检索结果-内蒙古大学图书馆

Subcellular Composition Based On Light-Element EELS

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

TRACE ELEMENT QUANTITATION IN BIOLOGICAL X-RAY MICROANALYSIS

引用

Microscopy and Microanalysis 1998年第S2期4卷 212-213页

作者： Leapman, R.D. Swyt-Thomas, C.R. Agoston, D.V. Pivovarova, N. Andrews, S.B. Biomedical Engineering & Instrumentation Program DIRS ORS United States Laboratory of Developmental Neurobiology NICHD United States Laboratory of Neurobiology NINDS National Institutes of Health Bethesda 20892 MD United States

In high-resolution biological energy-dispersive x-ray (EDX) microanalysis it is often necessary to measure very low elemental concentrations. As an example, calcium, a physiologically important element, typically occurs in subcellular compartments at concentrations of 10-100 atomic parts per million (corresponding to 1-10 millimole/kg dry weight of sample) and it is ultimately desirable to measure the concentration of this element with a standard error of ±1 atomic ppm (or ± 0.1 millimole/kg). Detection of calcium in biological specimens is further complicated by the presence of relatively high levels of potassium (around 0.5 atomic % or 500 millimole/kg), which gives rise to overlap of the K Kβ and Ca Kα peaks in the EDX spectrum. Counting statistics are frequently the limiting factor for detectability, but this is not necessarily the case because in the analytical electron microscope it is possible to collect spectra for long periods using a high probe current. © Microscopy Society of America 1998.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Scalable Stereolithography-Based Monolithic Microfluidic Device Creation for Rapid Biological Sample Analyses 25

Scalable Stereolithography-Based Monolithic Microfluidic Dev...

引用

25th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2021

作者： Markoski, Alex Wong, Ian Y. Borenstein, Jeffrey T. Department of Synthetic Biology and Bio Instrumentation Draper Bioengineering Division CambridgeMA United States School of Engineering Center for Biomedical Engineering Joint Program in Cancer Biology Brown University ProvidenceRI United States

ISBN: (纸本)9781733419031

Microfluidic manipulation and perfusion of multicellular spheroids often utilize device geometries with relatively large channels but smaller trapping features, which are tricky to fabricate with robust bonding. Here, we demonstrate one-step light-directed 3D printing of a sealed monolithic device with enclosed channels and pillar arrays, which we validate for capturing and imaging multicellular spheroids in varying flow. Our approach links computer-aided design with finite element simulations of flow and oxygen conditions, which were experimentally realized. We envision these design and fabrication approaches may be useful in generating rapidly designed multiplexed monolithic arrays for preclinical drug testing in cancer. © 2021 MicroTAS 2021 - 25th International Conference on Miniaturized Systems for Chemistry and Life Sciences. All rights reserved.

关键词： Microfluidics

来源：评论

学校读者我要写书评

暂无评论

Stationary low-coherence light imaging and spectroscopy using a CCD camera

Stationary low-coherence light imaging and spectroscopy usin...

引用

Advances in Laser and Light Spectroscopy to Diagnose Cancer and Other Diseases 1994

作者： Knüttelt, A. Schmitt, J.M. Shayt, M. Knutsont, J.R. Laboratory of Cell Biology NHLBI National Institutes of Health BethesdaMD20892 United States Biomedical Engineering and Instrumentation Program National Institutes of Health BethesdaMD20892 United States

We describe a new optical low-coherence reflectometer (interferometer) for depth profiling and lateral scanning without moving parts which can also be employed as a stationary FT-JR spectrometer. The reflectometer covers a range of 0.45 mm and 1 mm in the depth and lateral dimensions, respectively. The entire depth range is recorded simultaneously in one scan using a cooled 16-bit CCD camera;the lateral dimension is covered by scanning the probe beam sequentially across the sample with an acousto-optic deflector. The frequency shift generated by this deflector and an additional one placed in the reference arm creates an AC heterodyne signal with a frequency of 2 kHz. Since the CCD camera cannot record the AC signal directly, a special readout scheme is employed. Stationary imaging was demonstrated using an artificial phantom. Using the same interferometer configured as a stationary FT-IR spectrometer, we measured the emission spectrum of an LED with a resolution of 0.74 nm at a central wavelength of 820 nm. We discuss the performance of the stationary CCD imaging system and compare it to that of a singledetector system employing moving parts. © 1994 SPIE.

关键词： CCD cameras

来源：评论

学校读者我要写书评

暂无评论

Spline multiresolutions and wavelet transforms

Spline multiresolutions and wavelet transforms

引用

1992 IEEE-SP International Symposium on Time-Frequency and Time-Scale Analysis

作者： Unser, M. Aldroubi, A. Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health Bldg. 13 Room 3W13 BethesdaMD20892 United States

ISBN: (纸本)0780308050

We present an extension of the family of BattlefimariB spline wavelet transforms. By relaxing the intra-level orthogonality constraint, we show how to construct generalized polynomial spline scaling functions and wavelets that span the same multiresolution spaces, but can also exhibit very distinct properties. Particular examples in this family include the Bspline wavelets of compact support that are optimally localized in time-frequency;the cardinal spline wavelets that have the fundamental interpolation property;and the dual spline wavelets (the biorthogonal complement of the B-spline wavelets). We provide a full characterization of the digital filters for the corresponding fast wavelet transform algorithms. We also discuss the asymptotic properties of these representations, and indicate the link with Shannon's sampling theory and the Gabor transform. © 1992 IEEE.

