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The solute (i)—solute interaction in terms of enthalpy, Hi-iE=N(∂2HE/∂ni2)=(1-xi)(∂2HE/∂ni∂xi), the third derivative of G, was experimentally determined using a Thermal Activity Monitor isothermal titration calorimeter for aqueous solutions of 2-butoxyethanol (BE) and 1-propanol (1P). This was done using both calorimetric reference and sample vessels actively. We simultaneously titrate small and exactly equal amounts of solute i (=BE or 1P) into both cells which contain the binary mixtures at an average mole fraction, xi, which differs by a small amount Δxi. The appropriate amount of titrant δni was chosen so that the quotient (δHE/δni) can be approximated as (∂HE/∂ni), and so that the scatter of the results is reasonable. δHE is the thermal response from an individual cell on titration, and we measure directly the difference in the thermal response between the two cells, Δ(δHE). The resulting quotient, Δ(δHE)/δni/Δxi, can be approximated as (∂2HE/∂ni∂xi) and hence provides a direct experimental avenue for the enthalpy interaction function. We varied the value of Δxi to seek its appropriate size. Since HE contains the first derivative of G with respect to T, the result is the third derivative quantity. Thus we present here a third derivative quantity directly determined experimentally for the first time. [ABSTRACT FROM AUTHOR]

Differential scanning calorimetry, in conjunction with x-ray and electron diffraction, is used to investigate the A1 to L10 ordering transformation in binary FePt films with compositions in the range of 47.5–54.4 at. % Fe. The kinetic ordering temperature, taken as the calorimetric peak temperature at a heating rate of 40 °C/min, decreases from 447 to 357 °C in this composition range. In contrast with the kinetic ordering temperature, the Curie temperature of the L10 ordered phase increases from 384 to 455 °C as the Fe content is increased. The activation energies of ordering lie between 1.4 and 2.0 eV, and the transformation enthalpies are in the range of -8.2 to -13.6 kJ/g-at. The Avrami exponent for the transformation is lower than expected and lies in the range of 1.1–1.8. The lattice parameter of the A1 phase and the c/a ratio of the L10 phase decrease with increasing Fe content. [ABSTRACT FROM AUTHOR]

The structural and thermal properties of potassium nitrate (KNO3): polyvinylidene fluoride composite films have been studied. Differential scanning calorimetry has been employed to characterize the phase transitions in the composite and x-ray diffraction has been used to quantify the crystalline phases. The ferroelectric phase (III) of KNO3 is stabilized relative to the paraelectric phase (II) at room temperature at concentration <=50 wt %, with the largest proportion at 50 wt %. The enthalpies and transition temperature width are also affected in the composite. The polarization hysteresis loops also show that the remanent polarization is largest at 50 wt % of KNO3. The capacitance–voltage characteristics exhibit strong hysteresis with pronounced peaks and some asymmetry. The switching current behavior of the composite film was also investigated and supports the presence of ferroelectric phase in the composite film at room temperature. [ABSTRACT FROM AUTHOR]

The dynamics of protein folding result from both enthalpic and entropic contributions to the free energy. In this paper we focus on entropic volume exclusion effects. We carry out computer simulations using a model that allows us to independently change the size or biochemical properties of amino acid residues. To determine the importance of excluded volume effects, we investigate the effects of changing the size of side chains on the unfolding dynamics of a model four-helix bundle protein. In addition, we also investigate the effects of changing the thickness of the chain’s backbone. This has relevance to the behavior of synthetic polymers where the size of the constituent units can be varied. We find that entropic excluded volume effects are crucially important for stabilizing the organized native state relative to the molten globule. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Discusses a study which detailed the construction of a pyroelectric enthalpimetric calorimeter for the H-O reaction using palladium (Pd) and gold (Au) electrodes on a LiTaO[sub3] wafer. Factors obtained on the Pd and Au electrodes; Reason for using pyroelectric materials; Purpose of designing and constructing a pyroelectric gas analyzer.

Structural relaxation during isothermal annealing, quantified by enthalpy recovery of Zr 44 Ti 11 Cu 10 Ni 10 Be 25 towards its metastable equilibrium and correlation to embrittlement, quantified through fracture toughness, K Q , is studied. Enthalpy relaxation over time obeys the Kohlrausch-William-Watts (KWW) stretch exponent with β = 0.74 and τ = 11,000 s. Such β and τ are used to fit experimental K Q ( t ) with KWW, resulting in R 2 = 0.79. This finding combined with a controlled characterization of the glasses' K Q versus temperature, fictive temperature, and their combination, revealed that embrittlement in metallic glasses is predominantly controlled by structural rearrangements, whereas volume changes from thermal expansion have negligible influence. [ABSTRACT FROM AUTHOR]

Hydrogen direct injection (HDI) in cylinder is considered as an effective method to improve natural gas engine performance. The present study aims to bridge the gap on the HDI in rotary engine, and to investigate the effect of hydrogen injection timing (IT) and hydrogen injection duration (ID) on mixture formation and combustion process of a hydrogen direct injection plus natural gas port injection (HDI + NGPI) rotary engine. Numerical approach was used in this study for obtaining some critical information, which was difficult to obtain through experiment, such as flow field, fuel distribution and some intermediate concentration fields in cylinder. The research results showed that for mixture formation, the distribution law of the hydrogen and the natural gas at the late stages of the compression stroke (100 ° CA (BTDC)), was as follows: at a fixed ID of 24 ° CA, with retarded hydrogen IT, the stratification phenomenon of hydrogen became obvious increasingly, and the hydrogen distribution area moved towards the back of the combustion chamber continuously. At a fixed IT of 210 ° CA (BTDC), with the extension in ID, the accumulation area of hydrogen reduced significantly, and the hydrogen continued to gather in the middle of the combustion chamber. For combustion process, the overall combustion rate for the hydrogen injection strategy which had an IT of 210 ° CA (BTDC) and ID of 40 ° CA (case ID5), was the fastest. This was due to the fact that compared with the leading spark plug (LSP), the combustion condition around the trailing spark plug (TSP) has a great influence on the combustion process. For case ID5 at ignition timing, the hydrogen concentration near the TSP is high enough for the rapid formation of flame kernel. Compared with case IT1 which had an IT of 390 ° CA (BTDC) and an ID of 24 ° CA, the improved combustion rate of case ID5 had a 11.7% increase in peak pressure, and a 7% decrease in NO emissions. [ABSTRACT FROM AUTHOR]

