Search

Aims. We introduce a method for extracting spectral information from energy-resolved light curves folded at the neutron star spin period (known as pulse profiles) in accreting X-ray binaries. Spectra of these sources are sometimes characterized by features superimposed on a smooth continuum, such as iron emission lines and cyclotron resonant scattering features. We address here the question on how to derive quantitative constraints on such features from energy-dependent changes in the pulse profiles. Methods. We developed a robust method for determining in each energy-selected bin the value of the pulsed fraction using the fast Fourier transform opportunely truncated at the number of harmonics needed to satisfactorily describe the actual profile. We determined the uncertainty on this value by sampling through Monte Carlo simulations a total of 1000 faked profiles. We rebinned the energy-resolved pulse profiles to have a constant minimum signal-to-noise ratio throughout the whole energy band. Finally we characterize the dependence of the energy-resolved pulsed fraction using a phenomenological polynomial model and search for features corresponding to spectral signatures of iron emission or cyclotron lines using Gaussian line profiles. Results. We apply our method to a representative sample of NuSTAR observations of well-known accreting X-ray pulsars. We show that, with this method, it is possible to characterize the pulsed fraction spectra, and to constrain the position and widths of such features with a precision comparable with the spectral results. We also explore how harmonic decomposition, correlation, and lag spectra might be used as additional probes for detection and characterization of such features. [ABSTRACT FROM AUTHOR]

We studied the spectral changes of the high-mass X-ray binary system LMC X-4 to understand the origin and mechanisms beyond its superorbital modulation (30.4 d). To this aim, we obtained a monitoring campaign with Swift /XRT (0.3–10 keV) and complemented these data with the years-long Swift /BAT survey data (15–60 keV). We found a self-consistent, physically motivated, description of the broad-band X-ray spectrum using a Swift /XRT and a NuSTAR observation at the epoch of maximum flux. We decomposed the spectrum into the sum of a bulk + thermal Comptonization, a disc reflection component, and a soft contribution from a standard Shakura–Sunyaev accretion disc. We applied this model to 20 phase-selected Swift spectra along the superorbital period. We found a phase-dependent flux ratio of the different components, whereas the absorption column does not vary significantly. The disc emission is decoupled with respect to the hard flux. We interpret this as a geometrical effect in which the inner parts of the disc are tilted with respect to the obscuring outer regions. [ABSTRACT FROM AUTHOR]

Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a few systems, dips have been observed. The mechanism behind this state transition and the dips nature are still debated. To investigate these issues, we obtained a long XMM–Newton monitoring campaign of a member of this class, NGC 247 ULX-1. We computed the hardness–intensity diagram for the whole data set and identified two different branches: the normal branch and the dipping branch, which we study with four and three hardness–intensity resolved spectra, respectively. All seven spectra are well described by two thermal components: a colder (kT bb ∼ 0.1–0.2 keV) blackbody, interpreted as emission from the photosphere of a radiatively driven wind, and a hotter (kT disc ∼ 0.6 keV) multicolour disc blackbody, likely due to reprocessing of radiation emitted from the innermost regions. In addition, a complex pattern of emission and absorption lines has been taken into account based on previous high-resolution spectroscopic results. We studied the evolution of spectral parameters and flux of the two thermal components along the two branches and discuss two scenarios possibly connecting the state transition and the dipping phenomenon. One is based on geometrical occultation of the emitting regions, the other invokes the onset of a propeller effect. [ABSTRACT FROM AUTHOR]

We analysed 13 yr of the Neil Gehrels Swift Observatory survey data collected on the high-mass X-ray binary IGR J18214-1318. Performing the timing analysis, we detected a periodic signal of 5.42 d. From the companion star characteristics, we derived an average orbital separation of |$\sim 41 \rm R_{\odot }\simeq 2 R_{\star }$|⁠. The spectral type of the companion star (O9) and the tight orbital separation suggest that IGR J18214-1318 is a wind-accreting source with eccentricity lower than 0.17. The intensity profile folded at the orbital period shows a deep minimum compatible with an eclipse of the source by the companion star. In addition, we report on the broad-band 0.6–100 keV spectrum using data from XMM–Newton , NuSTAR , and Swift , applying self-consistent physical models. We find that the spectrum is well fitted either by a pure thermal Comptonization component, or, assuming that the source is a neutron star accreting above the critical regime, by a combined thermal and bulk motion Comptonization model. In both cases, the presence of a local neutral absorption (possibly related to the thick wind of the companion star) is required. [ABSTRACT FROM AUTHOR]

We present a multiband search for X-ray, optical, and γ-ray emission of the radio binary millisecond pulsar J1836-2354A, hosted in the globular cluster M22. X-ray emission is significantly detected in two Chandra observations, performed in 2005 and 2014, at a luminosity of ∼2–3 × 1030 erg s−1, in the 0.5–8 keV energy range. The radio and the X-ray source positions are found consistent within 1σ error box. No detection is found in archival XMM–Newton and Swift /XRT observations, compatible with the Chandra flux level. The low statistics prevents us to assess if the X-ray source varied between the two observations. The X-ray spectrum is consistent with a power-law of photon index ∼1.5. We favour as the most probable origin of the X-ray emission an intrabinary shock scenario. We searched for optical and γ-ray counterparts to the radio source using data from Hubble Space Telescope and Fermi –LAT catalogues, respectively. No optical counterpart down to V = 25.9 and I = 24.7 (3σ) is detected, which suggests a companion mass of 0.1–0.2 M ⊙. Combined with the low X-ray luminosity, this is consistent with a black widow nature of PSR J1636-2354A. Inspecting the 8-year Fermi –LAT catalogue, we found a γ-ray source, 4FGL J1836.8–2354, with a positional uncertainty consistent with the globular cluster, but not with the radio position of the millisecond pulsar. [ABSTRACT FROM AUTHOR]

