Equilibrium Moisture Content Research Articles

Moisture desorption behavior and thermodynamic properties of pulp and seed of jambolan (Syzygium cumini)

The study objectives were to establish isotherms and thermodynamic properties for the moisture desorption process of jambolan pulp (JP) and jambolan seed (JS), harvested in the city of Belém (Brazil). These characteristics can contribute for the proper selection of the operating drying conditions. Thus, the following essays were made for both JP and JS. Firstly, proximate composition was performed, followed by moisture desorption essays at 25, 35, 45 and 55 °C. In addition, six mathematical models were fitted to the experimental data to simulate the desorption behavior; and based on the chosen models, the thermodynamic properties were calculated. The results have shown that JP isotherms followed the typical behavior of products rich soluble solids, and JS isotherms were more influenced by protein components. The influence of temperature was evidenced throughout the entire range of water activity (aw) studied. The GAB and Oswin models represented the best fitted equations for the JP and JS, respectively. In general, the energies involved in the desorption process of jambolan showed a greater dependence of JP with the equilibrium moisture content (EMC), in comparison with JS. Still, there was an increasing tendency of the thermodynamic properties with EMC decreasing. Besides of being non-spontaneous processes, desorption phenomena of JP and JS were enthalpy-driven mechanisms.

Water content in Annona squamosa seeds under different temperature and relative humidity conditions of storage environment

The conditions of the storage environment, mainly related to temperature and relative humidity, influence the interaction of seeds with the environment and, consequently, the water content of the product. The study aimed to analyze the influence of ambient temperature and relative humidity on the water content of Annona squamosa seeds. The experiment was carried out in a completely randomized design with a 5x7 factorial scheme, with five temperatures (15, 20 and 25, 35, 40ºC) and seven conditions of relative humidity with nine replications. The equilibrium moisture content of the seeds was analyzed by mass difference. Data were subjected to analysis of variance by the F test and regression analysis. For significant interaction between the sources of variation, multivariate analysis was performed. Through regression analysis, linear models were obtained for the analyzed temperatures. Through multivariate analysis, a mathematical model was obtained to predict the equilibrium humidity of the pinecone considering temperature and relative humidity. The moisture in A. squamosa seeds is influenced by the temperature and relative humidity of the environment. Obtaining a mathematical model by multivariate analysis allows an adequate prediction of equilibrium moisture.

Nanostructural Changes Correlated to Decay Resistance of Chemically Modified Wood Fibers

Reactive chemical modifications have been shown to impart decay resistance to wood. These modifications change hydroxyl availability, water uptake, surface energy, and the nanostructure of wood. Because fungal action occurs on the micro and nano scale, further investigation into the nanostructure may lead to better strategies to prevent fungal decay. The aim of this article is to introduce our findings using small angle neutron scattering (SANS) to probe the effects of chemical modifications on the nanostructure of wood fibers. Southern pine wood fiber samples were chemically modified to various weight percentage gains (WPG) using propylene oxide (PO), butylene oxide (BO), or acetic anhydride (AA). After modification, the samples were water leached for two weeks to remove any unreacted reagents, homopolymers or by-products and then the equilibrium moisture content (EMC) was determined. Laboratory soil-block-decay evaluations against the brown rot fungus Gloeophyllum trabeum were performed to determine weight loss and decay resistance of the modifications. To assist in understanding the mechanism behind fungal decay resistance, SANS was used to study samples that were fully immersed in deuterium oxide (D2O). These measurements revealed that modifying the fibers led to differences in the swollen wood nanostructure compared to unmodified wood fibers. Moreover, the modifications led to differences in the nanoscale features observed in samples that were exposed to brown rot fungal attack compared to unmodified wood fibers and solid wood blocks modified with alkylene oxides.

