bluuebunny/crossref_metadata_2025 huggingface dataset:
Managing Childcare: The Experiences of Mothers and Childcare Workers
Authors: Fothergill Alice
Published: May 2013

This paper discusses the findings from an ethnographic study of childcare. It examines employed mothers and their experiences with sending their young children to childcare centers, and childcare workers and their perspectives on their work. In this 2‐year‐long research project, I studied two large, urban childcare centers, one independent, non‐profit and one part of a national, for‐profit chain. Methods included participant observation, in‐depth interviewing, and focus groups. I found that mothers’ experiences with childcare are shaped by three factors: (1) cultural messages; (2) feelings of anxiety and guilt; and (3) the perceived quality of the childcare. I explore these three factors and discuss how the mothers are affected by the “intensive mothering” ideology. For the childcare workers, their work is affected by: (1) the level of respect and economic rewards they receive, (2) their commitment to the children, and (3) their role as expert or authority and other issues of power. By examining the two groups of women together, it becomes clear that both groups of women face interwoven challenges in a culture that devalues children and childrearing, and that alliances to address these interwoven concerns are essential.
Digital Imaging Methodology for Measuring Early Shrinkage Cracking in Concrete
Authors: Ruiz‐Ripoll L. , Barragán B. E. , Moro S. , Turmo J.
Published: May 2013

The measurement of early shrinkage cracking in concrete is important to prevent aesthetic issues and avoid surface cracking that could lead to reinforcement corrosion and reduce the durability, long‐term service life and integrity of a structure. Moreover, the lack of standards and subjectivity of the very few methodologies proposed so far complicate its estimation.

This research presents a new imaging methodology for evaluating and quantifying early shrinkage cracking patterns. The methodology was developed testing highly restrained square concrete slabs subjected to severe conditions of restraint and moisture loss. Its quantification consisted of photographing, processing the pictures and highlighting the cracks. For the first time, early shrinkage cracking in concrete can be measured through an experimental technique and quantified by means of geometric figures. In this way, more precise and automatic results are achieved, as flat figures adapt to the shape of cracks and store their properties. Therefore, parameters such as the total cracked area, total crack length, maximum crack width or average crack width were easily calculated.

The results demonstrated the suitability of the wind tunnel test to produce significant cracking patterns, as well as the great capacity of the imaging methodology to identify and characterize the cracking pattern.
FEASIBILITY AND REPEATABILITY FOR IN VIVO MEASUREMENTS OF STIFFNESS GRADIENTS IN THE CANINE GASTROCNEMIUS TENDON USING AN ACOUSTOELASTIC STRAIN GAUGE
Authors: Ellison Michelle , Kobayashi Hirohito , Delaney Fern , Danielson Kelson , Vanderby Ray , Muir Peter , Forrest Lisa J.
Published: May 2013

B‐mode ultrasound is an established imaging modality for evaluating canine tendon injury. However, full extent of tendon injury often remains difficult to estimate, as small changes in sonographic appearance are associated with large changes in biomechanical strength. The acoustoelastic strain gauge (ASG) is an ultrasound‐based tissue evaluation technique that relates the change in echo intensity observed during relaxation or stretching of tendons to the tissue's mechanical properties. This technique deduces stiffness gradient (the rate of change of normalized stiffness as a function of tissue strain) by analyzing the ultrasound dynamic images captured from gradually deforming tissue.ASGhas been proven to accurately model strain and stiffness within tendons in vitro. To determine the feasibility and repeatability for in vivo ASG measurements of canine tendon function, stiffness gradients for the gastrocnemius tendons of 10 clinically normal dogs were recorded by two nonindependent observers at three sites (musculotendinous junction, mid tendon, and insertion). Average stiffness gradient indices (0.0132, 0.0141, 0.0136) and dispersion values (0.0053, 0.0054, 0.0057) for each site, respectively, were consistent with published mechanical properties for normal canine tendon. Mean differences of the average stiffness gradient index and dispersion value between observers and between limbs for each site were less than 16%. Using interclass coefficients (ICC), intra‐observer (ICC0.79–0.98) and interobserver (ICC0.77–0.95) reproducibility was good to excellent. Right and left limb values were symmetric (ICC0.74–0.92). Findings from this study indicated thatASGis a feasible and repeatable technique for measuring stiffness gradients in canine tendons.
Improving sachet water quality – does Hazard Analysis and Critical Control Points apply?
Authors: Opatunji Olufemi , Odhiambo Francis
Published: May 2013

Sachet water is growing in importance as a source of drinking water for many people in Nigeria. In recent years, doubts over the quality of sachet water have grown. Commentators often cite poor distribution and storage practice for contamination of sachets. However, the integrity of the production process has been shown to be a weakness but has not received attention from the regulator or producers because of a lack of proper regulation of the industry. This study implemented the hazards analysis and critical control points (HACCP) framework in eight sachet water factories in Ibadan, Nigeria. The objective was to test HACCP's viability as a proactive management tool for improving sachet water quality. The findings show that HACCP can be adopted within the sachet water industry. However, the implementation of HACCP requires both technical and behavioural changes within the production process.
Nitric oxide‐dependent long‐term depression but not endocannabinoid‐mediated long‐term potentiation is crucial for visual recognition memory
Authors: Tamagnini Francesco , Barker Gareth , Warburton E. Clea , Burattini Costanza , Aicardi Giorgio , Bashir Zafar I.
Published: May 2013

Key points

Perirhinal cortex (Prh) is critically involved in visual recognition memory and synaptic plasticity.

