bluuebunny/crossref_metadata_2025 huggingface dataset:
A study for the bias control of indium–tin–oxide films synthesized by cesium assisted radio frequency magnetron sputtering
Authors: Lee Deuk Yeon , Lee Se-Jong , Song Kie Moon , Baik Hong Koo
Published: July 2003

In order to synthesize low resistive and high transparent indium–tin–oxide (ITO) films at room temperature, cesium assisted rf plasma sputtering was performed with additional substrate bias. We tried to control positive ions by negative substrate bias and negative ions by positive substrate bias. Plasma parameters, such as plasma density and electron temperature, were also controlled by the addition of cesium. The lowest specific resistivity of 4.4×10−4 Ω cm and high preferred oriented plane of (400) spectra from x-ray diffraction were obtained at the deposition condition of −100 V substrate bias. Our method proves to be very effective in low temperature growth of high quality ITO films.
Microstructure evolution of Al–Mg–B thin films by thermal annealing
Authors: Tian Y. , Constant A. , Lo C. C. H. , Anderegg J. W. , Russell A. M. , Snyder J. E. , Molian P.
Published: July 2003

The growth of Al–Mg–B thin films on SiO2/Si(100) substrates was performed by nanosecond pulsed laser deposition at three different substrate temperatures (300 K, 573 K, and 873 K). The as-deposited films were then annealed at 1173 K or 1273 K for 2 h. X-ray photoelectron spectroscopy, x-ray diffraction (XRD), and atomic force microscope were employed to investigate the effects of processing conditions on the composition, microstructure evolution, and surface morphology of the Al–Mg–B films. The substrate temperatures were found to affect the composition of as-deposited films in that the Mg content decreases and C content increases at higher substrate temperatures, in particular for the 873 K-deposited film. XRD results show that the as-deposited films were amorphous, and this structure may be stable up to 1173 K. Annealing at 1273 K was found to fully crystallize the room temperature and 573 K-deposited Al–Mg–B films with the formation of the polycrystalline orthorhombic AlMgB14 phase, accompanied by the development of a pronounced (011) preferred orientation. Nevertheless, high C incorporation in the 873 K-deposited Al–Mg–B film inhibits the crystallization and the amorphous structure remains stable even during 1273 K annealing. The presence of Si in the room-temperature-deposited 1273 K-annealed film due to the interdiffusion between the substrate and film leads to the formation of an additional tetragonal α-FeSi2 phase, which is thought to cause the surface cracking and microstructural instability observed in this film.
Electronic and structural properties of doped amorphous and nanocrystalline silicon deposited at low substrate temperatures by radio-frequency plasma-enhanced chemical vapor deposition
Authors: Alpuim P. , Chu V. , Conde J. P.
Published: July 2003

The gas phase doping of hydrogenated amorphous silicon and hydrogenated nanocrystalline silicon thin films deposited on glass and on plastic (polyethylene terephthalate) substrates is reported. Two substrate temperatures were used during deposition: 25 °C and 100 °C. Films were deposited by radio-frequency plasma-enhanced chemical vapor deposition using phosphine or diborane for n- or p-type doping, respectively. Similar electronic and structural properties are obtained for the doped films deposited on either substrate. Hydrogen dilution of silane is used to improve the electronic and structural properties of the amorphous films and to obtain nanocrystalline films. The most conductive amorphous films have n-type dark conductivity at room temperature ∼10−3 Ω−1 cm−1 and ∼10−5 Ω−1 cm−1 when deposited at 100 °C and 25 °C, respectively, or p-type room-temperature dark conductivity ∼10−7 Ω−1 cm−1 at both substrate temperatures. The most conductive nanocrystalline films deposited at 100 °C have n- and p-type dark conductivity at room temperature above 10−2 Ω−1 cm−1 while nanocrystalline films deposited at 25 °C only have p-type conductivity higher than 10−2 Ω−1 cm−1 at room temperature. Isochronal annealing at temperatures up to 300 °C showed that the dopants are fully activated at the deposition temperature in doped nanocrystalline samples and that they are only partially activated in amorphous films deposited at low substrate temperatures.
Effect of N2 annealing on AlZrO oxide
Authors: Pétry J. , Richard O. , Vandervorst W. , Conard T. , Chen J. , Cosnier V.
Published: July 2003

