IOFF generally extends fluorophore longevity in the presence of an optical trap.

The combination of optical tweezers force microscopy and single molecule fluorescence has previously been complicated by trap-induced photobleaching. Recent studies have suggested that this effect is caused by a sequential absorption of photons, leading to ionization of the fluorescent singlet state. In this work, we show the range of effects of optical trapping radiation on common fluorescent dyes. Using the interlaced optical force fluorescence (IOFF) laser modulation technique, we show that the removal of simultaneous near infrared radiation dramatically reduces photobleaching effects. However, these studies show that the sequential addition of near infrared radiation in some cases extends photobleaching longevity beyond the natural intrinsic decay. We suggest a refined photoelectronic mechanism that accounts for the possibility of reverse intersystem crossing from a reactive triplet state and explains the nature of trap-induced photobleaching.

Carotid artery restenosis in a Hispanic population.

BACKGROUND AND PURPOSE: Carotid endarterectomy is one of the main surgical procedures used for carotid stenosis and its recurrence. Besides the setting of a randomized controlled trial for asymptomatic and symptomatic carotid artery stenosis, there is little information about the rate of restenosis after carotid endarterectomy in Hispanics. The purpose of this study is to describe the results of carotid endarterectomy on the basis of restenosis in a Hispanic population. METHOD: A retrospective revision of 47 endarterectomies performed on 43 patients by a single surgeon at the VA Caribbean Health Care System and Pavia Hospital, during an eight year period (1990-1998), was conducted. Information about endarterectomies, restenosis and known risk factors for carotid stenosis were obtained from medical records. RESULTS: Of the 43 patients, 31 were male (72%) and 12 female (28%), with a mean age of 67.9 years. Re-operations for recurrent carotid stenosis were performed in 2 patients (4.7%). Restenosis cases were asymptomatic, hence diagnosed through followup ultrasound Duplex studies and confirmed by angiography after 3 and 4 years of the first surgical procedure. The degree of restenosis (70% to 99%) after the initial endarterectomy was 4.3%. The major risk factors found among patients were hypertension (58%), hypercholesterolemia (50%), smoking (46%), and alcohol (34%). CONCLUSIONS: Carotid endarterectomy with primary closure is safe and durable. Repeated surgery using patch grafts in this Hispanic population was also safe. The concordance of risk factors and incidence of carotid stenosis correlated well with other studies.