Tube Shape Research Articles

Simplifying the creation of iron compound inserted, nitrogen-doped carbon nanotubes and its catalytic application

The applicability of metals or their compound inserted, nitrogen-doped carbon nanotubes is blocked by the production although that its unique properties are outstanding in many fields. In this report, a synthetic strategy is developed to carbonize melamine in a CaCl2/FeCl3 molten salt medium and to prepare uniform iron or iron compound (including Fe3O4, Fe3C and Fe) inserted nitrogen-doped carbon nanotubes. The mechanism study of forming Fe3C@NCNTs find that the nanotubes with uniform structure are obtained from graphite sheets, which are formed at a relatively low temperature, and then the obtained graphite sheets transfer to tube shape with the catalysis of Fe at high temperature. The high catalytic activity of Fe3C@NCNTs is demonstrated by an onset oxidation potential of 0.27 V (vs. RHE) in the hydrazine oxidation reaction and an onset potential of 0.96 V (vs. RHE) for the oxygen reduction reaction. Based on DFT calculations, the good catalytic activity of Fe3C@NCNTs may be related to the decreased local work function on its surface. Fe3C@NCNTs also exhibit an enhanced reaction kinetics at higher potential, which make it a promising bifunctional catalyst for direct hydrazine fuel cells.

Effect of tube shape on thermo-fluid performance of a winglet supported fin-and-tube heat exchanger having staggered tubes

Abstract The heat transfer and pressure drop performance of a fin-and-tube heat transfer surface has been presented in this paper. The circular and elliptical tube geometries have been considered for the present analysis. The two tube geometries are compared for both baseline (without winglet) and winglet supported fin-and-tube heat transfer surface. Three staggered tube rows have been considered and rectangular winglets have been selected as heat transfer enhancement tool. The heat transfer and pressure drop performance of the heat transfer surface has been described in terms of Nu and f respectively. To account for the combined effect of Nu and f, an enhancement factor η has also been presented. The winglets are placed at three different stream-wise locations with respect to the tubes and optimum winglet locations for both the tube geometries are presented based on the highest enhancement factor.

Anisotropic momentum broadening in the 2+1D glasma: Analytic weak field approximation and lattice simulations

In heavy ion collisions, transverse momentum broadening quantifies the modification of a hard probe due to interactions with the quark-gluon plasma (QGP). We calculate momentum broadening in the Glasma, which is the highly non-isotropic precursor stage of the QGP right after the collision. We show that the Glasma leads to anisotropic momentum broadening: high energy partons accumulate more momentum along the beam axis than transverse to it. The physical origin of anisotropic broadening can be traced back to differences in the shapes of chromo-electric and chromo-magnetic flux tubes in the Glasma. We provide semi-analytic results for momentum broadening in the dilute Glasma and numerical results from real-time lattice simulations of the non-perturbative dense Glasma.

Kinase Partner Protein Plays a Key Role in Controlling the Speed and Shape of Pollen Tube Growth in Tomato.

The rapid and responsive growth of a pollen tube requires delicate coordination of membrane receptor signaling, Rho-of-Plants (ROP) GTPase activity switching, and actin cytoskeleton assembly. The tomato (Solanum lycopersicum) kinase partner protein (KPP), is a ROP guanine nucleotide exchange factor (GEF) that activates ROP GTPases and interacts with the tomato pollen receptor kinases LePRK1 and LePRK2. It remains unclear how KPP relays signals from plasma membrane-localized LePRKs to ROP switches and other cellular machineries to modulate pollen tube growth. Here, we biochemically verified KPP's activity on ROP4 and showed that KPP RNA interference transgenic pollen tubes grew slower while KPP-overexpressing pollen tubes grew faster, suggesting that KPP functions as a rheostat for speed control in LePRK2-mediated pollen tube growth. The N terminus of KPP is required for self-inhibition of its ROPGEF activity, and expression of truncated KPP lacking the N terminus caused pollen tube tip enlargement. The C-terminus of KPP is required for its interaction with LePRK1 and LePRK2, and the expression of a truncated KPP lacking the C-terminus triggered pollen tube bifurcation. Furthermore, coexpression assays showed that self-associated KPP recruited actin-nucleating Actin-Related Protein2/3 (ARP2/3) complexes to the tip membrane. Interfering with ARP2/3 activity reduced the pollen tube abnormalities caused by overexpressing KPP fragments. In conclusion, KPP plays a key role in pollen tube speed and shape control by recruiting the branched actin nucleator ARP2/3 complex and an actin bundler to the membrane-localized receptors LePRK1 and LePRK2.

