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We describe a laboratory-scale process for recycling rare earth metals from end-of-life rare-earth/iron/boron alloy permanent magnets using a 2-h chlorine gas treatment at 673 K. This treatment does not require any special preparation of the magnets; they can be used without demagnetization, crushing or milling. Following treatment at 673 K, a clinker powder consisting of rare earth metal chlorides with minimal amounts of other metals is obtained, while hematite and iron oxychloride sublimate. Following literature sources, we suggest that the rare earth metal chlorides in the clinker may be readily reduced to metal, either by electrolysis in relatively low temperature eutectic melts or by metallothermic reduction in mixtures with alkali or alkaline earth metals.

A new technique for promoting nucleation and growth of membrane protein (MP) crystals from micellar environments is reported. It relies on the conjugation of micelles that sequester MPs in protein detergent complexes (PDCs). Conjugation via amphiphilic [metal:chelator] complexes presumably takes place at the micelle/water interface, thereby bringing the PDCs into proximity, promoting crystal nucleation and growth. We have successfully applied this approach to two light-driven proton pumps: bacteriorhodopsin (bR) and the recently discovered King Sejong 1–2 (KS1–2), using the amphiphilic 4,4′-dinonyl-2,2′-dipyridyl (Dinonyl) (0.7 mM) chelator in combination with Zn2+, Fe2+, or Ni2+ (0.1 mM). Crystal growth in the presence of the [metal–chelator] complexes leads to purple, hexagonal crystals (50–75 µm in size) of bR or pink, rectangular/square crystals (5–15 µm) of KS1–2. The effects of divalent cation identity and concentration, chelator structure and concentration, ionic strength and pH on crystal size, morphology and process kinetics, are described.

Industrial scale production of therapeutic monoclonal antibodies (mAbs) is commonly achieved with Protein A chromatography, a process that requires exposure of the antibody to strongly acidic conditions during the eluting step. Exposure to acid inactivates virus contaminants but may, in parallel, lead to antibody aggregation that must be eliminated or kept at acceptably low levels. This report seeks to provide a practical method for overcoming a long-standing problem. We show how Brij-O20 detergent micelles, conjugated by the amphiphilic [(bathophenanthroline)3:Fe2+] complex in the presence of amino acid monomers: phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp), isoleucine (Ile) or valine (Val), efficiently capture polyclonal human IgG (hIgG) at neutral pH and allow its recovery by extraction either at pH 4 (85-97% yield) or at pH 6.3 (72-84% yield). Of the five amino acid monomers surveyed, Phe or Tyr produced the highest overall process yield at both pH 4 and 6.3. The monomeric state of the purified hIgG’s was confirmed by dynamic light scattering (DLS). Potential advantages of the purification method are discussed.

In the decades'-long quest for high-quality membrane protein (MP) crystals, non-ionic detergent micelles have primarily served as a passive shield against protein aggregation in aqueous solution and/or as a conformation stabilizing environment. We have focused on exploiting the physical chemistry of detergent micelles in order to direct intrinsic MP/detergent complexes to assemble via conjugation under ambient conditions, thereby permitting finely tuned control over the micelle cloud point. In the current work, three commercially available amphiphilic, bipyridine chelators in combination with Fe

Immunoglobulin M (IgM) antibodies hold promise as anticancer drugs and as agents for promoting immune homeostasis. This promise has not been realized due to low expression levels in mammalian cells producing IgM class antibodies, and the failure of protein A chromatography for IgM purification. Here, we describe a nonchromatographic platform for quantitatively capturing IgMs at neutral pH, which is then recovered with 86%-94% yield and95% purity at pH 3. The platform contains micelles conjugated with the [(bathophenanthroline)

Young's, shear and bulk moduli of Ce1-xSmxO2-x/2 (x ≤ 0.55) were studied using ultrasonic time of flight and nanoindentation techniques. Sound velocity measurements, corrected for sample porosity, demonstrate decrease in the unrelaxed ceramic moduli with increasing Sm-content. Room temperature creep under indenter load-hold, as well as time-dependent material stiffness, reveal a transition from prominent anelasticity in the fluorite phase to prominent elasticity in the double fluorite phase. This supports rearrangement of elastic dipoles under anisotropic stress, which occurs more readily when oxygen vacancies are not ordered on the crystal lattice, as the source of ceria anelastic behavior.

