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Femtosecond (fs) laser modification on single crystal silicon carbide (SiC) was studied from the viewpoints of electric conductivity. Fourier transform infrared (FTIR) spectroscopy was carried out on femtosecond laser modified area. The intensity decrease of reststrahlen band due to the modification was observed, and this decrease was explained by the degradation of crystallinity due to the laser irradiation. Polarization dependence of reststrahlen band was also observed on laser modified samples. Current-voltage characteristics and Hall measurements on fs-laser modified region were carried out by fabricating the metal contacts on the ion implanted areas. The specific resistance up to 5.9×10-2 m was obtained for fs-laser modified area.

By means of the non-local theory of the pulse response and the analysis of the exciton–radiation coupled modes, we elucidate a recently observed short response time of degenerate four-wave mixing (DFWM) of weakly confined excitons in a thin film. Especially, it is expected that the excitons with non-dipole type of center-of-mass wavefunctions exhibit a peculiar thickness dependence owing to a spatial structure of the radiation field. The experimental results of the three-beam DFWM of GaAs thin layers strongly support our theoretical explanation of the radiative decay that is beyond the long wavelength approximation.

Abstract: The purpose of this study was to determine factors that might be involved in neurological deterioration and the role of surgical treatment in patients with lumbosacral spinal lipoma. Pre- and postoperative courses of 34 patients were retrospectively analyzed. The age at surgery ranged from 1 month to 47 years. The records of preoperative neurological status indicated that older patients had more severe deficits, while all 8 asymptomatic patients were under 5 years of age. Motor deficits were noted in 9 patients, in 7 of whom the lipoma extended cranially beyond the L5 level. Transitional-type lipomas were accompanied by more severe deficits (asymptomatic 1, symptomatic 17) than other types (asymptomatic 7, symptomatic 9). Postoperative follow-up periods ranged from 5 months to 13 years. During these periods, 7 of the 8 asymptomatic patients remained neurologically intact. Nine of the 26 symptomatic patients improved. Age, extension of the lipoma in the spinal canal and type of lipoma will influence the preoperative neurological status of the patients. Early untethering surgery is recommended in patients with large lipomas extending beyond the L5 level.

Ultrathin-layer (AlAs)m(GaAs)m superlattices withm = 1, 2, and 3 were grown by molecular beam epitaxy and characterized by x-ray diffraction and photoluminescence measurements. The appearance of distinct satellite peaks around the Bragg reflections demonstrate the formation of high-quality layered crystals. The observed luminescence shows a maximum at 2.033 eV form = 3, and the emission energy decreases form = 2 andm = 1 as well as for them = 4 superlattice. This result for the monolayer superlattice is in good agreement with recent theoretical calculations, and it shows that the (AlAs)1(GaAs)1 superlattice represents a new artificial semiconductor material with novel electronic properties.

Active-nitrogen-doped p-ZnSe, ZnSSe and MgZnSSe layers are successfully grown by GSMBE employing group VI hydride sources. We performed a SIMS analysis for the p-ZnSe layers and a hydrogen -concentration of about 1 × 1018cm−3was detected. With regard to the nitrogen activation as acceptors, data of GSMBE-grown p-ZnSe are not different from those of solid-source MBE. A p-ZnSe layer with a resistivity of 1 Ω · cm and a net acceptor concentration of 1 × 1018cm−3and a p-MgxZnSySe layer (x= 0.10 and y= 0.15) with a net acceptor concentration of 1.8 × 1017cm−3is obtained. These values are comparable to the best values ever attained by various growth methods. We conclude that incorporated hydrogen has no significant effect on the electrical properties of GSMBE-grown p-ZnSe layers.

The clinical features of 31 cases of syringomyelic syndrome, confirmed by metrizamide CT myelography (CTM) or magnetic resonance imaging (MRI), were analysed. Bilateral suspended sensory disturbance, previously regarded as a characteristic feature, was encountered in only 2 cases (6.5%). Thirteen patients (41.9%) showed no motor deficits of the upper limbs and 7 patients (22.6%) did not have weakness or atrophy in any of the four extremities. Cervical segmental signs were absent in 7 cases (22.6%) and in 2 (6.5%) signs were only present in the lower limbs. Scoliosis and foot deformity, such as pes cavus or equinovarus, were seen in 17 (54.8%) and 5 cases (16.1%) respectively. These skeletal abnormalities were initial symptoms in some childhood cases. In syringomyelic syndrome, clinical features are variable with many atypical clinical manifestations, apart from the previously recognized characteristic clinical features.

