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Second Layer (second + layer)
Selected AbstractsAtomistic simulation of the self-diffusion in Mg (001) surfaceCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2008Jian-Min Zhang Abstract Both the formation energies and the intra- and inter-layer diffuse activation energies of a vacancy in the first six lattice planes of Mg (001) surface have been calculated by combining the modified analytical embedded-atom method (MAEAM) with molecular dynamics (MD). The results show that the effect of the surface on the formation and migration of the vacancy is only down to the third-layer. It is easer for a single vacancy to form and to migrate in the first layer. Furthermore, the vacancy in the second layer is favorable to migrate to the first layer. This is in agreement with the experimental results that the first layer has the highest concentration of the vacancy. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ultrastructure of an integumental organ with probable sensory function in Paragordius varius (nematomorpha)ACTA ZOOLOGICA, Issue 1 2004Andreas Schmidt-Rhaesa Abstract The cuticle of late parasitic stages of Paragordius varius (Leidy, 1851) is composed of a layer with large fibres and a second layer (often named the areolar layer) distal from it. In this paper, organs are described that start at the basal side of the epidermis, pass the epidermis and the fibrous layer of the cuticle and merge with large, cushion-like structures in the distal layer of the cuticle. The epidermal part of the organs is composed of darkly stained cells, which are probably in contact with the basi-epidermal nervous system. Up to four processes of this cell traverse the cuticle. These processes might include cilia, because they contain microtubule-like structures. The probable connection to nerve cells and the connection to the cushion-like structures in the outer cuticular layer make it likely that the organs described here are sensory in function. [source] Runoff and soil loss under individual plants of a semi-arid Mediterranean shrubland: influence of plant morphology and rainfall intensityEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2006E. Bochet Abstract The influence of plant morphology and rainfall intensity on soil loss and runoff was determined at the plant scale for three representative species of a semi-arid patchy shrubland vegetation of east Spain, representing contrasting canopy structures and plant phenologies (Rosmarinus officinalis, Anthyllis cytisoides and Stipa tenacissima). Twenty-seven microplots of less than 1 m2, each containing one single plant, were built to quantify runoff volume and sediment yield under the canopies of the three species. Runoff and rates of soil loss measured in these plots under natural rainfall conditions were compared with control microplots built in the bare inter-plant areas. Precipitation was automatic-ally recorded and rainfall intensity calculated over a two-year period. Results indicated that individual plants played a relevant role in interrill erosion control at the microscale. Compared with a bare soil surface, rates of soil loss and runoff reduction varied strongly depending on the species. Cumulative soil loss was reduced by 94·3, 88·0 and 30·2 per cent, and cumulative runoff volume was reduced by 66·4, 50·8 and 18·4 per cent under the Rosmarinus, Stipa and Anthyllis canopies, respectively, compared with a bare surface. Anthyllis was significantly less efficient than the two other species in reducing runoff volume under its canopy. Differences between species could only be identified above a rainfall intensity threshold of 20 mm h,1. The different plant morphologies and plant compon-ents explained the different erosive responses of the three species. Canopy cover played a major role in runoff and soil loss reduction. The presence of a second layer of protection at the soil surface (litter cover) was fundamental for erosion control during intense rainfall. Rainfall intensity and soil water status prior to rainfall strongly influenced runoff and soil loss rates. The possible use of these species in restoration programmes of degraded areas is discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Swelling-Induced Surface Patterns in Hydrogels with Gradient Crosslinking DensityADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Murat Guvendiren Abstract Hydrogels with controlled surface patterns are useful for a range of applications, including in microdevices, sensors, coatings, and adhesives. In this work, a simple and robust method to generate a wide range of osmotically driven surface patterns, including random, lamellar, peanut, and hexagonal structures is developed. This method does not require the use of organic solvents for swelling, pre-patterning of the film surface, or coating of a second layer on the gel. The patterns are fabricated by exposing a photocurable formulation to light while open to air and then swelling, using oxygen inhibition of the radical polymerization at the surface to create a gradient of crosslinking with depth, which was confirmed by measuring the double bond conversion at the surface, surface mechanics, and molecule diffusion into the network. The modulus