bluuebunny/crossref_metadata_2025 huggingface dataset:
Baroreceptor function during exercise: resetting the record
Authors: Joyner Michael J.
Published: November 2005

This paper briefly reviews the historical evolution of ideas about how baroreflexes operate and continue to regulate arterial blood pressure during exercise. Observations from studies conducted in conscious humans and animals are emphasized and three main questions are asked. First, do baroreflexes contribute to arterial blood pressure regulation during exercise? Second, if baroreflexes contribute to blood pressure regulation during exercise, how do they do it? Third, are there any pathophysiological conditions in which manipulation of baroreflexes or baroreflex ‘dysfunction’ might alter exercise responses? In this context, ideas related to baroreflex resetting during exercise are emphasized, and the potential improvement in exercise tolerance in cardiovascular disease that might be achieved by electrical stimulation of the carotid sinus nerve is highlighted. Additionally, the key contributions of John Shepherd and the late David Donald (along with their colleagues) on related issues are noted.
Mathematical models of periodic breathing and their usefulness in understanding cardiovascular and respiratory disorders
Authors: Cherniack Neil S. , Longobardo Guy S.
Published: November 2005

Periodic breathing is an unusual form of breathing with oscillations in minute ventilations and with repetitive apnoeas or near apnoeas. Reported initially in patients with heart failure or stroke, it was later recognized to occur especially during sleep. The recurrent hypoxia and surges of sympathetic activity that often occur during the apnoeas have serious health consequences. Mathematical models have helped greatly in the understanding of the causes of recurrent apnoeas. It is unlikely that every instance of periodic breathing has the same cause, but many result from instability in the feedback control involved in the chemical regulation of breathing caused by increased controller and plant gains and delays in information transfer. Even when it is not the main cause of the periodic breathing, unstable control modifies the ventilatory pattern and sometimes intensifies the recurrent apnoeas. The characteristics of disturbances to breathing and their interaction with the control system can be critical in determining ventilation responses and the occurrence of periodic breathing. Large abrupt changes in ventilation produced, for example, in the transition from waking to sleep and vice versa, or in the transition from breathing to apnoea, are potent factors causing periodic breathing. Mathematical models show that periodic breathing is a ‘systems disorder’ produced by the interplay of multiple factors. Multiple factors contribute to the occurrence of periodic breathing in congestive heart failure and cerebrovascular disease, increasing treatment options.
The receptor site of the spider toxin PcTx1 on the proton‐gated cation channel ASIC1a
Authors: Salinas Miguel , Rash Lachlan D. , Baron Anne , Lambeau Gérard , Escoubas Pierre , Lazdunski Michel
Published: November 2005

Acid‐sensing ion channels (ASICs) are excitatory neuronal cation channels, involved in physiopathological processes related to extracellular pH fluctuation such as nociception, ischaemia, perception of sour taste and synaptic transmission. The spider peptide toxin psalmotoxin 1 (PcTx1) has previously been shown to inhibit specifically the proton‐gated cation channel ASIC1a. To identify the binding site of PcTx1, we produced an iodinated form of the toxin (125I‐PcTx1YN) and developed a set of binding and electrophysiological experiments on several chimeras of ASIC1a and the PcTx1‐insensitive channels ASIC1b and ASIC2a. We show that 125I‐PcTx1YN binds specifically to ASIC1a at a single site, with an IC50 of 128 pm, distinct from the amiloride blocking site. Results obtained from chimeras indicate that PcTx1 does not bind to ASIC1a transmembrane domains (M1 and M2), involved in formation of the ion pore, but binds principally on both cysteine‐rich domains I and II (CRDI and CRDII) of the extracellular loop. The post‐M1 and pre‐M2 regions, although not involved in the binding site, are crucial for the ability of PcTx1 to inhibit ASIC1a current. The linker domain between CRDI and CRDII is important for their correct spatial positioning to form the PcTx1 binding site. These results will be useful for the future identification or design of new molecules acting on ASICs.
Preparing for the first breath: prenatal maturation of respiratory neural control
Authors: Greer John J. , Funk Gregory D. , Ballanyi Klaus
Published: November 2005

By birth, the regulatory neural network responsible for respiratory control is capable of generating robust rhythm‐driving ventilation that can adjust to homeostatic needs. The advent of in vitro models isolated from prenatal rodents has significantly advanced our understanding of these processes. In this topical review, we examine the development of medullary respiratory rhythm‐generating centres and phrenic motoneurone–diaphragm properties during the prenatal period.
Ca2+–calmodulin‐dependent myosin light chain kinase is essential for activation of TRPC5 channels expressed in HEK293 cells
Authors: Shimizu Shunichi , Yoshida Takashi , Wakamori Minoru , Ishii Masakazu , Okada Takaharu , Takahashi Masami , Seto Minoru , Sakurada Katsuhiko , Kiuchi Yuji , Mori Yasuo
Published: November 2005

