Excellent Dielectric Properties and Finite Element Simulation of Al-Epoxy Composites with Constructed Ultrathin Al2O3 Parallel-Plate Microcapacitors.

Metal-polymer dielectric composites show promising potential as embedded capacitors, whereas it remains a great challenge to achieve a high dielectric constant (εr) and low dielectric loss (tan δ) simultaneously. This work demonstrates a strategy for overcoming this challenge. Al nanoparticles with self-passivated ultrathin Al2O3 shells are compacted under the uniaxial pressure (P), and Al-epoxy composites are prepared by curing the liquid epoxy monomer that infiltrates into Al compacts. The contacting regions between adjacent Al nanoparticles are flattened and enlarged during the compacting process, so that the ultrathin Al2O3 parallel-plate microcapacitors are constructed by the insulating Al2O3 shells and conductive Al cores. The composite with P of 100 MPa and Al volume fraction (υAl) of 53.7% exhibits the εr of 189 at 10 kHz, which is much higher than the εr (48-102) of 0-3 type Al-polymer composites with similar υAl and even higher than the highest εr (160) reported in the Al-polymer composite with υAl > 80%. Furthermore, the present composites show low tan δ (<0.03) and good frequency and temperature stability of εr. The finite element simulation proves that the construction and enlargement of ultrathin Al2O3 parallel-plate microcapacitors dramatically increase the electric energy stored in Al2O3 and therefore greatly improve the εr.

Hexagonal Lu1-xInxFeO3 Room-Temperature Multiferroic Thin Films.

The hexagonal rare earth ferrites h-RFeO3(R = rare earth element) have been recognized as promising candidates for a room-temperature multiferroic system, and the primary issue for these materials is how to get a stable hexagonal structure since the centrosymmetric orthorhombic structure is generally stable for most RFeO3 at room-temperature, while the hexagonal phase is only stable under some strict conditions. In the present work, h-Lu1-xInxFeO3 (x = 0-1) thin films were prepared on a Nb-SrTiO3 (111) single-crystal substrate by a pulsed laser deposition (PLD) process, and the multiferroic characterization was performed at room temperature. With the combined effects of chemical pressure and epitaxial strain, the stable hexagonal structure was achieved in a wide composition range (x = 0.5-0.7), and the results of XRD (X-ray diffraction) and SAED (selected area electron diffraction) indicate the super-cell match relations between the h-Lu0.3In0.7FeO3 thin film and substrate. The saturated P-E hysteresis loop was obtained at room temperature with a remanent polarization of about 4.3 µC/cm2, and polarization switching was also confirmed by PFM measurement. Furthermore, a strong magnetoelectric coupling with a linear magnetoelectric coefficient of 1.9 V/cm Oe was determined, which was about three orders of magnitude larger than that of h-RFeO3 ceramics. The present results indicate that the h-Lu1-xInxFeO3 thin films are expected to have great application potential for magnetoelectric memory and detection devices.

Obtaining Greatly Improved Dielectric Constant in BaTiO3-Epoxy Composites with Low Ceramic Volume Fraction by Enhancing the Connectivity of Ceramic Phase.

Ceramic-polymer dielectric composites show promising potential as embedded capacitors, whereas it is a great challenge to obtain a high dielectric constant (εr) at a low ceramic volume fraction (Vc). This work demonstrates a strategy for overcoming this challange. By employing a high sintering temperature (Ts) and introducing porogen, BaTiO3 ceramics with both great connectivity and high porosity are obtained, and the composites with improved εr at a low Vc are prepared after curing the epoxy monomer, which is infiltrated into the porous ceramic bodies. For the composite with a Ts of 1300 °C and a Vc of 38.1%, the εr is as high as 466.8 at 1 kHz, which is improved by about nine times compared to the 0-3 counterpart with a higher Vc of 60.8%. Furthermore, the composite exhibits low dielectric loss and good frequency and temperature stability of εr, indicating the great potential for practical applications. Finite element simulation shows that the enhanced connectivity of BaTiO3 increases the electric field intensity in high-εr BaTiO3 dramatically and therefore plays a key role in the dielectric response of the composite. This work not only sheds light on the high-εr ceramic-polymer composites but also deepens the understanding on the relationship between their properties and microstructures.

