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Stabilization of an oil phase is crucial in many industrial processes. SAXS quantifies the ordering of nanoparticles on Pickering emulsion droplets, stabilized by complex amphiphilic Interactions.

Lipophile induced modulations of self-assembly characteristics in aqueous Pluronic systems merit attention because of wide-ranging uses of Pluronics as solubilizing agents of lipophilic substances. In this paper, we report unusual evolutions of structural and hydration properties in lavender essential oil (LO) solubilized Pluronic P85 aqueous micellar systems as a function of micellar volume fraction and temperature. Our DLS, SANS, and viscometry studies show that the spherical-to-wormlike micellar structural transition observed in 1% P85 solutions upon solubilization of LO quite unexpectedly gets suppressed with increased P85 concentration to ≥5%. Detailed SANS studies reveal that the core sizes of the oil solubilized micelles cannot attain the threshold value required for the onset of structural transition at higher copolymer concentrations due to their progressive shrinking with an increase in P85 concentration. Oil solubilized P85 solutions show two cloud points and very interestingly exhibit micellar growth upon cooling to their lower cloud points. Steady state fluorescence studies explain this based on increasing dehydration of micellar corona with a decrease in temperature, very much opposite to what is observed in pure aqueous Pluronic systems. The results give new insight into viscous flow properties and low temperature storage possibilities of oil solubilized aqueous Pluronic systems.

Quasars and other active galactic nuclei (AGN) are now commonly believed to be powered through accretion of material from an accretion disk onto a supermassive black hole (SMBH), which can have an impact on the evolution of the quasar's host galaxy through feedback processes such as outflows in the form of accretion disk winds. The ultimate goal of this work is to better understand the characteristics of these outflowing winds and their relations to the host quasar. We do this using quasar spectra at both high redshift and low redshift using a combination of archival data and our own observations. First, we use the spectra of 73 quasars (1.5 2000 km/s) and 4 mini-BALs (500 km/s

Polysorbate 80 is one of the most widely used solubilizing agents in food, cosmetic and pharmaceutical industries. Influences of different classes of solubilizates and additives on its self-assembly characteristics are however, not sufficiently understood yet. In this manuscript, we show how common water structure making salt NaCl, and lipophilic phytochemicals like curcumin and lavender oil help in modulating the structure of Polysorbate 80 micelles in aqueous medium. Our DLS, SANS and rheological studies show that NaCl induces sphere-to-rod growth of polysorbate 80 micelles at the room temperature. Micellar solubilizations of the phytochemicals, which were found to be facilitated with increase in temperature, induce only a marginal growth of the micelles up to the highest level of solubilization. Their presence however, helps in modulating the NaCl induced micellar growth behavior in the tween 80 solutions leading to observation of micelle-to-vesicle structural transition at 2% lavender oil concentration. The phytochemical solubilized micellar solutions could be converted to alginate based hydrogel beads and patches that can freely release micellar phytochemical in aqueous medium. Our results shed light on possible ways of modulating the solubilization behavior, self-assembly characteristics and rheological properties of aqueous system of polysorbate 80, which could be important for their applications.

Importance of pluronic P85 as carrier for drugs arises due to its ability to sensitize cell membranes for delivery of drugs across multi drug resistant cancer cells and blood brain barrier. It is thus necessary to understand how lipophilic drugs and phytochemicals influence its self-assembly characteristics and how the therapeutic properties of these lipophiles are modulated upon encapsulation in P85 micelles. We have investigated solubilization characteristics of Lavender essential oil (LO) in P85 and P85-P123 micellar systems and studied the associated structural and therapeutic properties by DLS, SANS, viscosity, ITC, antimicrobial and in vitro cancer cell viability studies. We observed that LO induces micellar structural transitions in aqueous P85 and P85-P123 systems leading to the formations of worm like micelles and vesicles. LO solubilized systems exhibit anticancer and antimicrobial properties, and show existence of double cloud points namely, upper and lower cloud points (UCP & LCP). A spherical-to-elliptical micellar structural transition is observed in these LO solubilized systems upon cooling down to LCP, which is unusual and not reported hitherto in aqueous pluronic systems. The observed results show how essential oils can influence the self-assembly characteristics of P85 based micellar systems and how their therapeutic properties are manifested under micellar encapsulation.

Aqueous solutions of cetyltrimethylammonium bromide (CTAB) show micellar growth in the presence of various organic and inorganic additives. The simultaneous presence of some of these additives exhibit synergistic effects on micellar growth in this system due to their diverse nature of influences on the critical packing parameter of CTAB micelles. In this manuscript, we report dynamic light scattering, small-angle neutron scattering and rheological studies on influences of the widely used preservative butyl paraben and NaCl on the growth and interaction of CTAB micelles. These additives show synergism in micellar growth and induce micellar attraction-driven phase separations of both upper consolute temperature and lower consolute temperature regimes in aqueous solutions of CTAB. Quite interestingly, such micellar attraction-driven phase separations are also induced in aqueous systems of other cationic and anionic surfactants in the simultaneous presence of a hydrophobic substance and NaCl. These systematic observations of micellar attraction-driven phase separation are the first of this kind in aqueous systems of ionic surfactants. The results also suggest that the use of parabens as preservatives in some ionic surfactantbased formulations can also help in tuning their rheological characteristics.

Pluronics P123 and F127 mixed micellar system has been studied extensively for drug delivery applications because of its non-toxic nature, good solubilization capacity of lipophilic substances and its effectiveness against multi drug resistance (MDR) cancer cells. The constituent pluronics of this system have large difference in their hydrophilic lipophilic balance (HLB) and consequently are strikingly different in their self-assembly characteristics. In this work, we show how the properties of this system compare vis-a-vis the aqueous systems of its constituent pluronics and how pluronics P123 and F127 behave as drug delivery agents in antimicrobial and wound healing applications. DLS, SANS, ITC and rheological studies show that aggregation characteristics in the mixed micellar system is dictated by P123 up to its mole fraction of as low as 0.30. Thus, like pure aqueous P123 solutions, the mixed micellar systems exhibit spherical-to-worm like micelles-to-vesicular structural transitions in the presence of additives like NaCl and tea tree essential oil (TTO), and the dynamics of such structural transitions remains slow at the room temperature. TTO is chosen as additive as it exhibits anticancer, antimicrobial and wound healing properties and like water structure making salt NaCl, it brings about micellar structural changes in aqueous surfactant systems by increasing the hydrophobicity of the surfactant aggregates. ITC and phytochemical solubilization studies suggest that the mixed micellar system does not exhibit synergism in aggregation and lipophile solubilization characteristics. Our antimicrobial and wound healing studies quite interestingly reveal that hydrophobic pluronic P123 remains more effective than F127 as carrier for antimicrobial agent, whereas pluronic F127 based liquid crystalline hydrogel stands superior as topical drug delivery matrix than its P123 counterpart because of its better wound healing abilities. The observed results give insight into the structural and therapeutic properties of P123/F127 system, which were not understood hitherto.

