Expanded State Research Articles

An analysis of the CoRoT-2 system: a young spotted star and its inflated giant planet

Context: CoRoT-2b is one of the most anomalously large exoplanet known. Given its large mass, its large radius cannot be explained by standard evolution models. Interestingly, the planet's parent star is an active, rapidly rotating solar-like star with a large fraction (7 to 20%) of spots. Aims: We want to provide constraints on the properties of the star-planet system and understand whether the planet's inferred large size may be due to a systematic error on the inferred parameters, and if not, how it may be explained. Methods: We combine stellar and planetary evolution codes based on all available spectroscopic and photometric data to obtain self-consistent constraints on the system parameters. Results: We find no systematic error in the stellar modeling (including spots and stellar activity) that would yield the required ~10% reduction in size for the star and thus the planet. Two classes of solutions are found: the usual main sequence solution for the star yields for the planet a mass of 3.67+/-0.13 Mjup, a radius of 1.55+/-0.03 Rjup for an age that is at least 130Ma, and should be less than 500Ma given the star's fast rotation and significant activity. We identify another class of solutions on the pre-main sequence, in which case the planet's mass is 3.45\pm 0.27 Mjup, its radius is 1.50+/-0.06 Rjup for an age between 30 and 40 Ma. These extremely young solutions provide the simplest explanation for the planet's size which can then be matched by a simple contraction from an initially hot, expanded state, provided the atmospheric opacities are increased by a factor ~3 compared to usual assumptions for solar compositions atmospheres. Other solutions imply in any case that the present inflated radius of CoRoT-2b is transient and the result of an event that occurred less than 20 Ma ago: a giant impact with another Jupiter-mass planet, or interactions with another object in the system which caused a significant rise of the eccentricity followed by the rapid circularization of its orbit. Conclusions: Additional observations of CoRoT-2 that could help understanding this system include searches for infrared excess and the presence of a debris disk and searches for additional companions. The determination of a complete infrared lightcurve including both the primary and secondary transits would also be extremely valuable to constrain the planet's atmospheric properties and to determine the planet-to-star radius ratio in a manner less vulnerable to systematic errors due to stellar activity.

Synthesis and characterization of nanogels of poly(N-isopropylacrylamide) by a combination of light and small-angle X-ray scattering

Thermo-responsive crosslinked nanogels of N-isopropylacrylamide (NIPAM) were synthesized by emulsion polymerization and the size was varied using different concentrations of surfactant (sodium dodecyl sulfate, SDS) in the polymerization process. The collapse behavior of the nanogels at the lower critical solution temperature at around 32 °C was investigated by dynamic light scattering, and by combined static light scattering (SLS) and small-angle X-ray scattering (SAXS). The combined data from SLS and SAXS were analyzed by a model for the nanogels which at intermediate temperatures included a central core and a more diffuse outer layer describing pending polymer chains with a low degree of cross linking. In the expanded state, the particles were modeled with a single component with a broad graded surface. In the collapsed state the nanogels were modeled as homogeneous and relatively compact particles. The amount of surfactant used had a profound effect on the final size of the nanogels owing to the phenomenon of colloidal stabilization of the emulsion droplets during polymerization. The combination of SLS and SAXS as applied to the nanogels is an attractive method for particle characterization as it spans a very large range of scattering vector from q = 0.0004 to 0.22 Å(-1).

Antimicrobial surface grafted thermally responsive PNIPAM-co-ALA nano-gels

Thermally responsive Poly(N-isopropylacrylamide) co-allylamine (PNIPAM-co-ALA) nano-gels were synthesised and grafted onto non-woven polypropylene. Silver nitrate was incorporated into the nano-gels in their expanded state and their antimicrobial properties tested. Bacterial growth was measured before and after the Lower Critical Solution Temperature. Below the LCST, bacteria grew, above the LCST bacterial growth was prevented or retarded.

