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Plastic
Kinds of Plastic Terms modified by Plastic Selected AbstractsSelf-Organized Organic Thin-Film Transistors on Plastic,ADVANCED MATERIALS, Issue 8 2004Y. Choi The development of the self-organized growth of pentacence thin films on the channel region of a thin-film transistor (TFT) using surface modifications induced by organic vapor phase deposition is reported (see Figure). A bottom-contact TFT on plastic using an organic gate insulator of cross-linked poly-(4-vinylphenol) exhibited a field-effect mobility of 1.2 cm2/Vs and an on/off current ratio of ,,107. [source] High-Performance Organic Light-Emitting Diodes Using ITO Anodes Grown on Plastic by Room- Temperature Ion-Assisted Deposition,ADVANCED MATERIALS, Issue 4 2004Y. Yang Ion-assisted deposition (IAD) was used to deposit smooth, adherent, and electrically/optically high-quality indium tin oxide (ITO) films on glass and plastic substrates at room temperature. These films afforded organic light-emitting diode performance comparable to devices with commercial ITO/glass anodes, indicating that IAD is an attractive technique for low-temperature ITO deposition, especially on plastics (see Figure). [source] "Plastic Trash goes Biohybrid",Rapid and Selective Functionalization of Inert Plastic Surfaces with Biomolecules,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2010Stefan M. Schiller Abstract The covalent functionalization of "inert" polymers such as polypropylene with biomolecules for biocompatible or biosensor surfaces is challenging. Here we present a powerful approach to covalently modify "inert" macromolecular surfaces with biomacromolecules reusing old plastic material. A special emphasis was placed on easily accessible materials and a process which is easy, fast, efficient, cheap, and reliable. "Plastic trash" (lids from Eppendorf® pipet tip containers) was used as a polymer substrate to demonstrate the use/reuse of commercial packing material to covalently modify this material with a thin reactive plasma polymerized maleic anhydride nanolayer network, which can be subsequently modified with biomolecules for various applications, e.g., in tissue engineering and as biochips. [source] The Effect of Cook-Off on the Bulk Permeability of a Plastic Bonded ExplosivePROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 5 2006Guillermo Terrones Abstract Plastic bonded explosives when exposed to prolonged heating environments undergo a variety of changes that affect their bulk chemical, thermophysical, and mechanical properties. During slow heating conditions, referred to as cook-off, the thermal behavior of the polymeric binder plays an important role in the transformations of these composite energetic materials. The recently introduced Darcian flow hypothesis for PBX-9501 implies that, during preignition, temperature gradients will lead to pressure gradients which in turn will drive convection of decomposition gases throughout the explosive, thus affecting ignition time and location. Here, we focus on the cook-off behavior of PBX-9501 and investigate its effects on bulk permeability to gases produced as a result of thermal decomposition. The concept of Darcian convection through porous media is defined and illustrated in detail by the derivation of the governing equations for a permeameter. Based on a systematic analysis involving: 1) our current understanding about binder behavior as a function of temperature, 2) the physics of the gas permeameter apparatus, 3) the concept of liquid drainage by gas, and 4) the experimental record of four permeameter experiments with cooked PBX-9501, we conclude that samples heated up to 186,°C were not permeable in the Darcy-flow sense. [source] Dedicated Applications of Carbon Fiber Reinforced Plastics in Machine EngineeringADVANCED ENGINEERING MATERIALS, Issue 3 2004B. Wielage Machine engineering has an inherent potential concerning the use of high performance material like Carbon Fibre Reinforced Plastics. The authors show some successful substitutions of formerly conventionally designed components by CFRP-parts. The examples are taken from several branches of machine engineering, especially from textile machine engineering. [source] Estimation of elongational viscosity of polymers from entrance loss data using individual parameter optimizationADVANCES IN POLYMER TECHNOLOGY, Issue 2 2002Mahesh Gupta The elongational viscosity model proposed by Sarkar and Gupta (Journal of Reinforced Plastics and Composites 2001, 20, 1473), along with the Carreau model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the elongational viscosity model. To improve the computational efficiency, various elongational viscosity parameters are optimized individually. Estimated elongational viscosity for a Low Density Polyethylene (Dow 132i) is reported for two different temperatures. