Big Cavity Research Articles

Effect of Material Extrusion Method on the Microstructure and Mechanical Properties of Copper Parts

In the present study, three extrusion-based Additive Manufacturing (AM) technologies were considered: Fused Filament Fabrication (FFF), Pellet Extrusion Process (PEP) and Atomic Diffusion Additive Manufacturing (ADAM). In order to compare these technologies, the same initial material was employed: a copper filament commercialized by Markforged® (Waltham, MA, USA). The copper filament was employed as received for ADAM and FFF technologies and shredded for PEP technology. Different printing parameters were studied for each technology (except for ADAM, which does not allow it) and the manufactured disc-shaped and tensile test parts were debindered and sintered under the same conditions. Part density, micrography and mechanical properties were analyzed. The density was observed to change with geometry, showing a relative density of around 95% for the tensile test parts through all the technologies but lower relative densities for the disc-shaped parts: around 90% for ADAM, between 85–88% for PEP and between 90–94% for optimized FFF printing parameters. The micrographies present big cavities between infill and contour for ADAM, whereas such cavities were not observed in either PEP or FFF parts. On the other hand, the parts made with PEP showed less and smaller porosity, but they had poor surface finishing, indicating that some printing parameters should be readjusted. Finally, the FFF parts had a better finishing but exhibited a non-uniform pore distribution. Concerning the mechanical properties, all the printed parts show similar properties.

Spectroscopic and Molecular Docking Studies of the Interaction of Non-steroidal Anti-inflammatory Drugs with a Carrier Protein: an Interesting Case of Inner Filter Effect and Intensity Enhancement in Protein Fluorescence.

Interaction of diclofenac and indomethacin with lysozyme was studied using several spectroscopic and molecular docking methods. Difference UV-visible spectra showed that the absorption profile of lysozyme changed when both diclofenac and indomethacin were mixed with the former. The sequential addition of both drugs to the lysozyme solution caused the decrease of the intrinsic fluorescence of the latter, however, when the data were corrected for inner filter effect, an enhancement in the fluorescence of lysozyme was detected. Accordingly, the fluorescence enhancement data were analyzed using Benesi-Hildebrand equation. Both, diclofenac and indomethacin showed good interaction with lysozyme, although, the association constants of indomethacin were nearly two-fold higher as compared to that of diclofenac. The binding was slightly more spontaneous in case of indomethacin and the major forces involved in the binding of both drugs with lysozyme were hydrogen bonding and hydrophobic interactions. Secondary structural analysis revealed that both drugs partially unfolded lysozyme. Results obtained through molecular docking were also in good agreement with the experimental outcomes. Both, diclofenac and indomethacin, are bounded at the same site inside lysozyme which is located in the big hydrophobic cavity of the protein.

Bandgap mechanisms and wave characteristics analysis of a three-dimensional elastic metastructure

PurposeIn order to investigate the vibration reduction properties of a three-dimensional elastic metastructure with spherical cavities at low frequencies.Design/methodology/approachThe bandgap characteristics of a three-dimensional elastic metastructure with spherical cavities are studied based on analytical and numerical approaches.FindingsThe results of both method revealed that the vibration of the vertexes masses is important for opening bandgaps. The fact that the big sphere cavity radius or short side length of the cube unit leads to a wider bandgap, is noteworthy.Originality/valueThis research provides theoretical guidance for realizing the vibration attenuation application of EMs in practical engineering.

Flavonoids as P-glycoprotein inhibitors for multidrug resistance in cancer: an in-silico approach

Cancer has become a leading cause of mortality due to non-communicable diseases after cardiovascular disease worldwide and is increasing day by day at a daunting pace. According to an estimate by 2040 there will be 28.4 million cancer cases. Occurrence of multidrug resistance has further worsened the scenario of available cancer treatment. Among different mechanisms of multidrug resistance efflux of xenobiotics by ABC transporter is of prime importance. P-glycoprotein (P-gp) is the major factor behind occurrence of multidrug resistance due to its wide distribution and invariably big binding cavity. Various generations of chemical inhibitors for P-gp have been designed and tested are not devoid of major side effects. Thus, in present study flavonoids a major class of natural compounds was virtually screened in order to find molecules which can be used as selective P-gp inhibitors to be used along with chemotherapeutics. After screening 4275 molecules from different classes of flavonoids i.e. flavan, flavanol, flavonone, flavone, anthocyanins, and isoflavone, through Glide docking top ten hit molecules were selected based on their binding affinity, binding energy calculation and pharmacokinetic properties. All the hit molecules were found to have docking score within the range of −11.202 to −9.699 kcal/mol showing very strong interaction with the amino acid residues of binding pocket. Whereas, dock score of standard P-gp inhibitor verapamil was −4.984 kcal/mol. The ligand and protein complex were found to be quite stable while run through molecular dynamics simulations. Communicated by Ramaswamy H. Sarma

