bluuebunny/crossref_metadata_2025 huggingface dataset:
Feasibility of observing dayside aurora using NIR camera onboard high‐altitude balloons
Authors: Zhou X.‐Y. , Lummerzheim D. , Gladstone R. , Gunapala S.
Published: February 2007

This letter reports a feasibility study on dayside auroral observation using a near‐infrared (NIR) InGaAs camera from high‐altitude, long‐duration balloons. This effort is motivated by science interest in the dayside aurora. Model predictions indicate daytime observations are possible because the sky brightness significantly decreases towards longer wavelengths at certain altitude in the upper atmosphere, and the NIR ambient sky brightness substantially decreases with increasing altitude. To address the question whether aurora can indeed be detected in the upper atmosphere, auroral test observations were conducted at the Poker Flat Research Range from March 22 to April 26, 2005. The InGaAs camera used in this test covers a waveband from 900 to 1700 nm with a 320 × 256 focal plane array, 30 × 30 μm pixels, and a 9° field of view. For one evening event, we estimate the NIR sky brightness using the MODTRAN atmospheric radiance model and compare it with the expected sky brightness at 30–50 km altitudes. The comparison indicates that the N2+ Meinel emission at ∼1100 nm should be seen at 35–40 km altitudes and above, and therefore, confirms that such dayside auroral observations are feasible. Auroral studies using this method include, e.g., studies of interplanetary shock and pressure pulse induced auroras as well as conjugate auroras.
Acoustic source localization model using in-skull reverberation and time reversal
Authors: Catheline Stefan , Fink Mathias , Quieffin Nicolas , Ing Ros Kiri
Published: February 2007

A processing model of localization based on time reversal of the reverberated sound in a human skull is proposed. The underlying general idea is that bones act as antenna, gathering and conducting information about spatial positioning. Decoding this information is achieved with a time reversal analysis. Tested in a model experiment, the localization works in the azimuthal and sagittal plans, for single or multiple sound sources. Its efficiency is also demonstrated for one sided hearing people. The authors anticipate that this general antennalike concept can be applied to many animals that use sound localization as well as to future design for microphone devices or sonars.
From A to B in free energy space
Authors: Branduardi Davide , Gervasio Francesco Luigi , Parrinello Michele
Published: February 2007

The authors present a new method for searching low free energy paths in complex molecular systems at finite temperature. They introduce two variables that are able to describe the position of a point in configurational space relative to a preassigned path. With the help of these two variables the authors combine features of approaches such as metadynamics or umbrella sampling with those of path based methods. This allows global searches in the space of paths to be performed and a new variational principle for the determination of low free energy paths to be established. Contrary to metadynamics or umbrella sampling the path can be described by an arbitrary large number of variables, still the energy profile along the path can be calculated. The authors exemplify the method numerically by studying the conformational changes of alanine dipeptide.
Characteristics of HfOxNy thin films by rf reactive sputtering at different deposition temperatures
Authors: Liu M. , Fang Q. , He G. , Zhu L. Q. , Zhang L. D.
Published: February 2007

The microstructure and optical dielectric constants of HfOxNy thin films deposited by using radio frequency reactive magnetron sputtering have been investigated at various substrate temperatures. Fourier transform infrared spectroscopy spectra indicate that an interfacial layer has been formed between the Si substrate and the HfOxNy thin film during deposition. Spectroscopy ellipsometry (SE) results show that the substrate temperature has a strong effect on physical properties of HfOxNy thin films such as refractive index n and extinction coefficient k. Meanwhile, the optical dielectric functions of the films have determined using SE data and optical absorption properties of HfOxNy thin films deposited at different substrate temperatures have also been studied.
Electronic structure and band alignment at the HfO2∕4H-SiC interface
Authors: Tanner Carey M. , Choi Jongwoo , Chang Jane P.
Published: February 2007

To evaluate the potential of HfO2 as a gate dielectric in SiC power metal-oxide-semiconductor field effect transistors (MOSFETs), the band alignment at the HfO2∕4H-SiC interface was determined by x-ray photoelectron spectroscopy (XPS) measurements and first-principles calculations using density functional theory (DFT). For XPS studies, HfO2 films were grown on 4H-SiC (0001) by a thermal atomic layer deposition process. A valence band offset of 1.74eV and a conduction band offset of 0.70eV were determined based on the valence band and core-level spectra. DFT simulations of the Si-terminated 4H-SiC (0001) surface found a 1×1 relaxed structure whereas simulations of the C-terminated surface observed a 2×1 reconstruction to form C–C dimers. We studied two m-HfO2∕4H-SiC (0001) supercells based on these surfaces and valence band offset values of 2.09 and 1.47eV, and conduction band offset values of 0.35 and 0.97eV, respectively, were predicted. The consistently low conduction band offset may not provide an adequate barrier height for electron injection from the substrate and further electrical studies are necessary to determine the viability of integrating HfO2 in SiC power MOSFETs.
Electrical conductivity of cellular Si∕SiC ceramic composites prepared from plant precursors
Authors: Mallick Debopriyo , Chakrabarti Omprakash , Bhattacharya Dipten , Mukherjee Manabendra , Maiti Himadri S. , Majumdar Rabindranath
Published: February 2007

