Dietary fiber (DF) is receiving increasing attention, and its importance in pig nutrition is now acknowledged. Although DF for pigs was frowned upon for a long time because of reductions in energy intake and digestibility of other nutrients, it has become clear that feeding DF to pigs can affect their well-being and health. This review aims to summarize the state of knowledge of studies on DF in pigs, with an emphasis on the underlying mode of action, by considering research using DF in sows as well as suckling and weaned piglets, and fattening pigs. These studies indicate that DF can benefit the digestive tracts and the health of pigs, if certain conditions or restrictions are considered, such as concentration in the feed and fermentability. Besides the chemical composition and the impact on energy and nutrient digestibility, it is also necessary to evaluate the possible physical and physiologic effects on intestinal function and intestinal microbiota, to better understand the relation of DF to animal health and welfare. Future research should be designed to provide a better mechanistic understanding of the physiologic effects of DF in pigs.

We report on the optical and charge transport properties of novel alkali metal chalcogenides, Cs2Hg6S7 and Cs2Cd3Te4, pertaining to their use in radiation detection. Optical absorption, photoconductivity, and gamma ray response measurements for undoped crystals were measured. The band gap energies of the Cs2Hg6S7 and Cs2Cd3Te4 compounds are 1.63 eV and 2.45 eV, respectively. The mobility-lifetime products for charge carriers are of the order of ~10-3 cm2/V for electrons and ~10-4 cm2/V for holes. Detectors fabricated from the ternary compound Cs2Hg6S7 shows well-resolved spectroscopic features at room temperature in response to ϒ -rays at 122 keV from a 57Co source, indicating its potential as a radiation detector.

We used the Advanced Photon Source (APS) at Argonne National Laboratory to perform fast (ps range) time-resolved diffraction measurements of the dynamic characteristics in BaTiO3 films subjected to strong high-frequency electric fields. The time-dependent lattice response measured at frequencies between 6.5 MHz and 1.3 GHz revealed damped domain movements with attenuation time rapidly increasing with electric field frequency, v. We found that at frequencies higher than ν ∼ 600 MHz the domain motions in BaTiO3 films become heavily damped, information that may be important to future device operation. A minimum attenuation time, τ ∼ 330 ps, measured at ν = 1.3 GHz was limited by the time constant of the electrical circuit.

The dielectric properties of high-k dielectric BaTiO3 and Ba0.68Sr0.32TiO3 thick films deposited on alumina substrates using a plasma-spray process were investigated. The as-deposited films were predominantly crystalline but contained an amorphous second phase, the amount of which depended on spray conditions. The effect of the spray conditions on crystallinity was studied and related to the dielectric properties of the films. The presence of a low dielectric constant interfacial layer in plasma-spray-deposited films was determined from the dependence of the dielectric constant on film thickness. After annealing at 500 °C for 20 h in air, the crystallinity and dielectric constant increased. Annealing was also found to affect the interfacial layer properties.

The phase stability of epitaxial KTaxNb1−xO3 (0 ≤ x ≤ 1) thin films, with compositions over the entire solid solution range, was investigated. KTaxNb1−xO3 thin films were deposited on (100) MgAl2O4 substrates by metalorganic chemical vapor deposition. Films with compositions x ≤ 0.30 were orthorhombic, as determined by x-ray diffraction. Dielectric measurements at room temperature indicated the presence of morphotropic phase boundaries at x = 0.30 and at x = 0.74. Temperature-dependent measurements of the dielectric constant for KNbO3 from 80 to 800 K indicated three structural phase transitions at 710, 520, and 240 K. For intermediate compositions, a decrease in the Curie and tetragonal–orthorhombic transition temperatures was observed with increasing Ta atomic percent, similar to the bulk phase equilibrium. In contrast to bulk materials, an increase in the orthorhombic–rhombohedral transition temperature with increasing x was observed for the films, resulting in the stabilization of a rhombohedral phase at room temperature for compositions 0.45 ≤ x ≤ 0.73. Differences between the phase stability for the thin films and bulk were attributed to lattice misfit strain.

