bluuebunny/crossref_metadata_2025 huggingface dataset:
l-2-Oxothiazolidine-4-Carboxylic Acid or α-Lipoic Acid Attenuates Airway Remodeling: Involvement of Nuclear Factor-κB (NF-κB), Nuclear Factor Erythroid 2p45-Related Factor-2 (Nrf2), and Hypoxia-Inducible Factor (HIF)
Authors: Park Seoung Ju , Lee Kyung Sun , Lee Su Jeong , Kim So Ri , Park Seung Yong , Jeon Myoung Shin , Lee Heung Bum , Lee Yong Chul
Published: June 2012

Reactive oxygen species (ROS) play a crucial role in the pathogenesis of acute and chronic respiratory diseases. Antioxidants have been found to ameliorate airway inflammation and hyperresponsiveness in animal models employing short-term exposure to allergen. However, little data are available on the effect of antioxidants on airway remodeling and signaling pathways in chronic asthma. In the present study, we used a long-term exposure murine model of allergic airway disease to evaluate the effects of an antioxidant, l-2-oxothiazolidine-4-carboxylic acid (OTC) or α-lipoic acid (LA) on airway remodeling, focusing on the ROS-related hypoxia-inducible signaling. Long-term challenge of ovalbumin (OVA) increased ROS production, airway inflammation, and airway hyperresponsiveness, and developed features of airway remodeling such as excessive mucus secretion, subepithelial fibrosis, and thickening of the peribronchial smooth muscle layer. Administration of OTC or LA reduced these features of asthma, including airway remodeling, which was accompanied by suppression of transforming growth factor-β1, vascular endothelial growth factor, and T-helper 2 cytokines. In addition, OVA-induced activation of nuclear factor-κB (NF-κB), nuclear factor erythroid 2p45-related factor-2 (Nrf2), hypoxia-inducible factor (HIF)-1α, and HIF-2α was reduced by OTC or LA. Our results also showed that OTC or LA down-regulated phosphoinositide 3-kinase activity and decreased phosphorylation of p38 mitogen-activated protein kinase but not extracellular signal-regulated kinase 1/2 or c-Jun N-terminal kinase. These findings demonstrate that OTC and LA can inhibit activation of NF-κB, Nrf2, and HIF, leading to attenuate allergen-induced airway remodeling.
Contact Toxicity and Residual Efficacy of Indoxacarb against the European Earwig (Dermaptera: Forficulidae)
Authors: Jones Susan C. , Bryant Joshua L.
Published: June 2012

Indoxacarb (Arilon 20WG) was evaluated against a nuisance pest, the European earwig (Forficula auricularia), and was found to be an effective contact toxicant with residual activity on substrates commonly encountered in urban environments. Within 16 h of being directly sprayed with indoxacarb, ≥90% of earwigs from two populations were either ataxic, moribund, or dead, and 100% displayed these symptoms of severe intoxication at 1 d. Brief exposure (5 min or 1 h) to dried residues on either a porous (pine wood) or non-porous (ceramic tile) substrate also was sufficient to cause severe intoxication of earwigs within 1 d. In all bioassays, indoxacarb-treated earwigs showed no signs of recovery during the 21-d observation period. In outdoor urban habitats, intoxicated earwigs would be more vulnerable to desiccation, predation, or pathogens leading to higher mortality than in a laboratory setting.
Dehydrogenation Kinetics and Modeling Studies of MgH2 Enhanced by Transition Metal Oxide Catalysts Using Constant Pressure Thermodynamic Driving Forces
Authors: Sabitu Saidi Temitope , Goudy Andrew J.
Published: June 2012

The influence of transition metal oxide catalysts (ZrO2, CeO2, Fe3O4 and Nb2O5) on the hydrogen desorption kinetics of MgH2 was investigated using constant pressure thermodynamic driving forces in which the ratio of the equilibrium plateau pressure (pm) to the opposing plateau (pop) was the same in all the reactions studied. The results showed Nb2O5 to be vastly superior to other catalysts for improving the thermodynamics and kinetics of MgH2. The modeling studies showed reaction at the phase boundary to be likely process controlling the reaction rates of all the systems studied.
A New Benzofuran Derivative from Flemingia philippinensis Merr. et Rolfe
Authors: Li Hua , Zhai Fengyan , Yang Meihua , Li Xiaowan , Wang Pingli , Ma Xiaojun
Published: June 2012

A new prenylated benzofuran derivative, named flemiphilippinone A, was isolated together with ten known flavonoids from the roots of Flemingia philippinensis. Flemiphilippinone A was identified as (2S,3aS)-5-(1-hydroxy-3-(4-methoxyphenyl)- propylidene)-2-(2-hydroxypropan-2-yl)-3a,7-bis(3-methylbut-2-en-1-yl)tetrahydrobenzo- furan-4,6(2H,5H)-dione, and its structure was established by a combination of HR EIMS, 1H-NMR, 13C-NMR, HMQC, HMBC and NOESY spectra data.
Butylated Hydroxytoluene Analogs: Synthesis and Evaluation of Their Multipotent Antioxidant Activities
Authors: Yehye Wageeh A. , Abdul Rahman Noorsaadah , A. Alhadi Abeer , Khaledi Hamid , Ng Seik Weng , Ariffin Azhar
Published: June 2012

