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Structural Diversity (structural + diversity)
Selected AbstractsThe Craniofacial Reconstruction from the Local Structural Diversity of SkullsCOMPUTER GRAPHICS FORUM, Issue 7 2008Yuru Pei Abstract The craniofacial reconstruction is employed as an initialization of the identification from skulls in forensics. In this paper, we present a two-level craniofacial reconstruction framework based on the local structural diversity of the skulls. On the low level, the holistic reconstruction is formulated as the superimposition of the selected tissue map on the novel skull. The crux is the accurate map registration, which is implemented as a warping guided by the 2D feature curve patterns. The curve pattern extraction under an energy minimization framework is proposed for the automatic feature labeling on the skull depth map. The feature configuration on the warped tissue map is expected to resemble that on the novel skull. In order to make the reconstructed faces personalized, on the high level, the local facial features are estimated from the skull measurements via a RBF model. The RBF model is learnt from a dataset of the skull and the face feature pairs extracted from the head volume data. The experiments demonstrate the facial outlooks can be reconstructed feasibly and efficiently. [source] Structural Diversity in Organotin Compounds Derived from Bulky Monoaryl Phosphates: Dimeric, Tetrameric, and Polymeric Tin Phosphate ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2008Ramaswamy Murugavel Abstract Monoaryl phosphates with a bulky aryl substituent have been used to synthesize new organotin clusters and polymers. The equimolar reaction between 2,6-diisopropylphenylphosphate (dipp-H2) and Me2SnCl2 in ethanol at 25 °C leads to the formation of [Me2Sn(,3 -dipp)]n (1), while the reaction of 2,6-dimethylphenylphosphate (dmpp-H2) with Me2SnCl2 in either a 1:1 or 2:1 molar ratio proceeds to produce exclusively [Me2Sn(,-dmpp-H)2]n·nH2O (2). Compounds 1 and 2 are 1D polymers with different architectures. In compound 1, the tin atom is five-coordinate (trigonal bipyramidal). Each dipp ligand bridges three different tin atoms to form an infinite ladder-chain structure. In 2, each six-coordinate (octahedral) tin atom is surrounded by four phosphate oxygen atoms originating from four different bridging dmpp-H ligands, thus forming a spirocyclic coordination polymeric chain. The use of nBu2SnO as the diorganotin source in its reaction with dipp-H2 leads to the isolation of dimeric [nBu2Sn(,-dipp-H)(dipp-H)]2 (4), which contains a central Sn2O4P2 unit. There are two chemically different half molecules of 4 in the asymmetric part of the unit cell and hence it actually exists as a 1:1 mixture of [nBu2Sn(,-dipp-H)(dipp-H)]2 and [nBu2Sn(,-dipp)(dipp-H2)]2 in the solid state. The reaction of the monoorgano tin precursor nBuSn(O)(OH)·xH2O with dipp-H2 takes place in acetone at room temperature to yield the tetrameric cluster 5, which has different structures in the solution and in the solid state. 31P NMR spectroscopy clearly suggests that 5 has the formula [nBu4Sn4(,-O)2(,-dipp-H)8] in solution. The single-crystal X-ray diffraction studies in the solid state, however, reveal that compound 5 exists as [nBu4Sn4(,-OH)2(,-dipp-H)6(,-dipp)2]. The use of compounds 1,4 as possible precursors for the preparation of ceramic tin phosphate materials has been investigated. The thermolysis of 1 at 500 °C leads to the formation of quantitative amounts of Sn2P2O7, while the thermolysis of 2, 3, and 4 under similar conditions results in the formation of SnP2O7. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Anion-Dependent Structural Diversity in Silver(I) Complexes of 4-Amino-3,5-diisopropyl-1,2,4-triazoleEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2007Guang Yang Abstract Reactions of silver salts with 4-amino-3,5-diisopropyl-1,2,4-triazole (L) afford dinuclear complex [Ag2L2(NO3)2(CH3CN)], triangular complex [Ag3L3](CF3SO3)3, and cyclic tetranuclear complexes [Ag4L6](BF4)4 and [Ag4L6](ClO4)4. On the basis of the X-ray analyses, anions are found to play an important role in determining the structures. Through coordination/noncoordination, anions can impart their influence on the coordination geometry of Ag atoms and the angles of N,Ag,N, which seems to be the main factor controlling the nuclearity of the reaction products in this system. 1H NMR and MS measurements suggest that these complexes probably retain their structural integrities in CH3CN solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Dinuclear Complexes of MII Thiocyanate (M = Ni and Cu) Containing a Tridentate Schiff-Base Ligand: Synthesis, Structural Diversity and Magnetic PropertiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2005Suparna Banerjee Abstract A dinuclear NiII complex, [Ni2(L)2(H2O)(NCS)2]·3H2O (1) in which the metal atoms are bridged by one water molecule and two ,2 -phenolate ions, and a thiocyanato-bridged dimeric CuII complex, [Cu(L)NCS]2 (2) [L = tridentate Schiff-base ligand, N -(3-aminopropyl)salicylaldimine, derived from 1:1 condensation of salicylaldehyde and 1,3-diaminopropane], have been synthesized and characterized by IR and UV/Vis spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction studies. The structure of 1 consists of dinuclear units with crystallographic C2 symmetry in which each NiII atom is in a distorted octahedral environment. The Ni,O distance and the Ni,O,Ni angle, through the bridged water molecule, are 2.240(11) Å and 82.5(5)°, respectively. The structure of 2 consists of dinuclear units bridged asymmetrically by di-,1,3 -NCS ions; each CuII ion is in a square-pyramidal environment with , = 0.25. