bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns in nutrient limitation and chlorophyll a along an anthropogenic eutrophication gradient in French Mediterranean coastal lagoons
Authors: Souchu Philippe , Bec Béatrice , Smith Val H. , Laugier Thierry , Fiandrino Annie , Benau Laurent , Orsoni Valérie , Collos Yves , Vaquer André
Published: March 2010

A cross-ecosystem comparison of data obtained from 20 French Mediterranean lagoons with contrasting eutrophication status provided the basis for investigating the variables that best predict chlorophyll a (Chl a) concentrations and nutrient limitation of phytoplankton biomass along a strong nutrient enrichment gradient. Summer concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) comprised only a small fraction of total nitrogen (TN) and total phosphorus (TP). On the basis of inorganic nutrient concentrations, the most oligotrophic lagoons appeared to be phosphorus-limited, with a tendency towards the development of nitrogen limitation as eutrophication increased, as evidenced by decreasing DIN:DIP ratios. A weak but significantly positive relationship was found between dissolved silicate (DSi) and Chl a, reflecting DSi accumulation in the water column along the trophic state gradient and implying a progressive shift away from potential Si limitation of phytoplankton growth. Observed concentrations of Chl a were far better explained by TN and TP than by DIN and DIP concentrations, suggesting that a total nutrient based approach is likely to be the most appropriate for managing eutrophication in Mediterranean lagoons and other coastal waters. These results give credence to the idea that marine and freshwater environments respond in a similar fashion to nutrient enrichment.
Reply to the comment by Francis on “Differences in predicted catch composition between two widely used catch equation formulations”Appears in Can. J. Fish. Aquat. Sci. 66: 126–132.
Authors: Branch Trevor A.
Published: March 2010

Francis (2010. Can. J. Fish. Aquat. Sci. 67: 763–765) writes a thoughtful response detailing concerns with my suggestion that the continuous (Baranov) catch formulation is preferable to the discrete catch formulation when fishing mortality is high (T.A. Branch. 2009. Can. J. Fish. Aquat. Sci. 66: 126–132). He suggests the discrete formulation allows for multiple gear encounters and that formulation choice should depend on which formulation better fits the data. Here I first distinguish between gear selectivity and availability and then show that our two views are complementary: the original assumes fish groups with differing gear selectivity but full availability, whereas Francis assumes fish groups fully selected by fishing gear but with differing availability. I maintain that the discrete formulation only models a single instantaneous interaction between fish and fishing gear and therefore only part of the population can be caught if fish groups have equal gear selectivity that is less than 100%, whereas under the same assumptions, the continuous formulation would allow the entire population to be caught. Finally, when the balance between gear selectivity and availability is unknown, I agree that formulation choice could be driven by model fits to the data, although formulation choice could also be based on how the fishery operates.
Patterns of conifer establishment and vigor on montane river floodplains in Olympic National Park, Washington, USA
Authors: Stolnack Scott A. , Naiman Robert J.
Published: March 2010

In the Pacific Coastal Ecoregion, coniferous trees are often prescribed for riparian restoration, yet little is known about their establishment on floodplains under natural conditions. In this study, 10- to 50-year-old floodplain surfaces of six rivers were surveyed to (1) quantify conifer distribution along study reaches, (2) describe relationships between conifer presence and selected biological and environmental variables, and (3) compare growth rates and relative vigor of conifers among sites. We found conifers on 17%–36% of the plots we sampled. Sitka spruce ( Picea sitchensis (Bong.) Carrière) was most common on the wetter sites, while Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) was most common on the drier sites. Other conifers common to adjacent terraces were extremely rare. Douglas-fir preferred elevated sites with shallower soils and fewer hardwood competitors (e.g., Alnus rubra Bong. and Salix spp.) than similar plots without conifers. For Sitka spruce, the variables examined revealed no statistical differences between conifer and non-conifer plots. Our findings suggest that the tolerance of Douglas-fir to drier conditions allows it to survive on relatively higher, drier sites where more moisture-demanding competitors fail. For Sitka spruce, factors other than those measured appear to be more important in spruce establishment and survival.
Assessing the impact of current and projected climates on Douglas-Fir productivity in British Columbia, Canada, using a process-based model (3-PG)
Authors: Coops Nicholas C. , Hember Robbie A. , Waring Richard H.
Published: March 2010

Predicted climate change is expected to significantly affect tree growth in many areas. We used a process-based model (Physiological Principles for Predicting Growth, 3-PG) to evaluate how climatic variation might alter growth of Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco and Pseudotsuga menziesii (Mirb.) Franco var. menziesii ) across biogeoclimatic zones in British Columbia. The results indicate that there will be significant changes in site index (defined as the height (in metres) of dominant trees at 50 years) over this century. In the interior, a reduction in site index is likely, particularly in stands with mid-range values of site index (25–30 m), with many of the interior bioecoclimatic zones predicted to experience a gradual mean decrease in site index by up to 10%. Individual sites may decrease by as much as 40% from current values. In contrast, site index along the coast overall is predicted to increase to a maximum of 43 m by 2080. In the Coastal Western Hemlock zone, however, mean site index is likely to increase from 26 m to only 34 m. We believe that combining process-based models with fine-spatial resolution climate forecasts offers a viable approach to assess future changes in forest productivity.
Sapflow and water use of freshwater wetland trees exposed to saltwater incursion in a tidally influenced South Carolina watershed
Authors: Krauss Ken W. , Duberstein Jamie A.
Published: March 2010

