8,796 research outputs found
A stalk fluid forming above the transition from the lamellar to the rhombohedral phase of lipid membranes
No full textIn this work, we present evidence for the formation of transient stalks in aligned multilamellar stacks of lipid membranes. Just above the phase transition from the fluid () lamellar phase to the rhombohedral phase (R), where lipid stalks crystallize on a super-lattice within the lipid bilayer stack, we observe a characteristic scattering pattern, which can be attributed to a correlated fluid of transient stalks. Excess (off-axis) diffuse scattering with a broad modulation around the position which later transforms to a sharp peak of the rhombohedral lattice, gives evidence for the stalk fluid forming as a pre-critical effect, reminiscent of critical phenomena in the vicinity of second-order phase transitions. Using high-resolution off-specular X-ray scattering and lineshape analysis we show that this pre-critical regime is accompanied by an anomalous elasticity behavior of the membrane stack, in particular an increase in inter-bilayer compressibility, i.e., a decrease in the compression modulus
Enseñanza de la escritura de Max Aub: comprensión y memoria
No full textEste texto analiza a obra testimonial de Max Aub sobre su experiencia en los campos de concentración en Francia desde una perspectiva de discursos comparados. Para destacar las estrategias de la escritura del autor recuperables por otros proyectos discursivos que persigan la sensibilización y la denuncia a través del cruce entre la comunicación y la éticaThis text analyses the testimonial work of Max Aub about his experience in the French concentration camps in France from comparative discourses approach. It emphasizes the writing strategies used by the author useful for other awareness and denounce discourses through the dialogue among communication and ethic
Max Brooks literary reading flier
No full text2012 Bismarck State College Visiting Writers Series and ArtsQuest present: Max Brooks. April 25, 7:30 p.m.; Belle Mehus Auditorium. Max Brooks is the author of World War Z: An Oral History of the Zombie War and the graphic novel The Zombie Survival Guide: Recorded Attacks
Max Frisch's novel: Stiller. A study
No full text The attempt is made in the following study to present an interpretation of the novel "Stiller" by the Swiss author, Max Frisch, by tracing through the novel the dominant themes of the graven-image or 'Bildnis' and that of the problem of freedom with reference to the novel's main character. ThesisMaster of Arts (MA
A Transfer Report on the Development of a Framework to Evaluate Search Interfaces for their Support of Different User Types and Search Tactics
No full textAs the understanding of search systems, user needs and seeking strategies is developing, the design of search user interfaces is evolving to support more complicated and exploratory forms of search. With the design of new search features that enable these richer modes of exploration, comes the need to better understand the support they provide. In this report a new evaluation framework is presented that analyses search features for how they a) contribute to an overall interface, b) allow users to carry out different search tactics, and c) support different types of users and their needs. The novel contributions of the framework improve on some of the limitations of typical user studies, and allow search systems to be systematically analysed in much more detail and in much less time. The presented evaluation framework is then validated in three ways. First the validity of the models used as the building blocks of the framework are investigated through related work. Second the method of integrating these building-block models is validated and strengthened by consensus of expert opinion. Third, the overall approach is validated by comparing its analyses to the results of previously carried out user studies. The validation process has shown both the value of the framework and identified areas of future work that should be addressed for the framework to be completed. This report concludes with the set of contributions that the framework makes, and why the remaining work will be challenging, but critical to the final design
Lipid composition of Collembola and their food resources in deciduous forest stands—Implications for feeding strategies
No full textThe lipid composition of Collembola and their potential food resources was assessed in three deciduous forest stands, in order to gain insight into food web linkages under field conditions. Fatty acids (FAs) previously assigned as trophic markers in laboratory experiments were used to investigate feeding strategies in situ. As potential food sources soil microbiota and plant debris were characterised by their phospholipid fatty acid (PLFA) composition. Both the amount and the pattern of PLFAs differed between sites and soil depth, in particular the bacterial and plant marker FAs in the upper soil layer. Thus, the availability of resources for micro-detritivores varied due to forest and soil layer. The lipid composition of vital and senescent beech leaves was predominantly influenced by metabolic status and represented a quite homogenous FA resource across forest stands. Comparing Folsomia quadrioculata, Lepidocyrtus lignorum, Neanura