Journal articles on the topic 'Transitional morphologies'
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Trisciuoglio, Marco, Michela Barosio, Ana Ricchiardi, Zeynep Tulumen, Martina Crapolicchio, and Rossella Gugliotta. "Transitional Morphologies and Urban Forms: Generation and Regeneration Processes—An Agenda." Sustainability 13, no. 11 (June 1, 2021): 6233. http://dx.doi.org/10.3390/su13116233.
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Grounded in the study of urban morphology, this position paper seeks to overcome the analysis of the permanent elements of a city in the search for a transitional paradigm in urban morphology, with the aim of grasping the dynamics of urban evolution and providing operative tools for the design of urban regeneration through an adaptive approach. Four actions for urban analysis are suggested here to highlight urban dynamics through the use of different tools: (a) sorting the transitional steps of urban morphologies (within rapid market processes), (b) underlining rules and processes that characterize urban coding in transitions, (c) mapping urban assemblages in an adaptive city, and (d) reading and representing the phenomenon of urban permutation. The results of this multifaceted and multidimensional set of analytical tools make it possible to outline a new paradigm for design thinking that moves towards a parametric approach to the urban design of cities in transition by broadening the extent of the urban regeneration process and supporting urban policies in the framework of a community-based approach.
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Sánchez, Pedro A., Tomás Sintes, Oreste Piro, and Julyan H. E. Cartwright. "Effects of microstructures on mesoscopic morphological transitions in deposition growth models." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, no. 2112 (October 7, 2009): 3875–84. http://dx.doi.org/10.1098/rspa.2009.0311.
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We study the influence of competing microstructure symmetries on the emergence of different morphologies during the growth by vapour deposition of thin solid films. We perform extensive numerical simulations with a minimal model that includes different microstructures, as well as thermal surface diffusion, to compute the corresponding structure zone model (SZM) and analyse, with statistical physics techniques, the details of transitional morphologies at border zones. We show that the maximum coordination number of the underlying microstructure provides a classification of the statistics of the transitional morphologies at the border between zones I (porous structures) and II (columnar faceted structures) of the SZM.
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Chen, Kuan-Ting, Wei-Chung Chang, Shu-Chen Lu, Po-Yuan Yang, and Hsing-Yu Tuan. "Facile Synthesis of Cu Nanocrystals with Morphology Evolution from Transitional Truncated Octahedra to Octahedra." Journal of Nanomaterials 2019 (December 26, 2019): 1–7. http://dx.doi.org/10.1155/2019/2890162.
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Growth of Cu polyhedral structures with well-defined and controllable shapes faced tremendous synthetic challenges in colloid nanocrystal synthesis in the past few decades. In this article, we report a facile approach for the synthesis of Cu nanocrystals with systematic morphological evolution. Transitional truncated octahedral, edge- and corner-truncated octahedral, all-corner-truncated octahedral, and octahedral structures were obtained in a solution-based reduction reaction by precise tuning reaction time. Four distinct morphologies of nanocrystals have been characterized by SEM technique. The optical properties of these various morphologies of nanocrystals were also investigated, and it indicates that the SPR band shifts red while the shape of nanoparticles evolves from transitional truncated octahedral to octahedral, whose resonant bands are transferred from 590 nm to 620 nm.
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Peng, Bangfa, Nan Jiang, Kefeng Shang, Na Lu, Jie Li, and Yan Wu. "Characteristics of three-electrode pulsed surface dielectric barrier discharge: streamer-to-spark transition and hydrodynamic expansion." Journal of Physics D: Applied Physics 55, no. 26 (April 8, 2022): 265202. http://dx.doi.org/10.1088/1361-6463/ac5a20.
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Abstract Streamer-to-spark transition and hydrodynamic expansion in a three-electrode pulsed surface dielectric barrier discharge are studied under atmospheric-pressure air. Three sequential discharge processes of the primary streamer, transitional streamer and spark phase during a single pulse are observed from the time-resolved plasma morphologies. The primary streamer and transitional streamer phases, with a rising voltage and low current, followed by a spark phase with a rapidly falling pulse and ascending current are characterized. Images of the discharge development show that the transitional streamer is maintained in the ionization channel after the primary streamer bridges the high-voltage electrode and the second grounded electrode. When the transitional streamer develops to a certain level, the streamer discharge transfers into the spark discharge. As a result, two shock waves are induced in the two exposed electrode domains, and then merge into a single ellipse during the process of hydrodynamic expansion. Boltzmann plots indicate that the electron temperature is 4.815 eV in the initial phase of spark discharge and gradually decreases in the spark phase. Stark broadening of the O atomic line shows that the electron density is 7.06 × 1017 cm−3 during the spark phase.
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Coates, M. I. "The Devonian tetrapod Acanthostega gunnari Jarvik: postcranial anatomy, basal tetrapod interrelationships and patterns of skeletal evolution." Transactions of the Royal Society of Edinburgh: Earth Sciences 87, no. 3 (1996): 363–421. http://dx.doi.org/10.1017/s0263593300006787.
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ABSTRACTThe postcranial skeleton of Acanthostega gunnari from the Famennian of East Greenland displays a unique, transitional, mixture of features conventionally associated with fishand tetrapod-like morphologies. The rhachitomous vertebral column has a primitive, barely differentiated atlas-axis complex, encloses an unconstricted notochordal canal, and the weakly ossified neural arches have poorly developed zygapophyses. More derived axial skeletal features include caudal vertebral proliferation and, transiently, neural radials supporting unbranched and unsegmented lepidotrichia. Sacral and post-sacral ribs reiterate uncinate cervical and anterior thoracic rib morphologies: a simple distal flange supplies a broad surface for iliac attachment. The octodactylous forelimb and hindlimb each articulate with an unsutured, foraminate endoskeletal girdle. A broad-bladed femoral shaft with extreme anterior torsion and associated flattened epipodials indicates a paddle-like hindlimb function. Phylogenetic analysis places Acanthostega as the sister-group of Ichthyostega plus all more advanced tetrapods. Tulerpeton appears to be a basal stemamniote plesion, tying the amphibian-amniote split to the uppermost Devonian. Caerorhachis may represent a more derived stem-amniote plesion. Postcranial evolutionary trends spanning the taxa traditionally associated with the fish-tetrapod transition are discussed in detail. Comparison between axial skeletons of primitive tetrapods suggests that plesiomorphic fish-like morphologies were re-patterned in a cranio-caudal direction with the emergence of tetrapod vertebral regionalisation. The evolution of digited limbs lags behind the initial enlargement of endoskeletal girdles, whereas digit evolution precedes the elaboration of complex carpal and tarsal articulations. Pentadactylous limbs appear to have stabilised independently in amniote and amphibian lineages; the colosteid Greererpeton has a pentadactylous manus, indicating that basal amphibian forelimbs may not be restricted to patterns of four digits or less.
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Nehm, Ross H., and Dana H. Geary. "A gradual morphological transition during a rapid speciation event in marginellid gastropods (Neogene; Dominican Republic)." Paleontological Society Special Publications 6 (1992): 222. http://dx.doi.org/10.1017/s2475262200007826.
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Paleontological studies can bring to light two important aspects of the speciation process: long term patterns of morphological change, and the paleoenvironmental context of such changes. We examined the temporal patterns of morphological change and their geographic and paleoenvironmental context in species of Prunum (Marginellidae; Gastropoda) from the Neogene of the northern Dominican Republic. We document a speciation event from P. coniforme (Sowerby 1849) to P. christineladdae (Maury 1917) which is unusual in both its temporal expression, and in the relative clarity of the ecological setting for speciation.We believe that the changes in morphology from P. coniforme to P. christineladdae represent a speciation event. The two species are distinguished by several shell features, including overall shape, spire height, relative height of the top of the lip, and apertural denticulations. The nature and magnitude of these differences, compared with morphological differences among extant species of Prunum, indicate that separate species designations are warranted for P. coniforme and P. christineladdae. A sequence of stratigraphic and morphological intermediates between these species provides strong stratophenetic evidence for speciation.The stratigraphic interval characterized by intermediate morphologies includes approximately 22 m of section. Sedimentation rates yield estimates of approximately 73,000–275,000 years for our interval of morphologic change. This transitional interval represents between 0.6–2.5 % of the total duration of the ancestral species.The patterns of morphological change exhibited by the two species generally fit the predictions of punctuated equilibrium; change from ancestor to descendent is relatively rapid, outside the transitional interval species exhibit no directional morphologic trends, and the ancestral species persists after speciation.Our data reveal some information on the mode of speciation. Prunum species from our study area exhibit well-defined depth ranges. P. christineladdae occurs only in deep water deposits, whereas P. coniforme is common in shallow water deposits. Based on distributional data, we suggest that depth, or one or more of its associated variables, was critical to the isolation and evolution of P. christineladdae.
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Heers, Ashley M., Kenneth P. Dial, and Bret W. Tobalske. "From baby birds to feathered dinosaurs: incipient wings and the evolution of flight." Paleobiology 40, no. 3 (2014): 459–76. http://dx.doi.org/10.1666/13057.
