Deriving Stellar Effective Temperatures of Metal-Poor Stars with the Excitation Potential Method

It is well established that stellar effective temperatures determined from photometry and spectroscopy yield systematically different results. We describe a new, simple method to correct spectroscopically derived temperatures ("excitation temperatures") of metal-poor stars based on a literature sample with -3.3<[Fe/H]<-2.5. Excitation temperatures were determined from FeI line abundances in high-resolution optical spectra in the wavelength range of ~3700 to ~7000A, although shorter wavelength ranges, up to 4750 to 6800A, can also be employed, and compared with photometric literature temperatures. Our adjustment scheme increases the temperatures up to several hundred degrees for cool red giants, while leaving the near-main-sequence stars mostly unchanged. Hence, it brings the excitation temperatures in good agreement with photometrically derived values. The modified temperature also influences other stellar parameters, as the FeI-FeII ionization balance is simultaneously used to determine the surface gravity, while also forcing no abundance trend on the absorption line strengths to obtain the microturbulent velocity. As a result of increasing the temperature, the often too low gravities and too high microturbulent velocities in red giants become higher and lower, respectively. Our adjustment scheme thus continues to build on the advantage of deriving temperatures from spectroscopy alone, independent of reddening, while at the same time producing stellar chemical abundances that are more straightforwardly comparable to studies based on photometrically derived temperatures. Hence, our method may prove beneficial for comparing different studies in the literature as well as the many high-resolution stellar spectroscopic surveys that are or will be carried out in the next few years.Comment: 12 pages, emulateapj, accepted for publication in Ap

The Aquarius Co-Moving Group is Not a Disrupted Classical Globular Cluster

We present a detailed analysis of high-resolution, high S/N spectra for 5 Aquarius stream stars observed with the MIKE spectrograph on the Magellan Clay telescope. Our sample represents one third of the 15 known members in the stream. We find the stream is not mono-metallic: the metallicity ranges from [Fe/H] = -0.63 to -1.58. No anti-correlation in Na-O abundances is present, and we find a strong positive Mg-Al relationship, similar to that observed in the thick disk. We find no evidence that the stream is a result of a disrupted classical globular cluster, contrary to a previously published claim. High [(Na, Ni, alpha)/Fe] and low [Ba/Y] abundance ratios in the stream suggests it is not a tidal tail from a disrupted dwarf galaxy, either. The stream is chemically indistinguishable from Milky Way field stars with the exception of one candidate, C222531-145437. From its position, velocity, and detailed chemical abundances, C222531-145437 is likely a star that was tidally disrupted from omega-Centauri. We propose the Aquarius stream is Galactic in origin, and could be the result from a disk-satellite perturbation in the Milky Way thick disk on the order of a few Gyr ago: derived orbits, UVW velocities, and angular momenta of the Aquarius members offer qualitative support for our hypothesis. Assuming C222531-145437 is a tidally disrupted member of omega-Centauri, this system is the most likely disk perturber. In the absence of compelling chemical and/or dynamical evidence that the Aquarius stream is the tidal tail of a disrupted satellite, we advocate the "Aquarius group" as a more appropriate description. Like the Canis Major over-density, as well as the Hercules and Monoceros groups, the Aquarius group joins the list of kinematically-identified substructures that are not actually accreted material: they are simply part of the rich complexity of the Milky Way structure.Comment: Accepted to MNRAS. Updated to journal versio

High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey

The SkyMapper Southern Sky Survey is carrying out a search for the most metal-poor stars in the Galaxy. It identifies candidates by way of its unique filter set that allows for estimation of stellar atmospheric parameters. The set includes a narrow filter centered on the Ca II K 3933A line, enabling a robust estimate of stellar metallicity. Promising candidates are then confirmed with spectroscopy. We present the analysis of Magellan-MIKE high-resolution spectroscopy of 122 metal-poor stars found by SkyMapper in the first two years of commissioning observations. 41 stars have [Fe/H] <= -3.0. Nine have [Fe/H] <= -3.5, with three at [Fe/H] ~ -4. A 1D LTE abundance analysis of the elements Li, C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, Ba and Eu shows these stars have [X/Fe] ratios typical of other halo stars. One star with low [X/Fe] [X/Fe values appears to be "Fe-enhanced," while another star has an extremely large [Sr/Ba] ratio: >2. Only one other star is known to have a comparable value. Seven stars are "CEMP-no" stars ([C/Fe] > 0.7, [Ba/Fe] < 0). 21 stars exhibit mild r-process element enhancements (0.3 <=[Eu/Fe] < 1.0), while four stars have [Eu/Fe] >= 1.0. These results demonstrate the ability to identify extremely metal-poor stars from SkyMapper photometry, pointing to increased sample sizes and a better characterization of the metal-poor tail of the halo metallicity distribution function in the future.Comment: Minor corrections to text, missing data added to Tables 3 and 4; updated to match published version. Complete tables included in sourc

Deriving stellar effective temperatures of metal-poor stars with the excitation potential method

It is well established that stellar effective temperatures determined from photometry and spectroscopy yield systematically different results. We describe a new, simple method to correct spectroscopically derived temperatures ("excitation temperatures")

Genome-Wide Identification and Expression Analysis of the <i>PpYUCCA</i> Gene Family in Weeping Peach Trees (<i>Prunus persica</i> ‘Pendula’)

