isothermal calorimetry
Recently Published Documents





2022 ◽  
Vol 23 (2) ◽  
pp. 950
Rosaria Russo ◽  
Margherita Romeo ◽  
Tim Schulte ◽  
Martina Maritan ◽  
Luca Oberti ◽  

Light chain amyloidosis (AL) is caused by the aberrant overproduction of immunoglobulin light chains (LCs). The resulting abnormally high LC concentrations in blood lead to deposit formation in the heart and other target organs. Organ damage is caused not only by the accumulation of bulky amyloid deposits, but extensive clinical data indicate that circulating soluble LCs also exert cardiotoxic effects. The nematode C. elegans has been validated to recapitulate LC soluble toxicity in vivo, and in such a model a role for copper ions in increasing LC soluble toxicity has been reported. Here, we applied microscale thermophoresis, isothermal calorimetry and thermal melting to demonstrate the specific binding of Cu2+ to the variable domain of amyloidogenic H7 with a sub-micromolar affinity. Histidine residues present in the LC sequence are not involved in the binding, and yet their mutation to Ala reduces the soluble toxicity of H7. Copper ions bind to and destabilize the variable domains and induce a limited stabilization in this domain. In summary, the data reported here, elucidate the biochemical bases of the Cu2+-induced toxicity; moreover, they also show that copper binding is just one of the several biochemical traits contributing to LC soluble in vivo toxicity.

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 459
Chiara D’Erme ◽  
Walter Remo Caseri ◽  
Maria Laura Santarelli

The use of nanocellulose in traditional lime-based mortars is a promising solution for green buildings in the frame of limiting the CO2 emissions resulting from Portland Cement production. The influence of the fibrillated cellulose (FC) on lime pastes and lime-based mortars was studied incorporating FC at dosages of 0%, 0.1%, 0.2% and 0.3wt% by weight of binder. The lime pastes were subjected to thermal and nitrogen gas sorption analyses to understand if FC affects the formation of hydraulic compounds and the mesoporosities volume and distribution. The setting and early hydration of the mortars were studied with isothermal calorimetry. The mechanical performances were investigated with compressive and three-point-bending tests. Furthermore, fragments resulting from the mechanical tests were microscopically studied to understand the reinforcement mechanism of the fibres. It was found that 0.3wt% of FC enhances the flexural and compressive strengths respectively by 57% and 44% while the crack propagation after the material failure is not affected.

Sandrine Marceau ◽  
Lucie Lacour ◽  
Dinarzed Diafi ◽  
Fabienne Farcas

Hemp concretes are the most widely used biobased concretes in France. However, their growth is still limited by the lack of knowledge and high variability of the performances of biobased concretes, especially for their mechanical properties. These results are related to interactions between the mineral binder and plant compounds that modify the hydration of the cement. In this work, the interactions between cement and eight types of hemp shiv, and a flax shiv are studied by isothermal calorimetry. The setting delays observed in the presence of plants are interpreted by analyzing the molecules extracted from these plants in water. A link can be observed between the setting delay and the coloration of the extract solutions or their concentration in reducing sugars and in polyphenols. These results constitute a basis in the objective to define an indicator enabling to predict the compatibility between plants and mineral binders.

