3,237 research outputs found
Bioactive calcium phosphate coating on sodium hydroxide-pretreated titanium substrate by electrodeposition
No full textThis study examined the characteristics of calcium phosphate coatings deposited on a NaOH-pretreated titanium substrate by electrodeposition in a modified simulated body fluid (SBF) immediately after electrodeposition as well as after the coatings had been immersed in the SBF for 5 d in order to determine the effects of a NaOH pretreatment on the bioactive coating prior to electrodeposition. The results showed that a dense and uniform coating that consisted of brushite and hydroxyapatite had formed on the NaOH-pretreated titanium substrate by electrodeposition. This coating had transformed to a bonelike apatite during immersion in the SBF. This was attributed to the increased surface area of the modified titanium formed after the NaOH treatment as well as the Na+ ions released from that surface. Therefore, a NaOH pretreatment is recommended as an effective method for preparing a bioactive calcium phosphate coating by electrodeposition
Photoionization of methylphenothiazine and photoluminescence of erbium 8-hydroxyquinolinate in transparent mesoporous silica films by spin-coating on silicon
No full textTransparent mesoporous silica films were successfully prepared by spin-coating on silicon wafers at room temperature. The X-ray diffraction patterns of the films indicate that both hexagonal and cubic mesoporous films can be formed by varying the surfactant to silicon mole ratio. These films have reasonable thermal stability and are calcinable up to 670 degreesC and crack free when thickness is less than 0.5 mum. The calcined films have a thickness of 433+/-2 nm as measured by cross-sectional scanning electron microscopy. Methylphenothiazine was incorporated into the mesoporous silica films and after photoionization by ultraviolet light, the radical cation photoproduced was characterized by electron spin resonance spectroscopy. Erbium 8-hydroxyquinolinate was incorporated into the mesoporous silica films and the mesoporous silica films with incorporated Er(III) were characterized by photoluminescence and isothermal nitrogen physisorption studies. The characteristics of the silica films were studied by X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, high resolution transmission electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy and isothermal nitrogen physisorption. (C) 2003 Elsevier Inc. All rights reserved.This research was supported by grant no. R01-2003-
000-10125-0 from the Basic Research Program of the
Korea Science and Engineering Foundation and the
Brain Korea 21 project
Service Bundling and the Role of Access Charge in the Broadband Internet Service Market
No full textUsing the classical Hotelling model, this paper analyzes the incentive for a CATV service provider to bundle broadband internet services when entering the broadband internet services market. In addition, the effect of such service bundling by an entrant on the market incumbent with ownership over existing bottleneck facilities is analyzed. Furthermore, an access charge that maximizes social welfare is explored and determined. Two cases are considered: in the first case, the market is fully covered; and in the second case, the market is not fully covered. With full market coverage, an entrant has an incentive for service bundling if there is sufficient service differentiation. The entrant's bundling strategy reduces the incumbent's profit. In this case, the total social welfare is independent of the level of the access charge and only has an effect of redistributing the net surplus between consumers and the incumbent. With partial market coverage, the entrant has an incentive for service bundling at a low access charge. The incumbent's profit increases if the access charge is higher than the cost of access provisioning. In this case, the total social welfare is dependent on the level of access charge and the welfare maximizing access charge is less than the unit cost of providing access.cable TV; broadband internet service; bundling; access charge; convergence
[[alternative]]The KT transition of YBCO films
No full text[[abstract]]我們想藉由觀察 YBaCuO 薄膜是否有 KT 變遷的現象,來瞭解薄膜厚度與
維度的關係。故我們製作二塊不同厚度 (240o,120o) 的薄膜,分別量測它
們的電阻率與 V-I 曲線, 並加以分析。其中240o 之 YBCO 薄膜由於厚度
較大,無法表現二維的行為。而120o 的薄膜其 V-I 曲線相關的次方定律
V=I,在 T<76.6K 時, n 滿足二維 Ginzberg- Landau 之線性關係式: n(
T)≒1+const(1-T/Tco)。以此直線與 n=1 之交點定出樣品的 T=79K。而
在n(T)約為5.1時, n 不再隨上述的線性關係式隨溫度下降,亦即發生了
KT 變遷中普遍躍遷的現象。我們分別以 n=3及 n=5.1 定出兩種不同的
Tkt, 來討論電阻率的結果。由電阻率的結果分析,無論那種決定 Tkt 的
方法在介於78.1及78.6K 間,其ln(R/Rn)與[(Tco-T)/(T-Tkt)]成線性關係
。亦就是出現 KT 理論中預測因二維渦流運動產生的特殊行為。所以其具
有二維的傳導現象。
In order to know the dimensionalities of YBCO films, we
measured the resistivities and I-V curves of two YBCO films(120
o,240o). According to our results,the film of 240o thickness
couldn't show the 2d behaviors.The power law of 120o film has
the universal jump phenomena and the resisti- vity behavior can
be explained by 2d free vortices mo- tion.We can say that the
YBCO film of 120o thickness is a 2d system.
