Value Of Δf Research Articles

Analysis of a Thermodynamic Determination of the Surface Tension of a Two-Component Vapor–Liquid System

A numerical analysis is performed of a thermodynamic determination of the surface tension (ST) of a vapor–liquid binary mixture and interfacial tension (IT) between two liquid phases as the excess value of free energy ΔF of a two-phase system with and without for a phase boundary. Calculations are made in the simplest version of the lattice gas model (LGM), allowing for the interaction of nearest neighbors in a quasi-chemical approximation. Each node of a two-component mixture in the LGM system can be occupied by mixture components A + B and vacancy V. The two main ways of calculating ST, expressed in terms of different partial contributions Miq to excess free energy ΔF (where i = A, B, V are vacancies; 1 ≤ q ≤ κ, q is the number of the monolayer inside the boundary; and κ is its width), are compared, as are calculations of ST and IT as excess free energy ΔF for a lattice model with no vacancies. The ambiguity of ST and IT values depending on the type of Miq functions is obtained by calculating the temperature dependence for a flat boundary and the dependence of ST and IT on droplet size at a fixed temperature. The role of vacancies in the LGM as the main mechanical characteristic of the system under the condition of strict phase equilibrium in three equilibria (mechanical, energy, and chemical) is discussed.

Nonlinear mechanical characteristics and damage constitutive model of coal under CO2 adsorption during geological sequestration

Geological sequestration of CO2 is an effective way to achieve the goal of reducing global warming and carbon neutralization. The complex CO2–coal interaction will lead to the change of mechanical properties of coal. Therefore, evaluating the mechanical characteristics of deep coal seam after CO2 adsorption is of great significance for analyzing the geological characteristics and structural stability of deep strata and storage site selection. In this study, the triaxial compression test and acoustic emission (AE) test were used to evaluate the effect of CO2 adsorption pressure on the mechanical properties of coal mass. On the basis of the evolution characteristics of AE ring down count (RDC), fractal theory was used to analyze the deformation and fracturing evolution of coal. Besides, an elastic damage constitutive model describing the nonlinear stress-strain relationship of coal under CO2 adsorption is established. Results show that the growth of adsorption pressure develops the risk of damage and fracturing of coal. With the increase in adsorption pressure, the value of singularity index width Δα presents a downward trend, indicating the development of internal cracks and the increase in the complexity of microunit fracturing process. When the adsorption pressure is low, the gas in large cracks and pores leads to the generation of small AE signal that occupies the dominant position. High adsorption pressure increases the complexity and nonlinearity of coal deformation, strengthens the proportion of large AE signal, and leads to the increase in the average value of multifractal spectrum width Δf. With the increase in adsorption pressure, the fracturing degree of coal is higher, a mass of large-size cracks appears, and more AE spectrum presents intensive distribution. In the plastic stage, the load level is close to the strength limit, the microcracks intersect with each other, and the average value of Δα in this stage is the smallest.

Collisional enhancement of energetic particle Alfvénic resonance width in tokamaks

The phase-space structure of resonances between fast ions and an Alfvénic mode and the associated modification of density profiles in tokamaks are studied as a function of particle collisions. Guiding-center simulations in a realistic tokamak equilibrium are employed to address the resonance broadening parametric dependencies with respect to changes in the pitch-angle scattering rate. The rate of collisional replenishment, along with resonance strength, given by the combination of eigenmode and resonance structures and equilibrium parameters, determines saturation amplitudes for a given damping rate. As seen from the distribution function flattening, collisions have an effect of broadening the resonances, while the absolute value of δf decreases with increasing collisionality. It is observed that the collisional broadening can be comparable to the collisionless resonance width due to the mode amplitude alone. The resonance broadening coefficients are compared with the existing theory based on analytically expected saturation levels, showing fair agreement. The results can be useful in assisting reduced kinetic models, such as quasilinear models, when prescribing the effective resonance phase-space width, i.e., the mode-particle interaction platform, due to collisional or turbulent processes.

