Carbon monoxide in an extremely metal-poor galaxy

Extremely metal-poor galaxies with metallicity below 10% of the solar value in the local universe are the best analogues to investigating the interstellar medium at a quasi-primitive environment in the early universe. In spite of the ongoing formation of stars in these galaxies, the presence of molecular gas (which is known to provide the material reservoir for star formation in galaxies, such as our Milky Way) remains unclear. Here, we report the detection of carbon monoxide (CO), the primary tracer of molecular gas, in a galaxy with 7% solar metallicity, with additional detections in two galaxies at higher metallicities. Such detections offer direct evidence for the existence of molecular gas in these galaxies that contain few metals. Using archived infrared data, it is shown that the molecular gas mass per CO luminosity at extremely low metallicity is approximately one-thousand times the Milky Way value.Comment: 12 pages, 3 figures, 1 table. Supplementary data at http://www.nature.com/article-assets/npg/ncomms/2016/161209/ncomms13789/extref/ncomms13789-s1.pd

1-Metilciklopropen ublažava oštećenja mahuna tijekom skladištenja pri niskim temperaturama povećanjem učinka antioksidacijskog sustava stanične zaštite

Research background. Chilling injury is a major disorder affecting the quality of tropical and subtropical vegetables during low temperature storage. Snap bean (Phaseolus vulgaris L.) is sensitive to chilling injury. The main purpose of the present study is to investigate the alleviating effects of 1-methylcyclopropene (1-MCP) on chilling injury of snap bean. In addition, the related mechanisms were also detected from the perspective of the changes of antioxidant defense system. Experimental approach. Snap beans were exposed to different volume fractions of 1-MCP. After 24 h of treatment, snap beans were stored at 4 °C for up to 14 days. Chilling injury index, electrolyte leakage, titratable acidity and total soluble solids were determined. Contents of chlorophyll, ascorbic acid and malondialdehyde were assessed. The total antioxidant capacity, Fe(II) ion chelating capacity, scavenging capacities on free radicals and activities of antioxidant enzymes were detected. Total phenol content and activities of related metabolic enzymes were also determined. Results and conclusions. 1-MCP treatment reduced chilling injury index, electrolyte leakage rate and malondialdehyde content of snap beans. The amounts of total soluble solids, titratable acid, ascorbic acid and total chlorophyll in 1-MCP-treated snap beans were significantly higher than those of control. The snap beans treated with 1-MCP showed stronger total antioxidant capacity and metal chelating activity. The 1-MCP treatment enhanced scavenging effects of snap beans on superoxide, hydroxyl and 1,1-diphenyl-2-trinitrophenylhydrazine radicals. The activities of peroxidase, ascorbate peroxidase, superoxide dismutase and catalase in 1-MCP-treated group were higher than of control. The treatment also enhanced the accumulation of phenolic compounds in snap beans by regulating the activities of phenol-metabolizing enzymes such as shikimate dehydrogenase, phenylalanine ammonia lyase enzyme, cinnamic acid 4-hydroxylase and polyphenol oxidase. In conclusion, with the mechanism that involves the activation of enzymatic and non-enzymatic antioxidant systems, 1-MCP has the ability to avoid chilling injury of snap bean. Novelty and scientific contribution. This study gives insights into whether 1-MCP can regulate postharvest cold resistance in vegetables by enhancing the enzymatic antioxidant system and inducing the accumulation of non-enzymatic antioxidants. Considering the results, 1-MCP treatment could be an effective method to alleviate postharvest chilling injury of snap beans during low temperature storage.Pozadina istraživanja. Oštećenje ploda tijekom skladištenja pri niskim temperaturama jedan je od primarnih uzroka smanjenja kakvoće tropskog i suptropskog povrća. Grah (Phaseolus vulgaris L.) je osjetljiv na oštećenja pri niskim temperaturama. Stoga je glavna svrha ovoga rada bila ispitati ublažavajući učinak 1-metilciklopropena na oštećenja mahuna pri niskim temperaturama. Osim toga, utvrđeni su mehanizmi promjene obrambenog antioksidacijskog sustava. Eksperimentalni pristup. Mahune su izložene različitim volumnim udjelima 1-metilciklopropena tijekom 24 sata. Nakon toga su uzorci mahuna skladišteni pri 4 °C do 14 dana. Mjereni su sljedeći parametri: indeks oštećenja pri niskim temperaturama, gubitak elektrolita, titracijska kiselost i udjel ukupnih topljivih tvari. Osim toga, utvrđeni su udjeli klorofila, askorbinske kiseline i malondialdehida. Određeni su ukupni antioksidacijski učinak, sposobnost keliranja Fe(II) iona, sposobnost uklanjanja reaktivnih kisikovih spojeva i aktivnost antioksidacijskih enzima. Također su određeni ukupni udjel fenola i s njima povezana metabolička aktivnost enzima. Rezultati i zaključci. Nakon obrade 1-metilciklopropenom smanjili su se indeks oštećenja pri niskim temperaturama, gubitak elektrolita i udjel malondialdehida u mahunama. Količine ukupnih topljivih suhih tvari, titracijske kiselosti, askorbinske kiseline i ukupnog klorofila u mahunama izloženim 1-metilciklopropenu bile su znatno veće nego u kontrolnom uzorku. Tretirane mahune imale su veću ukupnu antioksidacijsku aktivnost i sposobnost keliranja metala. Obradom 1-metilciklopropenom povećala se sposobnost uklanjanja radikala superoksida, hidroksila i 1,1-difenil-2-trinitrofenilhidrazina u mahunama. Aktivnosti peroksidaze, askorbat peroksidaze, superoksid dismutaze i katalaze bile su veće u tretiranim nego u kontrolnim uzorcima. Osim toga, obradom se povećalo nakupljanje fenolnih spojeva zbog regulacije enzima koji sudjeluju u metabolizmu fenola, kao što su šikimat-dehidrogenaza, fenilalanin amonijak-liaza, p-kumarinska kiselina i polifenol-oksidaza. Možemo zaključiti da 1-metilciklopropen može spriječiti oštećenje mahuna pri niskim temperaturama aktivacijom enzimskih i neenzimskih antioksidacijskih sustava. Novina i znanstveni doprinos. Ovaj rad daje uvid u mogućnost regulacije otpornosti povrća na niske temperature tijekom skladištenja poboljšanjem enzimskog antioksidacijskog sustava pomoću 1-metilciklopropena te nakupljanjem neenzimskih antioksidanasa. Dobiveni rezultati pokazuju da bi obrada 1-metilciklopropenom mogla biti učinkovita metoda ublažavanja oštećenja pri niskim temperaturama tijekom skladištenja graha

