Nonlocal Factors Research Articles

Surface geometry influences the shape of illusory contours

Geometric and neural models of illusory-contour (IC) synthesis currently use only local contour geometry to derive the shape of ICs. Work on the visual representation of shape, by contrast, points to the importance of both contour and surface geometry. We investigated the influence of surface-based geometric factors on IC shape. The local geometry of inducing-contour pairs was equated in stereoscopic IC displays, and the shape of the enclosed surface was varied by manipulating sign of curvature, cross-axial shape width, and medial-axis geometry. IC shapes were measured using a parametric shape-adjustment task (Experiment 1) and a dot-adjustment task (Experiment 2). Both methods revealed large influences of surface geometry. ICs enclosing locally concave regions were perceived to be systematically more angular than those enclosing locally convex regions. Importantly, the influence of sign of curvature was modulated significantly by shape width and medial-axis geometry: IC shape difference between convex and concave inducers was greater for narrow shapes than wider ones, and greater for shapes with straight axis and symmetric contours (diamond versus bowtie), than those with curved axis and parallel contours (bent tubes). Even at the level of illusory “contours,” there is a contribution of region-based geometry which is sensitive to nonlocal shape properties involving medial geometry and part decomposition. Models of IC synthesis must incorporate the role of nonlocal region-based geometric factors in a way that parallels their role in organizing visual shape representation more generally.

Model estimates for the interaction of wind waves and tides in the Pechora Basin-White Sea subsystem

The “weak-interaction” approximation is used to investigate the role of wind waves in tidal dynamics. The resulting expression for the drag coefficient in the wave-affected tidal flow is incorporated into the QUODDY-4 three-dimensional finite-element hydrothermodynamic model, and the thus modified model is used to calculate the K 1 diurnal tide in the Pechora Basin-White Sea subsystem. It is shown that, depending on a combination of local and nonlocal factors, wind waves can cause opposite variations in the amplitudes and phases of tidal oscillations of the level. Local factors control variations in the tidal regime nearly in the entire water area of the subsystem under consideration, apart from the eastern part of the Pechora Basin, the outlet from the White Sea Throat, and Dvina Bay. In the aforementioned areas, the tidal regime changes are due either to the displacement of the nearest amphidromy or to other nonlocal factors resulting from the reorganization of the fields of tidal characteristics. It is also shown that the variations in tidal characteristics induced by wind waves vary within a fairly wide range and that allowance for the interaction of wind waves and tides improves the agreement between calculated and observed values of the amplitudes and phases of tidal oscillations of the level.

Hamstring injury management—Part 2: Treatment

The management of hamstring injuries can be described as vexed at best. One reason for this may be because of a lack of high-quality research into the methods of treatment, rehabilitation and prevention. As a result, an evidence-based approach to injury management does not exist. Management is based on clinical experience, anecdotal evidence and the knowledge of the biological basis of tissue repair. Previous hamstring injury is the most recognized risk factor for injury, which indicates that treatment approaches may be suboptimal under certain conditions. The identification of these risk factors and the methods best designed to manage them should be addressed with future research efforts. Much anecdotal and indirect evidence exists to suggest that several non-local factors contribute to injury. Despite the knowledge that these factors may exist, the literature appears almost devoid of research investigating their possible identification and treatment. Treatment has traditionally been in the form of altering the muscle repair process through the application of electrophysical therapy and various soft-tissue-based and exercise-based techniques. Little research has investigated the role of other forms of manual therapy particularly when directed at non-local structures. This paper will explore and speculate on this potential connection and offer some new contributive factors for hamstring injury management.