Sea-level rise and anthropogenic activity promote salinity incursion into many tidal freshwater forested wetlands. Interestingly, individual trees can persist for decades after salt impact. To understand why, we documented sapflow (Js), reduction in Jswith sapwood depth, and water use (F) of baldcypress ( Taxodium distichum (L.) Rich.) trees undergoing exposure to salinity. The mean Jsof individual trees was reduced by 2.8 g H2O·m–2·s–1(or by 18%) in the outer sapwood on a saline site versus a freshwater site; however, the smallest trees, present only on the saline site, also registered the lowest Js. Hence, tree size significantly influenced the overall site effect on Js. Trees undergoing perennial exposure to salt used greater relative amounts of water in outer sapwood than in inner sapwood depths, which identifies a potentially different strategy for baldcypress trees coping with saline site conditions over decades. Overall, individual trees used 100 kg H2O·day–1on a site that remained relatively fresh versus 23.9 kg H2O·day–1on the saline site. We surmise that perennial salinization of coastal freshwater forests forces shifts in individual-tree osmotic balance and water-use strategy to extend survival time on suboptimal sites, which further influences growth and morphology.
CALABI–YAU CONSTRUCTION BY SMOOTHING NORMAL CROSSING VARIETIES
Authors: LEE NAM-HOON
Published: March 2010

We investigate a method of construction of Calabi–Yau manifolds, that is, by smoothing normal crossing varieties. We develop theories for calculating the Picard groups of the Calabi–Yau manifolds obtained in this method. As an application, we show that many examples of Kawamata and Namikawa are different Calabi–Yau three-folds although they have same Hodge numbers.
ON NORMAL CONTACT PAIRS
Authors: BANDE GIANLUCA , HADJAR AMINE
Published: March 2010

We consider manifolds endowed with a contact pair structure. To such a structure are naturally associated two almost complex structures. If they are both integrable, we call the structure a normal contact pair. We generalize Morimoto's Theorem on the product of almost contact manifolds to flat bundles. We construct some examples on Boothby–Wang fibrations over contact-symplectic manifolds. In particular, these results give new methods to construct complex manifolds.
FORMAL GROUPS ARISING FROM FORMAL PUNCTURED RIBBONS
Authors: KURKE HERBERT , OSIPOV DENIS V. , ZHEGLOV ALEXANDER B.
Published: March 2010

We investigate the Picard functor of a formal punctured ribbon. We prove that under some conditions this functor is representable by a formal group scheme.
EVALUATING DETERMINISTIC POLICIES IN TWO-PLAYER ITERATED GAMES
Authors: DILÃO RUI , GRACIANO JOÃO
Published: March 2010

We construct a statistical ensemble of games, wherein each independent subensemble we have two players playing the same game. We derive the mean payoffs per move of the representative players of the game, and we evaluate all the deterministic policies with finite memory. In particular, we show that if one of the players has a generalized tit-for-tat policy, the mean payoff per move of both players is the same, forcing the equalization of the mean payoffs per move. In the case of symmetric, noncooperative and dilemmatic games, we show that generalized tit-for-tat or imitation policies together with the condition of not being the first to defect, leads to the highest mean payoffs per move for the players. Within this approach, it can be decided which policies perform better than others. In particular, it shows that reciprocity in noncooperative iterated games forces equality of mean payoffs. We prove a simple ergodic theorem for symmetric and noncooperative games. The Prisoner's Dilemma and the Hawk–Dove games have been analyzed, and the equilibrium states of the infinitely iterated games have been determined. In infinitely iterated games with the player choosing their moves with equal probabilities, strict Nash solutions are not necessarily reachable equilibrium solutions of games.
EXISTENCE OF LIMIT CYCLES IN THE REPRESSILATOR EQUATIONS
Authors: BUŞE OLGUŢA , KUZNETSOV ALEXEY , PÉREZ RODRIGO A.
Published: March 2010

The Repressilator is a genetic regulatory network used to model oscillatory behavior of more complex regulatory networks like the circadian clock. We prove that the Repressilator equations undergo a supercritical Hopf bifurcation as the maximal rate of protein synthesis increases, and find a large range of parameters for which there is a cycle.
DETRENDED FLUCTUATION ANALYSIS OF THE TCP-RED ALGORITHM
Authors: CHEN XI , WONG SIU-CHUNG , TSE CHI K. , TRAJKOVIĆ LJILJANA
Published: March 2010

It has been observed that Internet gateways employing Transport Control Protocol (TCP) and the Random Early Detection (RED) control algorithm may exhibit instability and oscillatory behavior. Most control methods proposed in the past have been based on analytical models that rely on statistical measurements of network parameters. In this paper, we apply the detrended fluctuation analysis (DFA) method to analyze stability of the TCP-RED system. The DFA is used to analyze time-series data and generate power-law scaling exponents, which indicate the long-range correlations of the time series. We quantify the stability of the TCP-RED system by examining the variation of the DFA power-law scaling exponent when the system parameters are varied. We also study the long-range power-law correlations of TCP window periods.
ON A FUNCTIONAL LASALLE PRINCIPLE WITH APPLICATION TO CHAOS SYNCHRONIZATION
Authors: CHEN GUANRONG , ČELIKOVSKÝ SERGEJ , ZHOU JIN
Published: March 2010

