Combined ultrasound and infrared assisted conductive hydro-drying of apple slices

Abstract

Conductive hydro-drying also known as Refractance Window drying is a relatively new drying technology, which uses hot water to carry thermal energy to materials to be dehydrated. It has a high retention of heat sensitive quality parameters (vitamins, antioxidants, and color) with better energy efficiency than freeze-drying as well as many other conventional drying methods. A new ultrasound and infrared assisted conductive hydro-dryer (UIACHD) was developed to increase drying rate while reducing required hot water temperature and increasing the drying material thickness. The goal of this study was to evaluate the performance of the new dryer and to compare the performance of a pilot scale continuous UIACHD with a freeze-dryer and a cabinet dryer in drying apple slices. The physiochemical characteristics of the dried apple slices including flavonoid content, total phenolic compounds, antioxidant activity, vitamin C content and color were measured. In addition, the energy consumption and energy efficiency of the dying methods were evaluated. Results showed that combining ultrasound and infrared with conductive hydro-drying can result in higher drying rates and lower product moisture content. Quality of UIACHD dried apple slices was close to the freeze-dried products and it was significantly better than the cabinet dried products. Moreover, the energy efficiency of UIACHD was considerably better than the cabinet dryer and the freeze-dryer. The results of this study showed that combining ultrasound and infrared with conductive hydro-drying can lead to an energy-efficient process with good quality retention ability.     

Growth and pigment production of Synechocystis sp. PCC 6803 under shear stress

Cyanobacteria, such as Synechocystis, have recently become attractive hosts for sustainable production of biofuels and bio-fixation of CO₂ due to their genetic tractability and relatively fast growth. Cultivation of cyanobacteria requires shear stress, which is generated by mixing and air bubbling. In the present work, the impact of shear stress caused by stirring and air bubbling on the growth and pigment production of Synechocystis sp. PCC 6803 is investigated. For this purpose, agitated and airlift bubble column photobioreactors were used. The results showed that the growth and yield production were improved by mixing the culture system. However, there is a limit to this improvement: In the case of air bubbling, increasing shear stress (by rising air bubbling flow rate) to more than 185 mPa did not show any significant growth enhancement, while increasing the shear stress from 40 to 185 mPa improved the yield production up to 85%. At the optimal stirring rate, the yield production in the stirred photobioreactors increased by about 60% as compared to that of unstirred culture. The measurements of chlorophyll_a and carotenoid showed a strong correlation between biomass production and total pigment content. The highest level of cellular pigment (pigment per cell) was detected at the early stages of culture growth when cells were preparing for the rapid exponential growth phase.     

Sol–gel synthesis,characterization, and neurotoxicity effect of zinc oxide nanoparticles using gum tragacanth

The use of plant extract in the synthesis of nanomaterials can be a cost effective and eco-friendly approach. In this work we report the “green” and biosynthesis of zinc oxide nanoparticles (ZnO-NPs) using gum tragacanth. Spherical ZnO-NPs were synthesized at different calcination temperatures. Transmission electron microscopy (TEM) imaging showed the formation most of nanoparticles in the size range of below 50 nm. The powder X-ray diffraction (PXRD) analysis revealed wurtzite hexagonal ZnO with preferential orientation in (101) reflection plane. In vitro cytotoxicity studies on neuro2A cells showed a dose dependent toxicity with non-toxic effect of concentration below 2 µg/mL. The synthesized ZnO-NPs using gum tragacanth were found to be comparable to those obtained from conventional reduction methods using hazardous polymers or surfactants and this method can be an excellent alternative for the synthesis of ZnO-NPs using biomaterials.     

Effects of mechanical and geometrical properties of adhesive and metal layers on low-velocity impact behavior of metal laminate structures

In this study, the effects of mechanical and geometrical properties of the adhesive layers and mechanical properties of the metal layers on low-velocity impact behavior of adhesively bonded metal laminates (ABML) were investigated. The contact force, the transverse displacement, the contact duration, and the dissipated energy were considered as the main structure responses under impact loading. To study the effects of mechanical and geometrical properties of adhesive layers on low-velocity impact behavior of ABML, two different adhesive materials and two different adhesive thicknesses were considered. The results showed that the contact force was more depended on the adhesive thickness and nearly unaffected by the adhesive material, whereas the dissipated energy was more depended on the adhesive material rather than the adhesive thickness in case the overall structure thickness was remained fixed. To determine the effects of material parameters of the metal layers including the yield stress, the elastic modulus, the density, and the tangent modulus on the impact behavior of ABML, finite element analyses were carried out. The results showed that increasing the number of metal layers in a constant total thickness caused decrease of the total contact force and increase of the contact duration and transverse displacement of the structure due to more widespread plastic deformation occurred in the layers. The material yield stress and Young’s modulus were the most influencing material parameters on the mechanical behavior of ABML under low-velocity impact loading. The finite element models were well validated against the experimental and numerical results.     

