4Pi-Confocal Microscopy Provides Three-Dimensional Images of the Microtubule Network with 100- to 150-nm Resolution

We show the applicability of 4Pi-confocal microscopy to three-dimensional imaging of the microtubule network in a fixed mouse fibroblast cell. Comparison with two-photon confocal resolution reveals a fourfold better axial resolution in the 4Pi-confocal case. By combining 4Pi-confocal microscopy with Richardson–Lucy image restoration a further resolution increase is achieved. Featuring a three-dimensional resolution in the range 100–150 nm, the 4Pi-confocal (restored) images are intrinsically more detailed than their confocal counterparts. Our images constitute what to our knowledge are the best-resolved three-dimensional images of entangled cellular microtubules obtained with light to date.     

Mapping of intracellular halogenous molecules by low and high resolution SIMS microscopy.

The subcellular distribution of halogenous molecules has been studied by SIMS microscopy in cultured cells of a human breast carcinoma (MCF-7 cell line). Two instruments of microanalysis were used. A low lateral resolution ion microscope (SMI 300 CAMECA) and a prototype scanning ion microscope equipped with a cesium gun that gives high lateral resolution images. This apparatus has been developed by G Slodzian, in Onera Laboratories (Office National d'Etudes et de Recherches Aérospatiales). Molecules studied by low lateral resolution ion microscope were halogenous steroids: fluorometholone, triamcinolone, bromocriptine and bromoandrosterone. Analytical images show that the first two compounds are mainly localized in the nuclear structure of MCF-7 cells whereas the last two molecules are localized in cytoplasm of these cells. Images were obtained with a resolution of 1 micron. With the scanning ion microscope, it is now possible to obtain images at the ultrastructural level. Four analytical images can be simultaneously obtained by a single scan of the imaged area, corresponding to a depth of erosion of the section of ten nm. The intranuclear distributions of three pyrimidine analogs, 5-bromo-2'-deoxyuridine, 5-iodo-2'-deoxyuridine and 5-fluorouracil have been studied in phase S and M of MCF-7 cells and these images have been compared to the distribution of sulfur, nitrogen and phosphorus. All these images have been obtained with a lateral resolution better than 100 nm.     

山丘区苹果树花期冠层反射率的定量遥感反演

采用山东省栖霞市苹果树花期不同分辨率的TM和ALOS影像,充分考虑坡向系数和冠层花叶比,通过地形辐射校正获取地表反演反射率,再经混合像元分解获取苹果树冠层的反演反射率,将30个果园样方的反演结果与同时段实测反射率及表观反射率进行比较,分析反演效果和精度.结果表明:地形辐射校正有效减弱了地形和大气的影响,恢复了阴影处地物,地表反演反射率影像的解析力大幅提高;无论是TM还是ALOS影像,冠层反演反射率的绝对误差和相对误差均最小,所有波段的相对误差表现出一致性,且样方间变化趋势与实测值最一致,说明混合像元分解是必要的.反演方法应用于不同分辨率影像,表现出相似的反射率变化特点,高分辨率图像更具优势,但受波段限制,可与中分辨率影像结合使用.     

基于不同空间尺度遥感影像估算森林叶面积指数的差异

地面测量点对遥感像元的代表性如何,怎样获取像元的相对真值,多大的空间分辨率可以真实地反映森林区域的叶面积指数(LAI),这些都是定量遥感中的重要问题.本研究计算LAI-2200和TRAC两种冠层分析仪测量的空间范围,并结合GF-2(4.1 m)、Sentinel-2(10 m)、Landsat-8(30 m)3种不同空间分辨率遥感影像,找到各尺度下像元的相对真值,在保持真值观测面积和遥感获取面积一致的条件下,基于一元指数和多元回归模型,对比分析不同空间分辨率影像对估算森林LAI的影响,并对3种影像模型进行30和100 m尺度下的检验以及各自数据集的空间代表性评价,比较得出最适合表达研究区域森林LAI的尺度.结果表明:对于森林来说,高分辨率并不一定能充分反映森林LAI.基于3种分辨率影像的统计模型都能很好地估测森林LAI,其中,基于Sentinel-2的反演精度最高,基于GF-2的反演精度最低.30和100 m尺度下的检验结果表明,基于GF-2反演模型高估了森林LAI,基于Landsat-8的反演模型低估了森林LAI,基于Sentinel-2分辨率的统计模型可以很好地估测研究区域森林LAI.     

