Measuring the notched compressive strength of composite laminates: Specimen size effects

Large fibre reinforced composite structures can give much lower strengths than small test specimens, so a proper understanding of scaling is vital for their safe and efficient use. Small size (scale) specimens are commonly tested to justify allowable stresses, but could be dangerous if results are extrapolated without accounting for scaling effects. On the other hand large factors are sometimes applied to compensate for uncertainties, resulting in overweight designs. The most important variables of scaling effects on the strength of composites with open holes have been identified from experimental tests as notch size, ply and laminate thickness. In this study, these have been scaled both independently and simultaneously over a large range of combinations. The specimens are fabricated from commercially available (Hexcel Composites Ltd.) carbon/epoxy pre-impregnated tapes 0.125 mm thick (IM7/8552). The material is laid up by hand in unidirectional [04]ns with n = 2, 3, 4, and 8 (i.e., 2, 3, 4 and 8 mm thick) and multidirectional laminates; two generic quasi-isotropic lay-ups, one fabricated with blocked plies [45n/90n/−45n/0n]s and the other with distributed layers [45/90/−45/0]ns with n = 2, 4 and 8 are examined. It is shown that the critical failure mechanism in these laminates is in the form of fibre microbuckling or kinking. The unnotched compressive strength in unidirectional specimens thicker than 2 mm is found to be limited by the stress concentration developed at the end tabs and manufacturing induced defects in the form of ply waviness, fibre misalignment and voids rather than specimen size (scaling). In the open hole specimens, for both lay-ups, the strength reduction observed is due to hole size effect rather than specimen thickness or volume increase. The open hole (notched) compressive strength results obtained compare favourably to predictions by a linear softening cohesive zone fracture model developed in earlier work by the second author

