bluuebunny/crossref_metadata_2025 huggingface dataset:
Wissen und Erinnern
Authors: Knopf Monika , Mack Wolfgang , Kressley-Mba Regina
Published: April 2005

Zusammenfassung. In der entwicklungspsychologischen Säuglingsforschung interessiert man sich verstärkt für den Aufbau des Gedächtnissystems. Während früheste Gedächtniseinträge, wie sie in den ersten Lebenstagen (Vertrautheits-, Diskriminations-, Habituationsreaktionen) gefunden werden, dem nicht-deklarativen Gedächtnis zugerechnet werden, werden Imitationsleistungen, wie sie in der zweiten Hälfte des ersten Lebensjahres mittels der Aufgabe zur Verzögerten Imitation nachweisbar sind, dem deklarativen Gedächtnis zugerechnet. Es ist allerdings offen, ob ontogenetisch frühe verzögerte Imitationen anzeigen, dass hier semantisches Wissen oder episodische Erinnerung ausgedrückt wird. Insofern der allgemeine kognitive Entwicklungsstand auf dieser Altersstufe zur Beurteilung mit herangezogen wird, was in dieser Arbeit am Beispiel zweier Forschungsprogramme geschieht (Theorie des Geistes, Entwicklung des Selbst), erscheint es als hochwahrscheinlich, dass Verzögerte Imitationen von Säuglingen im ersten Lebensjahr einen semantischen Charakter haben. Voraussetzungen für Erinnerungen werden im Verlauf des zweiten Lebensjahres erkennbar und entwickeln sich zumindest bis zum vierten Lebensjahr sukzessive weiter.
Eine erweiterte Version des Semantisch-Prozeduralen Interface-Modells des Selbst:
Authors: Hannover Bettina , Pöhlmann Claudia , Roeder Ute , Springer Anne , Kühnen Ulrich
Published: April 2005

Zusammenfassung. Das Semantisch-Prozedurale Interface-Modell des Selbst (SPI, Hannover & Kühnen, 2002 ; Kühnen & Hannover, 2003 ; Kühnen, Hannover & Schubert, 2001 ) beschreibt, auf welche Weise unterschiedliche Selbstkonstruktionen Einfluss auf das Denken, Handeln und Fühlen von Personen nehmen. Vermittelt wird diese Einflussnahme zum einen durch die relative kognitive Zugänglichkeit von (interdependenten versus independenten) Selbstkonstruktionen, d.h. die Leichtigkeit, mit der Personen auf spezifisches Selbstwissen zugreifen. Zum anderen gelten unterschiedliche Informationsverarbeitungsstile, die mit den jeweiligen Selbstkonstruktionen assoziiert sind, als verantwortlich für den Einfluss von Selbstwissen auf individuelles Erleben: Ist überwiegend interdependentes Selbstwissen zugänglich, so werden Informationen tendenziell mit Bezug auf den Kontext verarbeitet, in dem sie erscheinen (kontextabhängiger Verarbeitungsmodus). Ist hingegen eher independentes Selbstwissen verfügbar, wird Information tendenziell unabhängig von ihrem Kontext verarbeitet (kontextunabhängiger Verarbeitungsmodus). Im vorliegenden Aufsatz stellen wir eine zweifache Erweiterung des SPI-Modells vor. Erstens bot das Modell bislang keine Erklärung dafür, durch welche kognitiven Prozesse die unterschiedlichen Verarbeitungsmodi der beiden Selbstkonzeptarten implementiert werden. Wir nehmen nun an, dass der Grad der Kontextabhängigkeit der Informationsverarbeitung von übergeordneten kognitiven Kontrollfunktionen abhängt, nämlich von der a) Fokussierung auf handlungsrelevante Information in einem Kontext, b) von der aktiven Inhibition aufgabenirrelevanter Information und c) vom Aufgaben-Management. Zum zweiten beansprucht unser erweitertes Modell - hinausgehend über die bisherige Betrachtung des Selbst als kognitives System - auch rein motivationale Effekte independenten versus interdependenten Selbstwissens zu erklären. Dazu integrieren wir neben Annahmen über das aktuelle Selbst Annahmen über angestrebte Selbstbilder in das SPI-Modell.
Psychobiological Theories of Smoking and Smoking Motivation
Authors: Lujic Claudia , Reuter Martin , Netter Petra
Published: April 2005

Abstract. Theories of smoking have been developed about the conditions and causes of smoking as well as for explaining its maintenance. Moreover, factors of smoking motivation have been identified, which describe incentives to smoke and types of smoking behavior. The most frequently reported motives are psychosocial smoking, sensorimotor smoking, indulgent smoking, stimulation smoking, sedation smoking, dependent smoking, and automatic smoking. In the first phase after the start of smoking, psychosocial smoking is the dominating motive, which is best represented by theories of social psychology. Sensorimotor smoking may be best explained by theories of classical and operant conditioning. Indulgent smoking (= smoking for pleasure) may be explained by neurochemical theories and by the neurobiological theories of dependence emphasizing nicotine-induced activation of mesolimbic dopaminergic reinforcement. Stimulation smoking and sedation smoking are related to arousal models. Moreover, sedation smoking is also explained by aspects of reducing negative affect (as claimed by theories of affect regulation) and by biochemical theories emphasizing serotonergic mechanisms in modulating anxiety as well as by theories of dependence. Dependent smoking, which is mostly based on negative reinforcement (suppression of withdrawal symptoms) may be explained by neurochemical theories as well as by neurobiological theories of psychological and physical dependence explaining blunted dopaminergic and serotonergic responsivity as due to desensitization of respective receptors. Also automatic smoking may be explained by processes of habit learning and neurobiological theories of dependence. Finally, personality theories have been applied to all of these smoking motives.
Polish Psychology in the Period of Political Transformation (1989-2003)
Authors: Brzeziński Jerzy , Strelau Jan
Published: April 2005