The accretion-powered X-ray pulsar 4U 1626-67 is one of the few highly magnetized pulsars that accretes through Roche lobe overflow from a low-mass companion. The characteristics of its broad-band spectrum are similar to those of X-ray pulsars hosted in a high-mass X-ray binary system, with a broad resonant cyclotron scattering feature (CRSF) at ~37 keV. In this work, we examine the pulse-resolved and the pulse-averaged broad-band spectrum using data from NuSTAR and Swift. We use the Becker &Wolff model of bulk+thermal Comptonization to infer key physical parameters of the accretion column flow and a broad-band model for the disc-reflected spectrum. In the softer X-ray band, we need to add a soft blackbody component with kTbb ~ 0.5 keV, whose characteristics indicate a possible origin from the neutron star surface. Residuals suggest that the shape of the cyclotron line could be more satisfactorily fitted using a narrow core and broader wings and, at higher energies, a second harmonic could be present at ~61 keV. [ABSTRACT FROM AUTHOR]

Tuning the electronic structureof 2D materials is a very powerful asset toward tailoring their propertiesto suit the demands of future applications in optoelectronics. Strainengineering is one of the most promising methods in this regard. Wedemonstrate that even very small out-of-plane axial compression readilymodifies the electronic structure of monolayer MoS2. Aswe show through in situ resonant and nonresonant Raman spectroscopyand photoluminescence measurements combined with theoretical calculations,the transition from direct to indirect band gap semiconductor takesplace at ∼0.5 GPa, and the transition to a semimetal occursat stress smaller than 3 GPa. [ABSTRACT FROM AUTHOR]

Althoughthe surface tension of complex mixtures determines thefate of many important natural processes, the property is notoriouslydifficult to interpret. Here we announce a new method that successfullypredicts the surface tension of two synthetic and one biological polyelectrolyte/surfactantmixtures in the phase-separation region after dynamic changes in thebulk phase behavior have reached completion. The approach is basedon the nonequilibrium framework of a lack of colloidal stability ofbulk complexes in compositions around the charge match point of theoppositely charged components and requires as input parameters onlythe surface tension isotherm of the pure surfactant and some bulkmeasurements of the mixtures; no surface measurements of the mixturesare required. The complexity of the problem is reduced to a singleempirical equation. This simplification in our understanding of thesurface properties of strongly interacting mixtures involving macromoleculescan lead to the optimization of applications involving synthetic polymersand biomacromolecules such as DNA at surfaces. [ABSTRACT FROM AUTHOR]

The rearrangement of aldoximes to primary amides hasbeen studiedusing the readily available arene-ruthenium(II) complex [RuCl2(η6-C6Me6){P(NMe2)3}] (5 mol %) as catalyst. Reactions proceededcleanly in pure water at 100 °C without the assistance of anycocatalyst, affording the desired amides in high yields (70–90%)after short reaction times (1–7 h). The process was operativewith both aromatic, heteroaromatic, α,β-unsaturated, andaliphatic aldoximes and tolerated several functional groups. Reactionprofiles and experiments using 18O-labeled water indicatethat two different mechanisms are implicated in these transformations.In both of them, nitrile intermediates are initially formed by dehydrationof the aldoximes. These intermediates are then hydrated to the correspondingamides by the action of a second molecule of aldoxime or water. Akinetic analysis of the rearrangement of benzaldoxime to benzamideis also discussed. [ABSTRACT FROM AUTHOR]

The individual steps of a model Pd-catalyzed Negishicoupling betweenvinyl bromide and MeZnClS2(S = THF), using Pd(PMe3)2as catalyst, have been examined with the aidof DFT computations in THF solution with the B97D functional to gainfurther insight into the role of Pd–Zn interactions on theoxidative addition and reductive elimination steps. Comparisons betweensuch processes taking place on monometallic Pd complexes and on bimetallicPd–Zn complexes reveal a detrimental effect of Pd–Zninteractions in oxidative addition, whereas reductive eliminationis favored by Pd–Zn cooperativity. Additionally, a cis transmetalationpathway has been characterized that complements previous studies involvingtrans complexes. [ABSTRACT FROM AUTHOR]

The synthesis of various silybin monogalloyl esters was developed, and their antiangiogenic activities were evaluated in a variety of in vitro tests with human umbilical vein endothelial cells (HUVECs). A structure–activity relationship (SAR) study found the regioselectivity of the silybin galloylation to be highly significant. Silybin (as an equimolar mixture of two diastereomers A and B) exhibited quite poor antiangiogenic activities, whereas its B stereoisomer is more active than silybin A. The galloylation of phenolic OH groups of natural silybin (a mixture of both isomers) leads to increases in their antiangiogenic activities, which is more apparent with the 7-OH than the 20-OH. In contrast, gallates at aliphatic OH groups either had a comparable activity to the parent compound or are even worse than silybin, which was observed in the case of 3-O-galloylsilybin. The most effective compound from this series (7-O-galloylsilybin) has also been prepared from stereochemically pure silybins A and B to evaluate the effect of stereochemistry on the activity. As with silybin itself, the B isomer of 7-O-galloylsilybin was more active than the A isomer. [ABSTRACT FROM AUTHOR]

The bursting pulsar, GRO J1744-28, went again in outburst after ~18 yr of quiescence in 2014 mid-January. We studied the broad-band, persistent, X-ray spectrum using X-ray data from a XMM-Newton observation, performed almost at the peak of the outburst, and from a close INTEGRAL observation, performed 3 d later, thus covering the 1.3-70.0 keV band. The spectrum shows a complex continuum shape that cannot be modelled with standard high-mass X-ray pulsar models, nor by two-components models. We observe broad-band and peaked residuals from 4 to 15 keV, and we propose a self-consistent interpretation of these residuals, assuming they are produced by cyclotron absorption features and by a moderately smeared, highly ionized, reflection component. We identify the cyclotron fundamental at ~4.7 keV, with hints for two possible harmonics at ~10.4 and ~15.8 keV. The position of the cyclotron fundamental allows an estimate for the pulsar magnetic field of (5.27 ± 0.06) × 1011 G, if the feature is produced at its surface. From the dynamical and relativistic smearing of the disc reflected component, we obtain a lower limit estimate for the truncated accretion disc inner radius (≳100 Rg) and for the inclination angle (18°-48°). We also detect the presence of a softer thermal component that we associate with the emission from an accretion disc truncated at a distance from the pulsar of 50-115 Rg. From these estimates, we derive the magnetospheric radius for disc accretion to be ~0.2 times the classical Alfvén radius for radial accretion. [ABSTRACT FROM AUTHOR]

