High Flux Ratios Research Articles

Effectiveness of cigarette butt filters as eco-friendly cellulose acetate membranes for organic contaminant removal

Abstract Cigarette waste is a persistent environmental problem that requires innovative solutions due to the inadequacy of traditional recycling methods. This paper explores the conversion of cigarette butt filters (CBFs) into raw material for cellulose acetate (CA) membrane production. This study prepared two types of membranes: 12% CBF and 12% CA as a control variable. The resulting material was evaluated for its properties and performance as an ultrafiltration membrane for organic contaminant removal. The result demonstrates that the CBF-based membrane exhibits superior characteristics to a CA-based membrane. This improvement is evident in the increased presence of hydroxyl (-OH) groups and enhanced porosity CA 18,37% and CBF 19,66%. Furthermore, the permeability of the CBF membrane has also increased, making it an efficient tool for maintaining humic acid removal CBF 79,02% and CA 66,18% while achieving a high flux ratio recovery CA 65,25 % and CBF 87,97%. The findings in this paper emphasize the promising potential of reusing cigarette waste as an eco-friendly membrane with high humic acid rejection and good antifouling properties.

A Strong He ii λ1640 Emitter with an Extremely Blue UV Spectral Slope at z = 8.16: Presence of Population III Stars?

Cosmic hydrogen reionization and cosmic production of the first metals are major phase transitions of the Universe occurring during the first billion years after the Big Bang; however, these are still underexplored observationally. Using the JWST/NIRSpec prism spectroscopy, we report the discovery of a sub-L * galaxy at z spec = 8.1623 ± 0.0007, dubbed RX J2129–z8He II, via the detection of a series of strong rest-frame UV/optical nebular emission lines and the clear Lyman break. RX J2129–z8He II shows a pronounced UV continuum with an extremely steep (i.e., blue) spectral slope of β=−2.53−0.07+0.06 , the steepest among all spectroscopically confirmed galaxies at z spec ≳ 7, in support of its very hard ionizing spectrum that could lead to a significant leakage of its ionizing flux. Therefore, RX J2129–z8He II is representative of the key galaxy population driving the cosmic reionization. More importantly, we detect a strong He II λ1640 emission line in its spectrum, one of the highest redshifts at which such a line is robustly detected. Its high rest-frame equivalent width (EW = 21 ± 4 Å) and extreme flux ratios with respect to UV metal and Balmer lines raise the possibility that part of RX J2129–z8He II’s stellar population could be Pop III (Pop III)-like. Through careful photoionization modeling, we show that the physically calibrated phenomenological models of the ionizing spectra of Pop III stars with strong mass loss can successfully reproduce the emission line flux ratios observed in RX J2129–z8He II. Assuming the Eddington limit, the total mass of the Pop III stars within this system is estimated to be 7.8 ± 1.4 × 105 M ⊙. To date, this galaxy presents the most compelling case in the early Universe where trace Pop III stars might coexist with metal-enriched populations.

Ultra-low work function of caesiated surfaces and impact of selected gas species

Modern high-power negative hydrogen ion sources rely predominantly on the surface production of negative hydrogen ions. Hence, low work function converter surfaces are mandatory, for which the alkali metal Cs is commonly evaporated into the ion source to lower the work function of refractory metals by surface adsorption. To study the work function behaviour upon caesiation under the typically given non-ultra-high vacuum conditions, investigations are performed at a dedicated laboratory experiment. In a vacuum environment dominated by water vapour, the work function evolution is found to be dependent on the flux ratio of Cs to H2O onto the surface. For sufficiently high flux ratios, ultra-low work functions in the range of 1.25±0.10 eV are generated with excellent reproducibility. In the absence of Cs evaporation, the work function gradually increases under the influence of the residual gases, and re-caesiation processes lead to lower quantum efficiencies and higher work functions of typically 1.9–2.1 eV. While the addition of hydrogen and deuterium gas at several Pa as well as the leakage of inert gases (argon and nitrogen) into the vacuum system have a negligible influence on the caesiation process, small amounts of oxygen with partial pressures of ∼10-2–10-1 Pa lead to an instant reduction of the Cs density in the gas phase by several orders of magnitude and to an increase in the work function of the order of 1 eV. After the oxygen exposure is terminated, however, the Cs density and work function fully recover within several minutes.