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 98,107, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10017 [source] Olefin metathesis applied to cellulose derivatives,Synthesis, analysis, and properties of new crosslinked cellulose plastic filmsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005Nicolas Joly Abstract New crosslinked cellulose-based plastic films were synthesized with olefin metathesis as a crosslinking reaction. Microcrystalline cellulose was first dissolved in a lithium chloride/N,N -dimethylacetamide solvent system and acylated by ,-undecenoyl chloride under microwave irradiation with N,N -dimethyl-4-aminopyridine as the catalyst. Cellulose unsaturated fatty acyl esters with a degree of substitution (DS) ranging from 1.4 to 2.0 were then crosslinked by olefin metathesis with a first generation Grubbs catalyst. Crosslinking ratios (T) ranging from 20 to 90% were obtained for low catalyst amounts (<1.2%), but gels appeared when T was too high. To avoid this gel formation, cellulose was acylated with a mixture of lauroyl and ,-undecenoyl chlorides. This internal dilution allowed us to obtain films of every case and various T (varying from 10 to 80% for a catalyst amount below 3.5%). Plastics were characterized by Fourier transform infrared (FTIR) spectroscopy, and the fatty acid mixture resulting from the hydrolysis of cellulose esters were analyzed by gas chromatography (GC) and NMR spectroscopy. Mechanical properties showed that the elastic modulus and tensile failure stress was higher when the plastic films were crosslinked. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 407,418, 2005 [source] Welding and Marking of Plastics with LasersLASER TECHNIK JOURNAL, Issue 5 2010New absorbers increase possibilities for application Today laser radiation as a tool for The Authors welding, cutting and marking in manufacturing of plastic components and products has achieved a good market acceptance. It offers an alternative to conventional processes such as ultrasonic, vibration or friction welding, mechanical cutting, milling or water jet cutting, tampon printing or ink jet printing. Main advantages for laser marking are flexibility and a contact free process [1]. Laser welding of plastics offers advantages in case of cleanness of processed components, low thermal and mechanical stress to components and inner sensitive parts as well as flexibility [2]. Although laser beam welding seems to be a relatively expensive processing method, savings can be achieved by entirely consideration of production process and logistics. [source] Laser Welding of Plastics , a Neat ThingLASER TECHNIK JOURNAL, Issue 5 2010The story of a popular laser application Industry has been dealing with the joining of plastics for over half a century. The wish for an economically viable method of joining components was there already when the injection molding process was developed. With the advent of industrial laser technology, laser welding developed into a practical solution for many plastics joining problems. [source] Role of Star-Like Hydroxylpropyl Lignin in Soy-Protein PlasticsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2006Ming Wei Abstract Summary: Star-like hydroxypropyl lignin (HL) was compounded into soy protein isolated (SPI) to develop a potential biodegradable plastic with better mechanical performance than pure sheet-SPI. The structure and properties of the composite materials were characterized by WAXD, DSC, SEM, TEM and tensile tests. The addition of just 2 wt.-% HL resulted in tensile strength (,b) of 16.8 MPa, 2.3 times that of pure sheet-SPI, with no accompanying decrease in elongation at break as a result of strong interaction and with good miscibility among components. As the HL content increased, the HL molecules could self-aggregate as oblate supramolecular domains, while the stronger interactions between HL and glycerol resulted in the detaching of glycerol from the SPI matrix. It can be concluded that the insertion of HL as single molecules into the SPI matrix would provide materials with optimum mechanical properties. Compared with other lignin/SPI composites, the stretching chains on HL play a key role in the improvement of mechanical properties because of a stronger adhesion of HL onto the SPI matrix as well as the interpenetration of SPI into supramolecular HL domains. Schematic illustration of the supramolecular domain created by the aggregation of hydroxypropyl lignin, which can interpenetrate with soy protein isolate. [source] Biodegradable Polylactide and Its Nanocomposites: Opening a New Dimension for Plastics and CompositesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2003Suprakas Sinha Ray Abstract The academic and industrial aspects of the preparation, characterization, mechanical and materials properties, crystallization behavior, melt rheology, and foam processing of pure polylactide (PLA) and PLA/layered silicate nanocomposites are described in this feature article. Recently, these materials have attracted considerable interest in polymer science research. PLA is linear aliphatic thermoplastic polyester and is made from agricultural products. Hectorite and montmorillonite are among the most commonly used smectite-type layered silicates for the preparation of nanocomposites. Smectites are a valuable mineral class for industrial applications because of their high cation exchange capacities, surface area, surface reactivity, adsorptive properties, and, in the case of hectorite, high viscosity, and transparency in solution. In their pristine form, they are hydrophilic in nature, and this property makes them very difficult to disperse into a polymer matrix. The most