Detecting New Allies: Modifier Screen Identifies a Genetic Interaction Between Imaginal disc growth factor 3 and combover, a Rho-kinase Substrate, During Dorsal Appendage Tube Formation in Drosophila.

Biological tube formation underlies organ development and, when disrupted, can cause severe birth defects. To investigate the genetic basis of tubulogenesis, we study the formation of Drosophila melanogaster eggshell structures, called dorsal appendages, which are produced by epithelial tubes. Previously we found that precise levels of Drosophila Chitinase-Like Proteins (CLPs), encoded by the Imaginal disc growth factor (Idgf) gene family, are needed to regulate dorsal-appendage tube closure and tube migration. To identify factors that act in the Idgf pathway, we developed a genetic modifier screen based on the finding that overexpressing Idgf3 causes dorsal appendage defects with ∼50% frequency. Using a library of partially overlapping heterozygous deficiencies, we scanned chromosome 3L and found regions that enhanced or suppressed the Idgf3-overexpression phenotype. Using smaller deletions, RNAi, and mutant alleles, we further mapped five regions and refined the interactions to 58 candidate genes. Importantly, mutant alleles identified combover (cmb), a substrate of Rho-kinase (Rok) and a component of the Planar Cell Polarity (PCP) pathway, as an Idgf3-interacting gene: loss of function enhanced while gain of function suppressed the dorsal appendage defects. Since PCP drives cell intercalation in other systems, we asked if cmb/+ affected cell intercalation in our model, but we found no evidence of its involvement in this step. Instead, we found that loss of cmb dominantly enhanced tube defects associated with Idgf3 overexpression by expanding the apical area of dorsal appendage cells. Apical surface area determines tube volume and shape; in this way, Idgf3 and cmb regulate tube morphology.

Effect of endotracheal tube plus stylet versus endotracheal tube alone on successful first-attempt tracheal intubation among critically ill patients: the multicentre randomised STYLETO study protocol

IntroductionTracheal intubation is one of the most daily practiced procedures performed in intensive care unit (ICU). It is associated with severe life-threatening complications, which can lead to intubation-related cardiac arrest....

Stylostome formation by parasitic larvae of Allothrombium fuliginosum (Trombidiformes: Trombidiidae): morphology of feeding tubes and factors affecting their size

The morphology and formation of stylostomes (feeding tubes) in hosts’ body during the parasitic phase of Allothrombium fuliginosum (Hermann) larvae were studied for the first time with light microscopy (LM) and transmission electron microscopy (TEM). The stylostomes were observed in three aphids species—Acyrthosiphon pisum (Harris), Elatobium abietinum (Walker), and Macrosiphum rosae (L.)—parasitized by mites under laboratory conditions. They consisted of 2–6 main branches, preliminarily unbranched, then producing secondary and sometimes also tertiary branches as finally formed structures. Their walls were uniformly electron-dense, without any longitudinal and transverse stratifications and showed rather irregular outlines. Distally, the stylostome branches revealed transparent pores and cavities in their walls, connecting the stylostome canal with surrounding haemocoelic space. The total length of stylostomes at the end of the parasitic phase was on average 16× greater than that recorded in the youngest stylostomes. No differences in the overall shape of feeding tubes between host species were stated. The stylostomes formed in different host species did not differ significantly, except their total length, which attained the highest value in tissues of Ac. pisum.

The histology and ultrastructure of the salivary glands of Neopanorpa longiprocessa (Mecoptera: Panorpidae).

