Cylinder-like Shape Research Articles

4D-Printed Tool for Compressing a Shape Memory Polyurethane Foam during Programming.

Although several force application concepts are known that can be used to deform shape memory polymers (SMPs) within the scope of programming, controlled deformation is challenging in the case of samples with a cylinder-like shape, which need to be homogeneously compressed starting from the lateral surface. To solve this problem, this contribution follows a material approach that takes advantage of four-dimensional (4D) printing. Fused filament fabrication (FFF) was used as an additive manufacturing (AM) technique to produce a thermoresponsive tool in a cylindrical shape from a polyether urethane (PEU) having a glass transition temperature (Tg) close to 55 °C, as determined by differential scanning calorimetry (DSC). Once it was 4D-printed, a sample of laser cut polyester urethane urea (PEUU) foam with a cylindrical wall was placed inside of it. Subsequent heating to 75 °C and keeping that temperature constant for 15 min resulted in the compression of the foam, because the internal stresses of the PEU were transferred to the PEUU, whose soft segments were completely molten at 65 °C as verified by DSC. Upon cooling to -15 °C and thus below the offset temperature of the soft segment crystallization transition of the PEUU, the foam was fixed in its new shape. After 900 days of storage at temperatures close to 23 °C, the foam recovered its original shape upon reheating to 75 °C. In another experiment, a 4D-printed cylinder was put into hibernation for 900 days before its thermoresponsiveness was investigated. In the future, 4D-printed tools may be produced in many geometries, which fit well to the shapes of the SMPs to be programmed. Beyond programming SMP foams, transferring the forces released by 4D-printed tools to other programmable materials can further expand technical possibilities.

Revisiting the mystery of centrioles at the beginning of mammalian embryogenesis.

The prevailing assumption has been that the human spermatozoon provides only one centriole to the zygote: the proximal centriole, with a canonical, cylinder-like shape. This overly simplistic view has come under challenge since discovering that the human spermatozoon provides a second, atypical centriole to the zygote. The study of human zygotes is challenging for ethical reasons, and bovine zygotes provide an important model due to a similarity in centrosome embryonic inherence and function. Detailed ultrastructural analyses by Uzbekov and colleagues identify the persistence of atypical centrioles in bovine early embryos, raising questions about the original single-centriole model. Whether the parental origin of nascent atypical centrioles or their wide structural diversity and deviation from the canonical centriolar form in blastomeres constitutes sufficient evidence to warrant a reconsideration of the single-centriole model is discussed herein. Because previous human studies identified only one canonical centriole in the zygote, atypical centrioles are likely present in the early human embryo; therefore, it is time to rethink the role of paternal centrioles in human development.

Analytical study on the inflated shape of a super pressure balloon covered with a diamond-shaped net

In the last two decades, extensive efforts have been made to develop a large super pressure balloon (SPB) capable of carrying heavy payloads for scientific observations of long durations. Due to recent achievements by the NASA Balloon Program Office, practical operations of large-scale lobed-pumpkin SPB will be realized in the near future. Meanwhile, the research team initiated the development of a lightweight SPB with an alternative design concept, in which the entire balloon is covered by a diamond-shaped net. In this work, the static structural response of the proposed SPB is analyzed by establishing a mathematical model to predict its inflated shape. This model is validated by comparing the generated results with those obtained from nonlinear finite element analysis. Excellent agreement between the analytical solutions and the corresponding finite element results was obtained. On the basis of the mathematical model, the inflated shape of the SPB is investigated and unique structural characteristics are deduced, i.e., the balloon inflates into a cylinder-like shape for a certain geometry of the cover net. This structural feature can be explained by considering the equilibrium of forces applied to the cover net.

Complexity revealed by membrane curvature induced by ABC transporters

ABCB1 is the best-characterized member of the ABC superfamily of transmembrane proteins. ABCB1 transports structurally diverse substrates, including anticancer drugs. This, in combination with protein overexpression in cancer cells, hampers interactions with the drugs intracellular targets and jeopardizes chemotherapy treatments. The ATP-driven transport mechanism allows ABCB1 to alternate between an inward-facing (IF) conformation, where the protein adopts an inverted conical shape, and an outward-facing (OF) conformation, with a cylinder-like shape.

