Persistent magnetic coherence in magnets.

When excited, the magnetization in a magnet precesses around the field in an anticlockwise manner on a timescale governed by viscous magnetization damping, after which any information carried by the initial actuation seems to be lost. This damping appears to be a fundamental bottleneck for the use of magnets in information processing. However, here we demonstrate the recall of the magnetization-precession phase after times that exceed the damping timescale by two orders of magnitude using dedicated two-colour microwave pump-probe experiments for a Y3Fe5O12 microstructured film. Time-resolved magnetization state tomography confirms the persistent magnetic coherence by revealing a double-exponential decay of magnetization correlation. We attribute persistent magnetic coherence to a feedback effect, that is, coherent coupling of the uniform precession with long-lived excitations at the minima of the spin-wave dispersion relation. Our finding liberates magnetic systems from the strong damping in nanostructures that has limited their use in coherent information storage and processing.

Observation of nuclear-spin Seebeck effect.

Thermoelectric effects have been applied to power generators and temperature sensors that convert waste heat into electricity. The effects, however, have been limited to electrons to occur, and inevitably disappear at low temperatures due to electronic entropy quenching. Here, we report thermoelectric generation caused by nuclear spins in a solid: nuclear-spin Seebeck effect. The sample is a magnetically ordered material MnCO3 having a large nuclear spin (I = 5/2) of 55Mn nuclei and strong hyperfine coupling, with a Pt contact. In the system, we observe low-temperature thermoelectric signals down to 100 mK due to nuclear-spin excitation. Our theoretical calculation in which interfacial Korringa process is taken into consideration quantitatively reproduces the results. The nuclear thermoelectric effect demonstrated here offers a way for exploring thermoelectric science and technologies at ultralow temperatures.

Multiple Diffusion-Freezing Mechanisms in Molecular-Hydrogen Films.

Molecular hydrogen is a fascinating candidate for novel bosonic and fermionic superfluids. We have studied diffusion dynamics of thin films of H_{2}, HD, and D_{2} adsorbed on a glass substrate by measurements of elasticity. The elasticity shows multiple anomalies well below the bulk triple point temperature. They are attributed to three different diffusion mechanisms of admolecules and their "freezing" into a localized state: classical thermal diffusion of vacancies, quantum tunneling of vacancies, and diffusion of molecules in the uppermost surface. The surface diffusion is active down to 1 K, below which the molecules become localized. This suggests that the surface layer of hydrogen films is on the verge of quantum phase transition to a superfluid state.

A case of sigmoid sinus dural arteriovenous fistula after treated cavernous dural arteriovenous fistula.

SUMMARY: Transvenous embolization has been recommended recently as the primary treatment for symptomatic cavernous dural arteriovenous fistula (dural AVF). We present a case of sigmoid sinus dural AVF which developed after transvenous embolization of cavernous dural AVF. A 43-year-old man was admitted to our hospital because of left conjunctivill chemosis, exophthalmus and abducens nerve palsy. Cerebral angiograms showed left cavernous dural AVF fed by the bilateral internal and external carqtid arteries and draining into the enlarged left superior ophthalmic vein. Transfemoral approach in the cqvernous sinus via inferior petrosal sinus (IPS) was difficult because of the occlusive change of IPS. Then, direct canulation of the left superior ophthalmic vein and transvenous embolization using interlocking detachable coils (IDC) were performed. Dural AVF and clinical symptoms were disappeard rapidly after embolization. Six months later, follow-up cerebral angiograms showed development of a dural AVF in the left sigmoid sinus. The pathogenesis of dural AVF remains unclear. We suggest that injury to the sinus wall during endovascular procedures may have provoked the development of dural AVF in our case. Clinical and angiographical follow-up are important.

[Stellate ganglion blocks as the suspected route of infection in a case of cervical epidural abscess].

