Effectiveness and relationship between biased and unbiased measures of dopamine release and clearance

Fast-scan cyclic voltammetry (FSCV) is an effective tool for measuring dopamine (DA) release and clearance throughout the brain, including the ventral and dorsal striatum. Striatal DA terminals are abundant with signals heavily regulated by release machinery and the dopamine transporter (DAT). Peak height is a common method for measuring release but can be affected by changes in clearance. The Michaelis-Menten model has been a standard in measuring DA clearance, but requires experimenter fitted modeling subject to experimenter bias. The current study presents the use of the first derivative (velocity) of evoked DA signals as an alternative approach for measuring dopamine release and clearance and can be used to distinguish the two measures. Maximal upwards velocity predicts reductions in DA peak height due to D2 and GABAB receptor stimulation and by alterations in calcium concentrations. The Michaelis-Menten maximal velocity (Vmax) measure, an approximation for DAT numbers, predicted maximal downward velocity in slices and in vivo. Dopamine peak height and upward velocity were similar between wildtype C57 (WT) and DAT knock out (DATKO) mice. In contrast, downward velocity was considerably reduced and exponential decay (tau) was increased in DATKO mice, supporting use of both measures for changes in DAT activity. In slices, the competitive DAT inhibitors cocaine, PTT and WF23 increased peak height and upward velocity differentially across increasing concentrations, with PTT and cocaine reducing these measures at high concentrations. Downward velocity and tau values decreased and increased respectively across concentrations, with greater potency and efficacy observed with WF23 and PTT. In vivo recordings demonstrated similar effects of WF23 and PTT on measures of release and clearance. Tau was a more sensitive measure at low concentrations, supporting its use as a surrogate for the Michaelis-Menten measure of apparent affinity (Km). Together, these results inform on the use of these measures for DA release and clearance.

Drilling mud upward velocity modelling in Ansys CFX software

Drilling mud has various functions, one of which is to carry cuttings to the surface. All other things being equal, the removal of cuttings is characterized by the upward velocity. This paper simulates the rheology of polymer-glycolic non-dispersing mud (in particular viscosity) to achieve the required upward velocity in the «Ansys CFX» software. The viscosity of the mud varies from 6 to 12 mPa·s, on production casing drilling in Arctic conditions. The results of the study showed that for such conditions, the viscosity should be in the range from 6 to 8 mPa·s.

Flow Characterization Near the Nozzle Exit of the Supersonic Steam Jet Injecting into the Stagnant Water

There has been a large amount of work being conducted on the thermo-dynamics of the Direct Contact Condensation (DCC), however, not much attention was given to the phenomena particularly active near the steam’s nozzle exit. A transparent rectangular upright duct of 4 ft high, was built with a supersonic nozzle positioned at the bottom of the channel to characterize flow behavior near the steam nozzle’s exit. Particle image velocimetry (PIV) was applied to draw information on the steam’s jet penetration into the water as well as the entrainment and mixing between the two phases under the steam’s inlet pressure ranging from 1.5 – 3.0 bars. PIV normalized contour measurements depicted not appreciable changes in the radial velocity of the jet. Whereas, in the core region of the jet, the change in the jet’s velocity was not much till Y/De ~ 4.3 and the vertical velocity of the jet decreased slowly till Y/De ~ 8. The jet’s normalized upward velocity attained an optimized value between Y/De ~ 8 and Y/De ~ 9.8. With varying pressures, 1.5 bars to 3.0 bars, the jet expanded radially in water. It was also found in the near nozzle exit region, the shear layer’s thickness remained within 0.2 – 0.5 De over the 1.5 – 3.0 bars pressure. Probability Density Function (PDF) analysis of Reynolds shear and normal stresses confirmed the existence of the velocity fluctuations across the shear layer, owing to the large eddies across the steam-water interface.

