Tournament Auctions

We examine ``tournament'' second-price auctions in which N bidders compete for the right to participate in a second stage and contend against bidder N+1. When the first N bidders are committed so that their bids cannot be changed in the second stage, the analysis yields some unexpected results. The first N bidders consistently bid above their values in equilibrium. When bidder N+1 is sufficiently stronger than the first N, overbidding leads to an increase in expected revenue in comparison to the standard second-price auction when $N$ is large

Tournament Auctions

We examine ``tournament'' second-price auctions in which $N$ bidders compete for the right to participate in a second stage and contend against bidder $N+1$. When the first $N$ bidders are committed so that their bids cannot be changed in the second stage, the analysis yields some unexpected results. The first $N$ bidders consistently bid above their values in equilibrium. When bidder $N+1$ is sufficiently stronger than the first $N$, overbidding leads to an increase in expected revenue in comparison to the standard second-price auction when $N$ is large.Comment: 19 page

Direct Preference-based Policy Optimization without Reward Modeling

Preference-based reinforcement learning (PbRL) is an approach that enables RL agents to learn from preference, which is particularly useful when formulating a reward function is challenging. Existing PbRL methods generally involve a two-step procedure: they first learn a reward model based on given preference data and then employ off-the-shelf reinforcement learning algorithms using the learned reward model. However, obtaining an accurate reward model solely from preference information, especially when the preference is from human teachers, can be difficult. Instead, we propose a PbRL algorithm that directly learns from preference without requiring any reward modeling. To achieve this, we adopt a contrastive learning framework to design a novel policy scoring metric that assigns a high score to policies that align with the given preferences. We apply our algorithm to offline RL tasks with actual human preference labels and show that our algorithm outperforms or is on par with the existing PbRL methods. Notably, on high-dimensional control tasks, our algorithm surpasses offline RL methods that learn with ground-truth reward information. Finally, we show that our algorithm can be successfully applied to fine-tune large language models.Comment: NeurIPS 202

T-DNA insertion mutants reveal complex expression patterns of the aldehyde dehydrogenase 3H1 locus in Arabidopsis thaliana

The Arabidopsis thaliana aldehyde dehydrogenase 3H1 gene (ALDH3H1; AT1G44170) belongs to family 3 of the plant aldehyde dehydrogenase superfamily. The full-length transcript of the corresponding gene comprises an open reading frame of 1583 bp and encodes a protein of 484 amino acid residues. Gene expression studies have shown that this transcript accumulates mainly in the roots of 4-week-old plants following abscisic acid, dehydration, and NaCl treatments. The current study provided experimental data that the ALDH3H1 locus generates at least five alternative transcript variants in addition to the previously described ALDH3H1 mRNA. The alternative transcripts accumulated in wild-type plants at a low level but were upregulated in a mutant that carried a T-DNA insertion in the first exon of the gene. Expression of the transcript isoforms involved alternative gene splicing combined with an alternative promoter. The transcript isoforms were differentially expressed in the roots and shoots and showed developmental stage- and tissue-specific expression patterns. These data support the hypothesis that alternative isoforms produced by gene splicing or alternative promoters regulate the abundance of the constitutively spliced and functional variants

Involvement of the nuclear cap-binding protein complex in alternative splicing in Arabidopsis thaliana

The nuclear cap-binding protein complex (CBC) participates in 5′ splice site selection of introns that are proximal to the mRNA cap. However, it is not known whether CBC has a role in alternative splicing. Using an RT–PCR alternative splicing panel, we analysed 435 alternative splicing events in Arabidopsis thaliana genes, encoding mainly transcription factors, splicing factors and stress-related proteins. Splicing profiles were determined in wild type plants, the cbp20 and cbp80(abh1) single mutants and the cbp20/80 double mutant. The alternative splicing events included alternative 5′ and 3′ splice site selection, exon skipping and intron retention. Significant changes in the ratios of alternative splicing isoforms were found in 101 genes. Of these, 41% were common to all three CBC mutants and 15% were observed only in the double mutant. The cbp80(abh1) and cbp20/80 mutants had many more changes in alternative splicing in common than did cbp20 and cbp20/80 suggesting that CBP80 plays a more significant role in alternative splicing than CBP20, probably being a platform for interactions with other splicing factors. Cap-binding proteins and the CBC are therefore directly involved in alternative splicing of some Arabidopsis genes and in most cases influenced alternative splicing of the first intron, particularly at the 5′ splice site

