A solution to Darwin’s dilemma of 1859 : Exceptional preservation in Salter’s material from the late Ediacaran Longmyndian Supergroup, England

Peer reviewedPostprin

Amphiphilic modified-styrene copolymer films: Antifouling/fouling release properties against the green alga Ulva linza

Surface-active copolymers of a styrene carrying a polysiloxane side chain (SSi) and a triethyleneglycol monomethyl ether-modified pentafluorostyrene (EFS) (39 and 77 mol% EFS) were prepared and incorporated (8 wt% loading) into a polydimethyl siloxane (PDMS) matrix to produce crosslinked blend films. The wettability of the surface-active copolymer films and PDMS-blend films was investigated by contact angle measurements. An angle-resolved X-ray photoelectron spectroscopy (XPS) of the surface chemical composition before and after immersion in water for 7 days enabled location of the hydrophilic oxyethylenic segments of EFS within the top 10 nm from the film surface. Laboratory bioassays on the blend films against the marine green alga Ulva linza evidenced that the films containing the copolymer with the larger EFS content showed greater resistance to settlement of zoospores of U. linza, whereas both films had superior fouling-release properties of sporelings (young plants) compared to the PDMS standard films

Annotated Bibliography of Fire Literature Relative to Northern Grasslands in South-Central Canada and North-Central United States

This publication provides a condensed reference of fire literature for those with an interest in fire ecology

Annotated Bibliography of Fire Literature

Natural resource managers have greatly increased the use of fire to manage grassland habitats during the past two decades in the northern Great Plains region of the United States and Canada. In support of these efforts, we have compiled this annotated bibliography to provide a condensed reference of fire literature for those managers with an interest in fire ecology. References are arranged alphabetically by author and year, numbered consecutively, and referenced by number in the author and subject indexes that follow the bibliography. The intent in compiling the bibliography and indexes is more to identify subject matter and to direct the reader to sources rather than to provide a digested interpretation of each manuscript

Surface modification of hydrophobic polymers for improvement of endothelial cell-surface interactions

The aim of this study is to improve the interaction of endothelial cells with polymers used in vascular prostheses. Polytetrafluoroethylene (PTFE; Teflon) films were treated by means of nitrogen and oxygen plasmas. Depending on the plasma exposure time, modified PTFE surfaces showed water-contact angles of 15¿58° versus 96° for unmodified PTFE. Electron spectroscopy in chemical analysis (ESCA) measurements revealed incorporation of both nitrogenand oxygen-containing groups into the PTFE surfaces, dependent on the plasma composition and exposure time. In-vitro biological evaluation of unmodified and modified PTFE surfaces showed that human endothelial cells, seeded from 20% human serum-containing culture medium, adhered well on to modified PTFE surfaces, but not on to unmodified films. Adhesion of endothelial cells on to expanded PTFE graft material (Gore-Tex) was also stimulated by plasma treatment of this substrate. On plasma-treated expanded PTFE, the adhering endothelial cells formed a monolayer, which covered the textured surface. The latter observation is important in view of the hemocompatibility of vascular grafts seeded with endothelial cells before implantation

Martin Brasier's contribution to the palaeobiology of the Ediacaran–Cambrian transition

Martin Brasier's work spanned almost the entire geological column, but the origin of animals and the nature of the Cambrian explosion were areas of particular interest to him. Martin adopted a holistic approach to the study of these topics that considered the interplay between multiple geological and biological phenomena and he sought to interpret the fossil record within the broad context of geological, biogeochemical and ecological changes in the Earth system. Here we summarize Martin's main contributions to this area of research and assess the impact of his findings on the development of this field

Hippocampal Functional Connectivity and Memory Performance After Exercise Intervention in Older Adults with Mild Cognitive Impairment

Background: Exercise training (ET) has neuroprotective effects in the hippocampus, a key brain region for memory that is vulnerable to age-related dysfunction. Objective: We investigated the effects of ET on functional connectivity (FC) of the hippocampus in older adults with mild cognitive impairment (MCI) and a cognitively normal (CN) control group. We also assessed whether the ET-induced changes in hippocampal FC (Δhippocampal-FC) are associated with changes in memory task performance (Δmemory performance). Methods: 32 older adults (77.0±7.6 years; 16 MCI and 16 CN) participated in the present study. Cardiorespiratory fitness tests, memory tasks (Rey Auditory Verbal Learning Test (RAVLT) and Logical Memory Test (LM)), and resting-state fMRI were administered before and after a 12-week walking ET intervention. We utilized a seed-based correlation analysis using the bilateral anterior and posterior hippocampi as priori seed regions of interest. The associations of residualized ET-induced Δhippocampal-FC and Δmemory performance were assessed using linear regression. Results: There were significant improvements in RAVLT Trial 1 and LM test performance after ET across participants. At baseline, MCI, compared to CN, demonstrated significantly lower posterior hippocampal FC. ET was associated with increased hippocampal FC across groups. Greater ET-related anterior and posterior hippocampal FC with right posterior cingulate were associated with improved LM recognition performance in MCI participants. Conclusion: Our findings indicate that hippocampal FC is significantly increased following 12-weeks of ET in older adults and, moreover, suggest that increased hippocampal FC may reflect neural network plasticity associated with ET-related improvements in memory performance in individuals diagnosed with MCI

