One-dimensional (1D) semiconductor metal oxide nanostructures, such as nanowires, nanobelts, and nanotubes, have attracted considerable attention due to their prominent electrical, optical, and chemical properties and potential applications in nanoscale electronic and optoelectronic devices. [1][2][3][4][5] However, the properties and applications of those nanomaterials are limited by their simple binary systems.[6] Therefore, synthesis of complex functional nanomaterials with controlled size and morphology, such as core/shell quantum dots, [7] nanowires and nanobelts, [8][9][10][11] heterostructures, [6,12] superlattices, [13] and nanotubes, [14][15][16] are highly desirable. Furthermore, 1Dternary nanocomposites, such as Zn 2 SnO 4 , [8][9][10]17] Zn 2 TiO 4 , [18] ZnGa 2 O 4 , [11,16] MgAl 2 O 4 , [14] CoFe 2 O 4 , [19] exhibit specific functions that are unattainable by common binary composites. Conventional synthesis methods of those ternary composites usually involve high-energy ball milling of two binary solid oxides [18] or a high-temperature solid reaction, [20,21] which are not suitable for 1D nanostructure growth. Only recently, syntheses of single-crystal ternary oxide nanowires and nanotubes have been achieved by using Ga 2 O 3 , MgO, or ZnO nanowires as template. [11,14,15] For face-centered cubic (fcc) nanostructures, twinning is probably the most common structural defect, especially in metal and metal alloy nanoparticles, [22,23] where two subcrystallites share a facet to form a mirror image of each other. Twinning is occasionally observed in binary systems, such as cubic ZnS and InP nanowires, [24,25] both of which have a preferential <111> growth direction. However, reports on the synthesis of twinned structures of fcc ternary nanowires are rare; [10] that is, the formation of twinned nanowires has yet to be revealed.Zinc titanate (Zn 2 TiO 4 ) is an inverse spinel, which has been used as a catalyst and pigment in industry. It is one of the leading regenerable catalysts and has been demonstrated to be a good sorbent for removing sulfur-related compounds at high temperature. [26,27] As a dielectric material, its physical, electrical, and optical properties have been studied for various applications. [21,28,29] In this Communication, we shall demonstrate a three-stage synthesis of twinned Zn 2 TiO 4 nanowires using ZnO nanowires as template, which could be further developed for controlled synthesis of ternary oxide nanostructures. Figure 1a-c shows the scanning electron microscopy (SEM) images of ZnO nanowires and ZnO/Ti core/shell nanowires before and after annealing, respectively. The as-grown ZnO nanowires shown in Figure 1a are randomly aligned, of about 40-60 nm in diameter, and 10 lm in length. It can be seen clearly that the morphology of the ZnO nanowires is reserved after coating with Ti (Fig. 1b). The surface is smooth and the diameter of the Ti-coated nanowires is increased to 70-100 nm. No aggregated Ti particles could be seen in Figure 1b, indicating a uniform deposition of Ti on ZnO ...

The source of hyperpolarized (HP) [13C]bicarbonate in the liver during metabolism of HP [1-13C]pyruvate is uncertain and likely changes with physiology. Multiple processes including decarboxylation through pyruvate dehydrogenase or pyruvate carboxylase followed by subsequent decarboxylation via phosphoenolpyruvate carboxykinase (gluconeogenesis) could play a role. Here we tested which metabolic fate of pyruvate contributed to the appearance of HP [13C]bicarbonate during metabolism of HP [1-13C]pyruvate by the liver in rats after 21 hours of fasting compared to rats with free access to food. The 13C NMR of HP [13C]bicarbonate was observed in the liver of fed rats, but not in fasted rats where pyruvate carboxylation and gluconeogenesis was active. To further explore the relative fluxes through pyruvate carboxylase versus pyruvate dehydrogenase in the liver under typical conditions of hyperpolarization studies, separate parallel experiments were performed with rats given non-hyperpolarized [2,3-13C]pyruvate. 13C NMR analysis of glutamate isolated from the liver of rats revealed that flux from injected pyruvate through pyruvate dehydrogenase was dominant under fed conditions whereas flux through pyruvate carboxylase dominated under fasted conditions. The NMR signal of HP [13C]bicarbonate does not parallel pyruvate carboxylase activity followed by subsequent decarboxylation reaction leading to glucose production. In the liver of healthy well-fed rats, the appearance of HP [13C]bicarbonate exclusively reflects decarboxylation of HP [1-13C]pyruvate via pyruvate dehydrogenase.

Purpose Chemical-shift imaging (CSI) has long been considered the gold standard method for in-vivo hyperpolarized 13C metabolite imaging because of its high sensitivity. However, CSI requires a large number of excitations so it is desirable to reduce the number of RF excitations and the total acquisition time. Methods Centric phase encoding and 3D compressed sensing methods were adopted into a CSI acquisition to improve efficiency and reduce the number of excitations required for imaging hyperpolarized metabolites. The new method was implemented on a GE MR750W scanner for routine real time metabolic imaging experiments. Results Imaging results from phantoms and in-vivo animals using hyperpolarized 13C tracers demonstrate that when the entire CSI data set is treated as a single object, compressed sensing can be satisfactorily applied to spectroscopic CSI. Centric k-space trajectory data collection also greatly improves the acquisition efficiency. This combination of compressed sensing CSI and acquisition time reduction was used to perform a hyperpolarized 13C dynamic study. Discussion Compressed sensing can be satisfactorily applied to conventional CSI in hyperpolarized 13C metabolite MR imaging to reduce the number of RF excitations and accelerate the imaging speed to take advantage of conventional CSI in providing high sensitivity and a large spectral bandwidth.