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Reconstructing the tree of life requires deciphering major evolutionary transformations and the functional capacities of fossils with “transitional” morphologies. Some of the most iconic, well-studied fossils with transitional features are theropod dinosaurs, whose skeletons and feathered forelimbs record the origin and evolution of bird flight. However, in spite of over a century of discussion, the functions of forelimb feathers during the evolution of flight remain enigmatic. Both aerodynamic and non-aerodynamic roles have been proposed, but few of the form-function relationships assumed by these scenarios have been tested. Here, we use the developing wings of a typical extant ground bird (Chukar Partridge) as possible analogues/homologues of historical wing forms to provide the first empirical evaluation of aerodynamic potential in flapping theropod “protowings.” Immature ground birds with underdeveloped, rudimentary wings generate useful aerodynamic forces for a variety of locomotor tasks. Feather development in these birds resembles feather evolution in theropod dinosaurs, and reveals a predictable relationship between wing morphology and aerodynamic performance that can be used to infer performance in extinct theropods. By spinning an ontogenetic series of spread-wing preparations on a rotating propeller apparatus across a range of flow conditions and measuring aerodynamic force, we explored how changes in wing size, feather structure, and angular velocity might have affected aerodynamic performance in dinosaurs choosing to flap their incipient wings. At slow angular velocities, wings produced aerodynamic forces similar in magnitude to those produced by immature birds during behaviors like wing-assisted incline running. At fast angular velocities, wings produced forces sufficient to support body weight during flight. These findings provide a quantitative, biologically relevant bracket for theropod performance and suggest that protowings could have provided useful aerodynamic function early in maniraptoran history, with improvements in aerodynamic performance attending the evolution of larger wings, more effective feather morphologies, and faster angular velocities.
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BAHAT, D., A. RABINOVITCH, and V. FRID. "Correlation of plume morphologies on joint surfaces with their fracture mechanic implications." Geological Magazine 145, no. 5 (June 13, 2008): 733–44. http://dx.doi.org/10.1017/s0016756808004974.
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AbstractThe fractography and conditions of propagation of joints that cut Devonian siltstones in the Appalachian Plateau, New York, and Eocene chalks from the Beer Sheva Syncline, Israel, are investigated. The joints cutting the siltstones are marked by S-type and C-type plumes, and the joints cutting the Lower Eocene and Middle Eocene chalks are marked by coarse and delicate plumes, respectively. The four plume types propagated under sub-critical (slow propagation) conditions. On the semi-quantitative fracture velocity (v) versus the tensile stress intensity (KI) curves, the S and C plume types fall in the KI=0.073–0.79 MPa m1/2 and v=2×10−4–10−2 m/s and KI=0.073–0.79 MPa m1/2 and v=10−6–10−4 m/s ranges respectively. The coarse and delicate plumes fall in the KI=0.03–0.17 MPa m1/2 and v=10−6–4×10−5 m/s and KI=0.03–0.17 MPa m1/2 and v=10−4–5×10−3 m/s ranges, respectively. Generally, slow plumes are relatively short, show periodicity, and typically exhibit superposition of arrest marks. On the other hand, faster plumes are longer and continuous, occur particularly in thinner layers, and show no superposition of arrest marks. There is a clear distinction between two en échelon segmentation end-members in the joint fringe, the ‘discontinuous breakdown type’ and the ‘continuous breakdown type’. There are also ‘transitional’ variations between the end-members. Only curved ‘discontinuous breakdown type’ boundaries of en échelon fringes can be equated with mirror boundaries.
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Grant, Roger I., David A. Hartmann, Robert G. Underly, Andrée-Anne Berthiaume, Narayan R. Bhat, and Andy Y. Shih. "Organizational hierarchy and structural diversity of microvascular pericytes in adult mouse cortex." Journal of Cerebral Blood Flow & Metabolism 39, no. 3 (September 21, 2017): 411–25. http://dx.doi.org/10.1177/0271678x17732229.
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Smooth muscle cells and pericytes, together called mural cells, coordinate many distinct vascular functions. Canonically, smooth muscle cells are ring-shaped and cover arterioles with circumferential processes, whereas pericytes extend thin processes that run longitudinally along capillaries. In between these canonical mural cell types are cells with features of both smooth muscle cells and pericytes. Recent studies suggest that these transitional cells are critical for controlling blood flow to the capillary bed during health and disease, but there remains confusion on how to identify them and where they are located in the brain microvasculature. To address this issue, we measured the morphology, vascular territory, and α-smooth muscle actin content of structurally diverse mural cells in adult mouse cortex. We first imaged intact 3D vascular networks to establish the locations of major gradations in mural cell appearance as arterioles branched into capillaries. We then imaged individual mural cells occupying the regions within these gradations. This revealed two transitional cells that were often similar in appearance, but with sharply contrasting levels of α-smooth muscle actin. Our findings highlight the diversity of mural cell morphologies in brain microvasculature, and provide guidance for identification and categorization of mural cell types.
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Huth, Miriam A., Axel Huth, and Kerstin Koch. "Morphological diversity of β-diketone wax tubules on Eucalyptus gunnii leaves and real time observation of self-healing of defects in the wax layer." Australian Journal of Botany 66, no. 4 (2018): 313. http://dx.doi.org/10.1071/bt18035.
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As part of the plant cuticle, epicuticular waxes build the boundary layer of a plant to its environment, fulfilling many vital functions. Epicuticular waxes are small crystalline structures which originate by self-assembly. The morphology of β-diketone tubules on Eucalyptus gunnii Hook.f. leaves was studied by field emission scanning electron microscopy (FE-SEM) and regeneration of removed waxes was investigated in real time by atomic force microscopy (AFM) on leaf surfaces. Smooth tubules as well as helically wound ribbons and transitional forms of tubules were found on adaxial leaf surfaces. Leaves of different developmental stages revealed no differences in their wax morphologies, but in the amount of wax allocation. After removal of the waxes regeneration was observed on leaves of all investigated ages. The regeneration of wax crystals started directly after wax removal and tubule growth could be observed in real time.
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Karádi, Viktor, Tea Kolar-Jurkovšek, Luka Gale, and Bogdan Jurkovšek. "New Advances in Biostratigraphy of the Lower/Middle Norian Transition: Conodonts of the Dovško Section, Slovenia." Journal of Earth Science 32, no. 3 (March 26, 2021): 677–99. http://dx.doi.org/10.1007/s12583-020-1382-y.
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AbstractThis study presents the results of the conodont biostratigraphy and microfacies analysis carried out on the pelagic limestones of the Upper Triassic Dovško Section in Slovenia, which represents the eastern part of the Slovenian Basin. The age of the section ranges from the Lacian 1 to the Alaunian 1. The Lacian part of the succession is predominantly characterized by the representatives of the genus Ancyrogondolella. Transitional morphologies towards Alaunian faunas first appear in the Lacian 3 and become common during the Lacian-Alaunian transition. This evolutionary development coincides with a shift in microfacies from a dominantly radiolarian-bearing mudstone-wackestone-packstone to a filament- dominated wackestone-packstone, and the formation of small neptunian dykes, which may reflect environmental perturbations and/or a change in basin geometry. The proliferation of the genera Epigondolella and Mockina is observed in the Alaunian part of the section, though the genus Ancyrogondolella is still present in this interval. Systematic description of the conodont taxa is provided, and seven new species and two new subspecies are established. The new advances will be of great value in further biostratigraphic studies, especially in areas without ammonoid faunas, and in the reconstruction of the paleogeography of the Slovenian Basin.
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Lees, John J., Grigorios Dimitriadis, and Robert L. Nudds. "The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces." PeerJ 4 (October 20, 2016): e2495. http://dx.doi.org/10.7717/peerj.2495.
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The diversity of wing morphologies in birds reflects their variety of flight styles and the associated aerodynamic and inertial requirements. Although the aerodynamics underlying wing morphology can be informed by aeronautical research, important differences exist between planes and birds. In particular, birds operate at lower, transitional Reynolds numbers than do most aircraft. To date, few quantitative studies have investigated the aerodynamic performance of avian wings as fixed lifting surfaces and none have focused upon the differences between wings from different flight style groups. Dried wings from 10 bird species representing three distinct flight style groups were mounted on a force/torque sensor within a wind tunnel in order to test the hypothesis that wing morphologies associated with different flight styles exhibit different aerodynamic properties. Morphological differences manifested primarily as differences in drag rather than lift. Maximum lift coefficients did not differ between groups, whereas minimum drag coefficients were lowest in undulating flyers (Corvids). The lift to drag ratios were lower than in conventional aerofoils and data from free-flying soaring species; particularly in high frequency, flapping flyers (Anseriformes), which do not rely heavily on glide performance. The results illustrate important aerodynamic differences between the wings of different flight style groups that cannot be explained solely by simple wing-shape measures. Taken at face value, the results also suggest that wing-shape is linked principally to changes in aerodynamic drag, but, of course, it is aerodynamics during flapping and not gliding that is likely to be the primary driver.
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UENO, Katsumi, and Elisa VILLA. "Demarcation problem in fusuline classi? cation: A case for Verella/Eofusulina discrimination." Spanish Journal of Palaeontology 33, no. 1 (October 31, 2018): 215. http://dx.doi.org/10.7203/sjp.33.1.13251.
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The eofusulinin genera Verella and Eofusulina formed an important lineage among fusulines to de? ne the Bashkirian/Moscovian transitional interval in the Pennsylvanian (Upper Carboniferous) subsystem. We studied morphologies of Verella transiens, a highly evolved form in the genus, and the ?rst Eofusulina species from the Los Tornos section in the Cantabrian Zone of northern Spain, to understand the discriminating diagnosis of these two genera. We conclude that Eofusulina is distinguishable from Verella in having stronger septal fluting, lesser development of secondary deposits, generally larger proloculus, absence of early tightly coiled volutions, and with some lesser extent slightly larger diameter of shell and absence of polar torsion. No single morphological character provides a reliable criterion to distinguish the two genera, but rather only a combination of all these morphological criteria enables reliable generic discrimination. In order to better understand the morphology, we emphasise the usefulness of non-oriented specimens in this study.
