Hollow Cavity Research Articles

Hyperthermostable recombinant human heteropolymer ferritin derived from a novel plasmid design.

Mammalian ferritins are predominantly heteropolymeric species consisting of 2 structurally similar, but functionally and genetically distinct subunit types, called H (Heavy) and L (Light). The two subunits co-assemble in different H and L ratios to form 24-mer shell-like protein nanocages where thousands of iron atoms can be mineralized inside a hollow cavity. Here, we use differential scanning calorimetry (DSC) to study ferritin stability and understand how various combinations of H and L subunits confer aspects of protein structure-function relationships. Using a recently engineered plasmid design that enables the synthesis of complex ferritin nanostructures with specific H to L subunit ratios, we show that homopolymer L and heteropolymer L-rich ferritins have a remarkable hyperthermostability (Tm=115 ± 1°C) compared to their H-ferritin homologues (Tm=93 ± 1°C). Our data reveal a significant linear correlation between protein thermal stability and the number of L subunits present on the ferritin shell. A strong and unexpected iron-induced protein thermal destabilization effect (ΔTm up to 20°C) is observed. To our knowledge, this is the first report of recombinant human homo- and hetero-polymer ferritins that exhibit surprisingly high dissociation temperatures, the highest among all known ferritin species, including many known hyperthermophilic proteins and enzymes. This extreme thermostability of our L and L-rich ferritins may have great potential for biotechnological applications.

Evaporation Caused Invaginations of Acoustically Levitated Colloidal Droplets.

Controlled buckling of colloidal droplets via acoustic levitation plays an important role in pharmaceutical, coating, and material self-assembly. In this study, the evaporation process of PTFE colloidal droplets with two particle concentrations (60 wt% and 20 wt%) was investigated under acoustic levitation. We report the occurrence of surface invagination caused by evaporation. For the high particle concentration droplet, the upper surface was invaginated, eventually forming a bowl-shaped structure. While for the low particle concentration droplet, both the upper and lower surfaces of the droplet were invaginated, resulting in a doughnut-like structure. For the acoustically levitated oblate spherical droplet, the dispersant loss at the equatorial area of the droplet is greater than that at the two poles. Therefore, the thickness of the solid shell on the surface of the droplet was not uniform, resulting in invagination at the weaker pole area. Moreover, once the droplet surface was buckling, the hollow cavity on the droplet surface would absorb the sound energy and results in strong positive acoustic radiation pressure at bottom of the invagination, thus further prompting the invagination process.

Au–CuxOy Nanoparticles Encapsulated in Hollow Porous Silica Nanospheres as Efficient Catalysts for Nitrophenol Reduction

In this work, Au–CuxOy hybrid nanoparticle-encapsulated hollow porous silica nanospheres (Au–CuxOy in HPSNs) were synthesized by immobilizing the catalytic functionality inside hollow cavities by using polyethyleneimine in a reverse microemulsion system as the void template as well as the platform to deliver the metals into the central voids. Compared with individual Au in HPSNs and CuxOy in HPSNs, the prepared Au–CuxOy in HPSNs demonstrate significantly improved catalytic efficiency for the reduction of various nitrophenols with NaBH4. At the molar ratio of 4-nitrophenol/Au of 30/1, the 4-nitrophenol conversions over Au–CuxOy in HPSNs reach 100% within 5.5 min, and catalytic efficiency is maintained during five cycles of catalytic reactions. The enhanced performance can be ascribed to the synergistic effect between Au and CuxOy, and the protection of silica shells to inner Au–CuxOy improve their catalytic stability.

Microstructure and mechanical properties of open-cell Ni-foams with hollow struts and NiO oxide layers

Based on electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS), open-cell Ni foams fabricated by electroplating on a removable template were investigated. Hollow struts or cavities inside the Ni foams were observed, implying traces of a removable template. The crystallographic orientations and grain structures of the Ni foam struts were also examined. Individual grains of Ni foams covered the struts completely through the thickness direction. The crystallographic orientations of the Ni foam struts display a random distribution. Σ3 twinning boundaries were also observed in the Ni matrix. During a two-hour heat treatment at 1273 K under atmospheric condition, refined NiO layers clearly formed on the surface of the Ni matrix. The overall grain sizes of the NiO are smaller than those of the Ni matrix. The obvious crystallographic relationship between the Ni matrix and the NiO layers was observed at the high misorientation angles. Ni foams with high porosity revealed a stress drop and NiO layers that formed during atmospheric annealing caused a predominant stress drop. Young’s modulus and the hardness of the Ni matrix and NiO layers were measured from a Ni foam cell structure consisting of nodes, by means of nano-indentation tests.

