The Biology of Canadian Weeds. 126. \u3cem\u3eAmaranthus albus\u3c/em\u3e L., \u3cem\u3eA. blitoides\u3c/em\u3e S. Watson and \u3cem\u3eA. blitum\u3c/em\u3e L.

A review of biological information is provided for three species of the genus Amaranthus: A. albus L., A. blitoides S. Watson and A. blitum L. The last species has been revised taxonomically and a new subspecies for Canada is presented—A. blitum subsp. emarginatus (Moq. ex Uline & Bray) Carretero, Munoz Garmendia & Pedrol. Amaranthus albus and A. blitoides are native to the U.S.A. and introduced to Canada. Both species are annual ruderal and agrestal weeds. During the past 100 yr the two species have spread across most provinces of Canada, but the greatest frequency and abundance have been recorded in Saskatchewan. Originating from Europe, Asia and North Africa, A. blitum was initially considered a non-persistent species. The present study shows that A. blitum especially, subsp. emarginatus, has continued to spread in Québec. The three species are alternate hosts to many insects, nematodes, viruses, bacteria and fungi that affect cultivated plants. In other areas (U.S.A., Europe and Asia), the three species have developed multiple resistance to triazine and acetolactate-synthase-inhibiting herbicides

The Biology of Canadian Weeds. 131. \u3cem\u3ePolygonum aviculare\u3c/em\u3e L.

A review and assessment of biological information as well as personal data are provided for Polygonum aviculare in Canada. The species has been revised taxonomically and the six subspecies that occur in Canada are presented. Three of the subspecies, P. aviculare subsp. aviculare, P. aviculare subsp. neglectum and P. aviculare subsp. depressum are weeds introduced to Canada from Europe. A fourth subspecies, P. aviculare subsp. buxiforme is apparently native to North America. The geographical distribution of the latter four subspecies is very wide. Plants exhibit a high phenotypic plasticity and genetic variability, and they easily adapt to a multitude of agrestal and ruderal habitats. The seeds have a variable dormancy and polymorphic germination as a result of heterocarpy, genetic and environmental factors. In other areas (Europe), the species has developed resistance to triazines. Plants are hosts to nematodes, viruses, and fungi that also affect cultivated plants

The Biology of Canadian Weeds. 133. \u3cem\u3eCuscuta campestris\u3c/em\u3e Yuncker, \u3cem\u3eC. gronovii\u3c/em\u3e Willd. ex Schult., \u3cem\u3eC. umbrosa\u3c/em\u3e Beyr. ex Hook., \u3cem\u3eC. epithymum\u3c/em\u3e (L.) L. and \u3cem\u3eC. epilinum\u3c/em\u3e Weihe

Cuscuta spp. (dodders) are rootless, holoparasitic herbs with filiform stems attached to the host by numerous haustoria. In Canada, Cuscuta gronovii is the most common native species of the genus followed by Cuscuta campestris and C. umbrosa. Cuscuta epithymum and C. epilinum, both introduced species in Canada, occur occasionally. Infestation by Cuscuta spp. can result in serious yield losses and dodders are listed as noxious weeds in British Columbia, Ontario and Québec, and as restricted weeds in Alberta. These plants have evolved special adaptations to ensure their success: germination occurs late in the season when potential hosts are already established; seedlings selectively forage in plant communities and they may survive relatively long periods during the autotrophic stage. Invasion occurs via extremely elaborate mechanisms designed to match the biological processes of their host and bypass defense mechanisms. The principal means of dispersal of Cuscuta weeds world-wide (including Canada) has been through contaminated seeds of previously infested forage legumes. In other areas (e.g., Israel), C. campestris has developed resistance to ALS inhibitors (chlorsulfuron, and sulfometuron-methyl) and AABI herbicides. Complete descriptions and illustrations are provided for discussed species

Dualities and dual pairs in Heyting algebras

We extract the abstract core of finite homomorphism dualities using the techniques of Heyting algebras and (combinatorial) categories.Comment: 17 pages; v2: minor correction

On infinite-finite duality pairs of directed graphs

The (A,D) duality pairs play crucial role in the theory of general relational structures and in the Constraint Satisfaction Problem. The case where both classes are finite is fully characterized. The case when both side are infinite seems to be very complex. It is also known that no finite-infinite duality pair is possible if we make the additional restriction that both classes are antichains. In this paper (which is the first one of a series) we start the detailed study of the infinite-finite case. Here we concentrate on directed graphs. We prove some elementary properties of the infinite-finite duality pairs, including lower and upper bounds on the size of D, and show that the elements of A must be equivalent to forests if A is an antichain. Then we construct instructive examples, where the elements of A are paths or trees. Note that the existence of infinite-finite antichain dualities was not previously known

The Biology of Canadian Weeds. 126. \u3cem\u3eAmaranthus albus\u3c/em\u3e L., \u3cem\u3eA. blitoides\u3c/em\u3e S. Watson and \u3cem\u3eA. blitum\u3c/em\u3e L.

