Outflow Velocity Research Articles

MR 4D flow–derived left atrial acceleration factor for differentiating advanced left ventricular diastolic dysfunction

ObjectivesThe magnetic resonance (MR) 4D flow imaging–derived left atrial (LA) acceleration factor α was recently introduced as a means to non-invasively estimate LA pressure. We aimed to investigate the association of α with the severity of left ventricular (LV) diastolic dysfunction using echocardiography as the reference method.MethodsEchocardiographic assessment of LV diastolic function and 3-T cardiac MR 4D flow imaging were prospectively performed in 94 subjects (44 male/50 female; mean age, 62 ± 12 years). LA early diastolic peak outflow velocity (vE), systolic peak inflow velocity (vS), and early diastolic peak inflow velocity (vD) were evaluated from 4D flow data. α was calculated from α = vE / [(vS + vD) / 2]. Mean parameter values were compared by t-test; diagnostic performance of α in predicting diastolic (dys)function was investigated by receiver operating characteristic curve analysis.ResultsMean α values were 1.17 ± 0.14, 1.20 ± 0.08, 1.33 ± 0.15, 1.77 ± 0.18, and 2.79 ± 0.69 for grade 0 (n = 51), indeterminate (n = 9), grade I (n = 13), grade II (n = 13), and grade III (n = 8) LV diastolic (dys)function, respectively. α differed between subjects with non-advanced (grade < II) and advanced (grade ≥ II) diastolic dysfunction (1.20 ± 0.15 vs. 2.16 ± 0.66, p < 0.001). The area under the curve (AUC) for detection of advanced diastolic dysfunction was 0.998 (95% CI: 0.958–1.000), yielding sensitivity of 100% (95% CI: 84–100%) and specificity of 99% (95% CI: 93–100%) at cut-off α ≥ 1.58. The AUC for differentiating grade III diastolic dysfunction was also 0.998 (95% CI: 0.976–1.000) at cut-off α ≥ 2.14.ConclusionThe 4D flow–derived LA acceleration factor α allows grade II and grade III diastolic dysfunction to be distinguished from non-advanced grades as well as from each other.Clinical relevance statementAs a single continuous parameter, the 4D flow–derived LA acceleration factor α shows potential to simplify the multi-parametric imaging algorithm for diagnosis of advanced LV diastolic dysfunction, thereby identifying patients at increased risk for cardiovascular events.Key Points• Detection of advanced diastolic dysfunction is typically performed using a complex, multi-parametric approach.• The 4D flow–derived left atrial acceleration factor α alone allows accurate detection of advanced left ventricular diastolic dysfunction.• As a single continuous parameter, the left atrial acceleration factor α could simplify the diagnosis of advanced diastolic dysfunction.

Increased cardiac output and left ventricular contractility in pigs paced with vs. without restored respiratory sinus arrhythmia - proof of principle of a newly developed pacing device

Abstract Background Heart rate variability (HRV) correlates with the severity and mortality of heart failure. Respiratory sinus arrhythmia (RSA) is defined by the dynamic increase and decrease in heart rate between breaths. Restoration of RSA might be beneficial in patients with heart failure and/or patients in need of permanent pacing. Purpose The aim of this translational, proof-of-principle study was to investigate the effect of pacing with or without RSA using a newly designed pacing device on the left ventricular contractility and cardiac output. Methods The project was initiated with the aim of designing a new pacing device capable of restoring RSA in paced hearts with the help of lung inflation sensors. Neuronal networks were designed to reconstruct the human brain using ultra-low energy-consuming technology. The lung inflation sensor fed the detected inspiration data back to the pacing device, which paced the heart via pacing leads (DDD) in the right atrium and ventricle. In total, 5 intubated but spontaneously breathing landrace pigs were paced without RSA (fixed-rate pacing) and with restored RSA. Stroke volume and cardiac output were measured by echocardiography (diameter of left ventricular outflow tract and velocity time integral measured by pulsed wave doppler averaged over three heart beats). Preload-independent cardiac contractility was measured via a pressure-volume loop catheter in the left ventricle during occlusion of the inferior vena cava. Fig. 1 indicates the setup of the trial. The trials were conducted according to the relevant rules (NIH Publication no. 85-23 revised 1985) and in accordance with national law. Results Echocardiography (n=5) showed a mean left ventricular outflow tract diameter of 21 ± 0.1 mm. The mean intrinsic heart rate was 87 ± 14 bpm, and the mean paced heart rate was 104 ± 5 bpm in the pigs (65 ± 3 kg). The main outcomes are displayed in Fig. 2: The left ventricular stroke volume increased by 11ml (+21%, p=0.036) with 100% RSA compared to pacing without RSA, while cardiac output increased by 1.14 l/min (+21%, p=0.037). The pressure volume area is proportional to the total myocardial oxygen consumption and decreased by 6234 mmHg*ml (-39%, p=0.004). Cardiac efficiency represents the relative amount of blood being pumped consuming one unit energy and increased by 0.163 (+72%, p=0.033). End-systolic pressure volume relationship demonstrated a non-significant increase by 0.183 mmHg/ml (+45%, p=0.25). Parameters of diastolic function (Tau) did not differ between the groups. Conclusion Restoration of RSA by our newly developed pacing device significantly improved the cardiac contractility/output in our proof-of-principle large animal translational model. Chronic trials will be required to definitively confirm the positive effects of RSA on cardiac remodeling.Fig. 1: Set-up of the animal trials.Fig. 2: Main results (mean/std error)

