Authors:S. -P. Ding, J. Fan, J. L. Green, Q. Lu, E. Sanchez, and C. A. Angell
Trehalose dihydrate, on careful dehydration below its fusion point, retains its original crystal facets but becomes X-ray amorphous, an unusual example of direct crystal-to-glass transformation. From DSC studies, the glass obtained by this route seems to be of abnormally low enthalpy, but after an initial scan, the normal form of glass transition is exhibited, withTg=115‡C, a higher value than previously reported. We give a preliminary thermal and mechanical characterization of this material and find it to be a very fragile liquid. The highTg is shown to rationalize the exceptionally high water content of the trehalose+water solution that vitrifies at ambient temperature (i.e.Tg=298 K), and hence helps explain its use by Nature as a desiccation protectant. The spontaneous vitrification of crystalline materials during desolvation is related to the phenomenology of pressure-induced or decompression-induced vitrification of crystals via the concept of limiting metastability.
Authors:P. Sánchez-Soto, M. Villacampa, J. Ginés, A. Ruiz-Conde, M. Avilés, and M. Arias
Several derivatives containing a new organic ring system, the tropane-6-spiro-5′-hydantoin structure (namely 8-alkyl-8-azabicyclo
[3.2.1.] octane-6-spiro-5′-imidazoline-2′,4′-diones) have been characterized by thermal (DSC and simultaneous DTA-TG-DTG)
and spectroscopic techniques (IR,1 H-NMR,13 C-NMR). X-ray powder diffraction and elemental analysis were applied for structural and molecular characterization. All the
compounds melt in the range 160–250°C and undergo decomposition with progressive mass loss after the solid-liquid thermal
transition with molecular degradation. It was found that tropane-6-spiro-5′-hydantoin derivatives with the hydantoin ring
in β position are thermally less stable than those containing this ring in α position.
Authors:J. A. García, Rosa Rodriguez-Sánchez, J. Fdez-Valdivia, Daniel Torres-Salinas, and Francisco Herrera
A university may be considered as having dimension-specific prestige in a scientific field (e.g., physics) when a particular bibliometric research performance indicator exceeds a threshold value. But a university has multidimensional prestige in a field of study only if it is influential with respect to a number of dimensions. The multidimensional prestige of influential fields at a given university takes into account that several prestige indicators should be used for a distinct analysis of the influence of a university in a particular field of study. After having identified the multidimensionally influential fields of study at a university their prestige scores can be aggregated to produce a summary measure of the multidimensional prestige of influential fields at this university, which satisfies numerous properties. Here we use this summary measure of multidimensional prestige to assess the comparative performance of Spanish Universities during the period 2006–2010.
Authors:E. Stepkowska, J. Bijen, J. Perez-Rodriguez, A. Justo, P. Sanchez-Soto, and M. Aviles
A simple water sorption/retention (WS/WR) test, followed by stepwise static heating, was applied to the study of cement quality and the reactivity of its grain surface.
The physically bound water and hence the specific surface both in the unhydrated and in the hydrated state were estimated
as a function of the hydration time. Rehydration after heating at 220°C and contact with air was different inWS from that inWR samples, which indicates a difference in microstructure. XRD proved the formation of portlandite during the sorption test
and eventual heating at 200°C, and its transformation into carbonates on contact with air, especially on heating at 400°C.
The contents of these compounds were estimated from the mass difference between 400 and 800°C, which was compatible with the
mass change between 220 and 400°C and this indicates surface reactivity. The test may serve for the routine study of cement.
Authors:J. Ginés, M. Arias, C. Novák, P. Sánchez-Soto, A. Ruiz-Conde, and E. Morillo
The formation of crystalline inclusion complex of triamterene with β-cyclodextrin (β-CD) was studied, evaluating the thermal
behaviour and dispersion state of this drug in different types of binary systems. Spray-drying and co-grinding (oscillating
mill) mixtures of triameterene with β-CD were prepared in 1∶1 molar ratio. The changes of crystalline properties of original
(untreated) triamterene, β-CD, and composites obtained by co-grinding and spray-drying were investigated in comparison with
those produced in simple physical mixtures. The thermal behaviour of the different samples was investigated using DTA. X-ray
diffraction was applied as a complementary technique. The results have been explained by formation of amorphous drug particles
on spray-drying samples and co-grinding or alternatively by means of a solid dispersion formation or a combination of these
two. A contamination effect by grinding media was also observed as increasing grinding time.
