Optical and structural properties of InAlN/GaN Bragg reflectors examined by transmission electron microscopy and electron energy loss spectroscopy

Molecular beam epitaxy growth of ten-period lattice-matched InAlN/GaN distributed Bragg reflectors (DBRs) with peak reflectivity centered around 400nm is reported including optical and transmission electron microscopy (TEM) measurements [1]. Good periodicity heterostructures with crack-free surfaces were confirmed, but, also a significant residual optical absorption below the bandgap was measured. The TEM characterization ascribes the origin of this problem to polymorfism and planar defects in the GaN layers and to the existence of an In-rich layer at the InAlN/GaN interfaces. In this work, several TEM based techniques have been combined.

Microstructural and mechanical characterization of annealed tungsten (W) and potassium-doped tungsten foils

Here we show that potassium-doped tungsten foil should be preferred to pure tungsten foil when considering tungsten laminate pipes for structural divertor applications. Potassium-doped tungsten materials are well known from the bulb industry and show an enhanced creep and recrystallization behaviour that can be explained by the formation of potassium-filled bubbles that are surrounding the elongated grains, leading to an interlocking of the microstructure. In this way, the ultra-fine grained (UFG) microstructure of tungsten foil can be stabilized and with it the extraordinary mechanical properties of the foil in terms of ductility, toughness, brittle-to-ductile transition, and radiation resistance. In this paper we show the results of three-point bending tests performed at room temperature on annealed pure tungsten and potassium-doped tungsten foils (800, 900, 1000, 1100, 1200, 1300, 1400, 1600, 1800, 2000, 2200, and 2400 °C for 1 h in vacuum). The microstructural assessment covers the measurement of the hardness and analyses of fractured surfaces as well as a comparison of the microstructure by optical microscopy. The results show that there is a positive effect of potassium-doped tungsten foils compared to pure tungsten foil and demonstrate the potential of the doped foil

Combination of optical and on-destructivemechanicaltechniques for the measurement of maturity in peach

Increasing consumer dissatisfaction related with lack of ripeness in peach has been repeatedly reported since 1990 to the present day. There is thus, a great interest in improving the assessment of peach maturity, currently based on Magness Taylor firmness (destructive, highly variable, and time consuming) and colour (not reliable for highly coloured varieties). The present research studies as an alternative several non-destructive (ND) measurements, based on multispectral imaging, visible spectra, and low mass impact response. Their relationship with maturity, as well as the potential of their combination was studied. As a result, two rather independent (R2 = 0.3) groups of non-destructive measurements, chlorophyll related optical indexes and low mass impact (LMI) measurements, were identified. Optical measurements showed the best behaviour for assessing maturity at harvest, while LMI measurements reflected handling incidences, showing a promising potential to be used to control transport and postharvest handling.

Sintering and microstuctural characterization of W6+, Nb5+ and Ti4+ iron-substituted BiFeO3

The sintering behaviour and the microstructural evolution of W6+, Nb5+ and Ti4+iron-substituted BiFeO3 ceramics have been analyzed. The obtained results show that W6+ and Nb5+ ions interact with the secondary phases usually present in these materials, thus altering the solid state formation of the BiFeO3 phase. In contrast, Ti4+ ions incorporate into the perovskite structure, leading to an exceptionally low proportion of secondary phases. In addition to this, BiFe0.95Ti0.05O3 materials present a dense microstructure with submicronic and nanostructured grains, clearly smaller than those in the undoped materials.

Cysteine-proteases and cystatins from barley: molecular and functional characterization in housekeeping and defense processes

Plant cysteine-proteases (CysProt) represent a well-characterized type of proteolytic enzymes that fulfill tightly regulated physiological functions (senescence and seed germination among others) and defense roles. This article is focused on the group of papain-proteases C1A (family C1, clan CA) and their inhibitors, phytocystatins (PhyCys). In particular, the protease–inhibitor interaction and their mutual participation in specific pathways throughout the plant's life are reviewed. C1A CysProt and PhyCys have been molecularly characterized, and comparative sequence analyses have identified consensus functional motifs. A correlation can be established between the number of identified CysProt and PhyCys in angiosperms. Thus, evolutionary forces may have determined a control role of cystatins on both endogenous and pest-exogenous proteases in these species. Tagging the proteases and inhibitors with fluorescence proteins revealed common patterns of subcellular localization in the endoplasmic reticulum–Golgi network in transiently transformed onion epidermal cells. Further in vivo interactions were demonstrated by bimolecular fluorescent complementation, suggesting their participation in the same physiological processes.

