Elementary Structural Units Research Articles

Effect of ovarian hormones on genes promoting dendritic spines in laser-captured serotonin neurons from macaques

Dendritic spines are the elementary structural units of neuronal plasticity and the cascades that promote dendrite spine remodeling center on Rho GTPases and downstream effectors of actin dynamics. In a model of hormone replacement therapy (HT), we sought the effect of estradiol (E) and progesterone (P) on gene expression in these cascades in laser captured serotonin neurons from rhesus macaques with cDNA array analysis. Spayed rhesus macaques were treated with either placebo, E or E+P via Silastic implant for 1 month prior to euthanasia after which the midbrain was obtained, sectioned and immunostained for TPH. TPH-positive neurons were laser captured using an Arcturus Laser Dissection Microscope (PixCell II). RNA from laser captured serotonin neurons (n=2 animals/treatment) was hybridized to Rhesus Affymetrix GeneChips. There was a significant change in 744 probe sets (ANOVA, p < 0.05), but 10,493 probe sets exhibited a 2-fold or greater change. Pivotal changes in pathways leading to dendrite spine proliferation and transformation included 2-fold or greater increases in expression of the Rho GTPases called CDC42, Rac1 and RhoA. In addition, 2-fold or greater increases occurred in downstream effectors of actin dynamics including PAK1, ROCK, PIP5K, IRSp53, WASP, WAVE, MLC, cofilin, gelsolin, profilin and 3 subunits of ARP2/3. Finally, 2-fold or greater decreases occurred in CRIPAK, LIMK2 and MLCK. The regulation of RhoA, Rac1, CDC42, ROCK, PIP5k, IRSp53, WASP, WAVE, LIMK2, CRIPAK1, MLCK, ARP2/3 subunit 3, gelsolin, profilin and cofilin was confirmed with nested qRT-PCR on laser captured RNA (n=3 animals/treatment). The data indicate that ovarian steroids target gene expression of the Rho GTPases and pivotal downstream proteins that in turn, would promote dendritic spine proliferation and stabilization on serotonin neurons of the dorsal raphe nucleus.

Nature of the hyper-Raman active vibrations of lithium borate glasses

Hyper-Raman spectra of two lithium borate glasses,4B2O3:Li2O and 2B2O3:Li2O, are compared to those of pure boron oxide glass,v-B2O3. A mode analysis is performed using a structural model based on thesymmetry of the elementary structural units (ESUs) constituting theglasses. Most spectral components arise from internal vibrations ofBO3 triangles,B3O3 boroxolrings, and BO4 tetrahedra. In particular, a mode associated with stretching motions ofBO4 units can be assignedto a vibration of F2 symmetry in the Td tetrahedral point group. The hyper-Raman scattering intensity of itstransverse optic component appears to be proportional to the number ofBO4 units in the glass. The boson peak observed in hyper-Raman scattering arises from externalmodes of rigid ESUs which correspond to librational motions coupled to their translations. Thescattering strength of these modes strongly decreases with increasing Li concentration. In purev-B2O3, external modes of boroxols presumably dominate this scattering. The decrease in theboroxol concentration in lithium borate glasses correlates with the apparent hardening ofthe boson peak.

Effect of microstructure on the electrical conductivity of clay-rich systems

It is well established that the electrical conductivity of clayey materials has two components: (a) a volume conductivity, proportional to the salted water content and (b) a surface conductivity, proportional to the cation exchange capacity. For a good understanding of the surface component associated with the electrical double layer, two fundamental aspects have to be taken into account: (a) the physical and chemical processes in the electrical double layer and (b) the effect of the clay distribution in the material. The present paper proposes a numerical approach to study the impact of clay microstructure on the macroscopic electrical conductivity. The application of such an approach is illustrated for three topics. In the first, a sensitivity analysis of the effect of the elementary structural units (platelet and aggregate) shows the significant impacts of the aggregation process and the anisotropy of the elementary structural units (platelet and aggregate). The second corresponds to a low mineralized water–clay gel: when some montmorillonite clay is added in to the gel, the surface conductivity should increase in order to reproduce experimental data. The third is related to a clay rock consisting in aggregates and pores, which are saturated or not: the numerical results show that the effective conductivity of the saturated and the unsaturated clay rock depends linearly on the volumetric water content.