gradient, and hence osmotic pressure, is controlled by the crosslinker concentration, and the characteristic size of the patterns is determined by the initial film thickness. The patterns are stable in both swollen and dry states, creating a versatile approach that is useful for diverse polymers to create complex patterns with long-range order. [source] Analytical solution for the electric potential in arbitrary anisotropic layered media applying the set of Hankel transforms of integer orderGEOPHYSICAL PROSPECTING, Issue 5 2006E. Pervago ABSTRACT The analytical solution and algorithm for simulating the electric potential in an arbitrarily anisotropic multilayered medium produced by a point DC source is here proposed. The solution is presented as a combination of Hankel transforms of integer order and Fourier transforms based on the analytical recurrent equations obtained for the potential spectrum. For the conversion of the potential spectrum into the space domain, we have applied the algorithm of the Fast Fourier Transform for logarithmically spaced points. A comparison of the modelling results with the power-series solution for two-layered anisotropic structures demonstrated the high accuracy and computing-time efficiency of the method proposed. The results of the apparent-resistivity calculation for both traditional pole-pole and tensor arrays above three-layered sequence with an azimuthally anisotropic second layer are presented. The numerical simulations show that both arrays have the same sensitivity to the anisotropy parameters. This sensitivity depends significantly on the resistivity ratio between anisotropic and adjacent layers and increases for the models with a conductive second layer. [source] Solution-Deposited Zinc Oxide and Zinc Oxide/Pentacene Bilayer Transistors: High Mobility n-Channel, Ambipolar, and Nonvolatile Devices,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2008Bhola Nath Pal Abstract A solution processed n-channel zinc oxide (ZnO) field effect transistor (FET) was fabricated by simple dip coating and subsequent heat treatment of a zinc acetate film. The field effect mobility of electrons depends on ZnO grain size, controlled by changing the number of coatings and zinc acetate solution concentration. The highest electron mobility achieved by this method is 7.2,cm2 V,1 s,1 with On/Off ratio of 70. This electron mobility is higher than for the most recently reported solution processed ZnO transistor. We also fabricated bilayer transistors where the first layer is ZnO, and the second layer is pentacene, a p-channel organic which is deposited by thermal evaporation. By changing the ZnO grain size (or thickness) this type of bilayer transistor shows p-channel, ambipolar and n-channel behavior. For the ambipolar transistor, well balanced electron and hole mobilities are 7.6,×,10,3 and 6.3,×,10,3,cm2 V,1 s,1 respectively. When the ZnO layer is very thin, the transistor shows p-channel behavior with very high reversible hysteresis. The nonvolatile tuning function of this transistor was investigated. [source] Enhancement of Interconnectivity in the Channels of Pentacene Thin-Film Transistors and Its Effect on Field-Effect Mobility,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2006S. Lee Abstract With the aim of improving the field-effect mobility of transistors by promoting the interconnectivity of the grains in pentacene thin films, deposition conditions of the pentacene molecules using one-step (total thickness of layer 50,nm: 0.1,Å,s,1) and two-step (first layer 10,nm: 0.1,Å,s,1, second layer 40,nm: 4.0,Å,s,1) depositions are controlled. Significantly, it is found that the continuities of the pentacene thin films vary with the deposition conditions of the pentacene molecules. Specifically, a smaller number of voids is observed at the interface for the two-step deposition, which results in field-effect mobilities as high as 1.2,cm2,V,1,s,1; these are higher by more than a factor of two than those of the pentacene films deposited in one step. This remarkable increase in field-effect mobility is due in particular to the interconnectivity of the pentacene grains near the insulator substrate. [source] Observation of Unusual Homoepitaxy in Ultrathin Pentacene Films and Correlation with Surface Electrostatic PotentialADVANCED MATERIALS, Issue 30 2009Vivek Kalihari Pentacene second layer grows with a twist (,76,°) on the first layer, while the third and subsequent layers show commensurism with their respective underlayers. The preferred twisting of the second layer on the first layer gives rise to epitaxial and non-epitaxial domains which also reflect in the surface electrostatic potential measurements. [source] Entrepreneurial nurses and midwives in the United Kingdom: an integrative reviewJOURNAL OF ADVANCED NURSING, Issue 5 2007Vari Drennan Abstract Title.,Entrepreneurial nurses and midwives in the United Kingdom: an integrative review Aim., This paper is a report of an integrative literature review to investigate: (a) the extent of entrepreneurial activity by nurses, midwives and health visitors in the United Kingdom and (b) the factors that influenced these activities. Background., Internationally, social and commercial entrepreneurial activity is regarded as