127 results on '"Vélez M."'
Search Results
2. Desarrollo de nuevos procesos de operación y administración, soportados en innovación organizacional y herramientas de tecnologías de información para una empresa del sector automotor.
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Vélez, M. A., Sánchez, C. M., and Fuquen, H. S.
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HONDA motorcycle , *DIGITAL technology , *MOTORCYCLE dealers , *ECONOMIES of scale , *BUSINESS expansion - Abstract
The following article shows how the growing motorcycle market has created the need to innovate the business architecture of the assemblers and the distribution and commercialization networks, in order to obtain economies of scale and to improve productivity and competitiveness. The text provides a brief description of concepts relating to the digital business transformation methodology, as well as a description of its application in the technological and organizational development project in FANALCA S.A and the HONDA Motorcycles dealership network. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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3. Magnetic order of Cr thin films in Nb/Cr/Fe-nanoisland hybrid: A comparative study between magnetic and superconducting properties.
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Navarro, E., Vélez, M., Huttel, Y., Junquera, A. Pérez, Martín, J. I., de Lima, O. F., Cebollada, A., Alameda, J. M., and Vicent, J. L.
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ELECTROMAGNETIC induction , *DIELECTRICS , *HYSTERESIS loop , *MAGNETIC materials , *THIN films , *SOLID state electronics - Abstract
Shifted hysteresis loops characteristic of the exchange bias effect between a ferromagnet and an antiferromagnet are demonstrated in structures formed by a 2.5 nm Cr layer deposited on top of an array of Fe nanoislands (Cr/Fe-nanoislands). This effect evidences the persistence of antiferromagnetic (AF) order for Cr layers much thinner than the thickness reported in the literature. The field shift measured is found to increase for the smallest island sizes, which can be related with the enhancement of the Fe-nanoisland surface to volume ratio. The comparative study between superconducting proximity effects in Nb/Cr/Fe-nanoislands and Nb/normal metal/Fe-nanoisland hybrids (where the normal metals used are Al and Pt) confirms the presence of AF order in the 2.5 nm Cr spacer layer. A much shorter penetration depth of the Cooper pairs into the AF Cr layers than in the normal metal Pt and Al spacer layers is deduced. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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4. Behavior and gut bacteria of Partamona helleri under sublethal exposure to a bioinsecticide and a leaf fertilizer.
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Botina, L.L., Vélez, M., Barbosa, W.F., Mendonça, A.C., Pylro, V.S., Tótola, M.R., and Martins, G.F.
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FERTILIZERS , *STINGLESS bees , *SPINOSAD , *COPPER sulfate , *BIOFERTILIZERS , *FOOD consumption , *GUT microbiome , *FERTILIZER application - Abstract
The exposure of bees to agrochemicals during foraging and feeding has been associated with their population decline. Sublethal exposure to agrochemicals can affect behavior and the microbiota. Gut microbiota is associated with insect nutritional health, immunocompetence, and is essential for neutralizing the damage caused by pathogens and xenobiotics. Research on the effect of the bioinsecticides and fertilizers on the microbiota of bees remains neglected. In this study, we assessed the sublethal effect of both bioinsecticide spinosad and the fertilizer copper sulfate (CuSO 4) on the behavior and gut microbiota in forager adults of the stingless bee Partamona helleri (Friese), which is an important pollinator in the Neotropical region. Behavioral assays and gut microbiota profiles were assessed on bees orally exposed to estimated LC 5 values for spinosad and CuSO 4. The microbiota were characterized through 16S rRNA gene target sequencing. Acute and oral sublethal exposure to spinosad and CuSO 4 did not affect the overall activity, flight take-off, and food consumption. However, CuSO 4 decreased bee respiration rate and copper accumulated in exposed bees. Exposure to spinosad increased the proportional abundance of the genus Gilliamella, but CuSO 4 did not alter the composition of the gut microbiota. In conclusion, sublethal exposure to CuSO 4 induces changes in respiration, and spinosad changes the abundance of gut microorganisms of P. helleri. Image 108 • Partamona helleri survival was affected by exposures to spinosad and copper sulfate. • The overall behavior was not affected by the exposures. • The respiration rate of bees changed after exposure to copper sulfate. • The richness of the gut bacteria was not affected by the exposures. • Abundance of bacteria of the genus Gilliamella increased after spinosad exposure. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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5. Application of Saccharomyces cerevisiae var. boulardii in food processing: a review.
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Lazo‐Vélez, M. A., Serna‐Saldívar, S. O., Rosales‐Medina, M. F., Tinoco‐Alvear, M., and Briones‐García, M.
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SACCHAROMYCES cerevisiae , *EFFECT of food processing on nutrition , *FERMENTED foods , *PROBIOTICS , *FUNCTIONAL foods - Abstract
Summary: Probiotics are increasingly being added to food in order to develop products with health‐promoting properties. Particularly, Saccharomyces cereviceae var. boulardii yeast is recently being investigated like a starting‐culture for development of functional and probiotic foods. Although the literature is abundant on the beneficial effects of S. boulardii on health, slight information is available on the effects of supplementing this probiotic to food systems. The aim of this paper is to examine the applications of S. boulardii to different food matrices and its implication in food processing (stability, sensorial properties and other technological implications) and the concomitant effects on nutrition and health. [ABSTRACT FROM AUTHOR]
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- 2018
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6. Resultados funcionales y complicaciones del uso del clavo cefalomedular en el tratamiento de las fracturas de cadera.
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Vélez, M., Palacios-Barahona, U., Arango-Posada, M. M., and Ramos-Castañeda, J.
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Introduction: Cephalomedullary nails are used for the treatment of hip fractures; however, there are few studies that allow identifying data on the complications of the use of these devices and the results in terms of restoration of the functionality of the patient. Methods: A cross-sectional study of patients with femur fracture was conducted during the period from January 2008 to December 2012. Data on demographic and clinical variables were collected. Telephone follow-up was performed up to six postoperative months. A descriptive analysis was done using absolute and relative frequency measurements. Quantitative variables are presented with averages and standard deviation or median and interquartile range, according to the normality of the data. Results: 82.9% of the patients managed to walk with or without help within six months after surgery; anemia (16.2%), urinary tract infection (9.7%), pneumonia (9.5%) and myocardial infarction (0.7%) were the main complications. Of the patients included, 57.1% had an ASA level ≥ 3; a mortality rate of 16% was identified. Discussion: Cephalomedullary nails show positive results regarding recovery of functional mobility and a low prevalence of complications, with similar mortality to that reported in the literature at 6 months of follow up. [ABSTRACT FROM AUTHOR]
- Published
- 2018
7. Effect of fiber surface treatment on the incorporation of carbon nanotubes and on the micromechanical properties of a single-carbon fiber-epoxy matrix composite.
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Muñoz-Vélez, M. F., Valadez-González, A., and Herrera-Franco, P. J.
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SURFACE preparation , *CARBON nanotubes , *MULTIWALLED carbon nanotubes , *CARBON fibers , *CATIONIC polymers , *FIBER-matrix interfaces - Abstract
Multiwall carbon nanotubes (MWCNTs) previously treated with a cationic polymer were incorporated on the surface of carbon fibers modified by three different chemical treatments, namely, oxidation, oxidation-silanization and oxidation- pre-impregnation. Prior to the incorporation of the MWCNTs, the physical surface properties of the fibers were studied by contact angle and the chemical surface properties by X-ray photoelectron spectroscopy (XPS). The interfacial shear strength (IFSS) of the different systems carbon fiber-MWCNTs-matrix was evaluated using the single-fiber fragmentation test (SFFT) and it was observed that the IFSS of the oxidized-pre-impregnated fibers, was considerably higher than that observed for the other fiber-matrix systems. This was attributed to enhanced interfacial interactions because the fiber surface treatments improved the wettability of the carbon fiber and the MWCNTs, which resulted in a better fiber-matrix mechanical interlocking and to the formation of covalent bonds between the different phases of the composite. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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8. Magnetic stripes and holes: Complex domain patterns in perforated films with weak perpendicular anisotropy.