Hierarchical Natural Pollen Cell-Derived Composite Sorbents for Efficient Atmospheric Water Harvesting.

Freshwater scarcity is a critical challenge threatening human survival especially due to poverty and arid and off-grid regions. Sorption-based atmospheric water harvesting (AWH) has emerged as a promising strategy for clean water production. However, most of the high-capacity sorbents are limited by the poor sorption/desorption kinetics and uncontrollable liquid leakage problem. Inspired by the plant transpiration process, we develop an environmentally friendly LiCl@pollen cell-polypyrrole (LiCl@PC-PPy) composite sorbent by confining the LiCl hygroscopic agent in the cages of the PC-PPy. The composite sorbent exhibits much improved sorption/desorption kinetics owing to the hydrophilicity of the hierarchical porous structure of the pollen cells, which provides abundant water sorption active sites and diffusion pathways and forms a concave meniscus on cell skeletons to maximize the thermal utilization efficiency. Moreover, the big cavities of the PC-PPy cages can serve as a water reservoir to reduce liquid leakage. As a result, the sorbent can capture atmospheric water to 85% of its own weight under 60% relative humidity (RH) within 2 h and rapidly release the water within 1 h under weak light irradiation of 0.8 sun. As a proof-of-concept demonstration, the fabricated AWH device can absorb 1.55 gwater/gsorbent at night and collect 1.53 gwater/gsorbent of water in 1-day outdoor operation, and the collected water can meet the drinking water standards defined by the World Health Organization (WHO) and Environmental Protection Agency (EPA).

Old‐growth structural attributes associated with the last giant subtropical conifers in South America

AbstractGiant Araucaria trees in Brazilian Atlantic forests today are rare but remain critically important for structuring these ecosystems, providing unique and rare habitat elements that can serve as points of reference for their management. Old‐growth Araucaria trees, with their complex crowns and big trunk cavities, supply more important ecological services than smaller trees with simple crowns. Forest ecology managers lack information on the old‐growth structures of Brazilian Araucaria forest, their ecological importance and their potential societal values and uses. In this study, we investigated old‐growth attributes of Araucaria angustifolia and relate their wide structural variability to ecological management goals. In this study, we used currently available data on the last large old Araucaria trees, as well as our own new records, from large trees of 1.6–3.2 m diameter in the Araucaria forests in southern Brazil. In order to quantify the structural attributes of these remnant trees, their main trunks, any reiterated canopy trunks and trunk cavities were measured for diameters, heights and volumes. These old‐growth trees had an average height of 38.4 m, and total tree volumes ranged from 21.5 to 106.6 m3. The biggest reiterated trunk was 1.1 m in diameter and 17 m long, which is larger than most adult Araucaria trees. Number of cavities and number of reiterated trunks were all significantly related to the diameters of these large remnant Araucaria trees; both features are absent in Araucaria <50 cm in diameter. The maximum diameter and average length of reiterated trunks were correlated with the number and size of trunk cavities. Commercial wood values and uses are limited for all trees with main trunk diameters exceeding 1.5 m due to large internal cavities—however, these rare, relictual old‐growth structures are of high ecological value for the local fauna and flora.

