bluuebunny/crossref_metadata_2025 huggingface dataset:
Biomass and productivity of the woody strata of forested bogs in northern Minnesota
Authors: Grigal D. F. , Buttleman C. G. , Kernik L. K.
Published: May 2010

Biomass and net primary productivity of three forested perched and three forested raised ombrotrophic bogs were determined and compared. The tree stratum was dominated by Picea mariana (Mill.) B.S.P. and the low shrub stratum by Ledum groenlandicum Oeder and Chamaedaphne calyculata (L.) Moench. Based on a modified forest growth and yield model (STEMS), aboveground living biomass of the tree stratum on the perched bogs was declining by about 0.5 t ha−1 year−1 from a base of 100.7 t ha−1, and on the raised bogs it was increasing by 0.2 t ha−1 year−1 on a base of 31.0 t ha−1. Net primary productivity of that stratum was 3.1 and l.0 t ha−1 year−1 on the perched and raised bogs, respectively. Low shrub aboveground productivity, equal to mortality, was 0.4 and 2.0 t ha−1 year−1 on the perched and raised bogs, respectively. This was about 40% of the standing biomass of shrubs in both bog types. Aboveground net primary productivity of woody strata was 3.5 and 3.0 t ha−1 year−1 on the perched and raised bogs, respectively. These data are comparable to earlier estimates of Sphagnum production on the same bogs: 3.8 t ha−1 year−1 on perched bogs and 3.2 t ha−1 year−1 on raised bogs. Vascular herbs contributed an additional 0.2 t ha−1 year−1 to aboveground production on the perched bogs and 0.1 t ha−1 year−1 on the raised bogs. The higher productivity of perched bogs is probably related to slightly higher nutrient status related to their landscape position. The total productivity of all strata of these ombrotrophic sites approaches that of upland sites in the same region.
Monodictys pelagica, the anamorph of Nereiospora cristata (Halosphaeriaceae)
Authors: Mouzouras R. , Jones E. B. Gareth
Published: May 2010

Single-ascospore isolates of Nereiospora cristata gave rise to conidia of Monodictys pelagica. Repeated isolations confirmed that M. pelagica was the anamorph of N. cristata. These findings are discussed and compared with the other known anamorph–teleomorph stages of marine fungi, especially the anamorph stages of Corollospora and Nereiospora.
Évolution de la teneur en lipides de Leptosphaeria typhae en fonction de sa croissance et de sa reproduction sexuée : activité de synthèse et étude des lipides neutres et polaires
Authors: Vidal Gérard
Published: May 2010

When perithecia appear (on the 7th day of growth), the mycelial lipid content falls and the degree of fat insaturation increases; fatty acid synthetase activity greatly increases. Lipid turnover is therefore accelerated. Among neutral lipids, triglycerides constitute the largest pool and their proportion increases when perithecia appear. Free fatty acids also increase, confirming the lipid turnover's acceleration. Polar lipids especially disappear; the phosphatidylcholine/phosphatidylethanolamine ratio increases when the fungus ascosporulates.
OPEN STRING IN (3+1)-DIMENSIONAL REISSNER–NORDSTRÖM BLACK HOLE
Authors: SUZUKI HIROMI
Published: May 2010

Previously we investigated the Nambu–Goto string and the wiggly cosmic string in (3+1)-dimensional Schwarzschild black hole. As an extension the solutions in (3+1)-dimensional spherically symmetric charged black holes are investigated. The solution for the wiggly string exhibits open strings lying along the circular orbit in the equatorial plane outside horizon, while the Nambu–Goto string has only a point-like solution.
A BRIEF REVIEW OF MINOS NEUTRINO OSCILLATION RESULTS
Authors: HABIG ALEC
Published: May 2010

The MINOS long-baseline experiment is using the NuMI neutrino beam to make precise measurements of neutrino flavor oscillations in the "atmospheric" neutrino sector. MINOS observes the νμ disappearance oscillations seen in atmospheric neutrinos, tests possible disappearance to sterile ν by measuring the neutral current flux, and extends our reach towards the so far unseen θ13 by looking for νe appearance in this νμ beam. The magnetized MINOS detectors also allow tests of CPT conservation by discriminating between neutrinos and anti-neutrinos on an event-by-event basis. The intense, well-understood NuMI neutrino beam created at Fermilab is observed 735 km away at the Soudan Mine in Northeast Minnesota. High-statistics studies of the neutrino interactions themselves and the cosmic rays seen by the MINOS detectors have also been made. MINOS started taking beam data in May 2005 and is now nearing the end of its five-year run. This paper reviews results published based on the first several years of data.
THE SCATTERING APPROACH TO THE CASIMIR FORCE
Authors: REYNAUD S. , CANAGUIER-DURAND A. , MESSINA R. , LAMBRECHT A. , MAIA NETO P. A.
Published: May 2010

We present the scattering approach which is nowadays the best tool for describing the Casimir force in realistic experimental configurations. After reminders on the simple geometries of 1d space and specular scatterers in 3d space, we discuss the case of stationary arbitrarily shaped mirrors in electromagnetic vacuum. We then review specific calculations based on the scattering approach, dealing for example with the forces or torques between nanostructured surfaces and with the force between a plane and a sphere. In these various cases, we account for the material dependence of the forces, and show that the geometry dependence goes beyond the trivial Proximity Force Approximation often used for discussing experiments.
DEMONSTRATING THE STRONG GEOMETRY DEPENDENCE OF THE CASIMIR FORCE ON A SURFACE WITH DEEP, NANOSCALE CORRUGATIONS
Authors: CHAN H. B. , BAO Y. , ZOU J. , CIRELLI R. A. , KLEMENS F. , MANSFIELD W. M. , PAI C. S.
Published: May 2010

