Microscopic mechanisms of cooperative communications within single nanocatalysts

Catalysis is a method of accelerating chemical reactions that is critically important for fundamental research as well as for industrial applications. It has been recently discovered that catalytic reactions on metal nanoparticles exhibit cooperative effects. The mechanism of these observations, however, remains not well understood. In this work, we present a theoretical investigation on possible microscopic origin of cooperative communications in nanocatalysts. In our approach, the main role is played by positively charged holes on metal surfaces. A corresponding discrete-state stochastic model for the dynamics of holes is developed and explicitly solved. It is shown that the observed spatial correlation lengths are given by the average distances migrated by the holes before they disappear, while the temporal memory is determined by their lifetimes. Our theoretical approach is able to explain the universality of cooperative communications as well as the effect of external electric fields. Theoretical predictions are in agreement with experimental observations. The proposed theoretical framework quantitatively clarifies some important aspects of the microscopic mechanisms of heterogeneous catalysis.

Testing the adequacy of a simple theoretical model of dehydration optical clearing of collagen bundles: OCT measurements

Using optical coherence tomography, the scattering coefficients of collagen bundles are estimated at different levels of tissue hydration. We test the validity of a simple theoretical model of dehydration changes in the optical characteristics of a collagen bundle, which is considered as a system of parallel cylinders that model the collagen fibrils forming the bundle. The characteristics of scattering by individual scatterers are calculated using the Mie theory. To take into account the cooperative effects caused by the close packing of the scatterers, use is made of the standard packing function for a system of identical cylinders. The theoretical model also relies on a certain empirical law of changes in the hydration level of fibrils with a change in the water content in the tissue, which predetermines changes in the diameter and refractive index of fibrils during dehydration and rehydration of the tissue. It is shown that the theoretical estimates obtained using this model are in good agreement with the experimental data, which makes it possible to consider this model as reliable.

Cooperative effects of control parameters on the dynamic responses of vehicle powertrain during start-up process

The degradation of the frictional characteristics of a wet clutch, with repeated engagements throughout its full life, alters the dynamic responses of the powertrain, which weakens the effect of the control system with a fixed control law. To solve this problem, cooperative effects of control parameters on the dynamic responses of the vehicle start-up process throughout the full life cycle of the wet clutch were studied. First, the degradation law of the wet clutch frictional characteristics was obtained with a test rig, and the life cycle of wet clutch was divided into three stages, based on statistical data from the automobile factory. Then, the powertrain model of start-up process was developed and verified with a test. Finally, the cooperative effects of the hydraulic-pressure rising rate and the initial relative speed on the dynamic responses of the vehicle powertrain at the three stages of the clutch life were studied. The results revealed that the control parameters have different influences on the dynamic responses of the vehicle start-up at the different stages of wet clutch service life. To obtain good start-up performance, different optimal combinations of controllable parameters should be adopted at different stages of the wet-clutch service life.

Singularity Transition in Biosystem with Infinite Number of Conserved Links with Surroundings

Stages of natural evolution such as biogenesis and abiogenesis are the well-recognized terms to characterize the very different phases of life development. Traditionally, an abiogenesis is believed as the early stage of evolution that is mainly the chemistry phase dealing with intercoupling between the complex polymer chains when manifestations of life assumes substantial participation of cooperative effects. It its turn, a biogenesis as the subsequent stage of evolution is the period for prevalence of Darwin’s laws showing, in particular, in battle among separate species in the way of variability-heredity contest. In this article, we discuss possible nature of the transition between above stages as a normal result of progress in an evolutionary system simulated by mathematical model of open system with infinite number of conserved links with system surroundings. It is shown that the biosystem, in transition point experiences the deep reconstruction in existing pattern of energy exchange which leads to emergence of the more complicated and advanced stage of evolution. Our study showed that the found transition point can be considered as a singularity point in system evolution. In its turn, the evolution stages with the dissimilar meaning are the physical placeholders for stage of abiogenesis and biogenesis in natural evolution, correspondingly.