Raman spectroscopy has recently been applied for non-destructive characterization of strain in crystalline thin films. It makes use of the numerical value of the mode Grüneisen parameter γ , which equals (minus) the ratio of the relative change in the frequency of a Raman-active vibrational mode and the strain-induced relative change in the unit cell volume. In the presence of in-plane, compressive biaxial strain, aliovalent doped CeO2-films exhibit values of γ which are ~30% smaller than the literature values for the bulk ceramics under isostatic stress. This discrepancy is due in large part to the negative contribution from the anelastic (time-dependent) mechanical properties of oxygen-deficient ceria, thereby raising questions concerning the relationship between Raman mode frequency and anelastic strain. Here we propose a way to "separate" anelastic and elastic contributions to the Grüneisen parameter. 500-650nm thick films , x=0.1-0.2, were deposited by RF magnetron sputtering on (100) p-Si wafers (1Ω-cm, tSi=280mm). The films (S-films) were in the fluorite phase with pronounced (111) texture and exhibited biaxial , compressive strain. The in- and out-of-plane lattice parameters (aS || , aS ⊥ ) of the S-films were determined by XRD at different sample tilt angles. The in-plane stress (σbi) in the S-films was determined by profilometry from the change in Si-wafer curvature following film deposition. From σbi and the film biaxial modulus, the elastic component of the in-plane compressive strain (ue ) was calculated (~ -0.2%). Strain-free (relaxed) R-films were obtained by partial substrate removal, forming 2 mm diameter self-supported membranes. Pronounced membrane buckling indicated that residual strain was negligible (aR || ≈ aR ^ ). From the increase in area upon substrate removal, measured with optical profilometry, the total S-film in-plane strain (ut ) was calculated from aS ||/aR-1 ≈ -0.5%. The anelastic strain component may be calculated as ua= ut-ue . The small, anisotropic strain-induced blue shift of the frequency of the F2g -phonon mode for S-films suggests that the F2g mode responds primarily to the elastic component of the strain. As a control, 430nm thick films of mechanically elastic Y2O3 were deposited by sputtering on a Si wafer covered with a 1.5 µm thick PECVD deposited SiO2 layer. This layer supported the Y2O3-films upon membrane formation, but prevented complete strain relaxation. The Y2O3-films were in the double fluorite phase with strong (222) texture and, as with the S-films, were under in-plane compressive strain. The Y2O3 S-film lattice parameters were determined by acquiring XRD-patterns at different sample tilt angles, while membrane in- and out-of-plane lattice parameters were determined with XRD in the transmission and reflection modes, respectively. The values of γ calculated from the Raman frequency of the [Fg +Ag ] peak position were close to the literature values for bulk yttria under isostatic stress. This work should serve as a sample protocol for strain characterization of doped ceria thin films. It supports the concept that the discrepancy between the behavior of Raman modes of isostatically and anisotropically strained doped ceria is related to anelasticity. Our results shed light upon strain characterization by Raman spectroscopy and may lay the foundation for future studies to elucidate selective sensitivity to various strain components.

The majority of commonly used electrostrictive ceramics are based on lead manganese niobate. These ceramics display large electrostriction strain coefficients ≈ 10-16 m2/V2 at frequencies up to a few kHz. However, they suffer from major drawbacks: they require high driving currents (dielectric constant >10000), contain toxic elements, and are incompatible with thin film Si-microfabrication techniques. We have recently reported that ceria ceramics doped with aliovalent cations having crystal radii smaller than that of cerium, display increased high frequency (f >100Hz) longitudinal electrostriction strain coefficients |M|. For instance, with 10 mol% Lu3+ or Yb3+ lanthanide dopants, |M| ~ 10-17 m2/V2 is observed for f >100Hz . Despite Yceria ~200GPa and eceria ~ , these electrostriction strain coefficients are 100-fold larger than estimated on the basis of Newnham’s scaling law for “classical” electrostrictors. Such “non-classical” behavior has been attributed to the formation of highly polarizable, elastic dipoles reorienting under external electric field. Surprisingly, doping with small isovalent dopants, such as Zr and Hf , produces an increase in |M| to , independent of frequency up to several kHz, as determined by converse electrostriction measurements. The introduction of Zr raises the dielectric constant more than predicted by the Clausius-Mossotti relation. This suggests that the presence of a small dopant creates a highly polarizable unit which may be responsible for the large electrostriction strain coefficient. Our results demonstrate that, by systematically adjusting the composition of ceria-based solid solutions, the possibility exists for development of technologically useful electrostrictive materials which are, at the same time, ecologically sound and fully compatible with Si-microfabrication.

