Evaluation of the temperature responses in colorimetric measurements of chemisorption enthalpies on metal films

1979 ◽  
Vol 44 (12) ◽  
pp. 3425-3433 ◽  
Author(s):  
Miloš Smutek ◽  
Slavoj Černý
Keyword(s):  
Heat Evolution ◽  
Adiabatic Temperature ◽  
Time Curve ◽  
Model Calculations ◽  
Colorimetric Measurements ◽  
Reliable Procedure ◽  
Temperature Responses ◽  
Temperature Time ◽  
Zero Time ◽  
Cooling Part

An analysis was performed of various estimates of the adiabatic temperature Ttot that corresponds to the total heat liberated by a gas dose adsorbed on a metal film in the calorimeter for measurement of chemisorption enthalpies. Besides the two common procedures consisting either in the construction of the adiabatic temperature-time curve or in the extrapolation of the single-exponential cooling part of the actual temperature-time curve to zero time, we have examined estimates of Ttot by extrapolating the cooling exponential to the mid-point between zero time and the temperature maximum (t = tmax/2). Model calculations have shown the merit of the latter extrapolation, particularly in the cases of slow heat evolution. This has been verified on the data measured in the chemisorption of methane and ethane on molybdenum films. Extrapolation to tmax/2 has turned out to be a simple and reasonably reliable procedure for handling the data obtained in film calorimeters.

scholarly journals Material properties and the energy balance in standardized fire testing

2018 ◽  
Vol 163 ◽  
pp. 07004 ◽  
Author(s):  
Wojciech Węgrzyński ◽  
Piotr Turkowski
Keyword(s):  
Energy Balance ◽  
Material Properties ◽  
Fire Tests ◽  
Fire Testing ◽  
Time Curve ◽  
Conservation Of Energy ◽  
Certification Process ◽  
Standard Temperature ◽  
In Fire ◽  
Temperature Time

The origins of standardised fire testing can be traced back to 1870’s, and the origin of the standard temperature-time curve to 1917. This approach, based on a 19th-century intuition is still in use up to this day, to design the 21st-century structures. Standardized fire-testing ultimately disregards the conservation of energy in the fire, as in every test the resulting temperature of the test must be the same (precisely as the temp.-time curve). To maintain this, different amount of heat is required in every test, which means that every time a different fire is modelled within the furnace. The differences between furnace fire sizes are ignored in the certification process, but can be interesting for fire researchers to understand how different materials behave in fire conditions. In this paper, Authors explore this topic by investigating the energy balance within the furnace, and comparing different fire tests together.

scholarly journals Sensitivity analysis of fire resistance of a composite floor slab

2018 ◽  
Vol 174 ◽  
pp. 01019
Author(s):  
Joanna Kaliszuk ◽  
Elżbieta Grochowska
Keyword(s):  
Sensitivity Analysis ◽  
Fire Resistance ◽  
Simple Calculation ◽  
Calculation Model ◽  
Time Curve ◽  
Composite Slab ◽  
Standard Temperature ◽  
Supporting Structure ◽  
Bending Resistance ◽  
Temperature Time

The paper presents a sensitivity analysis of design bending resistance of a composite slab rib in a fire situation to a change of the value of basic variables. The analysis was carried out for a composite slab being an element of a supporting structure of a reinforced floor referred to in [1, 2]. The calculations were made for a simple calculation model and the standard temperature-time curve according to [6, 7]. The set of basic variables was limited to X1 = {(y, z), h1, fy,a, fy,s, fc}.

Isoperibol Reaction-Solution Calorimetry

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Accurate Method ◽  
Solution Calorimetry ◽  
Combustion Calorimetry ◽  
Separate Experiment ◽  
Time Curve ◽  
Reaction Solution ◽  
Static Bomb ◽  
The One ◽  
Temperature Time

