Value Of kJ Research Articles

Enthalpies of formation of piperazinium dinitrate, C4H12N2(NO3)2, dichloride, C4H12N2Cl2, and dichloride monohydrate, C4H12N2Cl2·H2O

Standard formation enthalpies of some solid piperazine salts: C4H12N2(NO3)2, C4H12N2Cl2 and C4H12N2Cl2·H2O at 298.15 K were measured using combustion and solution calorimetry. The following values were obtained: ΔfH298°(C4H12N2(NO3)2) = (-594.4 ± 2.7) kJ·mol−1, ΔfH298°(C4H12N2Cl2) = (-475.6 ± 2.9) kJ·mol−1, ΔfH298°(C4H12N2Cl2·H2O) = (-772.3 ± 2.9) kJ·mol−1 (expanded uncertainties, 95% confidence level). The hydration enthalpies of piperazinium dichloride by gaseous and liquid water were found to be equal to (-54.82 ± 0.09) kJ·mol−1(H2O) and (-10.83 ± 0.09) kJ·mol−1(H2O), respectively (expanded uncertainties, 95% confidence level). The results obtained allowed estimating ΔfH298° of aqueous C4H12N22+ ions as (-128.5 ± 2.9) kJ·mol−1 (expanded uncertainty, 95% confidence level), which is in good agreement with the value of (-129.0 ± 3.3) kJ·mol−1 (expanded uncertainty, 95% confidence level) that was calculated using the literature data.

Phylogenetical Relationships between Kejobong Goat and Other Goats Based on Mt-DNA D-loop Sequence Analysis

The aim of this study was to investigate phylogenetical relationships between Kejobong goat and Kacang goat as well as Etawah Grade goat using genetic diversity, haplotype, and genetic distance analysis based on D-loop sequences. A total of 76 blood samples belonged to three local goats, namely Kacang goat (KC), Etawah Grade goat (EG), and Kejobong goat (KJ). The DNA genome was extracted based on the manufacturer’s standard protocol using gSYNC DNA Mini Kit (Geneaid Biotech Ltd.) for sequence analysis control region (D-loop) in mitochondrial DNA (mtDNA) using specific primer. The results revealed that there were a total of 36 nucleotide substitutions, those were 1 indel (insertion or deletion), 34 haplotypes with Pi = 0.00253±0.00029 and Hd = 0.925±0.018 in three local goats, while intra-breed in this study showed Pi value of EG, KC, and KJ were 0.00452±0.00077, 0.00214±0.00028 and 0.00143±0.00018, respectively and Hd value were 0.985±0.025, 0.926±0.032, and 0.855±0.044, respectively. Genetic distances between KJ and KC, KJ and EG, and between KC and EG were 0.0018; 0.0034, and 0.0036, respectively. The highest NHap was observed in KC (17), followed by EG (15) and KJ (11); and all three local goats were in the same cluster in phylogeny tree. In conclusion, genetically, Kejobong goat is a crossbred of Kacang goat and Etawah Grade goat and has closer genetic relationships to Kacang goat than to Etawah Grade goat.