The effects of 0.2% (w/v) methylparaben (0.2MP) on the micellization, intermicellar association and gelation characteristics of poloxamer 407 (PX) in aqueous solution as well as the water distribution in PX based samples have been investigated. Differential scanning calorimetry (DSC) studies demonstrated that 0.2MP shifted the critical micellization temperature (CMT) of PX to a lower temperature. According to sub-ambient DSC determination, 0.2MP disturbed interfacial water surrounding PX and decreased CMT. Flow curves revealed that intermicellar association of PX was promoted by 0.2MP. Since more intermicellar packing facilitated the thermoresponsive gelation, the reduction of the sol-gel transition temperature of PX was also substantiated in the presence of 0.2MP as indicated by temperature sweep tests. [ABSTRACT FROM AUTHOR]

Solvation free energies can now be calculated precisely from molecular simulations, providing a valuable test of the energy functions underlying these simulations. Here we briefly review "alchemical" approaches for calculating the solvation free energies of small, neutral organic molecules from molecular simulations and illustrate these approaches by applying them to calculate aqueous solvation free energies (hydration free energies). These approaches use a nonphysical pathway to compute free energy differences from a simulation or set of simulations and appear to be a particularly robust and general-purpose approach for this task. We also present an update (version 0.5) to our FreeSolv database of experimental and calculated hydration free energies of neutral compounds and provide input files in formats for several simulation packages. This revision to FreeSolv provides calculated values generated with a single protocol and software version rather than the heterogeneous protocols used in the prior version of the database. We also further update the database to provide calculated enthalpies and entropies of hydration and some experimental enthalpies and entropies as well as electrostatic and nonpolar components of solvation free energies. [ABSTRACT FROM AUTHOR]

Infrared thermal imaging was combined with disposable microplates to perform enthalpimetric analysis using an infrared camera to monitor temperature without contact. The proposed thermal infrared enthalpimetry (TIE) method was used to determine the total, fixed and volatile acidities of vinegars. Sample preparation and analysis were performed in the same vessel, avoiding excessive sample handling and reducing energy expenditure by more than ten times. The results agreed with those of the conventional method for different kinds of vinegars, with values of 1.7%, and 2.3% for repeatability and intermediate precision, respectively. A linear calibration curve was obtained from 0.040 to 1.30 mol L −1 . The proposed method provided rapid results (within 10 s) for four samples simultaneously, a sample throughput of up to 480 samples per hour. In addition, the method complies with at least eight of twelve recommendations for green analytical chemistry, making TIE a promising tool for routine vinegar analysis. [ABSTRACT FROM AUTHOR]

In this work, the feasibility of infrared thermal imaging (ITI) is demonstrated to show its potential application in analytical chemistry. A system of ITI was combined with disposable microplates to perform enthalpimetric analysis, which was selected as an example in order to show the reliability of this method. In this way, the novel thermal infrared enthalpimetry (TIE) method was evaluated in neutralization, precipitation, redox, and complexation reactions, with a multichannel pipet for adding the reagent and an infrared camera to monitor the temperature of multiple reactions (up to 24 simultaneous reactions) in a contactless way. Analytical signals were obtained in only 10 s, and the difference in temperature (ΔT) before and after the reaction was used for the construction of calibration curves by use of reference solutions. More than 10 000 values were considered for the temperature determination for each reaction. The proposed method was applied for determination of the total acidity of vinegar as well as the chloride, iron, and calcium content of pharmaceuticals. The results were compared with those from conventional techniques (titration), and agreement between 96% and 101% was obtained. Sample throughput could even reach thousands of samples analyzed in 1 h. These preliminary results demonstrate the important features of TIE and possible application for other matrices and analytical parameters. The proposed TIE could be spread to cover other enthalpimetric techniques, different reactors (e.g., microfluidic and paper analytical devices), and portable devices, thus reaching other fields of chemistry. [ABSTRACT FROM AUTHOR]

The purpose of this study was to develop a basal buffer system for a biobetter version of recombinant human interferon-β 1a (rhIFN-β 1a), termed R27T, to optimize its biophysical stability. The protein was pre-screened in solution as a function of pH (2–11) using differential scanning calorimetry (DSC) and dynamic light scattering (DLS). According to the result, its experimental p I and optimal pH range were 5.8 and 3.6–4.4, respectively. Design of experiment (DoE) approach was developed as a practical tool to aid formulation studies as a function of pH (2.9–5.7), buffer (phosphate, acetate, citrate, and histidine), and buffer concentration (20 mM and 50 mM). This method employed a weight-based procedure to interpret complex data sets and to investigate critical key factors representing protein stability. The factors used were T m , enthalpy, and relative helix contents which were obtained by DSC and Fourier Transform Infrared spectroscopy (FT-IR). Although the weights changed by three responses, objective functions from a set of experimental designs based on four buffers were highest in 20 mM acetate buffer at pH 3.6 among all 19 scenarios tested. Size exclusion chromatography (SEC) was adopted to investigate accelerated storage stability in order to optimize the pH value with susceptible stability since the low pH was not patient-compliant. Interestingly, relative helix contents and storage stability (monomer remaining) increased with pH and was the highest at pH 4.0. On the other hand, relative helix contents and thermodynamic stability decreased at pH 4.2 and 4.4, suggesting protein aggregation issues. Therefore, the optimized basal buffer system for the novel biobetter was proposed to be 20 mM acetate buffer at pH 3.8 ± 0.2. [ABSTRACT FROM AUTHOR]