Embedded atom simulations of titanium systems with grain boundaries

The atomistic simulation of polycrystalline growth with an empirical potential requires an accurate modeling of the atomic configurations at grain boundaries. We refine an existing embedded-atom potential for bulk titanium to reproduce systems with small atomic coordination, namely, clusters of up to nine atoms, the relaxation of the s0001d surface and the adatom diffusion on this surface. We find that simulating Ti growth can be limited to the s0001d surface and the rather small class of grain boundaries with angles of coincidence-site lattices. We determine the atomic structure of the Tis0001d S = 7 grain boundary with molecular statics and find exclusively pentagonal elementary structural units. The potential energy surface shows that this grain boundary imposes a massive barrier on surface diffusion. We use the elementary cells of the coincidence-site lattice to construct two periodic systems with grain boundaries: an isolated grain within an environment of different crystalline orientation and two antiparallel grain boundaries. Molecular dynamic simulations show that this isolated grain is not stable and that the growth evolution of the system with two antiparallel grain boundaries depends strongly on the angle of incidence.

A New Molecular Theory of Non-Linear Viscoelasticity for Vitrifiable (or Crystallizable) Thermoplastic Polyurethane Elastomers

The molecular theory of non-linear viscoelasticity for vitrifiable thermoplastic polyurethane elastomers (VTPUE) is a refinement and extension of viscoelastic theory of thermoplastic elastomers and polyurethanes to glassy transition, a structural model and a mechanism of vitrification for glassy polymers were proposed. Five kinds of constituent chains with Nagai chain constraint consisting of soft-domains, hard-domains, and entanglements are used as the elementary structural and statistical ensemble units for the correlation of molecular and phase-domain structures to the static and dynamic mechanical behaviors. So the influences of non-Gaussian in character, the phase separation of domain, the network topology of structure, the affined deformation of constituent chains, and the thermal history are all taken into account in the constituent chains of the theory. Free energies of deformation for the VTPUE segment copolymer were calculated by the statistical mechanics with the probability distribution functions of the sizes for the five kinds of constituent chains. Then the static constitutive equations and modulus of four types of deformation and the dynamic shear viscosity, modulus and loss tangent of VTPUE are derived from the proposed theory. The theory is successful in relating the molecular chain parameters C100, C020, and C200 to the constitutive equations and modulus under large deformations and the micro-domain structure to the complex shear viscosity and modulus and the loss tangent. The dynamic shear modulus and loss tangent of VTPUE are related to the domain structures through the fraction of hard segments (Wh), the molecular weight of soft segment (Mns), and the growth dimensional parameters of hard and soft domains (β). Two series of linear VTPUE copolymers (ES and ET) with different fractions(Wh) of hard segments and molecular weight (Mns) of soft segments were prepared. Their static and dynamic mechanical properties were studied by uni-axial extension and dynamic analysis tests. Then the constitutive equation at uni-axial extension and the expressions of shear modulus and loss tangent are verified by these experimental data, and excellent agreement between the theory and experiments is achieved. It is shown, that the proposed theory can predict the viscoelastic behavior of vitrifiable thermoplastic polyurethanes.

Dendritic spines: elementary structural units of neuronal plasticity

Dendritic spines: elementary structural units of neuronal plasticity

Elementary structural units of the biosphere

Elementary structural units of the biosphere

Elementary structural units of the biosphere and landscapes.

Elementary structural units of the biosphere and landscapes.

Electronic spectrum of a two-dimensional Fibonacci lattice

The electronic spectrum and wave functions of a new quasicrystal structure—a two-dimensional Fibonacci lattice—are investigated in the tight-binding approximation using the method of the level statistics. This is a self-similar structure consisting of three elementary structural units. The “central” and “nodal” decoration of this structure are examined. It is shown that the electronic energy spectrum of a two-dimensional Fibonacci lattice contains a singular part, but in contrast to a one-dimensional Fibonacci lattice the spectrum does not contain a hierarchical gap structure. The measure of allowed states (Lebesgue measure) of the spectrum is different from zero, and for “central” decoration it is close to 1. The character of the localization of the wave functions is investigated, and it is found that the wave functions are “critical.”

Computerised structural analysis of zeolitic networks: Conceptualisation of a zeolite scene through graphs comparison

Molecular modelling techniques have demonstrated their power as helpful tools in the design of molecular sieves. Seeking to automate and optimise this step of the design process in the field of zeolite structure-property relationship studies, we present a computerised procedure for the acquisition of the visual perception of a zeolite three-dimensional structure, and the interpretation of the structure in terms of elementary structural units. The memorisation of the visual perception in a semantic network form, the prospects for its chemical interpretation and its usefulness in an artificial intelligence-oriented structure-property study, as if a ‘seeing’ computer, instead of the chemist, observes another computer screen, are presented.

