bluuebunny/crossref_metadata_2025 huggingface dataset:
Human-like control strategy of a bipedal walking model
Authors: Olenšek Andrej , Matjačić Zlatko
Published: December 2007

This paper presents a two-level control strategy for bipedal walking mechanism that accounts for implicit control of push-off on the between-step control level and tracking of imposed holonomic constraints on kinematic variables via feedback control on within-step control level. The proposed control strategy was tested in a biologically inspired model with minimal set of segments that allows evolution of human-like push-off and power absorption. We investigated controller's stability characteristics by using Poincaré return map analysis in eight simulation cases and further evaluated the performance of the biped walking model in terms of how variations in torso position and gait velocity relate to push-off and power absorption. The results show that the proposed control strategy, with the same set of controller's gains, enables stable walking in a variety of chosen gait parameters and can accommodate to various trunk inclinations and gait velocities in a similar way as seen in humans.
Prediction of stress in fillet portion of spur gears using artificial neural networks
Authors: Shunmugam M.S. , Prasad N. Siva
Published: December 2007

A fillet curve is provided at the root of the spur gear tooth, as stresses are high in this portion. The fillet curve may be a trochoid or an arc of suitable size as specified by designer. The fillet stress is influenced by the fillet geometry as well as the number of teeth, modules, and the pressure angle of the gear. Because the relationship is nonlinear and complex, an artificial neural network and a backpropagation algorithm are used in the present work to predict the fillet stresses. Training data are obtained from finite element simulations that are greatly reduced using Taguchi's design of experiments. Each simulation takes around 30 min. The 4-5-1 network and a sigmoid activation function are chosen. TRAINLM function is used for training the network with a learning rate parameter of 0.01 and a momentum constant of 0.8. The neural network is able to predict the fillet stresses in 0.03 s with reasonable accuracy for spur gears having 25–125 teeth, a 1–5 mm module, a 0.05–0.45 mm fillet radius, and a 15°–25° pressure angle.
Roll waves and plugs in two-layer flows
Authors: BOUDLAL A.
Published: December 2007

In this paper I consider a system of equations describing two stratified fluids flowing in closed, slightly inclined ducts. In the framework of the shallow water approximation with turbulent friction acting on the wall and at the interface, I investigate a special class of periodic travelling waves containing stable moving jumps, namely, roll waves and periodic slug flows. The modulation equations of roll waves and slugs are derived and a nonlinear stability criterion is obtained. As for plug flow, only a gas–liquid system is considered. The stability criterion is expressed in terms of an integro-differential relation. For self-similar cross-section, this criterion is simplified to a relation for a function of one variable only.
Assisting Practice Development in Africa
Authors: Woodhead Kate
Published: December 2007

ABSTRACT

Friends of African Nursing (FoAN) is a small UK based charity which has been teaching perioperative nurses in Africa since 2001. Run entirely by volunteers from amongst the UK perioperative community, it aims to leave a sustainable legacy of educational resource to African nurses working in difficult and sometimes impossible conditions without access to continuing education. This article describes the appalling clinical conditions in which the nurses have to work and the educational framework which has been developed by FoAN to support the nurses learning needs and how that is delivered.
A Study into Postoperative Urine Retention in the Recovery Ward
Authors: Olsen Susanne Winther , Nielsen Jette
Published: December 2007

ABSTRACT

On the basis of hypothesis from our own practice, a study dealing with postoperative urine retention (PUR) in patients in the recovery ward was completed during 2006 in Odense University Hospital.

Three hundred and seven patients took part in the study with a view to monitoring the occurrence of PUR and to identify the relationship between risk factors and the development of PUR. Defining PUR as >300 mL in the bladder with the inability to urinate, the study showed that 28.7% of the patients had PUR at arrival to the recovery ward.

The study showed a positive correlation between patients with ascending age, rising anaesthesia duration, regional anaesthesia (RA) and developing PUR.

PUR occurred in half of the patients with diabetes and approximately half of the patients treated with ephedrine. Furthermore, the type of surgery had significance, as considerably more patients with plastic and orthopaedic surgery developed PUR. On the other hand, the study showed no correlation between subjective symptoms, e.g. like a strong desire to void, and the occurrence of PUR.

The results highlight the necessity for greater attention to screening patients for PUR.
Effects of ozone cooling in the tropical lower stratosphere and upper troposphere
Authors: Forster Piers M. , Bodeker Greg , Schofield Robyn , Solomon Susan , Thompson David
Published: December 2007

In this paper, we examine the tropical lower stratosphere and upper troposphere and elucidate the key role of ozone changes in driving temperature trends in this region. We use a radiative fixed dynamical heating model to show that the effects of tropical ozone decreases at 70 hPa and lower pressures can lead to significant cooling not only at stratospheric levels, but also in the “sub‐stratosphere/upper tropospheric” region around 150–70 hPa. The impact of stratospheric ozone depletion on upper tropospheric temperatures stems from reduced longwave emission from above. The results provide a possible explanation for the long‐standing discrepancy between modeled and measured temperature trends in the uppermost tropical troposphere and can explain the latitudinal near‐homogeneity of recent stratospheric temperature trends.
A general fractal model of flow and solute transport in randomly heterogeneous porous media
Authors: Chen Kuan‐Chih , Hsu Kuo‐Chin
Published: December 2007