important for economic growth and social cohesion. Methods., Seventeen bibliographic databases were searched using single and combined search terms: ,entrepreneur$', ,business', ,private practice', ,self-employ$', ,intrapreneur$',social enterprise$',mutuals', ,collectives', ,co-op' and ,social capital' which were related to a second layer of terms ,Nurs$', ,Midwi$', ,Visit$'. ,Entrepreneur$' Private Midwi$, Independent Midwi$, and ,nursing workforce'. In addition, hand searches of non-indexed journals and grey literature searches were completed. The following inclusion criteria were: (a) describing nurses, midwife and/or health visitor entrepreneurship (b) undertaken in the UK, and (c) reported between January 1996 and December 2005. Results., Of 154 items included only three were empirical studies; the remainder were narrative accounts. While quality of these accounts cannot be verified, they provide as complete an account as possible in this under-researched area. The numbers of nurses, midwives and health visitors acting entrepreneurially were very small and mirror international evidence. A categorization of entrepreneurial activity was inductively constructed by employment status and product offered. ,Push' and ,pull' influencing factors varied between types of entrepreneurial activity. Conclusion., Empirical investigation into the extent to which nurses and midwives respond to calls for greater entrepreneurialism should take account of the complex interplay of contextual factors (e.g. healthcare legislation), professional and managerial experience and demographic factors. [source] Retinal pigment epithelial cells promote spatial reorganization and differentiation of retina photoreceptorsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 16 2008Olga L. German Abstract Retina differentiation involves the acquisition of a precise layered arrangement, with RPE cells in the first layer in intimate contact with photoreceptors in the second layer. Here, we developed an in vitro coculture model, to test the hypothesis that RPE cells play a pivotal role in organizing the spatial structure of the retina. We cocultured rat retinal neurons with ARPE-19 epithelial cells under various experimental conditions. Strikingly, when seeded over RPE cells, photoreceptors attached to their apical surfaces and proceeded with their development, including the increased synthesis of rhodopsin. Conversely, when we seeded RPE cells over neurons, the RPE cells rapidly detached photoreceptors from their substrata and positioned themselves underneath, thus restoring the normal in vivo arrangement. Treatment with the metalloproteinase inhibitor TIMP-1 blocked this reorganization, suggesting the involvement of metalloproteinases in this process. Reorganization was highly selective for photoreceptors because 98% of photoreceptors but very few amacrine neurons were found to redistribute on top of RPE cells. Interestingly, RPE cells were much more efficient than other epithelial or nonepithelial cells in promoting this reorganization. RPE cells also promoted the growth of photoreceptor axons away from them. An additional factor that contributed to the distal arrangement of photoreceptor axons was the migration of photoreceptor cell bodies along their own neurites toward the RPE cells. Our results demonstrate that RPE and photoreceptor cells interact in vitro in very specific ways. They also show that in vitro studies may provide important insights into the process of pattern formation in the retina. © 2008 Wiley-Liss, Inc. [source] Prioritization strategies for video storyboard keyframesJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 5 2007Hemalata Iyer This exploratory study investigates one type of video surrogate, storyboards, in terms of their ability to summarize and communicate the themes of arts-related videos. An HTML interface containing the storyboards, videos, and instructions was developed and run in a standard browser. Three phases,consisting of storyboard evaluation, full-length video evaluation, and their comparison,were completed by each user for three different videos. The data were analyzed for issues relating to keywords, summaries, and recognition of visual style for both the storyboards and the full-length videos. The linear sequence and narrative structure of storyboards are questioned, and a three-tiered model is proposed. The first layer consists of keyframes representing the "entity" and "action" of the video's central theme, the second layer consists of "entity" and "action" keyframes with regard to background or supporting information, and the third layer is composed of keyframes representing attributes, locations, and time periods. This structure facilitates the identification of appropriate keyframes for storyboards, eliminating redundant or peripheral images, and improves the storyboard's ability to communicate the essential message of videos. The tiered model is motivated and supported by the user study as well as current research on video surrogates and classical indexing theory. [source] Growth and characterization of bilayer InAs/GaAs quantum dot structuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2006B. L. Liang Abstract One of the difficulties in understanding energy transfer in bilayer quantum dot structures is the complex role of carrier tunneling. This limitation is due to the fact that, for most studies to date, QDs in each layer have only one confined energy level making it difficult to study resonant tunneling effects. In this work, we have investigated the low growth-rate technique to produce dislocation-free very large QDs in the second layer that are characterized by several confined energy levels. The high quality surface morphology and optical behavior of these structures were demonstrated by AFM and PL measurements. