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A giant negative electrocaloric (EC) effect in a PbZrO3/(0.88BaTiO3-0.12 Bi(Mg1/2,Ti1/2)O3) (PZ/(BT-BMT)) multilayered composite ferroelectric (MCFE) thin film which is grown on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method is investigated in this work. The negative EC effect in the PZ/(BMT-BT) MCFE thin film is greatly higher than that in the PZ AFE thin film with an adiabatic temperature change (ATC) ΔT = 1.5 K. The ATC ΔT of the PZ/(BMT-BT) MCFE thin film is -32 K under the applied electric field change ΔE = 1151 kV/cm. The result is conducive to enhance the EC refrigeration efficiency greatly. [ABSTRACT FROM AUTHOR]

Hepatitis E virus recombinant genomes transcribed in vitro from two cDNA clones differing by two nucleotides were infectious for chimpanzees. However, one cDNA clone encoded a virus that was attenuated for chimpanzees and unable to infect rhesus monkeys. The second cDNA clone encoded a virus that infected both chimpanzees and rhesus monkeys and caused acute hepatitis in both. One mutation differentiating the two clones identified a cisreactive element that appeared to overlap the 3' end of the capsid gene and part of the 3' noncoding region. Capping of the RNA transcripts was essential for infectivity.

It is generally believed that epitaxial thin films are subject to compressive strain by the nearest layer with a smaller lattice constant or to tensile strain by the nearest layer with a larger lattice constant. Our experimental and theoretical results show that the above viewpoint is not always effective if the interface is anisotropic in the plane. We propose a novel strain mechanism that takes into account the pre-strain state as a key factor rather than considering only the lattice mismatch. Therefore, this anomalous strain model is potentially important for various multifunctional devices based on strain coupling. [ABSTRACT FROM AUTHOR]

By using ionic implantation and wafer bonding technologies, we peeled off a single-crystal LiNbO3 thin film in the atomic-layer smoothness from the surface of a bulk Z-cut LiNbO3 single crystal. X-ray diffraction patterns showed only (00l) orientation of the film. From positive-up-negative-down pulse characterization, we measured domain switching current transients under various short-pulse voltages, where we observed domain switching currents to occur separately at time after initial capacitor charging currents. This is similar to early observations in bulk ferroelectric single crystals, where apparent positive/negative coercive fields of domain switching determined from polarization-electric field hysteresis loops always equal maximum/minimum applied fields. However, after pulse stressing of the film for more than 1000 cycles, the domain switching speed is accelerated, where domain switching current overlaps with the initial capacitor charging current with a well-defined coercive field independent of the applied-field strength. Finally, we simulated the whole domain switching current transients with the assumption of the resistance degradation across interfacial passive layers between the film and electrodes. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The current study was designed to investigate the functionality of lncRNA CCHE1 in nasopharyngeal carcinoma. MATERIALS AND METHODS: MiRNA levels of lncRNA CCHE1 were examined by RT-qPCR. CCK8 assay and colony formation assay were together performed to detect cell proliferation viability. Furthermore, wound healing assay and transwell assay were respectively conducted to assess cell migration and invasion. In addition, proteins related to MEK/ERK/c-MYC pathway were detected by Western blot. RESULTS: Elevated levels of CCHE1 were verified in NPC cell lines. Downregulation of CCHE1 significantly inhibited tumor growth and suppressed A549 cell proliferation, migration and invasion. MEK/ERK/c-MYC pathway was activated in nasopharyngeal carcinoma. Treatment of PD98059 (MEK inhibitor) or SCH772984 (ERK inhibitor) reversed the effects of CCHE1 on cell proliferation, migration and invasion in NPC. CONCLUSIONS: The present study suggested that downregulation of lncRNA CCHE1 could inhibit cell proliferation, migration and invasion by suppressing MEK/ERK/c-MYC pathway in nasopharyngeal carcinoma. [ABSTRACT FROM AUTHOR]

Recently, a large amount of effort has been devoted to bringing p- and n-type two-dimensional (2D) materials in close contact to promise a p–n junction for photodetectors and photovoltaic devices. However, all solar cells based on 2D materials are single p–n junctions so far, where the open circuit voltage is usually limited by the bandgap of semiconductor materials. Here, by using a scanning-probe domain patterning method to polarize the ferroelectric film, we demonstrate a series connected MoTe2 photovoltaic cell with an additive open circuit voltage and output electrical power. The nonvolatile MoTe2 p–n diodes exhibit a rectification ratio of 100. As a photodetector, the device presents a responsivity of 220 mA/W and an external quantum efficiency of 41% without any gate or bias voltages. The open circuit voltage increases linearly with the number of series connected p–n junctions and can be beyond the bandgap of the multilayer MoTe2. [ABSTRACT FROM AUTHOR]

