Large Ring Structure Research Articles

Proton-conductive properties of a stable three-dimensional aluminum(III)-organic framework constructed by porphyrinlcarboxylate

The proton conductivity (σ) of the highly stable metal-organic frameworks (MOFs) built by carboxylic acid ligand and aluminum metal has not been fully investigated. Herein, a three-dimensional aluminum-based MOF, [(AlOH)2TCPP]n (namely Al-TCPP) with exceptional structural stability was solvothermally synthesized using an organic multifunctional bridging ligand, meso-tetra(4-carboxyphenyl)porphine (H4TCPP) with a large stiff ring structure and Al(NO3)3⋅9H2O as raw materials. The dependency of σ on temperature and relative humidity (RH) was surveyed using the AC impedance test after the MOF's thermal, water, and chemical stabilities, as well as nitrogen and H2O vapor adsorptions, were all characterized. Experimental results demonstrated that this highly stable MOF with a high specific surface area exhibited impressive proton conductivity, with an optimal σ of 3.2 × 10-4 S/cm under 100 °C/98% RH. Furthermore, the proton-conducting mechanism inside the framework was highlighted using computed activation energy and structural analysis. This study provides new inspiration for designing and searching for high-performance proton-conductive materials.

A parallel ring-ring capacitive proximity sensor for detection of approaching conductor

PurposeTo solve the problem of low sensitivity of traditional capacitive proximity sensor, this paper aims to propose a novel capacitive sensor for detection of an approaching conductor.Design/methodology/approachFive capacitive proximity sensors with different structures are designed and the performance is compared with the traditional capacitive sensor. The impacts of geometrical parameters on the performance of the proposed capacitive sensor are studied. Furthermore, the sensitivity of the proposed capacitive sensor to an approaching conductor with different sizes is discussed. Also, how the designed capacitive sensor is sensitive to the lateral placement of the approaching object is analyzed.FindingsSeveral capacitive proximity sensor structures have been designed and analyzed. It is found that the capacitive sensor with the top small ring-bottom large ring structure shows stronger electric field distribution around the top electrode and higher sensitivity to the approaching conductor than other sensors. Through further analysis of the proposed sensor, the results demonstrate that proposed capacitive sensor is effective for proximity object detection.Originality/valueThis paper proposes a novel capacitive proximity sensor with top small ring-bottom large ring structure. Compared with the traditional capacitive sensor, the proposed capacitive sensor is more sensitive to the approaching object. This would be helpful for the accurate detection of the approaching object. Also, the top and bottom electrodes are much smaller.

Experimental study on the impulsively started motion of a close-to-neutral buoyancy freely decelerating sphere

An experimental study is presented that addresses the problem of a freely decelerating sphere in a still water tank. The diameter of the sphere was 0.04 m. Three different solid-to-fluid density ratios were considered: 0.78, 0.88, and 0.94. The submerged sphere was impulsively started upon being rammed by an actuator-mass system. Six initial velocities were considered: 0.91, 2.03, 2.54, 2.94, 3.29, and 3.78 m/s. The Reynolds number of the initial velocities based on the sphere diameter was 3.6 × 104, 8.1 × 104, 1.01 × 105, 1.17 × 105, 1.31 × 105, and 1.51 × 105 (subcritical). It was observed that both sphere dynamics and associated flow topology (identified via an optical system and a particle image velocimetry system, respectively) differed significantly from the case of an accelerating sphere. In the present case, a large vortex ring structure (both torus diameters of the order of the sphere's diameter) formed and attached to the sphere surface. This vortex ring followed the sphere motion all the way down the falling trajectory. From the data reduction standpoint, it was found that a suitably defined dimensionless acceleration parameter allowed for collapsing the kinematics variables of the sphere trajectory, namely, position, velocity, and acceleration, into a single ordinary differential equation.