Structural distortions, orbital ordering and physical properties of double perovskite R2CoMnO6 calculated by first-principles.

The structural distortions, orbital ordering, magnetic and electronic properties of double perovskite R2CoMnO6 (R = rare-earth element) have been systematically calculated by first-principles. Structural distortions, including Co-O and Mn-O bond length splitting, the antiferroelectric motions of R ions, the tilting of octahedral (the resulted Co-O-Mn bond angle) are obviously affected by the rare-earth ions' radius. The bond length splitting behavior of Co-O and Mn-O are rather different because of the Jahn-Teller active ion Co2+ and the Jahn-Teller nonactive ion Mn4+. Taking Gd2CoMnO6 as an example, the t 2g orbitals of Co ions are predicted to be orbital ordered. That is, the spin down channel of d xz orbital for one Co ion and d yz orbital for another Co ion are basically vacant. Finally, the physical properties, including the magnetic Curie temperature and electronic band gap of R2CoMnO6 are almost linear dependent on the average value of cos2 θ (θ is the Co-O-Mn exchange-angle).

Improper electric polarization in simple perovskite oxides with two magnetic sublattices.

ABO3 perovskite oxides with magnetic A and B cations offer a unique playground to explore interactions involving two spin sublattices and the emergent effects they may drive. Of particular interest is the possibility of having magnetically driven improper ferroelectricity, as in the much studied families of rare-earth orthoferrites and orthochromites; yet, the mechanisms behind such effects remain to be understood in detail. Here we show that the strongest polar order corresponds to collinear spin configurations and is driven by non-relativistic exchange-strictive mechanisms. Our first-principles simulations reveal the dominant magnetostructural couplings underlying the observed ferroelectricity, including a striking magnetically driven piezoelectric effect. Further, we derive phenomenological and atomistic theories that describe such couplings in a generic perovskite lattice. This allows us to predict how the observed effects can be enhanced, and even how similar ones can be obtained in other perovskite families.

Altered glutamate metabolism contributes to antiepileptogenic effects in the progression from focal seizure to generalized seizure by low-frequency stimulation in the ventral hippocampus.

As a promising method for treating intractable epilepsy, the inhibitory effect of low-frequency stimulation (LFS) is well known, although its mechanisms remain unclear. Excessive levels of cerebral glutamate are considered a crucial factor for epilepsy. Therefore, we designed experiments to investigate the crucial parts of the glutamate cycle. We evaluated glutamine synthetase (GS, metabolizes glutamate), glutaminase (synthesizes glutamate), and glutamic acid decarboxylase (GAD, a γ-aminobutyric acid [GABA] synthetase) in different regions of the brain, including the dentate gyrus (DG), CA3, and CA1 subregions of the hippocampus, and the cortex, using western blots, immunohistochemistry, and enzyme activity assays. Additionally, the concentrations of glutamate, GABA, and glutamine (a product of GS) were measured using high-performance liquid chromatography (HPLC) in the same subregions. The results indicated that a transiently promoted glutamate cycle was closely involved in the progression from focal to generalized seizure. Low-frequency stimulation (LFS) delivered to the ventral hippocampus had an antiepileptogenic effect in rats exposed to amygdaloid-kindling stimulation. Simultaneously, LFS could partly reverse the effects of the promoted glutamate cycle, including increased GS function, accelerated glutamate-glutamine cycling, and an unbalanced glutamate/GABA ratio, all of which were induced by amygdaloid kindling in the DG when seizures progressed to stage 4. Moreover, glutamine treatment reversed the antiepileptic effect of LFS with regard to both epileptic severity and susceptibility. Our results suggest that the effects of LFS on the glutamate cycle may contribute to the antiepileptogenic role of LFS in the progression from focal to generalized seizure.

Biological significance of PinX1 telomerase inhibitor in esophageal carcinoma treatment.

