bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogeny of snake trypanosomes inferred by SSU rDNA sequences, their possible transmission by phlebotomines, and taxonomic appraisal by molecular, cross-infection and morphological analysis
Authors: VIOLA L. B. , CAMPANER M. , TAKATA C. S. A. , FERREIRA R. C. , RODRIGUES A. C. , FREITAS R. A. , DUARTE M. R. , GREGO K. F. , BARRETT T. V. , CAMARGO E. P. , TEIXEIRA M. M. G.
Published: March 2008

Blood examination by microhaematocrit and haemoculture of 459 snakes belonging to 37 species revealed 2·4% trypanosome prevalence in species of Viperidae (Crotalus durissusandBothrops jararaca) and Colubridae (Pseudoboa nigra). Trypanosome cultures fromC. durissusandP. nigrawere behaviourally and morphologically indistinguishable. In addition, the growth and morphological features of a trypanosome from the sand flyViannamyia tuberculatawere similar to those of snake isolates. Cross-infection experiments revealed a lack of host restriction, as snakes of 3 species were infected with the trypanosome fromC. durissus. Phylogeny based on ribosomal sequences revealed that snake trypanosomes clustered together with the sand fly trypanosome, forming a new phylogenetic lineage withinTrypanosomaclosest to a clade of lizard trypanosomes transmitted by sand flies†. The clade of trypanosomes from snakes and lizards suggests an association between the evolutionary histories of these trypanosomes and their squamate hosts. Moreover, data strongly indicated that these trypanosomes are transmitted by sand flies. The flaws of the current taxonomy of snake trypanosomes are discussed, and the need for molecular parameters to be adopted is emphasized. To our knowledge, this is the first molecular phylogenetic study of snake trypanosomes.
Do we see more than we can access?
Authors: Byrne Alex , Hilbert David R. , Siegel Susanna
Published: March 2008

One of Block's conclusions, motivated by partial-report superiority experiments, is that there is phenomenally conscious information that is not cognitively accessible. We argue that this conclusion is not supported by the data.
Why babies are more conscious than we are
Authors: Gopnik Alison
Published: March 2008

Block argues for a method and a substantive thesis – that consciousness overflows accessibility. The method can help answer the question of what it is like to be a baby. Substantively, infant consciousness may be accessible in some ways but not others. But development itself can also add important methodological tools and substantive insights to the study of consciousness.
What is cognitively accessed?
Authors: Harman Gilbert
Published: March 2008

Is Block's issue about accessing an experience or its object? Having certain “flow” experiences appears to be incompatible with accessing the experience itself. And any experience of an object accesses that object. Such access either counts as cognitive or does not. Either way, Block's issue seems resolvable without appeal to the scientific considerations he describes.
The “mesh” as evidence – model comparison and alternative interpretations of feedback
Authors: Hulme Oliver J. , Whiteley Louise
Published: March 2008

We agree that the relationship between phenomenology and accessibility can be fruitfully investigated via meshing, but we want to emphasise the importance of proper comparison between meshes, as well as considerations that make comparison especially difficult in this domain. We also argue that Block's interpretation of the neural data in his exemplar mesh is incorrect, and propose an alternative.
Reuniting (scene) phenomenology with (scene) access
Authors: Papineau David
Published: March 2008

Block shows that we can consciously see a scene without being able to identify all the individual items in it. But in itself this fails to drive a wedge between phenomenology and access. Once we distinguish scene phenomenology from item phenomenology, the link between phenomenology and access is restored.
Conscious access overflows overt report
Authors: Sergent Claire , Rees Geraint
Published: March 2008

Block proposes that phenomenal experience overflows conscious access. In contrast, we propose that conscious access overflows overt report. We argue that a theory of phenomenal experience cannot discard subjective report and that Block's examples of phenomenal “overflow” relate to two different types of perception. We propose that conscious access is more than simply readout of a pre-existing phenomenal experience.
Overflow, access, and attention
Authors: Block Ned
Published: March 2008

In this response to 32 commentators, I start by clarifying the overflow argument. I explain why the distinction between generic and specific phenomenology is important and why we are justified in acknowledging specific phenomenology in the overflow experiments. Other issues discussed are the relations among report, cognitive access, and attention; panpsychic disaster; the mesh between psychology and neuroscience; and whether consciousness exists.
Vibration control of elastodynamic response of a 3-PRR flexible parallel manipulator using PZT transducers
Authors: Zhang Xuping , Mills James K. , Cleghorn William L.
Published: March 2008

This paper addresses the dynamic simulation and control of structural vibrations of a 3-PRR parallel manipulator with three flexible intermediate links, to which are bonded lead zirconate titanate (PZT) actuators and sensors. Flexible intermediate links are modelled as Euler–Bernoulli beams with pinned-pinned boundary conditions. A PZT actuator controller is designed based on strain rate feedback (SRF) control. Control moments from PZT actuators are transformed to force vectors in modal space and are incorporated in the dynamic model of the manipulator. The dynamic equations are developed based on the assumed mode method for the flexible parallel manipulator with multiple PZT actuator and sensor patches. Numerical simulation is performed and the results indicate that the proposed active vibration control strategy is effective. Spectral analyses of structural vibrations further illustrate that deformations from structural vibration of flexible links are suppressed to a significant extent when the proposed vibration control strategy is employed, while the deflections caused by inertial and coupling forces are not reduced.
Robot multiple contact control
Authors: Park Jaeheung , Khatib Oussama
Published: March 2008

