Star-shaped Clusters Research Articles

Polyamide thin-film nanocomposite membrane containing star-shaped ZIF-8 with enhanced water permeance and PPCPs removal

Pharmaceuticals and personal care products (PPCPs) are universally detected in natural waters, posing potential risks to drinking water safety. Nanofiltration (NF) is an advanced technology for water purification; however, its removals of PPCPs are unsatisfying, especially for hydrophobic species. In this study, the 3D architecture of nanomaterials were used to manipulate the performance the polyamide (PA) thin-film nanocomposite (TFN) membrane. In-situ addition of polyethyleneimine (PEI) successfully induced the assembly of ZIF-8 nanocrystals into star-shaped clusters (ZIF-8-PEI) due to the coordination between PEI and Zn2+. Together with the improved hydrophilicity, these ZIF-8-PEI clusters became excellent scaffolds for water drop retention after discretely loading onto the porous substrate. The conical protrusions of the ZIF-8-PEI clusters supported the defect-free PA film produced by the interfacial polymerization (IP), leaving big interfacial cavities underneath. These cavities worked as gutters for water transport, and the water permeance of the optimal TFN was 79% higher than that of the pristine thin-film composite (TFC) membrane. Moreover, the water impregnated cavities markedly alleviated the hydrophobic interaction between the PA film and hydrophobic PPCPs, impeding the transport of PPCPs across the membrane. Our results demonstrated the importance of the 3D architecture of nanofillers for the improving membrane performance.

Influence of Quaternary environmental changes on mole populations inferred from mitochondrial sequences and evolutionary rate estimation

Quaternary environmental changes fundamentally influenced the genetic diversity of temperate-zone terrestrial animals, including those in the Japanese Archipelago. The genetic diversity of present-day populations is taxon- and region-specific, but its determinants are poorly understood. Here, we analyzed cytochrome b gene (Cytb) sequences (1140 bp) of mitochondrial DNA (mtDNA) to elucidate the factors determining the genetic variation in three species of large moles: Mogera imaizumii and Mogera wogura, which occur in central and southern mainland Japan (Honshu, Shikoku, and Kyushu), and Mogera robusta, which occurs on the nearby Asian continent. Network construction with the Cytb sequences revealed 10 star-shaped clusters with apparent geographic affinity. Mismatch distribution analysis showed that modes of pairwise nucleotide differences (τ values) were grouped into five classes in terms of the level, implying the occurrence of five stages for rapid expansion. It is conceivable that severe cold periods and subsequent warm periods during the late Quaternary were responsible for the population expansion events. The first and third oldest events included island-derived haplotypes, indicative of the involvement of land bridge formation between remote islands, hence suggesting an association of the ends of the penultimate (PGM, ca. 130,000 years ago) and last (LGM, ca. 15,000 years ago) glacial maxima, respectively. Since the third event was followed by the fourth, it is plausible that the termination of the Younger Dryas and subsequent abrupt warming ca. 11,500 years ago facilitated the fourth expansion event. The second event most likely corresponded to early marine isotope stage (MIS) 3 (ca. 53,000 years ago) when the glaciation and subsequent warming period were predicted to have influenced biodiversity. Utilization of the critical times of 130,000, 53,000, 15,000, and 11,500 years ago as calibration points yielded evolutionary rates of 0.03, 0.045, 0.10 and 0.10 substitutions/site/million years, respectively, showing a time-dependent manner whose pattern was similar to that seen in small rodents reported in our previous studies. The age of the fifth expansion event was calculated to be 5800 years ago with a rate of 0.10 substitutions/site/million years ago during the mid-Holocene, suggestive of the influence of humans or other unspecified reasons, such as the Jomon marine transgression.