Work Performed Above The Respiratory Compensation Point Is Not Equivalent To W′

The hyperbolic power-time relationship for severe-intensity cycling exercise is defined by two physiological parameters: (i) the asymptote, critical power (CP); and (ii) the curvature constant, W′. Recently, we reported that the respiratory compensation point (RCP) displays poor measurement agreement with the CP. However, it is unknown whether the amount of supra-RCP mechanical work (RCP′) performed during ramp-incremental cycling is similar to that performed above the CP (i.e., W′). PURPOSE: We sought to determine the measurement agreement between W′ and RCP′ obtained during incremental cycling of varying ramp slopes. METHODS: Twelve male cyclists completed three separate ramp-incremental cycling protocols, where the work rate increment was slow (SR, 15 W[BULLET OPERATOR]min-1), medium (MR, 30 W[BULLET OPERATOR]min-1), or fast (FR, 45 W[BULLET OPERATOR]min-1). Initially, the RCP (adjusted for mean response time) was obtained using the ventilatory equivalent for CO method. To assess RCP′, we calculated the power–time integral between the RCP and the instantaneous power output observed at exercise termination for each ramp-incremental test, separately. W′ was determined via Morton’s model for ramp-incremental exercise. The assumption that W′ and RCP′ occur at equivalent kilojoule (kJ) values was assessed by one-way repeated- measures ANOVA and by evaluating the concordance correlation coefficient (CCC) and typical error (root-mean-square error [RMSE]) for each ramp-incremental test, separately. RESULTS:RCP′ decreased with increases in the ramp-incremental slope (P < 0.05). RCP′ in SR (21.5 ± 6.5 kJ), MR (16.8 ± 5.6 kJ) and FR (13.3 ± 4.3 kJ) were not different from W′ (15.7 ± 6.9 kJ). The degree to which the relationship between W′ and RCP′ approximated the line of identity was poor for SR (CCC = -0.09 and RMSE = 11.3 kJ), MR (CCC = 0.23 and RMSE = 7.5 kJ) and FR (CCC = 0.37 and RMSE = 6.5 kJ). CONCLUSION: Our data demonstrate that RCP′ is lower when the ramp-incremental slope is increased. Furthermore, despite occurring at similar kJ values, we observed poor measurement agreement between W′ and RCP′, as evidenced by the low CCC and the large RMSE values, irrespective of the ramp-incremental protocol. Together, these findings indicate that RCP′ obtained during ramp-incremental cycling is not equivalent to W′.

Analytical approximations for effective relative permeability in the capillary limit

We present an analytical method for calculating two-phase effective relative permeability, krjeff, where j designates phase (here CO2 and water), under steady state and capillary limit assumptions. These effective relative permeabilities may be applied in experimental settings and for upscaling in the context of numerical flow simulations, e.g., for CO2 storage. An exact solution for effective absolute permeability, keff, in two-dimensional log-normally distributed isotropic permeability (k) fields is the geometric mean. We show that this does not hold for since log normality is not maintained in the capillary limit phase permeability field (kkrj) when capillary pressure, and thus the saturation field, is varied. Nevertheless, the geometric mean is still shown to be suitable for approximating krjeff when the variance of ln k is low. For high variance cases, we apply a correction to the geometric-average gas effective relative permeability using a Winsorized mean, which neglects large and small Kj values symmetrically. The analytical method is extended to anisotropically correlated log-normal permeability fields using power law averaging. In these cases the Winsorized mean treatment is applied to the gas curves for cases described by negative power law exponents (flow across incomplete layers). The accuracy of our analytical expressions for is demonstrated through extensive numerical tests, using low- and high-variance permeability realizations with a range of correlation structures. We also present integral expressions for geometric-mean and power law average krjeff for the systems considered, which enable derivation of closed-form series solutions for without generating permeability realizations. This article is protected by copyright. All rights reserved.

Comparison of the exact thermodynamics of the AF Blume–Emery–Grifiths and of the spin-1 ferromagnetic Ising models

We study in detail the thermodynamics of the anti-ferromagnetic Blume–Emery–Griffiths (AF BEG) model in the presence of a longitudinal magnetic field. Its thermodynamics is derived from the exact Helmholtz free energy (HFE) of the model, valid for T>0. Numerical simulations of this model on a periodic space chain with 10 sites (N=10) yield the energy spectra of the model at KJ=2 for DJ=1 and DJ=2, thus helping us compare, for a broad range of temperature, how some (per site) thermodynamic functions with the same value of KJ but distinct values of DJ behave, namely: the z-component of the magnetization, the specific heat and the entropy. These thermodynamic functions of the AF BEG model at K|J|=2 are compared to those of the spin-1 ferromagnetic Ising model with D|J|>1.5, for which the T=0 phase diagrams of both models are identical. This comparison is done in a large interval of temperature.

The vapor pressure and vaporization enthalpy of R-(+)-menthofuran, a hepatotoxin metabolically derived from the abortifacient terpene, (R)-(+)-pulegone by correlation gas chromatography

The vapor pressure as a function of temperature and its vaporization enthalpy at T=298.15K of R-(+)-menthofuran, a substance metabolically derived from R-(+)-pulegone that is both a flavoring agent at low concentrations and a hepatotoxin at larger ones, is evaluated by correlation-gas chromatography. A vapor pressure p/Pa=(36±12) has been evaluated at T=298.15K, and a normal boiling temperature of Tb/K=482.4K is predicted. A boiling temperature of Tb/K=374.3 compares with the literature value of Tb/K=371.2 at reduced pressure, p/kPa=2.93. The vaporization enthalpy of (56.5±3.0)kJ·mol−1 compares to an estimated value of (57.8±2.9)kJ·mol−1.

