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Such as flying creatures, morphing aircraft can expand their aerodynamic flight envelopes by changing aerodynamic shapes, significantly improving the scope of application and flight efficiency. A novel 3D Zero Poisson’s Ratio (ZPR) honeycomb structure is designed to meet the flexible deformation requirements of morphing aircraft. The 3D ZPR honeycomb can deform in the three principal directions with smooth borders and isotropic. Analytical models related to the uniaxial and shear stiffnesses are derived using the Timoshenko beam model and validated using the quasi-static compression test. The Poisson’s ratio of the 3D ZPR honeycomb structure has an average value of 0.0038, proving the feasibility of the 3D ZPR concept. Some pneumatic muscle fibers are introduced into the system as flexible actuators to drive the active deformation of the 3D ZPR honeycomb. The active 3D ZPR honeycomb can contract by 14.4%, unidirectionally bend by 7.8°, and multi-directions bend under 0.4 Mpa pressure. Both ZPR properties and flexible morphing capabilities show the potential of this novel 3D ZPR configuration for morphing wings.

Background With the advance of new massively parallel genotyping technologies, quantitative trait loci (QTL) fine mapping and map-based cloning become more achievable in identifying genes for important and complex traits. Development of high-density genetic markers in the QTL regions of specific mapping populations is essential for fine-mapping and map-based cloning of economically important genes. Single nucleotide polymorphisms (SNPs) are the most abundant form of genetic variation existing between any diverse genotypes that are usually used for QTL mapping studies. The massively parallel sequencing technologies (Roche GS/454, Illumina GA/Solexa, and ABI/SOLiD), have been widely applied to identify genome-wide sequence variations. However, it is still remains unclear whether sequence data at a low sequencing depth are enough to detect the variations existing in any QTL regions of interest in a crop genome, and how to prepare sequencing samples for a complex genome such as soybean. Therefore, with the aims of identifying SNP markers in a cost effective way for fine-mapping several QTL regions, and testing the validation rate of the putative SNPs predicted with Solexa short sequence reads at a low sequencing depth, we evaluated a pooled DNA fragment reduced representation library and SNP detection methods applied to short read sequences generated by Solexa high-throughput sequencing technology. Results A total of 39,022 putative SNPs were identified by the Illumina/Solexa sequencing system using a reduced representation DNA library of two parental lines of a mapping population. The validation rates of these putative SNPs predicted with low and high stringency were 72% and 85%, respectively. One hundred sixty four SNP markers resulted from the validation of putative SNPs and have been selectively chosen to target a known QTL, thereby increasing the marker density of the targeted region to one marker per 42 K bp. Conclusions We have demonstrated how to quickly identify large numbers of SNPs for fine mapping of QTL regions by applying massively parallel sequencing combined with genome complexity reduction techniques. This SNP discovery approach is more efficient for targeting multiple QTL regions in a same genetic population, which can be applied to other crops.

The honeycomb sandwich structure is widely used in energy-absorbing facilities because it is lightweight, has a high specific stiffness and high specific strength, and is easy to process. It also has dynamic mechanical characteristics such as a high impact resistance and high energy absorption. To explore the influence of the Poisson’s ratio on the local impact resistance, this paper compares and analyzes the local impact resistance of a series of honeycomb cores with different Poisson’s ratios under the impact of a spherical projectile at different speeds. Three typical honeycombs with negative/zero/positive Poisson ratios (re-entrant hexagon, semi-re-entrant hexagon, and hexagon) are selected to change the geometric parameters in order to have the same relative density and different Poisson ratios (−2.76–3.63). The relative magnitude of the rear face sheet displacement is in the order of negative Poisson’s ratio > zero Poisson’s ratio > positive Poisson’s ratio, which reveals that the honeycomb structure with the positive Poisson’s ratio has better protection ability than the others. Finally, a dual-wall hexagonal honeycomb is proposed. The rear face sheet displacement of the dual-wall hexagonal honeycomb sandwich structure is reduced by 34.4% at 25 m/s compared with the hexagonal honeycomb, which has a better local impact resistance.

