MICROSTRUCTURE ANALYSIS OF 3 SEGMENTED COPOLYMERS CONTAINING POLYDIMETHYLSILOXANE BY SOLID-STATE HIGH-RESOLUTION NMR

The microstructure of two bicomponent and one tricomponent segmented copolymers, based on polydimethylsiloxane, poly(p-hydroxystyrene) or/and polysulfone, were investigated using an extended Goldman-Shen pulse sequence, proton spin-spin relaxation measurements, and C-13 and Si-29 NMR spectra. The results indicate that there exist four phases with different sizes, components and morphological structure in the segmented copolymers studied in this work, i. e., a rigid-chain phase of very slow motion, a rigid-chain-rich phase of slow motion, a flexible-chain-rich phase of fast motion and a flexible-chain phase of faster motion. The sizes of different domains, calculated from the spin diffusion rates, are about 50-100 angstrom for the flexible-chain-rich phase of fast motion and 200-300 angstrom for the flexible-chain phase of faster motion. The relative quantities of polydimethylsiloxane in the flexible-chain phase of fast motion are slightly different in different kinds of segmented copolymers.

Formation of nano-crystalline corrosion products on Zn-Al alloy coating exposed to seawater

Hot dip Zn-Al alloy coating performs better than hot dip galvanized coating and 55% Al-Zn-Si coating as well with regard to general seawater corrosion protection. A characterization of the corrosion products on Zn-Al alloy coating immersed in dynamic aerated seawater has been performed mainly based on transmission electron microscopy (TEM) for morphological analysis and X-ray diffraction (XRD) technique for crystalline phase identification. The XRD and TEM analyses showed that the corrosion products mainly were typical nanometer Zn4CO3(OH)(6).H2O, Zn-5(OH)(8)Cl-2 and Zn6Al2CO3(OH)(16). 4H(2)O microcrystals. This probably is connected to the co-precipitation of Zn2+ and Al3+ ions caused by adsorption. Zn-Al alloy coating being suffered seawater attacks, AI(OH)(3) gel was first produced on the coating surface. Zn and Al hydroxides would co-precipitate and form double-hydroxide when the concentration of adsorbed Zn2+ ions by the newly produced gel exceeded the critical degree of supersaturation of the interphase nucleation. However, because the growth of the crystals was too low to keep in step with the nucleation, a layer of nano-crystalline corrosion products were produced on the surface of the coating finally. (C) 2001 Elsevier Science Ltd. All rights reserved.

Karyomorphology of Biebersteinia Stephan (Geraniaceae) and its systematic and taxonomic significance

The systematic and taxonomic position of Biebersteinia Stephan has long been in dispute. The present paper describes for the first time the karyomorphology of two species in Biebersteinia Stephan. Both species commonly showed the interphase nuclei of the simple chromocenter type and the mitotic prophase chromosomes of the interstitial type. The karyotype formulae of both B. heterostemon and B. odora were 2n=10=2m(2sec)+8sm(2sec), belonging to the 3A type of Stebbins' classification. The karyotype of this genus is recorded for the first time. The basic chromosome numbers of four of the five known species of Biebersteinia have been recorded as x=5. The combination of resting nuclei of the simple chromocenter type, mitotic prophase chromosomes of the interstitial type, two pairs of chromosomes with four obvious secondary constrictions at the mitotic prophase and metaphase stages, and the peculiar 3A karyotype in Biebersteinia can be regarded as the karymorphological marker of this genus. The karyomorphological data presented here do not support the traditional grouping of this genus in Geraniaceae. The unique karyomorphology of Biebersteinia justifies its familiar or ordinal status, which is congruent with embryological, anatomical, chemical and molecular data. The systematic position of Biebersteinia needs further study.