Context. The source GX 13+1 is a persistent, bright Galactic X-ray binary hosting an accreting neutron star. It shows highly ionized absorption features, with a blueshift of ∼400 km s-1 and an outflow-mass rate similar to the accretion rate. Many other X-ray sources exhibit warm absorption features, and they all show periodic dipping behavior at the same time. Recently, a dipping periodicity has also been determined for GX 13+1 using long-term X-ray folded light-curves, leading to a clear identification of one of such periodic dips in an archival Chandra observation. Aims. We give the first spectral characterization of the periodic dip of GX 13+1 found in this archival Chandra observation performed in 2010. Methods. We used Chandra/HETGS data (1.0-10 keV band) and contemporaneous RXTE/PCA data (3.5-25 keV) to analyze the broad-band X-ray spectrum. We adopted different spectral models to describe the continuum emission and used the XSTAR-derived warm absorber component to constrain the highly ionized absorption features. Results. The 1.0-25 keV continuum emission is consistent with a model of soft accretion-disk emission and an optically thick, harder Comptonized component. The dip event, lasting ∼450 s, is spectrally resolved with an increase in the column density of the neutral absorber, while we do not find significant variations in the column density and ionization parameter of the warm absorber with respect to the out-of-dip spectrum. Conclusions. We argue that the very low dipping duty-cycle with respect to other sources of the same class can be ascribed to its long orbital period and the mostly neutral bulge that is relatively small compared with the dimensions of the outer disk radius. [ABSTRACT FROM AUTHOR]

Inthis work experimental vapor–liquid equilibrium (VLE)data and three-phase vapor–liquid–liquid equilibrium(VLLE) data are presented for the carbon dioxide 1-decanol system.The VLE data were measured at five temperatures, (303.2, 308.2, 323.2,333.2, and 343.2) K, and pressures up to 16 MPa. The VLLE data coverpressure–temperature (P–T) values from289 K and 5 MPa to the upper critical end point (UCEP). We have usedtwo models to represent the complex fluid phase behavior (P–Tcritical curve, VLLE line, and VLE isotherms)of the carbon dioxide 1-decanol system: the cubic general equationof state (GEOS) and Peng–Robinson (PR) equation in conjunctionwith van der Waals two parameters conventional mixing rules (2PCMR).A correlation method involving temperature-dependent interaction parametersand a semipredictive approach with independent temperature interactionparameters have been used. Comparisons with experimental data reportedin this work and available in the literature indicate that the topologyof fluid phase behavior is satisfactorily given by the semipredictiveprocedure both for the critical line and in subcritical region, consideringthe relative simple used cubic equations of state. [ABSTRACT FROM AUTHOR]

Enzymaticalcoholysis of fish oil can produce monoacylglycerolsrich in polyunsaturated fatty acids at atmospheric pressure and lowtemperature. Biocatalysis in organic solvents helps to create a homogeneousreaction system for the reactants, ethanol and fish oil. This workpresents liquid–liquid equilibrium at two different temperatures(303.2 K and 323.2 K) and at atmospheric pressure for two solvent-systemsin the ethanolysis of fish oil: ethanol oil tert-pentanol and ethanol oil hexane. Experimental solubility (binodal)curves were obtained by the cloud point method and tie-line compositionwas obtained by density and high-temperature gas chromatography. Theconsistency of experimental tie-line data was checked by using theOthmer–Tobias equation. The experimental liquid–liquiddata were correlated satisfactorily by the nonrandom two liquid modelfor activity coefficient calculations. [ABSTRACT FROM AUTHOR]

A versatile,photochemical surface-modification approach usingnitrene-insertion reactions has been employed to develop an ultrathin,two-component, polymer-gradient coating. Perfluorophenyl azide (PFPA)acted as the photosensitive moiety, forming a nitrene radical upon254 nm UV exposure. Cationic poly(allyl amine) was grafted with PFPAand surface-anchored onto silicon wafers by means of electrostaticself-assembly. After spin-coating of polystyrene (PS), the substratewas illuminated from behind a moving shutter, thereby controllingthe azide-to-nitrene conversion degree across the substrate, and leadingto a gradually varying PS density after rinsing. Backfilling withpoly(vinyl pyrrolidone) (PVP) and re-exposing to UV light formed atwo-component polymer-density gradient. The composition varied linearlyfollowing exposure to a linear UV exposure profile, as determinedwith spectroscopic ellipsometry (ELM) and X-ray photoelectron spectroscopy(XPS). High-spatial-resolution, time-of-flight secondary ion massspectrometry (ToF-SIMS) revealed a high degree of mixing between thetwo incompatible polymers on the micrometer scale. The dynamic water-contactangle (dCA) was found to depend strongly on the sample history, suggestingadaptive properties of the coating, which was further confirmed byangle-resolved XPS (ARXPS). To confirm the applicability of the systemfor biological investigations, gradients were exposed to zoosporesof the macrofouling alga Ulva linza, and a critical PS composition of 70% was identified, above whichsettlement started to increase. It has been shown that a two-componentpolymer-density gradient can provide a high-throughput platform fordetermining critical surface properties of polymer blend materials. [ABSTRACT FROM AUTHOR]

Fourflavonols, namely quercetin, morin, kaempferol, and myricetin,were studied using spectrophotometry (UV–vis) in aqueous solution.The study was performed varying the pH to analyze the stability ofthese compounds, and to estimate their acidity constants. In addition,the deprotonation mechanisms were studied using computational chemistrywithin the density functional theory framework. The calculations wereperformed in aqueous solution using the SMD continuum model, and theresults are reported as deprotonation energies. Our results show thatboth quercetin and myricetin are highly unstable at basic pH. Kaempferol,on the other hand, is much more stable, and morin is the only oneamong the studied compounds that was not affected by pH. In spiteof this inconvenience, their acidity constants were estimated throughanalysis of their decomposition kinetics, correcting the spectra accordingly,and obtaining a correlation of values between the experimentally observedpKaand the calculated ΔGof successive deprotonations. [ABSTRACT FROM AUTHOR]

