bluuebunny/crossref_metadata_2025 huggingface dataset:
Density functional theory study on the catalytic degradation mechanism of polystyrene
Authors: Huang Jinbao , Cheng Xiaocai , Meng Hanxian , Pan Guiying , Wang Shengquan , Wang Daiqiang
Published: August 2020

The density functional theory method of B3LYP/6-311G(d) was used to study two catalytic degradation (acid-catalyzed and alkali-catalyzed) reaction mechanisms of polystyrene (PS). The geometric structure optimization and frequency calculations of all the molecules involved in the catalytic degradation were performed, and the standard thermodynamic parameters of each catalytic cracking path were obtained. The calculation results show that the energy barrier of the optimal reaction path’s rate control step to form styrene monomer is 68.2 kJ/mol in the alkali-catalyzed degradation reaction paths. In the acid-catalyzed cracking paths, the energy barrier of the optimal path’s rate control step to form styrene is 151.9 kJ/mol. The energy barriers of rate control steps for the formation of styrene monomer in both types of these catalytic cracking reactions are lower than those for other products, so the main degradation product in the two types of catalytic degradation is styrene monomer. Compared with pure thermal degradation, an obvious feature of acid-catalyzed degradation is the formation of benzene, indene, and derivatives of indene. The formation of benzene reduces the phenyl content of the PS main chain, which results in a reduction in the yield of styrene monomer. However, an alkali catalyst shows a positive catalytic effect, which increases the yield of styrene monomer.
Artificial neural networks for the inverse design of nanoparticles with preferential nano-bio behaviors
Authors: Hassan Sergio A.
Published: August 2020

Safe and efficient use of ultrasmall nanoparticles (NPs) in biomedicine requires numerous independent conditions to be met, including colloidal stability, selectivity for proteins and membranes, binding specificity, and low affinity for plasma proteins. The ability of a NP to satisfy one or more of these requirements depends on its physicochemical characteristics, such as size, shape, and surface chemistry. Multiscale and pattern recognition techniques are here integrated to guide the design of NPs with preferential nano-bio behaviors. Data systematically collected from simulations (or experiments, if available) are first used to train one or more artificial neural networks, each optimized for a specific kind of nano–bio interaction; the trained networks are then interconnected in suitable arrays to obtain the NP core morphology and layer composition that best satisfy all the nano–bio interactions underlying more complex behaviors. This reverse engineering approach is illustrated in the case of NP-membrane interactions, using binding modes and affinities and early stage membrane penetrations as training data. Adaptations for designing NPs with preferential nano-protein interactions and for optimizing solution conditions in the test tube are discussed.
Photoelectron–photofragment coincidence spectroscopy of the mixed trihalides
Authors: Gibbard J. A. , Castracane E. , Continetti R. E.
Published: August 2020

Photoelectron–photofragment coincidence (PPC) spectroscopy is used to study the photodetachment, photodissociation, and dissociative photodetachment (DPD) of I2Br−, IBr2−, I2Cl−, and ICl2− at 266 nm. The mixed trihalides are asymmetric analogs of the well-studied I3− anion, with distinguishable dissociation asymptotes and the potential for selective bond breaking. The high beam energy PPC spectrometer used in this study couples an electrospray ionization source, a hexapole accumulation ion trap, and a linear accelerator to produce a 21 keV beam of a particular trihalide. Total, stable, and dissociative photoelectron spectra have been recorded for all the anions, except ICl2− that does not photodetach at 266 nm. A bound ground state (X) is observed for all the anions, and a dissociative first excited (A) state is also seen for I2Br− and I2Cl− at low electron kinetic energies (eKE). A 258 nm photoelectron spectrum recorded for I2Br− and I2Cl− rules out autodetachment of a dipole-bound state as the origin of the low eKE feature. The threshold detachment energy (TDE) of I2X− to the X state of the radical is similar to I3−, whereas the TDE to the radical A state increases with substitution of iodine for a lighter halogen. Two-body DPD is observed for I2Br− and I2Cl−, resulting in IBr/ICl + I + e−. For IBr2− and ICl2−, the charge symmetric three-body photodissociation of [Br–I–Br]− and [Cl–I–Cl]− is seen yielding Br + Br and Br + Br*, and Cl + Cl and Cl + Cl* neutral fragments. Evidence for the minimum energy anion structure is observed in all cases, where the iodine atom is located at the center of the trihalide.
Stability and control of an annular rotor/stator cavity limit cycle
Authors: Queguineur Matthieu , Gicquel L. Y. M. , Staffelbach G.
Published: August 2020

