Chemical Substructure of High Mass Star Forming Regions

High mass stars (stars with mass M > 8 Msolar) are one of the most fundamental building blocks in the Universe. Deeply embedded in the dense clouds at further distances than their low mass counterparts, the forming processes of these fast evolving objects are still unclear. In the earliest phases of the high mass star forming regions (HMSFRs), many complicated astrophysical processes, such as fragmentation, accretion, inflows and outflows are coexistent that dynamic studies are not enough to understand all the mysteries. Therefore, chemistry has developed into a powerful tool in probing the nature of them. With the aim of understanding the chemical and physical processes in the very beginning of high mass star formation, I selected a series of HMSFRs at different evolutionary stages, and studied their chemical-physical properties via high spatial resolution observations at (sub)mm wavelengths. The results can be summarised shortly as follows: 1. At a spatial resolution of 10 Msolar) than the Jeans mass of the large-scale clump, indicating that thermal motions is not the dominant support to against collapse, and high mass stars may form in a “scaled up” version similar to the low mass stars. 2. Observations at a spatial resolution of 1 000 AU resolve NGC 7538 S into at least 3 fragments, having comparable sizes and masses derived from continuum emissions. However, these fragments exhibit distinguishing spectral line emissions at 1.3 mm wavelength, revealing different evolutionary stages. Combing with a 1-D gas-grain model fitting, for the first time, this project suggests that these fragments may result from different warm-up paces after synchronised fragmentation, and that the warm-up processes from one stage to another is rapid. 3. Chemical variations at small scales may be caused by the evolutionary stage diversity of fragments, but may also come from chemical difference of molecular species. With the first complimentary data obtained from both interferometric and single-dish telescopes at 1.3 mm, I analysed the continuum and spectral line features at a spatial resolution of 1 200 AU in Orion-KL. From the central warmer condensations to the cooler outflow regions, gas temperatures and densities differ, leading to spatial distribution inhomogeneity and abundance diversity of nitrogen (N-) bearing, sulfur (S-) bearing and oxygen (O-) bearing molecules. 4. Even at a spatial resolution of 1 000 AU, NGC 7538 IRS1 remains unresolved. At 1.3 mm, this core has a unique spectrum at the continuum peak: a majority of the lines exhibit absorption feature, while at least 3 lines from CH3OH and HCOOCH3 exhibit strong, pure emission. I proposed several hypotheses, attempting to interpret this by source geometry and/or line excitation states. 5. Complex organic molecules (COMs) are ubiquitously detected in the hot molecular cores (HMCs). Thanks to the high sensitivity observations, I identified several low abundant COMs demonstrating complicated chemistry in my sources. 6. In addition to the fragmentation process, the high mass starless cores are not completely chemically quiescent. None line detection in 4 infrared dark clouds at 1.1 mm may indicate these regions are in the early, cold evolutionary stage. However, detection of several dense gas tracers (> 5rms) especially at 3 mm, implies the presence of active gas phase chemistry. From our study, chemistry is an efficient tool in diagnosing evolutionary events coexistent at the small scales of HMSFRs

Three Essays On Agricultural and Forestry Offsets In Climate Change Mitigation

This dissertation is composed of three essays, investigating two aspects of the role of agricultural sector in climate change mitigation: leakage and additionality. Leakage happens when mitigation policies reduce net GHG emissions in one context, but increase (decrease) prices, which in turn causes production (demand) expansion resulting in an offsetting rise in emissions elsewhere. The first essay documents an integration of a US domestic agricultural sectoral model and a global agricultural sectoral model, with the aim to deliver better leakage assessment. The second essay investigates the trend of US crop yield growth and its implication on the international leakage effect. We find that the slowdowns have occurred to the growth rates of most US major crops. The implementation of climate change mitigation strategies, such as the expansion of bioenergy production, causes demand for the agricultural sector to increase substantially. The new demand would cause noticeable leakage effect if crop yields continue to grow at the current rates. Such effect may be potentially alleviated by higher crop yield growth rates; but the extent of alleviation depends on the mix of technological progress obtained across crops as well. Additionality is often a concern in programs designed to incentivize the production of environmental services. Additionality is satisfied if payments are made to services that would not have occurred without the payment. However, because of the information asymmetry between service buyers and sellers, ensuring additionality poses a challenge to program designers. The third essay investigates how the pursuit of ensuring additionality would complicate environmental policy design with a theoretical model. Specifically, we examine 4 types of policy design, including 2 discriminating schemes and 2 simpler non-discriminating schemes. We found that under certain conditions, some of the non-discriminating schemes can be almost as good as the discriminating ones. Findings in this dissertation contribute to inform policy makers about the potential impacts of climate change mitigation policies in the agricultural sector and also help to improve understanding of environmental program design

