Dynamic Vapor Sorption Analysis Research Articles

Leucine as a Moisture-Protective Excipient in Spray-Dried Protein/Trehalose Formulation

The incorporation of leucine (Leu), a hydrophobic amino acid, into pharmaceutically relevant particles via spray-drying can improve the physicochemical and particulate properties, stability, and ultimately bioavailability of the final product. More specifically, Leu has been proposed to form a shell on the surface of spray-dried (SD) particles. The aim of this study was to explore the potential of Leu in the SD protein/trehalose (Tre) formulation to control the water uptake and moisture-induced recrystallization of amorphous Tre, using lysozyme (LZM) as a model protein. LZM/Tre (1:1, w/w) were dissolved in water with varied amounts of Leu (0 - 40 %, w/w) and processed by spray-drying. The solid form, residual moisture content (RMC), hygroscopicity, and morphology of SD LZM/Tre/Leu powders were evaluated, before and after storage under 22 °C/55 % RH conditions for 90 and 180 days. The X-ray powder diffraction results showed that Leu was in crystalline form when the amount of Leu in the formulation was at least 20 % (w/w). Thermo-gravimetric analysis and scanning electron microscopy results showed that 0 %, 5 %, and 10 % Leu formulations led to comparable RMC and raisin-like round particles. In contrast, higher Leu contents resulted in a lower RMC and increased surface corrugation of the SD particles. Dynamic vapor sorption analysis showed that in the 0 % Leu formulation, partial recrystallization of amorphous Tre to crystalline Tre·dihydrate occurred, and the addition of as little as 5 % Leu could inhibit the recrystallization of amorphous Tre during the water sorption/desorption cycle. In addition, after storage, formulations with higher Leu contents resulted in less water uptake. Rather than recrystallization of amorphous Tre in 0 %, 5 %, and 10 % Leu formulations, recrystallization of amorphous Leu was observed in both 5 % and 10 % Leu formulations after storage. In summary, our study demonstrated that the addition of Leu has the potential to reduce water uptake and inhibit moisture-induced recrystallization of amorphous Tre in the SD protein/Tre powder system.

Hygroscopicity in Epoxy Powder Composites

Epoxy powders offer a low-cost way of manufacturing thick-section composite parts, such as those found in wind and tidal turbines. Currently, their processing cycle includes a lengthy drying stage (≥15 h) to remove ambient moisture. This drying stage prevents void defect formation and, thereby, a reduction in mechanical properties; however, it constitutes up to 60% of the processing time. Little research has been published which studies the drying stage or its optimisation. In the present work, experimental and simulated analyses are used to investigate the effects of hygroscopicity in epoxy powder composites. Tests are performed to quantify the void content of dried and undried laminates and to measure its impact on transverse flexural strength. Dynamic vapour sorption analysis is used to study the sorption behaviour of the epoxy powder. It is shown that the epoxy powder is slightly hygroscopic (1.36 wt%) and exhibits sorption behaviour that is characteristic of glassy polymers. This results in up to 4.8% voids (by volume) if processed in an undried state, leading to a 43% reduction in transverse flexural strength. A modified linear driving force model is fitted to the desorption data and then implemented in existing process-simulation tools. The drying of a thick epoxy powder composite section is simulated to investigate the influence of powder sintering on the duration of the drying stage. Process simulations reveal that a standard drying cycle prematurely sinters the powder, which inhibits moisture release. By maintaining the powder state, simulations show that the drying cycle can be reduced to 5 h.

Effect of Heat Treatment on Hygroscopicity of Chinese Fir (Cunninghamia lanceolata [Lamb.] Hook.) Wood