The enthalpy of formation of the isomeric 2,3- and 2,5-dihydrofuran

In a recent study on oxygen-containing heterocycles, two of the current authors suggested the gas phase enthalpy of formation of 2,5-dihydrofuran in lieu of an experimentally determined quantity. The current study provides new analysis with well-precedented assumptions and literature measurements to result in the value (−63±4)kJ·mol−1. For the isomeric 2,3-dihydrofuran the value of (−77±3)kJ·mol−1 is suggested in satisfactory accord with the combustion calorimetric combustion result of (−72.2±0.4)kJ·mol−1.

Enthalpies of mixing in binary Fe–Sb, Ce–Fe and ternary Ce–Fe–Sb liquid alloys

Abstract The enthalpies of mixing in liquid alloys in the binary Fe–Sb, Ce–Fe and ternary Ce–Fe–Sb systems were determined over a wide range of composition by means of isoperibolic calorimetry in the temperature range 1600–1830 K. The minimum values of the integral enthalpy of mixing (ΔH min) were determined to be (−2.32 ± 0.22) kJ · mol−1 at x Sb = 0.5 in the Fe–Sb system, and (−0.97 ± 0.19) kJ · mol−1 at x Ce = 0.35 in the Ce–Fe system. The enthalpies of mixing in liquid ternary Ce–Fe–Sb alloys were found to increase smoothly from the binary boundary systems Ce–Fe and Fe–Sb towards the Ce–Sb system, reaching the minimum value of (−107.5 ± 3.6) kJ · mol−1 in the vicinity of the phase CeSb.

Vaporization, Sublimation Enthalpy, and Crystal Structures of Imidazo[1,2-a]pyrazine and Phthalazine

The vaporization enthalpy of imidazo[1,2-a]pyrazine is evaluated by correlation gas chromatography using two sets of standards and by transpiration. Vaporization enthalpies were evaluated using heterocyclic standards with dipole moments that vary from 0 to 3.0 D and using standards with dipole moments > 3.0 D. A value of (70.7 ± 1.0) kJ·mol–1 measured by transpiration compares to (67.9 ± 1.4) kJ·mol–1 measured by correlation gas chromatography using standards characterized by dipole moments > 3.0 D. The results suggest that imidazo[1,2-a]pyrazine is a member of this series of compounds whose vaporization enthalpies exceed those less polar heterocycles by a fairly constant amount, (6.9 ± 0.3) kJ·mol–1, in this case by (5.9 ± 3.0) kJ·mol–1 using the less polar heterocycles. The crystal structures of phthalazine, another member of the polar series, and of imidazo[1,2-a]pyrazine were determined to examine whether π–π stacking, present in the solid state of two other members of the polar series, was a characteristic of this series. If present in the liquid, π–π stacking could offer a possible explanation for the vaporization enthalpy differences observed. The sublimation enthalpy of imidazo[1,2-a]pyrazine was also evaluated.

Fatigue crack propagation behavior and fracture toughness in a Ni-free ZrCuFeAlAg bulk metallic glass

The fatigue crack propagation and fracture toughness of a Ni-free Zr60.14Cu22.31Fe4.85Al9.7Ag3 bulk metallic glass (BMG) have been studied by using single edge notched beam (SE(B)) samples prepared from the as-cast BMG plates. It is shown that the metallic glass follows similar fatigue crack propagation behavior to traditional ductile polycrystalline metals, i.e., exhibiting “S” shape of da/dN∼ΔK curve with a fatigue threshold (ΔKth) of 3.71MPa√m and a Paris law exponent of 3.52 in Paris regime. The fatigue-fractured surfaces show universal fatigue striations at different stress intensity levels. The striation spacing (d) fits well with the fatigue crack propagation rate (da/dN) in high stress intensity regime, but deviates significantly from crack propagation rate in low stress intensity regime, i.e., d is larger than da/dN, reflecting that the crack propagation in low stress intensity range was driven by the accumulation of damage from a number of cyclic loadings. A shear slip pair model based on STZ theory and linear-elastic-fracture mechanics (LEFM) analysis are established to interpret the mechanism of fatigue striation formation and crack propagation of the BMG. In addition, the fracture toughness of the BMG was also studied by three-point bending test of pre-cracked samples, which yields a high KJ value of 116.7MPa√m. The high fracture toughness is believed to be related to the high Poisson’s ratio (ν=0.368) of the BMG, which helps to the formation of abundant shear bands in front of crack tip and to the retardation of crack propagation by crack path deflection.

