No abstract available

[en] Poly N, N-dimethylaminoethyl methacrylate (polyDMAEMA) hydrogels were synthesized by γ-irradiation technology, and the conditions of synthesis, such as total dose, dose rate, concentration of monomer and crosslinker in aqueous solution, were investigated. The property measurements of the hydrogels showed that they exhibited temperature sensitivity in a temperature range of 38-40 deg. C and pH sensitivity at pH=2.5. They also had electric responsive behavior although it was not typical. The hydrogels synthesized were transparent and elastic and displayed good swelling behavior in water, therefore, they can be used as a kind of carrying material in drug delivery systems

[en] The photodetachment partial cross sections for the H^-(2p²³P^e) state leaving the hydrogen atom in the n=2 state are calculated using a semi-empirical adiabatic hyperspherical coordinate approximation. Near threshold the cross sections are found to be very large. Radiative attachment coefficients for the inverse processes are also calculated. These results are compared in detail with results of close-coupling calculations by Jacobs

[en] An eighth-order Landau–Devonshire theory is constructed to investigate the piezoelectric and electro–optic properties of tetragonal (1 − x)Pb(Mg_1_/_3Nb_2_/_3)O_3–xPbTiO_3 single crystals (x = 0.38 and x = 0.4). The dielectric stiffness coefficients of the Landau potential are obtained by fitting to the dielectric properties and the phase transition temperature between cubic phase and tetragonal phase. It is indicated that tetragonal (1 − x)Pb(Mg_1_/_3Nb_2_/_3)O_3–xPbTiO_3 single crystals have the first-order cubic-tetragonal phase transitions. The dielectric constants are in great agreement with the experimental results. The piezoelectric coefficients d_3_3 and d_3_1 at room temperature are about 145 pC/N and −62 pC/N respectively which are smaller than that of (1 − x)Pb(Mg_1_/_3Nb_2_/_3)O_3–xPbTiO_3 single crystals around the morphotropic phase boundary. Moreover, tetragonal (1 − x)Pb(Mg_1_/_3Nb_2_/_3)O_3–xPbTiO_3 single crystals have the linear electro–optic coefficients r_c = 33.7 pm/V and r_c = 28.8 pm/V for x = 0.38 and x = 0.4, respectively which are in accordance with the measurements. (paper)

[en] A highly sensitive and selective fluorometric method is described for determination of mercury(II). It is based on (a) the use of graphene oxide (GO) acting as a quencher of the fluoresence of the carboxy-fluorescein (FAM), and (b) of Hg(II)-triggered cleavage of the newly formed nucleic acid sequences harbored blunt 3′-hydroxyl termini by exonuclease III (Exo III) that leads to signal amplification. Two DNA probes are used, viz. a capture probe (CP) and a help probe; HP) that is partially complementary. In the absence of Hg(II), the FAM-labeled hairpin (signal probe, SP) is adsorbed onto the surface of GO via π-stacking interactions. CP blocks the release of the HP for binding to SP. This results in quenching of the green fluorescence of the label. Upon addition of Hg(II), the linear structure of CP is converted to a hairpin structure due to the formation of thymidine–Hg(II)–thymidine duplexes. HP is released from the CP/HP hybrids, and this causes SP to be released from from GO and fluorescence to be recovered. The signal is strongly amplified by using Exo III-assisted targeting and recycling of HP. Hence, Hg(II) can be detected via the strong increase in fluorescence. The method has a linear response in the 0.1 to 30 nM Hg(II) concentration range and a 10 pM detection limit. It was applied to the determination of Hg(II) in three (spiked) Chinese medicines.

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[en] The effect of misfit strain on the electrocaloric effect in polydomain epitaxial BaTiO₃ thin films at room temperature is investigated using the Ginzburg—Landau—Devonshire thermodynamic theory. Numerical calculations indicate that the misfit strain has a large impact on the ferroelectric polarization states and the electrocaloric effect. Most importantly, the electrocaloric effect in the polydomain ca₁/ca₂/ca₁/ca₂ phase is much larger than that in the monodomain c phase and the other polydomain phases. Consequently, a large electrocaloric effect can be obtained by carefully controlling the misfit strain, which may provide potential applications in refrigeration devices

[en] A Landau—Devonshire thermodynamic theory is employed to investigate the effects of composition and misfit strain on the room-temperature electrocaloric effect of epitaxial Pb_1−xSr_xTiO₃ thin films. The “temperature-misfit strain” phase diagrams with the Sr composition x of 0.1, 0.3, and 0.5 are constructed. The introduction of Sr composition reduces the Curie temperature greatly, and enhances the electrocaloric effect. Moreover, the electrocaloric effect largely depends on the misfit strain. Therefore, the Sr composition and the misfit strain can be controlled to obtain the giant room-temperature electrocaloric effect. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] Composition dependence of electrocaloric effect is investigated in (1 − x)Pb(Mg_1_/_3Nb_2_/_3)O_3 − xPbTiO_3 single crystals by using an eighth-order Landau–Devonshire theory. The applied electric field along [001] direction reduces the ferroelectric-ferroelectric phase transition temperatures, but increases the Curie temperatures. The electrocaloric coefficients of tetragonal phase are much larger than that of rhombohedral and monoclinic phase. A negative electrocaloric effect is observed near the M_C–T phase transition in 0.69Pb(Mg_1_/_3Nb_2_/_3)O_3–0.31PbTiO_3 single crystal. The application of a strong enough electric field results in a high adiabatic temperature change over a broad range of temperature. Therefore, it would be useful to construct a solid state cooling cycle over a broad temperature range for practical applications. (paper)

No abstract available

[en] A phenomenological thermodynamic theory is applied to investigate the effect of misfit strain and electric field on the electrocaloric effect of P(VDF-TrFE)/SrTiO₃ bilayer thin films. Theoretical results indicate that the low electric field results in the decrease of the average polarization with the increase of the relative thickness of SrTiO₃ layer, and the high electric field has an opposite effect on it. Moreover, the electrocaloric effect strongly depends on the electric field. The low electric field and the small field change can lead to a maximum of the electrocaloric effect, meanwhile the high electric field or the large field change results in the opposite trend. (condensed matter: electronic structure, electrical, magnetic, and optical properties)