Advancing Chemical Separations: Unraveling the Structure and Dynamics of Phase Splitting in Liquid-Liquid Extraction.

Liquid-liquid extraction (LLE), the go-to process for a variety of chemical separations, is limited by spontaneous organic phase splitting upon sufficient solute loading, called third phase formation. In this study we explore the applicability of critical phenomena theory to gain insight into this deleterious phase behavior with the goal of improving separations efficiency and minimizing waste. A series of samples representative of rare earth purification were constructed to include each of one light and one heavy lanthanide (cerium and lutetium) paired with one of two common malonamide extractants (DMDOHEMA and DMDBTDMA). The resulting postextraction organic phases are chemically complex and often form rich hierarchical structures whose statics and dynamics near the critical point were probed herein with small-angle X-ray scattering and high-speed X-ray photon correlation spectroscopy. Despite their different extraction behaviors, all samples show remarkably similar critical behavior with exponents well described by classical critical point theory consistent with the 3D Ising model, where the critical behavior is characterized by fluctuations with a single diverging length scale. This unexpected result indicates a significant reduction in relevant chemical parameters at the critical point, indicating that the underlying behavior of phase transitions in LLE rely on far fewer variables than are generally assumed. The obtained scalar order parameter is attributed to the extractant fraction of the extractant/diluent mixture, revealing that other solution components and their respective concentrations simply shift the critical temperature but do not affect the nature of the critical fluctuations. These findings point to an opportunity to drastically simplify studies of liquid-liquid phase separation and phase diagram development in general while providing insights into LLE process improvement.

Nanoscale Critical Phenomena in a Complex Fluid Studied by X-Ray Photon Correlation Spectroscopy.

The advent of high-speed x-ray photon correlation spectroscopy now allows the study of critical phenomena in fluids to much smaller length scales and over a wider range of temperatures than is possible with dynamic light scattering. We present an x-ray photon correlation spectroscopy study of critical fluctuation dynamics in a complex fluid typical of those used in liquid-liquid extraction (LLE) of ions, dodecane-DMDBTDMA with extracted aqueous Ce(NO_{3})_{3}. We observe good agreement with both static and dynamic scaling without the need for significant noncritical background corrections. Critical exponents agree with 3D Ising values, and the fluctuation dynamics are described by simple exponential relaxation. The form of the dynamic master curve deviates somewhat from the Kawasaki result, with a more abrupt transition between the critical and noncritical asymptotic behavior. The concepts of critical phenomena thus provide a quantitative framework for understanding the structure and dynamics of LLE systems and a path forward to new LLE processes.

Non-invasive in vivo quantification of human skin tension lines.

Human skin is a composite tissue that exhibits anisotropic mechanical properties. This anisotropy arises primarily from the alignment of collagen and elastin fibers in the dermis, which causes the skin to exhibit greater tension in one direction, making it appear stiffer. A diverse number of skin tension guidelines have been developed to assist surgeons in making incisions that produce the least conspicuous scars. However, skin anisotropy is believed to vary from subject to subject, and no single guideline is universally recognized as the best to implement for surgical applications. To date, no system exists that can rapidly and non-invasively measure lines of skin tension in vivo. In this article, we evaluate the ability of a new aspiration system to measure the anisotropy of human skin. The device painlessly applies a radial stress of 17 kPa to a region of skin, and captures radially asymmetric skin deformations via a dermal camera. These deformations are used to quantify orientations of strain extrema and the direction of greatest skin stiffness. The ratio of these asymmetric strains varies between 1 and -0.75. A simple 2D transverse isotropic model captures this behavior for multiple anatomical sites. Clinical trials reveal that skin tension line orientations are comparable with existing skin tension maps and generally agree across subjects, however orientations statistically differ between individuals. As such, existing guidelines appear to provide only approximate estimates of skin tension orientation. STATEMENT OF SIGNIFICANCE: Skin tension lines (STL) in human skin arise primarily from collagen fiber alignment in the dermis. These lines are used by surgeons to guide incisions that produce the least conspicuous scars. While numerous anatomical STL maps exist, no single guideline is universally recognized as the most reliable. Moreover, manual methods of quantifying STL are imprecise. For the first time, we have developed a device capable of rapidly and non-invasively measuring STL orientations in vivo, using a single test. Our results are used to establish a simple constitutive model of mechanical skin anisotropy. Clinical trials further reveal STL orientations are comparable with existing maps, but statistically differ between individuals. Existing guidelines therefore appear to provide only approximate estimates of STL orientation.

A short-pulse X-ray beamline for spectroscopy and scattering.

