Itinerant U 5f band states in the layered compound UFeGa5 observed by soft X-ray angle-resolved photoemission spectroscopy

We have performed angle-resolved photoemission spectroscopy (ARPES) experiments on paramagnetic UFeGa5 using soft X-ray synchrotron radiation (hn=500eV) and derived the bulk- and U 5f-sensitive electronic structure of UFeGa5. Although the agreement between the experimental band structure and the LDA calculation treating U 5f electrons as being itinerant is qualitative, the morphology of the Fermi surface is well explained by the calculation, suggesting that the U 5f states can be essentially understood within the itinerant-electron model.Comment: 13 pages, 4 figur

Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nano-particles

We have studied the electronic structure of Zn$_{0.9}$Fe$_{0.1}$O nano-particles, which have been reported to show ferromagnetism at room temperature, by x-ray photoemission spectroscopy (XPS), resonant photoemission spectroscopy (RPES), x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD). From the experimental and cluster-model calculation results, we find that Fe atoms are predominantly in the Fe$^{3+}$ ionic state with mixture of a small amount of Fe$^{2+}$ and that Fe$^{3+}$ ions are dominant in the surface region of the nano-particles. It is shown that the room temperature ferromagnetism in the Zn$_{0.9}$Fe$_{0.1}$O nano-particles is primarily originated from the antiferromagnetic coupling between unequal amounts of Fe$^{3+}$ ions occupying two sets of nonequivalent positions in the region of the XMCD probing depth of $\sim$ 2-3 nm.Comment: Single column, 12 pages, 8 figures, 1 tabl

Photoemission and x-ray absorption studies of valence states in (Ni,Zn,Fe,Ti)3_{3}O4_{4} thin films exhibiting photo-induced magnetization

By means of photoemission and x-ray absorption spectroscopy, we have studied the electronic structure of (Ni,Zn,Fe,Ti)$_{3}$O$_{4}$ thin films, which exhibits a cluster glass behavior with a spin-freezing temperature $T_f$ of $\sim 230$ K and photo-induced magnetization (PIM) below $T_f$. The Ni and Zn ions were found to be in the divalent states. Most of the Fe and Ti ions in the thin films were trivalent (Fe$^{3+}$) and tetravalent (Ti$^{4+}$), respectively. While Ti doping did not affect the valence states of the Ni and Zn ions, a small amount of Fe$^{2+}$ ions increased with Ti concentration, consistent with the proposed charge-transfer mechanism of PIM.Comment: 4 pages, 4 figure

Electronic structure of Ga1−x_{1-x}Crx_{x}N and Si-doping effects studied by photoemission and X-ray absorption spectroscopy

The electronic structure of the magnetic semiconductor Ga$_{1-x}$Cr$_{x}$N and the effect of Si doping on it have been investigated by photoemission and soft x-ray absorption spectroscopy. We have confirmed that Cr in GaN is predominantly trivalent substituting for Ga, and that Cr 3$d$ states appear within the band gap of GaN just above the N 2$p$-derived valence-band maximum. As a result of Si doping, downward shifts of the core levels (except for Cr 2$p$) and the formation of new states near the Fermi level were observed, which we attribute to the upward chemical potential shift and the formation of a small amount of Cr$^{2+}$ species caused by the electron doping. Possibility of Cr-rich cluster growth by Si doping are discussed based on the spectroscopic and magnetization data.Comment: 5 pages, 3 figure

Local electronic structure of Cr in the II-VI diluted ferromagnetic semiconductor Zn1−x_{1-x}Crx_xTe

