Zigzag Arrangement Research Articles

Influence of momentum ratio on heat release rate and noise of co/counter-swirl non-premixed diluted CO/H2 flames

Understanding co/counter-swirl or twin-swirl flames remains challenging due to the complex interaction of two swirling streams. In the present study, we investigate the heat release features of non-premixed co/counter-swirl syngas/air flames and their’ influence on combustor noise in a ∼20 kW combustor using simultaneous high-speed OH*-chemiluminescence (5 kHz) and microphone measurement (50 kHz) by varying the momentum ratio (M) from 0.4 to 0.95. Furthermore, the velocity field is examined using a low-speed two-dimensional particle image velocimetry (2D-PIV, frequency = 7 Hz). For all studied momentum ratios, the frequency spectra of noise measurements for both co/counter-swirl flames consistently exhibit a dominant frequency (∼285 Hz), close to the fundamental axial mode of the combustor. A further analysis using spectrograms, phase spaces, and recurrence plots reveals intermittent patterns in noise measurements, featuring periodic (P) and aperiodic regions (A). In periodic regions (P), noise synchronizes with the global fluctuation of the heat release rate as observed in chemiluminescence. Along with global fluctuation, the chemiluminescence also reveals a rotational component of heat release rate with distinct frequencies for co and counter-swirl configurations. This rotational motion possibly originated from a precessing vortex core (PVC) as indicated by the zig-zag arrangements of vortices in the inner shear layer. Furthermore, the impact of M on global fluctuation and rotational motion has been investigated using the frequency spectrum of OH*-intensity and the distribution of peaks in noise measurement. The global fluctuation is found to be suppressed when M increases while the rotational component becomes prominent at higher M. Therefore, the study elucidates the co-existence of global fluctuation and rotational motion and how these motions evolve with the varying momentum ratio (M), thus enhancing the understanding of combustion characteristics of the complex twin-swirl (co/counter-swirl) flames.

In Situ Synthesis and Visualization of Membrane SNAP25 Nano-Organization.

Cryo-electron tomography (cryo-ET) can provide insights into the structure and states of natural membrane environments to explore the role of SNARE proteins at membrane fusion and understand the relationship between their subcellular localization/formation and action mechanism. Nevertheless, the identification of individual molecules in crowded and low signal-to-noise ratio membrane environments remains a significant challenge. In this study, cryo-ET is employed to image near-physiological state 293T cell membranes, specifically utilizing in situ synthesized gold nanoparticles (AuNPs) bound with cysteine-rich protein tags to single-molecularly labeled synaptosomal-associated protein 25 (SNAP25) on the membrane surface. The high-resolution images reveal that SNAP25 is predominantly located in regions of high molecular density within the cell membrane and aggregates into smaller clusters, which may increase the fusion efficiency. Remarkably, a zigzag arrangement of SNAP25 is observed on the cell membrane. These findings provide valuable insights into the functional mechanisms of SNARE proteins.

Manipulating the topological phase of coupled modes in a plasmonic array via engineering near-field asymmetry: From zigzag arrangement to dielectric substrate

Manipulating the topological phase of coupled modes in a plasmonic array via engineering near-field asymmetry: From zigzag arrangement to dielectric substrate

Sono-photocatalytic degradation of Tetracycline and Ciprofloxacin antibiotics using microwave-reflux of NiO-MoS2/rGO ternary nanocomposite

