Population dynamics and pathogenicity of Bursaphelenchus xylophilus in seven- to eight-year-old Pinus sylvestris trees

Der Kiefernholznematode, Bursaphelenchus xylophilus, ist der schädlichste pflanzenparasitäre Nematode an Bäumen in Asien und Europa und führt bei anfälligen Koniferenarten, hauptsächlich Pinus spp., zur sogenannten Kiefernwelkekrankheit. Die Krankheit ist lediglich außer­halb seines natürlichen Verbreitungsgebietes (Nordamerika) oder an nicht einheimischen Kiefernarten aufgetreten. In Gewächshausversuchen mit Sämlingen war Pinus sylvestris eine der anfälligsten europäischen Kiefern­arten. Um die Aussagefähigkeit dieser auf Sämlingen basieren­den Analysen bezüglich der Populationsdynamik und der Pathogenität für erwachsene P. sylvestris Bäume zu überprüfen, wurden Untersuchungen an sieben- bis achtjährigen Bäumen durchgeführt. Die Bäume wurden mit einer Suspension bestehend aus 10.000 B. xylophilus in 600 μl Leitungswasser pro Baum künstlich inokuliert. Für die Populationsdynamikuntersuchung wurden die Kiefern zur Nematodenextraktion in 48 Segmente geteilt. Die Entwicklung der Welkesymptome und physiologischen Änderungen wurden bis zum Tod der Bäume beobachtet.Während der Populationsdynamikuntersuchung war B. xylophilus in den ersten 11 Tagen nach Inokulation in der Inokulationsstelle und den benachbarten Segmenten lokalisiert. Am Tag 16 war B. xylophilus im gesamten Stamm, den benachbarten Astsegmenten, Wurzelhals und Wurzeln verteilt, noch bevor äußere Welkesymptome erschienen. Mit zunehmender Kiefernwelkeerkrankung war B. xylophilus schließlich in allen Holz- und Wurzelsegmenten zu finden. Hohe Nematodendichten traten auf. Kurz vor dem vollständigen Absterben der Bäume zeigte die Baumspitze mehrere nematodenfreie Segmente. Die restlichen Stamm- und benachbarten Astsegmente und der Wurzelhals waren in hohem Maße mit Nematoden befallen. Während der Pathogenitätsuntersuchung starben alle B. xylophilus-inokulierten Kiefern innerhalb von 84 Tagen. Der signifikante Abfall des Wasserpotentials in den Nadeln war steiler und stärker mit den zunehmenden Welkesymptomen korreliert als bei einer trocken­gestressten Vergleichsvariante. Der Abfall des Wasser­potentials in den Nadeln trat jedoch bei der trocken­gestressten Kiefernvariante früher ein. Schlussfolgend betrachtet waren die Populationsdynamik von B. xylophilus in sieben- bis achtjährigen P. sylvestris Bäumen und die pathologischen Reaktionen der Kiefern vergleichbar zu denen in Sämlingsuntersuchungen, auch wenn das Erreichen eines Populationsmaximums und die Entwicklung von Welkesymptomen zeitlich verzögert waren. Aus diesem Grund sind P. sylvestris Sämlinge gute Indikatorbäume für B. xylophilus Populationsdynamik- und Pathogenitätsuntersuchungen.The pinewood nematode, Bursaphelenchus xylophilus, is the most harmful plant parasitic nematode on trees in Asia and Europe and is the causal agent of the so-called pine wilt disease of susceptible conifer species, mainly Pinus spp. The disease has occurred only outside its natural range of distribution (North America) or on non-native pine species. In greenhouse trials using saplings, Pinus sylvestris was one of the most susceptible European pine species. To examine the significance of these sapling-based analyses concerning the population dynamics and pathogenicity for mature P. sylvestris trees, investigations using seven- to eight-year-old trees were carried out. The trees were artificially inoculated using a suspension of 10,000 B. xylophilus in 600 μl of tap water per tree. For the population dynamics investigation, the pines were divided into 48 segments for nematode extraction. The development of wilt symptoms as well as physiological changes were observed until tree death.During the population dynamics investigation, B. xylophilus was located at the inoculation site and in adjacent segments during the first 11 days after inoculation. On day 16, B. xylophilus was distributed throughout the entire stem, adjacent branch segments, root collar and roots before any external wilt symptoms appeared. With increasing pine wilt disease, B. xylophilus was finally found in all wood and root segments. High nematode densities appeared. Shortly before tree death, the treetop showed several nematode-free segments. The rest of the stem and adjacent branch segments and root collar were highly nematode-infested. During the pathogenicity investigation, all B. xylophilus-inoculated pines died within 84 days. The significant decline in the water potential in the needles was steeper and more strongly correlated with increasing wilt symptoms compared to a drought-stressed variant. However, the decline in the water potential in the needles started earlier in the drought-stressed pine variant. In conclusion, the population dynamics of B. xylophilus in seven- to eight-year-old P. sylvestris trees and the pathological reactions of the pines were comparable to those observed in assays with saplings, although delayed in reaching a population peak and developing wilt symptoms. Therefore, P. sylvestris saplings are good indicator trees for B. xylophilus population dynamics and pathogenicity investigations