Hydration of C3S, C2S and their Blends. Micro- and Nanoscale Characterization

This study forms part of wider research conducted under a EU 7 th Framework Programme (COmputationally Driven design of Innovative CEment-based materials or CODICE). The ultimate aim is the multi-scale modelling of the variations in mechanical performance in degraded and non-degraded cementitious matrices. The model is being experimentally validated by hydrating the main tri-calcium silicate (T1-C3S) and bi-calcium silicate (β-C2S), phases present in Portland cement and their blends. The present paper discusses micro- and nanoscale studies of the cementitious skeletons forming during the hydration of C3S, C2S and 70 % / 30 % blends of both C3S/C2S and C2S/C3S with a water/cement ratio of 0.4. The hydrated pastes were characterized at different curing ages with 29 Si NMR, SEM/TEM/EDS, BET, and nanoindentation. The findings served as a basis for the micro- and nanoscale characterization of the hydration products formed, especially C-S-H gels. Differences were identified in composition, structure and mechanical behaviour (nanoindentation), depending on whether the gels formed in C3S or C2S pastes. The C3S gels had more compact morphologies, smaller BET-N2 specific surface area and lesser porosity than the gels from C2S-rich pastes. The results of nanoindentation tests appear to indicate that the various C-S-H phases formed in hydrated C3S and C2S have the same mechanical properties as those formed in Portland cement paste. Compared to the C3S sample, the hydrated C2S specimen was dominated by the loose-packed (LP) and the low-density (LD) C-S-H phases, and had a much lower content of the high density (HD) C-S-H phase

Individualization and Electrical Characterization of SiGe Nanowires

SiGe nanowires of different Ge atomic fractions up to 15% were grown and ex-situ n-type doped by diffusion from a solid source in contact with the sample. The phenomenon of dielectrophoresis was used to locate single nanowires between pairs of electrodes in order to carry out electrical measurements. The measured resistance of the as-grown nanowires is very high, but it decreases more than three orders of magnitude upon doping, indicating that the doping procedure used has been effective

Clones Identification and Genetic Characterization of Garnacha Grapevine by Means of Different PCR-Derived Marker Systems

This study uses PCR-derived marker systems to investigate the extent and distribution of genetic variability of 53 Garnacha accessions coming from Italy, France and Spain. The samples studied include 28 Italian accessions (named Tocai rosso in Vicenza area; Alicante in Sicily and Elba island; Gamay perugino in Perugia province; Cannonau in Sardinia), 19 Spanish accessions of different types (named Garnacha tinta, Garnacha blanca, Garnacha peluda, Garnacha roja, Garnacha erguida, Garnacha roya) and 6 French accessions (named Grenache and Grenache noir). In order to verify the varietal identity of the samples, analyses based on 14 simple sequence repeat (SSR) loci were performed. The presence of an additional allele at ISV3 locus (151 bp) was found in four Tocai rosso accessions and in a Sardinian Cannonau clone, that are, incidentally, chimeras. In addition to microsatellite analysis, intravarietal variability study was performed using AFLP, SAMPL and M-AFLP molecular markers. AFLPs could discriminate among several Garnacha samples; SAMPLs allowed distinguishing few genotypes on the basis of their geographic origin, whereas M-AFLPs revealed plant-specific markers, differentiating all accessions. Italian samples showed the greatest variability among themselves, especially on the basis of their different provenance, while Spanish samples were the most similar, in spite of their morphological diversity.