MXene-Coated Nickel Ion-Exchanged ZIF Skeleton-Cavity Layered Double Hydroxides for Supercapacitors

A NiCo layered double hydroxide (LDH) has been regarded as a promising electrode material for supercapacitors. However, the low electronic conductivity, limited electroactive sites, and self-agglomeration hinder its large-scale application. Herein, MXene-coated nickel ion-exchanged ZIF skeleton-cavity LDHs (ZSC-LDH@MXene) were fabricated to enhance the electrochemical performance of NiCo LDHs. The ZSC-LDH@MXene integrated the advantages of various materials, providing abundant metal active sites and fast redox reaction kinetics and enhancing the specific capacity of the electrode. The MXene nanosheets can construct abundant conductive networks, enhancing the electronic conductivity of the NiCo LDH. The nanosheet-assembled ZIF skeleton-cavity structure can facilitate electron/ion transport, enlarge the electrolyte accessibility, and expose abundant electroactive sites. Furthermore, the hollow cavity can relieve the volume expansion during the charging/discharging cycles. Ultimately, the as-obtained ZSC-LDH@MXene electrode manifested a large specific capacity of 1029.6 C g–1 at 1 A g–1, a superior rate capability of 62.6% at 30 A g–1, as well as outstanding cycling performance with a 92.0% capacity retention at 10 A g–1 over 10,000 cycles. The assembled ZSC-LDH@MXene//AC hybrid supercapacitor exhibited a superb energy density of 43.7 W h kg–1 at 789 W kg–1.

Swift Photochromic Smart Window Based on Plasmonic Yolk‐Shell Nanophosphors

AbstractHerein, the fabrication of eccentric Ag@Void@Y2SiO5:Pr3+ plasmonic yolk‐shell nanophosphors (PYSNPs) with high up‐conversion efficiency, and their incorporation on photochromic WO3 layers, is demonstrated to fabricate photochromic smart windows with high coloration contrast and swift color change. The up‐conversion efficiency of the Pr3+ ion‐doped Y2SiO5 (Y2SiO5:Pr3+) nanoshells is enhanced by about 50% through the incorporation of carefully designed plasmonic Ag cores placed inside their hollow cavities. Introduction of these geometry‐optimized plasmonic nanophosphors at the surface of photochromic WO3 films results in about 24‐fold and tenfold enhancements of their coloration rate and kinetic constant, respectively. The strategy adopted for designing and fabricating the Ag@Void@Y2SiO5:Pr3+ PYSNPs and their subsequent incorporation in conventional photochromic films offers an exciting approach for fabricating photochromic smart windows with dynamically controlled transmission of solar radiation, which is a promising technology for reducing energy consumption associated with heating, ventilation, and air‐conditioning of buildings.

Determination and measurement of Imatinib by a fluorescence quenching sensor based on halloysite nanotubes modified by zirconium metal organic framework

HNTs with nanotubular structure and hollow cavities and large aspect ratio, are a type of natural clay minerals which are widely used. In this work, Zirconium metal organic framework (Zr-MOF), as an efficient fluorescent nanomaterial, was synthesized by a one-step solvothermal procedure using terephthalic acid as ligand. The obtained Zr-MOF was used for modifying the halloysite nanotubes (HNT). The synthesized HNT/MOF was evaluated by different characterization techniques including FT-IR, XRD, FE-SEM, and EDS. The HNT/MOF depicted highly fluorescent emission with a maximum fluorescence emission at 396 nm using 270 nm excitation. The function of the presented assay for imatinib (IMA) is based on “turn-off” the fluorescence signal in accordance with enhancing the analyte concentration. To obtain best function, the effect of different parameters including pH, temperature, ionic strength and time were evaluated. By using the Stern-Volmer equation and at optimal conditions, HNT/MOF offered a broad linear range of 4–165 μM along with limit of quantification and detection of 2.53 and 0.72 μM, respectively. The method was successfully applied in determining IMA concentrations in biological and environmental samples include human urine and sea water respectively with recoveries between 94.38 and 99.1%.