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Valdés-Bango, F., Vélez, M., Alvarez-Prado, L. M., Alameda, J. M., and Martín, J. I.
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CRYSTALLOGRAPHY , *ANISOTROPY - Abstract
Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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9. Plasmin and coagulant activities in a minicurd model system: Study of technological parameters.
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Vélez, M. A., Perotti, M. C., Candioti, M. C., Bergamini, C. V., and Hynes, E. R.
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CURD (Dairy product) , *PLASMIN , *COAGULANTS , *CHEESE , *WHEY , *ELECTROPHORESIS , *COOKING - Abstract
The effect of scalding temperature of the curd, the inclusion of a washing step, and the pH at whey drainage on plasmin and coagulant activities were assessed in a minicurd model of young hard cooked cheese. The variables were tested as follows: draining pH was assayed at 3 levels (4.6, 5.6, and 6.4), curd scalding temperature was tested at 50 and 56°C, and washing of the curd was examined at 2 levels (no washing step, and the replacement of the whey by water). Increase in pH at whey drainage and washing of the curd had a positive effect on plasmin activity, which was also evidenced by compatible changes in soluble peptide profiles. No effect of increased cooking temperature was found on plasmin activity. Plasminogen activation was not verified in any treatment. As for coagulant, lower pH values at whey drainage and a decrease in curd cooking temperature increased its activity; washing of the curd showed no influence on coagulant residual activity. These results were consistent with proteolysis described by peptide profiles, electrophoresis, and soluble nitrogen fractions. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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10. Female digit length ratio (2D:4D) and time-to-pregnancy.
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Vélez, M. P., Arbuckle, T. E., Monnier, P., and Fraser, W. D.
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HUMAN fertility , *PREGNANCY , *FETAL development , *STEROID hormones , *EPIDEMIOLOGY , *FINGERS , *ANTHROPOMETRY , *FERTILITY , *QUESTIONNAIRES , *RESEARCH funding , *BODY mass index , *ANATOMY - Abstract
Study Question: Is the female 2th- to 4th-finger ratio (2D:4D) associated with fecundity as measured by time-to-pregnancy (TTP)?Summary Answer: Our study does not support an association between female 2D:4D and TTP.What Is Known Already: The 2th- to 4th-finger ratio (2D:4D) has been proposed as a potential indicator of greater androgen exposure during fetal development. Women exposed in utero to unbalanced steroid hormones may have impaired fecundity in the adulthood. Fecundity is often measured by TTP, an epidemiological tool commonly used to assess the impact of environmental factors in human conception.Study Design, Size, Duration: The Maternal-Infant Research on Environmental Chemicals (MIREC) Study is a pregnancy and birth cohort of 2001 women recruited before 14 weeks of gestation in 10 cities across Canada between 2008 and 2011. The present analysis is part of MIREC-CD Plus, a follow-up study in a subsample of some 800 MIREC mothers and their children from 2012 to 2015.Participants/materials, Setting, Methods: TTP and maternal characteristics were collected from questionnaires administered during the first trimester of pregnancy as part of the MIREC study. Digital pictures of the ventral surface of both hands were obtained in the MIREC mothers at the MIREC-CD Plus follow-up study. The 2D:4D was calculated as the ratio of the second and fourth fingers of each hand. The exposure of interest was the 2D:4D of the women categorized by tertiles, or dichotomized as ≥1 (index finger longer than the ring finger) or <1 (ring finger longer than the index finger, implying greater androgen exposure during fetal development). The final sample included 696 mothers. Statistical analyses included discrete-time Cox proportional hazard models, allowing adjustment for potential confounding factors.Main Results and the Role Of Chance: There was no evidence of diminished/increased fecundability according to the 2D:4D, neither on the right nor on the left hand. In our analysis by tertiles, the smallest 2D:4D (i.e. higher androgen exposure during fetal life) resulted in FORs higher than 1 (i.e. shorter TTP) in both hands, although this was not statistically significant (FOR 1.19 [95% CI 0.93, 1.51] in the right hand and 1.16 [95% CI 0.91, 1.47] in the left hand). In the dichotomous analysis, 2D:4D <1 resulted in FORs higher than 1 (i.e. shorter TTP), but this was also not statistically significant (FOR 1.08 [95% CI 0.88, 1.33] in the right hand and 1.14 [95% CI 0.92, 1.42] in the left hand). Our large sample size resulted in a high statistical power to exclude an association between female 2D:4D and TTP.Limitations, Reasons For Caution: The MIREC Study is a cohort of pregnant women, and therefore, women with infertility were excluded by design from our study.Wider Implications Of the Findings: Our data do not provide evidence for an association between female 2D:4D and fecundity as measured by TTP. Whether the female 2D:4D is a marker of in utero androgen exposure and whether it is associated with fecundity have yet to be determined.Study Funding/competing Interest: The MIREC Study was funded by Health Canada's Chemicals Management Plan, the Canadian Institute of Health Research (CIHR grant # MOP - 81285), and the Ontario Ministry of the Environment. MIREC-CD Plus was funded by Health Canada's Chemicals Management Plan Research Fund. The 2D:4D component was funded by a research grant from the CIHR-Quebec Training Network in Perinatal Research (QTNPR). M.P. Vélez was supported by a CIHR Fellowship Award, and a QTNPR scholarship. P. Monnier is supported by the Research Institute of the McGill University Health Centre. W.D Fraser is supported by a CIHR Canada Research Chair. There are no conflicts of interest to declare. [ABSTRACT FROM AUTHOR]- Published
- 2016
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11. Action of fosetyl-al and metalaxyl against Phytophthora austrocedri.
- Author
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Silva, P. V., Vélez, M. L., Hernández Otaño, D., Nuñez, C., Greslebin, A. G., and Osswald, W.
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PHYTOPHTHORA , *METALAXYL , *AUSTROCEDRUS , *FUNGAL diseases of plants , *FORESTS & forestry - Abstract
Fosetyl-Al and metalaxyl, the most commonly used systemic fungicides against Phytophthora, were evaluated for their efficacy to control Phytophthora austrocedri, the pathogen that causes a serious disease at the Austrocedrus chilensis forests in Patagonia. The effect of the chemicals on pathogen development in vitro and in planta was analysed. Both chemicals were shown to protect plants from the pathogen. In vitro assays showed that asexual reproduction was sensitive to both chemicals. However, mycelial growth and sexual reproduction, which were clearly sensitive to metalaxyl, were sensitive only to high concentrations of fosetyl-Al. Fosetyl-Al and metalaxyl had almost the same efficacy when applied preventively by soil drench to seedlings. This difference between in vitro and in planta results can be attributed to the dual action of fosetyl-Al, not only inhibiting the pathogen but also stimulating host defence. In adult trees, preventive and curative treatments were tested, but only the fosetyl-Al preventive treatment was effective in the assayed conditions. Interestingly, seedlings pretreated with both fungicides were less susceptible to the effectors secreted by the pathogen. Our results indicate that fosetyl-Al and metalaxyl provide some resistance to the plant besides the fungistatic direct action on the pathogen. Further studies to elucidate a possible resistance-inducing activity of these chemicals and the mechanisms involved are underway. [ABSTRACT FROM AUTHOR]
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- 2016
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12. Biofilm formation and motility of Xanthomonas strains with different citrus host range.
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Sena‐Vélez, M., Redondo, C., Gell, I., Ferragud, E., Johnson, E., Graham, J. H., and Cubero, J.
