Total Heat Evolution Research Articles

The study of the biotoxicity effect of alumina nanoparticle on soil microbes

Due to the unique properties, nanoparticles (NPs) have been widely used both in industrial products and individual life. However, with the huge benefits, NPs also possess potential toxicity to human health and ecosystem. Aluminum oxide NPs is so significant in industry that it occupies the second important position in US nanomaterials market. Aluminum oxide NPs belong to metal oxide nanoparticles which may have strong antimicrobial properties. As there is limited prior research on the toxicity of alumina NPs, the main goal of present research is to study the effects of alumina NPs on microorganisms in soils by combination methods of microcalorimetry and urease. Power-time curves and thermo-kinetic parameters (such as total heat evolution QT, growth rate constant k and maximum power output Pmax) were applied to evaluate the microbial community activities of the soil samples. A range of concentration of Aluminum oxide NPs gradient from 0 mg/L to 1000 mg/L was applied. The results showed that the concentration under 500 mg/L has negligible inhibitory effects on soil microorganisms while concentrations at 500mg/L and 1000 mg/L only have mild inhibition on microbes in soil. Urease experiments verified this result, therefore, it suggests that combination of microcalorimetry and urease may provide practical method for microorganism activity evaluating.

Influence of fly ash on mechanical properties and hydration of calcium sulfoaluminate-activated supersulfated cement.

This paper aimed to report the effects of fly ash (FA) on the mechanical properties and hydration of calcium sulfoaluminate-activated supersulfated cement (CSA-SSC). The CSA-SSC comprises of 80% granulated blast furnace slag (GBFS), 15% anhydrite, and 5% high-belite calcium sulfoaluminate cement (HB-CSA) clinker. The hydration products of CSA-SSC with or without FA were investigated by X-ray diffraction and thermogravimetric analysis. The experimental results indicated that the addition of FA by 10% to 30% resulted in a decrease in the rate of heat evolution and total heat evolution of CSA-SSC. As the content of FA was increased in the CSA-SSC system, the compressive and flexural strengths of the CSA-SSC with FA after 1 day of hydration were decreased. After 7 days of hydration, the compressive and flexural strength of CSA-SSC mixed with 10 wt.% and 20 wt.% of FA rapidly increased and exceeded that of ordinary Portland cement (OPC), especially the flexural strength. Moreover, the compressive strength of CSA-SSC mixed with 30 wt.% of FA after 90 days of hydration was close to that of OPC, and flexural strength of CSA-SSC mixed with 30 wt.% of FA after 7 days of hydration was close to that of OPC. The hydration products of the CSA-SSC and CSA-SSC mixed with FA were mainly ettringite and calcium silicate hydrate (C-S-H).

Heat Content Anomaly and Decay of Warm‐Core Rings: the Case of the Gulf of Mexico

AbstractIn this study, we harness the 25‐year satellite‐altimeter record, in concert with a vast array of in situ measurements, to estimate the heat content anomaly of 32 warm‐core rings in the Gulf of Mexico (GoM). The decay rate of these mesoscale eddies is studied in detail, and it is shown that they release the majority of their heat as they drift in the central GoM (away from topographic obstacles). The surface heat fluxes from the eddies are shown to be small in comparison to the total rate of heat loss from the eddies, suggesting that heat is primarily released toward the surrounding water masses. Integrating the total heat evolution equation over the warm‐core rings yields an estimate of their effective lateral diffusivity coefficient. The long‐term impact of warm‐core rings on heat and salt balance in the GoM is also discussed.

The effect of blast-furnace slag particle size on the hydration of slag–Portland cement grouts at elevated temperatures

The UK nuclear industry has historically used a unique specification of cement powder that differs from construction industry requirements. However, the slags that complied with this specification have become unavailable. The material now used to meet the requirements of the specification is a blend of standard construction industry ground granulated blast-furnace slag (GGBS), which has high fineness, with Calumite which is a coarser slag powder. Both materials have very similar chemical compositions, and the main reason for blending is to control the particle size distribution (PSD) to replicate the performance of the previous supply. The effect of changing the PSD on the performance properties of the cement paste was investigated. Isothermal conduction calorimetry at elevated temperatures was carried out to monitor the heat of hydration; it was found that the peak heat and total heat evolution increased with an increase in GGBS content. It was also found that Calumite contributes very little to the hydration reaction and thus behaves similarly to an inert filler. As the GGBS content was decreased, the fluidity of the pastes increased up to a certain point, but decreased again for systems dominated by very coarse particles, indicating that there is an optimum balance between the finer and coarser slag particles within this cementing system.

