Spatial profile of Al-ZnO thin film on polycarbonate deposited by ring-shaped magnetized rf plasma sputtering with two facing cylindrical Al2O3 - ZnO targets

Radial profiles of the ion saturation current are measured in a ring-shaped magnetized radio-frequency plasma sputtering process with two facing cylindrical ZnO targets including Al2O3 (2% wt.). The profile has a non-uniform shape with a peak whose position corresponds to the target near the electrode due to the effect of the magnetic field distribution. It becomes uniform at large distances between the substrate and a target (d st ≥ 50 mm). The radial profile of the resistivity of the Al-ZnO (AZO) films deposited on a polycarbonate plate at Ar gas pressure of 0.27 Pa is uniform at about 10-3 Ω·cm for d st ≥ 50 mm. The films deposited at various positions and room-substrate-temperature also show a good crystallinity based on an X-ray diffraction peak of about 33.95 - 34.44°. The grains exhibit a preferential orientation along the [002] axis with its size ranging from 18.15 to 28.17 nm. A higher transmittance of 95.6 % in the visible region is also obtained.

Transport and losses of fusion-born alpha particles in the presence of tearing modes using the new Toroidal Accelerated P Article Simulator (TAPAS)

The transport and losses of fusion-born alpha particles is studied in the presence of a single-helicity tearing mode, characterized by (m=2,n=1). The analysis is performed by means of the recently developed Toroidal Accelerated PArticle Simulator (TAPAS). Although such modes have been usually believed to result only in a local flattening of the radial profiles, it is shown that the density profile can exhibit a global modification leading to significant losses of alpha particles. This is due to the fact that, although the magnetic field does not exhibit any chaotic behaviour, the trajectories of alpha particles do, as revealed by their Poincaré maps. Such result is in qualitative agreement with past observations and simulations of energetic particles generated by neutral beam injection in TFTR, DIII-D and AUG tokamaks. In-depth analysis is carried out to characterize the impact of the tearing mode on the transport and losses of fusion-born alpha-particles with a realistic density profile. The impact of the amplitude is evidenced. Moreover, the effect of the island rotation frequency is assessed based on a detailed analysis of the linear resonances in phase-space, in agreement with the simulation results. Finally, the probability density function of the exit time has been computed and the transport of alpha particles has been found to be anomalous.

Quantification of STEM Images in High Resolution SEM for Segmented and Pixelated Detectors

The segmented semiconductor detectors for transmitted electrons in ultrahigh resolution scanning electron microscopes allow observing samples in various imaging modes. Typically, two standard modes of objective lens, with and without a magnetic field, differ by their resolution. If the beam deceleration mode is selected, then an electrostatic field around the sample is added. The trajectories of transmitted electrons are influenced by the fields below the sample. The goal of this paper is a quantification of measured images and theoretical study of the capability of the detector to collect signal electrons by its individual segments. Comparison of measured and ray-traced simulated data were difficult in the past. This motivated us to present a new method that enables better comparison of the two datasets at the cost of additional measurements, so-called calibration curves. Furthermore, we also analyze the measurements acquired using 2D pixel array detector (PAD) that provide a more detailed angular profile. We demonstrate that the radial profiles of STEM and/or 2D-PAD data are sensitive to material composition. Moreover, scattering processes are affected by thickness of the sample as well. Hence, comparing the two experimental and simulation data can help to estimate composition or the thickness of the sample.

Characterisation and asymmetry analysis of rainfall distribution associated with tropical cyclones over Bay of Bengal : NISHA (2008), LAILA (2010) and JAL (2010)

The precipitation characteristics and spatial rainfall asymmetry in respect of three tropical cyclones (TCs) of Bay of Bengal, viz., NISHA (2008), LAILA (2010) and JAL(2010) that affected coastal Tamil Nadu are studied using TRMM based rain rate data. The analysis is carried out by dividing the life cycle of the TC into various stages of intensification and weakening. Percentage frequency distribution, radial profile and quadrant-wise mean rain rates are determined stage-wise for each TC. Further, spatio-temporal variations in the rainfall asymmetry is studied using Fourier analysis by computing the first order wave number-1 asymmetry around the TC centre. The results indicate a shifting of higher frequency rain rates from higher to lower rain rate side when the TC passes from intensification to weakening stages. The azimuthally averaged mean rain rates indicate a peak rain rate of 4-5 mm/hr over 50-100 km from the TC centre during intensification stages which decreases to a very low rate of about 1 mm/hr during the final stages of weakening. For the same intensity category, the radial profiles of mean rain rates show marked difference between the intensification and weakening stages. The quadrant mean rain rates show large asymmetries in the radial rainfall distribution with more rainfall concentrated in front left quadrant during the stages of intensification. Such TC rainfall asymmetries are shown to be influenced by the environmental vertical wind shear and translational speed of the TC. When the wind shear and storm motion vectors are in the same direction, a dominant down shear left asymmetry is observed. Evolution of wave number-1 asymmetry indicates that, by and large, asymmetry amplitude increases from the centre outwards and a cyclonic (anti-cyclonic) shift during the intensification (weakening) stages of the TCs.

