Equilibrium Form Research Articles

On carbon dioxide capture: An accurate ab initio study of the Li3N + CO2 insertion reaction

The picture of an insertion reaction with formation of a fully lithiated carbamate is presented inspired in recent experimental information and based on accurate electronic structure calculations. A study is performed of the Li3N+CO2 reaction, which was recently suggested as a candidate to capture carbon dioxide and yield useful chemicals. Investigated in the gas phase, the results predict Li3N to leave its planar equilibrium form when capturing CO2 that bends itself during the capture process. A species with the sum formula Li3NCO2 is formed which, jointly with its fragments, is characterized in detail by Møller–Plesset perturbation theory and the coupled cluster method. The practical interest of the title reaction and work ahead are also assessed.

Equilibrium transformations of meso-methylated thiacarbocyanine in aqueous solutions

Equilibrium processes of dimerization and H*- and J-aggregation of 3,3′-di-(γ-sulfopropyl)-5,5′-dichloro-9-methylthiacarbocyanine (TCC) in aqueous solutions have been investigated, and the thermodynamic parameters of the processes have been calculated. At least seven equilibrium forms of TCC have been found in aqueous solution for the first time. The absorption bands of the dye have been attributed to various forms (M, D, H*, and J) with allowance for existence of stereoisomers. The aggregation numbers for J- and H*-aggregates have calculated from the dependence of the absorption spectra on the dye concentration in solutions. It has been shown that the TCC aggregates consisting of a large number of molecules are formed by the “block” mechanism via intermediate steps of the formation of dimers, J- or H*-tetramers, octamers, etc.

Geomorphic and stratigraphic signals of postglacial meltwater pulses on continental shelves

Selective development and preservation of major shoreline complexes on the continental shelf provide geomorphic evidence in support of alternating periods of Holocene sea-level stillstand and rapid rise during meltwater pulses. On a tectonically stable far-fi eld setting (the southeast African shelf), regionally developed, well-preserved shoreline complexes occur at ~‐100 m and ~‐60 m within an overall shelf sequence dominated by transgressive ravinement (non-preservation of shorelines). The development of geomorphically mature submerged shorelines with equilibrium forms is attributed to extended periods of sea-level stability, and their preservation is the result of early cementation followed by very rapid sea-level rise (several centimeters per year) that caused overstepping. Meltwater Pulses 1A and 1B are recorded in the shelf stratigraphy and geomorphology. Setting aside local infl uences of topography and sediment supply, we hypothesize that shelf stratigraphies should preferentially preserve shorelines at water depths associated with the stillstands or slowstands immediately preceding meltwater pulses. A reappraisal of shelf stratigraphy and geomorphology, in particular the preservation potential of former shorelines, is required in the light of contemporary understanding of postglacial sea-level history.

Estimates of the turbulent kinetic energy budget in the oceanic convective boundary layer

The terms of the steady-state turbulent kinetic energy (TKE) budget in the oceanic convective boundary layer (CBL) are estimated by use of microstructure data obtained over the continental shelf of the East China Sea. The dissipation term is calculated from the micro-scale vertical shear of horizontal velocity measured directly using a freely-falling microstructure profiler, whereas the buoyancy flux and shear production terms are estimated indirectly by integrating vertically the one-dimensional conservation equation of density and by applying similarity theory, respectively. The transport term, calculated as the residual of the other three terms, vertically redistributes the TKE from the upper half of the CBL to the lower half, consistent with the TKE budgets in the atmospheric CBL and in shear-free and slightly-sheared CBLs simulated by large eddy-simulation models. The relatively large contribution of the transport term to the TKE budget shows that a local equilibrium form of the TKE equation is not appropriate for the TKE budget in the oceanic CBL.

Non-Equilibrium Phase Behaviour in Giant Lipid Vesicles Following Very Rapid Temperature Changes

