Copying low spatial frequency diffraction gratings in photopolymer as phase holograms

Abstract

Photopolymers are studied as holographic recording materials for recording computer-generated phase holograms. The recording was performed using a holographic copying process, in which the master is produced by means of a high resolution graphic device. To our knowledge it is the first time a photopolymer has been used to obtain copies with this technique. As it does not work in real time, it is possible to store the diffractive optical element for a long time because the dye is finished during exposition and no wet processing is needed after exposition. The photopolymer used in these experiments was composed of acrylamide and triethanolamine as the co-initiator, photo-initiated with a dye, yellow eoxine. Components were supported by a film of poly-(vinylalcohol) (PVA). The resulting thickness of the film was 70 & plusmn; 5 μm, symmetrical and asymmetrical diffraction gratings were obtained as phase holograms by index and thickness modulation, monitored with an electron microscope, and the low spatial frequency response of the photopolymer was studied. Diffraction efficiency achieved for copied gratings was about 30%. With this study we get a complete characterization of the photopolymer for the full range of the typical spatial frequencies that can be recorded with the high resolution graphic device used.     

Silver halide sensitized gelatin holograms in Slavich PFG-01 red-sensitive emulsion

Abstract

Silver halide sensitized gelatin (SHSG) is an interesting technique for the production of holographic optical elements. It combines the high sensitivity of photographic emulsions with the well-known low scattering and high diffraction efficiency corresponding to dichromated gelatin. In this paper we describe SHSG holograms recorded on Slavich PFG-01 emulsions. We will show that real high diffraction efficiencies can be obtained (as high as 93% allowing for reflections) when using this material for recording phase transmission holograms. The influence of the bleach bath temperature and a hardening bath in the processing was studied and the procedure was optimized for these two parameters. Our investigations reveal that PFG-01 emulsion is not only a substitute for Agfa material, but also offers better results, at a moment in which Agfa has stopped its production of holographic material.     

Phenolic composition of Tempranillo wines following early defoliation of the vines

BACKGROUND: Early defoliation is a viticultural practice aimed at crop control. So far, the impact of early leaf removal on the monomeric phenolic composition of wines has not been explored. This study examines the effects of early defoliation on the phenolic profile and content in Tempranillo wines. The influence of the defoliation method (manual vs mechanical) and the timing of leaf removal (pre‐bloom vs fruit set) was investigated. RESULTS: Over two consecutive seasons, 2007 and 2008, the monomeric phenolic composition in Tempranillo wines was studied by high‐performance liquid chromatography with photodiode array detection, and 22 compounds were identified and quantified. Overall, early defoliation led to wines more intensely coloured, of higher alcohol content and with larger concentrations of hydroxycinnamic acids, flavonols and anthocyanins (in 2008 only for mechanical treatments). In the absence of fungal infection, resveratrol was found to increase in wines corresponding to early defoliation treatments. The method of leaf removal seemed to be more critical than the timing of intervention, and larger effects on wine phenolic composition were observed for mechanical treatments. CONCLUSION: Early defoliation proved to be an effective technique for improving the phenolic composition of Tempranillo wines, by favouring the accumulation of hydroxycinnamics, flavonols and anthocyanins. This is an important achievement, as wine quality is often described by its colour and phenolic attributes. Copyright © 2011 Society of Chemical Industry     

Functional properties and microstructure of cowpea cultivated in north-east Argentina

The goal of this work was to analyze the effect of different treatments on functional properties (Color parameters, water holding capacity, oil holding capacity, water imbibition capacity, protein solubility and apparent viscosity) and microstructure of three cowpea varieties. Proteins present in flours obtained from heat-treated seeds exhibited a significant increase in water and oil absorption values, water imbibition capacity, and apparent viscosity, whereas solubility decreased. Color determinations on flours showed a reduction in L* and H*, and an increment in C* with treatment intensity. Structural changes in seeds would explain the variations in the functionality of flours. This study shows that cooking and autoclaving affect significantly the functional properties of flours, while soaking had a lower impact. The knowledge about these changes will be very useful for developing and obtaining new preparations based on cowpea flour.     

Deposition of functionalized single wall carbon nanotubes through matrix assisted pulsed laser evaporation

Single-wall carbon nanotubes (SWCNTs) functionalized with oxygen-containing groups were deposited onto glass substrates by matrix assisted pulsed laser evaporation (MAPLE). The experiments were performed by subjecting ultraviolet laser pulses (KrF¹ excimer laser, 248 nm wavelength) to frozen SWCNT-toluene targets placed in a parallel plane a few cm in front of the substrate. The morphology, structure, and chemical composition of the deposited materials were studied through atomic force microscopy, high resolution transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The influence of the laser fluence on the material structure was investigated. The results indicate that the functionalized SWCNTs can be transferred by MAPLE at low laser fluences without the alteration of the structure of the initial material used as targets in MAPLE experiments. An increase of the fluence leads to the decomposition of the functional groups, mainly carboxylic acid groups, without degradation of the SWCNT structure whereas, at the highest fluences, the amorphization and even coalescence of the carbon nanotubes takes place.     