A computer-aided predictions of antioxidant activities were performed with the Prediction Activity Spectra of Substances (PASS) program. Antioxidant activity of compounds 1, 3, 4 and 5 were studied using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and lipid peroxidation assays to verify the predictions obtained by the PASS program. Compounds 3 and 5 showed more inhibition of DPPH stable free radical at 10−4 M than the well-known standard antioxidant, butylated hydroxytoluene (BHT). Compound 5 exhibited promising in vitro inhibition of Fe2+-induced lipid peroxidation of the essential egg yolk as a lipid-rich medium (83.99%, IC50 16.07 ± 3.51 µM/mL) compared to a-tocopherol (a-TOH, 84.6%, IC50 5.6 ± 1.09 µM/mL). The parameters for drug-likeness of these BHT analogues were also evaluated according to the Lipinski’s “rule-of-five” (RO5). All the BHT analogues were found to violate one of the Lipinski’s parameters (LogP > 5), even though they have been found to be soluble in protic solvents. The predictive polar surface area (PSA) and absorption percent (% ABS) data allow us to conclude that they could have a good capacity for penetrating cell membranes. Therefore, one can propose these new multipotent antioxidants (MPAOs) as potential antioxidants for tackling oxidative stress and lipid peroxidation processes.
Residue-Ligand Interaction Energy (ReLIE) on a Receptor-Dependent 3D-QSAR Analysis of S- and NH-DABOs as Non-Nucleoside Reverse Transcriptase Inhibitors
Authors: De Brito Monique Araújo , Rodrigues Carlos Rangel , Cirino José Jair Viana , Araújo Jocley Queiroz , Honório Thiago , Cabral Lúcio Mendes , De Alencastro Ricardo Bicca , Castro Helena Carla , Albuquerque Magaly Girão
Published: June 2012

A series of 74 dihydroalkoxybenzyloxopyrimidines (DABOs), a class of highly potent non-nucleoside reverse transcriptase inhibitors (NNRTIs), was retrieved from the literature and studied by receptor-dependent (RD) three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis to derive RD-3D-QSAR models. The descriptors in this new method are the steric and electrostatic interaction energies of the protein-ligand complexes (per residue) simulated by molecular dynamics, an approach named Residue-Ligand Interaction Energy (ReLIE). This study was performed using a training set of 59 compounds and the MKC-442/RT complex structure as reference. The ReLIE-3D-QSAR models were constructed and evaluated by genetic algorithm (GA) and partial least squares (PLS). In the best equations, at least one term is related to one of the amino acid residues of the p51 subunit: Asn136, Asn137, Glu138, and Thr139. This fact implies the importance of interchain interaction (p66-p51) in the equations that best describe the structure-activity relationship for this class of compounds. The best equation shows q2 = 0.660, SEcv = 0.500, r2 = 0.930, and SEE = 0.226. The external predictive ability of this best model was evaluated using a test set of 15 compounds. In order to design more potent DABO analogues as anti-HIV/AIDS agents, substituents capable of interactions with residues like Ile94, Lys101, Tyr181, and Tyr188 should be selected. Also, given the importance of the conserved Asn136, this residue could become an attractive target for the design of novel NNRTIs with improved potency and increased ability to avoid the development of drug-resistant viruses.
Restoration of Electric Footshock-Induced Immunosuppression in Mice by Gynostemma pentaphyllum Components
Authors: Im Sun-A , Choi Hyun Sook , Choi Soon Ok , Kim Ki-Hyang , Lee Seungjeong , Hwang Bang Yeon , Lee Myung Koo , Lee Chong Kil
Published: June 2012

The immunomodulatory effects of the ethanol extract of Gynostemma pentaphyllum (GP-EX) were examined in electric footshock (EFS)-stressed mice. The mice were orally administered various doses of GP-EX for 7 days before exposure to EFS (duration: 3 min, interval: 10 s, intensity: 2 mA) once a day from day 8 for 14 days with continuous daily feeding of GP-EX. Oral administration of GP-EX to mice prevented EFS stress-induced immunosuppression as determined by the lymphoid organ (thymus and spleen) weight and cellularity. In addition, oral administration of GP-EX restored EFS-suppressed functional properties of mature lymphocytes in terms of concanavalin A-induced proliferation of splenocytes and lipopolysaccharide-induced cytokine production (TNF-α, IL-1β). Furthermore, we found that mice that were orally administered with GP-EX generated much more potent ovalbumin-specific cytotoxic T lymphocyte responses upon intravenous ovalbumin injection compared to the untreated controls. These results demonstrate that oral administration of the ethanol extract of Gynostemma pentaphyllum could increase host defense in immunocompromised situations such as stress-induced immunosuppression.
A Further Contribution to the Study of Sagittamide A: Synthesis of a Pivotal Intermediate Belonging to a Rare L-Series
Authors: Humbert Anne , Plé Karen , Harakat Dominique , Martinez Agathe , Haudrechy Arnaud
Published: June 2012

A key saggitamide intermediate corresponding to a rare sugar framework has been obtained. This approach should help to establish the overall configuration of more complex structures of the sagittamide family.
In Situ Electrochemical SFG/DFG Study of CN− and Nitrile Adsorption at Au from 1-Butyl-1-methyl-pyrrolidinium Bis(trifluoromethylsulfonyl) Amide Ionic Liquid ([BMP][TFSA]) Containing 4-{2-[1-(2-Cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]diazenyl} Benzonitrile (CTDB) and K[Au(CN)2]
Authors: Bozzini Benedetto , Busson Bertrand , Gayral Audrey , Humbert Christophe , Mele Claudio , Six Catherine , Tadjeddine Abderrahmane
Published: June 2012