muscorum and Pogonognathellus longicornis between the different forests revealed FA profiles to be predominantly affected by site, suggesting a diet shift depending on resources at hand. However, species-specific differences in individual FAs occurred, likely related to feeding strategy and physiological activity. Lipids of Collembola comprised low amounts of bacterial marker FAs, and bacterial consumption may occur to some extent, particularly on Gram-positives. The marker FA for predatory feeding, 20: 1 omega 9, was found in several species, although in low amounts. This contradicts known feeding habits and caution is advisable in using 20: 1 omega 9 as trophic marker. Overall, as indicated by high proportions of oleic (18: 1 omega 9) or linoleic (18: 2 omega 6, 9) acid, most species were either plant litter or fungal feeders, with some transitions. The ratio 18: 1 omega 9/18: 2 omega 6,9 is proposed as a tool to distinguish between these two major feeding strategies in Collembola. (c) 2007 Elsevier Ltd. All rights reserved
The subzero microbiome: Microbial activity in frozen and thawing soils
No full textMost of the Earth's biosphere is characterized by low temperatures (<5 °C) and cold-adapted microorganisms are widespread. These psychrophiles have evolved a complex range of adaptations of all cellular constituents to counteract the potentially deleterious effects of low kinetic energy environments and the freezing of water. Microbial life continues into the subzero temperature range, and this activity contributes to carbon and nitrogen flux in and out of ecosystems, ultimately affecting global processes. Microbial responses to climate warming and in particular, thawing of frozen soils are not yet well understood although the threat of microbial contribution to positive feedback of carbon flux is substantial. To date, several studies have examined microbial community dynamics in frozen soils and permafrost due to changing environmental conditions, and some have undertaken the complicated task of characterizing microbial functional groups and how their activity changes with changing conditions, either in situ or by isolating and characterizing macromolecules. With increasing temperature and wetter conditions microbial activity of key microbes and subsequent efflux of greenhouse gases also increase. In this review, we aim to provide an overview of microbial activity in seasonally frozen soils and permafrost. With a more detailed understanding of the microbiological activities in these vulnerable soil ecosystems, we can begin to predict and model future expectations for carbon release and climate change.Peer reviewe
Frontline Timor : to resist is to win. by Max Stahl
No full texttag=1 data=Frontline Timor : to resist is to win. by Max Stahl
tag=2 data=Stahl, Max
tag=3 data=The Australian Magazine,
tag=6 data=18/19 January 1992
tag=7 data=6-12.
tag=8 data=SOUTH-EAST ASIA
tag=9 data=EAST TIMOR
tag=10 data=The author describes a rarely permitted visit to the secret camps of the Timorese guerillas who, despite the Dili massacre and the crushing presence of the Indonesian military, continue to hold out and plot for independence.
tag=11 data=1992/4/2
tag=12 data=92/0116
tag=13 data=CABThe author describes a rarely permitted visit to the secret camps of the Timorese guerillas who, despite the Dili massacre and the crushing presence of the Indonesian military, continue to hold out and plot for independence
Studies on linear systems and the eigenvalue problem over the max-plus algebra
No full textMax-plus代数は，実数全体に無限小元を付加した集合に，加法として最大値をとる演算，乗法として通常の加法を考えた代数系である．本論文では，max-plus線形方程式に対するCramerの公式の類似物を用いて，線形方程式の解空間の基底が構成できることを示した．さらに固有値問題に関連して，max-plus行列の固有ベクトルの概念を2通りの観点から拡張した．The max-plus algebra is the semiring with addition "max" and multiplication "+". In the present thesis, the author gives a combinatorial characterization of solutions of linear systems in terms of the max-plus Cramer's rule. Further, the author extends the concept of eigenvectors of max-plus matrices from two different perspectives.doctoral thesi
Artificial groundwater recharge in forests : soil fauna and microbiology
No full textAt present, approximately half of the drinking water for the city of Basel (Switzerland) is obtained by an artificial groundwater recharge system in a former floodplain area called “Lange Erlen”. Generally, the use of groundwater for drinking water production may lower groundwater tables. Artificial groundwater recharge is a practice of directing and simultaneously purifying water into aquifers, thereby raising the groundwater table and guaranteeing sufficient drinking water sources. Water purification through artificial groundwater recharge is widespread. However, it more commonly involves areas without vegetation, i.e. slow sand filters, dunes or channels and is combined with long flooding periods. In contrast, at the “Lange Erlen”, forested areas are periodically flooded (max. 10 days) with water from the river Rhine. This routine is interrupted by longer regeneration periods. To date, water infiltration and purification processes have remained constant and satisfactory since the system has been established almost 100 years ago. However, detailed knowledge on the belowground processes that have been sustaining the water purification capacity of “Lange Erlen” is scarce.