CMOS technology over Transistor is an important contribution in Very Large Scale Integrated technique for the last two decades. Quantum Dot Cellular Automata (QCA) brings as a replacement solution to the fundamental limits of CMOS technology. This paper is a proposal of making Quantum dot cellular automata (QCA) based Nano-calculator. In this Calculator we've simulated four basic operations: addition, subtraction, multiplication and division. QCA is an advance technology which overcomes some limitations of CMOS such as switching speed. QCA generated circuits operates in the order of terahertz frequency range where circuits does not require any extra power supply for operation.

To characterize the absorption properties of this circumgalactic medium (CGM) and its relation to the LG we present the so-far largest survey of metal absorption in Galactic high-velocity clouds (HVCs) using archival ultraviolet (UV) spectra of extragalactic background sources. The UV data are obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST) and are supplemented by 21 cm radio observations of neutral hydrogen. Along 270 sightlines we measure metal absorption in the lines of SiII, SiIII, CII, and CIV and associated HI 21 cm emission in HVCs in the velocity range |v_LSR|=100-500 km s^-1. With this unprecedented large HVC sample we were able to improve the statistics on HVC covering fractions, ionization conditions, small-scale structure, CGM mass, and inflow rate. For the first time, we determine robustly the angular two point correlation function of the high-velocity absorbers, systematically analyze antipodal sightlines on the celestial sphere, and compare the absorption characteristics with that of Damped Lyman alpha absorbers (DLAs) and constrained cosmological simulations of the LG. Our study demonstrates that the Milky Way CGM contains sufficient gaseous material to maintain the Galactic star-formation rate at its current level. We show that the CGM is composed of discrete gaseous structures that exhibit a large-scale kinematics together with small-scale variations in physical conditions. The Magellanic Stream clearly dominates both the cross section and mass flow of high-velocity gas in the Milky Way's CGM. The possible presence of high-velocity LG gas underlines the important role of the local cosmological environment in the large-scale gas-circulation processes in and around the Milky Way (abridged)., Comment: 37 pages, 25 figures, 8 tables, accepted for publication in A&A

Pluronic F127 is considered to be the most prominent member amongst Pluronics owing to its uses in the fields of drug delivery and fabrication of mesoporous materials. Though extensive studies were carried out on the phase behavior of this copolymer, the effect of additives on restructuring and growth processes of its micelles is not understood yet. In this manuscript we report DLS, SANS, fluorescence and rheological studies on the effects of NaCl and butan-1-ol on the properties of Pluronic F127 micelles in the aqueous medium. The studies show that corona specific micellar dehydration by NaCl induces inter micellar attraction and consequent formation of micellar clusters. Core specific micellar dehydration by butan-1-ol on the other hand, brings about sphere-to-rod micellar shape transition on approaching the cloud point of copolymer solutions. A room temperature sphere-to-rod shape transition of Pluronic F127 micelles can also be induced in the combined presence of butan-1-ol and NaCl. Observation of such micellar shape transition in aqueous Pluronic F127 system is first of its kind, which can have important bearing with their application in mesoporous structure formation and drug delivery.

The influence of methyl paraben (MP) and butyl paraben (BP) on the aggregation characteristics of Pluronics in an aqueous medium has been investigated by DLS, SANS, viscometry, and fluorescence measurement techniques. Parabens are extensively used as preservatives in cosmetic, pharmaceutical, and food products. In this paper, we show that their influence on the restructuring and growth of Pluronics micelles vary quite significantly with their aqueous solubility and with the composition of Pluronics. In the case of P105 and P104, MP reduces the sphere-to-rod transition temperature down to room temperature, but BP with significantly less aqueous solubility than MP suppresses such micellar transition and leads to the formation of micellar clusters due to the onset of intermicellar attractive interaction. In the case of more hydrophobic Pluronic P103, on the other hand, both MP and BP are able to induce rapid room temperature sphere-to-rod micellar growth, which is not observed in the presence of water structure making salts like NaCl and Na(3)PO(4). These observations have been attributed to modulation of growth and restructuring processes of the Pluronic micelles arising due to different locations of parabens within the micellar corona as determined by their aqueous solubility and the hydrophobicity of the Pluronics.

The temperature dependence of the phase behavior of the TODGA-based water in oil (w/o) microemulsions in dodecane has been investigated by dynamic light scattering (DLS) and viscometry techniques. These microemulsions have been found to undergo phase separation into dilute and concentrated reverse micellar solutions at their respective upper consolute temperatures (UCTs). DLS and viscometry studies attribute this to a progressive strengthening of the inter-micellar attractive interaction with decrease in temperature. The UCT of these microemulsions has been found to increase quite significantly with increase in the aqueous HNO3 concentration due to an enhancement in the inter-micellar attractive interaction. Besides identifying the existence of an upper consolute temperature in this system, we have also observed that these reverse micellar solutions show critical behavior in the form of divergence of the apparent hydrodynamic size of the reverse micelles on approaching the UCT. Viscometry studies and their modeling based on Baxter adhesive hard sphere theory suggest that the stickiness parameter of the reverse micellar aggregates in this system remains much lower than the critical value (τc−1 ≈ 10.25) on approaching the UCT. This suggests that the observed phase separation in these microemulsions cannot be explained based on a gas–liquid type phase transition.

