NMR methods for beer characterization and quality control.

The use of high-resolution NMR spectroscopy in the brewing industry is described; most studies having aimed at assessing the composition of beer and its raw materials and correlating it to a variety of quality parameters. First, the application of NMR to the qualitative characterization of beer is reviewed, addressing both targeted and untargeted methods and focusing on both beer extracts and direct beer analysis. A subsequent chapter addresses the NMR studies, which envisage the development of new rapid methods for beer analysis and quality control, such as site-specific natural fractionation-NMR and multivariate data analysis methods for marker search or rapid compound quantification. Finally, possible future perspectives toward a deeper and more complete understanding of beer and its brewing process are discussed.

Synergy of diffraction and spectroscopic techniques to unveil the crystal structure of antimonic acid.

The elusive crystal structure of the so-called 'antimonic acid' has been investigated by means of robust and state-of-the-art techniques. The synergic results of solid-state magic-angle spinning nuclear magnetic resonance spectroscopy and a combined Rietveld refinement from synchrotron X-ray and neutron powder diffraction data reveal that this compound contains two types of protons, in a pyrochlore-type structure of stoichiometric formula (H3O)1.20(7)H0.77(9)Sb2O6. Some protons belong to heavily delocalized H3O+ subunits, while some H+ are directly bonded to the oxygen atoms of the covalent framework of the pyrochlore structure, with O-H distances close to 1 Å. A proton diffusion mechanism is proposed relying on percolation pathways determined by bond-valence energy landscape analysis. X-ray absorption spectroscopy results corroborate the structural data around Sb5+ ions at short-range order. Thermogravimetric analysis and differential scanning calorimetry endorsed the conclusions on the water content within antimonic acid. Additional 0.7 water molecules per formula were assessed as moisture water by thermal analysis.

A comprehensive examination of the local- and long-range structure of Sb6O13 pyrochlore oxide.

The crystal structure of the Sb6O13 oxide, exhibiting a defect pyrochlore crystal structure with atomic vacancies, has been studied using a complete set of state-of-the-art techniques. The degree of antimony disproportionation in Sb3+ and Sb5+ valence states has been directly determined around 36% and 64%, respectively, using X-ray absorption near edge structure (XANES). These findings are in excellent agreement with our Rietveld analysis of synchrotron X-ray (SXRD) and neutron powder diffraction (NPD) results. Moreover, the highly distorted Sb3+ coordination due to its lone electron pair has been critically revisited. The bonding distances and coordination of Sb3+ and Sb5+ species closely agree with an extensive dynamic and crystallographic determination using the Extended X-ray Absorption Fine Structure (EXAFS) technique. Most importantly, the specific local disorder of the two distinctive Sb ions has been crosschecked monitoring their unusual Debye-Waller factors.

First-principles calculations and Raman scattering evidence for local symmetry lowering in rhombohedral ilmenite: temperature- and pressure-dependent studies.

ATiO3-type materials may exist in two different crystalline forms: the perovskite and ilmenite. While many papers have devoted their attention to evaluating the structural properties of the perovskite phase, the structural stability of the ilmenite one still remains unsolved. Here, we present our results based on the lattice dynamics and first-principles calculations (density functional theory) of the CdTiO3 ilmenite phase, which are confronted with experimental data obtained through micro Raman spectroscopy that is a very good tool to probe the local crystal structure. Additional Raman bands, which are not foreseen from group-theory for the ilmenite rhombohedral structure, appeared in both low temperature (under vacuum condition) and high-pressure (at room temperature) spectra. The behavior can be explained by considering the local loss of inversion symmetry operation which reduces the overall space group from [Formula: see text] ([Formula: see text]) to [Formula: see text] ([Formula: see text]). Our results can also be extended to other ilmenite-type compositions.

[Pharmacoeconomic study of antibiotic therapy for exacerbations of chronic bronchitis and chronic obstructive pulmonary disease in Latin America]. / Estudio farmacoeconómico del tratamiento antibiótico de las agudizaciones de la bronquites crónica y la EPOC en Latinoamérica.

Chronic obstructive pulmonary disease (COPD) and chronic bronchitis are highly prevalent diseases. Studies designed to analyze the economic impact of these diseases in Latin American countries have not previously been published. In the present study we analyzed the direct health care costs of treating patients with exacerbations of chronic bronchitis and COPD in Argentina, Brazil, Colombia, Ecuador, Mexico, Peru, and Venezuela, applying the real cost of drugs and medical acts in those 7 countries to the pattern of treatment and outcomes obtained from a study carried out in primary care settings in Spain. The mean direct health care cost ranged from US $98 in Colombia to $329 in Argentina. Most of the cost was related to failure of therapy, which accounted for 52% of the total cost of exacerbation, with the lowest rate in Colombia at 28.6% and the highest in Ecuador at 59.3% The cost of antibiotic therapy represented 19% of the total cost; the rest was owing to other drugs or medical visits. Exacerbations generate significant costs for health care systems. There are considerable variations related mainly to differences between systems. Antibiotic therapy represents a small part of the overall cost. The use of more effective antibiotics, if they can reduce failure rates, may be a cost-effective strategy.

Quantification of organic acids in beer by nuclear magnetic resonance (NMR)-based methods.

The organic acids present in beer provide important information on the product's quality and history, determining organoleptic properties and being useful indicators of fermentation performance. NMR spectroscopy may be used for rapid quantification of organic acids in beer and different NMR-based methodologies are hereby compared for the six main acids found in beer (acetic, citric, lactic, malic, pyruvic and succinic). The use of partial least squares (PLS) regression enables faster quantification, compared to traditional integration methods, and the performance of PLS models built using different reference methods (capillary electrophoresis (CE), both with direct and indirect UV detection, and enzymatic essays) was investigated. The best multivariate models were obtained using CE/indirect detection and enzymatic essays as reference and their response was compared with NMR integration, either using an internal reference or an electrical reference signal (Electronic REference To access In vivo Concentrations, ERETIC). NMR integration results generally agree with those obtained by PLS, with some overestimation for malic and pyruvic acids, probably due to peak overlap and subsequent integral errors, and an apparent relative underestimation for citric acid. Overall, these results make the PLS-NMR method an interesting choice for organic acid quantification in beer.