Multilayer Character Research Articles

Versican targeting by RNA interference suppresses aggregative growth of dermal papilla cells

Dermal papilla cells (DPCs) are specialized fibroblasts found in the hair follicle papilla, which are associated with the development and cycle regulation of hair follicles (HFs). DPCs exhibit a multilayer aggregative growth character, which is closely related to induction of HF formation. Versican, a large chondroitin sulphate proteoglycan and one of the major components of the extracellular matrix, is involved in the formation of HF. To confirm the relationship between versican and the aggregative growth of DPCs, we first induced and established an aggregative cell model in DPCs in vitro, with cells taken to passage 8. Simultaneously, aggregative passage 2 DPCs and nonaggregative passage 8 DPCs were selected as parallel controls. RNA interference (RNAi) targeted to versican was used in passage 2 DPCs using a lentiviral vector. Reverse transcriptase (RT)-PCR and western blotting were used to assay the expression of versican in DPCs. RNAi targeted to versican efficiently suppressed the aggregative growth of passage 2 DPCs, and the inhibitory effect was significant 3 days after RNAi treatment. The mRNA and protein levels of versican were also downregulated in passage 2 DPCs, and were lower than levels in nonaggregative passage 8 DPCs. Notably, the aggregative growth of nonaggregative passage 8 DPCs was restored after induction in a 1 : 1 v/v mixture of fresh DMEM and medium recycled from a previous passage. Versican is a key gene for the aggregative growth of DPCs, and might be significant in the regeneration of HF.

Effects of interparticle interactions in magneticFe/Si3N4granular systems

An experimental evidence of the progressive modification in the magnetic behavior of granular $\text{Fe}/{\text{Si}}_{3}{\text{N}}_{4}$ samples due to interaction effects between particles is reported. Microstructural features and local structure were determined by x-ray absorption spectroscopy and transmission electron microscopy to select granular samples with predetermined cluster size. $\text{Fe}/{\text{Si}}_{3}{\text{N}}_{4}$ systems have been characterized by ac- and dc-magnetization measurements to study the gradual evolution of magnetic properties of granular systems, where three different behaviors have been observed. As-deposited samples with Fe thickness layers of 2.5 nm, present a modified superparamagnetic behavior, due to very weak interactions between very small Fe clusters separated by a nonmagnetic FeN phase. An evolution of the average blocking temperature at intermediate fields $({T}_{\text{B}}\ensuremath{\sim}{H}^{3/2})$ is observed, similar to noninteracting systems, but first signatures of a frozen spin state at low temperatures appear. Annealed samples exhibit a noticeable modification from the multilayer character to a random three-dimensional organization of Fe clusters embedded in a ${\text{Si}}_{3}{\text{N}}_{4}$ matrix. After annealing, samples with initial Fe layer thickness of 0.7 nm provide iron cluster in the range of 1.3 nm and exhibit a superspin-glass state, with a de Almeida-Thouless evolution of the energy barriers $({T}_{\text{B}}\ensuremath{\sim}{H}^{2/3})$ that is explained in terms of increasing interparticle interactions. Moreover, annealed samples, with initial layer thickness of 1.3 nm, supply iron cluster of near 3 nm that present stronger interactions and yield a superferromagnetic state, likely provided by residual ultrasmall particles between the blocked clusters.

Hydromagnetic Oscillatory Flow and Heat Transfer of a Viscous Liquid Past a Vertical Porous Plate in a Rotating Medium

Unsteady oscillatory flow of an incompressible, electrically conducting viscous liquid through a porous medium past an infinite vertical porous plate with constant suction has been studied. A transverse uniform magnetic field has been applied in a rotating frame of reference. The porous medium is bounded by a vertical plane surface. The temperature on the vertical surface fluctuates in time about a non-zero constant mean. The analytical expressions for the velocity, temperature, skin friction and Nusselt number are presented showing the effects of pertinent parameters. It is observed that steady part of the velocity field has two layers character viz thermal layer and suction layer, while the oscillatory part exhibits a multilayer character.

