In the summer of 2022, Tulane University, in collaboration with archaeologists from other institutions, began excavations at the site of Pompeii. The archaeological work was focused on Insula 14 of Region 1, located in the southeastern sector of the site. To overcome the challenges of recording a complex urban excavation, and of working with a collaborative team, we designed and implemented a unique workflow that combines paperless and 3D data-capture methods through the use of GIS technologies. The final product of our documentation workflow was a robust and easy-to-use online geodatabase where archaeologists can revisit, explore, visualize, and analyze each excavated context using virtual tools. We present our workflow for digitally documenting observational and spatial data in the field, and how we made these data available to project archaeologists during and after the field season. First, we describe the development of digital forms in ESRI's Survey123. Then, we explain our procedures for 3D documentation through SfM photogrammetric methods and discuss how we integrated the data and transformed it into an accessible format by using interactive dashboards and online 3D web scenes. Finally, we discuss the components of our workflow that are broadly applicable and that can easily be adapted to other projects.

This paper presents a novel concept in the thermodynamic derivation of phase diagrams for clay minerals that incorporates fuzzy transition zones. This new technique yields phase diagrams that have graded (fuzzy) zones of mineral occurrences and includes compositional variability within mineral groups. For the construction of these diagrams, 170 minerals belonging to nine different subgroups were used, based on a fuzzy mathematical description of their ‘grades’ or ‘belonging-ness’. Standard free energies of formation of all the minerals were derived and all possible pairs of mineral equilibria were evaluated. Relative intensities of mineral occurrences were determined and membership values of each type of mineral at various zones in a 2D or 3D space were graphically represented. Computations and graphical representations were carried out using programs developed in Mathematica. Diagrams were derived for 25°C, 1 bar with a solution phase containing Si(OH)4, K+, Na+, H+, Ca2+ and Mg2+ under conditions of gibbsite, goethite and ferrous oxide saturation. The resulting diagrams, unlike conventional phase diagrams, show multimineral assemblages, with varying occurrences of different minerals and provide a realistic representation of clay mineral occurrences formed by surface geochemical processes. They show that on the Earth’s surface, only montmorillonite can almost completely predominate the inorganic phase followed by kaolinite, illite and beidellite. Nontronite, glauconite, celadonite and vermiculite would not be neoformed in substantial amounts. A general conformity of derived phase equilibria with experimentally observed equilibria is also observed.

Virtual reality (VR) is increasingly used in learning and can be experienced with a head-mounted display as a 3D immersive version (immersive virtual reality [IVR]) or with a PC (or another computer) as a 2D desktop-based version (desktop virtual reality [DVR]). A research gap is the effect of IVR and DVR on learners’ skill retention. To address this gap, we designed an experiment in which learners were trained and tested for the assembly of a procedural industrial task. We found nonsignificant differences in the number of errors, the time to completion, satisfaction, self-efficacy, and motivation. The results support the view that DVR and IVR are similarly useful for learning retention. These insights may help researchers and practitioners to decide which form of VR they should use.

Tomography using a focused ion beam (FIB) combined with a scanning electron microscope (SEM) is well-established for a wide range of conducting materials. However, performing FIB–SEM tomography on ion- and electron-beam-sensitive materials as well as poorly conducting soft materials remains challenging. Some common challenges include cross-sectioning artifacts, shadowing effects, and charging. Fully dense materials provide a planar cross section, whereas pores also expose subsurface areas of the planar cross-section surface. The image intensity of the subsurface areas gives rise to overlap between the grayscale intensity levels of the solid and pore areas, which complicates image processing and segmentation for three-dimensional (3D) reconstruction. To avoid the introduction of artifacts, the goal is to examine porous and poorly conducting soft materials as close as possible to their original state. This work presents a protocol for the optimization of FIB–SEM tomography parameters for porous and poorly conducting soft materials. The protocol reduces cross-sectioning artifacts, charging, and eliminates shadowing effects. In addition, it handles the subsurface and grayscale intensity overlap problems in image segmentation. The protocol was evaluated on porous polymer films which have both poor conductivity and pores. 3D reconstructions, with automated data segmentation, from three films with different porosities were successfully obtained.

This paper discusses the importance of learning to understand the three-dimensionality of astronomical objects, in particular nebulae. After collecting data from students’ and professors’ discernment of 3D we finds that this is difficult for both students and professors, which highlights the importance of addressing extrapolating three-dimensionality in astronomy education.

