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Search Results: 1 - 10 of 1747 matches for " Sanghoon Kwon "
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Effective Mixing and Counting in Bruhat-Tits Trees
Sanghoon Kwon
Mathematics , 2015,
Abstract: Let $\mathcal{T}$ be a locally finite tree, $\Gamma$ be a discrete subgroup of $\textrm{Aut}(\mathcal{T})$ and $\widetilde{F}$ be a $\Gamma$-invariant potential. Suppose that the length spectrum of $\Gamma$ is not arithmetic. In this case, we prove the exponential mixing property of the geodesic translation map $\phi\colon \Gamma\backslash S\mathcal{T}\to \Gamma\backslash S\mathcal{T}$ with respect to the measure $m_{\Gamma,F}^{\nu^-,\nu^+}$ under the assumption that $\Gamma$ is full and $(\Gamma,\widetilde{F})$ has weighted spectral gap property. We also obtain the effective formula for the number of $\Gamma$-orbits with weights in a Bruhat-Tits tree $\mathcal{T}$ of an algebraic group.
ASB9 interacts with ubiquitous mitochondrial creatine kinase and inhibits mitochondrial function
Sanghoon Kwon, Dongbum Kim, Jae Rhee, Jeong-A Park, Dae-Won Kim, Doo-Sik Kim, Younghee Lee, Hyung-Joo Kwon
BMC Biology , 2010, DOI: 10.1186/1741-7007-8-23
Abstract: We found that a variant of ASB9 that lacks the SOCS box (ASB9ΔSOCS) was naturally detected in human cell lines but not in peripheral blood mononuclear cells or normal hepatocytes. We also identified ubiquitous mitochondrial creatine kinase (uMtCK) as a new target of ASB9 in human embryonic kidney 293 (HEK293) cells. The ankyrin repeat domains of ASB9 can associate with the substrate binding site of uMtCK in a SOCS box-independent manner. The overexpression of ASB9, but not ASB9ΔSOCS, induces ubiquitination of uMtCK. ASB9 and ASB9ΔSOCS can interact and colocalise with uMtCK in the mitochondria. However, only expression of ASB9 induced abnormal mitochondrial structure and a decrease of mitochondrial membrane potential. Furthermore, the creatine kinase activities and cell growth were significantly reduced by ASB9 but not by ASB9ΔSOCS.ASB9 interacts with the creatine kinase system and negatively regulates cell growth. The differential expression and function of ASB9 and ASB9ΔSOCS may be a key factor in the growth of human cell lines and primary cells.The largest family of suppressor of cytokine signalling (SOCS) box-containing superfamily proteins are the ankyrin repeat and SOCS box proteins (Asbs; ASBs in humans). Although 18 members of the Asb family have been identified in mice and humans, the function of Asbs has not been clearly defined. The Asbs have two functional domains, a SOCS box and a variable number of N-terminal ankyrin (ANK) repeats [1]. The SOCS box of Asb proteins has two subdomains: a BC box and a Cul2/Cul5 box. Highly conserved amino acid sequences of the BC box and the Cul5 box, which are essential for ensuring that the interaction with elongins B/C and Cullin 5-Rbx2 forms E3 ubiquitin (Ub) ligase complexes, are important in a ubiquitination-mediated proteolysis pathway [2-6]. While SOCS family members use the SH2 domain to recruit substrates, the ANK repeat regions of Asb family members serve as specific protein-protein interaction platforms to recr
Open heavy flavor measurements in $d$$+$Au collisions at PHENIX experiment
Sanghoon Lim
Physics , 2014, DOI: 10.1051/epjconf/20147100074
Abstract: The heavy quarks produced in the early stage of heavy-ion collisions are very effective probes of the dense partonic medium produced at RHIC. PHENIX has the ability to measure heavy quark production through single electrons in the central arm spectrometers ($|\eta|<0.35$) and single muons in the forward (backward) muon spectrometers ($1.2<|\eta|<2.2$). As these single leptons are from open heavy-flavor meson semi-leptonic decays, initial state cold nuclear matter effects on heavy quark production can be probed by measuring the single leptons in $d$$+$Au collisions. PHENIX have observed a large enhancement of heavy-flavor electrons in $d$$+$Au collisions at mid-rapidity, which indicates strong CNM effects on heavy quark production, in contrast to the suppression observed in Au$+$Au collisions. Measurement of single muons from open heavy flavor in $d$$+$Au collisions at forward (backward) rapidity provide detailed look into rapidity dependent CNM effects as well as the low (high) $x$ parton distribution function within Au nucleus. We discuss recent PHENIX heavy flavor measurements and how they expand our understanding of CNM effects and contribute to the interpretation of other results in heavy-ion collisions.
