Flattened Profiles Research Articles

A wind tunnel study on cyclic yaw control: Power performance and wake characteristics

In this study, wind-tunnel experiments are used to investigate cyclic yaw control as a wake mitigation strategy aiming to improve wind farm power production. The control strategy is applied to a single wind turbine and a wind farm comprising of a column of three wind turbines in full wake state. The power performance of the wind farm is optimized by adjusting the control parameters, which include the yaw angle amplitude and yaw Strouhal number, and the wake flows are investigated using particle-image velocimetry measurements. The yaw angle of the controlled turbine is varied dynamically in a sinusoidal manner. A power gain of more than 10 % compared to an uncontrolled wind farm is achieved when the yaw angle amplitude and yaw Strouhal number are in the range of 10°–35° and 0.09-0.22, respectively, with a peak power gain of 15.2 %. The power consumed to generate the control is found to be small and predictable. Results from wake measurements reveal that by deflecting the wake cyclically, this control strategy can lead to relatively flattened mean wake velocity deficit profiles, faster wake recovery and very different wake turbulence intensity distributions, compared to the uncontrolled case. The results show that cyclic yaw control has a great potential in improving the power production of wind farms. A scaling of the control parameters based on the kinematic similarity between the wind-tunnel scale and utility-scale wind farms is also proposed.

Cortisol levels in rural Latina breast cancer survivors participating in a peer-delivered cognitive-behavioral stress management intervention: The Nuevo Amanecer-II RCT

BackgroundCompared to their White counterparts, Latina breast cancer survivors have poorer survival rates and health-related quality of life, and higher rates of depression and anxiety which may be a result of chronic stress. Chronic stress impacts the hypothalamic-pituitary-adrenal (HPA) axis, resulting in cortisol dysregulation which may be associated with breast cancer survival. However, cortisol levels and cortisol profiles of Latina breast cancer survivors are poorly characterized due to their underrepresentation in biomedical research. ObjectiveThe objective of this study was to describe cortisol levels and patterns of cortisol secretions in rural Latina breast cancer survivors participating in an RCT study of Nuevo Amanecer-II, an evidence-based peer-delivered cognitive behavioral stress management intervention. MethodsParticipant-centered recruitment and collection strategies were used to obtain biospecimens for cortisol analysis. Nine saliva samples (3/day for 3 days) and a hair sample were obtained at baseline and 6-months (3-months post-intervention). We describe cortisol levels and profiles, explore correlations of biomarkers with self-report measures of stress and psychological distress, and compare women who received the intervention with a delayed intervention group on biomarkers of stress. Mean hair cortisol concentration (HCC) was used to assess chronic stress. Based on daily measures of cortisol (awakening, 30 min post-awakening, and bedtime), we calculated three summary measures of the dynamic nature of the cortisol awakening response (CAR): 1) the CAR slope, 2) whether CAR demonstrates a percent change ≥40, and 3) total daily cortisol output (AUCg). Linear and log-binomial regression, accounting for multiple samples per participant, were used to compare cortisol measures at 6-month follow-up by treatment arm. ResultsParticipants (n = 103) were from two rural California communities; 76 provided at least one saliva sample at baseline and follow-up and were included in the analysis. At baseline, mean age was 57 years, mean years since diagnosis was 2 years, 76% had a high school education or less, and 34% reported financial hardship. The overall median CAR slope was 0.10, and median cortisol AUCg (in thousands) was 11.34 (range = 0.93, 36.66). Mean hair cortisol concentration was 1751.6 pg/mg (SD = 1148.6). Forty-two percent of samples had a ≥40% change in CAR. We found no statistically significant correlations between the cortisol measures and self-reported measures of stress and psychological distress. At follow-up, no differences were seen in HCC (mean difference between intervention and control: −0.11, 95% CI -0.48, 0.25), CAR slope (0.001, 95% CI -0.005, 0.008), cortisol AUCg (−0.15, 95% CI -0.42, 0.13), or ≥40% change in CAR (prevalence ratio 0.87, 95% CI 0.42, 1.77) between treatment arms. ConclusionOur findings of flattened cortisol profiles among more than half of the sample suggest potential HPA-axis dysregulation among rural Spanish-speaking Latina breast cancer survivors that merits further study due to its implications for long-term survival. Trial registrationhttp://www.ClinicalTrials.gov identifier NCT02931552.