In this study, NiO-MoS2/rGO nanocomposites were synthesized successfully by a simple microwave assisted refluxing method by varying the mass ratios of rGO. The NiMG-50 ternary nanocomposite has been applied by sonocatalytic, photocatalytic and sono-photocatalytic degradation for the removal of tetracycline (TTC) and ciprofloxacin (CIP) antibiotics. Physicochemical properties of the synthesized samples were characterized by Powder X-ray Diffraction (PXRD), Energy Dispersive X-ray Spectroscopy (EDAX) and X-ray Photoelectron Spectroscopy (XPS) corroborated the phase purity of NiMG-50 nanocomposite. The High Resolution Scanning Electron Microscopy (HR-SEM) image reveals the zigzag arrangements of NiO nanoflakes over MoS2 and rGO sheets. The tight contact of platelet shaped-NiO NP’s and curled layer-MoS2 on the sheets of rGO results in the separation of photo-induced e--h+ pairs as demonstrated by the High Resolution Transmission Electron Microscopy (HR-TEM) analysis. Optical properties reveal a reduced band gap and enhanced separation efficiency with fast charge transfer rate, improving the organic pollutant degradation efficiency. NiMG-50 demonstrated a good catalytic activity against TTC and CIP in sono-photocatalytic process with an efficiency of 94.10 % and 83.96 % at 35 and 90 min, respectively. Simultaneously, the experimental results showed that the NiMG-50 composite follows the pseudo-first order reaction kinetics with a rate constant (KSP) value of 0.077 min−1 and 0.015 min−1 for TTC and CIP. The radical trapping test and degradation mechanism indicated that the continuous contribution of ̇OH and ̇O2– reactive radicals are the major ones responsible for the active involvement in the degradation reaction. This research work gives a fresh prospects to the as prepared NiMG catalyst as an efficient composite with a good applicability for the sono-photocatalytic degradation of pharmaceutical products.

Supramolecular polymerization of [6]helicene-based cyano-luminogens: on the overall efficiency of self-assembled circularly polarized emitters.

The synthesis of the [6]helicene-based luminophores 1 and 2 is reported. These chiral systems, endowed with cyano-stilbene fragments, form supramolecular polymers by the operation of intermolecular H-bonding interactions between the amides present in the peripheral side chains. The dissimilar disubstitution of 1 and 2 plays a crucial role in their self-assembling features. Thus, 1 does not show an efficient π-stacking of the central aromatic moiety. Instead, its self-assembling process results in a zig-zag arrangement of the monomeric units to form the aggregated species. On the other hand, 2 presents an efficient overlap of the aromatic backbones that affords a co-facial arrangement of the monomeric units. The solvent-dependent studies indicate that both [6]helicenes self-assemble following a cooperative supramolecular polymerization mechanism with a higher degree of cooperativity and stability for compound 2. The enantioenriched samples of both 1 and 2 display a rich dichroic pattern that changes when the supramolecular polymerization takes place. Furthermore, the presence of the cyano-stilbene moieties gives rise to an aggregation induced emission effect. The inherent chirality of both the monomeric and aggregated species of 1 and 2 provides the systems with CPL-emitting properties, presenting a remarkable overall CPL-efficiency, quantified by the BCPL parameter, that increases upon supramolecular polymerization.

N-(4-methoxybenzyl)-L-tyrosine ethyl ester: Synthesis, structural analysis, and reaction with formaldehyde

This paper describes the structural analysis by single crystal X-ray diffraction (SCXRD) of N-(4-methoxybenzyl)-L-tyrosine ethyl ester; a scorpion-like conformation was revealed between the ethoxycarbonyl group and the 4-hydroxyphenyl group. Zig-zag linear arrangements having head-to-tail intermolecular hydrogen bonds (OH⋯N) were also observed between N-(4-methoxybenzyl)-l-tyrosine ethyl ester units. It was determined that this amine reacts with formaldehyde to form linear dimers, trimers, and tetramers made up of N-(4-methoxybenzyl)-l-tyrosine ethyl ester units linked by methylene bridges.

Phenylalanine-Based Co2+ and Cd2+ 1D Coordination Polymers: Structural Properties and Catalytic Application for Solvent-Free Aerobic Oxidation of Cycloalkene.

Two 1D coordination polymers (CPs) with general formula [M(L)(H2O)(AcO)]n, (M = Co (1) or Cd (2), AcO = acetate anion and L denotes l-phenylalanine based ligand), were synthesized and fully characterized by various spectroscopies (UV-vis, FTIR, and NMR), thermal techniques, magnetic measurements (for 1), and single-crystal and powder X-ray diffraction studies. They can be described as "ribbon-like" 1D polymers constructed through a zigzag arrangement. The polymeric structure is developed due to the coordination mode adopted by the amino acid ligand, classified as μ3-N1O1:O1:O2, which simultaneously links three metal centers. This moiety also plays an important role as a magnetic coupler between metal centers in the cobalt system, which shows a weak antiferromagnetic interaction. Both CPs have also been used in the catalytic oxidation of cyclohexene with molecular oxygen (O2) as an oxidant. Under mild conditions, both compounds demonstrated remarkable catalytic activity, with the cobalt system being more efficient than the cadmium analogue (conversion: 73 and 58% and selectivity for the major product, 2-cyclohexanone: 63 and 55%, for 1 and 2, respectively). Leaching experiments and the results obtained using a radical quencher are consistent with a radical-mediated mechanism for the Co compound. The presence of the superoxide radical was also confirmed using EPR spectroscopy and DMPO as a spin trap, which was further validated by DFT calculations. The activity observed for the Cd analogue is attributed to the organic scaffold assisted by the templating effect of the metal ion.