The management of hamstring injury—Part 1: Issues in diagnosis

Hamstring injuries are the most prevalent muscle injury in sports involving rapid acceleration and maximum speed running. Injury typically occurs in an acute manner through an eccentric mechanism at the terminal stages of the swing phase of gait. Biceps femoris is most commonly injured. Re-injury rates are high and management is a challenge given the complex multi-factorial aetiology. The high rates of hamstring injury and re-injury may result from a lack of high-quality research into the aetiological factors underlying injury. Re-injury may also result from inaccuracy in diagnosis that results from the potential multi-factorial causes of these conditions. Inaccuracy in diagnosis could lead to multiple potential diagnoses that may result in the implementation of variable management protocols. Whilst potentially useful, such variability may also lead to the implementation of sub-optimal management strategies. Previous hamstring injury is the most recognized risk factor for injury, which indicates that future research should be directed at preventative measures. Much anecdotal and indirect evidence exists to suggest that several non-local factors contribute to injury, which may be addressed through the application of manual therapy. However, this connection has been neglected in previous research and literature. This paper will explore and speculate on this potential connection and offer some new contributive factors for hamstring injury management. This first paper of a two part series on hamstring injury will explore diagnostic issues relevant to hamstring injury and the second will investigate various established and speculative management approaches.

Measuring electoral control

If voters do not pay attention to whatrepresentatives do, representatives are not stimulatedto be responsive. Therefore, electoral control, theextent to which voters base their vote on thebehaviour of representatives is, at least potentially,an important variable in the explanation of thebehaviour of representatives. Moreover, electoralcontrol seems to be an important variable from anormative point of view. In this article four ways tomeasure the minimal level of local electoral controlusing the outcomes of local elections (electoralstatistics) are presented. The general idea behind themeasures is fairly simple. If local elections arecompletely determined by nonlocal factors, then thelosses and gains of local divisions of nationalparties from one local election to another are`identical' across municipalities. A deviation fromthis pattern can be interpreted as an indication ofthe minimal level of local electoral control in aspecific municipality. The measures are externally validated using data from a survey among council members.

Local Uniqueness in the Global Village: Heritage Tourism in Singapore

It is commonly assumed that the development of tourist attractions, the formulation of tourism policies, and the marketing of destination areas are dictated by the needs and interests of foreign visitors. What is ignored is the role that local factors and agencies play in these processes. This paper explores the way local and non-local factors are responsible for shaping the form and function of tourism development. Drawing upon the case of Singapore, I examine the country's heritage tourism phenomenon as the outcome of “local” and “global” forces. This argument is elaborated along three lines of enquiry. They include: (a) a study of the government's tourism policies; (b) an examination of marketing and promotional strategies; and (c) a look at a particular urban landscape—the Little India Historic District. To conceptualize the global-local nexus, the paper embraces two bodies of theory. They are the “locality concept” advanced by industrial geographers in the 1980s, and writings on “globalism/localism” by cultural/economic geographers in the 1990s. Both theoretical discussions reinforce the argument that place uniqueness need not be sacrificed as a result of globalization. They also provide a way of viewing tourism geographies as the product of global and local forces.

Context-dependent secondary structure formation of a designed protein sequence.

Protein secondary structures have been viewed as fundamental building blocks for protein folding, structure and design. Previous studies indicate that the propensities of individual amino acids to form particular secondary structures are the result of a combination of local conformational preferences and non-local factors. To examine the extent to which non-local factors influence the formation of secondary structural elements, we have designed an 11-amino-acid sequence (dubbed the 'chameleon' sequence) that folds as an alpha-helix when in one position but as a beta-sheet when in another position of the primary sequence of the IgG-binding domain of protein G (GB1). Both proteins, chameleon-alpha and chameleon-beta, are folded into structures similar to native GB1, as judged by several biophysical criteria. Our results demonstrate that non-local interactions can determine the secondary structure of peptide sequences of substantial length. They also support views of protein folding that favour tertiary interactions as dominant determinants of structure.

Low frequency current variability on the shelf break northeast of Taiwan

A buoy-mounted Acoustic Doppler Current Profiler was deployed on the shelf break off the northeast coast of Taiwan to monitor current variations in the upper ocean. The acquired data show that the flow in the upper water column was initially southwest and then abruptly turned northwest. This abrupt change occurred in mid-October, starting from the surface layer and then gradually extending to the deeper layer. In contrast with this flow, the flow in the lower water column was southwest over the entire record, but its amplitude was reduced after the middle of October. The abrupt change of current from southwest to northwest is related to the intrusion of Kuroshio. Examination of two CTD casts showed the salinity of the upper ocean to have increased after the directional shift in mid-October, further indicating the Kuroshio intrusion. The sea level data at Keelung provided other evidence for the intrusion of Kuroshio. The sea level descended as the intrusion occurred and kept the low value until the end of the record. The northwest flow, which carried the water away from the northern coast of Taiwan, is responsible for this descent. Although the intrusion of Kuroshio was mainly confined to the upper ocean, it did have influence on the whole water column. Examination of the wind record at Pengchiayu showed that the time of Kuroshio intrusion was not coincident with the intensification of the northeasterly monsoon. The local wind and the current at 20 m were incoherent. Both the variation of Kuroshio current and the fluctuation of Kuroshio path may be responsible for the variation of the local current. Since the intrusion of Kuroshio has a weak relationship with local wind variation, it appears to be induced by non-local factors.

