Carbon Dioxide Production Rate Research Articles

Organic matter processing by heterotrophic bacterioplankton in a large tropical river: Relating elemental composition and potential carbon mineralization.

River hydrology shapes the sources, concentration, and stoichiometry of organic matter within drainage basins. However, our understanding of how the microbes process dissolved organic matter (DOM) and recycle nutrients in tropical rivers needs to be improved. This study explores the relationships between elemental DOM composition (carbon/nitrogen/phosphorus: C/N/P), C and N uptake, and C mineralization by autochthonous bacterioplankton in the Usumacinta River, one of the most important fluvial systems in Mexico. Our study investigated changes in the composition and concentration of DOM and evaluated carbon dioxide (CO2)production rates (C-CO2) through laboratory experiments. We compared three sites representing the middle and lower river basins, including their transitional zones, during the rainy and dry seasons. After incubation (120 h at 25°C), the DOM decreased between 25% and 89% of C content. Notably, the initial high proportion of C in DOM in samples from the middle-forested zone and the transition led to elevated C-CO2 rates (>10 mg l-1 day-1), in contrast to the lower initial C proportion and subsequent C-CO2 rates (<7 mg l-1 day-1) in the lower river basin. We also found that dissolved organic carbon uptake and NO3- and NH4+ production were higher during the dry season than in the rainy season. The low water flow in the river during the dry season accentuated the differences in elemental composition and microbial processing of DOM among the sites, while the high water flow of the rainy season homogenized these factors. Our findings indicate that microbial metabolism operates with reduced efficiency in C-rich environments like forests, particularly when faced with high C/N and C/P ratios in DOM. This study highlights the influence of the tropical hydrological regime (rainy and dry seasons) and the longitudinal changes in the river basin (middle and lower) topography and land cover on microbial metabolism by constraining DOM characteristics, emphasizing the crucial role of elemental ratios in river DOM processing.

Assessment of entropy accumulation in human subjects when exposed to low energy availability

Background & aimsAdequate energy availability is essential for the body to maintain its physiological functions and achieve optimal health, especially among athletes. Unfortunately, low energy availability (LEA) is common among athletes, and it has been associated with impairments in health and performance. In contrast, an energy-restricted diet has been linked to longevity, but it is unclear how LEA affects athletes’ lifespans. The goal of the present study was to assess the impact of LEA thermodynamically on the lifespan of athletes. MethodsData from seven healthy young endurance-trained athletes (24 ± 4 years) who underwent short-term low energy availability (125 (kJ/day) per kg FFM) once with low protein content (LEA-LP; 0.8 g/kg) and with high protein content (LEA-HP; 125 (kJ/day) per kg FFM, 1.7 g/kg), as well as a control diet (CON; 230 (kJ/day) per kg FFM, 1.7 g/kg), were used in the calculations. The athletes followed each diet for five days and expended 67.5 (kJ/day) per kg FFM. entropy generation-based thermodynamic calculations were performed based on the metabolic activity of the athletes, which was determined from oxygen consumption and carbon dioxide production rates. ResultsLow energy availability was successfully induced during LEA-LP (62 ± 8 (kJ/day) per kg FFM; 95%Cl: 53–70) and LEA-HP (64 ± 8 (kJ/day) per kg FFM; 95%Cl: 56–71) diets. Despite of achieving energy deficit of −6658 ± 2110 kJ/day (95%Cl: 8609-(−) 4707) (LEA-LP), −5781 ± 623 (95%Cl: 26591-(−)4707) (LEA-HP) and excessive energy of 772 ± 1915 (95%Cl: 845-2388) (CON) statistical analyses revealed no significant differences in lifespan estimations among diets (CON: 72 ± 8 years (95%Cl: 65–79), LEA-LP: 74 ± 7 years (95%Cl: 68–80), and LEA-HP: 73 ± 11 (95%Cl: 62–83)). ConclusionsThis study suggests valuable insights into the intricate relationship between energy availability, entropy generation, and lifespan among athletes. Whereas entropy generation levels and the lifespan of athletes remained stable depending on diets, the distinguished differences in energy deficiency and energy availability underline the need for a profounder investigation of underlying physiological mechanisms to improve the health and performance of athletes.

