Symmetry relations in chemical kinetics arising from microscopic reversibility

It is shown that the kinetics of time-reversible chemical reactions having the same equilibrium constant but different initial conditions are closely related to one another by a directly measurable symmetry relation analogous to chemical detailed balance. In contrast to detailed balance, however, this relation does not require knowledge of the elementary steps that underlie the reaction, and remains valid in regimes where the concept of rate constants is ill-defined, such as at very short times and in the presence of low activation barriers. Numerical simulations of a model of isomerization in solution are provided to illustrate the symmetry under such conditions, and potential applications in protein folding-unfolding are pointed out.Comment: 4 pages, 1 figure, accepted to Phys Rev Let

Entropy and density of states from isoenergetic nonequilibrium processes

Two identities in statistical mechanics involving entropy differences (or ratios of density of states) at constant energy are derived. The first provides a nontrivial extension of the Jarzynski equality to the microcanonical ensemble [C. Jarzynski, Phys. Rev. Lett. 78, 2690 (1997)], which can be seen as a ``fast-switching'' version of the adiabatic switching method for computing entropies [M. Watanabe, W. P. Reinhardt, Phys. Rev. Lett. 65, 3301 (1990)]. The second is a thermodynamic integration formula analogous to a well-known expression for free energies, and follows after taking the quasistatic limit of the first. Both identities can be conveniently used in conjunction with a scaling relation (herein derived) that allows one to extrapolate measurements taken at a single energy to a wide range of energy values. Practical aspects of these identities in the context of numerical simulations are discussed.Comment: 5 pages, no figure

Jarzynski Equality for an Energy-Controlled System

The Jarzynski equality (JE) is known as an exact identity for nonequillibrium systems. The JE was originally formulated for isolated and isothermal systems, while Adib reported an JE extended to an isoenergetic process. In this paper, we extend the JE to an energy-controlled system. We make it possible to control the instantaneous value of the energy arbitrarily in a nonequilibrium process. Under our extension, the new JE is more practical and useful to calculate the number of states and the entropy than the isoenergetic one. We also show application of our JE to a kind of optimization problems.Comment: 6 pages, 1 figur

Path integral analysis of Jarzynski's equality: Analytical results

We apply path integrals to study nonequilibrium work theorems in the context of Brownian dynamics, deriving in particular the equations of motion governing the most typical and most dominant trajectories. For the analytically soluble cases of a moving harmonic potential and a harmonic oscillator with time-dependent natural frequency, we find such trajectories, evaluate the work-weighted propagators, and validate Jarzynski's equality.Comment: 10 pages, 1 figur

Does the Boltzmann principle need a dynamical correction?

In an attempt to derive thermodynamics from classical mechanics, an approximate expression for the equilibrium temperature of a finite system has been derived [M. Bianucci, R. Mannella, B. J. West, and P. Grigolini, Phys. Rev. E 51, 3002 (1995)] which differs from the one that follows from the Boltzmann principle S = k log (Omega(E)) via the thermodynamic relation 1/T= dS/dE by additional terms of "dynamical" character, which are argued to correct and generalize the Boltzmann principle for small systems (here Omega(E) is the area of the constant-energy surface). In the present work, the underlying definition of temperature in the Fokker-Planck formalism of Bianucci et al. is investigated and shown to coincide with an approximate form of the equipartition temperature. Its exact form, however, is strictly related to the "volume" entropy S = k log (Phi(E)) via the thermodynamic relation above for systems of any number of degrees of freedom (Phi(E) is the phase space volume enclosed by the constant-energy surface). This observation explains and clarifies the numerical results of Bianucci et al. and shows that a dynamical correction for either the temperature or the entropy is unnecessary, at least within the class of systems considered by those authors. Explicit analytical and numerical results for a particle coupled to a small chain (N~10) of quartic oscillators are also provided to further illustrate these facts.Comment: REVTeX 4, 10 pages, 2 figures. Accepted to J. Stat. Phy

Peran Manajemen Sumber Daya Insani: Kajian di Baznas Ponorogo

This study examines the management pattern and Human Resource utilization in Baznaz Ponorogo. The goal is to find out how far the principles of HR management are implemented in the agency. The result of the study shows that the pattern of management and human resources utilization in Baznas Ponorogo covers all aspects, from the recruitment process, placement, until the evaluation of employee performance. In every stage of the process, Baznas Ponorogo not only relies on the principle of professionalism but also considers personal integrity and spiritual maturity aspects. Such is done based on the consideration that a job, if done professionally and sincerely, will yield ina higher value and quality

Comparing the effects of acupressure at LI4 and BL32 points on intramuscular injection pain

Introduction The effectiveness of some acupressure techniques in relieving the acute pain of intramuscular injection pain has been assessed in previous studies. However, the effects of acupressure at LI4 point have still remained unknown. The aim of this study was to compare the effects of acupressure at LI4 and BL32 points on intramuscular injection pain. Methods This after-only interventional study was made on 90 women were who referred to the injection unit of the Central Emergency Department, Kashan, Iran, in 2015 for receiving an intramuscular injection of penicillin. The women were randomly allocated to three 30-person groups, namely control, LI4 acupressure, and BL32 acupressure groups. After intramuscular injection of penicillin, the level of intramuscular injection pain of all women was assessed by using a 0–10 visual analog scale. Data were analyzed through doing the Kruskal–Wallis, the Chi-square, and the Fisher's exact tests, and Spearman correlation coefficient. Results The means of pain intensity in the control, LI4 acupressure, and BL32 acupressure groups were 2.76 ± 1.75, 2.33 ± 1.80, and 1.76 ± 2.45, respectively. In other words, the mean pain intensity in the control group was significantly higher than the LI4 and BL32 acupressure groups by 0.43 and 1.0 points, respectively (p = 0.011). Except for educational status, intramuscular injection pain was not significantly correlated with the participants’ other demographic characteristics as well as injection time. Conclusion Acupressure can significantly relieve intramuscular injection pain. This simple, cost-effective, and easily applicable therapy can be used in all healthcare settings for relieving intramuscular injection pain

Optimized free energies from bidirectional single-molecule force spectroscopy

An optimized method for estimating path-ensemble averages using data from processes driven in opposite directions is presented. Based on this estimator, bidirectional expressions for reconstructing free energies and potentials of mean force from single-molecule force spectroscopy - valid for biasing potentials of arbitrary stiffness - are developed. Numerical simulations on a model potential indicate that these methods perform better than unidirectional strategies.Comment: 4 pages, 2 figure

NP-hardness of the cluster minimization problem revisited

The computational complexity of the "cluster minimization problem" is revisited [L. T. Wille and J. Vennik, J. Phys. A 18, L419 (1985)]. It is argued that the original NP-hardness proof does not apply to pairwise potentials of physical interest, such as those that depend on the geometric distance between the particles. A geometric analog of the original problem is formulated, and a new proof for such potentials is provided by polynomial time transformation from the independent set problem for unit disk graphs. Limitations of this formulation are pointed out, and new subproblems that bear more direct consequences to the numerical study of clusters are suggested.Comment: 8 pages, 2 figures, accepted to J. Phys. A: Math. and Ge