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Liu, Yan Ping, Jin Xiang Xue, and Pei De Han. "Electrochemical Corrosion Behaviors Using Double Glow Forming TiN Multi-Permeation Layer." Materials Science Forum 654-656 (June 2010): 1968–71. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1968.
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A new process technique that TiN permeation layer consisted of diffusion and deposition layer was synthesized on the surface of mild carbon steel has been firstly introduced, mainly according to plasma point discharge, hollow cathode effect and reactive vapor deposition technique. The surface appearance of this layer formed was uniform, compact and fine TiN cellular structure, a diffusion transitional region existing between the deposition layer and substrate. The surface texture was TiN deposition layer + TiN + Ti solid solution diffusion layer. From surface to inner Ti and N elements appeared graded distribution. This paper also mainly investigated the electrochemical corrosion behaviors of this multilayer. The polarization curves of specimens in 10% H2SO4 corrosive media were measured. The eroded surface morphologies were also surveyed by SEM. The results indicated that the erosion resistance of multi-permeation layer was increased many times than PVDTiN and a mild steel substrate, and almost equaled to that of compound process TiN layers.
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Yang, Hongru, Xiangchu Yin, Xiaodan Lin, Chen Wang, Chungkun Shih, Weiwei Zhang, Dong Ren, and Taiping Gao. "Cretaceous winged stick insects clarify the early evolution of Phasmatodea." Proceedings of the Royal Society B: Biological Sciences 286, no. 1909 (August 21, 2019): 20191085. http://dx.doi.org/10.1098/rspb.2019.1085.
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Wingless and shorter winged stick insects are very common today, but most known extinct stick insects had fully developed wings, leading to contentious affinities among the extinct winged and extant groups. We report herein three male winged stick insects, assigned to Pterophasmatidae fam. nov., from mid-Cretaceous Myanmar (Burmese) amber. Pterophasmatidae fam. nov. are regarded as transitional taxa from extinct winged to modern wingless and shorter winged stick insects based on their similar tegmina venation with extinct Susumanioidea and some body features the same as extant Phasmatodea. However, their symmetric phallic organs comprising two consistent phallomeres are different from those of all living groups. Phylogenetic analyses suggest that the extinct winged taxa, including the new family, are the stem groups of modern stick and leaf insects, and all of them constitute the clade of Phasmatodea. New findings indicate winged and wingless stick insects' morphologies diversified significantly during or before the mid-Cretaceous.
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Moir, Hamish J., Chris N. Gibbins, Chris Soulsby, and John H. Webb. "Discharge and hydraulic interactions in contrasting channel morphologies and their influence on site utilization by spawning Atlantic salmon (Salmo salar)." Canadian Journal of Fisheries and Aquatic Sciences 63, no. 11 (November 1, 2006): 2567–85. http://dx.doi.org/10.1139/f06-137.
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Six study sites were selected to represent the range of channel morphologies, extending from dynamic pool–riffle to transitional step–pool/plane bed reach types, used by spawning Atlantic salmon (Salmo salar) in a small upland Scottish stream. The hydraulic functioning of reaches over the range of discharges used by spawning fish was characterized, and the influence of hydraulic heterogeneity and rates of change in discharge on the frequency of spawning was assessed. Relationships between discharge and depths and velocities differed significantly between sites; thus, hydraulic responses to changes in discharge were different. The range of discharges used for spawning differed between sites, although optimum discharges were similar. Integration of hydraulic information with microhabitat suitability predicted that spawning conditions should occur at discharges higher than those utilized by fish. There was no evidence that hydraulically heterogeneous sites were used more frequently than homogeneous ones. Rather, data suggest that the frequency of utilization of sites was governed principally by the availability of suitable sediment. Flow stability was important for spawning, with periods of rapidly varying discharge avoided. It is suggested that the rate of change in discharge should be considered more explicitly when assessing environmental flow needs.
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Charbonneau, Bianca R., and Stephanie M. Dohner. "Microscale and Mesoscale Aeolian Processes of Sandy Coastal Foredunes from Background to Extreme Conditions." Remote Sensing 13, no. 21 (November 8, 2021): 4488. http://dx.doi.org/10.3390/rs13214488.
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Aeolian transport affects beach and foredune pre-storm morphologies, which directly contribute to storm responses. However, significant spatiotemporal variation exists within beach-dune systems regarding how biotic and abiotic factors affect topography. There are multiple metrics for quantifying topographic change, with varying pros and cons, but understanding how a system changes across spatiotemporal scales relative to varying forcings is necessary to accurately model and more effectively manage these systems. Beach and foredune micro- and mesoscale elevation changes (Δz) were quantified remotely and in situ across a mid-Atlantic coastal system. The microscale field collections consisted of 27 repeat measurements of 73 elevation pins located in vegetated, transitional, and unvegetated foredune microhabitats over three years (2015 to 2018) during seasonal, event-based, and background wind-condition collections. Unoccupied aerial System (UAS) surveys were collected to link microscale point Δz to mesoscale topographic change. Microscale measurements highlight how Δz varies more pre- to post-event than seasonally or monthly, but regardless of collection type (i.e., seasonal, monthly, or event-based), there was lower Δz in the vegetated areas than in the associated unvegetated and partially vegetated microhabitats. Despite lower Δz values per pin measurement, over the study duration, vegetated pins had a net elevation increase of ≈20 cm, whereas transitional and unvegetated microhabitats had much lower change, near-zero net gain. These results support vegetated microhabitats being more stable and having better sediment retention than unvegetated and transitional areas. Comparatively, mesoscale UAS surfaces typically overestimated Δz, such that variation stemming from vegetation across microhabitats was obscured. However, these data highlight larger mesoscale habitat impacts that cannot be determined from point measurements regarding volumetric change and feature mapping. Changes in features, such as beach access paths, that are associated with increased dynamism are quantifiable using mesoscale remote sensing methods rather than microscale methods. Regardless of the metric, maintaining baseline data is critical for assessing what is captured and missed across spatiotemporal scales and is necessary for understanding the contributors to heterogeneous topographic change in sandy coastal foredunes.
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Ying, Jiru, Xiaolin Xie, Shaoxian Peng, Huamin Zhou, and Dequn Li. "Morphology and rheology of PP/POE blends in high shear stress field." Journal of Thermoplastic Composite Materials 31, no. 9 (October 23, 2017): 1263–80. http://dx.doi.org/10.1177/0892705717734908.
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Polypropylene (PP)/polyolefin elastomer (POE; ethylene–octene copolymer) blends with varying weight percentages of POE were prepared in a twin-screw extruder and molded through high shear rate injection-molding process. The morphologies and rheology of the PP/POE blends were systematically investigated based on rheological data and experimental analysis. The results indicate that the polymer blends of plastic and rubber in a high shear stress field result in a multilayered microstructure, which can be divided into skin, transitional, shear, and core layers according to the morphology of the dispersed phase. The morphology formation of the dispersed phase depends on the shear field and temperature field in the processing. Morphological evolution of the dispersed POE phases in PP matrix was described and quantified. A dragging ellipsoid model and capillary number were employed to describe the morphological evolution of the dispersed phase, and the morphological parameters were obtained. The results show that the dragging ellipsoid model is well suited to explain the morphological evolution of the dispersed phase in polymer blends molded under high shear rate.
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Zhao, Dan Dan, Zhi Yang, Hao Wei, and Ya Fei Zhang. "Controlled Growth and Supercapacitive Behaviors of CVD Carbon Nanotube Arrays." Materials Science Forum 688 (June 2011): 11–18. http://dx.doi.org/10.4028/www.scientific.net/msf.688.11.
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Low-pressure chemical vapor deposition (LP-CVD) technique has been utilized for controlled growth of carbon nanotube (CNT) arrays on silicon wafers. The tube-diameters of CNTs and the number of graphene layers are controlled by varying the thickness of catalyst films. The catalyst particle density and the growth conditions such as the ambient gas and the local environment are all crucial for the formation of vertically aligned CNT arrays. The length of CNT arrays can be controlled by altering the growth time. In addition, the supercapacitive properties of CNT arrays with various morphologies growing on different current collectors have been investigated using a less corrosive 0.5 M Na2SO4aqueous solution as the electrolyte. Vertically aligned CNT arrays on Ti-Si substrate produce a higher capacitance compared to randomly oriented CNTs on the same current collector. Furthermore, Ni foam enables better utilization of active materials than Ti-Si substrate. CNT arrays electrodes fabricated by this simple, low cost approach demonstrate stable and consistent capacitor behaviors for a wide range of scan rates. Moreover, CNT arrays electrodes provide better platform for further integration with transitional metal oxide, via simple sputtering or electrodeposition technique, to enhance the supercapacitive performance.
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Kostic, Svetlana, Daniele Casalbore, Francesco Chiocci, Jörg Lang, and Jutta Winsemann. "Role of Upper-Flow-Regime Bedforms Emplaced by Sediment Gravity Flows in the Evolution of Deltas." Journal of Marine Science and Engineering 7, no. 1 (January 4, 2019): 5. http://dx.doi.org/10.3390/jmse7010005.