Itis known that conical intersections (CIs) can be induced bylaser light even in diatomics. In the close vicinity of these laser-inducedCIs (LICIs) the nonadiabatic effects are infinitely strong, as isthe case for naturally appearing CIs in field-free polyatomics. Inthe present work we study the photodissociation dynamics of the D2骉干 inan intense laser field to investigate the role of the LICI. Specifically,the kinetic energy release (KER) and the angular distribution of thephotodissociation products are calculated with and without LICI fordifferent initial conditions and for different values of the laserparameters. To do so, both one- and two-dimensional calculations wereperformed. In the first model the molecules were rotationally frozen,whereas in the latter one, the molecular rotation is included as afull additional dynamic variable. The results obtained undoubtedlydemonstrate the strong impact of the coupling of the rotation to thevibrational and electronic motions and hence of the LICI on the dissociationdynamics of the D2骉干. [ABSTRACT FROM AUTHOR]

We present a study of the accretion flow to the intermittent accreting millisecond pulsar, HETE J1900.1−2455, based on observations made simultaneously by XMM–Newton and RXTE. The 0.33–50 keV energy spectrum is described by the sum of a hard Comptonized component produced in an optically thin τ ≃ 1 corona, a soft thermal kTin ≃ 0.2 keV component interpreted as accretion disc emission, and of disc reflection of the hard component. Two emission features are detected at energies of 0.98(1) and 6.58(7) keV, respectively. The latter is identified as Kα transition of Fe xxiii–xxv. A simultaneous detection in the European Photon Imaging Camera (EPIC-pn), EPIC-MOS2 and Reflection Grating Spectrometer (RGS) spectra favours an astrophysical origin also for the latter, which has an energy compatible with Fe-Lα and helium-like Ne-Kα transitions. The broadness of the two features, σ/E ≃ 0.1, suggests a common origin, resulting from reflection in an accretion disc with inclination of (30+ 4− 3)°, and extending down to Rin = 25+ 16− 11 gravitational radii from the compact object. However, the strength of the feature at lower energy measured by EPIC-pn cannot be entirely reconciled with the amplitude of the Fe-Kα line, hampering the possibility of describing it in terms of a broad-band reflection model, and preventing a firm identification. Pulsations at the known 377.3 Hz spin frequency could not be detected with an upper limit of 0.4 per cent at 3σ confidence level on the pulsed fractional amplitude.We interpret the value of the inner disc radius estimated from spectral modelling and the lack of significant detection of coherent X-ray pulsations as an indication of a disc accretion flow truncated by some mechanism connected to the overall evolution of the accretion disc, rather than by the neutron star magnetic field. This is compatible with the extremely close similarity of spectral and temporal properties of this source with respect to other, non-pulsing atoll sources in the hard state. [ABSTRACT FROM AUTHOR]

The polarity of the ionic liquids [N4111][Tf2N], [N4441][Tf2N], and [choline][Tf2N], as well as their binary mixtures with ethanol has beeninvestigatedusing solvatochromic dyes and expressed in terms of the Reichardtparameter, ETN, and the Kamlet–Taft parameters (π*,α, and β), at 298.15 K. The synergetic behavior revealedessentially by the ethanol [N4441][Tf2N] systemfor the acidity of the solvent shows the potential importance of thissolvent media for some chemical applications. Even though the preferentialsolvation model of Bosch and co-workers has been applied with somestatistical success to the whole composition range of EtOH [N4111][Tf2N] and EtOH [N4441][Tf2N] binary mixtures, the interpretation of the results is somehowdifficult due to the competition of molecular interactions in theevaluation of transition energies for the pairs: dye–solvent(dye–cation and/or dye–anion, dye–EtOH, dye–complexentity) and cation–anion, depending on the composition range.Different patterns of solvent polarity behavior are shown along theentire ionic liquid (IL) composition. [ABSTRACT FROM AUTHOR]

One of the most significant recent developments (in 2009)is the discovery of the clusters M@Ge103–(M = Fe, Co) in which the outer Ge10polyhedron is apentagonal prism rather than a deltahedral structure of the type predictedby the Wade–Mingos rules. Consistent with this experimentalobservation, density functional theory shows the lowest energy structuresto be pentagonal prisms for the iron-centered clusters Fe@Ge10zin all nine charge states ranging from−5 to . This contrasts with the previously studied cobalt-centeredgermanium clusters Co@Ge10zfor which the lowest energy structures are pentagonal prisms onlyfor the electron richest systems where zranges from−3 to −5. The C3vstructures derived from the tetracapped trigonal prism foundas lowest energy structures of the electron poorer Co@Ge10z(z= 0, −1,−2) systems are higher energy structures for the iron-centeredgermanium clusters Fe@Ge10z(z= 0, −1, −2). The strong energeticpreference for pentagonal prismatic structures in the Fe@Ge10zclusters can be attributed to the needfor the larger volume of the pentagonal prism relative to other 10-vertexclosed polyhedra to accommodate the interstitial iron atom. [ABSTRACT FROM AUTHOR]

Transesterification of triolein in excess methanol oversodium-loadedcatalysts prepared from Na-ion exchange with zeolites at a relativelylower reaction temperature, namely, at 60 °C, is studied in thiswork. Two zeolites, i.e., as-synthesized ZeoliteMCM-22 and commercial Zeolite HY (CBV-780), are employed in this study.Althoughboth zeolites show to some extent the capability of catalyzing transesterificationof triolein in methanol to biodiesel, the resulting yields are onlyca. 90% for CBV-780 after a 40-h reaction and 16.3% for MCM-22 aftera90-h reaction. In contrast, the conversion yields are much improvedwith Na-ion exchange to the surface of zeolite catalysts. For example,the yields of triolein to biodiesel have reached 98% and 99% withina 5.5-h reaction, respectively, using the NaOH-treated CBV-780 andMCM-22 catalysts, even if these NaOH-treated catalysts become amorphousand have suffered a loss of the Brunauer–Emmett–Tellersurface area. Furthermore, no saponification was observed using theseNaOH-treated catalysts. [ABSTRACT FROM AUTHOR]