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) is a widely planted species of plantation forest in China, and heat treatment can improve its dimensional stability defects and improve its performance. The wood samples were heat-treated at various temperatures (160, 180, 200, and 220 °C) for 2 h. To clarify the effect of heat treatment on wood hygroscopicity, the equilibrium moisture content (EMC) was measured, the moisture adsorption and desorption rates were determined, the hygroscopic hysteresis was examined, and the Guggenheim, Anderson, and de Boer (GAB) model was fitted to the experimental data. The moisture absorption isotherms of all samples belonged to the Type II adsorption isotherm, but the shape of the desorption isotherm was more linear for heat-treated wood samples, especially when the heat treatment temperature was higher. According to the results analyzed with ANOVA, there were significant differences in equilibrium moisture content between the control samples and the heat-treated samples under the conditions of 30%, 60%, and 95% relative humidity (RH, p < 0.05), and the results of multiple comparisons were similar. The decrease in hygroscopicity was more pronounced in wood treated at higher temperatures. The EMC of the 160–220 °C heat-treated samples of the control samples was 14.00%, 22.37%, 28.95%, and 39.63% lower than that of the control sample at 95% RH. Under low RH conditions (30%), water is taken up mainly via monolayer sorption, and multilayer sorption gradually predominates over monolayer sorption with the increase in RH. The dynamic vapor sorption (DVS) analysis indicated that the heat-treated wood revealed an increase in isotherm hysteresis, which was due to the change in cell wall chemical components and microstructure caused by heat treatment. In addition, the effective specific surface area of wood samples decreased significantly after heat treatment, and the change trend was similar to that of equilibrium moisture content.

A 3D coordination polymer of Cd(II) with conformationally flexible mixed ligands as an active filler for silicone elastomers

The electronic configuration of d10 metals enables for a wide range of coordination numbers and geometries which, together with the use of mixtures of ligands for their coordination, allows fine-tuning of the properties of the complexes formed. By treating Cd(ClO4)2 with 1,3-bis(carboxypropyl)tetramethyldisiloxane (H2Cx) and 4,4′-azopyridyne (AzPy) in solution, a 3D coordination polymer, [Cd(Cx)(AzPy)·1.85H2O]n (1), was mostly formed. The compound was investigated by elemental and spectral analysis, as well as by powder and single crystal X-ray diffraction. Thermal behavior of compound 1 was evaluated by TGA and DSC, while the moisture behavior was studied by dynamic vapor sorption (DVS) analysis. Compound 1 contains a five-dentate Cx2− ligand with Cd atoms in a pentagonal-bipyramidal geometry, as determined by X-ray analysis. The conformational flexibility of the ligands allows the establishment of all possible intermolecular interactions in a very dense packing, the resulting structure having an extremely low free volume (14.8%). The compound is hydrophobic, adsorbing up to 2.4 wt% water vapor, thermally stable up to 160 °C, and has a phase transition around 6 °C, which, based on analysis by polarized optical microscopy (POM), is considered as a second-order crystal-to-crystal transition, facilitated by the mobility of the siloxane fragment. Due to the constraints imposed by the covalent 3D architecture, the conformational photoisomerization of 1 is extremely limited, as indicated by UV–Vis spectroscopy studies on solutions with solvents of different polarities as well as dielectric spectroscopy studies on silicone composites in which it is in solid state with 5 and 20 wt% loading. Instead, it was found that compound 1 significantly increases the dielectric strength of the resulting materials (up to 46 V/μm compared to 18 V/μm in the empty matrix) by incorporating it as a filler, making them suitable for dielectric elastomer generators, as the results of theoretical calculations indicate. In the purification process, a 2D coordination polymer, [Cd(Cx)(AzPy)·H2Cx]n (2), was also identified in traces.

Super adsorbent bio-polymer additive to improve hygroscopic and acoustic properties of a conventional lime plaster

The paper introduces a new lime plaster composition, with a Super Bio-Polymeric Adsorbent (SABP), for interior applications to improve hygrothermal and acoustic comfort. Alginate SABP is added to a conventional lime plaster to improve hygroscopic and acoustic performance. The hygrothermal and acoustic properties of the modified plaster are compared with the ones of the original plaster with a preliminary moisture uptake test, the evaluation of the sorption isotherm, the moisture buffering value (MBV), and the acoustic absorption. The results show a significant increase in the equilibrium moisture contents and the MBV (from 0.7 to 6.2 g/(m2⋅%RH)). At the same time, the sound absorption coefficient is slightly improved, increasing 0.1-0.2 at frequencies higher than 500 Hz compared to the reference conventional lime plaster. The paper describes the material characterization: the sorption isotherm and the MBV are obtained using a dynamic vapor sorption (DVS) analyzer. The acoustic absorption is measured using the impedance tube method.

