Dynamic Process In Order Research Articles

The thermodynamics of gas absorption and guest-induced flexibility in zeolite Y

The interaction of water, carbon dioxide and methane with faujasite zeolite Y has been probed by gas absorption calorimetry. The energetics of water sorption reveals guest-induced framework flexibility with transition from a less hydrated form to a more hydrated phase. The differential enthalpy of absorption directly measures strengths of guest-host interactions at different sites and possible binding mechanisms. Interactions of CO2 and CH4 with the faujasite framework are weaker and no phase transition is seen. The most negative enthalpies in water, CO2 and CH4 absorption occur near zero loading with exothermic values (relative to the vapor) of −110.59 ± 1.5 kJ/mol, −34.40 ± 0.47 kJ/mol and −21.87 ± 0.78 kJ/mol respectively. The initial entropy of CO2 sorption, unlike that of water sorption, is not the lowest near zero loading but falls to a stable plateau of lowest level before increasing, reflecting a possible dynamic ordering process of absorbed CO2 molecules. The entropy of CH4 sorption follows a monotonic change upon loading. Thus the chemical potential obtained directly from the absorption isotherm and the calorimetrically measured enthalpy can be used to calculate the entropy of sorption and together provide a detailed map of thermodynamic behavior of H2O, CO2 and CH4) in this flexible zeolite framework.

Time evolution of the vortex configuration associated with dynamic ordering detected by dc drive

When a periodic shear force with a small amplitude dinp is applied to vortex assemblies having a random distribution, the vortices gradually self-organize to avoid future collisions and transform into an organized configuration. We showed recently that this random-organization or dynamic-ordering process can be detected from the time-evolution of voltage V(t) that increases to a steady-state voltage. We also showed from the subsequent readout experiment of V(t) using various ac amplitudes d that the transient vortex configuration during random organization is not microscopically homogeneous but consists of the disordered and organized regions. In this work, we develop an alternative readout method using a dc drive. It is found that the dc method gives the same results as obtained from the ac one, which further supports our view of the coexistence regions. It is expected that both methods will be applied complementarily to detect the vortex configuration over a wide range of disorder.

Role of Mitochondrial Dysfunction in Hypertension and Obesity.

Mitochondria are essential for the maintenance of normal physiological function of tissue cells. Mitochondria are subject to dynamic processes in order to establish a control system related to survival or cell death and adaptation to changes in the metabolic environment of cells. Mitochondrial dynamics includes fusion and fission processes, biogenesis, and mitophagy. Modifications of mitochondrial dynamics in organs involved in energy metabolism such as the pancreas, liver, skeletal muscle, and white adipose tissue could be of relevance for the development of insulin resistance, obesity, and type 2 diabetes. Mitochondrial dynamics and the factors involved in its regulation are also critical for neuronal development, survival, and function. Modifications in mitochondrial dynamics in either agouti-related peptide (AgRP) or pro-opiomelanocortin (POMC), circuits which regulates feeding behavior, are related to changes of food intake, energy balance, and obesity development. Activation of the sympathetic nervous system has been considered as a crucial point in the pathogenesis of hypertension among obese individuals and it also plays a key role in cardiac remodeling. Hypertension-related cardiac hypertrophy is associated with changes in metabolic substrate utilization, dysfunction of the electron transport chain, and ATP synthesis. Alterations in both mitochondrial dynamics and ROS production have been associated with endothelial dysfunction, development of hypertension, and cardiac hypertrophy. Finally, it might be postulated that alterations of mitochondrial dynamics in white adipose tissue could contribute to the development and maintenance of hypertension in obesity situations through leptin overproduction. Leptin, together with insulin, will induce activation of sympathetic nervous system with consequences at renal, vascular, and cardiac levels, driving to sodium retention, hypertension, and left ventricular hypertrophy. Moreover, both leptin and insulin will induce mitochondrial alterations into arcuate nucleus leading to signals driving to increased food intake and reduced energy expenditure. This, in turn would perpetuate white adipose tissue excess and its well-known metabolic and cardiovascular consequences.

