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Biomedical subjects

M Tsubota

Publications and source records attributed to M Tsubota.

At least 19 recordsLinked to original sources
PubMed2006

Anomalous translational velocity of vortex ring with finite-amplitude Kelvin waves.

We consider finite-amplitude Kelvin waves on an inviscid vortex assuming that the vortex core has infinitesimal thickness. By numerically solving the governing Biot-Savart equation of motion, we study how the frequency of the Kelvin waves and the velocity of the perturbed ring depend on the Kelvin wave amplitude. In particular, we show that, if the amplitude of the Kelvin waves is sufficiently large, the perturbed vortex ring moves backwards.

Journal Article↗
PubMed2006

Twisted vortex state.

We study a twisted vortex bundle where quantized vortices form helices circling around the axis of the bundle in a "force-free" configuration. Such a state is created by injecting vortices into a rotating vortex-free superfluid. Using continuum theory we determine the structure and the relaxation of the twisted state. This is confirmed by numerical calculations. We also present experimental evidence of the twisted vortex state in superfluid 3He-B.

Journal Article↗
PubMed2006

Vortex multiplication in applied flow: A precursor to superfluid turbulence.

A surface-mediated process is identified in 3He-B which generates vortices at a roughly constant rate. It precedes a faster form of turbulence where intervortex interactions dominate. This precursor becomes observable when vortex loops are introduced in low-velocity rotating flow at sufficiently low mutual friction dissipation at temperatures below 0.5Tc. Our measurements indicate that the formation of new loops is associated with a single vortex interacting in the applied flow with the sample boundary. Numerical calculations show that the single-vortex instability arises when a helical Kelvin wave expands from a reconnection kink at the wall and then intersects again with the wall.

Journal Article↗
PubMed2005

Momentum dependence of charge excitations in the electron-doped superconductor Nd1.85 Ce0.15 CuO4: a resonant inelastic x-ray scattering study.

We report a resonant inelastic x-ray scattering (RIXS) study of charge excitations in the electron-doped high-T(c) superconductor Nd1.85 Ce0.15 CuO4. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with q-dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Journal Article↗
PubMed2004

Determination of the orbital polarization in YTiO3 by using soft X-ray linear dichroism.

We report measurements of linear dichroism in x-ray absorption at Ti L(2,3) edges of a Mott-insulating ferromagnet YTiO3, where orbital ordering occurs in the triply degenerate Ti 3d t(2g) states. Dichroic spectra and their integrated intensities are obtained for the incident electric field with polarizations parallel to a, b, and c axes. The comparison of the spectra with atomic multiplet calculations removes the ambiguity about the orbital polarization, i.e., the relative weights of |xy>, |yz>, and |zx> orbits, which are crucial for the origin of ferromagnetism. The result is consistent with the previous analysis of nuclear magnetic resonance in the Mizokawa-Fujimori scheme.

Journal Article↗
PubMed2003

An intrinsic velocity-independent criterion for superfluid turbulence.

Hydrodynamic flow in classical and quantum fluids can be either laminar or turbulent. Vorticity in turbulent flow is often modelled with vortex filaments. While this represents an idealization in classical fluids, vortices are topologically stable quantized objects in superfluids. Superfluid turbulence is therefore thought to be important for the understanding of turbulence more generally. The fermionic 3He superfluids are attractive systems to study because their characteristics vary widely over the experimentally accessible temperature regime. Here we report nuclear magnetic resonance measurements and numerical simulations indicating the existence of sharp transition to turbulence in the B phase of superfluid 3He. Above 0.60T(c) (where T(c) is the transition temperature for superfluidity) the hydrodynamics are regular, while below this temperature we see turbulent behaviour. The transition is insensitive to the fluid velocity, in striking contrast to current textbook knowledge of turbulence. Rather, it is controlled by an intrinsic parameter of the superfluid: the mutual friction between the normal and superfluid components of the flow, which causes damping of the vortex motion.

Journal Article↗
PubMed2002

Expression of MMP-8 and MMP-13 mRNAs in rat periodontium during tooth eruption.

The present study was designed to investigate mRNA expression of matrix metalloproteinase-8 (MMP-8) and MMP-13 in forming periodontium during tooth eruption in the rat. RT-PCR for the decalcified paraffin sections indicated expression of MMP-8 and MMP-13 in the periodontal tissues. In situ hydridization demonstrated expression of MMP-8 in osteoblasts, osteocytes, periodontal ligament cells, cementoblasts, and cementocytes along with collagen types I and III. In contrast, transcripts of MMP-13 were confined to a small population of osteoblasts and osteocytes in alveolar bone. The results suggested that MMP-8 may be involved in remodeling the periodontium during tooth eruption, and its expression may be coordinated with that of collagen types I and III, whereas the participation of MMP-13 may be rather limited.