Previous studies have shown that hybrid fermentation–pervaporationsystems can be attractive for ethanol production. Simultaneous removalof the ethanol produced promises to improve yield and to reduce operationtime and the energy required for ethanol purification. This paperexperimentally explores the effect of pH (3–5.7), CO2(at saturated conditions), and high glucose concentrations (50–400g/L) on the flux and selectivity of PDMS (polydimethylsiloxane) pervaporationmembranes at several ethanol concentrations (50–100 g/L) andtemperatures (278–313 K). Membrane performance has been simulatedusing a Henry solution model combined with a Maxwell–Stefandescription of mass transport through the membrane. By adjusting themodel to the water–ethanol experimental data, it was possibleto calculate the relative solubility and diffusion between ethanoland water in the polymeric membrane. Experimental results showed thatthe higher the glucose concentration is, the higher the membrane selectivityto ethanol will be due to a reduction on water flux. However, at aglucose concentration of 400 g/L a strong drop of total flux was measured.CO2permeates through the PDMS membrane, but it does nothave any effect on ethanol or water flux and, consequently, on selectivity.On the contrary, as pH is reduced so does selectivity while the totalflux increases. Low pH values produce a decrease in membrane hydrophobicity,increasing water transport. The results presented in this paper contributeto the design of hybrid fermentation and pervaporation units, especiallythose that can operate at high glucose concentrations. [ABSTRACT FROM AUTHOR]

Full dimensional quantum dynamics calculations of thethree lowestisomers of the He4Br2van der Waals moleculein its ground electronic state are reported. The calculations areperformed using the multiconfiguration time-dependent Hartree (MCTDH)method and a realistic potential form that includes the sum of threebody ab initio coupled-cluster single double triple [CCSD(T)] He–Br2interactions plus the He–He and Br–Br interactions.This potential exhibits several multiple minima, with the three lowestones lying very close in energy, just within 2 cm–1. Such small differences are also found in the calculated bindingenergies of the three most stable conformers, indicating the floppinessof the system and, thus, the need of accurate potential forms andquantum full dynamics methods to treat this kind of complexes. The12 dimensional results reported in this work present benchmark dataand, thus, can serve to evaluate approximate methods aiming to describehigher order rare gas–dihalogen (N> 4)complexes.A comparison with previous studies using different potential formsand approaches to the energetics for the He4Br2cluster is also presented. [ABSTRACT FROM AUTHOR]

The friction and adhesion between pairs of materials(silica, alumina,and polytetrafluoroethylene) have been studied and interpreted interms of the long-ranged interactions present. In ambient laboratoryair, the interactions are dominated by van der Waals attraction andstrong adhesion leading to significant frictional forces. In the presenceof the ionic liquid (IL) ethylammonium nitrate (EAN) the van der Waalsinteraction is suppressed and the attractive/adhesive interactionswhich lead to “stiction” are removed, resulting in anat least a 10-fold reduction in the friction force at large appliedloads. The friction coefficient for each system was determined; coefficientsobtained in air were significantly larger than those obtained in thepresence of EAN (which ranged between 0.1 and 0.25), and variationin the friction coefficients between systems was correlated with changesin surface roughness. As the viscosity of ILs can be relatively high,which has implications for the lubricating properties, the hydrodynamicforces between the surfaces have therefore also been studied. Thelinear increase in repulsive force with speed, expected from hydrodynamicinteractions, is clearly observed, and these forces further inhibitthe potential for stiction. Remarkably, the viscosity extracted fromthe data is dramatically reduced compared to the bulk value, indicativeof a surface ordering effect which significantly reduces viscous losses. [ABSTRACT FROM AUTHOR]

Context. Circinus X-1 is a neutron-star-accreting X-ray binary in a wide (Porb = 16.6 d), eccentric orbit. After two years of relatively low X-ray luminosity, in May 2010 Circinus X-1 went into outburst, reaching 0.4 Crab flux. This outburst lasted for about two orbital cycles and was followed by another shorter and fainter outburst in June. Aims. We focus here on the broadband X-ray spectral evolution of the source as it spans about three order of magnitudes in flux. We attempt to relate luminosity, spectral shape, local absorption, and orbital phase. Methods. We use multiple Rossi-XTE/PCA (3.0-25 keV) and Swift/XRT (1.0-9.0 keV) observations and a 20 ks long Chandra/HETGS observation (1.0-9.0 keV), to comprehensively track the spectral evolution of the source during all the outbursting phases. These observations were taken every two/three days and cover about four orbital cycles. The PCA data mostly cover the major outburst, the XRT data monitor the declining phase of the major outburst and all the phases of the minor outburst, and Chandra data provide an essential snapshot of the end of this overall outbursting phase. Results. The X-ray spectrum can be satisfactorily described by a thermal Comptonization model with variable neutral local absorption in all phases of the outburst. No other additive component is statistically required. The first outburst decays linearly, with an ankle in the light curve as the flux decreases below ∼5 × 10-10 erg cm-2 s-1. At the same time, the source shows a clear spectral state transition from an optically thick to an optically thin state. While the characteristics of the first, bright, outburst can be interpreted within the disk-instability scenario, the following, minor, outburst shows peculiarities that cannot be easily reconciled in this framework. [ABSTRACT FROM AUTHOR]

An in-depth study of the ion transfer facilitated bycomplexationin the organic phase (TOC mechanism) in liquid membrane systems ofone and two polarized interfaces is carried out by taking into accountthe kinetic effects associated with the complexation reaction. Explicitanalytical equations for the normal pulse voltammetric (I/E) and chronoamperometric (I/t) responses with an explicit dependence on the kineticparameters of the chemical complexation are presented for both kindsof membrane system, which could be useful for modeling artificialand biological membranes. The equations are compared with those obtainedby using the widely used approximation of total equilibrium conditionsthat leads to the transfer by interfacial complexation mechanism (TIC),which only depends on thermodynamic parameters. Simple methods areproposed that allow quantitative determination of the equilibriumand kinetic constants of the complexation reaction in the organicphase for both kinds of membrane system. [ABSTRACT FROM AUTHOR]

In this article, we report the findings of a comprehensivestructure–activityrelationship study of N-(6-ferrocenyl-2-naphthoyl)dipeptide ethyl esters, in which novel analogues were designed, synthesized,and evaluated in vitrofor antiproliferative effect.Two new compounds, 2and 16, showed potentnanomolar activity in the H1299 NSCLC cell line, with exceptionalIC50values of 0.13 and 0.14 μM, respectively. Thesecompounds were also found to have significant activity in the Sk-Mel-28malignant melanoma cell line (IC50values of 1.10 and 1.06μM, respectively). Studies were also conducted to elucidatethe mode of action of these novel organometallic anticancer compounds.Cell cycle analysis in the H1299 cell line suggests these compoundsinduce apoptosis, while guanine oxidation studies confirm that 2is capable of generating oxidative damage via a ROS-mediatedmechanism. [ABSTRACT FROM AUTHOR]