Flow coupling between active and passive fluids across water\u2013oil interfaces

Active fluid droplets surrounded by oil can spontaneously develop circulatory flows. However, the dynamics of the surrounding oil and their influence on the active fluid remain poorly understood. To investigate interactions between the active fluid and the passive oil across their interface, kinesin-driven microtubule-based active fluid droplets were immersed in oil and compressed into a cylinder-like shape. The droplet geometry supported intradroplet circulatory flows, but the circulation was suppressed when the thickness of the oil layer surrounding the droplet decreased. Experiments with tracers and network structure analyses and continuum models based on the dynamics of self-elongating rods demonstrated that the flow transition resulted from flow coupling across the interface between active fluid and oil, with a millimeter–scale coupling length. In addition, two novel millifluidic devices were developed that could trigger and suppress intradroplet circulatory flows in real time: one by changing the thickness of the surrounding oil layer and the other by locally deforming the droplet. This work highlights the role of interfacial dynamics in the active fluid droplet system and shows that circulatory flows within droplets can be affected by millimeter–scale flow coupling across the interface between the active fluid and the oil.

Preparation of cylinder-like polystyrene-silica composite particles

The cylinder-like shape is one of the most common shapes in geometry and polymer-silica composite particles have been one of the most commonly reported organic-inorganic composite particles, while cylinder-like polymer-silica composite particles are seldom reported in literature. In this work, we report a facile method to prepare cylinder-like polystyrene-silica (PS–SiO2) composite particles by judicious combination of PVP-involved dispersion polymerization and magnetic stirring. First, spherical PS-SiO2 composite particles were synthesized by dispersion polymerization of styrene in an ethanol/water mixture. Second, cylinder-like PS-SiO2 composite particles were prepared by stirring the spherical PS-SiO2 particles in a water medium in the presence of PVP. The effects of PVP molecular weight, PVP concentration, stirring rate, stirring time and stirring temperature on the morphology of the composite particles were investigated. Optimization of the stirring conditions allowed relatively high percentage (up to ~73%) of cylindrical particles to be achieved. This method is expected to expand the morphology library of polymer-silica composite particles.

Fluid\u2013structure interaction of flexible submerged vegetation stems and kinetic turbine blades

A fluid–structure interaction (FSI) methodology is presented for simulating elastic bodies embedded and/or encapsulating viscous incompressible fluid. The fluid solver is based on finite volume and the large eddy simulation approach to account for turbulent flow. The structural dynamic solver is based on the combined finite element method–discrete element method (FEM-DEM). The two solvers are tied up using an immersed boundary method (IBM) iterative algorithm to improve information transfer between the two solvers. The FSI solver is applied to submerged vegetation stems and blades of small-scale horizontal axis kinetic turbines. Both bodies are slender and of cylinder-like shape. While the stem mostly experiences a dominant drag force, the blade experiences a dominant lift force. Following verification cases of a single-stem deformation and a spinning Magnus blade in laminar flows, vegetation flexible stems and flexible rotor blades are analysed, while they are embedded in turbulent flow. It is shown that the single stem’s flexibility has higher effect on the flow as compared to the rigid stem than when in a dense vegetation patch. Making a marine kinetic turbine rotor flexible has the potential of significantly reducing the power production due to undesired twisting and bending of the blades. These studies point to the importance of FSI in flow problems where there is a noticeable deflection of a cylinder-shaped body and the capability of coupling FEM-DEM with flow solver through IBM.

Catanionic AOT/BDAC micelles on gold {111} surfaces

A sodium dioctyl sulfosuccinate (AOT)/benzyl hexadecyl dimethyl ammonium chloride (BDAC) mixed micelle self-organization and adsorption on gold Au(111) surfaces have been investigated using a molecular dynamics approach. The spherical AOT/BDAC mixed micelle is strongly adsorbed on the gold surface and is disoriented to a cylinder-like shape.