Abstract. In a referendum held in July, 2003, 79% of the Polish people, citizens of an independent country, opted for joining the European Union. This nation, which on the turn of the first millennium chose a pro-European course of development, once again confirmed its authentically European identity. It is, in fact, an identity never lost, despite the decrees of history and all ominous events of the second half of the twentieth century. Psychologists and students of psychology also have their share in this majority “yes” for the European Union. Poland is a relatively large country with numerous universities and colleges. At 15 of them, students have the possibility of completing psychology as their major faculty with a 5-year schedule of varied courses and subsequently graduating with the degree of MA. Much has changed in our country since the memorable year of 1989 and these transformations obviously also apply to Polish universities, including the community of psychologists who will soon join, with no further limitations, the European community of psychologists. While educating future psychologists, we will be aware of the fact that we are now no longer cultivating them for Poland alone but for Europe as a whole. We, therefore, regard it as worthwhile to delineate for our European colleagues a general overview of Polish academic psychology, and especially of the most recent developments that have taken place during the major socio-political transformation begun in 1989.
Modelling Behaviour with Multivariate Multilevel Growth Curves
Authors: Plewis Ian
Published: April 2005

Abstract. Developmental data are often both longitudinal and multivariate and can be handled within a multilevel framework. This paper fits a range of multivariate multilevel models to both continuous and binary data to examine the ways in which a set of behavioural measures change together with age. These data were collected by researchers in Montreal, Canada. Methodologically, we find that within and between individual correlations vary only a little according to the ways in which the models are specified. Substantively, we find that measures of aggression and opposition are closely related but both are less closely related to a measure of hyperactivity. Models for the effects of socio-economic status on levels and changes are fitted, as are models that examine change conditional on an initial measure. The findings are compared with those previously obtained using a growth trajectories approach.
Comparing landslides to fluidized crater ejecta on Mars
Authors: Barnouin‐Jha O. S. , Baloga S. , Glaze L.
Published: April 2005

We use the Mars Global Surveyor and Viking data sets to compare and contrast the geomorphology of four large Martian landslides located in Valles Marineris to fluidized ejecta of seven fresh Martian craters located in Lunae Planum. Both mass movements have flowed over the Martian surface and possess characteristics seen in terrestrial mass movements. We combine these comparisons with simple flow models to determine how the planar geometry of landslides and the cylindrical geometry of ejecta can generate different topographic expressions for the same input constraints. Our purpose is to better understand the emplacement processes of both types of mass movements. Our geomorphic analyses are consistent with previous views that the large Martian landslides resemble large terrestrial long‐run‐out flows. The planar flow model supports this inference: Martian landslides probably flowed as a basal glide, where motion is limited to a narrow interface at the base of the mass movement. Geomorphic investigations of fresh multilayered ejecta indicate that their inner portions with their subtle rampart probably flowed like their landslide counterparts as a basal glide. Distal pronounced contiguous ramparts, however, resemble features akin to terrestrial debris flows. The cylindrical flow model shows that differences in geometry can mask the dynamics of flow emplacement. This model suggests, as expected, a basal glide origin for the inner portions of the ejecta. Surprisingly, basal glide also best explains the topography of the distal ejecta ramparts.
Advancing dynamical prediction of Indian monsoon rainfall
Authors: Krishna Kumar K. , Hoerling Martin , Rajagopalan Balaji
Published: April 2005

Despite advances in seasonal climate forecasting using dynamical models, skill in predicting the Indian monsoon by such methods has proven poor. Our analysis identifies a flaw in the hitherto popular design of prediction systems in which atmospheric models are driven with a projected ocean surface temperature. Such a configuration presupposes Indian monsoon variability to be a consequence solely of the atmosphere reacting to the ocean. It is becoming increasingly evident that the Indian monsoon is suitably described as a fully coupled ocean‐land‐atmospheric system, though implications for skill have not been demonstrated. We discover significant improvements in the skill of Indian monsoon predictions when atmospheric models are not constrained by specified observed SSTs in the Indian Ocean warm pool region. Evidence comes from intercomparing 50‐years of monsoon skill in atmospheric models using specified SSTs with skill in coupled ocean atmosphere models.
Magnetosheath compression: Role of characteristic compression time, alpha particle abundance, and alpha/proton relative velocity
Authors: Hellinger Petr , Trávníček Pavel
Published: April 2005