Study on the hygroscopic performances of poplar wood fiber biomass brick

Poplar fiber biomass brick is an energy-saving and environmentally friendly biomass building material developed in recent years. It has good hygroscopic performance, can adjust indoor air humidity, helps reduce building energy consumption for dehumidification and humidification, and improves indoor air comfort. This paper studies the hygroscopic performance of poplar fiber brick from the microscopic pore structure experiment, nitrogen physical adsorption experiment, equilibrium moisture content experiment, moisture sorption and desorption cycle experiment, and water vapor transmission experiment. The model of the sorption-desorption curve of poplar fiber biomass brick at 23 °C is established. Moreover, the ideal moisture buffering value (MBV) of poplar fiber brick and the ideal and practical MBV values under the experimental procedures of this article are calculated. The results show that the Peleg model is most suitable for poplar fiber brick's moisture absorption and desorption curve at 23 °C. The MBV value is the “Excellent” level and has good moisture sorption and desorption performance. The obtained data and models provide potent data support for promoting and applying biomass bricks and theoretical model research.

Moisture sorption isotherms and estimation of isosteric heat of sorption of donkey milk powder

The moisture sorption isotherms of donkey milk powder were studied at 20, 25 and 30°C for 0.22 to 0.93 aw through gravimetric method. GAB, Peleg, Smith and Oswin mathematical models were fitted to experimental data. Equilibrium moisture content of the sample increased from 0.0499 to 0.3255, 0.0447 to 0.2904, 0.0426 to 0.2618 kg.kg−1 solid at 20, 25 and 30°C with increasing aw from 0.22 to 0.93. Isotherm curves showed type II behavior. Monolayer moisture content decreased from 0.0373 to 0.0301 g.100 g−1 solids at 20 to 30°C. The net isosteric heat of sorption decreased from 98.55 to 0.74 kJ.mol−1 with increased moisture content from 2 to 20% (d.b.). The adsorption isotherm curves suggest that the sample requires more attention when handled in RH higher than 24, 33 and 42% at 20, 25 and 30°C. Novelty impact statement Donkey milk powder was stable below 42% RH at 30°C. The best-fitting Oswin model equation provides a solid foundation for future research on drying and storage of donkey milk powder. Isosteric heat of sorption of donkey milk powder decreases with increase in moisture content.

A Comprehensive Analysis of the Risks Associated with the Determination of Biofuels’ Calorific Value by Bomb Calorimetry

Two of the most commonly used solid biomass sources for fuel are wood chips and wood pellets. The calorific value and the moisture content of those biofuels determine the efficiency of the CHP and the biorefinery plants. Therefore, with the increased shift towards a biobased economy, the biomass cost and its physical properties must be precisely determined. Most of the current standards are lacking and provide neither enough details about the issues caused by the biomass heterogeneity nor with the variation in experimental practice. Phenomena such as data scattering, poor repeatability and wide uncertainty, are mostly observed during the measurements of the calorific value and the moisture content. To overcome such issues, an interlaboratory comparison between three national metrology institutes using bomb calorimetry has taken place. The comparison helped to identify the root causes behind the poor reproducibility of the wood samples. Factors such as the equilibrium moisture content of the biomass, the pellet mass, the applied pressure to form the pellet, the handling techniques and the determination errors are highlighted and analyzed. The final results paved the way to provide an enhanced detailed experimental practice where the repeatability and reproducibility have been strongly improved. Moreover, the detailed uncertainty sources and calculations are presented. It has been found that by fulfilling the recommended approach the measurement repeatability improved by up to 50–80%, while the final uncertainty improved by 10–30%. This enhancement leads to a maximum relative expanded uncertainty of around ±1% (coverage factor of k = 2 and a confidence level of 95%).

Supercritical carbon dioxide extrusion of milk protein concentrate and rice flour blend: A new dairy nutrition delivery platform

