Block copolymer-mediated synthesis of silver nanoparticles from silver ions in aqueous media

We report here on the silver (Ag) nanoparticle synthesis in aqueous solutions of poly(ethylene oxide)poly(propylene oxide) (PEO-PPO) block copolymers in the absence of any additional agents. In particular, we examined the effect of reaction temperature, molecular weight of PEO-PPO block copolymer and PEO-PPO block copolymer concentration on the reduction of silver ions (Ag+) and the resulting formation of Ag nanoparticles in aqueous PEO-PPO block copolymer solutions. We found that Ag nanoparticles were formed from aqueous silver nitrate (AgNO3) solutions containing PEO-PPO block copolymer above 100 degrees C. This is most likely due to the dehydration of Ag+ caused by thermal motion of water molecules in higher-temperature aqueous solution at high vapor pressure. We also found that the formation of Ag nanoparticles in aqueous PEO-PPO block copolymer solutions was enhanced with larger molecular weight of PEO-PPO block copolymer and with increase in the concentration of PEO-PPO block copolymer in aqueous solutions. (C) 2015 Elsevier B.V. All rights reserved.ArticleCOLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS. 487:84-91 (2015)journal articl

Meson mass and confinement force driven by dilaton

Meson spectra given as fluctuations of a D7 brane are studied under the background driven by the dilaton. This leads to a dual gauge theory with quark confinement due to the gauge condensate. We find that the effect of the gauge condensate on the meson spectrum is essential in order to make a realistic hadron spectrum in the non-supersymmetric case. In the supersymmetric case, however, only the spectra of the scalars are affected, but they are changed in an opposite way compared to the non-supersymmetric case.Comment: 11 pages, 2 figure

Tide-induced reworking of planktonic foraminifers on the outer shelf and slope off the Miyako Island, southern Ryukyus, Japan: Preliminary results

Significance of sediment reworking to a shallower environment is preliminarily discussed by occurrences and oxygen isotopes of planktonic foraminifer (Globolotalia inflata) tests collected from the sea bottom sediments on the insular shelf to slope, off the Miyako Islands, southern Ryukyus, Japan. The isotopic data and comparison with the present water temperature-depth profile indicate that vertical distribution of G. inflata with size of 300-355µm ranges from 135 to 250m (average 160m). Strong tidal currents between the East China Sea and the Pacific Ocean developed in the study area may induce the transpotation of sediment particles to a shallower environment. This is demonstrated by the occurrences of this species in sediment deposited in depth shallower than inhabiting depth. The analyzed tests were not altered by long-time contact with bottom water because they preserve surface structures and a narrow range of oxygen isotopic composition. Shortly after G. inflata died and settled on sea bottom, the tests were commonly transported to the shallower environment by the upwelling, which may result from strong tidal currents and the topographic feature of the Ryukyu Island Arc

Cement generations and diagenetic history of the upper Ordovician Cliefden Caves Limestone Group of New South Wales, Australia

Diagenetic features of the upper Ordovician (Caradocian) Cliefden Caves Limestone Group (N. S. W., Australia) were studied by the cathodoluminescence (CL) method, and their relation with depositional environments was discussed. The Cliefden Caves Limestone Group was deposited on a shallow marine carbonate platform developed on a volcanic island. The limestone succession reveals intertidal-subtidal lithofacies and consists of the Fossil Hill, Belubula, and Vandon Limestones, in ascending order. The Fossil Hill Limestone mostly consists of bedded limestone rich in brachiopods and sedentary organisms. The Belubula Limestone is a typical Middle-Upper Ordovician peritidal succession with syn-depositional dolomite and silicified fossil grains. The Vandon Limestone consists of fossiliferous stratified limestone occasionally containing red brown argillaceous limestone beds. The Cliefden Caves Limestone Group was subjected to various diagenetic processes. The investigation of CL is the best or only method to differentiate the diagenetic products. There are at least three cementation stages and a dissolution stage. The cements of the first stage are mainly dull fine-grained (10-30 µm) calcite crystals fringing inter- and intra-granular porosity, which typically indicate a marine phreatic environment. In some specimens of the Belubula Limestone, cement of the first generation exhibits meniscus fabrics suggesting precipitation in a marine vadose environment. The dissolution formed both molds of aragonitic skeletal grains and fabric-unrelated void spaces which can exceed several cm in diameter. Lack of the first generation cement within the dissolution voids indicates that the dissolution postdated the marine cementation. After the dissolution stage, the second cementation precipitated granular calcite crystals composed of non-luminescence, dull, and bright zones in the peripheral order. The relative thickness of non-luminescence and bright zones probably related with a redox condition during their diagenesis. The last generation of cements formed in a deep burial environment, is normally dull and filled almost all remained porosity. This diagenetic history fits to the change of depositional environment which may have been controlled by both of local and global environmental settings

