Series Of High-resolution Images Research Articles

Single-Neuron Labeling in Fixed Tissue and Targeted Volume Electron Microscopy.

The structural complexity of nervous tissue makes it very difficult to unravel the connectivity between neural elements at different scales. Numerous methods are available to trace long-range projections at the light microscopic level, and to identify the actual synaptic connections at the electron microscopic level. However, correlating mesoscopic and nanoscopic scales in the same cell, cell population or brain region is a problematic, laborious and technically demanding task. Here we present an effective method for the 3D reconstruction of labeled subcellular structures at the ultrastructural level, after single-neuron labeling in fixed tissue. The brain is fixed by intracardial perfusion of aldehydes and thick vibratome sections (250 μm) are obtained. Single cells in these vibratome sections are intracellularly injected with horseradish peroxidase (HRP), so that the cell body and its processes can be identified. The thick sections are later flat-embedded in epoxy resin and re-sectioned into a series of thinner (7 μm) sections. The sections containing the regions of interest of the labeled cells are then imaged with automated focused ion beam milling and scanning electron microscopy (FIB-SEM), acquiring long series of high-resolution images that can be reconstructed, visualized, and analyzed in 3D. With this methodology, we can accurately select any cellular segment at the light microscopic level (e.g., proximal, intermediate or distal dendrites, collateral branches, axonal segments, etc.) and analyze its synaptic connections at the electron microscopic level, along with other ultrastructural features. Thus, this method not only facilitates the mapping of the synaptic connectivity of single-labeled neurons, but also the analysis of the surrounding neuropil. Since the labeled processes can be located at different layers or subregions, this method can also be used to obtain data on the differences in local synaptic organization that may exist at different portions of the labeled neurons.

Sequential Replicas: Method for In Vivo Imaging of Plant Organ Surfaces that Undergo Deformation.

Complex geometry of plant organs and various types of organ surface deformation, including growth or hygroscopic movements, can be analyzed using sequential replica method. It enables obtaining a time-lapse series of high resolution images visualizing details of the examined surface and provides data sufficient for detailed computation of parameters characterizing surface deformation and geometry. Series of molds, made in dental polymer, representing the examined surface are used to obtain casts in epoxy resin or nail polish replicas, which are ready for microscopic examination, while the structure itself remains intact. Images obtained from the epoxy casts in scanning electron microscopy can be further used for 3D reconstruction and computation of local geometry. The sequential replica method is a universal method and can be applied to image complex shapes of a range of structures, like meristems, flowers, leaves, scarious bracts, or trichomes. Different plant species growing in various conditions can be studied.

Spiking neural networks for computer vision.

State-of-the-art computer vision systems use frame-based cameras that sample the visual scene as a series of high-resolution images. These are then processed using convolutional neural networks using neurons with continuous outputs. Biological vision systems use a quite different approach, where the eyes (cameras) sample the visual scene continuously, often with a non-uniform resolution, and generate neural spike events in response to changes in the scene. The resulting spatio-temporal patterns of events are then processed through networks of spiking neurons. Such event-based processing offers advantages in terms of focusing constrained resources on the most salient features of the perceived scene, and those advantages should also accrue to engineered vision systems based upon similar principles. Event-based vision sensors, and event-based processing exemplified by the SpiNNaker (Spiking Neural Network Architecture) machine, can be used to model the biological vision pathway at various levels of detail. Here we use this approach to explore structural synaptic plasticity as a possible mechanism whereby biological vision systems may learn the statistics of their inputs without supervision, pointing the way to engineered vision systems with similar online learning capabilities.

