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Studies of the pollen abortion mechanism in thermo-sensitive male sterile lines may provide a strong foundation for breeding hybrid wheat and establishing a theoretical basis for marker-assisted selection. To investigate the cause of pollen abortion in Bainong thermo – sensitive male sterile (BNS) lines, we analyzed the properties of pollen grains, changes in the tapetum and microspores in different anther developmental stages, and the distribution and deposition of nutrient substances in microspores. We found that tapetum degraded in the early uninucleate stage in sterile BNS (S-BNS), which was earlier than that of fertile BNS (F-BNS) tapetum. Large amounts of insoluble polysaccharides, lipids, and proteins were deposited until the trinucleate pollen stage in the nutritive cells in F-BNS. At the binucleate stage, the vacuoles disappeared and pollen inclusion increased gradually. At the trinucleate stage, these nutrients would help pollen grains mature and participate in fertilization normally. Therefore, early degradation of the tapetum, which inhibits normal microspore development, and the limited content of nutrient substances in pollen may be the main factors responsible for male sterility in BNS lines.

A novel concept for simplification of heat treatment process in a tool steel by the addition of aluminium has been proposed in this research. The addition of 1.08 wt-% aluminium leads to an approximately fully pearlitic state, of which the cementite lamellae are largely spheroidised. Excessive addition of 1.58 wt-% aluminium would result in the formation of a large amount of δ-ferrite. These results are mainly attributed to the synthetic effect of aluminium on the driving force of pearlite transformation and the inter-spacing distance between the proeutectoid carbides. The mechanical properties’ analyses show that aluminium has promising potential to substantially simplify the processing method for developing a relative low-cost mould steel without the concomitant mechanical properties’ reductions.

A novel concept for simplification of heat treatment process in a tool steel by the addition of aluminium has been proposed in this research. The addition of 1.08 wt-% aluminium leads to an approximately fully pearlitic state, of which the cementite lamellae are largely spheroidised. Excessive addition of 1.58 wt-% aluminium would result in the formation of a large amount of d-ferrite. These results are mainly attributed to the synthetic effect of aluminium on the driving force of pearlite transformation and the inter-spacing distance between the proeutectoid carbides. The mechanical properties’ analyses show that aluminium has promising potential to substantially simplify the processing method for developing a relative low-cost mould steel without the concomitant mechanical properties’ reductions.

The influence of Mn content on flow behaviour and constitutive equations of Fe–(20/27)Mn–4Al–0.3C austenitic steels was investigated by uniaxial hot compression tests. The recrystallisation fraction was also measured using electron backscattered diffraction. Although dynamic recrystallisation is slightly delayed by the increased Mn content, the peak stress still has a pronounced decline especially during the deformation at relatively low temperature. The reason should be ascribed to the enhanced stacking fault energy, by which workhardening rate before the onset of dynamic recrystallisation is diminished significantly with the reinforced cross-slip process. The hot deformation activation energy is decreased under the condition of higher Mn addition, while the strain rate sensitivity of flow stress almost remains unchanged.

In this study, we employed electron microscopy to investigate the cytogenetic and embryologic mechanisms of parthenogenesis induced in the 1BL/1RS male sterile lines of wheat. Analysis of the root tips and acid polyacrylamide gel electrophoresis indicated that all of the male sterile lines and their maintainer lines were 1BL/1RS translocation lines, whereas the restorer lines were non-1BL/1RS translocation lines. Furthermore, the chromosomes of 1BL/1RS wheat lines with T. aestivumcytoplasm and Aegilopscytoplasm (include Ae. kotschyi, Ae. ventricosa, Ae. variabilis)paired abnormally at different rates during meiotic metaphase I (MMI). The translocated segment size of the 1RS chromosome and the specific nuclear—alloplasm interaction impaired the pairing of homologous chromosome in the background of the specific Aegilopscytoplasm at MMI. In addition, the frequency of abnormal chromosomal pairing was directly affected by the frequency of haploid production induced by parthenogenesis. The results of this study provide significant insights into the mechanism of parthenogenesis, which is probably due to the abnormal fertilization of synergid cells in alloplasmic 1BL/1RS wheat.

The influence of Mn content on flow behaviour and constitutive equations of Fe–(20/27)Mn–4Al–0.3C austenitic steels was investigated by uniaxial hot compression tests. The recrystallisation fraction was also measured using electron backscattered diffraction. Although dynamic recrystallisation is slightly delayed by the increased Mn content, the peak stress still has a pronounced decline especially during the deformation at relatively low temperature. The reason should be ascribed to the enhanced stacking fault energy, by which workhardening rate before the onset of dynamic recrystallisation is diminished significantly with the reinforced cross-slip process. The hot deformation activation energy is decreased under the condition of higher Mn addition, while the strain rate sensitivity of flow stress almost remains unchanged.

