Magnetoelectric coupling in the paramagnetic state of a metal-organic framework

Although the magnetoelectric effects - the mutual control of electric polarization by magnetic fields and magnetism by electric fields, have been intensively studied in a large number of inorganic compounds and heterostructures, they have been rarely observed in organic materials. Here we demonstrate magnetoelectric coupling in a metal-organic framework [(CH3)2NH2]Mn(HCOO)3 which exhibits an order-disorder type of ferroelectricity below 185 K. The magnetic susceptibility starts to deviate from the Curie-Weiss law at the paraelectric-ferroelectric transition temperature, suggesting an enhancement of short-range magnetic correlation in the ferroelectric state. Electron spin resonance study further confirms that the magnetic state indeed changes following the ferroelectric phase transition. Inversely, the ferroelectric polarization can be improved by applying high magnetic fields. We interpret the magnetoelectric coupling in the paramagnetic state in the metal-organic framework as a consequence of the magnetoelastic effect that modifies both the superexchange interaction and the hydrogen bonding.

Development of high-speed and wide-angle visible observation diagnostics on Experimental Advanced Superconducting Tokamak using catadioptric optics

A new wide-angle endoscope for visible light observation on the Experimental Advanced Superconducting Tokamak (EAST) has been recently developed. The head section of the optical system is based on a mirror reflection design that is similar to the International Thermonuclear Experimental Reactor-like wide-angle observation diagnostic on the Joint European Torus. However, the optical system design has been simplified and improved. As a result, the global transmittance of the system is as high as 79.6% in the wavelength range from 380 to 780 nm, and the spatial resolution is <5 mm for the full depth of field (4000 mm). The optical system also has a large relative aperture (1:2.4) and can be applied in high-speed camera diagnostics. As an important diagnostic tool, the optical system has been installed on the HT-7 (Hefei Tokamak-7) for its final experimental campaign, and the experiments confirmed that it can be applied to the investigation of transient processes in plasma, such as ELMy eruptions in H-mode, on EAST.

Effects of energy and protein restriction, followed by nutritional recovery on morphological development of the gastrointestinal tract of weaned kids

Effects of energy, protein, or both energy and protein restriction on gastrointestinal morphological development were investigated in 60 Liuyang Black kids, which were sourced from local farms and weaned at 28 d of age. Weaned kids were randomly assigned to receive 1 of 4 dietary treatments (15 kids per treatment), which consisted of adequate nutrient supply (CON), energy restriction (ER), protein restriction (PR), or energy and protein restriction (EPR). The entire experiment included adaptation period (0 to 6 d), nutritional restriction period (7 to 48 d), and recovery period (49 to 111 d). Three kids from each group were killed at d 48 and 111, and the rumen, duodenum, jejunum, and ileum were harvested. On d 48 (end of nutritional restriction), lengths of the duodenum (P = 0.005), jejunum (P = 0.003), and ileum (P = 0.003), and weights of the rumen (P = 0.004), duodenum (P = 0.006), jejunum (P = 0.006), and ileum (P = 0.004) of kids in ER, PR, and EPR were less than those of kids in CON. Compared with CON, PR decreased papillae width (P = 0.03) and surface area (P = 0.05) of the rumen epithelium, villus surface area (P = 0.05), and N concentration (P = 0.02) of the jejunum mucosa on d 48. Compared with CON, EPR decreased papillae height (P = 0.001), width (P = 0.001), and surface area (P = 0.003), N concentration (P = 0.01), and the ratio of N to DNA (P = 0.03) of the rumen epithelium. Compared with CON, EPR also decreased villus height (P = 0.01), width (P = 0.006), and surface area (P = 0.006), N concentration (P < 0.001), and the ratio of N to DNA (P < 0.001) of the jejunum mucosa on d 48. On d 111 (end of nutritional recovery), lengths of the duodenum (P = 0.001), jejunum (P = 0.001), and ileum (P = 0.001), weights of the rumen (P < 0.001), duodenum (P = 0.001), jejunum (P < 0.001), and ileum (P < 0.001) of kids in ER, PR, and EPR were still less than those of kids in CON; N concentrations of rumen epithelium of kids in PR (P = 0.01) and EPR (P = 0.001), and the ratio of N to DNA of jejunum mucosa of kids in EPR (P < 0.001) were greater than those of kids in CON. Results indicate that nutritional restriction of 6 wk can retard gastrointestinal morphological development for kids weaned at 28 d of age and retarded development remains evident, even after nutritional recovery of 9 wk.

