Long and skinny molecular filaments running along Galactic spiral arms are known as “bones,” since they make up the skeleton of the Milky Way. However, their origin is still an open question. Here, we compare spectral images of HI taken by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) with archival CO and Herschel dust emission to investigate the conversion from HI to H2 in two typical Galactic bones, CFG028.68-0.28 and CFG047.06+0.26. Sensitive FAST HI images and an improved methodology enabled us to extract HI narrow self-absorption (HINSA) features associated with CO line emission on and off the filaments, revealing the ubiquity of HINSA toward distant clouds for the first time. The derived cold HI abundances, [HI]/[H2], of the two bones range from ∼(0.5 to 44.7) × 10−3, which reveal different degrees of HI–H2 conversion, and are similar to those of nearby, low-mass star-forming clouds, Planck Galactic cold clumps, and a nearby active high-mass star-forming region G176.51+00.20. The HI–H2 conversion has been ongoing for 2.2–13.2 Myr in the bones, a timescale comparable to that of massive star formation therein. Therefore, we are witnessing young giant molecular clouds (GMCs) with rapid massive star formation. Our study paves the way of using HINSA to study cloud formation in Galactic bones and, more generally, in distant GMCs in the FAST era.
Liquid loading presents a formidable challenge for mature gas wells, often resulting in substantial economic losses. Traditional research has predominantly centered on the analysis of gas-liquid two-phase flow within the wellbore to predict critical gas velocity or rate, aiding in identifying the onset of liquid loading. This study introduces a fully coupled compositional wellbore-reservoir simulator designed to detect liquid loading in both vertical and inclined gas wells. Leveraging the drift-flux model to evaluate flow pattern transitions, this simulator employs pressure or rate constraints at the wellhead as boundary conditions. It comprehensively captures the flow dynamics in both the wellbore and reservoir, unveiling significant changes in gas production rate, water production rate, gas velocity, flow regime, and the reserved position of the liquid film under liquid-loaded conditions. Moreover, the accumulation of liquid at the bottom hole leads to increased reservoir pressure and gas saturation near the wellbore. The simulator predicts a typical unstable production period, emphasizing its crucial role in implementing effective strategies to mitigate liquid loading. This paper investigates the capability of the coupled wellbore-reservoir model to characterize transient liquid loading phenomena from a systematic perspective. The proposed model can function as a real-time tool for predicting the status of liquid loading in gas wells.
Tryptophan (Trp) plays a critical role in the regulation of protein structure, interactions and functions through its π system and indole N–H group. A generalizable method for blocking and rescuing Trp interactions would enable the gain-of-function manipulation of various Trp-containing proteins in vivo, but generating such a platform remains challenging. Here we develop a genetically encoded N1-vinyl-caged Trp capable of rapid and bioorthogonal decaging through an optimized inverse electron-demand Diels–Alder reaction, allowing site-specific activation of Trp on a protein of interest in living cells. This chemical activation of a genetically encoded caged-tryptophan (Trp-CAGE) strategy enables precise activation of the Trp of interest underlying diverse important molecular interactions. We demonstrate the utility of Trp-CAGE across various protein families, such as catalase-peroxidases and kinases, as translation initiators and posttranslational modification readers, allowing the modulation of epigenetic signalling in a temporally controlled manner. Coupled with computer-aided prediction, our strategy paves the way for bioorthogonal Trp activation on more than 28,000 candidate proteins within their native cellular settings.
This study assesses the health benefits of better air quality by examining the causal impact of China’s stringent “2+26” regional air pollution control policy on local air quality and population health. Employing a spatial regression discontinuity design that capitalizes on the policy’s location-specific features, we present compelling evidence that the 2+26 policy results in an average reduction of 12.2 units in the local Air Quality Index (AQI) and a 47.0% decrease in per capita medical expenditure from 2014 to 2018. A one-unit reduction in AQI corresponds to a 0.88% reduction in per capita annual medical spending, equivalent to RMB 30.2 (US$4.6). These health gains stem from reduced chronic disease prevalence and improved subjective well-being. Nationally, air quality improvement during 2014–2018 could save RMB 674billion (US$104billion) annually in national direct medical costs, constituting 11.6% of national medical expenditure in 2018. Our findings underscore the substantial health and welfare gains achievable through pollution controls in developing countries.
