Time-, spin-, and angle-resolved photoemission spectroscopy with a 1-MHz 10.7-eV pulse laser.

We describe a setup of time-, spin-, and angle-resolved photoemission spectroscopy (tr-SARPES) employing a 10.7 eV (λ = 115.6 nm) pulse laser at a 1 MHz repetition rate as a probe photon source. This equipment effectively combines the technologies of a high-power Yb:fiber laser, ultraviolet-driven harmonic generation in Xe gas, and a SARPES apparatus equipped with very-low-energy-electron-diffraction spin detectors. A high repetition rate (1 MHz) of the probe laser allows experiments with the photoemission space-charge effects significantly reduced, despite a high flux of 1013 photons/s on the sample. The relatively high photon energy (10.7 eV) also brings the capability of observing a wide momentum range that covers the entire Brillouin zone of many materials while ensuring high momentum resolution. The experimental setup overcomes the low efficiency of spin-resolved measurements, which gets even more severe for the pump-probed unoccupied states, and affords the opportunity to investigate ultrafast electron and spin dynamics of modern quantum materials with energy and time resolutions of 25 meV and 360 fs, respectively.

Publisher Correction: A weak topological insulator state in quasi-one-dimensional bismuth iodide.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A weak topological insulator state in quasi-one-dimensional bismuth iodide.

The major breakthroughs in understanding of topological materials over the past decade were all triggered by the discovery of the Z2-type topological insulator-a type of material that is insulating in its interior but allows electron flow on its surface. In three dimensions, a topological insulator is classified as either 'strong' or 'weak'1,2, and experimental confirmations of the strong topological insulator rapidly followed theoretical predictions3-5. By contrast, the weak topological insulator (WTI) has so far eluded experimental verification, because the topological surface states emerge only on particular side surfaces, which are typically undetectable in real three-dimensional crystals6-10. Here we provide experimental evidence for the WTI state in a bismuth iodide, ß-Bi4I4. Notably, the crystal has naturally cleavable top and side planes-stacked via van der Waals forces-which have long been desirable for the experimental realization of the WTI state11,12. As a definitive signature of this state, we find a quasi-one-dimensional Dirac topological surface state at the side surface (the (100) plane), while the top surface (the (001) plane) is topologically dark with an absence of topological surface states. We also find that a crystal transition from the ß-phase to the α-phase drives a topological phase transition from a nontrivial WTI to a normal insulator at roughly room temperature. The weak topological phase-viewed as quantum spin Hall insulators stacked three-dimensionally13,14-will lay a foundation for technology that benefits from highly directional, dense spin currents that are protected against backscattering.

Valley-dependent spin polarization in bulk MoS2 with broken inversion symmetry.

The valley degree of freedom of electrons is attracting growing interest as a carrier of information in various materials, including graphene, diamond and monolayer transition-metal dichalcogenides. The monolayer transition-metal dichalcogenides are semiconducting and are unique due to the coupling between the spin and valley degrees of freedom originating from the relativistic spin-orbit interaction. Here, we report the direct observation of valley-dependent out-of-plane spin polarization in an archetypal transition-metal dichalcogenide--MoS2--using spin- and angle-resolved photoemission spectroscopy. The result is in fair agreement with a first-principles theoretical prediction. This was made possible by choosing a 3R polytype crystal, which has a non-centrosymmetric structure, rather than the conventional centrosymmetric 2H form. We also confirm robust valley polarization in the 3R form by means of circularly polarized photoluminescence spectroscopy. Non-centrosymmetric transition-metal dichalcogenide crystals may provide a firm basis for the development of magnetic and electric manipulation of spin/valley degrees of freedom.

Electronic structure study of ultrathin Ag(111) films modified by a Si(111) substrate and √3 × âˆš3-Ag2Bi surface.

Angle-resolved photoemission spectroscopy experiments show that the electronic structure of a Ag(111) film grown on Si(111) is markedly perturbed by the formation of a √3 × âˆš3-Ag(2)Bi Rashba-type surface alloy. Four spin-split surface states, with different band dispersions and energy contours, intercept and hybridize selectively with the sp-derived quantum well states of the Ag layer. Detailed two-dimensional band mapping of the system was carried out and constant energy contours at different energies result in hexagonal-, star- and flower-like distortions of the quantum well states as a result of various interactions. Further wavy-like modulations of the electronic structure of the film are found to originate from umklapp reflections of the Ag film states according to the surface periodicity.