Effects of maternal protein or energy restriction during late gestation on antioxidant status of plasma and immune tissues in postnatal goats

Maternal malnutrition can have temporary or long-lasting effects on development and physiological function of offspring. Our objective was to investigate whether maternal protein or energy restriction in late gestation affects the antioxidant status of plasma, immune organs (thymus and spleen), and natural barrier organs (jejunum) in neonatal goats and whether the effects could be reversed after nutritional recovery. Forty-five pregnant goats (Liuyang Blacks) of similar age (2.0 ± 0.3 yr) and BW (22.2 ± 1.5 kg at d 90 of gestation) were assigned to 3 dietary treatments during late gestation: control (ME = 9.34 MJ/kg and CP = 12.5%, DM basis), 40% protein restricted (PR), and 40% energy restricted (ER) until parturition, after which offspring received the normal diet for nutritional recovery. Plasma and tissues of kids were sampled to determine antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and catalase (CAT)] and gene expression of antioxidant enzymes (Cu/Zn-SOD [SOD1], CAT, and peroxiredoxin 2 [PRDX2]). Maternal protein or energy restriction decreased (P < 0.05) SOD activities in plasma, liver, thymus, and spleen and SOD1 expression in thymus, and maternal energy restriction also decreased (P < 0.05) plasma GSH-Px activity and expressions of SOD1 and CAT in liver at birth. After nutritional recovery of 6 wk, SOD activities in thymus (both in PR and ER) and spleen (only in PR) were greater (P < 0.05), but CAT activity of thymus (both in PR and ER) and CAT expression (only in ER) were less (P < 0.01) than those in control. After nutritional recovery of 22 wk, SOD1 and PRDX2 expression in thymus (both in PR and ER) and SOD1 expression in liver (only in ER) were greater (P < 0.05) whereas CAT expression in thymus (both in PR and ER) was less (P < 0.001) than in control. The current results indicate that maternal protein or energy restriction can decrease the antioxidant capacity of the neonatal kids and result in an imbalance of SOD and hydrogen peroxide-inactivating systems in thymus, even after 6 or 22 wk of nutritional recovery.

Wire network behavior in superconducting Nb films with diluted triangular arrays of holes

We present results of transport measurements on superconducting Nb films with diluted triangular arrays (honeycomb and kagomé) of holes. The patterned films have large disk-shaped interstitial regions even when the edge-to-edge separations between nearest neighboring holes are comparable to the coherence length. Changes in the field interval of two consecutive minima in the field dependent resistance R(H) curves are observed. In the low field region, fine structures in the R(H) and T(c)(H) curves are identified in both arrays. Comparison of experimental data with calculation results reveals that these structures observed in honeycomb and kagomé hole arrays resemble those in wire networks with triangular and T(3) symmetries, respectively. The findings suggest that even in these specified periodic hole arrays with very large interstitial regions, the low field fine structures are determined by the connectivity of the nanostructures.

Electric-field control of nonvolatile magnetization in Co40Fe40B20/Pb(Mg(1/3)Nb(2/3))(0.7)Ti(0.3)O3 structure at room temperature

We report a large and nonvolatile bipolar-electric-field-controlled magnetization at room temperature in a Co(40)Fe(40)B(20)/Pb(Mg(1/3)Nb(2/3))(0.7)Ti(0.3)O(3) structure, which exhibits an electric-field-controlled looplike magnetization. Investigations on the ferroelectric domains and crystal structures with in situ electric fields reveal that the effect is related to the combined action of 109° ferroelastic domain switching and the absence of magnetocrystalline anisotropy in Co(40)Fe(40)B(20). This work provides a route to realize large and nonvolatile magnetoelectric coupling at room temperature and is significant for applications.

