Residual Moisture Content Research Articles

Measurement and approximate critical path analysis of the pore‐scale‐induced anisotropy factor of an unsaturated porous medium

Nonspherical particles aligned parallel to preferential bedding planes form sedimentary rocks and soils, which are anisotropic in their resistance to flow of fluids, solutes, heat, and electrical current at the microscopic scale. Understanding the extent of the anisotropy of an unsaturated medium, containing both water and air, and its quantification is of major importance for improving our prediction capability of pollutant transport occurring in those media. The anisotropy factor is defined as the ratio of the conductivities parallel to the bedding plane and perpendicular to it. Measurements of the anisotropy factor of the apparent electrical conductivity in initially saturated packings of platy mica particles resulted in an initial moderate increase of the anisotropy factor with desaturation, followed by its decrease when approaching the drier region of residual moisture contents. The anisotropy factor for the hydraulic conductivity is expected to follow a pattern similar to that found for the apparent electrical conductivity. This behavior is opposite to that predicted by previous theoretical models, which suggest a possible initial decrease of the anisotropy factor of the hydraulic conductivity with desaturation, followed by its divergence to infinity toward the dry end. A critical path analysis of a simplified three‐dimensional pore network model, based on different characterization of the pores parallel and normal to the bedding plane, served to evaluate the saturation degree‐dependent anisotropy factors. The critical path analysis reconstructed the experimentally determined pattern qualitatively and helped to explain the observed dependence of the apparent electrical conductivity's anisotropy factor on saturation degree. The critical path analysis also provided an indication of the anisotropy factor for hydraulic conductivity, which is expected to be of higher magnitude than that of the apparent electrical conductivity.

A re-examination of modeled and measured soil moisture spatial variability and its implications for land surface modeling

Using a spatially distributed water and energy balance model, we investigate the spatial structure of surface fluxes and states for the Washita '92 field experiment and the August campaign of the Washita '94 field experiments. For Washita '92, the model is validated against gravimetric and remotely sensed soil moisture, and for Washita '94, the model is validated against gravimetric soil moisture and measured energy fluxes. The model is shown to reasonably represent land–atmosphere interactions during the experimental periods. Scaling analysis of remotely sensed and modeled soil moisture and modeled latent heat flux is indicative of multiscaling behavior. The temporal behavior of the soil moisture scaling exponents for various moments suggests the existence of three distinct regimes during a dry-down. The multiscaling behavior inferred from simulated soil moisture and latent heat flux is hypothesized as a relationship which is a function of average soil moisture. Similar scaling analysis of important land surface properties indicates simple scaling for porosity, field capacity and wilting point, and multiscaling for residual soil moisture, leaf area index and the soils-topographic index. This is consistent with model results, which indicate a transition from simple scaling to multiscaling with dry-down. It is hypothesized that this transition is governed by the scaling properties which in wet conditions control infiltration (porosity, field capacity, leaf area index) to properties which in dry conditions control drainage (residual moisture content and soils-topographic index) and evaporation (wilting point, leaf area index). Land surface models which fail to incorporate these features will most likely be unable to capture the dynamic nature of soil moisture spatial variability.

Effect of tillage and field condition on soil physical properties, cane and sugar yields in Vertisols of Kenana Sugar Estate, Sudan

An experiment was conducted to study the effect of heavy disc harrowing in combination with chisel ploughing to depths of 10, 20, and 30 cm, on soil physical properties, cane yield, and sugar yield. The experiment was executed in two non-fallow, two semi-fallow and one fallow field conditions, in Kenana Sugar Estate, Sudan. Results showed that the final surfaces for all tillage treatments were clean and smooth. Percent residue cover ranged from 4.2 to 5.4. After seedbed preparation percent clods greater than 1 cm in diameter ranged from 31.1 to 35.8, while gravimetric moisture content in the tillage zone ranged from 29.9 to 30.5. No significant differences were observed between treatments in residue cover, clod size and moisture content. Soil penetration resistance in the five sites measured after the last irrigation showed no significant differences. Cone index ranged from 802 to 934 kPa. Bulk density measurements also showed no significant differences between tillage treatments. Yield data showed that chisel ploughing to depths of 20 and 30 cm before disc harrowing, significantly increased cane and sugar yields than conventional tillage at Kenana. The highest field productivity (105.27 Mg ha −1) was obtained with the combined disc harrowing and 20 cm chisel ploughing. Yield of cane per hectare under this method was 8.38 Mg ha −1 higher than that under the conventional method. Sugar yield per hectare increased by 1 metric ton, which was 8.6% higher than that of the conventional method. The relation between tillage depth ( x) and cane yield ( Y), in tons of cane per hectare, for average Kenana field condition could be expressed by the third-order polynomial: Y=158.141−7.725x+0.293x 2−0.003x 3 The fallow, semi-fallow and non-fallow sites were not significantly different in cane yield. All tillage methods studied were more intensive than adequate levels for soil conservation practices found in the reviewed literature; it is suggested to omit the re-harrowing operation of Kenana conventional tillage.