扬子地区上奥陶－下志留统黑色岩系形成机理

The black rock series of the Upper Ordovician - Lower Silurian in Yangtze area are important source rocks and have exceptional characteristics of sediment, biology, element geochemistry, carbon and oxygen isotope, organic geochemistry and etc. These characteristics are the reflection of important geology events. Due to scarce system research, many problems that relate to the development mechanism of source rocks are not solved. And this restricts the exploration of Oil and gas in South China. In this paper, author studied the palaeo-climate, palaeo-structure and palaeo-environment of the Upper Ordovician - Lower Silurian in Yangtze area by sedimentology, palaeobiology and geochemistry, especially the element geochemistry and isotope geochemistry. The environment model of source rocks is established and some conclusions are drawn. The Upper Ordovician - Lower Silurian sediment types in Yangtze area are mostly black shales, next, mudstone, shell limestone and siltystone. During the Late Ordovician and Earily Silurian periods, a series of big upheaval and depressed are distributed in Yangtze area, and the strata pattern of interphase upheaval and depressed led to Yangtze palaeosea isolated with outside sea. So the stagnant and anoxic environment that are the favorable factor of rich organic black shales sediment is formed in Yangtze area. That Chemical Index of Alteration (CIA) values of the lower Wufeng formation and Longmaxi formation exhibits moderate chemistry weathering suggests they were deposited under the circumstances of the warm and humid climate. However, the large difference of the CIA values of N.extraordinarius-N.ojsuensis biozone suggests that climate is changeful. Therefore, there were two different kinds of climates in the course of the deposition of the Wufeng formation and Longmaxi formation. During the Late Ordovician - Earily Silurian periods, in Yangtze palaeosea, the surface water which is full of rich nutriment and abundant bacterium - algae has high palaeo-productivity that is obvious difference in the different space – time. The content of sulphate changes gradually from the surface water columns to the deep water columns. That is, salinity in the surface water columns is serious low and the salinity in deep water columns is normal. Salinity delamination is favor of the forming of deep anoxic environment. During Wufeng period, the oxidated and low sulfate environment exists in the upper Yangtze palaeosea, while the anoxic and normal salinity environment occurs in the lower Yangtze palaeosea. During the Late Wufeng and Guanyinqiao periods, the steady anoxic environment is replaced by oxidated environment. During the Longmaxi period, layered and anoxic environment recur. In Yangtze area, studies of δ13C of sedimentary organic carbon show a positive δ13C excursion up to 4‰ in the Guanyinqiao stage and then, acute negative excursion in the earily Longmaxi stage. These organic carbon isotopes curve are not only efficient measure of carving up strata borderline, but also reflected the change of originality productivity. These organic carbon isotopes curves showed the process of the enhanced embedding of the global organic carbon. Anoxic event is the main factor of increasing organic carbon embedding speed. And the reduced organic carbon embedding in Hirnantian stage is due to the water column with abundant oxygen. The δ34S values are gradually positive excursion from P.pacificus biozone to N.extraordinarius biozone, and reach the maximum in the Upper Hirnantian stage. Then, the δ34S values are negative excursion. The excursions of δ13C and δ34S reflect the acute change of environment. The formation of source rocks is largely dependent on the nature of organisms from which kerogen is derived and the preservation conditions of organic matter, which are fundamentally dependent on a favourable combination of various elements in which organisms live and are subsequently buried. These elements include palaeoclimate, palaeostructure and palaeoenvironmental conditions. Based on above mentioned circumstance, the coupling connection of source rock and the palaeoclimate, and of palaeostructure and palaeoenvironmental conditions are confirmed, and the “anoxic-marginal depression-photosynthesis” environemental model is established. It is indicated that anoxic played important role in production of organic matter. The produced organic matter was accumulated in marginal depression of the Yangtze area. The photosynthesis is favor of the high productivity. Source rocks have a good perspective, like that of “hot shale” deposited in North Africa.