In order to know the dimensionalities of YBCO films, we
DEVELOPMENT OF THE PF SYSTEM-DESIGN AND OPERATION SCENARIOS OF THE LARGE-ASPECT-RATIO MIDSIZE DIVERTOR TOKAMAK KT-2 AT KAERI
No full textA large-aspect-ratio (LAR), midsize, diverted tokamak KT-2 with intense RF heating(5-7 MW) is under conceptual design process at KAERI. The machine parameters are: R/a(m) = 1.4/0.25 (reduceable to 0.20), B-t = 3 Tesla, I-p = 500+ kA, current flat-top 4.5 sec at maximum field and current (OH-only). The PF system concept design resulted in five KT-2 operation modes, and allows extended discharges for >30sec at 2T/200kA in the ''5MW HiBS'' mode. Construction will start in 1995, and the machine will start operation in 1998.X111sciescopu
Inhibition of acetylcholine-mediated effects by borneol
No full textWe previously reported that the aqueous extract from a medicinal plant Dryobalanops aromatica specifically inhibits the nicotinic acetylcholine receptor (nAChR) (Oh et al. Pharmacol Res 2000;42(6):559-64). Here, the effect of bomeol, the main constituent of D. aromatica, on nAChR activity was investigated in bovine adrenal chromaffin cells. Bomeol inhibited a nAChR agonist 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP)-induced calcium increase with a half maximal inhibitory concentration (IC50) of 56 +/- 9 muM. In contrast, borneol did not affect the calcium increases induced by high K+, veratridine, and bradykinin. The sodium increase induced by DMPP was also inhibited by bomeol with similar potency (49 +/- 12 muM), suggesting that the activity of nAChRs is inhibited by borneol. Bomeol inhibited DMPP-induced secretion of [H-3]norepinephrine with an IC50 of 70 +/- 12 muM. Carbon-fiber amperometry also confirmed the inhibition of DMPP-induced exocytosis by bomeol in single chromaffin cells. [H-3]nicotine binding, however, was not affected by bomeol. The inhibitory effect by bomeol is more potent than the effect by lidocaine, a commonly used local anesthetic. The data suggest that bomeol specifically inhibits the nAChR-mediated effects in a noncompetitive way. (C) 2002 Elsevier Science Inc. All rights reserved.X1162sciescopu
Numerical analysis and discussion on the hot-spot stress concept applied to welded tubular KT joints
No full textNominal stresses have been used for a long time for the assessment of fatigue resistance of welded joints, however, this approach has strong limitations since the definition of the nominal stress may be subjective for complex welded details and/or complex loading. On the other hand, the hot-spot stress approach has been proposed to overcome these limitations considering the structural geometrical discontinuities. However, the hot-spot stress methods also present certain limitations, and the present study aims at evaluating the available numerical and analytical hot-spot stress methods proposed by DNVGL (2016) and IIW (2014). The particular case of an offshore tubular KT joint has been considered herein and discretized in two planes. It has been studied numerically using the ABAQUS software coupled with the hot-spot stress extrapolation methods described in IIW (2014) and DNVGL (2016). The influence of the weld geometry has been considered and evaluated. In addition to the numerical method, the present study has also considered the analytical approach proposed in DNVGL (2016) derived from the combination of Efthymiou solutions for the stress concentration factor with the method of superposition of stresses. The numerical models according to IIW (2014) have been found to be more conservative when compared with the mesh-size methods proposed by DNVGL (2016), both in numerical modelling without the weld or with weld. For the numerical models with weld cord, the mean values of normalized difference index obtained for all braces together, as a result of comparing numerical results with analytical solutions, are lower, when compared with results obtained from the numerical models without weld cord.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure
Unstabilized DNA breaks in HTLV-1 Tax expressing cells correlate with functional targeting of Ku80, not PKcs, XRCC4, or H2AX.