common way to overcome this difficulty is to replace interlayer cations with quaternized ammonium or phosphonium cations, preferably with long alkyl chains. In general, polymer/layered silicate nanocomposites are of three different types: (1) intercalated nanocomposites, in which insertion of polymer chains into the layered silicate structure occurs in a crystallographically regular fashion, regardless of polymer to layered silicate ratio, with a repeat distance of few nanometer; (2) flocculated nanocomposites, in which intercalated and stacked silicate layers are sometimes flocculated due to the hydroxylated edge,edge interactions between the silicate layers; (3) exfoliated nanocomposites, in which individual silicate layers are uniformly distributed in the polymer matrix by average distances that totally depend on the layered silicate loading. This new family of composite materials frequently exhibits remarkable improvements in its material properties when compared with those of virgin PLA. Improved properties can include a high storage modulus both in the solid and melt states, increased flexural properties, a decrease in gas permeability, increased heat distortion temperature, an increase in the rate of biodegradability of pure PLA, and so forth. Illustration of the biodegradability of PLA and various nanocomposites. [source] Corrosion Books: An Introduction to Plastics.MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 10 2004By: Hans-Georg Elias [source] Analytic Model of Laminar-Turbulent Transition for Bingham PlasticsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2006K. C. Wilson Abstract It is often desirable to operate industrial pipelines transporting non-Newtonian materials near the transition from laminar to turbulent flow. For the commonly used Bingham plastic model, the Hedström technique overestimates turbulent flow friction losses because it does not take account of viscous-layer thickening. In the present paper, the Wilson-Thomas model is applied to predict the transition point for Bingham plastics. Laminar and turbulent friction losses are calculated to show that conditions at transition depend only on the Hedström number. The results are approximated by simplified fit functions. Comparison with existing empirical correlations and experimental data from various sources shows satisfactory agreement. Il est souvent préférable d'utiliser les pipelines industriels transportant des matériaux non newtoniens près de la transition entre l'écoulement laminaire et l'écoulement turbulent. Pour le modèle classique des fluides de Bingham, la technique d'Hedström surestime les pertes de friction de l'écoulement turbulent parce qu'elle ne prend pas en compte l'épaississement de la couche visqueuse. Dans le présent article, on applique le modèle de Wilson-Thomas pour prédire le point de transition pour des fluides de Bingham. Les pertes de friction laminaires et turbulentes sont calculées et montrent que les conditions lors de la transition dépendent uniquement du nombre d'Hedström. Les résultats sont exprimés sous forme approximative par des fonctions de calage simplifiées. La comparaison avec des corrélations empiriques et des données expérimentales provenant de diverses sources montre un accord satisfaisant. [source] AL01 SURGICAL AUDIT IN DIFFICULT SITUATIONSANZ JOURNAL OF SURGERY, Issue 2009A. J. Green Approved peer reviewed surgical audit activity is a necessary for annual and Triannual Professional Standards requirements. Surgeons working in large hospitals, usually as part of surgical teams have resources to facilitate this. There are situations where the surgeon or surgeons need to organise a process themselves and may need more assistance. Three problem areas that will be particularly discussed include: 1Audit for remote surgeons 2Audit for urban/suburban surgeons with no teaching hospital attachments (often in smaller private facilities with no audit programs) 3Regional surgeons particularly in the Specialities eg ENT, Urology, Plastics where there are small numbers (1,3) Practical ways to achieve successful audits will be addressed [source] Plastics from E. coli: Metabolic engineering for PLA and its copolymersBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010Article first published online: 23 NOV 200 No abstract is available for this article. [source] Coloring of Plastics, Fundamentals 2nd Ed.COLOR RESEARCH & APPLICATION, Issue 4 2004Johnny F. Suthers No abstract is available for this article. [source] Representation of Pseudo Inter-reflection and Transparency by Considering Characteristics of Human VisionCOMPUTER GRAPHICS FORUM, Issue 3 2002H. Matsuoka We have succeeded in developing a quick and fully automated system that can generate photo-realistic 3D CG data based on a real object. A major factor in this success comes from our findings through psychophysical experiments that human observers do not have an accurate idea of what should be actually reflected as inter-reflections on the surface of an object. Taking advantage of this characteristic of human vision, we propose a new inter-reflection representation technique in which inter-reflections are simulated by allowing the same quantity of reflection components as there are in the background to pass through the object. Since