The hybrid expanding box (HEB) is used to study a slow compression of the magnetosheath plasma. The HEB simulations confirm the previous results of Hellinger et al. (2003b) that the slowly compressed plasma follows a marginal stability path of the proton cyclotron instability in a low‐beta plasma, whereas in a high‐beta plasma the mirror instability becomes dominant. For a faster compression the marginal stability path shifts further inside the unstable region in order to balance the faster anisotropization rate due to the faster compression. The presence of alpha particles strongly changes the dispersive properties of the plasma and introduces the alpha cyclotron instability. The theoretical description of the system becomes intricate, since the alpha particles introduce additional parameters. The plasma evolution during the compression gets more complex; a transition between the proton and the alpha cyclotron instabilities appears. The overall behavior of the simulated system is not qualitatively different from the behavior of the pure electron‐proton plasma. When an additional parameter, a nonzero alpha/proton relative velocity, is included, the theoretical understanding becomes even more complicated. The behavior of the compressed system is nevertheless similar to the results in the pure electron‐proton plasma. An important qualitative change from the zero alpha/proton relative velocity case is that the proton cyclotron instability is able to efficiently accelerate alpha particles with respect to protons, whereas the alpha cyclotron and the mirror instabilities decelerate them.
A critique of methods of determining the position of the focus of the Sq current system
Authors: Stening Robert , Reztsova Tamara , Ivers David , Turner Jon , Winch Denis
Published: April 2005

We examine three methods of determining the latitude of the focus of the Sq current system using data from an array of more than 50 magnetometers operating on the Australian mainland from November 1989 to July 1990. The magnetometer array enables the location of the Sq focus with more certainty than usual. Chains of stations within the array are then used to test the various methods of determining the focus latitude. The most accurate method was that which first determined the time when the magnetic eastward component ΔY passes through zero and then used northward magnetic components ΔX at that time, in a least squares linear fit, to find that latitude at which ΔX went to zero. This was found preferable to an alternative method which uses maximum and minimum values of ΔX. The reliability of these methods was examined on days with some magnetic disturbance present and on days when the focus latitude lay outside the chain of stations being used. The third method uses a principal component analysis to determine eigenvector elements for the daily variations of each station in the chain and fits the associated coefficients of the eigenvector elements to a straight line. This method had several shortcomings, especially if the procedure for determining the focus position were to be automated. For all methods the value of the correlation coefficient associated with the linear fit gave a good indication of the reliability of the estimation.
Stratospheric water vapor predicted from the Lagrangian temperature history of air entering the stratosphere in the tropics
Authors: Fueglistaler S. , Bonazzola M. , Haynes P. H. , Peter T.
Published: April 2005

We present results of Lagrangian troposphere‐to‐stratosphere transport (TST) in the tropics based on trajectory calculations for the period 1979–2001. The trajectories and corresponding temperature histories are calculated from wind and temperature fields provided by the reanalysis data ERA‐40 of the European Centre for Medium‐Range Weather Forecasts (ECMWF). The water vapor mixing ratio of air entering the tropical stratosphere is calculated from the minimum saturation mixing ratio over ice encountered by each trajectory. We show that this Lagrangian approach, which considers the global‐scale to synoptic‐scale dynamics of tropical TST but neglects mesoscale dynamics and details of cloud microphysics, substantially improves estimates of stratospheric humidity compared to calculations based on Eulerian mean tropical tropopause temperatures. For the period 1979–2001 we estimate from the Lagrangian calculation that the mean water mixing ratio of air entering the stratosphere is 3.5 ppmv, which is in good agreement with measurements during the same period, ranging from 3.3 ppmv to 4 ppmv, whereas an estimate based on an Eulerian mean calculation is about 6 ppmv. The amplitude of the annual cycle in water vapor mixing ratio at a potential temperature of 400 K in the tropics estimated from the Lagrangian calculation is compared with measurements of water vapor from the Halogen Occultation Experiment (HALOE). For the period 1992–2001, when HALOE measurements and ERA‐40 data overlap, we calculate a peak‐to‐peak amplitude of ∼1.7 ppmv, in good agreement with ∼1.6 ppmv seen in HALOE data. On average, the Lagrangian calculations have a moist bias of ∼0.2 ppmv, equivalent to a warm bias of the Lagrangian cold point of about 0.5 K. We conclude that the Lagrangian calculation based on synoptic‐scale velocity and temperature fields yields estimates for stratospheric water vapor in good agreement with observations and that mesoscale and cloud microphysical processes need not be invoked, at first order, to explain annual mean and seasonal variation of water vapor mixing ratios in the tropical lower stratosphere.
Influence of transient atmospheric circulation on the surface heating of the western Pacific warm pool
Authors: Chou Ming‐Dah , Chou Shu‐Hsien , Chan Pui‐King
Published: April 2005