Open-pit mine geomorphic changes analysis using multi-temporal UAV survey

Mining activities, and especially open-pit mines, have a significant impact on the Earth’s surface. They influence vegetation cover, soil properties, and hydrological conditions, both during mining and for many years after the mines have been deactivated. Exploring a fast, accurate, and low-cost method to monitor changes, through years, in such an anthropogenic environment is, therefore, an open challenge for the Earth Science community. We selected a case study located in the northeast of Beijing, to assess geomorphic changes related to mining activities. In 2014 and 2016, an unmanned aerial vehicle (UAV) collected two series of high-resolution images. Through the structure-from-motion photogrammetric technique, the images were used to generate high-resolution digital elevation models (DEMs). The assessment of geomorphic changes was carried out by two methodologies. At first, we quantitatively estimated the detectable area, volumetric changes, and the mined tonnage by using the DEM of difference (DoD), which calculated the differences between two DEMs on a cells-by-cells basis. Secondly, the slope local length of autocorrelation (SLLAC) allowed determining the surface covered by open-pit mining by using an empirical model extracting the extent of the open-pit. The analysis of the DoD allows estimating the areal changes and the volumetric changes. The analysis of the SLLAC and its derived parameter allows for the accurate depiction of terraces and the extent of changes within the open-pit mine. Our results underlined how UAVs equipped with high-resolution cameras can be fast, precise, and low-cost instruments for obtaining multi-temporal topographic information, especially when combined with suitable methodologies to analyze the surface geomorphology, for dynamic monitoring of open-pit mines.

Characterization and analysis of Coscinodiscus genus frustule based on FIB-SEM

Coscinodiscus genus, a type of diatoms with complex frustule, has been widely studied and reported because of their delicate nanostructures. In this paper, a dual beam system focused ion beam and scanning electron microscope (FIB-SEM) were applied to precisely investigate the microstructure of diatom cell walls, in particular, aiming to reveal the hierarchical pores of the valve. The microstructures of the valve, valve mantle and girdle bands were illustrated in details through a series of high resolution images after performing the cross section milling of the specific region. The 3D morphology of frustule valve was reconstructed based on the 2D image series, which demonstrated the presence of cribellum in valve, the external foramen, hexagonal cavity and the internal foramen. The four dense porous membranes and girdle bands were characterized clearly based on FIB-SEM dual beam system. An integrated model of Coscinodiscus frustule could be simulated based on the 2D and 3D results. This study provided a systematic approach to measure the morphological features of diatoms at a nanoscale, which could be applied to other nanoporous structure in three dimensions.

OBJECT-BASED FOREST COVER MONITORING USING GAOFEN-2 HIGH RESOLUTION SATELLITE IMAGES

Abstract. Forest cover monitoring is an important part of forest management in local or regional area. The structure and tones of forest can be identified in high spatial remote sensing images. When forests cover change, the spectral characteristics of forests is also changed. In this paper a method on object-based forest cover monitoring with data transformation from time series of high resolution images is put forward. First the NDVI difference image and the composite of PC3,PC4, PC5 of the stacked 8 layers of time series of high resolution satellites are segmented into homogeneous objects. With development of the object-based ruleset classification system, the spatial extent of deforestation and afforestation can be identified over time across the landscape. Finally the change accuracy is achieved with reference data.

A Multi-Temporal and Multi-Spectral Method to Estimate Aerosol Optical Thickness over Land, for the Atmospheric Correction of FormoSat-2, LandSat, VENμS and Sentinel-2 Images

The correction of atmospheric effects is one of the preliminary steps required to make quantitative use of time series of high resolution images from optical remote sensing satellites. An accurate atmospheric correction requires good knowledge of the aerosol optical thickness (AOT) and of the aerosol type. As a first step, this study compares the performances of two kinds of AOT estimation methods applied to FormoSat-2 and LandSat time series of images: a multi-spectral method that assumes a constant relationship between surface reflectance measurements and a multi-temporal method that assumes that the surface reflectances are stable with time. In a second step, these methods are combined to obtain more accurate and robust estimates. The estimated AOTs are compared to in situ measurements on several sites of the AERONET (Aerosol Robotic Network). The methods, based on either spectral or temporal criteria, provide accuracies better than 0.07 in most cases, but show degraded accuracies in some special cases, such as the absence of vegetation for the spectral method or a very quick variation of landscape for the temporal method. The combination of both methods in a new spectro-temporal method increases the robustness of the results in all cases.

