Strong Density Research Articles

Impacts of run‐of‐river hydropower on coho salmon (Oncorhynchus kisutch): the role of density‐dependent survival

AbstractPredicting whether anthropogenic sources of mortality have negative consequences at the level of population dynamics is challenged by mechanisms like density‐dependent survival that can amplify or offset the loss of individuals from anthropogenic disturbances. Run‐of‐river (RoR) hydropower is a growing industry that can cause frequent mortality of salmonid fry through rapid reductions in streamflow, leading to stranding on dewatered shores. However, whether individual‐level impacts reduce population growth rates or increase local extinction risk is difficult to predict. We used a stochastic stage‐structured matrix model to evaluate how the timing and magnitude of anthropogenic flow fluctuations impacted population abundance and extinction risk of coho salmon (Oncorhynchus kisutch), which spend up to 1.5 yr in many streams regulated by RoR hydropower. We additionally assessed how the timing (spring, winter) and strength (weak, moderate, high) of natural density‐dependent bottlenecks experienced by salmon in freshwaters tempers or amplifies the potential for RoR‐induced mortality to scale to emergent population dynamics. We compared population sizes and the 45‐yr probability of quasi‐extinction under 12 scenarios that varied the frequency (0–20 events per year) and magnitude (1–10% mortality per event) of RoR‐induced flow fluctuations, as well as the timing and strength of density‐dependent bottlenecks occurring during the first year in freshwater. We found that even mild flow fluctuations by RoR hydropower can impact coho salmon population dynamics, especially if density dependence is weak or occurs early in freshwater residency (spring). When density dependence was strong and during winter, the potential for population‐level impact was lessened, but populations still declined by 13–42% when RoR‐induced mortality was severe (5–10%) or frequent (10–20 events/yr). We conclude that strong density‐dependent survival bottlenecks could partially mitigate the loss of fry from anthropogenic flow fluctuations, especially if bottlenecks occur late in freshwater residency, but not for all intensities of flow fluctuations. Even with strong density dependence in winter, our models predict declining populations by up to 70% under strong and very frequent flow fluctuations, which should serve to caution those tasked with regulating flows in streams affected by RoR hydropower.

Properties of Skyrme force as a residual interaction in beyond-mean-field theories

Abstract In an effort to find an effective interaction that can consistently be used for both the mean-field part and the residual part in beyond-mean-field theories, the properties of the Skyrme interactions as a residual interaction are investigated. The time-dependent density-matrix theory (TDDM) is used as a beyond-mean-field theory and the ground states of $^{16}$O and $^{40}$Ca are calculated using the five standard parametrizations of the Skyrme interaction, which differ in density and momentum dependence. It is found that the Skyrme interaction, which has strong density dependence and weak momentum dependence, induces substantial ground-state correlations comparable to the results of other theoretical calculations.

Comparison of Terrestrial Gravity and EGM 2008 Data on Extracted Lineaments: A Case Study of the Adamawa Massif, North Cameroon

A structural study on the Adamawa Massif highlights the major structures (faults) of the shear zone as well as the igneous intrusion near Mayo Baleo. Through this study, a comparison on the use of gravity data from the EGM 2008 and terrestrial models was carried out on the basis of gridded gradient data obtained by applying the MAGMAP filtering algorithm on the Oasis Montaj software system. Using the gradients has an advantage in that they contain much information especially on geological structures. The resulting maxima have strong density contrasts, enabling them to be used as tools in explaining geological contacts. Gravimetric lineaments marked by the geometry of the peaks (elongated shape) and the igneous intrusion corresponding to the circular peak were detected on the horizontal gradient maps. Reconciliation with the geology, the slope map and satellite images justifies the presence of the Djohong-Ngaoundal-Dir-Tibati, Tibati-Banyo and Tignere-Banyo lineaments which indicate the underlying Foumban (extension), Tibati and Tchollire-Banyo faults respectively, comprising the shear system residing in the massif underlain by a gneiss-migmatite bedrock. The limitation on the use of gravity data from the EGM 2008 model is manifested through the Djohong lineament correlating with the large mylonitized feature trending NE-SW, defined as a steep relief (27° to 60°), separating the Mbere basin from the upper unit with about 358 m in height difference. This terrain is a small area of relief with morphological units adapted as in the case of the mountainous areas of the West to the use of gravity data from the EGM2008. The other lineaments that are part of the shear zone fault system are not elucidated because they correspond to deep mega structures that the EGM 2008 model resolution cannot attain at depth. The use of this model is suitable for studies of superficial structures which are associated with huge formations such as the volcanic dome of Mayo Baleo, an intrusion of young trachytes with steep slopes (27° to 60°) at an altitude of 2419 m.