Pectin methyl esterase (PME) (EC 3.1.1.11) catalyzes the hydrolysis of methylester groups of cell wall pectins. We investigated the role of this enzyme in dormancy termination and germination of yellow cedar (Chamaecyparis nootkatensis [D. Don] Spach) seeds. PME activity was not detected in dormant seeds of yellow cedar but was induced and gradually increased during moist chilling; high activity coincided with dormancy breakage and germination. PME activity was positively correlated to the degree of dormancy breakage of yellow cedar seeds. The enzyme produced in different seed parts and in seeds at different times during moist chilling, germination, and early post-germinative growth consisted of two isoforms, both basic with isoelectric points of 8.7 and 8.9 and the same molecular mass of 62 kD. The pH optimum for the enzyme was between 7.4 and 8.4. In intact yellow cedar seeds, activities of the two basic isoforms of PME that were induced in embryos and in megagametophytes following dormancy breakage were significantly suppressed by abscisic acid. Gibberellic acid had a stimulatory effect on the activities of these isoforms in embryos and megagametophytes of intact seeds at the germinative stage. We hypothesize that PME plays a role in weakening of the megagametophyte, allowing radicle emergence and the completion of germination.

Dry or fully imbibed seeds of western white pine (Pinus monticola Dougl. ex D. Don) were studied using high-resolution magnetic resonance imaging (MRI). Analyses of the dry seed revealed many of the gross anatomical features of seed structure. Furthermore, the non-invasive nature of MRI allowed for a study of the dynamics of water and oil distribution during in situ imbibition of a single seed with time-lapse chemical shift selective MRI. During soaking of the dry seed, water penetrated through the seed coat and megagametophyte. The cotyledons of the embryo (located in the chalazal end of the seed) were the first to show hydration followed by the hypocotyl and later the radicle. After penetrating the seed coat, water in the micropylar end of the seed likely also contributed to further hydration of the embryo; however, the micropyle itself did not appear to be a site for water entry into the seed. A model that describes the kinetics of the earlier stages of imbibition is proposed. Non-viable pine seeds captured with MRI displayed atypical imbibition kinetics and were distinguished by their rapid and uncontrolled water uptake. The potential of MR microimaging for detailed studies of water uptake and distribution during the soaking, moist chilling (\"stratification\"), and germination of conifer seeds is discussed.

We herein report a detailed physical map of the horse Y chromosome. The euchromatic region of the chromosome comprises ≈ 15 megabases (Mb) of the total 45- to 50-Mb size and lies in the distal one-third of the long arm, where the pseudoautosomal region (PAR) is located terminally. The rest of the chromosome is predominantly heterochromatic. Because of the unusual organization of the chromosome (common to all mammalian Y chromosomes), a number of approaches were used to crossvalidate the results. Analysis of the 5,000-rad horse × hamster radiation hybrid panel produced a map spanning 88 centirays with 8 genes and 15 sequence-tagged site (STS) markers. The map was verified by several fluorescence in situ hybridization approaches. Isolation of bacterial artificial chromosome (BAC) clones for the radiation hybrid-mapped markers, end sequencing of the BACs, STS development, and bidirectional chromosome walking yielded 109 markers (100 STS and 9 genes) contained in 73 BACs. STS content mapping grouped the BACs into seven physically ordered contigs (of which one is predominantly ampliconic) that were verified by metaphase-, interphase-, and fiber-fluorescence in situ hybridization and also BAC fingerprinting. The map spans almost the entire euchromatic region of the chromosome, of which 20-25% (≈4 Mb) is covered by isolated BACs. The map is presently the most informative among Y chromosome maps in domesticated species, third only to the human and mouse maps. The foundation laid through the map will be critical in obtaining complete sequence of the euchromatic region of the horse Y chromosome, with an aim to identify Y specific factors governing male infertility and phenotypic sex variation.

Incremental Learning is a particular form of machine learning that enables a model to be modified incrementally, when new data becomes available. In this way, the model can adapt to the new data without the lengthy and time-consuming process required for complete model re-training. However, existing incremental learning methods face two significant problems: 1) noise in the classification sample data, 2) poor accuracy of modern classification algorithms when applied to modern classification problems. In order to deal with these issues, this paper proposes an integrated classification model, known as a Pre-trained Truncated Gradient Confidence-weighted (Pt-TGCW) model. Since the pre-trained model can extract and transform image information into a feature vector, the integrated model also shows its advantages in the field of image classification. Experimental results on ten datasets demonstrate that the proposed method outperform the original counterparts.