The technologically important frequency range for the application of electrostrictors and piezoelectrics is tens of Hz to tens of kHz. Sm3+- and Gd3+-doped ceria ceramics, excellent intermediate-temperature ion conductors, have been shown to exhibit very large electrostriction below 1 Hz. Why this is so is still not understood. While optimal design of ceria-based devices requires an in-depth understanding of their mechanical and electromechanical properties, systematic investigation of the influence of dopant size on frequency response is lacking. In this report, the mechanical and electromechanical properties of dense ceria ceramics doped with trivalent lanthanides (RE0.1Ce0.9O1.95, RE = Lu, Yb, Er, Gd, Sm, and Nd) were investigated. Young's, shear, and bulk moduli were obtained from ultrasound pulse echo measurements. Nanoindentation measurements revealed room-temperature creep in all samples as well as the dependence of Young's modulus on the unloading rate. Both are evidence for viscoelastic behavior, in this case anelasticity. For all samples, within the frequency range f = 0.15-150 Hz and electric field E ≤ 0.7 MV/m, the longitudinal electrostriction strain coefficient (|M33|) was 102 to 104-fold larger than expected for classical (Newnham) electrostrictors. However, electrostrictive strain in Er-, Gd-, Sm-, and Nd-doped ceramics exhibited marked frequency relaxation, with the Debye-type characteristic relaxation time τ ≤ 1 s, while for the smallest dopants-Lu and Yb-little change in electrostrictive strain was detected over the complete frequency range studied. We find that only the small, less-studied dopants continue to produce useable electrostrictive strain at the higher frequencies. We suggest that this striking difference in frequency response may be explained by postulating that introduction of a dopant induces two types of polarizable elastic dipoles and that the dopant size determines which of the two will be dominant.

Electromechanically active ceramic materials, piezoelectrics and electrostrictors, provide the backbone of a variety of consumer technologies. Gd- and Sm-doped ceria are ion conducting ceramics, finding application in fuel cells, oxygen sensors, and, potentially, as memristor materials. While optimal design of ceria-based devices requires a thorough understanding of their mechanical and electromechanical properties, reports of systematic study of the effect of dopant concentration on the electromechanical behavior of ceria-based ceramics are lacking. Here we report the longitudinal electrostriction strain coefficient (M33) of dense RExCe1-xO2-x/2 (x ≤ 0.25) ceramic pellets, where RE = Gd or Sm, measured under ambient conditions as a function of dopant concentration within the frequency range f = 0.15-350 Hz and electric field amplitude E ≤ 0.5 MV/m. For >100 Hz, all ceramic pellets tested, independent of dopant concentration, exhibit longitudinal electrostriction strain coefficient with magnitude on the order of 10-18 m2/V2. The quasi-static (f < 1 Hz) electrostriction strain coefficient for undoped ceria is comparable in magnitude, while introducing 5 mol % Gd or 5 mol % Sm produces an increase in M33 by up to 2 orders of magnitude. For x ≤ 0.1 (Gd)-0.15 (Sm), the Debye-type relaxation time constant (τ) is in the range 60-300 ms. The inverse relationship between dopant concentration and quasi-static electrostrictive strain parallels the anelasticity and ionic conductivity of Gd- and Sm-doped ceria ceramics, indicating that electrostriction is partially governed by ordering of vacancies and changes in local symmetry.

We have recently described a non-chromatographic, ligand-free approach for antibody (Ab) purification based on specially designed [Tween-20:bathophenanthroline:Fe2+] aggregates. To assess the potential generality of this approach, a variety of detergents belonging to four nonionic detergent families (Tween, Brij, Triton and Pluronic) have now been studied. All surfactant aggregates led to high purity of the recovered Ab’s (>95 %, by gel densitometry). Good overall Ab recovery yields were observed with Tween-20 (80–83 %), Brij-O20 (85–87 %) and Triton X-100 (87−90 %), while Pluronic F-127 was less efficient (42–53 %). Of additional importance is the finding that the process was performed by filtration rather than centrifugation, thereby allowing a continuous purification mode that led to the recovery of monomeric IgG, as determined by dynamic light scattering and preservation of Ab specificity as measured by ELISA. The amphiphilic chelator, bathophenanthroline (batho) was recycled almost quantitatively (95 %) by crystallization. Good IgG recovery yields of ∼80 % were also observed when Ab concentrations were increased from 1 mg/mL to 3−5 mg/mL. Potential advantages of the purification platform for industrial downstream processing of therapeutic monoclonal antibodies, are discussed.

Solid-state drawing to high extension ratios of melt-extruded VGCF-iPP nanocomposite filaments results in remarkable increases in modulus and strength, which mask any contribution of nano-reinforcement or inter-particle confinement observed previously. Based on X-ray diffraction and thermal analyses it is shown that the drawing process involves crumpling of the original 'shish-kebab' structure, accompanied by lateral shrinkage of the 'kebabs', disappearance and reorientation of daughter lamellae and significant increases in the degree of crystallinity by solid-state recrystallization. The effects of the initial diameter of the as-extruded filaments and those of the nanofibers and the 'shish-kebab' structure are dominated by the drawing process, which produces a highly aligned fibrillar structure with superior mechanical properties. A cartoon model of the effect of solid-state drawing of extruded iPP and nanocomposite filaments on the transition from 'shish-kebab' to fibril morphology is presented.

