Tetrahedral Shape Research Articles

Modeling thermodynamic properties of Ni, Sn, Al and Cu nanosolids

Surface atoms and dangling bonds on the surface affect the thermodynamic properties. A thermodynamical model, based on cohesive energy is presented to discuss the melting properties of materials at nanoscale. The model is used to realize the effect of size and shape on melting temperature Tmn, melting entropy Smn and enthalpy Hmn of Ni, Sn, Al and Cu metallic nanoparticles. The variation in Tmn, Smn and Hmn are examined for nanowire, film, spherical, regular tetrahedral, hexahedral and octahedral shaped nanoparticles. It is reported that Tmn, Smn and Hmn decrease with decreasing the size of the nanoparticles and smaller the particle size, greater are the size and shape effects and when size is less than 10 nm, it has been predicted that on decreasing size, Tmn, Smn and Hmn reduce appreciably. Also, at the same size, more the shape of nanoparticles departs from that of the sphere, smaller is the Smn and Hmn of nanoparticles and its changes are less for nanowire shape and more for regular tetrahedral shape. Our theoretical results are compared with the available experimental or simulation data. Results predicted by our model are in good agreement with experimental observations.

Engineering of inorganic nanostructures with hierarchy of chiral geometries at multiple scales

Engineering of inorganic nanostructures with hierarchy of chiral geometries at multiple scales

Teleostomata rackii gen. et sp. nov.: an acritarch from the Devonian (Givetian) of south-central Poland

The acritarch Teleostomata rackii gen. et sp. nov. is described and illustrated from the Middle Devonian Skały Beds that outcrop at Miłoszów, Holy Cross Mountains, Poland. At the type locality, its stratigraphical range is within the ‘Geminospora’ extensa (Ex) Miospore Zone (= hemiansatus–varcus Conodont Zones), which correspond to the early and middle Givetian. The same acritarch has been illustrated from the Eifelian strata of the Gondwanan shelf in Tunisia, but it was unnamed at the time. This acritarch from Miłoszów can be distinguished from other phytoplankton genera of tetrahedral shape because of its broad processes with distal pore-like openings.

Synthesis and characterization and biological study of pyridylazo ligand and its compounds of Co, Ni and Cu divalent ions

In this work, we synthesized and characterized an azo dye of amino pyridine namely 6-[3- pyridylazo]-2,4-dichlorophenol (PADCP) furthermore its complexes of cobalt, nickel and copper divalent ions. The infrared spectra refereed that PADCP ligand coordinates by oxygen and nitrogen atoms to the metals in the complexes as bidentate ligand. The synthesized complexes have general formula [M(PADCP)2] which confirmed by elemental analysis, magnetic moments, molar conductivity and electronic spectra. The synthesized complexes of PADCP have tetrahedral shape and non-ionic. The PADCP dye exhibit clear color changes under pH changes. The PADCP ligand and its complexes shown notable biological activity against E.coli, Staph.aureus and Aspergillus Niger

Core/Shell Magic-Sized CdSe Nanocrystals.

Magic-sized semiconductor nanocrystals (MSNCs) grow via discrete jumps between specific sizes. Despite their potential to offer atomically precise structures, their use has been limited by poor stability and trap-dominated photoluminescence. Recently, CdSe MSNCs have been grown to larger sizes. We exploit such particles and demonstrate a method to grow shells on CdSe MSNC cores via high-temperature synthesis. Thin CdS shells lead to dramatic improvements in the emissive properties of the MSNCs, narrowing their fluorescence line widths, enhancing photoluminescence quantum yields, and eliminating trap emission. Although thicker CdS shells lead to decreased performance, CdxZn1-xS alloyed shells maintain efficient and narrow emission lines. These alloyed core/shell crystallites exhibit a tetrahedral shape, in agreement with a recent model for MSNC growth. Our results indicate that MSNCs can compete with other state-of-the-art semiconductor nanocrystals. Furthermore, these core/shell structures will allow further study of MSNCs and their potential for atomically precise growth.