Analysis of grain boundary dynamics using event detection and cumulative averaging

To analyze extended time series of high resolution images, we have employed automated frame-by-frame comparisons that are able to detect dynamic changes in the structure of a grain boundary in Au. Using cumulative averaging of images between events allowed high resolution measurements of the atomic relaxation in the interface with sufficient accuracy for comparison with atomistic models. Cumulative averaging was also used to observe the structural rearrangement of atomic columns at a moving step in the grain boundary. The technique of analyzing changing features in high resolution images by averaging between incidents can be used to deconvolute stochastic events that occur at random intervals and on time scales well beyond that accessible to single-shot imaging.

1232 A REAL-TIME MOTION ANALYSIS OF HUMAN EJACULATION

You have accessJournal of UrologySexual Function/Dysfunction/Andrology: Evaluation (I)1 Apr 20131232 A REAL-TIME MOTION ANALYSIS OF HUMAN EJACULATION Jintetsu Soh, Noriyuki Kanemitsu, Yoshio Naya, Yasuyuki Naitoh, Atsushi Ochiai, kazumi Kamoi, Akihiro Kawauchi, and Tsuneharu Miki Jintetsu SohJintetsu Soh Kyoto, Japan More articles by this author , Noriyuki KanemitsuNoriyuki Kanemitsu Kyoto, Japan More articles by this author , Yoshio NayaYoshio Naya Kyoto, Japan More articles by this author , Yasuyuki NaitohYasuyuki Naitoh Kyoto, Japan More articles by this author , Atsushi OchiaiAtsushi Ochiai Kyoto, Japan More articles by this author , kazumi Kamoikazumi Kamoi Kyoto, Japan More articles by this author , Akihiro KawauchiAkihiro Kawauchi Kyoto, Japan More articles by this author , and Tsuneharu MikiTsuneharu Miki Kyoto, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.2586AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES There have been no reports of real-time image analysis of human ejaculation. Using Turbo-FLASH MRI, we were able to obtain a series of high resolution images through human ejaculation. The aim of this study was to analyze the dynamic morphological changes in the prostate and seminal vesicle during a normal ejaculation. METHODS The participants in this study included 5 healthy volunteers without experience of erctile dysfunction and ejaculation disorder. Ages ranged from 20 to 33 (median 25) years. IIEF-5 score ranged from 23 to 25 (median 24) points. Audio-visual sexual stimulation was used to induce erection and ejaculation. MRI was conducted using Siemens MAGNETOM Sonata 1.5T with body array and spine coils. True-FISP sequence was used with conditions of TR: 4.38 ms, TE: 2.19 ms, and scan time: 0.85 sec/slice. Using dynamic images, the length and width of the prostate plus seminal vesicle were consecutively calculated in sagittal section during all phases of a normal ejaculation. Morphological changes were evaluated with the changes in length and width of the prostate plus seminal vesicle. RESULTS The mean length of the prostate plus seminal vesicle were 6.85 to 1.2 cm and the mean width were 2.67 to 0.6 cm in sagittal section. The length changed from 6.21 to 7.69 cm and the width changed from 2.6 to 3.28 cm in sagittal section. The width changed from 2.6 to 3.28 cm and the width changed from 2.6 to 3.28 cm in sagittal section. Increasing rate of the length was 24 % and increasing rate of the width was 26 % in sagittal section during all phases of a normal ejaculation. CONCLUSIONS By using Turbo-FLASH MRI, dynamic phases of a normal ejaculation can be analyzed calculating the changes in length and width of the prostate plus seminal vesicle. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e505 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jintetsu Soh Kyoto, Japan More articles by this author Noriyuki Kanemitsu Kyoto, Japan More articles by this author Yoshio Naya Kyoto, Japan More articles by this author Yasuyuki Naitoh Kyoto, Japan More articles by this author Atsushi Ochiai Kyoto, Japan More articles by this author kazumi Kamoi Kyoto, Japan More articles by this author Akihiro Kawauchi Kyoto, Japan More articles by this author Tsuneharu Miki Kyoto, Japan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

