Capsule Shape Research Articles

Preparation and properties of n-hexane microcapsules by complex coacervation

In order to improve the encapsulation efficiency of low density core material microcapsules, the complex condensation method was used to prepare microcapsules with n-hexane as the core material and gelatin and Arabic gum as the wall material.For n-hexane with low density, the influence of wall material concentration on microcapsule morphology, the influence of core wall ratio on microcapsule wall thickness, the influence of emulsifying speed on emulsifying effect, the influence of crosslinking curing reaction pH on thermal stability, and the influence of complex coacervation pH on turbidity were studied by turbidimetric titration. The experimental results show that: For the low-density core microcapsules, the spherical multi-core microcapsules prepared are regular in capsule shape, but the encapsulation efficiency is lower than 30%, and the waste of wall material is serious. The wall material concentration is 2%, the core-to-wall ratio is 3:1, the emulsification speed is 10000 r/min, the pH of complex oacervation is 4.0, and the pH of crosslinking curing reaction is 10.0. The microcapsules prepared on this basis are monocytic and irregular. Although the shape and phase of the capsules are irregular, they have good encapsulation effect, with the yield up to 71.86% and encapsulation efficiency up to 70%. Meanwhile, they have good thermal stability.

CFD Simulation on Aerodynamic Performance of Hyperloop Vehicle

Aerodynamic drag is one of the most opposing factors for ground vehicle. This becomes even more difficult while travelling through a tunnel. The Evacuated- Tube Trains (ETTs) or Hyperloop’s are a new concept of ground transportation presently being developed by many different companies. The main purpose of an Hyperloop can be displayed as a cheaper medium of ground transport, which could allow its consumers to propagate to different places at a cheaper and faster rate compared to the present day locomotives and road transport. Passengers can travel at over 700 mph in floating capsules that swoop along within gigantic low-pressure tubes that are either below or above surface. This study analyses the Hyperloop designs using Computational Fluid Dynamics software ANSYS FLUENT. The effects of operating speed, Capsule shape and internal tube pressure have been studied in this paper. The flow inside the tube is considered as turbulent and incompressible. The software simulation results show the significant effects of inside pressure and operating speed on the aerodynamic drag of the capsule. Study with different shapes for the Capsule’s front and rear end suggest the most optimum shape for least aerodynamic drag.

Hypersonic flow over spherically blunted cone capsules for atmospheric entry. Part 2. Vibrational non-equilibrium effects

Atmospheric entry capsules shaped as spherically blunted, large apex-angle cones are widely used in space missions. In Part 1 of this study (Hornung, Martinez Schramm & Hannemann, J. Fluid Mech., vol. 871, 2019, pp. 1097–1116) we explored flows over the two elements of the capsule shape, the sphere and the sharp cone with detached shock, theoretically and computationally. Using a large number of inviscid, perfect-gas computations, analytical functions of two independent variables, the normal-shock density ratio $\varepsilon$ and a cone-angle parameter $\eta$ (which is a function of $\varepsilon$ and the cone half-angle $\theta$ ) were found for the dimensionless shock wave stand-off distance and the drag coefficient of a sharp cone. An analytical description was found for the shock stand-off distance in the transition from the 90 $^\circ$ cone (flat-faced cylinder) to the sphere. In Part 1, it was speculated that the perfect-gas results have relevance to non-equilibrium situations if the normal-shock density ratio is replaced by the density ratio based on the average density along the stagnation streamline. In Part 2, the investigation is extended to blunted-cone capsule shapes. High-precision force measurements and schlieren image analysis are performed in the High-Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Centre using air as the test gas, at conditions where vibrational non-equilibrium effects are significant. Accordingly, results are compared with viscous numerical predictions using different physico-chemical models. A theoretical model is constructed for the density profile along the stagnation streamline that is determined by the free stream conditions and gives the average density. Comparisons of the experimental and numerical results for the dimensionless shock stand-off distance and the drag coefficient, with the extension of the analytical functions of Part 1 to vibrationally relaxing flow, exhibit very good agreement in all of a range of geometries.

