Density Loss Rate Research Articles

Mechanical strength and durability of GBFS geopolymer modified with metakaolin and functionalized beta-silicon carbide whiskers

Durability is crucial for materials development in construction and transportation industries. This paper investigates the mechanical strength and durability of alkali-activated granulated blast-furnace slag (GBFS) and modified geopolymer with varying contents of metakaolin (MK) and functionalized beta-silicon carbide whiskers (β-SiCw). Functionalized β-SiCw were prepared utilizing successful chemical methods. Macroscopic experiments tested mechanical strength, bulk density loss rate after exposure to severe conditions, and durability through sulfate wet-dry and freeze-thaw cycles. Microscopic experiments, including SEM-EDS, XRD, TG-DSC, and BET, revealed the microstructure mechanisms. Results showed that MK and functionalized β-SiCw improved mechanical strength by creating a more reactive phase and denser pore structures. Reduced bulk density loss rates and enhanced durability were observed, with a 71.9 % mass loss and 63.4 % compressive strength loss reduction after 50 freeze-thaw cycles, and a 12.2 % decrease in compressive strength loss after 56 days of sulfate wet-dry cycles, compared to control groups. The modified geopolymer had higher tortuosity and finer porosity due to more gel formation and nucleation sites, and functionalized β-SiCw effectively bridged micro-cracks and micro-pores.

Al-doped Li4SiO4 for cyclic solar energy storage and CO2 capture: An experimental and DFT study

The substantial consumption of fossil fuels gives rise to excessive carbon dioxide emissions, and mitigating them has emerged as a pressing global priority. The use of renewable energy and carbon capture, utilization, and storage are recognized as two major approaches for carbon neutrality. Li4SiO4 materials exhibit promising prospects in both thermochemical heat storage for solar energy power and cyclic high-temperature CO2 capture. The reactivity between Li4SiO4 and CO2 plays the vital role in its energy storage and CO2 capture performance. Herein, we prepare Al-doped Li4SiO4 materials through an impregnated suspension technique, simultaneously achieving high contact areas and lattice defects to enhance both fast chemisorption and ion diffusion processes. The results show that Al-doped Li4SiO4 exhibits high average energy density of 56677.08 kJ/kmol within 30 cycles. Additionally, the granulated Al-doped Li4SiO4-based pellets, produced via the freeze-drying technique, exhibit negligible energy density loss rate of less than 9 % and acceptable mechanical strength. Furthermore, the CO2 sorption performance also reaches a high value of 0.27 g/g. The reaction mechanism between Li4SiO4 and CO2 has been investigated at both macroscopic and microscopic levels through kinetic analysis and DFT calculations. The simulated Al-doped Li4SiO4/CO2 sorption system possesses increased adsorption energy level from −0.81 eV for the undoped one to −0.95 eV, thereby leading to the improved CO2 sorption. In general, Al-doped Li4SiO4 materials demonstrate great potential for applications in thermochemical heat storage and CO2 capture.

Pelvic Bone Marrow Sparing Intensity Modulated Radiation Therapy Reduces the Bone Mineral Density Loss of Patients With Cervical Cancer

