Materials Science

Multi-physics coupled simulations are performed to study the temperature field in a turbine blade placed in the high pressure distributor of a helicopter engine. Large Eddy Simulation (LES) is used to calculate the unsteady reacting flow in the chamber and is coupled to the simulation of radiation and heat conduction in the high pressure stator (HPS). This implies the use of three different solvers, running simultaneously on a parallel machine with an optimized processor distribution. Results are shown for the LES alone, for the LES coupled to heat conduction only and for the three coupled codes. The present demonstrate that the temperature field in the fluid and in the HPS are sensitive to both heat conduction and radiation, and that these two phenomena must be included to accurately predict the HPS temperature.

The mathematical model of a flexible cantilever beam with a constrained viscoelastic layer and shape memory alloy layer called smart damping treatment (SDT) is presented. It is shown that a change of the elastic modulus of the shape memory alloy layer will affect the system loss factor and resonance frequency. The recovery stress of the SMA layer leads to an inhomogeneity in the governing differential equation. The recovery stress also functions as an excitation to the system. The effects of the different parameters found in the analysis are discussed in the paper.

This investigation focuses on the feasibility of reaction synthesis of Ti 3 SiC 2 phase using plasma spraying of powder mixture of Ti, SiC and graphite. In-flight particle diagnostics suggested that dwell (reaction) time of these powder mixture is very short (∼10 -4 s) during plasma spraying. Phase identification and microstructural characterizations of the as-sprayed coatings were conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Thermodynamic calculations on Ti-SiC-C system were also made. Reaction mechanism of Ti 3 SiC 2 synthesis during plasma spray is proposed. Although relatively lower volume percentage of Ti 3 SiC 2 (∼15-19%) phase was found in the plasma sprayed coating, reaction synthesis of Ti 3 SiC 2 phase using plasma spray provides a potential processing technique to fabricate Ti 3 SiC 2 as a protective coating on large engineering components.

The temperature effects on frequency, loss factor and control of a flexible beam with a constrained viscoelastic layer and shape memory alloy layer(SMA) are discussed. It is shown that the temperature in the SMA (actuation) layer is very important in the determination of frequency and loss factor of such a structure. The effects of damping layer shear modulus and damping layer height as affected by the temperature are also discussed. As temperature plays such an important role, it is, therefore, imperative to evaluate temperature effects on the control of the system as well. Results with and without active control are discussed.

The goal of this work is to develop and investigate the properties of a new type of multifunctional composite which is based on multi-walled carbon nanotubes (MWCNT). The composite was prepared from a MWCNT "bucky paper" film which was sandwiched between two adhesive layers. Both two point probe and four point probe methods were used to test its mechanical strain sensing properties. The Young' modulus and shear modulus of MWCNT film composite were acquired by the nanoindentation test and direct shear test. A free vibration test was also performed to investigate its structural damping properties. Our research indicated that this new type of carbon nanotube based composite is potentially capable of functioning as a strain sensor and damping device simultaneously for structural vibration control.

The main drawback of phase change materials (PCMs) is their low thermal conductivity, which limits the possibilities of a wide range of implementations. Therefore, the researchers, as found in the literature, proposed several methods to improve the thermal conductivity of PCMs, including inserting high thermal conductivity materials in nano-, micro-, and macro-scales, as well as encapsulation of PCMs. However, these inserts impact the other properties of PCMs like latent heat, melting temperature, thermal stability, and cycling stability. Hence, this paper aims to review the available in the open literature research on the main properties of enhanced PCMs that undergo solid–liquid transition. It is found that inserting high thermal conductivity materials and encapsulation results in improved thermal conductivity of PCMs, but it decreases their latent heat. Moreover, the insertions can act as nucleating agents, and the supercooling degree can be reduced. Some of the thermal conductiv...

