Protein adsorption on heterogeneous surfaces

The adsorption of the protein bovine serum albumin from an aqueous solution onto substrata made from pure silica, pure zirconia, and a mixture of the two has revealed that the adsorption behavior of the protein onto the mixture very significantly diverges from the corresponding mean of the behaviors with the pure substrata. A tentative explanation in terms of matching substratum heterogeneity with protein surface heterogeneity is offered

Colorectal Cancer Through Simulation and Experiment

Colorectal cancer has continued to generate a huge amount of research interest over several decades, forming a canonical example of tumourigenesis since its use in Fearon and Vogelstein’s linear model of genetic mutation. Over time, the field has witnessed a transition from solely experimental work to the inclusion of mathematical biology and computer-based modelling. The fusion of these disciplines has the potential to provide valuable insights into oncologic processes, but also presents the challenge of uniting many diverse perspectives. Furthermore, the cancer cell phenotype defined by the ‘Hallmarks of Cancer’ has been extended in recent times and provides an excellent basis for future research. We present a timely summary of the literature relating to colorectal cancer, addressing the traditional experimental findings, summarising the key mathematical and computational approaches, and emphasising the role of the Hallmarks in current and future developments. We conclude with a discussion of interdisciplinary work, outlining areas of experimental interest which would benefit from the insight that mathematical and computational modelling can provide

Plant Diversity and Cover after Wildfire on Anthropogenically Disturbed and Undisturbed Sites in Subarctic Upland Picea mariana Forest

Postfire development of cover and diversity was studied in an upland Picea mariana-dominated forest in the Canadian Subarctic. Short-term vegetation responses of 10- and 22-year-old cleared rights-of-way and a forest site were investigated two and three growing seasons after a wildfire. Prefire and postfire investigation of the study site allowed direct comparison of species cover and frequency values, as well as the Shannon-Wiener diversity index, before and after the fire. The fire considerably reduced diversity on all sites. Species diversity increased with the level of prefire disturbance. Prefire disturbance influenced the fire's characteristics by altering the fuel load and soil moisture, which in turn affected the postfire revegetation through different soil and microclimatic conditions. The sites that were most severely disturbed before the fire experienced the most rapid revegetation, including the highest diversity index and highest plant cover. Of the sites that were undisturbed before the fire, the natural drainage swales offered the best growing conditions after the burn. Furthermore, prefire disturbance increased the patchiness of the burned area, and the residual flora of unburned patches added to postfire floristic diversity.On a étudié le développement du couvert et de la diversité après un incendie dans une forêt de haute terre dominée par Picea mariana, au Canada subarctique. Les réactions à court terme des plantes poussant dans les emprises dégagées vieilles de 10 et 22 ans, ainsi qu'un site forestier ont été l'objet de recherches deux et trois saisons de croissance après un incendie de forêt. Les travaux réalisés sur le site de l'étude avant et après le feu ont permis une comparaison directe du couvert et de la fréquence des espèces ainsi que de l'index de diversité Shannon-Wiener avant et après le feu. L'incendie a considérablement réduit la diversité sur tous les sites. La diversité des espèces augmentait avec le niveau de perturbation existant avant l'incendie. La perturbation pré-incendie a influencé la nature du feu en modifiant la masse de combustible et l'humidité du sol, qui, à leur tour, ont affecté le reverdissement post-incendie en modifiant l'état du sol et les conditions microclimatiques. Les sites qui avaient été le plus perturbés avant le feu ont connu le reverdissement le plus rapide, y compris l'index de diversité et le couvert végétal les plus élevés. Parmi les sites qui n'avaient pas été perturbés avant l'incendie, les dépressions de drainage naturelles offraient les meilleures conditions de croissance après le feu. De plus, la perturbation pré-incendie a intensifié le morcellement de la surface brûlée, et la flore résiduelle des parcelles non brûlées a ajouté à la diversité floristique présente après l'incendie

Nonequilibrium Green's function theory for nonadiabatic effects in quantum electron transport

We develop nonequilibribrium Green's function based transport theory, which includes effects of nonadiabatic nuclear motion in the calculation of the electric current in molecular junctions. Our approach is based on the separation of slow and fast timescales in the equations of motion for the Green's functions by means of the Wigner representation. Time derivatives with respect to central time serves as a small parameter in the perturbative expansion enabling the computation of nonadiabatic corrections to molecular Green's functions. Consequently, we produce series of analytic expressions for non-adiabatic electronic Green's functions (up to the second order in the central time derivatives); which depend not solely on instantaneous molecular geometry but likewise on nuclear velocities and accelerations. Extended formula for electric current is derived which accounts for the non-adiabatic corrections. This theory is concisely illustrated by the calculations on a model molecular junction

Vegetation Response to a Subsurface Crude Oil Spill on a Subarctic Right-of-way, Tulita (Fort Norman), Northwest Territories, Canada