Experimental facilities for picosecond X-ray spectroscopy and scattering based on RF deflection of stored electron beams face a series of optical design challenges. Beamlines designed around such a source enable time-resolved diffraction, spectroscopy and imaging studies in chemical, condensed matter and nanoscale materials science using few-picosecond-duration pulses possessing the stability, high repetition rate and spectral range of synchrotron light sources. The RF-deflected chirped electron beam produces a vertical fan of undulator radiation with a correlation between angle and time. The duration of the X-ray pulses delivered to experiments is selected by a vertical aperture. In addition to the radiation at the fundamental photon energy in the central cone, the undulator also emits the same photon energy in concentric rings around the central cone, which can potentially compromise the time resolution of experiments. A detailed analysis of this issue is presented for the proposed SPXSS beamline for the Advanced Photon Source. An optical design that minimizes the effects of off-axis radiation in lengthening the duration of pulses and provides variable X-ray pulse duration between 2.4 and 16 ps is presented.

Transient crystalline superlattice generated by a photoacoustic transducer.

Designing an efficient and simple method for modulating the intensity of x-ray radiation on a picosecond time-scale has the potential to produce ultrafast pulses of hard x-rays. In this work, we generate a tunable transient superlattice, in an otherwise perfect crystal, by photoexciting a metal film on a crystalline substrate. The resulting transient strain has amplitudes approaching 1%, wavevectors greater than [Formula: see text], and lifetimes approaching 1 ns. This method has the potential to generate isolated picosecond x-ray bursts with scattering efficiencies in excess of 10%.

Surfactant treatments influence drying mechanics in human stratum corneum.

We describe a high-throughput method capable of quantifying the elastic modulus and drying stress of ex vivo samples of human stratum corneum. Spatially resolved drying deformations in circular tissue samples are measured, azimuthally averaged and fitted with a profile based on a linear elastic model. Our approach enables the comparison of the physical effects of different cleansers. We find that cleansing can cause dramatic changes to the mechanical properties of stratum corneum. In some cases, cleansing can lead to an order of magnitude increase in elastic modulus and drying stress. We expect that these mechanical properties have a direct impact on cracking and chapping skin as well as the milder sensation of perceived tightness often experienced after washing. Mechanical drying studies are also combined with drop wetting studies and pyranine staining experiments. This combination of techniques allows one to establish a multidimensional profile of stratum corneum including stiffness, susceptibility to drying, hydrophilicity and barrier functionality.

Optical design of the short pulse x-ray imaging and microscopy time-angle correlated diffraction beamline at the Advanced Photon Source.

The short pulse x-ray imaging and microscopy beamline is one of the two x-ray beamlines that will take full advantage of the short pulse x-ray source in the Advanced Photon Source (APS) upgrade. A horizontally diffracting double crystal monochromator which includes a sagittally focusing second crystal will collect most of the photons generated when the chirped electron beam traverses the undulator. A Kirkpatrick-Baez mirror system after the monochromator will deliver to the sample a beam which has an approximately linear correlation between time and vertical beam angle. The correlation at the sample position has a slope of 0.052 ps/µrad extending over an angular range of 800 µrad for a cavity deflection voltage of 2 MV. The expected time resolution of the whole system is 2.6 ps. The total flux expected at the sample position at 10 keV with a 0.9 eV energy resolution is 5.7 × 10(12) photons/s at a spot having horizontal and vertical full width at half maximum of 33 µm horizontal by 14 µm vertical. This new beamline will enable novel time-dispersed diffraction experiments on small samples using the full repetition rate of the APS.

Heterogeneous drying stresses in stratum corneum.

We study the drying of stratum corneum, the skin's outermost layer and an essential barrier to mechanical and chemical stresses from the environment. Even though stratum corneum exhibits structural features across multiple length-scales, contemporary understanding of the mechanical properties of stratum corneum is based on the assumption that its thickness and composition are homogeneous. We quantify spatially resolved in-plane traction stress and deformation at the interface between a macroscopic sample of porcine stratum corneum and an adherent deformable elastomer substrate. At length-scales greater than a millimeter, the skin behaves as a homogeneous elastic material. At this scale, a linear elastic model captures the spatial distribution of traction stresses and the dependence of drying behavior on the elastic modulus of the substrate. At smaller scales, the traction stresses are strikingly heterogeneous and dominated by the heterogeneous structure of the stratum corneum.

Short-range order and near-field effects on optical scattering and structural coloration.