PurposeTo test the efficacy and feasibility of pelvic bone marrow sparing intensity modulated radiotherapy (PBMS-IMRT) in reducing bone density loss for patients with cervical cancer undergoing pelvic radiotherapy (RT). Methods and MaterialsNon-surgical cervical cancer patients with Stage Ib2–IIIc cancer were randomly allocated into the PBMS group or the control group. The PBMS group additionally received PBM dose constraint. Computed tomography (CT) imaging sets were acquired at baseline and at 1, 3, 6, 9, and 12 months after treatment. Radiation dose and Hounsfield unit (HU) were registered. Bone density loss rates and fracture events at different follow-up time points were recorded. ResultsData from 90 patients in the PBMS group and 86 patients in the control group were used for statistical analysis, which included 30 and 26 patients with extended-field RT (EFR), respectively. The median follow-up for all patients was 12 months. Compared to baseline, the bone density of all bones at the last follow-up had decreased by 43% and 53% in the PBMS and control groups, respectively, with the most significant decline at 1 month after treatment. Although patients without extended-field radiation received minimal irradiation in the upper lumbar spine, a 22.33% decrease in bone density was detected. In the group of patients with EFR, the decrease was 51.18% (P < 0.01). Lumbar or pelvic fracture incidence rates of patients in the PBMS and control groups were 7.8% and 12.79%, respectively. Among the dosimetric parameters, mean dose had the strongest correlation with bone density loss. ConclusionIn patients undergoing pelvic RT, the loss of bone density can begin to appear early after RT, and it can occur either inside or outside of the irradiation field. Results of this study showed that PBMS-IMRT reduced bone mineral density loss compared with IMRT alone.

Unraveling carbon stock dynamics and their determinants in China's Loess Plateau over the past 40 years

Synergies and trade-offs among land use and land covers (LULCs) pose considerable uncertainties in achieving the dual carbon goals for China's Loess Plateau (CLP). In this context, we unraveled the carbon stock dynamics induced by land use and land cover change (LUCC) in the CLP over the past 40 years using the satellite-derived annual LULC maps and the InVEST model. Then, mixed measures were employed to quantify the global and local responses of the carbon stock dynamics to both natural and anthropogenic factors. We found that approximately a total of 5.58 × 109 Mg of carbon was stored in the CLP's ecosystems in 2019. Chronologically, the total carbon stock showed a slight decrease in the CLP from 1980 to 2019 due to the extensive LUCCs linked to socioeconomic activities. Specifically, the total carbon density loss rate accelerated in urban–rural-wild continuum (RUWC) types with higher human activity intensity, such as villages and urban, while it decelerated in woodlands, and croplands, where the human activity intensity is lower. Moreover, the total carbon density gain rate in wildlands was accelerating. Finally, we revealed that the carbon stock dynamics in the CLP over the past 40 years were primarily influenced by socioeconomic variables and have responded diversely to the drivers in space.

Visual evaluation of warehousing humidity and time on bamboo performance

The inventories of Moso bamboo (Phyllostachys pubescens) resources are considered to be one of the most important strategic resources for economic construction and ecological building materials. Warehousing humidity is one of the objective factors that induce mold deterioration and quality deterioration of bamboo. To investigate the effect of environment humidity on the use value of bamboo, humidity levels of 45 %, 60 %, 75 % and 95 % and indoor environments were artificially simulated and regularly monitored for changes in quality during warehousing. During the 56-day storage period, with the increase of humidity in the warehousing environment, the dimensional expansion rate of the cortex side of bamboo was larger than that of the pith side and the cavity diameter ratio gradually decreased, Total color difference value, and mass density loss rate gradually decreased, and the peak compressive stress-strain displacement gradually increased, respectively. 95 % RH is beneficial to mold reproduction and only infect the surface, Fourier Transform Infrared Spectroscopy analysis showed that the quality changes during storage were more related to the decrease in the signal peak of the hemicellulose functional group of the material itself accompanied by the degradation of various monosaccharides, the lignin functional group corresponded to the decrease in L* and Total color difference, and the degree of pyrolysis tolerance was inversely proportional to the signal intensity of the cellulose functional group. Redundancy analysis showed that the positive contribution of humidity in the storage environment to the physical quality of bamboo was Bamboo pith linear > Width dimension > Bamboo cortex linear > Water content > Weight loss rate > Length Dimension > a*, and the storage time was closely related to the L* value and compression strength.