A ratiometric fluorescent metal ion indicator based on dansyl labeled poly(N-isopropylacrylamide) responds to a quenching metal ion

The fluorescence emission of poly(N-isopropylacrylamide) (PNIPAM) covalently tagged with a 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore and an iminodiacetic acid (IDA) chelator changes with temperature and with Cu(II) complexation. Increasing the temperature above the lower critical solution temperature (LCST) causes the polymer to collapse from a coil to a compact globule. This changes the environment experienced by the fluorophore causing a shift in maximum emission wavelength from 546 to 508 nm and an increase in the ratio of emission intensity at 508 nm to emission intensity at 546 nm from 0.70 to almost 1.40. Metal ions can be sensed by working at a temperature where the uncomplexed polymer is in an expanded state due to the charges on the ligand. Complexation with a metal ion such as Cu(II) neutralizes the charges on the ligand causing the polymer to collapse. At 35 °C, the emission intensity maximum shifted from 535 to 510 nm as Cu(II) concentration was increased and the intensity ratio increased from 0.84 to 1.28. By decoupling complexation from fluorescence, we have prepared a ratiometric fluorescent indicator for a metal ion that normally quenches fluorescence. The affinity for Cu(II) was found to be thermally tunable. The log apparent formation constants for the indicator-Cu(II) complex were estimated as the half way point in the intensity ratio vs. pCu curve. The values were determined to be 4.3 at 35 °C and 3.2 at 34 °C respectively.

Centennial-scale climate change from decadally-paced explosive volcanism: a coupled sea ice-ocean mechanism

Northern Hemisphere summer cooling through the Holocene is largely driven by the steady decrease in summer insolation tied to the precession of the equinoxes. However, centennial-scale climate departures, such as the Little Ice Age, must be caused by other forcings, most likely explosive volcanism and changes in solar irradiance. Stratospheric volcanic aerosols have the stronger forcing, but their short residence time likely precludes a lasting climate impact from a single eruption. Decadally paced explosive volcanism may produce a greater climate impact because the long response time of ocean surface waters allows for a cumulative decrease in sea-surface tempera- tures that exceeds that of any single eruption. Here we use a global climate model to evaluate the potential long-term climate impacts from four decadally paced large tropical eruptions. Direct forcing results in a rapid expansion of Arctic Ocean sea ice that persists throughout the eruption period. The expanded sea ice increases the flux of sea ice exported to the northern North Atlantic long enough that it reduces the convective warming of surface waters in the subpolar North Atlantic. In two of our four simulations the cooler surface waters being advected into the Arctic Ocean reduced the rate of basal sea-ice melt in the Atlantic sector of the Arctic Ocean, allowing sea ice to remain in an expanded state for ( 100 model years after volcanic aerosols were removed from the stratosphere. In these simulations the coupled sea ice-ocean mechanism main- tains the strong positive feedbacks of an expanded Arctic Ocean sea ice cover, allowing the initial cooling related to the direct effect of volcanic aerosols to be perpetuated, potentially resulting in a centennial-scale or longer change of state in Arctic climate. The fact that the sea ice-ocean mechanism was not established in two of our four simu- lations suggests that a long-term sea ice response to vol- canic forcing is sensitive to the stability of the seawater column, wind, and ocean currents in the North Atlantic during the eruptions.

Optimal Trajectory Generation With Probabilistic System Uncertainty Using Polynomial Chaos

In this paper, we develop a framework for solving optimal trajectory generation problems with probabilistic uncertainty in system parameters. The framework is based on the generalized polynomial chaos theory. We consider both linear and nonlinear dynamics in this paper and demonstrate transformation of stochastic dynamics to equivalent deterministic dynamics in higher dimensional state space. Minimum expectation and variance cost function are shown to be equivalent to standard quadratic cost functions of the expanded state vector. Results are shown on a stochastic Van der Pol oscillator.

