Thursday, March 11, 2021

2021-03-16 / 12:00 ~ 13:00

학과 세미나/콜로퀴엄 - 대학원생 세미나: Synthetic multistability in mammalian cells

by 정의민()

We will discuss about “Synthetic multistability in mammalian cells”, Zhu et al., bioRxiv (2021) In multicellular organisms, gene regulatory circuits generate thousands of molecularly distinct, mitotically heritable states, through the property of multistability. Designing synthetic multistable circuits would provide insight into natural cell fate control circuit architectures and allow engineering of multicellular programs that require interactions among cells in distinct states. Here we introduce MultiFate, a naturally-inspired, synthetic circuit that supports long-term, controllable, and expandable multistability in mammalian cells. MultiFate uses engineered zinc finger transcription factors that transcriptionally self-activate as homodimers and mutually inhibit one another through heterodimerization. Using model-based design, we engineered MultiFate circuits that generate up to seven states, each stable for at least 18 days. MultiFate permits controlled state-switching and modulation of state stability through external inputs, and can be easily expanded with additional transcription factors. Together, these results provide a foundation for engineering multicellular behaviors in mammalian cells.

2021-03-12 / 10:00 ~ 12:00

학과 세미나/콜로퀴엄 - SAARC 세미나:

by 조경현(CDS, NYU)

In this talk, I start by giving a brief overview of the practice in deep learning with focus on learning (optimization) and model selection (hyperparameter optimization). In particular, I will describe and discuss black-box optimization approaches to model selection, followed by discussion on how these two stages in deep learning can be collapsed into a single optimization problem, often referred to as bilevel optimization. This allows us to extend the applicability of gradient-based optimization into model selection, although existing gradient-based model selection, or hyperparameter optimization, approaches have been limited because they require an extensive numbers of so-called roll-out. I will then explain how we can view gradient-based optimization as a recurrent network and how this enables us to view hyperparameter optimization as training a recurrent network. This is an insight that leads to a novel paradigm of online hyperparameter optimization which does not require any simulated roll-out.

2021-03-11 / 10:00 ~ 12:00

학과 세미나/콜로퀴엄 - SAARC 세미나:

by 남경식()

Abstract: The large deviation problem for the spectrum of random matrices has attracted immense interest. It was first studied for GUE and GOE, which are exactly solvable, and subsequently studied for Wigner matrices with general distributions. Once the sparsity is induced (i.e. each entry is multiplied by the independent Bernoulli distribution, Ber(p)), eigenvalues can exhibit a drastically different behavior. For a large class of Wigner matrices, including Gaussian ensembles and the adjacency matrix of Erdos-Renyi graphs, dense behavior ceases to hold near the constant average degree of sparsity, p~1/n (up to a poly-logarithmic factor). In this talk, I will talk about the spectral large deviation for Gaussian ensembles with a sparsity p=1/n. Joint work with Shirshendu Ganguly.

2021-03-11 / 15:30 ~ 16:30

학과 세미나/콜로퀴엄 - 대수기하학:

by ()

Introduction: In this lecture series, we'll discuss algebro-geometric study on fundamental problems concerning tensors via higher secant varieties. We start by recalling definition of tensors, basic properties and small examples and proceed to discussion on tensor rank, decomposition, and X-rank for any nondegenerate variety $X$ in a projective space. Higher secant varieties of Segre (resp. Veronese) embeddings will be regarded as a natural parameter space of general (resp. symmetric) tensors in the lectures. We also review known results on dimensions of secants of Segre and Veronese, and consider various techniques to provide equations on the secants. In the end, we'll finish the lectures by introducing some open problems related to the theme such as syzygy structures and singularities of higher secant varieties.

2021-03-18 / 16:15 ~ 17:15

학과 세미나/콜로퀴엄 - 콜로퀴엄: A region with simply-connected-boundary is not necessarily simply-connected.

by 최경수(고등과학원)

It is a gentle introduction to the mean curvature flow and its application to knot theory for undergraduate students. J.W.Alexander discovered a knotted sphere embedded in 3-dimensional Euclidean space in 1924. This example has provoked curiosity to find simple conditions under which embedded spheres are unknotted. In this talk we will sketch theorems and conjectures in the mean curvature flow for the knot theory, in analogy to the Ricci flow for the smooth 4-dimensional Poincare conjecture.

2021-03-11 / 16:15 ~ 17:15

학과 세미나/콜로퀴엄 - 콜로퀴엄: Well-posedness problem for compressible Euler system

by 강문진(KAIST)

The compressible Euler system was first formulated by Euler in 1752, and was complemented by Laplace and Clausius in the 19th century, by introducing the energy conservation law and the concept of entropy based on thermodynamics. The most important feature of the Euler system is the finite-time breakdown of smooth solutions, especially, appearance of a shock wave as severe singularity to irreversibility(-in time) and discontinuity(-in space). Therefore, a fundamental question (since Riemann 1858) is on what happens after a shock occurs. This is the problem on well-posedness (that is, existence, uniqueness, stability) of weak solutions satisfying the 2nd law of thermodynamics, which is called entropy solution. This issue has been conjectured as follows: Well-posedness of entropy solutions for CE can be obtained in a class of vanishing viscosity limits of solutions to the Navier-Stokes system. This conjecture for the fundamental issue remains wide open even for the one-dimensional CE. This talk will give an overview of the conjecture, and recent progress on it.

Events for the 취소된 행사 포함