Saturated Salt Solution Method Research Articles

Moisture absorption and desorption characteristics and prediction model analysis of building thermal insulation materials

Understanding the isothermal moisture absorption and desorption characteristics of building thermal insulation materials and how they affect thermal conductivity, is curial for accurate building thermal design and energy-saving calculation. In this paper, five types of building thermal insulation materials are selected for investigation. First, the variation trend of the equilibrium mass moisture content of materials in different moisture absorption and desorption stages is studied employing the saturated salt solution method and the constant temperature and humidity box method, and the effect of temperature on the moisture absorption and desorption processes is evaluated. Additionally, the applicable model of the material in the moisture absorption and desorption process is obtained through a fitting analysis of the experimental data. Finally, the influence of the material’s moisture absorption and desorption characteristics on the thermal conductivity is analyzed using the transient thermal conductivity test method. The results highlight that there is a need to consider the moisture absorption and desorption processes to accurately determine the wet material thermal conductivity, and the hysteresis effect of the material in the moisture absorption and desorption processes is directly related to its microstructure and the relative humidity at the initial moisture desorption. At a temperature of 25 oC, the autoclaved aerated concrete exhibits its highest hysteresis rate of thermal conductivity during the moisture desorption process of third stage, reaching 13.2%.

Desorption and Sorption Isotherms of Different Varieties of Hemp Seeds with Different Percentages of Dockage under Different Temperatures and Different Relative Humidities

Hemp cultivation faces challenges due to the adoption of dioecious cultivars, which suffer from biomass loss and fibre heterogeneity. In contrast, monoecious cultivars offer simultaneous fibre and seed production, albeit with lower fibre quality. Understanding the drying characteristics and storage requirements of hemp seeds is crucial for effective post-harvest management. This study explored the moisture sorption and desorption isotherms of two common Canadian hemp seed varieties, Altair (dioecious) and CanMa (monoecious), by using both saturated salt solution (SSS) and thin-layer drying methods. Their isotherms were also compared with the published isotherm of Finola—a common dioecious variety in Europe. The thin-layer drying method yielded higher EMC values than the SSS method due to incomplete equilibrium attainment. Larger EMC differences existed between different seed types (dioecious vs. monoecious), and this difference was small between the same seed types (dioecious vs. dioecious). The GAB equation provided the most accurate prediction of equilibrium moisture contents for both varieties.

Equilibrium Moisture Sorption Isotherms of Aspirin

Equilibrium Moisture sorption isotherms are very important in drying and storage analysis. Experimental moisture equilibrium data (adsorption and desorption) of Aspirin were determined using the static method of saturated salt solutions and that by exposing the material to different conditions of temperatures and water activities. Three different temperatures (25, 30, 40Cº) and water activities in the range of (6.3- 83.6%) were used. The results showed that the equilibrium moisture content increased with the increase in water activity at any temperature and decreased with temperature increase at constant water activity. The water activity increases with increasing in temperature when moisture content was kept constant. The sorption isotherm curves are of type II according to Brunauer`s classification. The hysteresis effect was not distinctly expressed only for equilibrium sorption values of Aspirin at 25ºC. The experimental results were fitted to two sorption models (GAB and Henderson).The average relative deviation between the experimental and calculated data were obtained to select the best model. The GAB and Henderson models, obtaining values of 3.54 and 1.42 % average relative deviation and coefficient of regression of 0.98 and 0.977 respectively. The Henderson model was found to be the best fit out of the two models to predict the sorption behavior of Aspirin.