Rotating cavity flows have been widely studied for years because of many implications that these have on industrial applications. These flows can indeed generate, under specific conditions, self-sustained oscillations that can be noisy or even dangerous for the integrity of a system. The coherent structures or flow modes composing this unsteady phenomenon usually called “pressure band phenomenon” are misunderstood and therefore difficult to control. In the present study, the dynamics of an annular rotor/stator cavity is investigated to shed some light on the flow organization and identify control strategies based on reliable theory and analysis to stabilize the observed undesired flow modes. No specific tool is known today to control a multi-frequency phenomenon. To address this first issue, the mode dominance and interactions appearing in this multi-frequency problem are investigated, thanks to dynamic mode tracking and control [M. Queguineur et al., “Dynamic mode tracking and control with a relaxation method,” Phys. Fluids 31, 034101 (2019)]. The benefit of this method is to be able to follow in time several modes while controlling them one by one and observe mode dominance and interactions. This purely numerical controller shows that, here, the dominant mode of the annular cavity is at the source of another low frequency mode. Based on this information and to develop a physically relevant control strategy, the global linear stability framework previously used by Queguineur et al. [“Large eddy simulations and global stability analyses of an annular and cylindrical rotor/stator cavity limit cycles,” Phys. Fluids 31, 104109 (2019)] is further developed to make use of the sensitivity to a base flow modification theory. This specific analysis indeed enables us to point out the exact location where the base flow should be modified to shift the dominant mode frequency and/or growth rate. In this context, passive controller positioning is identified for the studied annular cavity flow. Such strategies are then validated through new large eddy simulations of a controlled cavity using low amplitude injection/suction demonstrating the adequacy of the analysis and control strategy.
Effect of seasoning-layer stress on fluorine diffusion
Authors: Kim Min Su , Lee Jeong Woo
Published: August 2020

In semiconductor thin-film deposition equipment in which a fluorine- or chlorine-based gas is used as a cleaning gas, reducing residual fluorine or chlorine inside the equipment is important for increasing production efficiency and reducing production costs. In the plasma-enhanced chemical vapor deposition process, where cleaning, seasoning, and deposition are sequentially repeated, an AlF3 layer is formed during the cleaning step with fluorine; the physical properties of the seasoning layer in contact with the AlF3 layer play an important role in fluorine diffusion. When the seasoning layer exhibits high compressive stress, the adsorbed fluorine does not diffuse and accelerates damage as it continuously concentrates on the surface of the aluminum component. We demonstrate the relationship between stress in the seasoning layer and fluorine diffusion and show that relieving compressive stress promotes fluorine diffusion, which, in turn, reduces the amount of fluorine inside aluminum components.
Large structure-dependent room temperature exchange bias in self-assembled BiFeO3 nanoparticles
Authors: Goswami Sudipta , Sahoo Aditi , Bhattacharya Dipten , Karci Ozgur , Mohanty P. K.
Published: August 2020

We studied the magnetic properties of self-assembled aggregates of BiFeO3 nanoparticles (∼20 nm–40 nm). The aggregates formed two different structures—one with limited and another with massive crosslinking—via the “drying-mediated self-assembly” process following dispersion of the nanoparticles within different organic solvents. They exhibit large coercivity HC (>1000 Oe) and exchange bias field HE (∼350–900 Oe) in comparison to what is observed in isolated nanoparticles (HC ∼ 250 Oe; HE ∼ 0). HE turns out to be switching from negative to positive depending on the structure of the aggregates, with ∣+HE∣ being larger. Magnetic force microscopy reveals the magnetic domains (extending across 7–10 nanoparticles) as well as the domain switching characteristics and corroborates the results of magnetic measurements. Numerical simulation of the “drying-mediated self-assembly” process shows that the nanoparticle–solvent interaction plays an important role in forming the “nanoparticle aggregate structures” observed experimentally. Numerical simulation of the magnetic hysteresis loops, on the other hand, points out the importance of spin pinning at the surface of nanoparticles as a result of surface functionalization of the particles in different suspension media. Depending on the concentration of pinned spins at the surface pointing preferably along the easy-axis direction—from greater than 50% to less than 50%—HE switches from negative to positive. Quite aside from the bulk sample and isolated nanoparticle, nanoparticle aggregates—resulting from surface functionalization—therefore offer remarkable tunability of properties depending on structures.
Flow of yield stress materials through annular abrupt expansion–contractions
Authors: Varges P. R. , Fonseca B. S. , de Souza Mendes P. R. , Naccache M. F. , de Miranda C. R.
Published: August 2020

We present an experimental study of the flow of yield stress materials through annular abrupt expansions–contractions, to evaluate the flow invasion into the cavity formed in the larger cross section region. Steady inertialess flows of Carbopol® aqueous dispersions were investigated. The flow pattern reveals yielded and unyielded regions, which were visualized using tracer particles, laser sheets, and a digital camera. The yield surfaces were identified in the experiments by choosing large enough exposure times that allow sufficient particle displacement in the yielded region. To estimate the amount of fluid that remains stagnant in the cavity, we defined the invasion ratio, a quantity that was determined through image processing for different combinations of the governing parameters. The influence of the cavity diameter and axial length, eccentricity, and inlet velocity on the invasion ratio was investigated. Fore-aft asymmetric yield surfaces were observed for all tests, probably due to elastic effects.
Numerical investigation of the patterns of the flow past nine cylinders at low Reynolds number
Authors: Yin Jian-jun , Jia Tao , Gao Di , Xiao Feng
Published: August 2020