This paper considers the connectedness of the two ports-of-call of Amastris and Heraclea Pontica in the eparcheia of Pontus during the Roman principate. Stanford's ORBIS platform offers a heuristic model of connectedness. We find the two ports-of-call the most popular segments along the south for maritime traffic coming from eastern Pontus and the Bosporus.Where the two is most different concerns their connections with the interior. Heraclea Pontica connected Ancyra to the Pontic coast, while Amastris had none. ORBIS is understandably non- granular in the sense that it "restrict[s] coverage to the more important elements of the Roman communication system," but if this is the case, it means that Heraclea Pontica and Amastris were connected in other ways as well, and the Amastrian mountainous interior, which couldbe described as the "previously unconjoined, or at least the previously less well-connected" segment of Anatolia (Horden 2020: 204), could have also been connected with the wider ancient Mediterranean world. Low visibility of settlements beyond known the one known urbanized area in modern Amasra makes discussions of broader connectedness difficult, but at least from recent field survey results suggest that the number and vibrancy of settlements likely increased in the Roman period (Bes 2015: 288-289; Çam et al. 2019; Çam 2021). The question then is whether recent studies contribute to a new assessment of Amastrian connectedness, and how it compares with existing impressions of both Amastris and its peer poleis, with Heraclea Pontica serving as the primary example.Building upon Alexandru Avram's assumption that the aggregate of attestations of persons who have spent time in a city other than their homeland can serve as proxy for gauging their mobility (Avram 2013: 7-8), this paper uses the Prosopographia Ponti Euxini externa to test whether Amastrian connectedness reached currently unknown areas, particularly theinterior. Comparison between Amastrian data (n=136) and Heracleote specimens (n=1101)
may seem disproportionate, but this paper focuses on persons from the first to the third centuries CE and privileges locations instead of volumes so to visualize connectedness in the Roman world. The same concept is applied to persons of locales beyond the two subjects in question – foreigners who left records in Heracleote (n=5) and Amastrian territory (n=11) – and visualized together. In addition, though coins are a poor proxy as they may be transmitted in a variety of ways that do not reflect direct connections between Amastris and the cities that issued them, this paper considers coins from the Amasra Museum as published by Stanley Ireland and Soner Atesogullari (1996) to complement Amastris relatively poor prosopographical record and increase the potential to capture connections. The overall impression gleaned from this exercise is that Amastris could have played a comparable (though potentially less pronounced) role as that of Heraclea Pontica in terms of a hub-like node that connected interior land routes with maritime traffic, particularly for Hadrianopolis and Pompeiopolis (Corsten 2007; Ruscu 2017), but also potentially for centers such as Caesarea in Cappadocia.Bibliography:Avram, A. 2013. Prosopographia Ponti Euxini externa. Leuven.Bes, P. 2015. "The Cide-Şenpazar Region in the Roman Period," in Kinetic Landscapes. The Cide Archaeological Project: Surveying the Turkish Western Black Sea Region, Bleda Düring and Claudia Glatz, eds., Warsaw/Berlin, pp. 260-293.Çam, F. et al. 2019. "New Archaeological Expeditions in the Ancient City of Amastris,"Settlements and Necropoleis of the Black Sea and its Hinterland in Antiquity, Select Papers from the Third International Conference 'The Black Sea in Antiquity and Tekkeköy: An Ancient Settlement on the Southern Black Sea Coast', 27-29 October 2017, Tekkeköy, Samsun, Gocha Tsetskhladze and Sümer Atasoy, eds., Oxford, pp. 190-207.Çam, F. 2022. "Ancient Settlements in Bartin Province: 2017-2019 Research Results," in Bartın İli ve İlçeleri Yüzey Araştırması (Biya) İlk Tespitler ve Belgeler - Paphlagonia'dan Parthenios'a - I, Fatima Çam, ed., Istanbul, pp. 13-112.Corsten, T. 2007. "Prosoporaphische und Onomastische Notizen III," Gephyra 4, pp. 133-144. Horden, P. 2020. "Knitting Together the Unconjoined," Zeitschrift für Ethnologie 145.2 (2020)197-218.Irland, S. and Soner Atesogul. 1996. "The Ancient Coins in the Amasra Museum," in Studies in Ancient Coinage from Turkey, Richard Ashton, ed., London, pp. 115-137.Ruscu, L. 2017. "Über Sex. Vibius Gallus aus Amastris," Journal of Historical Researches 28, pp. 52-68.
