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1.
Dr. Shanahan has published two papers (Thermochim. Acta 428 (2005) 207, Thermochim. Acta 382 (2002) 95) in which he argues that excess heat claimed to be produced by cold fusion is actually caused by errors in heat measurement. In particular, he proposes that unrecognized changes in the calibration constant are produced by changes in the locations where heat is being generated within the electrolytic cell over the duration of the measurement. Because these papers may lend unwarranted support to rejection of cold fusion claims, these erroneous arguments used by Shanahan need to be answered. 相似文献
2.
We comment the Letter ‘A novel experimental method: electrochemical detection of phase transition in ferroelectric single crystals’, Chem. Phys. Lett. 384 (2004) 262 by K. Gatner and R. Jakubas. We indicate that the method used in this Letter is not ‘A novel method’ but the application of the method described in Refs. [M. Matlak, M. Pietruszka, E. Rówiński, Phys. Rev. B 63 (2001) 52101; M. Matlak, M. Pietruszka, E. Rówiński, Phys. Stat. Sol. A 184 (2001) 335; W. Gaweł, E. Zaleska, Z. Sztuba, Met. Sci. Eng. A 324 (2002) 255], well known to Gatner, but not cited in the commented Letter. Additionally Gatner, cooperating with us, has used our TGS samples and published the results in the commented Letter without our knowledge and permission. 相似文献
3.
Two methods for the absolute calibration of flow calorimeters (used for measuring the differences in heat capacities of two fluids) have been investigated. In the recommended method of calibration, a change in the flow rate of the fluids is used to minic a change in the heat capacity of the fluid. In the other method of calibration, heat loss is measured using a fluid of known heat capacity, and it is assumed this heat loss is constant. This calibration method is not recommended because the heat loss is, in general, not constant. For some calorimeters the difference between the two methods of calibration is negligible, while for others erros as high as 40% are caused by choosing the wrong method. A detailed analysis of the heat losses in this kind of calorimetry shows why the two calibration methods give different results and leads to various methods of improving calorimeter construction and operation. Because chemical standardization is far more convenient for routine use, the recommended absolute calibration method has been used to establish 3.00 mol-kg –1 aqueous NaCl as a chemical standard for temperatures between 325 and 600K at 17.7 MPa. 相似文献
4.
Low-temperature calorimetry has been used to determine the ice content in concrete at different temperatures when exposed to low-temperature environments. However, the analysis of the ice content from the measured data of heat flow is not straightforward. In this study, two important factors influencing the ice content calculation are discussed. The importance of the baseline determination for the calculation of the ice content is realized. Two different methods of generating the baseline are discussed. First, the ‘J-baseline’ is discussed which is a recently proposed extrapolation method based on the accumulated heat curves measured in the freezing and the melting process. Second, the ‘C-baseline’ is discussed in which a calculated baseline is used where the heat capacity of both water and ice and the phase changing behaviour under different testing temperatures are considered. It turns out that both the ‘J-baseline’ method and the ‘C-baseline’ method can be used to calculate the approximate baseline. The heat of fusion of the water confined in small pores is another important parameter to be considered in ice content calculation. This property must be carefully analyzed in order to accurately calculate the ice contents at different temperatures in the freezing and melting process. It should be noted that there is no general agreement on how to obtain the important temperature dependence of the heat of fusion of water confined in small pores. By performing comparison studies, the present study shows the influence of the different values of the heat of fusion commonly adopted on the calculated ice content for the studied concrete samples. The importance and necessity to use an accurate value of the heat of fusion is emphasized. Based on the calculation of the baseline proposed in this work and by carefully selecting the values for the heat of fusion, the ice content in a hardened concrete sample is expected to be estimated with an acceptable accuracy. 相似文献
5.
A new metrological approach is proposed by the Laboratoire National de Metrologie et d’Essais to lower the uncertainty of measurements of enthalpy of fusion from 23 to 1000 °C. It consists, as in our previous works, in putting the studied sample inside a calibration crucible and in performing the heat calibration of the calorimeter by electrical substitution at two temperatures before and after the temperature of fusion of the sample during the same low-rate heating run. The novelty lies in the “electrical compensation” of the endothermic reaction of fusion. The quantification of the electrical energy needed to melt the sample, which can be measured with high accuracy, and the integrated remaining heat flow rate divided by the calibration factor (sensitivity) of the calorimeter at the temperature of fusion, leads to the determination of the enthalpy of fusion of the sample with low uncertainty. This methodology reduces the influence of the uncertainty component associated with the area of the peak of fusion by comparison with the former procedure when no electrical compensation was applied. The relative expanded uncertainty (k = 2) associated with the enthalpy of fusion measurements, performed using this facility and this new procedure, has been assessed to be < 0.2% for tin and indium and to be about 0.3% in the case of silver. 相似文献
6.
