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Advances in cMUT technology accelerated research efforts in the design of driver/receiver front-end integrated circuits (ICs) for transducer arrays. Considering ASIC manufacturing costs and turn-around times, a thorough assessment of the front-end circuit before tape-out is compulsory. For an accurate evaluation, circuit simulations have to be run on a system-level model that includes the post-layout extracted netlist of the IC and an equivalent circuit for the transducers pulse-echo behavior. In this paper, we present the modeling, design and test of a front-end IC for 2D cMUT arrays. To evaluate the circuit response, we first developed a pulse-echo model for an array element. The model is a modified version of the Mason Equivalent Circuit where the radiation impedance term has been replaced by an RLC network to include the effects of finite transducer size and diffraction loss. The model has been verified by running transient FEA simulations using ANSYS. Meanwhile, we designed a driver/receiver front-end circuit for a 2D cMUT array element. The circuit was composed of a high voltage (50 Volt) pulse driver, an NMOS protection switch and a trans-impedance amplifier. We then used the transducer model to simulate the response of the front-end circuit using Cadence Spectre. The simulation results are then verified by comparing them to experimental data obtained from the manufactured front-end IC. We demonstrated that information obtained from a model describing the behavior of the front-end circuit together with the transducer element is consistent with the experimental data and hence can be used to assess system performance.

The method for magneto-fluid analysis of an electromagnetic fluid pump taking account of eddy currents due to velocity effects is proposed. In both analyses, Lagrange coordinate system is applied in time differential terms. The proposed method is applied to a simplified electromagnetic pump model. It is shown that the eddy currents due to velocity effects should be considered

At the Japan Aerospace Exploration Agency, a zero magnetic field is required to test the magnetic characteristics of spacecrafts, satellites and to calibrate magnetometers. This zero-magnetic field is realized by means of a three-axis coil system which can cancel the uniform earth's magnetic field, but cannot cancel magnetic disturbance because of no magnetically shielded room. Therefore, the magnetic disturbance within and in the vicinity of the zero-magnetic field of a Spacecraft Magnetic Test Site (SMTS) is investigated by comparing the results of three-dimensional (3-D) finite-element analysis with measurements. Distributions of the magnetic disturbance due to three hemispherical objects-the roof, the foundation made of concrete, and the hole in the ground for the SMTS building-are analyzed and compared with those measured by a proton magnetometer. Consequently, it is shown that the hemispherical hole in the ground for the SMTS building, which has weak magnetism and is a little higher than that of concrete, generates a weak magnetic disturbance in the zero-magnetic field of the SMTS

Imaging of dopaminergic function is useful in the investigation of patients with Parkinson disease (iPD) and other extrapyramidal diseases. Using agents that bind to dopamine transporters ([123I]beta-CIT) and receptors ([123I]IBF SPECT), we investigated SPECT in 9 healthy volunteers and 24 patients for dopamine transporters as well as 15 patients for dopamine receptors. In beta-CIT SPECT studies, we examined 17 iPD patients (63.3 +/- 9.9 y/o), 3 multiple system atrophy (MSA) patients (OPCA type) (64.0 +/- 8.0 y/o), 2 vascular parkinsonism (VP) patients (71.0 +/- 0.0 y/o), 1 progressive supranuclear palsy (PSP) patient (69 y/o), 1 cortico-basal degeneration (CBD) patient (50 y/o) and nine healthy controls (39.1 +/- 9.3 y/o). For IBF SPECT studies 11 iPD patients (60.6 +/- 10.9 y/o), 3 MSA patients (2 OPCA type (50.5 +/- 3.5 y/o) and 1 SND type (65 y/o)) and 1 PSP patient (60 y/o) underwent SPECT scans after the injection of [123I]IBF. The specific to nonspecific striatal uptake ratio(St/Oc-1), ratio of putaminal uptake to caudatal uptake (Pu/Ca), and asymmetry indices (AI) were estimated. beta-CIT studies showed St/Oc-1 as follows; iPD: 2.66 +/- 1.09 (n = 17), VP: 5.73 and 7.39, MSA: 1.84 +/- 0.46 (n = 3), PSP: 2.34, CBD: 2.16. In all extrapyramidal diseases except VP, St/Oc-1 ratios were significantly lower than those in normal volunteers (6.46 +/- 1.08) (p0.01). Also in early-phase iPD patients (Yahr I-II), St/Oc-1 (3.16 +/- 1.49: n = 4) was significantly lower than those in normal volunteers (p0.01). In IBF studies, St/Oc-1 ratios were significantly higher in early-phase (Yahr I-II) iPD patients (1.82 +/- 0.25: n = 5) than those in late-phase (Yahr III-IV) iPD patients (1.38 +/- 0.32: n = 6) (p0.05). The Pu/Ca ratios in iPD patients (1.12 +/- 0.13) and MSA (OPCA type) patients (0.95 +/- 0.05) were higher than that in MSA (SND type) patient (0.78) and were lower than that in PSP patient (1.55). In conclusion, beta-CIT-SPECT is useful for the diagnosis of early-phase iPD patients and for differentiating VP from other extrapyramidal diseases. IBF-SPECT is useful for the diagnosis of the severity of iPD and has the possibility for ruling out MSA (SND type) or PSP from iPD. Both tracers are useful for investigating the pathophysiology of patients with iPD and other extrapyramidal diseases.