Resumo. Informações sobre a nutrição da amoreira ainda são insipientes e para viabilizar a produção das mudas tem-se buscado alternativas para reduzir os custos de produção e o tempo da muda no viveiro. A utilização de composto com resíduo da indústria têxtil apresenta-se como alternativa favorável, pois evita a poluição do ambiente e serve como fonte de nutrientes. O trabalho foi realizado com o objetivo de avaliar a formulação do substrato com composto de resíduo da indústria têxtil sobre a absorção de macro e micronutrientes da amoreira preta cv. Brazos. Foi utilizado o delineamento inteiramente casualizado, com quatro formulações de substratos, cinco repetições e cinco mudas por parcelas. O substrato foi formulado com composto de resíduos da indústria têxtil e Latossolo nas seguintes proporções: 0:1, 1:2, 1:1 e 2:1 (v/v). As mudas foram obtidas a partir de estaquia e colocadas em recipientes de 650 mL, contendo o substrato preparado. Aos 90 dias após o transplantio das mudas, foram retiradas amostras de folhas para determinação dos teores de nutrientes acumulados na massa seca. Os resultados observados demonstraram que o resíduo da indústria têxtil pode ser utilizado para formular substratos para a produção de mudas de amoreira em proporções que não ultrapasse 50%. Os substratos com 33% e 50% do composto atenderam a demanda de nitrogênio, potássio, magnésio, boro e zinco das mudas de amoreira sem a necessidade do fornecimento de fertilizantes comerciais.

We present experimental data and numerical simulation results obtained during investigation of synchronously pumped optical parametric oscillators (SPOPOs) pumped by second harmonic (515 nm) of femtosecond Yb:KGW laser. We used two different nonlinear media for parametric generationlithium triborate (LBO) and beta barium borate (BBO) in slightly different experimental setups. Maximum parametric light conversion efficiency from pump power to signal power was more than 25% whereas the largest achieved signal wave tuning ranges were from 670 nm to 1030 nm for BBO SPOPO and from 780 nm to 940 nm for LBO SPOPO. We also used intracavity group delay dispersion (GDD) compensation to achieve shorter signal pulses and investigated changes of various SPOPO output characteristics when changing net cavity GDD.

Vibrations exist widely in tall buildings, vehicle systems, and ocean platform suffering from environmental loading such as wind, wave or earthquake. With the global concern on energy and environmental issues, energy absorbing from large-scale vibrations becomes a research frontier. A type of damped dynamics vibration energy absorber is built and analyzed in this paper, in which an added mass is connected to the vibration system with the electromagnetic transducer and spring. The relationships between electrical damping ratio, excitation frequency ratio and dimensionless power are analyzed in frequency domain. The optimal parameters for maximizing the power output are discussed in analytical form while taking the inherent mechanical damping of the system into account. The results indicate that when the system has suitable optimal excitation frequency ratio and damping ratio and so on, more power can be obtained. It is helpful for the design of energy absorber devices.

Infection control is a challenging task in the treatment of wounds and a rise in antimicrobial resistance wound pathogens which is a barrier for the wound regeneration rapidly. Therefore, there is an urgent requirement of novel antimicrobial agents to target the wound pathogens and their biofilms. Silver nanoparticles (AgNPs) are the predominant antimicrobial agent for wound treatment due to their broad spectrum antimicrobial potential against various wound pathogens. Silver nanoparticles (AgNPs) were prepared from aqueous Adenanthera pavonina seed extract. This extract plays as a reducing agent for reduction of silver nitrate to silver oxide nanoparticles. An absorption peak at 428 nm with characteristic feature of surface plasmon resonance was observed. The average size of AgNPs was found to be ~200 nm and cube in shape of AgNPs. FTIR data revealed the presence of phenolic groups that were responsible for reduction and stabilization of silver nanoparticles. Face centered cubic (FCC) crystalline structure was revealed from XRD relating to silver oxide (AgO) with good antibacterial potential. The antioxidant activity of extract increases when the concentration increases, and it can be used in the inhibition of free radicals at wound site. Antibacterial activities showed effective inhibition against various pathogens such as E.coli, Salmonella typhi, Sphingomonas, and Bacillus. Given this correspondence, the green synthesized AgNPs would be a potential antimicrobial agent for various wound treatments.

Poly(Methyl Methacrylate) (PMMA) and CaCu 3 Ti 4 O 12 (CCTO) composites were fabricated via melt mixing followed by hot pressing technique. These were characterized using X-ray diffraction (XRD), thermo gravimetric (TGA), Thermo Mechanical (TMA), Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and Impedance analyser for their structural, thermal and dielectric properties. Composites were found to have better thermal stability than that of pure PMMA. However, there was no significant difference in the glass transition (T g ) temperature between the polymer and the composite. The appearance of additional vibrational frequencies in the range 400-600 cm -1 in FTIR spectra indicated a possible interaction between PMMA and CCTO. The composite, with 38 Vol % of CCTO (in PMMA), exhibited remarkably low dielectric loss at high frequencies and the low frequency relaxation is attributed to the space charge polarization/MWS effect. The origin of AC conductivity particularly in the high frequency region was attributed to the electronic polarization. Keywords: Poly(Methyl Methacrylate) (PMMA), CaCu 3 Ti 4 O 12 (CCTO), Polymer composite, thermal properties.