Few-layer graphene on SiC, pyrolitic graphite, and graphene: A Raman scattering study

The results of micro-Raman scattering measurements performed on three different “graphitic” materials: microstructured disks of highly oriented pyrolytic graphite, graphene multilayers thermally decomposed from carbon-terminated surface of 4H-SiC and an exfoliated graphene monolayer are presented. Despite its multilayer character, most parts of the surface of the graphitized SiC substrates shows a single component, Lorentzian shape, double resonance Raman feature in striking similarity to the case of a single graphene monolayer. Our observation suggests a very weak electronic coupling between graphitic layers on the SiC surface, which therefore can be considered to be graphene multilayers with a simple (Dirac-like) band structure.

Electrolytical Obtaining of Ni-Mo Coatings with Polypyrrole

Electrolytic coatings Ni-Mo with PPy were obtained by electrodeposition and electropolymerization from a galvanic bath containing Ni2+, MoO4 2–, ClO4 – ions and pyrrole (Py). The cyclic chronovoltamperommetric curve was used to determine the potential and current density of electrodeposition process. As the electropolymerization is anodic process while the electrodeposition is cathodic one, the electrode was working alternately as anode and cathode. The process was conducted under alternating potentiostatic or galvanostatic conditions. Comparative tests were carried out for Ni-Mo alloy. The results of structural investigation of the obtained coatings by the X-ray diffraction method show, the Ni-Mo layers are nanocrystalline solid solution of molybdenum in nickel (α phase), whereas the Ni-Mo+PPy coatings are characterized by decreased peaks coming from Ni-Mo base. Surface morphology of obtained Ni-Mo+PPy and Ni-Mo coatings was investigated by scanning microscope. It was stated, that the coatings obtained by alternating potentiostatic method exhibit multilayer character, whereas the coatings obtained under alternating galvanostatic conditions are characterized by the presence of Ni-Mo nanoagglomerates plated on polymer surface.

Calculating the temperature fields that appear when laser radiation interacts with multilayer biological material

Green's functions of the response of a medium to a single external stimulus were used to model the propagation of optical radiation in biological tissues and scattering media. The algorithm makes it possible to take into account the multilayer character of the medium, the finite size of the incident beam, and also the interaction of the surface of the tissue with the external medium. A solution of the thermal-conductivity equation using the method of finite elements is presented, the temperature fields are calculated that arise when biological material is irradiated with low-intensity laser radiation at various instants, and graphs are also constructed to show how the temperature depends on the time at which the material is irradiated with constant and pulsed action.

High resolution electron microscopy of CrN–TiN thin films grown on Si(100) by magnetron sputtering

CrN–TiN thin films were deposited as successive, alternating layers on Si(100) substrates using a closed field unbalanced reactive magnetron sputtering method (CF-UBRMS) at various substrate biases ( V b) and substrate rotation speeds. High resolution electron microscopy (HREM) study showed that the nanostructural characteristics of the films depend on the growing conditions. For the case of substrate bias V b = − 50 V and high rotation speed of the substrate, the film is polycrystalline with no preferential growth mode, while for lower speeds two nanocrystalline layers are formed with preferential growth orientations: [100] nitrides//[100] Si in the first zone and [111] nitrides//[100] Si in the second one. Epitaxial growth is observed sometimes locally in grains of the first zone. The multilayer character of the films was partially preserved only for films grown with the substrate at floating potential and low substrate rotation speed. For a higher speed, the growth takes place also with the two-zone growth mode.