Energetics and Basic Stroke Kinematics of Swimming With Different Styles of Wetsuits.

Lim, B, Villalobos, A, Mercer, JA, and Crocker, GH. Energetics and basic stroke kinematics of swimming with different styles of wetsuits. J Strength Cond Res XX(X): 000-000, 2024-This study investigated the physiological responses and basic stroke kinematics while wearing different styles of wetsuits during submaximal intensity front-crawl swimming. Fourteen subjects (6 men and 8 women) completed a swimming-graded exercise test to determine maximal aerobic capacity (V̇O2max) and four 4-minute submaximal front-crawl swims at a pace that elicited 80% of V̇O2max with different wetsuits: regular swimsuit (no wetsuit [NWS]), buoyancy shorts (BS), sleeveless wetsuit (SLW), and full-sleeve wetsuit (FSW). The rate of oxygen consumption (V̇O2), rate of carbon dioxide production (V̇CO2), minute ventilation (V̇E), heart rate (HR), respiratory exchange ratio, and cost of swimming (CS) were determined as the average for the last minute of each trial. The rating of perceived exertion was assessed after each swimming bout. In addition, stroke length and index were determined from swimming pace and stroke rate. V̇O2, V̇CO2, V̇E, HR, and CS differed significantly among wetsuit conditions (p < 0.01). Respiratory exchange ratio and rating of perceived exertion also varied by wetsuit conditions (p < 0.05). However, stroke rate, length, and index were not significantly different across wetsuit conditions (p > 0.05). No differences existed between SLW and FSW for any dependent variable (p > 0.05). Results from this study suggest that swimming at the same pace without a wetsuit is the least economical, and both SLW and FSW are most and equally economical without significant kinematic changes. In addition, BS could be beneficial during training and racing in terms of less physiological demands than a regular swimsuit but not as economical as the SLW or FSW.

Alternativa para el incremento de la actividad enzimática y liberación de azúcares en residuos sólidos orgánicos durante un proceso de degradación aerobia

The impact of inoculum (mature compost) was assessed in an aerobic system for the rapid degradation of organic solid waste, with a focus on the release of reducing sugars. Isothermal (35 and 55 °C) and non-isothermal (35-55 °C) treatments were conducted. Key indicators, including the rate of oxygen consumption (O2) and carbon dioxide production (CO2), were measured to assess microbial activity. Additionally, the concentration of reducing sugars, pH, enzymatic activity, and the presence of pathogens were evaluated. Treatments with inoculum at 35 °C and without inoculum at 55 °C exhibited an increase in oxygen consumption and CO2 production, indicating heightened microbial activity and, consequently, greater mineralization of organic matter. The treatment without inoculum at 35-55 °C presented the highest concentration of reducing sugars (160 mg/g dry weight), suggesting its potential as a pretreatment for bioconversion processes aimed at generating value-added products. At a temperature of 55 °C, there was a reduction of 84.4, 87.28, and 67.33 % in the concentrations of fecal coliforms, Escherichia coli, and parasites, respectively. This result suggests that elevated temperature contributes to the effectiveness of pathogen elimination.

Changes in sediment greenhouse gases production dynamics in an estuarine wetland following invasion by Spartina alterniflora.

Invasive Spartina alterniflora (S. alterniflora) has significant impacts on sediment biogeochemical cycling in the tidal wetlands of estuaries and coasts. However, the impact of exotic Spartina alterniflora invasion on greenhouse gases (GHGs) production dynamics in sediments remain limited. Here, we investigated the dynamics of sediment physicochemical properties, GHGs production rates, and microbial gene abundances in a native Cyperus malacensis habitat and three invasive S. alterniflora habitats (6-, 10-, and 14-year) in the Minjiang River Estuary, China. The methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) production rates varied both spatially and seasonally, while microbial gene abundances (bacterial and fungal gene abundances) and organic matter (TOC and TN) only varied spatially. GHGs production rates were also characterized by higher values in surface sediment (0-10 cm) compared to subsurface sediment (10-20 cm) and by seasonal variations with higher values in summer than in winter. S. alterniflora invasion can significantly increase CH4 and CO2 production rates, organic matter, and microbial gene abundances (p < 0.05). Temperature, organic matter and microbial gene abundances were the most dominating factor controlling the spatio-temporal variations of CH4 and CO2 production rates. Overall, our findings highlighted the significant role of S. alterniflora invasion in regulating GHGs production rates in coastal wetland sediments and provided fundamental data for estimating GHGs emissions and carbon sequestration in the complex tidal wetlands.