Mammalian homologues of Drosophila transient receptor potential (TRP) proteins are responsible for receptor‐activated Ca2+ influx in vertebrate cells. We previously reported the involvement of intracellular Ca2+ in the receptor‐mediated activation of mammalian canonical transient receptor potential 5 (TRPC5) channels. Here we investigated the role of calmodulin, an important sensor of changes in intracellular Ca2+, and its downstream cascades in the activation of recombinant TRPC5 channels in human embryonic kidney (HEK) 293 cells. Ca2+ entry through TRPC5 channels, induced upon stimulation of the G‐protein‐coupled ATP receptor, was abolished by treatment with W‐13, an inhibitor of calmodulin. ML‐9 and wortmannin, inhibitors of Ca2+–calmodulin‐dependent myosin light chain kinase (MLCK), and the expression of a dominant‐negative mutant of MLCK inhibited the TRPC5 channel activity, revealing an essential role of MLCK in maintaining TRPC5 channel activity. It is important to note that ML‐9 impaired the plasma membrane localization of TRPC5 channels. Furthermore, TRPC5 channel activity measured using the whole‐cell patch‐clamp technique was inhibited by ML‐9, whereas TRPC5 channel activity observed in the cell‐excised, inside‐out patch was unaffected by ML‐9. An antibody that recognizes phosphorylated myosin light chain (MLC) revealed that the basal level of phosphorylated MLC under unstimulated conditions was reduced by ML‐9 in HEK293 cells. These findings strongly suggest that intracellular Ca2+–calmodulin constitutively activates MLCK, thereby maintaining TRPC5 channel activity through the promotion of plasma membrane TRPC5 channel distribution under the control of phosphorylation/dephosphorylation equilibrium of MLC.
Retinal ganglion cell activity from the multifocal electroretinogram in pig: optic nerve section, anaesthesia and intravitreal tetrodotoxin
Authors: Lalonde Mélanie R. , Chauhan Balwantray C. , Tremblay François
Published: November 2005

Non‐invasive recordings of the retinal activity have an important role to play in the diagnosis of retinal pathologies. The detection of diseases that involve retinal ganglion cells (RGCs), such as optic atrophy and glaucoma, may be improved by isolating the RGC contribution from the multifocal electroretinogram (mfERG). In this study, mfERGs were performed on 20 pigs, 1–6 weeks following unilateral retrobulbar optic nerve section (ONS). The stimuli were 103 non‐scaled high‐contrast hexagons from which summed and individual mfERG responses were obtained in experimental and control fellow eyes under conditions of ketamine (n= 11) or isoflurane anaesthesia (n= 9). The effect of intravitreal injection of tetrodotoxin (TTX; n= 6) was also investigated. The summed mfERG responses showed a first positive peak (P1) with a short latency (21 ms) followed by two smaller peaks (P2 and P3) of longer latency (46 and 65 ms, respectively). While P2 and P3 amplitude were highly correlated with the time post‐optic nerve section (ONS) (P2: r2= 0.669; P= 0.007; P3: r2= 0.651; P= 0.005), P1 was not (r2= 0.193; P= 0.38). P1 and P2 showed no implicit time variation as a function of retinal location, while P3 implicit time varied along the axis of the visual streak, generating a naso‐temporal asymmetry. However, the P3 implicit time did not vary consistently with distance away from the optic nerve head. Intravitreal injections of TTX reduced P2 and P3 in the control eyes, consistent with the effect of ONS, and also induced a series of regular oscillations lasting up to 200 ms post stimulus. Under isoflurane anaesthesia, all components of the mfERG ifn experimental and control eyes were, at all time points post‐ONS, of similar amplitude and without naso‐temporal asymmetry, suggesting a reduced participation of RGCs under these anaesthesic conditions. These data clearly demonstrate that it is possible to isolate the RGC contribution from non‐invasive multifocal electroretinography.
Spatial segregation of neuronal calcium signals encodes different forms of LTP in rat hippocampus
Authors: Raymond Clarke R. , Redman Stephen J.
Published: November 2005

Calcium regulates numerous processes in the brain. How one signal can coordinate so many diverse actions, even within the same neurone, is the subject of intense investigation. Here we have used two‐photon calcium imaging to determine the mechanism that enables calcium to selectively and appropriately induce different forms of long‐term potentiation (LTP) in rat hippocampus. Short‐lasting LTP (LTP 1) required activation of ryanodine receptors (RyRs), which selectively increased calcium in synaptic spines. LTP of intermediate duration (LTP 2) was dependent on activation of inositol 1,4,5‐trisphosphate (IP3) receptors (IP3Rs) and subsequent calcium release specifically in dendrites. Long‐lasting LTP (LTP 3) was selectively dependent on L‐type voltage‐dependent calcium channels (L‐VDCCs), which generated somatic calcium influx. Activation of NMDA receptors was necessary, but not sufficient, for the generation of appropriate calcium signals in spines and dendrites, and the induction of LTP 1 and LTP 2. These results suggest that the selective induction of different forms of LTP is achieved via spatial segregation of functionally distinct calcium signals.
Adenosine concentration in the porcine coronary artery wall and A2A receptor involvement in hypoxia‐induced vasodilatation
Authors: Frøbert Ole , Haink Gesine , Simonsen Ulf , Gravholt Claus H. , Levin Max , Deussen Andreas
Published: November 2005