Effect of the External Velocity on the Exfoliation Properties of Graphene from Amorphous SiO2 Surface

External action has a significant influence on the formation of high-quality graphene and the adhesion of graphene on the surface of the MEMS/NEMS device. The atomic-scale simulation and calculation can further study the exfoliation process of graphene by external actions. In multilayer graphene systems where graphene layers were simulated weakly contacted with SiO2 substrate, a constant vertical upward velocity (Vup) was applied to the topmost layer. Then two critical velocities were found, and three kinds of distinct exfoliation processes determined by critical upward velocities were observed in multilayer graphene systems. The first critical velocities are in the range of 0.5 Å/ps–3.18 Å/ps, and the second critical velocities are in the range of 9.5 Å/ps–12.1 Å/ps. When the Vup is less than the first critical velocity, all graphene layers will not be exfoliated. When Vup is between the first and second critical Vup, all layers can be exfoliated almost synchronously at last. When Vup is larger than the second critical Vup, the topmost layer can be exfoliated alone, transferring energy to the underlying layers, and the underlying layers are slowly exfoliated. The maximum exfoliation force to exfoliate the topmost layer of graphene is 3200 times larger than that of all graphene layers. Moreover, it is required 149.26 mJ/m2 to get monolayer graphene from multilayers, while peeling off all layers without effort. This study explains the difficulty to get monolayer graphene and why graphene falls off easily during the transfer process.

Arctic observations and numerical simulations of surface wind effects on Multi-Angle Snowflake Camera measurements

Ground-based measurements of frozen precipitation are heavily influenced by interactions of surface winds with gauge-shield geometry. The Multi-Angle Snowflake Camera (MASC), which photographs hydrometeors in free-fall from three different angles while simultaneously measuring their fall speed, has been used in the field at multiple midlatitude and polar locations both with and without wind shielding. Here, we present an analysis of Arctic field observations – with and without a Belfort double Alter shield – and compare the results to computational fluid dynamics (CFD) simulations of the airflow and corresponding particle trajectories around the unshielded MASC. MASC-measured fall speeds compare well with Ka-band Atmospheric Radiation Measurement (ARM) Zenith Radar (KAZR) mean Doppler velocities only when winds are light (≤5ms-1) and the MASC is shielded. MASC-measured fall speeds that do not match KAZR-measured velocities tend to fall below a threshold value that increases approximately linearly with wind speed but is generally <0.5ms-1. For those events with wind speeds ≤1.5ms-1, hydrometeors fall with an orientation angle mode of 12∘ from the horizontal plane, and large, low-density aggregates are as much as 5 times more likely to be observed. Simulations in the absence of a wind shield show a separation of flow at the upstream side of the instrument, with an upward velocity component just above the aperture, which decreases the mean particle fall speed by 55 % (74 %) for a wind speed of 5 m s−1 (10 m s−1). We conclude that accurate MASC observations of the microphysical, orientation, and fall speed characteristics of snow particles require shielding by a double wind fence and restriction of analysis to events where winds are light (≤5ms-1). Hydrometeors do not generally fall in still air, so adjustments to these properties' distributions within natural turbulence remain to be determined.

Effects of Solar Activity on Ionospheric Ion Upflow During Geomagnetic Quiet Periods: DMSP Observations

Based on the Defense Meteorological Satellite Program (DMSP) observations during Solar Cycle 23, this paper examines solar activity dependence of ionospheric bulk ion upflow events (IUEs) in the Southern Hemisphere (SH). Much previous similar work was conducted over the Northern Hemisphere (NH) with measurements from European Incoherent Scatter (EISCAT). To eliminate the influence of geomagnetic disturbance on IUEs, we pick out observations during geomagnetic quiet periods (with Kp ≤ 2+). Results show that, ion upward densities and fluxes are dramatically elevated at times of high solar activity (HSA) but ion upward drifts and occurrences are increased at times of low solar activity (LSA) in the SH, which is consistent with the situation in the NH. The ratios between HSA and LSA for these four parameters (IUEs’ density, flux, upward drift and occurrence) are ~2.71, ~1.98, ~0.76 and ~0.57, respectively. Furthermore, lower flux event takes place frequently at LSA as the background ion density is low but the upward drift is large, while higher flux event happens commonly at times of HSA accompanied by high ion density but low upward velocity. Quantitatively, an increase in unit of solar activity (characterized by P index) causes a 4.2×108 m−3 increase in ion density and a 1.2×1011 m−2·s−1 enhancement in upward flux, together with a 0.6 m·s−1 and 0.02 % decrease in ion upward velocity and uprate, respectively. The acceleration from the ambipolar electric field is thought to be a possible mechanism affecting the dependence of IUEs on solar variations. For HSA, the acceleration from the ambipolar electric field weakens, but a large number of background ions provide abundant seeds for acceleration and upflow, which maintains a high IUE flux. It is inferred that upflow events and upward drifts are inhibited by the enhanced ionospheric background density.