Influence of vitamin D on the histostructure of the testis and morphometric indications of spermatogenesis of intact rats

One of the current problems is the study of the effects of vitamin D on the body, and in men its action is closely related to the pathogenesis of androgen deficiency and hypofertility. Particular attention needs to be paid to determining whether cholecalciferol (D3) has a negative effect on the gonads and spermatogenesis of intact individuals, as vitamin D therapy is used in reproductive disorders with or without vitamin D deficiency. The aim of the study was to determine the effect of vitamin D on the histological structure of gonads and morphometric parameters of spermatogenesis of adult intact male rats. The studies were performed on adult sexually active male Wistar rats. Vitamin D3 was administered orally in doses of 1000 IU, 4000 IU and 10000 IU. The solutions were made on seed oil. The control was intact rats. Vitamin D and its solvent were administered throughout the period of spermatogenesis and the time of maturation of sperm in the epididymis, after which the structural organization of the testes was determined. Gonadal samples were fixed in 10 % formalin solution, leave in alcohols of increasing strength, and embedded in paraffin. In addition to survey microscopy, morphometric evaluation of the process of spermatogenesis was performed on sections of gonads stained with hematoxylin and eosin. Micropreparations were examined using a Granum L 30 (03) light microscope, and microscopic images were taken with a Granum DSM 310 digital video camera. Photographs were processed on a Pentium 2.4 GHz computer using Toup View. Statistical processing of data results was performed in the standard software package "Statistica 6.0" using Student's t-test and using a non-parametric analogue of one-way analysis of variance – Kruskal-Wallis criterion. In rat testicular sections, seminiferous tubules were located transversely or obliquely and were oval or round in shape. The diameter of the tubules is normal, the tubular membrane, as well as the protein and vascular membranes were normal. The basal department contains the youngest cells of the germinal epithelium – spermatogonia. Cells have a pronounced functional activity. Morphometric characteristics of spermatogenesis of intact rats corresponded to the physiological norm. The introduction of the solvent throughout the period of spermatogenesis and maturation of mature sperm in the epididymis did not affect the histoarchitectonics of the testicles. The testicular lobes are filled with concentric or flattened profiles of sections of the seminal tubules, which are close enough to each other. The diameter of the tubules is normal, the intrinsic membrane of the tubules, as well as the protein and vascular membranes corresponded to those in intact animals. 3-4 generations of spermatogenic cells, which were at different stages of development, can be seen in the tubules. However, few tubules with focal destruction of the germinal epithelium and exfoliation of germ cells in the lumen of the tubules have been observed. No significant changes in the microstructure of the seminal tubules were observed after administration of vitamin D at all doses studied. Not only spermatogenesis but also spermiogenesis is clearly traced in different tubules of rats – stages of cellular transformations from spermatid to sperm. Morphometric parameters of the process of spermatogenesis of rats receiving different doses of vitamin D3 do not differ from those of intact rats. Thus, the use of vitamin D in these doses revealed the safety of its effect on the number of spermatogonia and tubules with stage 12 meiosis. When cholecaciferol was used in male rats for 68 days, the spermatogenesis index remained at the level of animals that did not receive the test substance. The use of vitamin D3 in intact adult male rats does not adversely affect the histological structure of the testes.