Artificial lipid bilayers are useful models of biological membranes, appealing for applicative purposes, and an interesting example of quasi-2D liquid systems on which to investigate new physics. It is well known that ternary-component lipid membranes, depending on the relevant thermodynamic parameters (composition, temperature and pressure), can show phase coexistence between two liquid phases, Lo and Ld, that can be imaged by fluorescence microscopy.We have performed experiments observing both equilibrium and non-equilibrium morphology of lipid phases. Specifically we have investigated a new dynamical regime in which we follow the diffusive mixing of miscible phases, and observe pattern formation out of equilibrium. This has been possible thanks to the development of a method to induce rapid temperature changes, by infrared irradiation. In this fashion, a temperature change can be imposed faster (in about 1s) than the diffusive time over relevant lengthscales (several 10s).Our observations are that the line tension rapidly vanishes upon heating the system above the miscibility transition temperature. After a few seconds, the spectrum of the interface fluctuations becomes very different from the equilibrium capillary waves, growing in amplitude and losing the characteristic 1/wave-vector2 equilibrium form. The interface from then blurs out, resembling fractal growth fronts, until the phases are fully mixed.The same fast temperature change allows us to very rapidly cool the system. This extends previous measurements by other groups, giving insight into processes that take place over the first few seconds of phase separation.Investigating these non-equilibrium conditions is relevant because biological membranes in living systems are not in a steady state: they are continually subject to rapid changes in composition, temperature and curvature, and their response is known to couple into a variety of biochemical processes by mediating protein binding and interactions.

POSSIBLE STATEMENTS OF PROBLEMS OF LOSS OF STABILITY DESIGNS

The technique of definition of group of a limit condition of thin-walled systems on a condition of loss of stability of equilibrium forms is given. It is noted that for unambiguous definition of a condition of a design it is necessary to reveal "nature" of a critical point on which character after critical deformation of a design depends. To be brought one possible classification of statements of problems of loss of stability.

Convergent evolution of abrading flow obstacles: Insights from analogue modelling of fluvial bedrock abrasion by coarse bedload

Upstream-facing convex surfaces (UFCS) are formed by bedload abrasion in bedrock rivers and indicate the recent, significant action of bedload abrasion in causing channel incision. Beyond this, little is known of the dynamics of UFCS and the effect of substrate and bedload properties on rates and distribution of bedload abrasion for these bed roughness elements. Grain size populations from 1 to 8cm (b-axis, in 1- or 2-cm bin widths) were used to bombard preshaped marble and limestone targets bolted to the base of an annular flume. The control of initial shape and lithology of the target and the erodent grain size and lithology were investigated by monitoring the evolution of the target form using laser scanning at predefined time intervals. Eleven experiment suites were carried out containing three initial target shapes constructed from two lithologies, four bedload (erodent) grain sizes of either granodiorites or limestone, or clear water flow. All 10 targets abraded by bedload evolved from their initial form into a steady state (time invariant) form, producing UFCSs. Steady state forms were closely similar for all targets despite different initial conditions. Bedload grain size has a strong control on this equilibrium form, related to the transit path of the grains when moving over the target, whilst initial target form has only a weak control. Steady state morphology is achieved more rapidly with harder erodent bedload particles and/or softer targets. Upstream-facing convex surface stoss sides were characterised by a brighter, sugary, granular appearance on the rock-forming grain scale. Increasing erodent grain size, for a fixed bedload mass, increased the bulk abrasion rate at fixed flow speed and discharge. No detectable erosion occurred for a limestone block in clear water flows under the same flow conditions, indicating solution and cavitation were insignificant mechanisms of erosion in this study. During the experiment suites, suspended load abrasion was also found to be an insignificant mechanism in eroding lee or lateral sides. In natural settings, the initial formation of UFCSs can occur for homogenous and/or jointed substrates in close association with plucking or, alternatively, for heterogeneous substrates by variation in substrate erodibility.

Structural characterization of inclusion complexes between cyanidin-3-O-glucoside and β-cyclodextrin

Inclusion complex formation between the multiple equilibrium forms of cyanidin-3-O-glucoside (cy3glc) and β-cyclodextrin (β-CD) was investigated using a combined approach of NMR spectroscopy and Molecular Dynamics simulation. Diffusion ordered NMR spectroscopy (DOSY) and study of nuclear Overhauser effects (NOE) were used to determine the selective intermolecular interactions and structure of these complexes in aqueous solution.The observed chemical shift displacements of resonance signals of protons from the interior of β-CD cavity and protons belonging to the hemiketal (B) and cis-chalcone forms (Cc), the diffusion measurements using DOSY and the NOE studies have anticipated the formation of an inclusion complex between these two forms and β-CD. The analysis of the NMR spectral data has shown no evidence of internal interaction between β-CD and the flavylium cation (AH+) or trans-chalcone (Ct) forms of cy3glc.The hemiketal formed a 1:1 inclusion complex with β-cyclodextrin in which the pyranic C ring is deeply included inside the β-CD cavity while B ring lies on the plane of the wider rim of β-CD. The structure of the complexes was also clarified through a theoretical approach by Molecular Dynamics simulation.