Intensive flooding may detrimentally affect earthworm populations and result in clogging of the topsoil, which is a common problem in groundwater recharge systems. Earthworms are known to influence water infiltration and aeration of soils, but most of the existing knowledge relates to grasslands and little is known about the role of earthworms for water infiltration in forests. To better understand the “Lange Erlen” system in the shallow soil layer, earthworm populations, microbial parameters (substrate induced respiration, SIR) and water infiltration rates were studied at the recharge areas. The findings suggest that earthworms are an important factor of the long-term sustainability of this system (for the past ~100 years). The total earthworm
numbers and biomass in watered sites exceeded those of non-watered sites (+51% and +71%, respectively). Total earthworm numbers, numbers of endogeic (mineral forms) and epigeic (litter dwellers) earthworms, and numbers of two species (Lumbricus rubellus and Allolobophora chlorotica) significantly and positively correlated with water infiltration rates. Microbial biomass and activity was significantly enhanced in the top soil layer of the watered sites. The results imply that the flooding regime at the “Lange Erlen” favors earthworm populations which in turn prevent soil clogging, aerate the top soil layer, and stimulate microbial growth.
Groundwater quality is directly influenced by subsurface microbial, chemical and physical soil processes. However, most studies on microbial communities have been limited to the top soil layer. These studies disregarded deeper soil horizons although subsurface microorganisms are crucial for the degradation of natural organic compounds or contaminants and the maintenance of groundwater quality. Therefore, vertical soil profiles down to approximately 4 m of depth from two watered sites and one non-watered site were investigated for the structural (phospholipid fatty acids, PLFAs) and the functional (extracellular hydrolytic enzymes) microbial community composition. Furthermore, additional microbial (by SIR), physical and chemical soil parameters were obtained from the same soil samples.
The microbial biomass did not differ between watered sites and the non-watered site, however considerable fractions of the microbial biomass (25-42% by PLFA and 42-58% by SIR) were located in 40-340 cm depth at all sites. The microbial activity (CO2 emission) and the specific respiration (qCO2) were highest at the watered sites. The microbial community structure differed significantly between watered and non-watered sites (predominantly below 100 cm depth), whereas the functional structure (based on the relative enzyme pattern) differed significantly between all sites. The latter finding could probably be explained by different soil structures in each soil
profile rather than by flooding. Proportions of the bacterial PLFAs 16:1ω5, 16:1ω7, cy17:0 and 18:1ω9t, and the long chained PLFAs 22:1ω9 and 24:1ω9 were more prominent at the watered sites, whereas branched, saturated PLFAs (iso/anteiso) dominated at the non-watered site. The PLFA community indices indicated stress response and higher nutrient availability due to flooding. The analysis of extracellular soil enzymes revealed that acid phosphatase showed highest absolute activities at all field sites throughout the soil depth transect and was followed by L-leucine aminopeptidase and β-glucosidase. Combining the structural and the functional diversity of the microbial community in one analysis revealed significant correlations between the PLFA pattern and specific enzymes activities in the non-watered site. However, at the watered sites these relationships were not detected and the same factors appeared uncoupled from each other.
Overall, this implies that adding labile nutrients (i.e. DOC or DON by flooding) to a soil where other nutrients are limiting microbial growth (i.e. P as indicated by acid phosphatase) increases microbial activity but not biomass. This in turn results in waste respiration by overflow metabolism. Additionally, slight nutrient leaching (e.g. nitrate) into the groundwater is observed due to P-limiting conditions.
No differences in absolute and specific enzyme activities between watered sites and the non-watered site indicated complex organic matter input at the recharge sites to be impeded by flooding water pretreatment. In conclusion, water recharge processes resulted in a microbial community adapted to resource and environmental conditions, which was predominantly located in the upper (100-220 cm depth) and partly in the lower vadose zone (220-280 cm depth). Given a better understanding, the system may be more widely adopted and used to provide sufficient and reliable drinking water to the city of Basel
- …
