Freezing of Nonlinear Bloch Oscillations in the Generalized Discrete Nonlinear Schrodinger Equation

The dynamics in a nonlinear Schrodinger chain in an homogeneous electric field is studied. We show that discrete translational invariant integrability-breaking terms can freeze the Bloch nonlinear oscillations and introduce new faster frequencies in their dynamics. These phenomena are studied by direct numerical integration and through an adiabatic approximation. The adiabatic approximation allows a description in terms of an effective potential that greatly clarifies the phenomenon.Comment: LaTeX, 7 pages, 6 figures. Improved version to appear in Phys. Rev.

Design and experimental assessment of a novel damper with high endurance to seismic loads

The study presents the design and the experimental characterization of a new energy dissipation device aimed at providing improved resistance to repeated seismic loads. Differently from conventional steel hysteretic dampers, which dissipate energy by yielding of a mild steel core and are noted to suffer low-cycle fatigue, the new damper provides energy dissipation by the friction that is activated between a moving shaft and a lead core prestressed within a tube. The prestress level is controlled during the assembling process, allowing to adjust the axial strength of the damper. Thanks to the ability of lead to restore its properties by static recrystallization taking place immediately after deformation, repeated cycles of loading do not produce damages that may accrue and eventually lead to failure of the device. Moreover, prestressing of the lead core allows to achieve high specific strength (i.e., high force to volume ratio), thereby providing low dimensions which help to reduce the architectural invasiveness. Prototypes of the damper were subjected to the test procedure established in the European standard EN 15129 for Displacement Dependent Devices, fulfilling the relevant requirements. The damper provides a robust and stable response over repeated cycles, characterized by essentially rectangular hysteresis loops with an equivalent viscous damping ratio ξeff of about 55%. Moreover, it shows low sensitivity of mechanical properties on the loading rate and the ability to withstand multiple cycles of motion at the design earthquake displacement without deterioration of performance, demonstrating maintenance-free operation in presence of repeated ground shakes. Its ability to survive several strong motions without being damaged, and its high damping capability coupled to a compact design and low manufacturing cost, are the distinctive features that make it suitable for social housing

3D numerical characterization of a dissipative connection system for retrofit of prefabricated existing RC sheds

Prefabricated industrial sheds featured a high seismic vulnerability during the 2012 Emilia earthquake (Italy). The buildings typically exhibited a rigid collapse mechanism that was a consequence of the loss of support between columns, beams and roof elements. The study presents a numerical characterization of a novel dissipative connection system (DCS) designed to improve the seismic performance of industrial sheds. The device, which is placed on the top of the columns, exploits the movement of a rigid body on a sloped surface to provide horizontal stiffness and control the lateral displacement of the beam. A 3D finite element model of the prototype is formulated in Abaqus and used to switch the backbone curve from the scaled model to the full-scale device. A parametric study is conducted to evaluate the influence of the slope of the contact surface and the coefficient of friction on the output force of the system. In the second part of the study, non-linear dynamic analyses are performed on a finite element model of a portal frame implementing, at beam-column joints, either the DCS or a pure friction connection. The results highlight the effectiveness of the DCS in controlling beam-to-column displacements, reducing shear forces on the top of columns, and limiting residual displacements that can accrue during ground motion sequence

ASSESSMENT OF THE SHEAR PROPERTIES OF HDRBS UNDER DIFFERENT COMPRESSION LEVELS

Despite it is well known that the shear properties of High Damping Rubber Bearings (HDRBs) are affected by the instantaneous compression load developed during the seismic ground motion, only permissible variations of their design properties with frequency, temperature and ageing are prescribed in the standards while the influence of the compression level is usually disregarded. Within this framework, this research addresses this drawback through both experimental and numerical investigations. In the first part of the study, small scale laminated isolators are tested on a custom biaxial machine in order to assess the secant modulus, and damping factor of the elastomeric compound under different compression levels. In the second part, the same phenomenon is investigated through cyclic shear tests on full scale HDRBs under three different levels of axial load. In the last part, a 3D finite element model of the isolator is eventually formulated in Abaqus FEM software. The mechanical response of the elastomer is simulated by means of a hyperelastic strain energy function combined with a relaxation function. The experimental results highlight the substantial influence of the axial load on the damping capacity of the elastomer, while the shear modulus is less affected. The numerical analyses demonstrate that the vertical – horizontal coupled response of HDRBs can be accurately predicted, within the proposed formulation, with constitutive parameters estimated from simple uniaxial tests

