Restructuring Behavior Research Articles

Single-Molecule Nanocatalysis Reveals Facet-Dependent Catalytic Kinetics and Dynamics of Pallidium Nanoparticles

By studying the nanocatalysis of individual Pd nanoparticles (Pd NPs) in two shapes (cube with (100) facet and octahedron with (111) facet) with single-turnover resolution, the facet-dependent activities and dynamics were apparently observed. The results indicate that Pd octahedrons possess higher intrinsic catalytic activity per site than Pd nanocubes. Within a competitive Langmuir–Hinshelwood mechanism, the facet-dependent activities are derived at single-particle level, and the facet-dependent adsorption behaviors of substrate molecules on Pd(111) and Pd(100) are revealed and clarified by theoretical calculation. Furthermore, the facet-dependent restructuring behaviors of the particle surfaces were also observed. This study gives deeper insight into Pd-based nanocatalysts.

Comment caractériser et traiter les plaintes de sommeil dans les troubles bipolaires ?

ObjectivesSleep complaints are very common in bipolar disorders (BD) both during acute phases (manic and depressive episodes) and remission (about 80 % of patients with remitted BD have poor sleep quality). Sleep complaints during remission are of particular importance since they are associated with more mood relapses and worse outcomes. In this context, this review discusses the characterization and treatment of sleep complaints in BD. MethodsWe examined the international scientific literature in June 2016 and performed a literature search with PubMed electronic database using the following headings: “bipolar disorder” and (“sleep” or “insomnia” or “hypersomnia” or “circadian” or “apnoea” or “apnea” or “restless legs”). ResultsPatients with BD suffer from sleep and circadian rhythm abnormalities during major depressive episodes (insomnia or hypersomnia, nightmares, nocturnal and/or early awakenings, non-restorative sleep) and manic episodes (insomnia, decreased need for sleep without fatigue), but also some of these abnormalities may persist during remission. These remission phases are characterized by a reduced quality and quantity of sleep, with a longer sleep duration, increased sleep latency, a lengthening of the wake time after sleep onset (WASO), a decrease of sleep efficiency, and greater variability in sleep/wake rhythms. Patients also present frequent sleep comorbidities: chronic insomnia, sleepiness, sleep phase delay syndrome, obstructive sleep apnea/hypopnea syndrome (OSAHS), and restless legs syndrome (RLS). These disorders are insufficiently diagnosed and treated whereas they are associated with mood relapses, treatment resistance, affect cognitive global functioning, reduce the quality of life, and contribute to weight gain or metabolic syndrome. Sleep and circadian rhythm abnormalities have been also associated with suicidal behaviors. Therefore, a clinical exploration with characterization of these abnormalities and disorders is essential. This exploration should be helped by questionnaires and documented on sleep diaries or even actimetric objective measures. Explorations such as ventilatory polygraphy, polysomnography or a more comprehensive assessment in a sleep laboratory may be required to complete the diagnostic assessment. Treatments obviously depend on the cause identified through assessment procedures. Treatment of chronic insomnia is primarily based on non-drug techniques (by restructuring behavior and sleep patterns), on psychotherapy (cognitive behavioral therapy for insomnia [CBT-I]; relaxation; interpersonal and social rhythm therapy [IPSRT]; etc.), and if necessary with hypnotics during less than four weeks. Specific treatments are needed in phase delay syndrome, OSAHS, or other more rare sleep disorders. ConclusionsBD are defined by several sleep and circadian rhythm abnormalities during all phases of the disorder. These abnormalities and disorders, especially during remitted phases, should be characterized and diagnosed to reduce mood relapses, treatment resistance and improve BD outcomes.

Portfolio Restructuring in Family and Non-Family-Controlled Firms

Are family firms’ corporate restructuring behaviors distinct from those of non-family firms? Although the corporate restructuring literature has drawn on economic motives for restructuring, recent ...

Structural Reorganization and Fibrinogen Adsorption Behaviors on the Polyrotaxane Surfaces Investigated by Sum Frequency Generation Spectroscopy.