Hydrodynamics and mixing mechanisms in a subtropical reservoir

ABSTRACT With the aim to improve current knowledge on physical processes in tropical and subtropical reservoirs, we explored the dynamics of prevailing hydrodynamic processes in a small- to medium-sized reservoir based on 1-year continuous measurements of temperature, flow velocity, and turbulence. The mixing regime of the reservoir is characterized as warm polymictic, and extended periods of comparably strong density stratification were observed during all seasons, interrupted by several mixing periods between autumn and winter. The stratification was affected by lateral, density-driven flows from the main river inflow. A forebay through which the river enters the reservoir influenced the density currents and reduced the occurrence of underflows. Flow velocities in the middle of the reservoir were generally small, and higher velocities (currents >3.5 cm s−1) were driven by wind. These currents were more frequent during stratified than during mixed periods. No basin-scale internal waves (seiches) were observed, but, high-frequency internal waves propagating, with periods between 2 and 17 min were present in all seasons. Dissipation rates of turbulent kinetic energy were generally small (10−10–10−9 W kg−1). Wind-driven currents were associated with enhanced dissipation rates at the bottom-boundary layer but represented only 10% of the total monitored period. We identified several aspects in which the observed hydrodynamics of the reservoir differed from those of more commonly studied temperate aquatic systems. We expect that our findings are representative for a large number of small- to medium-sized lakes and for a growing number of reservoirs located in the tropical and subtropical zone.

TEN YEARS OF JURNAL AKUNTANSI DAN KEUANGAN INDONESIA: A BIBLIOMETRIC STUDY

This study aims to map articles in the Jurnal Akuntansi dan Keuangan Indonesia (JAKI) published by the Faculty of Economics and Business, Universitas Indonesia, for ten years (2011 to 2020). This study deployed a bibliometric analysis as an investigative method. The data were analyzed with R biblioshiny analytical framework. The findings revealed that JAKI was considerably consistent in publishing articles every period. JAKI publishes six articles each number and two publication numbers annually. In particular, there were 120 articles gained from 2011 to 2020. Based on the analysed articles, the most frequently emerging word from unigrams was ‘study’ and ‘earnings management’ from bigrams. Additionally, the most popular topics during those years (2011 to 2020) were 'income', 'risk', 'slack', 'foreign', and 'direct.’ Moreover, the most closely related words to other words encompassed ‘study’, ‘result’, and ‘research.’ Further, the words ‘study', 'result', and 'effect' represented a strong density and centrality of words. Therefore, they should be cultivated.

UJI KUAT TEKAN DAYA SERAP AIR DAN MASSA JENIS BATU BATA MERAH BERBAHAN TAMBAHAN ABU KULIT DAN JANGGEL JAGUNG DI WULUHAN JEMBER

The increase in Indonesia's development activities increases people's consumption of more quality construction materials and is easy to reach in terms of price. Building materials with good quality can improve the quality of building construction. The increasing need of the community for building materials triggered the development of the brick-making industry. Redbrick is an element of building used in building construction made from clay base material with or without other mixed materials. This research is a type of experimental research. The purpose of this study is to know and analyze the composition of the addition of corn bark ash and ash corn cob appropriately to produce the quality of bricks with high compressive strength, low water absorption, and large density. Additional materials in this study in the form of corn bark ash and ash corn cob. The quality of red bricks is seen from three aspects, namely compressive strength, water absorption, and density. The largest compressive strength was obtained in the addition of ash corn cob by 2.5% by 37.2 Kg/Cm2 and the compressive strength of 49.5 Kg/Cm2 on the addition of corn skin ash by 2.5%. Water absorption measurement of all types of red bricks the results of the study showed all the results of water absorption is not eligible sni. The highest density was obtained from a mixture of 2.5% ash corn cob material of 17.5 gr/Cm3. the best composition to produce bricks with strong compressive value and high density and have low water absorption is 2.5% addition of ash corn cob and the addition of 2.5% corn skin ash.
 Keywords: Red bricks, strong press, water absorption, density.