In this paper we report an in situ electrochemical Sum-/Difference Frequency Generation (SFG/DFG) spectroscopy investigation of the adsorption of nitrile and CN− from the ionic liquid 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) containing 4-{2-[1-(2-cyanoethyl)-1,2,3,4-tetrahydroquinolin-6-yl]- diazenyl}benzonitrile (CTDB) at Au electrodes in the absence and in the presence of the Au-electrodeposition process from K[Au(CN)2]. The adsorption of nitrile and its coadsorption with CN− resulting either from the cathodic decomposition of the dye or from ligand release from the Au(I) cyanocomplex yield potential-dependent single or double SFG bands in the range 2,125–2,140 cm−1, exhibiting Stark tuning values of ca. 3 and 1 cm−1 V−1 in the absence and presence of electrodeposition, respectively. The low Stark tuning found during electrodeposition correlates with the cathodic inhibiting effect of CTDB, giving rise to its levelling properties. The essential insensitivity of the other DFG parameters to the electrodeposition process is due to the growth of smooth Au.
Characterization of the Antibacterial Activity and the Chemical Components of the Volatile Oil of the Leaves of Rubus parvifolius L.
Authors: Cai Yongqing , Hu Xiaogang , Huang Mingchun , Sun Fengjun , Yang Bo , He Juying , Wang Xianfeng , Xia Peiyuan , Chen Jianhong
Published: June 2012

Rubus parvifolius L. (Rp) is a medicinal herb that possesses antibacterial activity. In this study, we extracted the volatile oil from the leaves of Rp to assess its antibacterial activity and analyze its chemical composition. A uniform distribution design was used to optimize the extraction procedure, which yielded 0.36% (w/w) of light yellowish oil from the water extract of Rp leaves. We found that the extracted oil effectively inhibited the growth of a wide range of Gram positive and negative bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumanii, Bacillus cloacae, and Klebsiella pneumoniae. We further analyzed the components contained in the hydro-distillated Rp volatile oil by gas chromatography-mass spectroscopy. Twenty nine compounds were identified, including 4-hydroxy-3-methoxystyrene (66%), 3,7,11,15-tetramethyl-2-hexadecen-1-ol (10%) and 4-tert-butylbenzoic acid (2%). Our results suggest that one or multiple constituents contained in Rp volatile oil may account for its antibacterial activity.
Half-Metallic Properties of Single-Walled Polymeric Manganese Phthalocyanine Nanotubes
Authors: Jiang Hongbin , Bai Meilin , Wei Peng , Sun Lili , Shen Ziyong , Hou Shimin
Published: June 2012

We present a theoretical study of the electronic and magnetic properties of single-walled manganese phthalocyanine (MnPc) nanotubes which can be thought of as rolled-up ribbons of the two-dimensional (2D) polymeric MnPc sheet. Our density functional theory calculations show that all of the MnPc nanotubes investigated here are half-metals with 100% spin polarization around the Fermi level. Following the increase of the tube diameter, the number of spin-down energy bands of MnPc nanotubes is always increased while the spin-up band gap of MnPc nanotubes approaches that of the 2D MnPc sheet in an oscillatory manner. Because the half-metallic character of MnPc nanotubes is deeply rooted in the distribution of electrons in the energy bands dominated by the Mn 3d atomic orbitals, adsorption of CO molecules on the Mn ions leads to a redistribution of electrons in the Mn 3d orbitals and thus can tune precisely the spin state and electronic transport properties of MnPc nanotubes, demonstrating promising applications of MnPc nanotubes in future molecular spintronics and single-molecule sensors.
Development of An Automatic Approaching System for Electrochemical Nanofabrication Using Visual and Force-Displacement Sensing
Authors: Lai Lei-Jie , Zhou Shi-Yu , Gu Guo-Ying , Zhu Li-Min
Published: June 2012

In this paper, a fast automatic precision approaching system is developed for electrochemical nanofabrication using visual and force-displacement sensing. Before the substrate is fabricated, the template should approach the substrate accurately to establish the initial gap between the template and substrate. During the approaching process, the template is first quickly moved towards the substrate by the stepping motor until a specified gap is detected by the visual feedback. Then, the successive approach using the switch of macro-micro motion with a force-displacement sensing module is triggered to make the template contact with the substrate to nanometre accuracy. The contact force is measured by the force-displacement sensing module which employs the high-resolution capacitive displacement sensor and flexure compliant mechanism. The high sensitivity of this capacitive displacement sensor ensures high accuracy of the template-substrate contact. The experimental results show that the template can reach the substrate accurately and smoothly, which verifies the effectiveness of the proposed approaching system with the visual and the force-displacement sensing modules.
Variable-State-Dimension Kalman-Based Filter for Orientation Determination Using Inertial and Magnetic Sensors
Authors: Sabatini Angelo Maria
Published: June 2012

