A conceptual framework for invasion in microbial communities

There is a growing interest in controlling-promoting or avoiding-the invasion of microbial communities by new community members. Resource availability and community structure have been reported as determinants of invasion success. However, most invasion studies do not adhere to a coherent and consistent terminology nor always include rigorous interpretations of the processes behind invasion. Therefore, we suggest that a consistent set of definitions and a rigorous conceptual framework are needed. We define invasion in a microbial community as the establishment of an alien microbial type in a resident community and argue how simple criteria to define aliens, residents, and alien establishment can be applied for a wide variety of communities. In addition, we suggest an adoption of the community ecology framework advanced by Vellend (2010) to clarify potential determinants of invasion. This framework identifies four fundamental processes that control community dynamics: dispersal, selection, drift and diversification. While selection has received ample attention in microbial community invasion research, the three other processes are often overlooked. Here, we elaborate on the relevance of all four processes and conclude that invasion experiments should be designed to elucidate the role of dispersal, drift and diversification, in order to obtain a complete picture of invasion as a community process

Nasal morphology and blood flow during augmented air pressure breathing therapies

Air delivered under augmented pressure during breathing therapy normally requires external humidification in order to avoid upper airways dryness and discomfort. Nasal heat and water flux between air and mucosa is dynamically regulated through changes in the erectile tissue volume. This investigation utilizes magnetic resonance imaging to investigate the effects augmented air pressure has on the erectile tissue size and blood flow. Eight healthy participants, aging from 18 to 56 years of mixed gender and ethnicity, undertook head MRI scans during two breathing conditions, ambient and pressurized air. For the latter, each participant experienced one augmented pressure level, ranging from 6 to 15 cmWG in increments of 3 cmWG. This was delivered through a nasal mask using a commercially available continuous positive airway pressure device. Geometrical analysis of images obtained for the region spanning the anterior inferior turbinate to the posterior choanae was undertaken. Results demonstrate a reduction in patent airway volume occurs during breathing at low pressure augmentation whist the congested airway volume remains relatively constant. Increasing pressure results in an opposite response where the congested airway volume increases whilst the patent volume remains unchanged. Only at the highest pressure (15 cmWG) did both patent and congested airways respond in a way consistent with previous observations of tissue compliance (which were based on acoustic rhinometry and modeling). The counter response of the patent airway and independence of reaction between each nasal passage at low to mid pressures is inconsistent with earlier work which detected no differences in morphological response between patent and congested nasal airways. This inter-nasal variation in behavior may be attributed to redistribution in blood occurring within the nasal erectile tissue. Using arterial spin labeling, this research has also qualitatively assessed the changes in nasal blood flow to each side of the nose. Whilst this technique does not indicate total blood volume and hence state of erectile-tissue engorgement, it does identify changes in blood flow occur in both congested and patent airways during pressurized breathing

Erratum to "Development and illustrative outputs of the Community Integrated Assessment System (CIAS), a multi-institutional modular integrated assessment approach for modelling climate change" Environ Model Softw 23(5) (2008) 592-610 (DOI:10.1016/j.envsoft.2007.09.002)

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