Kinematics of the X-shaped Milky Way Bulge: Expectations from a Self-consistent N-body Model

We explore the kinematics (both the radial velocity and the proper motion) of the vertical X-shaped feature in the Milky Way with an N-body bar/bulge model. From the solar perspective, the distance distribution of particles is double-peaked in fields passing through the X-shape. The separation and amplitude ratio between the two peaks qualitatively match the observed trends towards the Galactic bulge. We confirm clear signatures of cylindrical rotation in the pattern of mean radial velocity across the bar/bulge region. We also find possible imprints of coherent orbital motion inside the bar structure in the radial velocity distribution along l=0 degree, where the near and far sides of the bar/bulge show excesses of approaching and receding particles. The coherent orbital motion is also reflected in the slight displacement of the zero-velocity-line in the mean radial velocity, and the displacement of the maximum/minimum in the mean longitudinal proper motion across the bulge region. We find some degree of anisotropy in the stellar velocity within the X-shape, but the underlying orbital family of the X-shape cannot be clearly distinguished. Two potential applications of the X-shape in previous literature are tested, i.e., bulge rotation and Galactic center measurements. We find that the proper motion difference between the two sides of the X-shape can be used to estimate the mean azimuthal streaming motion of the bulge, but not the pattern speed of the bar. We also demonstrate that the Galactic center can be located with the X-shape, but the accuracy depends on the fitting scheme, the number of fields, and their latitudinal coverage.Comment: Minor changes to match the ApJ accepted version; 17 pages; emulateapj format. The electronic tables of our model result are available upon reques

Research Progress on Global Food Traceability Based on Bibliometric Analysis

Food traceability is an important means to ensure food quality and safety. For the purpose of providing a reference for future research on food traceability in China, a comprehensive bibliometric and visual analysis of papers concerning global food traceability included in the Science Citation Index Expanded (SCIE) database from 2001 to 2022 was performed. The results showed that 3 020 authors from 1 136 research institutions in 80 countries/regions published their research on food traceability in 255 journals, indicating frequent cross-national and cross-regional cooperation and cross-disciplinary integration. China, Italy, the United States, Spain, the Netherlands produced a large volume of research and built strong cooperation. The overall quality of food traceability research in Italy, the United States, the Netherlands, and Spain was high. The research fields were concentrated in food science and technology, chemistry, agriculture, and engineering. Additionally, many research achievements were made in the fields of computer science, ecology and environmental science, nutrition and dietetics. The research focuses included food quality and safety, food supply chain management, geographical origin, traceability technology, food authentication and certification, and willingness to pay. In the future, the academic frontier will focus on three aspects: intelligent food traceability system based on Industry 4.0, food authentication and detection technology represented by genomics and next-generation sequencing technology, and the mechanisms of the motivation of participants, interest game and premium payment in food traceability system

Recent Intensified Winter Coldness in the Mid-High Latitudes of Eurasia and Its Relationship with Daily Extreme Low Temperature Variability

Observational records in recent decades show a large-scale decrease in the cold-season temperature variance in the Northern Hemisphere midlatitudes under continuous global warming. However, severe low temperature events in winter frequently occurred in midlatitude Eurasia (MEA) in the last decade. Here, we define a new coldness intensity (CI) index for the near-surface based on the amplitude of daily anomalously cold temperatures in winter to demonstrate the CI of the variability of low temperature extremes. The results show that a sign-consistent mode dominates the CI variation in MEA, with a marked intensification during the last decade via empirical orthogonal function (EOF) analysis. This leading mode is significantly related to the frequency of winter extreme events. The associated circulations are characterized by a remarkable anomalous anticyclone in Northwest Eurasia, which induced substantial cold advection in MEA. The widespread intensified CI in MEA is closely linked with strong surface anticyclones and synoptic blocking in the mid-high latitudes (25 ∘ E-85 ∘ E). Coincidently, positive phase shifts of the first two leading modes of the extratropical circulation, which feature similar blocking-like anomalies in the northwestern Eurasian subarctic, jointly play an important role in the recent frequency of severe winters

