Effect of Cement/Wood Ratio on Bending Properties of Cement-Bonded Southern Pine Excelsior Board

The price of southern pine excelsior is much higher than that of Portland cement on the weight basis. This study was undertaken to investigate the possibility of using more cement and less excelsior in order to reduce the manufacturing cost of cement excelsior board (CEB). The experimental boards were made at three cement/wood (oven-dry weight basis) ratios: 2.0/1, 2.3/1, and 2.6/1. The results indicated that the bending properties of CEB made at these cement/wood ratios met the requirements of commercial standards. However, the increase of cement/wood ratio above 2.0/1 had an adverse effect on bending properties of CEB

Effect of CCA-Treating and Air-Drying on the Properties of Southern Pine Lumber and Plywood

Matched samples of southern pine lumber and plywood were treated with CCA-preservative and then air-dried. When conditioned at the same relative humidity and temperature, the treated lumber and plywood had significantly higher moisture content than untreated samples. The CCA-treating and air-drying did not affect the bending and shear properties of lumber when retention level was 0.6 PCF. Compressive strength of treated lumber was reduced by 9% and it was attributed to the higher EMC associated with treated lumber. Bending and glueline properties of treated plywood were reduced by about 10% because of the increased EMC of treated material

Unsteady-State Diffusion of Moisture In Giant Timber Bamboo (Phyllostachys Bambusoides Sieb. & Zucc.)

This paper presents the results of a study to determine the rate of moisture movement in giant timber bamboo (Phyllostachys bambusoides Sieb. & Zucc.) when exposed to three different temperatures (20 C, 30 C, and 40 C) at two ranges of moisture content (0 to 7.5%, and 7.5 to 15%). Edge-coated samples measuring 6 mm (R) x 30 mm (T) x 150 mm (L) were exposed to a given temperature-humidity combination in a conditioning chamber. The weight of a sample was continuously monitored over time and the weight-time data were analyzed using the Boltzmann solution to the unsteady-state form of Fick's diffusion equation.Diffusion coefficients ranged from 7.3 x 10~12 to 7.8 x 10~11 m2/sec. They were greater at the higher moisture content range. They increased with temperature such that the Arrhenius equation fits the data well, giving mean activation energies of 39,875 and 35,889 J/mole for the lower and higher moisture ranges, respectively. The calculated diffusion coefficient was approximately twice as high during desorption as during adsorption

Effect of Cement/Wood Ratios and Wood Storage Conditions on Hydration Temperature, Hydration Time, and Compressive Strength of Wood-Cement Mixtures

This study investigated the effect of cement/wood ratios and wood storage conditions on hydration temperature, hydration time, and compressive strength of wood-cement mixtures made from six wood species: southern pine, white oak, southern red oak, yellow-poplar, sweetgum, and hickory. Cement/wood ratios varied from 13/1 to 4/1. Wood storage conditions consisted of air-dried and cold-stored wood. Results indicate that hydration temperature was drastically reduced, hydration time was prolonged, and compressive strength was reduced as cement/wood ratio was decreased. This effect was more pronounced for hardwood species and at lower cement/wood ratios. Cold storage of wood slightly increased hydration temperature and shortened hydration time of white oak and sweetgum but did not have any beneficial effect on the other four species. Results also indicate that mixtures with high cement/wood ratios used traditionally in laboratory for research purposes may not truly reflect the wood-cement compatibility at lower cement/wood ratios used in commercial production

Finite Element Analysis of Moso Bamboo-Reinforced Southern Pine Osb Composite Beams

A finite element (FE) analysis was performed to investigate the flexural properties of a structural composite lumber—Moso bamboo (Phyllostachys pubescens) reinforced southern pine oriented strand-board (OSB). Parametric analyses were conducted to investigate the stress and displacement distributions. Various beam configurations as affected by glue, web structure, flange composition, and bamboo-OSB combination were considered. The comparison of the numerical results from the selected models with those from bending tests was also performed. Finally, a rational design criterion for this type of composite beam was proposed based on the analytical and experimental studies. Bamboo is capable of improving the flexural properties of the OSB for use as a structural beam or joist. At a given cross section of about 30 X 140 mm, for instance, two-layer (6.4-mm thickness each) laminated bamboo flange can increase the OSB beam's maximum bending stress by 60 to 70% and double its stiffness. The total flange thickness, rather than the thickness of each layer, controls the beam deflection while the flange with a thinner layer (3.2 mm) resulted in higher bending, vertical, and transverse stresses but lower in-plane shear stress. More reinforcing material in the composite beam could reduce the maximum bending stress but would likely increase beam weight and processing cost. From this study, it is suggested that a two-layer flanged composite beam would be favorable from a material processing standpoint as well as superior in engineering performance over other configurations of bamboo-OSB composite beam product