One of the challenges of hydrology is modeling flow and solute transport through media that are not uniformly porous. This paper proposes a general fractal model of flow and solute transport in randomly heterogeneous porous media. We describe the random field using fractional Levy motion (fLm), which more effectively represents a field with a high degree of variability. Understanding flow and solute transport in the fLm field expands the applicability of stochastic theory. Following the work of V. Di Federico and S. P. Neuman (1997) and V. Di Federico et al. (1999), we derive truncated isotropic and anisotropic power variograms for the fLm fields. The results are analogous to but more general than those of fractional Brownian motion (fBm) (V. Di Federico and S. P. Neuman (1997) and V. Di Federico et al. (1999)). For a random field, when the Levy index α in fLm is replaced by a constant of 2, fBm is recovered. This study employs first‐order perturbation analyses of flow and solute transport in two‐dimensional fLm fields. For the stationary, fBm, and fLm fields, macrodispersion coefficients are compared. The plume is found to grow slowest in the fLm field but will show highest concentration. The proposed fractal model is general in the sense that when the Levy index of fLm α equals 2, the results of flow and solute transport for the commonly used fBm model are recovered. When the upper cutoff of the truncated power variogram is close to the lower cutoff, the results for the stationary exponential or Gaussian model can be well approximated. Since the proposed general fractal model has broader applications than the stationary and fBm models, it simulates flow and solute transport in more different scenarios to yield more accurate modeling results.
Imaging studies of the photodissociation of H2S+ cations. II
Authors: Webb Alexander D. , Kawanaka Noboru , Dixon Richard N. , Ashfold Michael N. R.
Published: December 2007

Ion imaging methods have been used to explore the photodissociation dynamics of state-selected H2S+ and D2S+ cations. Predissociation following one photon excitation to the ÃA12 state at wavelengths (385⩽λphot⩽420nm) in the vicinity of the first dissociation threshold results in formation of ground state S+ fragment ions; the partner H2(D2) fragments are deduced to be rotationally “cold.” Two photon dissociation processes are also observed, resonance enhanced at the energy of one absorbed photon by the predissociating Ã state levels. Two photon excitation at these wavelengths is deduced to populate an excited state of A12 symmetry, which dissociates to electronically excited S+(D2) products, together with vibrationally excited H2(D2) cofragments. Ground state SH+(SD+) fragments, attributable to a one photon dissociation process, are observed once λphot⩽325nm. Two photon induced production of SH+(SD+) fragments is also observed, at all wavelengths studied (i.e., at all λphot⩽420nm). These SH+(SD+) fragments are deduced to be formed in their singlet (i.e., aΔ1 and bΣ+1) excited states, with high levels of rotational excitation. The observed product branching and energy disposals are discussed within the context of the (limited) available knowledge relating to the excited electronic states of the H2S+ cation.
Site-dependent electron-stimulated reactions in water films on TiO2(110)
Authors: Lane Christopher D. , Petrik Nikolay G. , Orlando Thomas M. , Kimmel Greg A.
Published: December 2007

Electron-stimulated reactions in thin [<3 ML (monolayer)] water films adsorbed on TiO2(110) are investigated. Irradiation with 100eV electrons results in electron-stimulated dissociation and electron-stimulated desorption (ESD) of adsorbed water molecules. The molecular water ESD yield increases linearly with water coverage θ for 0⩽θ⩽1 ML and 1<θ⩽2 ML. However, for θ>1 ML, the water ESD yield per additional water molecule adsorbed (i.e., the slope of the ESD yield versus coverage) is 3.5 times larger than for θ<1 ML. In contrast, the number of water molecules dissociated per incident electron increases linearly for θ⩽2 ML without changing slope at θ=1 ML. The total electron-stimulated sputtering rate, as measured by postirradiation temperature programed desorption of the remaining water, is larger for θ>1 ML due to the increased water ESD for those coverages. The water ESD yields versus electron energy (for 5–50eV) are qualitatively similar for 1, 2, and 40 ML water films. In each case, the observed ESD threshold is at ∼10eV and the yield increases monotonically with increasing electron energy. The results indicate that excitations in the adsorbed water layer are primarily responsible for the ESD in thin water films on TiO2(110). Experiments on “isotopically layered” films with D2O adsorbed on the Ti4+ sites (D2OTi) and H2O adsorbed on the bridging oxygen atoms (H2OBBO) demonstrate that increasing the water coverage above 1 ML rapidly suppresses the electron-stimulated desorption of D2OTi and D atoms, despite the fact that the total water ESD and atomic hydrogen ESD yields increase with increasing coverage. The coverage dependence of the electron-stimulated reactions is probably related to the different bonding geometries for H2OTi and H2OBBO and its influence on the desorption probability of the reaction products.
Rydberg spectra of trans-1,2-dibromoethylene
Authors: Shi W. , Lipson R. H.
Published: December 2007