Facile preparation of ultralight porous carbon hollow nanoboxes for electromagnetic wave absorption

Strong absorption, thin thickness, low density and broad band are ideal characteristics of electromagnetic wave absorption (EWA) materials. In this work, ultralight porous carbon hollow nanoboxes (PCHN), which have low density and high specific surface area, are successfully prepared by the vapor deposition and etching process. Excellent EWA performances are achieved in the filler with only 3 wt%. A minimum reflection loss (RLmin)value of −30.46 dB (2.2 mm) along with an efficient absorption bandwidth (EAB) (RL ≤ −10 dB) of 5.44 GHz is achieved. And the EAB (RL ≤ −20 dB, corresponding to 99% absorption) can be tuned in the frequency band of 4.88–17.04 GHz via adjusting the thickness from 6.0 to 1.9 mm. The excellent EWA performance is attributed to conduction loss, interfacial polarization, and good impedance matching. Moreover, the adjacent carbon micro-sheets can provide multiple positions for EW reflection, which prolongs the propagation paths of EW and is conducive to the consumption of EW energy. The light weight, broad band and superior RLmin value make the as-prepared PCHN promising candidates for practical EWA applications.

One-dimensional planar topological laser

Abstract Topological interface states are formed when two photonic crystals with overlapping band gaps are brought into contact. In this work, we show a planar binary structure with such an interface state in the visible spectral region. Furthermore, we incorporate a thin layer of an active organic material into the structure, providing gain under optical excitation. We observe a transition from fluorescence to lasing under sufficiently strong pump energy density. These results are the first realization of a planar topological laser, based on a topological interface state instead of a cavity like most of other laser devices. We show that the topological nature of the resonance leads to a so-called “topological protection”, i.e. stability against layer thickness variations as long as inversion symmetry is preserved: even for large changes in thickness of layers next to the interface, the resonant state remains relatively stable, enabling design flexibility superior to conventional planar microcavity devices.

Conditions for Justifying Single-fluid Approximation for Charged and Neutral Dust Fluids and a Smoothed Particle Magnetohydrodynamics Method for Dust–Gas Mixture

Abstract We describe a numerical scheme for magnetohydrodynamics simulations of dust–gas mixture by extending smoothed particle magnetohydrodynamics. We employ the single-species particle approach to describe dust–gas mixture with several modifications from the previous studies. We assume that the charged and neutral dust can be treated as single-fluid, that the electromagnetic force acts on the gas, and that that acting on the charged dust is negligible. The validity of these assumptions in the context of protostar formation is not obvious and is extensively evaluated. By investigating the electromagnetic force and electric current with terminal velocity approximation, it is found that as the dust size increases, the contribution of dust to them becomes smaller and negligible. We conclude that our assumption that the electromagnetic force on the dusts is negligible is valid for the dust size with a d ≳ 10 μm. On the other hand, they do not produce the numerical artifact for the dust a d ≲ 10 μm in the envelope and disk, where the perfect coupling between gas and dust is realized. However, we also found that our assumptions may break down in outflow (or under an environment with very strong magnetic field and low density) for the dust a d ≲ 10 μm. We conclude that our assumptions are valid in almost all cases where macroscopic dust dynamics is important in the context of protostar formation. We conduct numerical tests of dusty waves, dusty magnetohydrodynamics shocks, and gravitational collapse of magnetized cloud cores with our simulation code. The results show that our numerical scheme well reproduces the dust dynamics in the magnetized medium.