Feasibility and Safety of Regenerated Wild Antheraea pernyi Silk Fibroin/Polyvinyl Alcohol Scaffold in Repair of Calcaneal Tendon Defects

This research discussed the value of regenerated wild Antheraea pernyi silk fibroin (RWSF)/polyvinyl alcohol (PVA) nanofiber scaffold (NFS) in repairing the calcaneal tendon defect (CTD). RWSF was prepared by saturated salt solution (SSS) method, and then RWSF/PVA NFS was prepared by electrospinning using RWSF and PVA as raw materials. Fourier transform infrared spectroscopy (FTIS) was applied to detect the characteristic absorption spectra of WSF, RWSF, and RWSF/PVA. The ultimate tensile strength (UTS) and elongation at break (BE) of RWSF/PVA NFS were analyzed by mechanical tester. The cytotoxicity of RWSF/PVA NFS was determined by MTT assay. 18 SD rats were randomly rolled into an operation group, control group, and experimental group, with 6 rats in each. Meanwhile, 27 rats were randomly grouped into three: blank group, model group, and experimental group. HE staining, Masson staining, and biomechanical properties of the regenerated fibers were analyzed in the calcaneal tendon tissues (CTTs) of rats in different groups. Expressions of tendon-related genes and inflammatory factors in CTTs in various groups were compared by RT-PCR. The results revealed that the UTS and BE of PVA and RWSF/PVA were much higher than those of natural acellular tendon (P <0.01). On day 15 after operation, the hair in the incision area of rats in the Ope, Con, and Exp groups grew normally. The implanted RWSF/PVA NFS in the Exp group adhered closely to the surrounding muscle tissue and degraded gradually, and there were still trace inflammatory cells at the junction. The tendon cross sectional area (CSA) in the Model group and RWSF/PVA group was greatly higher based on that in the Blank group (P <0.05), and the UTS in of Model group was much higher than that in the Blank group but lower to the Model group, showing great differences with P <0.05. The Collagen I, Collagen III, TGF-β1, BGN, and TNMD in CTTs in the RWSF/PVA group were higher to the Model group 2 months ago (P <0.05); while Collagen I, TGF-β1, BGN, and TNMD were still much higher 3 months later (P <0.01) but Collagen III was lower with an obvious difference (P <0.05). At 5 months, IL-1β and TNF-α in the RWSF/PVA group were greatly lower in contrast to the model group, presenting extremely obvious differences (P <0.001). The results indicated that the RWSF/PVA NFS exhibited a good biocompatibility, can accelerate the collagen secretion, promote TGF-β1, inhibit IL-1β and TNF-α factors, thus being conductive to repair of CTD. In conclusion, RWSF/PVA NFS possessed a good biocompatibility, can promote collagen secretion, elevate the TGF-β1, and inhibit IL-1β and TNF-α factors to participate in calcaneal CTD repair, showing a high value in repair of CTD.

A simplified approach to estimating the evolution of residual shear strength of unsaturated soils with suction

Several researchers have investigated the effect of suction and partial saturation on the angle of residual shear strength. Most of these investigations involve the adoption and application of a method of controlling suction on the ring shear apparatus and performing ring shear tests on the same soil for various values of suction. Methods adopted include both the axis translation technique for control of suction over the range 50-1500 kPa and the saturated salt solutions method for control of suction in the range of several MPa. The general picture from these investigations is that the residual shear strength failure envelope remains linear but corresponding to higher values of the angle of residual shearing resistance for constant suction; this value increasing with increasing suction. The paper presents an attempt to normalise values of measured angle of residual shearing resistance for various suction values with the angle of residual shear strength of the corresponding fully saturated soil. This normalisation verified the linear increase of the ratio tanφres(s)/tanφres(s=0)with suction. This linear increase allows for estimation of the evolution of tanφres(s)with suction if φres(s)for one specific suction can be measured. This observation led to the measurement of tanφres(s)of clayey soils in conventional ring shear apparatus without suction control, simply by removing water from the shear box while shearing continues and measuring shear strength until its stabilisation, taking place after the specimen in the shear box came to equilibrium with prevailing laboratory atmospheric conditions. Using the chilled mirror hygrometer to measure equilibrium suction after ring shear completion indicated that equilibrium suction due to laboratory atmospheric conditions is practically constant over the time needed for a single test on one soil. This observation along with the previous observation on the linear increase of the ratio tanφres(s)/tanφres(s=0)with suction, makes valid the estimation of evolution of residual shear strength of unsaturated soils with suction using only a conventional ring shear apparatus and a chilled mirror hygrometer. The paper concludes by outlining the approach, presenting measurements and a relation obtained between tanφres(s)/tanφres(s=0), suction and liquid limit.

