21,695 research outputs found
Face pairing graphs and 3-manifold enumeration
The face pairing graph of a 3-manifold triangulation is a 4-valent graph
denoting which tetrahedron faces are identified with which others. We present a
series of properties that must be satisfied by the face pairing graph of a
closed minimal P^2-irreducible triangulation. In addition we present
constraints upon the combinatorial structure of such a triangulation that can
be deduced from its face pairing graph. These results are then applied to the
enumeration of closed minimal P^2-irreducible 3-manifold triangulations,
leading to a significant improvement in the performance of the enumeration
algorithm. Results are offered for both orientable and non-orientable
triangulations.Comment: 30 pages, 57 figures; v2: clarified some passages and generalised the
final theorem to the non-orientable case; v3: fixed a flaw in the proof of
the conical face lemm
When Stock Options Fail to Motivate: Attribution and Context Effects on Stock Price Expectancy
This study draws on attribution theory and literature from compensation and strategy to investigate executivesâ perceptions about their influence over the firmâs stock price. We define stock price expectancy as the extent to which executives feel that they can influence the firmâs stock price. Results from of a survey of 435 U.S. executives suggest that stock price expectancy is related to both attributional and contextual antecedents. Based on these findings we discuss implications for the extension of expectancy theory and the design and administration of incentive systems
âYouâre Nobody âtil Somebody Loves Youâ: The Use of Job Search for Bargaining Leverage
The purpose of this research is to investigate a previously overlooked yet important objective for an employee engaging in job search â seeking alternative employment to obtain leverage against the current employer. We focus specifically on how employees conduct job search to obtain leverage, and then turn to the question of what motivates employees to adopt this objective. Using a sample of high-level managers, our results indicate the leverage-seeking job search predicts both preparatory and active search beyond the more traditional reason for engaging in job search (i.e., to change jobs). However, as expected, leverage-seeking search was a weaker predictor of the job search processes compared to searching to leave and was not significantly related to job satisfaction. Hierarchical level, perceived alternatives, financial independence, and the meaning attached to money significantly predicted leverage-seeking search, while compensation level, equity, and career plateau showed little effect. Implications for practice and future research on job search and employee retention more generally are discussed
The Relationship Between Job Search Objectives and Job Search Behavior
This research expands the notion of âjob searchâ beyond traditional models of searching for an alternative yet similar job, arguing that motivations for search are varied. Specifically, we investigate whether search objectives associate with use of different search processes. A study of high-level managers found mixed support for the hypotheses
Observations and models for needle-tissue interactions
The asymmetry of a bevel-tip needle results in the needle naturally bending when it is inserted into soft tissue. In this study we present a mechanics-based model that calculates the deflection of the needle embedded in an elastic medium. Microscopic observations for several needle- gel interactions were used to characterize the interactions at the bevel tip and along the needle shaft. The model design was guided by microscopic observations of several needle- gel interactions. The energy-based model formulation incor- porates tissue-specific parameters such as rupture toughness, nonlinear material elasticity, and interaction stiffness, and needle geometric and material properties. Simulation results follow similar trends (deflection and radius of curvature) to those observed in macroscopic experimental studies of a robot- driven needle interacting with different kinds of gels. These results contribute to a mechanics-based model of robotic needle steering, extending previous work on kinematic models
Fully three dimensional breather solitons can be created using Feshbach resonance
We investigate the stability properties of breather solitons in a
three-dimensional Bose-Einstein Condensate with Feshbach Resonance Management
of the scattering length and con ned only by a one dimensional optical lattice.
We compare regions of stability in parameter space obtained from a fully 3D
analysis with those from a quasi two-dimensional treatment. For moderate con
nement we discover a new island of stability in the 3D case, not present in the
quasi 2D treatment. Stable solutions from this region have nontrivial dynamics
in the lattice direction, hence they describe fully 3D breather solitons. We
demonstrate these solutions in direct numerical simulations and outline a
possible way of creating robust 3D solitons in experiments in a Bose Einstein
Condensate in a one-dimensional lattice. We point other possible applications.Comment: 4 pages, 4 figures; accepted to Physical Review Letter
Lattice QCD Evidence that the Lambda(1405) Resonance is an Antikaon-Nucleon Molecule
For almost 50 years the structure of the Lambda(1405) resonance has been a
mystery. Even though it contains a heavy strange quark and has odd parity, its
mass is lower than any other excited spin-1/2 baryon. Dalitz and co-workers
speculated that it might be a molecular state of an antikaon bound to a
nucleon. However, a standard quark-model structure is also admissible. Although
the intervening years have seen considerable effort, there has been no
convincing resolution. Here we present a new lattice QCD simulation showing
that the strange magnetic form factor of the Lambda(1405) vanishes, signaling
the formation of an antikaon-nucleon molecule. Together with a Hamiltonian
effective-field-theory model analysis of the lattice QCD energy levels, this
strongly suggests that the structure is dominated by a bound antikaon-nucleon
component. This result clarifies that not all states occurring in nature can be
described within a simple quark model framework and points to the existence of
exotic molecular meson-nucleon bound states.Comment: Manuscript accepted for publication. 4 figures, 5 page
Initial Scientific Results from Phase-Referenced Astrometry of Sub-Arcsecond Binaries
The Palomar Testbed Interferometer has observed several binary star systems
whose separations fall between the interferometric coherence length (a few
hundredths of an arcsecond) and the typical atmospheric seeing limit of one
arcsecond. Using phase-referencing techniques we measure the relative
separations of the systems to precisions of a few tens of micro-arcseconds. We
present the first scientific results of these observations, including the
astrometric detection of the faint third stellar component of the kappa Pegasi
system.Comment: 8 pages, 5 figures. To appear in SPIE conference proceedings volume
5491, "New Frontiers in Stellar Interferometery
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