Структура и свойства экзотических нано- и мезоалмазов пентагональной симметрии

A review of studies on the structures of exotic nano-, meso- and microdiamonds with dodecahedral and icosahedral symmetry (N/MDPS) is presented. The unique, complex atomic and electronic structure of N/MDPS, due to its high dodecahedral or icosahedral symmetry, leads to promising transport and mechanical properties that are very promising for photonic, quantum and nanomechanical applications. To explain the nature of diamonds, theoretical models were proposed based on the formation of twinned structures consisting of 5 and 20 symmetrically equivalent tetrahedral and prismatic fragments of a face-centered cubic lattice with the formation of star-shaped and icosahedral clusters. It was shown that these twinned nano- and meso-diamonds are limited in size due to the accumulation of uncompensated structural stresses arising from the deviation of angles from the ideal 72º between diamond <111> facets in tetrahedral fragments of a face-centered cubic lattice, up to 70.5º between five symmetrically equivalent twinned fragments.

A green algae (Chaetophorales: Chaetophoraceae) in Burmese amber

ABSTRACT A green alga in Burmese amber is described as Electrophycus astroplethus gen. et spec. nov. and tentatively placed in the extant family Chaetophoraceae. The new species is characterised by apical–basal polarity as defined by a holdfast located at the base of the filament cluster, and uniseriate filaments with many attached star-shaped clusters of spines. Reproductive units are produced in the spines. The species is considered to represent a terrestrial aerial alga that quite possibly was growing on the bark of the resin-producing tree. The presence of an oribatid mite (Acari: Oribatida), species of which are known to feed on algae, adjacent to the filaments, supports this view.

AUTOMATON: A Program That Combines a Probabilistic Cellular Automata and a Genetic Algorithm for Global Minimum Search of Clusters and Molecules.

A novel program for the search of global minimum structures of atomic clusters and molecules in the gas phase, AUTOMATON, is introduced in this work. This program involves the following: first, the generation of an initial population, using a simplified probabilistic cellular automaton method, which allows easy control of the adequate distribution of atoms in space; second, the fittest individuals are selected to evolve, through genetic operations (mating and mutations), until the best candidate for a global minimum surfaces. In addition, we propose a simple way to build the descendant structures by establishing a ranking of genes to be inherited. Thus, by means of a chemical formula checker procedure, genes are transferred to the offspring, ensuring that they always have the appropriate type and number of atoms. It is worth noting that a fraction of the fittest group is subject to mutation operations. This program also includes algorithms to identify duplicate structures: one based on geometric similarity and another on the similar distribution of atomic charges. The effectiveness of the program was evaluated in a group of 45 molecules, considering organic and organometallic compounds (benzene, cyclopentadienyl anion, and ferrocene), Zintl ion clusters [Sn9- m- nGe mBi n](4- n)- ( n = 1-4 and m = 0-(9- n)), star-shaped clusters (Li7E5+, E = BH, C, Si, Ge) and a variety of boron-based clusters. The global minimum and the lowest-energy isomers reported in the literature were found for all the cases considered in this article. These results successfully prove AUTOMATON's effectiveness on the identification of energetically preferred structures of a wide variety of chemical species.

Temporal Order in Periodically Driven Spins in Star-Shaped Clusters.

We experimentally study the response of star-shaped clusters of initially unentangled N=4, 10, and 37 nuclear spin-1/2 moments to an inexact π-pulse sequence and show that an Ising coupling between the center and the satellite spins results in robust period-2 magnetization oscillations. The period is stable against bath effects, but the amplitude decays with a timescale that depends on the inexactness of the pulse. Simulations reveal a semiclassical picture in which the rigidity of the period is due to a randomizing effect of the Larmor precession under the magnetization of surrounding spins. The timescales with stable periodicity increase with net initial magnetization, even in the presence of perturbations, indicating a robust temporal ordered phase for large systems with finite magnetization per spin.