Quantification of the effects of adjuvants on droplet behaviour on plant surfaces is needed to improve pesticide spray application efficiency for soybeans. Dispersion and evaporation of single 300-mm diameter droplets amended with each of four spray adjuvants at five concentrations were investigated for four soybean plant surfaces (abaxial and adaxial leaflet surfaces, petiole, basal stem). The four adjuvants were a crop oil concentrate (COC), a modified seed oil (MSO), a non-ionic surfactant (NIS) and an oil surfactant blend (OSB). A single-droplet generator was used to produce and deposit 300-mm diameter droplets on target surfaces under controlled environmental conditions. Adjuvants significantly increased the dispersion (or wetted area) of droplets on plant surfaces. Droplet-wetted areas increased with increased adjuvant concentrations but not in direct proportion. The average increases of wetted areas across the four soybean plant surfaces were 443, 462, 416, or 343% when the spray mixture was amended with COC, MSO, NIS or OSB at the manufacturer-recommended concentrations, respectively. Among the four surfaces, the largest wetted area was on the abaxial surface, followed by the adaxial surface, the petiole and then the basal stem. Droplet evaporation times were inversely proportional to the wetted areas. The evaporation time of 300-mm diameter droplets ranged from 36 to 142 s on the four surfaces when the spray mixture was amended with an adjuvant, whereas the water-only droplets ranged from 161 to 190 s. The results demonstrated that use of adjuvants offers great potential to improve the homogeneity of sprayed pesticides, to increase spray coverage and to reduce pesticide application rates on soybean plants. These effects could benefit farmers economically and reduce environmental contamination by pesticides.

Fully-implantable, bi-directional brain-computer interfaces (BCIs) necessitate simultaneous cortical recording and stimulation. This is challenging since electrostimulation of cortical tissue typically causes strong artifacts that may saturate ultra-low power (ULP) analog front-ends of fullyimplantable BCIs. To address this problem, we propose an efficient hardware-based method for artifact suppression that employs an auxiliary stimulator with polarity opposite to that of the primary stimulator. The feasibility of this method was explored first in simulations, and then experimentally with brain phantom tissue and electrocorticogram (ECoG) electrode grids. We find that the canceling stimulator can reduce stimulation artifacts below the saturation limit of a typical ULP front-end, while delivering only ∼10% of the primary stimulator's voltage.

This paper presents a silicon-based waveguide structure employing split ring resonators (SRRs) and distributed loss compensation mechanism suitable for fabrication. Higher phase constant is obtained by periodically loading waveguide (WG) with SRRs in sub-wavelength dimensions at the cost of extra large amount of losses. To relieve the losses problem, a circuitry is introduced in each SRR to compensate the loss while retaining the high phase constant achieved around the resonant frequency. This proposed waveguide with SRRs whose losses are compensated shows higher phase constant, lower attenuation constant and additional tunability compared to common waveguide.

This paper presents a W-band fully on-chip bowtie slot antenna over a grounded low resistivity silicon substrate fabricated in 180 nm BiCMOS process. The measured results show that the proposed antenna could provide a wide input bandwidth covering the whole W-band. The simulated gain at 90 GHz is -1 dBi when considering several realistic effects.

A highly efficient push-push voltage controlled oscillator (VCO) with a new varactor-less-based frequencytuning topology for terahertz (THz) frequencies is presented. The tuning technique is based on a variable inductance seen at the emitter node of a base degenerated transistor. Fabricated in a 130nm SiGe BiCMOS process, the VCO achieves a tuning range of 3.5% and output power of ----7.2 dBm at 201.5GHz. The VCO consumes 30mW of DC power, resulting in a record-breaking power efficiency of 0.6%. To demonstrate the functionality of the tuning technique, three other VCO prototypes at different oscillation frequencies, including one operating at 222.7~229 GHz range, have been implemented.

