Seeded optical parametric generator with efficiency-enhanced mid-wave infrared beam output

A novel device with a simple architecture for high-power mid-wave infrared beam generation is proposed and analyzed using a realistic model that takes the diffraction of the beams into account. The device is a seeded efficiency-enhanced optical parametric generator based on an aperiodically poled MgO-doped LiNbO₃ grating in which two optical parametric amplification (OPA) processes are simultaneously phase matched. When pumped by a high-repetition-rate nanosecond-pulsed laser operating at 1064 nm, power conversion efficiency enhancement of the mid-wave infrared output at a wavelength of 3.8 μm (compared to what is achievable with a single OPA process) occurs. Also, a difference-frequency beam is generated. Multiple aperiodic gratings with varying relative strengths of the two optical parametric amplification processes are designed. The developed model is used for determining the optimum relative strengths of the two processes and input pump power levels for achieving the maximum mid-wave infrared conversion efficiency and output power for various crystal lengths.     

Kinetics of colour,chlorophyll, and ascorbic acid content in spinach baked in different types of oven

Spinach was baked in steam-assisted hybrid ovens, natural and forced convection ovens, and saturated steam ovens at different temperatures and baking times. The moisture content, water activity, peroxidise activity, colour, ascorbic acid, and chlorophyll content were determined for each baking time and kinetic analysis of thermal degradation of the colour, chlorophyll, and ascorbic acid were evaluated. Degradation of green colour, total chlorophyll, and ascorbic acid in spinach leaves during the baking process was considered as first order reaction kinetics and temperature dependency of degradation was described by the Arrhenius equation. Baking in steam-assisted hybrid ovens resulted in the highest rate of reaction for both colour change and chlorophyll degradation, followed by forced convection and then natural convection ovens. The existence of steam in the baking chamber resulted in an acceleration of the baking process and better ascorbic acid retention in spinach was determined by baking in steam-assisted hybrid ovens. Degradation kinetics could allow definition of optimum baking temperatures and times in different types of ovens and shorter baking times should be preferred in steam-assisted hybrid ovens if fresh appearance (high greenness) is desired.     

In-situ observation of crack opening displacement (COD) in a metastable β titanium composite

The interfacial strength of β-Ti composites was increased via ageing, to investigate the effects of interfacial strength on the crack opening. Prior to crack opening displacement (COD) measurements, the number and location of fractured fibres were identified by acoustic emission and fibre probing techniques. This was later used to model the crack opening for number of tests conditions, such as different values of applied stress intensity factor, interfacial strengths and test temperatures. COD measurements were performed on bridged cracks, which were obtained by cycling the specimens under tension–tension loading. Test results have shown that crack opening is affected by both intrinsic factors such as interfacial debonding and frictional sliding stresses and extrinsic factors such as the maximum applied stress intensity factor and test temperature.     

Improving functionality of whole egg powder by the addition of gelatine, lactose, and pullulan

The addition of gelatine (G), lactose (L), pullulan (P), and their mixtures at equal ratios (gelatine + lactose [GL] and gelatin + pullulan [GP]) to whole egg prior to drying was studied. Their effects on the functional properties (emulsion and gelling ability, water holding capacity of gel, foaming, color) and soluble protein content of spray dried egg powder during the 6 mo of storage at 20 °C and 50% relative humidity were investigated. It was demonstrated that the emulsion and foaming stability, water holding capacity of gel, and color change were significantly affected by the storage time, whereas storage time did not affect the strength of gel texture prepared by egg powders. Gelatine and pullulan improved the foaming stability and water holding capacity. Lactose caused a decrease in emulsion and foaming stability values. The maximum color change was observed for the plain egg powder, showing that mixing whole egg with carbohydrate- and/or protein-based additives before the drying process preserved the color of egg powder. Adding carbohydrate and/or protein caused significant changes in functional properties of egg powder.     

Photon transmission method for studying void‐closure kinetics during coalescence of hard latex particles

The contribution of viscous flow to void‐closure processes during film formation with hard latex particles was studied. Film optical clarity was used to follow the progress of this event. The latex films were prepared from poly (methyl methacrylate) (PMMA) particles and annealed in 10 min time intervals above the glass transition (T_g) temperature. Scanning electron microscopy (SEM) was used to detect the variation in the physical structure of the annealed films. To mimic the latex film‐formation process, Monte Carlo simulations were performed for photon transmission through the latex film and the number of transmitted and scattered photons are calculated as a function of the mean free path. A relation for transmitted light intensity, I_tr versus void closure (time)^1/2 (t^1/2) was derived by using the Vogel–Fulcher viscosity equation. The viscosity constant, B, was produced using this I_tr(t^1/2) relation at various temperatures and found to be 12.8 × 10³ K. It is shown that Monte Carlo results justified the I_tr(t^1/2) relation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 981–988, 1999     