Alveolar Process↗
PubMed2001

Two cases of off-pump coronary artery bypass grafting combined with abdominal aortic aneurysm repair.

Two cases of coronary artery disease coexisting with abdominal aortic aneurysm were treated with off-pump coronary artery bypass grafting combined with repair of the aneurysm. The first patient was a 67-year-old man exhibiting a large pulsating abdominal mass. Abdominal computed tomography demonstrated a 9-cm aneurysm and coronary angiogram revealed a 90% stenosis of the obtuse marginal branch for which percutaneous transluminal angioplasty could not be performed. He underwent simultaneous single coronary artery bypass grafting without cardiopulmonary bypass, and bifurcated graft replacement. The second patient was a 71-year-old man who had acute myocardial infarction, and one month later underwent coronary angiogram which revealed three vessel disease in the coronary artery. Computed tomography revealed a 4-cm aneurysm, and angiography showed a 90% stenosis of the left renal artery. He underwent a single stage operation that involved three coronary artery bypass grafting without cardiopulmonary bypass, straight graft replacement, and reconstruction of the left renal artery using the saphenous vein graft. The postoperative course was uneventful in both cases. We currently recommend a single stage operation involving off-pump coronary artery bypass grafting.

Aged↗
PubMed2000

Significance of percutaneous cardiopulmonary bypass support for volume reduction surgery with severe hypercapnia.

In patients with reduced respiratory function, lung resection is associated with high risk because separate ventilation is generally needed for safe management. For patients with end-stage emphysema, intraoperative respiratory management is important and particularly difficult because neither incomplete oxygenation nor selective ventilation can be performed, so the operation may be interrupted. In this study, we assess the effectiveness of the percutaneous cardiopulmonary support (PCPS) system for lung volume reduction surgery in patients with severe hypercapnia (arterial carbon dioxide tension >50 mm Hg) and discuss the significance of PCPS for patients who are beyond the standard criteria for lung volume reduction surgery (LVRS). We studied 3 patients with severe hypercapnia due to emphysema who underwent volume reduction surgery. One patient was previously treated surgically for contralateral pneumothorax. All patients had a severe smoking history and were suspected to have fragile lungs. During the operation. PCPS provided sufficient support flow. Intraoperative management using PCPS was easy, and no severe complications were observed. One patient exhibited severe hemodynamic deterioration on postoperative Day 15. Other patients' PaCO2 improved postoperatively. One had a calcification of a femoral artery, but there was no trouble inserting a cannula. Bilateral or unilateral volume reduction surgery was performed under PCPS in patients with end-stage emphysema. We conclude that PCPS is an adjunct to LVRS, useful for intraoperative management of some patients with severe hypercapnea, and the LVRS indications can be extended.

Aged↗
PubMed2000

[Malignant cardiac lymphoma].

A 65-year-old male was admitted to the hospital in shock. The transesophageal echocardiography showed cardiac tumor in the right atrium. The tumor was resected under cardiopulmonary bypass. It was diagnosed as malignant lymphoma of B-cell type by histological examination. After operation, his general condition became satisfactory. Then he received chemotherapy. Twenty days after operation, however, a mass appeared in the right side of chin. It was diagnosed as malignant lymphoma of the same cell type as in the heart. We searched his body with CT and Ga-scanning. No other lesions were found. After the chemotherapy (CHOP, 6 cycles), the mass disappeared. No recurrence was been observed for six months.

Aged↗
PubMed1998

Surgical Procedure for Right Anteroseptal Accessory Conduction Pathways in Wolff-Parkinson-White Syndrome.

In patients with Wolff-Parkinson-White syndrome, the right anteroseptal accessory conduction pathway is rare, and exists from the atrium to the ventricle in close anatomic proximity to the normal atrioventricular conduction system. Catheter ablation of this lesion is reported to interrupt atrioventricular node-His bundle conduction more easily than that of other lesions. At our institute, there were 10 patients with right anteroseptal accessory conduction pathway among 454 patients (2.2%) who underwent the surgical division of the accessory pathway. Our procedure involved the the endocardial approach with knife dissection and cryocoagulation. With the heart beating under normothermal cardiopulmonary bypass, delta wave disappearance was easily noted. Neither complete atrioventricular block nor recurrent conduction occurred. Cryoablation used by our endocardial surgical division, is a safe and accurate procedure.