Nitric oxide and endocannabinoids (eCBs) have been shown to act as retrograde messengers in synaptic plasticity in several brain areas, but no study has yet investigated their role in synaptic plasticity in Prh.

Evidence is still lacking of a retrograde messenger involved in synaptic plasticity in Prh.

In this study, we show that NO is involved in long‐term depression (LTD) but not in long‐term potentiation (LTP). Conversely, eCBs are involved in LTP but not in LTD. Crucially, inhibiition of NO signalling prevents visual recognition memory acquisition, whilst inhibition of eCB signalling does not affect recognition memory.

These results suggest that LTD but not LTP is a neuronal correlate of visual recognition memory.

Abstract  Synaptic plasticity in perirhinal cortex is essential for recognition memory. Nitric oxide and endocannabinoids (eCBs), which are produced in the postsynaptic cell and act on the presynaptic terminal, are implicated in mechanisms of long‐term potentiation (LTP) and long‐term depression (LTD) in other brain regions. In this study, we examine these two retrograde signalling cascades in perirhinal cortex synaptic plasticity and in visual recognition memory in the rat. We show that inhibition of NO‐dependent signalling prevented both carbachol‐ and activity (5 Hz)‐dependent LTD but not activity (100 Hz theta burst)‐dependent LTP in the rat perirhinal cortex in vitro. In contrast, inhibition of the eCB‐dependent signalling prevented LTP but not the two forms of LTD in vitro. Local administration into perirhinal cortex of the nitric oxide synthase inhibitor NPA (2 μm) disrupted acquisition of long‐term visual recognition memory. In contrast, AM251 (10 μm), a cannabinoid receptor 1 antagonist, did not impair visual recognition memory. The results of this study demonstrate dissociation between putative retrograde signalling mechanisms in LTD and LTP in perirhinal cortex. Thus, LTP relies on cannabinoid but not NO signalling, whilst LTD relies on NO‐ but not eCB‐dependent signalling. Critically, these results also establish, for the first time, that NO‐ but not eCB‐dependent signalling is important in perirhinal cortex‐dependent visual recognition memory.
An Effective Combined Finite Element-Upwind Finite Volume Method for a Transient Multiphysics Two-Phase Transport Model of a Proton Exchange Membrane Fuel Cell
Authors: Sun Pengtao , Zhou Su , Hu Qiya
Published: May 2013

In this paper, an effective combined finite element-upwind finite volume method is studied for a three-dimensional transient multiphysics transport model of a proton exchange membrane fuel cell (PEMFC), in which Navier–Stokes–Darcy coupling flow, species transports, heat transfer, electrochemical processes, and charge transports are fully considered. Multiphase mixture (M2) formulation is employed to define the involved two-phase model. Kirchhoff transformation is introduced to overcome the discontinuous and degenerate water diffusivity that is induced by the M2 model. By means of an adaptive time-stepping fourth-order multistep backward differencing formula (BDF), we design an effective temporal integration scheme to deal with the stiff phenomena arising from different time scales. In addition, all the governing equations are discretized by a combined finite element-upwind finite volume method to conquer the dominant convection effect in gas channels, while the diffusion and reaction effects are still dealt with by finite element method. Numerical simulations demonstrate that the presented techniques are effective to obtain a fast and convergent nonlinear iteration within a maximum 36 steps at each time step; in contrast to the oscillatory and nonconvergent iteration conducted by commercial CFD solvers and standard finite element/finite volume methods.
The Use of the Differential Transform Method to Solve Time-Invariant State-Feedback Optimal Control Problems
Authors: Nik H. Saberi
Published: May 2013

In this paper, the differential transform method (DTM) is applied for solving time-invariant state-feedback control problems. The optimal equations are obtained using the Pontryagin's maximum principle (PMP) and Bellman's Dynamic Programming. We present the closed-loop optimal control of linear plants with quadratic performance index. The results reveal that the proposed methods are very effective and simple. Comparisons are made between the results of two proposed methods and the exact solutions.
Biomechanical Evaluation of an Endplate-Conformed Polycaprolactone-Hydroxyapatite Intervertebral Fusion Graft and Its Comparison With a Typical Nonconformed Cortical Graft
Authors: Agarwal Aakash , Palepu Vivek , Agarwal Anand K. , Goel Vijay K. , Yildirim Eda D.
Published: May 2013

In the thoracolumbar region, between 7% and 30% of spinal fusion failures are at risk for pseudarthrosis. From a biomechanical perspective, the nonconformity of the intervertebral graft to the endplate surface could contribute to pseudarthrosis, given suboptimal stress distributions. The objective of this study was to quantify the effect of endplate-graft conformation on endplate stress distribution, maximum Von Mises stress development, and stability. The study design used an experimentally validated finite element (FE) model of the L4–L5 functional spinal unit to simulate two types of interbody grafts (cortical bone and polycaprolactone (PCL)-hydroxyapatite (HA) graft), with and without endplate-conformed surfaces. Two case studies were completed. In Case Study I, the endplate-conformed grafts and nonconformed grafts were compared under without posterior instrumentation condition, while in Case Study II, the endplate-conformed and nonconformed grafts were compared with posterior instrumentation. In both case studies, the results suggested that the increased endplate-graft conformity reduced the maximum stress on the endplate, created uniform stress distribution on endplate surfaces, and reduced the range of motion of L4–L5 segments by increasing the contact surface area between the graft and the endplate. The stress distributions in the endplate suggest that the load sharing is greater with the endplate-conformed PCL-HA graft, which might reduce the graft subsidence possibility.
Convergence Rates of a Class of Uncertain Dynamic Systems
Authors: Mulero-Martínez Juan Ignacio
Published: May 2013