This paper addresses the problem of contact force control for multiple contacts distributed over multiple links in a robot. This is of importance when performing complex tasks in unstructured environment, particularly in humanoid robot applications. The proposed multicontact control framework provides a new way of defining the operational space coordinates, which facilitates the specification of multiple contact control. The contact force space on multiple links is constructed as an operational space for the highest priority task. Motion control, given lower priority, can be executed using the rest of degree of freedom within the null-space of the force control. The dynamic control structure, then, provides a means to control each contact force and motion independently. This dynamic decoupling enables each contact force controller to utilize linear control theories. In particular, the contact force controllers adopt full state feedback control and estimation methods to produce robust performance with respect to modeling and parameter uncertainties. The effectiveness of the multiple contact control framework was demonstrated using a PUMA560 manipulator, with multiple contacts on the end-effector and third link. The demonstrated tasks involved controlling each of the contact forces with null-space motion.
Multiobjective trajectory planner for industrial robots with payload constraints
Authors: Saravanan R. , Ramabalan S. , Balamurugan C.
Published: March 2008

A general new methodology using evolutionary algorithms viz., Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi-objective Differential Evolution (MODE), for obtaining optimal trajectory planning of an industrial robot manipulator (PUMA 560 robot) in the presence of fixed and moving obstacles with payload constraint is presented. The problem has a multi-criterion character in which six objective functions, 32 constraints and 288 variables are considered. A cubic NURBS curve is used to define the trajectory. The average fuzzy membership function method is used to select the best optimal solution from Pareto optimal fronts. Two multi-objective performance measures namely solution spread measure and ratio of non-dominated individuals are used to evaluate the strength of Pareto optimal fronts. Two more multi-objective performance measures namely optimiser overhead and algorithm effort are used to find computational effort of the NSGA-II and MODE algorithms. The Pareto optimal fronts and results obtained from various techniques are compared and analysed. Both NSGA-II and MODE are best for this problem.
Harmonic morphisms with one-dimensional fibres on conformally-flat Riemannian manifolds
Authors: PANTILIE RADU
Published: March 2008

We classify the harmonic morphisms with one-dimensional fibres (1) from real-analytic conformally-flat Riemannian manifolds of dimension at least four (Theorem 3.1), and (2) between conformally-flat Riemannian manifolds of dimensions at least three (Corollaries 3.4 and 3.6).

Also, we prove (Proposition 2.5) an integrability result for any real-analytic submersion, from a constant curvature Riemannian manifold of dimensionn+2 to a Riemannian manifold of dimension 2, which can be factorised as ann-harmonic morphism with two-dimensional fibres, to a conformally-flat Riemannian manifold, followed by a horizontally conformal submersion, (n≥4).
Upper bounds of Hilbert coefficients and Hilbert functions
Authors: ELIAS JUAN
Published: March 2008

Let (R, m) be a d-dimensional Cohen–Macaulay local ring. In this paper we prove, in a very elementary way, an upper bound of the first normalized Hilbert coefficient of a m-primary ideal I ⊂ R that improves all known upper bounds unless for a finite number of cases, see Remark 2.3. We also provide new upper bounds of the Hilbert functions of I extending the known bounds for the maximal ideal.
Building the Holocene clinothem in the Gulf of Papua: An ocean circulation study
Authors: Slingerland Rudy , Selover Robert W. , Ogston Andrea S. , Keen Timothy R. , Driscoll Neal W. , Milliman John D.
Published: March 2008

This paper investigates the role that tidal and wind‐driven flows and buoyant river plumes play in the development of the Holocene clinothem in the Gulf of Papua. Time series data from bottom tripods and a mooring were obtained at four locations near the mouth of the Fly River during portions of 2003 and 2004. Flows in the Gulf of Papua during calendar year 2003 were hindcast every 3 h using the Navy Coastal Ocean Model (NCOM) with boundary conditions from the Navy Atmospheric Prediction System, the east Asian seas implementation of NCOM, and the OTIS Tidal Inversion System. Results show that tidal flows on the modern clinoform are strong and are landward and seaward directed. Peak spring tidal velocities can provide the shear stresses necessary to keep sediment up to sand size in motion as the wind‐driven and baroclinic currents distribute it from the river mouths across and along the shelf in two circulation states. During the monsoon season, the clinoform topset is swept by a seaward surface flow and landward bottom flow, reflecting river plumes and coastal upwelling. Seaward, this structure evolves into a SW directed surface current over the clinothem foreset with accompanying landward directed near‐bed currents that trend obliquely up the foreset to the WSW over much of the clinothem. During the trade wind season, the inner and outer topset are swept by NE directed, contour‐parallel surface currents, underneath which lie obliquely landward near‐bed currents. These modeled flows and complex gyres in shallow water coupled with wave‐ and current‐supported gravity flows or river floods can explain the form, internal clinoform shapes, and mineralogy of the modern Gulf of Papua clinothem.
Ionospheric electron upflow in the polar cap region: Derived from ISIS 2 measurements
Authors: Nsumei Patrick A. , Song Paul , Reinisch Bodo W. , Tu Jiannan , Huang Xueqin
Published: March 2008