An adaptive nonlinear function controlled by kurtosis for blind source separation

金沢大学大学院自然科学研究科情報システムIn blind source separation, convergence and separation performances are highly dependent on a relation between probability density functions (pdf) of signal sources and nonlinear functions used in updating coefficients of a separation block. This relation was analyzed based on kurtosis κ4. It was suggested that tanh y and y3, where y is the output, are useful nonlinear functions for super-Gaussian (κ4 > 0) and sub-Gaussian (κ4 < 0), respectively. In this paper, an adaptive nonlinear function is proposed. It has a form of f(y) = a tanh y + (1 - a)y3/4, where a is controlled by the kurtosis of the output signal yκ(n). It is assumed that the pdf p(y) of the output signal satisfies the stability condition f(y) = -(dp(y)/dy)/p(y). Based on this assumption, the parameter a and the kurtosis is related. This relation approximated by a function a = q(κ4). In a learning process, κ4(n) of the output signal is calculated at each sample n, and a(n) is determined by a(n) = q(κ4(n)). Then, the nonlinear function f(y) is adjusted. Blind separation of music signals of 2-5 channels were simulated. The proposed method is superior to a method, which switches tanh y and y3 based on polarity of κ4(n)

Photoionization-induced large-amplitude pendular motion in phenol(+)-Kr

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The dynamics of the intermolecular motion of the phenol+–Kr cation generated by photoionization of the neutral π-structure is probed by picosecond time-resolved infrared spectroscopy. The spectrum at zero delay displays only the free OH stretch band of the π-structure. The appearance of the hydrogen-bonded OH stretch band of the H-structure after a few ps is due to ionization-induced π → H site switching. Spectra at long delay (>20 ns) show that the Kr atom delocalizes from one π-site of the aromatic ring to the opposite π-site via the OH-site, like a pendular motion in the classical picture

Glucocorticoids synergize with IL-1β to induce TLR2 expression via MAP Kinase Phosphatase-1-dependent dual Inhibition of MAPK JNK and p38 in epithelial cells

BACKGROUND: Despite the importance of glucocorticoids in suppressing immune and inflammatory responses, their role in enhancing host immune and defense response against invading bacteria is poorly understood. Toll-like receptor 2 (TLR2) has recently gained importance as one of the major host defense receptors. The increased expression of TLR2 in response to bacteria-induced cytokines has been thought to be crucial for the accelerated immune response and resensitization of epithelial cells to invading pathogens. RESULTS: We show that IL-1β, a key proinflammatory cytokine, greatly up-regulates TLR2 expression in human epithelial cells via a positive IKKβ-IκBα-dependent NF-κB pathway and negative MEKK1-MKK4/7-JNK1/2 and MKK3/6-p38 α/β pathways. Glucocorticoids synergistically enhance IL-1β-induced TLR2 expression via specific up-regulation of the MAP kinase phosphatase-1 that, in turn, leads to dephosphorylation and inactivation of both MAPK JNK and p38, the negative regulators for TLR2 induction. CONCLUSION: These results indicate that glucocorticoids not only suppress immune and inflammatory response, but also enhance the expression of the host defense receptor, TLR2. Thus, our studies may bring new insights into the novel role of glucocorticoids in orchestrating and optimizing host immune and defense responses during bacterial infections and enhance our understanding of the signaling mechanisms underlying the glucocorticoid-mediated attenuation of MAPK