The onset and solidification path of a basaltic melt by in situ differential scanning calorimetry (DSC) and ex situ investigations

The in situ differential scanning calorimetry (DSC) technique has been applied to investigate the solidification paths of a basaltic liquid. The starting glass was heated up to 1300◦C, kept at this superliquidus temperature for 2 h and cooled at rates (∆T/∆t) of 7, 60, 180, 1000, and 1800◦C/h, down to 800 and 600◦C. Glass transition temperature (Tg), crystallization temperature (Tx_HR) and melting temperature (Tm) were measured by in situ DSC spectra on heating. Tx measured along the cooling paths (Tx_CR) shows exothermic peaks that change from a single symmetric shape (7 and 60◦C/h) to multi-component patterns (180, 1000, and 1800◦C/h). The recovered products characterized by field emission gun source of the scanning electron microscopy and electron probe micro-analyzer-wavelength dispersive spectrometers show a phase assemblage of spinel (sp), clinopyroxene (cpx), melilite (mel), plagioclase (plg), and glass. Moreover, crystal size distributions (CSDs) and growth rates (Gmax and GCSD) were also determined. The crystal content slightly increases from 7 to 1800◦C/h. Faceted sp are present in all the run products with an amount always <2 area%. Cpx increases from 7 to 1800◦C/h, changing its texture from almost faceted to dendritic between 60 and 180◦C/h. The area% of mel follows an asymmetric Gaussian trend, while plg nucleates only at 7◦C/h with a content <2 area%. The coupling of DSC and SEM outcomes indicate that sp nucleate first, followed by cpx and mel (and/or plg). The increment of ∆T/∆t causes an increase of the CSD slope (m) and crystal population density per size (n0 ), as well as a decrease of the crystal size, for both cpx and sp. The log-linear CSD segments with different slopes at 7 and 60◦C/h suggest multiple nucleation events and crystal growth by coarsening. Gmax and GCSD for cpx and sp directly measured on the actual crystallization time by DSC spectra, both increase with the increasing of ∆T/∆t. The onset temperature of crystallization (Txi ) decreases as ∆T/∆t increases, following an exponential trend that defines the uppermost portion of a time-transformation-temperature-like curve. This analytical model allows us to quantitatively model the kinetic crystallization paths of dry basalts

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Evaluation of radical scavenging activity of fresh and air-dried tomatoes by three model reactions

The radical scavenging activity and the antioxidant content of fresh and air-dried tomatoes were investigated. Tomato halves were dried in a pilot-scale dryer under the following conditions: air temperature, 80 \ub0C; air flow rate, 1.5 m/s; drying time, 400 min; final moisture, 25%. Carotenoid (lycopene, \ue2-carotene, lutein) and ascorbic acid were analyzed by HPLC with a pectrophotometric and an electrochemical detector, respectively. Total phenolics were determined by using the Folin-Ciocalteu reagent. The radical scavenging activity was studied in three model systems: (a) the xanthine oxidase and xanthine system, which generates superoxide radical and hydrogen peroxide; (b) the 3-morpholinosydnonimine system, which releases spontaneously superoxide radical and nitrogen monoxide, forming peroxynitrite; (c) the linoleic acid and CuSO4 system, which promotes lipid peroxidation. These model systems allow the simulation of key reactions involved in the pathogenesis of certain chronic diseases and may be related to the in vivo activity of tomato antioxidants. Hence, these measurements can be used for optimizing tomato processing and storage. The drying process resulted in a decrease of ascorbic acid content, whereas phenol reagent reducing compounds increased. Carotenoid levels were substantially unchanged upon drying. Fresh and airdried tomato extracts could act as radical scavengers both in the reactive oxygen species-mediated reactions and in lipid peroxidation. Drying affected the antioxidant effectiveness as measured in the xanthine/xanthine oxidase system, which was found to be the most sensitive method for the measurement of tomato antioxidant activity (lower I50) but retained the antioxidant effectiveness in the other two systems