Yellow cedar (Chamaecyparis nootkatensis) seeds exhibit prolonged dormancy following their dispersal from the parent plant. Embryos excised fully from their enclosing seed tissues exhibit 100% germination, indicating that the seed tissues enclosing the embryo (the testa, remnants of the nucellus and the megagametophyte) play an inhibitory role and prevent radicle emergence. As part of an assessment of the role of seed tissues in the dormancy mechanism of yellow cedar seeds, light microscopy was used to examine changes within the major structures of the seed following a 90 d warm (26 degrees C)/cold (4 degrees C) moist treatment ('stratification') and during germination. In the micropylar tip of the seed, the nucellus forms a hard nucellar cap covering the radicle. The nucellar cap is composed primarily of degenerated cells; histological staining with ruthenium red revealed a predominance of pectins. There were no obvious cellular or morphological differences (detected by light microscopy) between mature seeds subjected to a 3 d soak and seeds subjected to a 3 d soak and the 90 d dormancy-breaking treatment. However, just prior to germination there was an outward projection of the nucellar cap through the micropyle, which appeared to be caused by the extension of highly folded proteinaceous strands lying immediately in front of the radicle. When the testa was removed, the embryo enclosed within the intact megagametophyte was incapable of germination. If, however, the megagametophyte surrounding the embryo was slit or the embryo surrounded by an intact megagametophyte was subjected to a 3 d rinse in water, some germination occurred, perhaps as a result of an enhanced release of inhibitors from the megagametophyte. After stratification, dormancy of yellow cedar seeds is broken; concurrent with dormancy breakage, there was a mechanical weakening of the megagametophyte. The embryo also underwent changes that included an increase in turgor and a reduced sensitivity to highly negative osmotic potential. It is concluded that coat-imposed dormancy of yellow cedar seeds is enforced by mechanical restraint of the megagametophyte as well as a leachable chemical inhibitor (most probably ABA).

During germination in the siliquae of developing seeds of a precociously germinating (PG) line of Chinese cabbage (Brassica rapa ssp. Pekinensis), the synthesis of cruciferin and oleosins was maintained and the activities of isocitrate lyase and malate synthase increased. Thus, both developmental and germinative/post-germinative events coexisted within the same PG seeds. Drying of the seeds resulted in the developmental events being switched off and germinative/post-germinative ones being initiated. Only about 18% of the seeds of the PG line completed germination in the siliquae, so the potential for germination of the remaining non-germinating seeds was tested during their development. Isolation of these developing seeds from the siliquae and imbibition in water induced PG, but developmental events were terminated and the seeds entered a germ inative/post-germinative programme. This termination of developmental events in the induced PG seeds was not permanent, however, and they could be re-induced by incubating the seeds in ABA on Murashige and Skoog (MS) medium. If incubated on MS medium plus a low concentration of ABA, both developmental and germ inative/post-germinative events could be induced to coexist in the PG seeds up to the time of establishment of the seedlings. Control of the developmental and germ inative/postgerminative events in the seeds was influenced by the environment in which they were developing, which could be mimicked by manipulating the nutritional status and ABA content in which the seeds were in contact.

This paper investigates a class of reaction-diffusion population models defined on a bounded domain, characterized by a general time-delayed per capita growth rate and a general advection term. Notably, the growth rate encompasses both Logistic-type and weak Allee effect-type dynamical behaviors. By applying the Lyapunov method, we establish the existence of spatially inhomogeneous steady states when a parameter approaches the principal eigenvalue of a non-self-adjoint elliptic operator. A detailed analysis of the characteristic equation further confirms the existence of Hopf bifurcations originating from these steady states. Subsequently, by applying center manifold reduction and normal form theory, we ascertain the direction of these Hopf bifurcations and the stability of the resulting periodic orbits. Finally, the proposed general theoretical results are successfully applied to a \"food-limited\" population model and a weak Allee effect-driven population model, each of which incorporates diffusion, time delay, and advection, thus confirming the validity of our approach.