The Use of a Custom-Built Coulometric Karl Fischer Instrument for the Determination of Water Content in Chocolate

A Karl Fischer (KF) coulometric titration method was designed and optimized for the quantitative determination of water in chocolate. A number of essential KF experimental parameters were investigated and assessed, including a study of polar extraction solvents, extraction times, interfering side reactions, and a comparison of pyridine-free KF coulometric reagents. The optimized protocol was found to be applicable to a wide variety of chocolate samples. Typical coulometric titration times for the chocolate samples were between 1 and 5 min, translating to water contents from 0.18 to 0.38 %?w/w. With this contribution, the quantification of water in chocolate using KF titration methods is now a simple, safe, and reliable process, comparable in terms of precision and accuracy to any commercially available KF coulometric apparatus.     

Copigmentation and anti-copigmentation in grape extracts studied by spectrophotometry and post-column-reaction HPLC

Copigmentation is a very important contributor to colour in young red wines. Further understanding of the copigmentation effect has been elucidated by investigating the contribution of various fractions of grapes – skin, pulp, and seed – in varieties Shiraz, Sangiovese and Pinot Noir. A series of spectrophotometric and HPLC experiments elucidated the effect of this interaction in grape extracts simulating wine conditions. A post-column reaction method was developed to permit the evaluation of the reactivity of each grape anthocyanin with different reagents: pure compounds (quercetin and caffeic acid) and extracts of grape sections (seed, Semillon skin, Semillon pulp). Certain extracts produced a decrease in colour, suggesting that competing equilibria are important in the copigmentation effect and that an “anti-copigmentation” effect is possible. Flavonols appear to be the best copigmentation cofactors, and the concentration of quercetin 3-O-glucoside was found to correlate with the strength of copigmentation. Flavonols appear capable of displacing cofactors derived from seed extracts.     

An Improved Switched Diversity Combining Using Fuzzy Adaptive Control

Diversity combining techniques, due to their extreme effectiveness incounteracting fading effects in wireless environment, have been extensivelystudied in recent years. In this paper, we propose an improved switchedcombining scheme using fuzzy adaptive control, namely, fuzzy adaptive switcheddiversity (FASD), which is applicable for implementation at mobile units.Specifically, the fuzzy adaptive control dynamically adjusts the thresholdlevel, at which switching is performed, based on the present varying channelconditions. By incorporating the statistics of mobile fading channels andextensive simulations, we have achieved an effective system design of FASDwhich has a significant improvement in system performance in terms of both thediversity gain and BER (bit error rate), while maintaining reasonablesimplicity in implementation.     

An analysis of daylighting and solar heat for cooling-dominated office buildings

Computer simulation techniques were used to assess the energy performance of a generic commercial office building in Hong Kong. The simulation tool was DOE-2.1E. The thermal and energy performance of daylighting schemes were analysed in terms of the reduction in electric lighting requirement and the cooling penalty due to solar heat. Regression analysis was conducted to correlate the peak electricity demand and annual incremental electricity use with two fenestration variables, namely the solar aperture and the daylighting aperture. Contours of equal annual incremental electricity use were shown to be a function of the solar and daylighting apertures. It is envisaged that these simple charts can be a useful design tool for architects and engineers to assess the relative energy performance of different fenestration designs, particularly during the initial design stage when different building design schemes and concepts are being considered and developed.     

Organ-on-a-Chip for Studying Gut-Brain Interaction Mediated by Extracellular Vesicles in the Gut Microenvironment

Extracellular vesicles (EVs) are a group of membrane vesicles that play important roles in cell-to-cell and interspecies/interkingdom communications by modulating the pathophysiological conditions of recipient cells. Recent evidence has implied their potential roles in the gut–brain axis (GBA), which is a complex bidirectional communication system between the gut environment and brain pathophysiology. Despite the evidence, the roles of EVs in the gut microenvironment in the GBA are less highlighted. Moreover, there are critical challenges in the current GBA models and analyzing techniques for EVs, which may hinder the research. Currently, advances in organ-on-a-chip (OOC) technologies have provided a promising solution. Here, we review the potential effects of EVs occurring in the gut environment on brain physiology and behavior and discuss how to apply OOCs to research the GBA mediated by EVs in the gut microenvironment.     

Architecture and performance of a MAC protocol for the HFC system

The IEEE 802.14 standard committee is currently working on a project to find a cost-effective means of providing access to integrated networks for people to enjoy multimedia programs and to work at home. An advanced system based on the cable TV system called hybrid fibre coax (HFC) is being studied. Since some properties of the HFC system preclude the possibility of directly using existing medium access control (MAC) protocols for its data link layer, a MAC scheme based on time division is discussed in this paper. This MAC scheme can be extended for wireless networks. © 1997 John Wiley & Sons, Ltd.     

Solid State 13C NMR and Diffuse Reflectance Mid-Infrared Spectroscopic Analysis of the Effects of Retting on the Chemical Composition of KenafFibre

Bast ribbons from Tainung 1 (T₁) and Guatemala 45 (G₄₅) cultivars of kenaf ( Hibiscus cannabinus ) were subjected to a chemical retting process. The resulting changes at the base and tip regions of each cultivar were analysed using solid-state ¹³C NMR and diffuse reflectance mid-infrared spectroscopies. Chemical retting was performed by boiling the substrates in NaOH (70 g litre⁻¹) +NaHSO₃ (5 g litre⁻¹) for 1 h, after which they were neutralised, washed and air dried. This process produced large decreases in the non-cellulosic components, though 25% of the phenolic component was left undegraded, and cellulose crystallinity was increased by ∽5% over that in unretted samples.     

Psychophysical verification of the accuracy of color and color-difference simulations of surface samples on a CRT display

We describe an experiment to visually quantify the accuracy of the simulation of the color and color-difference of surface samples on a CRT display unit. A gray-scale-anchored, magnitude-estimation experiment was performed to assess the absolute quality of the simulations and a forced-choice, paired-comparisons experiment was performed to assess the relative quality of the simulations. Results indicate that an average color difference for overall simulation accuracy can be under 3.0 CIELAB color-difference units for highcolor-temperature sources, and slightly worse for low-colortemperature sources. All simulations were well under the 6 to 12 unit differences reported for typical color reproduction. Possible reasons for the residual color differences between the current simulations and the theoretical limit are presented.     

5-Ethynyluridine: A Bio-orthogonal Uridine Variant for mRNA-Based Therapies and Vaccines

The identification of pseudo- and N¹-methylpseudo-uridine (Ψ and mΨ, respectively) as immunosilent uridine analogues has propelled the development of mRNA-based vaccines and therapeutics. Here, we have characterised another uridine analogue, 5-ethynyluridine (EU), which has an ethynyl moiety. We show that this uridine analogue does not cause immune activation in human macrophages, as it does not induce interleukin-6 secretion or expression of the inflammatory and antiviral genes MX1, PKR, and TAP2. Moreover, EU allows for prolonged expression, as shown with mRNA coding for yellow fluorescent protein (YFP). Side-by-side comparisons of EU with unmodified, Ψ, and mΨ revealed that EU-modified mRNA is expressed at lower levels, but confers similar stability and low immunogenicity to the other uridine analogues. Furthermore, structure analysis of modified mRNAs suggests that the observed phenotype is largely independent of RNA folding. Thus, EU is a potential candidate for RNA-based vaccines and therapeutics.