One-Dimensional Soil Moisture Profile Retrieval by Assimilation of Near-Surface Measurements: A Simplified Soil Moisture Model and Field Application

The Kalman filter assimilation technique is applied to a simplified soil moisture model for retrieval of the soil moisture profile from near-surface soil moisture measurements. First, the simplified soil moisture model is developed, based on an approximation to the Buckingham‐Darcy equation. This model is then used in a 12month one-dimensional field application, with updating at 1-, 5-, 10-, and 20-day intervals. The data used are for the Nerrigundah field site, New South Wales, Australia. This study has identified (i) the importance of knowing the depth over which the near-surface soil moisture measurements are representative (i.e., observation depth), (ii) soil porosity and residual soil moisture content as the most important soil parameters for correct retrieval of the soil moisture profile, (iii) the importance of a soil moisture model that represents the dominant soil physical processes correctly, and (iv) an appropriate forecasting model as far more important than the temporal resolution of near-surface soil moisture measurements. Although the soil moisture model developed here is a good approximation to the Richards equation, it requires a root water uptake term or calibration to an extreme drying event to model extremely dry periods at the field site correctly.

Development of a Lyophilized Formulation for (R,R)-Formoterol (L)-Tartrate

(R,R)-formoterol is a β-agonist for inhalation. Aqueous instability suggested the need for a reconstitutable lyophilized dosage form. The objective of these studies was to devise a stable, rapid-dissolving, therapeutically compatible dosage form. The effects of diluents and residual moisture on the stability of thermally stressed formoterol formulations were investigated. Drug and various excipients (acetate, lactose, and mannitol) were lyophilized and placed in humidity chambers (0 to 90% relative humidity) at 25 to 50°C. Stability was characterized by time-dependent changes using HPLC, pH, and XRD. Residual moistures were determined by Karl Fisher methods. Regression models were developed to quantify the effects of formulation and environmental variation on drug stability. Solid-state instability was observed as a function of high residual moisture and diluent type. Although the residual moistures in mannitol formulations were typically below 1%, the degradation rate (50°C) varied from 2 to 10 mcg/day, which was 1.3- to 20-fold high than observed for lactose formulations under the same relative humidity conditions. At high relative humidity, the presence of acetate significantly increased the degradation rate (p < 0.04). The critical residual moisture content for lactose formulations was 3%. The amount of lactose was optimized by evaluating the degradation over the temperature range 25 to 50°C. Mannitol and acetate were shown to be unsuitable excipients, and an optimal lactose amount was 50 mg for vials containing 50 mcg of drug.

ChemInform Abstract: Solid-State Chemistry of a Novel Carbapenem with a Releasable Sidechain.