Characterising brain network topologies: A dynamic analysis approach using heat kernels

Network theory provides a principled abstraction of the human brain: reducing a complex system into a simpler representation from which to investigate brain organisation. Recent advancement in the neuroimaging field is towards representing brain connectivity as a dynamic process in order to gain a deeper understanding of how the brain is organised for information transport. In this paper we propose a network modelling approach based on the heat kernel to capture the process of heat diffusion in complex networks. By applying the heat kernel to structural brain networks, we define new features which quantify change in heat propagation. Identifying suitable features which can classify networks between cohorts is useful towards understanding the effect of disease on brain architecture. We demonstrate the discriminative power of heat kernel features in both synthetic and clinical preterm data. By generating an extensive range of synthetic networks with varying density and randomisation, we investigate heat diffusion in relation to changes in network topology. We demonstrate that our proposed features provide a metric of network efficiency and may be indicative of organisational principles commonly associated with, for example, small-world architecture. In addition, we show the potential of these features to characterise and classify between network topologies. We further demonstrate our methodology in a clinical setting by applying it to a large cohort of preterm babies scanned at term equivalent age from which diffusion networks were computed. We show that our heat kernel features are able to successfully predict motor function measured at two years of age (sensitivity, specificity, F-score, accuracy = 75.0, 82.5, 78.6, and 82.3%, respectively).

Economic hardship in childhood and adult health trajectories: An alternative approach to investigating life-course processes.

In this study, we advance existing research on health as a life course process by conceptualizing and measuring both childhood disadvantage and health as dynamic processes in order to investigate the relationship between trajectories of early life socioeconomic conditions and trajectories of health in midlife. We utilize a trajectory-based analysis that takes a disaggregated, person-centered approach to understand dynamic trajectories of health as latent variables that reflect the timing, duration and change in health conditions experienced by respondents over a period of 10 years in midlife as a function of stability and change in exposure to economic hardship in early life. Results from repeated-measures latent class analysis of longitudinal data from the Panel Study of Income Dynamics indicate that economic hardship in childhood has long-term, negative consequences for health both among individuals beginning life and remaining in poverty as well as those moving into poverty. In contrast, adults with more advantaged early life experiences, or who moved out of poverty during the period of observation, were at a lower risk of experiencing health trajectories characterized by the early onset or increasing risk of disease. We argue that a person-centered, disaggregated approach to the study of the relationship between socioeconomic status and health across the life course holds potential for the study of health inequality and that a greater focus on trajectory-based analysis is needed.

Directional Input Adaptation in Parametric Optimal Control Problems

This paper deals with input adaptation in dynamic processes in order to guarantee feasible and optimal operation despite the presence of uncertainty. For those optimal control problems having terminal and mixed control-state path constraints, two orthogonal sets of adaptation directions can be distinguished in the input space: the sensitivity-seeking directions, along which a small variation from an optimal nominal solution will not affect the respective active constraints, and the complementary constraint-seeking directions, along which a variation will affect the respective constraints. It follows that selective input adaptation strategies can be defined, namely, adaptation in the sensitivity- and constraint-seeking directions. This paper proves the important result that, for small parametric perturbations, the cost variation resulting from adaptation in the sensitivity-seeking directions (over no input adaptation) is typically smaller than the cost variation due to adaptation in the constraint-seeking directions. It is also established that no selective input adaptation along a sensitivity-seeking direction can reduce the dominant, first-order term in the optimality gap; adaptation along a constraint-seeking direction is necessary to cancel it out. These results are illustrated with two numerical case studies.

Selective Input Adaptation in Parametric Optimal Control Problems with Path Constraints

This paper is concerned with input adaptation in dynamic processes in order to guarantee feasible and optimal operation despite the presence of uncertainty. For optimal control problems having mixed control-state constraints, two sets of directions can be distinguished in the input function space: the so-called sensitivity-seeking directions, along which a small input variation does not affect the active constraints, and the complementary constraint-seeking directions, along which an input variation does affect the respective constraints. Two selective input adaptation scenarios can be defined, namely, adaptation along each set of input directions. This paper proves the important result that the cost variation due to the adaptation along the sensitivity-seeking directions is typically smaller than that due to the adaptation along the constraint-seeking directions.

Geometric changes and mass balance of the Austfonna ice cap, Svalbard

Abstract. The dynamics and mass balance regime of the Austfonna ice cap, the largest glacier on Svalbard, deviates significantly from most other glaciers in the region and is not fully understood. We have compared ICESat laser altimetry, airborne laser altimetry, GNSS surface profiles and radio echo-sounding data to estimate elevation change rates for the periods 1983–2007 and 2002–2008. The data sets indicate a pronounced interior thickening of up to 0.5 m y−1, at the same time as the margins are thinning at a rate of 1–3 m y−1. The southern basins are thickening at a higher rate than the northern basins due to a higher accumulation rate. The overall volume change in the 2002–2008 period is estimated to be −1.3±0.5 km3 w.e. y−1 (or −0.16±0.06 m w.e. y−1) where the entire net loss is due to a rapid retreat of the calving fronts. Since most of the marine ice loss occurs below sea level, Austfonna's current contribution to sea level change is close to zero. The geodetic results are compared to in-situ mass balance measurements which indicate that the 2004–2008 surface net mass balance has been slightly positive (0.05 m w.e. y−1) though with large annual variations. Similarities between local net mass balances and local elevation changes indicate that most of the ice cap is slow-moving and not in dynamic equilibrium with the current climate. More knowledge is needed about century-scale dynamic processes in order to predict the future evolution of Austfonna based on climate scenarios.