Optimising a nantenna array at 1550 nm band

The theoretical analysis and simulated design of a plasmonic equilateral triangular dielectric resonator nantenna fed via a 1 × 2 corporate feed network are presented. Utilising full wave electromagnetic simulation software Computer Simulation Technology (CST) Microwave Studio (MWS) and verifying results via high-frequency structure simulator, the working of the proposed nantenna at optical C-band (1.55 μm) is demonstrated and confirmed. Numerical results prove that the proposed nantenna exhibits a directivity of 9.57 dB with an impedance bandwidth of 2.58% (189–194 THz) covering the standard optical C-band transmission window. Furthermore, by selecting the appropriate orientation of the triangular dielectric resonators, the proposed nantenna structure can be tuned to operate at the higher or lower optical bands offering a threshold value of directivity and bandwidth Δf. By tuning the nantenna they achieve an increase in bandwidth of 4.96% (185.1–194.7 THz) and directivity also improves to 9.7 dB. The wideband and directive properties make the proposed nantenna attractive for a wide range of applications including broadband nanophotonics, optical sensing, optical imaging and energy harvesting applications.

Energy intervals between Rydberg states nD and nF in lithium-7

Using recently developed diagnostic technique we measured the frequency intervals between Rydberg states nF and nD (n = 38-48) of lithium-7 atoms. The obtained value of the quantum defect δF for Rydberg states nF is 0.000478(24).

Number of trials required to estimate a free-energy difference, using fluctuation relations.

The difference ΔF between free energies has applications in biology, chemistry, and pharmacology. The value of ΔF can be estimated from experiments or simulations, via fluctuation theorems developed in statistical mechanics. Calculating the error in a ΔF estimate is difficult. Worse, atypical trials dominate estimates. How many trials one should perform was estimated roughly by Jarzynski [Phys. Rev. E 73, 046105 (2006)PLEEE81539-375510.1103/PhysRevE.73.046105]. We enhance the approximation with the following information-theoretic strategies. We quantify "dominance" with a tolerance parameter chosen by the experimenter or simulator. We bound the number of trials one should expect to perform, using the order-∞ Rényi entropy. The bound can be estimated if one implements the "good practice" of bidirectionality, known to improve estimates of ΔF. Estimating ΔF from this number of trials leads to an error that we bound approximately. Numerical experiments on a weakly interacting dilute classical gas support our analytical calculations.

A new fluorescence biosensor for nitric oxide detection based on cytochrome P450 55B1

Nitric oxide (NO) is an important biological signaling molecule, which plays an important role in the regulation of cell function of the nervous, vascular and immune systems. Nitric oxide also is involved in the parthenogenesis of Parkinson’s disease and tumor angiogenesis. Thus, the detection of nitric oxide is essential to understand its physiological and pathological process. Cytochrome P450 55B1 from Chlamydomonas reinhardtii is known to function as nitric oxide reductase (NOR). Here we describe the development of a new fluorescence biosensor for NO based on the NOR activity of P450 55B1. In this paper, we constructed pET28a-55b1 vector and expressed P450 55B1 in Escherichia coli successfully. We studied the interaction between P450 55B1 and NO by spectrometric method. The result show that the fluorescence intensity of iron porphyrin of P450 55B1 increase gradually with the addition of NO. When the concentration of NO is below 22.5μM, the fluorescence intensity increase linearly with the concentration of NO from a baseline value of ΔF=0.0675+0.15 CNO (in μM), which is slightly affected by potentially interfering chemicals. NO release from the rat liver homogenate stimulated by l-arginine was determined by the fluorescence NO biosensor. The results demonstrated that our strategy can be used to detect the concentration of NO in biologically samples.

Tip induced mechanical deformation of epitaxial graphene grown on reconstructed 6H–SiC(0001) surface during scanning tunneling and atomic force microscopy studies

The structural and mechanical properties of an epitaxial graphene (EG) monolayer thermally grown on top of a 6H–SiC(0001) surface were studied by combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM). Experimental STM, dynamic STM and AFM images of EG on 6H–SiC(0001) show a lattice with a 1.9 nm period corresponding to the (6 × 6) quasi-cell of the SiC surface. The corrugation amplitude of this (6 × 6) quasi-cell, measured from AFM topographies, increases with the setpoint value of the frequency shift Δf (15–20 Hz, repulsive interaction). Excitation variations map obtained simultaneously with the AFM topography shows that larger dissipation values are measured in between the topographical bumps of the (6 × 6) quasi-cell. These results demonstrate that the AFM tip deforms the graphene monolayer. During recording in dynamic STM mode, a frequency shift (Δf) map is obtained in which Δf values range from 41 to 47 Hz (repulsive interaction). As a result, we deduced that the STM tip, also, provokes local mechanical distortions of the graphene monolayer. The origin of these tip-induced distortions is discussed in terms of electronic and mechanical properties of EG on 6H–SiC(0001).

