Effective-Range Expansion of the Neutron-Deuteron Scattering Studied by a Quark-Model Nonlocal Gaussian Potential

The S-wave effective range parameters of the neutron-deuteron (nd) scattering are derived in the Faddeev formalism, using a nonlocal Gaussian potential based on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy eigenphase shift is sufficiently attractive to reproduce predictions by the AV18 plus Urbana three-nucleon force, yielding the observed value of the doublet scattering length and the correct differential cross sections below the deuteron breakup threshold. This conclusion is consistent with the previous result for the triton binding energy, which is nearly reproduced by fss2 without reinforcing it with the three-nucleon force.Comment: 21 pages, 6 figures and 6 tables, submitted to Prog. Theor. Phy

Functional Electrical Stimulation of Intrinsic Laryngeal Muscles under Varying Loads in Exercising Horses

Bilateral vocal fold paralysis (BVCP) is a life threatening condition and appears to be a good candidate for therapy using functional electrical stimulation (FES). Developing a working FES system has been technically difficult due to the inaccessible location and small size of the sole arytenoid abductor, the posterior cricoarytenoid (PCA) muscle. A naturally-occurring disease in horses shares many functional and etiological features with BVCP. In this study, the feasibility of FES for equine vocal fold paralysis was explored by testing arytenoid abduction evoked by electrical stimulation of the PCA muscle. Rheobase and chronaxie were determined for innervated PCA muscle. We then tested the hypothesis that direct muscle stimulation can maintain airway patency during strenuous exercise in horses with induced transient conduction block of the laryngeal motor nerve. Six adult horses were instrumented with a single bipolar intra-muscular electrode in the left PCA muscle. Rheobase and chronaxie were within the normal range for innervated muscle at 0.55±0.38 v and 0.38±0.19 ms respectively. Intramuscular stimulation of the PCA muscle significantly improved arytenoid abduction at all levels of exercise intensity and there was no significant difference between the level of abduction achieved with stimulation and control values under moderate loads. The equine larynx may provide a useful model for the study of bilateral fold paralysis

Postoperative atrial fibrillation:mechanisms, manifestations and management

Postoperative atrial fibrillation (POAF) complicates 20-40% of cardiac surgical procedures and 10-20% of non-cardiac thoracic operations. Typical features include onset at 2-4 days postoperatively, episodes that are often fleeting and a self-limited time course. Associated adverse consequences of POAF include haemodynamic instability, increased risk of stroke, lengthened hospital and intensive care unit stays and greater costs. Underlying mechanisms are incompletely defined but include intraoperative and postoperative phenomena, such as inflammation, sympathetic activation and cardiac ischaemia, that combine to trigger atrial fibrillation, often in the presence of pre-existing factors, making the atria vulnerable to atrial fibrillation induction and maintenance. A better understanding of the underlying mechanisms might enable the identification of new therapeutic targets. POAF can be prevented by targeting autonomic alterations and inflammation. beta-Blocker prophylaxis is the best-established preventive therapy and should be started or continued before cardiac surgery, unless contraindicated. When POAF occurs, rate control usually suffices, and routine rhythm control is unnecessary; rhythm control should be reserved for patients who develop haemodynamic instability or show other indications that rate control alone will be insufficient. In this Review, we summarize the epidemiological and clinical features of POAF, the available pathophysiological evidence from clinical and experimental investigations, the results of prophylactic and therapeutic approaches and the consensus recommendations of various national and international societies