We measure the Casimir force gradient between silicon surfaces with nanoscale, rectangular corrugations and a gold sphere attached to a micromechanical torsional oscillator. By comparing the force gradients on the corrugated surfaces to that on a smooth, flat surface of the same material, we demonstrate that the Casimir force deviates from the value expected from the pairwise additive approximation and the proximity force approximation. The observed deviation qualitatively agrees with calculations that take into account the interplay between finite conductivity and geometry effects. However, the agreement is not exact, possibly due to uncertainties in the optical properties of the silicon substrate.
NEW RESULTS FOR THE CASIMIR INTERACTION: SAMPLE CHARACTERIZATION AND LOW TEMPERATURE MEASUREMENTS
Authors: DECCA R. S. , LÓPEZ D. , OSQUIGUIL E.
Published: May 2010

We describe our latest results in the separation dependence of the Casimir interaction in the sphere-plane geometry for two Au-coated surfaces. All results are obtained by measuring the change in the resonant frequency of a sensitive microelectromechanical torsional oscillator as the separation between the sphere and the plane is changed. By means of the proximity force approximation, the change in resonant frequency yields the Casimir pressure between two parallel plates at the same separation. We present results for a new sample at room temperature, where the dielectric function has been measured in the 190-825 nm range. We show that the results of the Casimir force in this sample and in previous samples are virtually indistinguishable. Furthermore, the observed differences between measured and tabulated optical properties data do not show any effect on the calculation of the Casimir interaction. We also present results of the measurement of the Casimir force between a sphere and a plane at 300, 77, 4.2 and 2.1 K. While low temperature results are noisier than room temperature ones, precluding a direct exclusion of either the Drude or the plasma model, the average of the measurements coincide at all temperatures.
REPULSIVE CASIMIR AND VAN DER WAALS FORCES: FROM MEASUREMENTS TO FUTURE TECHNOLOGIES
Authors: MUNDAY J. N. , CAPASSO FEDERICO
Published: May 2010

By engineering the boundary conditions of electromagnetic fields between material interfaces, one can dramatically change the Casimir-Lifshitz force between surfaces as a result of the modified zero-point energy density of the system. Repulsive interactions between macroscopic bodies occur when their dielectric responses obey a particular inequality, as pointed out by Dzyaloshinskii, Lifshitz, and Pitaevskii. We discuss experimental verification of this behavior as well as a description of how this can be used to develop a scheme for quantum levitation. Based on these concepts, we discuss the possible development of a new class of devices based on ultra-low static friction and the ability to sort objects based on their dielectric functions.
MACROSCOPIC QUANTUM VACUUM AND MICROSCOPIC GRAVITATION
Authors: ONOFRIO ROBERTO
Published: May 2010

Macroscopic quantum vacuum and modern theories of gravitation share the strong interplay between geometry and physical phenomena. We review selected issues related to the accuracy of the measurement of Casimir forces with particular emphasis on the implications for the search of non-Newtonian gravitational forces in the micrometer range. We then discuss the interplay of the Higgs particle with gravitation, arguing that spectroscopic shifts in atomic transitions due to the modifications of the vacuum expectation value of the Higgs field in regions with strong curvature of space-time may be of conceptual and observational relevance.
GEOMETRY-TEMPERATURE INTERPLAY IN THE CASIMIR EFFECT
Authors: GIES H. , WEBER A.
Published: May 2010

We discuss Casimir phenomena which are dominated by long-range fluctuations. A prime example is given by "geothermal" Casimir phenomena where thermal fluctuations in open Casimir geometries can induce significantly enhanced thermal corrections. We illustrate the underlying mechanism with the aid of the inclined-plates configuration, giving rise to enhanced power-law temperature dependences compared to the parallel-plates case. In limiting cases, we find numerical evidence even for fractional power laws induced by long-range fluctuations. We demonstrate that thermal energy densities for open geometries are typically distributed over length scales of 1/T. As an important consequence, approximation methods for thermal corrections based on local energy-density estimates such as the proximity-force approximation are expected to become unreliable even at small surface separations.
THERMAL CASIMIR FORCE BETWEEN MAGNETIC MATERIALS
Authors: KLIMCHITSKAYA G. L. , GEYER B. , MOSTEPANENKO V. M.
Published: May 2010

We investigate the Casimir pressure between two parallel plates made of magnetic materials at nonzero temperature. It is shown that for real magnetodielectric materials only the magnetic properties of ferromagnets can influence the Casimir pressure. This influence is accomplished through the contribution of the zero-frequency term of the Lifshitz formula. The possibility of the Casimir repulsion through the vacuum gap is analyzed depending on the model used for the description of the dielectric properties of the metal plates.
THE CASIMIR EFFECT AND THE FOUNDATIONS OF STATISTICAL PHYSICS
Authors: MOSTEPANENKO V. M. , KLIMCHITSKAYA G. L.
Published: May 2010

The Lifshitz theory and its modifications are discussed with respect to the Nernst heat theorem and the experimental data of several recent experiments. An analysis of all available information leads to the conclusion that some concepts of statistical physics might need reconsideration.
NOBLE GAS, ALKALI AND ALKALINE ATOMS INTERACTING WITH A GOLD SURFACE
Authors: ŁACH GRZEGORZ , DEKIEVIET MAARTEN , JENTSCHURA ULRICH D.
Published: May 2010