Polyamide thin-film nanocomposite membrane containing star-shaped ZIF-8 with enhanced water permeance and PPCPs removal

Pharmaceuticals and personal care products (PPCPs) are universally detected in natural waters, posing potential risks to drinking water safety. Nanofiltration (NF) is an advanced technology for water purification; however, its removals of PPCPs are unsatisfying, especially for hydrophobic species. In this study, the 3D architecture of nanomaterials were used to manipulate the performance the polyamide (PA) thin-film nanocomposite (TFN) membrane. In-situ addition of polyethyleneimine (PEI) successfully induced the assembly of ZIF-8 nanocrystals into star-shaped clusters (ZIF-8-PEI) due to the coordination between PEI and Zn2+. Together with the improved hydrophilicity, these ZIF-8-PEI clusters became excellent scaffolds for water drop retention after discretely loading onto the porous substrate. The conical protrusions of the ZIF-8-PEI clusters supported the defect-free PA film produced by the interfacial polymerization (IP), leaving big interfacial cavities underneath. These cavities worked as gutters for water transport, and the water permeance of the optimal TFN was 79% higher than that of the pristine thin-film composite (TFC) membrane. Moreover, the water impregnated cavities markedly alleviated the hydrophobic interaction between the PA film and hydrophobic PPCPs, impeding the transport of PPCPs across the membrane. Our results demonstrated the importance of the 3D architecture of nanofillers for the improving membrane performance.

The Use of GPR and Microwave Tomography for the Assessment of the Internal Structure of Hollow Trees

Internal decays in trees can rapidly escalate into a full decomposition of the inner structural layer, i.e., the “heartwood” layer, due to the action of aggressive diseases and fungal infections. This process leads to the formation of big cavities and hollows, which remain surrounded by the sapwood layer only. Estimating the thickness of the sapwood layer with a high degree of accuracy is therefore crucial for correct assessment of the structural integrity of hollow trees, as well as an extremely challenging task. In this context, ground-penetrating radar (GPR) has proven effective in providing details of the internal structure of trees. Nevertheless, the existing GPR processing methods still offer limited information on their internal configuration. This study investigates the effectiveness of GPR enhanced by a microwave tomography inversion approach in the assessment of hollow trees. To this aim, a living hollow tree was investigated by performing a set of pseudocircular scans along the bark perimeter with a hand-held common-offset GPR system. The tree was then felled, and sections were cut for testing purposes. A dedicated data processing framework was developed and tested through numerical simulations of hollow tree sections. The internal structure of the real trunk was therefore reconstructed via a tomographic imaging approach and the outcomes were quantitatively analyzed by way of comparison with the real sections’ main geometric features. The tomographic approach has proven very accurate in locating the sapwood–cavity interface and in the evaluation of the sapwood layer thickness, with a centimeter prediction accuracy.

HIRSHFELD SURFACE ANALYSIS OF CRYSTALS OF COMPLEXES - PRODUCTS OF REACTION IN SYSTEMS МХ2 – 1,10-PHENANTHROLINE – GeO2 – CITRIC ACID (М = Ni, Co; X = Cl, CH3COO)

Intermolecular interactions in the coordination compounds of cation-anionic type [Ni(phen)3][Ge(HCit)2]·2H2O (I), [Co(phen)3][Ge(HCit)2]⋅2H2O (II), [Co(H2O)2(phen)2]2[Ge(Cit)2]·4H2O (III) were characterized using Hirshfeld surface analysis. It was established that the biggest contribution in the Hirshfeld surface of anions have been made by the bonds H … В / О …Н (57,8 % (I), 59,6 % (II), 63,9 % (III)), H … H (28,2 % (I), 24,9 % (II), 31,4 % (III)). At the same time interactions C … H / Н … С are less significant (9,6 %, 11,2 % and 3,2 % for I, II, III, respectively). The calculated percentage contribution of different intermolecular interactions of cations in the crystals showed, that, unlike the anions, contacts H … Н (37,9 % (IА), 38,6 % (IB), 36,2 % (IIА и IIB), 38,8 % (III)) play dominating role, while contribution of H … В / О … Н is less (26,5 % (IA and IB), 28,3 % (IIA), 24,5 % (IIB), 26 2 % (III)). Furthermore, interactions C … H / Н … С are more significant than in anions (24,8 % (IА), 27,2 % (IB), 25,6 % (IIА), 26,2 % (IIB), 21,3 % (III). It is typical for cations to have С …С bonds (5,5 % in average) that give contribution less then 1 %. It was determined that voids volume in the crystals of compounds I–III is 751,74 (I), 778,21 (II) and 423,23 (III) Å3 and surface area is 1772,28 (I), 1821,36 (II) and 628,38 (III) Å2. The total volume of the voids (15 % in I, 15,7 %, in II, 22,4 % in III) testifies the lack of big cavities in the frames of the studied compounds. Thereby analysis of intermolecular interactions with the help of Hirshfeld surface analysis showed the dominating role of hydrogen bonds H … O / O …H and contacts H … H, and minor contribution of C … H / H … C and С … С bonds for all studied compounds. The absence of p-p stacking interactions between aromatic rings of 1,10-phenanthroline in the cations of complexes I–III was also pointed out.