The salivary glands of Panorpidae usually exhibit distinct sexual dimorphism and are closely related to the nuptial feeding behavior. In this study, the salivary glands of Neopanorpa longiprocessa were investigated using light microscopy and transmission electron microscopy. The salivary glands are tubular labial glands and consist of a scoop-shaped salivary pump, a common salivary duct, and a pair of salivary tubes. The male and female salivary glands are remarkably different in the bifurcation position of the common salivary duct and the length and shape of the secretory tubes. Compared with the simple female salivary glands, the male's are more developed as their paired elongated salivary tubes can be divided into two parts, the glabrate anterior tube and the posterior tube with many secretory tubules. The ultrastructural study shows that the male salivary tubes have strong secretory function. The existence of different secretion granules indicates that there are some chemical reactions or mixing occurring in the lumen. Based on the ultrastructural characteristics, the functions of the different regions of the salivary tube have been speculated. The relationship between the salivary glands and nuptial feeding behavior of N. longiprocessa has been briefly discussed based on the structure of the salivary glands.

Characterization of zinc oxide nanocrystals with different morphology for application in ultraviolet‐light photocatalytic performances on rhodamine B

ZnO nanostructures of different morphology (nanorods, nano-leaf, nanotubes) were favourably grown using a chemical precipitation process. The prepared ZnO nanostructures were characterized systematically using absorption spectroscopy, emission spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared studies. XRD results showed the hexagonal wurtzite phase of the synthesized ZnO nanostructures. Structural properties such as average crystallite size, lattice constants, volume of the unit cell, atomic fraction, and structural bonds were also studied. The optical band gap of the synthesized ZnO nanocrystals varied from 3.52 eV to 3.69 eV with high quantum yield of the blue emission (~420 nm). Urbach energy for ZnO nanocrystals was calculated to be 0.702 eV, 0.901 eV, and 0.993 eV for nanorods, nano-leaf, and tube like ZnO crystals, respectively. Morphology of the fabricated nanostructures was investigated using SEM. Photocatalytic degradation of rhodamine B (Rh B) in solution under UV irradiation was explored with different ZnO morphology. Photocatalytic experiments showed that ZnO nano-leaf had a higher degradation rate of photocatalytic activity of photodegrading Rh B compared with the other tube shape and rods shape nanostructures. The Rh B dye degraded considerably by ∼79.05%, 74.41%, and 69.8% within 120 min in the presence of the as-fabricated fern nano-leaf, nanotubes, and nanorods of the ZnO nanocrystals at room temperature.

Cuscuta sect. Californicae (Convolvulaceae) Revisited: ‘Cryptic’ Speciation and Host Range Differentiation

Abstract—Cuscuta californica complex (sensu lato, s. l.) is a western North American group of species in which the infrastaminal scales are reduced, making the morphological delimitation of species particularly challenging. A revision of this group was prompted by the discovery of an apparent new species from central California based primarily on molecular means. Driven by this finding, the morphological limits of C. californica s. l. species were comprehensively re-evaluated through a morphometric study. DNA sequences from plastid (trnL‐F region and rbcL), nuclear ribosomal ITS and 26S rDNA, as well as a low-copy nuclear pentatricopeptide repeat (PPR) gene were used to reconstruct evolutionary relationships among taxa. Last but not least, the host range of relevant taxa was determined using herbarium specimens. Molecular results strongly supported the new species, C. difficilis, which was found to be morphologically separated from C. brachycalyx only by subtle calyx lobe and corolla tube shape differences. Despite sharing some of the hosts, all the members of C. californica s. l. exhibited a differentiation of their host ranges. An identification key and description of the new species were provided together with a discussion on the systematics and host range of C. californica s. l.. Hybridization, accompanied by plastid capture, was suggested as a possible mechanism of speciation for C. brachycalyx.