We tested whether hypoxia‐induced coronary artery dilatation could be mediated by an increase in adenosine concentration within the coronary artery wall or by an increase in adenosine sensitivity. Porcine left anterior descendent coronary arteries, precontracted with prostaglandin F2α (10−5m), were mounted in a pressure myograph and microdialysis catheters were inserted into the tunica media. Dialysate adenosine concentrations were analysed by HPLC. Glucose, lactate and pyruvate were measured by an automated spectrophotometric kinetic enzymatic analyser. The exchange fraction of [14C]adenosine over the microdialysis membrane increased from 0.32 ± 0.02 to 0.46 ± 0.02 (n= 4, P < 0.01) during the study period. At baseline, interstitial adenosine was in the region of 10 nm which is significantly less than previously found myocardial concentrations. Hypoxia (P 30 mmHg for 60 min, n= 5) increased coronary diameters by 20.0 ± 2.6% (versus continuous oxygenation −3.1 ± 2.4%, n= 6, P < 0.001) but interstitial adenosine concentration fell. Blockade of adenosine deaminase (with erythro‐9‐(2‐hydroxy‐3‐nonyl‐)‐adenine, 5 μm), adenosine kinase (with iodotubericidine, 10 μm) and adenosine transport (with n‐nitrobenzylthioinosine, 1 μm) increased interstitial adenosine but the increase was unrelated to hypoxia or diameter. A coronary dilatation similar to that during hypoxia could be obtained with 30 μm of adenosine in the organ bath and the resulting interstitial adenosine concentrations (n= 5) were 20 times higher than the adenosine concentration measured during hypoxia. Adenosine concentration–response experiments showed vasodilatation to be more pronounced during hypoxia (n= 9) than during normoxia (n= 9, P < 0.001) and the A2A receptor antagonist ZM241385 (20 nm, n= 5), attenuated hypoxia‐induced vasodilatation while the selective A2B receptor antagonist MRS1754 (20 nm, n= 4), had no effect. The lactate/pyruvate ratio was significantly increased in hypoxic arteries but did not correlate with adenosine concentration. We conclude that hypoxia‐induced coronary artery dilatation is not mediated by increased adenosine produced within the artery wall but might be facilitated by increased adenosine sensitivity at the A2A receptor level.
The Physical Reason and the Analytical Condition for the Onset of Dry Whip in Rotor-to-Stator Contact Systems
Authors: Jiang Jun , Ulbrich Heinz
Published: November 2005

Dry whip is an instability of rotor-to-stator contact systems and may lead to a catastrophic failure of rotating machinery. The physical reason for the onset of dry whip in rotor/stator systems with imbalance is not yet well understood. This paper explores the development of the rotor response into dry whip of a specific rotor-to-stator contact model and finds that the rotor in resonance at a negative (natural) frequency of the coupled nonlinear rotor/stator system is the physical reason for the onset of dry whip with imbalance. Based on this find, the equations of motion of the rotor/stator system are formulated in a different way that includes the dynamic characteristics in the vicinity of the onset point of dry whip. The onset condition of dry whip with imbalance is then derived by using the multiple scale method. As shown by examples, the analytical onset condition of dry whip agrees well with the numerically simulated one. In addition, the results are consistent with phenomena observed in tests.
Vibration Analysis of One-Dimensional Structures with Discontinuities Using the Acoustical Wave Propagator Technique
Authors: Peng S. Z.
Published: November 2005

A numerical technique, named the acoustical wave propagator technique, is introduced to describe the dynamic characteristics of one-dimensional structures with discontinuities. A scheme combining Chebyshev polynomial expansion and fast Fourier transforms is introduced in detail. Comparison between exact analytical solutions and predicted results obtained by the acoustical wave propagator technique shows that this scheme has highly accurate and computationally efficient. Furthermore, this technique is extended to investigate the wave propagation and reflection of elastic waves in beams at the location of a sudden change in cross section.
System Identification of Nonlinear Mechanical Systems Using Embedded Sensitivity Functions
Authors: Yang Chulho , Adams Douglas E. , Ciray Sam
Published: November 2005

A novel method of experimental sensitivity analysis for nonlinear system identification of mechanical systems is examined here. It has been shown previously that embedded sensitivity functions, which are quadratic algebraic products of frequency response function data, can be used to identify structural design modifications for reducing vibration levels. It is shown here that embedded sensitivity functions can also be used to characterize and identify mechanical nonlinearities. Embedded sensitivity functions represent the rate of change of the response with variation in input amplitude, and yield estimates of system parameters without being explicitly dependent on them. Frequency response functions are measured at multiple input amplitudes and combined using embedded sensitivity analysis to extract spectral patterns for characterizing systems with stiffness and damping nonlinearities. By comparing embedded sensitivity functions with finite difference frequency response sensitivities, which incorporate the amplitude-dependent behavior of mechanical nonlinearities, models can be determined using an inverse problem that uses system sensitivity to estimate parameters. Expressions for estimating nonlinear parameters are derived using Taylor series expansions of frequency response functions in conjunction with the method of harmonic balance for periodic signals. Using both simulated and experimental data, this procedure is applied to estimate the nonlinear parameters of a two degree-of-freedom model and a vehicle exhaust system to verify the approach.
Near Field Acoustic Holography for Cyclostationary Sound Field and its Partial Source Decomposition Procedure
Authors: Wan Quan , Jiang W. K.
Published: November 2005

The cyclostationary near field acoustic holography (NAH) technique is proposed to overcome the limitations of the current NAH in analyzing cyclostationary sound field. The proposed technique adopts the cyclic spectrum density as the reconstructed physical quantity, instead of the spectrum of sound pressure. Moreover, introducing the principal component analysis into the technique, a partial source decomposition procedure is suggested to decompose the sound field radiated by multiple sound sources into some incoherent partial fields. More information about cyclostationary sound field can be shown clearly on the hologram of the proposed technique than NAH can, which is validated by the simulation results.
Probability Distribution of Extremes of Von Mises Stress in Randomly
Vibrating Structures
Authors: Gupta Sayan , Manohar C. S.
Published: November 2005

