On the fundamental group of the complement of a complex hyperplane arrangement

We construct two combinatorially equivalent line arrangements in the complex projective plane such that the fundamental groups of their complements are not isomorphic. The proof uses a new invariant of the fundamental group of the complement to a line arrangement of a given combinatorial type with respect to isomorphisms inducing the canonical isomorphism of the first homology groups.Comment: 12 pages, Latex2e with AMSLaTeX 1.2, no figures; this last version is almost the same as published in Functional Analysis and its Applications 45:2 (2011), 137-14

XML-structured documents: Retrievable units and inheritance

We consider the retrieval of XML-structured documents, and of passages from such documents, defined as elements of the XML structure. These are considered from the point of view of passage retrieval, as a form of document retrieval. A retrievable unit (an element chosen as defining suitable passages for retrieval) is a textual document in its own right, but may inherit information from the other parts of the same document. Again, this inheritance is defined in terms of the XML structure. All retrievable units are mapped onto a common field structure, and the ranking function is a standard document retrieval function with a suitable field weighting. A small experiment to demonstrate the idea, using INEX data, is described

A Global lake ecological observatory network (GLEON) for synthesising high-frequency sensor data for validation of deterministic ecological models

A Global Lake Ecological Observatory Network (GLEON; www.gleon.org) has formed to provide a coordinated response to the need for scientific understanding of lake processes, utilising technological advances available from autonomous sensors. The organisation embraces a grassroots approach to engage researchers from varying disciplines, sites spanning geographic and ecological gradients, and novel sensor and cyberinfrastructure to synthesise high-frequency lake data at scales ranging from local to global. The high-frequency data provide a platform to rigorously validate processbased ecological models because model simulation time steps are better aligned with sensor measurements than with lower-frequency, manual samples. Two case studies from Trout Bog, Wisconsin, USA, and Lake Rotoehu, North Island, New Zealand, are presented to demonstrate that in the past, ecological model outputs (e.g., temperature, chlorophyll) have been relatively poorly validated based on a limited number of directly comparable measurements, both in time and space. The case studies demonstrate some of the difficulties of mapping sensor measurements directly to model state variable outputs as well as the opportunities to use deviations between sensor measurements and model simulations to better inform process understanding. Well-validated ecological models provide a mechanism to extrapolate high-frequency sensor data in space and time, thereby potentially creating a fully 3-dimensional simulation of key variables of interest

Physical and chemical consequences of artificially deepened thermocline in a small humic lake - a paired whole-lake climate change experiment

Peer reviewe

Pharmacological Preconditioning with Diazoxide in the Experimental Hypothermic Circulatory Arrest Model

Background: Hypothermic circulatory arrest includes a remarkable risk for neurological injury. Diazoxide, a mitochondrial adenosine triphosphate-dependent potassium ion (K+ATP) channel opener, is known to have cardioprotective effects. We assessed its efficacy in preventing ischemic injury in a clinically relevant animal model.Methods: Eighteen piglets were randomized into a diazoxide group (n = 9) and a control group (n = 9). Animals underwent 60 minutes of hypothermic circulatory arrest at 18 degrees C. Diazoxide (5 mg/kg + 10 mL NaOH + 40 mL NaCl) was infused during the cooling phase. Metabolic and hemodynamic data were collected throughout the experiment. After 24-hour follow-up, whole brain, heart, and kidney biopsy specimens were collected for analysis.Results: Cerebellar Cytochrome-C and caspase-3 activation was higher in the control group (P = .02 and P = .016, respectively). Antioxidant activity tended to be higher in the diazoxide group (P = .099). Throughout the experiment, the oxygen consumption ratio was higher in the control animals (P-g = .04), as were the lactate levels (P-g = .02). Cardiac function tended to be better in diazoxide-treated animals.Conclusion: Diazoxide might confer neuroprotective effect as implied by the immunohistochemical analysis of the brain. Additionally, the circulatory effects of diazoxide were beneficial, supporting its neuroprotective effect

Daphniaperformance on diets containing different combinations of high-quality algae, heterotrophic bacteria, and allochthonous particulate organic matter

Filter-feeding zooplankton in lakes feed on a mixture of phytoplankton, bacteria, and terrestrial particles and the proportions and nutritional value of these components can be highly variable. However, the extent to which food quality interacts with food quantity in affecting overall zooplankton performance is not yet fully resolved. Here we performed laboratory feeding experiments to test how the performance of the unselective filter feederDaphnia galeatawas affected if various quantities of high-quality food (the phytoplanktonRhodomonas) were diluted with low-quality food such as heterotrophic bacteria (Pseudomonas) or terrestrial detritus particles (t-POM) from the riparian zone of a boreal forest stream. We hypothesised: that increased proportions of bacteria and t-POM in the diet will lead to decreased survival, somatic growth; and reproduction ofDaphniadespite the presence of phytoplankton; that these effects are more pronounced for t-POM than for heterotrophic bacteria; and that this response is stronger when phytoplankton availability is low. Increasing the concentrations ofPseudomonasaffectedDaphniasurvival, growth, and reproduction negatively whenRhodomonaswas available at intermediate (0.37 mgC/L) and high (0.55 mgC/L) quantities. WhenRhodomonasquantity was low (0.22 mgC/L), the addition ofPseudomonasgenerally resulted in betterDaphniaperformance except at very high concentrations of the bacterium relative toRhodomonas. In contrast, the addition of t-POM was detrimental for overallDaphniaperformance at allRhodomonasconcentrations. Daphniaperformance was best described by a model including the interaction between food quality and quantity, with stronger negative effects onDaphniawhen high-quality food was supplemented with t-POM than withPseudomonas. The results indicate that the ability of zooplankton to use low-quality food is affected by the concurrent availability of high-quality food. Furthermore, food sources that can be used but do not fulfil dietary requirements of grazers (e.g. bacteria), may still provide nutritional benefits as long as other complementary food components are available in sufficient quantities to compensate for biochemical deficiencies. Therefore, we conclude that heterotrophic bacteria, but not peat layer t-POM, can be an important component of zooplankton diets in boreal lakes, especially if the concentration of phytoplankton is low

Data Descriptor : Long-term chloride concentrations in North American and European freshwater lakes

Anthropogenic sources of chloride in a lake catchment, including road salt, fertilizer, and wastewater, can elevate the chloride concentration in freshwater lakes above background levels. Rising chloride concentrations can impact lake ecology and ecosystem services such as fisheries and the use of lakes as drinking water sources. To analyze the spatial extent and magnitude of increasing chloride concentrations in freshwater lakes, we amassed a database of 529 lakes in Europe and North America that had greater than or equal to ten years of chloride data. For each lake, we calculated climate statistics of mean annual total precipitation and mean monthly air temperatures from gridded global datasets. We also quantified land cover metrics, including road density and impervious surface, in buffer zones of 100 to 1,500m surrounding the perimeter of each lake. This database represents the largest global collection of lake chloride data. We hope that long-term water quality measurements in areas outside Europe and North America can be added to the database as they become available in the future.Peer reviewe