The thickness dependence of the dielectric properties of epitaxial BaTiO3 thin films was investigated for thicknesses ranging from 15 to 320 nm. The films were deposited by low-pressure metalorganic chemical vapor deposition on (100) MgO substrates. The relative dielectric permittivity and the loss tangent values decreased with decreasing thickness. High-temperature dielectric measurements showed that with decreasing film thickness, the ferroelectric-to-paraelectric transition temperature decreased, the relative dielectric permittivity decreased, and the phase transition was diffuse. The c/a ratio also decreased with decreasing film thickness. The observed behavior for epitaxial films of BaTiO3 was attributed to the presence of strain in the films.

The dielectric response of KNbO3 epitaxial ferroelectric thin films was measured as a function of bias, frequency, and temperature. Thin films with a thickness of 80 to 350 nm were deposited on spinel substrates by low-pressure metalorganic chemical vapor deposition. Bias dependence measurements showed hysteresis in the dielectric response. The dielectric constant decreased with bias, and the tunability was calculated to be between 35% and 42% for an applied field of 7 MV/cm. The frequency dependence of the dielectric constant followed a power law. A pronounced thickness effect was observed in the dielectric response, especially at the Curie temperature. With decreasing thickness, the dielectric constant and the loss tangent decreased. A diffuse ferroelectric phase transition was observed for films with a thickness less than 350 nm.

Deep level defects in oxygen doped GaN grown by metal-organic vapor phase epitaxy were investigated. Using steady-state photocapacitance (SSPC) spectroscopy, three deep levels with optical ionization energies of 1.0, 1.4, and 3.25 eV were observed in both nominally undoped and oxygen-doped samples. The total deep level defect concentrations ranged from 6 × 1015 cm-3 in undoped films to 3 × 1016 cm-3 in oxygen-doped films. The concentration of the 3.25 eV level defect increased upon oxygen doping, while the concentrationof the 1.0 and 1.4 eV levels were essentially dopant independent. From the measured concentrations the formation energies of the defects were calculated and compared to energies calculated using density functional theory.

The optical properties of Mn-doped GaN were investigated. The films were grown by metalorganic vapor phase epitaxy using tricarbonyl (methylcyclopentadienyl) manganese as the dopant source. Two characteristic bands were observed in the absorption spectra of Mn-doped epilayers. The low energy band had a threshold at 1.4 ± 0.05 eV with a maximum at 1.5 ± 0.02 eV, with a full width half maximum of 245 ± 10 meV at 296 K. A second higher energy band was observed as a shoulder to the band edge absorption with a threshold energy of 2.06 eV at room temperature. Using photoluminescence spectroscopy, a new broad band was observed in the infrared spectra of GaN:Mn at 1.27 ± 0.02 eV with a full width half maximum of 0.26 ± 0.01 eV at 20K. From analysis of optical absorption and emission spectra Mn forms a deep acceptor level with optical transitions at 1.4 and 2.06 eV. The deep level nature of Mn indicates that it is a potential dopant for semi-insulating GaN.

The low temperature photoluminescence (PL) of Mg-doped GaN co-doped with oxygen is investigated. Two PL bands are observed at low temperature at 2.5 and 2.8 eV in the p-type oxygen co-doped samples. Both the 2.5 eV and 2.8 eV bands are attributed to donor-acceptor (DA) transitions involving deep donors of different origin and a shallow MgGa acceptor. The integrated intensity of the 2.8 eV band in p-type GaN decreases as the oxygen partial pressure is increased. The decrease is attributed to reduced compensation by deep native donors. The two bands are not formed in n-type (n > 1019 cm−3) GaN:Mg over-doped with oxygen indicating that the deep donors responsible for these transitions have high formation energies in n-type material.

Behavior of the photoluminescence band at about 2.8 eV in heavily Mg doped GaN has been studied at different temperatures and excitation intensities. The 2.8 eV band is attributed to donor-acceptor transitions involving a Mg acceptor. The large blue shift of the band with increasing excitation intensity is explained by variation in the contribution of close and distant pairs to the luminescence. The red shift of the band with increasing temperature under high excitation intensity conditions results from thermal release of carriers from close pairs. The thermal activation energy of the deep donor, about 0.4 eV, is determined from the quenching of the 2.8 eV luminescence band at high temperatures.