Numerical investigations of the flow patterns around nine cylinders under the condition of Reynolds number around 200 are carried out. The change in the mean lift coefficient, the mean drag coefficient, Strouhal number, and mean streamwise velocity with the change in the pitch ratio is revealed. The Shannon entropy is calculated in the sample region to qualitatively measure the randomness of the velocity field in the region. It is shown that in flow regimes there are three patterns, including shield flow (1.1 < L/D < 2), reattachment of the shear layer (2 < L/D < 3.5), and vortex impact (3.5 < L/D < 5). The gap flow under different wake patterns has different effects on the change in hydrodynamic characteristics. The mean streamwise velocity is not strictly symmetrical about y/D when 2 < L/D < 3.5, and this asymmetry becomes more obvious as the pitch ratio increases. This asymmetry phenomenon is caused by deflection wake and instability of the shear layer falling from the surface of the upper and lower cylinders. The Shannon entropy of the velocity field decreases with an increase in the pitch ratio.
Smoothed particle hydrodynamics simulation of converging Richtmyer–Meshkov instability
Authors: Huang Shenghong , Xu Jianyu , Luo Yifan , Sun Pengyue , Luo Xisheng , Ding Juchun
Published: August 2020

The Smoothed Particle Hydrodynamics (SPH) method based on the Harten–Lax–van Leer Riemann solver is improved to study converging Richtmyer–Meshkov instability (RMI). A new density summation algorithm is proposed, which greatly suppresses the pressure oscillation at the material interface. The one-dimensional Sod problem is first simulated for code verification. Then, the SPH program is extended to two dimensions to simulate the converging RMI at a square air/SF6 interface, and the numerical results compare well with the experimental ones [Si et al., “Experimental investigation of cylindrical converging shock waves interacting with a polygonal heavy gas cylinder,” J. Fluid Mech. 784, 225–251 (2015)]. Nonlinear mode coupling and pressure disturbance are found to act evidently, causing a very fast growth spike. Performing a Fourier analysis of the interface profiles, amplitude growths of the first three harmonics are obtained. The first harmonic presents an increasing growth rate at early stages due to geometric convergence. The second harmonic experiences a long period of linear growth due to the counteraction between geometric convergence and nonlinearity, whereas the third harmonic saturates very early for stronger nonlinearity. For all three harmonics, the perturbation growth rate reduces evidently at the late stage due to the Rayleigh–Taylor stabilization caused by interface deceleration. It is found that the instability growth at early stages depends heavily on the incident shock strength, while the late-stage asymptotic growth rate is nearly constant, regardless of shock strength. It is also found that intensifying the incident shock is an effective way to produce extreme thermodynamic state at the geometric center even though it causes a faster instability growth.
Influence of grain size on the electrocaloric and pyroelectric properties in non-reducible BaTiO3 ceramics
Authors: Patel Satyanarayan , Kumar Manish
Published: August 2020

The present work demonstrates the effect of the grain size on electrocaloric and pyroelectric properties in BaTiO3-based ceramics prepared by a chemical coating method and then sintered in a reducing atmosphere at different temperatures. In a grain size of 136 ± 50 nm to 529 ± 245 nm, the electrocaloric temperature change increases from 0.30 K to 0.63 K under the electric field of 4 MV/m at the ferroelectric–paraelectric phase transition. The corresponding entropy change, heat extraction capacity, coefficient of performance, and electrocaloric strength exhibit a twofold increase (i.e., 0.31 J/kg K–0.75 J/kg K, 148 J/kg–303 J/kg, 7–14, and 0.0075 K cm/kV–0.016 K cm/kV, respectively). The effects of the grain size on the pyroelectric properties are established from the pyroelectric coefficient and the associated pyroelectric figures of merit (FOMs). The pyroelectric coefficient and pyroelectric FOMs exhibit about a fivefold increase with the increasing grain size. The pyroelectric energy harvesting is calculated for the Olsen cycle. The energy harvesting capabilities enhance from ∼96 kJ/m3 to ∼135 kJ/m3 when the cycle is operated at temperatures between 303 K and 423 K and an electric field between 1 MV/m and 4 MV/m. The results show that the increase in the grain size significantly improves the electrocaloric and pyroelectric properties. Furthermore, it is established that the pyroelectric properties are more sensitive to the grain size as compared to the electrocaloric effect when ceramics are prepared by the chemical coating-cum-sintering route. In summary, the present study suggests that microstructure control in BaTiO3 fabrication with the enhanced grain size can be an effective approach to enhance the pyroelectric and electrocaloric properties.
Conformers, electronic states, and diabolical conical intersections in the valence photoelectron spectroscopy of halocyclohexanes
Authors: Wu Xiangkun , Zhou Xiaoguo , Hemberger Patrick , Bodi Andras
Published: August 2020