A functional version of the LaSalle invariance principle is introduced. Rather than the usual pointwise Lyapunov-like functions, this extended version of the principle uses specially constructed functionals along system trajectories. This modification enables the original principle to handle not only autonomous, but also some nonautonomous systems. The new theoretical result is used to study robust synchronization of general Liénard-type nonlinear systems. The new technique is finally applied to coupled chaotic van der Pol oscillators to achieve synchronization. Numerical simulation is included to demonstrate the effectiveness of the proposed methodology.
SYNCHRONIZATION OF CHAOTIC FRACTIONAL-ORDER SYSTEMS VIA LINEAR CONTROL
Authors: ODIBAT ZAID M. , CORSON NATHALIE , AZIZ-ALAOUI M. A. , BERTELLE CYRILLE
Published: March 2010

The chaotic dynamics of fractional-order systems has attracted much attention recently. Chaotic synchronization of fractional-order systems is further studied in this paper. We investigate the chaos synchronization of two identical systems via a suitable linear controller applied to the response system. Based on the stability results of linear fractional-order systems, sufficient conditions for chaos synchronization of these systems are given. Control laws are derived analytically to achieve synchronization of the chaotic fractional-order Chen, Rössler and modified Chua systems. Numerical simulations are provided to verify the theoretical analysis.
MANDELBROT-LIKE BIFURCATION STRUCTURES IN CHAOS BAND SCENARIO OF SWITCHED CONVERTER WITH DELAYED-PWM CONTROL
Authors: TABORDA J. A. , ANGULO F. , OLIVAR G.
Published: March 2010

In this paper, we report Mandelbrot-like bifurcation structures in a one-dimensional parameter space of real numbers corresponding to a dc-dc power converter modeled as a piecewise-smooth system with three zones. These fractal patterns have been studied in two-dimensional parameter space for smooth systems, but for nonsmooth systems has not been reported yet. The Mandelbrot-like sets we found are created in transition from the torus band to chaos band scenarios exhibited by a dc-dc buck power converter controlled by Delayed Pulse-Width Modulator (PWM) based on Zero Average Dynamics (or ZAD strategy), which corresponds to a piecewise-smooth system (PWS). The real parameter is provided by the PWM control strategy, namely ZAD strategy, and it can be varied in a large range, ideally (-∞, +∞). At -∞ and +∞ the dynamical behavior is the same, and thus we will describe the synamics in an ring-like parameter space. Mandelbrot-like borders are built by four chaotic bands, therefore these structures can be thought as instability islands where the state variables cannot be located. Using the Poincaré map approach we characterize the bifurcation structures and we describe recurrent patterns in different scales.
EPIDEMIC SELF-SYNCHRONIZATION IN COMPLEX NETWORKS OF KURAMOTO OSCILLATORS
Authors: SCHOLTES INGO , BOTEV JEAN , ESCH MARKUS , STURM PETER
Published: March 2010

In this article, we present and evaluate an epidemic scheme for the synchronization of coupled Kuramoto oscillators in communication networks. It addresses the problem of efficiently providing globally synchronous time epochs in complex, dynamic Peer-to-Peer network topologies. Rather than the usual model of continuously coupled nodes, a discretized version with sporadic message-based couplings to nearest neighbors is considered. This article empirically studies the emergence of coherent oscillator states for different network topologies, coupling functions, and sporadic coupling intensities. It further investigates the protocol's minimum bandwidth requirements in small-world network topologies. Synchronization resilience under the effect of random perturbations is studied for two coupling variations. Finally, the potential utilization of the scheme for a local inference of global network topology characteristics is discussed.
GAME THEORETIC BEST-RESPONSE DYNAMICS FOR EVACUEES' EXIT SELECTION
Authors: EHTAMO HARRI , HELIÖVAARA SIMO , KORHONEN TIMO , HOSTIKKA SIMO
Published: March 2010

We present a model for evacuees' exit selection in emergency evacuations. The model is based on the game theoretic concept of best-response dynamics, where each player updates his strategy periodically by reacting optimally to other players' strategies. A fixed point of the system of all players' best-response functions defines a Nash equilibrium (NE) of the game. In the model, the players are the evacuees and the strategies are the possible target exits. We present a mathematical formulation for the model and show that the game has a NE with pure strategies. We also analyze different iterative methods for finding the NE and derive an upper bound for the number of iterations needed to find the equilibrium. Numerical simulations are used to analyze the properties of the model.
A GENETIC ALGORITHM FOR DETECTING COMMUNITIES IN LARGE-SCALE COMPLEX NETWORKS
Authors: SHI CHUAN , YAN ZHENYU , WANG YI , CAI YANAN , WU BIN
Published: March 2010

Network model recently becomes a popular tool for studying complex systems. Detecting meaningful communities in complex networks, as an important task in network modeling and analysis, has attracted great interests in various research areas. This paper proposes a genetic algorithm with a special encoding schema for community detection in complex networks. The algorithm employs a metric, named modularity Q as the fitness function and applies a special locus-based adjacency encoding schema to represent the community partitions. The encoding schema enables the algorithm to determine the number of communities adaptively and automatically, which provides great flexibility to the detection process. In addition, the schema also significantly reduces the search space. Extensive experiments demonstrate the effectiveness of the proposed algorithm.
THERMOCHEMICAL PROPERTIES OF THE THIOCARBONYLTHIO COMPOUNDS FROM CONVENTIONAL DENSITY FUNCTIONAL THEORY CALCULATIONS
Authors: ZHANG ZHI-HUI , GAO TAO , TIAN XIAO-FENG , HE NA
Published: March 2010