Scatterometer wind speed bias induced by the large‐scale component of the wave field

The entire set of Seasat A satellite Scatterometer (SASS) wind speed observations, Us, colocated with the buoy measurements of the wind speed Ub and wave height H1/3 is analyzed. The “error” Ub ‐ Us is found to be influenced by the degree of wind‐wave coupling. This coupling is quantified employing the ratio of the wave‐to‐wind energy densities: X ∼ ρwg〈ζ2〉/ρaUb2. For the special case of a fetch‐limited wave growth, X is shown to coincide with the wind fetch. It is found that when the coupling is weak, i.e., at large X, the SASS tends to overestimate the wind speed, and vice versa. The magnitude of the trend is evaluated roughly as 0.5 m/s per 100 km of X. The increased radar backscatter at large X is explained by invoking the concept (due to V. Zakharov and his collaborators) of a Kolmogorov equilibrium range appearing in wave spectra of sufficiently developed seas when the wind input is concentrated at high frequencies. In this extreme case, the surface density of steep wavelet occurrence would be at its highest owing to a pronounced cascade pattern in the surface geometry. The fractal dimension DH of such an idealized surface is estimated to be about 2.333. Further, it is suggested that DH for a general case is a function of sea maturity. Finally, it is concluded that both the probability and the surface density of steep wavelet events are increasing functions of X. A major implication with respect to the electromagnetic scattering is that the so‐called spike component of the backscattering coefficient, formed from the individual radar returns caused by the steep and/or breaking wavelets, is controlled primarily by the large‐scale features of surface geometry, hence by such nonlocal factors of the wave development as the wind fetch.

INTRA‐ORGANIZATIONAL POLITICS IN LOCAL AUTHORITIES: TOWARDS A NEW APPROACH

Much of the recent literature on local government has emphasized the impact of non‐local factors on local authority decision‐making. This article argues that the administrative processes, power structures and conflicts of interest inside local authorities can often affect policy processes by mediating external influences and providing an internal dynamic of their own. We suggest that most of the current literature concentrates too narrowly on officer‐councillor relationships and invariably emphasizes the total dominance of an officer‐councillor elite. Our new approach identifies six possible arenas of policy influence within local authorities (of which the officer‐councillor elite is just one) and emphasizes the dynamics of intra‐organizational politics inside local authorities.

Measure for moduli The Polyakov string has no nonlocal anomalies

The functional measure of the bosonic Polyakov string contains nonlocal determinantal factors which seem to spoil its gauge invariances even in the critical dimension. We show that in fact both conformal invariance and reparameterization invariance are maintained for every world-sheet topology.

The effect of self-stress on diffusion in solids

We demonstrate that the local diffusion flux in solids depends on stresses arising from compositional inhomogeneities (and even the shape) of the entire specimen. This dependence of local flux on distant inhomogeneity is considered to be a failure of Fickt's law. From an eluation relating stress and composition field, we can find special cases in which a diffusion law resembling Fickt's law occurs, but the anisotropy of the apparent diffusion coefficient reveals that non-local factors are still present. le also examine the case of diffusion through a thin plate for the functional dependence of diffusion on the composition field and predict much deeper diffusional penetration and accumulation on the far side.

Nonlocal energy deposition in the ionosphere and the photoelectron escape flux

The theory of nonlocal energy deposition in the ionosphere developed by Geisler and Bowhill is generalized to include the absence of thermal equilibrium among the neutral, ion and electron gases. Analytic expressions for certain ratios of the electron-to-neutral scale heights are presented. These include both the nonlocal energy deposition factors and the escape flux density of photoelectrons.