1,377 research outputs found
Measurement of the Current-Phase Relation in Josephson Junctions Rhombi Chains
We present low temperature transport measurements in one dimensional
Josephson junctions rhombi chains. We have measured the current phase relation
of a chain of 8 rhombi. The junctions are either in the classical phase regime
with the Josephson energy much larger than the charging energy, , or in the quantum phase regime where . In the
strong Josephson coupling regime () we observe a
sawtooth-like supercurrent as a function of the phase difference over the
chain. The period of the supercurrent oscillations changes abruptly from one
flux quantum to half the flux quantum as the rhombi are
tuned in the vicinity of full frustration. The main observed features can be
understood from the complex energy ground state of the chain. For
we do observe a dramatic suppression and rounding of the
switching current dependence which we found to be consistent with the model
developed by Matveev et al.(Phys. Rev. Lett. {\bf 89}, 096802(2002)) for long
Josephson junctions chains.Comment: to appear in Phys. Rev.
Prospects, challenges and perspectives in harnessing natural selection to solve the 'varroa problem' of honey bees.
Honey bees, Apis mellifera, of European origin are major pollinators of crops and wild flora. Their endemic and exported populations are threatened by a variety of abiotic and biotic factors. Among the latter, the ectoparasitic mite Varroa destructor is the most important single cause behind colony mortality. The selection of mite resistance in honey bee populations has been deemed a more sustainable solution to its control than varroacidal treatments. Because natural selection has led to the survival of some European and African honey bee populations to V. destructor infestations, harnessing its principles has recently been highlighted as a more efficient way to provide honey bee lineages that survive infestations when compared with conventional selection on resistance traits against the parasite. However, the challenges and drawbacks of harnessing natural selection to solve the varroa problem have only been minimally addressed. We argue that failing to consider these issues could lead to counterproductive results, such as increased mite virulence, loss of genetic diversity reducing host resilience, population collapses or poor acceptance by beekeepers. Therefore, it appears timely to evaluate the prospects for the success of such programmes and the qualities of the populations obtained. After reviewing the approaches proposed in the literature and their outcomes, we consider their advantages and drawbacks and propose perspectives to overcome their limitations. In these considerations, we not only reflect on the theoretical aspects of host-parasite relationships but also on the currently largely neglected practical constraints, that is, the requirements for productive beekeeping, conservation or rewilding objectives. To optimize natural selection-based programmes towards these objectives, we suggest designs based on a combination of nature-driven phenotypic differentiation and human-directed selection of traits. Such a dual strategy aims at allowing field-realistic evolutionary approaches towards the survival of V. destructor infestations and the improvement of honey bee health
A V-shape superconducting artificial atom based on two inductively coupled transmons
Circuit quantum electrodynamics systems are typically built from resonators
and two-level artificial atoms, but the use of multi-level artificial atoms
instead can enable promising applications in quantum technology. Here we
present an implementation of a Josephson junction circuit dedicated to operate
as a V-shape artificial atom. Based on a concept of two internal degrees of
freedom, the device consists of two transmon qubits coupled by an inductance.
The Josephson nonlinearity introduces a strong diagonal coupling between the
two degrees of freedom that finds applications in quantum non-demolition
readout schemes, and in the realization of microwave cross-Kerr media based on
superconducting circuits.Comment: 5 pages, 3 figure
Advances and perspectives in selecting resistance traits against the parasitic mite Varroa destructor in honey bees.
In spite of the implementation of control strategies in honey bee (Apis mellifera) keeping, the invasive parasitic mite Varroa destructor remains one of the main causes of colony losses in numerous countries. Therefore, this parasite represents a serious threat to beekeeping and agro-ecosystems that benefit from the pollination services provided by honey bees. To maintain their stocks, beekeepers have to treat their colonies with acaricides every year. Selecting lineages that are resistant to infestations is deemed to be a more sustainable approach.
Over the last three decades, numerous selection programs have been initiated to improve the host-parasite relationship and to support honey bee survival in the presence of the parasite without the need for acaricide treatments. Although resistance traits have been included in the selection strategy of honey bees, it has not been possible to globally solve the V. destructor problem. In this study, we review the literature on the reasons that have potentially limited the success of such selection programs. We compile the available information to assess the relevance of selected traits and the potential environmental effects that distort trait expression and colony survival. Limitations to the implementation of these traits in the field are also discussed.
