• Kyungpook Mathematical Journal
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• 제58권4호
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• pp.761-779
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• 2018

The object of the present paper is to study weakly Z symmetric spacetimes $(WZS)_4$. At first we prove that a weakly Z symmetric spacetime is a quasi-Einstein spacetime and hence a perfect fluid spacetime. Next, we consider conformally flat $(WZS)_4$ spacetimes and prove that such a spacetime is infinitesimally spatially isotropic relative to the unit timelike vector field ${\rho}$. We also study $(WZS)_4$ spacetimes with divergence free conformal curvature tensor. Moreover, we characterize dust fluid and viscous fluid $(WZS)_4$ spacetimes. Finally, we construct an example of a $(WZS)_4$ spacetime.

• Korean Journal of Mathematics
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• 제28권4호
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• pp.739-751
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• 2020

The object of the offering exposition is to study almost Ricci soliton and gradient almost Ricci soliton in 3-dimensional para-Sasakian manifolds. At first, it is shown that if (g, V, λ) be an almost Ricci soliton on a 3-dimensional para-Sasakian manifold M, then it reduces to a Ricci soliton and the soliton is expanding for λ=-2. Besides these, in this section, we prove that if V is pointwise collinear with ξ, then V is a constant multiple of ξ and the manifold is of constant sectional curvature -1. Moreover, it is proved that if a 3-dimensional para-Sasakian manifold admits gradient almost Ricci soliton under certain conditions then either the manifold is of constant sectional curvature -1 or it reduces to a gradient Ricci soliton. Finally, we consider an example to justify some results of our paper.

• 대한수학회논문집
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• 제37권3호
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• pp.825-837
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• 2022

We characterize a three-dimensional Riemannian manifold endowed with a type of semi-symmetric metric P-connection. At first, it is proven that if the metric of such a manifold is a gradient m-quasi-Einstein metric, then either the gradient of the potential function 𝜓 is collinear with the vector field P or, λ = -(m + 2) and the manifold is of constant sectional curvature -1, provided P𝜓 ≠ m. Next, it is shown that if the metric of the manifold under consideration is a gradient 𝜌-Einstein soliton, then the gradient of the potential function is collinear with the vector field P. Also, we prove that if the metric of a 3-dimensional manifold with semi-symmetric metric P-connection is a gradient 𝜔-Ricci soliton, then the manifold is of constant sectional curvature -1 and λ + 𝜇 = -2. Finally, we consider an example to verify our results.

• 대한수학회보
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• 제60권3호
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• pp.763-774
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• 2023

If a paraSasakian manifold of dimension (2n + 1) represents Bach almost solitons, then the Bach tensor is a scalar multiple of the metric tensor and the manifold is of constant scalar curvature. Additionally it is shown that the Ricci operator of the metric g has a constant norm. Next, we characterize 3-dimensional paraSasakian manifolds admitting Bach almost solitons and it is proven that if a 3-dimensional paraSasakian manifold admits Bach almost solitons, then the manifold is of constant scalar curvature. Moreover, in dimension 3 the Bach almost solitons are steady if r = -6; shrinking if r > -6; expanding if r < -6.

• Parasites, Hosts and Diseases
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• 제24권1호
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• pp.3-141
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• 1986