关键词： Digital filters

来源：评论

学校读者我要写书评

暂无评论

Head surface digitization and registration: A method for mapping positions on the head onto magnetic resonance images

引用

Brain Topography 1994年第3期6卷 185-192页

作者： Wang, Binseng Toro, Camilo Zeffiro, Thomas A. Hallett, Mark Biomedical Engineering and Instrumentation Program National Center for Research Resources and Human Motor Control Section Medical Neurology Branch National Institute of Neurological Disorders and Stroke National Institutes of Health Bethesda 20892 MD United States

We have developed a method for mapping positions on the head, such as anatomical landmarks, electrode locations, and stimulation sites, onto magnetic resonance (MR) images of the head. This method is based on the registration of two representations of the head surface: a series of contours obtained from MR images and a set of points measured from the head. The three-dimensional coordinates of each head point were acquired with the use of a magnetic digitizer, whose source was removed from the equipment and mounted on top of the subject's head. This arrangement seemed less uncomfortable for the subject than head immobilization and allowed the acquisition of many points without compromising the precision of the measurements. The digitized head surface was registered to MR image head contours using a surface registration algorithm. The registration provided the rotation and translation parameters needed for mapping head positions onto MR images. The precision of this mapping method has been estimated to be in the range of 3 to 8 mm. This method has been used to map dipole sources in electroencephalography and magnetoencephalography and to impose maps of scalp sites used in transcranial magnetic stimulation onto MR and PET images of the brain. © 1994 Human Sciences Press, Inc.

关键词： Head positions Head surface digitization Mapping positions onto images MRI Surface registration

来源：评论

学校读者我要写书评

暂无评论

Segmentation of gated SPECT images for automatic computation of myocardial volume and ejection fraction

Segmentation of gated SPECT images for automatic computation...

引用

IEEE International Conference on Image Processing

作者： P. Brigger S. Bacharach A. Aldroubi M. Unser Biomedical Engineering and Instrumentation Program National Institute of Health Bethesda MD USA

Describes an image processing system for the automatic assessment of ejection fraction (EF) from noisy SPECT left ventricular myocardial perfusion images. A segmentation scheme consisting of an elliptical coordinate transformation, matched filtering and dynamic contour tracking detects the endo- and epicardial boundaries. Computation of EF is performed based on the epi- rather than the endocardial boundary, which proves to be more robust for images with low signal-to-noise ratios. The computation incorporates anatomical constraints of constant myocardial mass and smooth cardiac variation. The algorithm was tested on different image modalities and shows good linear agreement with EFs obtained from conventional approaches based on planar gated blood pool imaging (PET: y=8.7+1.07x, r=0.84, Technetium-99m MIBI SPECT: y=5.0+0.80x, r=0.90, Thallium-201 SPECT: y=23.5+0.82x, r=0.77, RMS error=10.0). The proposed scheme may be an alternative for EF computation without the need for additional image acquisitions.

关键词： Image segmentation Myocardium Image processing Matched filters Filtering Robustness Signal to noise ratio Testing Blood Positron emission tomography

来源：评论

学校读者我要写书评

暂无评论

Use of the wavelet transform to investigate differences in brain PET images between patient groups 2

Use of the wavelet transform to investigate differences in b...

引用

Mathematical Methods in Medical Imaging II 1993

作者： Ruttimann, Urs E. Unser, Michael Rio, Daniel Rawlings, Robert R. National Institute on Alcohol Abuse and Alcoholism National Institutes of Health BethesdaMD20892 United States Biomedical Engineering and Instrumentation Program National Institutes of Health BethesdaMD20892 United States

Suitability of the wavelet transform was studied for the analysis of glucose utilization differences between subject groups as displayed in PET images. To strengthen statistical inference, it was of particular interest investigating the tradeoff between signal localization and image decomposition into uncorrected components. This tradeoff is shown to be controlled by wavelet regularity, with the optimal compromise attained by third-order orthogonal spline wavelets. Testing of the ensuing wavelet coefficients identified only about 1.5% as statistically different (p © 1993 SPIE. All rights reserved.

关键词： Medical imaging

来源：评论

学校读者我要写书评

暂无评论

The L/sub 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： M. Unser A. Aldroubi M. Eden Biomedical Engineering and Instrumentation Program National Center for Research Resources National Institutes of Health DHHS Bethesda MD USA

The authors are concerned with the derivation of general methods for the L/sub 2/ approximation of signals by polynomial splines. The main result is that the expansion coefficients of the approximation are obtained by linear filtering and sampling. The authors apply those results to construct a L/sub 2/ 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. It is demonstrated 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： Spline Signal resolution Spatial resolution Nonlinear filters Polynomials Wavelet transforms Laplace equations Image processing Data structures Multigrid methods

来源：评论

学校读者我要写书评

暂无评论

Fast computation of the continuous wavelet transform through oblique projections

Fast computation of the continuous wavelet transform through...

引用

International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： M. Vrhel Chulhee Lee M. Unser Biomedical Engineering and Instrumentation Program National Institutes of Health DHHS Bethesda MD USA

We introduce a fast simple method for computing the real continuous wavelet transform (CWT). The approach achieves O(N) complexity per scale and the filter coefficients can be analytically obtained by a simple integration. Our method is to use P wavelets per octave and to approximate them with their oblique projection onto a space defined by a compact scaling function. The wavelet templates are expanded to larger sizes (octaves) using the two-scale relation and zero padded filtering. Error bounds are presented to justify the use of an oblique projection over an orthogonal one.

关键词： Continuous wavelet transforms Wavelet transforms Finite impulse response filter Wavelet analysis biomedical computing Sampling methods Shape Convolution biomedical engineering Instruments

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：