Using the mass conservation equation, the parallel electron upflow velocity normalized by the base velocity in the polar cap region of the topside ionosphere is derived as a function of electron density and neutral species densities. The normalized parallel velocity profiles are evaluated using ISIS 2 electron density observations and neutral species density profiles from the MSIS model. From the cases analyzed, the derived velocity profiles show a similar trend of (a) a region of slow acceleration below an altitude of ∼500 km, (b) a region of fast acceleration (∼500 km–1100 km), and (c) another region of weak or no acceleration (>∼1100 km). A simple analytical function is proposed to empirically describe the normalized parallel velocity profile. The parameters in the function have been determined by a multivariate least squares fit of calculated profiles to the analytical expression. These parameters define the magnitude and the height of maximum acceleration. For the cases studied the maximum acceleration height occurred in the range of 731–908 km. The parallel velocity can increase by a factor of up to 6 within the acceleration region. The results from the cases studied suggest that the chosen analytical function suitably describes the normalized parallel electron velocity in the high‐latitude topside ionosphere. Furthermore, the acceleration mechanisms have been investigated using the electron momentum equation. On the basis of an existing model of the electron temperature, our results suggest that the enhanced pressure gradient force may be the main driver of the observed acceleration in the electron upflow.
Crust and upper mantle velocity structure of the Yellowstone hot spot and surroundings
Authors: Schutt Derek L. , Dueker Ken , Yuan Huaiyu
Published: March 2008

The Yellowstone hot spot has recently been shown to be a plume that extends into the transition zone. At roughly 60–120 km depth, the plume material rising beneath Yellowstone Park is sheared SW by North America Plate motion, producing a profound low velocity layer emplaced beneath the thin lithosphere. To constrain the absolute seismic velocity of the plate‐sheared plume layer, fundamental mode Rayleigh wave observations have been inverted for phase velocity using the two plane wave technique. The resulting phase velocity models are inverted with Moho‐converted P to S arrival times to better constrain crustal thickness and absolute S wave velocity structure to ∼120 km depth. A regionalized S wave velocity model has an extremely low velocity minimum of 3.8 ± 0.1 km/s at 80 km depth beneath the hot spot track. Nonregionalized 3‐D velocity models find a velocity minimum of 3.9 km/s beneath the hot spot track. Below 120 km depth, our resolution diminishes such that the lateral spreading of the plume track is not resolved. The volume of the low velocity plume layer is small and the estimated buoyancy flux for the Yellowstone plume is <0.1 Mg/s which contrasts with the ∼9 Mg/s value for Hawaii. In addition, a notable region of thick crust and high lower crustal velocities is found around Billings, Montana, consistent with previous refraction and receiver function studies that interpret this as evidence for a massive Precambrian underplating event.
Observed and modeled meridional overturning circulation related flow into the Caribbean
Authors: Kirchner Kerstin , Rhein Monika , Mertens Christian , Böning Claus W. , Hüttl Sabine
Published: March 2008

A major pathway of the Atlantic meridional overturning circulation (MOC) is the warm inflow into the Caribbean Sea. The transport and the contribution of water from the South Atlantic is calculated from observations (ADCP data and hydrography) and compared to the results of the ° FLAME model. The model and the observations show high consistency in the strength of the mean total inflow and its range of variability as well as in the general distribution of water from South Atlantic origin. The measurements give an annual mean South Atlantic Water (SAW) transport into the Caribbean of 9.3 Sv with high variability. This estimate has to be regarded as a lower bound since the present method (using temperature and salinity data) cannot identify the SAW included in the North Equatorial Current (NEC), which recirculated and was transformed in the interior tropical Atlantic. The model transport reproduces the observational values rather closely, with an annual mean inflow of 8.6 Sv and similar high variability. Closer inspection of the SAW pathways in the model suggest that the additional contribution by the NEC‐pathway is only about 2 Sv. The model results confirm the relative importance of the MOC pathways suggested by observations: the Caribbean inflow seems to be the main pathway (63%) for the warm and central water (σθ < 27.1 kg m−3), whereas for the intermediate water a larger fraction (59%) is transported northward at the eastern side of the Lesser Antilles.
Seasonally dependent changes of precipitation extremes over Germany since 1950 from a very dense observational network
Authors: Zolina Olga , Simmer Clemens , Kapala Alice , Bachner Susanne , Gulev Sergey , Maechel Hermann
Published: March 2008