Dynamic experiments of acid mine drainage with Rhodopseudomonas spheroides activated lignite immobilized sulfate-reducing bacteria particles treatment

Aiming at the problem that the treatment of acid mine drainage (AMD) by sulfate-reducing bacteria (SRB) biological method is susceptible to pH, metal ions, sulfate and carbon source. Lignite immobilized SRB particles (SRB-LP) and Rhodopseudomonas spheroides (R. spheroides) activated lignite immobilized SRB particles (R-SRB-LP) were prepared using microbial immobilization technology with SRB, R. spheroides and lignite as the main substrates. The dynamic experimental columns 1# and 2# were constructed with SRB-LP and R-SRB-LP as fillers, respectively, to investigate the dynamic repair effect of SRB-LP and R-SRB-LP on AMD. The mechanism of AMD treated with R-L-SRB particles was analyzed by scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectrometer and low-temperature nitrogen adsorption. The result showed that the combination of R. spheroides and lignite could continuously provide carbon source for SRB, so that the highest removal rates of SO42−, Cu2+ and Zn2+ in AMD by R-SRB-LP were 93.97%, 98.52% and 94.42%, respectively, and the highest pH value was 7.60. The dynamic repair effect of R-SRB-LP on AMD was significantly better than that of SRB-LP. The characterization results indicated that after R-SRB-LP reaction, the functional groups of −OH and large benzene ring structure in lignite were broken, the lignite structure was destroyed, and the specific surface area was 1.58 times larger than before reaction. It illustrated that R. spheroides provided carbon source for SRB by degrading lignite. The strong SRB activity in R-SRB-LP, SRB can co-treat AMD with lignite, so that the dynamic treatment effect of R-SRB-LP on AMD is significantly better than that of SRB-LP.

Geomorphologic and geologic Analysis of Satellite Data of the Betic and Rif orogenic Belts in the Western Mediterranean Sea

This study is focused on the description of the arcuated geomorphology and the structural pattern of the Betic and Rif Domain surrounding the West-Alboran Sea bordering S-Spain and N-Morocco based on remote sensing data. Sentinel 2, Landsat 8 and ASTER-images and Sentinel 1 radar images help to identify the structural pattern. Digital Elevation Model (DEM) data and the DEM derived morphometric maps support these investigations being integrated into a GeoInformation System (GIS). The evaluations of the various satellite data, especially after digital image processing of the Landsat thermal bands, contribute to the inventory of a large ring structure with more than 130 km in diameter. This distinct expressed ring structure becomes evident even more on slope gradient and dropraster maps.

Synthesis of a Hexameric Magnesium 4-pyridyl Complex with Cyclohexane-like Ring Structure via Reductive C-N Activation.

The reaction of [{(Arnacnac)Mg}2] (Arnacnac = HC{MeC(NAr)}2, Ar = 2,6-diisopropylphenyl, Dip, or 2,6-diethylphenyl, Dep) with 4-dimethylaminopyridine (DMAP) at elevated temperatures afforded the hexameric magnesium 4-pyridyl complex [{(Arnacnac)Mg(4-C5H4N)}6] via reductive cleavage of the DMAP C-N bond. The title compound contains a large s-block organometallic cyclohexane-like ring structure comprising tetrahedral (Arnacnac)Mg nodes and linked by linear 4-pyridyl bridging ligands, and the structure is compared with other ring systems. [(Dipnacnac)Mg(DMAP)(NMe2)] was structurally characterised as a by-product.

The Per-Tau Shell: A Giant Star-forming Spherical Shell Revealed by 3D Dust Observations

Abstract A major question in the field of star formation is how molecular clouds form out of the diffuse interstellar medium (ISM). Recent advances in 3D dust mapping are revolutionizing our view of the structure of the ISM. Using the highest-resolution 3D dust map to date, we explore the structure of a nearby star-forming region, which includes the well-known Perseus and Taurus molecular clouds. We reveal an extended near-spherical shell, 156 pc in diameter (hereafter called the “Per-Tau Shell”), in which the Perseus and Taurus clouds are embedded. We also find a large ring structure at the location of Taurus (hereafter called the “Tau Ring”). We discuss a formation scenario for the Per-Tau Shell, in which previous stellar and supernova feedback events formed a large expanding shell, where the swept-up ISM has condensed to form both the shell and the Perseus and Taurus molecular clouds within it. We present auxiliary observations of H i, Hα, 26Al, and X-rays that further support this scenario, and estimate the Per-Tau Shell’s age to be ≈6–22 Myrs. The Per-Tau shell offers the first 3D observational view of a phenomenon long-hypothesized theoretically, molecular cloud formation and star formation triggered by previous stellar and supernova feedback.

