regenerative medicine and remains a major challenge. A multitude of technologies have been described to control the spatial organization of cells in 3D engineered heart constructs including mechanical strain/load [1] and chronic electrical stimulation. [2] Other approaches to guide cellular organization have been reported using microfluidic platforms, [3] light-triggered activation of biomolecules, [4] and 3D bioprinting. [5] However, these techniques often involve elaborate, macroscale stimulation systems and are not always suitable for the fabrication of detailed microarchitectures in vitro as each pattern requires new molds, posts, or frames. [6] The next generation of dynamic systems may be designed to respond to user-defined size and shape triggers for controlling cellular organization on the macroscale without the need for external mechanical supports or material cues. Magnetic procedures to manipulate and remotely control cellular behavior represent a promising approach for fabrication of tissuelike constructs. In particular, magnetic nanoparticles (MNPs) have gained increased attention for use in biomedical applications such as magnetic targeting of stem cells [7] and genes, [8] development of scaffold-free multilayer structures, [9] and spatial patterning of aggregates. [10] Magnetic techniques are advantageous due to their high precision and accuracy. To date, magnetic fabrication of biological structures has been illustrated by the assembly of biomembranes made of organized yeast, [11] the formation of "artificial retinas" by magnetic field modulation of chiromagnetic nanoparticles, [12] or the engineering of vocal folds, [13] among others.Here, we report a new platform for engineering tissue morphologies with controlled geometries. Specifically, we used magnetic fields to direct the assembly and patterning of magnetized human cardiomyocytes (CMs) labeled with MNPs in collagenbased hydrogels. Our system enables dynamic manipulation of cells within 3D biomaterials that can be applied to engineer patterned tissues to investigate cellular and tissue behavior. Furthermore, the simplicity and the faithful reproduction of our approach will enable the creation of customized 3D constructs with a new range of complementary implementations such as in biomedical devices, soft robotics, and flexible electronics.First, we designed functionalized MNPs to target and label human induced pluripotent-stem-cell-derived cardiomyocytes (hiPSC-CMs, Figure 1a). For that purpose, we conjugated an antisignal-regulatory protein alpha (SIRPA) cell surface mono clonal antibody [14] labeled with a fluorophore to three types of MNPsThe ability to manipulate cellular organization within soft materials has important potential in biomedicine and regenerative medicine; however, it often requires complex fabrication procedures. Here, a simple, cost-effective, and one-step approach that enables the control of cell orientation within 3D collagen hydrogels is developed to dynamically create various tailored microstructures of cardiac...

The Affine Coherent State Quantization procedure is applied to the case of a FRLW universe in the presence of a cosmological constant. The quantum corrections alter the dynamics of the system in the semiclassical regime, providing a potential barrier term which avoids all classical singularities, as already suggested in other models studied in the literature. Furthermore the quantum corrections are responsible for an accelerated cosmic expansion. This work intends to explore some of the implications of the recently proposed "Enhanced Quantization" procedure in a simplified model of cosmology.

A two dimensional matter coupled model of quantum gravity is studied in the Dirac approach to constrained dynamics in the presence of a cosmological constant. It is shown that after partial fixing to the conformal gauge the requirement of a quantum realization of the conformal algebra for physical quantum states of the fields naturally constrains the cosmological constant to take values in a well determined and mostly discrete spectrum. Furthermore the contribution of the quantum fluctuations of the single dynamical degree of freedom in the gravitational sector, namely the conformal mode, to the cosmological constant is negative, in contrast to the positive contributions of the quantum fluctuations of the matter fields, possibly opening an avenue towards addressing the cosmological constant problem in a more general context.

We report on both experiments and theory of low-terahertz frequency range (up to 400 GHz) magnetoplasmons in a gated two-dimensional electron gas at low (<4K) temperatures. The evolution of magnetoplasmon resonances was observed as a function of magnetic field at frequencies up to ∼400 GHz. Full-wave 3D simulations of the system predicted the spatial distribution of plasmon modes in the 2D channel, along with their frequency response, allowing us to distinguish those resonances caused by bulk and edge magnetoplasmons in the experiments. Our methodology is anticipated to be applicable to the low temperature (<4K) on-chip terahertz measurements of a wide range of other low-dimensional mesoscopic systems.

The problem of time is an unsolved issue of canonical General Relativity. A possible solution is the Brown-Kuchař mechanism which couples matter to the gravitational field and recovers a physical, i.e. non vanishing, observable Hamiltonian functional by manipulating the set of constraints. Two cases are analyzed. A generalized scalar fluid model provides an evolutionary picture, but only in a singular case. The Schutz' model provides an interesting singularity free result: the entropy per baryon enters the definition of the physical Hamiltonian. Moreover in the co-moving frame one is able to identify the time variable τ with the logarithm of entropy.

Plasmons in two-dimensional waveguides are traditionally analysed within the electrostatic approximation, which assumes that the plasmon phase velocity is much smaller than the velocity of light. However, novel effects have recently been demonstrated for plasmons whose velocity is comparable to the velocity of light. In this retardation regime, electrostatic models are inaccurate. For a junction between two plasmonic waveguides, we present an analytical and a numerical model both valid in the retardation regime and compare them to an electrostatic model. We quantify the reflected and transmitted powers and the radiation loss in several scenarios. We found that power is radiated from a junction at the expense of the power of the reflected plasmon, but retardation has little effect on the phases of the reflected and transmitted plasmons. The radiation loss is typically below several percent when the plasmon velocities are five or more times below the light velocity. However, radiation still persists for slower plasmon velocities for a junction between a twodimensional waveguide and a perfectly conducting sheet. As a result, retardation is expected to degrade the quality factors of plasmonic resonators without affecting their eigenfrequencies.

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The Brown-Kuchař mechanism is applied in the case of general relativity coupled with Schutz' model for a perfect fluid. Using the canonical formalism and manipulating the set of modified constraints one is able to recover the definition of a time-evolution operator, i.e. a physical Hamiltonian, expressed as a functional of gravitational variables and the entropy.