Degree Of Irreversibility Research Articles

Mechanic Insight into Aggregation of Lysozyme by Ultrasensitive Differential Scanning Calorimetry and Sedimentation Velocity.

Folding and aggregation of proteins profoundly influence their functions. We have investigated the effects of thermal history, concentration and pH on the denaturation and refolding of lysozyme by using ultrasensitive differential scanning calorimetry (US-DSC) and sedimentation velocity (SV) via analytical ultracentrifugation (AUC). The former is sensitive to small energy change whereas the latter can differentiate the oligomers such as dimer and trimer from individual protein molecules. Our studies reveal that the degree of denaturation irreversibility increases as heating times increases. The denaturation temperature (Td) and enthalpy change (ΔH) are influenced by heating rate since the denaturation is not in equilibrium during the heating. We can obtain Td and ΔH in equilibrium by extrapolation of heating rate to zero. In a dilute solution, no aggregation but unfolding happens in the denaturation. However, when the concentration is above a critical value (∼15.0 mg/mL), lysozyme molecules readily form trimers or other oligomers. Lysozyme molecules unfold into stretched chains at pH > 6.0, which would further forms large aggregates. The formation of aggregates makes the refolding of lysozyme impossible.

A study of entropy generation in tree-shaped flow structures

This paper examines the degree of irreversibility, or thermodynamic nonideality, in a tree-shaped flow network with a constant wall heat flux. The tree network is a dichotomic and homothetic structure, and a fully developed laminar flow of Newtonian and non-Newtonian power law fluids is assumed. We investigate (i) the characteristics of the tubes composing the network (i.e., variation in the homothetic ratios of length and diameters, as well as variation in wall permeability of tubes), (ii) the existence of blocked (obstructed) tubes in the network, (iii) fluid characteristics, and (iv) frictional and thermal effects on entropy generation. The influence of parameters like the fluid behavior index, Reynolds number, Nusselt number, homothety ratios for length and diameters, and wall permeability is hence evaluated. Finally, the degree of thermodynamic irreversibility associated to tree networks designed for a maximum flow access is determined.

Policy Uncertainty and Corporate Investment

Using a news-based index of policy uncertainty, we document a strong negative relationship between firm-level capital investment and the aggregate level of uncertainty associated with future policy and regulatory outcomes. More importantly, we find evidence that the relation between policy uncertainty and capital investment is not uniform in the cross-section, being significantly stronger for firms with a higher degree of investment irreversibility and for firms that are more dependent on government spending. Our results lend empirical support to the notion that policy uncertainty can depress corporate investment by inducing precautionary delays due to investment irreversibility.

Time reversibility from visibility graphs of nonstationary processes.

Visibility algorithms are a family of methods to map time series into networks, with the aim of describing the structure of time series and their underlying dynamical properties in graph-theoretical terms. Here we explore some properties of both natural and horizontal visibility graphs associated to several nonstationary processes, and we pay particular attention to their capacity to assess time irreversibility. Nonstationary signals are (infinitely) irreversible by definition (independently of whether the process is Markovian or producing entropy at a positive rate), and thus the link between entropy production and time series irreversibility has only been explored in nonequilibrium stationary states. Here we show that the visibility formalism naturally induces a new working definition of time irreversibility, which allows us to quantify several degrees of irreversibility for stationary and nonstationary series, yielding finite values that can be used to efficiently assess the presence of memory and off-equilibrium dynamics in nonstationary processes without the need to differentiate or detrend them. We provide rigorous results complemented by extensive numerical simulations on several classes of stochastic processes.

Nonlinear Gamow vectors, shock waves, and irreversibility in optically nonlocal media