Conditions du développement de la tourbière de Farnham, Québec

Les analyses polliniques et macrofossiles d'une carotte de sédiments provenant de la marge de la tourbière de Farnham ont permis de retracer cinq étapes dans le développement de la tourbière. L'accumulation des sédiments a débuté au sein d'un marais situé au centre de la dépression à la suite du retrait de la Mer de Champlain vers 8500 ans BP. L'entourbement centrifuge subséquent a atteint le point d'échantillonnage vers 8100 ans BP. À cette époque, un mélèzin (1) a laissé place en quelques décennies à un fen arboré (2) jusque vers 6900 ans BP. Par la suite, un fen au couvert arborescent très ouvert (3) s'est mis en place et des mares se sont constituées à la surface de la tourbière jusque vers 5800 ans BP. L'accumulation de la tourbe a provoqué (4) l'ombrotrophication de la tourbière, ce changement trophique ayant persisté jusqu'à nos jours. L'action des feux et l'activité anthropique ont entraîné récemment (5) l'implantation d'espèces arborescentes de milieux perturbés. L'entourbement et les différentes étapes du développement de la marge de la tourbière ont été déterminés par l'accumulation de la tourbe, l'hydrologie locale, le climat et les feux. La formation des mares à la surface de la tourbière vers 6900 ans BP, à la charnière entre les régimes de fen et de bog, ainsi que l'expansion synchrone de Tsuga canadensis au sein des forêts environnantes, témoignent de conditions climatiques plus humides associées à une hausse des précipitations ou à une baisse de l'évapotranspiration.Pollen and plant macrofossil sequence of a core at the margin of the Farnham bog provide a local developmental record that can be subdivided into five main stages for this part of the peatland. Organic sedimentation began around 8500 year BP in a shallow pound at the centre of the depression following the retreat of the Champlain Sea. Subsequent centrifugal paludification caused the onset of peat accumulation at the sampling point about 8100 year BP. An initial forested fen dominated by larch (1) has been rapidly followed by a treed fen (2) until 6900 year BP. This stage was succeeded by a fen characterized by sparse trees and the development of open-water pools (3) until 5800 year BP. At that time, the vegetation changed to oligotrophic bog (4) until the present. Recently, the influence of external factors such as fire and anthropogenic activity resulted (5) in the establishment of tree species typical of disturbed environments. Paludification and local developmental trends are closely controlled primarily by continuous peat accumulation, local hydrology, climate and fire. The formation of pools around 6900 year BP and the synchronous spread of Tsuga canadensis populations in the surrounding forests suggest an increasing trend towards moister conditions with higher precipitation and/or reduced summer évapotranspiration.Die Analyse von Pollen und Makrofossilen eines Sedimentbohrkerns vom Rand des Torfmoors von Farnham fuhrten zur Aufdeckung von funf Etappen bei der Entwicklung des Torfmoors. Die Ansammlung der Sedimente hat um 8500 v.u.Z mitten in einem Sumpf im Zentrum der Niederung begonnen, nachdem das Meer von Champlain sich zuruckgezogen hatte. Die darauffolgende zentrifugale Vertorfung hat den Ort der Probenahme gegen 8100 Jahre v.u.Z. erreicht. Zu dieser Zeit ist ein von Làrchen beherrschtes Torfmoor (1) in einigen Jahrzehnten einem Baum-Torfmoor (2) gewichen bis gegen 6900 v.u.Z. Danach hat sich ein Torfmoor mit sehr offener baumartiger Bewachsung (3) angesiedelt und bis gegen 5800 v.u.Z. haben sich Tumpel an der Oberflâche des Torfmoores gebildet. Die Anhâufung des Torfs fùhrte zur Nàhrstoffverarmung (4) des Torfmoors, welche bis heute angehalten hat. Die Einwirkung von Brânden und menschlicher Aktivitât haben in heutiger Zeit (5) zur Ansiedlung von Baumarten gefuhrt, die fur gestôrte Milieus typisch sind. Die Vertorfung und die verschiedenen Entwicklungsetappen des Torfmoorrands waren durch die Torfanhàufung, den lokalen Wasserhaushalt, das Klima und die Brànde bestimmt. Die Bildung der Tùmpel an der Oberflâche des Torfmoors gegen 6900 v.u.Z., an der Umbiegung zwischen dem Torfmoor- und dem Sumpf-System, sowie die gleichzeitige Ausdehnung von Tsuga canadiensis in den umliegenden Wâldern bezeugen feuchtere klimatische Bedingungen in Verbindung mit einer Zunahme der Niederschlàge oder einer Abnahme der Verdunstung

Phase formation and thermal stability of ultrathin nickel-silicides on Si(100)

The solid-state reaction and agglomeration of thin nickel-silicide films was investigated from sputter deposited nickel films (1-10 nm) on silicon-on-insulator (100) substrates. For typical anneals at a ramp rate of 3 degrees C/s, 5-10 nm Ni films react with silicon and form NiSi, which agglomerates at 550-650 degrees C, whereas films with a thickness of 3.7 nm of less were found to form an epitaxylike nickel-silicide layer. The resulting films show an increased thermal stability with a low electrical resistivity up to 800 degrees C

Iminodiacetic acid (IDA) cation-exchange nonwoven membranes for efficient capture of antibodies and antibody fragments

There is strong need to reduce the manufacturing costs and increase the downstream purification efficiency of high-value therapeutic monoclonal antibodies (mAbs). This paper explores the performance of a weak cation-exchange membrane based on the coupling of IDA to poly(butylene terephthalate) (PBT) nonwoven fabrics. Uniform and conformal layers of poly(glycidyl methacrylate) (GMA) were first grafted to the surface of the nonwovens. Then IDA was coupled to the polyGMA layers under optimized conditions, resulting in membranes with very high permeability and binding capacity. This resulted in IgG dynamic binding capacities at very short residence times (0.1–2.0 min) that are much higher than those achieved by the best cation-exchange resins. Similar results were obtained in the purification of a single-chain (scFv) antibody fragment. As is customary with membrane systems, the dynamic binding capacities did not change significantly over a wide range of residence times. Finally, the excellent separation efficiency and potential reusability of the membrane were confirmed by five consecutive cycles of mAb capture from its cell culture harvest. The present work provides significant evidence that this weak cation-exchange nonwoven fabric platform might be a suitable alternative to packed resin chromatography for low-cost, higher productivity manufacturing of therapeutic mAbs and antibody fragments