inter-reflection and transparency are calculated by the same algorithm, our system can capture 3D CG data from various real objects having a strong inter-reflection, such as plastic and porcelain items or translucent glass and acrylic resin objects. The synthetic images from the 3D CG data generated with this pseudo inter-reflection and transparency look very natural. In addition, the 3D CG data and synthetic images are produced quickly at a lower cost. [source] Epigenetic control of skeletal muscle fibre typeACTA PHYSIOLOGICA, Issue 4 2010K. Baar Abstract Adult muscle is extremely plastic. However, the muscle precursor cells associated with those fibres show stable and heritable differences in gene expression indicative of epigenetic imprinting. Epigenetic processes in the development of skeletal muscle have been appreciated for over a decade; however, there are a paucity of studies looking at whether epigenetics determines the phenotype of adult and/or ageing skeletal muscle. This review presents the evidence that epigenetics plays a role in determining adult muscle function and a series of unanswered questions that would greatly increase our understanding of how epigenetics works in adult muscle. With the increased interest in epigenetics, over the next few years this field will begin to unfold in unimaginable directions. [source] Sensitivity of alveolar macrophages to substrate mechanical and adhesive propertiesCYTOSKELETON, Issue 6 2006Sophie Féréol Abstract In order to understand the sensitivity of alveolar macrophages (AMs) to substrate properties, we have developed a new model of macrophages cultured on substrates of increasing Young's modulus: (i) a monolayer of alveolar epithelial cells representing the supple (,0.1 kPa) physiological substrate, (ii) polyacrylamide gels with two concentrations of bis-acrylamide representing low and high intermediate stiffness (respectively 40 kPa and 160 kPa) and, (iii) a highly rigid surface of plastic or glass (respectively 3 MPa and 70 MPa), the two latter being or not functionalized with type I-collagen. The macrophage response was studied through their shape (characterized by 3D-reconstructions of F-actin structure) and their cytoskeletal stiffness (estimated by transient twisting of magnetic RGD-coated beads and corrected for actual bead immersion). Macrophage shape dramatically changed from rounded to flattened as substrate stiffness increased from soft ((i) and (ii)) to rigid (iii) substrates, indicating a net sensitivity of alveolar macrophages to substrate stiffness but without generating F-actin stress fibers. Macrophage stiffness was also increased by large substrate stiffness increase but this increase was not due to an increase in internal tension assessed by the negligible effect of a F-actin depolymerizing drug (cytochalasine D) on bead twisting. The mechanical sensitivity of AMs could be partly explained by an idealized numerical model describing how low cell height enhances the substrate-stiffness-dependence of the apparent (measured) AM stiffness. Altogether, these results suggest that macrophages are able to probe their physical environment but the mechanosensitive mechanism behind appears quite different from tissue cells, since it occurs at no significant cell-scale prestress, shape changes through minimal actin remodeling and finally an AMs stiffness not affected by the loss in F-actin integrity. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] Adaptation of microglomerular complexes in the honeybee mushroom body lip to manipulations of behavioral maturation and sensory experienceDEVELOPMENTAL NEUROBIOLOGY, Issue 8 2008Sabine Krofczik Abstract Worker honeybees proceed through a sequence of tasks, passing from hive and guard duties to foraging activities. The underlying neuronal changes accompanying and possibly mediating these behavioral transitions are not well understood. We studied changes in the microglomerular organization of the mushroom bodies, a brain region involved in sensory integration, learning, and memory, during adult maturation. We visualized the MB lips' microglomerular organization by applying double labeling of presynaptic projection neuron boutons and postsynaptic Kenyon cell spines, which form microglomerular complexes. Their number and density, as well as the bouton volume, were measured using 3D-based techniques. Our results show that the number of microglomerular complexes and the bouton volumes increased during maturation, independent of environmental conditions. In contrast, manipulations of behavior and sensory experience caused a decrease in the number of microglomerular complexes, but an increase in bouton volume. This may indicate an outgrowth of synaptic connections within the MB lips during honeybee maturation. Moreover, manipulations of behavioral and sensory experience led to adaptive changes, which indicate that the microglomerular organization of the MB lips is not static and determined by maturation, but rather that their organization is plastic, enabling the brain to retain its synaptic efficacy. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008. [source] An investigation of the cranial evolution of Asian pitvipers (Serpentes: Crotalinae), with comments on the phylogenetic position of Peltopelor macrolepisACTA ZOOLOGICA, Issue 4 2010Peng Guo Abstract Guo, P., Jadin, R.C., Malhotra, A. and Li, C. 2009. An investigation of the cranial evolution of Asian pitvipers (Serpentes: Crotalinae), with comments on the phylogenetic position of Peltopelor macrolepis,Acta Zoologica (Stockholm) 91: 402,407. We investigated the evolution of 12 cranial characters of 31 species of Asian pitvipers by examining the character state changes on a consensus tree modified from broadly consistent molecular results. We found that these characters appear stable with only one intraspecific polymorphism. Nine of the 12 characters form useful synapomorphies, whereas three are ambiguous and evolutionarily plastic. Clades that are supported with numerous apomorphies are the Trimeresurus group [consisting of the recently defined genera Trimeresurus sensuMalhotra and Thorpe (2004), Parias, Popeia, Viridovipera, Himalayophis, and Cryptelytrops] and the genera Protobothrops, Parias, and Viridovipera. Two species previously considered as congeners but now known to be distantly related, Ovophis monticola and ,Ovophis'okinavensis, have nearly identical character states, demonstrating substantial convergence in cranial characters. Finally, we attempt to infer the phylogenetic position of Peltopelor macrolepis by comparing its cranial features with that of other pitvipers. [source] BILIARY STENTING FOR MALIGNANT BILIARY OBSTRUCTIONDIGESTIVE ENDOSCOPY, Issue 1 2006Toshio Tsuyuguchi Management of patients with malignant biliary obstruction remains controversial. We reviewed our current status of biliary stenting for malignancy. The initial step in our management is endoscopic nasobiliary drainage, which is used not only for preoperative drainage but also to decide whether or not surgery is appropriate treatment. Although a metal stent has a longer patency time than a plastic stent, it costs up to thirty-fold more than the latter in Japan. Therefore, stent selection, metal or plastic, should be dependent on the expected prognosis of each patient with malignant biliary strictures. In the present paper, we also discuss the efficacy of the covered metal stent and stenting for malignant hilar obstruction. [source] Gelifluction: viscous flow or plastic creep?EARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2003Charles Harris Abstract This paper reports results from two scaled centrifuge modelling experiments, designed to simulate thaw-related geli,uction. A planar 12° prototype slope was modelled in each experiment, using the same natural ,ne sandy silt soil. However two different scales were used. In Experiment 1, the model scale was 1/10, tested in the centrifuge at 10 gravities (g) and in Experiment 2, the scale was 1/30, tested at 30 g. Centrifuge scaling laws indicate that the time scaling factor for thaw consolidation between model and prototype is N2, where N is the number of gravities under which the model was tested. However, the equivalent time scaling for viscous ,ow is 1/1. If geli,uction is a viscosity-controlled ,ow process, scaling con,icts will therefore arise during centrifuge modelling of thawing slopes, and rates of displacement will not scale accurately to the prototype. If, however, no such scaling con,icts are observed, we may conclude that geli,uction is not controlled by viscosity, but rather by elasto-plastic soil deformation in which frictional shear strength depends on effective stress, itself a function of the thaw consolidation process. Models were saturated, consolidated and frozen from the surface downwards on the laboratory ,oor. The frozen models were then placed in the geotechnical centrifuge and thawed from the surface down. Each model was subjected to four freeze,thaw cycles. Soil temperatures and pore water pressures were monitored, and frost heave, thaw settlement and downslope displacements measured. Pore water pressures, displacement rates and displacement pro,les re,ecting accumulated shear strain, were all similar at the two model scales and volumetric soil transport per freeze,thaw cycle, when scaled to prototype, were virtually identical. Displacement rates and pro,les were also similar to those observed in earlier full-scale laboratory ,oor experiments. It is concluded therefore that the modelled geli,uction was not a time-dependent viscosity-controlled ,ow phenomenon, but rather elasto-plastic in nature. A ,rst approximation ,,ow' law is proposed, based on the ,Cam Clay' constitutive model for soils. Copyright © 2003 John Wiley & Sons, Ltd. [source] Multiobjective heuristic approaches to seismic design of steel frames with standard sectionsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2007M. Ohsaki Abstract Seismic design problem of a steel moment-resisting frame is formulated as a multiobjective programming problem. The total structural (material) volume and the plastic dissipated energy at the collapse state against severe seismic motions are considered as performance measures. Geometrically nonlinear inelastic time-history analysis is carried out against recorded ground motions that are incrementally scaled to reach the predefined collapse state. The frame members are chosen from the lists of the available standard sections. Simulated annealing (SA) and tabu search (TS), which are categorized as