Density functional theory (DFT) calculations employed at two levels, B3LYP/6-31G+(d) and B3P86/6-31G+(d), are reported for the geometry, enthalpy, and free energy of reaction of a number of dithiobenzoate reversible addition fragmentation transfer (RAFT) reagents ( S=C(Ph)S–R , S=C(Z)S–CH2Ph ). Based on these theoretical data, the effectiveness of these RAFT reagents is analyzed. The conclusions, especially obtained at B3LYP/6-31G+(d) level, are in good agreement with the experimental results. Our calculations suggest that the dithiobenzoate ( S=C(Z)S–CH2Ph ), where Z is OC6H5 or N(alkyl)2 , is a poor RAFT reagent. Contrarily, the compound S=C(Ph)S–R , where R is C(Me)2Ph or C(Me)2CN , is a highly efficient RAFT reagent. Our results reveal the utility of the theoretical calculations of physical magnitudes for the rationalization of judging the effectiveness of RAFT reagents and demonstrated that DFT is a good method to calculate these data. In addition, our results on the enthalpies and Gibbs free energies of formation for the R radicals are calculated with the same method. These data are important for the design of logical and economical chemical process. Finally, the B3LYP hybrid functional is employed to predict the values of thermodynamic magnitudes for several new ithiobenzoates. Those results need to be verified by future experimental measurements or theoretical calculations.
EFFECT OF HIGH-LEVEL LAYER SELECTION IN ONIOM ON Na+ ADSORPTION IN ZSM-5 ZEOLITE
Authors: CHU ZHEN-KUN , FU GANG , GUO WEN-PING , XU XIN
Published: March 2010

Here we present a systematical investigation on the effect of high-level layer selection in our own N-layered integrated molecular orbital + molecular mechanics (ONIOM) method. We used the adsorption of Na+ in the M7 site of ZSM-5 as an instructive example. We embedded n tetrahedral sites (nT= 7, 19, 22, 33) for high-level layer into a low-level layer represented by 75T (denoted as nT@75T). Our calculations showed that 7T@75T behaved poorly in both structure optimization and interaction energy calculation. Hence only including the first coordination circle of the ion (i.e. 7T), as commonly used in literature, is not sufficiently good. However, for n ≥ 19, both structure optimization and interaction energy calculation by ONIOM are in good agreement with the full 75T model calculation. Such a reliable ONIOM calculation needs only 1/10 to 1/5 computational time for each self-consistent field (SCF) iteration as compared to the full 75T model calculation, highlighting its pivotal role in zeolite simulation.
QUANTITATIVE STRUCTURE–PROPERTY RELATIONSHIPS ON DISSOLVABILITY OF PCDD/Fs USING QUANTUM CHEMICAL DESCRIPTORS AND PARTIAL LEAST SQUARES
Authors: LU GUI-NING , TAO XUE-QIN , DANG ZHI , HUANG WEILIN , LI ZHONG
Published: March 2010

The environmental fate of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) has become a major issue in recent decades. Quantitative structure–property relationship (QSPR) modeling is a powerful approach for predicting the properties of environmental organic pollutants from their structure descriptors. In this study, QSPR models were established for estimating water solubility (- log SW) and n-octanol/water partition coefficient ( log KOW) of PCDD/Fs. Quantum chemical descriptors computed with density functional theory at the B3LYP/6-31G(d) level and partial least squares (PLS) analysis with an optimizing procedure were used to generate QSPR models for - log SWand log KOWof PCDD/Fs. Optimized models with high correlation coefficients (R2> 0.983) were obtained for estimating - log SWand log KOWof PCDD/Fs. Both the internal cross validation test [Formula: see text] and external validation test (R2> 0.965) results showed that the obtained models had high-precision and good prediction capability. The - log SW} and log KOWvalues predicted by the obtained models are very close to those observed. The PLS analysis indicated that PCDD/Fs with larger electronic spatial extent (Re), lower molecular total energy (ET), and smaller energy gap between the lowest unoccupied and the highest occupied molecular orbitals (ELUMO-EHOMO) tend to be less soluble in water but more lipophilic.
A survey of online failure prediction methods
Authors: Salfner Felix , Lenk Maren , Malek Miroslaw
Published: March 2010

With the ever-growing complexity and dynamicity of computer systems, proactive fault management is an effective approach to enhancing availability. Online failure prediction is the key to such techniques. In contrast to classical reliability methods, online failure prediction is based on runtime monitoring and a variety of models and methods that use the current state of a system and, frequently, the past experience as well. This survey describes these methods. To capture the wide spectrum of approaches concerning this area, a taxonomy has been developed, whose different approaches are explained and major concepts are described in detail.
A discriminative model for semi-supervised learning
Authors: Balcan Maria-Florina , Blum Avrim
Published: March 2010

Supervised learning—that is, learning from labeled examples—is an area of Machine Learning that has reached substantial maturity. It has generated general-purpose and practically successful algorithms and the foundations are quite well understood and captured by theoretical frameworks such as the PAC-learning model and the Statistical Learning theory framework. However, for many contemporary practical problems such as classifying web pages or detecting spam, there is often additional information available in the form of
unlabeled
data, which is often much cheaper and more plentiful than labeled data. As a consequence, there has recently been substantial interest in
semi-supervised
learning—using unlabeled data together with labeled data—since any useful information that reduces the amount of labeled data needed can be a significant benefit. Several techniques have been developed for doing this, along with experimental results on a variety of different learning problems. Unfortunately, the standard learning frameworks for reasoning about supervised learning do not capture the key aspects and the assumptions underlying these
semi
-supervised learning methods.