Computerized tomographic measures of recurrent cerebral infarctions, atrophy and local perfusion were all prospectively correlated with cognitive testing during treatment of risk factors plus antiplatelet therapy among vascular dementia patients. Neurological and cognitive status were quantified among 22 demented patients with small strokes and compared with 22 age-matched normal volunteers. In vascular dementia, risk factor control plus antiplatelet therapy reduced cerebral infarctions, increased perfusion, and stabilized or improved cognitive test performance, despite age-related, progressive cerebral atrophy.

Cerebral CT changes are correlated with cognitive declines among 18 patients with probable dementia of Alzheimer type (DAT) (7 men, 11 women, mean age 75.4 years) and are compared for control purposes with similar measures among 18 age-matched normal volunteers (8 men, 10 women, mean age 73.7 years). Mean follow-up intervals are 28.6 months for DAT and 27.0 months for controls. For DAT, annual rates for ventricular volume enlargement are + 9.2% and for cortical atrophy are −2.1%. Annual reductions in regional cerebral perfusions per 100 g brain/min, are: total cortex −1.1 ml, frontal −1.2 ml, temporal and parietal −0.9 ml, basal ganglia −1.6 ml, thalamus −2.5 ml, total white matter −0.6 ml, frontal white matter −0.7 ml. At entry evaluation, compared to normals, DAT patients had reduced CT densities in white matter, but not in cortex. Nevertheless, cortical CT densities declined progressively at annual rates of −0.72 Hounsfield units (HU), but remained constant in white matter. Annual point score declines for Cognitive Capacity Screening Examinations were −2.0 and for Mini Mental State: −2.8. Controls showed no cognitive change. Multiple regression analyses correlate cognitive declines with: (1) reductions in perfusion within parietal cortex ( p = 0.015), (2) decreases in cortical volume ( p = 0.019), and (3) decreases in HU within subcortical gray matter ( p = 0.007).

CT was used to measure changes in cerebral gray and white matter tissue densities associated with normal aging, using a cross-sectional design, in order to provide normative data for comparisons with abnormal aging such as dementias of Alzheimer's and vascular types. Cerebral compartmental densities were measured using plain CT, and their perfusion values were recorded during stable xenon inhalation (CT-CBF), among 81 neurologically and cognitively normal volunteers of different ages. Results led to the conclusion that cortical gray matter tissue densities progressively decline (polio-araiosis) after age 60. Cortical polio-araiosis is coupled with regional hypoperfusion but not with cortical atrophy. It is speculated that the cortical hypodensity identified by CT imaging parallels declines in cortical synaptic density, as reported from autopsy studies using anti-synaptophysin staining of cerebral cortex obtained from normal people above and below age 60. The coupling of cortical hypoperfusion with polio-araiosis is believed to reflect age-related reductions of cortical metabolic demands as reported by PET. During normal aging leuko-araiosis correlates directly with cortical atrophy, suggesting that anterograde axonal degeneration resulting from cortical neuronal dearborization play a role in its causation.

Following acute, localized lesions of the central nervous system, arising from any cause, there are immediate depressions of neuronal synaptic functions in other areas of the central nervous system remote from the lesion. These remote effects result from deafferentation, a phenomenon known as "diaschisis". After an interval of time, which will vary directly with the severity of the lesion, functional recovery occurs due to synaptic reactivation of neurones. This is favourably influenced by rehabilitation. Diaschisis most commonly manifests itself by such neurological signs as impaired consciousness or cognitive impairments including dementia, dyspraxias, dystaxias, dysphasias, incoordination and sensory neglect. The nature of diaschisis has been demonstrated by widespread depressions of local cerebral blood flow and metabolism extending far beyond the anatomical lesion. Recovery of function is associated with recovery of local perfusion and metabolism.