The problem of determining the probability distribution function of extremes of Von Mises stress, over a specified duration, in linear vibrating structures subjected to stationary, Gaussian random excitations, is considered. In the steady state, the Von Mises stress is a stationary, non-Gaussian random process. The number of times the process crosses a specified threshold in a given duration, is modeled as a Poisson random variable. The determination of the parameter of this model, in turn, requires the knowledge of the joint probability density function of the Von Mises stress and its time derivative. Alternative models for this joint probability density function, based on the translation process model, combined Laguerre-Hermite polynomial expansion and the maximum entropy model are considered. In implementing the maximum entropy method, the unknown parameters of the model are derived by solving a set of linear algebraic equations, in terms of the marginal and joint moments of the process and its time derivative. This method is shown to be capable of taking into account non-Gaussian features of the Von Mises stress depicted via higher order expectations. For the purpose of illustration, the extremes of the Von Mises stress in a pipe support structure under random earthquake loads, are examined. The results based on maximum entropy model are shown to compare well with Monte Carlo simulation results.
On the Fatigue Analysis of Non-Gaussian Stress Processes With Asymmetric Distribution
Authors: Wang Xiangyu , Sun J. Q.
Published: November 2005

This paper presents a multistage regression method to obtain an empirical joint probability density function (PDF) for rainflow amplitudes and means of non-Gaussian stress processes with asymmetric distribution. The proposed PDF model captures a wide range of non-Gaussian stress processes characterized by five parameters: Standard deviation, skewness, kurtosis, irregularity factor and mean frequency. It is shown that the fatigue prediction from the closed-form empirical PDF based on the multistage regression analysis agrees well with that from extensive Monte Carlo simulations. The ultimate purpose of the method is to provide a tool for engineers to predict the remaining fatigue life of a structure with direct measurements of stress responses at critical locations on a structure or stress responses at various hot-spots on a structure from the finite element analysis without conducting further Monte Carlo simulations.
Structural-Acoustic Coupling Analysis of Two Cavities Connected by Boundary Structures and Small Holes
Authors: Ahn Chang-Gi , Choi Hyoung Gil , Lee Jang Moo
Published: November 2005

In some passenger vehicles, unexpected acoustic modes in the low-frequency range may be observed that cannot be explained by the conventional vibro-acoustic coupling analysis. It is because these methods only use the dynamic characteristics of a vehicle structure and its compartment cavity. However, some small holes or gaps existing at the boundaries between the compartment cavity and the trunk cavity of the vehicles change the modal characteristics of a coupled system. In this paper, a new analytical method is presented to investigate the structural-acoustic coupling characteristics of two cavities connected by small holes and in-between boundary structures. Small holes are modeled as an equivalent mass-spring-damper system in the analysis. A theoretical formulation for vibro-acoustic characteristics of this system is made, and the modal expansion method is used to obtain eigenvalues and their mode shapes. The validity of the proposed method is successfully examined by comparing the results of the analytical predictions with those of experiments.
Free and Forced Wave Vibration Analysis of Axially Loaded Materially Coupled Composite Timoshenko Beam Structures
Authors: Mei C.
Published: November 2005

In this paper, wave vibration analysis of axially loaded bending-torsion coupled composite beam structures is presented. It includes the effects of axial force, shear deformation, and rotary inertia; namely, it is for an axially loaded composite Timoshenko beam. The study also includes the material coupling between the bending and torsional modes of deformations that is usually present in laminated composite beam due to ply orientation. From a wave standpoint, vibrations propagate, reflect, and transmit in a structure. The transmission and reflection matrices for various discontinuities on an axially loaded materially coupled composite Timoshenko beam are derived. Such discontinuities include general point supports, boundaries, and changes in section. The matrix relations between the injected waves and externally applied forces and moments are also derived. These matrices can be combined to provide a concise and systematic approach to vibration analysis of axially loaded materially coupled composite Timoshenko beams or complex structures consisting of such beam components. The systematic approach is illustrated through numerical examples for which comparative results are available in the literature.
Sonic-Boom Minimization
Authors: Seebass R. , George A. R.
Published: November 2005

There have been many attempts to reduce or eliminate the sonic boom. Such attempts fall into two categories: (1) aerodynamic minimization and (2) exotic configurations. In the first category changes in the entropy and the Bernoulli constant are neglected and equivalent body shapes required to minimize the overpressure, the shock pressure rise and the impulse are deduced. These results include the beneficial effects of atmospheric stratification. In the second category, the effective length of the aircraft is increased or its base area decreased by modifying the Bernoulli constant a significant fraction of the flow past the aircraft. A figure of merit is introduced which makes it possible to judge the effectiveness of the latter schemes.
Sonic-Boom Propagation through a Stratified Atmosphere
Authors: Hayes Wallace D. , Runyan Harry L.
Published: November 2005

The evolution of the sonic-boom signature from a supersonic aircraft is discussed and treated. This treatment is the basis for a general algorithm and computer program for sonic-boom prediction in a stratified atmosphere with steady winds. The treatment is based upon geometric acoustics with calculation of nonlinear distortion, and takes arbitrary maneuvers of the aircraft into account.
Human Response to Sonic Boom in the Laboratory and the Community
Authors: von Gierke H. E. , Nixon C. W.
Published: November 2005