In the path to the introduction of high-k dielectric into integrated circuit components, a large number of challenges has to be solved. Subsequent to the film deposition, the high-k film is exposed to additional high-temperature anneals for polycrystalline Si activation but also to improve its own electrical properties. Hence, concerns can be raised regarding the thermal stability of these stacks upon annealing. In this study, we investigated the effect of N2 annealing (700 to 900 °C) of atomic layer chemical vapor deposition AlZrO layers using x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOFSIMS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The effect of the Si surface preparation [H–Si, 0.5 nm rapid thermal oxide (RTO), Al2O3] on the modification of the high-k oxide and the interfacial layer upon annealing was also analyzed. Compositional changes can be observed for all temperature and surface preparations. In particular, we observe a segregation of Al(oxide) toward the surface of the mixed oxide. In addition, an increase of the Si concentration in the high-k film itself can be seen with a diffusion profile extending toward the surface of the film. On the other hand, the modification of the interfacial layer is strongly dependent on the system considered. In the case of mixed oxide grown on 0.5 nm RTO, no differences are observed between the as-deposited layer and the layer annealed at 700 °C. At 800 °C, a radical change occurs: The initial RTO layer seems to be converted into a mixed layer composed of the initial SiO2 and Al2O3 coming from the mixed oxide, however without forming an Al-silicate layer. A similar situation is found for anneals at 900 °C, as well. When grown on 1.5 nm Al2O3 on 0.5 nm RTO, the only difference with the previous system is the observation of an Al-silicate fraction in the interfacial layer for the as-deposited and 700 °C annealed samples, which disappears at higher temperatures. Finally, considering layers deposited on a H–Si surface, we observe a slight increase of the interfacial thickness after annealing at 700 °C and no further changes for a higher annealing temperature.
Shape transformation of silicon trenches during hydrogen annealing
Authors: Kuribayashi Hitoshi , Hiruta Reiko , Shimizu Ryosuke , Sudoh Koichi , Iwasaki Hiroshi
Published: July 2003

Shape transformation of silicon trenches during annealing at high temperatures in a hydrogen ambient was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). By SEM observation of the trench profiles, we found that the rate of shape transformation increases with decreasing hydrogen pressure. Performing the simulation based on a continuum surface model, we show that the shape transformation during annealing in a hydrogen ambient is due to surface self-diffusion. By quantitative comparison of the results between the experiment and simulation, we estimated the diffusion coefficients. The obtained activation energy for surface diffusion under a hydrogen pressure of 40 Torr was much higher than that measured under ultrahigh-vacuum conditions. Furthermore, it was found by AFM observation of the trench sidewall surfaces that, during the thermal treatment, the large roughness of the as-etched trench sidewall surface decreased significantly due to surface self-diffusion of silicon atoms, resulting structures with atomically flat terraces and steps.
Pumping performance investigation of a turbobooster vacuum pump equipped with spiral-grooved rotor and inner housing by the computational fluids dynamics method
Authors: Cheng H.-P. , Chiang M.-T.
Published: July 2003

This article estimates the pumping performance of a turbobooster vacuum pump (TBP), with spiral-grooved rotor and inner housing, by the computational fluid dynamics method. The computational domain comprises the flow channels in the rotor and inner housing. Thus, the simulated gas can flow continuously from the inlet of the rotor through the outlet, into the inner housing, and then out the exit port of the pump. The calculations show that the pumping performance of the TBP can be enhanced when the spiral-grooved inner housing is integrated. The spiral angle of the rotor, the groove number, and the spiral angle of the inner housing have to be designed carefully to increase the effective pumping length of the flow channel of the TBP to gain further energy from the rotational energy, overcome the subsequent increased friction force, and increase the pumping performance. The calculations also show that the compression ratio and the pumping speed in this case, which comprises the rotor with five grooves and 15° spiral angle and the inner housing with five grooves and 27° spiral angle, are the largest among all cases studied in this article.
Development of radio-frequency magnetron sputtered indium molybdenum oxide
Authors: Yoshida Y. , Gessert T. A. , Perkins C. L. , Coutts T. J.
Published: July 2003

Molybdenum-doped indium oxide (IMO), an n-type transparent conducting oxide, was deposited using radio-frequency magnetron sputtering. The effects of oxygen concentration in an argon ambient and substrate temperature on film properties were studied. Compared to undoped indium oxide (In2O3) films, IMO films demonstrated higher electron mobility and more than an order-of-magnitude higher carrier concentration. The highest conductivity IMO film demonstrated a mobility of 44 cm2 V−1 s−1 and a carrier concentration of 1.3×1020 cm−3. The properties of both In2O3 and IMO films were very sensitive to the oxygen concentration, but not to the substrate temperature. Average visible transmittance of In2O3 and IMO films were 86% and 80%, respectively. Both optical and x-ray photoelectron spectroscopy analyses indicate a possible second phase in IMO films deposited at lower (⩽1%) oxygen concentrations.
Investigation of oxide (V2O5) thin films as electrodes for rechargeable microbatteries using Li
Authors: Talledo Arturo , Valdivia Héctor , Benndorf Carsten
Published: July 2003

V 2 O 5 thin films were prepared by reactive rf sputtering and used in the application as electrodes in rechargeable battery with Li as a counterelectrode. The V2O5 films were deposited onto uncoated and SnO2 coated glass by sputtering a V cathode using Ar+O2 gas mixtures. The structural properties of the V2O5 films were characterized by x-ray diffraction, infrared spectroscopy, and photoelectron spectroscopy (XPS: x-ray induced and UPS: UV induced photoelectron spectroscopy). Microbatteries were constructed using the V2O5 thin films as cathode, LiClO4+propylene carbonate as the electrolyte and Li metal as the anode. The V2O5 electrodes were characterized by there electrochemical behavior (current–voltage curves during charging and recharging). X-ray diffraction measurement demonstrated that unannealed V2O5 films were amorphous with no sharp reflexes. Annealing to 350 °C was sufficient to produce crystalline β-V2O5 (monoclinic) on uncoated glass or orthorhombic V2O5 on SnO2 coated glass. XPS spectra revealed the expected V/O ratio and line positions. However, the O 1s peak was split into two components, one from the V2O5 component (530.4 eV), the other at 532.9 eV is attributed to the uptake of water from the atmosphere. The charged microbattery resulted in a maximum voltage of 3.4 V for the currentless circuit and a capacity of 34.5 mC/cm2. With XPS we could demonstrate the migration of Sn (from the conductive coating of the glass substrate) into the V2O5 layer for the Li intercalated electrodes. Further, UPS spectra from charged and uncharged V2O5 indicate band-gap changes due to the Li uptake.
Formation of polycrystalline silicon germanium/HfO2 gate stack structure using inductively coupled plasma etching
Authors: Chen Jinghao , Tan Kian Ming , Wu Nan , Yoo Won Jong , Chan Daniel SH
Published: July 2003