The influence of alloying on the phase formation sequence of ultra-thin nickel silicide films and on the inheritance of texture

The controlled formation of silicide materials is an ongoing challenge to facilitate the electrical contact of Si-based transistors. Due to the ongoing miniaturisation of the transistor, the silicide is trending to ever-thinner thickness's. The corresponding increase in surface-to-volume ratio emphasises the importance of low-energetic interfaces. Intriguingly, the thickness reduction of nickel silicides results in an abrupt change in phase sequence. This paper investigates the sequence of the silicides phases and their preferential orientation with respect to the Si(001) substrate, for both "thin" (i.e., 9 nm) and "ultra-thin" (i.e., 3 nm) Ni films. Furthermore, as the addition of ternary elements is often considered in order to tailor the silicides' properties, additives of Al, Co, and Pt are also included in this study. Our results show that the first silicide formed is epitaxial theta-Ni2Si, regardless of initial thickness or alloyed composition. The transformations towards subsequent silicides are changed through the additive elements, which can be understood through solubility arguments and classical nucleation theory. The crystalline alignment of the formed silicides with the substrate significantly differs through alloying. The observed textures of sequential silicides could be linked through texture inheritance. Our study illustrates the nucleation of a new phase drive to reduce the interfacial energy at the silicide-substrate interface as well as at the interface with the silicide which is being consumed for these sub-10 nm thin films

Archipelago-Wide Island Restoration in the Galápagos Islands: Reducing Costs of Invasive Mammal Eradication Programs and Reinvasion Risk

Invasive alien mammals are the major driver of biodiversity loss and ecosystem degradation on islands. Over the past three decades, invasive mammal eradication from islands has become one of society's most powerful tools for preventing extinction of insular endemics and restoring insular ecosystems. As practitioners tackle larger islands for restoration, three factors will heavily influence success and outcomes: the degree of local support, the ability to mitigate for non-target impacts, and the ability to eradicate non-native species more cost-effectively. Investments in removing invasive species, however, must be weighed against the risk of reintroduction. One way to reduce reintroduction risks is to eradicate the target invasive species from an entire archipelago, and thus eliminate readily available sources. We illustrate the costs and benefits of this approach with the efforts to remove invasive goats from the Galápagos Islands. Project Isabela, the world's largest island restoration effort to date, removed >140,000 goats from >500,000 ha for a cost of US$10.5 million. Leveraging the capacity built during Project Isabela, and given that goat reintroductions have been common over the past decade, we implemented an archipelago-wide goat eradication strategy. Feral goats remain on three islands in the archipelago, and removal efforts are underway. Efforts on the Galápagos Islands demonstrate that for some species, island size is no longer the limiting factor with respect to eradication. Rather, bureaucratic processes, financing, political will, and stakeholder approval appear to be the new challenges. Eradication efforts have delivered a suite of biodiversity benefits that are in the process of revealing themselves. The costs of rectifying intentional reintroductions are high in terms of financial and human resources. Reducing the archipelago-wide goat density to low levels is a technical approach to reducing reintroduction risk in the short-term, and is being complemented with a longer-term social approach focused on education and governance

Movement of Translocated Adult Sicklefin Redhorse (\u3ci\u3eMoxostoma\u3c/i\u3e sp.) in the Oconaluftee River, North Carolina: Implications for Species Restoration