Dynamic Water Transport through the Perfluorinated Sulfonic-Acid Membrane

IntroductionThe proton exchange membrane (PEM) is indispensable material for proton transport in PEFC. Since RH affects the effective proton conductivity and the effective oxygen diffusivity through the catalyst layer as well as the proton conductivity, the electroosmotic drag coefficient, the effective diffusivity of water, and the gas permeances of PEM, water behavior which determines relative humidity is most important.To estimate the PEFC performance over time, the dynamic change in transport properties of PEM should be reproduced over full range of operating temperature and moisture content. Though water diffusion in Nafion™ membrane was extensively investigated [1, 2], the transport properties have not been formulated as the function of both temperature and moisture content. In this study, the effective water diffusivity and the skin layer water transfer coefficient were formulated from the experimental results measured by the permeation method and the sorption/desorption method.Experimental–Permeation experimentsA Nafion™ membrane, NR-212, N115 or N117 with different thickness (at relative humidity, RH of 50 %), 51 μm, 127 μm, and 183 μm, respectively, was set in a Japan Automobile Research Institute (JARI) standard cell whose active area was reduced to 2.0 cm×2.0 cm. The cell was placed in the constant temperature and humidity oven (ESPEC, LHL-113). Nitrogen was supplied to both sides of the cell at 300 cm3/min (20 °C, 1 atm). The relative humidity of the supplied gas was controlled by the bubbler temperature. The water vapor flowing out of the cell was collected with an ice-cooled trap to estimate the water permeation flux of the membrane.–Sorption/desorption experimentsThe membrane was placed in a desiccator in which RH was controlled by saturated salt solution method at room temperature (22 °C). The weight of the membrane was recorded constantly. After reaching equilibrium, the membrane was placed in another RH condition and weighed.Results and discussionThe moisture content of the membrane, λ was calculated by a GAB sorption equation in which paraments were fit using reported water equilibrium experimental data [3, 4, 5, 6] as shown in Fig. 1. Schematic diagram of permeation mechanism is shown in Fig. 2. Water permeation flux through the membrane, N A (M) is expressed as follows: N A (M)=c (M) ρ (M) (λ -m -λm )/(1/k A++1/k A-+δ (M)/D eA (M)) (1)where c (M) is the ion-exchange capacity [mol/kg], ρ (M) is the density of dry membrane [kg/m3], λ is the moisture content, k A is the skin layer mass transfer coefficient [m/s], δ (M) is the membrane thickness [m] and D eA (M) is the effective diffusivity [m2/s]. The subscript A means absorbed water, m is the surface of the membrane, - is the supply side and + is the permeate side. Total resistances calculated by eq. (1) were plotted against the membrane thickness. D eA (M) and k A calculated from the trendlines are shown in Figs. 3 and 4, and Arrhenius plots of D eA (M) are shown in Fig. 5.Skin layer mass transfer coefficient, k A can be obtained directly from the sorption/desorption experiments at low temperature. k A obtained from the permeation and sorption/desorption experiments are summarized in Fig. 6 and they are located on an identical line. The transport properties at λ= 5 are expressed as follows as an example: D eA (M) = 3.35×10–5 m2 s–1 exp(–3760 K/T) k A = 1.27×105 ms–1 exp(–8330 K/T)Since these transport properties depend on the moisture content, the desorption is faster than sorption and vice versa even at completely same range of moisture content. This is because the moisture content in the skin layer is always different during sorption and desorption even with the same moisture content variation range.ConclusionsFrom the permeation experiments and the sorption/desorption experiments, the transport properties over wide range of temperature and moisture content of the perfluorinated sulfonic-acid membrane were formulated. Considering the change in k A and D eA depending on the moisture content, the sorption and desorption rate are unequal even in identical RH range.AcknowledgementThis work was supported by the FC Platform Program: Development of design-for-purpose numerical simulators for attaining long life and high-performance project (FY 2020–FY 2022) conducted by the New Energy and Industrial Technology Development Organization (NEDO), Japan.