Electrical conductivity (σdc) of the cellular Si∕SiC ceramic composites has been measured over a temperature range of 25–1073K, while the thermoelectric power (S) has been measured over 25–300K. Remarkably, these cellular compounds developed through the biomimetic route—where the ceramic system grows within a plant biotemplate retaining the imprint of structural intricacies of the native templates—are found to exhibit excellent mechanical, thermal, and electrical properties quite comparable to or even better than those of the systems prepared through the conventional ceramic route. The electrical conductivity, measured parallel (σ‖) and perpendicular (σ⊥) to the growth axes of the native plants, depicts nearly temperature-independent anisotropy (σ⊥∕σ‖) of the order ∼2, while the thermoelectric power is nearly isotropic. The charge conduction across the entire temperature regime is found to follow closely the variable range hopping mechanism. The conductivity anisotropy appears to be driven primarily by the unique microcellular morphology of the biotemplates, which can be exploited in many electrical applications.
Trap state spectroscopy studies and wettability modification of hydroxyapatite nanobioceramics
Authors: Aronov Daniel , Rosenman Gil
Published: February 2007

Sintered hydroxyapatite coatings on titanium-based implants demonstrate beneficial biocompatibility and osteoconductivity. It has been shown that charged surface states and bulk traps located in the vicinity of the surface of the hydroxyapatite coatings strongly influence wettability properties of the hydroxyapatite and may modify biocompatibility of these nanostructured bioceramics. Combination of high-resolution electron state spectroscopy methods, thermostimulated exoelectron emission, and thermoluminescence methods, applied in this work, have allowed studying electron trap energy spectrum of the hydroxyapatite bioceramics.
Collisionless kinetic-fluid model of zonal flows in toroidal plasmas
Authors: Sugama H. , Watanabe T.-H. , Horton W.
Published: February 2007

A novel kinetic-fluid model is presented, which describes collisionless time evolution of zonal flows in tokamaks. In the new zonal-flow closure relations, the parallel heat fluxes are written by the sum of short- and long-time-evolution parts. The former part is given in the dissipative form of the parallel heat diffusion and relates to collisionless damping processes. The latter is derived from the long-time-averaged gyrocenter distribution and plays a major role in describing low-frequency or stationary zonal flows, for which the parallel heat fluxes are expressed in terms of the parallel flow as well as the nonlinear-source and initial-condition terms. It is shown analytically and numerically that, when applied to the zonal flow driven by either ion or electron temperature gradient turbulence, the kinetic-fluid equations including the new closure relations can reproduce the same long-time zonal-flow responses to the initial condition and to the turbulence source as those obtained from the gyrokinetic model.
Highly sensitive silicon crystal torque sensor operating at the thermal noise limit
Authors: Haiberger L. , Weingran M. , Schiller S.
Published: February 2007

We describe a sensitive torque detector, based on a silicon single-crystal double-paddle oscillator (DPO). The high Q-factor (∼105 at room temperature and in vacuum) makes DPOs well suited for the detection of weak forces. The limiting sensitivity of a sensor is given by Brownian (thermal) noise if all external disturbances are eliminated. In this case, the minimum detectable force can be decreased by measuring over a time significantly longer than the oscillator’s relaxation time. We demonstrate operation in this regime, with integration times of up to 14 h. A resulting torque sensitivity of 2×10−18 N m is reached. Tests are performed to show that the sensor is only affected by thermal noise. The present sensor is well suited for measurements of extremely weak forces, e.g., of gravitational attraction between laboratory masses.
Modified buffer layers for polymer photovoltaic devices
Authors: Ko Chu-Jung , Lin Yi-Kai , Chen Fang-Chung , Chu Chi-Wei
Published: February 2007

The influence of anode buffer layers on the performance of polymer photovoltaic devices based on blends of poly(3-hexylthiophene) and [6,6]-phenyl-C-61-buytyric acid methyl ester has been investigated. The buffer layers consist of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT-PSS) doped with different concentrations of mannitol. Improved power conversion efficiency, up to 5.2%, has been observed by reducing the resistance of PEDOT:PSS after doping. One extrapolation method has been developed to exclude the resistance from the connection of the electrodes from the total device resistance. The results confirm that the device improvement is due to the reduction of series resistance of the PEDOT:PSS after the mannitol doping.
Nitrogen doping of ZnTe and its influence on CdTe∕ZnTe interfaces
Authors: Späth B. , Fritsche J. , Klein A. , Jaegermann W.
Published: February 2007

The properties of nitrogen doped ZnTe films and in situ formed heterointerfaces to CdTe were investigated using photoelectron spectroscopy and electrical measurements. The p doping of ZnTe with nitrogen is controlled during physical vapor deposition with an additional nitrogen plasma source. The resistivity was determined by four-point measurements and a minimum resistivity of ρ=0.04Ωcm was found. The valence band offset of the CdTe∕ZnTe interface is EVBO=0.05eV.
Wafer-bonded surface plasmon waveguides
Authors: Berini Pierre , Mattiussi Greg , Lahoud Nancy , Charbonneau Robert
Published: February 2007

Direct wafer bonding and thinning were explored as an approach for constructing long-range surface plasmon waveguides. The structures consist of a thin metal stripe deposited into a shallow trench etched into one of the claddings, to which another cladding of the same material is directly bonded. The approach was developed first using Pyrex wafers in order to assess feasibility and then using lithium niobate wafers. Optical and electro-optical measurements validate the approach.
Concentration-dependent near-infrared quantum cutting in GdBO3:Tb3+,Yb3+ nanophosphors
Authors: Zhang Q. Y. , Yang C. H. , Jiang Z. H. , Ji X. H.
Published: February 2007