Nanostructured Nonionic Thymidine Nucleolipid Self-Assembly Materials

Three nucleoside lipids have been synthesized: 3'-oleoylthymidine, 3',5'-dioleoylthymidine, and 3'-phytanoylthymidine. Differential scanning calorimetry and X-ray diffraction have been employed to characterize the physical properties of these neat lipids. Polarizing optical microscopy, small-angle X-ray scattering, and cryo-transmission electron microscopy techniques have been used to investigate the phase behavior in aqueous systems. Both oleoyl-based nucleoside lipids adopted a lamellar crystalline phase in the neat form at room temperature, and the phytanoyl derivative exhibited a fluid isotropic phase. Under excess water conditions, the presence of one branched (phytanoyl) or one unsaturated (oleoyl) chain promoted the formation of a liquid-crystalline lamellar phase at physiological temperatures. In contrast, the 3',5'-dioleoylthymidine derivative is nonswelling and does not exhibit lyotropic liquid-crystalline phase behavior. The nucleolipids' propensity for DNA-type binding and recognition has been evaluated by using a monolayer system to measure surface pressure-area isotherms in a Langmuir trough and indicates that the nucleoside base is available for nonspecific hydrogen bonding in the monolayer liquid expanded state for the single-chain nucleolipids but not for the dual-chain amphiphile.

Thermoresponsive shape memory characteristics of polyurethane electrospun web

AbstractElectrospun web (ESW) was manufactured and its performance was evaluated to investigate its applicability as an intelligent clothing material using shape memory polymers. Mixtures of various compositions were applied to make the shape memory polyurethane (SMPU) films and the polyurethane with the best shape memory performance was then selected to make the ESWs. The structural and thermal properties, as well as the shape memory behavior were evaluated. The air permeability, the water vapor transmission, and the water resistance were measured. The ESW having a high orientation due to an elongation in the process of the electrospinning showed a higher melting point than the film and its shape recovery was improved. The ESW showed a good moisture and air permeability due to the fact that its structural characteristics incorporate countless nano‐sized pores. Because of this, the ESW maintained in its expanded state below the transition temperature showed improved moisture and air permeabilities. Therefore, it can be concluded that the SMPU web proved to have potential for intelligent clothing material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Langmuir-Blodgett Monolayers of Cationic Dyes in the Presence and Absence of Clay Mineral Layers: N,N′-Dioctadecyl Thiacyanine, Octadecyl Rhodamine B and Laponite

Langmuir-Blodgett (LB) films of N,N'-dioctadecyl thiacyanine perchlorate (TC18) and octadecyl rhodamine B chloride (RhB18) and their mixtures in the presence and absence of clay mineral layers were investigated by recording surface pressure-area (pi-A) isotherms and by UV-vis and fluorescence spectroscopies. The pi-A isotherms of TC18, RhB18, and their mixtures are characteristic of liquid expanded state behavior with repulsive interactions between the two cationic dyes. In the presence of laponite, the pi-A isotherms show liquid expanded and condensed-state behavior. In laponite dispersions and in monolayers, TC18 has a strong tendency to aggregate with formation of H- and J- aggregates. The absorption and fluorescence maxima of the monomers in the films are at 435 nm and at 480 nm; H-dimers have an absorption maximum around 410 nm and do not fluoresce. J-dimers are present in all the films with absorption maximum at 461 nm and fluorescence at 463 nm. RhB18 is mainly present as monomers in the LB films with an absorption maximum at 576 nm and fluorescence at 595 nm. Fluorescence resonance energy transfer from TC18 to RhB18 has been observed in clay dispersions and in films with and without laponite. The optimum condition for TC18 --> RhB18 fluorescence energy transfer in the films is 90 mol % TC18 + 10 mol % RhB18.

Unique Features of the Folding Landscape of a Repeat Protein Revealed by Pressure Perturbation

The volumetric properties of proteins yield information about the changes in packing and hydration between various states along the folding reaction coordinate and are also intimately linked to the energetics and dynamics of these conformations. These volumetric characteristics can be accessed via pressure perturbation methods. In this work, we report high-pressure unfolding studies of the ankyrin domain of the Notch receptor (Nank1–7) using fluorescence, small-angle x-ray scattering, and Fourier transform infrared spectroscopy. Both equilibrium and pressure-jump kinetic fluorescence experiments were consistent with a simple two-state folding/unfolding transition under pressure, with a rather small volume change for unfolding compared to proteins of similar molecular weight. High-pressure fluorescence, Fourier transform infrared spectroscopy, and small-angle x-ray scattering measurements revealed that increasing urea over a very small range leads to a more expanded pressure unfolded state with a significant decrease in helical content. These observations underscore the conformational diversity of the unfolded-state basin. The temperature dependence of pressure-jump fluorescence relaxation measurements demonstrated that at low temperatures, the folding transition state ensemble (TSE) lies close in volume to the folded state, consistent with significant dehydration at the barrier. In contrast, the thermal expansivity of the TSE was found to be equivalent to that of the unfolded state, indicating that the interactions that constrain the folded-state thermal expansivity have not been established at the folding barrier. This behavior reveals a high degree of plasticity of the TSE of Nank1–7.