Phase contrast imaging measurements and numerical simulations of turbulent density fluctuations in gas-fuelled ECRH discharges in Wendelstein 7-X

The fundamental nature of turbulent density fluctuations in standard Wendelstein 7-X (W7-X) stellarator discharges is investigated experimentally via phase contrast imaging (PCI) in combination with gyrokinetic simulations with the code GENE. We find that density fluctuations are ion-temperature-gradient-driven and radially localised in the outer half of the plasma. It is shown that the line-integrated PCI measurements cover the right range of wavenumbers and a favourable toroidal and poloidal location to capture some of the strongest density fluctuations in W7-X. Due to the radial localisation of fluctuations, measured wavenumber–frequency spectra exhibit a dominant phase velocity, which can be related to the$\boldsymbol {E\times B}$rotation velocity at the radial position of a well in the neoclassical radial electric field. The match is robust against variations of heating power and line-integrated density, which is partly due to the localisation of fluctuations and partly due to effects of the radial gradient in the$\boldsymbol {E\times B}$velocity profile on the wavenumber–frequency spectrum. The latter effect is studied with a newly built synthetic PCI diagnostic and global gyrokinetic simulations with GENE-3D.

A cost-efficient low-weight autonomous profiler for measurements in polar coastal waters and other regions with strong density gradients

The rapid warming of our planet has resulted in accelerated melting of ice in polar regions. Currently we have limited knowledge on how, where and when the surface meltwater layer is mixed with the underlying ocean due to lack of observations in these remote areas. We present a lightweight (17 kg) and low-cost (6000€) instrument for autonomous profiling across the strongly stratified upper layer in Arctic coastal waters, freshened by the riverine input and meltwater from glaciers, icebergs, and sea ice. The profiler uses a specially designed plunger buoyancy engine to displace up to 700 cm3 of water and allows for autonomous dives to 200 m depth. It can carry different sensor packages and convey its location by satellite communication. Two modes are available: (a) a free-floating mode and (b) a moored mode, where the instrument is anchored to the seafloor. In both modes, the profiler controls its velocity of 12 ± 0.3 cm/s resulting in 510 ± 22 data points per 100 m depth. Equipped with several sensors, e.g. conductivity, temperature, oxygen, and pressure, the autonomous profiler was successfully tested in a remote Northeast Greenlandic fjord. Data has been compared to traditional CTD instrument casts performed nearby.

Lipid-dense and pre-functionalized post-hydrolysis spent coffee grounds as raw material for the production of fatty acid methyl ester

In this study, lipid-dense post-hydrolysis spent coffee grounds (PHSCG), containing ~23 wt% lipid, was utilized as feedstock in the production of fatty acid methyl esters (FAME) via in-situ (trans)esterification (ISTE). The collected PHSCG were pre-functionalized (~0.86 mmol H+/g dried, lipid-free PHSCG) after sufficient drying of wet residues obtained from the dilute acid hydrolysis (DAH) of spent coffee grounds (SCG). Taguchi method and regression analysis were adopted in the optimization of the ISTE, with temperature, solvent-to-solid ratio (SSR), and reaction time, as the main factors investigated. An optimum yield of 19.47 ± 2.44 g FAME/100 g PHSCG, corresponding to ~96% conversion, could be achieved during ISTE in a batch reactor system. The ISTE of lipids in PHSCG were carried out without catalyst addition due to the inherent catalytic activity of the pre-functionalized PHSCG. Elemental and FT-IR analyses were conducted to determine the extent of the functionalization. The strong acid density of the material increased 21.5 times upon sufficient drying after DAH. Although, some of the functionalized material were solubilized during ISTE, the post-ISTE residue still had significant a strong acid site, 2.47 times of the native SCG, and exhibited appreciable activity when used as solid acid catalyst for the esterification of oleic acid and methanol while having good stability. The DAH and subsequent drying to induce simultaneous carbonization and sulfonation, may be adopted as a means of generating raw materials for biodiesel production from lipid-containing lignocellulosic residues like SCG.