Polycyclic aromatic hydrocarbon luminous galaxies in JWST CEERS data

ABSTRACT It has been an unanswered question how many dusty galaxies have been undetected from the state-of-the-art observational surveys. JWST enables us to detect faint infrared (IR) galaxies that have prominent polycyclic aromatic hydrocarbon (PAH) features in the mid-IR wavelengths. PAH is a valuable tracer of star formation and dust properties in the mid-IR wavelength. The JWST Cosmic Evolution Early Release Science (CEERS) fields provide us with wavelength coverage from 7.7 to 21 μm using six photometric bands of the mid-IR instrument (MIRI). We have identified galaxies dominated by mid-IR emission from PAHs, termed PAH galaxies. From our multiband photometry catalogue, we selected 10 PAH galaxies displaying high flux ratios of log (S15/S10) > 0.8. The SED fitting analysis indicates that these galaxies are star-forming galaxies with total IR luminosities of 1010 ∼ 1011.5 L⊙ at z ∼1. The morphology of PAH galaxies does not show any clear signatures of major merging or interaction within the MIRI resolution. The majority of them are on the star-formation main sequence at z ∼ 1. Our result demonstrates that JWST can detect PAH emissions from normal star-forming galaxies at z ∼ 1, in addition to ultra-luminous infrared galaxies or luminous IR galaxies (LIRGs).

Accelerating Uranium Extraction from Water via Synergy of Adsorption and Filtration by MOF Hybrid Membrane

AbstractIn this paper, novel UiO‐66‐AO‐based adsorption‐filtration hybrid membranes (UAMs) are prepared via an irradiation‐mediated growth strategy to simultaneously improve water flux and accelerate uranium extraction from water resources. The UAM shows an equilibrium adsorption that is four times faster than UiO‐66‐AO powder and an adsorption capacity that is over two times higher. UAM also achieves a record synergy of high flux and high uranium removal ratio from simulated seawater (1358.8 L m−2 h−1, 84.5%) by one‐time filtration under ambient temperature and pressure (the adsorption is 1.83 mg g−1 in 90 min). The excellent uranium extraction performance is attributed to the unique UAM structure, in which water flows through the channels of thin metal‐organic framework (MOF) film without blocking by substrate leading to the high flux during filtration, and the full contact of uranium with abundant exposed active sites promotes the adsorption. This work will be conducive to overcoming the bottleneck problems of uranium extraction from water resources.

Multi‐assembled nanofiltration membranes with excellent separation and catalytic performance

AbstractBACKGROUNDAccording to the characteristics of various nanomaterials, assembling these nanomaterials is an effective way to control the structure and properties of nanocomposites.RESULTSIn this work, nanofiltration membranes (NM) were prepared by assembling several nanomaterials that have excellent separation and catalytic properties. SiO2 nanoparticles were employed to optimize the water nanochannels between graphene oxide (GO) nanosheets to fabricate GO/SiO2 NM, whose water flux was 73.2 L m−2 h−1 and the rejection ratio was 99.1%. The combination of high‐conductivity hydroxylated graphene (G‐OH) with flake NiCo‐BDC (BDC refers to deprotonated terephthalic acid) ultra‐thin metal organic framework (UMOF) to obtain UMOF&G‐OH could improve the catalytic performance of the UMOF by about 23.5%. In order to realize the synchronous catalysis and separation performance of nanofiltration membrane, UMOF&G‐OH was reassembled with GO and SiO2. The pure water flux of (UMOF&G‐OH)/GO/SiO2 nanofiltration membrane was 95.8 L m−2 h−1 and the rejection ratio was 99.1%. TiO2 nanoparticles were added to the membrane to regulate the distance between the flake, and the selective permeation of the composite membrane was further improved to 99.9%; the pure water flux reached 92.6 L m−2 h−1.CONCLUSIONThe introduction of G‐OH would be beneficial in improving the migration and separation efficiency of the photogenerated electron holes, and effectively improve the catalytic performance of the semiconductor catalyst. Through the assembly of a variety of nanoparticles and lamellar materials, the water nanochannel could be accurately controlled and the catalytic performance of the membrane could be given, so as to obtain a nanofiltration membrane with high water flux and high rejection ratio. © 2023 Society of Chemical Industry.