Numerical simulations and Arctic observations of surface wind effects on Multi-Angle Snowflake Camera measurements

Ground-based measurements of frozen precipitation are heavily influenced by interactions of surface winds with gauge-shield geometry. The Multi-Angle Snowflake Camera (MASC), which photographs hydrometeors in free-fall from three different angles while simultaneously measuring their fall speed, has been used in the field at multiple mid-latitude and polar locations both with and without wind shielding. Here we show results of computational fluid dynamics (CFD) simulations of the airflow and corresponding particle trajectories around the unshielded MASC and compare these results to Arctic field observations with and without a Belfort double Alter shield. Simulations in the absence of a wind shield show a separation of flow at the upstream side of the instrument, with an upward velocity component just above the aperture, which decreases the mean particle fall speed by 55 % (74 %) for a wind speed of 5 m s−1 (10 m s−1). MASC-measured fall speeds compare well with Ka-band Atmospheric Radiation Measurement (ARM) Zenith Radar (KAZR) mean Doppler velocities only when winds are light (< 5 m s−1) and the MASC is shielded. MASC-measured fall speeds that do not match KAZR measured velocities tend to fall below a threshold value that increases approximately linearly with wind speed but is generally

Artificial acceleration of the Brewer-Dobson circulation due to stratospheric cooling

&lt;p&gt;There is robust observational evidence that the troposphere is warming and the stratosphere is cooling in response to the radiative forcing of anthropogenic greenhouse gas (GHG) emissions. Temperature changes directly influence the vertical structure of the atmopshere. Numerous studies have analysed the thermal expansion of the troposphere, in particular the tropopause rise and its interaction with the Brewer-Dobson circulation (BDC). Stratospheric cooling, however, reduces the upward shift of pressure levels with increasing altitude so that it reverses sign at some height, leading to a downward shift of the middle to upper stratosphere. This &quot;stratospheric shrinkage&amp;#8220; effect is a strong and robust feature of climate change and it is well documented through observations. Still, literature on this effect is relatively sparse and its impact on stratospheric dynamics is generally neglected.&lt;/p&gt;&lt;p&gt;In this study, we report and quantify the uncertainty in residual upward velocity (w*) trends that arises from the implicit neglection of stratospheric shrinkage in the data model request for the Chemistry-Climate Model Initiative part 1 (CCMI-1). Tropical w* is often taken as a proxy for diagnosing the BDC strength. In the data request, a constant scale height is assumed for conversion of w* from Pa/s to m/s . However, the scale height significantly decreases over time in the climate simulations as a result of stratospheric shrinkage.&lt;/p&gt;&lt;p&gt;We show that stratospheric cooling enhances the w* trends if the unit conversion is made with constant scale height, which can be misinterpreted as BDC acceleration. We quantify this effect to account for around 20% of the w* trend across the 21st century, consistently among the CCMI-1 climate projection simulations. Past studies that based w* trend analyses on these data therefore made a 20% error. Moreover, we call attention that other dynamical diagnostics are affected by the neglection of stratospheric shrinkage too and also the data requests of other multi-model assessments use the constant scale height assumtion for unit conversion in climate change simulations.&lt;/p&gt;

Association of Diurnal Rainfall in Northeastern Tibetan Plateau with the Retreat of the South Asian High

The characteristics of intense diurnal precipitation occurring beneath the South Asian High (SAH) are diagnosed in the summer monsoon season from 2010 to 2015 using observational data. The diagnostics indicate that summer nighttime rainfall events in the northeastern Tibetan Plateau can intensify towards the end of the monsoon period. By defining a transition index to identify the transition day during which the episodes of diurnal convection start to decline, daily thermodynamic properties and precipitation from each year were composited before and after the transition date. The analysis reveals that warmer air, increased moisture, and stronger upward velocity are present in the atmosphere before the transition day, potentially elevating nighttime convective precipitation. Enhanced upward velocity that is present through the two months prior to transition date coincides with the timing of the peak SAH, while weakened upward velocity afterwards coincides with its subsequent retreat. The large-scale lift due to terrain-ambient air interaction underneath the SAH and the increased moisture content can enhance the potential for diurnal convection, which lends support to the nighttime peak of rainfall. This feature persists until the transition date, after which the SAH starts to retreat.