Complex Three-dimensional Environment Research Articles

Crawling cells need to explore.

Cell Biology As it crawls, a cell explores the space in front of it by extending protrusions. These are formed by the branching of actin filaments in the cytoskeleton at the leading edge that push the cell membrane outward. Leithner et al. disrupted actin branching in crawling leukocytes and observed profound changes in cell shape. The cells were able to move but were unable to change direction or navigate, whereas wild-type cells oriented in response to chemical gradients and navigated obstacles. Thus, although actin filament branching is not required to move a crawling cell forward, it is essential for generating the protrusions necessary to explore and navigate a complex three-dimensional environment. ![Figure][1] Actin filaments allow cells to explore. PHOTO: A. LEITHNER ET AL., NATURE CELL BIOLOGY 18 , 1253 (24 OCTOBER 2016) © 2016 MACMILLAN PUBLISHERS LIMITED Nat. Cell Biol. 18 , 1253 (2016). [1]: pending:yes

Navigating in multi-level buildings: the effect of rotation

The existence of the complexity in layout and physical parameters are still under investigation in urban architecture in cognitive science. Current research seems to pay more attention to wayfinding in two-dimensional environments investigating it in public buildings such as hospitals, airports or university departments, where it is more common to experience disorientation. Also, the presence of turning walks or staircases undermines the users’ cognitive map. As a consequence, the sense of disorientation would depend on various factors such as the number of ramps, their location and orientation with respect to the building’s main facade. We carry out two case studies: the first one is a qualitative experiment at the University of Bremen; the second one is a quantitative analysis at the Technical University of Bari. In both studies we select a random sample in which respondents perform a series of tests. . Participants are not familiar with the building in which the experiment is conducted but have some knowledge with the surrounding environment. Main results suggest the importance of building layouts as an important element affecting human cognitive map in wayfinding. They seem to support the hypothesis that the direction of stairs plays an important role on the disorientation when navigating complex three-dimensional environments. This paper is an attempt to understand how the location of staircases affects disorientation and how this aspect, in turn, affects knowledge acquisition for wayfinding. These findings, coming from experimentations in indoor environments, seem to evoke a peculiar extension to outdoor environments, too. There is fair interest toward convenient investigation for outdoor integration and/or generalization. An intriguing future perspective for the present research would be the extension to the urban level of spatial cognition.

Transformable multirotor with two-dimensional multilinks: modeling, control, and motion planning for aerial transformation

In this study, we investigated a novel type of the multirotor aerial vehicle with two-dimensional multilinks to demonstrate stable aerial transformation for high mobility in three-dimensional environments. Our goal was to tackle the challenge of traversing narrow spaces or gaps, which is one of the difficulties for existing structure of multirotors, especially in the cluttered indoor environment of disaster sites. The research involved three steps. First, we developed the modeling of the link modules that compose a multirotor with two-dimensional multilinks and conducted a quadrotor prototype. Second, we derived a stable flight control method for aerial transformation on the basis of linear-quadratic-integral optimal control. Third, we investigated the motion planning for the aerial transformation using a state validation method and path optimization in the joint space to maintain the stability during transformation. Successful aerial transformation and the ability of the prototype to negotiate narrow gaps were demonstrated, confirming the feasibility and utility of our proposed transformable multirotor for aerial maneuvering in complex three-dimensional environments.

A proto-object based saliency model in three-dimensional space

Most models of visual saliency operate on two-dimensional images, using elementary image features such as intensity, color, or orientation. The human visual system, however, needs to function in complex three-dimensional environments, where depth information is often available and may be used to guide the bottom-up attentional selection process. In this report we extend a model of proto-object based saliency to include depth information and evaluate its performance on three separate three-dimensional eye tracking datasets. Our results show that the additional depth information provides a small, but statistically significant, improvement in the model’s ability to predict perceptual saliency (eye fixations) in natural scenes. The computational mechanisms of our model have direct neural correlates, and our results provide further evidence that proto-objects help to establish perceptual organization of the scene.