AbstractThe main objective of this study was to develop milk protein concentrate (MPC) and rice flour blend ready‐to‐eat extrudates using supercritical fluid carbon dioxide extrusion (SCFX) that have comparable physical characteristics with selected commercial products because the conventional, steam‐based extrusion process is a high‐temperature and high‐shear process that degrades the product quality. Three formulations, in the ratio of 30:66.5, 60:36.5, and 90:6.5 of MPC:rice flour, were blended with 2% emulsifier (dimodan and lecithin) and 1.5% salt. The blended formulations were extruded using a Wenger twin‐screw extruder designed and built for use with supercritical CO2. The mechanical and physical properties of the extrudates were determined and compared with two commercial carbohydrate cereal products. The extrudates were equilibrated to 43%, 23%, and 11% relative humidity (RH) and their stress and stain relationships were quantified. The power law model was used to model the modulus of elasticity of the extrudates with a good fit (R2 = 0.98–0.99). The extrudates and commercial samples were rehydrated until attaining their equilibrium moisture contents and the data were used to model the rehydration kinetics and determine the diffusivity values using Fick's law. The results revealed that MPC (30%–90%) and rice flour (66.5%–6.5%) blend extrudates had physical and mechanical properties that were within the range of commercial samples tested. The overall findings of this study indicated that the physical characteristics of extrudates containing 60% and 90% MPC can be successfully used to produce ready‐to‐eat cereals and high MPC nutribars.

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.

Effect of the thermal treatment on the chemical components, sorption, and shrinkage properties of Tectona grandis juvenile wood

The effect of thermal treatment on the chemical components, equilibrium moisture content (EMC), and shrinkage of teak juvenile wood was studied. Heartwood and sapwood samples were thermally-treated at 180 ºC and 200 ºC. Extractive, Klason lignin, holocellulose, and α-cellulose contents, as well as pH on untreated and thermally-treated woods, were determined. The EMC was reached at five relative humidity (RH) levels using saturated salt solutions: 86 % (KCl), 76 % (NaCl), 58 % (NaBr), 33 % (MgCl2), and 0 % (P2O5). Linear and volumetric shrinkages were calculated for all EMCs. The ratio of sorption (S), coefficient of shrinkage (h), and fiber saturation point (FSP) were also determined. Thermally-treated wood exhibited lower holocellulose and α-cellulose contents than untreated wood and increased acidity due to degradation of the hemicelluloses. The thermal treatment reduced the EMC of heartwood and sapwood. However, sapwood was more sensitive to RH variations than heartwood regardless of the treatment. Thermally-treated woods had higher hygroscopic and dimensional stabilities, and lower FSP than untreated wood. The thermal treatment did not affect radial shrinkage of the heartwood between 33 % and 86 % RH. Heartwood was more sensitive to the effect of the thermal treatment on shrinkage and degradation of cell wall polymers compared to sapwood.

English

African rosewood (Pterocarpus erinaceus) is an endemic, highly exploited and endangered tree species in arid and semi-arid zones of West Africa. Identifying optimum conditions for seed propagation and storage is critical for its conservation. This study assessed the effects of four pretreatments on seed germination and seedling vigour. Varying temperature, duration and packaging on storage deterioration were also evaluated for 12-months. Moisture sorption isotherms at 20, 25 and 30°C were characterized by equilibrating seed samples on series of lithium chloride (LiCl) solutions, generating relative humidity (RH) range of 3-95%. Data were fitted to four mathematical models; Chung Pfost, Halsey, Henderson and Oswin to determine the most suitable for describing the water activity (aw), equilibrium moisture content (EMC) and temperature relationship. Results indicate that whole fruit sowing reduced germination capacity by more than 50% compared with extracted seeds at 5% probability level. Seeds stored at -10°C recorded the lowest rate of seed deterioration compared with ambient storage, regardless of packaging. Moisture sorption isotherms for rosewood showed a sigmoid (S-shaped) profile characteristic of orthodox seeds, and best described by the Henderson equation. Our findings highlight the need for adopting improved seed extraction technology and orthodox seed storage protocols for P. erinaceus conservation. Key words: seed germination, storability, African rosewood, sorption isotherms.