간흡충은 우리나라를 비롯하여 중국, 대만, 일본 및 월남등지에 널리 분포되어 있으며 1947년에 Stoll씨의 통계에 의하면 세계적으로 1,900만명이 넘는 감염자가 있다고 하였다. 현재 우리나라에서만 약 200만명의 간흡충 감염자가 있을 것으로 추산되고 있다. 간흡충은 McConnell이 1874년에 인도의 Calcutta에서 한 중국인의 간담도에서 본충을 처음 발견한 것이다. 이것을 Cobbold(1875)가 Distoma sinense라고 명명하였다가 후에 Looss (1907)가 Clonorchis sinensis라고 하였다. Kobayashi (1910)는 담수어가 간흡충감염의 중간숙주로 작용한다는 것을 처음으로 발견하였고 Muto (1918)에 의하여 왜우렁이가 제1중간숙주임을 발견함으로서 간흉충의 생활사가 확실해 졌다. Faust 및 Khaw (1927)에 의하여 중국에서 간흡충의 생물학 및 역학에 관한 광범한 연구업적이 발표된 이래 일본, 한국, 중국등 여러곳에서 많은 사람들에 의하여 연구되어 왔다. 그러나 적절한 치료방법이 없었고 또 민물고기를 생식하는 식습관과 위생시설의 미비등 여러가지 요인때문에 예방이 어려움에 직면하였다. 최근 다행히 새로이 개 발된 praziquantel이 간흡충중에 대하여 우수한 치료효과를 나타내고 집단치료에도 적합하다는 것이 증명됨으로서 간흡충증 예방과 관리에 큰 서광이 보이게 되었다. 따라서 간흉충증의 발생과 임상적 병증의 중요성을 좀 더 이해하기 위하여 간흡충체의 미세구조, 병인, 역학, 임상증상등 최근 알려진 새로운 지견과 우리나라에 있어서 간흡충증의 분포 및 유행지 형성 상황을 수학적으로 역학적 분석을 시도하였다. 그리고 과거 간흡충중의 화학치료에 관한 연구성적을 종합하여 화학요법제의 특성 빚 치료 적용여부에 대하여 논하였고 각약제의 시험관내 및 실험동물에 있어서의 살충효과와 임상시험에 있어서의 치료효과 및 부작용에 대하여 기술하였다. 그리고 새로 개발된 praziquantel의 간흡충에 대한 작용기전에 대하여도 논하였다. (중략)

• Kyungpook Mathematical Journal
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• 제49권3호
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• pp.457-471
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• 2009

Let S = {a, b, c, ...} and ${\Gamma}$ = {${\alpha}$, ${\beta}$, ${\gamma}$, ...} be two nonempty sets. S is called a ${\Gamma}$-semigroup if $a{\alpha}b{\in}S$, for all ${\alpha}{\in}{\Gamma}$ and a, b ${\in}$ S and $(a{\alpha}b){\beta}c=a{\alpha}(b{\beta}c)$, for all a, b, c ${\in}$ S and for all ${\alpha}$, ${\beta}$ ${\in}$ ${\Gamma}$. An element $e{\in}S$ is said to be an ${\alpha}$-idempotent for some ${\alpha}{\in}{\Gamma}$ if $e{\alpha}e$ = e. A ${\Gamma}$-semigroup S is called an E-inversive ${\Gamma}$-semigroup if for each $a{\in}S$ there exist $x{\in}S$ and ${\alpha}{\in}{\Gamma}$ such that a${\alpha}$x is a ${\beta}$-idempotent for some ${\beta}{\in}{\Gamma}$. A ${\Gamma}$-semigroup is called a right E-${\Gamma}$-semigroup if for each ${\alpha}$-idempotent e and ${\beta}$-idempotent f, $e{\alpha}$ is a ${\beta}$-idempotent. In this paper we investigate different properties of E-inversive ${\Gamma}$-semigroup and right E-${\Gamma}$-semigroup.

• 대한수학회논문집
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• 제29권2호
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• pp.319-329
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• 2014

In this paper we study the properties of conformally recurrent pseudo Riemannian manifolds admitting a proper conformal vector field with respect to the scalar field ${\sigma}$, focusing particularly on the 4-dimensional Lorentzian case. Some general properties already proven by one of the present authors for pseudo conformally symmetric manifolds endowed with a conformal vector field are proven also in the case, and some new others are stated. Moreover interesting results are pointed out; for example, it is proven that the Ricci tensor under certain conditions is Weyl compatible: this notion was recently introduced and investigated by one of the present authors. Further we study conformally recurrent 4-dimensional Lorentzian manifolds (space-times) admitting a conformal vector field: it is proven that the covector ${\sigma}_j$ is null and unique up to scaling; moreover it is shown that the same vector is an eigenvector of the Ricci tensor. Finally, it is stated that such space-time is of Petrov type N with respect to ${\sigma}_j$.