Three-Dimensional Balance of Cortical Tension and Axial Contractility Enables Fast Amoeboid Migration

Fast amoeboid migration requires cells to apply mechanical forces on their surroundings via transient adhesions. However, the role these forces play in controlling cell migration speed remains largely unknown. We used three-dimensional force microscopy to measure the three-dimensional forces exerted by chemotaxing Dictyostelium cells, and examined wild-type cells as well as mutants with defects in contractility, internal F-actin crosslinking, and cortical integrity. We showed that cells pull on their substrate adhesions using two distinct, yet interconnected mechanisms: axial actomyosin contractility and cortical tension. We found that the migration speed increases when axial contractility overcomes cortical tension to produce the cell shape changes needed for locomotion. We demonstrated that the three-dimensional pulling forces generated by both mechanisms are internally balanced by an increase in cytoplasmic pressure that allows cells to push on their substrate without adhering to it, and which may be relevant for amoeboid migration in complex three-dimensional environments.

In vitro three-dimensional bone tissue models: from cells to controlled and dynamic environment.

Most of our knowledge of bone cell physiology is derived from experiments carried out in vitro on polystyrene substrates. However, these traditional monolayer cell cultures do not reproduce the complex and dynamic three-dimensional (3D) environment experienced by cells in vivo. Thus, there is a growing interest in the use of 3D culture systems as tools for understanding bone biology. These in-vitro-engineered systems, less complex than in vivo models, should ultimately recapitulate and control the main biophysical, biochemical, and biomechanical cues that define the in vivo bone environment, while allowing their monitoring. This review focuses on state-of-the-art and the current advances in the development of 3D culture systems for bone biology research. It describes more specifically advantages related to the use of such systems, and details main characteristics and challenges associated with its three main components, that is, scaffold, cells, and perfusion bioreactor systems. Finally, future challenges for noninvasive imaging technologies are addressed.

Three-Dimensional Balance of Cortical Tension and Axial Contractility Enables Fast Amoeboid Migration

Fast amoeboid migration requires cells to apply mechanical forces on their surroundings via transient adhesions. However, the mechanistic role of forces in controlling cell shape changes and cell migration speed remains largely unknown. To address these questions, we used three-dimensional force microscopy to measure the in-plane (tangential) and out-of-plane (normal) forces exerted by cells crawling on flat surfaces. From the measured normal forces, we estimated the cells’ cortical tension using a Young-Laplace's model. We examined chemotaxing wild-type Dictyostelium cells, as well as mutants with defects in contractility, internal F-actin crosslinking, and cortical integrity, and demonstrated that once the cells initiate their migration and polarize, they generate tangential traction forces by myosin II contractility, which requires an internal crosslinked F-actin network. Simultaneously, cortical tension provides an additional mechanism that generates the normal forces and that does not require myosin II. The 3-D pulling forces generated by both mechanisms are internally balanced by an increase in cytoplasmic pressure that allows cells to push down on their substrate without adhering to it. These compressive pressure-induced forces are not associated to adhesion sites, and may allow amoeboid cells to push off surrounding structures when migrating in complex three-dimensional environments. Our findings are consistent with a model in which the two force-generating cellular domains are mechanically connected by myosin I crosslinking that enables the communication of forces between the domains. Furthermore, we found that the balance between axial myosin II contractility and cortical tension is important to produce the cell shape changes needed for locomotion, as cell migration speed correlates with the ratio of the magnitudes of the tangential traction forces to the normal ones. These results reveal a novel role for 3-D cellular forces in establishing the efficiency of amoeboid cell movement.

Leveling Up to Immersive Dispute Resolution (IDR) in 3-D Virtual Worlds: Learning and Employing Key IDR Skills to Resolve In-World Developer-Participant Conflicts