Identification of Novel Genes Involved in Hyperglycemia in Mice

Current attempts to prevent and manage type 2 diabetes have been moderately effective, and a better understanding of the molecular roots of this complex disease is important to develop more successful and precise treatment options. Recently, we initiated the collective diabetes cross, where four mouse inbred strains differing in their diabetes susceptibility were crossed with the obese and diabetes-prone NZO strain and identified the quantitative trait loci (QTL) Nidd13/NZO, a genomic region on chromosome 13 that correlates with hyperglycemia in NZO allele carriers compared to B6 controls. Subsequent analysis of the critical region, harboring 644 genes, included expression studies in pancreatic islets of congenic Nidd13/NZO mice, integration of single-cell data from parental NZO and B6 islets as well as haplotype analysis. Finally, of the five genes (Acot12, S100z, Ankrd55, Rnf180, and Iqgap2) within the polymorphic haplotype block that are differently expressed in islets of B6 compared to NZO mice, we identified the calcium-binding protein S100z gene to affect islet cell proliferation as well as apoptosis when overexpressed in MIN6 cells. In summary, we define S100z as the most striking gene to be causal for the diabetes QTL Nidd13/NZO by affecting β-cell proliferation and apoptosis. Thus, S100z is an entirely novel diabetes gene regulating islet cell function.     

Mechanism of the Inhibitory Effect of Hydroxytyrosol on Lipid Oxidation in Different Bulk Oil Systems

The autoxidation of purified triacylglycerols obtained from fish, canola, and olive oils in the presence of different concentrations of hydroxytyrosol at 60–100 °C was evaluated by different kinetic parameters including the stabilizing factor (F) as a measure of effectiveness, the oxidation rate ratio (ORR) as a measure strength, and the antioxidant activity (A) which combines the F and ORR parameters. The overall performance of hydroxytyrosol was attributed to the main reaction of chain termination () as competed with the main oxidation reaction of chain propagation () and, additionally, the antioxidative side reactions of chain propagation ( and ), and the pro‐oxidative side reaction of chain initiation () in some cases.     

Oxygen is not required for degradation of DNA by glutathione and Cu(II)

Previous studies by others have shown that thiols, such as glutathione, cause cleavage of DNA in the presence of Cu(II) ions and that the hydroxyl radical derived from molecular oxygen is the major cleaving species. In this paper, we present several lines of evidence that strongly suggest that molecular oxygen is not essential for DNA cleavage and that thiyl radicals may also be involved. Indirect evidence is presented to indicate that glutathione may substitute oxygen as an electron acceptor. In addition, DNA degradation occurs to a significant extent under anaerobic conditions and no inhibition of single-strand cleavage of supercoiled plasmid DNA is seen in the presence of superoxide dismutase and catalase. In view of the ubiquitous presence of glutathione, these results could be of interest under certain diseased conditions where copper concentrations are elevated.     

PML absorbing boundary condition for the integral‐based high‐order FV24 FDTD algorithm

An integral equations‐based perfectly matched layers (PML) implementation is presented for the highly phase‐coherent FV24 finite‐difference time‐domain (FDTD) algorithm. The implementation allows including field values off the grid axes in the split‐field PML formulation conserving in the process the continuity and phase coherency of the FV24 algorithm when modeling absorbing boundary conditions (ABCs). It also eliminates the need for cumbersome subgridded low‐order FDTD subregions that until now were required to model PML ABCs within integral‐based high‐order FDTD simulations. The developed approach was numerically tested and found to match the PML behavior of the standard FDTD method at normal wave incidence on ABC boundaries and exceeds it at highly oblique wave incidence. This development serves to improve the capability and practicality of the computationally efficient FV24 algorithm when modeling electrically large structures in 3‐D space. Copyright © 2010 John Wiley & Sons, Ltd.