1143 A REAL-TIME MOTION ANALYSIS OF PENILE ERECTION WITH TURBO-FLASH MR IMAGING SYSTEM

You have accessJournal of UrologySexual Function/Dysfunction/Andrology: Evaluation I1 Apr 20121143 A REAL-TIME MOTION ANALYSIS OF PENILE ERECTION WITH TURBO-FLASH MR IMAGING SYSTEM Jintetsu Soh, Noriyuki Kanemitsu, Atsushi Ochiai, Yasuyuki Naitoh, Yoshio Naya, kazumi Kamoi, Akihiro Kawauchi, and Tsuneharu Miki Jintetsu SohJintetsu Soh Kyoto, Japan More articles by this author , Noriyuki KanemitsuNoriyuki Kanemitsu Kyoto, Japan More articles by this author , Atsushi OchiaiAtsushi Ochiai Kyoto, Japan More articles by this author , Yasuyuki NaitohYasuyuki Naitoh Kyoto, Japan More articles by this author , Yoshio NayaYoshio Naya Kyoto, Japan More articles by this author , kazumi Kamoikazumi Kamoi Kyoto, Japan More articles by this author , Akihiro KawauchiAkihiro Kawauchi Kyoto, Japan More articles by this author , and Tsuneharu MikiTsuneharu Miki Kyoto, Japan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.1253AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES There have been no reports of real-time image analysis in the corpus cavernosum from the initiation to the end of erection without artificial induction. Using Turbo-FLASH MRI, we were able to obtain a series of high resolution images through tumescence, maintenance and detumescence phases of erection. The aim of this study was to analyze the dynamic morphological changes in the penis during a normal erection. METHODS The participants in this study included 5 healthy volunteers without experience of erectile dysfunction. Ages ranged from 22 to 47 (median 33) years. IIEF-5 score ranged from 22 to 25 (median 23) points. Audio-visual sexual stimulation was used to induce erection. MRI was conducted using Siemens MAGNETOM Sonata 1.5T with body array and spine coils. True-FISP sequence was used with conditions of TR: 4.38 ms, TE: 2.19 ms, and scan time: 0.85 sec/slice. Using dynamic images, the volume of the corpus cavernosum within the tunica albuginea were consecutively calculated by measuring length, width, and thickness in sagittal and coronal section during all phases of a normal erection (Figure 1). Morphological changes were evaluated with indices including the maximum changes in the volume between latent and full erection phases of the corpus cavernosum as well as the consecutive volume increase rate per second. RESULTS From initiation to completion of erection, range of time required from 110 to 120 (median 115) seconds, changes in volume of corpus cavernosum ranged from 28 to 35 (median 32) ml. Maximum volume increase rate ranged from0.5 to 0.8 (median 0.66) ml/sec (Figure 2). CONCLUSIONS By using Turbo-FLASH MRI, dynamic phases of a normal erection can be analyzed calculating the maximum changes in volume of corpus cavernosum as well as volume increase rate per second. Further study is warranted to prove these novel parameters as a measurement of vascular function. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e463-e464 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jintetsu Soh Kyoto, Japan More articles by this author Noriyuki Kanemitsu Kyoto, Japan More articles by this author Atsushi Ochiai Kyoto, Japan More articles by this author Yasuyuki Naitoh Kyoto, Japan More articles by this author Yoshio Naya Kyoto, Japan More articles by this author kazumi Kamoi Kyoto, Japan More articles by this author Akihiro Kawauchi Kyoto, Japan More articles by this author Tsuneharu Miki Kyoto, Japan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

A Kinase Anchor Protein 150 (AKAP150)-associated Protein Kinase A Limits Dendritic Spine Density

