RESUMO
Rheumatoid meningitis is a rare neurological manifestation that is difficult to diagnose. Here we report a 77-year-old woman who developed a left hemiparesis because of an arachnoid cyst with rheumatoid meningitis. The patient had a 13 year history of rheumatoid arthritis, which had been successfully treated. She developed left hemiparesis and visited our hospital. MRI showed a high signal intensity lesion in the right frontal subarachnoid space and an arachnoid cyst on Fluid attenuated inversion recovery (FLAIR). A gadolinium enhanced T1 weighted image revealed associated abnormal enhancement. We removed the arachnoid cyst and diagnosed the patient as having rheumatoid meningitis. Her symptoms and MRI findings improved rapidly by methylprednisolone pulse therapy. Rheumatoid meningitis is rare, but a case of arachnoid cyst associated with rheumatoid meningitis was extremely rare. This is the first report of such a case.
Assuntos
Cistos , Meningite , Humanos , Feminino , Idoso , Hospitais , Meningite/etiologiaRESUMO
Early recurrent ischemic stroke (ERIS), as well as symptomatic intracranial hemorrhage (SICH) and progressive stroke (PS), causes early neurological deterioration. Here we report a case of a patient with right internal carotid artery (ICA) occlusion immediately after intravenous recombinant tissue plasminogen activator (rt-PA) treatment for left middle cerebral artery (MCA) occlusion. A 79-year-old woman with drowsiness, aphasia and right hemiparesis was brought to our hospital. MRI showed acute infarction in the left internal capsule and occlusion of the left middle cerebral artery. rt-PA was administered intravenously to the patient 2 hours after the onset of the event. Her consciousness disturbance and aphasia improved, but the right hemiparesis did not. We performed emergent endovascular thrombectomy, but the right ICA (cervical portion) was occluded during the surgery. Finally, the endovascular thrombectomy achieved the recanalization of the left MCA and right ICA. When performing intravenous thrombolysis, we should beware the possibility of re-occlusion and prepare for interventional treatment.
Assuntos
Acidente Vascular Cerebral , Ativador de Plasminogênio Tecidual , Humanos , Feminino , Idoso , Infarto da Artéria Cerebral Média/tratamento farmacológico , Infarto da Artéria Cerebral Média/complicações , Infarto da Artéria Cerebral Média/cirurgia , Artéria Carótida Interna/cirurgia , Resultado do Tratamento , Paresia/complicações , Artéria Cerebral MédiaRESUMO
Hemifacial spasm is commonly caused by compression of the facial nerve due to overlying vessels, and also due to various types of tumor or aneurysm, and other factors. It occurs, although rarely, as a secondary effect of cerebellar or brainstem shift resulting from a tumor. In such a case, the presence of a large tumor often leads to additional neurological deficits. We present a case of hemifacial spasm caused by a peritorcular type of large tentorial meningioma in the posterior fossa. A 68-year-old woman presented with right facial numbness 4 months ago and right hemifacial spasm 2 weeks ago. Upon visiting our hospital, she displayed no neurological deficits other than the right hemifacial spasm. MRI revealed a peritorcular type of large tentorial meningioma in the posterior fossa with perifocal edema. The right cerebellopontine cistern was narrowed, and the cerebellar tonsil was herniated. The right facial nerve ran adjacent to the anterior inferior cerebellar artery (AICA). Angiography showed that only the left posterior meningeal artery (PMA) flowed to the tumor. The loop of the right AICA extended into the right cerebellopontine cistern. After embolization of the PMA, the tumor was surgically removed, leading to an improvement in the patient's hemifacial spasm. Postoperative MRI confirmed complete removal of the tentorial meningioma without any contact with the right facial nerve. The hemifacial spasm was caused secondarily by the cerebellar or brainstem shift due to the large tentorial meningioma in the posterior fossa. This large tumor had not produced any other neurological deficits before the hemifacial spasm appeared. We report this case because it is extremely rare.
