SciCombinator

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Concept: Drywall

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Uncontrolled excess moisture in buildings is a common problem that can lead to changes in fungal communities. In buildings, moisture parameters can be classified by location and include assessments of moisture in the air, at a surface, or within a material. These parameters are not equivalent in dynamic indoor environments, which makes moisture-induced fungal growth in buildings a complex occurrence. In order to determine the circumstances that lead to such growth, it is essential to have a thorough understanding of in situ moisture measurement, the influence of building factors on moisture parameters, and the levels of these moisture parameters that lead to indoor fungal growth. Currently, there are disagreements in the literature on this topic. A literature review was conducted specifically on moisture-induced fungal growth on gypsum drywall. This review revealed that there is no consistent measurement approach used to characterize moisture in laboratory and field studies, with relative humidity measurements being most common. Additionally, many studies identify a critical moisture value, below which fungal growth will not occur. The values defined by relative humidity encompassed the largest range, while those defined by moisture content exhibited the highest variation. Critical values defined by equilibrium relative humidity were most consistent, and this is likely due to equilibrium relative humidity being the most relevant moisture parameter to microbial growth, since it is a reasonable measure of moisture available at surfaces, where fungi often proliferate. Several sources concur that surface moisture, particularly liquid water, is the prominent factor influencing microbial changes and that moisture in the air and within a material are of lesser importance. However, even if surface moisture is assessed, a single critical moisture level to prevent fungal growth cannot be defined, due to a number of factors, including variations in fungal genera and/or species, temperature, and nutrient availability. Despite these complexities, meaningful measurements can still be made to inform fungal growth by making localised, long-term, and continuous measurements of surface moisture. Such an approach will capture variations in a material’s surface moisture, which could provide insight on a number of conditions that could lead to fungal proliferation.

Concepts: Fungus, Water, Measurement, Humidity, Relative humidity, Hygrometer, Gypsum, Drywall

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Due to the contamination of construction and demolition debris (CDD) by gypsum drywall, especially, its sand fraction (CDD sand, CDDS), the sulfate content in CDDS exceeds the posed limit of the maximum amount of sulfate present in building sand (1.73g sulfate per kg of sand for the Netherlands). Therefore, the CDDS cannot be reused for construction. The CDDS has to be washed in order to remove most of the impurities and to obtain the right sulfate content, thus generating a leachate, containing high sulfate and calcium concentrations. This study aimed at developing a biological sulfate reduction system for CDDS leachate treatment and compared three different reactor configurations for the sulfate reduction step: the upflow anaerobic sludge blanket (UASB) reactor, inverse fluidized bed (IFB) reactor and gas lift anaerobic membrane bioreactor (GL-AnMBR). This investigation demonstrated that all three systems can be applied for the treatment of CDDS leachate. The highest sulfate removal efficiency of 75-85% was achieved at a hydraulic retention time (HRT) of 15.5h. A high calcium concentration up to 1000mgL(-1) did not give any adverse effect on the sulfate removal efficiency of the IFB and GL-AnMBR systems.

Concepts: Electrochemistry, Concentration, Anaerobic digestion, Fluidized bed, Gypsum, Plaster, Calcium sulfate, Drywall

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A 30-year-old right hand male with a history of schizophrenia presented with two self-inflicted drywall screws in the skull. The patient was sleepy but easily arousable with blood tests showing he had taken methamphetamines. Computed Tomography (CT) and Computed Tomography angiography (CTA) of the head showed the frontal screw abutted left of the superior sagittal sinus while the posterior screw went through the superior sagittal sinus with no extravasation of contrast at either site. Both screws were removed with exposure of the sagittal sinus using “U” shape craniectomies. There was no bleeding on the removal of the screws. It appears the posterior screw entered between the leaflets of the sagittal sinus dura. The patient in follow-up 1 month later had returned to work without any sequellae to his injuries.