Full field spatially-variant image-based resolution modelling reconstruction for the HRRT

Accurate characterisation of the scanner's point spread function across the entire field of view (FOV) is crucial in order to account for spatially dependent factors that degrade the resolution of the reconstructed images. The HRRT users' community resolution modelling reconstruction software includes a shift-invariant resolution kernel, which leads to transaxially non-uniform resolution in the reconstructed images. Unlike previous work to date in this field, this work is the first to model the spatially variant resolution across the entire FOV of the HRRT, which is the highest resolution human brain PET scanner in the world. In this paper we developed a spatially variant image-based resolution modelling reconstruction dedicated to the HRRT, using an experimentally measured shift-variant resolution kernel. Previously, the system response was measured and characterised in detail across the entire FOV of the HRRT, using a printed point source array. The newly developed resolution modelling reconstruction was applied on measured phantom, as well as clinical data and was compared against the HRRT users' community resolution modelling reconstruction, which is currently in use. Results demonstrated improvements both in contrast and resolution recovery, particularly for regions close to the edges of the FOV, with almost uniform resolution recovery across the entire transverse FOV. In addition, because the newly measured resolution kernel is slightly broader with wider tails, compared to the deliberately conservative kernel employed in the HRRT users' community software, the reconstructed images appear to have not only improved contrast recovery (up to 20% for small regions), but also better noise characteristics.     

Artifacts in single-molecule localization microscopy

Single-molecule localization microscopy provides subdiffraction resolution images with virtually molecular resolution. Through the availability of commercial instruments and open-source reconstruction software, achieving super resolution is now public domain. However, despite its conceptual simplicity, localization microscopy remains prone to user errors. Using direct stochastic optical reconstruction microscopy, we investigate the impact of irradiation intensity, label density and photoswitching behavior on the distribution of membrane proteins in reconstructed super-resolution images. We demonstrate that high emitter densities in combination with inappropriate photoswitching rates give rise to the appearance of artificial membrane clusters. Especially, two-dimensional imaging of intrinsically three-dimensional membrane structures like microvilli, filopodia, overlapping membranes and vesicles with high local emitter densities is prone to generate artifacts. To judge the quality and reliability of super-resolution images, the single-molecule movies recorded to reconstruct the images have to be carefully investigated especially when investigating membrane organization and cluster analysis.     

High-resolution three-dimensional-pQCT images can be an adequate basis for in-vivo microFE analysis of bone

Micro-finite element (microFE) models based on high-resolution images have enabled the calculation of elastic properties of trabecular bone in vitro. Recently, techniques have been developed to image trabecular bone structure in vivo, albeit at a lesser resolution. The present work studies the usefulness of such in-vivo images for microFE analyses, by comparing their microFE results to those of models based on high-resolution micro-CT (microCT) images. Fifteen specimens obtained from human femoral heads were imaged first with a 3D-pQCT scanner at 165 microns resolution and a second time with a microCT scanner at 56 microns resolution. A third set of images with a resolution of 165 microns was created by downscaling the microCT measurements. The microFE models were created directly from these images. Orthotropic elastic properties and the average tissue von Mises stress of the specimens were calculated from six FE-analyses per specimen. The results of the 165 microns models were compared to those of the 56 microns model, which was taken as the reference model. The results calculated from the pQCT-based models, correlated excellent with those calculated from the reference model for both moduli (R2 > 0.95) and for the average tissue von Mises stress (R2 > 0.83). Results calculated from the downscaled micro-CT models correlated even better with those of the reference models (R2 > 0.99 for the moduli and R2 > 0.96 for the average von Mises stress). In the case of the 3D-pQCT based models, however, the slopes of the regression lines were less than one and had to be corrected. The prediction of the Poisson's ratios was less accurate (R2 > 0.45 and R2 > 0.67) for the models based on 3D-pQCT and downscaled microCT images respectively). The fact that the results from the downscaled and original microCT images were nearly identical indicates that the need for a correction in the case of the 3D-pQCT measurements was not due to the voxel size of the images but due to a higher noise level and a lower contrast in these images, in combination with the application of a filtering procedure at 165 micron images. In summary: the results of microFE models based on in-vivo images of the 3D-pQCT can closely resemble those obtained from microFE models based on higher resolution microCT system.     