Polyrotaxanes, such as supramolecular assemblies with methylated α-cyclodextrins (α-CDs) as host molecules noncovalently threaded on the linear polymer backbone, are promising materials for biomedical applications because they allow adsorbed proteins possessing a high surface flexibility as well as control of the cellular morphology and adhesion. To provide a general design principle for biomedical materials, we examined the surface reorganization behaviors and adsorption conformations of fibrinogen on the polyrotaxane surfaces with comparison to several random copolymers by sum frequency generation (SFG) vibrational spectroscopy. We showed that the polyrotaxane (OMe-PRX-PMB) with methylated α-CDs as the host molecule exhibited unique surface structures in an aqueous environment. The hydrophobic interaction between the methoxy groups of the methylated α-CD molecules and methyl groups of the n-butyl methacrylate (BMA) side chains may dominate the surface restructuring behavior of the OMe-PRX-PMB. The orientation analysis revealed that the orientation of the fibrinogen adsorbed on the OMe-PRX-PMB surface is close to a single distribution, which is different from the adsorption behaviors of fibrinogen on other polyrotaxane or random copolymer surfaces.

Stability of restructured non-fractal aggregates in simple shear flow

The restructuring behavior of non-fractal aggregates in simple shear flow is numerically investigated. The change in internal structure of aggregates having different packing properties is examined by Lagrangian simulation method. The many-body hydrodynamic interaction is rigorously estimated by Stokesian dynamics approach while the adhesion of aggregate is manifested via particle–particle interaction. The simulation results show that the restructuring of aggregate originates from the superimposition of rotational and extensional component of simple shear flow. The aggregate rearranges its particles so that a stable structure corresponding to the applied shear flow is obtained. The stable structure is considered as dynamic equilibrium resulting from the balance of the forming and the disintegrating of the bonds between particles. The stable structure of aggregate is dependent strongly on shear condition but weakly on initial structure of aggregate. Despite of the significant difference in the initial packing properties, the stable structure reveals only slightly different. The dependence of stable structure on high shear tress condition is similar for all aggregates. The difference in stable structure of aggregate at low shear stress arises from the irreversible behavior of particle from quasi-stable structure to static structure.

Regional Unemployment and the Restructuring of Distressed State-owned Enterprises: Evidence from China

:Using Chinese listed companies as the sample, we investigate the effects and corresponding consequences of regional unemployment rates on the restructuring behavior of distressed state-owned enterprises (SOEs). We find that layoffs and asset downsizing of local SOEs will be limited greatly when the unemployment rates of the areas where SOEs are located are high, even though these firms are already in distress. Additional evidence shows that this kind of limitation causes these firms to show a long-term decline in performance. The CEOs of these firms, however, are not easily dismissed after the distress. These results provide empirical support for the “grabbing hand“ theory.

In Situ Probing the Surface Restructuring of Antibiofouling Amphiphilic Polybetaines in Water.

Antibiofouling materials have a wide range of applications in biomedical devices and marine coatings. Due to the amphiphilic nature of proteins and organisms, amphiphilic materials have been designed to resist their unspecific adsorption. Surface restructuring behavior of amphiphilic materials in water is believed to play a key role in the antibiofouling mechanisms. In this work, the surface structures of several amphiphilic polybetaine coatings in water have been probed in situ using sum frequency generation (SFG) vibrational spectroscopy. These are novel polybetaines constructed from functionalized polynorbornenes. The polybetaines with oligo(ethylene glycol) (OEG), octyl (C8), or fluorinated (F13) side chains exhibit different surface restructuring behaviors upon contacting water due to their different surface hydrophobicity. The OEG and C8 chains were present and ordered at the water interface, while the F13 chain withdrew from water. The hydrophilic betaine group extended into the water and formed hydrogen bonds with water molecules. The surface restructuring of these materials detected using SFG can be well correlated to their antibiofouling performance, providing an understanding of their antibiofouling mechanisms.

Corporate restructuring and product market behaviour

This article investigates the relationship between product market behaviour and corporate restructuring policies. We focus on two types of corporate restructuring events: acquisitions and divestitures. We find that 1 year after acquisition, acquiring firms on average experience long-term deteriorating product market performance. In addition, acquiring firms in industries with less competition have worse performance in subsequent years. In comparison, divesting firms experience no significant change in the performance after divestitures. Last, we document that a sustainable product market improvement is related to higher stock market valuation while a temporary improvement have negative effects. Therefore, we show that corporate restructuring has an important firm-value implication through the channel of product market effects.