The influence of sodium hydroxide (NaOH) on the aggregation characteristics of the Tetronic 904 (T904) has been studied in the aqueous medium by dynamic light scattering (DLS), small angle neutron scattering (SANS), and viscometry methods. This polyethylene oxide (PEO)-polypropylene oxide (PPO) based X-shaped triblock copolymer shows pH sensitive aggregation characteristics due to the presence of a central amine group attached with the PPO block. The aqueous micellar solutions of this copolymer have been found to show a large increase in the room temperature (30 °C) relative viscosity with an increase in NaOH concentration, before they undergo phase separation at 1.25 M NaOH concentration. SANS and DLS studies ascribe this behavior to a sphere to rod growth of the copolymer micelles on approaching the cloud points of the copolymer solutions. DLS studies show that the observed micellar growth is accompanied by critical scattering due to the onset of an attractive intermicellar interaction. To understand the role of NaOH in inducing the observed micellar shape transition, we have also studied the effect of NaOH on the micellar solutions of Pluronic P84, which does not show pH sensitivity due to the absence of the central amine group but has the same weight fraction of the PEO block (40%) as that of T904. Quite interestingly, the P84 micelles too have been found to undergo a similar room temperature sphere to rod shape transition in the presence of NaOH. The observed growth and interaction of the Tetronic micelles have thus been attributed to the dual effects of NaOH in influencing the aggregation characteristics of the Tetronic molecules. On one hand, it stabilizes these micelles by the deprotonation of the copolymer molecules, and on the other hand, its dehydrating effect on the copolymer molecules promotes the onset of micellar growth and intermicellar attractive interaction at the room temperature. The observed results are the first of their kind in the aqueous Tetronic system.

N,N,N',N'-tetraoctyl diglycolamide abbreviated as TODGA, is one of the most promising extractant for actinide partitioning from high level nuclear waste. It forms reverse micelles in non polar solvents on equilibration with aqueous HNO(3) solutions. This reverse micellar system undergoes phase separation into dilute and concentrated reverse micellar solutions at high aqueous acid concentration. Small angle neutron scattering (SANS) studies reported in the literature explained this phenomenon based on gas-liquid type phase transition in the framework of Baxter adhesive hard sphere theory in the presence of a strong inter-micellar attractive interaction. The present investigation attempts to throw further light on this system by carrying out systematic dynamic light scattering (DLS) and viscometry studies, and their modeling on the TODGA reverse micellar solutions in the dodecane medium. The variation of the diffusion coefficient with the micellar volume fraction observed from the DLS studies is suggestive of the presence of an attractive interaction between the TODGA reverse micelles, which weakens at the high micellar volume fraction due to the increased dominance of the excluded volume effect. It is suggested that this weakened interaction is responsible for the absence of phase separation in this system at high TODGA concentration. The results thus highlight the importance of the presence of an attractive interaction between the TODGA micelles in determining the observed phase separation in the TODGA reverse micellar systems. The modeling of the DLS and viscosity data, however, suggest that the characteristic stickiness parameter of this system could be smaller than the critical value required for inducing a gas-liquid type phase transition.

Water dispersible Fe3O4 nanoparticles (coated with Poly Vinyl Pyrolidone (PVP) and Poly oxy ethylene 25-propylene glycol stearate (POES)) and complexed with Doxorubicin has been prepared and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The antitumor activity of these particles has been studied by targeting the complex to the tumor site, using an externally applied magnetic field, after oral administration of the magnetic nanoparticle-drug complexes. Our results reveal that the chemotherapy effect of Doxorubicin could be considerably enhanced by combination of the application of the drug-conjugated magnetic Fe3O4 nanoparticles, which are biocompatible and stable, and targeted drug delivery with a magnet. The present report provides the first evidence for the promising application of this novel approach with PVP coated Fe3O4 nanoparticles for cancer therapy using an in vivo murine model.

The sphere-to-rod growth behavior of the triblock copolymer EO(20)PO(70)EO(20) (P123) micelles has been studied in an aqueous medium by dynamic light scattering (DLS), viscometry, and small angle neutron scattering (SANS) techniques. Unlike the other aqueous pluronic systems, the P123 solutions show a time dependent sphere-to-rod micellar growth in the aqueous medium on approaching their cloud points. The rate of micellar growth increases with increase in temperature, but quite interestingly, it improves rather dramatically when the copolymer solutions are subjected to heat cycling, i.e., heating them to the phase separation and subsequently cooling them back to below their cloud points. The observed kinetically restricted micellar growth has been attributed to the slow dynamics of the micellar restructuring processes essential to arrive at the temperature dependent equilibrium structure. It has been suggested that the improvement in the micellar growth rate upon heat cycling is due to overcoming of the activation energy associated with the micellar restructuring process. In the presence of water-structure-making salts like NaCl, such heat cycling produces kinetically stable wormlike micelles at room temperature, which is observed for the first time in the aqueous pluronic systems.

Steady-state and time-resolved fluorescence anisotropy measurements using probes coumarin 153 (C153) and 4-heptadecylumbelliferon (HUF) have been carried out to understand the micelle to gel transition of an aqueous triblock copolymer P123 ((EO)(20)-(PO)(70)-(EO)(20)) (EO = ethylene oxide; PO = propylene oxide) solution. Anisotropy results with a normal fluorescent probe, C153, do not show a characteristic change due to the micelle to gel transition. However, the probe HUF having a long hydrocarbon chain that helps its strong association with the micelle shows an increase in anisotropy above the sol-gel transition point. This difference has been explained as invoking a substantial contribution from the micellar structural fluctuations to the depolarization of HUF as its hydrocarbon chain is embedded in the micellar structure, which is not sensed significantly by the normal probe C153. That the extent of change in anisotropy for HUF upon gelation is not that large is possibly caused by the collective motion of the physically interconnected nodes, as observed from the dynamic light scattering studies, which acts in favor of a relatively faster depolarization in the gel phase. Similar studies in other copolymers, such as P85 ((EO)(26)-(PO)(40)-(EO)(26)) and F127 ((EO)(100)-(PO)(65)-(EO)(100)), further demonstrate the potential of probes latched with hydrocarbon chains in displaying a characteristic change for the micelle to gel transition which otherwise remains obscured for normal fluorescent probes.