Dispersive shock waves dominate wave-breaking phenomena in Hamiltonian systems. In the absence of loss, these highly irregular and disordered waves are potentially reversible. However, no experimental evidence has been given about the possibility of inverting the dynamics of a dispersive shock wave and turn it into a regular wave-front. Nevertheless, the opposite scenario, i.e., a smooth wave generating turbulent dynamics is well studied and observed in experiments. Here we introduce a new theoretical formulation for the dynamics in a highly nonlocal and defocusing medium described by the nonlinear Schroedinger equation. Our theory unveils a mechanism that enhances the degree of irreversibility. This mechanism explains why a dispersive shock cannot be reversed in evolution even for an arbitrarirly small amount of loss. Our theory is based on the concept of nonlinear Gamow vectors, i.e., power dependent generalizations of the counter-intuitive and hereto elusive exponentially decaying states in Hamiltonian systems. We theoretically show that nonlinear Gamow vectors play a fundamental role in nonlinear Schroedinger models: they may be used as a generalized basis for describing the dynamics of the shock waves, and affect the degree of irreversibility of wave-breaking phenomena. Gamow vectors allow to analytically calculate the amount of breaking of time-reversal with a quantitative agreement with numerical solutions. We also show that a nonlocal nonlinear optical medium may act as a simulator for the experimental investigation of quantum irreversible models, as the reversed harmonic oscillator.

Quantification of Electrochemical Nanoscale Processes in Lithium Batteries By Operando EC-(S)TEM

Lithium (Li)-ion batteries are currently used for a wide variety of portable electronic devices, electric vehicles and renewable energy applications [1,2]. In addition, extensive worldwide research efforts are now being devoted to more advanced “beyond Li-ion” battery chemistries - such as lithium-sulfur (Li-S) [3] and lithium-air (Li-O2) [4] - in which the carbon anode is replaced with Li metal. However, the practical application of Li metal anode systems has been highly problematic. The main challenges involve controlling the formation of a solid-electrolyte interphase (SEI) layer and the suppression of Li dendrite growth during the charge/discharge process (achieving “dendrite-free” cycling). The SEI layer formation continuously consumes the electrolyte components creating highly resistive layer, which leads to the rapid decrease of cycling performance and degradation of the Li anode [5]. The growth of Li metal dendrites at the anode contributes to rapid capacity fading (the presence of “dead Li” created during the discharge leads to an increased overpotential) and, in the case of continuous growth, leads to internal short circuits and extreme safety issues [6]. Here we demonstrate the application of an operando electrochemical scanning transmission electron microscopy (ec-(S)TEM) cell to study the SEI layer formation and the initial stages of Li dendrite growth - the goal is to develop a mechanism for mitigating the degradation processes and increasing safety. Bright field (BF) STEM images in Figure 1 A-C show Li metal deposition and dissolution processes at the interface between the Pt working electrode and the lithium hexafluorophosphate (LiPF6) in propylene carbonate (PC) electrolyte during three charge/discharge cycles. A contrast reversal caused by Li metal being lighter/less dense than surrounding electrolyte (Li appears brighter than the background in BF STEM images) allows Li to be uniquely identified from the other components in the system - the only solid material that is less dense than the electrolyte is Li metal. Using these images, we can precisely quantify the total volume of Li deposition, the thickness of the SEI layer (observed as a ring of positive contrast around the electrode) and alloy formation due to Li+ ion insertion during each cycle. Furthermore, at the end of each discharge cycle we can quantify the presence of “dead Li” detached from the Pt electrode, thereby demonstrating the degree of irreversibility (and degradation of Pt electrode) associated with insertion/removal of Li+during this process with direct correlation to electrochemical performance. Such analyses provide significant insights into Li metal dendrite growth, which is critical to understand the complex interfacial reactions needed to be controlled for future Li-based and next generation energy storage systems. [7]

What explains the value premium? The case of adjustment costs, operating leverage and financial leverage

Abstract This paper empirically examines and compares the different theoretical predictions on how adjustment costs, operating and financial leverage influence the value premium. Consistent with Ozdagli (2012), financial leverage plays a dominant role, supported by adjustment costs (which represent the degree of investment irreversibility). Specifically, the observed value premium is driven by the financial leverage differences between value and growth firms, partially neutralized by investment irreversibility. The relation between the value premium and investment irreversibility is contrary to the intuition in Zhang (2005) and Cooper (2006). Operating leverage does not significantly influence the value premium.