An efficient near-infrared (NIR) quantum-cutting (QC), involving the emission of two low-energy NIR photons from an absorbed visible photon via a cooperative downconversion mechanism in GdBO3:Tb3+,Yb3+ nanophosphors, has been demonstrated. Upon excitation of Tb3+ with a visible photon at 486nm, two NIR photons could be emitted by Yb3+ through cooperative energy transfer from Tb3+ to two Yb3+ ions. The dependence of Yb3+ doping concentration on the visible and NIR emissions, decay lifetime, and quantum efficiencies from the QC phosphors has been investigated. Calculations indicate that the optimal NIR quantum efficiency approaches 182% before reaching concentration quenching threshold. Application of the QC nanophosphors in silicon-based solar cells might greatly enhance its response.
Modeling the fragmentation dynamics of ionic clusters inside helium nanodroplets: The case of He100Ne4+
Authors: Bonhommeau D. , Lake P. T. , Le Quiniou C. , Lewerenz M. , Halberstadt N.
Published: February 2007

We present simulation results on the effect of a helium nanodroplet environment on the fragmentation dynamics of embedded molecular systems. The helium atoms are treated explicitly, with zero-point effects taken into account through an effective helium-helium interaction potential. The ionized neon tetramer is used as a model molecular system because, like all the small rare-gas clusters, it fragments extensively upon ionization. All the nonadiabatic effects between electronic states of the ionized neon cluster are taken into account. The results reveal a predominance of Ne2+ and HepNe2+ fragments and the absence of bare Ne+ fragments, in agreement with available experimental data. The neutral monomer fragments exhibit a rather wide kinetic energy distribution that can be fitted to the sum of two Boltzmann distributions, one with a low kinetic energy and the other with a higher kinetic energy. This indicates that cooling by helium atom evaporation is more efficient than was believed so far, as suggested by recent experimental results. Purely classical calculations are shown to strongly overestimate the amount of cage effect (cooling), clearly indicating the need to take into account zero-point effects.
Observation of the predissociated, quasilinear B̃(A′1) state of CHF by optical-optical double resonance
Authors: Tao Chong , Reid Scott A. , Schmidt Timothy W. , Kable Scott H.
Published: February 2007

We report the first observation of the predissociative B̃ state of a halocarbene molecule. Rovibronic energy levels were measured in the B̃(A′1) state of CHF by fluorescence dip detected optical-optical double resonance spectroscopy via the Ã state. The origin was found to lie 30817.4cm−1 above the zero point level of the X̃ state. Rotational transitions within six purely bending states, and states involving one or two quanta of CF-stretch were observed, including the vibrational angular momentum components. Interpretation of the spectrum, with support of ab initio calculations, shows that CHF is quasilinear in the B̃ state with a small (−200cm−1) barrier to linearity which lies below the zero-point level. The rotational constant, B=1.04 to 1.09cm−1, depending on vibrational state, again in good agreement with theory. All observed B̃ state levels were predissociative, as evidenced by Lorentzian line broadening. Linewidths varied with initial state from 0.7–10.8cm−1, corresponding to excited state lifetimes of 0.5–8ps.
Acute postnatal ablation of
Hif-2
α results in anemia
Authors: Gruber Michaela , Hu Cheng-Jun , Johnson Randall S. , Brown Eric J. , Keith Brian , Simon M. Celeste
Published: February 2007

Adaptive transcriptional responses to oxygen deprivation (hypoxia) are mediated by the hypoxia-inducible factors (HIFs), heterodimeric transcription factors composed of two basic helix–loop–helix–PAS family proteins. The transcriptional activity of HIF is determined by the hypoxic stabilization of the HIF-α proteins. HIF-1α and HIF-2α exhibit high sequence homology but have different mRNA expression patterns; HIF-1α is expressed ubiquitously whereas HIF-2α expression is more restricted to certain tissues, e.g., the endothelium, lung, brain, and neural crest derivatives. Germ-line deletion of either HIF subunit is embryonic lethal with unique features suggesting important roles for both HIF-α isoforms. Global deletion of
Hif-2
α results in distinct phenotypes depending on the mouse strain used for the mutation, clearly demonstrating an important role for HIF-2α in mouse development. The function of HIF-2α in adult life, however, remains incompletely understood. In this study, we describe the generation of a conditional murine
Hif-2
α allele and the effect of its acute postnatal ablation. Under very stringent conditions, we ablate
Hif-2
α after birth and compare the effect of acute global deletion of
Hif-2
α and
Hif-1
α. Our results demonstrate that HIF-2α plays a critical role in adult erythropoiesis, with acute deletion leading to anemia. Furthermore, although HIF-1α was first purified and cloned based on its affinity for the human erythropoietin (EPO) 3′ enhancer hypoxia response element (HRE) and regulates
Epo
expression during mouse embryogenesis, HIF-2α is the critical α isoform regulating
Epo
under physiologic and stress conditions in adults.
Reactive oxygen species detoxification by catalase is a major determinant of fecundity in the mosquito
Anopheles gambiae
Authors: DeJong Randall J. , Miller Lisa M. , Molina-Cruz Alvaro , Gupta Lalita , Kumar Sanjeev , Barillas-Mury Carolina
Published: February 2007