Salt-Enhanced Oxidative Addition of Iodobenzene to Pd: an Inter-play Between Cation, Anion and Pd-Pd Cooperative Effects

Halide salts facilitate the oxidative addition of organic halides to Pd(0). This phenomenon originates from a combina-tion of anionic, cationic and Pd-Pd cooperative effects. Exhaustive computational exploration at the DFT level of the com-plexes obtained from [Pd0(PPh3)2] and a salt (NMe4Cl or LiCl) showed that chlorides promote phosphine release, leading to a mixture of mononuclear and dinuclear Pd(0) complexes. Anionic Pd(0) dinuclear complexes exhibit a cooperativity between Pd(0) centers which favors the oxidative addition of iodobenzene. The higher activity of Pd(0) dimers toward oxidative addition rationalizes the previously reported kinetic laws. In the presence of Li+, the oxidative addition to mon-onuclear [Pd0L(Li2Cl2)] is estimated barrierless. LiCl coordination polarizes Pd(0), enlarging both the electrophilicity and the nucleophilicity of the complex, which promotes both coordination of the substrate and the subsequent insertion into the C-I bond. These conclusions are paving the way to the rational use of salt effect in catalysis for the activation of more challenging bonds.

Efficient light harvesting and photon sensing via engineered cooperative effects

Efficient devices for light harvesting and photon sensing are fundamental building blocks of basic energy science and many essential technologies. Recent efforts have turned to biomimicry to design the next generation of light-capturing devices, partially fueled by an appreciation of the fantastic efficiency of the initial stages of natural photosynthetic systems at capturing photons. In such systems extended excitonic states are thought to play a fundamental functional role, inducing cooperative coherent effects, such as superabsorption of light and supertransfer of photoexcitations. Inspired by this observation, we design an artificial light-harvesting and photodetection device that maximally harnesses cooperative effects to enhance efficiency. The design relies on separating absorption and transfer processes (energetically and spatially) in order to overcome the fundamental obstacle to exploiting cooperative effects to enhance light capture: the enhanced emission processes that accompany superabsorption. This engineered separation of processes greatly improves the efficiency and the scalability of the system.

Increase in Chymase-Positive Mast Cells in Recurrent Pleomorphic Adenoma and Carcinoma Ex Pleomorphic Adenoma of the Parotid Gland

Incomplete excision of pleomorphic adenoma (PA) may result in recurrent pleomorphic adenoma (RPA). Furthermore, long-term neglected PA may become carcinoma ex pleomorphic adenoma (CXPA). In the present study, the relationships between mast cell-derived chymase and these tumors were examined. The tumor tissues of PA consisted of either or both glandular and fibrotic structures. Histological features of RPA were almost similar to those of PA, except that they showed multinodular structures. CXPA is composed of a mixture of PA and carcinoma. The main stromal cells in PA were myofibroblasts, whereas fibroblasts constituted the main cellular portion in the stromal tissue of RPA. Cancer-associated fibroblasts (CAFs) were present abundantly in CXPA. With increased VEGF expression, neovascularization tended to increase in RPA or CXPA. Compared with PA, chymase-positive mast cells, as well as chymase gene expression, were increased in the tumor tissues from patients with RPA or CXPA. SCF, TGFβ1, and PCNA-positive staining was widely observed in these tumor tissues. The above results suggest that mast cell-derived chymase through its direct or cooperative effects with other mediators may participate in the pathophysiology of RPA and CXPA.