Slit-scan flow cytometry: separability properties of cell features

A model is presented to compare the separability of cell populations described by features measured in low resolution slit-scanning flow systems with their separability when the features are extracted from high resolution digitized cell images. The results show that although the accuracy of the feature measurements deteriorates for increasing slit width, this is not necessarily true for the discriminatory power of the features. Depending on their original position in the high resolution feature space, the cell populations may be located even farther apart in the space of low resolution slit-scan features for reasonably small widths of the slit. The results presented with high resolution images of cells from gynecological specimens and simulated slit-scan measurements can be explained by the model. For the features nuclear DNA content and diameter the abnormal populations are shifted closer to the normal populations in the slit-scan simulations as compared to the high resolution measurements. The cell classifier errors rates are unacceptably high.     

基于频域反卷积滤波器的光声成像

采用探测器的脉冲响应在频域反卷积滤波光声信号以进一步提高光声成像的分辨率.由仿真和实验结果表明,频域反卷积滤波重建相对于时域反投影重建和滤波反投影重建具有更好的成像效果,明显地提高重建图像的分辨率,经仿真结果的计算,其重建图像的分辨率由2.58 mm提高到了0.16 mm.实验所用的光源为YAG激光器,波长为1064 ...     

南方红壤水土流失区土地利用动态变化——以长汀河田盆地区为例

福建省长汀县曾是我国南方红壤地区水土流失最严重的县份之一,经过20多年的艰辛努力,长汀已成为中国水土流失治理的典范.采用遥感技术和景观格局分析技术,基于1988、1998、2004、2009和2011年的遥感影像,对长汀县水土流失最为严重的河田盆地区进行土地利用动态变化检测与景观格局变化分析.结果表明,研究区在这23a间的土地利用发生了很大变化,其中最主要的特征就是以针叶林为主的林地面积的快速增长和地表裸土面积的大幅下降.景观分析表明,水土流失治理新增的小块林地正逐渐形成连片分布,而裸土面积在大幅减少的同时,其斑块也趋于破碎.总的看来,这23a间的水土流失治理已使得研究区的生态明显趋于好转.     

Issues of resolution and polymorphism in single-particle reconstruction

Three-dimensional reconstruction from electron microscopic (EM) images of isolated macromolecular complexes is being employed by many laboratories. This approach is extremely powerful and continues to improve in resolution. In the absence of stereochemical constraints that can be used to assess the quality of a reconstruction, as exist in X-ray crystallography, several other measures have typically been used. A very useful assessment of quality can be made in the comparison between the projections of the three-dimensional reconstruction and averages generated from classes of images. The main quantitative measure has been that of resolution statistics, typically based upon Fourier shell correlations. We show, using only simulated noise for images, that impressive resolution statistics are generated that can even extend the apparent resolution of the starting model. When truly independent reconstructions are generated starting from different initial models, however, such artefacts are not possible. We also show, using real images of DnaB rings, that in the presence of polymorphism artefactual reconstructions can be generated whose projections match class averages. These averages, however, are themselves artefactual as they involve heterogeneous images. The issues presented here need to be considered when single-particle EM reconstructions are evaluated.     