The newly updated collection of daily precipitation measurements over Western Germany (more than 2000 stations in total) is used to analyze linear trends in extreme and heavy precipitation for different seasons over the period 1950–2004. Heavy and extreme precipitation has been quantified using the 95% and 99% percentiles with respect to the Gamma distribution fitted to daily precipitation data. The significance of linear trends was quantified using several statistical tests including estimates of field significance. Positive linear tendencies in heavy precipitation for the winter, spring and autumn seasons were found for the whole domain with the largest increase of 13% per decade in Central and Southern Germany. For the summer season, however, heavy precipitation exhibits mostly negative trends of up to 8% per decade e.g., for the Central and Southwestern parts of Germany. Trends derived from the estimates of heavy precipitation without seasonal breakdown, however, do not show any clear spatial pattern. Estimates of field significance show that the conclusions concerning the seasonal diversity in trend sign hold for most of Western Germany. The results are insensitive to changes of the beginning and the end of the records by several years; thus the seasonal linear trend patterns are not influenced by interdecadal variability. Seasonality is also identified in the linear trends of mean precipitation characteristics. Analysis performed for different classes of precipitation intensity shows that during winter the linear increase of heavy and extreme precipitation is associated with downward linear tendencies for weak precipitation. In summer statistically significant negative linear trends were identified for all classes of precipitation intensities. Our results also imply that the amplitude of the annual cycle of heavy and extreme precipitation underwent a considerable decrease during the last 55 years between 30% to 60% per decade.
Propagation and localization of random plane waves in two‐dimensional homogeneous and isotropic random medium
Authors: Ding Rui , Wang Zhiliang , Ogura Hisanao
Published: March 2008

Random plane wave in two‐dimensional (2D) homogeneous and isotropic random medium is studied by means of stochastic functional approach. The random medium is assumed to be an omnidirectional Gaussian random field with isotropic narrowband spectrum centered at 2k twice as much as the wave number. The approximate stochastic solutions are obtained based on some theoretic considerations of the translation operator associated with the homogeneity of the random medium. The random plane wave is exponentially decaying or expanding with distance in the propagating direction indicating that the wave is in the cutoff state as was expected in the study of random cylindrical waves. Comparisons among these solutions and those obtained earlier by Ogura are given to demonstrate that the statistical behaviors of propagating waves have nothing to do with the shape of the wavefront, but are solely determined by the spectral form of the random medium. The presence of wave localization is verified by computer simulations for such a random plane wave field. Also the average and variance for the phase shift and log‐amplitude of the wave are measured from the simulated data to compare with the theoretical values. The agreements between the theory and the simulation are shown to be satisfactory in spite of the approximate theoretical formulas.
Programming Obesity and Poor Fitness: The Long‐term Impact of Childhood Television
Authors: Landhuis C. Erik , Poulton Richie , Welch David , Hancox Robert J.
Published: March 2008

Objective: To assess whether the long‐term effects of childhood television viewing on BMI and cardiorespiratory fitness are mediated by adult viewing.

Methods and Procedures: This prospective study included an unselected birth cohort of 1,037 participants (535 men) born in Dunedin, New Zealand in 1972/1973. Hours of television viewing on weekdays were reported at ages 5, 7, 9, 11, 13, 15, and 32 years. BMI and cardiorespiratory fitness were measured at age 32 years.

Results: Both childhood and adult television viewing times were significantly associated with higher BMI and lower cardiorespiratory fitness at age 32 years. Childhood television viewing was a better predictor of adult BMI and fitness than adult viewing and remained a significant predictor of these outcomes after adjusting for adult viewing time. After adjusting for adult viewing, the odds (95% confidence interval) of adult obesity increased by a factor of 1.25 (1.01, 1.53) and poor fitness increased by a factor of 1.40 (1.16, 1.70) for each hour of mean weekday television viewing during childhood.

Discussion: The association between childhood television viewing and obesity and poor fitness in adulthood is not mediated by adult viewing. The detrimental health effects of watching too much television during childhood persist into adulthood. Attempts to reduce adult obesity and poor fitness by modifying television viewing habits need to begin in childhood.
Visceral Fat Accumulation Induced by a High‐fat Diet Causes the Atrophy of Mesenteric Lymph Nodes in Obese Mice
Authors: Kim C.S. , Lee S.C. , Kim Y.M. , Kim B.S. , Choi H.S. , Kawada T. , Kwon B.S. , Yu R.
Published: March 2008

Objective: A high intake of fat in the diet plays a crucial role in promoting obesity and obesity‐related pathologies, and especially visceral obesity is closely associated with obesity‐related complications. Because adipose tissue is anatomically associated with lymph nodes, the secondary lymphoid organ, we hypothesized that fat tissue‐derived factors may influence the cellularity of lymphoid tissue embedded in fat.

Methods and Procedures: Mesenteric and inguinal lymph nodes were isolated from obese mice fed a high‐fat diet and control mice fed a regular diet. T‐cell population, activation state, and the extent of apoptosis were determined by flow cytometric analysis or terminal deoxynucleotidyl transferase biotin‐dUTP nick end labeling (TUNEL) assay.

