The potential of color measurements with the CIEDE2000 equation in wood science

This study seeks to assess the potential use of the CIEDE2000 color difference equation in wood science. Therefore, a set of oak wood samples were prepared and assessed by experts. The visual perception of the observers was correlated with the two different color difference equations CIELAB from DIN 6174 and the CIEDE2000 equation. For a practical example two different types of wood were bleached and exposed to UV-light. The results showed that the CIEDE2000 equation outperformed the CIELAB equation. The CIELAB equation showed generally an overestimation of the color change (ΔE) for wood applications, compared to the nontrivial CIEDE2000 equation from 2001.     

Wood colour of central European wood species: CIELAB characterisation and colour intensification

In this project, 24 central European wood species have been characterized spectrophotometrically using the CIELAB-colour-system. Special focus has been put on the analysis of colour intensification of wood surfaces due to surface wetting. The analysis shows how the various wood species react to wetting and how the colour is changed. Especially darker hardwood species are susceptible to the colour intensification effect, resulting in a more intensive colour appearance. Additionally, an idealised model to describe the appearance of the wood colour is proposed: The recognized wood colour is a function of: first the reflected wavelength of the visible light, second the surface roughness and third the inner structure of the specific wood piece and the resulting refraction properties of the interacting substances. This model is supported by colour and gloss measurements of the wood species and selected coating investigations with oil and clear lacquer. Furthermore, a novel characteristic value, namely the light-reflection-depth (LRD), is introduced to describe wood properties according to light penetration. All this helps to understand how the wood colour impression is created for a standard observer. Particularly, the intensification effect can be described and explained by structural changes, which affect a change in colour. Understanding the reasons for the colour intensification supports innovative natural colour engineering of specific wood species.     

All-optical XOR in a semiconductor optical amplifier-assisted fiberSagnac gate

All-optical Boolean XOR is demonstrated on a high-speed serial bit stream with a three-optical input fiber Sagnac interferometer switch, which uses a semiconductor optical amplifier. Full duty cycle bit switching has been demonstrated up to 5 GHz with contrast ratio as high as 14.6 dB     

Temperature dependence of distributions of conformations of a small peptide

Multicanonical Monte Carlo simulations of the pentapeptide Met-enkephalin were used to study its low-energy conformations in detail. The resulting conformations are classified into six categories of similar structures based on the pattern of intrachain hydrogen bonds. Several thermodynamic quantities such as the distributions of hydrogen bonds and those of backbone dihedral angles were obtained as a function of temperature. From these results, it was concluded that at least four of the six categories are well-defined local minimum energy states. These four categories are in agreement with our prior results based on root-mean-square interatomic distances.     

Artificial weathering of wood surfaces modified by melamine formaldehyde resins

Spruce and poplar samples were treated with different melamine formaldehyde resins. A long term artificial weathering experiment was performed in order to clarify the resistance to weathering regarding wood colour and surface hardness. The increase in hardness due to melamine treatment was well preserved after simulated long term weathering. The treated samples also showed advantages compared to untreated reference samples regarding discolouration and crack formation. Low molar mass and low degree of methylolation of the melamine resin used was found to be favourable for a successful treatment.     

Gold‐Catalyzed Highly Diastereoselective Synthesis of Functionalized 3,4‐Disubstituted Butyrolactams via Phosphatyloxy or Carbonate Double Migrations

A gold‐catalyzed highly diastereoselective synthesis of functionalised 3,4‐disubstituted butyrolactams via phosphatyloxy or carbonate double migrations is reported, which is proposed to proceed by a tandem 1,3‐phosphatyloxy or carbonate migration and a “long‐range” 1,5‐phosphatyloxy or carbonate migration, which overall corresponds to a formal 1,6‐migration.     

AN EXPERIMENTAL FRUIT DEHYDRATION SYSTEM

An experimental dehydration system comprising two dehydration units, and in which control and data acquisition functions were computerized, was developed. Product mass is continuously monitored using a built-in weighbridge which facilitates drying rate studies. Product temperatures are also monitored on a continuous basis. Control of wet bulb temperature is achieved by varying the rate of recirculation of air, in conjunction with humidification. Dehydration under isothermal conditions as well as programmed temperature control is supported. In the latter mode temperature programming is performed according to change in mass to simulate the typical air temperature profiles encountered in commercial dehydration tunnels during parallel- and counter- flow operations.     

EFFECT OF TEMPERATURE AND RELATIVE HUMIDITY ON THE DRYING RATES AND DRYING TIMES OF GREEN BELL PEPPERS (CAPSICUM ANNUUM L)

Green bell pepper dices were dehydrated at different dry bulb air temperatures (55°, 60°, 65°, 70° and 75°C) and relative humidities (15, 20, 25, 30, 35 and 40%). The effects of temperature and relative humidity (RH) on the drying rates and drying period of diced green bell peppers were determined. Drying rate curves were characterized by a short induction (heating) phase followed by a falling rate period. Near constant rate drying was observed only at 55°C at 15% RH and at 65°C (15% RH). Drying rates generally increased with increasing temperatures and decreasing RH. The effect of temperature on the drying rates became less pronounced with increasing RH Drying rate maxima at 70°C and RH of 15, 20 25 and 40% exceeded those at 75°C, possibly due to case-hardening.