Experimental and computational study on the energetics of N-acetyl-l-cysteine

The standard (p°=0.1MPa) molar enthalpy of formation, in the crystalline phase, of N-acetyl-l-cysteine, NAC, at T=298.15K, was derived from the standard molar energy of combustion in oxygen, measured by static bomb combustion calorimetry. A value of −(737.8±1.9)kJ·mol−1 was obtained. For this compound, the standard molar enthalpy of sublimation, at T=298.15K, could not be determined due to the decomposition of the compound during the corresponding experiments.A theoretical study at the G3 and G4 levels has been carried out, and a value of −(610.7±4.0)kJ·mol−1 is recommend for the enthalpy of formation in the gas phase. Using this theoretical value and the experimental enthalpy of formation in the crystalline phase, it is possible to estimate a value of (127.1±4.4)kJ·mol−1 for the enthalpy of sublimation of this compound.

Experimental Study of Chemical Equilibria in the Liquid-Phase Reaction between 1-Octanol and Ethanol to 1-Ethoxyoctane

The equilibrium constants for the liquid-phase dehydration reaction between 1-octanol and ethanol to 1-ethoxyoctane (EOE) and water and the dehydration reaction between two ethanol molecules to ethoxyethane (DEE) and water were determined over Amberlyst 70 in the temperature range (410 to 463) K in a batch reactor. Both reactions were greatly shifted to products at the chemical equilibrium. In particular, product concentrations found for EOE synthesis were higher than those measured for DEE formation. Besides, both liquid-phase etherification reactions proved to be exothermic, with a reaction enthalpy change of (−18.9 ± 1.3) kJ·mol–1 for EOE synthesis and (−13.1 ± 0.9) kJ·mol–1 for DEE one, at 298 K. The EOE standard formation enthalpy value of (−436 ± 7) kJ·mol–1, in good agreement with the estimated value by a modified Benson method, and the EOE standard molar entropy value in the liquid phase of (434 ± 11) J·mol–1·K–1, slightly underestimated by the Benson method, are found.

RELIABILITY OF A MULTI-STATE CONSECUTIVE k-OUT-OF-n: G SYSTEM

Fortunately traditional reliability theory, where the system and the components are always described simply as functioning or failed, is on the way to being replaced by a theory for multistate systems of multistate components. In this paper, we treat the consecutive k-out-of-n systems. Such systems have caught the attention of many engineers and researchers because of their wide range of application. We define a multistate consecutive k-out-of-n system: G as follows: Each component and the system can be in 1 of M + 1 possible states: 0, 1, 2, …, M. The system is in state ≥ j iff at least kj consecutive components are in state ≥ j. The value of kj can be different for different required minimum system state levels. We propose a method based on the combinatorial approach for computing the system's reliability and we give examples to illustrate this method.

Preparation, Crystal Structure and Enthalpy Change of Formation of the Reaction in Liquid Phase of a New Three‐Dimensional Mixed‐Ligand Holmium(III) Coordination Polymer Based on Strong π‐π Stacking Interactions