Assuntos
Espasmo Hemifacial , Neoplasias Meníngeas , Meningioma , Feminino , Humanos , Idoso , Espasmo Hemifacial/cirurgia , Espasmo Hemifacial/complicações , Meningioma/complicações , Meningioma/diagnóstico por imagem , Meningioma/cirurgia , Imageamento por Ressonância Magnética/efeitos adversos , Neoplasias Meníngeas/complicações , Neoplasias Meníngeas/diagnóstico por imagem , Neoplasias Meníngeas/cirurgiaRESUMO
The detailed changes in disc properties after intradiscal injection of condoliase remain controversial. At 3 and 9 months after administration, radiographic changes in discs were investigated. A total of 41 patients (men, 25; median age, 46 years) who underwent regular follow-up magnetic resonance imaging at 3 and 9 months after administration without additional invasive therapy were retrospectively investigated. The intensity changes of the nucleus pulposus based on the Pfirrmann disc grading system, midsagittal disc height, and maximum protrusion length of herniation were assessed. In addition, disc height changes were compared between 24 patients aged <50 years (young group) and 17 patients aged ≥50 years (over 50s group). The overall mean disc heights were 9.1, 7.5, and 7.6 mm preoperatively, at 3 months, and at 9 months, respectively, with a significant reduction at 3 months (P < 0.001) and no significant changes thereafter. The mean maximum protrusion length of herniation significantly and gradually decreased. The overall proportions of Pfirrmann disc grades after administration were equivalent between 3 and 9 months. However, the recovery from Pfirrmann disc grades IV to III was confirmed in 8 of 17 cases (47.1%) between 3 and 9 months, whereas 6 of 20 cases (30.0%) showed a decline from III to IV. Patients in the young group with pretreatment disc height >11 mm had the greatest reduction in disc height than the over 50s group. In conclusion, the clinical outcomes in the over 50s group were comparable to those in the young group after injection of condoliase, whereas young patients with higher disc were more susceptible to disc height reduction.
Assuntos
Deslocamento do Disco Intervertebral , Vértebras Lombares , Humanos , Deslocamento do Disco Intervertebral/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Feminino , Adulto , Vértebras Lombares/diagnóstico por imagem , Estudos Retrospectivos , Idoso , Disco Intervertebral/diagnóstico por imagem , Hialuronoglucosaminidase/administração & dosagem , Hialuronoglucosaminidase/uso terapêutico , Imageamento por Ressonância MagnéticaRESUMO
BACKGROUND: Endovascular revascularization has recently been established as a less invasive treatment method for chronic mesenteric ischemia. However, intestinal necrosis caused by distal embolization following this procedure has not been emphasized. CASE PRESENTATION: The present report describes a 59-year-old man who was treated with endovascular revascularization for chronic mesenteric ischemia. After the procedure, he was diagnosed with intestinal necrosis caused by distal embolization. Despite emergent bowel resection, he died on postoperative day 109. CONCLUSION: Although endovascular revascularization for chronic mesenteric ischemia is less invasive and may be suitable for high-risk patients, attention should be paid to avoid embolic complications that can cause intestinal infarction possibly leading to a fatal condition.