A cadaveric perfused model with antegrade arteriovenous pulsatile circulation: a new tool for teaching endovascular skills.

Background:The benefits of using cadaveric humans in surgical training are well documented, and knowledge of the latest endovascular techniques is essential in the daily practice of vascular surgeons. Our study explores the feasibility of an affordable human cadaveric model with pulsatile and heated antegrade perfusion for reliable and reproducible endovascular or surgical simulation.Methods:We undertook cannulation of 7 human cadavers embalmed in a saturated salt solution to create a left-to-right central perfusion with a heated solution, from the ascending thoracic aorta to the right atrium. To that end, we used surgically created carotidojugular and femorofemoral arteriovenous fistulas. Biomedical engineers designed a prototype pump for pulsatile circulation. We monitored invasive blood pressure and temperature. We used this model for training for endovascular thoracic aortic procedures and open vascular surgeries.Results:The prototype pump achieved a pulsatile flow rate of 4.7 L/min. Effective cadaveric perfusion was achieved for several hours, not only with an arterioarterial pathway but also with arteriovenous circulation. The arterial pressures and in situ temperatures accurately restored vascular functions for life-like conditions. This new model made it possible to successfully perform thoracic endovascular aortic repair, subclavian artery stenting and simulation of abdominal open vascular trauma management. The saturated salt solution method and a specifically designed pump improved cost competitiveness.Conclusion:Endovascular simulation on human cadavers, optimized with the pulsatile and heated perfusion system, can be a dynamic adjunct for surgical training and familiarization with new devices. This reproducible teaching tool could be relevant in all surgery programs.

Training on skin flap elevation in hand surgery using cadavers embalmed by the saturated salt solution method: effectiveness and usefulness.

Thiel embalmed and fresh-frozen cadavers have been mainly used for hand surgery training. We held a training seminar on skin flap elevation using cadavers embalmed by the saturated salt solution method. This study aimed to evaluate the usefulness of such training and to validate the suitability of saturated salt solution-embalmed cadavers for hand surgery training. Participants were trained in elevation procedures for the oblique triangular, reverse digital artery, reverse radial forearm, and reverse dorsal metacarpal artery flaps. Forty-eight surgeons participated in three seminars (one held in 2017, 2018, and 2019 each). A self-assessment of the participants' confidence levels for their surgical skills was performed before and immediately after the seminar, and the suitability of saturated salt solution-embalmed cadavers was determined in terms of visual perception, tactility, comparison with real-world surgical settings, and usefulness. The confidence level for all skills increased immediately after the seminar. The surgeons reported that the visual perception and tactility of the saturated salt solution-embalmed cadavers were comparable to those of a living body, and the cadavers were rated higher with respect to their usefulness. Hand surgery seminars using cadavers embalmed by the saturated salt solution method are considered useful for training in skin flap techniques.