Authors:Hossain Anawar, N. Canha, M. Freitas, I. Santa Regina, and A. Garcia-Sanchez
The drying process of fresh plant materials may affect the porous structure, dehydration and a number of quality characteristics
of these materials. Therefore, this study has investigated the effect of different drying processes on the variation of metal
and metalloid concentrations in the dried plant materials. Seven varieties of native plant species collected from São Domingos
mine were analyzed by instrumental neutron activation analysis (INAA) to investigate the effects of freeze-drying (FD), ambient
air-drying (AAD) and oven-drying (OD) process on the concentrations of metals and metalloids in the plant biomass. Comparison
of ambient air-dried, oven-dried and freeze-dried preparations allows a phenomenological description of the dehydration artefacts.
In the quantitative analysis of metals and metalloids, FD and OD plant samples show the higher concentrations of metals and
metalloids when compared to those in the AAD plant biomass. The freeze-drying process is comparatively reliable for determination
of metals and metalloids concentrations in plant materials.
Authors:P. Sánchez-Soto, J. Ginés, M. Arias, Cs. Novák, and A. Ruiz-Conde
This paper studies the effect of molecular mass on the melting temperature, enthalpy and entropy of hydroxy-terminated poly(ethylene oxide) (PEO). It aims to correlate the thermal behaviour of PEO polymers and their variation of molecular mass (MW). Samples ranging from 1500 to 200,000 isothermally treated at 373 K during 10 min, were investigated using DSC and Hot Stage Microscopy (HSM). On the basis of DSC and HSM results, melting temperatures were determined, and melting enthalpies and entropies were calculated. Considering the melting temperatures, it was found that the maximum or critical value of MW was found around 4000, and then these remain almost constant. This behaviour was interpreted assuming that lower MW fractions (MW<4000) crystallize in the form of extended chains and higher MW fractions (MW>4000), as folded chains. The melting enthalpies showed a scattering effect at least up to MW 35,000. It was difficult to obtain any relationship between melting enthalpies in J g–1 and MW. These variations seem to be of statistical nature. Corrected enthalpy data on a molar basis (kJ mol–1) exhibited a linear relationship with MW. Considering the solid—liquid equilibrium, the melting entropies (in kJ mol–1) were calculated. These values were more negative as compared with molar enthalpy increases. It was explained because the changes in melting temperatures are much smaller than those observed in the enthalpy values. Linear relationship between enthalpies andentropies as a function of MW was deduced.
Authors:J. A. García, Rosa Rodriguez-Sánchez, J. Fdez-Valdivia, and J. Martinez-Baena
Here we study the relationship between journal quartile rankings of ISI impact factor (at the 2010) and journal classification in four impact classes, i.e., highest impact, medium highest impact, medium lowest impact, and lowest impact journals in subject category computer science artificial intelligence. To this aim, we use fuzzy maximum likelihood estimation clustering in order to identify groups of journals sharing similar characteristics in a multivariate indicator space. The seven variables used in this analysis are: (1) Scimago Journal Ranking (SJR); (2) H-Index (H); (3) ISI impact factor (IF); (4) 5-Year Impact Factor (5IF); (5) Immediacy Index (II); (6) Eigenfactor Score (ES); and (7) Article Influence Score (AIS). The fuzzy clustering allows impact classes to overlap, thereby accommodating for uncertainty related to the confusion about the impact class attribution for a journal and vagueness in impact classes definition. This paper demonstrates the complex relationship between quartiles of ISI impact factor and journal impact classes in the multivariate indicator space. And that several indicators should be used for a distinct analysis of structural changes at the score distribution of journals in a subject category. Here we propose it can be performed in a multivariate indicator space using a fuzzy classifier.