Resistive Magnetohydrodynamic Equilibria in a Torus

It was recently demonstrated that static, resistive, magnetohydrodynamic equilibria, in the presence of spatially-uniform electrical conductivity, do not exist in a torus under a standard set of assumed symmetries and boundary conditions. The difficulty, which goes away in the ``periodic straight cylinder approximation,'' is associated with the necessarily non-vanishing character of the curl of the Lorentz force, j x B. Here, we ask if there exists a spatial profile of electrical conductivity that permits the existence of zero-flow, axisymmetric r esistive equilibria in a torus, and answer the question in the affirmative. However, the physical properties of the conductivity profile are unusual (the conductivity cannot be constant on a magnetic surface, for example) and whether such equilibria are to be considered physically possible remains an open question.Comment: 17 pages, 4 figure

Passive Vibration Suppression Using Multiple Inerter-based Devices for a Multi-storey Building Structure

This paper investigates the application of multiple passive absorbers incorporating inerter(s), spring(s) and damper(s) to suppress vibrations in a multi-story structure. Different from the one terminal mass element, the inerter was proposed as a two-terminal element, with the property that the applied force is proportional to the relative acceleration across its terminals. The device can be configured to include gearing, hence allowing a far higher inertence than device mass. The advantage of using aTID as a suppression device mounted at the bottom of a multi-storey building has been identified. In this paper, a five-storey building model with two TIDs subjected to the base excitation is studied. Both of the these devices are located at the bottom. The criterion selected for the optimisation is the minimisation of the maximum relative displacement of the building. Further more, the resulting structural responses are compared to the case where a single TID is used at the bottom, to show the potential benefits that arise from using multiple devices. In addition, we show that the resulting optimal inertance needed for each device is smaller compared to the case where a single TID is used between the ground and the first floor, which makes the suppression system easier to manufacture

Chronic TREM2 activation exacerbates Aβ-associated tau seeding and spreading

Variants in the triggering receptor expressed on myeloid cells 2 (TREM2) gene are associated with increased risk for late-onset AD. Genetic loss of or decreased TREM2 function impairs the microglial response to amyloid-β (Aβ) plaques, resulting in more diffuse Aβ plaques and increased peri-plaque neuritic dystrophy and AD-tau seeding. Thus, microglia and TREM2 are at a critical intersection of Aβ and tau pathologies in AD. Since genetically decreasing TREM2 function increases Aβ-induced tau seeding, we hypothesized that chronically increasing TREM2 signaling would decrease amyloid-induced tau-seeding and spreading. Using a mouse model of amyloidosis in which AD-tau is injected into the brain to induce Aβ-dependent tau seeding/spreading, we found that chronic administration of an activating TREM2 antibody increases peri-plaque microglial activation but surprisingly increases peri-plaque NP-tau pathology and neuritic dystrophy, without altering Aβ plaque burden. Our data suggest that sustained microglial activation through TREM2 that does not result in strong amyloid removal may exacerbate Aβ-induced tau pathology, which may have important clinical implications

Reproduction and Dispersal of Biological Soil Crust Organisms

Biological soil crusts (BSCs) consist of a diverse and highly integrated community of organisms that effectively colonize and collectively stabilize soil surfaces. BSCs vary in terms of soil chemistry and texture as well as the environmental parameters that combine to support unique combinations of organisms—including cyanobacteria dominated, lichen-dominated, and bryophyte-dominated crusts. The list of organismal groups that make up BSC communities in various and unique combinations include—free living, lichenized, and mycorrhizal fungi, chemoheterotrophic bacteria, cyanobacteria, diazotrophic bacteria and archaea, eukaryotic algae, and bryophytes. The various BSC organismal groups demonstrate several common characteristics including—desiccation and extreme temperature tolerance, production of various soil binding chemistries, a near exclusive dependency on asexual reproduction, a pattern of aerial dispersal over impressive distances, and a universal vulnerability to a wide range of human-related perturbations. With this publication, we provide literature-based insights as to how each organismal group contributes to the formation and maintenance of the structural and functional attributes of BSCs, how they reproduce, and how they are dispersed. We also emphasize the importance of effective application of molecular and microenvironment sampling and assessment tools in order to provide cogent and essential answers that will allow scientists and land managers to better understand and manage the biodiversity and functional relationships of soil crust communities