In this study, kinetics of formic acid-catalyzed xylosedehydrationinto furfural and furfural decomposition was investigated using batchexperiments within a temperature range of 130–200 °C.Initial xylose and furfural concentrations up to 0.2 and 0.08 mol/L,respectively, were used. The room temperature pH of the formic acidcatalyst solution was between 0.9 and 1.7. The kinetic model usedwas based on a specific acid catalysis model and included the prevailinghydrogen ion concentration in reaction conditions. The study showedthat the modeling must account for other reactions for xylose besidesdehydration into furfural. Moreover, the reactions between xyloseintermediate and furfural play only a minor role. The study also showedthat kinetic modeling of xylose and furfural decomposition reactionsmust take the uncatalyzed reaction in water solvent into account. [ABSTRACT FROM AUTHOR]

Thin and narrow conductive patterns of metal (silver)and organicpolymer (polyaniline) were printed on various coated paper samples.A detailed characterization of the physical properties (i.e., shortlength scale roughness, surface energy, and air permeability) of thepaper samples was conducted. These properties were correlated withprint quality (print resolution and edge waviness) and electricalperformance (resistance) of the printed wires. A plastic film wasused as a reference substrate. The print resolution and the magnitudeof the edge waviness were affected by the complex interplay of differentphysical properties of both the substrate and the ink. On the otherhand, the resistance of the printed wires was found to correlate linearlywith the short length scale roughness of the print substrate. Theelectrical performance of the paper substrates showing the highestconductivity for the printed patterns was comparable to that of theplastic film. The paper substrate on which the printed wires showedthe best electrical performance was used as a substrate for fabricationof an organic transistor with low operating voltage. [ABSTRACT FROM AUTHOR]

In this article, we investigate experimentally a widerange ofsituations where charge inversion (i.e., overcompensation of the surfacecharge of a colloidal particle by the countercharge) can occur. Tothat end, the electrophoretic mobility of sodium montmorillonite,silica, and polystyrene latex as functions of pH and concentrationof different salts is presented, and conditions are established wherecharge inversion occurs. The reason for this study is to provide experimentalevidence for distinguishing between two existing models for the explanationof charge inversion. One of these is the specific adsorption of ionslocated in the Stern layer in combination with a Gouy–Chapmandiffuse part of the double layer. The other ion-correlation theoriesexplain the phenomenon in terms of purely physical arguments basedon Coulombic pair interactions between ions and surface charges andon excluded volume effects. In distinguishing between these two interpretations,the influence of the pH plays a central role because of its effecton the hydrolysis of multivalent cations. In our experiments, it isfound that although 1–2 and 2–2 electrolytes provokea decrease in the absolute values of the electrophoretic mobilitieswhen their concentration in solution is increased, they never leadto charge inversion, whatever the surface charge or the pH. However,in the case of salts of trivalent cations, electrokinetic charge reversalis often observed above a certain critical electrolyte concentration.In addition, the extent of overcharging increases when the concentrationis raised above the critical value. This trend occurs for any systemin which the surface charge is pH-independent, as in polystyrene latexand montmorillonite. Most of the results presented here are compatiblewith the specific adsorption of hydrolyzed metal ions as the maindriving force for charge inversion. At low pH, when the hydrolysisof trivalent cations is likely to be absent, overcharging can be attributedto ion correlation effects. [ABSTRACT FROM AUTHOR]

The recrystallization of caffeine extracted with dichloromethanefrom coffee beans by a supercritical antisolvent (SAS) process wasstudied. Acicular crystalline particles with a particle size downto 2.5 μm were obtained, and product purity was increased asa result of SAS processing. Furthermore, by modification of processconditions, it was possible to vary the proportion between the metastableand stable crystalline polymorphic forms of caffeine, obtaining fractionsof stable form ranging from 40% to nearly 100%. [ABSTRACT FROM AUTHOR]

A computational study of the reaction of P(3P) with acetylene has been carried out. The only exothermicproducts correlating with the reactants are PCCH(2Π) H(2S). Two different pathways leadingto these products that are apparently barrier-free have been found.Both pathways involve isomerization into open-chain intermediatesfollowed by direct elimination of a hydrogen atom. The possibilityof spin-crossing has been considered because the species on the singletsurface are considerably more stable than those on the triplet one.On the singlet surface, there are other possible channels for thereaction, namely, cyclic PC2H(2A′) H(2S) and CCP(1Σ) H2(1Σg). A computationalkinetic study shows that, in agreement with the experimental evidence,the major products are PCCH(2Π) H(2S) at all temperatures. Only at very high temperatures isCCP(1Σ) H2(1Σg) formed in non-negligible amounts.Therefore, only PCCH눚⺕ be formed in the interstellarmedium. [ABSTRACT FROM AUTHOR]

The relaxation dynamics of the isolated indole molecule has been tracked by femtosecond time-resolved ionization. The excitation region explored (283–243 nm) covers three excited states: the two ππ* Lband Lastates, and the dark πσ* state with dissociative character. In the low energy region (λ > 273 nm) the transients collected reflect the absorption of the long living Lbstate. The Lastate is met 1000–1500 cm–1above the Lborigin, giving rise to an ultrafast lifetime of 40 fs caused by the internal conversion to the lower Lbminimum through a conical intersection. An additional ∼400 fs component, found at excitation wavelengths shorter than 263 nm, is ascribed to dynamics along the πσ* state, which is likely populated through coupling to the photoexcited Lastate. The study provides a general view of the indole photophysics, which is driven by the interplay between these three excited surfaces and the ground state. [ABSTRACT FROM AUTHOR]

We present a detailed study for the short-time dynamics through conical intersections in molecular systems related to the quadratic vibronic coupling (QVC) Hamiltonian [Müller, H.; Köppel, H.; Cederbaum, L. S. NewJ. Chem. 1993, 17, 7–29] and the effective-mode formalism [Cederbaum, L. S.; Gindensperger, E.; Burghardt, I. Phys. Rev. Lett. 2005, 94, 113003]. Our approach is based on splitting the nuclear degrees of freedom of the whole system into system modes and environment modes. It was found that only three-effective environmental modes together with the system’s modes are needed to describe the short-time dynamics of the complex system correctly. In addition, a detailed mathematical proof is given in the appendix to demonstrate that the exact cumulants are recovered up to the second order within the cumulant expansion of the autocorrelation function. The butatriene molecule is studied as an explicit showcase example to stress the viability of our proposed scheme and to compare with other systems. [ABSTRACT FROM AUTHOR]