The attractive branch of the interaction potentials with the surface of gold have been computed for a large variety of atomic systems: the hydrogen atom, noble gases ( He , Ne , Ar , Kr , Xe ), alkali atoms ( Li , Na , K , Rb , Cs ) and alkaline atoms ( Be , Mg , Ca , Sr , Ba ). The results include highly accurate dynamic polarizabilities for the helium atom calculated using a variational method and explicitly correlated wavefunctions. For other atoms considered we used the data available in the literature. The interaction potentials include both the effects of retardation of the electromagnetic interactions and a realistic representation of the optical response function of gold (beyond the approximation of a perfect conductor). An explicit comparison of our result to the interaction between an atom and a perfect conductor is given.
REPULSIVE CASIMIR FORCES AND ALTERNATIVES TO EINSTEINIAN GRAVITY
Authors: ELIZALDE E.
Published: May 2010

A basic property of the Casimir force is that, in most cases, it is attractive. The quest for workable configurations which exhibit repulsion is, at the same time, important and difficult, both in the nanophysics laboratory (e.g. to avoid stickness) and at cosmological scales (to account for the accelerated expansion of our universe). We shall here report on some configurations which exhibit the two signs of the Casimir force in function of the distance, and also on some alternatives to Einsteinian gravitation with the eventual aim to try to get around the cosmological constant problem.
VACUUM ENERGY DENSITY AND PRESSURE NEAR BOUNDARIES
Authors: FULLING S. A.
Published: May 2010

In vacuum energy calculations with an ultraviolet cutoff, divergences arise that clearly are related to the physics of boundaries. We point out how to find the cut-off energy density and pressure most directly from a Green function. Then we discuss three apparent paradoxes arising in this work that are in various stages of resolution.
THE SEARCH FOR THE SCHWINGER EFFECT: NONPERTURBATIVE VACUUM PAIR PRODUCTION
Authors: DUNNE GERALD V.
Published: May 2010

The Schwinger effect is the non-perturbative production of electron-positron pairs when an external electric field is applied to the quantum electrodynamical (QED) vacuum. The inherent instability of the vacuum in an electric field was one of the first non-trivial predictions of QED, but the effect is so weak that it has not yet been directly observed. However, there are exciting new developments in ultra-high intensity lasers, which may bring us to the verge of this extreme ultra-relativistic regime. This necessitates a fresh look at both experimental and theoretical aspects of the Schwinger effect. I describe some new theoretical ideas aimed at making this elusive effect observable, by careful shaping of the laser pulses, much as is done [in a different intensity regime] in the fast-developing field of atto-science.
FAST VALUATION OF FORWARD-STARTING BASKET DEFAULT SWAPS
Authors: JACKSON KEN , KREININ ALEX , ZHANG WANHE
Published: May 2010

A basket default swap (BDS) is a credit derivative with contingent payments that are triggered by a combination of default events of the reference entities. A forward-starting basket default swap (FBDS) is a BDS starting at a specified future time. Existing analytic or semi-analytic methods for pricing FBDS are time consuming due to the large number of possible default combinations before the BDS starts. This paper develops a fast approximation method for FBDS based on the conditional independence framework. The method converts the pricing of a FBDS to an equivalent BDS pricing problem and combines Monte Carlo simulation with an analytic approach to achieve an effective method. This hybrid method is a novel technique which can be viewed either as a means to accelerate the convergence of Monte Carlo simulation or as a way to estimate parameters in an analytic method that are difficult to compute directly. Numerical results demonstrate the accuracy and efficiency of the proposed hybrid method.
A REGULARIZED FOURIER TRANSFORM APPROACH FOR VALUING OPTIONS UNDER STOCHASTIC DIVIDEND YIELDS
Authors: DIA BAYE M.
Published: May 2010

This paper studies the option pricing problem in a class of models in which dividend yields follow a time-homogeneous diffusion. Within this framework, we develop a new approach for valuing options based on the use of a regularized Fourier transform. We derive a pricing formula for European options which gives the option price in the form of an inverse Fourier transform and propose two methods for numerically implementing this formula. As an application of this pricing approach, we introduce the Ornstein-Uhlenbeck and the square-root dividend yield models in which we explicitly solve the pricing problem for European options. Finally we highlight the main effects of a stochastic dividend yield on option prices.
LOCAL ESTIMATION OF DYNAMIC COPULA MODELS
Authors: MENDES BEATRIZ V. M. , DE MELO EDUARDO F. L.
Published: May 2010

It has been empirically verified that the strength of dependence in stock markets usually rises with volatility. In this paper we exploit this stylized fact combined with local maximum likelihood estimation of copula models to analyze the dynamic joint behavior of series of financial log returns. Explanatory variables based on the estimated GARCH volatilities are considered as potential regressors for explaining the dynamics in the copula parameters. The proposed model can assess and discriminate how much of the strength of dependence is due just to the time-varying volatility. The final local-parametric estimates may be used to compute risk measures, to simulate portfolio behavior, and so on. We illustrate our methods using two American indexes. Results indicate that volatility does affect the strength of dependence. The in-sample Value-at-Risk based on the dynamic model outperforms those based on the empirical estimates.
A DECISION-MAKER'S TOOL FOR SUSTAINABILITY-CENTRED STRATEGIC ENVIRONMENTAL ASSESSMENT
Authors: CROAL PETER , GIBSON ROBERT B. , ALTON CHARLES , BROWNLIE SUSIE , WINDIBANK ERIN
Published: May 2010

This paper outlines a Decision-Maker's Tool (DM Tool), designed to guide practitioners and their inter-disciplinary teams through a typical strategic environmental assessment (SEA) process. While SEA properly includes post-decision follow-up, the DM Tool covers the SEA process up to the creation of a Briefing Note for the decision maker. Together, use of the DM Tool and the Briefing Note should facilitate positive contributions to sustainability through well considered and aligned policies, plans and programmes (PPPs), by enhancing the comprehensiveness, consistency, clarity, accessibility and credibility of decision making information.