Dynamic crushing performance of bio-inspired sandwich structures with beetle forewing cores

A novel design of Sandwich Structure inspired by Beetle Forewing (SSBF) is proposed in this study by mimicking the internal structure of beetle forewing. The viscoelastic material and the arch shape of hollow cavity structures found inside the forewing structure of the beetle are imitated by utilising the shear thickening fluid (STF) and semi-arch cores, respectively. The coupling interaction between fluid and structural components is analysed using a fluid-structure interaction (FSI) technique in LS-DYNA. It is found that the proposed SSBF by partially filling the core with STF generates a higher mean crushing force and stabilises the crushing force-displacement profile without a noticeably high initial peak crushing force as compared with the empty, polyurethane (PU) foam-filled, or Newtonian viscous fluid-filled counterparts. Furthermore, this stable crushing force of SSBF enhances with the increase of crushing speed, showing ideal behaviour for energy absorption and crushing resistance for the adaptation to the design of structures to resist impact loads.

Temperature-Regulated Core Swelling and Asymmetric Shrinkage for Tunable Yolk@Shell Polydopamine@Mesoporous Silica Nanostructures.

Facile and controllable synthesis of functional yolk@shell structured nanospheres with a tunable inner core ('yolk') and mesoporous shell is highly desirable, yet it remains a great challenge. Herein, xx developed a strategy based on temperature-regulated swelling and restricted asymmetric shrinkage of polydopamine (PDA) nanospheres, combined with heterogeneous interface self-assembly growth. This method allows a simple and versatile preparation of PDA@mesoporous silica (MS) nanospheres exhibiting tunable yolk@shell architectures and shell pore sizes. Through reaction temperature-regulated swelling degree and confined shrinkage of PDA nanospheres, the volume ratio of the hollow cavity that the PDA core occupies can easily be tuned from ca. 2/3 to ca. 1/2, then to ca. 2/5, finally to ca. 1/3. Owing to the presence of PDA with excellent photothermal conversion capacity, the PDA@MS nanocomposites with asymmetric yolk distributions can become a colloidal nanomotor propelled by near-infrared (NIR) light. Noteworthily, the PDA@MS with half PDA yolk and microcracks in silica shell reaches 2.18 µm2 s-1 of effective diffusion coefficient (De) in the presence of 1.0 W cm-2 NIR light. This temperature-controlled swelling approach may provide new insight into the design and facile preparation of functional PDA-based yolk@shell structured nanocomposites for wide applications in biology and medicine.

Biohybrid Magnetic Microrobots for Tumor Assassination and Active Tissue Regeneration.

Magnetic microrobots have attracted increasing research interest for diverse biomedical applications, such as targeted therapy and tissue regeneration. However, multifunctional microrobots with complex morphology at the microscale are urgently needed to be fabricated, actively controlled, and functionalized. In this study, the chrysanthemum pollen-derived biohybrid magnetic microrobots (CDBMRs) with spiny protrusion, hollow cavity, and porous surface structure were proposed for tumor assassination and active tissue regeneration. By exquisitely designing the sequential treatment process, CDBMRs were fabricated and the innate morphology of pollen templates was well preserved. Under magnetic field, CDBMR exhibited various individual and collective behaviors. CDBMRs were utilized for synergetic tumor treatment by the combination of magnetically controlled physical assassination and active drug delivery. Meanwhile, CDBMRs showed excellent ability for active cell delivery and tissue regeneration, which was further proved by enhanced osteogenesis ability. By making full use of the natural morphology of pollen grains, the biohybrid microrobots presented a promising strategy for effective tumor therapeutics and tissue regeneration.