Construction material properties of high temperature arc gasification slag as a portland cement replacement

Abstract This study investigates a potential beneficial reuse application for high-temperature arc gasification slag (HTAG), a waste product of electricity generated using municipal solid waste as fuel. The potential for the beneficial use of this material for a partial replacement for portland cement was investigated at four levels of replacement (5, 20, 35, and 50%). The heat of hydration was measured for the reference and slag samples by isothermal conduction calorimetry. Results from the study demonstrate that at low replacement percentages the total heat evolution and the compressive strength of the control cement and slag-cement blends are similar. The compressive strength of mortars amended with pulverized and finely milled HTAG slag was measured at 7, 28 and 56 days and the results demonstrate that low replacement percentages (5%) of portland cement with HTAG slag produces comparable strength. Significant decreases in strength and heat were seen when higher replacement percentages (20–50%) were used, however these decreases were partially offset using finer slag. Although the activity index of the slag was relatively low compared to portland cement, an increased activity index can be reached by decreasing the average particle size, suggesting that properly processed HTAG slag does offer potential as a supplementary cementitious material.

Exploring an in situ LED-illuminated isothermal micro-calorimetric method to investigating the thermodynamic behavior of Chlorella vulgaris during CO2 bio-fixation.

Much endeavor has been dispensed recently to evaluate the potential of CO2 mitigation by microalgae. We introduce an alternative, novel, LED-illumination isothermal microcalorimetric method to assess the thermodynamic behaviors of microalgae for better understanding of their carbon sequestration capacity. Microalgae thermodynamic behaviors were recorded as power-time curves, and their indices such as total heat evolution (QT), maximum power output (Pmax) and heat generated by per algae cell (JN/Q) were obtained. The values for highest (74.80gL-1) and control sample (0.00gL-1) of QT, Pmax and JN/Q were 20.85 and 2.32J; 252.17 and 57.67μW; 7.91 × -06 and 8.80 × -07Jcell-1, respectively. According to the values of QT, a general order to promote the CO2 sequestration was found at 74.8gL-1> 29.92gL-1> 14.96gL-1> 7.48gL-1> 0gL-1 of C sources, which directly corresponded to carbon availability in the growth medium. Chlorella vulgaris GIEC-179 showed the highest peak Pmax at 74.8gL-1 concentration which was directly transformed to their biomass during bio-fixation of CO2 process. This study is applicable for better understanding of CO2 fixation performance of algae.

Partitioning effect on natural convection in a circular enclosure with an asymmetrically placed inclined plate

This work presents a numerical investigation on steady-state laminar natural convection in a circular enclosure with an inner flat plate at Ra=106. The plate is inclined placed along the radial direction but is asymmetric about the center of enclosure, with eccentricity defined as the distance between the centers of two entities. The enclosure and plate are kept at low and high temperatures, respectively. The objective of this study is to explore the effects of two significant parameters, i.e., eccentricity (r) and inclination (α) of the plate, on the flow and heat transfer characteristics of the enclosure-plate system. The numerical simulation is performed using our in-house fourth-order finite difference code which is well validated. The effects of the two parameters are analyzed by the total heat transfer rate, temperature distribution, formation and evolution of various vortices, and distribution of local heat transfer rate for r/D=0.00(0.05)0.20 and α=0°(5°)180° where D is the enclosure diameter. Numerical results reveal that natural convection is weakened by the partitioning effect of nearly horizontal plate since fluid circulation is greatly constrained, while the effect is minor at low and high inclinations where fluid circulation is pronounced. Depending on the eccentricity and inclination, there could be at most two and three vortices in the left and right halves of the enclosure, respectively, whose formation and spatial evolution behaviors and intensity variations exhibit complex patterns, and are closely related with the heat transfer characteristics. For high eccentricity configurations, the heat transfer in the gap can be dominated by either convection or conduction depending on the gap size, the latter of which is characterized by the expected linear variation of circumferential position of maximum local heat transfer rate with the inclination.

Effect of limestone powder on the water stability of magnesium phosphate cement-based materials

Addition of limestone to Porland cement can significantly increase the hydration and high early strength of Porland cement. However its application in the magnesium phosphate cement is less known. In this paper, magnesium potassium phosphate cement (MKPC) pastes in which magnesium oxide was replaced by up to 30% limestone were studied. The effect of limestone content on the hydration temperature, setting time, compressive strength, and early water stability were investigated. The deterioration mechanism in water was explored by analyzing the pH value of the immersed solution, leached substances, total phosphorus content and microstructural analyses including X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TG/DTG) and mercury intrusion porosimetry (MIP). The results showed that addition of limestone into the magnesium phosphate cement matrix accelerated the setting time, decreased the total heat evolution of MKPC, and clearly degraded the strengths. The poor water stability of MKPC with limestone powder might be caused by the poor crystallinity and crystal morphologies of hydration products, worsened pore structure and increased dissolution of hydration products. Considering the materials costs and the strength development, the optimum addition of limestone powder should be no more than 10%.