10 mol% Gd-doped ceria (10GDC) ceramics, with grain size in the single micron range, display electrostrictive behavior under ambient conditions of temperature and pressure. In weak, quasi-static electric fields, i.e.

We show that platinum (Pt) and palladium (Pd) can be efficiently removed from spent catalytic converters by means of a sintering process involving chloride salts. For Pt, mixing the crushed catalyst in an aqueous solution of chloride salts at catalyst/salt weight ratios ranging from 2.5 to 6.7, followed by drying, and 2-h sintering in the reactor furnace at 1100 °C, results in extraction of 80 ± 4% of the metal. For Pd, the addition of fumed silica to the dry chlorination agents was necessary in order to optimize extraction using fractional factorial design of experiments (DOE). Maximum Pd extraction of 93 ± 5% was achieved at 1100 °C with weight ratios of the catalyst material: CaCl2·2H2O:SiO2 = 1:0.6:1.2. Application of a similar protocol to Pt-containing catalytic converters would be expected to result in a similar high level of extraction efficiency. The primary advantage of the proposed extraction process is that it does not involve hazardous chemicals, strong bases/acids, or corrosive gases, and produces, as a byproduct, only small quantities of nontoxic silicate waste.

The magnetic properties of undoped, bulk CeO2 are not fully understood. In contrast to nanocrystalline ceria that exhibits paramagnetism attributed to Ce3+ at grain surfaces, bulk ceria is weakly paramagnetic, despite the absence of magnetic ions. In the present work, the magnetic susceptibility of bulk ceria ceramics doped with Lu3+, which has neither spin nor orbital angular momentum, was measured in order to assess the relative contributions of the crystal lattice, residual Ce3+ and oxygen vacancies to the overall bulk magnetization. We observed a magnetic response consisting of two parts: temperature independent (5-300 K) magnetic susceptibility, and Curie-Weiss paramagnetism. The temperature independent susceptibility decreases linearly with Lu content, and becomes diamagnetic at 30 mol% Lu. The Curie-Weiss magnetism visible at low temperatures was identified as resulting from a few ppm of Fe contaminant. However, Fe contamination does not contribute to the temperature independent paramagnetism. No contribution from Ce3+ could be detected. The fact that the magnetization decreases with Lu content, even though the concentration of oxygen vacancies, and the lattice defects associated with them, increases, indicates that neither is coupled to the magnetic field. Weak, temperature-independent paramagnetism in non-metals is usually attributed to a second order, Van Vleck-type magnetization. However, Van Vleck paramagnetism requires that the population of the first excited state be constant within the range of temperatures investigated. We discuss possible modifications of the large band gap electronic structure of undoped ceria which could account for our observations.

In this study, we explored the feasibility of employing Gd-doped ceria (GDC) thin films (1–2 μm) as functional, mechanically reliable material for microelectromechanical systems (MEMS). Self-supported structures, based on microscopic-scale GDC membranes, bridges, and cantilevers, were fabricated using Si-compatible processes and materials. With voltages of different amplitudes and frequencies and a variety of metal electrodes, we monitored structural stability and device response. The membrane-based structures displayed much higher stability under voltage and better mechanical robustness than those based on bridges or cantilevers. At low frequencies (a few Hz), the use of Ti contacts resulted in observable displacement of the membranes in the presence of moderately low voltage (≤10 V/1.6 μm), while Al, Cr, and Ni contacts did not provide such functionality. Although for all contact metals tested, formation of a blocking layer at room temperature is evident, for the case of Ti, the barrier height is much lower. In view of the fact that the crystallographic space group of weakly doped GDC is Fm-3 m, the electromechanical response of the microfabricated GDC membranes is most likely electrostrictive, but a strict proof is not yet available. At high frequencies (>100 kHz), the membranes produce lateral displacement as large as several microns due to Joule heating, i.e., a thermo-electromechanical response.

Micro-Raman spectroscopy and X-ray diffraction were used to study time-dependent structural changes in sputtered Ce1-xGdxO2-x/2 films. The F2g peak position was measured at five well-defined film locations; X-ray diffraction assessed in-plane compressive strain and unit cell volume. For x = 0.05, at all locations monitored post-annealing, the F2g frequency continued to increase during two weeks and for x = 0.10, at 4 of 5 locations during six weeks. This time-dependent behavior is attributed to relaxation of local elastic dipolar strain fields. Raman spectroscopy can properly evaluate strain in thin films of these materials only when mechanical properties, defect structure, temporal and thermal history are considered.