The threshold photoelectron spectrum (TPES) of halocyclohexanes C6H11X (X = Cl, Br, and I) was recorded at the Swiss Light Source and assigned with the help of density functional theory and equation-of-motion ionization potential coupled cluster calculations. Dyson orbitals show that the first two electronic states of the cation arise by symmetry breaking of the doubly degenerate eg orbitals in cyclohexane as perturbed by the halogen or by perturbation of the halogen lone pair by the cyclohexane ring scaffold in the case of light and heavy halogen substituents, respectively. When the resulting two states (A″ and A′) are coupled via a conical intersection in CS symmetry, they are smoothly connected by molecular orbital rotation when the nuclear symmetry is relaxed. Even then, barriers at avoided crossings lead to distinct A′ and pseudo-A″ minima, which contribute to the TPES separately. As axial and equatorial conformers are present in commensurate abundance at room temperature, four transitions are conceivable for each substituent in the low-energy range. Three of these could be identified, and their energy could be determined for each sample. Transitions to A′ states are associated with a smaller geometry change and exhibit stronger origin transitions. Yet, most notably in X = Br, they do not correspond to the adiabatic ionization energy, which is indicated by a weak and broad band to the pseudo-A″ state with a lower onset energy. Franck–Condon vibrational analysis of the TPES coupled with quantum chemical calculations can provide insights into the behavior of conformers as well as strongly coupled electronic states.
Identification and functional characterisation of late blight resistance polymorphic genes in Russet Burbank potato cultivar
Authors: Hegde Niranjan , Doddamani Dadakhalandar , Kushalappa Ajjamada C.
Published: August 2020

In plants, the biosynthesis of the phenylpropanoid, flavonoid and fatty acid pathway monomers, polymers and conjugated metabolites play a vital role in disease resistance. These are generally deposited to reinforce cell walls to contain the pathogen to the site of infection. Identification of sequence variants in genes that biosynthesise these resistance metabolites can explain the mechanisms of disease resistance. The resistant and susceptible genotypes inoculated with Phytophthora infestans were RNA sequenced to identify the single nucleotide polymorphisms (SNPs) and insertion/deletion (InDel) variations. The SNPs/InDels were annotated and classified into different categories based on their effect on gene functions. In the selected 25 biosynthetic genes overlapping 39 transcripts, a total of 52 SNPs/InDels were identified in the protein-coding (CDS) regions. These were categorised as deleterious based on prediction of their effects on protein structure and function. The SNPs/InDels data obtained in this study can be used in genome editing to enhance late blight resistance in Russet Burbank and other potato cultivars.
Characterisation, expression and possible functions of prohibitin during spermatogenesis in the silver pomfret Pampus argenteus
Authors: Gao Xinming , Du Chen , Zheng Xuebin , Hou Congcong , Wang Yajun , Xu Shanliang , Yang Yang , Zhu Junquan , Jin Shan
Published: August 2020

Mitochondria play an important role in spermatogenesis, and some mitochondrial proteins are specifically related to this process. In this study we investigated the cytological characteristics of spermatogenic cells, including mitochondrial dynamics, during spermatogenesis in Pampus argenteus. In addition, we characterised the mitochondria-related protein prohibitin (PHB), which has been reported to play roles in mitochondrial dynamics and animal fertility. The full-length cDNA of the P. argenteus phb gene (Pa-phb) is 1687bp, including a 102-bp 5′-untranslated region (UTR), a 772-bp 3′-UTR and an 813-bp open reading frame encoding 271 amino acids. The predicted P. argenteus PHB protein (Pa-PHB) contains three functional domains (a transmembrane domain, an SPFH domain (the conserved region of stomatins, prohibitins, flotillins and HflK/C) and a coiled-coil domain) and exhibits high similarity with its homologue in other animals. The Pa-phb gene was widely expressed in all tissues examined, especially the liver and heart. We primarily focused on Pa-phb expression during spermatogenesis after observing the cytological features of male germ cells, and found that Pa-phb transcripts were detected throughout the course of development of male germ cells. Notably, we observed colocalised signals of Pa-PHB and mitochondria, which were distributed in the cytoplasm around the nucleus in spermatogonia, spermatocytes and early spermatids, tended to move to one side of the cell in middle spermatids and, finally, were colocalised in the sperm midpiece. These observations indicate that Pa-PHB is primarily localised in mitochondria during spermatogenesis, indicating that it has a role in mitochondria. Based on the results of this and previous studies regarding the essential roles of PHB in mitochondria and spermatogenesis in animals, we propose a functional model for PHB during spermatogenesis, including possible roles in the proliferation of spermatogonia and in the regulation of mitochondrial morphology and function in spermatogenic cells.
Anti-stress effects of rosemary (Rosmarinus officinalis L.) leaf extract on intestinal goblet cells and immobility of forced-swimming test in BALB/c mice
Authors: Kayashima Tomoko , Nagao Koji , Umino Mituki , Kaikiri Hiroko , Shibata Sachi , Matsubara Kiminori
Published: August 2020

We investigated the anti-stress effect of rosemary (Rosmarinus officinalis L.) leaf extract (RLE) on restraint-stressed mice and found that RLE alleviated decreases in the number of intestinal goblet cells and amount of hepatic triglycerides. It also decreased the immobility time in the forced-swimming test and activation of microglia in the brain, suggesting that RLE has beneficial effects on stress-induced dysfunctions.
Quantitative Mitigation Analysis: An ecosystem valuation tool to facilitate planning, restoration and mitigation
Authors: Reilly Tim
Published: August 2020

Globally, human development has proceeded at a rapid pace for the past several decades for both terrestrial and aquatic/marine environments. Project developers, government decision-makers and the public have had little data regarding the relative values of natural resources, or losses thereof, to facilitate project – and corresponding natural resource takings/ecosystem degradation – decision-making, resulting in intrinsic, but poorly quantified, environmental degradation.