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BIOFILMS , *XANTHOMONAS , *CITRUS canker , *HOSTS (Biology) , *SCANNING electron microscopy - Abstract
Xanthomonas citri subsp . citri (Xcc) strain A is the causal agent of citrus bacterial canker ( CBC) on most Citrus spp. and close relatives. Two restricted host range strains of CBC, Aw and A*, from Florida and southwest Asia, respectively, infect Mexican lime. Several studies have linked biofilm formation by Xcc to bacterial colonization prior to and after plant ingress, but none have evaluated connections between biofilm formation and the behaviour of different strains of Xcc on citrus hosts and non-hosts. In this study biofilm formation and swimming motility were evaluated for citrus pathogenic xanthomonads including wide and restricted host range strains of Xcc, X. alfalfae subsp. citrumelonis (Xac) (the causal agent of citrus bacterial spot) and X. campestris pv. campestris (Xc). Differential biofilm formation was observed in vitro and in planta among the Xanthomonas strains assayed. Minimal medium XVM2 increased biofilm formation, especially for those strains with a host range restricted to Mexican lime. In planta, strains produced more biofilm on leaves or fruits of their host than on non-hosts. Scanning electron microscopy of biofilms on leaf and fruit surfaces revealed differences in structure of bacterial aggregates with respect to the strain's host range. In addition, swimming motility varied widely depending on the host range of the strain. It was concluded that biofilm formation in vitro and in planta for strains of Xcc and Xac was related to their host range, as these processes affect colonization at the early stages of the infection process. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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13. Short communication: A new minicurd model system for hard cooked cheeses.
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Vélez, M. A., Perotti, M. C., Rebechi, S. R., and Hynes, E. R.
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CURD (Dairy product) , *CHEESE , *CHEESE industry , *FREEZING , *CHEESEMAKING - Abstract
The aim of this study was to propose and validate a new minicurd model of young hard cheese. Curd particles and whey obtained from conventional cheese making of Reggianito Argentino were separated and frozen. Then, both fractions were thawed and the mixture of whey and curds was reconstituted, from which minicurds were made on the laboratory scale. Repeatability and the effect of freezing on minicurd composition were investigated by assessing pH, protein and moisture contents, sodium chloride content, and total thermophilic lactic flora counts. Good repeatability was achieved, and no significant differences were found between minicurds made from fresh compared with frozen materials. Composition of the minicurd was appropriate for modeling Reggianito Argentino cheese. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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14. Tratamiento con vitamina E en pacientes con esteatohepatitis no alcohólica.
- Author
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Vélez M., Jhonathan Ferney, Crespo H., Gustavo Amador, and Restrepo G., Juan Carlos
- Abstract
Nonalcoholic Steatohepatitis (NASH) is characterized histologically by the ballooning of hepatocytes, lobular inflammation and steatosis. If this diagnosis is suspected, it is important to exclude other causes of liver damage, especially excessive consumption of alcohol. Nevertheless, to date, a biopsy is the only method available to confirm the diagnosis. Vitamin E should be considered a first-line therapy for treatment of this disease because several clinical studies have shown that a dose of 800 UI/day improves the histology of non-diabetic adults suffering from NASH even when there is no significant impact on fibrosis. These results were confirmed by biopsies. Despite the proven benefits of the use of this drug, it is important to be aware that its use cannot replace changes in diet and exercise but rather should be seen as a complement to these measures. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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15. Low voltage distribution system planning using diversified demand curves.
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Vélez M., Víctor M., Hincapíe I., Ricardo A., and Gallego R., Ramón A.
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LOW voltage systems , *ELECTRIC power distribution , *ELECTRIC transformers , *NODAL analysis , *PARAMETER estimation - Abstract
Highlights: [•] This paper solves the problem of low voltage distribution system planning. [•] It takes into account diversified peak demand to estimate nodal power injection. [•] It considers installation of new elements and upgrading of existing elements. [•] Additionally it introduces relocation of distribution transformers. [•] This paper compares the results of three scenarios of demand. [Copyright &y& Elsevier]
- Published
- 2014
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16. Universal coverage of IVF pays off.
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Vélez, M P, Connolly, M P, Kadoch, I-J, Phillips, S, and Bissonnette, F
- Published
- 2014
17. Evidence of low levels of genetic diversity for the Phytophthora austrocedrae population in Patagonia, Argentina.
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Vélez, M. L., Coetzee, M. P. A., Wingfield, M. J., Rajchenberg, M., and Greslebin, A. G.
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PLANT diversity , *PHYTOPHTHORA , *PLANT populations , *PATHOGENIC microorganisms , *DISEASE susceptibility , *AMPLIFIED fragment length polymorphism - Abstract
Phytophthora austrocedrae is a recently discovered pathogen that causes severe mortality of Austrocedrus chilensis in Patagonia. The high level of susceptibility of the host tree, together with the distribution pattern of the pathogen, have led to the hypothesis that P. austrocedrae was introduced into Argentina. The aim of this study was to assess the population structure of P. austrocedrae isolates from Argentina in order to gain an understanding of the origin and spread of the pathogen. Genetic diversity was determined based on amplified fragment length polymorphisms ( AFLPs). In total, 48 isolates of P. austrocedrae were obtained from infected A. chilensis trees, representing the geographical range of the host. Four primer combinations were used for the AFLP analysis. Of the 332 scored bands, 12% were polymorphic. Gene diversity ( h) ranged from 0·01 to 0·03; the Shannon index ( I) ranged from 0·01 to 0·04. A high degree of genetic similarity was observed among the isolates (pairwise S values = 0·958-1; 0·993 ± 0·009, mean ± SD). A frequency histogram showed that most of the isolate pairs were identical. Principal coordinate analysis using three-dimensional plots did not group any of the isolates based on their geographical origin. The low genetic diversity (within and between sites) and absence of population structure linked to geographic origin, together with the aggressiveness of the pathogen and the disease progression pattern, suggest that P. austrocedrae might have been introduced into Argentina. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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18. Controlled nucleation of topological defects in the stripe domain patterns of lateral multilayers with perpendicular magnetic anisotropy.
- Author
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Hierro-Rodriguez, A., Vélez, M., Morales, R., Soriano, N., Rodríguez-Rodríguez, G., Álvarez-Prado, L. M., Martín, J. I., and Alameda, J. M.
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NUCLEATION , *MAGNETIC anisotropy , *TOPOLOGICAL defects (Physics) , *MAGNETIC domain , *MAGNETIZATION - Abstract
Magnetic lateral multilayers have been fabricated on weak perpendicular magnetic anisotropy amorphous Nd-Co films in order to perform a systematic study on the conditions for controlled nucleation of topological defects within their magnetic stripe domain pattern. A lateral thickness modulation of period w is defined on the nanostructured samples that, in turn, induces a lateral modulation of both magnetic stripe domain periods w and average in-plane magnetization component Min-plane. Depending on lateral multilayer period and in-plane applied field, thin and thick regions switch independently during in-plane magnetization reversal and domain walls are created within the in-plane magnetization configuration coupled to variable angle grain boundaries and disclinations within the magnetic stripe domain patterns. This process is mainly driven by the competition between rotatable anisotropy (that couples the magnetic stripe pattern to in-plane magnetization) and in-plane shape anisotropy induced by the periodic thickness modulation. However, as the structural period w becomes comparable to magnetic stripe period λ, the nucleation of topological defects at the interfaces between thin and thick regions is hindered by a size effect and stripe domains in the different thickness regions become strongly coupled. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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19. Double percolation effects and fractal behavior in magnetic/superconducting hybrids.
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Ruiz-Valdepeñas, L, Vélez, M, Valdés-Bango, F, Álvarez-Prado, L M, Martín, J I, Navarro, E, Alameda, J M, and Vicent, J L
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MAGNETIC anisotropy , *MAGNETIC properties , *FERROMAGNETIC materials , *MAGNETIC domain , *SUPERCONDUCTIVITY , *FRACTAL dimensions , *NUCLEATION - Abstract
Perpendicular magnetic anisotropy ferromagnetic/superconducting (FM/SC) bilayers with a labyrinth domain structure are used to study nucleation of superconductivity on a fractal network, tunable through magnetic history. As clusters of reversed domains appear in the FM layer, the SC film shows a percolative behavior that depends on two independent processes: the arrangement of initial reversed domains and the fractal geometry of expanding clusters. For a full labyrinth structure, the behavior of the upper critical field is typical of confined superconductivity on a fractal network. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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20. Rapid policy change to single-embryo transfer while maintaining pregnancy rates per initiated cycle.
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Vélez, M. P., Kadoch, I.-J., Phillips, S. J., and Bissonnette, F.