In the present study, to investigate the expression of PinX1 gene and its functional effects in human esophageal carcinoma (Eca)-109 cell line, expression vectors of human PinX1 (pEGFP-C3-PinX1) and its small interfering RNA (PinX1-FAM-siRNA) were constructed and transfected into Eca-109 cells using Lipofectamine 2000. Firstly, the mRNA expression level of PinX1 was examined using reverse transcription-polymerase chain reaction (RT-PCR). Once successful transfection was achieved, the effects on the mRNA level of human telomerase reverse transcriptase (hTERT), telomerase activity, cell proliferation and apoptosis were examined by semi-quantitative RT-PCR, stretch PCR, MTT assay and flow cytometry, respectively. Analysis of restriction and sequencing demonstrated that the recombining plasmids were successfully constructed. The results also indicated that transfection with pEGFP-C3-PinX1 and PinX1-FAM-siRNA into Eca-109 cells significantly increased PinX1 mRNA, decreased hTERT mRNA by 29.9% (P<0.05), and significantly reduced telomerase activity (P<0.05), inhibited cell growth, and increased the cell apoptotic index from 19.27±0.76 to 49.73±2%. The transfected PinX1-FAM-SiRNA exhibited PinX1 mRNA expression levels that were significantly decreased by 70% (P<0.05), whereas the remaining characteristics of Eca-109 cells, including cell growth, mRNA level of hTERT, telomerase activity and cell apoptotic index were not altered. Exogenous PinX1 has been demonstrated to be highly expressed in human Eca. PinX1 can inhibit human telomerase activity and the expression of hTERT mRNA, reduce tumor cell growth and induce apoptosis. Notably, these inhibitory functions were inhibited by silencing PinX1 in Eca with PinX1-FAM-siRNA. PinX1 was successfully increased and decreased in the present study, demonstrating that it may be a potential telomerase activity inhibitor. As PinX1 is an endogenous telomerase inhibitor, it may be used as a novel tumor-targeted gene therapy.

Piezoelectric and Dielectric Properties of Multilayered BaTiO3/(Ba,Ca)TiO3/CaTiO3 Thin Films.

Highly oriented multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films were fabricated on Nb-doped (001) SrTiO3 (Nb:STO) substrates by pulsed laser deposition. The configurations of multilayered BaTiO3-(Ba,Ca)TiO3-CaTiO3 thin films are designed with the thickness ratio of 1:1:1 and 2:1:1 and total thickness ∼300 nm. Microstructural characterization by X-ray diffraction indicates that the as-deposited thin films are highly c-axis oriented and large in-plane strain is determined in BaTiO3 and CaTiO3 layers. Piezoresponse force microscopy (PFM) studies reveal an intense in-plane polarization component, whereas the out-of-plane shows inferior phase contrast. The optimized combination is found to be the BaTiO3-(Ba0.85Ca0.15)TiO3-CaTiO3 structure with combination ratio 2:1:1, which displays the largest domain switching amplitude under DC electric field, the largest room-temperature dielectric constant ∼646, a small dielectric loss of 0.03, and the largest dielectric tunability of ∼50% at 400 kV/cm. These results suggest that the enhanced dielectric and tunability performance are greatly associated with the large in-plane polarization component and domain switching.

A sub-threshold dose of pilocarpine increases glutamine synthetase in reactive astrocytes and enhances the progression of amygdaloid-kindling epilepsy in rats.

The prognosis of patients exposed to a sub-threshold dose of a proconvulsant is difficult to establish. In this study, we investigated the effect of a single sub-threshold dose of the proconvulsant pilocarpine (PILO) on the progression of seizures that were subsequently induced by daily electrical stimulation (kindling) of the amygdaloid formation. Male Sprague­Dawley rats were each implanted with an electrode in the right basolateral amygdala and an indwelling cannula in the right ventricle. The animals were randomized into groups and were administered one of the following treatments: saline, PILO, saline+L-α-aminoadipic acid (L-AAA; one dosage tested), PILO+L-AAA, or PILO+L-methionine sulfoximine (three dosages tested). Amygdaloid stimulation and electroencephalography were performed once daily. We performed immunohistochemistry and western blot for glial fibrillary acidic protein and glutamine synthetase (GS). We also assayed the enzymic activity of GS in discrete brain regions. An intraperitoneal injection of a sub-threshold PILO dose enhanced the progression of amygdaloid-kindling seizures and was accompanied by an increase in reactive-astrocyte and GS (content and activity) in the hippocampus and piriform cortex. L-AAA and L-methionine sulfoximine, inhibitors of astrocytic and GS function, respectively, abolished the effect of PILO on amygdaloid-kindling seizures. We conclude that one sub-threshold dose of a proconvulsant may enhance the progression of subsequent epilepsy and astrocytic GS may play a role in this phenomenon. Thus, a future therapy for epilepsy could be inhibition of astrocytes and/or GS.