Efficacy of grape seed procyanidins for inhibiting denitrification varies by source, soil texture, and cropping history

Plant-derived denitrification inhibitors, such as procyanidins derived from grape seed extract (GSE), hold potential in mitigating nitrous oxide (N2O) emissions, a potent greenhouse gas and stratospheric ozone depleter. A deeper understanding of the effects of GSE – considering aspects like rate, source, application timing, storage, and interactions with soil properties and cropping histories – on denitrification inhibition remains elusive. We conducted a series of laboratory microcosm experiments to assess these effects using denitrification enzyme activity (DEA) and measurements of N2O and carbon dioxide (CO2) production rates under both anaerobic and aerobic conditions, soil inorganic nitrogen (N), and other major soil properties. Our results revealed that one commercial GSE brand (USP GSE) inhibited DEA, while another source was ineffective. Two non-procyanidin compounds in commercial GSE mixtures, tartaric acid and gallic acid, actually enhanced DEA. Inhibition efficiency of the USP GSE varied significantly across soils with differing crop histories and physical properties, exhibiting a positive dose-response in three out of the five soils examined. Greater efficiency was observed in sandy soils compared to silt loam soils and in soils with a history of continuous corn production as opposed to soybean. The GSE application timing relative to urea addition and a one-week room temperature storage had minor effects on denitrification inhibition. In corn-cultivated soil, co-application of GSE and urea reduced cumulative N2O production by 27 % compared to soils treated with urea alone. The CO2 production and nitrate levels remained largely unaffected by GSE application. These findings supported the potential of GSE as a soil amendment to reduce N2O emissions in corn-cultivated soils. However, challenges including purity of procyanidins, cost-effectiveness, and inconsistent performance under various systems warrant consideration for broader field applications.

Facile preparation of ladder-like polyphenyl silsesquioxanes-sodium benzenesulfonate micro-nano compound with novel pyrolysis model and high flame retardancy for epoxy resin

To reduce the fire hazard of epoxy resin and expand its application scenarios, a novel micro-nano compound of ladder-like polyhedral oligomeric silsesquioxane (PPSQ) and sodium benzenesulfonate (BSNa) was successfully developed. Due to the addition of BSNa, the thermal decomposition behaviour of ladder-like PPSQ was completely changed, making it an effective additive to improve the flame retardancy of epoxy resin. Compared with neat epoxy resin, at 3wt% addition, the peak of heat release rate(p-HRR), the peak of carbonic oxide production rate(p-COP), the peak of smoke production rate(p-SPR) and the peak of carbon dioxide production rate(p-CO2P) were reduced significantly. In addition, the mechanism of the negative influence of PPSQ-BSNa on the flame retardancy of epoxy resin at excessive addition was detailed and analyzed in this work. Finally, this work provides a new prospect and strategy of synthesis metal containing POSS to reduce the fire hazards of epoxy resin.

Physiological characteristics of a 92-yr-old four-time world champion indoor rower.