The determination of enthalpies of reaction in solution, using isoperibol reaction-solution calorimetry, is often the easiest and most accurate method of determining enthalpies of formation of compounds that cannot be studied by combustion calorimetry. The technique was pioneered by Thomsen who, between 1882 and 1886, performed thermochemical measurements involving the solution of various substances in liquids (e.g., diluted acids). Many types of isoperibol reaction-solution calorimeters have been developed since then. The designs vary according to the nature of the reactions of interest. One of the most widely used consists of a vessel, such as the one shown in figure 8.1, immersed in a thermostatic water bath. The sample is sealed inside a thin-walled glass ampule A, fixed to an ampule breaking system B in the calorimeter head C. The calorimeter head also supports the temperature sensor D, the stirrer E, and an electrical resistance F, used for calibration of the apparatus. The Dewar vessel G, containing the solution to be reacted with the sample, is adjusted to C. The assembled calorimetric vessel is transferred to the thermostatic bath, and from then on, the experimental procedure closely follows that already described in section 7.1 for isoperibol static-bomb combustion calorimetry. The reaction is initiated at the end of the fore period by pushing down the plunger H and breaking the ampule against a pin situated at the bottom of the ampule breaking system B. As a result of the calorimetric experiment, a temperature-time curve such as the one in figure 7.2 is obtained. Note that figure 7.2 is typical of an exothermic process. In the case of an endothermic process, a decrease of the temperature of the calorimetric system is observed during the reaction period. The experiments are usually carried out at atmospheric pressure and the initial goal is the determination of the enthalpy change associated with the calorimetric process under isothermal conditions, ΔHICP, usually at the reference temperature of 298.15 K. This involves the determination of the corresponding adiabatic temperature change, ΔTad, from the temperature-time curve just mentioned, by using one of the methods discussed in section 7.1; the determination of the energy equivalent of the calorimeter in a separate experiment.

Factors in the pattern, timing and predictability of hibernation in the squirrel, Citellus beecheyi

1958 ◽  
Vol 196 (1) ◽  
pp. 8-14 ◽  
Author(s):  
Felix Strumwasser
Keyword(s):  
Brain Temperature ◽  
Temperature Drop ◽  
Internal Clock ◽  
Ground Squirrels ◽  
Thermoregulatory Behavior ◽  
Time Curve ◽  
Test Drop ◽  
Deep Hibernation ◽  
Temperature Time ◽  
Three Factor

Ground squirrels, Citellus beecheyi, bearing permanently implanted brain thermocouples never entered deep hibernation in one simple temperature decline. The pattern consisted of entering into and arousing from hibernation several times, each succeeding hibernation terminating at a lower brain temperature until a final plateau was reached. The entrances before the final plateau are considered test drops and evidence is presented that each of the low brain temperatures reached is a critical point. This pattern of hibernation was independent of season. The critical brain temperature/time curve is suggestive of the integrated rate of metabolic preparations necessary for entering hibernation. From the thermoregulatory behavior of the critical points, it appears that the temperature regulating mechanism is being informed of the state of biochemical preparations for hypothermia and controls the depth of each temperature drop accordingly. Arousals from hibernation, particularly during the test drop period, occur at preferred times, at statistically significant 1-hour intervals, but the time of entrance and the first plateau are randomly distributed within two selected portions of the day. Evidence is presented that this species' time sense is due to a temperature-independent internal clock. A ‘three-factor theory’ explaining the triggering of hibernation is proposed and developed.

Resistivity Study on Early Hydration Process of Phosphoaluminate Cementitious Material

2009 ◽  
Vol 79-82 ◽  
pp. 95-98 ◽  
Author(s):  
Ming Zhang ◽  
Zhu Ding ◽  
Feng Xing ◽  
Peng Liu
Keyword(s):  
Resistivity Measurement ◽  
Heat Evolution ◽  
Hydration Process ◽  
Early Age ◽  
Hydration Products ◽  
Microstructure Formation ◽  
Time Curve ◽  
Early Hydration ◽  
Hydration Mechanism ◽  
Acceleration And Deceleration

An electrodeless resistivity measurement system developed recently can provide a reliable method for monitoring the hydration process of cement-based materials continuously and accurately. Phosphoaluminate cement (PAC) sets quickly and develops high early strength. In order to understand the mechanism, the hydration products and microstructure formation of PAC in early age need to be studied. In the study, early hydration process of PAC with different dosage of retarder was investigated by the electrodeless resistivity equipment. According to resistivity-time curve, resistivity of freshly mixed PAC paste decreases sharply and then rises slowly, some characteristic peaks appear at different hydration stages of PAC. Heat evolution of PAC was also measured. The hydration mechanism and structure formation were studied according to these results. Depending on the dosage of retarder, the hydration process of PAC includes four stages which are dissolution, induction, acceleration and deceleration.

