Learning single-image 3D reconstruction by generative modelling of shape, pose and shading

We present a unified framework tackling two problems: class-specific 3D reconstruction from a single image, and generation of new 3D shape samples. These tasks have received considerable attention recently; however, most existing approaches rely on 3D supervision, annotation of 2D images with keypoints or poses, and/or training with multiple views of each object instance. Our framework is very general: it can be trained in similar settings to existing approaches, while also supporting weaker supervision. Importantly, it can be trained purely from 2D images, without pose annotations, and with only a single view per instance. We employ meshes as an output representation, instead of voxels used in most prior work. This allows us to reason over lighting parameters and exploit shading information during training, which previous 2D-supervised methods cannot. Thus, our method can learn to generate and reconstruct concave object classes. We evaluate our approach in various settings, showing that: (i) it learns to disentangle shape from pose and lighting; (ii) using shading in the loss improves performance compared to just silhouettes; (iii) when using a standard single white light, our model outperforms state-of-the-art 2D-supervised methods, both with and without pose supervision, thanks to exploiting shading cues; (iv) performance improves further when using multiple coloured lights, even approaching that of state-of-the-art 3D-supervised methods; (v) shapes produced by our model capture smooth surfaces and fine details better than voxel-based approaches; and (vi) our approach supports concave classes such as bathtubs and sofas, which methods based on silhouettes cannot learn.Comment: Extension of arXiv:1807.09259, accepted to IJCV. Differentiable renderer available at https://github.com/pmh47/dir

Transformation of the paradigm in intestinal failure: future prognostication and quality of life, not just survival

No abstract available

Conversion Efficiencies of Heteronuclear Feshbach Molecules

We study the conversion efficiency of heteronuclear Feshbach molecules in population imbalanced atomic gases formed by ramping the magnetic field adiabatically. We extend the recent work [J. E. Williams et al., New J. Phys., 8, 150 (2006)] on the theory of Feshbach molecule formations to various combinations of quantum statistics of each atomic component. A simple calculation for a harmonically trapped ideal gas is in good agreement with the recent experiment [S. B. Papp and C. E. Wieman, Phys. Rev. Lett., 97, 180404 (2006)] without any fitting parameters. We also give the conversion efficiency as an explicit function of initial peak phase space density of the majority species for population imbalanced gases. In the low-density region where Bose-Einstein condensation does not appear, the conversion efficiency is a monotonic function of the initial peak phase space density, but independent of statistics of a minority component. The quantum statistics of majority atoms has a significant effect on the conversion efficiency. In addition, Bose-Einstein condensation of an atomic component is the key element determining the maximum conversion efficiency.Comment: 46 pages, 32 figure

Structured Visions In The Novels Of John Hawkes

John Hawkes\u27 novels can be seen as expressing a dialectic between the act of fictional ordering and the chaos of a reality which is potentially subject to the ordering process but which ultimately threatens to dissolve such designs as are present in created or fictional reality. Both Hawkes and many of his protagonists, particularly his first-person narrators, are determined to create a world. As creators and visionary artists, they manifest a need to transform or transcend those forces which oppress them and oppose their efforts to create self-contained worlds based on principles of order, design and clarity; as embodiments of an ordering aesthetic, they battle against the powers of anti-art and often a specific antagonist who represents these powers.;The worlds of such visionary artists are unstable; they reflect creative man\u27s endeavors to impose meaningful order rather than the enduring strength of aesthetic imperatives. In Hawkes\u27 earliest fiction, the artist-figure is stifled by external forces; anti-art in its various forms dominates the worlds of The Cannibal and The Beetle Leg. It is Hawkes himself, through linguistic and stylistic devices, through the structuring capacity, who exhibits the authorial (and authoritarian) need to impose a sense of order and coherence on a world characterized by random eruptions of violence and chaotic disturbances emanating from undefined and unacknowledged human motivations and impulses. From the constant authorial presence manifested in early novels, Hawkes becomes concerned, in his first-person narratives, with filtering a sense of authoritarian will through the visions of narrators who are intent on shaping their own worlds and utilizing the energies of the unconscious and their imaginative capacity. The artist comes to define himself through his thorough isolation from others and from external reality: his quest is for an artistic purity to which he obsessively dedicates himself.;As the worlds of these artists become more confining, they also become more problematical. Many of the concerns of the visionary artist reflect Hawkes\u27 own fictional values. In novels like Travesty and Virginie Hawkes seems to be testing these values, exploring the ultimate reaches of a fictional aesthetic he has consistently expressed in interviews and essays throughout his career