Liquid–liquid equilibrium (LLE) data are presentedfor ammoniumbased ionic liquids (ILs) dibenzothiophene (DBT) n-dodecane at 298.2 K and atmospheric pressure (∼95 kPa). Molefractions were determined by the refractometry or graphical method.DBT phase distribution, ionic liquid selectivity, and DBT percentextraction were determined. Ionic liquids used here were comparedwith imidazolium in terms of sulfur removal. Hand and Othmer–Tobiascorrelations were used to test the LLE data and gave σ <0.09 (R2> 0.90). The nonrandom two-liquidmodel (NRTL) was used to correlate the LLE data, giving percent root-mean-squaredeviations < 0.22 between experimental and calculated mole fractions. [ABSTRACT FROM AUTHOR]

The paper reports the isothermal vapor–liquidequilibria(VLE) of five binary mixtures containing 2-butanol heptane, 2,2,4-trimethylpentane, dodecane, cyclohexane, and methylbenzene at 313.15 K. A statictechnique has been used for the measurements. Data reduction by Barker'smethod provides the parameters of GEmodels.The six-parameter Margules equation, Wilson, nonrandom two-liquid(NRTL), and universal quasichemical activity coefficient (UNIQUAC)models have been used for the correlation of the experimental data.Good results have been obtained for all. The five investigated mixturesexhibit a positive deviation from ideality, and four of them showa maximum pressure azeotrope. Only the mixture 2-butanol dodecanedoes not present an azeotrope. [ABSTRACT FROM AUTHOR]

The E 3Πgstate of the iodinemolecule is studied by ab initio multireference methods coupled witheffective core potentials and large basis sets. Two potential minimaare found, a global featuring an ion-pair character, and a local presentinga purely Rydberg nature. Four avoided crossings along the dissociationcoordinate attribute an interesting topology to its potential energycurve, and their effect on the vibrational levels of I2is discussed. [ABSTRACT FROM AUTHOR]

The spectroscopy and kinetics of the tyrosinase catalyzed trans-resveratrol oxidation were investigated by measuringboth UV–vis absorption spectra over the 200–500 nm rangeand Raman spectra over the 600–1800 cm–1region.Room temperature UV–vis absorption spectra, as a function oftime, showed the presence of two isosbestic points located at λ1= 270 nm and λ2= 345.5 nm delimiting twodifferent regions: the reactant region around 300 nm, where the absorptiondecreased with time, and the product region over the low wavelength(λ < 260 nm) and high wavelength (λ > 390 nm) wavelengthzone in which the absorption increased with time until, in both cases,constant values were achieved. A first-order kinetics was deducedwith a rate coefficient of k1= (0.10± 0.001) min–1, which turned out to be independentof substrate concentration over the 50–5 μM range; afeature that was rationalized by invoking the limiting case of theMichaelis–Menten scheme appropriate for substrate concentrationmuch lower than the respective Michaelis constant. The observationof the distinct resonance enhanced Raman lines, specifically thosepeaking at 830 cm–1, 753 cm–1,and 642 cm–1together with their time evolution,permitted us to gain insight into some crucial features and stepsof the catalytic reaction. Namely, that the formation of the so-called trans-resveratrol and tyrosinase SP complex withits O–O bridge plays a crucial role in the first steps of thisenzymatic reaction and that the hydroxylation of the ortho C–Hbond of the trans-resveratrol OH group occurs afterO–O bond cleavage in the tyrosinase activesite. The present study makes clear that a class of potential inhibitorsof tyrosinase can be found in compounds able to bind the two Cu (II)ions of the enzyme bidentate form. [ABSTRACT FROM AUTHOR]

Epitaxial growth of SrRuO3/CoFe2O4/La2/3Sr1/3MnO3trilayerson SrTiO3(001) substrates has been successfully achievedusing pulsedlaser deposition. This trilayer configuration, which consists of twoconducting ferromagnetic oxides separated by a thin insulating ferritefilm, is a promising candidate for all-oxide magnetic tunnel junctions.Structural analyses carried out using transmission electron microscopyand X-ray diffraction demonstrate a remarkable continuation of thein-plane and out-plane crystallographic relations across the entirestructure. Magnetic measurements on SrRuO3/CoFe2O4/La2/3Sr1/3MnO3trilayersindicate independent magnetic switching in an external magnetic field,which is one of the prerequisites for large tunneling magnetoresistanceeffects. [ABSTRACT FROM AUTHOR]

Generalized least-squares and maximum likelihood approaches for parameter estimation in multivariate response models have been prevalent in the chemical kinetics literature to date. In contrast, robust alternatives have received considerably less attention. These methods safeguard against possible deviations from the assumptions, such as the presence of outliers or non-normality of the random errors. We compare, through Monte Carlo simulation, the performance of the classical Box–Draper determinant criterion (ML) to those of two robust estimators: the multivariate Huber’s M-estimator and the multivariate least-trimmed squares estimator (MLTS). Although the results are not entirely conclusive, overall, we find no compelling evidence for preferring any one of the two robust methods over the conventional ML estimates. At the same time, it was unexpected to find that ML is still reasonable under mild outlier contamination and mild deviations from normality. This notwithstanding, one loses nothing by comparing ML together with MLTS to cross-check each other as a safety measure. [ABSTRACT FROM AUTHOR]

Experimental results are reported for the solubility of carbon dioxide in liquid mixtures of water and the ionic liquid 1-n-butyl-3-methylimidazolium methylsulfate ([bmim][CH3SO4]). Three (gas-free) solvent compositions were considered with mass fractions of [bmim][CH3SO4] of w′ ≈ 0.15, 0.50, and 0.87 (mole fractions x′ ≈ 0.013, 0.066, and 0.33). In the isothermal experimental series, the temperature was about (293, 333, and 373) K. The total pressure ranged up to about 10 MPa. The molality of carbon dioxide in the solvent mixture of (water [bmim][CH3SO4]) (the mole fraction of carbon dioxide in the liquid) ranged up to approximately 1.64 mol·kg–1(about 0.0332). The experimental results are used to determine Henry's constant of carbon dioxide in the liquid mixtures of (water [bmim][CH3SO4]) as well as the partial molar volume of that gas at infinite dilution in those solvent mixtures. The phase equilibrium is described by applying an extension (to solvent mixtures) of Pitzer's molality scale-based equation for the Gibbs excess energy. [ABSTRACT FROM AUTHOR]