Investigating temperature change rate and pore confinement effect on thermal properties of phase change materials for de-icing and low-temperature applications in cementitious composites

Incorporation techniques of phase change materials (PCM) in cementitious composites have a significant influence on thermal properties. This study investigated the thermal behavior of low-temperature PCM when subjected to varying temperature change rates and pore confinement inside the porous network of lightweight aggregates (LWA) and encapsulation using melamine-formaldehyde-based polymer. Three categories of thermal energy storage (TES) specimens were prepared: (i) Bulk PCM (i.e., liquid PCM), (ii) micro-encapsulated PCM (MPCM), and (iii) four different LWAs infused with PCM (PCM-LWA). The thermal properties of small-scale individual TES specimens were analyzed using a low-temperature differential scanning calorimeter (LT-DSC) to evaluate the effect of ramp rates. Dynamic vapor sorption (DVS) analysis was utilized to characterize the pore structure of LWAs. LT-DSC results show that undercooling of the PCM significantly increases with the rise in ramp rate for all the specimens; temperature change rate affects the nucleation and crystallization growth process during the phase transition. Pore structure characterization of LWAs indicates that the majority of the pores (> 92 %) were larger than 17.3 nm (i.e., macropores). Confined liquid properties are subjected to modification due to interaction with the confining surfaces, as explained by Gibbs-Thomson theory. PCM incorporated in the LWA porous network experienced variable degree of supercooling during phase transition; magnitude of confinement pressure is dependent on the pore diameter, structure, and tortuosity. Experimental evidence suggested that PCM-LWA will exhibit gradual expulsion of enthalpy of fusion over a larger temperature range (i.e., ∼−5 °C to 4.28 °C) in comparison to MPCM (i.e., ∼4.28 °C).

Radial cracks in Castanopsis hystrix wood and its dimensional stability improvement by resin-impregnated modification

Abstract This study investigated the characteristics of radial cracks in Castanopsis hystrix wood and evaluated its dimensional stability after impregnation with low-molecular-weight polyacrylate (PA), melamine-urea-glyoxal (MUG), and melamine-urea-formaldehyde (MUF) resins. The physical properties were examined by dimensional stability measurements, dynamic vapor sorption (DVS) analysis, and scanning electron microscopy (SEM). The results showed that radial cracks were easily produced in the transverse section of untreated wood during drying. The surfaces of the radial cracks exhibited an even and clean structure without fluffs on the pair of surfaces, and cracks spanned 4–5 annual rings. The resin-impregnated wood showed no radial cracks on its transverse surface. C. hystrix wood modified with MUG and MUF exhibited a higher weight percentage gain (WPG) than wood modified with the same concentration of PA resin. The resin-impregnated C. hystrix wood also showed reduced anisotropy and improved dimensional stability. The SEM images of the modified wood showed that the wood pits and cells were filled with resin, while the cell wall surfaces were covered with a layer of resin.

Evaluation of the colour parameters on hygroscopicity and dimensional stability of thermally modified Populus tomentosa Carr.

The water vapour sorption and viscoelastic characteristic of thermally modified poplar wood (Populus tomentosa Carr.) based upon colour changes were studied to provide insights into the changes in hygroscopicity and dimensional stability properties by using dynamic vapour sorption (DVS) and dynamical mechanical analysis (DMA). The thermal treatments at 180, 200, and 220 ℃ for 2, 4, 6, 8, and/or 10 h under air atmosphere were applied to cause the component degradation and crosslinking reactions within the cell wall. As the thermal treatment temperature and time increased, the lightness (L*) value of wood showed a gradual decrease. After the removal of hydroxyl groups, the hydrophobicity and dimensional stability had been significantly improved, especially at low L* value. A gauss function (R2 up to 0.99) relationship was observed between water adsorption property and L* value. Based on the analysis of the multiple sorption parameters against L* value, thermal treatment degraded the hemicellulose and reduced the moisture sorption of wood cell wall and the diffusion of water through the cell wall matrix. As the L* value declined, the trend that slow moving of side chains, increasing glass transition point temperature of hemicellulose, and more additional covalent bonds resulted in increased E″ and decreased E′ values was becoming evident. From these perspectives, it could be deduced that reduced water diffusion and high polymer stiffness confined expansion of the cell wall to endow thermally modified wood with improved hydrophilicity and dimensional stability.