Field‐Aligned Currents Originating From the Chaotic Motion of Electrons in the Tilted Current Sheet: MMS Observations

AbstractField‐aligned currents often appear at the neutral sheet in the tilted current sheet, however, their origins are still unclear. Here we investigate two flapping motion events using the Magnetospheric Multiscale mission data. Strong current densities mainly contributed by electrons appear near the neutral sheet in the severely titled current sheet in both events. The perpendicular current can be explained by the electron drift motions, among which the diamagnetic drift is the main contributor. We find that electrons can be non‐adiabatic at the neutral sheet, which is able to scatter their pitch angle distribution. The field‐aligned current is associated with non‐adiabatic electrons in the energy range of ∼0.2–3 keV, which curvature parameter κ is in the range of 0.9–3. By contrast, adiabatic electrons have almost no contribution to the field‐aligned current. We suggest that non‐adiabatic electrons are the key factor in generating field‐aligned currents at the neutral sheet.

Suppressing passivation layer of Al anode in aqueous electrolytes by complexation of H2PO4− to Al3+ and an electrochromic Al ion battery

Aqueous aluminum ion batteries (AIBs) are attractive alternatives for post-lithium energy storage systems. However, the short lifespan seriously limits the development of AIBs, arising from the formation of a passivation layer on the Al electrode surface as well as the strong electrostatic interaction between bulky Al3+ ions and host materials. Herein, we developed a hybrid electrolyte based on aluminum trifluoromethanesulphonate (Al(TOF)3) and H3PO4 which can effectively alleviate the passivation and exhibit superior stability. A full aqueous AIB based on this electrolyte and polyaniline (PANI) cathode exhibits a record-breaking lifespan of 3850 cycles and superior rate capability. Mechanism study suggests that Al3+ ions are bonded to both the H2PO4− and TOF− to form complex ions Al(H2PO4−)x(TOF−)y+(H2O)n, which can mitigate the strong charge densities of trivalent Al3+ and contribute to fast reaction kinetics. Besides, the ex-situ study reveals that PANI cathode experiences a co-intercalation/deintercalation process of Al(H2PO4−)x(TOF−)y+(H2O)n, TOF−, and H+ during the charging/discharging process with high reversibility and stability. As a proof of concept, an electrochromic Al//PANI battery is fabricated, which combines both electrochromism and energy storage and delivers a higher coloration efficiency of 84 cm2C−1 at a wavelength of 630 nm. This work presents an effective and facile strategy to developing long-life aqueous Al//PANI batteries and may promote the application of AIBs with electrochromic function.

The superconducting transition temperature for P-doped hydrogenated penta-graphene

In this paper, we theoretically study superconductivity in hydrogenated penta-graphene (HPG). HPG has thermodynamical, mechanical and structural stability. By decreasing the Fermi energy of HPG, both manually and p-doping, we get strong density of states at the Fermi level. Therefore, one could expect that decreasing the Fermi energy may increase the superconducting transition temperature similar to graphane. We predict the superconducting transition temperature about 90 K for B-doped HPG. This high superconducting transition temperature suggests that p-doped HPG could be a decent candidate for a nanoscale superconductor.

Synthesis of Oil Palm Empty Fruit Bunch Derived Magnetic Solid Acid Catalyst for Levulinate Production

Ethyl levulinate is widely known as a fuel additive, flavour, and fragrance components. In this study, the biomass-derived magnetic catalyst was synthesised, and its efficiency was evaluated in the esterification reaction. Oil palm empty fruit bunch (EFB) was used in the preparation of the solid magnetic catalyst. The synthesised catalyst was analysed by scanning electron microscope (SEM), electron dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) analyses, and acidic test. The magnetisation value of 24.97 emu/g for EFB fiber-MAC was reported that the catalyst has excellent magnetic properties and a strong acid density of 2.4 mmol/g. The catalytic performance was evaluated via the esterification of levulinic acid. The highest ethyl levulinate conversion of 66.78 mol% and yield of 84.87 mol% were recorded corresponding to 10 wt% catalyst loading and 10:1 ethanol to levulinic acid molar ratio with reaction temperature of 70 °C for 5 h. FTIR and GC-FID analysis confirmed the appearance of the ester group after the esterification reaction. Finally, the magnetically separable catalyst can be easily separated, and it shows a potential solution to the utilisation of heterogeneous catalysts in the esterification reaction.