In this paper a quaternion-based Variable-State-Dimension Extended Kalman Filter (VSD-EKF) is developed for estimating the three-dimensional orientation of a rigid body using the measurements from an Inertial Measurement Unit (IMU) integrated with a triaxial magnetic sensor. Gyro bias and magnetic disturbances are modeled and compensated by including them in the filter state vector. The VSD-EKF switches between a quiescent EKF, where the magnetic disturbance is modeled as a first-order Gauss-Markov stochastic process (GM-1), and a higher-order EKF where extra state components are introduced to model the time-rate of change of the magnetic field as a GM-1 stochastic process, namely the magnetic disturbance is modeled as a second-order Gauss-Markov stochastic process (GM-2). Experimental validation tests show the effectiveness of the VSD-EKF, as compared to either the quiescent EKF or the higher-order EKF when they run separately.
Analysis and Design of a Speed and Position System for Maglev Vehicles
Authors: Dai Chunhui , Dou Fengshan , Song Xianglei , Long Zhiqiang
Published: June 2012

This paper mainly researches one method of speed and location detection for maglev vehicles. As the maglev train doesn’t have any physical contact with the rails, it has to use non-contact measuring methods. The technology based on the inductive loop-cable could fulfill the requirement by using an on-board antenna which could detect the alternating magnetic field produced by the loop-cable on rails. This paper introduces the structure of a speed and position system, and analyses the electromagnetic field produced by the loop-cable. The equivalent model of the loop-cable is given and the most suitable component of the magnetic flux density is selected. Then the paper also compares the alternating current (AC) resistance and the quality factor between two kinds of coils which the antenna is composed of. The effect of the rails to the signal receiving is also researched and then the structure of the coils is improved. Finally, considering the common-mode interference, 8-word coils are designed and analyzed.
Configuring a Context-Aware Middleware for Wireless Sensor Networks
Authors: Gámez Nadia , Cubo Javier , Fuentes Lidia , Pimentel Ernesto
Published: June 2012

In the Future Internet, applications based on Wireless Sensor Networks will have to support reconfiguration with minimum human intervention, depending on dynamic context changes in their environment. These situations create a need for building these applications as adaptive software and including techniques that allow the context acquisition and decisions about adaptation. However, contexts use to be made up of complex information acquired from heterogeneous devices and user characteristics, making them difficult to manage. So, instead of building context-aware applications from scratch, we propose to use FamiWare, a family of middleware for Ambient Intelligence specifically designed to be aware of contexts in sensor and smartphone devices. It provides both, several monitoring services to acquire contexts from devices and users, and a context-awareness service to analyze and detect context changes. However, the current version of FamiWare does not allow the automatic incorporation related to the management of new contexts into the FamiWare family. To overcome this shortcoming, in this work, we first present how to model the context using a metamodel to define the contexts that must to be taken into account in an instantiation of FamiWare for a certain Ambient Intelligence system. Then, to configure a new context-aware version of FamiWare and to generate code ready-to-install within heterogeneous devices, we define a mapping that automatically transforms metamodel elements defining contexts into elements of the FamiWare family, and we also use the FamiWare configuration process to customize the new context-aware variant. Finally, we evaluate the benefits of our process, and we analyze both that the new version of the middleware works as expected and that it manages the contexts in an efficient way.
Energy Information Augmented Community-Based Energy Reduction
Authors: Hallinan Kevin , Enns Harvey , Ritchey Stephenie , Brodrick Phil , Lammers Nathan , Hanus Nichole , Rembert Mark , Rainsberger Tony
Published: June 2012

More than one-half of all U.S. states have instituted energy efficiency mandates requiring utilities to reduce energy use. To achieve these goals, utilities have been permitted rate structures to help them incentivize energy reduction projects. This strategy is proving to be only modestly successful in stemming energy consumption growth. By the same token, community energy reduction programs have achieved moderate to very significant energy reduction. The research described here offers an important tool to strengthen the community energy reduction efforts—by providing such efforts energy information tailored to the energy use patterns of each building occupant. The information provided most importantly helps each individual energy customer understand their potential for energy savings and what reduction measures are most important to them. This information can be leveraged by the leading community organization to prompt greater action in its community. A number of case studies of this model are shown. Early results are promising.
A Single-Step Purification and Molecular Characterization of Functional Shiga Toxin 2 Variants from Pathogenic Escherichia coli
Authors: He Xiaohua , Quiñones Beatriz , McMahon Stephanie , Mandrell Robert E.
Published: June 2012

A one-step affinity chromatography method was developed to purify Shiga toxin 2 variants (Stx2) Stx2a, Stx2c, Stx2d and Stx2g from bacterial culture supernatants. Analysis of the purified Stx2 variants by denaturing gel electrophoresis revealed 32 kDa and 7 kDa protein bands, corresponding to the Stx2A- and B-subunits, respectively. However, native gel electrophoresis indicated that purified Stx2c and Stx2d were significantly higher in molecular weight than Stx2a and Stx2g. In a cytotoxicity assay with Hela cells, the 50% cytotoxic dose of Stx2a and Stx2g were 100 pg and 10 pg, respectively, but 1 ng each for Stx2c and Stx2d. Interestingly, analysis of the 50% inhibitory dose in a cell-free translational system from rabbit reticulocyte lysates indicated that Stx2g had a lower capacity to inhibit protein synthesis than the other Stx2 variants. The cytotoxicities in Hela cells were neutralized with an anti-Stx2B antibody and were denatured at 80 °C for 1 h. These findings demonstrated that Stx2 variants exhibited different toxicities, holotoxin structure, and stabilities using distinct systems for assessing toxin activities. The development of a simple method for purification of Stx2 variants will enable further studies of Stx2-mediated toxicity in various model systems.
An abstract approach to weak convergence of spectral shift functions and applications to multi-dimensional Schrödinger operators
Authors: Gesztesy Fritz , Nichols Roger
Published: June 2012