Granular-type activated carbons were prepared from African palm shells ( Elaeis guineensis) by chemical activation with aqueous solutions of MgCl and CaCl at concentrations of 3, 5 and 7 % w/v, at temperatures between 773 and 1073 K. The textural parameters were obtained from N adsorption isotherms of the prepared activated carbons. The textural parameters included the surface area and pore volume, with values between 10 and 501 m g and 0.01 and 0.29 cm g, respectively. Enthalpic characterisation of the activated carbons was performed through the immersion calorimetry technique in three different solvents: benzene, cyclohexane and water. The enthalpies of immersion values of the solids in water were between −7.4 and −42.7 J g; for the immersion in benzene, the values were between −13.9 and −38.6 J g and were between −6.4 and −24.2 J g for the immersion in cyclohexane. The results show that activation with MgCl and CaCl salts produces activated carbons with differences in their characteristics of energy and affinity for the calorimetric liquids that are related to the surface properties. [ABSTRACT FROM AUTHOR]

We reduced the reaction volume in microfabricated suspended-membrane titration calorimeters to nanoliter droplets and improved the sensitivities to below a nanowatt with time constants of around 100 ms. The device performance was characterized using exothermic acid-base neutralizations and a detailed numerical model. The finite element based numerical model allowed us to determine the sensitivities within 1% and the temporal dynamics of the temperature rise in neutralization reactions as a function of droplet size. The model was used to determine the optimum calorimeter design (membrane size and thickness, junction area, and thermopile thickness) and sensitivities for sample volumes of 1 nL for silicon nitride and polymer membranes. We obtained a maximum sensitivity of 153 pW/(Hz)1/2 for a 1 μm SiN membrane and 79 pW/(Hz)1/2 for a 1 μm polymer membrane. The time constant of the calorimeter system was determined experimentally using a pulsed laser to increase the temperature of nanoliter sample volumes. For a 2.5 nanoliter sample volume, we experimentally determined a noise equivalent power of 500 pW/(Hz)1/2 and a 1/e time constant of 110 ms for a modified commercially available infrared sensor with a thin-film thermopile. Furthermore, we demonstrated detection of 1.4 nJ reaction energies from injection of 25 pL of 1 mM HCl into a 2.5 nL droplet of 1 mM NaOH. [ABSTRACT FROM AUTHOR]

The change in enthalpy with grain size of dense nanograined yttria-stabilized zirconia (YSZ) was measured by oxide melt solution calorimetry of cubic 10 YSZ and 15 YSZ dense nanograined ceramic samples prepared by spark plasma sintering of nanopowders. The derived grain-boundary enthalpies are 0.68 J/m² for 10 YSZ and 0.64 J/m² for 15YSZ, with an estimated uncertainty of about+0.13 J/m², arising mostly from the roughly 120%uncertainty in interface area calculated from the particle size distribution. These values are similar to a previous value of 0.73±0.19 J/m² for 8 YSZ, suggesting a possible weak concentration dependence (decrease of grain-boundary energy with increasing dopant concentration) that may not be outside experimental error. Previously published interface enthalpies of 0.6-1.0 J/m² for partially agglomerated nanopowders of 8, 10, and 12 YSZ, are in general agreement with the present data on densified nanoceramics. These data, taken together, suggest the ratio of surface to interface energy increases slightly with doping level, providing a slightly higher driving force for densification and pore elimination as the yttria content is increased. [ABSTRACT FROM AUTHOR]

Abstract: Diocleinae lectins are highly homologous in their primary structure which features metal binding sites and a carbohydrate recognition domain (CRD). Differences in the biological activity of legume lectins have been widely investigated using hemagglutination inhibition assays, isothermal titration microcalorimetry and co-crystallization with mono- and oligosaccharides. Here we report a new lectin crystal structure (ConBr) extracted from seeds of Canavalia brasiliensis, predict dimannoside binding by docking, identify the α-aminobutyric acid (Abu) binding pocket and compare the CRD of ConBr to that of homologous lectins. Based on the hypothesis that the carbohydrate affinity of lectins depends on CRD configuration, the relationship between tridimensional structure and endothelial NO synthase activation was used to clarify differences in biological activity. Our study established a correlation between the position of CRD amino acid side chains and the stimulation of NO release from endothelium. [Copyright &y& Elsevier]

Abstract: The total chromium oxide (Cr2O3) solubility is measured in the liquids belonging to the Na2O–SiO2 system using a thermochemical reactor which allows the independent control of temperature (1125°C

Abstract: In this communication, we present an interesting reversal in the enthalpic behavior from endothermic to exothermic on increasing the carbon chain length attached to the imidazolium ring in the imidazolium-based ionic liquids. A systematic investigation is presented on the excess partial molar enthalpy, directly measured using isothermal titration calorimeter at 298.15K for the interactions operating between cation and anion of four imidazolium ionic liquids with aqueous and various non-aqueous solvents. This reversal behavior is analyzed in terms of hydrophobic and solvation effects. [ABSTRACT FROM AUTHOR]

An experimental thermokinetic study of reaction sintering reveals that there are various irreversible paths in a nonequilibrium system. When the external temperature is in the contact melting range and the equilibrium condition of the mixture is in the solid-state range, the thermokinetic path is usually exponential with abrupt increase in the temperature and volume of the samples. Active compaction is observed in the case of thermokinetic oscillations [ABSTRACT FROM AUTHOR]