Assuntos
Embolia/etiologia , Procedimentos Endovasculares/efeitos adversos , Doenças do Íleo/etiologia , Isquemia/cirurgia , Doenças Vasculares/cirurgia , Evolução Fatal , Humanos , Doenças do Íleo/cirurgia , Masculino , Isquemia Mesentérica , Pessoa de Meia-Idade , Necrose/etiologiaRESUMO
OBJECTIVE: Hepatitis B virus (HBV) has been classified into 8 genotypes that have different geographic distributions. The clinical outcomes of acute hepatitis are dependent on genotype. The aim of this study was to investigate the distribution of HBV subgenotypes and basal core promoter (BCP)/precore (PC) regions in acute hepatitis patients in Central Vietnam to clarify the distributions and the clinical and virological differences. METHODS: 27 patients with acute hepatitis B were studied. HBV subgenotypes and BCP/PC variants were determined by direct sequencing of the preS, BCP/PC regions, respectively. RESULTS: HBV subgenotypes B4/Ba (n = 22) and C1/Cs (n = 5) were detected. Of the 27 patients, 3 developed fulminant hepatic failure, and all were infected with B4/Ba. Three patients had a BCP mutation, and 10 patients had a PC mutation in subgenotype B4/Ba. Three patients with C1/Cs had a BCP mutation. Two of 3 patients who progressed to fulminant hepatic failure had T1762, A1764, and A1896 simultaneously. None of the patients with acute, self-limited hepatitis carried these triple mutations. CONCLUSION: The prevalent HBV subgenotypes in patients with acute hepatitis B in Central Vietnam were B4/Ba and C1/Cs. BCP/PC variants have an association with the development of fulminant hepatic failure in subgenotype B4/Ba.
Assuntos
Variação Genética , Vírus da Hepatite B/genética , Hepatite B/epidemiologia , Hepatite B/virologia , Doença Aguda , Adulto , Sequência de Bases , DNA Viral/isolamento & purificação , Progressão da Doença , Feminino , Hepatite B/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Filogenia , Prevalência , Regiões Promotoras Genéticas , Vietnã/epidemiologiaRESUMO
We report a deformation phenomenon occurring at the interface between two immiscible liquids. The two liquids are in a cylindrical container and set into motion by a rotating lid positioned above the interface. The upper liquid is more viscous than the lower and the difference in densities between the liquids is fairly small. As the rotational speed of the lid (Omega) is increased in small increments, the center of the interface rises and the height increases. Depending on Omega , the topology of the interface changes drastically. The shape of the interface depends strongly on Omega and also the volume fraction of the liquids. Some dynamical behavior of the interface accompanies the changes in topology: interfacial waves, the generation of droplets, and interfacial instability.
RESUMO
To investigate whether bone marrow-derived cells (BMC) would migrate and engraft into the sensory epithelium of the inner ear, BMC of green fluorescence protein (GFP) mice were transplanted into lethally irradiated recipient mice. Then the recipient mice were treated with streptomycin and immunohistochemical staining was performed to evaluate the migration and engraftment of donor BMC into the sensory epithelium of the inner ear. Immunohistochemical staining for GFP was found initially in the vascular epithelium and oral mucosa but not in the sensory epithelium of the inner ear. In the case of mouse, BMC may not migrate and be engrafted into the sensory epithelium of the inner ear.
Assuntos
Transplante de Medula Óssea/métodos , Estreptomicina/farmacologia , Animais , Transplante de Medula Óssea/efeitos adversos , Movimento Celular/fisiologia , Modelos Animais de Doenças , Orelha Interna/metabolismo , Orelha Interna/patologia , Orelha Interna/cirurgia , Feminino , Rejeição de Enxerto , Sobrevivência de Enxerto , Proteínas de Fluorescência Verde/biossíntese , Imuno-Histoquímica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas do Tecido Nervoso/metabolismo , Distribuição Aleatória , Fatores de Risco , Sensibilidade e Especificidade , Coleta de Tecidos e Órgãos/métodosRESUMO
BACKGROUND: In endemic areas, including Japan, basal core promoter (BCP) and precore (PC) variants of hepatitis B virus (HBV) have been reported to be associated with the clinical outcome of acute hepatitis B patients. However, the associations of BCP/PC variants with clinical outcomes have not been observed in nonendemic areas. HBV subgenotypes, which show geographic variations in prevalence, may underlie this discrepancy in clinical outcomes. Little is known about the differences in the clinical and virological features of HBV subgenotypes and BCP/PC variants. The aim of this study was to investigate the distributions of subgenotypes and BCP/PC variants to identify clinical differences in acute hepatitis B patients. METHODS: One hundred thirty-nine patients with acute hepatitis were enrolled. Nested polymerase chain reaction was used to amplify the pre-S region of HBV for genotyping and the BCP/PC regions for variant screening. RESULTS: HBV subgenotypes A1 (n = 3), A2 (n = 28), B1 (n = 3), B2 (n = 9), C1 (n = 5), C2 (n = 84), C variant (n = 1), D2 (n = 3), and H (n = 3) were detected. BCP/PC variants were not associated with progression to chronic hepatitis. Patients infected with subgenotype C2 who progressed to fulminant hepatic failure frequently carried variants at nucleotides non-T1753 and non-T1754 and T1762, A1764, and A1896. CONCLUSIONS: BCP/PC variants would be associated with progression to fulminant hepatitis in subgenotype C2. Knowledge of HBV subgenotypes and BCP/PC variants is useful for developing strategies to treat acute hepatitis B patients.
