Isothermal Calorimeter Research Articles

ZnAl2O4 Nanomaterial as a Naked-Eye Arsenate Sensor: A Combined Experimental and Computational Mechanistic Approach.

Raising public awareness over the emerging health risk due to intake of arsenic-contaminated potable water is a matter of great concern. Exploration of cost-effective, self-testing kits is a substantial way to reach out to the masses and detect the presence of arsenate in water. With this agenda, a photoluminescent Mannich base Zn(II) complex (ZnMC = [Zn2(ML)2]·(ClO4)2·(H2O); HML = Mannich base ligand) has been synthesized, and its dinuclearity was verified with single-crystal X-ray diffraction structural analysis. Among a range of anions, ZnMC was found to detect arsenate selectively by showing a turn-off emission with a color change from bright green to dark under UV light. The real-life applicability of the ZnMC probe is somewhat restricted to only sensing of arsenate, but not its removal owing to the fact of its homogeneity. Considering the efficacy of ZnMC as well as a need for its easy removal from water, slight modification has been done with chloride ions in the form of ZnMC″ (=[Zn2(ML)2(Cl)2]), and finally, an interface between homogeneous and heterogeneous solid support has been explored with a strategic fabrication of ZnMC″ grafted ZnAl2O4, named as ZAZ nanomaterial. This not only imparts successful segregation of arsenate from drinking water but also provides naked-eye detection under ambient light as well as UV light. Thermodynamic parameters associated with the binding of arsenate to ZnMC and ZAZ have been evaluated through isothermal calorimetric (ITC) measurements. Steady-state and time-resolved fluorescence titration study, absorption titration study, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and computational calculations have been performed to get deep insights into the sensing properties. Proper justification of the sensing mechanism is the highlight of this work. ZAZ nanomaterial has been exploited to produce a self-test paper kit for arsenate detection with a limit of 9.86 ppb, which potentially enables applications in environmental monitoring.

Method of internal curing cement concrete used for 3D printing technology in construction

Currently, 3D printing technology in construction is becoming more popular every day in many countries and regions in the world. In parallel with the development of 3D printers, the research, design and application of materials as "ink" for this technology is also an urgent direction in materials science. Improvement of 3D printing technology with the use of concrete mixtures based on Portland cement largely depends on the sustainable solution of the problem of ensuring normal hardening of extruded concrete layers. A violation of hardening has known negative consequences and entails significant economic losses. It has been suggested to use polyacrylate solutions, preparation of which before application in concrete mixture allows controlling the process of their polymerization, postponing the sorption function of the additive in time to ensure the required rheology. Influence of super absorbent polymer (SAP) solution on structural formation processes and properties of cement materials is studied. Assessment of the degree of hydration was carried out by the calorimetric method for total thermal power using the isothermal calorimeter TAM AIR. Identification of main phases of cement stone (CS) by X-ray phase analysis was performed on XRD-6000 diffractometer. It is established that the use of SAP solutions has a positive effect on the mobility of cement mixtures due to the delayed polymerization and the corresponding water absorption by the polymer. The flexural strength range is 6.7–7.2 Mpa and the compression strength range is 68.5–71.7 MPa. It is established that the range of concentrations of SAP less than 1.5 % provides close to the reference composition (without SAP) the total hydration heat power of Portland cement at the age of 86 hours. The dependences of rheological and mechanical properties of cement materials on SAP concentration have been established. It has been proved that the use of SAP solutions is an effective engineering solution to ensure the hardening of concrete in adverse conditions. Further development of the topic may be aimed at studying the effect of SAP solutions on the properties of concrete mixtures of different compositions for 3D printing.