Phenolic Characterization and Geographical Classification of Commercial Extra Virgin Olive Oils Produced in Turkey

The aim of this research was to characterize the extra virgin olive oil samples from different locations in the Aegean coastal area of Turkey in terms of their phenolic compositions for two consecutive years to show the classification of oil samples with respect to harvest year and geography. Forty seven commercial olive oil samples were analyzed with HPLC–DAD, and 17 phenolic compounds were quantified. Hydroxytyrosol, tyrosol, vanillic acid, p-coumaric acid, ferulic acid, cinnamic acid, luteolin and apigenin were the characteristic phenols observed in all oil samples for two harvest years. Syringic acid, vanillin and m-coumaric acid were the phenolic compounds appeared in the olive oil depending on the harvest year. Partial least square-discriminant analysis (PLS-DA) of data revealed that oils from the north Aegean and south Aegean areas had different phenolic profiles. The phenolic compounds, which played significant roles in the discrimination of the olive oils, were tyrosol, oleuropein aglycon, cinnamic acid, apigenin and hydroxytyrosol to tyrosol ratio. The Aegean coastal region is the largest olive oil producer and exporter of Turkey. This study shows that the olive oils from different parts of the region have their own defining characteristics that can be used in the authentication studies and geographical labeling of Turkish olive oils.     

Closing the hydrogen cycle with the couple sodium borohydride-methanol,via the formation of sodium tetramethoxyborate and sodium metaborate

Methanolysis of sodium borohydride (NaBH₄) is one of the methods efficient enough to release, on demand, the hydrogen stored in the hydride as well as in 4 equiv of methanol (CH₃OH). It is generally reported that, in methanolysis, sodium tetramethoxyborate (NaB(OCH₃)₄) forms as single component of the spent fuel. It is, however, necessary to clearly investigate some critical aspects related to it. We first focused on the methanolysis reaction where NaBH₄ was reacted with 2, 4, 8, 16, or 32 equiv of CH₃OH. With 2 equiv of CH₃OH, the conversion of NaBH₄ is not complete. With 4 to 32 equiv of CH₃OH, NaBH₄ is totally methanolized (conversion of 100%). The best conditions are those involving 4 equiv of CH₃OH as they offer the highest effective gravimetric hydrogen storage capacity with 4.8 wt%, an attractive H₂ generation rate with 331 mL(H₂) min⁻¹—a performance achieved without any catalyst—and the formation of NaB(OCH₃)₄ as single product as identified by X-ray diffraction, Fourier transform infrared spectroscopy, and nuclear magnetic resonance. We then focused on the transformation of this product NaB(OCH₃)₄ into sodium metaborate (NaBO₂), via the formation of sodium tetrahydroxyborate (NaB(OH)₄). NaB(OCH₃)₄ is easily transformed in water, by hydrolysis, at 80°C and for 90 minutes, into NaB(OH)₄ and 4 equiv of CH₃OH. In doing so, the cycle with CH₃OH is closed. Subsequently, NaB(OH)₄ is recovered and converted into NaBO₂ under heating at 500°C. This reaction liberates 4 equiv of H₂O, which allows to close the cycle with water. Based on these achievements, we have finally proposed a triangular recycling scheme aiming at closing the cycle with the protic reactants of the aforementioned reactions. This scheme may be used as base for implementing a closed cycle with the couple NaBH₄-CH₃OH.     

Control of lactic acid bacteria in fermented beverages using lysozyme and nisin: test of traditional beverage boza as a model food system

The objective of this study was to increase quality and limited shelf‐life of boza (3–15 days), a traditional Balkan origin fermented beverage using lysozyme (LYS) and/or nisin (NIS). For this purpose, the effectiveness of NIS, LYS and LYS:NIS combinations was first tested in a broth medium at 4 °C for 3 weeks on Lactobacillus plantarum, one of the frequently isolated lactic acid bacteria in boza. Stability of LYS and NIS in boza, their effects on LAB counts, and chemical and sensory properties of boza were then evaluated during cold storage at 4 °C. Results of LAB counts as well as pH, d ‐ and l ‐lactic acid, and titratable acidity measurements showed that LAB in boza containing NIS (250 μg g^?1) or LYS:NIS (500:250 μg g^?1) could be controlled without reducing LAB counts below 6 log CFU mL^?1 during 2 weeks shelf‐life. In contrast, LYS (500 μg g^?1) alone could not control LAB in boza to delay its acidic spoilage. Positive effects of NIS and LYS:NIS application on quality of boza were also proved with sensory analysis by panelists and e‐nose measurements. This work showed that use of natural GRAS agents in preservation of fermented beverages containing probiotic LAB is possible without affecting their characteristic aroma and flavour.