The Sicklefin Redhorse is a rare, undescribed species of Moxostoma, endemic to the Hiwassee and Little Tennessee River basins of western North Carolina and northern Georgia, where it has been eliminated from much of its native range. It is listed as endangered in Georgia and threatened in North Carolina. Although it has not been granted federal protected status, this species is the subject of a Candidate Conservation Agreement between federal, state, tribal, and private stakeholders, of which one objective calls for the re-establishment of Sicklefin Redhorse populations throughout its historical range. The objective of our study was to evaluate suitability of North Carolina’s upper Oconaluftee River for reintroduction of Sicklefin Redhorse, by tracking movement patterns of translocated individuals. Ten native Sicklefin Redhorse were collected from the Tuckasegee River in Swain County, NC, implanted with radio transmitters and translocated into the Oconaluftee River upstream from Ela Dam. Fish were tracked individually using radio telemetry for six months. Movement patterns for newly translocated fish, as well as seasonal patterns for females, were comparable to those shown in previous studies within the current range of Sicklefin Redhorse. Although some fish moved extensively, the sedentary patterns observed in females suggests that the upper Oconaluftee River may provide suitable overwinter habitat for the Sicklefin Redhorse. However, additional data are needed concerning spawning suitability and rates of downstream migration past Ela Dam before reintroducing Sicklefin Redhorse back to this portion of its native range

Low-dimensional quite noisy bound entanglement with cryptographic key

We provide a class of bound entangled states that have positive distillable secure key rate. The smallest state of this kind is 4 \bigotimes 4. Our class is a generalization of the class presented in [1] (IEEE Trans. Inf. Theory 54, 2621 (2008); arXiv:quant-ph/0506203). It is much wider, containing, in particular, states from the boundary of PPT entangled states (all of the states in the class in [1] were of this kind) but also states inside the set of PPT entangled states, even, approaching the separable states. This generalization comes with a price: for the wider class a positive key rate requires, in general, apart from the one-way Devetak-Winter protocol (used in [1]) also the recurrence preprocessing and thus effectively is a two-way protocol. We also analyze the amount of noise that can be admixtured to the states of our class without losing key distillability property which may be crucial for experimental realization. The wider class contains key-distillable states with higher entropy (up to 3.524, as opposed to 2.564 for the class in [1]).Comment: 10 pages, final version for J. Phys. A: Math. Theo

Hsp27 regulates podocyte cytoskeletal changes in an in vitro model of podocyte process retraction

Nephrotic syndrome (NS) is characterized by structural changes in the actin‐rich foot processes of glomerular podocytes. We previously identified high concentrations of the small heat shock protein hsp27 within podocytes as well as increased glomerular accumulation and phosphorylation of hsp27 in puromycin aminonucleoside (PAN) ‐induced experimental NS. Here we analyzed murine podocytes stably transfected with hsp27 sense, antisense, and vector control constructs using a newly developed in vitro PAN model system. Cell morphology and the microfilament structure of untreated sense and antisense transfectants were altered compared with controls. Vector cell survival, polymerized actin content, cell area, and hsp27 content increased after 1.25 μg/ml PAN treatment and decreased after 5.0 μg/ml treatment. In contrast, sense cells were unaffected by 1.25 μg/ml PAN treatment whereas antisense cells showed decreases or no changes in all parameters. Treatment of sense cells with 5.0 μ g/ml PAN resulted in increased cell survival and cell area whereas antisense cells underwent significant decreases in all parameters. Hsp27 provided dramatic protection against PAN‐induced microfilament disruption in sense > vector > antisense cells. We conclude that hsp27 is able to regulate both the morphological and actin cytoskeletal response of podocytes in an in vitro model of podocyte injury.—Smoyer, W. E., Ransom, R. F. Hsp27 regulates podocyte cytoskeletal changes in an in vitro model of podocyte process retraction. FASEB J. 16, 315–326 (2002)Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154256/1/fsb2fj010681com.pd