2022 ◽  
Vol 9 ◽  
Omar Abdelrahman ◽  
Nishant Garg

To address the high CO2 footprint associated with cement production, many alternative, sustainable binders are now gaining worldwide attention–including alkali-activated materials. The alkali-activation reaction of metakaolin is a fairly complex process involving transformation of one amorphous reactant (precursor metakaolin) into another amorphous product or products (N-A-S-H gel and/or disordered zeolite type phases). In spite of this complexity, researchers in the past 2 decades have gained significant knowledge on the nature of this reaction at multiple scales. Understanding and developing a clear relationship between the alkalinity of the mix and the extent of reaction is of high interest for practical applications. However, detailed and thorough investigations on this important relationship are limited. Here, in this study, we address this gap by systematically investigating a series of alkali-activated materials samples with a wide range of Na/Al ratios (0.5–1.8) using seven different yet complementary analytical techniques (isothermal calorimetry, FTIR, XRD, TGA, NMR, and Raman imaging). Applied in tandem, these tools reveal a clear but non-linear relationship between the Na/Al ratio and the extent of alkali-activation reaction indicating diminishing returns at higher Na/Al ratios, where higher Na/Al ratios cause an increase in the degree of reaction until a certain point at which the increase in Na/Al ratio does not significantly affect the reaction kinetics, but may affect the gel polymerization. These findings could potentially aid decision making for commercial applications of AAMs where alkalinity of the mix is an important parameter for performance as well as safety.

Agronomy ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 110
Magdalena Rys ◽  
Diana Saja-Garbarz ◽  
Andrzej Skoczowski

The use of plants that have high allelopathic potential as natural herbicides in the form of aqueous extracts is gaining popularity in environmentally friendly agriculture. Usually, their effect on the germination and growth of weeds is investigated. However, less attention is paid to the effect of the allelopathic compounds from extracts on cultivated plants. Therefore, the aim of this study was to evaluate the impact of herbal extracts that have allelopathic properties on selected physiological and biochemical processes of two plants of great economic importance—white mustard (Sinapis alba L.) and oilseed rape (Brassica napus L. var. oleifera). The extracts were prepared from mountain arnica (Arnica montana L.), ribwort (Plantago lanceolata L.), hypericum (Hypericum perforatum L.), common milfoil (Achillea millefolium L.), sunflower (Helianthus annuus L.) and sage (Salvia officinalis L.). The germination of white mustard and oilseed rape was most inhibited by the extracts that were prepared from sage and sunflower. Additionally, in the germinating plants, the sunflower extracts increased the membrane permeability, which indicates membrane injuries. The metabolic changes in the plants were monitored using isothermal calorimetry and FT-Raman spectroscopy. The total heat production, which provided information about the metabolic activity of the white mustard and oilseed rape, was decreased the most by the sage extract but generally all of the tested extracts disturbed the shape of the heat emission curves compared to the water control. The impact of the allelopathic compounds that are present in the herbal extracts on the metabolism of the seedlings was clearly visible on the FT-Raman spectra—in the fatty acids and flavonoids range, confirmed using a cluster analysis. In conclusion, the herbal extracts from medicinal plants that have herbicidal activity could be used as a natural herbicide for weed control, but since they may also have negative impacts on cultivated plants, preliminary tests are advisable to find the extract from the species that has the least negative effect on a protected crop.

2021 ◽  
Bohuslav Slánský ◽  
Vit Šmilauer ◽  
Jiří Hlavatý ◽  
Richard Dvořák

A jointed plain concrete pavement represents a reliable, historically proven technical solution for highly loaded roads, highways, airports and other industrial surfaces. Excellent resistance to permanent deformations (rutting) and also durability and maintenance costs play key roles in assessing the economic benefits, rehabilitation plans, traffic closures, consumption and recycling of materials. In the history of concrete pavement construction, slow-to-normal hardening Portland cement was used in Czechoslovakia during the 1970s-1980s. The pavements are being replaced after 40-50 years of service, mostly due to vertical slab displacements due to missing dowel bars. However, pavements built after 1996 used rapid hardening cements, resulting in long-term surface cracking and decreased durability. In order to build durable concrete pavements, slower hardening slag-blended binders were designed and tested in the restrained ring shrinkage test and in isothermal calorimetry. Corresponding concretes were tested mainly for the compressive/tensile strength evolution and deicing salt-frost scaling to meet current specifications. The pilot project was executed on a 14 km highway, where a unique temperature-strain monitoring system was installed to provide long-term data from the concrete pavement. A thermo-mechanical coupled model served for data validation, showing a beneficial role of slower hydration kinetics. Continuous monitoring interim results at 24 months have revealed small curling induced by drying and the overall small differential shrinkage of the slab.

