Giant Cluster Research Articles

Cooperative Soft-Cluster Glass in Giant Molecular Clusters

Three-dimensional giant molecular clusters, OPOSS16 and OPOSS24, have been designed and precisely synthesized. They have 16 or 24 octyl polyhedral oligomeric silsesquioxane (OPOSS) building blocks ...

Evolutionary framework of the human interactome: Unicellular and multicellular giant clusters

The main contradiction of multicellularity (MCM) is between the unicellular (UC) and multicellular (MC) levels. In human interactome we revealed two giant clusters with MC and UC medians (and several smaller ones with MC medians). The enrichment of these clusters by phylostrata and by functions support the MC versus UC division. The total interactome and the giant clusters show a core-periphery evolutionary growth. From viewpoint of the MCM, the most important is the placement of genes, appearing at UC evolutionary stage, in the MC clusters. Thus, genes involved in vesicle-mediated transport, cell cycle, cellular responses to stress, post-translational modifications and many diseases appeared at UC evolutionary stage but are placed mostly in MC clusters. Genes downregulated with age are enriched in UC cluster, whereas the upregulated genes are preferentially placed in MC giant cluster. The tumor suppressor and pluripotency regulating pathways are also enriched in MC giant cluster. Therefore, this cluster probably operates as 'internal manager' constraining runaway unicellularity. The clusters have denser interactions within than between them, therefore they can serve as attractors (stable states of dynamic systems) of cellular programs. Importantly, the UC cluster have a higher inside/outside connection ratio compared with MC clusters, which suggests a stronger attractor effect and may explain why cells of MC organisms are prone to oncogenesis. The evolutionary clustering of human interactome elucidates the MC control over functions appearing at UC evolutionary stage and can build a framework for biosystems studies focusing on the interplay between UC and MC levels.

The Giant SALR Cluster Fluid: A Review

AbstractRecent developments in understanding the behavior of equilibrium fluids with competing short‐range attractions and long‐range repulsions at low concentration are reviewed. Typically, this SALR model system is used to represent solutions where at least one of the solute species interacts via a screened‐Coulomb potential, which includes many colloidal, nanoparticle, and polyelectrolyte solutions among others. Provided neither the short‐range nor long‐range interactions are too strong, and the concentration remains sufficiently low, discrete spherical clusters of solute are expected, here called “Giant SALR clusters.” Because these clusters can themselves be disordered, as though fluid particles with a renormalized interaction, such cluster fluids cannot be treated using standard mean field methods. This review therefore focuses on theoretical routes that aim to overcome this difficulty. The main outcomes of these theories are highlighted and their application to soft matter and especially biology, including complex coacervates, membraneless organelles, and the origin of life is discussed.

Beam dynamics of the racetrack-shape fixed field induction accelerator

Beam dynamics of the racetrack-shape fixed field induction accelerator for giant cluster ions were established. Linear optics theory and Runge-Kutta particle tracking approaches were developed, and the consistency between two approaches was confirmed. Use of gradient field bending magnets with a reverse field strip and ramping quadrupole doublets were crucial to achieve the orbit stability. A physically limited size of the huge bending magnet in the longitudinal direction generated the inherent closed-orbit distortion that substantially affected the orbit stability. In addition, the inherent field component ${B}_{s}$ along the orbit coordinate ``$s$'' induced horizontal-vertical (H-V) couplings. A possible correction method of this closed-orbit distortion was proposed. A net effect of the H-V coupling was evaluated. Longitudinal motion with a time-varying transition energy, which is one of characteristic features in the racetrack-shape fixed field induction accelerator, was studied with the help of computer simulations.

Fragility and anomalous susceptibility of weakly interacting networks.