Present-day estimates regarding the acceptability of sonic booms by man are derived from various observations, overflight programs, and experimental field and laboratory studies conducted both within and outside the United States. The loudness and annoyance of individual booms and their dependence on the boom overpressure and pressure-time function as well as the complex reaction of individuals, groups, and communities exposed to sonic booms of varied magnitude and frequency are discussed. The few experiments available proving that even sonic booms of the maximum intensity presently feasible do not produce direct medical injury are described. Based on the integrated body of results of recent physiological, psychoacoustic, behavioral, and sociological studies in various countries, estimates of the effects and acceptability of regular, frequent supersonic commercial overland flight schedules are presented and discussed in terms of aircraft noise pollution in general, and of potential certification of aircraft with respect to noise and sonic boom. Findings support the current policy that commercial supersonic transport aircraft will not be permitted to fly over the United States unless and until the noise factors are brought within acceptable limits.
Recent Sonic-Bang Studies in the United Kingdom
Authors: Warren C. H. E.
Published: November 2005

The paper summarizes the sonic-bang studies that have been made in the United Kingdom since 1965, which embrace flight trials, field experiments, and laboratory studies. The main flight trial concerns the measurement of the sonic bang from the Concorde. It is shown that, when the Concorde is flying at 45 000 ft, the waveform at the ground has attained its farfield N-wave shape, although this is not quite so when it is flying at 37 000 ft. The measured characteristic overpressures for these two altitudes and a Mach number of 1.3 are 110 N/m2 and 120 N/m2, respectively. The effects of sonic bangs on cathedrals are discussed and the vibrational responses likely to be induced by the sonic bang are compared with those already arising from other environmental causes. Finally, the results of a study of the effects of simulated sonic bangs on some greenhouses are discussed; these results seem to indicate that most damages can be ascribed to a triggering effect.
Mach-Zehnder Interferometry in a Strongly Driven Superconducting Qubit
Authors: Oliver William D. , Yu Yang , Lee Janice C. , Berggren Karl K. , Levitov Leonid S. , Orlando Terry P.
Published: November 2005

We demonstrate Mach-Zehnder–type interferometry in a superconducting flux qubit. The qubit is a tunable artificial atom, the ground and excited states of which exhibit an avoided crossing. Strongly driving the qubit with harmonic excitation sweeps it through the avoided crossing two times per period. Because the induced Landau-Zener transitions act as coherent beamsplitters, the accumulated phase between transitions, which varies with microwave amplitude, results in quantum interference fringes for
n
= 1 to 20 photon transitions. The generalization of optical Mach-Zehnder interferometry, performed in qubit phase space, provides an alternative means to manipulate and characterize the qubit in the strongly driven regime.
A Role for the Phagosome in Cytokine Secretion
Authors: Murray Rachael Z. , Kay Jason G. , Sangermani Daniele G. , Stow Jennifer L.
Published: November 2005

Membrane traffic in activated macrophages is required for two critical events in innate immunity: proinflammatory cytokine secretion and phagocytosis of pathogens. We found a joint trafficking pathway linking both actions, which may economize membrane transport and augment the immune response. Tumor necrosis factor α (TNFα) is trafficked from the Golgi to the recycling endosome (RE), where vesicle-associated membrane protein 3 mediates its delivery to the cell surface at the site of phagocytic cup formation. Fusion of the RE at the cup simultaneously allows rapid release of TNFα and expands the membrane for phagocytosis.
Real-Time Observation of Molecular Motion on a Surface
Authors: Backus Ellen H. G. , Eichler Andreas , Kleyn Aart W. , Bonn Mischa
Published: November 2005

The laser-induced movement of CO molecules over a platinum surface was followed in real time by means of ultrafast vibrational spectroscopy. Because the CO molecules bound on different surface sites exhibit different C–O stretch vibrational frequencies, the site-to-site hopping, triggered by excitation with a laser pulse, can be determined from subpicosecond changes in the vibrational spectra. The unexpectedly fast motion—characterized by a 500-femtosecond time constant—reveals that a rotational motion of the CO molecules, rather than pure translation, is required for this diffusion process. This conclusion is corroborated by density functional theory calculations.
An Unusual Marine Crocodyliform from the Jurassic-Cretaceous Boundary of Patagonia
Authors: Gasparini Zulma , Pol Diego , Spalletti Luis A.
Published: November 2005

Remains of the marine crocodyliform Dakosaurus andiniensis from western South America reveal a lineage that drastically deviated from the skull morphology that characterizes marine crocodyliforms. The snout and lower jaw are extremely robust, short, and high and only bear a few large teeth with serrated edges (resembling those of some terrestrial carnivorous archosaurs). This unusual morphology contrasts with the long and gracile snout and lower jaws bearing numerous teeth, which are present in the closest relatives of D. andiniensis (and interpreted as indicating feeding on small fish or mollusks). Thus, the morphological diversity of pelagic marine crocodyliforms was wider than had been thought.
SOME COMMENTS ON THE HIGH ENERGY EMISSION FROM REGIONS OF STAR FORMATION BEYOND THE GALAXY
Authors: TORRES DIEGO F. , DOMINGO-SANTAMARÍA EVA
Published: November 2005

