bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient entanglements and clusters in dilute polymer solutions
Authors: Bednar F. , de Oliveira M. H. , Paris J. , van de Ven T. G. M.
Published: December 2007

A convenient method to monitor polymer dissolution is to measure the pressure drop created by passing a polymer solution through a capillary constriction rheometer. In this work, we studied the dissolution of polyethylene oxide (PEO) and cationic starch (C‐starch). We found that for freshly dissolved and entangled PEO, the main contribution to the overall pressure drop is due to the contraction and expansion of PEO entanglements at the entrance and exit of the capillary, and that the friction in the capillary plays a minor role. On the other hand, for well‐dissolved PEO, because of the absence of PEO entanglements, the loss of pressure is mainly due to friction. At high velocities the contraction and expansion coefficient for freshly dissolved PEO was more than 20 times higher than for well‐dissolved PEO, resulting in a three times higher overall pressure drop. C‐starch consists of amylopectin (∼ 85%) and amylose and is known to contain clusters when freshly dissolved, likely formed from the globular amylopectin molecules. For C‐starch, the main contribution to the overall pressure drop is due to friction. Entrance and exit effects contribute only 10% to the overall pressure drop, which might be due to the linear amylose molecules in C‐starch. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 253–262, 2008
Reorientation of crystalline and noncrystalline regions in regenerated cellulose fibers and films tested in uniaxial tension
Authors: Gindl Wolfgang , Reifferscheid Moritz , Martinschitz Klaus J. , Boesecke Peter , Keckes Jozef
Published: December 2007

The orientation of molecular chains in regenerated cellulose films and fibers was characterized using in situ wide‐angle X‐ray diffraction and birefringence measurements coupled with tensile tests. Generally, an increase in the degree of preferred orientation in the direction of applied strain was observed during testing. For both types of specimen this relationship was clearly linear, irrespective of whether the volume‐averaged preferred orientation or the orientation in the crystalline and noncrystalline regions was considered. Interestingly, the rate of change in orientation induced by external strain was significantly higher for noncrystalline regions when compared with that of crystalline regions. This difference was more pronounced for cellulose fibers when compared with films. Upon the reversal of straining in cellulose films until zero stress, the degree of orientation diminished in a linear fashion. However, a large part of the orientation, both crystalline and noncrystalline, induced by tensile straining remained permanent and increased further when straining was resumed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 297–304, 2008
Uniaxially aligned carbon nanofibers derived from electrospun precursor yarns
Authors: Okuzaki Hidenori , Takahashi Takui , Hara Yusuke , Yan Hu
Published: December 2007

Unlike conventional electrospun polymer fibers deposited on a target electrode as a randomly oriented mesh, poly(p‐xylenetetrahydrothiophenium chloride) was electrospun into centimeters‐long yarns vertically on the surface of the electrode but parallel to the electric field. The diameter of the yarn was strongly affected by the concentration, spinning rate, and viscosity of the polymer solution, but less dependent on the applied voltage. The subsequent carbonization of thus‐electrospun yarns at 600–1000 °C resulted in uniaxially aligned carbon nanofibers with average diameters of 127–184 nm. On the basis of Raman spectra, the graphitic crystallite size and the molar fraction of graphite were estimated to be 1.2–1.4 and 0.21–0.24 nm, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 305–310, 2008
A 3‐factor model for the FACIT‐Sp
Authors: Canada Andrea L. , Murphy Patricia E. , Fitchett George , Peterman Amy H. , Schover Leslie R.
Published: December 2007

Objective: The 12‐item Functional Assessment of Chronic Illness Therapy—Spiritual Well‐being Scale (FACIT‐Sp) is a popular measure of the religious/spiritual (R/S) components of quality of life (QoL) in patients with cancer. The original factor analyses of the FACIT‐Sp supported two factors: Meaning/Peace and Faith. Because Meaning suggests a cognitive aspect of R/S and Peace an affective component, we hypothesized a 3‐factor solution: Meaning, Peace, and Faith.

Methods: Participants were 240 long‐term female survivors of cancer who completed the FACIT‐Sp, the SF‐12, and the BSI 18. We used confirmatory factor analysis to compare the 2‐ and 3‐factor models of the FACIT‐Sp and subsequently assessed associations between the resulting solutions and QoL domains.

Results: Survivors averaged 44 years of age and 10 years post‐diagnosis. A 3‐factor solution of the FACIT‐Sp significantly improved the fit of the model to the data over the original 2‐factor structure (Δχ2=72.36, df=2, p<0.001). Further adjustments to the 3‐factor model resulted in a final solution with even better goodness‐of‐fit indices (χ2=59.11, df=1, p=0.13, CFI=1.00, SMRM=0.05).

The original Meaning/Peace factor controlling for Faith was associated with mental (r=0.63, p<0.000) and physical (r=0.22, p<0.01) health on the SF‐12, and the original Faith factor controlling for Meaning/Peace was negatively associated with mental health (r=−0.15, p<0.05). The 3‐factor model was more informative. Specifically, using partial correlations, the Peace factor was only related to mental health (r=0.53, p<0.001); Meaning was related to both physical (r=0.18, p<0.01) and mental (r=0.17, p<0.01) health; and Faith was negatively associated with mental health (r=−0.17, p<0.05).