A gate stack structure consisting of a polycrystalline silicon germanium (poly-SiGe) conductor and a HfO2 dielectric on a silicon substrate was formed by inductively coupled plasma etching using HBr/Cl2/O2. Etch rates of poly-SiGe with 46% Ge were 1.7–2.0 times higher than those of polycrystalline silicon, depending on processing conditions. In the small feature sized devices of 100 nm gates, the notching at the sidewall of poly-SiGe was pronounced up to the depth of 50 nm. The amount of notching increased with increasing inductive power and pressure, and decreasing rf bias power. A HfO2 etch rate of 950 Å/min was obtained at the condition of 550 W inductive power, 360 W rf bias power, and 10 mTorr pressure. Etch rates of HfO2 increased with increasing inductive power and rf bias power. Etching selectivity of poly-SiGe with respect to HfO2 increased significantly with the addition of 3.8% O2 to HBr, and it was possible to control the selectivity in the range of 15–70 by changing the rf bias power. The change in etching selectivity was considered mainly due to the change in HfO2 film property, originating from the incorporation of O into the remaining nonvolatile Hf and the reformation of HfOx during etching.
Improvement of luminance and luminous efficiency for optimal Penning gas mixtures in alternating current plasma display panels
Authors: Lee Seung-Joon , Lee Jae-Kyung , Kang Eu-Seok , Kim Tae-Won , Hwang Ho-Jung
Published: July 2003

We propose the optimal mixing ratio of Ar or Kr in Ne (96%)–Xe (4%) and He (70%)–Ne (27%)–Xe (3%) to improve the luminance and luminous efficiency for alternating current plasma display panels. To verify the improvements, we measured the voltage, current, and luminance experimentally. We analyzed the luminous efficiency and the wall charge using the Q–V method and compared the results with the calculated values from a two-dimensional simulation. When a small amount of Ar (0.01%–0.1%) or Kr (0.01%–0.1%) was added to Ne–Xe or He–Ne–Xe at 200 Torr, we found that the luminance increased by more than 20%, the luminous efficiency increased by more than 25% and the wall charge increased by more than 25%. When a small amount of Ar (0.005%–0.1%) was added to He–Ne–Xe–Kr (0.005%) at 400 Torr, the luminance increased by more than 8%, the luminous efficiency increased by more than 18%, and the wall charge increased by more than 12%. In conclusion, these results showed that the additional Penning effect between He and Ne and Ar and Kr particles improved the luminance and luminous efficiency.
A classroom experiment to demonstrate ferroelectric hysteresis
Authors: Dawber M. , Farnan I. , Scott J. F.
Published: July 2003

We have developed a classroom experiment suitable for undergraduate students in which they fabricate a ferroelectric capacitor from potassium nitrate and then observe the electrical behavior as the film is cooled through its transition temperature. The experiment can be carried out using a capacitance bridge that is simple to construct and inexpensive. The experiment gives students a hands-on experience with ferroelectric phenomena, a subject of considerable interest from both a fundamental and a technological standpoint.
Delta functions in spherical coordinates and how to avoid losing them: Fields of point charges and dipoles
Authors: Blinder S. M.
Published: July 2003

In calculations involving the divergence, curl, or Laplacian operators in spherical polar coordinates, the radial delta function contributions are sometimes inadvertently lost. This loss can be avoided by the judicious introduction of a step function. We apply this trick to confirm some subtle details about the fields of point electric and magnetic dipoles.
Verification of Bohr’s frequency condition and Moseley’s law: An undergraduate laboratory experiment
Authors: Gudennavar S. B. , Badiger N. M. , Thontadarya S. R. , Hanumaiah B.
Published: July 2003

We describe an undergraduate laboratory experiment to verify Bohr’s frequency condition and Moseley’s law using a thin NaI(Tl) detector spectrometer and a weak Co57 source. The slope of the plot of Kα x-ray energy versus (Z−1)2 yields a value for the Rydberg constant, R=(1.19±0.01)×107 m−1, which is in fair agreement with the best literature value, R=10 973 731.534(13) m−1.
The evaporation of a drop of mercury
Authors: Winter Thomas G.
Published: July 2003

The evaporative rates of two drops of mercury at room temperature are determined experimentally and theoretically. The resulting mercury vapor levels are estimated and measured, compared with the OSHA permissible exposure limit, and found to be small by comparison.
Deflection of light to second order: A tool for illustrating principles of general relativity
Authors: Bodenner Jeremiah , Will Clifford M.
Published: July 2003

