Non-calorimetric Methods Research Articles

A non-calorimetric approach for investigating the moisture-induced ageing of a pyrotechnic delay material using spectroscopies

The degradation of thermal properties due to ageing such as burning rate and exothermic heat release are unsolved issues faced during a long-term storage of the pyrotechnic substances. Accordingly, we employed various non-calorimetric methods to investigate the thermal performance of pyrotechnic delay, which is exposed to various moisture-rich conditions at extended durations. The chemical and physical changes in the compositions of a pyrotechnic delay comprised of metal fuel (Zr-Ni alloy) and oxidants (KClO4, BaCrO4) are analysed for four different relative humidity levels using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope and laser-induced breakdown spectroscopy. The calculations using the NASA Chemical Equilibrium with Applications (CEA) software indicated that the heat of reaction for the components stored under the moisture-rich conditions is reduced by more than 50%. Unlike the conventional calorimetric analysis, the present non-calorimetric approach provided the compositional changes as well as the cause and effect of the relevant ageing process of pyrotechnic delay.

Non-calorimetric determination of absorbed power during magnetic nanoparticle based hyperthermia

Nanomagnetic hyperthermia (NMH) is intensively studied with the prospect of cancer therapy. A major challenge is to determine the dissipated power during in vivo conditions and conventional methods are either invasive or inaccurate. We present a non-calorimetric method which yields the heat absorbed during hyperthermia: it is based on accurately measuring the quality factor change of a resonant radio frequency circuit which is employed for the irradiation. The approach provides the absorbed power in real-time, without the need to monitor the sample temperature as a function of time. As such, it is free from the problems caused by the non-adiabatic heating conditions of the usual calorimetry. We validate the method by comparing the dissipated power with a conventional calorimetric measurement. We present the validation for two types of resonators with very different filling factors: a solenoid and a so-called birdcage coil. The latter is a volume coil, which is generally used in magnetic resonance imaging (MRI) under in vivo condition. The presented method therefore allows to effectively combine MRI and thermotherapy and is thus readily adaptable to existing imaging hardware.

Analysis of a non-calorimetric method for assessment of in-situ thermal transmittance and solar factor of glazed systems

The performance of glazing systems is usually assessed through the thermal transmittance and the solar factor, two metrics characterised either through calorimetric laboratory tests or calculations. In this paper, the analysis of the performance of a non-calorimetric method for obtaining the in-situ thermal transmittance and solar factor of glazing systems is presented. This method, developed as a trade-off between accurate (and expensive) laboratory tests (which characterise the systems under standardised, “averaged” conditions), and easy and less expensive tests on systems installed in real buildings (under real operative conditions), has been previously adopted for the characterisation of different glazed systems, but never presented and discussed in full detail.The method, suitable for full-scale glazing systems installed in buildings or in test cells, is based on the acquisition of temperature, heat flux, and solar irradiance values. Experimental data are then processed through simple equations and linear regressions to determine the thermal transmittance and the solar factor under real boundary conditions. In this paper, a detailed description of the method, the experimental test rig, and the related expected accuracy is reported. The method is then applied to a case study (a conventional double glazed unit) to give an example of the proposed procedure and to validate it.The results of the case study show the capability of the assessed in-situ thermal transmittance and solar factor to replicate the thermophysical behaviour of the glazing system within a satisfactory degree of accuracy. An in-depth discussion on the observed outcomes from the case study deepens the understanding of the method’s performance and the results’ significance.

Synergetic Determination of Thermodynamic and Kinetic Signatures Using Isothermal Titration Calorimetry: A Full-Curve-Fitting Approach.

Thermodynamic and kinetic signatures are pivotal information for revealing the binding mechanisms of biomolecules, and they play an indispensable role in drug discovery and optimization. While noncalorimetric methods measure only a part of these signatures, isothermal titration calorimetry (ITC) is considered to have the potential to acquire full signatures in an experiment. However, kinetic parameters are generally difficult to extract from ITC curves, as they are inevitably affected by the instrument-response function and the collateral heat of associated process during titrations. Thus, we herein report the development and validation of a full-curve-fitting method to resolve thermal power curves and to maximize the signal extraction using ITC. This method is then employed to quantify the dilution of an aqueous n-propanol solution and examine the inhibition of carbonic anhydrase by 4-carboxybenzenesulfonamide using a commercial instrument with a long apparent response time of ∼13 s.