( 2 + 1 ) resonance-enhanced multiphoton ionization spectra of jet-cooled trans-1,2-dibromoethylene are reported for the first time. The two-photon spectral region between 149.7 and 141.2nm was examined. A 4pz←π Rydberg transition between 66 800 and 68000cm−1 with Ag excited state symmetry was analyzed, as well as two 4f←π Rydberg transitions with Bg excited state symmetry and one 4f←π Rydberg transition with Ag excited state symmetry between 68 000 and 70800cm−1. All Rydberg transitions observed in this work belong to series that converge to the first ionization potential of the molecule. The short vibrational progressions observed involve two totally symmetric in-plane normal modes: CC–H bending (ν3) and CC–Br bending (ν5) with average excited state frequencies of 829 and 226cm−1, respectively.
Raman imaging of doping domains in graphene on SiO2
Authors: Stampfer C. , Molitor F. , Graf D. , Ensslin K. , Jungen A. , Hierold C. , Wirtz L.
Published: December 2007

We present spatially resolved Raman images of the G and 2D lines of single-layer graphene flakes. The spatial fluctuations of G and 2D lines are correlated and are thus shown to be affiliated with local doping domains. We investigate the position of the 2D line—the most significant Raman peak to identify single-layer graphene—as a function of charging up to ∣n∣≈4×1012cm−2. Contrary to the G line which exhibits a strong and symmetric stiffening with respect to electron and hole doping, the 2D line shows a weak and slightly asymmetric stiffening for low doping. Additionally, the linewidth of the 2D line is, in contrast to the G line, doping independent making this quantity a reliable measure for identifying single-layer graphene.
Frequency multiplication of light back-reflected from a relativistic wake wave
Authors: Pirozhkov A. S. , Ma J. , Kando M. , Esirkepov T. Zh. , Fukuda Y. , Chen L.-M. , Daito I. , Ogura K. , Homma T. , Hayashi Y. , Kotaki H. , Sagisaka A. , Mori M. , Koga J. K. , Kawachi T. , Daido H. , Bulanov S. V. , Kimura T. , Kato Y. , Tajima T.
Published: December 2007

A method of coherent high-frequency electromagnetic radiation generation, proposed by Bulanov, Esirkepov, and Tajima [Phys. Rev. Lett. 91, 085001 (2003)], is experimentally demonstrated. This method is based on the radiation frequency multiplication during reflection at a mirror flying with relativistic velocity. The relativistic mirror is formed by the electron density modulations in a strongly nonlinear wake wave, excited in an underdense plasma in the wake behind an ultrashort laser pulse. In our experiments, the reflection of a countercrossing laser pulse from the wake wave is observed. The detected frequency multiplication factor is in the range from 55 to 114, corresponding to a reflected radiation wavelength from 7 to 15nm. This may open a way towards tunable high-intensity sources of ultrashort coherent electromagnetic pulses in the extreme ultraviolet and x-ray spectral regions. Parameters of the reflecting wake wave can be determined using the reflected radiation as a probe.
A promising p-type transparent conducting material: Layered oxysulfide [Cu2S2][Sr3Sc2O5]
Authors: Liu Min-Ling , Wu Li-Bin , Huang Fu-Qiang , Chen Li-Dong , Chen I.-Wei
Published: December 2007

Sr 3 Cu 2 Sc 2 O 5 S 2 , a layered oxysulfide, composed of anti-PbO-like [Cu2S2] slabs alternating with perovskitelike [Sr3Sc2O5] slabs, was systematically studied as a p-type transparent conducting material. The material has a wide energy gap of 3.1eV and a p-type electrical conductivity of 2.8Scm−1 at room temperature. The hole mobility of +150cm2V−1S−1 at room temperature, which is much higher than the typical value of ∼10−1–10cm2V−1S−1 found in other copper compounds. The performances of bulk undoped Sr3Cu2Sc2O5S2 show the promise of copper oxysulfides as a class of p-type transparent conductive materials that is essential for optoelectronic applications.
Analysis of the constant-excitation mode in frequency-modulation atomic force microscopy with active Q-Control applied in ambient conditions and liquids
Authors: Ebeling D. , Hölscher H.
Published: December 2007

The constant-excitation mode of the frequency modulation technique can be used to perform atomic force microscopy experiments in vacuum, air, and liquids. Adding an additional Q-Control feedback to the cantilever driving the effective Q-factor of the cantilever can be increased. This is especially useful for applications in air and liquids where the cantilever is damped by the surrounding medium. Here, we present an experimental and theoretical analysis of this technique. Based on the analytical solution of the equation of motion, we give an explicit formula for the tip-sample indentation for a Hertzian tip-sample force. In addition, we studied the imaging capabilities of the new operation mode in liquids, which revealed a significantly smaller tip-sample indentation for increased effective Q-factors. Furthermore, we measured the tip-sample interaction force between a silicon tip and a graphite(0001) surface in water with and without Q-Control.
Spin-dependent scattering off neutral antimony donors in Si28 field-effect transistors
Authors: Lo C. C. , Bokor J. , Schenkel T. , Tyryshkin A. M. , Lyon S. A.
Published: December 2007

We report measurements of spin-dependent scattering of conduction electrons by neutral donors in accumulation-mode field-effect transistors formed in isotopically enriched silicon. Spin-dependent scattering was detected using electrically detected magnetic resonance where spectra show resonant changes in the source-drain voltage for conduction electrons and electrons bound to donors. We discuss the utilization of spin-dependent scattering for the readout of donor spin states in silicon based quantum computers.
H
1
nuclear magnetic resonance study of the benzene ring vibration in poly(phenylenevinylene)
Authors: Bang H. S. , Oh I. H. , Lee K. W. , Han J. H. , Lee Cheol Eui , Jin J.-I.
Published: December 2007