Journal Article↗
PubMed1998

[A case of surgical treatment for Löffler's endomyocarditis].

We performed surgical treatment in a case of löffler's endocarditis. The patient was a 32-year-old male whose first symptom was easy fatigability. Blood count showed eosinophilia (eosinocyte count 6720/mm3). Echocardiography and vetriculography showed thickened bilateral endocardium and extension disturbance. We diagnosed this case as löffler's endocarditis and performed surgical treatment because medical treatment was unsuccessful. Removal of the thrombus the bilateral ventricles, endocardectomy and mitral valve replacement were performed. Endocardectomy required close attention because the border between thickened endocardium and normal myocardium was obscure. The patient survived surgery, but postoperative echocardiography (15 days) revealed slightly thickened endocardium of the right ventricle. He died of left heart failure 1 month after surgery. At that time, eosinocyte count was 110,000/mm3.

Adult↗
PubMed1998

[Significance of systemic inflammatory response syndrome after surgical treatment for thoracic esophageal cancer].

We studied the significance of Systemic Inflammatory Response Syndrome (SIRS) state after surgical treatment of thoracic esophageal cancer. From January 1991 to December 1995, 35 patients received thoracic esophageal cancer surgery. Thirty three patients (94.3%) were in the SIRS state after surgery and mean duration of SIRS was 3.4 days. Duration of SIRS was statistically longer in patients with pulmonary complications. Patients with hyperbilirubinemia (> or = 3.0 mg/dl) after surgery had longer duration of SIRS. Induction therapy did not affect the duration of SIRS. Collectively, duration of SIRS is an indication of complications, especially of pulmonary complications, after surgical treatment of thoracic esophageal cancer, and blood bililubin score after surgery correlates to duration of SIRS. These suggest that we must pay special attention to patients with long duration of SIRS or hyperbilirubinemia after thoracic esophageal surgery.

Aged↗
PubMed1998

[Advantages and disadvantages of harmonic scalpel in thoracic surgery].

We evaluated the usefulness of Harmonic Scalpel in thoracic surgery. Harmonic Scalpel is an ultrasonically activated surgical device which can coagulate and cut the vessels or tissues. The instrument made thoracoscopic resection of the neurogenic tumor and the mediastinal lymph node and thoracoscopic sympatectomy safetier and easier, because it does not conduct an electric current to the nerve and has high ability of hemostasis. Harmonic Scalpel will be very useful device in the future if its shapes of blades or handpieces are improved.

Aged↗
PubMed1998

[Treatment of mediastinal infection by continuous closed irrigation with an antibiotic solution in a new bone baby].

The patient was a three-week-old girl. Four days after thoracic surgery, mild fever developed, and turbid fluid was drained from the incision. Culture of the discharge showed Pseudomonas aeruginosa and Serratia marcescens. Débridement was immediately performed and continuous closed irrigation with an antibiotic solution started and maintained for 17 days. During this period, the upper half of the body was elevated. Ten days after irrigation started culture of the drainage fluid became negative. We emphasize early diagnosis, and the usefulness of continuous closed irrigation with an antibiotic solution in neonates.

Drug Therapy, Combination↗
PubMed1997

[A case of Ellis-van Creveld syndrome with partial atrioventricular septal defect and double orifice mitral valve].

Ellis-van Creveld Syndrome (ECS) is characterized by chondrodysplasia, ectodermal dysplasia, polydactyly, and congenital cardiac defects. As congenital cardiac defects, single atrium and endocardial cusion defect are frequent in literatures. We described a case, a 68-year-old woman, presenting with ECS with partial atrioventricular septal defect and double orifice mitral valve. The partial atrioventricular septal defect was repaired by closure with a Dacron patch. The accessory orifice was located at the anterior cusp of the mitral valve, which was left, untouched, because no regurgitation had been detected preoperatively. Her postoperative course was uneventful, and the patient was discharged on 25th postoperative day.

Aged↗
PubMed1997

[A case of mediastinal angiomyolipoma].

A 53-year-old woman was referred to our hospital for further evaluation of a mediastinal tumor. The tumor was diagnosed as a mediastinal angiomyolipoma by computed tomography and angiographic findings. Transarterial embolization was performed three times, then the tumor was completely organized. Although angiomyolipomas are often found in the kidney, those in the mediastinum are very rare. Angiomyolipoma is a benign tumor, then small asymptomatic tumor may be conserved. When the tumor is large in size and has a high risk of spontaneous rupture, arterial embolization is valuable for treatment of the tumor.

Angiomyolipoma↗