57 research outputs found
Synthesis and characterization of mixed-metal germanates
No full textMixed-metal germanates with the general formula ABB’Ge4O12 have been synthesised using the ceramic method and their properties characterised by X-ray diffraction, neutron diffraction, dc and ac magnetometry, specific heat and Mossbauer spectroscopy. DFT calculations were conducted on two compounds ZrM2Ge4O12 (M = Mn, Co). All compositions adopt a tetragonal structure (space group P4/nbm with the unit-cell parameters a = b ~ 2c). The cation A occupies the 2b site and is coordinated by eight oxide ions at the corners of a square antiprism whereas B and B' are disordered over the 4f site which is at the centre of a distorted octahedron of oxide ions. They can be considered to lie in layers perpendicular to the [001] axis. These layers are separated from each other by layers containing [Ge4O12]8- rings, each ring being comprised of four vertex-sharing GeO4 tetrahedra. CeMn2−xCoxGe4O12 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) become anti-ferromagnetic (x = 0.0, 1.5, 2.0) or weakly ferromagnetic (x = 0.5, 1.0) at 4.2 ≤ T ≤ 7.6 K. The ordered moments lie along [001] when x = 0.0 and in the (001) plane otherwise. The unit cell doubles along [001] when x = 1.5 and 2.0, but the doubling is lost when a first-order metamagnetic transition occurs on the application of a 10 kOe magnetic field. The ordered moments at 1.6 K for x = 0.0 and 2.0 are 4.61(2) and 2.58(2) μB, respectively; the corresponding effective moments in the paramagnetic phase are 5.91 and 5.36 μB. CeM1.5M'0.5Ge4O12 (M = Mn, Co; M' = Zn, Ni, Cu) show similar magnetic properties as CeM2Ge4O12 albeit with changes in the Néel temperature and Weiss constant due to the differences between the cations used. ZrMn2−xCoxGe4O12 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) show long-range magnetic order with transition temperatures, TC, in the range 2 ≤ TC/K ≤ 10. The underlying magnetic structure is the same in each case but the ordered spins lie along [001] when x = 0.0 and in the (001) plane for all other compositions. In all cases the magnetically-ordered phase is a weak ferromagnet although the magnitude of the spontaneous magnetisation and the strength of the coercive field are composition-dependent. The magnetic structure can be rationalized by considering the strengths of the interactions along the distinct M–O–Ge–O–M superexchange pathways in the crystal and the observed magnetic structure is entirely consistent with the predictions of ab initio calculations. LnFeMGe4O12 (Ln = Y, Eu, Gd, Lu; M = Mn, Zn) show long-range antiferromagnetic order with transition temperatures 15 ≤ TN/K &;e; 30. The magnetic structure is the same in each case and consists of an A-type ordering of (001) planes; the ordered spins lie in the (001) plane. Comparison with isostructural compounds leads to the conclusion that subtle structural changes play a greater role than the electronic configuration of the cation in determining the magnetic structure. Ln2MGe4O12 (Ln = Gd-Yb; M = Ca, Mn, Co) and LnBCoGe4O12 (B = Sc or Lu) show various magnetic behaviours. The calcium-, holmium- and erbium-containing compositions remain paramagnetic down to 2 K; the other cases show a transition at the temperatures ~ 4 K. Dy2CoGe4O12 and DyScCoGe4O12 behave as spin glasses and the terbium- and gadolinium-cobalt-containing compounds show long-range magnetic order. Tb2MnGe4O12 shows a weakly ferromagnetic phase and Gd2MnGe4O12, Dy2MnGe4O12 are antiferromagnets. The data can be rationalized qualitatively in terms of the interplay between magnetic anisotropy and crystal field effects
Magnetic properties of GdBB’Ge4O12; BB’ = FeZn or GdCa
No full textPolycrystalline samples of Gd2CaGe4O12 and GdFeZnGe4O12 have been synthesized via a ceramic route. Both were characterised by X-ray diffraction, magnetometry and Mössbauer spectroscopy; GdFeZnGe4O12 was also studied by neutron diffraction. They adopt the SrNa2P4O12 structure: space group P4/nbm with a = 10.0766(1), c = 5.1043(1) Å for Gd2CaGe4O12; a = 9.7298(1), c = 4.7515(1) Å for GdFeZnGe4O12 at 293 K. Gd2CaGe4O12 is paramagnetic for 2 ≤ T/K ≤ 300 whereas GdFeZnGe4O12 is antiferromagnetic below 13.8(2) K. The six-coordinate Fe3+ and Zn2+ cations are disordered over the pseudo-cubic 4 f sublattice and the Gd3+ cations occupy the eight-coordinate 2b sites. The Fe3+ and Gd3+ cations adopt an A-type, k = [0,0,½] antiferromagnetic arrangement with their ordered moments aligning in the xy plane. The Fe/Zn disorder results in relatively low ordered cation moments (Gd3+ = 6.02(13), Fe3+ = 3.84(15) µB) in the antiferromagnetic phase
Variance of Zein Protein and Starch Granule Morphology between Corn and Steam Flaked Products Determined Starch Ruminal Degradability Through Altering Starch Hydrolyzing Bacteria Attachment