Aerothermodynamic analysis of Neptune ballistic entry and aerocapture flows

An aerothermodynamic analysis of representative aerocapture (29 km/s) and entry (18 km/s) flows in Neptune is discussed. Two 60° and 45° sphere-cone shapes are considered, and chemically-reactive, nonequilibrium flowfield solutions are computed for the forebody region, yielding surface heat fluxes from convective heating. A radiative transfer calculation using a line-by-line approach coupled with a ray-tracing routine, yields surface heat fluxes from radiative heating.If the trace amounts of CH4 in Neptune’s atmosphere are accounted for, they dramatically enchance radiative heating, as a result of strong radiative emission from carbonaceous species in the shock layer. For the 18 km/s entry point, radiative heat fluxes accordingly increase by several orders of magnitude, from 0% to about 50% of the total heat fluxes.The post-shock flow features further differ significantly depending on the capsule shape. The sonic line is near the sphere-cone transition zone for the 45° shape and starts detaching from the boundary layer for angles above 55°. The post-shock flow becomes entirely subsonic up to the spacecraft shoulder at 60°. More streamlined shapes will accordingly be more aerodynamically stable.

Numerical simulation of inhibition characteristics of wall temperature rise of phase change microcapsule in liquid-cooled microchannel

Phase change microcapsule suspension is a new type of heat-storage and heat-transfer functional fluid. Owing to the lack of understanding of flow-solid interaction, there exists a difference in research result of the heat transfer performance of suspension fluid. Therefore, the arbitrary Lagrangian-Euler method is used to simulate the flow-solid transfer characteristics of phase-change microcapsules in the liquid-cooled microchannel. Furthermore, the comparison of heat-transfer between particle and phase-change capsules is conducted. The influences of the position, shape, and number of capsules on the inhibition of the wall temperature rise are investigated. The results show that the wall-temperature-rise inhibition mainly occurs in the upstream area of the capsules. The phase change of capsules can reduce the wall temperature rise. On the other hand, the spin movement is faster when the capsule is closer to the wall, and the heat transfer is enhanced. As a result, the inhibitory effect on the wall temperature rise becomes stronger, especially near the heating surface. The circular capsules spin movement is faster and the inhibition performance is better than the ellipse. With the capsules number increasing, the wall temperature inhibition effect also gradually strengthens.

Photomechanical Motions in Organoboron-Based Phosphorescent Molecular Crystals Driven by a Crystal-State [2 + 2] Cycloaddition Reaction.

Photoluminescent molecular crystals integrated with the ability to transform light energy into macroscopic mechanical motions are a promising choice of materials for both actuating and photonic devices. However, such dynamic photomechanical effects, based on molecular organoboron compounds as well as phosphorescent crystalline materials, are not yet known. Here we present an intriguing example of photomechanical molecular single crystals of a newly synthesized organoboron containing Lewis acid-base molecular adduct (BN1, substituted triphenylboroxine and 1,2-di(4-pyridyl)ethylene) having a capsule shape molecular geometry. The single crystals of BN1 under UV light exhibit controllable rapid bending-shape recovery, delamination, violent splitting-jumping, and expanding features. The detailed structural investigation by single-crystal X-ray diffraction and 1H NMR spectroscopy reveals that the photosalient behavior of the BN1 single crystals is driven by a crystal-to-crystal [2 + 2] cycloaddition reaction, supported by four donor-acceptor type B←N bonds. The instant photomechanical reaction in the BN1 crystals occurs under UV on account of sudden release of stress associated with the strained molecular geometry, significant solid-state molecular movements (supramolecular change), and cleavage of half intermolecular B←N linkages to result in a complete photodimerized single-crystalline product via the existence of two other intermediate photoproducts. In addition, the BN1 crystals display short-lived room temperature phosphorescence, and the photodynamic events are accompanied by the enhancement of their phosphorescence intensity to yield the photoproduct. Interestingly, the molecular crystals of the final photoproduct polymerize at ambient conditions when recrystallized from the solution forming a 2D supramolecular crystalline polymer stabilized by the retention of all B←N coordination modes.