The mosquito
Anopheles gambiae
is a primary vector of
Plasmodium
parasites in Africa. The effect of aging on reproductive output in
A. gambiae
females from three strains that differ in their ability to melanize
Plasmodium
and in their systemic levels of hydrogen peroxide (H
2
O
2
), a reactive oxygen species (ROS), was analyzed. The number of eggs oviposited after the first blood meal decreases with age in all strains; however, this decline was much more pronounced in the G3 (unselected) and R (refractory to
Plasmodium
infection) strains than in the S (highly susceptible to
Plasmodium
) strain. Reduction of ROS levels in G3 and R females by administration of antioxidants reversed this age-related decline in fecundity. The S and G3 strains were fixed for two functionally different catalase alleles that differ at the second amino acid position (Ser2Trp). Biochemical analysis of recombinant proteins revealed that the
Trp
isoform has lower specific activity and higher
K
m
than the
Ser
isoform, indicating that the former is a less efficient enzyme. The Trp-for-Ser substitution appears to destabilize the functional tetrameric form of the enzyme. Both alleles are present in the R strain, and Ser/Ser females had significantly higher fecundity than Trp/Trp females. Finally, a systemic reduction in catalase activity by dsRNA-mediated knockdown significantly reduced the reproductive output of mosquito females, indicating that catalase plays a central role in protecting the oocyte and early embryo from ROS damage.
Common mechanisms of target cell recognition and immunity for class II bacteriocins
Authors: Diep Dzung B. , Skaugen Morten , Salehian Zhian , Holo Helge , Nes Ingolf F.
Published: February 2007

The mechanisms of target cell recognition and producer cell self-protection (immunity) are both important yet poorly understood issues in the biology of peptide bacteriocins. In this report, we provide genetic and biochemical evidence that lactococcin A, a permeabilizing peptide–bacteriocin from
Lactococcus lactis
, uses components of the mannose phosphotransferase system (man-PTS) of susceptible cells as target/receptor. We present experimental evidence that the immunity protein LciA forms a strong complex with the receptor proteins and the bacteriocin, thereby preventing cells from being killed. Importantly, the complex between LciA and the man-PTS components (IIAB, IIC, and IID) appears to involve an on–off type mechanism that allows complex formation only in the presence of bacteriocin; otherwise no complexes were observed between LciA and the receptor proteins. Deletion of the man-PTS operon combined with biochemical studies revealed that the presence of the membrane-located components IIC and IID was sufficient for sensitivity to lactococcin A as well as complex formation with LciA. The cytoplasmic component of the man-PTS, IIAB, was not required for the biological sensitivity or for complex formation. Furthermore, heterologous expression of the lactococcal man-PTS operon rendered the insensitive
Lactobacillus sakei
susceptible to lactococcin A. We also provide evidence that, not only lactococcin A, but other class II peptide-bacteriocins including lactococcin B and some
Listeria
-active pediocin-like bacteriocins also target the man-PTS components IIC and IID on susceptible cells and that their immunity proteins involve a mechanism in producer cell self-protection similar to that observed for LciA.
Qualitative Scientific Modeling and Loop Analysis
Authors: Justus James
Published: February 2007

Loop analysis is a method of qualitative modeling anticipated by Sewall Wright (1921) and systematically developed by Richard Levins. In Levins’ (1966) distinctions between modeling strategies, loop analysis sacrifices precision for generality and realism. Besides criticizing the clarity of these distinctions, Orzack and Sober (1993) argued qualitative modeling is conceptually and methodologically problematic. Loop analysis of the stability of ecological communities shows this criticism is unjustified. It presupposes an overly narrow view of qualitative modeling and underestimates the broad role models play in scientific research, especially in helping scientists represent and understand complex systems.
Measurement Outside the Laboratory
Authors: Boumans Marcel
Published: February 2007

The kinds of models discussed in this paper function as measuring instruments. We will concentrate on two necessary steps for measurement: (1) one should search for a mathematical representation of the phenomenon; (2) this representation about the phenomenon should cover an invariant relationship between properties of the phenomenon to be measured and observable associated attributes of a measuring instrument. Therefore, the measuring instrument should function as a nomological machine. However, invariant relationships are not necessarily ceteris paribus regularities, but could also occur when the influence of the environment is negligible. Then we are able to achieve accurate measurements outside the laboratory.
Indeterminism in Neurobiology
Authors: Weber Marcel
Published: February 2007

I examine different arguments that could be used to establish indeterminism of neurological processes. Even though scenarios where single events at the molecular level make the difference in the outcome of such processes are realistic, this falls short of establishing indeterminism, because it is not clear that these molecular events are subject to quantum mechanical uncertainty. Furthermore, attempts to argue for indeterminism autonomously (i.e., independently of quantum mechanics) fail, because both deterministic and indeterministic models can account for the empirically observed behavior of ion channels.
Counterfactuals and the Past Hypothesis
Authors: Frisch Mathias
Published: February 2007

Albert (2000) provides a sketch of an entropy account of the causal and counterfactual asymmetries. This paper critically examines a proposal that may be thought to fill in some of the lacunae in Albert's account.
Confirmation for a Modest Realism
Authors: Snyder Laura J.
Published: February 2007