Steady-state motion of a Mode-III crack on imperfect interfaces

Mishuris, Gennady; Movchan, N.V.; Movchan, A.B., (2006) 'Steady-state motion of a Mode-III crack on imperfect interfaces', Quarterly Journal of Mechanics and Applied Mathematics 59(4) pp.487-516 RAE2008

Nuclear dispositions of subtelomeric and pericentromeric chromosomal domains during meiosis in asynaptic mutants of rye (Secale cereale L.)

EI Mikhailova, SP Sosnikhina, GA Kirillova, OA Tikholiz, VG Smirnov, RN Jones and G Jenkins (2001). Nuclear dispositions of subtelomeric and pericentromeric chromosomal domains during meiosis in asynaptic mutants of rye (Secale cereale L.). Journal of Cell Science, 114 (10), 1875-1882. Sponsorship: Russian Foundation for Basic Research (grants 00-04-48522/ 99-04-48182) RAE2008

Cytokinesis proteins Tum and Pav have a nuclear role in Wnt regulation.

Wg/Wnt signals specify cell fates in both invertebrate and vertebrate embryos and maintain stem-cell populations in many adult tissues. Deregulation of the Wnt pathway can transform cells to a proliferative fate, leading to cancer. We have discovered that two Drosophila proteins that are crucial for cytokinesis have a second, largely independent, role in restricting activity of the Wnt pathway. The fly homolog of RacGAP1, Tumbleweed (Tum)/RacGAP50C, and its binding partner, the kinesin-like protein Pavarotti (Pav), negatively regulate Wnt activity in fly embryos and in cultured mammalian cells. Unlike many known regulators of the Wnt pathway, these molecules do not affect stabilization of Arm/beta-catenin (betacat), the principal effector molecule in Wnt signal transduction. Rather, they appear to act downstream of betacat stabilization to control target-gene transcription. Both Tum and Pav accumulate in the nuclei of interphase cells, a location that is spatially distinct from their cleavage-furrow localization during cytokinesis. We show that this nuclear localization is essential for their role in Wnt regulation. Thus, we have identified two modulators of the Wnt pathway that have shared functions in cell division, which hints at a possible link between cytokinesis and Wnt activity during tumorigenesis.

Control of cyclin B1 localization through regulated binding of the nuclear export factor CRM1.

Activation of the Cyclin B/Cdc2 kinase complex triggers entry into mitosis in all eukaryotic cells. Cyclin B1 localization changes dramatically during the cell cycle, precipitously transiting from the cytoplasm to the nucleus at the beginning of mitosis. Presumably, this relocalization promotes the phosphorylation of nuclear targets critical for chromatin condensation and nuclear envelope breakdown. We show here that the previously characterized cytoplasmic retention sequence of Cyclin B1, responsible for its interphase cytoplasmic localization, is actually an autonomous nuclear export sequence, capable of directing nuclear export of a heterologous protein, and able to bind specifically to the recently identified export mediator, CRM1. We propose that the observed cytoplasmic localization of Cyclin B1 during interphase reflects the equilibrium between ongoing nuclear import and rapid CRM1-mediated export. In support of this hypothesis, we found that treatment of cells with leptomycin B, which disrupted Cyclin B1-CRM1 interactions, led to a marked nuclear accumulation of Cyclin B1. In mitosis, Cyclin B1 undergoes phosphorylation at several sites, a subset of which have been proposed to play a role in Cyclin B1 accumulation in the nucleus. Both CRM1 binding and the ability to direct nuclear export were affected by mutation of these phosphorylation sites; thus, we propose that Cyclin B1 phosphorylation at the G2/M transition prevents its interaction with CRM1, thereby reducing nuclear export and facilitating nuclear accumulation.