The structure and the properties of the (Ethylene Oxide)(13)(Propylene Oxide)(30)(Ethylene Oxide)(13) (Pluronic L64, MW approximately 2900) micelles have been studied in the aqueous medium by small angle neutron scattering (SANS), dynamic light scattering (DLS) and viscometry measurements. The aqueous solutions of this triblock copolymer are unique among the pluronic solutions in showing critical concentration fluctuations and a concomitant enhancement in viscosity on approaching their cloud point. So far these results have been attributed solely to the presence of attractive interaction between the spherical L64 micelles. Recent theoretical studies, on the other hand, suggest that L64 micelles prefer a prolate ellipsoidal structure to sphere (Bedrov et al. Langmuir 2007, 23, 12032) and have a predominantly repulsive intermicellar interaction. A comparative analysis of our SANS data based on the spherical and prolate ellipsoidal structure shows that the L64 micelles can be best described by a prolate ellipsoidal structure, the aspect ratios of which increase progressively with increase in temperature. This, together with our viscosity and DLS studies, suggests that the enhanced viscosity of the copolymer solution near the cloud point arises largely due to the anisotropic growth of the micelles to the worm-like structures. The role of the intermicellar attractive interaction has thus been limited to the observed critical concentration fluctuation, and its effect decreases progressively with increase in copolymer concentration. It has also been shown that the water structure making salts like NaCl reduces the micellar growth temperature and helps in forming worm-like micelles at the room temperature. These studies thus identify the effect of micellar growth and interaction in determining the properties of the copolymer solution near the cloud point, which are the first of its kind in the case of the pluronics.

LiCl-induced changes in the micellar hydration and gelation characteristics of aqueous solutions of the two triblock copolymers F127 (EO(100)PO(70)EO(100)) and P123 (EO(20)PO(70)EO(20)) (where EO represents the ethylene oxide block and PO represents the propylene oxide block) have been studied by small-angle neutron scattering (SANS) and viscometry. The effect of LiCl was found to be significantly different from those observed for other alkali metal chloride salts such as NaCl and KCl. This can be explained on the basis of the complexation of hydrated Li(+) ions with the PEO chains in the micellar corona region. The interaction between the chains and the ions is more significant in the case F127 because of its larger PEO block size, and therefore, micelles of this copolymer show an enhanced degree of hydration in the presence of LiCl. The presence of the hydrated Li(+) ions in the micellar corona increases the amount of mechanically trapped water there and compensates more than the water molecules lost through the dehydration of the PEO chains in the presence of the Cl(-) ions. The enhancement in micellar hydration leads to a decrease in the minimum concentration required for the F127 solution to form a room-temperature cubic gel phase from 18% to 14%. Moreover, for both copolymers, the temperature range of stability of the cubic gel phase also increases with increasing LiCl concentration, presumably because of the ability of the Li(+) ions to reduce micellar dehydration with increasing temperature. Viscosity studies on a poly(ethylene glycol) (PEG) homopolymer with a size equivalent to that of the PEO block in F127 (4000 g/mol) also suggest that the dehydrating effect of the Cl(-) ion on the PEG chain is compensated by its interaction with the hydrated Li(+) ions.

We investigate the relationship between galaxies and metal-line absorption systems in a large-scale cosmological simulation with galaxy formation. Our detailed treatment of metal enrichment and non-equilibrium calculation of oxygen species allow us, for the first time, to carry out quantitative calculations of the cross-correlations between galaxies and O VI absorbers. We find the following: (1) The cross-correlation strength depends weakly on the absorption strength but strongly on the luminosity of the galaxy. (2) The correlation distance increases monotonically with luminosity from ~0.5-1h^-1 Mpc for 0.1L* galaxies to ~3-5h^-1 Mpc for L* galaxies. (3) The correlation distance has a complicated dependence on absorber strength, with a luminosity-dependent peak. (4) Only 15% of O VI absorbers lie near >=Lz* galaxies. The remaining 85%, then, must arise ``near'' lower-luminosity galaxies, though, the positions of those galaxies is not well-correlated with the absorbers. This may point to pollution of intergalactic gas predominantly by smaller galaxies. (5) There is a subtle trend that for >~0.5Lz* galaxies, there is a positive correlation between absorber strength and galaxy luminosity in the sense that stronger absorbers have a slightly higher probability of finding such a large galaxy at a given projection distance. For less luminous galaxies, there seems to be a negative correlation between luminosity and absorber strength., uses emulateapj, 5 pages including 2 color figures and 2 tables, accepted for publication in ApJ Letters

Dynamic Stokes' shift and fluorescence anisotropy measurements of coumarin 153 (C153) and coumarin 151 (C151) as fluorescence probes have been carried out to understand the influence of electrolytes (NaCl and LiCl) on the hydration behavior of aqueous (ethylene oxide)100-(propylene oxide)70-(ethylene oxide)100 (EO100-PO70-EO100, F127) block copolymer micelles. A small blue shift in the fluorescence spectra of C153 has been observed in presence of electrolytes due to the dehydration of the oxyethylene chains in the PEO-PPO region, although fluorescence spectra of C151 remain unaltered. The close vicinity of bulk water for C151 probably negates the effect of dehydration in the PEO region. Fluorescence anisotropy measurements indicate a gradual increase in microviscosity with electrolyte concentrations. The partial collapse of copolymer blocks in the presence of electrolytes has been suggested as a reason for the increase in microviscosity along with the strong hydration of ions in the corona region. The interplay between the ion hydration and the mechanically trapped water content, and specific interaction of ions, such as complexation of Li+ ions with the copolymer block, is found to control solvation dynamics in the corona region. In addition to that, it has been established that Na+ ions reside deep into the corona region whereas Li+ ions prefer to reside closer to the surface. Owing to its higher lyotropicity, LiCl influences the corona hydration to a greater extent than NaCl and sets in micelle-micelle interaction above the 2 M LiCl concentration, as reflected in the saturation of solvation time constants. The formation of larger clusters of F127 micelles above 2 M LiCl has been confirmed by dynamic light scattering measurements; however, such cluster formation is not evident with NaCl.