As technology improves, bandwidth expands and devices proliferate, hundreds of millions of people are engaging with ever-more realistic and complex three-dimensional (3-D) immersive environments for up to thirty hours per week. The growing variety of online 3-D spaces allows individuals to try on new identities as avatars and to interact, explore and shape either reality- or fantasy-based online worlds. In some of these virtual worlds, the emphasis is on developing personal relationships through social networking while others revolve primarily around achieving competitive game objectives. Participants may engage in a laundry list of mundane or whimsical activities from decorating your virtual home and chatting with fellow avatars to slaying mythical monsters or accomplishing quests in a hero’s journey. In a review of forty-five 3-D environments, one activity typically missing within the contours of the virtual world is an effective, in-world conflict resolution process to handle developer (or owner)-participant (or player) conflicts within the contours of the virtual world. Most of these virtual environments require adversarial conflict resolution either traditional courts or arbitration to process disputes between game developers and members. A few sites’ terms of use refer vaguely to “non-appearance based” conflict resolution options without further explanation of the nature of these processes. In other instances, developers can unilaterally take action against players through a variety of self-help remedies which have led to further court challenges. Incongruously, these virtual realities often teach some of the key skills necessary for collaborative conflict resolution methods outside of traditional litigation, including strategic analysis of one’s own and third party interests, understanding other’s perspectives through shifting online identities, balancing collaborative and competitive interactions with other parties, and exploring creative solutions to achieve objectives. Yet these virtual spaces seldom offer any meaningful opportunity for these skills learned in-world to be applied using the existing 3-D infrastructure to resolve these disagreements. This article calls for a new conflict resolution approach; the utilization of “immersive dispute resolution (IDR)” to leverage both the communication and graphical technological advancements in 3-D virtual worlds and the collaborative and strategic thinking skills virtual participants readily acquire in these digital experiences. In this paper, Part I will discuss research on learning in virtual worlds with a special emphasis on the key collaborative conflict resolution skills garnered through exploration, engagement and play in virtual environments. Part II examines current dispute resolution processes in forty-five 3-D worlds which emphasize adversarial methods and illustrate a failure to leverage the 3-D immersive technologies or the collaborative skills learned in these immersive environments. Part III will call for established dispute resolution professional and organizational providers to spearhead greater integration of 3-D technologies with facilitative IDR processes to help leverage player-acquired collaborative skills in resolving owner-participant disputes.

Volume perception: Disparity extraction and depth representation in complex three-dimensional environments.

Our sensitivity to binocular disparity is exquisite under the best conditions, typically in uncluttered scenes with few small objects. Yet binocular vision can deliver a very strong impression of depth for complex, cluttered scenes with lots of objects and overlaps. How good is disparity processing under these conditions? Here we explored a novel task: depth volume perception, to study how a global representation of depth is obtained using binocular disparity information. We found that the human visual system is sensitive to depth volume but that the volume perceived is dependent on the local and global arrangement of scene content. We also show how a model of early disparity extraction and combination can account for some of the biases found. Our work shows that the visual system is not able to correctly represent and interpret disparity for all locations in a complex three-dimensional scene.

Robust and Efficient Treatment of Temperature Feedback in Fluid–Thermal–Structural Analysis

One of the primary challenges in the development of high-speed systems is accurate and efficient prediction of the aerodynamic heating, particularly for lightweight systems where there is a potential for strong coupling between the aerothermodynamic loads and the structural response. A novel approach is developed that corrects heat flux predictions from a pointwise dependency on surface temperature in order to account for surface temperature gradients. This enables efficient construction of a computational fluid dynamics surrogate for aerodynamic heating without a priori assumptions on the surface temperature profile while also accurately maintaining the critical feedback behavior of the surface temperature profile for a coupled fluid–thermal–structural analysis. The method is compared, in terms of accuracy and efficiency, with a hierarchy of approaches for aerodynamic heating prediction. Comparison cases include simple flat-plate heating, as well as shock impingements in two-dimensional and three-dimensional flows. Typically, the approach yields less than 6% error relative to full-order computational fluid dynamics predictions, and it clearly outperforms all other simple prediction methods in terms of accuracy. Furthermore, it maintains excellent computational efficiency, enabling long-time-record fluid–thermal–structural analysis in complex three-dimensional flow environments.

Modeling persistence in mesenchymal cell motility using explicit fibers.

