Synthesis, characterization, and biocompatible properties of alanine-grafted chitosan copolymers

In order to overcome major problems regarding the lack of affinity to solvents and limited reactivity of the free amines of chitosan, introduction of appropriate spacer arms having terminal amine function is considered of interest. L-Alanine-N-carboxyanhydride was grafted onto chitosan via anionic ring-opening polymerization. The chemical and structural characterizations of L-alanine-grafted chitosan (Ala-g-Cts) were confirmed through Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy ((1)H NMR). In addition, the viscoelastic properties of Ala-g-Cts were examined by means of a rotational viscometer, and thermal analysis was carried out with a thermogravimetric analyzer and differential scanning calorimetry. Morphological changes in the chitosan L-alanine moiety were determined by x-ray diffraction. To determine the feasibility of using these films as biomedical materials, we investigated the effects of their L-alanine content on physical and mechanical properties. The biodegradation results of crosslinked Ala-g-Cts films were evaluated in phosphate-buffered solution containing lysozyme at 37℃. Proliferation of MC3T3-E1 cells on crosslinked Ala-g-Cts films was also investigated with use of the CCK-8 assay

A Reaction Between High Mn-High Al Steel and CaO-SiO2-Type Molten Mold Flux: Part I. Composition Evolution in Molten Mold Flux

In order to elucidate the reaction mechanism between high Mn-high Al steel such as twin-induced plasticity steel and molten mold flux composed mainly of CaO-SiO2 during continuous casting process, a series of laboratory-scale experiments were carried out in the present study. Molten steel and molten flux were brought to react in a refractory crucible in a temperature range between 1713 K to 1823 K (1440 A degrees C to 1550 A degrees C) and composition evolution in the steel and the flux was analyzed using inductively coupled plasma atomic emission spectroscopy, X-ray fluorescence, and electron probe microanalysis. The amount of SiO2 in the flux was significantly reduced by Al in the steelthus, Al2O3 was accumulated in the flux as a result of a chemical reaction, 4[Al] + 3(SiO2) = 3[Si] + 2(Al2O3). In order to find a major factor which governs the reaction, a number of factors ((pct CaO/pct SiO2), (pct Al2O3), [pct Al], [pct Si], and temperature) were varied in the experiments. It was found that the above chemical reaction was mostly governed by [pct Al] in the molten steel. Temperature had a mild effect on the reaction. On the other hand, (pct CaO/pct SiO2), (pct Al2O3), and [pct Si] did not show any noticeable effect on the reaction. Apart from the above reaction, the following reactions are also thought to happen simultaneously: 2[Mn] + (SiO2) = [Si] + 2(MnO) and 2[Fe] + (SiO2) = [Si] + 2(FeO). These oxide components were subsequently reduced by Al in the molten steel. Na2O in the molten flux was gradually decreased and the decrease was accelerated by increasing [pct Al] and temperature. Possible reactions affecting the Al2O3 accumulation are summarized.ope

Anti-Neuroinflammatory Effects of Houttuynia cordata Extract on LPS-Stimulated BV-2 Microglia

Purpose: To evaluate the anti-neuroinflammatory effects of Houttuynia cordata extract (H. cordata) in lipopolysaccharide (LPS)-stimulated BV-2 microglial cells, and its anti-oxidant properties.Methods: Anti-oxidant properties were evaluated by 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay. Cell viability was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyl-tetrazolium bromide (MTT) assay. LPS was used to stimulate BV-2 cells. Nitric oxide (NO) levels were measured using Griess assay. Inducible NO synthase (iNOS) expression, interleukin (IL)-6 expressional level were determined by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis.Results: Ethyl actetae (HC-EA) extract of H. cordata significantly scavenged DPPH free radicals in a concentration-dependent fashion. The increased levels of NO, iNOS and IL-6 in LPS-stimulated BV-2 microglial cells were also suppressed by HC-EA extract in a concentration-dependent manner.Conclusion:The result indicate that the HC-EA extract exhibited strong anti-oxidant properties and inhibited the excessive production of pro-inflammatory mediators, including NO, iNOS and IL-6, in LPSstimulated BV-2 cells. The anti-oxidant phenolic compounds present in HC-EA extract might play an important role in ameliorating neuroinflammatory processes in LPS-stimulated BV-2 microglial cells.Keywords: Houttuynia cordata, DPPH radicals, antioxidant, neuroinflammation, BV-2 cells, iNOS, COX-2, IL-6