Adaptive Workplace with Indoor Health and Comfort Approach Toward Sustainable City

The Covid-19 pandemic has an impact on public health, including workplace occupant. The spread of the coronavirus occurs a lot in the workplace. Indoor health and comfort play an important role in providing a healthy and comfortable workplace. Work patterns during the Covid-19 pandemic have changed with the work from home and physical distancing policies. The arrangement of the workplace interior accompanied by indoor health comfort can affect the work experience of occupant. This study aims to produce an adaptive workplace layout design with an indoor health and comfort approach based on occupant perception toward sustainable city. This study uses mix methods with observation and questionnaire survey techniques. The object of research is ten offices in the Medan city, Indonesia. Observations were made to analyze the layout of the workplace, then questionnaires were distributed to employees to analyze their perceptions of comfort and the application of health protection in the workplace. The variables are lighting, ventilation, temperature and humidity, distance of workbench, and health protection. The results showed that the workplace must provide good air quality with the exchange of air through ventilation. Workbench spacing and the use of barriers are most recommended. A workplace with cubical layouts can be arranged parallel to the desk divider as a screen between desks. Whereas in a workplace with non-cubical layouts, work desks can use zig-zag or non-parallel seating arrangements and dividers between tables. Office buildings should prepare a workplace that concerned with space efficiency and comfortable indoor space.

Monomeric and dimeric cadmium(II) complexes of N4-phenyl semicarbazones: Spectral features, thermogravimetric analysis, DFT study and crystal structure of a bromido bridged complex

Seven cadmium(II) complexes ([Cd(HPySc)Br2] (1), [Cd(HPySc)(OAc)2]·3H2O (2), [Cd(HPySc)Cl2] (3), [Cd(PySc)N3] (4), [Cd(BpSc)(OAc)] (5), [Cd(HBpSc)Cl2] (6), and [Cd2(BpSc)2Br4]) (7) were synthesized using two semicarbazone ligands (HPySc and HBpSc) and characterized by elemental analyses, IR, UV–Vis, thermogravimetric analyses, conductance and single crystal XRD studies. It is found that all the complexes are non-electrolytes in nature and one of the compounds has three molecules of lattice water in the complex. Single crystal study of the complex 7 exhibits a binuclear centrosymmetric structure with a distorted octahedron arrangement around the cadmium(II) centre with Cd⋯Cd non-bonding distance of 4.0809(14) Å. A two-dimensional supramolecular hydrogen bonding network with a zig-zag arrangement is found in the crystal system supported by means of a non-classical hydrogen bonding. DFT calculations reveal that the dimeric complex is the softest and having high chemical reactivity, low stability and high polarizability compared to the other complexes. The NPA and charge distribution analysis indicate that the complexes have significant coordinating sites and potential preferred electron donor sites to metal centers.

In situ architecture of the ER-mitochondria encounter structure.

The endoplasmic reticulum and mitochondria are main hubs of eukaryotic membrane biogenesis that rely on lipid exchange via membrane contact sites1-3, but the underpinning mechanisms remain poorly understood. In yeast, tethering and lipid transfer between the two organelles is mediated by the endoplasmic reticulum-mitochondria encounter structure (ERMES), a four-subunit complex of unresolved stoichiometry and architecture4-6. Here we determined the molecular organization of ERMES within Saccharomyces cerevisiae cells using integrative structural biology by combining quantitative live imaging, cryo-correlative microscopy, subtomogram averaging and molecular modelling. We found that ERMES assembles into approximately 25 discrete bridge-like complexes distributed irregularly across a contact site. Each bridge consists of three synaptotagmin-like mitochondrial lipid binding protein domains oriented in a zig-zag arrangement. Our molecular model of ERMES reveals a pathway for lipids. These findings resolve the in situ supramolecular architecture of a major inter-organelle lipid transfer machinery and provide a basis for the mechanistic understanding of lipid fluxes in eukaryotic cells.