We calculate the deflection of light by a spherically symmetric body in general relativity, to second order in the quantity GM/dc2, where M is the mass of the body and d is a measure of the distance of closest approach of the ray. Using three different coordinate systems for the Schwarzschild metric we show that the answers for the deflection, while the same at order GM/dc2, differ at order (GM/dc2)2. We demonstrate that all three expressions are really the same by expressing them in terms of measurable, coordinate-independent quantities. These results provide concrete illustrations of the meaning of coordinates and coordinate invariance, which may be useful in teaching general relativity.
A simple vibrating sample magnetometer for use in a materials physics course
Authors: Burgei Wesley , Pechan Michael J. , Jaeger Herbert
Published: July 2003

An inexpensive vibrating sample magnetometer (VSM) has been developed for use in a materials physics course. An exercise using the VSM allows students to measure the magnetic properties of various materials and thus gain experience applicable to contemporary research on magnetic materials. This paper describes specific aspects of the construction of a VSM and presents measurements for two 5-mm-long Ni wires of different diameters and for floppy disk media. A 178-μm-diam Ni wire served as a calibration sample for the system; the results from a 51-μm-diam Ni wire set the limit of precision for this system at approximately 5×10−3 emu.
Resource Letter: CC-1: Controlling chaos
Authors: Gauthier Daniel J.
Published: July 2003

This Resource Letter provides a guide to the literature on controlling chaos. Journal articles, books, and web pages are provided for the following: controlling chaos, controlling chaos with weak periodic perturbations, controlling chaos in electronic circuits, controlling spatiotemporal chaos, targeting trajectories of nonlinear dynamical systems, synchronizing chaos, communicating with chaos, applications of chaos control in physical systems, and applications of chaos control in biological systems.
Gödel’s trip
Authors: Ozsváth István , Schucking Engelbert
Published: July 2003

We discuss the geometrical light cone structure in Gödel’s rigidly rotating cosmos and correct a picture in the standard literature.
The Roget Illusion, the anorthoscope and the persistence of vision
Authors: Hunt James L.
Published: July 2003

When a spoked wheel is observed rolling behind a picket fence, a striking pattern (the Roget Illusion) is observed that arises as a result of the motion and the persistence of vision. The mathematical description of the illusion is developed and an apparatus briefly described that demonstrates it. The inverse process of de-convoluting a distorted object utilizing motion and the persistence of vision is employed in a device called the “anorthoscope.” The analysis of this device is discussed and a simple instrument is shown.
The drag force on an American football
Authors: Watts Robert G. , Moore Gary
Published: July 2003

We have measured the drag coefficient on an American football oriented so that its major axis is pointed directly into the wind. The football was suspended from the top of a wind tunnel by bicycle spokes attached to small bearings. The results are similar to the drag coefficients reported by Rouse (1946) for the case of an ellipsoid with major diameter/minor diameter similar to the length/diameter for the football. The drag coefficient for a spinning football is slightly lower than that for a nonspinning football. Both are in the range of 0.05–0.06, about half the value assumed by Brancazio (1985), about one-third that reported by Rae and Streit (2002) and far smaller than that reported by Cunningham and Dowell (1976).
Simple acoustic source radiation near a large wall
Authors: Moloney Michael J.
Published: July 2003

An acoustic simple source is predicted to radiate twice as much sound near an infinite rigid wall as it does in free space. As the simple source becomes more distant from the wall, its radiated power is predicted to decrease in an oscillatory way toward the value it has in free space. This behavior can be observed indirectly by fitting a 10-s signal of decaying amplitude from a tuning fork resonator box at various distances from a large unobstructed wall. Each fit determines the damping constant β, which reflects power losses, including radiated acoustic power. In a plot of β versus distance from the wall, the oscillatory part of the damping constant closely matches the theoretical curve of total radiated power from a simple acoustic source near an infinite rigid wall.
Verifying the diode–capacitor circuit voltage decay
Authors: Hellen Edward H.
Published: July 2003

The voltage on a capacitor discharging through a forward biased diode is calculated from basic equations and is found to be in good agreement with experimental measurements. In contrast to the exponential time decay for a RC circuit, the nonlinear characteristics of the diode result in a nonexponential decay for the diode–capacitor circuit. For a silicon diode the decay is predominantly a logarithmic function of time.
The critical temperature of two-dimensional and three-dimensional Ising models
Authors: Liu B. , Gitterman M.
Published: July 2003

The critical temperatures of the Ising model can be obtained by considering the elementary cells of the corresponding lattice, namely the square lattice in two dimensions and the cube in three dimensions. The configurations in the statistical sum of a cell are divided into nondegenerate and degenerate cases. At the critical temperature of the infinite lattice the contributions of these two groups of configurations are assumed to be equal. This conjecture reproduces the exact Onsager result for two dimensions and the numerical result for the three-dimensional Ising lattices. Although this conjecture is not exact, it gives insight into the nature of the transitions.
Using computer algebra to investigate the motion of an electric charge in magnetic and electric dipole fields
Authors: McGuire George C.
Published: July 2003