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complex 1 with J = 3.1 cm,1, whereas complex 2 exhibits weak antiferromagnetic coupling between the CuII centers with J = ,1.7 cm,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis, Structural Diversity, and Ligand-Transfer Potential of (Carbene)copper(I) ComplexesHELVETICA CHIMICA ACTA, Issue 6 2009Galmari Venkatachalam Abstract Copper(I) complexes comprising different N-heterocyclic carbene ligands were prepared via in situ deprotonation and metallation. Depending on the wingtip groups on the carbene ligand (alkyl vs. aryl, chelating or monodentate), a variety of different structural motifs were identified, such as a trigonal planar geometry (alkyl wingtips) and an unprecedented see-saw-type structure (pyridinyl wingtip groups). While aryl wingtip groups increase the stability of the complexes, alkyl substituents induce rapid demetallation in the presence of moisture. The reactivity of these complexes was used to establish a carbene-transfer protocol, which is illustrated by the formation of new cyclic thiourea compounds (transfer to sulfur) and new (carbene)ruthenium(II) complexes (transfer to ruthenium). This suggests that (carbene)copper(I) complexes could become valuable alternatives to (carbene)silver(I) complexes for synthesizing (carbene)metal systems via transmetallation. [source] Structural Diversity of PDZ,Lipid InteractionsCHEMBIOCHEM, Issue 4 2010Rodrigo Gallardo Abstract PDZ domains are globular protein modules that are over-and-above appreciated for their interaction with short peptide motifs found in the cytosolic tail of membrane receptors, channels, and adhesion molecules. These domains predominate in scaffold molecules that control the assembly and the location of large signaling complexes. Studies have now emerged showing that PDZ domains can also interact with membrane lipids, and in particular with phosphoinositides. Phosphoinositides control various aspects of cell signaling, vesicular trafficking, and cytoskeleton remodeling. When investigated, lipid binding appears to be extremely relevant for PDZ protein functionality. Studies point to more than one mechanism for PDZ domains to associate with lipids. Few studies have been focused on the structural basis of PDZ,phosphoinositide interactions, and the biological consequences of such interactions. Using the current knowledge on syntenin-1, syntenin-2, PTP-Bas, PAR-3 and PICK1, we recapitulate our understanding of the structural and biochemical aspects of PDZ,lipid interactions and the consequences for peptide interactions. [source] Filtering and Counting of Extended Connectivity Fingerprint Features Maximizes Compound Recall and the Structural Diversity of HitsCHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2009Ye Hu Extended connectivity fingerprints produce variable numbers of structural features for molecules and quantitative comparison of feature ensembles is typically carried out as a measure of molecular similarity. As an alternative way to utilize the information content of extended connectivity fingerprint features, we have introduced a compound class-directed feature filtering technique. In combination with a simple feature counting protocol, feature filtering significantly improves the performance of extended connectivity fingerprint similarity searching compared with state-of-the-art fingerprint search methods. Subsets of extended connectivity fingerprint features that are unique to active compounds are found to be responsible for high compound recall. Moreover, feature filtering and counting is shown to result in significantly higher scaffold hopping potential than data fusion or fingerprint averaging methods. Extended connectivity fingerprint feature filtering and counting represents one of the simplest similarity search methods introduced to date, yet it produces top compound recall and maximizes the scaffold diversity of hits, which is a longstanding goal of similarity searching. [source] Organically Directed Iron Sulfate Chains: Structural Diversity Based on Hydrogen Bonding Interactions.CHEMINFORM, Issue 1 2007Yunlong Fu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Structural Diversity of Low-Dimensional Compounds in [M(en)2]2+/ [Re6Q8(CN)6]4- Systems (M: Mn, Ni, Cu).CHEMINFORM, Issue 15 2005Konstantin A. Brylev Abstract For Abstract see ChemInform Abstract in Full Text. [source] Structural Diversity in the Self-Assembly of Pseudopeptidic MacrocyclesCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2010Ignacio Alfonso Dr. Abstract The self-assembling abilities of several pseudopeptidic macrocycles have been thoroughly studied both in the solid (SEM, TEM, FTIR) and in solution (NMR, UV, CD, FTIR) states. Detailed microscopy revealed large differences in the morphology of the self-assembling micro/nanostructures depending on the macrocyclic chemical structures. Self-assembly was triggered by the presence of additional methylene groups or by changing from para to meta geometry of the aromatic phenylene backbone moiety. More interestingly, the nature of the side chain also plays a fundamental role in some of the obtained nanostructures, thus producing structures from long fibers to hollow spheres. These nanostructures were obtained in different