51
|
Scheffold F, Wilking JN, Haberko J, Cardinaux F, Mason TG. The jamming elasticity of emulsions stabilized by ionic surfactants. SOFT MATTER 2014; 10:5040-5044. [PMID: 24913542 DOI: 10.1039/c4sm00389f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Oil-in-water emulsions composed of colloidal-scale droplets are often stabilized using ionic surfactants that provide a repulsive interaction between neighboring droplet interfaces, thereby inhibiting coalescence. If the droplet volume fraction is raised rapidly by applying an osmotic pressure, the droplets remain disordered, undergo an ergodic-nonergodic transition, and jam. If the applied osmotic pressure approaches the Laplace pressure of the droplets, then the jammed droplets also deform. Because solid friction and entanglements cannot play a role, as they might with solid particulate or microgel dispersions, the shear mechanical response of monodisperse emulsions can provide critical insight into the interplay of entropic, electrostatic, and interfacial forces. Here, we introduce a model that can be used to predict the plateau storage modulus and yield stress of a uniform charge-stabilized emulsion accurately if the droplet radius, interfacial tension, surface potential, Debye screening length, and droplet volume fraction are known.
Collapse
|
52
|
Fryd MM, Mason TG. Self-limiting droplet fusion in ionic emulsions. SOFT MATTER 2014; 10:4662-4673. [PMID: 24839170 DOI: 10.1039/c4sm00453a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We make an oil-in-water emulsion, which is initially stabilized using a first ionic surfactant, and mix it with a solution of a second ionic surfactant having the opposite charge, thereby inducing massively parallel droplet fusion. A transient disruption of the screened-charge repulsive barrier between interacting droplets, caused by the second ionic surfactant, arises from significant yet temporary charge neutralization of the first ionic surfactant on the surfaces of the oil droplets while mixing occurs. Interestingly, if a moderate molar excess of one surfactant exists, then the resulting emulsion re-stabilizes after limited droplet fusion. By adjusting the droplet volume fraction, concentrations of first and second surfactants, and volumes of the emulsion and the solution of the second surfactant, we control the degree of droplet coalescence and achieve a self-limiting droplet fusion process. Using optical microscopy, we observe that flat, thin, crystalline films can form between the two oil compartments after fusion of two or more immiscible microscale droplets. However, no such crystalline films are seen on the highly curved oil-oil interfaces inside nanoscale droplets that are composed of two or more immiscible oils and have been fused in the same manner, as revealed by cryogenic transmission electron microscopy.
Collapse
|
53
|
Mayoral K, Mason TG. Entropic chiral symmetry breaking in self-organized two-dimensional colloidal crystals. SOFT MATTER 2014; 10:4471-4478. [PMID: 24825352 DOI: 10.1039/c4sm00261j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Long-range chiral symmetry breaking (CSB) has been recently observed in 2D self-organized rhombic crystals of hard, achiral, 72 degree rhombic microparticles. However, purely entropic selection of a CSB crystal in an idealized system of hard achiral shapes, in which attractions are entirely absent and the shape does not dictate a chiral tiling, has not yet been quantitatively predicted. Overcoming limitations of a purely rotational cage model, we investigate a translational-rotational cage model (TRCM) of dense systems of hard achiral rhombs and quantitatively demonstrate that entropy can spontaneously drive the preferential self-organization of a chiral crystal composed of achiral shapes that also tile into an achiral crystal. At different particle area fractions, ϕA, we calculate the number of accessible translational-rotational microstates, Ω, of a mobile central rhomb in a static cage of neighboring rhombs, which can have different orientation angles, γ, relative to the bisector of the crystalline axes. As we raise ϕA, two maxima emerge in Ω(γ) at non-zero cage orientation angles, ±γmax. These maxima correspond to additional translational microstates that become accessible in the CSB crystalline polymorph through reduced translational tip-tip interference. Thus, entropy, often associated with structural disorder, can drive CSB in condensed phase systems of non-attractive achiral objects that do not tile into chiral structures. The success of the TRCM in explaining the entropic origin of CSB in systems of hard rhombs indicates that the TRCM will have significant utility in predicting the self-organized behavior of dense systems of other hard shapes in 2D.