Evaluation of Different Reverse Osmosis Membranes for Textile Dyeing and Finishing Wastewater Reuse

Different commercial reverse osmosis (RO) membranes from Vontron and DuPont Filmtec were evaluated for textile dyeing and finishing wastewater (TDFW) reuse in China. All six tested RO membranes produced qualified permeate meeting TDFW reuse standards at a water recovery ratio (WRR) of 70% in single batch tests. The rapid decline of apparent specific flux at WRR over 50% was mainly ascribed to feed osmotic pressure increase caused by concentrating effects. Multiple batch tests using Vontron HOR and DuPont Filmtec BW RO membranes with comparable permeability and selectivity demonstrated the reproducibility and showed low fouling development. The occurrence of carbonate scaling on both RO membranes was identified by scanning electron microscopy and energy disperse spectroscopy. No obvious organic fouling was detected on both RO membranes by attenuated total reflectance Fourier transform infrared spectrometry. From the orthogonal tests, with an integrated RO membrane performance index (i.e., 25% rejection ratio of total organic carbon + 25% rejection ratio of conductivity + 50% flux ratio of final to initial) as a target, the optimal parameters were determined as WRR of 60%, cross-flow velocity (CFV) of 1.0 m/s, temperature (T) of 20 °C for both RO membranes, while trans-membrane pressures (TMP) of 2 and 4 MPa were optimal for Vontron HOR RO membrane and DuPont Filmtec BW RO membrane, respectively. Both RO membranes with the optimal parameters produced good permeate quality for TDFW reuse and kept a high flux ratio of final to initial, demonstrating the effectiveness of the orthogonal tests.

Effect of Radiation Quality and Relative Humidity on Intumescence Injury and Growth of Tomato Seedlings

Intumescence is a physiological disorder that affects some tomato (Solanum lycopersicum) cultivars grown in environments lacking ultraviolet radiation. Both far-red (FR) radiation and blue light have been shown to help mitigate this disorder. Thus, the objectives of this study were to characterize and compare intumescence injury and growth of various tomato cultivars propagated under different radiation qualities (Expt. 1) and to evaluate plant responses to the interactive effect of radiation quality and relative humidity (RH) (Expt. 2). Seedlings of six cultivars in Expt. 1 were grown under broad band white light (W), W and blue with (WBFR) or without (WB) FR radiation, and blue and red light with FR radiation (BRFR). Seedlings of four cultivars in Expt. 2 were grown under W or WBFR and a low (≈50%) or high (≈95%) RH. In both experiments, seedlings were grown under a daily light integral of ≈13 mol·m‒2·d‒1 (200 ± 4 μmol·m‒2·s‒1 for 18 h·d−1). FR radiation was provided using 20 ± 2 μmol·m−2·s−1 delivered throughout the entire photoperiod or at the end-of-day (EOD) in Expts. 1 or 2, respectively. Intumescence was generally suppressed when seedlings in Expt. 1 were grown under BRFR and WBFR, which also corresponded with the general response to stomatal conductance (gs). In contrast, seedlings grown under W had the highest incidence of intumescence, ranging from 23% to 69% across cultivars. The high blue photon flux (PF) ratio in WB was not effective at suppressing intumescence injury without FR radiation, although incidence and severity were lower compared with W. In Expt. 2, intumescence incidence was generally lower in seedlings grown under WBFR, and RH had small effects on intumescence. In both experiments, younger leaves were relatively less affected by intumescence, suggesting that a developmental factor is associated with the disorder. As expected, providing FR radiation resulted in a general increase in stem height across cultivars and in both experiments. The high RH provided in Expt. 2 also resulted in an increase in stem height. However, seedlings under low RH produced larger leaves, lower specific leaf area, and more shoot dry mass than those under high RH. Overall, our findings show that applying FR radiation helps suppress intumescence, but strategies are needed to minimize issues with excessive stem elongation.