English

The current study examines the physical and mechanical properties of branch wood from Holarrhena floribunda and Nesogordonia papaverifera, two of Ghana's least researched deciduous species. At an equilibrium moisture content of 12±2%, H. floribunda and N. papaverifera specimens had average density values of 467.53 and 720.80 kgm-3, respectively. The overall tangential and radial shrinkage was 3.8 and 3.2%, respectively, while the radial shrinkage was 2.8 and 1.8%. For H. floribunda and N. papaverifera, the modulus of rupture was 80.2 and 122.3 N/mm2, respectively, whereas the static modulus of elasticity was 8213.8 and 12902.8 N/mm2. Shear strength parallel to grain was around 11.9 and 16.5 N/mm2, whereas compression strength parallel to grain was approximately 36.6 and 52.3 N/mm2. H. floribunda and N. papaverifera have Janka hardness values of 6.2 and 10.3 N/mm2 tangentially, and 4.3 and 8.9 N/mm2 radially, respectively. The qualities of the branch wood of H. floribunda and N. papaverifera were equivalent to those of their stem wood and other known wood species, indicating that they might be used in a variety of wood-related applications.   Key words: Branchwood, Holarrhena floribunda, Nesogordonia papaverifera, Ghana.

Effect of Acetylation and Accelerated Weathering of Nigerian Grown Rubberwood (Hevea brasiliensis, Müll. Arg.) on Equilibrium Moisture Content and Colour Change

This study was conducted to investigate the effect of acetylation on equilibrium moisture content (EMC) of Nigerian-grown rubberwood and its effect on colour change in exposure of rubberwood to surface degradation through accelerated weathering. The samples were modified to two levels of acetylation, which yielded weight percent gain (WPG) of 7 % and 10 % after 8hr (8-hr Acetyl) and 48hr of acetylation (48-hr Acetyl), respectively. Accelerated weathering of unmodified (Ref) and acetylated wood was done using QUV-Accelerated Weathering Tester for four weeks. The unmodified and acetylated samples (weathered and unweathered) were oven-dried and conditioned in climate rooms at different relative humidity of 50 %, 65 % and 95 %, with samples being moved to each room after 14 days. Results showed that acetylation led to a significant decrease in equilibrium moisture content of rubberwood. After weathering, there was a decrease in EMC of rubberwood due to removal of hemicelluloses alongside the degraded lignin, and a slight increase in EMC of the acetylated wood. In terms of colour change, photo-bleaching of the acetylated samples was higher (10.46 for 48-hr Acetyl) after four weeks of weathering compared to the unmodified samples (6.43). Hence, the outcome of this study has shown that, although acetylation is effective in minimizing moisture ingress into wood, it resulted in photo-bleaching of the weathered samples. Additional surface coating is recommended to serve as a protective layer, preventing partial washing out of the acetyl groups, minimize photo-bleaching during weathering and prolong the aesthetic value of the wood especially in outdoor applications such as wall cladding and façade.

Drying of green veneer hollow tubes monitored using stereo digital images correlation

The present study is based on the patent FR3052379A1, which consists of rolling and gluing green veneers to form structural size hollow tubes. The objective was to study the drying behavior of circular hollow tubes and investigate the method of crack detection using image correlation from green conditions to equilibrium moisture content. The manufactured tubes are composed of six plies. Three different configurations of global grain angle orientations with respect to the tube longitudinal axis are used: {0, 0, 0}°, {10, 0, 10}°, and {− 10, 0, 10}°. Each grain angle was made up of two plies. The tubes deformation and crack formation due to drying shrinkage were measured using a stereo digital image correlation system. The stereo correlation is suitable for measuring tangential shrinkage and studying the opening and/or closing of cracks on the surface of the tubes subjected to internal moisture variations and blocked deformations. The influence of grain angle was discussed in this paper; however, due to the very few numbers of samples, no conclusive findings can be made.

Thermodynamic analysis and modeling of water vapor adsorption isotherms of roasted specialty coffee (Coffee arabica L. cv. Colombia)

The experimental assessment and computer modeling of the water vapor adsorption isotherms of roasted specialty coffee is addressed in this study. Thus, both coffee beans and ground coffee of medium (850 μm) and fine (600 μm) particle sizes were analyzed over a range of water activities of between 0.1 and 0.9 and at temperatures of 25, 35, and 45 °C. The adsorption isotherms were determined using the dynamic dew point (DDI) method. The computer modeling of adsorption isotherms was addressed in order to describe the influence of the water activity and temperature on the equilibrium moisture content. Furthermore, the hygroscopic capacity of roasted coffee was analyzed by differential thermodynamic analysis. Experimental results and modeling showed that the high level of moisture adsorption found in the ground coffee was related to a large adsorption area, suggesting that specialty coffee should preferably be stored as beans. The Peleg empirical model was the most suitable at representing both type III upward concave adsorption behavior and the effect of temperature on the adsorption isotherms. Differential thermodynamic analysis revealed an increase in the water adsorption energy at low equilibrium moisture content, while negative Gibbs free energy values revealed the spontaneity of the adsorption process.

