Switching to Hidden Metallic Crystal Phase in Phase-Change Materials by Photoenhanced Metavalent Bonding.

Metavalent bonding is crucial for the determination of phase transition and improvement of device performance in phase-change materials, which are attracting interest for use in memory devices. Although monitoring dielectric and phononic parameters provides a direct measure of the metavalent bonding, the control of phase-change phenomena and metavalent bonding in the dynamical regime has yet to be demonstrated. This study reports the photoenhanced metavalent bonding and resulting hidden metallic crystalline state of Ti-doped Sb2Te3, a representative phase-change material with ultralong sustainability. Using ultrafast terahertz spectroscopy, Ti0.4Sb2Te3 was discovered to possess ultralong pump-probe dynamics, which is retained over hundreds of picoseconds, unlike the short-lived state of undoped Sb2Te3. Moreover, for Ti0.4Sb2Te3 during the long-lived transmission change, the infrared-active phonon is highly softened, even more than the amount of a thermal phonon shift, indicating the photoenhancement of lattice anharmonicity. Such a long-lived relaxation implies photoinduced transition into a crystalline state of ultrastrong metavalent bonding in Ti0.4Sb2Te3, on the basis of comparisons of the dynamical dielectric constant and temporal phonon shift. Our results show the realization of photoengineering of phase-change materials by tuning electron sharing or transferring.

Topological Phase Control of Surface States in Bi2Se3 via Spin-Orbit Coupling Modulation through Interface Engineering between HfO2-X.

The direct control of topological surface states in topological insulators is an important prerequisite for the application of these materials. Conventional attempts to utilize magnetic doping, mechanical tuning, structural engineering, external bias, and external magnetic fields suffer from a lack of reversible switching and have limited tunability. We demonstrate the direct control of topological phases in a bismuth selenide (Bi2Se3) topological insulator in 3 nm molecular beam epitaxy-grown films through the hybridization of the topological surface states with the hafnium (Hf) d-orbitals in the topmost layer of an underlying oxygen-deficient hafnium oxide (HfO2) substrate. The higher angular momentum of the d-orbitals of Hf is hybridized strongly by topological insulators, thereby enhancing the spin-orbit coupling and perturbing the topological surface states asymmetry in Bi2Se3. As the oxygen defect is cured or generated reversibly by external electric fields, our research facilitates the complete electrical control of the topological phases of topological insulators by controlling the defect density in the adjacent transition metal oxide. In addition, this mechanism can be applied in other related topological materials such as Weyl and Dirac semimetals in future endeavors to facilitate practical applications in unit-element devices for quantum computing and quantum communication.

Organic matter and heavy metal in river sediments of southwestern coastal Korea: Spatial distributions, pollution, and ecological risk assessment.

This study identifies the impact of river sediments on coastal ecosystems in the southwestern coastal region of Korea. Surface sediments were analyzed for their spatial distributions of organic matter, nutrients, and heavy metal concentrations. Furthermore, pollutants were identified according to the pollution load index (PLI) and potential ecological risk index (RI). Concentrations did not show serious pollution levels compared to generalized guidelines; however, some sites exceeded the PLI pollution standard, and were also identified as potential ecological risks. Through cluster analyses the sediment sites were classified into three groups: rivers with relatively high concentrations of organic matter and nutrients, rivers affected largely by artificial heavy metal pollution, and rivers with low levels of pollution by organic matter, nutrients, and heavy metals. It is evident that continuous monitoring and management are required to prevent major pollution from industrial complexes, agriculture, and commercial activities in the regions near these rivers.

Phase-change like process through bond switching in distorted and resonantly bonded crystal.

Although some methods to improve phase-change memory efficiency have been proposed, an effective experimental approach to induce a phase-change like process without external heat energy has not yet been reported. Herein we have shown that GeTe is a prototype phase-change material, which can exhibit a non-thermal phase-change-like process under uniaxial stress. Due to its structural characteristics like directional structural instability and resonance bonding under 1% uniaxial stress, we observed that bond switching in the GeTe film between short and long bonds is possible. Due to this phase change, GeTe displays the same phase-change as crystal layer rotation. Crystal layer rotation has not been observed in the conventional phase change process using intermediate states, but it is related to the structural characteristics required for maintaining local coordination. Moreover, since the resonance bonding characteristics are effectively turned off upon applying uniaxial stress, the high-frequency dielectric constant can be significantly decreased. Our results also show that the most significant process in the non-thermal phase transition of phase-change materials is the modulation of the lattice relaxation process after the initial perturbation, rather than the method inducing the perturbation itself. Finally, these consequences suggest that a new type of phase-change memory is possible through changes in the optical properties under stress.

The different effects of gonadotropin-releasing hormone agonist therapy on body mass index and growth between normal-weight and overweight girls with central precocious puberty.