Warburg effect and translocation-induced genomic instability: two yeast models for cancer cells

Yeast has been established as an efficient model system to study biological principles underpinning human health. In this review we focus on yeast models covering two aspects of cancer formation and progression (i) the activity of pyruvate kinase (PK), which recapitulates metabolic features of cancer cells, including the Warburg effect, and (ii) chromosome bridge-induced translocation (BIT) mimiking genome instability in cancer. Saccharomyces cerevisiae is an excellent model to study cancer cell metabolism, as exponentially growing yeast cells exhibit many metabolic similarities with rapidly proliferating cancer cells. The metabolic reconfiguration includes an increase in glucose uptake and fermentation, at the expense of respiration and oxidative phosphorylation (the Warburg effect), and involves a broad reconfiguration of nucleotide and amino acid metabolism. Both in yeast and humans, the regulation of this process seems to have a central player, PK, which is up-regulated in cancer, and to occur mostly on a post-transcriptional and post-translational basis. Furthermore, BIT allows to generate selectable translocation-derived recombinants ("translocants"), between any two desired chromosomal locations, in wild-type yeast strains transformed with a linear DNA cassette carrying a selectable marker flanked by two DNA sequences homologous to different chromosomes. Using the BIT system, targeted non-reciprocal translocations in mitosis are easily inducible. An extensive collection of different yeast translocants exhibiting genome instability and aberrant phenotypes similar to cancer cells has been produced and subjected to analysis. In this review, we hence provide an overview upon two yeast cancer models, and extrapolate general principles for mimicking human disease mechanisms in yeast

Indução de estro em cabras da raça Toggenburg com dois diferentes dispositivos intravaginais.

Doze cabras nuliparas da raça Toggenburg foram distribuidas em dois tratamentos (Tl e T2) para induçao do estro. 0 T1 (n=6) consistiu na inserçao da esponja imnpregnada com 60mg de acetato de medroxiprogesterona, associado a aplicaçao de 50mg do analogo sintetico d-cloprostenol (PGF). No quarto dia, foram aplicadas 250UI de gonadotropina corionica equina (eCG) e, no quinto, a esponja foi retirada. 0 T2 (n=6) diferiu somente quanto ao dispositivo empregado, que foi 0 CIDR-G@. Seis cabras do Tl e seis do T2 entraram em estro depois da retirada dos dispositivos, sendo que 83,3 (5/6) e 33,3% (2/6) ficaram gestantes em Tl e T2, respectivamente. 0 intervalo da retirada do dispositivo ao inicio do estro nao diferiu entre tratamentos (P>O,O5). As caracteristicas ovulatorias nao foram influenciadas pelos tratamentos. 0 intervalo da retirada do dispositivo a ovulaçao, para ambos os protocolos de induçao do estro, nao diferiu (P>O,O5) entre tratamentos. Ambos os dispositivos foram eficientes em induzir O estro. [Estrous induction in Toggenburg goats using intravaginal devices]. Abstract: Twelve Toggenburg breed nuliparous female goats were randomly assigned to two treatments intended to induce estrus. On day zero, animals on T1 (n=6) were treated with an intravaginal sponge impregnated with 60mg of medroxyprogesterone acetate plus 50µg of PGF analogue. The T1 goats received eCG (250IU) on day 4, and on day 5 the sponge was removed. The T2 goats (n=6) received CIDR-G® as intravaginal sponge plus 50mg of PGF analogue. All goats expressed behavioral estrus, and the pregnancy rates were 83.3 (5/6) and 33.3% (2/6) for T1 and T2, respectively. The interval from withdrawal of the device to onset of estrus did not differ between treatments (P>0.05). Ovulatory traits also were not affected by treatments. The interval between CIDR-G® removal and ovulation for T1 and T2 goats were similar (P>0.05). Both sponge and CIDR-G were equally efficient in inducing the estrus behavior in goats

Relativistic quantum clocks

The conflict between quantum theory and the theory of relativity is exemplified in their treatment of time. We examine the ways in which their conceptions differ, and describe a semiclassical clock model combining elements of both theories. The results obtained with this clock model in flat spacetime are reviewed, and the problem of generalizing the model to curved spacetime is discussed, before briefly describing an experimental setup which could be used to test of the model. Taking an operationalist view, where time is that which is measured by a clock, we discuss the conclusions that can be drawn from these results, and what clues they contain for a full quantum relativistic theory of time.Comment: 12 pages, 4 figures. Invited contribution for the proceedings for "Workshop on Time in Physics" Zurich 201