Abstract 14190: Simultaneous Analysis of Myocardial Flow Reserve and Intra-Ventricular 4D Flow Using Hybrid 13 N-ammonia Positron Emission Tomography/Magnetic Resonance Imaging in Patients With Coronary Artery Disease

Introduction: Intra-left ventricular (LV) blood flow dynamics is closely related to wall kinetics and myocardial perfusion. 4D flow magnetic resonance imaging (MR) has been developed to simulate and quantify intra-LV blood flow. We aimed to evaluate the usefulness of simultaneous analysis of myocardial flow reserve (MFR) and intra-LV 4D flow measured by hybrid 13 N-ammonia positron emission tomography (PET)/MR in patients with coronary artery disease (CAD). Methods: Forty patients (mean 65±18 years, male 32) with CAD who underwent pharmacological stress PET/MR were enrolled. MFR was calculated from a series of dynamic rest-stress PET scans. Simultaneously, 4D flow MR acquisition was performed during the stress PET scan. The intra-LV 4D flow was visually assessed, where the smooth flow was defined as normal pattern, and random, or reverse flow was defined as abnormal (Figure A). The velocity of LV inflow and outflow were measured. Results: A normal flow pattern was found in 22 patients, while abnormal pattern was found in 18. MFR showed a significant correlation with the velocity of LV inflow and outflow (inflow: R = 0.552, P &lt; 0.001; outflow: R = 0.563, P &lt; 0.001). MFR was significantly lower in the abnormal flow compared to the normal flow (1.484 ± 0.559 vs. 1.931 ± 0.775, P = 0.041, Figure B). Additionally, when analyzing MFR in coronary artery territories, MFR in the left anterior descending artery was significantly lower in the abnormal flow compared to the normal flow (1.405 ± 0.526 vs. 1.881 ± 0.791, P = 0.029, Figure C). Conclusion: Simultaneous analysis of MFR and intra-LV 4D flow has a potential to serve as a novel indicator for assessing the severity of ischemia in patients with CAD.

Segmental biomechanics of the normal and glaucomatous human aqueous outflow pathway

The conventional aqueous outflow pathway, encompassing the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and inner wall endothelium of Schlemm's canal (SC), governs intraocular pressure (IOP) regulation. This study targets the biomechanics of low-flow (LF) and high-flow (HF) regions within the aqueous humor outflow pathway in normal and glaucomatous human donor eyes, using a combined experimental and computational approach. LF and HF TM/JCT/SC complex tissues from normal and glaucomatous eyes underwent uniaxial tensile testing. Dynamic motion of the TM/JCT/SC complex was recorded using customized green-light optical coherence tomography during SC pressurization in cannulated anterior segment wedges. A hyperviscoelastic model quantified TM/JCT/SC complex properties. A fluid-structure interaction model simulated tissue-aqueous humor interaction. FluoSpheres were introduced into the pathway via negative pressure in the SC, with their motion tracked using two-photon excitation microscopy. Tensile test results revealed that the elastic moduli of the LF and HF regions in glaucomatous eyes are 3.5- and 1.5-fold stiffer than the normal eyes, respectively. The FE results also showed significantly larger shear moduli in the TM, JCT, and SC of the glaucomatous eyes compared to the normal subjects. The LF regions in normal eyes demonstrated larger elastic moduli compared to the HF regions in glaucomatous eyes. The resultant strain in the outflow tissues and velocity of the aqueous humor in the FSI models were in good agreement with the digital volume correlation and 3D particle image velocimetry data, respectively. This study uncovers stiffer biomechanical responses in glaucomatous eyes, with LF regions stiffer than HF regions in both normal and glaucomatous eyes. Statement of significanceThis study delves into the biomechanics of the conventional aqueous outflow pathway, a crucial regulator of intraocular pressure and ocular health. By analyzing mechanical differences in low-flow and high-flow regions of normal and glaucomatous eyes, this research unveils the stiffer response in glaucomatous eyes. The distinction between regions' properties offers insights into aqueous humor outflow regulation, while the integration of experimental and computational methods enhances credibility. These findings have potential implications for disease management and present a vital step toward innovative ophthalmic interventions. This study advances our understanding of glaucoma's biomechanical basis and its broader impact on ocular health.