Perovskite Aurivillius structure Bi5Ti3FeO15 (BTF) polycrystalline thin films were prepared by a chemical solution deposition route. The microstructure, electrical, and magnetic properties were investigated and in particular the optical properties of the BTF films were addressed. The coexistence of the ferroelectric and weak ferromagnetic properties at room temperature demonstrates the multiferroic behavior of the BTF films. The optical dielectric functions in the photon energy range of 1.13-4.13 eV have been extracted by fitting the experimental data in terms of the Tauc-Lorentz and Cauchy models. A direct interband transition is allowed and the energy bandgap is determined to be ∼3.3 eV for the BTF films. The weak absorption below the bandgap edge was observed and described by the Urbach band tail rule. Finally, the optical dispersion behaviors of the BTF films in the transparent region were explained using a single oscillator model. [ABSTRACT FROM AUTHOR]

The 2 mol % Mn doped Pb0.5Sr0.5TiO3 films were fabricated on sapphire substrates by chemical solution deposition. The complex dielectric functions and optical parameters of the films determined by transmittance spectroscopy in a broad temperature range of 80-500 K were investigated. Apparent thermally-driven band-gap energy shrinkage, line-width of interband electron transition broadening and the Urbach band tail behaviors were observed. The results can be mainly correlated with the renormalization of electronic band structure and band-gap energy due to the electron-phonon interaction, which is well established in terms of the Bose-Einstein model. [ABSTRACT FROM AUTHOR]

The highly (l00) oriented Pb(Zr0.5Ti0.5)O3 thin films with different Fe3+ doping concentrations were fabricated on LaNiO3-coated silicon substrates by chemical solution deposition. And the microstructure, ferroelectric, leakage, and magnetic properties were investigated. The results indicate that incorporation of Fe3+ into PZT thin films can promote the degree of the lattice distortion and greatly improve the surface roughness. In comparison with the pure PZT sample, the ferroelectric hysteresis loops of Fe-doped PZT samples demonstrate larger and larger polarizations and coercive fields with the increase in Fe3+ doping amount. Moreover, leakage mechanism of present films evolves from the space charge limited conduction to the “modified” space charge limited conduction, and then returns to the space charge limited conduction with increasing Fe3+ doping concentration. The occurrence of exchange bias in these Fe-doped PZT samples implies that the magnetic exchange interaction can be explained by the bound magnetic polaron model. [ABSTRACT FROM AUTHOR]

The ac field (Eac) amplitude dependence of dielectric response has been investigated for poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) relaxor terpolymer films. The frequency dependence of the temperature of the permittivity maximum Tm can be well described by the Vogel–Fulcher relation for Eac in the range from 1.33 to 80 MV/m. Tm remains nearly constant at an Eac level lower than 13.3 MV/m, and starts decreasing with Eac increases further. The two parameters fitting to the Vogel–Fulcher relation, freezing temperature Tf and activation energy Ea, vary little for Eac below 26.7 MV/m and then Tf decreases, while Ea increases for higher Eac level. [ABSTRACT FROM AUTHOR]

The dc bias dependence of dielectric properties has been investigated for poly (vinylindene fluoride-trifluoroethylene-chlorofluoroethylene) relaxor terpolymer films. The frequency dependence of the temperature of the permittivity maximum, Tm, was analyzed using the Vogel–Fulcher (VF) relation. Two threshold fields, ∼30 and 160 MV/m were found in the electric-field dependence of Tm. Tm shows a minimum at ∼30 MV/m and a maximum at ∼160 MV/m. The VF parameters activation energy Ea and freezing temperature Tf respectively show a maximum and a minimum at ∼25 MV/m. [ABSTRACT FROM AUTHOR]

