Stages Of Cluster Growth Research Articles

Transcriptomic analysis of alternative splicing events for different stages of growth and development in Sistan Yaghooti grape clusters

Sistan Yaghooti grape variety, despite characteristics such as early ripening, is vulnerable to cluster rot due to small berries and dense clusters. In this regard, AS may serve as a regulatory mechanism during developmental processes and in response to environmental signals. RNA-Seq analysis was performed to measure gene expression and the extent of AS events in the cluster growth and development stages of Sistan Yaghooti grape. The number of AS events increased during stages, suggesting that it contributes to the grapevine's adaptability to various stresses. In addition, DEG and DAS genes showed little overlap in cluster growth stages. Functional analysis of 19,194 DAS -gene sets showed that VIT_06s0004g06670 gene is involved in the activation of calcium channels (Ca2+) through the activation of 5 PLC biosynthetic pathways. Among the 27,229 DEG -sets, VIT_07s0005g05320 gene showed higher expression. Interestingly, this gene is involved in the synthesis of an EF -hand domain-containing protein capable of binding to Ca2+ by activating 4 biochemical pathways. These genes increase cytosolic Ca2+ concentration, enhancing plant stress tolerance and resistance to cracking. These results show that AS can respond independently to different types of stress. Among the other DAS genes, the GA2ox gene (VvGA2ox) showed an increase in AS events during cluster development. This gene is critical for initiating the degradation process of GA and plays a crucial role in different stages of seed development. Therefore, it is very likely that this gene is one of the main factors responsible for the density and seedlessness of Sistan Yaghooti grape.

In Situ Study of Sputtering Nanometer-Thick Gold Films onto 100-nm-Thick Spiro-OMeTAD Films: Implications for Perovskite Solar Cells

The performance of many perovskite solar cells is closely related to the spiro-OMeTAD/gold interface since gold is used as top contacts, which renders the detailed understanding of the interface formation very important. In this work, sputter deposition as an industry-relevant, high-rate, large-scale, and well-controllable deposition technique is used to prepare gold electrodes on top of a 100-nm-thick spiro-OMeTAD film. In situ grazing-incidence small-angle X-ray scattering (GISAXS) is used to study the nanostructure-growth kinetics of the gold contact on top of the spiro-OMeTAD film during the sputter process. The results show that the gold grows in nanoscale clusters, which then coalesce into a complete yet still nanogranular layer forming the top contact with a thickness of 90 nm. Based on simulations of the two-dimensional GISAXS patterns, additional information about the shape of the nanosized gold cluster is gained at the different cluster growth stages. Furthermore, the diffusion of gold into the spiro-OMeTAD film occurs during the sputter process as verified with X-ray reflectivity. In a depth of 3.5 nm below the gold contact, the gold doping level of the spiro-OMeTAD film is 6.3% irrespective of the final gold contact thickness. Thus, the interface between the spiro-OMeTAD film and the Au contact is not sharp as commonly sketched and the contact is grainy, which will be both of importance for the performance of devices such as perovskite solar cells.

First Report of Pseudomonas syringae pv. syringae Associated with Bacterial Blossom Blast on Apple (Malus pumila) in the United States