Assuntos
Genótipo , Vírus da Hepatite B/genética , Hepatite B/virologia , Regiões Promotoras Genéticas/genética , Proteínas do Core Viral/genética , Doença Aguda , Adulto , Progressão da Doença , Feminino , Variação Genética , Hepatite B/diagnóstico , Vírus da Hepatite B/classificação , Humanos , Falência Hepática Aguda/virologia , Masculino , Análise de Sequência de DNARESUMO
CONCLUSION: Notch signaling pathway may play an important role in the development of the olfactory epithelium (OE). Objectives. To elucidate whether the Notch signaling pathway mediates the developmental processes in the developing OE. MATERIALS AND METHODS: The expression of Notch1 and Hes5 in the developing OE of mice with ages ranging from embryonic day (E) 11 to postnatal day (PN) 14 was examined. RESULTS: As detected by in situ hybridization, Notch1 was expressed in scattered cells located in the basal portion of the embryonic OE and later in the cell layer adjacent to the basal lamina from E11 to PN14. Hes5 was expressed in scattered cells located in the basal portion of the embryonic OE from E11. However, at the late embryonic stage, the number of Hes5-positive cells decreased and after birth distinct Hes5-positive cells were not observed in the OE.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Mucosa Olfatória/crescimento & desenvolvimento , Receptor Notch1/genética , Proteínas Repressoras/genética , Animais , Animais Recém-Nascidos , Feminino , Expressão Gênica/fisiologia , Idade Gestacional , Hibridização In Situ , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Mucosa Olfatória/metabolismo , Gravidez , Transdução de Sinais/genéticaAssuntos
Meningite Pneumocócica , Síndrome de Linfonodos Mucocutâneos , Criança , Humanos , Lactente , Meningite Pneumocócica/tratamento farmacológico , Síndrome de Linfonodos Mucocutâneos/complicações , Síndrome de Linfonodos Mucocutâneos/diagnóstico , Síndrome de Linfonodos Mucocutâneos/tratamento farmacológico , Vacinas Pneumocócicas , Streptococcus pneumoniaeRESUMO
To investigate whether bone marrow cells migrate and are engrafted into the olfactory epithelium and differentiate into olfactory neurons, bone marrow cells of green fluorescence protein (GFP) mice were transplanted into lethally irradiated recipient mice. Immunohistochemical staining was performed to evaluate the engraftment of donor bone marrow cells into the olfactory epithelium. Immunostaining for GFP was found initially in the olfactory epithelium 2 weeks after bone marrow reconstruction. The percentage of GFP positive cells increased up to 12 months after bone marrow reconstruction. Double staining for GFP and olfactory marker protein showed that a population of the GFP-positive cells had characteristics of olfactory neurons. These results demonstrate that bone marrow cells can be engrafted in the olfactory epithelium and then differentiate into olfactory neuron cells.