G-quadruplexes are higher-order nucleic acids structures formed by G-rich sequences that are stabilized by tetrads of hydrogen-bonded guanine bases. Recently, there has been growing interest in the study of G-quadruplexes because of their possible involvement in many biological processes. Isothermal titration calorimetry (ITC) has been proven to be a useful tool to study the energetic aspects of G-quadruplex interactions. Particularly, ITC has been applied many times to determine the thermodynamic properties of drug-quadruplex interactions to screening among various drugs and to address drug design. In the present review, we will focus on the ITC studies of G-quadruplex structures and their interaction with proteins and drugs and the most significant results will be discussed. [ABSTRACT FROM AUTHOR]

The correct determination of the energy generated or absorbed in the sample cell of an Isothermal Titration Calorimeter (ITC) requires a thorough analysis of the calorimetric signal. This means the identification and quantification of any thermal effect inherent to the working method. In this work, it is carried out a review on several thermal effects, studied by us in previous work, and which appear when an ITC is used for measuring the heats of mixing of liquids in a continuous mode. These effects are due to: (i) the difference between the temperature of the injected liquid and the temperature of the mixture during the mixing process, (ii) the increase of the liquid volume located in the mixing cell and (iii) the stirring velocity. Besides, methods for the identification and quantification of the mentioned effects are suggested. [ABSTRACT FROM AUTHOR]

Lauroyl peroxide (LPO) is a typical organic peroxide that has caused many thermal runaway reactions and explosions. Differential scanning calorimetry (DSC) was employed to determine the fundamental thermokinetic parameters that involved exothermic onset temperature (T0), heat of decomposition (ΔHd), and other safety parameters for loss prevention of runaway reactions and thermal explosions. Frequency factor (A) and activation energy (Ea) were calculated by Kissinger model, Ozawa equation, and thermal safety software (TSS) series via DSC experimental data. Liquid thermal explosion (LTE) by TSS was employed to simulate the thermal explosion development for various types of storage tank. In view of loss prevention, calorimetric application and model analysis to integrate thermal hazard development were necessary and useful for inherently safer design. [ABSTRACT FROM AUTHOR]

Biodiesel is susceptible to autoxidation if exposed to air, light and temperature, during its storage. Physic nut ( Jatropha curcas L.) seeds show potential application for biodiesel production since its oil yields high quality biodiesel. This work aims to evaluate the thermal behavior of the physic nut oil and biodiesel, from several Brazilian crops, by means of thermoanalytical techniques. Thermogravimetry (TG) and pressurized-differential scanning calorimetry (PDSC) were used in order to determine the applicability of physic nut biodiesel as fuel. Results suggest that physic nut biodiesel is a practical alternative as renewable and biodegradable fuel able to be used in diesel motors. [ABSTRACT FROM AUTHOR]

Abstract  Natural monocrystalline chalcopyrite and galena as new indicator electrodes for the potentiometric titration of weak acids in N,N-dimethylformamide and N-methylpyrrolidone were used. The investigated electrodes showed a linear dynamic response for p-toluenesulfonic acid concentrations in the range from 0.1 to 0.001 M, with a Nernstian slope of 59.0 mV for chalcopyrite and 33 mV per decade for galena in N,N-dimethylformamide, 56.1 mV for chalcopyrite, and 32.0 mV per decade for galena in N-methylpyrrolidone. The potential in the course of the titration and at the titration end point was rapidly established. Sodium methylate, potassium hydroxide, and tetrabutylammonium hydroxide proved to be very suitable titrating agents for these titrations. The response time was less than 10–11 s, and the lifetime of the electrodes is limitless. The advantages of the electrodes are log-term stability, fast response, reproducibility, easy preparation, and low cost. The results obtained in the determination of the investigated weak acids deviated on average by ±0.04–0.34% from those obtained with a glass electrode. [ABSTRACT FROM AUTHOR]

Cartilage thermoforming is an emerging surgical technology which uses heat to accelerate stress relaxation in mechanically deformed tissue specimens. Heat induced shape change in cartilage is associated with complex thermo-mechanical behavior of which the mechanisms are still a subject of debate. Differential scanning calorimetry (DSC) was used to characterize the threshold temperatures and enthalpies in cartilage as a function of water content. The DSC identified two enthalpic events in porcine nasal septal cartilage, which depend on the water content. The change in the water content of cartilage impacts the interactions between matrix macromolecules and water molecules, which may be associated with a bound-free water transformation (reversible process) and a denaturation of cartilage (irreversible process). [ABSTRACT FROM AUTHOR]

Thermal stability of pharmaceutical ingredients is an important aspect. In this study, we adopted differential scanning calorimetry (DSC) to investigate thermal stability of suppository bases, theobroma oil (cocoa butter) and a palm kernel oil (PKO) blend. The study shows theobroma oil possesses six polymorphic forms whilst the palm kernel oil blend has three. Upon rescanning, the PKO blend does not show changes in the enthalpy of fusion and the melting point with time, whilst the theobroma oil shows significant reduction, and only regained its thermal stable state after 10 days. This indicates that PKO blend possesses better thermal stability. [ABSTRACT FROM AUTHOR]

Abstract: The thermodynamics of RNA polymerase (RNAP) binding to a 108 base pair (bp) synthetic promoter with consensus sequences at the −35 and −10 bp binding regions upstream from the transcription start point were determined using isothermal titration calorimetry (ITC). The binding constant at 25 °C is 2.37±0.18×107 M−1, which is reduced to 0.17±0.06×107 M−1 with mutations in the −10 bp region but remained the same with mutations in the −35 binding region. The binding reactions were enthalpically-driven with exothermic binding enthalpies ranging from −57±6 kJ mol−1 at 15 °C to −271±20 kJ mol−1 at 35 °C yielding a large binding heat capacity change of −10.7±1.9 kJ mol−1 K−1, indicating a conformational change upon binding to the RNAP. Differential scanning calorimetry (DSC) scans of the thermal unfolding of RNAP and the promoter–RNAP complex exhibited an unfolding transition at 55.5±0.6 °C and at 58.9±0.5 °C for the RNAP but only one transition at 60.5±1.1 °C for the complex with van''t Hoff enthalpy to transition enthalpy ratios of, resp., 3.2±0.3 and 4.3±0.5. The single transition of the complex results from a shift to 60.5 °C of the low temperature transition upon promoter binding to the structural unit unfolding at the lower temperature in RNAP. The large transition enthalpy ratios indicate that the σ, α, α, β, and β′ subunits unfold as almost independent entities. The dissociation thermodynamics of short transcription “bubble” duplexes of 7 promoters sequenced from −1 to −12 bp were determined from ITC and DSC measurements. The free energy change of the promoter binding to the RNAP and the free energy requirement for formation of the transcription bubble at the low promoter concentrations in the cell are sufficient to drive the initiation of transcription through the isomerization of the closed to the open form step of the RNAP–promoter complex. [Copyright &y& Elsevier]

