Influence of predominant patterns of coordination on the exploitation of interaction torques in a two-joint rhythmic arm movement

In this study we investigate the coordination between rhythmic flexion-extension (FE) and supination-pronation (SP) movements at the elbow joint-complex, while manipulating the intersegmental dynamics by means of a 2-degrees of freedom (df) robot arm. We hypothesized that constraints imposed by the structure of the neuromuscular-skeletal system would (1) result in predominant pattern(s) of coordination in the absence of interaction torques and (2) influence the capabilities of participants to exploit artificially induced interaction torques. Two experiments were conducted in which different conditions of interaction torques were applied on the SP-axis as a function of FE movements. These conditions promoted different patterns of coordination between the 2-df. Control trials conducted in the absence of interaction torques revealed that both the in-phase (supination synchronized with flexion) and the anti-phase (pronation synchronized with flexion) patterns were spontaneously established by participants. The predominance of these patterns of coordination is explained in terms of the mechanical action of bi-articular muscles acting at the elbow joint-complex, and in terms of the reflexes that link the activity of the muscles involved. Results obtained in the different conditions of interaction torques revealed that those neuromuscular-skeletal constraints either impede or favor the exploitation of intersegmental dynamics depending on the context. Interaction torques were indeed found to be exploited to a greater extent in conditions in which the profiles of interaction torques favored one of the two predominant patterns of coordination (i.e., in-phase or anti-phase) as opposed to other patterns of coordination (e.g., 90 degrees or 270 degrees). Those results are discussed in relation to recent studies reporting exploitation of interaction torques in the context of rhythmic movements.

Neuromuscular-skeletal origins of predominant patterns of coordination in a rhythmic two-joint arm movement

The authors tested for predominant patterns of coordination in the combination of rhythmic flexion-extension (FE) and supination-pronation (SP) at the elbow-joint complex. Participants (N = 10) spontaneously established in-phase (supination synchronized with flexion) and antiphase (pronation synchronized with flexion) patterns. In addition, the authors used a motorized robot arm to generate involuntary SP movements with different phase relations with respect to voluntary FE. The involuntarily induced in-phase pattern was accentuated and was more consistent than other patterns. That result provides evidence that the predominance of the in-phase pattern originates in the influence of neuro-muscular-skeletal constraints rather than in a preference dictated by perceptual-cognitive factors implicated in voluntary control. Neuromuscular-skeletal constraints involved in the predominance of the in-phase and the antiphase patterns are discussed.

'Leaving Nothing to Chance'?: Joint Tenancies, The 'Right' of Survivorship and Unilateral Severance

The joint tenancy with its inherent right of survivorship is the most prevalent form of co-ownership in the common law world today. Most couples will be joint tenants of a family home, while relations (such as siblings) who purchase property together may opt for this arrangement. Inter vivos acquisitions aside, the huge intergenerational transfer of wealth within families on death can result in a joint tenancy, and it may also be a convenient estate planning device. The fact that property automatically vests in the surviving joint tenants on death is the reason why many people choose this form of co-ownership. However, there is one serious disadvantage. A joint tenancy is an inflexible form of landholding where relationships sour or family circumstances change over time, and co-owners want their respective `shares' of the property to pass to someone else on death. Where consensual severance is not possible, one joint tenant can sever unilaterally. The latter mechanism is vital in terms of giving effect to the wishes of the severing joint tenant, especially in situations of discord or a breakdown in relations with their fellow co-owners. However, unilateral severance also has serious implications for the non-severing joint tenant(s) who expected to inherit property through survivorship, and can impact significantly on ownership of the home and other family property. This article looks at unilateral severance as a means of subverting the right of survivorship. The focus is on personal and inter-family relationships, and the various legal issues and policy considerations associated with unilateral severance across the common law jurisdictions of Britain, Ireland, Australia, Canada, and New Zealand. It assesses the various methods of effecting unilateral severance and proposes specific measures, as well as considering novel arguments for preventing unilateral severance based on contractual agreements to the contrary and proprietary estoppel.

Failure of Local Realism Revealed by Extremely-Coarse-Grained Measurements

We show that failure of local realism can be revealed to observers for whom only extremely-coarse-grained measurements are available. In our instances, Bell's inequality is violated even up to the maximum limit while both the local measurements and the initial local states under scrutiny approach the classical limit. Furthermore, we can observe failure of local realism when an inequality enforced by nonlocal realistic theories is satisfied. This suggests that locality alone may be violated while realism cannot be excluded for specific observables and states. Small-scale experimental demonstration of our examples may be possible in the foreseeable future.

Development of operator independent bone cement vacuum mixing system for joint replacement surgery,

(2006) Vol. 35 No. 8 317

Low-energy electron attachment to chloroform (CHCl3) molecules: A joint experimental and theoretical study

Results from a joint experimental and theoretical study of electron attachment to chloroform (CHCl3) molecules in the gas phase are reported. In an electron swarm study involving a pulsed Townsend technique with equal gas and electron temperatures, accurate attachment rate coefficients were determined over the temperature range 295-373 K; they show an Arrhenius-type rise with increasing temperature, corresponding to an activation energy of 0.11 (1) eV. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for Cl- formation from CHCl3 over the energy range 0.001-1.25 eV at the gas temperature T-G = 300 K was measured. It exhibits clear downward cusp structure at the threshold for excitation of one quantum of the vibrational symmetric deformation mode nu(3), indicating that this mode is active in the primary attachment process. With reference to our thermal attachment rate coefficient k(T = 300 K) = 3.9(2) x 10(-9) cm(3) s(-1), a new highly resolved absolute attachment cross section for T-G = 300 K was determined. This cross section is extended to higher energies by measurements, carried out with a pulsed electron beam apparatus which also provided new data for the distinctly weaker fragment anions HCl2- and CCl2-. The resulting total absolute cross section for anion formation is used to calculate the dependence of the attachment rate coefficient k(T-e;T-G) on electron temperature T-e over the range 50-15000 K at the fixed gas temperature T-G = 300 K. In addition, we report the dependence of the relative cross section for Cl- formation on gas temperature T-G = 310-435 K). For comparison with the experimental data, R-matrix calculations have been carried out for the dominant anion channel Cl-. The results recover the main experimental observations and predict the dependence of the DEA cross section on the initial vibrational level nu(3) and on the vibrational temperature. Our results are compared with those of previous electron beam and electron swarm experiments.