solvents and on different surfaces, thus implying that the chemical information for the self-assembly is contained in the molecular structure. Dilution NMR studies (chemical shift and self-diffusion rates) suggest the formation of incipient aggregates in solution by a combination of hydrogen-bonding and ,,, interactions, thus implicating amide and aryl groups, respectively. Electronic spectroscopy further supports the ,,, interactions because the compounds that lead to fibers show large hypochromic shifts in the UV spectra. Moreover, the fiber-forming macrocycles also showed a more intense CD signature. The hydrogen-bonding interactions within the nanostructures were also characterized by attenuated total-reflectance FTIR spectroscopy, which allowed us to monitor the complete transition from the solution to the dried nanostructure. Overall, we concluded that the self-assembly of this family of pseudopeptidic macrocycles is dictated by a synergic action of hydrogen-bonding and ,,, interactions. The feasibility and geometrical disposition of these interactions finally render a hierarchical organization, which has been rationalized with a proposal of a model. The understanding of the process at the molecular level has allowed us to prepare hybrid soft materials. [source] Unexpected Structural Diversity in Alkali Metal Azide-Crown Ether Complexes: Syntheses, X-ray Structures, and Quantum-Chemical CalculationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2006Michael D. Brown Abstract A series of alkali metal azide-crown ether complexes, [Li([12]crown-4)(N3)], [Na([15]crown-5)(N3)], [Na([15]crown-5)(H2O)2]N3, [K([18]crown-6)(N3)(H2O)], [Rb([18]crown-6)(N3)(H2O)], [Cs([18]crown-6)(N3)]2, and [Cs([18]crown-6)(N3)(H2O)(MeOH)], has been synthesised. In most cases, single crystals were obtained, which allowed X-ray crystal structures to be derived. The structures obtained have been compared with molecular structures computed by density functional theory (DFT) calculations. This has allowed the effects of the crystal lattice on the structures to be investigated. Also, a study of the MNterminal metal,azide bond length and charge densities on the metal (M) and terminal nitrogen centre (Nterminal) in these complexes has allowed the nature of the metal,azide bond to be probed in each case. The bonding in these complexes is believed to be predominantly ionic or ion-dipole in character, with the differences in geometries reflecting the balance between maximising the coordination number of the metal centre and minimising ligand-ligand repulsions. The structures of the crown ether complexes determined in this work show the subtle interplay of such factors. The significant role of hydrogen bonding is also demonstrated, most clearly in the structures of the K and Rb dimers, but also in the chain structure of the hydrated Cs complex. [source] Structural diversity of bacterial communities in a heavy metal mineralized granite outcropENVIRONMENTAL MICROBIOLOGY, Issue 3 2006Deirdre Gleeson Summary This laboratory study of a variably mineralized and hydrothermally altered granite outcrop investigated the influences of rock-surface chemistry and heavy metal content on resident bacterial populations. Results indicated that elevated heavy metal concentrations had a profound impact on bacterial community structure, with strong relationships found between certain ribotypes and particular chemical/heavy metal elements. Automated ribosomal intergenic sequence analysis (ARISA) was used to assess the nature and extent of bacterial diversity, and this was combined with chemical analysis and multivariate statistics to identify the main geochemical factors influencing bacterial community structure. A randomization test revealed significant changes in bacterial structure between samples, while canonical correspondence analysis (CCA) related each individual ARISA profile to linear combinations of the chemical variables (mineralogy, major element and heavy metal concentrations) revealing the geochemical factors that correlated with changes in the ARISA data. anova was performed to further explore interactions between individual ribotypes and chemical/heavy metal composition, and revealed that a high proportion of ribotypes correlated significantly with heavy metals. [source] Developmental morphology of Saxicolella amicorum and S. submersa (Podostemaceae: Podostemoideae) from GhanaBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2002K. GABRIEL AMEKA Saxicolella (six spp.) is a podostemoid genus occurring in tropical west Africa (Cameroon, Ghana, Nigeria). Taxonomically used characters such as root (with holdfasts), pollen (dyads in many Podostemoideae), capsules (with ribs) and seeds are demonstrated and discussed. This paper deals with the structure and development of two species, which are endemic to rivers in southern Ghana: Saxicolella amicorum J.B.Hall and Saxicolella submersa (J.B.Hall) C.D.K.Cook & Rutish. (syn. Polypleurum submersum J.B.Hall).,Saxicolella amicorum has simple, one-flowered stems up to 3 cm long, whereas S. submersa has branched, many-flowered stems up to 25 cm long. Vegetative shoots can reach 12 cm (S. amicorum) and even 50 cm (S. submersa) in length. The latter species was previously placed in the Asian genus Polypleurum because the long floating axis was misinterpreted as a root which would be typical for Polypleurum. The long floating axis of S. submersa develops exogenous leaves and is actually a stem. Both S. amicorum and S. submersa