Masataka Tanaka

Transient heat conduction problems in inhomogeneous media discretized by means of boundary-volume element

Abstract An integral equation formulation is presented for the transient heat conduction problems in inhomogeneous media. The material constants are assumed to be prescribed as arbitrary, continuous and differentiable functions of position vector. The governing integral equations are derived from the weighted residual statement of the problems in which the fundamental solution to the corresponding heat conduction problems in homogeneous media is used as the weight function. The whole domain of interest is discretized into a series of boundary-volume-time elements, and then a set of linear simultaneous equations are obtained. Their solutions yield the temperature in the whole domain as well as the heat flux on the boundary.

Detection of Epileptic Seizures Using Phase–Amplitude Coupling in Intracranial Electroencephalography

Seizure detection using intracranial electroencephalography (iEEG) contributes to improved treatment of patients with refractory epilepsy. For that purpose, a feature of iEEG to characterize the ictal state with high specificity and sensitivity is necessary. We evaluated the use of phase–amplitude coupling (PAC) of iEEG signals over a period of 24 h to detect the ictal and interictal states. PAC was estimated by using a synchronisation index (SI) for iEEG signals from seven patients with refractory temporal lobe epilepsy. iEEG signals of the ictal state was characterised by a strong PAC between the phase of β and the amplitude of high γ. Furthermore, using SI values, the ictal state was successfully detected with significantly higher accuracy than by using the amplitude of high γ alone. In conclusion, PAC accurately distinguished the ictal state from the interictal state.

Time-space boundary elements for transient heat conduction problems

Abstract This paper is concerned with a generalized time-space boundary element formulation for transient heat conduction problems in anisotropic media. A weighted residual form of the governing equation is used to obtain the boundary integral equation in terms of the fundamental solution. The resulting boundary integral equation is discretized by means of a wide variety of boundary elements from constant-elements to higher-order isoparametric elements located both in time and space.

A boundary element formulation in linear piezoelectric problems

A new boundary element formulation is presented for linear piezoelectric problems under the assumption of electrodynamic quasi-static approximation. The domain, its boundary and the time region are fully discretized into a finite number of boundary-volume-time elements, and then a set of linear equations are derived from the governing integral equations. The solving scheme for the discretized linear equations in which the displacement vector, the electric potential and the corresponding fluxes are included as unknowns, is discussed.ZusammenfassungEine neue Randelement-Formulierung wird für piezoelektrische Probleme vorgeschlagen. Dabei wird eine elektrodynamische quasistatische Näherung angenommen. Das Gebiet, der Rand und der Zeitbereich werden in eine endliche Zahl von Rand-Volumen-Zeit-Elementen diskretisiert, und dann wird aus den beherrschenden Integralgleichungen eine Reihe linearer Gleichungen hergeleitet. Das Lösungsverfahren für die diskretisierten linearen Gleichungen, in denen der Verschiebungsvektor, das elektrische Potential und die zugehörigen Flüsse als Unbekannte eingehen, wird diskutiert.

On boundary-volume element discretization of inhomogenous elastodynamic problems

Abstract This paper presents an integral equation formulation and its discretization scheme for the elastodynamic problem in which the material properties are prescribed as arbitrary, continuous and differentiable functions of the spatial coordinates. The formulation is made by using the Greens function for the corresponding problem in homogenous elasticity. From a weighted residual statement of the problem, the governing differential equation is transformed into a set of the integral equations in the inner domain as well as on the boundary. These integral equations are discretized by introducing a finite number of the boundary-volume-time elements, and the solution for the system of linear equations thus obtained is discussed.

Time-space boundary element formulation for boundary-value problems

Abstract A time-space boundary element formulation is presented for the boundary-value problems with a governing equation expressed in terms of a certain type of linear operator. The boundary as well as the time domain are divided into a finite series of time-space elements, and the interpolation functions in time and space are introduced in order to construct a final discretized equation for the assembled system. The solving scheme is discussed, and the relation to the practical engineering problems is shown.

