Wahrnehmung von Wirtsdüften durch Forstschädlinge : Vergleich zwischen einem Holzbrüter und einem Rindenbrüter

The blue pine wood borer (Phaenops cyanea) and the black pine sawyer beetle (Monochamus galloprovincialis) (Fig. 1) both are pests of the white pine (Pinus silvestris) and other Pinus species. Both insects have nearly the same demands regarding their breeding site. Larval development requires a fresh, unwilted inner bark. An infestation occurs on freshly cut trees or on trees suffering from stress (e.g. after dry seasons, loss of needles caused by feeding caterpillars or damage by forest fires). Phaenops cyanea detects susceptible pines by their volatile emissions (SCHÜTZ et al. 2004) and is able to infest the trees already at a low stress level. During feeding the larvae avoid the resin ducts of the tree and thus evade the oleoresin defence. The beetle is endemic in Europe and – under favourable climatic conditions – can cause substantial damage to pine forests. It is the most significant bark-breeding beetle of white pine in the lowlands of north-eastern Germany. Monochamus galloprovincialis is found in Europe and northern Africa. The larvae tend to a more copious feeding which makes them more susceptible to the oleoresin defence of the tree. Thus, M. galloprovincialis prefers trees that are weakened by a higher degree of stress. The economic damage caused by feeding of thebeetle is low. However, the beetle has gained a special attention of forest scientists because of its association with the nematode Bursaphelenchus xylophilus which is causing the pine wilt disease (PWD) in Pinus. The only outbreak of the PWD within Europe is limited to an area of 258.000 ha in Portugal. (MOTA et al. 1999).Die Forstschädlinge Phaenops cyanea (Coleoptera: Buprestidae) und Monochamus galloprovincialis (Coleoptera: Cerambycidae) befallen beide Kiefern (Pinus sylvestris), die geschwächt sind, z.B. durch Wasser-Stress. Die Larven von P. cyanea entwickeln sich in oder unter der Rinde, während Larven von M. galloprovincialis nach einem Fraß im Kambium des befallenen Baumes auch tief in das Holz eindringen. P. cyanea befällt bereits Bäume, die nur einem geringen Stress ausgesetzt waren, während M. galloprovincialis Bäume bevorzugt, die erheblich geschwächt oder bereits tot sind. Die vorliegende Studie soll anhand elektrophysiologischer Experimente untersuchen, welchen olfaktorischen Hinweisen die beiden Insekten bei ihrer Suche nach einem geeigneten Eiablageplatz folgen. Duftstoffe von Pinus sylvestris wurden auf Aktivkohle gesammelt und mit Gaschromatographie, Massenspektroskopie und Elektroantennographie untersucht (GC-MS/ EAD). Die stärksten Signale von P. cyanea traten im Retentionsindex-Bereich von 936 (α-Pinen) bis 1200 auf, wobei insbesondere bizyklische Terpene und Terpenoide wie α-Pinen, β-Pinen, 1,8-Cineol und trans- Verbenol detektiert wurden. M. galloprovincialis reagierte auf einen weiteren Bereich von Stoffen, ebenfalls beginnend mit α-Pinen, bis hin zu Stoffen mit einem Retentionsindex von ca. 1300. Es scheint eine spezifische Empfindlichkeit für monozyklische und azyklische Terpene und Terpenoide vorzuliegen, insbesondere für γ-Terpinen, Terpinolen, β-Myrcen und p-Cymen

Isogeometric analysis of the Laplace eigenvalue problem on circular sectors: Regularity properties, graded meshes & variational crimes

The Laplace eigenvalue problem on circular sectors has eigenfunctions with corner singularities. Standard methods may produce suboptimal approximation results. To address this issue, a novel numerical algorithm that enhances standard isogeometric analysis is proposed in this paper by using a single-patch graded mesh refinement scheme. Numerical tests demonstrate optimal convergence rates for both the eigenvalues and eigenfunctions. Furthermore, the results show that smooth splines possess a superior approximation constant compared to their $C^0$-continuous counterparts for the lower part of the Laplace spectrum. This is an extension of previous findings about excellent spectral approximation properties of smooth splines on rectangular domains to circular sectors. In addition, graded meshes prove to be particularly advantageous for an accurate approximation of a limited number of eigenvalues. The novel algorithm applied here has a drawback in the singularity of the isogeometric parameterization. It results in some basis functions not belonging to the solution space of the corresponding weak problem, which is considered a variational crime. However, the approach proves to be robust. Finally, a hierarchical mesh structure is presented to avoid anisotropic elements, omit redundant degrees of freedom and keep the number of basis functions contributing to the variational crime constant, independent of the mesh size. Numerical results validate the effectiveness of hierarchical mesh grading for the simulation of eigenfunctions with and without corner singularities.Comment: 35 pages, 19 figure

Do Some Business Models Perform Better than Others?

This paper defines four basic business models based on what asset rights are sold (Creators, Distributors, Landlords and Brokers) and four variations of each based on what type of assets are involved (Financial, Physical, Intangible, and Human). Using this framework, we classified the business models of all 10,970 publicly traded firms in the US economy from 1998 through 2002. Some of these classifications were done manually, based on the firms' descriptions of sources of revenue in their financial reports; the rest were done automatically by a rule-based system using the same data. Based on this analysis, we first document important stylized facts about the distribution of business models in the U.S. economy. Then we analyze the firms' financial performance in three categories: market value, profitability, and operating efficiency. We find that no model outperforms others on all dimensions. Surprisingly, however, we find that some models do, indeed, have better financial performance than others. For instance, Physical Creators (which we call Manufacturers) and Physical Landlords have greater cash flow on assets, and Intellectual Landlords have poorer q's, than Physical Distributors (Wholesaler/Retailers). These findings are robust to a large number of robustness checks and alternative interpretations. We conclude with some hypotheses to explain our findings.business models; performance

Do Some Business Models Perform Better than Others?

This paper defines four basic business models based on what asset rights are sold (Creators, Distributors, Landlords and Brokers) and four variations of each based on what type of assets are involved (Financial, Physical, Intangible, and Human). Using this framework, we classified the business models of all 10,970 publicly traded firms in the US economy from 1998 through 2002. Some of these classifications were done manually, based on the firms' descriptions of sources of revenue in their financial reports; the rest were done automatically by a rule-based system using the same data. Based on this analysis, we first document important stylized facts about the distribution of business models in the U.S. economy. Then we analyze the firms' financial performance in three categories: market value, profitability, and operating efficiency. We find that no model outperforms others on all dimensions. Surprisingly, however, we find that some models do, indeed, have better financial performance than others. For instance, Physical Creators (which we call Manufacturers) and Physical Landlords have greater cash flow on assets, and Intellectual Landlords have poorer q's, than Physical Distributors (Wholesaler/Retailers). These findings are robust to a large number of robustness checks and alternative interpretations. We conclude with some hypotheses to explain our findings.business models; performance