Small Molecules for Controlling Stem Cell Differentiation

Stem cell homeostasis and differentiation are controlled by the complex interplay of a wide range of signalling pathways and small molecules, including all-trans-retinoic acid (ATRA). The endogenous effects elicited by ATRA, have led to its use in numerous in vitro protocols as a tool for cell differentiation. However, ATRA isomerises and degrades under standard laboratory conditions and furthermore, is rapidly metabolised in vivo, which leads to pleotropic effects and a high efficacious dose response. Consequently, synthetic analogues that are structurally and/or functionally equivalent to ATRA have been developed, as alternative pharmacological tools to further the understanding of this molecular pathway and control cell differentiation.In this study a small library of synthetic retinoids were prepared, which were designed to probe structural size, conformation and biological function, while being more resistant to cellular metabolism and isomerisation. Their stability towards fluorescent light was examined along with their activity in four different stem cell models. Two compounds, AH60 and AH61 were found to inhibit cellular proliferation and induce neural differentiation, through acting on the retinoic acid receptor pathway. Compared to ATRA, AH60 was approximately 10-fold more active, while AH61 was 100-fold more active in two of the cell models tested. These compounds are described comprehensively herein, and should be suitable and convenient alternatives to ATRA and 13cRA for use in in vitro studies carried out by cell and molecular biologists. In addition, an unrelated small molecule, neuropathiazol, has been synthesised to further characterise both the chemistry involved in its production and its biological activity in controlling cell differentiation. This compound was highlighted in the literature as an alternative to ATRA, for inducing neural differentiation in neural progenitor cells. We have further investigated its potential to differentiate other neural stem cell types and pluripotent stem cells. In addition potential analogues of neuropathiazol are discussed, as compounds of this nature are potentially highly useful for selectively controlling neural differentiation. 

Dynamics Of Base-isolated Buildings

Base isolation is a novel concept for the protection of buildings up to eight storeys against severe earthquakes. The reduction in seismic forces on the building is achieved by inserting horizontally soft isolation elements between the superstructure and the foundation. As a result, inelastic deformations are limited to the isolators and the fundamental frequency is reduced from 2-3 Hz to typically 0.5 Hz. With the adoption of the base isolation concept, and the research already devoted to it, the questions remain as to the effect of soil-structure interaction, the reponse to turbulent wind in view of the increased flexibility and approximate methods of analysis for both seismic and wind loading.;In the first part of the study, the complex eigenvalue analysis is used to study the modal properties of three and five storey plane frames. The effect of soil-structure interaction is investigated for footings acting independently and also with dynamic interaction (cross-interaction) included. The effect of introducing vertical flexibility in the isolators (rocking) is examined. The suitability of approximate methods for free vibration analysis, idealizing the buildings as a sliding mass or as a rigid body on springs, is verified.;In the second part of the study, the seismic analysis of a five storey plane frame is performed in the time domain. The effect of base isolation in reducing the accelerations induced in the building is demonstrated. An approximate procedure for the time domain analysis of the multi-degree-of-freedom system using equivalent linearization is verified.;In the third part of the study, the wind characteristics of the lower portion of the boundary layer are studied in a wind tunnel and the forces acting on models of low-rise buildings are established. The response theory, with modifications based on the measured parameters, is used to compute the alongwind and torsional response of base-isolated buildings. For comparison, the response is computed using existing codes. A procedure, similar to the Canadian Code, is presented for computing both the alongwind and torsional response and is facilitated by a set of design charts