A new species of Monanthotaxis from Gabon with a unique inflorescence type for Annonaceae

Monanthotaxis Baillon (1890: 878) currently consists of 56 species (Rainer & Chatrou 2006) confined to tropical Africa and Madagascar and is the second most species-rich genus of Annonaceae in Africa after Uvaria Linnaeus (1753: 536). Both genera belong to the tribe Uvarieae Hooker & Thomson (1855: 91, 92). Circumscription of this tribe has recently been modified to comply with the principle of monophyly, and it now almost exclusively consists of climbing species, all from the Old World tropics (Chatrou et al. 2012). Generic circumscription within Uvarieae has been in disarray for considerable time. Delimitation of Uvaria and related genera has recently been modified based on phylogenetic relationships (Zhou et al. 2010, Zhou et al. 2009). Monanthotaxis was monophyletic in Wang et al. (2012), based on a limited sampling of seven species. Subsequent study with increased sampling (Hoekstra, unpub.) has revealed that the African species of Friesodielsia van Steenis (1948: 458) and Exellia Boutique (1951b: 117) are nested in Monanthotaxis. Whatever the solution and taxonomic consequences, the name Monanthotaxis with the type Monanthotaxis congoensis Baillon (1890: 879) will be retained as it is the oldest valid generic name. Along with phylogenetic analysis, we are conducting a taxonomic revision. The last revision of Monanthotaxis and allied genera was published over a century ago by Engler & Diels (1901). Since then, only contributions to local floras have been published (e.g. Boutique 1951a, Le Thomas 1969, Robson 1960, Verdcourt 1971a). While studying the material of Monanthotaxis, we encountered a remarkable new species, which differs from all other species of Annonaceae in its large and lax panicle-like inflorescence. Panicle-like inflorescences are rare in Annonaceae, and those that have been recorded are either congested, as in e.g. Unonopsis and Guatteria (Erkens et al. 2008, Maas et al. 2007), or with only a few flowers, as in Monanthotaxis le-testui Pellegrin (1950: 75). This new species is probably closely related to M. congoensis since they share several characters. Verdcourt (1971b) divided the genus in three subgenera and five sections. In his classification, this new species would join M. congoensis in the typical section Monanthotaxis, which is easily distinguished by having flowers with the four to six petals in a single whorl and less than 17 stamens. Because it is so similar to M. congoensis, our new species will almost certainly be classified within Monanthotaxis, and we decided to publish it before a new generic classification has been completed

A nonet of novel species of Monanthotaxis (Annonaceae) from around Africa

As part of an ongoing revision of the genus Monanthotaxis Baill. (Annonaceae), nine new species are described and one variety is reinstated to species rank. Two new species from West Africa (Monanthotaxis aquila P.H. Hoekstra, sp. nov. and Monanthotaxis atewensis P.H. Hoekstra, sp. nov.), four new species from Central Africa (Monanthotaxis couvreurii P.H. Hoekstra, sp. nov., Monanthotaxis latistamina P.H. Hoekstra, sp. nov., Monanthotaxis tripetala P.H. Hoekstra, sp. nov. and Monanthotaxis zenkeri P.H. Hoekstra, sp. nov.), one new species from Tanzania (Monanthotaxis filipes P.H. Hoekstra, sp. nov.), one new species from the area around Maputo (Monanthotaxis maputensis P.H. Hoekstra, sp. nov.), one new species from the Comoro Islands (Monanthotaxis komorensis P.H. Hoekstra, sp. nov.) and Monanthotaxis klainei (Engl.) Verdc. var. angustifolia (Boutique) Verdc. is raised to species level leading to the replacement name Monanthotaxis atopostema P.H. Hoekstra, nom. nov. (not Monanthotaxis angustifolia (Exell) Verdc.). Complete descriptions, comparisons with related species, ecological information and IUCN conservation assessments are given for the new species. Five species were classified as critical endangered, two species as endangered, one as vulnerable and one as least concern, warranting the need of further collecting and studying those species

eXtended Variational Quasicontinuum Methodology for Lattice Networks with Damage and Crack Propagation