Effects of the shape of tube and flow field on fluid flow and heat transfer

The arc tube is an innovative heat exchange device that has the advantages of high heat exchange efficiency, which slows down the damage thermal stress to the pipeline and high mass transfer rate, in comparison to the traditional straight wall tubes. Therefore, it is widely applied in the field of heat and mass transfer, particularly in heat exchanger. To study the influence of the ratio of the circumscribed arc radius of the arc tube on the heat transfer and flow resistance characteristics of the fluid inside the tube, geometric models of sine wave wall tubes with various radius ratio i, and the same size parameters have been established. The flow field and temperature field in the tube have been analyzed by numerical simulation and experiment, and the comprehensive heat transfer performance of different wave-wall tubes has been evaluated using the performance evaluation factor PEC. The results show that the heat transfer capacity is stronger for the smaller i. Further, Nu decreases with increasing i, and the reduction decreases with increasing Re. The frictional resistance coefficient at 1 is proportional to i at radius ratio between 0.1 and 1, and the frictional resistance coefficient is inversely proportional to i at 1 < i < 10. When i = 1, the frictional resistance coefficient appears to be the maximum, PEC increases as Re increases and the PEC of external tangential arc wave wall tube is higher than the sine wave wall tube. To improve the heat transfer efficiency of the sine wave wall tube, a pulsating flow field has been applied to the flowing fluid in the wave wall tube. It has been found that the application of the pulsating flow field can improve the heat transfer coefficient of the fluid in the wave wall tube, and the pulsation parameter has a greater impact on the heat transfer coefficient.

Design, additive manufacturing, and performance of heat exchanger with a novel flow-path architecture

A novel heat exchanger architecture was investigated, in which each fluid pathway transitions through the heat exchanger from tube-flow to shell-flow, or from shell-flow to tube-flow. The heat exchangers (HX) consisted of two plenums filled with tube bundles and a solid core of Counterflow channels Sandwiched between Plenums (CSP). To allow a high packing in the core region, a non-circular, e.g., triangular, cross-section tube shape was employed. In this exploratory study of the proposed CSP HXs, prototypes were fabricated by Laser Powder Bed Fusion additive manufacturing. Several challenges posed by the laser-powder-bed fabrication were presented and design solutions for additive manufacturing were discussed. Two different CSP HX were 3D printed, one in which the core region was placed midway between the end plates in the HX, and another one in which the core region was offset toward one end of the HX. The performance of the CSP HXs was evaluated against an off-the-shelf 5 kW shell-and-tube heat exchanger, considered as the baseline heat exchanger. Each of the baseline HX and six CSP HXs configurations were tested at three different flow rates for R245fa (cold fluid) while inlet conditions for the water (hot fluid) were not changed, for a total of 21 tests. It was found that the heat load for three CSP HXs configurations shows excellent thermal performance as compared to that of the baseline HX. The overall heat transfer coefficient for two CSP HX configurations was higher than that of the baseline by 16 to 32%. Although the proposed HXs did not outperform the commercial baseline HX in all aspects, the reported thermohydraulic performance in this first embodiment of the proposed HX concept indicated that the CSP concept offers a new path towards more efficient and more compact heat exchangers.

Two-dimensional numerical model for predicting fouling shape growth based on immersed boundary method and lattice Boltzmann method

Fouling and ash deposition are important problems for the heat exchangers. The numerical models are efficient ways to understand the fouling processes and guide the design of heat exchangers. Because the shape of the fouling layer can influence the flow and heat transfer, modeling the shape change of the fouling layer is essential for the numerical models. In this work, a new numerical model based on the immersed boundary method is proposed for 2D fouling processes. The flow is modeled by a multiblock lattice Boltzmann method with a fixed Eulerian mesh, and the fouling layer is represented by an immersed boundary with Lagrangian points. The shape change of the fouling layer can be carried out by deforming the immersed boundary, while keeping the mesh of flow simulation unchanged. The particle motion, deposition models and a time ratio for fouling time scale are also included in the model. The particle depositions on a single row of tube and tube bundles with different tube shapes are simulated by the proposed model as examples. The influences of particle size and flow velocity on the particle deposition on windward and leeward sides of a circular tube are analyzed. As for the tube bundles, the elliptical tube can reduce the fouling rate. The evolution of the shape of the fouling layer can be obtained by the proposed model.