Collapse
|
54
|
Zhao K, Mason TG. Self-organized chiral colloidal crystals of Brownian square crosses. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:152101. [PMID: 24675056 DOI: 10.1088/0953-8984/26/15/152101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We study aqueous Brownian dispersions of microscale, hard, monodisperse platelets, shaped as achiral square crosses, in two dimensions (2D). When slowly concentrated while experiencing thermal excitations, the crosses self-organize into fluctuating 2D colloidal crystals. As the particle area fraction φA is raised, an achiral rhombic crystal phase forms at φA ≈ 0.52. Above φA ≈ 0.56, the rhombic crystal gives way to a square crystal phase that exhibits long-range chiral symmetry breaking (CSB) via a crystal-crystal phase transition; the observed chirality in a particular square crystallite has either a positive or a negative enantiomeric sense. By contrast to triangles and rhombs, which exhibit weak CSB as a result of total entropy maximization, square crosses display robust long-range CSB that is primarily dictated by how they tile space at high densities. We measure the thermal distribution of orientation angles γ of the crosses' arms relative to the diagonal bisector of the local square crystal lattice as a function of φA, and the average measured γ (φA) agrees with a re-scaled model involving efficient packing of rotated cross shapes. Our findings imply that a variety of hard achiral shapes can be designed to form equilibrium chiral phases by considering their tiling at high densities.
Collapse
|
55
|
Khan M, Mason TG. Random walks of colloidal probes in viscoelastic materials. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:042309. [PMID: 24827253 DOI: 10.1103/physreve.89.042309] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Indexed: 06/03/2023]
Abstract
To overcome limitations of using a single fixed time step in random walk simulations, such as those that rely on the classic Wiener approach, we have developed an algorithm for exploring random walks based on random temporal steps that are uniformly distributed in logarithmic time. This improvement enables us to generate random-walk trajectories of probe particles that span a highly extended dynamic range in time, thereby facilitating the exploration of probe motion in soft viscoelastic materials. By combining this faster approach with a Maxwell-Voigt model (MVM) of linear viscoelasticity, based on a slowly diffusing harmonically bound Brownian particle, we rapidly create trajectories of spherical probes in soft viscoelastic materials over more than 12 orders of magnitude in time. Appropriate windowing of these trajectories over different time intervals demonstrates that random walk for the MVM is neither self-similar nor self-affine, even if the viscoelastic material is isotropic. We extend this approach to spatially anisotropic viscoelastic materials, using binning to calculate the anisotropic mean square displacements and creep compliances along different orthogonal directions. The elimination of a fixed time step in simulations of random processes, including random walks, opens up interesting possibilities for modeling dynamics and response over a highly extended temporal dynamic range.
Collapse
|
56
|
Bongartz T, Glazebrook KN, Kavros SJ, Murthy NS, Merry SP, Franz WB, Michet CJ, Veetil BMA, Davis JM, Mason TG, Warrington KJ, Ytterberg SR, Matteson EL, Crowson CS, Leng S, McCollough CH. Dual-energy CT for the diagnosis of gout: an accuracy and diagnostic yield study. Ann Rheum Dis 2014; 74:1072-7. [PMID: 24671771 PMCID: PMC4431329 DOI: 10.1136/annrheumdis-2013-205095] [Citation(s) in RCA: 158] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 03/01/2014] [Indexed: 02/06/2023]
Abstract
Objectives To assess the accuracy of dual-energy CT (DECT) for diagnosing gout, and to explore whether it can have any impact on clinical decision making beyond the established diagnostic approach using polarising microscopy of synovial fluid (diagnostic yield). Methods Diagnostic single-centre study of 40 patients with active gout, and 41 individuals with other types of joint disease. Sensitivity and specificity of DECT for diagnosing gout was calculated against a combined reference standard (polarising and electron microscopy of synovial fluid). To explore the diagnostic yield of DECT scanning, a third cohort was assembled consisting of patients with inflammatory arthritis and risk factors for gout who had negative synovial fluid polarising microscopy results. Among these patients, the proportion of subjects with DECT findings indicating a diagnosis of gout was assessed. Results The sensitivity and specificity of DECT for diagnosing gout was 0.90 (95% CI 0.76 to 0.97) and 0.83 (95% CI 0.68 to 0.93), respectively. All false negative patients were observed among patients with acute, recent-onset gout. All false positive patients had advanced knee osteoarthritis. DECT in the diagnostic yield cohort revealed evidence of uric acid deposition in 14 out of 30 patients (46.7%). Conclusions DECT provides good diagnostic accuracy for detection of monosodium urate (MSU) deposits in patients with gout. However, sensitivity is lower in patients with recent-onset disease. DECT has a significant impact on clinical decision making when gout is suspected, but polarising microscopy of synovial fluid fails to demonstrate the presence of MSU crystals.