Relativistic X-ray reflection and highly ionized absorption in the spectrum of NS LMXB 1A 1744−361

ABSTRACT We present the results from the spectral and timing analysis of the accreting neutron star (NS) 1A 1744−361 from the Nuclear Spectroscopic Telescope ARray observation performed in its 2022 outbursts. The unabsorbed bolometric X-ray luminosity during this observation in the energy band 0.1–100 keV is 3.9 × 1037 erg s−1, assuming a distance of 9 kpc. During this observation, the source was in the banana branch of the atoll track. The source spectrum exhibits relativistic disc reflection and clear absorption features when an absorbed blackbody and cut-off power-law model describes the continuum emission. The 3–50 keV source spectrum is well fitted using a model combination consisting of an absorbed single-temperature blackbody and a reflection model along with the addition of a warm absorber component. The inner-disc radius, Rin, obtained from the reflection fit is ∼(1.61–2.86)RISCO = (8.4–14.9)Rg (17.6–31.2 km for a 1.4 M⊙ NS). This measurement allowed us to further constrain the magnetic field strength to B ≲ 0.94 × 109 G. The strong absorption features ∼6.91 keV and ∼7.99 keV imply the presence of highly ionized absorbing material with a column density NH of ∼3 × 1022 cm−2, emanating from the accretion disc in the form of disc wind with an outflow velocity of vout ≃ 0.021c ≃ 6300 km s−1.

Searching for C ii Emission from the First Sample of z ∼ 6 O i Absorption-associated Galaxies with the Atacama Large Millimeter/submillimeter Array

We report the first statistical analyses of [C ii] and dust continuum observations in six strong O i absorber fields at the end of the reionization epoch obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combined with one [C ii] emitter reported in Wu et al., we detect one O i-associated [C ii] emitter in six fields. At redshifts of O i absorbers in nondetection fields, no emitters are brighter than our detection limit within impact parameters of 50 kpc and velocity offsets between ±200 km s−1. The averaged [C ii]-detection upper limit is <0.06 Jy km s−1(3σ), corresponding to the [C ii] luminosity of L [C II]< 5.8 × 107 L ⊙ and the [C ii]-based star formation rate of SFR[C II]<5.5 M ⊙ yr−1. Cosmological simulations suggest that only ∼10−2.5 [C ii] emitters around O i absorbers have comparable SFR to our detection limit. Although the detection in one out of six fields is reported, an order of magnitude number excess of emitters obtained from our ALMA observations supports that the contribution of massive galaxies that caused the metal enrichment cannot be ignored. Further, we also found 14 tentative galaxy candidates with a signal-to-noise ratio of ≈4.3 at large impact parameters (>50 kpc) and having larger outflow velocities within ±600 km s−1. If these detections are confirmed in the future, then the mechanism of pushing metals at larger distances with higher velocities needs to be further explored from the theoretical side.