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Upper-flow-regime bedforms and their role in the evolution of marine and lacustrine deltas are not well understood. Wave-like undulations on delta foresets are by far the most commonly reported bedforms on deltas and it will take time before many of these features get identified as upper-flow-regime bedforms. This study aims at: (1) Providing a summary of our knowledge to date on deltaic bedforms emplaced by sediment gravity flows; (2) illustrating that these features are most likely transitional upper-flow-regime bedforms; and (3) using field case studies of two markedly different deltas in order to examine their role in the evolution of deltas. The study combines numerical analysis with digital elevation models, outcrop, borehole, and high-resolution seismic data. The Mazzarrà river delta in the Gulf of Patti, Italy, is selected to show that upper-flow-regime bedforms in gullies can be linked to the onset, growth, and evolution of marine deltas via processes of gully initiation, filling, and maintenance. Ice-marginal lacustrine deltas in Germany are selected as they illustrate the importance of unconfined upper-flow-regime bedforms in the onset and evolution of distinct delta morphologies under different lake-level trends.
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Shahid, Farzeen, Jing-Shan Zhao, and Pascal Godefroit. "Design of flying robots inspired by the evolution of avian flight." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, no. 23-24 (July 10, 2019): 7669–86. http://dx.doi.org/10.1177/0954406219861995.
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Bionic design of flying robots based on natural models has become a hot topic in mechanical engineering. The research going on in this direction considers that there is a lot to learn from flying animals such as birds, insects, and bats, from walking on the ground to getting enough power to be airborne. To get an efficient design of flying robots, we must better understand the origin of flight. This paper focuses on the review of avian flight and its possible application in the design of flying robots. Different hypotheses have been proposed to tackle the origin and evolution of avian flight from cursorial dinosaurs to modern birds, including the famous ground-up and tree-down theories. During the past decade, discoveries of feathered and winged dinosaurs from Liaoning, China, strongly supported the theory that birds originated from theropod dinosaurs. The transition from running on the ground to maneuver in the sky involves various stages of flights and plumages, which can be now illustrated by several representative paravian dinosaurs from Liaoning. Those fossils provide good research bases for the design of flying robots. Microraptor is one of those important transitional stages in the evolution of flight. This paravian dinosaur is characterized by the presence of pennaceous feathers along both its arms and its legs, but how it could actually fly is still debated. It is of course difficult to evaluate the flight performances of an extinct animal, but aerodynamics of a four-wing robot can be developed to get some knowledge about its flying capacity. Fossil and living flying animals with different morphologies, stability, and control mechanism can be a source of inspiration for designing socially relevant products.
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Stevenson, Christopher J., Jeff Peakall, David M. Hodgson, Daniel Bell, and Aurélia Privat. "TB or not TB: banding in turbidite sandstones." Journal of Sedimentary Research 90, no. 8 (August 19, 2020): 821–42. http://dx.doi.org/10.2110/jsr.2020.43.
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ABSTRACT Recognition and interpretation of sedimentary structures is fundamental to understanding sedimentary processes. Banded sandstones are an enigmatic sedimentary facies comprising alternating mud-rich (as matrix and/or mud clasts) and cleaner sand layers. The juxtaposition of hydrodynamically different grain sizes contradicts established models of cleaner-sand bedform development. Here, outcrop, subsurface core, and petrographic data from three deep-water systems, with well-constrained paleogeographic contexts, are used to describe the range of sedimentary textures, bedform morphologies, and facies associations, and to quantify the mud content of banding. Banding can occur in any part of a bed (base, middle, or top), but it typically overlies a structureless basal sandstone or mud-clast conglomerate lag, and is overlain by clean parallel-laminated sandstone and/or ripple cross-lamination. Banding morphology ranges from sub-parallel to bedforms that comprise low-angle laminae with discontinuous lenses of mudstone, or asymmetric bedforms comprising steeply dipping foresets that transition downstream into low-amplitude bedwaves, or steeply dipping ripple-like bedforms with heterolithic foresets. This style of banding is interpreted as a range of bedforms that form progressively in the upper-stage plane-bed flow regime via tractional reworking beneath mud-laden transitional plug flows. The balance of cohesive and turbulent forces, and the rate of flow deceleration (aggradation rate), govern the style of deposit. Banded sandstones and linked debrites are rarely found juxtaposed together in the same bed because they are distributed preferentially in proximal and distal settings, respectively. Understanding the origins of banding in turbidite sandstones, the conditions under which it forms, and its distribution across deep-water systems and relationship to linked debrites, is important for it to be used effectively as a tool to interpret the geological record.
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Silva, Isabella Premoli, Dario Marcello Soldan, and Maria Rose Petrizzo. "Upper Hauterivian-upper Barremian Planktonic Foraminiferal Assemblages from the Arroyo Gilico Section (southern Spain)." Journal of Foraminiferal Research 48, no. 4 (October 29, 2018): 314–55. http://dx.doi.org/10.2113/gsjfr.48.4.314.
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Abstract Late Hauterivian−earliest late Barremian planktonic foraminifera from the Arroyo Gilico section (Subbetic domain, Betic Cordillera) have been investigated to correlate their distribution to ammonite zonation and calcareous nannofossil bioevents. The 72-m-thick section spans the interval between the upper Hauterivian ammonite Crioceratites binelli Subzone, Crioceratites baleraris Zone and the lowermost upper Barremian ammonite Barrancyloceras barremense Subzone, Toxancyloceras vandenheckii Zone. Planktonic foraminiferal assemblages are rich and relatively diverse. At the base of the section in the C. binelli Subzone, as already known, Hedbergella sigali, H. infracretacea, H. daminiae, and Lilliputianella semielongata are recorded. New findings include common Hedbergella praetrocoidea and H. aptiana along with rare specimens resembling H. excelsa based on their long and elevated spire. Early appearances of taxa continue up-section with the lowest occurrences (LOs) of H. ventriosa, then Lilliputianella eocretacea in the overlying Crioceratites krenkeli Subzone, followed by H. gorbachikae, while the LO of the ‘clavate’ Lilliputianella pauliani occurs just before the end of the Hauterivian within the topmost Pseudothurmannia picteti Subzone. The lower Barremian is punctuated by a number of successive appearances, including the typical Globigerinelloides blowi recorded in the upper lower Barremian Kotetishvilia compressissima Zone. The acme of the ‘clavate’ morphotypes occurs in the Moutoniceras moutonianum Zone across the Mid-Barremian Event (MBE); besides common L. semielongata, the taxa consistently present are L. pauliani with both typical and transitional morphologies, L. eocretacea, and to a minor extent “Globigerinelloides” sigali.
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Brown, H. Roger, Thomas M. Monticello, Robert R. Maronpot, Holly W. Randall, John R. Hotchkiss, and Kevin T. Morgan. "Proliferative and Neoplastic Lesions in the Rodent Nasal Cavity." Toxicologic Pathology 19, no. 4_part_1 (November 1991): 358–72. http://dx.doi.org/10.1177/0192623391019004-105.
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Proliferative lesions in the rodent nasal cavity are reviewed; attempt was made to compare species affected, sex differences, strain differences, route of administration and tumor types occurring both spontaneously and after induction by different chemicals. This review is not meant to be all inclusive but to be representative of observed trends. Our general conclusions in this paper are that: 1) spontaneous nasal tumors in rodents are very rare; 2) spontaneous nasal tumors in rats are most often squamous cell tumors, whereas hemangiomas or respiratory adenomas predominate in mice and squamous cell tumors are rare; 3) rats are usually more susceptible to the induction of epithelial tumors of the nasal cavity than mice; 4) chemically-induced hemangiomas and hemangiosarcomas of the nasal cavity have only been reported in mice; 5) tumors of the olfactory epithelium are almost uniformly malignant and invasive, while nonsquamous tumors of the respiratory epithelium are typically less invasive; 6) chemically-induced tumors of the olfactory region, either mesenchymal or epithelial, do not always require an inhalation route of exposure but may occur by systemic targeting of this region; and 7) chemicals inducing tumors in the olfactory region often produce a variety of tumor morphologies in this location as well as squamous and polypoid tumors of the transitional region. More work will be needed to illucidate the mechanisms of nasal carcinogenesis and to further refine the current tumor classification system.
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Gagliardi, Karina Bertechine, Inês Cordeiro, and Diego Demarco. "Flower development in species of Croton (Euphorbiaceae) and its implications for floral morphological diversity in the genus." Australian Journal of Botany 65, no. 7 (2017): 538. http://dx.doi.org/10.1071/bt17045.
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The Euphorbiaceae are notable for floral diversity and evolutionary complexity. Croton is the second largest genus in the family and exhibits particular diversity in its flowers. The aim of this study was to investigate the floral ontogeny and structure of three Croton species with distinct morphologies, with a focus on testing the hypothesis that the filaments of female flowers, which have received different interpretations in the literature and are currently described as reduced petals, are staminodes and part of a vestigial androecium. With the ontogenetic study we can understand the origin of the organs and associate these with flower evolution in the genus. Flowers in several stages of development were analysed using light microscopy and scanning electron microscopy. In the early stage of development, the sepals are the first structures to be formed, although they do not continue to grow in female Croton fuscescens Spreng. flowers. Petals are absent in female flowers, with filamentous, petaloid structures, interpreted here as staminodes, alternating with the sepals in Croton lundianus (Didr.) Müll. Arg. In Croton sphaerogynus Baill., the staminodes are located between the nectary lobes. The stamens exhibit centripetal development in the flower bud stage, and the carpels are post-genitally connate, with differences in style branching. Besides the ontogenetic interpretation for the filamentous structures, the genus shows transitional structures that we consider evolutionary reductions. Our results can explain how developmental alterations have influenced the suppression and modification of floral organs in the genus.