Design and investigation of a high integrated reliable ceramic package for surface mount technology

With the development of automobile, communication, computer, aerospace and artificial intelligence, Small Outline Packages (SOP) are difficult to meet the needs of putting more integrated circuits, analog-digital signal processing circuit, storage or multi-functional modules into one package, and letting them work on the same voltage for compacted space and high reliable application. Unlike conventional SOP packages, a ceramic package of CSOP64 with larger outline and bigger cavity is designed and fabricated for surface mount technology in this paper. Also fairly strict conditions of environmental reliabilities compared to criterions commonly used on accelerated testing, such as temperature cycling, thermal shock, mechanical shock, constant acceleration and gas leakage are carried out to assure the reliabilities of package. Coffin-Manson model, dual capillary model, finite element simulation and theory calculation methods are applied to explain the mechanism of reliability problems in this investigation. Experiment results showed that all samples passed tests. The reliability of fabricated package samples meet the requirement in application.

In vitro digestibility of gels from different starches: Relationship between kinetic parameters and microstructure

Starch performance along digestion is becoming of utmost importance owing to the extensive presence of starch in foods and its association to the foods glycaemic index. However, scarce information exists on the relationship between the digestibility of starch gels and their microstructure. The aim of the study was to identify the rate and degree of digestion of starch gels from different botanical sources and the impact of gels microstructure with the in vitro starch digestibility (IVSD) by fitting the hydrolysis kinetics. Starch gels from cereals, tubers, and pulses were structurally analyzed and subjected to a standardized oro-gastrointestinal IVSD. The gel microstructure was significantly different among starches. Cereal gels had thinner walls than tuber and pulses gels, and this discrimination was not evident in the area of the gel cavities. Starches hydrolysis was well fitted to a first-order kinetics model, except for rice starch gel. Potato and chickpea gels showed the slowest digestion, and in the case of potato gel some starch remained undigested at the end of the digestion. The amylose content of gels was correlated with starch hydrolysis rate. Moreover, starch gels with thinner walls and/or bigger cavities seems to facilitate the enzyme action, and therefore, the starch digestibility.

Noncovalent molecular interactions between antineoplastic drug gemcitabine and a carrier protein identified through spectroscopic and in silico methods

Herein we have studied the noncovalent molecular interactions between hen egg white lysozyme (HEWL) and the commonly employed antineoplastic drug gemcitabine through the cumulative implementation of spectroscopic techniques and in silico approaches. The formation of a complex between HEWL and gemcitabine was made evident by the differences between the UV–visible spectra of the protein and protein-gemcitabine complex. Fluorescence quenching of HEWL by gemcitabine was hardly detectable at room temperature, but it became prominent at higher temperatures. Very low values for the bimolecular quenching constant and the non-reciprocal dependence of quenching on temperature indicated that dynamic quenching was taking place. Analysis of experimental data indicated that the interaction was dominated by hydrophobic forces, while the results of a computational investigation suggested the concomitant contribution of hydrogen bonding. Gemcitabine binding induced modifications of the secondary structure of HEWL by slightly increasing the α-helical content of the protein. Finally, gemcitabine binding site was inferred to be located in HEWL big hydrophobic cavity.