New theoretical expressions for the five adsorption type isotherms classified by BET based on statistical physics treatment

New theoretical expressions to model the five adsorption isotherm types have been established. Using the grand canonical ensemble in statistical physics, we give an analytical expression to each of five physical adsorption isotherm types classified by Brunauer, Emett, and Teller, often called BET isotherms. The establishment of these expressions is based on statistical physics and theoretical considerations. This method allowed estimation of all the mathematical parameters in the models. The physicochemical parameters intervening in the adsorption process that the models present could be deduced directly from the experimental adsorption isotherms by numerical simulation. We determine the adequate model for each type of isotherm, which fixes by direct numerical simulation the monolayer, multilayer, or condensation character. New equations are discussed and results obtained are verified for experimental data from the literature. The new theoretical expressions that we have proposed, based on statistical physics treatment, are rather powerful to better understand and interpret the various five physical adsorption type isotherms at a microscopic level.

New Theoretical Expressions for the Five Adsorption Type Isotherms Classified by Bet Basing on Statistical Physics Treatment

New theoretical expressions to model the five adsorption Type isotherms have been established. Using the grand canonical ensemble in statistical physics, we could give an analytical expression to each five physical adsorption Type isotherms classified by Brunauer-Emetter-Teller, called often BET isotherms [1]. The establishment of these expressions is based on statistical physics treatment and theoretical considerations. This method allowed an estimation of all the mathematical parameters in the models. The physico-chemical parameters intervening in the adsorption process that present the models could deduced directly from the adsorption isotherms with numerical simulation. We determine the adequate model for each Type isotherm, which fixes with direct numerical simulation the monlayer, multilayer or condensation character. The new theoretical expressions that we have proposed, basing on statistical physics treatment, are rather powerful to better understand and interpret the various five physical adsorption Type isotherms at a microscopic level. (Af. J. of Science and Technology: 2002 3(2): 67-75)

Similarity of crystalline structure of BSCCO single crystal and multi-layer film

Bi 2Sr 2CaCu 2O y single crystal was studied by means of high-resolution X-ray diffraction and the local work function measurement with scanning tunneling microscope (STM). The results show that the single crystal is natively inhomogeneous. The rocking curve of 0 0 l reflection indicates that the c-axis lattice constant of the crystal varies in a narrow range, clearly showing a multi-layer character. The reflectivity measurement supports this result. It shows an obvious multi-layer character too. The small angle scattering indicates that although the c-axis lattice constant is little different in the crystal, it shows a long period of about 340 Å. The local work function measurement with STM demonstrates that the crystal is inhomogeneous. Some part in the crystal acts like thin film and some part like substrate, supporting the results of X-ray analyses.

Mechanical properties of Al/Al2O3 nanolaminated films: correlation to microstructure

Wear resistance and the hardness of Al/Al2O3 nanolaminated films were investigated in this study. Monolithic films and multilayers were deposited on a silicon substrate with two different substrate temperatures: Ts=25°C and Ts=−90°C. The period thickness of multilayers was lowering from 40 to 2nm. From nanoindentation measurements, it appears that the hardness of multilayers has an intermediate value between those of metal (Al) and ceramic (Al2O3). The tribological test was conducted by the pin-on-disc method. The Ts=25°C deposited multilayers, as well as single films, demonstrated poor wear resistance. The best wear resistance was obtained for multilayers deposited at the lowest substrate temperature (Ts=−90°C). The results are in good agreement with structural characterization. X-ray reflectometry demonstrated that the multilayer character of Al/Al2O3 is more pronounced for Ts=−90°C.