Enhanced silicon oxidation on titanium-covered Si(001).

We report on a core level photoemission study of the formation of an ultrathin SiO(x) layer grown at the interface of a titanium-covered Si(001) surface. Oxygen exposure at room temperature induces a large chemical shift of the Si 2p state, predominantly assigned to Si(4+). The results indicate that a SiO(2 - δ) layer, close to the stoichiometry of SiO(2), is formed below the TiO(x) film. The thickness of the SiO(2 - δ) layer is estimated to be ∼ 0.9 nm, corresponding to three to four oxide layers. Further chemical shift caused by annealing is attributed to the formation of titanium silicate (TiSi(x)O(y)).

New and reliable MRI diagnosis for progressive supranuclear palsy.

OBJECTIVE: To evaluate the area of the midbrain and pons on mid-sagittal MRI in patients with progressive supranuclear palsy (PSP), Parkinson disease (PD), and multiple-system atrophy of the Parkinson type (MSA-P), compare these appearances and values with those of normal control subjects, and establish diagnostic MRI criteria for the diagnosis of PSP. METHODS: The authors prospectively studied MRI of 21 patients with PSP, 23 patients with PD, 25 patients with MSA-P, and 31 age-matched normal control subjects. The areas of the midbrain tegmentum and the pons were measured on mid-sagittal MRI using the display tools of a workstation. The ratio of the area of the midbrain to the area of the pons was also evaluated in all subjects. RESULTS: The average midbrain area of the patients with PSP (56.0 mm2) was significantly smaller than that of the patients with PD (103.0 mm2) and MSA-P (97.2 mm2) and that of the age-matched control group (117.7 mm2). The values of the area of the midbrain showed no overlap between patients with PSP and patients with PD or normal control subjects. However, patients with MSA-P showed some overlap of the values of individual areas with values from patients with PSP. The ratio of the area of the midbrain to the area of pons in the patients with PSP (0.124) was significantly smaller than that in those with PD (0.208) and MSA-P (0.266) and in normal control subjects (0.237). Use of the ratio allowed differentiation between the PSP group and the MSA-P group. CONCLUSION: The area of the midbrain on mid-sagittal MRI can differentiate PSP from PD, MSA-P, and normal aging.

Evaluation of acetabular dysplasia using a top view of the hip on three-dimensional CT.

We assessed coverage over the femoral head, using three-dimensional computed tomography (CT) imaging on 20 hips in 18 patients before rotational acetabular osteotomy, and on 18 normal hips as control. In particular, we introduced a "top view of the hip" in three-dimensional CT evaluation in order to detect posterolateral deficiency, which needs special attention in regard to rotational transfer of the acetabular fragment. We determined the horizontal plane passing through 5 mm cranial to the top of the femoral head on the coronal view of a multiplanar reconstruction image. Then, we erased the images of the ilium that were more cranial than this horizontal plane from the conventional cranial view of the pelvis and the proximal femur, and defined this view as the "top view of the hip". This top view clearly showed any uncovered area on the femoral head. Of the 20 hips, 6 were deficient anterolaterally (anterolateral type), 9 were deficient laterally (lateral type), and 5 were deficient posterolaterally (posterolateral type). On plain anteroposterior radiographs, 7 of the 20 hips had the cross-over sign of Reynolds. Five of these 7 hips with the cross-over sign were the posterolateral type in top view, while none of the 13 hips without the cross-over sign was the posterolateral type. We recommend preoperative evaluation using a top-view on three-dimensional CT images in patients who have the cross-over sign on an anteroposterior radiograph.

Emergent right coronary artery thrombectomy with a jet aspiration thrombectomy catheter.

A saline-jet aspiration thrombectomy (JAT) catheter was used in a patient with acute myocardial infarction. A right coronary arteriogram showed complete thrombotic occlusion at the proximal segment. With this catheter the thrombus was removed without complications in 5 sec. The patient underwent percutaneous transluminal coronary angioplasty and placement of a Palmaz-Schatz stent after successful thrombectomy. Thrombectomy with a JAT catheter was very useful in this patient.