L-GALAXIES 2020: The formation and chemical evolution of stellar haloes in Milky Way Analogues and galaxy clusters

We present an analysis of the formation and chemical evolution of stellar haloes around (a) Milky Way Analogue (MWA) galaxies and (b) galaxy clusters in the L-Galaxies 2020 semi-analytic model of galaxy evolution. Observed stellar halo properties are better reproduced when assuming a gradual stripping model for the removal of cold gas and stars from satellites, compared to an instantaneous stripping model. The slope of the stellar mass – metallicity relation for MWA stellar haloes is in good agreement with that observed in the local Universe. This extends the good agreement between L-Galaxies 2020 and metallicity observations from the gas and stars inside galaxies to those outside. Halo stars contribute on average only ∼0.1 per cent of the total circumgalactic medium (CGM) enrichment by z = 0 in MWAs, ejecting predominantly carbon produced by AGB stars. Around a quarter of MWAs have a single ‘significant progenitor’ with a mean mass of ∼ 2.3 × 109M⊙, similar to that measured for Gaia Enceladus. For galaxy clusters, L-Galaxies 2020 shows good correspondence with observations of stellar halo mass fractions, but slightly over-predicts stellar masses. Assuming a Navarro-Frenk-White profile for the stellar halo mass distribution provides the best agreement. On average, the intracluster stellar component (ICS) is responsible for 5.4 per cent of the total intracluster medium (ICM) iron enrichment, exceeding the contribution from the brightest cluster galaxy (BCG) by z = 0. We find that considering gradual stripping of satellites and realistic radial profiles is crucial for accurately modelling stellar halo formation on all scales in semi-analytic models.

VLA and NOEMA Views of Bok Globule CB 17: The Starless Nature of a Proposed First Hydrostatic Core Candidate

We use 3 mm continuum NOrthern Extended Millimeter Array and NH3 Very Large Array observations toward the First Hydrostatic Core (FHSC) candidate CB 17 MMS in order to reveal the dust structure and gas properties to 600–1100 au scales and to constrain its evolutionary stage. We do not detect any compact source at the previously identified 1.3 mm point source, despite expecting a minimum signal-to-noise ratio of 9. The gas traced by NH3 exhibits subsonic motions, with an average temperature of 10.4 K. A fit of the radial column density profile derived from the ammonia emission finds a flat inner region of radius ∼1800 au and a central density of ∼6 × 105 cm−3. Virial and density structure analysis reveals the core is marginally bound (α vir = 0.73). The region is entirely consistent with that of a young starless core, hence ruling out CB 17 MMS as an FHSC candidate. Additionally, the core exhibits a velocity gradient aligned with the major axis, showing an arc-like structure in the position–velocity diagram and an off-center region with high velocity dispersion, caused by two distinct velocity peaks. These features could be due to interactions with the nearby outflow, which appears to deflect due to the dense gas near the NH3 column density peak. We investigate the specific angular momentum profile of the starless core, finding that it aligns closely with previous studies of similar radial profiles in Class 0 sources. This similarity to more evolved objects suggests that motions at 1000 au scales are determined by large-scale dense cloud motions, and may be preserved throughout the early stages of star formation.

An IFU View of the Active Galactic Nuclei in MaNGA Galaxy Pairs

The role of active galactic nuclei (AGNs) during galaxy interactions and how they influence the star formation in the system are still under debate. We use a sample of 1156 galaxies in galaxy pairs or mergers (hereafter “pairs”) from the MaNGA survey. This pair sample is selected by the velocity offset, projected separation, and morphology, and is further classified into four cases along the merger sequence based on morphological signatures. We then identify a total of 61 (5.5%) AGNs in pairs based on the emission-line diagnostics. No evolution of the AGN fraction is found, either along the merger sequence or compared to isolated galaxies (5.0%). We observe a higher fraction of passive galaxies in galaxy pairs, especially in the pre-merging cases, and associate the higher fraction to their environmental dependence. The isolated AGN and AGNs in pairs show similar distributions in their global stellar mass, star-formation rate (SFR), and central [O iii] surface brightness. AGNs in pairs show radial profiles of increasing specific SFR and declining Dn4000 from center to outskirts, and no significant difference from the isolated AGNs. This is clearly different from star-forming galaxies (SFGs) in our pair sample, which show enhanced central star formation, as reported before. AGNs in pairs have lower Balmer decrements at outer regions, possibly indicating less dust attenuation. Our findings suggest that AGNs are likely follow an inside-out quenching and the merger impact on the star formation in AGNs is less prominent than in SFGs.