In May 2017, dead buds at pink and tight cluster growth stages were observed on young apple trees of cultivar SnapDragon at two orchard sites in Marlboro, NY. Disease symptoms included necrosis of lateral and terminal flower buds that were wilted and drooping. Bark below the dead buds on severely affected trees showed black streaking with or without interspersing white streaks. On the cross-section of branch wood, just below the buds, light brown xylem and glossy water-soaked sections resembling frost damage were observed. After bark shaving, dark xylem tissue was visible along the branch length, in contrast to the light or pale color of the healthy tissue. The incidence of the disease on trees was 3 to 5%, and 0.5% of trees died. There were five near-frost events recorded on 4, 8, 9, 10, and 11 May 2017, leading us to suspect that the observed symptoms were blossom blast caused by the ice-nucleating strains of Pseudomonas syringae. Isolation from the affected tree samples was performed on King’s B (KB) and nutrient sucrose agar (NSA) media. After 3 days at 25°C, most of bacterial isolates formed round, shiny, gray-white colonies producing green fluorescent pigment on KB medium and typical levan-positive colonies on NSA. Eight isolates, inducing a hypersensitive reaction on tobacco plants, were further characterized by conventional bacteriological and molecular tests (Braun-Kiewnick and Sands 2001). The analyzed bacterial isolates were Gram-negative, aerobic, hydrolyzed gelatin and aesculin, but not pectate, and were negative for oxidase and arginine-dihydrolase activity. All strains were ice-nucleation active and utilized sucrose, sorbitol, and inositol as carbon sources, but not tyrosine and tartaric acid. Results of levan, cytochrome c oxidase, potato soft rot, arginine dihydrolase, and tobacco hypersensitive reaction (LOPAT) tests indicated that the isolates belong to P. syringae group Ia, and gelatin hydrolysis, aesculin hydrolysis, tyrosinase activity, and tartrate utilization (GATTa) tests designated them as pathovar (pv.) syringae (Kaluzna et al. 2012). Polymerase chain reaction (PCR) with specific primers B1/B2 (Sorensen et al. 1998) and SyD1/SyD2 (Bultreys and Gheysen 1999) showed that isolates possessed genes responsible for synthesis (syrB) and secretion (syrD) of syringomycin, respectively. Partial sequencing of the 16S rDNA gene of three isolates (GenBank MG788015 to MG788017) showed 99 to 100% identity with sequences of P. syringae pv. syringae previously deposited in the NCBI GenBank database. To complete Koch’s postulates, pathogenicity of the four isolates was confirmed by inoculation of 1-month-old potted apple plantlets grown from seeds collected from mature apple fruit of cultivar SnapDragon. One plant per isolate was inoculated multiple times as follows: using a needleless syringe, two leaves per plant were spot-infiltrated with bacterial suspension (10⁶ CFU/ml); on the same plants, stem was also inoculated by inserting a sterile toothpick previously dipped into a bacterial colony. Sterile distilled water was used as a negative control. Inoculated plantlets were sealed within plastic bags for 48 h and further incubated at 22°C. Inoculation test was repeated in two independent experiments. Necrosis of the leaf and stem tissue developed at the point of inoculation, and its progression was observed daily for 2 weeks. No symptoms developed on the control plants. Bacteria were reisolated from inoculated tissues and confirmed as P. syringae pv. syringae by PCR for syrB and syrD genes. This is the first report of P. syringae pv. syringae causing blossom blast symptoms on developing apple buds in commercial orchards in the United States. Even though it rarely occurs on apples, with most recent frosts significantly lowering apple yields in Michigan (2012) and New York (2016), blossom blast might become a more common problem in U.S. orchards. Previously, P. syringae pv. syringae was isolated from dormant apple buds without and with internal necrosis in the United States (Burr and Katz 1984).

Pulsed gas aggregation for improved nanocluster growth and flux

Growth of Cu nanoparticles in a pulsed gas aggregation cluster source was studied. The cluster growth is enhanced by an energy transport inside the aggregation chamber fed by argon that is delivered in short pulses repeated with low frequency. The effect of pressure, varied during the pulse, on the cluster growth was estimated from time‐resolved measurements of mass/size cluster distribution. The cluster mass and the cluster production well correlate with pressure changes. Several stages of cluster growth during the gas‐pulse were recognized. Not only larger clusters but also significantly enhanced particle and mass fluxes were observed.

Protses formuvannya nanostruktur na VdV-poverkhni krystaliv CdI2

Morphological characteristics of nano-sized defects and nanostructures formed on the surface of CdI2 layered crystals have been studied, and the processes of their growth under conditions close to the thermodynamic equilibrium have been analyzed. The formation of nano-sized structures – nanoclusters and nanopores – emerging on the CdI2 surface after holding the crystals in air for some time is revealed for the first time. A mechanism of cluster formation is proposed, which includes a number of stages of cluster growth; these are the nucleation, formation of separate noninteracting nanoaggregates, and association of the latter into agglomerates. The major morphometric characteristics of nanostructures – their average radius and height, and the average distance between the nearest neighbors – are analyzed.

Particle aggregation rate in a microchannel due to a dilute suspension flow

Particle-laden flow in a microchannel results in cluster formation and growth on the channel surface and the cluster growth, due to aggregation of polystyrene micropar- ticles, has been investigated in this study. In particular, the initial stage of cluster growth is examined, where particle- cluster interaction is the dominant growth mechanism. Both experimental measurements and theoretical considerations were utilized to explore the functional dependence of the cluster growth rate on the following parameters: suspension void fraction, flow shear strain rate, and channel-height to particle-diameter ratio. The growth rate of an average cluster is found to increase linearly with suspension void fraction which is consistent with previous reports. The growth rate coefficient is found to obey a power-law relationship with respect to the shear strain rate, and predictions based on the modernized flocculation theory agree well with the experi- mental results. Furthermore, the growth rate coefficient obeys a power-law relationship with respect to the channel-height to particle-diameter ratio as well, qualitatively similar to other reported studies. However, to our knowledge, the exponent value estimated in this study does not agree with any previ- ously published values; this disagreement is likely due to differences in experimental conditions.