Cluster After 20 Years of Operations: Science Highlights and Technical Challenges

AbstractThe Cluster mission was the first constellation using four identical spacecraft to study Sun‐Earth connection plasma processes. Using four spacecraft in a tetrahedron shape, it could measure, for the first time, 3D quantities such as electrical currents, plasma gradients or divergence of the electron pressure tensor and 3D structures such as boundaries, surface waves or vortices. Launched in pairs in July and August 2000, on two Soyuz rockets from Baikonur, the four spacecraft have been collecting data continuously for more than 20 years. The mission faced many challenges during the years of operations as some spacecraft subsystems had a lifetime of a few years beyond the initial two‐year mission. The major one was to operate without functioning batteries and to successfully pass short and long eclipses, up to 3 h long, without damaging the on‐board computers and transmitters and without freezing the fuel. More than 1,000 eclipses have been successfully passed since 2010 using a specially made procedure which switches off the complete spacecraft before entering into eclipse and switches it on when the Sun is again illuminating the solar panels. During 20 years, many discoveries and science results have been published in more than 2,700 scientific papers. A few highlights are presented here, focusing on how varying the spacecraft separation was essential to achieve the science goals of the mission. The Cluster Science Data System and the Cluster archive allows public access to all science data as well as spacecraft ancillary data.

Transformations of micron-sized PbTe surface structures induced by low energy ions

Formation and transformation of micron-sized structures on PbTe crystal surfaces under impact of low energy Ar+ ions is studied. New phenomena occurring due to interaction of energetic ions and atoms forming the main crystallographic planes of solid crystalline compounds, namely the transformation of ion-induced conical structures into pyramidal ones and the formation of facets of the micropyramids with well-ordered ripples during the process of transformation are revealed. We show that conical-pyramidal transformations occur on any PbTe sputtering surface, but the shape of pyramidal structures depends on the surface crystallographic orientation. If the pyramid originates from the ion-induced conical structure on PbTe target of (100) orientation it has the tetrahedral shape and its facets are covered with pronounced well-ordered ripples arranged in parallel to the base of the pyramid and closed at its edges. We show that: (i) micro-sized conical structures ion-induced on PbTe surface are transformed into pyramidal ones due to the tendency of the PbTe compound to the easy cleavage along crystallographic planes of high reticular density; (ii) the well-ordered ripples on the facets of the tetrahedral pyramids forming from conical structures appear due to self-organization of {111} and {110} crystallographic planes shaping pyramidal facets.

Novel magnetically separable tetrahedral Ag3PO4/NrGO/CuFe2O4 photocatalyst for efficient detoxification of 2,4-dichlorophenol

An effective as well as eco-friendly photodegradation methods by atoxic and easily reusable photocatalysts are essential for wastewater treatment. Silver phosphate (Ag3PO4) specifically in tetrahedral shape is one of the superior catalysts under visible light but its photocorrosion, poor electron transfer ability and low surface adsorption properties limits its applications. Combination of Ag3PO4 and nitrogen doped reduced graphene oxide (NrGO) having higher in surface area, ample functional groups and hetero atom doping is expected to get over the problem. Further addition of a spinel ferrite (CuFe2O4) could enhance the visible light response activity and helps in easy separation of catalyst for reuse. Given the merits of Ag3PO4, NrGO and CuFe2O4 we rationally integrated a novel magnetically separable stable Ag3PO4/NrGO/CuFe2O4 photocatalyst for efficient detoxification of 2,4-dichlorophenol (2,4-DCP). About 95.3% degradation efficiency was achieved by Ag3PO4/NrGO/CuFe2O4 (k = 0.01978 min−1) which was ~2.6 times higher than pure Ag3PO4 (k = 0.00747 min−1) in 60 min of visible light irradiation. The Ag3PO4/NrGO/CuFe2O4 heterojunction was able to separate and recycle easily using an external magnetic field due to its strong magnetism, and after 5 recycles it showed 88.6% of degradation efficiency revealed its higher stability and recyclability. The photocatalytic mechanism of Ag3PO4/NrGO/CuFe2O4 was explained by heterojunction energy-band theory. In addition, the plausible intermediate products of 2,4-dichlorophenol were analyzed by ESI/LC-MS and proposed the pathway. Moreover, the phytotoxicity was also studied on V. radiata in which GI (germination index) was found to be 11.97% before degradation, while 80.31% of GI was observed in 60 min of degradation which revealed that more significant reduction in toxicity was attained on this photodegradation.

Design and locomotion analysis of the tetrahedral mobile robot with only revolute joints (TMRR)

Purpose The purpose of this paper is to introduce a tetrahedral mobile robot with only revolute joints (TMRR). By using rotation actuators, the mechanism of the robot gains favorable working space and eliminates the engineering difficulties caused by the multilevel extension compared with liner actuators. Furthermore, the rolling locomotion is improved to reduce displacement error based on dynamics analysis. Design/methodology/approach The main body of deforming mechanism with a tetrahedral exterior shape is composed of four vertexes and six RRR chains. The mobile robot can achieve the rolling locomotion and reach any position on the ground by orderly driving the rotation actuators. The global kinematics of the mobile modes are analyzed. Dynamics analysis of the robot falling process is carried out during the rolling locomotion, and the rolling locomotion is improved by reducing the collision impulse along with the moving direction. Findings Based on global kinematics analysis of TMRR, the robot can realize the continuous mobility based on rolling gait planning. The main cause of robot displacement error and the corresponding improvement locomotion are gained through dynamic analysis. The results of the theoretical analysis are verified by experiments on a physical prototype. Originality/value The work introduced in this paper is a novel exploration of applying the mechanism with only revolute joints to the field of tetrahedral rolling robots. It is also an attempt to use the improved rolling locomotion making this kind of mobile robot more practical. Meanwhile, the reasonable engineering structure of the robot provides feasibility for load carrying.

