Localized energy for wave equations with degenerate trapping

Localized energy estimates have become a fundamental tool when studying wave equations in the presence of asymptotically at background geometry. Trapped rays necessitate a loss when compared to the estimate on Minkowski space. A loss of regularity is a common way to incorporate such. When trapping is sufficiently weak, a logarithmic loss of regularity suffices. Here, by studying a warped product manifold introduced by Christianson and Wunsch, we encounter the first explicit example of a situation where an estimate with an algebraic loss of regularity exists and this loss is sharp. Due to the global-in-time nature of the estimate for the wave equation, the situation is more complicated than for the Schr\"{o}dinger equation. An initial estimate with sub-optimal loss is first obtained, where extra care is required due to the low frequency contributions. An improved estimate is then established using energy functionals that are inspired by WKB analysis. Finally, it is shown that the loss cannot be improved by any power by saturating the estimate with a quasimode.Comment: 18 page

Lysine and novel hydroxylysine lipids in soil bacteria: amino acid membrane lipid response to temperature and pH in <i>Pseudopedobacter saltans</i>

Microbial decomposition of organic matter is an essential process in the global carbon cycle. The soil bacteria Pseudopedobacter saltans and Flavobacterium johnsoniae are both able to degrade complex organic molecules, but it is not fully known how their membrane structures are adapted to their environmental niche. The membrane lipids of these species were extracted and analyzed using high performance liquid chromatography-electrospray ionization/ion trap/mass spectrometry (HPLC-ESI/IT/MS) and high resolution accurate mass/mass spectrometry (HRAM/MS). Abundant unknown intact polar lipids (IPLs) from P. saltans were isolated and further characterized using amino acid analysis and two dimensional nuclear magnetic resonance (NMR) spectroscopy. Ornithine IPLs (OLs) with variable (hydroxy) fatty acid composition were observed in both bacterial species. Lysine-containing IPLs (LLs) were also detected in both species and were characterized here for the first time using HPLC-MS. Novel LLs containing hydroxy fatty acids and novel hydroxylysine lipids with variable (hydroxy) fatty acid composition were identified in P. saltans. The confirmation of OL and LL formation in F. johnsoniae and P. saltans and the presence of OlsF putative homologs in P. saltans suggest the OlsF gene coding protein is possibly involved in OL and LL biosynthesis in both species, however, potential pathways of OL and LL hydroxylation in P. saltans are still undetermined. Triplicate cultures of P. saltans were grown at three temperature/pH combinations: 30°C/pH 7, 15°C/pH 7, and 15°C/pH 9. The fractional abundance of total amino acid containing IPLs containing hydroxylated fatty acids was significantly higher at higher temperature, and the fractional abundance of lysine-containing IPLs was significantly higher at lower temperature and higher pH. These results suggest that these amino acid-containing IPLs, including the novel hydroxylysine lipids, could be involved in temperature and pH stress response of soil bacteria

Cryptic invasion of a parasitic copepod: Compromised identification when morphologically similar invaders co-occur in invaded ecosystems

Despite their frequent occurrence and strong impacts on native biota, biological invasions can long remain undetected. One reason for this is that an invasive species can be morphologically similar to either native species or introduced species previously established in the same region, and thus be subject to mistaken identification. One recent case involves congeneric invasive parasites, copepods that now infect bivalve hosts along European Atlantic coasts, after having been introduced independently first from the Mediterranean Sea (Mytilicola intestinalis Steuer, 1902) and later from Japan (Mytilicola orientalis Mori, 1935). At least one report on M. intestinalis may have actually concerned M. orientalis, and M. orientalis thus qualifies as a "cryptic invader". Because these two parasitic copepods are morphologically similar, knowledge about their distribution, impact and interactions depends crucially on reliable species identification. In this study, we evaluated the reliability of morphological identification of these two species in parts of their invasive range in Europe (Dutch Delta and Wadden Sea) in comparison with molecular methods of well-established accuracy based on COI gene sequences and ITS1 restriction fragment length polymorphism. Based on seven easily measured or scored macro-morphological variables that were recorded for 182 individual copepods isolated from blue mussels (Mytilus edulis Linnaeus, 1758), principal component analysis showed two relatively distinct but overlapping morphological species groups for females, but no clear separation in males. Discriminant function analysis showed that the females can be discriminated reasonably well based on some of the morphological characteristics (identification error rate of 7%) while males cannot (error rate of 25%). The direction of the dorsolateral thoracic protuberances was identified as the most important trait for species discrimination, but among the morphological features checked, none could flawlessly discriminate between both species. We recommend the use of molecular techniques in future studies of invasive Mytilicola to reliably discriminate between the species. The morphological similarity of these two invaders suggests a more general problem of cryptic invasions and compromised identification of parasites in invaded ecosystems. This problem should be borne in mind whenever invasive parasites are investigated