X-ray microdensitometry for assessing the resistance of hybrid larch to fungus Coniophora puteana

X-ray microdensitometry was performed on small wood samples after fungal exposure to assess wood density loss and its variability within a hybrid larch population. Microdensitometry was applied to thin wood slices obtained from increment cores collected from standing trees before and after 4 weeks of exposure to Coniophora puteana fungus. Density loss rates were measured and compared to mass loss percentages calculated on wood blocks following a 16-week decay test according to CEN TS 15083-1 (2005). The relationship between the standard mass loss and the density loss percentages was weak. Several explanations for the results are presented in this work, and methodological improvements are suggested to achieve a more accurate comparison. The proposed screening test has several advantages over the current standard method, as it is less invasive for the tree, less time consuming, and is therefore better suited for genetic studies and breeding. As predicted, due to extractive content variation and fungus behaviour, density loss after 4 w was more important in earlywood than in latewood and in inner heartwood than in outer heartwood. The new method also better determined the differences in decay among trees within the larch population than the standard method at 16 w.

Dairy intake is not associated with improvements in bone mineral density or risk of fractures across the menopause transition: data from the Study of Women's Health Across the Nation.

Objective:Menopause represents a period in which bone deterioration is accelerated; thus, primary prevention strategies to address age-related bone loss are crucial. Dairy products contain more than a dozen essential nutrients, including calcium, phosphorus, vitamin D, and high-quality protein, as well as bioactive compounds that may promote bone mineralization. However, the relationship between dairy consumption and bone health across the menopause transition remains largely unknown. The purpose of this analysis was to estimate the change in lumbar spine and femoral neck bone mineral density and the risk of bone fracture by the frequency of dairy intakes among women across the menopausal transition using the publicly available data from the Study of Women's Health Across the Nation.Methods:We analyzed total dairy foods in four categories of <0.5, 0.5 to <1.5, 1.5 to <2.5, and ≥2.5 servings/d or <1.5 and ≥1.5 servings/d. A general linear model was used to estimate the association of dairy intake with the 10-year bone mineral density loss rate and a linear mixed model was used to estimate the annualized bone mineral density loss rate of the femoral neck and lumbar spine. A Cox proportional hazard model was applied to calculate hazard ratios and 95% confidence intervals of the nontraumatic fractures. Poisson regression was used to determine the relative risks and 95% confidence intervals of the nontraumatic fractures. The models were controlled for race/ethnicity, age, height, weight, smoking status, physical activity, alcohol consumption, calcium use, menopausal status, and total caloric intake.Results:No significant differences in bone mineral density change were observed, regardless of baseline menopausal status. No significant differences in the risk of nontraumatic fracture were observed.Conclusions:In this group of US women undergoing the menopausal transition, dairy food intake was neither associated with femoral and spine bone mineral density loss nor the risk of fractures.

Dairy Intake Is Not Associated with Improvements in Bone Mineral Density or Risk of Fractures Across the Menopause Transition

Abstract Objectives Menopause represents a period in which bone deterioration is accelerated; thus, primary prevention strategies to address age-related bone loss are crucial. Dairy products contain more than a dozen essential nutrients, including calcium, phosphorus, vitamin D, and high-quality protein, as well as bioactive compounds that may promote bone mineralization. However, the relationship between dairy consumption and bone health across the menopause transition remains largely unknown. The purpose of this analysis was to estimate the change in lumbar spine and femoral neck bone mineral density and the risk of bone fracture by the frequency of dairy intakes among women across the menopausal transition using the publicly available data from the Study of Women's Health Across the Nation. Methods A general linear model was used to estimate the association of dairy intake with the 10-year bone mineral density loss rate and a linear mixed model was used to estimate the annualized bone mineral density loss rate of the femoral neck and lumbar spine. A Cox proportional hazard model was applied to calculate hazard ratios and 95% confidence intervals of the nontraumatic fractures. A Poisson regression model with a log link function was used to determine the relative risks and 95% confidence intervals of the nontraumatic fractures. The models were controlled for race/ethnicity, age, height, weight, smoking status, physical activity, alcohol consumption, calcium use, menopausal status, and total caloric intake. Results No significant differences in bone mineral density change were observed, regardless of baseline menopausal status. No significant differences in the risk of nontraumatic fracture were observed. Conclusions In this group of US women undergoing the menopausal transition, dairy food intake was not associated with femoral and spine bone mineral density loss nor the risk of fractures. Funding Sources National Dairy Council.