Thermal and flow characteristics of nonequilibrium monatomic, diatomic, and polyatomic gases in cylindrical Couette flow based on second-order non-Navier–Fourier constitutive model

The thermal and flow characteristics of nonequilibrium monatomic, diatomic, and polyatomic gases in cylindrical Couette flow are investigated using first- and second-order Boltzmann–Curtiss-based constitutive models. The mixed modal discontinuous Galerkin scheme is used for solving the conservation laws in conjunction with the Maxwell velocity-slip and Smoluchowski temperature-jump boundary conditions. Also derived are new analytic solutions for compressible cylindrical Couette gas flow including the temperature profile, and they are used to verify the numerical scheme. Further, the second-order non-Navier–Fourier constitutive relations are derived for the cylindrical coordinates. Various abnormal behaviour is found in the second-order constitutive model, such as non-zero normal stress and excess normal stress, non-zero tangential heat flux, and flattened pressure and density profiles. The physical mechanisms behind this abnormal behaviour are found to be similar to the Knudsen layer in planar Couette gas flow, and the curvature of the cylindrical geometry does not affect the fundamental second-order physics. Moreover, two new abnormal mechanisms are found in diatomic and polyatomic gases: (i) the subtle interplay of excess normal stress (and bulk viscosity) with the nonlinear coupled constitutive relation, and (ii) the combined role of the bulk viscosity ratio and the specific heat ratio.

New Degree of Freedom in Determining Superior Piezoelectricity at the Lead-Free Morphotropic Phase Boundary: The Invisible Ferroelectric Crossover.

The morphotropic phase boundary (MPB) in lead-free ferroelectrics, starting from a quadruple point (QP), often displays large piezoelectric responses due to the flattened free-energy profiles. In this work, we found that the QP composition rendering most flattened energy profiles could also exhibit abnormally low piezoelectric constants in Hf-doped BaTiO3. Such an anomaly in the strength of piezoelectricity can be ascribed to the progressive influence of additional strain heterogeneity induced by the substitution of Hf4+ for Ti4+ in BaTiO3, which was overlooked previously. An intermediate level of strain heterogeneity can form an invisible ferroelectric crossover consisting of both micro- and nanodomains, resulting in a large elastic softening and high piezoelectricity. With a further increase in the level of strain heterogeneity, the extinction of regular ferroelectric domain structures and pinned polar dynamics resulted in the feeble piezoelectric outputs near the QP composition. Impressively, a giant d33 of ∼610 pC/N has been accordingly obtained through employing a ferroelectric crossover at off-QP composition in Zr-doped BaTiO3, further underpinning the critical role of uncovered ferroelectric crossover on piezoelectricity along MPB. This work offers another degree of freedom in the design of high-performance eco-friendly piezoelectric ceramics.

Linking high- and low-mass star formation

Context. Astronomers have yet to establish whether high-mass protostars form from high-mass prestellar cores, similar to their lower-mass counterparts, or from lower-mass fragments at the heart of a pre-protostellar cluster undergoing large-scale collapse. Part of the uncertainty is due to a shortage of envelope structure data on protostars of a few tens of solar masses, where we expect to see a transition from intermediate-mass star formation to the high-mass process. Aims. We sought to derive the masses, luminosities, and envelope density profiles for eight sources in Cygnus-X, whose mass estimates in the literature placed them in the sampling gap. Combining these sources with similarly evolved sources in the literature enabled us to perform a meta-analysis of protostellar envelope parameters over six decades in source luminosity. Methods. We performed spectral energy distribution fitting on archival broadband photometric continuum data from 1.2 to 850 μm to derive bolometric luminosities for our eight sources plus initial mass and radius estimates for modelling density and temperature profiles with the radiative-transfer package Transphere. Results. The envelope masses, densities at 1000 AU, outer envelope radii, and density power law indices as functions of bolometric luminosity all follow established trends in the literature spanning six decades in luminosity. Most of our sources occupy an intermediate to moderately high range of masses and luminosities, which helps to more firmly establish the continuity between low- and high-mass star formation mechanisms. Our density power law indices are consistent with observed values in the literature, which show no discernible trends with luminosity, and have a mean p = −1.4 ± 0.4. However, our sub-sample, with a mean power law index of −1.1 ± 0.3, is slightly flatter than would be expected for spherical envelopes in free fall (p = −1.5). Conclusions. We attribute flattened density profiles for our eight sources to one or more of the following: ongoing accretion from their natal filaments, convolution of sources with neighbours or the larger filament, spherical averaging of asymmetric features (for example fragments), or inflation of the envelope by a moderate far-ultraviolet field. Finally, we show that the trends in all of the envelope parameters for high-mass protostars are statistically indistinguishable from trends in the same variables for low-mass protostars.