A 300 GHz frequency synthesizer incorporating a triple-push VCO with Colpitts-based active varactor (CAV) and a divider with three-phase injection is introduced. The CAV provides frequency tunability, enhances harmonic power, and buffers/injects the VCO fundamental signal from/to the divider. The locking range of the divider is vastly improved due to the fact that the three-phase injection introduces larger allowable phase change and injection power into the divider loop. Implemented in 90 nm SiGe BiCMOS, the synthesizer achieves a phase-noise of -77.8 dBc/Hz (-82.5 dBc/Hz) at 100 kHz (1 MHz) offset with a crystal reference, and an overall locking range of 280.32-303.36 GHz (7.9%).

The coupling of propagating surface plasmon waves and localized plasmon oscillations in nanostructures is an essential phenomenon determining electromagnetic field enhancement on the nanoscale. Here, we use our recently developed ultrafast photoemission near-field probing technique to investigate the fundamental question of plasmon-plasmon coupling and its effect on large field enhancement factors. By measuring and analyzing plasmon field enhancement values at different nanostructured surfaces, we can separate the contributions from propagating and localized plasmons. When resonance conditions are met, a significant field enhancement factor can be attributed to the generation of localized plasmons on surface nanostructures, acting as dipole sources resonantly driven by the propagating plasmon field. Our plasmon-plasmon coupling results can contribute directly to applications in surface-enhanced Raman scattering (SERS) and the development of plasmonic sensors and nanostructured photo...

Plasmonic metamaterials and metasurfaces are important for many linear and nonlinear photonic applications. Here we show that it is possible to control a nanostructured layer spontaneously formed near an interface of a thin film of silver where the interplay between a grain boundary structure and surface segregation of germanium atoms in silver films leads to encapsulation of the grains and, as a result, formation of a composite metamaterial near the film surface. This Ag/Ge composite exhibits strong localized surface plasmon resonances at

We report on the roughness of 70nm thick Al films deposited on fused silica and sapphire substrates using an e-beam physical vapour deposition (PVD) system with exact control of substrates temperature. Before evaporation both types of epi-polished substrates are cleaned using low-energy Argon ion bombardment. The roughness of films deposited at 450, 297, 170 and 92K is measured with an atomic force microscope (AFM). The lowest average root mean square (RMS) roughness of 0.98 nm is obtained for a 70nm Al film on sapphire deposited at 170K. The decrease of surface roughness and interface irregularities should allow for building optical transmission lines with long range surface plasmons as signal carriers . Most of the research in the field is devoted to the properties of silver layers; however, more lossy aluminium/dielectric interfaces are interesting because of wide applications. Studies on Al films are motivated by the use of aluminium in optoelectronics, solar cells and in tapered-fiber metal-coated probes for scanning near field optical microscopes (SNOM) [5]- . In a compilation of Drude model parameters for the optical constants of metals in the infrared and far infrared, the authors claimed that in the case of Al, the free electron model and consequently plasma frequency, damping frequency, dc resistivity, and optical frequency resistivity values should be valid even in the visible range under the condition that the Al layer is smooth. The relation between surface morphology and scattering of plasmons on thin Al films continues to be of interest [10]- . Liu et al. [10] reported the deposition of Al on an Si(111) wafer at 145K and a base pressure of 10 -10 Torr. Starting from 4 monolayers, Al films became atomically flat with RMS =0.05nm. Cheng and Lee [12] simulated 3D molecular dynamics of Al nanolayer growth to determine the dependence of surface roughness on temperature of substrates. Simulations performed for the temperature range 300-700K showed that the smallest roughness of an Al film is achieved at temperatures 450-600K. In [10] and [11] plasmons in a few monolayers thin Al films on silicon were studied to measure dispersion as

We characterize the sensitivity of imaging properties of a layered silver-TiO2 flat lens to fabrication inaccuracies. The lens is designed for approximately diffraction-free imaging with subwavelength resolution at distances in the order of a wavelength. Its operation may be attributed to self-collimation with a secondary role of Fabry-Perot resonant transmission, even though the first order effective medium description of the structure is inaccurate. Super-resolution is maintained for a broad range of overall thicknesses and the total thickness of the multilayer is limited by absorption. The tolerance analysis indicates that the resolution and transmission efficiency are highly sensitive to small changes of layer thicknesses.