The analysis of inter- and intrapopulation variability of Milnesium eurystomum Maucci, 1991 reveals high genetic divergence and a novel type of ontogenetic variation in the order Apochela

Tardigrada are a phylum of cosmopolitan invertebrates inhabiting both terrestrial and marine ecosystems. The carnivorous species are usually characterized by a wide buccal tube, which constitutes the first and rigid part of the digestive system. Among tardigrades, only the genus Milnesium is considered exclusively carnivorous and includes the largest known species in the phylum. Some members of the genus exhibit developmental variability in taxonomically important morphological traits such as the number of points on the secondary branches of claws and cuticular sculpturing. Milnesium eurystomum is one of the largest tardigrades, with body length reaching 1.2 mm, and it is equipped with an exceptionally wide buccal tube, enabling this animal to feed on various prey, including other tardigrade species. Importantly, M. eurystomum, as well as other species with wide buccal tubes, were described solely using mature females, thus their developmental variability remains unknown. Interestingly, small Milnesium specimens with remarkably wide buccal tubes have never been reported, raising a question of whether such hatchlings and juveniles (first and second life stages) are extremely rare and simply have never been reported, or their buccal apparatus morphology is different from adults and thus constitutes as an undescribed buccal tube developmental variability. To answer this question, we analysed four populations of M. eurystomum originating from Greenland, Svalbard and Scotland. Due to discrepancies in species delineation based on different types of data, we parallelly applied various methods of species delimitation, both morphological and molecular. Thanks to ontogenetic analysis, we show and describe a novel type of developmental variability in the size and shape of the buccal tube. We also provide novel morphological traits and data for this species, together with the first record and characterization of males. Finally, we discuss the consequences of our findings for the taxonomy of Milnesium and tardigrades in general.

&lt;p&gt;&lt;strong&gt;&lt;em&gt;Quararibea bragae &lt;/em&gt;&lt;/strong&gt;&lt;strong&gt;(Malvaceae; Malvoideae):&lt;em&gt; &lt;/em&gt;a new species with multiple domatia from Brazil&lt;/strong&gt;&lt;/p&gt;

Quararibea bragae from the Atlantic Forest of Espírito Santo State (Brazil) is proposed as a new species. Quararibea bragae is similar to Q. turbinata in vegetative characteristics, such as the shape and consistency of its leaves and type of domatia. However, it can be distinguished by the leaves’ indumentum and by the positioning and quantity of domatia on the abaxial surface of the leaves. Reproductive characteristics are differentiated by the shape and indumentum of the staminal tube and the shape of the fruit. We present a morphological description and comments, illustration, notes on ecology and distribution, and identification key of Atlantic Forest species.

Effect of Design and Surface Treatments on Fracture Resistance of Zirconia Inlay-Retained Fixed Dental Prosthesis After Thermo-Mechanical Cycling: An in vitro study

Objective: This study evaluated the effect of preparation designs and surface treatment on the fracture resistance of zirconia inlay retained fixed dental prosthesis (IR-FDPs). Material and Methods: Twenty secondary premolar and twenty secondary molar were used in this study. Twenty zirconia IR-FDPs were constructed, divided into two main groups, ten specimens each, according to abutment preparation (box & tube shape), each main group was subdivided into two sub groups according to surface treatment (Air abrasion & MDP primer surface treatment). The IR-FDPs were cemented using dual cure resin cement, then the specimens were subjected to thermo-mechanical cyclic loading (TMCL). The fracture resistance was measured. Results: The results showed that there was no statistically significant difference between air abrasion and MDP for both designs (box & tube shape).The effect of design,showed that there was statistically significant difference for both surface treatments between tube and box design where box design showed higher fracture resistance than tube design for both surface treatments. Conclusion: Inlay retained fixed dental prosthesis (IR-FDPs) with box shape provide more fracture resistance than with tube shape. The air abrasion surface treatment shows similar fracture as the MDP primer surface treatment.

Magnetic self-assembly of toroidal hepatic microstructures for micro-tissue fabrication

In this study, we developed a procedure for assembling hepatic microstructures into tube shapes using magnetic self-assembly for in vitro 3D micro-tissue fabrication. To this end, biocompatible hydrogels, which have a toroidal shape, were made using the micro-patterned electrodeposition method. Ferrite particles were used to coat the fabricated toroidal hydrogel microcapsules using a poly-L-lysine membrane. The microcapsules were then magnetized with a 3 T magnetic field, and assembled using a magnetic self-assembly process. During electrodeposition, hepatic cells were trapped inside the microcapsules, and they were cultured to construct tissue-like structures. The magnetized toroidal microstructures then automatically assembled to form tube structures. Shaking was used to enhance the assembly process, and the shaking speed was experimentally optimized to achieve the high-speed assembly of longer tube structures. The flow velocity inside the dish during shaking was measured by particle image velocimetry. Hepatic functions were evaluated to check for side-effects of the magnetized ferrite particles on the microstructures. Collectively, our findings indicated that the developed method can achieve the high-speed assembly of a large number of microstructures to form tissue-like hepatic structures.