Designing heterogeneous MOF-on-MOF membrane with hierarchical pores for effective water treatment

Rationally regulating the separation pores is an effective way to achieve efficient separation membrane. However, the developed metal-organic framework (MOF) membranes for water treatment are all formed by one kind of MOF, which can only provide rigid pores, makes it difficult to achieve high flux and excellent rejection ratio simultaneity. Here, we proposed a facile strategy for the synthesis of heterogeneous MOF-on-MOF membrane with hierarchical pores, by site-specific grown ZIF-8 layer on UiO-66-NH2 layer. Thus unique architecture of the obtained double-layered MOF membrane (UiO-66-NH2@ZIF-8) endows multidimensional separation pores: (i) the large pores of UiO-66-NH2 can facilitate water transportation, (ii) the molecular-sieving pores of ZIF-8 can intercept dyes, (iii) UiO-66-NH2 acting as active sites can promote the growth of ZIF-8. As a result, the optimized UiO-66-NH2@ZIF-8 membrane exhibits high flux (36.7 L m−2 h−1 bar−1) and excellent dye rejections (>97.0%). Through analysis and comparison, the regulated multi-type pores play an important role in membrane performance. Coupled with the facile membrane preparing method, this work can used as a potential approach of designing other advanced MOF membrane for water treatment.

Top-heavy stellar mass distribution in galactic nuclei inferred from the universally high abundance ratio of [Fe/Mg

ABSTRACT Recent observations of active galactic nuclei (AGNs) have shown a high Fe ii/Mg ii line-flux ratio in their broad-line regions, nearly independent of redshift up to z ≳ 6. The high flux ratio requires rapid production of iron in galactic nuclei to reach an abundance ratio of [Fe/Mg] ≳ 0.2 as high as those observed in matured galaxies in the local universe. We propose a possible explanation of rapid iron enrichment in AGNs by massive star formation that follows a top-heavy initial mass function (IMF) with a power-law index of Γ larger than the canonical value of Γ = −2.35 for a Salpeter IMF. Taking into account metal production channels from different types of SNe, we find that the high value of [Fe/Mg] ≳ 0.2 requires the IMF to be characterized with Γ ≳ −1 (Γ ≳ 0) and a high-mass cutoff at Mmax ≃ 100–150 M⊙ (Mmax ≳ 250 M⊙). Given the conditions, core-collapse SNe with M* ≳ 70 M⊙ and pair-instability SNe give a major contribution for iron enrichment. Such top-heavy stellar IMFs would be a natural consequence from mass growth of stars formed in dense AGN discs under Bondi-like gas accretion that is regulated by feedback at M* ≳ 10 M⊙. The massive stellar population formed in AGN discs also leave stellar-mass black hole remnants, whose mergers associated with gravitational-wave emission account for at most 10 per cent of the merger rate inferred from LIGO/Virgo observations to simultaneously explain the high [Fe/Mg] ratio with metal ejection.

Improvement in the Filtration Performance of an Ultraporous Nanofiber Membrane by Atmospheric Pressure Plasma-Induced Surface Modification.

Nanofiber membranes have outstanding potential for filtration applications due to their great specific surface area, high porosity, and modifiable structure. Compared to conventional membranes, nanofiber membranes offer substantial high flux and high rejection ratios. This paper provides a comprehensive analysis on the filtration performance of plasma treatment on the polyacrylonitrile nanofiber membrane. The pores in the original membrane were utilized about a mere 10%, while those of the plasma-irradiated membrane were utilized nearly 60%. The membrane modification was performed using N2, O2, and Ar plasma. It was found that Ar plasma was most effective for etching the membrane structure. Fourier transform infrared spectroscopy was applied to detect the chemical changes on the membranes. The contact angle of the water droplets on the original membrane was 96.1°; however, after the Ar plasma treatment, it declined to 0°. Finally, the particle retention details in different cross sections of the filtered membranes were observed via a scanning electron microscope. The main innovation is to clarify the changes in the mechanism of the nanofiber membrane trapping particles before and after plasma treatment. In the filtration test after plasma treatment, the internal space of the membrane was fully and effectively utilized, and the flux was also improved. The obtained results suggest a potential application of the plasma-treated nanofiber membrane in water treatment.

