Tracking the motion of charges in a terahertz light field by femtosecond X-ray diffraction.

In condensed matter, light propagation near resonances is described in terms of polaritons, electro-mechanical excitations in which the time-dependent electric field is coupled to the oscillation of charged masses. This description underpins our understanding of the macroscopic optical properties of solids, liquids and plasmas, as well as of their dispersion with frequency. In ferroelectric materials, terahertz radiation propagates by driving infrared-active lattice vibrations, resulting in phonon-polariton waves. Electro-optic sampling with femtosecond optical pulses can measure the time-dependent electrical polarization, providing a phase-sensitive analogue to optical Raman scattering. Here we use femtosecond time-resolved X-ray diffraction, a phase-sensitive analogue to inelastic X-ray scattering, to measure the corresponding displacements of ions in ferroelectric lithium tantalate, LiTaO(3). Amplitude and phase of all degrees of freedom in a light field are thus directly measured in the time domain. Notably, extension of other X-ray techniques to the femtosecond timescale (for example, magnetic or anomalous scattering) would allow for studies in complex systems, where electric fields couple to multiple degrees of freedom.

Metrics for negative-refractive-index materials.

The importance of loss in the field solution for left-handed media, and in particular, the impact on what would otherwise be a purely evanescent field, is addressed. Using an equivalent electric current source, field solutions are constructed in semi-infinite and finite thickness left-handed media. In the slab case, field growth and power dissipation metrics with uniform amplitude and uniform power excitation, respectively, provide a means to evaluate the potential of a left-handed material lens. Power dissipation suggests that field growth will be adversely impacted.

Enantioselective ruthenium-catalyzed ring-closing metathesis.

[reaction: see text] The first enantioselective ruthenium olefin metathesis catalysts have been prepared, and high enantiomeric excesses (up to 90%) are observed in the desymmetrization of achiral trienes. A model consistent with the stereochemical outcome of the reactions is described and suggests side-on olefin binding and reorganization of the halide ligands.

Syndesmotic ankle sprain in a recreational hockey player.

OBJECTIVE: To present a case of distal tibiofibular sprain, a rare injury among ubiquitous lateral ligament sprains of the ankle. CLINICAL FEATURES: A 45-yr-old recreational hockey player was treated for an ankle sprain demonstrating increased translation on the drawer test and pain with inversion stress, but also pain with external rotation and dorsiflexion. X-rays demonstrated no fractures. INTERVENTION AND OUTCOME: The conventional protocol of protect, rest, ice, compress and elevate (PRICE), employed for the more common lateral ankle sprains, was followed by early mobilization and proprioceptive training with a tilt board. Recovery was prolonged, and ossification of the ankle syndesmosis was seen in follow-up radiographs. CONCLUSION: Because management implications and outcome sequelae of the uncommon syndesmotic sprain are more severe than the commonly seen lateral ankle sprain, simple physical examination procedures useful in identifying syndesmotic sprains in the routine examination of the injured ankle are emphasized. These include dorsiflexion and external rotation stress and the "squeeze test."

Flecainide acetate in the treatment of tachycardias associated with Mahaim fibres.

Patients with Mahaim fibres are susceptible to tachycardias which can be refractory to conventional drug therapy, leading to treatment with surgery and catheter ablation. The effects of flecainide acetate were studied in 3 patients (61, 21 and 35 years of age) with Mahaim fibres presenting with tachycardias refractory to beta-blockers, quinidine and verapamil. One also had ophthalmic side-effects from amiodarone. Three types of tachycardias were induced: a reentrant tachycardia with left bundle branch block morphology (LBBBM) in all 3 patients, atrial flutter in one and atrial fibrillation in another. Intravenous flecainide acetate (2 mg kg-1) terminated reentrant tachycardia and abolished duality of atrioventricular conduction in patient 1. In patient 2, it abolished preexcitation during atrial flutter prior to termination. Atrial fibrillation could not be induced in patient 3 after flecainide acetate. In all patients, retrograde conduction was blocked, preexcitation was not present with atrial pacing and no tachycardia was induced after flecainide. All have remained asymptomatic on oral flecainide acetate (100 mg bd) for a mean follow-up period of 9 months. We conclude that (1) flecainide acetate is effective for the treatment of various tachycardias associated with Mahaim fibres; (2) since different mechanisms responsible for the tachycardia with LBBBM may be present in the same patient and difficult to determine in some, treatment with flecainide acetate which affects both the atrioventricular node and Mahaim fibre conduction may be appropriate for the condition and; (3) its use should be considered before more aggressive therapies.

A manometric assessment of oesophagogastrostomy.

Intraluminal pressures were recorded in 14 patients who had undergone oesophagogastrectomy. Seven of these had a mid-thoracic and seven a high cervical oesophagogastrostomy. The incidence of postoperative reflux complications in each group was noted. No pressure gradient across the anastomosis was detected in any patient but the upper oesophageal sphincter was shown to be retained as a functioning unit in all cases. It is considered that the thoracic anastomosis provides no demonstrable barrier to reflux. In addition, a high cervical oesophagogastrostomy does not adversely affect the upper oesophageal sphincter. The wider application of this latter procedure may be associated with a decreased incidence of postoperative reflux complications.

Association between Previous Tuberculous Infection and Cerebal Glioma.

An increased incidence of previous infection with tuberculosis has been found in a series of patients with cerebral gliomas, and it is suggested that such an association may be due to defective immunity acting as a common aetiological factor.