A Super-Flag Landau Model

We consider the quantum mechanics of a particle on the coset superspace $SU(2|1)/[U(1)\times U(1)]$, which is a super-flag manifold with $SU(2)/U(1)\cong S^2$ `body'. By incorporating the Wess-Zumino terms associated with the $U(1)\times U(1)$ stability group, we obtain an exactly solvable super-generalization of the Landau model for a charged particle on the sphere. We solve this model using the factorization method. Remarkably, the physical Hilbert space is finite-dimensional because the number of admissible Landau levels is bounded by a combination of the U(1) charges. The level saturating the bound has a wavefunction in a shortened, degenerate, irrep of $SU(2|1)$

Non-functional biomimicry : utilising natural patterns to provoke attention responses

Natural reoccurring patterns arise from chaos and are prevalent throughout nature. The formation of these patterns is controlled by, or produces, underlying geometrical structures. Biomimicry is the study of nature’s structure, processes and systems, as models and solutions for design challenges and is being widely utilized in order to address many issues of contemporary engineering. Many academics now believe that aesthetics stem from pattern recognition, consequently, aesthetic preference may be a result of individuals recognising, and interacting with, natural patterns. The goal of this research was to investigate the impact of specific naturally occurring pattern types (spiral, branching, and fractal patterns) on user behaviour; investigating the potential of such patterns to control and influence how individuals interact with their surrounding environment. The results showed that the underlying geometry of natural patterns has the potential to induce attention responses to a statistically significant level

T-cadherin upregulation correlates with cell-cycle progression and promotes proliferation of vascular cells

Objective: In vascular tissue, T-cadherin (T-cad) levels correlate with the progression of atherosclerosis, restenosis and tumour neovascularization. This study investigates whether T-cad influences proliferation of vascular cells. Methods and Results: Cultures of human umbilical vein endothelial cells (HUVEC) and rat and human aortic smooth muscle cells (rSMC, hSMC) were used. T-cad was overexpressed in HUVEC and hSMC using an adenoviral expression system. In cultures released from G1/G0 synchrony parallel immunoblot analysis of T-cad and cell cycle phase specific markers (p27Kip1, cyclin D1, E2F1, PCNA, cyclin B) showed increased T-cad protein levels subsequent to entry into early S-phase with sustained elevation through S-and M-phases. T-cad was increased in G2/M-phase (colchicine) synchronized cultures. In FACS-sorted cell populations, expression of T-cad in S-and G2/M-phase was higher than G1/G0-phase. Compared with empty-and LacZ-vector infected controls, HUVEC and hSMC overexpressing T-cad exhibited increased proliferation as assessed in enumeration and DNA synthesis assays. Additionally, following release from G1/G0 synchrony, HUVEC and hSMC overexpressing T-cad enter S-phase more rapidly. Flow cytometry after BrdU/propidium labelling confirmed increased cell cycle progression in T-cad overexpressing cells. Conclusion: In vascular cells, T-cad is dynamically regulated during the cell cycle and its expression functions in the promotion of proliferation. T-cad may facilitate progression of proliferative vascular disorders such as atherosclerosis, restenosis and tumour angiogenesi

Polarisation of T-cadherin to the leading edge of migrating vascular cells in vitro: a function in vascular cell motility?

Both histological and in vitro studies indicate a relationship between T-cadherin levels and acquisition of a modulated, migratory phenotype by vascular cells. This study further examines a role for T-cadherin in relation to cell migration and adhesion. Fluorescence microscopic examination of T-cadherin localisation in confluent cultures of human umbilical vein endothelial cells (HUVEC), human aortic smooth muscle cells and the human carcinoma cell line ECV-304 revealed global distribution over the entire cell body, and with only slight enrichment at cell borders. This contrasts with restricted cell-cell junction localisation of classical cadherin (for example, VE-cadherin in HUVEC). In wounded cultures, T-cadherin polarised to the leading edge of cells migrating into the wound area, again contrasting with classical VE-cadherin, which was undetectable in this region. Confocal microscopy demonstrated that potential signalling functions of T-cadherin at the leading edge are unrelated to physical interactions with caveolin. Adherence of HUVEC onto a monolayer of T-cadherin-transfected L929 cells is significantly reduced compared with adhesion onto control (T-cadherin-negative) L929. Thus T-cadherin is not required for maintenance of intercellular adhesion, but may rather function as a signalling molecule involved in cell-cell recognition and sensing of the environment in processes where cell detachment occur