Fission Track Detection Using Automated Microscopy

Detection of microscopic fission track (FT) star-shaped clusters, developed in a solid state nuclear track detector (SSNTD) by etching, created by fission fragments emitted from particles of fissile materials irradiated by neutrons, is a key technique in nuclear forensics and safeguards investigation. It involves scanning and imaging of a large area, typically 100–400 mm2, of a translucent SSNTD (e.g., polycarbonate sheet, mica, etc.) to identify the FT clusters, sparse as they may be, that must be distinguished from dirt and other artifacts present in the image. This task, if done manually, is time consuming, operator dependent, and prone to human errors. To solve this problem, an automated workflow has been developed for (a) scanning large area detectors, in order to acquire large images with adequate high resolution, and (b) processing the images with a scheme, implemented in ImageJ, to automatically detect the FT clusters. The scheme combines intensity-based segmentation approaches with a morphological algorithm capable of detecting and counting endpoints in putative FT clusters in order to reject non-FT artifacts. In this paper, the workflow is described, and very promising preliminary results are shown.

Building and Analyzing of Enterprise Network

Social business moves beyond linear, process-driven organizations to create new, dynamic, networked businesses that focus on customer value. Enterprise network (EN) is used to support social business by maximizing current and future opportunities and facilitate network-enabled processes, which can lead to value co-creation. EN is a multi-level hypergraph model with enterprises, employees, products and other related entities. In this paper the authors refine the EN model and present the foundation of EN to support social businesses. Then they introduce a case study on China automobile supply network (CASN). For the similarity with social networks, they verify power-law and small world theories in EN with statistical results on this data set. These theories are fitful in EN, but some new characteristics exist. The structure of EN consists of star-shaped clusters and the authors extract ego networks taking suppliers and manufacturers as the ego respectively. With the structure and distribution features of EN, they present the enterprise business similarity analysis method based on common-neighbors. And they also introduce the tentative work to detect Dunbar circles in EN. To analyze the data in a more intuitional and effective way, the authors use some data visualization tools to process the data in EN.

Optimization of the Processing of Data Streams on Roughly Characterized Distributed Resources

The AS4DR (Adaptive Scheduling for Distributed Resources) scheduling method presented in this paper aims at maximizing throughput, when processing several data streams by divisible load applications on star-shaped distributed memory platforms, with available speeds for communicating and computing which may be poorly estimated, or varying over time. The total workload is supposed to be unknown. According to the computation cost model, AS4DR can either maximize throughput, or CPU utilization by avoiding data-starvation of the computing units. An experimental assessment of the adaptation of the workload distribution to the variation of the communicating and computing speeds has been performed that shows that the use of AS4DR can significantly improve the throughput. This paper also experimentally assesses a resource selection method to set up star-shaped clusters of distributed resources, so as to process efficiently a set of data streams with AS4DR.

Phylogenetic analysis of Aceh cattle breed of Indonesia through mitochondrial D-Loop region.

The objective of this research was to find the basic data on genetic diversity of mtDNA D-Loop in Aceh cattle and its association with Bhutanese, Chinese, and Indian cattle. There were sixty samples of DNA which had been sequenced; i.e. Banda Aceh (11), Saree (20), and Indrapuri (29). To the best of our knowledge this is the first published data on the complete mitochondrial D-Loop sequence of Aceh cattle. Results show that Aceh cattle have the closest relationship to Bos indicus and have been influenced by Bos taurus. The closest genetic ranges among Aceh cattle, Bhutanese, Chinese, Indian and Zebu were Aceh–Zebu (0.0138), Aceh–Bhutanese (0.0156), Aceh–Chinese (0.0190) and Aceh–Indian (0.0193). D-Loop mtDNA analyses showed that there were 27 haplotypes in which twenty-one samples spread in haplotype 1, two samples were in haplotype 2, and the other four haplotypes had various samples in the range of three to seventeen samples. One sample of Aceh cattle from Saree has a closest maternal genetic with B. taurus. One of the four mutations among the star-shaped clusters on median joining network was a new specific haploid-group in Aceh cattle. From this finding it could be assumed that Aceh cattle form a specific haplotype and it can be conclude that Aceh cattle are animal genetic resources from Aceh in Sumatera Island that have to be preserved.