Syntheses and identification of cefotaxime-non-transition metal complexes

The coordination chemistry of the biologically active cefotaxime sodium and, in particular, the mode of its interaction with some metal ions of electronic configuration d0 (alkaline earth) and others, Zn(II), Pb(II), and Ce ions with the electronic configuration d10 has been investigated. Seven complexes were synthesized, isolated in the solid-state, and characterized by elemental analyses, conductivity measurements, IR and UV/VIS spectra, as well as thermal analyses. Based on the obtained experimental data and literature, the structural formulae to these complexes were suggested and formulated as [Mg(cef)2].2H2O (1), [Ca(cef)2].2H2O (2) [Sr(cef)2].2H2O (3), [Ba(cef)2].2H2O (4), [Zn(cef)2(H2O)2] (5), [Pb(cef)2(H2O)2].4H2O (6) and [Ce(cef)2(H2O)2].3H2O (7). The data obtained show that cefotaxime interacted with metal in a molar ratio of 2:1, respectively. Cefotaxime bonded to metal ions in the anionic form as a bidentate ligand through the lactam carbonyl (C=O) and the carboxylate group (COO-). Tetrahedral and octahedral shapes were proposed as the most likely geometries associated with a metal having such electronic configurations. The absorption bands observed in the electronic spectrum of free cefotaxime are also observed with some shifts in the spectra of its complexes, indicating their formation. The absorption bands of free cefotaxime and its complexes were assigned to electronic transitions. The thermal analyses date strongly support the structures proposed for the complexes and indicate the formation of the corresponding metal oxide as a final decomposition product.

Effects of Mesh Generation on Modelling Aluminium Anode Baking Furnaces

Anode baking is critical in carbon anode production for aluminium extraction. Operational and geometrical parameters have a direct impact on the performance of anode baking furnaces (ABF), and hence on the resulting anode quality. Gas flow patterns, velocity field, pressure drop, shear stress and turbulent dissipation rate are the main operational parameters to be optimised, considering a specific geometry that is discretised as a mesh. Therefore, this paper aims to establish the need to generate an appropriate mesh to perform accurate numerical simulations of three-dimensional turbulent flow in a single section of an ABF. Two geometries are considered for generating three meshes, using COMSOL and cfMesh, with different refinement zones. The three meshes are used for creating nine incompressible isothermal turbulent flow models, with varying operational parameters. Velocity field, convergence and turbulent viscosity ratio in the outlet of fuel inlet pipes are the quantification criteria. Quantification criteria have shown that a better physical representation is obtained by refining in the whole combustion zone. COMSOL Multiphysics’ built-in mesh generator allows quadrilateral, tetrahedron and hexahedron shapes. Adaptive cell sizes and shapes have a place within modelling, since refining a mesh in appropriate zones brings the Peclet number down when the incompressible isothermal turbulent flow is simulated.

Unraveling the Growth Mechanism of Magic-Sized Semiconductor Nanocrystals.

Magic-sized clusters (MSCs) of semiconductor are typically defined as specific molecular-scale arrangements of atoms that exhibit enhanced stability. They often grow in discrete jumps, creating a series of crystallites, without the appearance of intermediate sizes. However, despite their long history, the mechanism behind their special stability and growth remains poorly understood. It is particularly difficult to explain experiments that have shown discrete evolution of MSCs to larger sizes well beyond the "cluster" regime and into the size range of colloidal quantum dots. Here, we study the growth of MSCs, including these larger magic-sized CdSe nanocrystals, to unravel the underlying growth mechanism. We first introduce a synthetic protocol that yields a series of nine magic-sized nanocrystals of increasing size. By investigating these crystallites, we obtain important clues about the mechanism. We then develop a microscopic model that uses classical nucleation theory to determine kinetic barriers and simulate the growth. We show that magic-sized nanocrystals are consistent with a series of zinc-blende crystallites that grow layer by layer under surface-reaction-limited conditions. They have a tetrahedral shape, which is preserved when a monolayer is added to any of its four identical facets, leading to a series of discrete nanocrystals with special stability. Our analysis also identifies strong similarities with the growth of semiconductor nanoplatelets, which we then exploit to further increase the size range of our magic-sized nanocrystals. Although we focus here on CdSe, these results reveal a fundamental growth mechanism that can provide a different approach to nearly monodisperse nanocrystals.