The benzene ring vibrational motion in poly(phenylenevinylene) has been studied by H1 nuclear magnetic resonance (NMR) measurements. By employing a simple model of the out-of-plane phenylene oscillation giving rise to a change in the dipolar splitting of the H1 NMR line shape, the oscillation angle of the benzene ring was obtained as a function of temperature.
Study of BNKLBT-1.5 lead-free ceramic/epoxy 1-3 composites
Authors: Choy S. H. , Li W. K. , Li H. K. , Lam K. H. , Chan H. L. W.
Published: December 2007

Bismuth sodium titanate based lead-free ceramic fiber with the chemical formula of 0.885(Bi0.5Na0.5)TiO3–0.05(Bi0.5K0.5)TiO3–0.015(Bi0.5Li0.5)TiO3–0.05BaTiO3, BNKLBT-1.5, has been fabricated by a powder-based extrusion method. The ceramic fibers with 400μm diameter were well crystallized after being calcined at 800°C and sintered at 1170°C. The piezoelectric and ferroelectric properties of the single fiber were found to be 155pC∕N and ∼34.5μC∕cm2, respectively, which is comparable with that in bulk sample. 1-3 ceramic/polymer composites were fabricated by two routes, including dice and filled method and fiber pick-and-place method. Theoretical models were used to calculate the piezoelectric properties of the composites and compared with experimental results.
Magnetomagnon resonances and oscillations of conductivity in diluted magnetic semiconductor quantum wires
Authors: Souto E. , Nunes O. A. C. , Fonseca A. L. A. , Agrello D. A. , da Silva E. F.
Published: December 2007

We set up a theory of magnetomagnon resonances in diluted magnetic semiconductor quantum wires in the case of electron-magnon scattering. The magnetoconductivity σxx is calculated using the usual Kubo formula. We found that for a nondegenerate statistics of quasi-one-dimensional electron gas σxx shows oscillatory behavior characteristic of structures presenting manifestations of the size quantization effect in the presence of a quantizing magnetic field. Moreover, magnetomagnon resonances are predicted in the σxx behavior as function of the electron cyclotron frequency. Another contribution to the conductivity σpc, which is caused by the current carried by electron motion affected by the confinement potential, is calculated. As the confinement potential increases, for a fixed magnetic field value, σpc decreases steeply similar to the case of GaAs quantum wires. For typical parameters of a Ga1−xMnxAs quantum wire we find σxx=10−9S for a magnetic field of 10T and temperature T=20K. This magnon effect is two orders of magnitude greater than the magnetoconductivity due to phonons as reported in the literature thereby implying that in diluted magnetic semiconductor Ga1−xMnxAs quantum wires the exchange interaction is the main electron interaction channel.
Collector characteristics and the differential optical gain of a quantum-well transistor laser
Authors: Then H. W. , Walter G. , Feng M. , Holonyak N.
Published: December 2007

The collector electrical characteristics (I-V) of a transistor laser (TL) manifest directly the transport and recombination dynamics of the vital quantum-well (QW) base region, including as described here QW recombination state changes. By employing the continuity equations and an extension of the classic charge control model, we extract from the dc I-V characteristics the differential optical gain of a single QW TL showing the QW state changes. The results agree in form with calculations employing Fermi’s golden rule and the “staircaselike” density of states of a QW.
Assessment of the risk of inadvertently exporting from Australia a genetically modified immunocontraceptive virus in live mice (Mus musculus domesticus)
Authors: Williams C. K.
Published: December 2007

Controlling mouse plagues in the Australian grain-growing regions using a proposed species-specific, genetically modified, immunocontraceptive (IC) murine cytomegalovirus (icMCMV) may risk infected mice infesting export cargo and, subsequently in other countries, infecting closely related, susceptible and valued Mus species. This paper uses simple simulation models to examine (a) how design of an IC virus and deployment strategy could affect the likelihood of inadvertent export, and (b) where intervention may minimise the likelihood of export effectively and economically. Field efficacy is best in an IC virus with an immunocontraceptive efficacy of 75–100% and high transmissibility, and the likelihood of export is lower than for some less efficacious designs. Greatest likelihood of export arises from using an IC virus with low (or zero) immunocontraceptive efficacy and high transmissibility. Lower transmissibility of the IC virus relative to field strains reduces field efficacy and the likelihood of export. Conversely, higher relative transmissibility increases field efficacy and modestly increases the likelihood of export. Effective control of mice in the field requires the IC virus to infect a high proportion of the mouse population while numbers are very low. Deviation from this strategy through (a) underestimation of mouse abundance, and (b) late deployment during population increase, diminishes effectiveness in the field and increases the likelihood of export. Intervention at ports seems the most effective strategy to mitigate export risk. Australian legislation and codes of practice specify export quarantine procedures for particular types of goods but are silent for others. Current practices for shipping container movements also leave gaps in the export quarantine barrier.
Prospects for the future: is there a role for virally vectored immunocontraception in vertebrate pest management?
Authors: McLeod S. R. , Saunders G. , Twigg L. E. , Arthur A. D. , Ramsey D. , Hinds L. A.
Published: December 2007