Hygroscopic properties of six tree species with four tangential thicknesses

The differences of hygroscopic property among six tree species with four thicknesses were examined. The density, chemical composition, crystallinity, equilibrium moisture content (EMC), and moisture absorption rate were measured by static saturated salt solution method, and the isothermal moisture absorption curve was fitted by the H-H model to analyze monolayer molecular adsorption and multilayer molecular adsorption. The results show that under the same relative humidity (RH), the EMC of Picea asperata and Populus deltoides were increased with increasing thickness, while that of Quercus spp. and Xanthostemon melanoxylon were decreased. The moisture absorption rate of P. asperata was the largest and that of X. melanoxylon was the smallest. When RH ranged from 0 to 97%, the monolayer molecular adsorption water amount of samples with different thicknesses of the six tree species gradually became close. With the increase of tree species density, the monolayer molecular adsorption water amount of the thinner sample is gradually greater than that of the thicker sample. The change of multi-layer molecular adsorption water content is consistent with that of EMC, Moisture absorption rate, monolayer molecular adsorption water, and multilayer molecular adsorption water are related to the chemical composition content, density, and thickness of tree species.

The risk of Creutzfeldt–Jakob disease infection in cadaveric surgical training

The usefulness of cadaver surgical training in the clinical field is already well known. In Japan, the number of universities introducing cadaver surgical training is increasing. In addition to formalin fixation, various fixation methods are used, such as the Thiel method, saturated salt solution method, N-vinyl-2-pyrrolidone method, and fresh-frozen cadavers. Although protection against infections during fixation and cadaver surgical training has been implemented in most universities, it is currently inadequate. Furthermore, the possibility of undiagnosed infectious diseases in donors cannot be excluded. Prion diseases, such as Creutzfeldt-Jakob disease, are relatively rare, but they are fatal, with no effective treatment. The abnormal prion protein that causes prion diseases is resistant to formaldehyde and cannot be inactivated by all methods of cadaver fixation presently in use. Recently developed real-time quaking-induced conversion has been reported to be a useful screening method for prion infection. In addition, this article aims to raise awareness of prion diseases in cadaver surgical training by reviewing the current understanding of prion diseases in cadavers and their screening methods.

Radar Cross Section-Based Chipless Tag With Built-In Reference for Relative Humidity Monitoring of Packaged Food Commodities

Dry food commodities like grains and pulses can be stored safely for several years under controlled storage conditions. The equilibrium moisture content of the packaged grain is one of the most important parameters required to be monitored and controlled for extended safe storage. This paper presents a single element dual-polarized sensing tag based on an annular slot antenna operating at two closely spaced resonant frequencies for radar cross-section-based monitoring of relative humidity in hermetically packaged food commodities. One of the resonant frequencies is functionalized for sensing while the other acts as a built-in reference, mitigating the effects of environmental loading. A polyvinyl alcohol coated interdigitated capacitor, integrated onto the antenna is used as a capacitive transducer for the sensing element. Laboratory scale measurements were carried out using the saturated salt solution method. Results show that the proposed sensor can be used for monitoring a wide range of humidity conditions.

An accurate water activity model for glycerol solutions and its implementation on moisture sorption isotherm determination

H2SO4 and glycerol solutions are two commonly used unsaturated solutions for humidity control in moisture sorption isotherm (MSI) experiments. In a previous study, we reported an accurate water activity (a w) model for H2SO4 solutions for use in MSI measurements. The current study aimed to construct a reliable a w model of glycerol solutions and apply it to MSI measurements. Our research showed that the Wilson model could accurately predict a w of glycerol solutions, with a root mean square deviation of 0.0096 a w, in the concentration range of 9.47–99.62% glycerol by mass and in the temperature range of 0–100 °C. This a w model considerably simplified the conventional glycerol solution (GSL) method. Finally, the reliability of this simplified GSL method was tested by comparing with the standard saturated salt solution method for MSI measurements of microcrystalline cellulose and apple at 25 °C. This proposed GSL method, based on the Wilson model, might be a reliable, safe, and inexpensive alternative method for MSI measurements in food areas in the future. Highlights The Wilson model can precisely predict a w of glycerol solutions. The Wilson model can remarkably simplify the known glycerol solution (GSL) method. The simplified GSL method is reliable and applicable for use in microcrystalline cellulose and apples. A working table of a w of glycerol solutions was generated for convenience of use.