Conclusion: The results of this study support a 3‐factor solution of the FACIT‐Sp. The new solution not only represents a psychometric improvement over the original, but also enables a more detailed examination of the contribution of different dimensions of R/S to QoL. Copyright © 2007 John Wiley & Sons, Ltd.
The University of New Brunswick's Renaissance College: Curricular evolution and assessment at the faculty level
Authors: Zundel Pierre , Mengel Thomas
Published: December 2007

This chapter introduces a comprehensive model of curricular evolution and assessment at the faculty level as developed and implemented in a core program at Renaissance College, University of New Brunswick.
On entropy conditions and traffic flow models
Authors: Knowles J.K.
Published: December 2007

This paper is concerned with “entropy conditions” for traffic flow models governed by one‐dimensional nonlinear scalar conservation laws. The classical conditions of this type serve as selection principles used to overcome the lack of uniqueness of weak solutions for such laws. These principles select solutions in accord with observations for the simplest traffic flow models, but they seem not to do so when the constitutive law underlying the model is refined so as to be more realistic. The classical conditions are here compared with an analog of the second law of thermodynamics based on an entropy density that crudely measures the disorder of the traffic flow.
Kinetic Studies on Oxirane Cleavage of Epoxidized Soybean Oil by Methanol and Characterization of Polyols
Authors: Lin Bo , Yang Liting , Dai Honghai , Yi Aihua
Published: December 2007

The kinetics of the oxirane cleavage of epoxidized soybean oil (ESO) by methanol (Me) without a catalyst was studied at 50, 60, 65, 70 °C. The rate of oxirane ring opening is given by k[Ep][Me]2, where [Ep] and [Me] are the concentrations of oxiranes in ESO and methanol, respectively and k is a rate constant. From the temperature dependence of the kinetics thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), free energy of activation (ΔF) and activation energy (ΔEa) were found to be 76.08 (±1.06) kJ mol−1, −118.42 (±3.12) J mol−1 k−1, 111.39 (±2.86) kJ mol−1, and 78.56 (±1.63) kJ mol−1, respectively. The methoxylated polyols formed from the oxirane cleavage reaction , were liquid at room temperature and had three low temperature melting peaks. The results of chemical analysis via titration for residual oxiranes in the reaction system showed good agreement with IR spectroscopy especially the disappearance of epoxy groups at 825, 843 cm−1 and the emergence of hydroxy groups at the OH characteristic absorption peak from 3,100 to 3,800 cm−1.
Involvement of MAPK signaling molecules and Runx2 in the NELL1‐induced osteoblastic differentiation
Authors: Bokui Nobuyuki , Otani Takayuki , Igarashi Koichi , Kaku Junichiro , Oda Mitsuo , Nagaoka Tadahiro , Seno Masaharu , Tatematsu Kenji , Okajima Toshihide , Matsuzaki Takashi , Ting Kang , Tanizawa Katsuyuki , Kuroda Shun'ichi
Published: December 2007

NELL1 is an extracellular protein inducing osteogenic differentiation and bone formation of osteoblastic cells. To elucidate the intracellular signaling cascade evoked by NELL1, we have shown that NELL1 protein transiently activates the MAPK signaling cascade, induces the phosphorylation of Runx2, and promotes the rapid intracellular accumulation of Tyr‐phosphorylated proteins. Unlike BMP2, NELL1 protein does not activate the Smad signaling cascade. These findings suggest that upon binding to a specific receptor NELL1 transduces an osteogenic signal through activation of certain Tyr‐kinases associated with the Ras‐MAPK cascade, and finally leads to the osteogenic differentiation.
Melanoma cell sensitivity to Docetaxel‐induced apoptosis is determined by class III β‐tubulin levels
Authors: Mhaidat Nizar M. , Thorne Rick F. , de Bock Charles Edo , Zhang Xu Dong , Hersey Peter
Published: December 2007

We have previously shown that Docetaxel‐induced variable degrees of apoptosis in melanoma. In this report, we studied the β‐tubulin repertoire of melanoma cell lines and show that class III β‐tubulin expression correlated with Docetaxel‐resistance. Sensitive cells showed low levels of class III β‐tubulin with little microtubular incorporation, whereas class III β‐tubulin expression was higher in resistant cells and was incorporated into the cytoskeleton. As proof of concept, abrogation of class III by siRNA reverted Docetaxel‐resistant cells to a sensitive phenotype, restoring the microtubular polymerisation response and promoting high levels of apoptosis through Bax activation. These results suggest that phenotypic expression of β‐tubulin class III in melanoma may help identify patients with melanoma that can respond to taxanes.
On Simmel's Pure Concept of Money: A Response to Ingham
Authors: Dodd Nigel
Published: December 2007

