Conditions Of High Coverage Research Articles

Understanding the Enhanced Separation Mechanism of C2H4/C2H6 at Low Pressure by HKUST−1

The production of ethylene (C2H4) is typically accompanied by the formation of impurities like ethane (C2H6), making the separation of C2H4 and C2H6 crucial in industrial processes. Here, we investigated the S-shaped adsorption phenomenon of C2H6 on the metal–organic framework HKUST−1. The virial equation is used to fit the C2H6 and C2H4 adsorption isotherms under low coverage. The results showed that the repulsion energy between neighboring C2H6 molecules was significantly higher than that between neighboring C2H4 molecules, which was an important reason for the lower adsorption of C2H6 by HKUST−1 at low coverage. As more molecules are adsorbed, gas molecules aggregate within pores, leading to more hydrogen bonds formed between HKUST−1 and larger-sized C2H6 under high coverage conditions. This phenomenon plays a crucial role in the S-shaped adsorption behavior of HKUST−1 on C2H6. Additionally, this unique adsorption behavior allows for the efficient separation of C2H4/C2H6 mixtures at low pressures. The ideal adsorbed solution theory (IAST) selectivity of HKUST−1 for C2H4/C2H6 mixtures was 3.78 at 283 K and 1 bar, but increased significantly to 7.53 under low pressure. This unique mechanism provides a theoretical basis for the low-pressure separation of C2H4/C2H6 by HKUST−1 and establishes a solid foundation for future practical research applications.

A Sampling-Based Distributed Exploration Method for UAV Cluster in Unknown Environments

Rapidly completing the exploration and construction of unknown environments is an important task of a UAV cluster. However, the formulation of an online autonomous exploration strategy based on a real-time detection map is still a problem that needs to be discussed and optimized. In this paper, we propose a distributed unknown environment exploration framework for a UAV cluster that comprehensively considers the path and terminal state gain, which is called the Distributed Next-Best-Path and Terminal (DNBPT) method. This method calculates the gain by comprehensively calculating the new exploration grid brought by the exploration path and the guidance of the terminal state to the unexplored area to guide the UAV’s next decision. We propose a suitable multistep selective sampling method and an improved Discrete Binary Particle Swarm Optimization algorithm for path optimization. The simulation results show that the DNBPT can realize rapid exploration under high coverage conditions in multiple scenes.

Influence of vegetation maintenance on flow and mixing: case study comparing fully cut with high-coverage conditions

Abstract. In temperate climates, agricultural ditches are generally bounded by seasonal vegetation, which affects the hydrodynamics and mixing processes within the channel and acts as a buffer strip to reduce a load of pollutants coming from the surrounding cultivated fields. However, even if the control of such vegetation represents a key strategy to support sediment and nutrient management, the studies that investigated the effect of different vegetation maintenance scenarios or vegetation coverage on the flow and mixing dynamics at the reach scale are very limited. To overcome these limitations and provide additional insights into the involved processes, tracer tests were conducted in an agricultural ditch roughly 500 m long close to Warsaw in Poland, focusing on two different vegetation scenarios: highly vegetated and fully cut. Under the highly vegetated scenario, sub-reaches differing in surficial vegetation coverage are analysed separately to better understand the influence of the vegetation conditions on the flow and mixing parameters. Special attention has been paid to the longitudinal dispersion coefficient in complex natural conditions and its dependency on vegetation coverage (V). The vegetation maintenance decreased the travel and residence times of the solute by 3–5 times, moderately increasing the peak concentrations. We found that the dispersion coefficient decreased approximately linearly with the increase of vegetation coverage at V>68 %. Further research is needed at lower vegetation coverage values and different spatial plant distributions. The obtained longitudinal dispersion coefficient values complement dispersion value datasets previously published in the literature, which are barely available for small natural streams. The new process understanding supports the design of future investigations with more environmentally sound vegetation maintenance scenarios.