Abstract 3998: Discovery of a small molecule inhibitor for triple-negative breast cancer (TNBC)

Abstract Introduction: Little progress has been made towards developing alternative therapeutic strategies for triple-negative breast cancer (TNBC). Aberrant Notch1 activation, particularly in breast cancer stem cells (BCSCs) in TNBC tumors, enhances this cancer's aggressivity and resistance and consequently contributes to the poor overall survival of patients with TNBC. In contrast, inhibition of Notch1 has been shown to suppress TNBC growth. Thus, Notch1 presents as an attractive target for inhibiting TNBC growth. This study aims to overcome the limitations of current Notch1 inhibitors and identify a more specific inhibitor. Methods: Small molecule screening was performed using structure-activity relationship (SAR) studies, and molecular docking and isothermal calorimetric (ITC) assays were used to determine the target sites of our rationally designed Notch1 inhibitor on the Notch1 receptor. The therapeutic potential of the identified small molecule Notch1 inhibitor was determined on BCSC and TNBC (ALDH+, BCSC, ALDH-, MDA-MB-231) cell lines using molecular studies and in vivo assays. Results: We identified ASR490, a small molecule that binds to the NRR (the activation switch of the Notch receptor) of Notch1. Molecular docking studies indicated a strong interaction between ASR490 and the NRR domain with binding energy of -52.55 kcal/mol. Residue-wise interaction analysis estimated three hydrogen-bond interactions between ASR490 and NRR residues Asn-1483, Glu-1673, and Gly-1664 mediated by water molecules. The finding was further confirmed using biophysical assays (thermal shift assay and isothermal calorimetric analysis) using recombinant Notch1 protein. In vitro results demonstrated that ASR490 significantly inhibited TNBC growth (p <0.001) at nM concentrations, with an IC50 of 760 nM at 24h. Further, the inhibitory effect was confirmed by TNBC’s colony-forming abilities. Western blot analysis confirmed that ASR490 downregulated the expressions of NICD (the active form of Notch1) and its downstream effectors Hey-1 and HES1 by ubiquitinating NRR of Notch1. ASR490 was found to be non-toxic to healthy cells. Moreover, ASR490 exhibited a maximum tolerated dose of more than 100 mg/kg body weight in mice and abrogated TNBC tumor growth in vivo xenograft models. Conclusion: Our results demonstrate ASR490 as a potential therapeutic agent that abolishes Notch1 signaling in TNBC and BCSCs by specifically targeting Notch1 NRR. Further investigation is required for the clinical translational potential of this agent. Citation Format: Uttara Saran, Balaji Chandrasekaran, Ashish Tyagi, Amandeep Singh, Murali K. Ankem, Arun K. Sharma, Chendil Damodaran. Discovery of a small molecule inhibitor for triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3998.

Effect of simulated different concentrations of sulfate on early properties of mineral admixture-cement-liquid accelerator system

The effects of simulated groundwater with different concentrations of sodium sulfate (0 g/L, 5 g/L, 15 g/L, and 25 g/L) as mixed water on the early performance of alkali-free accelerator-cement-mineral admixture system were investigated. The results show that sulfate groundwater promotes the setting time and strength of the alkali-free accelerator-cement-mineral admixture system. Combined with isothermal calorimeter, X-ray diffraction, and scanning electron microscopy, the hydration process and hydration products of sulfate-containing groundwater were analyzed. In addition, the hydration degree of each hydration stage was calculated by hydration heat curve, and the hydration mechanism of different concentrations of sulfur-containing groundwater on cement pastes mixed with AS (alkali-free accelerator) was proposed by microscopic analysis.

Effect of nutrient types on the hydration of cementitious materials with co-cultured bacteria

This study investigated the effect of nutrient types on the hydration of cementitious materials incorporated with co-cultured bacteria. The medium consisted of co-cultured bacteria (Sporosarcina pasteurii and Bacillus thuringiensis), urea, nutrient, and calcium lactate. Different nutrient types were added in the form of a bacterial culture solution or medium solution in the mixing process of cementitious specimens. Thirteen different types of specimens were fabricated with various media, dry-cured for 56 days, and subsequently, isothermal calorimeter analysis, X-ray diffraction analysis, and thermogravimetry analysis were performed to investigate the hydration kinetics and hydrates of the specimens. Finally, compressive strength of the specimens was measured. When bacteria, calcium lactate, and each nutrient were incorporated, as a comparison of compressive strength with the control specimens on the 28thday, 8% compressive strength was increased when TSB was incorporated, but NB and YE were incorporated, the compressive strength decreased by 21% and 22%. The results showed that the incorporation of nutrients and co-cultured bacteria suppressed the hydration of the specimens, whereas the reduction in compressive strength caused by delayed hydration was significantly compensated by CaCO3 amount which was increased by 3.3 times owing to the bio-mineralization of the co-cultured bacteria with TSB.