Trade and monsoonal winds converge to regions of the highest sea surface temperature (SST) in the equatorial western Pacific. These regions have the largest cloud cover and smallest wind speed. Both surface solar heating and evaporative cooling are weak. Data on surface heat fluxes show that the reduced evaporative cooling due to weakened winds exceeds the reduced solar heating due to enhanced cloudiness. The result is a maximum surface heating in the strong convective and high SST regions, which follow the seasonal march of the sun. As the Sun moves away from a convective region, the strong trade and monsoonal winds set in, and the evaporative cooling enhances, resulting in a net cooling of the surface. We conclude that the seasonal variation of evaporation associated with the seasonal variation of trade and monsoonal winds is one of the major factors that modulate the SST distribution of the Pacific warm pool.
Altered Functional Connectivity Related to White Matter Changes inside the Working Memory Network at the Very Early Stage of MS
Authors: Duong My-Van Au , Audoin Bertrand , Boulanouar Kader , Ibarrola Daniella , Malikova Irina , Confort-Gouny Sylrane , Celsis Pierre , Pelletier Jean , Cozzone Patrick J , Ranjeva Jean-Philippe
Published: April 2005

Functional magnetic resonance imaging (fMRI) using paced auditory serial addition test (PASAT) as paradigm was used to study the functional connectivity in 18 patients at the very early stage of multiple sclerosis (MS) compared with 18 controls, to determine the existence of circuitry disturbance inside the working memory network and its relationship with white matter abnormalities assessed by conventional MRI and magnetization transfer ratio (MTR) imaging. The left BA 45/46 was selected as the seed region to compute correlation maps with other brain regions. After obtaining the correlation map for each subject, between-group comparisons were performed using random effect procedure. Compared with controls, patients did not show any greater functional connectivity between left BA 45/46 and other regions during PASAT. In contrast, decrease in functional connectivity was observed in patients between left BA 45/46 and left BA 9, right BA 3, and the anterior cingulate cortex (BA 24). In patients, no correlations were found between altered functional connectivity and clinical data. However, functional connectivity observed between left BA 45/46 and BA 24 in patients was correlated with the MTR of normal appearing white matter, and with brain T2 lesion load. Altered functional connectivity is present inside the working memory network of patients at the very early stage of MS and is related to the extent of diffuse white matter changes.
High-frequency modeling of GaN∕SiC blue light-emitting diodes
Authors: Antoranz P. , Miranda J. M. , Sebastián J. L. , Cámara M. , Fonseca V.
Published: April 2005

We report on this work a model to accurately predict the electrical behavior of double-heterostructure GaN∕SiC blue light-emitting diodes up to microwave frequencies. A procedure to extract the series resistance (Rs) from the reflection coefficient is suggested. This procedure offers the advantage of using measurements without any bias current and therefore the obtained values of Rs are influenced neither by the device heating nor by inaccuracies in the calculation of the ideality factor. The junction capacitance and conductance measured in the range 1kHz–10MHz shows two different relaxation mechanisms, and the total capacitance can be fitted very accurately to a double Lorentzian function. Blue light-emitting diodes and lasers based on gallium nitride (GaN) semiconductor compounds represent one of the most important breakthroughs in electronics and optoelectronics of recent years. The combination of silicon carbide (SiC) and GaN has recently enabled low-cost blue-emitting diodes to be introduced in industry.
The elastic and piezoelectric properties of tungsten bronze ferroelectric crystals (Sr0.7Ba0.3)2NaNb5O15 and (Sr0.3Ba0.7)2NaNb5O15
Authors: Jiang Wenhua , Cao Wenwu , Yi Xiujie , Chen Huanchu
Published: April 2005

The elastic and piezoelectric constants of tungsten bronze ferroelectric crystals (Sr0.7Ba0.3)2NaNb5O15 (SBNN70) and (Sr0.3Ba0.7)2NaNb5O15 (SBNN30) are determined by using the ultrasonic and resonance methods. The measured results show that these single crystals have larger dielectric constant and good piezoelectric property compared to other known lead-free perovskite ferroelectric crystals. The measurements show that the SBNN70 has larger dielectric and piezoelectric constants than SBNN30 since the former is near the morphotropic phase boundary composition. Our results confirmed that the SBNN single-crystal system is another good candidate as lead-free piezoelectric and dielectric materials.
Interaction of defects and H in proton-irradiated GaN(Mg, H)
Authors: Myers S. M. , Seager C. H.
Published: April 2005

Magnesium-doped, p-type GaN containing H was irradiated with MeV protons at room temperature and then annealed at a succession of increasing temperatures, with the behavior of defects and H in the material being followed through infrared absorption spectroscopy, nuclear-reaction analysis of the H, and photoluminescence. The results support the annihilation of Ga Frenkel pairs near room temperature, leaving the N interstitial and N vacancy to influence the elevated-temperature behavior. Multiple changes are observed with increasing temperature, ending with thermal release of the H above 700°C. These effects are interpreted in terms of a succession of complexes involving Mg, the point defects, and H.
Sputtered Zn1−xGa2O4:Mn thin-film electroluminescent devices prepared using cadmium-assisted processing
Authors: Flynn M. , Kitai A. H.
Published: April 2005

Incorporating cadmium in the sputtering targets used to grow green-emitting zinc gallate doped with manganese is found to provide improvements in crystallinity, photoluminesience (PL), and electroluminescence (EL) performance, while reducing the annealing temperature requirements. It is shown that as-grown thin films do contain cadmium. The cadmium is then lost during thin-film annealing. The effect of cadmium is interpreted as an enhancement in vacancy concentration during the thin-film annealing process, which improves crystallinity, EL, and PL. X-ray diffraction and microscopy results are carefully studied and discussed.
Tuneability of amplified spontaneous emission through control of the thickness in organic-based waveguides
Authors: Calzado Eva M. , Villalvilla José M. , Boj Pedro G. , Quintana José A. , Díaz-García María A.
Published: April 2005

