Irreversible Phenomena Research Articles

TIPOLOGÍA Y USOS DEL SUELO EN AGROECOSISTEMAS DEL VALLE DEL GUAMUEZ, PUTUMAYO – COLOMBIA

RESUMEN Esta investigación tuvo como objetivo analizar diferentes agroecosistemas existentes en una región del departamento de Putumayo (Colombia) y su relación sociocultural con los contextos productivos y de conservación del territorio, con base en los elementos conceptuales y metodológicos que ofrece la agroecología. Para ello se diseñó un estudio de métodos mixtos por el cual se aplicaron metodologías de análisis de suelos y valoración de aspectos culturales por medio de herramientas cualitativas tipo entrevista y grupos de discusión. En el análisis se tuvo como base el concepto de estructura ecológica principal del paisaje (EEP) y principios de la agroecología, orientado por un análisis etno-agrícola del fenómeno. Como resultado se identificaron tres tipos de sistemas productivos, donde coexisten grupos de indígenas con colonos y población flotante que han desarrollado diferentes procesos de adaptación ecosistémicos. Esta heterogeneidad implica, por lo menos, dos modos de vida diferentes: uno, de tipo “endógeno”, campesino – colonos y ligado con las comunidades indígenas, y el otro, mediado por la visión clásica del desarrollo económico. En este sentido, todos los habitantes, sin importar en qué modo de vida se inscriben, se ven abocados a superar las limitantes biofísicas y ecosistémicas del territorio, agravadas en la región por los procesos de tala y mal uso de las tierras, que han generado, en muchos sectores, procesos severos de degradación del medio natural incluyendo fenómenos irreversibles de erosión en surcos y cárcavas. Este deterioro se expresa en disminuciones que limitan significativamente las posibilidades de subsistencia y de acumulación de los habitantes locales.

Explaining irreversible hygroscopic strains in paper: a multi-scale modelling study on the role of fibre activation and micro-compressions

This paper proposes a meso-structural model for the discrete fibrous network of paper, which is able to upscale the irreversible phenomena from the underlying hygro-mechanics towards the effective behaviour at the macro-scale. The swelling of individual fibres, induced by moisture content variations, is transmitted to the network through inter-fibre bonds and governs the resulting effective material response. The present approach is based on a recently developed discrete meso-structural model for the reversible part of the response, which distinguishes between the influence on the hygroscopic behaviour of free-standing fibre segments and inter-fibre bonds. The network structure, fibre and bond geometries and hygro-elastic properties are explicitly incorporated. The major novelty of this contribution is the extended fibre constitutive model, enabling to describe some typical irreversible mechanisms and instability effects related to the history of the manufacturing. This extension strongly affects the effective material behaviour beyond the elastic range. Despite the valuable work in the literature, no papers can be found dedicated to meso-structural models including these phenomena. Using an appropriate homogenization strategy, the unit-cell is solved analytically, capturing irreversible shrinkage in restrained dried paper and the occurrence of local buckling within the bond for freely dried material. The proposed scale transition offers a deeper insight into the complex relation between the events occurring at the different length scales. The potential of the proposed methodology is demonstrated through the convincing agreement with experimental data obtained from the literature.

Pressure enhanced fouling and adapted anti-fouling strategy in pressure assisted osmosis (PAO)

The concept of pressure assisted osmosis (PAO) has proven to be promising to tackle current flux limitations in forward osmosis (FO), but implementation of this concept in practice requires further research, especially in the context of wastewater reuse, for which organic fouling normally occurs. This study focuses on the impact of pressure addition in the PAO operation and on the assessment of the respective impact of osmotic and hydraulic driving forces on fouling behavior in accelerated fouling conditions. The evidence that the application of moderate hydraulic pressure (4bar) lead to more severe fouling phenomena in PAO process was clearly demonstrated. Foulant cake compaction due to the applied pressure resulted in detrimental additional resistance to water permeation, thus impacting filtration flux. A high cross flow velocity (CFV) cleaning strategy, already proven to be effective for FO operation, was shown to be inappropriate for PAO. The efficiency of osmotic backwashing to clean membranes after PAO operation was extensively evaluated for both membrane orientations. The results demonstrated that the specific combination of osmotic backwashing with subsequent water flushing used in this study cleaned effectively the highly fouled membrane. Importantly, osmotic backwash also allowed for complete cleaning of the membrane support layer when using the membrane with the support layer facing the feed, thus tackling previously irreversible fouling phenomena, and potentially enabling FO/PAO operation in both membrane orientations in practice. Finally, a mechanistic model to illustrate fouling and cleaning in PAO was proposed.