Cell motility is central to a variety of fundamental processes ranging from cancer metastasis to immune responses, but it is still poorly understood in realistic native environments. Previous theoretical work has tended to focus on intracellular mechanisms or on small pieces of interaction with the environment. In this article, we present a simulation which accounts for mesenchymal movement in a 3D environment with explicit collagen fibers and show that this representation highlights the importance of both the concentration and alignment of fibers. We show good agreement with experimental results regarding cell motility and persistence in 3D environments and predict a specific effect on average instantaneous cell speed and persistence. Importantly, we show that a significant part of persistence in 3D is directly dependent on the physical environment, instead of indirectly dependent on the environment through the biochemical feedback that occurs in cell motility. Thus, new models of motility in three dimensions will need to account for the effects of explicit individual fibers on cells. This model can also be used to analyze cellular persistence in both mesenchymal and nonmesenchymal motility in complex three-dimensional environments to provide insights into mechanisms of cell motion seen in various cancer cell types in vivo.

A rapid and sensitive automated image-based approach for in vitro and in vivo characterization of cell morphology and quantification of cell number and neurite architecture.

Stereological methods for tissue cell counting, specifically for neuron quantification, decrease systematic error and sampling bias; however, they are tedious, labor intensive, and time consuming. Approaches for cell (neuron) quantification in vitro are not accurate, sensitive, or subsequently reproducible. Neuronal phenotype is related to alterations in cell morphology and neurite pattern. The techniques currently available for quantification of these features present several limitations. In this unit, we provide validated automated procedures for in vivo and in vitro quantification of cell number, morphological cell changes, and neurite morphometry in a fast, simple, and reliable manner. Our method counts up to 8 times as many neurons in less than 5% to 10% of the time required for stereological analysis (optical fractionator). In summary, this technology offers an unparalleled opportunity to examine features of cells at high resolution in a complex three-dimensional environment. These techniques provide an exceptional in vivo and in vitro system for neurotoxicity studies, disease modeling, and drug discovery.

Seismic Imaging of the Geologic Framework and Structures Related to Volcanogenic Massive Sulfide Deposits in the Archean Rouyn-Noranda District, Quebec, Canada

Two seismic reflection profiles acquired by Xstrata Canada in the Noranda mining camp were reprocessed and interpreted with the objective of providing key information on the geologic contacts and structures associated with volcanogenic massive sulfide (VMS) deposits at depth. The Amulet and Ribago seismic profiles run approximately from east to west and cross the volcanic rocks of the Noranda formation, which host most of the ore deposits in this camp. The seismic data interpretation relies strongly on a detailed three-dimensional geologic model built from an extensive number of exploration boreholes available in this area and is further supported by physical rock property measurements from in situ borehole logging data. Some reflections observed on the Amulet and Ribago seismic profiles correlate with rhyolite/andesite or silicified-andesite/andesite contacts that host the prospective exhalites of the Noranda formation. In particular, the silicified-andesite/andesite contact hosting the C-contact exhalite is imaged clearly down to a vertical depth of 1,100 m along the Ribago profile. The processing sequence included dip moveout (DMO) corrections and poststack migration. The seismic data reprocessing allowed the identification of two diffractions that correlate with known sulfide bodies intersected in boreholes located close to the Ribago profile. One of these diffractions, at approximately 1,200-m depth, coincides with the main massive sulfide intersection of the subeconomical Ribago orebody. Diorites cause several reflections observed within the Flavrian pluton. Some diorite units also have sufficient acoustic impedance contrast to produce strong reflections when juxtaposed against volcanic rocks. However, such reflections do not predominate in the Amulet and Ribago profiles, possibly because reflective diorite units are not so significant or have limited lateral continuity in this part of the Noranda formation. The reconciliation of the detailed three-dimensional geologic model and two-dimensional seismic data was not necessarily a straightforward task. A significant complication results from the inherent limitations of two-dimensional seismic imaging techniques in a complex three-dimensional geologic environment. Nevertheless, results presented in this paper indicate that seismic methods can image prospective contacts and deep-seated massive sulfide mineralization and can be a valuable exploration tool in the Noranda mining camp.