The thickness dependence of amplified spontaneous emission (ASE) in optically pumped polystyrene films containing 15 wt % of the luminescent and hole-transporting organic molecule N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) is reported. It is observed that the position of ASE can be tuned between 404 and 417 nm by changing the film thickness from 100 to 200 nm. By measuring and modeling the waveguide modes, we demonstrate that the calculated cut-off thickness for the propagation of one mode determine the thickness below which ASE disappears although they do not perfectly correlate with the observed wavelength shifts. Results show that the position of ASE depends on the shape of the photoluminescence spectrum, that is composed of various vibronic peaks whose relative intensities change with film thickness due to the existence of the cut-off thickness. Finally, it is also observed that both the position and the threshold of ASE depend on the different confinement of the propagation modes due to thickness variations.
Fe thin films grown on single-crystal and virtual Ge(001) substrates
Authors: Cantoni M. , Riva M. , Isella G. , Bertacco R. , Ciccacci F.
Published: April 2005

Thin Fe films have been epitaxially grown at room temperature on standard single-crystal Ge(001) substrates and virtual Ge∕Si(001) substrates. Their structural, magnetic, and electronic properties have been investigated in situ by spin-polarized inverse photoemission, x-ray photoemission spectroscopy, x-ray photoelectron diffraction, low-energy electron diffraction, and magneto-optical Kerr effect. In both cases Fe grows in a layer-by-layer fashion with very low Ge incorporation in the film (less than 3%) and the bcc local structure becomes evident for coverage larger than 5 ML. The onset of ferromagnetism appears definitively at 3 ML, while the coercive field and the spin polarization of unoccupied Fe states increase with thickness up to 30 ML. The overall behavior is very similar in the case of standard and virtual substrates, so the latter can be employed for growing high-quality Fe∕Ge interfaces.
Cooling of bulk material by electron-tunneling refrigerators
Authors: Clark A. M. , Miller N. A. , Williams A. , Ruggiero S. T. , Hilton G. C. , Vale L. R. , Beall J. A. , Irwin K. D. , Ullom J. N.
Published: April 2005

Improved refrigeration techniques have lead to scientific discoveries such as superconductivity and Bose-Einstein condensation. Improved refrigeration techniques also enhance our quality of life. Semiconductor processing equipment and magnetic-resonance imaging machines incorporate mechanical coolers operating below 10 K. There is a pressing need for refrigeration techniques to reach even lower temperatures because many next-generation analytical and astronomical instruments will rely on sensors cooled to temperatures near 100 mK. Here we demonstrate a solid-state, on-chip refrigerator capable of reaching 100 mK based on the quantum-mechanical tunneling of electrons through normal metal-insulator-superconductor junctions. The cooling power and temperature reduction of our refrigerator are sufficient for practical applications and we have used it to cool bulk material that has no electrical connection to the refrigerating elements.
Ultrafast carrier capture at room temperature in InAs∕InP quantum dots emitting in the 1.55μm wavelength region
Authors: Bogaart E. W. , Nötzel R. , Gong Q. , Haverkort J. E. M. , Wolter J. H.
Published: April 2005

The energy and excitation density dependence of the carrier dynamics in self-assembled InAs∕InP quantum dots (QDs), emitting in the 1.55μm wavelength region, is investigated by means of time-resolved pump-probe differential reflection spectroscopy at room temperature. We observe ultrafast carrier capture and subsequential carrier relaxation into the QD ground state within 2.5 ps. The carrier lifetime in the QDs strongly depends on the QD optical transition energy within the QD ensemble as well as the carrier density, and ranges from 560 up to 2600 ps.
Retention behavior of the electric-pulse-induced reversible resistance change effect in Ag–La0.7Ca0.3MnO3–Pt sandwiches
Authors: Dong R. , Wang Q. , Chen L. D. , Shang D. S. , Chen T. L. , Li X. M. , Zhang W. Q.
Published: April 2005

Materials showing reversible resistance switching at room temperature are attractive for today’s semiconductor technology with its wide interest in nonvolatile random access memories. In this letter, the retention behavior of the electric-pulse-induced reversible (EPIR) resistance change effect in Ag–La0.7Ca0.3MnO3–Pt sandwiches was demonstrated. The results suggest that the retention property of the EPIR materials depends on both the resistance states and the resistance switching history, and it can be modified using the proper modes of applied electric pulse.
Optical conveyor belt for delivery of submicron objects
Authors: Čižmár Tomáš , Garcés-Chávez Veneranda , Dholakia Kishan , Zemánek Pavel
Published: April 2005

We demonstrate an optical conveyor belt that provides trapping and subsequent precise delivery of several submicron particles over a distance of hundreds of micrometers. This tool is based on a standing wave (SW) created from two counter-propagating nondiffracting beams where the phase of one of the beams can be changed. Therefore, the whole structure of SW nodes and antinodes moves delivering confined micro-objects to specific regions in space. Based on the theoretical calculations, we confirm experimentally that certain sizes of polystyrene particles jump more easily between neighboring axial traps and the influence of the SW is much weaker for certain sizes of trapped object. Moreover, the measured ratios of longitudinal and lateral optical trap stiffnesses are generally an order of magnitude higher compared to the classical single beam optical trap.
Rf-assisted magnetohydrodynamic power generation in a pure-argon plasma
Authors: Murakami Tomoyuki , Okuno Yoshihiro , Yamasaki Hiroyuki
Published: April 2005