The importance of hypoxia and extra physiologic oxygen shock/stress for collection and processing of stem and progenitor cells to understand true physiology/pathology of these cells ex vivo.

Hematopoietic stem (HSCs) and progenitor (HPCs) cells reside in a hypoxic (lowered oxygen tension) environment, in vivo. We review literature on growth of HSCs and HPCs under hypoxic and normoxic (ambient air) conditions with a focus on our recent work demonstrating the detrimental effects of collecting and processing cells in ambient air through a phenomenon termed extra physiologic oxygen shock/stress (EPHOSS), and we describe means to counteract EPHOSS for enhanced collection of HSCs. Collection and processing of bone marrow and cord blood cells in ambient air cause rapid differentiation and loss of HSCs, with increases in HPCs. This apparently irreversible EPHOSS phenomenon results from increased mitochondrial reactive oxygen species, mediated by a p53-cyclophilin D-mitochondrial permeability transition pore axis, and involves hypoxia inducing factor-1α and micro-RNA 210. EPHOSS can be mitigated by collecting and processing cells in lowered (3%) oxygen, or in ambient air in the presence of, cyclosporine A which effects the mitochondrial permeability transition pore, resulting in increased HSC collections. Our recent findings may be advantageous for HSC collection for hematopoietic cell transplantation, and likely for enhanced collection of other stem cell types. EPHOSS should be considered when ex-vivo cell analysis is utilized for personalized medicine, as metabolism of cells and their response to targeted drug treatment ex vivo may not mimic what occurs in vivo.

Universal ideal behavior and macroscopic work relation of linear irreversible stochastic thermodynamics

We revisit the Ornstein–Uhlenbeck (OU) process as the fundamental mathematical description of linear irreversible phenomena, with fluctuations, near an equilibrium. By identifying the underlying circulating dynamics in a stationary process as the natural generalization of classical conservative mechanics, a bridge between a family of OU processes with equilibrium fluctuations and thermodynamics is established through the celebrated Helmholtz theorem. The Helmholtz theorem provides an emergent macroscopic ‘equation of state’ of the entire system, which exhibits a universal ideal thermodynamic behavior. Fluctuating macroscopic quantities are studied from the stochastic thermodynamic point of view and a non-equilibrium work relation is obtained in the macroscopic picture, which may facilitate experimental study and application of the equalities due to Jarzynski, Crooks, and Hatano and Sasa.

Exact Formulation of Subloading Surface Model: Unified Constitutive Law for Irreversible Mechanical Phenomena in Solids

The subloading surface model is endowed with the intrinsic far-reaching ability to describe the wide classes of irreversible mechanical behavior, e.g. the monotonic and the cyclic loading behavior of elastoplastic and viscoplastic materials, the friction behavior and the crystal plastic behavior as has been examined in the former paper (Hashiguchi in Arch Comput Methods Eng 20:361–417, 2013). However, the past formulations of the subloading surface model have contained several inexact equations, which have been modified repeatedly since the concept of the subloading surface was proposed in 1977 (Hashiguchi and Ueno 1977). The exact formulation is presented first in this article for the hypoelastic-based plasticity, which enjoys the distinguished superiority in the both aspects of the description of material behavior in high accuracy and of the numerical calculation in high efficiency. It is further provided for all the four basic frameworks, i.e. the infinitesimal hypoelastic-based plasticity, the infinitesimal hyperelastic-based plasticity, the hypoelastic-based plasticity and the multiplicative hyperelastic-based plasticity for finite strain. Further, the subloading-crystal plasticity model is formulated modifying the former one (Hashiguchi 2013) by incorporating the decomposition of the crystalline shear strain rate into the elastic and the plastic parts. This would be the guidebook to the subloading surface model and also the memorial monograph for the historical development of the subloading surface model.