No full textBACKGROUND:
Expression of the human T-cell leukemia virus type 1 (HTLV-1) Tax oncoprotein rapidily induces a significant increase of micronuclei (MN) and unstabilized DNA breaks in cells. Unstabilized DNA breaks can have free 3' OH ends accessible to in situ addition of digoxygenin (DIG)-labeled dUTP using terminal deoxynucleotidyl transferase. In the present work, we used a GFP-Tax (green fluorescent protein) plasmid, which produces a functionally active GFP-tagged Tax protein, to detect the cellular target(s) for Tax which might mechanistically explain the clastogenic phenomenon. We examined the induction of MN and unstabilized DNA breaks in wild type cells and cells individually knocked out for Ku80, PKcs, XRCC4, and H2AX proteins. We also assessed in the same cells, the signal strengths produced by DIG-dUTP incorporation at the unstable DNA breaks in the presence and absence of Tax.
RESULTS:
Cells mutated for PKcs, XRCC4 and H2AX showed increased frequency of MN and unstabilized DNA breaks in response to the expression of Tax, while cells genetically mutated for Ku80 were refractory to Tax's induction of these cytogenetic effects. Moreover, by measuring the size of DIG-dUTP incorporation signal, which indicates the extent of unstable DNA ends, we found that Tax induces larger signals than those in control cells. However, in xrs-6 cells deficient for Ku80, this Tax effect was not seen.
CONCLUSIONS:
The data here demonstrate that clastogenic DNA damage in Tax expressing cells is explained by Tax targeting of Ku80, but not PKcs, XRCC4 or H2AX, which are all proteins directly or indirectly related to the non-homologous end-joining (NHEJ) repair system. Of note, the Ku80 protein plays an important role at the initial stage of the NHEJ repair system, protecting and stabilizing DNA-breaks. Accordingly, HTLV-1 Tax is shown to interfere with a normal cellular protective mechanism for stabilizing DNA breaks. These DNA breaks, unprotected by Ku80, are unstable and are subject to erosion or end-to-end fusion, ultimately leading to additional chromosomal aberrations
P-V-T behavior of FeO(OH) and MnO(OH)
No full textThe P-V-T behavior of FeO(OH) and MnO(OH) has been determined under high pressure and high temperature up to 7.5 GPa and 500 °C using a MAX 80 cubic anvil high-pressure apparatus. The samples, synthetic goethite, α-FeO(OH), respectively, a natural groutite/manganite, α-MnO(OH)/γ-MnO(OH), specimen were mixed with Vaseline to ensure hydrostatic pressure-transmitting conditions, and NaCl served as an internal standard for pressure calibration. Energy-dispersive diffraction patterns were collected at a fixed 2θ angle (θ ≈ 4.52°). At pressures >7.1 GPa and temperatures >310 °C, respectively, P > 6.3 GPa and T > 350 °C, the transformation goethite ↔ ε-FeO(OH) was observed. Between 400 and 450 °C, the sample dehydrated to magnetite due to the reducing conditions caused by the graphite-tube furnace. By fitting a Birch–Murnaghan equation of state to the data, the bulk modulus of goethite was determined as (112.26 ± 2.26) GPa, (K′ = 4), V = (138.79 ± 0.10) Å·exp [∫(0.497 ± 0.103) × 10 dT], (∂KT/∂T)P = (–0.033 ± 0.020) GPa K. For ε-FeO(OH), the values K = (142.8 ± 15.1) GPa, V0 = (66.18 ± 0.16) Å, (K′ = 4), were obtained. Groutite and manganite are more compressible than their Fe analogues. K(groutite) = (84.0 ± 2.9) GPa, V = (139.92 ± 0.13) Å, (K′ = 4). K(manganite) = (82.2 ± 3.0) GPa, V = (135.37 ± 0.15) Å, (K′ = 4). Groutite disappeared at P ≈ 5.5 GPa and T = 300 °C, only manganite remained. At T > 400 °C, the sample dehydrated first to MnO [II] and then to manganosite (MnO) again pointing to reducing conditions
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