Exploring surface science and restructuring in reactive atmospheres of colloidally prepared bimetallic CuNi and CuCo nanoparticles on SiO2in situ using ambient pressure X-ray photoelectron spectroscopy

Bimetallic nanoparticles (to approximately 11 nm diameter) of CuNi and CuCo were prepared by a new synthetic route and the 1:1 atomic ratio of their constituent elements confirmed using STEM-EDS at a single particle level. These nanoparticles, supported on the native oxide layer of a silicon wafer, were studied in situ in a series of reactive gas atmospheres (H2 --> CO or CO/H2 --> O2 --> H2) using ambient pressure X-ray photoelectron spectroscopy (AP-XPS). Despite the deliberate similarity of nickel and cobalt with respect to copper, their restructuring behaviour is different. CuNi nanoparticles were found to surface segregate nickel in H2, but copper in O2 reversibly, while CuCo nanoparticles were found to surface segregate copper irreversibly when exposed to O2, such that the surface remains copper rich when re-exposed to H2. Both systems also restructure in opposition to the behaviour predicted by the surface free energies and enthalpies of oxide formation of the elements from which they are comprised--factors that are seen to control restructuring and surface segregation in many similar systems.

Subsidiary divestiture and acquisition in a financial crisis: Operational focus, financial constraints, and ownership

We exploit parent- and subsidiary-level data for publicly listed firms in Thailand before, during, and after the 1997 Asian Financial Crisis to investigate the extent to which firms with different types of ownership restructure their business portfolios, in terms of divestitures and acquisitions. We compare restructuring choices made by firms mostly owned by (a) domestic individuals with block shares (family firms), (b) domestic firms and/or institutions (DI firms), and (c) foreign investors (foreign firms). We show that following the crisis (1) foreign firms' restructuring behavior is the least affected; (2) domestic firms owned by families and domestic institutions (DI) behave similarly to one another; (3) domestic firms do not increase divestiture in their peripheral segments to improve operational focus or to obtain cash in a credit crunch; they actually reduce divestiture in core segments; and (4) domestic firms also significantly reduce the acquisition of new subsidiaries. Our results challenge traditional explanations for divestiture such as corporate governance, operational refocus, and financial constraints. They indicate that in the great uncertainty of a crisis, domestic firms are able to hold onto their core assets to avoid fire-sale. In essence, they act more conservatively in churning their business portfolios.

Evolution of Structure and Chemistry of Bimetallic Nanoparticle Catalysts under Reaction Conditions

Three series of bimetallic nanoparticle catalysts (Rh(x)Pd(1-x), Rh(x)Pt(1-x), and Pd(x)Pt(1-x), x = 0.2, 0.5, 0.8) were synthesized using one-step colloidal chemistry. X-ray photoelectron spectroscopy (XPS) depth profiles using different X-ray energies and scanning transmission electron microscopy showed that the as-synthesized Rh(x)Pd(1-x) and Pd(x)Pt(1-x) nanoparticles have a core-shell structure whereas the Rh(x)Pt(1-x) alloys are more homogeneous in structure. The evolution of their structures and chemistry under oxidizing and reducing conditions was studied with ambient-pressure XPS (AP-XPS) in the Torr pressure range. The Rh(x)Pd(1-x) and Rh(x)Pt(1-x) nanoparticles undergo reversible changes of surface composition and chemical state when the reactant gases change from oxidizing (NO or O(2) at 300 degrees C) to reducing (H(2) or CO at 300 degrees C) or catalytic (mixture of NO and CO at 300 degrees C). In contrast, no significant change in the distribution of the Pd and Pt atoms in the Pd(x)Pt(1-x) nanoparticles was observed. The difference in restructuring behavior under these reaction conditions in the three series of bimetallic nanoparticle catalysts is correlated with the surface free energy of the metals and the heat of formation of the metallic oxides. The observation of structural evolution of bimetallic nanoparticles under different reaction conditions suggests the importance of in situ studies of surface structures of nanoparticle catalysts.

Restructuring of colloidal aggregates in shear flows and limitations of the free-draining approximation

We investigated the restructuring behavior of colloidal aggregates by means of the discrete element method. We used a recently proposed model [V. Becker, H. Briesen, Physical Review E 78 (6) (2008) 061404] for tangential inter-particle forces, capable of supporting bending moments. We extended this model by the capability of supporting torsional moments. The time evolution of the aggregates’ radius of gyration was tracked and a power law relation between the number of primary particles and the final radius of gyration was found. For the hydrodynamic drag forces the free-draining approximation is employed. We investigated the quality of the free-draining approximation by fully resolved finite element simulations for small aggregates. We found that the free-draining approximation overestimates the drag forces and we identified the usage of effective shear rates as a possible ansatz for reduced modeling of hydrodynamic forces.