Ceria doped with trivalent dopants exhibits nonclassical electrostriction, strong anelasticity, and room-temperature (RT) mechanical creep. These phenomena, unexpected for a ceramic material with a large Young's modulus, have been attributed to the generation of local strain in the vicinity of the host Ce cations due to symmetry-breaking point defects, including oxygen vacancies. However, understanding why strain is generated at the host rather than at the dopant site, as well as predicting these effects as a function of dopant size and concentration, remains a challenge. We have used the evolutionary-algorithm-based reverse Monte Carlo modeling to reconcile the experimental data of extended X-ray absorption fine structure and X-ray diffraction in a combined model structure. By extracting the details of the radial distribution function (RDF) around the host (Ce) and trivalent dopants (Sm or Y), we find that RDF of the first-nearest neighbor (1NN) of host and dopant cations as well as the second-nearest neighbor (2NN) of the dopant are each best modeled with two separate populations corresponding to short and long interatomic distances. This heterogeneity indicates that fluorite symmetry is not preserved locally, especially for the dopant first-and second-NN sites, appearing at surprisingly low doping fractions (5 mol % Sm and 10 mol % Y). Given that Ce rather than dopant sites act as the source of local strain for electrostriction and RT creep, we conclude that the environment around the dopant does not respond to electrical and mechanical excitations, likely because of its similarity to the double fluorite structure which has poor electrostrictive and anelastic properties. The trends we observe in the RDFs around the Ce sites as a function of dopant size and concentration suggest that the response of these sites can be controlled by the extent of doping: Increasing dopant size to increase strain magnitude at the 1NN shell of Ce and decreasing dopant fraction to decrease strain propagation to the 2NN shell of Ce should produce stronger electrostrictive response and RT creep.

Sulfur emission in the form of SO2 in flue gases is the one of the most serious atmospheric pollutants associated with coal combustion and non-ferrous metal production. The carbonate eutectic method for removing SO2 from flue gases at 723–923 K was initially proposed in the 1970's but despite its great efficiency (SO2 concentration in the flue gas after purification reached 0.003 vol%) it could not be implemented by industry due to the complexity of the carbonate melt regeneration stage. Earlier we proposed a method suited to coal-firing power stations where the melt was regenerated using CO as a reducing agent. However, most metallurgical plants do not use coal and therefore lack a large source of CO. Here we propose a method for removing sulfur from the carbonate eutectic melt by purging it with natural gas or a natural gas/air mixture, which are available in the vast majority of metallurgical plants. This reaction leads to the reduction of sulfate to H2S gas that leaves the melt. The experiments we conducted show that nearly complete sulfur removal from the melt is possible at 823 K and that the reaction rate is sufficiently high for a large scale process. The proposed modifications provide solutions to two major problems previously encountered: (i) high temperature corrosion of the reaction cell can be avoided, since a stainless steel cell with high chromium content is stable with respect to the carbonate eutectic melt at 823 K, and (ii) removal of sulfur in the form of H2S provides considerable freedom in choosing the final industrially useful product: either sulfuric acid, using H2S dry combustion, or elemental sulfur via the Claus process. One can foresee that this carbonate melt-based SO2 removal technique may become a practical and economically attractive method for limiting sulfur emission to the atmosphere from non-ferrous metallurgical processing plants.

The Young's, shear and bulk moduli of dense (> 95%) Gd-doped ceria (Ce1 - xGdxO2 - x/2) ceramics were determined as a function of Gd content using the ultrasonic pulse-echo method and corrected for porosity according to both static and dynamic models. With increasing defect concentration (0–20 mol% Gd), the Young's and shear moduli decrease linearly by 10% while for 29 mol%, the values lie above the linear fit; the bulk modulus decreases linearly within the complete range. We conclude that structural changes, induced by oxygen vacancy ordering for x > 0.2, may influence the uniaxial and shear moduli, leaving the bulk modulus unaffected.

Cholesterol has limited solubility in phospholipid bilayers. The solubility limit is strongly dependent on the nature of the lipid with which the cholesterol is mixed while properties of the crystals formed can be modified by phospholipid-cholesterol interactions. In this review we summarize the various methods that have been developed to prepare hydrated mixtures of cholesterol and phospholipid. We point out some of the factors that determine the form adopted when cholesterol crystallizes in such mixtures, i.e. two- or three-dimensional, monohydrate or anhydrous. These differences can greatly affect the ability to experimentally detect the presence of these crystals in a membrane. Several methods for detecting cholesterol crystals are discussed and compared including DSC, X-ray and GIXRD diffraction methods, NMR and EPR spectroscopy. The importance of the history of the sample in determining the amount and nature of the cholesterol crystals formed is emphasized.