We study the manner in which a sequence of spectral shift functions

\xi(\cdot;H_j,H_{0,j})

associated with abstract pairs of self-adjoint operators

(H_j, H_{0,j})

in Hilbert spaces

\mathcal H_j

,

j\in\mathbb N

, converge to a limiting spectral shift function

\xi(\cdot;H,H_0)

associated with a pair

(H,H_0)

in the limiting Hilbert space

\mathcal H

as

j\to\infty

(mimicking the infinite volume limit in concrete applications to multi-dimensional Schrödinger operators). Our techniques rely on a Fredholm determinant approach combined with certain measure theoretic facts. In particular, we show that prior vague convergence results for spectral shift functions in the literature actually extend to the notion of weak convergence. More precisely, in the concrete case of multi-dimensional Schrödinger operators on a sequence of domains

\Omega_j

exhausting

\mathbb R^n

as

j\to\infty

, we extend the convergence of associated spectral shift functions from vague to weak convergence and also from Dirichlet boundary conditions to more general self-adjoint boundary conditions on

\partial\Omega_j

.
Eigenvalues of Hermitian Toeplitz matrices with polynomially increasing entries
Authors: Bogoya Johan M. , Böttcher Albrecht , Grudsky Sergei M.
Published: June 2012

The paper is concerned with finite Hermitian Toeplitz matrices whose entries in the first row grow like a polynomial. Such matrices cannot be viewed as truncations of an infinite Toeplitz matrix which is generated by an integrable function or a nice measure. The main results describe the first-order asymptotics of the extreme eigenvalues as the matrix dimension goes to infinity and also deliver unexpected barriers for the eigenvalues. One purpose of the paper is to popularize once more that questions on the eigenvalues of matrices can be answered in a very elegant way by passing to integral operators. This idea was introduced by Harold Widom about fifty years ago. In this way one can also give an alternative proof to results by William F. Trench on Hermitian Toeplitz matrices with increasing entries.
Eigenvalues in spectral gaps of differential operators
Authors: Marletta Marco , Scheichl Rob
Published: June 2012

Spectral problems with band-gap spectral structure arise in numerous applications, including the study of crystalline structure and the determination of transmitted frequencies in photonic waveguides. Numerical discretization of these problems can result in spurious results, a phenomenon known as
spectral pollution
. We present a method for calculating eigenvalues in the gaps of self-adjoint operators which avoids spectral pollution. The method perturbs the problem into a dissipative problem in which the eigenvalues to be calculated are lifted out of the convex hull of the essential spectrum, away from the spectral pollution. The method is analysed here in the context of one-dimensional Schrodinger equations on the half line, but is applicable in a much wider variety of contexts, including PDEs, block operator matrices, multiplication operators, and others.
Absence of bound states implies non-negativity of the scattering length
Authors: Seiringer Robert
Published: June 2012

We show that bosons interacting via pair potentials with negative scattering length form bound states for a suitable number of particles. In other words, the absence of many-particle bound states of any kind implies the non-negativity of the scattering length of the interaction potential.
Generalized Weyl theorems and spectral pollution in the Galerkin method
Authors: Boulton Lyonell , Boussaïd Nabile , Lewin Mathieu
Published: June 2012

We consider a general framework for investigating spectral pollution in the Galerkin method. We show how this phenomenon is characterised via the existence of particular Weyl sequences which are singular in a suitable sense. For a given semi-bounded selfadjoint operator A, we identify relative compactness conditions on a selfadjoint perturbation B, ensuring that the limiting set of spectral pollution of A and B coincide. Our results show that, under perturbation, this limiting set behaves in a similar fashion as the essential spectrum.
Polynomials of almost normal arguments in $C^*$-algebras
Authors: Filonov Nikolai D. , Kachkovskiy Ilya
Published: June 2012

The functional calculus for normal elements in

C^*

-algebras is an important tool of analysis. We suggest an approximate substitute for such calculus for elements

a

with the small self-commutator norm

\|[a,a^*]\|\le \delta

. We show that many properties of the functional calculus are conserved up to order

\delta

.
A new approach to ratio asymptotics for orthogonal polynomials
Authors: Simanek Brian
Published: June 2012

We use a non-linear characterization of orthonormal polynomials due to Saff in order to prove an equivalence of norm asymptotics and strong asymptotics for polynomials. Several applications of this equivalence are also discussed. One of our main results is that for regular measures on the closed unit disk - including, but not limited to the unit circle - or the interval [-2,2], one has ratio asymptotics along a sequence of asymptotic density 1.
Laplacians on infinite graphs: Dirichlet and Neumann boundary conditions
Authors: Haeseler Sebastian , Keller Matthias , Lenz H. Daniel , Wojciechowski Radosław K.
Published: June 2012

We study Laplacians associated to a graph and single out a class of such operators with special regularity properties. In the case of locally finite graphs, this class consists of all selfadjoint, non-negative restrictions of the standard formal Laplacian and we can characterize the Dirichlet and Neumann Laplacians as the largest and smallest Markovian restrictions of the standard formal Laplacian. In the case of general graphs, this class contains the Dirichlet and Neumann Laplacians and we describe howthesemay differ fromeach other, characterize when they agree, and study connections to essential selfadjointness and stochastic completeness.