We provide examples of how a computer algebra system can be used to investigate the motion of an electric charge in an electric or magnetic dipole field.
Detection of Quantum Noise from an Electrically Driven Two-Level System
Authors: Deblock Richard , Onac Eugen , Gurevich Leonid , Kouwenhoven Leo P.
Published: July 2003

The electrical noise of mesoscopic devices can be strongly influenced by the quantum motion of electrons. To probe this effect, we have measured the current fluctuations at high frequency (5 to 90 gigahertz) using a superconductor-insulator-superconductor tunnel junction as an on-chip spectrum analyzer. By coupling this frequency-resolved noise detector to a quantum device, we can measure the high-frequency, nonsymmetrized noise as demonstrated for a Josephson junction. The same scheme is used to detect the current fluctuations arising from coherent charge oscillations in a two-level system, a superconducting charge qubit. A narrow band peak is observed in the spectral noise density at the frequency of the coherent charge oscillations.
Neuronal Correlates of Goal-Based Motor Selection in the Prefrontal Cortex
Authors: Matsumoto Kenji , Suzuki Wataru , Tanaka Keiji
Published: July 2003

Choosing an action that leads to a desired goal requires an understanding of the linkages between actions and their outcomes. We investigated neural mechanisms of such goal-based action selection. We trained monkeys on a task in which the relation between visual cues, action types, and reward conditions changed regularly, such that the monkeys selected their actions based on anticipated reward conditions. A significant number of neurons in the medial prefrontal cortex were activated, after cue presentation and before motor execution, only by particular action-reward combinations. This prefrontal activity is likely to underlie goal-based action selection.
Superluminal and Slow Light Propagation in a Room-Temperature Solid
Authors: Bigelow Matthew S. , Lepeshkin Nick N. , Boyd Robert W.
Published: July 2003

We have observed both superluminal and ultraslow light propagation in an alexandrite crystal at room temperature. Group velocities as slow as 91 meters per second to as fast as –800 meters per second were measured and attributed to the influence of coherent population oscillations involving chromium ions in either mirror or inversion sites within the crystal lattice. Namely, ions in mirror sites are inversely saturable and cause superluminal light propagation, whereas ions in inversion sites experience conventional saturable absorption and produce slow light. This technique for producing large group indices is considerably easier than the existing methods to implement and is therefore suitable for diverse applications.
Biodiversity Meets the Atmosphere: A Global View of Forest Canopies
Authors: Ozanne C. M. P. , Anhuf D. , Boulter S. L. , Keller M. , Kitching R. L. , Körner C. , Meinzer F. C. , Mitchell A. W. , Nakashizuka T. , Dias P. L. Silva , Stork N. E. , Wright S. J. , Yoshimura M.
Published: July 2003

The forest canopy is the functional interface between 90% of Earth's terrestrial biomass and the atmosphere. Multidisciplinary research in the canopy has expanded concepts of global species richness, physiological processes, and the provision of ecosystem services. Trees respond in a species-specific manner to elevated carbon dioxide levels, while climate change threatens plant-animal interactions in the canopy and will likely alter the production of biogenic aerosols that affect cloud formation and atmospheric chemistry.
5-HT
4(a)
Receptors Avert Opioid-Induced Breathing Depression Without Loss of Analgesia
Authors: Manzke Till , Guenther Ulf , Ponimaskin Evgeni G. , Haller Miriam , Dutschmann Mathias , Schwarzacher Stephan , Richter Diethelm W.
Published: July 2003

Opiates are widely used analgesics in anesthesiology, but they have serious adverse effects such as depression of breathing. This is caused by direct inhibition of rhythm-generating respiratory neurons in the Pre-Boetzinger complex (PBC) of the brainstem. We report that serotonin 4(a) [5-HT
4(
a
)
] receptors are strongly expressed in respiratory PBCneurons and that their selective activation protects spontaneous respiratory activity. Treatment of rats with a 5-HT
4
receptor–specific agonist overcame fentanyl-induced respiratory depression and reestablished stable respiratory rhythm without loss of fentanyl's analgesic effect. These findings imply the prospect of a fine-tuned recovery from opioid-induced respiratory depression, through adjustment of intracellular adenosine 3′,5′-monophosphate levels through the convergent signaling pathways in neurons.
Conversion of Working Memory to Motor Sequence in the Monkey Premotor Cortex
Authors: Ohbayashi Machiko , Ohki Kenichi , Miyashita Yasushi
Published: July 2003

To plan a serial order behavior, we hold serial sensory information in our minds and convert it to a movement program. We trained monkeys to memorize a sequence of positional cues and to reproduce it by making saccades in either the original or reverse order. The order was determined in the middle of a trial on the basis of an instruction stimulus. Triggered by the instruction stimulus, single neurons in the dorsal premotor cortex became transiently active only when the order needed to be determined. These transient neurons, together with nearby sustained neurons that hold information on cue or movement sequences, appear to mediate the generation of a motor program from the maintained information.
A B Cell-Based Sensor for Rapid Identification of Pathogens
Authors: Rider Todd H. , Petrovick Martha S. , Nargi Frances E. , Harper James D. , Schwoebel Eric D. , Mathews Richard H. , Blanchard David J. , Bortolin Laura T. , Young Albert M. , Chen Jianzhu , Hollis Mark A.
Published: July 2003