A new discovery space opened by eROSITA

Context.In the context of an evolutionary model, the outflow phase of an active galactic nucleus (AGN) occurs at the peak of its activity, once the central supermassive black hole (SMBH) is massive enough to generate sufficient power to counterbalance the potential well of the host galaxy. This outflow feedback phase plays a vital role in galaxy evolution.Aims.Our aim in this paper is to apply various selection methods to isolate powerful AGNs in the feedback phase, trace and characterise outflows in these AGNs, and explore the link between AGN luminosity and outflow properties.Methods.We applied a combination of methods to the Spectrum Roentgen Gamma (SRG) eROSITA Final Equatorial Depth survey (eFEDS) catalogue and isolated ∼1400 candidates atz &gt; 0.5 out of ∼11 750 AGNs (∼12%). Furthermore, we narrowed down our selection to 427 sources that have 0.5 &lt; z &lt; 1. We tested the robustness of our selection on the small subsample of 50 sources with available good quality SDSS spectra at 0.5 &lt; z &lt; 1 and, for which we fitted the [OIII] emission line complex and searched for the presence of ionised gas outflow signatures.Results.Out of the 50 good quality SDSS spectra, we identified 23 quasars (∼45%) with evidence of ionised outflows based on the presence of significant broad and/or shifted components in [OIII]λ5007 Å. They are on average more luminous (logLbol ∼ 45.2 erg s−1) and more obscured (NH ∼ 1022cm−2) than the parent sample of ∼427 candidates, although this may be ascribed to selection effects affecting the good quality SDSS spectra sample. By adding 118 quasars at 0.5 &lt; z &lt; 3.5 with evidence of outflows reported in the literature, we find a weak correlation between the maximum outflow velocity and the AGN bolometric luminosity. On the contrary, we recovered strong correlations between the mass outflow rate and outflow kinetic power with the AGN bolometric luminosity.Conclusions.About 30% of our sample have kinetic coupling efficiencies,Ė/Lbol&gt; 1%, suggesting that the outflows could have a significant effect on their host galaxies. We find that the majority of the outflows have momentum flux ratios lower than 20 which rules out an energy-conserving nature. Our present work points to the unequivocal existence of a rather short AGN outflow phase, paving the way towards a new avenue to dissect AGN outflows in large samples within eROSITA and beyond.

Transonic galactic wind model including stellar feedbacks and application to outflows in high/low-z galaxies

Abstract Galactic winds play a crucial role in the ejection of the interstellar medium (ISM) into intergalactic space. This study presents a model that classifies possible transonic solutions of galactic winds in the gravitational potential of the dark matter halo and stellar component under spherically symmetric and steady assumptions. Our model includes injections of mass and energy resulting from supernova feedback along a flow line. The mass flux in galactic winds is a critical factor in determining the acceleration process of the flow and revealing the impact of galactic winds on galaxy evolution. We apply the transonic galactic wind model to the observed outflow velocities of star-forming galaxies to estimate the mass flux. Dividing the mass flux by the star formation rate (SFR) yields the mass loading rate (and mass loading factor), which indicates the entrainment effect of the ISM by the hot gas flow. Our results demonstrate that the mass loading rate is inversely correlated with galaxy mass and SFR. In less massive galaxies (stellar mass ∼107−8 M⊙), the mass loading rate exceeds unity, indicating effective ejection of the ISM into intergalactic space. However, in massive galaxies (stellar mass ∼1010−11 M⊙), the mass loading rate falls below unity, meaning that the mass flux cannot exceed the injected mass by supernovae, thus resulting in ineffective ejection of the ISM.

Experimental investigation of inflow-outflow asymmetry in induced-charge electro-osmosis

Induced-charge electro-osmosis (ICEO) is a research hotspot in bioengineering and analytical chemistry. Inflow-outflow asymmetry of ICEO was reported in the existing literatures, but systematic study on this phenomenon is insufficient. In this experimental study, we found that in strong electric fields, not only the velocity magnitude but also the vortex positions of ICEO are asymmetrical along the inflow and outflow directions because of the pronounced non-uniform surface electrokinetic transport. On the inflow and outflow directions, the amplitudes of velocities are unequal, ICEO maximum velocity positions change depending on the electric field intensity and sodium chloride (NaCl) concentration. Additionally, the distances between vortex centers are different. At NaCl solution concentration of 0.001 mol·L–1, the outflow velocity almost vanishes. The asymmetry rises with the increasing electric field intensity. The new discoveries can direct the application of microscale devices.