Hydration of ternary cementitious system: Portland cement, fly ash and silica fume

Hydration of ternary OPC–FA–SF cements has been studied using number of techniques. Heat of hydration studies were made with the help of TAM AIR calorimeter, and it was found that fly ash retarded the hydration of OPC and reduced the total heat evolution. However, fly ash and silica fume together improved the heat evolution, but the values were lower than that of OPC. Differential scanning calorimetric studies of cements hydrated for 28 days were made, and it was found that Ca(OH)2 produced during the hydration of OPC reacted with fly ash and silica fume. SEM pictures of hydrated cements were recorded. The results have shown that silica fume accelerates the hydration and minimizes the deficiencies of fly ash blended cement. Mechanism of hydration has been proposed.

Influence of short-time imidacloprid and acetamiprid application on soil microbial metabolic activity and enzymatic activity.

The influence of two neonicotinoids, i.e., imidacloprid (IMI) and acetamiprid (ACE), on soil microbial activities was investigated in a short period of time using a combination of the microcalorimetric approach and enzyme tests. Thermodynamic parameters such as Q T (J g(-1) soil), ∆H met (kJ mol(-1)), J Q/S (J g(-1) h(-1)), k (h(-1)), and soil enzymatic activities, dehydrogenase, phosphomonoesterase, arginine deaminase, and urease, were used to evaluate whole metabolic activity changes and acute toxicity following IMI and ACE treatment. Various profiles of thermogenic curves reflect different soil microbial activities. The microbial growth rate constant k, total heat evolution Q T (expect for IMI), and inhibitory ratio I show linear relationship with the doses of IMI and ACE. Q T for IMI increases at 0.0-20 μg g(-1) and then decreases at 20-80 μg g(-1), possibly attributing to the presence of tolerant microorganisms. The 50 % inhibitory ratios (IC50) of IMI and ACE are 95.7 and 77.2 μg g(-1), respectively. ACE displays slightly higher toxicity than IMI. Plots of k and Q T against microbial biomass-C indicate that the k and Q T are growth yield-dependent. IMI and ACE show 29.6; 40.4 and 23.0; and 23.3, 21.7, and 30.5 % inhibition of dehydrogenase, phosphomonoesterase, and urease activity, respectively. By contrast, the arginine deaminase activity is enhanced by 15.2 and 13.2 % with IMI and ACE, respectively. The parametric indices selected give a quantitative dose-response relationship of both insecticides and indicate that ACE is more toxic than IMI due to their difference in molecular structures.

Evaluate the heavy metal toxicity to Pseudomonas fluorescens in a low levels of metal-chelates minimal medium.

A 2-(n-morpholino)ethane sulfonic acid (MES)-buffered minimal medium with low levels of metal chelates was used to evaluate the heavy metal (Co+2, Pb+2, Zn+2, Fe+2, Fe+3, Cd+2, Cu+2, and Cr+6) toxicity to Pseudomonas fluorescens through minimizing the limitation of the existing medium. The interaction between bacteria and heavy metals was real-time monitored by microcalorimetry and reflected by thermogenic curves. Compared with the main parameters, microbial growth rate constant k and total heat evolution Q total, a general order of toxicity was found to be Fe+3<Co+2<Fe+2<Cu+2<Cr+6<Zn+2<Pb+2<Cd+2. The main metal speciation was Co+2, Zn+2, Fe+2, Cd+2, PbOH+, Fe(OH)+2, CuOH+, HCrO4-, and CrO4(-2) at pH 6.4. These metal speciations are main factors to exhibit the metal toxicity to bacteria. To validate their interaction, the surface chemical functional groups of P. fluorescens biomass identified by Fourier transform infrared (FTIR) were amino, carboxyl, hydroxyl, and phosphoryl groups, which maybe involved in the biosorption of metal ions.