The problem of stabilization of uncertain systems plays a broad and fundamental role in robust control theory. The paper examines a boundedness theorem for a class of uncertain systems characterized as having a decreasing Lyapunov function in a ringlike region. It is a systematic study on stability that embraces both the transient and steady analysis, covering such aspects as the maximum overshoot of the system state, the stability region and the exponential convergence rate. The emphasis throughout is on deriving dominant time constants and explicit time expressions for a state to reach an invariant set. The central theorem provides a complete treatment of the time evolution of trajectories depending on the specific compact set of initial conditions. Toward this end, the comparison lemma along with a particular Riccati differential equation are essential and conclusive. The scope of questions addressed in the paper, the uniformity of their treatment, the novelty of the proposed theorem, and the obtained results make it very useful with respect to other works on the problem of robust nonlinear control.
A Finite Element Study on Variations in Mass Transport in Stented Porcine Coronary Arteries Based on Location in the Coronary Arterial Tree
Authors: Keyes Joseph T. , Simon Bruce R. , Vande Geest Jonathan P.
Published: May 2013

Drug-eluting stents have a significant clinical advantage in late-stage restenosis due to the antiproliferative drug release. Understanding how drug transport occurs between coronary arterial locations can better help guide localized drug treatment options. Finite element models with properties from specific porcine coronary artery sections (left anterior descending (LAD), right (RCA); proximal, middle, distal regions) were created for stent deployment and drug delivery simulations. Stress, strain, pore fluid velocity, and drug concentrations were exported at different time points of simulation (0–180 days). Tests indicated that the highest stresses occurred in LAD sections. Higher-than-resting homeostatic levels of stress and strain existed at upwards of 3.0 mm away from the stented region, whereas concentration of species only reached 2.7 mm away from the stented region. Region-specific concentration showed 2.2 times higher concentrations in RCA artery sections at times corresponding to vascular remodeling (peak in the middle segment) compared to all other segments. These results suggest that wall transport can occur differently based on coronary artery location. Awareness of peak growth stimulators and where drug accumulation occurs in the vasculature can better help guide local drug delivery therapies.
Nickel nanoparticle size and density effects on non-volatile memory performance
Authors: Verrelli Emanuele , Galanopoulos Giorgos , Zouboulis Ilias , Tsoukalas Dimitris
Published: May 2013

In this work, the authors present non-volatile memory devices based on nickel nanoparticles deposited by a novel sputtering process at room temperature and demonstrate and discuss the effect of nanoparticle size and density upon optimum device performance. The devices use a mixed dielectric stack comprised of a silicon dioxide tunneling layer and a hafnium oxide layer formed at low temperature. This allows for fabrication of devices with a relatively small thermal budget and superior performance in terms of memory windows and operating voltages. At voltages as low as 8 V, the memory window of the devices is as large as 5 V. Charge retention measurements confirm the non-volatility of these devices for up to 10 years, and analysis of the leakage currents sheds light on the mechanisms involved that create these charge retention characteristics.
Ballistic phonon thermal conductance in graphene nanoribbons
Authors: Tomita Hiroki , Nakamura Jun
Published: May 2013

Phonon dispersions for graphene nanoribbons (GNRs) have been derived from the first-principles calculations, and ballistic phonon thermal conductances have been evaluated using the Landauer theory. The phonon thermal conductance per unit width for GNR is larger than that for graphene and increases with decreasing ribbon width. The normalized thermal conductance with a unit of thermal quantum for the zigzag GNR is higher than that for the single-walled carbon nanotube that has a circumferential length corresponding to the width of GNR.
Raman spectra exploring breast tissues: Comparison of principal component analysis and support vector machine‐recursive feature elimination
Authors: Hu Chengxu , Wang Juexin , Zheng Chao , Xu Shuping , Zhang Haipeng , Liang Yanchun , Bi Lirong , Fan Zhimin , Han Bing , Xu Weiqing
Published: May 2013

Purpose:

Raman spectroscopy was explored to diagnose normal, benign, and malignant human breast tissues based on principal component analysis (PCA) and support vector machine‐recursive feature elimination (SVM‐RFE), and SVM‐RFE results were compared with PCA.

Methods:

1800 Raman spectra were acquired from fresh samples of human breast tissues (normal, fibroadenoma, adenosis, galactoma, and invasive ductal carcinoma) from 168 patients. After set up the SVM‐RFE and PCA models, Mahalanobis distance, spectral residuals, sensitivity, specificity, and Matthews correlation coefficient (MCC) were used as the discriminating criteria for evaluating these two methods.

Results:

The comparison shows that SVM‐RFE based on the selection of characteristic peaks better reflects the nature of biopsy and it produces better discrimination, sensitivity, specificity, and MCC for normal (1, 1, 1), malignant (0.93, 0.97, 0.91), and benign (0.95, 0.97, 0.91) breast tissues.