Seeding Pattern Impact at Crop Density Establishment and Grain Yield of Maize

Maize is the most represented grain crop on the world’s arable land. It is mostly grown using standard sowing at an inter-row distance of 70 cm. However, growing in two rows (double-row sowing) is increasingly common today. The aim of this research was to determine the influence of different spatial distributions of the same population of maize plants on the yield of maize grains in a larger range of the FAO maize hybrid maturing group. The experiment lasted 5 years and was set up at two locations in Jakšić (Požeško-Slavonia County) and Lužani (Brodsko-Posavina County). Maize sowing with standard sowing was carried out with a PSK OLT seed drill with an inter-row spacing of 70 cm, while double-row sowing was carried out with a MaterMacc Twin Row-2 seed drill in two rows spaced 22 cm apart in a zigzag arrangement and 48 cm apart between adjacent sowing furrows. In the experiment, a total of three types of maize hybrids were used: H1-Kashmir (FAO 390 maturing group), H2-Kapitolis (FAO 400 maturing group) and H3-Konfites (FAO 450 maturing group). With standard maize sowing, an average set of plants was achieved: 71,946 plants ha−1 (Kashmir), 71,714 plants ha−1 (Kapitolis) and 72,205 plants ha−1 (Konfites), while the double-row sowing achieved a set of plants of 72,166 plants ha−1, 72,104 plants ha−1 and 72,576 plants ha−1. The two-row sowing of the hybrid Kapitolis and Konfites recorded a statistically significant higher set of maize plants. The yield of maize grains in all three types of the hybrid was statistically and significantly higher by 943 kg ha−1 using two-row sowing, and the highest yield was achieved by the Kashmir hybrid (13,406 kg ha−1).

Fluorogenic response from DNA templated micrometer range self-assembled gold nanorod.

Plasmonic gold nanorod (AuNR) on a macromolecular matrix exhibits an end-to-end (ETE) long-range self-assembly (AuNR)n with n > 100. In the case of small molecules as a template, the pre-synthesized macromolecular matrix is missing and this brings a synthetic challenge in directed long-range assembly of AuNR. Self-assembly with thiol-modified small DNA and AuNR shows a much short-range ETE assembly with n < 25 via a simple evaporation technique on a solid surface. In this study, the introduction of two short amine modified probe DNAs (∼2.5 nm) and one 22-mer complementary single strand (ss)-DNA template (∼7 nm) show the long-range ETE self-assembly of (AuNR)n with n > 130. In the solution state, the zigzag arrangement within the assembled structure controls the typical change in the absorption behavior for (AuNR)n ETE assembly. The formation of this long-range ETE self-assembly in a solution state was verified from the combined effect of fluorescence resonance energy transfer (FRET) and hotspot-induced fluorescence enhancement. The probe DNAs and templated DNA concentration on fluorescence enhancement have been varied to monitor the effect of (AuNR)n with n = ∼5-130 in ETE self-assembly. Primarily quenched FRET acceptor in the presence of AuNR decisively exhibits remarkable fluorogenic response in ETE self-assembly with maximum n value. Although the FRET efficiencies among the fluorophores are comparable, the fluorogenic boost in ETE AuNR is due to the increased number of intrinsic navigated hotspots in these assemblies.

Synthesis, crystal structure and theoretical studies of 1-sulfonyl-1,2,3-triazole derivatives

The first crystal structures of 1-sulfonyl-1,2,3-triazoles are described and studied by X-ray diffraction analyses. The referred compounds displayed C–H···O and C–H···N interactions on 1,2,3-triazole moiety, which are involved in a zigzag arrangement along the edge plane observed in these structures. The sulfonyl group has a high electrophilic character, which is increased by electronegative atoms, and is likely the cause of the sulfonyl group's significant reactivity compared to other five-membered heterocyclic rings, according to theoretical studies of molecular and electronic properties determined on 1-sulfonyl-1,2,3-triazoles.