Compressive behavior of FRP-confined steel-reinforced high strength concrete columns

Few studies have prospectively examined the axial compressive behavior of FRP-confined steel-reinforced concrete (FCSRC) columns employing high strength concrete (HSC) with a compressive cylinder strength up to 120 MPa. In FCSRC columns, the encased steel sections would ensure a ductile response under the large axial deformation and provide additionally axial and shear load-carrying capacities. Therefore, the FCSRC column with HSC is a promising type of hybrid structural element that enables effective utilization of both HSC and high-performance FRP. In this study, a comprehensive experimental study has been conducted to evaluate the compressive performance of FCSRC columns with HSC, considering the effects of steel section shape and thickness of FRP tube. For comparison purpose, the compressive behaviors of FCSRC columns using normal strength concrete (NSC), concrete-filled FRP tubes (CFFTs), and steel-reinforced concrete (SRC) columns were also investigated. The load and deformation capacities, dilation behaviors, failure modes and failure mechanism, composite effect between constituent materials, and enhancement effect of FRP confinement on SRC columns were discussed in this paper. This study revealed that the use of HSC produced higher axial stiffness as well as higher axial compressive capacity for the FCSRC columns, although the deformation capacity was reduced as compared to the use of NSC.

Effect of tube shape on the performance of a fin and tube heat exchanger

A numerical study is carried out to test the effect of tube shape on heat transfer and fluid flow in a finned tube heat exchanger. The effects of different shapes (circular, flat, elliptical and oval in both orientations: left and right) are analyzed. The simulations are carried out for two-dimensional and external flow of an incompressible fluid with Reynolds numbers varying between 3000 and 20000. The results obtained indicate that the shape of the tube directly affects the thermal and dynamic behaviors of a fin and tube heat exchanger. Where the circular tube ensures higher heat transfer coefficient of about 18% than the flat tube, and it generate a moderate pressure drop of about 10% in the same conditions. Also, some reliable empirical correlations are proposed to predict the Nusselt number and the friction factor.

Human skin-inspired multiresponsive actuators based on graphene oxide/polydimethylsiloxane bilayer film: bi-directional transformation of semi-tube into plane sheet/tube under different stimuli

Multiresponsive soft actuators comprised of carbon nanostructured-polymer hybrid smart materials have received enormous attention recently. However, it is always desirable and interesting to explore new types of stimuli which can trigger actuation in such materials. Inspired by human skin which can respond to multiple stimuli, we report here multiresponsive soft actuators based on graphene oxide (GO)-polydimethylsiloxane (PDMS) bilayer structure. These actuators exhibit reversible actuation under different stimuli viz. infrared (IR) light, acetone vapors and temperature. The actuation behavior under the influence of temperature is further investigated with its values in the heating as well as cooling modes. Therefore, the use of the different stimuli imparts the functionalities of photomechanical, vapomechanical, thermomechanical and cryomechanical actuation, respectively to these actuators. The actuators are realized by spin coating of PDMS film (200 μm) on GO film (15 μm) followed by curing at 120 °C. The thermal residual stress generated during curing process causes the structure to become tubular upon release which was then sliced to form semi-tube so that its bi-directional actuation could be observed. The semi-tubular actuators reversibly get transformed into plane sheet shape under the influence of IR light, heating and acetone vapors within about 4, 5 and 1 s, respectively which causes change of curvature from 2.1 to 0 cm−1. Further, it is transformed into full tube shape under the influence of cooling within about 12 s that changes the curvature from 2.1 to 4.2 cm−1. Finally, the actuators are utilized to demonstrate one of the prototype applications as IR light-driven soft gripper. It is believed that these actuators may also find potential applications in the fields of biomimics and realization of artificial intelligence components for military/industrial use.