Mathematical model for estimating the economic effectiveness of production process in coal panels and an example of its practical application

The paper includes the application foundations of the integrational method of mine production process modelling to planning the extraction process in coal panels. The main idea of mathematical model creation based on the principle of the integration of elementary structural units according to spatial, engineering, and time structures of the production process in longwall and exploitation panels is briefly described. The model can be used as an investigation tool for making optimal planning decisions according to the economic criterion assumed. An example of practical application of the method is briefly described. It takes into consideration the impact of exploitation panel dimensions on the optimal longwall face length. Selected conclusions derived from the calculation results are presented.

Geometry of ?9 and ?11 asymmetrical grain boundaries

It is shown how the decomposition scheme into structural units can be developed for rational asymmetrical tilt grain boundaries without computer simulations. The method is illustrated on the Σ9 and Σ11 grain boundaries in the f.c.c. lattice for which experimental observations of the boundary structures are available. Besides short-period boundaries, which may serve as elementary structural units, the irrational aperiodic asymmetrical boundaries are also considered. There are clear experimental indications that some of them, namely those composed of dense-packed atomic planes, and called “special” asymmetrical boundaries, behave differently from the other more general boundaries.

Effect of alloying with silver on intermediate-range order in bulk germanium diselenide glasses

Neutron diffraction, inelastic scattering and Raman scattering measurements have been made on well characterized samples of GeSe 2 and Ag 4Ge 3Se 9 glass. The alloying with Ag causes pronounced effects on both static and dynamic structure, the former characterized by a sharp decrease in the amplitude of the first sharp diffraction peak and the latter by a reduction in the number of modes corresponding to the v 3 vibrations of a Ge(Se 1/2) 4 tetrahedron and an increase in the number between v 4 and v 1. The neutron data are compared with a model based on the consideration of elementary structural units such as Ge(Se 1/2) 4 and Ag(Se 1/2) 3. The Raman spectrum is characterized by the disappearance of the “companion” line in the v 1 breathing mode upon doping with silver.

Nucleation of quasi-crystalline and amorphous structures

The structural characteristics of quasi-crystalline phases obtained by ion irradiation are compared with those of the corresponding amorphous structures. Chemical forces drive the formation of atomic clusters and their spatial organization under specific geometric constraints. The same elementary structural units exist in quasi-crystalline and glassy phases which display identical local order, their main difference being the degree of defect organization at the interface between locally ordered atomic groups.

Ion-induced crystal-to-glass transition in alloys

Bombardment of a thin film with energetic particles provides a typical case of a system internally driven to a state far from equilibrium, which is suitable for the occurrence of the crystal-to-glass transition. In this paper, critical experiments, on both ion implantation and ion mixing, are re-examined and correlated to interpretative models with the aim of identifying important features in such glass formation processes. Attention is devoted to materials presenting intermediate quasi-crystalline phases, whose characteristic structural and compositional properties constitute a bridge between crystalline and amorphous states. Recent research on glass-forming materials, their chemical stability and local properties is discussed with reference to a recent interpretative model of glass nucleation. Correlations between the structural properties of small metal clusters and those of elementary structural units in amorphous alloys are presented.

Moolooite, a naturally occurring hydrated copper oxalate from Western Australia

AbstractMoolooite, a naturally occurring hydrated copper oxalate has been identified in a sulphide-bearing quartz outcrop 12 km east of Mooloo Downs station homestead (25° 01′ 30″ S., 116° 06′ 30″ E.), Western Australia. It has apparently formed by the interaction of solutions derived from bird guano and weathering copper sulphides. Partial microchemical analysis indicates a composition corresponding to CuC2O4 · 0.44H2O. The infra-red spectrum is similar to that of the artificial compound with diagnostic absorption bands at 3490, 2975, 2935, 1980, 1940, 1660, 1365,1320, 830, 510, 390, and 315 cm−1. Powder X-ray diffraction patterns indicate a disordered structure with orthorhombic symmetry; a 5.35, b 5.63, c 2.56 Å, Z = 1. The strongest lines of the powder pattern are [d Å, I, hkl]: 3.88, 100, (110); 2.50, 30, (120); 2.33, 18, (011); 2.31, 25,(101); 2.14, 20, (111); 1.938, 18, (220); 1.787, 25, (121); 1.753, 30, (211); 1.216, 15, (112). Unindexed very weak diffuse lines on some patterns can be indexed assuming a supercell with a′ = a, b′ = 2b, c′ = 2c indicating the presence of ordered crystallites.Moolooite occurs as micro-concretionary crusts and powder in cracks and solution cavities resulting from sulphide oxidation. It is found associated with opaline silica, gypsum, broehantite, antlerite, atacamite, whewellite, sampleite, and libethenite. It is turquoise-green in colour with similar streak, lustre dull to waxy, calculated density 3.43 g/cm3. Moolooite is composed of aggregates of generally sub-micrometre sized equidimensional crystallites with α ∼ 1.57 and γ ∼ 1.95.By analogy with artificial copper oxalate, moolooite is constructed from infinite ribbon-like elementary structural units consisting of alternating Cu2+ and (C2O4)2− ions. These units are arranged en echelon in layers which are stacked with displacements so that octahedral coordination of copper ions is completed by oxygen atoms in adjacent layers. The minimal role played by water in the structure and composition of moolooite distinguish it from other oxalate minerals. Because of the zeolitic character of the water a general formula CuC2O4 · nH2O (0 ⩽ n ⩽ 1) appears to be appropriate.