Dissecting a 30 kpc galactic outflow at z ~ 1.7

ABSTRACT We present the spatially resolved measurements of a cool galactic outflow in the gravitationally lensed galaxy RCS0327 at z ≈ 1.703 using VLT/MUSE IFU observations. We probe the cool outflowing gas, traced by blueshifted Mg ii and Fe ii absorption lines, in 15 distinct regions of the same galaxy in its image-plane. Different physical regions, 5 – 7 kpc apart within the galaxy, drive the outflows at different velocities (Vout ∼ −161 to −240 km s−1), and mass outflow rates ($\dot{M}_{out} \sim 183$ – 527 ${\rm M}_{\odot }\, \mathrm{yr}^{-1}$). The outflow velocities from different regions of the same galaxy vary by 80 km s−1, which is comparable to the variation seen in a large sample of star-burst galaxies in the local universe. Using multiply lensed images of RCS0327, we probe the same star-forming region at different spatial scales (0.5–25 kpc2), we find that outflow velocities vary between ∼ −120 and −242 km s−1, and the mass outflow rates vary between ∼37 and 254 ${\rm M}_{\odot }\, \mathrm{yr}^{-1}$. The outflow momentum flux in this galaxy is ≥ 100% of the momentum flux provided by star formation in individual regions, and outflow energy flux is ≈ 10% of the total energy flux provided by star formation. These estimates suggest that the outflow in RCS0327 is energy driven. This work shows the importance of small scale variations of outflow properties due to the variations of local stellar properties of the host galaxy in the context of galaxy evolution.

Feasibility study on evaluating right ventricular diastolic function by new Tei’-Index

ObjectiveDoppler-derived myocardial performance index (Tei) has been used in the evaluation of right ventricular (RV) function. However, the usage in isolated diastolic dysfunction is limited.We sought to find a new Tei’-index that is more appropriate for evaluating isolated diastolic dysfunction (IDD) based on the symmetry of cardiac structure and function. Methods21 patients with impaired RV relaxation were compared to 44 control subjects. Tei and Tei’ including their components, isovolumetric relaxation time (IRT), isovolumetric contraction time (ICT), the ejection time (ET), and RV rapid filling time (RFT) were measured from RV outflow and tricuspid inflow Doppler velocity profiles. ResultsTei-index have no change between IDD group and control subjects (0.21 ± 0.08 vs 0.23 ± 0.07 PNS). The Tei’-index was significantly shortened in IDD group(0.24 ± 0.09 vs 0.32 ± 0.12,p＜0.05).The decrease in Tei’-index was due to the prolongation of both IRT and RFT, and in the abbreviation of ICT. Tei’-index cutoff value of ≥0.31 identified impaired RV relaxation with a sensitivity of 50 % and specificity of 86 %.We also find that the Tei’-index correlated well with doppler measures of diastolic parameters like E/A, E/e’, DT, which suggests its potential use as a noninvasive indicator of the right ventricular (RV) relaxation in patients with heart failure of different causes. ConclusionNew Tei's index is highly effective and specific in the evaluation of early diastolic dysfunction of right ventricle, and can be used as an indicator for the detection of IDD in clinic.

CLASSY VII Lyα Profiles: The Structure and Kinematics of Neutral Gas and Implications for LyC Escape in Reionization-era Analogs* * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Lyα line profiles are a powerful probe of interstellar medium (ISM) structure, outflow speed, and Lyman-continuum escape fraction. In this paper, we present the Lyα line profiles of the Cosmic Origins Spectrograph (COS) Legacy Archive Spectroscopic SurveY, a sample rich in spectroscopic analogs of reionization-era galaxies. A large fraction of the spectra show a complex profile, consisting of a double-peaked Lyα emission profile in the bottom of a damped, Lyα absorption trough. Such profiles reveal an inhomogeneous ISM. We successfully fit the damped Lyα absorption and the Lyα emission profiles separately, but with complementary covering factors, a surprising result because this approach requires no Lyα exchange between high-N H i and low-N H i paths. The combined distribution of column densities is qualitatively similar to the bimodal distributions observed in numerical simulations. We find an inverse relation between Lyα peak separation and the [O iii]/[O ii] flux ratio, confirming that the covering fraction of Lyman-continuum-thin sightlines increases as the Lyα peak separation decreases. We combine measurements of Lyα peak separation and Lyα red peak asymmetry in a diagnostic diagram, which identifies six Lyman-continuum leakers in the COS Legacy Archive Spectrocopy SurveY (CLASSY) sample. We find a strong correlation between the Lyα trough velocity and the outflow velocity measured from interstellar absorption lines. We argue that greater vignetting of the blueshifted Lyα peak, relative to the redshifted peak, is the source of the well-known discrepancy between shell-model parameters and directly measured outflow properties. The CLASSY sample illustrates how scattering of Lyα photons outside the spectroscopic aperture reshapes Lyα profiles because the distances to these compact starbursts span a large range.

