PubMed Health⌕ Search

Biomedical subjects

G Mikaelian

Publications and source records attributed to G Mikaelian.

4 recordsLinked to original sources

Atomic scale control of single molecule charging.

A scanning tunneling microscope was used to study charging of single copper phthalocyanine molecules adsorbed on an ultrathin Al(2)O(3) film grown on a NiAl(110) surface. A double-barrier tunnel junction is formed by a vacuum barrier between the tip and the molecule and an oxide barrier between the molecule and the NiAl. In this geometry the molecule can be charged by the tunneling electrons. This charging was found to be strongly dependent on the position of the tip above the molecule and the applied bias voltage.

Journal Article↗

Electronic properties of artificial Au chains with individual Pd impurities.

Artificial Au atomic chains with individual Pd impurities were assembled from single metal atoms with a scanning tunneling microscope on a NiAl(110) surface. Scanning tunneling spectroscopy (STS) revealed an electronic resonance 2.15 eV above the Fermi energy localized within 4 A of single Pd atom impurities and two electronic resonances 2.25 eV and 2.95 eV above the Fermi energy localized within 8 A of Pd dimer impurities. The emergence of these localized resonances was studied by STS at each stage of the atom-by-atom assembly. Additionally, conductance images of the chains revealed delocalized electronic density oscillations in the pure Au segments of the chains.

Journal Article↗

Comparative in vitro activity of gemifloxacin against gram-positive and gram-negative clinical isolates in Argentina.

The in vitro activity of gemifloxacin against 1,000 clinical isolates of 147 Streptococcus pneumoniae (115, penicilin susceptible; 26, intermediate penicillin-resistant and 6, penicillin-resistant), 127 Hemophilus influenzae (109, beta lactamasa non-producer; 18, beta lactamase producers), 95 Streptococcus pyogenes (6, azytromycin-resistant), 84 Moraxella catarrhalis (79, beta lactamase producers), 110 Staphilococcus aureus (89, methicillin-susceptible; 21, methicilin-resistant), 98 Eenterococcus faecalis and 339 Enterobacteriacea, (recovered from patients with respiratory tract infection; skin and soft tissue infection and urinary tract infection), was compared with the activities of four fluorquinolones and five other antimicrobial agents. Of the quinolones tested, gemifloxacin was the most potent against Streptococcus pneumoniae, including penicillin intermediate and resistant strains. Mic(90) values obtained for gemifloxacin, ciprofloxacin, ofloxacin, levofloxacin and trvafloxacin were 0.03, 2, 2, 1 and 0.25 mg/L respectively. Gemifloxacin was 16 fold more potent than ciprofloxacin against methicillin-susceptible Staphylococcus aureus and 32 fold more potent than ciprofloxacin against Streptococcus pyogenes. When tested against Hemophilus influenzae, Moraxella catarrhalis and Enterobacteriaceae, all the quinolones showed similar activity. Our results demonstrate that gemifloxacin has similar activity than the other quinolones tested against Gram-negative organisms and is considerably more potent against Gram-positive organisms.

Anti-Infective Agents↗

[Microbiology and conservative surgery of serious infections of the diabetic foot].

Between June of 1987 and August 1988 we evaluated 31 diabetic patients hospitalized for severe foot infections to determine the etiologic agents, the value of the bacteriologic samples obtained, the benefits of conservative surgery and variable predictors of a major amputation. Sixteen patients suffered from necrosis, 16 osteomyelitis, 14 ulcers, 5 cellulitis, and/or abscesses and 22 had vascular compromise. Samples were taken from these infections excluding necrotic material. We isolate 76 microorganisms (2.4/pt), 57% Gram-positive cocci (predominantly S. aureus and enterococci), and 43% Gram-negative bacilli. Anaerobes were not isolated probably secondary to the exclusion of necrotic samples. There was high incidence of skin and soft tissue sampling (79%) bone (13/16) and surgical curettage (11/11). In 9 patients the correlation of soft tissue sampling and bone sampling was assessed with a positive correlation with respect to Gram-positive cocci. Twenty-one patients required conservative surgeries of the foot (9 underwent revascularization), 67% of which avoided a mayor amputation. However no significant variables predictive of a major amputation were detected in this study. In summary, the conservative surgery allowed to 2 out of 3 patients to preserve the foot.

Adult↗