Geological structure recognition model based on improved random forest algorithm

Seismic attributes are often used for structural interpretation and prediction. In order to overcome the problems of multiple solutions and uncertainty caused by single seismic attribute prediction, seismic multi-attribute fusion technology is used to interpret and predict geological structures. Based on the classical machine learning random forest algorithm model, an improved random forest algorithm is proposed to fuse and classify multiple seismic attributes. Combining the seismic multi-attribute fusion technology with the improved random forest algorithm, a geological structure recognition model based on the improved random forest algorithm is established. Taking the second mining area of the second belt of Shanxi Xinyuan Coal Co., Ltd. as the research area, based on the twelve seismic attributes extracted from the three-dimensional seismic exploration results, through the attribute correlation analysis and feature importance analysis of the twelve attributes, according to the results, all twelve attributes are retained for subsequent attribute fusion. Using the exposed and verified geological structure faults and collapse columns as sample labels, an improved grid search optimization algorithm is proposed. The number of classifiers and the maximum feature number of a single decision tree are combined to search the grid. The algorithm model is established based on Python language platform. The experimental results show that the prediction accuracy of the improved algorithm model reaches 97%, After subsequent model verification, it is proved that compared with several algorithms such as logistic regression, gradient lifting and decision tree, the improved random forest algorithm can more effectively identify abnormal bodies such as faults and collapse columns in geological structures, with higher recognition accuracy and wider applicability

Tectonic Proteins Are Important Players in Non-Motile Ciliopathies

Primary cilium is a ubiquitous, tiny organelle on the apex of the mammalian cells. Non-motile (primary) ciliopathies are diseases caused by the dysfunction of the primary cilium and they are characterized by diverse clinical and genetic heterogeneity. To date, nearly 200 genes have been shown to be associated with primary ciliopathies. Among them, tectonic genes are the important causative genes of ciliopathies. Tectonic proteins including TCTN1, TCTN2, and TCTN3 are important component proteins residing at the transition zone of cilia. Indeed, many ciliopathies have been reported to involve tectonics mutations, highlighting a pivotal role for tectonic proteins in ciliary functions. However, the specific functions of tectonic proteins remain largely enigmatic. Herein, we discuss the recent advances on the localization and structure of tectonic proteins and the functions of tectonic proteins. The increasing line of evidences demonstrates that tectonic proteins are required for ciliogenesis and regulate ciliary membrane composition. More importantly, Tectonic proteins play a vital role in the regulation of the Sonic Hedgehog (Shh) pathway; Tectonic deficient mice show the Shh pathway-related developmental defects. Tectonic proteins share similar functions including neural patterning and Gli3 processing but also each has a unique and indispensable role in the ciliogenesis and signaling pathways. At the same time, the mutations of tectonic genes are the causes of a serial of primary ciliopathies including Meckel-Gruber syndrome, Oral-facial-digital syndrome, and Joubert syndrome. Therefore, full understanding of functions of tectonic proteins will help to crack ciliopathies and improve life quality of patients by future gene therapy

An improved method to measure 12C/13C\rm ^{12}C/^{13}C and 14N/15N\rm ^{14}N/^{15}N abundance ratios: revisiting CN isotopologues in the Galactic outer disk

The variations of elemental abundance and their ratios along the Galactocentric radius result from the chemical evolution of the Milky Way disks. The $\rm ^{12}C/^{13}C$ ratio in particular is often used as a proxy to determine other isotopic ratios, such as $\rm ^{16}O/^{18}O$ and $\rm ^{14}N/^{15}N$. Measurements of $\rm ^{12}CN$ and $\rm ^{13}CN$ (or $\rm C^{15}N$) -- with their optical depths corrected via their hyper-fine structure lines -- have traditionally been exploited to constrain the Galactocentric gradients of the CNO isotopic ratios. Such methods typically make several simplifying assumptions (e.g. a filling factor of unity, the Rayleigh-Jeans approximation, and the neglect of the cosmic microwave background) while adopting a single average gas phase. However, these simplifications introduce significant biases to the measured $\rm ^{12}C/^{13}C$ and $\rm ^{14}N/^{15}N$. We demonstrate that exploiting the optically thin satellite lines of $\rm ^{12}CN$ constitutes a more reliable new method to derive $\rm ^{12}C/^{13}C$ and $\rm ^{14}N/^{15}N$ from CN isotopologues. We apply this satellite-line method to new IRAM 30-m observations of $\rm ^{12}CN$, $\rm ^{13}CN$, and $\rm C^{15}N$ $N=1\to0$ towards 15 metal-poor molecular clouds in the Galactic outer disk ($R_{\rm gc} >$ 12 kpc), supplemented by data from the literature. After updating their Galactocentric distances, we find that $\rm ^{12}C/^{13}C$ and $\rm ^{14}N/^{15}N$ gradients are in good agreement with those derived using independent optically thin molecular tracers, even in regions with the lowest metallicities. We therefore recommend using optically thin tracers for Galactic and extragalactic CNO isotopic measurements, which avoids the biases associated with the traditional method.Comment: 41 pages, 29 figures, accepted by MNRAS. Meeting materials related to this work at https://box.nju.edu.cn/d/5035a574e236408eab94

