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Assessment of left ventricular (LV) function with an emphasis on contractility has been a challenge in cardiac mechanics during the recent decades. The LV function is usually described by the LV pressure-volume (P-V) diagram. The standard P-V diagrams are easy to interpret but difficult to obtain and require invasive instrumentation for measuring the corresponding volume and pressure data. In the...
Left ventricular ejection fraction (EF) is perhaps the most clinically significant index of global ventricular function. EF is measured in clinical practice via imaging methods such as echocardiography. However, these methods generally require a well-trained operator and expensive capital equipment. Thus, EF measurements are only obtained in the clinical setting and are usually made few and far between...
We evaluated the stress distribution in a geometrical shape model and a shape model obtained from human heart using two different fiber orientations. For both orientation models, the results showed large differences of the stress distributions between the mathematical shape model and the maesurement based shape model. These results suggest that stress distribution is highly dependent on the model...
Quantitative measurement of left ventricular wall motion can improve clinical diagnosis by providing a more objective approach than qualitative analysis, which i s subject to large inter-observer variability. We have developed novel techniques for quantifying left ventricular wall motion in three-dimensional image data sets. In this study, finite element models simulating regional ischemia in the...
The current techniques applied in biotechnology allow to obtain many types of molecules that must be tested on cell cultures (High Throughput Screening HTS). Although such tests are usually carried out automatically on mini or microwell plates, the procedures in the preindustrial stage are performed almost manually on higher volume recipients known as bioreactors. The growth conditions in both stages...
Three-dimensional (3-D) models of neural cell culture may provide researchers with a more physiologically-relevant setting to study neurobiological phenomena than traditional two-dimensional (2-D) culture models. However, in the development of thick (≫500 ??m) 3-D cultures, diffusion limited mass transport necessitated the use of cell densities much lower than those found in the central nervous system...
Force generation and directed motion of molecular motors using a simple two-state model are studied in the paper. Here we consider the asymmetric and periodic potential in the model. The symmetric and periodic potential is adopted to describe the interactions between motor proteins and filaments that are periodic and polar. The flux and the slope of the effective potential as functions of the temperature...
Many implantable devices require large capacity batteries implanted in the body. Transcutaneous battery recharging can effectively maintain the longevity of these implants. Based on this consideration we have developed a transcutaneous battery recharging circuit unit which takes advantages of skin volume conduction. This unit is able to pass 2.8 mA from the outside to the inside of pig skin with a...
Conventional multielectrode arrays (MEAs) cannot always access desired neurons due to low electrode density and small number of electrode. To overcome this problem, we propose a light-addressable planar electrode on a glass substrate. The electrode has a 3-layer structure, namely a transparent SnO2 layer, an hydrogenated amorphous silicon (a-Si:H) layer, and a passivation layer. Illumination to the...
For extracellular recordings from neurons, it is desirable to use the same electrode for stimulation as well as for recording. Since neural preamplifiers usually exhibit high-pass filtering at frequencies as low as 0.1 Hz, the recovery from saturation is typically very slow. Consequently, following stimulation, no signal can be detected for up to several seconds. This is unacceptably slow response...
On chip signal compression is one of the key technologies driving development of energy efficient biotelemetry devices. In this paper, we describe a novel architecture for analog-to-digital (A/D) conversion that combines sigma delta conversion with the spatial data compression in a single module. The architecture called multiple-input multiple-output (MIMO) sigma-delta is based on a min-max gradient...
Two types of intracortical multichannel flexible neural probes coated with a hybrid biodegradable polymer were designed and fabricated. The hybrid biodegradable polymer was made of polyethylene glycol and biodegradable polymeric microspheres containing nerve growth factor (NGF) and incorporated to improve the stiffness for flexible neural probe insertion, and promote regrowth of damaged neural tissues...
We have used the genetically-encoded fluorescent exocytosis indicator synaptopHluorin (spH), expressed selectively in mouse olfactory receptor neurons, to image odor representations at the input to the olfactory bulb. The olfactory bulb is a powerful system for in vivo fluorescence imaging because its inputs are segregated into receptor-specific functional units (glomeruli) that are optically accessible...
We are investigating the computational properties of principal neurons in the mammalian brain. To manage the small size and intricate structure of neuronal dendrites, we employ advanced optical imaging techniques in combination with automatic image reconstruction and computational modeling to study their complex spatio-temporal pattern of activity.
In this work, we have adapted the directed transfer function (DTF) to fMRI for the analysis of cortical network dynamics. While modern fMRI sequences are capable of sampling at second or sub-second rates, the underlying hemodynamic response limits the true temporal resolution to the order of 6-12 seconds. Therefore, DTF analysis of fMRI is appropriate for characterizing dynamics in brain response...
Radiofrequency (RF) tumor ablation has become an accepted treatment modality for tumors not amenable to surgery. The need for larger ablation zones has required increase in RF generator power, with current generation devices delivering 200 - 250 W. Skin burns due to ground pad heating have become a common complication and are now a limiting factor for further increase in ablation zone and generator...
The advantages of delivering injections via needle-free methods are numerous. However, conventional methods for needle-free injection lack sufficient control over depth of penetration and shape of injection. Thus, a needle-free injector was designed, constructed, and tested, using a controllable linear Lorentz-force actuator. This actuator allows rapid control of the injection pressure during injections...
Brain therapy using focused ultrasound remains very limited due to the strong aberrations induced by the skull. A technique using time-reversal was validated recently in-vivo on 20 sheeps [1]. The principal handicap of this technique is the need of an hydrophone at the focal point for the first step of the time-reversal procedure, which is minimally invasive but lightly traumatizing. A completely...
A method for tracking locally the 3D motion of biological tissues is developed and applied to the correction of motion during High Intensity Focused Ultrasound (HIFU) therapy. The motion estimation technique is based on an accurate ultrasonic speckle tracking method. A pulse-echo sequence is performed for a subset of the transducers of a phased array. For each of these sub-apertures, the displacement...
We developed a modified trail-making test using a PC and touch panel and compared it with the Mini Mental State Examination (MMSE). Methods and Patients: The test consisted of a series of numbers from 1 to 36, randomly arranged across the display. The object of the test was for the subject to touch the numbers in order, beginning with 1 and ending with 36, in as little time as possible. The system...
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