Physiological male sterility induced by the chemical hybridizing agent (CHA) overcomes problems of maintenance of sterile lines and restorers. However, the mechanism of sterility is unclear. The process of tapetum of CHA-treated ‘Xi’nong 2611’ at uninucleate, binucleate and trinucleate were compared with control to determine if tapetum varying differently during developmental stages. Tapetal degradation in CHA-treated ‘Xi’nong 2611’ began at late uninucleate stage, somewhat earlier than control plants. Cytological observations indicated that the gradual degradation of the tapetum in CHA-treated ‘Xi’nong 2611’ was initiated and terminated earlier than in the control. These findings implied that CHA-induced male sterility was related to abnormally early tapetal degradation. In order to indicate the role of the SKP1gene in fertility/sterility in wheat, its expression was assessed in anthers at uninucleate, binucleate and trinucleate stages. SKP1expression was reduced in the later developmental stages, and there was an obvious decrease from the uninucleate to trinucleate stages. Higher expression of the SKP1gene occurred in ‘Xi’nong 2611’ compared to CHA-treated ‘Xi’nong 2611’. This implied that SKP1gene expression was inhibited during the fertility transformation process and was related to transformation from fertility to sterility. Moreover, the results from this study suggest that SKP1plays an essential role of conducting fertility in physiological male sterility.

The opposed dies shearing process is a precision shearing process and can be applied to low plasticity blanked materials due to its special tool design and process kinematics. In the present study, a two-dimensional (2D) rigid plastic finite element model of opposed dies shearing of an AISI 70 steel blanked part was developed under the DEFORM-2D platform. Based on this model, important field variables such as metal flow velocity field, effective strain and damage variations at the tracking points were investigated in detail. and the cut surface features as well as the forming loads were predicted. The results indicate that the opposed dies shearing process is beneficial in improving the quality of low plasticity blanked parts and prolong the service lives of cutting tools.

For a typical tailor welded blank (TWB), the mechanical performances of the weld metal vary dramatically with different distances to the longitudinal centreline of the weld. Constructive models that can describe this laterally inhomogeneous behaviour of welds, however, have rarely been reported. In this work, the elastoplastic properties (i.e. hardness, Young’s modulus, initial yield stress, strength coefficient and strain hardening exponent) of a laser welded bead, made of DX56D and DP600 automotive steel sheets of different gauges, were determined according to the nanoindentation response. Based on the measured data, a constructive model of the weld bead, which has taken into account the performance inhomogeneity traversing the weld line, was built. This constructive model was justified by the fact that the numerical results of Erichsen cupping tests for TWB specimens are in good agreement with the corresponding experimental ones.

ABSTRACTTwo groups of unknown bacteria, which phenotypically resemble members of the Bacteroides fragilisgroup but phylogenetically display >5% 16S rRNA gene sequence divergence from their nearest validly described species, Bacteroides thetaiotaomicron, were characterized by phenotypic and molecular taxonomic methods. Phylogenetically and phenotypically, the unidentified bacteria displayed a relatively close association with each other. However, a 16S rRNA gene sequence divergence of approximately 4% between the two unknown bacteria, as well as distinguishable biochemical characteristics, demonstrates that these organisms are genotypically and phenotypically distinct, and each group may represent a previously unknown subline within the Bacteroidesphylogenetic cluster. Subsequent DNA-DNA hybridization studies confirmed that the two novel organisms were indeed distinct from each other. The previously described species closest to both of them is B. thetaiotaomicron(approximately 94% sequence similarity), but they can be differentiated easily from B. thetaiotaomicronby virtue of not utilizing trehalose. DNA-DNA pairing studies also documented the separateness of the unknown species and B. thetaiotaomicron. Based on the phenotypic and phylogenetic findings, two new species, “Bacteroides nordii” sp. nov. and “Bacteroides salyersae” sp. nov, are proposed. The G+C content of the DNA is 41.4 mol% for Bacteroides nordiiand 42.0 mol% for Bacteroides salyersae. The type strains of Bacteroides nordiiand Bacteroides salyersaeare WAL 11050 (ATCC BAA-998 or CCUG 48943) and WAL 10018 (ATCC BAA-997 or CCUG 48945), respectively.