UbiPhysio: Support Daily Functioning, Fitness, and Rehabilitation with Action Understanding and Feedback in Natural Language

We introduce UbiPhysio, a milestone framework that delivers fine-grained action description and feedback in natural language to support people's daily functioning, fitness, and rehabilitation activities. This expert-like capability assists users in properly executing actions and maintaining engagement in remote fitness and rehabilitation programs. Specifically, the proposed UbiPhysio framework comprises a fine-grained action descriptor and a knowledge retrieval-enhanced feedback module. The action descriptor translates action data, represented by a set of biomechanical movement features we designed based on clinical priors, into textual descriptions of action types and potential movement patterns. Building on physiotherapeutic domain knowledge, the feedback module provides clear and engaging expert feedback. We evaluated UbiPhysio's performance through extensive experiments with data from 104 diverse participants, collected in a home-like setting during 25 types of everyday activities and exercises. We assessed the quality of the language output under different tuning strategies using standard benchmarks. We conducted a user study to gather insights from clinical experts and potential users on our framework. Our initial tests show promise for deploying UbiPhysio in real-life settings without specialized devices.Comment: 27 pages, 14 figures, 5 table

Filamentary Fragmentation and Accretion in High-Mass Star-Forming Molecular Clouds

Filamentary structures are ubiquitous in high-mass star-forming molecular clouds. Their relation with high-mass star formation is still to be understood. Here we report interferometric observations toward 8 filamentary high-mass star-forming clouds. A total of 50 dense cores are identified in these clouds, most of which present signatures of high-mass star formation. Five of them are not associated with any star formation indicators, hence are prestellar core candidates. Evolutionary phases of these cores and their linewidths, temperatures, NH$_3$ abundances, and virial parameters are found to be correlated. In a sub-sample of 4 morphologically well-defined filaments, we find that their fragmentation can not be solely explained by thermal or turbulence pressure support. We also investigate distributions of gas temperatures and non-thermal motions along the filaments, and find a spatial correlation between non-thermal linewidths and star formation activities. We find evidence of gas flows along these filaments, and derive an accretion rate along filaments of $\sim$10$^{-4}$ M$_\odot$ yr$^{-1}$. These results suggest a strong relationship between massive filaments and high-mass star formation, through i) filamentary fragmentation in very early evolutionary phases to form dense cores, ii) accretion flows along filaments that are important for the growth of dense cores and protostars, and iii) enhancement of non-thermal motion in the filaments by the feedback or accretion during star formation.Comment: 31 pages, 11 figures, 8 tables, ApJ Accepted. 3-D interactive figures to visualize outflows (see Figure 7) will be published online, and are available at https://xinglunju.github.io/outflows.htm

Hierarchical fragmentation and collapse signatures in a high-mass starless region

Aims: We study the fragmentation and collapse properties of the dense gas during the onset of high-mass star formation. Methods: We observed the massive (~800 M⊙) starless gas clump IRDC 18310-4 with the Plateau de Bure Interferometer (PdBI) at subarcsecond resolution in the 1.07 mm continuum and N2H+(3-2) line emission. Results: Zooming from a single-dish low-resolution map to previous 3 mm PdBI data, and now the new 1.07 mm continuum observations, the substructures hierarchically fragment on the increasingly smaller spatial scales. While the fragment separations may still be roughly consistent with pure thermal Jeans fragmentation, the derived core masses are almost two orders of magnitude larger than the typical Jeans mass at the given densities and temperatures. However, the data can be reconciled with models using non-homogeneous initial density structures, turbulence, and/or magnetic fields. While most subcores remain (far-)infrared dark even at 70 μm, we identify weak 70 μm emission toward one core with a comparably low luminosity of ~16 L⊙, supporting the notion of the general youth of the region. The spectral line data always exhibit multiple spectral components toward each core with comparably small line widths for the individual components (in the 0.3 to 1.0 km s-1 regime). Based on single-dish C18O(2-1) data we estimate a low virial-to-gas-mass ratio ≤ 0.25. We propose that the likely origin of these spectral properties may be the global collapse of the original gas clump that results in multiple spectral components along each line of sight. Even within this dynamic picture the individual collapsing gas cores appear to have very low levels of internal turbulence