Observation of edge states derived from topological helix chains.

Introducing the concept of topology has revolutionized materials classification, leading to the discovery of topological insulators and Dirac-Weyl semimetals1-3. One of the most fundamental theories underpinning topological materials is the Su-Schrieffer-Heeger (SSH) model4,5, which was developed in 1979-decades before the recognition of topological insulators-to describe conducting polymers. Distinct from the vast majority of known topological insulators with two and three dimensions1-3, the SSH model predicts a one-dimensional analogue of topological insulators, which hosts topological bound states at the endpoints of a chain4-8. To establish this unique and pivotal state, it is crucial to identify the low-energy excitations stemming from bound states, but this has remained unknown in solids because of the absence of suitable platforms. Here we report unusual electronic states that support the emergent bound states in elemental tellurium, the single helix of which was recently proposed to realize an extended version of the SSH chain9,10. Using spin- and angle-resolved photoemission spectroscopy with a micro-focused beam, we have shown spin-polarized in-gap states confined to the edges of the (0001) surface. Our density functional theory calculations indicate that these states are attributed to the interacting bound states originating from the one-dimensional array of SSH tellurium chains. Helices in solids offer a promising experimental platform for investigating exotic properties associated with the SSH chain and exploring topological phases through dimensionality control.

Evolution of Electronic States and Emergence of Superconductivity in the Polar Semiconductor GeTe by Doping Valence-Skipping Indium.

GeTe is a chemically simple IV-VI semiconductor which bears a rich plethora of different physical properties induced by doping and external stimuli. Here, we report a superconductor-semiconductor-superconductor transition controlled by finely-tuned In doping. Our results reveal the existence of a critical doping concentration x_{c}=0.12 in Ge_{1-x}In_{x}Te, where various properties, including structure, resistivity, charge carrier type, and the density of states, take either an extremum or change their character. At the same time, we find indications of a change in the In-valence state from In^{3+} to In^{1+} with increasing x by core-level photoemission spectroscopy, suggesting that this system is a new promising playground to probe valence fluctuations and their possible impact on structural, electronic, and thermodynamic properties of their host.

Element Selectivity in Second-Harmonic Generation of GaFeO_{3} by a Soft-X-Ray Free-Electron Laser.

Nonlinear optical frequency conversion has been challenged to move down to the extreme ultraviolet and x-ray region. However, the extremely low signals have allowed researchers to only perform transmission experiments of the gas phase or ultrathin films. Here, we report second harmonic generation (SHG) of the reflected beam of a soft x-ray free-electron laser from a solid, which is enhanced by the resonant effect. The observation revealed that the double resonance condition can be met by absorption edges for transition metal oxides in the soft x-ray range, and this suggests that the resonant SHG technique can be applicable to a wide range of materials. We discuss the possibility of element-selective SHG spectroscopy measurements in the soft x-ray range.

Antiferromagnetic topological insulator with selectively gapped Dirac cones.

Antiferromagnetic (AF) topological materials offer a fertile ground to explore a variety of quantum phenomena such as axion magnetoelectric dynamics and chiral Majorana fermions. To realize such intriguing states, it is essential to establish a direct link between electronic states and topology in the AF phase, whereas this has been challenging because of the lack of a suitable materials platform. Here we report the experimental realization of the AF topological-insulator phase in NdBi. By using micro-focused angle-resolved photoemission spectroscopy, we discovered contrasting surface electronic states for two types of AF domains; the surface having the out-of-plane component in the AF-ordering vector displays Dirac-cone states with a gigantic energy gap, whereas the surface parallel to the AF-ordering vector hosts gapless Dirac states despite the time-reversal-symmetry breaking. The present results establish an essential role of combined symmetry to protect massless Dirac fermions under the presence of AF order and widen opportunities to realize exotic phenomena utilizing AF topological materials.

Self-energy on the low- to high-energy electronic structure of correlated metal SrVO3.