Effect of tea catechins on regulation of cell proliferation and antioxidant enzyme expression in H2 O2 -induced primary hepatocytes of goat in vitro

Tea catechins (TC) are polyphenols that have potent antioxidant activity. The objectives of this study were to determine the effects of TC on antioxidant status of hepatocytes challenged with H2 O2 . Primary hepatocytes of goat were exposed to 1 mm H2 O2 without or with 5, 50 and 500 μg/ml TC. The cells were harvested at 48 h post-treatment to determine effects of TC on proliferation, apoptotic features and membrane integrity of cells, and expression of genes and activities of antioxidant enzymes. H2 O2 exposure caused damage to cells (p < 0.001). A lower concentration of TC (5 μg/ml) displayed a protective effect by inhibiting exorbitant cell proliferation and DNA degradation. Both H2 O2 exposure and TC pre-incubation affected expression of antioxidant enzymes at mRNA and protein levels (p < 0.001). The activities of catalase (CAT) (p = 0.027), CuZn-superoxide dismutase (CuZn-SOD) (p < 0.001) and glutathione peroxidase (GPx) (p < 0.001) increased with TC pre-incubation followed by H2 O2 challenge. Changes of CuZn-SOD activity induced by H2 O2 and TC basically paralleled the changes in the corresponding mRNA and protein levels, but the correlation in CAT and GPx expression displayed slightly different patterns at different concentrations of TC. These findings infer that oxidative stress can induce deleterious cellular responses and this unfavourable condition may be alleviated by treatment with TC.

Study of magnetization reversal by minor loops in IrMn/CoFe exchange-biased bilayers

We report a detailed investigation of the magnetization reversal by minor loops in Co75Fe25 (t) single layer and Ir22Mn78(10 nm)/CoFe(t) exchange-biased bilayers with different CoFe thicknesses. With increasing CoFe layer thickness in IrMn/CoFe bilayers, the magnetization reversal process shows a transition from the coherent rotation to the domain-wall motion, which is attributed to the competition among the antiferromagnetic domain wall energy, ferromagnetic domain wall energy, and the interface coupling between antiferromagnetic and ferromagnetic layers.

Interface characterization of epitaxial Fe/MgO/Fe magnetic tunnel junctions

Following predictions by first-principles theory of a huge tunnel magnetoresistance (TMR) effect in epitaxial Fe/MgO/Fe magnetic tunnel junctions (MTJs), measured magnetoresistance (MR) ratios of about 200% at room temperature (RT) have been reported in MgO-based epitaxial MTJs. Recently, a MR ratio of about 600% has been reported at RT in MgO-based MTJs prepared by magnetron sputtering, using amorphous CoFeB as the ferromagnetic electrode. These MTJs show great potential for application in spintronic devices. Fully epitaxial MTJs are excellent model systems that enhance our understanding of the spin-dependent tunneling process as the interface is well defined and can be fully characterized. Both theoretical calculations and experimental results clearly indicate that the interfacial structure plays a crucial role in the coherent tunneling across a single crystal MgO barrier, especially in epitaxial MgO-based MTJs grown by molecular beam epitaxy (MBE). Surface X-ray diffraction, Auger electron spectroscopy, X-ray absorption spectra, and X-ray magnetic circular dichroism techniques have been reported previously for interface characterization. However, no consistent viewpoint has been reached on the interfacial structures (such as FeO layer formation at the bottom Fe/MgO interface), and it is still an open issue. In this article, our recent studies on the interface characterization of MgO-based epitaxial MTJs by X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and spin-dependent tunneling spectroscopy, will be presented.