single-point-search heuristics, are applied to the multiobjective optimization problem. It is shown in the numerical examples that the frames that collapse with uniform interstorey drift ratios against various levels of ground motions can be obtained as a set of Pareto optimal solutions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Evolution in ecological field experiments: implications for effect sizeECOLOGY LETTERS, Issue 3 2008Sharon Y. Strauss Abstract Rapid evolution in response to strong selection, much of which is human-induced, has been indisputably documented. In this perspective, we suggest that adaptation may influence the effect size of treatments in ecological field experiments and alter our predictions of future dynamics in ecological systems. Field experiments often impose very strong and consistent selection over multiple generations. Focal populations may adapt to these treatments and, in the process, increase or decrease the magnitude of the treatment effect through time. We argue that how effect size changes through time will depend on the evolutionary history of the experimental population, the type of experimental manipulation, and the traits involved in adaptive responses. While no field study has conclusively demonstrated evolution in response to treatments with concomitant changes in ecological effect size, we present several examples that provide strong circumstantial evidence that such effects occur. We conclude with a consideration of the differences between plastic and genetic responses to treatments and discuss future research directions linking adaptation to ecological effect size. [source] Use of vegetative furrows to mitigate copper loads and soil loss in runoff from polyethylene (plastic) mulch vegetable production systemsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2004Pamela J. Rice Abstract The transport of runoff with high copper concentrations and sediment loads into adjacent surface waters can have adverse effects on nontarget organisms as a result of increased turbidity and degraded water quality. Runoff from vegetable production utilizing polyethylene mulch can contain up to 35% of applied copper, a widely used fungicide/bactericide that has adverse effects on aquatic organisms. Copper is primarily transported in runoff with suspended particulates; therefore, implementation of management practices that minimize soil erosion will reduce copper loads. Replacing bare-soil furrows with furrows planted in rye (Secale cereale) significantly improved the sustainability of vegetable production with polyethylene mulch and reduced the potential environmental impact of this management practice. Vegetative furrows decreased runoff volume by >40% and soil erosion by >80%. Copper loads with runoff were reduced by 72% in 2001, primarily as a result of reduced soil erosion since more than 88% of the total copper loads were transported in runoff with suspended soil particulates. Tomato yields in both years were similar between the polyethylene mulch plots containing either bare-soil or vegetative furrows. Replacing bare-soil furrows with vegetative furrows greatly reduces the effects of sediments and agrochemicals on sensitive ecosystems while maintaining crop yields. [source] Changes in alternative brain-derived neurotrophic factor transcript expression in the developing human prefrontal cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2009Jenny Wong Abstract In this study, we determined when and through which promoter brain-derived neurotrophic factor (BDNF) transcription is regulated during the protracted period of human frontal cortex development. Using quantitative real-time polymerase chain reaction, we examined the expression of the four most abundant alternative 5, exons of the BDNF gene (exons I, II, IV, and VI) in RNA extracted from the prefrontal cortex. We found that expression of transcripts I,IX and VI,IX was highest during infancy, whereas that of transcript II,IX was lowest just after birth, slowly increasing to reach a peak in toddlers. Transcript IV,IX was significantly upregulated within the first year of life, and was maintained at this level until school age. Quantification of BDNF protein revealed that levels followed a similar developmental pattern as transcript IV,IX. In situ hybridization of mRNA in cortical sections showed the highest expression in layers V and VI for all four BDNF transcripts, whereas moderate expression was observed in layers II and III. Interestingly, although low expression of BDNF was observed in cortical layer IV, this BDNF mRNA low-zone decreased in prominence with age and showed an increase in neuronal mRNA localization. In summary, our findings show that dynamic regulation of BDNF expression occurs through differential use of alternative promoters during the development of the human prefrontal cortex, particularly in the younger age groups, when the prefrontal cortex is more plastic. [source] Post-lesion transcommissural growth of olivary climbing fibres creates functional synaptic microzonesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003Izumi Sugihara Abstract In the adult mammalian central nervous system, reinnervation and recovery from trauma is limited. During development, however, postlesion plasticity may generate