HIV patients' decision of switching to second-line antiretroviral therapy in India

The objective is to examine when patients should switch to second-line antiretroviral therapy (ART) under health uncertainty and in the absence of viral load monitoring. We formalize and solve the therapeutic dilemma about whether or not, and when, to switch a therapy. The model's main value-added consists in the concrete application to patients with HIV in India. In our dynamic stochastic model, health level volatility can be understood as the variation in CD4 count and the trend of health level as increases in CD4 count and, thus, decreases in the incidence of opportunistic infections and mortality. The results of the empirical application suggest that the theoretical model can explain ART treatment switch. Treatment switch depends negatively on the volatility of patients' health, and on trend of health, i.e., the greater the variation in CD4 count and the more CD4 count increase, the fewer treatment switches one expects to occur. Treatment switch also depends negatively on the degree of irreversibility. Under irreversibility, low-risk patients must begin the second-line treatment as soon as possible, which is precisely when the second-line treatment is least valuable. The existence of an option value means that ART first-line regimen may be the better choice when considering lifetime welfare. Conversely, treatment switch depends positively on the discount rate and on the correlation between the patient's health under first- and second-line treatments. This means that treatment switch is likelier to succeed in second-line treatments that are similar to the first-line treatments, implying that a decision-maker should not rely on treatment switch as a risk diversification tool.

Real Options and Urban Land Values: A Review of the Literature

The central and unifying theme of this review is the value of urban land and its effect on investments in durable capital. More specifically, because structures are expensive to build, have an extensive construction time, and are long lasting, investments in durable capital entail a significant degree of uncertainty and irreversibility. I examine the estimation of the redevelopment option and explore the relationship between real options and land values. I also examine the determinants of the decision to redevelop physical capital either in whole (teardowns) or in part (renovations). Overall, this critical analysis contributes to a better understanding of urban land values by unifying the real option and redevelopment decision literatures within a broader context of real estate valuation. Both academics and practitioners should find the analysis relevant to their own real estate studies or investment decisions.

Study of electrode processes and deposition of cobalt thin films from ionic liquid analogues based on choline chloride

The cathodic processes of cobalt ion in ionic liquids consisting in binary mixtures of choline chloride (ChCl) with urea, ethylene glycol, malonic acid or oxalic acid were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The as-received hexahydrate cobalt chloride has been the precursor of cobalt ionic species. It was found that the reduction mechanism of Co2+ in ChCl-urea and ChCl-ethylene glycol is a quasi-reversible (or with high degree of irreversibility at high scan rate) and diffusion controlled process, whereas in ChCl-carboxilic acid solvents the cathodic process of Co2+ is overlapped with reduction of protons. By using Pt and vitreous carbon electrodes, one has computed the value for the Co2+ diffusion coefficient in ChCl-urea at 80 °C; in comparison with values obtained in aqueous solutions, this is up to two orders of magnitude lower. The paper also describes preliminary experiments concerning electrodeposition of cobalt thin films on copper substrate from the four ionic liquid analogue solvents containing choline chloride. The crystalline morphology and structural constitution of Co deposits were examined by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Good results regarding the quality and cobalt content in films were obtained for Co deposits using ChCl-urea or ChCl-ethylene glycol mixtures as solvents. The behaviour of Co films grown from these media was typical for a ferromagnetic material.

Local stability of a non-endoreversible Carnot refrigerator working at the maximum ecological function

Local stability of a non-endoreversible Carnot refrigerator at the maximum ecological function is studied with Newton’s heat transfer law between working fluid and heat reservoirs. The steady state of the refrigerator working at the maximum ecological function is steady. It is derived that a general expression of relaxation time described as stability of the system refers to heat capacity C, total heat exchange area F, temperature ratio of heat reservoirs τ, the degree of internal irreversibility ϕ, heat transfer coefficients α and β. Distributing information of phase portraits of system is obtained. The results can provide some theoretical guidelines for the designs of practical refrigerator.

The Effects of Irreversibility and Uncertainty on Business Investments: A New View of Investment

This article presents a survey of recent theoretical, as well as empirical, contributions concerning business investments, which help to explain the investment decision making of companies. These contributions emphasize the relevance of idiosyncratic factors affecting investment decisions such as the degree of irreversibility and uncertainty, interactions between these factors may generate an opportunity cost equivalent to the exercise of an option and so they add an important dimension to the neoclassical theory of investment (also called standard or orthodox theory of investment). This theory has not recognized the important qualitative and quantitative implications of this interaction, what can explain some of its failures. We investigate the irreversibility of investments and the impact this has on the nature of the relationship between investment and uncertainty in the way of empirical analysis. The empirical analysis uses firm – level data and is based on a survey of 53 automotive suppliers, which was carried out during the year 2011. We find supportive evidence for the fact that uncertainty is negatively associated with planned investments of the companies surveyed, which remains true also in the presence of irreversibility. At the end we demonstrate the core of the real options approach in a form of a practical example.