Luminescence during anodization of magnesium alloy AZ31

In this paper, we have presented our recent investigation of luminescence during anodization of magnesium alloy AZ31 at 100 mA/cm² in water solution containing 4 g/L Na₂SiO₃·5H₂O + 4 g/L KOH. Spectral characterization of anodic luminescence (galvanoluminescence GL) showed that there are wide GL bands in the range from 375 nm to 875 nm, with three spectral peaks around 430 nm, 600 nm and 780 nm. As the anodization voltage approaches the breakdown voltage, a large number of microdischarges appear superimposed on the GL. The microdischarges characteristics above breakdown (so-called plasma electrolytic oxidation PEO) were studied using real-time imaging. The spatial density of microdischarges is the highest in the early stage of PEO, while the percentage of oxide coating area covered by active discharge sites has maximum after about 120 s from the beginning of PEO and then stays almost constant. The elements present in PEO microdischares were identified using optical emission spectroscopy technique.     

Ultrafast Doppler imaging of blood flow dynamics in the myocardium

Imaging intramyocardial vascular flows in real-time could strongly help to achieve better diagnostic of cardiovascular diseases. To date, no standard imaging modality allows describing accurately myocardial blood flow dynamics with good spatial and temporal resolution. We recently introduced a novel ultrasonic Doppler imaging technique based on compounded plane waves transmissions at ultrafast frame rate. The high sensitivity of this ultrafast Doppler technique permits to image the intramyocardial blood flow and its dynamics. A dedicated demodulation-filtering process is implemented to compensate for the large tissue velocity of the myocardium during the cardiac cycle. A signed power Doppler processing provides the discrimination between arterial and venous flows. Experiments were performed in vivo in a large animal open chest model ( N = 5 sheep) using a conventional ultrasonic probe placed at the surface of the heart. Results show the capability of the technique to image intramyocardial vascular flows in normal physiological conditions with good spatial (200 μm) and temporal resolution (10 ms). Flow dynamics over the cardiac cycle were investigated and the imaging method demonstrated a phase opposition of flow waveforms between arterial and venous flows. Finally, ultrafast Doppler combined with tissue motion compensation was found able to reveal vascular flow disruption in ischemic regions during occlusion of the main diagonal coronary artery.     

Aromatic Profile of Ciders by Chemical Quantitative,Gas Chromatography‐Olfactometry,and Sensory Analysis

Nine samples of Asturias cider have been analyzed for volatile, olfactometric, and sensorial profiles. The aromatic composition was mainly constituted by fusel alcohols and ethyl esters. Among the minor volatile compounds, fatty acids, volatile phenols, and alcohols were the main components. The olfactometric analysis revealed the existence of 55 aromatic areas, exhibiting a wide range of intensities. Components like amyl alcohols, 2‐phenylethanol, ethyl esters such as 2‐methylbutyrate, hexanoate and octanoate, hexanoic and octanoic acids 2‐phenylethyl acetate, 4‐ethyl guaiacol, and 4‐ethyl phenol could be considered as being part of the structure of cider aroma. The extract dilution analysis of one extract identified 2 volatile phenols (4‐ethyl guaiacol and 4‐ethyl phenol) among the most powerful odorants in cider. These components gave significant correlations with the sensory attributes sweet, spicy, and lees.     

Development of a polymerase chain reaction assay for species identification of goose and mule duck in foie gras products

Polymerase chain reaction amplification of a conserved region of the -actin gene has been used for the specific identification of goose (Anser anser) and mule duck (Anas platyrhynchos×Cairina moschata) foie gras. Universal primers were used for the amplification of a DNA fragment containing three introns and four exons of the -actin gene in goose and mule duck. Sequence analysis of the amplified fragments was necessary for the design of forward species-specific primers in the goose and mule duck -actin genes. The use of species-specific forward primers, together with a reverse universal primer, produced amplicons of different length, allowing clear identification of goose and mule duck foie gras samples. Analysis of experimental mixtures demonstrated that 1% of duck can be easily detected in goose foie gras using the PCR method developed here. This genetic marker can be very useful for the accurate identification of these two species in foie gras products.