Kite aerial photography: a low‐cost method for monitoring seabird colonies

Obtaining aerial high‐resolution images of bird nesting colonies using remote‐sensing technology such as satellite‐based remote sensing, manned aircraft, or Unmanned Aerial Vehicles might not be possible for many researchers due to financial constraints. Kite Aerial Photography (KAP) provides a possible low‐cost alternative. We collected digital images of ground‐nesting seabirds (i.e., cormorants and penguins) in two different ecosystems using a kite‐based platform equipped with consumer‐grade digital cameras with time‐lapse capability to obtain estimates of breeding population size. KAP proved to be an efficient method for acquiring high‐resolution aerial images. We obtained images of colonies of seabirds ranging in size from hundreds to several hundreds of thousands breeding pairs during flights lasting from a few minutes up to three hours, from flat to very steep areas, and in contrasted wind conditions (from 0.5 to 6 Beaufort force). KAP is an efficient low‐cost method for acquiring high‐resolution aerial images and an alternative to ground‐based censuses, especially useful in rugged areas.     

单排CT轴位螺旋扫描联合冠状面重组技术对鼻腔鼻窦检查的意义

目的：研究在单排CT轴位螺旋扫描联合多层面重组技术重建冠状面影像诊断鼻腔疾病,评价其诊断价值和可行性。方法：对2012年1月-2013年3月我院耳鼻咽喉科进行单排CT轴位螺旋扫描的患者,共219例,对这些患者加做冠状位扫描,比较重建后的影像资料与直接冠状位扫描的图像的分辨率情况,并评估重建质量及运用价值。,结果：单排CT轴位螺旋扫描后冠状面重组的图像：边界清楚、完整,数据无丢失。利用重组技术后重建的结构清晰、连续,能够真实地反映鼻腔、鼻窦及病变结构的实际情况。但分辨率较直接冠状位平扫的患者稍差。结论：单排CT轴位螺旋扫描后冠状面重组的图像,虽然分辨率不如直接冠状位扫描图像高,但与解剖结构、原图像等相结合仍能分辨出病变情况,基本可以满足诊断要求和临床需要。     

Two-photon confocal microscopy: a nondestructive method for studying wound healing

Two-photon confocal microscopy is a new technology useful in nondestructive analysis of tissue. The pattern generated from laser-excited autofluorescence and second harmonic signals can be analyzed to construct a three-dimensional, microanatomical, structural image. The healing of full-thickness guinea pig skin wounds was studied over a period of 28 days using two-photon confocal microscopy. Three-dimensional data were rendered from two-dimensional images and compared with conventional, en face, histologic sections. Two-photon confocal microscopy images show resolution of muscle, fascia fibers, collagen fibers, inflammatory cells, blood vessels, and hair. Although these images do not currently have the resolution of standard histology, the ability to noninvasively acquire three-dimensional images of skin promises to be an important tool in wound-healing studies.     

基于多光谱影像的森林树种识别及其空间尺度响应

当前,不同空间分辨率卫星影像对森林类型识别结果中普遍存在的尺度效应,而且纹理参量对不同尺度下树种识别精度的影响仍缺乏广泛认知.本研究以中国东北旺业甸林场为研究区,采用观测时相同步、地理坐标匹配的GF-1 PMS、GF-2 PMS、GF-1 WFV,以及Landsat-8 OLI卫星传感器数据组成空间尺度观测序列(1、2、4、8、16、30 m),并结合支持向量机(SVM)模型,探讨了区域内5种优势树种遥感识别结果的尺度变化规律及其纹理特征参数的影响,同时检验了基于尺度上推转换影像的树种识别结果差异.结果表明: 影像空间分辨率对区域树种识别结果具有显著影响,其中,研究区森林树种识别的最佳影像分辨率为4 m,当分辨率降低至30 m时,树种识别结果最差.在1～8 m影像分辨率范围内,增加纹理信息能够显著提高不同优势树种的识别精度,使总分类精度提升了2.0%～3.6%,但纹理信息对16～30 m影像的识别结果没有显著影响.与真实尺度卫星影像相比,基于升尺度转换影像的树种识别结果及其尺度响应特征存在显著差异,表明在面向多个空间尺度的遥感观测和应用研究中,需要采用真实分辨率影像以确保结果的准确性.     