In this work we studied 65-nm-thick poly(vinylidene fluoride-trifluoroethylene) ferroelectric polymers films grown by Langmuir–Blodgett onto silicon substrates. Three dielectric anomalies have been unambiguously evidenced. The high temperature one near 380 K corresponds to the ferroelectric-paraelectric transition. The low temperature one near 270 K which is characterized by a β relaxation is attributed to structural defects in the crystalline phase leading to inhomogeneous strains detected by x-ray diffraction. At approximately 320 K, a Debye-like relaxation is clearly evidenced. Possible origins for this later relaxation are discussed. [ABSTRACT FROM AUTHOR]

A series of Mn doped Pb0.5Sr0.5TiO3 (PSMT) films with dopant concentrations from 0 to 10 mol % was fabricated on (111) Pt/Ti/SiO2/Si substrates by chemical solution deposition. Their microstructure, ferroelectric, and dielectric properties were investigated, and Mn doping was found to have a significant influence on the properties of (Pb,Sr)TiO3 film. The improved microstructure with increased grain size, remnant polarization, dielectric permittivity and its tunability by dc electric field, and reduced coercive field and dielectric loss was observed in the Mn doped samples. A PSMT film with 0.5 mol % Mn dopants exhibits the optimum characteristics with maximal remnant polarization (2Pr=25.28 μC/cm2), dielectric permittivity (1427) and tunability (74.5%, at 100 kHz), and minimal dielectric loss (0.015) at 1 kHz. The improvement was attributed to the improved microstructure, enhanced displacement of polar ions, and, most importantly, the suppression of oxygen-vacancy-induced ferroelectric domain pinning, which was well verified in terms of Rayleigh law. Finally, the evolution of oxygen-vacancy concentration modulated by the Mn doping in PSMT films was discussed. [ABSTRACT FROM AUTHOR]

In this work we studied 90 nm thick copolymer thin films of vinylidene fluoride (70%) with trifluoroethylene (30%) grown by Langmuir–Blodgett onto silicon substrates. The effects of two different bottom electrodes, namely, Al and LaNiO3 (LNO) are investigated. A Debye-like relaxation near 320 K is enlarged by LNO bottom electrode. X-ray diffraction pattern attests that two different crystallographic structures coexist below 340 K in film deposited on LNO. Compared with Al electrode, LNO electrode strongly increases defects or gauche segments in film and further weakens properties of film. [ABSTRACT FROM AUTHOR]

Using Landau–Devonshire (LD) phenomenological model, we investigate the dielectric and pyroelectric behaviors of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] ferroelectric Langmuir–Blodgett super thin films. Effects of homogeneous in-plane misfit strains and external electric field on the dielectric properties are combined to be investigated. The theoretical analysis indicates that phase transition temperature can be changed by in-plane misfit strains. Furthermore results show in-plane strains only change the position of peak but value of dielectric constant and pyroelectric coefficient. At one temperature (below phase transition temperature), compressive strain is more beneficial. Consequently the dielectric and pyroelectric responses can be optimized to satisfy various demands by the applied electric fields and tuning in-plane misfit strains. [ABSTRACT FROM AUTHOR]

The highly (00l)-oriented 5 mol % Mn doped Pb0.5Sr0.5TiO3 films with remarkable ferroelectric properties (2Pr=27.1 μC/cm2 and 2Ec=55.5 kV/cm) were fabricated on LaNiO3 coated silicon substrates by chemical solution deposition. The ac conductivity and the dielectric response of the films at various temperatures were studied. Hopping conduction accompanied by the dielectric relaxation at low frequencies was observed. The results can be correlated with the thermal-activated short range hopping of localized charge carriers through trap sites separated by potential barriers with different heights, i.e., localized electrons hopping between multivalence Mn sites (the activation energy of this hopping process is ∼0.4 eV), which is also established in terms of the correlated barrier hopping model. [ABSTRACT FROM AUTHOR]

Dielectric properties of the copolymer of vinylidene fluoride and trifluoroethylene films derived from the Langmuir–Blodgett technology have been investigated over the temperature range from 300 to 150 K at various frequencies. Below ∼240 K, peaks in the dielectric loss were observed to increase with increasing frequency. Nonlinear dielectric susceptibility and ferroelectric properties have been studied at different temperatures. The results show that the nonlinear dielectric susceptibility undergoes a remarkable change at ∼230 K. The results suggest a β relaxation, which is related to the freezing of the molecular motions in the amorphous phase in the polymer films. The anomaly in the electrical properties at ∼230 K is due to the freezing of the molecular chains motions. [ABSTRACT FROM AUTHOR]