Simultaneous in Situ X-ray Diffraction and Calorimetric Studies as a Tool To Evaluate Gas Adsorption in Microporous Materials

Combined application of in situ X-ray diffraction (XRD) and differential scanning calorimetry (DSC) is a novel technique for rapidly evaluating the suitability of microporous materials for postcombustion CO2 capture. Further, while many microporous materials show promise for CO2 capture, most are not evaluated in the presence of water vapor, a major component of postcombustion flue gas. As a demonstration of the versatility of XRD-DSC techniques, representatives of the classes of materials typically proposed for CO2 capture, zeolites, and metal–organic frameworks (MOFs) were studied: zeolite NaX, Ni-MOF-74 [Ni2(dobdc); dobdc = 2,5-dihydroxyterephthalate], ZIF-7 [ZIF: zeolitic imidazole framework, Zn(phim)2; phim: benzimidazole], and SBMOF-1 [Ca(sdb); sdb: 4,4′-sulfonyldibenzoate]. Although NaX and Ni-MOF-74 show very high affinity toward CO2 under idealized dry conditions, they are also very sensitive to the presence of water vapor and experience significant performance loss above 25% relative humidity (RH) at room temperature. Relative to NaX and Ni-MOF-74, ZIF-7 and SBMOF-1 show strong CO2 affinity even in the presence of 75% RH and may be more ideally suited for postcombustion flue gas CO2 capture than compounds with unsaturated metal sites. XRD-DSC is particularly powerful for evaluating the consequences of framework flexibility, with XRD providing the signature indicative of the structural rearrangement and the DSC providing the enthalpies of adsorption for each structure. This kind of detailed energy evaluation is not possible with other noncalorimetric methods.

Non-Calorimetric Determination of the Adsorption Heat of Volatile Organic Compounds under Dynamic Conditions

Avoiding strong chemical bonding, as indicated by lower heat of adsorption value, is among the selection criteria for Volatile Organic Compounds adsorbents. In this work, we highlight a non-calorimetric approach to estimating the energy of adsorption and desorption based on measurement of involved amounts, under dynamic conditions, with gaseous Fourier Transform Infrared spectroscopy. The collected data were used for obtaining adsorption heat values through the application of three different methods, namely, isosteric, temperature programmed desorption (TPD), and temperature-programmed adsorption equilibrium (TPAE). The resulting values were compared and discussed with the scope of turning determination of the heat of adsorption with non-calorimetric methods into a relevant decision making tool for designing cost-effective and safe operating of adsorption facilities.

Comparison of accuracy of various non-calorimetric methods measuring energy expenditure at different intensities

PurposeThe purpose of the study was to evaluate the accuracy of three non-calorimetric methods’ measurements of energy expenditure (EE) in laboratory conditions and to compare the results obtained by each method in free-living condition in a group of adult subjects.MethodsMeasurement was performed on 20 individuals aged 19-39 years. An assessment of EE at different intensities of physical activity was conducted by: monitoring heart rate with a S-610 Polar Sport Tester (HRM), measuring body movement by an ActiGraph GT1M accelerometer (AM), and recording METs (MR) by a physical activity questionnaire, for different activities (leisure and exercise) at various intensities in laboratory and free-living conditions. Indirect calorimetry (Cosmed K4b2 respirometer) was used as a reference standard.ResultsThe most reliable tool for EE assessment was HRM (100% accurate). AM overestimated EE (about 60%) for activity at moderate-intensity and underestimated EE (about 40%) at vigorous-intensity. MR overestimated the results, with measurement errors increasing with an increase in physical activity intensity (about 40-120%).ConclusionsAlthough AM and MR provided less accurate results than HRM in laboratory conditions, there were no significant differences between the three methods (HRM, AM and MR) when total daily energy expenditure was calculated for the participants in free-living condition.

The thermodynamics of protein folding: a critique of widely used quasi-thermodynamic interpretations and a restatement based on the Gibbs–Duhem relation and consistent with the Phase Rule

Interpretations of data in the extensive literature on the unfolding of proteins in aqueous solution follow a variety of methods involving assumptions leading to estimates of thermodynamic quantities associated with the unfolding transition. Inconsistencies and thermodynamic errors in these methods are identified. Estimates of standard molar free energies and enthalpies of unfolding using incompletely defined equilibrium constants and the van't Hoff relation are unsound, and typically contradict model-free interpretation of the data. A widely used routine for estimating the change in heat capacity associated with unfolding based on changes in the unfolding temperature and enthalpy co-induced by addition of denaturant or protective additives is thermodynamically incorrect by neglect of the Phase Rule. Many models and simulations predicting thermodynamic measures of unfolding are presently making comparisons with insecure quantities derived by incorrect thermodynamic analyses of experimental data. Analysis of unfolding via the Gibbs-Duhem equation with the correct Phase Rule constraints avoids the assumptions associated with incomplete equilibrium constants and misuse of the van't Hoff relation, and applies equally to positive, negative, sitewise or diffuse solute binding to the protein. The method gives the necessary relations between the thermodynamic parameters for thermal and isothermal unfolding and is developed for the case of two-state unfolding. The differences in binding of denaturants or stabilizers to the folded and unfolded forms of the protein are identified as major determinants of the unfolding process. The Phase Rule requires the temperature and enthalpy of unfolding to depend generally on the protein concentration. The available evidence bears out this expectation for thermal unfolding, indicating that protein-protein interactions influence folding. A parallel dependence of the denaturant concentrations for isothermal unfolding on the protein concentration is anticipated. The degree of unfolding as measured by UV, CD, fluorescence and other non-calorimetric methods may not show the same temperature and concentration ranges for unfolding among themselves or as compared to DSC or isothermal calorimetry. Such disparities indicate distinct stages in unfolding detectable by particular methods.