Summary: We describe a surgical technique for a vertebral column autograft using the intervertebral disc for cervical disc disease for patients whose major problem is not spinal instability. Of a total of 41 patients with cervical disc disease suffering from cervical spondylotic radiculomyelopathy, 33 patients were operated on at one level and 8 patients were operated on at two levels. Postoperative X-ray film showed some movement at the “operated” disc level in all patients (average postoperative follow-up period was 43 months, range two years to 5 years). A significant decrease in motion in the extension position was observed postoperatively (p<0.0001), but no significant difference was observed between the preoperative motion and the postoperative motion in the flexion position. Anterior angulation was found in two (5%) of the 41 patients. This surgical procedure has two major advantages: 1) no complications related to the iliac donor site, allowing early patient mobilization; 2) the extensive posterior spur can be removed safely and easily under a wide operative field. We believe that this surgical procedure is suitable for preserving the mobility of the spine and may avoid stress concentration at adjacent levels of the “operated” disc. However, in patients whose major problem is spinal instability, anterior cervical fusion should be performed.

Seven cases of acute cervical cord injury examined by CT-myelography are reported. Cord swelling was observed in 2 patients who developed complete lesions. Another 5 cases had an incomplete lesions. Spinal cord swelling indicated severe cord damage. External decompression seemed to have little effect on cord swelling. When cord swelling is absent, neurological improvement was expected though the initial neurological state showed severe deficits. A further 4 patients who had an acute cervical cord injury who were treated by myelotomy at the injury site are also reported. Two patients obtained significant improvement in upper limb function. The presence or absence of cord swelling as shown by CT-myelography is important for diagnosing the severity of cord damage. Myelotomy in the immediate post-accident period may relieve the effects of cord swelling.

Summary The authors report the surgical results of 28 patients with syringomyelia associated with Chiari malformation (type 1). 28 patients underwent 34 operative procedures. Syringo-subarachnoid shunt was performed in 28 patients, foramen magnum decompression with syringo-subarachnoid shunt in three, ventriculo-peritoneal shunt in one, terminal syringostomy in one, and foramen magnum decompression with terminal syringostomy in one. In an average postoperative follow-up period of 3 years and 9 months ranging from one year to 7 years and one month, neurological symptoms and signs improved in 24 out of 28 patients (82%). Some improvement was noted in sensory deficit and motor weakness. In 3 patients, the symptoms did not change. In 3 patients whose symptoms were unchanged, preoperative studies demonstrated atrophy of the spinal cord, in which irreversible changes were shown. The symptoms deteriorated in one patient. In one patient whose symptoms increased 3 months after syringo-subarachnoid shunt, shunt insufficiency due to postoperative adhesive arachnoiditis was responsible for neurological deterioration.

Summary In a case of cavernous angioma, a remote gyrus, which was found to contain an epileptogenic focus by intraoperative electrocorticography (ECoG), was resected simultaneously with lesionectomy.

Summary The facial electromyographic response was monitored intraoperatively in 40 patients with hemifacial spasm who were operated on by microvascular decompression of the facial nerve. All 40 patients showed an abnormal facial electromyographic response (lateral spread response) with a latency of about 10 msec after stimulation. The abnormal response resolved before decompression in 22, resolved immediately with decompression in 16, and failed to resolve in two. Of the 38 patients in whom the abnormal response disappeared during surgery, 36 were postoperatively free from hemifacial spasm and two had mild hemifacial spasm. The two patients in whom the lateral spread response did not disappear during surgery showed persistent hemifacial spasm.

We describe the epitaxial growth of GaAsxP1-x(0

Scanning tunneling microscope has been employed for nanoscale manipulation of C60 molecules on Si(111) clean surfaces at room temperature. It was demonstrated that C60 molecules were positioned by moving individual C60 molecules with a STM tip. There exists threshold height between the tip and the Si surface for moving the molecules. The difference in the threshold height between tungsten tip and platinum-iridium alloy tip was estimated to be 0.16 nm from planar electrode model. The mechanism of moving C60 molecules with STM tip can be explained by atomic forces between tip and molecule.

