(2018)
Data and metadata in datasets experience many different kinds of change. Values axe inserted, deleted or updated; rows appear and disappear; columns are added or repurposed, etc. In such a dynamic situation, users might have many questions related to changes in the dataset, for instance which parts of the data are trustworthy and which are not? Users will wonder: How many changes have there been in the recent minutes, days or years? What kind of changes were made at which points of time? How dirty is the data? Is data cleansing required? The fact that data changed can hint at different hidden processes or agendas: a frequently crowd-updated city name may be controversial; a person whose name has been recently changed may be the target of vandalism; and so on. We show various use cases that benefit from recognizing and exploring such change. We envision a system and methods to interactively explore such change, addressing the variability dimension of big data challenges. To this end, we propose a model to capture change and the process of exploring dynamic data to identify salient changes. We provide exploration primitives along with motivational examples and measures for the volatility of data. We identify technical challenges that need to be addressed to make our vision a reality, and propose directions of future work for the data management community.
Rock glaciers in semiarid mountains contain large amounts of ice and might be important water stores aside from glaciers, lakes, and rivers. Yet whether and how rock glaciers interact with river channels in mountain valleys remains largely unresolved. We examine the potential for rock glaciers to block or disrupt river channels, using a new inventory of more than 2000 intact rock glaciers that we mapped from remotely sensed imagery in the Karakoram (KR), Tien Shan (TS), and Altai (ALT) mountains. We find that between 5% and 14% of the rock glaciers partly buried, blocked, diverted or constricted at least 95 km of mountain rivers in the entire study area. We use a Bayesian robust logistic regression with multiple topographic and climatic inputs to discern those rock glaciers disrupting mountain rivers from those with no obvious impacts. We identify elevation and potential incoming solar radiation (PISR), together with the size of feeder basins, as dominant predictors, so that lower-lying and larger rock glaciers from larger basins are more likely to disrupt river channels. Given that elevation and PISR are key inputs for modelling the regional distribution of mountain permafrost from the positions of rock-glacier toes, we infer that river-blocking rock glaciers may be diagnostic of non-equilibrated permafrost. Principal component analysis adds temperature evenness and wet-season precipitation to the controls that characterise rock glaciers impacting on rivers. Depending on the choice of predictors, the accuracy of our classification is moderate to good with median posterior area-under-the-curve values of 0.71-0.89. Clarifying whether rapidly advancing rock glaciers can physically impound rivers, or fortify existing dams instead, deserves future field investigation. We suspect that rock-glacier dams are conspicuous features that have a polygenetic history and encourage more research on the geomorphic coupling between permafrost lobes, river channels, and the sediment cascades of semiarid mountain belts. (c) 2018 John Wiley & Sons, Ltd.
We present a system-level synthesis approach for heterogeneous multi-processor on chip, based on Answer Set Programming(ASP). Starting with a high-level description of an application, its timing constraints and the physical constraints of the target device, our goal is to produce the optimal computing infrastructure made of heterogeneous processors, peripherals, memories and communication components. Optimization aims at maximizing speed, while minimizing chip area. Also, a scheduler must be produced that fulfills the real-time requirements of the application. Even though our approach will work for application specific integrated circuits, we have chosen FPGA as target device in this work because of their reconfiguration capabilities which makes it possible to explore several design alternatives. This paper addresses the bottleneck of problem representation size by providing a direct and compact ASP encoding for automatic synthesis that is semantically equivalent to previously established ILP and ASP models. We describe a use-case in which designers specify their applications in C/C++ from which optimum systems can be derived. We demonstrate the superiority of our approach toward existing heuristics and exact methods with synthesis results on a set of realistic case studies. (C) 2018 Elsevier Inc. All rights reserved.