Conductive 3D networks in a 2D layer for high performance ultrafiltration membrane with high flux-retention and robust cyclic stability

A series of highly performing ultrafiltration membranes have been recently developed, but it is still a withstanding challenge that the ultrafiltration membrane can retain both high flux and high retention ratio without sacrificing the cycle life. In this paper, we construct a novel conductive 3D network in a 2D layer for polyethersulfone membrane, which is self-assembled by graphene oxide, carbon nanotubes, and polyaniline based on the non-solvent induced phase-inversion separation method. The unique 3D network structure and the distinctive selective layer of polyethersulfone membrane possesses molecule transport channels, double-layer intercepted area, and rigid hybrid structure, which contributes effectively to the small molecule's flux, high molecule's retention, and the membrane cyclic stability. The fabricated ultrafiltration membrane exhibits high retention of solute molecules (over 99%), high flux, and extended life span and stability, due to the improvement in the anti-fouling property. Furthermore, the pseudocapacitance of the conductive polymer polyaniline is used to in-situ monitor the fouling behavior, in order to achieve precise decontamination and prolong the long-term life. The results show that the prepared membrane would have high potential applications in relevant environmental separation processes.

Experimental Study on Film Cooling Effectiveness of Blade With Chevron-Shaped Holes Under Wake Influence

Abstract Gas turbines have been widely used. With the continuous improvement of the performance of gas turbines, the turbine inlet temperature has greatly exceeded the heat-resistance limit of the turbine blade material, so advanced cooling technology is required. The film cooling effectiveness distribution over the blade under the effect of wake was obtained by the pressure-sensitive paint (PSP) technique. The test blade has five rows of chevron film holes on the pressure side, three rows of cylindrical film holes on the leading edge, and three rows of chevron film holes on the suction side. The mainstream Reynolds number is 130,000 based on the blade chord length, and the mainstream turbulence intensity is 2.7%. The upstream wake was simulated by the spoken-wheel type wake generator. The film cooling effectiveness was measured at three wake Strouhal numbers (0, 0.12, and 0.36) and three mass flux ratios (MFR1, MFR2, and MFR3). The results show that the increase of mass flux ratio leads to a decrease of the film cooling effectiveness on the suction surface. In the wake condition, the effect of mass flux ratio is weakened. Wake leads to a marked decrease of the film cooling effectiveness over most blade surface except for the surface near leading edge on the pressure surface. In the high mass flux ratio condition, the effect of wake on the film cooling effectiveness is weakened on the suction surface and strengthened on the pressure surface.

Templating metal-organic framework into fibrous nanohybrids for large-capacity and high-flux filtration interception

Engineering metal-organic-frameworks (MOFs) into flexible hybrid membranes has been endeavored to entrap various molecules through a conventional filtration process. In most cases, both the rejection ratio and adsorption capacity may be limited by a low MOF loading amount, polymeric coating barrier, or large flow flux. It remains challenging to achieve the combination of large-capacity adsorption, high flux and large rejection ratio in an individual filtration setup. Herein through an in-situ templating synthesis, nanofibers of zeolitic imidazolate frame work-8 (ZIF-8) with the distinct diameters of ~20 nm and ~100 nm were produced by coating on aramid nanofibrils and silk microfibrils, respectively. With the super loading amount of ZIF-8 up to ~70 wt%, these fibrous nanohybrids enabled to produce spider-web-like membranes with both the high rejection ratio (>99%) and large flow flux (up to ~390 L m-2 h-1 bar-1 at thickness of ~120 μm). Their superior adsorption capacities for organic dyes also ensured the maintenance of high rejection ratios at high flow flux for large-volume filtration. Thus, the template of two types of nanofibrils may offer a facile method to design web-like MOF membranes with hierarchical microstructures and to intercept a large amount of specific molecules through a continuous “one-pass” filtration process for practical applications.

Adsorption-controlled growth of MnTe(Bi2Te3)n by molecular beam epitaxy exhibiting stoichiometry-controlled magnetism

We report the growth of the intrinsic magnetic topological system MnTe(Bi2Te3)n by molecular beam epitaxy. By mapping the temperature and the Bi:Mn flux ratio, it is shown that there is a narrow growth window for the n=1 phase MnBi2Te4 with 2.0<Bi:Mn<2.6 at 225 {\deg}C. Here the films are stoichiometric and excess Bi and Te is not incorporated. At higher flux ratios (Bi:Mn>4.5) it is found that the n = 2 MnBi4Te7 phase is stabilized. Transport measurements indicate that the MnBi2Te4 and MnBi4Te7 undergo magnetic transitions around 25 K, and 10 K, respectively, consistent with antiferromagnetic phases found in the bulk. Further, for Mn-rich conditions (Bi:Mn<2), ferromagnetism emerges that exhibits a clear hysteretic state in the Hall effect, which likely indicates Mn-doped MnBi2Te4. Understanding how to grow ternary chalcogenide phases is the key to synthesizing new materials and to interface magnetism and topology, which together are routes to realize and control exotic quantum phenomena.