Finally, we study basic common features of all Laplacians associated to a graph. In particular, we characterize when the associated semigroup is positivity improving and present some basic estimates on its long term behavior. We also discuss some situations in which the Laplacian associated to a graph is unique and, in this context, characterize its boundedness.
Basin‐scale inputs of cobalt, iron, and manganese from the Benguela‐Angola front to the South Atlantic Ocean
Authors: Noble Abigail E. , Lamborg Carl H. , Ohnemus Dan C. , Lam Phoebe J. , Goepfert Tyler J. , Measures Chris I. , Frame Caitlin H. , Casciotti Karen L. , DiTullio Giacomo R. , Jennings Joe , Saito Mak A.
Published: June 2012

We present full‐depth zonal sections of total dissolved cobalt, iron, manganese, and labile cobalt from the South Atlantic Ocean. A basin‐scale plume from the African coast appeared to be a major source of dissolved metals to this region, with high cobalt concentrations in the oxygen minimum zone of the Angola Dome and extending 2500 km into the subtropical gyre. Metal concentrations were elevated along the coastal shelf, likely due to reductive dissolution and resuspension of particulate matter. Linear relationships between cobalt, N2O, and O2, as well as low surface aluminum supported a coastal rather than atmospheric cobalt source. Lateral advection coupled with upwelling, biological uptake, and remineralization delivered these metals to the basin, as evident in two zonal transects with distinct physical processes that exhibited different metal distributions. Scavenging rates within the coastal plume differed for the three metals; iron was removed fastest, manganese removal was 2.5 times slower, and cobalt scavenging could not be discerned from water mass mixing. Because scavenging, biological utilization, and export constantly deplete the oceanic inventories of these three hybrid‐type metals, point sources of the scale observed here likely serve as vital drivers of their oceanic cycles. Manganese concentrations were elevated in surface waters across the basin, likely due to coupled redox processes acting to concentrate the dissolved species there. These observations of basin‐scale hybrid metal plumes combined with the recent projections of expanding oxygen minimum zones suggest a potential mechanism for effects on ocean primary production and nitrogen fixation via increases in trace metal source inputs.
Nitrogen isotopic composition of planktonic foraminifera from the modern ocean and recent sediments
Authors: Ren Haojia , Sigman Daniel M. , Thunell Robert C. , Prokopenko Maria G.
Published: June 2012

We investigated the controls on the δ15N values of shell‐bound organic matter of planktonic foraminifera (foraminifera‐bound δ15N, or FB‐δ15N). The bulk biomass δ15N of live foraminifera collected from plankton tows at Sta. S in the Sargasso Sea is within ∼1‰ of the FB‐δ15N of the same species picked from surface sediments from the low‐latitude North Atlantic. The FB‐δ15N value in the surface sediments is strongly correlated with the δ15N of thermocline nitrate, the dominant source of new N to the euphotic zone. The three euphotic‐zone‐dwelling, symbiotic, spinose species, Globigerinoides ruber, Globigerinoides sacculifer, and Orbulina universa, have a FB‐δ15N similar to or slightly higher than that of the nitrate supply to the euphotic zone, whereas the deeper‐dwelling, non‐spinose, and/or asymbiotic forms have higher δ15N. In the Cariaco Basin sediment trap samples, the FB‐δ15N of O. universa varies substantially (1.2‰ between the lowest and highest value), in some cases in step with δ15N changes in the bulk sinking N, while the subeuphotic‐zone‐dwelling, asymbiotic, and/or non‐spinose species are generally higher in FB‐δ15N and less variable through the time series. The higher and less temporally variable FB‐δ15N values of the deeper dwellers are consistent with their partial reliance on subsurface suspended particulate nitrogen, the δ15N of which is elevated and relatively stable over time. As an alternative, possibly additional explanation for the lower FB‐δ15N of the euphotic‐zone dwellers (despite their likely tendency to feed on high‐δ15N zooplankton), the dinoflagellate symbionts may reduce the δ15N elevation of a foraminifera's biomass relative to its diet by reducing the efflux of low‐δ15N ammonium.
Terrestrial organic matter support of lake food webs: Evidence from lake metabolism and stable hydrogen isotopes of consumers
Authors: Karlsson Jan , Berggren Martin , Ask Jenny , Byström Pär , Jonsson Anders , Laudon Hjalmar , Jansson Mats
Published: June 2012

We quantified the utilization of terrestrial organic matter (OM) in the food web of a humic lake by analyzing the metabolism and the consumers' stable isotopic (C, H, N) composition in benthic and pelagic habitats. Terrestrial OM inputs (3 g C m−2 d−1) to the lake greatly exceeded autochthonous OM production (3 mg C m−2 d−1) in the lake. Heterotrophic bacterial growth (19 mg C m−2 d−1) and community respiration (115 mg C m−2 d−1) were high relative to algal photosynthesis and were predominantly (> 85%) supported by terrestrial OM in both habitats. Consequently, terrestrial OM fueled most (85%) of the total production at the base of the lake's food web (i.e., the sum of primary and bacterial production). Despite the uncertainties of quantitatively estimating resource use based on stable isotopes, terrestrial OM clearly also supported around half the zooplankton (47%), macrozoobenthos (63%), and fish (57%) biomass. These results indicate that, although rates of terrestrial OM inputs were around three orders of magnitude greater than that of autochthonous OM production, the use of the two resources by higher trophic levels was roughly equal. The disproportionally low reliance on terrestrial OM at higher trophic levels, compared with its high rates of input and high support of basic biomass production in the lake, suggests that autochthonous resources could not be completely replaced by terrestrial resources and indicates an upper limit to terrestrial support of lake food webs.
Ciliates as the crucial food source of larval fish in a shallow eutrophic lake
Authors: Zingel Priit , Paaver Tiit , Karus Katrit , Agasild Helen , Nõges Tiina
Published: June 2012