The electronic structure of the Cr ions in the diluted ferromagnetic semiconductor Zn$_{1-x}$Cr$_x$Te ($x=0.03$ and 0.15) thin films has been investigated using x-ray magnetic circular dichroism (XMCD) and photoemission spectroscopy (PES). Magnetic-field ($H$) and temperature ($T$) dependences of the Cr $2p$ XMCD spectra well correspond to the magnetization measured by a SQUID magnetometer. The line shape of the Cr $2p$ XMCD spectra is independent of $H$, $T$, and $x$, indicating that the ferromagnetism is originated from the same electronic states of the Cr ion. Cluster-model analysis indicates that although there are two or more kinds of Cr ions in the Zn$_{1-x}$Cr$_x$Te samples, the ferromagnetic XMCD signal is originated from Cr ions substituted for the Zn site. The Cr 3d partial density of states extracted using Cr $2p \to 3d$ resonant PES shows a broad feature near the top of the valence band, suggesting strong $s$,$p$-$d$ hybridization. No density of states is detected at the Fermi level, consistent with their insulating behavior. Based on these findings, we conclude that double exchange mechanism cannot explain the ferromagnetism in Zn$_{1-x}$Cr$_{x}$Te.Comment: Accepted for New Journal of Physics. Single column, 21 pages, 7 figure

High-resolution imaging of human atherosclerotic carotid plaques with micro18F-FDG PET scanning exploring plaque vulnerability

FDG-PET can be used to identify vulnerable plaques in atherosclerotic disease. Clinical FDG-PET camera systems are restricted in terms of resolution for the visualization of detailed inflammation patterns in smaller vascular structures. The aim of the study is to evaluate the possible added value of a high-resolution microPET system in excised carotid plaques using FDG. In this study, 17 patients with planned carotid endarterectomy were included. Excised plaques were incubated in FDG and subsequently imaged with microPET. Macrophage presence in plaques was evaluated semi-quantitatively by immunohistochemistry. Plaque calcification was assessed additionally with CT and correlated to FDG uptake. Finally, FDG uptake and macrophage infiltration were compared with patient symptomatology. Heterogeneous distributions and variable intensities of FDG uptake were found within the plaques. A positive correlation between the distribution of macrophages and the FDG uptake (r = 0.68, P <.01) was found. A negative correlation was found between areas of calcifications and FDG uptake (r = -0.84, P <.001). Ratio FDG(max) values as well as degree of CD68 accumulation were significantly higher in CVA patients compared with TIA or amaurosis fugax patients (P <.05) and CVA patients compared with asymptomatic patients (P <.05). This ex vivo study demonstrates that excised carotid plaques can be visualized in detail using FDG microPET. Enhancement of clinical PET/CT resolution for similar imaging results in patients is needed

Collagen-Binding Peptidoglycans Inhibit MMP Mediated Collagen Degradation and Reduce Dermal Scarring

Scarring of the skin is a large unmet clinical problem that is of high patient concern and impact. Wound healing is complex and involves numerous pathways that are highly orchestrated, leaving the skin sealed, but with abnormal organization and composition of tissue components, namely collagen and proteoglycans, that are then remodeled over time. To improve healing and reduce or eliminate scarring, more rapid restoration of healthy tissue composition and organization offers a unique approach for development of new therapeutics. A synthetic collagen-binding peptidoglycan has been developed that inhibits matrix metalloproteinase-1 and 13 (MMP-1 and MMP-13) mediated collagen degradation. We investigated the synthetic peptidoglycan in a rat incisional model in which a single dose was delivered in a hyaluronic acid (HA) vehicle at the time of surgery prior to wound closure. The peptidoglycan treatment resulted in a significant reduction in scar tissue at 21 days as measured by histology and visual analysis. Improved collagen architecture of the treated wounds was demonstrated by increased tensile strength and transmission electron microscopy (TEM) analysis of collagen fibril diameters compared to untreated and HA controls. The peptidoglycan's mechanism of action includes masking existing collagen and inhibiting MMP-mediated collagen degradation while modulating collagen organization. The peptidoglycan can be synthesized at low cost with unique design control, and together with demonstrated preclinical efficacy in reducing scarring, warrants further investigation for dermal wound healing