Percolation is a fundamental concept that has brought new understanding of the robustness properties of complex systems. Here we consider percolation on weakly interacting networks, that is, network layers coupled together by much fewer interlinks than the connections within each layer. For these kinds of structures, both continuous and abrupt phase transitions are observed in the size of the giant component. The continuous (second-order) transition corresponds to the formation of a giant cluster inside one layer and has a well-defined percolation threshold. The abrupt transition instead corresponds to the merger of coexisting giant clusters among different layers and is characterized by a remarkable uncertainty in the percolation threshold, which in turns causes an anomalous behavior of the observed susceptibility. We develop a simple mathematical model able to describe this phenomenon, using a susceptibility measure that defines the range where the abrupt transition is more likely to occur. Finite-size scaling analysis in the abrupt region supports the hypothesis of a genuine first-order phase transition.

Giant Water Clusters: Where Are They From?

A new mechanism for the formation and destruction of giant water clusters (ten to hundreds of micrometers) is proposed. Our earlier hypothesis was that the clusters are associates of liquid-crystal spheres (LCS), each of which is formed around a seed particle, a microcrystal of sodium chloride. In this study, we show that the ingress of LCSs into water from the surrounding air is highly likely. We followed the evolution of giant clusters during the evaporation of water. When a certain threshold of the ionic strength of a solution is exceeded, the LCSs begin to “melt”, passing into free water, and the salt crystals dissolve, ensuring re-growth of larger crystals as a precipitate on the substrate. A schematic diagram of the dynamics of phase transitions in water containing LCSs during evaporation is proposed. The results illustrate the salt dust cycle in nature.

Assembly of the Actin Catalyst WASP by Giant SALR Cluster Formation

AbstractSome structures in living cells behave like organelles, but lack individual membranes. The mechanisms that produce such "membraneless organelles" are not understood, but are commonly thought to involve the formation of separate phases via liquid–liquid phase separation. Here, an alternative mechanism is investigated involving short‐range attraction, long‐range repulsion (SALR) fluids, applied at model biological membrane–cytoplasm interfaces. Using Monte Carlo simulations, it is found that giant SALR clusters can form at the membrane surface even when they are unstable in the bulk, for suitably chosen model parameters. It is also found that the formation and location of giant SALR clusters at the interface can be controlled by a third protein species confined to the membrane surface. This behavior mimics that of WASP puncta at the cell membrane, thought to involve WASP and Nck protein aggregates controlled by clathrin. The SALR mechanism is thus a good model for this system, and for membraneless organelles more generally.

Variable stars in Palomar 13; an evaporating globular cluster

We present new CCD VI photometry of the distant globular cluster Pal 13. Fourier decomposition of the light curves of the three cluster member RRab stars lead to estimations of [Fe/H] = −1.65, and a distance of 23.67 ± 0.57 kpc. Light and colour near minimum phases for RRab stars leads to an estimate of E(B−V)=0.104 ± 0.001. A V/(V−I) colour-magnitude diagram, built exclusively with likely star members, shows consistency with the above parameters and an age of 12 Gyrs. A search of variable stars in the field of view of our images revealed the variability of a red giant cluster member and of three probably non-member stars; two RRab stars and one W Virginis star or CW. The GAIA proper motions of member stars in Pal 13 show a significant scatter, consistent with the scenario of the cluster being tidally stripped.

Big to Small: Ultrafine Mo2 C Particles Derived from Giant Polyoxomolybdate Clusters for Hydrogen Evolution Reaction.

Due to its electronic structure, similar to platinum, molybdenum carbides (Mo2 C) hold great promise as a cost-effective catalyst platform. However, the realization of high-performance Mo2 C catalysts is still limited because controlling their particle size and catalytic activity is challenging with current synthesis methods. Here, the synthesis of ultrafine β-Mo2 C nanoparticles with narrow size distribution (2.5 ± 0.7 nm) and high mass loading (up to 27.5 wt%) on graphene substrate using a giant Mo-based polyoxomolybdate cluster, Mo132 ((NH4 )42 [Mo132 O372 (CH3 COO)30 (H2 O)72 ]·10CH3 COONH4 ·300H2 O) is demonstrated. Moreover, a nitrogen-containing polymeric binder (polyethyleneimine) is used to create MoN bonds between Mo2 C nanoparticles and nitrogen-doped graphene layers, which significantly enhance the catalytic activity of Mo2 C for the hydrogen evolution reaction, as is revealed by X-ray photoelectron spectroscopy and density functional theory calculations. The optimal Mo2 C catalyst shows a large exchange current density of 1.19 mA cm-2 , a high turnover frequency of 0.70 s-1 as well as excellent durability. The demonstrated new strategy opens up the possibility of developing practical platinum substitutes based on Mo2 C for various catalytic applications.