We assessed feeding of planktivorous fish larvae on ciliate protozooplankton in shallow eutrophic Lake Võrtsjärv, Estonia to determine whether ciliates are an important part of larval fish diet. We collected larvae of the most common fish species and examined their gut contents by gut segmentation and epifluorescence microscopy. Ciliates were present in the gut of all fish larvae. Gut segmentation analysis showed clear differences in food composition between gut quarters. The hard‐bodied food items were quite evenly distributed in the gut, but the soft‐bodied ciliates and rotifers were present only in the first gut quarters. Neglecting differences in prey digestion rate leads to underestimation of diet amount and composition and, especially, to underestimation of the role of protists in food. In Võrtsjärv, ciliates account for ∼ 60% of the total carbon biomass consumed by fish larvae. The food requirement of fish larvae during first feeding stages (May‐Jun) would not be met without consumption of ciliates.
Natural hybridization between Calanus finmarchicus and C. glacialis (Copepoda) in the Arctic and Northwest Atlantic
Authors: Parent Geneviève J. , Plourde Stéphane , Turgeon Julie
Published: June 2012

Calanus glacialis and Calanus finmarchicus dominate the zooplankton community in the Arctic and North Atlantic, respectively. The vast zone of sympatry between these species, the potential for overlap between reproductive seasons, and the evidence for intermediate values of discriminant traits suggest that these species hybridize. We genotyped 684 individuals from 14 Arctic to Atlantic stations using one mitochondrial (16S) and 10 nuclear loci (microsatellites). Strong genetic differentiation between parental species confidently identified hybrids in areas of sympatry. Hybrid frequency was highly variable among stations and did not covary with mean annual sea surface temperature. In the St. Lawrence Estuary, parental and hybrid genotypes were nonrandomly distributed between depth layers (300–100 m and 100–0 m) and across sampling dates, and hybrids seemed more frequent in July than in May and September. Overall, the bimodal frequency distribution of parental and hybrid genotypes suggests that reproductive barriers limit gene flow between these species. The opportunity for interbreeding is more likely restricted by differences in species reproductive phenology than by dispersal. Hybridization also affects prosome length, a morphological trait widely used to discriminate Calanus species, and thus possibly contributes to species misidentification. Highly introgressed individuals indicate that hybrids are fertile and reproduce, suggesting that hybrid fitness could affect estimates and models of these species population dynamics. This is the first evidence for interspecific hybridization between marine zooplankton species, but similar cases could be uncovered using nuclear genetic markers in groups of closely related and morphologically similar marine zooplankton species.
Rates of dinitrogen fixation and the abundance of diazotrophs in North American coastal waters between Cape Hatteras and Georges Bank
Authors: Mulholland M. R. , Bernhardt P. W. , Blanco-Garcia J. L. , Mannino A. , Hyde K. , Mondragon E. , Turk K. , Moisander P. H. , Zehr J. P.
Published: June 2012

We coupled dinitrogen (N2) fixation rate estimates with molecular biological methods to determine the activity and abundance of diazotrophs in coastal waters along the temperate North American Mid‐Atlantic continental shelf during multiple seasons and cruises. Volumetric rates of N2 fixation were as high as 49.8 nmol N L−1 d−1 and areal rates as high as 837.9 µmol N m−2 d−1 in our study area. Our results suggest that N2 fixation occurs at high rates in coastal shelf waters that were previously thought to be unimportant sites of N2 fixation and so were excluded from calculations of pelagic marine N2 fixation. Unicellular N2‐fixing group A cyanobacteria were the most abundant diazotrophs in the Atlantic coastal waters and their abundance was comparable to, or higher than, that measured in oceanic regimes where they were discovered. High rates of N2 fixation and the high abundance of diazotrophs along the North American Mid‐Atlantic continental shelf highlight the need to revise marine N budgets to include coastal N2 fixation. Integrating areal rates of N2 fixation over the continental shelf area between Cape Hatteras and Nova Scotia, the estimated N2 fixation in this temperate shelf system is about 0.02 Tmol N yr−1, the amount previously calculated for the entire North Atlantic continental shelf. Additional studies should provide spatially, temporally, and seasonally resolved rate estimates from coastal systems to better constrain N inputs via N2 fixation from the neritic zone.
Increased kinetic efficiency for silicic acid uptake as a driver of summer diatom blooms in the North Pacific subtropical gyre
Authors: Krause Jeffrey W. , Brzezinski Mark A. , Villareal Tracy A. , Wilson Cara
Published: June 2012