The Development of Abrasion Resistance and Breaking Strength in Durable-Press Cotton Fabrics

Textile properties of the cured fabric resulting from the wet-fixation process are functions of the duration of the fixation step. As duration of this step is extended with reagent systems involving dimethyloldihydroxyethyleneurea together with highly methylated hexamethylolmelamines, resilience of cured fabric is high and constant, whereas Stoll flex abrasion resistance and breaking strength (strength properties) show progressive increases. This is evidently the first observation of increasing strength properties at a constant high level of resilience during a durable-press finishing process. The development of strength properties is considered to be critically dependent upon the penetration of reagent into the fabric, yarns, and fibers for reaction on elementary structural units of the cotton fibers. This unique degree of penetration to the less accessible regions in cotton fibers is believed to relieve internal strains within the fibers before crosslinking takes place. Other features of the mechanism of develolment of strength properties in durable-press cottons are discussed.

All-Cotton Durable-Press Fabrics of High Strength from Slack-Mercerized, Partially Restretched Yarn

The virtual elimination of break and tear strength losses in cotton sheeting during conventional pad-dry-cure treat ments with DMEU, formaldehyde, APO, and bis(2-hydroxyethyl) sulfone has been observed. At wrinkle recovery angles of 270-300° (W + F), the tearing and breaking strength retention, or the average of these, in yarn-mercerized fabric were often equal to the values for untreated unmercerized fabric. Yet the cross-linking of unmercerized fabric produced 33- 55% losses in breaking strength and 45-68% losses in tearing strength. Moreover the scoured fabrics, yarn-mercerized and unmercerized, were nearly identical in strength prior to cross-linking. The experimental fabrics, woven of yarn only partially restretched after slack-mercerization, possessed higher elongation when cross-linked than did unpretreated cross linked fabric. Since strength losses during cross-linking can be varied or nearly eliminated without changing the wrinkle resistance ob tained, strength losses and wrinkle recovery are evidently produced by separate and, in some cases, independent cross-link mechanisms. Work of others indicates strength and elongation losses in conventional cross-linking processes are due to the spiral structure of fibrillar windings in the secondary wall of the cotton fiber. The fibrils cannot unwind fully and equally under stress after being cross-linked. Present findings suggest conditioned wrinkle recovery, as imparted here, arises in more elementary structural units, such as cross-linked microfibrils, where tensioning has little effect. The possibility that a strength maximum can occur in cotton at optimal levels of cross-linking is re-examined, in view of evidence that swelling and tensioning pretreatments, as well as polymer inclusion during cross-linking, can alter the amount and type of cross-linking already present in cotton because of hydrogen-bonding and crystallinity.

A study of structure formation in the degradation of vulcanized rubbers

It has been shown in previous communications that breakdown of supermolecular structures occurs on prolonged vulcanization of chloroprene rubbers. Subsequently, during storage under normal conditions, ordering again takes place, as far as the formation of spherulites [1]. These results were explained in the following way. The vulcanized network is formed not between individual polymer chains but between primary structural elements present in the rubbers. Thus the elementary structural units, forming the component elements for the construction of more complex structures, must obviously be preserved even when the vulcanized rubbers are degraded. Hence the objective of the present work was to study the structure-formation processes occurring in degraded vulcanizates.

Comparative study of the oxidation reactions of pectic substances, of cellulose, and of the structural units of these substances

1. Under the conditions studied methyl α -galactosiduronic acid was more readily. oxidized than methyl α -glucoside. 2. It was shown that the difference in the reactivities of these models, and therefore of the elementary structural units of the corresponding polymers, is determined by the difference in spatial configuration at C-4 of the pyranose ring.