[Redo-operation for the cusp perforation 5 years after aortic valve replacement with stentless bioprosthesis; report of a case].

A 31-year-old male presented with increase of aortic valve regurgitation 5 years after implantation of Prima Plus Stentless bioprosthesis in a bicuspid aortic valve. He underwent redo aortic valve replacement with a mechanical valve concomitant with replacement of the ascending aorta. Pathological examination of the explanted stentless valve presented no inflammatory cell infiltration. The prosthetic valve regurgitation was considered to be due to small injury at the 1st operation.

A new digital pulse-mode neuron with adjustable activation function.

This paper describes a new pulse-mode digital neuron which is based on voting neuron. The signal level of the neuron is represented by frequency of pulse signals. The proposed neuron provides adjustable nonlinear function, which resembles the sigmoid function. The proposed neuron and experimental multilayer neural network (MNN) are implemented on field programmable gate array (FPGA) and various experiments are conducted to test the performance of the proposed system. The experimental results show that the proposed neuron has rigid adjustable nonlinear function.

A digital hardware pulse-mode neuron with piecewise linear activation function.

This paper proposes a new type of digital pulse-mode neuron that employs piecewise-linear function as its activation function. The neuron is implemented on field programmable gate array (FPGA) and tested by experiments. As well as theoretical analysis, the experimental results show that the piecewise-linear function of the proposed neuron is programmable and robust against the change in the number of input signals. To demonstrate the effect of piecewise-linear activation function, pulse-mode multilayer neural network with on-chip learning is implemented on FPGA with the proposed neuron, and its learning performance is verified by experiments. By approximating the sigmoid function by the piecewise-linear function, the convergence rate of the learning and generalization capability are improved.

Repression of starch degradation under anaerobic conditions by irregularly high levels of ATP in Chlamydomonas sp. MGA161.

It is generally known that in green algal species the acceleration of starch degradation upon transition from aerobic to anaerobic conditions is a result of the Pasteur effect in glycolysis. However, the acceleration of starch degradation did not occur in cells of Chlamydomonas sp. MGA161. In MGA161 cells, the anaerobic ATP level, which decreased to about half of the aerobic ATP level in cells of Chlamydomonas reinhardtii after fermentation for 2 h, was kept higher than its aerobic ATP level. Gramicidin D, a monovalent cation ionophore, markedly decreased the anaerobic and aerobic ATP levels due to the increase in ATP demand, accompanied by the acceleration of starch degradation in MGA161 cells. Although the anaerobic ATP level of C. reinhardtii cells was partially decreased by gramicidin D, starch degradation did not accelerate markedly when compared with the result in MGA161 cells. Therefore, starch was degraded at nearly the maximum rate in C. reinhardtii cells under anaerobic conditions; in contrast, the high level of ATP in MGA161 cells repressed starch degradation even under anaerobic conditions, resulting in the absence of the Pasteur effect.

Frequency-based multilayer neural network with on-chip learning and enhanced neuron characteristics.

A new digital architecture of the frequency-based multilayer neural network (MNN) with on-chip learning is proposed. As the signal level is expressed by the frequency, the multiplier is replaced by a simple frequency converter, and the neuron unit uses the voting circuit as the nonlinear adder to improve the nonlinear characteristic. In addition, the pulse multiplier is employed to enhance the neuron characteristics. The backpropagation algorithm is modified for the on-chip learning. The proposed MNN architecture is implemented on field programmable gate arrays (FPGA's) and the various experiments are conducted to test the performance of the system. The experimental results show that the proposed neuron has a very good nonlinear function owing to the voting circuit. The learning behavior of the MNN with on-chip learning is also tested by experiments, which show that the proposed MNN has good learning and generalization capabilities. Simple and modular structure of the proposed MNN leads to a massive parallel and flexible network architecture, which is well suited for very large scale integration (VLSI) implementation.

["Separate hypothermia" retrograde cerebral perfusion for repair of aortic arch].

We have developed a new technique of retrograde cerebral perfusion. To avoid the disadvantages by deep hypothermia, and to protect the brain for longer time, we perfused from SVC cannula with blood cooled at 10-15 degrees C, at the same time from femoral artery with blood cooled at 20-26 degrees C. From October 1991 to December 1992, 8 patients underwent surgical repair using this method. By this method, the cases of which cerebral perfusion time were 147, 134, 125, 119, 110 minutes, did not have neurological deficits.

[A case report of surgical treatment for aortic valve papillary fibroelastoma].

A 71-year-old woman was referred to our hospital for aortic valve replacement because of the vegetation of aortic valve. She had transient right arm weakness and aphasia in November 1991. On two-dimensional echocardiogram, she was found to have a mobile, pedunculated mass attached to the non-coronary cusp of the aortic valve. At operation, multiple frond-like tumor measuring 7*7 mm was found attached to the free-edge of the non-coronary cusp of the aortic valve. The aortic valve with this tumor was excised and replaced with a 21-mm Carpentier-Edwards prosthesis. Microscopic sections revealed the typical findings of a papillary fibroelastoma. The patient's postoperative course was unremarkable.

[Surgical treatment of total anomalous pulmonary venous connection Darling type Ib using pedicled right atrial flap].

A one-month-old baby with total anomalous pulmonary venous connection (TAPVC) type Ib underwent a total correction with a pedicled right atrial (RA) flap, which was made by incising the RA wall in a quadrangular configuration. The common pulmonary vein (PV) was cut back into the left atrium (LA). Then the RA flap was sutured along the limbus of PV recess and atrial septal defect (ASD) to create a new pulmonary venous channel. The defect in the RA wall was directly closed without any prosthetic patch. Absorbable sutures (# 6-0 PDS) were used throughout. Postoperative course was uneventful and echocardiogram showed widely opened PV channel draining into the LA. We think that this procedure could be applied in various types of total and partial anomalous pulmonary venous connection, avoiding pulmonary venous obstruction on the assumption that the RA flap should grow.