Conclusions:

The Raman spectroscopy combined with SVM‐RFE opens great future in the clinical applications of mammary disease diagnosis.
Everything You Would Like to Know About Wnt SignalingReview and commentary on
Wnt Signaling
, edited by Roel Nusse, Xi He, and Renée van Amerongen. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 2013, 454 pp. ISBN: 978-1-936113-23-1.
Authors: Behrens Jürgen
Published: May 2013

A new book reviews the mechanisms and biological outputs of Wnt signaling.
Characterization of Antiviral Activity of Benzamide Derivative AH0109 against HIV-1 Infection
Authors: Chen Liyu , Ao Zhujun , Jayappa Kallesh Danappa , Kobinger Gary , Liu ShuiPing , Wu Guojun , Wainberg Mark A. , Yao Xiaojian
Published: May 2013

In the absence of an effective vaccine against HIV-1 infection, anti-HIV-1 strategies play a major role in disease control. However, the rapid emergence of drug resistance against all currently used anti-HIV-1 molecules necessitates the development of new antiviral molecules and/or strategies against HIV-1 infection. In this study, we have identified a benzamide derivative named AH0109 that exhibits potent anti-HIV-1 activity at an 50% effective concentration of 0.7 μM in HIV-1-susceptible CD4
+
C8166 T cells. Mechanistic analysis revealed that AH0109 significantly inhibits both HIV-1 reverse transcription and viral cDNA nuclear import. Furthermore, our infection experiments indicated that AH0109 is capable of disrupting the replication of HIV-1 strains that are resistant to the routinely used anti-HIV-1 drugs zidovudine, lamivudine, nevirapine, and raltegravir. Together, these findings provide evidence for a newly identified antiviral molecule that can potentially be developed as an anti-HIV-1 agent.
Population-specific ranges of oceanic migration for adult Atlantic salmon (Salmo salar) documented using pop-up satellite archival tags
Authors: Lacroix Gilles L.
Published: May 2013

Pop-up satellite archival tags identified differences in oceanic migration of Atlantic salmon (Salmo salar) kelts from three distinct Canadian populations. Kelts from two endangered populations were restricted to coastal areas near home rivers, whereas kelts from a persisting nearby population migrated to the Labrador Sea and towards the Flemish Cap. Kelts spent most time near the surface (0–5 m), but coastal migrants undertook repeated daytime dives (10–40 m), associated with feeding, upon marine entry and progress was slow (8–23 km·day−1). Distant migrants moved rapidly along the continental shelf (10–50 km·day−1) against prevailing ocean currents, remaining near the surface, except for deep dives (100–1000 m) when crossing ocean channels and at the shelf edge. Home range water temperatures (0–15 °C) indicated that kelts avoided warmer adjacent areas in summer. Kelts did not avoid cold coastal habitat (0–5 °C) in winter, but avoided the surface layers. Kelt migration mimicked that of postsmolts of similar origins, with water temperature acting as a directive or controlling factor. Containment of kelts from endangered populations in coastal habitat was probably responsible for the disappearance of repeat spawners.
Regulatory evolution at the host–pathogen interface
Authors: Coombes Brian K.
Published: May 2013

Horizontal gene transfer plays a major role in microbial evolution by innovating the bacterial genome with new genetic blueprints to adapt to previously unexploited niches. However, to benefit from these genetic acquisitions, the bacterium must integrate the expression of these new genes into existing regulatory nodes and deploy them at the right time. There is much to gain from uncovering the genetic diversity in noncoding DNA that is selective during host infection because of the beneficial effect it has on bacterial gene expression. By identifying genes that have undergone regulatory evolution, a deeper understanding of the arms race between host and pathogen is gained.
TOWARDS MORE EFFICIENT INFECTION AND FIRE FIGHTING
Authors: FLODERUS PETER , LINGAS ANDRZEJ , PERSSON MIA
Published: May 2013

The firefighter problem models the situation where an infection, a computer virus, an idea or fire etc. is spreading through a network and the goal is to save as many as possible nodes of the network through targeted vaccinations. The number of nodes that can be vaccinated at a single time-step is typically one, or more generally O(1). In a non-standard model, the so called spreading model, the vaccinations also spread in contrast to the standard model.

Our main results are concerned with general graphs in the spreading model.

We provide a very simple exact [Formula: see text]-time algorithm. In the special case of trees, where the standard and spreading model are equivalent, our algorithm is substantially simpler than that exact subexponential algorithm for trees presented in Ref. 2. On the other hand, we show that the firefighter problem on weighted directed graphs in the spreading model cannot be approximated within a constant factor better than 1 − 1/e unless NP ⊆ DTIME (nO( log log n)).

We also present several results in the standard model. We provide approximation algorithms for planar graphs in case when at least two vaccinations can be performed at a time-step. We also derive trade-offs between approximation factors for polynomial-time solutions and the time complexity of exact or nearly exact solutions for instances of the firefighter problem for the so called directed layered graphs.
A TECHNIQUE FOR EXACT COMPUTATION OF PRECOLORING EXTENSION ON INTERVAL GRAPHS
Authors: EHMSEN MARTIN R. , LARSEN KIM S.
Published: May 2013

Inspired by a real-life application, we investigate the computationally hard problem of extending a precoloring of an interval graph to a proper coloring under some bound on the number of available colors. We are interested in quickly determining whether or not such an extension exists on instances occurring in practice in connection with campsite bookings on a campground. A naive exhaustive search does not terminate in reasonable time. We have formulated a new approach which moves the computation time within the usable range on all the data samples available to us.
FUNCTIONAL CONSTRUCTIONS BETWEEN REACTION SYSTEMS AND PROPOSITIONAL LOGIC
Authors: SALOMAA ARTO
Published: May 2013

We investigate formal properties, mainly issues connected with propositional logic, of reaction systems introduced by Ehrenfeucht and Rozenberg. We are concerned only with the most simple variant of the systems. Basic properties of propositional formulas are expressed in terms of reaction systems. This leads to NP-completeness (resp. co-NP-completeness) of many problems concerning reaction systems. Among such problems are: (i) deciding whether the function defined by the system is total, (ii) determining the inverse of the function, (iii) deciding whether state sequences always end with a loop. Propositional formulas with monotonic truth-functions yield a particularly simple representation in terms of reaction systems.
SHAPE DYNAMICS AND EFFECTIVE FIELD THEORY
Authors: KOSLOWSKI TIM A.
Published: May 2013