Auxin is an important endogenous plant hormone that is usually present as indole-3-acetic acid (IAA). The flavin monooxygenase YUCCA is the rate-limiting enzyme of IAA biosynthesis and plays an important regulatory role in plant growth and development. To further investigate the function of the YUCCA gene family in weeping peach trees, members of the YUCCA gene family were identified via bioinformatics analysis. The gene structure and conserved domains of the weeping peach YUCCA genes were investigated, and phylogenetic analysis and gene annotation were carried out. Fourteen PpYUCCAs were identified in the weeping peach variety ‘Hongchuizhi’ and were found to be randomly located on five different chromosomes. Moreover, the prediction of subcellular localization showed that most of the YUCCA proteins were localized in the cytoplasm. Based on our transcriptome analysis, only nine PpYUCCAs, including PpYUCCA1, PpYUCCA3/4/5/6, PpYUCCA9, and PpYUCCA12/13/14, were expressed in the weeping peach branches, which could result in the accumulation of auxin. PpYUCCA6/12 may play a critical role in the appearance of the weeping trait, as indicated by the higher expression levels found in the Hongchuizhi variety compared with the Xiahui 6 variety. The results of this study provide a foundation for further research on the biological functions of PpYUCCAs in weeping peach trees

Rapid Assessment of Ocular Toxicity from Environmental Contaminants Based on Visually Mediated Zebrafish Behavior Studies

The presence of contaminants in the environment has increased in recent years, and studies have demonstrated that these contaminants have the ability to penetrate the blood–retinal barrier and directly affect the visual systems of organisms. Zebrafish are recognized as an ideal model for human eye diseases due to their anatomical and functional similarities to the human eye, making them an efficient and versatile organism for studying ocular toxicity caused by environmental contaminants in the field of environmental toxicology. Meanwhile, zebrafish exhibit a diverse repertoire of visually mediated behaviors, and their visual system undergoes complex changes in behavioral responses when exposed to environmental contaminants, enabling rapid assessment of the ocular toxicity induced by such pollutants. Therefore, this review aimed to highlight the effectiveness of zebrafish as a model for examining the effects of environmental contaminants on ocular development. Special attention is given to the visually mediated behavior of zebrafish, which allows for a rapid assessment of ocular toxicity resulting from exposure to environmental contaminants. Additionally, the potential mechanisms by which environmental contaminants may induce ocular toxicity are briefly outlined

Hand Sanitizer Gels: Classification, Challenges, and the Future of Multipurpose Hand Hygiene Products

Hand hygiene is a crucial measure in the prevention and control of infections, and there is a growing awareness among individuals who are making a conscious effort to maintain hand cleanliness. With the advent of the SARS-CoV-2 outbreak, the demand for hand hygiene products has also gradually shifted towards those with antimicrobial properties. Among these products, hand sanitizer gels (HSGs) have gained considerable popularity as an efficient method of hand cleaning, due to their rapid drying and sustained antimicrobial efficacy. Concurrently, there has been a growing interest in novel HSGs that offer additional functions such as skin whitening, moisturizing, and anti-inflammatory effects. These novel HSGs effectively address concerns associated with the ingestion of antimicrobial ingredients and demonstrate reduced skin irritation, thereby alleviating hand dermatological issues. This review provides an extensive overview of the application scenarios, classification, and challenges associated with HSGs while emphasizing the emergence of novel components with biological functions, aiming to contribute to the advancement of hand hygiene practices and offer novel insights for the development of novel HSGs with outstanding antimicrobial properties with other multiple biological functions and desirable biosafety profiles

The invisible Threat: Assessing the reproductive and transgenerational impacts of micro- and nanoplastics on fish

Micro- and nanoplastics (MNPs), emerging as pervasive environmental pollutants, present multifaceted threats to diverse ecosystems. This review critically examines the ability of MNPs to traverse biological barriers in fish, leading to their accumulation in gonadal tissues and subsequent reproductive toxicity. A focal concern is the potential transgenerational harm, where offspring not directly exposed to MNPs exhibit toxic effects. Characterized by extensive specific surface areas and marked surface hydrophobicity, MNPs readily adsorb and concentrate other environmental contaminants, potentially intensifying reproductive and transgenerational toxicity. This comprehensive analysis aims to provide profound insights into the repercussions of MNPs on fish reproductive health and progeny, highlighting the intricate interplay between MNPs and other pollutants. We delve into the mechanisms of MNPs-induced reproductive toxicity, including gonadal histopathologic alterations, oxidative stress, and disruptions in the hypothalamic-pituitary–gonadal axis. The review also underscores the urgency for future research to explore the size-specific toxic dynamics of MNPs and the long-term implications of chronic exposure. Understanding these aspects is crucial for assessing the ecological risks posed by MNPs and formulating strategies to safeguard aquatic life

Behavioral Studies of Zebrafish Reveal a New Perspective on the Reproductive Toxicity of Micro- and Nanoplastics

The escalating prevalence of microplastics and nanoplastics in aquatic environments is a major challenge affecting the behavior and reproductive health of aquatic organisms while posing potential risks to human health and ecosystems. This review focuses on the neurobehavioral changes and reproductive toxicity of MNPs in zebrafish and their relationships. At the same time, the neurobehavioral changes caused by MNPs were studied, and the synergistic effects of the interaction of these pollutants with other environmental contaminants were explored. In addition, zebrafish, as a model organism, provide valuable insights into the subtle but important effects of MNPs on reproductive behavior, which is critical for understanding reproductive success, suggesting that behavioral changes can serve as an early biomarker of reproductive toxicity. In addition, based on classical endocrine disruptor models and behavioral research methods, the current status of the research on the reproductive toxicity of MNPs in zebrafish was reviewed, which further indicated that the behavioral parameters of zebrafish can be used as an effective and rapid tool to evaluate the reproductive toxicity of MNPs. However, behavioral methods for rapidly assessing the toxicity of MNPs are still an area of exploration. To address limitations and challenges in the current scope of research, this review outlines future research directions with the aim of improving our understanding of the environmental and health impacts of MNPs. This work aims to inform targeted environmental policies and advance public health strategies to address the growing challenge of MNPs pollution