Influence of the Ground-State Topology on the Domain-Wall Energy in the Edwards-Anderson +/- J Spin Glass Model

We study the phase stability of the Edwards-Anderson spin-glass model by analyzing the domain-wall energy. For the bimodal distribution of bonds, a topological analysis of the ground state allows us to separate the system into two regions: the backbone and its environment. We find that the distributions of domain-wall energies are very different in these two regions for the three dimensional (3D) case. Although the backbone turns out to have a very high phase stability, the combined effect of these excitations and correlations produces the low global stability displayed by the system as a whole. On the other hand, in two dimensions (2D) we find that the surface of the excitations avoids the backbone. Our results confirm that a narrow connection exists between the phase stability of the system and the internal structure of the ground-state. In addition, for both 3D and 2D we are able to obtain the fractal dimension of the domain wall by direct means.Comment: 4 pages, 3 figures. Accepted for publication in Rapid Communications of Phys. Rev.

Radio Observations of the AGN and Gas in Low Surface Brightness Galaxies

LSB galaxies have low metallicities, diffuse stellar disks, and massive HI disks. We have detected molecular gas in two giant LSB galaxies, UGC 6614 and F568-6. A millimeter continuum source has been detected in UGC 6614 as well. At centimeter wavelengths we have detected and mapped the continuum emission from the giant LSB galaxy 1300+0144. The emission is extended about the nucleus and is most likely originating from the AGN in the galaxy. The HI gas distribution and velocity field in 1300+0144 was also mapped. The HI disk extends well beyond the optical disk and appears lopsided in the intensity maps.Comment: one page; submitted to proceedings of IAU Symposium 235: Galaxy Evolution across the Hubble Tim

A multi-centennial record of past floods and earthquakes in Valle d'Aosta, Mediterranean Italian Alps

Mediterranean Alpine populations are particularly exposed to natural hazards like floods and earthquakes because of both the close Mediterranean humidity source and the seismically active Alpine region. Knowledge of long-term variability in flood and earthquake occurrences is of high value since it can be useful to improve risk assessment and mitigation. In this context, we explore the potential of a lake-sediment sequence from Lago Inferiore de Laures in Valle d'Aosta (Northern Italy) as a long-term record of past floods and earthquakes. The high-resolution sedimentological study revealed 76 event layers over the last ca. 270 years; 8 are interpreted as most probably induced by earthquakes and 68 by flood events. Comparison to historical seismic data suggests that the recorded earthquakes are strong (epicentral Medvedev–Sponheuer–Kárník (MSK) intensity of VI–IX) and/or close to the lake (distance of 25–120 km). Compared to other lake-sediment sequences, Lago Inferiore de Laures sediments appear to be regionally the most sensitive to earthquake shaking, offering a great potential to reconstruct the past regional seismicity further back in time. Comparison to historical and palaeoflood records suggests that the flood signal reconstructed from Lago Inferiore de Laures sediments represents the regional and (multi-)decadal variability of summer–autumn floods well, in connection to Mediterranean mesoscale precipitation events. Overall, our results reveal the high potential of Lago Inferiore de Laures sediments to extend the regional earthquake and flood catalogues far back in time

Myosin motors fragment and compact membrane-bound actin filaments

Cell cortex remodeling during cell division is a result of myofilament-driven contractility of the cortical membrane-bound actin meshwork. Little is known about the interaction between individual myofilaments and membrane-bound actin filaments. Here we reconstituted a minimal actin cortex to directly visualize the action of individual myofilaments on membrane-bound actin filaments using TIRF microscopy. We show that synthetic myofilaments fragment and compact membrane-bound actin while processively moving along actin filaments. We propose a mechanism by which tension builds up between the ends of myofilaments, resulting in compressive stress exerted to single actin filaments, causing their buckling and breakage. Modeling of this mechanism revealed that sufficient force (∼20 pN) can be generated by single myofilaments to buckle and break actin filaments. This mechanism of filament fragmentation and compaction may contribute to actin turnover and cortex reorganization during cytokinesis

Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer in FeNi/Al_2\_2O_3\_3/Co magnetic tunnel junctions