Abstract The solid-state chemistry of amorphous and crystalline forms of a novel cationic 1-β-methyl carbapenem antibiotic 2 is described. The lyophilized chloride salt of 2 ( 2 ·Cl) is amorphous and exhibits moisture-dependent β-lactam hydrolysis rates. Hydrolysis is concomitant with ejection of the sidechain naphthosultam moiety 4 . In the lyophilized solid (with 1.8% w/w water or less), a significant contribution from a Hofmann-like elimination reaction within the sidechain structure to give products 6 and 7 is observed. Another less significant elimination pathway involving loss of acetamide from the sidechain to form 8 is also operating at low residual moisture contents. Co-lyophilization of 2 ·Cl with sucrose decreases the rate of the reactions within the sidechain as well as β-lactam hydrolysis, concomitant with a slight increase in the strength of the glassy lyophilized product based on modulated differential scanning calorimetry (MDSC). Kinetics of degradation of 2 ·Cl lyophilized in the presence of 1% trisodium citrate and 50% weight of sucrose showed a 30–40% increase in overall initial rate of degradation at 25 and 40°C with increasing moisture from 0.3 to 1.1% residual water. Moisture enhances the stability of the N , N ′-dialkyl 1,4-diaza[2.2.2]bicyclooctane (DABCO) sidechain structure in 2 ·Cl, and this protective effect slightly offsets the increase in hydrolysis rate observed with increasing moisture. The crystalline benzenesulfonate trihydrate ( 2 ·PhSO 3 ) was characterized and found to have improved thermal stability in the solid state relative to the amorphous 2 ·Cl, particularly in terms of the elimination pathway.

Solid-State Chemistry of a Novel Carbapenem with a Releasable Sidechain

The solid-state chemistry of amorphous and crystalline forms of a novel cationic 1-β-methyl carbapenem antibiotic 2 is described. The lyophilized chloride salt of 2 (2·Cl) is amorphous and exhibits moisture-dependent β-lactam hydrolysis rates. Hydrolysis is concomitant with ejection of the sidechain naphthosultam moiety 4. In the lyophilized solid (with 1.8% w/w water or less), a significant contribution from a Hofmann-like elimination reaction within the sidechain structure to give products 6 and 7 is observed. Another less significant elimination pathway involving loss of acetamide from the sidechain to form 8 is also operating at low residual moisture contents. Co-lyophilization of 2·Cl with sucrose decreases the rate of the reactions within the sidechain as well as β-lactam hydrolysis, concomitant with a slight increase in the strength of the glassy lyophilized product based on modulated differential scanning calorimetry (MDSC). Kinetics of degradation of 2·Cl lyophilized in the presence of 1% trisodium citrate and 50% weight of sucrose showed a 30–40% increase in overall initial rate of degradation at 25 and 40°C with increasing moisture from 0.3 to 1.1% residual water. Moisture enhances the stability of the N,N′-dialkyl 1,4-diaza[2.2.2]bicyclooctane (DABCO) sidechain structure in 2·Cl, and this protective effect slightly offsets the increase in hydrolysis rate observed with increasing moisture. The crystalline benzenesulfonate trihydrate (2·PhSO3) was characterized and found to have improved thermal stability in the solid state relative to the amorphous 2·Cl, particularly in terms of the elimination pathway.

Model for Moisture-Content Evolution in Porous Building Elements with Hygro-Thermal Bridges and Air-Voids

Addressing the effects of moisture movement and residual moisture-con tents is becoming a recognized part of performance-based design of buildings. However, the multi-directional moisture-movement and subsequent moisture-content evolution in most common building elements with hygro-thermal bridges, without or with air-voids, has yet not been investigated. An integral presentation was utilized to establish the coupled heat and mass transfer field equations for these cases, and for their reduction to a discrete set of alge braic equations. An interactive converging numerical process solves the implicit set of alge braic non-linear equations. Results address some examples for verification of the computational procedure, and a symmetric drying process of an autoclaved-aerated- concrete block-wall with cementitious-mortar joints and renderings, with and without air- voids.

Effect of Moisture Absorption on Hot/Wet Compressive Strength of T800HIPMR-15 Carbon/Polyimide

The objective of this study is to statistically investigate the effect of moisture absorption on the hot/wet compressive strength of a T800H/PMR-15 carbon/polyimide composite with a quasi-isotropic stacking sequence. Compression tests on the moisture absorbed specimens were conducted at 260'C. These tests clarified the compression fracture mode, the effect of moisture absorption on hot/wet compressive strength, statistical properties and a design allowable of hot/wet compressive strength, the effectiveness of a traveler coupon to monitor moisture absorption, and the relationship between specimen thickness and hot/wet compressive strength. Important results are as follows: (1) hot/wet compressive strength was closely related with the residual moisture content measured immediately after the test, and (2) the coefficient of variation of hot/wet compressive strength was approximately twice as large as that of room temperature/dry compressive strength.