Measurements of ppm (v/v) level COg concentration is conveniently performed by its preconcentration in alkaline absorber solution of Ag+-(4)- HCO2-C6H4-SO2NH2 complex, followed by a spectral measurement of the reduced silver sol. In this study, the transitory nature of this latter species and its subsequent real-time transformation to silver nanoparticle are presented. These results were based on spectral measurements made under varying concentrations of alkali, (4)-HCO2-C6H4-SO2NH2, and Ag+ in the absorber solution, and in the presence of a wide range of sampled COg concentration. The initially created light yellow colored sol with its broad absorption profile peaking at 380 nm and absorption coefficient 3500 ± 300 cm−1 M−1 (related to the amount of sampled [COg] as standardized by gas chromatographic analysis) changed into the characteristic yellow orange nanoparticle with its plasmon band peak absorption at 425 nm and absorption coefficient 6350 ± 300 cm−1 M−1. Under different sampling conditions, the respective first-order conversion rates varied between 0.03 and 0.15 h−1, whereas simultaneous dynamic light scattering measurements revealed steady growth of the averaged particle size ranging from 60 to 300 nm.

We present FUSE and HST/STIS observations of the absorption line system near the emission redshift of the radio-quiet, X-ray bright quasar HE0226-4110 (z = 0.495, V=15.2). The spectra cover the rest-frame wavelength range 610--1150 A, and we detect a wide range of ionization species, including four adjacent stages of oxygen (O III-VI), which reveal a striking change in gas kinematics with ionization. Examination of the O VI 1031, 1037 doublet profiles reveals no evidence for partial coverage or unresolved saturated structure. O III is only detected in a narrow feature which is also traced by H I and C III, suggesting that they arise in the same gas. Absorption at the same velocity is also present in other species N IV, O IV-VI, S IV, and possibly N VIII, but the kinematics differ from the O III, implying production in separate gaseous phases. The H I, O II-IV, and C III information in yield an estimate of both the photoionization parameter and metallicity of the O III-bearing gas: [O/H]=+0.12(-0.03/+0.16), log U=-2.29(-0.23/+0.02). We discuss two possible locations for the gas in this associated absorption-line system: the narrow emission line region of the quasar, and the halo of the quasar host galaxy. An additional narrow (thus, photoionized) component that is only detected in O VI appears 58 km/s redward of the O III-bearing gas with -0.35 < log U < 0.02. Additional structure is detected in the associated absorber in the form of two broad components which only appear in moderate to high ionization species. [highly abridged], 25 pages, including 14 figures; uses emulateapj.cls document class; accepted for publication in The Astrophysical Journal

Nanocrystalline Mn3O4 has been synthesized by ultrasonic irradiation of Mn acetate solution in water. Analysis of its X-ray diffraction data shows formation of a phase-pure compound with an average particle size of about 15 nm. DC magnetization measurements as a function of temperature and field show a reduced ferrimagnetic transition temperature ( T c ≈ 39 K ) as compared to those reported for the bulk ( T c ≈ 43 K ) , and a subsequent observation of superparamagnetic behavior at 40 K. The observed magnetic properties are suggestive of formation of a single domain magnetically ordered Mn3O4 nanoparticles below their ferrimagnetic transition temperature.

Dynamic light scattering (DLS), small-angle neutron scattering (SANS), and viscosity studies have been carried out to examine the influence of NaCl and ethanol on the structure of triblock copolymer [(EO)20(PO)70(EO)20] (EO = ethylene oxide; PO = propylene oxide) micelles in aqueous medium. The studies show that while the pure triblock copolymer solutions do not show any significant growth of the micelles on approaching the cloud point, the presence of a small amount of ethanol (5-10%) induces a sphere to rod shape transition of micelles at high temperatures. Interestingly, this ethanol induced sphere to rod transition of micelles can be brought down to room temperature (25 degrees C) with the addition of NaCl. It is also found that NaCl alone cannot induce such sphere to rod transitions and excess ethanol suppresses them by increasing their transition temperature.

Inter and intragranular pinning potentials of 116 MeV oxygen ion irradiated textured polycrystalline Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi-2212) and Bi 1.84 Pb 0.34 Sr 1.91 Ca 2.03 Cu 3.06 O 10+ δ (Bi-2223) have been studied from dc magnetization at low (50 Oe) and high (10,000 Oe) fields respectively. There is an increase in intergranular pinning potential ( U 0 ) in Bi-2223 in contrast to anomalous decreases in Bi-2212 with increasing dislocation density. Intragranular pinning potential is governed by the concentration of vacancy type defects rather than its size as observed in proton irradiation. Pinning has been explained in the light of statistical dilute pinning model.

A room temperature sphere-to-rod transition of the polyethylene oxide-polypropylene oxide-polyethylene oxide-based triblock copolymer, (PEO)20(PPO)70 (PEO)20 micelles have been observed in aqueous medium under the influence of ethanol and sodium chloride. Addition of 5–10% ethanol induces a high temperature sphere-to-rod transition of the micelles, which is brought to room temperature upon addition of NaCl. The inference about the change in the shape of the micelles has been drawn from small-angle neutron scattering (SANS) and viscosity studies.

Sodium hexametaphosphate (HMP) stabilized nickel hexacyanoferrate (NiHCF) nanoparticles were prepared in aqueous solution and were successfully extracted into an organic phase using cetyltrimethylammonium bromide (CTAB) as the surfactant. Dynamic Light Scattering (DLS) studies suggest that the average size of the nanoparticles is retained during the extraction process from the aqueous to the organic phase. X-Ray diffraction, cyclic voltammetry, IR spectroscopy and magnetic measurements carried on the organic phase shows specific signatures of the presence of the surfactant encapsulated NiHCF nanoparticles. Transmission Electron Microscopy (TEM) measurements show that the average size of these surfactant encapsulated nanoparticles in the organic phase is about 22 nm, and as has been suggested by DLS studies, it does not change with respect to repeated evaporation and re-extraction processes of the organic phase. Pressure–area isotherms of the organic phase in a Langmuir–Blodgett (LB) trough, with water as subphase, indicate stable monolayer formation of the surfactant-encapsulated NiHCF nanoparticles at the air–water interface. Multi-layered deposition of the surfactant-encapsulated nanoparticles onto an indium tin oxide (ITO) coated glass slide could also be carried out using the LB technique. Cyclic voltammetry studies on these LB multilayers confirm regular and systematic transfer of the NiHCF nanoparticles on the ITO substrate. The method described here is the first of its kind with respect to the synthesis of surfactant encapsulated molecular magnetic nanoparticles and subsequent deposition of their LB films.