Intravital FLIM-FRET Imaging Reveals Dasatinib-Induced Spatial Control of Src in Pancreatic Cancer

Cancer invasion and metastasis occur in a complex three-dimensional (3D) environment, with reciprocal feedback from the surrounding host tissue and vasculature-governing behavior. In this study, we used a novel intravital method that revealed spatiotemporal regulation of Src activity in response to the anti-invasive Src inhibitor dasatinib. A fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer (FLIM-FRET) Src biosensor was used to monitor drug-targeting efficacy in a transgenic p53-mutant mouse model of pancreatic cancer. In contrast to conventional techniques, FLIM-FRET analysis allowed for accurate, time-dependent, live monitoring of drug efficacy and clearance in live tumors. In 3D organotypic cultures, we showed that a spatially distinct gradient of Src activity exists within invading tumor cells, governed by the depth of penetration into complex matrices. In parallel, this gradient was also found to exist within live tumors, where Src activity is enhanced at the invasive border relative to the tumor cortex. Upon treatment with dasatinib, we observed a switch in activity at the invasive borders, correlating with impaired metastatic capacity in vivo. Src regulation was governed by the proximity of cells to the host vasculature, as cells distal to the vasculature were regulated differentially in response to drug treatment compared with cells proximal to the vasculature. Overall, our results in live tumors revealed that a threshold of drug penetrance exists in vivo and that this can be used to map areas of poor drug-targeting efficiency within specific tumor microenvironments. We propose that using FLIM-FRET in this capacity could provide a useful preclinical tool in animal models before clinical translation.

Exocytosis through the Lens

Exocytosis, the process in which material is transported from the cell interior to the extracellular space, proceeds through a complex mechanism. Defects in this process are linked to a number of serious illnesses including diabetes, cancer, and a range of neuropathologies. In neuroendocrine cells, exocytosis involves the fusion of secretory vesicles, carrying signaling molecules, with the plasma membrane through the coordinated interplay of proteins, lipids, and small molecules. This process is highly regulated and occurs in a complex three-dimensional environment within the cell precisely coupled to the stimulus. The study of exocytosis poses significant challenges, involving rapidly changing, nano-scale, protein–protein, and protein–lipid interactions, at specialized sites in the cell. Over the last decade our understanding of neuroendocrine exocytosis has been greatly enhanced by developments in fluorescence microscopy. Modern microscopy encompasses a toolbox of advanced techniques, pushing the limits of sensitivity and resolution, to probe different properties of exocytosis. In more recent years, the development of super-resolution microscopy techniques, side-stepping the limits of optical resolution imposed by the physical properties of light, have started to provide an unparalleled view of exocytosis. In this review we will discuss how advances in fluorescence microscopy are shedding light on the spatial and temporal organization of the exocytotic machinery.

Stability Control and Simulation of Wheel-Legged Mobile Robot in Mechanical Engineering

The wheel-legged mobile robot in a complex three-dimensional environment has strong through capacity .Study is very critical for the stability of the control of their body systems. In this paper , based on analysis of the structure of wheel-legged mobile robot designed, the stability is evaluated by the use of (Effective Mass Center) EMC , and the stability domain is established accordingly. A fuzzy adaptive PID control method is created , and verified by ADAMS and MATLAB co-simulation . Simulation results show that the robot in different terrestrial environment, can maintain good stability.

Quantitative Locomotion Study of Freely Swimming Micro-organisms Using Laser Diffraction

Soil and aquatic microscopic organisms live and behave in a complex three-dimensional environment. Most studies of microscopic organism behavior, in contrast, have been conducted using microscope-based approaches, which limit the movement and behavior to a narrow, nearly two-dimensional focal field.1 We present a novel analytical approach that provides real-time analysis of freely swimming C. elegans in a cuvette without dependence on microscope-based equipment. This approach consists of tracking the temporal periodicity of diffraction patterns generated by directing laser light through the cuvette. We measure oscillation frequencies for freely swimming nematodes. Analysis of the far-field diffraction patterns reveals clues about the waveforms of the nematodes. Diffraction is the process of light bending around an object. In this case light is diffracted by the organisms. The light waves interfere and can form a diffraction pattern. A far-field, or Fraunhofer, diffraction pattern is formed if the screen-to-object distance is much larger than the diffracting object. In this case, the diffraction pattern can be calculated (modeled) using a Fourier transform.2 C. elegans are free-living soil-dwelling nematodes that navigate in three dimensions. They move both on a solid matrix like soil or agar in a sinusoidal locomotory pattern called crawling and in liquid in a different pattern called swimming.3 The roles played by sensory information provided by mechanosensory, chemosensory, and thermosensory cells that govern plastic changes in locomotory patterns and switches in patterns are only beginning to be elucidated.4 We describe an optical approach to measuring nematode locomotion in three dimensions that does not require a microscope and will enable us to begin to explore the complexities of nematode locomotion under different conditions.