• Journal of the Korean Statistical Society
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• 제30권1호
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• pp.41-61
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• 2001

The minimum negative exponential disparity estimator(MNEDE), introduced by Lindsay(1994), is an excellenet competitor to the minimum Hellinger distance estimator(Beran 1977) as a robust and yet efficient alternative to the maximum likelihood estimator in parametric models. In this paper we define the negative exponential deviance test(NEDT) as an analog of the likelihood ratio test(LRT), and show that the NEDT is asymptotically equivalent to he LRT at the model and under a sequence of contiguous alternatives. We establish that the asymptotic strong breakdown point for a class of minimum disparity estimators, containing the MNEDE, is at least 1/2 in continuous models. This result leads us to anticipate robustness of the NEDT under data contamination, and we demonstrate it empirically. In fact, in the simulation settings considered here the empirical level of the NEDT show more stability than the Hellinger deviance test(Simpson 1989). The NEDT is illustrated through an example data set. We also define a goodness-of-fit statistic to assess adequacy of a specified parametric model, and establish its asymptotic normality under the null hypothesis.

• 한국미생물·생명공학회지
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• 제47권4호
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• pp.585-595
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• 2019

Analysis of bacterial communities based on their 16S rDNA sequences revealed the predominance of Proteobacteria (Aeromonas sp., Acinetobacter sp. and Thaueraamino aromatica sp.) and uncultured bacterium in activated sludge from the effluent treatment plant (ETP) of Mother Dairy, Calcutta (India). Each isolate was used for bioremediation of dairy wastewater with simultaneous conversion of nitrogenous pollutants into ammonia. A consortium developed using seven of these isolates and three Bacillus strains from different environmental origins could reduce 93% nitrate with simultaneous production of ammonia (626 ㎍/100 ml) within 20 h in non-aerated, immobilized conditions as compared to 82% nitrate reduction producing 2.4 ㎍/100 ml ammonia in 96 h with extensive aeration in a conventional ETP. The treated ammonia-rich effluent could be used instead of freshwater and fertilizer during cultivation of mung bean with 1.6-fold increase in grain yield. The ETP with the surrounding agricultural land makes this process a zero liquid discharge technology for using the biofertilizer generated. In addition, the process requires minimal energy supporting sustained environmental health. This method is thus proposed as an alternative approach for small-scale dairy ETPs.

• Asian Pacific Journal of Cancer Prevention
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• 제15권1호
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• pp.419-422
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• 2014

Background: Lymphadenopathy is a common presentation in both benign and malignant diseases which need to be diagnosed without delay. Fine needle aspiration cytology (FNAC) helps us diagnose a disease and follow its course, including the response to therapy. Aim: This study aimed to analyze the clinicopathological features of metastatic lymphadenopathy and the diagnostic utility of FNAC in our setting. Materials and Methods: This two-year prospective study included all the patients with metastatic lymphadenopathy, diagnosed with FNAC. Results: A total of 412 cases (male:female ratio, 1.3:1; age range, 3 to 90 years) were studied. Supraclavicular lymph nodes were involved most commonly (50.5%). The commonest metastatic tumor was squamous cell carcinoma in general (30.1%) and in males (37.6%), and infiltrating ductal carcinoma (25.3%) in females. Lung, with 64 (15.5%) cases followed by esophagus, 60 (14.6%) cases; breast, 49 (11.9%) cases; skin, 32 (7.8%) cases; and stomach, 25 (6.1%) cases were the most common primary sites of malignancy. In 69 patients, excision biopsy was performed. Histopathological findings correlated well with that of cytology in all these cases. Conclusions: FNAC is an important tool in the diagnostic work up of metastatic lymphadenopathy, which in the hands of an experienced and skilful cytopathologist can avoid the need for excision biopsy.