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EMBRYO transfer , *PREGNANCY , *HUMAN reproductive technology , *HUMAN in vitro fertilization , *MULTIPLE pregnancy - Abstract
Public financing of IVF aims at increasing access to treatment while decreasing the expenses associated with multiple pregnancies. Critics argue that it is associated with lower pregnancy rates. This study compared cycles performed during 2009 (before implementation of Quebec's public IVF programme; period I) to those performed in the year following implementation (period II) in a single IVF centre. First fresh cycles in period I (499 women) and first fresh cycles (815 women) along with their corresponding first vitrified--warmed transfer (271 women) in period II were evaluated. From period I to period II, single-embryo transfer increased from 17.3% to 85.0% (P< 0.001), multiple ongoing pregnancy rate decreased from 25.8% to 1.6% (P < 0.001) and ongoing pregnancy rate decreased from 31.9% to 23.3% (P = 0.001). During period II, the ongoing pregnancy rate per vitrified--warmed embryo transfer was 19.2%, leading to a cumulative ongoing pregnancy rate per initiated cycle of 29.7%, which was not different to the pregnancy rate per fresh cycle during period I (31.9%). To conclude, Quebec's public IVF programme decreased multiple pregnancy rates while maintaining an acceptable cumulative ongoing pregnancy rate, a more precise outcome to evaluate the impact of public IVF programmes. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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21. Tatuajes y su eliminación por láser.
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Castro, T., Vélez, M., and Trelles, M. A.
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TATTOO removal , *LASER surgery , *TATTOOING , *PLASTIC surgery , *PLASTIC surgeons - Abstract
Tattoo elimination with optimum cosmetic results is a concern that has always existed. The introduction of laser treatments has represented an important step forward to achieve good results with a minimum of side effects. This study presents the different types of tattoos with their pigment characteristics, origin, and treatment methods, including the use of laser technology and more specifically those lasers with Q-Switch emission, their advantages and limitations The evolution and future applications of laser tattoo removal are also outlined in this study. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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22. Delayed self-incompatibility causes morphological alterations and crop reduction in ‘Ataúlfo’ mango ( Mangifera indica L.).
- Author
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Gehrke-Vélez, M, Castillo-Vera, A, Ruiz-Bello, C, Moreno-Martinez, JL, and Moreno-Basurto, G
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MANGO , *PLANT morphology , *FRUIT culture , *POLLINATION by insects , *GERMINATION , *EMBRYO sac (Botany) , *POLLEN tube , *SEEDLINGS - Abstract
Poor fruit set, premature fruit drop and excessive nubbin production are causing crop reduction in ‘Ataúlfo’ mango orchards in southeastern Mexico. Fruit set was measured in self- and cross-pollinated Ataúlfo mangoes in the field using houseflies (Musca domesticaL.) as pollinators and pollen from donor varieties. Pollen tube kinesis was monitored from pollen germination to arrival at the ovule sac following manual self- and cross-pollination. Cross-pollinated inflorescences produced more fruit set than selfed ones. ‘Joe Welch’ and ‘Criollo’ varieties were the most efficient pollen donors tested. Seedling germination in Ataúlfo mangoes averaged 3% during 2 consecutive years. Pollen tube development in vivo revealed positive contact with the micropyle and normal zygote formation in cross-pollinated flowers. Selfed pollen tubes entered the embryo sac but produced atrophied embryos and aborted or malformed fruit. Seedlessness was not observed although selfed fruitlets contained malformed or necrotic embryos, suggesting delayed self-incompatibility. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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23. Alteration of physiological parameters of Austrocedrus chilensis by the pathogen Phytophthora austrocedrae.
- Author
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Vélez, M. L., Silva, P. V., Troncoso, O. A., and Greslebin, A. G.
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PHYTOPHTHORA diseases , *PLANT-pathogen relationships , *SOIL permeability , *WATER efficiency , *PLANT cells & tissue physiology - Abstract
The effect of the pathogen Phytophthora austrocedrae on tree physiology of Austrocedrus chilensis in Patagonia was studied in a 4-week study. In the first week, stem-inoculated saplings showed a significant decrease in photosynthesis (A) without alteration of stomatal conductance ( gs) or stem-specific hydraulic conductivity (Ks). From the second week on, progressive decreases in A, gs and Ks were observed, concomitantly with development of significant stem lesions. Water use efficiency (WUE) increased in the second week and declined progressively from the third week. Hyphae and resinous materials were observed in tracheids and rays below lesions. Necrosis of parenchyma ray cells and blockage of tracheids torus were observed. Healthy xylem showed no resinous materials or tracheid blockage, but abundant starch in rays, which was absent in altered xylem. The culture filtrate (CF) of the pathogen was shown to induce changes in extracellular pH and conductivity, and increased necrosis in tissues of leaves and stem challenged with CF in vitro. Similar results were obtained in leaf tissues of the inoculated saplings in vivo. CF injection into xylem of saplings induced a decline in A and disturbance of leaf tissue integrity, without altering gs, WUE or Ks. The decrease of A correlated with changes in tissue integrity. A possible mechanism of A. chilensis decline induced by P. austrocedrae is discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
24. Assessment of the uniformity and stability of grapevine cultivars using a set of microsatellite markers.
- Author
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Vélez, M. and Ibáñez, Javier
- Subjects
- *
GRAPE varieties , *MICROSATELLITE repeats in plants , *CULTIVARS , *UNIFORMITY , *PLANT breeders , *ALLELES - Abstract
Solidity of microsatellite markers is a key issue for varietal identification, especially when they are used for legal purposes, what includes their probable future use in the distinctness, uniformity and stability testing of new varieties needed for the granting of Plant Breeders' Rights. Nine grapevine microsatellites (VVS2, VVMD5, VVMD27, VVMD28, ssrVrZAG29, ssrVrZAG62, ssrVrZAG67, ssrVrZAG83 and ssrVrZAG112), which had previously demonstrated its capacity to discriminate any grapevine variety, have been assessed to evaluate its uniformity and stability. 19 varieties were selected, representative of a high diversity for morphological, agronomical, cultural and historical aspects, as well as for microsatellite allele variability. Then, for each variety, uniformity and stability were evaluated through the analysis of 50 plants from each of three different plots, and five plants from each of seven additional plots. Material from 4,137 plants of 229 plots of the 19 varieties was sampled in seven countries. Of 3,654 plants analyzed with the set of nine microsatellites, 3,299 were of the right variety and used for the survey. An average of 172 individual values was studied for each allele of each microsatellite of each variety, and none differences were detected that could not be explained as technical variations, with the exception of several putative chimeras in two varieties. Of the total of 171 variety x microsatellite combinations, only in one combination ('Merlot' x VVMD27) the number of off-types exceeded the threshold allowed. The remaining 170 combinations have been found uniform and stable according to internationally accepted rules. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
25. Somatic Mosaicism Caused by Monoallelic Reversion of a Mutation in T Cells of a Patient with ADA-SCID and the Effects of Enzyme Replacement Therapy on the Revertant Phenotype.
- Author
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Moncada-Vélez, M., Vélez-Ortega, A., Orrego, J., Santisteban, I., Jagadeesh, J., Olivares, M., Olaya, N., Hershfield, M., Candotti, F., and Franco, J.
- Subjects
- *
MOSAICISM , *GENETIC mutation , *T cells , *ADENOSINE deaminase deficiency , *CELLULAR immunity , *GENETIC disorders , *STEM cell transplantation , *NUCLEOTIDE sequence , *PATIENTS - Abstract
Patients with adenosine deaminase (ADA) deficiency exhibit spontaneous and partial clinical remission associated with somatic reversion of inherited mutations. We report a child with severe combined immunodeficiency (T-B- SCID) due to ADA deficiency diagnosed at the age of 1 month, whose lymphocyte counts including CD4+ and CD8+ T and NK cells began to improve after several months with normalization of ADA activity in Peripheral blood lymphocytes (PBL), as a result of somatic mosaicism caused by monoallelic reversion of the causative mutation in the ADA gene. He was not eligible for haematopoietic stem cell transplantation (HSCT) or gene therapy (GT); therefore he was placed on enzyme replacement therapy (ERT) with bovine PEG-ADA. The follow-up of metabolic and immunologic responses to ERT included gradual improvement in ADA activity in erythrocytes and transient expansion of most lymphocyte subsets, followed by gradual stabilization of CD4+ and CD8+ T (with naïve phenotype) and NK cells, and sustained expansion of TCRγδ+ T cells. This was accompanied by the disappearance of the revertant T cells as shown by DNA sequencing from PBL. Although the patient's clinical condition improved marginally, he later developed a germinal cell tumour and eventually died at the age of 67 months from sepsis. This case adds to our current knowledge of spontaneous reversion of mutations in ADA deficiency and shows that the effects of the ERT may vary among these patients, suggesting that it could depend on the cell and type in which the somatic mosaicism is established upon reversion. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
26. Study of serum antioxidant capacity and relation with CA 19-9 and PSA in patients with gastrointestinal tract and prostate tumors
- Author
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López Vélez, M. and Martínez Martínez, F.