Cell-Free Biocatalysis for the Production of Platform Chemicals

Genetically engineered host bacteria have an extensive history for the production of specific proteins including the synthesis of single enzymes for the modification of compounds produced for industrial purposes by biological or chemical processes. Such processes have been developed largely through the process of discovery. The ability to assemble multiple enzymes into synthetic pathways is a new development aided by the synthetic biology approach of constructing and assembling suitable enzymes into pathways that may or may not occur in Nature to provide a high-impact platform for bio-manufacturing of chemicals, biofuels and pharmaceuticals. Industry has depended on chemical catalysts because of the known constraints experienced frequently with biological catalysts but when high stereochemistry, mild synthesis conditions and environmentally friendly processes are significant, application of enzymes is preferred, especially in the case of drug synthesis where enantioselectivity is important. However, many whole cell production processes are beset by toxicity problems, metabolite competition, the production of side products, sub-optimal enzyme ratios and varying temperature optima. As a result, a cell-free biocatalysis allows the manipulation of substrate ratios, provision of regenerated cofactors and adjustment of high energy flux ratios that are difficult or impossible to control in whole cell synthesis. We discuss here the construction of cell free biocatalytic pathways as added free enzymes or multi-enzyme modules that may contain heterologous catalysts. We examine the status of applications leading to commercialisation, emphasizing the importance of economical cofactor regeneration. Nevertheless, problems remain, particularly protein post-translational modifications including glycosylation, phosphorylation, ubiquination, acetylation, proteolysis, etc. The National Renewable Energy Laboratory and Pacific North West Laboratory have published lists of top value-added chemicals from biomass that include glucaric acid. There have been few reports on the combination of synthetic biology and cell-free protein synthesis to set up pathways for these valuable intermediate compounds. This observation is despite the existence of at least one large scale but specialised cell-free production of antibody conjugates. This review will provide a description of one successful attempt at the cell-free production of glucaric acid and will evaluate progress for other key intermediate and platform chemicals.

Investigation of Plume Offset Characteristics in Bubble Columns by Euler–Euler Simulation

Based on low-cost and easy to enlarge, the bubble column device has been widely concerned in chemical industry. This paper focuses on bubble plumes in laboratory-scale three-dimensional rectangular air-water columns. Static behavior has been investigated in many experiments and simulations, and our present investigations consider the dynamic behavior of bubble plume offset in three dimensions. The investigations are conducted with a set of closure models by the Euler–Euler approach, and subsequently, literature data for rectangular bubble columns are analyzed for comparison purposes. Moreover, the transient evolution characteristics of the bubble plume in the bubble column and the gas phase distribution in sections are introduced, and the offset characteristics and the oscillation period of the plume are analyzed. In addition, the distributions of the vector diagram of velocity and vortex intensity in the domain are given. The effects of different fluxes and column aspect ratios on bubble plumes are studied, and the offset and plume oscillation period (POP) characteristics of bubbles are examined. The investigations reveal quantitative correlations of operating conditions (gas volume flux) and aspect ratios that have not been reported so far, and the simulated and experimental POP results agree well. An interesting phenomenon is that POP does not occur under conditions of a high flux and aspect ratio, and the corresponding prediction values for the conditions with and without POP are given as well. The results reported in this paper may open up a new way for further study of the mass transfer of bubble plumes and development of chemical equipment.