Shape dynamics is a gauge theory based on spatial diffeomorphism- and Weyl-invariance which is locally indistinguishable from classical general relativity. If taken seriously, it suggests that the space–time geometry picture that underlies general relativity can be replaced by a picture based on spatial conformal geometry. This classically well-understood trading of gauge symmetries opens new conceptual avenues in many approaches to quantum gravity. This paper focusses on the general implications for quantum gravity and effective field theory and considers the application of the shape dynamics picture in the exact renormalization group approaches to gravity, loop- and polymer-quantization approaches to gravity and low energy effective field theories. Also, the interpretation of known results is discussed through the shape dynamics picture, particularly holographic renormalization and the problem of time in canonical quantum gravity.
FIRST-PRINCIPLE INVESTIGATION OF ELECTRIC STRUCTURES AND THERMODYNAMIC PROPERTIES FOR ZIRCONIUM NITRIDE UNDER HIGH PRESSURE
Authors: TANG CUI-MING , CHEN XIAO-XU , WANG JUN , HU YAN-FEI , WANG HONG-YAN
Published: May 2013

In the frame of density functional theory, first-principles calculations have been carried out to investigate the structures, elastic constants, structural phase transition between B1 and B2 phases and thermodynamic properties of the zirconium nitride ( ZrN ) by means of the generalized gradient approximation. The equilibrium lattice parameter we obtained for ZrN in B1 phase is closer to the experiment results than previous theoretical results. In addition, the calculations of the elastic constants show that ZrN is a brittle material. What is more, based on third-order natural strain equation of state, the phase transition pressure 338 GPa for ZrN is predicted for B1–B2 transition. According to the quasi-harmonic Debye model, the thermodynamic parameters of ZrN have been investigated systematically.
2D ELEMENTARY CELLULAR AUTOMATA WITH FOUR NEIGHBORS
Authors: FREITAS JOSÉ ANTÓNIO , SEVERINO RICARDO
Published: May 2013

This paper is focused on the study of square boolean synchronous four-neighbor peripheral cellular automata. It is first shown that, due to conjugation and plane reflection symmetry transformations, the number of dynamically nonequivalent such automata is equal to 4856. The cellular automata for which the homogeneous final states play a significant role are then identified. Finally, it is shown that, contrary to what happens in the case of one-dimensional boolean three-neighbor cellular automata, for some peripheral automata, there is coexistence between a homogeneous final state and other dynamics.
ESTIMATION OF CHAOTIC THRESHOLDS FOR THE RECENTLY PROPOSED ROTATING PENDULUM
Authors: HAN N. , CAO Q. J. , WIERCIGROCH M.
Published: May 2013

In this paper, we investigate the nonlinear behavior of the recently proposed rotating pendulum which is a cylindrically nonlinear system with irrational type having smooth and discontinuous characteristics depending on the value of a smoothness parameter. We introduce a cylindrical approximate system whose analytical solutions can be obtained successfully to reflect the nature of the original system without the barrier of irrationalities. Furthermore, Melnikov method is employed to detect the chaotic thresholds for the homoclinic orbits of the second-type, a pair of homoclinic orbits of the first and second-type and the double heteroclinic orbits under the perturbation of viscous damping and external harmonic forcing within the smooth regime. Numerical simulations show the efficiency of the proposed method and the results presented herein this paper demonstrate the predicated chaotic attractors of pendulum-type, SD-type and their mixture depending on the coupling of the nonlinearities.
OPTICAL BISTABILITY IN ONE-DIMENSIONAL COUPLED RESONATOR NONLINEAR OPTICAL WAVEGUIDE
Authors: HAMIDI S. M. , ESLAMIAT Z.
Published: May 2013

In this paper, the optical bistability in finite size one-dimensional coupled resonator nonlinear optical waveguide has been investigated. To calculate the bistable switching manner in five proposed structures, we use the linear and nonlinear transfer matrices with fixed point iteration method. Our results show that the threshold and domain of bistable switching answer depend on the defect region in one-dimensional coupled resonator nonlinear optical waveguides. Also, the best answer of switch takes place at the left and right edges of the photonic band gap of the structures depending on the defect regions. In fact, due to the presence of the photonic band gap in the slow wave system, the density of states of the electromagnetic fields is large at the photonic band edge and photonic defect modes and thus the group velocity is small, and the local field is enhanced. All these factors contribute to a significant decrease in the threshold of optical bistable switching devices.
CLASSICAL ELECTROMAGNETICALLY-INDUCED TRANSPARENCY-LIKE SWITCHING CONTROLLED BY POLARIZATION IN METAMATERIALS
Authors: JIN XING RI , PARK JINWOO , ZHENG HAIYU , LEE YOUNGPAK , RHEE JOO YULL , KIM KI WON , JANG WON HO
Published: May 2013

The classical electromagnetically-induced transparency (EIT)-like switching in metamaterials was experimentally demonstrated in the microwave-frequency region. The metameterial unit cell consists of two identical split-ring resonators, which are arranged on both sides of a dielectric substrate with 90°-rotation asymmetry. In our scheme, the classical EIT-like switching can be achieved by changing the polarization of the incident electromagnetic wave.
SPATIAL XPM-PAIRED SOLITONS IN NONLINEAR METAMATERIALS
Authors: FANG ANLE , XIANG YUANJIANG , ZHUANG BINXIAN , JIANG LEYONG , DAI XIAOYU , WEN SHUANGCHUN
Published: May 2013