Density Functional Calculations of the Sequential Adsorption of Hydrogen on Single Atom and Small Clusters of Pd and Pt Supported on Au(111)

We have used density functional theory calculations to study the sequential adsorption of hydrogen on Pd and Pt atomic site catalysts such as single-atom alloy catalysts (SAAC), single-atom catalysts (SAC), and single cluster catalysts (SCC) on Au(111). The results show that Pd systems tend to have near-zero free energy of hydrogen adsorption (\(\Delta {G}_{{\mathrm{H}}_{\mathrm{ads}}}\approx 0\)) under various coverage conditions of adsorbed hydrogen. In the case of Pt systems, \(\Delta {G}_{{\mathrm{H}}_{\mathrm{ads}}}\approx 0\) only at high coverage conditions of adsorbed hydrogen. Such differences come from the preference of hydrogen for high-coordination and low-coordination sites on Pd and Pt, respectively. The low coordination of hydrogen results in multiple adsorption sites with \(\Delta {G}_{{\mathrm{H}}_{\mathrm{ads}}}\approx 0\) in SCC of Pt/Au. These results can help to understand the different catalytic properties of Pd/Au and Pt/Au.Graphical Abstract

Drivers and barriers to sustained use of Blair ventilated improved pit latrine after nearly four decades in rural Zimbabwe.

BackgroundSome latrines remain unused even under conditions of high coverage in rural areas of low- and middle-income countries. Not much is known on household latrine use in the long term in the absence of an intervention. The current work assesses drivers and barriers to sustained use of a ventilated improved pit latrine (Blair VIP) design where it originated and how rural households adapt it to climate change.MethodsA mixed methods study was conducted from November 2020 to May 2021 among rural households of Mbire district, Zimbabwe. A cross sectional survey of 238 households with Blair ventilated improved pit (BVIP) latrines was conducted using a questionnaire and a latrine observation checklist. Data were analysed using logistic regression. Qualitative data were collected using six focus groups among house heads and analysed by thematic analysis.ResultThe latrine has perceived health, non-health and hygiene benefits for its sustained use. However, there are design, environmental and social barriers. The quantitative study indicated that determinants of latrine use were contextual (individual and household levels) and technology (individual level) factors. Focus groups indicated that latrine use was influenced by social, technology and contextual factors at multiple level factors. Interplay of factors influenced the intention to adapt the BVIP latrine to climate change. Local climate change adaptation strategies for the latrine were odour and erosion control, construction of the conventional latrine design and raised structures.ConclusionThe conventional BVIP latrine design is durable and relatively resilient to climate change with high local household use. High construction cost of the latrine causes households to build incomplete and poor quality designs which affect odour and fly control. These are barriers to sustained latrine use. The government should implement the new sanitation policy which considers alternative sanitation options and offer community support for adapting sanitation to climate change.

Effect of Peening Process on Corrosion Fatigue Life for TiNi Shape Memory Alloy

The effect of ultrasonic shot peening on corrosion fatigue properties of a TiNi shape memory alloy was investigated. In this study, the surface condition of the peened specimens was optically observed and the arithmetic mean roughness of the specimen surface was measured. The main points of the results obtained in this study are as follows: (1) The surface roughness of as-peened specimen decreases with increasing the peening coverage because of smoothing effect by shot media. (2) Surface roughing derived from adhesion of Fe in the shot media was observed on the as-peened specimen, especially under high coverage conditions. (3) Mechanical polishing after the peening reduces the surface roughness to the level before peening. (4) No change was observed on the specimen surface even if the peened and then polished materials were heated to induce the reverse transformation.