Four two-armed chiral calix[4]arenes (1a-1d) functionalised at the lower ring with amino acid units have been synthesised and the structures of these compounds were characterised by IR, MS, 1H NMR, 13C NMR spectra and elemental analysis. Their molecular recognition abilities towards amino alcohol were examined by fluorescence titration experiment in three kinds of solution. The results indicated that these receptors exhibited excellent fluorescent response to phenylglycinol and could distinguish phenylglycinol from phenylalaninol rapidly through the obvious difference in the fluorescent response. Solvent comparative experiments also indicated that acetonitrile was the best solvent to detect these phenomena. [ABSTRACT FROM AUTHOR]

Abstract: The use of food grade biopolymers, such as starch, has been suggested as a technological solution for the controlled delivery of health promoting ingredients. This staple food carbohydrate may form molecular inclusion complexes, termed V-amylose, with numerous ligands. This study aimed to develop and assess a continuous production process for the formation of such complexes using three starches varying in the amylose:amylopectin ratio. The heart of the technique is the use of dual feed homogenizer for in situ complexation in accord with homogenization, to form micron and sub micron particles. Results show that pre-dissolving high amylose corn starch or corn starch in a hot alkali solution leads to the formation of a bi-modal population of 0.04–20 μm or a mixed population of 0.04–3 μm V-type particles, respectively. These stearic acid-loaded particles exhibit V-type X-ray diffraction and release the stearic acid mainly upon pancreatic amylases treatment. This technology could prospectively be used in numerous applications including as a delivery system for the controlled delivery of bioactives. Industrial relevance: Introduction of nutraceuticals and bioactive nutrients into foods is a major technological challenge since many of these compounds have low chemical stability during product processing, storage and consumption. One of the industrial approaches to overcome this drawback is the use of encapsulation technologies, mainly with cheap, common and safe food ingredients. This study describes a unique continuous process to exploit starches’ natural and spontaneous tendency to form single helical molecular inclusion complexes, termed V-amylose, as a possible platform for nano and micro-encapsulation. This process involves coupling pH titration, which induces complexation, to a pressurized homogenization which induces rapid complexation and particle size reduction. Thus, it is suggested to help overcome the main drawbacks of current batch processing, i.e. large particle size, particle aggregation and prolonged duration of production. Additionally, the continuity of the process offers the technological possibility of incorporating the process in existing industrial settings of continuous manufacturing. These molecular inclusion complexes could prospectively be used in a wide variety of applications in the food, pharmaceutical and biotechnology industries including as a delivery system for the controlled and targeted delivery of nutrients, nutraceuticals and/or drugs to the lower gastrointestinal tract. [Copyright &y& Elsevier]

In this paper we use the results from all-atom molecular dynamics (MD) simulations of proteins and peptides to assess the individual contribution of charged atomic groups to the enthalpic stability of the native state of globular proteins and investigate how the distribution of charged atomic groups in terms of solvent accessibility relates to protein enthalpic stability. The contributions of charged groups is calculated using a comparison of nonbonded interaction energy terms from equilibrium simulations of charged amino acid dipeptides in water (the “unfolded state”) and charged amino acids in globular proteins (the “folded state”). Contrary to expectation, the analysis shows that many buried, charged atomic groups contribute favorably to protein enthalpic stability. The strongest enthalpic contributions favoring the folded state come from the carboxylate (COO-) groups of either Glu or Asp. The contributions from Arg guanidinium groups are generally somewhat stabilizing, while N%@mt;sys@%H%@sx@%3%@be@%%@sxx@%%@mx@%groups from Lys contribute little toward stabilizing the folded state. The average enthalpic gain due to the transfer of a methyl group in an apolar amino acid from solution to the protein interior is described for comparison. Notably, charged groups that are less exposed to solvent contribute more favorably to protein native-state enthalpic stability than charged groups that are solvent exposed. While solvent reorganization/release has favorable contributions to folding for all charged atomic groups, the variation in folded state stability among proteins comes mainly from the change in the nonbonded interaction energy of charged groups between the unfolded and folded states. A key outcome is that the calculated enthalpic stabilization is found to be inversely proportional to the excess charge density on the surface, in support of an hypothesis proposed previously. [ABSTRACT FROM AUTHOR]

Gas-phase C−H bond dissociation enthalpies (BDEs) in norbornane were determined by quantum chemistry calculations and the C2−H BDE was experimentally obtained for the first time by time-resolved photoacoustic calorimetry. CBS-Q and CBS-QB3 methods were used to derive the values DH°(C1−H) 449 kJ mol-1, DH°(C7−H) 439 kJ mol-1, and DH°(C2−H) 413 kJ mol-1. The experimental result DH°(C2−H) 414.6 ± 5.4 kJ mol-1is in excellent agreement with the theoretical value. The trend DH°(C1−H) > DH°(C7−H) > DH°(C2−H) is discussed. [ABSTRACT FROM AUTHOR]