Bryophytes constitute an important and permanent component of the grassland flora and diversity in Europe. As most bryophyte species are sensitive to habitat change, their diversity is likely to decline following land-use intensification. Most previous studies on bryophyte diversity focused on specific habitats of high bryophyte diversity, such as bogs, montane grasslands, or calcareous dry grasslands. In contrast, mesic grasslands are rarely studied, although they are the most common grassland habitat in Europe. They are secondary vegetation, maintained by agricultural use and thus, are influenced by different forms of land use. We studied bryophyte species richness in three regions in Germany, in 707 plots of 16 m(2) representing different land-use types and environmental conditions. Our study is one of the few to inspect the relationships between bryophyte richness and land use across contrasting regions and using a high number of replicates. Among the managed grasslands, pastures harboured 2.5 times more bryophyte species than meadows and mown pastures. Similarly, bryophyte cover was about twice as high in fallows and pastures than in meadows and mown pastures. Among the pastures, bryophyte species richness was about three times higher in sheep grazed plots than in the ones grazed by cattle or horses. In general, bryophyte species richness and cover was more than 50% lower in fertilized than in unfertilized plots. Moreover, the amount of suitable substrates was linked to bryophyte diversity. Species richness of bryophytes growing on stones increased with stone cover, and the one of bryophytes growing on bark and deadwood increased with larger values of woody plant species and deadwood cover. Our findings highlight the importance of low-intensity land use and high structural heterogeneity for bryophyte conservation. They also caution against an intensification of traditionally managed pastures. In the light of our results, we recommend to maintain low-intensity sheep grazing on sites with low productivity, such as slopes on shallow soils.
As tall as my peers
(2018)
Background: We define migrants as people who move from their place of birth to a new place of residence. Migration usually is directed by "Push-Pull" factors, for example to escape from poor living conditions or to find more prosperous socio-economic conditions. Migrant children tend to assimilate quickly, and soon perceive themselves as peers within their new social networks. Differences exist between growth of first generation and second generation migrants. Methods: We review body heights and height distributions of historic and modern migrant populations to test two hypotheses: 1) that migrant and adopted children coming from lower social status localities to higher status localities adjust their height growth toward the mean of the dominant recipient social network, and 2) social dominant colonial and military migrants display growth that significantly surpasses the median height of both the conquered population and the population of origin. Our analytical framework also considered social networks. Recent publications indicate that spatial connectedness (community effects) and social competitiveness can affect human growth. Results: Migrant children and adolescents of lower social status rapidly adjust in height towards average height of their hosts, but tend to mature earlier, and are prone to overweight. The mean height of colonial/military migrants does surpass that of the conquered and origin population. Conclusion: Observations on human social networks, non-human animal strategic growth adjustments, and competitive growth processes strengthen the concept of social connectedness being involved in the regulation of human migrant growth.
Human life course biology
(2018)
Soil pollutants such as hydrocarbons can induce toxic effects in plants and associated arbuscular mycorrhizal fungi (AMF). This study was conducted to evaluate if the legume Lotus corniculatus and the grass Elymus trachycaulus and arbuscular mycorrhizal fungi could grow in two oil sands processing by-products after bitumen extraction from the oil sands in northern Alberta, Canada. Substrate treatments were coarse tailings sand (CTS), a mix of dry mature fine tailings (MFT) with CTS (1: 1) and Pleistocene sandy soil (hydrocarbon free); microbial treatments were without AMF, with AMF and AMF plus soil bacteria isolated from oil sands reclamation sites. Plant biomass, root morphology, leaf water content, shoot tissue phosphorus content and mycorrhizal colonization were evaluated. Both plant species had reduced growth in CTS and tailings mix relative to sandy soil. AMF frequency and intensity in roots of E. trachycaulus was not influenced by soil hydrocarbons; however, it decreased significantly over time in roots of L. corniculatus without bacteria in CTS. Mycorrhizal inoculation alone did not significantly improve plant growth in CTS and tailings mix; however, inoculation with mycorrhizae plus bacteria led to a significantly positive response of both plant species in CTS. Thus, combined inoculation with selected mycorrhizae and bacteria led to synergistic effects. Such combinations may be used in future to improve plant growth in reclamation of CTS and tailings mix.