In the nineteenth century, William Whewell claimed that his confirmation criterion of consilience was a truth-guarantor: we could, he believed, be certain that a consilient theory was true. Since that time Whewell has been much ridiculed for this claim by critics such as J. S. Mill and Bas van Fraassen. I have argued elsewhere that, while Whewell's claim that consilience canguaranteethe truth of a theory is clearly wrong, consilience is indeed quite useful as a confirmation criterion (Snyder 2005). Here I will show that, even when consilience gives evidence for a theory that turns out to be false, there is an important sense in which consilience shows that the theory has captured something correct about the natural-kind structure of the physical world. Whewell was therefore correct to claim that consilience provides a “criterion of reality” (Whewell [1847] 1967, vol. 2, 68). Consilience provides this by giving justification for the claim that we have really ‘cut nature at its causal joints’, to adapt Plato's famous phrase. Because of this, consilience can play a role in an argument for scientific realism.
A Case for Old-Fashioned Observability, and a Reconstructed Constructive Empiricism
Authors: Chang Hasok
Published: February 2007

I develop a concept of observability that pertains to qualities rather than objects: A quality is observable if it can be registered by human sensation (possibly with the aid of instruments) without involving optional interpretations. This concept supports a better description of observations in science and everyday life than the object-based observability concepts presupposing causal information-transfer from the object to the observer. It also allows a rehabilitation of the traditional empiricist distinction between observations and their interpretations, but without a presumption that observations are infallible. Using this concept of observability, I also propose a re-formulation of constructive empiricism that is easier to defend against realist attacks, while open to reasonable realist intuitions.
Exploratory Experiments
Authors: Franklin L. R.
Published: February 2007

Philosophers of experiment have acknowledged that experiments are often more than mere hypothesis-tests, once thought to be an experiment's exclusive calling. Drawing on examples from contemporary biology, I make an additional amendment to our understanding of experiment by examining the way that `wide' instrumentation can, for reasons of efficiency, lead scientists away from traditional hypothesis-directed methods of experimentation and towards exploratory methods.
The Notion of ‘Group’ and Tests of Group Selection
Authors: Shavit Ayelet
Published: February 2007

This paper examines the empirical aspect of the debates over group selection. I argue that specific narrow readings of the notion of ‘group’ result in a deficient experimentation of the group selection process. Criteria for empirical testability are presented and used to reexamine two well-known experiments of group selection. I argue that the former holds a narrow image of ‘group’ that does not distinguish group selection from selection at other levels; while the latter holds a multifaceted image of ‘group’ that offers a way to achieve substantive progress in the debate. However, most supporters and opponent of group selection maintain a narrow and restricted image of ‘group’, which implicitly undermines informative details regarding population dynamics and population structure. These details may improve our understanding of the evolution of altruism and the evolution of sociality. To conclude, adopting a wide-ranging meaning of ‘group’ may empirically advance the group selection debates.
The Similarity of Causal Inference in Experimental and Non-experimental Studies
Authors: Scheines Richard
Published: February 2007

For nearly as long as the word ‘correlation’ has been part of statistical parlance, students have been warned that correlation does not prove causation, and that only experimental studies, e.g., randomized clinical trials, can establish the existence of a causal relationship. Over the last few decades, somewhat of a consensus has emerged between statisticians, computer scientists, and philosophers on how to represent causal claims and connect them to probabilistic relations. One strand of this work studies the conditions under which evidence accumulated from non-experimental (observational) studies can be used to infer a causal relationship. In this paper, I compare the typical conditions required to infer that one variable is a direct cause of another in observational and experimental studies. I argue that they are essentially the same.
Causal Instrumental Variables and Interventions
Authors: Reiss Julian
Published: February 2007

The aim of this paper is to introduce the instrumental variables technique to the discussion about causal inference in econometrics. I show that it may lead to causally incorrect conclusions unless some fairly strong causal background assumptions are made, assumptions which are usually left implicit by econometricians. These assumptions are very similar to, albeit not identical with, James Woodward's definition of an ‘intervention’. I discuss similarities and differences of the two points of view and argue that—understood as a practical method of causal inference—the set presented here is superior.
Empirical Success or Explanatory Success: What Does Current Scientific Realism Need to Explain?
Authors: Doppelt Gerald
Published: February 2007

Against the well-known objection that in the history of science there are many theories that are successful but false, Psillos offers a three-pronged defense of scientific realism as the best explanation for the success of science. Focusing on these, I criticize Psillos’ defense, arguing that each prong is weakened when we recognize that according to realist rebuttals of the underdetermination argument and versions of empiricism, realists are committed to accounting for the explanatory success of theories, not their mere empirical adequacy or instrumental reliability. I conclude by indicating how ‘explanationist’ realism might be recast to accommodate my arguments.
Spacetime Substantivalism and Einstein's Cosmological Constant
Authors: Baker David J.
Published: February 2007

I offer a novel argument for spacetime substantivalism: We should take the spacetime of general relativity to be a substance because of its active role in gravitational causation. As a clear example of this causal behavior I offer the cosmological constant, a term in the most general form of the Einstein field equations which causes free floating objects to accelerate apart. This acceleration cannot, I claim, be causally explained except by reference to spacetime itself.
Asymptotic states in quantum electrodynamics
Authors: K-E Eriksson
Published: February 2007

The time evolution of a system of charged particles due to the long-range part of the Coulomb interaction and the interaction with the soft part of the transverse radiation field is studied within the frame-work of frist-quantized theory of the charged particles and second-quantized theory of the electromagnetic field.

