4,511 research outputs found
Contagion: China Evergrande Group’s Collapse and its impact on Belt and Road Stock Indices
The Evergrande Group is a giant: a company that has liabilities proportional to 2% of China’s overall GDP. While there is evidence that Evergrande’s collapse harmed China and its surrounding economies, this thesis analyzes Evergrande’s default within the context of China’s central foreign policy: the Belt and Road Initiative. Through four selected event dates, a difference in means and medians test and standard panel regression is conducted to analyze differences in impacts for Belt and Road and non-Belt and Road participating countries’ stock indices. This paper’s hypothesis implies that Belt and Road countries would see comparatively more negative impacts on their stock indices. Empirical analysis reveals that events before and after Evergrande’s September 2021 warning were statistically different for both Belt and Road and non-Belt and Road groups, with Fitch Ratings’ declaration of Evergrande’s default being the most detrimental. On the other hand, warnings the year prior to Evergrande’s widespread media coverage in September 2020 opposed the hypothesis, seeing non-Belt and Road countries being more negatively affected. Further findings suggest, however, that Belt and Road countries relative to non-Belt and Road countries showcase comparatively worse stock return performance across the majority of the events, fortifying the hypothesis that Belt and Road countries were more negatively impacted by Evergrande’s default relative to non-Belt and Road countries
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DGR mutagenic transposition occurs via hypermutagenic reverse transcription primed by nicked template RNA.
Diversity-generating retroelements (DGRs) are molecular evolution machines that facilitate microbial adaptation to environmental changes. Hypervariation occurs via a mutagenic retrotransposition process from a template repeat (TR) to a variable repeat (VR) that results in adenine-to-random nucleotide conversions. Here we show that reverse transcription of the Bordetella phage DGR is primed by an adenine residue in TR RNA and is dependent on the DGR-encoded reverse transcriptase (bRT) and accessory variability determinant (Avd ), but is VR-independent. We also find that the catalytic center of bRT plays an essential role in site-specific cleavage of TR RNA for cDNA priming. Adenine-specific mutagenesis occurs during reverse transcription and does not involve dUTP incorporation, indicating it results from bRT-catalyzed misincorporation of standard deoxyribonucleotides. In vivo assays show that this hybrid RNA-cDNA molecule is required for mutagenic transposition, revealing a unique mechanism of DNA hypervariation for microbial adaptation
Numerical Modeling of Dust Dynamics around Small Asteroids
Dynamics of dust transport around an airless body has been a focused area of research in recent years, however, various challenging aspects still remain to be addressed. This paper presents an investigation of charged dust transport and distribution around small asteroids utilizing a full particle Particle-in-Cell (PIC) model to simulate plasma flow around an asteroid and calculate surface charging self-consistently from charge deposition on asteroid. Material properties of asteroid are also explicitly included in the simulation. PIC simulation results are fed into a 3D dust dynamics model to simulate charged dust levitation, transport and distribution. In addition to electrostatic and gravitational forces, the dynamics of dust surface impacts and asteroid body rotation are also included in the model. We discuss the effects on dust levitation and transport by comparing dust grain charge-mass ratio, local electrostatic field and dust grain size. We present simulation results of dust distribution around small spherical asteroids. The study highlights the sensitivity to electrostatic field and grain characteristics while following the general trend that gravity dominates in the far field, where as local electric field prevails at low altitude
Scattering of swell by currents
The refraction of surface gravity waves by currents leads to spatial
modulations in the wave field and, in particular, in the significant wave
height. We examine this phenomenon in the case of waves scattered by a
localised current feature, assuming (i) the smallness of the ratio between
current velocity and wave group speed, and (ii) a swell-like, highly
directional wave spectrum.
We apply matched asymptotics to the equation governing the conservation of
wave action in the four-dimensional position--wavenumber space. The resulting
explicit formulas show that the modulations in wave action and significant wave
height past the localised current are controlled by the vorticity of the
current integrated along the primary direction of the swell.
We assess the asymptotic predictions against numerical simulations using
WAVEWATCH III for a Gaussian vortex. We also consider vortex dipoles to
demonstrate the possibility of `vortex cloaking' whereby certain currents have
(asymptotically) no impact on the significant wave height. We discuss the role
of the ratio of the two small parameters characterising assumptions (i) and
(ii) above and show that caustics are only significant for unrealistically
large values of this ratio, corresponding to unrealistically narrow directional
spectra
MMSum: A Dataset for Multimodal Summarization and Thumbnail Generation of Videos
Multimodal summarization with multimodal output (MSMO) has emerged as a
promising research direction. Nonetheless, numerous limitations exist within
existing public MSMO datasets, including insufficient maintenance, data
inaccessibility, limited size, and the absence of proper categorization, which
pose significant challenges. To address these challenges and provide a
comprehensive dataset for this new direction, we have meticulously curated the
\textbf{MMSum} dataset. Our new dataset features (1) Human-validated summaries
for both video and textual content, providing superior human instruction and
labels for multimodal learning. (2) Comprehensively and meticulously arranged
categorization, spanning 17 principal categories and 170 subcategories to
encapsulate a diverse array of real-world scenarios. (3) Benchmark tests
performed on the proposed dataset to assess various tasks and methods,
including \textit{video summarization}, \textit{text summarization}, and
\textit{multimodal summarization}. To champion accessibility and collaboration,
we will release the \textbf{MMSum} dataset and the data collection tool as
fully open-source resources, fostering transparency and accelerating future
developments. Our project website can be found
at~\url{https://mmsum-dataset.github.io/}Comment: Project website: https://mmsum-dataset.github.io
Broad-Wavevector Spin Pumping of Flat-Band Magnons
We report the experimental observation of large spin pumping signals in
YIG/Pt system driven by broad-wavevector spin-wave spin current. 280 nm-wide
microwave inductive antennas offer broad-wavevector excitation which, in
combination with quasi-flatband of YIG, allows a large number of magnons to
participate in spin pumping at a given frequency. Through comparison with
ferromagnetic resonance spin pumping, we attribute the enhancement of the spin
current to the multichromatic magnons. The high efficiency of spin current
generation enables us to uncover nontrivial propagating properties in ultra-low
power regions. Additionally, our study achieves the spatially separated
detection of magnons, allowing the direct extraction of the decay length. The
synergistic combination of the capability of broad-wavevector excitation,
enhanced voltage signals, and nonlocal detection provides a new avenue for the
electrical exploration of spin waves dynamics
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