This study assessed the physiological, performance, nutritional intake, and training characteristics of a 92-yr-old four-time master world champion indoor male rower. Body composition was assessed via bioelectrical impedance. Oxygen uptake, carbon dioxide production, ventilation, and heart rate were measured at rest and during a 2,000-m time trial on a rowing ergometer. Maximal power was assessed to compute anaerobic power reserve. Training included ≈ 30 km/wk on the rowing ergometer. Herein, 70% of distances were covered at light intensities (RPE, 10-12), 20% at hard (RPE, 13-17), and 10% at near maximal or maximal (RPE, 17-20). Resistance training was performed during ≈ 2 sessions/wk, and involved three sets of dumbbell lunges, rows, and curls, respectively, taken close (or to) failure. Dietary intake was high in protein [2.3 ± 0.1 g·kg-1 lean body mass (LBM)], conferring a caloric intake of 33.4 ± 1.7 kcal·kg-1 LBM. The participant demonstrated muscle mass of 47.7 kg, fat mass of 9.1 kg (15.4% body fat), forced vital capacity of 3.36 L, time constant (τ) to steady state of 30.2 s, peak relative oxygen pulse of 0.18 ([mL·O2/beats/min]/kg), peak heart rate of 153 beats/min, and maximum power of 220 W (140 W anaerobic power reserve). This 92-yr-old athlete demonstrated remarkably fast oxygen uptake kinetics, akin to values for a healthy young adult, indicating well-developed and/or maintained cardiopulmonary function. The high values for cardiopulmonary function, muscle mass, metabolic efficiency, and maximum power output may infer the pliability of these systems to maintain high functionality at an advanced age.NEW & NOTEWORTHY To our knowledge, this study is the first to characterize the physiological attributes of a competitive rower (4-time master world champion) at an advanced age (≥ 85 yr). The participant demonstrated a high muscle mass (47.7 kg; 80.6% body mass), maximal power (220 W), and exceptional oxygen uptake kinetics (τ of 30.2 s), similar to values reported for healthy young adults.

Loss of Farnesoid X receptor (FXR) accelerates dysregulated glucose and renal injury in db/db mice.

End-stage renal disease is primarily caused by diabetic kidney disease (DKD). The Farnesoid X receptor (FXR), a member of the nuclear receptor superfamily, has anti-inflammatory, lipid-lowering and hypoglycemic properties. It also inhibits renal fibrosis. Although its physiological role is not fully understood, it also plays a role in the control of diabetic nephropathy (DN). In the present study, we examined male FXR & leptin receptor double knockout mice, in which weight, blood glucose, body fat, and other indicators were monitored. After 6 months of rearing, blood and urine samples were collected and biochemical parameters were measured. Fibrosis was assessed by Masson's stain, while the assessment of the resuscitation case's condition was performed using succinate dehydrogenase (SDHA) stain immunohistochemistry, which measures aerobic respiration. Expression of molecules such as connective tissue growth factor (CTGF), SMAD family members 3 (Smad3) and 7 (Smad7), and small heterodimer partner were detected by RT-PCR and Western blotting as part of the application. FXR knockout decreased body weight and body fat in db/db mice, but increased blood glucose, urine output, and renal fibrosis. Primary mesangial cells (P-MCs) from FXR+/+ mice stimulated with transforming growth factor β1 (TGFβ1) showed significantly higher levels of related fibrosis factors, TGFβ1 and Smad3 mRNA and protein, and significantly reduced levels of Smad7. These effects were reversed by the action of FXR agonist chenodeoxycholic acid (CDCA). P-MCs from FXR-/- mice stimulated with TGFβ1 resulted in an increase in the expression and protein levels of collagen I and TGFβ1, and the addition of CDCA had no significant effect on TGFβ1 stimulation. However, compared with FXR+/+db/db mice, the rate of oxygen consumption, the rate of carbon dioxide production, and the rate of energy conversion were increased in FXR-/-db/db mice, whereas the SDHA succinate dehydrogenase, a marker enzyme for aerobic respiration, was significantly decreased. These results provide evidence that FXR plays a critical role in the regulation of mesangial cells in DN. The likely mechanism is that aberrant FXR expression activates TGFβ1, which induces extracellular matrix accumulation through the classical Smad signaling pathway, leading to mitochondrial dysfunction.