- Subjects
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PROSTATE cancer , *DIAGNOSIS , *ANTIOXIDANTS , *GASTROINTESTINAL system , *TUMOR markers , *FREE radicals , *PROSTATE-specific antigen , *OXIDATIVE stress , *SERUM - Abstract
Abstract: Objectives: We undertook the present study to investigate the possible relation between total antioxidant capacity (TAC) and tumor marker (TM) values in serum samples of patients with and without gastrointestinal tract and prostate tumors. Design and methods: We measured the TAC using trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorption capacity (ORAC) assays in 80 serum samples: 20 presented elevated values of CA 19-9; 20 had elevated PSA levels and two groups of 20 samples had values within reference ranges respectively. Results: Total antioxidant capacity – measured using the two different analytical methods – was higher in serum samples from patients with elevated CA 19-9 and PSA levels. This antioxidant status, measured by ORAC assay, correlated significantly with CA 19-9 (r: 0.502, P <0.05) and PSA (r:0.792, P <0.001) when the values of these tumor markers were pathological. Conclusions: We concluded that increased serum TAC of the patients with altered levels of CA 19-9 and PSA may be due to the response of increased reactive oxygen species and can be considered as a sign of oxidative stress of these patients. We know that tumor markers are a useful tool for follow-up care of oncologic patients, whereas their role in the diagnosis of a malignancy is controversial. Therefore, the evaluation of serum antioxidant capacity in these pathological processes could contribute to improve diagnosis of these patients. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
27. Reproductive Isolation Between Two Populations of Spodopterafrugiperda (Lepidoptera: Noctuidae) Collected in Corn and Rice Fields From Central Colombia.
- Author
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VELÁSQUEZ-VÉLEZ, M. I., SALDAMANDO-BENJUMEA, C. I., and RÍOS-DIEZ, J. D.
- Abstract
Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a Neotropical moth that has diverged into corn, Zea mays L., and rice, Oryza sativa L., host strains because these plants are their most frequently used hosts. The corn strain also has been found in cotton, Gossypium hirsutum L., and sorghum, Sorghum bicolor (L.) Moench, and the rice strain in small grasses and pasture grasses. Studies of the reproductive isolation between these two strains have provided ambiguous results from populations in the United States. In Colombia, we tested pre- and postzygotic isolation in these strains. Both strains showed postzygotic isolation for several life-history traits, including number of egg masses, number of larvae, number of females, pupal developmental time, female and male longevity, and female and male pupal weight. We observed a reduction of the number of hybrid females and a reduction in fertility in hybrids in S. frugiperda. These results suggest the possibility of Haldane's rule. Heterosis in the F1(2) and F2(1) generations was observed for number of larvae and adult longevity. This line presented a high standard deviation, suggesting instability in this cross. A possible effect of the X chromosome may explain the reduction in viability and sterility in F1 hybrids of host strains of S. frugiperda. No temporal isolation was observed between the corn and rice strains. Differences in longevity between corn and rice strains might be another form of temporal isolation between these strains, because differences in adulthood time might reduce the encounters between them and thus hybridization. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
28. Optical Investigation of ZnO Nanowires.
- Author
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Martínez-Criado, G., Hernández-Vélez, M., Letard, I., Cros, A., Cantarero, A., Mínguez-Bacho, I., Susini, J., Tucoulou, R., Sans, J. A., Sanz, R., and Vázquez, M.
- Subjects
- *
ZINC oxide , *X-ray spectroscopy , *PHOTOLUMINESCENCE , *RAMAN effect , *NANOWIRES , *NANOSTRUCTURED materials , *OXIDATION-reduction reaction , *ALUMINUM oxide , *OXIDES - Abstract
In this study we report the application of synchrotron X-ray fluorescence, photoluminescence and Raman scattering techniques to the analysis of the incorporation of impurities in unintentionally doped ZnO nanowires. Highly ordered one-dimensional ZnO arrays were fabricated by an oxidation process of Zn metal electrodeposited in nanoporous anodic alumina template. X-ray fluorescence data show the contribution of residual elements into the ZnO nanowires growth. A rough analytical quantification of the main light and heavy chemical contents derives impurity concentrations below 1%. The optical efficiency of ZnO nanowires is strongly affected by non-radiative centers up to temperatures as low as 100 K. The photoluminescence was found to be totally dominated by optical transitions associated with the anodic alumina template. Finally, the Raman scattering provides no evidence of local vibrational modes or secondary phases, but it shows the unambiguous signature of the ZnO hexagonal phase. [ABSTRACT FROM AUTHOR]
- Published
- 2010
29. Molecular markers for establishing distinctness in vegetatively propagated crops: a case study in grapevine.
- Author
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Ibáñez, Javier, Vélez, M. Dolores, de Andrés, M. Teresa, and Borrego, Joaquín
- Subjects
- *
LOCUS (Genetics) , *GENETIC polymorphisms , *POPULATION genetics , *GENES - Abstract
Distinctness, uniformity and stability (DUS) testing of varieties is usually required to apply for Plant Breeders’ Rights. This exam is currently carried out using morphological traits, where the establishment of distinctness through a minimum distance is the key issue. In this study, the possibility of using microsatellite markers for establishing the minimum distance in a vegetatively propagated crop (grapevine) has been evaluated. A collection of 991 accessions have been studied with nine microsatellite markers and pair-wise compared, and the highest intra-variety distance and the lowest inter-variety distance determined. The collection included 489 different genotypes, and synonyms and sports. Average values for number of alleles per locus (19), Polymorphic Information Content (0.764) and heterozygosities observed (0.773) and expected (0.785) indicated the high level of polymorphism existing in grapevine. The maximum intra-variety variability found was one allele between two accessions of the same variety, of a total of 3,171 pair-wise comparisons. The minimum inter-variety variability found was two alleles between two pairs of varieties, of a total of 119,316 pair-wise comparisons. In base to these results, the minimum distance required to set distinctness in grapevine with the nine microsatellite markers used could be established in two alleles. General rules for the use of the system as a support for establishing distinctness in vegetatively propagated crops are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
30. Superconducting vortex pinning with artificial magnetic nanostructures
- Author
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Vélez, M., Martín, J.I., Villegas, J.E., Hoffmann, A., González, E.M., Vicent, J.L., and Schuller, Ivan K.
- Subjects
- *
MAGNETIC structure , *NANOELECTROMECHANICAL systems , *NANOSTRUCTURES , *THIN films - Abstract
Abstract: This review is dedicated to summarizing the recent research on vortex dynamics and pinning effects in superconducting films with artificial magnetic structures. The fabrication of hybrid superconducting/magnetic systems is presented together with the wide variety of properties that arise from the interaction between the superconducting vortex lattice and the artificial magnetic nanostructures. Specifically, we review the role that the most important parameters in the vortex dynamics of films with regular array of dots play. In particular, we discuss the phenomena that appear when the symmetry of a regular dot array is distorted from regularity towards complete disorder including rectangular, asymmetric, and aperiodic arrays. The interesting phenomena that appear include vortex-lattice reconfigurations, anisotropic dynamics, channeling, and guided motion as well as ratchet effects. The different regimes are summarized in a phase diagram indicating the transitions that take place as the characteristic distances of the array are modified respect to the superconducting coherence length. Future directions are sketched out indicating the vast open area of research in this field. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
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31. Identification and characterization of starter lactic acid bacteria and probiotics from Columbian dairy products.