Impact of aortic root annuloplasty on 3D aortic root geometry

BackgroundThe aim was to evaluate the impact of aortic root (AoR) annuloplasty on 3D AoR deformation. MethodsIn experimental setup, Yacoub procedure and Yacoub with annuloplasty were performed. Results were compared to native AoR. In each AoR modality, six microsonometric (2 mm, 200 Hz) crystals were implanted at the sinotubular junction (STJ) and at the AoR base (AoB). 3D deformation of the AoR was determined by AoR tilt (α) and rotation (β) angle changes. ResultsTilt angle in Yacoub AoR with annuloplasty and in Yacoub AoR was maximal at ejection, 26.71 ± 0.18° and 24.91 ± 0.13°, respectively, and minimal at diastole, 25.34 ± 0.15° and 21.90 ± 0.15°, respectively. Rotation angle in Yacoub AoR with and without annuloplasty was maximal at ejection, 27.04 ± 0.25° and 23.53 ± 0.54°, respectively, and minimal at diastole, 24.84 ± 0.14° and 21.62 ± 0.16°, respectively. In native AoR, tilt angle and rotation were minimal at ejection, 14.34 ± 0.81° and 18.1 ± 3.20°, respectively, and maximal at diastole, 18.78 ± 0.84° and 21.23 ± 021°, respectively. AoB and STJ had maximal expansion at ejection; 2.59 ± 2.40% and 6.05 ± 0.66 for Yacoub and 3.75 ± 0.66% and 3.08 ± 0.24% for Yacoub with annuloplasty. In native AoR, the expansion at ejection for AoB was 7.13 ± 2.68% and for STJ was 16.42 ± 0.63%. ConclusionsAoB annuloplasty reduces AoB deformation and has an impact on STJ dynamics. In both the Yacoub AoR modalities, during ejection, the AoR takes on more of a cone-like geometry, whereas in native AoR, it is of a cylinder-like shape.

Worm Selector: Volume Selection in a 3D Point Cloud Through Adaptive Modelling

3D point clouds are more and more widely used, especially because of the proliferation of manual and cheap 3D scanners and 3D printers. Due to the large size of the 3D point clouds, selecting part of them is very often required. Existing interaction techniques include ray/cone casting and predefined or free-form selection volume. In order to cope with the traditional trade-off between accuracy, ease of use and flexibility of these different forms of selection techniques in a 3D point cloud, we present the Worm Selector. It allows to select complex shapes while remaining simple to use and accurate. Using the Worm Selector relies on three principles: 1) points are selected by progressively constructing a cylinder-like shape (the adaptative worm) through the sequential definition of several sections; 2) a section is defined as a set of two contours linked together with straight lines; 3) each contour is a freely drawn closed shape. A user study reveals that the Worm Selector is significantly faster than a classical selection mechanism based on predefined volumes such as spheres or cuboids, while maintaining a comparable level of precision and recall.

Fabrication of ZnO/Fe rod-like core-shell structure as high-performance microwave absorber

This research reports on design and synthesis of rod-like ZnO@Fe core-shell composite. In this type of composite, hexagonal-rod like of ZnO was prepared first by the hydrothermal route and then coated by the Fe nanoparticles. Subsequently, it leaded to the core-shell structure, original hexagonal-rod simultaneously converted into cylinder-like shape. Enhanced electromagnetic absorption properties could be found for the ZnO@Fe sample as compared to the single component ZnO. A minimum reflection loss value of −48.0 dB was achieved for this ZnO@Fe at the layer thickness of 1.5 mm. The bandwidth (RLmin < −10 dB) could reach to 4.0 GHz. When d = 2.0 mm, the frequency bandwidth approximately 6.4 GHz. This superior electromagnetic absorption mechanism is probably due to the synergy effect of dielectric and magnetic loss, as discussed in depth.

Visible-Light-Induced Morphological Changes of Giant Vesicles by Photoisomerization of a Ruthenium Aqua Complex.

Visible- and red-light responsive vesicles were prepared by incorporating a ruthenium aqua complex having two alkyl chains on tridentate and asymmetrical bidentate ligands (proximal-2: [Ru(C10 tpy)(C10 pyqu)OH2 ](2+) , C10 tpy=4'-decyloxy-2,2';6',2"-terpyridine, C10 pyqu=2-[2'-(6'-decyloxy)-pyridyl]quinoline). The ruthenium complex of proximal-2 with closed alkyl chain geometry and a cylinder-like molecular shape exhibited photoisomerization to distal-2 with an open alkyl chain geometry and a cone-like shape, both in an aqueous solution and in vesicle dispersions. We observed that light irradiation of giant vesicles containing proximal-2 induced diverse morphological changes.