Tunable construction of fire safe and mechanically strong hierarchical composites towards electromagnetic interference shielding

Cotton fabric composites were designed to be protected by fire safe thermoplastic polyurethane (TPU) composites for developing electromagnetic interference (EMI) shielding polymer composites with superior mechanical properties. Herein, the as-prepared MXene was coated onto the fiber surface of cotton and then thermally compressed with TPU composites, which were filled with the sodium dodecyl sulfate modified layered double hydroxides functionalized the short carbon fiber hybrids through melt blending method. Then, a series of highly fire safe cotton/TPU hierarchical composites were constructed by a designed thermal compression technique. For instance, the obtained cotton/TPU hierarchical sample showed greatly reduced peak of heat release rate, peak of carbon monoxide production rate and peak of carbon dioxide production rate of TPU by 50.1%, 52.1% and 55.4%, respectively. Furthermore, the cotton/TPU hierarchical composites possessed the EMI shielding effectiveness of 40.0 dB in the X band and 54.6 dB in the K band. The mechanical property of the cotton/TPU hierarchical composites was also reinforced, where the elongation at break and toughness values of the TPU/SCF/mLDH1/C2 hierarchical composite were 21.47 and 18.30 times higher than those of pure TPU, respectively. These mechanically strong hierarchical composites have brought a promising attempt to broaden their practical application, removing the fire hazards and electromagnetic waves radiation from the environment.

Estimation of the metabolic rate in the occupational field: a regression model using accelerometers

The aim of this study is to investigate the ability of the acceleration vector magnitude (VM) to predict the metabolic rate (M) for a variety of work activities. Accurate knowledge of M is of vital importance to evaluate the energy cost of work activity. While precise estimates of M can be achieved using direct calorimetry, this is not a viable option in workplaces. Ten healthy subjects (5 males, 5 females) were enrolled in six tasks simulating specific work activities. During each test, oxygen consumption rate (V˙O2), carbon dioxide production rate (V˙CO2) and accelerations at three body positions were measured. V˙O2 and V˙CO2 were used to obtain M and accelerations to calculate VM. Three mono-linear zero-intercept regression models based on center-of-mass VM were developed. A zero-intercept functional relation between M and VM was applied to the whole data set yielding the Global model. A R2 of 0.30 was obtained which indicates limited predictive ability. Two other (Vertical and Horizontal) models were also developed by separating tasks with different kinematics. With R2 = 0.56 and 0.61 they represent a significant improvement over the Global model. The results reveal a low R2 for the Global model due to collecting in the same sample many tasks that have little in common. A large R2 improvement is achieved when the dominant direction of movement is considered. The proposed method is based on a non-invasive easy-to-measure physiological parameter and can be used to track the activity level during work activity in the industrial sector.

Deployed Veterans exhibit distinct respiratory patterns and greater dyspnea during maximal cardiopulmonary exercise: A case-control study.

Exertional dyspnea and exercise intolerance are frequently endorsed in Veterans of post 9/11 conflicts in Southwest Asia (SWA). Studying the dynamic behavior of ventilation during exercise may provide mechanistic insight into these symptoms. Using maximal cardiopulmonary exercise testing (CPET) to experimentally induce exertional symptoms, we aimed to identify potential physiological differences between deployed Veterans and non-deployed controls. Deployed (n = 31) and non-deployed (n = 17) participants performed a maximal effort CPET via the Bruce treadmill protocol. Indirect calorimetry and perceptual rating scales were used to measure rate of oxygen consumption ([Formula: see text]), rate of carbon dioxide production ([Formula: see text]), respiratory frequency (f R), tidal volume (VT), minute ventilation ([Formula: see text]), heart rate (HR), perceived exertion (RPE; 6-20 scale), and dyspnea (Borg Breathlessness Scale; 0-10 scale). A repeated measures analysis of variance (RM-ANOVA) model (2 groups: deployed vs non-deployed X 6 timepoints: 0%, 20%, 40%, 60%, 80%, and 100% [Formula: see text]) was conducted for participants meeting valid effort criteria (deployed = 25; non-deployed = 11). Significant group (η2partial = 0.26) and interaction (η2partial = 0.10) effects were observed such that deployed Veterans exhibited reduced f R and a greater change over time relative to non-deployed controls. There was also a significant group effect for dyspnea ratings (η2partial = 0.18) showing higher values in deployed participants. Exploratory correlational analyses revealed significant associations between dyspnea ratings and fR at 80% (R2 = 0.34) and 100% (R2 = 0.17) of [Formula: see text], but only in deployed Veterans. Relative to non-deployed controls, Veterans deployed to SWA exhibited reduced fR and greater dyspnea during maximal exercise. Further, associations between these parameters occurred only in deployed Veterans. These findings support an association between SWA deployment and affected respiratory health, and also highlight the utility of CPET in the clinical evaluation of deployment-related dyspnea in Veterans.