Multi-Gaussian random variables for modeling optical phenomena.

A generalization of the classic Gaussian random variable to the family of multi-Gaussian (MG) random variables characterized by shape parameter M > 0, in addition to the mean and the standard deviation, is introduced. The probability density function (PDF) of the MG family members is an alternating series of Gaussian functions with suitably chosen heights and widths. In particular, for integer values of M, the series has a finite number of terms and leads to flattened profiles, while reducing to the classic Gaussian PDF for M = 1. For non-integer, positive values of M, a convergent infinite series of Gaussian functions is obtained that can be truncated in practical problems. For all M > 1, the MG PDF has flattened profiles, while for 0 < M < 1, the MG PDF has cusped profiles. Moreover, the multivariate extension of the MG random variable is obtained and the log-multi-Gaussian random variable is introduced. In order to illustrate the usefulness of these new random variables for optics, the application of MG random variables to the characterization of novel speckle fields is discussed, both theoretically and via numerical simulations.

The MUSE-Faint survey. II. The dark matter-density profile of the ultra-faint dwarf galaxy Eridanus 2

Aims. We use stellar line-of-sight velocities to constrain the dark-matter density profile of Eridanus 2, an ultra-faint dwarf galaxy with an absolute V-band magnitude MV = −7.1 that corresponds to a stellar mass M* ≈ 9 × 104 M⊙. We furthermore derive constraints on fundamental properties of self-interacting and fuzzy dark matter scenarios. Methods. We present new observations of Eridanus 2 from MUSE-Faint, a survey of ultra-faint dwarf galaxies with the Multi Unit Spectroscopic Explorer on the Very Large Telescope, and determine line-of-sight velocities for stars inside the half-light radius. Combined with literature data, we have 92 stellar tracers out to twice the half-light radius. With these tracers we constrain models of cold dark matter, self-interacting dark matter, and fuzzy dark matter, using CJAM and pyGravSphere for the dynamical analysis. The models of self-interacting and fuzzy dark matter relate the density profile to the self-interaction coefficient and the dark-matter particle mass, respectively. Results. We find substantial evidence (Bayes factor ∼10−0.6) for cold dark matter (a cuspy halo) over self-interacting dark matter (a cored halo) and weak evidence (Bayes factor ∼10−0.4) for fuzzy dark matter over cold dark matter. We find a virial mass M200 ∼ 108 M⊙ and astrophysical factors J(αcJ) ~ 1011 M⊙2 kpc−5 and D(αcD) ~ 102 − 102.5 M⊙ kpc−2 (proportional to dark-matter annihilation and decay signals, respectively), the exact values of which depend on the density profile model. The mass-to-light ratio within the half-light radius is consistent with the literature. We do not resolve a core (rc &lt; 47 pc, 68% confidence level) or a soliton (rsol &lt; 7.2 pc, 68% confidence level). These limits are equivalent to an effective self-interaction coefficient fΓ &lt; 2.2 × 10−29 cm3 s−1 eV−1 c2 and a fuzzy-dark-matter particle mass ma &gt; 4.0 × 10−20 eV c−2. The constraint on self-interaction is complementary to those from gamma-ray searches. The constraint on fuzzy-dark-matter particle mass is inconsistent with those obtained for larger dwarf galaxies, suggesting that the flattened density profiles of those galaxies are not caused by fuzzy dark matter.

Generation of clinical 177Lu SPECT/CT images based on Monte Carlo simulation with GATE.