Solubility, Crystallization, and Characterization of Cytidine Sulfate.

Cytidine is an important kind of nucleoside that can be applied to drug development and food industry. Cytidine sulfate is one of its popular forms, which is promising as a medicinal intermediate, especially in antiviral and antitumor drugs. Product refining is the key point of industrial development, and crystallization is a significant way of refining. In this work, the solubility of cytidine sulfate in pure water from 278.15 to 328.15 K and in water-ethanol binary solvents at 298.15 K was measured by the UV spectroscopic method. The solubility data were correlated with temperature and solvent composition using the modified Apelblat, van't Hoff, and CNIBS/R-K equations. On this basis, we investigated and compared three crystallization processes, and the coupling method was developed to prepare crystals with a large particle size, concentrated distribution, and high yield and packing density. In addition, the structure and stability of the products were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and dynamic vapor sorption analysis. It was found that cytidine sulfate has only one crystal form in our research process, and the product of coupling crystallization is stable and favorable for industrial development.

Enhancement of the hygroscopic and acoustic properties of indoor plasters with a Super Adsorbent Calcium Alginate BioPolymer

The present study introduces a novel-composition lime plaster that contains a Super Adsorbent BioPolymer (SABP) based on Calcium Alginate (CaAlg) for indoor applications, to improve hygrothermal and acoustic comfort. The sorption isotherm of the plaster, the moisture buffering value (MBV), the acoustic absorption, and the thermal conductivity have been assessed. The hygrothermal and acoustic properties of the modified plaster have been compared with those of the original composition to evaluate its performance under different concentrations of CaAlg (between 10 and 30% wt). Adding the CaAlg SABP to a conventional lime plaster consistently enhanced its hygroscopic properties. The results show a substantial increase in the equilibrium moisture uptake (between 10 and 23 fold) and MBV, from 0.9 to 9.3 g/(m2⋅%RH). The sound absorption coefficient improved by 0.1–0.2 at higher frequencies than 500 Hz. This paper provides detailed information on the characterization of the material. It includes details about using a dynamic vapor sorption (DVS) analyzer to evaluate the sorption isotherm and MBV. It also contains information on the impedance tube method used to measure the acoustic absorption of the material.

Sorption property, excess enthalpy, and solvatochromic parameters of choline lactate

Sorption properties, including isotherm shape, adsorption energy, maximum uptake, and cyclic hydrothermal stability, have a significant influence on the optimization of absorbents for diverse desiccant air conditioning systems. The sorption behavior of the water/choline lactate ([ch][lac]) pair was examined using a dynamic vapor sorption (DVS) analyzer. Data analysis identified type-III isotherms. The Dubinin-Astakhov (D-A) formulation, defined by a temperature-independent Polani potential, was successfully applied to the sorption equilibrium curve. The Kamlet-Taft polarity parameters were tested using solvatochromic probes with a UV/Vis spectrophotometer. Multivariate regression analysis was performed to correlate the water affinity coefficient of the D-A model with the Kamlet-Taft polarity parameters using linear solvation energy relationships (ISERs). The solvatochromic parameter of dipolarity/palarizability (π*) had a positive contribution to the water affinity coefficient of ionic liquid (IL) desiccants, and the general trend of influence was hydrogenbondacidity(α)>π*>hydrogenbondbasicity(β). Excess enthalpies were correlated well with solvatochromic parameters. The differential enthalpies and entropies, first virial coefficient (A0), and isosteric enthalpies of sorption at zero surface coverage were also discussed. The enthalpy of activation at zero surface coverage was deduced from sorption kinetics. The hydrothermal cyclic stabilities and ambient regenerabilities were determined by cycle stress tests.