Describing many-body bosonic waveguide scattering with the truncated Wigner method

We consider quasi-stationary scattering of interacting bosonic matter waves in one-dimensional waveguides, as they arise in guided atom lasers. We show how the truncated Wigner (tW) method, which corresponds to the semiclassical description of the bosonic many-body system on the level of the diagonal approximation, can be utilized in order to describe such many-body bosonic scattering processes. Special emphasis is put on the discretization of space at the exact quantum level, in order to properly implement the semiclassical approximation and the tW method, as well as on the discussion of the results to be obtained in the continuous limit.Comment: 9 pages, 3 figure

Improved test of Lorentz Invariance in Electrodynamics using Rotating Cryogenic Sapphire Oscillators

We present new results from our test of Lorentz invariance, which compares two orthogonal cryogenic sapphire microwave oscillators rotating in the lab. We have now acquired over 1 year of data, allowing us to avoid the short data set approximation (less than 1 year) that assumes no cancelation occurs between the $\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters from the photon sector of the standard model extension. Thus, we are able to place independent limits on all eight $\tilde{\kappa}_{e-}$ and $\tilde{\kappa}_{o+}$ parameters. Our results represents up to a factor of 10 improvement over previous non rotating measurements (which independently constrained 7 parameters), and is a slight improvement (except for $\tilde{\kappa}_{e-}^{ZZ}$) over results from previous rotating experiments that assumed the short data set approximation. Also, an analysis in the Robertson-Mansouri-Sexl framework allows us to place a new limit on the isotropy parameter $P_{MM}=\delta-\beta+{1/2}$ of $9.4(8.1)\times10^{-11}$, an improvement of a factor of 2.Comment: Accepted for publication in Phys. Rev.

Deep Contract Design via Discontinuous Networks

Contract design involves a principal who establishes contractual agreements about payments for outcomes that arise from the actions of an agent. In this paper, we initiate the study of deep learning for the automated design of optimal contracts. We introduce a novel representation: the Discontinuous ReLU (DeLU) network, which models the principal's utility as a discontinuous piecewise affine function of the design of a contract where each piece corresponds to the agent taking a particular action. DeLU networks implicitly learn closed-form expressions for the incentive compatibility constraints of the agent and the utility maximization objective of the principal, and support parallel inference on each piece through linear programming or interior-point methods that solve for optimal contracts. We provide empirical results that demonstrate success in approximating the principal's utility function with a small number of training samples and scaling to find approximately optimal contracts on problems with a large number of actions and outcomes

Laser-sub-cycle two-dimensional electron momentum mapping using orthogonal two-color fields

The two-dimensional sub-cycle-time to electron momentum mapping provided by orthogonal two-color laser fields is applied to photoelectron spectroscopy. Using neon as the example we gain experimental access to the dynamics of emitted electron wave packets in electron momenta spectra measured by coincidence momentum imaging. We demonstrate the opportunities provided by this time-to-momentum mapping by investigating the influence of the parent ion on the emitted electrons on laser-sub-cycle times. It is found that depending on their sub-cycle birth time the trajectories of photoelectrons are affected differently by the ion's Coulomb field

Dramatic changes in the 3s autoionization process at the beginning of the Ar I sequence

The 3s→np resonances were observed to change dramatically in appearance with increasing ionization along the Ar I sequence, and within the 3s→np channel of Ca2+. By applying the Dyson equation method to positive ions for the first time, newly investigated double-electron processes were shown to play a crucial role in the interpretation of the resonance structure. The changes within the resonances result from their position relative to the Cooper minima in the 3s and 3p photoabsorption