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Billah, Motasim, Amir Hamza, Muhammad Ali Anjum, Sarah Yunus, Sabika Hussain, and Nadia Majeed. "Variable Morphology of Sacrum in General Population." Pakistan Journal of Medical and Health Sciences 16, no. 10 (October 30, 2022): 538–40. http://dx.doi.org/10.53350/pjmhs221610538.
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Background: One of the large trilateral bones present at the base of the vertebral column is named as sacrum. The body weight transfers from trunk to pelvis and lower extremities. Different studies considering sacral morphological variations are conducted in the western world. The scope and knowledge of these studies in the eastern world is limited. Different sacral anatomies are reported by the scientists. Objective: The purpose of the study was to investigate and measure thoroughly the variable morphologies of sacrum. Study design: It is an investigational and cross-sectional study facilitated by statistical approach. Material and Methods: The study was conducted on 223 skeleton samples. These samples were preserved in the anatomy department of Mufti Mehmood Teaching Hospital Dera Ismail Khan and Bacha Khan Medical Complex Swabi during the period from October 2021 to June 2022. The human research ethical committee of the hospital approved the study. The vernier caliper was used to measure the correlation parameters of variability. The morphological features were calculated. The study also calculated the sacral variation incidence. The sacra with any kind of bony defects were excluded from the study. Results: The anatomical differences reported in the 223 samples were observed to be 59%. Out of the 223 patients the 81 were females and 142 were males. The five variations were reported in the sacral regions, while two samples have the rare sacral variations. The mean age of the included sample was observed to be 44 years. The age of the people whose sacral samples were included in the study was between 21-72 years. The percentage incidence of accessory auricular faces was observed to be 12.5%. The sacral skewness was observed in 24% cases. The 17% showed the transitional vertebra, while sacral spina bifida occulta was seen in 28% samples. Conclusion: This large scale anatomical study provides information about the apparent changes in the morphology of different sacral variables. This study provides comprehensive data about the different sacral variations. The detailed information about the human sacrum is provided. The apparent identification methods by western medical officers are also considered in this work which may help our medical staff to identify the sacral variations. Keywords: Sacrum variations, Sacrum morphology, Accessory auricular faces, Transitional vertebra and Sacral spina bifida occulta
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Liao, Fen, Ling-Ying Shi, Li-Chen Cheng, Sangho Lee, Rong Ran, Kevin G. Yager, and Caroline A. Ross. "Self-assembly of a silicon-containing side-chain liquid crystalline block copolymer in bulk and in thin films: kinetic pathway of a cylinder to sphere transition." Nanoscale 11, no. 1 (2019): 285–93. http://dx.doi.org/10.1039/c8nr07685e.
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Vayner, Andrey, Nadia L. Zakamska, Rogemar A. Riffel, Rachael Alexandroff, Maren Cosens, Fred Hamann, Serena Perrotta, et al. "Powerful winds in high-redshift obscured and red quasars." Monthly Notices of the Royal Astronomical Society 504, no. 3 (April 26, 2021): 4445–59. http://dx.doi.org/10.1093/mnras/stab1176.
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ABSTRACT Quasar-driven outflows must have made their most significant impact on galaxy formation during the epoch when massive galaxies were forming most rapidly. To study the impact of quasar feedback, we conducted rest-frame optical integral field spectrograph (IFS) observations of three extremely red quasars (ERQs) and one type-2 quasar at z = 2–3, obtained with the NIFS and OSIRIS instruments at the Gemini North and W. M. Keck Observatory with the assistance of laser-guided adaptive optics. We use the kinematics and morphologies of the [O iii] 5007 Å and H α 6563 Å emission lines redshifted into the near-infrared to gauge the extents, kinetic energies and momentum fluxes of the ionized outflows in the quasars host galaxies. For the ERQs, the galactic-scale outflows are likely driven by radiation pressure in a high column density environment or due to an adiabatic shock. The outflows in the ERQs carry a significant amount of energy ranging from 0.05 to 5 ${{\ \rm per\ cent}}$ of the quasar’s bolometric luminosity, powerful enough to have a significant impact on the quasar host galaxies. The outflows are resolved on kpc scales, the observed outflow sizes are generally smaller than other ionized outflows observed at high redshift. The high ratio between the momentum flux of the ionized outflow and the photon momentum flux from the quasar accretion disc and high nuclear obscuration makes these ERQs great candidates for transitional objects where the outflows are likely responsible for clearing material in the inner regions of each galaxy, unveiling the quasar accretion disc at optical wavelengths.
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Maier, Katherine L., Charles K. Paull, David W. Caress, Krystle Anderson, Nora M. Nieminski, Eve Lundsten, Benjamin E. Erwin, Roberto Gwiazda, and Andrea Fildani. "Submarine-fan development revealed by integrated high-resolution datasets from La Jolla Fan, offshore California, U.S.A." Journal of Sedimentary Research 90, no. 5 (May 7, 2020): 468–79. http://dx.doi.org/10.2110/jsr.2020.22.
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ABSTRACT New high-resolution datasets across La Jolla submarine fan, offshore California, illuminate low-relief, down-dip widening conduits emanating from a deep-sea channel that deposited a combination of laterally extensive sand strata seemingly crisscrossed by distributary patterns. Extensive coverage of this sector of the seafloor shows submarine-fan architecture and morphologies essentially different than distributary channelized patterns characteristic of subaerial systems and previous conceptual models of submarine fans. The main La Jolla channel, connected to La Jolla Canyon, loses confinement by widening, decreasing in relief, and developing scoured margins across kilometers-long down-slope and lateral distances. Two scales of distributary patterns are associated with sand-rich deposits down-system from, and outside of, fully formed channels. A larger-scale distributary pattern is identified in backscatter and bathymetry from trains of preferential erosion associated with laterally continuous repetitive steps that extend for kilometers outside channel confinement and may represent net erosional upper-flow-regime transitional bedforms. Smaller-scale distributary backscatter patterns in unconfined sand-rich deposits originate from the wide, low-relief channel. We suggest that the newly imaged La Jolla seascape displays sedimentary features that may be common on deep-sea fans but missed in previous lower resolution studies of submarine fans. Thus, La Jolla provides the basis for integrating previously enigmatic and (or) incomplete images of submarine fans. High-resolution seafloor, subsurface, and sample datasets highlight the importance of channel widening, headward erosion, and unconfined flows in La Jolla submarine-fan development, and may be relevant to other sandy submarine fan systems.
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Maillard, Damien, and Robert E. Prud’homme. "The crystallization of ultrathin films of polylactides — Morphologies and transitions." Canadian Journal of Chemistry 86, no. 6 (June 1, 2008): 556–63. http://dx.doi.org/10.1139/v08-045.
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Poly(L-lactide) ultrathin films of thicknesses between 10 and 80 nm were crystallized between 100 and 170 °C. Four different morphologies were obtained: single crystals, hedrites, dendrites, and spherulites. Dendrites were always obtained below 20 nm due to chain diffusion limitations, whereas, at larger thicknesses, the morphology heavily depends on the crystallization temperature. The thickness-temperature morphological map led to the observation of two transition temperatures, at 115 and 145 °C. Other parameters such as the lamellar thickness, melting temperature, and dendricity of the lamellae for 15 nm thick films show significant changes at these two temperatures. Those transitions occur at the same temperatures as Regime III/Regime II, and Regime II/Regime I transitions of the Lauritzen–Hoffman crystallization theory.Key words: polylactide, ultrathin film, crystalline morphology, single crystal, dendrite, spherulite, transition temperature, regime of crystallization.
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Yan, Qiangu, and Zhiyong Cai. "Effect of Solvents on Fe–Lignin Precursors for Production Graphene-Based Nanostructures." Molecules 25, no. 9 (May 6, 2020): 2167. http://dx.doi.org/10.3390/molecules25092167.
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Kraft lignin was catalytically graphitized to graphene-based nanostructures at high temperature under non-oxidative atmospheres. To obtain the best catalytic performance, a uniform catalyst–lignin mixture must be made by bonding transitional metal (M) ions to oxygen (O), sulfur (S) or nitrogen (N)-containing functional groups in kraft lignin. One of the strategies is to dissolve or disperse kraft lignin in a suitable solvent, whereby the polymer chains in the condensed lignin molecules will be detangled and stretched out while the functional groups are solvated, and when mixing lignin solution with catalyst metal solution, the solvated metal ions in an aqueous solution can diffuse and migrate onto lignin chains to form M-O, M-S, or M-N bonds during the mixing process. Therefore, solvent effects are important in preparing M–lignin mixture for production of graphene-based nanostructures. Fe–lignin precursors were prepared by dissolving lignin with different solvents, including water, methanol, acetone, and tetrahydrofuran (THF). Solvent effects on the catalytic performance, size and morphology of graphene-based nanostructures were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), and nitrogen sorption measurements. The sizes, morphologies, and catalytic properties of the products obtained from Fe–lignin precursors are greatly influenced by the solvents used. It was found that Fe–lignin (THF) had the highest iron dispersion and the smallest iron particle size. Furthermore, Fe–lignin (THF) exhibited the best catalytic performance for graphitization of kraft lignin while the graphitization degree decreased in the order: Fe–lignin(THF) > Fe–lignin(Acetone) > Fe–lignin(methanol) > Fe–lignin(water).