Equilibrium moisture content map for Laos

Providing the equilibrium moisture content values for territories is important for avoiding major problems due to dimensional changes in wooden products. This study evaluated the average equilibrium moisture content values for twelve months (from 1981 to 2020) for Laos and produced an equilibrium moisture content map. A model was used to generate the equilibrium moisture content values based on temperature and relative humidity data obtained from the POWER Data Access Viewer v2.0.0. for 18 provinces (148 districts) based on the geographic coordinates of each district in Laos. The lowest equilibrium moisture content (12% to 13%) values were found in Vientiane Capital City, Vientiane province, Louangprabang, Bokeo, Attapeu, Louang Namtha, Oudomxay, Houaphan, Sayaburi, Savannakhet, Salavan, and Champasak province. The rest of the districts, which had an equilibrium moisture content ranging from 13% to 16%, were mostly found on the eastern part of Laos and a small part of Northern Laos. The monthly swinging average value of the equilibrium moisture content ranged from 10% to 18% across the country. The equilibrium moisture content values for each district in Laos were also defined.

KINETICS AND MATHEMATICAL MODELING OF THE DRYING PROCESS OF MACAÚBA ALMONDS

ABSTRACT The study of drying kinetics is fundamental for making the correct choice of time and temperature to be used in the drying process. In addition, mathematical modeling enables the simulation, optimization, sizing, and determination of the commercial application of the drying system. Therefore, the objective of this study was to investigate the kinetics and mathematical modeling of the drying process of macaúba almond [Acrocomia aculeata (Jacq.) Lodd. ex Mart] performed at different temperatures. For this purpose, the drying was performed under three different temperatures: 40 °C, 50 °C, and 60 °C. Four repetitions were performed for each temperature. The experimental data were fitted by nine different mathematical models. The choice of the best model was based on the following statistical parameters: magnitude of the adjusted coefficient of determination, magnitude of the mean relative error, and standard error of the estimate. It was observed that an increase in the drying temperature resulted in a reduction of drying time. The shortest drying time was observed in the treatment performed under 60 °C in which the almonds attained equilibrium moisture content at 34.08 h. The longest drying time was observed in the treatment performed under 40 °C, with the almonds attaining equilibrium moisture content at 404.40 h. Approximation of Diffusion, Midilli, Page, and Modified Page were the models that best described the drying process of macaúba almonds with the aim of subsidizing the design of industrial dryers.

Effect of maltodextrin weight fraction on the amorphous state and critical storage conditions of freeze‐dried juices

SummaryDiagrams relating to water activity (aw), equilibrium moisture content (Xw) and glass transition temperature (Tg) are valuable tools for predicting amorphous fruit powders' storage procedure and stability. Thus, Tg–aw–Xw diagrams were constructed to characterise the amorphous state and define the critical values of water content (Xwc) and water activity (awc) of freeze‐dried juices of strawberry, pineapple, kiwi and prickly pear prepared with maltodextrin at the dry mass fraction (WMD) of 0, 0.4 and 0.8. The Tg and sorption data were fitted with a polynomial equation and the Guggenheim–Anderson–de Boer (GAB) model respectively. A Tukey test was performed to evaluate the difference between critical values of the powders (P < 0.05). The awc and Xwc increase with WMD and depend on the chemical composition of the powders. The highest critical values were found in pineapple powders, ranging from 0.174 to 0.632 and 0.029 to 0.142 dry basis (d.b.), and the lowest ones in kiwi juice powders ranging from 0.029 to 0.550 and 0.013 to 0.129 (d.b.). For WMD of 0.8, however, regardless of juice composition, stable powders in an amorphous state were obtained up to an aw of 0.52 at 25°C.