We report the first observation of an efficient, native membrane conjugation mechanism via positively charged, linear oligo-amines. Clustering of membrane fragments relies on electrostatic interactions between the net negative charge of the membranes and the positively charged, water-soluble mediators. This conjugation principle is demonstrated with two different bacterial membranes in which are embedded either the intrinsic membrane protein (MP) bacteriorhodopsin (bR) or the more recently identified xanthorhodopsin (XR). As determined by their characteristic UV-vis absorption spectra and by circular dichroism, the MPs are not significantly perturbed by the oligo-amines carrying from +3 to +6 positive charges. Light microscopy and scanning electron microscope (SEM) imaging provide direct evidence for membrane conjugation. Process efficiency was found to be correlated with the net charge of the oligo-amine used. Membrane conjugation is accomplished within a wide range of pH values (7-2.5); is reversed by NaCl; and does not require the presence of a precipitant (e.g. PEG) nor Ca2+ ions. Some evidence for bilayer fusion is also observed, but only in the presence of the +6 oligo-amine analog.

We introduce a new concept and potentially general platform for antibody (Ab) purification that does not rely on chromatography or specific ligands (e.g., Protein A); rather, it makes use of detergent aggregates capable of efficiently capturing Ab while rejecting hydrophilic impurities. Captured Ab are then extracted from the aggregates in pure form without co-extraction of hydrophobic impurities or aggregate dissolution. The aggregates studied consist of conjugated “Engineered-micelles” built from the nonionic detergent, Tween-20; bathophenanthroline, a hydrophobic metal chelator, and Fe(2+)ions. When tested in serum-free media with or without bovine serum albumin as additive, human or mouse IgGs were recovered with good overall yields (70–80%, by densitometry). Extraction of IgGs with 7 different buffers at pH 3.8 sheds light on possible interactions between captured Ab and their surrounding detergent matrix that lead to purity very similar to that obtained via Protein A or Protein G resins. Extracted Ab preserve their secondary structure, specificity and monomeric character as determined by circular dichroism, enzyme-linked immunosorbent assay and dynamic light scattering, respectively.

We report the first demonstration of nonionic detergent micelle conjugation and phase separation using purpose-synthesized, peptide amphiphiles, C10 -(Asp)5 and C10 -(Lys)5 . Clustering is achieved in two different ways. Micelles containing the negatively charged peptide amphiphile C10 -(Asp)5 are conjugated (a) via a water-soluble, penta-Lys mediator or (b) to micelles containing the C10 -(Lys)5 peptide amphiphile. Both routes lead to phase separation in the form of oil-rich globules visible in the light microscope. The hydrophobic nature of these regions leads to spontaneous partitioning of hydrophobic dyes into globules that were found to be stable for weeks to months. Extension of the conjugation mechanism to micelles containing a recently discovered, light-driven proton pump King Sejong 1-2 (KS1-2) demonstrates that a membrane protein may be concentrated using peptide amphiphiles while preserving its native conformation as determined by characteristic UV absorption. The potential utility of these peptide amphiphiles for biophysical and biomedical applications is discussed.

Identifying the rate-determining step (RDS) for oxygen incorporation into mixed ionic and electronic conducting electrodes is very challenging, particularly since the local composition changes during the reaction. Now, a generally applicable method for identifying the RDS is presented, with the example of a Pr0.1Ce0.9O2–x electrode.

Classical electrostriction, describing a second-order electromechanical response of insulating solids, scales with elastic compliance, S, and inversely with dielectric susceptibility, e. This behavior, first noted 20 years ago by Robert Newnham, is shown to apply to a wide range of electrostrictors including polymers, glasses, crystalline linear dielectrics, and relaxor ferroelectrics. Electrostriction in fluorite ceramics of (Y, Nb)-stabilized δ-Bi2O3 is examined with 16%–23% vacant oxygen sites. Given the values of compliance and dielectric susceptibility, the electrostriction coefficients are orders of magnitude larger than those expected from Newnham's scaling law. In ambient temperature nanoindentation measurements, (Y, Nb)-stabilized δ-Bi2O3 displays primary creep. These findings, which are strikingly similar to those reported for Gd-doped ceria, support the suggestion that ion conducting ceramics with the fluorite structure, a large concentration of anion vacancies and anelastic behavior, may constitute a previously unknown class of electrostrictors.

