Browsing by Author "Rodrigues, R."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Correction of the misclassification of species in the Portuguese collection of Cucurbita pepo L. using DNA markersPublication . Rodrigues, R.; Veiga, I.; Marreiros, A.; Rocha, F.; Leitão, J. M.In this study, the genetic variability among 130 accessions of the Portuguese germplasm collection of Cucurbita pepo L. maintained at the Banco Portugues de Germoplasma Vegetal was assessed using AFLP (amplified fragment length polymorphism) and RAPD (random amplified polymorphic DNA) techniques for the identification of a genetically diverse core group of accessions for field phenotypic analysis. The surprisingly completely different molecular patterns exhibited by multiple accessions was later confirmed in the distribution of the putative C. pepo plants into two clusters drastically separated at a very low level of genetic similarity (DICE coefficient = 0.37). Additional analyses with RAPD and ISSR (inter single sequence repeat) markers and the introduction of standard genotypes of C. maxima L. and C. moschata L. into the analyses allowed the identification of multiple accessions of the last species wrongly included in the C. pepo collection. This study is a good example of the usefulness of DNA markers in the establishment and management of plant germplasm collections.
- Unfocused laser ignition of high-pressure He–H2-O2 combustible mixturesPublication . Grosso Ferreira, R.; Carvalho, B.; Rodrigues, José-António; Rodrigues, R.; Smith, A.; Marraffa, L.; Lino da Silva, M.We report consistent ignition of high-pressure (p(fill)>20-30 bar) hydrogen-oxygen mixtures diluted with helium in two different combustion vessels, using an unfocused Nd:YAG laser. This corresponds to laser irradiances several orders of magnitude below the minimum ignition energies reported in the literature. This unusual phenomena has led us to try to measure the amount of laser radiation absorbed by the gas medium. By placing a mirror inside a cylindrical vessel and filling it up to 100 bar with He-H-2 or He-O-2 non-combustible mixtures, we obtain the pressure-dependent absorptivity of the combustible He-H-2-O-2 mixture. We find no measurable absorption of the laser signal by the medium, for the overall pressure range, to the experimental apparatus sensitivity (about 1% of the laser irradiance). The exact mechanism for ignition remains henceforth unknown. One possibility could the creation of seed electrons created by autofocusing ionization of dust/impurities in the gas, but this has yet to be experimentally confirmed.