have various features in common: vegetative parts (roots, stems, leaves) are elongate and very thin (diameter less than 1 mm); prostrate roots are narrow ribbons (twice as wide as thick); endogenous shoots in opposite pairs along the root; leaves usually simple and filiform; leaf bases with two attached ear-like stipules; spathella club-shaped to ellipsoidal; erect flowers with a solitary stamen; ovary ellipsoidal to fusiform, bilocular; capsules nearly isolobous, with three prominent ribs per valve (i.e. eight ribs per capsule including sutural ribs). Evolutionary dynamics of the root structures in African Podostemoideae such as Saxicolella include: formation of green prostrate ribbons as a result of dorsoventral root flattening; reduction of root caps; occurrence of adhesive hairs and exogenous holdfasts which are disk- or finger-like. Structural diversity and developmental patterns in the Ghanaian Saxicolella species are compared with other African Podostemoideae. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 2002, 139, 255,273. [source] The Craniofacial Reconstruction from the Local Structural Diversity of SkullsCOMPUTER GRAPHICS FORUM, Issue 7 2008Yuru Pei Abstract The craniofacial reconstruction is employed as an initialization of the identification from skulls in forensics. In this paper, we present a two-level craniofacial reconstruction framework based on the local structural diversity of the skulls. On the low level, the holistic reconstruction is formulated as the superimposition of the selected tissue map on the novel skull. The crux is the accurate map registration, which is implemented as a warping guided by the 2D feature curve patterns. The curve pattern extraction under an energy minimization framework is proposed for the automatic feature labeling on the skull depth map. The feature configuration on the warped tissue map is expected to resemble that on the novel skull. In order to make the reconstructed faces personalized, on the high level, the local facial features are estimated from the skull measurements via a RBF model. The RBF model is learnt from a dataset of the skull and the face feature pairs extracted from the head volume data. The experiments demonstrate the facial outlooks can be reconstructed feasibly and efficiently. [source] Shade-Coffee Plantations as Refuges for Tropical Wild Orchids in Central Veracruz, MexicoCONSERVATION BIOLOGY, Issue 3 2005LISLIE SOLIS-MONTERO biología reproductiva; epifitas vasculares; estratificación vertical; estructura poblacional; limitación de polinizador Abstract:,In central Veracruz, Mexico, coffee plantations have replaced large areas of lower montane cloud forest. Shade-coffee plantations with high levels of structural diversity provide refuge for forest-dependent biota (e.g., birds and insects). Orchids typical of natural forest may also be found in the canopy of shade-coffee agroecosystems. It is not known, however, whether these are relicts from the original forest vegetation or if the plantations themselves provide the necessary conditions to support a self-sustained orchid population. We studied the population structure of the epiphytic orchids Jacquiniella teretifolia (Sw.) Britton & Willson, Scaphyglottis livida (Lindl.) Schltr., and Maxillaria densa Lindl. in a shade-coffee plantation (commercial polyculture) in central Veracruz. We also studied the previously undescribed reproductive biology of the latter two species. Our results show that the three orchid species had high population densities (>800 plants/ha). In our study site, 50% to 68% of the orchid plants of the target species were young individuals (less than five shoots). Reproductive structures were present in 80% of individuals larger than 30 shoots in the three species. M. densa is self-incompatible, and the fruit set obtained from cross pollination (42.7%) was higher than that obtained from natural pollination (18.2%), suggesting that this species could be pollinator limited. S. livida is autocompatible, not autogamous, and was not pollinator limited. Our results show that the coffee plantation had abundant orchid populations with log-normal size/age structures. Two of the target species, M. densa and S. livida, depend on pollinators to reproduce. It is clear that pollinators that allow orchids to set a high proportion of fruits persist in shade-coffee plantations. Coffee plantations may not replace the original conditions of a forest, but it is possible that these and other orchid species survive and reproduce in coffee plantations that provide appropriate microclimate conditions for the plants, including pollinators. Resumen:,En el centro de Veracruz, México, las plantaciones de café han reemplazado a extensas áreas de bosque nublado montano. Las plantaciones cafetaleras de sombra con altos niveles de diversidad estructural proporcionan refugio a biota dependiente de bosques (e. g., aves e insectos). En el dosel de agroecosistemas de café de sombra también se pueden encontrar orquídeas típicas de bosques naturales. Sin embargo, no se conoce si son relictos de la vegetación del bosque original o si las plantaciones mismas proporcionan los recursos necesarios para soportar a una población de orquídeas auto sostenida. Estudiamos la estructura de la población de orquídeas epifitas Jacquiniella teretifolia (Sw.) Britton & Willson, Scaphyglottis livida (Lindl.) Schltr y Maxillaria densa Lindl en una plantación de café de sombra (policultivo comercial) en el centro de Veracruz. También