Achievable resolution from images of biological specimens acquired from a 4k x 4k CCD camera in a 300-kV electron cryomicroscope

Bacteriorhodopsin and ε 15 bacteriophage were used as biological test specimens to evaluate the potential structural resolution with images captured from a 4k × 4k charge-coupled device (CCD) camera in a 300-kV electron cryomicroscope. The phase residuals computed from the bacteriorhodopsin CCD images taken at 84,000× effective magnification averaged 15.7° out to 5.8-Å resolution relative to Henderson’s published values. Using a single-particle reconstruction technique, we obtained an 8.2-Å icosahedral structure of ε 15 bacteriophage with the CCD images collected at an effective magnification of 56,000×. These results demonstrate that it is feasible to retrieve biological structures to a resolution close to 2/3 of the Nyquist frequency from the CCD images recorded in a 300-kV electron cryomicroscope at a moderately high but practically acceptable microscope magnification.     

Atomic force microscopy of RecA--DNA complexes using a carbon nanotube tip

We report high resolution images of RecA-double stranded (ds) DNA complexes obtained by atomic force microscopy (AFM). When a carbon nanotube (CNT) tip was used, AFM images visualized the 10-nm pitch of RecA-dsDNA complexes and RecA filaments as three-dimensional surface topography without reconstruction analysis. The depth of the notch between two pitches was less than 1 nm. When adsorbed on a soft surface covered with proteins, naked DNA, RecA monomers, RecA hexamers, and short RecA filaments were all clearly resolved in one image. The high resolution images with a CNT tip provided valuable information on the initiation process of RecA-dsDNA complex formation.     

One- and Two-Dimensional Electron Paramagnetic Resonance Imaging in Skin

EPR imaging with modulated field gradients provides the possibility for obtaining an EPR spectrum in a selected volume We demonstrate the feasibility of X-band (9.5GHz) electron paramagnetic resonance (EPR) imaging in skin biopsies of hairless mice. One- (ID) and two-dimensional (2D) EPR images of the persistent free radical di-tertiary-butyl-nitroxide are measured. At a microwave frequency of 9.5 GHz (X-band), 2D images are obtained in skin biopsies with an actual point distinction resolution of 25 μm. In a biological model system. 2D images are measured at L-band frequency (2.0 GHz) with a pixel resolution of 61 μm. and a theoretical spatial resolution of 12.5 μm. In combination with the spin labeling and spin trapping technique. EPR imaging is the most direct approach to analyzing spatial distribution of physico-chemical properties in skin, such as membrane fluidity and polarity. as well as detection of free radicals.     

One- and Two-Dimensional Electron Paramagnetic Resonance Imaging in Skin

EPR imaging with modulated field gradients provides the possibility for obtaining an EPR spectrum in a selected volume We demonstrate the feasibility of X-band (9.5GHz) electron paramagnetic resonance (EPR) imaging in skin biopsies of hairless mice. One- (ID) and two-dimensional (2D) EPR images of the persistent free radical di-tertiary-butyl-nitroxide are measured. At a microwave frequency of 9.5 GHz (X-band), 2D images are obtained in skin biopsies with an actual point distinction resolution of 25 μm. In a biological model system. 2D images are measured at L-band frequency (2.0 GHz) with a pixel resolution of 61 μm. and a theoretical spatial resolution of 12.5 μm. In combination with the spin labeling and spin trapping technique. EPR imaging is the most direct approach to analyzing spatial distribution of physico-chemical properties in skin, such as membrane fluidity and polarity. as well as detection of free radicals.