The A kinase anchor protein AKAP150 recruits the cAMP-dependent protein kinase (PKA) to dendritic spines. Here we show that in AKAP150 (AKAP5) knock-out (KO) mice frequency of miniature excitatory post-synaptic currents (mEPSC) and inhibitory post-synaptic currents (mIPSC) are elevated at 2 weeks and, more modestly, 4 weeks of age in the hippocampal CA1 area versus litter mate WT mice. Linear spine density and ratio of AMPAR to NMDAR EPSC amplitudes were also increased. Amplitude and decay time of mEPSCs, decay time of mIPSCs, and spine size were unaltered. Mice in which the PKA anchoring C-terminal 36 residues of AKAP150 are deleted (D36) showed similar changes. Furthermore, whereas acute stimulation of PKA (2-4 h) increases spine density, prolonged PKA stimulation (48 h) reduces spine density in apical dendrites of CA1 pyramidal neurons in organotypic slice cultures. The data from the AKAP150 mutant mice show that AKAP150-anchored PKA chronically limits the number of spines with functional AMPARs at 2-4 weeks of age. However, synaptic transmission and spine density was normal at 8 weeks in KO and D36 mice. Thus AKAP150-independent mechanisms correct the aberrantly high number of active spines in juvenile AKAP150 KO and D36 mice during development.

Crack propagation of single crystal -Sn during in situ TEM straining

In situ tensile process of single-crystal Sn was investigated by transmission electron microscopy (TEM). Despite the traditional wedge microcrack, a new tetragonal microcrack was observed during crack propagation in the single-crystal Sn. During in situ tensile straining, the dislocation dipoles formed at the front of the wedge microcrack tip, the coalescence of which is the source of microvoids at the crack tip, and then the wedge microcrack propagated deeply by aggregation of discontinuous microvoids. The tetragonal microcrack propagated by the intersection along two vertical slip planes. Moreover, the series of high-resolution images showed that Sn islands formed at the center of the frontier crack plane due to the anisotropic self-diffusion of Sn atoms along different crystallographic planes.

Reciprocating flow-based centrifugal microfluidics mixer

Proper mixing of reagents is of paramount importance for an efficient chemical reaction. While on a large scale there are many good solutions for quantitative mixing of reagents, as of today, efficient and inexpensive fluid mixing in the nanoliter and microliter volume range is still a challenge. Complete, i.e., quantitative mixing is of special importance in any small-scale analytical application because the scarcity of analytes and the low volume of the reagents demand efficient utilization of all available reaction components. In this paper we demonstrate the design and fabrication of a novel centrifugal force-based unit for fast mixing of fluids in the nanoliter to microliter volume range. The device consists of a number of chambers (including two loading chambers, one pressure chamber, and one mixing chamber) that are connected through a network of microchannels, and is made by bonding a slab of polydimethylsiloxane (PDMS) to a glass slide. The PDMS slab was cast using a SU-8 master mold fabricated by a two-level photolithography process. This microfluidic mixer exploits centrifugal force and pneumatic pressure to reciprocate the flow of fluid samples in order to minimize the amount of sample and the time of mixing. The process of mixing was monitored by utilizing the planar laser induced fluorescence (PLIF) technique. A time series of high resolution images of the mixing chamber were analyzed for the spatial distribution of light intensities as the two fluids (suspension of red fluorescent particles and water) mixed. Histograms of the fluorescent emissions within the mixing chamber during different stages of the mixing process were created to quantify the level of mixing of the mixing fluids. The results suggest that quantitative mixing was achieved in less than 3 min. This device can be employed as a stand alone mixing unit or may be integrated into a disk-based microfluidic system where, in addition to mixing, several other sample preparation steps may be included.

Dynamic changes in murine vessel geometry assessed by high‐resolution magnetic resonance angiography: A 9.4T study

To establish high-resolution magnetic resonance angiography (MRA) protocols to monitor and quantify dynamic changes of vascular remodeling in pathologic mouse models. Time-of-flight (TOF) MRA of murine vessels was performed at 9.4T to monitor temporal alterations in the vessel structure in two frequently used injury models (wire denudation of carotid artery and femoral artery occlusion). Quantification of vessel morphology was performed with the use of in-house-developed software and validated by estimation of inter- and intraobserver variabilities and reproducibility, and by correlation with histological data. MRA-based volume determination exhibited low intra- and interobserver variabilities and high reproducibility. Furthermore, good correlations with histological data were found four weeks after injury (R2=0.970). Two high-resolution image series are presented to demonstrate the applicability of the technique: 1) the time course of a vessel stenosis that reopens by thrombus recanalization, and 2) the continuous restoration of blood flow by collateral vessel formation during arteriogenesis after induction of hindlimb ischemia. We describe high-resolution MRA imaging protocols that are suitable for sensitively measuring the extent and time course of changes in vessel morphology in mice in a repetitive manner without any contrast agent. This methodology provides a reliable tool for noninvasive monitoring of vascular lesion development or neovascularization in transgenic mice.