Flight–crash events in turbulence

The statistical properties of turbulence differ in an essential way from those of systems in or near thermal equilibrium because of the flux of energy between vastly different scales at which energy is supplied and at which it is dissipated. We elucidate this difference by studying experimentally and numerically the fluctuations of the energy of a small fluid particle moving in a turbulent fluid. We demonstrate how the fundamental property of detailed balance is broken, so that the probabilities of forward and backward transitions are not equal for turbulence. In physical terms, we found that in a large set of flow configurations, fluid elements decelerate faster than accelerate, a feature known all too well from driving in dense traffic. The statistical signature of rare "flight-crash" events, associated with fast particle deceleration, provides a way to quantify irreversibility in a turbulent flow. Namely, we find that the third moment of the power fluctuations along a trajectory, nondimensionalized by the energy flux, displays a remarkable power law as a function of the Reynolds number, both in two and in three spatial dimensions. This establishes a relation between the irreversibility of the system and the range of active scales. We speculate that the breakdown of the detailed balance characterized here is a general feature of other systems very far from equilibrium, displaying a wide range of spatial scales.

An ideal internally heat integrated batch distillation with a jacketed still with application to a reactive system

Batch distillation is an irreversible process and consumes many times the theoretical minimum energy requirement. The present work focuses on the development of an internally heat integrated batch distillation with a jacketed still (IHIBDJS) aiming to reduce the degree of irreversibility towards zero. The IHIBDJS scheme consists of a rectifying tower equipped with an overhead condenser and a still pot or reboiler that surrounds the tower concentrically. For improving the energy efficiency by the reduction of external energy input, the rectifier is operated at an elevated pressure so that a thermal driving force should exist between the rectifying tower and the concentric still. For this purpose, an isentropic compression system is mounted in the reboiled vapor line. Aiming to reduce further the degree of process irreversibility, we propose an additional thermal arrangement into the IHIBDJS configuration that couples the overhead vapor with the reboiler liquid, thereby reducing further the external heat consumption. It is investigated for a reactive batch distillation column that the effective use of internal heat sources would make the heat integrated column an independent scheme of external heat source.

Externalities of public firm presence: Evidence from private firms' investment decisions

Public firms provide a large amount of information through their disclosures. In addition, information intermediaries publicly analyze, discuss, and disseminate these disclosures. Thus, greater public firm presence in an industry should reduce uncertainty in that industry. Following the theoretical prediction of investment under uncertainty, we hypothesize and find that private firms are more responsive to their investment opportunities when they operate in industries with greater public firm presence. Further, we find that the effect of public firm presence is greater in industries with better information quality and in industries characterized by a greater degree of investment irreversibility. Our results suggest that public firms generate positive externalities by reducing industry uncertainty and facilitating more efficient private firm investment.

Effect of phosphorus on the attenuation of lead and chromium transport in soils

This study analyses the adsorption of Pb(II) and Cr(III) in soils. These metals are commonly found together in nature in urban wastes or industrial spillages, and the theoretical approach of the work was to evaluate the response of the soil to continuous Cr and Pb spillages to soil in terms of several physicochemical parameters. The influence of an anthropogenic input of phosphorus was evaluated. Continuous flow experiments were run in duplicates in acrylic columns (25 cm × 3.2 cm). The influent Cr(III) and Pb(II) solutions of 10 mg l−1 and 25 mg l−1 at pH 5 were pumped upward through the bottom of the columns to ensure saturation flow conditions. Also, successive experiments were run with the above concentrations of Cr(III) and Pb(II) and NaH2PO4, keeping metal to phosphorus ratio of 1:0, 1:0.1 and 1:1. Modelling parameters included Freundlich and Langmuir equations, together with the Two-site adsorption model using CXTFIT code. Results obtained allowed concluding that Pb(II) adsorption presents a certain degree of irreversibility and the continued spillages over soil increment the fraction which is not easily desorbed. Cr(III) desorption was almost complete, evidencing its high mobility in nature. The presence of an anthropogenic input of phosphorus leads to a marked increase of both Pb(II) and Cr(III) adsorption in soils. Z-potential measurements allow to discard the electrostatic attraction of Cr(III) and Pb(II) with the surface charged soil as the dominant process of metal sorption. Instead, CheaqsPro simulation allows to identify PbH2PO4 +, PbHPO4 (aq) and CrHPO4 + as the dominant species which regulate Cr(III) and Pb(II) transport in soils.