Clinical fnd epidemiological features of measles by adults in modern period

Positive results have been achieved during the implementation of the measles elimination program in the Russian Federation and in the Northwestern Federal District (NWFD). However, measles remains an urgent problem for some regions due to the peculiarities of this infection.Purpose of the work: to characterize the clinical, epidemiological and molecular genetic characteristics of measles in adults during the period of increasing incidence in St. Petersburg.Materials and methods: the incidence of measles in the Northwestern Federal District was analyzed in 2006–2020, and the data of 30 patients of S.P. Botkin clinical infectious diseases hospital over 18 years old (2018). The diagnosis of measles is confirmed by enzyme immunoassay. Molecular genetic studies (PCR, sequencing) were carried out at the National Scientific and Methodological Center for the Surveillance of Measles and Rubella of G.N. Gabrichevsky Moscow Scientific Research Institute of Epidemiology and Microbiology, biological material was used (nasopharyngeal washings, urine).Results: there was an increase in morbidity in some regions of the Northwestern Federal District in conditions of high coverage of the population with measles vaccinations. In the age structure in 2018–2019 the proportion of adults was 65%. 74% of patients were not vaccinated against measles. A moderate-severe course (100%) was noted, regardless of the genotypes of the virus. Clinical manifestations were characterized by febrile, catarrhal and exanthema syndrome. Diarrhea was found in 36,7% of patients, hepatomegaly in 43.4%, and an increase in transaminases in 87%. 66,7% of patients traveled outside St. Petersburg. The genotypes of the virus were identified: B3 Kabul and B3 Dublin of African origin, D8 Girsomnath of Indian origin.Conclusions: measles remains an urgent problem, in recent years, adults prevail among patients, both local and imported cases are recorded. The clinical course of the disease may be accompanied by intestinal complications and other symptoms that make it difficult to diagnose at the prehospital stage. The use of molecular genetic methods makes it possible to identify the pathogen, assess the identity of viral isolates, and improve the epidemiological surveillance of the infection.

Hydrogen Adsorption on Au-Supported Pt and Pd Nanoislands: A Computational Study of Hydrogen Coverage Effects.

We have studied the dissociative adsorption of hydrogen under high coverage conditions of adsorbed hydrogen on Pd and Pt nanoislands supported on Au(111) using Density Functional Theory calculations. The results reveal that for Pd/Au(111), the free energy of hydrogen adsorption ΔG is close to 0 kJ/mol when the coverage of adsorbed hydrogen is near 1 ML, where the available catalytic sites are located at the edges of the Pd nanoislands. In the case of Pt/Au(111), ΔG ≈ 0 kJ/mol under a broad range of hydrogen coverage conditions, from 1 ML to 3 ML, depending on the size of the Pt nanoislands. This is the case because the available catalytic sites are located at both the steps and terraces of Pt nanoislands. These findings indicate that Au surfaces with Pd or Pt nanoislands offer catalytic sites with ΔG ≈ 0 for hydrogen reactions, one key factor for an ideal electrocatalyst for hydrogen reactions.

Nuclear quantum effect for hydrogen adsorption on Pt(111)

Nuclear quantum effect and many-body interaction importantly interplay in the hydrogen on the Pt(111) system under the high coverage conditions of electrochemical interest, as revealed by our ab initio path integral and ring polymer molecular dynamics simulations done at room temperature. At the full monolayer coverage, hydrogen atoms are close-packed either at the atop sites or the fcc sites owing to their strong repulsion and the nearly degenerate nature of the adsorption sites. While at the 2/3 monolayer, they are delocalized over the fcc and hcp sites via the bridge sites because of the hopping. The quantum many-body effect is thus crucially important in determining the coverage dependence and provides a clue for reconciling the long-standing controversy on this system.

Phylogenomics of tomato chloroplasts using assembly and alignment-free method

Phylogenetics and population genetics are central disciplines in evolutionary biology. Both are based on the comparison of single DNA sequences, or a concatenation of a number of these. However, with the advent of next-generation DNA sequencing technologies, the approaches that consider large genomic data sets are of growing importance for the elucidation of evolutionary relationships among species. Among these approaches, the assembly and alignment-free methods which allow an efficient distance computation and phylogeny reconstruction are of great importance. However, it is not yet clear under what quality conditions and abundance of genomic data such methods are able to infer phylogenies accurately. In the present study we assess the method originally proposed by Fan et al. for whole genome data, in the elucidation of Tomatoes' chloroplast phylogenetics using short read sequences. We find that this assembly and alignment-free method is capable of reproducing previous results under conditions of high coverage, given that low frequency k-mers (i.e. error prone data) are effectively filtered out. Finally, we present a complete chloroplast phylogeny for the best data quality candidates of the recently published 360 tomato genomes.