Regions that currently are or have been subject to a strong process of star formation are good candidates to be intense γ-ray and neutrino emitters. They may even perhaps be sites where ultra high energy cosmic rays are produced. Outside the Galaxy, the more powerful sites of star formation are found within very active galaxies such as starbursts (SGs) and Luminous or Ultra-Luminous Infrared Galaxies (LIRGs or ULIRGs). Some general characteristic of these objects are herein reviewed from the point of view of their possible status as high energy emitters. Revised estimations of the high energy gamma-ray yield of Arp 220 are presented.
SQUEEZING EFFECTS IN THE SUM AND DIFFERENCE OF THE FIELD AMPLITUDE IN THE RAMAN PROCESS
Authors: GIRI DILIP KUMAR , GUPTA P. S.
Published: November 2005

Sum and difference squeezing of the field amplitude are higher-order squeezing effects. These effects are studied in the Raman process under the short-time approximation based on a fully quantum mechanical approach. It is shown that for uncorrelated modes, the normal squeezing in the sum and difference-frequency field depends on the sum and difference squeezing of input field modes respectively, which can generate normal squeezing in the sum and difference-frequency field mode. All the possibilities for obtaining sum and difference squeezing in two modes and its dependence on squeezing of individual field modes are investigated. We have also shown that if the high-frequency mode is in a coherent state and the low-frequency mode is squeezed, the field state will be difference squeezed if the amplitude of the high-frequency mode is large enough; otherwise the state may or may not be difference squeezed. If both modes are squeezed, then the state may or may not be difference squeezed. These higher-order squeezing effects are useful in the production of squeezing in the Raman process.
SURFACE EFFECTS ON THE STATISTICS OF THE LOCAL DENSITY OF STATES IN METALLIC NANOPARTICLES: MANIFESTATION ON THE NMR SPECTRA
Authors: GASCÓN JOSÉ A. , PASTAWSKI HORACIO M.
Published: November 2005

In metallic nanoparticles, shifts in the ionization energy of surface atoms with respect to bulk atoms can lead to surface bands. Within a simple Tight Binding model we find that the projection of the electronic density of states on these sites presents two overlapping structures. One of them is characterized by the level spacing coming from bulk states and the other arises from the surface states. In very small particles, this effect contributes to an over-broadening of the NMR absorption spectra, determined by the Knight shift distribution of magnetic nuclei. We compare our calculated Knight shifts with experiments on aluminum nanoparticles, and show that the deviation of the scaling law as a function of temperature and particle size can be explained in terms of surface states.
INTERPLAY OF D-WAVE SUPERCONDUCTIVITY AND ANTIFERROMAGNETISM IN THE CUPRATE SUPERCONDUCTORS: PHASE SEPARATION AND THE PSEUDOGAP PHASE DIAGRAM
Authors: SU W. P.
Published: November 2005

To understand the interplay of d-wave superconductivity and antiferromagnetism in the cuprates, we consider a two-dimensional extended Hubbard model with nearest neighbor attractive interaction. Free energy of the homogeneous (coexisting superconducting and antiferromagnetic) state calculated as a function of the band filling shows a region of phase separation. The phase separation caused by the intersite attractive force leads to novel insights into salient features of the pseudogap phase diagram. In particular, the upper crossover curve can be identified with the phase separation boundary. At zero temperature, the boundary constitutes a critical point. The inhomogeneity observed in the underdoped cuprates is a consequence of incomplete phase separation. The disorder (inhomogeneity) brings about the disparity between the high pseudogap temperature and the low bulk superconducting transition temperature.
MELTING-THERMODYNAMIC CHARACTERISTICS OF Fe, Co, Ni MAGNETIC NANOCRYSTALS
Authors: CAO L. F. , WANG M. P. , XIE D. , LI Z. , XU G. Y.
Published: November 2005

A simplified model that describes the size and shape dependence of melting thermodynamics of full free nanocrystals was established. Critical sizes of Fe , Co , Ni magnetic nanocrystals when the crystals keep their crystallinity were calculated and the corresponding minimum melting temperature was predicted. Theoretical predictions were consistent with experimental results.
THE MAXIMUM OF MULTIFRACTAL CASCADES: EXACT DISTRIBUTION AND APPROXIMATIONS
Authors: VENEZIANO DANIELE , LANGOUSIS ANDREAS
Published: November 2005

We study the distribution of the maximum M of multifractal measures using discrete cascade representations. For such discrete cascades, the exact distribution of M can be found numerically. We evaluate the sensitivity of the distribution of M to simplifying approximations, including independence of the measure among the cascade tiles and replacement of the dressing factor by a random variable with the same distribution type as the cascade generator. We also examine how the distribution of M varies with the dimensionality of the support and the multiplicity of the cascade. Of these factors, dependence of the measure among different cascade tiles has the highest effect on the distribution of M. This effect comes mainly from long-range dependence. We use these findings to propose a simple approximation to the distribution of M and give charts to implement the approximation for beta-lognormal cascades.
EVIDENCE OF FRACTAL BEHAVIOR OF PIONS AND PROTONS IN HIGH ENERGY INTERACTIONS — AN EXPERIMENTAL INVESTIGATION
Authors: GHOSH DIPAK , DEB ARGHA , PAL SITARAM , HALDAR PRABIR KUMAR , BHATTACHARYYA SWARNAPRATIM , MANDAL PASUPATI , BISWAS SUBRATA , MONDAL MITALI
Published: November 2005