TEM and SAED Characterization of Metakaolin. Pozzolanic Activity

The present study deals with a characterization of metakaolin pozzolanic activity and its chemical character exhibited in the Ordinary Portland Cement (OPC) blends by means of Transmission Electron Microscopy (TEM) and Selected-Area Electron Diffraction (SAED) techniques principally. Metakaolin sample was prepared by calcination of kaolin rock (Guadalajara, Spain) at 780°C. Two OPC of different chemical composition from the tricalcium aluminate content point of view were chosen and Portland cement blends series elaborated and then submitted to the pozzolanic activity test (EN 196-5 or Frattini test). The main mineralogical components of the metakaolin are determined qualitatively: χ-alumina and quartz. The chemical character of the metakaolin is described because of its final composition as well as due to its Al atoms possible coordination. The crystalline order of the material is found to be of both amorphous and polycrystalline, being an intimate amorphous mixture of alumina and silica. Finally, all the alumina capable of reacting chemically is denominated and classified as reactive alumina component, Al2O3r−, of pozzolans, as well as the aluminic chemical character of metakaolin in OPC blends is once again proved and exhibited by means of Friedel's salt formation studied already at 4 h-age.

X-Ray Diffraction, Calorimetric and Dielectric Relaxation Study of the Amorphous and Smectic States of a Main Chain Liquid Crystalline Polymer

Los polímeros cristales líquidos (LCP) son sistemas complejos que forman mesofases que presentan orden orientacional y polímeros amorfos. Con frecuencia, el estado amorfo isotrópico no puede ser estudiado debido a la rápida formación de mesofases. En este trabajo se ha sintetizado y estudiado un nuevo LCP: poli(trietilenglicol metil p, p '-bibenzoato), PTEMeB. Este polímero presenta una formación de mesofase bastante lenta haciendo posible estudiar de forma independiente tanto los estados amorfo y de cristal líquidos. La estructura y las transiciones de fase del PTEMeB han sido investigados por calorimetría (DSC), con MAXS / WAXS con temperatura variable que emplean radiación de sincrotrón y con difracción de rayos X. Estos estudios han mostrado la existencia de dos transiciones vítreas, relacionadas con las fases amorfa y cristal líquido. Se ha realizado un estudio de relajación dieléctrica en amplios intervalos de temperatura y presión. Se ha encontrado que la transición vítrea dinámica de la fase amorfa es más lenta que la del cristal líquido. El estudio de la relajación ? nos ha permitido seguir la formación isoterma de la mesofase a presión atmosférica. Además, con el estudio el comportamiento dinámico a alta presión se ha encontrado que se produce la formación rápida de la mesofase inducida por cambios bruscos de presión. Liquid crystalline polymers (LCPs) are complex systems that include features of both orientationally ordered mesophases and amorphous polymers. Frequently, the isotropic amorphous state cannot be studied due to the rapid mesophase formation. Here, a new main chain LCP, poly(triethyleneglycol methyl p,p'-bibenzoate), PTEMeB, has been synthesized. It shows a rather slow mesophase formation making possible to study independently both the amorphous and the liquid crystalline states. The structure and phase transitions of PTEMeB have been investigated by calorimetry, variable-temperature MAXS/WAXS employing synchrotron radiation, and X-ray diffraction in oriented fibers. These experiments have pointed out the presence of two glass transitions, related to the amorphous or to the liquid crystal phases. Additionally, the mesophase seems to be a coexistence of orthogonal and tilted smectic phases. A dielectric relaxation study of PTEMeB over broad ranges of temperature and pressure has been performed. The dynamic glass transition turns out to be slower for the amorphous state than for the liquid crystal. Monitoring of the α relaxation has allowed us to follow the isothermal mesophase formation at atmospheric pressure. Additionally, the dynamical behavior at high pressures has pointed out the fast formation of the mesophase induced by sudden pressure changes.

