Showing papers by "Young Jin Suh published in 2012"
TL;DR: In this article, the curvature tensor of a real hypersurface M in complex two-plane Grassmannians G2(ℂm+2) was derived from the Gauss equation.
Abstract: We introduce the full expression of the curvature tensor of a real hypersurface M in complex two-plane Grassmannians G2(ℂm+2) from the Gauss equation. We then derive a new formula for the Ricci tensor of M in G2(ℂm+2). Finally, we prove that there does not exist any Hopf real hypersurface in complex two-plane Grassmannians G2(ℂm+2) with parallel Ricci tensor.
62 citations
TL;DR: In this article, the authors introduced a new notion of Z-tensor and a new kind of Riemannian manifold called pseudoZ symmetric manifold and denoted by (PZS)n.
Abstract: In this paper we introduce a new notion of Z-tensor and a new kind of Riemannian manifold that generalize the concept of both pseudo Ricci symmetric manifold and pseudo projective Ricci symmetric manifold. Here the Z-tensor is a general notion of the Einstein gravitational tensor in General Relativity. Such a new class of manifolds with Z-tensor is named pseudoZ symmetric manifold and denoted by (PZS)n. Various properties of such an n-dimensional manifold are studied, especially focusing the cases with harmonic curvature tensors giving the conditions of closeness of the associated one-form. We study (PZS)n manifolds with harmonic conformal and quasi-conformal curvature tensor. We also show the closeness of the associated 1-form when the (PZS)n manifold becomes pseudo Ricci symmetric in the sense of Deszcz (see [A. Derdzinsky and C. L. Shen, Codazzi tensor fields, curvature and Pontryagin forms, Proc. London Math. Soc.47(3) (1983) 15–26; R. Deszcz, On pseudo symmetric spaces, Bull. Soc. Math. Belg. Ser. A44 (1992) 1–34]). Finally, we study some properties of (PZS)4 spacetime manifolds.
51 citations
Asan Medical Center1, Seoul National University Bundang Hospital2, New Generation University College3, Soonchunhyang University4, Hallym University5, Ajou University6, Ewha Womans University7, Catholic University of Korea8, Sungkyunkwan University9, Soonchunhyang University Hospital10, Chonbuk National University11, Yonsei University12, Konkuk University13
TL;DR: BRCA1/2 mutations for non-familial Korean breast cancer patients were detected at a high rate, particularly, in patients with early onset of less than 35 years of age, bilateral breast cancer, and breast and ovarian cancer.
Abstract: Prevalence and phenotype of BRCA mutation can vary by race. The purpose of this study is to evaluate the prevalence of BRCA1/2 mutations in non-familial breast cancer patients with high risks in Korea. A subset of 758 patients was selected for this study from the KOHBRA nationwide multicenter prospective cohort study. Mutations in BRCA1/2 genes were tested using fluorescent-conformation sensitive gel electrophoresis, denaturing high performance liquid chromatography or direct sequencing. Mutation of BRCA1/2 genes were identified in 65 (8.6%) patients among total 758 patients [BRCA1 mutation: 25 (3.3%), BRCA2 mutation: 40 (5.3%)]. According to risk groups, mutation of BRCA1/2 genes were identified in 53 (8.5%) of 625 early onset patients (age ≤40), in 22 (17.7%) of 124 bilateral breast cancer patients, in 3 (50.0%) of 6 breast and ovarian cancer patients, in one (5.9%) of 17 male breast cancer patients, in 5 cases (7.6%) of 66 multiple organ cancer patients. The most common mutation was 509C>A for BRCA1 and 7708C>T for BRCA2. The prevalence of BRCA1/2 mutations by age in early onset patients was significantly different (age <35 vs age ≥35; 10.0 vs 2.9%, p = 0.0007). BRCA1/2 mutations for non-familial Korean breast cancer patients were detected at a high rate, particularly, in patients with early onset of less than 35 years of age, bilateral breast cancer, and breast and ovarian cancer. Individualized genetic counseling should be offered for non-familial breast cancer patients with these risk factors.