Atomic force microscopy investigation of the kinetic growth mechanisms of sputtered nanostructured Au film on mica: towards a nanoscale morphology control

The study of surface morphology of Au deposited on mica is crucial for the fabrication of flat Au films for applications in biological, electronic, and optical devices. The understanding of the growth mechanisms of Au on mica allows to tune the process parameters to obtain ultra-flat film as suitable platform for anchoring self-assembling monolayers, molecules, nanotubes, and nanoparticles. Furthermore, atomically flat Au substrates are ideal for imaging adsorbate layers using scanning probe microscopy techniques. The control of these mechanisms is a prerequisite for control of the film nano- and micro-structure to obtain materials with desired morphological properties. We report on an atomic force microscopy (AFM) study of the morphology evolution of Au film deposited on mica by room-temperature sputtering as a function of subsequent annealing processes. Starting from an Au continuous film on the mica substrate, the AFM technique allowed us to observe nucleation and growth of Au clusters when annealing process is performed in the 573-773 K temperature range and 900-3600 s time range. The evolution of the clusters size was quantified allowing us to evaluate the growth exponent 〈z〉 = 1.88 ± 0.06. Furthermore, we observed that the late stage of cluster growth is accompanied by the formation of circular depletion zones around the largest clusters. From the quantification of the evolution of the size of these zones, the Au surface diffusion coefficient was evaluated in . These quantitative data and their correlation with existing theoretical models elucidate the kinetic growth mechanisms of the sputtered Au on mica. As a consequence we acquired a methodology to control the morphological characteristics of the Au film simply controlling the annealing temperature and time.

Dilute wet granular particles: Nonequilibrium dynamics and structure formation

We investigate a gas of wet granular particles covered by a thin liquid film. The dynamic evolution is governed by two-particle interactions, which are mainly due to interfacial forces in contrast to dry granular gases. When two wet grains collide, a capillary bridge is formed and stays intact up to a certain distance of withdrawal when the bridge ruptures, dissipating a fixed amount of energy. A freely cooling system is shown to undergo a nonequilibrium dynamic phase transition from a state with mainly single particles and fast cooling to a state with growing aggregates such that bridge rupture becomes a rare event and cooling is slow. In the early stage of cluster growth, aggregation is a self-similar process with a fractal dimension of the aggregates approximately equal to Df approximately 2 . At later times, a percolating cluster is observed which ultimately absorbs all the particles. The final cluster is compact on large length scales, but fractal with Df approximately 2 on small length scales.

S-dhybridization and evolution of the electronic and magnetic properties in small Co and Ni clusters

Photoelectron spectra of cold ${\mathrm{Ni}}_{n}^{\ensuremath{-}}$ and ${\mathrm{Co}}_{n}^{\ensuremath{-}}$ clusters revealed discrete electronic features for $n<10$ for Ni and 20 for Co. These features, mainly due to detachment of $4s$ electrons, merge with $3d$-derived features at larger cluster sizes, indicating the onset of significant s-d hybridization. The current results clearly revealed how the electronic structure of Ni and Co clusters evolves from molecular to bulklike in the early stage of cluster growth. They also provide insight into the origin of the enhanced magnetism in small Ni and Co clusters, due to the localized nature of the $3d$ electrons.

Rate equation approach to the late stages of cluster ripening

Off-critical phase separation processes are frequently described in literature on the basis of a set of rate equations describing the change rate of number of clusters of given size. This approach works very well for nucleation, but computational limitations and the complexity of processes impede its applicability in the early stages of cluster growth. Late stage clustering in mass conserved systems, which starts much later during the evolution of the morphology of the system, is well understood on the basis of the Lifshitz–Slyozov–Wagner (LSW) theory. In this paper both concepts are connected analytically, showing that identical predictions resulted for the same (simplified) assumptions. Significance of the equivalency of both models has been further explored, particularly in bridging the early stage of clustering, which is not well understood.

REFLECTION ELECTRON MICROSCOPY METHODOLOGY FOR QUANTIFICATION OF CLUSTER GROWTH: INDIUM CLUSTERS ON THE InP(110) SURFACE

Dynamical reflection electron microscopy (REM) can provide a wealth of time-resolved data pertinent to the initial and intermediate stages of cluster growth. REM allows one to follow and quantify the size and shape evolution of individual clusters. Average cluster size and cluster density data can be obtained as a function of time due to the large field of view produced by REM image foreshortening. We describe here a methodology for extracting these data from dynamical REM experiments, based on a geometrical model for the interpretation of REM images from two- and three-dimensional clusters. This methodology has been applied to studies of In cluster growth on InP (110) surfaces at 650°C. The average In cluster height and length initially increased as a fourth root of time, with a constant contact angle with the surface, consistent with surface-diffusion-limited growth of 3D clusters. The same behavior was found in the later stage of cluster growth, but the intermediate stage showed anomalous power laws for the cluster height and base length, accompanied by a decrease in the contact angle between the In clusters and the InP (110) surface. This anomalous regime can be explained by growth of In clusters into the InP substrate, when the true contact angle is no longer defined with respect to the InP(110) surface.