Determination of the concrete heat emission during its hardening in isothermal conditions

Introduction. The heat emission of concrete during its hardening in adiabatic conditions is typically determined according to the GOST 24316 State Satndard. This method is quite limited in research possibilities, since under the conditions of constantly increasing temperature, it appears impossible to adequately assess the influence of various components or hardening conditions on the processes occurring during the concrete hardening. The assessment of the heat emission during the isothermal hardening allows much more information about the hardening process of the studied material to be obtained. The direct determination of the concrete heat emission during hardening in isothermal conditions appears to be extremely difficult in technical aspect.Aim. The study is aimed at developing a method for determining the heat emission of the concrete in isothermal conditions.Materials and methods. The GOST 31108-2016 TsEM I 52.5N portland cement, quartz sand, crushed gabbrodiabase, and the GOST 23732-2011 mixing water were used in the study. The strength of concrete samples was determined in accordance with the GOST 10180-2012 State Standard. The TAM Air (TA Instruments) isothermal calorimeter was used for calorimetric studies.Results. As a result of the performed studies, a method for determining the concrete heat emission in isothermal conditions was developed on the basis of assessment of the heat emission during the hardening of model mixtures reflecting the composition of the studied concrete. The optimal particle size of the sand and crushed stone fractions for model mixtures comprises 0.16–0.315 mm. The heat emission during the isothermal hardening of 10 model mixtures reflecting the composition of the studied concrete grades was determined. The strength class of 10 concrete compositions differing in cement content was established. The dependence of the heat emitted by model mixtures on the strength classes of the studied concrete compositions was determined. The heat emission of model mixtures during the isothermal hardening was established to be directly dependent on the strength of the studied concrete compositions.Conclusions. The determination of the amount of heat emitted by model mixtures reflecting the composition of concrete mixtures during the isothermal hardening represents a useful cost-effective test significantly accelerating and facilitating the process of control and design of concrete compositions.

Novel perspective into the interaction behavior study of the cyanidin with human serum albumin-holo transferrin complex: Spectroscopic, calorimetric and molecular modeling approaches

We examined the inducement of an interaction between two carrier proteins, human serum albumin (HSA) and human holo transferrin (HTF) within the presence of cyanidinin the form of binary and ternary systems, which was conducted by different spectroscopic, isothermal titration calorimetric (ITC), and molecular dynamics simulation techniques. The results of fluorescence spectroscopy verified the occurrence of this interaction by displaying the regular quenching of emission spectra of proteins as single and complex forms by cyanidin. Moreover, fluorescence emission suggested that, HSA-cyanidin, HTF-cyanidin and (HSA-HTF) cyanidin complexes follows an static mechanism with the binding constants of 8.81 × 104, 3.40 × 104, and 7.10 × 104 M−1, respectively, which were strongly reflected to moderate the affinity of cyanidin to both single and complex forms of proteins. The measured thermodynamic parameters obtained by ITC, determined the necessity of electrostatic forces for binding of cyanidin to HSA and HTF. Besides, obtaining a negative ΔG0 is indicative of spontaneous mode of binding process in both conditions. The different values of thermodynamic parameters of cyanidin binding to the forms of HSA, HTF and HSA-HTF complex clearly proved the similarity in the type of interaction forces between cyanidin and proteins as single and complex forms with various values. The observed changes in synchronous fluorescence results were related to the micro-environment properties of Tyr and Trp residues. The induced alternations in the secondary construction of both proteins were confirmed through the outcomes of quantitative analysis performed by circular dichroism spectroscopy (CD) techniques. FRET theory was exerted to calculate, the existing distance across the donor and acceptor, which were reported to be 1.85 nm, 1.97 nm, and 1.91 nm for the cases of HSA-cyanidin, HTF-cyanidin and (HSA-HTF) cyanidin complexes, respectively. Molecular displacement and protein–ligand docking simulations confirmed the binding of cyanidin to HSA and HTF through the binary and ternary systems.

