检索结果-内蒙古大学图书馆

A monitoring system for energy transduction by bacteriorhodopsin liposomes

JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 1996年第2期33卷 89-104页

作者： Hendler, RW Mukhopadhyay, AK Smith, PD Cascio, HE Laboratory of Cell Biology National Heart Lung and Blood Institute Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bethesda MD 20892 USA

A computer-controlled system and custom software are described that collect information and perform computations to quantify important parameters of energy transduction during the conversion of photons into a proton electrochemical gradient (Delta<(mu)over tilde>(H+)) by bacteriorhodopsin (BR)-liposomes. The strong actinic light used to energize the BR-liposomes causes several serious problems for the approaches commonly used to measure these parameters. This paper identifies these problems and presents solutions that permit the acquisition of the desired information, namely, the initial (1st sec) rate and total extent of H+ translocation, rate of H+ leakage (driven by an existing Delta<(mu)over tilde>(H+)), external, internal and delta pH values, and Delta Psi values. The system is presented with representative experimental data.

关键词： membrane potential delta pH proton pump light activation fluorescence probe photobleaching of probe SCN--selective electrode computer-controlled system

来源：评论

学校读者我要写书评

暂无评论

Dose-dependent smooth muscle cell proliferation induced by thermal injury with pulsed infrared lasers 14

Dose-dependent smooth muscle cell proliferation induced by t...

引用

14th Annual International Conference of the IEEE engineering in Medicine and Biology Society, EMBS 1992

作者： Douek, Philippe C. Correa, Rosaly Unger, Ellis F. Neville, Richard Banai, Shmuel Epstein, Stephen E. Leon, Martin B. Bonner, And Robert F. Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health BethesdaMD United States

ISBN: (纸本)0780307852

Pulsed infrared laser irradiation induced localized thermal lesions in arteries by transiently heating to ∼30°C above ambient and subsequent SMC proliferation in rabbits by 3-4 weeks. Neointimal proliferation exhibited a clear dose dependence both as laser fluence was increased (R=0.83) and for a fixed surface irradiation as the depth of the nearest arterial media was decreased (R=0.95). Thermal injury to the arterial wall is shown to be potent stimulus for SMC proliferation, favoring reduction in energies used in laser or thermal angioplasty. © 1992 IEEE.

关键词： Cell proliferation

来源：评论

学校读者我要写书评

暂无评论

REGISTRATION AND STATISTICAL-ANALYSIS OF PET IMAGES USING THE WAVELET TRANSFORM

引用

IEEE engineering IN MEDICINE AND BIOLOGY MAGAZINE 1995年第5期14卷 603-611页

作者： UNSER, M THEVENAZ, P LEE, CH RUTTIMANN, UE Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health DHHS USA Laboratory of Clinical Studies National Institute on Alcohol Abuse and Alcoholism National Institutes of Health DHHS USA

We have described a general procedure for the processing and analysis of PET data. We have used the multiresolution framework of the wavelet transform to derive new solutions for the two main processing steps. The first task was to align the various brain images using a general affine deformation model. Our registration procedure uses a continuous polynomial spline image model and takes advantage of the multiresolution structure of the underlying function spaces. This method implements a nonlinear least squares optimization technique with a coarse-to-fine iteration strategy that substantially improves the overall performance of the algorithm. The second task was to analyze the series of registered images and to detect the between group differences in metabolic brain activity. We chose to take advantage of the orthogonality and localization properties of the wavelet transform. Our approach was to apply this transform to the group-difference image and identify the wavelet channels that are globally significantly different from noise.< >

关键词： Statistical analysis Positron emission tomography Wavelet transforms Data analysis Continuous wavelet transforms Brain modeling Deformable models Polynomials Spline Image resolution

来源：评论

学校读者我要写书评

暂无评论

HOW THE ANISOTROPY OF THE INTRACELLULAR AND EXTRACELLULAR CONDUCTIVITIES INFLUENCES STIMULATION OF CARDIAC-MUSCLE

引用

JOURNAL OF MATHEMATICAL BIOLOGY 1992年第6期30卷 633-646页

作者： ROTH, BJ 1. Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bldg. 13 Rm. 3W13 20892 Bethesda MD USA