The method of coating the metallic implant made of paramagnetic materials with diamagnetic materials has been proposed to reduce the magnetic disturbance of metallic implants which causes artifact in magnetic resonance imaging. The optimal thicknesses of the diamagnetic coatings have been obtained for a straight cylindrical hip joint and an aneurysm clip by using the magnetic field analysis of the finite element method (FEM). Whereas in the manufacturing, with respect to the mechanical force of the diamagnetic material, etc., the new structure of dual-material model with diamagnetic material inside and paramagnetic material outside is considered better. In this paper, first the effectiveness of the structure of the dual-material model with actual diamagnetic material inside and paramagnetic material outside is investigated by using the FEM. Then optimal thicknesses of paramagnetic coating of two models are obtained. Finally the effectiveness of the dual-material model is verified by the experiment.

Periventricular or deep white-matter lesions on brain imaging, so-called leukoaraiosis [8], have been frequently observed in elderly subjects with or without dementia. They are associated with age, increased systolic blood pressure, motor and reflex deficits, and with deficits in cognitive function [1,19]. Recently these changes have attracted the attention of clinicians and pathologists in relation to Binswanger’s disease [3,6,12,17,18] or senile dementia [15]. The pathological significance of these changes are, however, still in dispute. Hachinski and his coworkers [8,19,20] concluded from their studies that white-matter changes were associated with intellectual impairment and sometimes with vascular disease. On the other hand, Leys et al. [14] reported that periventricular and white-matter hyperintensities on magnetic resonance imaging (MRI) were frequent incidental findings in the elderly and did not significantly differ between patients with Alzheimer’s disease and healthy controls. In order to clarify the underlying pathophysiological mechanism of these changes, we investigated cerebral hemodynamics in patients with periventricular white-matter lesions on brain imaging and correlated the data with severity of white-matter changes, mental function, and other clinical findings.

We evaluated the effects of cilostazol, a selective inhibitor of cyclic adenosine monophosphate phosphodiesterase, on the pial vessels of adult cats subjected to endothelial damage followed by middle cerebral artery occlusion. Six cats were treated with cilostazol and four with 30% N,N-dimethylformamide in 70% saline (solvent). The brain surface was irradiated with ultraviolet rays through a cranial window for 3 minutes to selectively damage the endothelium of the pial vessels in both groups. Beginning 32 minutes after termination of the irradiation, the middle cerebral artery was occluded for 30 minutes. Thirty minutes before occlusion, intravenous infusion of 30 micrograms/kg/min cilostazol or 0.1 ml/kg/min solvent was begun and continued until the end of the study. Before occlusion, the infusion of cilostazol induced a significant (p less than 0.05) dilatation while the infusion of solvent produced no significant changes in the diameter of the pial arteries. The pial veins of solvent-treated cats showed significant (p less than 0.05) constriction during occlusion, whereas cilostazol-treated cats exhibited only mild constriction of the pial veins. The formation of platelet thrombi after occlusion was significantly (p less than 0.05) inhibited in the pial veins of cilostazol-treated compared with solvent-treated cats. Similarly, the microcirculation of the pial veins was effectively restored after reopening of the middle cerebral artery in cilostazol-treated compared with solvent-treated cats. Our data suggest that cilostazol is an effective antithrombotic agent as well as a potent vasodilator acting on vascular smooth muscle.

To achieve economical compensation for the huge-capacity negative sequence currents generated by high-speed railway load, an electromagnetic hybrid compensation system (EHCS) and control strategy is proposed. The EHCS is made up of a small-capacity railway static power conditioner (RPC) and a large-capacity magnetic static var compensator (MSVC). Compared with traditional compensation methods, the EHCS makes full use of the SVC's advantages of economy and reliability and of RPC's advantages of technical capability and flexibility. Based on the idea of injecting a negative sequence, the compensation principle of the EHCS is analyzed in detail. Then the minimum installation capacity of an EHCS is theoretically deduced. Furthermore, a constraint optimization compensation strategy that meets national standards, which reduces compensation capacity further, is proposed. An experimental platform based on a digital signal processor (DSP) and a programmable logic controller (PLC) is built to verify the analysis. Simulated and experimental results are given to demonstrate the effectiveness and feasibility of the proposed method.