Weak-strong uniqueness and energy-variational solutions for a class of viscoelastoplastic fluid models

We study a model for a fluid showing viscoelastic and viscoplastic behavior, which describes the flow in terms of the fluid velocity and a symmetric deviatoric stress tensor. This stress tensor is transported via the Zaremba-Jaumann rate, and it is subject to two dissipation processes: one induced by a nonsmooth convex potential and one by stress diffusion. We show short-time existence of strong solutions as well as their uniqueness in a class of Leray-Hopf-type weak solutions satisfying the tensorial component in the sense of an evolutionary variational inequality. The global-in-time existence of such generalized solutions has been established in a previous work. We further study the limit when stress diffusion vanishes. In this case, the above notion of generalized solutions is no longer suitable, and we introduce the concept of energy-variational solutions, which is based on an inequality for the relative energy. We derive general properties of energy-variational solutions and show their existence by passing to the nondiffusive limit in the relative energy inequality satisfied by generalized solutions for nonzero stress diffusion

Leray-Hopf solutions to a viscoelastic fluid model with nonsmooth stress-strain relation

We consider a fluid model including viscoelastic and viscoplastic effects. The state is given by the fluid velocity and an internal stress tensor that is transported along the flow with the Zaremba-Jaumann derivative. Moreover, the stress tensor obeys a nonlinear and nonsmooth dissipation law as well as stress diffusion. We prove the existence of global-in-time weak solutions satisfying an energy inequality under general Dirichlet conditions for the velocity field and Neumann conditions for the stress tensor

Retreatment with interferon-alpha and ribavirin in primary interferon-alpha non-responders with chronic hepatitis C

Background/Aims: Combination therapy with interferon-alpha (IFN-alpha) plus ribavirin is more efficacious than IFN-alpha monotherapy in previously untreated patients with chronic hepatitis C and patients with IFN-alpha relapse. Only limited data are available in IFN-alpha non-responders. In a multicenter trial we therefore evaluated the efficacy of combination therapy in IFN-alpha-resistant chronic hepatitis C. Methods: Eighty-two patients (mean age 46.8 years, 54 males, 28 females) with chronic hepatitis C were treated with IFN-alpha-2a (3 x 6 MIU/week) and ribavirin (14 mg/kg daily) for 12 weeks. Thereafter, treatment was continued only in virological responders (undetectable serum HCV RNA at week 12) with an IFN-alpha dose of 3 x 3 MIU/week and without ribavirin for a further 9 months. The primary study endpoint was an undetectable HCV RNA by RT-PCR at the end of the 24-week follow-up period. Results: After 12 weeks of combination therapy, an initial virological response was observed in 29 of 82 (35.4%) patients. Due to a high breakthrough rate after IFN-a dose reduction and ribavirin discontinuation, an end-of-treatment response was only achieved in 12 of 82 (14.6%) patients. After the follow-up period, a sustained virological response was observed in 8 of 82 (9.8%) patients. Infection with HCV genotype 3 was the only pretreatment parameter, which could predict a sustained response (HCV-1, 5%; HCV-3, 57.1%; p < 0.001). Conclusions: Despite a high initial response rate of 35.4%, sustained viral clearance was achieved only in 9.8% of the retreated primary IFN-alpha non-responders. Higher IFN-alpha induction and maintenance dose, as well as prolonged ribavirin treatment may possibly increase the virological response rates in non-responders, particularly in those infected by HCV-1