We present HST/STIS and FUSE spectra of the quasar RXJ1230.8+0115 (V=14.4, z=0.117). In addition to Galactic, Virgo, and intervening absorption, this quasar is host to a remarkable intrinsic absorption complex. Four narrow absorption line systems, strong in CIV, NV, and OVI, lie within 5000 km/s of the QSO redshift. Three of the systems appear to be line-locked, two in NV, and two in OVI, with the common system residing in between the other two (in velocity). All three systems show signs of an intrinsic origin -- smooth wind-like profiles, high ionization, and partial coverage of the central engine. The fourth system, which appears at the systemic redshift of the QSO, may originate from host galaxy or intervening gas. Photoionization analyses imply column densities in the range 19.1, Comment: 16 pages using emulateapj latex document class, including 6 color figures, to appear in ApJ v598 n2

The 3C 273 and RX J1230.8+0115 sightlines probe the outskirts of the Virgo Cluster at physical separations between the sightlines of 200-500 h_70 kpc. We present an analysis of HST STIS echelle and FUSE UV spectroscopy of RX J1230.8+0115 in which we detect five Lyman-alpha absorbers at Virgo distances. One of these absorbers is a blend of two strong metal line absorbers coincident in velocity with the highest neutral hydrogen column density absorber in the 3C 273 sightline ~350 h_70 kpc away. The consistency of the metal line column density ratios in the RX J1230.8+0115 sightline allows us to determine the ionization mechanism (photoionization) for these absorbers. While the low signal-to-noise ratio of the FUSE spectrum limits our ability to model the neutral hydrogen column density of these absorbers, we are able to constrain them to be in the range 10^{16-17} cm^-2. The properties of these absorbers are similar to those of the 3C 273 absorber studied by Tripp et al. However, the inferred line-of-sight size for the 3C 273 absorber is only 70 pc, much smaller than those inferred in RX J1230.8+0115, which are 10-30 h_70 kpc. The small sizes of all three absorbers are at odds with the >~350 h_70 kpc minimum transverse size implied by an application of the standard QSO line pairs analysis. On the basis of absorber associations between these two sight lines we conclude that a large-scale structure filament produces a correlated, not contiguous, gaseous structure in this region of the Virgo Supercluster. These data may indicate that we are detecting overdensities in the large scale structure filaments in this region. Alternatively, the presence of a galaxy 71 h_70 kpc from a 3C 273 absorber may indicate that we have probed outflowing, starburst driven shells of gas associated with nearby galaxies.

The effects of substitution of chromium and ruthenium for manganese on the magnetic and transport properties of electron-doped manganite Ca0.9Ce0.1MnO3, with dz2 orbital-ordered and the associated antiferromagnetic (AFM) characters, have been studied. As expected, due to the participation of the Cr3+ (t2g3 e g0) and Ru4+/5+ [t2g4 e g0/t 2g3 e g0)] ions in the eg band broadening for the Mn3+ (t2g3 e g1) and Mn4+ (t2g3 e g0) species, the suppression of the AFM transition by Ru and Cr doping is accompanied by an increase in the ferromagnetic (FM) character. The coexistence of FM and AFM phases in these Ru-and Cr-substituted compounds leads to the observations of cluster glass behaviour, the giant magneto-resistive memory (GMM) effect and other magnetic-history-dependent magnetic and transport properties. Our observation of the GMM effect in these Cr-and Ru-doped compounds is the first of its kind in the magnetically phase-separated bulk polycrystalline compounds.

The ac and dc magnetic properties of hole-doped cobaltites with compositions La0.5Sr0.5-xAxCoO3 (A = Ca, Ba) and La0.5-xRxSr0.5CoO3 (R = Nd, Eu) have been studied. The suppression of the cluster glass behaviour of the parent compound, La0.5Sr0.5CoO3, by substitutions for either the lanthanum or the strontium ions is accompanied by an increase in coercive field (HC) and thermomagnetic irreversibility. The results suggest that the large thermomagnetic irreversibility and coercive fields observed in the hole-doped perovskite cobaltites, arising due to the anisotropic nature of their ferromagnetic character, cannot be correlated with the cluster glass freezing observed in them.

We have studied the structural, magnetic and electrical properties of hole-doped cobaltites with compositions, La0.7(Ca1-xBax)0.3CoO3 (x = 0.0, 0.5 and 1.0). Due to the large difference in size between the Ca and Ba ions (size mismatch), these compounds show interesting changes in the magnetic and transport behaviours with an increase in the concentration of Ba. The distortion in the perovskite structure decreases with the substitution of Ba for Ca. Magnetic studies indicate that the anisotropy in their ferromagnetic characters, which contribute to the observations of large thermomagnetic irreversibilities and large coercive fields in these compounds, change significantly with the substitution of Ba for Ca. The unusual magnetic behaviour of the La0.7Ba0.3CoO3 compound, as reflected in its M-H behaviour, has been explained on the basis of a possible coexistence of different magnetic phases. Observations of the low-temperature resistivity minimum, and negative magnetoresistance up to 26% in the low-temperature insulating regions of these polycrystalline compounds, have been ascribed to grain boundary effects.

AC susceptibility, resistivity and dc magnetization measurements on the (La 0.757 Dy 0.243 ) 0.7 Ca 0.3 MnO 3 perovskite reveal a clear departure from the well-behaved (collinear) ferromagnetic nature observed in the parent material La 0.7 Ca 0.3 MnO 3 at low temperatures. Neutron diffraction structural study shows that the buckling of the MnO 6 octahedra increases with the Dy substitution. This in turn gives a weaker double exchange (ferromagnetic) interaction, as the transfer integral, t o, describing the hopping of eg electrons between Mn 3+ and Mn 4+ decreases resulting in the observed deterioration of ferromagnetism and metallic conduction.

We present two low resolution (R~1300) high signal-to-noise spectra (Wr,lim~50mA) of the quasar CSO 118 (zem=2.97) taken with the Hobby-Eberly Telescope Marcario Low Resolution Spectrograph. We detect eight absorbers selected by the CIV 1548,1550 absorption doublet in the redshift range {2.23 2.68. In the redshift range covered by the seven zabs > 2.68 systems, one expects to find two absorbers. We discuss possible explanations for such an excess of absorbers in a small velocity range. Only superclustering at high redshift and absorption due to intrinsic gas are feasibly allowed.