In “Laundering ‘Money’: On the Need for Conceptual Clarity within the Sociology of Money”, I explored the conceptual ramifications of recent developments in the sociology of money. These developments corresponded to what appear to be two countervailing trends in the world of money: homogenisation and diversification. The second trend, particularly, raises important conceptual questions about how money should be defined, and I sought to address these through an analysis of the work of prominent monetary scholars such as Cohen, Hart, Ingham and Zelizer. My central aim was to bring greater clarity to a field – the sociology of money – lacking a commonly agreed definition of its core object of study, namely money. The article was motivated by an underlying sense that these scholars were talking past each other. One significant reason seemed to be that two terms that should be central to a meaningful engagement among leading sociologists of money – money and currency – were being used in different and incompatible ways. This was the “conceptual confusion” I referred to: not a confusion specific to any individual monetary scholar, but rather a confusion bound to arise from any comparison of their work. I aimed to propose a conceptual framework wherein their different analyses could be more usefully compared (2). Of these scholars, both Hart (3) and Zelizer have constructively responded to my proposals without, of course, agreeing with them all.
THE IMPORTANCE OF METAPHYSICAL REALISM FOR ETHICAL KNOWLEDGE
Authors: Rasmussen Douglas B.
Published: December 2007

In this essay, I consider whether the alleged demise of metaphysical realism does actually provide a better way for defending the cognitive status of ethical judgments. I argue that the rejection of a realist ontology and epistemology does not help to establish the claim that ethical knowledge is possible. More specifically, I argue that Hilary Putnam's argument does not succeed in making a case for ethical knowledge. In fact, his account of the procedures by which our valuations are warranted—the criteria of idealized inquiry—ultimately begs the question in a number of crucial ways. Moreover, it prejudices the moral and political discussion in certain ideological respects. Finally, though Putnam has apparently modified to some extent his approach to the issue of realism in recent years, I will point out that these modifications are not fundamental and do not help to advance the case for ethical knowledge. I note also that Martha C. Nussbaum's appeal to Putnam’s argument actually works against her attempt to make a case for an Aristotelian conception of human flourishing. Ultimately, I conclude that metaphysical realism is vital for ethical knowledge.
CONSTRUCTING NORMATIVE OBJECTIVITY IN ETHICS
Authors: Wong David B.
Published: December 2007

This essay explains the inescapability of moral demands. I deny that the individual has genuine reason to comply with these demands only if she has desires that would be served by doing so. Rather, the learning of moral reasons helps to shape and channel self- and other-interested motivations so as to facilitate and promote social cooperation. This shaping happens through the “embedding” of reasons in the intentional objects of motivational propensities. The dominance of the instrumental conception of reason, according to which reasons must be based in desires of the individual, has made it harder to recognize that reasons shape desires. I attempt to undermine this dominance by arguing that the concept of a self that extends over time is constructed to meet the demands of social cooperation. Prudential reasons to act on behalf of the persisting self's desires are often taken to constitute the paradigm of reasons based on desires of the individual. But such reasons, along with the very concept of the persisting self, are constructed to promote human cooperation and to shape the individual's desires.
Recent eruptive history and magma reservoir dynamics on the southern East Pacific Rise at 17°30′S
Authors: Bergmanis Eric C. , Sinton John , Rubin Kenneth H.
Published: December 2007

Submersible‐based geologic observations and geochemical, magnetic paleointensity, and (210Pb/226Ra) radioactive disequilibria data indicate that at least five distinct lava sequences (three normal mid‐ocean ridge basalt (N‐MORB) and two transitional mid‐ocean ridge basalt (T‐MORB)) have been erupted within the last several hundred years along a 27‐km‐long portion of the fast spreading East Pacific Rise near 17°30′S. Isotopic and geochemical variations, both within and between eruptive units, indicate mixing of different primary magmas concurrently with differentiation in shallow‐level subaxial magma reservoirs. Differentiation trends are linked to geographical variations in axial magma chamber (AMC) characteristics, with the lowest MgO samples erupted above the shallowest portion of the AMC, suggesting that pre‐eruptive magma temperature is in part controlled by the depth‐dependent efficacy of hydrothermal cooling. A third‐order axial discontinuity at ∼17°29′S coincides with a narrowing of the subaxial melt lens and an increase in lava MgO to the south; we interpret the latter to reflect a sharp increase in the mixing proportion of recharge to low‐MgO magma residing in the melt lens. Magmatic evolution of this area over the last few hundred years reflects continually evolving conditions in the subsurface and mantle melting processes that vary rapidly at rates that are at least as great as the eruption rate.
Inverse modeling of surface NOx anthropogenic emission fluxes in the Paris area during the Air Pollution Over Paris Region (ESQUIF) campaign
Authors: Pison Isabelle , Menut Laurent , Bergametti Gilles
Published: December 2007

An inverse modeling approach has been developed to optimize urban NOx emission fluxes. We used the chemistry‐transport model CHIMERE and its adjoint to develop a new methodology that includes kriging of measurements and a dynamic spatial aggregation model taking into account surface morphology of emission fluxes and ozone plumes to determine areas where emissions are inverted. This method is first applied to a seasonal approach over the Paris area. All emission fluxes were inverted hourly for the months of July and August of years 1998 and 1999. This leads to a significant reduction of the differences between simulated and measured concentrations of ozone and NOx. The results suggest that in the first‐guess inventory, NOx fluxes are overestimated in the city of Paris and underestimated in the suburban areas. For the two periods the differences between optimized and first‐guess profiles are about 15%. Comparisons between time profiles showed that Mondays and Wednesdays in August had characteristics that made them differ from the other days of the week. Two intensive observation periods of the Air Pollution Over Paris Region (ESQUIF) campaign are focused on and hourly results are discussed in order to refine the climatological results.
Biogeochemical evolution of cryoconite holes on Canada Glacier, Taylor Valley, Antarctica
Authors: Bagshaw Elizabeth A. , Tranter Martyn , Fountain Andrew G. , Welch Kathleen A. , Basagic Hassan , Lyons W. Berry
Published: December 2007