DCE-MR imaging of orbital lesions: diagnostic performance of the tumor flow residence time τ calculated by a multi-compartmental pharmacokinetic tumor model based on individual factors

2018 ◽  
Vol 60 (5) ◽  
pp. 643-652 ◽  
Author(s):  
Katharina Erb-Eigner ◽  
Patrick Asbach ◽  
Sa-Ra Ro ◽  
Matthias Haas ◽  
Eckart Bertelmann ◽  
...  
Keyword(s):  
Residence Time ◽  
Diagnostic Performance ◽  
Area Under The Curve ◽  
Tumor Model ◽  
Blood Flow Rate ◽  
Whole Body ◽  
Time Curve ◽  
Model Calculations ◽  
Orbital Masses ◽  
Orbital Lesions

Background Differentiating benign from malignant orbital lesions by imaging and clinical presentation can be challenging. Purpose To differentiate benign from malignant orbital masses using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) based on tumor flow residence time τ calculated with the aid of a pharmacokinetic tumor model. Material and Methods Sixty patients with orbital masses were investigated by 3-T MRI including dynamic sequences. The signal intensity-time curve after i.v. contrast medium administration within lesions was approximated by Gd-concentration profiles on the basis of model calculations where the tumor is embedded in a whole-body kinetic model. One output of the model was tumor flow residence time τ, defined as the ratio of the tumor volume and the tumor blood flow rate. Receiver operating characteristic (ROC) curves were used to analyze the diagnostic performance of τ. The results were compared with those of Ktrans, kep, ve, iAUC, and ADC. Results Thirty-one benign and 29 malignant orbital masses were identified (reference standard: histopathology, clinical characteristics). Mean τ was significantly longer for benign masses (94 ± 48 s) than for malignant masses (21 ± 19 s, P < 0.001). ROC analysis revealed the highest area under the curve (AUC = 0.94) for τ in orbital masses compared to standard methods. Conclusion Tumor flow residence times τ of benign and malignant orbital masses are valuable in the diagnostic work-up of orbital tumors. Measures of diagnostic accuracy were superior for τ compared to ADC, Ktrans, ve, and iAUC.

scholarly journals Pharmacokinetic Study of NADPH Oxidase Inhibitor Ewha-18278, a Pyrazole Derivative

Pharmaceutics ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 482
Author(s):  
Seul Gee Lee ◽  
Jaeok Lee ◽  
Kyung Min Kim ◽  
Kee-In Lee ◽  
Yun Soo Bae ◽  
...  
Keyword(s):  
Statistical Significance ◽  
Oxidase Inhibitor ◽  
High Concentration ◽  
Time Curve ◽  
Suitable Candidate ◽  
Nadph Oxidase Inhibitor ◽  
Concentration Time ◽  
Zero Time

In a previous study, the specific NOX1/2/4 inhibitor Ewha-18278 was confirmed as a possible treatment for osteoporosis both in vitro and in vivo. Here, we investigated the pharmacokinetics (PK) of the compound by intravenous (IV) and oral administrations to rats. Dimethyl sulfoxide (DMSO)-based and diazepam injection-based formulations were used to dissolve the compound. In the latter formulation applicable to humans, the changes in PK parameters were monitored at two different concentrations (1 mg/mL and 2 mg/mL). The area under the plasma concentration-time curve from zero time to infinity (AUCinf) of Ewha-18278 was highest in the DMSO-based formulation (2 mg/mL). Also, the concentration was increased 1.6-fold at the low concentration of the diazepam injection-based formulation compared to the high concentration. There was no statistical significance in the AUCinf of the compound between DMSO-based formulation (2 mg/mL) and diazepam injection-based formulation (1 mg/mL). These results suggest that Ewha-18278 can be delivered to humans by both IV and oral routes. In addition, the diazepam injection-based formulation of Ewha-18278 appears to be a suitable candidate for dosage development for future toxicity test and clinical trial.

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