371 research outputs found
Modified propagation of gravitational waves from the early radiation era
We study the propagation of cosmological gravitational wave (GW) backgrounds
from the early radiation era until the present day in modified theories of
gravity. Comparing to general relativity (GR), we study the effects that
Horndeski parameters, such as the run rate of the effective Planck mass
and the tensor speed excess , have on the
present-day GW spectrum. We use both the WKB estimate, which provides an
analytical description but fails at superhorizon scales, and numerical
simulations that allow us to go beyond the WKB approximation. We show that
makes relatively insignificant changes to the GR solution,
especially taking into account the constraints on its value from GW
observations by the LIGO-Virgo collaboration, while can
introduce modifications to the spectral slopes of the GW energy spectrum in the
low-frequency regime depending on the considered time evolution of . The latter effect is additional to the damping or growth occurring equally
at all scales that can be predicted by the WKB approximation. In light of the
recent observations by pulsar timing array collaborations and future detectors
such as SKA, LISA, DECIGO, BBO, or ET, we show that, in most of the cases,
constraints can not be placed on the effects of and the
initial GW energy density separately, but only on the
combined effects of the two.Comment: 31 pages, 11 figures, 2 table
Determinants of Executive Compensation in China: The Role and Effect of Corporate Governance and Firm Performance ——Empirical Evidence from Listed Manufacturing Firms
In response to public outrage over the executive pay scandals, this paper examines the role and effect of firm performance and corporate governance (CG) on executive compensation in China based on the optimal contract theory and the managerial power theory, contributing to the empirical research on compensation in developing countries.
The sample in this research includes 1078 listed manufacturing firms whose executive compensation, performance and corporate governance data from 2015 to 2018 are collected through the CSMAR and CCER databases. On top of that, quantitative analysis is employed to analyze this panel data. By conducting two-way fixed-effect regression models, this research finds the positive connections between firm performance and executive cash compensation, among which the pay-for-market-performance sensitivity is limited and generally lower than the pay-for-operation-performance sensitivity. However, it is also found that CEOs of non-state-owned enterprises (non-SOEs) might increase their pay and decouple the positive connection between executive pay and operation performance when they concurrently serve as the chairman of the board of directors.
Moreover, little evidence is found to support the direct and moderating effect of the board independence, presence of compensation committee and the ownership concentration. It indicates that the quality and monitoring role of large shareholders and the board might be overestimated. Therefore, in the future policymaking process, it is necessary to find a way to truly enhance the monitoring role and to increase the bargaining power of large shareholders and the board regarding the design and implementation of optimal executive compensation contracts
Enhanced cancer therapy with cold-controlled drug release and photothermal warming enabled by one nanoplatform
Stimuli-responsive nanoparticles hold great promise for drug delivery to improve the safety and efficacy of cancer therapy. One of the most investigated stimuli-responsive strategies is to induce drug release by heating with laser, ultrasound, or electromagnetic field. More recently, cryosurgery (also called cryotherapy and cryoablation), destruction of diseased tissues by first cooling/freezing and then warming back, has been used to treat various diseases including cancer in the clinic. Here we developed a cold-responsive nanoparticle for controlled drug release as a result of the irreversible disassembly of the nanoparticle when cooled to below ∼10 °C. Furthermore, this nanoparticle can be used to generate localized heating under near infrared (NIR) laser irradiation, which can facilitate the warming process after cooling/freezing during cryosurgery. Indeed, the combination of this cold-responsive nanoparticle with ice cooling and NIR laser irradiation can greatly augment cancer destruction both in vitro and in vivo with no evident systemic toxicity
CSP: Self-Supervised Contrastive Spatial Pre-Training for Geospatial-Visual Representations
Geo-tagged images are publicly available in large quantities, whereas labels
such as object classes are rather scarce and expensive to collect. Meanwhile,
contrastive learning has achieved tremendous success in various natural image
and language tasks with limited labeled data. However, existing methods fail to
fully leverage geospatial information, which can be paramount to distinguishing
objects that are visually similar. To directly leverage the abundant geospatial
information associated with images in pre-training, fine-tuning, and inference
stages, we present Contrastive Spatial Pre-Training (CSP), a self-supervised
learning framework for geo-tagged images. We use a dual-encoder to separately
encode the images and their corresponding geo-locations, and use contrastive
objectives to learn effective location representations from images, which can
be transferred to downstream supervised tasks such as image classification.