HUMAN BRAIN

Aging is an irreversible and universal phenomenon of every living organism’slife. Many recent studies provide evidences that is strictly related to decline in cognitive functionimpairment but along with various causes behind these abnormal changes, change in brain!unction and structure is one of the most important factors are being widely used to studythe hypothesis that ‘the deficits in and temporal order memory are closely related. Increasein age causes reduction in memory processing tasks, which involve information storage andprocessing. In other explanation it is mentioned that frontal activity, differences underlyingaging is associated with recruitment of brain areas and neural circuit efficiency reduction. Incase of young subjects increase in activity mean shorter reaction time but in older subjectsresults are opposite.

Axiomatic foundations of entropic theorems for hard-sphere systems

Following the recent establishment of an exact kinetic theory describing the statistical behavior of the Boltzmann-Sinai Classical Dynamical System and realized by the Master kinetic equation, in this paper the problem is posed of the construction of related appropriate entropic theorems. The same equation is proved to warrant, in particular, an exact constant H-theorem, referred to here as Master constant H-theorem, which holds for the 1-body (i.e., kinetic) Boltzmann-Shannon entropy. The relationship with the customary Boltzmann H-theorem holding for the Boltzmann equation and the physical origin of the related phenomenon of macroscopic irreversibility are investigated.

Tu1973 The Novel Observation of Irreversible Electroporation Phenomenon on Gastrointestinal Cancer Cells in Physiological Conditions, With Sub-Micrometer Resolution by Scanning Ion Conductance Microscopy

G A A b st ra ct s enhanced MEK/ERK activation coincided with those that inhibited mTORC2-mediated Akt phosphorylation on Ser473, suggesting a role of mTORC2. Knockdown of Rictor markedly increased baseline levels of ERK phosphorylation and treatment with NVP-BEZ235 did not produce further enhancement of ERK activation. These results imply that Rictor or mTORC2 exerts feedback inhibition of the MEK/ERK pathway in pancreatic cancer cells. Conclusion: We propose that dual PI3K/mTOR inhibitors suppress a novel negative feedback loop mediated by mTORC2 thereby leading to enhanced MEK/ERK pathway activity in pancreatic cancer cells.

Pinning Loss Power Density in Superconductors

The pinning loss power density is theoretically derived based on the resistive energy dissipation when the flux lines are driven by the Lorentz force in a superconductor. The obtained loss power density does not depend on the viscosity or flow resistivity, but is proportional to the pinning force density only, and it possesses the nature of hysteresis loss, as commonly measured in experiments. These features are predicted by the critical state model, which was recently proved theoretically. The obtained pinning force density is consistent with the prediction of the coherent potential approximation theory, a kind of statistical summation theory, for flux pinning. Thus, the irreversible properties associated with the flux pinning can be comprehensively described by these flux pinning theories. The irreversible flux pinning in the superconductor is compared with similar irreversible phenomena such as the motion of magnetic domain walls in ferromagnetic materials and the friction in mechanical systems. The po...

Thermal displacements of concrete dams: Accounting for water temperature in statistical models

Measurements of concrete dam displacements are influenced by various factors such as hydrostatic load, thermal effect and irreversible phenomena (creep, swelling, etc.). To interpret measurements and improve the assessment of irreversible effects, splitting the different influences is necessary. For this purpose, models based on statistics and physics are commonly employed in engineering studies. Although they are efficient in most cases to analyse the displacement of concrete dams, these models are built on a certain number of hypotheses, necessary to write “simple” mathematical relationships, but leading to uncertainties. To evaluate the suitability of these physico-statistical models (importance of the hypotheses) and to improve it, a 2D finite element (FE) model has been developed as a heuristic case. This study shows the importance of water temperature and temperature gradient in the assessment of the thermal displacements. So, a new physico-statistical model is proposed to account for these phenomena. The evaluation of its performance on both the FE heuristic case and real cases shows that the improved assessment of thermal effects on reversible phenomena leads to a reduced uncertainty on residuals. Thus, the proposed approach yields to a better assessment of irreversible trends.