The bidomain model, which describes the behavior of many electrically active tissues, is equivalent to a multi-dimensional cable model and can be represented by a network of resistors and capacitors. For a two-dimensional sheet of tissue, the intracellular and extracellular conductivity tensors can be visualized as two ellipses. For any pair of conductivity tensors, a coordinate transformation can be found that reduces the extracellular ellipse to a circle and aligns the intracellular ellipse with the coordinate axes. The eccentricity of the intracellular ellipse in this new coordinate system is an important parameter. It can have two special values: zero (in which case the tissue has equal anisotropy ratios) or one (in which case the tissue is comprised of one-dimensional fibers coupled through the two-dimensional extracellular space). Thus the bidomain model provides a unifying framework within which the electrical behavior of a wide variety of nerve and muscle tissues can be studied. When the anisotropy ratios in the intracellular and extracellular domains are not equal, stimulation with an anode always causes depolarization of some region of tissue. An analogous effect occurs in models that describe one-dimensional fibers, in which an "activating function" determines the site of stimulation. Experiments indicate that cardiac muscle does not have equal anisotropy ratios. Therefore, models developed to describe stimulation of axons may also help in understanding stimulation of two- or three-dimensional cardiac tissue, and may explain the concept of anodal stimulation of cardiac tissue through a "virtual cathode".

关键词： BIDOMAIN VIRTUAL CATHODE CONDUCTIVITY ANISOTROPY CARDIAC MUSCLE

来源：评论

学校读者我要写书评

暂无评论

Fast continuous wavelet transform: A least-squares formulation

引用

SIGNAL PROCESSING 1997年第2期57卷 103-119页

作者： Vrhel, MJ Lee, C Unser, M Biomedical Engineering and Instrumentation Program Bldg. 13 Room 3N17 National Center for Research Resources National Institutes of Health Bethesda MD 20892 USA Electrical Engineering Department Yonsei University 134 Shinchon-Dong Seodaemun-Ku Seoul 120-749 South Korea

We introduce a general framework for the efficient computation of the real continuous wavelet transform (CWT) using a filter bank. The method allows arbitrary sampling along the scale axis, and achieves O(N) complexity per scale where N is the length of the signal. Previous algorithms that calculated non-dyadic samples along the scale axis had O(N log(N)) computations per scale. Our approach approximates the analyzing wavelet by its orthogonal projection (least-squares solution) onto a space defined by a compactly supported scaling function. We discuss the theory which uses a duality principle and recursive digital filtering for rapid calculation of the CWT. We derive error bounds on the wavelet approximation and show how to obtain any desired level of accuracy through the use of longer filters. Finally, we present examples of implementation for real symmetric and anti-symmetric wavelets. (C) 1997 Published by Elsevier Science B.V.

关键词： wavelet transform approximation theory B-splines

来源：评论

学校读者我要写书评

暂无评论

Design considerations in making a broad-range fiber-optic pH sensor

Design considerations in making a broad-range fiber-optic pH...

引用

Fiber Optic Sensors in Medical Diagnostics 1993

作者： Peterson, John I. Netto, Eden J. Biomedical Engineering and Instrumentation Program NCRR National Institutes of Health Building 13 Room 3N17 BethesdaMD20892 United States

The general background and theoretical aspects involved in making a broad-range fiber-optic pH sensor will be discussed. © 1993 Proceedings of SPIE - The International Society for Optical engineering. All rights ... 详细信息

关键词： Fiber optics

来源：评论

学校读者我要写书评

暂无评论

Affine transformations of images: A least squares formulation

Affine transformations of images: A least squares formulatio...

引用

The 1994 1st IEEE International Conference on Image Processing

作者： Unser, M. Neimark, M.A. Lee, C. Biomedical Engineering and Instrumentation Program NCRR National Institutes of Health Bldg. 13 Room 3W13 BethesdaMD20892 United States

We present a general framework for the design of discrete geometrical transformation operators, including rotations and scaling. The first step is to fit the discrete input image with a continuous model that provides an exact interpolation at the pixel locations. The corresponding image model is selected within a certain subspace V(φ)⊂L2(RP) that is generated from the integer translates of a generating function φ;particular examples of this construction include polynomial spline and bandlimited signal representations. Next, the geometrical transformation is applied to the fitted model, and the result is re-projected onto the representation space. This procedure yields a solution that is optimal in the least squares sense. We show that this method can be implemented exactly using a combination of digital filters and a re-sampling step that uses a modified sampling kernel. We then derive explicit implementation formulas for the piecewise constant and cubic spline image models. Finally, we consider image processing examples and show that the present method compares very favorably with a standard interpolation that uses the same model. © 1994 IEEE.

