5,422 research outputs found
Injury Risk Estimation Expertise Assessing the ACL Injury Risk Estimation Quiz
Background: Available methods for screening anterior cruciate ligament (ACL) injury risk are effective but limited in application as
they generally rely on expensive and time-consuming biomechanical movement analysis. A potential efficient alternative to biomechanical
screening is skilled movement analysis via visual inspection (ie, having experts estimate injury risk factors based on
observations of athletes’ movements).
Purpose: To develop a brief, valid psychometric assessment of ACL injury risk factor estimation skill: the ACL Injury Risk Estimation
Quiz (ACL-IQ).
Study Design: Cohort study (diagnosis); Level of evidence, 3.
Methods: A total of 660 individuals participated in various stages of the study, including athletes, physicians, physical therapists,
athletic trainers, exercise science researchers/students, and members of the general public in the United States. The ACL-IQ was
fully computerized and made available online (www.ACL-IQ.org). Item sampling/reduction, reliability analysis, cross-validation,
and convergent/discriminant validity analysis were conducted to optimize the efficiency and validity of the assessment.
Results: Psychometric optimization techniques identified a short (mean time, 2 min 24 s), robust, 5-item assessment with high
reliability (test-retest: r = 0.90) and consistent discriminability (average difference of exercise science professionals vs general
population: Cohen d = 1.98). Exercise science professionals and general population individuals scored 74% and 53% correct,
respectively. Convergent and discriminant validity was demonstrated. Scores on the ACL-IQ were most associated with ACL
knowledge and various cue utilities and were least associated with domain-general spatial/decision-making ability, personality,
or other demographic variables. Overall, 23% of the total sample (40% exercise science professionals; 6% general population)
performed better than or equal to the ACL nomogram.
Conclusion: This study presents the results of a systematic approach to assess individual differences in ACL injury risk factor
estimation skill; the assessment approach is efficient (ie, it can be completed in\3 min) and psychometrically robust. The results
provide evidence that some individuals have the ability to visually estimate ACL injury risk factors more accurately than other
instrument-based ACL risk estimation methods (ie, ACL nomogram). The ACL-IQ provides the foundation for assessing the efficacy
of observational ACL injury risk factor assessment (ie, does simple skilled visual inspection reduce ACL injuries?). It also
provides a representative task environment that can be used to increase our understanding of the perceptual-cognitive mechanisms
underlying observational movement analysis and to improve injury risk assessment performance
Global asymmetry of many-qubit correlations: A lattice gauge theory approach
We introduce a novel bridge between the familiar gauge field theory
approaches used in many areas of modern physics such as quantum field theory
and the SLOCC protocols familiar in quantum information. Although the
mathematical methods are the same the meaning of the gauge group will be
different. The measure we introduce, `twist', is constructed as a Wilson loop
from a correlation induced holonomy. The measure can be understood as the
global asymmetry of the bipartite correlations in a loop of three or more
qubits; if the holonomy is trivial (the identity matrix), the bipartite
correlations can be globally untwisted using general local qubit operations,
the gauge group of our theory, which turns out to be the group of Lorentz
transformations familiar from special relativity. If it is not possible to
globally untwist the bipartite correlations in a state globally using local
operations, the twistedness is given by a non-trivial element of the Lorentz
group, the correlation induced holonomy. We provide several analytical examples
of twisted and untwisted states for three qubits, the most elementary
non-trivial loop one can imagine.Comment: 13 pages, 3 figures, title changed, results and content remain
unchange
Correlation induced non-Abelian quantum holonomies
In the context of two-particle interferometry, we construct a parallel
transport condition that is based on the maximization of coincidence intensity
with respect to local unitary operations on one of the subsystems. The
dependence on correlation is investigated and it is found that the holonomy
group is generally non-Abelian, but Abelian for uncorrelated systems. It is
found that our framework contains the L\'{e}vay geometric phase [2004 {\it J.
Phys. A: Math. Gen.} {\bf 37} 1821] in the case of two-qubit systems undergoing
local SU(2) evolutions.Comment: Minor corrections; journal reference adde
Geometric local invariants and pure three-qubit states
We explore a geometric approach to generating local SU(2) and
invariants for a collection of qubits inspired by lattice
gauge theory. Each local invariant or 'gauge' invariant is associated to a
distinct closed path (or plaquette) joining some or all of the qubits. In
lattice gauge theory, the lattice points are the discrete space-time points,
the transformations between the points of the lattice are defined by parallel
transporters and the gauge invariant observable associated to a particular
closed path is given by the Wilson loop. In our approach the points of the
lattice are qubits, the link-transformations between the qubits are defined by
the correlations between them and the gauge invariant observable, the local
invariants associated to a particular closed path are also given by a Wilson
loop-like construction. The link transformations share many of the properties
of parallel transporters although they are not undone when one retraces one's
steps through the lattice. This feature is used to generate many of the
invariants. We consider a pure three qubit state as a test case and find we can
generate a complete set of algebraically independent local invariants in this
way, however the framework given here is applicable to mixed states composed of
any number of level quantum systems. We give an operational interpretation
of these invariants in terms of observables.Comment: 9 pages, 3 figure
Geometric phases for mixed states in interferometry
We provide a physical prescription based on interferometry for introducing
the total phase of a mixed state undergoing unitary evolution, which has been
an elusive concept in the past. We define the parallel transport condition that
provides a connection-form for obtaining the geometric phase for mixed states.
The expression for the geometric phase for mixed state reduces to well known
formulas in the pure state case when a system undergoes noncyclic and unitary
quantum evolution.Comment: Two column, 4 pages, Latex file, No figures, Few change
Multi-Layer Cyber-Physical Security and Resilience for Smart Grid
The smart grid is a large-scale complex system that integrates communication
technologies with the physical layer operation of the energy systems. Security
and resilience mechanisms by design are important to provide guarantee
operations for the system. This chapter provides a layered perspective of the
smart grid security and discusses game and decision theory as a tool to model
the interactions among system components and the interaction between attackers
and the system. We discuss game-theoretic applications and challenges in the
design of cross-layer robust and resilient controller, secure network routing
protocol at the data communication and networking layers, and the challenges of
the information security at the management layer of the grid. The chapter will
discuss the future directions of using game-theoretic tools in addressing
multi-layer security issues in the smart grid.Comment: 16 page
Geometric Effects and Computation in Spin Networks
When initially introduced, a Hamiltonian that realises perfect transfer of a
quantum state was found to be analogous to an x-rotation of a large spin. In
this paper we extend the analogy further to demonstrate geometric effects by
performing rotations on the spin. Such effects can be used to determine
properties of the chain, such as its length, in a robust manner. Alternatively,
they can form the basis of a spin network quantum computer. We demonstrate a
universal set of gates in such a system by both dynamical and geometrical
means
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