An electrochemical cell containing molten Li2CO3-Li2O has been proposed for the conversion of the greenhouse gas CO2 to CO, which can then either be used to power gas turbines or converted to methanol. Since efficient electrolysis takes place at 900°C, the materials which can be used in such a cell must satisfy stringent requirements. In the current work, we have examined the static corrosion resistance of zirconia, beryllia and magnesia ceramics at 900°C in the Li2CO3-Li2O mixture and in a Li-Na-K carbonate eutectic mixture with the ultimate objective of identifying suitable electrically insulating materials. Conclusions regarding material stability were based on elemental analysis of the melt, primarily via X-ray photoelectron spectroscopy, a particularly sensitive technique. It was found that magnesia is completely stable for at least 33 hrs in a Li2CO3-Li2O melt, while a combined lithium titanate/lithium zirconate layer forms on the zirconia ceramic as detected by XRD. Under the same melt conditions, beryllia shows considerable leaching into solution. In a Li-Na-K carbonate eutectic mixture containing 10.2 mol% oxide at 900°C under standard atmospheric conditions, magnesia showed no signs of degradation. Stabilization of the zirconia content of the eutectic mixture at 0.01-0.02 at% after 2 hrs is again explained by the formation of a lithium titanate/ lithium zirconate coating. On the basis of these results, we conclude that only magnesia can be satisfactorily used as an insulating material in electrolysis cells containing Li2CO3-Li2O melts.

We describe the use of null-ellipsometry with lock-in detection to monitor grain core oxygen diffusion in thin films of the solid-state ionic conductor Ce 0.8 Gd 0.2 O 1.9 . Application of an electric field perpendicular to the film surface—probe alternating voltage ( U A ) in addition to perturbation bias voltage ( U B )—produces ellipsometer optical response at the probe frequency. The signal amplitude and time dependence can be interpreted in terms of changes in the local material polarizability. Since the ionic contribution to the material polarizability is much larger than that of electrons or protons, the diffusion of ions can be distinguished. Because grain cores occupy the majority of the film volume, ion diffusion in the grain cores dominates the optical response. This effect was studied as a function of temperature (75–160 °C), amplitude and frequency of the electric field. The activation energy for oxygen diffusion in the grain cores was found to be 1.1 ± 0.1 eV and 1.5 ± 0.1 eV for films with in-plane compressive strain of 0.34 ± 0.06% and in-plane tensile strain 0.16 ± 0.03%, respectively.

The alignment of carbon nanotubes has been the subject of extensive research. Among the different alignment methods, surface alignment, such as alignment along favorable directions on the anisotropic surface of single-crystal substrates, including sapphire and quartz, has stood out as very effective and robust. Recently, this method was shown to also be highly effective for the guided growth of semiconducting nanowires. Interestingly, while the same directions of alignment were found for the growth of nanotubes and nanowires on R-plane (1102) and A-plane (1120) sapphire (α-Al2O3), nanotubes, unlike nanowires, have been reported not to align on M-plane (1010) sapphire. Here we report the alignment of carbon nanotubes on M-plane sapphire, as well as on the annealed M-plane, which is periodically faceted, in directions that match the directions reported for aligned nanowires. We go on to discuss a possible common alignment mechanism for nanowires and nanotubes on sapphire surfaces.

Room-temperature mechanical properties of thin films and ceramics of doped and undoped ceria are reviewed with an emphasis on the anelastic behavior of the material. Notably, the unrelaxed Young's modulus of Gd-doped ceria ceramics measured by ultrasonic pulse-echo techniques is >200 GPa, while the relaxed biaxial modulus, calculated from the stress/strain ratio of thin films, is ≈10 times smaller. Oxygen-deficient ceria exhibits a number of anelastic effects, such as hysteresis of the lattice parameter, strain-dependent Poisson's ratio, room-temperature creep, and nonclassical electrostriction. Methods of measuring these properties are discussed, as well as the applicability of Raman spectroscopy for evaluating strain in thin films of Gd-doped ceria. Special attention is paid to detection of the time dependence of anelastic effects. Both the practical advantages and disadvantages of anelasticity on the design and stability of microscopic devices dependent on ceria thin films are discussed, and methods of mitigating the latter are suggested, with the aim of providing a cautionary note for materials scientists and engineers designing devices containing thin films or bulk ceria, as well as providing data-based constraints for theoreticians who are involved in modeling of the unusual electrical and electromechanical properties of undoped and doped ceria.

Nanocomposites of VGCF reinforced polypropylene monofilaments were created using melt compounding extrusion. The monofilament diameter and VGCF loading were varied to characterize the effects of spinline stress and imposed confinement on material properties, including crystalline structure and thermodynamic behavior. A correlation was found between spinline stress, degree of confinement, depression of the melting temperature, and changes in crystallite dimensions and orientation. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