The discussion presumes that the SEA is central to the PPP development process, rather than being a separate exercise. The DM Tool and Briefing Note are designed to recommend PPP action based on clearly stated needs and purposes, addressing the key issues, and application of explicit sustainability criteria in the comparative evaluation of feasible alternatives. Particular attention is paid to recognising trade-offs and residual risks, and presenting all this information concisely for the decision maker.
Expanding Roles for Diverse Physical Phenomena During the Origin of Life
Authors: Budin Itay , Szostak Jack W.
Published: May 2010

Recent synthetic approaches to understanding the origin of life have yielded insights into plausible pathways for the emergence of the first cells. Here we review current experiments with implications for the origin of life, emphasizing the ability of unexpected physical processes to facilitate the self-assembly and self-replication of the first biological systems. These laboratory efforts have uncovered novel physical mechanisms for the emergence of homochirality; the concentration and purification of prebiotic building blocks; and the ability of the first cells to assemble, grow, divide, and acquire greater complexity. In the absence of evolved biochemical capabilities, such physical processes likely played an essential role in early biology.
Eukaryotic Chemotaxis: A Network of Signaling Pathways Controls Motility, Directional Sensing, and Polarity
Authors: Swaney Kristen F. , Huang Chuan-Hsiang , Devreotes Peter N.
Published: May 2010

Chemotaxis, the directed migration of cells in chemical gradients, is a vital process in normal physiology and in the pathogenesis of many diseases. Chemotactic cells display motility, directional sensing, and polarity. Motility refers to the random extension of pseudopodia, which may be driven by spontaneous actin waves that propagate through the cytoskeleton. Directional sensing is mediated by a system that detects temporal and spatial stimuli and biases motility toward the gradient. Polarity gives cells morphologically and functionally distinct leading and lagging edges by relocating proteins or their activities selectively to the poles. By exploiting the genetic advantages of Dictyostelium, investigators are working out the complex network of interactions between the proteins that have been implicated in the chemotactic processes of motility, directional sensing, and polarity.
Phase Separation in Biological Membranes: Integration of Theory and Experiment
Authors: Elson Elliot L. , Fried Eliot , Dolbow John E. , Genin Guy M.
Published: May 2010

Lipid bilayer model membranes that contain a single lipid species can undergo transitions between ordered and disordered phases, and membranes that contain a mixture of lipid species can undergo phase separations. Studies of these transformations are of interest for what they can tell us about the interaction energies of lipid molecules of different species and conformations. Nanoscopic phases (<200 nm) can provide a model for membrane rafts, specialized membrane domains enriched in cholesterol and sphingomyelin, which are believed to have essential biological functions in cell membranes. Crucial questions are whether lipid nanodomains can exist in stable equilibrium in membranes and what is the distribution of their sizes and lifetimes in membranes of different composition. Theoretical methods have supplied much information on these questions, but better experimental methods are needed to detect and characterize nanodomains under normal membrane conditions. This review summarizes linkages between theoretical and experimental studies of phase separation in lipid bilayer model membranes.
Simplified Models of Biological Networks
Authors: Sneppen Kim , Krishna Sandeep , Semsey Szabolcs
Published: May 2010

The function of living cells is controlled by complex regulatory networks that are built of a wide diversity of interacting molecular components. The sheer size and intricacy of molecular networks of even the simplest organisms are obstacles toward understanding network functionality. This review discusses the achievements and promise of a bottom-up approach that uses well-characterized subnetworks as model systems for understanding larger networks. It highlights the interplay between the structure, logic, and function of various types of small regulatory circuits. The bottom-up approach advocates understanding regulatory networks as a collection of entangled motifs. We therefore emphasize the potential of negative and positive feedback, as well as their combinations, to generate robust homeostasis, epigenetics, and oscillations.
Optical Control of Neuronal Activity
Authors: Szobota Stephanie , Isacoff Ehud Y.
Published: May 2010

Advances in optics, genetics, and chemistry have enabled the investigation of brain function at all levels, from intracellular signals to single synapses, whole cells, circuits, and behavior. Until recent years, these research tools have been utilized in an observational capacity: imaging neural activity with fluorescent reporters, for example, or correlating aberrant neural activity with loss-of-function and gain-of-function pharmacological or genetic manipulations. However, optics, genetics, and chemistry have now combined to yield a new strategy: using light to drive and halt neuronal activity with molecular specificity and millisecond precision. Photostimulation of neurons is noninvasive, has unmatched spatial and temporal resolution, and can be targeted to specific classes of neurons. The optical methods developed to date encompass a broad array of strategies, including photorelease of caged neurotransmitters, engineered light-gated receptors and channels, and naturally light-sensitive ion channels and pumps. In this review, we describe photostimulation methods, their applications, and opportunities for further advancement.
Biophysics of Knotting
Authors: Meluzzi Dario , Smith Douglas E. , Arya Gaurav
Published: May 2010

