88 research outputs found

    Ever Westward to the Far East: the Story of Chester Fritz

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    Published in 1982, Ever Westward to the Far East tells the story of UND benefactor Chester Fritz. The book was written with Dan Rylance of the Chester Fritz Library.https://commons.und.edu/und-books/1102/thumbnail.jp

    The Journal of Chester Fritz: Travels Through Western China in 1917

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    Chester Fritz embarked on a six month journey through China in 1917. He kept a detailed journal and took many photographs along the way. This journal was edited by UND History Professor Dr. James Vivian and published by the University of North Dakota Press in 1981. Dan Rylance, curator of the Orin G. Libby Manuscript Collection at the the Chester Fritz Library, wrote the introduction.https://commons.und.edu/und-books/1101/thumbnail.jp

    Far-infrared observations of an unbiased sample of gamma-ray burst host galaxies

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    Gamma-ray bursts (GRBs) are the most energetic phenomena in the Universe; believed to result from the collapse and subsequent explosion of massive stars. Even though it has profound consequences for our understanding of their nature and selection biases, little is known about the dust properties of the galaxies hosting GRBs. We present analysis of the far-infrared properties of an unbiased sample of 20 BeppoSAX and Swift GRB host galaxies (at an average redshift of z = 3.1) located in the Herschel Astrophysical Terahertz Large Area Survey, the Herschel Virgo Cluster Survey, the Herschel Fornax Cluster Survey, the Herschel Stripe 82 Survey and the Herschel Multi-tiered Extragalactic Survey, totalling 880 deg2, or ∌3 per cent of the sky in total. Our sample selection is serendipitous, based only on whether the X-ray position of a GRB lies within a large-scale Herschel survey – therefore our sample can be considered completely unbiased. Using deep data at wavelengths of 100–500 Όm, we tentatively detected 1 out of 20 GRB hosts located in these fields. We constrain their dust masses and star formation rates (SFRs), and discuss these in the context of recent measurements of submillimetre galaxies and ultraluminous infrared galaxies. The average far-infrared flux of our sample gives an upper limit on SFR of 500 M⊙ yr−1 is consistent with the contribution of such luminous galaxies to the cosmic star formation density

    The hyporheic zone as an invertebrate refuge: a review of variability in space, time, taxa and behaviour

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    The hyporheic zone is a potential refuge that can promote persistence of benthic invertebrates during adverse conditions in surface streams. For decades, changes in invertebrate depth distribution have been investigated in relation to flood, low flow and drying events, but evidence for use of the hyporheic refuge remains equivocal. This review examines the evidence for the hyporheic zone’s refugial role during adverse hydrological conditions. Refuge potential is influenced by determinants in four categories. First, refuge use varies spatially in relation to physical habitat parameters, including sediment porosity and hydrologic exchange. Second, refuge use is temporally variable and reflects disturbance characteristics including rate of onset. Third, refuge use is taxon-specific, depending on a range of morphological, behavioural and physiological traits. Fourth, the behaviours governing refuge use vary, with both active migrations and passive habitat use playing important roles in community persistence. These four determinants interact to influence refuge use; for example, the physical habitat providing an adequate refuge will vary between taxa. Despite this variability, the hyporheic zone is an important component in the suite of refuges that facilitate community resilience to disturbance events. As such, its ecological integrity should be safeguarded through sensitive management and effective rehabilitation schemes

    Biological indices to characterize community responses to drying in streams with contrasting flow permanence regimes

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    Many river networks include temporary reaches that stop flowing and may dry during unpredictable droughts (near-perennial) or more frequently (intermittent). A few biological indices have been developed to assess invertebrate community responses to hydrological variability, including the instream conditions associated with drought, but their performance in temporary streams remains poorly known. We evaluated the ability of two such indices, the Lotic-invertebrate Index for Flow Evaluation (LIFE) and the Drought Effect of Habitat Loss on Invertebrates (DEHLI), to predict responses to flow cessation and drying in temporary streams with contrasting flow permanence regimes. We used a 26-year dataset comprising spring-season invertebrate community samples and daily discharge measurements from 46 sites in a cool, wet temperate region, to examine relationships between hydrological variables and changes in index scores. We also identified taxon-specific thresholds at which occurrence changed with increasing drying and flowing durations. Both indices effectively characterized responses to increasing no-flow durations. DEHLI also reflected community changes following flow resumptions, identified differences in responses among flow permanence groups, and was particularly able to predict community responses at near-perennial sites. DEHLI scores at near-perennial sites took on average three years after a drying event to return to values typical of perennial sites, whereas responses to increasing flow duration were more erratic at intermittent sites. Lotic specialists declined whereas lentic and semi-aquatic taxa increased in occurrence with no-flow duration after summers with <50 days without flow, due to changes in the availability of preferred habitat types. Community responses to drying events were less predictable among intermittent than near-perennial sites, likely because differences in habitat conditions and connectivity may lead intermittent communities to harbour contrasting pools of species with strategies that promote persistence during and/or recolonization after drying. We identify DEHLI as an index that can characterize community responses to drying in temporary streams with contrasting flow permanence regimes. We also recommend the development of new indices that include lentic, semi-aquatic and terrestrial as well as lotic taxa, to more comprehensively describe and predict community responses to changing instream conditions

    Recognition of stream drying based on benthic macroinvertebrates: a new tool in Central Europe

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    Many streams in the extensive Central European region have an intermittent flow regime. Conventional hydrological methods used to identify zero-flow conditions, and in particular drying events, have limited use when assessing large areas dominated by low-order streams. We developed a novel multimetric index to recognise antecedent stream drying based on the analysis of benthic macroinvertebrate communities. The data used to develop the index were collected in pristine streams with different flow permanence regimes between 2012 and 2014, using standard sampling methods for ecological status assessment. The data include 64 perennial, 19 near-perennial and 27 intermittent benthic macroinvertebrate samples. Metrics considered for the index included variables based on (i) the occurrence of indicator taxa, (ii) the proportion of biological and ecological traits, and (iii) structural community metrics. Linear discriminant analysis identified the metric combinations that best discriminated among the three flow permanence categories. Different metrics were used in the final multimetric index calculation for the autumn and spring season that followed stream drying. In both seasons, the index included the proportion of indicator taxa and the proportion of taxa with high body flexibility. In addition, the autumn index included the proportion of taxa with a preference for organic substrates, whereas in spring the index included total abundance. Independent data from regulatory monitoring activity were used to validate the accuracy of the index. The correct classification of independent samples was 92% and 96% for samples from perennial and non-perennial sites, respectively. The index can be calculated using data collected by routine monitoring programmes used to assess ecological status and provides information about stream intermittence where conventional hydrological monitoring is limited. As intermittent streams increase in extent in global regions including Central Europe, the tool may be of particular interest to those who use invertebrates to monitor or manage these ecosystems

    Study of bubble growth at conical nucleation sites with reduced wettability

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