Global Maize Trade and Food Security: Implications from a Social Network Model

In this study, we developed a social network model of the global trade of maize: one of the most important food, feed, and industrial crops worldwide, and critical to food security. We used this model to analyze patterns of maize trade among nations, and to determine where vulnerabilities in food security might arise if maize availability was decreased due to factors such as diversion to nonfood uses, climatic factors, or plant diseases. Using data on imports and exports from the U.N. Commodity Trade Statistics Database for each year from 2000 to 2009 inclusive, we summarized statistics on volumes of maize trade between pairs of nations for 217 nations. There is evidence of market segregation among clusters of nations; with three prominent clusters representing Europe, Brazil and Argentina, and the United States. The United States is by far the largest exporter of maize worldwide, whereas Japan and the Republic of Korea are the largest maize importers. In particular, the star-shaped cluster of the network that represents U.S. maize trade to other nations indicates the potential for food security risks because of the lack of trade these other nations conduct with other maize exporters. If a scenario arose in which U.S. maize could not be exported in as large quantities, maize supplies in many nations could be jeopardized. We discuss this in the context of recent maize ethanol production and its attendant impacts on food prices elsewhere worldwide.

Empty liquid state and self-assembly of high valence non-spherical colloidal systems

A vapour–liquid phase coexistence with vanishing critical volume fraction (empty liquid) is predicted in some model systems of attractive hard ellipsoids. The trends in critical density and temperature do not depend on the ellipsoid shape and the range of the square-well attraction. Our theoretical and simulation studies show transparently that the empty liquid limit is due to the competition between the anisotropic attractive and repulsive interactions. Additionally, the nematic phase is destabilized by the square-well attraction for both prolate and oblate shapes. The demand to maximize the number of bonds while keeping a relatively low excluded volume leads to special structures such as the cubatic and star-shaped cluster phases at low temperatures. The liquid branch of the vapour–liquid binodal is always isotropic for oblates, while it can be isotropic or cluster-like for prolates. Our results predict the occurrence of an empty liquid state in high valence anisotropic colloidal systems.

A Novel Approach for Finding Clusters from Complex Networks

A feasible structural clustering method based on breadth-first-search is proposed for graphs. Clustering is very important and widely used in analyzing complex networks such as community identification. There are clusters with different shapes such as cliques and stars in practical application. Some existing algorithms can find clique-shaped clusters, but they are unable to identify star-shaped clusters that are familiar in scale free networks. A feasible solution is provided to solve the problem. It is super ior to other algorithms in one or several of the following aspects: An algorithm without any input parameters, Running time on a network with n nodes and m links is O ( n ), Extracting clusters of mixed shapes.

A Search Algorithm for Clusters in a Network or Graph

A novel breadth-first based structural clustering method for graphs is proposed. Clustering is an important task for analyzing complex networks such as biological networks, World Wide Web and social networks. The clusters are of various shapes such as cliques and stars, for example, in ProteinProtein Interactive(PPI) networks. Traditional algorithms may detect clique-shaped clusters, but they fail to identify star-shaped clusters that are common in scale free networks, including PPI networks. We propose a novel clustering algorithm to solve the problem. Experimental results demonstrate it outperforms other algorithms in one or several aspects: Detecting clusters of mixed shapes, including both cliques and stars; Faster. Its running time on a network with n nodes and m links is O(n), which is much faster than O(mdlogn) of the fastest modularity-based algorithm(where d is the depth of the dendrogram describing the hierarchical cluster structure); A non-parametric algorithm. It can accomplish all goals without requiring any input parameters.