Degradation assessment of archaeological oak (Quercus spp.) buried under oxygen-limited condition

Abstract The biological deterioration of archaeological wood under oxygen-limited conditions varies due to the limited activities of microorganisms. It is essential to expand the knowledge of the degradation types and the status of archaeological monuments for selecting the proper consolidates. The physical, chemical, and anatomical properties of approximately 600–650 year old archaeological oak collected from an archaeological site in Iasi-Romania were analysed to assess the quality and to identify the degradation types. The results were compared with similar tests on recently-cut oak. X-ray photoelectron spectroscopy (XPS) revealed the presence of more lignin-related peaks in the archaeological oak, which likely reflected the degradation of the wood carbohydrates as evidenced by the decreased oxygen-to-carbon ratio C ox/C non-ox. The differences in cellulose crystallinity were not significant suggesting that any cellulose degradation occurred in the amorphous regions. This was also reflected in the dynamic water vapor sorption analysis where the differences in sorption isotherms and hysteresis of archaeological and recently-cut oaks were marginal. Microscopic analysis of the oak cells illustrated bacterial degradation patterns, while the field emission scanning electron microscopy (FESEM) showed the presence of erosion bacteria in the archaeological oak collected from the site with low oxygen conditions.

Bio-grafted silica to make an asphalt road a sink for reactive environmental pollutants

Asphalt-surfaced areas such as roads have been reported as major non-combustion sources of reactive organic compounds in urban areas. Emission of latter compounds from asphalt is exacerbated due to exposure to sunlight and high temperature, contributing to negative human and environmental health outcomes. Furthermore, loss of asphalt components over time is linked to bitumen's aging that reduces service life of roads. Here, we introduce a designed bio-grafted-silica nano-filler derived from wood pellet as a sink for latter volatile compounds in an asphalt mixture. Molecular modeling calculations showed the remarkable adsorptive activity of the bio-grafted silica for trapping select asphalt volatiles, especially for the sulfur-containing aromatics and the oxygen-containing aromatics. Laboratory experiment revealed that the bitumen modified with bio-grafted silica exhibited up to 23% lower signs of aging. Thermogravimetric analysis proved that the modified bitumen exhibited a 16% reduction in mass loss compared to neat bitumen. Dynamic vapor sorption analysis also showed bio-grafted silica adsorbed higher amounts of a candidate volatile than pristine silica. The study outcomes highlights the advantages of a bio-derived modifier in asphalt to address concerns associated with the loss of hazardous compounds.

Engineering properties and pore structure of lightweight aggregates produced from off-spec fly ash

• High- and low-calcium off-spec fly ash based lightweight aggregate (LWA) was produced. • Engineering properties and pore structure of LWA was characterized. • Small dose of NaOH as fluxing agent can result in off-spec fly ash based LWA with desired engineering properties. This study characterizes the engineering properties of lightweight aggregate (LWA) manufactured from low calcium (F-FA) and high calcium (C-FA) waste fly ash that were designed using a previously-developed thermodynamics-guided process. LWA properties that were characterized include specific gravity, vacuum water absorption, water absorption over time, water desorption, porosity, pore size distribution, and permeability. The LWA studied had a low oven dry specific gravity ranging from 1.22 to 1.45. The vacuum absorption and total open porosity of F-FA LWA decreased as the fluxing agent (NaOH) concentration increased while the values for C-FA LWA varied with increasing amounts of fluxing agent. All LWA passed the ASTM C1761 water absorption/desorption requirements for application to the internal curing of concrete. X-ray computed tomography (XCT) and dynamic vapor sorption analyzer (DVSA) techniques were used to characterize the LWA pore structure. It was found that for F-FA LWA the normalized porosity, counting only pores smaller than 50 nm (gelpores + mesopores), ranged from 4 % to 11.5 %, while for C-FA LWA, this same pore size range had porosity ranging from 1.7 % to 2.8 %. Pore size distribution measurements of F-FA LWA using XCT showed that the pores became larger and the predicted permeability coefficient increased as the fluxing agent concentration increased. For C-FA LWA, the predicted permeability increased with increasing NaOH concentration. Since the pore size distribution had greater variability and did not follow a specific increasing trend, the increase in C-FA permeability could only be due to an increase in pore connectivity.