A polymer containing 3‘-[trifluoromethyl-4,3‘-dibenzoazo] dyes in the side chains has been synthesized, and a monolayer of this polymer has been transferred onto solid substrate by the Langmuir−Blodgett (LB) technique. The reversible processes of photoisomerization of the LB films induced by light are observed by UV−vis absorption spectra, in situ atomic force microscopy, and friction force microscopy. In addition, the physisorbed monolayers of the monomer of the polymer at liquid/solid interface are investigated by scanning tunneling microscopy. The films of the polymer show the reversible change of morphological and friction force responses under alternate UV (365 ± 10 nm) and visible (436 ± 10 nm) irradiation. The films also undergo reversible wettability changes with UV and visible light irradiation, which are directly confirmed by contact angle measurement. The largest photoinduced change of contact angle is 11 ± 1°. The larger value of the contact angles measured corresponds to films mainly composed of the trans isomers of the molecules. Evidence shows that the photoinduced surface energy changes have an important influence on the wettability changes.

This paper presents an experimental study on the structural behaviour of short spun concrete tubes and short steel–concrete composite spun tubular columns under axial loading. The results showed that high-strength spun concrete tubes are very brittle and work linearly until close to failure. Steel–concrete composite spun tubular columns have much better ductility and integrity than spun concrete tubes. The progress of concrete confinement provided by the steel tube during the whole loading process has been observed by analysing the strain measurements on the steel tubular walls.

p73 is structurally and functionally related to p53 and is possibly a tumor suppressor gene. Using 15 surgically resected frozen esophageal specimens containing both squamous cell carcinomas (ESCC) and neighboring normal epithelia, we studied p73 gene alterations and mRNA expression. Loss of heterozygosity of the p73 loci was found in nine of 14 informative cases (64%). A polymorphism at codon 173 (Thr) of p73 was identified (eight samples had ACC and seven had ACT), but mutation was not detected in tumor samples. Nine of the 15 ESCC samples (60%) displayed significantly elevated expression of p73 over the neighboring normal epithelium; of these nine samples, four displayed loss of imprinting (LOI) and one switched the expressed allele. Hypermethylation of exon 1 of the p73 gene was not detected, using the bisulfite modification method, in normal or tumor samples. Twelve of the 15 (80%) ESCC samples contained p53 defects, including missense mutation, non-frameshift small deletion or insertion, non-detectable transcripts and protein accumulation. The ESCC samples with p53 defects were significantly correlated with those which had elevated expression of p73 (Fisher's exact test, P < 0.05). The results suggest that increased expression of p73, including that by LOI, could be a partial compensatory mechanism for defective p53.

An organic thin film of N, N-dimethyl-N'(3-nitrobenzylidene)-p-phenylenediamine with electrical bistability properties was prepared by the vacuum deposition method. The film was observed with a scanning tunnelling microscope (STM). Ultrahigh-density data storage is demonstrated on the organic film, produced by applying a voltage pulse between the STM tip and the substrate of the thin film under ambient conditions. The average size of the recording marks is about 0.7 nm, corresponding to a data storage density of about 1013bits cm?2. The local current-voltage curves of the film suggest that the recorded area is conductive, while the unrecorded region possesses high resistance. The recording mechanism is also discussed.

Three types of cement-stabilized macadam materials and raw materials mixed with a self-made early-strength agent were prepared and subjected to freeze-thaw cycle tests. Based on the unconfined compression and freeze-thaw cyclic tests, the compressive strength and mass loss rate, and frost resistance coefficients of these samples were assessed and compared. The change of material properties caused by different content of early-strength agent was analyzed. The results show that three kinds of early-strength agents can improve the compressive strength and freezing resistance of cement-stabilized macadam. The compressive strength of cement-stabilized macadam with 2.0% anhydrous sodium sulfate and 1.0% triethanolamine is the best; the compressive strength is increased by 73.8%. Cement-stabilized macadam material with 1.5% anhydrous sodium sulfate and 1.0% triethanolamine has the best frost resistance, and its mass loss rate is reduced by 0.733%. The curves of mass loss rate and freeze-thaw cycle times of four groups of material are established, and the trend of positive correlation between the content of anhydrous sodium sulfate and the freezing resistance is obtained.

TiB2-TiC-SiC composites were prepared by high-gravity activated SHS using (Ti+B4C+Si) mixing powders. XRD, FESEM and FETEM results showed that the matrix of composites was mainly composed of TiB2, TiC and b-SiC. Uniformly-distributed TiB2 platelets formed the skeleton of composites, and irregular TiC and b-SiC solids were embedded between TiB2 matrix. It is supposed that TiB2 phases firstly precipitate prior to TiC from the molten reactive product in high-gravity field due to higher concentration of boron atom, and SiC solids solidify at final solidification stage and feed the TiB2 platelet skeleton, which effectively reduce the porosity and promote the relative density of composites.