Accordingly, we have found that an effective strategy for communicating the value of ecosystems and related natural resources to facilitate smart resource management is to monetize the replacement value of resource losses from development. A number of tools have been developed for monetizing resource value, including quantitative mitigation analysis to address compensating for ecosystem and related natural resource losses due to human development.

Quantitative Mitigation Analysis is a methodology developed to assist project developers and regulatory agencies alike with developing or evaluating cost-effective, defensible, quantitatively based compensatory mitigation strategies for developments that result in the taking of, or diminution in quality to, habitats and related natural resources. Quantitative Mitigation Analysis quantifies loss of ecological function from proposed developments and determines the amount of mitigation required as compensation. This paper introduces and describes Quantitative Mitigation Analysis and presents a case example that demonstrates how Quantitative Mitigation Analysis may be applied to construction projects resulting in substantive habitat destruction for the benefit of project developers and the regulatory community alike.
Marine life mortalities and Harmful Algal Blooms in the Northern Arabian Gulf
Authors: Al-Yamani Faiza Y. , Polikarpov Igor , Saburova Maria
Published: August 2020

Kuwait, which is located in the northwestern Arabian Gulf, has experienced several incidences of marine life mortality during the past two decades. Mortalities included pelagic and benthic fish, Sea Cucumbers and Mollusks including pearl oysters. Most of the mortalities occurred in Kuwait Bay, which is shallow and semi-enclosed. The Bay encompasses Sulaibikhat Bay, whose coastal waters are nutrient-rich and eutrophicated due to sewage discharge into its waters. Other mortalities were reported outside Kuwait Bay, especially in marinas and southern waters of Kuwait. Kuwait’s marine environment has been increasingly affected by harmful algal blooms, which increased by frequency and severity. Other Gulf countries experienced serious mortality incidences as well. Different causes were responsible for the different marine mortalities in Kuwait and the region, including untreated sewage input, eutrophication, bacterial infection, algal blooms, hypoxic conditions, pollution, and dredging. The above mortalities impacted the economy, and affected aquaculture activities, the fishing operations, coastal tourism, damaged coral reefs, and forced the closure of desalination plants. This study summarizes the different mortality incidents that occurred in the northwestern Arabian Gulf during the period of 1999 to 2019 and their possible causes. Efforts, taken by Kuwait to improve the environmental conditions of the degraded coastal area of Kuwait Bay, include for example, the designation of a marine protected area in southern Kuwait Bay that would ensure the continued production of ecological services of the protected Bay area.
Spatial and temporal variation patterns of Total Suspended Solids around the coastal areas of Bahrain, a water quality guideline
Authors: Zainal Khadija , Isa Ali , Mandeel Qaher
Published: August 2020

The study provides an assessment of sand dredging activities from the bottom of the sea during 2016 in the Kingdom of Bahrain. Total Suspended Solids were analyzed from 2010 until 2016 in the northern and eastern locations according to the Manual of oceanographic observations and pollutant analyses methods. Fifty five percent of sand dredging companies complied with some legislation such as air quality and occupational health. Almost all lacked any compliancy evidence supporting environmental protection. Only 9% of these sand companies use siltation processes to the dredged materials. Siltation is an important step to avoid dispersion of sand into the marine environment. Ambient Total Suspended Solids was around 6.1 mgl−1 ± Standard Error and the study recommends 10 mgl−1 level as an accepted concentration in samples taken from 500 meters away from the dredgers and 100 mgl−1 in samples taken from the middle of the generated silt plumes. The effect of climatic temperatures, dust storms and rain levels on seawater Total Suspended Solids concentration has been briefly discussed. The study concludes no significance seasonal or spatial variation on the ambient Total Suspended Solids concentration. It recommends coupling remote sensing with the conventional data collection and integration of modelling efforts for effective cost benefit monitoring and management of the coastal waters.
On the influence of Earth’s rotation on light propagation in waveguides
Authors: Mieling Thomas B
Published: August 2020

We analyse the influence of Earth’s rotation on the propagation of light in optical media. This is done using both geometrical optics and a perturbative calculation based on Maxwell’s equations in rotating coordinates in flat spacetime. Considering light propagation in cylindrical step-index waveguides in particular, the first order correction to electromagnetic modes is computed. The calculation shows that Earth’s spin causes a weak mode coupling, giving rise to sidebands, whose amplitudes are computed as well. The correction to the dispersion relation derived here allows to assess the anisotropy of light propagation due to Earth’s rotation. The linearisation of this result is found to agree numerically with a simple formula derived from geometrical optics.
Analysis of a localised nonlinear ensemble Kalman Bucy filter with complete and accurate observations
Authors: de Wiljes Jana , Tong Xin T
Published: August 2020