Teaching Human Gross Anatomy to the Home-Based Electronic Learner Without Cadaver Dissection (1998-2002)

Over the past decade, electronic learning (EL) has become an established method for delivering courses as many colleges and universities try to expand their pool of potential applicants and serve an aging and geographically diverse student population. To accommodate this pool of potential applicants, the East Carolina University (ECU) Department of Physician Assistant Studies started an EL curriculum to train primary health care providers. ECU faculty have previously reported on the broader aspects of teaching distance learning to the physician assistant (PA) students at home.1 Here we report our experience with teaching human gross anatomy course to PA students without cadaver dissection. From 1984 to 1997, instruction in gross anatomy for allied health students used cadaver dissection and intranet-based library multimedia tools. The gross anatomy EL course (1998) was the first course in the curriculum to be taught to the PA electronic learners. The EL gross anatomy course had two major problems to overcome. The first was, “How do we teach human gross anatomy without the ELs dissecting the cadaver?” The second challenge was, “How do we get the beginning EL students to adapt to computer-based instruction and improve their Internet skills, allowing them to succeed in an 11-week summer session course?” The second challenge was discussed by Heinan, while Winn et al addressed the issue of using the Internet to teach a subject matter by means of high definition graphics.1,2 But other problems and results specific to teaching gross anatomy to ELs were not addressed. In this article, we discuss the specific problems and results of teaching human gross anatomy—which has traditionally been a laboratory intensive course—to the home-based electronic learner. To replace the dissection lab, the PA faculty proposed using a broadband Internet-based approach to deliver the course’s educational objectives. A review of the literature showed that the inclusion of CAI in an anatomy course would probably not negatively affect the learning process and would likely permit the electronic learning students obtain course objectives in reduced time.3 But these studies involved various faceto-face teaching modalities using CAI to augment, not replace, cadaver dissection.4 Nevertheless, based on this literature, we redesigned the PA electronic learning course to extend these studies a step further—to deliver the gross anatomy course without laboratory cadaver dissection. In the first EL course for PA students, we relied heavily on the Gold Standard Multimedia Inc.—on-line dissector for gross anatomy and radiology. Several FTF courses and at least one other on-line course from other universities have used this system.4-6 We have also used the Gold Standard dissector (GSM.com) for both FTF and the EL sections. In the 2000 EL course, a series of high-resolution images for each laboratory were taken from each day’s FTF lab dissection and was

Screw Dislocations in MBE GaN Layers Grown on Top of HVPE Layers: Are They Different?

ABSTRACTTransmission Electron Microscopy was applied to study HVPE template and MBE over-layers in plan-view and cross-section. It was observed that screw dislocations in the HVPE layers are decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers grown with excess Ga, despite the fact that Ga droplets were observed on the layer surface as well as imbedded in the layer. By applying a direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images, the core structures of screw dislocations in both materials have been studied and show that all screw dislocations have filled cores. Dislocation cores in MBE samples grown Ga-rich and N-rich show no substantial differences and no stoichiometric change compared to the matrix. However, in HVPE materials, single atomic columns show substantial differences in intensities and indicate the possibility of Ga presence. These Ga-rich cores might be responsible for the attraction impurities forming voids in their close vicinity.