Structural evolution of rubber-wood char under different pyrolysis conditions

In order to explore the effect of different pyrolysis conditio ns on the structural characteristics of rubber wood biomass pyrolysis, rubber wood char was prepared under fast pyrolysis and slow pyrolysis conditions. The char was analyzed by BET, SEM, FT-IR and Raman spectroscopy to explore the effects of different pyrolysis conditions on pore characteristics, surface structure and chemical structure. The results showed that the nitrogen isothermal adsorption/desorption curves of slow pyrolysis at 900°C are obviously different, and the char structure has a certain amount of mesopores and macropores. With the pyrolysis temperature increased, the alkane side chain of rubber wood char broke, and formeda large number of active sites, which promoted the condensation of small aromatic rings into large aromatic ring structures, and deepened the aromatization of char structures. The rapid pyrolysis method causes the content of the small aromatic ring structure to be greater than that of the large aromatic ring structure at low temperature. The slow pyrolysis method causes the increase of the large aromatic ring structure to be greater than that of the small aromatic ring at a lower temperature contrarily.

Encapsulation of positive ion [Ni(Im)6]2+ in a cage structure based on imidazole sulfate supramolecules self-assemble: Preparation, structure, hirshfeld surface analysis and electrochemical study

An interesting compound of supramolecular architecture has been reported in this paper. The molecular formula is [(NiIm6)SO4]2[(HIm)2SO4]4·6H2O (Im= imidazole). Analysis of crystal structure data shows that the imidazole sulfate [(HIm)2SO4] and water molecules form a cage-like structure, then surround the metal nickel complex in the center of the cage. Six water molecules form a large ring structure with six SO42− by strong hydrogen bonding. The tetrahedron structure of six SO42− and eight imidazole positive ions pass through N-H···O hydrogen bonds form a cage-like structure, enclosing [NiIm6]2+ positive ions. The compound was characterized by single-crystal X-ray diffraction, Hirshfeld surface analysis, thermogravimetric analysis, infrared spectroscopy and cyclic voltammogram analysis.

Magnaporthe oryzae CK2 Accumulates in Nuclei, Nucleoli, at Septal Pores and Forms a Large Ring Structure in Appressoria, and Is Involved in Rice Blast Pathogenesis.

Magnaporthe oryzae (Mo) is a model pathogen causing rice blast resulting in yield and economic losses world-wide. CK2 is a constitutively active, serine/threonine kinase in eukaryotes, having a wide array of known substrates, and involved in many cellular processes. We investigated the localization and role of MoCK2 during growth and infection. BLAST search for MoCK2 components and targeted deletion of subunits was combined with protein-GFP fusions to investigate localization. We found one CKa and two CKb subunits of the CK2 holoenzyme. Deletion of the catalytic subunit CKa was not possible and might indicate that such deletions are lethal. The CKb subunits could be deleted but they were both necessary for normal growth and pathogenicity. Localization studies showed that the CK2 holoenzyme needed to be intact for normal localization at septal pores and at appressorium penetration pores. Nuclear localization of CKa was however not dependent on the intact CK2 holoenzyme. In appressoria, CK2 formed a large ring perpendicular to the penetration pore and the ring formation was dependent on the presence of all CK2 subunits. The effects on growth and pathogenicity of deletion of the b subunits combined with the localization indicate that CK2 can have important regulatory functions not only in the nucleus/nucleolus but also at fungal specific structures such as septa and appressorial pores.

Local loop opening in untangled ring polymer melts: a detailed "Feynman test" of models for the large scale structure.