This study presents the design and processing of interlocked interfaces of graded bioactive calcium phosphate coatings on a load-bearing zirconia substrate. Such interfacial structures can effectively enhance bonding between the coating and substrate, and suppress the residual stress across the interfacial region. Multiple coating layers with graded interconnected micropore structures, and common phases across the layer boundary have been considered to minimize the likelihood of interfacial cracking/delamination. The Focused Ion Beam (FIB) technique was used to reveal microscopic details of the interlocked interface formed by the common calcium phosphate and zirconia phases in both the microporous coating and the dense substrate. The interface microstructure and phase characteristics in the substrate and coatings were confirmed by means of FIB-SEM and X-ray diffraction (XRD) analysis respectively. A preliminary Finite Element Modelling (FEM) study shows that graded and interconnecte...

Polymer-based matrix hybrid composites meet their demand in various engineering applications and food industries due to their excellent mechanical, thermal, corrosion, and biodegradable performance. The polymer-based hybrid composites have been a better choice for high thermal insulation at low cost. This experiment attempted to find the thermal adsorption characteristics, heat deflection temperature, linear thermal expansion, and thermal conductivity of epoxy hybrid composites, which contained four different layers of Kevlar and basalt fiber fabricated via a low-cost conventional hand mold layup technique. This experiment revealed that the effect of basalt/Kevlar fiber on epoxy increased thermal performance. The results noted that the hybrid composite consists of less Kevlar fiber with the maximum basalt fiber of sample 4, showed excellent thermal adsorption effect on weight loss limited at 70.98%, and a better heat deflection temperature and 11.78 × 10 − 6 per °C linear thermal ex...

The need for watching the catalytic reaction in operation got to be the focus of the light sources where number of dedicated experiments have been developed to track the electronic and molecular structural dynamics in operation. Two major challenges are coming together for this

Current sub-millisecond time-resolved broadband infrared spectroscopy, one of the most frequently used techniques to study structure-function relationships in life sciences, is typically limited to fast-cycling reactions that can be repeated thousands of times with high frequency. Notably, the majority of chemical and biological processes do not comply with this requirement. For example, the activation of vertebrate rhodopsin, prototype of many protein receptors in biological organisms that mediate basic functions of life including vision, smell, and taste, is irreversible. Here we present a dispersive single-shot Féry spectrometer setup that extends such spectroscopy to irreversible and slow-cycling systems by exploiting the unique properties of brilliant synchrotron infrared light combined with an advanced focal-plane detector array embedded in a dispersive optical concept. We demonstrate our single-shot method on microbial actinorhodopsin with a slow photocycle, and on vertebrate rhodopsin with irreversible activation.

Spontaneous formation of nanostructured materials of defined structure and morphology is a crucial milestone toward realizing true bottom-up nanofabrication. Supramolecular recognition offers unparalleled specificity, selectivity and geometric flexibility to design hierarchical nanostructures. However, competition between similar binding motifs and the dynamic nature of the attachment imposes a severe limitation on the complexity of the achievable structures. Here we outline a design based on two distinct binding motifs in a supramolecular fibrous assembly to realize a metallosupramolecular framework (MSF). Controlled geometries were achieved by one-dimensional supramolecular assembly of substituted oligoamide units. The assembly of the monomers yields nanorods of sub-nanometer diameter and lengths in the 100 mm range. Addition of Cu 2+ led to the formation of well aligned two-dimensional arrays on mica surface. Vibrational spectroscopy confirmed that the backbone amide moieties are not affected by metal addition. XPS and NEXAFS results suggest that Cu(II) is reduced in the process to a mixture of Cu(I) and Cu(0), likely in an interaction with the amine moiety of the imidazole side chain. Our results indicate that the two dimensional superstructure is based on the formation of polynuclear metal complexes between the oligoamide nanorods, thus the structure is confirmed to be a metallosupramolecular framework.

iLTP) their functional link with the synaptic terminals has been highlighted. The insight provided at the molecular level makes IML techniques the suitable tool for a quantitative study of Gephyrin distribution at synaptic level. Quantitative approach based on clustering analysis [4] provided access to a more comprehensive set of parameters able to define the response to iLTP, such as the area and the density of the scaffold protein. At the fluorescent tag level, to fulfill the requests of the quantitative analysis, an irreversibly photoactivatable fluorescent protein has been used (mEos), knowing its photophysical properties [5].