Background Aggrecan is the major non-collagenous component of the intervertebral disc. It is a large proteoglycan possessing numerous glycosaminoglycan chains and the ability to form aggregates in association with hyaluronan. Its abundance and unique molecular features provide the disc with its osmotic properties and ability to withstand compressive loads. Degradation and loss of aggrecan result in impairment of disc function and the onset of degeneration. Scope of review This review summarizes current knowledge concerning the structure and function of aggrecan in the normal intervertebral disc and how and why these change in aging and degenerative disc disease. It also outlines how supplementation with aggrecan or a biomimetic may be of therapeutic value in treating the degenerate disc. Major conclusions Aggrecan abundance reaches a plateau in the early twenties, declining thereafter due to proteolysis, mainly by matrix metalloproteinases and aggrecanases, though degradation of hyaluronan and non-enzymic glycation may also participate. Aggrecan loss is an early event in disc degeneration, although it is a lengthy process as degradation products may accumulate in the disc for decades. The low turnover rate of the remaining aggrecan is an additional contributing factor, preventing protein renewal. It may be possible to retard the degenerative process by restoring the aggrecan content of the disc, or by supplementing with a bioimimetic possessing similar osmotic properties. General significance This review provides a basis for scientists and clinicians to understand and appreciate the central role of aggrecan in the function, degeneration and repair of the intervertebral disc.

We describe a technique for measuring the activation energy of ion diffusion in ionic and mixed ionic/electronic conductors. The technique is based on monitoring small changes in refractive index near the interface of a semitransparent gold electrode with the sample surface. Constant bias voltage is applied to the sample to weakly perturb the distribution of charge carriers near this front electrode. The relaxation process induced by bias removal is probed by applying alternating voltage and monitoring by ellipsometry with lock-in detection the changes in the refractive index dominated by changes in material polarizability. Since the ionic contribution to the total material polarizability is much larger than that of electrons or protons, the diffusion of ions can be distinguished. Measurements were made as a function of temperature on single crystals of 8 mol% Y-stabilized zirconia (YSZ8), on ceramic pellets of 20 mol% Gd doped CeO 2 (GDC20) and on single crystals of 0.03 mol% Fe-doped SrTiO 3 (Fe-STO). In YSZ8, a single moving species (oxygen vacancies) with activation energy of 0.8 eV was detected. The “wet” and “dry” states of GDC20 can be clearly distinguished: in the “wet” state there are mobile species other than oxygen vacancies, most likely protons. In Fe-doped SrTiO 3 , the proposed technique can reliably measure the activation energy of oxygen ion diffusion on a background of the much larger electronic conductivity.

We have adapted the X-ray diffraction technique of measuring crystal lattice parameters as a function of sample orientation in order to investigate the Poisson ratio (ν) of thin films of Ce 0.8 Gd 0.2 O 1.9 with different degrees of in-plane compressive strain. Since Gd-doped ceria is mechanically inelastic, the unstrained lattice constant is not well-defined. Therefore in order to determine the Poisson ratio, more than one strain state of the same sample must be characterized. We have accomplished this with a home-built, diffractometer-compatible sample-bender. Using this device, we find that the Poisson ratio of as-deposited thin films of Gd-doped ceria is a decreasing function of the in-plane compressive strain. At total strain ≈ −0.9 %, ν is > 0.45, indicating that the material tends to preserve volume. Increase of the in-plane strain to ≈ −2 % produces a monotonic decrease in the Poisson ratio to ~0.2. Such low values are indicative of reduced volume. We explain this behavior by noting earlier results from our group suggesting that, at temperatures below 200 °C and at low strain values, Ce 0.8 Gd 0.2 O 1.9 responds to non-isotropic mechanical stress by reorienting the locally distorted CeCe-VO –O7 units. At higher strain values this mechanism is apparently no longer effective. Measurement of the Poisson ratio of inelastic thin films by this technique is straightforward and not diffractometer-dependent. It therefore represents a practical method for ceramic thin film characterization.

We have recently introduced a non-chromatographic alternative for antibody (Ab) purification, one which does not require the use of Protein A. With this approach, polyclonal human or mouse immunoglobulins (IgG’s) are captured almost quantitatively by Tween-20 micelles conjugated with a [chelator:divalent metal cation] complex. Target IgG structure remains native even following extraction from the surfactant aggregate. In the present work, we explore the effect of varying both components of the [metal:chelator] pair on the yield of purified Ab. Capture efficiency is observed to correlate with the formation of sufficiently large detergent aggregates, as determined by dynamic light scattering (DLS) and polyacrylamide gel electrophoresis (PAGE). This, in turn, depends on the rigidity and aromaticity of the chelator. Detergent aggregates are stable over a wide range of pH values (pH = 3–9). Under acidic conditions (3–3.8) they lead to good IgG recovery yields (70–78%) with purity similar to that obtained with Protein A chromatography while maintaining the monomeric state of the IgG's. Finally, the influence of the environment and the presence of various water-soluble chelators (e.g. EDTA, histidine, imidazole) on process efficiency, is described.