The cryoconite holes of the McMurdo Dry Valleys are simple, closed biogeochemical systems involving water, ice, mineral and organic debris, which serve as ecosystems for consortia of microorganisms. This study is the first to document the seasonal and annual chemical evolution of solutes in cryoconite holes. Samples of glacier ice, frozen cryoconite holes and those containing water were collected during the austral summer of 2005–2006. The isolation age was calculated from the excess Cl− in the holes, and varied from 0 to 5 years (a), consistent with the last hot summer when the cryoconite holes were open to the atmosphere. The holes progressively deepen with isolation age. Variations in DIC, DOC, K+ and SO42− suggest that dissolution of primary minerals in the cryoconite debris, cyclical precipitation and dissolution of secondary carbonates, net photosynthesis over summer and net respiration during the autumnal freeze are the principal reactions which perturb the seasonal and annual solute concentrations in the holes. DOC is generated in the holes at a rate of 7.5 μg C cm−2 a−1, and non‐sea‐salt K+ accumulates in frozen holes at a rate of 0.073 μeq cm−2 a−1. We infer that C cycling is complex even in these otherwise simple systems.
Arabian Sea response to monsoon variations
Authors: Murtugudde Raghu , Seager Richard , Thoppil Prasad
Published: December 2007

This study aims to quantify the impact of strong monsoons on the mixed layer heat budget in the Arabian Sea by contrasting forced ocean general circulation model simulations with composite strong and weak monsoon winds. Strong (weak) monsoons are defined as years with zonal component of the Somali Jet being greater (smaller) by more than a standard deviation of the long‐term mean of the National Centers for Environmental Prediction reanalysis winds. Coastal upwelling is shown to be demonstrably stronger for strong monsoons leading to significant surface cooling, shallower thermoclines, and deeper mixed layers. A coupled ecosystem model shows that surface chlorophyll, primary, and export production are indeed higher for strong monsoons compared to weak monsoons driven by the supply of colder, nutrient‐rich waters from greater than 100 m depths. The surprising result is that a strong monsoon results in stronger negative wind stress curl away from the coasts and drives Ekman pumping that results in a deeper thermocline. The weaker stratification and larger turbulent kinetic energy from the winds drive deeper mixed layers leading entrainment cooling with some contribution from the advection of colder upwelled waters from the coastal upwelling regions. Thus the strong monsoons, in fact, enhance oceanic heat uptake indicating that ocean dynamics are cooling the surface and driving the lower atmosphere which has implications for the interpretation of monsoon variability from paleorecords.
Purine sensing by riboswitches
Authors: Kim Jane N. , Breaker Ronald R.
Published: December 2007

Structured mRNA elements called riboswitches control gene expression by binding to small metabolites. Over a dozen riboswitch classes have been characterized that target a broad range of molecules and vary widely in size and secondary structure. Four of the known riboswitch classes recognize purines or modified purines. Three of these classes are closely related in conserved sequence and secondary structure, but members of these classes selectively recognize guanine, adenine or 2′‐deoxyguanosine. Members of the fourth riboswitch class adopt a distinct structure to form a selective binding pocket for the guanine analogue preQ1 (7‐aminomethyl‐7‐deazaguanine). All four classes of purine‐sensing riboswitches are most likely to recognize their respective metabolites by utilizing a riboswitch residue to make a canonical Watson—Crick base‐pair with the ligand. This review will provide a summary of the purine‐sensing riboswitches, as well as discuss the complex functions and applications of these RNAs.
Hydrogen bonding lights up overtones in pyrazoles
Authors: Wassermann T. N. , Rice C. A. , Suhm M. A. , Luckhaus D.
Published: December 2007

The spectral complexity in the NH stretching mode of hydrogen-bonded pyrazoles is traced back to an extensive Fermi resonance system involving combinations and overtones of at least four aromatic ring modes with significant in plane hydride bending character. The couplings are shown to be inherent in the monomer, but hydrogen bonding is required to bring them into resonance with the NH stretching chromophore. A cost-efficient variational “monomers-in-clusters” model is presented and applied to a five-dimensional subspace of pyrazole. Spectra of substituted pyrazoles confirm the robustness of the coupling, which remains dark in strained dimers, but lights up in linearly hydrogen-bonded trimers.
A theoretical study on the frequency-dependent electric conductivity of electrolyte solutions
Authors: Yamaguchi T. , Matsuoka T. , Koda S.
Published: December 2007

The theory on the ultrasonic absorption of electrolyte solutions we have proposed previously [T. Yamaguchi et al., J. Chem. Phys. 126, 144505 (2007)] is extended to calculate the frequency-dependent electric conductivity of the solution. The ionic contribution of the dielectric relaxation spectrum is obtained at the same time. The theory is able to handle the contributions of both the ion-pair dynamics and the relaxation of ionic atmosphere, as is the case of ultrasonic absorption. The effect of the barrier height between the contact and solvent-separated ion pairs is investigated in detail. It is clarified that the competition between the dissociation and reorientational relaxation rates of the contact ion pair is an important factor for the ion pair to be regarded as the ion pair in terms of ionic conductivity.
Generation of fast ions by an efficient coupling of high power laser into snow nanotubes
Authors: Palchan T. , Henis Z. , Faenov A. Y. , Magunov A. I. , Pikuz S. A. , Gasilov S. V. , Skobelev I. Yu. , Zigler A.
Published: December 2007