We investigate spatial XPM-paired solitons in nonlinear metamaterials (MMs) based on the (1 + 1)-dimensional coupled nonlinear Schrodinger equation (NLSE) describing the co-propagation of two optical beams of different frequencies in the MM with a Kerr-type nonlinear polarization. Three types of XPM-paired solitons including bright-bright, bright-dark and dark-dark solitons for different combination of the signs of refractive index experienced by the two beams, respectively, are obtained by using a generalized hyperbolic function method, which makes the temporal XPM-paired solitons in optical fibers find their spatial counterparts in MMs. Numerical simulations are performed to confirm the theoretical predictions and further identify the propagation properties of the spatial XPM-paired solitons in MMs described by Drude model.
SEVEN-DIMENSIONAL QUANTUM DYNAMICS STUDY OF THEH2+NH2→H+NH3REACTION ON AN INTERPOLATED POTENTIAL ENERGY SURFACE
Authors: YANG YANG , LIU RUI , WAN RENZHUO , YANG MINGHUI
Published: May 2013

Initial-state-selected time-dependent wave packet dynamics studies have been performed for the H2+ NH2→ H + NH3reaction with a seven-dimensional model on a new interpolated ab initio potential energy surface (PES). The PES is constructed using modified Shepard interpolation Scheme and contains 1967 data points with ab initio calculations carried out on UCCSD(T)/aug-cc-pVTZ level. In the seven-dimensional model, NH2group keeps C2vsymmetry and two NH bonds are fixed at their equilibrium values. The total reaction probabilities are calculated when (1) the two reactants are initially at their ground states; (2) NH2bending mode is excited, and (3) H2is on its first vibrational excited state. The integral cross sections are also reported for these initial states with centrifugal-sudden approximation. Thermal rate constants are calculated for the temperature range of 200–2000 K and compared with the previous calculated values and available experimental data. Good agreements between theory and experiments for the rate constants at intermediate temperature are achieved on this PES.
Dissociation of charge movement from calcium release and calcium current in skeletal myotubes by gabapentin
Authors: Alden Kris J. , Garcı́a Jesús
Published: May 2013

The skeletal muscle L-type calcium channel or dihydropyridine receptor (DHPR) plays an integral role in excitation-contraction (E-C) coupling. Its activation initiates three sequential events: charge movement (Qr), calcium release, and calcium current ( I Ca,L). This relationship suggests that changes in Qr might affect release and I Ca,L. Here we studied the effect of gabapentin (GBP) on the three events generated by DHPRs in skeletal myotubes in culture. GBP specifically binds to the α2/δ1 subunit of the brain and skeletal muscle DHPR. Myotubes were stimulated with a protocol that included a depolarizing prepulse to inactivate voltage-dependent proteins other than DHPRs. Gabapentin (50 μM) significantly increased Qr while decreasing the rate of rise of calcium transients. Gabapentin also reduced the maximum amplitude of the I Ca,L (as we previously reported) without modifying the kinetics of activation. Exposure of GBP-treated myotubes to 10 μM nifedipine prevented the increase of Qr promoted by this drug, indicating that the extra charge recorded originated from DHPRs. Our data suggest that GBP dissociates the functions of the DHPR from the initial voltage-sensing step and implicates a role for the α2/δ1 subunit in E-C coupling.
Caveolin-1-deficient mice show insulin resistance and defective insulin receptor protein expression in adipose tissue
Authors: Cohen Alex W. , Razani Babak , Wang Xiao Bo , Combs Terry P. , Williams Terence M. , Scherer Philipp E. , Lisanti Michael P.
Published: May 2013

Several lines of evidence suggest that a functional relationship exists between caveolin-1 and insulin signaling. However, it remains unknown whether caveolin-1 is normally required for proper insulin receptor signaling in vivo. To address this issue, we examined the status of insulin receptor signaling in caveolin-1 (–/–)-deficient (Cav-1 null) mice. Here, we show that Cav-1 null mice placed on a high-fat diet for 9 mo develop postprandial hyperinsulinemia. An insulin tolerance test (ITT) revealed that young Cav-1 null mice on a normal chow diet are significantly unresponsive to insulin, compared with their wild-type counterparts. This insulin resistance is due to a primary defect in adipose tissue, as evidenced by drastically reduced insulin receptor protein levels (>90%), without any changes in insulin receptor mRNA levels. These data suggest that caveolin-1 acts as a molecular chaperone that is necessary for the proper stabilization of the insulin receptor in adipocytes in vivo. In support of this notion, we demonstrate that recombinant expression of caveolin-1 in Cav-1 null mouse embryo fibroblasts rescues insulin receptor protein expression. These data provide evidence that the lean body phenotype observed in the Cav-1 knockout mice is due, at least in part, to a defect in insulin-regulated lipogenesis.
Rho GTPases show differential sensitivity to nucleotide triphosphate depletion in a model of ischemic cell injury
Authors: Hallett Mark A. , Dagher Pierre C. , Atkinson Simon J.
Published: May 2013