Externalities of Public Firms’ Disclosures: Evidence from Private Firms’ Investment Decisions

Public firms provide a large amount of information through their disclosures. In addition, information intermediaries publicly analyze, discuss and disseminate these disclosures. Thus, greater public firm presence in an industry should reduce uncertainty in that industry. Following the theoretical prediction of investment under uncertainty, we hypothesize and find that private firms are more responsive to their investment opportunities when they operate in industries with greater public firm presence. Further, we find that the effect of public firm presence is greater in industries with better information quality and in industries characterized by a greater degree of investment irreversibility. Our results suggest that public firms generate positive externalities by reducing industry uncertainty and facilitating more efficient private firm investment.

Irreversibility, mean reversion, and investment timing

This paper examines the effect of irreversibility on investment under mean reversion. We develop a continuous-time model wherein a risk-neutral firm is endowed with a perpetual option to invest in a project at any time by incurring a fixed investment cost at that instant. The project, once undertaken, generates a stream of cash flows that are governed by a mean-reverting stochastic process. The firm is then allowed to liquidate its project at any time to partially recover the fixed investment cost. The recovery rate of the fixed investment cost inversely gauges the degree of irreversibility of investment. Using a real options approach, we derive an analytical solution to the value of the firm that is analogous with an American compound option. We show that greater irreversibility of investment induces the firm to raise its investment trigger, thereby deferring the undertaking of the project. We further show that greater irreversibility of investment has a detrimental effect that makes the firm less valuable.

The Impact of Profit Taxation on Capitalized Investment with Options to Delay and Divest

In entrepreneurial decisions making uncertain future profits often are a main characteristics of real investment opportunities. If investors can react to uncertainty the degree of irreversibility and timing flexibility inherent in the available project should be integrated into the decision calculus. In this paper we investigate the interdependencies of effects from profit taxation and real options. We model an investment decision including an option to invest and an option to abandon. We show that increasing the tax rate can lead to paradoxical tax effects, i.e. may foster an investor’s willingness to invest into a capitalized investment. Instead, if we abstract from the possibility to abandon the investment object such paradoxical effect cannot be identified. Determining the after-tax value of the option to enter the investment project with and without an abandonment option we receive a critical cash flow cut-off level. We find that the value of the option to abandon depends on the tax rate and the amount of periodical cash flows. The option value can be increasing or decreasing in the tax rate. We find scenarios with paradoxical tax effects and show that the observed paradoxical effects are due to the presence of the real abandonment option itself. This finding contributes to the stream of literature that explains potential sources of paradoxical tax effects. The generated decision rules are helpful for investors facing risky investment opportunities and for discussing the economic impact of tax reforms. Furthermore, we highlight the overwhelming importance of integrating taxes in typically applied valuation approaches.

Time series irreversibility: a visibility graph approach

We propose a method to measure real-valued time series irreversibility which combines two differ- ent tools: the horizontal visibility algorithm and the Kullback-Leibler divergence. This method maps a time series to a directed network according to a geometric criterion. The degree of irreversibility of the series is then estimated by the Kullback-Leibler divergence (i.e. the distinguishability) between the in and out degree distributions of the associated graph. The method is computationally effi- cient, does not require any ad hoc symbolization process, and naturally takes into account multiple scales. We find that the method correctly distinguishes between reversible and irreversible station- ary time series, including analytical and numerical studies of its performance for: (i) reversible stochastic processes (uncorrelated and Gaussian linearly correlated), (ii) irreversible stochastic pro- cesses (a discrete flashing ratchet in an asymmetric potential), (iii) reversible (conservative) and irreversible (dissipative) chaotic maps, and (iv) dissipative chaotic maps in the presence of noise. Two alternative graph functionals, the degree and the degree-degree distributions, can be used as the Kullback-Leibler divergence argument. The former is simpler and more intuitive and can be used as a benchmark, but in the case of an irreversible process with null net current, the degree-degree distribution has to be considered to identifiy the irreversible nature of the series.