Knots appear in a wide variety of biophysical systems, ranging from biopolymers, such as DNA and proteins, to macroscopic objects, such as umbilical cords and catheters. Although significant advancements have been made in the mathematical theory of knots and some progress has been made in the statistical mechanics of knots in idealized chains, the mechanisms and dynamics of knotting in biophysical systems remain far from fully understood. We report on recent progress in the biophysics of knotting—the formation, characterization, and dynamics of knots in various biophysical contexts.
Eukaryotic Mechanosensitive Channels
Authors: Árnadóttir Jóhanna , Chalfie Martin
Published: May 2010

Mechanosensitive ion channels are gated directly by physical stimuli and transduce these stimuli into electrical signals. Several criteria must apply for a channel to be considered mechanically gated. Mechanosensitive channels from bacterial systems have met these criteria, but few eukaryotic channels have been confirmed by the same standards. Recent work has suggested or confirmed that diverse types of channels, including TRP channels, K2P channels, MscS-like proteins, and DEG/ENaC channels, are mechanically gated. Several studies point to the importance of the plasma membrane for channel gating, but intracellular and/or extracellular structures may also be required.
Obese carboxypeptidase E knockout mice exhibit multiple defects in peptide hormone processing contributing to low bone mineral density
Authors: Cawley Niamh X. , Yanik Tulin , Woronowicz Alicja , Chang Weizhong , Marini Joan C. , Loh Y. Peng
Published: May 2010

Carboxypeptidase E (CPE) is a prohormone/proneuropeptide processing enzyme, and mice bearing CPE mutations exhibit an obese and diabetic phenotype. Studies on CPE knockout (KO) mice revealed poor prohormone processing, resulting in deficiencies in peptide hormones/neuropeptides such as insulin, gonadotropin-releasing hormone, and cocaine- and amphetamine-regulated transcript (CART). Here, we show that CPE KO mice, an obese animal model, have low bone mineral density (BMD) accompanied by elevated plasma CTX-1 (carboxy-terminal collagen crosslinks), and osteocalcin, indicators of increased bone turnover. Receptor activator for NF-κB ligand (RANKL) expression was elevated ∼2-fold relative to osteoprotegerin in the femur of KO animals, suggesting increased osteoclastic activity in the KO mice. In the hypothalamus, mature CART, a peptide involved in eating behavior and implicated in bone metabolism, was undetectable. The melanocortin and neuropeptide Y (NPY) systems in the hypothalamus have also been implicated in bone remodeling, since MC4R KO and NPY KO mice have increased BMD. However, reduction of α-MSH, the primary ligand of MC4R by up to 94% and the lack of detectable NPY in the hypothalamus of CPE KO do not recapitulate the single-gene KO phenotypes. This study highlights the complex physiological interplay between peptides involved in energy metabolism and bone formation and furthermore suggests the possibility that patients, bearing CPE and CART mutations leading to inactive forms of these molecules, may be at a higher risk of developing osteoporosis.
Choosing to Make an Effort: The Role of Striatum in Signaling Physical Effort of a Chosen Action
Authors: Kurniawan I. T. , Seymour B. , Talmi D. , Yoshida W. , Chater N. , Dolan R. J.
Published: May 2010

The possibility that we will have to invest effort influences our future choice behavior. Indeed deciding whether an action is actually worth taking is a key element in the expression of human apathy or inertia. There is a well developed literature on brain activity related to the anticipation of effort, but how effort affects actual choice is less well understood. Furthermore, prior work is largely restricted to mental as opposed to physical effort or has confounded temporal with effortful costs. Here we investigated choice behavior and brain activity, using functional magnetic resonance imaging, in a study where healthy participants are required to make decisions between effortful gripping, where the factors of force (high and low) and reward (high and low) were varied, and a choice of merely holding a grip device for minimal monetary reward. Behaviorally, we show that force level influences the likelihood of choosing an effortful grip. We observed greater activity in the putamen when participants opt to grip an option with low effort compared with when they opt to grip an option with high effort. The results suggest that, over and above a nonspecific role in movement anticipation and salience, the putamen plays a crucial role in computations for choice that involves effort costs.
Highly conserved transcriptional responses to mechanical ventilation of the lung
Authors: Kompass Kenneth S. , Deslee Gaetan , Moore Carla , McCurnin Donald , Pierce Richard A.
Published: May 2010

Cross-species analysis of microarray data has shown improved discriminating power between healthy and diseased states. Computational approaches have proven effective in deciphering the complexity of human disease by identifying upstream regulatory elements and the transcription factors that interact with them. Here we used both methods to identify highly conserved transcriptional responses during mechanical ventilation, an important therapeutic treatment that has injurious side effects. We generated control and ventilated whole lung samples from the premature baboon model of bronchopulmonary dysplasia (BPD), processed them for microarray, and combined them with existing whole lung oligonucleotide microarray data from 85 additional control samples from mouse, rat, and human and 19 additional ventilated samples from mouse and rat. Of the 2,531 orthologs shared by all 114 samples, 60 were modulated by mechanical ventilation [false discovery rate (FDR)-adjusted q value ( qFDR) = 0.005, ANOVA]. These included transcripts encoding the transcription factors ATF3 and FOS. Because of compelling known roles for these transcription factors, we used computational methods to predict their targets in the premature baboon model of BPD, which included elastin (ELN), gastrin-releasing polypeptide (GRP), and connective tissue growth factor (CTGF). This approach identified highly conserved transcriptional responses to mechanical ventilation and may facilitate identification of therapeutic targets to reduce the side effects of this valuable treatment.
The Numerical Convergence of the Landau‐Lifshitz Equations and Its Simulation
Authors: Zhong Penghong , Wang Shu , Wang Ke , Bai Yiping
Published: May 2010