Patient-specific dosimetry in MRT relies on quantitative imaging, pharmacokinetic assessment and absorbed dose calculation. The DosiTest project was initiated to evaluate the uncertainties associated with each step of the clinical dosimetry workflow through a virtual multicentric clinical trial. This work presents the generation of simulated clinical SPECT datasets based on GATE Monte Carlo modelling with its corresponding experimental CT image, which can subsequently be processed by commercial image workstations. This study considers a therapy cycle of 6.85GBq 177Lu-labelled DOTATATE derived from an IAEA-Coordinated Research Project (E23005) on "Dosimetry in Radiopharmaceutical therapy for personalised patient treatment". Patient images were acquired on a GE Infinia-Hawkeye 4 gamma camera using a medium energy (ME) collimator. Simulated SPECT projections were generated based on experimental time points and validated against experimental SPECT projections using flattened profiles and gamma index. The simulated projections were then incorporated into the patient SPECT/CT DICOM envelopes for processing and their reconstruction within a commercial image workstation. Gamma index passing rate (2% - 1 pixel criteria) between 95 and 98% and average gamma between 0.28 and 0.35 among different time points revealed high similarity between simulated and experimental images. Image reconstruction of the simulated projections was successful on HERMES and Xeleris workstations, a major step forward for the initiation of a multicentric virtual clinical dosimetry trial based on simulated SPECT/CT images. Realistic 177Lu patient SPECT projections were generated in GATE. These modelled datasets will be circulated to different clinical departments to perform dosimetry in order to assess the uncertainties in the entire dosimetric chain.

A Study of Gas Entropy Profiles of 47 Galaxy Clusters and Groups out to the Virial Radius

Abstract Some observations, such as those presented in Walker et al., show that the observed entropy profiles of the intracluster medium (ICM) deviate from the power-law prediction of adiabatic simulations. This implies that nongravitational processes, which are absent in the simulations, may be important in the evolution of the ICM, and by quantifying the deviation, we may be able to estimate the feedback energy in the ICM and use it as a probe of the nongravitational processes. To address this issue, we calculate the ICM entropy profiles in a sample of 47 galaxy clusters and groups, which have been observed out to at least ∼r 500 with Chandra, XMM-Newton, and/or Suzaku, by constructing a physical model to incorporate the effects of both gravity and nongravitational processes to fit the observed gas temperature and surface brightness profiles via Bayesian statistics. After carefully evaluating the effects of systematic errors, we find that the gas entropy profiles derived with best-fit results of our model are consistent with the simulation-predicted power-law profile near the virial radius, while the flattened profiles reported previously can be explained by introducing the gas clumping effect, the existence of which is confirmed in 19 luminous targets in our sample. We calculate the total feedback energy per particle and find that it decreases from ∼10 keV at the center to about zero at ∼0.35r 200 and is consistent with zero outside ∼0.35r 200, implying an upper limit of the feedback efficiency of ∼0.02 for the supermassive black holes hosted in the brightest cluster galaxies.

Pair plasma instability in homogeneous magnetic guide fields

Pair plasmas, collections of both matter and antimatter particles of equal mass, represent a paradigm for the study of basic plasma science, and many open questions exist regarding these unique systems. They are found in many astrophysical settings, such as gamma-ray bursts, and have recently also been produced in carefully designed laboratory experiments. A central research topic in plasma physics is instability; however, unlike their more common ion–electron siblings, pair plasmas are generally thought to be stable to cross field pressure gradients in homogeneous magnetic fields. It is shown here by means of kinetic full-f simulations that, when a pressure gradient is first established, the Gradient-driven Drift Coupling mode is destabilized and becomes turbulent. Force balance is eventually achieved by a combination of flattened pressure profiles due to turbulent transport and establishment of a magnetic field gradient, saturating the growth. During the unstable phase, key physics can be captured by a δf gyrokinetic description, where it is shown analytically and numerically that parallel particle motion results in a coupling of all electromagnetic field components. A fluid model derived therefrom accurately predicts linear eigenmodes and is used to resolve global profile effects. For laser-based electron–positron plasma experiments, prompt instability is predicted with growth times much shorter than plasma lifetimes. Similarly, growth rates are calculated for the planned APEX experiment as well as gamma-ray burst scenarios, suggesting that the instability may contribute to the early evolution of these systems.