The research advances and genetic model of the giant Dexing Cu-Au ore cluster

The research advances and genetic model of the giant Dexing Cu-Au ore cluster

Suppression effect on the Berezinskii-Kosterlitz-Thouless transition in growing networks

Since the discovery a half century ago that 1/r^2-type long-range interactions in the one-dimensional Ising model change the phase transition type, long-range interactions in diverse systems have received considerable attention. Recently, this interest extended to global suppression dynamics in the percolation transition, which changes a second-order transition to first order. Here, we investigate how the Berezinskii-Kosterlitz-Thouless (BKT) transition is changed by the global suppression effect. In fact, this effect often arises in real-world complex systems, yet it is not appropriately accounted for in models. We find that the BKT transition breaks down, but the features of infinite-, second-, and first-order transitions all emerge as the link occupation probability is controlled. Moreover, we find that such growing networks exhibit maximum diversity, causing the mean cluster size to diverge without formation of a giant cluster. We elucidate the underlying mechanisms and show that such anomalous transitions are universal.

Cooperation percolation in spatial evolutionary games

It has been known that the formation of cooperator clusters plays an important role in spatial evolutionary games. By gathering together, cooperators assist each other and the benefits of mutual cooperation can outweigh the losses against the defector. In this letter, we study the dynamical organization of cooperator clusters in the spatial Stag Hunt game, the Prisoner's Dilemma game and the Snowdrift game. For the above games in square lattices, there exists a continuous phase transition characterized by the emergence of a large spanning cooperator cluster which occurs when the initial fraction of the cooperators exceeds a certain threshold. For games in random graphs, there exist two different kinds of phase transitions. At the first the normalized size of the giant cooperator cluster increases continuously from zero, and at the second the normalized size of the giant cooperator cluster jumps from a low value to a very high value.

Popularity enhances the interdependent network reciprocity

Interdependent networks (IN) are collections of non-trivially interrelated graphs that are not physically connected, and provide a more realistic representation of real-world networked systems as compared to traditional isolated networks. In particular, they are an efficient tool to study the evolution of cooperative behavior from the viewpoint of statistical physics. Here, we consider a prisoner dilemma game taking place in IN, and introduce a simple rule for the calculation of fitness that incorporates individual popularity, which in its turn is represented by one parameter α. We show that interdependence between agents in different networks influences the cooperative behavior trait. Namely, intermediate α values guarantee an optimal environment for the evolution of cooperation, while too high or excessively low α values impede cooperation. These results originate from an enhanced synchronization of strategies in different networks, which is beneficial for the formation of giant cooperative clusters wherein cooperators are protected from exploitation by defectors.

Emergence of Shear Bands in Confined Granular Systems: Singularity of the q-Statistics.

The statistics of grain displacements probability distribution function (pdf) during the shear of a granular medium displays an unusual dependence with the shear increment upscaling as recently evinced (see “experimental validation of a nonextensive scaling law in confined granular media”). Basically, the pdf of grain displacements has clear nonextensive (q-Gaussian) features at small scales, but approaches to Gaussian characteristics at large shear window scales—the granulence effect. Here, we extend this analysis studying a larger system (more grains considered in the experimental setup), which exhibits a severe shear band fault during the macroscopic straining. We calculate the pdf of grain displacements and the dependency of the q-statistics with the shear increment. This analysis has shown a singular behavior of q at large scales, displaying a non-monotonic dependence with the shear increment. By means of an independent image analysis, we demonstrate that this singular non-monotonicity could be associated with the emergence of a shear band within the confined system. We show that the exact point where the q-value inverts its tendency coincides with the emergence of a giant percolation cluster along the system, caused by the shear band. We believe that this original approach using Statistical Mechanics tools to identify shear bands can be a very useful piece to solve the complex puzzle of the rheology of dense granular systems.