Generation of fast ions in snow nanotubes irradiated by femtosecond laser pulses in the intensity range of 1016–1017W∕cm2 was investigated. The fast ion energy was measured through x-ray emission spectra of multicharged ions of oxygen. The profile of the He-β and Ly-α in He-like and H-like oxygen lines demonstrates a significant broadening, which may indicate generation of fast He-like and H-like ions with energies of up to 100keV.
Interacting quantum gases in confined space: Two- and three-dimensional equations of state
Authors: Dai Wu-Sheng , Xie Mi
Published: December 2007

In this paper, we calculate the equations of state and the thermodynamic quantities for two- and three-dimensional hard-sphere Bose and Fermi gases in finite-size containers. The approach we used to deal with interacting gases is to convert the effect of interparticle hard-sphere interaction to a kind of boundary effect, and then the problem of a confined hard-sphere quantum gas is converted to the problem of a confined ideal quantum gas with a complex boundary. For this purpose, we first develop an approach for calculating the boundary effect on d-dimensional ideal quantum gases and then calculate the equation of state for confined quantum hard-sphere gases. The thermodynamic quantities and their low-temperature and high-density expansions are also given. In higher-order contributions, there are cross terms involving both the influences of the boundary and of the interparticle interaction. We compare the effect of the boundary and the effect of the interparticle interaction. Our result shows that, at low temperatures and high densities, the ratios of the effect of the boundary to the effect of the interparticle interaction in two dimensions are essentially different to those in three dimensions: in two dimensions, the ratios for Bose systems and for Fermi systems are the same and are independent of temperatures, while in three dimensions, the ratio for Bose systems depends on temperatures, but the ratio for Fermi systems is independent of temperatures. Moreover, for three-dimensional Fermi cases, compared with the contributions from the boundary, the contributions from the interparticle interaction to entropies and specific heats are negligible.
Analytical and numerical stability analysis of Soret-driven convection in a horizontal porous layer
Authors: Charrier-Mojtabi M. C. , Elhajjar B. , Mojtabi A.
Published: December 2007

We present an analytical and numerical stability analysis of Soret-driven convection in a porous cavity saturated by a binary fluid. Both the mechanical equilibrium solution and the monocellular flow obtained for particular ranges of the physical parameters of the problem are considered. The porous cavity, bounded by horizontal infinite or finite boundaries, is heated from below or from above. The two horizontal plates are maintained at different constant temperatures while no mass flux is imposed. The influence of the governing parameters and more particularly the role of the separation ratio, ψ, characterizing the Soret effect and the normalized porosity, ε, are investigated theoretically and numerically. From the linear stability analysis, we find that the equilibrium solution loses its stability via a stationary bifurcation or a Hopf bifurcation depending on the separation ratio and the normalized porosity of the medium. The role of the porosity is important, when it decreases, the stability of the equilibrium solution is reinforced. For a cell heated from below, the equilibrium solution loses its stability via a stationary bifurcation when the separation ratio ψ>ψ0(Le,ε), while for ψ<ψ0(Le,ε), it loses stability via a Hopf subcritical bifurcation. The oscillatory solution is unstable and becomes stationary. For a cell heated from above, the equilibrium solution is linearly stable if ψ>0, while a stationary or an oscillatory bifurcation occurs if ψ<0. The results obtained from the linear stability analysis are widely corroborated by direct 2D numerical simulations. In the case of long-wave disturbances, for ψ<0 and for ψ higher than a particular value called ψmono, we observe that the monocellular flow leads to a separation of the species between the two ends of the cell. First, we determined the velocity, temperature, and concentration fields analytically for monocellular flow. Then we studied the stability of this flow. For a cell heated from below and for ψ>ψmono the monocellular flow loses stability via a Hopf bifurcation. As the Rayleigh number increases, the resulting oscillatory solution evolves to a stationary multicellular flow. For a cell heated from above and ψ<0, the monocellular flow remains linearly stable. We verified numerically that this problem admits other stable multicellular stationary solutions for this range of parameters.
Mid-infrared optical coherence tomography
Authors: Colley Christopher S. , Hebden Jeremy C. , Delpy David T. , Cambrey Alison D. , Brown Robert A. , Zibik Evgeny A. , Ng Wing H. , Wilson Luke R. , Cockburn John W.
Published: December 2007

A time domain optical coherence tomography (OCT) system is described that uses mid-infrared light (6–8μm). To the best of our knowledge, this is the first OCT system that operates in the mid-infrared spectral region. It has been designed to characterize bioengineered tissues in terms of their structure and biochemical composition. The system is based upon a free-space Michelson interferometer with a germanium beam splitter and a liquid nitrogen cooled HgCdTe detector. A key component of this work has been the development of a broadband quantum cascade laser source (InGaAs∕AlInAs containing 11 different active regions of the three well vertical transition type) that emits continuously over the 6–8μm wavelength range. This wavelength range corresponds to the so called “mid-infrared fingerprint region” which exhibits well-defined absorption bands that are specifically attributable to the absorbing molecules. Therefore, this technology provides an opportunity for optical coherence molecular imaging without the need for molecular contrast agents. Preliminary measurements are presented.
Scalar flux spectrum in isotropic steady turbulence with a uniform mean gradient
Authors: Watanabe Takeshi , Gotoh Toshiyuki
Published: December 2007

