Interaction-induced current-reversals in driven lattices

We demonstrate that long-range interactions can cause, as time evolves, consecutive reversals of directed currents for dilute ensembles of particles in driven lattices. These current-reversals are based on a general mechanism which leads to an interaction-induced accumulation of particles in the regular regions of the underlying single-particle phase space and to a synchronized single-particle motion as well as an enhanced efficiency of Hamiltonian ratchets.Comment: 5 pages, 5 figure

Graphs of large girth and surfaces of large systole

The systole of a hyperbolic surface is bounded by a logarithmic function of its genus. This bound is sharp, in that there exist sequences of surfaces with genera tending to infinity that attain logarithmically large systoles. These are constructed by taking congruence covers of arithmetic surfaces. In this article we provide a new construction for a sequence of surfaces with systoles that grow logarithmically in their genera. We do this by combining a construction for graphs of large girth and a count of the number of $\mathrm{SL}_2(\mathbb{Z})$ matrices with positive entries and bounded trace

Pheochromocytomas and paragangliomas: from DNA to the daily clinical practice

The neuroendocrine system is a diffuse system in which the nervous system and the hormones of the endocrine glands interact. The neuroendocrine organs of the sympathetic and parasympathetic autonomic nervous system are called paraganglia. These organs usually manifest as anatomically discrete bodies, which derive from the neural crest and produce catecholamines and various peptides. Various localizations of paraganglia in the human body are known, including the adrenal gland, organs of Zuckerkandl, and carotid and aortic bodies. Paraganglia are divided into two functional groups, i.e. the sympathoadrenal and the parasympathetic autonomic nervous system. Sympathetic paraganglia are predominantly located in the prevertebral and paravertebral sympathetic trunks, and along the fibers of the hypogastric plexus, innervating pelvic and retroperitoneal organs. Parasympathetic paraganglia are almost exclusively located in the region of cranial as well as thoracic branches of the of the glossopharyngeal nerves and vagal nerves. The principal glossopharyngeal paraganglia are the tympanic (located in the wall of the middle ear), and the carotid bodies (Figure 1). Neoplasms of the paraganglia are called pheochromocytomas (PCC), sympathetic and parasympathetic paragangliomas. The name PCC is derived from the Greek synonym “dark colored tumor”, because it was first described by Pick as a chromium salt-reactive tumor which lead to dark coloration. PCC are tumors which originate in the adrenal medulla. Sympathetic paragangliomas (sPGL), in the literature often described as extra-adrenal PCC, usually produce catecholamines and occur in the abdominal cavity and the aorticopulmonary bodies, but not in the adrenal medulla. Parasympathetic paragangliomas, also called head and neck paraganglioma, usually do not produce catecholamines and are situated in the wall of the middle ear, along the vagal nerve, and the carotid and jugular bodies. In the literature they are still often referred to as chemodectomas, glomus tumors, or carotid body tumors

A thermodynamical fiber bundle model for the fracture of disordered materials

We investigate a disordered version of a thermodynamic fiber bundle model proposed by Selinger, Wang, Gelbart, and Ben-Shaul a few years ago. For simple forms of disorder, the model is analytically tractable and displays some new features. At either constant stress or constant strain, there is a non monotonic increase of the fraction of broken fibers as a function of temperature. Moreover, the same values of some macroscopic quantities as stress and strain may correspond to different microscopic cofigurations, which can be essential for determining the thermal activation time of the fracture. We argue that different microscopic states may be characterized by an experimentally accessible analog of the Edwards-Anderson parameter. At zero temperature, we recover the behavior of the irreversible fiber bundle model.Comment: 18 pages, 10 figure

Exponential torsion growth for random 3-manifolds

We show that a random 3-manifold with positive first Betti number admits a tower of cyclic covers with exponential torsion growth

Directed transport and localization in phase-modulated driven lattices

We explore the dynamics of non-interacting particles loaded into a phase-modulated one-dimensional lattice formed by laterally oscillating square barriers. Tuning the parameters of the driven unit cell of the lattice selected parts of the classical phase space can be manipulated in a controllable manner. We find superdiffusion in position space for all parameters regimes. A directed current of an ensemble of particles can be created through locally breaking the spatiotemporal symmetries of the time-driven potential. Magnitude and direction of the current are tunable. Several mechanisms for transient localization and trapping of particles in different wells of the driven unit cell are presented and analyzed

A virtual collaborative platform to support building information modeling implementation for energy efficiency

There is increased interest in complying with the new regulations and policies associated with the climate change. In particular industries such as the AEC (Architecture, Engineering and Construction) industry seek to find new strategies and practices for facilitating sustainability but also new regulations to improve efficiency at the building level. Institutions and industrial bodies are now in the process of alignment with new legislative stipulations regarding carbon emissions with wider reflection into environment, social and economic models. At building level such strategies refer to decarbonisation and energy efficiency supported with data driven techniques enriched with virtual collaboration and optimization methods. The increased interest of the research community in Building Information Modeling (BIM) has facilitated numerous solutions ranging from digital products, information retrieval, and optimization techniques all aiming at addressing energy optimization and performance gap reduction. In this paper we present how a virtual collaborative system can be efficiently used for implementing BIM based energy optimization for controlling, monitoring buildings and running energy optimization, greatly contributing to creating a BIM construction community with energy practices. The solution described, known as energy-bim.com platform, disseminates energy efficient practices and community engagement and provides support for building managers in implementing energy efficient optimization plans

Hard-needle elastomer in one spatial dimension

We perform exact Statistical Mechanics calculations for a system of elongated objects (hard needles) that are restricted to translate along a line and rotate within a plane, and that interact via both excluded-volume steric repulsion and harmonic elastic forces between neighbors. This system represents a one-dimensional model of a liquid crystal elastomer, and has a zero-tension critical point that we describe using the transfer-matrix method. In the absence of elastic interactions, we build on previous results by Kantor and Kardar, and find that the nematic order parameter $Q$ decays linearly with tension $\sigma$. In the presence of elastic interactions, the system exhibits a standard universal scaling form, with $Q / |\sigma|$ being a function of the rescaled elastic energy constant $k / |\sigma|^\Delta$, where $\Delta$ is a critical exponent equal to $2$ for this model. At zero tension, simple scaling arguments lead to the asymptotic behavior $Q \sim k^{1/\Delta}$, which does not depend on the equilibrium distance of the springs in this model.Comment: 6 pages, 4 figures, to be submitted to a special issue in Brazilian Journal of Physics in honor of Prof. Silvio R. Salina