POLARIMETRIC RESEARCH OF PHARMACEUTICAL SUBSTANCES IN AQUEOUS SOLUTIONS WITH DIFFERENT WATER ISOTOPOLOGUES RATIO

Objective: Methodology development for quality control of optically active pharmaceutical substances based on water isotopologues.Methods: Solutions of L-ascorbic acid, glucose, galactose and valine stereoisomers were prepared using deuterium depleted water (DDW-«light» water, D/H=4 ppm), natural deionized high-ohmic water (BD, D/H=140 ppm), heavy water (99.9% D2O). The optical rotation was observed using an automatic polarimeter Atago POL-1/2. The size distribution of giant heterogeneous clusters (GHC) of water was recorded by low angle laser light scattering (LALLS) method.Results: The infringement of Biot’s Law was found for solutions of ascorbic acid, expressed in the absence of a constant value of the specific optical rotation at a concentration of below 0.1%, depends on the D/H ratio. The inequality was established in absolute values of optical rotation for L-and D-isomers of valine in solutions with different ratios of hydrogen isotopologues. The mutarotation of glucose confirmed the first-order kinetics, and the activation energies were statistically distinguishable for BD and DDW. The mutarotation of the natural galactose D-isomer proceeded with a lower energy consumption compared to the L-isomer. In heavy water, the mutarotation of monosaccharides had different kinetic mechanisms. Polarimetric results correlated with the number and size of GHC, which confirmed the possibility of chiral solvent structures induction by optically active pharmaceutical substances.Conclusion: In the optically active pharmaceutical substances quality control there should be considered the contribution of induced chiral GHC of water to the optical rotation value that depends on the isotopic D/H ratio, the substance nature and the form of its existence at a given pH.

Incorporation of Ions into Giant Molybdenum-oxide Cluster as a General Phenomenon

In spite of the integration and concomitant release of all 16 {Mo1} (necessary for ions Recently, the integration of different kinds of matter into giant wheel-shaped molybdenum-oxide clusters has been investigated with so-called chemical adaptability phenomenon. This refers to the integration of a large number of appropriate cations and anions even of the large “salt like” {M(SO4)}16 rings (M = K+ or NH4+) based on the cooperative/synergetic activation of silent receptor sites. An even more remarkable consequence of the flexibility behavior of the molecular giant wheel-shaped molybdenum-oxides of the type {Mo176} and {Mo154}: the possibility of the integration of Cu2+ as tetrahedrally coordinated divalent cations at the same wheel area. In this study and in order to make the phenomenon as a general, the incorporation of ions into giant molybdenum-oxide cluster was expanded to involve the integration of some other cations (Fe2+, Co2+, Ni2+ or Zn2+) or salt like ring{Tl(SO4)}16. Uptake and almost half of the 16 {Mo2} units the parent ring structure is maintained in the following resulting hybrids {(Mo146) (K(SO4))16} 1compound, {(Mo146) (NH4(SO4))16} 2 compound and {(Mo146) (Tl(SO4))16} 3. Moreover, the integrating of a tetrahedrally coordinated divalent cation like Fe2+, Co2+, Ni2+ or Zn2+ in addition to Cu2+, at the same wheel area (after releasing six {Mo2}-type building blocks of the parent wheel-shaped cluster) produced hybrid compounds with the general formula: [H4MIIn MoV28MoVI114O432(H2O)58]-26+2(n-5) (where MII= Fe2+, Co2+, Ni2+ or Cu2+, n=5, but with Zn2+, n=6) compounds (4–8). The result corresponds to the extreme flexibility of molybdenum-oxide building block linking resulting in the formation of a huge variety of structures from “molybdate” containing solutions (a unique molybdenum-oxide diversity phenomenon). The prepared compounds were characterized by CHN, Cit.Tit for the determination of the number of the MoV centers, spectroscopic methods (IR and UV-Vis) and X-ray crystallography (determination of the characteristic unit cell dimensions).