alternate paths, providing models to investigate reinnervating axon,target interactions. After unilateral transection of the neonatal rat olivocerebellar path, axons from the ipsilateral inferior olive grow into the denervated hemicerebellum and develop climbing fibre (CF)-like arbors on Purkinje cells (PCs). However, the synaptic function and extent of PC reinnervation remain unknown. In adult rats pedunculotomized on postnatal day 3 the morphological and electrophysiological properties of reinnervating olivocerebellar axons were studied, using axonal reconstruction and patch-clamp PC recording of CF-induced synaptic currents. Reinnervated PCs displayed normal CF currents, and the frequency of PC reinnervation decreased with increasing laterality. Reinnervating CF arbors were predominantly normal but 6% branched within the molecular layer forming smaller secondary arbors. CFs arose from transcommissural olivary axons, which branched extensively near their target PCs to produce on average 36 CFs, which is six times more than normal. Axons terminating in the hemisphere developed more CFs than those terminating in the vermis. However, the precise parasagittal microzone organization was preserved. Transcommissural axons also branched, although to a lesser extent, to the deep cerebellar nuclei and terminated in a distribution indicative of the olivo-cortico-nuclear circuit. These results show that reinnervating olivocerebellar axons are highly plastic in the cerebellum, compensating anatomically and functionally for early postnatal denervation, and that this reparation obeys precise topographic constraints although axonal plasticity is modified by target (PC or deep nuclear neurons) interactions. [source] Structural characteristics of clay-dominated soils of a marsh and a palaeosol in a crossed diagramEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2007M. Bernard Summary Although the shrink-swell phenomenon of clays has been thoroughly studied, the in situ relation of the shrinkage curve to the structure profile is rarely presented from the shrinkage limit to the liquid limit. We studied the consolidated structure of clay-dominated (<2 ,m) soils formed on ,pseudo-liquid' marsh sediments in the ,Marais de l'Ouest' (France). The profiles were studied in a grassland field and in a sunflower field from unsaturated surface soils down to deeper, saturated, levels characterized by a very large water content (100% by weight). The consolidation states were quantified recording cone resistance (Qd) profiles using a dynamic penetrometer in successive seasons. These Qd profiles were compared with the associated wet density and gravimetric water-content profiles. Two consolidation depths were evident, the surface soil and a 130-cm deep palaeosol. The seasonal Qd profiles demonstrate the partial irreversibility of the consolidation peaks associated with the surface soil and with the palaeosol. The shrinkage properties were established through drying curves of undisturbed test samples. In the void ratio (e) - water content (W) and water content (W) - saturation index (Sr) diagrams, the profiles as a whole exhibit only one clay soil behaviour from their pseudo-liquid to plastic to solid states. Each Qd profile is represented by a hyperbolic curve in the e/Qd diagram. Represented in a (e , W , Qd ,Sr) crossed diagram, the vertical evolution of the successive profiles shows the soil structure behaviour from the initial pseudo-liquid sediment to the consolidated soil. A simple cone resistance recording associated with gravimetric water-content profiles, characterizes the evolution of structural layers of soils for the seasonal drying-wetting cycles, for the over-consolidation associated with the palaeosol, and also for the effect of ploughing. [source] ADAPTIVE PLASTICITY OF THE PENIS IN A SIMULTANEOUS HERMAPHRODITEEVOLUTION, Issue 8 2009J. Matthew Hoch Acorn barnacles are important model organisms for the study of sex allocation. They are sessile, nonselfing hermaphrodites that copulate with penises that have been suggested to be phenotypically plastic. On wave-exposed shores, Semibalanus balanoides develop penises with relatively greater diameter whereas in wave-protected sites they are thinner. A reciprocal transplant experiment between wave-exposed and protected sites tested whether these exposure-specific morphologies have adaptive value. Mating success was compared over a range of distances to compare the ability of barnacles to reach mates. Barnacles that grew in the wave-protected site and mated in the wave-protected site fertilized more broods at increasing distances than those transplanted to the wave-exposed site. For barnacles that developed in the wave-exposed site, there was no difference in the ability to fertilize neighbors between sites of differing exposure. This study demonstrates the adaptive value of plasticity in penis morphology. The results suggest a trade-off between development of a penis adapted to wave exposure and the ability to fertilize distant mates. Barnacles in different physical environments are limited by different factors, which may limit numbers of potential mates, constrain optimal sex allocation strategies and alter reproductive behavior. [source] | ||||||||||||||||||||||||||||||||||||||||||||||