[Minimum intensity projection image and curved reformation image of the main pancreatic duct obtained by helical CT in patients with main pancreatic duct dilation].

Contrast enhanced CT was performed in seven patients with pancreatic disease (chronic pancreatitis, n = 3; pancreatic head cancer, n = 2; mucin-producing pancreatic tumor, n = 2) who showed dilation of the main pancreatic duct (MPD) Minimum intensity projection (Min-IP) images of the pancreas were obtained using multi-projection volume reconstruction (MPVR) software by selecting an oblique slab that contained the entire MPD. Curved reformation (CR) images were obtained using multiplanar reformation (MPR) software by tracing the MPD on the Min-IP image. Both Min-IP images and CR images clearly showed the dilated main pancreatic duct in all seven patients. In three of the seven, obstruction of the MPD in the pancreatic head and the cause of obstruction (tumor mass, n = 2; caliculus, n = 1) were also clearly seen. Min-IP and CR images seem to be useful for the diagnosis of pancreatic diseases.

Intramuscular solitary fibrous tumor: a clinicopathological case study.

We present a case of extrapleural solitary fibrous tumor arising within the muscle, an unusual and hitherto-undescribed tumor lesion. A 42-year-old woman presented a painless mass in her left thigh. The lesion was depicted as an intramuscular mass that enhanced on both CT and MRI, showing quite rich tumor vascularity. The histological features of the tumor were spindle cell proliferation with various histological patterns, typical fibrocollagenous background, and positive immunoreactivity for CD-34.

Retroperitoneal malignant mesenchymoma: imaging findings in five cases.

BACKGROUND: To describe computed tomographic (CT), magnetic resonance (MR), ultrasonographic (US), and angiographic findings of retroperitoneal malignant mesenchymoma with emphasis on CT findings. METHODS: Five CT, four US, four angiography, and two MR studies were obtained in five patients with pathologically proven retroperitoneal malignant mesenchymoma. RESULTS: Tumors were larger than 10 cm (n = 4), well-circumscribed and heterogeneous (n = 4), and with massive intratumorous calcifications (n = 3) on plain CT or US. Tumors showed heterogeneous enhancement on contrast-enhanced CT scans (n = 4) and moderate hypervascularity with heterogeneous staining on angiography (n = 3). Tumors were essentially hypointense on T1-weighted MR images (n = 2) and heterogeneous hyperintense on T2-weighted MR images (n = 2). Plain CT showed a fat-dense structure in a tumor in one patient. CONCLUSIONS: The radiologic findings of large expansile heterogeneous masses in the retroperitoneum, especially with massive calcifications, were considered to be typical of malignant mesenchymomas.

Hydraulic analysis of the functional properties of saline-jet aspiration thrombectomy catheters.

The purpose of this paper is to clarify the functional properties of a saline-jet aspiration thrombectomy catheter based on hydraulics. This catheter, developed by the authors, aspirates intravascular thrombi by means of the effect of a high-speed jet. We have derived the relationships between Qs, Qa, and p(n), where Qs is the water supply rate, Qa is the water aspiration rate and p(n) is the negative pressure created in the distal lumen of the catheter. The relationships are represented by simple equations using c1 and c2, where c1 and c2 are coefficients proper to the catheter. We have obtained c1 and c2 experimentally for three types of catheter with different distal shapes. Two practical conclusions are derived from this study. First, making a short taper at the distal end increases the negative pressure created and is advantageous for thrombus aspiration. Second, making the diameter of the inner tube and nozzle smaller is essential for improving the aspiration ability of the catheter.

A new compact spin- and angle-resolving photoelectron spectrometer with a high efficiency.

A portable spin- and angle-resolving photoelectron spectrometer has been constructed, equipped with a newly developed compact retarding-potential Mott-scattering electron spin polarimeter with an efficiency of 1.9 x 10(-4) for a gold target. Based on Monte Carlo calculations for the spin-dependent electron-scattering process and electron ray-tracing calculations, a novel design of the retarding-field electron optics with 0.59 sr collection solid angle for scattered electrons has been accomplished. Utilizing this spectrometer, the spin- and angle-resolved photoelectron spectra have been measured and the spin-dependent electronic structure of Ni(110), Ni(110)-p(2 x 1)O and Ni(110)-c(2 x 2)S along the ${\overline {\Gamma S}}$ line of the Ni(110) surface Brillouin zone have been studied.