Hydrothermal synthesis and luminescent properties of color-tunable Dy3+ doped and Eu3+/Tb3+ co-doped MMoO4 (M=Ca, Sr, Ba) phosphors

Dy3+ doped and Eu3+/Tb3+ co-doped MMoO4 (M=Ca, Sr, Ba) phosphors have been successfully prepared via a simple surfactant-free hydrothermal method. Their crystal structure, morphology, and luminescent characteristics were investigated. The results show that the as-prepared CaMoO4 particles have the cylinder-like shape, SrMoO4 samples present dumbbell-like shape, and the as-prepared BaMoO4 products show micro-rods shape with a length of 5–15μm. MMoO4:Dy3+ phosphors exhibited the characteristic excitation and emission transitions of Dy3+ and most of the chromaticity coordinates are located in the white-light region. In addition, with increasing Dy3+ ions concentration the color changes gradually from near blue to near yellow. All the characteristic emissions of Eu3+ and Tb3+ can be observed in Eu3+/Tb3+ co-doped MMoO4 phosphors, and the emission color can be easily tuned from red, through yellow or green-yellow, to green by simply adjusting the relative doping concentrations of the Eu3+ and Tb3+ ions. The present work suggests that these phosphors may have potential application for light-emitting diodes (LEDs).

Motion of 90° and 180° ferroelectric domain wall structures

An analysis of complex 90° and 180° domain wall structures is presented, taking as a departure point the behaviour of a 90° domain wall structure. When contour conditions are taken into account, “180° inclusions” must take a cylinder-like shape, parallel to the mean polarization vector. The volume ratios can be described by only two parameters, denoted as α and β. The domains can be structured by following different patterns leading to different connectivity, and geometrical parameters can be defined in each case. When an action is applied, the response depends on the connectivity, on the geometrical parameter, and on α and β. Due to the coupling between 180° and 90° domain walls, a motion of the former can induce a motion of the latter, so that 180° walls are also involved in the piezoelectric effect. A mechanism of ageing and fatigue is suggested, which is based on the evolution of the domain shape.

USAXS studies of monosaccharide gels. II. The common features of structural changes

The results of SAXS studies are compared for two groups of samples: (i) obtained by in situ process of gelation of α-galactose-based gel with benzene as solvent, (ii) gels of various concentrations prepared from glucofuranose-based gelator with toluene. The experimental conditions of sample preparation and SAXS measurements were very similar for both groups. The results include fractal analysis of aggregates, and – for aggregate envelopes – the radii of gyration, pair functions, and simulated models. For both groups only two aggregate types were found to be formed: the first – of simple, loose fractal structure and disk-like shape, and the second – smaller aggregates, of well-developed fractal structure and cylinder-like shape. The conditions of the change from the first type to the second one are discussed. In addition, it was verified by the SAXS method on the basis of kind of fractal analysis for the loose structure that the fractal aggregate is built of gelator molecules joined by hydrogen interaction.

Symmetry-breaking in the response of the parametrically excited pendulum model

Abstract A planar pendulum is considered which is parametrically excited by a periodic vertical force. The amplitude and frequency of the excitation are used as control parameters. The downward, hanging and the upward, inverted positions correspond to equilibrium positions if we only consider the variation in angle measured from the downward position. For moderate levels of forcing, there are zones that exist in the space of control parameters, where the downward hanging position is unstable and initial conditions that are close to the hanging position lead to steady state oscillations of period-2. To review this situation, this paper describes the development of these oscillations as the amplitude of forcing is varied. In the largest zone, a symmetry-breaking occurs which brings about a pair of asymmetric oscillations. This break in symmetry of the period-2 solution can lead to either an increase or decrease in the amplitude of the forthcoming swing and reference to the experimental significance of this angle change is noted in this paper. Typically, further increases of the parameter produce a cascade of period doubling bifurcations, before most oscillating solutions eventually lose their stability so that the system must experience a rotation. As a result, symmetry-breaking becomes an effective precursor to escape from the local potential well around the hanging position. Here we compare this behaviour with that in other resonance zones. The change of geometric structure when the symmetry-breaking bifurcation occurs is examined and graphically represented as a ‘pinched’ cylinder-like shape, compared with the Mobius strip that has been associated with the period-doubling bifurcation. The paper also refers to practical problems, where the introduction of nonlinearity means that potentially all frequencies below the main zone of the control space lead to dangerous effects and in some scenarios disastrous outcomes.