A difference scheme of Landau‐Lifshitz (LL for short) equations is studied. Their convergence and stability are proved. Furthermore, a new solution of LL equation is given for testing our scheme. At the end, three subcases of this LL equation are concerned about, and some properties about these equations are shown by a numeric simulation way.
The Application of Nonlinear Spectral Subtraction Method on Millimeter Wave Conducted Speech Enhancement
Authors: Li Sheng , Wang Jian Qi , Jing Xi Jing
Published: May 2010

A nonlinear multiband spectral subtraction method is investigated in this study to reduce the colored electronic noise in millimeter wave (MMW) radar conducted speech. Because the over‐subtraction factor of each Bark frequency band can be adaptively adjusted, the nonuniform effects of colored noise in the spectrum of the MMW radar speech can be taken into account in the enhancement process. Both the results of the time‐frequency distribution analysis and perceptual evaluation test suggest that a better whole‐frequency noise reduction effect is obtained, and the perceptually annoying musical noise was efficiently reduced, with little distortion to speech information as compared to the other standard speech enhancement algorithm.
Fractional Order Calculus: Basic Concepts and Engineering Applications
Authors: Gutiérrez Ricardo Enrique , Rosário João Maurício , Tenreiro Machado José
Published: May 2010

The fractional order calculus (FOC) is as old as the integer one although up to recently its application was exclusively in mathematics. Many real systems are better described with FOC differential equations as it is a well‐suited tool to analyze problems of fractal dimension, with long‐term “memory” and chaotic behavior. Those characteristics have attracted the engineers′ interest in the latter years, and now it is a tool used in almost every area of science. This paper introduces the fundamentals of the FOC and some applications in systems′ identification, control, mechatronics, and robotics, where it is a promissory research field.
The Excited Electronic States Calculated for Cd1−xZnxS Quantum Dots Grown by the Sol‐Gel Technique
Authors: Sakly A. , Safta N. , Mejri A. , Mejri H. , Ben Lamine A.
Published: May 2010

The present paper is aimed to investigate theoretically the quantum confinement in Cd1−xZnxS‐related quantum dots with x the atomic fraction of Zn. For both electrons and holes, we have calculated the excited bound states with use of the spherical geometry model and assuming a finite potential at the boundary. For electrons, calculations were made by using Bessel function as an orthonormal basis. However, for holes, the confined subbands have been calculated based on squared quantum well envelope wave functions. The subband energies were evaluated for both electrons and holes versus zinc composition as well.
Pathways of Proliferation and Antiapoptosis Driven in Breast Cancer Stem Cells by Stem Cell Protein Piwil2
Authors: Lee Jae Ho , Jung Cornelia , Javadian-Elyaderani Parisa , Schweyer Stefan , Schütte Dorothea , Shoukier Moneef , Karimi-Busheri Feridoun , Weinfeld Michael , Rasouli-Nia Aghdass , Hengstler Jan G. , Mantilla Alejandra , Soleimanpour-Lichaei Hamid Reza , Engel Wolfgang , Robson Craig N. , Nayernia Karim
Published: May 2010

Cancer stem cell studies may improve understanding of tumor pathophysiology and identify more effective strategies for cancer treatment. In a variety of organisms, Piwil2 has been implicated in multiple roles including stem cell self-renewal, RNA silencing, and translational control. In this study, we documented specific expression of the stem cell protein Piwil2 in breast cancer with predominant expression in breast cancer stem cells. In patients who were evaluated, we determined that 90% of invasive carcinomas and 81% of carcinomas in situ exhibited highest expression of Piwil2. In breast cancer cells, Piwil2 silencing suppressed the expression of signal transducer and activator of transcription 3, a pivotal regulator of Bcl-XL and cyclin D1, whose downregulation paralleled a reduction in cell proliferation and survival. Our findings define Piwil2 and its effector signaling pathways as key factors in the proliferation and survival of breast cancer stem cells. Cancer Res; 70(11); 4569–79. ©2010 AACR.
Oncogene-Induced Sensitization to Chemotherapy-Induced Death Requires Induction as well as Deregulation of E2F1
Authors: Helgason G. Vignir , O'Prey Jim , Ryan Kevin M.
Published: May 2010

The analysis of DNA tumor viruses has provided landmark insights into the molecular pathogenesis of cancer. A paradigm for this field has been the study of the adenoviral E1a protein, which has led to the identification of proteins such as p300, p400, and members of the retinoblastoma family. Through binding Rb family members, E1a causes deregulation of E2F proteins—an event common to most human cancers and a central pathway in which oncogenes, including E1a, sensitize cells to chemotherapy-induced programmed cell death. We report here, however, that E1a not only causes deregulation of E2F, but importantly that it also causes the posttranscriptional upregulation of E2F1 protein levels. This effect is distinct from the deregulation of E2F1, however, as mutants of E2F1 impaired in pRb binding are induced by E1a and E2F1 induction can also be observed in Rb-null cells. Analysis of E1a mutants selectively deficient in cellular protein binding revealed that induction of E2F1 is instead intrinsically linked to p400. Mutants unable to bind p400, despite being able to deregulate E2F1, do not increase E2F1 protein levels and they do not sensitize cells to apoptotic death. These mutants can, however, be complemented by either the knockdown of p400, resulting in the restoration of the ability to induce E2F1, or by the overexpression of E2F1, with both events reenabling sensitization to chemotherapy-induced death. Due to the frequent deregulation of E2F1 in human cancer, these studies reveal potentially important insights into E2F1-mediated chemotherapeutic responses that may aid the development of novel targeted therapies for malignant disease. Cancer Res; 70(10); 4074–80. ©2010 AACR.
Inhibition of Histone Deacetylase in Cancer Cells Slows Down Replication Forks, Activates Dormant Origins, and Induces DNA Damage
Authors: Conti Chiara , Leo Elisabetta , Eichler Gabriel S. , Sordet Olivier , Martin Melvenia M. , Fan Angela , Aladjem Mirit I. , Pommier Yves
Published: May 2010