Why Sing and Dance: an Examination of the Cooperative Effects of Group Synchrony

<p>The universality and antiquity of music and dance suggest that they may serve some important adaptive function. Why are music and dance cultural universals? One popular theory is that music and dance function to enhance mutually benefiting cooperation. While the cooperation hypothesis finds support from anthropological observations and recent experiments, the proximate mechanisms remain unclear. In this thesis, I examine if being in synchrony is a critical factor underlying music and dance’s cooperative effects. I define synchrony as rhythmically moving or vocalising in time with others. In support of synchrony’s role in fostering cooperation, a number of studies exploring two person interactions have found positive social effects from synchrony. However, it is not clear whether synchrony enhances cooperation in groups larger than two as typical with music and dance. This thesis describes five laboratory experiments that were conducted to investigate: (1) whether group synchrony increases cooperation; and (2) which psychological mechanisms are involved in producing synchrony’s cooperative effects. In the first three experiments, small groups of participants were asked to perform body movements or to vocalise words in time with the same (synchrony condition) or different (asynchrony condition) metronome beats. Cooperative behaviour was measured with a helping scenario and an economic game. A small increase in cooperation was found with synchronous movement compared to asynchronous movement (experiment 1 and 3). However, this difference was only significant with the economic game measure (experiment 3). When vocalisation was isolated (experiment 2), contrary to expectations, the highest level of helping occurred after the asynchrony vocal condition. A plausible explanation for such small and inconsistent effects comes from the method in which synchrony was manipulated. Following previous methodologies, the goal for participants was to entrain to their own beat. Yet in natural human ecologies, synchrony is a product of shared intentionality – the sharing of psychological states to produce collaborative behaviour. To better understand the contribution of shared intentionality, experiments 4 and 5 varied synchrony with shared intentionality, and then measured cooperation. These experiments revealed that when participants worked together to create synchrony, substantial increases in cooperation were found, for both synchronous vocalisations (experiment 4) and for synchronous movements (experiment 5). Synchrony was also found to significantly amplify two key hypothesised mediating variables: perceived similarity and entitativity (the degree to which a collection of people are perceived as a group). Path analysis supported a proposed mechanism by which synchrony combines with shared intentionality to produce greater cooperation through: (1) increased attention to the behaviours of other participants; and (2) reinforcement of successful cooperation. This thesis, therefore, extends previous research on group music and dance in three ways. First, the combined effect of synchrony and shared intentionality is identified as critical to the cooperation enhancing effects of music and dance. Second, it describes plausible mechanisms for how synchrony may lead to increased cooperation. Third, it provides empirical evidence in support of these mechanisms.</p>

Why Sing and Dance: an Examination of the Cooperative Effects of Group Synchrony

<p>The universality and antiquity of music and dance suggest that they may serve some important adaptive function. Why are music and dance cultural universals? One popular theory is that music and dance function to enhance mutually benefiting cooperation. While the cooperation hypothesis finds support from anthropological observations and recent experiments, the proximate mechanisms remain unclear. In this thesis, I examine if being in synchrony is a critical factor underlying music and dance’s cooperative effects. I define synchrony as rhythmically moving or vocalising in time with others. In support of synchrony’s role in fostering cooperation, a number of studies exploring two person interactions have found positive social effects from synchrony. However, it is not clear whether synchrony enhances cooperation in groups larger than two as typical with music and dance. This thesis describes five laboratory experiments that were conducted to investigate: (1) whether group synchrony increases cooperation; and (2) which psychological mechanisms are involved in producing synchrony’s cooperative effects. In the first three experiments, small groups of participants were asked to perform body movements or to vocalise words in time with the same (synchrony condition) or different (asynchrony condition) metronome beats. Cooperative behaviour was measured with a helping scenario and an economic game. A small increase in cooperation was found with synchronous movement compared to asynchronous movement (experiment 1 and 3). However, this difference was only significant with the economic game measure (experiment 3). When vocalisation was isolated (experiment 2), contrary to expectations, the highest level of helping occurred after the asynchrony vocal condition. A plausible explanation for such small and inconsistent effects comes from the method in which synchrony was manipulated. Following previous methodologies, the goal for participants was to entrain to their own beat. Yet in natural human ecologies, synchrony is a product of shared intentionality – the sharing of psychological states to produce collaborative behaviour. To better understand the contribution of shared intentionality, experiments 4 and 5 varied synchrony with shared intentionality, and then measured cooperation. These experiments revealed that when participants worked together to create synchrony, substantial increases in cooperation were found, for both synchronous vocalisations (experiment 4) and for synchronous movements (experiment 5). Synchrony was also found to significantly amplify two key hypothesised mediating variables: perceived similarity and entitativity (the degree to which a collection of people are perceived as a group). Path analysis supported a proposed mechanism by which synchrony combines with shared intentionality to produce greater cooperation through: (1) increased attention to the behaviours of other participants; and (2) reinforcement of successful cooperation. This thesis, therefore, extends previous research on group music and dance in three ways. First, the combined effect of synchrony and shared intentionality is identified as critical to the cooperation enhancing effects of music and dance. Second, it describes plausible mechanisms for how synchrony may lead to increased cooperation. Third, it provides empirical evidence in support of these mechanisms.</p>