B. Widom

Bio: B. Widom is an academic researcher from Cornell University. The author has contributed to research in topics: Rate equation & Collision frequency. The author has an hindex of 1, co-authored 1 publications receiving 11 citations.

Effects of Melamine Addition Stage on the Performance and Curing Behavior of Melamine-Urea-Formaldehyde (MUF) Resin

Abstract: Three formaldehyde-based resins were prepared: urea-formaldehyde (UF) resin without melamine modifier (named UF0 resin) and melamine-urea-formaldehyde (MUF) resins with melamine modifier added at two different synthesis stages (named MUF1 resin and MUF2 resin). The effects of the melamine addition stage on the performance and curing behavior of MUF resin were studied. Three-ply plywood bonded by these adhesives was manufactured, and its bond strength and formaldehyde emissions were measured. The curing behavior and functional groups of the resins were measured by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). Their activation energies were calculated using the Kissinger equation and the Kissinger-Akahira-Sunose (KAS) method. The results showed that melamine addition and the addition stage had significant influences on the characteristics of resins. The plywood bonded by MUF1 resin showed the highest bond strength and the lowest formaldehyde emissions. The activation energies of UF0 resin, MUF1 resin, and MUF2 resin were significantly different; the values were 99.44 kJ/mol, 105.75 kJ/mol, and 150.65 kJ/mol, respectively. According to the FT-IR spectra, the amount of methylene and methylene-ether bonds in cured MUF2 resin was the lowest, which meant that the cross-linking degree of MUF2 resin was the lowest.

A comparative study of black mulberry juice concentrates by thermal evaporation and osmotic distillation as influenced by storage

Abstract: In the present study, black mulberry juice was concentrated using thermal evaporation and osmotic distillation after clarification and pasteurization. The main quality parameters of the concentrates were comparatively investigated after reconstitution with different storage times and temperatures. The parameters investigated were: color, turbidity, pH, titratable acidity, anthocyanin content, percent polymeric color, antioxidant activity, 5-hydroxymethylfurfural (HMF) content and volatile profile. The anthocyanin content, volatile content and turbidity values of osmotically distillated samples were found to be higher than those of the thermal concentrates. Neither HMF nor furfural was detected in the samples soon after the processing; however, levels of process contaminants were found to increase gradually throughout the storage period in both concentrates. Thermal evaporation resulted in markedly higher HMF and furfural formation in comparison to the osmotic distillation process. The anthocyanin content and antioxidant activity of the concentrates decreased, whereas polymeric color ratio and turbidity values increased within longer storage time and higher storage temperature. Industrial relevance Concentration is one of the key steps affects the chemical and physical properties of black mulberry juice since black mulberry phytochemicals, mainly anthocyanins, are labile to heat treatment and storage. Thermal evaporation has some drawbacks such as loss of fresh juice flavors, color degradation, reduction of nutritional value and formation of mutagenic compounds such as HMF and furfural. These drawbacks require alternative methods that involve minimal processing. Osmotic distillation can be recommended for black mulberry juice concentration in order to preserve its heat-sensitive components and to produce high-quality product.

Optimization of green extraction of phytochemicals from red grape pomace by homogenizer assisted extraction

Abstract: Grape pomace is a by-product that contains high amounts of phytochemicals such as phenolic acids, flavonoids, and anthocyanins. For the efficient extraction of these compounds, extraction optimization was done in the present study. Glycerol concentration, a cheap, non-toxic and abundant green solvent, and liquid–solid ratio were evaluated as the independent factor of the optimization and total phenolic content, total flavonoid content, free radical scavenging activity, total monomeric anthocyanin content, total proanthocyanidin content and ascorbic acid content was analyzed as responses. The result showed that glycerol concentration significantly affected all responses and increasing the concentration resulted in higher extraction of the phytochemicals. Additionally, liquid–solid ratio affected total phenolic content, total flavonoid content, total proanthocyanidin content and ascorbic acid content of the extracts. Glycerol concentration of 50% (w/v) and liquid–solid ratio of 22.4 was determined to be optimum condition to maximize all responses. The optimum conditions were experimentally validated. Overall, the study showed that homogenizer assisted extraction using glycerol as a green solvent is a good method for extraction of phytochemicals from food processing by-products.

When Rate Constants Are Not Enough.

Abstract: Real-world chemical systems consisting of multiple isomers and multiple reaction channels often react significantly prior to attaining a steady state energy distribution (SED). Detailed elementary reaction models, which implicitly require SED conditions, may be invalid when non-steady-state energy distributions (NSED) exist. NSED conditions may result in reaction rates and product yields that are different from those expected for SED conditions, although this problem is to some extent reduced by using phenomenological models and rate constants. The present study defines pragmatic diagnostics useful for identifying NSED conditions in stochastic master equation simulations. A representative example is presented for each of four classes of common combustion species: RO2 radicals, aliphatic hydrocarbons, alkyl radicals, and polyaromatic radicals. An example selected from the seminal work of Tsang et al. demonstrates that stochastic simulations and eigenvalue methods for solving the master equation predict the...