Effect of lithium citrate on hydration of cement paste

This paper systematically investigated the influence of lithium citrate on the properties of cement. Its effect on hydration heat and internal pore structures was examined by isothermal calorimeter and mercury intrusion porosimetry (MIP) analysis, respectively. The evolution of hydration products and changes of the ion concentration in the pore solution were also investigated by thermal gravimetric (TG), X-ray diffraction (XRD)and Inductively Coupled Plasma (ICP). Thermodynamic model was used to further reveal the relationship between lithium citrate and hydration products. The results showed that lithium citrate first retarded the cement hydration, but improved the strength subsequently functioning as an accelerator as early as 7 curing days. This was because upon the addition in the cement, lithium citrate immediately formed a protective outer layer wrapping around cement clinker particles. As hydration further proceeded, the protective layers were gradually broken down, and the released lithium ions then promoted the hydration of C3A to form a lithium aluminate amorphous gel compound, providing new sites for cement hydration and contributing to a higher content of portlandite and calcite, which in turn augmented the strength.

Binding studies of dopamine HCl drug with the mixed {sodium bis(2-ethylhexyl) sulfosuccinate + sodium dodecylsulfate} micelles: Physicochemical, spectroscopic, calorimetric and computational approach

Taking into consideration the importance of dopamine HCl as neurotransmitter in controlling central nervous system activities, the studies of binding interactions of dopamine HCl drug with micellar system (imitator of biomembranes) have been conducted by utilizing experimental as well as computational techniques. The systematic knowledge of physicochemical, spectroscopic and calorimetric properties is helpful to understand the physiological actions of biologically active additives in the living organisms. Therefore, mixed aggregation behavior of sodium bis(2-ethylhexyl) sulfosuccinate, AOT and sodium dodecylsulfate, SDS has been explored at diverse mole fractions of AOT, αAOT = 0.25, 0.39 and 0.50 in (1, 2 and 3) × 10−3 mol kg−1 dopamine HCl(aq) solutions by employing different techniques. From conductivity studies, the thermodynamic parameters (∆G°m, ∆H°m and ∆S°m), the molecular interaction parameter (βint) and the excess Gibbs free energy of micellization (∆Gmex) were ascertained at T = (298.15, 308.15, and 318.15) K. Isentropic compressibility (κs), partial specific volume (φv) and partial specific isentropic compressibility (φκ) parameters were computed from the density and sound velocity studies. Binding constant (Kb) and standard Gibbs free energy of binding (∆Gbο) have been evaluated from UV–visible absorption studies for dopamine HCl(aq) solutions at all the studied mole fractions of surfactant mixtures. Through dynamic light scattering (DLS) measurements, the hydrodynamic diameters (Dh) of mixed micellar aggregates have been acquired. Isothermal titration calorimetric (ITC) studies were executed to obtain the values of partitioning constant / binding constant (K), standard molar enthalpy of binding (ΔrHᴼ), standard molar entropy of binding (ΔrSᴼ), and stoichiometry of partitioning / binding (n) of drug with micellar system. Through density functional theory (DFT) calculations, the band gap between HOMO and LUMO for the dopamine-HCl bound mixed micelle system, and interactive features have been obtained. Aforementioned studies favor the supremacy of hydrophilic-hydrophilic / ionic and electrostatic interactions causing the binding among the hydrophilic / ionic groups of dopamine HCl (−OH, H+, Cl−), AOT (–SO3−, –OCO, Na+), and SDS (–OSO3−, Na+).

Recycling of arsenic-containing biohydrometallurgy waste to produce a binder for cemented paste backfill: Mix proportion optimization

Arsenic-containing biohydrometallurgy waste (BW) is used to prepare a cementitious material, on the one hand, to solve the problem of lack of cheaper and greener binder for cemented paste backfill (CPB), on the other hand, to alleviate the arsenic pollution caused by BW. The binders were prepared by mixing blast furnace slag (BFS), BW, and ordinary Portland cement (OPC). The influence of mix proportions on the binder properties was investigated, including reaction kinetics, strength development, phase assembles of hydration products and arsenic (As) immobilization effects. Isothermal calorimeter analysis suggests that the binder reaction kinetics were highly determined by the mix proportions, and more BW addition decreased the reaction rate according to the Krstulovic-Dabic model. The optimal mix proportion of binder is 65–30-5, i.e., 65 wt% blast furnace slag, 30 wt% BW, and 5 wt% OPC. The compressive strength of this sample after curing for 3 days and 60 days is about 9.25 MPa and 40.88 MPa, respectively, and the hydration products mainly consist of ettringite and calcium silicate aluminate hydrate (C-(A)-S-H). Additionally, arsenic can be effectively immobilized in the binder, resulting from the denser structure (physical encapsulation) and ion exchange between arsenate and sulfate in ettringite.