Lattice networks with dissipative interactions are often employed to analyze materials with discrete micro- or meso-structures, or for a description of heterogeneous materials which can be modelled discretely. They are, however, computationally prohibitive for engineering-scale applications. The (variational) QuasiContinuum (QC) method is a concurrent multiscale approach that reduces their computational cost by fully resolving the (dissipative) lattice network in small regions of interest while coarsening elsewhere. When applied to damageable lattices, moving crack tips can be captured by adaptive mesh refinement schemes, whereas fully-resolved trails in crack wakes can be removed by mesh coarsening. In order to address crack propagation efficiently and accurately, we develop in this contribution the necessary generalizations of the variational QC methodology. First, a suitable definition of crack paths in discrete systems is introduced, which allows for their geometrical representation in terms of the signed distance function. Second, special function enrichments based on the partition of unity concept are adopted, in order to capture kinematics in the wakes of crack tips. Third, a summation rule that reflects the adopted enrichment functions with sufficient degree of accuracy is developed. Finally, as our standpoint is variational, we discuss implications of the mesh refinement and coarsening from an energy-consistency point of view. All theoretical considerations are demonstrated using two numerical examples for which the resulting reaction forces, energy evolutions, and crack paths are compared to those of the direct numerical simulations.Comment: 36 pages, 23 figures, 1 table, 2 algorithms; small changes after review, paper title change

Sticky Particles and Stochastic Flows

Gaw\c{e}dzki and Horvai have studied a model for the motion of particles carried in a turbulent fluid and shown that in a limiting regime with low levels of viscosity and molecular diffusivity, pairs of particles exhibit the phenomena of stickiness when they meet. In this paper we characterise the motion of an arbitrary number of particles in a simplified version of their model

Compressing Random Microstructures via Stochastic Wang Tilings

This paper presents a stochastic Wang tiling based technique to compress or reconstruct disordered microstructures on the basis of given spatial statistics. Unlike the existing approaches based on a single unit cell, it utilizes a finite set of tiles assembled by a stochastic tiling algorithm, thereby allowing to accurately reproduce long-range orientation orders in a computationally efficient manner. Although the basic features of the method are demonstrated for a two-dimensional particulate suspension, the present framework is fully extensible to generic multi-dimensional media.Comment: 4 pages, 6 figures, v2: minor changes as suggested by reviewers, v3: corrected two typos in the revised versio

Effects of Tariffication: Tariffs, Quotas and VERs under Monopolistic Competition

Recent rounds of GATT and later WTO have advocated widespread tariffication, meaning that existing non-tariff barriers be converted into import equivalent tariffs. From an economic point of view, the effects of such tariffication are not entirely clear. The paper presents a general equilibrium model with monopolistic competition to examine the welfare effects of tariffication. The ranking of pre- and post-tariffication welfare depends crucially on the nature of the initial trade barrier and the tariff tool applied. Tariffication using a specific (an ad valorem) tariff results in the same (a reduced) welfare level compared to an initial quota, whereas welfare is increased (the same) compared to an initial VER.Trade policy, tariffication, specific tariff, ad valorem tariff, quota, VER

Tariffs and Firm-Level Heterogeneous Fixed Export Costs

Recent literature on the workhorse model of intra-industry trade has explored heterogeneous cost structures at the firm level. These approaches have proven to add realism and predictive power. This note shows, however, that this added realism also implies that there may exist a positive bilateral tariff that maximizes national and world welfare. Applying one of the simplest specifications possible, namely a symmetric two-country intra-industry trade model with fixed export costs that are heterogeneous across firms, we find that the reciprocal reduction of small tariffs reduces welfare.Optimal tariff; Welfare; Intra-industry trade; Monopolistic competition; Protectionism

Response calculations based on an independent particle system with the exact one-particle density matrix: polarizabilities

Recently, we have demonstrated that the problems finding a suitable adiabatic approximation in time-dependent one-body reduced density matrix functional theory can be remedied by introducing an additional degree of freedom to describe the system: the phase of the natural orbitals [Phys. Rev. Lett. 105, 013002 (2010), J. Chem. Phys. 133, 174119 (2010)]. In this article we will show in detail how the frequency-dependent response equations give the proper static limit ($\omega\to0$), including the perturbation in the chemical potential, which is required in static response theory to ensure the correct number of particles. Additionally we show results for the polarizability for H$_2$ and compare the performance of two different two-electron functionals: the phase-including L\"owdin-Shull functional and the density matrix form of the L\"owdin-Shull functional.Comment: 10 pages, 6 figure