- Author
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Vélez, M. Perea, Hermans, K., Verhoeven, T. L. A., Lebeer, S. E., Vanderleyden, J., and De Keersmaecker, S. C. J.
- Subjects
- *
ANTIBIOSIS , *BILE acids , *YOGURT , *LACTIC acid bacteria , *EPITHELIAL cells , *MICROBIOLOGY - Abstract
Aims: Considering the significant rise in the probiotic market in Columbia, and given the lack of reports concerning the microbial population and strain performance in products from different producers, this study aims at determining the number of viable starter bacteria and probiotics in bio-yoghurts available at the Columbian market, identifying the species and analysing the performance of the isolated strains in bile acid resistance, antagonistic activity against pathogens, and adherence capacity to human intestinal epithelial cells. Methods and Results: Seven bio-yoghurts were analysed for the bacterial species present. Species identification was carried out using 16S rRNA gene targeted PCR. The cultured bacteria were tested for bile acid resistance, adherence to a human intestinal epithelial cell line, and antagonism against the pathogen Salmonella enterica serovar Typhimurium. A total of 17 different strains were identified. Based on plate counting, all bio-yoghurts have at least total viable cells of ∼107 CFU ml−1. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus were the most frequently isolated bacteria. Viable Bifidobacterium was only recovered from one product. However, after PCR analysis, DNA of this genus was confirmed in five out of seven products. Major differences were found for S. typhimurium antagonism. The adherence capacity to Caco-2 cells was observed in 10 of the isolated strains. In general, low survival to simulated gastric juice was observed. Conclusions: Some of the isolated strains have probiotic potential, although not all of them were present in the advised amount to exert beneficial health effects. However, the full correct scientific name of the isolated bacteria and their viable counts were not included on the product label. Significance and Impact of the Study: This is the first report describing the identification and functionality of starter bacteria and probiotics present in dairy products on the Columbian market. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
32. Effects of type of flow, plants and addition of organic carbon in the removal of zinc and chromium in small-scale model wetlands.
- Author
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Paredes, D., Vélez, M. E., Kuschk, P., and Mueller, R. A.
- Subjects
- *
WATER quality management , *CHROMIUM removal (Sewage purification) , *PHYTOREMEDIATION , *BIOREMEDIATION , *TYPHA latifolia , *WETLANDS , *ZINC - Abstract
Constructed wetlands are used for the treatment of wastewater containing metals. In order to clarify the role of plants, flow and the impact of organic matter, an investigation of three factors, each at two different levels, was carried out in small-scale model wetlands. The evaluated factors and levels were: type of flow (subsurface and surface); presence of plants (planted with Typha latifolia and unplanted) and addition of organic matter (with and without). Eight different experimental units were run for a year. The units were fed with synthetic wastewater containing chromium (VI) (1.5mg L-1), zinc (1.5mg L-1), macro, micronutrients and organic matter (to those units in which this factor was being investigated). Subsurface flow wetlands showed a significantly higher rate of chromium removal in comparison with surface flow systems (97 and 60mg m-2 d-1, respectively). Planted systems removed significantly more chromium compared to unplanted systems (85 and 76mg m-2 d-1, respectively), and the addition of organic matter increased the removal rate in a comparison with the units without it (88 and 69mg m-2 d-1, respectively). Similar results were found for zinc; however, the addition of organic matter made no significant difference to zinc removal. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
33. INITIAL STAGES OF GROWTH OF BaMgF4 ON (111)-SILICON.
- Author
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Gómez-Uribe, W. A., Rodríguez-Vélez, M., Majumder, S., and Martínez-Collazo, A.
- Subjects
- *
THIN films , *BARIUM , *MAGNESIUM fluoride , *SILICON , *CRYSTAL growth , *X-ray photoelectron spectroscopy , *MOLECULAR beam epitaxy - Abstract
We have grown BaMgF4 films on (111)-oriented Si substrates with existing native oxide layers using molecular beam epitaxy. The early stages of growth were studied through the application of x-ray photoelectron spectroscopy measurements on interrupted growth runs without exposing films to atmosphere. Exposure of the Si substrates to the BaMgF4 vapor at a substrate temperature of 950°C resulted in the formation of silicate species and a reduction of the SiO2 species on the substrate. Subsequent growth onto this silicate buffer layer resulted in highly textured (020)-oriented BaMgF4 films, as evidenced by x-ray diffraction studies. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
34. Preparation and properties of novel magnetic composite nanostructures: Arrays of nanowires in porous membranes
- Author
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Vázquez, M., Hernández-Vélez, M., Asenjo, A., Navas, D., Pirota, K., Prida, V., Sánchez, O., and Baldonedo, J.L.
- Subjects
- *
NANOSTRUCTURES , *NANOWIRES , *MAGNETIC properties , *ANISOTROPY - Abstract
Abstract: In the present work, we introduce our latest achievements in the development of novel highly ordered composite magnetic nanostructures employing anodized nanoporous membranes as precursor templates where long-range hexagonal symmetry is induced by self-assembling during anodization process. Subsequent processing as electroplating, sputtering or pressing are employed to prepare arrays of metallic, semiconductor or polymeric nanowires embedded in oxide or metallic membranes. Particular attention is paid to recent results on controlling the magnetic anisotropy in arrays of metallic nanowires, particularly Co, and nanohole arrays in Ni membranes. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
35. Temporal trends of preterm birth subtypes and neonatal outcomes.
- Author
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Barros FC and del Pilar Vélez M
- Published
- 2006
- Full Text
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36. Functional nanostructured titanium nitride films obtained by sputtering magnetron
- Author
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Sánchez, O., Hernández-Vélez, M., Navas, D., Auger, M.A., Baldonedo, J.L., Sanz, R., Pirota, K.R., and Vázquez, M.
- Subjects
- *
NANOTUBES , *FULLERENES , *NANOSTRUCTURES , *ELECTRON microscopy - Abstract
Abstract: Development of new methods in the formation of hollow structures, in particular, nanotubes and nanocages are currently generating a great interest as a consequence of the growing relevance of these nanostructures on many technological fields, ranging from optoelectronics to biotechnology. In this work, we report the formation of titanium nitride (TiN) nanotubes and nanohills via reactive sputtering magnetron processes. Anodic Alumina Membranes (AAM) were used as template substrates to grow the TiN nanostructures. The AAM were obtained through electrochemical anodization processes by using oxalic acid solutions as electrolytes. The nanotubes were produced at temperatures below 100 °C, and using a pure titanium (99.995%) sputtering target and nitrogen as reactive gas. The obtained TiN thin films showed surface morphologies adjusted to pore diameter and interpore distance of the substrates, as well as ordered arrays of nanotubes or nanohills depending on the sputtering and template conditions. High Resolution Scanning Electron Microscopy (HRSEM) was used to elucidate both the surface order and morphology of the different grown nanostructures. The crystalline structure of the samples was examined using X-ray Diffraction (XRD) patterns and their qualitative chemical composition by using X-ray Energy Dispersive Spectroscopy (XEDS) in a scanning electron microscopy. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
37. Nanowires and 1D arrays fabrication: An overview
- Author
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Hernández-Vélez, M.
- Subjects
- *
NANOSTRUCTURED materials , *NANOSTRUCTURES , *NANOTUBES , *FULLERENES - Abstract
Abstract: Since the discovery of M41S materials family in 1992, some special features like aligned pores perpendicularly to the substrate surface and long range order, have been looked for with great interest for many applications of these kind of nanomaterials. The growth of thin films displaying meso- and nano-porous structures have attracted the attention of many research groups in the last decade and, with that aim several techniques such as: MBE, CVD, AFM, ion beam lithography, etc., have been used. On the other hand, a lot of down–top techniques, particularly those in which, self-assembly processes play a relevant role in the growth mechanisms of that nanostructures have been reported. Among them, electrochemical techniques constitute one of the most used to fabricate highly ordered nanostructures to be used as templates for replicating other nanostructured materials and for growing functionalized material arrays. In this paper, a brief overview on the nanofabrication techniques is done mainly of those related with the nanowires and, in general, 1D nanostructures fabrication. In addition, we show some results on ordered and disordered nanoporous anodic alumina membranes (AAM) and anodic titania membranes (ATM), respectively. Besides some functionalized systems based on these membranes used as templates are presented such as, magnetic nanowire arrays, biosensors, and carbon nanotubes. The potentiality of these systems for applications on diverse field, such as, nanoelectronic, magneto-optic, biotechnology and optoelectronic is demonstrated. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
38. Magnetic nanowire arrays in anodic alumina membranes: Rutherford backscattering characterization.
- Author
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Hernández-Vélez, M., Pirota, K. R., Pászti, F., Navas, D., Climent, A., and Vázquez, M.