We describe seed-free pure-argon-plasma magnetohydrodynamic (MHD) power generation assisted by an external radio-frequency electromagnetic field to enhance the nonequilibrium plasma excitation process. The rf heating induces nonequilibrium ionization under a low total argon-gas temperature at which thermal ionization is insufficient. The rf-assisted plasma, the behavior of which is rather stable, contributes to continuous MHD energy conversion.
Mixing with the radio frequency single-electron transistor
Authors: Swenson L. J. , Schmidt D. R. , Aldridge J. S. , Wood D. K. , Cleland A. N.
Published: April 2005

By configuring a radio frequency single-electron transistor as a mixer, we demonstrate a unique implementation of this device, that achieves good charge sensitivity with large bandwidth about a tunable center frequency. In our implementation we achieve a measurement bandwidth of 16 MHz, with a tunable center frequency from 0 to 1.2 GHz, demonstrated with the transistor operating at 300 mK. Ultimately this device is limited in center frequency by the RC time of the transistor’s center island, which for our device is ∼1.6GHz, close to the measured value. The measurement bandwidth is determined by the quality factor of the readout tank circuit.
A folding-dependent mechanism of antimicrobial peptide resistance to degradation unveiled by solution structure of distinctin
Authors: Raimondo Domenico , Andreotti Giuseppina , Saint Nathalie , Amodeo Pietro , Renzone Giovanni , Sanseverino Marina , Zocchi Ivana , Molle Gerard , Motta Andrea , Scaloni Andrea
Published: April 2005

Many bioactive peptides, presenting an unstructured conformation in aqueous solution, are made resistant to degradation by posttranslational modifications. Here, we describe how molecular oligomerization in aqueous solution can generate a still unknown transport form for amphipathic peptides, which is more compact and resistant to proteases than forms related to any possible monomer. This phenomenon emerged from 3D structure, function, and degradation properties of distinctin, a heterodimeric antimicrobial compound consisting of two peptide chains linked by a disulfide bond. After homodimerization in water, this peptide exhibited a fold consisting of a symmetrical full-parallel four-helix bundle, with a well secluded hydrophobic core and exposed basic residues. This fold significantly stabilizes distinctin against proteases compared with other linear amphipathic peptides, without affecting its antimicrobial, hemolytic, and ion-channel formation properties after membrane interaction. This full-parallel helical orientation represents a perfect compromise between formation of a stable structure in water and requirement of a drastic structural rearrangement in membranes to elicit antimicrobial potential. Thus, distinctin can be claimed as a prototype of a previously unrecognized class of antimicrobial derivatives. These results suggest a critical revision of the role of peptide oligomerization whenever solubility or resistance to proteases is known to affect biological properties.
Positive affect and health-related neuroendocrine, cardiovascular, and inflammatory processes
Authors: Steptoe Andrew , Wardle Jane , Marmot Michael
Published: April 2005

Negative affective states such as depression are associated with premature mortality and increased risk of coronary heart disease, type 2 diabetes, and disability. It has been suggested that positive affective states are protective, but the pathways through which such effects might be mediated are poorly understood. Here we show that positive affect in middle-aged men and women is associated with reduced neuroendocrine, inflammatory, and cardiovascular activity. Positive affect was assessed by aggregating momentary experience samples of happiness over a working day and was inversely related to cortisol output over the day, independently of age, gender, socioeconomic position, body mass, and smoking. Similar patterns were observed on a leisure day. Happiness was also inversely related to heart rate assessed by using ambulatory monitoring methods over the day. Participants underwent mental stress testing in the laboratory, where plasma fibrinogen stress responses were smaller in happier individuals. These effects were independent of psychological distress, supporting the notion that positive well-being is directly related to health-relevant biological processes.
Gain-of-function amino acid substitutions drive positive selection of
FGFR2
mutations in human spermatogonia
Authors: Goriely Anne , McVean Gilean A. T. , van Pelt Ans M. M. , O'Rourke Anthony W. , Wall Steven A. , de Rooij Dirk G. , Wilkie Andrew O. M.
Published: April 2005