Development of an Earthworm-Based Intestinal Soft Robot Equipped with a Gripper

An endoscopy is a tool that is used to examine the interior of a hollow organ or cavity of the body by inserting directly into the organ. However, intestinal endoscopy is not friendly to patients due to discomfort, and it can easily cause intestinal damage or even perforation due to the use of the rigid materials of the endoscopy. Here, we provide an earthworm-based intestinal soft robot equipped with a gripper for application on intestinal exams or surgery. The intestinal soft robot is composed of a frontal radial actuator, a central axial actuator, a rear radial actuator and a gripper. The first three actuators drive the robot to move freely in some specific pipes by altering its own deformation, and the gripper, fixed at the end of the frontal radial actuator, is used to pick up “foreign bodies” into and out of the pipes for the purpose of intestinal applications. The different experiments validated that the intestinal soft robot could move forward and backward autonomously in a rigid pipe, a flexible pipe, and a mucus-containing pipe and could extract objects from these pipes. The ultimate weight that the intestinal soft robot extracts is up to 220 g, and the maximum moving speed is 12.0 cm/min in the rigid pipe. This intestinal soft robot is non-destructive to the operating environment, providing a friendly and novel method for the application of intestinal diseases.

Low-cost 3D-printed anthropomorphic cardiac phantom, for computed tomography automatic left ventricle segmentation and volumetry – A pilot study

IntroductionAccurate cardiac left ventricle (LV) delineation is essential to CT-derived left ventricular ejection fraction (LVEF). To evaluate dose-reduction potential, an anatomically accurate heart phantom, with realistic X-ray attenuation is required. We demonstrated and tested a custom-made phantom using 3D-printing, and examined the influence of image noise on automatically measured LV volumes MethodsA single coronary CT angiography (CCTA) dataset was segmented and converted to Standard Tessellation Language (STL) mesh, using open-source software. A 3D-printed model, with hollow left heart chambers, was printed and cavities filled with gelatinized contrast media. This was CT-scanned in an anthropomorphic chest phantom, at different exposure conditions. LV and “myocardium” noise and attenuation was measured. LV volume was automatically measured using two different methods. We calculated Spearmans’ correlation of LV volume with noise and contrast-noise ratio respectively om 486 scans of the phantom. Source images were compared to one phantom series with similar parameters. This was done using Dice coefficient on LV short-axis segmentations. ResultsPhantom “Myocardium” and LV attenuation was comparable to measurements on source images. Automatic volume measurement succeeded, with mean volume deviation to patient images less than 2 ml. There was a moderate correlation of volume with CNR, and strong correlation of volume with image noise. With papillary muscles included in LV volume, the correlation was positive, but negative when excluded. Variation of volumes was lowest at 90–100 kVp for both methods in the 486 repeat scans. The Dice coefficient was 0.87, indicating high overlap between the single phantom series and source scan. Cost of 3D-printer and materials was 400 and 30 Euro respectively. ConclusionBoth anatomically and radiologically the phantom mimicked the source scans closely. LV volumetry was reliably performed with automatic algorithms. Implications for practicePatient-specific cardiac phantoms may be produced at minimal cost and can potentially be used for other anatomies and pathologies. This enables radiographic phantom studies without need for dedicated 3D-labs or expensive commercial phantoms.

Ice template-assisting activation strategy to prepare biomass-derived porous carbon cages for high-performance Zn-ion hybrid supercapacitors

Biomass-derived porous carbons are desirable electrode material for supercapacitors, but the blocked carbon morphology leading to the poor accessibility and long diffusion distance hinders the practical application. Exposing the inner carbon space for smooth ion transport is crucial for the enhanced capacitive performance. Herein, porous carbon cages were prepared from heavy bio-oil using an ice template-assisting activation method. Ice crystals played crucial roles in the fabrication of cage-like morphology. By tuning the volume, ice crystals grew as templates to create cavities, prevent the shrinkage of carbon framework and transport activators into carbon bulks for high accessible surface area. The resultant porous carbons possess open structure with hollow cavities and layered shells, allowing the both excellent energy and power performance for symmetric supercapacitors and Zn-based hybrid supercapacitors. The assembled Zn-based hybrid supercapacitors achieve a favorable energy density of 119.02 Wh kg−1.

