Real-Space Interpretation of Interatomic Charge Transfer and Electron Exchange Effects by Combining Static and Kinetic Potentials and Associated Vector Fields

Intricate behavior of one-electron potentials from the Euler equation for electron density and corresponding gradient force fields in crystals was studied. Bosonic and fermionic quantum potentials were utilized in bonding analysis as descriptors of the localization of electrons and electron pairs. Channels of locally enhanced kinetic potential and the corresponding saddle Lagrange points were found between chemically bonded atoms linked by the bond paths. Superposition of electrostatic φ_es (r) and kinetic φ_k (r) potentials and electron density ρ(r) allowed partitioning any molecules and crystals into atomic ρ- and potential-based φ-basins; the φ_k-basins explicitly account for electron exchange effect, which is missed for φ_es-ones. Phenomena of interatomic charge transfer and related electron exchange were explained in terms of space gaps between ρ- and φ-zero-flux surfaces. The gap between φ_es- and ρ-basins represents the charge transfer, while the gap between φ_k- and ρ-basins is proposed to be a real-space manifestation of sharing the transferred electrons. The position of φ_k-boundary between φ_es- and ρ-ones within an electron occupier atom determines the extent of electron sharing. The stronger an H‧‧‧O hydrogen bond is, the deeper hydrogen atom’s φ_k-basin penetrates oxygen atom’s ρ-basin. For covalent bonds, a φ_k-boundary closely approaches a φ_es-one indicating almost complete sharing the transferred electrons, while for ionic bonds, the same region corresponds to electron pairing within the ρ-basin of an electron occupier atom.

Water and Salt Transports in the Hengsha Channel of Changjiang Estuary

In a multilevel bifurcated estuary, the channels between the bifurcated branches play important roles in the exchanges of water and salt. In the Changjiang Estuary, the Hengsha Channel (HC) connects the North Channel (NC) and the North Passage (NP). In this paper, based on a two-way nesting unstructured quadrilateral grid, finite-differencing, three-dimensional estuarine and coastal ocean model, the tidal and seasonal variations in the water and salt transports in the HC were simulated, and their dynamic mechanism was analyzed. The residual water and salt transports in the HC both flow southward from the NC to the NP. In wet season, the residual water transport in the HC is 677 m3/s during neap tide and 245 m3/s during spring tide, and the residual salt transport is 0. In dry season, the residual water and salt transports in the HC are 1278 m3/s and 0.38 t/s during neap tide, respectively, and 1328 m3/s and 12.61 t/s during spring tide. Affected by the northerly wind and the southeastward baroclinic gradient force, the water and salt fluxes in dry season are much larger than those in wet season. The dynamic mechanism responsible for the water transport in the HC was numerically simulated and analyzed.

Emergence of a nocturnal low-level jet from a broad baroclinic zone

An analytical model is presented for the generation of a Blackadar-like nocturnal low-level jet in a broad baroclinic zone. The flow is forced from below (flat ground) by a surface buoyancy gradient and from above (free atmosphere) by a constant pressure gradient force. Diurnally-varying mixing coefficients are specified to increase abruptly at sunrise and decrease abruptly at sunset. With attention restricted to a surface buoyancy that varies linearly with a horizontal coordinate, the Boussinesq-approximated equations of motion, thermal energy, and mass conservation reduce to a system of one-dimensional equations that can be solved analytically. Sensitivity tests with southerly jets suggest that (i) stronger jets are associated with larger decreases of the eddy viscosity at sunset (as in Blackadar theory), (ii) the nighttime surface buoyancy gradient has little impact on jet strength, and (iii) for pure baroclinic forcing (no free-atmosphere geostrophic wind), the nighttime eddy diffusivity has little impact on jet strength, but the daytime eddy diffusivity is very important and has a larger impact than the daytime eddy viscosity. The model was applied to a jet that developed in fair weather conditions over the Great Plains from southern Texas to northern South Dakota on 1 May 2020. The ECMWF Reanalysis v5 (ERA5) for the afternoon prior to jet formation showed that a broad north-south-oriented baroclinic zone covered much of the region. The peak model-predicted winds were in good agreement with ERA5 winds and lidar data from the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) central facility in north-central Oklahoma.

Meridional temperature gradient and the midlatitude storm track

<p>The southern hemisphere’s atmospheric circulation experiences several annual and seasonal changes that are well documented and studied. The teleconnections between different variables are verified and used to explain variability in everyday climate and weather. Theories using physics are taught and published in textbooks to help us understand the connectivity and complexity of such a system. One theory is the meridional temperature gradient has a direct impact on the storm track. This thesis investigates that theory using the ERA-Interim dataset. The temperature gradient is a direct result of the temperature field, and depending on the latitudes you decide in which to constrain your gradient, the gradient experiences several changes. In the high latitudes, the southern annual oscillation created a two peaked pattern; the mid-latitudes display the expected seasonal mono peak pattern. The strong correlations seen in the high latitudes means that the gradient is driven by the patterns experienced at higher latitudes. The independence of behaviours displayed by the ocean sectors led to the research investigating the influences, looking at not just the hemisphere, but also each basin separately. The Pacific and Indian Ocean showed in several results to act independently from one another, in temperature gradients, wind field, and storm track position. The strong correlations between the temperature gradient and the wind field, as well as the storm track field show that the two are connected, as the theory suggests. If temperatures rise in the tropics, or decrease in the poles, then the temperature gradient will steepen. The pressure gradient force increases which pushes the thermal wind balance poleward, shifting the position of the westerlies. The area with the largest variation in the wind speed becomes the storm track, which would also shift poleward. Climatic factors such as the southern oscillation index, southern annular mode or Indian Ocean dipole show slight correlations with the temperature field, but have little to no influence on the temperature gradient itself. Precipitation levels in New Zealand are highly variable due to the nature of the countries location and topography. What was found was little connection between the northern part of the country and the storm track. However, closer proximity to the storm track, such as the south of the country, do experience a small amount of variation due to the storm tracks influence.</p>