The conformational statistics of ring polymers in melts or dense solutions is strongly affected by their quenched microscopic topological state. The effect is particularly strong for untangled (i.e. non-concatenated and unknotted) rings, which are known to crumple and segregate. Here we study these systems using a computationally efficient multi-scale approach, where we combine massive simulations on the fiber level with the explicit construction of untangled ring melt configurations based on theoretical ideas for their large scale structure. We find (i) that topological constraints may be neglected on scales below the standard entanglement length, Le, (ii) that rings with a size 1 ≤ Lr/Le ≤ 30 exhibit nearly ideal lattice tree behavior characterized by primitive paths which are randomly branched on the entanglement scale, and (iii) that larger rings are compact with gyration radii Rg2(Lr) ∝ Lr2/3. The detailed comparison between equilibrated and constructed ensembles allows us to perform a "Feynman test" of our understanding of untangled rings: can we convert ideas for the large scale ring structure into algorithms for constructing (nearly) equilibrated ring melt samples? We show that most structural observables are quantitatively reproduced by two different construction schemes: hierarchical crumpling and ring melts derived from the analogy to interacting branched polymers. However, the latter fail the "Feynman test" with respect to the magnetic radius, Rm, which we have defined based on an analogy to magnetostatics. While Rm is expected to vanish for double-folded structures, the observed values of Rm2(Lr) ∝ Rg2(Lr) provide a simple and computationally convenient measure of the presence of a non-negligible amount of local loop opening in crumpled rings.

Cyclic ADP-Carbocyclic-Ribose and -4-Thioribose, as Stable Mimics of Cyclic ADP-Ribose, a Ca2+-Mobilizing Second Messenger.

Cyclic ADP-ribose (cADPR), a general mediator involved in Ca2+ signaling, has the characteristic 18-membered ring consisting of an adenine, two riboses and a pyrophosphate, in which the two primary hydroxy groups of the riboses are linked by a pyrophosphate unit. This review focuses on chemical synthetic studies of cADPR analogues of biological importance. Although cADPR analogues can be synthesized by enzymatic and chemo-enzymatic methods using ADP-ribosyl cyclase, the analogues obtained by these methods are limited due to the substrate-specificity of the enzymes. Consequently, chemical synthetic methods providing a greater variety of cADPR analogues are required. Although early chemical synthetic studies demonstrated that construction of the large 18-membered ring structure is difficult, the construction was achieved using the phenylthiophosphate-type substrates by treating with AgNO3 or I2. This is now a general method for synthesizing these types of biologically important cyclic nucleotides. Using this method as the key step, the chemically and biologically stable cADPR mimic, cADP-carbocyclic-ribose (cADPcR) and -4-thioribose (cADPtR), were synthesized.

Paleostrukture of East Orenburg region

The article states new views on structural features of East Orenburg Oblast. Results of long-term research of geological party of Mineral Deposits and their Investigation Department in RUDN formed the basis of writing the article. Unlike the predecessors considering this territory as a fragment of a double-fold structure of Ural, the authors of the article realize the thought of paleovolcanic structure of the territory. Having carried out photointerpretation of multiband satellite images, the scheme of tectonic disturbances, which is a combination of ring and radial faults, has been received. These disturbances emphasize the large ring structure, the center of which settles down near the Zhetykol lake. The carried-out facies analysis of volcanogenic and sedimentary rocks showed that groups of rocks corresponding to the main facies of volcanic constructions - vent, slope and distal - are outstanding for the territory. Rocks of these facies were formed in two independent tectono-magmatic cycles: the Baikal - Ordovician-Silurian age, and Caledonian - Upper Devonian-Upper Carboniferous age. The magmatism sequence is homodromous in both cycles and particular intrusive facies correspond to each cycle. For the Baikal cycle the intrusions are presented by serpentinite and ultramafite. For the Caledonian cycle the intrusive rocks are presented by complex granitoid intrusions of three-facies composition (the initial stages of intrusion are presented by gabbro and gabbro-diorites, the second phase of intrusion - by diorites, syenites and granodiorites, the third phase - by various granites). Interaction of granitoids with serpentinite leads to remobilization of dunite from serpentinite and to formation of chromite industrial mineralization in the latter. The research results open new opportunities in the analysis of allocation and confinedness of the known endogenous ore objects and predicting the new.