Water vapor sorption behavior of bamboo pertaining to its hierarchical structure

Bamboo is an anisotropic, hierarchical, and hygroscopic material. Moisture transport in bamboo is one of the most fundamental properties affecting almost all other physical and mechanical properties of the material. This study investigated the water vapor sorption behaviors of bamboo at various structural levels: cell walls, cells (with pits) and bamboo blocks. The specimens with two sorption directions, longitudinal (L) and transverse (T), were measured by saturated salt solution method and dynamic vapor sorption. The parallel exponential kinetics model was used to analyze the sorption kinetics. The results showed that at the cell wall level, the sorption rate and equilibrium moisture content (EMC) of cell wall in the L specimens were larger than those in the T specimens. The differences were probably caused by the looser cell wall layers in the L specimens. At the cellular scale, pits in the cell wall resulted in an enhanced sorption rate and EMC of the T specimens compared with the L specimens where the pits in the parenchyma cells were only distributed in the lateral walls but not in end walls. At the macro scale, the sorption rate and moisture content of bamboo blocks were largely controlled by the vessel cells. As a hierarchically-structured plant, bamboo performs the biological function of moisture transport at all these scales. This work helps improve the understanding of water transport behavior in bamboo, which may lead to better bamboo drying and impregnation processes.

Effects of Contact Angle on the Hysteresis Effect of Soil-Water Characteristic Curves during Dry-Wet Cycles

The hysteresis characteristics of soil-water characteristic curves (SWCCs) under dry-wet cycling conditions are very important for understanding unsaturated soil properties, so it is crucial to propose an accurate and efficient method for predicting the hysteretic behaviors of SWCCs. To this end, this paper investigates the hysteresis characteristics of SWCCs in the full suction range of seven kinds of Hunan red clay with different initial dry densities by combination of the pressure plate method, the paper filter method, and the saturated salt solution method. It is found that there are, respectively, strong and weak hysteresis zones in the drying and wetting SWCCs under dry-wet cycling conditions. By combining this feature and based on the drying curve, the soil volume and contact angle changes during the drying and wetting processes are employed to predict the hysteretic behaviors of SWCCs. To verify the validity of the prediction method, the predicted curves of the samples with different initial dry densities are compared with the measured curves. The results show that in the strong hysteresis zone, the hysteresis characteristics of the drying and wetting SWCCs are mainly resulted from the changes in the soil pore structure; in the weak hysteresis zone, the hysteresis characteristics are mainly influenced by the changes in the receding and advancing contact angles corresponding to the drying and wetting processes. The Young–Laplace theory is used to transform the changes of contact angle during the drying and wetting processes into the proportional relationship k of matric suction, and the corresponding wetting curve is obtained by smoothing the drying curve. It is found that the prediction effect in the high suction part (the strong hysteresis zone) is better than that in the weak hysteresis zone, which confirms that the hysteresis effect of SWCCs in the high suction part is influenced by the contact angle. Our proposed method can greatly reduce the test period and has a significant practical application value, which provides a new idea for the prediction of SWCCs under dry-wet cycling conditions.

The effect of relative humidity on the survival and growth rate of the yellow mealworm larvae (Tenebrio molitor, Linnaeus 1758)

The current livestock sector is a large contributor to the environmental challenges facing the world. To reduce the environmental impact of food production, a change of the sector is necessary. Entomophagy could be a step towards a more sustainable protein production. However, the insect farming community has a short history compared to conventional livestock, thus, it lacks knowledge of how a profitable mass production of insects is established. In this study we aimed to find the optimal relative humidity (RH) for production of larvae of a popular species for insect farming; the yellow mealworm,Tenebrio molitor. More specifically we tested the effect of a RH of 43, 51, 68, 75 and 84% on the survival rate, mass and length ofT. molitor larvae, from hatching and two weeks forward. Control of RH was achieved using the saturated salt solution method, and the temperature was kept at 30 °C. Experiments were carried out over 12 weeks. The sample size was 100 larvae and eight replicates per treatment. Results showed that the RH had no effect on larval survival rate but had a significant effect on individual larvae mass and length after three weeks. Larval mass and length increased with humidity, and larvae reared at a RH of 84% were 1.96 times heavier and 1.31 times longer than larvae raised at 43%. Hence, for an industrial mass producer ofT. molitor larvae, applying close to the optimal RH of 84% would likely result in an increased larvae size at harvest and a faster growth rate, ultimately leading to a higher yield.