Different fractal methods (Factorial moment, Takagi moment) have been used for the analysis of fractal behavior of multiparticle production in π-- AgBr interaction at 350 GeV/c of compound multiplicity distribution in emission angle (cos θ) space and azimuthal angle (ϕ) space. The generalized fractal dimensions Dq are determined according to two methods. Results indicate multifractal behavior in compound multiplicity distribution. From the knowledge of Dq, the multifractal specific heat is calculated. Results are compared with the corresponding results of shower multiplicity.
SCALING OF FLOW DISTANCE IN RANDOM SELF-SIMILAR CHANNEL NETWORKS
Authors: TROUTMAN BRENT M.
Published: November 2005

Natural river channel networks have been shown in empirical studies to exhibit power-law scaling behavior characteristic of self-similar and self-affine structures. Of particular interest is to describe how the distribution of distance to the outlet changes as a function of network size. In this paper, networks are modeled as random self-similar rooted tree graphs and scaling of distance to the root is studied using methods in stochastic branching theory. In particular, the asymptotic expectation of the width function (number of nodes as a function of distance to the outlet) is derived under conditions on the replacement generators. It is demonstrated further that the branching number describing rate of growth of node distance to the outlet is identical to the length ratio under a Horton-Strahler ordering scheme as order gets large, again under certain restrictions on the generators. These results are discussed in relation to drainage basin allometry and an application to an actual drainage network is presented.
SOME CASES OF CROSSOVER BEHAVIOR IN HEART INTERBEAT AND ELECTROSEISMIC TIME SERIES
Authors: MUÑOZ-DIOSDADO A. , GUZMÁN-VARGAS L. , RAMÍREZ-ROJAS A. , DEL RÍO-CORREA J. L. , ANGULO-BROWN F.
Published: November 2005

Fractal time series with scaling properties expressed through power laws appear in many contexts. These properties are very important from several viewpoints. For instance, they reveal the nature of the correlations present in the fractal signals. It is common that the scaling properties characterized by means of invariant quantities suffer changes along with the dynamical evolution of the studied systems. One of these changes is a crossover in the scaling properties reflecting an important change in the system dynamical behavior. In this article, we present two cases of crossover behavior corresponding to interbeat and electroseismic time series, we observe the crossovers in time series of experimental data and their corresponding simulation with simple models. We suggest a possible explanation of the observed crossovers in terms of the models considered.
GEOMETRY AND BIAS DEPENDENCE OF LOW-FREQUENCY RANDOM TELEGRAPH SIGNAL AND 1/f NOISE LEVELS IN MOSFETS
Authors: TOITA MASATO , VANDAMME LODE K. J. , SUGAWA SHIGETOSHI , TERAMOTO AKINOBU , OHMI TADAHIRO
Published: November 2005

Low-frequency noise in MOSFETs is considered to originate from two distinctive sources: Random Telegraph Signal caused by carrier traps at the border of the SiO 2/ Si interface and 1/f fluctuation due to inherent nature of lattice scattering in a Si crystal. It is very important to distinguish these two mechanisms. Relative amplitude of RTS and 1/f noise depends on the number of carriers under the gate electrode, which makes it channel size as well as gate-bias dependent. In this paper, we discuss the dependence of the amplitudes of RTS and 1/f noise in MOSFETs on sample geometry and gate bias condition. We discuss low-frequency noise reduction by utilizing low electron-temperature plasma for gate oxidation as well.
ATTRACTORS AND NEO-ATTRACTORS FOR 3D STOCHASTIC NAVIER–STOKES EQUATIONS
Authors: CUTLAND NIGEL J. , KEISLER H. JEROME
Published: November 2005

In [14] nonstandard analysis was used to construct a (standard) global attractor for the 3D stochastic Navier–Stokes equations with general multiplicative noise, living on a Loeb space, using Sell's approach [26]. The attractor had somewhat ad hoc attracting and compactness properties. We strengthen this result by showing that the attractor has stronger properties making it a neo-attractor — a notion introduced here that arises naturally from the Keisler–Fajardo theory of neometric spaces [18].

To set this result in context we first survey the use of Loeb space and nonstandard techniques in the study of attractors, with special emphasis on results obtained for the Navier–Stokes equations both deterministic and stochastic, showing that such methods are well-suited to this enterprise.
A FAMILY OF CHAOTIC BILLIARDS WITH VARIABLE MIXING RATES
Authors: CHERNOV N. , ZHANG H.-K.
Published: November 2005

We describe a one-parameter family of dispersing (hence hyperbolic, ergodic and mixing) billiards where the correlation function of the collision map decays as 1/na (here n denotes the discrete time), in which the degree a ∈ (1, ∞) changes continuously with the parameter of the family, β. We also derive an explicit relation between the degree a and the family parameter β.
DIRICHLET PROBLEM WITH STOCHASTIC COEFFICIENTS
Authors: BULLA INGO
Published: November 2005

We consider general second-order linear elliptic partial differential equations having random coefficients and random data and fulfilling the homogeneous Dirichlet condition. We prove the existence and uniqueness of the weak solution in a certain tensor product space which is suitably completed to make it a Hilbert space. The factors of this space are a Sobolev space of functions depending on the space variable and a general Sobolev space of functions depending on the stochastic variable.
BENFORD'S LAW IN POWER-LIKE DYNAMICAL SYSTEMS
Authors: BERGER ARNO
Published: November 2005