We report the use of genetically engineered cells in a pathogen identification sensor. This sensor uses B lymphocytes that have been engineered to emit light within seconds of exposure to specific bacteria and viruses. We demonstrated rapid screening of relevant samples and identification of a variety of pathogens at very low levels. Because of its speed, sensitivity, and specificity, this pathogen identification technology could prove useful for medical diagnostics, biowarfare defense, food- and water-quality monitoring, and other applications.
Chloride Methylation by Plant Pectin: An Efficient Environmentally Significant Process
Authors: Hamilton John T. G. , McRoberts W. Colin , Keppler Frank , Kalin Robert M. , Harper David B.
Published: July 2003

Atmospheric chloromethane (CH
3
Cl) plays an important role in stratospheric ozone destruction, but many uncertainties exist regarding the strengths of its sources and sinks and particularly regarding the processes generating this naturally occurring gas. Evidence is presented here that CH
3
Cl is produced in many terrestrial environments by a common mechanism. Abiotic conversion of chloride to CH
3
Cl occurs readily in plant material, with the widespread plant component pectin acting as a methyl donor. Significant CH
3
Cl emissions from senescent and dead leaves were observed at ambient temperatures; those emissions rose dramatically when temperatures increased. This ubiquitous process acting in terrestrial ecosystems and during biomass burning could contribute the bulk of atmospheric CH
3
Cl.
Switching Skeletons: Hydrostatic Support in Molting Crabs
Authors: Taylor Jennifer R. A. , Kier William M.
Published: July 2003

Skeletal support systems are essential for support, movement, muscular antagonism, and locomotion. Crustaceans shed their rigid exoskeleton at each molt yet are still capable of forceful movement. We hypothesize that the soft water-inflated body of newly molted crabs may rely on a hydrostatic skeleton, similar to that of worms and polyps. We measured internal hydrostatic pressure and the force exerted during claw adduction and observed a strong correlation between force and hydrostatic pressure, consistent with hydrostatic skeletal support. This alternation between the two basic skeletal types may be widespread among arthropods.
A Young White Dwarf Companion to Pulsar B1620-26: Evidence for Early Planet Formation
Authors: Sigurdsson Steinn , Richer Harvey B. , Hansen Brad M. , Stairs Ingrid H. , Thorsett Stephen E.
Published: July 2003

The pulsar B1620-26 has two companions, one of stellar mass and one of planetary mass. We detected the stellar companion with the use of Hubble Space Telescope observations. The color and magnitude of the stellar companion indicate that it is an undermassive white dwarf (0.34 ± 0.04 solar mass) of age 480 × 10
6
± 140 × 10
6
years. This places a constraint on the recent history of this triple system and supports a scenario in which the current configuration arose through a dynamical exchange interaction in the cluster core. This implies that planets may be relatively common in low-metallicity globular clusters and that planet formation is more widespread and has happened earlier than previously believed.
Suppression of Ovarian Follicle Activation in Mice by the Transcription Factor Foxo3a
Authors: Castrillon Diego H. , Miao Lili , Kollipara Ramya , Horner James W. , DePinho Ronald A.
Published: July 2003

Foxo transcription factors have been implicated in diverse biological processes, including metabolism, cellular stress responses, and aging. Here, we show that
Foxo3a
–/–
female mice exhibit a distinctive ovarian phenotype of global follicular activation leading to oocyte death, early depletion of functional ovarian follicles, and secondary infertility. Foxo3a thus functions at the earliest stages of follicular growth as a suppressor of follicular activation. In addition to providing a molecular entry point for studying the regulation of follicular growth, these results raise the possibility that accelerated follicular initiation plays a role in premature ovarian failure, a common cause of infertility and premature aging in women.
Making Sense of Complex Population Cycles
Authors: Ranta Esa
Published: July 2003

Complex Population Dynamics
A Theoretical/Empirical Synthesis. Peter Turchin. Princeton University Press, Princeton, NJ, 2003. 468 pp. $75, £49.95. ISBN 0-691-09020-3. Paper, $29.95, £19.95. ISBN 0-691-09021-1.

In a synthesis that highlights our improved understanding of the behavior of nonlinear dynamical systems, Turchin offers a theory of population oscillations that integrates mathematical models, statistical analyses, and field experiments.
Phyllotaxis — The Way Ahead, A View on Open Questions and Directions of Research
Authors: Jean Roger V. , Barabé Denis
Published: July 2003

Suggestions are made for future research in the multidisciplinary subject of phyllotaxis, and various promising viewpoints for the study of the phenomenon are pointed out.
Discrete Versus Continuous Controlled System
Authors: Béné Christophe , Lobry Claude
Published: July 2003