Stability Analysis for ESO in Frequency Domain Based on Description Function Methodology

Expanded State Observer (ESO) can be used in the control of plants with uncertainties to achieve better effects. Many theoretical and practical researches have been done on design of systems equipped with ESO. Nevertheless, those on the stability of ESO are relatively rare. In this paper, stability analysis for ESO was conducted based on the methodology of description function. Stability conditions for nonlinear ESO with (2+1)th order were presented. It was proved in this paper that stability conditions that were same with that of linear state observers could be obtained and better tracking performance could be achieved if nonlinear parameters were chosen appropriately. The proposed analysis methodology was also applicable for nonlinear ESO with (n+1)th order.

Investigation of internal microstructure and thermo-responsive properties of composite PNIPAM/silica microcapsules

Composite microcapsules consisting of a thermo-responsive hydrogel poly- N-isopropylacrylamide (PNIPAM) and coated by silica (SiO 2) nanoparticles have been synthesized by the inverse Pickering emulsion polymerization method. The composite capsules, whose mean diameter is in the 25–86 μm range in the expanded state, were characterized by static light scattering, atomic force microscopy (AFM), scanning electron microscopy (SEM), and laser scanning confocal microscopy (LSCM). It is reported that the hydrogel surface is uniformly covered by a monolayer of silica nanoparticles and that depending on the capsule size and degree of polymer cross-linking, either hollow-core or partially-filled hydrogel-core microcapsules can be created. Equilibrium thermo-responsive behavior of the composite microcapsules is investigated and it is found that after heating the particles above the lower critical solution temperature (LCST) of PNIPAM, the shrinkage ratio V/ V max varies from 0.8 to 0.4 for a cross-linking ratio from 0.6% to 9% on a mass basis. Dynamic temperature cycling studies reveal no hysteresis in the shrinking and recovery phases, but a small measurable dependence of the asymptotic shrinkage ratio V/ V max on the rate of temperature change exists. The composite capsules are stable under long-term storage in both dried and hydrated states and easily re-dispersible in water.

Effective Charge and Coil−Globule Transition of a Polyelectrolyte Chain

Considering the adsorption of counterions on an isolated polyelectrolyte (PE) chain and using a variational theory, phase boundaries and the critical point for the first-order coil-globule transition are calculated. The transition is induced cooperatively by counterion adsorption and chain conformations and the calculation is done self-consistently. The size of the PE chain is a single-valued function of charge. The discontinuous transition of the coil size is accompanied by a discontinuous transition of the charge. Phase boundaries for the coil-globule transitions induced by both Coulomb strength (inverse temperature or dielectric constant) and ionic strength (salt) show that the PE chain collapses at a substantially lower Coulomb strength in the presence of salt. In the expanded state of the coil, an analytical formula is derived for the effective charge of the chain for conditions where the coupling between chain conformations and counterion adsorption is weak. In general, the dielectric heterogeneity of the solvent close to the polymer backbone is found to play a crucial role in the charge regularization and the chain collapse.

Conformational State-Dependent Anion Binding in Prestin: Evidence for Allosteric Modulation

Outer hair cells boost auditory performance in mammals. This amplification relies on an expansive array of intramembranous molecular motors, identified as prestin, that drive somatic electromotility. By measuring nonlinear capacitance, the electrical signature of electromotility, we are able to assess prestin's conformational state and interrogate the effectiveness of anions on prestin's activity. We find that the affinity of anions depends on the state of prestin that we set with a variety of perturbations (in membrane tension, temperature, and voltage), and that movement into the expanded state reduces the affinity of prestin for anions. These data signify that anions work allosterically on prestin. Consequently, anions are released from prestin's binding site during expansion, i.e., during hyperpolarization. This is at odds with the extrinsic voltage sensor model, which suggests that prestin-bound intracellular anions are propelled deep into the membrane. Furthermore, we hypothesize that prestin's susceptibility to many biophysical forces, and notably its piezoelectric nature, may reflect anion interactions with the motor.