Rho GTPases are critical for actin cytoskeletal regulation, and alterations in their activity may contribute to altered cytoskeletal organization that characterizes many pathological conditions, including ischemia. G protein activity is a function of the ratio of GTP-bound (active) to GDP-bound (inactive) protein, but the effect of altered energy metabolism on Rho protein activity has not been determined. We used antimycin A and substrate depletion to induce depletion of intracellular ATP and GTP in the kidney proximal tubule cell line LLC-PK10 and measured the activity of RhoA, Rac1, and Cdc42 with GTPase effector binding domains fused to glutathione S-transferase. RhoA activity decreased in parallel with the concentration of ATP and GTP during depletion, so that by 60 min there was no detectable RhoA-GTP, and recovered rapidly when cells were returned to normal culture conditions. Dissociation of the membrane-actin linker ezrin, a target of RhoA signaling, from the cytoskeletal fraction paralleled the decrease in RhoA activity and was augmented by treatment with the Rho kinase inhibitor Y27632. The activity of Cdc42 did not decrease significantly during depletion or recovery. Rac1 activity decreased moderately to a minimum at 30 min of depletion but then increased from 30 to 90 min of depletion, even as ATP and GTP levels continued to fall. Our data are consistent with a principal role for RhoA in cytoskeletal reorganization during ischemia and demonstrate that the activity of Rho GTPases can be maintained even at low GTP concentrations.
Regulation of adherens junctions and epithelial paracellular permeability: a novel function for polyamines
Authors: Guo Xin , Rao Jaladanki N. , Liu Lan , Zou Tong-Tong , Turner Douglas J. , Bass Barbara L. , Wang Jian-Ying
Published: May 2013

Maintenance of intestinal mucosal epithelial integrity requires polyamines that are involved in the multiple signaling pathways controlling gene expression and different epithelial cell functions. Integrity of the intestinal epithelial barrier depends on a complex of proteins composing different intercellular junctions, including tight junctions, adherens junctions, and desmosomes. E-cadherin is primarily found at the adherens junctions and plays a critical role in cell-cell adhesions that are fundamental to formation of the intestinal epithelial barrier. The current study determined whether polyamines regulate intestinal epithelial barrier function by altering E-cadherin expression. Depletion of cellular polyamines by α-difluoromethylornithine (DFMO) reduced intracellular free Ca2+ concentration ([Ca2+]cyt), decreased E-cadherin expression, and increased paracellular permeability in normal intestinal epithelial cells (IEC-6 line). Polyamine depletion did not alter expression of tight junction proteins such as zona occludens (ZO)-1, ZO-2, and junctional adhesion molecule (JAM)-1. Addition of exogenous polyamine spermidine reversed the effects of DFMO on [Ca2+]cyt and E-cadherin expression and restored paracellular permeability to near normal. Elevation of [Ca2+]cyt by the Ca2+ ionophore ionomycin increased E-cadherin expression in polyamine-deficient cells. In contrast, reduction of [Ca2+]cyt by polyamine depletion or removal of extracellular Ca2+ not only inhibited expression of E-cadherin mRNA but also decreased the half-life of E-cadherin protein. These results indicate that polyamines regulate intestinal epithelial paracellular barrier function by altering E-cadherin expression and that polyamines are essential for E-cadherin expression at least partially through [Ca2+]cyt.
Differential autophosphorylation of CaM kinase II from phasic and tonic smooth muscle tissues
Authors: Lorenz Jillinda M. , Riddervold Marilyn H. , Beckett Elizabeth A. H. , Baker Salah A. , Perrino Brian A.
Published: May 2013

Ca+/calmodulin-dependent protein kinase II (CaM kinase II) is regulated by calcium oscillations, autophosphorylation, and its subunit composition. All four subunit isoforms were detected in gastric fundus and proximal colon smooth muscles by RT-PCR, but only the γ and δ isoforms are expressed in myocytes. Relative γ and δ message levels were quantitated by real-time PCR. CaM kinase II protein and Ca2+/calmodulin-stimulated (total) activity levels are higher in proximal colon smooth muscle lysates than in fundus lysates, but Ca2+/calmodulin-independent (autonomous) activity is higher in fundus lysates. CaM kinase II in fundus lysates is relatively unresponsive to Ca2+/calmodulin. Alkaline phosphatase decreased CaM kinase II autonomous activity in fundus lysates and restored its responsiveness to Ca2+/calmodulin. Acetylcholine (ACh) increased autonomous CaM kinase II activity in fundus and proximal colon smooth muscles in a time- and dose-dependent manner. KN-93 enhanced ACh-induced fundus contractions but inhibited proximal colon contractions. The different properties of CaM kinase II from fundus and proximal colon smooth muscles suggest differential regulation of its autophosphorylation and activity in tonic and phasic gastrointestinal smooth muscles.
Cross-bridge blocker BTS permits direct measurement of SR Ca2+ pump ATP utilization in toadfish swimbladder muscle fibers
Authors: Young Iain S. , Harwood Claire L. , Rome Lawrence C.
Published: May 2013

Because the major processes involved in muscle contraction require rapid utilization of ATP, measurement of ATP utilization can provide important insights into the mechanisms of contraction. It is necessary, however, to differentiate between the contribution made by cross-bridges and that of the sarcoplasmic reticulum (SR) Ca2+ pumps. Specific and potent SR Ca2+ pump blockers have been used in skinned fibers to permit direct measurement of cross-bridge ATP utilization. Up to now, there was no analogous cross-bridge blocker. Recently, N-benzyl- p-toluene sulfonamide (BTS) was found to suppress force generation at micromolar concentrations. We tested whether BTS could be used to block cross-bridge ATP utilization, thereby permitting direct measurement of SR Ca2+ pump ATP utilization in saponin-skinned fibers. At 25 μM, BTS virtually eliminates force and cross-bridge ATP utilization (both <4% of control value). By taking advantage of the toadfish swimbladder muscle's unique right shift in its force-Ca2+ concentration ([Ca2+]) relationship, we measured SR Ca2+ pump ATP utilization in the presence and absence of BTS. At 25 μM, BTS had no effect on SR pump ATP utilization. Hence, we used BTS to make some of the first direct measurements of ATP utilization of intact SR over a physiological range of [Ca2+]at 15°C. Curve fits to SR Ca2+ pump ATP utilization vs. pCa indicate that they have much lower Hill coefficients (1.49) than that describing cross-bridge force generation vs. pCa (∼5). Furthermore, we found that BTS also effectively eliminates force generation in bundles of intact swimbladder muscle, suggesting that it will be an important tool for studying integrated SR function during normal motor behavior.
Endogenous and exogenous glucocorticoid regulation of ENaC mRNA expression in developing kidney and lung
Authors: Nakamura Kenzo , Stokes John B. , McCray Paul B.
Published: May 2013