The heterogeneous coprecipitation of nanocrystals with metals on substrates plays a significant role in both natural and engineered systems. Due to the small dimensions and thereby the large specific surface area, nanocrystal coprecipitation with metals, which is ubiquitous in natural settings, exerts drastic effects on the biogeochemical cycling of metals on the earth’s crust. Meanwhile, the controlled synthesis of nanocrystals with metal doping to achieve tunable size/composition enables their broad applications as adsorbents and catalysts in many engineered settings. Despite their importance, complex interactions among aqueous ions/polymers, nanocrystals, substrates, and metals are far from being well-understood, leaving the controlling mechanisms for nanocrystal formation with metals on substrates uncovered.
In this Account, we discuss our systematic investigation over the past 10 years of the heterogeneous formation of representative nanocrystals with metals on typical substrates. We chose Fe(OH)3 and BaSO4 as representative nanocrystals. Mechanisms for varied metal coprecipitation were also investigated for both types of nanocrystals (i.e., Fe, Al, Cr, Cu, and Pb)(OH)3 and (Ba, Sr)(SO4, SeO4, and SeO3)). Bare SiO2 and Al2O3, as well as those coated with varied organics, were selected as geologically or synthetically representative substrates. Through the integration of state-of-the-art nanoscale interfacial characterization techniques with theoretical calculations, the complex interactions during nanocrystal formation at interfaces were probed and the controlling mechanisms were identified.
For BaSO4 and Fe(OH)3 formation on substrates, the local supersaturation levels near substrates were controlled by Ba2+ adsorption and the electrostatic attraction of Fe(OH)3 monomer/polymer to substrates, respectively. Meanwhile, substrate hydrophobicity controlled the interfacial energy for the nucleation of both nanocrystals on (in)organic substrates. Metal ions’ (i.e., Cr/Al/Cu/Pb) hydrolysis constants and substrates’ dielectric constants controlled metal ion adsorption onto substrates, which altered the surface charges of substrates, thus controlling heterogeneous Fe(OH)3 nanocrystal formation on substrates by electrostatic interactions. The sizes and compositions of heterogeneous (Fe, Cr)(OH)3 and (Ba, Sr)(SO4, SeO4, SeO3) formed on substrates were found to be distinct from those of homogeneous precipitates formed in solution. The substrate (de)protonation could alter the local solution’s pH and the substrates’ surface charge; substrates could also adsorb cations, affecting local Fe/Cr/Ba/Sr ion concentrations at solid–water interfaces, thus controlling the amount/size/composition of nanocrystals by tuning their nucleation/growth/deposition on substrates. From slightly supersaturated solution, homogeneous coprecipitates of microsized (Ba, Sr)(SO4, SeO4, SeO3) formed through growth, with little Sr/Se(VI) incorporation due to higher solubilities of SrSO4 and BaSeO4 over BaSO4. While cation enrichment near substrates made the local solution highly supersaturated, nanosized coprecipitates formed on substrates through nucleation, with more Sr/Se(VI) incorporation due to lower interfacial energies of SrSO4 and BaSeO4 over BaSO4. The new insights gained advanced our understanding of the biogeochemical cycling of varied elements at solid–water interfaces and of the controlled synthesis of functional nanocrystals.
