Formation of graphitic films on Cu(111) via electron beam induced deposition

Electron beam induced deposition using ethylene as precursor gas is used to generate carbonaceous films on Cu(111). The study was performed in an ultrahigh vacuum chamber for two different precursor gas pressures, and two substrate temperatures. Auger electron spectroscopy and reflection electron energy loss spectroscopy were used to characterize the film growth process in-situ. These techniques allowed us to determine how the deposited film covers the Cu(111) substrate as a function of the ethylene exposure, obtaining a final coverage of up to 0.8 monolayer, depending on the growing conditions. Based on the CKLL Auger line shape and on the reflection electron energy loss (REELS) spectra we can conclude on the graphitic characteristics of the grown film and on the optimum growing conditions: lower substrate temperature and higher ethylene pressure. Raman spectroscopy and scanning tunneling spectroscopy were used as ex-situ techniques to assess the properties of the grown film. Results from both techniques indicate that the film consists of small (10–20 nm in size) nanocrystals of few (1–2) layers graphene. Once optimized, this method may allow growing graphene with a predesigned pattern, without the need to heat the substrate at high temperatures.Fil: Bonetto, Fernando Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Silva, C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Ferreira, E.H. Martins. Instituto Nacional de Metrologia, Qualidade E Tecnologi; BrasilFil: Candia, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Passeggi, Mario Cesar Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Montoro, Silvia Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Vidal, Ricardo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentin

Prevalence and antibiotic susceptibility of coagulase-negative Staphylococcus species from bovine subclinical mastitis in dairy herds in the central region of Argentina

AbstractCoagulase-negative staphylococci (CNS) are a common cause of bovine subclinical mastitis (SCM). The prevalence of CNS species causing SCM identified by genotyping varies among countries. Overall, the antimicrobial resistance in this group of organisms is increasing worldwide; however, little information exists about a CNS species resistant to antibiotics. The aim of the present study was to genotypically characterize CNS at species level and to determine the prevalence and antibiotic resistance profiles of CNS species isolated from bovine SCM in 51 dairy herds located in the central region of the province of Cordoba, Argentina. In this study, we identified 219 CNS isolates at species level by PCR-restriction fragment length polymorphism of the groEL gene. Staphylococcus chromogenes (46.6%) and Staphylococcus haemolyticus (32%) were the most prevalent species. A minimum of three different CNS species were present in 41.2% of the herds. S. chromogenes was isolated from most of the herds (86.3%), whereas S. haemolyticus was isolated from 66.7% of them. The broth microdilution method was used to test in vitro antimicrobial susceptibility. Resistance to a single compound or two related compounds was expressed in 43.8% of the isolates. S. chromogenes and S. haemolyticus showed a very high proportion of isolates resistant to penicillin. Resistance to two or more non-related antimicrobials was found in 30.6% of all CNS. S. haemolyticus exhibited a higher frequency of resistance to two or more non-related antimicrobials than S. chromogenes