Continuous Monitoring of the Early-Age Properties of Activated GGBFS with Alkaline Solutions of Different Concentrations

AbstractThis study monitors the early-age reaction kinetics and measures the heat of reaction of alkali-activated ground granulated blast-furnace slag (GGBFS) using an isothermal calorimeter, and t...

Effect of TEA·H3PO4 and TEA·C18H30O3S on the mechanical properties and hydration characteristics of cement paste

In this study, TEA·H3PO4 (TP) and TEA·C18H30O3S (TDS) have been used as organic admixtures in cementitious materials. Mortar specimens with different TP and TDS dosages were subjected to mechanical, setting time, hydration degree, isothermal calorimeter tests, as well as to XRD, TG, SEM and MIP analyses. Results show that less than 0.10% TP and 0.05% TDS shorten the initial setting time, while more than 0.50% TDS can lead to a retarding effect in mortar specimens. TP is beneficial to increase the early age strength, but a sharp decrease in both compressive and flexural strengths is found when TDS is introduced. The XRD and TG analyses indicate that the introduction of TDS brings more generation of the portlandite (CH), ettringite (AFt), and monosulfate (AFm), whereas TP leads to the reduction of CH content in the cement pastes. Moreover, the SEM observations reveal that the decline in strength may result from the air-entraining effect caused by the incorporation of TDS which increase the amount and size of hydration pores, and the variation of mechanical properties of mortar specimens with TP is closely linked to the size of CH generated in mortar specimens.

Crystallographic and biophysical analyses of Pseudomonas aeruginosa ketopantoate reductase: Implications of ligand induced conformational changes in cofactor recognition

Ketopantoate reductases (KPRs) catalyse NADPH-dependent reduction of ketopantoate to pantoate, the rate-limiting step of pantothenate biosynthetic pathway. In our recent study, we showed KPRs are under dynamic evolutionary selection and highlighted the possible role of ordered substrate binding kinetics for cofactor selection. To further delineate this at molecular level, here, we perform X-ray crystallographic and biophysical analyses of KPR in presence of non-canonical cofactor NAD+. In our structure, NAD+ was found to be highly dynamic in catalytic pocket of KPR, which could attain stable conformation only in presence of ketopantoate. Further, isothermal calorimetric (ITC) titrations showed that affinity of KPR for ketopantoate is higher in presence of NADP+ than in presence of NAD+ and lowest in absence of redox cofactors. In sum, our results clearly depict two modes of redox cofactor selections in KPRs, firstly by specific salt bridge interactions with unique phosphate moiety of NADP+ and secondly via ordered sequential heterotrophic cooperative binding of substrate ketopantoate.

Effects of Different Content of Phosphorus Slag Composite Concrete: Heat Evolution, Sulphate-Corrosion Resistance and Volume Deformation

Phosphorus slag (PS) and limestone (LS) composite (PLC) were prepared with a mass ratio of 1:1. The effects of the content of PLC and the water/binder ratio on the mechanical properties, durability and dry shrinkage of concrete were studied via compressive strength, electric flux, sulfate dry/wet cycle method, saturated drainage method, isothermal calorimeter, adiabatic temperature rise instrument and shrinkage deformation instrument. The results show that PLC can greatly reduce the adiabatic temperature rise of concrete. The adiabatic temperature rise is 55 °C with 33 wt.% PLC, 10 °C lower than that of the control sample. The addition in the content of PLC does not affect the long-term strength of concrete. When the water/binder ratio decreases by 0.1–0.15, the long-term strength of concrete with PLC increases by about 10%, compared with the control group. At the age of 360 days, the chloride permeability of L-11 (i.e., the content of PLC was 20%, the water/binder ratio was 0.418) and L-22 (i.e., the content of PLC was 33%, the water/binder ratio was 0.39) decrease to the “very low” grade. The strength loss rate of L-11 and L-22 after 150 sulfate dry/wet cycles is about 18.5% and 19%, respectively, which is 60% of the strength loss rate of the control sample. The drying shrinkage of L-11 and L-22 reduces by 4.7% and 9.5%, respectively, indicating that PLC can also reduce the drying shrinkage.