A generalized shadowing lemma is used to study the generation of Benford sequences under non-autonomous iteration of power-like maps Tj: x ↦ αjxβj(1 - fj(x)), with αj, βj> 0 and fj∈ C1, fj(0) = 0, near the fixed point at x = 0. Under mild regularity conditions almost all orbits close to the fixed point asymptotically exhibit Benford's logarithmic mantissa distribution with respect to all bases, provided that the family (Tj) is contracting on average, i.e. [Formula: see text]. The technique presented here also applies if the maps are chosen at random, in which case the contraction condition reads 𝔼 log β > 0. These results complement, unify and widely extend previous work. Also, they supplement recent empirical observations in experiments with and simulations of deterministic as well as stochastic dynamical systems.
Ecology and Evolution of Aphid-Ant Interactions
Authors: Stadler Bernhard , Dixon Anthony F.G.
Published: November 2005

▪ Abstract  Aphids and ants are two abundant and highly successful insect groups, which often live in the same habitat and therefore are likely to interact with one another. Whether the outcome of such an interaction is a predator-prey or mutualistic one is dependent on what each partner has to offer relative to the needs of the other. Consequently, understanding why some aphids enter mutualistic interactions with ants is dependent on understanding the physiological, ecological, and evolutionary traits of both partners. This includes an appreciation of the spatial, temporal, and taxonomic context in which mutualistic interactions developed. In this review, we use aphid-ant interactions to illustrate the whole range of interactions from antagonistic to mutualistic as well as to identify the processes affecting the degree of association and in particular the context within which such interactions evolved. The constraints of establishing and maintaining beneficial interactions between aphids and ants is addressed from a cost-benefit perspective. Prospects for future research are identified to further the understanding of the patterns and processes associated with aphid-ant relationships.
Functional and biochemical characterization of epithelial bactericidal/permeability-increasing protein
Authors: Canny Geraldine , Cario Elke , Lennartsson Andreas , Gullberg Urban , Brennan Ciara , Levy Ofer , Colgan Sean P.
Published: November 2005

Epithelial cells of many mucosal organs have adapted to coexist with microbes and microbial products. In general, most studies suggest that epithelial cells benefit from interactions with commensal microorganisms present at the lumenal surface. However, potentially injurious molecules found in this microenvironment also have the capacity to elicit local inflammatory responses and even systemic disease. We have recently demonstrated that epithelia cells express the anti-infective molecule bactericidal/permeability-increasing protein (BPI). Here, we extend these findings to examine molecular mechanisms of intestinal epithelial cell (IEC) BPI expression and function. Initial experiments revealed a variance of BPI mRNA and protein expression among various IEC lines. Studies of BPI promoter expression in IECs identified regulatory regions of the BPI promoter and revealed a prominent role for CCAAT/enhancer binding protein and especially Sp1/Sp3 in the basal regulation of BPI. To assess the functional significance of this protein, we generated an IEC line stably transfected with full-length BPI. We demonstrated that, whereas epithelia express markedly less BPI protein than neutrophils, epithelial BPI contributes significantly to bacterial killing and attenuating bacterial-elicted proinflammatory signals. Additional studies in murine tissue ex vivo revealed that BPI is diffusely expressed along the crypt-villous axis and that epithelial BPI levels decrease along the length of the intestine. Taken together, these data confirm the transcriptional regulation of BPI in intestinal epithelia and provide insight into the relevance of BPI as an anti-infective molecule at intestinal surfaces.
Substrate specificity of human ABCC4 (MRP4)-mediated cotransport of bile acids and reduced glutathione
Authors: Rius Maria , Hummel-Eisenbeiss Johanna , Hofmann Alan F. , Keppler Dietrich
Published: November 2005

The multidrug resistance protein ABCC4 (MRP4), a member of the ATP-binding cassette superfamily, mediates ATP-dependent unidirectional efflux of organic anions out of cells. Previous studies showed that human ABCC4 is localized to the sinusoidal membrane of hepatocytes and mediates, among other substrates, the cotransport of reduced glutathione (GSH) with bile acids. In the present study, using inside-out membrane vesicles, we demonstrated that human ABCC4 in the presence of physiological concentrations of GSH has a high affinity for the taurine and glycine conjugates of the common natural bile acids as well as the unconjugated bile acid cholate. Chenodeoxycholyltaurine and chenodeoxycholylglycine were the GSH cosubstrates with the highest affinities for ABCC4, with Kmvalues of 3.6 and 5.9 μM, respectively. Ursodeoxycholyltaurine and ursodeoxycholylglycine were cotransported together with GSH by ABCC4 with Kmvalues of 7.8 and 12.5 μM, respectively, but no transport of ursodeoxycholate and deoxycholate was observed. The simultaneous transport of labeled GSH and cholyltaurine or cholylglycine was demonstrated in double-labeled cotransport experiments with a bile acid-to-GSH ratio of ∼1:22. Kmvalues of the bile acids for ABCC4 were in a range similar to those reported for the canalicular bile salt export pump ABCB11. Under physiological conditions, the sinusoidal ABCC4 may compete with canalicular ABCB11 for bile acids and thereby play a key role in determining the hepatocyte concentration of bile acids. In cholestatic conditions, ABCC4 may become a key pathway for efflux of bile acids from hepatocytes into blood.