Physical and biotic factors driving the diversity of spider assemblages in tree hollows of MediterraneanQuercusforests

AbstractTree hollows are keystone structures that promote forest biodiversity. This study analyses the spatio‐temporal diversity of spiders in these microhabitats.Forty‐eight emergence traps were installed in tree cavities ofQuercus pyrenaicaforests in the Iberian Peninsula. Traps were collected monthly during a complete year.Generalised linear models and canonical correspondence analysis were used to evaluate the effect of two physical (hollow volume and height above ground) and three biotic variables (beetle richness and abundance and isopod abundance) on the spider diversity and composition of the entire assemblage and of the foraging guilds. Moreover, we examined the temporal segregation of the species using beta diversity metrics.Tree hollows hosted a rich spider assemblage (87 species) including 10 endemic and one vulnerable species. We registered four tree‐bark obligate and one hollow‐dependent species.Hollow height and beetle richness were the variables that better explained richness, while all variables analysed influenced spider abundances. However, contrary to the observed effect for other taxa (i.e. beetles), bigger cavities did not host more spider species.Temporal beta diversity throughout the year was very high and primarily explained by species turnover suggesting a temporal species segregation.We conclude that tree hollows constitute a key habitat for forest spiders and that special attention must be paid to the preservation of this microhabitat in forest ecosystems.

3,6-Fluoren[5]arenes: synthesis, structure and complexation with fullerenes C60 and C70.

A new class of macrocyclic arenes, 3,6-fluoren[5]arenes, were conveniently synthesized in good yields by one-step reaction. The 3,6-fluoren[5]arenes had symmetric pentagon structures with big and rich-electron cavities, which made them form 1 : 1 complexes with fullerenes C60 and C70. The association constants of the complexes were all greater than 105 M-1.

Mn3O4 encapsulated in hollow carbon spheres coated by graphene layer for enhanced magnetization and lithium-ion batteries performance

We report a facile method to prepare graphene coated core-shell Mn3O4 nanoparticles encapsulated in hollow carbon sphere (HCS) (G–HCS–Mn3O4). HCSs were firstly prepared at high temperature based on a core-shell template, leading to good electrical conductivity of 21.6 S m−1. The porous shells of HCSs provide passage for the manganese precursors and big cavities to store the inorganic particles. Furthermore, the Mn3O4 filling is proven by magnetization measurements showing characteristic ferrimagnetic ordering at 41 K. Electrochemical studies show that the Mn3O4 nanoparticles encapsulated in HCS are electrochemical active and there is full access to the theoretical capacity of Mn3O4. When used as anode material, G–HCS–Mn3O4 impresses by superior properties compared to pristine HCS. It can achieve a high specific charge capacity of 557 mAh g−1 at the current density of 100 mA g−1 and even 374 at 500 mA g−1. The approach of exploiting HCS-based nanocomposites can be expanded to encapsulate a variety of inorganic materials with controllable size and amount, providing new choices for electrode materials and other potential applications.

A Function Reconfigurable Antenna Based on Liquid Metal

To meet the demands of maritime transportation on ships, including satellite positioning, wireless communication, and radio frequency identification (RFID) for cargo handling management, a function reconfigurable antenna based on liquid metal is proposed in this paper. The antenna is composed of 3-D-printed hollow cavities, a two-step impedance feeding sheet, and two feeding probes. The 3-D-printed hollow cavities contain a big hollow helix cavity, a hollow cone loaded cylinder cavity, four hollow cylinder cavities, and four small hollow helix cavities. By filling the liquid metal into different hollow cavities, reconfigurable functions are generated, including right-handed circular polarization (RHCP), omnidirectional linear polarization (O-LP), pattern reconfigurable circular polarization, and omnidirectional left-handed circular polarization (O-LHCP). To illustrate this, a prototype is fabricated using 3-D-printed photopolymer resin and etching technology. The measurement results agree well with the simulated ones in terms of return loss, radiation pattern, gain, and axial ratio (AR). For the five reconfigurable states, the measured relative bandwidths for |S11| < −10 dB are 44.7%, 41.7%, 30.4%, 28.1%, and 10.8%, respectively, which covers the bands of a global navigation satellite system (GNSS), wireless communication system, and RFID communication system. Attributing to the advantages of its compact structure, flexible conversion, and good performance, the proposed antenna is a good candidate for maritime transportation applications.

Spectroscopic and Molecular Docking Investigation on the Noncovalent Interaction of Lysozyme with Saffron Constituent "Safranal".