Gut CD4+ T cell phenotypes are a continuum molded by microbes, not by TH archetypes

CD4+ effector lymphocytes (Teff) are traditionally classified by the cytokines they produce. To determine the states that Teff cells actually adopt in frontline tissues in vivo, we applied single-cell transcriptome and chromatin analyses to colonic Teff cells in germ-free or conventional mice or in mice after challenge with a range of phenotypically biasing microbes. Unexpected subsets were marked by the expression of the interferon (IFN) signature or myeloid-specific transcripts, but transcriptome or chromatin structure could not resolve discrete clusters fitting classic helper T cell (TH) subsets. At baseline or at different times of infection, transcripts encoding cytokines or proteins commonly used as TH markers were distributed in a polarized continuum, which was functionally validated. Clones derived from single progenitors gave rise to both IFN-γ- and interleukin (IL)-17-producing cells. Most of the transcriptional variance was tied to the infecting agent, independent of the cytokines produced, and chromatin variance primarily reflected activities of activator protein (AP)-1 and IFN-regulatory factor (IRF) transcription factor (TF) families, not the canonical subset master regulators T-bet, GATA3 or RORγ

A practical guide to single-cell RNA-sequencing for biomedical research and clinical applications.

RNA sequencing (RNA-seq) is a genomic approach for the detection and quantitative analysis of messenger RNA molecules in a biological sample and is useful for studying cellular responses. RNA-seq has fueled much discovery and innovation in medicine over recent years. For practical reasons, the technique is usually conducted on samples comprising thousands to millions of cells. However, this has hindered direct assessment of the fundamental unit of biology-the cell. Since the first single-cell RNA-sequencing (scRNA-seq) study was published in 2009, many more have been conducted, mostly by specialist laboratories with unique skills in wet-lab single-cell genomics, bioinformatics, and computation. However, with the increasing commercial availability of scRNA-seq platforms, and the rapid ongoing maturation of bioinformatics approaches, a point has been reached where any biomedical researcher or clinician can use scRNA-seq to make exciting discoveries. In this review, we present a practical guide to help researchers design their first scRNA-seq studies, including introductory information on experimental hardware, protocol choice, quality control, data analysis and biological interpretation

사회적 고립 쥐에서의 동역학적으로 변하는 대뇌피질 네트워크 변화

학위논문(석사) - 한국과학기술원 : 바이오및뇌공학과, 2020.8,[iii, 52 p. :]Psychiatric well-being is as important as physical soundness. Accordingly, abundant studies of post-weaning social isolation have enlightened the behavioral traits and neurobiological underpinnings of social stress. However, the characterization of its imaging correlates are critically lacking. Resting state functional connectivity (RSFC) studies can henceforth extend the understanding of the effects of social isolation. In this thesis, I utilized RSFC with wide field optical mapping (WFOM) to observe both the neuronal and hemodynamic signals over a large cortical field of view in socially isolated mice. I focused on twelve regions based on the functional cortical boundaries and conducted a seed based approach. Next, using graph theoretical analysis, the network architectural changes were examined. Substantial changes in functional connectivity were found in both of the approaches as there were functional connectivity disruptions in the frontal and retrosplenial regions. In addition, graph metrics that demonstrate functional segregation decreased overall in isolated mice. This led to the question of resocialization's effect on socially isolated mice. On that account, I resocialized the isolated mice and conducted WFOM to observe the subsequent effects. Recovered tendencies were detected in the frontal regions as well as through graph theory network analysis. Current mouse RSFC data using other social stress models support the hypothesis that social stress has long term effects on neural connectivity. My results corroborate such studies and offer a chance for rescue through resocialization, emphasizing the call for further functional connectivity studies to deepen the comprehension and further enhance translation connectivity between animal and human RSFC studies to develop novel preventative measures and treatments for psychiatric health.한국과학기술원 :바이오및뇌공학과

Procurement with a Strong Insider

We consider a procurement auction with a “strong” insider and outside bidders. Within the confines of uniformly distributed independent private values, we compare a standard second price auction with a “tournament” in which the outsiders bid first to win the right to compete with the insider. The bids of the outsiders are binding and the highest bidder proceeds to a second-price competition with the insider. We take the insider to be “sufficiently strong” relative to the insiders. The outsiders bid above their values and the expected revenue exceeds that of the standard second price auction. This is true for any finite N, and in the limit as N grows large