In angiosperms, the gynoecium is the last structure to develop within the flower due to the determinate fate of floral meristem (FM) stem cells. The maintenance of stem cell activity before its arrest at the stage called FM termination affects the number of carpels that develop. The necessary inhibition at this stage of WUSCHEL (WUS), which is responsible for stem cell maintenance, involves a two-step mechanism. Direct repression mediated by the MADS domain transcription factor AGAMOUS (AG), followed by indirect repression requiring the C2H2 zinc-finger protein KNUCKLES (KNU), allow for the complete termination of floral stem cell activity. Here, we show that Arabidopsis thaliana MINI ZINC FINGER2 (AtMIF2) and its homolog in tomato (Solanum lycopersicum), INHIBITOR OF MERISTEM ACTIVITY (SlIMA), participate in the FM termination process by functioning as adaptor proteins. AtMIF2 and SlIMA recruit AtKNU and SlKNU, respectively, to form a transcriptional repressor complex together with TOPLESS and HISTONE DEACETYLASE19. AtMIF2 and SlIMA bind to the WUS and SIWUS loci in the respective plants, leading to their repression. These results provide important insights into the molecular mechanisms governing (FM) termination and highlight the essential role of AtMIF2/SlIMA during this developmental step, which determines carpel number and therefore fruit size.
We consider chimera states in a one-dimensional medium of nonlinear nonlocally coupled phase oscillators. In terms of a local coarse-grained complex order parameter, the problem of finding stationary rotating nonhomogeneous solutions reduces to a third-order ordinary differential equation. This allows finding chimera-type and other inhomogeneous states as periodic orbits of this equation. Stability calculations reveal that only some of these states are stable. We demonstrate that an oscillatory instability leads to a breathing chimera, for which the synchronous domain splits into subdomains with different mean frequencies. Further development of instability leads to turbulent chimeras. Published by AIP Publishing.
Is bad intent negligible?
(2018)
The hostile attribution bias (HAB) is a well-established risk factor for aggression. It is considered part of the suspicious mindset that may cause highly victim-justice sensitive individuals to behave uncooperatively. Thus, links of victim justice sensitivity (JS) with negative behavior, such as aggression, may be better explained by HAB. The present study tested this hypothesis in N=279 German adolescents who rated their JS, HAB, and physical, relational, verbal, reactive, and proactive aggression. Victim JS predicted physical, relational, verbal, reactive, and proactive aggression when HAB was controlled. HAB only predicted physical and proactive aggression. There were no moderator effects. Injustice seems an important reason for aggression irrespective of whether or not it is intentionally caused, particularly among those high in victim JS. Thus, victim JS should be considered as a potential important risk factor for aggression and receive more attention by research on aggression and preventive efforts.
This paper presents the first investigation of the effects of optimal energy taxation in an urban spatial setting, where emissions are produced both by residences and commuting. When levying an optimal direct tax on energy or carbon use is not feasible, the analysis shows that exactly the same adjustments in resource allocation can be generated by the combination of a land tax, a housing tax, and a commuting tax. We then analyze the effects of these taxes on urban spatial structure, showing that they reduce the extent of commuting and the level of housing consumption while increasing building heights, generating a more-compact city with a lower level of emissions per capita.
Spatial and social mobility
(2018)
This paper analyzes the relationship between spatial mobility and social mobility. It develops a two-skill-type spatial equilibrium model of two regions with location preferences where each region consists of an urban area that is home to workplaces and residences and an exclusively residential suburban area. The paper demonstrates that relative regional social mobility is negatively correlated with segregation and inequality. In the model, segregation, income inequality, and social mobility are driven by differences between urban and residential areas in commuting cost differences between high-skilled and low-skilled workers, and also by the magnitude of taste heterogeneity.
In this paper, we consider the computational power of a new variant of networks of splicing processors in which each processor as well as the data navigating throughout the network are now considered to be polarized. While the polarization of every processor is predefined (negative, neutral, positive), the polarization of data is dynamically computed by means of a valuation mapping. Consequently, the protocol of communication is naturally defined by means of this polarization. We show that networks of polarized splicing processors (NPSP) of size 2 are computationally complete, which immediately settles the question of designing computationally complete NPSPs of minimal size. With two more nodes we can simulate every nondeterministic Turing machine without increasing the time complexity. Particularly, we prove that NPSP of size 4 can accept all languages in NP in polynomial time. Furthermore, another computational model that is universal, namely the 2-tag system, can be simulated by NPSP of size 3 preserving the time complexity. All these results can be obtained with NPSPs with valuations in the set as well. We finally show that Turing machines can simulate a variant of NPSPs and discuss the time complexity of this simulation.