Minor ampullate silks from Nephila and Argiope spiders: tensile properties and microstructural characterization

The mechanical behavior and microstructure of minor ampullate gland silk (miS) of two orb-web spinning species, Argiope trifasciata and Nephila inaurata, were extensively characterized, enabling detailed comparison with other silks. The similarities and differences exhibited by miS when compared with the intensively studied major ampullate gland silk (MAS) and silkworm (Bombyx mori) silk offer a genuine opportunity for testing some of the hypotheses proposed to correlate microstructure and tensile properties in silk. In this work, we show that miSs of different species show similar properties, even when fibers spun by spiders that diverged over 100 million years are compared. The tensile properties of miS are comparable to those of MAS when tested in air, significantly in terms of work to fracture, but differ considerably when tested in water. In particular, miS does not show a supercontraction effect and an associated ground state. In this regard, the behavior of miS in water is similar to that of B. mori silk, and it is shown that the initial elastic modulus of both fibers can be explained using a common model. Intriguingly, the microstructural parameters measured in miS are comparable to those of MAS and considerably different from those found in B. mori. This fact suggests that some critical microstructural information is still missing in our description of silks, and our results suggest that the hydrophilicity of the lateral groups or the large scale organization of the sequences might be routes worth exploring.

Instrumental quality assessment of fresh peaches: Optical and mechanical parameters.

In developing instrumentation for the measurement of fruit quality, there is the need for fast and non-destructive devices, based on sensors, to be installed on-line. In the case of some fruits, like peaches, post-harvest ripeness, which is closely related to high quality for the consumer, is a priority. During ripening, external appearance (colour) and internal mechanical (firmness) and chemical (sugars and acids) quality are main features that evolve rapidly from and unripe to a ripe (high quality) stage. When considering the evolution of fruit quality in this scheme, external colour and firmness are shown to evolve in a parallel pattern, if monitored from the time of harvest to full consumer ripeness ( Rood, 1957; Crisosto et al, 1995; Kader, 1996). The visible (VIS) reflectance spectrum is a fast and easy reference that can be used to estimate quality of peaches, if we could show it to be reliably correlated with peach ripening rate during postharvest (Genard et al. 1994; Moras, 1995; Delwiche and Baumgartner, 1983; Delwiche et al. 1987; Slaughter, 1995; Lleo et al., 1998). Taste, described as an expert acceptance score, improves with ripeness (firmness and colour evolution), when considering the fruits on the tree, and also post-harvest.

Identification and functional characterization of Rhizobium leguminosarum bv. viciae genetic systems involved in nickel homeostasis.

A collection of Rhizobium leguminosarum bv. viciae strains isolated from ultramafic and contaminated soils in Italy and Germany, respectively, was analyzed for resistance to nickel and cobalt ions. These assays led to the identification of strain UPM1137, which is able to grow at high concentrations of nickel and cobalt. In order to identify genetic systems involved in the homeostasis to these metals, a random mutagenesis was carried out in UPM1137 by inserting a Tn5-derivative minitransposon. As a result 4313 transconjugants were obtained, being 39 of them (0.90%) unable to grow at 1.5 mM NiCl2. The identification of the transposon insertion site in these mutants showed that the disrupted genes encode proteins belonging to different functional categories, where the secreted and membrane proteins were the most numerous. The analysis of heavy metal resistance and phenotypes in symbiotic and free –living cells will define the contribution of these genes to metal homeostasis.

Cycling Dof Factors: Molecular and functional characterization of Arabidopsis thaliana AtCDF3 and tomato (Solanum lycopersicum L.) SlCDF3 in response to abiotic stress