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Packed bed structure: Evaluation of radial particle distributionTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2002Néstor J. Mariani Abstract A model describing the radial distribution of monosized spheres in randomly packed beds up to distances of about two particle diameters from the vessel wall is presented here. The model is based on the existence of a highly ordered layer of particles adjacent to the wall followed by a more diffuse, but still identifiable, second layer. Expressions generated from simple geometrical concepts (intersection between a cylindrical surface and a sphere) straightforwardly allow calculating the radial voidage profile given the radial distribution of particle centers and vice versa. These expressions are employed to fit the model to measures of voidage profiles within a wide range of aspect ratios, a = (RT/RP). The model can be used to accurately predict radial voidage profiles, but it is stressed that the identification of particle distribution constitutes more valuable information than an empirical expression for describing voidage variations. On présente ici un modèle décrivant la distribution radiale de sphères monodisperses dans des lits garnis aléatoires jusqu'à des distances d'environ deux diamètres de particules de la paroi du réservoir. Le modèle s'appuie sur l'existence d'une couche très ordonnée de particules adjacentes à la paroi, suivie d'une seconde couche, plus diffuse mais cependant identifiable. Les expressions provenant de concepts géométriques simples (intersection entre une surface cylindrique et une sphère) permettent de calculer directement le profil de vide radial lorsque la distribution radiale des centres de particules est donnée et vice versa. Ces expressions servent à caler le modèle de mesures de profils de vide dans une vaste gamme de paramètres d'élancement, a = (RT/RP. Le modèle peut être utile pour prédire de manière précise les profils de vide radiaux, mais il faut dire que la détermination de la distribution des particules constitue une information plus valable qu'une expression empirique pour décrire les variations de vide. [source] Analysis of lattice-translocation disorder in the layered hexagonal structure of carboxysome shell protein CsoS1CACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2009Yingssu Tsai Lattice-translocation or crystal order,disorder phenomena occur when some layers or groups of molecules in a crystal are randomly displaced relative to other groups of molecules by a discrete set of vectors. In previous work, the effects of lattice translocation on diffraction intensities have been corrected by considering that the observed intensities are the product of the intensities from an ideal crystal (lacking disorder) multiplied by the squared magnitude of the Fourier transform of the set of translocation vectors. Here, the structure determination is presented of carboxysome protein CsoS1C from Halothiobacillius neapolitanus in a crystal exhibiting a lattice translocation with unique features. The diffraction data are fully accounted for by a crystal unit cell composed of two layers of cyclic protein hexamers. The first layer is fully ordered (i.e. has one fixed position), while the second layer randomly takes one of three alternative positions whose displacements are related to each other by threefold symmetry. Remarkably, the highest symmetry present in the crystal is P3, yet the intensity data (and the Patterson map) obey 6/m instead of symmetry; the intensities exceed the symmetry expected from combining the crystal space group with an inversion center. The origin of this rare phenomenon, known as symmetry enhancement, is discussed and shown to be possible even for a perfectly ordered crystal. The lattice-translocation treatment described here may be useful in analyzing other cases of disorder in which layers or groups of molecules are shifted in multiple symmetry-related directions. [source] Photo- and Redox-Active Dendritic Molecules with Soft, Layered NanostructuresCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2006Yoshihiro Kikuzawa Abstract Molecules with one photoactive group (porphyrin) and multiple redox-active groups (ferrocenes) are described. The molecules are based on dendritic frameworks, with the ferrocenyl groups attached at the "internal" positions and the porphyrin attached at the focal point, leading to a characteristic layer architecture. Molecules of up to the third generation were synthesized and examined. The results of 1H,NMR spectroscopy and fluorescence quenching indicated that the ferrocenyl groups at the second layer approach the core porphyrin most closely, which is consistent with the results of molecular-dynamics simulations. The electrochemistry of the molecules was also examined in detail, and a new formula is proposed for the analysis of multiple-electron transfer in these "redox-pool" molecules. [source] Possible Pathways of CVD Processes Leading to III,V Semiconductors via a Two-Dimensional Growth,CHEMPHYSCHEM, Issue 4 2005Hans-Jörg Himmel Priv.