The isosteric heat of adsorption of a pure compound dissolved in a solution in equilibrium with a solid adsorbent was determined, based on the Gibbs surface excess model. The exact isosteric heat of adsorption differs from the usual value derived from the variation of the Henry’s constant with the reciprocal temperature because this procedure assumes ideal behavior of the bulk liquid solution, which, in most cases, is only approximately so. An experimental protocol, based on the determination of the excess adsorption isotherms by combining frontal analysis (for strongly adsorbed components) and spectrometric tracer pulse chromatography (for weakly adsorbed compounds) is proposed. It allows the determination of the exact isosteric heat of adsorption provided that the activity coefficient of the compound in the bulk solution can be explicitly expressed as a function of the bulk liquid composition. 相似文献
7.
In a recent development we proposed a quantum chemical approach to compute free energy change for chemical reactions in condensed phases by combining the QM/MM method with the theory of energy representation (QM/MM-ER). We extend in this Letter the novel approach to compute reduction free energy of isoalloxazine ring of FAD (flavin adenine dinucleotide) immersed in water within the framework of the QM/MM-ER method. The characteristic feature of our approach is that the excess electron to be attached on the FAD is identified as a solute. The reduction free energy has been obtained as −80.1 kcal/mol in the aqueous solution. 相似文献
8.
A qualitative interpretation is proposed to interpret isosteric heats of adsorption by considering contributions from three general classes of interaction energy: fluid–fluid heat, fluid–solid heat, and fluid—high‐energy site (HES) heat. Multiple temperature adsorption isotherms are defined for nitrogen, T=(75, 77, 79) K, argon at T=(85, 87, 89) K, and for water and methanol at T=(278, 288, 298) K on a well‐characterized polymer‐based, activated carbon. Nitrogen and argon are subjected to isosteric heat analyses; their zero filling isosteric heats of adsorption are consistent with slit‐pore, adsorption energy enhancement modelling. Water adsorbs entirely via specific interactions, offering decreasing isosteric heat at low pore filling followed by a constant heat slightly in excess of water condensation enthalpy, demonstrating the effects of micropores. Methanol offers both specific adsorption via the alcohol group and non‐specific interactions via its methyl group; the isosteric heat increases at low pore filling, indicating the predominance of non‐specific interactions. 相似文献
9.
Temperature modulated DSC (TMDSC) at low temperatures requires attention to the selection of experimental parameters that
are within the capability of the instrumentation as well as special care in calibration of heat capacity measurement when
high precision is required. Data are presented to facilitate selection of appropriate modulation periods and amplitudes at
low temperature when using a mechanical cooling accessory. The standard error of the mean heat capacity measurement for a
sapphire standard increased with decreasing temperature, decreasing period, and increasing pan mass. For ice in hermetically
sealed pans, the standard error of the mean heat capacity measurement was larger than for sapphire and did not follow a predictable
trend with changes in temperature and period of modulation. This was attributed to changes in sample geometry between successive
measurements due to melting and resolidification. A simple one-point temperature calibration by TMDSC may be unsuitable for
precise measurement of heat capacity because of the random error caused by sample placement and the systematic error caused
by cell asymmetry, temperature dependence of the calibration constant, and different sample thermal conductivities. An alternative
calibration procedure using standard DSC and either a linear or second order fit of the calibration constant over the temperature
range of interest is proposed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
In this Letter the interaction of Li atoms with terrace sites of MgO(0 0 1) surfaces is characterized by combining EPR spectroscopy with theoretical calculations. The Li atoms adsorbed to MgO terrace sites show a reduction of the isotropic hyperfine coupling constant by approximately 50% with respect to Li atoms in the gas phase. In combination with theoretical calculations it can be shown that this reduction of the hyperfine coupling constant is not due to a charge transfer between Li and MgO but can be understood by a polarization of the Li atoms which are essentially neutral. 相似文献
11.
A new strategy is proposed for verifying if recovery factor is constant and independent of the real analyte content of samples.
A signal-recovery function has been developed on the basis of measurement of spiked test samples before and after a pre-treatment
step and considering, as starting point, a recent IUPAC recommendation which distinguishes between two terms—recovery factor,
R, and apparent recovery, R*. Apparent recovery includes recovery factor and a new recovery term proposed in a previous paper by the authors, named calibration recovery, R
C. The signal-recovery function is obtained directly from the measured analytical signals instead of from the concentrations,
simplifying the calculations. A linear signal-recovery curve indicates that the recovery factor is constant in the analyte
concentration range studied experimentally and, in this way, a single recovery factor can be calculated. The usefulness of
the proposed method has been shown by quantification of the pesticide carbaryl by two different flow-injection analysis methods
with chemiluminescent detection based on the luminol and TCPO systems. Good results were obtained from both methods. 相似文献
12.