Mixing performance of an expansive mixer on viscoelastic solutions under alternating current electric field

Development of effective technologies for mixing viscoelastic solutions with reagents is still a challenge, which plays an important role in the fields of disease diagnosis, water desalination, and immunoassay. The purpose of this paper is to numerically study the mixing performance of an expansive mixer on the viscoelastic solution under the impact of an alternating current (AC) electric field through the analyzation of mixing efficiency, the concentration distribution, and average outlet velocity. A poly acrylic acid (PAA) water solution with different concentrations characterized by the Oldroyd-B constitutive model is used as a mixed medium, and an open-source toolbox called rheoTool based on finite volume algorithm is applied to solve the governing equations. We quantitatively determine the mixing efficiency for different PAA concentrations, AC electric field strengths, and frequencies and compare the mixing efficiency created by AC and direct current (DC) electric fields. Our investigation indicates that the mixing efficiency of the mixer diminishes with the PAA concentrations but enhances with the AC electric field strengths for a relatively high polymer concentration, and AC electric fields with different frequencies lead to a larger mixing efficiency than DC electric fields for a low polymer concentration. Additionally, the influence of the model parameters on the average outlet velocity and concentration distribution is discussed at length. Our numerical simulation results show that the mixer has an excellent mixing performance for both Newtonian and viscoelastic solutions, with a mixing efficiency of more than 99% at a low polymer concentration and a stable outflow velocity.

A SPectroscopic Survey of Biased Halos in the Reionization Era (ASPIRE): JWST Discovers an Overdensity around a Metal Absorption-selected Galaxy at z ∼ 5.5

The launch of JWST opens a new window for studying the connection between metal-line absorbers and galaxies at the end of the Epoch of Reionization. Previous studies have detected absorber–galaxy pairs in limited quantities through ground-based observations. To enhance our understanding of the relationship between absorbers and their host galaxies at z > 5, we utilized the NIRCam wide-field slitless spectroscopy to search for absorber-associated galaxies by detecting their rest-frame optical emission lines (e.g., [O III] + Hβ). We report the discovery of a Mg ii-associated galaxy at z = 5.428 using data from the JWST ASPIRE program. The Mg ii absorber is detected on the spectrum of quasar J0305–3150 with a rest-frame equivalent width of 0.74 Å. The associated galaxy has an [O III] luminosity of 1042.5 erg s−1 with an impact parameter of 24.9 pkpc. The joint Hubble Space Telescope–JWST spectral energy distribution (SED) implies a stellar mass and star formation rate of M * ≈ 108.8 M ⊙, star-formation rate ≈ 10 M ⊙ yr−1. Its [O III] equivalent width and stellar mass are typical of [O III] emitters at this redshift. Furthermore, connecting the outflow starting time to the SED-derived stellar age, the outflow velocity of this galaxy is ∼300 km s−1, consistent with theoretical expectations. We identified six additional [O III] emitters with impact parameters of up to ∼300 pkpc at similar redshifts (∣dv∣ < 1000 km s−1). The observed number is consistent with that in cosmological simulations. This pilot study suggests that systematically investigating the absorber–galaxy connection within the ASPIRE program will provide insights into the metal-enrichment history in the early Universe.

Comparative Study of Numerical Simulation and Experiment on Temperature Distribution and Central Vent Flow Velocity in Ceiling-vented Compartment Fire

In this study, we conducted numerical simulations to analyze fire phenomena in a compartment with a ceiling vent and compared these numerical simulation results with previous experimental data. Based on the previous experimental conditions, under the heat release rate of 1.5 kW, the vent areas of 1% and 10% of the floor area and the fire sources both at the center and side of the floor were tested. Overall trends of temperature distribution and central vent flow velocity in the present numerical simulations were consistent with those in the previous experiments. The temperature within the compartment was observed to be higher when the vent area was smaller. For compartment with a smaller vent area, the temperature distribution showed minor variations with the fire source location. However, with a larger vent area, temperatures were notably higher when the fire source was at the side than at the center. The present numerical simulations slightly overestimated the temperatures from the previous experimental results, resulting in a bias factor of 1.07 and a model's relative standard deviation of 0.07 for temperature. Regarding the flow velocity at the center of ceiling vent, the fluctuations over time were more pronounced when the fire source was centrally located. When the fire source was at the center, the average central vent outflow velocity was higher for compartment with a larger vent area. When the fire source was positioned to the side, the vent area appeared to have minimal impact on the average central vent outflow velocity. It was also observed that the average central vent outflow velocity was higher when the fire source was centrally placed when compared to a side location. The present numerical simulations underestimated the previous experimental results for the average central vent outflow velocity, and the bias factor and the model’s relative standard deviation for the average central vent outflow velocity were 0.63 and 0.39, respectively.