Measurement of electrons from heavy-flavor decays from $p$+$p$, $d$+Au, and Cu+Cu collisions in the PHENIX experiment
Sanghoon Lim
Physics , 2014, DOI: 10.1016/j.nuclphysa.2014.08.059
Abstract: Charm and bottom quarks are formed predominantly by gluon fusion in the initial hard scatterings at RHIC, making them good probes of the full medium evolution. Previous measurements at RHIC have shown large suppression and azimuthal anisotropy of open heavy-flavor hadrons in Au+Au collisions at $\sqrt{s_{NN}}=200~{\rm GeV}$. Explaining the simultaneously large suppression and flow of heavy quarks has been challenging. To further understand the heavy-flavor transport in the hot and dense medium, it is imperative to also measure cold nuclear matter effects which affect the initial distribution of heavy quarks as well as the system size dependence of the final state suppression. In this talk, new measurements by the PHENIX collaboration of electrons from heavy-flavor decays in $p$+$p$, $d$+Au, and Cu+Cu collisions at $\sqrt{s_{NN}}=200~{\rm GeV}$ are presented. In particular, a surprising enhancement of intermediate transverse momentum heavy-flavor decay leptons in $d$+Au at mid and backward rapidity are also seen in mid-central Cu+Cu collisions. This enhancement is much larger than the expectation from anti-shadowing of the parton distributions and is theoretically unexplained.
Essential dimension of simple algebras in positive characteristic
Sanghoon Baek
Mathematics , 2010,
Abstract: Let $p$ be a prime integer, $1\leq s\leq r$ integers, $F$ a field of characteristic $p$. Let $\cat{Dec}_{p^r}$ denote the class of the tensor product of $r$ $p$-symbols and $\cat{Alg}_{p^r,p^s}$ denote the class of central simple algebras of degree $p^r$ and exponent dividing $p^s$. For any integers $s
Semiorthogonal decompositions for twisted grassmannians
Sanghoon Baek
Mathematics , 2012,
Abstract: In this article, we present semiorthogonal decompositions for twisted forms of grassmannians
A lower bound on the essential dimension of $\operatorname{\mathbf{PGL}}_{4}$ in characteristic $2$
Sanghoon Baek
Mathematics , 2014,
Abstract: In the present paper, we provide a lower bound of the essential dimension over a field of positive characteristic via Kato's cohomology group, defined by cokernel of a general Artin-Schreier operator. Combining this with Tignol's result on the second trace form of simple algebras of degree $4$, we show that $\operatorname{ed}(\operatorname{\mathbf{PGL}}_{4})\geq 4$ over a field of characteristic $2$.
Essential dimension of projective orthogonal and symplectic groups of small degree
Sanghoon Baek
Mathematics , 2011,
Abstract: In this paper, we study the essential dimension of classes of central simple algebras with involutions of index less or equal to 4. Using structural theorems for simple algebras with involutions, we obtain the essential dimension of projective and symplectic groups of small degree.
Chow groups of products of Severi-Brauer varieties and invariants of degree 3
Sanghoon Baek
Mathematics , 2015,
Abstract: We study the semi-decomposable invariants of a split semisimple group and their extension to a split reductive group by using the torsion in the codimension $2$ Chow groups of a product of Severi-Brauer varieties. In particular, for any $n\geq 2$ we completely determine the degree $3$ invariants of a split semisimple group, the quotient of $(\operatorname{\mathbf{SL}}_{2})^{n}$ by its maximal central subgroup, as well as of the corresponding split reductive group. We also provide an example illustrating that a modification of our method can be applied to find the semi-decomposable invariants of a split semisimple group of type A.
On the exponent of spinor groups
Sanghoon Baek
Mathematics , 2012,
Abstract: In this paper, we show that all the exponents of degree greater than 2 of spinor groups divide the Dynkin index 2.
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