Exercise Training-Related Changes in Cortical Gray Matter Diffusivity and Cognitive Function in Mild Cognitive Impairment and Healthy Older Adults

Individuals with Mild Cognitive Impairment (MCI) are at an elevated risk of dementia and exhibit deficits in cognition and cortical gray matter (GM) volume, thickness, and microstructure. Meanwhile, exercise training appears to preserve brain function and macrostructure may help delay or prevent the onset of dementia in individuals with MCI. Yet, our understanding of the neurophysiological effects of exercise training in individuals with MCI remains limited. Recent work suggests that the measures of gray matter microstructure using diffusion imaging may be sensitive to early cognitive and neurophysiological changes in the aging brain. Therefore, this study is aimed to determine the effects of exercise training in cognition and cortical gray matter microstructure in individuals with MCI vs. cognitively healthy older adults. Fifteen MCI participants and 17 cognitively intact controls (HC) volunteered for a 12-week supervised walking intervention. Following the intervention, MCI and HC saw improvements in cardiorespiratory fitness, performance on Trial 1 of the Rey Auditory Verbal Learning Test (RAVLT), a measure of verbal memory, and the Controlled Oral Word Association Test (COWAT), a measure of verbal fluency. After controlling for age, a voxel-wise analysis of cortical gray matter diffusivity showed individuals with MCI exhibited greater increases in mean diffusivity (MD) in the left insular cortex than HC. This increase in MD was positively associated with improvements in COWAT performance. Additionally, after controlling for age, the voxel-wise analysis indicated a main effect of Time with both groups experiencing an increase in left insular and left and right cerebellar MD. Increases in left insular diffusivity were similarly found to be positively associated with improvements in COWAT performance in both groups, while increases in cerebellar MD were related to gains in episodic memory performance. These findings suggest that exercise training may be related to improvements in neural circuits that govern verbal fluency performance in older adults through the microstructural remodeling of cortical gray matter. Furthermore, changes in left insular cortex microstructure may be particularly relevant to improvements in verbal fluency among individuals diagnosed with MCI

Nanostructure of cellulose microfibrils in spruce wood

The structure of cellulose microfibrils in wood is not known in detail, despite the abundance of cellulose in woody biomass and its importance for biology, energy, and engineering. The structure of the microfibrils of spruce wood cellulose was investigated using a range of spectroscopic methods coupled to small-angle neutron and wide-angle X-ray scattering. The scattering data were consistent with 24-chain microfibrils and favored a “rectangular” model with both hydrophobic and hydrophilic surfaces exposed. Disorder in chain packing and hydrogen bonding was shown to increase outwards from the microfibril center. The extent of disorder blurred the distinction between the I alpha and I beta allomorphs. Chains at the surface were distinct in conformation, with high levels of conformational disorder at C-6, less intramolecular hydrogen bonding and more outward-directed hydrogen bonding. Axial disorder could be explained in terms of twisting of the microfibrils, with implications for their biosynthesis

Scanning Electron Microscopy Analysis of Polyethylene Oxide Hydrogels for Blood Contact

Hydrogels are a class of synthetic material, composed of a polymer-water matrix and have been proposed as tissue substitutes and drug delivery vehicles. Polyethylene oxide (PEO) hydrogels were synthesized and used to produce coated wires and conduits for baboon blood compatibility studies. Blood-material interactions were studied both by Scanning Electron Microscopy (SEM) and 111In labeled platelet deposition. SEM processing modifications were first evaluated in order to reduce shrinkage and surface distortion incurred during sample preparation of these high water content materials. Pretreatment with 1% tannic acid reduced bulk shrinkage associated with critical point drying by 10-20%. This effect is small, nevertheless, it prevented major sample disruption. Coated guidewires were exposed to baboon blood for one hour in the inferior vena cava and conduits were placed for either 30 or 60 minutes in an ex vivo femoral arteriovenous shunt. Reference materials included Gore-tex®, polyethylene and silica-free polydimethyl siloxane (PDMS). In the guidewire studies, 111In labeled platelet levels were highest on Gore-tex® (6568.97 platelets/ 1000 μm2) and large thrombotic deposits were well visualized by SEM. Formulations containing PEO had low levels of platelet deposition and little evidence of platelet activation was noted by SEM. Shunt studies demonstrated that materials of high PEO content and molecular weight had the lowest levels of platelet deposition. After 60 minutes of blood flow, mean platelet deposition on PDMS and Gore-tex® was 50 and 1000 fold higher than on a network composed of 65% PEO 20,000 (p \u3c 0.05). SEM confirmed these findings