Efficacy study and field application of an inactivated new type gosling viral enteritis virus vaccine for domestic geese

New type gosling viral enteritis virus (NGVEV) caused a serious disease in naive juvenile goslings. In the described studies the performance of 2 vaccines was analyzed: a vaccine containing adjuvanted inactivated NGVEV and a vaccine containing adjuvanted inactivated NGVEV and recombinant goose IL-2. Breeder geese were subcutaneously vaccinated at the beginning of the egg production period with the vaccines. Breeder geese sham vaccinated with PBS served as control. The cellular and humoral immune responses of the vaccinated breeder geese, as well as the presence of maternally derived antibody to NGVEV, were investigated by ELISA, virus neutralization test, and lymphocyte proliferation assay, respectively. A significantly higher immunogenicity (P < 0.05) was induced by the inactivated NGVEV-recombinant goose IL-2 adjuvant vaccine compared with the inactivated NGVEV vaccine. The offspring of the vaccinated birds were challenged with virulent NGVEV (100 50% lethal dose) and the protective efficacy of the vaccines was determined. Furthermore, in a field trial the efficacy of the inactivated NGVEV vaccine was recorded from years 2003 to 2007. No clinical signs or abnormal health status were observed in the vaccinated breeder geese and the progeny. After a single application, >80% protection was shown in the progeny of geese vaccinated against NGVEV challenge for approximately 5 mo. The extensive field trials further demonstrated that vaccination of breeder geese with the inactivated NGVEV vaccine could be a safe and efficacious means to control NGVE disease. Moreover, the level of maternally derived NGVEV antibody titer in the egg yolk reflected the level of NGVEV antibodies in the breeder geese, suggesting that the egg yolk could be used to monitor the vaccination efficacy in commercial goose breeder flocks.

Milk powder induced lipid peroxidation reduction using Ku Ding tea (Lactuca taiwaniana Maxim) in rats

The effects of Ku Ding tea (Lactuca taiwaniana Maxim) and milk powder on biochemical and immunological parameters of Sprague-Dawley rats were investigated and the possibility of use of Ku Ding tea to reduce physiological discomfort of drinking milk powder was assessed. Eighty rats were randomly assigned to four treatments: basal diet (control), basal diet plus whole milk powder (WM), basal diet plus Ku Ding tea (KD) and basal diet plus whole milk powder and Ku Ding tea (MK). Data was collected on animals' final body weight, hematological values, blood biochemical parameters, antioxidation parameters and immune organ weight index. Results showed that final body weight of male KD was significantly lower than that of WM. White blood cell count, monocyte count and granulocyte count of KD rats were significantly lower than those of WM. Compared to the control, single milk powder supplementation numerically increased plasma malondialdehyde. The malondialdehyde in the male KD and MK rats were lower than those in WM and control, although the differences were not significant. No significant differences were found in Na(+)K(+)-adenosine triphosphatase activity, spleen and thymus index in each group. Consumption of Ku Ding tea appeared to lower lipid peroxidation that was induced by milk powder in the rats.

Effects of variety, sowing season and maturity stage on ruminal phosphorus release from whole maize stover and its morphological fractions

An in situ degradation technique was used to investigate the effects of variety, season and maturity stage on ruminal Phosphorus (P) release from whole maize stover and morphological fractions from five varieties of maize (conventional maize, CM; sweet maize, SM; waxy maize, WM; high oil maize, HOM; and fodder maize, FM). Maize plants were harvested in 2005, 17 and 31 days after tasselling and manually separated into leaf blade, leaf sheath, stem and husk. Results showed that the values of rapidly released P fractions (a), slowly released P fractions (b), rate constant of P release for fraction b (c) and effective disappearance (ED) of P were significantly influenced by variety, sowing season and maturity stage (p < 0.05). The ED of P in whole maize stover among the varieties decreased in the following order: FM (89.8%) > HOM (87.9%) > CM (87.0%) > SM (86.9%) > WM (83.9%). Advanced maturity stage increased (p < 0.001) the a and ED values of P in the leaf blade and leaf sheath, but decreased (p < 0.001) these parameters in the husk. The a fraction and ED of P were higher (p < 0.001) for maize sown in spring than those sown in summer. Significant (p < 0.05) interactions among variety, sowing season and maturity stage were noted in the a and ED values of P. Effective disappearance of morphological fraction varied significantly (p < 0.001) and followed the order: stem (90.3%) > leaf sheath (88.2%) > leaf blade (85.2%) > husk (84.9%). In conclusion, most of P in maize stover could be released in the rumen. The potential pollution resulting from P excretion in faeces may be alleviated, when maize stover is largely used as the main forage source of ruminants.