Results: The weight of mesenteric lymph nodes and the total number of lymphoid cells in the obese mice significantly decreased compared with those in the control mice; however, no change was observed in the weight of inguinal lymph nodes. The numbers of CD4+ and CD8+ T cells in the mesenteric lymph nodes of obese mice significantly decreased compared with those of the control. Enhanced T‐cell activation and apoptosis were observed in the mesenteric lymph node cells of the obese mice. The treatment of lymph node cells with free fatty acids, oxidative stress, and chylomicrons, which are obesity‐related factors, resulted in lymph node T‐cell activation and apoptosis.

Discussion: These results suggest that visceral fat accumulation with a high‐fat diet can cause the atrophy of mesenteric lymph nodes by enhancing activation‐induced lymphoid cell apoptosis. Dietary fat‐induced visceral obesity may be crucial for obesity‐related immune dysfunction.
Self‐reported Comorbidities Among Self‐described Overweight African‐American and Hispanic Adults in the United States: Results of a National Survey
Authors: Burroughs Valentine J. , Nonas Cathy , Sweeney Christine T. , Rohay Jeffrey M. , Harkins Andrea M. , Kyle Theodore K. , Burton Steven L.
Published: March 2008

Objective: To examine the concordance between self‐described weight status and BMI, the prevalence of self‐reported comorbidities, and the association between comorbidities and self‐rated health among overweight African‐American and Hispanic US adults.

Methods and Procedures: A nationally representative sample of 537 African‐American and 526 Hispanic adults who were identified using a combination of random digit dialing and listed household sampling and self‐described as being slightly or very overweight participated in a telephone interview. Self‐reported height and weight were used to calculate BMI.

Results: More than half of African Americans (56%) and one‐third of Hispanics (34%) who self‐described as “slightly” overweight would be classified as obese based on BMI. One‐third (33%) of African Americans reported high blood pressure, followed by arthritis (20%), high cholesterol (18%), and diabetes (15%). Among Hispanics, high cholesterol was the most frequently reported comorbidity (17%), followed by high blood pressure (15%), and difficulty sleeping (12%). Almost three‐quarters of African Americans surveyed (72%) reported that their overall health was good to excellent compared to 62% for Hispanics.

Discussion: Self‐reported rates of obesity‐related comorbidities fall below what would be expected based on prevalence data derived from physiologic measures, suggesting a lack of awareness of actual risk. Despite the greater self‐reported prevalence of certain risk factors for poor health, African Americans have a more optimistic view of their overall health and weight status compared to Hispanics. Physicians have an important opportunity to communicate to their minority patients the serious health consequences associated with excess weight.
Enhanced Effects of Xanthohumol Plus Honokiol on Apoptosis in 3T3‐L1 Adipocytes
Authors: Yang Jeong‐Yeh , Della‐Fera Mary Anne , Rayalam Srujana , Baile Clifton A.
Published: March 2008

Objective: To study the effects of xanthohumol (XN), a flavonoid found in hops (Humulus lupulus) and honokiol (HK), a lignan isolated from Magnolia officinalis, alone and in combination, on apoptotic signaling in 3T3‐L1 adipocytes.

Methods and Procedures: 3T3‐L1 mature adipocytes were incubated with various concentrations of XN and HK alone and in combination. Viability and apoptosis were quantified using an MTS‐based cell viability assay and single‐stranded DNA assay, respectively. Expression of apoptosis related proteins including cleaved poly(ADP‐ribose) polymerase (PARP), cytochrome c, Bcl‐2, caspase‐3/7, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and Akt was analyzed by western blotting.

Results: Combinations of XN and HK significantly decreased viability and induced apoptosis in a dose‐dependent manner and more than the additive responses to XN and HK alone. Western blot analysis showed an increase in cleaved PARP and cytochrome c release and decrease in expression of Bcl‐2 protein by XN plus HK, whereas XN and HK individually had no effect. Furthermore, the combination of XN and HK activated PTEN and inactivated Akt by decreasing levels of phosphorylated PTEN and phosphorylated Akt.

Discussion: We demonstrated that although XN and HK showed little or no effect as individual compounds, in combination (XN plus HK) they showed enhanced activity in inducing apoptosis via the cytochrome c/caspase‐3/PARP and PTEN/Akt pathways in 3T3‐L1 adipocytes.
Mixed-mode oscillations and cluster patterns in an electrochemical relaxation oscillator under galvanostatic control
Authors: Baba Nilüfer , Krischer Katharina
Published: March 2008