Stability and surface activity of lactate dehydrogenase in spray‐dried trehalose

The stability of the model protein lactate dehydrogenase (LDH) during spray‐drying and also on subsequent dry storage was examined. Trehalose was used as a carrier. The spray‐drying temperatures Tinlet and Toutlet have a measurable effect on LDH inactivation. Low Tinlet produced the least process inactivation, but gave a high residual moisture content making the protein's storage stability poor. High Tinlet reduced residual moisture and improved storage stability, but at the cost of high process inactivation. As already found for other systems, addition of a surfactant (in this case polysorbate 80) could ameliorate process inactivation of LDH at Tinlet = 150 °C. Surfactant had, however, a deleterious effect on storage stability of LDH, the vital factor being the molar ratio of surfactant/protein in the dried product. By using electron spectroscopy it was shown that LDH has a 10 times higher surface concentration in the dried trehalose particles than expected for a homogeneous distribution. Surface tension measurements at the water/air interface proved that LDH is surface active, although the Gibbs equation appeared to be inapplicable. Calculations of spray‐droplet formation time and drying time indicate than the extent of diffusion‐driven LDH adsorption to the liquid/air interface is sufficient to account for the measured amount of LDH inactivation during spray‐drying. The presence of 0.1% polysorbate 80 to the spray solution prevents LDH from appearing at the surface of the dried particles. As a negative control, the phosphatide Lipoid E 80 does not prevent the appearance of LDH in the surface according to electron spectroscopy and does not therefore prevent LDH inactivation during spray‐drying at Tinlet = 150 °C.

Effect of Moisture Profile and Noncombustible Matter in Recycled Paper-Mill Sludge on Energy Recovery

Calorific values of solid sludge obtained from paper recycling mill rejects were estimated by first drying the sludge in a pilot scale rotary dryer and then determining the heal of combustion of these sludge samples. Sludge samples with varying moisture and inorganic contents were studied. Study revealed that a net thermal energy saving was possible by optimizing final moisture content of sludge before combustion. Sludge containing high amount of inorganic components needs to be dried to a final moisture content sufficient enough to ensure a net energy saving after drying and combustion. Thus, high inorganic containing sludge samples from a fine paper recycling mill generated significantly less energy compared to that of a deinking mill sludge which was more rich in fiber content. Although the presence of inorganic components, decomposable fillers in particular, and moisture in sludge negatively influenced the energy recovery, a net gain in the thermal energy was obtainable from all the three studied sludge compositions by optimizing the residual moisture content during drying of the wet sludge.

The use of near-infrared spectroscopy in the efficient prediction of a specification for the residual moisture content of a freeze-dried product

The purpose of this study is to improve the efficiency in the search for a suitable specification for the residual moisture content in a freeze-dried product. A near-infrared spectroscopic (NIRS) method was developed for the measurement of the residual moisture content. Samples with a wide range of residual moisture contents were stored for two months at 8, 50, and 60°C. Because of the non-destructive character of the NIRS method initially the residual moisture content and, subsequently, the content of the active ingredient could be measured in the same sample vials after storage. Plots of the residual moisture content against the content of the active ingredient were made for storage at 50 and 60°C. For this only 69 samples were needed in the stability study for the assay determination while traditionally a five-fold of samples is needed because of the high intra-batch variability of the residual moisture content. The plots at 50 and 60°C were combined with the Arrhenius relationship between degradation rate constant and temperature. The maximal allowable residual moisture content was calculated for product shelf-lives of 2 and 3 years and storage temperatures of 20, 25, and 30°C, respectively.