Microvascular anatomy of ovary and oviduct in the adult African Clawed Toad (Xenopus laevis DAUDIN, 1802)-Histomorphology and scanning electron microscopy of vascular corrosion casts.

Ovaries and oviducts of the adult African Clawed Toad (Xenopus laevis DAUDIN, 1802) were studied by light microscopy (LM) of paraplast embedded tissue sections and scanning electron microscopy (SEM) of vascular corrosion casts (VCCs). Histomorphology revealed that ovarian vessels located in the thecal layers. Ovarian and interlobar arteries displayed a horse‐shoe shaped longitudinally running bundle of vascular smooth muscle cells. Follicular blood vessels showed flattened profiles, which were confirmed by scanning electron microscopy in vascular corrosion casts. The flattened profiles obviously led to high intravasal pressures, which locally prevented filling of the follicular capillary bed. Oviduct arteries pierced the fibrous stroma surrounding the oviduct mucosa. In the pars convoluta, the mucosa consisted of a ciliated simple columnar epithelium and tubular oviduct glands that opened between ciliated epithelial cells into the oviduct lumen. Oviduct arteries branched at the basolateral surfaces of tubular glands. After a short tangential course, arterioles branched into capillaries which ran radially between oviduct glands towards the subepithelium. Anastomoses at different heights connected capillaries of neighbouring glands. Subepithelially, capillaries ran longitudinally and undulated. Postcapillary venules radiated centrifugally towards the stroma to finally drain into oviduct veins located in the stroma. Oviduct vascular densities clearly reflected non‐ovulatory and ovulatory states.

Mid-infrared supercontinuum generation with high spectral flatness in dispersion flattened tellurite all-solid hybrid microstructured optical fibers

Tellurite all-solid hybrid microstructured optical fibers are proposed for chromatic dispersion control. An ultra-flattened chromatic dispersion profile with variation as small as ±0.2 ps/km/nm over the wavelength range from 2.5 to 3.7 μm can be obtained. The fibers with flattened chromatic dispersion profiles have high potential for broadband mid-infrared supercontinuum generation. Fabrication of the fiber is successfully performed and by pumping the fabricated fiber at 2 μm, a broad and highly coherent supercontinuum with high spectral flatness is generated.

Numerical investigation on coherent mid-infrared supercontinuum generation in chalcogenide PCFs with near-zero flattened all-normal dispersion profiles**Project supported by the National Natural Science Foundation of China (Grant Nos. 61421002 and 61435003).

We design a novel all-normal flat near-zero dispersion chalcogenide photonic crystal fiber (PCF) for generating mid-infrared (MIR) supercontinuum (SC). The proposed PCF with a core made of As2Se3 glass and uniform air holes in the cladding is selectively filled with As2S5 glass. By carefully engineering the PCF with an all-normal flat near-zero dispersion profile, the anomalous-dispersion soliton effect is reduced, thus enabling broadband highly coherent SC to be generated. We also investigate the influence of the pulse parameters on the SC generation. Broadband SC covering with perfect coherence is achieved by pumping the proposed 3-cm-long PCF with 3- 100-fs pulses. The results provide a potential all-fiber realization of the broadband coherent MIR-SC.

Demand Side Management Effects on Substation Transformer Capacity Limits

In high penetrations, demand side management (DMS) applications augment a substation power transformer’s load profile, which can ultimately affect the unit’s capacity limits. Energy storage (ES) applications reduce the evening peaking demand, while time-of-use rates incentivize end-users to charge electric vehicles overnight. The daily load profile is further augmented by high penetrations of photovoltaic (PV) systems, which reduce the midday demand. The resulting load profile exhibits a more flattened characteristic when compared to the historical cyclic profile. Although the initial impact of PV and ES applications may reduce a unit’s peak demand, long-term system planning and emergency conditions may require operation near or above the nameplate rating. Researchers have already determined that a flattened load profile excessively ages a unit’s dielectrics more rapidly. The focus of this research was to identify an approach for establishing new transformer capacity limits for units serving flattened load profiles with a high harmonic content. The analysis utilizes IEEE standards C57.91 and C57.110 to develop an aging model of a 50 MVA SPX Waukesha transformer. The results establish a guideline for determining transformer capacity limits for normal operation, long-term emergency operation, and short-term emergency operation when serving systems with high penetrations of DSM applications.