We studied the dynamics of a prototypical electrochemical model, the electro-oxidation of hydrogen in the presence of poisons, under galvanostatic conditions. The lumped system exhibits relaxation oscillations, which develop mixed-mode oscillations (MMOs) for low preset currents. A fast-slow analysis of the homogeneous dynamics reveals that the MMOs arise from a fast oscillating subsystem and a one-dimensional slow manifold. In the spatially extended system, the galvanostatic constraint imposes a synchronizing global coupling that drives the system into cluster patterns. The properties of the cluster patterns (CPs) result from an intricate interplay of the nature of the local oscillators, the global constraint, and a nonlocal coupling through the electrolyte. In particular, we find that the global constraint suppresses small-amplitude oscillations of MMOs and prevents domains oscillating out of phase from occupying equal regions in phase space. The nonlocal coupling causes each individual clustered region to oscillate on a different limit cycle. Typically multistability of CPs is found. Coexisting patterns possess different oscillation periods and a different total fraction in space that occupies the in-phase or out-of-phase state, respectively.
Mixed-mode oscillations in a three time-scale model for the dopaminergic neuron
Authors: Krupa Martin , Popović Nikola , Kopell Nancy , Rotstein Horacio G.
Published: March 2008

Mixed-mode dynamics is a complex type of dynamical behavior that has been observed both numerically and experimentally in numerous prototypical systems in the natural sciences. The compartmental Wilson-Callaway model for the dopaminergic neuron is an example of a system that exhibits a wide variety of mixed-mode patterns upon variation of a control parameter. One characteristic feature of this system is the presence of multiple time scales. In this article, we study the Wilson-Callaway model from a geometric point of view. We show that the observed mixed-mode dynamics is caused by a slowly varying canard structure. By appropriately transforming the model equations, we reduce them to an underlying three-dimensional canonical form that can be analyzed via a slight adaptation of the approach developed by M. Krupa, N. Popović, and N. Kopell (unpublished).
Faraday waves, streaming flow, and relaxation oscillations in nearly circular containers
Authors: Higuera M. , Porter J. , Knobloch E.
Published: March 2008

Faraday waves near onset in an elliptical container are described by a third-order system of ordinary differential equations with characteristic slow-fast structure. These equations describe the interaction of standing waves with a weakly damped streaming flow driven by Reynolds stresses in boundary layers at the free surface and the rigid walls, and capture the proliferation with decreasing damping of periodic and nonperiodic relaxation oscillations observed near onset in previous simulations. These structures are the result of slow drift through symmetry-related Hopf bifurcations.
Mixed-mode oscillations and slow manifolds in the self-coupled FitzHugh-Nagumo system
Authors: Desroches Mathieu , Krauskopf Bernd , Osinga Hinke M.
Published: March 2008

We investigate the organization of mixed-mode oscillations in the self-coupled FitzHugh-Nagumo system. These types of oscillations can be explained as a combination of relaxation oscillations and small-amplitude oscillations controlled by canard solutions that are associated with a folded singularity on a critical manifold. The self-coupled FitzHugh-Nagumo system has a cubic critical manifold for a range of parameters, and an associated folded singularity of node-type. Hence, there exist corresponding attracting and repelling slow manifolds that intersect in canard solutions. We present a general technique for the computation of two-dimensional slow manifolds (smooth surfaces). It is based on a boundary value problem approach where the manifolds are computed as one-parameter families of orbit segments. Visualization of the computed surfaces gives unprecedented insight into the geometry of the system. In particular, our techniques allow us to find and visualize canard solutions as the intersection curves of the attracting and repelling slow manifolds.
Feedback control of canards
Authors: Durham Joseph , Moehlis Jeff
Published: March 2008

We present a control mechanism for tuning a fast-slow dynamical system undergoing a supercritical Hopf bifurcation to be in the canard regime, the tiny parameter window between small and large periodic behavior. Our control strategy uses continuous feedback control via a slow control variable to cause the system to drift on average toward canard orbits. We apply this to tune the FitzHugh-Nagumo model to produce maximal canard orbits. When the controller is improperly configured, periodic or chaotic mixed-mode oscillations are found. We also investigate the effects of noise on this control mechanism. Finally, we demonstrate that a sensor tuned in this way to operate near the canard regime can detect tiny changes in system parameters.
Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source
Authors: Leitner D. , Benitez J. Y. , Lyneis C. M. , Todd D. S. , Ropponen T. , Ropponen J. , Koivisto H. , Gammino S.
Published: March 2008

High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.
Integration of magneto-optical active bismuth iron garnet on nongarnet substrates
Authors: Körner Timo , Heinrich Andreas , Weckerle Martin , Roocks Patrick , Stritzker Bernd
Published: March 2008