Unraveling the adsorption mechanism of aromatic and aliphatic diols on the TiO2 surface: a density functional theory analysis

Understanding the adsorption mechanism of organic molecules on inorganic semiconductors is of great importance for generating and control functions in organic-inorganic materials. Here we have comprehensively investigated, by means of the density functional theory, the adsorption structure and energetic stability of aliphatic and aromatic diols on TiO2 using ethylene glycol, 1,2-n-decanediol, and catechol. Our calculations clearly show that the non-dissociative bidentate adsorption is more stable than the dissociative one for the aliphatic diol, both at low and high coverage conditions, result far differently from many other chemical anchor cases for which the dissociative mechanism usually prevails. On the other hand, for catechol the dissociative bidentate is the most stable at low coverage conditions, whereas, surprisingly, increasing the coverage with catechol makes the non-dissociative mechanism the most stable one, revealing possible coexistence of a dissociative and non-dissociative anchoring at high coverage. This work unraveled a variety of adsorption fashions of the diol compounds in conjunction with the impact of the coverage effect, highly dependent on the nature of the lateral chain of the anchor group.

The chemistry of nitrogen oxides on small size-selected cobalt clusters, Con+

Fourier transform ion cyclotron resonance mass spectrometry has been employed to study the reactions of gas-phase cationic cobalt clusters, Co(n) (+) (n=4-30), with nitric oxide, NO, and nitrous oxide, N(2)O, under single collision conditions. Isolation of the initial cluster permits detailed investigation of fragmentation channels which characterize the reactions of all but the largest clusters studied. In reaction with N(2)O, most clusters generate the monoxides Co(n)O(+) without fragmentation, cobalt atom loss accompanying only subsequent reactions. By contrast, chemisorption of even a single NO molecule is accompanied by fragmentation of the cluster. The measured rate coefficients for the Co(n) (+)+N(2)O reaction as a function of cluster size are significantly smaller than those calculated using the surface charge capture model, while for NO the rates are comparable. The reactions have been studied under high coverage conditions by storing clusters for extended periods to permit multiple reactions to occur. This leads to interesting chemistry on the surface of the cluster resulting in the formation of stable oxide clusters and/or the decomposition of nitric oxide on the cluster with the resulting loss of molecular nitrogen.

Modeling message propagation in random graph networks

Message propagation is used in a wide range of applications, such as search in unstructured P2P overlays, modeling infection spread in epidemiology, and modeling the spread of gossip in social networks. For example, in a P2P network that has an unstructured overlay, search for a piece of information is conducted by propagating the query message within the network, usually with the desire that as many nodes as possible are covered with as few message forwardings as possible. In this paper, we study the behavior of the message propagation process in random graph networks and give a simple model to describe this process. When applied to a large network with random graph topology, the message propagation process can usually be modeled as a random pick process or the coupon collection problem. We show that these models are less accurate when the number of covered nodes becomes large. We investigate the inaccuracy and then propose refined models which remedy the factors that cause the error. The refined models have been confirmed by our simulations to effectively compensate for the errors, especially under high coverage conditions. Thus, when a large number of messages is expected to be used in the message propagation process, the refined models of higher orders are essential.

Preparation of Novel Core‐Shell Nanocomposite Particles by Controlled Polymer Bridging

Ceramics that are composed of nanosized granules show enhanced properties in various applications. A layer‐by‐layer deposition process is developed in this study to prepare core—shell nanocomposite particles, using controlled polymer adsorption. Submicrometer‐sized alumina particles that have been chosen as the starting core particles are first dispersed by pH control and then modified by adsorption of anionic poly(acrylic acid) to facilitate the subsequent deposition of nanoparticles on them. A key step in the processing involves the removal of excess polymer in the supernatant after the adsorption by controlled washing, so that the added nanoparticles do not self‐flocculate among themselves. A coating of nanosized particles is indicated by the charge reversal of the micrometer‐sized composite particles. The isoelectric point of the composite particle is similar to that of nanosized particles under both low and high coverage conditions. Scanning electron microscopic observation of coated particles shows full monolayer coverage of the nanoparticles on core particles, which confirms the efficiency of the coating scheme that is discussed here. The present study reveals the feasibility of coating nanoparticles onto micrometer‐sized core particles, using controlled polymer bridging, for the preparation of the multilayer nanocomposite powders.