Cohomogeneity one manifolds and selfmaps of nontrivial degree

We construct natural selfmaps of compact cohomgeneity one manifolds with finite Weyl group and compute their degrees and Lefschetz numbers. On manifolds with simple cohomology rings this yields in certain cases relations between the order of the Weyl group and the Euler characteristic of a principal orbit. We apply our construction to the compact Lie group SU(3) where we extend identity and transposition to an infinite family of selfmaps of every odd degree. The compositions of these selfmaps with the power maps realize all possible degrees of selfmaps of SU(3).Comment: v2, v3: minor improvement

Substantia nigra activity level predicts trial-to-trial adjustments in cognitive control

Effective adaptation to the demands of a changing environment requires flexible cognitive control. The medial and the lateral frontal cortices are involved in such control processes, putatively in close interplay with the BG. In particular, dopaminergic projections from the midbrain (i.e., from the substantia nigra [SN] and the ventral tegmental area) have been proposed to play a pivotal role in modulating the activity in these areas for cognitive control purposes. In that dopaminergic involvement has been strongly implicated in reinforcement learning, these ideas suggest functional links between reinforcement learning, where the outcome of actions shapes behavior over time, and cognitive control in a more general context, where no direct reward is involved. Here, we provide evidence from functional MRI in humans that activity in the SN predicts systematic subsequent trial-to-trial RT prolongations that are thought to reflect cognitive control in a stop-signal paradigm. In particular, variations in the activity level of the SN in one trial predicted the degree of RT prolongation on the subsequent trial, consistent with a modulating output signal from the SN being involved in enhancing cognitive control. This link between SN activity and subsequent behavioral adjustments lends support to theoretical accounts that propose dopaminergic control signals that shape behavior both in the presence and in the absence of direct reward. This SN-based modulatory mechanism is presumably mediated via a wider network that determines response speed in this task, including frontal and parietal control regions, along with the BG and the associated subthalamic nucleus

FreeContact: fast and free software for protein contact prediction from residue co-evolution

Background: 20 years of improved technology and growing sequences now renders residue-residue contact constraints in large protein families through correlated mutations accurate enough to drive de novo predictions of protein three-dimensional structure. The method EVfold broke new ground using mean-field Direct Coupling Analysis (EVfold-mfDCA); the method PSICOV applied a related concept by estimating a sparse inverse covariance matrix. Both methods (EVfold-mfDCA and PSICOV) are publicly available, but both require too much CPU time for interactive applications. On top, EVfold-mfDCA depends on proprietary software. Results: Here, we present FreeContact, a fast, open source implementation of EVfold-mfDCA and PSICOV. On a test set of 140 proteins, FreeContact was almost eight times faster than PSICOV without decreasing prediction performance. The EVfold-mfDCA implementation of FreeContact was over 220 times faster than PSICOV with negligible performance decrease. EVfold-mfDCA was unavailable for testing due to its dependency on proprietary software. FreeContact is implemented as the free C++ library “libfreecontact”, complete with command line tool “freecontact”, as well as Perl and Python modules. All components are available as Debian packages. FreeContact supports the BioXSD format for interoperability. Conclusions: FreeContact provides the opportunity to compute reliable contact predictions in any environment (desktop or cloud)

Lehrerhandbücher zur zweidimensional-dynamischen Mechanik

In den Jahren 2008 bis 2010 wurde das umfangreiche Forschungsprojekt „Zweidimensional-dynamische Einführung in die Mechanik“ in der Jahrgangsstufe 7 durchgeführt. Dieses Konzept wurde dann erweitert und dazu mittlerweile zwei Lehrerhandbücher erstellt (Mechanik I: 2011, Mechanik II: 2013), wofür viele verschiedene Vorarbeiten aufgegriffen wurden. Diese beiden Handbücher decken in etwa die gesamte Mechanik der Sekundarstufe I bis Jahrgangsstufe 10 ab und enthalten sehr umfangreiche Unterrichtsmaterialien. Da sie lehrplanunabhängig sein sollen, bieten sie vieles zur Auswahl an. U.a. gibt es zahlreiche Videos mit diversen Einblendungen wie z.B. Geschwindigkeitspfeile. Die didaktischen Entscheidungen des erweiterten Konzeptes werden vorgestellt