Risk Factors for Cystoid Macular Edema After Descemet Membrane Endothelial Keratoplasty.

To investigate factors associated with cystoid macular edema (CME) after Descemet membrane endothelial keratoplasty (DMEK) in Asian eyes. In this retrospective, interventional, consecutive case series, 77 eyes of 65 patients who underwent DMEK were evaluated; in 53 eyes, cataract surgery was performed 1 month before DMEK (staged DMEK), and 24 eyes underwent DMEK alone (simple DMEK). Central retinal thickness, incidence of CME, postoperative best-corrected visual acuity, central corneal thickness, and corneal endothelial cell density were assessed at 1, 3, and 6 months after surgery. Multiple regression analysis and stepwise variable selection were performed for parameters such as type of surgery, iris damage scores, age, sex, axial length, preoperative visual acuity, rebubbling, air volume in the anterior chamber on postoperative day 1, history of diabetes, and endothelial cell density loss rates at 6 months after surgery. CME occurred in 12 (15.6%) of 77 eyes. There was no significant difference in best-corrected visual acuity between eyes with and without CME (P = 0.27). Multivariable analysis revealed that the difference in iris damage scores between before and after DMEK (P < 0.001), air volume in the anterior chamber (P = 0.012), simple DMEK (P = 0.020), and rebubbling (P = 0.036) were significantly associated with CME. Stepwise variable selection indicated that iris damage (P < 0.001) was the most important risk factor for CME. Iris damage due to DMEK might be a possible risk and aggravating factor for the development of CME after DMEK. Surgeons should attempt to minimize damage to the iris.

Influence of calcium carbonate whisker and polyvinyl alcohol- steel hybrid fiber on ultrasonic velocity and resonant frequency of cementitious composites

Inclusion of hybrid fiber in cementitious composites could restrict the growth of cracks at different stages and improve the mechanical properties of concrete, and adding calcium carbonate (CaCO3) whisker would further improve the mechanical properties of cementitious composites. Nevertheless, no attention has been paid to the effects of steel- polyvinyl alcohol (PVA) hybrid fiber and whisker on ultrasonic pulse velocity (UPV) and resonant frequency (RF) of hybrid fiber reinforced cementitious composites (HyFRCC), although they have been used widely in quality assessment of concrete. In this research, 114 specimens have been used to explore the influences of steel-PVA hybrid fiber and whisker on the UPV, RF parameters and the mechanical properties. The results of this research present that there may exists “fiber gradation” in HyFRCC, because there is always a best fiber combination to reach the greatest compactness and highest non-destructive testing results. In addition, the partial substitution of PVA fiber by whisker decreased UPV and RF and increased density loss rate and compressive strength except for one mixture. Therefore, UPV, RF can reflect the effect of whisker on the inner structure and detect the variation, and have potential use to evaluate HyFRCC in engineering applications.

Analysis on Ink Layer Rub Resistance for Coated Paper Prints

Having been coated, the surface unevenness and pores on paper were covered by a coating layer composed of fine particles and binders, which can absorb ink well, thereby a good uniformity and smoothness of paper could be obtained, consequently, the reproducing capability for printing dot and good whiteness, gloss and opacity can be improved. In theory, the ink rub resistance for coated paper print is mainly affected by the ink absorbance property of paper, printing conditions, ink components, rub medium and so on. In this study, seven different kinds of coated papers, the viscosities of the inks were adjusted with a viscosity adjusting agent, and then the prints were prepared by proofing with the ink with different viscosities. After drying, the prints were used for rub testing. The impact of the basic properties of coated paper and the content of reducer in inks on rub resistance were discussed on the basis of a comparative analysis of the experimental data. Printing color density loss rate and print color difference were exploited in this paper to characterize the ink rub resistance for coated paper prints. In this study, it was found that ink rub resistance was mainly influenced by ink absorbency and smoothness of the paper. Under the similar conditions, the color density of coated paper print decreases with the rub strength increasing, color difference increased gradually, but not linearly. With the increase of ink viscosity reducer content, printing density loss rates as well as color difference changed, but not be linearly.