AbstractA new three‐dimensional coordination polymer, [Ho(5‐nip)(phen)(NO3)(DMF)] (5‐nip=5‐nitroisophthalic acid and phen=1,10‐phenanthroline), was prepared and characterized by single crystal X‐ray diffraction, elemental analysis, IR spectrum and DTG‐DSC techniques. The results show that the title complex crystallizes in space group P2/m with a=1.0906(3) nm, b=1.2804 (3) nm, c=1.6987(4) nm, β=91.400(5)°, Z=4, Dc1.931 Mg/m3, F(000)= 1352. Each Ho(III) ion is nine‐coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate NO−3 anion, one DMF molecule and one 1,10‐phenanthroline molecule. The complex is constructed with one‐dimensional ribbons featuring dinuclear units and the one‐dimensional ribbons are further assembled into two‐dimensional networks by strong π‐π stacking interactions with the distance of 0.327 nm, then the networks are arranged into three‐dimensional structure according to ABAB fashion. The complex exhibits high stability up to 600 °C. Its enthalpy change of formation of the reaction in liquid‐phase in solvent DMF was measured using an RD496‐III type microcalorimeter with a value of (−11.016±0.184) kJ·mol−1.

Vapor Pressure of Palladium from 1473 K to 1973 K

The vapor pressure of palladium was studied using a Knudsen effusion cell and a commercial thermogravimetric balance. Vapor pressures were measured using four Knudsen cells of different effusion areas with consistent results. Most of the available vapor pressure data for palladium has been taken below the fusion temperature, and only a few experimental studies exist on the vapor pressure of liquid palladium. In this current study, vapor pressures were measured from 1473 K to 1973 K (from well above and well below the melting point). In addition, the range in temperature covered in the current study represents one of the largest continuous investigations of palladium vapor pressure to date. The standard enthalpy of sublimation calculated via a third-law analysis of the vapor pressure data is (377.7 ± 0.2) kJ·mol-1, in excellent agreement with the recommended value of (377 ± 5) kJ·mol-1 from the most recent review of available palladium vapor pressure data.

Thermochemistry of Ethyl 3-Oxobutanoate Revisited: Observance of a Non-Zero Enthalpy of Mixing between Tautomers and Its Effects on Enthalpies of Formation

The enthalpies of formation of pure liquid and gas-phase ethyl 3-oxobutanoate and ethyl Z-3-hydroxy-2-butenoate are examined in the light of some recent NMR studies on the enthalpy differences between gas-phase enthalpies of the two tautomers. Correlation-gas chromatography experiments are used to evaluate the vaporization enthalpies of the pure tautomers. Values of (61.6 ± 2.2) and (54.7 ± 1.3) kJ·mol-1 at T = 298.15 K are measured for pure ethyl 3-oxobutanoate and ethyl Z-3-hydroxy-2-butenoate, respectively. These values can be contrasted to a value of (54.2 ± 1.0) kJ·mol-1 when the vaporization enthalpy is measured as a mixture of tautomers. The difference is attributed to an endothermic enthalpy of mixing term of (7.1 ± 2.1) kJ·mol-1, which destabilizes the mixture relative to the pure components. Using the existing liquid-phase enthalpy differences measured by NMR, the endothermic enthalpy of mixing term and the condensed phase enthalpy of formation of the equilibrium mixture, new enthalpies of forma...

Calorimetric data on intercalation of some aromatic amines into barium phenylphosphonate at the solid/liquid interface

Layered crystalline hydrated barium phenylphosphonate, Ba(HO 3PC 6H 5) 2 · H 2O compound was employed as host for aromatic amines pyridine and α-, β- and γ-picolines, intercalation by using the batch method in ethanol at 298 ± 1 K, gave maximum amounts of (1.13, 0.76, 0.84 and 0.97) mmol · g −1, respectively. The original interlamellar distance of 1532 pm increased after all intercalations. The thermochemical data were obtained on a differential isothermic microcalorimetric instrument by means of a titration procedure. From thermal effect data, the variation in enthalpy of intercalation for each system gave exothermic values of (−43.55 ± 0.32, −2.36 ± 0.04, −2.61 ± 0.01 and −3.07 ± 0.05) kJ · mol −1 for the above sequence. The variation in enthalpic values for pyridine derivatives can be interpreted through the influence of steric hindrance associated with the methyl group attached to the heterocyclic ring. In addition to exothermic enthalpy, the spontaneous negative Gibbs free energy and the positive entropic values indicate favorable thermodynamic data for such intercalations.