Cycloplatinated neutral [Pt(C∧N){H2B(pz)2}] (1–3) [C∧N = benzoquinolate (bzq), 2-phenylpyridinate (ppy), and 2-phenylquinolate (pq)] and [Pt(pq){HB(pz)3}] 10and cationic [Pt(C∧N){H2C(pz)2}](4–6) and [Pt(C∧N){HC(pz)3}](7–9) complexes were synthesized by the reaction of the corresponding precursors [Pt(C∧N)(μ-Cl)]2with the adequate poly(pyrazolyl)-borate or -methane ligand. However, the reactions of [Pt(C∧N)(μ-Cl)]2(C∧N = bzq, ppy) with [HB(pz)3]−evolve with B–N bond cleavage, yielding the binuclear systems [Pt(C∧N)(μ-pz)]2as a mixture of cis and trans isomers. Complexes were characterized in solution by multinuclear and multidimensional NMR spectroscopy. The solid-state structures of 1, 3, 6, 7–9, and [Pt(bzq)(μ-pz)]2were confirmed by X-ray single-crystal studies. The absorption, emission, and electrochemical properties of these complexes are mainly dominated by the nature of the cyclometalated ligand and the charge of the complex. On the basis of TD-DFT calculations (1, 7–9), the lowest-energy absorption for neutral 1has been ascribed to a mixed 1ILCT/1MLCT transition, whereas for the cationic 7–9, it is mainly attributed to 1ILCT combined with some CT to both ligands in 9(1MLCT/ML′CT 9) or to the HC(pz)3in 7and 8(1ML′CT). These compounds are emissive in all media (except 4and 10in the solid state at 298 K). In the solid state at 298 K and at 77 K, these complexes display intense phosphorescence, which is typical of monomers. In deoxygenated CH3CN solutions at 298 K, phosphorescence is accompanied by higher-energy fluorescence in complexes 1, 4, and 8, which disappears at concentrated solutions and at 77 K. Complex 7displays a special behavior, observing fluorescence and/or excimer fluorescence only at 298 K and excimeric emission (diluted glasses) and emission from aggregates in concentrated glasses. TD-DFT of the lowest-lying excited states responsible for the phosphorescence of 1and 7–9reveals a 3ILCT origin with a mixed 3MLCT character for 1and, in the case of the cationic 7–9, a 3ILCT transition mixed with 3ML′CT (especially in 8) and with some 3MLCT in 9. [ABSTRACT FROM AUTHOR]

The surface tension of (2-methyl-2-butanol ethanol), (3-methyl-1-butanol ethanol), and (2-methyl-1-butanol ethanol) binary solutions was measured over the entire composition range and at temperatures from (293.15 to 323.15) K. The experimental data were correlated with the temperature, the maximum deviation being less than 0.4 %. [ABSTRACT FROM AUTHOR]

A concentrated colloidal dispersion is studied by applying an integral equations theory to the colloidal primitive model fluid. Important effects, attributed to large size and charge and to the finite concentration of colloidal particles, are found. We observe a polarity inversion of ζ-potential for concentrated colloidal dispersions, while it is not present for a single colloidal particle at infinite dilution. An excellent qualitative agreement between our theoretical predictions and our computer simulations is observed. [ABSTRACT FROM AUTHOR]

The solubility of solid bisphenol A (4,4′-(propane-2,2-diyl)diphenol) in supercritical carbon dioxide (SC-CO2) has been measured at temperatures of T= 313 K, T= 333 K, and T= 353 K and in the pressure range 12 MPa < P< 20 MPa, using a variable-volume view cell according to the synthetic method. The solubility increases with increasing pressure and temperature, ranging from 1.8·10–5(mole fraction) at T= 313 K and P= 16.4 MPa to 7.7·10–5(mole fraction) at T= 353 K and P= 14.6 MPa. The solubility data obtained have been correlated using the Peng–Robinson equation of state with quadratic mixing rules. The results obtained are useful for the design of processes for the synthesis or recycling of polycarbonate in supercritical CO2. [ABSTRACT FROM AUTHOR]

The synthesis and biological activity of oleylN-acetyl-α- and β-d-glucosaminides (1and 2, respectively) and their thioglycosyl analogues (3and 4, respectively) are reported. The compounds exhibited antimitotic activity on rat glioma (C6) and human lung carcinoma (A549) cell cultures in the micromolar range. Analysis of cell extracts using ultra performance liquid chromatography–mass spectrometry showed that the synthetic glycosides produce alterations in glycosphingolipid metabolism, with variable effect on the level of glucosylceramide depending on the configuration of the antimitotic used. In vivo experiments in nude mice bearing an implanted C6 glioma showed that the α-thioglycoside 3reduced tumor volume, while the O-glycosyl derivative was inactive, highlighting the importance of using enzyme resistant glycosides. [ABSTRACT FROM AUTHOR]

A novel catalyzed intermolecular heterodehydro-Diels–Alder reaction between push–pull 1,3-dien-5-ynes and aldimines or silylaldimines is reported. The sequence is promoted both by gold(I) or silver(I) catalysts and leads to the diastereo- and regioselective formation of 5,6-dihydropyridin-2-ones. [ABSTRACT FROM AUTHOR]

A new two-state polymer folding model is proposed, in which the folding of a stiff helical polymer is enabled by allowing for short sequences of coils connecting shorter and separated helices. The folding is driven by short-range attraction energy among stacked helices and is opposed by the free-energy cost of forming coils from helical monomers. Principal outcomes of the model are equilibrium distribution of the number of helices and their length in helical polymers. The proposed model is applied to α-helical polyalanine. The distribution of the number of α-helices as a function of number of alanine residues is fitted to the corresponding result from molecular dynamics simulation employing an all-atom potential model with very good agreement. The influence and significance of the fitting parameters and possible use of the two-state folding model are discussed. [ABSTRACT FROM AUTHOR]