Controlled crystallization of poly(vinylidene fluoride) chains from mixed solvents composed of its good solvent and nonsolvent

AbstractPoly(vinylidene fluoride) (PVDF) chains with the same expanded state were obtained by dissolving PVDF resin in good solvent. Then, the crystallization of PVDF chains from mixed solvents composed of its good solvent and nonsolvent was investigated. N,N‐dimethylformamide (DMF) and ethanol were used as good solvent and nonsolvent of PVDF, respectively. The crystalline phases of PVDF were characterized by Fourier transform infrared (FTIR) spectroscopy and wide angle X‐ray diffraction (WAXD). For the crystallization of PVDF chains from mixed solvents, low ethanol content favored the formation of β phase, while high ethanol content resulted predominantly in the α phase. Different crystallization morphology was observed from the scanning electron microscopy (SEM) images. The obvious spherulite morphology disappeared with the increase in ethanol content in mixed solvent. According to thermal analyses, the crystallized PVDF from mixed solvents with high ethanol content had lower onset melting temperatures than that from low ethanol content. Smaller lamellar thickness calculated from WAXD data reasoned the low onset melting temperatures. The above results indicated that the crystallization of PVDF chains from mixed solvent was a “controlled” process by ethanol content. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 575–581, 2010

Scanning electron microscopic analysis of different drug eluting stents after failed implantation: From nearly undamaged to major damaged polymers

Implantation of drug eluting stents (DES) in tortuous and/or calcified vessels is much more demanding compared with implantation of bare metal stents (BMS) due to their larger diameters. It is unknown whether drug eluting stent coatings get damaged while crossing these lesions. In 42 patients (34 male, 68.1 +/- 10 years) with 45 calcified lesions (15.9 mm +/- 7.9 mm), DES could not be implanted, even after predilatation. Diabetes was present in 19 patients (45%). Sixty-one stents were used; 19 Cypher select, 18 Taxus Liberté, 10 CoStar, 5 Endeavor RX, 4 Xience V. 3 Janus Carbostent, 1 Yukon Choice S, and 1 Axxion DES. The entire accessible surface area of these stents, in either the unexpanded and expanded state, were examined with an environmental scanning electron microscope (XL30 ESEM, Philips) to evaluate polymer or surface damage. The polymers of Taxus Liberte, Cypher Select, Xience V, CoStar, and Janus DES were only slightly damaged (less than 3% of surface area), whereas the Endeavor RX Stents showed up to 20% damaged surface area. In DES without a polymer (Yukon and Axxion), it could be shown that most of the stent surface (up to 40%) were without any layer of drug. Placement of drug eluting stents in tortuous vessels and/or calcified lesions could cause major surface damage by scratching and scraping of the polymer or drug by the arterial wall, even before implantation. There were remarkable differences among the stents examined, only minor damage with the Cypher, Taxus Costar, Janus, and Xience V, whereas the Endeavor, the Yukon, and the Janus DES showed large areas of surface injury.

International Law and the Responsibility to Protect: Clarifying or Expanding States' Responsibilities?

AbstractThe Responsibility to Protect (R2P) invokes one of the most powerful moral and legal terms in contemporary international politics – namely, responsibility. The nature of the relationship between R2P and international law and morality, however, remains contested, giving rise to questions lying at the core of R2P's normative foundations. What is the source of R2P? To whom is this responsibility attributable, and under what circumstances? Does R2P give rise to legal obligations? Such questions challenge International Relations (IR) theorists to look beyond their discipline for more insightful tools and methods of analysis. In this article, we apply a broadened theoretical framework to explain the ongoing controversy about R2P. In Part II, we borrow tools from moral philosophy to identify the source and the bearer of the responsibility to protect in today's international society. In Part III, we draw on international legal scholarship to analyse whether R2P has emerged as a 'new' norm of customary international law. We find that international endorsement of R2P has helped to clarify existing obligations in international law, but that intrinsic ambiguities in its articulation currently limit R2P's capacity to entrench new obligations for states to protect strangers. At the same time, our finding that R2P is an example of 'soft law' leads us to conclude that R2P can nonetheless exert significant influence on how states interpret their legal obligations and, in the coming decade, it may also help catalyse diplomatic efforts to reform the international architecture for preventing and responding to mass atrocities.