-Doz. Abstract Quantum-chemical calculations were carried out to shed more light upon possible first intermediates formed during chemical vapour deposition (CVD) processes leading to III,V semiconductors. Information about possible structures of intermediates and about thermodynamic properties in dependence of the temperature were collected. Because some of the systems calculated herein contain a substantial number of atoms (up to 144), it is limited to intermediates on the way to solid AlN. According to our suggestion, the first intermediates are species with the overall formula AlNH2, Al2N2H4, Al3N3H6, Al5N5H8, Al7N7H, and Al9N9H, Al12N12H12. In further calculations the growth of a second layer, on top of the first layer, which is modelled by the Al12N12H12 cluster, is simulated. The Al12N12H12 "surface" offers two places for the attachment of an Al3N3H6 ring. At temperatures of 1000 K, the ,G value for this attachment is only slightly negative, which suggests that the molecules can move relatively freely on the surface. This might be of importance for a defect-free growth process. Up to four layers are built on top of the first Al12N12H12 layer leading to Al24N24H24 (two layers), Al36N36H36 (three layers) and Al48N48H48 (four layers). The structures are compared with that of solid AlN in its most stable Wurzit-type structure. [source] Surface Electromigration Patterns in a Confined Adsorbed Metal Film: Ga on GaNCHEMPHYSCHEM, Issue 12 2002Alexei Barinov Dr. Abstract The mass transport of gallium adatoms in a confined gallium bilayer on GaN(0001) is studied with photoelectron spectromicroscopy with the goal to identify the diffusing species and their lateral distribution during directional surface electromigration and/or "random" thermal diffusion. It has been found that only the gallium atoms from the second layer undergo biased diffusion involving formation of three-dimensional islands. The development of different gallium concentration patterns is described by means of a general model, considering the presence of vacancies and trapping centres for the diffusing atoms. [source] Artificial neural network inversion of magnetotelluric data in terms of three-dimensional earth macroparametersGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2000Vjacheslav Spichak The possibility of solving the three-dimensional (3-D) inverse problem of geoelectrics using the artificial neural network (ANN) approach is investigated. The properties of a supervised ANN based on the back-propagation scheme with three layers of neurons are studied, and the ANN architecture is adjusted. A model class consisting of a dipping dyke in the basement of a two-layer earth with the dyke in contact with the overburden is used for numerical experiments. Six macroparameters of the 3-D model, namely the thickness of the top layer, which coincides with the depth of the dyke (D), the conductivity ratio between the first and second layers (C1,/C2,), the conductivity contrast of the dyke (C/C2,), and the width (W ), length (L ) and dip angle of the dyke (A), are used. Various groups of magnetotelluric field components and their transformations are studied in order to estimate the effect of the data type used on the ANN recognition ability. It is found that use of only the xy - and yx -components of impedance phases results in reasonable recognition errors for all unknown parameters (D: 0.02 per cent, C1/C2: 8.4 per cent, C/C2: 26.8 per cent, W : 0.02 per cent, L : 0.02 per cent, A: 0.24 per cent). The influence of the size and shape of the training data pool (including the ,gaps in education' and ,no target' effects) on the recognition properties is studied. Results from numerous ANN tests demonstrate that the ANN possesses good enough interpolation and extrapolation abilities if the training data pool contains a sufficient number of representative data sets. The effect of noise is estimated by means of mixing the synthetic data with 30, 50 and 100 per cent Gaussian noise. The unusual behaviour of the recognition errors for some of the model parameters when the data become more noisy (in particular, the fact that an increase in error is followed by a decrease) indicates that the use of standard techniques of noise reduction may give an opposite result, so the development of a special noise treatment methodology is required. Thus, it is shown that ANN-based recognition can be successfully used for inversion if the data correspond to the model class familiar to the ANN. No initial guess regarding the parameters of the 3-D target or 1-D layering is required. The ability of the ANN to teach itself using real geophysical (not only electromagnetic) data measured at a given location over a sufficiently long period means that there is the potential to use this approach for interpreting monitoring data. [source] | ||||||||||||||||||||||