For optical communication, high quality magneto-optical active iron garnet films such as Y3Fe5O12 are important ceramic systems with extensive applications, e.g., as optical isolators [H. Dötsch et al., J. Opt. Soc. Am. B 22, 240 (2005)], optical modulators, etc. Thereby, garnets stand out due to their high Faraday rotation and low optical losses in the near infrared. Currently, it is desirable to integrate such macroscopic optical components on a single chip (Si, SiO2, etc.) to build up optical circuits as in the case of microelectronics (integrated optics) or the use for magneto-optical imaging. Up to now, Bi3Fe5O12 shows the highest Faraday rotation over 20°∕μm. Unfortunately, Bi3Fe5O12 forms in a nonthermodynamical way. Thus, it can only be grown on garnet substrates which prevent it from direct deposition on substrates such as Si or SiO2. In our present work, we studied the integration of Bi3Fe5O12 on different SiO2 substrates using the pulsed laser deposition method. Therefore, we deposited an Y3Fe5O12 buffer first which was optimized in a postannealing step above 900°C in order to form a polycrystalline garnet phase, which is needed for further Bi3Fe5O12 growth. We measured the Faraday rotation of the double layered films and intensely studied them with x-ray diffraction, Rutherford backscattering spectroscopy, environmental scanning electron microscopy, and high-resolution transmission electron microscopy. The attained Faraday rotation can be compared with epitaxial Bi3Fe5O12 films grown on Gd3Ga5O12 substrates or even overcome them due to interference effects in the double layer. So they are highly attractive for magneto-optical imaging. For the determination of the film thicknesses which is usually done by Rutherford backscattering or profilometry, we used another approach. We measured the transmission spectra of the stack which we also derived from a theoretical model that uses a transfer matrix formalism. The thickness of the multilayer can be gained by fitting the spectra.
Geometry of sets of quantum maps: A generic positive map acting on a high-dimensional system is not completely positive
Authors: Szarek Stanisław J. , Werner Elisabeth , Życzkowski Karol
Published: March 2008

We investigate the set (a) of positive, trace preserving maps acting on density matrices of size N and a sequence of its nested subsets: the sets of maps which are (b) decomposable, (c) completely positive, and (d) extended by identity impose positive partial transpose and (e) are superpositive. Working with the Hilbert–Schmidt (Euclidean) measure, we derive tight explicit two-sided bounds for the volumes of all five sets. A sample consequence is the fact that, as N increases, a generic positive map becomes not decomposable and, a fortiori, not completely positive. Due to the Jamiołkowski isomorphism, the results obtained for quantum maps are closely connected to similar relations between the volume of the set of quantum states and the volumes of its subsets (such as states with positive partial transpose or separable states) or supersets. Our approach depends on the systematic use of duality to derive quantitative estimates and on various tools of classical convexity, high-dimensional probability, and geometry of Banach spaces, some of which are not standard.
Resonance properties and microstructure of ultracompliant metallic nanoelectromechanical systems resonators synthesized from Al–32at.%Mo amorphous-nanocrystalline metallic composites
Authors: Ophus C. , Nelson Fitzpatrick N. , Lee Z. , Luber E. , Harrower C. , Westra K. , Dahmen U. , Radmilovic V. , Evoy S. , Mitlin D.
Published: March 2008

This study details the resonance properties of 20nm thick nanoelectromechanical system scale cantilevers fabricated from a metallic Al–32at.%Mo nanocomposite. The advantage of the Al–32at.%Mo alloy is that its strength and near-atomic surface smoothness enable fabrication of single-anchored metallic cantilevers with extreme length-to-thickness ratios, as high as 400:1. This yields uniquely compliant structures with exquisite force sensitivity. For example, an 8μm long, 20nm thick Al–32at.%Mo device has a spring constant of K≅280μN∕m. We show through transmission electron microscope analysis and continuum modeling that the relevant damping mechanisms are related to the device microstructure.
Equilibrium partitioning of macromolecules in confining geometries: Improved universality with a new molecular size parameter
Authors: Wang Yanwei , Peters Günther H. , Hansen Flemming Y. , Hassager Ole
Published: March 2008

We present a new framework for the description of macromolecules subject to confining geometries. The two main ingredients are a new computational method and the definition of a new molecular size parameter. The computational method, hereafter referred to the confinement analysis from bulk structures (CABS), allows the computation of equilibrium partition coefficients as a function of confinement size solely based on a single sampling of the configuration space of a macromolecule in bulk. Superior in computational speed to previous computational methods, CABS is capable of handling slits, channels, and box confining geometries for all molecular architectures. The new molecular size parameter, hereafter referred to the steric exclusion radius Rs, is explicitly defined and computed for a number of rigid objects and flexible polymers. We suggest that Rs is the relevant molecular size parameter for characterization of spatial confinement effects on macromolecules. Results for the equilibrium partition coefficient in the weak confinement regime depend only on the ratio of Rs to the confinement size regardless of molecular details.
Examination of the optimum arrangement of magnetic sensors for nondestructive crack system in distribution line
Authors: Owada Goichi , Sato Fumihiro , Matsuki Hidetoshi , Nonaka Takashi , Sato Tadakuni
Published: March 2008

In our laboratory, the method of nondestructive crack detection on the distribution line by measuring the magnetic field around the distribution line has been proposed. In this paper, we examined the detecting crack system for the distribution line that consists of seven conductive wires. As the result, the optimum combination of sensors to calculate estimated center points was confirmed. It was also shown that the method is resistant to shift of position between the sensor and the distribution line and that it may be possible to detect the crack automatically.
Solutions of the equations for piezoelectromagnetism in polarized ceramics: Infinite medium and slab
Authors: Iadonisi G. , Perroni C. A. , Cantele G. , Ninno D.
Published: March 2008