Virally vectored immunocontraception (VVIC) has been studied and promoted as an alternative to lethal methods for vertebrate pest control in Australia and New Zealand. Virally vectored immunocontraception offers a potentially humane and species-specific control method with potential for a good benefit–cost outcome, but its applicability for broad-scale management remains unknown. We present case studies for the house mouse, European rabbit, red fox and common brushtail possum and describe the current status of research into the use of VVIC as a broad-scale pest-management tool. All case studies indicated that there are significant problems with delivery and efficacy. The current state of development suggests that VVIC is not presently a viable alternative for the management of these vertebrate pests, and it is highly unlikely that this will change in the foreseeable future. An absence of benefit–cost data also hinders decision-making, and until benefit–cost data become available it will not be clear if there are short- or long-term benefits resulting from the use of VVIC for broad-scale pest management.
The genetic basis of a plant–insect coevolutionary key innovation
Authors: Wheat Christopher W. , Vogel Heiko , Wittstock Ute , Braby Michael F. , Underwood Dessie , Mitchell-Olds Thomas
Published: December 2007

Ehrlich and Raven formally introduced the concept of stepwise coevolution using butterfly and angiosperm interactions in an attempt to account for the impressive biological diversity of these groups. However, many biologists currently envision butterflies evolving 50 to 30 million years (Myr) after the major angiosperm radiation and thus reject coevolutionary origins of butterfly biodiversity. The unresolved central tenet of Ehrlich and Raven's theory is that evolution of plant chemical defenses is followed closely by biochemical adaptation in insect herbivores, and that newly evolved detoxification mechanisms result in adaptive radiation of herbivore lineages. Using one of their original butterfly-host plant systems, the Pieridae, we identify a pierid glucosinolate detoxification mechanism, nitrile-specifier protein (NSP), as a key innovation. Larval NSP activity matches the distribution of glucosinolate in their host plants. Moreover, by using five different temporal estimates, NSP seems to have evolved shortly after the evolution of the host plant group (Brassicales) (≈10 Myr). An adaptive radiation of these glucosinolate-feeding Pierinae followed, resulting in significantly elevated species numbers compared with related clades. Mechanistic understanding in its proper historical context documents more ancient and dynamic plant–insect interactions than previously envisioned. Moreover, these mechanistic insights provide the tools for detailed molecular studies of coevolution from both the plant and insect perspectives.
Oncogenic H-Ras V12 promotes anchorage-independent cytokinesis in human fibroblasts
Authors: Thullberg Minna , Gad Annica , Le Guyader Sylvie , Strömblad Staffan
Published: December 2007

Cell anchorage is required for cell proliferation of untransformed cells, whereas anchorage-independent growth can be induced by oncogenes and is a hallmark of transformation. Whereas anchorage-dependent control of the progression of the G
1
phase of the cell cycle has been extensively studied, it is less clear whether and how anchorage may control other cell cycle phases and whether oncogenes may affect such controls. Here, we found that lack of cell anchorage did not influence progression through the cell cycle S phase, G
2
phase, or most of mitosis of primary human fibroblasts. However, unanchored fibroblasts could not complete cytokinesis. The cleavage furrow and central spindle were still formed in the absence of anchorage, but cells were unable to complete ingression, causing binucleation. Importantly, V12 H-Ras-transformed fibroblasts and two cancer cell lines progressed through the entire cell cycle without anchorage, including through cytokinesis. This indicates that oncogenic signaling may contribute to anchorage-independent growth and tumorigenesis by promoting the final cleavage furrow ingression during cytokinesis.
Dodecamer rotor ring defines H
+
/ATP ratio for ATP synthesis of prokaryotic V-ATPase from
Thermus thermophilus
Authors: Toei Masashi , Gerle Christoph , Nakano Masahiro , Tani Kazutoshi , Gyobu Nobuhiko , Tamakoshi Masatada , Sone Nobuhito , Yoshida Masasuke , Fujiyoshi Yoshinori , Mitsuoka Kaoru , Yokoyama Ken
Published: December 2007

ATP synthesis by V-ATPase from the thermophilic bacterium
Thermus thermophilus
driven by the acid-base transition was investigated. The rate of ATP synthesis increased in parallel with the increase in proton motive force (PMF) >110 mV, which is composed of a difference in proton concentration (ΔpH) and the electrical potential differences (ΔΨ) across membranes. The optimum rate of synthesis reached 85 s
−1
, and the H
+
/ATP ratio of 4.0 ± 0.1 was obtained. ATP was synthesized at a considerable rate solely by ΔpH, indicating ΔΨ was not absolutely required for synthesis. Consistent with the H
+
/ATP ratio, cryoelectron micrograph images of 2D crystals of the membrane-bound rotor ring of the V-ATPase at 7.0-Å resolution showed the presence of 12 V
o
-c subunits, each composed of two transmembrane helices. These results indicate that symmetry mismatch between the rotor and catalytic domains is not obligatory for rotary ATPases/synthases.
A unified framework for linkage and association analysis of quantitative traits
Authors: Dupuis Josée , Siegmund David O. , Yakir Benjamin
Published: December 2007