Determination of Adequate Moisture Content for Efficient Dry-Heat Viral Inactivation in Lyophilized Factor VIII by Loss on Drying and by Near Infrared Spectroscopy

A requirement for a minimal threshold level of moisture in order for efficient virus inactivation to occur during dry heat treatment of freeze-dried coagulation factor concentrates is described.Techniques used to determine moisture content during heating were Loss on Drying and Karl Fischer. The Loss on Drying was suspected to have occasional errors as a result of sample preparation being influenced by interference from atmospheric moisture. Therefore, a non-invasive, non-destructive method for determination of residual moisture content using near infrared spectrometry (NIR) was developed for freeze-dried antihaemophilic factor (AHF). Calibration equations were determined againts Loss on Drying and Karl Fischer assay methods and these equations evaluated for the predictive efficiency. Both Loss on Drying and NIR were used to evaluate the effect of moisture content on the efficiency of virus inactivation by dry heat at 80°C. A minimum level of moisture of greater than 0.7%, as determined by Loss on Drying, was necessary for a virus reduction in the magnitude of 4 log10for hepatitis A virus, porcine parvovirus and pseudorabies virus.

Outgassing Behavior of Organic Spin-on-Glass Modified by Ion Implantation

The difficulty in the use of spin-on-glass (SOG) for multilevel interconnections leads to the requirement of higher-temperature (800–850°C) curing of the material, since the low-temperature annealed SOG may result in a significant amount of moisture during subsequent heat cycles leading to reliability problems. However, the application of an ion implantation method can improve the outgassing behavior of SOG annealed at 425°C. The temperature of the ion implantation treatment is made lower so as to be compatible with aluminum which is used as the conductive material. Ion implantation treatment using P+ (phosphorous) and As+ (arsenic) which are applied to the siloxane-type SOG is proposed in this paper. The thermal desorption analysis from experiments shows that the implanted SOG has a much lower water content and does not have a moisture desorption peak up to 600°C for both P+ and As+ implantations. The combination of the thermal curing and ion implantation treatments is beneficial for reducing the residual moisture content and promoting the thermal stability of SOG films. In addition, the results show that the implanted SOG is more insensitive to moisture absorption than the unimplanted SOG under the condition of 48-h air exposure. This implies that both water reabsorption and desorption performances of SOG can be further improved by ion implantation.

Effect of spray drying and subsequent processing conditions on residual moisture content and physical/biochemical stability of protein inhalation powders.

To understand the effect of spray drying and powder processing environments on the residual moisture content and aerosol performance of inhalation protein powders. Also, the long-term effect of storage conditions on the powder's physical and biochemical stability was presented. Excipient-free as well as mannitol-formulated powders of a humanized monoclonal antibody (anti-IgE) and recombinant human deoxyribonuclease (rhDNase) were prepared using a Buchi 190 model spray dryer. Residual moisture content and moisture uptake behavior of the powder were measured using thermal gravimetric analysis and gravimetric moisture sorption isotherm, respectively. Protein aggregation, the primary degradation product observed upon storage, was determined by size-exclusion HPLC. Aerosol performance of the dry powders was evaluated after blending with lactose carriers using a multi-stage liquid impinger (MSLI). Spray-dried powders with a moisture level (approximately 3%) equivalent to the freeze-dried materials could only be achieved using high-temperature spray-drying conditions, which were not favorable to large-male manufacturing, or subsequent vacuum drying. These dry powders would equilibrate with the subsequent processing and storage environments regardless of the manufacturing condition. As long as the relative humidity of air during processing and storage was lower than 50%, powders maintained their aerosol performance (fine particle fraction). However, powders stored under drier conditions exhibited better long-term protein biochemical stability. Manufacturing, powder processing, and storage environments affected powder's residual moisture level in a reversible fashion. Therefore, the storage condition determined powder's overall stability, but residual moisture had a greater impact on protein chemical stability than on powder physical stability.

非水系バインダーによるスプレー造粒粉を用いたＮｄ‐Ｆｅ‐Ｂ焼結磁石の磁気特性

Nd-Fe-B alloy powder was granulated by a spray drying method using an organic binder in order to improve the powder flowability during feeding and compacting. In this experiment, the organic binder consisted of poly(methyl methacrylate) (PMMA) and di-n-butyl phthalate, and 1, 4-dioxane as a solvent was used in granulating process, to suppress the residual moisture content in granulated powders and the reaction of alloy powders with its moisture, which result in marked degradation in powder characteristics and magnetic characteristics, respectively. By increasing the additional polymer content, powder characteristics were improved. However in comparison with the case of aqueous binder consisted of poly(vinyl alcohol) (PVA) and plasticizer, powder characteristics lowered slightly because of lower tensile strength of PMMA than PVA. In the case of PMMA the residual moisture contents in granulated powders were much smaller than those of PVA, independently of additional polymer content. The residual oxygen contents of green bodies after debinding were also smaller than those obtained using PVA. By using PMMA the magnetic characteristics (remanences and maximum energy product) of sintered magnets were improved remarkably, as compared with those of PVA. These facts mean that the high magnetic characteristics would be caused by both using low tensile strength polymer and restraining oxidation reaction of alloy powders.