Assuntos
Transplante de Medula Óssea , Neurônios/fisiologia , Mucosa Olfatória/fisiologia , Análise de Variância , Animais , Contagem de Células/métodos , Diferenciação Celular/fisiologia , Movimento Celular/fisiologia , Feminino , Proteínas de Fluorescência Verde/biossíntese , Imuno-Histoquímica/métodos , Indóis , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas do Tecido Nervoso/metabolismo , Proteína de Marcador Olfatório , Mucosa Olfatória/citologiaRESUMO
Tympanoplasty operations to improve hearing impairment require a wide middle ear cavity and reconstruction of columellar formations. There is no specific material for use in the reconstruction of columellar formations. Tissue response to BMP has been employed as regenerative material. To our knowledge, however, there are no reports of the reconstruction of columellar formations using recombinant human bone morphogenetic protein-2/bovine collagen composites in the middle ear. The purpose of this study is to investigate whether recombinant human bone morphogenetic protein-2/bovine collagen composites (rhBMP-2 composites) are appropriate for use as regenerative material for tympanoplasty. In the form of pellets, rhBMP-2 composites were implanted as columellae into the tympanic cavity. At 2, 4, 6, 8, and 12 weeks after surgery, the middle ear of the animals (n = 4 at each week) was stained with hematoxylin-eosin for light microscopic observation. All composites were in the process of ossification or had ossified according to their developmental stages and were covered with a single layer of squamous or cuboidal epithelium. The new bone formed in these composites was persistently stable and displayed some columellar conditions assessed by histological examination. This study led to the conclusion that rhBMP-2 composites make excellent regenerative material for auditory ossicles.
Assuntos
Proteínas Morfogenéticas Ósseas , Regeneração Óssea/fisiologia , Colágeno , Ossículos da Orelha/fisiologia , Proteínas Recombinantes , Fator de Crescimento Transformador beta , Animais , Proteína Morfogenética Óssea 2 , Humanos , Ratos , Fatores de Tempo , Membrana TimpânicaRESUMO
The present study reports the case of a 68-year-old male patient who presented to Tokyo Rosai Hospital for the treatment of alcoholic liver disease. A high density was observed in liver segment S2, while a tumor, 30 mm in size, exhibiting a low density was observed in the delayed phase upon contrast-enhanced computed tomography (CT), which was performed prior to admission. The tumor appeared slightly poorly defined upon abdominal ultrasound and was observed as a 30 mm low-echoic nodule that was internally heterogeneous. A 5-mm thick contrast enhancement effect was observed in the tumor border in the vascular phase on Sonazoid contrast-enhanced ultrasonography, while a defect in the entire tumor was observed in the post-vascular phase. Dysphagia had commenced three months prior to presentation and a weight loss of ~3 kg was observed. Therefore, the patient was admitted to Tokyo Rosai Hospital due to the presence of a hepatic tumor, and to undergo a close inspection of the cause of the tumor. Upon close inspection, it was determined that the weight loss and aphagia were caused by progressive bulbar paralysis. A contrast-enhanced CT was performed on post-admission day 29 as a follow-up regarding the hepatic tumor. As a result, although no change in the tumor size was observed, the contrast enhancement in the tumor borderline had disappeared. Necrosis of the tumor was considered. However, as viable persistence of the malignant tumor could not be excluded, a hepatic left lobe excision was performed. The patient was diagnosed with hepatocellular carcinoma (HCC) based on the morphology of the cellular necrosis. In addition, occlusion due to thrombus was observed within the blood vessels passing inside the fibrous capsule. It was hypothesized that the formation of a thick fibrous capsule and occlusion due to thrombus in the feeding vessel were possibly involved as the cause of complete spontaneous necrosis. Written informed consent was obtained from the patient.
