6,193 research outputs found
Defect Motion and Lattice Pinning Barrier in Josephson-Junction Ladders
We study motion of domain wall defects in a fully frustrated
Josephson-unction ladder system, driven by small applied currents. For small
system sizes, the energy barrier E_B to the defect motion is computed
analytically via symmetry and topological considerations. More generally, we
perform numerical simulations directly on the equations of motion, based on the
resistively-shunted junction model, to study the dynamics of defects, varying
the system size. Coherent motion of domain walls is observed for large system
sizes. In the thermodynamical limit, we find E_B=0.1827 in units of the
Josephson coupling energy.Comment: 7 pages, and to apear in Phys. Rev.
SM(2,4k) fermionic characters and restricted jagged partitions
A derivation of the basis of states for the superconformal minimal
models is presented. It relies on a general hypothesis concerning the role of
the null field of dimension . The basis is expressed solely in terms of
modes and it takes the form of simple exclusion conditions (being thus a
quasi-particle-type basis). Its elements are in correspondence with
-restricted jagged partitions. The generating functions of the latter
provide novel fermionic forms for the characters of the irreducible
representations in both Ramond and Neveu-Schwarz sectors.Comment: 12 page
Recent developments in the determination of the amplitude and phase of quantum oscillations for the linear chain of coupled orbits
De Haas-van Alphen oscillations are studied for Fermi surfaces (FS)
illustrating the model proposed by Pippard in the early sixties, namely the
linear chain of orbits coupled by magnetic breakdown. This FS topology is
relevant for many multiband quasi-two dimensional (q-2D) organic metals such as
-(BEDT-TTF)Cu(NCS) and
-(BEDT-TTF)CoBr(CHCl) which are considered in
detail. Whereas the Lifshits-Kosevich model only involves a first order
development of field- and temperature-dependent damping factors, second order
terms may have significant contribution on the Fourier components amplitude for
such q-2D systems at high magnetic field and low temperature. The strength of
these second order terms depends on the relative value of the involved damping
factors, which are in turns strongly dependent on parameters such as the
magnetic breakdown field, effective masses and, most of all, effective
Land\'{e} factors. In addition, the influence of field-dependent Onsager phase
factors on the oscillation spectra is considered.Comment: arXiv admin note: text overlap with arXiv:1304.665
Reply to Comment on " Universal Fluctuations in Correlated Systems"
Reply to the comment, cond-mat/0209398 by by N.W. Watkins, S.C. Chapman, and
G. RowlandsComment: To appear In Physical Review Letter
Impact of water stress on plant water relations, growth and mycorhization of Acacia tortilis ssp. raddiana: Interactions of the stress severity and duration, and the AM fungal species.
Mycorrhizae are commonly reported to improve drought resistance of the host plant. Investigating factors controlling the plant-resistance strategy to water stress can however lead to a suitable management of mycorrhizal plants under drought. Here, we focused on the impact of interactions of the AM fungal species and water stress severity and duration on mycorrhizal Acacia tortilis ssp. raddiana in terms of plant growth, mycorhization and water relations. We used three Glomus species, which were G. mosseae, G. deserticola and G. intraradices. We applied three watering regimes that were maximum water holding non-stress regime, mild-severe water stress and severe water stress. Measurements were performed at four stage durations named pre-drought (one day before applying water stress), early-drought (30 days after applying water stress), mid-drought (60 days after applying water stress), and late-drought (90 days after applying water stress). Under maximum water holding regime, G. mosseae was more infective than G. deserticola and G. intraradices, but differences were not significantly different (P < 0.05). Predawn water potential was analogous for both mycorrhizal and control treatments whilst midday water potential was lower for control than for AMF treatments. Under mild and late drought, G. deserticola and G. intraradices were more infective than G. mosseae. Plants inoculated with G. intraradices had the highest predawn water potential and MWP. Mid-morning and midday stomatal conductance were similar and higher in seedlings inoculated with G. deserticola and G. intraradices. Under severe and late drought, infectivity was comparable and higher for both G. deserticola and G. intraradices. However, plants inoculated with G. intraradices displayed the highest growth, midday water potential, stomatal conductance and relative water content. Seedlings inoculated with G. mosseae and the controls had lost their leaves at -4 MPa water potential. Difference between Glomus species in the host response to water stress seemed to be related to the severity and duration of the stress. On the whole, inoculation of A. tortilis ssp. raddiana with G. intraradices resulted in increased plant growth and improved water status under severe and long-lasting drought, relative to G. deserticola and G. mosseae
Random site dilution properties of frustrated magnets on a hierarchical lattice
We present a method to analyze magnetic properties of frustrated Ising spin
models on specific hierarchical lattices with random dilution. Disorder is
induced by dilution and geometrical frustration rather than randomness in the
internal couplings of the original Hamiltonian. The two-dimensional model
presented here possesses a macroscopic entropy at zero temperature in the large
size limit, very close to the Pauling estimate for spin-ice on pyrochlore
lattice, and a crossover towards a paramagnetic phase. The disorder due to
dilution is taken into account by considering a replicated version of the
recursion equations between partition functions at different lattice sizes. An
analysis at first order in replica number allows for a systematic
reorganization of the disorder configurations, leading to a recurrence scheme.
This method is numerically implemented to evaluate the thermodynamical
quantities such as specific heat and susceptibility in an external field.Comment: 26 pages, 11 figure
Structural network heterogeneities and network dynamics: a possible dynamical mechanism for hippocampal memory reactivation
The hippocampus has the capacity for reactivating recently acquired memories
[1-3] and it is hypothesized that one of the functions of sleep reactivation is
the facilitation of consolidation of novel memory traces [4-11]. The dynamic
and network processes underlying such a reactivation remain, however, unknown.
We show that such a reactivation characterized by local, self-sustained
activity of a network region may be an inherent property of the recurrent
excitatory-inhibitory network with a heterogeneous structure. The entry into
the reactivation phase is mediated through a physiologically feasible
regulation of global excitability and external input sources, while the
reactivated component of the network is formed through induced network
heterogeneities during learning. We show that structural changes needed for
robust reactivation of a given network region are well within known
physiological parameters [12,13].Comment: 16 pages, 5 figure
Gender in Contemporary Europe: Rethinking Equality and the Backlash
European Social Survey Round 11: Question Module Design Teams (QDT) - Stage 2 ApplicationDecades of policy efforts and campaigns by governments, international organizations and social movements have brought significant progress towards gender equality. Many would argue, however, that gender equality still remains largely out of reach. Furthermore, there are visible backlashes against gender equality partly driven by the rhetoric of the radical right against âgender ideologyâ. Additionally there is evidence there has been retrenchment on key indicators measuring the status of women in society. In response to these seemingly countervailing trends, we propose a module that will allow researchers to examine contemporary attitudes about gender and gender equality, sexism, gender-based discrimination and policy responses to gender equality. We propose measuring five dimensions: identity, sexism, experiences, salience and policy instruments. While these five dimensions draw on a wealth of existing measures about gender attitudes, the proposed module would, we argue, redress some blind spots in current cross-national survey items such as experiences of gender-based discrimination, perceptions of masculinity and femininity; and attitudes about the role of gender equality in society
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