The plant species on a simulated pipeline corridor near Tulita (Fort Norman), Northwest Territories were studied prior to and for three years after an experimental point-spill of 3273 L (20 imperial barrels) of crude oil. Two distinct environments were examined: a cleared right-of-way (ROW) and a simulated pipeline trench. Each environment was subdivided on the basis of oil concentration into heavily oiled, lightly oiled, and unoiled sections. Total plant cover on the heavily oiled ROW declined by 73% in the first growing season; however, significant recovery took place in subsequent years. All other oiled environments had significant increases in total plant cover, but not until at least the second year after the spill. Of the 34 taxa identified, 13 declined significantly in abundance by the third growing season after the oil spill, mainly on the heavily oiled ROW. By the third post-spill growing season, mosses, Carex spp., Eriophorum spp., and agronomic grasses (Alopecurus arundinacea, Phleum pratense, Poa glauca and P. pratensis) had increased in abundance on at least one type of oiled substrate. However, the agronomic grasses, species sown on the Norman Wells pipeline, also declined significantly on the heavily oiled Trench. In contrast, the native grass Arctagrostis latifolia declined only on the heavily oiled ROW.On a étudié les espèces végétales présentes sur un corridor pipelinier simulé près de Tulita (Fort Norman), dans les Territoires du Nord-Ouest, avant un déversement expérimental ponctuel de pétrole brut de 3273 L (soit 20 barils impériaux) et durant les trois années suivantes. On a examiné deux environnements distincts: une emprise dégagée et une tranchée simulée de pipeline. On a divisé chaque environnement en sections en se basant sur la concentration en pétrole: forte, faible et nulle. Durant la première saison de croissance, l'ensemble du couvert végétal a diminué de 73 p. cent sur les sections de l'emprise où existait une forte concentration; un important reverdissement a toutefois pris place durant les années suivantes. Tous les autres endroits qui avaient reçu du pétrole ont connu d'importantes augmentations de l'ensemble du couvert végétal, mais, au plus tôt, à partir de la deuxième année suivant le déversement. Sur les 34 taxons identifiés, 13 avaient largement diminué en abondance à la troisième saison de croissance suivant le déversement, surtout dans les sections de l'emprise à forte concentration de pétrole. À la troisième saison de croissance suivant le déversement, les mousses des espèces Carex et Eriophorum et les herbes agronomiques (Alopecurus arundinacea, Phleum pratense, Poa glauca et P. pratensis) avaient augmenté en abondance à au moins un type de milieu où avait été déversé du pétrole. Toutefois, les herbes agronomiques - espèces semées sur le parcours du pipeline de Norman Wells - avaient aussi diminué de façon significative sur la tranchée où se trouvait une forte concentration de pétrole. Par contre, l'herbe indigène Arctagrostis latifolia n'avait diminué que sur l'emprise à forte concentration

Palaeobiology, ecology, and distribution of stromatoporoid faunas in biostromes of the mid-Ludlow of Gotland

Six well exposed mid−Ludlow stromatoporoid−dominated reef biostromes in four localities from the Hemse Group in southeastern Gotland, Sweden comprise a stromatoporoid assemblage dominated by four species; Clathrodictyon mohicanum, “Stromatopora” bekkeri, Plectostroma scaniense, and Lophiostroma schmidtii. All biostromes investigated in this area (of approximately 30 km2) are interpreted to belong to a single faunal assemblage forming a dense accumulation of fossils that is probably the best exposed stromatoporoid−rich deposit of the Silurian. The results from this comprehensive study strengthen earlier interpretations of a combination of genetic and environmental control on growth−forms of the stromatoporoids. Growth styles are similar for stromatoporoids in all six biostromes. Differences in biostrome fabric are due to variations in the degree of disturbance by storms. The uniformity of facies and the widespread low−diversity fauna support the view that palaeoenvironmental conditions were similar across the area where these biostromes crop out, and promoted the extraordinary growth of stromatoporoids in this shallow shelf area

An iron(ii) spin-crossover metallacycle from a back-to-back bis-[dipyrazolylpyridine]

The syntheses of 4-mercapto-2,6-di(pyrazol-1-yl)pyridine (bppSH) and bis[2,6-di(pyrazol-1-yl)pyrid-4-yl]disulfide (bppSSbpp) are reported. In contrast to previously published “back-to-back” bis-[2,6-di(pyrazol-1-yl)pyridine] derivatives, which form coordination polymers with transition ions that are usually insoluble, bppSSbpp yields soluble oligomeric complexes with iron(II) and zinc(II). Mass spectrometry and DOSY data show that [{Fe(μ-bppSSbpp)}n]2n+ and [{Zn(μ-bppSSbpp)}n]2n+ form tetranuclear metallacycles in nitromethane solution (n = 4), although 1H NMR and conductivity measurements imply the iron compound may undergo more fragmentation than its zinc congener. Both [{Fe(bppSH)2]2+ and [{Fe(μ-bppSSbpp)}n]2n+ exhibit thermal spin-crossover in CD3NO2 solution, with midpoint temperatures near 245 K. The similarity of these equilibria implies there is little cooperativity between the iron centres in the metallacyclic structures