Quantitative Locomotion Study of Freely Swimming Micro-organisms Using Laser Diffraction

Soil and aquatic microscopic organisms live and behave in a complex three-dimensional environment. Most studies of microscopic organism behavior, in contrast, have been conducted using microscope-based approaches, which limit the movement and behavior to a narrow, nearly two-dimensional focal field.1 We present a novel analytical approach that provides real-time analysis of freely swimming C. elegans in a cuvette without dependence on microscope-based equipment. This approach consists of tracking the temporal periodicity of diffraction patterns generated by directing laser light through the cuvette. We measure oscillation frequencies for freely swimming nematodes.Analysis of the far-field diffraction patterns reveals clues about the waveforms of the nematodes. Diffraction is the process of light bending around an object. In this case light is diffracted by the organisms. The light waves interfere and can form a diffraction pattern. A far-field, or Fraunhofer, diffraction pattern is formed if the screen-to-object distance is much larger than the diffracting object. In this case, the diffraction pattern can be calculated (modeled) using a Fourier transform.2C. elegans are free-living soil-dwelling nematodes that navigate in three dimensions. They move both on a solid matrix like soil or agar in a sinusoidal locomotory pattern called crawling and in liquid in a different pattern called swimming.3 The roles played by sensory information provided by mechanosensory, chemosensory, and thermosensory cells that govern plastic changes in locomotory patterns and switches in patterns are only beginning to be elucidated.4 We describe an optical approach to measuring nematode locomotion in three dimensions that does not require a microscope and will enable us to begin to explore the complexities of nematode locomotion under different conditions.

Peptide hydrogels: mimicking the extracellular matrix

The extracellular matrix (ECM) is a complex and dynamic three-dimensional (3D) environment consisting largely of a variety of collagenous and non-collagenous fibres, non-fibrous proteins and proteoglycans. Other components often overlooked include various growth factors and other signalling molecules which can diffuse through and bind to various components. The fibrous components of the ECM have a nanoscale architecture to which cells embedded in the ECM, and other biomolecules can attach. Many strategies are being explored to create ECM mimics for tissue engineering applications and as 3D cell-culture environments. These range from fibrous scaffolds composed of synthetic polymers or biopolymers, to fibrous and non-fibrous hydrogel systems. This review will focus on the field of self-assembled nanofibrous hydrogels as ECM mimics and their application to cell and tissue engineering.

Analysis of Freely Swimming C. elegans Using Laser Diffraction

Soil and aquatic multicellular microorganisms play a critical role in the nutrient-cycling and organismal ecology of soil and aquatic ecosystems. These organisms live and behave in a complex three-dimensional environment. Most studies of microorganismal behavior, in contrast, have been conducted using microscope-based approaches, which limit the movement and behavior to a narrow, nearly two-dimensional focal field. We report on a novel analytical approach that provides real-time analysis of freely swimming C. elegans without dependence on microscope-based equipment. This approach consists of tracking the temporal periodicity of diffraction patterns generated by directing laser light onto nematodes in a cuvette. We measured oscillation frequencies for freely swimming nematodes in cuvettes of different sizes to provide different physical constraints on their swimming. We compared these frequencies with those obtained for nematodes swimming within a small droplet of water on a microscope slide, a strategy used by microscope-based locomotion analysis systems. We collected data from diffraction patterns using two methods: video analysis and real time data acquisition using a fast photodiode. Swimming frequencies of nematodes in a droplet of ionic solution on a microscope slide was confirmed to be 2.00 Hz with a variance of 0.05 Hz for the video analysis method and 0.03 Hz for the real time data acquisition using a photodiode; this result agrees with previously published estimates using microscope-based analytical techniques. We find the swimming frequency of unconstrained worms within larger cuvettes to be 2.37 Hz with a variance of 0.02 Hz. As the cuvette size decreased, so did the oscillation frequency, indicating a change in locomotion when physical constraints are introduced.