Diversity of soil arthropods in sugarcane in the Brazilian Cerrado: Influence of tillage systems, extraction methods, and sampling time

No-till sugarcane (Saccharum spp.) systems is considered as an interesting option to reduce the cost of production and allow the conservation of both soil quality and biological activity. This study was conducted at a sugarcane mill in Goiatuba, in the state of Goiás, Brazil, which grows sugarcane variety SP 813250. An experiment based on a factorial design (2 × 2 × 2) was set up to compare the diversity of soil arthropods in sugarcane grown under no-till and conventional tillage systems, the efficiency of two methods used to extract soil arthropods (Berlese-Tullgren funnel and flotation in saturated salt solution), and the effects of sampling time (morning or afternoon) at different times of the year (September 2015, November 2015, April 2016, and June 2016). A total of 2776 arthropods belonging to 11 taxa were collected. Acari, Hymenoptera, and Isoptera were the most abundant arthropods (89.3%). The tillage system and sampling time did not affect soil arthropod diversity. The Berlese-Tullgren funnel method was more efficient at extracting arthropods in the rainy season (September and November), whereas the saturated salt solution method was more efficient in the dry season (April and June). The highest soil arthropod abundance was recorded in the rainy season. Our results suggest that the soil disturbance caused by tilling has no effect on soil arthropod diversity in sugarcane plantations.

Experimental Investigation of Moisture Sorption Isotherms for Mefenamic Acid Tablets

The moisture sorption isotherms of Mefenamic acid tablets were investigated by measuring the experimental equilibrium moisture content (EMC) using the static method of saturated salt solutions at three temperatures (25, 35, and 45°C) and water activity range from 0.056 to 0.8434. The results showed that EMC increased when relative humidity increased and the sorption capacity decreased, the tablets became less hygroscopic and more stable when the temperature increased at constant water activity. The sorption curves had a sigmoid shape, type II according to Brunauer’s classification. The hysteresis effect was significant along with the whole sorption process. The results were fitted to three models: Oswin, Smith, and Guggenhein - Anderson and de Boer. According to the fitting results, the GAB model was the most appropriate model to describe the sorption behavior of Mefenamic acid; it had a regression coefficient range (0.9803-0.994), %E (0.69-4.06), and low values of SEE (0.85-2.2). The monolayer moisture content was calculated using the GAB model and it was concluded that the tablets should be stored at moisture content equal or slightly higher than (0.2046, 0.1843, and 0.1437 %) for desorption and (0.2073, 0.1269, and 0.1452 %) for adsorption for the three temperatures.

An accurate water activity model for sulfuric acid solutions and its implementation on moisture sorption isotherm determination

Because of a lack of reliable models to predict the water activity (a w) of H2SO4 solutions, the standard sulfuric acid solution (SSL) method requires a periodic check and adjustment of the acid concentration to ensure that equilibrium will be reached at a predetermined a w point. To establish a reliable equation describing the a w of H2SO4 solutions, five molecular activity models, i.e. nonrandom two-liquid (NRTL), Wilson, universal quasi-chemical (UNIQUAC), modified NRTL-1 (M-NRTL 1) and modified NRTL-2 (M-NRTL 2), were introduced and compared in this study. Each of the models was applied to the 542 literature vapor-liquid equilibrium data points of H2SO4 solutions. The results showed that the NRTL model was the best with respect to its accuracy and simplicity. This NRTL model significantly simplified the implementation of the sulfuric acid solution method for MSI measurements. Excellent agreement was found between this simplified SSL method and the conventional saturated salt solution (SSS) method for MSI measurements of both microcrystalline cellulose (MCC) and apples at 25 °C. Therefore, this newly improved SSL method, based on the NRTL model, could be an inexpensive, convenient and reliable alternative to the conventional SSS method in food MSI measurements in the future. Highlights The NRTL model can accurately predict the a w of H2SO4 solutions. The NRTL model can significantly simplify the known sulfuric acid solution (SSL) method. This improved SSL method is valid and reliable for use in MCC and apples. A working table of the a w of H2SO4 solutions was developed for ease of use.