A review of biological information is provided for three species of the genus Amaranthus: A. albus L., A. blitoides S. Watson and A. blitum L. The last species has been revised taxonomically and a new subspecies for Canada is presented—A. blitum subsp. emarginatus (Moq. ex Uline & Bray) Carretero, Munoz Garmendia & Pedrol. Amaranthus albus and A. blitoides are native to the U.S.A. and introduced to Canada. Both species are annual ruderal and agrestal weeds. During the past 100 yr the two species have spread across most provinces of Canada, but the greatest frequency and abundance have been recorded in Saskatchewan. Originating from Europe, Asia and North Africa, A. blitum was initially considered a non-persistent species. The present study shows that A. blitum especially, subsp. emarginatus, has continued to spread in Québec. The three species are alternate hosts to many insects, nematodes, viruses, bacteria and fungi that affect cultivated plants. In other areas (U.S.A., Europe and Asia), the three species have developed multiple resistance to triazine and acetolactate-synthase-inhibiting herbicides

Investigating microstructural variation in the human hippocampus using non-negative matrix factorization

In this work we use non-negative matrix factorization to identify patterns of microstructural variance in the human hippocampus. We utilize high-resolution structural and diffusion magnetic resonance imaging data from the Human Connectome Project to query hippocampus microstructure on a multivariate, voxelwise basis. Application of non-negative matrix factorization identifies spatial components (clusters of voxels sharing similar covariance patterns), as well as subject weightings (individual variance across hippocampus microstructure). By assessing the stability of spatial components as well as the accuracy of factorization, we identified 4 distinct microstructural components. Furthermore, we quantified the benefit of using multiple microstructural metrics by demonstrating that using three microstructural metrics (T1-weighted/T2-weighted signal, mean diffusivity and fractional anisotropy) produced more stable spatial components than when assessing metrics individually. Finally, we related individual subject weightings to demographic and behavioural measures using a partial least squares analysis. Through this approach we identified interpretable relationships between hippocampus microstructure and demographic and behavioural measures. Taken together, our work suggests non-negative matrix factorization as a spatially specific analytical approach for neuroimaging studies and advocates for the use of multiple metrics for data-driven component analyses

Gaps and dualities in Heyting categories

summary:We present an algebraic treatment of the correspondence of gaps and dualities in partial ordered classes induced by the morphism structures of certain categories which we call Heyting (such are for instance all cartesian closed categories, but there are other important examples). This allows to extend the results of [14] to a wide range of more general structures. Also, we introduce a notion of combined dualities and discuss the relation of their structure to that of the plain ones

Frequency-Dependent Streaming Potential of Porous Media—Part 2: Experimental Measurement of Unconsolidated Materials

Frequency-dependent streaming potential coefficient measurements have been made upon Ottawa sand and glass bead packs using a new apparatus that is based on an electromagnetic drive. The apparatus operates in the range 1 Hz to 1 kHz with samples of 25.4 mm diameter up to 150 mm long. The results have been analysed using theoretical models that are either (i) based upon vibrational mechanics, (ii) treat the geological material as a bundle of capillary tubes, or (iii) treat the material as a porous medium. The best fit was provided by the Pride model and its simplification, which is satisfying as this model was conceived for porous media rather than capillary tube bundles. Values for the transition frequency were derived from each of the models for each sample and were found to be in good agreement with those expected from the independently measured effective pore radius of each material. The fit to the Pride model for all four samples was also found to be consistent with the independently measured steady-state permeability, while the value of the streaming potential coefficient in the low-frequency limit was found to be in good agreement with other steady-state streaming potential coefficient data

Exchange bias in GeMn nanocolumns: the role of surface oxidation

We report on the exchange biasing of self-assembled ferromagnetic GeMn nanocolumns by GeMn-oxide caps. The x-ray absorption spectroscopy analysis of this surface oxide shows a multiplet fine structure that is typical of the Mn2+ valence state in MnO. A magnetization hysteresis shift |HE|~100 Oe and a coercivity enhancement of about 70 Oe have been obtained upon cooling (300-5 K) in a magnetic field as low as 0.25 T. This exchange bias is attributed to the interface coupling between the ferromagnetic nanocolumns and the antiferromagnetic MnO-like caps. The effect enhancement is achieved by depositing a MnO layer on the GeMn nanocolumns.Comment: 7 pages, 5 figure