Concurrent observation technologies have made high-precision real-time data available in large quantities. Data assimilation (DA) is concerned with how to combine this data with physical models to produce accurate predictions. For spatial–temporal models, the ensemble Kalman filter with proper localisation techniques is considered to be a state-of-the-art DA methodology. This article proposes and investigates a localised ensemble Kalman Bucy filter for nonlinear models with short-range interactions. We derive dimension-independent and component-wise error bounds and show the long time path-wise error only has logarithmic dependence on the time range. The theoretical results are verified through some simple numerical tests.
Growth of α- and β-Ga2O3 epitaxial layers on sapphire substrates using liquid-injection MOCVD
Authors: Egyenes-Pörsök F , Gucmann F , Hušeková K , Dobročka E , Sobota M , Mikolášek M , Fröhlich K , Ťapajna M
Published: August 2020

Ga2O3, a wide-bandgap semiconductor material, offers a great potential for power and high-voltage electronic devices. We report on the growth of undoped α- and β-phase Ga2O3 using liquid-injection metal-organic chemical vapor deposition (LI-MOCVD) on sapphire substrates. Using the same precursor (gallium acetylacetonate) and deposition temperature of 700 °C, the phase selection was controlled by the sapphire substrate orientation, where the growth of α- and β-phase Ga2O3 was achieved on m- and c-plane surface, respectively. As deduced from x-ray diffraction, α-Ga2O3 films show epitaxial character, while β- Ga2O3 films exhibit highly textured structure. Oxygen flow was also found to have a strong impact on the phase purity of α-Ga2O3 for the flow rates examined. Optical and electrical properties of the layers grown at different oxygen flow rates were also studied systematically. LI-MOCVD growth of α-phase Ga2O3 layers at relatively high deposition temperature widens the high-temperature processing of the Ga2O3-based electronic and optoelectronic devices.
Monitoring the looseness of a bolt through laser ultrasonic
Authors: Zhou Yang , Yuan Ci , Sun Xinyao , Yang Yanqi , Wang Chao , Li Dalei
Published: August 2020

laser ultrasonic was applied to monitor the looseness of a bolt, aiming at the phenomenon that bolts can be loose after being assembled in a machine. We expound the experimental principle to monitor the bolt looseness by wave energy dissipation based on Hertzian theory of contact, taking only the asperity elastic deformation into account in our research. In the experiment, guided wave was induced by the laser, which was stimulated on the plate, to realize the goal of non-contact excitation. A piezoelectric sensor was used to receive the guided wave signal in the experiment. The distribution of guided wave power with frequency was observed by a Welch power spectral density (WPSD) image, and then the power of guided wave was calculated by power spectral density(PSD). We found that the power of guided wave is positively correlated with bolt torque. This conclusion is feasible for plates of different roughness (Ra0.5 ∼ Ra1.5), clamped by a bolt, verifying the efficiency of the method to monitor the bolt looseness through laser ultrasonic.This was verified by numerical analysis. Finally, the formula between power and bolt torque was fitted for bolted-joints in our experiment.
The ultimate state of convection: a unifying picture of very high Rayleigh numbers experiments
Authors: Roche Philippe-E
Published: August 2020

The long-standing puzzle of diverging heat transport measurements at very high Rayleigh numbers (Ra) is addressed by a simple model based on well-known properties of classical boundary layers. The transition to the ‘ultimate state’ of convection in Rayleigh–Bénard cells is modeled as sub-critical transition controlled by the instability of large-scale boundary-layer eddies. These eddies are restricted in size either by the lateral wall or by the horizontal plates depending on the cell aspect ratio (in cylindrical cells, the cross-over occurs for a diameter-to-height ratio around 2 or 3). The large-scale wind known to settle across convection cells is assumed to have antagonist effects on the transition depending on its strength, leading to wind-immune, wind-hindered or wind-assisted routes to the ultimate regime. In particular winds of intermediate strength are assumed to hinder the transition by disrupting heat transfer, contrary to what is assumed in standard models. This phenomenological model is able to reconcile observations from more than a dozen of convection cells from Grenoble, Eugene, Trieste, Göttingen and Brno. In particular, it accounts for unexplained observations at high Ra, such as Prandtl number and aspect ratio dependences, great receptivity to details of the sidewall and differences in heat transfer efficiency between experiments.
Running vacuum model in a non-flat universe *
Authors: Geng Chao-Qiang , Hsu Yan-Ting , Yin Lu , Zhang Kaituo
Published: August 2020

We investigate observational constraints on the running vacuum model (RVM) of

in a spatially curved universe, where

is the model parameter,

corresponds to the spatial curvature constant,

represents the scalar factor, and

is a constant defined by the boundary conditions. We study the CMB power spectra with several sets of

and

in the RVM. By fitting the cosmological data, we find that the best fitted

value for RVM is slightly smaller than that of

CDM in the non-flat universe, along with the constraints of

(68% C.L.) and

(95% C.L.). In particular, our results favor the open universe in both

CDM and RVM. In addition, we show that the cosmological constraints of

(RVM) and

(

CDM) at 95% C.L. for the neutrino mass sum are relaxed in both models in the spatially curved universe.
Revisiting black hole thermodynamics in massive gravity: charged particle absorption and infalling shell of dust *
Authors: Hu Shi-Qian , Liu Bo , Kuang Xiao-Mei , Yue Rui-Hong
Published: August 2020