We give a unified treatment of the statistical foundations of population based association mapping and of family based linkage mapping of quantitative traits in humans. A central ingredient in the unification involves the efficient score statistic. The discussion focuses on generalized linear models with an additional illustration of the Cox (proportional hazards) model for age of onset data. We give analytic expressions for noncentrality parameters and show how they give qualitative insight into the loss of power that occurs if the scientist‘s assumed genetic model differs from nature's “true” genetic model. Issues to be studied in detail in the future development of this approach are discussed.
Prion strain discrimination in cell culture: The cell panel assay
Authors: Mahal Sukhvir P. , Baker Christopher A. , Demczyk Cheryl A. , Smith Emery W. , Julius Christian , Weissmann Charles
Published: December 2007

Prions are thought to consist mainly or entirely of misfolded PrP, a constitutively expressed host protein. Prions associated with the same PrP sequence may occur in the form of different strains; the strain phenotype is believed to be encoded by the conformation of the PrP. Some cell lines can be persistently infected by prions and, interestingly, show preference for certain strains. We report that a cloned murine neuroblastoma cell population, N2a-PK1, is highly heterogeneous in regard to its susceptibility to RML and 22L prions. Remarkably, sibling subclones may show very different relative susceptibilities to the two strains, indicating that the responses can vary independently. We have assembled four cell lines, N2a-PK1, N2a-R33, LD9 and CAD5, which show widely different responses to prion strains RML, 22L, 301C, and Me7, into a panel that allows their discrimination
in vitro
within 2 weeks, using the standard scrapie cell assay (SSCA).
Notch regulates cell fate and dendrite morphology of newborn neurons in the postnatal dentate gyrus
Authors: Breunig Joshua J. , Silbereis John , Vaccarino Flora M. , Šestan Nenad , Rakic Pasko
Published: December 2007

The lifelong addition of neurons to the hippocampus is a remarkable form of structural plasticity, yet the molecular controls over proliferation, neuronal fate determination, survival, and maturation are poorly understood. Expression of Notch1 was found to change dynamically depending on the differentiation state of neural precursor cells. Through the use of inducible gain- and loss-of-function of Notch1 mice we show that this membrane receptor is essential to these distinct processes. We found
in vivo
that activated Notch1 overexpression induces proliferation, whereas γ-secretase inhibition or genetic ablation of Notch1 promotes cell cycle exit, indicating that the level of activated Notch1 regulates the magnitude of neurogenesis from postnatal progenitor cells. Abrogation of Notch signaling
in vivo
or
in vitro
leads to a transition from neural stem or precursor cells to transit-amplifying cells or neurons. Further, genetic Notch1 manipulation modulates survival and dendritic morphology of newborn granule cells. These results provide evidence for the expansive prevalence of Notch signaling in hippocampal morphogenesis and plasticity, suggesting that Notch1 could be a target of diverse traumatic and environmental modulators of adult neurogenesis.
CHANGING SPATIAL RELATIONS IN THE BALTIC REGION AND THE ROLE OF THE MEDIA
Authors: Vihalemm Peeter
Published: December 2007

This article presents an analysis of changing spatial relations in the Baltic region from an Estonian viewpoint. Changes in spatial relations during the last decade are indicated by the density of personal contacts, news flows, cultural exchanges and trade relations between Estonia and other countries. The empirical analysis is based on statistical data and survey results. Analysis of media content has been conducted to reveal the level of attention given to different foreign countries. The results show that the structure of mediated spatial relations differs from the social space of practical interactions between people. The spaces of direct economic relations and personal contacts in Estonia are centred on the Baltic Sea, illustrated by the dominant roles of Finland and Sweden, an increasing proximity to other EU countries and the weakening role of Russia. At the same time the mediated social space of Estonia is changing following EU enlargement; from the representation of a bi-polar world dominated by political centres located in Russia and USA towards a multi-centred international space, demonstrated in the growing influence of core EU countries.
THE BIRTH OF A EUROPEAN PUBLIC SPHERE THROUGH EUROPEAN MEDIA REPORTING OF RISK COMMUNICATION
Authors: Neverla Irene
Published: December 2007

In this article I argue that journalistic coverage on environmental risk issues can contribute to the emergence of a European public sphere. The transnational character of environmental issues and the need to find political solutions for them on national and transnational levels pose challenges to the journalistic coverage. I examine this by considering three empirical studies, all of which use content analysis as their main methodology. These studies compare the coverage of issues such as biotechnology, air pollution and BSE in European media outlets. My conclusion is that coverage on environmental risk issues in national media, though not synchronous and consensual but rather asynchronous and controversial and stressing the own national point of view, does contribute to the emergence of a European public sphere.
MAPPING NEWS ON CHILDREN IN THE MAINSTREAM PRESS
Authors: Ponte Cristina
Published: December 2007

Research on the ways children are presented in the mainstream news media has recently become a focus of attention in Media Studies, stressing news approaches that oscillate between demonizing children and picturing them as a powerful symbol of victimization. Furthermore, children themselves do not make any statements: they are simply not heard. Similarly, there is an emphasis on episodic events, imbued with emotional or moral components. There is also a focus on risk situations, delinquency or parental advice on how to deal with new generations. This contrasts with little attention being paid to economic and social policies based on the UN Convention on the Rights of the Child. Based on these ambivalences, a longitudinal analysis of Portuguese newspapers (1970–2000) and a comparative analysis of European newspapers during a week in 2000, have been carried out in order to determine what and how they report children and related issues, and what frames have been changed or maintained. Consequently, the article explores the many facets of reporting and the implications for our public life, particularly with regards to children.
EUROCRATS, TECHNOCRATS, AND DEMOCRATS
Authors: Golding Peter
Published: December 2007