The scaling law of a scalar flux spectrum (velocity-scalar cospectrum) in the inertial convective range of passive scalar turbulence under a uniform mean scalar gradient is examined using direct numerical simulation with a resolution of up to 20483 grid points. When the Reynolds number Reλ is increased up to Reλ=585, the scalar flux spectrum tends to obey the power law k−7∕3, as predicted by Lumley [J. Atmos. Sci. 21, 99 (1964); Phys. Fluids 10, 855 (1967)], with a nondimensional constant of Cuθ=1.50±0.08 at Reλ=585. The Reλ effect on the scaling of the scalar flux spectrum is well compensated using the mean molecular destruction of the scalar flux ϵ¯uθ. The Reλ dependence of Cuθ is also compared with the results of previous studies, and its asymptotic state at an infinite Reynolds number is discussed.
Transmission of microwaves through a stepped subwavelength slit
Authors: Lockyear Matthew J. , Hibbins Alastair P. , Sambles J. Roy
Published: December 2007

The transmission of normally incident plane wave microwaves through a single stepped subwavelength slit in a thick metal plate is explored. The presence of the step substantially increases the radiation wavelength which may be resonantly transmitted to well beyond twice the plate thickness. Insight into the resonant behavior is provided through analysis of field solutions produced by a finite element model.
Control of two-phase flow in a microfluidic system using ac electric fields
Authors: Morgan H. , Green N. G. , Ramos A. , Garcia-Sanchez P.
Published: December 2007

The control and handling of fluids are central to many applications of the lab on chip. We report how alternating current (ac) electric fields can deflect and manipulate coflowing streams of two different electrolytes within a microfluidic channel. The two different electrolytes flow side by side over an array of interdigitated electrodes which occupies the width of the channel. Application of a 20V (peak to peak) voltage at 1MHz to the electrodes causes the liquid with higher conductivity to occupy a larger region of the channel. This effect causes a significant displacement of the boundary between the two fluids.
How I Managed to Hide My Shadow
Authors: Casati Roberto
Published: December 2007

A special type of visual stimulus is described which gives the perceiver the impression that a shadow has been hidden behind a surface in the image, contrary to expectations based on ecological situations in which covering a shadow only passes it on to the cover.
Defects in XRCC4 and KU80 differentially affect the joining of distal nonhomologous ends
Authors: Guirouilh-Barbat Josée , Rass Emilie , Plo Isabelle , Bertrand Pascale , Lopez Bernard S.
Published: December 2007

XRCC4-null mice have a more severe phenotype than KU80-null mice. Here, we address whether this difference in phenotype is connected to nonhomologous end-joining (NHEJ). We used intrachromosomal substrates to monitor NHEJ of two distal double-strand breaks (DSBs) targeted by I-SceI, in living cells. In
xrcc4
-defective XR-1 cells, a residual but significant end-joining process exists, which primarily uses microhomologies distal from the DSB. However, NHEJ efficiency was strongly reduced in
xrcc4
-defective XR-1 cells versus complemented cells, contrasting with KU-deficient xrs6 cells, which showed levels of end-joining similar to those of complemented cells. Nevertheless, sequence analysis of the repair junctions indicated that the accuracy of end-joining was strongly affected in both
xrcc4
-deficient and KU-deficient cells. More specifically, these data showed that the KU80/XRCC4 pathway is conservative and not intrinsically error-prone but can accommodate non-fully complementary ends at the cost of limited mutagenesis.
Chemical mimicry of viral capsid self-assembly
Authors: Olson Arthur J. , Hu Yunfeng H. E. , Keinan Ehud
Published: December 2007

Stable structures of icosahedral symmetry can serve numerous functional roles, including chemical microencapsulation and delivery of drugs and biomolecules, epitope presentation to allow for an efficient immunization process, synthesis of nanoparticles of uniform size, observation of encapsulated reactive intermediates, formation of structural elements for supramolecular constructs, and molecular computing. By examining physical models of spherical virus assembly we have arrived at a general synthetic strategy for producing chemical capsids at size scales between fullerenes and spherical viruses. Such capsids can be formed by self-assembly from a class of molecules developed from a symmetric pentagonal core. By designing chemical complementarity into the five interface edges of the molecule, we can produce self-assembling stable structures of icosahedral symmetry. We considered three different binding mechanisms: hydrogen bonding, metal binding, and formation of disulfide bonds. These structures can be designed to assemble and disassemble under controlled environmental conditions. We have conducted molecular dynamics simulation on a class of corannulene-based molecules to demonstrate the characteristics of self-assembly and to aid in the design of the molecular subunits. The edge complementarities can be of diverse structure, and they need not reflect the fivefold symmetry of the molecular core. Thus, self-assembling capsids formed from coded subunits can serve as addressable nanocontainers or custom-made structural elements.
Durable effects of concentrated disadvantage on verbal ability among African-American children
Authors: Sampson Robert J. , Sharkey Patrick , Raudenbush Stephen W.
Published: December 2007