Is there a better evolutionary outcome in a 4-cell tetrahedron embryo?

With the growing understanding of in vitro fertilization and reproductive technology, the magnitude of studies related to embryonic evolution has also increased. The optimization of embryo selection is crucial to minimize the risk of multiple pregnancies and to guarantee successful implantation and pregnancy. On the second day of culture, the four-cell embryo can be shaped into different arrangements, such as tetrahedral and planar. Previous studies have shown that mammalian embryos have a tetrahedral shape and that any deviation from this ideal configuration can negatively affect blastocyst development. A few studies have also found that planar embryos would be linked to negative predictors of success for reaching the blastocyst stage and its good quality. Therefore, it seems that tetrahedral should be preferred over planar-shaped embryos for embryonic transfers, but there is still little understanding and evidence about this subject. Thus, the objective of the present paper was to review the available literature on study tendencies to compare tetrahedral and planar-shaped embryos considering their effect on implantation and pregnancy results.

Production of silver nanoparticles via green method using banana raja peel extract as a reducing agent

In this study, biosynthesis of silver nanoparticles using the extract of a local banana peel (variant name: Raja) as bio-reductor was carried out. This study aimed to determine the effect of two different ratios of Banana Peel Extract (BPE)/distilled water on the synthesis of silver nanoparticles. The two of BPE/water ratios were 1% (v/v) and 5%(v/v), named as Sample A and Sample B, respectively. Whereas, the concentrations of AgNO3 solution as the precursor were varied as follows: 0.125; 0.1; 0.075; and 0.05 M. The synthesized colloidal silver nanoparticles were characterized using a UV-Vis spectrometer, while the BPE solution was analyzed using Fourier Transform Infra-Red (FT-IR) to study its functional groups. While, the solid silver nanoparticles was characterized using a Scanning Electron Microscopy (SEM) with an Energy-dispersive X-ray spectroscopy (EDX) analysis. The UV-Vis spectrometer results qualitatively showed that sample A produced better silver nanoparticles than that of sample B. All samples showed absorbance peaks at wavelength of 450 nm. It was found that the highest absorbance value (i.e. 1.59) occurred at sample A with a concentration of AgNO3 solution 0.1 M. Additionally, FT-IR analysis result showed the presence of a hydroxyl group specifically for alcohols as phenols, which indicated the possibility of polyphenol compounds. The SEM micrograph showed that some of the silver nanoparticles were in the shape of tetrahedron or triangular like particle and spherical The SEM image analysis results using ImageJ software showed that most of the silver nanoparticles produced had the size of 100-300 nm. Furthermore, the EDX analysis result showed a peak count at 3 keV, which confirmed the formation of silver nanoparticles.

The energetic characteristics of surface atoms in Cu clusters: Size and site consideration by first-principle calculation

A systematic study of the binding and adsorption energies of the surface atoms on different sites of Cun clusters with tetrahedral shape is performed using density functional theory. The atom number n ranging from 10 to 120 and atop adsorption of carbon monoxide on these clusters are tested. The obvious size and site dependence of the binding energy Ec-x of the surface atoms and their adsorption energy Ead-x for CO molecule respectively located on vertex (v), edge (e), and (111) facet (f) are observed, with x meaning site and being v, e and f. Even though the obvious size dependence on both Ec-x and Ead-x exist, their regular changes with size disappear. For the site influence on the surface atom in these Cu clusters, the binding energies and adsorption energies have the sequence: Ec-v > Ec-e > Ec-f and Ead-v > Ead-e > Ead-f, but Cu35 and Cu56 are the exceptions in Ead-x. In these clusters, Cu20 shows the lowest Ec-v, Ec-e and Ec-f values, while the strongest adsorption happens on the edge of Cu35 and the weakest one on Cu84 facet site. This means a scaling relation between Ec-x and Ead-x is broken in smaller systems, and both size and site are required knowing in understanding the atomic properties on small clusters.

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand.