Spinal epidural abscess is a comparatively rare disease. Its prognosis reportedly depends on degree and duration of the neurological symptoms before the treatment. Thus, the importance of early diagnosis and prompt surgical treatment has been emphasized repeatedly. In the case reported here stellate ganglion blocks were considered to be involved in the etiology of a cervical epidural abscess. The 47-year old woman complained of tinnitus and vertigo and repeatedly underwent stellate ganglion blocks over a period of 10 months. In August, 1991, the patient complained of back pain and developed fever. A few days later she noticed motor weakness and sensory disturbances in the legs. Ten days after the onset of these neurological symptoms she complained of rapidly progressive tetraplegia and was referred to this hospital for admission. On admission, she was fully conscious but febrile. Neurologically, she presented tetraplegia, hypesthesia below level of C7 and slight cervical rigidity. Bladder and bowel dysfunction were also observed. MRI examination showed an epidural mass behind vertebral bodies C6-7 compressing the spinal cord. Antibiotic therapy was initiated immediately and emergency surgical decompression was performed through an anterior approach. Intraoperative findings showed a discitis and yellowish liquid pus in the epidural space. Culture of the pus revealed staphylococcus aureus. In this case repeated stellate ganglion blocks before onset of the symptoms were the suspected route of infection. Postoperative MR images confirmed satisfactory decompression of the spinal cord and motor power was gradually recovered after surgery. Approximately 4 months after surgery she could walk independently. Cervical epidural abscess has been rarely reported as a complication of stellate ganglion block.(ABSTRACT TRUNCATED AT 250 WORDS)

[Multiple meningiomas of thoracic spinal cord: report of two cases].

Multiple spinal meningiomas are relatively rare and account for from only 2 to 3.5% of all spinal meningiomas. Two cases of multiple meningiomas of the thoracic spinal cord were reported. Case 1. A 73-year-old woman was admitted with a 5 month history of progressive motor weakness and sensory disturbance in the legs bilaterally. Neurological findings on admission revealed paraparesis, hypesthesia and hypalgesia under the Th10 level, hyperreflexia of both legs, and urinary incontinence. Myelography and MRI revealed two intradural extramedullary lesions at the Th7 and Th10 level. Both tumors were removed completely. Histopathological examination showed psammomatous meningiomas. Case 2. A 52-year-old man was admitted with a 2 month history of progressive motor weakness and numbness of both legs. Neurological findings on admission revealed paraparesis, hypesthesia and hypalgesia under the Th10 level, hyperreflexia of both legs, and genitourinary incontinence. Lumbar myelography showed complete block at the Th9 level. MRI showed stenosis of the spinal canal at the Th8/9 level, and a deviation of the spinal cord. MRI with Gd-DTPA showed that the spinal cord was compressed by intradural extramedullary tumors. However, myelography and MRI could not detect the multiplicity of tumors. CT myelography demonstrated three separate tumors from the Th7 to the Th9. Three tumors were totally removed. Histopathologically, they were meningotheliomatous meningiomas. These cases were considered as being multiple meningiomas of the spine. Both patients showed no manifestations of von Recklinghausen's disease. The cause of the multiplicity in these cases was uncertain. Multiple spinal tumor is very difficult to diagnose because of unusual clinical symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)

[A report of a transsphenoidal operation during pregnancy for a pituitary adenoma].

A 29-year old female, in her second pregnancy, complained of headache, nausea, vomiting and left blurred vision. In spite of improvement of these symptoms in the second postpartum, she complained of recurrent symptoms in her third pregnancy. CT and MRI showed a pituitary adenoma with hematoma. It was totally removed using the transsphenoidal approach during pregnancy at 8 months. The histological examination revealed that the tumor was an acidophilic adenoma with a hemorrhagic change. A healthy baby was born at the full term after the operation. Our transsphenoidal operation during pregnancy was only the second such attempt reported in our collected literature. The management of the pituitary tumor during pregnancy is discussed.

[Arachnoid cyst of the fourth ventricle. Case report].

A 65-year-old female was admitted because of progressive vertigo, truncal ataxia, and unsteadiness of gait for the past 6 years. Computed tomography (CT) and magnetic resonance imaging revealed a non-enhanced, large midline cyst in the posterior fossa and slightly dilated lateral and third ventricles. Metrizamide CT cisternography showed no communication between the cyst and the subarachnoid space. Suboccipital craniectomy, laminectomy of the atlas, and membranectomy of the cyst were performed. On light microscopic examination, the cyst wall was composed of arachnoid cells and connective tissues. Thus, this lesion was not an epithelial cyst but an arachnoid cyst occupying the fourth ventricle. An arachnoid cyst of the fourth ventricle is extremely rare, and only two cases were previously reported.