Microplastics are found in various human tissues and are considered harmful, raising concerns about human exposure to microplastics in the environment. Existing research has analyzed indoor and occupational scenarios, but long-term monitoring of ambient atmospheric microplastics (AMPs), especially in highly polluted urban regions, needs to be further investigated. This study estimated human environmental exposure to AMPs by considering inhalation, dust ingestion, and dermal exposure in three urban functional zones within a megacity. The annual exposure quantity was 7.37 * 104 items for children and 1.06 * 105 items for adults, comparable with the human microplastic consumption from food and water. Significant spatiotemporal differences were observed in the characteristics of AMPs that humans were exposed to, with wind speed and rainfall frequency mainly driving these changes. The annual human AMP exposure quantity in urban green land spaces, which were recognized as relatively low polluted zones, was comparable with that in public service zones and residential zones. Notably, significant positive correlations between the AMP characteristics and the pathogenicity of the airborne bacterial community were discovered. AMP size and immune-mediated disease risks brought by atmospheric microbes showed the most significant relationship, where Sphingomonas might act as the potential key mediator.
Creating an immersive scene relies on detailed spatial sound. Traditional methods, using probe points for impulse responses, need lots of storage. Meanwhile, geometry-based simulations struggle with complex sound effects. Now, neural-based methods are improving accuracy and slashing storage needs. In our study, we propose a hybrid time and time-frequency domain strategy to model the time series of Ambisonic acoustic fields. The networks excels in generating high-fidelity time-domain impulse responses at arbitrary source-recceiver positions by learning a continuous representation of the acoustic field. Our experimental results demonstrate that the proposed model outperforms baseline methods in various aspects of sound representation and rendering for different source-receiver positions.
Atmospheric organic peroxides (POs) play a key role in the formation of O3 and secondary organic aerosol (SOA), impacting both air quality and human health. However, there still remain technical challenges in investigating the reactivity of POs in ambient aerosols due to the instability and lack of standards for POs, impeding accurate evaluation of their environmental impacts. In the present study, we conducted the first attempt to categorize and quantify POs in ambient PM2.5 through hydrolysis, which is an important transformation pathway for POs, thus revealing the reactivities of various POs. POs were generally categorized into hydrolyzable POs (HPO) and unhydrolyzable POs (UPO). HPO were further categorized into three groups: short-lifetime HPO (S-HPO), intermediate-lifetime HPO (I-HPO), and long-lifetime HPO (L-HPO). S-HPO and L-HPO are typically formed from Criegee intermediate (CI) and RO2 radical reactions, respectively. Results show that L-HPO are the most abundant HPO, indicating the dominant role of RO2 pathway in HPO formation. Despite their lower concentration compared to L-HPO, S-HPO make a major contribution to the HPO hydrolysis rate due to their faster rate constants. The hydrolysis of PM2.5 POs accounts for 19% of the nighttime gas-phase H2O2 growth during the summer observation, constituting a noteworthy source of gas-phase H2O2 and contributing to the atmospheric oxidation capacity. Seasonal and weather conditions significantly impact the composition of POs, with HPO concentrations in summer being significantly higher than those in winter and elevated under rainy and nighttime conditions. POs are mainly composed of HPO in summer, while in winter, POs are dominated by UPO.
A comprehensive and accurate assessment of the policy effect of national tourism days is of great significance to further promote urban inbound tourism. Based on the panel data of 59 cities in China from 2000 to 2017, this paper evaluates the local and spatial spillover effects of the China Tourism Day policy on urban inbound tourism using a spatial difference-in-differences model based on the establishment of the China Tourism Day as a quasi-natural experiment. The study found that the China Tourism Day policy significantly increased the number of foreign tourists in cities but significantly reduced their average length of stay, with a positive spatial spillover effect on inbound tourism in surrounding cities.