Type IX secretion: the generation of bacterial cell surface coatings involved in virulence, gliding motility and the degradation of complex biopolymers.

The Type IX secretion system (T9SS) is present in over 1000 sequenced species/strains of the Fibrobacteres-Chlorobi-Bacteroidetes superphylum. Proteins secreted by the T9SS have an N-terminal signal peptide for translocation across the inner membrane via the SEC translocon and a C-terminal signal for secretion across the outer membrane via the T9SS. Nineteen protein components of the T9SS have been identified including three, SigP, PorX and PorY that are involved in regulation. The inner membrane proteins PorL and PorM and the outer membrane proteins PorK and PorN interact and a complex comprising PorK and PorN forms a large ring structure of 50 nm in diameter. PorU, PorV, PorQ and PorZ form an attachment complex on the cell surface of the oral pathogen, Porphyromonas gingivalis. P. gingivalis T9SS substrates bind to PorV suggesting that after translocation PorV functions as a shuttle protein to deliver T9SS substrates to the attachment complex. The PorU component of the attachment complex is a novel Gram negative sortase which catalyses the cleavage of the C-terminal signal and conjugation of the protein substrates to lipopolysaccharide, anchoring them to the cell surface. This review presents an overview of the T9SS focusing on the function of T9SS substrates and machinery components.

Changes of biochar physiochemical structures during tar H2O and CO2 heterogeneous reforming with biochar

In order to investigate the detail changes of biochar physiochemical structures during the tar heterogeneous reforming with biochar under H2O and CO2 atmosphere, the experiment was carried out by a two-stage fluidized bed/fixed bed reactor. The physiochemical structures of biochar samples were analyzed by the SEM-EDX, XPS, FTIR and Raman. The results show that during the heterogeneous reforming of biomass tar with biochar, H2O/CO2 not only has a direct effect on the cracking of tar, but also indirectly affects tar H2O/CO2 reforming by changing biochar structures. The tar heterogeneous reforming in H2O atmosphere takes place from the interior of biochar particles to the surface, while it only occurs on biochar surface under CO2 atmosphere. H2O increases the concentration of metal catalysts (mainly K and Ca) on the surface of biochar, while CO2 have little effect on it. Tar is thermally decomposed and reformed on biochar under H2O or CO2 atmosphere, resulting in the increase of hydrocarbon CH. With the concentration of reforming agent increasing, the effect of H2O on the surface oxygen-containing functional groups plays a more dominant role than that of CO2. The increase of H2O/CO2 concentration greatly promotes the transformation of small aromatic ring system to large aromatic ring structure in biochar during tar reforming.

Synthesis, Crystal Structural, and Spectral Characterisation of Dabigatran Etexilate Tetrahydrate

Dabigatran etexilate tetrahydrate, C34H49N7O9, has been crystallised at ambient conditions. The colourless crystal was investigated using X-ray crystallography with single crystals and powder techniques, and was characterised by thermogravimetric-differential thermal analysis (TG-DTA) and infrared spectroscopy (IR). The compound was shown to be a tetrahydrate. A dabigatran etexilate molecule and four water molecules form a large ring structure, and intra-molecular hydrogen bonds contribute to the formation of a stable molecule in the unit cell.

Structural Insights into Ring Formation of Cohesin and Related Smc Complexes.

Cohesin facilitates sister chromatid cohesion through the formation of a large ring structure that encircles DNA. Its function relies on two structural maintenance of chromosomes (Smc) proteins, which are found in almost all organisms tested, from bacteria to humans. In accordance with their ubiquity, Smc complexes, such as cohesin, condensin, Smc5-6, and the dosage compensation complex, affect almost all processes of DNA homeostasis. Although their precise molecular mechanism remains enigmatic, here we provide an overview of the architecture of eukaryotic Smc complexes with a particular focus on cohesin, which has seen the most progress recently. Given the evident conservation of many structural features between Smc complexes, it is expected that architecture and topology will have a significant role when deciphering their precise molecular mechanisms.

