Quantum-based Mechanical Force Realization in Pico-Newton Range

We propose mechanical force realization based on flux quantization in the pico-Newton range. By controlling the number of flux quantum in a superconducting annulus, a force can be created as integer multiples of a constant step. For a 50 nm-thick Nb annulus with the inner and outer radii of 5 $\mu$m and 10 $\mu$m, respectively, and the field gradient of 10 T/m the force step is estimated to be 184 fN. The stability against thermal fluctuations is also addressed.Comment: 5 pages; 4 figure

Three essays on corporate governance in Korea

This thesis analyzes three topics regarding Korean firms’ corporate governance. The first chapter examines whether organized employees play a role in limiting executive compensation. Considering that employees’ voices and power are best represented by labor unions and unionization rates, I conclude that labor union existence and rates are both negatively associated with cash compensation. I also find that such negative association is progressively stronger for upper percentile executive pay. I show that the existence of labor unions has a strong negative correlation with stock option use as well, but that the union rate does not. This implies that, if a firm has an organized union, it may become more difficult for that firm to introduce a new payment method such as an executive stock option. The second chapter tests owner-managed firms’ demand for the Directors’ and officers’ liability insurance (D&O insurance). D&O insurance covers the litigation costs that have to be paid by the directors and officers in case they are sued by other stakeholders. Because D&O insurance premium is paid by the corporation (shareholders), not by directors and officers, even though it primarily protects these people, the agency cost related benefits that shareholders could draw from this insurance were frequently discussed in previous studies. In this chapter, I hypothesize that, because such functions of D&O insurance are less useful in case there are few interest conflicts, firms that rarely suffer from agency issues should demand the insurance less. I focus on owner-manager firms as examples of where there is little agency issue and test the hypothesis. I show that both the probability of purchase and the size of insurance coverage are lower in owner-managed firms. The price of insurance was also lower in owner-manager firms, implying that owner-managership signals lower litigation risks. The third chapter seeks to answer the fundamental question in insurance research: Does corporate risk increase corporate insurance demand? I run a natural experiment using a legislative change which increases litigation risk as an exogenous shock, and provide empirical evidence that firms increase insurance demand when they are exposed to increased risks. The Korean Government has decided to adopt shareholder class action law for public firms with assets over a certain threshold. With shareholder class action, even small shareholders can raise litigation against a board of directors, executives, or a firm itself, so increasing the firm’s litigation risk. In a differences-in-differences model, I find that the firms that are subject to the law increase the insurance demand significantly more during the period than the firms that are free from class action law

Orai1 inhibitor STIM2?? regulates myogenesis by controlling SOCE dependent transcriptional factors

Store-operated Ca2+ entry (SOCE), the fundamental Ca2+ signaling mechanism in myogenesis, is mediated by stromal interaction molecule (STIM), which senses the depletion of endoplasmic reticulum Ca2+ stores and induces Ca2+ influx by activating Orai channels in the plasma membrane. Recently, STIM2??, an eight-residue-inserted splice variant of STIM2, was found to act as an inhibitor of SOCE. Although a previous study demonstrated an increase in STIM2?? splicing during in vitro differentiation of skeletal muscle, the underlying mechanism and detailed function of STIM2?? in myogenesis remain unclear. In this study, we investigated the function of STIM2?? in myogenesis using the C2C12 cell line with RNA interference-mediated knockdown and CRISPR-Cas-mediated knockout approaches. Deletion of STIM2?? delayed myogenic differentiation through the MEF2C and NFAT4 pathway in C2C12 cells. Further, loss of STIM2?? increased cell proliferation by altering Ca2+ homeostasis and inhibited cell cycle arrest mediated by the cyclin D1-CDK4 degradation pathway. Thus, this study identified a previously unknown function of STIM2?? in myogenesis and improves the understanding of how cells effectively regulate the development process via alternative splicing

Functional enhancement of neuronal cell behaviors and differentiation by elastin-mimetic recombinant protein presenting Arg-Gly-Asp peptides