This article addresses the growing concern about a communication deficit in the European Union, and specifically with the notion that communication technologies may be deployed to overcome existing deficiencies in the dialogue between the union and its citizens. It examines proposed solutions to the deficit, including the notion of a European public sphere, and the creation of ‘e-Europe’ with the increasing digitalisation of many processes and institutions in the hope that this would make them more accessible, accountable, and effective. It argues that these hopes are rooted in myths, both technocratic and bureaucratic, that ignore the persistence of social divisions in media and communications technology use, and in the necessity of universal values as part of the national and parochial experiential of European citizens before it could be expanded to a trans-national level.
A Resolution of Bertrand's Paradox
Authors: Marinoff Louis
Published: December 2007

Bertrand's random-chord paradox purports to illustrate the inconsistency of the principle of indifference when applied to problems in which the number of possible cases is infinite. This paper shows that Bertrand's original problem is vaguely posed, but demonstrates that clearly stated variations lead to different, but theoretically and empirically self-consistent solutions. The resolution of the paradox lies in appreciating how different geometric entities, represented by uniformly distributed random variables, give rise to respectively different nonuniform distributions of random chords, and hence to different probabilities. The principle of indifference appears consistently applicable to infinite sets provided that problems can be formulated unambiguously.
The Epistemology of a Spectrometer
Authors: Rothbart Daniel , Slayden Suzanne W.
Published: December 2007

Contrary to the assumptions of empiricist philosophies of science, the theory-laden character of data will not imply the inherent failure (subjectivity, circularity, or rationalization) of instruments to expose nature's secrets. The success of instruments is credited to scientists' capacity to create artificial technological analogs to familiar physical systems. The design of absorption spectrometers illustrates the point: Progress in designing many modern instruments is generated by analogically projecting theoretical insights from known physical systems to unknown terrain. An experimental realism is defended.
Analog Simulation
Authors: Trenholme Russell
Published: December 2007

The distinction betweenanaloganddigital representationis reexamined; it emerges that a more fundamental distinction is that between symbolic and analogsimulation. Analog simulationis analyzed in terms of a (near) isomorphism of causal structures between a simulating and a simulated process. It is then argued that a core concept,naturalistic analog simulation, may play a role in a bottom-up theory of adaptive behavior which provides an alternative to representational analyses. The appendix discusses some formal conditions for naturalistic analog simulation.
Cladistic Classification and Functional Explanation
Authors: Griffiths P. E.
Published: December 2007

I adopt a cladistic view of species, and explore the possibility that there exists an equally valuable cladistic view of organismic traits. This suggestion seems to run counter to the stress on functional views of biological traits in recent work in philosophy and psychology. I show how the tension between these two views can be defused with a multilevel view of biological explanation. Despite the attractions of this compromise, I conclude that we must reject it, and adopt an essentially cladistic conception of biological traits.
Applied Ecology and the Logic of Case Studies
Authors: Shrader-Frechette Kristin , McCoy Earl D.
Published: December 2007

Because of the problems associated with ecological concepts, generalizations, and proposed general theories, applied ecology may require a new “logic” of explanation characterized neither by the traditional accounts of confirmation nor by the logic of discovery. Building on the works of Grünbaum, Kuhn, and Wittgenstein, we use detailed descriptions from research on conserving the Northern Spotted Owl, a case typical of problem solving in applied ecology, to (1) characterize the method of case studies; (2) survey its strengths; (3) summarize and respond to its shortcomings; and (4) investigate and defend its underlying “logic”.
Causality Without Counterfactuals
Authors: Salmon Wesley C.
Published: December 2007

This paper presents a drastically revised version of the theory of causality, based on analyses of causal processes and causal interactions, advocated in Salmon (1984). Relying heavily on modified versions of proposals by P. Dowe, this article answers penetrating objections by Dowe and P. Kitcher to the earlier theory. It shows how the new theory circumvents a host of difficulties that have been raised in the literature. The result is, I hope, a more satisfactory analysis of physical causality.
Interpretations of Quantum Field Theory
Authors: Huggett Nick , Weingard Robert
Published: December 2007

In this paper we critically review the various attempts that have been made to understand quantum field theory. We focus on Teller's (1990) harmonic oscillator interpretation, and Bohm et al.'s (1987) causal interpretation. The former unabashedly aims to be a purely heuristic account, but we show that it is only interestingly applicable to the free bosonic field. Along the way we suggest alternative models. Bohm's interpretation provides an ontology for the theory—a classical field, with a quantum equation of motion. This too has problems; it is not Lorentz invariant.
Is Algebraic Lorentz-Covariant Quantum Field Theory Stochastic Einstein Local?
Authors: Muller F. A. , Butterfield Jeremy
Published: December 2007

The general context of this paper is the locality problem in quantum theory. In a recent issue of this journal, Rédei (1991) offered a proof of the proposition that algebraic Lorentz-covariant quantum field theory is past stochastic Einstein local. We show that Rédei's proof is either spurious or circular, and that it contains two deductive fallacies. Furthermore, we prove that the mentioned theory meets the stronger condition of stochastic Haag locality.
Reasons for the Failure of Theories
Authors: Mayr Ernst
Published: December 2007