Catalyst-free synthesis of β-SiC polyhedra and α-SiC nano-platelets by RF thermal plasma

Based on the reuse of by-products in the silicone industry, a simple catalyst-free method has been developed for the synthesis of SiC powders in a thermal plasma system. Detailed structures of the as-prepared products were characterized. Crystals collected showed two types of morphologies, which were spheres and crystals with specific exposed facets. The spherical nanoparticles were attributed to high cooling rate of droplets. The latter ones can formed according to their crystal growth habits. As a result, the equilibrium forms of β-SiC were found to be polyhedra with regular or irregular shapes, while for α-SiC were mainly nano-platelets with (001) faces on the upper and basal planes and a few polyhedra based on platelets. By improving diffusion of reactants, the contaminations of products can be significantly reduced.

Finite-layer method: a unified approach to a numerical analysis of interlaminar stresses, large deflections, and delamination stability of composites

A square-law version of the geometrically nonlinear theory of bending of laminated composites with account of transverse normal and transverse shear strains is developed. The finite-layer method is used to analyze the effect of geometric nonlinearity on the stresses and deflections of an adhesively bonded joint and to reveal and estimate the stability of various equilibrium forms of a laminated plate with delaminations under compression.

Network of carboxypyranomalvidin-3-O-glucoside (vitisin A) equilibrium forms in aqueous solution

Abstract The equilibrium forms of carboxypyranomalvidin-3- O -glucoside (vitisin A) were studied in aqueous solution at different pH values by NMR and UV–Visible spectroscopy. The results obtained revealed the presence of three deprotonation reactions at positions 10-COOH, 7-OH and 4′-OH: p K a1 = 1.09 ± 0.09; p K a2 = 4.93 ± 0.02; p K a3 = 9.14 ± 0.05, data obtained from NMR titration. The titration by NMR confirmed the absence of hydration reactions since no characteristic peaks of the hemiketal form were observed in the NMR spectrum at any pD value studied (pD 0.67–10.99).

Probing the pattern of holographic thermalization with photons

We investigate the behavior of the retarded Green’s function of a U(1) gauge field in holographic $ \mathcal{N} $ = 4 Super Yang-Mills plasma, taking the leading strong coupling corrections into account. First, we use the thermal limit of this quantity to determine the flow of the photon quasinormal mode spectrum away from the infinite ’t Hooft coupling limit, and after this specialize to a specific model of holographic thermalization, in which we evaluate the corresponding spectral density. In the latter case, our primary interest lies in the pattern, with which the spectral density approaches its equilibrium form, and how this process depends on the value of the coupling as well as the photon virtuality. All of the results obtained point consistently towards the weakening of the usual top-down pattern of holographic thermalization, once the coupling is decreased from the λ = ∞ limit.

The incentive effect of acceptance sampling plans in a supply chain with endogenous product quality

AbstractThis article studies a firm that procures a product from a supplier. The quality of each product unit is measured by a continuous variable that follows a normal distribution and is correlated within a batch. The firm conducts an inspection and pays the supplier only if the product batch passes the inspection. The inspection not only serves the purpose of preventing a bad batch from reaching customers but also offers the supplier an incentive to improve product quality. The firm determines the acceptance sampling plan, and the supplier determines the quality effort level in either a simultaneous game or a Stackelberg leadership game, in which both parties share inspection cost and recall loss caused by low product quality. In the simultaneous game, we identify the Nash equilibrium form, provide sufficient conditions that guarantee the existence of a pure strategy Nash equilibrium, and find parameter settings under which the decentralized and centralized supply chains achieve the same outcome. By numerical experiments, we show that the firm's acceptance sampling plan and the supplier's quality effort level are sensitive to both the recall loss sharing ratio and the game format (i.e., the precommitment assumption of the inspection policy). © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013

Boradipyrromethenecyanines on the base of a BODIPY nucleus annelated with a pyridone ring: a new approach to long-wavelength dual fluorescent probe design

A number of polymethine dyes based on a BODIPY nucleus annelated with a pyridone ring have been synthesized. The merocyanines of this series are long-wavelength and intensive dyes. Obtained for the first time, asymmetrical anionic boradipyrromethenecyanines are also interesting from another viewpoint. These compounds are able to exist in several equilibrium forms which belong to polymethine or boradipyrromethene chromophoric systems. This results in the appearance of multicomponent bands in absorption and fluorescence spectra that may be used in the design of dual fluorescent probes.

Types of stable network structures based on exhaustive search

Based on the works of Doreian [Doreian, P., 2006. Actor network utilities and network evolution. Social Networks 28, 137–164] and Xie and Cui [Xie, F., Cui, W., 2008b. A note on the paper ‘cost range and the stable network structures’. Social Networks 30, 102–103], the paper applies exhaustive search and inductive approaches to analyze possible transitions among isomeric social networks with five vertices. A total of seven types of stable network structures are identified, which include the complete, star, chain, cycle, near-chain, near-cycle and null graphs. Then, a modified theorem for the equilibrium forms which corrects the previous work is presented.