The Septin-Binding Protein Anillin is Over-Expressed in Diverse Human Tumours

Anillin is an actin-binding protein that can bind septins and is a component of the cytokinetic ring. We assessed the anillin expression in 7,579 human tissue samples and cell lines by DNA micro-array analysis. Anillin is expressed ubiquitously but with variable levels of expression, being highest in the central nervous system. The median level of anillin mRNA expression was higher in tumors than normal tissues (median fold increase 2.58; 95% confidence intervals, 2.19-5.68, P < 0.0001) except in the central nervous system where anillin in RNA levels were lower in tumors. We developed a sensitive reverse transcription-PCR strategy to show that anillin mRNA is expressed in cell lines and in cDNA panels derived from fetal and adult tissues, thus validating the microarray data. We compared anillin with Ki67 in RNA expression and found a significant linear relationship between anillin and Ki67 mRNA expression (Spearmann r similar to 0.6, P < 0.0001). Anillin mRNA expression was analyzed during tumor progression in breast, ovarian, kidney, colorectal, hepatic, lung, endometrial, and pancreatic tumors and in all tissues there was progressive, increase in anillin mRNA expression from normal to benign to malignant to metastatic disease. Finally, we used anti-anillin sera and found nuclear anillin immuncireactivity to be widespread in normal tissues, often not correlating with proliferative compartments. These data provide insight into the existence of non proliferation-associated activities of anillin and roles in interphase nuclei. Thus, anillin is overexpressed in diverse common human tumors, but not simply as a consequence of being a proliferation marker. Anillin may have potential as a novel biomarker.

Fatigue Damage of Composite Structures Applying a Micromechanical Approach

Fatigue damage calculations of unidirectional polymer composites is presented applying micromechanics theory. An orthotropic micromechanical damage model is integrated with an isotropic fatigue evolution model to predict the micromechanical fatigue damage of the composite structure. The orthotropic micromechanical damage model is used to predict the orthotropic damage evolution within a single cycle. The isotropic fatigue model is used to predict the magnitude of fatigue damage accumulated as a function of the number of cycles. The advantage of using this approach is the cheap determination of model parameters since the orthotropic damage model parameters can be determined using available data from quasi-static loading tests. Decomposition of the state variables down to the constituent scale is accomplished by micromechanics theory. Phenomenological damage evolution models are then postulated for each constituent and for interphase among them. Comparison between model predictions and experimental data is presented.

A micromechanics approach for damage modeling of polymer matrix composites

A new model for damage evolution in polymer matrix composites is presented. The model is based on a combination of two constituent-level models and an interphase model. This approach reduces the number of empirical parameters since the two constituent- level models are formulated for isotropic materials, namely fiber and matrix. Decomposition of the state variables down to the micro-scale is accomplished by micromechanics. Phenomenological damage evolution models are then postulated for each constituent. Determination of material parameters is made from available experimental data. The required experimental data can be obtained with standard tests. Comparison between model predictions and additional experimental data is presented.

Control of the AtMAP65-1 interaction with microtubules through the cell cycle

Cell division depends on the fine control of both microtubule dynamics and microtubule organisation. The microtubule bundling protein MAP65 is a 'midzone MAP' essential for the integrity of the anaphase spindle and cell division. Arabidopsis thaliana MAP65-1 (AtMAP65-1) binds and bundles microtubules by forming 25 nm cross-bridges. Moreover, as AtMAP65-1 bundles microtubules in interphase, anaphase and telophase but does not bind microtubules in prophase or metaphase, its activity through the cell cycle must be under tight control. Here we show that AtMAP65-1 is hyperphosphorylated during prometaphase and metaphase and that CDK and MAPK are involved in this phosphorylation. This phosphorylation inhibits AtMAP65-1 activity. Expression of nonphosphorylatable AtMAP65-1 has a negative effect on mitotic progression resulting in excessive accumulation of microtubules in the metaphase spindle midzone causing a delay in mitosis. We conclude that normal metaphase spindle organisation and the transition to anaphase is dependent on inactivation of AtMAP65-1.