The correlated electronic structure of SrVO(3) has been investigated by angle-resolved photoemission spectroscopy using in situ prepared thin films. Pronounced features of band renormalization have been observed: a sharp kink ∼60 meV below the Fermi level (E(F)) and a broad so-called "high-energy kink" ∼0.3 eV below E(F) as in the high-T(c) cuprates, although SrVO(3) does not show magnetic fluctuations. We have deduced the self-energy in a wide energy range by applying the Kramers-Kronig relation to the observed spectra. The obtained self-energy clearly shows a large energy scale of ∼0.7 eV, which is attributed to electron-electron interaction and gives rise to the ∼0.3 eV kink in the band dispersion as well as the incoherent peak ∼1.5 eV below E(F). The present analysis enables us to obtain a consistent picture for both the incoherent spectra and the band renormalization.

Resonant tunneling driven metal-insulator transition in double quantum-well structures of strongly correlated oxide.

The metal-insulator transition (MIT), a fascinating phenomenon occurring in some strongly correlated materials, is of central interest in modern condensed-matter physics. Controlling the MIT by external stimuli is a key technological goal for applications in future electronic devices. However, the standard control by means of the field effect, which works extremely well for semiconductor transistors, faces severe difficulties when applied to the MIT. Hence, a radically different approach is needed. Here, we report an MIT induced by resonant tunneling (RT) in double quantum well (QW) structures of strongly correlated oxides. In our structures, two layers of the strongly correlated conductive oxide SrVO3 (SVO) sandwich a barrier layer of the band insulator SrTiO3. The top QW is a marginal Mott-insulating SVO layer, while the bottom QW is a metallic SVO layer. Angle-resolved photoemission spectroscopy experiments reveal that the top QW layer becomes metallized when the thickness of the tunneling barrier layer is reduced. An analysis based on band structure calculations indicates that RT between the quantized states of the double QW induces the MIT. Our work opens avenues for realizing the Mott-transistor based on the wave-function engineering of strongly correlated electrons.

Surface Proton Conduction of Sm-Doped CeO2-δ Thin Film Preferentially Grown on Al2O3 (0001).

Sm-doped CeO2-δ (Ce0.9Sm0.1O2-δ; SDC) thin films were prepared on Al2O3 (0001) substrates by radio frequency magnetron sputtering. The prepared thin films were preferentially grown along the [111] direction, with the spacing of the (111) plane (d111) expanded by 2.6% to compensate for a lattice mismatch against the substrate. The wet-annealed SDC thin film, with the reduced d111 value, exhibited surface protonic conduction in the low-temperature region below 100 °C. The O1s photoemission spectrum exhibits H2O and OH- peaks on the SDC surface. These results indicate the presence of physisorbed water layers and the generation of protons on the SDC (111) surface with oxygen vacancies. The protons generated on the SDC surface were conducted through a physisorbed water layer by the Grotthuss mechanism.

Switching of band inversion and topological surface states by charge density wave.

Topologically nontrivial materials host protected edge states associated with the bulk band inversion through the bulk-edge correspondence. Manipulating such edge states is highly desired for developing new functions and devices practically using their dissipation-less nature and spin-momentum locking. Here we introduce a transition-metal dichalcogenide VTe2, that hosts a charge density wave (CDW) coupled with the band inversion involving V3d and Te5p orbitals. Spin- and angle-resolved photoemission spectroscopy with first-principles calculations reveal the huge anisotropic modification of the bulk electronic structure by the CDW formation, accompanying the selective disappearance of Dirac-type spin-polarized topological surface states that exist in the normal state. Thorough three dimensional investigation of bulk states indicates that the corresponding band inversion at the Brillouin zone boundary dissolves upon the CDW formation, by transforming into anomalous flat bands. Our finding provides a new insight to the topological manipulation of matters by utilizing CDWs' flexible characters to external stimuli.

Epitaxial synthesis and physical properties of double-perovskite oxide Sr2CoRuO6 thin films.

