2,238 research outputs found
Marxism, cultural studies and sport, edited by Carrington, B. and McDonald, I.
Review of Marxism, cultural studies and sport, edited by Carrington, B. and McDonald, I
Optically controlled spin-glasses in multi-qubit cavity systems
Recent advances in nanostructure fabrication and optical control, suggest
that it will soon be possible to prepare collections of interacting two-level
systems (i.e. qubits) within an optical cavity. Here we show theoretically that
such systems could exhibit novel phase transition phenomena involving
spin-glass phases. By contrast with traditional realizations using magnetic
solids, these phase transition phenomena are associated with both matter and
radiation subsystems. Moreover the various phase transitions should be tunable
simply by varying the matter-radiation coupling strength.Comment: 4 pages, 3 figure
Orthogonality catastrophe in a composite fermion liquid
We discuss the emergence of an orthogonality catastrophe in the response of a
composite fermion liquid as the filling factor \nu approaches 1/2m, where
m=1,2,3.... A tunneling experiment is proposed in which dramatic changes in the
I-V characteristic should be observable as \nu is varied. Explicit I-V
characteristics calculated within the so-called Modified Random Phase
Approximation, are provided for \nu=1/3 -> \nu=1/2.Comment: Latex two-column 6 pages including 5 figure
Efficiency of energy transfer in a light-harvesting system under quantum coherence
We investigate the role of quantum coherence in the efficiency of excitation
transfer in a ring-hub arrangement of interacting two-level systems, mimicking
a light-harvesting antenna connected to a reaction center as it is found in
natural photosynthetic systems. By using a quantum jump approach, we
demonstrate that in the presence of quantum coherent energy transfer and
energetic disorder, the efficiency of excitation transfer from the antenna to
the reaction center depends intimately on the quantum superposition properties
of the initial state. In particular, we find that efficiency is sensitive to
symmetric and asymmetric superposition of states in the basis of localized
excitations, indicating that initial state properties can be used as a
efficiency control parameter at low temperatures.Comment: Extended version of original paper. 7 pages, 2 figure
Accelerating networks
Evolving out-of-equilibrium networks have been under intense scrutiny
recently. In many real-world settings the number of links added per new node is
not constant but depends on the time at which the node is introduced in the
system. This simple idea gives rise to the concept of accelerating networks,
for which we review an existing definition and -- after finding it somewhat
constrictive -- offer a new definition. The new definition provided here views
network acceleration as a time dependent property of a given system, as opposed
to being a property of the specific algorithm applied to grow the network. The
defnition also covers both unweighted and weighted networks. As time-stamped
network data becomes increasingly available, the proposed measures may be
easily carried out on empirical datasets. As a simple case study we apply the
concepts to study the evolution of three different instances of Wikipedia,
namely, those in English, German, and Japanese, and find that the networks
undergo different acceleration regimes in their evolution.Comment: 12 pages, 8 figure
Dynamics of quantum correlations and linear entropy in a multi-qubit-cavity system
We present a theoretical study of the relationship between entanglement and
entropy in multi-qubit quantum optical systems. Specifically we investigate
quantitative relations between the concurrence and linear entropy for a
two-qubit mixed system, implemented as two two-level atoms interacting with a
single-mode cavity field. The dynamical evolutions of the entanglement and
entropy, are controlled via time-dependent cavity-atom couplings. Our
theoretical findings lead us to propose an alternative measure of entanglement,
which could be used to develop a much needed correlation measure for more
general multi-partite quantum systems.Comment: New discussions on the generality of entanglement-entropy
relationship, one new reference, and other minor changes. 10 pages, 6
figures, accepted for publication in J.Opt. B: "Special Issue on Fluctuations
& Noise in Photonics & Quantum Optics.
Educational outcomes in extremely preterm children : neuropsychological correlates and predictors of attainment
This study assessed the impact of extremely preterm birth on academic attainment at 11 years of
age, investigated neuropsychological antecedents of attainment in reading and mathematics, and
examined early predictors of educational outcomes. Children born extremely preterm had significantly
poorer academic attainment and a higher prevalence of learning difficulties than their term
peers. General cognitive ability and specific deficits in visuospatial skills or phoneme deletion at 6
years were predictive of mathematics and reading attainment at 11 years in both extremely preterm
and term children. Phonological processing, attention, and executive functions at 6 years were also
associated with academic attainment in children born extremely preterm. Furthermore, social factors,
neonatal factors (necrotizing enterocolitis, breech delivery, abnormal cerebral ultrasound, early
breast milk provision), and developmental factors at 30 months (head circumference, cognitive development),
were independent predictors of educational outcomes at 11 years. Neonatal complications
combined with assessments of early cognitive function provide moderate prediction for educational
outcomes in children born extremely preterm
An NMR-based nanostructure switch for quantum logic
We propose a nanostructure switch based on nuclear magnetic resonance (NMR)
which offers reliable quantum gate operation, an essential ingredient for
building a quantum computer. The nuclear resonance is controlled by the magic
number transitions of a few-electron quantum dot in an external magnetic field.Comment: 4 pages, 2 separate PostScript figures. Minor changes included. One
reference adde
Mathematics difficulties in extremely preterm children : evidence of a specific deficit in basic mathematics processing
Background:
Extremely preterm (EP, <26 wk gestation) children have been observed to have poor academic achievement in comparison to their term-born peers, especially in mathematics. This study investigated potential underlying causes of this difficulty.
Methods:
A total of 219 EP participants were compared with 153 term-born control children at 11 y of age. All children were assessed by a psychologist on a battery of standardized cognitive tests and a number estimation test assessing children’s numerical representations.
Results:
EP children underperformed in all tests in comparison with the term controls (the majority of Ps < 0.001). Different underlying relationships between performance on the number estimation test and mathematical achievement were found in EP as compared with control children. That is, even after controlling for cognitive ability, a relationship between number representations and mathematical performance persisted for EP children only (EP: r = 0.346, n = 186, P < 0.001; control: r = 0.095, n = 146, P = 0.256).
Conclusion:
Interventions for EP children may target improving children’s numerical representations in order to subsequently remediate their mathematical skills
Special Project: Public Housing
Despite the general prosperity of this country, a cursory survey of any American town or city will reveal that many Americans live in housing which is substandard. Frequently one sees unpainted houses characterized by broken windows and inadequate sanitary facilities. In urban areas, the ever present tenement is often filled with too many people and not enough toilets; stairs are dangerous and refuse lies uncollected in the halls. Rooms without windows are common, while those blessed with windows frequently receive little light--the only view is another window of another building. Disease and discomfort are everywhere.These conditions, however, are neither new nor unnoticed.Throughout American history, individuals as well as various levels of government have attempted to remedy, or at least alleviate, the housing problem. This study will explore one such effort--the federally-financed, locally-administered public housing program created by the Housing Act of 1937. Consequently, throughout this study, the term public housing, describing any period after 1937,refers only to the product of this Act, unless otherwise indicated. This study does not concern federally-funded housing programs such as Federal Housing Authority mortgage guarantees, rehabilitation of existing dwellings, and self-help programs
- …