Interfacial segregation has long been studied because of its impact on various properties of materials. Usually, theoretical descriptions are based on thermodynamic terms such as segregation enthalpy and entropy. Comparisons of published papers of different authors reveal fundamental differences in our understanding and application of these thermodynamic characteristics. To clarify this situation, the report reviews several types of segregation isotherms and their derivations. Individual sets of thermodynamic state functions appearing in segregation isotherms—Gibbs energy, enthalpy and entropy—are interpreted in detail. We identify the sources of controversial interpretations and the physical meaning of particular sets of thermodynamic state functions. It is shown that for a correct interpretation an unambiguous and systematic use of the term excess in thermodynamic terminology is necessary, as well as a correct evaluation scheme for data obtained with Auger Electron Sepctroscopy (AES). Successful applications of segregation isotherms based on standard thermodynamic state functions of segregation are demonstrated for three examples: anisotropy of grain boundary segregation and its consequences for the classification of grain boundaries, compensation effect applied to grain boundary segregation, and quantitative prediction of grain boundary segregation (including anisotropy). [ABSTRACT FROM AUTHOR]

Abstract: A high pressure flow-mixing isothermal microcalorimeter was used to determine molar excess enthalpies of six binary systems for 2,4-pentanedione + (1-butanol, + 2-methyl-1-propanol, + 1-pentanol, + 1-heptane, + ethyl acetate, and + water) at T =298.15, 313.15, and 328.15K and p =0.1 and 10.0MPa. The molar excess enthalpies increased with an increase of the temperature and the molecular size of alcohols and decreased slightly with an increase of pressure. The experimental data were correlated by the Redlich–Kister equation and three local composition models (Wilson, NRTL, and UNIQUAC). [Copyright &y& Elsevier]

We have examined the relaxation that occurs in the supercooled plastic crystalline phases of pentachloronitrobenzene (PCNB), dichlorotetramethylbenzene (DCTMB), trichlorotrimethylbenzene (TCTMB) along with some of their deuterated samples, and 1-cyanoadamantane (CNADM) in the presence of intentionally added dopants. The experimental techniques used in the present study are dielectric spectroscopy and differential scanning calorimetry (DSC). Only one relaxation process similar to that of the primary (or -) relaxation characteristic of glass-forming materials is found, but there is no indication of any observable secondary relaxation within the resolution of our experimental setup. The -process can reasonably be described by a Havriliak−Negami (HN) shape function throughout the frequency range. However, in the case of PCNB the dielectric strength () of the above said -process does not change appreciably with temperature, though interestingly, a small addition of a dopant such as pentachlorobenzene (PCB), trichlorobenzene (TCB), and chloroadamantane (CLADM) to the molten state of PCNB drastically lowers the dielectric strength by a factor of 4 to 8. Powder X-ray diffraction measurements at room temperature and DSC data do not indicate any appreciable change in the crystalline structure. It is noticed that the effect of PCB as a dopant on the magnitude of -process of CNADM is moderate, whereas both PCB and TCB as dopants show a much reduced effect on the relaxation in DCTMB and TCTMB. It is suggested that the drastic changes in the dielectric strength of the -process is due to the rotational hindrance caused by the presence of a small number of dopant molecules in the host crystalline lattice. In the above context, the possibility of a certain degree of antiparallel ordering of dipoles is also discussed. [ABSTRACT FROM AUTHOR]

Kinetics of exothermal decomposition of 2-nitrophenylhydrazine (2-NPH) and 4-nitrophenylhydrazine (4-NPH) was investigated by differential scanning calorimetry. The isoconversional methods, Friedman and Flynn-Wall-Ozawa, were applied to determine the activation parameters from the common analysis of multiple curves measured at different heating rates. For the processes involving two-step reactions the multivariate non-linear regression was used. A good agreement between the experimental and the fitted data was found. [ABSTRACT FROM AUTHOR]

Abstract: Lethocerus indirect flight muscle has two isoforms of troponin C, TnC-F1 and F2, which are unusual in having only a single C-terminal calcium binding site (site IV, isoform F1) or one C-terminal and one N-terminal site (sites IV and II, isoform F2). We show here that thin filaments assembled from rabbit actin and Lethocerus tropomyosin (Tm) and troponin (Tn) regulate the binding of rabbit myosin to rabbit actin in much the same way as the mammalian regulatory proteins. The removal of calcium reduces the rate constant for S1 binding to regulated actin about threefold, independent of which TmTn is used. This is consistent with calcium removal causing the TmTn to occupy the B or blocked state to about 70% of the total. The mid point pCa for the switch differed for TnC-F1 and F2 (pCa 6.9 and 6.0, respectively) consistent with the reported calcium affinities for the two TnCs. Equilibrium titration of S1 binding to regulated actin filaments confirms calcium regulated binding of S1 to actin and shows that in the absence of calcium the three actin filaments (TnC-F1, TnC-F2 and mammalian control) are almost indistinguishable in terms of occupancy of the B and C states of the filament. In the presence of calcium TnC-F2 is very similar to the control with ∼80% of the filament in the C-state and 10–15% in the fully on M-State while TnC-F1 has almost 50% in each of the C and M states. This higher occupancy of the M-state for TnC-F1, which occurs above pCa 6.9, is consistent with this isoform being involved in the calcium activation of stretch activation. However, it leaves unanswered how a C-terminal calcium binding site of TnC can activate the thin filament. [Copyright &y& Elsevier]

Abstract  The enthalpy of Ho5Ge3 is measured by drop calorimetry between 463 and 2314 K for the first time. The temperature dependences of enthalpy, heat capacity, entropy, and Gibbs free energy are plotted and, enthalpy and entropy of melting are calculated. [ABSTRACT FROM AUTHOR]

Abstract  The enthalpy of Ho5Ge3 is measured by drop calorimetry between 463 and 2314 K for the first time. The temperature dependences of enthalpy, heat capacity, entropy, and Gibbs free energy are plotted and, enthalpy and entropy of melting are calculated. [ABSTRACT FROM AUTHOR]