Solid Phase Combinatorial Library of 1,3‐Azole Containing Peptides for the Discovery of Matrix Metallo Proteinase Inhibitors

AbstractA solid phase combinatorial library of approximately 240,000 putative inhibitors were prepared and screened for activity against MMP‐14. The compounds of the library had the common structure H‐XX‐azole‐XX‐NH2 in which X is an arbitrary amino acid and azole is one of four oxazole or thiazole dipeptidomimetics (8a–d). The library was generated by the split and mix strategy resulting in a one‐bead‐two‐compounds library format in such a way that each bead contained a common quenched fluorogenic substrate and a different putative inhibitor. Application of ladder synthesis [22] during library construction enabled full sequence determination by MALDI‐TOF mass spectrometry. The library was screened against MMP‐14 activity, by performing multiple, sequential incubations in which beads containing active inhibitors were selected by a novel automated “bead‐sorting” apparatus, in order to isolate only the best inhibitors. Statistical analysis of the sequences obtained from overall 184 beads gave rise to a series of 20 sequences; 4 truncated and 16 full sequences were resynthesized. The inhibitors were investigated in an enzyme kinetic assay with MMP‐14 revealing compounds with Ki values in the low micromolar area, whereas the truncated sequences derived from the library showed poor inhibitor activity.

The enthalpies of vaporization and sublimation of exo- and endo-tetrahydrodicyclopentadienes at T=298.15 K

The vaporization enthalpies {Δ g l H m (298.15 K)} of endo- and exo-tetrahydrodicyclopentadiene (THDCPD) have been measured by correlation gas chromatography. Values of (50.2±2.3) kJ· mol −1 and (49.1±2.3) kJ· mol −1 have been obtained for the endo and exo isomers, respectively. The sublimation enthalpy of the endo isomer { Δ g cr H m (298.15 K)=(51.2±2.4) kJ· mol −1} has been obtained by combining fusion and vaporization enthalpies adjusted as necessary to T=298.15 K. Low-temperature d.s.c. studies of both isomers reveal solid-to-solid phase transitions. The endo isomer, which is a plastic crystal at room temperature, exhibits a solid-to-solid phase transition at T=214 K { Δ cr(1) cr(2) H m (214 K)=(10.7±0.13) kJ· mol −1} and a melting temperature of 356.8 K { Δ l cr(1) H m (356.8 K)=(3.48±0.2) kJ· mol −1} with some evidence of polymorphism. The exo isomer exhibits a solid phase transition at T=162.1 K { Δ cr(1) cr(2) H m (162.1 K)=(3.18±0.11) kJ· mol −1} and a melting temperature of 183.2 K { Δ l cr(1) H m (183.2 K)=(1.20±0.04) kJ· mol −1} . Enthalpies of vaporization and sublimation are combined with the respective enthalpies of formation previously reported to yield the following gas-phase values: for endo THDCPD, Δ f H ∘ m =−(61.9±3.2) kJ· mol −1 ; and for exo-THDCPD, Δ f H ∘ m =−(73.7±2.7) kJ· mol −1 .

The enthalpy of vaporization and sublimation of corannulene, coronene, and perylene at T = 298.15 K

The sublimation enthalpy of corannuleneΔcrgHm (298.15 K) has been measured by head space analysis and by combining the fusion and vaporization enthalpies. A mean value of (118.3 ± 3.3)kJ · mol−1was obtained. The vaporization enthalpies of perylene and coronene were also measured by correlation gas chromatography. Combining the vaporization enthalpy of perylene with the fusion enthalpy adjusted to T= 298.15 K affords a sublimation enthalpy at 298.15 K of (138.1 ± 6.2)kJ · mol−1. This value permits a distinction to be made between several discordant sublimation enthalpies in the literature. The vaporization enthalpy of coronene measured in this work permits an identification of the most probable sublimation enthalpy value among a series of varying literature values. A value of ( 155 ± 7.0) kJ · mol−1is recommended forΔcrgHm (298.15 K) of coronene. The new data reported here complete the experimental determination of gas-phase enthalpy of formation values,ΔfHmo (g, 298.15 K): for corannulene ( 460.6 ± 6.5) kJ · mol−1, perylene ( 319.4 ± 2.2) kJ · mol−1, and coronene ( 307.5 ± 9.8) kJ · mol−1.