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Liver bioengineering has been a field of intense research and popular excitement in the past decades. It experiences great interest since the introduction of whole liver acellular scaffolds generated by perfusion decellularization. Nevertheless, the different strategies developed so far have failed to generate hepatic tissue in vitro bioequivalent to native liver tissue. Even notable novel strategies that rely on iPSC-derived liver progenitor cells potential to self-organize in association with endothelial cells in hepatic organoids are lacking critical components of the native tissue (e.g., bile ducts, functional vascular network, hepatic microarchitecture, etc) . Hence, it is vital to understand the strengths and short comes of our current strategies in this quest to re-create liver organogenesis in vitro. To shed some light into these issues, this review describes the different actors that play crucial roles in liver organogenesis and highlights the steps still missing to successfully generate whole livers and hepatic organoids in vitro for multiple applications. [ABSTRACT FROM AUTHOR]

On 2002, a novel initiative was undertaken by the local water administration of Catalonia (the Agència Catalana de l'Aigua) and the Universitat Autònoma de Barcelona, leading to a ten-year project where a high number of medium resolution satellite images (MODIS and Landsat) were integrated to the daily water management to improve decision making effectiveness. This paper describes the methodology followed in the successful application of remote sensing, as well as the main problems that had to be overcome during its execution. It also presents the products that have been calculated. These are integrated into the Agency's corporate GIS and immediately available via the intranet for the staff, and a selection is available on the Internet. [ABSTRACT FROM AUTHOR]

The effect of length-bidispersity on the stability of nematic, smectic and columnar phases of rod-like particles is studied in the perfect alignment limit using Onsager's second virial theory. The rod-like particles are modelled as hard cylinders of equal diameters (D) but different lengths ( [image omitted]). Three different smectic structures are observed: (i) the conventional smectic (S1) phase, where both components accommodate in the same layer; (ii) the microsegregated smectic (S2) phase, which can be considered as an alternation of fluid layers rich in short and long rods, respectively; and (iii) two layers of short rods accommodate inside one layer of long rods, which gives the third smectic (S3) structure. Due to the inefficient packing of the short and long rods into a layered structure along the symmetry axes of the rods, the smectic phase is destabilised with respect to nematic and columnar phases upon mixing the short and long components. With decreasing length ratio ( [image omitted]) the smectic phase is destabilised with respect to the nematic phase at compositions rich in short rods and two forms of smectic phases, namely S1 and S2, take place in alternation. The alternation of the structure is the consequence of the minimisation of the number of overlapping layers of the short rods with one long rod. In mixtures rich in long rods, the short and long rods are in the same layer up to l = 0.39, while the short rods can accommodate into the interstitial region of long rods for l < 0.39 and the system forms a S2 phase. The S3 phase is observed in the range 0.57 < l < 0.39 and is due to the efficient packing of two layers of short rods inside one smectic layer of long rods. Our theoretical predictions for the three smectic structures are in close agreement with the smectic phase behaviour of a binary mixture of short and long helical polysilanes (Okoshi et al., Macromolecules 42, 3443 (2009)). It seems reasonable that the helical polysilanes can be considered as an ideal system for testing the hard-body theories. Finally, it is interesting that the stabilisation process of the columnar phase with respect to the smectic ordering with decreasing length ratio turns over at l = 0.3. [ABSTRACT FROM AUTHOR]

We analyse demixing and ordering transitions in systems of hard cylindrical particles. The second virial approximation of Onsager and a bifurcation analysis, as introduced by Koda and Kimura, are used to evaluate the free energies, pressures, and density distribution functions in mixtures of equally long but differently wide cylinders. The spatial density distribution along the one relevant coordinate is of particular importance as it provides more detailed information concerning the nature of the phase transition than the bare bifurcation diagnosis. Detailed results are given for the nematic-nematic spinodal and the nematic-smectic transitions. Allowing for the absence of an isotropic phase, our results are in good qualitative agreement with those for freely orienting rods reported previously, and indicate a complex sequence of phase diagrams as the diameter dissimilarity of the two components is increased, with upper and lower critical points bounding nematic and smectic demixing regions. However, experimental results on colloidal rods show that nematic demixing occurs at a diameter ratio much smaller than ours or those for freely rotating fluids, indicating that Onsager-type theories may be insufficient to reproduce this phenomenon in a quantitative manner and, consequently, that more sophisticated approaches, presumably incorporating particle flexibility and additional interactions, are required. [ABSTRACT FROM AUTHOR]

The article discusses the contributions of James Gregory, a mathematician in the early 1670s. Due to his premature death in 1675, most of his research notes were lost and ignored and thus he was only second to Isaac Newton. However, his important contributions to the field were revealed to the world after Herbert Westren Turnbull released a memorial volume that contains Gregory's manuscripts. It was made clear that he had proven the rules of differentiation and that he was in possession of the chain rule before Leibniz had written it. It was also revealed that he had discovered Taylor's theorem before Taylor and created the binomial theorem from his formula. He also developed basic results of the calculus and had written a book which is considered the first of a systematic textbook.

Results of recent calculations aimed at predicting the liquid-crystalline phase behavior of binary mixtures of hard spherocylinders are shortly reviewed. These calculations have been made by adopting a simple, re-summed second-virial Onsager-type theory, and include, among the usual isotropic and nematic phases, smectic phases too. The paradigmatic hard spherocylinders with diameter D and length of the cylindrical part equal to 5D have been taken as reference component, to which hard spherocylinders of different geometry are added. The liquid-crystalline phase diagram of the bidisperse mixtures so generated have been traced in all range of composition as a function of pressure. Various phenomena, such as strong demixing, presence of triple, critical and azeotropic points, and smectic phases with different symmetries, have been observed. [ABSTRACT FROM AUTHOR]

Monte Carlo simulations of bulk liquid crystals in the isotropic, nematic and smectic phases were performed. The simulations were carried out using different box shapes. The diagonal components of the pressure tensor were calculated to verify that the system is in mechanical equilibrium. For simulations in cubic boxes it was found that the three components of the pressure tensor had the same values in the isotropic and nematic phases but they were different in the smectic phase, i.e. the system seemed to be under anisotropic stress. NVT and NPT simulations in the smectic phase were performed by allowing the box sides to fluctuate independently; in this case, the average diagonal components of the pressure tensor had the same value. Inaccurate calculation of the total pressure produces incorrect equilibrium boundaries in the phase diagram. Microphases and poorly defined layering can be found in simulations of smectic phases when they are performed on cubic boxes. Although the pressure anisotropy is relaxed out, the layering structure in smectic phases seems to depend on the initial configuration, regardless of the simulation method. [ABSTRACT FROM AUTHOR]