Solute-surface interactions are critical in membrane science and dominate a number of diffusion and selectivity parameters. In water treatment particularly, the charge on the membrane has been shown to affect ion transport selectivity as well as fouling mechanisms. The development of advanced surface technologies that allow for potential customization of the surface charge for specific applications, without compromising the essential performance of the membrane, is therefore desirable. In this paper, a novel plasma polymerization strategy was applied to commercial reverse osmosis membrane in order to tune the surface charge. Two monomers, maleic anhydride and vinylimidazole, were plasma polymerized onto the membrane resulting in a modification of the surface energy with resultant iso-electric points of approx. pH 3 and pH 7 respectively. This required only a short 5 min plasma polymerization treatment in each case. Thus, in addition to enhancing the water permeation by up to 10 %, in comparison to the reference membranes, the overall charge of the membranes was shifted from highly negatively charged upon maleic anhydride polymerization to highly positively charged upon vinylimidazole polymerization. A comprehensive morphological and chemical analysis was performed to correlate the changes to the presence of functional groups and the alteration of the surface texture. Short treatments were found to smooth the surface whilst enriching the surface with either carboxylic or amine/amide groups. This work opens new avenues to engineer advanced membranes with improved performance and selectivity.

Synchrotron FTIR microscopy has been used to probe the structure of model boundary lubricant layers confined at the solid-solid interface. The combination of high brightness of the IR source and a novel contact geometry that uses a hemispherical internal reflection element as the means for light delivery has enabled the detection of <2.5 nm thin monolayer lubricant layers in the solid-solid contact, in addition to allowing for spectral acquisition from specific regions of the contact. Spectra of hydration water from within a confined polyelectrolyte multilayer film have also been acquired, highlighting the altered hydrogen bonding environment within the polymer layer.

The characterization of novel metal reinforced electro-dialysis ion exchange membranes, for water desalination, by attenuated total reflectance Fourier Transform infra-red spectroscopy mapping is presented in this paper. The surface of the porous stainless steel fibre meshes was treated in order to enhance the amount of surface oxide groups and increase the material hydrophilicity. Then, the metal membranes were functionalized through a sol-gel reaction with silane coupling agents to enhance the affinity with the ion exchange resins and avoid premature metal oxidation due to redox reactions at the metalpolymer interface. Polished cross sections of the composite membranes embedded into an epoxy resin revealed interfaces between metallic frameworks and the silane layer at the interface with the ion exchange material. The morphology of the metalpolymer interface was investigated with scanning electron microscopy and Fourier transform infra-red micro-spectroscopy. Fourier transform infra-red mapping of the interfaces was performed using the attenuated total reflectance mode on the polished cross-sections at the Australian Synchrotron. The nature of the interface between the metal framework and the ion exchange resin was shown to be homogeneous and the coating thickness was found to be around 1 μm determined by Fourier transform infra-red micro-spectroscopy mapping. The impact of the coating on the properties of the membranes and their potential for water desalination by electro-dialysis are also discussed.

High spatial resolution, 7 mm  7 mm confocal image plane masking, and 1 mm step size mapping were used to image small areas of an organically modified silicate (ORMOSIL) film. The film was prepared by the sol-gel process from separately hydrolyzed isobutyltrimethoxysilane and tetraethoxysilane sols that were mixed just prior to being spin cast onto a polished silicon substrate. Detailed mapping was performed in a reflection absorption mode with an infrared microspectrometer at beamline U10B of the National Synchrotron Light Source of Brookhaven National Laboratory. The main objective of this study was to characterize the spatial distribution of organic (i.e. butyl) components within the film. Functional group maps of each film region were produced from the peak areas of the CH, OH, and Si-O stretching bands. The organic content (relative to total silicate) was obtained by ratioing the peak areas of the CH and Si-O absorption bands. Functional group maps of a relatively large region (230 mm  230 mm) with a 10 mm  10 mm mask size and a 10 mm step size reveal heterogeneity on a larger scale. These data demonstrate the utility of IR imaging in the study of ORMOSIL film chemical heterogeneity.

Infrared polarized microspectra of transverse leaf sections of Sorghum bicolor show significant anisotropy of vibrational modes. They reveal the preferential orientation of the sub-micron cellulose fibrils and other biopolymers in single cell walls.