Abstract: Molecular tweezers based on calix[4]arene- or thiacalix[4]arene–porphyrin conjugates have been prepared starting from tetraformyl calixarenes and aminoporphyrin moieties. As proven by NMR and UV/vis titration experiments, these compounds form 1:1 complexes with C60 and C70 fullerenes in solution while possessing a high selectivity towards fullerene C70. [Copyright &y& Elsevier]

The dilution enthalpies of D-mannitol and D-sorbitol in aqueous sodium chloride solution at various concentrations have been determined by isothermal microcalorimetry at 298.15 K. The homogeneous enthalpic interaction coefficients over a quite large range of concentration of aqueous sodium chloride solutions have been calculated according to the excess enthalpy concept. The results show that enthalpic pairwise interaction coefficients ( h 2) of D-mannitol and D-sorbitol are positive in aqueous sodium chloride solution and become more positive with increase of the concentration of sodium chloride. The results are interpreted in terms of the different conformations of the two polyols, solute-solute and solute-solvent interactions involved by solvent effects. [ABSTRACT FROM AUTHOR]

The constitutive androstane receptor (CAR) enhances transcription of specific target genes that regulate several metabolic pathways. CAR functions as an obligate heterodimer (CAR—RXR) with the retinoid X receptor (RXR). Also part of the active receptor complex is the steroid receptor coactivator-1 (SRC-1) which interacts with the receptor complex via specific receptor interaction domains (RIDs). A peptide derived from SRC-1 RID2 is used to study the thermodynamic properties of the interaction with the CAR—RXR ligand binding domain (LBD) complex. In the absence of ligands for both CAR and RXR, binding of coactivator peptide to the CAR—RXR heterodimer is characterized by a favorable enthalpy change and an unfavorable entropy change. The addition of the CAR agonist, TCPOBOP, increases the affinity for coactivator by decreasing the unfavorable entropy and increasing the favorable intrinsic enthalpy of the interaction. The RXR ligand, 9-cis-RA, generates a second SRC-1 site and increases the affinity by improving the entropic component of binding. There is an additional increase in affinity for one of the two sites in the presence of both ligands. The change in heat capacity (ΔCp) is also investigated. A 2-fold difference in ΔCp is observed between liganded and unliganded CAR—RXR. The observed thermodynamic parameters for binding of SRC-1 peptide to liganded and apo CAR—RXR as well as the difference in the ΔCp data provide evidence that the apo CAR—RXR heterodimer is conformationally mobile. The more favorable enthalpic contribution for TCPOBOP-bound CAR—RXR indicates that preformation of the binding site improves the complementarity of the coactivator—receptor interaction. [ABSTRACT FROM AUTHOR]

The enthalpies of mixing of oxides in the binary systems PbO-Y2O3 and PbO-MoO3 have been determined for near-eutectic compositions by solution calorimetry. The results, combined with earlier solution calorimetry data for these systems, provide clear evidence for self-organization of the interacting substructures in the melt (formation of nonautonomous phases similar to supramolecular ensembles). [ABSTRACT FROM AUTHOR]

Abstract: Isothermal titration calorimetry has been applied to determine the stability constants, stoichiometry, formation enthalpies, entropies, and Gibbs free energies for the complexes of α-cyclodextrin (α-CD) with a series of bis-quarternary ammonium surfactants, (C n N)2Cl2 (n =12, 14, 16), in aqueous solutions at 293.15K. The observed stability constants of the complexes are very large. For these quite stable inclusion complexes, the stoichiometry of most stable complexes changes from 2:1 to 6:1 as the number of methylenes (–CH2–) in each of the hydrophobic tail is increased from 12 to 16. According to the same change of the hydrophobic chain, both formation enthalpy and formation entropy evidently decrease. The results also indicate that the association processes are characterized by both favorable enthalpy changes and unfavorable entropy changes. Chemical shift data of all protons in the CD molecule, induced by the formation of the (α-CD+(C12N)2Cl2) complexes have been determined by Proton NMR spectroscopy. [Copyright &y& Elsevier]

Abstract: The standard enthalpies of formation of some intermetallic compounds of transition metals have been measured by high temperature direct synthesis calorimetry at 1373±2K. The following results (in kJ/mol of atoms) are reported: The values are compared with some earlier experimental results obtained by EMF and by calorimetry. They are also compared with the predicted values of Miedema and co-workers. We will present a systematic picture of how the enthalpies of formation may be related to the atomic number of the transition metal. [Copyright &y& Elsevier]

We have previously shown that the linkage of temperature-dependent protonation and DNA base unstacking equilibria contribute significantly to both the negative enthalpy change (ΔHobs) and the negative heat capacity change (ΔCp,obs) for Escherichia coli SSB homotetramer binding to single-stranded (ss) DNA. Using isothermal titration calorimetry we have now examined ΔHobs over a much wider temperature range (5–60 °C) and as a function of monovalent salt concentration and type for SSB binding to (dT)70 under solution conditions that favor the fully wrapped (SSB)65 complex (monovalent salt concentration ≥0.20 M). Over this wider temperature range we observe a strongly temperature-dependent ΔCp,obs. The ΔHobs decreases as temperature increases from 5 to 35 °C (ΔCp,obs <0) but then increases at higher temperatures up to 60 °C (ΔCp,obs >0). Both salt concentration and anion type have large effects on ΔHobs and ΔCp,obs. These observations can be explained by a model in which SSB protein can undergo a temperature- and salt-dependent conformational transition (below 35 °C), the midpoint of which shifts to higher temperature (above 35 °C) for SSB bound to ssDNA. Anions bind weakly to free SSB, with the preference Br- > Cl- > F-, and these anions are then released upon binding ssDNA, affecting both ΔHobs and ΔCp,obs. We conclude that the experimentally measured values of ΔCp,obs for SSB binding to ssDNA cannot be explained solely on the basis of changes in accessible surface area (ASA) upon complex formation but rather result from a series of temperature-dependent equilibria (ion binding, protonation, and protein conformational changes) that are coupled to the SSB-ssDNA binding equilibrium. This is also likely true for many other protein-nucleic acid interactions. [ABSTRACT FROM AUTHOR]