One-step on-chip microfluidic synthesis of the hybrid capsules using aqueous two-phase system

Hydrogel capsules synthesized by conventional water-in-oil emulsion systems are the less preferred choice for biomedical applications due to the use of oils and surfactants. An aqueous two-phase system (ATPS), which allows the formation of water-in-water emulsion, is considered a green alternative and therefore has been explored a lot for its application in the biomedical field. Herein, we present the synthesis of hydrogel capsules using a set-up consisting of a pneumatic valve integrated with the ATPS microfluidic system. In this arrangement, at first, a pneumatic valve facilitates the generation of the droplets of one aqueous system i.e. sodium alginate (SA) containing dextran solution into another aqueous phase comprising polyethylene glycol solution. The present approach allows good control over droplet generation by tuning the pressure of the pneumatic valve and the flow rates of the core and middle phases. The synthesis of hybrid capsules within the microfluidic device is carried out mainly by using the interfacial complexation of oppositely charged polyelectrolytes, chitosan with SA via electrostatic interactions. The interfacial complexed SA and chitosan hydrogel capsules were collected via the settling collection method, which ensures the retaining of the shape of the hybrid capsules. The morphological properties of as-synthesized droplets and hybrid capsules were examined via optical microscopy. The hydrogel capsules show good encapsulation capability for the magnetic particles. Even though this study mainly focuses on the synthesis part, we anticipate that the proposed approach will enable the encapsulation of cells within the hybrid capsules as well as enhance the cell adhesion on the surface of the hydrogel capsules hence, these hydrogel capsules can find the potent application in the biomedical engineering.

Campanula adiyamanensis (Campanulaceae), a New Species from East Anatolia, Turkey

Campanula adiyamanensis Yıldırım & K. Özcan sp. nova (Campanulaceae) is described, illustrated, and classified based on morphological data. The species is restricted to eastern Anatolia (Turkey), and currently known from one locality in Adıyaman Province. Campanula adiyamanensis morphologically resembles C. alisan-kilincii, but differs from it especially by its indumentum type, longer cauline leaves, more deeply lobed corolla, corolla color, lacking or short calyx appendages, distinctly exserted style, and capsule shape.

Effect of Mushy Zone Parameter on Phase Change Behavior of Different Configurations Storage Unit: Numerical Simulation and Experimental Validation

The melting process of paraffin wax placed in storage capsules of different shapes was experimentally and numerically studied. The phase change material (PCM) was initially at 27 °C. The effect of the mushy zone parameter (Amush) value on the melting process of the PCM was studied with storage capsules of different shapes (circular, vertical oval, and horizontal oval). The results of the numerical model were validated with the experimental results to obtain the optimum Amush value for each shape of the latent heat storage unit. The results showed that the value of the Amush has a great impact on the numerical results of the PCM melting process and changes with the shape of the storage capsule. The rate of heat transfer, convection, and fluid velocity all decrease as the Amush value rises. The experimental results of the circular, vertical oval, and horizontal oval capsules match very well with the numerical model with Amush values equal to 2 × 106, 1 × 105, and 1 × 106, respectively.

Relationships between the shape of the hoof capsule and orientation of the distal phalanx in long toe underrun heels in donkeys