Concepts: Blood, Medical imaging, Radiography, Computed tomography angiography, Skull, Wall, Drywall, Falx cerebri

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In this study, we evaluated the long-term antifungal effectiveness of 3 types of interior building materials (gypsum board (GB), cement board (CB) and softwood plywood (S-PW)) impregnated with thermally reduced silver nanoparticles supported by titanium dioxide (AgNPs/TiO2 ) under 95% relative humidity for four weeks. AgNPs/TiO2 was synthesized at two thermal reduction temperatures (TRTs, 120 and 200°C) with two different AgNP weight percentages (2 and 5 wt%). Four different silver loading levels (SLLs, 0.025, 0.05, and 0.5 μg/cm2 and the critical concentration required to inhibit fungal growth on agar plates) and three fungal species (A. niger, P. spinulosum and S. chartarum) were used in the experiments. Higher temperature reduced more ionic Ag+ to metallic Ag0 and increased the dispersion of Ag on TiO2 surface. The 200°C thermally reduced AgNPs/TiO2 demonstrated excellent antifungal efficiency: mold growth was almost completely inhibited for 28 days at the low SLL of 0.5 μg/cm2 . Additionally, AgNPs/TiO2 exhibited higher antifungal activity on GB and CB than on S-PW. The stepwise regression results indicated that the TRT of AgNPs/TiO2 (β =-0.739–0.51), the SLL (β =-0.477–0.269), and the Ag0 level in the AgNPs (β=-0.379–0.136) were the major factors influencing antifungal activity and TRT might be the most significant one. This article is protected by copyright. All rights reserved.

Concepts: Fungus, Titanium dioxide, Relative humidity, Titanium, Pigment, All rights reserved, Copyright, Drywall

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A facile method to transform flue gas desulfurization gypsum (FGD gypsum) to α- calcium sulfate hemihydrate (α-HH) whiskers with high aspect ratios mediated by cetyltrimethylammonium bromide (CTAB) and KCl in glycerol-water solutions was studied. Addition of KCl facilitated the dissolution of calcium sulfate dihydrate (DH) and created a much higher supersaturation, which could come into being a larger driving force for the phase transformation from DH to α-HH. CTAB as the crystal modifier can significantly promoted 1-D growth of α-HH whiskers along the c axis and the presence of 0.25% CTAB (by weight of FGD gypsum) resulted in the increase of the average aspect ratio of α-HH whiskers from 28.9 to 188.4, which might be attributed to the preferential adsorption of C16H33(CH3)3N(+) on the negative side facets of α-HH crystal.

Concepts: Calcium, Ratio, Sulfur, Aspect ratio, Ratios, Gypsum, Calcium sulfate, Drywall

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The effects of sulfide levels on arsenic leaching and speciation were investigated using leachate generated from laboratory-scale construction and demolition (C&D) debris landfills, which were simulated lysimeters containing various percentages of gypsum drywall. The drywall percentages in lysimeters were 0, 1, 6, and 12.4wt% (weight percent) respectively. With the exception of a control lysimeter that contained 12.4wt% of drywall, each lysimeter contained chromated copper arsenate (CCA) treated wood, which accounts for 10wt% of the C&D waste. During the period of study, lysimeters were mostly under anaerobic conditions. Leachate analysis results showed that sulfide levels increased as the percentage of drywall increased in landfills, but arsenic concentrations in leachate were not linearly correlated with sulfide levels. Instead, the arsenic concentrations decreased as sulfide increased up to approximately 1000μg/L, but had an increase with further increase in sulfide levels, forming a V-shape on the arsenic vs. sulfide plot. The analysis of arsenic speciation in leachate showed different species distribution as sulfide levels changed; the fraction of arsenite (As(III)) increased as the sulfide level increased, and thioarsenate anions (As(V)) were detected when the sulfide level further increased (>10(4)μg/L). The formation of insoluble arsenic sulfide minerals at a lower range of sulfide and soluble thioarsenic anionic species at a higher range of sulfide likely contributed to the decreasing and increasing trend of arsenic leaching.

Concepts: Concentration, Solution, Wood preservation, Arsenic, Parts-per notation, Gypsum, Drywall, Chromated copper arsenate

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Recently, gypsum drywall products imported to the United States (US) were found to cause metal corrosion and tarnishing in some homes, often necessitating that this drywall be discarded. Research assessed the potential implications of recycling and landfilling corrosive/imported drywall. Samples of corrosive drywall were collected from homes in Florida, US and these characteristics were assessed relative to domestically-produced drywall purchased from retail outlets. The total and synthetic precipitation leaching procedure (SPLP) leachable heavy metal concentrations were measured and compared to risk-based regulatory thresholds to assess the possible land application risk. In a majority of samples, concentrations were below levels of regulatory concern. The mean concentration of several elements exceeded the thresholds in a few samples for the direct exposure assessment (As) and the groundwater leaching assessment (Al, B, Hg, Mn, Sr and V); but the results did not suggest that corrosive drywall would present a greater risk than domestic drywall. To assess landfilling concerns, the potential for sulfur gases emissions upon disposal was evaluated. Experiments indicated that corrosive drywall would not pose a greater risk of long-term H2S emissions compared to domestic drywall.