Comparative thallus anatomy of two Parmotrema (Parmeliaceae, lichenized Ascomycetes) with reticulate maculae

Using conventional techniques for structural studies under conventional microscopy, polarizing light microscopy and scanning electron microscopy this work describes and compares the thallus anatomy of two Parmotrema species with reticulate maculae, previously included in the genus Rimelia: Parmotrema cetratum (Ach.) Hale and P. clavuliferum (Räsänen) Streimann. The data showed that the species are anatomically similar, including the presence of epicortex, the upper cortex anatomy and the characteristics of rhizines and ciliae. In the medulla of the two species there are star-shaped clusters of hyphae associated with the presence of salazinic acid. This study showed that the anatomical characteristics are constant for the Parmotrema group studied.

A candidate gene association study on muscat flavor in grapevine (Vitis vinifera L.)

BackgroundThe sweet, floral flavor typical of Muscat varieties (Muscats), due to high levels of monoterpenoids (geraniol, linalool and nerol), is highly distinct and has been greatly appreciated both in table grapes and in wine since ancient times. Muscat flavor determination in grape (Vitis vinifera L.) has up to now been studied by evaluating monoterpenoid levels through QTL analysis. These studies have revealed co-localization of 1-deoxy-D-xylulose 5-phosphate synthase (VvDXS) with the major QTL positioned on chromosome 5.ResultsWe resequenced VvDXS in an ad hoc association population of 148 grape varieties, which included muscat-flavored, aromatic and neutral accessions as well as muscat-like aromatic mutants and non-aromatic offsprings of Muscats. Gene nucleotide diversity and intragenic linkage disequilibrium (LD) were evaluated. Structured association analysis revealed three SNPs in moderate LD to be significantly associated with muscat-flavored varieties. We identified a putative causal SNP responsible for a predicted non-neutral substitution and we discuss its possible implications for flavor metabolism. Network analysis revealed a major star-shaped cluster of reconstructed haplotypes unique to muscat-flavored varieties. Moreover, muscat-like aromatic mutants displayed unique non-synonymous mutations near the mutated site of Muscat genotypes.ConclusionsThis study is a crucial step forward in understanding the genetic regulation of muscat flavor in grapevine and it also sheds light on the domestication history of Muscats. VvDXS appears to be a possible human-selected locus in grapevine domestication and post-domestication. The putative causal SNP identified in Muscat varieties as well as the unique mutations identifying the muscat-like aromatic mutants under study may be immediately applied in marker-assisted breeding programs aimed at enhancing fragrance and aroma complexity respectively in table grape and wine cultivars.

Phylogeography of native ploidy levels and invasive tetraploids of Solidago gigantea

Ploidy level is an important aspect of the genetic makeup of a plant, and can strongly influence ecological characteristics such as invasiveness. We used a phylogeographical approach to elucidate the history of polyploidization and colonization success of diploid and tetraploid Solidago gigantea Aiton (Asteraceae) within its native range in North America. We were also able to identify the probable source material of the haplotype lineages invasive in Europe and Asia, where only tetraploid plants occur. To do this, we sequenced 1275 bp of chloroplast intergenic spacer DNA in 268 individuals from 57 populations. In addition, we performed a crossing experiment, which supported the hypothesis that chloroplast inheritance in this species is maternal. The phylogeographical analysis showed a complex pattern of 20 haplotypes of diploid and tetraploid plants. In North America, we found significant differentiation among regions, private haplotypes, and isolation by distance. Ploidy levels were more differentiated in the northern regions than in the South. The haplotype network was shallow and included one tetraploid-only, star-shaped cluster of haplotypes that were particularly successful colonizers. Post-glacial migration of diploid S. gigantea occurred mainly northwards east of the Appalachian Mountains, and to a lesser degree also southward. Our data suggest that tetraploids have formed several times in North America. Haplotype number and diversity were lower in European populations than in the native range, and we found evidence that four haplotypes were introduced to Europe from two source areas, New England and the Southern Appalachian Mountains.