In this study, we apply two methods to consider the variation of massive black holes in both normal and extended thermodynamic phase spaces. The first method considers a charged particle being absorbed by the black hole, whereas the second considers a shell of dust falling into it. With the former method, the first and second laws of thermodynamics are always satisfied in the normal phase space; however, in the extended phase space, the first law is satisfied but the validity of the second law of thermodynamics depends upon the model parameters. With the latter method, both laws are valid. We argue that the former method's violation of the second law of thermodynamics may be attributable to the assumption that the change of internal energy of the black hole is equal to the energy of the particle. Finally, we demonstrate that the event horizon always ensures the validity of weak cosmic censorship in both phase spaces; this means that the violation of the second law of thermodynamics, arising under the aforementioned assumption, does not affect the weak cosmic censorship conjecture. This further supports our argument that the assumption in the first method is responsible for the violation and requires deeper treatment.
The effective potential originating from swampland and the non-trivial Brans-Dicke coupling *
Authors: Li Qi , Li Jing , Zhou Yongxiang , Xue Xun
Published: August 2020

The effective vacuum energy density contributed by the non-trivial contortion distribution and the bare vacuum energy density can be viewed as the energy density of the auxiliary quintessence field potential. We find that the negative bare vacuum energy density from string landscape leads to a monotonically decreasing quintessence potential while the positive one from swampland leads to the metastable or stable de Sitter-like potential. Moreover, the non-trivial Brans-Dicke like coupling between the quintessence field and gravitation field is necessary in the latter case.
A semi-automated finite difference mesh creation method for use with immersed boundary software IB2d and IBAMR
Authors: Senter D Michael , Douglas Dylan R , Strickland W Christopher , Thomas Steven G , Talkington Anne M , Miller Laura A , Battista Nicholas A
Published: August 2020

Numerous fluid-structure interaction problems in biology have been investigated using the immersed boundary method. The advantage of this method is that complex geometries, e.g., internal or external morphology, can easily be handled without the need to generate matching grids for both the fluid and the structure. Consequently, the difficulty of modeling the structure lies often in discretizing the boundary of the complex geometry (morphology). Both commercial and open source mesh generators for finite element methods have long been established; however, the traditional immersed boundary method is based on a finite difference discretization of the structure. Here we present a software library for obtaining finite difference discretizations of boundaries for direct use in the 2D immersed boundary method. This library provides tools for extracting such boundaries as discrete mesh points from digital images. We give several examples of how the method can be applied that include passing flow through the veins of insect wings, within lymphatic capillaries, and around starfish using open-source immersed boundary software.
Effect of surface patterning using femtosecond laser on micromechanical and structural properties of micromechanical sensors
Authors: Al-Gawati Mahmoud A , Alhazaa Abdulaziz , Albrithen Hamad , Alnofiay Jamal , Alodhayb Abdullah
Published: August 2020

A femtosecond laser can be used to fabricate microstructures on a silicon microcantilever surface with high precession and minimal sidewall defects. The aim of this study is to investigate the effect of the creation of microgrooves and sub-microgrooves on the resonance frequency, quality factor, and spring constant of a silicon microcantilever. A single pass of a femtosecond laser with a wavelength of 1026 nm was used to fabricate microgrooves on the microcantilever surface. Different numbers of microgrooves were fabricated on each microcantilever using the femtosecond laser micromachining technique. The separation distance between the center of the two microgrooves was 7 μm. The microstructure of the fabricated microgrooves was investigated through field emission electron microscopy. The resonance frequency increased with the number of microgrooves, but the quality factor of the patterned microcantilever was higher than that of the unpatterned microcantilever. The spring constant increased with the number of microgrooves, increasing from 18.96 to 38.04 mN/m for microcantilevers with 1 and 7 microgrooves, respectively.
Thermogravimetric study of the kinetics and characteristics of the pyrolysis of pulverized coal
Authors: Shi-Xin Zhang , Chang-Rong Li , Run Huang , Yang-Wu Xiao , Rui Mao , Jun Huang , Cheng-Lin Zhou
Published: August 2020

Simultaneous thermogravimetric-mass spectrometric (TG-MS) analyzer was used to investigate the pyrolysis characteristics and gas generation rule of three coal samples. Results indicated that Jing-mei (JM), Xinjiang-mei (XM), and Yan-mei (YM) coals had similar pyrolysis characteristics and gas generation law. Their pyrolysis process could be roughly divided into three stages. YM had the highest weight loss and gas generation rates among all the samples. CO and CO2 components in the escaping gas continued to increase when the temperature reached 800 °C. Coats–Redfern method was employed to calculate the activation energy of three kinds of coal at four temperature stages with different mode functions. The activation energy of the four stages of JM pyrolysis was 33.3 kJ mol−1, 2.66kJ mol−1, 88.51kJ mol−1, and 33.26 kJ mol−1. The result of XM pyrolysis was 51.29 kJ mol−1, 6.84 kJ mol−1, 47.38 kJ mol−1, and 15.65 kJ mol−1. Calculations of XM pyrolysis were 51.35 kJ mol−1, 5.11 kJ mol−1, and 117.49 kJ mol−1, 31.15 kJ mol−1 respectively.
Geometric measurement and characterization of a microchannel heat exchanger for performance validation
Authors: Yih James , Wang Hailei
Published: August 2020

