FIELD OBSERVATIONS AND MODEL PREDICTIONS OF WAVE TRANSFORMATION ON A MACRO-TIDAL BEACH, KOREA

Macro-tidal beach processes are influenced by complicated interactions of tide actions, coastal waves and morphological changes. Tidal cycles may be a primary forcing responsible for specific characteristics of hydrodynamic and morphological processes complicated on the intertidal flat in space and time. Macro-tidal sandy beaches are frequently developed in the west coast of Korea, experiencing seasonal variations of inter-tidal processes caused by a monsoonal climate in the Yellow Sea. Large winter waves tend to excite active beach morphological processes, inducing beach erosion and seaward-directed sediment transports. This study is intended to investigate and characterize intertidal hydrodynamics including wave dynamics in a macro-tide environment in Korea, by using a numerical model named COBRAS. The measured water surface elevation data are divided into wave and tidal components, in order to be used as inputs of the model. Tidal components in terms of water level change are implemented in the model by adding constant currents at the offshore boundary. Comparisons of the measurements and the predictions show a good performance of the model for wave height transformation and wave set-up across the macro-tidal beach</jats:p

Laboratory Investigations on Effects of Water Level Change on Surf-zone Processes

Tidal level and current often influence the rip current and the morphological changes in the macro-tidal beaches. Effects of water level change on surf zone processes were investigated through laboratory experiments conducted in a two dimensional wave flume. A movable beach was installed using a find sand in the flume starting with 1/50 slope from the offshore and ending with 1/20 slope near the shore. Irregular waves were generated by a piston type wave maker with active absorption. In the meantime, water level was changed gradually by using a pump and drain system to consider waves and tide simultaneously. Herein, three different tidal phases (i.e. flood tide, full tide and ebb tide) were conditioned with a gradual depth change of about 10 15 cm in the offshore during a period of about 30 minutes per phase except the full tide, while only one wave condition was kept targeting a significant wave height of 12 cm and significant wave period of 1.7 s. Measurements of wave attenuations in the wave breaking zone influenced by the tidal change were made using in-situ sensors and an image-based analysis method. The rates of wave attenuation (i.e. the ratio of wave height to water depth) measured during the both of flood and ebb tides were found to be larger, ranging from about 0.8 to 1.4, compared to those recorded during the full tide with little depth change. In addition, the attenuation coefficient of the flood tide tends to be larger than that of the ebb tide.11sciescopu

Remote sensing of wave runup over breakwater slope in field using optical imagery

In this paper, wave run-up on the seaward slope of a breakwater in field was measured remotely using optical video imagery and investigated through comparisons with an empirical formula. In order to extract properties of wave run-up and over-topping on the breakwater slope from field videos, individual image frames were sequentially sampled at 3 Hz from a video burst first. Then, the sampled sequential image frames were rectified into real world coordinates. A cross-shore image timestack was generated by collecting an image pixel array, which was defined along the cross-shore transect on the seaward breakwater face of interest. Trajectory of the run-up on the seaward face evolving in time was extracted from the image timestack using a line detection method. The properties of the run-up estimated from field video bursts were combined to the measurements of incident waves, in order to derive an empirical relation between incident waves and run-up. The video-based relative wave run-up height (i.e. R-u,R-2%/ Hs) at a typical armored breakwater with tetrapods was found to be about 2.15. This value is about in the range of the general formula, which was derived from laboratory experiments in earlier studies.11sciescopu

Neural Stem Cells Restore Hair Growth through Activation of the Hair Follicle Niche

Several types of hair loss result from the inability of hair follicles to initiate the anagen phase of the hair regeneration cycle. Modulating signaling pathways in the hair follicle niche can stimulate entry into the anagen phase. Despite much effort, stem cell-based or pharmacological therapies to activate the hair follicle niche have not been successful. Here, we set out to test the effect of neural stem cell (NSC) extract on the hair follicle niche for hair regrowth. NSC extracts were applied to the immortalized cell lines HaCaT keratinocytes and dermal papilla cells (DPCs) and the shaven dorsal skin of mice. Treatment with NSC extract dramatically improved the growth of HaCaT keratinocytes and DPCs. In addition, NSC extract enhanced the hair growth of the shaven dorsal skin of mice. In order to determine the molecular signaling pathways regulated by NSCs, we evaluated the expression levels of multiple growth and signaling factors, such as insulin-like growth factor-1 (IGF-1), hepatocyte growth factor (HGF), keratinocyte growth factor (KGF), vascular endothelial growth factor (VEGF), transforming growth factor-β (TGF-β), and bone morphogenetic protein (BMP) family members. We found that treatment with an NSC extract enhanced hair growth by activating hair follicle niches via coregulation of TGF-β and BMP signaling pathways in the telogen phase. We also observed activation and differentiation of intrafollicular hair follicle stem cells, matrix cells, and extrafollicular DPCs in vivo and in vitro. We tested whether activation of growth factor pathways is a major effect of NSC treatment on hair growth by applying the growth factors to mouse skin. Combined growth factors, including TGF-β, significantly increased the hair shaft length and growth rate. DNA damage and cell death were not observed in skin cells of mice treated with the NSC extract for a prolonged period. Overall, our data demonstrate that NSC extract provides an effective approach for promoting hair growth by directly regulating hair follicle niches through TGF-β and BMP signaling pathways as well as induction of core growth factors. </jats:p

Tissue inhibitor of metalloproteinase proteins inhibit teratoma growth in mice transplanted with pluripotent stem cells

Abstract Pluripotent stem cells (PSCs) can serve as an unlimited cell source for transplantation therapies for treating various devastating diseases, such as cardiovascular diseases, diabetes, and Parkinson's disease. However, PSC transplantation has some associated risks, including teratoma formation from the remaining undifferentiated PSCs. Thus, for successful clinical application, it is essential to ablate the proliferative PSCs before or after transplantation. In this study, neural stem cell-derived conditioned medium (NSC-CM) inhibited the proliferation of PSCs and PSC-derived neural precursor (NP) cells without influencing the potential of PSC-NP cells to differentiate into neurons in vitro and prevented teratoma growth in vivo. Moreover, we found that the NSC-CM remarkably decreased the expression levels of Oct4 and cyclin D1 that Oct4 directly binds to and increased the cleaved-caspase 3-positive cell death through the DNA damage response in PSCs and PSC-NPs. Interestingly, we found that NSCs distinctly secreted the tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 proteins. These proteins suppressed not only the proliferation of PSCs in cell culture but also teratoma growth in mice transplanted with PSCs through inhibition of matrix metalloproteinase (MMP)-2 and MMP-9 activity. Taken together, these results suggest that the TIMP proteins may improve the efficacy and safety of the PSC-based transplantation therapy. </jats:sec