We report epitaxial structures and physical properties of double-perovskite Sr2CoRuO6 films grown using pulsed-laser deposition. Samples with a degree of Co/Ru order of 2-73% were obtained by changing growth temperature. X-ray absorption spectroscopy (XAS) on the highest ordered sample revealed that Co ions were trivalent with a high-spin configuration and Ru ions were pentavalent. We found large differences in magnetization and resistivity between the highest and lowest ordered samples as well as the absence of strong magnetism and metallicity, which are common characteristics of SrCoO3 and SrRuO3. Using resonant photoemission spectroscopy and XAS, dominant d-orbital components at the top of the occupied state (the bottom of the unoccupied state) were identified to be Ru 4d t 2g (Co 3d and Ru 4d t 2g ). These results suggest that the ground state of double-perovskite Sr2CoRuO6 is a ferrimagnetic insulator.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in bronchial squamous preinvasive lesions.

Metalloproteinases and their inhibitors are known to play an important role in the extracellular matrix remodeling associated with preinvasive lesions and invasive carcinomas; however, little is known about their role in early lung carcinoma. Immunohistochemical studies were made of the reactivity of bronchial squamous preneoplastic lesions from cigarette smokers, including basal cell hyperplasia, squamous metaplasia, dysplasia, carcinoma in situ, and invasive squamous cell carcinoma for matrix metalloproteinases (MMPs), their tissue inhibitors (TIMPs), and type IV collagen in 13 patients. Staining for type IV collagen disclosed discontinuities in basement membranes from basal cell hyperplasia to dysplasia, progressing to destruction in carcinoma in situ and invasive carcinoma. Reactivity for MMP-9 was mild in basal cell hyperplasia and squamous metaplasia, increasing in carcinoma in situ and invasive carcinoma. In contrast, reactivity for MMP-1 was strong in basal cell hyperplasia and squamous metaplasia, decreasing in carcinoma in situ and invasive carcinoma. Some neoplastic cells in carcinoma in situ and invasive carcinoma were MMP-3 positive. Staining for MMP-2 and TIMP-1 was moderate to strong in all squamous preinvasive lesions. Confocal microscopy showed MMP-9-positive cells passing through fragmented basement membranes in which type IV collagen and MMP-9 were colocalized. Type IV collagen colocalized with MMP-2 in all lesions and with TIMP-1 in basal cell hyperplasia and squamous metaplasia. The inverse relationships between the reactivity for MMP-1 and MMP-9 with progression of bronchial squamous preinvasive lesions suggest important roles for these MMPs in basement membrane remodeling in these lesions.

Comprehensive evaluation of 35 patients with lymphangioleiomyomatosis.

OBJECTIVES: To evaluate comprehensively the characteristics of lymphangioleiomyomatosis (LAM), with emphasis on the application of imaging and immunohistochemical methods. DESIGN: Prospective study. PATIENTS: Thirty-five female subjects with LAM. SETTING: Clinical Center, National Institutes of Health. INTERVENTIONS: BAL, pulmonary function test, ventilation/perfusion lung scans, CT of the chest and abdomen, ultrasonography of abdomen, and immunohistochemical study of lung biopsy specimens. RESULTS: Most patients had exertional dyspnea (83%) and pneumothorax (69%). BAL did not show diagnostic changes. The most common abnormalities on pulmonary function tests were decreased diffusing capacity of carbon monoxide (83%), hypoxemia (57%), and airway obstruction (51%). Bronchodilator response was found in 26% of patients. CT, which is almost pathognomonic, showed numerous thin-walled cysts throughout both lungs in all patients. Thirty-four patients (97%) had abnormal ventilation and/or perfusion lung scans. An unusual "speckling" pattern was observed on ventilation scans of 74% of patients. Common extrapulmonary features were retroperitoneal adenopathy (77%) and renal angiomyolipomas (60%). The percentage of abnormal smooth muscle cells (LAM cells), reactive with HMB45, varied from 17 to 67% in 10 lung biopsy specimens. CONCLUSIONS: Improved diagnostic methods have defined the abnormalities in patients with pulmonary LAM and increased the potential for early recognition and treatment of this disorder. Patients with LAM should be evaluated for bronchodilator responsiveness and may benefit from a trial of bronchodilators.