A Magnetic Resonance Realization of Decoherence-Free Quantum Computation

We report the realization, using nuclear magnetic resonance techniques, of the first quantum computer that reliably executes an algorithm in the presence of strong decoherence. The computer is based on a quantum error avoidance code that protects against a class of multiple-qubit errors. The code stores two decoherence-free logical qubits in four noisy physical qubits. The computer successfully executes Grover's search algorithm in the presence of arbitrarily strong engineered decoherence. A control computer with no decoherence protection consistently fails under the same conditions.Comment: 5 pages with 3 figures, revtex4, accepted by Physical Review Letters; v2 minor revisions to conten

Interactive Voice Response-An Innovative Approach to Post-Stroke Depression Self-Management Support

Automated interactive voice response (IVR) call systems can provide systematic monitoring and self-management support to depressed patients, but it is unknown if stroke patients are able and willing to engage in IVR interactions. We sought to assess the feasibility and acceptability of IVR as an adjunct to post-stroke depression follow-up care. The CarePartner program is a mobile health program designed to optimize depression self-management, facilitate social support from a caregiver, and strengthen connections between stroke survivors and primary care providers (PCPs). Ischemic stroke patients and an informal caregiver, if available, were recruited during the patient's acute stroke hospitalization or follow-up appointment. The CarePartner program was activated in patients with depressive symptoms during their stroke hospitalization or follow-up. The 3-month intervention consisted of weekly IVR calls monitoring both depressive symptoms and medication adherence along with tailored suggestions for depressive symptom self-management. After each completed IVR call, informal caregivers were automatically updated, and, if needed, the subject's PCP was notified. Of the 56 stroke patients who enrolled, depressive symptoms were identified in 13 (23 %) subjects. Subjects completed 74 % of the weekly IVR assessments. A total of six subjects did not complete the outcome assessment, including two non-study-related deaths. PCPs were notified five times, including two times for suicidal ideation and three times for medication non-adherence. Stroke patients with depressive symptoms were able to engage in an IVR call system. Future studies are needed to explore the efficacy of an IVR approach for post-stroke self-management and monitoring of stroke-related outcomes

Plant Colonization of Green Roofs Is Affected by Composition of Established Native Plant Communities

Human activities associated with urbanization have negatively affected the biodiversity of native plant communities globally. Establishing native species assemblages on green roofs may help conserve native plant diversity in urban areas, but these assemblages are susceptible to colonization by species from the surrounding landscape. In natural communities, colonization from the regional species pool reflects the filtering effects of both abiotic and biotic factors, but the relative effects of these factors on green roof colonization are not well-understood. To address this knowledge gap, we studied colonization dynamics of 10 green roofs in New York City (NY, United States), each established at the same time with the same source materials. On each roof, 12 plots were established, with one-half of each plot planted with an erect C4 graminoid dominant (Hempstead Plains: HP) and the other half with a tuft C3 graminoid and forb dominant (Rocky Summit: RS) species assemblage derived from native communities. Six of the 12 split-plots contained shallow growing medium, while the other six contained deeper growing medium. Resident plants were planted in October 2010. Fifty-eight non-resident plant species colonized plots between August 2011 and August 2012, with two native and 10 non-native species accounting for 90% of total colonist dry mass. Colonist dry mass and richness decreased with increasing resident plant cover, but the effects of growing medium depth on colonist dry mass and richness differed between assemblages. Forbs accounted for 81% of the colonist dry mass from the HP assemblage, but just 31% in the RS assemblage. Further, forbs accounted for over 95% of colonist dry mass in June and July, while graminoids accounted for over 95% of colonist dry mass in August. These results indicate colonization of planted green roofs may be strongly affected by the composition of established plant assemblages and that these effects may vary temporally with colonist management regime, even within a single growing season. Further, the inconsistent effects of growing medium depth suggest that niche overlap and complementarity in rhizosphere dynamics may influence colonization more in some systems compared with others. Additional research is required to describe the effects of colonist management strategies, as well as the roles of priority effects, niche complementarity and community assembly, on long-term dynamics of colonization on green roofs planted with native plants