[Study on Chemical Constituents and Content Determination of Feifukang Mistura].

Objective: To identify the main chemical constituents and to determine the content in Feifukang mistura. Methods: HPLC-MS technique was used to profile and identify the chemical constituents by comparing the retention time,MS data with the reference standard. The content determination of all the chemical constituents were carried on a HPLC system. Results: Five compounds were separated from Feifukang mistura,which were identified as neomangiferin,mangiferin,calycosin-7-O-glucoside,calycosin,and schizandrol A. The standard curves of them showed good linearity on the range of 2. 08 ~ 104. 0 µg/m L,2. 00 ~ 100. 0 µg/m L,2. 00 ~ 100. 0µg/m L,2. 09 ~ 104. 5 µg/m L,and 1. 98 ~ 99. 0 µg/m L,respectively. The average recoveries were all in the range of 91. 3 ~ 103. 8%. Conclusion: The methods of chemical constituents identification and content determination were established,which may offer better revealing the material basis and controlling quality of Feifukang mistura.

Predicted energetics and properties of rare-earth ferrites films grown on cubic (111)- and hexagonal (0001)-oriented substrates.

First-principles calculations are performed to compare the energetics of several phases, including hexagonal polar P6(3)cm and perovskite non-polar Pbnm-like states, of epitaxial RFeO3 films (with R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Lu) grown on different cubic (1 1 1)- and hexagonal (0 0 0 1)-oriented substrates. The P63cm phase is found to be the ground state for large enough in-plane lattice parameters in all investigated RFeO3 films, and its polarization is tunable by the amount of epitaxial strain. Series of available substrates allowing the growth of hexagonal polar RFeO3 films, as well as other phenomena of fundamental and technological importance (e.g. different ground states and coexistence between several phases) are also predicted.

Predicted pressure-induced spin and electronic transition in double perovskite R2CoMnO6 (R = rare-earth ion).

Specific first-principles calculations are performed to predict structural, magnetic and electronic properties of seven double perovskite R2CoMnO6 materials, with R being a rare-earth ion, under hydrostatic pressure. All these compounds are found to undergo a first-order transition from a high spin (HS) to low spin (LS) state at a critical pressure (whose value is dependent on the R ion). Such transition not only results in a significant volume collapse but also yields a dramatic change in electronic structure. More precisely, the HS-to-LS transition is accompanied by a transition from an insulator to a half-metallic state in the R2CoMnO6 compounds having the largest rare-earth ionic radius (i.e., Nd, Sm, Gd and Tb) while it induces a change from an insulator to a semiconductor having a narrow band gap for the smallest rare-earth ions (i.e., R = Dy, Ho and Er). Experiments are called for to confirm these predictions.

Creating multiferroics with large tunable electrical polarization from paraelectric rare-earth orthoferrites.

The quest for materials possessing both a magnetic ordering temperature above room temperature and a large electrical polarization is an important research direction in order to design novel spintronic and memory devices. Up to now, BiFeO3 and related systems are the only known compounds simultaneously possessing such characteristics. Here, first-principles calculations predict that another family of materials, namely epitaxial films made of rare-earth orthoferrites (RFeO3), can also exhibit such desired features. As a matter of fact, applying a large enough strain to these compounds, which are nominally paraelectric and have a high magnetic transition temperature, is predicted to render them ferroelectric, and thus multiferroic. At high compressive strain, the resulting ferroelectric phase of RFeO3 systems having large rare-earth ions is even a tetragonal state characterized by a giant polarization and axial ratio. For large tensile strain, two striking inhomogenous ferroelectric phases--including one never observed before in any perovskite--are further predicted as having significant polarization. A multiphase boundary also occurs, which may lead to optimization of properties or unusual features. Finally, many quantities, including electrical polarization and magnetic ordering temperature, are tunable by varying the epitaxial strain and/or chemical pressure.