[Three-dimensional images of hepatic tumors and hepatic vessels obtained by helical computed tomography].

Helical computed tomography was performed with intravenous contrast material administration in ten patients with hepatic tumors (metastatic tumor, n = 6; hepatocellular carcinoma, n = 4). Maximum intensity projection (MIP) images of intrahepatic portal venous branches and hepatic veins, and shaded surface display (SSD) images of the hepatic tumors were reconstructed for each patient. The MIP image and SSD image were fitted to overlap on a single display to obtain three-dimensional (3-D) images showing both the hepatic vessels and hepatic tumors. Subsegmental localization of the tumors determined from the 3-D images proved to be correct in all of the six patients who received hepatic resection after examination. 3-D images seem to be useful for preoperative assessment of hepatic tumors.

Test performances of three diagnostic procedures in evaluating thyroid nodules: physical examination, ultrasonography and fine needle aspiration cytology.

A retrospective study was performed to determine the reliability of physical examination (PE), ultrasonography (US) and fine-needle aspiration cytology (FNA) in the evaluation of thyroid nodules. Preoperative diagnoses of 252 euthyroid patients comprised 126 with benign lesions, 114 with papillary carcinoma and 12 with follicular carcinoma made by PE, US and FNA were reviewed. The specificity of PE, US and FNA for malignancy was 98%, 90% and 98%, respectively. The sensitivity of PE, US and FNA for malignancy was 63%, 78% and 80%. The sensitivity for papillary carcinoma of the three procedures was 68%, 83%, 88%, whereas that for follicular carcinoma was 25%, 25%, 8%, respectively. When all the test results were negative, the likelihood ratio favoring papillary carcinoma was 0.008 whereas that favoring follicular carcinoma was 0.6. The histological category of carcinoma should be considered when evaluating diagnostic procedures for thyroid nodules. No negative test result is conclusive for ruling out the possibility of follicular carcinoma.

Ultrasonographic features of recurrent parotitis in childhood.

Six children with recurrent parotitis were studied by ultrasound. Of the 12 parotid glands thus observed, 5 were swollen and 7 were not enlarged. Multiple round hypoechoic areas measuring 2-4 mm in diameter were seen in all 5 enlarged parotid glands and in 5 non-enlarged glands. These small hypoechoic areas were larger than the punctate pools of contrast medium shown by sialography. We consider that these hypoechoic areas represented both peripheral sialectasis and surrounding lymphocytic infiltration. We propose that ultrasonography may be useful for the diagnosis and follow-up of recurrent parotitis in childhood.

Anomalous left brachiocephalic vein: CT findings.

Eight cases of anomalous position of the left brachiocephalic vein were demonstrated by CT. Six coursed downward lateral to and below the aortic arch to enter the superior vena cava (SVC). Two cases were double left brachiocephalic veins. The superior branch was in the normal position, but the inferior vessel coursed below the aortic arch. Most of these subaortic left brachiocephalic veins enter the SVC at the same level or caudal to the azygous arch. Only two cases were associated with congenital heart disease. This anomalously positioned vessel is asymptomatic but must be distinguished from the pulmonary artery and persistent left SVC, especially when open heart surgery for cardiac malformations is being considered.

[A case of tuberculous arthritis of shoulder].

A rara case of tuberculous arthritis of right shoulder was reported. Plain X ray and CT showed bone destruction in humerus and glenoid process and soft tissue swelling with calcification was also demonstrated. T2 weighted images showed extension of abscess clearly. And extension to bone marrow was showed on CT and T1 weighted MR images.

[MR imaging of splenic masses].

It has been reported that MR imaging of the spleen is unsuccessful in detecting focal lesions because there is not a significant difference in relaxation times between most tumors and surrounding normal spleen. We reviewed the MR imaging of 15 patients (5 cysts, 2 abscesses, 1 hemangioma, 5 malignant lymphomas, 2 metastatic tumors). In all cases, the difference in signal intensities between splenic tissue and mass lesions permitted detection of splenic lesions on MR images. But, malignant lesions were less visible than benign lesions.