Understanding the functional consequences of biodiversity loss is a major goal of ecology. Animal-mediated pollination is an essential ecosystem function and service provided to mankind. However, ...little is known how pollinator diversity could affect pollination services. Using a substitutive design, we experimentally manipulated functional group (FG) and species richness of pollinator communities to investigate their consequences on the reproductive success of an obligate out-crossing model plant species, Raphanus sativus. Both fruit and seed set increased with pollinator FG richness. Furthermore, seed set increased with species richness in pollinator communities composed of a single FG. However, in multiple-FG communities, highest species richness resulted in slightly reduced pollination services compared with intermediate species richness. Our analysis indicates that the presence of social bees, which showed roughly four times higher visitation rates than solitary bees or hoverflies, was an important factor contributing to the positive pollinator diversity–pollination service relationship, in particular, for fruit set. Visitation rate at different daytimes, and less so among flower heights, varied among social bees, solitary bees and hoverflies, indicating a niche complementarity among these pollinator groups. Our study demonstrates enhanced pollination services of diverse pollinator communities at the plant population level and suggests that both the niche complementarity and the presence of specific taxa in a pollinator community drive this positive relationship.
We consider two models for estimating the expected states of nodes in networks where the observations at nodes are given by random states and measurement errors. In the first model, we assume ...independent successive observations at the nodes and the design question is how often the nodes should be observed to obtain a precise estimation of the expected states. In the second model, all nodes are observed simultaneously and the design question is to determine the nodes which need larger precision of the measurements than other nodes. Both models lead to the same design problem. We derive explicitly
A
-optimal designs for the most simple network with star configuration. Moreover, we consider the network with wheel configuration and derive some conditions which simplify the numerical calculation of the corresponding
A
-optimal designs.
Ecology Letters (2010) 13: 442-452 Species extinctions pose serious threats to the functioning of ecological communities worldwide. We used two qualitative and quantitative pollination networks to ...simulate extinction patterns following three removal scenarios: random removal and systematic removal of the strongest and weakest interactors. We accounted for pollinator behaviour by including potential links into temporal snapshots (12 consecutive 2-week networks) to reflect mutualists' ability to 'switch' interaction partners (re-wiring). Qualitative data suggested a linear or slower than linear secondary extinction while quantitative data showed sigmoidal decline of plant interaction strength upon removal of the strongest interactor. Temporal snapshots indicated greater stability of re-wired networks over static systems. Tolerance of generalized networks to species extinctions was high in the random removal scenario, with an increase in network stability if species formed new interactions. Anthropogenic disturbance, however, that promote the extinction of the strongest interactors might induce a sudden collapse of pollination networks.
The efflux pumps ABCB1 (p-gp, MDR1) and ABCG2 (BCRP) are expressed to a high extent by endothelial cells at the blood−brain barrier (BBB) and other barrier tissues and are involved in drug resistance ...of tumor (stem) cells. Whereas numerous ABCB1 inhibitors are known, only a few ABCG2 modulators with submicromolar activity have been published. Starting from tariquidar (4) analogues as ABCB1 modulators, minimal structural modifications resulted in a drastic shift in favor of ABCG2 inhibition. Highest potency was found when the 3,4-dimethoxy-2-(quinoline-3-carbonylamino)benzoyl moiety in 4 was replaced with a 4-methoxycarbonylbenzoyl moiety bearing a hetarylcarboxamido group in 3-position, e.g., quinoline-3-carboxamido (5, IC50: 119 nM) or quinoline-2-carboxamido (6, IC50: 60 nM, flow cytometric mitoxantrone efflux assay, topotecan-resistant MCF-7 breast cancer cells); the selectivity for ABCG2 over ABCB1 was about 100−500 fold and the compounds were inactive at ABCC2 (MRP2). Chemosensitivity assays against MCF-7/Topo cells revealed that the nontoxic inhibitor 6 completely reverted ABCG2-mediated topotecan resistance at concentrations >100 nM, whereas 5 showed ABCG2 independent cytotoxicity. ABCG2 inhibitors might be useful for cancer treatment with respect to reversal of multidrug resistance, overcoming the BBB and targeting of tumor stem cells.
Up to now, powerful outlier robust tests for linear models are based on M-estimators and are quite complicated. On the other hand, the simple robust classical sign test usually provides very bad ...power for certain alternatives. We present a generalization of the sign test which is similarly easy to comprehend but much more powerful. It is based on
K
-sign depth, shortly denoted by
K
-depth. These so-called
K
-depth tests are motivated by simplicial regression depth, but are not restricted to regression problems. They can be applied as soon as the true model leads to independent residuals with median equal to zero. Moreover, general hypotheses on the unknown parameter vector can be tested. While the 2-depth test, i.e. the
K
-depth test for
K
=
2
, is equivalent to the classical sign test,
K
-depth test with
K
≥
3
turn out to be much more powerful in many applications. A drawback of the
K
-depth test is its fairly high computational effort when implemented naively. However, we show how this inherent computational complexity can be reduced. In order to see why
K
-depth tests with
K
≥
3
are more powerful than the classical sign test, we discuss the asymptotic behavior of its test statistic for residual vectors with only few sign changes, which is in particular the case for some alternatives the classical sign test cannot reject. In contrast, we also consider residual vectors with alternating signs, representing models that fit the data very well. Finally, we demonstrate the good power of the
K
-depth tests for some examples including high-dimensional multiple regression.