On the potential application of polar and temperate marine microalgae for EPA and DHA production

Long chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are considered essential omega-3 fatty acids in human nutrition. In marine microalgae EPA and/or DHA are allegedly involved in the regulation of membrane fluidity and thylakoid membrane functioning. The cellular content of EPA and DHA may therefore be enhanced at low temperature and irradiance conditions. As a result, polar and cold temperate marine microalgal species might potentially be suitable candidates for commercial EPA and DHA production, given their adaptation to low temperature and irradiance habitats. In the present study we investigated inter- and intraspecific EPA and DHA variability in five polar and (cold) temperate microalgae. Intraspecific EPA and DHA content did not vary significantly in an Antarctic (Chaetoceros brevis) and a temperate (Thalassiosira weissflogii) centric diatom after acclimation to a range of irradiance levels at two temperatures. Interspecific variability was investigated for two Antarctic (Chaetoceros brevis and Pyramimonas sp. (Prasinophyceae)) and three cold-temperate species (Thalassiosira weissflogii, Emiliania huxleyi (Prymnesiophyceae) and Fibrocapsa japonica (Raphidophyceae)) during exponential growth. Interspecific variability was shown to be much more important than intraspecific variability. Highest relative and absolute levels of DHA were measured in the prymnesiophyte E. huxleyi and the prasinophyte Pyramimonas sp., while levels of EPA were high in the raphidophyte F. japonica and the diatoms C. brevis and T. weissflogii. Yet, no significant differences in LC-PUFA content were found between polar and cold-temperate species. Also, EPA and DHA production rates varied strongly between species. Highest EPA production rate (174 μg L(-1) day(-1)) was found in the Antarctic diatom Chaetoceros brevis, while DHA production was highest in the cold-temperate prymnesiophyte Emiliania huxleyi (164 μg L(-1) day(-1)). We show that, following careful species selection, effective mass cultivation of marine microalgae for EPA and DHA production may be possible under low temperature and irradiance conditions

Rapid sulfurisation of highly branched isoprenoid (HBI) alkenes in sulfidic Holocene sediments from Ellis Fjord, Antarctica

Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Organic Geochemistry 38 (2007): 128-139, doi:10.1016/j.orggeochem.2006.08.003.Samples of particulate organic matter from the water column and anoxic Holocene sediment layers from the Small Meromictic Basin (SMB) in Ellis Fjord (eastern Antarctica) were analyzed to study the early incorporation of reduced inorganic sulfur species into highly branched isoprenoid (HBI) alkenes. HBIs were not detected in the water column samples from austral winter, whereas compounds containing the C25 HBI skeleton were abundant in all analyzed Holocene sediment layers. The structure of the C25:2 HBI alkene together with its enriched stable carbon isotopic composition suggest that the HBI alkene is produced by a diatom or diatoms probably belonging to the Navicula genus present in the sea-ice which covers the area most of the year. Within just 500 years of deposition, all of the HBI alkene was sulfurised. A mixture of products was formed, including components tentatively identified as a C25 HBI thiane and three S-containing dimers composed of two C25:1 HBI skeletons linked together by a sulfide bond. Most of the HBI alkene, however, was converted to polar S-containing compounds. The observed reaction rate for sulfurisation the C25:2 HBI alkene is the highest observed so far in natural systems. Sterols and other lipids known to be prone to sulfurisation were only minimally sulfurised under these depositional conditions. The reason for this is presently unclear.Funding for the collection of the sediment and water samples (by MJLC and CW) was provided by ASAC grant 1166 to JKV. This work was further supported by a grant from the Netherlands Organization for Scientific Research (NWO; Netherlands Antarctic Research Proposals 851.20.006 to JSSD)