RESUMO
In recent years, artificial biological materials have been commonly used for the treatment of bone tissue defects caused by trauma, tumors, or surgical stress. Although tricalcium phosphate (TCP) is a promising absorbent bone tissue reconstruction biomaterial, it has been reported that its biocompatibility and osteoconductivity depend on its preparation method and sintering temperature. In addition, although it is thought that the microenvironment produced by the extracellular matrix plays an important role in cell growth and differentiation, there have been few studies on how the geometric structure of artificial biological materials affects cells. In the present study, a new honeycomb TCP scaffold containing through-holes with diameters of 300 µm has been developed. The influence of the sintering temperature on the crystal structure and material properties of the honeycomb TCP scaffold was investigated using scanning electron microscopy and X-ray diffraction. Its biocompatibility and osteoconductivity were also evaluated by implantation into experimental animals. It was found that a ß-TCP scaffold sintered at 1200°C exhibited high biocompatibility and osteoconductivity, and when it was loaded with BMP-2, it exhibited both osteoconductivity and osteoinductivity, promoting rapid bone formation in both ectopic and orthotopic areas. It is thus a highly promising bone reconstruction material that is expected to find clinical applications.
Assuntos
Proteína Morfogenética Óssea 2/administração & dosagem , Regeneração Óssea/efeitos dos fármacos , Substitutos Ósseos/química , Fosfatos de Cálcio/química , Alicerces Teciduais/química , Animais , Proteína Morfogenética Óssea 2/farmacologia , Masculino , Porosidade , Ratos Wistar , Difração de Raios XRESUMO
We performed laboratory experiments of Rayleigh-Bénard convection with liquid gallium under various intensities of a uniform imposed horizontal magnetic field. An ultrasonic velocity profiling method was used to visualize the spatiotemporal structure of the flows with simultaneous monitoring of the temperature fluctuations in the liquid gallium layer. The explored Rayleigh numbers Ra range from the critical value for onset of convection to 10(5); the Chandrasekhar number Q covers values up to 1100. A regime diagram of the convection patterns was established in relation to the Ra and Q values for a square vessel with aspect ratio 5. We identified five flow regimes: (I) a fluctuating large-scale pattern without rolls, (II) weakly constrained rolls with fluctuations, (III) a continuous oscillation of rolls, (IV) repeated roll number transitions with random reversals of the flow direction, and (V) steady two-dimensional (2D) rolls. These flow regimes are classified by the Ra/Q values, the ratio of the buoyancy to the Lorentz force. Power spectra from the temperature time series indicate that regimes I and II have the features of developed turbulence, while the other regimes do not. The region of steady 2D rolls (Busse balloon) extends to high Ra values in the present setting by a horizontal magnetic field and regime V is located inside the Busse balloon. Concerning the instabilities of the steady 2D rolls, regime III is the traveling wave convection developed from the oscillatory instability. Regime IV can be regarded as a state of phase turbulence, which is induced by intermittent occurrences of the skewed-varicose instability.
RESUMO
The intraductal papillary neoplasm of the bile duct (IPNB) is a novel disease concept that was recently classified as a biliary cystic tumor by the revised World Health Organization classification. This is the case report of a 70-year-old female patient who experienced repeated episodes of obstructive jaundice and cholangitis since 2000, attributed to a mucus-producing hepatic tumor. Surgery was advised due to the repeated episodes; however, the patient refused. In May, 2011, the patient developed jaundice and fever and was treated with antibiotics. Since there was no improvement, the patient was admitted to the Tokyo Rosai Hospital. Abdominal computed tomography (CT) revealed a 50-mm cystic mass with an internal septum in the left hepatic lobe. Although the tumor size had remained almost unchanged compared to the initial CT scan performed in 2000, intra- and extra-hepatic bile duct dilation was more prominent on the second CT scan. Following admission, endoscopic retrograde cholangiopancreatography was performed and revealed an expanded papilla of Vater due to a mucous plug. A balloon catheter was inserted into the bile duct to remove the mucous plug, resulting in the drainage of copious amounts of mucus and infected bile. The patient finally consented to surgery and left hepatic lobectomy was performed. Consequently, the diagnosis of low-grade IPNB was made. Branch duct type IPNB, which is characterized by imaging appearance of a cystic mass and slow progression, is attracting increasing attention. In the present case, a cystic mass was identified in the left hepatic lobe, with no significant change in size after 11 years of follow-up, leading to the diagnosis of branch duct type IPNB. Considering the fact that IPNB is usually treated surgically at the time of diagnosis, the present case, due to the long-term follow-up, provides valuable insight into the natural history of the tumor.