estudiamos la biología reproductiva, no descrita previamente, de las últimas dos especies. Nuestros resultados muestran que las tres especies de orquídea tuvieron densidades poblacionales altas (>800 plantas/ha). En nuestro sitio de estudio, entre 50% y 68% de las plantas de las especies estudiadas eran individuos jóvenes (menos de cinco rebrotes). En las tres especies hubo presencia de estructuras reproductivas en 80% de los individuos con más de 30 rebrotes. M. densa es auto incompatible, y el conjunto de frutos obtenido por polinización cruzada (42.7%) fue mayor que el obtenido por polinización natural (18.2%), lo que sugiere que esta especie puede estar limitada por polinizadores. S. livida es autocompatible no autogama, y no fue limitada por polinizadores. Nuestros resultados muestran que la plantación de café tenía poblaciones de orquídeas abundantes con estructuras tamaño/edad log normales. Dos de las especies, M. densa y S. livida, dependen de polinizadores para su reproducción. Es claro que los polinizadores que permiten una alta proporción de frutos a las orquídeas persisten en las plantaciones. Puede que las plantaciones de café no sustituyan las condiciones originales de un bosque, pero es posible que estas, y otras, especies de orquídeas sobrevivan y se reproduzcan en plantaciones de café que proporcionen condiciones microclimáticas adecuadas, incluyendo polinizadores, para las plantas. [source] Landscape composition influences patterns of native and exotic lady beetle abundanceDIVERSITY AND DISTRIBUTIONS, Issue 4 2009M. M. Gardiner Abstract Aim, Coccinellid beetles are important predators that contribute to pest suppression in agricultural landscapes. Since the introduction of the exotic coccinellids Coccinella septempunctata L. and Harmonia axyridis Pallas into the USA, several studies have reported a decline of native Coccinellidae in agroecosystems. We aimed to investigate the influence of landscape composition on native and exotic coccinellid abundance within soybean fields. Location, Iowa, Michigan, Minnesota and Wisconsin. Methods, As part of a 2-year study (2005,06) on the biological control of the soybean aphid, Aphis glycines Matsumura, we examined coccinellid communities in 33 soybean fields using yellow sticky card traps. Landscape heterogeneity and composition were measured at multiple spatial scales ranging 1,3.5 km from focal soybean fields where coccinellid sampling took place. Results, Exotic species made up 90% of the total coccinellid community in Michigan soybean fields followed by Wisconsin (84%), Minnesota (66%) and Iowa (57%). Harmonia axyridis was the dominant exotic coccinellid in all states comprising 45,62% of the total coccinellid community, followed by C. septempunctata (13,30%). Two additional exotic species, Hippodamia variegata (Goeze) and Propylea quatuordecimpunctata (L.) were also found in the region. Overall, the most abundant native coccinellid was Hippodamia convergens Guerin-Meneville; however, its abundance varied across the region, comprising 0% (Michigan) to 28% (Iowa) of the total coccinellid community. Landscape structure significantly influenced the composition of coccinellid communities in soybean agroecosystems. We found that native coccinellids were most abundant in low-diversity landscapes with an abundance of grassland habitat while exotic coccinellids were associated with the abundance of forested habitats. Main conclusion, We propose that grassland dominated landscapes with low structural diversity and low amounts of forested habitat may be resistant to exotic coccinellid build-up, particularly H. axyridis and therefore represent landscape-scale refuges for native coccinellid biodiversity. [source] Assessing the habitat quality of oil mallees and other planted farmland vegetation with reference to natural woodlandECOLOGICAL MANAGEMENT & RESTORATION, Issue 3 2009F. Patrick Smith Summary, Much of the tree and shrub planting that has been conducted on farms in Western Australia over the past three decades has not been done with the specific intention of creating habitat or conserving biodiversity, particularly commercially oriented monocultures like oil mallee plantings. However, such plantings may nonetheless provide some habitat resources for native plants and animals. This study assessed the habitat quality of farm plantings (most of which were not planted with the primary intention of biodiversity conservation) at 72 sites across a study region in the central wheatbelt of Western Australia. Widely accepted habitat metrics were used to compare the habitat resources provided by planted farmland vegetation with those provided by remnant woodland on the same farms. The impact of adjacency of plantings to woodland and, in the case of oil mallees, the planting configuration on predicted habitat quality is assessed. Condition Benchmarks for five local native vegetation communities are proposed. Farmland plantings achieved an average Vegetation Condition Score (VCS) of 46 out of a possible 100, while remnant woodland on the same farms scored an average 72. The average scores for farm plantings ranged from 38,59 depending on which of five natural vegetation communities was used as its benchmark, but farm plantings always scored significantly less than remnant woodland (P < 0.001). Mixed species plantings on average were rated more highly than oil mallees (e.g. scores of 42 and 36 respectively using the Wandoo benchmark) and adjacency to remnant woodland improved the