Online parameter identification in time-dependent differential equations as a non-linear inverse problem

Online parameter identification in time-dependent differential equations from time course observations related to the physical state can be understood as a non-linear inverse and ill-posed problem and appears in a variety of applications in science and engineering. The feature as well as the challenge of online identification is that sensor data have to be continuously processed during the operation of the real dynamic process in order to support simulation-based decision making. In this paper we present an online parameter identification method that is based on a non-linear parameter-to-output operator and, as opposed to methods available so far, works both for finite- and infinite-dimensional dynamical systems, e.g., both for ordinary differential equations and time-dependent partial differential equations. A further advantage of the method suggested is that it renders typical restrictive assumptions such as full state observability, linear parametrisation of the underlying model and data differentiation or filtering unnecessary. Assuming existence of a solution for exact data, a convergence analysis based on Lyapunov theory is presented. Numerical illustrations given are by means of online identification both of aerodynamic coefficients in a 3DoF-longitudinal aircraft model and of a (distributed) conductivity coefficient in a heat equation.

Reporting systems in healthcare from a case-by-case experience to a general framework: an example in anaesthesia

Reporting systems are becoming more widespread in healthcare. Since they may become mandatory under the pressure of insurance companies and administrative organizations, it is important to begin to go beyond a case-by-case approach and to move to a system where there is a general reflection on the best conditions of development and setting up of such systems in medicine. In this paper, we review existing reporting systems, break down their components, examine how they are constructed and propose some ideas on how to articulate them in a dynamic process in order to improve the validity of the tool as mediator of safety, quality and well-being at work.

Towards a Discrete Event Formalization of Sachem's Perception Based Monitoring

This paper aims at introducing the basis of the formalization of the Sachem perception based monitoring and diagnosis approach. Sachem is an extensive large-scale real time knowledge based system designed to monitor and diagnose blast furnaces. In this paper, Sachem is considered as a monitoring cognitive agent that analyzes a continuous dynamic process in order to generate discrete events (alarms) that inform about unsatisfactory process states occurences. The paper shows how the knowledge about the behavior of a continuous process can be formalized in terms of relation between discrete events so that a recursive recognition process of signatures can be used in order to design monitoring cognitive agents. The paper concludes on the main property of the discrete event representation of continuous process, the compactness.

Exocyclic push–pull conjugated compounds. Part 3. An experimental NMR and theoretical MO ab initio study of the structure, the electronic properties and barriers to rotation about the exocyclic partial double bond in 2- exo-methylene- and 2-cyanoimino-quinazolines and -benzodiazepines

The structure of a number of 2- exo-methylene substituted quinazolines and benzodiazepines, respectively, 1, 3a, b, 4 ( X=–CN, –COOEt ) and their 2-cyanoimino substituted analogues 2, 3c, d ( X=–CN, –SO 2C 6H 4–Me (p) was completely assigned by the whole arsenal of 1D and 2D NMR spectroscopic methods. The E/ Z isomerism at the exo-cyclic double bond was determined by both NMR spectroscopy and confirmed by ab initio quantum chemical calculations; the Z isomer is the preferred one, its amount proved dependent on steric hindrance. Due to the push–pull effect in this part of the molecules the restricted rotation about the partial C 2,C 11 and C 2,N 11 double bonds, could also be studied and the barrier to rotation measured by dynamic NMR spectroscopy. The free energies of activation of this dynamic process proved very similar along the compounds studied but being dependent on the polarity of the solvent. Quantum chemical calculations at the ab initio level were employed to prove the stereochemistry at the exo-cyclic partial double bonds of 1– 4, to calculate the barriers to rotation but also to discuss in detail both the ground and the transition state of the latter dynamic process in order to better understand electronic, inter- and intramolecular effects on the barrier to rotation which could be determined experimentally. In the cyanoimino substituted compounds 2, 3c, d, the MO ab initio calculations evidence the isomer interconversion to be better described by the internal rotation process than by the lateral shift mechanism.