- Subjects
- *
NANOWIRES , *ALUMINUM oxide , *BACKSCATTERING , *SPECTRUM analysis , *ATOMIC force microscopy - Abstract
Systematic study of magnetic nanowire arrays grown in anodic alumina membranes (AAM) has been done by means of Rutherford backscattering spectroscopy (RBS). The AAM used as templates were morphologically characterized by using high resolution scanning electron microscopy (HRSEM), fast Fourier transform (FFT) and atomic force microscopy (AFM). The highly ordered templates with a mean pore diameter size of 30 nanometers, a mean inter-pore spacing of 100 nm and lengths ranging from 4 to 180 microns were obtained through two-steps anodization process, and the Ni and Co nanowire arrays were grown by electrodeposition techniques. The main attention is addressed to Ni nanowire arrays. RBS results allowed us to determine the real depth profile of atomic composition of the obtained nanowire arrays. In addition, the RBS spectra fitting showed that the porosity increased from the top to the bottom of the samples. Two phenomenological models are proposed to understand the apparition of that secondary porosity and a linear relation between the total amount of electrodeposited Ni and the electrodeposition time was obtained. As an example, it is also reported the relation between RBS results and magnetic properties, such as coercive field and remanence/saturation magnetization ratio of the samples. Particularly, for Ni nanowires arrays obtained by using voltage pulses, it is demonstrated that the larger the nanowires, the higher the definition for easy axis parallel to the nanowire length is possible. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
39. Amorphous to polycrystalline transition in CoSialloy thin films.
- Author
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Vélez, M., Mény, C., Valvidares, S. M., Diaz, J., Morales, R., Alvarez-Prado, L. M., Panissod, P., and Alameda, J. M.
- Subjects
- *
POLYCRYSTALS , *ALLOYS , *THIN films , *NUCLEAR magnetic resonance , *ANISOTROPY - Abstract
The transition from amorphous to polycrystalline microstructure has been studied in sputtered CoxSi1-x alloy films by structural, magneto-optical and Nuclear Magnetic Resonance measurements. For, Si is diluted into Co without significantly altering the polycrystalline microstructure, composed of a mixture of hcp and fcc grains. However, the fraction of Co atoms that contribute to the Nuclear Magnetic Resonance signal is found to decrease steeply (down to about 60atx= 0.76) suggesting a microscopic segregation of a Si rich phase that induces a large degree of disorder. This is reflected in a harder magnetic behavior and a strong anisotropy dispersion. Belowx= 0.75, the transition to an amorphous microstructure results in a sudden increase in the fraction of Co atoms within a ferromagnetic phase, indicating the recovery of the microscopic homogeneity. Also a significant enhancement of the macroscopic magnetic anisotropy is found for amorphous films with compositions right below the transition. Within the amorphous phase a second regime of Si segregation appears characterized by a constant Co local environment and constant magnetic properties. Finally, forx= 0.65 there is a significant Si enrichment in the Co environment and the films become non magnetic for compositions below this point. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
40. Arrays of Ni nanowires in alumina membranes: magnetic properties and spatial ordering.
- Author
-
Vázquez, M., Hernández-Vélez, M., Pirota, K., Asenjo, A., Navas, D., Velázquez, J., Vargas, P., and Ramos, C.
- Subjects
- *
NANOWIRES , *NICKEL , *ALUMINUM oxide , *MAGNETICS , *NANOSTRUCTURES - Abstract
Magnetic characteristics of arrays of Ni nanowires embedded in porous alumina are reviewed as a function of their spatial ordering. The different steps for the controlled production of highly-ordered nanowires is firstly described. Nanopores are formed into an hexagonal symmetry arrangement by self-organized process during anodization of pure Al. Parameters of the anodization allow us to control their diameter, hexagonal lattice parameter and size of crystalline domains. Subsequently, Ni nanowires are grown inside the pores by electrodeposition. Control of the pores filling and of geometrical ordering characteristics has been performed by SEM, HRSEM, RBS and AFM techniques. The magnetic characterisation of the arrays has been achieved by SQUID and VSM magnetometers, while information on the magnetic state of individual nanowires is obtained by MFM. Experimental studies are presented, particularly coercivity and remanence, for arrays with different degree of ordering (crystalline domains up to around 1 µm), and for ratio diameter to lattice parameter (diameter ranging between 20 and 180 nm, and distance between 35 and 500 nm). FMR studies have allows us to obtain complementary information of the anisotropy and magnetic characteristics. A modelling of multipolar interacting nanowires is introduced to account for the influence of short and long range ordering degree of the arrays. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
41. Cadmium sulphide clusters grown on zeolite and MCM-41-type matrices.
- Author
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Díaz, I., Hernández-Vélez, M., Palma, R.J. Martín, García, H. Villavicencio, Pariente, J. Pérez, and Martínez-Duart, J.M.
- Subjects
- *
CADMIUM , *SULFIDES , *RAMAN spectroscopy , *SURFACE chemistry , *LUMINESCENCE , *SPECTRUM analysis - Abstract
Cadmium sulphide clusters were grown on mordenite and Al-MCM41 matrices by using hydrothermal synthesis. X-ray fluorescence and diffraction, Raman spectroscopy, N2-adsorption isotherms, UV-visible and photoluminescence spectroscopies were used for sample characterisation. The results confirm the growth of CdS clusters mainly on the mordenite surface, whereas they could grow inside the mesoporous MCM-41 matrix. The final products showed approximately the same band-gap value (2.35 eV) as that calculated for bulk CdS synthesised in this work for comparison. Refractive indexes and extinction and absorption coefficients of the samples were evaluated by using a computational program. The mean values of those magnitudes and their connections with the structure, morphology and composition of the CdS-doped matrices were analysed. The relation between optical non-linearities and the growth of other species, like SiOx, during the synthesis processes is also discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2004
42. The Study of Phenolic Compounds as Natural Antioxidants in Wine.
- Author
-
López-Vélez, M., Martínez-Martínez, F., and Del Valle-Ribes, C.
- Subjects
- *
POLYPHENOLS , *WINES , *ANTIOXIDANTS - Abstract
Plant phenolics present in fruit and vegetables, and that are particularly rich in red wine, have received considerable attention because of their potential antioxidant activity. Human consumption of antioxidants has many alleged health benefits, including protection against cardiovascular diseases, and, most recently, cancer. Red wines contain a variety of polyphenolic antioxidants. Five samples of commercial red wines from Spain and four phenolic compounds of red wine: gallic acid, trans-resveratrol, quercetin and rutin, have been studied. The total phenolics content and the total antioxidant activity (TAA) of wines was determined. The total phenolic content, determined according to the Folin-Ciocalteu method, varied from 1800 to 2300 mg/L, expressed as gallic acid equivalents (GAE). The antioxidative effects of wine phenolics were determined using a system based on the inhibition by antioxidants of the absorbance of the radical cation. The relationship between antioxidant activity of phenolic comounds, as hydrogen donating free radical scavengers, and their chemical structures was studied. Furthermore, the total antioxidant activity of the wines investigated was well correlated with phenol content. Thus, the results confirm that red wine polyphenols are,in vitro, significant antioxidants. [ABSTRACT FROM AUTHOR]
- Published
- 2003
43. Interplay between the vortex lattice and arrays of submicrometric pinning centers
- Author
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Martın, J.I., Vélez, M., González, E.M., Hoffmann, A., Jaque, D., Montero, M.I., Navarro, E., Villegas, J.E., Schuller, Ivan K., and Vicent, J.L.