Abstract: Clinical and radiological features of syringomyelia in 15 patients with spinal dysraphism are reported. There were 8 patients with occult spinal dysraphism (lumbosacral lipoma) and 7 with spina bifida aperta (meningomyelocele). Syringomyelia with spinal dysraphism can be radiologically divided into two types according to the dysraphic state. The syrinx in the patients with occult spinal dysraphism occurred immediately rostral to the lipoma and was localized to the lower thoracic to lumbar levels, while in the meningomyelocele patients the syrinx extended from the cervical to the thoracic level. Large syrinx formation was recognized in 1 of the 7 occult spinal dysraphism cases and 3 of the 8 meningomyelocele cases. For syringomyelia with occult spinal dysraphism, 4 patients underwent syringo-subarachnoid shunting (S-S shunt, 2 cases) or syringostomy (2 cases) during an untethering operation. In the case of meningomyelocele, S-S shunts were placed in 2 patients. Collapse of the syrinx was achieved in all 6 patients who underwent S-S shunting or syringostomy. Decreased size of the syrinx was also noted in 3 occult spinal dysraphism patients who underwent untethering operations alone. In conclusion, a large syrinx in the case of spinal dysraphism should be surgically treated. S-S shunting is effective in both types of syringomyelia. Foramen magnum decompression may be an alternative method of surgical treatment for syringomyelia in patients with meningomyelocele.

Abstract: We retrospectively evaluated the pre- and postoperative course of 34 tethered cord patients with occult spinal dysraphism in an attempt to infer the natural history of this disorder and to determine the effectiveness of the surgical treatment. There were 32 cases with lumbosacral lipoma and 2 with tight filum terminale. The age at surgery ranged from 1 month to 47 years old. Eight patients, aged 1 month to 4 years old, were asymptomatic; 26 had neurogenic bladder (26 cases) or motor problems affecting the legs (8 cases). None of the patients older than 5 years of age were asymptomatic. Untethering of the spinal cord was performed in all cases. The postoperative follow-up period ranged from 5 months to 11 years. During these periods, 7 (88%) of the 8 asymptomatic patients remained neurologically intact, 6 (23%) of the 26 symptomatic patients showed improved symptoms, and 15 patients (58%) remained unchanged. These results indicate that the neurological symptoms will appear progressively in the tethered cord patients, and that prophylactic surgery should be considered as early as possible.

Herniated nuclear material of the cervical disc often perforates the posterior longitudinal ligament. Of 22 patients who were operated on by an anterior approach, 10 were of this type (the subligamentous type of cervical disc protrusion), while in the remaining 12 patients and 15 discs the protruded disc caused no tear in the ligament (the epiligamentous type). Myelography and CT myelography of these patients were reviewed. On CT myelography a localized and sharply demarcated excavation of the metrizamide ring was commonly found in the subligamentous type. Myelographic lateral view in this group shows a moderate or large indentation of the metrizamide column, since the herniated nucleus pulposus sometimes migrates caudally or cephalically. A small myelographic deformity coupled with diffuse excavation of the metrizamide ring on a CT myelogram leads us to the diagnosis of the epiligamentous type of cervical disc protrusion. In such cases, excision of the ligament is unnecessary during exploration of the discs, except when there is marked depression in the posterior longitudinal ligament. Presurgical recognition of both anatomical processes must be stressed for anterior discectomy.

In this study, the authors evaluate the importance of computed tomography (CT) in 15 patients who underwent surgical treatment for cervical disc disease. In nine operated on by an anterior approach, all CT examinations were interpreted as positive for disc herniation and correlated precisely with surgical observations. CT demonstrated protrusion of the disc, centrally in four and posterolaterally in five in all of whom disc material was found posterior to the vertebral body. Of six who underwent laminectomy, either thickening or calcification of the ligamentum flavum was demonstrated by CT and confirmed at surgery in five. Vacuum phenomenon in the intervertebral space and hypertrophy of the intervertebral joint were not infrequently associated. CT can exactly delineate cervical disc lesions and associated pathological changes.

Ultrathin-layer (AlAs)(GaAs) superlattices with m = 1, 2, and 3 were grown by molecular beam epitaxy and characterized by x-ray diffraction and photoluminescence measurements. The appearance of distinct satellite peaks around the Bragg reflections demonstrate the formation of high-quality layered crystals. The observed luminescence shows a maximum at 2.033 eV for m = 3, and the emission energy decreases for m = 2 and m = 1 as well as for the m = 4 superlattice. This result for the monolayer superlattice is in good agreement with recent theoretical calculations, and it shows that the (AlAs)(GaAs) superlattice represents a new artificial semiconductor material with novel electronic properties. [ABSTRACT FROM AUTHOR]

In antiferromagnetic KCoF3having residual orbital moment, a new mechanism of the nuclear spin-lattice relaxation involving strong magnon-phonon interaction is presented. The calculated temperature and field dependences of the relaxation time of the fluorine nuclear spin are in good agreement with the observed results.