We have studied the magnetization reversal dynamics of FeNi/Al$\_2$O$\_3$/Co magnetic tunnel junctions deposited on step-bunched Si substrates using magneto-optical Kerr effect and time-resolved x-ray photoelectron emission microscopy combined with x-ray magnetic circular dichroism (XMCD-PEEM). Different reversal mechanisms have been found depending on the substrate miscut angle. Larger terraces (smaller miscut angles) lead to a higher nucleation density and stronger domain wall pinning. The width of domain walls with respect to the size of the terraces seems to play an important role in the reversal. We used the element selectivity of XMCD-PEEM to reveal the strong influence of the stray field of domain walls in the hard magnetic layer on the magnetic switching of the soft magnetic layer.Comment: 8 Pages, 7 Figure

Muonium-Antimuonium Oscillations in an extended Minimal Supersymmetric Standard Model with right-handed neutrinos

The electron and muon number violating muonium-antimuonium oscillation process in an extended Minimal Supersymmetric Standard Model is investigated. The Minimal Supersymmetric Standard Model is modified by the inclusion of three right-handed neutrino superfields. While the model allows the neutrino mass terms to mix among the different generations, the sneutrino and slepton mass terms have only intra-generation lepton number violation but not inter-generation lepton number mixing. So doing, the muonium-antimuonium conversion can then be used to constrain those model parameters which avoid further constraint from the $\mu\to e\gamma$ decay bounds. For a wide range of parameter values, the contributions to the muonium-antimuonium oscillation time scale are at least two orders of magnitude below the sensivity of current experiments. However, if the ratio of the two Higgs field VEVs, $\tan\beta$, is very small, there is a limited possibility that the contributions are large enough for the present experimental limit to provide an inequality relating $\tan\beta$ with the light neutrino mass scale $m_\nu$ which is generated by see-saw mechanism. The resultant lower bound on $\tan\beta$ as a function of $m_\nu$ is more stringent than the analogous bounds arising from the muon and electron anomalous magnetic moments as computed using this model.Comment: 29 pages, 7 figures, 3 tables, Late

Status of the Jamaican Iguana (Cyclura collei): Assessing 15 Years of Conservation Effort

Following its rediscovery in 1990 in the remote Hellshire Hills, the Jamaican Iguana (Cyclura collei) has been the focus of a sustained conservation effort aimed at securing the species’ short- and long-term survival. Major threats to the iguana’s persistence include habitat destruction by humans and predation by introduced mammals such as dogs, cats, and the Indian Mongoose.Beginning in 1990 with field surveys of the remnant C. collei population and the formation of the Jamaican Iguana Research and Conservation Group (JIRCG), a variety of conservation measures have been implemented. Protection and monitoring of known nesting areas have facilitated the collection of founder stock for captive breeding and “headstart” programs, and have resulted in the collection, mark, and release of hundreds of C. collei hatchlings. As hedges against extinction in the wild, breeding nuclei of C. collei have been established at the Hope Zoo in Kingston and also at six U. S. zoos (Central Florida, Fort Worth, Gladys Porter in Brownsville, Texas, Indianapolis, San Diego, and Sedgwick County in Wichita, Kansas). The first captive-bred hatchlings were produced in September 2004 at the Hope Zoo. Adult-sized, headstarted C. collei reared at the Hope Zoo have been successfully repatriated into the Hellshire Hills, and we have now verified post-release survival of up to eight years. Egg-laying has been observed in repatriated females, suggesting that this zoo-based augmentation effort is having a positive effect on the remaining wild population.Ongoing exotic predator removal efforts seek to maintain a conservation zone that is largely devoid of nonnative mammalian predators such as cats and mongooses. To date, hundreds of these invasive predators have been trapped and removed from the core C. collei area, and preliminary data suggest that the iguana may be benefiting from this predator control program. More recently (2003–2004), efforts to control feral dog and pig populations have been intensified.Overall, the biological interventions directed at C. collei appear to have been highly successful. Unfortunately, C. collei’s dry forest habitat is at risk of ecological destruction. The remaining primary forest in Hellshire is under constant assault from the activities of illegal tree cutters, primarily charcoal burners. The JIRCG has protected a small portion of the forest in the vicinity of the known nesting areas and major iguana concentration, and attempts to discourage charcoal burners from penetrating farther into the undisturbed forest. If implemented, tabled government plans from the 1960s for large-scale commercial and residential development would likely cause the extinction of C. collei. Encouragingly, increased national and international appreciation of Hellshire’s stature as one of the finest remaining examples of Caribbean dry forest, together with considerable interest in the iguana’s plight, give hope that this unique ecosystem and its endangered occupants will receive adequate protection. Indeed, the Jamaican government’s declaration of the Portland Bight Protected Area (PBPA) in 1999 (including the Hellshire Hills and the Goat Islands) and the recent (2004) delegation of management authority to the Urban Development Corporation (UDC) is a positive step in that direction