RESUMO
A 63-year-old woman was admitted to hospital with pain in the right lower quadrant. Abdominal computed tomography (CT) revealed a 60-mm cystic mass at a site corresponding to the appendix. The mass wall on the appendicular ostium was thickened and enhanced by contrast, while calcification was observed in the mass wall on the appendicular tip. No projection was observed in the mass cavity. On abdominal ultrasonography (US), the mass wall on the appendicular ostium was thickened and projections were observed at two sites in the mass cavity. On contrast-enhanced US (CEUS), only one of these projections was enhanced. Based on the thickened and contrast-enhanced wall of the mass on the appendicular ostium on CT and US, as well as the contrast enhancement of a projection on US, the mass was diagnosed as mucinous cystadenocarcinoma of the appendix. Ileocecal resection was subsequently performed on day 10. A detailed examination of the surgical specimen revealed carcinoma cells in the mass wall on the appendicular ostium. The contrast-enhanced projection was identified as granulation tissue that had grown to come into contact with the tumor, while the non-contrast-enhanced projection was identified as solidified mucus. US enabled successful visualization of projections in the mass cavity that were not visible on abdominal CT. CEUS also proved useful for assessing blood flow in these projections.
RESUMO
We report a finding of spontaneous flow reversals of roll-like patterns in liquid gallium Rayleigh-Bénard convection. The vessel has a square geometry with an aspect ratio of 5, and a horizontal magnetic field is applied to align the rolls. The flow patterns were visualized by ultrasonic velocity measurements, and the processes of the reversal were clearly observed. The basic flow pattern observed in the vessel is a four-roll structure with its axis parallel to the magnetic field. Emergence of a new circulation at a corner of the vessel causes flow reversal with reorganization of the whole pattern. The flow keeps relatively steady four-roll structure for most of the duration, while the reversal of it is over in a short time. The reversals of the flow occur randomly with the interval time between reversals being much longer than the circulation time.
RESUMO
Thermal convection experiments in a liquid gallium layer were carried out with various intensities of uniform horizontal magnetic fields. The gallium layer was in a rectangular vessel with a 4:1:1 length ratio (1 is the height), where the magnetic field is applied in the direction normal to the longest vertical wall. An ultrasonic velocity profiling method was used to visualize the spatiotemporal variations in the flow pattern, and the temperature fluctuations in the gallium layer were also monitored. The observed flow pattern without a magnetic field shows oscillating rolls with axes normal to the longest vertical wall of the vessel. The oscillatory motion of the flow pattern was suppressed when increasing the applied magnetic field. The flow behavior was characterized by the fluctuation amplitude of the oscillation and the frequency in the range of Rayleigh numbers from 9.3 x 10³ to 3.5 x 105 and Chandrasekhar numbers 0-1900. The effect of the horizontal magnetic field on the flow pattern may be summarized into three regimes with increases in the magnetic intensity: (1) no effect of the magnetic field, (2) a decrease in the oscillation of the roll structure, and (3) a steady two-dimensional roll structure with no oscillation. These regimes may be explained as a result of an increase in the dominance of Lorentz forces over inertial forces. The power spectrum from the temperature time series showed the presence of a convective-inertial subrange above Rayleigh numbers of 7 x 104, which suggests that turbulence has developed, and such a subrange was commonly observed above this Rayleigh number even with applied magnetic fields when the rolls oscillate.