PURPOSE: The effects of gonadotropin-releasing hormone agonist (GnRHa) treatment on body mass index (BMI) are controversial in girls with central precocious puberty (CPP). We therefore evaluated auxological parameters during GnRHa therapy in patients with CPP, specifically focusing on changes in BMI. METHODS: Seventy-seven girls with idiopathic CPP who underwent GnRHa therapy were retrospectively recruited. We investigated BMI changes during the treatment period after stratifying them according to baseline BMI status as follows: normal (BMI percentile of <85th) and overweight groups (BMI percentile of ≥85th). RESULTS: The incidence of overweight/obesity (40.3%/23.4%) was very high in the girls with CPP. In the overall study population, no significant BMI change was observed during the GnRHa treatment period. However, when stratified according to baseline BMI status, the normal-weight group showed a significant increase in BMI-standard deviation score (SDS), whereas the overweight group showed no change in BMI-SDS. Baseline BMI-SDS was an independent predictor of changes in BMI during the GnRHa treatment period. Changes in weight-SDS were similar, but changes in height-SDS were significantly greater in the overweight group than in the normal-weight group, which explains the observed difference in BMI-SDS. CONCLUSION: Our results demonstrate that the difference in the pattern of BMI changes among our CPP patients suggests that delayed puberty induced by GnRHa treatment may have different effects on linear growth according to baseline body composition. This study underscores the importance of individualized lifestyle intervention in CPP children.

Epigallocatechin-3-O-Gallate-Loaded Poly(lactic-co-glycolic acid) Fibrous Sheets as Anti-Adhesion Barriers.

Epigallocatechin-3-O-gallate (EGCG), the main polyphenolic component of green tea, has a wide range of pharmacological activities, including antioxidant, anti-inflammatory, and anti-fibrotic effects. In this study, EGCG-loaded poly(lactic-co-glycolic acid) (PLGA) sheets were prepared by electrospinning nanofibers and evaluating their potential as tissue-adhesion barriers. EGCG-loaded PLGA (E-PLGA) fibrous sheets were electrospun from a PLGA solution containing 8% (w/v) EGCG. The average diameter of E-PLGA fibers was 397 ± 159 nm, which was comparable to that of pure PLGA fibers (459 ± 154 nm). EGCG was uniformly dispersed in E-PLGA sheets without direct chemical interactions. E-PLGA fibrous sheets showed sustained release of EGCG by controlled diffusion and PLGA degradation. The attachment and proliferation of L-929 fibroblastic cells were significantly (p < 0.05) suppressed in E-PLGA sheets. Furthermore, E-PLGA fibrous sheets did not induce any inflammatory response to J774A.1 macrophages. The anti-adhesion efficacy of E-PLGA fibrous sheets was evaluated in the intraperitoneal adhesion model in rats. Two weeks after surgical treatment, macroscopic adhesion (extent and severity) scores and histopathological tissue responses of E-PLGA fibrous sheets were significantly lower than those of non-treated controls and pure PLGA sheets. The results suggest that the scores are comparable, and in some cases superior, to those of other commercialized tissue-adhesion barriers. In conclusion, our study findings suggest that E-PLGA fibrous sheets may be exploited as potential tissue-adhesion barriers for the prevention of post-surgical adhesion formation.

Effect of the Thermal Conductivity on Resistive Switching in GeTe and Ge2Sb2Te5 Nanowires.

The thermal conduction characteristics of GeTe and Ge2Sb2Te5(GST) nanowires were investigated using an optical method to determine the local temperature by Raman spectroscopy. Since the localization of surface charge in a single-crystalline nanostructure can enhance charge-phonon scattering, the thermal conductivity value (κ) of single crystalline GeTe and GST nanowires was decreased significantly to 1.44 Wm(-1) K(-1) for GeTe and 1.13 Wm(-1) K(-1) for GST, compared to reported values for polycrystalline structures. The SET-to-RESET state in single-crystalline GeTe and GST nanowires are characteristic of a memory device. Unlike previous reports using GeTe and GST nanowires, the SET-to-RESET characteristics showed a bipolar switching shape and no unipolar switching. In addition, after multiple cycles of operation, a significant change in morphology and composition was observed without any structural phase transition, indicating that atoms migrate toward the cathode or anode, depending on their electronegativities. This change caused by a field effect indicates that the structural phase transition does not occur in the case of GeTe and GST nanowires with a significantly lowered thermal conductivity and stable crystalline structure. Finally, the formation of voids and hillocks as the result of the electromigration critically degrades device reliability.

PLGA nanofiber membranes loaded with epigallocatechin-3-O-gallate are beneficial to prevention of postsurgical adhesions.