SummaryBackgroundThere is limited information on the morphology, radiography and orientation of the distal phalanx in the hoof capsule in long toe underrun heels in donkeys.ObjectivesThis study aimed to determine the relationships between the hoof capsule shape and distal phalanx radiographic parameters.Study designPost‐mortem collected feet.MethodsA total of 68 cadaver front hooves with long toe underrun heels were used in the study. Lateral photographic and lateromedial radiographic parameters of the feet were obtained.ResultsThe mean hoof wall angle (HWA) was strongly significantly correlated with heel angle (HA), dorsal HWA, HA measured through radiography and distal phalanx to toe distance and was modestly correlated with distal phalanx angle, solar border of the distal phalanx angle, coronet angle and distal phalanx to frog distance. The linear hoof wall length (HWL) and heel length showed a strong and modest significant correlation with distal phalanx to bottom, dorsal HWL and distal phalanx to toe distance.Main limitationsThe feet included in the study were obtained from many yards and different body sizes.ConclusionsThis study supports an association between radiographic and morphologic parameters in long toe underrun heels. The strong and modest correlations between measured photographic and radiographic parameters may indicate the relationships between the hoof capsule shape and distal phalanx orientation.

Genetic control of the operculum and capsule morphology of Eucalyptus globulus.

Background and aimsThe petaline operculum that covers the inner whorls until anthesis and the woody capsule that develops after fertilization are reproductive structures of eucalypts that protect the flower and seeds. Although they are distinct organs, they both develop from flower buds and this common ontogeny suggests shared genetic control. In Eucalyptus globulus their morphology is variable and we aimed to identify the quantitative trait loci (QTL) underlying this variation and determine whether there is common genetic control of these ecologically and taxonomically important reproductive structures.MethodsSamples of opercula and capsules were collected from 206 trees that belong to a large outcrossed F2E. globulus mapping population. The morphological variation in these structures was characterized by measuring six operculum and five capsule traits. QTL analysis was performed using these data and a linkage map consisting of 480 markers.Key resultsA total of 27 QTL were detected for operculum traits and 28 for capsule traits, with the logarithm of odds ranging from 2.8 to 11.8. There were many co-located QTL associated with operculum or capsule traits, generally reflecting allometric relationships. A key finding was five genomic regions where co-located QTL affected both operculum and capsule morphology, and the overall trend for these QTL was to affect elongation of both organs. Some of these QTL appear to have a significant effect on the phenotype, with the strongest QTL explaining 26.4 % of the variation in operculum shape and 16.4 % in capsule shape. Flower bud measurements suggest the expression of these QTL starts during bud development. Several candidate genes were found associated with the QTL and their putative function is discussed.ConclusionsVariation in both operculum and capsule traits in E. globulus is under strong genetic control. Our results suggest that these reproductive structures share a common genetic pathway during flower bud development.

Unraveling the distinct germination processes of sporopollenin-based pollen grains and spores through morphological analyses upon natural nano-architectonics process

The outermost exine capsules of many pollen and spore grains are composed of a chemically inert yet mechanically robust sporopollenin biopolymer. These dynamically expansible and foldable capsules have great potential as renewable functional biomaterials with industrial applications. However, the mechanical and morphological variations in the shape, size, robustness, and apertural strength of the exine capsules across taxa of angiosperms and cryptogamic plants remains poorly understood. Thus, in this study, we unraveled the abortive microgel transformation of spores inspired by their germination mechanism, being compared with eudicot-based pollen microgels. After chemical treatments, significant mechanical degradation of exine was clearly observed for the Camellia pollen, whereas crosslinking density and modulus of spore exine remained almost constant. The significant volume expansion of Camellia pollen was observed akin to sunflower pollen; in contrast, the spores ballooned showed limited volume changes under equal levels of turgor pressure. Furthermore, spore underwent marked changes in volume when their aperture sutures were softened and ruptured, which are prerequisites for spore germination. Therefore, this study disentangled mechanical and morphological origins of biochemical pathways of pollen and spore germination, and germination-like hydration and desiccation, which will give clues about selection of pollen and spore species for potential biomaterial applications.

A new species of small myrmicine ant in the genus Eurhopalothrix Brown & Kempf, 1961 (Hymenoptera: Formicidae) from Colombia

A new species of Eurhopalothrix Brown & Kempf, E. amati Fiorentino, Tocora and Fernández, n. sp. is described based on workers collected in northwestern Colombia. A taxonomic key and distributional map for the new species in the country are provided. This new species differs from other Eurhopalothrix ants by the configuration of specialized setation, a decrease in its propodeal spines, its irregular metanotum profile, and the triangular shape of the head capsule.