Background: Integrin-mediated interaction of neuronal cells with extracellular matrix (ECM) is important for the control of cell adhesion, morphology, motility, and differentiation in both in vitro and in vivo systems. Arg-Gly-Asp (RGD) sequence is one of the most potent integrin-binding ligand found in many native ECM proteins. An elastin-mimetic recombinant protein, TGPG[VGRGD(VGVPG)6]20WPC, referred to as [RGD-V6]20, contains multiple RGD motifs to bind cell-surface integrins. This study aimed to investigate how surface-adsorbed recombinant protein can be used to modulate the behaviors and differentiation of neuronal cells in vitro. For this purpose, biomimetic ECM surfaces were prepared by isothermal adsorption of [RGD-V6]20 onto the tissue culture polystyrene (TCPS), and the effects of protein-coated surfaces on neuronal cell adhesion, spreading, migration, and differentiation were quantitatively measured using N2a neuroblastoma cells.Results: The [RGD-V6]20 was expressed in E. coli and purified by thermally-induced phase transition. N2a cell attachment to either [RGD-V6]20 or fibronectin followed hyperbolic binding kinetics saturating around 2 μM protein concentration. The apparent maximum cell binding to [RGD-V6]20 was approximately 96% of fibronectin, with half-maximal adhesion on [RGD-V6]20 and fibronectin occurring at a coating concentration of 2.4 × 10-7 and 1.4 × 10-7 M, respectively. The percentage of spreading cells was in the following order of proteins: fibronectin (84.3% ± 6.9%) > [RGD-V6]20 (42.9% ± 6.5%) > [V7]20 (15.5% ± 3.2%) > TCPS (less than 10%). The migration speed of N2a cells on [RGD-V6]20 was similar to that of cells on fibronectin. The expression of neuronal marker proteins Tuj1, MAP2, and GFAP was approximately 1.5-fold up-regulated by [RGD-V6]20 relative to TCPS. Moreover, by the presence of both [RGD-V6]20 and RA, the expression levels of NSE, TuJ1, NF68, MAP2, and GFAP were significantly elevated.Conclusion: We have shown that an elastin-mimetic protein consisting of alternating tropoelastin structural domains and cell-binding RGD motifs is able to stimulate neuronal cell behaviors and differentiation. In particular, adhesion-induced neural differentiation is highly desirable for neural development and nerve repair. In this context, our data emphasize that the combination of biomimetically engineered recombinant protein and isothermal adsorption approach allows for the facile preparation of bioactive matrix or coating for neural tissue regeneration. © 2012 Jeon et al.; licensee BioMed Central Ltd.1

An Annular Array MPT for Enhanced Generation of Omnidirectional SH Waves in a Plate

If guided wave transducers are fabricated in an annular array type, the excitation and measurement of target guided wave modes could be considerably enhanced (see, e.g., [1]). Accordingly, various annular array transducers have been developed, including those generating omnidirectional Lamb waves in a plate. Here, we newly consider an annular array type MPT (magnetostrictive patch transducer) to generate enhanced SH (shear-horizontal) waves in a plate. This annular array MPT is based on our earlier development of an omnidirectional SH wave MPT [2]. For wave field analysis by the annular array SH wave MPT, the strain response in a plate due to wave excitation by the MPT is calculated by using the Green’s function approach [3]. Using the analysis, an optimal configuration of the annular array MPT which can maximize the transducer output at the given frequency is determined. For the validation of numerical predictions, a series of experiments with varying frequencies were carried out and the numerical results were found to be in good agreement with the experimental results

Helicobacter pylori Infection and Halitosis – Evidence, Hypothesis, and Korean Red Ginseng to Mitigate Its Effect

Halitosis is a common and ignored condition, but in some, it is a disease-associated health problem, suggestive of overt disease conditions and hasaffected about 25–30% of world’s population, bothering nonmedical social disturbance in many people. Although two kinds, pseudohalitosis and halitophobia, are also concerned, genuine halitosis originated from the oral cavity, such as gingivitis, caries, and poor oral hygiene, in 80% and the remaining 20% are extraoral sources of halitosis, which should not be ignored because of stigmata suggestive of overt tissue dysfunctions, for instance, poor nutrition and hygiene, alcohol abuse, smoking, and systemic illness such as chronic obstructive pulmonary disease, liver cirrhosis, diabetes mellitus, and chronic renal diseases. In this chapter, Helicobacter pylori (H. pylori)–associated halitosis as one of the extragastric manifestations is introduced. Since diagnostics of halitosis includes subjective methods (examiner’s sense of smell) and objective methods (instrumental analysis), under the hypothesis of a possible relationship between H. pylori infection and objective halitosis, the real levels of volatile sulfur compounds (VSCs) in the breath showed significant correlation between VSC levels and the degree of H. pylori–associated erosive gastritis as well as gastric cancer. These findings are further validated through either measuring H2S level in gastric juices of H. pylori–infected gastritis or checking the expressions of cystathionine-γ-lyase (CSE) and cystathionine-β-synthase (CBS) responsible for H2S generation in biopsied stomach. The eradication of H. pylori significantly ameliorated halitosis, accompanied with significant reductions in gastric H2S levels (p<0.01). Korean red ginseng was very effective in either reducing H. pylori–associated H2S or alleviating halitosis in patients with H. pylori–associated chronic atrophic gastritis. Conclusively, H. pylori infection demonstrates to have an important relationship with the development of halitosis, and its eradication could possibly promote the improvement of this condition