Diverse properties of Ly α emission in low-redshift compact star-forming galaxies with extremely high [O iii]/[O ii] ratios

ABSTRACT We present observations with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope of eight compact star-forming galaxies at redshifts z = 0.02811–0.06540, with low oxygen abundances 12 + log(O/H) = 7.43–7.82 and extremely high emission-line flux ratios O32 = [O iii] λ5007/[O ii] λ3727 ∼ 22–39, aiming to study the properties of Ly α emission in such conditions. We find a diversity in Ly α properties. In five galaxies Ly α emission line is strong, with equivalent width (EW) in the range 45–190 Å. In the remaining galaxies, weak Ly α emission with EW(Ly α) ∼ 2–7 Å is superposed on a broad Ly α absorption line, indicating a high neutral hydrogen column density N(H i) ∼ (1 – 3)× 1021 cm−2. We examine the relation between the Ly α escape fraction fesc(Ly α) and the Lyman continuum escape fraction fesc(LyC), using direct measures of the latter in eleven low-redshift LyC leakers, to verify whether fesc(Ly α) can be an indirect measure of escaping LyC radiation. The usefulness of O32, of the Ly α equivalent width EW(Ly α), and of the Ly α peak separation Vsep as indirect indicators of Ly α leakage is also discussed. It is shown that there is no correlation between O32 and fesc(Ly α). We find an increase of fesc(Ly α) with increasing EW(Ly α) for EW(Ly α) &lt;100 Å, but for higher EW(Ly$\alpha)\gtrsim$150 Å the fesc(Ly α) is nearly constant attaining the value of ∼0.25. We find an anticorrelation between fesc(Ly α) and Vsep, though not as tight as the one found earlier between fesc(LyC) and Vsep. This finding makes Vsep a promising indirect indicator of both the Ly α and ionizing radiation leakage.

APOGEE/Kepler Overlap Yields Orbital Solutions for a Variety of Eclipsing Binaries

Abstract Spectroscopic eclipsing binaries (SEBs) are fundamental benchmarks in stellar astrophysics and today are observed in breathtaking detail by missions like the Transiting Exoplanet Survey Satellite (TESS), Kepler, and Apache Point Observatory Galactic Evolution Experiment (APOGEE). We develop a methodology for simultaneous analysis of high-precision Kepler light curves and high-resolution near-infrared spectra from APOGEE and present orbital solutions and evolutionary histories for a subset of SEBs within this overlap. Radial velocities extracted from APOGEE spectra using the broadening function (BF) technique are combined with Kepler light curves and to yield binary orbital solutions. The BF approach yields more precise radial velocities than the standard cross-correlation function, which in turn yields more precise orbital parameters and enables the identification of tertiary stars. The orbital periods of these seven SEBs range from 4 to 40 days. Four of the systems (KIC 5285607, KIC 6864859, KIC 6778289, and KIC 4285087) are well-detached binaries. The remaining three systems have apparent tertiary companions, but each exhibit two eclipses along with at least one spectroscopically varying component (KIC 6449358, KIC 6131659, and KIC 6781535). Gaia distances are available for four targets which we use to estimate temperatures of both members of these SEBs. We explore evolutionary histories in H–R diagram space and estimate ages for this subset of our sample. Finally, we consider the implications for the formation pathways of close binary systems via interactions with tertiary companions. Our methodology combined with the era of big data and observation overlap opens up the possibility of discovering and analyzing large numbers of diverse SEBs, including those with high flux ratios and those in triple systems.

Electrospun polyvinylidene fluoride/fluorinated acrylate copolymer tree-like nanofiber membrane with high flux and salt rejection ratio for direct contact membrane distillation

A hierarchical tree-like nanofiber membrane (TLNM) with high hydrophobicity was prepared via electrospinning polyvinylidene fluoride (PVDF) blended with tetrabutylammonium chloride (TBAC) and fluorinated acrylate copolymer (FA). Then, the hydrophobicity of PVDF/TBAC/FA TLNMs was further enhanced after ultrasonic treatment. The introduction of TBAC and FA promoted the formation of tree-like structures and the as-prepared PVDF/TBAC/FA TLNMs showed strong hydrophobicity with a water contact angle of 137 ± 3°, extremely small pore size of 0.21–0.26 μm, outstanding mechanical strength of 7.90 MPa and high liquid entry pressure of 0.23 MPa, making the membrane possess excellent performance in the direct contact membrane distillation (DCMD) process. The PVDF/TBAC/3% FA TLNMs with a thickness of 60 ± 3 μm showed a superior permeate flux of 54.39 L/m2 h and the salt rejection rate kept above 99.5% after 9 h using a 3.5 wt% NaCl as the feed solution while with the feed and permeate temperatures were set as 60 °C and 20 °C, respectively. This work highlights the promising application of this TLNMs in the field of membrane distillation.