Lung liquid absorption at birth is crucial for the successful onset of respiration. Na absorption by the renal collecting duct plays an important role in renal fluid and electrolyte homeostasis during the early postnatal period. The epithelial Na channel (ENaC) plays a central role in mediating these functions, and its subunit expression is developmentally regulated in a temporal and tissue specific pattern. Several lines of evidence suggest that the prenatal increase in circulating glucocorticoids may play an important role in increasing ENaC expression during maturation. We tested the role of the prenatal surge using corticotropin-releasing hormone (CRH) knockout (KO) mice. Relative ENaC expression in lungs of KO mice increased at the same rate as in wild-type (WT) mice, but absolute expression was only 20–30% of WT. In contrast, relative and absolute expression of all three subunits in kidneys was not different between KO and WT mice. Dexamethasone (Dex) increased α-ENaC mRNA in fetal lung and kidney explants within 24 h but had different effects on β- or γ-ENaC. Dex increased β- and γ-ENaC in lung, but only after >48 h of exposure, and had no effect on kidney. The results suggest that the kidney metabolizes endogenous glucocorticoids, but the lung does not. Furthermore, the marked difference between lung and kidney responsiveness to glucocorticoids in β- and γ-ENaC expression suggests that factors other than steroids may be important in regulating functional ENaC expression during development.
Mechanisms of leptin secretion from white adipocytes
Authors: Cammisotto Philippe G. , Bukowiecki Ludwik J.
Published: May 2013

The mechanisms regulating leptin secretion were investigated in isolated rat white adipocytes. Insulin (1–100 nM) linearly stimulated leptin secretion from incubated adipocytes for at least 2 h. The adrenergic agonists norepinephrine, isoproterenol (two nonselective β-agonists), or CL-316243 (potent β3) all inhibited insulin (10 nM)-stimulated leptin release. The inhibitory effects of norepinephrine and isoproterenol could be reversed not only by the nonselective antagonist propranolol but also by the selective antagonists ICI-89406 (β1) or ICI-118551 (β2), the β2-antagonist being less effective than the β1. Insulin-stimulated leptin secretion could also be inhibited by a series of agents increasing intracellular cAMP levels, such as lipolytic hormones (ACTH and thyrotropin-stimulating hormone), various nonhydrolyzable cAMP analogs, pertussis toxin, forskolin, methylxanthines (caffeine, theophylline, IBMX), and specific inhibitors of phosphodiesterase III (imazodan, milrinone, and amrinone). Significantly, antilipolytic agents other than insulin (adenosine, nicotinic acid, acipimox, and orthovanadate) did not mimic the acute stimulatory effects of insulin on leptin secretion under these conditions. We conclude that norepinephrine specifically inhibits insulin-stimulated leptin secretion not only via the low-affinity β3-adrenoceptors but also via the high-affinity β1/β2-adrenoceptors. Moreover, it is suggested that 1) activation of phosphodiesterase III by insulin represents an important metabolic step in stimulation of leptin secretion, and 2) lipolytic hormones competitively counterregulate the stimulatory effects of insulin by activating the adenylate cyclase system.
Mechanism by which cAMP activates PI3-kinase and increases bile acid secretion in WIF-B9 cells
Authors: Kagawa Tatehiro , Varticovski Lyuba , Sai Yoshimichi , Arias Irwin M.
Published: May 2013

Previous studies in rat bile canalicular membrane vesicles and WIF-B9 cells revealed that cAMP-induced trafficking of ATP-binding cassette (ABC) transporters to the canalicular membrane and their activation require phosphoinositide 3-kinase (PI3-K) products. In the present studies, canalicular secretion of fluorescein isothiocyanate-glycocholate in WIF-B9 cells was increased by cAMP and a decapeptide that enhances PI3-K activity; these effects were inhibited by wortmannin. To determine the mechanism(s) whereby cAMP activates PI3-K, we examined signal transduction pathways in WIF-B9 and COS-7 cells. cAMP activated PI3-K in both cell lines in a phosphotyrosine-independent manner. PI3-K activity increased in association with p110β in both cell lines. The effect of cAMP was KT-5720 sensitive, suggesting involvement of protein kinase A. Expression of a dominant-negative β-adrenergic receptor kinase COOH terminus (β-ARKct), which blocks Gβγ signaling, decreased PI3-K activation in both cell lines. cAMP increased GTP-bound Ras in COS-7 but not WIF-B9 cells. Expression of dominant-negative Ras abolished cAMP-mediated PI3-K, which suggests that the effect is downstream of Ras and Gβγ. These data indicate that cAMP activates PI3-K in a cell type-specific manner and provide insight regarding mechanisms of PI3-K activation required for bile acid secretion.