The globalisation challenge: Surviving at the margins

Globalisation is crucial to understanding international political economy, for it directs attention to fundamental changes underway in the post-Cold War era. The manifestations of globalisation include the spatial reorganisation of production, the interpenetration of industries across borders, the spread of financial markets, the diffusion of identical consumer goods to distant countries, massive transfers of population within the South as well as from the South and the East to the West, resultant conflicts between immigrant and established communities in formerly tight-knit neighbourhoods, and an emerging worldwide preference for democracy. A rubric for varied phenomena, the concept of globalisation interrelates multiple levels of analysis-economics, politics, culture and ideology. But what explains globalisation? What are its causes, mechanisms, and possibilities for transformation? Where to focus an analysis? On the inner workings and logic of capital itself? On strategies and actors seeking to optimise their positions? On empirical indicators or trends said to comprise this process? On the complementary and contradictory interactions among localisation, regionalisation and globalisation? On the social and political consequences? I contend that world society is entering a new era in the relationship between power and the division of labour, which is globalised. What sets the context for conflict and cooperation in the post-Cold War period is an integrating and yet disintegrating process known as globalisation. Although any given world problem has many sources, globalisation establishes novel opportunities and challenges for solving it. In developing this argument, I will first explore varied meanings of the concept of division of labour and the multilayer character of the globalisation process. The next section anchors the discussion by examining one region-East Asia-within this framework. This section is obviously not a detailed account but a synopsis of the impact of globalisation on a specific regional division of labour. Finally, I will turn to the seeds of future conflict sown by globalisation and, also, the implications for adaptation to a rapidly changing and highly competitive environment.

The influence of the structure of the surface of a liquid on the properties of a supported monolayer

This paper describes a simple lattice model of a liquid supported monolayer of long chain amphiphile molecules. The new feature which this model possesses is incorporation of the structure of the surface of the support liquid. The liquid–monolayer interface is represented as a multilayer region, and its structure is described in terms of the associated inhomogeneous density distributions of the support liquid molecules and of the segments of the chain molecules. The properties of this diffuse surface–amphiphile monolayer model are compared with the properties of the smooth surface–amphiphile monolayer model described in our previous work [J. Chem. Phys. 92, 1427 (1990)]. The general behavior of the monolayer equation of state, including the prediction of two successive fluid–fluid phase transitions, is preserved in the present model. We find that the existence of the diffuse surface structure of the supporting liquid leads to an increase in the number of the amphiphile chain segments that lie in the surface region, particularly at low surface densities. We also find that the multilayer character of the diffuse surface region can alter the equation of state of the monolayer at high surface densities. The two layer diffuse surface–amphiphile monolayer model supports a change in the slope of the surface pressure versus area isotherm in the very high surface density region, which can be ascribed to a conformational ‘‘freezing’’ of the chain molecules. The theory illustrates the qualitative features of the system which define the close interplay between the structure and properties of the monolayer and the structure of the surface of the support liquid.

The deposition of Langmuir-Blodgett films containing purple membrane on lipid- and paraffin-impregnated filters

Langmuir-Blodgett films containing the light-driven proton pump, bacteriorhodopsin, in the form of purple membrane were deposited onto cellulose ester filters previously impregnated with hexadecane and soya lecithin. The effect of the K +-selective ionophore, valinomycin, on the photopotential generated across these combined films was examined. A simple equivalent electrical circuit was developed in order that the potential of this system as a light-driven ion exchanger might be evaluated. A major rearrangement of the Langmuir-Blodgett film occurred on deposition onto the filters, removing one of the attractions of these films in this application: their multilayer character. The equivalent circuit analysis of the apparent K +H + exchange indicates that the film rearrangements may be similar to the process of lipid rearrangement that occurs when liposomes are fused to a filter.

The gas phase autophobicity of alcohols adsorbed on alumina

The adsorption isotherms for n-aliphatic alcohols (C 1C 4) have been obtained on two alumina surfaces of widely different surface area. The isotherms exhibit strong monolayer binding with little tendency toward multilayer formation. However, attempts to ascribe all multilayer adsorption to pendular ring condensate were not successful, and some multilayer contribution remains at high relative pressures. The residual multilayer character is higher for the low specific surface area alumina and decreases for both surfaces in going from C 1 to C 4. The enhanced multilayer character for the low area alumina is understandable in terms of its supposedly higher electrostatic field strength. The variation with hydrocarbon chain length is due to a gradual isolation of the surface from any multilayer adsorption in the context of previously developed autophobicity concepts presuming strongly oriented first-layer adsorption.