Effect of Ice Shape Fidelity on Swept-Wing Aerodynamic Performance

Low-Reynolds number testing was conducted at the 7 ft. x 10 ft. Walter H. Beech Memorial Wind Tunnel at Wichita State University to study the aerodynamic effects of ice shapes on a swept wing. A total of 17 ice shape configurations of varying geometric detail were tested. Simplified versions of an ice shape may help improve current ice accretion simulation methods and therefore aircraft design, certification, and testing. For each configuration, surface pressure, force balance, and fluorescent mini-tuft data were collected and for a selected subset of configurations oil-flow visualization and wake survey data were collected. A comparison of two ice shape geometries and two configurations with simplified geometric detail for each ice shape geometry is presented in this paper

Predicting sepsis severity at first clinical presentation:The role of endotypes and mechanistic signatures

BACKGROUND: Inter-individual variability during sepsis limits appropriate triage of patients. Identifying, at first clinical presentation, gene expression signatures that predict subsequent severity will allow clinicians to identify the most at-risk groups of patients and enable appropriate antibiotic use. METHODS: Blood RNA-Seq and clinical data were collected from 348 patients in four emergency rooms (ER) and one intensive-care-unit (ICU), and 44 healthy controls. Gene expression profiles were analyzed using machine learning and data mining to identify clinically relevant gene signatures reflecting disease severity, organ dysfunction, mortality, and specific endotypes/mechanisms. FINDINGS: Gene expression signatures were obtained that predicted severity/organ dysfunction and mortality in both ER and ICU patients with accuracy/AUC of 77–80%. Network analysis revealed these signatures formed a coherent biological program, with specific but overlapping mechanisms/pathways. Given the heterogeneity of sepsis, we asked if patients could be assorted into discrete groups with distinct mechanisms (endotypes) and varying severity. Patients with early sepsis could be stratified into five distinct and novel mechanistic endotypes, named Neutrophilic-Suppressive/NPS, Inflammatory/INF, Innate-Host-Defense/IHD, Interferon/IFN, and Adaptive/ADA, each based on ∼200 unique gene expression differences, and distinct pathways/mechanisms (e.g., IL6/STAT3 in NPS). Endotypes had varying overall severity with two severe (NPS/INF) and one relatively benign (ADA) groupings, consistent with reanalysis of previous endotype studies. A 40 gene-classification tool (accuracy=96%) and several gene-pairs (accuracy=89–97%) accurately predicted endotype status in both ER and ICU validation cohorts. INTERPRETATION: The severity and endotype signatures indicate that distinct immune signatures precede the onset of severe sepsis and lethality, providing a method to triage early sepsis patients

Severe COVID-19 and non-COVID-19 severe sepsis converge transcriptionally after a week in the intensive care unit, indicating common disease mechanisms

IntroductionSevere COVID-19 and non-COVID-19 pulmonary sepsis share pathophysiological, immunological, and clinical features. To what extent they share mechanistically-based gene expression trajectories throughout hospitalization was unknown. Our objective was to compare gene expression trajectories between severe COVID-19 patients and contemporaneous non-COVID-19 severe sepsis patients in the intensive care unit (ICU).MethodsIn this prospective single-center observational cohort study, whole blood was drawn from 20 COVID-19 patients and 22 non-COVID-19 adult sepsis patients at two timepoints: ICU admission and approximately a week later. RNA-Seq was performed on whole blood to identify differentially expressed genes and significantly enriched pathways.ResultsAt ICU admission, despite COVID-19 patients being almost clinically indistinguishable from non-COVID-19 sepsis patients, COVID-19 patients had 1,215 differentially expressed genes compared to non-COVID-19 sepsis patients. After one week in the ICU, the number of differentially expressed genes dropped to just 9 genes. This drop coincided with decreased expression of antiviral genes and relatively increased expression of heme metabolism genes over time in COVID-19 patients, eventually reaching expression levels seen in non-COVID-19 sepsis patients. Both groups also had similar underlying immune dysfunction, with upregulation of immune processes such as “Interleukin-1 signaling” and “Interleukin-6/JAK/STAT3 signaling” throughout disease compared to healthy controls.DiscussionEarly on, COVID-19 patients had elevated antiviral responses and suppressed heme metabolism processes compared to non-COVID-19 severe sepsis patients, although both had similar underlying immune dysfunction. However, after one week in the ICU, these diseases became indistinguishable on a gene expression level. These findings highlight the importance of early antiviral treatment for COVID-19, the potential for heme-related therapeutics, and consideration of immunomodulatory therapies for both diseases to treat shared immune dysfunction