Protein acetylation is a reversible process regulated by histone deacetylases (HDAC) that is often altered in human cancers. Suberoylanilide hydroxamic acid (SAHA) is the first HDAC inhibitor to be approved for clinical use as an anticancer agent. Given that histone acetylation is a key determinant of chromatin structure, we investigated how SAHA may affect DNA replication and integrity to gain deeper insights into the basis for its anticancer activity. Nuclear replication factories were visualized with confocal immunofluorescence microscopy and single-replicon analyses were conducted by genome-wide molecular combing after pulse labeling with two thymidine analogues. We found that pharmacologic concentrations of SAHA induce replication-mediated DNA damage with activation of histone γH2AX. Single DNA molecule analyses indicated slowdown in replication speed along with activation of dormant replication origins in response to SAHA. Similar results were obtained using siRNA-mediated depletion of HDAC3 expression, implicating this HDAC member as a likely target in the SAHA response. Activation of dormant origins was confirmed by molecular analyses of the β-globin locus control region. Our findings demonstrate that SAHA produces profound alterations in DNA replication that cause DNA damage, establishing a critical link between robust chromatin acetylation and DNA replication in human cancer cells. Cancer Res; 70(11); 4470–80. ©2010 AACR.
The Limitations of the G1-S Checkpoint
Authors: Deckbar Dorothee , Stiff Thomas , Koch Barbara , Reis Caroline , Löbrich Markus , Jeggo Penny A.
Published: May 2010

It has been proposed that the G1-S checkpoint is the critical regulator of genomic stability, preventing the cell cycle progression of cells with a single DNA double-strand break. Using fluorescence-activated cell sorting analysis of asynchronous cells and microscopic analysis of asynchronous and synchronized cells, we show that full blockage of S-phase entry is only observed >4 hours after irradiation. The process is ataxia-telangiectasia mutated (ATM) dependent and Chk1/2 independent and can be activated throughout G1 phase. By monitoring S-phase entry of irradiated synchronized cells, we show that the duration of arrest is dose dependent, with S-phase entry recommencing after arrest with kinetics similar to that observed in unirradiated cells. Thus, G1-S checkpoint arrest is not always permanent. Following exposure to higher doses (≥2 Gy), G1-S arrest is inefficiently maintained, allowing progression of G1-phase cells into G2 with elevated γH2AX foci and chromosome breaks. At early times after irradiation (≤4 h), G1-S checkpoint arrest is not established but cells enter S phase at a reduced rate. This early slowing in S-phase entry is ATM and Chk2 dependent and detectable after 100 mGy, showing a novel and sensitive damage response. However, the time needed to establish G1-S checkpoint arrest provides a window when cells can progress to G2 and form chromosome breaks. Our findings detail the efficacy of the G1-S checkpoint and define two significant limitations: At early times after IR, the activated checkpoint fails to efficiently prevent S-phase entry, and at later times, the checkpoint is inefficiently maintained. Cancer Res; 70(11); 4412–21. ©2010 AACR.
Identification of ASF/SF2 as a Critical, Allele-Specific Effector of the Cyclin D1b Oncogene
Authors: Olshavsky Nicholas A. , Comstock Clay E.S. , Schiewer Matthew J. , Augello Michael A. , Hyslop Terry , Sette Claudio , Zhang Jinsong , Parysek Linda M. , Knudsen Karen E.
Published: May 2010

The cyclin D1b oncogene arises from alternative splicing of the CCND1 transcript, and harbors markedly enhanced oncogenic functions not shared by full-length cyclin D1 (cyclin D1a). Recent studies showed that cyclin D1b is selectively induced in a subset of tissues as a function of tumorigenesis; however, the underlying mechanism(s) that control tumor-specific cyclin D1b induction remain unsolved. Here, we identify the RNA-binding protein ASF/SF2 as a critical, allele-specific, disease-relevant effector of cyclin D1b production. Initially, it was observed that SF2 associates with cyclin D1b mRNA (transcript-b) in minigene analyses and with endogenous transcript in prostate cancer (PCa) cells. SF2 association was altered by the CCND1 G/A870 polymorphism, which resides in the splice donor site controlling transcript-b production. This finding was significant, as the A870 allele promotes cyclin D1b in benign prostate tissue, but in primary PCa, cyclin D1b production is independent of A870 status. Data herein provide a basis for this disparity, as tumor-associated induction of SF2 predominantly results in binding to and accumulation of G870-derived transcript-b. Finally, the relevance of SF2 function was established, as SF2 strongly correlated with cyclin D1b (but not cyclin D1a) in human PCa. Together, these studies identify a novel mechanism by which cyclin D1b is induced in cancer, and reveal significant evidence of a factor that cooperates with a risk-associated polymorphism to alter cyclin D1 isoform production. Identification of SF2 as a disease-relevant effector of cyclin D1b provides a basis for future studies designed to suppress the oncogenic alternative splicing event. Cancer Res; 70(10); 3975–84. ©2010 AACR.
Strategic Workshops on Cancer Nanotechnology
Authors: Nagahara Larry A. , Lee Jerry S.H. , Molnar Linda K. , Panaro Nicholas J. , Farrell Dorothy , Ptak Krzysztof , Alper Joseph , Grodzinski Piotr
Published: May 2010