Concepts: United States, Assessment, United Kingdom, Heavy metal music, Corrosion, Gypsum, Calcium sulfate, Drywall

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Fungal growth in indoor environments is associated with many negative health effects. Many studies focus on brown- and white-rot fungi and their effect on wood, but there is none that reveals the influence of soft-rot fungi, such as Stachybotrys spp. and Chaetomium spp., on the structure of building materials such as plywood and gypsum wallboard. This study focuses on using micro-computed tomography (microCT) to investigate changes of the structure of plywood and gypsum wallboard during fungal degradation by S. chartarum and C. globosum. Changes in the materials as a result of dampness and fungal growth were determined by measuring porosity and pore shape via microCT. The results show that the composition of the building material influenced the level of penetration by fungi as shown by scanning electron microscopy (SEM). Plywood appeared to be the most affected, with the penetration of moisture and fungi throughout the whole thickness of the sample. Conversely, fungi grew only on the top cardboard in the gypsum wallboard and they did not have significant influence on the gypsum wallboard structure. The majority of the observed changes in gypsum wallboard occurred due to moisture. This paper suggests that the mycelium distribution within building materials and the structural changes, caused by dampness and fungal growth, depend on the type of the material.

Concepts: Fungus, Mycorrhiza, Scanning electron microscope, Mushroom, Stachybotrys, Building materials, Gypsum, Drywall

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Starting in the 1940s, gypsum drywall began replacing plaster and lathe in the U.S. home construction industry. Our goal was to evaluate whether some mold populations differ in water- damaged homes primarily constructed with gypsum drywall compared to plaster. The dust samples from the 2006 Department of Housing and Urban Development’s (HUD) American Health Homes Survey (AHHS) were the subject of this analysis. The concentrations of the 36 Environmental Relative Moldiness Index (ERMI) molds were compared in homes of different ages. The homes (n=301) were built between 1878 and 2005. Homes with ERMI values >5 (n=126) were defined as water-damaged. Homes with ERMI values >5 were divided in the years 1976 to 1977 into two groups, i.e., older (n=61) and newer (n=65). Newer water-damaged homes had significantly (p=0.002) higher mean ERMI values than older water-damaged homes, 11.18 and 8.86, respectively. The Group 1 molds Aspergillus flavus, Ammophilus fumigatus, Aspergillus ochraceus, Cladosporium sphaerospermum and Trichoderma viride were found in significantly higher concentrations in newer compared to older high-ERMI homes. Some mold populations in water-damaged homes may have changed after the introduction of gypsum drywall.

Concepts: Aspergillus flavus, Aspergillus, Ascomycota, Mold, Gypsum, Plaster, Cladosporium, Drywall

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Plastering is one of the most ancient of the building handicrafts. Plaster is the common name for calcium sulphate hemi hydrate made by heating the mineral gypsum, the common name for sulphate of lime. In the tenth century the Arabs used liquid plaster in orthopaedic treatment. At the beginning of the nineteenth century, patients with fractures of the lower extremities-and often of the upper extremities as well-were treated in bed with restriction of all activity for many weeks until the fractures united. It was the practice of surgeons to dress wounds and fractures at frequent intervals. The bandages, pads, and splints were removed, the fractures manipulated, and the dressings reapplied. The search for simpler, less cumbersome methods of treatment led to the development of occlusive dressings, stiffened at first with starch and later with plaster of Paris. The ambulatory treatment of fractures was the direct result of these innovations. Two military surgeons, Antonius Mathijsen of the Netherlands, and Nikolai Ivanovitch Pirogov of Russia, were responsible for the introduction of the new plaster bandage technique. At the beginning of the twentieth century the technique was improved by Jean-François Calot, a French surgeon, who invented the hand manufacture of plaster bandage as a roll. During the twentieth century, walking cast and ambulation for fresh fractures were developed with plaster and pin incorporated in plaster; the open fracture care concept was introduced with plaster of Paris by Trueta before the external fixation.

Concepts: Bone, Bone fracture, Orthopedic surgery, Distraction osteogenesis, Gypsum, Plaster, Stucco, Drywall