Disparities in verbal ability, a major predictor of later life outcomes, have generated widespread debate, but few studies have been able to isolate neighborhood-level causes in a developmentally and ecologically appropriate way. This study presents longitudinal evidence from a large-scale study of >2,000 children ages 6–12 living in Chicago, along with their caretakers, who were followed wherever they moved in the U.S. for up to 7 years. African-American children are exposed in such disproportionate numbers to concentrated disadvantage that white and Latino children cannot be reliably compared, calling into question traditional research strategies assuming common points of overlap in ecological risk. We therefore focus on trajectories of verbal ability among African-American children, extending recently developed counterfactual methods for time-varying causes and outcomes to adjust for a wide range of predictors of selection into and out of neighborhoods. The results indicate that living in a severely disadvantaged neighborhood reduces the later verbal ability of black children on average by ≈ 4 points, a magnitude that rivals missing a year or more of schooling.
The subunit composition of hinokiresinol synthase controls geometrical selectivity in norlignan formation
Authors: Suzuki Shiro , Yamamura Masaomi , Hattori Takefumi , Nakatsubo Tomoyuki , Umezawa Toshiaki
Published: December 2007

The selective formation of
E
- or
Z
-isomers is an important process in natural product metabolism. We show that the subunit composition of an enzyme can alter the geometrical composition of the enzymatic products. Hinokiresinol synthase, purified from
Asparagus officinalis
cell cultures, is responsible for the conversion of (7
E
,7′
E
)-4-coumaryl 4-coumarate to (
Z
)-hinokiresinol, the first step in norlignan formation. The protein is most likely a heterodimer composed of two distinct subunits, which share identity with members of the phloem protein 2 gene superfamily. Interestingly, each recombinant subunit of hinokiresinol synthase expressed in
Escherichia coli
solely converted (7
E
,7′
E
)-4-coumaryl 4-coumarate to the unnatural (
E
)-hinokiresinol, the
E
-isomer of (
Z
)-hinokiresinol. By contrast, a mixture of recombinant subunits catalyzed the formation of (
Z
)-hinokiresinol from the same substrate.
Three-dimensional structure of cytoplasmic dynein bound to microtubules
Authors: Mizuno Naoko , Narita Akihiro , Kon Takahide , Sutoh Kazuo , Kikkawa Masahide
Published: December 2007

Cytoplasmic dynein is a large, microtubule-dependent molecular motor (1.2 MDa). Although the structure of dynein by itself has been characterized, its conformation in complex with microtubules is still unknown. Here, we used cryoelectron microscopy (cryo-EM) to visualize the interaction between dynein and microtubules. Most dynein molecules in the nucleotide-free state are bound to the microtubule in a defined conformation and orientation. A 3D image reconstruction revealed that dynein's head domain, formed by a ring-like arrangement of AAA+ domains, is located ≈280 Å away from the center of the microtubule. The order of the AAA+ domains in the ring was determined by using recombinant markers. Furthermore, a 3D helical image reconstruction of microtubules with a dynein's microtubule binding domain [dynein stalk (DS)] revealed that the stalk extends perpendicular to the microtubule. By combining the 3D maps of the dynein-microtubule and DS-microtubule complexes, we present a model for how dynein in the nucleotide-free state binds to microtubules and discuss models for dynein's power stroke.
Circulating tumor antigen-specific regulatory T cells in patients with metastatic melanoma
Authors: Vence Luis , Palucka A. Karolina , Fay Joseph W. , Ito Tomoki , Liu Yong-Jun , Banchereau Jacques , Ueno Hideki
Published: December 2007

Although it is accepted that regulatory T cells (T regs) contribute to cancer progression, most studies in the field consider nonantigen-specific suppression. Here, we show the presence of tumor antigen-specific CD4+T regs in the blood of patients with metastatic melanoma. These CD4+T regs recognize a broad range of tumor antigens, including gp100 and TRP1 (melanoma tissue differentiation antigens), NY-ESO-1 (cancer/testis antigen) and survivin (inhibitor of apoptosis protein (IAP) family antigen). These tumor antigen-specific T regs proliferate in peripheral blood mononuclear cells (PBMC) cultures in response to specific 15-mer peptides, produce preferentially IL-10 and express high levels of FoxP3. They suppress autologous CD4+CD25−T cell responses in a cell contact-dependent manner and thus share properties of both naturally occurring regulatory T cells and type 1 regulatory T cells. Such tumor antigen-specific T regs were not detected in healthy individuals. These tumor antigen-specific T regs might thus represent another target for immunotherapy of metastatic melanoma.
Neighbourhood Deprivation, Social Capital and Regular Exercise during Adulthood: A Multilevel Study in Chicago
Authors: Ming Wen  , Browning Christopher R. , Cagney Kathleen A.
Published: December 2007

This multilevel research examines the contextual effects of neighbourhood SES and social capital indicators on physical activity over and above individual socio-demographic background. Using 1990 census data and two social surveys, the hypotheses are tested among 907 Chicagoans in 242 neighbourhoods in 1996. Significant interaction effects are found with gender and both neighbourhood SES and social capital; women's physical activity level is more responsive to neighbourhood context. Controlling for socio-demographic factors at the individual level and the interaction effects between neighbourhood variables and gender, social capital and neighbourhood SES appear to be significant correlates of individual physical activity. Moreover, contrary to most findings in the neighbourhood effects research on health, the data show that the effects of neighbourhood SES are stronger than the effects of household income. Interventions promoting physical activity should incorporate local environmental features into their designs.
A Unique Platform for H-Ras Signaling Involving Clathrin-independent Endocytosis
Authors: Porat-Shliom Natalie , Kloog Yoel , Donaldson Julie G.
Published: December 2007

