Cdc42 GTPase activating proteins Rga4 and Rga6 coordinate septum synthesis and membrane trafficking at the division plane during cytokinesis

Fission yeast cytokinesis is driven by simultaneous septum synthesis, membrane furrowing and actomyosin ring constriction. The septum consists of a primary septum flanked by secondary septa. First, delivery of the glucan synthase Bgs1 and membrane vesicles initiate primary septum synthesis and furrowing. Next, Bgs4 is delivered for secondary septum formation. It is unclear how septum synthesis is coordinated with membrane furrowing. Cdc42 promotes delivery of Bgs1 but not Bgs4. We find that after primary septum initiation, Cdc42 inactivators Rga4 and Rga6 localize to the division site. In rga4Δrga6Δ mutants Cdc42 activity is enhanced during late cytokinesis and cells take longer to separate. Electron micrographs of the division site in these mutants exhibit malformed septum with irregular membrane structures. These mutants have a larger division plane with enhanced Bgs1 delivery but fail to enhance accumulation of Bgs4 and several exocytic proteins. Additionally, these mutants show endocytic defects at the division site. This suggests that Cdc42 regulates only specific membrane trafficking events. Our data indicate that while active Cdc42 promotes primary septum synthesis, as cytokinesis progresses Rga4 and Rga6 localize to the division site to decrease Cdc42 activity. This couples specific membrane trafficking events with septum formation to allow proper septum morphology.

B2.5-Eunomia simulations of Magnum-PSI detachment experiments: II. Collisional processes and their relevance

Detachment is achieved in Magnum-PSI by increasing the neutral background pressure in the target chamber using gas puffing. The plasma is studied using the B2.5 multi fluid plasma code B2.5 coupled with Eunomia, a Monte Carlo solver for neutral species. This study focuses on the effect of increasing neutral background pressure to the plasma volumetric loss of particle, momentum and energy. The plasma particle and energy loss almost linearly scale with the increase of neutral background pressure, while the momentum loss does not scale as strongly. Plasma recombination processes include molecular activated recombination (MAR), dissociative attachment, and atomic recombination. Atomic recombination, which includes radiative and three-body recombination, is the most relevant plasma process in reducing the particle flux and, consequently, the heat flux to the target. The low temperature where atomic recombination becomes dominant is achieved by plasma cooling via elastic H+-H2 collisions. The transport of vibrationally excited H2 molecules out of the plasma serves as an additional electron cooling channel with relatively small contribution. Additionally, the transport of highly vibrational H2 has a significant impact in reducing the effective MAR and dissociative attachment collision rates and should be considered properly. The relevancy of MAR and atomic recombination occupy separate electron temperature regimes, respectively, at Te = 1.5 eV and Te = 0.3 eV, with dissociative attachment being relevant in the intermediary. Plasma cooling via elastic H+-H2 collisions is effective at Te ≤ 1 eV.

The Design of the Emission Layer for Electron Multipliers

The electron multipliers gain is closely related to the secondary electron emission coefficient (SEE) of the emission layer materials. The SEE is closely related to the thickness of the emission layer. If the emission layer is thin, the low SEE causes the low gain of electron multipliers. If the emission layer is thick, the conductive layer can't timely supplement charge to the emission layer, the electronic amplifier gain is low too. The electron multipliers usually choose Al2O3 and MgO film as the emission layer because of the high SEE level. MgO easy deliquescence into Mg(OH)2 Mg2(OH)2CO3 and MgCO3 resulting in the lower SEE level. The SEE level of Al2O3 is lower than MgO, but Al2O3 is stable. We designed a spherical system for testing the SEE level of materials, and proposed to use low-energy secondary electrons instead of low-energy electron beam for neutralization to measuring the SEE level of Al2O3, MgO, MgO/Al2O3, Al2O3/MgO, and precisely control the film thickness by using atomic layer deposition. We propose to compare the SEE under the adjacent incident electrons energy to partition the SEE value of the material, and obtain four empirical formulas for the relationship between SEE and thickness. Since the main materials that cause the decrease in SEE are Mg2(OH)2CO3 and MgCO3, we use the C element atomic concentration measured by XPS to study the deliquescent depth of the material. We propose to use the concept of transition layer for SEE interpretation of multilayer materials. Through experiments and calculations, we put forward a new emission layer for electron multipliers, including 2–3 nm Al2O3 buffer layer, 5–9 nm MgO main-body layer, 1 nm Al2O3 protective layer or 0.3 nm Al2O3 enhancement layer. We prepared this emission layer to microchannel plate (MCP), which significantly improved the gain of MCP. We can also apply this new emission layer to channel electron multiplier and separate electron multiplier.

