Integration of hyper-compliant microparticles into a 3D melanoma tumor model

Multicellular spheroids provide a physiologically relevant platform to study the microenvironment of tumors and therapeutic applications, such as microparticle-based drug delivery. The goal of this study was to investigate the incorporation/penetration of compliant polyacrylamide microparticles (MPs), into either cancer or normal human cell spheroids. Incorporation of collagen-1-coated MPs (stiffness: 0.1 and 9 kPa; diameter: 15–30 µm) into spheroids (diameter ∼100 µm) was tracked for up to 22 h. Results indicated that cells within melanoma spheroids were more influenced by MP mechanical properties than cells within normal cell spheroids. Melanoma spheroids had a greater propensity to incorporate and displace the more compliant MPs over time. Mature spheroids composed of either cell type were able to recognize and integrate MPs. While many tumor models exist to study drug delivery and efficacy, the study of uptake and incorporation of cell-sized MPs into established spheroids/tissues or tumors has been limited. The ability of hyper-compliant MPs to successfully penetrate 3D tumor models with natural extracellular matrix deposition provides a novel platform for potential delivery of drugs and other therapeutics into the core of tumors and micrometastases.     

A theory on the determination of 3D motion and 3D structure from features

The present paper proposes a mathematical theory and a method of recognition of both the 3D structure and the motion of a moving object from its monocular image. Initially, characteristic features are extracted from the 2D perspective image of the object. Because motion of the object induces a change in its 2D perspective image, it also induces a change in the features which depends on the 3D structure and the velocity of the object. This suggests the possibility of detecting the 3D structure and the motion directly from the features and their changing rate, without the need for calculating optical flows. An analysis is made of the relation between the 3D rigid motion of a surface element and the change in local linear features. From this relation, a method is proposed for calculating the velocity of and the normal to the surface element without considering any correspondence of points. An optical flow can also be calculated by this method. Two simple computer simulations are provided.     

Characterizing 3D printing in the fabrication of variable density phantoms for quality assurance of radiotherapy

PurposeTo present characterization, process flow, and applications of 3D fabricated low density phantoms for radiotherapy quality assurance (QA).Material and methodsA Rostock 3D printer using polystyrene was employed to print slabs of varying relative electron densities (0.18–0.75). A CT scan was used to calibrate infill-to-density and characterize uniformity of the print. Two printed low relative density rods (0.18, 0.52) were benchmarked against a commercial CT-electron-density phantom. Density scaling of Anisotropic Analytical Algorithm (AAA) was tested with EBT3 film for a 0.57 slab. Gamma criterion of 3% and 3 mm was used for analysis.Results3D printed slabs demonstrated uniformity for densities 0.4–0.75. The printed 0.52 rod had close agreement with the commercial phantom. Dosimetric comparison for 0.57 density slab showed >95% agreement between calculation and measurements.Conclusion3D printing allows fabrication of variable density phantoms for QA needs of a small clinic.     

On the inverse problem of binocular 3D motion perception

It is shown that existing processing schemes of 3D motion perception such as interocular velocity difference, changing disparity over time, as well as joint encoding of motion and disparity, do not offer a general solution to the inverse optics problem of local binocular 3D motion. Instead we suggest that local velocity constraints in combination with binocular disparity and other depth cues provide a more flexible framework for the solution of the inverse problem. In the context of the aperture problem we derive predictions from two plausible default strategies: (1) the vector normal prefers slow motion in 3D whereas (2) the cyclopean average is based on slow motion in 2D. Predicting perceived motion directions for ambiguous line motion provides an opportunity to distinguish between these strategies of 3D motion processing. Our theoretical results suggest that velocity constraints and disparity from feature tracking are needed to solve the inverse problem of 3D motion perception. It seems plausible that motion and disparity input is processed in parallel and integrated late in the visual processing hierarchy.     

Microdosimetry in 3D realistic mitochondria phantoms: Geant4 Monte Carlo tracking of 250 keV photons in phantoms reconstructed from microscopic images

Mitochondria are considered to be sensitive radiation targets since they control processes vital to the cell’s functioning. These organelles are starting to get attention and some studies are investigating the radiation dose inside them. In previous studies, mitochondria are represented as simple ellipsoids inside the cell not taking into consideration the complexity of their shape. In this study, realistic phantoms are built based on deconvolved widefield fluorescent microscopic images of the mitochondrial networks of fibroblast cells. The phantoms are imported into Geant4 as tessellated volumes taking into account the geometrical complexity of these organelles. Irradiation with 250 keV photons is performed and the lineal energy is calculated. The lineal energy distributions inside the produced phantoms are compared with those calculated inside simple volumes, a sphere and an ellipsoid, where the effect of the shape and volume is clearly seen on lineal energies.     

Detecting binocular 3D motion in static 3D noise: no effect of viewing distance

Relative binocular disparity cannot tell us the absolute 3D shape of an object, nor the 3D trajectory of its motion, unless the visual system has independent access to how far away the object is at any moment. Indeed, as the viewing distance is changed, the same disparate retinal motions will correspond to very different real 3D trajectories. In this paper we were interested in whether binocular 3D motion detection is affected by viewing distance. A visual search task was used, in which the observer is asked to detect a target dot, moving in 3D, amidst 3D stationary distractor dots. We found that distance does not affect detection performance. Motion-in-depth is consistently harder to detect than the equivalent lateral motion, for all viewing distances. For a constant retinal motion with both lateral and motion-in-depth components, detection performance is constant despite variations in viewing distance that produce large changes in the direction of the 3D trajectory. We conclude that binocular 3D motion detection relies on retinal, not absolute, visual signals.     