Synchronous appearance of fibronectin, integrin alpha 5 beta 1, vinculin and actin in epithelial cells and fibroblasts during rat tracheal wound healing.

The distribution of integrin alpha 5 beta 1 (alpha 5 beta 1) and associated components during wound healing was investigated in the rat trachea following mechanical injury. Under anesthesia, the ventral surface of the trachea was scratched, and tissue specimens were obtained from 6 h to 3 weeks after injury and studied using light and electron microscopy and immunohistochemistry. alpha 5 beta 1, vinculin and actin in regenerating epithelial cells and extracellular fibronectin appear virtually simultaneously after injury (from 12 h to 7 days) as do alpha 5 beta 1, vinculin and alpha-smooth muscle actin in fibroblasts and cellular fibronectin in granulation tissue (from 3 to 10 days). Immunoelectron microscopy 2 days after injury showed that alpha 5 beta 1 and vinculin were localized on the basal and lateral surfaces of regenerating epithelial cells and fibroblast surfaces, and fibronectin was localized just under the regenerating epithelial cells, around collagen fibrils and sporadically around fibroblasts. Bromodeoxyuridine labeling showed that the appearance of these components was associated with the period of cell proliferation. The appearances of fibronectin, alpha 5 beta 1, vinculin and actin in regenerating epithelial cells and fibroblasts during tracheal wound healing are well coordinated. During the initial cell migration phase, plasma fibronectin may stimulate cell migration before cellular fibronectin is produced in situ, and regenerating epithelial cells appear to begin to migrate into the wound before cell proliferation starts.

Unexpected extraction of a ventricular septal defect patch without an interventricular shunt.

We report the case of a mediastinocutaneous fistula, 13 years after the total correction of tetralogy of Fallot. During a fistula curettage operation, we unexpectedly extracted a ventricular septal defect patch. An interventricular shunt was not detected after the operation. The patient is well 3 years after the last operation.

Traumatic laceration of a saphenous vein graft: successful surgical repair.

Traumatic laceration of a saphenous vein grafted for coronary artery bypass is extremely rare. Successful surgical repair of a laceration was performed in a 64-year-old man who developed retrosternal hematoma from a saphenous vein graft after blunt injury to the chest.

Immunohistochemical analysis of proteins of the Bcl-2 family in pulmonary lymphangioleiomyomatosis: association of Bcl-2 expression with hormone receptor status.

BACKGROUND: Pulmonary lymphangioleiomyomatosis (LAM), a disease of young women, is characterized by proliferation of abnormal smooth muscle cells (LAM cells), which often differ from normal pulmonary smooth muscle cells by frequently having estrogen and progesterone receptors. OBJECTIVE: To evaluate the relationships among several factors related to proliferation and apoptosis in LAM cells, we employed immunohistochemical methods for the localization of Bcl-2 and Mcl-1 (inhibitors of apoptosis), Bax (a promoter of apoptosis), c-Myc (an apoptosis-related oncoprotein), proliferating cell nuclear antigen (an indicator of mitotic activity), and nick end labeling (to identify apoptotic cells) in lung tissues of 9 patients with LAM. RESULTS: In all patients, most LAM cells reacted positively for Bax. The LAM cells were positive for both Bcl-2 and estrogen receptor in 5 patients, positive for only Bcl-2 in 1 patient, positive for only estrogen receptor in another patient, and negative for both in 2 patients. More than 50% of the Bcl-2-positive LAM cells were also positive for estrogen receptor. The reaction for c-Myc was positive in all patients. The immunoreactivity for Bcl-2 and Mcl-1, which inhibit apoptosis, was more intense in LAM cells than in normal vascular and bronchial smooth muscle cells. In 6 patients, more than 50% of the LAM cells were positive for proliferating cell nuclear antigen. Apoptosis was infrequent in LAM cells. CONCLUSIONS: Our results suggest that the expression of Bcl-2 in LAM cells may be related to hormonal regulation, and that by decreasing apoptosis, Bcl-2 and related proteins contribute to the imbalance between proliferation and death of LAM cells.