Granitic melt inclusions were found in layers of garnet clinopyroxenites from orogenic peridotites hosted in high-pressure felsic granulites of the Granulitgebirge, central Europe. The inclusions are both glassy and crystallized, and occur as clusters in the garnet. Microstructural features suggest that the inclusions formed while garnet was growing as a peritectic phase, likely alongside clinopyroxene. The chemistry of the melt, in particular its trace element signature, shows a crustal contribution, probably due to the involvement of phengite in the melt-producing reaction, most likely in the presence of a fluid. The presence of a granitoid melt in mantle rocks may be the result of localized melting of a phengite-bearing protolith either already present in the peridotites or, more likely, within the local deeply subducted crustal units. In the latter case, the melt would have infiltrated the peridotites and generated pyroxenite via metasomatism. In either case, the presence of granitoid inclusions in orogenic peridotite provides direct evidence for a genetic connection between a high-pressure crustal melt and garnet pyroxenites. The in situ characterization of these remnants of natural melt provides direct quantitative constraints on (one of) the agents responsible for the interaction between crust and mantle.
In this study, 17 hydrologists with different experience in hydrological modelling applied the same conceptual catchment model (HBV) to a Greek catchment, using identical data and model code. Calibration was performed manually. Subsequently, the modellers were asked for their experience, their calibration strategy, and whether they enjoyed the exercise. The exercise revealed that there is considerable modellers’ uncertainty even among the experienced modellers. It seemed to be equally important whether the modellers followed a good calibration strategy, and whether they enjoyed modelling. The exercise confirmed previous studies about the benefit of model ensembles: Different combinations of the simulation results (median, mean) outperformed the individual model simulations, while filtering the simulations even improved the quality of the model ensembles. Modellers’ experience, decisions, and attitude, therefore, have an impact on the hydrological model application and should be considered as part of hydrological modelling uncertainty.
The aim of this review is to provide a selective overview of priming studies which have employed the event-related brain potential (ERP) technique in order to investigate bilingual language processing. The priming technique can reveal an implicit memory effect in which exposure to one stimulus influences the processing of another stimulus. Behavioral approaches, such as measuring reaction times, may not always be enough for providing a full view on the exact mechanisms and the time-course of language comprehension. Instead, ERPs have a time-resolution of a millisecond and hence they offer a precise temporal overview of the underlying neural processes involved in language processing. In our review, we summarize experimental research that has combined priming with ERP measurements, thus creating a valuable tool for examining the neurophysiological correlates of language processing in the bilingual brain.
We report strong evidence of Berry phase effects in intense laser dissociation of D-2(+) molecules, manifested as Aharonov-Bohm-like oscillations in the photofragment angular distribution (PAD). Our calculations show that this interference pattern strongly depends on the parity of the diatom initial rotational state, (-1)(j). Indeed, the PAD local maxima (minima) observed in one case (j odd) correspond to local minima (maxima) in the other case (j even). Using simple topological arguments, we clearly show that such interference conversion is a direct signature of the Berry phase. The sole effect of the latter on the rovibrational wave function is a sign change of the relative phase between two interfering components, which wind in opposite senses around a light-induced conical intersection (LICI). Therefore, encirclement of the LICI leads to constructive (j odd) or destructive (j even) self-interference of the initial nuclear wavepacket in the dissociative limit. To corroborate our theoretical findings, we suggest an experiment of strong-field indirect dissociation of D-2(+) molecules, comparing the PAD of the ortho and para molecular species in directions nearly perpendicular to the laser polarization axis.
We present a general analysis of the cooling produced by losses on condensates or quasi-condensates. We study how the occupations of the collective phonon modes evolve in time, assuming that the loss process is slow enough so that each mode adiabatically follows the decrease of the mean density. The theory is valid for any loss process whose rate is proportional to the jth power of the density, but otherwise spatially uniform. We cover both homogeneous gases and systems confined in a smooth potential. For a low-dimensional gas, we can take into account the modified equation of state due to the broadening of the cloud width along the tightly confined directions, which occurs for large interactions. We find that at large times, the temperature decreases proportionally to the energy scale mc(2), where m is the mass of the particles and c the sound velocity. We compute the asymptotic ratio of these two quantities for different limiting cases: a homogeneous gas in any dimension and a one-dimensional gas in a harmonic trap.