- Subjects
- *
SUPERCONDUCTORS , *ELECTRON beam lithography - Abstract
Ordered arrays of submicrometric magnetic pinning centers have been fabricated in superconducting Nb films by electron beam lithography. Periodic pinning effects, observed when the vortex lattice matches the array of dots, have been studied as a function of temperature, current and array geometry in order to analyze the physics of the interaction between the vortex lattice and the periodic array of microscopic pinning centers. These results have allowed pointing to the magnetic origin of the relevant pinning mechanism in this system and to dynamic ordering effects of the vortex lattices. The effect of the relative direction of the driving force with respect to the pinning potential is dependent on the anisotropy configuration of the artificial submicrometric array. [Copyright &y& Elsevier]
- Published
- 2002
44. Bee sting of the cornea. Case report.
- Author
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Vélez M, Salazar GI, and Monsalve P
- Abstract
Bee stings of the eye are uncommon entities and ocular reactions to the bee venom are wide, ranging from mild conjunctivitis to sudden vision loss. We present the case of a patient who suffered a bee sting of the cornea and the response to the poison components. We go through the bee venom properties, its actual treatment, and propose a new management alternative. [ABSTRACT FROM AUTHOR]
- Published
- 2010
45. Three-dimensional spin structure in exchange-biased antiferromagnetic/ferromagnetic thin films.
- Author
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Morales, R., Vélez, M., Petracic, O., Roshchin, Igor V., Li, Z.-P., Batlle, X., Alameda, J. M., and Schuller, Ivan K.
- Subjects
- *
ANTIFERROMAGNETISM , *FERROMAGNETISM , *THIN films , *SOLID state electronics , *ELECTROMAGNETIC induction , *FERROELECTRICITY - Abstract
A coexistence of lateral and in-depth domain walls in antiferromagnet/ferromagnet (AF/FM) thin films exhibiting double hysteresis loops (DHLs) is demonstrated. Comparison of single and DHLs together with local and global measurements confirms the formation of two oppositely oriented domains in the AF that imprint a lateral domain structure into the FM layer. Most significantly, the magnetization reversal mechanism within each opposite domain takes place by incoherent rotation of spring-like domain walls extending through the Ni thickness. Therefore, complex three-dimensional domain walls are created perpendicular and parallel to the AF/FM interface in exchange biased systems. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
46. Ordered Ni nanohole arrays with engineered geometrical aspects and magnetic anisotropy.
- Author
-
Navas, D., Hernández-Vélez, M., Vázquez, M., Lee, W., and Nielsch, K.
- Subjects
- *
NANOSTRUCTURES , *SPUTTERING (Physics) , *HYSTERESIS loop , *ANISOTROPY , *ELECTROPLATING , *MAGNETIZATION , *MAGNETIC force microscopy - Abstract
Ni nanohole arrays are prepared by a replication process involving sputtering, polymer molding pressing, and electroplating techniques, using anodic alumina membranes as templates. Nanohole diameter to interhole distance ratio is engineered by suitable template processing. From the analysis of the magnetization curves for increasing nanohole diameter, it is concluded that coercivity increases due to the pinning of domain walls to nanoholes, while in-plane anisotropy decreases owing to local shape anisotropy effects. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
47. Preparation and Magnetic Characterization of Ni Membranes With Controlled Highly Ordered Nanohole Arrays.
- Author
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Navas, D., Hernández-Vélez, M., Asenjo, A., Jaafar, M., Baldonedo, J. L., and Vázquez, M.
- Subjects
- *
NICKEL , *MAGNETIC testing , *MAGNETICS , *MAGNETIC materials , *ATOMIC force microscopy , *ANISOTROPY - Abstract
A replica/antireplica method is here proposed for the fabrication of metallic membranes reproducing the ordering of precursor nanoporous alumina membranes. Densely packed arrays of Ni nanoholes with long range ordering of hexagonal symmetry have been prepared. The study includes the magnetic properties of Ni nanohole arrays and those for a continuous Ni film. The magnetization process has been studied by analysis of in-plane and perpendicular hysteresis loops. In addition, combined magnetic force microscopy and atomic force microscopy have allowed us to observe triangular-shaped magnetic domains related to that hexagonal symmetry. An effective in-plane magnetic anisotropy is deduced that determines an in-plane magnetization process by wall displacement which is hindered by the nanoholes in the case of noncontinuous films. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
48. Reasoning about linkages with dynamic geometry.
- Author
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Kovács, Zoltán, Recio, Tomás, and Vélez, M. Pilar
- Subjects
- *
ALGEBRAIC curves , *GEOMETRY , *SYMBOLIC computation - Abstract
We illustrate an on-going work on the crossroad of mechanical linkages, dynamic geometry and automated reasoning. In particular, we exemplify how some automated reasoning tools (ART) based on symbolic computation and recently implemented in GeoGebra, can be used for linkage exploration. For instance, when considering linkages for generating specific algebraic curves, such as Peaucellier's construction of a straight line, we will show how these ART can help towards the verification (automatic proving) of the correctness of the linkage construction, as well as for finding (automatic discovery) a suitable modification on a given linkage for achieving a desired movement. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
49. Néel wall pinning on amorphous CoxSi1-x and CoyZr1-y films with arrays of antidots in the diluted regime.
- Author
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Pérez-Junquera, A., Rodríguez-Rodríguez, G., Vélez, M., Martín, J. I., Rubio, H., and Alameda, J. M.
- Subjects
- *
MAGNETIZATION , *MAGNETIC films , *AMORPHOUS substances , *ANISOTROPY , *MAGNETISM , *MAGNETIC flux , *MAGNETIC fields - Abstract
The magnetization reversal process has been studied in amorphous magnetic films patterned with ordered arrays of antidots in the diluted limit (i.e., with small enough antidot density so that the original film anisotropy is maintained and the flux closure structures around each dot are independent from each other). The role of the material parameters in the final behavior has been analyzed comparing the results on films made of two different Co-based amorphous alloys, CoxSi1-x and CoyZr1-y, that present a similar intrinsic uniaxial anisotropy but have a different saturation magnetization. The patterned holes are found to act as weak pinning centers for the motion of the Néel walls involved in the reversal process which results in an enhancement of coercivity in certain angular ranges. However, they are only effective in the material with the lower saturation magnetization (CoxSi1-x) which can be related with the different relative sizes of the patterned holes and the Néel walls in each case. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
50. Adsorption, desorption, and interdiffusion in atomic layer epitaxy of CdTe and CdZnTe.
- Author
-
Larramendi, E. M., de Melo, O., Hernández Vélez, M., and Tamargo, M. C.
- Subjects
- *
SURFACE chemistry , *CRYSTAL growth , *ATOMS , *ABSORPTION , *EPITAXY , *ADSORPTION (Chemistry) , *EVAPORATION (Chemistry) - Abstract
The mechanisms controlling the growth rate and composition of epitaxial CdTe and Cd1-xZnxTe films were studied. The films were grown by isothermal closed space configuration technique. A GaAs(100) substrate was exposed sequentially to the elemental sources (Zn, Te, and Cd) in isothermal conditions. While growth of ZnTe followed an atomic layer epitaxy (ALE) regime [self-regulated at one monolayer (ML) per cycle]; the CdTe films revealed different growth rates in dependence of the growth parameters (exposure and purge times). Combination of short purge times and larger Cd exposure times led to not self-regulated growth regime for CdTe. This is ascribed to large Cd coverages that were dependent on Cd exposure times (following a Brunauer-Emmett and Teller-type adsorption). However, for longer purge times and/or short Cd exposure times, an ALE self-regulated regime was achieved with 2 ML/cycle. In this sense, the self-regulation of the growth is limited by desorption, instead of absorption, as in the traditional growth technique. Cd atoms substitution by Zn atoms and subsequent evaporation of surface Cd atoms during Zn exposure has been proved. The influence of these facts on the growth and composition of the alloy is discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
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