We examined Si limitation of silica production as a factor contributing to summer‐bloom dynamics in the North Pacific subtropical gyre (NPSG). Substrate limitation of Si uptake was pervasive, but in most samples the degree of Si limitation was not severe enough to induce growth limitation as observed in the North Atlantic subtropical gyre. These results revise previous interpretations, because the difference in the degree of kinetic limitation between gyres appears to be driven by differences in both substrate and kinetic efficiency. In the NPSG, diatom bloom assemblages tended to show more efficient Si‐uptake kinetics and higher Si‐uptake rates than did nonbloom assemblages. A bloom dominated by Mastogloia woodiana exhibited the most efficient Si‐uptake kinetics observed in the ocean to date. Enhanced kinetic efficiency for Si uptake was previously hypothesized to facilitate bloom development, but we suggest the efficient kinetics indirectly affects blooms because [Si(OH)4] does not appear to limit growth or division rates. Rather, efficient kinetics allows further depletion of the prevailing low [Si(OH)4] without inducing secondary growth limitation by Si, thereby maximizing biomass yield. Si‐uptake limitation was not detected in the lower euphotic zone despite similar [Si(OH)4] as in well‐lit waters, which suggests transition to light limitation of Si uptake with depth. These results suggest that enhanced silica production in the M. woodiana bloom was driven by a synergy between diatom species composition, where M. woodiana was highly efficient at Si uptake, and high irradiance, which lead to enhanced diatom division rates in the upper euphotic zone.
Fund Managers—Why the Best Might Be the Worst: On the Evolutionary Vigor of Risk-Seeking Behavior
Authors: Witte Björn-Christopher
Published: June 2012

This article explores the influence of competitive conditions on the evolutionary fitness of different risk preferences. As a practical example, the professional competition between fund managers is considered. To explore how different settings of competition parameters, the exclusion rate and the exclusion interval, affect individual investment behavior, an evolutionary model is developed. Using a simple genetic algorithm, two attributes of virtual fund managers evolve: the share of capital invested in a risky asset and the amount of excessive risk accepted, where a positive value of the latter parameter points to an inefficient investment portfolio. The simulation experiments illustrate that the influence of competitive conditions on investment behavior and attitudes towards risk is significant. What is alarming is that intense competitive pressure generates risk-seeking behavior and undermines the predominance of the most skilled. In these conditions, evolution does not necessarily select managers with efficient portfolios. These results underline the institutional need for the creation of a competitive framework in which risk-taking does not provide an evolutionary advantage per se, and indicate measures on how to achieve this.
A Comparison of Retrieval Vantage Perspective of Positive and Negative Intrusive Memories
Authors: Moulds Michelle L. , Williams Alishia D. , Grisham Jessica R. , Nickerson Angela
Published: June 2012

Recalling distressing memories from a third-person, observer vantage perspective has been conceptualized as a form of avoidance of memory-related affect (McIsaac & Eich, 2004). The possibility that observer recall of positive events might similarly be linked to avoidance has not been explored. A mixed sample of undergraduate students and community members described a positive and negative intrusive memory and responded to items about features of each memory. Experiential avoidance was associated with a tendency to recall positive intrusive memories from an observer perspective, and this association approached significance for negative intrusive memories. For negative intrusions, field perspective recall was associated with greater memory-related distress. The opposite was true for positive intrusions: observer recall was linked to more distress. We also observed expected mood-congruent relationships: depression was associated with the frequency of negative but not positive intrusive memories, and there was a trend towards a relationship between depression and decreased vividness of positive memories. Finally, dysphoric participants reported less of a sense of reliving their positive intrusions than did their non-dysphoric counterparts. We speculate about the reasons for the direction of these effects and discuss the potential utility of therapeutic techniques that encourage patients to remember positive events from a field perspective.
The Role of Mental Imagery in Aberrant Perception: A Neurobiological Perspective
Authors: van de Ven Vincent , Linden David E. J
Published: June 2012

A number of mental disorders comprise aberrant perceptions that are often described as possessing a perceptual quality approaching real-life sensory experience, while at the same time lacking a sensory correlate in the real world. Healthy individuals can also have perceptual experience without an external correlate when they engage in mental imagery. Aberrant perceptions differ from mental imagery in their lack of voluntary control and the sense of reality. Early theories suggested that increased imagery vividness could lead to aberrant perceptions in a number of clinical disorders. However, cognitive and neuroimaging studies do not endorse this view, and instead suggest that mental imagery comprises a functional architecture that is at least partly shared with memory and perception. Miscommunication or disconnection between brain areas or functional modules within this architecture may give rise to aberrant perceptions and their sense of reality. We describe the evidence for this view in relation to psychotic hallucinations in schizophrenia, hallucinations in neurodegenerative disorders and flashbacks of traumatic events in post-traumatic stress disorder. We suggest that an impaired neural architecture of imagery, rather than merely increased intensity or vividness of imagery, underlies aberrant perceptions. This view fits with neurobiological models of mental disorders that suggest that psychopathological symptoms arise from disrupted communication between brain areas.
The Effect of Rumination on Intrusive Images and Mood: An Experimental Investigation Using the Trauma Film Paradigm
Authors: Ball Sarah C. , Brewin Chris R.
Published: June 2012

Rumination appears to predict and maintain posttraumatic stress disorder (PTSD) but evidence for a causal effect is lacking. This experimental study investigated the impact of manipulating film-related and non-film-related rumination on the development of post-trauma intrusive memories and mood. Sixty healthy participants selected for being moderate ruminators were exposed to a trauma film and then allocated to three conditions: film related rumination; non-film related rumination; and no task. Rumination tasks were completed post-film and daily for one week. The two rumination conditions combined resulted in more intrusive memories of the film over one week than the control condition but there were no differences between rumination conditions. In contrast, the two rumination conditions combined, compared to the control group, did not increase negative mood either in the short or long term. These results extend previous findings to show a causal effect of general and trauma-related rumination on intrusive memories.