Numerical investigation of the effect of porous titanium femoral prosthesis on bone remodeling

Porous titanium is a promising orthopedic implant material. As a potential use in total hip replacement, the effect of a porous titanium femoral prosthesis on bone remodeling is investigated in this paper. The stress and strain fields of a post-operative femur with a hip replacement are calculated by applying the three-dimensional finite element method. The effect of the implant material on the bone remodeling is evaluated by analyzing the loss of bone density following a strain magnitude based bone remodeling theory. Different implant materials, including currently used solid cobalt–chrome and solid titanium, potential porous titanium with different porosities, are considered in this study. This investigation confirms that bone loss around the implant strongly depends on the value of the elastic modulus of the prosthesis. There will be a sharp drop of the volume of the bone with density loss if a cobalt–chrome implant is replaced by a porous titanium implant. The numerical results show that both of the bone volume with density loss and the bone density loss rate decrease linearly with the increase of the porosity. However, increasing porosity will reduce the strength of porous titanium. With regard to material design for porous titanium-based femoral prosthesis, stress analysis is required to meet the strength requirement.

The effect of overpotential on performance degradation of the solid oxide fuel cell Ni/YSZ anode during exposure to syngas with phosphine contaminant

Phosphine (PH 3) as a contaminant in coal syngas has been shown to cause permanent degradation on solid oxide fuel cell (SOFC) anode performance. Previous studies on the performance degradation have been performed at constant current or constant voltage over the entire experiment. In this work, the effect of overpotential (difference between the open circuit voltage and the applied voltage) on rates of degradation of SOFC performance is examined. A commercial SOFC from MSRI is exposed in sequence to first hydrogen, then coal syngas and then coal syngas with 10 ppm PH 3. The rates of cell power density loss rates are monitored for three overpotentials (0.1, 0.2 and 0.3 V). There is no apparent correlation between the degradation rates and overpotential values. Post-mortem studies including SEM, XRD and XPS confirm the migration of nickel to the anode surface and the formation of a nickel phosphide phase.

Enhancement of the negative ion flux to surfaces from radio-frequency processing discharges

The relative flux of negative ions from rf discharges through CF4 and F2-He has been studied using mass spectrometry. The negative ion flux impinging on a surface in contact with a glow discharge is usually quite small because of the sheaths formed to contain the more mobile electrons. In the afterglow, however, these sheaths decay on the time scale of the electron density loss rate while negative ions can remain in the discharge region significantly longer. As a consequence, the negative ion flux to a surface in contact with the glow discharge can rise by a very large amount in the afterglow when the sheaths have diminished. It is shown here that the flux of the negative ions can be enhanced by factors of 50 to greater than 1000 by square wave amplitude modulating the rf discharge. This enhancement depends upon the dc self-bias voltage and the modulation frequency as well as the particular negative ion. Data are presented for both CF4 and F2-helium discharges, along with the correlation to simple models.

Decomposition of woody debris in a regenerating, clear-cut forest in the Southern Appalachians