score for mixed plantings, but not for oil mallees. Configuration of oil mallees as blocks or belts (i.e. as an alley farming system) had no impact on the VCS. Planted farmland vegetation fell short of remnant woodland in both floristic richness (51 planted native species in total compared with a total of more than 166 naturally occurring plant species in woodland) and structural diversity (with height, multiple vegetation strata, tree hollows and woody debris all absent in the relatively young 7,15-year-old farm plantings). Nonetheless farmland plantings do have measurable habitat values and recruitment and apparent recolonization of plantings with native plant species was observed. Habitat values might be expected to increase as the plantings age. The VCS approach, including the application of locally relevant Benchmarks is considered to be valuable for assessing potential habitat quality in farmland vegetation, particularly as a tool for engaging landholders and natural resource management practitioners. [source] Mixed-Anion and Mixed-Cation Borohydride KZn(BH4)Cl2: Synthesis, Structure and Thermal DecompositionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010Dorthe B. Ravnsbæk Abstract KZn(BH4)Cl2, synthesized for the first time, contains a heteroleptic complex anion [Zn(BH4)Cl2],, extending the structural diversity of metal borohydrides. In-situ synchrotron powder diffraction, NMR and Raman spectroscopy were used to characterize KZn(BH4)Cl2 and to evaluate the mechanism for its thermal decomposition. The title compound decomposes at a significantly lower temperature than KBH4 and may be used for inspiration for the design of novel hydrogen storage materials. Combining different ligands in modified metal borohydrides is proposed as a way to adjust stability with respect to hydrogen desorption. [source] D -Glucose as a Pentavalent Chiral ScaffoldEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2003Till Opatz Abstract A novel carbohydrate-based scaffold for combinatorial chemistry has been developed. This scaffold allows the selective attachment of five different side chains, giving rise to products of enormous structural diversity. As a demonstration of its usefulness, a series of model compounds has been prepared in high purity and yield by multistep parallel synthesis on a solid phase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Human telomeric G-quadruplex: structures of DNA and RNA sequencesFEBS JOURNAL, Issue 5 2010Anh Tuân Phan Telomeres play an important role in cellular aging and cancer. Human telomeric DNA and RNA G-rich sequences are capable of forming a four-stranded structure, known as the G-quadruplex. Such a structure might be important for telomere biology and a good target for drug design. This minireview describes the structural diversity or conservation of DNA and RNA human telomeric G-quadruplexes, discusses structural views on targeting these G-quadruplexes and presents some future challenges for structural studies. [source] Phylogenetic analysis of condensation domains in the nonribosomal peptide synthetasesFEMS MICROBIOLOGY LETTERS, Issue 1 2005Niran Roongsawang Abstract Condensation (C) domains in the nonribosomal peptide synthetases are capable of catalyzing peptide bond formation between two consecutively bound various amino acids. C-domains coincide in frequency with the number of peptide bonds in the product peptide. In this study, a phylogenetic approach was used to investigate structural diversity of bacterial C-domains. Phylogenetic trees show that the C-domains are clustered into three functional groups according to the types of substrate donor molecules. They are l -peptidyl donors, d -peptidyl donors, and N -acyl donors. The fact that C-domain structure is not subject to optical configuration of amino acid acceptor molecules supports an idea that the conversion from l to d -form of incorporating amino acid acceptor occurs during or after peptide bond formation. l -peptidyl donors and d -peptidyl donors are suggested to separate before separating the lineage of Gram-positive and Gram-negative bacteria in the evolution process. [source] Cell wall teichoic acids: structural diversity, species specificity in the genus Nocardiopsis, and chemotaxonomic perspectiveFEMS MICROBIOLOGY REVIEWS, Issue 3 2001Irina B Naumova Abstract Data on the structures of cell wall teichoic acids, the anionic carbohydrate-containing polymers, found in many Gram-positive bacteria have been summarized and the polymers of the actinomycete genus Nocardiopsis have been considered from the taxonomic standpoint. The structures of these polymers or their combinations have been demonstrated to be indicative of each of seven Nocardiopsis species and two subspecies, verified by the DNA,DNA relatedness data, and to correlate well with the grouping of the organisms based on 16S rDNA sequences. As each of the intrageneric taxa discussed is definable by the composition of teichoic acids, the polymers are considered to be valuable taxonomic markers for the Nocardiopsis species and subspecies. The 13C NMR spectra of the polymers, data on the products of their chemical degradation, and distinguishing constituents of whole cell walls derived from teichoic acids are discussed, which are useful for identification of certain polymers and members of the genus Nocardiopsis at the species and subspecies level in microbiological practice. [source] The processes of underthrusting and underplating in the geologic record: structural