Dynamics of cupcake baking: Coupled multiphase heat and mass transport in a deformable porous material

This study presents a coupled multiphase porous media transport model with evaporation, large deformation, and material transformation (phase change from starch gelatinization) for cupcake baking in a conventional oven. The governing equations for transport and deformation are energy, mass, and momentum conservation of the solid cupcake batter matrix, water, water vapor, and carbon dioxide produced during baking. They are solved numerically to predict the evolution of the cupcake batter's temperature, moisture, dimensional change, and color during baking. Cupcake-baking experiments are used to validate the model against measured temperature, moisture, color, and cupcake height during baking. The rate of carbon dioxide production, vapor generation, and the cupcake batter's mechanical properties determine the cupcake's final shape. The novelty of the numerical model is the coupling of the massive change in mechanical and thermophysical properties with multiphase transport and expansion due to pressure and moisture loss from shrinkage.

Modeling the microbial pretreatment of camelina straw and switchgrass by Trametes versicolor and Phanerochaete chrysosporium via solid-state fermentation process: A growth kinetic sub-model in the context of biomass-based biorefineries.

Advancing microbial pretreatment of lignocellulose has the potential not only to reduce the carbon footprint and environmental impacts of the pretreatment processes from cradle-to-grave, but also increase biomass valorization, support agricultural growers, and boost the bioeconomy. Mathematical modeling of microbial pretreatment of lignocellulose provides insights into the metabolic activities of the microorganisms as responses to substrate and environment and provides baseline targets for the design, development, and optimization of solid-state-fermentation (SSF) bioreactors, including substrate concentrations, heat and mass transfer. In this study, the growth of Trametes versicolor 52J (TV52J), Trametes versicolor m4D (TVm4D), and Phanerochaete chrysosporium (PC) on camelina straw (CS) and switchgrass (SG) during an SSF process was examined. While TV52J illustrated the highest specific growth rate and maximum cell concentration, a mutant strain deficient in cellulose catabolism, TVm4D, performed best in terms of holocellulose preservation and delignification. The hybrid logistic-Monod equation along with holocellulose consumption and delignification models described well the growth kinetics. The oxygen uptake rate and carbon dioxide production rate were directly correlated to the fungal biomass concentration; however, a more sophisticated non-linear relationship might explain those correlations better than a linear model. This study provides an informative baseline for developing SSF systems to integrate fungal pretreatment into a large-scale, on-farm, wet-storage process for the utilization of agricultural residues as feedstocks for biofuel production.

Acute ventilatory responses to swimming at increasing intensities.

Physical exercise is a source of stress to the human body, triggering different ventilatory responses through different regulatory mechanisms and the aquatic environment imposes several restrictions to the swimmer, particularly regarding the restricted ventilation. Thus, we aimed to assess the acute ventilatory responses and to characterize the adopted breathing patterns when swimming front crawl at increasing intensity domains. Eighteen well-trained swimmers performed 7 × 200 m front crawl (0.05 m∙s-1 velocity increments) and a maximal 100 m (30 s rest intervals). Pulmonary gas exchange and ventilation were continuously measured (breath-by-breath) and capillary blood samples for lactate concentration ([La-]) analysis were collected at rest, during intervals and at the end of the protocol, allowing the identification of the low, moderate, heavy, severe and extreme intensity domains. With the swimming velocity rise, respiratory frequency (f R), [La-] and stroke rate (SR) increased ([29.1-49.7] breaths∙min-1, [2.7-11.4] mmol∙L-1, [26.23-40.85] cycles; respectively) and stroke length (SL) decreased ([2.43-2.04] m∙min-1; respectively). Oxygen uptake (VO2), minute ventilation (VE), carbon dioxide production (VCO2) and heart rate (HR) increased until severe ([37.5-53.5] mL∙kg-1∙min-1, [55.8-96.3] L∙min-1, [32.2-51.5] mL∙kg-1∙min-1 and [152-182] bpm; respectively) and stabilized from severe to extreme (53.1 ± 8.4, mL∙kg-1∙min-1, 99.5 ± 19.1 L∙min-1, 49.7 ± 8.3 mL∙kg-1∙min-1 and 186 ± 11 bpm; respectively) while tidal volume (VT) was similar from low to severe ([2.02-2.18] L) and decreased at extreme intensities (2.08 ± 0.56 L). Lastly, the f R/SR ratio increased from low to heavy and decreased from severe to the extreme intensity domains (1.12 ± 0.24, 1.19 ± 0.25, 1.26 ± 0.26, 1.32 ± 0.26 and 1.23 ± 0.26). Our findings confirm a different ventilatory response pattern at extreme intensities when compared to the usually evaluated exertions. This novel insight helps to understand and characterize the maximal efforts in swimming and reinforces the importance to include extreme efforts in future swimming evaluations.