Elucidation of Structures, Electronic Properties, and Chemical Bonding of Monophosphorus-Substituted Boron Clusters in Neutral, Negative, and Positively Charged PBn/PBn–/PBn+ (n = 4–8)

This paper reports the computational study of phosphorus-doped boron clusters PBn/PBn–/PBn+ (n = 4–8). First, a global search and optimization of these clusters were performed to determine the stable structures. We used density functional theory (DFT) methods and ab initio calculations to study the stability of the atomic clusters and to explore the arrangement of stable structures. We found that the lowest energy structures of the smaller phosphorus-doped boron clusters tend to form planar or quasi-planar structures. As additional boron atoms are added to the smallest structures, the boron atoms expand in a zigzag arrangement or in a net-like manner, and the phosphorus atom is arranged on the periphery. For larger structures with seven or eight boron atoms, an unusual umbrella-like structure appears. We calculated the binding energy as well as other energies to study cluster stability. We calculated the ionization energy, electron affinity, and the HOMO–LUMO gaps. In addition, we used the adaptive natural density partitioning program to perform bond analysis so that we have a comprehensive understanding of the bonding. In order to have a suitable connection with the experiment, we simulated the infrared and photoelectron spectra.

Development of energy efficient structured plates with zigzag arrangement of multirow inclined oval trench dimples

A numerical study of the anomalous intensification of the turbulent heat transfer is performed for the initial hydrodynamic section of a long flat plate with a single row dense package of 16 inclined Oval Trench Dimples (OTD). Multiblock overlapping grids are used to solve Reynolds-Averaged Navier-Stokes (RANS) equations in the framework of VP2/3 in-house code. Firstly, applicability of RANS approach is confirmed by thorough comparison against the experimental measurements of the pressure distributions for a single inclined OTD mounted on a flat plate. Then, the dense package of OTD with the inclination angle of 60° is compared against Spherical Dimple (SD) at the same Reynolds number of 6000 based on the trench width and for the same trench depth and relatively high density of dimples. For OTD a progressive increase of the pressure drop is observed between the zone of deceleration of the free flow and the zone of low pressure near the inlet of spherical segments, where a tornado-like vortex is developed. Moreover, a gradual amplification of the reverse secondary flow is observed for OTD resulting in the minimum relative friction coefficient of −4 and the maximum relative Nusselt number of 4.4. Finally, acceleration and substantial thinning of the boundary layer above the upstream part of the OTD are observed. A new type of energy-efficient structured surfaces ready for additive technologies is proposed and justified for heat exchangers.

Densest packings from size segregation of particles in geometric confinement.

A correlation between density maximization and size segregation for packings of polydisperse particles in geometric confinement has been discovered, through the derivation of a general solution for the densest-packed zigzag arrangements of polydisperse particles. This solution is a size-graded structure in which the larger a particle the closer it is located to either end of the system, such that the smaller particles in the interior are encapsulated by the larger ones away from it. Any pair of different-sized adjacent particles is a grain-boundary-like configuration that reduces the overall packing efficiency of the system, and this solution corresponds to a minimization of excess-volume contributions from grain-boundary-like configurations of different-sized particles as a result of the clustering of equal- or like-sized particles. Our findings provide new insights into how structural order of polydisperse particles emerges in confined settings.

Degradation of ciprofloxacin in aqueous solution using ozone microbubbles: spectroscopic, kinetics, and antibacterial analysis

Ciprofloxacin (CIP) has been listed in the last version of the surface water due to its ability to kill human cells by inhibiting the activity of DNA topoisomerase IV. Thus, CIP, along with other antibiotic pollution has become a serious threat to the environment and public health. Ozonation has been used as an advanced technique that is applied in wastewater treatment to remove CIP, but the primary limitation of this method is the low solubility of ozone in water. This study is the first report of CIP removal in a scale-up of its aqueous solution using a self-developed aerator pump-enhanced ozonation (APO) system, which only employs a propeller and a zigzag arrangement of meshes. This aerator pump decreased the size of ozone bubbles by 90% and increased the effective ozone solubility to 0.47 ppm. The mechanism of degradation of CIP is attributed to an oxidation reaction of the antibiotic with reactive oxygen species, such as hydroxyl, oxygen, and hydroperoxyl radicals, generated on the surface of the ozone microbubbles. It was found that the rate and efficiency of degradation of CIP using the APO system were 3.64 × 10−3/min and 83.5%, respectively, which is higher compared with those of conventional flow ozonation (FO) systems (1.47 × 10−3/min and 60.9%). The higher degradation efficiency of CIP by the APO system was also revealed by its higher electrical energy efficiency (0.146 g/kWh), compared to that of the FO system (0.106 g/kWh). The degradation of CIP was also monitored by the resulting antibacterial activity against Escherichia coli and Staphylococcus aureus.