The molecular surface conformation of surface-tethered polyelectrolytes on PDMS surfaces

Surface properties of polymer materials are important for many applications such as biomedical materials, marine antifouling coatings, polymer membranes for biological and chemical molecule separations, and polymer adhesives. Surface properties are highly dependent on molecular surface structures. Presently, surface polymerization is one of the most effective methods to tailor and optimize molecular surface structures of many polymers. Herein, the surface structure of polydimethylsiloxane (PDMS) is modified by tethering polyelectrolytes (PEs) through surface-initiated ultraviolet (UV) polymerization. Using dimethylacrylamide, acrylic acid, and [2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium as monomers, cationic, anionic, and zwitterionic PEs are grafted onto PDMS surfaces using the “graft-from” method. Successful grafting of PEs onto PDMS surfaces has been verified by several analytical techniques, including Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurement. In particular, sum-frequency generation (SFG) vibrational spectroscopy has been employed to probe the molecular structure of modified PDMS surfaces in both the dry and hydrated states. It was found that in air, the surface dominating –Si–CH3groups of unmodified PDMS segregate to the PDMS surface along with the grafted PEs. These methyl groups have similar orientations to those on the unmodified PDMS surface: they more or less stand up on the surface, along the surface normal. Upon exposure to water, only SFG signals from the surface-tethered PE chains on the modified PDMS surface are observed, showing a substantial surface restructuring behavior. More details regarding such surface restructuring behavior can be deduced through SFG data analysis. With numerous PDMS applications in aqueous environments, it is of particular importance to modify its surface structures and characterize such surface structures in aqueous environments in situ.

Molecular Level Structures of Poly(n-alkyl methacrylate)s with Different Side Chain Lengths at the Polymer/Air and Polymer/Water Interfaces

Sum frequency generation (SFG) vibrational spectroscopy has been successfully applied to study molecular structures of several poly(n-alkyl methacrylate)s (PAMAs) with different side chain lengths at the PAMA/air and PAMA/water interfaces. We have observed that the ester side chains from all PAMAs always dominate the interface, but the orientation information of the methyl end group on the side chains varies, depending on the length of the side chain. The contributions from methylene groups on the side chains have been evaluated, and the surface structures have been related to the surface tension of these polymers. Different water restructuring behaviors have been observed for different PAMAs. This phenomenon and its reversibility are strongly dependent on the glass transition temperature of each polymer, which is influenced by the side chain length. Detailed data fitting and analysis has been discussed.

Conformational changes at polymer gel interfaces upon saturation with various liquids studied by infrared-visible sum frequency generation vibrational spectroscopy

Molecular restructuring at the free surface of poly(2-hydroxyethyl methacrylate) (PHEMA) films and the buried interface with a sapphire substrate due to submersion into deuterated water (D2O) and acetonitrile (d3ACN) was investigated by infrared-visible sum frequency generation (SFG) vibrational spectroscopy. Film hydration by saturation with D2O and d3ACN resulted in polymer swelling. Because of the amphiphilic nature of PHEMA, direct information about polymer restructuring was obtained due to the existence of hydrophilic and hydrophobic moieties. SFG results provided insight into the restructuring behavior at the PHEMA surface and buried interface upon swelling due to the diffusion of the two different liquids.

Comparison of surface structures of poly(ethyl methacrylate) and poly(ethyl acrylate) in different chemical environments

Sum frequency generation (SFG) vibrational spectroscopy has been applied to investigate and compare the chemical structures of poly(ethyl methacrylate) (PEMA) and poly(ethyl acrylate) (PEA) in air, in water, and in a non-polar solvent, FC-75. SFG spectra from both polymer surfaces in air are dominated by vibrational modes from the ester ethyl side groups. The average orientation of these ester ethyl groups on the two polymer surfaces is slightly different. In water, the two polymers show markedly different restructuring behavior. The ester ethyl side chains on the PEMA surface in water reorient to tilt more toward the surface, yet remain ordered. Such a restructuring of the PEMA surface in water is reversible. However, no SFG signal was detected from the PEA/water interface, showing that the surface of PEA becomes disordered upon contacting water, and this process is irreversible. SFG results collected from the C=O range indicate that hydrogen bonding is observed for both polymer/water interfaces, but the order of C=O at the PEA/water interface is much lower than that at the PEMA/water interface. Supplemental experiments support our hypothesis that the PEA surface becomes rough and loses order gradually as it interacts with water. We have demonstrated, for the first time, that the loss of surface structural order is due to the interaction between soft PEA chains with water molecules followed by reorganization of the polymer backbone. This causes the polymer surface to become rough and disordered. However, the surface structures of PEMA and PEA in FC-75 are similar and are also similar to those in air. This indicates that not only T(g), but also the contacting medium plays an important role in determining the surface restructuring behavior of polymer materials.