Many patients with epilepsy suffer from psychiatric comorbidities including depression, anxiety, psychotic disorders, cognitive, and personality changes, but the mechanisms underlying the association ...between epilepsy and psychopathology are only incompletely understood. Animal models of epilepsy, such as the pilocarpine model of acquired temporal lobe epilepsy (TLE), are useful to study the relationship between epilepsy and behavioral dysfunctions. In the present study, we examined behavioral and cognitive alterations, spontaneous seizures, and neuropathology developing after a pilocarpine-induced status epilepticus in the C57BL/6 (B6) inbred strain of mice, which is commonly used as background strain for genetically modified mice. For this study, we used the same pilocarpine ramping-up dosing protocol and behavioral test battery than in a previous study in NMRI mice, thus allowing direct comparison between these two mouse strains. All B6 mice that survived SE developed epilepsy with spontaneous recurrent seizures. Epileptic B6 mice exhibited significant increases of anxiety-related behavior in the open field and light–dark box, increased locomotor activity in the open field, elevated plus maze, hole board, and novel object exploration tests, and decreased immobility in the forced swimming and tail suspension tests. Furthermore, spatial learning and memory were severely impaired in the Morris water maze, although hippocampal damage was much less severe than previously determined in NMRI mice. B6 mice in which pilocarpine did not induce SE but only single seizures did not exhibit any detectable neurodegeneration, but differed behaviorally from sham controls in several tests of the test battery used. Our data indicate that the pilocarpine model of TLE in B6 mice is ideally suited to study the neurobiological mechanisms underlying the association between seizures, brain damage and psychopathology.
Sign depth tests in multiple regression Horn, Melanie; Müller, Christine H.
Journal of statistical computation and simulation,
05/2023, Letnik:
93, Številka:
7
Journal Article
Recenzirano
The recently proposed simple but powerful sign depth tests depend on the order of the residuals. While one-dimensional explanatory variables provide a natural order, there exists no canonical order ...for multidimensional explanatory variables. For this scenario, we present different approaches for ordering multidimensional explanatory variables and compare them regarding their performance with respect to the stability of the ordering, the usability for non-metric explanatory variables, the computational time complexity, and in the context of testing in linear models including high-dimensional multiple regression. It is shown that the sign depth tests based on orderings given by pairwise distances perform best. They are much more powerful than the classical sign test and also than the F-test when not having normally distributed errors. They are competitive to the much more complicated robust Wald test based on efficient MM-estimation. Additionally, the sign depth tests are more appropriate for outlier robust model checks.
The toxicity of lead has been known for a long time, and no safe uptake level can be derived for humans. Consumers' intake via food should therefore be kept as low as possible. Game meat can contain ...elevated levels of lead due to the use of lead ammunition for hunting. A risk assessment conducted in 2010 by the German Federal Institute for Risk Assessment including various consumption scenarios revealed a possible health risk for extreme consumers of game meat hunted with lead ammunition (i.e. hunters and members of hunters' households). Babies, infants, children and women of childbearing age were identified as vulnerable group with regards to the developmental neurotoxicity of lead. It was noted, that a sound data base was required in order to refine the assessment. Therefore, the research project "Safety of game meat obtained through hunting" (LEMISI) has been conducted in Germany, with the aims of determining the concentrations of lead (as well as of copper and zinc) brought into the edible parts of game meat (roe deer (Capreolus capreolus) and wild boar (Sus scrofa)) due to using either lead or non-lead hunting ammunition, whilst concurrently taking geogenic (i.e. "background") levels of lead into account. Compared to non-lead ammunition, lead ammunition significantly increased lead concentrations in the game meat. The use of both lead and non-lead ammunition deposited copper and zinc in the edible parts of game meat, and the concentrations were in the range of those detected regularly in meat of farm animals. For the average consumer of game meat in Germany the additional uptake of lead only makes a minor contribution to the average alimentary lead exposure. However, for consumers from hunters' households the resulting uptake of lead-due to lead ammunition-can be several times higher than the average alimentary lead exposure. Non-lead bullets in combination with suitable game meat hygienic measures are therefore recommended in order to ensure "state of the art consumer health protection".
Diamond impregnated tools are considered which are used to machine concrete. During their application, the bonding as well as the diamonds need to wear down in a certain way to gain a sharp tool. ...This required wear is called self-sharpening and means a continuous exposure of new diamonds. Within the development phase of diamond tools, time and cost intensive testing is necessary for the assessment of the tool performance. Hence, an extrapolation based on a minimal amount of testing is desirable to forecast the tool lifetime. A further reduction of the development and testing cost can be achieved by reducing the data needed to forecast the tool performance. Within this paper, the development of a statistical model is shown which was used to forecast the lifetime of the single diamonds on the tool. The statistical analysis is based on single segment tests which were carried out with different segment specification. During the tests, the exposed and broken out diamonds were counted to serve as the necessary input data for the statistical analysis. The counting of the diamonds on the segment was done in two different ways: based on the 2-dimensional microscopic pictures made after every minute of drilling and based on the 3-dimensional surface measurements made after every 5 min of drilling. It turns out that these two approaches of the wear analysis provide similar results.
Display omitted
•Tool wear analysis based on single segment tests with varying segment specification.•Two approaches to measure tool wear: 2D microscopic picture vs 3D surface measurement.•Development of a statistic model to forecast expected lifetime of single diamonds.•Essentially, no difference in statistical results based on 2- and 3-dimensional data.•The length of inspection intervals can be extended by factor 5 for used “segment/concrete”-combinations.
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