Stereolithography 3D printing of ceramic cores for hollow aeroengine turbine blades

Ceramic cores with complex double-walled hollow cavity structures are required for fabricating high-performance aeroengine turbine blades for fifth- and higher-generation fighter aircrafts. However, conventional approaches for ceramic core fabrication are unsuitable for producing such complex structures, which has hampered the innovation and application of hollow turbine blades. Herein, a high-performance stereolithography 3D printing (SLA-3DP) method is introduced based on digital light processing to fabricate complex ceramic cores with 60 vol.% solid loading. A ceramic suspension was prepared with excellent rheological and photopolymerization properties and the SLA-3DP processing parameters were optimized based on a systematic study of the microstructure, cracking, bending strength, shrinkage, and porosity of the sintered cores. Based on the systematic characterization of high-throughput samples, an evaluation and prediction system was established for the microstructure, properties, and defect analysis of SLA-3DP ceramic cores. Finally, double-walled ceramic cores and cast single-crystal hollow turbine blades were successfully prepared. The performance data and process parameters of SLA-3DP ceramic core obtained in this work could predict and guide the selection of the most effective process parameters.

Superhydrophobic hierarchical hollow carbon microspheres for microwave-absorbing and self-cleaning two-in-one applications

Advanced microwave absorbing materials with excellent microwave absorption properties and other fascinatingly additional functions continue to be highly sought after, while their fabrication still remains a huge challenge. Herein, through a facile and low-cost approach, we prepare a novel N-doped carbon microsphere with hierarchically micro-nano surface, multiporous shell, and hollow cavity to serve as a high-performance microwave absorbing material integrated with an exceptional superhydrophobicity. Specifically, the microwave absorption of the N-doped hollow carbon microspheres (N-HCMs) presents lightweight (a filler loading of 15 wt%), ultrastrong (a reflection loss of −61.2 dB), thin (a matching thickness of 1.45 mm), and very wide (an effective absorption bandwidth of 6.8 GHz) features. In particular, the absolute values of their specific reflection loss are far beyond the previously reported state-of-the-art carbon-based microwave absorbers with similar structures. Fascinatingly, the superhydrophobicity of N-HCMs is excellent and can tolerate the diversely harsh water-containing environments, which endows the microwave absorbing coatings with universally waterproof capacity as well as attractive self-cleaning function. We believe that this work can actively inspire the research of developing next-generation advanced microwave absorbing materials and pave the way for their multifunctional applications.

Shape modelling of the oropharynx distinguishes associations with body morphology but not whiplash-associated disorder.

Characterization of the oropharynx, a subdivision of the pharynx between the soft palate and the epiglottis, is limited to simple measurements. Structural changes in the oropharynx in whiplash-associated disorder (WAD) cohorts have been quantified using two-dimensional (2D) and three-dimensional (3D) measures but the results are inconsistent. Statistical shape modelling (SSM) may be a more useful tool for systematically comparing morphometric features between cohorts. This technique has been used to quantify the variability in boney and soft tissue structures, but has not been used to examine a hollow cavity such as the oropharynx. The primary aim of this project was to examine the utility of SSM for comparing the oropharynx between WAD cohorts and control; and WAD severity cohorts. The secondary aim was to determine whether shape is associated with sex, height, weight and neck length. Magnetic resonance (MR) T1-weighted images were obtained from healthy control (n= 20), acute WAD (n= 14) and chronic WAD (n= 14) participants aged 18-39 years. Demographic, WAD severity (neck disability index) and body morphometry data were collected from each participant. Manual segmentation of the oropharynx was undertaken by blinded researchers between the top of the soft palate and tip of the epiglottis. Digital 3D oropharynx models were constructed from the segmented images and principal component (PC) analysis was performed with the PC weights normalized to z-scores for consistency. Statistical analyses were undertaken using multivariate linear models. In the first statistical model the independent variable was group (acute WAD, chronic WAD, control); and in the second model the independent variable was WAD severity (recovered/mild, moderate/severe). The covariates for both models included height, weight, average neck length and sex. Shape models were constructed to visualize the effect of perturbing these covariates for each relevant mode. The shape model revealed five modes which explained 90% of the variance: mode 1 explained 59% of the variance and primarily described differences in isometric size of the oropharynx, including elongation; mode 2 (13%) primarily described lateral (width) and AP (depth) dimensions; mode 3 (8%) described retroglossal AP dimension; mode 4 (6%) described lateral dimensions at the retropalatal-retroglossal junction and mode 5 (4%) described the lateral dimension at the inferior retroglossal region. There was no difference in shape (mode 1 p= 0.52; mode 2 p= 0.96; mode 3 p= 0.07; mode 4 p= 0.54; mode 5 p= 0.74) between control, acute WAD and chronic WAD groups. There were no statistical differences for any mode (mode 1 p= 0.12; mode 2 p= 0.29; mode 3 p= 0.56; mode 4 p= 0.99; mode 5 p= 0.96) between recovered/mild and moderate/severe WAD. Sex was not significant in any of the models but for mode 1 there was a significant association with height (p= 0.007), mode 2 neck length (p= 0.044) and in mode 3 weight (p= 0.027). Although SSM did not detect differences between WAD cohorts, it did detect associations with body morphology indicating that it may be a useful tool for examining differences in the oropharynx.