Structural, electronic and magnetic properties of some adatoms adsorbed at the edges and Mg-doped SiC nanoribbons

In this paper, we use the density functional theory to study comprehensively the structural, electronic and magnetic properties of the B-, F- and H-terminated edges of SiC nanoribbons with armchair edge and seven dimer lines in width, 7-ASiCNR, and zigzag edge with six chains in width, 6-ZSiCNR. In all of the three asymmetric (terminal atoms of each edge are different) zigzag configurations, the metallic property is observed. In asymmetry armchair configurations, the semiconducting properties of H-7-ASiCNR-H are retained when it changed to F-7-ASiCNR-H structure, but in B-7-ASiCNR-H and B-7-ASiCNR-F configurations, they have a metallic behavior. By doping Mg atom in the initial symmetric zigzag and armchairs configurations, the half-metallic property is created, also by doping two Mg in zigzag configuration, the half metallicity is appeared. In all zigzag arrangements, there exist magnetic property whereas, in armchair structures, some of them such as H-7-ASiCNR-B, F-7-ASiCNR-B and Mg-doped configurations show magnetic property. The calculations show that, the Mg-doped H-7-ASiCNR-H is more stable than Mg-doped H-6-ZSiCNR-H. According to the mentioned properties, these nanoribbons could be suitable in making the electronic and magnetic devices such as nano-scale transistors or spintronic devices.

Histone H1 binding to nucleosome arrays depends on linker DNA length and trajectory

Throughout the genome, nucleosomes often form regular arrays that differ in nucleosome repeat length (NRL), occupancy of linker histone H1 and transcriptional activity. Here, we report cryo-EM structures of human H1-containing tetranucleosome arrays with four physiologically relevant NRLs. The structures show a zig-zag arrangement of nucleosomes, with nucleosomes 1 and 3 forming a stack. H1 binding to stacked nucleosomes depends on the NRL, whereas H1 always binds to the non-stacked nucleosomes 2 and 4. Short NRLs lead to altered trajectories of linker DNA, and these altered trajectories sterically impair H1 binding to the stacked nucleosomes in our structures. As the NRL increases, linker DNA trajectories relax, enabling H1 contacts and binding. Our results provide an explanation for why arrays with short NRLs are depleted of H1 and suited for transcription, whereas arrays with long NRLs show full H1 occupancy and can form transcriptionally silent heterochromatin regions.

Strong memory effect in higher α-olefin homopolymers with crystalline side chains

The homopolymers of higher α-olefins with 12–20 carbon atoms were successfully synthesized using the dimethylpyridylamidohafnium/organoboron catalyst. With these model samples, the relationship between crystallization and chain topology were investigated employing the differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). The DSC results show that for these homopolymers of higher α-olefins, the crystallization temperature is significantly elevated with increasing the length of side chains. The WAXD evidences demonstrate that cooling crystallization of these homopolymers at 10 °C/min can form the Type ІІ crystallites with zigzag arrangement of side chains. Interestingly, these higher α-olefin homopolymers exhibit the strong memory effect of crystallization, where the accelerated crystallization of poly(1-hexadecene) was observed after annealing at the elevated temperature up to 70 °C higher than melting range. Quantitatively, the temperature width of memory Domain II changes in a bell type with increasing side-chain length, where poly(1-hexadecene) shows the largest Domain II width of 74 °C. However, the strong memory effect beyond the melting range that is observed for the Type ІІ crystallites, is absent in Type І crystallites packed by the main chains, as demonstrated by the results of poly(1-tetradecene). Moreover, it was found that this memory effect of Type II crystallites is stable and independent on the annealing time.