In this article, we describe an augmented version of the PAC model designed for semi-supervised learning, that can be used to reason about many of the different approaches taken over the past decade in the Machine Learning community. This model provides a unified framework for analyzing when and why unlabeled data can help, in which one can analyze both sample-complexity and algorithmic issues. The model can be viewed as an extension of the standard PAC model where, in addition to a concept class
C
, one also proposes a compatibility notion: a type of compatibility that one believes the target concept should have with the underlying distribution of data. Unlabeled data is then potentially helpful in this setting because it allows one to estimate compatibility over the space of hypotheses, and to reduce the size of the search space from the whole set of hypotheses
C
down to those that, according to one's assumptions, are a-priori reasonable with respect to the distribution. As we show, many of the assumptions underlying existing semi-supervised learning algorithms can be formulated in this framework.

After proposing the model, we then analyze sample-complexity issues in this setting: that is, how much of each type of data one should expect to need in order to learn well, and what the key quantities are that these numbers depend on. We also consider the algorithmic question of how to efficiently optimize for natural classes and compatibility notions, and provide several algorithmic results including an improved bound for Co-Training with linear separators when the distribution satisfies independence given the label.
R-flurbiprofen suppresses distal nonmucin-producing colorectal tumors in azoxymethane-treated rats, without suppressing eicosanoid production
Authors: Martin Jonathan E. , Le Leu Richard K. , Hu Ying , Young Graeme P.
Published: March 2010

Toxicity and gastrointestinal side effects limits the use of nonsteroidal anti-inflammatory drugs (NSAIDs) as agents to prevent colorectal cancer. These undesirable effects appear to be related to the inhibition of cyclooxygenase-associated pathways. Using the azoxymethane (AOM)-rat model of carcinogenesis, we aimed to test the potency of a low-toxicity R-flurbiprofen and whether NSAIDs have differing effects on regional tumor subtypes. Groups of 50 rats were gavaged 6 days a week with drug. After 1 and 2 wk on drug, rats were given intraperitoneal injection of AOM (15 mg/kg body wt). Groups were controls, sulindac (nonselective cyclooxygenase inhibitor) 5 and 20 mg/kg body wt per day, and R-flurbiprofen 30 mg/kg body wt per day. Tumor location, size, and histological subtype (either mucinous or nonmucinous) were recorded after 30 wk. The incidence of colon tumors was significantly reduced in the sulindac 20 mg ( P < 0.001) and the R-flurbiprofen groups ( P < 0.03) compared with the control group. The sulindac 20 mg and R-flurbiprofen groups also showed a reduced number of distal colon tumors ( P < 0.03), whereas proximal tumors were not affected. Tumors only of the nonmucinous subtype were significantly reduced with the sulindac 20 mg and R-flurbiprofen groups ( P < 0.001). Tumor size was not significantly different between all groups. Only the sulindac 20 mg group showed a reduced colonic prostaglandin E2 concentration. The sulindac groups showed a dose-dependant reduction in body weight gain ( P < 0.001). In conclusion, R-flurbiprofen at a dose of 30 mg/kg body wt per day was well tolerated by the animals and, along with sulindac at 30 mg/day body wt, showed protection against the development of colon cancer in the rat-AOM model.
Burn serum causes a CD14-dependent mitochondrial damage in primary cardiomyocytes
Authors: Zang Qun S. , Maass David L. , Wigginton Jane G. , Barber Robert C. , Martinez Bobbie , Idris Ahamed H. , Horton Jureta W. , Nwariaku Fiemu E.
Published: March 2010

Studies from animal models suggest that myocardial mitochondrial damage contributes to cardiac dysfunction after burn injury. In this report, we used an ex vivo model of primary cardiomyocyte culture to investigate the mechanisms of burn-induced mitochondrial impairment. Briefly, blood serum was collected from Sprague-Dawley (SD) rats subjected to 40% total body surface area burn and added (10% vol/vol) to primary cardiomyocytes prepared from SD rats. The effect of the burn serum on mitochondrial function and membrane integrity in the myocytes was analyzed. Exposure of myocytes to burn serum doubled the mitochondrial membrane damage measured by two independent assays. This treatment also significantly elevated mitochondrial oxidative stress, indicated by a more than 30% increase in lipid oxidation. Downregulation of mitochondrial antioxidant defense was also evident since the activities of the antioxidant enzymes superoxide dismutase and glutathione peroxidase were reduced by about 30% and 50%, respectively. Burn serum also induced deficiency of mitochondrial metabolism, indicated by a 30% decrease in the activity of cytochrome c oxidase. These mitochondrial dysfunctions appear to be generated by oxidative stress because burn serum induced a significant increase of mitochondrial oxygen species (mtROS) in cardiomyocytes, and pretreatment of cardiomyocytes with the antioxidant N-acetyl-cysteine prevented the mitochondrial damages induced by burn serum. Remarkably, the increase in mtROS was abolished by an antibody-mediated blockade of CD14. Furthermore, burn injury-induced mitochondrial damage in cardiomyocytes was prevented in CD14 knockout mice. Taken together, these data suggested that burn injury produces CD14-dependent mitochondrial damage via oxidative stress in myocardium.
P2Y2receptors mediate ATP-induced resensitization of TRPV1 expressed by kidney projecting sensory neurons
Authors: Wang Hui , Wang Donna H. , Galligan James J.
Published: March 2010