Motives for (not) participating in a lifestyle intervention trial

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Brain areas involved in spatial working memory

Spatial working memory entails the ability to keep spatial information active in working memory over a short period of time. To study the areas of the brain that are involved in spatial working memory, a group of stroke patients was tested with a spatial search task. Patients and healthy controls were asked to search through a number of boxes shown at different locations on a touch-sensitive computer screen in order to find a target object. In subsequent trials, new target objects were hidden in boxes that were previously empty. Within-search errors were made if a participant returned to an already searched box; between-search errors occurred if a participant returned to a box that was already known to contain a target item. The use of a strategy to remember the locations of the target objects was calculated as well. Damage to the right posterior parietal and right dorsolateral prefrontal cortex impaired the ability to keep spatial information [`]on-line', as was indicated by performance on the Corsi Block-Tapping task and the within-search errors. Moreover, patients with damage to the right posterior parietal cortex, the right dorsolateral prefrontal cortex and the hippocampal formation bilaterally made more between-search errors, indicating the importance of these areas in maintaining spatial information in working memory over an extended time period.http://www.sciencedirect.com/science/article/B6T0D-4HM7WH2-2/1/b6b13c7b404377bae2b8cf632eb61fe

Telmatocola sphagniphila gen. nov., sp. nov., a Novel Dendriform Planctomycete from Northern Wetlands

Members of the phylum Planctomycetes are common inhabitants of northern wetlands. We used barcoded pyrosequencing to survey bacterial diversity in an acidic (pH 4.0) Sphagnum peat sampled from the peat bog Obukhovskoye, European North Russia. A total of 21189 bacterial 16S rRNA gene sequences were obtained, of which 1081 reads (5.1%) belonged to the Planctomycetes. Two-thirds of these sequences affiliated with planctomycete groups for which characterized representatives have not yet been available. Here, we describe two organisms from one of these previously uncultivated planctomycete groups. One isolate, strain OB3, was obtained from the peat sample used in our molecular study, while another strain, SP2T (=DSM 23888T = VKM B-2710T), was isolated from the peat bog Staroselsky moss. Both isolates are represented by aerobic, budding, pink-pigmented, non-motile, spherical cells that are arranged in unusual, dendriform-like structures during growth on solid media. These bacteria are moderately acidophilic and mesophilic, capable of growth at pH 4.0–7.0 (optimum pH 5.0–5.5) and at 6–30°C (optimum 20–26°C). The preferred growth substrates are various heteropolysaccharides and sugars, the latter being utilized only if provided in low concentrations (≤0.025%). In contrast to other described planctomycetes, strains SP2T and OB3 possess weak cellulolytic potential. The major fatty acids are C16:1ω5c, C18:1ω5c, C16:0, and C18:0. Characteristic lipids are the n-C31 polyunsaturated alkene (9–10 double bonds) and C30:1/C32:1 (ω-1) hydroxy fatty acids. The G + C content of the DNA is 58.5–59.0 mol%. Strains SP2T and OB3 share identical 16S rRNA gene sequences, which exhibit only 86 and 87% similarity to those of Gemmata obscuriglobus and Zavarzinella formosa. Based on the characteristics reported here, we propose to classify these novel planctomycetes as representatives of a novel genus and species, Telmatocola sphagniphila gen. nov., sp. nov