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Brooks, G. R., and D. E. Lawrence. "Geomorphic Effects of Flooding Along Reaches of Selected Rivers in the Saguenay Region, Québec, July 1996." Géographie physique et Quaternaire 54, no. 3 (October 2, 2002): 281–99. http://dx.doi.org/10.7202/005639ar.
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AbstractA severe rainstorm from July 18 to 21, 1996, caused widespread flooding along many rivers in southern Québec, particularly in the Lac-Saint-Jean-Chicoutimi area, along north-flowing tributaries of the Rivière Saguenay. Along study reaches located on the Rivière aux Sables, Rivière Chicoutimi, Rivière du Moulin and Rivière à Mars, the fluvial geomorphic effects of flooding varied considerably, reflecting differing channel morphologies (alluvial, non-alluvial and bedrock), flow energy, and the interaction of floodwaters and infrastructure. Catastrophic channel widening and floodplain reworking occurred along the Rivière à Mars study reach, transforming the river from a meandering to braided planform. Consistent with this, unit stream power of the flood flow exceeded the minimum erosive threshold (300 Wm-2) along most of the study reach. Morphological and empirical evidence indicates that the pre-flood Rivière à Mars channel exhibited a transitional planform, and thus was vulnerable to a planform transformation during an extreme flood. The most significant geomorphic effects along the Rivière aux Sables and Rivière Chicoutimi study reaches occurred at a number of run-of-the-river dams. Floodwaters overtopped four dams and eroded deeply into unconsolidated sediments adjacent to the dams, forming new channels that captured the flow of the river. Floodwaters also overtopped a fifth dam, scouring overburden and road beds, and damaging and destroying buildings within an urban subdivision. Elsewhere along these two rivers, as well as along the Rivière du Moulin study reach, there were localized erosional problems, particularly at bridges, but the geomorphic effects generally were limited or negligible, reflecting either low unit stream power or resistant substrates.
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Beadle, Steven C. "The biogeography of origin and radiation: dendrasterid sand dollars in the northeastern Pacific." Paleobiology 17, no. 4 (1991): 325–39. http://dx.doi.org/10.1017/s009483730001068x.
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Under favorable circumstances, biogeographic and biostratigraphic data can be combined to identify accurately the time and place of origin of a given taxon, and to reconstruct the pattern of its subsequent radiation. This study considers the dendrasterid sand dollars, which are abundant today along the Pacific Coast of North America. The Neogene sand dollar record in this region is particularly good; in fact, sand dollars have traditionally been used as provincial index fossils.The dendrasterids originated in central California at the end of the Miocene; the oldest forms are dated at about 6.0–6.5 Ma. They spread south to Baja California during the Pliocene, and then north to Alaska during the Quaternary. This historical pattern is not an artifact of the record; it is consistent with independent paleogeographic evidence. The dendrasterids supplanted an older Mio-Pliocene sand dollar fauna; they are now completely dominant in the temperate coastal waters of the northeastern Pacific. They have reached this position in less than 7 m.y. since their first local appearance. The rapid rise of dendrasterids could be related to their aberrant morphology and behavior; these adaptations allow dendrasterids to suspension-feed, in a manner unique among living echinoids.Dendrasterids are characterized by “eccentric” test morphologies. Even the oldest species are highly eccentric; transitional forms are unknown. The first dendrasterids appear suddenly in the provincial “Jacalitos Stage,” above an unconformity which represents no more than about 1 m.y. They do not occur in the underlying units, although other fossil sand dollars are abundant. The dendrasterids may have arisen rapidly, through a heterochronic change in the development of older, noneccentric forms. Recent ontogenetic studies have documented the feasibility of this process.
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Zhou, Gen-Tao, Qi-Zhi Yao, Sheng-Quan Fu, and Ye-Bin Guan. "Controlled crystallization of unstable vaterite with distinct morphologies and their polymorphic transition to stable calcite." European Journal of Mineralogy 22, no. 2 (April 13, 2010): 259–69. http://dx.doi.org/10.1127/0935-1221/2009/0022-2008.
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Beadle, Steven C. "Ontogenetic regulatory mechanisms, heterochrony, and eccentricity in dendrasterid sand dollars." Paleobiology 15, no. 3 (1989): 205–22. http://dx.doi.org/10.1017/s0094837300009428.
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Posterior eccentricity has evolved independently in three lineages of northern Pacific sand dollars; it is best known in the genus Dendraster. In these forms, the anterior areas of the aboral surface are much more highly developed than the posterior areas; consequently, the apical system is located posteriorly, rather than centrally. This morphology is linked to an unusual and highly successful mode of suspension-feeding. The evolution of eccentricity appears to be related to regulatory mechanisms found in many non-eccentric sand dollars, such as Echinarachnius parma. During the ontogeny of this form, the growth rates of the ambulacra and interambulacra are correlated with their position along the longitudinal axis. Early in ontogeny, the anterior areas develop at a faster rate than the posterior areas; later in ontogeny, this relationship is completely reversed. Normally, these two phases of unequal growth counterbalance each other, and the mature test appears symmetrical. However, if the balance between the two phases were upset, eccentricity would naturally ensue. In fact, aberrant Recent and fossil Echinarachnius with the predicted anteriorly-and posteriorly-eccentric morphologies actually do exist. Posterior eccentricity is apparently produced by retention of the earlier unequal growth pattern, which favors anterior development. This represents trait neoteny; however, since the retained trait is a regulatory mechanism that controls growth rates over the entire aboral surface, the morphological effects are particularly profound. Thus, the seemingly bizarre morphology of Dendraster can be derived by a change in the timing of an existing regulatory mechanism. This may help to explain the sudden appearance of Dendraster in the fossil record and the absence of transitional forms. The unusual suspension-feeding behavior of Dendraster may have been derived from a righting response that is common among other sand dollars.
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Wagner, Peter J. "Testing evolutionary constraint hypotheses with early Paleozoic gastropods." Paleobiology 21, no. 3 (1995): 248–72. http://dx.doi.org/10.1017/s0094837300013294.
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The evolution of higher taxa among early Paleozoic gastropods is similar to that among early metazoans as a whole, as higher taxa diversified rapidly and early. There are two issues pertinent to this pattern. First, were greater morphologic changes concentrated in the early phases of evolution? Second, does the pattern better fit models of increasing phylogenetic constraints or increasing ecologic restrictions? This paper presents a phylogeny-based method designed to test whether amounts of morphologic evolution decreased over time. It also explores whether the data better fits models of increasing phylogenetic (i.e., developmental or genetic) constraint or increasing ecologic restriction. Two metrics of morphologic separation (i.e., the morphologic difference between sister-species) are used: (1) Euclidean distance in morphospace and (2) transition magnitude. The latter metric is calculated by a multivariate analysis of sister-species contrasts, which determines both types and magnitudes of morphologic transitions. The advantage of using transition magnitudes is that it balances the effects of transitions that either affect more morphometric characters or occur more frequently. Both metrics indicate that larger morphologic separations between sister-species were concentrated early in gastropod evolution. Among gastropods, gross shell morphology often reflects basic trophic strategy and function whereas basic internal anatomy does not. Transition magnitudes can be broken down into transitions associated with differences in basic trophic strategies and shell functional biology (“external”), and those associated with differences in basic internal anatomy (“internal”). Internal transition magnitudes show a highly significant decrease over time (p < 10–04) whereas external transition magnitudes show a much less significant decrease over time (p < 0.10) and no significant decrease after the earliest Ordovician (p ≅ 0.50). The results therefore suggest that increasing phylogenetic constraints played a greater role in the early evolution of gastropods than did increasing ecologic ones.
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Walsh, S., J. R. Miles, E. C. Wright-Johnson, B. Keel, L. A. Rempel, and A. K. Pannier. "53 Transcriptomic profiles of uniform populations of invivo-produced spherical, ovoid, or tubular porcine embryos during the initiation of elongation." Reproduction, Fertility and Development 32, no. 2 (2020): 152. http://dx.doi.org/10.1071/rdv32n2ab53.
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Signalling interactions among littermate porcine conceptuses during embryo elongation can alter the expression of genes that are essential in promoting successful embryo elongation. Understanding the differential expression of critical genes from uniform littermate conceptuses as they undergo the initiation of elongation can help identify critical pathways and genes to facilitate improved synchronization of embryo elongation and birthweight uniformity. The objective of this study was to identify differential gene expression from uniform porcine conceptuses as they transition through spherical (S), ovoid (O), and tubular (T) morphologies during the initiation of elongation invivo. White crossbred gilts (n=22) were bred at oestrus (designated as Day 0 of gestation) and harvested at Day 9, 10, or 11 of gestation to obtain corresponding uniform populations of each embryo morphology. Reproductive tracts were immediately collected and flushed with 40mL of RPMI-1640 medium. Based on morphology, embryos were assigned to one of three treatment groups: (1) uniform S (n=8); (2) uniform O (n=8); or (3) uniform T (n=6) in which at least 80% of the embryos within each litter corresponded to the latest stage morphology. RNA-Seq was performed from 22 libraries constructed from a single invivo-produced embryo from the uniform populations of S, O, or T embryos. Differentially expressed genes (DEG) and pathway analysis were evaluated using DESEqn 2 and iPathwayGuide, respectively. For the S vs. O comparison, 5726 DEG and 7 pathways were significantly enriched, including ribosome biogenesis, spliceosome, pyrimidine metabolism, RNA polymerase, one carbon pool by folate, ECM-receptor interaction, and MAPK signaling pathways. For the S vs. T comparison, 5914 DEG and 7 pathways were significantly enriched, including ribosome biogenesis, DNA replication, pyrimidine metabolism, cell cycle, mismatch repair, spliceosome, and one carbon pool by folate pathways. Interestingly, most of the transcripts in pathways involving DNA processing, nucleotide metabolism, transcription, and post-transcriptional modifications were upregulated in S embryos compared with O and T embryos. For the O vs. T comparison, only 20 DEG were identified and no pathways were found to be significant after FDR adjustment. These data illustrate dramatic changes in the transcriptomes from pre-elongation stage S embryos compared with transitional stage O and T embryos, and provide putative genes and pathways involved in internal signals for the initiation of embryo elongation in pigs. The USDA is an equal opportunity provider and employer. Funding was provided by USDA-NIFA-AFRI grant no. 2017-67015-26456.