With substantial size and performance advantages, microchannel heat exchangers have been attracting increasing attention for various energy recovery and conversion processes. While much research and recent studies focus on their applications and performance, few studies have been devoted to the measurement and dimensional accuracy of actual microchannels in use. In this study, in-depth geometric characterization of a microchannel heat exchanger manufactured using standard photochemical etching and diffusion bonding processes is carried out. The measured channel dimensions are then compared with the design values, which can help better interpret experiment data of the heat exchanger for model validation. Two nondestructive methods were developed to measure cross-sectional areas and perimeters of the microchannels. The first method uses a stereoscopic microscope to take images of the exhaust channels at one end of the microchannel heat exchanger. An image processing routine was developed in MATLAB to measure the exhaust channel dimensions. For the second method, an optical profilometer was used to scan both the exhaust and oil channels from sample shims. Two additional MATLAB routines were developed to process the obtained 3D shim images with the capability of accounting for the bow in the shims. As results, both methods have close agreement on the measured channel dimensions. On average, the cross-sectional areas of the exhaust channels vary more significantly between individual shims due to the nature of the batch photochemical etching process; and the produced exhaust and oil channels are 11% and 8% smaller than the design values. These findings help explain the emerged discrepancy between modeling and experimental data.
Anaemia and physical and mental health in the very old: An individual participant data meta-analysis of four longitudinal studies of ageing
Authors: Palapar Leah , Kerse Ngaire , Rolleston Anna , den Elzen Wendy P J , Gussekloo Jacobijn , Blom Jeanet W , Robinson Louise , Martin-Ruiz Carmen , Duncan Rachel , Arai Yasumichi , Takayama Midori , Teh Ruth ,   for the TULIP Consortium
Published: August 2020

Objective

To determine the physical and mental health of very old people (aged 80+) with anaemia.

Methods

Individual level meta-analysis from five cohorts of octogenarians (n = 2,392): LiLACS NZ Māori, LiLACS NZ non-Māori, Leiden 85-plus Study, Newcastle 85+ Study, and TOOTH. Mixed models of change in functional ability, cognitive function, depressive symptoms, and self-rated health over time were separately fitted for each cohort. We combined individual cohort estimates of differences according to the presence of anaemia at baseline, adjusting for age at entry, sex, and time elapsed. Combined estimates are presented as differences in standard deviation units (i.e. standardised mean differences–SMDs).

Results

The combined prevalence of anaemia was 30.2%. Throughout follow-up, participants with anaemia, on average, had: worse functional ability (SMD −0.42 of a standard deviation across cohorts; CI -0.59,-0.25); worse cognitive scores (SMD -0.27; CI -0.39,-0.15); worse depression scores (SMD -0.20; CI -0.31,-0.08); and lower ratings of their own health (SMD -0.36; CI -0.47,-0.25). Differential rates of change observed were: larger declines in functional ability for those with anaemia (SMD −0.12 over five years; CI -0.21,-0.03) and smaller mean difference in depression scores over time between those with and without anaemia (SMD 0.18 over five years; CI 0.05,0.30).

Conclusion

Anaemia in the very old is a common condition associated with worse functional ability, cognitive function, depressive symptoms, and self-rated health, and a more rapid decline in functional ability over time. The question remains as to whether anaemia itself contributes to worse outcomes or is simply a marker of chronic diseases and nutrient deficiencies.
Care Experience and Friendship: Theory and International Evidence to Improve Practice and Future Research
Authors: Roesch-Marsh Autumn , Emond Ruth
Published: August 2020

Drawing on a review of recent international literature, this article argues for the first time that an understanding of, and engagement with, the theory and practice of friendship is essential to working alongside those who have care experience. Drawing on theory from philosophy, psychology and sociology, the care system is explored as a unique and challenging context for making and keeping the reciprocal, caring friendships which research suggests are important for a ‘happy, healthy life’. Our analysis shows how theories of friendship have failed to consider the friendship experiences of those in the care system. We suggest that including these experiences offers new opportunities to develop theory and practice in the field of friendship. We argue that friendship is an essential human need and, as such, should be placed centrally in assessment and intervention work, encouraging social workers to support positive and enduring friendships for the people they work with.
Why Contact Tracing Efforts Have Failed to Curb Coronavirus Disease 2019 (COVID-19) Transmission in Much of the United States
Authors: Clark Eva , Chiao Elizabeth Y , Amirian E Susan
Published: August 2020

By late April 2020, public discourse in the United States had shifted toward the idea of using more targeted case-based mitigation tactics (eg, contact tracing) to combat coronavirus disease 2019 (COVID-19) transmission while allowing for the safe “reopening” of society, in an effort to reduce the social, economic, and political ramifications associated with stricter approaches. Expanded tracing-testing efforts were touted as a key solution that would allow for a precision approach, thus preventing economies from having to shut down again. However, it is now clear that many regions of the United States were unable to mount robust enough testing-tracing programs to prevent major resurgences of disease. This viewpoint offers a discussion of why testing-tracing efforts failed to sufficiently mitigate COVID-19 across much of the nation, with the hope that such deliberation will help the US public health community better plan for the future.