We have investigated wavelength-dependent light scattering in biomimetic structures with short-range order. Coherent backscattering experiments are performed to measure the transport mean free path over a wide wavelength range. Overall scattering strength is reduced significantly due to short-range order and near-field effects. Our analysis explains why single scattering of light is dominant over multiple scattering in similar biological structures and is responsible for color generation.

Picosecond time-resolved laser pump/X-ray probe experiments using a gated single-photon-counting area detector.

The recent developments in X-ray detectors have opened new possibilities in the area of time-resolved pump/probe X-ray experiments; this article presents the novel use of a PILATUS detector to achieve X-ray pulse duration limited time-resolution at the Advanced Photon Source (APS), USA. The capability of the gated PILATUS detector to selectively detect the signal from a given X-ray pulse in 24 bunch mode at the APS storage ring is demonstrated. A test experiment performed on polycrystalline organic thin films of alpha-perylene illustrates the possibility of reaching an X-ray pulse duration limited time-resolution of 60 ps using the gated PILATUS detector. This is the first demonstration of X-ray pulse duration limited data recorded using an area detector without the use of a mechanical chopper array at the beamline.

Novel anti-VEGF chimeric molecules delivered by AAV vectors for inhibition of retinal neovascularization.

Vascular endothelial growth factor (VEGF) is important in pathological neovascularization, which is a key component of diseases such as the wet form of age-related macular degeneration, proliferative diabetic retinopathy and cancer. One of the most potent naturally occurring VEGF binders is VEGF receptor Flt-1. We have generated two novel chimeric VEGF-binding molecules, sFLT01 and sFLT02, which consist of the second immunoglobulin (IgG)-like domain of Flt-1 fused either to a human IgG1 Fc or solely to the CH3 domain of IgG1 Fc through a polyglycine linker 9Gly. In vitro analysis showed that these novel molecules are high-affinity VEGF binders. We have demonstrated that adeno-associated virus serotype 2 (AAV2)-mediated intravitreal gene delivery of sFLT01 efficiently inhibits angiogenesis in the mouse oxygen-induced retinopathy model. There were no histological observations of toxicity upon persistent ocular expression of sFLT01 for up to 12 months following intravitreal AAV2-based delivery in the rodent eye. Our data suggest that AAV2-mediated intravitreal gene delivery of our novel molecules may be a safe and effective treatment for retinal neovascularization.

Minimal model for kinetic arrest.

To elucidate slow dynamics in glassy materials, we introduce the figure-8 model in which N hard blocks undergo Brownian motion around a circuit in the shape of a figure 8. This system undergoes kinetic arrest at a critical packing fraction phi=phi g<1 , and for phi approximately phi g long-time diffusion is controlled by rare, cooperative, "junction-crossing" particle rearrangements. We find that the average time between junction crossings tau JC, and hence the structural relaxation time, does not simply scale with the configurational volume Omega c of transition states, because tau JC also depends on the time to complete a junction crossing. The importance of these results in understanding cage-breaking dynamics in glassy systems is discussed.

Comparison of two induction regimens using or not using muscle relaxant: impact on postoperative upper airway discomfort.

BACKGROUND: Muscle relaxants facilitate tracheal intubation, but they are often not used for short peripheral surgical procedures. The consequences of this practice on the upper airway are still a matter of controversy. We therefore compared the incidence of post-intubation symptoms in a randomized study comparing patients intubated with or without the use of a muscle relaxant. METHODS: A total of 300 adult patients requiring tracheal intubation for scheduled peripheral surgery were randomly assigned in a double-blind study to an anaesthetic protocol that either included or did not include a muscle relaxant (rocuronium). The primary end-point was the rate of post-intubation symptoms 2 and 24 h after extubation. The secondary end-points were the intubation conditions score (Copenhagen Consensus Conference), the rate of difficult intubations (Intubation Difficulty Scale), and the incidence of adverse haemodynamic events. RESULTS: Post-intubation symptoms were more frequent in patients intubated without the use of a muscle relaxant, whether 2 h (57% vs 43% of patients; P < 0.05) or 24 h (38% vs 26% of patients; P < 0.05) after extubation. Intubation conditions were better when the muscle relaxant was used. In patients intubated without a muscle relaxant, difficult intubation was more common (12% vs 1%; P < 0.05), as were arterial hypotension or bradycardia requiring treatment (12% vs 3% of patients; P < 0.05). CONCLUSIONS: The use of a muscle relaxant for tracheal intubation diminishes the incidence of adverse postoperative upper airway symptoms, results in better tracheal intubation conditions, and reduces the rate of adverse haemodynamic events.

X-ray microprobe of orbital alignment in strong-field ionized atoms.