Effect of iron on Shenfu coal char structure and its influence on gasification reactivity

The influence of iron on Shenfu coal char structure and its gasification reactivity was studied in the present paper. Acid-washing coal samples were loaded with different content of iron catalyst and then pyrolyzed at 1123K. X-ray diffraction apparatus and Raman spectra apparatus were used to characterize the structure of coal char. The char gasified with CO2 in a thermogravimetric analyzer to study the effect of iron loading on the gasification reactivity. Iron catalyzed steam gasification of char was carried out in a fluidized-bed reactor to investigate the impact of iron loading on the release characteristics of gas products. The results of XRD suggested that iron particle effectively hinders the trend of carbon graphitization in the process of pyrolysis. The intensity of (002) and (100) peaks of char decreased with the rise of iron loading. With the increase of iron loading, Lc and La reduced from 12.48Å and 41.40Å to 11.50Å and 35.70Å, respectively. Raman spectra analysis showed that iron inhibits the growth of large aromatic ring structure and increases the amount of amorphous carbon structure in char. Comparison of the reactivity of char loaded with various concentrations of iron catalyst, the char with 2wt% iron exhibited highest gasification reactivity. It was found that iron catalytic gasification reaction generates much more product gas than that of un-catalyzed. In particular, the presence of iron promotes the direct interaction between carbon and water.

Assembly and Function of the Archaeal Motility Structure, the Archaellum

Most archaea posses a motility structure, called the archaellum that is mainly used for swimming, but can also play a role in adherence to surfaces. Although the archaellum functionally resembles the bacterial flagellum, its structure and assembly is reminiscent of bacterial type IV pili.We use the crenarchaeal archaellum of Sulfolobus acidocaldarius as a model system to understand its assembly, subunit interactions and how it can rotate. The crenarchaeal archaellum is comprised of seven subunits: the archaellin, FlaB, the structural subunit, FlaXFG, small monotopic membrane proteins of unknown function, FlaH, an ATP-binding protein, FlaI, the motor ATPase and FlaJ, the only polytopic membrane protein.We showed that FlaI forms an ATP-dependent hexamer and its N-terminus is involved in the switch between the rotation and assembly of the filament. FlaH is a typical RecA like protein which can only bind ATP, but not hydrolyze it. Its function in motor rotation or assembly is so far unknown. FlaX, a conserved crenarchaeal archaellum protein, formed a large ring structure with a diameter of 22 nm and interacted with FlaH and FlaI, presumably acting as a stator like structure.Biophysical studies like tethered motion particle analysis and optical tweezer experiments are being used to understand the mode of rotation of the archaellum and will be presented.

Characterization of Low-k Dielectric SiCOH Films Deposited with Decamethylcyclopentasiloxane and Cyclohexane

Ultra low-k dielectric SiCOH films were deposited with decamethylcyclopentasiloxane (DMCPSO, C10H30O5Si5) and cyclohexane (C6H12) precursors by plasma-enhanced chemical vapor deposition at the deposition temperature between 25 and 200 degrees C and their chemical composition and deposition kinetics were investigated in this work. Low dielectric constants of 1.9-2.4 were obtained due to intrinsic nanoscale pores originating from the relatively large ring structure of DMCPSO and to the relatively large fraction of carbon contents in cyclohexane. Three different deposition regions were identified in the temperature range. Deposition rates increased with temperature below 40 degrees C and decreased as temperature increased to 75 degrees C with apparent activation energies of 56 kJ/mol x K at < 40 degrees C, -26 kJ/mol x K at 40-100 degrees C, respectively. In the temperature region of 40-100 degrees C hydrocarbon deposition and decomposition process compete each other and decomposition becomes dominant, which results in apparent negative activation energy. Deposition rates remain relatively unaffected with further increases of temperature above 100 degrees C. FTIR analysis and deposition kinetic analysis showed that hydrocarbon deposition is the major factor determining chemical composition and deposition rate. The hydrocarbon deposition dominates especially at lower temperatures below 40 degrees C and Si-O fraction increases above 40 degrees C. We believe that dielectric constants of low-k films can be controlled by manipulating the fraction of deposited hydrocarbon through temperature control.