diversity between the Franciscan Complex (California), the Kodiak Complex (Alaska) and the Internal Ligurian Units (Italy)GEOLOGICAL JOURNAL, Issue 2 2009F. Meneghini Abstract Existing studies on active subduction margins have documented the wide diversity in structural style between accretionary prisms, both in space and time. Together with physical boundary conditions of the margins, the thickness of sedimentary successions carried by the lower plate seems to play a key role in controlling the deformation and fluid flow during accretion. We have tested the influence of the subducting sedimentary section by comparing the structural style and fluid-related structures of four units from three fossil accretionary complexes characterized by similar physical conditions but different subducting sediment thicknesses: (1) the Franciscan Complex of California, (2) the Internal Ligurian Units of Italy and (3) the Kodiak Complex, Alaska. Subducting plates bearing a thick sedimentary cover generally result in coherent accretion through polyphase deformation represented by folding and thin thrusting events, while underplating of sediment-starved oceanic sections results in diffuse deformation and mélange formation. These two structural styles can alternate through time in a single complex with a long record of accretion such as Kodiak. The parallel analysis of the selected analogues show that although the volume of sediments carried by the lower plate determines different structural styles, deformation is strongly controlled by injection of overpressured fluids during underthrusting and accretion. Transient hydrofracturing occurs through the development of a system of dilatant fractures grossly parallel to the décollement zone. Copyright © 2009 John Wiley & Sons, Ltd. [source] Biomimetic Nanostructures: Diatomaceous Lessons in Nanotechnology and Advanced Materials (Adv. Mater.ADVANCED MATERIALS, Issue 29 200929/2009) The cover picture shows a series of SEM and AFM images of silica structures from several different diatom species. These images demonstrate remarkable structural diversity and unique porous architectures of diatoms justifying their status as the world's smallest nanofabrication factories. Further details can be found in the article by Nicolas Voelcker and co-workers on p. 2947. [source] Activated ,,,-Unsaturated Aldehydes as Substrate of Dihydroxyacetone Phosphate (DHAP)-Dependent Aldolases in the Context of a Multienzyme SystemADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Israel Sánchez-Moreno Abstract The utility for carbon-carbon bond formation of a multienzyme system composed of recombinant dihydroxyacetone kinase (DHAK) from Citrobacter freundii, the fructose bisphosphate aldolase from rabbit muscle (RAMA) and acetate kinase (AK) for adenosine triphosphate (ATP) regeneration has been studied. Several aldehydes with great structural diversity, including three ,,,-unsaturated aldehydes, have been analysed as acceptor substrates. It was found that ,,,-unsaturated aldehydes bearing an electron-withdrawing group in the , position to the double bond with a trans configuration are good acceptors for RAMA in this multienzyme system. The aldol reaction proceeds with excellent D - threo enantioselectivity and the aldol adduct is obtained in good overall yield. The L - threo and D - erythro enantiomers are also accessible from rhamnulose 1-phosphate aldolase (Rha-1PA) and fuculose 1-phosphate aldolase (Fuc-1PA) catalysed reactions, respectively. [source] Recent Advances in the Synthesis of 2-Imidazolines and Their Applications in Homogeneous CatalysisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Han Liu Abstract As an important class of heterocyclic scaffolds, 2-imidazolines have attracted the attention from the chemists interested in natural products, pharmaceutical chemistry, synthetic organic chemistry, coordination chemistry, and homogeneous catalysis. To fulfill the demand of structural diversity, many efficient methods towards 2-imidazolines, as well as modifications of traditional methods, have been reported in the past two decades. 2-Imidazolines have been developed as ligands in homogeneous catalysis, for the substitution on the nitrogen atom that provides an opportunity for fine-tuning of the electronic effect. This review summarizes recent advances in the synthesis of 2-imidazolines and their applications in homogeneous catalysis. [source] Imine Additions of Internal Alkynes for the Synthesis of Trisubstituted (E)-Alkene and Cyclopropane Peptide IsosteresADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005Peter Wipf Abstract Divergent multi-component reactions (DMCR) involving CC bond formations can provide large increases in structural diversity and allow the rapid assembly of complex products from readily available starting materials. Cascade hydrozirconation-Zr/Zn transmetalation-imine addition of alkynes represents a versatile methodology for the synthesis of (E)-alkene and cyclopropane dipeptide isosteres. Appropriate substitutions at the sp2 -carbon of (E)-alkene peptide isosteres allow a range of Pd-catalyzed cross-coupling reactions, which can be used for the fine-tuning of the conformational and electronic properties of the parent peptide bond mimic. CC bond formation by microwave-accelerated Stille coupling of stannylalkenes represents a fast, convergent synthetic approach toward trisubstituted (E)-alkene dipeptide isosteres. [source] Comparative foraging and nutrition of horses and cattle in European wetlandsJOURNAL OF APPLIED ECOLOGY, Issue 1 2002Catherine Menard Summary 1Equids are generalist herbivores that co-exist with bovids of similar body size in many ecosystems. There are two major hypotheses to explain their co-existence, but few comparative data are available to test them. The first postulates that the very different functioning of their digestive tracts leads to fundamentally different patterns of use of grasses of different fibre contents. The second postulates resource partitioning through the use of different plant species. As domestic horses and cattle are used widely in Europe for the management of conservation areas, particularly in wetlands, a good knowledge of their foraging behaviour and comparative nutrition is necessary. 