Beam brightness and its reduction in a 1.2-MV cold field-emission transmission electron microscope.

In this paper we discuss probe properties in terms of probe currents, probe sizes, energy spread, virtual source sizes, and brightness in a 1.2-MV cold field-emission (cold FE) transmission electron microscope (TEM) equipped with a magnetic gun lens. The probe size increased gradually in proportion to the (3/8)th power of the probe current, very unusual behavior in cold FE guns but typical behavior in thermionic guns. This is due to the magnetic gun lens, which caused large emission angles for electron beams in the probe before being limited by aberrations at the gun and acceleration tube. The brightness reached the maximum at 1.62 × 1014 A/(m2sr) and then decreased with increasing the emission current. The energy spread of the beam, including the Boersch effect, was 0.32-0.50 eV, comparable to that of conventional cold FE guns without magnetic gun lens. Experimental analysis indicated that neither noises nor aberrations caused the probe size increase under the optimized illumination condition. The virtual source size increased from 11.1 to 24.7 nm with the increase in the emission current. To describe this behavior, we conjecture that this brightness reduction is due to increase in the virtual source size caused by trajectory displacement created by stochastic Coulomb interactions near the emitter.

Sympathetic activity-mediated neuropathic facial pain following simple tooth extraction: a case report.

This is a report of a case of sympathetic activity-mediated neuropathic facial pain induced by a traumatic trigeminal nerve injury and by varicella zoster virus infection, following a simple tooth extraction. The patient had undergone extraction of the right lower third molar at a local dental clinic, and soon after the tooth extraction, she became aware of spontaneous pain in the right ear, right temporal region, and in the tooth socket. At our initial examination 30 days after the tooth extraction, the healing of the tooth socket was normal; however, the patient had a tingling and burning sensation (dysesthesia) and spontaneous pain of the right lower lip and the right temporal region, both of which were exacerbated by non-noxious stimuli (allodynia). The patient also showed paralysis of the marginal mandibular branch of the facial nerve, taste dysfunction, and increased varicella zoster serum titers. A diagnostic stellate ganglion block (SGB) 45 days after the tooth extraction using one percent lidocaine markedly alleviated the dysesthesia and allodynia. These symptoms are characteristic of neuropathic pain with sympathetic interaction. The patient was successfully treated with SGB and a tricyclic antidepressant.