Electron-hole symmetry in a semiconducting carbon nanotube quantum dot

Optical and electronic phenomena in solids arise from the behaviour of electrons and holes (unoccupied states in a filled electron sea). Electron-hole symmetry can often be invoked as a simplifying description, which states that electrons with energy above the Fermi sea behave the same as holes below the Fermi energy. In semiconductors, however, electron-hole symmetry is generally absent since the energy band structure of the conduction band differs from the valence band. Here we report on measurements of the discrete, quantized-energy spectrum of electrons and holes in a semiconducting carbon nanotube. Through a gate, an individual nanotube is filled controllably with a precise number of either electrons or holes, starting from one. The discrete excitation spectrum for a nanotube with N holes is strikingly similar to the corresponding spectrum for N electrons. This observation of near perfect electron-hole symmetry demonstrates for the first time that a semiconducting nanotube can be free of charged impurities, even in the limit of few-electrons or holes. We furthermore find an anomalously small Zeeman spin splitting and an excitation spectrum indicating strong electron-electron interactions.Comment: 12 pages, 4 figure

COORDINATIVE PATTERNS BETWEEN CARVING TURN AND SKIDDING TURN DURING ALPINE SKIING

The purpose of this study was to investigate the coordinative patterns between segments and ski using the continuous relative phase (CRP) on anteroposterior and vertical axis during carving and skidding turn. Fourteen alpine ski instructors were participated in this study. Eight inertial measurement units were used to collect segment kinematic data. Each skier was asked to perform ten carving turns and ten skidding turns on the groomed 15° slope, respectively. CRP angles between all segments and ski were significantly increased during carving turn on the vertical axis. On the other hand, CRP angles between all segments and ski were significantly increased during skidding turn on anteroposterior axis. Therefore, skiers should perform the anti-phase movements of the lower spine-ski, pelvis-ski, thigh-ski and shank-ski on the vertical axis during the carving turn and the in-phase movements of the lower spine-ski, pelvis-ski, thigh-ski and shank-ski on the anteroposterior axis during skidding turn

A trial for the use of qigong in the treatment of pre and mild essential hypertension: a study protocol for a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Hypertension is a risk factor for cardiovascular disease, and the prevalence of hypertension tends to increase with age. Current treatments for hypertension have side effects and poor adherence. Qigong has been studied as an alternative therapy for hypertension; however, the types of qigong used in those studies were diverse, and there have not been many well-designed randomized controlled trials.</p> <p>Our objectives are the following: 1) To evaluate the effects of qigong on blood pressure, health status and hormone levels for pre- or mild hypertension. 2) To test the methodological appropriateness of this clinical trial and calculate a sample size for future randomized trials.</p> <p>Methods</p> <p>Forty subjects with pre- or mild hypertension will be randomized to either the qigong exercise group or the non-treated group. Participants in the qigong group will conduct qigong exercises 5 times per week for 8 weeks, and participants in the non-treated group will maintain their current lifestyle, including diet and exercise. The use of antihypertensive medication is not permitted. The primary endpoint is a change in patient blood pressure. Secondary endpoints are patient health status (as measured by the SF-36 and the MYMOP2 questionnaires) and changes in hormone levels, including norepinephrine, epinephrine, and cortisol.</p> <p>Discussion</p> <p>This study will be the first randomized trial to investigate the effectiveness of qigong exercises for the treatment of pre- and mild hypertension. The results of this study will help to establish the optimal approach for the care of adults with pre- or mild hypertension.</p> <p>Trial registration</p> <p>Clinical Research Information Service KCT0000140</p