We study non-anti-invariant slant submanifolds of generalized S-space-forms with two structure vector felds in order to know if they inherit the ambient structure. In this context, we focus
on totally geodesic, totally umbilical, totally ƒ-geodesic and totally ƒ-umbilical non-anti-invariant slant submanifolds and obtain some obstructions. Moreover, we present some new interesting examples
of generalized S-space-forms.
In this note we use the Hopf map π: S3 → S2 to construct an interesting family of Riemannian metrics hfon the 3-sphere, which are parametrized on the space of positive smooth functions f on the 2-sphere. All these metrics make the Hopf map a Riemannian submersion. The Hopf tube over an immersed curve γ in S2 is the complete lift π-1(γ) of γ, and we prove that any geodesic of this Hopf tube satisfies a Clairaut relation. A Hopf tube plays the role in S3 of the surfaces of revolution in R3. Furthermore, we show a geometric integration method of the Frenet equations for curves in those non-standard S3. Finally, if we consider the sphere S3 equipped with a family hf of Lorentzian metrics, then a new Clairautrelation is also obtained for timelike geodesics of the Lorentzian Hopf tube, and
a geometric integration method for curves is still possible.
New measures of noncompactness for bounded sets and linear operators, in the setting of abstract measures and generalized limits, are constructed. A quantitative version of a classical criterion for compactness of bounded sets in Banach spaces by R. S. Phillips is provided. Properties of those measures are established and it is shown that they are equivalent to the classical measures of noncompactness. Applications to summable families of Banach spaces, interpolations of operators and some consequences are also given.
Authors:A. Rekondo, L. Irusta, and M. Fernández-Berridi
The thermal behaviour of a new kind of hybrid system based on silanized poly(ether-urethanes) (SPURs) has been analyzed by
thermogravimetric analysis (TG). The influence of the chemical nature of employed alkoxysilanes, polyether diol molecular
weight and the physical state of the obtained hybrids (cured and non-cured) has been studied. The results show that in the
non-cured state, aminosilane-based systems present a higher stability compared with those based on isocyanatesilane. However,
in the cured state, both types of hybrids present a similar thermal stability, but much higher than their corresponding partners
before the curing process. The presence of the inorganic silica network improves the thermal stability of all the systems
Authors:L. Núńez-Regueira, S. Gómez-Barreiro, and C. A. Gracia-Fernández
Modulated differential scanning calorimetry (MDSC) and dielectric analysis (DEA) have been used to characterize the cure process
of the system diglycidyl ether of bisphenol A (DGEBA(n=0)/1,2 diaminocyclohexane (1,2 DCH). The trans isomer and a mixture cis/trans(30-70% respectively) of 1,2 DCH were used to find their different behaviour. The study allowed to check the influence of
the cisisomer on the thermoset curing process. Gelation times were obtained through the equation proposed by Johari and vitrification
times from the point of inflection of the complex calorific capacity modulus.
Authors:L. Lugo, M. Comuñas, E. López, and J. Fernández
New densities are reported over the whole composition range for 1-iodoperfluorohexane+n-octane system at temperatures from 288.15 to 308.15
K at atmospheric pressure. These data have been used to compute the excess
molar volumes, VmE.
Large positive VmE
values have been obtained over the entire range of composition, which increases
when the temperature rises. The experimental data were used to calculate the
isobaric thermal expansivity, and the quantities (∂VmE/∂T)p and (∂HmE/∂p)T. Furthermore,
the results have been used to investigate the volumetric prediction ability
of the equations of state Soave–Redlich–Kwong, Peng–Robinson,
Patel–Teja and Soave–Redlich–Kwong with volume translation.
Authors:Ana Hidalgo, J. García, Ma. Alonso, L. Fernández, and Carmen Andrade
The most widely identified degradation process suffered by calcium aluminate cement (CAC) is the so-called conversion of hexagonal
calcium aluminate hydrate to cubic form. This conversion is usually followed by an increase in porosity determined by the
different densities of these hydrates and the subsequent loss of strength. Mixes of calcium aluminate cement (CAC) and silica
fume (SF) or fly ash (FA) represent an interesting alternative for the stabilization of CAC hydrates, which might be attributed
to a microstructure based mainly on aluminosilicates. This paper deals with the microstructure of cement pastes fabricated
with mixtures CAC-SF and CAC-FA and its evolution over time. Thermal analysis (DTA/TG), X-ray diffraction (XRD) and mid-infrared
spectroscopy (FTIR) have been used to assess the microstructure of these formulations.