Super-cooling effects and solidification of water inside a horizontal cylinder with a rough, sinusoidal surface shape

We examined how the outer shape of a cylindrical capsule, and the quantity of super-cooling, influenced the charging performance of a phase change material (water). The numerical method was validated using previous research and showed good agreement. Higher amplitude of roughness of the capsule shape was affirmed to affect solidification performance with or without super-cooling. The capsule with higher amplitude had an advantage in solidification performance, not only by increasing the heat transfer rate inside the capsule but also by reducing the quantity of super-cooling. Small super-cooling (∆TSmooth Surface = 4 °C) shows less impact (only 1%), while large super-cooling (∆TSmooth Surface = 8 °C) shows a prominent impact (10%) on the delay of solidification time. Typical results with no super-cooling and with super-cooling (∆TSmooth Surface = 8 °C) showed 10% and 15% shorter solidification time, respectively, for optimal shape with n = 6 compared to a matching smooth capsule (n = 0).

Spirocamallanus sindensis n. sp. from Catfish Rita rita (Siluriformes: Bagridae) of Pakistan

The aimed of present studies to examination of helminth parasites of Indus river Siluriformes catfishes. 57 (41 + and 16 ) specimens were collected from 31 hosts fishes Rita rita (F. Hamilton, 1822) belong to genus Spirocamallanus (Baylis, 1923) processes as live specimen were killed in hot 70% ethanol, preserved, made temporary mounts for detail study. On the basis of differential characters such as body shape and size, striated cuticle format, buccal capsule shape and 13-14 spiral numbers, cephalic and cervical papillae, basal ring shape, spicules shape and size, vulva position and shape, vagina shape, the new species Spirocamallanus sindensis identified.

Shape‐Anisotropic Microembolics Generated by Microfluidic Synthesis for Transarterial Embolization Treatment

Particulate embolic agents with calibrated sizes, which employ interventional procedures to achieve endovascular embolization, have recently attracted tremendous interest in therapeutic embolotherapies for a wide plethora of diseases. However, the particulate shape effect, which may play a critical role in embolization performances, has been rarely investigated. Here, polyvinyl alcohol (PVA)-based shape-anisotropic microembolics are developed using a facile droplet-based microfluidic fabrication method via heat-accelerated PVA-glutaraldehyde crosslinking reaction at a mild temperature of 38° C. Precise geometrical controls of the microembolics are achieved with a nearly capsule shape through regulating surfactant concentration and flow rate ratio between dispersed phase and continuous phase in the microfluidics. Two specific models are employed, i.e., in vitro decellularized rabbit liver embolization model and in vivo rabbit ear embolization model, to systematically evaluate the embolization behaviors of the nonspherical microembolics. Compared to microspheres of the same volume, the elongated microembolics demonstrated advantageous endovascular navigation capability, penetration depth and embolization stability due to their comparatively smaller radial diameter and their central cylindrical part providing larger contact area with distal vessels. Such nonspherical microembolics present a promising platform to apply shape anisotropy to achieve distinctive therapeutic effects for endovascular treatments.

In-plane subwavelength optical capsule for lab-on-a-chip nano-tweezers.

In this Letter, we propose a new, to the best of our knowledge, proof-of-concept of optical nano-tweezers based on a pair of dielectric rectangular structures that are capable of generating a finite-volume in-plane optical capsule. Finite-difference time-domain simulations of light spatial distributions and optical trapping forces of a gold nanoparticle immersed in water demonstrate the physical concept of an in-plane subwavelength optical capsule integrated with a microfluidic mesoscale device. It is shown that the refractive index of and the distance between the two dielectric rectangular structures can effectively control the shape and axial position of the optical capsule. Such an in-plane mesoscale structure provides a new path for manipulating absorbing nano-particles or bio-particles in a compact planar architecture, and should thus lead to promising perspectives in lab-on-a-chip domains.