Accurate systemic redshifts and outflow speeds for extremely red quasars (ERQs)

ABSTRACT Extremely Red Quasars (ERQs) are thought to represent a brief episode of young quasar and galactic evolution characterized by rapid outflows and obscured growth due to dusty environments. We use new redshift measurements from CO and narrow Ly α emission-lines to better constrain outflow velocities from previous line measurements. We present sample of 82 ERQs, and the analysis confirms that ERQs have a higher incidence of large C iv blueshifts, accompanied by large Rest Equivalent Width (REW) and narrower line Full Width at Half-Maximum (FWHM) than blue quasars. We find that strong blueshifts (&amp;gt;2000 km s−1) are present in 12/54 (22.2 per cent) of ERQs with the most robust redshift indicators. At least 4 out of 15 ERQs in the sample also have blueshifts in their H β and low-ionization ultraviolet lines ranging from −500 to −1500 km s−1. ERQs with strong C iv blueshifts are substantially offset in C iv REW and FWHM from typical blue quasars in the same velocity range. ERQs have average values of REW = 124 Å and FWHM = 5274 km s−1, while blue quasars have REW = 24 Å and FWHM = 6973 km s−1. The extreme nature of the outflows in ERQs might explain some of their other spectral properties, such as the large C iv REWs and peculiar wingless profiles owing to more extended broad-line regions participating in outflows. The physical reasons for the extreme outflow properties of ERQs are unclear; however, larger Eddington ratios and/or softer ionizing spectra incident on the outflow gas cannot be ruled out.

FOREVER22: Gas and metal outflow from massive galaxies in protocluster regions

Abstract We study gas and metal outflow from massive galaxies in protocluster regions at z = 3 − 9 by using the results of FOREVER22 simulation projects. Our simulations contain massive haloes with $M_{\rm h} \gtrsim 10^{13}~\rm {\rm M}_{\odot }$, showing high star formation rates of $&amp;gt; 100~\rm {\rm M}_{\odot }~yr^{-1}$ and hosting supermassive black holes with $M_{\rm BH} \gtrsim 10^{8}~\rm {\rm M}_{\odot }$. We show that the mass loading factor (ηM) sensitively depends on the halo mass and it is ηM = 1.2 (9.2) for $M_{\rm h}= 10^{13}~(10^{11})~{\rm {\rm M}_{\odot }}$. Once the halo mass exceeds $\sim 10^{12.5}~\rm {\rm {\rm M}_{\odot }}$, the outflow velocity of the gas rapidly decreases near a virial radius, and the gas returns to a galactic centre finally as a fountain flow. Also, the metal inflow and outflow rates sensitively depend on the halo mass and redshift. At z = 3, the inflow rate becomes larger than the outflow one if $M_{\rm h}\gtrsim 10^{13.0}~{\rm {\rm M}_{\odot }}$. Thus, we suggest that massive haloes cannot be efficient metal enrichment sources beyond virial radii that will be probed in future observations, e.g., studies of metal absorption lines with the Prime Focus Spectrograph on the Subaru telescope.

Star-formation-driven outflows in local dwarf galaxies as revealed from [CII] observations byHerschel