We report the synthesis of ferromagnetically ordered mononuclear compounds [M(II)(oxine)(N3)x] containing different metal ions, viz. M(II)=Co (1), Cr (2), Fe (3) and Ni (4), using azido as the main bridging ligand and oxine (8-hydroxy quinoline) as a new auxiliary ligand. Oxine was chosen because it is known to form a five-membered ring structure around the bivalent metal ions. A one-pot synthesis was carried out in each case. The compounds were characterised and their magnetic behaviour is studied. Ac susceptibility (χ′ and χ″) measurements, hysteresis plots (VSM) and χT behaviour indicate the onset of long-range ferromagnetic ordering below 18, 17, 9 and 34 K for the compounds 1, 2, 3 and 4, respectively.

We present a statistical analysis of the associated, high ionization narrow absorption line (NAL) systems in a sample of 59 QSOs defined from the HST QSO Absorption Line Key Project. We have compiled the QSO luminosities at 2500 A, 5 GHz, and 2 keV, spectral indices at 2500 A and 5 GHz, the H-beta emission line FWHM, the CIV emission line FWHM, and the radio core fraction. We find 17 associated NALs toward 15 QSOs, of which ~10 are statistically expected to be intrinsic. From a multivariate clustering analysis, the QSOs seem to group together based primarily on radio luminosity, followed by radio spectral index, CIV emission line FWHM, and soft X-ray luminosity. Radio-loud QSOs which have compact radio morphologies, flat radio spectra, and mediocre CIV FWHM (1.5 A] in our low redshift sample which implies evolution in the number of strong NALs with redshift. We interpret these results in the context of an accretion-disk model. In this framework, we suggest that the observational clues result from differences in orientation and wind properties, the latter presumably associated with the QSO radio properties. (abridged), Comment: Accepted for publication in ApJ, 20 pages text, 13 figures, 6 tables, 43 pages total, uses AASTeX 5.0, also available at http://www.astro.psu.edu/users/ganguly/ under Related Publications

Structural studies on the samples of nominal compositions of the series, La1.2(Sr1 − xCax)1.8Mn2O7 and Ca3 − yLayMn2O7, have been carried out using neutron and X-ray diffraction techniques. These studies show that, unlike the case of the (La,Sr)3Mn2O7 system, the samples belonging to the (La,Ca)3Mn2O7 system form layered Sr3Ti2O7-type structures in a very restricted composition range. Through a systematic study on the effect of substitution of La for Ca in the layered compound Ca3Mn2O7, the solubility of La in Ca3Mn2O7 has been determined. The results go against the literature reports, which claim that the samples of nominal compositions Ca3 − yLayMn2O7 (1.0 ≤ y ≤ 2.3) form with layered Sr3Ti2O7 structures. The usefulness of the neutron diffraction technique in unambiguous structural characterization of the layered compounds has also been discussed.

Recent reports, that the samples of nominal compositions, La1-xCexMnO3, form single-phase compounds with orthorhombically distorted perovskite structure, are questionable. Our studies on the sample of nominal composition, La0.7Ce0.3MnO3, and careful analysis of the structural data available in the literature, suggest that the above mentioned samples actually form multi-phase mixtures comprising hole doped lanthanum deficient lanthanum manganate phases and cerium oxide (CeO2).

Samples with nominal compositions La1.2 (Sr1-x Cax )1.8 Mn2 O7 (x = 0.00, 0.25, 0.50, 0.65, 0.80 and 1.00) have been prepared and characterized by x-ray diffraction (XRD) and ac susceptibility techniques. Drastic changes in the XRD pattern and in the ac susceptibility versus temperature behaviour at x = 0.65 indicate that single phase compounds with layered Sr3 Ti2 O7 structure are formed only up to x = 0.50. Rietveld refinement of the XRD patterns of x = 1.00 composition suggests that the compositions with x 0.65 form multiphase mixtures comprising hole doped perovskite manganates as majority phases and CaO as the minority phase. These results are at variance with the literature reports that the compound La1.2 Ca1.8 Mn2 O7 forms with layered Sr3 Ti2 O7 structure.

The compounds La 0.67 Ca 0.33 Mn 1− x Cr x O 3 ( x =0.00, 0.05, 0.10, 0.15, 0.20, 0.35, 0.50 and 0.60) have been studied by X-ray diffraction (XRD), AC and DC magnetization, and DC electrical resistivity measurement techniques. Ferromagnetism is observed up to as high as 60% of Cr substitution. Electrical resistivity behavior of the compounds as a function of temperature could be explained on the basis of adiabatic small polaron model.

The structural characteristics of La1.85Sr0.15Cu1−x Zn x O4 have been investigated over a wide composition range, viz. for x = 0.0, 0.1, 0.2, and 0.4, using powder neutron diffraction. The strong influence of substitution of the nonmagnetic Zn, which destroys superconductivity in the parent phase for rather low dopant concentration x ≲ 0.1, and the change of symmetry from the tetragonal to orthorhombic structure for x ≤ 0.2, are discussed.

The compounds La 0.7 A 0.3 CoO 3 [A=Ca, (Ca, Sr), Sr, (Sr, Ba), Ba] and La 0.5 Nd 0.2 Sr 0.234 Ba 0.066 CoO 3 have been studied by X-ray diffraction, AC and DC magnetization and DC electrical resistivity techniques. DC magnetization studies on these compounds suggest that large thermomagnetic irreversibility observed in hole-doped cobaltates arises not due to cluster glass behavior but from ferromagnetic behavior with exchange anisotropy. It is also observed that the size of the ions occupying the rare earth site has significant effect on the structural parameters, ferromagnetic transition temperature and electrical resistivity of these compounds.

La 0.67 Ca 0.33 Mn 1− x Co x O 3 ( x =0.00, 0.05, 0.075, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40) have been investigated by AC susceptibility, DC magnetization and DC electrical resistivity measurements. Substitution of Co for Mn did not cause any change in crystal symmetry, yet electrical conductivity as well as ferromagnetism have been consistently suppressed by the dopant. The results can be explained on the basis of weakening of the double exchange process and an increase in anisotropy of the exchange interaction consequent upon Co doping.