El tomate (Solanum lycopersicum L.) es considerado uno de los cultivos hortícolas de mayor importancia económica en el territorio Español. Sin embargo, su producción está seriamente afectada por condiciones ambientales adversas como, salinidad, sequía y temperaturas extremas. Para resolver los problemas que se presentan en condiciones de estrés, se han empleado una serie de técnicas culturales que disminuyen sus efectos negativos, siendo de gran interés el desarrollo de variedades tolerantes. En este sentido la obtención y análisis de plantas transgénicas, ha supuesto un avance tecnológico, que ha facilitado el estudio y la evaluación de genes seleccionados en relación con la tolerancia al estrés. Estudios recientes han mostrado que el uso de genes reguladores como factores de transcripción (FTs) es una gran herramienta para obtener nuevas variedades de tomate con mayor tolerancia a estreses abióticos. Las proteínas DOF (DNA binding with One Finger) son una familia de FTs específica de plantas (Yangisawa, 2002), que están involucrados en procesos fisiológicos exclusivos de plantas como: asimilación del nitrógeno y fijación del carbono fotosintético, germinación de semilla, metabolismo secundario y respuesta al fotoperiodo pero su preciso rol en la tolerancia a estrés abiótico se desconoce en gran parte. El trabajo descrito en esta tesis tiene como objetivo estudiar genes reguladores tipo DOF para incrementar la tolerancia a estrés abiotico tanto en especies modelo como en tomate. En el primer capítulo de esta tesis se muestra la caracterización funcional del gen CDF3 de Arabidopsis, así como su papel en la respuesta a estrés abiótico y otros procesos del desarrollo. La expresión del gen AtCDF3 es altamente inducido por sequía, temperaturas extremas, salinidad y tratamientos con ácido abscísico (ABA). La línea de inserción T-DNA cdf3-1 es más sensible al estrés por sequía y bajas temperaturas, mientras que líneas transgénicas de Arabidopsis 35S::AtCDF3 aumentan la tolerancia al estrés por sequía, osmótico y bajas temperaturas en comparación con plantas wild-type (WT). Además, estas plantas presentan un incremento en la tasa fotosintética y apertura estomática. El gen AtCDF3 se localiza en el núcleo y que muestran una unión específica al ADN con diferente afinidad a secuencias diana y presentan diversas capacidades de activación transcripcional en ensayos de protoplastos de Arabidopsis. El dominio C-terminal de AtCDF3 es esencial para esta localización y su capacidad activación, la delección de este dominio reduce la tolerancia a sequía en plantas transgénicas 35S::AtCDF3. Análisis por microarray revelan que el AtCDF3 regula un set de genes involucrados en el metabolismo del carbono y nitrógeno. Nuestros resultados demuestran que el gen AtCDF3 juega un doble papel en la regulación de la respuesta a estrés por sequía y bajas temperaturas y en el control del tiempo de floración. En el segundo capítulo de este trabajo se lleva a cabo la identificación de 34 genes Dof en tomate que se pueden clasificar en base a homología de secuencia en cuatro grupos A-D, similares a los descritos en Arabidopsis. Dentro del grupo D se han identificado cinco genes DOF que presentan características similares a los Cycling Dof Factors (CDFs) de Arabidopsis. Estos genes son considerados ortólogos de Arabidopsis CDF1-5, y han sido nombrados como Solanum lycopersicum CDFs o SlCDFs. Los SlCDF1-5 son proteínas nucleares que muestran una unión específica al ADN con diferente afinidad a secuencias diana y presentan diversas capacidades de activación transcripcional in vivo. Análisis de expresión de los genes SlCDF1-5 muestran diferentes patrones de expresión durante el día y son inducidos de forma diferente en respuesta a estrés osmótico, salino, y de altas y bajas temperaturas. Plantas de Arabidopsis que sobre-expresan SlCDF1 y SlCDF3 muestran un incremento de la tolerancia a la sequía y salinidad. Además, de la expresión de varios genes de respuesta estrés como AtCOR15, AtRD29A y AtERD10, son expresados de forma diferente en estas líneas. La sobre-expresión de SlCDF3 en Arabidopsis promueve un retardo en el tiempo de floración a través de la modulación de la expresión de genes que controlan la floración como CONSTANS (CO) y FLOWERING LOCUS T (FT). En general, nuestros datos demuestran que los SlCDFs están asociados a funciones aun no descritas, relacionadas con la tolerancia a estrés abiótico y el control del tiempo de floración a través de la regulación de genes específicos y a un aumento de metabolitos particulares. ABSTRACT Tomato (Solanum lycopersicum L.) is one of the horticultural crops of major economic importance in the Spanish territory. However, its production is being affected by adverse environmental conditions such as salinity, drought and extreme temperatures. To resolve the problems triggered by stress conditions, a number of agricultural techniques that reduce the negative effects of stress are being frequently applied. However, the development of stress tolerant varieties is of