Dynamic behaviors of capsules on rough surfaces induced by shear flow under gravity

We use a finite element method to investigate dynamic behaviors of capsules on rough surfaces induced by shear flow under gravity, which has a more practical significance for related applications such as medical implants. Our model is set as a neutral rough surface, which does not have the adhesive bonds normally assumed by micro-molecular simulations. Our results demonstrate that the capsule exhibits three motion modes: adhesion, slip, and detachment mainly depending on the shear rate, which are similar to the phenomena in which adhesive bonds (linear spring) are assumed between capsules and a smooth surface. At low shear rates, the capsule was slightly deformed, and its bottom in contact with the rough surface, hence, promotes adhesion. However, it is surprising to find that, at relatively high shear rates, the effect of capsule deformability on its adhesion dynamics is far more complex than just promoting adhesion. High deformability of the capsule gives it a concave shape at its bottom, thereby no adhesion formation in the middle. The appearance of this specific capsule shape inhibits the adhesion of the capsule but makes the capsule slip. In addition, it is interesting to note that when the shear rate exceeds a critical value, the slip state no longer appears but changes to detachment.

Unsteady simulation of Mitigation of Reentry Blackout by Air film

During reentry into the planetary atmosphere, the vehicle is surrounded by ionized and dissociated plasma caused by aerodynamic heating. The high-dense plasma near the vehicle blocks the electromagnetic wave propagation for telecommunication, and then, communication with the ground station is prevented. This problem is known as a reentry blackout. One method of mitigation of reentry blackout is air film technique, in which low-temperature gas is blown out of the vehicle to form a path for electromagnetic waves propagation. In this study, to clarify the effect of air film for blackout mitigation, the plasma flow around an experimental model conducted in the DLR was reproduced by a computational fluid dynamics approach. In the present analysis, three cases with different mass flow rates were analyzed. In the two cases with low mass flow rates, oscillations of the air film were observed. In the case with the highest mass flow rate, the results approached steady state with time. This indicated that a high mass flow rate can ensure a stable low electron number density region and mitigate reentry blackouts. In the future, it is necessary to apply the effect of air film to the reentry capsule shape and evaluate the effect on the mitigation of communication blackout and aerodynamic characteristics.

Modified Models for Predicting Malignancy Using Ultrasound Characters Have High Accuracy in Thyroid Nodules With Small Size.

To assess the malignancy risk of thyroid nodules, ten ultrasound characteristics are suggested as key diagnostic markers. The European Thyroid Association Guidelines (EU-TIRADS) and 2015 American Thyroid Association Management Guidelines (2015ATA) are mainly used for ultrasound malignancy risk stratification, but both are less accurate and do not appropriatetly classify high risk patients in clinical examination. Previous studies focus on papillary thyroid carcinoma (PTC), but follicular thyroid carcinoma (FTC) and medullary thyroid carcinoma (MTC) remained to be characterized. Thus, this study aimed to determine the diagnostic accuracy and establish models using all ultrasound features including the nodule size for predicting the malignancy of thyroid nodules (PTC, FTC, and MTC) in China. We applied logistic regression to the data of 1,500 patients who received medical treatment in Shanghai and Fujian. Ultrasound features including taller-than-wide shape and invasion of the thyroid capsule showed high odds ratio (OR 19.329 and 4.672) for PTC in this dataset. Invasion of the thyroid also showed the highest odds ratio (OR = 8.10) for MTC. For FTC, the halo sign has the highest odds ratio (OR = 13.40). Four ultrasound features revealed distinct OR in PTC nodule groups with different sizes. In this study, we constructed a logistic model with accuracy up to 80%. In addition, this model revealed more accuracy than TIRADS in 4b and 4c category nodules. Hence, this model could well predict malignancy in small nodules and classify high-risk patients.