Mathematical Modeling of Vascular Stents

We present a mathematical model for a study of the mechanical properties of endovascular stents in their expanded state. The model is based on the theory of slender curved rods. Stent struts are modeled as linearly elastic curved rods that satisfy the kinematic and dynamic contact conditions at the “vertices” where the struts meet. This defines a stent as a mesh of curved rods. A weak formulation for the stent problem is defined and a finite element method for a numerical computation of its solution was developed. Numerical simulations showing the pressure-displacement (axial and radial) relationship for the entire stent are presented. From the numerical data and from the energy of the problem we deduced an “effective” pressure-displacement relationship of the law of Laplace-type for the mechanical behavior of stents, where the proportionality constant in the Laplace law was expressed explicitly in terms of the geometric and mechanic properties of a stent.

The Effects of Employing Pillows for Postural Changes on Ventilation: An Investigation Using an Ultrasonic Imaging Device

[Purpose] We investigated the effects of compression on the posterior surface of the thorax caused by a pillow used for postural changes on the respiratory function. [Subjects] The subjects were 22 healthy males with no history of ailments of the respiratory and circulatory organs. [Methods] With the subjects placed in the supine position, a half-lateral position with a pillow supporting the posterior surface of the thorax (pillow-supported position (1)), and a half-lateral position with pillows supporting the shoulder girdle and the pelvic band (pillow- supported position (2)), the ventilatory volume per breath (hereinafter TV) and expiratory reserve volume (hereinafter ERV) were measured based on the respiratory function, and at the same time, the distanced moved by the diaphragm was measured using an ultrasonic imaging device. [Results] Significantly lower values for TV were observed in the pillow-supported position (1) in comparison to the other postures. Significantly higher values for ERV were observed in the pillow-supported position (1) in comparison to the other postures. Significantly lower values for the distance moved by the diaphragm were observed in the pillow-supported position (1) in comparison to the other postures. [Conclusion] Ventilation decreased in pillow-supported position (1). We therefore consider that the movement of the diaphragm was reduced due to an expanded state caused by increase in residual air in the lungs.

A Langmuir Monolayer Study of the Interaction of E1(145−162) Hepatitis G Virus Peptide with Phospholipid Membranes

E1(145-162), a peptide corresponding to the structural protein E1 of the GB virus C, has been shown earlier to bind at pH 7.4 to vesicles containing 1,2-dimyiristoyl-sn-glycero-3-phospho-rac-(1-glycerol)] (DMPG) and 1,2-dimyiristoyl-sn-glycero-3-phosphocholine (DMPC) phospholipids. To deepen the understanding of the interaction of E1(145-162) with the lipid membrane, in this paper, we report a detailed study of the surface properties of peptide, miscibility properties, and behavior of mixed monomolecular films of it and three phospholipids DMPG, DMPC, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPG). These studies were performed using the Langmuir balance by means of surface adsorption studies, surface pressure-mean molecular area compression isotherms, and penetration kinetics. The Brewster angle microscopy (BAM) was used to study the morphological properties of pure peptide and the mixed monolayers. The results show us that the peptide showed surface activity concentration dependent when injected beneath a buffered solution (HEPES/NaCl, pH 7.4). This tendency to accumulate into the air/water interface confirms its potential capacity to interact with membranes; the higher penetration of peptide into phospholipids is attained when the monolayers are in the liquid expanded state and the lipids are charged negatively maybe due to its negative electric charge that interacts with the positive global charge of the peptide sequence. The area per molecule values obtained suggested that the main arrangement structure for E1(145-162) peptide is the alpha-helical at the air-water interface that agreed with computational prediction calculations. Miscibility studies indicated that mixtures become thermodynamically favored at low peptide molar fraction.