Enthalpies of formation for alkylcarbonyl radicals

The data on enthalpies of formation (Δf H ○) of alkylcarbonyl radicals are expanded to 22 items. The reference value of Δf H ○ for diacetylperoxide in the gas phase (−485.5 kJ/mol) is determined via recalculation from evaporation enthalpy (n-C5H11C(O)O)2. The Δf H ○ values of 22 diacylperoxides (gaseous) are calculated and used in combination with the literature data on dissociation energies of D(O-O) bonds in them to determine the Δf H ○ of corresponding radicals. The interrelation between structure and properties (the enthalpy of formation) is considered, and the parameters for the calculated prediction of Δf H ○ are found.

Test particle simulations of resonant interactions between energetic electrons and discrete, multi-frequency artificial whistler waves in the plasmasphere

Modulated high frequency (HF) heating of the ionosphere provides a feasible means of artificially generating extremely low frequency (ELF)/very low frequency (VLF) whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency artificially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ∼ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval (Δf) of the discrete, multi-frequency waves. We find that there is a threshold value of Δf for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to Δf (proportional to the frequency components Nw) when Δf is below the threshold value but it remains unchanged with increasing Δf when Δf is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the ‘effective frequency band’. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better performance of controlled precipitation of high energy electrons in the plasmasphere by artificial ELF/VLF whistler waves can be achieved.

Direct Observation of Periodic Swelling and Collapse of Polymer Chain Induced by the Belousov–Zhabotinsky Reaction

By utilizing a quartz crystal microbalance with dissipation (QCM-D), we directly observed the self-oscillating behavior of a polymer chain induced by the Belousov-Zhabotinsky (BZ) reaction. We succeeded in measuring self-oscillations of the resonance frequency (Δf) and dissipation (ΔD), which originate in the self-oscillating behavior of the polymer chain on a gold surface induced by the BZ reaction. We synthesized a self-oscillating polymer chain with Ru as the catalyst of the BZ reaction and a chemical adsorption site, so as to directly observe its periodic swelling and collapse on the gold surface. Distinct self-oscillation of ΔD synchronized with the self-oscillation Δf was observed. The period of the Δf self-oscillation was about 400 s, and the induction time was about 6.5 h. In QCM-D measurements, we found that the peaks of Δf and ΔD oscillations did not coincide in time because the state of the Gaussian chain did not coincide with the maximum value of Δf. Moreover, examination of the relationship between Δf and ΔD revealed that their oscillatory waveforms were identical in frequency but differed in phase and amplitude.

Norovirus GII.4 virus-like particles recognize galactosylceramides in domains of planar supported lipid bilayers.

A sticky situation: Domain-dependent recognition of the glycosphingolipid galactosylceramide by norovirus-like particles (see picture; red/yellow) is shown using supported lipid bilayers (purple) as model membranes. Optimal ligand presentation is found to promote strong binding to GalCer. This presentation can be found at the edges of the glycosphingolipid-enriched domains (green) and binding is repressed in the absence of these domains.