Microcalorimetric evaluation of soil microbiological properties under plant residues and dogmatic water gradients in Red soil

A study of 6 months duration was carried out to investigate the effect of water regimes and organic amendments on the soil microbial biomass and microbial population under Red soil collected from Hunan Providence, China. The soil microbial biomass and population were measured with traditional methods and results obtained by conventional methods, corroborated with microcalorimetry. The incorporation of rice (Oryza sativa L.) straw (RS) and green manure (GM), especially at high rates, enhanced the soil microbial activities. We observed that the use of GM exhibited more significant stimulating effects on microbial activities than RS. Similarly, water regimes, 25% (W1) and 200% (W2) of water holding capacity, also had significant effects on microbial activities. Comparing the effects of water levels, we noticed that W2 had a significant negative influence on soil microbial biomass and population. To compare the results of conventional methods and to check the sensitivity of microcalorimetry, the thermodynamic parameters, microbial growth rate constant (k), total heat evolution (Q), peak height (Pmax) and peak time (tmax) were calculated. Highest Pmax, k and Q were observed in GM treatments at water regime W1, while highest tmax values were recorded in CK (control) and RS treatments at W2. The microcalorimetric parameters, Pmax, k and Q were positively correlated, whereas tmax negatively linked with microbial biomass and population at p < 0.01. Our results suggest that microcalorimetry successfully verified the results obtained from customary methods and microcalorimetric parameters Pmax, tmax, Q and k proved that they are highly sensitive to microbial properties and could be used as indices of microbial community shifts and activities in soil ecosystems.

Investigating Pseudomonas putida–Candida humicola Interactions as Affected by Chelate Fe(III) in Soil

Microcalorimetric technique was applied to assess the toxic effect of EDTA-chelated trivalent iron on Pseudomonas putida (P. putida) (bacterium), Candida humicola (C. humicola) (fungus) and their mixture in sterilized soil. Microbial growth rate constant k, total heat evolution Q T, metabolic enthalpy ∆H met, mass specific heat rate J Q/S, microbial biomass C and inhibitory ratio I were calculated. Results showed that microcalorimetric indexes decreased with the increasing Fe(III)-EDTA complex concentration. Comparing the single and mixed strains, the effect of Fe(III) on bacterium-fungus interaction was dominant at lower dose, whereas, the metal toxicity at high dose of Fe was the main factor affecting P. putida and C. humicola activity. Thus, the mixture had moderate tolerance to the iron overload, and exhibit synergistic interaction in exponential growth phase (0-0.3 mg g(-1)). The results of glucose degradation showed that glucose was consumed totally at the end of exponential phase of microbial growth.

Effect of boron phosphate on the mechanical, thermal and fire retardant properties of polypropylene and polyamide-6 fibers

The effect of boron phosphate (BPO4) nanoparticles on the mechanical, thermal, and flame retardant properties of polypropylene (PP) and polyamide 6 (PA-6) fibers are investigated by tensile testing, thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), and micro combustion calorimeter (MCC). The addition of BPO4 reduces the mechanical properties of the both PP and PA-6 fibers. According to the TGA results, the addition of BPO4 does not change the thermal behavior of PP fiber and slightly reduces the thermal stability of PA-6 fiber by about 30 °C. According to MCC results, the addition of BPO4 does not change the effective total heat evolution and heat release rate (HRR) peak for PP fibers. Although the inclusion of BPO4 does not change the total heat evolution of PA-6 fiber, it reduces the HRR peaks due to increase in barrier effect of char.

A Combination Method to Study the Effects of Petroleum on Soil Microbial Activity

TAM III multi-channel calorimetry was applied to study the effect of different concentrations petroleum on soil microbial activity and community. The microbial activities of the soil samples were recorded as power-time curves. The thermokinetic parameters such as microbial growth rate constant k, total heat evolution Q(T), metabolic enthalpy ∆H (met) and mass specific heat rate J(Q/S) were calculated. Results showed that petroleum had a certain extent effects to soil microorganisms. The results indicate that the soil microbial activity was promoted with a petroleum concentration lower than 0.52 % ± 0.24 %, but inhibited with further increase in petroleum.

Determination of Reduce of Arsenic (III) Toxicity to &lt;i&gt;Pseudomonas fluorescens&lt;/i&gt; Using Iron by Combined Methods

A series of microcalorimetric experiments were performed to evaluate the As(III), Fe(II), P and their joint effects by analyzing the thermodynamic parameters, microbial growth rate constant k, total heat evolution QT, inhibitory ratio I and highest heat flow Pmax. They were obtained from power-time curves of the growth of P. fluorescens. The effect of mixed As(III), Fe(II) and P were moderate, compared with control, single As(III) or Fe(II). In addition, FT-IR spectra of dry P. fluorescens after the adsoption of As(III) and Fe(II) and their mixture showed that Fe influenced the C-H bonds of the functional groups on the cellwall, the As(III) caused litter effect.