Artificial Water Channels—Progress Innovations and Prospects

Artificial Water Channels—Progress Innovations and Prospects

Fall and winter activity of two bat species in response to winter flooding and decreasing temperature

Mature trees with hollow cavities are an important resource as roost sites for Rafinesque’s big-eared bats (Corynorhinus rafinesquii) and Southeastern myotis (Myotis austroriparius). Southern populations of these bats typically remain active in the winter (ca. November-March) but seasonal flooding in bottomland forests may prevent them from exiting their roosts. Our objective was to determine if and how seasonal flooding affects activity and roost-switching patterns of these species in Cache River National Wildlife Refuge, Arkansas. In October-December of 2016 and 2017, we radio-tracked 21 Rafinesque’s big-eared bats and 17 Southeastern myotis to 33 and 42 confirmed roost trees, respectively. Tree species, cavity type (e.g., basal cavity), and GPS coordinates were recorded for each confirmed roost tree. Additionally, bat activity, temperature, and water level were monitored using acoustic devices, iButton data loggers, and gauges, respectively. Although both species remained active, some of their roosting habits changed in response to decreasing temperature (from ca. 30 ℃ to −6 ℃ at sunset) rather than flooding. Notably, Southeastern myotis used mainly water tupelo in the fall (86 %, n = 14 trees), but roosted in varied hardwood species located in adjacent floodplain forests in the winter. With adverse weather and higher water levels, behavioral changes exhibited by these species may coincide with changing priorities from foraging to avoiding seasonally rising flood waters, maintaining homeostatic balance, or breeding and social interaction. In conclusion, when creating or revising their management plans, managers will need to consider the variety of roosts that these species require at different times of the year.

Stimulus‐Responsive Tubular Conjugated Polymer 2D Nanosheets

AbstractCreation of new two‐dimensional (2D) architectures has attracted significant attention in the field of self‐assembly for structural diversity and new functionalization. Although numerous 2D polymer nanosheets have been reported, 2D nanosheets with tubular channels have been unexplored. Herein, we describe a new strategy for the fabrication of stimulus‐responsive conjugated polymer 2D nanosheets with hollow cavities. Amphiphilic macrocyclic diacetylenes self‐assembled in an aqueous solution in a columnar manner to afford bilayered 2D nanosheets with intrinsically tubular nanochannels. UV‐induced polymerization resulted in the generation of blue‐colored tubular conjugated polydiacetylene 2D nanosheets. Immobilization of gold nanoparticles, fluorescence labeling with FRET phenomenon and colorimetric DNA sensing were demonstrated with these new 2D nanosheets. In addition, the free NH2 containing polymerized 2D nanosheet was utilized for conductivity behavior and grafting on graphene oxide (GO).

Stimulus-Responsive Tubular Conjugated Polymer 2D Nanosheets.

Creation of new two-dimensional (2D) architectures has attracted significant attention in the field of self-assembly for structural diversity and new functionalization. Although numerous 2D polymer nanosheets have been reported, 2D nanosheets with tubular channels have been unexplored. Herein, we describe a new strategy for the fabrication of stimulus-responsive conjugated polymer 2D nanosheets with hollow cavities. Amphiphilic macrocyclic diacetylenes self-assembled in an aqueous solution in a columnar manner to afford bilayered 2D nanosheets with intrinsically tubular nanochannels. UV-induced polymerization resulted in the generation of blue-colored tubular conjugated polydiacetylene 2D nanosheets. Immobilization of gold nanoparticles, fluorescence labeling with FRET phenomenon and colorimetric DNA sensing were demonstrated with these new 2D nanosheets. In addition, the free NH2 containing polymerized 2D nanosheet was utilized for conductivity behavior and grafting on graphene oxide (GO).