Because decision making processes involve costly mechanisms, they seldom are implemented continuously but instead take place at discrete time intervals. The question is then: what is the impact of this process discreteness on the systems dynamics? This problem is set here in the context of fisheries. Through a very simple though realistic model representing a shrimp fishery, we show that a discrete decision making process may lead to dynamics that differ completely from those obtained with a continuous process. For this purpose, we consider the interaction between a shrimp stock and the exploiting fleet. We then focus on the decision process that governs the allocation of the fleet fishing effort between the two stages of this stock: the young adults living near the coast and the mature adults located offshore. We first analyze the behaviour of the system when the discreteness in the decision making is not accounted for. In that case, the system turns out to be globally stable. We then identify the behaviour of the system when the decision process is discretised. In that case the solutions of the system yield sustained periodic oscillations. Our conclusion is that discreteness which is known to occur in decision making processes of most anthropic systems should be taken into account, especially in studies aiming precisely at investigating the dynamics of such systems.
Modelling Vaccination Strategy Against Directly Transmitted Diseases Using a Series of Pulses
Authors: Yang Hyun Mo
Published: July 2003

When a SIR model with a constant contact rate is used to describe the dynamics of directly transmitted infections, oscillations, which decay exponentially as time goes on, are obtained. By using this kind of model, we obtained the natural- and inter-epidemics periods of the disease. These two quantities are quasi-periods, since we are considering damped oscillations.

The above two periods were estimated from rubella seroprevalence data from a small Brazilian community and, based on them, a vaccination strategy in a series of pulses was designed. The vaccination time lag between pulses is related to the natural-epidemics period, instead of the inter-epidemics period, multiplied by a fraction usually less than unity (the security factor). The results for different controlling scenarios showed that a series of pulses vaccination strategy can be a good option for developing countries.
Sex Classification of Face Areas
Authors: Edelman Betty , Valentin Dominique , Abdi Hervé
Published: July 2003

Human subjects and an artificial neural network, composed of an autoassociative memory and a perceptron, gender classified the same 160 frontal face images (80 male and 80 female). All 160 face images were presented under three conditions (1) full face image with the hair cropped (2) top portion only of the Condition 1 image (3) bottom portion only of the Condition 1 image. Predictions from simulations using Condition 1 stimuli for training and testing novel stimuli in Conditions 1, 2, and 3, were compared to human subject performance. Although the network showed a fair ability to generalize learning to new stimuli under the three conditions, performing from 66 to 78% correctly on novel faces, and predicted main effects, a more detailed comparison with the human data was not as promising. As expected, human accuracy declined with decreased image area, but showed a surprising interaction between the sex of the face and the partial image conditions. The network failed to predict this interaction, or the likelihood of correct human classification for a particular face. This analysis on an item level raises concern about the psychological relevance of the model.
Spanning the Face Space
Authors: Edelman Shimon
Published: July 2003

The paper outlines a computational approach to face representation and recognition, inspired by two major features of biological perceptual systems: graded-profile overlapping receptive fields, and object-specific responses in the higher visual areas. This approach, according to which a face is ultimately represented by its similarities to a number of reference faces, led to the development of a comprehensive theory of object representation in biological vision, and to its subsequent psychophysical exploration and computational modeling.
Fuzzy-Face
Authors: Huntsberger Terry , Rose John , Ramaka Shashidhar
Published: July 2003

The human face is one of the most important patterns our visual system receives. It establishes a person's identity and also plays a significant role in everyday communication. Humans can recognize familiar faces under varying lighting conditions, different scales, and even after the face has changed due to aging, hair style, glasses, or facial hair. Our ease at recognizing faces is a strong motivation for the investigation of computational models of face processing.

This paper presents a newly developed face processing system called Fuzzy-Face that combines wavelet pre-processing of input with a fuzzy self-organizing feature map algorithm. The wavelet-derived face space is partitioned into fuzzy sets which are characterized by face exemplars and membership values to those exemplars. This system learns faces using relatively few training epochs, has total recall for faces it has been shown, generalizes to face images that are acquired under different lighting conditions, and has rudimentary gender discrimination capabilities. We also include the results of some experimental studies.
Temporal Order in Human Object Recognition Learning
Authors: Wallis Guy
Published: July 2003

The view based approach to object recognition relies upon the co-activation of 2-D pictorial elements or features. This approach is limited to generalising recognition across transformations of objects in which considerable physical similarity is present in the stored 2-D images to which the object is being compared. It is, therefore, unclear how completely novel views of objects might correctly be assigned to known views of an object so as to allow correct recognition from any viewpoint.

The answer to this problem may lie in the fact that in the real world we are presented with a further cue as to how we should associate these images, namely that we tend to view objects over extended periods of time. In this paper, neural network and human psychophysics data on face recognition are presented which support the notion that recognition learning can be affected by the order in which images appear, as well as their spatial similarity.
The Proof of the Feynman–Kac Formula for Heat Equation on a Compact Riemannian Manifold
Authors: Obrezkov Oleg O.
Published: July 2003

A full proof of the Feynman–Kac-type formula for heat equation on a compact Riemannian manifold is obtained using some ideas originating from the papers of Smolyanov, Truman, Weizsaecker and Wittich.1-3 In particular, the technique exploited in the paper has some common lines with Chernoff theorem, which is one of the basic points of the approach to the topics undertaken in the above-mentioned papers.
A Unified Characterization Theorem in White Noise Theory
Authors: Ji Un Cig , Obata Nobuaki
Published: July 2003