43 citations
TL;DR: In this article, the rank two symmetric space SU2, m/S(U2Um) of non-compact type was investigated, and a general treatment of this problem for higher rank symmetric spaces is out of reach at present, and therefore it is desirable to understand this problem better in a few special cases.
Abstract: Consider a Riemannian manifold N equipped with an additional geometric structure, such as a Kahler structure or a quaternionic Kahler structure, and a hypersurface M in N. The geometric structure induces a decomposition of the tangent bundle TM of M into subbundles. A natural problem is to classify all hypersurfaces in N for which the second fundamental form of M preserves these subbundles. This problem is reasonably well understood for Riemannian symmetric spaces of rank one, but not for higher rank symmetric spaces. A general treatment of this problem for higher rank symmetric spaces is out of reach at present, and therefore it is desirable to understand this problem better in a few special cases. Due to some conceptual differences between symmetric spaces of compact type and of noncompact type it appears that one needs to consider these two cases separately. In this paper we investigate this problem for the rank two symmetric space SU2, m/S(U2Um) of noncompact type.
43 citations
TL;DR: In this article, the authors studied the closedness properties of generalized curvature 2-forms, which are said to be Riemannian, Conformal, Projective, Concircular and Conharmonic curvatures.
Abstract: In this paper we study the closedness properties of generalized cur- vature 2-forms, which are said to be Riemannian, Conformal, Projective, Concircular and Conharmonic curvature 2-forms, associated to each generalized curvature tensors on a Riemannian manifold. Corresponding to each curvature tensors, such generalized curvature 2-forms are the associated curvature 2-forms. In particular, we focus on the closedness of difierential 2-forms associated to the divergence of generalized curvature tensors, which is weaker than the notion of harmonic curvature. In this case, we give an algebraic condition involving the Riemann curvature tensor and the Ricci tensor arising from an old identity due to Lovelock.
36 citations
TL;DR: In this article, a new kind of Riemannian manifold is introduced, named (ZRF)n, which generalizes weakly Z-symmetric and pseudo-Z-Symmetric manifolds, and the existence of a proper concircular vector in the conformally harmonic case and the form of the Ricci tensor is confirmed for(ZRFn)n with rank(Zkl) > 2.
Abstract: In this paper, we introduce a new kind of Riemannian manifold that generalize the concept of weakly Z-symmetric and pseudo-Z-symmetric manifolds. First a Z form associated to the Z tensor is defined. Then the notion of Z recurrent form is introduced. We take into consideration Riemannian manifolds in which the Z form is recurrent. This kind of manifold is named (ZRF)n. The main result of the paper is that the closedness property of the associated covector is achieved also for rank(Zkl) > 2. Thus the existence of a proper concircular vector in the conformally harmonic case and the form of the Ricci tensor are confirmed for(ZRF)n manifolds with rank(Zkl) > 2. This includes and enlarges the corresponding results already proven for pseudo-Z-symmetric (PZS)n and weakly Z-symmetric manifolds (WZS)n in the case of non-singular Z tensor. In the last sections we study special conformally flat (ZRF)n and give a brief account of Z recurrent forms on Kaehler manifolds.
26 citations
TL;DR: An extremely rare case of left incarcerated diaphragmatic hernia of the transverse colon developed in an 81-year-old female patient as a late complication, 8 months after laparoscopy-assisted total gastrectomy for gastric cancer, with laparoscope successfully resumed and without the need to sacrifice any portion of the bowel.
Abstract: Through the advent of surgical techniques and the improvement of laparoscopic tools including the ultrasonic activated scissor, laparoscopic gastrectomy has been increasingly used in far more cases of benign or malignant gastric lesions for the benefit of patients without compromising therapeutic outcomes. Even though possible complications provoked by the ultrasonic activated scissor can be prevented during the procedure with increasing advanced laparoscopic experience and supervision, unexpected late complications after the operations rarely occur. An extremely rare case of left incarcerated diaphragmatic hernia of the transverse colon developed in an 81-year-old female patient as a late complication, 8 months after laparoscopy-assisted total gastrectomy for gastric cancer, with laparoscopy successfully resumed and without the need to sacrifice any portion of the bowel.