Fatigue life estimation of bellows based on elastic-plastic calculations

Abstract A procedure which estimates the low-cycle fatigue life of bellows on the basis of elastic-plastic calculations is treated. A U-shaped bellows is taken as an example for the analysis and comparison is made with the measured data. A design formula, in which Langers method is modified so that it includes in its expression the strain concentration factor, is proposed for the fatigue life estimation.

Mapping ECoG channel contributions to trajectory and muscle activity prediction in human sensorimotor cortex

Studies on brain-machine interface techniques have shown that electrocorticography (ECoG) is an effective modality for predicting limb trajectories and muscle activity in humans. Motor control studies have also identified distributions of “extrinsic-like” and “intrinsic-like” neurons in the premotor (PM) and primary motor (M1) cortices. Here, we investigated whether trajectories and muscle activity predicted from ECoG were obtained based on signals derived from extrinsic-like or intrinsic-like neurons. Three participants carried objects of three different masses along the same counterclockwise path on a table. Trajectories of the object and upper arm muscle activity were predicted using a sparse linear regression. Weight matrices for the predictors were then compared to determine if the ECoG channels contributed more information about trajectory or muscle activity. We found that channels over both PM and M1 contributed highly to trajectory prediction, while a channel over M1 was the highest contributor for muscle activity prediction.

Navigation-assisted trans-inferotemporal cortex selective amygdalohippocampectomy for mesial temporal lobe epilepsy; preserving the temporal stem

Abstract Objective: Selective amygdalohippocampectomy (SAH) can be used to obtain satisfactory seizure control in patients with mesial temporal lobe epilepsy (MTLE). Several SAH procedures have been reported to achieve satisfactory outcomes for seizure control, but none yield fully satisfactory outcomes for memory function. We hypothesized that preserving the temporal stem might play an important role. To preserve the temporal stem, we developed a minimally invasive surgical procedure, ‘neuronavigation-assisted trans-inferotemporal cortex SAH’ (TITC-SAH). Methods: TITC-SAH was performed in 23 patients with MTLE (MTLE on the language-non-dominant hemisphere, n = 11). The inferior horn of the lateral ventricle was approached via the inferior or middle temporal gyrus along the inferior temporal sulcus under neuronavigation guidance. The hippocampus was dissected in a subpial manner and resected en bloc together with the parahippocampal gyrus. Seizure control at one year and memory function at 6 months postoperatively were evaluated. Results: One year after TITC-SAH, 20 of the 23 patients were seizure-free (ILAE class 1), 2 were class 2, and 1 was class 3. Verbal memory improved significantly in 13 patients with a diagnosis of hippocampal sclerosis, for whom WMS-R scores were available both pre- and post-operatively. Improvements were seen regardless of whether the SAH was on the language-dominant or non-dominant hemisphere. No major complication was observed. Conclusion: Navigation-assisted TITC-SAH performed for MTLE offers a simple, minimally invasive procedure that appears to yield excellent outcomes in terms of seizure control and preservation of memory function, because this procedure does not damage the temporal stem. TITC-SAH should be one of the feasible surgical procedures for MTLE. Abbreviations: SAH: Amygdalohippocampectomy; MTLE: Mesial temporal lobe epilepsy (MTLE); TITC-SAH: Ttrans-inferotemporal cortex SAH; ILAE: International League Against Epilepsy (ILAE); MRI: Magnetic resonance imaging; EEG: Electroencephalography (EEG); FDG-PET: 8F-fluorodeoxyglucose (FDG)-positron emission tomography; ECoG: Electrocorticography; MEG: Magnetoencephalography; IMZ-SPECT: N-isopropyl-p(123I)-iodoamphetamine single photon emission computed tomography; WMS-R: Wechsler Memory Scale-Revised.

Clinical and radiological features of endodermal cyst in the oculomotor nerve: A case report.

Abstract We present a 9-year-old girl with an endodermal cyst of the oculomotor nerve in the left interpeduncular cistern, who had a history of left ptosis. We suggest that a cyst localized at the exit of the oculomotor nerve from the midbrain associated with oculomotor palsy may suggest this rare entity.