Exploring the binding mechanism and adverse toxic effects of persistent organic pollutant (dicofol) to human serum albumin: A biophysical, biochemical and computational approach

The organochlorine pesticide dicofol (DCF), a persistent organic pollutant, is used as acaricide worldwide. Considering its large consumption in the agriculture sector and potential toxic effects such as endocrine disruption, carcinogenicity, and environmental persistence are detrimental to human health. To take an extensive evaluation of its potential toxicity, the current study was aimed to explore the binding mechanism and adverse effect of DCF on human serum albumin (HSA) by using an array of biophysical techniques (UV–visible, fluorescence, 3D fluorescence, and circular dichroism spectroscopy), isothermal titration calorimetric (ITC), computational methods and biochemical approaches. Fluorescence quenching and UV–Visible spectra of the HSA-DCF system confirmed static quenching mechanism and complex formation between HSA and DCF. The thermodynamics results from ITC revealed DCF-HSA interaction was exothermic and spontaneous and involved hydrophobic interactions and hydrogen bonding. The esterase activity of HSA displayed constant Vmax and elevated Km values confirming DCF-HSA competitive interaction. Circular dichroism spectra results revealed structural changes in HSA protein on interaction with DCF. Furthermore, molecular-specific site marker and molecular modelling results affirmed that the binding Site of DCF is Site I of HSA. A significant carbonyl content level in DCF-HSA system suggested protein structure damage. This work is likely to add a better understanding of DCF toxicity in human health and helpful in fortifying the check on food safety.

Advancements in the development of the isothermal gas calorimeter based on Alexandrov’s principle

The Isothermal gas calorimeter based on Alexandov’s design is a robust and versatile device that can be used for the determination of the heat of combustion of new emerging gas mixtures, such as biogas, biomethane or hydrogen enriched gases. This calorimeter is easily adaptable to these new gas mixtures which, due to the large range of densities and compositions, challenge other more expensive techniques used for this purpose, namely gas chromatography. New technologies (new mass flow controllers and simulations heater) were implemented and the performance under the new circumstances analysed. The analysis showed relevant weaknesses that need to be addressed for an optimal performance for the new gas mixtures, such as heat losses, or the selection of the working fluid. The uncertainty budget performed under the new developments showed that the calorimeter can determine the calorific value of gas mixtures with a relative uncertainty lower than Ur = 0.5% (k = 2). However, this value will be improved further once the weaknesses discovered in the performed analysis are addressed.

Unsupervised bubble calorimetry analysis: Surface tension from isothermal titration calorimetry

HypothesisThe injection of air into the sample cell of an isothermal titration calorimeter containing a liquid provides a rich-in-information signal, with a periodic contribution arising from the creation, growing and release of bubbles. The identification and analysis of such contributions allow the accurate determination of the surface tension of the target liquid. ExperimentsAir is introduced at a constant rate into the sample cell of the calorimeter containing either a pure liquid or a solution. The resulting calorimetric signal is analyzed by a new algorithm, which is implemented into a computational code. FindingsThe thermal power generated by our experiments is often noisy, thus hiding the periodic signal arising from the bubbles’ formation and release. The new algorithm was tested with a range of different types of calorimetric raw data, some of them apparently being just noise. In all cases, the contribution of the bubbles to the signal was isolated and the corresponding period was successfully determined in an automated way. It is also shown that two reference measurements suffice to calibrate the instrument at a given temperature, regardless the injection rate, allowing the direct determination of surface tension values for the liquid contained in the sample cell.