Genome-Based Identification of a Plant-Associated Marine Bacterium as a Rich Natural Product Source.

The large number of sequenced bacterial genomes provides the opportunity to bioinformatically identify rich natural product sources among previously neglected microbial groups. Testing this discovery strategy, unusually high biosynthetic potential was suggested for the Oceanospirillales member Gynuella sunshinyii, a Gram-negative marine bacterium from the rhizosphere of the halophilic plant Carex scabrifolia. Its genome contains numerous unusual biosynthetic gene clusters for diverse types of metabolites. Genome-guided isolation yielded representatives of four different natural product classes, of which only alteramide A was known. Cytotoxic lacunalides were identified as products of a giant trans-acyltransferase polyketide synthase gene cluster, one of six present in this strain. Cytological profiling against HeLa cells suggested that lacunalide A disrupts CDK signaling in the cell cycle. In addition, chemical studies on model compounds were conducted, suggesting the structurally unusual ergoynes as products of a conjugated diyne-thiourea cyclization reaction.

The X-ray binary populations of M81 and M82

AbstractWe use deep Chandra and HST data to uniquely classify the X-ray binary (XRB) populations in M81 on the basis of their donor stars and local stellar populations (into early-type main sequence, yellow giant, supergiant, low-mass, and globular cluster). First, we find that more massive, redder, and denser globular clusters are more likely to be associated with XRBs. Second, we find that the high-mass XRBs (HMXBs) overall have a steeper X-ray luminosity function (XLF) than the canonical star-forming galaxy XLF, though there is some evidence of variations in the slopes of the sub-populations. On the other hand, the XLF of the prototypical starburst M82 is described by the canonical powerlaw (αcum ∼ 0.6) down to LX ∼ 1036 erg s−1. We attribute variations in XLF slopes to different mass transfer modes (Roche-lobe overflow versus wind-fed systems).

Cluster formation in binary fluids with competing short-range and long-range interactions

The equilibrium phase behaviour of a model binary fluid is investigated through Monte Carlo simulations and by developing a molecular thermodynamic model. Both fluid components interact through a hard core with short-range attractions (SA), but one of the components exhibits an additional long-range repulsion (SA+LR). We find that phase behaviour for this system is controlled by the cross-interaction between the two types of particles as well as their chemical potentials. For a weak cross-interaction, the system displays behaviour that is a composite of the behaviour of the individual components, i.e. the SA component can display bulk vapour/liquid phase separation, while the SALR component can display giant micelle-like clusters for a suitable combination of SA and LR interactions. For a strong cross-interaction, qualitatively different behaviour is observed, with the resulting clusters typically composed of a more equal mixture of SA and SALR particles. Moreover, these mixed clusters can exist even when the SA component by itself would be undersaturated or supercritical, and/or when the SALR component by itself would not form giant clusters. These insights should help to identify the mechanisms for clustering in experimental systems where giant equilibrium clusters are observed.

{Nb288 O768 (OH)48 (CO3 )12 }: A Macromolecular Polyoxometalate with Close to 300 Niobium Atoms.

A protein-sized (ca. 4.2×4.2×3.6 nm3 ) non-biologically derived molecule {Nb288 O768 (OH)48 (CO3 )12 } (Nb288 ) containing up to 288 niobium atoms has been obtained, which is by far the largest and the highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb288 is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb288 can be described as a giant windmill-like cluster aggregate of six nanoscale high-nuclearity PONb units {Nb47 O128 (OH)6 (CO3 )2 } (Nb47 ) joined together by six additional Nb ions. Interestingly, the 47-nuclearity Nb47 units generated in situ can be isolated and bridged by copper complexes to form an inorganic-organic hybrid three-dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb47 cluster also provides a new type of topology to very limited family of Nb-O clusters.