Seong-Min Kim

Thyroid Dysfunction Associated With Follicular Cell Steatosis in Obese Male Mice and Humans

Adult thyroid dysfunction is a common endocrine disorder associated with an increased risk of cardiovascular disease and mortality. A recent epidemiologic study revealed a link between obesity and increased prevalence of hypothyroidism. It is conceivable that excessive adiposity in obesity might lead to expansion of the interfollicular adipose (IFA) depot or steatosis in thyroid follicular cells (thyroid steatosis, TS). In this study, we investigated the morphological and functional changes in thyroid glands of obese humans and animal models, diet-induced obese (DIO), ob/ob, and db/db mice. Expanded IFA depot and TS were observed in obese patients. Furthermore, DIO mice showed increased expression of lipogenesis-regulation genes, such as sterol regulatory element binding protein 1 (SREBP-1), peroxisome proliferator-activated receptor γ (PPARγ), acetyl coenzyme A carboxylase (ACC), and fatty acid synthetase (FASN) in the thyroid gland. Steatosis and ultrastructural changes, including distension of the endoplasmic reticulum (ER) and mitochondrial distortion in thyroid follicular cells, were uniformly observed in DIO mice and genetically obese mouse models, ob/ob and db/db mice. Obese mice displayed a variable degree of primary thyroid hypofunction, which was not corrected by PPARγ agonist administration. We propose that systemically increased adiposity is associated with characteristic IFA depots and TS and may cause or influence the development of primary thyroid failure.

Synthesis of secondary and tertiary amine-containing MOFs: C–N bond cleavage during MOF synthesis

Secondary and tertiary amine-containing metal–organic frameworks (MOFs) have been synthesized, and unprecedented C–N bond cleavage phenomena were observed during MOF formation. Utilizing the secondary amine-containing ligand (BDC-NHMe), three new MOFs have been prepared, two of which are zinc(II)-based, IRMOF-NHMe (IRMOF = isoreticular MOF) and DMOF-1-NHMe (DMOF = dabco MOF), in addition to the zirconium(IV)-based UiO-66-NHMe (UiO = University of Oslo). The tertiary amine-containing ligand (BDC-NMe2) was converted to the secondary amine-containing ligand (BDC-NHMe) under both IRMOF and UiO-66 synthesis conditions, indicating an in situ C–N bond cleavage of ligand during MOF formation. In contrast, the tertiary amine-containing DMOF-1-NMe2 was successfully synthesized and studied for CO2 adsorption experiments.

An improved method for decision-directed blind equalization algorithm

The decision-directed blind equalization algorithm is often used due to its simplicity and good convergence property when the eye pattern is open. However, in a channel where the eye pattern is closed, the decision-directed algorithm is not guaranteed to converge. Hence, a modified decision-directed algorithm using a hyperbolic tangent function for zero-memory nonlinear function has been proposed and applied to avoid this problem by Filho et al. But application of this algorithm includes the calculation of hyperbolic tangent function and its derivative or a look-up table which may need a large amount of memory due to channel variations. To reduce the computational and/or hardware complexity of Filhos algorithm, in this paper, an improved method for the decision-directed algorithm is proposed. It is shown that the proposed scheme, when it is combined with decision-directed algorithm, reduces the computational complexity drastically while it retains the convergence and steady-state performance of the Filhos algorithm.

A New Bussgang Blind Equalization Algorithm with Reduced Computational Complexity

The decision-directed blind equalization algorithm is often used due to its simplicity and good convergence property when the eye pattern is open. However, in a channel where the eye pattern is closed, the decision-directed algorithm is not guaranteed to converge. Hence, a modified Bussgang-type algorithm using a hyperbolic tangent function for zero-memory nonlinear(ZNL) function has been proposed and applied to avoid this problem by Filho et al. But application of this algorithm includes the calculation of hyperbolic tangent function and its derivative or a look-up table which may need a large amount of memory due to channel variations. To reduce the computational and/or hardware complexity of Filho`s algorithm, in this paper, an improved method for the decision-directed algorithm is proposed. In the proposed scheme, the ZNL function and its derivative are respectively set to be the original signum function and a narrow rectangular pulse which is an approximation of Dirac delta function. It is shown that the proposed scheme, when it is combined with decision-directed algorithm, reduces the computational complexity drastically while it retains the convergence and steady-state performance of the Filho`s algorithm.