AA6060 F, al ser deformada mediante deformación plástica severa empleando el proceso de extrusión en canal angular (ECAE). Asimismo, se ha efectuado un estudio del efecto del envejecimiento artificial sobre la modificación de dichas propiedades mecánicas. Para ello, se han realizado tratamientos térmicos a diferentes temperaturas y tiempos de permanencia, efectuando mediciones de dureza, ensayos de tracción, ensayos con péndulo Charpy y técnicas de revelado metalográfico, para conocer los comportamientos mecánicos y el estado del material. Existe un elevado número de publicaciones, que han analizado el efecto de tratamientos térmicos de envejecimiento en aleaciones de la serie 6000. Sin embargo, la aleación AA6060 no ha sido tan ampliamente estudiada. Por ello, en este trabajo se parte de una aleación comercial AA6060 en estado de bruto de colada, lo cual no ha sido estudiado hasta la fecha.

The network of entangled multiwall carbon nanotubes is shown to be a conductor whose resistance is sensitive to compressive strain both in the course of strain growth and when loading/unloading cycles are imposed. The cycles at first lead at to the resistance decrease but with a higher number of cycles they fade away. To model the resistance/strain dependence, it is hypothesized that compression increases local contact forces between nanotubes and bends the nanotubes, which results in more conducting contacts. The lack of detailed knowledge of these mechanisms as well as an unclear shift from individual contacts description to the whole network resistance is circumvented using the statistical approach. In this respect, good data representation is reached using Weibull and Levy-stable distribution for the description of distribution of nanotubes contact resistances and contact formation, respectively.

In this study, the effects of homogenization pressure (125, 145, and 165 bars) and temperature (45, 60, and 75°C) on the properties of Sesame vegetable cream are investigated. The physical stability of cream was characterized by droplet size and syneresis, and chemical stability of it was evaluated by determining peroxide value and p‐anisidine. The results showed that the cream in the presence of high pressure and temperature treatment exhibits lower stability. At 75°C temperature and 165 bar, the vegetable cream had highest peroxide value (3.61) and p‐anisidine (2.16). However, pressure could protect the droplets against aggregation in the high pressure (165 bar) and greatly increased the physical stability. During increase in process parameters, the syneresis of cream was decreased with a rise of pressure and extension of temperature. The process condition in 145 bar and 60°C led to the high acceptability of vegetable cream.

We measure the coherent nonlinear response of excitons in a single-layer of molybdenum disulphide embedded in hexagonal boron nitride, forming a h-BN/MoS 2 /h-BN heterostructure. Using four-wave mixing microscopy and imaging, we correlate the exciton homogeneous and inhomogeneous broadenings. We find that the exciton dynamics is governed by microscopic disorder on top of the ideal crystal properties. Analyzing the exciton ultra-fast density dynamics using amplitude and phase of the response, we investigate the relaxation pathways of the resonantly driven exciton population. The surface protection via encapsulation provides stable monolayer samples with low disorder, avoiding surface contaminations and the resulting exciton broadening and modifications of the dynamics. We identify areas localized to a few microns where the optical response is totally dominated by homogeneous broadening. Across the sample of tens of micrometers, weak inhomogeneous broadening and strain effects are observed, attributed to the remaining interaction with the h-BN and imperfections in the encapsulation process.

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Binding of the heavy-hole excitons and biexcitons in GaAs/Al 0.3 Ga0.7As superlattices is studied using linear and nonlinear optical techniques. High biexciton binding energies characteristic of quasi two-dimensional biexcitons are observed in superlattices with considerable miniband dispersion.

We determine the propagation loss of GaAs photonic crystal waveguides by spectral imaging of the spontaneous emission from the embedded InAs/GaAs quantum dots. The results are compared with the loss obtained by imaging the near field of the out-of-plane radiation of the waveguide mode propagating within the light cone. From the corresponding far field, we furthermore measure the mode wavevector, from which we determine the waveguide dispersion. Additionally, we show that spectral imaging allows to determine the relative efficiencies of the couplers. Using the same experiment, and detailed photonic simulations, we have determined the beta factor and the directionality of the emission of the QDs, finding beta factors up to 99% and high directionalities.