In the course of a large survey of intervening Mg II absorbers in the spectra of quasars, the C IV emission lines of six of the target objects (three radio-loud and three radio-quiet) were observed serendipitously. In four of these six quasars, we detected "associated" narrow absorption lines with velocities within 5000 km s-1 of the quasar emission-line redshift (three of these four quasars are radio quiet while the other is radio loud). As a result of the original target selection, the small sample of six quasars is unbiased toward finding associated absorption lines. In three of these four cases, the absorption-line optical-depth ratios deviate from the prediction based on atomic physics, suggesting that the background photon source(s) are only partially covered by the absorbing medium and, by extension, that the absorption lines are intrinsic to the quasar. We have used the method of Barlow &Sargent to determine the effective coverage fraction of background source(s) and we have extended it to constrain the coverage fraction of the continuum and broad emission-line sources separately. We have also applied this refined method to the narrow intrinsic absorption lines in three additional quasars for which the necessary data were available from the literature. We find that in two objects from our sample, the continuum source must be partially covered regardless of the covering factor of the emission-line source. We discuss these results in the context of the properties of absorption lines observed in different types of active galaxies and related outflow phenomena. We cannot distinguish between possible mechanisms for the origin of the partial coverage signature, although we do consider possible observational tests. Finally, we speculate on how the gas responsible for the narrow lines may be related to the accretion disk wind that may be responsible for the broad absorption lines observed in some quasars.

In the z=1.94 C IV absorption-line system in the spectrum of quasar Q1222+228 (zem=2.04), we find two clouds that have contrasting physical conditions, although they are only at a 17 km s-1 velocity separation. In the first cloud, Si II, Si IV, and C II are detected, and Al II and Al III column density limits in conjunction with photoionization models allow us to infer that this cloud has a large Si abundance and a small Al abundance relative to a solar abundance pattern. This pattern resembles that of Galactic metal-poor halo stars, which must have formed from such high-redshift gas. The second cloud, in contrast, has detected Al II and Al III (also Si IV and C II) but no detected Si II. We demonstrate, using photoionization models, that Al/Si must be greater than (Al/Si)☉ in this unusual cloud. Such a ratio is not found in absorption profiles looking through Milky Way gas. It cannot be explained by dust depletion since Al depletes more severely than Si. Comparing this cloud with other Al-rich environments, we speculate about the processes and conditions that could give rise to this abundance pattern.

We have obtained IRTF/SpeX spectra of eight moderate-redshift (z=0.7-2.4), radio-selected (log R*~0.4-1.9) broad absorption line (BAL) quasars. The spectra cover the rest-frame optical band. We compare the optical properties of these quasars to those of canonically radio-quiet (log R*1) quasars. With our measurements of the optical properties, particularly the Balmer emission line widths and the continuum luminosity, we have used empirical scaling relations to estimate black hole masses and Eddington ratios. These lie in the range (0.4-2.6)x10^9 M_sun and 0.1-0.9, respectively. Despite their comparatively extreme radio properties relative to most BAL quasars, their optical properties are quite consistent with those of radio-quiet BAL quasars and dissimilar to those of radio-loud non-BAL quasars. While BAL quasars generally appear to have low values of [OIII]/FeII, an extreme of "Eigenvector 1", the Balmer line widths and Eddington ratios do not appear to significantly differ from those of unabsorbed quasars at similar redshifts and luminosities., 12 pages, 4 figures, 6 tables, accepted to MNRAS, updated to include references

We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD Imaging Spectrometer S-array (ACIS-S) observation of the reddened, radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We investigated a number of models of varied sophistication to fit the 531-photon spectrum. These models ranged from simple power laws to power laws absorbed by hydrogen gas in differing ionization states and degrees of partial covering. Preferred fits indicate that the intrinsic X-ray flux is consistent with that expected for quasars of similarly high luminosity, i.e., an intrinsic, dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot tightly constrain the intrinsic X-ray power-law slope, but find indications that it is flat (photon index Gamma = 1.7 or flatter at a >99% confidence for a neutral hydrogen absorber model). Absorption is present, with a column density a few times 10^23 cm^-2, with both partially ionized models and partially covering neutral hydrogen models providing good fits. We present several lines of argument that suggest the fraction of X-ray emissions associated with the radio jet is not large. We combine our Chandra data with observations from the literature to construct the spectral energy distribution of FIRST J1556+3517 from radio to X-ray energies. We make corrections for Doppler beaming for the pole-on radio jet, optical dust reddening, and X-ray absorption, in order to recover a probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a Doppler-boosted but intrinsically weak radio jet, and an X-ray absorber not dissimilar from that of other broad absorption line quasars., to be published in MNRAS

We present Spitzer InfraRed Spectrograph (IRS) low-resolution spectra of 16 spectroscopically selected post-starburst quasars (PSQs) at z ~ 0.3. The optical spectra of these broad-lined active galactic nuclei (AGNs) simultaneously show spectral signatures of massive intermediate-aged stellar populations making them good candidates for studying the connections between AGNs and their hosts. The resulting spectra show relatively strong polycyclic aromatic hydrocarbon (PAH) emission features at 6.2 and 11.3\micron and a very weak silicate feature, indicative of ongoing star formation and low dust obscuration levels for the AGNs. We find that the mid-infrared composite spectrum of PSQs has spectral properties between ULIRGs and QSOs, suggesting that PSQs are hybrid AGN and starburst systems as also seen in their optical spectra. We also find that PSQs in early-type host galaxies tend to have relatively strong AGN activities, while those in spiral hosts have stronger PAH emission, indicating more star formation., Comment: 18 pages, 7 figures, 2 tables; Accepted for publication in ApJ: May 24, 2013

Neutron structural studies are made on (Y1−xCax)(Ba2−xLa x )Cu3O7−δ for compositions corresponding to x=0.0, 0.2, and 0.4 in order to evaluate any correlation between the remarkably high chemical stability of the cosubstituted samples (x=0.2 and 0.4) and the structural parameters. It is suggested that the increased chemical stability is caused by a decrease in the puckering of the Cu-O planes with increase inx, causing them to flatten, which leads to a reduction in the internal stresses existing in the perovskite lattice of this technologically important material.