More about the structure of the high latitude Jovian aurorae

This study is based on the determination of a ‘reference’ main oval for Jupiter's aurora from a series of high-resolution images taken with the Faint Object Camera on board the Hubble Space Telescope in the H 2 Lyman bands centered near 1550 A ̊ . We have taken advantage of the visibility of the northern auroral oval over a large range of longitudes on June 24, 1994, especially for longitudes smaller than 170° where it is generally very faint and thus undetectable. In the south, where there is no such problem, we combined images taken from various points of view between June 1994 and September 1996. We find that the northern main oval is consistent in size and in general aspect with the footprint locus, in the Connerney (1998)'s VIP4 model, of magnetic field lines crossing the equator near 20 R J. However, the precise shape of this oval differs from the model (and from previous ‘reference’ main ovals) in that it exhibits a ‘bean-like’ aspect with excursions toward lower latitudes in the S III longitude range 190–240° (an already reported feature), and toward higher latitudes in the poorly documented 120–150° range. In the south, our reference oval covers an area about that of the 30 R J VIP4 model. As in the north, it is shifted from a VIP4 model oval, toward lower latitudes from 110 to 200° and toward higher latitudes from 310 to 100°. The accurate definition of these (magnetically conjugate) oval loci puts additional strong constraints on magnetic field models at high latitude. Based on our reference main oval, we have then extrapolated still higher latitude ovals. Very interestingly, we find that we can fit (i) the highest latitude arc of oval detected well inside the main oval at longitudes greater than 170°, and (ii) the high latitude edge of what we had previously named the ‘transpolar emission’ at longitudes less than 170° (both also detected on images taken at other dates), by a single empirical oval. We suggest that this oval indicates the location of the northern polar cap boundary, within the uncertainty related to the temporal variability of the actual emission features. We can also fit another secondary arc of oval and a second branch of our ‘transpolar emission’ by a slightly larger empirical oval, presumably connected to the outer magnetosphere. This implies that the region of permanent high latitude diffuse emission seen inside the main oval in the dusk sector must be at the footprint of closed field lines connected all the way out from the middle magnetosphere to the magnetopause. Finally a bright spot is sometimes observed just equatorward of the northern polar cap boundary with an average brightness of 0.5-1 MR (comparing with a bright main oval). We establish that this spot does not rotate with the planet, but rather remains close to magnetic noon. We thus tentitatively identify it, by reference to the Earth aurora, with the footprint of the northern Jovian polar cusp, or with a transient dayside aurora. We also highlight the differences observed in the southern high latitude structure.

Atomic structure of Σ7(0112) symmetrical tilt grain boundaries in α-Al2O3

Abstract High resolution transmission electron microscopy is used to study the atomic structure of a Σ7 grain boundary (Σ is equal to the reciprocal of the fraction of lattice sites in coincidence) in Al2O3. This grain boundary in Al2O3 has misorientation [0111]/180°. The grain boundary plane is (0112)1∥(0112)2. Four possible unrelaxed grain boundary structures can be constructed from the constrained coincidence-sitelattice (CCSL) patterns. The atomic structure of the boundary is determined from a through-focal series of high resolution images and computer image simulation. A DSC dislocation in the Σ7 grain boundary was identified. The Burgers vector of this dislocation is 1/14[0552] and it is a pure edge dislocation. Most of the boundary has a structure comprising oxygen terminating layers with an identical width of 0·135 nm, known as the α-domain. There are no unsaturated Al-O bonds in the boundary core of the a domain, but the Al-O bonds are slightly elongated. Coexistence of two interfacial domains, α...

The atomic structure of Σ = 1 and Σ = 3 NiSi2/Si interfaces

Abstract The high-resolution imaging technique is applied systematically to study the Σ=1 (type A) and Σ = 3 (type B) NiSi2/Si interfaces. Possible structural models for Σ = 1 (type A) and Σ = 3 (type B) NiSi2/Si interfaces can be completely deduced from the dichromatic constrained coincidence site lattice (CCSL) patterns. For the Σ = 1 NiSi2(001)/(001)Si interface, new interface structures have been found and a 2 × 1 reconstructed interface structure involving a difference in composition has also been observed. The new interface structures were confirmed from through-focal series of high-resolution images from two orthogonal 〈110〉 beam directions. Domain-related interface structures coexisting in Σ = 1 NiSi2(001)/(001)Si interfaces were found to be separated by a ¼〈111〉 type of dislocation which is associated with a demi-step. There is only one interface structure observed in both Σ = 1 and Σ = 3 NiSi2(111)/(111)Si interfaces where the interfacial Ni atoms has been determined to be sevenfold coordinated....