Employing 4-ethynylaniline as a simple organic ligand we were able to prepare the stable trans-bis(acetylide)platinum(II) complex [Pt(L1)2(PBu3)2] as a linear metalloligand. The reaction of this metalloligand with iron(II) cations and pyridine-2-carbaldehyde according to the subcomponent self-assembly approach yielded decanuclear heterobimetallic tetrahedron [Fe4Pt6(L2)12](OTf)8. Thus, combination of these two design concepts – the subcomponent self-assembly strategy and the complex-as-a-ligand approach – ensured a fast and easy synthesis of large heterobimetallic coordination cages of tetrahedral shape with a diameter of more than 3 nm as a mixture of all three possible T-, S4- and C3-symmetric diastereomers. The new complexes were characterized by NMR and UV–vis spectroscopy and ESI mass spectrometry. Using GFN2-xTB we generated energy-minimized models of the diastereomers of this cage that further corroborated the results from analytical findings.

Development of a Tetrahedral-Shaped Soft Robot Arm as a Wrist Rehabilitation Device Using Extension Type Flexible Pneumatic Actuators

Based on aging Japanese society, there has been a strong desire for development of rehabilitation devices that patients can use at home. The purpose of this study is to develop a home-based compact, lightweight, flexible, and safe rehabilitation device. In this study, a flexible robot arm for wrist rehabilitation that can be used, while patients hold the top of the robot arm, is proposed and tested. The proposed robot arm consists of three extension type flexible pneumatic actuators (EFPAs) restrained by 22 PET sheets. To achieve suitable bending stiffness of the robot arm, three EFPAs are restrained so as to form a tetrahedral shape. The robot arm can bend toward each radial direction. In this paper, the construction and operational principles of the tested robot arm are described. Additionally, the analytical model of the robot arm for attitude control is also described. In addition, the tracking control using the robot arm for the desired orbit is performed. As a result, the tested robot arm can trace the desired orbit based on the model. It is confirmed that the robot arm has the possibility for application as a wrist rehabilitation device for patients.

Higher-rank discrete symmetries in the IBM. III Tetrahedral shapes

In the context of the sf-IBM, the interacting boson model with s and f bosons, the conditions are derived for a rotationally invariant and parity-conserving Hamiltonian with up to two-body interactions to have a minimum with tetrahedral shape in its classical limit. A degenerate minimum that includes a shape with tetrahedral symmetry can be obtained in the classical limit of a Hamiltonian that is transitional between the two limits of the model, Uf(7) and SOsf(8). The conditions for the existence of such a minimum are derived. The system can be driven towards an isolated minimum with tetrahedral shape through a modification of two-body interactions between the f bosons. General comments are made on the observational consequences of the occurrence of shapes with a higher-rank discrete symmetry in the context of algebraic models.

Tetrahedral CuZnInSe3 nanocrystals: One-pot synthesis, properties, and solar cell application

Quaternary CuZnInSe3 (CZISe) nanocrystals (NCs) have been synthesized using a facile one-pot approach, which are suitable for large scale device applications. This synthesis was assisted with oleylaminde (OLA) as ligand for stabilization and shape control as well as dodecanethiol (DDT) for balancing the reactivity of metal precursors. The CZISe NCs crystallize in the zinc blende structure with unique tetrahedral shape that can potentially enhance interaction and facilitate charge transfer between NCs. The NCs show strong electronic absorption in the UV and visible regions and significant absorption in the near-infrared (NIR). A direct bandgap around 1.30 eV, inferred from the UV–Vis spectrum, suggests that the NCs can be an excellent absorber for thin film solar cells. Prototype solar cells fabricated from these CZISe NC films show a power conversion efficiency of 0.77% under standard AM1.5 illumination. This study demonstrates a new, simple and ecofriendly method to synthesize CZISe NCs with tetrahedral shape potentially useful for solar cell applications.

Influence of quantum dot shape on the formation energy of boron dopants in silicon

A series of the formation energies Ef of boron dopants in Si quantum dots with different shapes, including tetrahedron (TH), tetrahedron-centered (TC), and octahedron (OT), are investigated by the first-principle calculation. The site of B dopants can be simply divided into vertex (“′v”), edge (“e”), and facet (“f”) on the surfaces of the Si quantum dots. It is found that the Ef value is strongly relying on quantum dot shape. In particular, when the size is given, one finds that TH shape has the lowest Ef values, while OT shape possesses the largest ones, and thus there is a sequence of Ef(TH) < Ef(TC) < Ef(OT). This can be well explained by the shape factor λ since the same sequence of λ(TH) < λ(TC) < λ(OT) exists. Interestingly, for each shape of TH, TC, and OT, λ is not a constant, behaving as the increasing trend when the size increases, while it behaves in decreasing trend for Ef. This means that the shape and the size have the opposite roles in Ef. Thus, considering the shape influence, one can say that the Si quantum dot with a smaller λ value is in favor of B dopants in them.