Fracture strength of Type IV and Type V die stone as a function of time

Statement of problem. During the removal of casts from the impression there is the risk of stone fracture. Purpose. This study evaluated the fracture resistance of four die stone materials at different time intervals. Material and methods. Additional silicone impressions were made of a maxillary master cast. Two Type V, one Type IV die stones and one Type IV resin reinforced stone were tested. A total of 80 casts were prepared, separated, and tested on the Instron Universal Testing Machine at½, 1, 12, and 24 hours to measure resistance to fracture. Results. Significant differences to fracture resistance of the different die stone materials were observed at all time intervals except at 24 hours. The data were analyzed with ANOVA at α = 0.005 and n = 5. Conclusion. It is recommended to wait at least 12 to 24 hours when separating casts from impressions to avoid fracturing casts. Residual moisture content in a stone cast may contribute to fracture. (J Prosthet Dent 1997;78:554-9.)

Film‐coated Tablets of Ginseng Extract: Effect of Some Properties on Tablet Quality

The process of film-coating tablets of ginseng extract from the root of Panax ginseng (C. A. Meyer) in fluidized beds was investigated. The composition of film-coatings, based on an aqueous solution of methylcellulose, was considered, and the best coating included substrates shellac and polysorbate 80. The effects of temperature, residual moisture content and quantity of extract on the volume of tablets containing hygroscopic vegetable extracts was investigated. The hygroscopic moisture distribution in ginseng extract and ginseng extract tablets was also determined. It was established that hygroscopicity is determined mainly by polymolecular adsorption and capillary moisture. The optimum conditions for film-coating ginseng extract tablets in a fluidized bed were 60°C at a rate of 2.2 g min−1 using substrates shellac and polysorbate 80.

The Effect of Flocculants and Surfactants on the Filtration Dewatering of Iron Ore Fines

The filtration and separation characteristics of iron ore fines have been investigated. The experimental work included: characterization, evaluation of suitable flocculants to enhance settling and dewatering rate, determination of optimum dosages of flocculants, and influence of surfactants on nitration dewatering of both flocculated and unflocculated iron ore fines by vacuum filtration. The results showed that 1) the settling rate can be enhanced many-fold (from 2.52 to 90 m/h) by a suitable flocculant, 2) the residual filter cake moisture content can be reduced from 18.2% without reagents to 12.6% with suitable surfactant dewatering aids while the filtration rate can be enhanced from 4.8 to 97.2 L/h with suitable dewatering filter aids, and 3) the specific cake resistance to filtration can be brought down from 8.6 × 109 to 1.0 × 109 m/kg by using a surfactant sodium petroleum sulfonate at a concentration of 1.47 × 10−3 kg/t. The economics of using flocculant filter aids and surfactant dewatering aids before thermal drying is described and discussed.

Residual Moisture Content as Related to Collapse of Freeze‐dried Sugar Matrices

ABSTRACTAmorphous sugars were prepared by freeze‐drying 20% (w/w) aqueous solutions of lactose, sucrose, trehalose and maltose. The dried samples were further dehydrated over P2O5 for 1 wk at 25, 35 or 45°C, and the residual moisture content was determined using oven drying or a thermogravimetric balance. Results indicated a small amount of residual moisture (usually 1–2%) which was not removed by the desiccation treatment for 1 wk at 25°C over P2O5. The dried samples, heated at a temperature near the published “anhydrous” glass transition temperatures (Tg) exhibited different behavior depending on whether they were heated in open or sealed vials. Structural collapse, a sharply visible shrinkage of the matrix, was found in all samples in sealed vials, while those samples in open vials did not collapse. Thus, removal of the last amount of residual moisture by heating in uncovered vials increased Tg, preventing or delaying collapse.