Closed-Loop Control of Carbon Dioxide Concentration and Pressure Improves Response of Room Respiration Calorimeters

Large room calorimeters are capable of rapid measurements that are usually made in hoods or small rooms. We evaluated the performance gains of four calorimeters constructed with modern control systems, sample gas preparation and data processing. Calibration of the calorimeters and instruments was performed in place, with traceability to international standards. Performance was evaluated by infusion of N2-Co2 gas and 243 24-h studies of individuals. Our subjects included children weighing 20 kg and adults engaged in heavy exercise. Errors for 24-h infusion measurements (n = 23) were -0.34 ± 1.24% for oxygen consumption rate and 0.11 ± 0.98% for carbon dioxide production rate. Calorimeter 90% response times were 2 to 6 min over a range of oxygen consumption rates from 100 to >4000 mL/min. Closed-loop control of supply and exhaust air flows provided consistent 24-h mean CO2 levels (0.39 ± 0.015%) and pressures (13.2 ± 4.4 Pa). Room calorimeters operated with closed-loop control can be used for accurate measurement of energy expenditure rate dynamics for a wide range of individuals.

Mechanical, thermal, tribological, and flammability properties of polybutylene terephthalate composites: Comparing the effects of synthetic wollastonite nanofibers, natural wollastonite, and graphene oxide

AbstractPolybutylene terephthalate (PBT) composites were prepared with 1.0 phr synthetic wollastonite nanofibers (SWN), natural wollastonite (NW) and graphene oxide (GO) to study the effect of different fillers on mechanical, thermal, tribological, and flammability properties. The properties of PBT composites are related to the size, structure, and interfacial adhesion of the fillers in PBT matrix. PBT/SWN demonstrated the highest tensile strength and Young's modulus (6% and 9% increment), followed by PBT/NW (1.3% and 7% increment) and PBT/GO (2% decrement and 4% increment). PBT/SWN gave the highest degradation temperature (409°C), followed by PBT/GO (404.7°C). The maximum enhancement in wear resistance (73%) by PBT/SWN and anti‐friction performance (26%) by PBT/GO evinced the excellent load‐bearing ability of SWN and the great lubricating effect of GO. PBT/NW had the lowest peak heat release rate, smoke, and carbon dioxide production rate. This study shows that PBT composites have great potential in different automotive applications.

A novel concept for pure hydrogen production and a massive reduction in CO2 emissions from the formaldehyde absorption process

AbstractThe Formox process is a well‐known process for formalin generation, which uses iron‐molybdenum oxide as a catalyst. Typically, the off‐gas from the formaldehyde absorption column in Formox process is burnt in the emission control system (ECS), resulting to produce a huge amount of CO2. This work proposes a modified process to remove formaldehyde and volatile organic compounds from the stack of formaldehyde absorbing tower. Steam reforming reactions in a novel fixed‐bed tubular membrane reactor is used instead of combustion reactions in a conventional fixed‐bed reactor in ECS. The process was modeled to evaluate the role of membrane reactor for CO2 mitigation in Formox process. The collected data from a domestic formalin plant were used for modeling purposes. The model was validated against experimental measurements obtained from other works. A good consistency was observed. The improvement in CO2 emission mitigation, as well as H2 production, was achieved by applying the Pd‐Ag membrane reactor filled with copper‐based catalyst. The CO2 emission rate considerably changed from 6,700 to 575 kg/day. Furthermore, by using the proposed reactor, the emission of formaldehyde and methanol vapors throughout the ECS plant were eliminated. The essential parameters such as reactor pressure, temperature, and membrane thickness on reactor performance were evaluated. By increasing the feed temperature, the carbon dioxide production rate decreases, and pure hydrogen production rate increases. The higher CO2 generation was observed at elevated pressures. The effect of membrane thickness on CO2 emission was negligible.