Sorption properties of wood impregnated with the fire retardant Burnblock

The sorption properties of wood have a characteristic influence on some of its properties, such as the mechanical properties and susceptibility to fungal decay. Moist wood is more susceptible to fungal decay, and wood is often impregnated in order to protect it from fungal decomposition, photodegradation or fire. In particular, inorganic salts affect the sorption properties of wood. For this purpose, the sorption properties of Norway spruce wood impregnated with Burnblock refractory (uptake 38 kg/m³) were investigated. The microscopic analysis confirmed the presence of crystals of this in the cell lumina of wood tissue. Sorption properties were determined using an instrument capable of dynamic vapour sorption (DVS) assessment. DVS analysis confirmed that the sorption properties of impregnated spruce wood are comparable to those of non-impregnated spruce wood. However, the higher hysteresis at higher relative humidity is probably due to the presence of crystals in the cell lumina.

Mucoadhesive and Antimicrobial Allantoin/β Cyclodextrins-Loaded Carbopol Gels as Scaffolds for Regenerative Medicine.

Allantoin and its β-cyclodextrin and hydroxypropyl-β-cyclodextrin inclusion complexes 1:1 have been used to prepare carbopol-based mucoadhesive gels. The gelation process occurred by adjustment with glycerol 10% in the presence of triethanolamine. The structural features induced by the presence of allantoin and the corresponding β-cyclodextrins inclusion complexes have been first investigated by infrared spectroscopy highlighting strong interactions within the gels network and ideal crosslinks for the self-healing behavior. The hydrophilicity of the gels was investigated by the determination of the surface tension parameters and the free energy of hydration. The interfacial free energy values indicated prolonged biocompatibility with blood. The gels-water molecule interactions in terms of sorption, permeability, and diffusion coefficients were evaluated by dynamic vapor sorption analysis. The self-assembly process through intermolecular H-bonding, the high hydrophilicity, the mechanical performance, the hydrolytic stability in simulated biological media, the biocompatibility with normal human dermal fibroblast (NHDF) cells, the mucoadhesivity and antimicrobial activity on selected microorganism species (S. Aureus and C. albicans) of the allantoin-based gels recommend them as promising scaffold alternatives in regenerative medicine.

Off-spec fly ash-based lightweight aggregate properties and their influence on the fresh, mechanical, and hydration properties of lightweight concrete: A comparative study

An off-spec fly ash-based spherical lightweight aggregate (LWA), designated as Spherical Porous Reactive Aggregate (SPoRA), was manufactured through a lab pilot-scale production and its engineering properties, including specific gravity, dry rodded unit weight, water absorption, mechanical performance, and pore structure, were evaluated. Using SPoRA, lightweight concrete (LWC) samples were made and their fresh, mechanical, and hydration properties were assessed and compared with LWC samples made using two commercial LWA available in the US market. The results indicated that fine and coarse SPoRA had 72 h water absorption capacities of 16.4 % and 20.9 %, respectively, which were higher than that of the two commercial LWAs. Higher saturated surface dry specific gravity of SPoRA compared to commercial LWAs led to a higher fresh density for the corresponding LWC. Using X-ray computed tomography, large spherical type pores were observed in SPoRA similar to those in the commercial slate-based LWA. The pore size distribution of SPoRA, characterized by a dynamic vapor sorption analyzer, indicated that more than 97 % of the pores had diameters greater than 50 nm. SPoRA’s average bulk crushing strength was 6.8 MPa which was smaller than commercial LWA and was potentially attributed to the differences in manufacturing processes. Nonetheless, SPoRA LWC with 28 days compressive strength of 29 MPa passed the ASTM C330 requirement and had a comparable strength with LWC prepared with the commercial LWAs indicating lesser importance for the LWA strength. SPoRA LWC had a flowability of 5 % compared to LWC prepared with commercial LWAs having flowability of ≥ 18 %. This observation was potentially related to the fluxing agent used in the SPoRA production. SPoRA had a 70 % degree of hydration at 12 days which was comparable with that of LWC prepared with commercial LWA.

Preparation and Characterization of Heat-Treated Douglas Fir Wood with Core–Shell Structure

Wood heat treatment has been generally accepted as an effective wood modification technology as it improves the dimensional stability and biological durability of wood. However, the property improvements are obtained at the cost of reduced mechanical properties. In this study, heat-treated Douglas fir wood with thermally modified shell and unchanged inner core was prepared by surface heating to make possible the broader applications of heat-treated wood. Colour comparison, dynamic vapor sorption and dynamic mechanical analysis were performed to characterize the physico-mechanical performance of the shell and core of the treated wood. The results reveal a darkened, hydrophobic and rigid shell and a barely changed inner core. X-ray photoelectron spectroscopy shows pronounced degradation of polysaccharides in the surface layer. In contrast, the relative contents of different carbon components in the core layer are similar to that of the untreated wood, indicating the reason for the performance difference between the shell and the core of the treated wood. The initial wood moisture content plays an important role in controlling the temperature gap between the core and the shell during treatment and can be used as a key parameter to adjust the structure and performance of the heat-treated wood.