Effects of the nanoassociation of hexadecyltrimethoxysilane precursors on the sol–gel process

Modifications to the refractive indices of meso-structured organic–inorganic films caused by variations in the mole fraction of precursors in ethanolic solutions were investigated. The refractive indices were dependent on the mole fraction of C16TMS (hexadecyltrimethoxysilane) and of the C16TMS/TMOS (tetramethoxysilane) (1/1) mixture in ethanol. The dependency was determined to be nonlinear, and the phenomenon was attributed to self-assembly caused by the long alkyl groups (C16) on the C16TMS. Changes in the maximum decreasing rate of dn/dx values [(dn/dx)max—for dn/dx estimation, the curves from Fig. 1 were associated with a polynomial; using a dedicated program, dn/dx was calculated; maximum values of dn/dx were taken into account and were included in Table 1)] were used to distinguish the behavior of alcoholic precursor mixtures. In the case of using pyrene as a fluorescent probe, the ratio between two peaks from the pyrene emission spectra (I1/I3) strongly decreased as hydrophobic micro-surroundings formed due to the self-assembly process. The UV–VIS spectra of a cationic dye solution, R6G, was studied because dilute solutions of the dye in equilibrium form measurable ratios of dimers and monomers. The absorbance was modified as micro-surroundings with different polarities were formed. These three methods demonstrated that nano-structuration was present prior to the occurrence of the sol–gel process. The combination of C16TMS with other alkyltrialkoxysilane precursors having hydrocarbon chain lengths between C1 and C8 provided further evidence for a nonlinear dependence of the refractive indice and fluorescence spectra of pyrene. The properties of the final hybrids obtained by the sol–gel process were significantly affected by the precursor hydrocarbon chain lengths. DSC, XRD and FTIR measurements were used to show the plasticizing phenomena of C16 as other alkyltrialkoxysilanes (i.e., C1–C8) were added.

Quasi-geostrophic shallow-water vortex–patch equilibria and their stability

We examine the equilibrium form, properties, stability and nonlinear evolution of steadily-rotating simply-connected vortex patches in the single-layer quasi-geostrophic model of geophysical fluid dynamics. This model, valid for rotating shallow-water flow in the limit of small Rossby and Froude numbers, has an intrinsic length scale L D called the “Rossby deformation length” relating the strength of the stratification to that of the background rotation. Here, we generate steadily-rotating vortex equilibria for a wide range of γ = L/L D , where L is the typical horizontal length scale of the vortex. We vary both γ (over the range 0.02 ≤ γ ≤ 10) and the vortex aspect ratio λ (over the range 0 < λ < 1). We find two modes of instability arising at sufficiently small aspect ratio λ < λ c (γ): an asymmetric (dominantly wave 3) mode at small γ (or large L D ) and a symmetric (dominantly wave 4) mode at large γ (or small L D ). At marginal stability, the asymmetric mode dominates for γ ≲ 3, while the symmetric mode dominates for γ ≳ 3. The nonlinear evolution of weakly-perturbed unstable equilibria results in major structural changes, in most cases producing two dominant vortex patches and thin, quasi-passive filaments. Overall, the nonlinear evolution can be classified into three principal types: (1) vacillations for a limited range of aspect ratios λ when 5 ≤ γ ≤ 6, (2) filamentation and a single-dominant vortex for γ ≲ 1, and (3) vortex splitting – asymmetric for 1 ≲ γ ≲ 4 and symmetric for γ ≳ 4.