States are defined which may serve as asymptotic states in a scattering theory. They differ from the free states by a phase factor (generalization of the Coulomb phase) and by the presence of a coherent soft radiation field. The time development of the phase factor and of the wave function that describes the coherent field is studied in detail and expressed in terms of elementary functions.

An outline is made of anS-matrix theory based on the asymptotic states thus defined.
New Wavelength Measurements in Cs I
Authors: K B S Eriksson  , I Wenåker
Published: February 2007

The wavelengths of the Cs I transitions 6s-5d and 5d-nf, with n=4-14, have been measured by means of a high-dispersion Czerny-Turner spectrograph and a hollow-cathode discharge. From the recalculated levels 4-12f
2
F
7/2,5/2 and 6-11s
2
S
1/2, the ionization energy has been determined to 31 406.454±0.005 cm-1.
A Solution of Equations Describing Explosive Instabilities
Authors: L Stenflo  , J Weiland  , H Wilhelmsson
Published: February 2007

We have studied the basic equations, which describe three-wave interaction in a plasma, where collisional effects have to be taken into account. An analytical solution has been found and is compared with computer results.
Magnetic Susceptibility and Resistance Measurements on Magnesium and Strontium
Authors: H U Åström  , K Svensson
Published: February 2007

The magnetic susceptibility of pure magnesium and strontium has been measured from liquid helium temperatures to 295 K for magnesium and up to 474 K for strontium. On the same specimens resistance measurements were made between 1.3 K and about 30 K. For very pure magnesium the susceptibility was constant within 0.5% in the temperature range 64 to 295 K and equal to 0.530·10-6 gm-1. For this material no resistance minimum was found although less pure magnesium gave a minimum at about 6 K. For strontium the susceptibility decreased linearly with increasing temperature, the value at 67 K being 1.40·10-6 gm-1 and the value at 474 K 0.88·10-6 gm-1. No maximum in the susceptibility, as observed earlier by Rao and Savithri, was found.
The Ep=1146 keV and 1151 keV resonances in the 31P(p,γ)32S reaction
Authors: P Holmberg  , M Viitasalo
Published: February 2007

More evidence on the existence of resonances at E
p = 1146 keV and 1151 keV in the 31P(p,γ)32S reaction has been obtained. The decays of the resonances are investigated and decay schemes presented. Angular distributions of the strong transitions to the first excited state in 32S are measured. Spin and parity 2+ is suggested for both resonance states.
The Decay of Bound Isobaric Analogue States in 28Si and 32S Using (d,nγ) Reactions
Authors: L Nilsson  , A Nilsson  , I Bergqvist
Published: February 2007

A method has been developed for recording coincidences between neutrons and gamma-rays produced in (d,nγ) reactions. Neutron energies were measured by time-of-flight techniques and a large NaI(Tl) crystal was used to determine gamma-ray energies and intensities. The neutron detector was placed in the forward direction to emphasize the excitation of I
p = 0 levels in the residual nuclei. The method was applied to the 27Al(d,nγ)28Si and 31P(d,nγ)32S reactions at the deuteron energy 4.0 MeV. The gamma-ray decay of a number of levels below 12 MeV in 28Si and below 9 MeV in 32S was studied. The isobaric analogue levels are prominently populated by the (d,n) reaction. The method is in particular suitable for studies of the decay of these levels.
Mean Lives in Singly Ionized Potassium by the Beam-Foil Technique
Authors: H G Berry  , J Bromander  , R Buchta
Published: February 2007

The life times of nine of the ten 3p
54p levels in KII have been measured using the beam-foil technique. The values are compared with those of the same levels in ArI. Two each of the 3p
54d and 3p
55s levels in KII were also measured.
Some Mean Life Measurements in the Na I and Mg I Isoelectronic Sequences
Authors: H G Berry  , J Bromander  , R Buchta
Published: February 2007

The beam-foil technique has been used to observe the spectra of Na, Mg, and Al between 1 000 Å and 6 000 Å. Decay times of transitions in Na I, Mg I, II and Al II, III were measured. They are compared with other measurements and calculations.
X-ray Determination of Electron Momentum Distributions in BN and B4C
Authors: S Manninen  , O Inkinen
Published: February 2007

The Compton profiles of polycrystalline BN and B4C have been measured with MoKα X-rays. The valence-electron contributions to the measured profiles, from which the effects of finite instrumental resolution were effectively removed, were in marked disagreement with those calculated from Hartree-Fock free-atom wave functions. Comparison of the experimental and calculated valence-electron momentum distributions, deduced from the Compton profiles, indicated that the observed distributions are more extended in momentum space than the calculated ones.
An X-Ray Flash Tube with Exchangeable Electrode System
Authors: L Högberg  , A Mattsson  , N R Nilsson  , A Svedberg
Published: February 2007

Design and performance data of a field emission X-ray flash tube are presented. The electrode assembly is exchangeable. It is thus possible to adapt the tube impedance to the voltage source or to replace the anode tip when necessary. The tube has been tested in the voltage range 100-1 200 kV; the pulse width at 1 200 kV is typically 10 ns and the penetration 5 cm of steel at 1 m.
Current Algebra on the Mass-shell
Authors: H Snellman
Published: February 2007