A theory may be invalid, not owing to erroneous observations or the invocation of an inappropriate law, but because of the use of equivocal terms. This is demonstrated for Darwin's failed model of sympatric speciation through the principle of divergence.
Empirical Equivalence, Underdetermination, and Systems of the World
Authors: Hoefer Carl , Rosenberg Alexander
Published: December 2007

The underdetermination of theory by evidence must be distinguished from holism. The latter is a doctrine about the testing of scientific hypotheses; the former is a thesis about empirically adequate logically incompatible global theories or “systems of the world”. The distinction is crucial for an adequate assessment of the underdetermination thesis. The paper shows how some treatments of underdetermination are vitiated by failure to observe this distinction, and identifies some necessary conditions for the existence of multiple empirically equivalent global theories. We consider how empiricists should respond to the possibility of such systems of the world.
Mind, Society, and the Growth of Knowledge
Authors: Thagard Paul
Published: December 2007

Explanations of the growth of scientific knowledge can be characterized in terms of logical, cognitive, and social schemas. But cognitive and social schemas are complementary rather than competitive, and purely social explanations of scientific change are as inadequate as purely cognitive explanations. For example, cognitive explanations of the chemical revolution must be supplemented by and combined with social explanations, and social explanations of the rise of the mechanical worldview must be supplemented by and combined with cognitive explanations. Rational appraisal of cognitive and social strategies for improving knowledge should appreciate the interdependence of mind and society.
Content and Causal Powers
Authors: Saidel Eric
Published: December 2007

Owens (1993) argues that a tension exists between our commonsense view of mental states and the scientific view that psychological explanations not contradict supervenience. He suggests that one cannot accept the anti-individualistic conclusions of Twin-Earth thought experiments and continue to use folk psychological states to explain behavior. I argue that his conclusions are based on individuating content widely and causal powers narrowly, and that such individuation violates consistency assumptions about the terms of his discussion. Thus, I argue, the tension he points to evaporates when we adopt either a consistently wide view or a consistently narrow view.
Philip Kitcher's The Advancement of Science: Science Without Legend, Objectivity Without Illusion
Authors: Leplin Jarrett
Published: December 2007

Philosophy has an honorable tradition as interpreter and advocate of science. That role is in decline. While other science studies disciplines deconstruct “reality”, “truth”, “rationality”, “knowledge”, and “progress” into the political tools of an interested elite, philosophy finds itself too divided over the scope of these concepts to defend them. The debate over realism in the philosophy of science is at an impasse. Agreeing on the relevant evidence and cognizant of the opposing arguments, the disputants cannot see what it would take to break the impasse. The philosophies of individual sciences progress, but no general analysis of scientific knowledge is sufficiently secure to advance against science's detractors.
Hacking's Experimental Realism: An Untenable Middle Ground
Authors: Reiner Richard , Pierson Robert
Published: December 2007

As Laudan and Fine show, and Boyd concedes, the attempt to infer the truth of scientific realism from the fact that it putatively provides the best explanation of the instrumental success of science is circular, since what is to be shown is precisely the legitimacy of such abductive inferences. Hacking's “experimental argument for scientific realism about entities” is one of the few arguments for scientific realism that purports to avoid this circularity. We argue that Hacking's argument is as dependent on inference to the best explanation (IBE), and therefore as weak, as the other realist arguments.
The Languages of Thought
Authors: Kaye Lawrence J.
Published: December 2007

I critically explore various forms of the language of thought (LOT) hypothesis. Many considerations, including the complexity of representational content and the systematicity of language understanding, support the view that some, but not all, of our mental representations occur in a language. I examine several arguments concerning sententialism and the prepositional attitudes, Fodor's arguments concerning infant and animal thought, and Fodor's argument for radical concept nativism and show that none of these considerations require us to postulate a LOT that is innate or otherwise distinct from spoken languages. Instead, I suggest that we maintain the more conservative hypothesis, supported by introspection, that some of our thoughts occur in the languages that we speak.
An Empirical Reply to Empiricism: Protective Measurement Opens The Door for Quantum Realism
Authors: Dickson Michael
Published: December 2007

Quantum mechanics has sometimes been taken to be an empiricist (vs. realist) theory. I state the empiricist's argument, then outline a recently noticed type of measurement—protective measurement—that affords a good reply for the realist. This paper is a reply to scientific empiricism (about quantum mechanics), but is neither a refutation of that position, nor an argument in favor of scientific realism. Rather, my aim is to place realism and empiricism on an even score in regards to quantum theory.
Was Cartesian Science ever Meant to be a Priori? A Comment on Hatfield
Authors: Raftopoulos Athanasse
Published: December 2007

In a recent article G. Hatfield claims that Descartes for a certain time thought a purely a priori science to be possible. Hatfield's evidence consists of his reading of the Cartesian method in the Regulae and of a letter to Mersenne, written in May 1632. I argue that Hatfield misinterprets the Cartesian method and Descartes' claim in the letter to Mersenne. I first show that the latter does not argue for an a priori science. Then, I show that the method of the Regulae is not a priori. Finally, I propose a reading of Descartes' letter.