Irreversibility in redox molecular conduction: single versus double metal-molecule interfaces

In this work we analyze the onset and manifestation of irreversibility phenomena in the charge transport at single and double metal-redox molecule interfaces, with special emphasis on the role of the nuclear system reorganization energy in causing the distortion of cyclic voltammograms in the first case and the occurrence of hysteresis phenomena in the second case. Under physical conditions for which two states of the molecular system come into play, effects of irreversibility increase with the reorganization energy at a single interface, while an opposite trend is seen in the conduction through a molecular junction. The apparent contradiction between these two behaviors, which was raised in a previous work (Migliore, A.; Nitzan, A., J. Am. Chem. Soc. 2013, 135, 9420–32) is here resolved through detailed investigation of the connections between molecule reorganization energy, bias-dependent population of the molecular redox site(s), and threshold voltage scan rate for the onset of irreversible behavior. Moreover, our investigation of the effects of the reorganization energy on the voltammogram peaks proposes a strategy for extracting the value of the reorganization energy of the molecular system from the experimental behavior.

Dielectric Properties of Human Normal and Malignant Liver Tissue: A Non-Equilibrium Thermodynamics Approach

In this paper we will show the possibility of studying physical properties and irreversible phenomena that occur in biological tissues by applying the dielectric Kluitenberg’s non-equilibrium thermodynamic theory. Namely, we shall use some recent extensions of this theory that allows deducing its main characteristic parameters from experimental measurements. We determine frequency spectrum for phenomenological and state coefficients of the non-equilibrium thermodynamic approach. Applying these results to the study of human liver tumor and normal liver we show, for comparison, that it is possible to determine the difference, in some detail, of the amount of single irreversible phenomena occurring inside them.

Correlation between microstructural and mechanical behavior of nanostructured MgH2 upon hydrogen cycling

Highly reactive nanostructured powders are produced on a large scale by co-milling of MgH2 with transition metals. Composite materials with high thermal conductivity are produced by uniaxial compaction of these powders with expanded graphite. However, upon cycling, the MgH2 grains tend to recrystallize and a progressive swelling of the composites is observed. The purpose of this study is to understand this irreversible phenomenon, through correlations with microstructural evolutions.In-situ dilatometry measurements were performed on samples prepared with 2 different additives (pure vanadium or Ti–V–Cr alloy). We systematically observe a stabilization of the irreversible expansion after about 50cycles. A bi-modal distribution of the as-milled powders is observed by granulometry measurements. Upon cycling, the coalescence of the “small” MgH2 particles tends to create large agglomerates and results in mono-disperse powders. This behavior induces an increase in porosity, which explain the progressive swelling of the composites. The maximum of deformation strongly depends on the additive and is lower with vanadium addition than with Ti–V–Cr alloy.

Exergy-Based Formulation for Aircraft Aeropropulsive Performance Assessment: Theoretical Development

Aircraft have evolved into extremely complex systems that require adapted methodologies and tools for an efficient design process. A theoretical formulation based on exergy management is proposed for assessing the aeropropulsive performance of future aircraft configurations. It consists of the combination of a momentum balance and a fluid flow analysis involving the first and second laws of thermodynamics. The exergy supplied by the propulsion system and its partial destruction within the control volume is associated with the aircraft mechanical equilibrium. Characterization of the recoverable mechanical and thermal outflows is made along with the identification of the irreversible phenomena that destroy their work potential. Restriction of the formulation to unpowered configurations yields connections to some well-known far-field drag expressions and shows that their underlying theory can be related to exergy considerations. Because the exergy balance does not rely on the distinction of thrust and drag, it is especially suitable for the performance evaluation of highly integrated aeropropulsive concepts like boundary-layer ingestion.