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Malik, Faizan, Teresa Santiago, Armita Bahrami, Eric Davis, Beth McCarville, Scott Newman, Elizabeth M. Azzato, et al. "Dedifferentiation in SDH-Deficient Gastrointestinal Stromal Tumor: A Report With Histologic, Immunophenotypic, and Molecular Characterization." Pediatric and Developmental Pathology 22, no. 5 (May 9, 2019): 492–98. http://dx.doi.org/10.1177/1093526619846222.
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One-third of gastrointestinal stromal tumors (GISTs) that lack KIT or PDGFRA mutations show succinate dehydrogenase (SDH) mutations or promoter hypermethylation. Most SDH-deficient GISTs occur in the pediatric, adolescent, or young adult setting and have unique features including predilection for the stomach, multinodular plexiform architecture, epithelioid cytology, prominence of lymphovascular invasion, and predilection for nodal metastasis. Dedifferentiation in GIST is a rare histologic change which may occur de novo or secondary to imatinib therapy and is characterized by abrupt transition of well-differentiated (WD) GIST to a subclonal anaplastic process that shows loss of immunohistochemical marks (CD117, DOG1). We describe the case of a previously healthy 18-year-old man who presented with a large gastric wall mass that contained 2 distinct morphologic populations. The first was WD and characterized by sweeping fascicles of bland spindled cells. This population abruptly transitioned to dedifferentiated (DD) foci composed of large sheets of discohesive cells that displayed a spectrum of rhabdoid and epithelioid morphologies with marked pleomorphism and mitotic activity. Immunohistochemically, the tumor showed variable staining in the 2 components with diffuse DOG-1 and CD117 positivity in the WD component and complete absence in the DD foci. SDH-B staining was lost in both components. Whole exome and transcriptome analysis was performed on tissue from both components and both showed an SDHB mutation (c.286G>A) as well as unique mutational burden and copy number profiles. Herein, we describe the first case of a DD SDH-deficient GIST with morphologic, immunophenotypic, and molecular characterization.
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Arostegi, J., J. I. Baceta, V. Pujalte, and M. Carracedo. "Late Cretaceous—Palaeocene mid-latitude climates: inferences from clay mineralogy of continental-coastal sequences (Tremp-Graus area, southern Pyrenees, N Spain)." Clay Minerals 46, no. 1 (March 2011): 105–26. http://dx.doi.org/10.1180/claymin.2011.046.1.105.
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AbstractThe origin and distribution of late Maastrichtian–early Palaeocene clay mineral associations were investigated in the Tremp-Graus basin (South Pyrenees, Spain) to assess palaeoclimate changes during that period. The studied succession is made up of expanded continental and transitional terrigeneous and carbonate deposits accumulated in a coastal plain setting. X-ray diffraction, SEM-EDX and TEM-AEM analysis reveal that the main clay components are illite and smectite, but kaolinite, chlorite and illite-smectite mixed layers are present, although irregularly distributed, all of them showing a platy morphology typical of a detrital origin. Persistence of the chemical features of the Al-dioctahedral smectites throughout the whole succession demonstrates the persistence of the same source area during the interval studied. Palygorskite occurs in the late Danian and Selandian, within carbonate tidal flats as sabkha-like facies. In SEM images, the palygorskite displays straight fibre morphologies, both coating and branched curling out, a clear proof of authigenic origin.Physical or chemical weathering (PhW/ChW) determined as illite + chlorite/smectite + kaolinite ratio, smectite/kaolinite ratio and palygorskite distribution have been used as clay proxies for palaeoclimate reconstructions. Such data suggest a shift from temperate subhumid (perennial) conditions in late Maastrichtian times to a warm seasonal climate during early Palaeocene times. This trend, however, was dramatically altered during the late Danian–Selandian interval, when prevailing warm and semi-arid to arid climatic conditions caused intense evaporation and the development of an alkaline environment in which the palygorskite authigenesis took place.The proposed climatic trend partly concurs with that established for earliest Danian time by Domingoet al.(2007), also in the Tremp-Graus basin, from isotopic and geochemical proxies, as well as with the reconstruction of Cojan & Moreau (2006), in which a semiarid Danian phase for the near continental basin of Aix-en-Provence is postulated. However, it is at odds with the notion of a humid Danian state in the Pyrenees, as inferred by Gawendaet al.(1999) from clay mineral proxies of deep marine successions.
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Cohen, G. M., X. M. Sun, R. T. Snowden, M. G. Ormerod, and D. Dinsdale. "Identification of a transitional preapoptotic population of thymocytes." Journal of Immunology 151, no. 2 (July 15, 1993): 566–74. http://dx.doi.org/10.4049/jimmunol.151.2.566.
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Abstract Apoptosis, a major form of cell death in the immune system, is characterized by cell shrinkage, chromatin condensation, and cleavage into nucleosomal fragments. Apoptosis may be the mechanism for the elimination of autoreactive and unselected CD4+ CD8+ thymocytes in the thymus. A large number of diverse agents are capable of inducing apoptosis in immature thymocytes. Rat thymocytes were treated with etoposide, a DNA topoisomerase II reactive agent, or dexamethasone, a glucocorticoid, and separated on discontinuous Percoll gradients. We have identified and isolated a transitional preapoptotic population of thymocytes that exhibited early morphologic and biochemical changes associated with apoptosis. These preapoptotic cells were intermediate in size and density between normal and apoptotic thymocytes and exhibited a decreased surface expression of both CD4 and CD8 molecules compared to control thymocytes. On ultrastructural examination, they were shown to possess sharply defined clumps of condensed chromatin abutting onto the nuclear membrane. These morphologic changes, the first detectable signs of apoptosis, occurred prior to the internucleosomal cleavage of DNA, often regarded as the biochemical hallmark of apoptosis. Nucleosomal fragments of 180 to 200 base pairs or multiples thereof were, however, detected following subsequent dramatic changes in the nuclear structure of these preapoptotic cells that resulted in morphology typical of apoptosis. These results suggest that early critical events in apoptosis precede internucleosomal cleavage of DNA.
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Muhmond, Haji Muhammad, and Hasse Fredriksson. "Graphite Growth Morphologies in Cast Iron." Materials Science Forum 790-791 (May 2014): 458–63. http://dx.doi.org/10.4028/www.scientific.net/msf.790-791.458.
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Graphite growth morphology was studied by using InLense detector on FEG-SEM after performing ion etching on the samples. Star like and circumferential growth mechanism of graphite was observed in the graphite nodules. Pure ternary alloy of hypo eutectic and hyper eutectic composition was treated with pure Mg, Ca and Sr, to study the effect of O and S concentration in the melt, on the transition of graphite morphology from nodular to vermicular/compacted and flake graphite. The change in the melt composition between the austenite dendrites due to micro-segregation of S, O and inoculants and their possible effects on the transition of graphite morphologies as well as the nucleation of new oxides/sulfides particles is discussed with the help of thermodynamics.
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Morrissey, K. J., and C. B. Carter. "Structural Transitions in AI203." Proceedings, annual meeting, Electron Microscopy Society of America 43 (August 1985): 214–15. http://dx.doi.org/10.1017/s0424820100117996.
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The importance of A1203 materials in applications such as catalysis (γ-Al203) has brought about renewed interest both in the structures which form during the transition from γ- to α-Al203 and in the grain morphologies which accompany the transition. These transitions are especially important in the area of ceramic processing, as demonstrated by the recent reports. The structures of the transition aluminas, while still not completely understood, have been studied by several groups. The present paper reviews an on-going study of the transition from γ- to α-alumina where the emphasis is on the identifying the forms observed, and the morphology the grains adopt. Results from the initial parts of this study have previously been reported. The method of preparation determines the amounts and the forms of alumina present in the final sample.
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Qu, Yanbo, Yue Shu, Haining Zong, Hongyun Si, Zhiheng Yang, and Tiantian Liu. "Understanding the Characteristics and Realization Path of Urban Land Use Transition in the Bohai Economic Rim: An Analytical Framework of “Dominant-Recessive” Morphology Coupling." Land 10, no. 5 (May 6, 2021): 493. http://dx.doi.org/10.3390/land10050493.