Meridional temperature gradient and the midlatitude storm track

<p>The southern hemisphere’s atmospheric circulation experiences several annual and seasonal changes that are well documented and studied. The teleconnections between different variables are verified and used to explain variability in everyday climate and weather. Theories using physics are taught and published in textbooks to help us understand the connectivity and complexity of such a system. One theory is the meridional temperature gradient has a direct impact on the storm track. This thesis investigates that theory using the ERA-Interim dataset. The temperature gradient is a direct result of the temperature field, and depending on the latitudes you decide in which to constrain your gradient, the gradient experiences several changes. In the high latitudes, the southern annual oscillation created a two peaked pattern; the mid-latitudes display the expected seasonal mono peak pattern. The strong correlations seen in the high latitudes means that the gradient is driven by the patterns experienced at higher latitudes. The independence of behaviours displayed by the ocean sectors led to the research investigating the influences, looking at not just the hemisphere, but also each basin separately. The Pacific and Indian Ocean showed in several results to act independently from one another, in temperature gradients, wind field, and storm track position. The strong correlations between the temperature gradient and the wind field, as well as the storm track field show that the two are connected, as the theory suggests. If temperatures rise in the tropics, or decrease in the poles, then the temperature gradient will steepen. The pressure gradient force increases which pushes the thermal wind balance poleward, shifting the position of the westerlies. The area with the largest variation in the wind speed becomes the storm track, which would also shift poleward. Climatic factors such as the southern oscillation index, southern annular mode or Indian Ocean dipole show slight correlations with the temperature field, but have little to no influence on the temperature gradient itself. Precipitation levels in New Zealand are highly variable due to the nature of the countries location and topography. What was found was little connection between the northern part of the country and the storm track. However, closer proximity to the storm track, such as the south of the country, do experience a small amount of variation due to the storm tracks influence.</p>

Generation Mechanism of Tidally-driven Whirlpools at A Narrow Strait in An Estuary

This study investigates the generation mechanism and influence of the whirlpools in the Naruto Strait on the surrounding marine environment using state-of-the-art high-resolution numerical ocean circulation modeling in a quadruple nested configuration. The Naruto whirlpools is recognized as an extraordinary seascape that the local governments and the citizens seek to register as a world natural heritage site. We found that the pronounced pressure gradient force associated with the meridional surface elevation difference was induced by a phase difference of two bifurcating major tidal waves. These waves originate from the Kitan Strait, and ultimately produce intense tidal currents at the Naruto Strait. One branch of the tidal waves propagates counter-clockwise along Awaji Island through the Akashi Strait, while the other occurs directly from the Kii Channel. As such, the whirlpool emerges as a large number of sub-mesoscale eddies, primarily due to the horizontal shear instability of tidal currents energized at the narrow topography between two headlands that extend into the strait. A dipole of overturning vertical circulations appears underneath the whirlpools with convergent downward transport at the strongest tidal current near the center of the strait; this causes efficient vertical mixing. This three-dimensional non-linear mixing promotes a time-averaged southeastward mass transport that extracts water and materials from the Harima-nada Sea into the Kii Channel.

Recapitulation of First Pass Metabolism Using 3D Printed Microfluidic Chip and Organoid

The low bioavailability of oral drugs due to first pass metabolism is a major obstacle in drug development. With significant developments in the field of in vitro organ modeling and microfluidic chip three-dimensional (3D) printing, the challenge is to apply these for the production and evaluation of new drug candidates. This study aimed to produce a microfluidic chip to recapitulate and assess the feasibility of the first pass metabolism. The infill condition of the polycarbonate transparent filament and layer height was optimized to visualize and maintain the organoid or spheroid on the chip. Next, the chip was fabricated using a 3D printer after a computer-aided design (CAD). The chip consisted of three wells of different heights. The small intestinal (SI) organoid and colorectal adenocarcinoma spheroids were placed on the second and third wells, respectively. No additional equipment was assembled, and the tilted tunnel was connected to each well to transport the material by gradient force. The chip was fabricated using 50% and 0.1 um thickness. Among the three different prototypes of chip (chips 1, 2, and 3), the highest distribution of plasmids in the Matrigel of the second well was observed in Chip 2 at 48 h. The effect of first pass metabolism was analyzed using docetaxel. In the chip without an SI organoid, there was a marked decrease in the viability of colorectal adenocarcinoma spheroids due to drug efficacy. However, in the chip with the SI organoid, no significant change in viability was observed because of first pass metabolism. In conclusion, we presented a simple, fast, and low-cost microfluidic chip to analyze the efficacy change of candidate drug by the first pass metabolism.