6,171 research outputs found
A new perspective on GCRT J1745-3009
Two WSRT observations were performed and five archival VLA data were reduced
in order to redetect the enigmatic radio transient GCRT J1745-3009. The source
was not redetected. We were, however, able to extract important new information
from the discovery dataset. Our reanalysis excludes models that predict
symmetric bursts, but the transient white dwarf pulsar is favoured. Although we
now have more contraints on the properties of this source, we are still unsure
about its basic model.Comment: 11 pages, 5 figure
Percolation Transition in the random antiferromagnetic spin-1 chain
We give a physical description in terms of percolation theory of the phase
transition that occurs when the disorder increases in the random
antiferromagnetic spin-1 chain between a gapless phase with topological order
and a random singlet phase. We study the statistical properties of the
percolation clusters by numerical simulations, and we compute exact exponents
characterizing the transition by a real-space renormalization group
calculation.Comment: 9 pages, 4 encapsulated Postscript figures, REVTeX 3.
Ground State and Magnetization Process of the Mixture of Bond-Alternating and Uniform S=1/2 Antiferromagnetic Heisenberg Chains
The mixture of bond-alternating and uniform S=1/2 antiferromagnetic
Heisenberg chains is investigated by the density matrix renormalization group
method. The ground state magnetization curve is calculated and the exchange
parameters are determined by fitting to the experimentally measured
magnetization curve of \CuClBr(-pic). The low
field behavior of the magnetization curve and low temperature behavior of the
magnetic susceptibility are found to be sensitive to whether the
bond-alternation pattern (parity) is fixed all over the sample or randomly
distributed. The both quantities are compatible with the numerical results for
the random parity model.Comment: 5 pages, 7 figures. Final and enlarged version accepted for
publication in J. Phys. Soc. Jp
Children's influence on consumption-related decisions in single-mother families: A review and research agenda
Although social scientists have identified diverse behavioral patterns among children from dissimilarly structured families, marketing scholars have progressed little in relating family structure to consumption-related decisions. In particular, the roles played by members of single-mother families—which may include live-in grandparents, mother’s unmarried partner, and step-father with or without step-sibling(s)—may affect children’s influence on consumption-related decisions. For example, to offset a parental authority dynamic introduced by a new stepfather, the work-related constraints imposed on a breadwinning mother, or the imposition of adult-level household responsibilities on children, single-mother families may attend more to their children’s product preferences.
Without a profile that includes socio-economic, behavioral, and psychological aspects, efficient and socially responsible marketing to single-mother households is compromised. Relative to dual-parent families, single-mother families tend to have fewer resources and less buying power, children who consume more materialistic and compulsively, and children who more strongly influence decision making for both own-use and family-use products. Timely research would ensure that these and other tendencies now differentiate single-mother from dual-parent families in ways that marketers should address. Hence, our threefold goal is (1) to consolidate and highlight gaps in existing theory applied to studying children’s influence on consumption-related decision making in single-mother families, and (2) to propose a hybrid framework that merges two theories conducive to such research, and (3) to identify promising research propositions for future research
Evaluating Multiple Arthropod Taxa as Indicators of Invertebrate Diversity in Old Fields
Biodiversity, often quantified by species richness, is commonly used to evaluate and monitor the health of ecosystems and as a tool for conservation planning. The use of one or more focal taxa as surrogates or indicators of larger taxonomic diversity can greatly expedite the process of biodiversity measurement. This is especially true when studying diverse and abundant invertebrate fauna. Before indicator taxa are employed, however, research into their suitability as indicators of greater taxonomic diversity in an area is needed. We sampled invertebrate diversity in old fields in southern Michigan using pitfall trapping and morphospecies designations after identification to order or family. Correlation analysis was used to assess species richness relationships between focal arthropod taxa and general invertebrate diversity. Relationships were assessed at two fine spatial scales: within sampling patches, and locally across four sampling patches. Cumulative richness of all assessed taxa increased proportionately with cumulative invertebrate richness as sampling intensity increased within patches. At the among-patch scale, we tentatively identified Hemiptera and Coleoptera as effective indicator taxa of greater invertebrate richness. Although Hymenoptera, Araneae and Diptera exhibited high species richness, their total richness within patches was not associated with overall invertebrate richness among patches. Increased sampling throughout the active season and across a greater number of habitat patches should be conducted before adopting Hemiptera and Coleoptera as definitive indicators of general invertebrate richness in the Great Lakes region. Multiple sampling techniques, in addition to pitfall trapping, should also be added to overcome capture biases associated with each technique
Building a Socio-technical Perspective of Community Resilience with a Semiotic Approach
Situated in the diversity and adversity of real-life contexts facing crisis situations, this research aims at boosting the resilience process within communities supported by digital and social technology. In this paper, eight community leaders in different parts of the world are invited to express their issues and wishes regarding the support of technology to face social challenges. Methods and artefacts based on the Organisational Semiotics (OS) and the Socially-Aware computing have been applied to analyse and consolidate this data. By providing both a systemic view of the problem and also leading to the identification of requirements, the analysis evidences some benefits of the OS-based approach to consolidate perspectives from different real-life scenarios towards building a socio-technical solution
Negative Ion Drift and Diffusion in a TPC near 1 Bar
Drift velocity and longitudinal diffusion measurements are reported for a
Negative Ion TPC (NITPC) operating with Helium + carbon disulfide gas mixtures
at total pressures from 160 to 700 torr. Longitudinal diffusion at the
thermal-limit was observed for drift fields up to at least 700 V/cm in all gas
mixtures tested. The results are of particular interest in connection with
mechanical simplification of Dark Matter searches such as DRIFT, and for high
energy physics experiments in which a low-Z, low density, gaseous tracking
detector with no appreciable Lorentz drift is needed for operation in very high
magnetic fields.Comment: 7 pages, 3 figure
Real Space Renormalization Group Study of the S=1/2 XXZ Chains with Fibonacci Exchange Modulation
Ground state properties of the S=1/2 antiferromagnetic XXZ chain with
Fibonacci exchange modulation are studied using the real space renormalization
group method for strong modulation. The quantum dynamical critical behavior
with a new universality class is predicted in the isotropic case. Combining our
results with the weak coupling renormalization group results by Vidal et al.,
the ground state phase diagram is obtained.Comment: 9 pages, 9 figure
An easy to control all-metal in-line-series ohmic RF MEMS switch
Copyright @ 2010 Springer-VerlagThe analysis, design and simulation of a novel easy to control all-metal in-line-series ohmic RF MEMS switch is presented, for applications where the operating frequency ranges from DC to 4 GHz. The proposed switch, due to its unique shape and size, assures high isolation and great linearity fulfilling the necessary requirements as concerns loss, power handling and power consumption. Simplicity has been set as the key success factor implying robustness and high fabrication yield. On the other hand, the specially designed cantilever-shape (hammerhead) allows distributed actuation force ensuring high controllability as well as reliability making the presented RF MEMS switch one of its kind
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