Experiments show that CSP can improve model performance on both iNat2018 and
fMoW datasets. Especially, on iNat2018, CSP significantly boosts the model
performance with 10-34% relative improvement with various labeled training data
sampling ratios.Comment: In: ICML 2023, Jul 23 - 29, 2023, Honolulu, Hawaii, US
OEBench: Investigating Open Environment Challenges in Real-World Relational Data Streams
How to get insights from relational data streams in a timely manner is a hot
research topic. This type of data stream can present unique challenges, such as
distribution drifts, outliers, emerging classes, and changing features, which
have recently been described as open environment challenges for machine
learning. While existing studies have been done on incremental learning for
data streams, their evaluations are mostly conducted with manually partitioned
datasets. Thus, a natural question is how those open environment challenges
look like in real-world relational data streams and how existing incremental
learning algorithms perform on real datasets. To fill this gap, we develop an
Open Environment Benchmark named OEBench to evaluate open environment
challenges in relational data streams. Specifically, we investigate 55
real-world relational data streams and establish that open environment
scenarios are indeed widespread in real-world datasets, which presents
significant challenges for stream learning algorithms. Through benchmarks with
existing incremental learning algorithms, we find that increased data quantity
may not consistently enhance the model accuracy when applied in open
environment scenarios, where machine learning models can be significantly
compromised by missing values, distribution shifts, or anomalies in real-world
data streams. The current techniques are insufficient in effectively mitigating
these challenges posed by open environments. More researches are needed to
address real-world open environment challenges. All datasets and code are
open-sourced in https://github.com/sjtudyq/OEBench
MC3/SAINT-O-Somes, a novel liposomal delivery system for efficient and safe delivery of siRNA into endothelial cells
Increased understanding of chronic inflammatory diseases and the role of endothelial cell (EC) activation herein, have urged interest in sophisticated strategies to therapeutically intervene in activated EC to treat these diseases. Liposome-mediated delivery of therapeutic siRNA in inflammation-activated EC is such a strategy. In this study, we describe the design and characterisation of two liposomal siRNA delivery systems formulated with the cationic MC3 lipid or MC3/SAINT mixed lipids, referred to as MC3-O-Somes (MOS) and MC3/SAINT-O-Somes (MSS). The two formulations showed comparable physicochemical properties, except for better siRNA encapsulation efficiency in the MSS formulation. Antibody-mediated VCAM-1 targeting (AbVCAM-1) increased the association of the targeted MOS and MSS with activated EC, although the targeted MOS showed a significantly higher VCAM-1 specific association than the targeted MSS. AbVCAM-1 MSS containing RelA siRNA achieved significant downregulation of RelA expression, while AbVCAM-1 MOS containing RelA siRNA did not downregulate RelA expression in activated EC. Additionally, AbVCAM-1 MSS containing RelA siRNA showed low cytotoxicity in EC and at the same time prohibited endothelial inflammatory activation by reducing expression of cell adhesion molecules. The AbVCAM-1 MSS formulation is a novel siRNA delivery system based on a combination of the cationic lipids MC3 and SAINT, that shows good physicochemical characteristics, enhanced endothelial cell association, improved transfection activity, low toxicity and significant anti-inflammatory effect, thereby complying with the requirements for future in vivo investigations.</p
MC3/SAINT-O-Somes, a novel liposomal delivery system for efficient and safe delivery of siRNA into endothelial cells
Increased understanding of chronic inflammatory diseases and the role of endothelial cell (EC) activation herein, have urged interest in sophisticated strategies to therapeutically intervene in activated EC to treat these diseases. Liposome-mediated delivery of therapeutic siRNA in inflammation-activated EC is such a strategy. In this study, we describe the design and characterisation of two liposomal siRNA delivery systems formulated with the cationic MC3 lipid or MC3/SAINT mixed lipids, referred to as MC3-O-Somes (MOS) and MC3/SAINT-O-Somes (MSS). The two formulations showed comparable physicochemical properties, except for better siRNA encapsulation efficiency in the MSS formulation. Antibody-mediated VCAM-1 targeting (AbVCAM-1) increased the association of the targeted MOS and MSS with activated EC, although the targeted MOS showed a significantly higher VCAM-1 specific association than the targeted MSS. AbVCAM-1 MSS containing RelA siRNA achieved significant downregulation of RelA expression, while AbVCAM-1 MOS containing RelA siRNA did not downregulate RelA expression in activated EC. Additionally, AbVCAM-1 MSS containing RelA siRNA showed low cytotoxicity in EC and at the same time prohibited endothelial inflammatory activation by reducing expression of cell adhesion molecules. The AbVCAM-1 MSS formulation is a novel siRNA delivery system based on a combination of the cationic lipids MC3 and SAINT, that shows good physicochemical characteristics, enhanced endothelial cell association, improved transfection activity, low toxicity and significant anti-inflammatory effect, thereby complying with the requirements for future in vivo investigations.</p
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