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 231
Vlastimil Bílek ◽  
Petr Hrubý ◽  
Valeriia Iliushchenko ◽  
Jan Koplík ◽  
Jakub Kříkala ◽  

The very early stages of alkaline activation of slag control its rheology and setting, but also affect its hydration, which occurs later. Simultaneously, these parameters are dictated by the nature and dose of the alkaline activator. Therefore, we investigated and compared the changes in slag particles (SEM, BET, laser diffraction), as well as in the pore solution composition (ICP–OES), pH, and conductivity, of alkali-activated slag (AAS) pastes containing the three most common sodium activators (waterglass, hydroxide, and carbonate) and water during the first 24 h of its activation. To ensure the best possible comparability of the pastes, a fairly nontraditional mixture design was adopted, based on the same concentration of Na+ (4 mol/dm3) and the same volume fraction of slag in the paste (0.50). The results were correlated with the pastes’ hydration kinetics (isothermal calorimetry), structural build-up (oscillatory rheology), and setting times (Vicat). Great differences were observed in most of these properties, in the formation of hydration products, and in the composition of the pore solution for each activator. The results emphasize the role of the anionic groups in the activators and of the pH, which help predict the sample’s behavior based on its calorimetric curve, and offer data for further comparisons and for the modelling of AAS hydration for specific activators.

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 86
Zhanchen Li ◽  
Huaqiang Yuan ◽  
Faliang Gao ◽  
Hongzhi Zhang ◽  
Zhi Ge ◽  

This paper aims to study the feasibility of low cement content foamed concrete using waste lime mud (LM) and fly ash (FA) as mineral additives. The LM/FA ratio was first optimized based on the compressive strength. Isothermal calorimetry test, ESEM, and XRD were used to investigate the role of LM during hydration. Afterward, the optimized LM/FA ratio (1/5) was used to design foamed concrete with various wet densities (600, 700, 800 and 900 kg/m3) and LM–FA dosages (0%, 50%, 60%, 70% and 80%). Flowability measurements and mechanical measurements including compressive strength, flexural strength, splitting strength, elastic modulus, and California bearing ratio were conducted. The results show that the foamed concretes have excellent workability and stability with flowability within 170 and 190 mm. The high alkalinity of LM accelerated the hydration of FA, thereby increasing the early strength. The significant power functions were fitted for the relationships between flexural/splitting and compressive strength with all correlation coefficients (R2) larger with 0.95. The mechanical properties of the foamed concrete increased with the density increasing or LM–FA dosage decreasing. The compressive strength, tensile strength, CBR of all prepared foamed concretes were higher than the minimum requirements of 0.8 and 0.15 MPa and 8%, respectively in the standard.

2021 ◽  
pp. 1-32
Nancy Beuntner ◽  
Karl-Christian Thienel

The fundamental knowledge about the reaction mechanism of calcined clays in cement and the mutual interaction is important for their assessment as supplementary cementitious material and the resulting concrete properties. In this study, the hydration of two cements differing in alkali content and with the addition of a highly reactive, aluminum-rich metakaolin and one calcined common clay with low kaolinite content was investigated during the first 48 hours. For this purpose, four established methods that describe the early hydration were used: isothermal calorimetry, thermogravimetry, in-situ X-ray diffraction and chemical analysis of pore solution. This so far unique combination of methods enabled the understanding of the complex binder (cement-calcined clay) hydration behavior. The results showed considerable differences depending on type of calcined clay, its chemical-mineralogical composition, fineness and especially towards its reaction mechanism with aluminate clinker phases controlled by the composition of pore solution. The impact of calcined clay on the early clinker hydration exceeds significantly physical effects only.

Sign in / Sign up

Export Citation Format

Share Document