A method is proposed to calculate both acoustic and electromagnetic modes in piezoelectric hexagonal ceramics. In the infinite system, the five characteristic modes (three acoustic and two electromagnetic) are divided into two classes: the first one includes two modes (one acoustic and one electromagnetic) that are slightly interacting through the piezoelectric coupling; the second class comprises three modes (two acoustic and one electromagnetic) that show relevant effects due to piezoelectricity in their dispersion relations. Finally, acoustic and electromagnetic modes are analyzed in a slab surrounded by vacuum taking fully into account the effects of piezoelectric coupling.
The influence of metal work function on the barrier heights of metal/pentacene junctions
Authors: Jaeckel B. , Sambur J. B. , Parkinson B. A.
Published: March 2008

The electronic structure of Cu(111)/pentacene and Ag(111)/pentacene interfaces were investigated with photoelectron spectroscopy and the hole barrier heights were determined to be 0.74 and 0.90 eV, respectively. When combined with previous measurements of the Au(111)/pentacene interface, the slope of the plot of metal work function against barrier height for Schottky barrier formation was determined to be 0.36, in agreement with current-voltage (I−V) measurements in the literature. However, the absolute barrier heights from photoemission measurements are 0.16 eV higher. The offset between the I−V measurement and the x-ray and ultraviolet photoelectron spectroscopy measurements was attributed to differences in how the highest occupied molecular orbital position is determined. Photoemission data indicates that at low coverages the pentacene molecules lie flat on the metal substrates, whereas at higher coverages the molecular orientation changes to orient the long molecular axis normal to the surface. Thicker films then tend to form three-dimensional islands, resulting in structured rather than flat films forming on clean Ag(111) and Cu(111) at room temperature.
Three-dimensional shape optical measurement using constant gap control and error compensation
Authors: Park Kyihwan , Choi Kyosoon , Kim Sangyoo
Published: March 2008

The optical laser displacement sensor is widely used for noncontact measurement of the three-dimensional (3D) shape profile of the object surface. When the surface of an object has a slope variation, the sensor gain is proportionally varied according to that of the object surface. In order to solve the sensor gain variation problem, the constant gap control method is applied to adjust the gap to the nominal distance. Control error compensation is also proposed to cope with the situation even when the gap is not perfectly controlled to the nominal distance using an additional sensor attached to the actuator. 3D shape measurement applying the proposed constant gap control method shows better performances rather than the constant sensor height method.
Spatial hydration maps and dynamics of naphthalene in ambient and supercritical water
Authors: Svishchev Igor M. , Plugatyr Andriy , Nahtigal Istok G.
Published: March 2008

The hydration structures and dynamics of naphthalene in aqueous solution are examined using molecular-dynamics simulations. The simulations are performed at several state points along the coexistence curve of water up to the critical point, and above the critical point with the density fixed at 0.3g∕cm3. Spatial maps of local atomic pair-density are presented which show a detailed picture of the hydration shell around a bicyclic aromatic structure. The self-diffusion coefficient of naphthalene is also calculated. It is shown that water molecules tend to form π-type complexes with the two aromatic regions of naphthalene, where water acts as the H-bond donor. At ambient conditions, the hydration shell of naphthalene is comprised, on average, of about 39 water molecules. Within this shell, two water molecules can be identified as π-coordinating, forming close to one H-bond to the aromatic rings. With increasing temperature, the hydration of naphthalene changes dramatically, leading to the disappearance of the π-coordination near the critical point.
A thin conducting viscous film on an inclined plane in the presence of a uniform normal electric field: Bifurcation scenarios
Authors: Uma B. , Usha R.
Published: March 2008

A theory for two dimensional long and stationary waves of finite amplitude on a thin viscous liquid film down an inclined plane in the presence of uniform electric field at infinity is investigated. A set of exact averaged equations for the film flow system is described and linearized stability analysis of the uniform flow is performed using normal-mode formulation and the critical condition for linear instability is obtained. The linearized instability for the permanent wave equation, consistent to the second order in ϵ, is examined and the eigenvalue properties of the fixed points are classified in various parametric regimes. Numerical integration of the permanent wave equation as a third-order dynamical system is carried out. Different bifurcation scenarios leading to multiple-hump solitary waves or leading to chaos are exhibited in the parametric space.
Analysis and location of antisite defects in polycrystalline SiC
Authors: Takeshita Tetsuyoshi
Published: March 2008

Molecular dynamics simulations based on the empirical Tersoff potential were performed to examine the structure of the polycrystalline SiC containing antisite defects. To locate the defects, two types of crystallites were used as a model of the grain in polycrystalline SiC: the model structure I contains the defects located randomly in the crystallite; the structure II contains the defects located only on the surface of the crystallite. As a result of calculating the lattice parameters, the strain in structure I is one to two orders larger than that in structure II. The comparison between the simulation results with experimental observations indicates that the carbon antisite defects are easily incorporated into the crystallites in C-rich polycrystalline SiC, whereas the silicon antisites are difficult to locate in the crystallites in Si-rich polycrystalline SiC.