An Unexpected Whistler Wave Generation Around Dipolarization Front

AbstractDipolarization front (DF)—a sharp boundary separating hot tenuous plasmas from cold dense plasmas—is followed by a strong Bz region, which is termed flux pileup region (FPR) or dipolarizing flux bundle (DFB). Using 9‐year (2001–2009) Cluster data, we show that the FPR hosts whistler waves because of the pancake distribution of electrons, whereas the DF boundary hosts lower hybrid drift waves due to the strong density and magnetic gradients statistically. Different from statistical results, we report an unexpected case: whistler waves are generated at the DF boundary rather than inside the FPR. Using Cluster data, we observed strong whistler waves at DF boundaries but no whistlers inside FPRs, although flux tubes inside the FPRs are significantly compressed and suprathermal electrons there are perpendicularly anisotropic. We calculate wave growth rates and successfully explain the generation/damping of these whistlers. We find that 1–4 keV electrons are responsible for generation/damping of these whistlers.

Coupling a Mobile Hole to an Antiferromagnetic Spin Background: Transient Dynamics of a Magnetic Polaron

Understanding the interplay between charge and spin and its effects on transport is a ubiquitous challenge in quantum many-body systems. In the Fermi-Hubbard model, this interplay is thought to give rise to magnetic polarons, whose dynamics may explain emergent properties of quantum materials such as high-temperature superconductivity. In this work, we use a cold-atom quantum simulator to directly observe the formation dynamics and subsequent spreading of individual magnetic polarons. Measuring the density- and spin-resolved evolution of a single hole in a 2D Hubbard insulator with short-range antiferromagnetic correlations reveals fast initial delocalization and a dressing of the spin background, indicating polaron formation. At long times, we find that dynamics are slowed down by the spin exchange time, and they are compatible with a polaronic model with strong density and spin coupling. Our work enables the study of out-of-equilibrium emergent phenomena in the Fermi-Hubbard model, one dopant at a time.

Finite-size scaling analysis of localization transitions in the disordered two-dimensional Bose-Hubbard model within the fluctuation operator expansion method

The disordered Bose-Hubbard model in two dimensions at non-integer filling admits a superfluid to Bose-glass transition at weak disorder. Less understood are the properties of this system at strong disorder and energy densities corresponding to excited states. In this work we study the Bose-glass transition of the ground state and the related finite energy localization transition, the mobility edge of the quasiparticle spectrum, a critical energy separating extended from localized quasiparticle excitations. To study these the fluctuation operator expansion is used. The level spacing statistics of the quasiparticle excitations, the fractal dimension and decay of the corresponding wave functions are consistent with a many-body mobility edge. The finite-size scaling of the lowest gaps yields a correction to the mean-field prediction of the superfluid to Bose-glass transition. In its vicinity we discuss spectral properties of the ground state in terms of the dynamic structure factor and the spectral function which also shows distinct behavior above and below the mobility edge.

Evidence of Alfvenic Poynting Flux as the Primary Driver of Auroral Motion During a Geomagnetic Substorm

AbstractGeomagnetic substorms are major energy transfer events where energy stored in the Earth's magnetotail is released into the ionosphere. Substorm phenomena, including auroral activities, earthward Poynting flux, magnetic field dipolarization, etc, have been extensively studied. However, the complex interplay among them is not fully understood. In a fortuitous event on June 7, 2013, the twin Van Allen Probes (separated by 0.4 h in local time) observed bursts of earthward Alfvenic Poynting flux in the vicinity of the plasma sheet boundary layer (PSBL). The Poynting flux bursts correlate with enhancements of auroral brightness around the footpoints of both spacecraft. This indicates a temporal and spatial correlation between the auroral brightening and Poynting flux bursts, and that the auroral motion is directly linked to the perpendicular expansion of the Alfven wave. These observations suggest that the Alfvenic Poynting flux is a primary driver for the auroral electron acceleration. Around the time of auroral brightening, a dipolarization was seen to propagate more than 4 h in local time during a 20 min period. The azimuthal phase speed of this dipolarization (2 deg/min) is too small to explain the azimuthal motion of the aurora (13.6 deg/min), but the dipolarization could be related to the generation of the Alfvenic Poynting flux through phase mixing at strong density gradients like those in the PSBL.