Antisense oligodeoxynucleotide against human telomerase reverse transcriptase inhibits the proliferation of Eca-109 esophageal carcinoma cells.

Previous studies have demonstrated that the growth of tumor cells may be inhibited by antisense oligonucleotides (ASODNs) targeted against human telomerase (hTR) or human telomerase reverse transcriptase (hTERT), resulting in antitumor activity in a wide variety of tumors. However, few studies have investigated the effect of hTERT gene-targeted ASODNs on telomerase activity and cell proliferation in human esophageal cancer. In the present study, an MTT assay was used to determine the growth inhibition rate of Eca-109 cells treated with a hTERT-targeted phosphorothioate-ASODN (PS-ASODN). An inverted microscope was used to observe the morphologic changes of the cells following treatment with 5 µM PS-ASODN for 10 days. Telomerase activity was detected using the silver staining semi-quantitative telomeric repeat amplification protocol (TRAP) assay. Following treatment with the PS-ASODN (1-5 µmol/l), the proliferation of the Eca-109 cells was inhibited. The differences in inhibition rate between the PS-ASODN and blank control groups were statistically significant (P<0.05) when the concentration of the PS-ASODN was ≥2 µmol/l, whereas no statistically significant difference was identified between the non-specific-ASODN and blank control groups. The inhibition rate increased gradually as the concentration of the PS-ASODN increased and with time, suggesting that the PS-ASODN inhibited the growth of Eca-109 cells in a concentration-dependent, time-dependent and sequence-specific manner. The growth rate of the cells incubated with the PS-ASODN was reduced compared with that of the control cells. Cells treated with the PS-ASODN became round, suspended and reduced in size. The PS-ASODN was also found to inhibit telomerase activity. The ability of the PS-ASODN to inhibit the telomerase activity and cell proliferation of the Eca-109 cell line suggests that ASODNs have the potential to be novel therapeutic agents for the treatment of esophageal cancer.

Near room-temperature multiferroic materials with tunable ferromagnetic and electrical properties.

The quest for multiferroic materials with ferroelectric and ferromagnetic properties at room temperature continues to be fuelled by the promise of novel devices. Moreover, being able to tune the electrical polarization and the paramagnetic-to-ferromagnetic transition temperature constitutes another current research direction of fundamental and technological importance. Here we report on the first-principles-based prediction of a specific class of materials--namely, R2NiMnO6/La2NiMnO6 superlattices where R is a rare-earth ion--that exhibit an electrical polarization and strong ferromagnetic order near room temperature, and whose electrical and ferromagnetic properties can be tuned by means of chemical pressure and/or epitaxial strain. Analysis of the first-principles results naturally explains the origins of these highly desired features.

Effect of chemical and hydrostatic pressures on structural and magnetic properties of rare-earth orthoferrites: a first-principles study.

The dependence of structural and magnetic properties of rare-earth orthoferrites (in their Pbnm ground state) on the rare-earth ionic radius is systematically investigated from first principles. The effects of this 'chemical pressure' on lattice constants, Fe-O bond lengths, Fe-O-Fe bond angles and Fe-O bond length splittings are all well reproduced by these ab initio calculations. The simulations also offer novel predictions (on tiltings of FeO6 octahedra, cation antipolar displacements and weak magnetization) to be experimentally checked. In particular, the weak ferromagnetic moment of rare-earth orthoferrites is predicted to be a linear function of the rare-earth ionic radius. Finally, the effects of applying hydrostatic pressure on structural and magnetic behavior of SmFeO3 is also studied. It is found that, unlike previously assumed, hydrostatic pressure typically generates changes in physical properties that are quantitatively and even qualitatively different from those associated with the chemical pressure.