The factors limiting the efficiency of Er3+ luminescence at 1.54 μm (0.8 eV) in erbiumdoped barium titanate films were studied. To investigate the effect of film stoichiometry on luminescence efficiency films were annealed in oxygen and in vacuum. For films annealed in oxygen at temperatures of 700–900°C a nominal increase in the luminescence efficiency was observed. Vacuum annealing resulted in strong quenching of the emission intensity. Transient photoluminesence measurements showed that the emission lifetime also decreased for the reduced films. This effect was reversible; upon oxygen annealing both the emission intensity and lifetime were restored to their original values. These results indicate that the Er3+ luminescence efficiency strongly depends on film stoichiometry.

The dynamic response of the electro-optic coefficients and the electronic polarizability for epitaxial thin films of KnbO3 and BaTiO3 are measured. For these two systems a logarithmic dependence of the electro-optic response and the polarization on time was observed after removal of an applied electric field. The dynamic response of the electro-optic effect and the polarization of the films are attributed to the same physical mechanism, which we associate with the dynamic response of ferroelectric nanodomains.

Behavior of the photoluminescence band at about 2.8 eV in heavily Mg doped GaN has been studied at different temperatures and excitation intensities. The 2.8 eV band is attributed to donor-acceptor transitions involving a Mg acceptor. The large blue shift of the band with increasing excitation intensity is explained by variation in the contribution of close and distant pairs to the luminescence. The red shift of the band with increasing temperature under high excitation intensity conditions results from thermal release of carriers from close pairs. The thermal activation energy of the deep donor, about 0.4 eV, is determined from the quenching of the 2.8 eV luminescence band at high temperatures.

Domain stabilization in epitaxial potassium niobate films deposited by metalorganic chemical vapor deposition was studied. Stabilization was examined for films deposited on substrates with different coefficients of thermal expansion. X-ray diffraction of KNb03 films deposited on (100) MgAl204, (r) A1203, and (100)pseudocubic YAIO3 substrates shows a mixed domain structure consisting of (110) and (001) domains. However, KNb03 thin films deposited under identical conditions on (100) MgO, (100) SrTi03, and (100)pseudocubic LaA103 substrates exhibited only a single domain variant. A direct correlation between (001) domain volume fraction in the as-deposited KNb03 films and calculated strain resulting from thermal mismatch is observed.

Ferroelectric oxide epitaxial thin films are potentially important for a variety of guided-wave electro-optic and non-linear optical applications. Metalorganic chemical vapor deposition has been used to synthesize epitaxial thin films of a number of ferroelectric oxides. The films now have sufficient optical quality to enable the fabrication of waveguide devices including electro-optic modulators and optical amplifiers for 1.54 microns.

Guided-wave absorption and fluorescence in epitaxial Er:BaTiO3 thin film channel waveguides on MgO are reported. Guided- wave absorption is strongly dependent on post- growth annealing. Stimulated emission over a 40 nm bandwidth (λcente - 1.54 μm) has been achieved in oxygen-annealed waveguides. At 1.54 μm the absorption is reduced from ∼ -2 dB/cm to -∼-1.3 dB/cm in a 2.2 mm long 5 μm wide channel waveguide due the presence of the pump light.

Er-doped GaP diodes that exhibit strong room temperature characteristic 4f-shell luminescence under forward bias have been fabricated. The output of the diode increases linearly with current for low current densities but eventually saturates. The radiative decay lifetime is 2.6 msec and is independent of current. It is proposed that the observed intensity dependence on excitation power results from saturation of the optically active Er3+ centers. Some diodes showed a superlinear dependence, with a threshold of about 2 A/cm2.

The morphological stability of strained-layer thin films is analyzed using classical nucleation theory. For the case where strain relaxation occurs by formation of coherent islands, the model predicts that the critical thickness for transition from two-dimensional (2D) to three dimensional (3D) growth depends inversely on the square of the misfit. The predicted dependence of critical thickness on misfit is in agreement with recent experimental studies on the heteropitaxy of III-V compounds.