Refinement of noncalorimetric determination of the change in heat capacity, ΔCp, of protein unfolding and validation across a wide temperature range

The change in heat capacity, DeltaC(p), on protein unfolding has been usually determined by calorimetry. A noncalorimetric method which employs the Gibbs-Helmholtz relationship to determine DeltaC(p) has seen some use. Generally, in this method the free energy change on unfolding of the protein is determined at a variety of temperatures and the temperature at which DeltaG is zero, T(m), and change in enthalpy at T(m) are determined by thermal denaturation and DeltaC(p) is then calculated using the Gibbs-Helmholtz equation. We show here that an abbreviated method with stability determinations at just two temperatures gives values of DeltaC(p) consistent with values from free energy change on unfolding determination at a much wider range of temperatures. Further, even the free energy change on unfolding from a single solvent denaturation at the proper temperature, when coupled with the melting temperature, T(m), and the van't Hoff enthalpy, DeltaH(vH), from a thermal denaturation, gives a reasonable estimate of DeltaC(p), albeit with greater uncertainty than solvent denaturations at two temperatures. We also find that nonlinear regression of the Gibbs-Helmholtz equation as a function of stability and temperature while simultaneously fitting DeltaC(p), T(m), and DeltaH(vH) gives values for the last two parameters that are in excellent agreement with experimental values.

A new method for determining the constant-pressure heat capacity change associated with the protein denaturation induced by guanidinium chloride (or urea)

Differential scanning calorimetry (DSC) provides authentic and accurate value of Δ C p X, the constant-pressure heat capacity change associated with the N (native state)↔X (heat denatured state), the heat-induced denaturation equilibrium of the protein in the absence of a chemical denaturant. If X retains native-like buried hydrophobic interaction, Δ C p X must be less than Δ C p D, the constant-pressure heat capacity change associated with the transition, N↔D, where the state D is not only more unfolded than X but it also has its all groups exposed to water. One problem is that for most proteins D is observed only in the presence of chemical denaturants such as guanidinium chloride (GdmCl) and urea. Another problem is that DSC cannot yield authentic Δ C p D, for its measurement invokes the existence of putative specific binding sites for the chemical denaturants on N and D. We have developed a non-calorimetric method for the measurements of Δ C p D, which uses thermodynamic data obtained from the isothermal GdmCl (or urea)-induced denaturation and heat-induced denaturation in the presence of the chemical denaturant concentration at which significant concentrations of both N and D exist. We show that for each of the proteins (ribonuclease-A, lysozyme, α-lactalbumin and chymotrypsinogen) Δ C p D is significantly higher than Δ C p X. Δ C p D of the protein is also compared with that estimated using the known heat capacities of amino acid residues and their fractional area exposed on denaturation.

Measurement of energy expenditure

Measurement of energy expenditure in humans is required to assess metabolic needs, fuel utilisation, and the relative thermic effect of different food, drink, drug and emotional components. Indirect and direct calorimetric and non-calorimetric methods for measuring energy expenditure are reviewed, and their relative value for measurement in the laboratory and field settings is assessed. Where high accuracy is required and sufficient resources are available, an open-circuit indirect calorimeter can be used. Open-circuit indirect calorimeters can employ a mask, hood, canopy or room/chamber for collection of expired air. For short-term measurements, mask, hood or canopy systems suffice. Chamber-based systems are more accurate for the long-term measurement of specified activity patterns but behaviour constraints mean they do not reflect real life. Where resources are limited and/or optimum precision can be sacrificed, flexible total collection systems and non-calorimetric methods are potentially useful if the limitations of these methods are appreciated. The use of the stable isotope technique, doubly labelled water, enables total daily energy expenditure to be measured accurately in free-living subjects. The factorial method for combining activity logs and data on the energy costs of activities can also provide detailed information on free-living subjects.

A Noncalorimetric Method for Heat-Transfer Coefficient Measurement of Building Thermal Envelopes

A noncalorimetric method for measuring the heat-transfer coefficient (UA) of building thermal envelopes is proposed and applied in an indoor test cell. The UA value measured by this method agrees closely with that measured by a calorimetric method. This method creates a Single input and a Single output data Pair (SSP) from the measured data sets by using digital filters. The filter output and physical criteria are used to determine the correct transfer function, which yields the measured UA value. This method seems to have the following advantages over calorimetric methods: it uses shorter measurement times, uses simpler test equipment, and has minimum thermal intrusion on normal operating conditions.