Algunos aspectos del shock hemorrágico experimental

Aunque el shock hemorrágico viene siendo estudiado profusamente, la causa de su desenlace fatal, así como la de otras formas de shock, no ha sido completamente establecida. Nuestro propósito ha sido, en primer lugar, conocer el mecanismo de la acción protectora de la Clorpromazina, pero, al mismo tiempo hemos creído que quizás su investigación podría aportar alguna luz a la explicación del fenómeno de la irreversibilidad. Además, hemos querido saber si esta droga puede ser activa después que el shock se ha instalado, ya sea administrándola sola, o acompañada de la transfusión sanguínea, lo cual, además de ser de gran importancia práctica podría tener implicaciones teóricas de interés.

Towards a port-based formulation of macro-economic systems

This paper aims at extending the port-Hamiltonian approach to a simple class of macro-economic systems by considering the dynamics as the result of the interaction between a limited set of “atomic components,” e.g. inventories, (re)investments, suppliers and demand. Once flow, effort, and “power” (i.e., the cash flow) have been defined, the behaviour of these simple elements is provided, and their interconnection is described in terms of Dirac and contact structures. The first ones, associated to power conservation in physical modelling, correspond to the law of good bookkeeping (Walras׳s Law), in economy. Differently, contact structures appear in the description of irreversible phenomena, and in macro-economy they are employed in a more realistic formulation of the firm (or supplier) behaviour. The firm, in fact, is a profit maximising entity that interconnects the markets associated to the demand and to the input factors in order to create a profit. Several examples are provided to show to effectiveness of the approach.

Protein adsorption can be reversibly switched on and off on mixed PEO/PAA brushes

Adsorption of proteins on surfaces placed in biological fluids is a ubiquitous and mostly irreversible phenomenon, desirable or not, but often uncontrolled. Adsorption of most proteins on poly(ethylene oxide) (PEO) brushes is very limited, while the amount of proteins adsorbed on poly(acrylic acid) (PAA) brushes varies with the pH and ionic strength (I) of the protein solution. Mixed brushes of PEO and PAA are designed here to reversibly adsorb and desorb albumin, lysozyme, collagen and immunoglobulin G, four very different proteins in terms of size, solubility and isoelectric point. Protein adsorption and desorption are monitored using X-ray photoelectron spectroscopy, as well as with quartz crystal microbalance for in situ and real-time measurements. Large amounts of protein are adsorbed and then nearly completely desorbed on mixed PEO/PAA brushes by a simple pH and I trigger. The mixed brushes thus nicely combine the properties of pure PAA and pure PEO brushes. These adsorption/desorption cycles are shown to be repeated with high efficiency. The high-performance smart substrates created here could find applications in domains as diverse as biosensors, drug delivery and nanotransport.

Field-programmable optical devices based on resonance elimination.

Optical switches are among the essential building blocks in optical networks due to their unique role in routing data. In this Letter, for the first time to our knowledge, we have exploited a high-quality factor (Q) optical microresonator combined with the well-known irreversible dielectric breakdown phenomenon to introduce a simple field-programmable on/off optical switch. This simple unit can be thought of as a building block for more complex optical systems with different functionalities. By using this simple unit we have demonstrated an optical field-programmable 2×2 switch. After the device is programmed by the user, no external electrical signal is needed to maintain the state of the device. The same approach can readily be adopted to design a field-programmable arbitrary N×N optical switch.

Evidence of thermo-oxidation phenomena occurring during hygrothermal aging of thermosetting resins for RTM composite applications

This paper focuses on the humid aging of a high temperature thermosetting resin employed for the realization of aircraft parts manufactured by the RTM process. Accelerated humid aging at several different temperatures (40–90°C) and relative humidity values (50–100%) has been carried out by means of gravimetric tests. Anomalous behavior with respect to Fick’s diffusion law and a color gradient from the edge to the center of the samples has been observed. Drying of samples after aging and mechanical tests on aged and dried samples have shown the existence of irreversible phenomena taking place during humid ageing: uniform tensile tests revealed resin embrittlement, Ultra Micro Indentation tests allowed measuring a gradient of properties from the surface to the centre of the samples. This behavior – associated to the color changes observed on aged samples – indicates that oxidation phenomena take place during hygrothermal aging.