Abstract: Calorimetric titration and NMR experiments in aqueous phosphate buffer (pH 7.2) at 298.15K have been done to determine the binding mode, complex stability constants and thermodynamics (ΔG°, ΔH°, and TΔS°) for 1:1 inclusion complexation of water-soluble calix[n]arenesulfonates (CnAS, n =4 and 6) and thiacalix[4]arene tetrasulfonate (TCAS) with acethylcholine, carnitine, betaine and benzyltrimethylammonium ion. The results show the inclusion complexations are driven by enthalpy (ΔH°<0), accompanied by negative entropic changes (ΔS°<0). The binding affinities (C4AS>C6AS>TCAS) are discussed from the viewpoint of CH–π/π–π interactions, electrostatic interactions and size/shape-fit relationship between host and guest. [Copyright &y& Elsevier]

The standard molar enthalpies of combustion, sublimation, and formation of three nitrogen-containing heterocycles, namely, 2-benzimidazolinone, 2-benzoxazolinone and 3-indazolinone were determined calorimetrically. The standard ( p °?=?0.1?MPa) molar enthalpies of formation in the gas phase were derived from the standard molar enthalpies of combustion, in oxygen, at T ?=?298.15?K, measured by static bomb combustion calorimetry and from the standard molar enthalpies of sublimation at T ?=?298.15?K, measured by Calvet microcalorimetry. Møller–Plesset calculations at the MP2 level and density functional calculations with the B3LYP functional and extended basis sets were also performed to determine the energetically preferred tautomeric form of the molecules. The results were qualitatively independent of the calculational level, where in general the DFT calculations were in better agreement with experiment than those from MP2. The gas and solid phase enthalpic differences between imines and amides, wherein –CH=N- is contrasted with –CONH-, have been studied and roughly constant values have been found. [ABSTRACT FROM AUTHOR]

Abstract: Measuring and modeling the surface charge of clays, and more especially smectites, has become an important issue in the use of bentonites as a waste confinement material aimed at retarding migration of water and solutes. Therefore, many studies of the acid–base properties of montmorillonite have appeared recently in the literature, following older studies principally devoted to cation exchange. It is striking that beyond the consensus about the complex nature of the surface charge of clays, there are many discrepancies, especially concerning the dissociable charge, that prevents intercomparison among the published data. However, a general trend is observed regarding the absence of common intersection point on raw titration curves at different ionic strengths. Analysis of the literature shows that these discrepancies originate from the experimental procedures for the preparation of the clays and for the quantification of their surface charge. The present work is an attempt to understand how these procedures can impact the final results. Three critical operations can be identified as having significant effects on the surface properties of the studied clays. The first one is the preparation of purified clay from the raw material: the use of acid or chelation treatments, and the repeated washings in deionized water result in partial dissolution of the clays. Then storage of the purified clay in dry or wet conditions strongly influences the equilibria in the subsequent experiments respectively by precipitation or enhanced dissolution. The third critical operation is the quantification of the surface charge by potentiometric titration, which requires the use of strong acids and bases. As a consequence, besides dissociation of surface sites, many secondary titrant consuming reactions were described in the literature, such as cation exchange, dissolution, hydrolysis, or precipitation. The cumulated effects make it difficult to derive proper dissociation constants, and to build adequate models. The inadequation of the classical surface complexation models to describe the acid–base behavior of clays is illustrated by the electrokinetic behavior of smectites, which is independent from the pH and the ionic strength. Therefore, there is still a need on one hand for accurate data recorded in controlled conditions, and on the other hand for new models taking into account the complex nature of the charge of clays. [Copyright &y& Elsevier]

The thermal characteristics of ten kinds of para-aramid, meta-aramid, polyoxadiazole, and polyimide fibres were investigated by dynamic thermogravimetric analysis, differential scanning calorimetry, and thermomechanical analysis. It was shown that thermooxidative degradation of these fibres begins at 400–450° C and is intensified at higher temperatures. These fibres are characterized by dimensional stability up to the temperature of onset of thermooxidative processes (up to 400–450°C) except for meta-aramid fibres, which exhibit approximately 5% shrinkage at high temperatures. With respect to thermal stability, the fibres are in the following order: polyimide > heterocyclic para-aramid and polyoxadiazole > carbocyclic para-aramid > meta-aramid. [ABSTRACT FROM AUTHOR]

Abstract: The inhibitory effects of five hydroxyanthraquinones (HAQs) from root and rhizoma of Rheum officinale Baill, a traditional Chinese medicinal (TCM) herb, on Staphylococcus aureus growth were investigated by calorimetry. The power–time curves of S.aureus with and without HAQ were acquired and the extent and duration of inhibitory effects on the metabolism evaluated by growth rate constants (k 1, k 2), half inhibitory ratio (IC50), maximum heat output (P max) and peak time (t p). The value of k 1 and k 2 of S. aureus in the presence of the five HAQs decreased with the increasing concentrations of HAQs. Moreover, P max was reduced and the value of t p increased with increasing concentrations of the five drugs. The inhibitory activity varied for different drugs. IC50 of the five HAQs was 4μgml−1 for emodin, 3.5μgml−1 for rhein, 10μgml−1 for aloe-emodin, 1000μgml−1 for chrysophanol, 1600μgml−1 for physcion. The sequence of antimicrobial activity of the five HAQs: rhein>emodin>aloe-emodin>chrysophanol>physicion. [Copyright &y& Elsevier]