An optical fiber sensor based on polyimide coated fiber Bragg grating for measurement of relative humidity

Humidity is an important parameter in many industry fields and accurate humidity measurement is of great significance to improve production efficiency and ensure product quality. This paper presents a sensing model and scheme for utilizing thermoplastic polyimide (PI) coated fiber Bragg grating (FBG). The humidity sensitive PI layer was firstly prepared and coated on the FBG. The humidity calibration experiment was designed to verify the sensor performance based the saturated salt solution method. The experimental results show this FBG humidity sensor can work steady in the relative humidity (RH) condition ranging from 11%RH to 83% RH, with the sensitivity of the sensor less than 2 pm/% RH and measurement uncertainty of ±1% RH in the temperature range of 30 °C to 70 °C. In order to solve the problem that the PI-coated FBG is both sensitive to the humidity and temperature (cross sensitivity problem), a novel method of temperature compensation has been proposed. The method uses the character that the coefficients of expansion of the PI-coated layer for humidity and temperature are linearly superimposed and obtains the temperature compensation coefficient by linear interpolation of the function relationship between the measured temperature and the FBG central wavelength shift. The analysis of experimental data shows that within the temperature variation range of 20 °C, this temperature compensation method can effectively guarantee the average wavelength errors within 0.03 nm without reference grating. In this way, it can extend the FBG humidity measurement under environmental temperature up to 90 °C making it possible for application in the measurement the humidity in the high temperature environment.

Experimental Measurement of Isothermal Sorption, Microbiological and Physicochemical Analysis of Dried Tomatoes Cultivated in Adrar, Algeria

The fresh tomato is a very perishable product in arid regions for that the drying is an indsipendable technique to preserve this product and used at all times, in this study the fresh tomatoe was sampled from different farms in Adrar and subjected to the drying method using an indirect dryer solar. The dried tomatoes were screened for microbiological and physicochemical analysis including E. coli, Staphylococcus aureus, Salmonella Typhi, anaerobic sulfito- redactors, molds and yeasts in addition, the value of pH, water activity, dry matter, and assay of ash. The obtained results showed the presence of mesophilic aerobic total bacteria, and coliform total, the absence of Salmonella Typhi, Staphylococcus aureus, Clostridium perfringens and spores of anaerobic sulfito reducting and some colonies of yeasts, for the pH value, activity water, dray matter and assay of ash, the results were (4.10), (0.41), (9.63%) and (5.71%) respectively, which do not affect the final quality of the dried products and satisfactory to norms imposed by the commercial legislation of Algerian. On the other hand, the isothermal sorption is indispensable step to mastering the process of drying tomatoes, and to know the distribution and the intensity of the water connections in the products as a result, this experimental study aims to determine the physicochemical components' and the desorption isotherms curves for tomato harvested from the Touat region, in South-West Algeria, using the saturated salt solution method. The experiment is carried out for three temperature values 40℃, 50℃ and 60℃, to study the influence of the temperature on the equilibrium curves of the product and finally to describe the isothermal moisture desorption for tomato product for three temperatures using known models of GAB, GAB, modified BET who showing the best models isotherms sorption to model at and predict hygroscopic behavior during drying and storage. The results of this research can be used to determine characteristic drying curves and to have optimal storage conditions.