Spectroscopic Investigation of the Coloration and Fabrication Conditions of Medieval Blue Glasses

Potash‐ and soda‐lime‐stained glasses from the 12th–13th centuries, blue‐colored by cobalt, have been investigated by Mn, Fe, and Cu K‐edge X‐ray and optical absorption spectroscopies in order to determine the oxidation state of these elements and their impact on the blue color. Remelting these historical glasses in air at 1200°C, the estimated temperature of medieval furnaces, revealed that these four glasses are more reduced before remelting. This favors Mn as weakly absorbing Mn²⁺, Fe as Fe²⁺ and Cu as colorless Cu⁺. Therefore Fe²⁺ is the second blue chromophore and copper was not intentionally used by glassmakers to obtain a blue color. A colorimetric analysis indicates that these specific melting conditions have a limited effect on the blue color of these glasses. Based on the spectroscopic determination of the redox state of Fe, Mn, and Cu, we estimate the oxygen partial pressure in medieval furnaces to be 10^?7–10^?9 and 10^?5 bar for the potash‐ and soda‐lime samples, respectively. The comparison with previous results enables to prove the evolution of furnace technology over centuries.     

Effect of production systems on phenolic composition and oxygen radical absorbance capacity of ‘Orléans’ strawberry

The effect of two production systems, plastic mulch (PM) and plastic mulch with row covers (PMRC) versus the commonly used matted-row system (MRS) was evaluated on phenolic composition and oxygen radical absorbance capacity (ORAC) of ‘Orléans’ strawberry at three different harvest times during growing season. Six major groups of phenolic compounds, including anthocyanins, hydroxycinnamic acids, kaempferol, flavonols, ellagic and benzoic acids, were assessed in strawberry. Production systems significantly affect the antioxidant capacity and phenolic content of strawberry. PMRC generally enhanced the phenolic content and total antioxidant capacity compared to MRS and PM, but the effects varied during the harvest season. Therefore, PMRC could be a recommended production system to improve the nutraceutical value of strawberry fruits especially in cooler climates.     

Varifocal liquid lenses with integrated actuator, high focusing power and low operating voltage fabricated on 200 mm wafers

We developed an innovative type of varifocal liquid lens actuated by electrostatic parallel plates. The 3 mm diameter lens is made of a polymer membrane that encapsulates a high permittivity liquid in a cavity on top of a glass wafer. Annular electrodes situated below the membrane and on the glass wafer form the electrostatic parallel plates actuator. By applying a voltage between the electrodes, the electrostatic actuation generated reduces the gap and pushes the liquid towards the center of the lens changing the curvature of the membrane.Compared to previous liquid lenses, very compact devices (≤6 mm × 6 mm × 0.7 mm) working at a reduced supply voltage (<25 V) are demonstrated. Wave front measurements indicate an optical power change of 8 m⁻¹ at 22 V_RMS that can be further improved. The lenses were fabricated on 200 mm wafers using standard microelectronics processes that make our solution a promising small outline, low voltage and low cost candidate for auto-focus devices in camera phones.     

NUMERICAL ANALYSIS OF HEAT TRANSFER BY NATURAL CONVECTION AND RADIATION IN PARTICIPATING FLUIDS ENCLOSED IN SQUARE CAVITIES

The influence of thermal radiation on natural convection in a participating fluid contained in a square cavity is studied numerically. The radiative transfer process is solved from the PI approximation. The Navier-Stokes equations are solved by a finite difference scheme integrated over control volumes. A numerical study of the so-called window problem (thermally driven cavity) shows the influence of thermal radiation on this reference problem for Rayleigh numbers in the range of 10³-10⁷ and Planck numbers varying from 1 to 0.05. The isotherms, streamlines, and heat lines show an increase of the dynamical effects in the central part of the cavity and a significant modification of the boundary layers. Results obtained from the simulation of an isotropically scattering medium are given.     

Spectroscopic Evidences of Charge Transfer Phenomena and Stabilization of Unusual Phases at Iron Oxide Monolayers Grown on Pt(111)

Strong electrostatic coupling between the local structure of metal-supported oxide ultra-thin films and the charge state of adsorbed species (such as Au atoms and O₂ molecules) is at the origin of a co-existence of alternative adsorption configurations, with drastically different structural and electronic characteristics. This effect may contribute also to the stabilization of oxide phases of unusual stoichiometries, where the ion valences are compensated by an electron exchange with the metal substrate. We report an analysis of the spectroscopic signatures of such differently charged adsorbates and unusual oxide phases, including valence and core electrons spectroscopies and vibrational characteristics. We show that the adsorbate charge states can be identified by their signature in the electronic states around the Fermi level and by the modification of the vibrational frequencies of adsorbed probe molecules. Moreover, core level analysis may contribute to the identification of the oxygen-rich phase, formed at high oxygen exposure. The detailed theoretical investigation of the spectroscopic signatures of alternative adsorption configurations and adsorbate charge states supplies a set of data, which may help the experimental identification of such species.     

Comparison of two headspace sampling techniques for the analysis of off-flavour volatiles from oat based products

Two different headspace sampling techniques were compared for analysis of aroma volatiles from freshly produced and aged plain oatcakes. Solid phase microextraction (SPME) using a Carboxen–Polydimethylsiloxane (PDMS) fibre and entrainment on Tenax TA within an adsorbent tube were used for collection of volatiles. The effects of variation in the sampling method were also considered using SPME. The data obtained using both techniques were processed by multivariate statistical analysis (PCA). Both techniques showed similar capacities to discriminate between the samples at different ages. Discrimination between fresh and rancid samples could be made on the basis of changes in the relative abundances of 14–15 of the constituents in the volatile profiles. A significant effect on the detection level of volatile compounds was observed when samples were crushed and analysed by SPME–GC–MS, in comparison to undisturbed product. The applicability and cost effectiveness of both methods were considered.     

Air Drying Behaviour of Fresh and Osmotically Dehydrated Onion Slices (Allium cepa) and Tomato Fruits (Lycopersicon esculentum)

Onion slices (0.5 cm thick) and tomato fruits, fresh and osmotically dehydrated in sugar (600 g/l), salt (300 g/l) or mixed salt and sugar (45/15, w/w) solutions, were air dried at 60°C and drying constants determined. The air drying occurred in two falling rate periods, characterised each by a drying constant. The drying rate and the moisture diffusivity of osmosed samples were higher than that of fresh samples. The overall drying behaviour of osmosed onion slices was not influenced by osmotic conditions (solution and time), while the drying behaviour of osmosed tomato samples depended on osmotic solution and pre-treatment time. 15 minutes and 20 hours of pre osmosis seemed more convenient before drying of onion slices and tomato respectively. In this respect, the structural modification of cells of tomato membrane during extended pre treatment seemed to explain the variation in the drying behaviour.