Dark against luminous matter around isolated central galaxies: a comparative study between modern surveys and Illustris-TNG

Based on independent shear measurements using the DECaLS/DR8 imaging data, we measure the weak lensing signals around isolated central galaxies (ICGs) from SDSS/DR7 at $z\sim0.1$. The projected stellar mass density profiles of surrounding satellite galaxies are further deduced, using photometric sources from the Hyper Suprime-Cam (HSC) survey (pDR3). The signals of ICGs $+$ their extended stellar halos are taken from Wang et al.(2021). All measurements are compared with predictions by the Illustris-TNG300-1 simulation. We find, overall, a good agreement between observation and TNG300. In particular, a correction to the stellar mass of massive observed ICGs is applied based on the calibration of He et al.(2013), which brings a much better agreement with TNG300 predicted lensing signals at $\log_{10}M_\ast/M_\odot>11.1$. In real observation, red ICGs are hosted by more massive dark matter halos, have more satellites and more extended stellar halos than blue ICGs at fixed stellar mass. However, in TNG300 there are more satellites around blue ICGs at fixed stellar mass, and the outer stellar halos of red and blue ICGs are similar. The stellar halos of TNG galaxies are more extended compared with real observed galaxies, especially for blue ICGs with $\log_{10}M_\ast/M_\odot>10.8$. We find the same trend for TNG100 galaxies and for true halo central galaxies. The tensions between TNG and real galaxies might indicate that satellite disruptions are stronger in TNG. In both TNG300 and observation, satellites approximately trace the underlying dark matter distribution beyond $0.1R_{200}$, but the fraction of total stellar mass in TNG300 does not show the same radial distribution as real galaxies.Comment: 28 pages, 12 figure