Clustering of Zirconium Atoms in Zr5Te6: A Novel NiAs-Type-Related Telluride with Ordered Vacancies

Zr5Te6 has been synthesized and its structure determined by means of single crystal X-ray diffraction to be trigonal, , Z=3, Pearson symbol hP33, a=1172.8(2) pm, c=707.0(1) pm. Zr5Te6 adopts a metal-deficient, vacancy-ordered 3a×3a×1c superstructure of the NiAs type structure. In the Zr atom layers, alternately one and two out of nine Zr atoms are missing. The less densely populated layers (7/9) consist of star-shaped Zr7 clusters with intracluster contacts of 351.1 pm; the shortest Zr–Zr intercluster distance is 470.5 pm. In the more densely populated Zr atom layers (8/9), three quarters of the Zr atoms are arranged to pairs (326.4 pm). The distinctive distribution of the vacancies affords a topologically uniform fivefold Zr coordination (283.5–302.6 pm) for all three crystallographically inequivalent Te atoms. They are shifted towards the vacancies in the Zr atom layers. The associated corrugation of the Te atom layers is characterized by an amplitude of 28 pm. The Te–Te contacts are ≥368.1 pm. According to extended Huckel calculations, the defects in the Zr atom layers lead to a reduction in overall Zr–Te bonding interactions relative to ZrTe (NiAs). However, through the clustering the total attractive intralayer Zr–Zr interactions increase considerably, thus providing decisive stabilization of the structure. As revealed by thermal analyses, Zr5Te6 undergoes a reversible phase transition at 1513±5 K. On the Zr-rich side, Zr5Te6 coexists with ZrTe (WC), and, above 1438±5 K with the hitherto unknown ZrTe (MnP). Zr5Te6 exhibits temperature independent paramagnetic properties (χmol=0.7×10−3 cm3 mol−1) that are typical for a metallic conductor. An abrupt increase in the magnitude of the diamagnetic susceptibility below 2.2 K in a weak magnetic field indicates a superconducting transition.

Dual Origins of Finns Revealed by Y Chromosome Haplotype Variation

The Finnish population has often been viewed as an isolate founded 2, 000 years ago via a route across the Gulf of Finland. The founding event has been characterized as involving a limited number of homogeneous founders, isolation, and subsequent rapid population growth. Despite the purported isolation of the population, levels of gene diversity for the Finns at autosomal and mitochondrial DNA loci are indistinguishable from those of other Europeans. Thus, mixed or dual origins for the Finns have been proposed. Here we present genetic evidence for the dual origins of Finns by evaluating the pattern of Y chromosome variation in 280 unrelated males from nine Finnish provinces. Phylogenetic analysis of 77 haplotype configurations revealed two major star-shaped clusters of Y haplotypes, indicative of a population expansion from two common Y haplotypes. Dramatic and quite significant differences in Y haplotype variation were observed between eastern and western regions of Finland, revealing contributions from different paternal types. The geographic distribution and time of expansion for the two common Y haplotypes correlate well with archeological evidence for two culturally and geographically distinct groups of settlers. Also, a northeastern to southwestern gradient of Y haplotype frequencies provides convincing evidence for recent male migration from rural areas into urban Finland.

Movement of the tube cell in the lily style in the absence of the pollen grain and the spent pollen tube

Our model proposes that pollen tube growth is a form of cell movement where the tube tip can be considered analogous to a migrating cell which leaves a trail of extracellular matrix (the spent pollen tube) behind. We demonstrate that the tube cell can convey the sperm cells to the ovule and effect fertilization even in the absence of the pollen grain and the spent pollen tube. Adhesion is an integral part of cell attachment and movement in animal systems. We show that in vivo-grown pollen tubes grow beneath the cuticle of the stylar transmitting tract epidermis and directly adhere to one another and the outer wall of the epidermal cells. A fibrous wall material is found to cover the tip of the pollen tube cell wall and the surface of the transmitting tract cells where the two adhere. Fixation methods to preserve adhesive compounds were used. The pollen-tubes grown in vivo, but not in vitro, show star-shaped clusters of F-actin microfilaments in the region back from the tip, as seen by rhodamine-phalloidin staining. These configurations are similar to focal adhesions seen in moving animal cells.