Microcalorimetry study on the microbial activity of permafrost on the Tibetan plateau of China

Microcalorimetric techniques had been used to study the influence of different physicochemical parameters on microbial growth in different permafrosts on the Tibetan plateau. The total heat evolution of the permafrost samples amended with glucose, QT, the values of microbial growth rate constant, k, and the heat output power, Pt, were calculated from the power–time (P–t) curves. It is observed that the same coverage vegetation show similar P–t curves, which strongly suggest that the permafrost microorganisms of the homology vegetation coverage have similar structures of community. Furthermore, the vegetation degradation turns out to have significant influence, that is, the better the status of vegetation is, the higher the values of k, CFU and QT are.

Comparative toxicity of chlorpyrifos and its oxon derivatives to soil microbial activity by combined methods

The inhibitory effects of the pesticide Chlorpyrifos (CPF) and its oxon derivative (CPO) on soil microbial activity were evaluated through the measurement of metabolic parameters and the microbial urease enzyme. The thermodynamic parameters related to microbial activity were measured and recorded as power–time curves. Microbial growth rate constant k, total heat evolution Q T, metabolic enthalpy Δ H met, mass specific heat rate J Q/S, microbial biomass C and inhibitory ratio I were calculated. They showed the linear relationship with doses of CPF and CPO. Thereinto, the linear correlations, k versus biomass C and Δ H met versus biomass C, elucidated that k and Δ H met were growth yield dependent. In this work, 20% inhibitory ratio IC 20 was obtained with 9.8 μg g −1 for CPF and 0.37 μg g −1 CPO, meaning that the acute toxicity of CPO was 26 times that of CPF, since the CPO had more potent toxicity to living organism due to its active functional group. Comparing the change tendency of Δ H met and other parameter, the values almost kept constant when exposure to CPF (<5.0 μg g −1). It illustrates that individual reacted to stress resulted from environment change by shifting resources from other biological activities (such as reproduction or growth) toward survival to some extent. Urease activity responses in relation to the CPF and CPO exposure were observed and consistent with above thermodynamic parameters.

Short-time effect of heavy metals upon microbial community activity

Microcalorimetry was applied to assess and compare the toxic effect of heavy metals, such as As, Cu, Cd, Cr, Co, Pb and Zn, on the soil microbial activities and community. About 1.0 g soil spiked 5.0mg glucose and 5.0mg ammonium sulfate, the microbial activities were recorded as power-time curves, and their indices, microbial growth rate constant k, total heat evolution Q(T), metabolic enthalpy Delta H(met) and mass specific heat rate J(Q/S), were calculated. Comparing these thermodynamic parameters associated with growth yield, a general order of toxicity to the soil was found to be Cr>Pb>As>Co>Zn>Cd>Cu. When soil was exposed to heavy metals, the amount of bacteria and fungi decreased with the incubation time, and the bacterial number diminished sharply. It illustrates that fungi are more tolerant, and bacteria-fungi ratio would be altered under metal stress. To determine the status of the glucose consumed, a glucose biosensor with eggshell membrane was used to measure the remaining glucose in soil sample. Results showed that the time at which glucose was consumed completely was agreed with the microcalorimetric time to a large extent, and depended on the toxicity of heavy metals as well.

Microcalorimetric assessment of microbial activity in long-term fertilization experimental soils of Southern China

Microcalorimetry, plate count and PCR-denaturing gradient gel electrophoresis (DGGE) were employed to investigate microbial diversity and activity in soils from the Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences, Hunan Province, China, where a wheat-corn rotation with 12 fertilization treatments was established in 1990. Fertilization greatly increased microbial biomass carbon (C) and nitrogen (N) (C(mic) and N(mic)) as well as the activities of phosphatase, urease, invertase, protease, catalase and dehydrogenase. Manure alone (M) enhanced the number of denitrifying and aerobic bacteria by 54.4% and 20.5%, respectively, whereas fallow (H) increased the number of aerobic cellulose decomposing bacteria by 31.4%. Fallow and soils amended with mineral fertilizers plus pig manure or straw increased both the DGGE band patterns and the Shannon index compared with mineral fertilizers or the control. Mineral treatments with lower bacterial numbers enhanced the values of the peak time (t(max)) more than did organic treatments. The peak height (P(max)) was positively correlated (P<0.01), with soil enzymes, C(mic) and N(mic), and the number of microorganisms, whereas the peak time (t(max)) was negatively connected (P<0.01) with these parameters. The microbial growth rate constant (k) was linked to bacteria (P<0.01), actinomycetes (P<0.05) and catalase (P<0.05). The total heat evolution (Q) had no relationships with any soil microbial properties (except for catalase). We propose that P(max) and t(max) could be used as indices of soil microbial activity, while the values of k and Q are poor indicators.