Nanotechnology offers the potential for new approaches to detecting, treating, and preventing cancer. To determine the current status of the cancer nanotechnology field and the optimal path forward, the National Cancer Institute's Alliance for Nanotechnology in Cancer held three strategic workshops, covering the areas of in vitro diagnostics and prevention, therapy and post-treatment, and in vivo diagnosis and imaging. At each of these meetings, a wide range of experts from academia, industry, the nonprofit sector, and the U.S. government discussed opportunities in the field of cancer nanotechnology and barriers to its implementation. Cancer Res; 70(11); 4265–8. ©2010 AACR.
Extranuclear Functions of ER Impact Invasive Migration and Metastasis by Breast Cancer Cells
Authors: Chakravarty Dimple , Nair Sujit S. , Santhamma Bindu , Nair Binoj C. , Wang Long , Bandyopadhyay Abhik , Agyin Joseph K. , Brann Darrell , Sun Lu-Zhe , Yeh I-Tien , Lee Francis Y. , Tekmal Rajeshwar Rao , Kumar Rakesh , Vadlamudi Ratna K.
Published: May 2010

The molecular basis of breast cancer progression to metastasis and the role of estrogen receptor (ER) signaling in this process remain poorly understood. Emerging evidence suggests that ER participates in extranuclear signaling in addition to genomic functions. Recent studies identified proline-, glutamic acid–, and leucine-rich protein-1 (PELP1) as one of the components of ER signalosome in the cytoplasm. PELP1 expression is deregulated in metastatic breast tumors. We examined the mechanism and significance of ER-PELP1–mediated extranuclear signals in the cytoskeletal remodeling and metastasis. Using estrogen dendrimer conjugate (EDC) that uniquely activate ER extranuclear signaling and by using model cells that stably express PELP1 short hairpin RNA (shRNA), we show that PELP1 is required for optimal activation of ER extranuclear actions. Using a yeast two-hybrid screen, we identified integrin-linked kinase 1 (ILK1) as a novel PELP1-binding protein. Activation of extranuclear signaling by EDC uniquely enhanced E2-mediated ruffles and filopodia-like structures. Using dominant-negative and dominant-active reagents, we found that estrogen-mediated extranuclear signaling promotes cytoskeleton reorganization through the ER-Src-PELP1-phosphoinositide 3-kinase-ILK1 pathway. Using in vitro Boyden chamber assays and in vivo xenograft assays, we found that ER extranuclear actions contribute to cell migration. Collectively, our results suggest that ER extranuclear actions play a role in cell motility/metastasis, establishing for the first time that endogenous PELP1 serves as a critical component of ER extranuclear actions leading to cell motility/invasion and that the ER-Src-PELP1-ILK1 pathway represents a novel therapeutic target for preventing the emergence of ER-positive metastasis. Cancer Res; 70(10); 4092–101. ©2010 AACR.
Glioma Cell Populations Grouped by Different Cell Type Markers Drive Brain Tumor Growth
Authors: Prestegarden Lars , Svendsen Agnete , Wang Jian , Sleire Linda , Skaftnesmo Kai Ove , Bjerkvig Rolf , Yan Tao , Askland Lasse , Persson Andreas , Sakariassen Per Øystein , Enger Per Øyvind
Published: May 2010

Although CD133 has been proposed as a marker for brain tumor–initiating cells, studies show that a tumorigenic potential exists among CD133− glioma cells as well. However, it is not established whether the ability of CD133− cells to form tumors is a property confined to a small subpopulation, rather than a common trait associated with most glioma cell types. Thus, we used lentiviral vectors expressing green fluorescent protein under lineage-specific promoters to identify CD133− glioma cells expressing Nestin, glial fibrillary acidic protein (GFAP), and neuron-specific enolase (NSE). Flow cytometry analysis showed the presence of CD133− subpopulations expressing these markers in glioma cell lines and in primary cultures from human glioblastoma (GBM) biopsies. Moreover, analysis of cell cycle distribution showed that subgroups expressing Nestin, GFAP, and NSE uniformly contained actively cycling cells, when cultured in serum-containing medium and stem cell medium. These subpopulations were fluorescence-activated cell sorted from CD133− U373 glioma cells and implanted intracerebrally in severe combined immunodeficient mice. Moreover, we implanted Nestin-, GFAP-, and NSE-positive glioma cells sorted from a human GBM biopsy, following removal of CD133-positive cells. All the CD133− subpopulations produced tumors, with no significant differences in survival or tumor take rates. However, there was a trend toward lower take rates for CD133− glioma subpopulations expressing GFAP and NSE. These findings suggest that the ability to form tumors may be a general trait associated with different glioma cell phenotypes, rather than a property limited to an exclusive subpopulation of glioma stem cells. Cancer Res; 70(11); 4274–9. ©2010 AACR.