Advances in structure elucidation of small molecules using mass spectrometry

The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules

Detecting fragmentation of cover in desert grasslands using line intercept

Changes in the amount or spatial distribution of grass plants are thought to be indicative of the stability of desert grasslands. This study assessed, through simulation, the sensitivity of statistical properties for distance between plants (fetch length), measured with a line intercept transect, to changes in the spatial distribution and amount of plant cover. Monitoring plots, 30 X 30 m, were simulated for 1, 2.5, 5, 10 and 15% grass cover with random and fragmented spatial distribution. Fetch lengths were measured on 2 randomly placed 30 m transects. In addition to the median and interquartile range, the asymmetry of the sampling distributions was measured with a ratio [(maximum-median)/(median-minimum)] that would identify the presence of at least 1 large open space. The accuracy of the fetch length method was confirmed by the similarity of its sampling distribution to that for the well known random point-to-plant sampling procedure. In both the fetch length and the point-to-plant measures, the median and interquartile range increased with decreasing cover for random and fragmented distribution. The asymmetry estimate increased sharply with increasing cover for the fragmented distribution but asymmetry was nearly constant with increasing cover for the random distribution. The results suggest that the evaluation of changes over time at a monitoring site could use fetch lengths measured along a line intercept transect to detect changes in both absolute and spatial arrangement of cover.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Evolução histórica dos utensílios empregados para alimentar lactentes não amamentados Historical evolution of utensils used to feed non breastfed infants

O objetivo desse artigo de revisão é descrever os utensílios empregados ao longo da história para alimentar lactentes não amamentados. O levantamento bibliográfico foi realizado nas bases de dados MEDLINE, LILACS e SciELO, de 1966 a 2007. Para a análise documental, foram processadas buscas na Internet, em enciclopédias, livros de arte, história e museus. Utensílios manufaturados com materiais e formas variadas, dependendo da disponibilidade, poder aquisitivo e cultura, foram empregados desde os primórdios da história para alimentar bebês que, por diferentes motivos, deixaram de ser amamentados. Muitos objetos coexistiram na mesma época e local, outros em tempos e pontos geográficos distantes. A aceitação de uma nova alternativa ocorria sem evidência que comprovasse ou apontasse para os benefícios da mudança. Alguns utensílios voltaram a ser empregados embora a mortalidade infantil fosse elevada à época em que foram utilizados. No início do século XX, as mamadeiras assumiram a forma cilíndrica cônica. A tecnologia trouxe avanços no sentido de melhorar a higienização e possibilitar o controle da contaminação. O vidro deu lugar ao plástico e os bicos de borracha, aos de silicone, mas a mamadeira, como a conhecemos hoje, é a mesma de cem anos atrás.<br>The objective of this article is to describe the utensils used throughout history to feed non breastfed infants. The method used was article review, reference search on the MEDLINE, LILACS and SciELO databases from 1966 to 2007 and documental analysis based on data from the internet, encyclopedias, art and history books, and museums. Utensils manufactured in a variety of materials and shapes, depending on availability, purchasing power and culture have been used since early history to feed babies who for different reasons were not breastfed. Many objects coexisted at the same time and place, others at distant sites and times. New alternatives have been accepted without evidence to prove or point toward the benefits of the change. Some of these alternatives were adopted again, even if infant mortality was high at the time in which they were used at first. In the beginning of the 20th century, bottles became conic-cylindrical. Technology brought about progress as to improve hygiene and enable contamination control. Glass gave way to plastic, and rubber nipples to silicone ones, but the bottle as we know it today is still the same of a 100 years ago