Development of a novel ethylene scavenger made up of pumice and potassium permanganate and its effect on preservation quality of avocados

The purpose of this research was to develop a novel ethylene scavenger by combining pumice and potassium permanganate (KMnO 4 ) to preserve fruit and vegetables. The study showed that pumice with smaller particle sizes and lower relative humidity (RH) were favorable to ethylene adsorption. The optimal ratio was 1 g of pumice (<5 μm) to 100 mg of KMnO 4 with approximately 620 μL/g of ethylene adsorption capacity within 24 h at lab room RH (30%). Further, this novel ethylene scavenger restricted the ethylene production rate of avocados to 0 μL/kg/h for nine days, and simultaneously, the carbon dioxide (CO 2 ) production rate remained below 25 mL/kg/h. In addition, the firmness of avocados preserved by the novel ethylene scavenger was 4.04 × 10 5 N/m 2 on the 9th d. The results confirmed that the shelf life of avocados was extended by one week at 25 °C under the preservation of the novel ethylene scavenger. • Smaller particle size and lower relative humidity favored ethylene removal. • Pumice physically adsorbed ethylene and KMnO 4 oxidized ethylene. • Ethylene and CO 2 production rate were restricted by the ethylene scavenger. • The ethylene scavenger could extend shelf life of avocados by one week.

Multiple propane gas burn rates procedure to determine accuracy and linearity of indirect calorimetry systems: an experimental assessment of a method.

Indirect calorimetry (IC) systems measure the fractions of expired carbon dioxide (FeCO2), and oxygen (FeO2) recorded at the mouth to estimate whole-body energy production. The fundamental principle of IC relates to the catabolism of high-energy substrates such as carbohydrates and lipids to meet the body's energy needs through the oxidative process, which are reflected in the measured oxygen uptake rates (V̇O2) and carbon dioxide production rates (V̇CO2). Accordingly, it is important to know the accuracy and validity of V̇O2and V̇CO2 measurements when estimating energy production and substrate partitioning for research and clinical purposes. Although several techniques are readily available to assess the accuracy of IC systems at a single point for V̇CO2 and V̇O2, the validity of such procedures is limited when used in testing protocols that incorporate a wide range of energy production (e.g., basal metabolic rate and maximal exercise testing). Accordingly, we built an apparatus that allowed us to manipulate propane burn rates in such a way as to assess the linearity of IC systems. This technical report aimed to assess the accuracy and linearity of three IC systems using our in-house built validation procedure. A series of trials at different propane burn rates (PBR) (i.e., 200, 300, 400, 500, and 600 mL min-1) were run on three IC systems: Sable, Moxus, and Oxycon Pro. The experimental values for V̇O2 and V̇CO2 measured on the three IC systems were compared to theoretical stoichiometry values. A linear relationship was observed between increasing PBR and measured values for V̇O2and V̇CO2 (99.6%, 99.2%, 94.8% for the Sable, Moxus, and Jaeger IC systems, respectively). In terms of system error, the Jaeger system had significantly (p < 0.001) greater V̇O2(mean difference (M) = -0.057, standard error (SE) = 0.004), and V̇CO2(M = -0.048, SE = 0.002) error compared to either the Sable (V̇O2, M = 0.044, SE = 0.004; V̇CO2, M = 0.024, SE = 0.002) or the Moxus (V̇O2, M = 0.046, SE = 0.004; V̇CO2, M = 0.025, SE = 0.002) IC systems. There were no significant differences between the Sable or Moxus IC systems. The multiple PBR approach permitted the assessment of linearity of IC systems in addition to determining the accuracy of fractions of expired gases.