The Design of the Emission Layer for Electron Multipliers

The electron multipliers gain is closely related to the secondary electron emission coefficient (SEE) of the emission layer materials. The SEE is closely related to the thickness of the emission layer. If the emission layer is thin, the low SEE causes the low gain of electron multipliers. If the emission layer is thick, the conductive layer can't timely supplement charge to the emission layer, the electronic amplifier gain is low too. The electron multipliers usually choose Al2O3 and MgO film as the emission layer because of the high SEE level. MgO easy deliquescence into Mg(OH)2 resulting in the lower SEE level. The SEE level of Al2O3 is lower than MgO, but Al2O3 is stable. We designed a spherical system for testing the SEE level of materials, and proposed to use lowenergy secondary electrons instead of low-energy electron beam for neutralization to measuring the SEE level of Al2O3, MgO, MgO/Al2O3, Al2O3/MgO, and precisely control the film thickness by using atomic layer deposition (ALD). We propose to compare the SEE under the adjacent incident electrons energy to partition the SEE value of the material, and obtain four empirical formula for the relationship between SEE and thickness. Through experiments and calculations, we put forward a new emission layer for electron multipliers, including 2~3 nm Al2O3 buffer layer, 9nm MgO main-body layer, 1nm protective layer or 0.3nm enhancement layer. We can apply this new emission layer to channel electron multiplier (CEM), microchannel plate (MCP), separate electron multiplier.

Ultrafast nonequilibrium dynamic process of separate electron and hole during exciton formation in few-layer tungsten disulfide

Femtosecond transient absorption spectroscopy has been employed to unravel separate initial nonequilibrium dynamic process of photo-injected electrons and holes during the formation process of the lowest excitons at the K-valley...

Electron mirror branch: observational evidence from “historical” AMPTE-IRM and Equator-S measurements

Based on now “historical” magnetic observations, supported by few available plasma data, and wave spectra from the AMPTE-IRM spacecraft, and also on “historical” Equator-S high-cadence magnetic field observations of mirror modes in the magnetosheath near the dayside magnetopause, we present observational evidence for a recent theoretical evaluation by Noreen et al. (2017) of the contribution of a global (bulk) electron temperature anisotropy to the evolution of mirror modes, giving rise to a separate electron mirror branch. We also refer to related low-frequency lion roars (whistlers) excited by the trapped resonant electron component in the high-temperature anisotropic collisionless plasma of the magnetosheath. These old data most probably indicate that signatures of the anisotropic electron effect on mirror modes had indeed already been observed long ago in magnetic and wave data, though they had not been recognised as such. Unfortunately either poor time resolution or complete lack of plasma data would have inhibited the confirmation of the required pressure balance in the electron branch for unambiguous confirmation of a separate electron mirror mode. If confirmed by future high-resolution observations (like those provided by the MMS mission), in both cases the large mirror mode amplitudes suggest that mirror modes escape quasilinear saturation, being in a state of weak kinetic plasma turbulence. As a side product, this casts as erroneous the frequent claim that the excitation of lion roars (whistlers) would eventually saturate the mirror instability by depleting the bulk temperature anisotropy. Whistlers, excited in mirror modes, just flatten the anisotropy of the small population of resonant electrons responsible for them, without having any effect on the global electron-pressure anisotropy, which causes the electron branch and by no means at all on the ion-mirror instability. For the confirmation of both the electron mirror branch and its responsibility for trapping of electrons and resonantly exciting high-frequency whistlers, also known as lion roars, high time- and energy-resolution observations of electrons (as provided for instance by MMS) are required.

The Study of Photocatalytic Oxidation of Benzyl Alcohol with g-C3N4 under Visible Light: Effect of pH and Salt

Carbon nitride is a representative metal-free photocatalyst for green chemical technology. In this study, synthesized g-C3N4 carbon nitride was employed to study effect of pH and potassium salt loading on photocatalytic oxidation of benzyl alcohol. The result indicated that the maximum conversion could be achieved to 20.75% at a pH of 8.66 with a concentration of K2HPO4 of 0.6 mmol Suitable pH and salt concentration were important factor for promoting of proton on surface and electronic conductivity to separate electron in photocatalysis.

The photoelectric characteristics of a few-layer graphene/Si Schottky junction solar cell

We present a study of the photovoltaic effects of a graphene/n- Si Schottky junction solar cell. The graphene/Si solar cell was prepared by means of rapid chemical vapor deposition, while the graphene films were grown with a CH 4/ Ar mixed gas under a constant flow at 950°C and then annealed at 1000°C. It was found that the junction between the graphene film and the n- Si structure played an important role in determining the device performance. An energy conversion efficiency of 2.1% was achieved under an optical illumination of 100 mW. The strong photovoltaic effects of the cell were due to device junction's ability to efficiently generate and separate electron–hole pairs.