We have studied the polarization of surface and edge-emitted photoluminescence ͑PL͒ from structures with vertically coupled In 0.5 Ga 0.5 As/GaAs quantum dots ͑QD's͒ grown by molecular beam epitaxy. The PL polarization is found to be strongly dependent on the number of stacked layers. While single-layer and 3-layer structures show only a weak TE polarization, it is enhanced for 10-layer stacks. The 20-layer stacks additionally show a low-energy side-band of high TE polarization, which is attributed to laterally coupled QD's forming after the growth of many layers by lateral coalescence of QD's in the upper layers. While in the single, 3-and 10-layer stacks, both TE polarized PL components are stronger than the TM component, the ͓110͔ TE component is weaker than the TM component in the 20-layer stack. This polarization reversal is attributed to an increasing vertical coupling with increasing layer number due to increasing dot size.

We have studied both theoretically and experimentally the luminescence spectra and kinetics of crystalline, disordered solid solutions after pulsed excitation. First, we present the model calculations of the steady-state luminescence band shape caused by recombination of excitons localized in the wells of random potential induced by disorder. Classification of optically active tail states of the main exciton band into two groups is proposed. The majority of the states responsible for the optical absorption corresponds to the group of extended states belonging to the percolation cluster, whereas only a relatively small group of ''radiative'' states forms the steady-state luminescence band. The continuum percolation theory is applied to distinguish the ''radiative'' localized states, which are isolated in space and have no ways for nonradiative transitions along the tail states. It is found that the analysis of the exciton-phonon interaction gives the information about the character of the localization of excitons. We have shown that the model used describes quite well the experimental cw spectra of CdS (1Ϫc) Se c and ZnSe (1Ϫc) Te c solid solutions. Further, the experimental results are presented for the temporal evolution of the luminescence band. It is shown that the changes of band shape with time come from the interplay of population dynamics of extended states and spatially isolated ''radiative'' states. Finally, the measurements of the decay of the spectrally integrated luminescence intensity at long delay times are presented. It is shown that the observed temporal behavior can be described in terms of relaxation of separated pairs followed by subsequent exciton formation and radiative recombination. Electron tunneling processes are supposed to be responsible for the luminescence in the long-time limit at excitation below the exciton mobility edge. At excitation by photons with higher energies the diffusion of electrons can account for the observed behavior of the luminescence. ͓S0163-1829͑99͒11419-X͔

The objective of this research was to study the refining of calophyllum oils and its characterization as a biofuel substitute for diesel fuel. The dosage of phosphoric acid solution of 20% (0.2 -0.3%) and the NaOH concentration (14-18 °Be) were examined to determine the best performance of the refining process and the quality of refined calophyllum oil. The block experimental design and ANOVA (F-test at α = 0.05) were applied to study the effects of dosage of phosphoric acid solution of 20% and NaOH concentration on oil loss and its quality. Generally, the block and the NaOH concentration affected significantly the oil loss and the quality of refined oil. A significant increase of oil loss was observed as increasing of NaOH concentration. The dosage of phosphoric acid solution did not affect the oil loss and the quality of refined oil. However, an increase of the dosage of phosphoric acid solution tended to decrease the ash content and viscosity of refined oil, but did not affect any other parameters. The best treatment for calophyllum oil refining was obtained on the block 1, and the phosphoric acid solution dosage of 0.2% and NaOH concentration of 18 °Be. This treatment gave the oil loss of 36.8%, the acid value of 0.23 mg NaOH/g, the saponification value of 174.93 mg KOH/g, the peroxide value of 7 meq/kg, the ash content of 0.003% and the viscosity of 32.5 cP. The quality of refined calophyllum oil under this optimum condition fulfilled the Biofuel Standard.

The objective of this research was to study the refining of calophyllum oils and its characterization as a biofuel substitute for diesel fuel. The dosage of phosphoric acid solution of 20% (0.2 -0.3%) and the NaOH concentration (14-18 °Be) were examined to determine the best performance of the refining process and the quality of refined calophyllum oil. The block experimental design and ANOVA (F-test at α = 0.05) were applied to study the effects of dosage of phosphoric acid solution of 20% and NaOH concentration on oil loss and its quality. Generally, the block and the NaOH concentration affected significantly the oil loss and the quality of refined oil. A significant increase of oil loss was observed as increasing of NaOH concentration. The dosage of phosphoric acid solution did not affect the oil loss and the quality of refined oil. However, an increase of the dosage of phosphoric acid solution tended to decrease the ash content and viscosity of refined oil, but did not affect an...