Showing papers by "Polytechnic University of Valencia published in 1985"

Plant regeneration from calli of melon ( Cucumis melo L., cv. ‘Amarillo Oro’)

Abstract: Callus cultures from cotyledon and hypocotyl explants of a Spanish cultivar of melon (‘Amarillo Oro’) have been tested for their growth and morphogenic capacity on a series of media with different concentrations of indole-3-acetic acid (IAA) and 6-furfurylaminopurine (kinetin). Melon tissues were able to undergo morphogenesis both via organogenesis and embryogenesis, depending on culture conditions and explant source. Shoot buds were obtained at high rates in cotyledon explants. In response to 1.5 mg/l IAA and 6.0 mg/l kinetin, more than 90% of the calli produced well-developed shoots. Hypocotyls failed to form shoots but formed somatic embryos on auxin containing media while cotyledon explants usually gave abundant shoots but only rarely formed embryos. It was possible to maintain organogenic callus lines for at least 12 months under defined conditions. Plants were recovered from adventitious shoots produced both in cotyledon-derived calli and from organogenic cell lines.

Application of the method of brather for the determination of complex dielectric permittivity from measurements of isothermal polarization current

Abstract: Some years ago, Brather proposed a method for calculation of the real and imaginary parts of the complex dielectric permittivity starting from measurements of isothermal polarization current. This method shows some advantages over the Hamon method, which is normally used. Both methods are applied in this work to the β relaxation of poly(butyl methacrylate). It is concluded that, with the usual accuracy of measurement, a combination of the two methods is advisable; Hamon's method is taken to be a first approximation to that of Brather. Results following the two procedures are compared, and their respective advantages and disadvantages are discussed.

Influence of physical ageing on the α dielectric relaxation of poly(methyl acrylaie)

Abstract: In this work are examined changes of the α relaxation spectrum of PMA during the structural relaxation process which follows a quenching from a temperature To above Tg to another T1 below Tg, which is mantained constant. It is found that the relaxation times spectrum is shifted towards longer times as the ageing time increases. At the same time, its form becomes more and more wide, approaching the form of the relaxation times spectrum calculated at temperatures above Tg from alternative dielectric measurements. A parameter measuring the shift of the spectrum, a(ta), is defined and its dependence on ageing time and annealig temperature is studied. The effective relaxation time of the structural relaxation process is calculated from a(ta) and it is found dependent on the temperature of annealing as well as on the value of a(ta)itself.

PHOTOLYSIS OF ENOL ACETATES AND α-BROMO DERIVATIVES OF O-(ACYLOXY)ACETOPHENONES

Abstract: UV irradiation of enol acetates 3a – g in benzene gives mainly o-(acetoxy)acetophenones 2 and 2-methylchromones 4. Under the same conditions, the dimethyl derivatives 3h and 3i remain unaffected. The α-bromo ketone 5a gives rise to mixtures of o-(acetoxy)acetophenone (2a), the diketone 6, and/or α-acetoxy-o-hydroxyacetophenone (7), depending on the irradiation conditions. The similarities and differences between the two series of experiments, as well as their possible mechanistic implications, are discussed. Photolyse von Enolacetaten und α-Bromderivaten von o-(Acyloxy)acetophenonen UV-Bestrahlung der Enolacetate 3a – g in Benzol liefert o-(Acetoxy)acetophenone 2 und 2-Methyl-chromone 4 als Hauptprodukte. Unter den gleichen experimentellen Bedingungen bleiben die Dimethylderivate 3h und 3i unverandert. Das α-Bromketon 5a liefert in Abhangigkeit von den Bestrahlungsbedingungen Mischungen aus o-(Acetoxy)acetophenon (2a), dem Diketon 6 und/oder α-Acetoxy-o-hydroxyacetophenon (7). Die Ahnlichkeiten und Unterschiede zwischen beiden Reihen von Experimenten sowie mechanistische Uberlegungen werden diskutiert.