Effects of yeast culture and fibrolytic enzyme supplementation on in vitro fermentation characteristics of low-quality cereal straws

The effects of yeast culture and fibrolytic enzyme preparation (containing cellulase and xylanase) on in vitro fermentation characteristics of rice straw, wheat straw, maize stover, and maize stover silage were examined using an in vitro gas production technique. Four levels of yeast culture and fibrolytic enzyme supplements (0, 2.5, 5.0, and 7.5 g/kg of straw DM, respectively) were tested in a 4 x 4 factorial arrangement. Supplementation of yeast culture increased the cumulative gas production, theoretical maximum of gas production, rate of gas production, IVDMD, and in vitro OM disappearance (IVOMD), and decreased the lag time for each type of straw. Fibrolytic enzyme supplementation tended to increase cumulative gas production, theoretical maximum of gas production, and rate of gas production; prolonged lag time of gas production; and enhanced IVDMD and IVOMD for 4 types of cereal straws, with the significance of this effect being dependent on the level of supplemented enzymes. There were significant interactions between fibrolytic enzymes and yeast on all in vitro gas production parameters, IVDMD, and IVOMD of each type of straw. The outcome of this research indicated that the application of fibrolytic enzyme preparation and yeast culture could improve in vitro gas production fermentation of cereal straws.

Magnetic instability regions in patterned structures: influence of element shape on magnetization reversal dynamics

We report a time-resolved imaging study of the influence of shape on magnetic instabilities in patterned magnetic structures. We find that in rectangular structures magnetization reversal initiates at the ends and interior simultaneously, while in structures with tapered ends the reversal begins in the middle of the structures and spreads out to the ends. The degree of tapering is important for both the switching field and the time required for full reversal. A model based on the concept of local instability regions yields good agreement with the observed location of the reversal onsets.

Probing spin-flip scattering in ballistic nanosystems

Because spin-flip length is longer than the electron mean-free path in a metal, past studies of spin-flip scattering are limited to the diffusive regime. We propose to use a magnetic double barrier tunnel junction to study spin-flip scattering in the nanometer sized spacer layer near the ballistic limit. We extract the voltage and temperature dependence of the spin-flip conductance Gs in the spacer layer from magnetoresistance measurements. In addition to spin scattering information including the mean-free path (70 nm) and the spin-flip length (1.0-2.6 microm) at 4.2 K, this technique also yields information on the density of states and quantum well resonance in the spacer layer.

Optical studies on the surface-induced tilted layers in freestanding films of two no-layer-shrinkage liquid crystal compounds

Null transmission ellipsometry has been employed to study the molecular arrangements in freestanding films of two no-layer-shrinkage liquid crystal homologous compounds above the bulk smectic A-smectic C* (Sm C*) transition temperature. An unusual nonplanar-parallel or nonplanar-antiparallel-parallel transition has been observed in both compounds under a proper electric field. With the addition of one CH2 group, while the SmC* phase is more stable thermally, the magnitude of the critical field needed to induce a parallel-antiparallel transition decreases dramatically.