2In this paper we describe resource-use by horses and cattle in complementary studies in two French wetlands. Horses used marshes intensively during the warmer seasons; both species used grasslands intensively throughout the year; cattle used forbs and shrubs much more than horses. Niche breadth was similar and overlap was high (Kulczinski's index 0·58,0·77). Horses spent much more time feeding on short grass than cattle. These results from the two sites indicate strong potential for competition. 3Comparative daily food intake, measured in the field during this study for the first time, was 63% higher in horses (144 gDM kg W,0·75 day,1) than in cattle (88 gDM kg W,0·75 day,1). Digestibility of the cattle diets was a little higher, but daily intake of digestible dry matter (i.e. nutrient extraction) in all seasons was considerably higher in horses (78 gDM kg W,0·75 day,1) than in cattle (51 gDM kg W,0·75 day,1). When food is limiting, horses should outcompete cattle in habitats dominated by grasses because their functional response is steeper; under these circumstances cattle will require an ecological refuge for survival during winter, woodland or shrubland with abundant dicotyledons. 4Horses are a good tool for plant management because they remove more vegetation per unit body weight than cattle, and use the most productive plant communities and plant species (especially graminoids) to a greater extent. They feed closer to the ground, and maintain a mosaic of patches of short and tall grass that contributes to structural diversity at this scale. Cattle use broadleaved plants to a greater extent than horses, and can reduce the rate of encroachment by certain woody species. [source] Arborescent polymers and other dendrigraft polymers: A journey into structural diversityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2007Mario Gauthier Abstract Arborescent polymers are characterized by a dendritic, multilevel branched architecture derived from successive grafting reactions. In spite of their much larger size, these materials display properties analogous to dendrimers and hyperbranched polymers, the two other dendritic polymer families. The distinguishing features of arborescent polymers are their assembly from polymeric building blocks of uniform size and their very high molecular weights attained in few synthetic steps. This article offers an overview of the historical aspects of the development of dendrigraft polymers, starting from our initial efforts on the synthesis of arborescent polystyrenes. Major subsequent developments in the synthetic techniques from our and other research groups allowing the synthesis of dendrigraft copolymers, tailoring of the structural characteristics of the molecules, and further simplifications to their synthesis are also reviewed, with emphasis over the broad range of architectures attainable in these systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3803,3810, 2007 [source] Species and structural diversity of church forests in a fragmented Ethiopian Highland landscapeJOURNAL OF VEGETATION SCIENCE, Issue 5 2010Alemayehu Wassie Abstract Question: Thousands of small isolated forest fragments remain around churches ("church forests") in the almost completely deforested Ethiopian Highlands. We questioned how the forest structure and composition varied with altitude, forest area and human influence. Location: South Gondar, Amhara National Regional State, Northern Ethiopia. Methods: The structure and species composition was assessed for 810 plots in 28 church forests. All woody plants were inventoried, identified and measured (stem diameter) in seven to 56 10 m x 10-m plots per forest. Results: In total, 168 woody species were recorded, of which 160 were indigeneous. The basal area decreased with tree harvest intensity; understorey and middle-storey density (<5 cm DBH trees) decreased with grazing; overstorey density (>5 cm DBH trees) increased with altitude. The dominance of a small set of species increased with altitude and grazing intensity. Species richness decreased with altitude, mainly due to variation in the richness of the overstorey community. Moreover, species richness in the understorey decreased with grazing intensity. Conclusions: We show how tree harvesting intensity, grazing intensity and altitude contribute to observed variations in forest structure, composition and species richness. Species richness was, however, not related to forest area. Our study emphasizes the significant role played by the remaining church forests for conservation of woody plant species in North Ethiopian Highlands, and the need to protect these forests for plant species conservation purposes. [source] | |||||||||||||||||||||||||||||||||||||