Composite Materials Based on Gelatin and Iron Oxide Nanoparticles for MRI Accuracy.

The majority of recent studies have focused on obtaining MRI materials for internal use. However, this study focuses on a straightforward method for preparing gelatin-based materials with iron oxide nanoparticles (G–Fe2O3 and G–Fe3O4) for external use. The newly obtained materials must be precisely tuned to match the requirements and usage situation because they will be in close touch with human/animal skin. The biocompatible structures formed by gelatin, tannic acid, and iron oxide nanoparticles were investigated by using FTIR spectroscopy, SEM-EDAX analysis, and contact angle methods. The physico-chemical properties were obtained by using mechanical investigations, dynamic vapor sorption analysis, and bulk magnetic determination. The size and shape of iron oxide nanoparticles dictates the magnetic behavior of the gelatin-based samples. The magnetization curves revealed a typical S-shaped superparamagnetic behavior which is evidence of improved MRI image accuracy. In addition, the MTT assay was used to demonstrate the non-toxicity of the samples, and the antibacterial test confirmed satisfactory findings for all G-based materials.

Modeling Heat and Mass Transfer of Long-Grain Hybrid Rice in a Chilled Environment

HighlightsThis study determined adsorption and desorption isotherms of long-grain hybrid rough rice in chilled environments.Parameters of the sorption models were evaluated by fitting experimental data in a thin layer drying equation.The moisture diffusivity and activation energy values of rough rice subjected to chilled environments were determined.The finite element method was used to simulate the heat and mass transfer of long-grain hybrid rice at low temperatures. Abstract. While chilling aeration technology for grains has found use in other countries, application in the U.S. for rice has not yet been widely adapted by the industry. The aim of this study was to determine the moisture sorption behavior of rough rice in chilled environments. Such data is vital for automated grain conditioning monitoring and control of aeration systems at cool ambient conditions. Adsorption and desorption isotherms of hybrid long-grain rough rice (XL745) subjected to temperature environments which are typical in U.S. storage conditions (5°C to 15°C) were measured. A dynamic vapor sorption analyzer, the IGAsorp, which consists of an ultrasensitive microbalance within a controlled environment was used to accurately measure water sorption in rice. Changes in sample weight were continuously monitored across a range of equilibrium relative humidity (10% to 70%) until a steady-state mass was attained. Nonlinear regression analysis was used to estimate empirical constants of five models used for describing grain sorption isotherms. The appropriateness of each model in describing the equilibrium data was evaluated to minimize the root mean square error (RMSE). The modified Chung-Pfost equation best described the experimental data with RMSEs of 0.557 and 0.912 for adsorption and desorption data, respectively. The equilibrium moisture content (EMC) of rice measured at 5°C with 10% relative humidity (RH) was 12.5% (dry basis), which was higher than the EMC value predicted from other studies by extrapolation at 30°C (9.1% d.b.). All five prediction models (modified Chung-Pfost, modified Henderson, modified Oswin, modified Halsey, and GAB) were in good agreement for experimental data at moderate temperature conditions (e.g., at 30°C). The results indicated that it is more accurate to use newly developed constants for EMC models of rice in chilled environments. A three-dimensional ellipsoid shape was used to describe rough rice geometry. Mathematical models were developed to predict the moisture and temperature distribution during the drying processes at 5°C and 15°C. Models were solved by the finite element method using Comsol Multiphysics® simulation program. Increasing the drying temperature from 5°C to 15°C increased the effective moisture diffusivity from 9.0×10-13 to 1.1×10-12 m2/s. The drying activation energy value was 25.1 kJ/mol in the chilled environments investigated. Keywords: Activation energy, Chilled environment, Equilibrium moisture content, Mathematical modeling, Moisture diffusivity, Rough rice.