We have developed a synchrotron-based, time-resolved x-ray microprobe to investigate optical strong-field processes at intermediate intensities (10(14) - 10(15) W/cm2). This quantum-state specific probe has enabled the direct observation of orbital alignment in the residual ion produced by strong-field ionization of krypton atoms via resonant, polarized x-ray absorption. We found strong alignment to persist for a period long compared to the spin-orbit coupling time scale (6.2 fs). The observed degree of alignment can be explained by models that incorporate spin-orbit coupling. The methodology is applicable to a wide range of problems.

Dynamics of fracture in drying suspensions.

We investigate the dynamics of fracture in drying films of colloidal silica. Water loss quenches the nanoparticle dispersions to form a liquid-saturated elastic network of particles that relieves drying-induced strain by cracking. These cracks display intriguing intermittent motion originating from the deformation of arrested crack tips and aging of the elastic network. The dynamics of a single crack exhibits a universal evolution, described by a balance of the driving elastic power with the sum of interfacial power and the viscous dissipation rate of flowing interstitial fluid.

The influence of victim characteristics on potential jurors' perceptions of brain damage in mild traumatic brain injury.

PRIMARY OBJECTIVE: To determine the influence of victim/plaintiff sex, occupation and intoxication status at the time of injury on potential jurors' judgement about the presence of brain damage in mild traumatic brain injury (MTBI). RESEARCH DESIGN: Survey. METHODS AND PROCEDURES: One of eight scenarios describing a MTBI from a motor vehicle accident was presented to 460 participants at a Department of Motor Vehicles. Victim sex, occupation (accountant or cafeteria worker) and alcohol intoxication status at the time of injury (sober or intoxicated) were manipulated across eight scenarios. Participants rated whether the victim's complaints at 6 months post-injury were the result of brain damage. MAIN OUTCOMES AND RESULTS: Ratings were influenced by victim occupation and intoxication status (chi2>5.3, p<0.03), but not the sex of the victim. CONCLUSIONS: The occupational and intoxication status of MTBI victims may influence potential jurors' decision about the presence of brain damage.

Integration of the cognitive knowledge of activity in a service oriented architecture in the home care context.

The complex nature of a home care (HC) situation induces an important need for cooperation between the health care professionals. But even if this need is sometimes evocated in reports on HC issues, it is more difficult to get precise knowledge on this cooperative activity, and, consequently, propositions for computerized HC organization and management systems. We did some researches on this topic area. Previous phases of work let us highlight the actual need for cooperation, and obtain precise information on the HC activity processes and data. In this paper, we focused on the integration of this cognitive knowledge on the design of a HC cooperation architecture. Different levels of requirements for the cooperative system are mentioned: coordination, communication of information, delegation of activity, integration of services and personal access to the tasks to perform. A description of the usefulness and use of the cognitive knowledge is proposed, the architecture design, modular, distributed, and able to integrate external services is presented, and the results of a validation test of the implemented prototype, performed with actual HC professionals in an evaluation laboratory are presented.

Charge stabilization in nonpolar solvents.

While the important role of electrostatic interactions in aqueous colloidal suspensions is widely known and reasonably well-understood, their relevance to nonpolar suspensions remains mysterious. We measure the interaction potentials of colloidal particles in a nonpolar solvent with reverse micelles. We find surprisingly strong electrostatic interactions characterized by surface potentials, |ezeta|, from 2.0 to 4.4 k(B)T and screening lengths, kappa(-1), from 0.2 to 1.4 microm. Interactions depend on the concentration of reverse micelles and the degree of confinement. Furthermore, when the particles are weakly confined, the values of |ezeta| and kappa extracted from interaction measurements are consistent with bulk measurements of conductivity and electrophoretic mobility. A simple thermodynamic model, relating the structure of the micelles to the equilibrium ionic strength, is in good agreement with both conductivity and interaction measurements. Since dissociated ions are solubilized by reverse micelles, the entropic incentive to charge a particle surface is qualitatively changed from aqueous systems, and surface entropy plays an important role.

Onset of buckling in drying droplets of colloidal suspensions.

Minute concentrations of suspended particles can dramatically alter the behavior of a drying droplet. After a period of isotropic shrinkage, similar to droplets of a pure liquid, these droplets suddenly buckle like an elastic shell. While linear elasticity is able to describe the morphology of the buckled droplets, it fails to predict the onset of buckling. Instead, we find that buckling is coincident with a stress-induced fluid to solid transition in a shell of particles at a droplet's surface, occurring when attractive capillary forces overcome stabilizing electrostatic forces between particles.