ChemInform Abstract: Clusters of Clusters: Self‐Organization and Self‐Similarity in the Intermediate Stages of Cluster Growth of Gold‐Silver Supraclusters

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Clusters of clusters: self-organization and self-similarity in the intermediate stages of cluster growth of Au-Ag supraclusters.

A systematic structural investigation of a new series of high-nuclearity Au-Ag clusters containing 25, 37, 38, and 46 metal atoms led to the description of these clusters as "clusters of clusters" based on vertex-sharing icosahedra as building blocks. Based on the observed structures, a growth sequence is proposed here for the formation of these secondary clusters (clusters of clusters) from a single 13-atom icosahedron to a 127-atom icosahedron of icosahedra via successive additions of vertex-sharing icosahedral units. This cluster-of-clusters growth mechanism parallels the atom-by-atom growth pathway for the primary clusters from a single atom to a 13-atom icosahedron. It is hypothesized that the formation of these clusters of clusters is a manifestation of the spontaneous self-organization and self-similarity processes often observed in nature. It is conceivable that the concept of cluster of clusters may be important in the intermediate stages of some cluster growth as exemplified by the polyicosahedral growth of Au-Ag supraclusters.

First stages of matter growth in a dynamical percolation model

We simulate the first stages of cluster growth in a time-dependent percolation model which unifies nucleation and coagulation processes. Calculated cluster distributions are compared with experimental data and found to be in good agreement.

Time evolution of heterogeneous thin films during annealing

The dynamical behaviour of heterogeneous thin films during annealing is studied, starting from a random atomic configuration. A computer simulation is performed for the lattice gas model using the Metropolis method. The relaxation behaviour of the atomic structure of the film is clarified for the island mode, layer mode and roughening mode. Fluctuation of the cluster edges appears to be much stronger in the case of two-dimensional clusters in the layer mode than in the case of three-dimensional clusters in the island mode, and the roughening temperature becomes lower in the former case. The condensation process during the annealing is divided into two stages: the initial stage in which single atoms on the substrate are captured into clusters and attain to a quasi-thermal equilibrium with clusters, and the subsequent stage of cluster growth. The clusters grow mainly through the evaporation and condensation of single atoms on clusters in the case of the island mode, and through diffusion and coalescence of clusters in the case of the layer mode.

Observation of shell structures in the growth of microcluster ions

We have observed shell structure manifested in the size distributions of various non-metallic cluster ions sequentially grown on seed positive ions generated by electron impact ionization in a pulsed supersonic jet. The data suggest the identification of the core ion and the placement of equivalent ligands about the core during the embryonic stages of cluster growth. A crown structure similar to that of H 3 +·(H 2) n , is indicated for H 3O +·(H 2) n ( n⪕4). Pentagonal bipyramid structures with five neutrals surrounding a dimer ion core are suggested by the (CO) n + ( n⪕19) and (N 2) n + ( n⪕14) cluster size distributions, whereas (CO 2) n + ( n⪕ 16) clusters appear to have a relatively amorphous structure. Variations in the cluster size distributions of Xe n + ( n⪕26) are correlated with the elongated icosahedral structure.

Isolation and morphologic characterization of human ovarian carcinoma cell clusters present in effusions.

Serous, mucinous, endometrioid and clear cell human ovarian carcinoma cells were isolated as multicellular aggregates from patient effusions by filtration on nylon mesh of defined porosity and examined by light microscopy. The cell clusters ranged from compact to loosely adherent groups of cells to spheroids with a central lumen surrounded by a cell monolayer. There was considerable variation in cluster morphology between effusions from different patients as well as within effusion from the same patient. Apparent budding of clusters was observed as well as different stages of cluster growth and development. This was observed for all histologic types studied. Electron microscopy of serous, mucinous and clear cell types showed that cells forming clusters were attached to each other by desmosomes, demonstrating that cluster formation did not result from a nonspecific stickiness of cells. Irregular microvilli were present on the external periphery of the various carcinoma cells and a prominent glycocalyx was present on the surface of mucinous carcinoma cells. Extensive interdigitation of cytoplasmic extensions and extended villi was present in mucinous and serous clusters which appeared to strengthen cluster cohesiveness. Nuclei were irregular with prominent nucleoli frequently present. The cell clusters usually remained intact and viable in culture but generally did not attach to glass or plastic substrata, whereas mesothelial cells and nonactivated histiocytes rapidly attached. When carcinoma cell clusters did attach, they were resistant to detachment by trypsin-EDTA treatment, in contrast to the nonmalignant cells.