No full textThe current study investigated differences of γ-zein protein contents and starch granule characteristics between raw and steam flaked corns and their influences on ruminal starch hydrolyzing bacteria (SHB) attached to corn grain. Two types of raw (Corn1 and Corn2) and their steam-flaked products (SFCorn1 and SFCorn2) were applied to explore physiochemical structures and SHB attachment. SDS-PAGE was conducted to detect γ-zein protein patterns, scanning electron microscope, and small angle X-ray scattering were performed to obtain starch granule morphology, while crystallinity, DQ starch, and DAPI staining were applied to quantify SHB. The steam flaking process destroyed γ-zein proteins and gelatinized starch granules. The median particle size of Corn1 and Corn2 starch granules increased from 17.8 and 18.0 μm to 30.8 and 26.0 μm, but crystallinity decreased from 22.0 and 25.0% to 9.9 and 16.9%, respectively. The percentage of SHB attached to Corn1 residues decreased (p = 0.01) after 4 h incubation, but SHB attached to SFCorn1 residues increased (p = 0.03) after 12 h incubation. Thus, the differences of γ-zein proteins and starch granule physiochemical structures between raw and steam flaked corn played an important role in improving the rate and extent of starch ruminal degradation through altering the process of SHB attached to corn
Antiferromagnetism and metamagnetism in ErFeCuGe4O12
No full textPolycrystalline ErFeCuGe4O12 has been prepared in a solid-state reaction. It adopts a tetragonal crystal structure; space group P4/nbm with a = 9.6416(1), c = 4.7532(1) at room temperature. The Er3+ cations are in square-antiprismatic coordination and the Fe3+ and Cu2+ cations are disordered over one six-coordinate site. The magnetic moments of the three cations adopt an antiferromagnetic arrangement on cooling below 20 K in H = 0 kOe. The magnetic structure consists of ferromagnetic (001) sheets with the spin direction in neighbouring sheets alternating between [001] and [00
̅
At 5 K the ordered moment of Er3+ was determined by neutron diffraction to be 7.90(3) µB and the mean moment of Fe3+ and Cu2+ was 2.43(2) µB. The magnetic structure is unchanged in an applied field of 10 kOe but in fields ≥ 20 kOe the compound begins a metamagnetic transition to a ferromagnetic structure with all atomic moments aligned along [001]
Magnetic Properties of CeMn<sub>2–<i>x</i></sub>Co<sub><i>x</i></sub>Ge<sub>4</sub>O<sub>12</sub> (0 ≤ <i>x</i> ≤ 2) as a Function of Temperature and Magnetic Field
No full textPolycrystalline samples, prepared by a solid-state route, of compositions in the solid solution CeMn2-xCoxGe4O12 (x = 0.0, 0.5, 1.0, 1.5, and 2.0) were characterized by X-ray diffraction, neutron diffraction, and magnetometry. They adopt space group P4/nbm with a ≈ 9.78 and c ≈ 4.85 Å and become anti-ferromagnetic (x = 0.0, 1.5, 2.0) or weakly ferromagnetic (x = 0.5, 1.0) at 4.2 ≤ T ≤ 7.6 K. The ordered moments lie along [001] when x = 0.0 and in the (001) plane otherwise. The unit cell doubles along [001] when x = 1.5 and 2.0 order anti-ferromagnetically, but the doubling is lost when a first-order metamagnetic transition to weak ferromagnetism occurs on the application of a 10 kOe magnetic field. The ordered moments at 1.6 K for x = 0.0 and 2.0 are 4.61(2) and 2.58(2) μB, respectively; the corresponding effective moments in the paramagnetic phase are 5.91 and 5.36 μB
Constructing Concentration and Temperature Controllable Blue-Green Emission in a Single-Component Solid-State Phosphor
No full textControlling
dopant ion concentration and temperature are two effectual
methods to achieve color tuning and obtain white photoluminescent
phosphors. Research of the emission manipulation by both concentration
and temperature remains insufficient. In this work, we utilize the
host defect emission and rare-earth ion emission in Y2CaGe4O12:Tb3+ under various temperatures
to obtain a series of blue-green emissions widely distributed on the
Commission Internationale de L’Eclairage (CIE) map. Concentration
and thermal responses of the blue and the green emissions were analyzed
and the host to dopant energy transfer shows significant at low doping
concentration (<0.5%) and low temperature (<300 K). The overall
luminescent behavior suggests the blue and the green emissions could
be treated individually. A mathematical description (R2 = 0.982) was given to illustrate the successful controlling
of emission by concentration and temperature and several cold white
lights were observed at various conditions
Chassis Dynamometer and On-Road Evaluations of Emissions from a Diesel-Electric Hybrid Bus
No full text
Neuroimaging with light field microscopy: a mini review of imaging systems
No full textLight-field microscopy is an emerging technique that allows fast-speed volumetric imaging of the sample at microscale resolution. In the past years, the parallel development of light-field microscopy and genetically encoded calcium sensors has enabled a variety of fast-speed and large-scale neuroimaging at high resolution and sensitivity. These neuroimaging techniques have greatly enhanced our understanding of the mechanism under brain function and expedited our steps of decoding brain patterns. This review provides an overview of different versions of light-field microscopy used in neural imaging, and also offers a historic development outline of genetically encoded calcium sensors. Following that, the review intensively discussed light-field imaging of zebrafish neural activity. In the last section, we summarized the review and also envisioned the future of volumetric neuroimaging
Comparison of Particulate Emissions of a Range Extended Electric Vehicle under Different Energy Management Strategies
No full text- …