Authentication Beyond Desktops and Smartphones: Novel Approaches for Smart Devices and Environments

Much of the research on authentication in the past decades focused on developing authentication mechanisms for desktop computers and smartphones with the goal of making them both secure and usable. At the same time, the increasing number of smart devices that are becoming part of our everyday life creates new challenges for authentication, in particular since many of those devices are not designed and developed with authentication in mind. Examples include but are not limited to wearables, AR and VR glasses, devices in smart homes, and public displays. The goal of this workshop is to develop a common understanding of challenges and opportunities smart devices and environments create for secure and usable authentication. Therefore, we will bring together researchers and practitioners from HCI, usable security, and specific application areas (e.g., smart homes, wearables) to develop a research agenda for future approaches to authentication

Status of the Jamaican Iguana (Cyclura collei): Assessing 15 Years of Conservation Effort

Following its rediscovery in 1990 in the remote Hellshire Hills, the Jamaican Iguana (Cyclura collei) has been the focus of a sustained conservation effort aimed at securing the species’ short- and long-term survival. Major threats to the iguana’s persistence include habitat destruction by humans and predation by introduced mammals such as dogs, cats, and the Indian Mongoose.Beginning in 1990 with field surveys of the remnant C. collei population and the formation of the Jamaican Iguana Research and Conservation Group (JIRCG), a variety of conservation measures have been implemented. Protection and monitoring of known nesting areas have facilitated the collection of founder stock for captive breeding and “headstart” programs, and have resulted in the collection, mark, and release of hundreds of C. collei hatchlings. As hedges against extinction in the wild, breeding nuclei of C. collei have been established at the Hope Zoo in Kingston and also at six U. S. zoos (Central Florida, Fort Worth, Gladys Porter in Brownsville, Texas, Indianapolis, San Diego, and Sedgwick County in Wichita, Kansas). The first captive-bred hatchlings were produced in September 2004 at the Hope Zoo. Adult-sized, headstarted C. collei reared at the Hope Zoo have been successfully repatriated into the Hellshire Hills, and we have now verified post-release survival of up to eight years. Egg-laying has been observed in repatriated females, suggesting that this zoo-based augmentation effort is having a positive effect on the remaining wild population.Ongoing exotic predator removal efforts seek to maintain a conservation zone that is largely devoid of nonnative mammalian predators such as cats and mongooses. To date, hundreds of these invasive predators have been trapped and removed from the core C. collei area, and preliminary data suggest that the iguana may be benefiting from this predator control program. More recently (2003–2004), efforts to control feral dog and pig populations have been intensified.Overall, the biological interventions directed at C. collei appear to have been highly successful. Unfortunately, C. collei’s dry forest habitat is at risk of ecological destruction. The remaining primary forest in Hellshire is under constant assault from the activities of illegal tree cutters, primarily charcoal burners. The JIRCG has protected a small portion of the forest in the vicinity of the known nesting areas and major iguana concentration, and attempts to discourage charcoal burners from penetrating farther into the undisturbed forest. If implemented, tabled government plans from the 1960s for large-scale commercial and residential development would likely cause the extinction of C. collei. Encouragingly, increased national and international appreciation of Hellshire’s stature as one of the finest remaining examples of Caribbean dry forest, together with considerable interest in the iguana’s plight, give hope that this unique ecosystem and its endangered occupants will receive adequate protection. Indeed, the Jamaican government’s declaration of the Portland Bight Protected Area (PBPA) in 1999 (including the Hellshire Hills and the Goat Islands) and the recent (2004) delegation of management authority to the Urban Development Corporation (UDC) is a positive step in that direction