Distinguishing Tidal Disruption Events from Impostors

Recent claimed detections of tidal disruption events (TDEs) in multi-wavelength data have opened potential new windows into the evolution and properties of otherwise dormant supermassive black holes (SMBHs) in the centres of galaxies. At present, there are several dozen TDE candidates, which share some properties and differ in others. The range in properties is broad enough to overlap other transient types, such as active galactic nuclei (AGN) and supernovae (SNe), which can make TDE classification ambiguous. A further complication is that "TDE signatures" have not been uniformly observed to similar sensitivities or even targeted across all candidates. This chapter reviews those events that are unusual relative to other TDEs, including the possibility of TDEs in pre-existing AGN, and summarises those characteristics thought to best distinguish TDEs from continuously accreting AGN, strongly flaring AGN, SNe, and Gamma-Ray Bursts (GRBs), as well as other potential impostors like stellar collisions, "micro-TDEs," and circumbinary accretion flows. We conclude that multiple observables should be used to classify any one event as a TDE. We also consider the TDE candidate population as a whole, which, for certain host galaxy or SMBH characteristics, is distinguishable statistically from non-TDEs, suggesting that at least some TDE candidates do in fact arise from SMBH-disrupted stars.Comment: 57 pages, 17 figures. Accepted for publication in Springer Space Science Reviews. Chapter in ISSI review "The Tidal Disruption of Stars by Massive Black Holes" vol. 79. Corrected several typos from previous submissio

Gene Expression in Human Hippocampus from Cocaine Abusers Identifies Genes which Regulate Extracellular Matrix Remodeling

The chronic effects of cocaine abuse on brain structure and function are blamed for the inability of most addicts to remain abstinent. Part of the difficulty in preventing relapse is the persisting memory of the intense euphoria or cocaine “rush”. Most abused drugs and alcohol induce neuroplastic changes in brain pathways subserving emotion and cognition. Such changes may account for the consolidation and structural reconfiguration of synaptic connections with exposure to cocaine. Adaptive hippocampal plasticity could be related to specific patterns of gene expression with chronic cocaine abuse. Here, we compare gene expression profiles in the human hippocampus from cocaine addicts and age-matched drug-free control subjects. Cocaine abusers had 151 gene transcripts upregulated, while 91 gene transcripts were downregulated. Topping the list of cocaine-regulated transcripts was RECK in the human hippocampus (FC = 2.0; p<0.05). RECK is a membrane-anchored MMP inhibitor that is implicated in the coordinated regulation of extracellular matrix integrity and angiogenesis. In keeping with elevated RECK expression, active MMP9 protein levels were decreased in the hippocampus from cocaine abusers. Pathway analysis identified other genes regulated by cocaine that code for proteins involved in the remodeling of the cytomatrix and synaptic connections and the inhibition of blood vessel proliferation (PCDH8, LAMB1, ITGB6, CTGF and EphB4). The observed microarray phenotype in the human hippocampus identified RECK and other region-specific genes that may promote long-lasting structural changes with repeated cocaine abuse. Extracellular matrix remodeling in the hippocampus may be a persisting effect of chronic abuse that contributes to the compulsive and relapsing nature of cocaine addiction

Host Galaxies of Extragalactic Transients

Host galaxy properties of extragalactic transients provide valuable insights into the nature of their progenitors. This dissertation focuses on the automated identification of transient host galaxies, the systematic difference in host properties and rate dependencies across supernova subtypes, and the demographics and cosmic environments of supernovae without host galaxies detected.Chapter 1 presents a brief overview of transient-host connections. Chapter 2 describes a novel machine learning-based algorithm to identify transient host galaxies with high accuracy (above 97%). Based on this algorithm, we develop software pipelines to identify transient host galaxies, collect their measured properties across multiple sky surveys, and assemble the largest-ever value-added database of host galaxies. Chapter 3 compares host galaxy physical properties (stellar mass, star formation rate, metallicity) and photometric properties (absolute magnitude, rest-frame color) across supernova subtypes and characterizes how supernova rates depend on galaxy properties. We find subtle but statistically significant differences in host properties across several core-collapse supernova (CC SN) subtypes. Contrary to common belief, CC SN rates are not proportional to their host star formation rates -- either a fraction of long-lived progenitors or a metallicity-dependent supernova production efficiency better interpret the observed host properties. SN Ia subtypes feature heterogeneous host properties attributable to the dramatic contrast of progenitor ages. Chapter 4 presents the analysis of a supernova sample without hosts detected. There are more interacting and superluminous (especially hydrogen-deficient) subtypes among hostless supernovae than in a typical transient sample. Wide-field galaxy surveys put rigorous limits on their host luminosities -- the faintest ones are close to the typical luminosity of dwarf spheroidal galaxies or even globular clusters. The lack of spatial association with galaxy clusters and the excess of slowly-declining SN Ia imply a population of star-forming dwarf hosts in the field. Finally, Chapter 5 summarizes the main results and provides a future outlook