26 citations
TL;DR: Both BRCAPRO and Myriad II models are less sensitive in Korean women, and therefore a new BRCA mutation prediction model based on Korean data is needed for proper genetic counseling.
Abstract: BRCAPRO and Myriad II are widely used models for predicting BRCA1/2 mutation probability before genetic testing. However, the accuracy of these models in Koreans is not known. This study was performed to evaluate the accuracy of the BRCAPRO and Myriad II models. Two hundred thirty-six women with breast cancer who underwent comprehensive BRCA1/2 genetic testing at our hospital between 2003 and 2010 were included in this study. We evaluated the performance of each model by comparing the numbers of observed versus predicted mutation carriers. We calculated sensitivity, specificity, and predictive values at 10 % estimated probability. Forty-six individuals were identified to carry a deleterious BRCA mutation. The prevalence of BRCA mutation (19.5 %) was significantly higher than that predicted by BRCAPRO (9.0 %, p = 0.001) and Myriad (5.6 %, p 50 years), with only one relative with breast cancer, and with non-familial early-onset breast cancer or bilateral breast cancer. Using a 10 % cut-off, the sensitivities were 47.8 % (BRCAPRO) and 50.0 % (Myriad), and positive predictive values were 44.9 % (BRCAPRO) and 43.4 % (Myriad). Both BRCAPRO and Myriad II underestimated the risk of BRCA1/2 mutation in Koreans. Our findings suggest that these models are less sensitive in Korean women, and therefore a new BRCA mutation prediction model based on Korean data is needed for proper genetic counseling.
18 citations
TL;DR: The benefit of PMRT differed among subgroups with different breast cancer subtype and p53 overexpression, and more efficacious systemic treatment strategies are needed, especially in patients at high risk for distant metastasis to obtain optimal therapeutic gain.
Abstract: Although post-mastectomy radiation therapy (PMRT) has shown benefits, its effects in patient subpopulations remain uncertain. Therefore, we assessed whether breast cancer subtype and p53 overexpression were associated with outcome after modified radical mastectomy (MRM), with or without PMRT. We retrospectively analyzed the records of patients who underwent MRM, with or without PMRT, between January 1991 and December 2008. Patients were considered eligible if they had T3 or T4 stage disease; any T stage with N2 or N3 stage; any T or N stage with positive, close (<1 mm) resection margins; or skin, nipple, or pectoral muscle invasion. We used immunohistochemistry and/or fluorescent in situ hybridization to determine breast cancer subtypes and p53 overexpression status. We found that 104 patients were eligible, including 59 (56.7%) who underwent PMRT and 45 (43.3%) who did not. Median follow-up duration was 61.3 months (range 16.1–232.7). Overall survival (OS) was significantly longer in patients who underwent PMRT (P = 0.029). This trend was evident in the subgroup of luminal type A breast cancer (P = 0.017) and non-p53 overexpression (P = 0.026) patients. However, there was no significant survival benefit from PMRT in the subgroup of triple negative (TN) breast cancer (P = 0.528) and p53 overexpression (P = 0.189) patients. The benefit of PMRT differed among subgroups with different breast cancer subtype and p53 overexpression. More efficacious systemic treatment strategies are needed, especially in patients at high risk for distant metastasis, to obtain optimal therapeutic gain.
13 citations
TL;DR: In this article, necessary and sufficient conditions for a slant curve in a Sasakian 3-manifold to have a C-parallel mean curvature vector were given.