Modelling accretion disc emission with generalized temperature profile and its effect on AGN spectral energy distribution

The broadband spectral energy distribution (SED) of Active Galactic Nuclei (AGN) is investigated for a well-selected sample composed of $23$ Seyfert 1 galaxies observed simultaneously in the optical/UV and X-ray bands with the Neil Gehrels {\it Swift} Observatory. The optical to UV continuum spectra are modeled, for the first time, with emission from an accretion disk with a generalized radial temperature profile, in order to account for the intrinsic spectra which are found to be generally redder than the model prediction of the standard Shakura-Sunyaev disk (SSD) ($F_\nu\propto\nu^{+1/3}$). The power-law indices of the radial temperature profile ($T_{\rm eff}(R)\propto R^{-p}$, $R$ is the radius of the accretion disk) are inferred to be $p=0.5$ -- $0.75$ (a median of $0.63$), deviating from the canonical $p=0.75$ for the SSD model as widely adopted in previous studies. A marginal correlation of a flatter radial temperature profile (a smaller $p$ value) with increasing the Eddington ratio is suggested. Such a model produces generally a lower peak of accretion disk emission and thus a smaller bolometric luminosity in some of the AGN, particularly those with high Eddington ratios, than that based on the SSD model by a factor of several. The broadband SED, the bolometric correction factors and their dependence on some of the AGN parameters are re-visited. We suggest that such non-standard SSD disks may operate in AGN and are at least partly responsible for the reddened optical/UV spectra as observed. One possible explanation for these flattened temperature profiles is the mass loss process in form of disk winds/outflows.

The stellar halo of isolated central galaxies in the Hyper Suprime-Cam imaging survey

We study the faint stellar halo of isolated central galaxies, by stacking galaxy images in the HSC survey and accounting for the residual sky background sampled with random points. The surface brightness profiles in HSC $r$-band are measured for a wide range of galaxy stellar masses ($9.2<\log_{10}M_\ast/M_\odot<11.4$) and out to 120 kpc. Failing to account for the stellar halo below the noise level of individual images will lead to underestimates of the total luminosity by $\leq 15\%$. Splitting galaxies according to the concentration parameter of their light distributions, we find that the surface brightness profiles of low concentration galaxies drop faster between 20 and 100 kpc than those of high concentration galaxies. Albeit the large galaxy-to-galaxy scatter, we find a strong self-similarity of the stellar halo profiles. They show unified forms once the projected distance is scaled by the halo virial radius. The colour of galaxies is redder in the centre and bluer outside, with high concentration galaxies having redder and more flattened colour profiles. There are indications of a colour minimum, beyond which the colour of the outer stellar halo turns red again. This colour minimum, however, is very sensitive to the completeness in masking satellite galaxies. We also examine the effect of the extended PSF in the measurement of the stellar halo, which is particularly important for low mass or low concentration galaxies. The PSF-corrected surface brightness profile can be measured down to $\sim$31 $\mathrm{mag}/\mathrm{arcsec}^2$ at 3-$\sigma$ significance. PSF also slightly flattens the measured colour profiles.