This study concentrates on the development of biodegradable nanofiber membranes with controlled drug release to ensure reduced tissue adhesion and accelerated healing. Nanofibers of poly(lactic-co-glycolic acid) (PLGA) loaded with epigallocatechin-3-O-gallate (EGCG), the most bioactive polyphenolic compound in green tea, were electrospun. The physicochemical and biomechanical properties of EGCG-releasing PLGA (E-PLGA) nanofiber membranes were characterized by atomic force microscopy, EGCG release and degradation profiles, and tensile testing. In vitro antioxidant activity and hemocompatibility were evaluated by measuring scavenged reactive oxygen species levels and activated partial thromboplastin time, respectively. In vivo antiadhesion efficacy was examined on the rat peritonea with a surgical incision. The average fiber diameter of E-PLGA membranes was approximately 300-500 nm, which was almost similar to that of pure PLGA equivalents. E-PLGA membranes showed sustained EGCG release mediated by controlled diffusion and PLGA degradation over 28 days. EGCG did not adversely affect the tensile strength of PLGA membranes, whereas it significantly decreased the elastic modulus and increased the strain at break. E-PLGA membranes were significantly effective in both scavenging reactive oxygen species and extending activated partial thromboplastin time. Macroscopic observation after 1 week of surgical treatment revealed that the antiadhesion efficacy of E-PLGA nanofiber membranes was significantly superior to those of untreated controls and pure PLGA equivalents, which was comparable to that of a commercial tissue-adhesion barrier. In conclusion, the E-PLGA hybrid nanofiber can be exploited to craft strategies for the prevention of postsurgical adhesions.

Computational design of binding proteins to EGFR domain II.

We developed a process to produce novel interactions between two previously unrelated proteins. This process selects protein scaffolds and designs protein interfaces that bind to a surface patch of interest on a target protein. Scaffolds with shapes complementary to the target surface patch were screened using an exhaustive computational search of the human proteome and optimized by directed evolution using phage display. This method was applied to successfully design scaffolds that bind to epidermal growth factor receptor (EGFR) domain II, the interface of EGFR dimerization, with high reactivity toward the target surface patch of EGFR domain II. One potential application of these tailor-made protein interactions is the development of therapeutic agents against specific protein targets.

Difference between Toxicities of Iron Oxide Magnetic Nanoparticles with Various Surface-Functional Groups against Human Normal Fibroblasts and Fibrosarcoma Cells.

Recently, many nanomedical studies have been focused on magnetic nanoparticles (MNPs) because MNPs possess attractive properties for potential uses in imaging, drug delivery, and theranostics. MNPs must have optimized size as well as functionalized surface for such applications. However, careful cytotoxicity and genotoxicity assessments to ensure the biocompatibility and biosafety of MNPs are essential. In this study, Fe3O4 MNPs of different sizes (approximately 10 and 100-150 nm) were prepared with different functional groups, hydroxyl (-OH) and amine (-NH2) groups, by coating their surfaces with tetraethyl orthosilicate (TEOS), 3-aminopropyltrimethoxysilane (APTMS) or TEOS/APTMS. Differential cellular responses to those surface-functionalized MNPs were investigated in normal fibroblasts vs. fibrosarcoma cells. Following the characterization of MNP properties according to size, surface charge and functional groups, cellular responses to MNPs in normal fibroblasts and fibrosarcoma cells were determined by quantifying metabolic activity, membrane integrity, and DNA stability. While all MNPs induced just about 5% or less cytotoxicity and genotoxicity in fibrosarcoma cells at lower than 500 µg/mL, APTMS-coated MNPs resulted in greater than 10% toxicity against normal cells. Particularly, the genotoxicity of MNPs was dependent on their dose, size and surface charge, showing that positively charged (APTMS- or TEOS/APTMS-coated) MNPs induced appreciable DNA aberrations irrespective of cell type. Resultantly, smaller and positively charged (APTMS-coated) MNPs led to more severe toxicity in normal cells than their cancer counterparts. Although it was difficult to fully differentiate cellular responses to various MNPs between normal fibroblasts and their cancer counterparts, normal cells were shown to be more vulnerable to internalized MNPs than cancer cells. Our results suggest that functional groups and sizes of MNPs are critical determinants of degrees of cytotoxicity and genotoxicity, and potential mechanisms of toxicity.

Impact of acupuncture by using life-energy (qi) oriental needle on the paralysis of rats with experimental autoimmune encephalomyelitis.

In acupuncture, adaptation to energy flows in body cycles is the key to health and therapy. From the evolution of our thinking about acupuncture, we developed the Life-Energy (Qi) oriental needle (Qi needle). It contains a rotating electromagnetic wave and has a strong affinity for the meridians. We report for the first time on the effect of acupuncture by using a Qi needle (Qi acupuncture) on rat experimental autoimmune encephalomyelitis, a model of human demyelinating multiple sclerosis. Both Qi acupuncture (QA) and general acupuncture (GA) were used on the limbs, at the shaoshang (LU11) and zhongchong (PC9) acupoints, of rats from one day post-immunization (dpi) to 12 dpi. The therapy in the QA groups significantly blocked the onset of EAE paralysis (3/13, 77%, p < 0.05) while all rats in the control EAE groups (12/15) and GA groups (11/13) showed EAE paralysis. In addition, the duration of paralysis was shortened in QA groups (1.5 ± 0.5 days) compared with those of the vehicle (5.5 ± 0.2 days) and GA groups (3.6 ± 1.1 days). The numbers of inflammatory cells and CD4(+) T cells in the QA treated EAE group were significantly reduced compared with those of the EAE control and EAE with GA (p < 0.05). Collectively, the present findings suggest that QA ameliorates the paralysis in rats in an EAE model. The precise mechanism of the amelioration and human studies, however, needs further study.