Abstract: In this article, using the example of C. Camci((7)) we reconrm necessary suf- �cient condition for a slant curve. Next, wend some necessary and sufficient conditions for a slant curve in a Sasakian 3-manifold to have: (i) a C-parallel mean curvature vector
12 citations
TL;DR: Tanaka et al. as mentioned in this paper introduced a new notion of generalized Tanaka-Webster and#x1d507;⊥-parallel for a hypersurface M in G2(ℂm+2), and gave a characterization for a tube around a totally geodesic ℍ Pn in G 2(∆ m+2) where m = 2n.
Abstract: In a paper due to [I. Jeong, H. Lee and Y. J. Suh, Real hypersurfaces in complex two-plane Grassmannians with generalized Tanaka–Webster parallel shape operator, Kodai Math. J.34 (2011) 352–366] we have shown that there does not exist a hypersurface in G2(ℂm+2) with parallel shape operator in the generalized Tanaka–Webster connection (see [N. Tanaka, On non-degenerate real hypersurfaces, graded Lie algebras and Cartan connections, Japan J. Math.20 (1976) 131–190; S. Tanno, Variational problems on contact Riemannian manifolds, Trans. Amer. Math. Soc.314(1) (1989) 349–379]). In this paper, we introduce a new notion of generalized Tanaka–Webster 𝔇⊥-parallel for a hypersurface M in G2(ℂm+2), and give a characterization for a tube around a totally geodesic ℍ Pn in G2(ℂm+2) where m = 2n.
TL;DR: In this article, the authors introduced a new notion of commuting condition that φφ1A = Aφ 1φ between the shape operator A and the structure tensors φ and φ 1 for real hypersurfaces in G2(ℂm+2).
Abstract: In this paper, first we introduce a new notion of commuting condition that φφ1A = Aφ1φ between the shape operator A and the structure tensors φ and φ1 for real hypersurfaces in G2(ℂm+2). Suprisingly, real hypersurfaces of type (A), that is, a tube over a totally geodesic G2(ℂm+1) in complex two plane Grassmannians G2(ℂm+2) satisfy this commuting condition. Next we consider a complete classification of Hopf hypersurfaces in G2(ℂm+2) satisfying the commuting condition. Finally we get a characterization of Type (A) in terms of such commuting condition φφ1A = Aφ1φ.
TL;DR: Institutions should standardize their techniques and then provide fellowship training for newcomers of laparoscopic colon cancer surgery as this technique once mastered will become the gold standard approach to colon surgery as it is both safe and feasible considering the oncological and technical aspects.
Abstract: This retrospective study compared the clinicopathological results among three groups divided by time sequence to evaluate the impact of introducing laparoscopic surgery on long-term oncological outcomes for right-sided colon cancer. From April 1986 to December 2006, 200 patients who underwent elective surgery with stage II and III right-sided colon cancer were analyzed. The period for group I referred back to the time when laparoscopic approach had not yet been introduced. The period for group II was designated as the time when first laparoscopic approach for right colectomy was carried out until we overcame its learning curve. The period for group III was the period after overcoming this learning curve. When groups I and II, and groups II and III were compared, overall survival (OS) did not differ significantly whereas disease-free survival (DFS) in groups I and III were statistically higher than in group II (P = 0.042 and P = 0.050). In group III, laparoscopic surgery had a tendency to provide better long-term OS ( P = 0.2036) and DFS ( P = 0.2356) than open surgery. Also, the incidence of local recurrence in group III (2.6%) was significantly lower than that in groups II (7.4%) and I (12.1%) ( P = 0.013). Institutions should standardize their techniques and then provide fellowship training for newcomers of laparoscopic colon cancer surgery. This technique once mastered will become the gold standard approach to colon surgery as it is both safe and feasible considering the oncological and technical aspects.
TL;DR: In this article, a characterization of real hypersurfaces of type (A) in a complex two-plane Grassmannian G2(Cm+2) is given.
Abstract: In this paper we give a characterization of real hypersurfaces of type (A) in a complex two-plane Grassmannian G2(Cm+2) which is a tube over a totally geodesic G2(Cm+1) in G2(Cm+2), in terms of two com- muting conditions related to the normal Jacobi operator and the shape operator.
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