Surface Restructuring Behavior of Various Types of Poly(dimethylsiloxane) in Water Detected by SFG

Surface structures of several different poly(dimethylsiloxane) (PDMS) materials, tetraethoxysilane-cured hydroxy-terminated PDMS (TEOS-PDMS), platinum-cured vinyl-terminated PDMS (Pt-PDMS), platinum-cured vinyl-terminated poly(diphenylsiloxane)-co-poly(dimethylsiloxane) (PDPS-co-PDMS), and PDMS-co-polystyrene (PDMS-co-PS) copolymer in air and water have been investigated by sum frequency generation (SFG) vibrational spectroscopy. The SFG spectra collected from all PDMS surfaces in both air and water are dominated by methyl group stretches, indicating that all the surfaces are mainly covered by methyl groups. Other than surface-dominating methyl groups, some -Si-CH2-CH2- moieties on the Pt-PDMS surface have also been detected in air, which are present at cross-linking points. Information about the average orientation angle and angle distribution of the methyl groups on the PDMS surface has been evaluated. Surface restructuring of the methyl groups has been observed for all PDMS surfaces in water. Upon contacting water, the methyl groups on all PDMS surfaces tilt more toward the surface. The detailed restructuring behaviors of several PDMS surfaces in water and the effects of molecular weight on restructuring behaviors have been investigated. For comparison, in addition to air and water, surface structures of PDMS materials mentioned above in a nonpolar solvent, FC-75, have also been studied. By comparing the different response of phenyl groups to water on both PDPS-co-PDMS and PS-co-PDMS surfaces, we have demonstrated how the restructuring behaviors of surface phenyl groups are affected by the structural flexibility of the molecular chains where they are attached.

Morphology and chemical structure of poly(methyl methacrylate) surfaces and interfaces: restructuring behavior induced by the deposition of SiO 2

The surface morphology, molecular structure, and the surface restructuring behavior after the deposition of a SiO 2 layer on poly(methyl methacrylate) (PMMA) have been investigated by using atomic force microscopy (AFM) in contact mode and sum-frequency generation (SFG) vibrational spectroscopy. AFM images show that the surface of PMMA is quite flat and sporadically contains dendritic features, which are micro-crystalline structures of PMMA. From the SFG measurements, the ester methyl groups of PMMA are pointed away from the surface plane at least in the surface region. By depositing a SiO 2 film, the SFG signal intensity is significantly reduced, indicating that the CO and the ester methyl groups are aligned nearly parallel to the surface plane.

The Limits of Discipline: Ownership and Hard Budget Constraints in the Transition Economies

The existing literature on soft budget constraints suggests that firms may be subsidized for political reasons or because of the creditors' desire to recover a part of the sunk cost invested in an earlier period. In all these models hard budget constraints are viewed as being, in principle, capable of inducing the necessary restructuring behaviour on the level of the firm. This paper argues that the imposition of financial discipline is not sufficient to remedy ownership and governance‐related deficiencies of corporate performance. Using evidence from the post‐communist transition economies, the paper shows that a policy of hard budget constraints cannot induce successful revenue restructuring, which requires entrepreneurial incentives inherent in certain ownership types (most notably, outside investors). The paper also shows that the policy of hard budget constraints falters when state firms, because of inferior revenue performance and less willingness to meet payment obligations, continue to pose a higher credit risk than privatized firms. The brunt of state firms' lower creditworthiness falls on state creditors. But the ‘softness’ of these creditors, while harmful in many ways, is not necessarily irrational, if it prevents the demise of firms that are in principle capable of successful restructuring through ownership changes.

Particle network re-structuring in highly-concentrated ceramic suspensions

In this study, the restructuring behavior of particle networks in highly-concentrated zirconia-wax suspensions as model suspensions is investigated in terms of temperature and solids concentration. The restructuring kinetics is analytically determined such that it can be formulated by a linear correlation between the relative viscosity (ηr) of the suspensions and the logarithmic time (t) of isothermal annealing. Upon restructuring, a gelling point tgel, defined as the time period of which the discrete particle networks in the pre-sheared suspensions are observed to start to form a continuous structure. Above tgel, a sharp increase in suspension viscosity is commonly observed. The tgel varies as a function of both temperature and solids concentration, The temperature effect provides valuable information for a better understanding of the restructuring behavior from an energy viewpoint. The influence of solids concentration, i.e., the tgel decreased linearly with increasing solid concentration, suggests a stronger interparticle attraction that further accelerates flocculation.