a great interest. In this direction, the technological progress in obtaining and analysis of transgenic plants facilitated the study and evaluation of selected genes in relation to stress tolerance. Recent studies have shown that a use of regulatory genes such as transcription factors (TFs) is a great tool to obtain new tomato varieties with greater tolerance to abiotic stresses. The DOF (DNA binding with One Finger) proteins form a family of plant-specific TFs (Yangisawa, 2002) that are involved in the regulation of particular plant processes such as nitrogen assimilation, photosynthetic carbon fixation, seed germination, secondary metabolism and flowering time bur their precise roles in abiotic stress tolerance are largely unknown. The work described in this thesis aims at the study of the DOF type regulatory genes to increase tolerance to abiotic stress in both model species and the tomato. In the first chapter of this thesis, we present molecular characterization of the Arabidopsis CDF3 gene as well as its role in the response to abiotic stress and in other developmental processes. AtCDF3 is highly induced by drought, extreme temperatures, salt and abscisic acid (ABA) treatments. The cdf3-1 T-DNA insertion mutant was more sensitive to drought and low temperature stresses, whereas the AtCDF3 overexpression enhanced the tolerance of transgenic plants to drought, cold and osmotic stress comparing to the wild-type (WT) plants. In addition, these plants exhibit increased photosynthesis rates and stomatal aperture. AtCDF3 is localized in the nuclear region, displays specific binding to the canonical DNA target sequences and has a transcriptional activation activity in Arabidopsis protoplast assays. In addition, the C-terminal domain of AtCDF3 is essential for its localization and activation capabilities and the deletion of this domain significantly reduces the tolerance to drought in transgenic 35S::AtCDF3 overexpressing plants. Microarray analysis revealed that AtCDF3 regulated a set of genes involved in nitrogen and carbon metabolism. Our results demonstrate that AtCDF3 plays dual roles in regulating plant responses to drought and low temperature stress and in control of flowering time in vegetative tissues. In the second chapter this work, we carried out to identification of 34 tomato DOF genes that were classified by sequence similarity into four groups A-D, similar to the situation in Arabidopsis. In the D group we have identified five DOF genes that show similar characteristics to the Cycling Dof Factors (CDFs) of Arabidopsis. These genes were considered orthologous to the Arabidopsis CDF1 - 5 and were named Solanum lycopersicum CDFs or SlCDFs. SlCDF1-5 are nuclear proteins that display specific binding to canonical DNA target sequences and have transcriptional activation capacities in vivo. Expression analysis of SlCDF1-5 genes showed distinct diurnal expression patterns and were differentially induced in response to osmotic, salt and low and high temperature stresses. Arabidopsis plants overexpressing SlCDF1 and SlCDF3 showed increased drought and salt tolerance. In addition, various stress-responsive genes, such as AtCOR15, AtRD29A and AtERD10, were expressed differently in these lines. The overexpression of SlCDF3 in Arabidopsis also results in the late flowering phenotype through the modulation of the expression of flowering control genes such CONSTANS (CO) and FLOWERING LOCUS T (FT). Overall, our data connet SlCDFs to undescribed functions related to abiotic stress tolerance and flowering time through the regulation of specific target genes and an increase in particular metabolites.

Optical characterisation of semi-transparent PV modules for building integration

A complete characterisation of PV modules for building integration is needed in order to know their influence on the building’s global energy balance. Specifically, certain characteristic parameters should be obtained for each different PV module suitable for building integrated photovoltaics (BIPV), some by direct or indirect measurements at the laboratory, and others by monitoring the element performance mounted in real operating conditions. In the case of transparent building envelopes it is particularly important to perform an optical and thermal characterization of the PV modules that would be integrated in them. This paper addresses the optical characterization of some commercial thin-film PV modules having different degrees of transparency, suitable for building integration in façades. The approach is based on the measurement of the spectral UV/Vis/NIR reflectance and transmittance of the different considered samples, both at normal incidence and as a function of the angle of incidence. With the obtained results, the total and zoned UV, visible and NIR transmission and reflection values are calculated, enabling the correct characterization of the PV modules integrated in façades and the subsequent evaluation of their impact over the electrical, thermal and lighting performance in a building.