Thermodynamic studies on Sn–Te–O system

The standard Gibbs energy of formation of tin tellurate, SnTe3O8(s) was determined from its vapour pressure measurements over the temperature range 973–1,158 K by employing thermogravimetry-based transpiration method. The temperature dependence of vapour pressure of TeO2 over the mixture SnTe3O8(s) + SnO2(s) generated by the incongruent vapourisation reaction, SnTe3O8(s) → SnO2(s) + 3 TeO2(g) could be represented as: log (p (TeO2, g)/Pa ± 0.03) = 13.943–14,181 (K/T) (973–1,158 K). The standard Gibbs energy of formation of SnTe3O8(s) was also determined by measuring the oxygen potential of SnO2(s)–Te(s)–SnTe3O8(s) phase mixture by the electromotive force method. Enthalpy increments of SnTe3O8(s) were determined by inverse drop calorimetric method in the temperature range 523–973 K. The thermodynamic functions, viz., heat capacity, entropy and free energy functions were derived from the measured values of enthalpy increments. A mean value of −1,642 ± 2.0 kJ mol−1 was obtained for \( \Updelta_{\text{f}} H_{298}^{\circ } \)(SnTe3O8, s) by combining the value of Δf \( G^{\circ } \)(SnTe3O8, s) derived from vapour pressure data and the free energy functions derived from the drop calorimetric data.

Invariability of relationship between the polar cap magnetic activity and geoeffective interplanetary electric field

Abstract. The PC (polar cap) index characterizing the solar wind energy input into the magnetosphere is calculated with use of parameters α, β, and φ, determining the relationship between the interplanetary electric field (EKL) and the value of magnetic activity δF in the polar caps. These parameters were noted as valid for large and small EKL values, and as a result the suggestion was made (Troshichev et al., 2006) that the parameters should remain invariant irrespective of solar activity. To verify this suggestion, the independent sets of calibration parameters α, β, and φ were derived separately for the solar maximum (1998–2001) and solar minimum (1997, 2007–2009) epochs, with a proper choice of a quiet daily variation (QDC) as a level of reference for the polar cap magnetic activity value. The results presented in this paper demonstrate that parameters α, β, and φ, derived under conditions of solar maximum and solar minimum, are indeed in general conformity and provide consistent (within 10 % uncertainty) estimations of the PC index. It means that relationship between the geoeffective solar wind variations and the polar cap magnetic activity responding to these variations remains invariant irrespective of solar activity. The conclusion is made that parameters α, β, and φ derived in AARI#3 version for complete cycle of solar activity (1995–2005) can be regarded as forever valid.

Near-automorphisms of paths

The total relative displacement of a permutation f of vertices of a connected graph G is **image**, where the sum is taken over all **image** unordered pairs of distinct vertices of G. Let π(G) denote the smallest positive value of δf(G) among the n! permutations f. Aitken [J Combin Theory Series A 87 (1999), 1–21] proved that π(Pn) = 2n − 4 for the n-path Pn, which was conjectured by Chartrand et al. [Proceedings of the 1996 Eighth Quadrennial International Conference on Graph Theory, Combinatorics Algorithms, and Applications I, New Issues Press, Kalamazoo, 1999, pp. 181–192]. This article gives a short proof of the result. © 2011 Wiley Periodicals, Inc. J Graph Theory 68:323-325, 2011 © 2011 Wiley Periodicals, Inc.

THE EFFECTS OF MORPHOLOGY STRUCTURE FOR COPPER PHTHALOCYANINE SENSORS DETECT TO ORGANIC ACID

The copper phthalocyanine ( CuPc ) thin film gas sensors detect to organic acids that its detection behaviors will be affected morphology with quartz crystal microbalance (QCM) method. The amorphous structure has looser surface and finer particles; therefore, it has smaller surface area. Although it has more active sites to adsorb acid molecular, it gets smaller value of frequency change (Δf) than α-phase morphology. The β-phase morphology has the largest surface area, so it gets the smallest value of Δf. The response behavior is more rapid than recovery behavior with any morphology CuPc thin film gas sensors. The film surface of amorphous structure has more porous, it has faster response time and recovery time than other structures. The β-phase morphology can get slowest response and recovery time. The results show that the CuPc thin film gas sensors detect to organic acid behavior, for example methyl acid and ethyl acid, etc.; it was affected to its surface morphology change.