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Taking the Bohai Economic Rim as the research area and 44 prefecture-level cities as research objects, on the basis of deepening the connotation of urban land use morphology, we constructed a multi-dimensional indicator system for urban land use transition based on the dominant and recessive morphologies of land use. The patterns of change and transition type are described by single-morphology and comprehensive morphology indices, respectively, while a decoupling elastic coefficient model was used to analyze the coupling relationship and evolution process between the dominant and recessive morphologies of urban land use. The results showed the following: (1) From 2000 to 2020, the single-morphology and comprehensive morphology indices of urban land use in the Bohai Economic Rim both improved, to a certain extent. Overall, the transition types of dominant and recessive morphologies of urban land use showed a development trend, in which the degree of recessive morphology transition was higher than the degree of dominant morphology transition, and the spatial difference of its distribution pattern was obvious. (2) From 2000 to 2020, the type of coupling relationship between the dominant and recessive morphologies of urban land use in the Bohai Economic Rim experienced an evolution, from a single-morphology recession decoupling to a single-morphology leading positive hook. The whole region was in the benign development stage of close coupling, where the degree of transition showed the spatial characteristics of Beijing–Tianjin–Hebei > Liaodong Peninsula > Shandong Peninsula. (3) Differences in the economic levels and urbanization processes of different cities led to different paths, speeds, and degrees of urban land use transition, showing stable, volatile, and non-transition paths. The direct influence of different influencing factors, as well as their potential effects, drive the dominant and recessive morphologies of urban land use to grow, in terms of coupling and synergy, promoting the realization of urban land use transition.
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NESRULLAJEV, ARIF, and ŞENER OKTIK. "INDUCED CHANGES OF THERMOTROPIC PROPERTIES OF PHASE TRANSITIONS BETWEEN SMECTIC A MESOPHASE AND ISOTROPIC LIQUID: EFFECT OF SURFACES." Modern Physics Letters B 20, no. 14 (June 20, 2006): 821–33. http://dx.doi.org/10.1142/s0217984906010755.
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In this work, the effect of thin films on the thermotropic and thermo-optical properties and peculiarities of the phase transitions between the smectic A and isotropic liquid have been investigated. Peculiarities of the heterophase regions of the straight smectic A-isotropic liquid and reverse isotropic liquid-smectic A phase transitions have been studied. Change of morphologic properties of the heterophase regions, shift of the phase transition temperatures and the change of temperature widths of these heterophase regions under thin film influence have been observed.
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Chin, H. T., C. H. Shih, Y. P. Hsieh, C. C. Ting, J. N. Aoh, and M. Hofmann. "How does graphene grow on complex 3D morphologies?" Physical Chemistry Chemical Physics 19, no. 34 (2017): 23357–61. http://dx.doi.org/10.1039/c7cp03207b.
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Ratke, Lorenz, Anja Müller, Martin Seifert, and Galina Kapserovich. "Monotectic Alloys and their Growth Morphologies." Materials Science Forum 649 (May 2010): 137–42. http://dx.doi.org/10.4028/www.scientific.net/msf.649.137.
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Alloys of exact monotectic composition can decompose at the monotectic temperature into different two phase microstructures. The minority phase can be arranged as fibers similar to eutectics, as string of pearls or as irregularly distributed droplets. The directional solidification of three Al-base monotectic alloys was investigated: Al-Pb, Al-In and Al-Bi utilizing aerogel base furnace technology to ensure constant gradient and solidification velocity over the processing length. The solidified microstructures are characterized as a function of temperature gradient ahead of the solidification front and the solidification velocity. The experimental results are presented in form of stability diagrams for the three microstructures showing the regions in which fibers, string of pearls or irregular morphologies exist. The inter fiber spacing is analyzed and presented in from of Jackson and Hunt type relations and the transitions between the microstructures are discussed.
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Barai, Pallab, Mark Wolfman, Xiaoping Wang, Jiajun Chen, Arturo Gutierrez, Juan Garcia, Jianguo Wen, Tim Fister, Hakim Iddir, and Venkat Srinivasan. "Morphology of Transition Metal Carbonate Cathode Precursors." ECS Meeting Abstracts MA2022-02, no. 6 (October 9, 2022): 630. http://dx.doi.org/10.1149/ma2022-026630mtgabs.
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Increasing the capacity of cathode materials used for lithium-ion batteries is desirable, as it ultimately enhances the energy density. Due to their lower cost and reversible cycling capacity of 250 – 300 mAh/g, Li- and Mn-rich LMR-NMC oxides are strong candidates as next generation cathodes used in lithium-ion batteries. Apart from the atomic structure, morphology of the cathode particles also influence their performance. LMR-NMC cathode particles are usually constructed through a two-step cathode fabrication process, which involves initial coprecipitation of the Mn-rich carbonate based cathode precursors, and later calcination of these precursors with a lithium salt at elevated temperatures. The secondary particles generally maintain their as precipitated precursor morphologies even after high temperature calcination. Even though the primary particles do change their size during calcination, the rate of oxidation and lithiation experienced by the transition metal precursors depend substantially on the primary particle morphology. Hence, it is critical to understand and control both the primary and secondary particle morphologies obtained after the coprecipitation process. In the present context, carbonate based NMC cathode precursors containing only Mn, only Ni and only Co, is precipitated, along with equal amount of the transition metals (Ni0.33Mn0.33Co0.33CO3), using conventional batch reactors. NH4HCO3 is used as the source of carbonate anions during the coprecipitation process, and the entire reaction is conducted at 50°C. The obtained particle morphologies for different transition metals are shown in Figure 1(a) as visualized using high resolution TEM techniques. Except MnCO3, all other transition metals demonstrate aggregated morphologies, which most probably form through surface growth mechanisms. Competition between growth rate and surface energies that leads to the formation of single crystalline particles for MnCO3, and particulate features for other transition metals, are demonstrated in Figure 1(b). Multiscale computational methodologies are developed to elucidate the impact of reaction kinetics and thermodynamics on determining the overall primary and secondary particle morphologies. Influence of transition metal content and ammonia concentration in determining the final particle size and size distribution will be discussed as part of this study. Figure 1
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Truong, Nghia P., Michael R. Whittaker, Athina Anastasaki, David M. Haddleton, John F. Quinn, and Thomas P. Davis. "Facile production of nanoaggregates with tuneable morphologies from thermoresponsive P(DEGMA-co-HPMA)." Polymer Chemistry 7, no. 2 (2016): 430–40. http://dx.doi.org/10.1039/c5py01467k.
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WANG, DIANGANG, CHUANZHONG CHEN, QUANHE BAO, LIANG ZHANG, and TINGQUAN LEI. "BONDING ZONE MORPHOLOGIES CHARACTERISTICS OF LASER REMELTED HA COATINGS." Surface Review and Letters 13, no. 05 (October 2006): 655–60. http://dx.doi.org/10.1142/s0218625x0600861x.
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The low bonding strength between plasma sprayed hydroxyapatite (HA) coatings and substrates is one of the problems, which should be solved. In this paper, the as-sprayed HA coatings were retreated by laser remelting. The microstructure and element analysis in coatings were studied by electron probe microanalyzer (EPMA) and the accessory of energy spectrum analyzer. The results show that the bonding state can be improved greatly after laser remelting and it is a metallurgical combination between transition layers and substrates. Generally, with the increase of laser power and the decrease of scanning speed, the bonding state between the surface and transition layer will be improved much more, but the value of Ca / P ratio will deviate much more from 1.67. In this experiment, the optimum technological parameter is that the laser power is 600 W and the scanning speed is 11.2 mm/s.
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Kozman, D., S. Heneidi, A. Ullah, I. Ghleilib, L. Vemavarapu, and T. Dykes. "Urinary Bladder Transitional Cell Carcinoma with Chordoid Features-A Rare Entity." American Journal of Clinical Pathology 154, Supplement_1 (October 2020): S56—S57. http://dx.doi.org/10.1093/ajcp/aqaa161.122.
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Abstract Casestudy: Invasive urothelial carcinoma is heterogenous entity and show variant morphologic patterns, of which squamous differentiation is the most common. Other variants have been widely recognized and studied. Invasive urothelial carcinoma with chordoid features is a rare entity with only 16 reported cases to date in English literature. It has a significant morphologic overlap with other vesical and non-vesical myxoid neoplasms, including extra-skeletal myxoid chondrosarcoma and chordoma, which necessitate an extensive workup to reach an accurate diagnosis. To the best of our knowledge we report the 17th case of urothelial carcinoma with chordoid features in a 76-year-old male who underwent a cystoprostatectomy and bilateral pelvic lymph node dissection with confirmed diagnosis of high-grade invasive urothelial carcinoma on biopsy. Grossly, bladder showed a 4.2 x 3.4 x 0.6 cm firm white tumor entirely replacing the anterior wall, extending into perivesicular fat, and invading the prostate gland and seminal vesicles. Microscopically, tumor showed urothelial carcinoma in-situ transitioning into high-grade invasive carcinoma with chordoid features. The tumor characterized by round to elongated epithelial cells and eosinophilic cytoplasm arranged in a single file/complex cord-like architecture, in a prominent myxoid stromal background. No conventional high-grade spindle cell morphology was identified. Pelvic lymph nodes were positive for metastatic disease. Tumor cells were positive for GATA3, Pan-cytokeratin, 34BetaE12, and p63, while negative for AMCAR, supporting the urothelial origin of this tumor and confirming the diagnosis. Invasive urothelial carcinoma with chordoid features is a rare entity, generally present at high stage disease, that can be mistaken for other prominent myxoid stromal neoplasms and requires careful assessment. Although, it can demonstrate similar demographic, clinical and immunohistochemical staining pattern as of conventional urothelial carcinoma, special attention should be given to exclude sarcomatoid features which is an aggressive variant of urothelial carcinoma.