Improving our knowledge of the mechanisms underlying resistance to V. destructor to increase trait relevance, optimizing selection programs to reduce environmental effects, and communicating selection outcomes are all crucial to efforts aiming at establishing a balanced relationship between the invasive parasite and its new host
Experimental demonstration of Aharonov-Casher interference in a Josephson junction circuit
A neutral quantum particle with magnetic moment encircling a static electric
charge acquires a quantum mechanical phase (Aharonov-Casher effect). In
superconducting electronics the neutral particle becomes a fluxon that moves
around superconducting islands connected by Josephson junctions. The full
understanding of this effect in systems of many junctions is crucial for the
design of novel quantum circuits. Here we present measurements and quantitative
analysis of fluxon interference patterns in a six Josephson junction chain. In
this multi-junction circuit the fluxon can encircle any combination of charges
on five superconducting islands, resulting in a complex pattern. We compare the
experimental results with predictions of a simplified model that treats fluxons
as independent excitations and with the results of the full diagonalization of
the quantum problem. Our results demonstrate the accuracy of the fluxon
interference description and the quantum coherence of these arrays
NOVAS FORMAS DE ORGANIZAÇÃO NO SETOR PÚBLICO E SUAS CONSEQUÊNCIAS PARA A EDUCAÇÃO À DISTÂNCIA: UMA REVISÃO SISTEMÁTICA DE LITERATURA
O presente estudo de caso pretende realizar uma revisão sistemática da literatura científica sobre o tema da gestão no setor público e educação à distância. Por conseguinte, pretende também entender a trajetória da educação a distância permitindo absorver suas diferentes faces e sua relação com diferentes contextos educacionais, auxiliando na previsão do futuro, diante do contexto educacional que se apresenta o país. Nesse sentido, foram analisados trabalhos de pesquisa (Dissertações) da Universidade Federal de Santa Catarina. O objetivo desta pesquisa consiste em identificar a lacuna teórica sobre o tema de gestão da educação à distância em instituições de ensino superior do setor público. A natureza desta pesquisa é básica, classifica-se como qualitativa, uma vez que não requer o uso de métodos e técnicas estatísticas. O ambiente natural é a fonte direta para coleta de dados e o pesquisador é o instrumento-chave. É descritiva. O processo e seu significado são os focos principais de abordagem. Quanto aos fins, possui caráter descritivo. Quanto aos meios, será utilizada a Pesquisa Bibliográfica. A amostra será composta por seis dissertações na área de Educação à Distância dos cursos de Mestrado em Administração e Administração Universitária da Universidade Federal de Santa Catarina. Os instrumentos de coleta de dados a serem utilizados serão referências bibliográficas e pesquisa documental como fonte de dados primários. Paralelamente neste artigo serão revisados aspectos sobre EAD desde um histórico mundial e brasileiro, as diferentes definições sobre EAD apresentadas, assim como os aspectos positivos e negativos destacados nos trabalhos analisados. Por fim, será apresentada uma discussão sobre o cenário atual e perspectivas futuras da EAD no Brasil
Phase-Charge Duality of a Josephson junction in a fluctuating electromagnetic environment
We have measured the current-voltage characteristics of a single Josephson
junction placed in a high impedance environment. The transfer of Cooper pairs
through the junction is governed by overdamped quasicharge dynamics, leading to
Coulomb blockade and Bloch oscillations. Exact duality exists to the standard
overdamped phase dynamics of a Josephson junction, resulting in a dual shape of
the current-voltage characteristic, with current and voltage changing roles. We
demonstrate this duality with experiments which allow for a quantitative
comparison with a theory that includes the effect of fluctuations due to finite
temperature of the electromagnetic environment
Test results for the V0 detector in ALICE
In this report, we describe the V0 detector, a device made of two arrays of scintillating counters (V0L and V0R) installe d on both sides of the ALICE in teraction vertex. The light yield and the time resolution were measured for several prototype counter s which were tested on the PS T10 beam line and with cosmic rays. Results from the test and from simulations are reported
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