High-affinity aptamer of allergen β-lactoglobulin: Selection, recognition mechanism and application

β-Lactoglobulin (β-Lg), the main allergen of milk and dairy products, is capable of causing food allergies in some groups, especially infants and young children. Therefore, a sensitive, efficient and rapid method for β-Lg detection is urgently needed to protect allergy sufferers. In this study, aptamers against β-Lg were successfully selected by capture-SELEX. The aptamer Lg-18 was observed by isothermal titration calorimeter (ITC) and fluorescence assay to have high affinity to β-Lg. Furthermore, circular dichroism indicated that the secondary structure of Lg-18 contains typical hairpin structure, and thermodynamic parameters during bonding showed that the binding of aptamer Lg-18 to β-Lg was an enthalpically driven enthalpy-entropy compensation process. Docking simulations of Lg-18 and β-Lg were performed to further theoretically explain the experimental results and elucidate the recognition mechanism. Finally, the aptamer Lg-18 was used to construct a novel fluorescence-surface enhanced Raman scattering dual-mode aptasensor for efficient and sensitive detection of the allergen β-Lg. The aptasensor exhibited a broader linear range from 10−5000 ng/mL, with a lower detection limit of 0.05 ng/mL. The method showed good recoveries in spiked amino acid formula powder. These results demonstrated that the aptasensor can be applied for the detection of β-Lg in real samples with a good stability.

Influence of alkaline carbonates on the hydration characteristics of β-C2S

In this paper the microstructure of β-C2S hydrated pastes in the presence of alkaline carbonates was investigated. A hydration study of β-C2S stabilized by 0.5 wt% B2O3 was carried out in the presence of Li2CO3, Na2CO3, K2CO3 and deionized water. The rate of the hydration was measured using an isothermal calorimeter and the reaction products were characterized by TGA/DTG, SEM-EDS and 29Si MAS/NMR. The results showed that alkaline carbonates accelerated the hydration of β-C2S significantly compared to that of deionized water. K2CO3 was found to be the most effective followed by Na2CO3 while Li2CO3 was the least effective. The primary product was a C-S-H gel with the morphology depending on the solution used for the hydration. The hydration degree of β-C2S hydrated pastes achieved by activation with alkaline carbonates was ~ 70% at 28 days, while that of water hydrated paste was only 40%. The longer mean silica chain length and higher degree of polymerization of the C-S-H gel in the alkaline activated pastes results to the high mechanical strength at 28 days.

Heat Generation in Lithium Iron Phosphate/Graphite Batteries: Simulation with Validation through Isothermal and Adiabatic Calorimetric Measurements

This work evaluates the heat generation characteristics of a cylindrical lithium iron phosphate/graphite battery. Two experimental approaches are used: Heat flow measurements in an isothermal calorimeter and temperature measurement-based heat generation rate measurements in a quasi-adiabatic Accelerating Rate Calorimeter (ARC).The experimental results are compared to simulation results of an equivalent circuit model featuring a single resistance, voltage hysteresis representation, and reversible heat generation through entropy representation. The thermal model parameters are adapted to the respective experimental setups.Results visualize the specific use-cases of the experimental approaches. Isothermal calorimeter measurements enable a strict control of temperature for the battery, however, smooth the higher dynamics of the battery heat transfer due to the thermal mass of the setup. The high rate of heat transfer to ambient enables an evaluation of specific operating temperatures as well as long-duration tests, e.g., full cycles or dynamic current profiles.Instead, quasi-adiabatic measurements vary strongly in temperature during the operation but provide highly-dynamic information about heat generation rates. The rapid rise in temperature approaches safety limits and thus only low current, charge or discharge tests are possible, with a following rest period required.Simulation results are discussed with a focus on the heat generation rate and the heat transfer to ambient rate. While in general good agreements between simulation and experiment is achieved, specific differences reveal improvement potential for the model as well as for its parametrization. References M. Keyser, A. Pesaran, Q. Li, S. Santhanagopalan, K. Smith, E. Wood, S. Ahmed, I. Bloom, E. Dufek and M. Shirk, Journal of Power Sources, 367, 228 (2017).A. Pesaran, M. Keyser, G. Kim, S. Santhanagopalan and K. Smith, Tools for designing thermal management of batteries in electric drive vehicles (presentation), in, National Renewable Energy Lab.(NREL), Golden, CO (United States) (2013).M. Schimpe, M. Naumann, N. Truong, H. C. Hesse, S. Santhanagopalan, A. Saxon and A. Jossen, Applied Energy, 210, 211 (2018).A. R. Saxon, Battery Extreme Fast Charge: A Thermal Prospective, in, National Renewable Energy Lab.(NREL), Golden, CO (United States) (2019).J. Geder, R. Arunachala, S. Jairam and A. Jossen, in 2015 IEEE Green Energy and Systems Conference (IGESC), p. 24 (2015).