Wood-water interactions of thermally modified, acetylated and melamine formaldehyde resin impregnated beech wood

Abstract The wood-water interactions of modified beech wood (Fagus sylvatica L.) were studied. Specimens were thermally modified at 180 (TM1), 200 (TM2) and 220 °C (TM3), acetylated (Acet), and melamine formaldehyde (MF) resin (Mel) modified. Afterwards, the water vapour characteristics, i.e. water vapour sorption isotherms, equilibrium moisture content (EMC), dimensional stability of specimens conditioned at 30, 65 and 90% RH and liquid water characteristics, i.e. water absorption, maximum moisture content (MC), leachability and swelling kinetics, were determined and the results compared with reference (Ref) specimens. From the results, it is evident that the scale of wood-water interactions was highly dependent on the thermal modification temperature and type of chemical modification. The water vapour isotherms of thermally modified wood decreased, whereas more severe treatment exhibited more distinct reduction. The EMC values of the Mel and TM1 specimens decreased only at high RH, whereas the most significant decrease, within the whole range of observation, was found in the Acet group. The maximum MC reduction was achieved by acetylation. As a consequence of swelling reduction, dimensional stability expressed as anti-swelling efficiency (ASE) was considerably improved. A relatively high initial linear-phase swelling rate was found for the Ref specimens, whereas modified wood exhibited comparatively slow and gradual swelling.

Evaluating isotherms and isosteric heat utilization during sorption characteristics of feed barley

A well-formulated sorption model defines the grain moisture and also the energy expenses associated with drying and/or rehydration. Though literature contains adsorption and desorption models that are used to identify the hysteresis, they are not efficient to implement in sensors simultaneously when monitoring stored grain transient conditions. This study modifies the existing sorption model to fit transient monitoring criteria based on harvest moisture conditions between 11.3 and 85.9% RH at three temperatures (15, 25 and 35 °C). Feed barley was taken for the sorption study and fitted with equilibrium moisture content (EMC) and equilibrium relative humidity (ERH) equations of five widely used isotherm models, respectively. Model was fitted with EMC's attained at individual temperatures and the transfer phases between them.Sorption isotherms showed a non-smooth Type II sigmoidal trend with positive correlation between RH and EMC. The time taken to reach EMC irrespective of RH was inversely proportional to the temperature difference noted from the transfer phase. The Modified-Oswin equation (EMC) was found to be appropriate to represent the sorption isotherm of feed barley. For the transfer phases, EMC at higher temperature showed negligible difference with initial EMC phase except at 15 °C with higher RH (adsorption). Heat of sorption showed a decreasing trend with moisture and was 27% (average) higher than the latent heat of vaporization. Sorption heats for transfer phases were higher than initial EMC phases but not significantly different. Energy difference went up to 250 kJ kg−1 between 9 and 14% db moisture showing a normal distribution below and above the moisture range, respectively. Thus, future storage models should consider sorption heats for proper estimation of energy expenses during drying and rehydration.

Effects of flexural configuration and thermal modification on the physical and flexural properties of makino bamboo (Phyllostachys makinoi)

ABSTRACT The effects of thermal modification and flexural configuration on the physical and flexural properties of makino bamboo (Phyllostachys makinoi) with various density ranges were investigated. The density and equilibrium moisture content (EMC) of bamboo significantly decreased with increasing treatment temperature from 140°C to 220°C. Simultaneously, the modulus of rupture (MOR) and ductility factor (DF) of thermally modified bamboo showed a declining trend. In the flexural test, loading on the outer side in tension (OT) and loading on the outer side in compression (OC) of the bamboo specimens were applied using different flexural configurations. The MOR of the nontreated OC specimen (MOROC) was higher than that of the nontreated OT specimen (MOROT), while the MOROC of the 220°C-treated specimen was lower than the MOROT. Additionally, the nontreated OT specimen showed a higher DF than the nontreated OC specimen. Despite the density range and flexural configuration, the DF of the thermally modified specimen decreased when the treatment temperature increased above 140°C. However, the modulus of elasticity exhibited no significant differences among all the specimens under different treatment temperatures and flexural configurations.