Trafficking of H-Ras was examined to determine whether it can enter cells through clathrin-independent endocytosis (CIE). H-Ras colocalized with the CIE cargo protein, class I major histocompatibility complex, and it was sequestered in vacuoles that formed upon expression of an active mutant of Arf6, Q67L. Activation of Ras, either through epidermal growth factor stimulation or the expression of an active mutant of Ras, G12V, induced plasma membrane ruffling and macropinocytosis, a stimulated form of CIE. Live imaging of cells expressing H-RasG12V and fluorescent protein chimeras with pleckstrin homology domains that recognize specific phosphoinositides showed that incoming macropinosomes contained phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatiylinositol 3,4,5-trisphosphate (PIP3). PIP2loss from the macropinosome was followed by the recruitment of Rab5, a downstream target of Ras, and then PIP3loss. Our studies support a model whereby Ras can signal on macropinosomes that pass through three distinct stages: PIP2/PIP3, PIP3/Rab5, and Rab5. Vacuoles that form in cells expressing Arf6Q67L trap Ras signaling in the first stage, recruiting the active form of the Ras effectors extracellular signal-regulated kinase and protein kinase B (Akt) but not Rab5. Arf6 stimulation of macropinocytosis also involves passage through the distinct lipid phases, but recruitment of Akt is not observed.
Apparent fracture/adhesion energy of interfaces with periodic cohesive interactions
Authors: Chen Bin , Shi Xinghua , Gao Huajian
Published: December 2007

The apparent fracture/adhesion energy of an interface with periodic cohesive interactions is of general interest to understanding adhesion via periodic adhesion patches (e.g. between micro- and nanostructured surfaces). There are two important length scales for this class of problems: one corresponds to the period of cohesive interaction and the other is the size of the cohesive zone near the tip of a crack along the interface. By theoretical considerations and numerical simulations, we show that the apparent fracture/adhesion energy depends on the ratio between the period of cohesive interaction and the cohesive zone size: it is equal to the average cohesive energy of the interface if the former is much smaller than the latter but becomes the peak value of the local cohesive energy when the opposite is true. This prediction has been confirmed by numerical simulations on the peeling of a thin-film/strip adhering on a substrate via periodic discrete adhesion patches. Our analysis also provides explanations for a recent molecular dynamics simulation which showed that the apparent adhesion energy of a single-stranded DNA (ssDNA) adhering on a graphite sheet is equal to the peak, rather than the average, value of the van der Waals interaction energy between the ssDNA and the substrate.
Impact of plant nutrients on the relationship between a herbivorous insect and its symbiotic bacteria
Authors: Chandler S.M , Wilkinson T.L , Douglas A.E
Published: December 2007

The interactions between herbivorous insects and their symbiotic micro-organisms can be influenced by the plant species on which the insects are reared, but the underlying mechanisms are not understood. Here, we identify plant nutrients, specifically amino acids, as a candidate factor affecting the impact of symbiotic bacteria on the performance of the phloem-feeding aphidAphis fabae.Aphis fabaegrew more slowly on the labiate plantLamium purpureumthan on an alternative host plantVicia faba, and the negative effect ofL. purpureumon aphid growth was consistently exacerbated by the bacterial secondary symbiontsRegiella insecticolaandHamiltonella defensa, which attained high densities inL. purpureum-reared aphids. The amino acid content of the phloem sap ofL. purpureumwas very low; andA. fabaeon chemically defined diets of low amino acid content also grew slowly and had elevated secondary symbiont densities. It is suggested that the phloem nutrient profile ofL. purpureumpromotes deleterious traits in the secondary symbionts and disturbs insect controls over bacterial abundance.
Female Barbary macaque (
Macaca sylvanus
) copulation calls do not reveal the fertile phase but influence mating outcome
Authors: Pfefferle Dana , Brauch Katrin , Heistermann Michael , Hodges J. Keith , Fischer Julia
Published: December 2007

In a number of primate species, females utter loud and distinctive calls during mating. Here we aim to clarify the information content and function of Barbary macaque (
Macaca sylvanus
) copulation calls by testing (i) whether or not copulation calls advertise the female fertile phase and (ii) whether and how copulation calls influence male ejaculatory behaviour. In order to do this, we combined hormone measurements with acoustic analysis and behavioural observations. In contrast to a previous study implying that the structure of copulation calls indicates the timing of the fertile phase, our results, using objective endocrine criteria for assessing ovulation, provide evidence that the structure of copulation calls of female Barbary macaques does not reveal the timing of the fertile phase. More importantly, females seem to influence the likelihood of ejaculation by calling versus remaining silent and by adjusting the timing of call onset. Females make use of this ability to influence mating outcome to ensure ejaculatory matings with almost all males in the group. In addition, calls given during ejaculatory copulations differ from those during non-ejaculatory copulations, providing information about mating outcome for listeners. We conclude that in this species, copulation calls apparently serve to enhance sperm competition and maximize paternity confusion.