Application of surface chemical analysis tools for characterization of nanoparticles.

The important role that surface chemical analysis methods can and should play in the characterization of nanoparticles is described. The types of information that can be obtained from analysis of nanoparticles using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary-ion mass spectrometry (TOF-SIMS), low-energy ion scattering (LEIS), and scanning-probe microscopy (SPM), including scanning tunneling microscopy (STM) and atomic force microscopy (AFM), are briefly summarized. Examples describing the characterization of engineered nanoparticles are provided. Specific analysis considerations and issues associated with using surface-analysis methods for the characterization of nanoparticles are discussed and summarized, with the impact that shape instability, environmentally induced changes, deliberate and accidental coating, etc., have on nanoparticle properties.

Dieulafoy lesion: endoscopic and surgical management.

Dieulafoy lesion is characterized by exteriorization of a large pulsatile arterial vessel through a minimal mucosal tear surrounded by normal mucosa, causing massive and recurrent upper digestive bleeding in previously healthy patients. More frequently presented than diagnosed, with the increase of its knowledge among endoscopists, a large number of cases are expected in the literature. Data from patients with upper gastrointestinal bleeding submitted to endoscopy at the Federal University of São Paulo, Gastrointestinal Endoscopy Unit from 1991 through 2002 were reviewed for Dieulafoy lesion. We found 15 patients with typical Dieulafoy gastric lesion. Their ages ranged from 18 to 78 years (mean age 49.9); 5 patients were female and 10 were male. Bleeding presented as hematemesis and melena in 7 cases (46.6%), hematemesis alone in 4 cases (26.6%), and melena alone in the other 4 cases (26.6%). Initial hemostatic approaches employed were: alcoholization (2 cases), epinephrine associated with alcohol injection (5 cases), sclerosis in 7 cases and surgery in 1 case. Dieulafoy lesion is a distinct nosologic entity that must be suspected in patients with massive digestive bleeding. Endoscopy became the procedure of choice for diagnosis and treatment of this disease.

Phonons localized at step edges: a route to understanding forces at extended surface defects.

Inelastic helium atom scattering has been used to measure the phonons on a stepped metallic crystalline surface, Ni(977). When the scattering plane is oriented parallel to the step edges and perpendicular to the terraces, two branches of step-induced phonons are observed. These branches are identified as transversely polarized, step-localized modes that propagate along the step edge. Analysis reveals significant anisotropy in the force field near the step edge, with all forces near the step edge being substantially smaller than in the bulk. Such measurements provide valuable information on metallic bonding and interface stability near extended surface defects.