The effect of nitrogen (N) doping on surface chemical composition and optical properties of Ba0.6Sr0.4TiO3 (BST) thin films have been investigated using x-ray photoemission spectroscopy (XPS) and transmittance measurement. It was found that the nitrogen doping induced Ti3+/4+ states and formed Ti–N bonds in BST films. With lower implantation energy, the oxygen vacancies can be effectively eliminated because of N dopants substitution. Unfortunately, the oxygen vacancies possibly increased when enhance implantation energy. In addition, the N-doped BST films indicated larger amount of perovskite phase and lower content additional phase at surface. The chemical shifts in XPS confirmed the forming of Ba–N and Sr–N bonds in N-doped BST films. The optical properties for as-grown and N-doped BST films were considered at wavelength range from 190 to 1100 nm. The optical constants, including refractive index n and extinction coefficient k, were calculated by fitting transmittance spectra with single Tauc-Lorenz and Lorenz models. The refractive index decreased largely with nitrogen implantation. Oppositely, the extinction coefficient increased with N dopants. The dispersion of refractive index in transparent region agreed well with a single electronic oscillator for all samples. The band gaps of N-doped BST films were much smaller than that of as-grown BST films because of localized N 2p states above the valence band edge. [ABSTRACT FROM AUTHOR]

92%Pb(Mg1/3Nb2/3)O3–8%PbTiO3 (PMNT) thin films have been prepared on Pt/Ti/SiO2/Si substrate with a LaNiO3 buffer layer and on sapphire substrate by a chemical solution deposition method. X-ray diffraction analysis shows that the PMNT thin films on Pt/Ti/SiO2/Si substrate are polycrystalline with (110)-preferential orientation. The optical properties of PMNT thin film in 2.5–12.5 μm and 200–1100 nm ranges have been investigated using infrared spectroscopic ellipsometry and ultravisible transmission spectra, respectively. The optical constants and thickness of the thin films have been obtained by fitting the measured ellipsometric parameter (Δ and Ψ) data and transmission spectrum with classical infrared and Tauc-Lorentz models. The optical band gap energy of the PMNT thin films on sapphire substrate is derived to be about 4.02 eV. [ABSTRACT FROM AUTHOR]

SrTiO3 thin films were deposited on vitreous silica substrates at various substrate temperatures (300–700 °C) by rf magnetron sputtering technique. The transition from amorphous phase to polycrystalline phase for the films occurred at the substrate temperatures of 300–400 °C. Their optical properties were investigated by transmittance measurements. The fitting method was used to calculate the refractive index and the film thickness from the transparent region of the transmittance spectra. The refractive index increased and the film thickness decreased with the substrate temperatures increasing. The dispersion of the refractive index was studied by considering a single electronic oscillator model. The band gaps of the films were estimated from Tauc’s law and showed a decreasing tendency to that of the bulk SrTiO3 with the substrate temperatures increasing. These results provide some useful references for the potential application of SrTiO3 films in integrated optics devices. [ABSTRACT FROM AUTHOR]

In this paper, using wet chemical solution deposition processes, the (100)-highly oriented LaNiO3 buffer layers were grown on both silicon and platinized silicon wafers and, sequentially, the highly (100)-oriented PbZr1-xTixO3 thin films with various compositions were obtained on them. The misfit elastic strains were found to be critical factors to determine the orientation of PZT thin films, even though the used LaNiO3 buffer layer reduces the lattice mismatch between PZT films and silicon wafers. For the PZT thin films with x=0.5 and 0.6 on the LaNiO3/platinized silicon substrate, the infrared optical constant, ferroelectric, and dielectric properties were characterized and analyzed with relation to the film orientation and the film grain size. It was found that the finite grain size effect here played a key role in determining these optical and electrical properties. With nanoferroelectric thin films, it is the most useful way of controlling both grain size and crystallographic orientation to tune performance of commercial film devices. [ABSTRACT FROM AUTHOR]

Novel composites based on polymer ferroelectrics with graphene (G) and graphene oxide (GO) have many advantages over pristine materials. In this work, the results of the computational molecular modeling of the composite nanostructures are presented and analyzed. The calculations were focused on pyroelectric properties of the composites based on polyvinylidene fluoride (PVDF) films with G/GO layers. The pyroelectric effect was modeled and pyroelectric coefficients were calculated for several models using molecular dynamics simulation with quantum-chemical semi-empirical PM3 method from HyperChem tool. The obtained results present a new prospective for further studies of the ferroelectric polymer-graphene multifunctional nanomaterials and their applications. [ABSTRACT FROM AUTHOR]