Investigation of lipid membrane macro- and micro-structure using calorimetry and computer simulation: structural and functional relationships

The lipid bilayer part of biological membranes is a complex lipid mixture displaying cooperative phenomena. By means of differential scanning calorimetry and computer simulation techniques, the equilibrium and non-equilibrium properties of the large assembly of mutually interacting amphiphilic lipid molecules constituting the lipid bilayer have been investigated. The cooperative many-particle lipid bilayer behavior is manifested in terms of phase transitions and large-scale macroscopic phase equilibria. On a smaller nanometer length-scale, equilibrium structural and compositional fluctuations lead to the formation of a heterogeneous lateral bilayer structure composed of dynamic lipid domains and differentiated bilayer regions. In addition, the non-equilibrium dynamic ordering process of coexisting phases can give rise to the formation of local lipid structures on various length- and time-scales. The results suggest that the structural and dynamical lipid bilayer behavior and in particular the appearance of small-scale lipid structures might be of importance for membrane functionality, e.g., membrane compartmentalization, trans-membrane permeability, and the activity of membrane-associated enzymes and proteins.

Slow Nonequilibrium Dynamical Rearrangement of the Lateral Structure of a Lipid Membrane

The lipid bilayer of the biological membrane is a multicomponent molecular mixture capable of exhibiting compositional and structural heterogeneity. Using Fourier transform infrared spectroscopy and Monte Carlo computer simulation techniques, we report here for the first time the existence of a long-lived nonequilibrium heterogeneous lateral membrane structure composed of gel and fluid domains in a binary dipalmitoylphosphatidylcholine−dibehenoylphosphatidylcholine (DC16 PC−DC22 PC) lipid membrane. The nonequilibrium dynamic ordering process of coexisting phases following a thermal quench from the fluid state into the gel−fluid phase coexistence region is characterized by a relaxation time on the order of hours. This slow process leads to a long-lived compartmentalized percolative lateral membrane structure with a dynamic network of interfacial regions having properties different from the coexisting gel and fluid bulk phases.

Phase separation dynamics and lateral organization of two-component lipid membranes

The non-equilibrium dynamic ordering process of coexisting phases has been studied for two-component lipid bilayers composed of saturated di-acyl phospholipids with different acyl chain lengths, such as DC14PC-DC18PC and DC12PC-DC18PC. By means of a microscopic interaction model and computer-simulation techniques the non-equilibrium properties of these two mixtures have been determined with particular attention paid to the effects of the non-equilibrium ordering process on membrane heterogeneity in terms of local and global lateral membrane organization. The results reveal that a sudden temperature change that takes the lipid mixture from the fluid one-phase region into the gel-fluid phase-coexistence region leads to the formation of a large number of small lipid domains which slowly are growing in time. The growth of the lipid domains, which is limited by long-range diffusion of the lipid molecules within the two-dimensional membrane plane, gives rise to the existence of a highly heterogeneous percolative-like structure with a network of interfacial regions that have properties different from those of the phase-separated gel and fluid bulk phases. The results, which are discussed in relation to recent experimental observations interpreted in terms of a percolative-like membrane structure within the two phase region (Almeida, P.F.F., Vaz, W.L.C., and T.E. Thompson. 1992. Biochemistry 31:7198-7210), suggest that non-equilibrium effects may influence lipid domain formation and membrane organization on various length and time scales. Such effects might be of importance in relation to membrane processes that require molecular mobility of the membrane components in restricted geometrical environments of the compartmentalized lipid membrane.

Damping Characteristics of TiNi shape Memory Alloys

The damping characteristics of TiNi SMAs have been systematically studied by using techniques of resonant-bar and low-frequency inverted torsion pendulum. Experimental results show that both the martensite phase (M) and R phase (R) have high damping due to the movement of twin boundaries. Because the B2 parent phase (B2) has smaller damping, it is suggested that this may come from the dynamic ordering process of lattice defects. In the transformation re-gions of B2 ↔ M, B2 ↔ R, and R ↔ M, there are maxima of the damping capacity which are attributed to two contributions. One arises from the plastic strain and twin-interface move-ment during the thermal transformation, which obeys a linear variation of peak heightsQ −1 max vst att ≥ 1 °C/min. The other originates from the stress-induced transformation formed by the applied external stress which dominates atT < 1 °C/min. The elastic modulusE of martensite and the R phase is lower than that of the B2 phase, and a modulus minimum appears in the transformation region.

Morphological and kinetic evolution of surface patterns in gels during the swelling process: Evidence of dynamic pattern ordering.

A morphological and kinetic change is found in the late stage of surface pattern formation on a gel plate. It results from a dynamic ordering process originating from a strong constraint from the bottom surface. The scattering function changes its form from a single-peaked, broad function to a multipeaked one, reflecting the morphological change from a treelike pattern to a honeycomblike one. The characteristic size of the pattern initially grows as ${\mathit{t}}^{1/2}$, and then relaxes to its equilibrium value. This kinetic change coincides well with the morphological one.