Between cell‐level damage theories of ageing and whole organisms

In this issue, Vadim Gladyshev presents a framework for understanding cellular ageing and life-span and the distinction between the two 1. I start with this, and end by hinting at what a challenge now exists to integrate thinking at lower levels of organisational hierarchy to higher ones, and the reverse. Gladyshev's thesis 1 in brief: A typical enzyme with a single substrate will produce a product that is not 100% pure; a small percentage of ‘byproduct(s)’ is also produced. If the cell were a bottle factory (my analogy), this would equate to the accumulation of misshapen, useless, bottles. These would pile up and compromise the working of the factory: its production steadily declines, and in the end ceases. An accumulation of damage in the factory's machinery has the same effect, if not attended to. But the cell is not a factory: it can divide, hence diluting the unwanted byproducts and producing new, undamaged, cellular components. Division of damage is not strictly equal, however, and that has consequences, as we will see later. The bottom line: ageing is caused by myriad damaged forms, and life-span determined by mechanisms that dilute or combat them. A corollary that occurs to me is that a slight evolved ‘sloppiness’ is inherent to biological systems, because if it weren't, organisms would not demonstrate adaptive responses within and between generations. The procession of life is sustained by the same feature: propensity for, and response to, stochastic effects and imperfection/inhomogeneity. Perfect systems with predictable outputs do not ‘explore’ possibility space. But explorers expose themselves to more sources of damage than couch potatoes living a relatively predictable life. The scars and injuries of past adventures never fully heal. As a non-equilibrium manifestation of matter, life locally distorts the usual propensity for matter to order itself to the lowest energy – highest entropy – equilibrium form. By-products of energy metabolism and anabolic processes that order living organic matter accumulate slowly; slowly enough for no effective purging mechanisms to have evolved to combat many of them. Moreover, reactive oxygen species (ROS) even play a crucial role in the normal physiology of the cell, signalling mitochondria to expand. The cell does combat ROS, but it also ‘needs’ ROS. Cells also have mechanisms to repair damaged DNA, and dispose of damaged protein, but none functions perfectly: equilibrium chemistry and physics do leave their mark on life; but how much? If a cell divides at a fast rate, the mark is greatly lessened by damage dilution, according to Gladyshev 1. This conceptual framework elegantly accounts for certain properties of cancer cells, and the emergence of senescent cells during ageing: unequal division of damage upon cell division gradually leads to enough accumulated damage in the ‘mother’ cell to stop it dividing. And now for some ‘sleight of hand’, as we move up the systems biology hierarchy: senescence of a cell is bad news, alright, because damage can no longer be diluted by division; but worse still, for the whole organism – a mammal, to be precise – senescent cells are a positive ‘nuisance’. They don't just die, but contribute to ageing by releasing pro-inflammatory factors, compromising neighbours 2. Senescent cells are still far enough from the equilibrium organisation of matter to survive – just – but their host is in trouble. Immune surveillance culls such cells, but ever less efficiently as the immune system itself starts its own age-dependent decline. Organismal ageing-related phenomena can be partially de-coupled from cellular ageing by eliminating senescent cells 2, but it strikes me as interesting, also, to ascertain the damage threshold(s) for senescence and how they might vary. Gladyshev notes, importantly, that there are many types of damage-related processes and entities in cells; there is no single, simple, cause of cellular ageing. Therefore at the level of an organism – several organisational levels of hierarchy away from the individual cell – it would be surprising if the manifestation of ageing were anything but complex, and variable between organisms. Differences in immune systems and apoptotic thresholds in different organisms e.g. can also be claimed to be important factors influencing ageing. Which side is right? Both and neither. Systems biologists know that top-down causality exist as well as bottom-up; this could well mean that the symptoms of ageing – the organism-level effects, such as degenerative diseases – influence the cellular root. The nexus of cellular and organismal studies of ageing is an extremely fertile area that should receive more attention. Andrew Moore Editor-in-Chief

Numerical Solutions to the Logit Lane Assignment Model

The Logit lane assignment model is a macroscopic model for multi-lane flow. This model assumes that drivers evaluate the utility of available lanes, and that each driver chooses the lane with highest utility. The utility of a lane increases with the speed of traffic, and is stochastic with Gumbel random component. Since the speed of traffic on a lane, and hence the attractively of a lane, decreases with the number of cars using the lane, a (dynamic) equilibrium forms. This equilibrium results in the lane choice of drivers and the assignment of traffic between lanes. Formally it is a Logit model. The traffic flow is assumed multi-class, and FIFO on each lane, but not all lanes are available to all driver classes. The paper will address the homogeneous case, far from on-and off-ramps or intersections, where all lanes are accessible to all users. It will be shown that in the homogeneous case the total density follows a LWR model even though all lane speeds are different. The model can be expressed as a system of conservation laws with a smooth flux function, but analytical solutions are generally not available with very few exceptions. Thus numerical methods are required in order to use the model for applications. The paper will explore numerical methods in the case of a regular section.

Equilibrium forms of protein crystals

Models for equilibrium forms of protein crystals were suggested using classical methods, such as Stranski–Kaischew's mean-separation-work method and the Gibbs–Curie–Wulff law. Although absolute bonding energies in protein crystal lattices are unknown, their relative strength was estimated from the type of lattice contacts observed in the protein x-ray structures. Equilibrium forms of ferritin crystals deduced on this basis were compared with experimental observations of Yau and Vekilov.