We revisit a CKS-space from the viewpoint of standard setup of white noise calculus and prove a general characterization theorem for white noise operators from a CKS-space into another CKS-space. The usual characterizations so far obtained for white noise distributions, white noise test functions and white noise operators are all consequences of the unified characterization theorem.
Adelic Path Integrals for Quadratic Lagrangians
Authors: Djordjević Goran S. , Dragovich Branko , Nešić Ljubiša
Published: July 2003

Feynman's path integral in adelic quantum mechanics is considered. The propagator [Formula: see text] for one-dimensional adelic systems with quadratic Lagrangians is analytically evaluated. Obtained exact general formula has the form which is invariant under interchange of the number fields ℝ and ℚp.
On the Asymptotic Behaviour of Some Stochastic Differential Equations for Quantum States
Authors: Barchielli Alberto , Paganoni Anna M.
Published: July 2003

In this article we study the long time behaviour of a class of stochastic differential equations introduced in the theory of measurements continuous in time for quantum open systems. Such equations give the time evolution of the a posteriori states for a system underlying a continual measurement. First of all we give conditions for the equation to preserve pure states and then, in the case of a finite-dimensional Hilbert space, we obtain sufficient conditions from which the stochastic equation for a posteriori states is ensured to map, for t → +∞, mixed states into pure ones. Finally we study existence and uniqueness of an invariant measure for the equations which preserve pure states. We give a general theorem for the purely diffusive case, again in the finite-dimensional case; we then apply it to some physical examples. For the purely jump case, an example is discussed in which the invariant measure exists and is unique.
Spectral Gaps on Discretized Loop Spaces
Authors: Eberle Andreas
Published: July 2003

We study spectral gaps w.r.t. marginals of pinned Wiener measures on spaces of discrete loops (or, more generally, pinned paths) on a compact Riemannian manifold M. The asymptotic behaviour of the spectral gap as the time parameter T of the underlying Brownian bridge goes to 0 is investigated. It turns out that depending on the choice of a Riemannian metric on the base manifold, very different asymptotic behaviours can occur. For example, on discrete loop spaces over sufficiently round ellipsoids the gap grows of order α/T as T ↓ 0. The strictly positive rate α stabilizes as the discretization approaches the continuum limit. On the other extreme, if there exists a closed geodesic γ : S1 → M such that the sectional curvature on γ(S1) is strictly negative, and the loop is pinned close to γ(S1), then the gap decays of order exp (-β/T), and the decay rate β approaches +∞ as the discretization approaches the continuum limit.
2D Vortex Motion of an Incompressible Ideal Fluid: The Koopman–von Neumann Approach
Authors: Albeverio S. , Ferrario B.
Published: July 2003

An incompressible ideal fluid in the two-dimensional torus (i.e. the Euler equation in a rectangle with periodic boundary conditions) is considered. The flow for a vorticity field concentrated in any finite number of points is analyzed. A compound Poisson measure Π, invariant for this flow, is introduced. The Hilbert space ℒ2(Π) and the properties of the corresponding ℒ2-flow are investigated. In particular it is proven that the corresponding generator is Markov unique.
Singular Spacetime Itô's Integral and a Class of Singular Interacting Branching Particle Systems
Authors: Wang Hao
Published: July 2003

In Wang,8 a class of interacting measure-valued branching diffusions [Formula: see text] with singular coefficient were constructed and characterized as a unique solution to ℒε-martingale problem by a limiting duality method since in this case the dual process does not exist. In this paper, we prove that for any ε ≠ 0 the superprocess with singular motion coefficient is just the super-Brownian motion. The singular motion coefficient is handled as a sequential limit motivated by Antosik et al.1 Thus, the limiting superprocess is investigated and identified as the motion coefficient converges to a singular function. The representation of the singular spacetime Itô's integral is derived.
Hadamard and Liouville Type Results for Fully Nonlinear Partial Differential Inequalities
Authors: Capuzzo Dolcetta I. , Cutrì A.
Published: July 2003

In this paper we prove some Hadamard and Liouville type properties for nonnegative viscosity supersolutions of fully nonlinear uniformly elliptic partial differential inequalities in the whole space.
Equivariant N-Dof Hamiltonians Via Generalized Normal Forms
Authors: Palacián Jesús , Yanguas Patricia
Published: July 2003

In the present paper we study polynomial Hamiltonian systems depending on one or various real parameters. We determine the values that these parameters should take in order to be able to construct formal (asymptotic) integrals of the system. In this respect, a method to calculate the formal integrals of a polynomial Hamiltonian vector field is presented. The original Hamilton function represents a family of dynamical systems composed by a principal part (quadratic terms) plus the perturbation (terms of degree three or bigger). We extend an integral of the principal part to the perturbed system by means of Lie transformations for autonomous Hamiltonian systems. Thus, the procedure is carried out order by order starting with polynomials of degree three. We obtain the conditions that the external parameters have to satisfy so that the integral of the quadratic terms persists for the whole system up to a certain order of approximation. Once the formal integral is computed the departure system has been transformed into a generalized normal form, i.e. a system which is equivalent to the initial one but easier to be analysed by making use of reduction theory. The truncated normal form defines a system with less degrees of freedom than the original Hamiltonian and is written exactly in terms of the polynomial first integrals associated to the quadratic part of the new integral and it contains the qualitative description of the initial system. The theory is illustrated with two examples borrowed from Physics.