We characterize the physical properties of star-formation-driven outflows in a sample of 29 local dwarf galaxies drawn from the Dwarf Galaxy Survey. We made use ofHerschel/PACS archival data to search for atomic outflow signatures in the wings of individual [CII] 158 μm spectra and in their stacked line profile. We find a clear excess of emission in the high-velocity tails of 11 sources, which can be explained with an additional broad component (tracing the outflowing gas) in the modeling of their spectra. The remaining objects are likely hosts of weaker outflows that can still be detected in the average stacked spectrum. In both cases, we estimate the atomic mass outflow rates which result to be comparable with the star-formation rates of the galaxies, implying mass-loading factors (i.e., outflow efficiencies) of the order of unity. Outflow velocities in all the 11 galaxies with individual detections are larger than (or compatible with) the escape velocities of their dark matter halos, with an average fraction of 40% of gas escaping into the intergalactic medium (IGM). Depletion timescales due to outflows are lower than those due to gas consumption by star formation in most of our sources, ranging from one hundred million to a few billion years. From the energetic point of view, our outflows are mostly consistent with momentum-driven winds generated by the radiation pressure of young stellar populations on dust grains, although the energy-driven scenario is not excluded if considering a coupling efficiency up to 20% between the energy injected by supernovae and the interstellar medium. Overall, our results suggest that, despite their low efficiencies, galactic outflows can regulate the star-formation history of dwarf galaxies. Specifically, they are able to enrich with metals the circumgalactic medium of these sources, bringing on average a non-negligible amount of gas into the IGM, where it will no longer be available for new star formation. Our findings are suitable for tuning chemical evolution models attempting to describe the physical processes shaping the evolution of dwarf galaxies.

Numerical study of vortex breaker optimization in a first stage oxygen tank

One of the crucial factors affecting the carrying capacity of the cryogenic liquid launch vehicle is the effective volume of the tank. Theoretical and experimental investigations on vortex breaker mechanisms have proposed promising schemes applied in the oxygen tank of the liquid-propellant launch vehicle to ensure the normal operation of the engine. In this paper, the liquid surface profile functions of the laminar core when the vortex generates were derived based on the Rankine vortex model. The dimensionless residual volume V/d3 and the Froude number were applied to compare the theoretical prediction of critical height with the actual simulation data of liquid oxygen. This comparison method can improve the model's accuracy. The efficiency of different basic shapes of vortex breakers was tested by conducting CFD modelling on a non-vertical outflow tank under a specific operating condition. Simulation results suggest negligible effects of heat transfer and surface tension. A circular plate is considered the optimal vortex breaker shape in traditional vertical outflow tanks, while a higher optimize efficiency was discovered in the half baffle basic shape in a non-vertical outflow tank by comparing the dimensionless residual volume and flow coefficient. A 34.26% reduction in flow resistance of half baffle breaker can be reached when applying a twenty-degree outlet pipe chamfering setting compared to a zero-degree chamfer. Considering practical operating limitations, it is concluded that a vortex breaker mechanism in a half baffle basic shape with a radius of 2.5d and a height of 4/d is the optimal scheme, which is suitable for all types of tanks. Its optimization efficiency of the residual volume reduction is about 56.68% compared to a no-breaker installation case. Lastly, a general equation based on CFD simulation for predicting the residual volume under a certain outflow velocity was proposed: V/d3≅αFr0.3, which trend is consistent with that of mathematical prediction V/d3≅αFr1/3. This consistency proves the accuracy and applicability of optimization strategy in this paper.

The heart of Sakurai’s object revealed by ALMA

We present high-angular-resolution observations of Sakurai’s object using the Atacama Large Millimeter Array, shedding new light on its morpho-kinematical structure. The millimetre continuum emission observed at an angular resolution of 20 milliarcsec (corresponding to 70 AU) reveals a bright compact central component whose spectral index indicates that it is composed of amorphous carbon dust. Based on these findings, we conclude that this emission traces the previously suggested dust disc observed in mid-infrared observations, and therefore our observations provide the first direct imaging of this disc. The H12CN(J = 4 → 3) line emission observed at an angular resolution of 300 milliarcsec (corresponding to 1000 AU) displays a bipolar structure with a north–south velocity gradient. From the position–velocity diagram of this emission, we identify the presence of an expanding disc and a bipolar molecular outflow. The inclination of the disc is determined to be i = 72°. The derived values for the de-projected expansion velocity and the radius of the disc are vexp = 53 km s−1 and R = 277 AU, respectively. On the other hand, the de-projected expansion velocity of the bipolar outflow detected in the H12CN(J = 4 → 3) emission is of approximately 1000 km s−1. We propose that the molecular outflow has an hourglass morphology with an opening angle of around 60°. Our observations unambiguously show that an equatorial disc and bipolar outflows formed in Sakurai’s object during the 30 years following the occurrence of the born-again event, providing important constraints for future modelling efforts of this phenomenon.