Despite the importance of mutation in genetics, there are virtually no experimental data on the occurrence of specific nucleotide substitutions in human gametes. C>G transversions at position 755 of FGF receptor 2 (
FGFR2
) cause Apert syndrome; this mutation, encoding the gain-of-function substitution Ser252Trp, occurs with a birth rate elevated 200- to 800-fold above background and originates exclusively from the unaffected father. We previously demonstrated high levels of both 755C>G and 755C>T
FGFR2
mutations in human sperm and proposed that these particular mutations are enriched because the encoded proteins confer a selective advantage to spermatogonial cells. Here, we examine three corollaries of this hypothesis. First, we show that mutation levels at the adjacent
FGFR2
nucleotides 752-754 are low, excluding any general increase in local mutation rate. Second, we present three instances of double-nucleotide changes involving 755C, expected to be extremely rare as chance events. Two of these double-nucleotide substitutions are shown, either by assessment of the pedigree or by direct analysis of sperm, to have arisen in sequential steps; the third (encoding Ser252Tyr) was predicted from structural considerations. Finally, we demonstrate that both major alternative spliceforms of FGFR2 (
Fgfr2b
and
Fgfr2c
) are expressed in rat spermatogonial stem cell lines. Taken together, these observations show that specific
FGFR2
mutations attain high levels in sperm because they encode proteins with gain-of-function properties, favoring clonal expansion of mutant spermatogonial cells. Among FGFR2 mutations, those causing Apert syndrome may be especially prevalent because they enhance signaling by FGF ligands specific for each of the major expressed isoforms.
The question of C- vs. O-silylation of ketenes: Electrophilic triethylsilylation of diphenylketene
Authors: Prakash G. K. Surya , Bae Chulsung , Rasul Golam , Olah George A.
Published: April 2005

Electrophilic triethylsilylation of diphenylketene leads to exclusive C-silylation giving the diphenyl(triethylsilyl)acetyl cation in the solution phase even though density functional theory calculations at the B3LYP/6-311+G
*
level indicate that the O-silylation of diphenylketene is preferred over C-silylation by 5.4 kcal/mol in the gas phase. On the other hand, in the case of the parent ketene, similar density functional theory calculations show that C-silylation is preferred over O-silylation by 8.2 kcal/mol.
A polymerization-depolymerization model that accurately generates the self-sustained oscillatory system involved in bacterial division site placement
Authors: Drew Donald A. , Osborn Mary J. , Rothfield Lawrence I.
Published: April 2005

Determination of the proper site for division in
Escherichia coli
and other bacteria involves a unique spatial oscillatory system in which membrane-associated structures composed of the MinC, MinD and MinE proteins oscillate rapidly between the two cell poles.
In vitro
evidence indicates that this involves ordered cycles of assembly and disassembly of MinD polymers. We propose a mathematical model to explain this behavior. Unlike previous attempts, the present approach is based on the expected behavior of polymerization-depolymerization systems and incorporates current knowledge of the biochemical properties of MinD and MinE. Simulations based on the model reproduce all of the known topological and temporal characteristics of the
in vivo
oscillatory system.
A novel stop codon readthrough mechanism produces functional Headcase protein in Drosophila trachea
Authors: Steneberg Pär , Samakovlis Christos
Published: April 2005

Translational regulation provides an efficient means to control the localization and production of proteins. The headcase (hdc) mRNA in Drosophila generates two overlapping proteins as a result of translational readthrough of an internal UAA stop codon. This readthrough event is necessary for the function of hdc as a branching inhibitor during tracheal development. By ectopic expression of different Hdc proteins in the trachea, we show that the long Hdc form alone, can function as a potent branching inhibitor whose activity is proportional to its amount. The suppression of termination in the hdc mRNA is not stop‐codon dependent, suggesting that the readthrough does not involve codon specific suppressors. We have identified an 80 nucleotide sequence immediately downstream of the UAA, which is necessary and sufficient to confer termination readthrough in a heterologous mRNA. We present a novel mechanism of eukaryotic translational termination suppression that may regulate the amount of functional Hdc.
Metaxin is required for tumor necrosis factor‐induced cell death
Authors: Wang Xiaofei , Ono Koh , Ouk Kim Sung , Kravchenko Vladimir , Lin Sheng‐Cai , Han Jiahuai
Published: April 2005

We used retrovirus insertion‐mediated random mutagenesis and tumor necrosis factor (TNF) selection to generate TNF‐resistant lines from L929 cells. The metaxin gene, which encodes a protein located on the outer membrane of mitochondria, was identified to be the gene disrupted in one of the resistant lines. The requirement of metaxin in TNF‐induced cell death of L929 was confirmed by the restoration of TNF sensitivity after ectopic reconstitution of metaxin expression. Analysis of the cell death induced by other stimuli revealed that metaxin deficiency‐mediated death resistance was selective to certain stimuli. Studies using deletion mutants of metaxin showed that mitochondrial association of metaxin is required for the function of metaxin. Over‐expression of truncated metaxin lacking the mitochondria anchoring sequence mimicked metaxin deficiency in wild‐type cells. Interfering with metaxin prevented TNF‐induced necrotic cell death in L929 cells and apoptosis in MCF‐7 cells. Our work has thus defined a novel component in the death pathway used by TNF and some other death stimuli.
The Pricing of Dividends in Equity Valuation
Authors: Hand John R. M. , Landsman Wayne R.
Published: April 2005

Abstract:  This study uses Ohlson's (1995 and 2001) accounting‐based equity valuation model to structure tests of four explanations for the anomalously positive pricing of dividends reported by Rees (1997) and Fama and French (1998). First, we find that dividends are not simply a proxy for publicly available information that helps predict future abnormal earnings. Second, although dividends act as if they signal managers’ private information about future profitability, they remain positively priced for firms with low incentives to signal. Third, dividends do not signal management's willingness to abstain from incurring agency costs. Fourth, however, controlling for one‐year‐ahead realized forecast errors yields a pricing of dividends that is very close to that of dividend displacement. After showing that dividends are not simply a proxy for analysts’ misforecasting, we conclude that dividends appear to be positively priced because they are a proxy for the mispricing by investors of current earnings or book equity.
Cost of Capital, Strategic Disclosures and Accounting Choice
Authors: Gietzmann M. , Ireland J.
Published: April 2005