Effect of chemical pressure, misfit strain and hydrostatic pressure on structural and magnetic behaviors of rare-earth orthochromates.

First-principles calculations are performed to investigate structural and magnetic behaviors of rare-earth orthochromates as a function of 'chemical' pressure (that is, the rare-earth ionic radius), epitaxial misfit strain and hydrostatic pressure. From a structural point of view, (i) 'chemical' pressure significantly modifies antipolar displacements, Cr-O-Cr bond angles and the resulting oxygen octahedral tiltings; (ii) hydrostatic pressure mostly changes Cr-O bond lengths; and (iii) misfit strain affects all these quantities. The correlations between magnetic properties (Néel temperature and weak ferromagnetic moments) and unit cell volume are similar when varying the misfit strain or hydrostatic pressure, but differ from those associated with the 'chemical' pressure. Origins of such effects are also discussed.

Moderately hypofractionated conformal radiation treatment of thoracic esophageal carcinoma.

AIMS: To prospectively assess the efficacy and safety of moderately hypofractionated conformal radiotherapy in patients with thoracic esophageal cancer. METHODS AND MATERIALS: From Sept. 2002 to Oct. 2005, 150 eligible patients with T2-4N0-1M0 stage thoracic esophageal squamous cell cancers were enrolled to receive either conventional fractionated radiation (CFR) or moderately hypofractionated radiation (MHR) with a three- dimensional conformal radiation technique. Of the total, 74 received moderately hypofractionated radiation with total dose of 54-60 Gy/18-20 fractions for 3.5-4 weeks in the MHR arm, and 76 received conventional radiation with total dose of 60 Gy/30 fractions for 6 weeks in the CFR arm. Concurrent chemotherapy comprised of paclitaxel and cisplatin. Safety was evaluated, and local control and overall survival rates were calculated. RESULTS: Statistically significant differences between the CFR versus MHR arms were observed in local/regional failure rate (47.3% v 27.0%, P=0.034) and the percentage of patients with persistent local disease (26.3% v 10.8%, P=0.012). But 3 and 5-year overall survival rates (43.2%, 38.8% v 38.2%, 28.0%, respectively) were not different between the two arms (P=0.268). There were no significant differences in the incidences of grade 3 or higher acute toxicities (66.3% v 50.0%) and late complications rates (27.0% v 22.4%) between the MHR and CFR arms. CONCLUSIONS: Moderately hypofractionated, three-dimensional radiation treatment could improve the local control rate of esophageal cancer and potentially increase patient survival.

[Clinical observation on electroacupuncture combined with rehabilitation techniques for treatment of shoulder subluxation after stroke].

OBJECTIVE: To compare the therapeutic effect difference between electroacupuncture combined with rehabilitation techniques and simple rehabilitation techniques for treatment of the shoulder subluxation after stroke. METHODS: Sixty cases of shoulder subluxation patients were divided into an acupuncture combined with rehabilitation group (30 cases) and a rehabilitation group (30 cases). The acupuncture combined with rehabilitation group was treated with electroacupuncture at Jianyu (LI 15), Jianliao (TE 14) and Jianzhen (SI 9) etc. combined with rehabilitation treatment, the rehabilitation group was treated with rehabilitation only. The therapeutic effects were evaluated and the pain score of the shoulder joint, passive range of motion of shoulder joint, the muscle strength of middle group of the deltoid and the function grade of the upper limbs motion of the two groups were evaluated before and after treatment. RESULTS: The acupuncture combined with rehabilitation group was superior to that of the rehabilitation group in pain score of the shoulder joint, passive range of motion of shoulder joint, the muscle strength of middle group of the deltoid and the function grade of the upper limbs motion with significant differences between the two groups (all P<0.05); the total effective rate of 93. 3% in the acupuncture combined with rehabilitation group was superior to that of 73.3% in the rehabilitation group (P<0.05). CONCLUSION: The therapy of electroacupuncture combined with rehabilitation techniques can act a good regulating role on muscle strength and the muscular tension of shoulder joint and the muscles around the scapula through many steps, and can effectively improve the shoulder subluxation.