Combined tilt- and focal series scanning transmission electron microscopy is a recently developed method to obtain nanoscale three-dimensional (3D) information of thin specimens. In this study, we formulate the forward projection in this acquisition scheme as a linear operator and prove that it is a generalization of the Ray transform for parallel illumination. We analytically derive the corresponding backprojection operator as the adjoint of the forward projection. We further demonstrate that the matched backprojection operator drastically improves the convergence rate of iterative 3D reconstruction compared to the case where a backprojection based on heuristic weighting is used. In addition, we show that the 3D reconstruction is of better quality.

We evaluate the usefulness of digital volume data produced with the high-resolution episcopic microscopy (HREM) method for visualizing the three-dimensional (3D) arrangement of components of human skin, and present protocols designed for processing skin biopsies for HREM data generation. A total of 328 biopsies collected from normally appearing skin and from a melanocytic nevus were processed. Cuboidal data volumes with side lengths of ~2×3×6 mm3 and voxel sizes of 1.07×1.07×1.5 µm3 were produced. HREM data fit ideally for visualizing the epidermis at large, and for producing highly detailed volume and surface-rendered 3D representations of the dermal and hypodermal components at a structural level. The architecture of the collagen fiber bundles and the spatial distribution of nevus cells can be easily visualized with volume-rendering algorithms. We conclude that HREM has great potential to serve as a routine tool for researching and diagnosing skin pathologies.

This article summarizes recent technological improvements of focused ion beam tomography. New in-lens (in-column) detectors have a higher sensitivity for low energy electrons. In combination with energy filtering, this leads to better results for phase segmentation and quantitative analysis. The quality of the 3D reconstructions is also improved with a refined drift correction procedure. In addition, the new scanning strategies can increase the acquisition speed significantly. Furthermore, fast spectral and elemental mappings with silicon drift detectors open up new possibilities in chemical analysis. Examples of a porous superconductor and a solder with various precipitates are presented, which illustrate that combined analysis of two simultaneous detector signals (secondary and backscattered electrons) provides reliable segmentation results even for very complex 3D microstructures. In addition, high throughput elemental analysis is illustrated for a multi-phase Ni-Ti stainless steel. Overall, the improvements in resolution, contrast, stability, and throughput open new possibilities for 3D analysis of nanostructured materials.

Chemical nano-tomography of microbial cells in their natural, hydrated state provides direct evidence of metabolic and chemical processes. Cells of the nitrate-reducing Acidovorax sp. strain BoFeN1 were cultured in the presence of ferrous iron. Bacterial reduction of nitrate causes precipitation of Fe(III)-(oxyhydr)oxides in the periplasm and in direct vicinity of the cells. Nanoliter aliquots of cell-suspension were injected into custom-designed sample holders wherein polyimide membranes collapse around the cells by capillary forces. The immobilized, hydrated cells were analyzed by synchrotron-based scanning transmission X-ray microscopy in combination with angle-scan tomography. This approach provides three-dimensional (3D) maps of the chemical species in the sample by employing their intrinsic near-edge X-ray absorption properties. The cells were scanned through the focus of a monochromatic soft X-ray beam at different, chemically specific X-ray energies to acquire projection images of their corresponding X-ray absorbance. Based on these images, chemical composition maps were then calculated. Acquiring projections at different tilt angles allowed for 3D reconstruction of the chemical composition. Our approach allows for 3D chemical mapping of hydrated samples and thus provides direct evidence for the localization of metabolic and chemical processes in situ.

In this study, a combined tilt- and focal series is proposed as a new recording scheme for high-angle annular dark-field scanning transmission electron microscopy (STEM) tomography. Three-dimensional (3D) data were acquired by mechanically tilting the specimen, and recording a through-focal series at each tilt direction. The sample was a whole-mount macrophage cell with embedded gold nanoparticles. The tilt–focal algebraic reconstruction technique (TF-ART) is introduced as a new algorithm to reconstruct tomograms from such combined tilt- and focal series. The feasibility of TF-ART was demonstrated by 3D reconstruction of the experimental 3D data. The results were compared with a conventional STEM tilt series of a similar sample. The combined tilt- and focal series led to smaller “missing wedge” artifacts, and a higher axial resolution than obtained for the STEM tilt series, thus improving on one of the main issues of tilt series-based electron tomography.