Abstract:  Theory suggests a negative relationship between disclosure and the cost of capital. However, empirical research has not, in general, confirmed this. In particular, Botosan (1997) finds no evidence of a negative relationship for firms with a high analyst following, and moreover, Botosan and Plumlee (2002a) find that firms’ cost of capital increases with timely disclosures. There are several possible explanations for this puzzle. First, the theory‐driven hypothesis may be false and require re‐specification. Second, there may be correlated omitted variables contaminating the results. Finally, these inconclusive results may have arisen due to problems with the measurement of disclosure. We construct an innovative measure of timely disclosure, that attempts to capture quality rather than quantity of strategic disclosures. In addition, motivated by new theoretical research by Gietzmann and Trombetta (2003), we control for a possible omitted variable, namely accounting policy choice. With this revised research design, we find the expected negative relationship. Furthermore, as predicted by Gietzmann and Trombetta, this relationship is only significant for firms adopting aggressive accounting policies.
Performance of Private to Public MBOs: The Role of Venture Capital
Authors: Jelic Ranko , Saadouni Brahim , Wright Mike
Published: April 2005

Abstract:  Using a unique dataset, we examine financial performance, and venture capital involvement in 167 MBOs exiting through IPOs (MBO‐IPOs) on the London Stock Exchange, during the period 1964 –1997. VC backed MBOs seem to be more underpriced than MBOs without venture capital backing, based on average value‐weighted returns. MBOs backed by highly reputable VCs tend to be older companies, and exit earlier than MBOs backed by less reputable VCs. The results contradict ‘certification’ and ‘grandstanding’ hypotheses supported by US data (Megginson and Weiss, 1991; and Gompers, 1996, respectively). We found no evidence of either significant underperformance, or that VC backed MBOs perform better than their non‐VC backed counterparts in the long run. However, MBOs backed by highly reputable venture capital firms seem to be better long‐term investments as compared to those backed by less prestigious venture capitalist firms. The results remain robust after using different methods to measure performance, and after controlling for sample selectivity bias.
Identification of a novel cis‐acting element conferring sulfur deficiency response in Arabidopsis roots
Authors: Maruyama‐Nakashita Akiko , Nakamura Yumiko , Watanabe‐Takahashi Akiko , Inoue Eri , Yamaya Tomoyuki , Takahashi Hideki
Published: April 2005

SULTR1;1 high‐affinity sulfate transporter is highly regulated in the epidermis and cortex of Arabidopsis roots responding to sulfur deficiency (−S). We identified a novel cis‐acting element involved in the −S‐inducible expression of sulfur‐responsive genes in Arabidopsis. The promoter region of SULTR1;1 was dissected for deletion and gain‐of‐function analysis using luciferase (LUC) reporter gene in transgenic Arabidopsis. The 16‐bp sulfur‐responsive element (SURE) from −2777 to −2762 of SULTR1;1 promoter was sufficient and necessary for the −S‐responsive expression, which was reversed when supplied with cysteine and glutathione (GSH). The SURE sequence contained an auxin response factor (ARF) binding sequence (GAGACA). However, SURE was not responsive to naphthalene acetic acid, indicating its specific function in the sulfur response. The base substitution analysis indicated the significance of a 5‐bp sequence (GAGAC) within the conserved ARF binding site as a core element for the −S response. Microarray analysis of early −S response in Arabidopsis roots indicated the presence of SURE core sequences in the promoter regions of −S‐inducible genes on a full genome GeneChip array. It is suggested that SURE core sequences may commonly regulate the expression of a gene set required for adaptation to the −S environment.
A secreted lipase of Fusarium graminearum is a virulence factor required for infection of cereals
Authors: Voigt Christian A. , Schäfer Wilhelm , Salomon Siegfried
Published: April 2005

Fusarium graminearum is the causal agent of the Fusarium head blight (FHB) and a destructive pathogen of cereals accounting for high grain yield losses especially on wheat and maize. Like other fungal pathogens, F. graminearum secretes various extracellular enzymes, which are hypothesized to be involved in host infection. Extracellular lipolytic activity of F. graminearum was strongly induced in culture by wheat germ oil; this allowed us to isolate, clone, and characterize a gene (FGL1) encoding a secreted lipase. Expression analysis indicated that FGL1 is induced by lipid‐containing substrates and repressed by glucose. In planta, FGL1 transcription was detected 1 day post‐infection of wheat spikes. The function of the FGL1 gene product was verified by specifically demonstrating lipase activity after expression in a heterologous host. Ebelactone B, a known lipase inhibitor, repressed the lipolytic activity of the enzyme. Disease severity was strongly reduced when wild‐type conidia were supplemented with ebelactone B. Transformation‐mediated disruption of FGL1 led to reduced extracellular lipolytic activity in culture and to reduced virulence to both wheat and maize.