Much effort has been devoted to uncovering the biophysical mechanisms associated with energy-coupled active Ca transport. The issue presented here, which has received relatively little attention, concerns the mechanism(s) of physical delivery of calcium ions to their transport sites on the Ca-ATPase. Evidence suggests that if transport is below its maximum rate and free calcium is fixed, mobile Ca chelators (either native chelators such as calbindin and parvalbumin, or synthetic chelators such as EGTA) increase transport, both on intracellular- and plasma membrane-type calcium pumps (see, for example, Berman. 1982. J. Biol. Chem. 257:1953; Timmermans et al. 1995. J. Nutr. 125:1981S). These observations, however, oppose the theoretical expectation that Ca chelators should be unable to release calcium with enough speed to make much difference in the 'loading'' step of a 'Ca-starved' transport reaction. It must be concluded that we do not understand the mechanisms by which calcium transport sites become loaded or how chelators enhance a calcium loading/transport reaction. Such mechanisms, however. may be especially important for the transport activity of cells that must move large amounts of calcium, such as renal and intestinal epithelial cells and bone resorbing cells, or in certain types of myocytes and neurons that may need to transport calcium quickly into intracellular storage compartments. We have done experiments to examine the role of chelators in calcium transport in neurons. Microsomes isolated from rat brain accumulated [sup.45]Ca in a free (ionized) Ca concentration ([[Ca.sup.2+]])- and ATP-dependent manner. This accumulation was inhibited by thapsigargin, and was insensitive to mitochondrial inhibitors or to agents such as digitonin that selectively permeabilize plasma-membrane vesicles. Thus, these microsomes likely contain mainly endoplasmic reticular membranes. Adding the synthetic calcium chelator EGTA or the native Ca chelator parvalbumin increased the initial rate of uptake into the microsomes at a fixed [[Ca.sup.2+]]. The maximal uptake rate found in the presence of EGTA could also be achieved without chelator if [ [Ca.sup.2+]] was high enough. Spectrofluoremetric records of free [Ca.sup.2+] in microsome suspensions containing 1.5 [micro]M fura-2 also show that when 15 [micro]M EGTA is present, the microsomal Ca uptake rate is greater. A theoretical analysis suggests that chelator facilitation of calcium flux down a diffusion gradient to a 'Ca-starved' pump site is inadequate to explain these observations.

Meng, X.-J., R. T. Timmer, R. B. Gunn, and R. F. Abercrombie. Separate entry pathways for phosphate and oxalate in rat brain microsomes. Am J Physiol Cell Physiol 278: C1183-C1190, 2000.--ATP-dependent [sup.45]Ca uptake in rat brain microsomes was measured in intracellular-like media containing different concentrations of [PO.sub.4] and oxalate. In the absence of divalent anions, there was a transient [sup.45]Ca accumulation, lasting only a few minutes. Addition of [PO.sub.4] did not change the initial accumulation but added a second stage that increased with [PO.sub.4] concentration. Accumulation during the second stage was inhibited by the following anion transport inhibitors: niflumic acid (50 [micro]M), 4,4'-dinitrostilbene-2,2'-disulfonic acid (DNDS; 250 [micro]M), and DIDS (3-5 [micro]M); accumulation during the initial stage was unaffected. Higher concentrations of DIDS (100 [micro]M), however, inhibited the initial stage as well. Uptake was unaffected by 20 mM Na, an activator, or 1 mM arsenate, an inhibitor of Na-[PO.sub.4] cotransport. An oxalate-supported [sup.45]Ca uptake was larger, less sensitive to DIDS, and enhanced by the catalytic subunit of protein kinase A (40 U/ml). Combinations of [PO.sub.4] and oxalate had activating and inhibitory effects that could be explained by [PO.sub.4] inhibition of an oxalate-dependent pathway, but not vice versa. These results support the existence of separate transport pathways for oxalate and [PO.sub.4] in brain endoplasmic reticulum. 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid; 4,4'-dinitrostilbene-2,2'-disulfonic acid; niflumic acid; endoplasmic reticulum; adenosine 3',5'-cyclic monophosphate; active calcium transport; calcium homeostasis