Probing Galaxy Evolution in Massive Clusters Using ACT and DES: Splashback as a Cosmic Clock

We measure the projected number density profiles of galaxies and the splashback feature in clusters selected by the Sunyaev–Zel’dovich effect from the Advanced Atacama Cosmology Telescope (AdvACT) survey using galaxies observed by the Dark Energy Survey (DES). The splashback radius is consistent with CDM-only simulations and is located at 2.4 − 0.4 + 0.3 Mpc h − 1 . We split the galaxies on color and find significant differences in their profile shapes. Red and green-valley galaxies show a splashback-like minimum in their slope profile consistent with theory, while the bluest galaxies show a weak feature at a smaller radius. We develop a mapping of galaxies to subhalos in simulations and assign colors based on infall time onto their hosts. We find that the shift in location of the steepest slope and different profile shapes can be mapped to the average time of infall of galaxies of different colors. The steepest slope traces a discontinuity in the phase space of dark matter halos. By relating spatial profiles to infall time, we can use splashback as a clock to understand galaxy quenching. We find that red galaxies have on average been in clusters over 3.2 Gyr, green galaxies about 2.2 Gyr, while blue galaxies have been accreted most recently and have not reached apocenter. Using the full radial profiles, we fit a simple quenching model and find that the onset of galaxy quenching occurs after a delay of about a gigayear and that galaxies quench rapidly thereafter with an exponential timescale of 0.6 Gyr.

Simulation of nonlinear standing wave excitation in very-high-frequency asymmetric capacitive discharges: roles of radial plasma density profile and rf power

It is recognized that in large-area, very-high-frequency capacitively coupled plasma (VHF CCP) reactors, the higher harmonics generated by nonlinear sheath motion can lead to enhanced standing wave excitation. In this work, a self-consistent electromagnetic model, which couples a one-dimensional, radial nonlinear transmission line model with a bulk plasma fluid model, is employed to investigate the nonlinear standing wave excitation in a VHF driven, geometrically asymmetric capacitive argon discharge operated at low pressure. By considering a radially nonuniform plasma density profile (case I ) calculated self-consistently by the nonlinear electromagnetic model and the corresponding radially-averaged, uniform plasma density profile (case II ), we first examine the effect of the plasma density nonuniformity on the propagation of electromagnetic surface waves in a 3 Pa argon discharge driven at 100MHz and 90W. Compared to case II, the higher plasma density at the radial center in case I determines a higher plasma series resonance frequency, yielding stronger high-order harmonic excitations and more significant central peak in the harmonic current density Jz,n and the harmonic electron power absorption pn profiles. Therefore, under the assumption of the radially uniform plasma density in a CCP discharge, the self-excitation of higher harmonics at the radial center should be underestimated. Second, using the self-consistent electromagnetic model, the effect of the rf power on the excitation of nonlinear standing waves is investigated in a 3 Pa argon discharge driven at 100MHz. At a low power of 30W, the discharge is dominated by the first two harmonics. The higher harmonic excitations and the nonlinear standing waves are observed to be enhanced with increasing the rf power, resulting in a more pronounced central peak in the radial profiles of the total electron power absorption density pe, the electron temperature Te, and the electron density ne. For all rf powers, the calculated radial profiles of ne show good agreement with the experimental data obtained by a floating double probe.

Study on Convective Heat Transfer of Supercritical Nitrogen in a Vertical Tube for Liquid Air Energy Storage

The convective heat transfer behavior of supercritical nitrogen (S-N2) has played a significant role in optimizing the design of recently emerging cryogenic cold storage and recovery systems. However, studies on S-N2 heat transfer have been relatively scarce, not to mention that there is a legitimate urge for a robust numerical model to accurately predict and explain S-N2 heat transfer under various working conditions. In this paper, both experimental and numerical studies were conducted for convective heat transfer of S-N2 in a small vertical tube. The results demonstrated that the standard k-ε model performed better for predicting the key heat transfer characteristics of S-N2 than the SST k-ω model. The effects of heat flux and inlet pressure on the heat transfer characteristics under a large mass flux were evaluated. The variation mechanisms of local heat transfer performance were revealed by illustrating radial profiles of thermophysical properties and turbulent parameters of N2. It was found that the local performance variation along the flow direction was mainly determined by the radial profile of specific heat while the variation of the best local performance with the ratio of heat flux to mass flux was mainly determined by the radial profile of turbulent viscosity.