Pion-nucleon scattering on the mass-shell is studied in a field-theoretical framework where the weak currents together with their divergences are taken as interpolating fields for mesons and where the currents obey the Gell-Mann current-algebra (CA) scheme. On the mass-shell the PCAC assumption has a clear physical meaning and the condition for not having any polynomial high-energy behaviour in the πN scattering amplitude is an on mass-shell form of the Adler-Weisberger sum-rule. With this sum-rule we find gA
(m
π
2)=1.25±0.02 which is consistent with gA
(0)=1.23±0.01, the experimental value. The CA and PCAC πN threshold formula is discussed and finite mass corrections to the soft pion limit are considered. Finally we express the condition for the absence of polynomial high-energy behaviour in field-theoretic language as a new current commutation relation.
Nuclear Magnetic Moment and Hyperfine Structure Anomaly of 103Ag and Nuclear Spin of 13 m 102Ag
Authors: B Wannberg  , J O Jönsson  , L Sanner
Published: February 2007

The hfs of 103Ag (T
1/2 = 66 min) has been investigated with the atomic-beam magnetic-resonance (ABMR) method. Δν and μ
I
have been determined independently, and the results are Δν = 39 700 (500) MHz and μ
I
= + 4.45 (5) n.m. The hfs anomaly Δ107
103 has been determined to be + 3.4 (1.7)%. Theoretical calculations give Δ107
103 = 3.9%.

For I = 5, there is a component with a half-life of 13 min which may be 102Ag or 102Ag + 100Ag. Furthermore, signals with a half-life of 9(2) minutes have been obtained for I = 9/2. This activity is ascribed to 101Ag.
Measured86Kr I Wavelengths for a Microwave-excited Electrodeless Lamp
Authors: Karl B S Eriksson  , Göran Norlén
Published: February 2007

The wavelengths of 34 strong transitions in86Kr I, emitted by an air-cooled electrodeless Engelhard lamp excited in a cavity resonator, have been measured. The estimated uncertainty ranges from ±5 to ±15 × 10-5Å between 5 563 and 9 755 Å. Relative level values have been derived with an estimated uncertainty of about ±20 × 10-5cm-1.
Angular Distribution of Electrons in ESCA Spectra from a Single Crystal
Authors: Kai Siegbahn  , Ulrik Gelius  , Hans Siegbahn  , Erik Olson
Published: February 2007

The angular intensity variation of elastically scattered electrons expelled from various shells in a NaCl crystal by MgKα and AlKα radiation is reported. A discussion of some prominent features of the experimental results is presented.
Molecular Spectroscopy by Means of ESCA II. Sulfur compounds. Correlation of electron binding energy with structure
Authors: B J Lindberg  , K Hamrin  , G Johansson  , U Gelius  , A Fahlman  , C Nordling  , K Siegbahn
Published: February 2007

Electron spectra from an extensive series of sulfur compounds have been studied. A correlation has been established between the observed position of inner electron lines of sulfur and structure. The influence of structure on the electron binding energies is discussed in terms of a calculated atomic charge, based on the concepts of electronegativity and partial ionic character of bonds. The results are useful for the study of bonding and structure in sulfur chemistry, and are applied particularly to the discussion of the sulfur-oxygen bond (S=O).
Muscle Satellite Cells and Endothelial Cells: Close Neighbors and Privileged Partners
Authors: Christov Christo , Chrétien Fabrice , Abou-Khalil Rana , Bassez Guillaume , Vallet Grégoire , Authier François-Jérôme , Bassaglia Yann , Shinin Vasily , Tajbakhsh Shahragim , Chazaud Bénédicte , Gherardi Romain K.
Published: February 2007

Genetically engineered mice (Myf5nLacZ/+, Myf5GFP-P/+) allowing direct muscle satellite cell (SC) visualization indicate that, in addition to being located beneath myofiber basal laminae, SCs are strikingly close to capillaries. After GFP+ bone marrow transplantation, blood-borne cells occupying SC niches previously depleted by irradiation were similarly detected near vessels, thereby corroborating the anatomical stability of juxtavascular SC niches. Bromodeoxyuridine pulse-chase experiments also localize quiescent and less quiescent SCs near vessels. SCs, and to a lesser extent myonuclei, were nonrandomly associated with capillaries in humans. Significantly, they were correlated with capillarization of myofibers, regardless to their type, in normal muscle. They also varied in paradigmatic physiological and pathological situations associated with variations of capillary density, including amyopathic dermatomyositis, a unique condition in which muscle capillary loss occurs without myofiber damage, and in athletes in whom capillaries increase in number. Endothelial cell (EC) cultures specifically enhanced SC growth, through IGF-1, HGF, bFGF, PDGF-BB, and VEGF, and, accordingly, cycling SCs remained mainly juxtavascular. Conversely, differentiating myogenic cells were both proangiogenic in vitro and spatiotemporally associated with neoangiogenesis in muscular dystrophy. Thus, SCs are largely juxtavascular and reciprocally interact with ECs during differentiation to support angio-myogenesis.
Transplantation of undifferentiated murine embryonic stem cells in the heart: teratoma formation and immune response
Authors: Nussbaum Jeannette , Minami Elina , Laflamme Michael A. , Virag Jitka A. I. , Ware Carol B. , Masino Amanda , Muskheli Veronica , Pabon Lil , Reinecke Hans , Murry Charles E.
Published: February 2007