The transient receptor potential vanilloid type 1 (TRPV1) channel is a ligand-gated cation channel expressed by sensory nerves. P2Y receptors are G protein-coupled receptors that are also expressed by TRPV1-positive sensory neurons. Therefore, we studied interactions between P2Y receptors and TRPV1 function on kidney projecting sensory neurons. Application of Fast Blue (FB) to nerves surrounding the renal artery retrogradely labeled neurons in dorsal root ganglia of rats. Whole cell recording was performed on FB-labeled neurons maintained in primary culture. Capsaicin was used to activate TRPV1. Four types of kidney projecting neurons were identified based on capsaicin responses: 1) desensitizing (35%), 2) nondesensitizing (29%), 3) silent (3%), and 4) insensitive (30%). Silent neurons responded to capsaicin only after ATP (100 μM) pretreatment. ATP reversed desensitization in desensitizing neurons. Insensitive neurons never responded to capsaicin. UTP, a P2Y purinoceptor 2 (P2Y2)/P2Y4receptor agonist, reversed capsaicin-induced TRPV1 desensitization. 2-methyl-thio-ATP (2-Me-S-ATP), a P2Y1receptor agonist, did not change desensitization. MRS 2179 and pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS), drugs that block P2Y1receptors, did not block ATP-induced resensitization of TRPV1. Suramin, a P2Y2receptor antagonist, blocked resensitization caused by UTP. Immunocytochemical studies showed that FB-labeled neurons coexpressed P2Y2receptors and TRPV1. We conclude that P2Y2receptor activation can maintain TRPV1 function perhaps during sustained episodes of activity of kidney projecting sensory neurons.
CLIC5A, a component of the ezrin-podocalyxin complex in glomeruli, is a determinant of podocyte integrity
Authors: Wegner Binytha , Al-Momany Abass , Kulak Stephen C. , Kozlowski Kathy , Obeidat Marya , Jahroudi Nadia , Paes John , Berryman Mark , Ballermann Barbara J.
Published: March 2010

The chloride intracellular channel 5A (CLIC5A) protein, one of two isoforms produced by the CLIC5 gene, was isolated originally as part of a cytoskeletal protein complex containing ezrin from placental microvilli. Whether CLIC5A functions as a bona fide ion channel is controversial. We reported previously that a CLIC5 transcript is enriched ∼800-fold in human renal glomeruli relative to most other tissues. Therefore, this study sought to explore CLIC5 expression and function in glomeruli. RT-PCR and Western blots show that CLIC5A is the predominant CLIC5 isoform expressed in glomeruli. Confocal immunofluorescence and immunogold electron microscopy reveal high levels of CLIC5A protein in glomerular endothelial cells and podocytes. In podocytes, CLIC5A localizes to the apical plasma membrane of foot processes, similar to the known distribution of podocalyxin and ezrin. Ezrin and podocalyxin colocalize with CLIC5A in glomeruli, and podocalyxin coimmunoprecipitates with CLIC5A from glomerular lysates. In glomeruli of jitterbug ( jbg/jbg) mice, which lack the CLIC5A protein, ezrin and phospho-ERM levels in podocytes are markedly lower than in wild-type mice. Transmission electron microscopy reveals patchy broadening and effacement of podocyte foot processes as well as vacuolization of glomerular endothelial cells. These ultrastructural changes are associated with microalbuminuria at baseline and increased susceptibility to adriamycin-induced glomerular injury compared with wild-type mice. Together, the data suggest that CLIC5A is required for the development and/or maintenance of the proper glomerular endothelial cell and podocyte architecture. We postulate that the interaction between podocalyxin and subjacent filamentous actin, which requires ezrin, is compromised in podocytes of CLIC5A-deficient mice, leading to dysfunction under unfavorable genetic or environmental conditions.
Salt-sensitive splice variant of nNOS expressed in the macula densa cells
Authors: Lu Deyin , Fu Yiling , Lopez-Ruiz Arnaldo , Zhang Rui , Juncos Ramiro , Liu Haifeng , Manning R. Davis , Juncos Luis A. , Liu Ruisheng
Published: March 2010

Neuronal nitric oxide synthase (nNOS), which is abundantly expressed in the macula densa cells, attenuates tubuloglomerular feedback (TGF). We hypothesize that splice variants of nNOS are expressed in the macula densa, and nNOS-β is a salt-sensitive isoform that modulates TGF. Sprague-Dawley rats received a low-, normal-, or high-salt diet for 10 days and levels of the nNOS-α, nNOS-β, and nNOS-γ were measured in the macula densa cells isolated with laser capture microdissection. Three splice variants of nNOS, α-, β-, and γ-mRNAs, were detected in the macula densa cells. After 10 days of high-salt intake, nNOS-α decreased markedly, whereas nNOS-β increased two- to threefold in the macula densa measured with real-time PCR and in the renal cortex measured with Western blot. NO production in the macula densa was measured in the perfused thick ascending limb with an intact macula densa plaque with a fluorescent dye DAF-FM. When the tubular perfusate was switched from 10 to 80 mM NaCl, a maneuver to induce TGF, NO production by the macula densa was increased by 38 ± 3% in normal-salt rats and 52 ± 6% ( P < 0.05) in the high-salt group. We found 1) macula densa cells express nNOS-α, nNOS-β, and nNOS-γ, 2) a high-salt diet enhances nNOS-β, and 3) TGF-induced NO generation from macula densa is enhanced in high-salt diet possibly from nNOS-β. In conclusion, we found that the splice variants of nNOS expressed in macula densa cells were α-, β-, and γ-isoforms and propose that enhanced level of nNOS-β during high-salt intake may contribute to macula densa NO production and help attenuate TGF.
Diastolic function is strongly and independently associated with cardiorespiratory fitness in central obesity
Authors: Turzyniecka M. , Wild S. H. , Krentz A. J. , Chipperfield A. J. , Clough G. F. , Byrne C. D.
Published: March 2010