Tomography is a standard and invaluable technique that covers a large range of length scales. It gives access to the inner morphology of specimens and to the three-dimensional (3D) distribution of physical quantities such as elemental composition, crystalline phases, oxidation state, or strain. These data are necessary to determine the effective properties of investigated heterogeneous media. However, each tomographic technique relies on severe sampling conditions and physical principles that require the sample to be adequately shaped. For that purpose, a wide range of sample preparation techniques is used, including mechanical machining, polishing, sawing, ion milling, or chemical techniques. Here, we focus on the basics of tomography that justify such advanced sample preparation, before reviewing and illustrating the main techniques. Performances and limits are highlighted, and we identify the best preparation technique for a particular tomographic scale and application. The targeted tomography techniques include hard X-ray micro- and nanotomography, electron nanotomography, and atom probe tomography. The article mainly focuses on hard condensed matter, including porous materials, alloys, and microelectronics applications, but also includes, to a lesser extent, biological considerations.

Three-dimensional focused ion beam/scanning electron microscopy (FIB/SEM tomography) is currently an important technique to characterize in 3D a complex semiconductor device or a specific failure. However, the industrial context demands low turnaround time making the technique less useful. To make it more attractive, the following study focuses on a specific methodology going from sample preparation to the final volume reconstruction to reduce the global time analysis while keeping reliable results. The FIB/SEM parameters available will be first analyzed to acquire a relevant dataset in a reasonable time (few hours). Then, a new alignment strategy based on specific alignment marks [using tetraethoxylisane (TEOS) and Pt deposition] is proposed to improve the volume reconstruction speed. These points combined represent a considerable improvement regarding the reliability of the results and the time consumption (gain of factor 3). This method is then applied to various case studies illustrating the benefits of the FIB/SEM tomography technique such as the precise identification of the origin of 3D defects, or the capability to perform a virtual top-down deprocessing on soft material not possible by any mechanical solution.

The lateral and axial resolution of three-dimensional (3D) focal series aberration-corrected scanning transmission electron microscopy was studied for samples of different thicknesses. The samples consisted of gold nanoparticles placed on the top and at the bottom of silicon nitride membranes of thickness between 50 and 500 nm. Atomic resolution was obtained for nanoparticles on top of 50-, 100-, and 200-nm-thick membranes with respect to the electron beam traveling downward. Atomic resolution was also achieved for nanoparticles placed below 50-, 100-, and 200-nm-thick membranes but with a lower contrast at the larger thicknesses. Beam broadening led to a reduced resolution for a 500-nm-thick membrane. The influence of the beam broadening on the axial resolution was also studied using Monte Carlo simulations with a 3D sample geometry.

When fluid passes a cavitator in the supercavitating flow, a supercavity forms behind the cavitator. Variation of the cavitator attack angle can influence theshape of the formed supercavity behind the cavitator. Consequently, it will affect the stability of supercavity behind the supercavitating cavitator with after body. In this study, a direct boundary element method (DBEM) is being formulated and numerically solved for3D unbounded potential flowspassing supercavitating bodies of revolution at different attack angles. In the analysis of potential flows passing supercavitating bodies at non-zero attack angles, a cavity closure model must be employed in order to close the mathematical formulationand guarantee the solution uniqueness. In the present study, we employ modified Riabouchinsky closure model. Since the location of the cavity surface is unknown at prior, an iterative scheme is used and for the first stage, an arbitrary cavity surface is assumed. The flow field is then solved and by an iterative process, the location of the cavity surface is corrected. Upon convergence, the exact boundary conditions are satisfied on the body-cavity boundary. A powerful CFD codeis developed to solve the 3D supercavitating flows behind all types of axisymmetric cavitators (such as disk, cone, etc) at zero and non-zero attack angles. The predictions of the CFD code are compared with those generated by verified existing data. The predictions of the code for supercavitating cones and disks seem to be excellent. Using the obtained data from CFD code, we investigate the supercavity shapesand corresponding stability at different attack angles with a fixed cavitation number.

The combination of integrated focused ion beam–scanning electron microscope (FIB-SEM) serial sectioning and imaging techniques with image analysis provided quantitative characterization of three-dimensional (3D) pigment dispersion in dried paint films. The focused ion beam in a FIB-SEM dual beam system enables great control in slicing paints, and the sectioning process can be synchronized with SEM imaging providing high quality serial cross-section images for 3D reconstruction. Application of Euclidean distance map and ultimate eroded points image analysis methods can provide quantitative characterization of 3D particle distribution. It is concluded that 3D measurement of binder distribution in paints is effective to characterize the order of pigment dispersion in dried paint films.