[Sudden death due to massive pulmonary thromboembolism after pneumonectomy; report of a case].

A 76-year-old woman underwent a left pneumonectomy for a primary adenocarcinoma. On the fourth postoperative day, when walking to the toilet, she suddenly developed syncope followed by dyspnea and cardiopulmonary arrest. Although we performed cardiopulmonary resusciation, she died 1 hour later. With her family's approval, we performed autopsy. We found massive pulmonary thromboembolism was identified in the right main artery. To prevent postoperative thromboembolic complications, we use postoperatively continuous intravenous heparin sodium infusion (5,000-6,000/24 h) for the patients underwent thoracotomy and examine the ultrasonography for deep vein thrombosis before they begin to walk.

[Experience of predeposit autologous blood transfusion and medication of recombinant human erythropoietin in pediatric open heart surgery].

To avoid using the homologous blood, 11 children between the age of 5 and 15 years donated autologous blood of 10 ml/kg of body weight (upper limit 400 ml) once a week for two weeks prior to elective open heart surgery. Five of 11 children received erythropoietin (100 U/kg of body weight) intravenously three times a week for two weeks. Only one patient experienced a mild donor reaction but no adverse effects occurred in erythropoietin therapy. In all the patients cardiac operations were able to be completed without homologous blood transfusion. Patients treated with erythropoietin were not anemic despite of preoperative donation although without erythropoietin therapy patients were mildly anemic. Our experience documents safety and effectiveness of predeposit autologous blood transfusion and erythropoietin therapy in pediatrics.

[Application of epicardial approach technique to the anterior-paraseptal type Wolff-Parkinson-White syndrome].

The patient with the anterior-paraseptal type WPW syndrome was operated upon with closed heart technique (so-called epicardial approach) of cryosurgery. Following intraoperative electrophysiologic studies, with ultrasonic aspirator, the epiannular fat-pad of the anterior right atrium was completely dissected to the epicardial side of the tricuspid annulus. Then the anterior paraseptal accessory pathway on the tricuspid annulus was ablated by cryosurgery (-65 degrees C, 3 min, total 9 trials). With this method, cardiotomy and establishment of cardiopulmonary bypass were not necessary to divide the accessory pathway, and significant hemodynamic instability was not caused. But in the case of accessory pathway near interatrial septum (for example, anterior paraseptal or posteroseptal) WPW syndrome, although cryoprobe was applied just adjacent to the AV node, careful ECG monitoring throughout cryosurgery obviated the injury to the AV node.

[A case report of the pectoralis major muscle flap in the successful management of severe mediastinal infection].

A severe, post-mediansternotomy, mediastinitis was treated with pectoral muscle flap method. About 10 days after CABG this patient had purulent discharge, high fever, and unstable sternum. Under a diagnosis of mediastinitis, wound irrigation and systemic administration with antibiotics began, but these managements were ineffective. Therefore, we closed the chest primarily by the pectoral muscle flap method. Successful primary closure of the chest was accomplished.

Metallic quantum well states in artificial structures of strongly correlated oxide.

The quantum confinement of strongly correlated electrons in artificial structures provides a platform for studying the behavior of correlated Fermi-liquid states in reduced dimensions. We report the creation and control of two-dimensional electron-liquid states in ultrathin films of SrVO(3) grown on Nb:SrTiO(3) substrates, which are artificial oxide structures that can be varied in thickness by single monolayers. Angle-resolved photoemission from the SrVO(3)/Nb:SrTiO(3) samples shows metallic quantum well states that are adequately described by the well-known phase-shift quantization rule. The observed quantum well states in SrVO(3) ultrathin films exhibit distinctive features--such as orbital-selective quantization originating from the anisotropic orbital character of the V 3d states and unusual band renormalization of the subbands near the Fermi level--that reflect complex interactions in the quantum well.