雌酮与牛血清白蛋白共价结合,合成雌酮的完全抗原。利用此抗原免疫小鼠,通过细胞融合技术制备了雌酮的单克隆抗体,经纯化表征知,抗体是IgG1型,相对分子量为164000,与固定抗的亲和常数为8.2×10^8L/mol。以生物素化的羊抗鼠免疫球蛋白及辣根过氧化物酶标记的链亲和素为标记体系,通过竞争抑制的方式测定游离的雌酮,结果表明:雌酮在10~10000pg/mL内呈线性关系。 相似文献
13.
In high pressure calorimetry the pressure change is used to obtain the desired phenomenon (i.e. phase change) at constant
temperature. Two high pressure calorimeters have been developed to measure the latent heat of fusion of pure water (hexagonal
ice-type I) at subzero temperature. Both calorimeters used a constant pressurisation rate produced with a high pressure pump
driven by a step motor. The first calorimeter was a single cell calorimeter where mercury acted as the pressurisation fluid,
while the second one was differential (two cells) and was pressurised with pentane. Both calorimeters gave high accuracy data
of latent heat of fusion of pure water, which were determined taking into account that either the fluid used to pressurise
or the pressurisation rate affected the calorimetric signal.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
In order to study the thermal properties of new type environment-friendly binary hydrate for cold storage in air-conditioning system, tests have been carried out by DSC comprehensively on the phase-change temperature and fusion heat of TBAB hydrate, THF hydrate, and TBAB–THF hydrate mixture. The results show a good trend that TBAB–THF hydrate has the superiority for more proper phase-change temperature and increased fusion heat. A broader and more developed view is that adding appropriate amount of hydrate with lower phase-change temperature to hydrate with higher one can make the hydrate mixture more suitable for cold storage (especially for 278–281 K); some hydrates with lower phase-change temperature can even make the fusion heat of mixture hydrate increased greatly. Several new environmental working pairs for binary gas hydrates have been listed to help to promote the application. 相似文献
15.
Evaluation of uncertainty affecting predictions is a major trend in analytical chemistry and chemometrics. Several approximate expressions and resampling methods have been proposed for the estimation of prediction uncertainty when using multivariate calibration. This article proposes a new expression for the variance of prediction, adapted to near infrared spectroscopy specificities and particularly to the spectral error structure, induced by the high colinearity of the variables. The proposed analytical expression enables a detailed evaluation of the different contributions and components of uncertainty affecting the model. An application to real data of feedstuff near infrared spectra related to protein content has shown its advantages. 相似文献
16.
The possibilities for cold nuclear fusion in an electrochemical cell are discussed. It is suggested that the cold nuclear fusion can be triggered by rising the dielectric constant of the cathode material around a value of 20. 相似文献
17.
In this paper a method for the calibration of the heat transfer coefficient between pan and furnace is given. This (second) calibration is necessary in addition to the usual calibration of the temperature scale. Indeed, with increasing cooling rates as required for kinetic measurements, the finite heat flow resistance between pan and furnace becomes evident anyway. We also propose to enlarge this resistance deliberately, in order to separate the time scales of the control system and of the exponential return of the heat flow curve to the base line, as occurring after completion of the phase transition. Only in this way can the heat transfer coefficient be determined with some accuracy. Another advantage of a lowered heat transfer coefficient will be treated in a third paper. It enables an approximate treatment of polymer crystallization kinetics. 相似文献
18.
A new method to convert the potential of an ion-selective electrode to concentration or activity in potentiometric titration is proposed. The advantage of this method is that the electrode standard potential and the slope of the calibration curve do not have to be known. Instead two activities on the titration curve have to be estimated e.g. the starting activity before the titration begins and the activity at the end of the titration in the presence of large excess of titrant. This new method is beneficial when the analyte is in a complexed matrix or in a harsh environment which affects the properties of the electrode and the traditional calibration procedure with standard solutions cannot be used. The new method was implemented both in a method of linearization based on the Grans's plot and in determination of the stability constant of a complex and the concentration of the complexing ligand in the sample. The new method gave accurate results when using titrations data from experiments with samples of known composition and with real industrial harsh black liquor sample. A complexometric titration model was also developed. 相似文献
19.
The close proximity in melting temperature of the LGC Limited DSC standards indium and diphenylacetic acid, has enabled a direct assessment to be made of any differences resulting from the use of a metal or an organic compound in the calibration of DSC equipment. Following calibration with indium, the equilibrium fusion temperatures for diphenylacetic acid, were determined by both the stepwise heating and extrapolation to zero heating rate methods. The results were in excellent agreement with the certificate values and established that indium may be used as a calibrant when making accurate DSC measurements on organic materials in the same temperature range and that it has the advantage that it is non-volatile and can be used a number of times without significant change. Similar agreement was obtained in the measurement of the enthalpy of fusion, although the larger heat capacity change on fusion of diphenylacetic acid resulted in a greater uncertainty than with indium. 相似文献
20.
首次报道了应用PerfusionG蛋白亲和色谱法快速测定人体生长激素与抗体免疫反应活性和摩尔配比的方法。这一新方法与传统的免疫测试技术相比较,具有快速、易于自动化操作和低劳动强度的优点。 相似文献
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