Owing to the various beneficial properties of the popular spice saffron, the interaction of safranal, a secondary metabolite of the former, with hen egg white lysozyme was investigated. The formation of a complex was evidenced by UV–visible spectroscopy. Fluorescence quenching experiments were also performed to understand the binding mechanism and to evaluate the forces involved in binding. The strong absorption of safranal in the range of excitation and emission wavelengths of lysozyme fluorescence required the correction of the inner filter effect for fluorescence spectra to obtain the apparent extent of binding. There was a considerable difference between the observed spectra and corrected spectra, and a similar observation was found in the case of synchronous fluorescence spectra. From the analysis of quenching data, it was found that the mechanism involved in quenching was static with 1:1 binding between them. The interaction was found to be driven, mainly, by hydrophobic forces and hydrogen bonding. Safranal had negligible impact on the secondary structure of lysozyme. The interaction was also studied by molecular docking, and the results were in good agreement with the results obtained experimentally. The binding site of safranal was in the big hydrophobic cavity of lysozyme. The amino acids involved in the interaction were Asp52, Ile58, Gln57, Asn59, Trp62, Trp63, Trp108, Ile98, Asp101, and Ala107.

Three new rotundabaloghid mites (Acari: Uropodina) from Hong Kong

Three new species of the family Rotundabaloghidae are described from Hong Kong. Angulobaloghia staryi sp. nov. differs from the other AngulobaloghiaHirschmann, 1979 species in the shape and ornamentation of the genital shield of the female. Rotundabaloghia (Rotundabaloghia) hongkongensis sp. nov. has three pairs of short setae (St1, V2 and V6) on the ventral idiosoma, which is unique in the subgenus Rotundabaloghia (Rotundabaloghia)Hirschmann, 1975a. The long, robust and curved setae in the big ventral cavity of Depressorotunda (Depressorotunda) taurina sp. nov. is a character so far unknown in the subgenus Depressorotunda (Depressorotunda)Kontschan, 2010a.

Three-dimensional porous carbon with big cavities and hierarchical pores derived from leek for superior electrochemical capacitive energy storage

Great efforts have been devoted to designing porous carbons to improve energy density of supercapacitor, yet still impeded by high-cost and time-consuming procedures. The low capacitance and poor rate capability of various biomass-derived carbons in organic electrolyte remain a challenge for their practical application. Herein, to address these issues, biomass (leek) is used to produce three-dimensional (3D) porous carbon, which possesses big cavities, high specific surface area and well-defined hierarchical pores. In three-electrode system, it exhibits a high capacitance of 349 F g−1 at 0.5 A g−1 in 6 M KOH electrolyte and a superior cycling stability of no capacitance decay at 20 A g−1 over 10,000 cycles. Notably, the assembled symmetric cell reveals a high capacitance of 191 F g−1 at 0.5 A g−1 with a good rate capability (77% capacitance retention at 10 A g−1) in organic electrolyte. In addition, a high energy density of 86 Wh kg−1 at the power density of 450 W kg−1 is demonstrated, while it remains 55 Wh kg−1 at a high power density of 18 kW kg−1, superior to that of many biomass-derived carbon materials. The excellent electrochemical performance offers great potential as next-generation electrode material for supercapacitor.

Incorporation of PdCl2P2 Complexes in Ni‐MOF for Catalyzing Heck Arylation of Functionalized Olefins

Two palladium complexes of a PdCl2P2 type with P = tri(1‐piperidinyl)phosphine (Pd‐1) and triphenylphosphine (Pd‐2) were successfully immobilized on [Ni8(OH)4(OH2)2(L)6]n (Ni‐MOF) material [L=4,4′‐(benzene‐1,4‐diyldiethyne‐2,1‐diyl)bis(1‐H‐pyrazole)] to form Pd@Ni‐MOF composites. The presence of big octahedral cavities in the Ni‐MOF structure (2.4 nm) enabled incorporation of PdCl2P2 molecules inside the Ni‐MOF, as confirmed by physicochemical measurements and computer simulation. The Pd@Ni‐MOF composites catalyzed arylation of estragole by iodobenzene with an efficiency higher than that for the corresponding PdCl2P2 compounds without MOF. Arylation of eugenol by PhB(OH)2 unexpectedly resulted in the formation of ether as the main product. This was explained by the dominating activity of the Cu@MOF catalyst, formed in situ under the reaction conditions.