Process- and bio-inspired hydrogels for 3D bioprinting of soft free-standing neural and glial tissues

A bio-inspired hydrogel for 3D bioprinting of soft free-standing neural tissues is presented. The novel filler-free bioinks were designed by combining natural polymers for extracellular matrix biomimicry with synthetic polymers to endow desirable rheological properties for 3D bioprinting. Crosslinking of thiolated Pluronic F-127 with dopamine-conjugated (DC) gelatin and DC hyaluronic acid through a thiol–catechol reaction resulted in thermally gelling bioinks with Herschel–Bulkley fluid rheological behavior. Microextrusion 3D bioprinting was used to fabricate free-standing cell-laden tissue constructs. The bioinks exhibited flattened parabolic velocity profiles with tunable low shear regions. Two pathways were investigated for curing the bioink: chelation and photocuring. The storage modulus of the cured bioinks ranged from 6.7 to 11.7 kPa. The iron (III) chelation chemistry produced crosslinked neural tissues of relatively lower storage modulus than the photocuring approach. In vitro cell viability studies using the 3D bioprinted neural tissues showed that the cured bioink was biocompatible based on minimal cytotoxic response observed over seven days in culture relative to control studies using alginate hydrogels. Rodent Schwann cell-, rodent neuronal cell-, and human glioma cell-laden tissue constructs were printed and cultured over seven days and exhibited comparable viability relative to alginate bioink controls. The ability to fabricate soft, free-standing 3D neural tissues with low modulus has implications in the biofabrication of microphysiological neural systems for disease modeling as well as neural tissues and innervated tissues for regenerative medicine.

Investigation into the formation of the scrape-off layer density shoulder in JET ITER-like wall L-mode and H-mode plasmas

The low temperature boundary layer plasma (scrape-off layer or SOL) between the hot core and the surrounding vessel determines the level of power loading, erosion and implantation of material surfaces, and thus the viability of tokamak-based fusion as an energy source. This study explores mechanisms affecting the formation of flattened density profiles, so-called ‘density shoulders’, in the low-field side (LFS) SOL, which modify ion and neutral fluxes to surfaces—and subsequent erosion. There is evidence against local enhancement of ionization inducing shoulder formation. We find that increases in SOL parallel resistivity, Λdiv (=[L||νeiΩi]/csΩe), postulated to lead to shoulder growth through changes in SOL turbulence characteristics, correlates with increases in SOL shoulder amplitude, As, but only under a subset of conditions (D2-fuelled L-mode density scans with outer strike point on the horizontal target). Λdiv fails to correlate with As for cases of N2 seeding or during sweeping of the strike point across the horizontal target. The limited correlation of Λdiv and As is also found for H-mode discharges. Thus, while it may be necessary for Λdiv to be above a threshold of ~1 for shoulder formation and/or growth, another mechanism is required. More significantly, we find that in contrast to parallel resistivity, outer divertor recycling, as quantified by the total outer divertor Balmer Dα emission, I–Dα, does scale with As where Λdiv does and even where Λdiv does not. Divertor recycling could lead to SOL density shoulder formation through: (a) reducing the parallel to the field flow (loss) of ions out of the SOL to the divertor; and (b) changes in radial electric fields which lead to E × B poloidal flows as well as potentially affecting SOL turbulence birth characteristics. Thus, changes in divertor recycling may be the sole process involved in bringing about SOL density shoulders or it may be that it acts in tandem with parallel resistivity.

Swirl generator effect on a confined coaxial jet characteristics

The effect of a swirl generator placed in the central pipe of a cylindrical confinement on mixing process enhancement is numerically investigated. 3D simulations were carried out using the commercial code FLUENT. RANS calculations were conducted to investigate the effect of the swirler position, the central gas nature and the swirler geometry on the swirled flow behavior.Results show that for an annular swirl generator, the swirler location in the central pipe affects considerably the dynamic structure and the mixing process in the confined volume. Moreover, it has been shown that the optimal swirler position depends on the intended application: For non reacting case, the central pipe outlet is judged as the best test case to guarantee good mixing process. On the contrary, for reacting case, the annular swirler should be placed far from the main pipe outlet to ensure better mixture and avoid flashback problem caused by flattened radial concentration profiles. By modifying the central jet type (Helium, hydrogen and methane), it has been proven that hydrogen tends to mix more rapidly. However, the flattened radial concentration profiles problem persists for the different gases. Meanwhile, this problem can be solved by modifying the geometry of the swirler placed at the central pipe outlet.