Single camera photogrammetric technique for restricted 3D motion analysis

The purpose of this study was to use a single camera to determine the true elbow flexion angle with the arm plane oriented arbitrarily with respect to the camera. A mathematical theory was developed and a mechanical arm model was constructed to validate the theory. A static weightlifting skill was analysed to investigate the viability of the technique on the human subject. The validation of the theory showed the error associated with the elbow flexion angle was reduced from as high as 108° when uncorrected to within 3° when corrected by the technique. The elbow flexion angle of the human arm can be calculated to within 6° of error for static weightlifting skill analysis.     

Dynamic motion planning of 3D human locomotion using gradient-based optimization

Since humans can walk with an infinite variety of postures and limb movements, there is no unique solution to the modeling problem to predict human gait motions. Accordingly, we test herein the hypothesis that the redundancy of human walking mechanisms makes solving for human joint profiles and force time histories an indeterminate problem best solved by inverse dynamics and optimization methods. A new optimization-based human-modeling framework is thus described for predicting three-dimensional human gait motions on level and inclined planes. The basic unknowns in the framework are the joint motion time histories of a 25-degree-of-freedom human model and its six global degrees of freedom. The joint motion histories are calculated by minimizing an objective function such as deviation of the trunk from upright posture that relates to the human model's performance. A variety of important constraints are imposed on the optimization problem, including (1) satisfaction of dynamic equilibrium equations by requiring the model's zero moment point (ZMP) to lie within the instantaneous geometrical base of support, (2) foot collision avoidance, (3) limits on ground-foot friction, and (4) vanishing yawing moment. Analytical forms of objective and constraint functions are presented and discussed for the proposed human-modeling framework in which the resulting optimization problems are solved using gradient-based mathematical programming techniques. When the framework is applied to the modeling of bipedal locomotion on level and inclined planes, acyclic human walking motions that are smooth and realistic as opposed to less natural robotic motions are obtained. The aspects of the modeling framework requiring further investigation and refinement, as well as potential applications of the framework in biomechanics, are discussed.     

3D生物打印技术在微生物修复中的应用

排放到环境中的各种农药、多环芳烃、卤代芳烃等有机污染物以及阻燃剂等新兴污染物,对环境污染、农产品质量和环境安全造成了沉重负担。因此,有效去除环境中的有机污染物已成为迫在眉睫的挑战。3D生物打印技术已经在医学材料、制药等行业中发挥着重要作用。现在,越来越多的微生物被确定适合通过3D生物打印生产具有复杂结构和功能的生物材料。微生物的3D生物打印越来越受到环境微生物学家和生物技术专家的关注。本文综述了用于污染物微生物去除的不同3D生物打印技术的原理和优缺点,及用于微生物生物修复技术的可行性,并指出了可能遇到的限制和挑战。     

Integration of the bacteriophage phi 3T-coded thymidylate synthetase gene into the Bacillus subtilis chromosome

Transformation of Bacillus subtilis 168 Thy- auxotrophs with phi 3T deoxyribonucleic acid (DNA) to thymine independence was found to involve site-specific recombination of phi 3T DNA sequences with their homologous counterparts in the bacterial chromosome. During the transformation, the phage phi 3T-encoded thymidylate synthetase gene, thyP3, was shown to integrate at two genetically distinct sites in the B. Subtilis 168 chromosome. The first site was identified to be in the bacterial thymidylate synthetase gene, thyA. The second site was in a prophage (SPB) known to be carried in the host genome. The frequency of the integration of the thyP3 gene at each of the two loci and some of the parameters affecting this frequency were studied. The common origin of the thyP3 and thyA genes and their molecular evolution are also reported.     

Integration of phage Mu into the RP4::D3112A-plasmid in Escherichia coli cells

Hybrid plasmids obtained as a result of Mu phage insertions into the RP4::D3112 plasmid in Escherichia coli cells were studied. Stable maintenance of RP4::D3112 plasmid in E. coli cells was provided by using the D3112 phage genome with a point polar mutation in the A gene which prevented early genes' expression. The presence of D3112A- in the RP4 plasmid has been shown to have no effect on efficiency of phage Mu transposition into this plasmid. Moreover, RP4 and D3112 genomes were equivalent targets for Mu integration. The integration of transposable phage into genome of nonrelated phage can be used as one of the approaches to construct recombinant phage genomes in vivo in the absence of DNA homology.     

Optimal marker set assessment for motion capture of 3D mimic facial movements

Nowadays, facial mimicry studies have acquired a great importance in the clinical domain and 3D motion capture systems are becoming valid tools for analysing facial muscles movements, thanks to the remarkable developments achieved in the 1990s.However, the face analysis domain suffers from a lack of valid motion capture protocol, due to the complexity of the human face. Indeed, a framework for defining the optimal marker set layout does not exist yet and, up to date, researchers still use their traditional facial point sets with manually allocated markers.Therefore, the study proposes an automatic approach to compute a minimum optimized marker layout to be exploited in facial motion capture, able to simplify the marker allocation without decreasing the significance level. Specifically, the algorithm identifies the optimal facial marker layouts selecting the subsets of linear distances among markers that allow to automatically recognizing with the highest performances, through a k-nearest neighbours classification technique, the acted facial movements. The marker layouts are extracted from them. Various validation and testing phases have demonstrated the accuracy, robustness and usefulness of the custom approach.