First-principles theory of quantum well resonance in double barrier magnetic tunnel junctions

Quantum well (QW) resonances in Fe(001)/MgO/Fe/MgO/Fe double barrier magnetic tunnel junctions are calculated from first principles. By including the Coulomb blockade energy due to the finite size islands of the middle Fe film, we confirm that the oscillatory differential resistance observed in a recent experiment [T. Nozaki, Phys. Rev. Lett. 96, 027208 (2006)10.1103/PhysRevLett.96.027208] originates from the QW resonances from the Delta1 band of the Fe majority-spin channel. The primary source of smearing at low temperatures is shown to be the variation of the Coulomb blockade energy.

Magnetic vortex core dynamics in cylindrical ferromagnetic dots

We report direct imaging by means of x-ray photoemission electron microscopy of the dynamics of magnetic vortices confined in micron-sized circular permalloy dots that are 30 nm thick. The vortex core positions oscillate on a 10 ns time scale in a self-induced magnetostatic potential well after the in-plane magnetic field is turned off. The measured oscillation frequencies as a function of the aspect ratio of the dots are in agreement with theoretical calculations presented for the same geometry.

Optical investigations on the biaxial smectic- A phase of a bent-core compound

Several unique optical properties have been obtained from freestanding films of a bent-core compound. Our experimental results indicate the existence of the antiferroelectric biaxial smectic-A (Sm A) phase. The critical exponent associated with the biaxiality through the uniaxial-antiferroelectric biaxial Sm A transition has been measured to be 0.82+/-0.04 , which is in good agreement with our theoretical calculation. Our theoretical advances further demonstrate that the critical behavior of the optical biaxiality with the order parameter being a vector is described by the secondary-order parameter of the three-dimensional XY model. We also observe a remarkable even-odd layering effect exhibited by the surface layers of freestanding films under an applied electric field (approximately 20 V/cm) in the film plane.

Experimental investigations of one liquid-crystal compound exhibiting the no-layer-shrinkage effect near the Sm-A-Sm- C(*) transition

Three experimental probes have been employed to investigate the nature of the smectic- A -smectic- C ( Sm-A-Sm- C(*) ) phase transition of one liquid-crystal compound showing almost no layer-shrinkage effect through the transition. Results from both x-ray diffraction and optical studies indicate that the compound exhibits a crossover behavior of different molecular packing arrangements within the bulk Sm-A phase window. The calorimetry results show a significant critical anomaly near the Sm-A-Sm- C(*) transition, although it was found to be weakly first order.

Unusual behavior of the surface-induced tilted layers in free-standing films of a non-layer-shrinkage liquid crystal compound

Null-transmission ellipsometry has been conducted to study the molecular arrangements in free-standing films of one chiral compound above the bulk smectic-A-smectic-C* transition temperature. Upon cooling under a proper electric field, a nonplanar-anticlinic-synclinic or a nonplanar-synclinic transition has been observed. The nonplanar structure continuously evolves into the anticlinic or synclinic structures. Increasing electric field can induce a rare transition from a synclinic to an anticlinic structure.

Optical studies on free-standing films of an achiral smectic liquid crystal

Employing null transmission ellipsometry and depolarized reflected light microscopy, we have studied two smectic phases, Sm-C1 and Sm-C2, of one achiral mesogen. Our results show that Sm-C1 and Sm-C2 are the synclinic Sm-C and anticlinic Sm-C(A) phases, respectively. We find no evidence to support recent claims that the Sm-C1 is chiral and ferroelectric [R. Stannarius et al., Phys. Rev. Lett. 90, 025502 (2003)].

Optical characterization of a nanoscale incommensurate pitch in a new liquid-crystal phase

As a remarkable orientationally ordered soft-condensed matter system, the smectic-C*(alpha) phase exhibits an incommensurate nanoscale helical pitch of more than four smectic layers. Recent theoretical advances predict the existence of a new phase showing a helical pitch of less than four smectic layers (<16 nm). By applying a novel optical technique to the study of freestanding films with increments in thickness of one smectic layer, we have measured the size of this pitch using 633 nm HeNe laser light. Our results confirm the existence of the newly predicted phase in one unique compound.