SANS and SAXS study on aqueous mixtures of fullerene-based star ionomers and sodium dodecyl sulfate

Fullerene-based star ionomer C 60[ CO( CH 2) 5 O( CH 2) 4 SO 3 Na] 6 ( FC 10 S) , with six sodium-dodecyl-sulfate-like arms randomly bonded on the fullerene, has been synthesized. This novel molecule has a high water solubility and a structural shape resembling the skeleton of a micelle of sodium dodecyl sulfate (SDS). We study aqueous mixtures of the C 60-based ionomers and SDS using small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS). With a selected deuteration of SDS, we have identified the formation of complex aggregates of FC 10S with SDS in the mixtures. The structural information of the complex aggregates is extracted from the SANS and SAXS data measured for the mixtures. On the average, the complex aggregates observed have a cylinder-like shape with a radius of 19 A ̊ and a length of ≈100 A ̊ for the sample mixtures containing 2.3 or 1.2 mM of FC 10S and 6 mM of SDS. The mean aggregation numbers of FC 10S and SDS in each complex aggregate are 15 and 11, respectively.

Optical and structural properties of highly c-axis oriented aluminum nitride prepared by sputter-deposition in pure nitrogen

Nanocrystalline aluminum nitride films (70–1400 nm thick) were prepared by rf-magnetron sputtering from an Al-target at a substrate temperature of 540 K. For the first time, the influence of the pressure on the film properties was investigated for sputter-deposition in pure nitrogen-atmosphere. The pressure was varied in the range from 0.15 to 4.0 Pa. The deposition rate decreases monotonically from 0.35 to 0.17 nm/s with pressure. Films of 300 nm thickness show at 1 Pa nitrogen pressure a maximum of the crystallite size (in direction parallel to the film normal), which amounts to 30 nm. Highly strained crystallites grow at pressures below 0.5 Pa. The films are (excepted sputtering above 2 Pa) in general highly c-axis oriented. It is found that the crystallites are of a cylinder-like shape with axis orientation parallel to the film normal and a roughly constant length-to-diameter ratio of 4. The optical properties static refractive index and optical Tauc gap depend weakly on the pressure and are on average 2.0 and 5.0 eV, respectively. The bombardment of the growing AlN by energetic nitrogen neutrals originating from reflection at the target, which was simulated by TRIM.SP Monte-Carlo calculations, is suggested to be the general origin of the preferred c-axis growth of sputter-deposited films.

Characterization of porous GaP by photoacoustic spectroscopy: The relation between band-gap widening and visible photoluminescence

Photoacoustic and Raman spectroscopy as well as photoluminescence (PL) measurements have been used to investigate the effect of band-gap widening in porous GaP. A correlation between a blueshift of the absorption edge observed during photoacoustic measurements, accompanied by PL emissions in the blue and ultraviolet regions, and the occurance of a vibrational mode related to surface phonons is shown. Based on a simple scattering model, the structure of porous GaP is assumed to have a cylinderlike shape.

Super-secondary structure of oligopeptide aggregates in an organic solvent

For N-acetyl-L-glutamic acid hexamer α,γ-benzyl ester (A6Z), synthesized by a stepwise procedure, the shape and size of an aggregate formed in dioxane has been investigated in connection with the super-secondary structure of oligopeptides by the SANS method. The results are summarized as follows. An A6Z aggregate in dioxane has a cylinder-like shape having a radius of 13 Å and a height of 135 Å, and the aggregation number is 36. Probably, the cylinder aggregate has a stacking structure of the A6Z β-sheets.