Cardiorespiratory fitness [maximal O2 consumption (V̇o2max)] is an independent risk factor for type 2 diabetes; but in individuals at risk, factors influencing V̇o2max are poorly understood. We tested the hypothesis that V̇o2max is associated with diastolic function [subendocardial variability ratio (SEVR), %], as diastolic function influences myocardial perfusion. We studied 47 men and women with central obesity without diabetes. We measured fitness (V̇o2max) by treadmill testing and diastolic function (SEVR%) by pulse-wave analysis. We measured other factors influencing this relationship: insulin sensitivity [whole body glucose uptake-to-insulin concentration ratio (M/I)] by hyperinsulinemic euglycemic clamp, fatness by MR imaging and dual-energy X-ray absorptiometry, physical activity energy expenditure (metabolic equivalents of tasks) by the Sensewear Pro2 device, and muscle microvascular exchange capacity (capillary filtration coefficient) by venous plethysmography. Mean age of the subjects was 51 ± 9 (SD) yr. V̇o2max was associated with SEVR% ( r = 0.50, P = 0.001), fatness ( r = −0.39, P = 0.008), and HbA1c ( r = −0.35, P = 0.018), but not with whole body glucose uptake-to-insulin concentration ratio, metabolic equivalents of tasks, or capillary filtration coefficient. In regression modeling with age, sex, fatness, and SEVR% as explanatory variables, only age, sex, and SEVR% were independently associated with V̇o2max (SEVR% − standardized B coefficient = 0.37, 95% confidence interval = 0.003–0.18, P = 0.007). This model identified 46% of the variance in V̇o2max ( R2 = 0.46, P = 0.0001). There was a strong, independent association between V̇o2max and a measure of diastolic function in sedentary individuals with central obesity.
Recruitment and derecruitment characteristics of motor units in a hand muscle of young and old adults
Authors: Jesunathadas Mark , Marmon Adam R. , Gibb James M. , Enoka Roger M.
Published: March 2010

The significant decline in motor neuron number after ∼60 yr of age is accompanied by a remodeling of the neuromuscular system so that average motor unit force increases and the ability of old adults to produce an intended force declines. One possible explanation for the loss of movement precision is that the remodeling increases the difference in recruitment forces between successively recruited motor units in old adults and this augments force variability at motor unit recruitment. The purpose of the study was to compare the forces and discharge characteristics of motor units in a hand muscle of young and old adults at motor unit recruitment and derecruitment. The difference in recruitment force between pairs of motor units did not differ between young ( n = 54) and old adults ( n = 56; P = 0.702). However, old adults had a greater proportion of contractions in which motor units discharged action potentials transiently before discharging continuously during the ramp increase in force (young: 0.32; old: 0.41; P = 0.045). Force variability at motor unit recruitment was greater for old adults compared with young adults ( P ≤ 0.010), but discharge rate and discharge variability did not differ between age groups ( P ≥ 0.729). These results suggest that the difference in force between the recruitment of successive motor units does not differ between age groups, but that motor unit recruitment may be more transient and could contribute to the greater variability in force observed in old adults during graded ramp contractions.
Intrauterine inflammation causes pulmonary hypertension and cardiovascular sequelae in preterm lambs
Authors: Polglase Graeme R. , Hooper Stuart B. , Gill Andrew W. , Allison Beth J. , Crossley Kelly J. , Moss Timothy JM , Nitsos Ilias , Pillow J. Jane , Kluckow Martin
Published: March 2010

Chorioamnionitis increases the risk and severity of persistent pulmonary hypertension of the newborn in preterm infants. Exposure of preterm fetal lambs to intra-amniotic (IA) lipopolysaccharide (LPS) induces chorioamnionitis, causes hypertrophy of pulmonary resistance arterioles, and alters expression of pulmonary vascular growth proteins. We investigated the cardiopulmonary and systemic hemodynamic consequences of IA LPS in preterm lambs. Pregnant ewes received IA injection of LPS ( n = 6) or saline (controls; n = 8) at 122 days gestation, 7 days before exteriorization, instrumentation, and delivery of the fetus with pulmonary and systemic flow probes and catheters at 129 days gestation. Newborn lambs were ventilated, targeting a tidal volume of 6–7 ml/kg and a positive end-expiratory pressure (PEEP) of 4 cmH2O. At 30 min, all lambs underwent a PEEP challenge: PEEP was increased by 2 cmH2O at 10-min intervals to 10 cmH2O and then decreased similarly to 4 cmH2O. Ventilation parameters, arterial blood flows, and pressures were recorded in real-time for 90 min. LPS lambs had higher total protein in bronchoalveolar lavage fluid ( P < 0.002), increased medial thickness of arteriolar walls ( P = 0.013), and right ventricular hypertrophy ( P = 0.012). Compared with controls, LPS lambs had worse oxygenation ( P < 0.001), decreased pulmonary blood flow ( P = 0.05), and higher pulsatility index ( P < 0.001) and pulmonary ( P < 0.001) and systemic arterial pressures ( P = 0.005) than controls. Intra-amniotic LPS increased right-to-left shunting across the ductus arteriosus ( P = 0.018) and decreased left ventricular output ( P < 0.001). We conclude that inflammation and pulmonary remodeling induced by IA LPS adversely alters pulmonary hemodynamics with subsequent cardiovascular and systemic sequelae, which may predispose the preterm lamb to persistent pulmonary hypertension of the newborn.
The Vanishing Stenosis: ST Elevation Myocardial Infarction and Rhythm Disturbance due to Coronary Artery Spasm—Case Report and Review of the Literature
Authors: Gosai J. , Malkin C. J. , Grech E. D.
Published: March 2010