Melting of Crosslinked DNA: VI. Comparison of Influence of Interstrand Crosslinks and Other Chemical Modifications Formed by Antitumor Compounds on DNA Stability

A computer modeling of thermodynamic properties of a long DNA of N base pairs that includes ω interstrand crosslinks (ICLs), or ω chemical modifications involving one strand (monofunctional adducts, intrastrand crosslinks) has been carried out. It is supposed in our calculation that both types of chemical modifications change the free energy of the helix-coil transition at sites of their location by δF. The value δF>0 corresponds to stabilization, i.e. to the increase in melting temperature. It is also taken into account that ICLs form additional loops in melted regions and prohibit strand dissociation after full DNA melting. It is shown that the main effect of interstrand crosslinks on the stability of long DNA's is caused by the formation of additional loops in melted regions. This formation increases DNA melting temperature (Tm ) much stronger than replacing co base pairs of AT type with GC. A prohibition of strand dissociation after crosslinking, which strongly elevates the melting temperature of oligonucleotide duplexes, does not influence melting behavior of long DNA's (N≥1000 bp). As was demonstrated earlier for the modifications involving one or the other strand, the dependence of the shift of melting temperature δTm on the relative number of modifications r = ω/(2N) is a linear function for any δF, and δTm(r) = 0 for the ideal modifications (δF=0). We have shown that δTm(r) is the same for periodical and random distribution if the absolute value of δF is less 2 kcal. The absolute value of δTm(r) at δF>2 kcal and δF<−2 kcal is higher for periodical distribution. For interstrand crosslinks, the character of the dependence δTm(r) is quite different. It is nonlinear, and the shape of the corresponding curve is strongly dependent on δF. For “ideal” interstrand crosslinks (δF=0), the function δTm(r) is not zero. It is monotone positive nonlinear, and its slope decreases with r. If r<0.004, then the entropy stabilizing effect of interstrand crosslinking itself exceeds the influence of a distortion of the double helix at sites of their location. The resulting δTm(r) is positive even in the case of the infinite destabilization at sites of the ICLs (δF→ −∞). In general, stabilizing influence of interstrand crosslinks is almost fully compensated for by local structural distortions caused by them if 0< r <0.01 and −∞<δ F ≲−5 kcal per mole of ICLs. The absolute value of δTm(r) in this case is ∼10 times lower than for ideal ICLs as well as for local destabilization without crosslinking. Interstrand crosslinks formed by cisplatin do not change the melting temperature of long DNA's because of this compensation effect.

Annealing Study on Neutron Irradiation Effects in Resonance Frequencies of Zircaloy Plates by EMAR Method

To develop the nondestructive hydrogen concentration measurement method for the irradiated zirconium alloy, the effect of neutron irradiation damage on acoustic properties obtained by the electromagnetic acoustic resonance (EMAR) method was investigated through annealing tests. It is confirmed that the recovery of irradiation damage begins at a lower annealing temperature than that in unirradiated coldworked materials. Unirradiated recrystallization-annealed materials did not show any change in acoustic properties or hardness during the additional RX annealing at 580°C, whereas the acoustic anisotropy (Δf) of the as-cold-worked unirradiated specimen was significantly increased. Four-cycle irradiation clearly decreased the shear wave velocity of the specimen by 1% compared to the RX-annealed specimen. In comparison with the wave velocity change, the acoustic parameters defined in this study are found to be less sensitive to irradiation damage. From the annealing study of the as-irradiated specimens to the RX condition, it is concluded that the absolute value of (Δf) increases by 0.1% and the frequency ratio (fl/fr) by about 0.006 as a result of the damage induced by the four-cycle irradiation in BWRs. These values are applicable to the relationships between the acoustic parameters and hydrogen concentrations of unirradiated materials as the correction factors to compensate the effects of irradiation damage.

Behavior of the Resonant Frequency Shift of the Quartz Crystal Microbalance in NaCl Solution

We report the novel characteristics of the series resonant‐frequency shift (ΔF) of the single‐face sealed quartz crystal microbalance (QCM) in an electrolyte solution. In the present study, we used NaCl as an electrolyte. This study revealed that, in an electrolyte solution, the ΔF values vary linearly with an increase in the square root of the density‐viscosity product of the solution, and the immersion angle dependence of ΔF appears. Moreover, we have found that the intercept value of ΔF appears and is brought about by the electric double layer. We also suggest that the ΔF values are independent of the conductivity and the permittivity of the solution.

Comment on “Climate forcing by the volcanic eruption of Mount Pinatubo” by David H. Douglass and Robert S. Knox

Comment on “Climate forcing by the volcanic eruption of Mount Pinatubo” by David H. Douglass and Robert S. Knox