关键词： Interpolation

来源：评论

学校读者我要写书评

暂无评论

Multigrid adaptive image processing

Multigrid adaptive image processing

引用

IEEE International Conference on Image Processing

作者： M. Unser Biomedical Engineering and Instrumentation Program NCRR Bethesda MD USA

We consider a general weighted least squares approximation problem with a membrane spline regularization term. The key parameters in this formulation are the weighting factors which provide the possibility of a spatial adaptation. We prove that the corresponding space-varying variational problem is well posed, and propose a novel multigrid computational solution. This multiresolution relaxation scheme uses three image pyramids (input data, weights, and current solution) and allows for a very efficient computation with an effective O(N) complexity, where N is the number of pixels. This general multigrid solver can be useful for a variety of image processing tasks. In particular, we propose new multigrid solutions for noise reduction in images (adaptive smoothing spline), interpolation/reconstruction of missing image data, and image segmentation using an adaptive extension of the K-means clustering algorithm.

关键词： Image processing Spline Least squares approximation Biomembranes Spatial resolution Image resolution Pixel Noise reduction Smoothing methods Interpolation

来源：评论

学校读者我要写书评

暂无评论

Subcellular Composition Based On Light-Element EELS

引用

Microscopy and Microanalysis 2020年第S2期3卷 927-928页

作者： R.D. Leapman Biomedical Engineering & Instrumentation Program NCRR National Institutes of Health Bethesda MD 20892.

Recent work on biological electron energy-loss spectroscopy (EELS) in the analytical electron microscope has focused on measuring concentrations of the important elements, calcium and phosphorus. Analysis of the light elements, for which EELS was originally thought to be best suited, has so far not yielded much useful information from biological specimens. Whereas low-loss fine structure has been analyzed successfully to measure distributions of water and protein in frozen-hydrated cells, core-edge fine structure cannot be recorded at sufficiently low dose to obtain useful chemical information. However, the atomic ratios of the light elements (carbon, nitrogen and oxygen) obtained from EELS are less dependent on electron dose. Together with sulfur (in proteins) and phosphorus (in nucleic acids, phospholipids and phosphates) these ratios can help determine the types and proportions of compounds that are present at the subcellular level. Here we re-examine the potential for making these kinds of measurements.

关键词：

来源：评论

学校读者我要写书评

暂无评论

THE L(2) POLYNOMIAL SPLINE PYRAMID

引用

IEEE TRANSACTIONS ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE 1993年第4期15卷 364-379页

作者： UNSER, M ALDROUBI, A EDEN, M Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bethesda 20892 United States

The first part of this paper is concerned with the derivation of general methods for the L2 approximation of signals by polynomial splines. Such approximations can be represented in a variety of ways using different sets of shift-invariant basis functions (e.g., cardinal, dual, orthogonal or standard B-splines). The main result is that the expansion coefficients of the approximation are obtained by linear filtering and sampling. The second part applies those results to construct a L2 polynomial spline pyramid that is a parametric multiresolution representation of a signal. This hierarchical data structure is generated by repeated application of a REDUCE function (prefilter and down-sampler). A complementary EXPAND function (up-sampler and post-filter) allows a finer resolution mapping of any coarser level of the pyramid. Four equivalent representations of this pyramid are considered, and the corresponding REDUCE and EXPAND filters are determined explicitly for polynomial splines of any order n (odd). Some image processing examples are presented. The present formulation provides a number of interesting links with several other multiresolution techniques including the wavelet transform, scale-space filtering, and Burt's Gaussian and Laplacian pyramids. In particular, we demonstrate that the performance of the Laplacian pyramid can be improved significantly by using a modified EXPAND function associated with the dual representation of a cubic spline pyramid.

关键词： BINOMIAL FILTERS B-SPLINES DECIMATION INTERPOLATION MULTIGRID METHODS MULTIRESOLUTION POLYNOMIAL SPLINES PYRAMID RECURSIVE FILTERS SCALE SPACE SIGNAL APPROXIMATION SPLINE FILTERS WAVELET TRANSFORM

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：