A 62-year-old lady was admitted with clinical and electrocardiograph features of acute myocardial infarction. Urgent coronary arteriography was performed, demonstrating a single discrete stenosis of one coronary artery. Following intracoronary injection of GTN, this stenosis completely resolved, as the symptoms did. The causes of acute myocardial infarction with normal coronary arteries are reviewed.
On Two Systems of Difference Equations
Authors: Iričanin Bratislav , Stević Stevo
Published: March 2010

We give very short and elegant proofs of the main results in the work of Yalcinkaya et al. (2008).
Genetic Variation in Past and Current Landscapes: Conservation Implications Based on Six Endemic Florida Scrub Plants
Authors: Menges Eric S. , Dolan Rebecca W. , Pickert Roberta , Yahr Rebecca , Gordon Doria R.
Published: March 2010

If genetic variation is often positively correlated with population sizes and the presence of nearby populations and suitable habitats, landscape proxies could inform conservation decisions without genetic analyses. For six Florida scrub endemic plants (Dicerandra frutescens, Eryngium cuneifolium, Hypericum cumulicola, Liatris ohlingerae, Nolina brittoniana, and Warea carteri), we relate two measures of genetic variation, expected heterozygosity and alleles per polymorphic locus (APL), to population size and landscape variables. Presettlement areas were estimated based on soil preferences and GIS soils maps. Four species showed no genetic patterns related to population or landscape factors. The other two species showed significant but inconsistent patterns. ForLiatris ohlingerae, APL was negatively related to population density and weakly, positively related to remaining presettlement habitat within 32 km. ForNolina brittoniana, APL increased with population size. The rather weak effects of population area/size and both past and current landscape structures suggest that genetic variation needs to be directly measured and not inferred for conservation planning.
OP-KNN: Method and Applications
Authors: Yu Qi , Miche Yoan , Sorjamaa Antti , Guillen Alberto , Lendasse Amaury , Séverin Eric
Published: March 2010

This paper presents a methodology named Optimally Pruned K-Nearest Neighbors (OP-KNNs) which has the advantage of competing with state-of-the-art methods while remaining fast. It builds a one hidden-layer feedforward neural network using K-Nearest Neighbors as kernels to perform regression. Multiresponse Sparse Regression (MRSR) is used in order to rank each kth nearest neighbor and finally Leave-One-Out estimation is used to select the optimal number of neighbors and to estimate the generalization performances. Since computational time of this method is small, this paper presents a strategy using OP-KNN to perform Variable Selection which is tested successfully on eight real-life data sets from different application fields. In summary, the most significant characteristic of this method is that it provides good performance and a comparatively simple model at extremely high-learning speed.
Spatial Domain Resource Sharing for Overlapping Cells in Indoor Environment
Authors: Kudo Riichi , Takatori Yasushi , Nishimori Kentaro , Ichikawa Takeo , Murakami Tomoki , Mizoguchi Masato , Morikura Masahiro
Published: March 2010

As microcell wireless systems become more widespread, intercell interference among the access points will increase due to the limited frequency resource. In the overlapping cell scenario, radio resources should be shared by multiple cells. Although time and frequency resource sharing has been described in many papers, there is no detailed report on dynamic spatial resource sharing among multiple cells for microcell wireless systems. Thus, we present the effectiveness of spatial resource sharing among two access points. We introduce two scenarios based on the zero forcing method; one is the primary-secondary AP scenario and the other is the cooperative AP scenario. To evaluate the transmission performance of spatial resource sharing, channel matrices are measured in an indoor environment. The simulation results using the measured channel matrices show the potential of spatial resource sharing.
Ethical Issues in Fetal Management: A Cardiac Perspective
Authors: Malhotra Atul , Menahem Samuel , Gillam Lynn
Published: March 2010

The ethical issues behind the management of a fetus with a serious abnormality and the decisions made in relation to the outcome of the pregnancy are complex. This reflective paper deals with the ethical principles of managing a pregnancy with a congenital anomaly, with particular emphasis on the fetus with a serious cardiac abnormality. One major ethical concern is whether the fetus is or is not independent being to whom obligations of beneficence are owed. We review the debate on this matter, and suggest that it is ethically more appropriate for physicians who are involved in management of fetal abnormality not to adopt and insist on their own position on this matter. Rather, the appropriate course is to respect the pregnant woman's own view of her fetus and how it should be regarded. This is an application of the principle of respect for autonomy. Within this framework, we discuss the difficulties in counselling a pregnant woman or expectant couple in this situation, and recommend three key steps in ethically sound counselling.