Dynamic interaction of NtMAP65-1a with microtubules in vivo

Plant microtubules are intrinsically more dynamic than those from animals. We know little about the dynamics of the interaction of plant microtubule-associated proteins (MAPs) with microtubules. Here, we have used tobacco and Arabidopsis MAPs with relative molecular mass 65 kDa (NtMAP65-1a and AtMAP65-1), to study their interaction with microtubules in vivo. Using fluorescence recovery after photobleaching we report that the turnover of both NtMAP65-1a and AtMAP65-1 bound to microtubules is four- to fivefold faster than microtubule treadmilling (13 seconds compared with 56 seconds, respectively) and that the replacement of NtMAP65-1a on microtubules is by random association rather than by translocation along microtubules. MAP65 will only bind polymerised microtubules and not its component tubulin dimers. The turnover of NtMAP65-1a and AtMAP65-1 on microtubules is similar in the interphase cortical array, the preprophase band and the phragmoplast, strongly suggesting that their role in these arrays is the same. NtMAP65-1a and AtMAP65-1 are not observed to bind microtubules in the metaphase spindle and their rate of recovery is consistent with their cytoplasmic localisation. In addition, the dramatic reappearance of NtMAP65-1a on microtubules at the spindle midzone in anaphase B suggests that NtMAP65-1a is controlled post-translationally. We conclude that the dynamic properties of these MAPs in vivo taken together with the fact that they have been shown not to effect microtubule polymerisation in vitro, makes them ideally suited to a role in crossbridging microtubules that need to retain spatial organisation in rapidly reorganising microtubule arrays.

Transfer of amiprophosmethyl resistance from a Nicotiana plumbaginifolia mutant by somatic hybridisation

Transfer of resistance to the phosphorothioamidate herbicide, amiprophosmethyl (APM), from the P-tubulin mutant of Nicotiana plumbaginifolia to the interspecific N, plumbaginifolia (+) N, sylvestris is and to the intertribal N, plumbaginifolia (+) Atropa belladonna somatic hybrids has been demonstrated. Transfer to the recipient species was accomplished by: (1) symmetric hybridisation and (2) asymmetric hybridisation using gamma-irradiation of donor protoplasts. Cytogenetic analysis confirmed the hybrid origin of the hybrids obtained. It was established that most of them typically inherited no more than three donor chromosomes, although it was possible to obtain symmetric hybrids in the case of symmetric fusion. Immunofluorescent microscopy analysis has shown that protoplasts of the mutant, and of the N. plumbagini-folia (+) N. sylvestris and N. plumbaginifolia (+) A. belladonna hybrids, retained the normal structure of interphase microtubule (MT) arrays and mitotic figures after treatment with 5 mu M APM, whereas MTs of protoplasts of the recipients were destroyed under these conditions. It was also shown that hybrid clones contained an altered beta-tubulin isoform originating from the N. plumbaginifolia mutant. The selected hybrid clones were characterised by cross-resistance to trifluralin, a dinitroaniline herbicide with the same mode of anti-MT action. Some of the somatic hybrids which could flower were fertile. It was established that seeds of some fertile hybrids were able to germinate in the presence of 5 mu M APM. The results obtained thus support the conclusion that the technique of somatic hybridisation, especially asymmetric fusion, can be used to transfer APM resistance from the N. plumbaginifolia mutant to different (related and remote) plant species of the Solanaceae, including important crops.

Immunological homologues of the Arabidopsis thaliana beta 1 tubulin are polyglutamylated in Nicotiana tabacum

Peptide-specific antibody AABI, raised to the C-terminal 13 amino acids of Arabidopsis thaliana beta 1 tubulin, identifies a single electrophoretically separable beta-tubulin on 2-D-gel Western blots of total protein extracts from A. thaliana seedlings. We show that AABI crossreacts with two of the eight polyglutamylated beta-tubulin isoforms present in purified Nicotiana tabacum tubulin fractionated by high-resolution isoelectric focussing. Immunolocalisation studies using AAB1 revealed that the two N. tabacum polyglutamylated beta 1-tubulin isoforms are utilised in all four plant microtubule arrays (the interphase cortical array, the preprophase band, the spindle and the phragmoplast) indicating that there is no apparent subcellular sorting of these isotypes.