Mass losses were estimated for coarse (&gt;5 cm) and fine (≤5 cm) woody debris (CWD and FWD, respectively) during the first 7 years following clear-cutting of a mixed hardwood forest at the Coweeta Hydrologie Laboratory in the Southern Appalachians of North Carolina. Estimates were based on (i) precut forest biomass, (ii) volume and density of CWD and mass of FWD at year 1, and (iii) wood density changes of CWD by year 6 and mass changes of FWD by year 7. Mass estimates of CWD at years 0, 1, and 6 were 91.2, 74.8, and 53.0 Mg/ha, respectively. Mass estimates of FWD at years 0, 1, and 7 were 30.3, 21.3, and 7.8 Mg/ha, respectively. Decay constants (k) for mass losses were relatively high compared with other studies of wood decomposition, 0.083 and 0.185 year−1 for CWD and FWD, respectively, and 0.108 year−1 for total (CWD + FWD) debris. Mass loss of CWD occurred largely through wood density decreases and bark fragmentation. CO2−efflux estimates accounted for over 90% of the CWD density loss and for two-thirds (40.4 Mg/ha) of the total debris mass loss. The remaining mass loss of total debris (20.3 Mg/ha) is a source of large, organic matter inputs to the forest floor via solution fluxes and fragmentation of CWD bark and FWD. The large variation in wood-density loss among logs was examined statistically as a function of various decay factors. Density loss varied by more than 10-fold among tree species. Density loss rates were 40% higher in logs on the ground versus those off the ground, 100% higher in logs with observable fungi versus those without fungi, and 40% higher in logs that occurred in plots with south and east aspects versus those in plots with west aspects.

Amnestic aphasia

Inclusion of hybrid fiber in cementitious composites could restrict the growth of cracks at different stages and improve the mechanical properties of concrete, and adding calcium carbonate (CaCO3) whisker would further improve the mechanical properties of cementitious composites. Nevertheless, no attention has been paid to the effects of steel- polyvinyl alcohol (PVA) hybrid fiber and whisker on ultrasonic pulse velocity (UPV) and resonant frequency (RF) of hybrid fiber reinforced cementitious composites (HyFRCC), although they have been used widely in quality assessment of concrete. In this research, 114 specimens have been used to explore the influences of steel-PVA hybrid fiber and whisker on the UPV, RF parameters and the mechanical properties. The results of this research present that there may exists “fiber gradation” in HyFRCC, because there is always a best fiber combination to reach the greatest compactness and highest non-destructive testing results. In addition, the partial substitution of PVA fiber by whisker decreased UPV and RF and increased density loss rate and compressive strength except for one mixture. Therefore, UPV, RF can reflect the effect of whisker on the inner structure and detect the variation, and have potential use to evaluate HyFRCC in engineering applications.

Effect of magnetic field upon plasmas produced by laser-induced gas breakdown

The effect of a magnetic field upon the properties of a plasma created by CO2 laser-induced gas breakdown in helium has been investigated. Spatially and temporally resolved temperatures in the 7–20-eV range were observed using the spectral-line ratio technique, in particular the He II 468.6-nm line-to-continuum ratio. The continuum measurements were also employed to obtain relative values of electron density. The temporal dependences of electron density and temperature indicate that energy is lost from the plasma by an adiabaticlike expansion. The presence of the magnetic field significantly decreases both the energy and density loss rates.

Diffusion cooling in neon, argon, and krypton afterglow plasmas

Measurements are reported of ambipolar diffusion coefficients as determined from ion density loss rates, and of electron temperatures determined using the single Langmuir probe technique, in afterglow plasmas of spectroscopically pure neon, argon and krypton. In each gas there was a critical pressure,p 0 c , above which the product of the ambipolar diffusion coefficient,D a , and the reduced gas pressure,p 0, was pressure independent and above which the electron temperature was found to cool asymptotically to the gas temperature. For pressures belowp 0 c ,D a p 0 decreased with decreasing pressure, and the electron temperature cooled asymptotically to a steady equilibrium value,T eq, below the gas temperature, this equilibrium value itself decreasing with decreasing gas pressure. These results clearly show that diffusion cooling of electrons was taking place at these low gas pressures. A detailed study of the krypton afterglow showed that the values ofD a p 0 andT eq for a given gas pressure were related in a manner predicted by simple diffusion theory. During the course of these measurements values for the zero field mobilities of Ne+, Ar+ and Kr+ ions in their parent gases were obtained and are also reported.