Embryonic stem (ES) cells are promising for cardiac repair’ but directing their differentiation toward cardiomyocytes remains challenging. We investigated whether the heart guides ES cells toward cardiomyocytes in vivo and whether allogeneic ES cells were immunologically tolerated. Undifferentiated mouse ES cells consistently formed cardiac teratomas in nude or immunocompetent syngeneic mice. Cardiac teratomas contained no more cardiomyocytes than hind‐limb teratomas’ suggesting lack of guided differentiation. ES cells also formed teratomas in infarcted hearts’ indicating injury‐related signals did not direct cardiac differentiation. Allogeneic ES cells also caused cardiac teratomas’ but these were immunologically rejected after several weeks’ in association with increased inflammation and up‐regulation of class I and II histocompatibility antigens. Fusion between ES cells and cardiomyocytes occurred in vivo’ but was rare. Infarct autofluorescence was identified as an artifact that might be mistaken for enhanced GFP expression and true regeneration. Hence’ undifferentiated ES cells were not guided toward a cardiomyocyte fate in either normal or infarcted hearts’ and there was no evidence for allogeneic immune tolerance of ES cell derivatives. Successful cardiac repair strategies involving ES cells will need to control cardiac differentiation’ avoid introducing undifferentiated cells’ and will likely require immune modulation to avoid rejection.—Nussbaum, J., Minami, E., Laflamme, M. A., Virag, J. A. I., Ware, C. B., Masino, A., Muskheli, V., Pabon, L., Reinecke, H., Murry, C. E. Transplantation of undifferentiated mu‐rine embryonic stem cells in the heart: teratoma formation and immune response. FASEB J. 21, 1345–1357 (2007)
Cardiac effects of 3‐iodothyronamine: a new aminergic system modulating cardiac function
Authors: Chiellini Grazia , Frascarelli Sabina , Ghelardoni Sandra , Carnicelli Vittoria , Tobias Sandra C. , DeBarber Andrea , Brogioni Simona , Ronca-Testoni Simonetta , Cerbai Elisabetta , Grandy David K. , Scanlan Thomas S. , Zucchi Riccardo
Published: February 2007

3‐iodothyronamine T1AM is a novel endogenous thyroid hormone derivative that activates the G protein‐coupled receptor known as trace anime‐associated receptor 1 (TAAR1). In the isolated working rat heart and in rat cardiomyocytes, T1AM produced a reversible, dose‐dependent negative inotropic effect (e.g.,27±5, 51 ±3, and 65±2% decrease in cardiac output at 19, 25, and 38 μM concentration, respectively). An independent negative chronotropic effect was also observed. The hemodynamic effects of T1AM were remarkably increased in the presence of the tyrosine kinase inhibitor genistein, whereas they were attenuated in the presence of the tyrosine phosphatase inhibitor vanadate. No effect was produced by inhibitors of protein kinase A, protein kinase C, calcium‐calmodulin kinase II, phosphatidylinositol‐3‐kinase, or MAP kinases. Tissue cAMP levels were unchanged. In rat ventricular tissue, Western blot experiments with antiphosphotyrosine antibodies showed reduced phosphorylation of microsomal and cytosolic proteins after perfusion with synthetic T1AM;reverse transcriptase‐polymerase chain reaction experiments revealed the presence of transcripts for at least 5 TAAR subtypes; specific and saturable binding of [125I]T1AM was observed, with a dissociation constant in the low micromolar range (5 μM); and endogenous T1AM was detectable by tandem mass spectrometry. In conclusion, our findings provide evidence for the existence of a novel aminergic system modulating cardiac function.—Chiellini G., Frascarelli, S., Ghelardoni, S., Carnicelli, V., Tobias, S. C., DeBarber, A., Brogioni, S., Ronca‐Testoni, S., Cerbai, E., Grandy, D. K., Scanlan, T. S., Zucchi R. Cardiac effects of 3‐iodothyronamine: a new aminergic system modulating cardiac function. FASEB J. 21, 1597–1608 (2007)
Stress impacts telomere dynamics
Authors: Kotrschal Alexander , Ilmonen Petteri , Penn Dustin J
Published: February 2007

Telomeres are DNA–protein complexes at the ends of chromosomes that control genomic integrity but appear to become shorter with age and stress. To test whether stress causes telomere attrition, we exposed the offspring of wild-caught house mice (
Mus musculus
) to stressful conditions and examined the changes in telomere length over six months. We found that females exposed to males and reproductive stress (either with or without crowding) had significantly shorter telomeres than controls, and males exposed to crowding stress had shorter telomeres than males that were not crowded. Our results indicate that stress alters telomere dynamics, causing attrition and hindering restoration, and these effects are sex dependent. Telomeres may thus provide a biomarker for assessing an individual's cumulative exposure or ability to cope with stressful conditions.
Like mother, like daughter: inheritance of nest-site location in snakes
Authors: Brown Gregory P , Shine Richard
Published: February 2007

A trait can be passed from parents to offspring even if it has no genetic basis. For example, if daughters return to reproduce at the same sites where they were hatched themselves, nest-site location is consistent within matrilineages. Most cases of natal homing (nest-site philopatry) across generations have been inferred from molecular evidence rather than directly demonstrated, and involve species with low dispersal abilities. However, some animals disperse long distances but then return to their own place of birth to reproduce, based on cues imprinted early in their own development. Our field studies on tropical natricine snakes (
Tropidonophis mairii
, Colubridae) show that when they are ready to nest, females return to the sites where their mothers were captured pre-nesting, and where they themselves were released as hatchlings.