Collapse
|
57
|
Fryd MM, Mason TG. Cerberus nanoemulsions produced by multidroplet flow-induced fusion. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15787-15793. [PMID: 24328235 DOI: 10.1021/la403817a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Through extreme flow-induced fusion and rupturing of microscale droplets within a mixture of two or more oil-in-water emulsions, each having a different type of mutually immiscible oil, we create complex oil-in-water nanoemulsions composed of multicomponent compartmentalized nanodroplets. The extreme flow temporarily overcomes the repulsive barrier between oil droplets, arising from stabilizing surfactant molecules on the droplet interfaces, thereby causing multidroplet fusion as well as droplet fission down to the nanoscale. After the droplets leave the vicinity of extreme flow, they remain stable against subsequent coarsening and coalescence. Using this highly parallel, top-down, nonequilibrium synthetic approach, we create bulk quantities of engulfed-linear Cerberus oil-in-water nanoemulsions. Each Cerberus nanodroplet contains three different immiscible oils that form complex-shaped internal compartments, as revealed by cryogenic transmission electron microscopy (cryo-TEM). Within a given Cerberus nanodroplet, depending upon the interfacial tensions and relative volume fractions of the different oils, the internal oil-oil interfaces can be significantly deformed. Such multicomponent compartmentalized oil nanodroplets have the capacity of holding different types of oil-soluble cargo molecules, including fluorinated drug molecules, which have a wide variety of functional capacities and the potential for local synergistic effects. Their size range is small enough to permit a wide variety of pharmaceutical applications. As such, Cerberus nanoemulsions open up possibilities for simultaneously delivering several different types of oil-soluble drug molecules, each of which is readily soluble in at least one of the different types of immiscible oils, to the same cell or tissue.
Collapse
|
58
|
Scheffold F, Cardinaux F, Mason TG. Linear and nonlinear rheology of dense emulsions across the glass and the jamming regimes. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:502101. [PMID: 24222446 DOI: 10.1088/0953-8984/25/50/502101] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We discuss the linear and nonlinear rheology of concentrated microscale emulsions, amorphous disordered solids composed of repulsive and deformable soft colloidal spheres. Based on recent results from simulation and theory, we derive quantitative predictions for the dependences of the elastic shear modulus and the yield stress on the droplet volume fraction. The remarkable agreement with experiments we observe supports the scenario that the repulsive glass and the jammed state can be clearly identified in the rheology of soft spheres at finite temperature while crossing continuously from a liquid to a highly compressed yet disordered solid.
Collapse
|
59
|
Clark APZ, Shi C, Ng BC, Wilking JN, Ayzner AL, Stieg AZ, Schwartz BJ, Mason TG, Rubin Y, Tolbert SH. Self-assembling semiconducting polymers--rods and gels from electronic materials. ACS NANO 2013; 7:962-977. [PMID: 23346927 DOI: 10.1021/nn304437k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In an effort to favor the formation of straight polymer chains without crystalline grain boundaries, we have synthesized an amphiphilic conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT), which self-assembles in aqueous solutions to form cylindrical micelles. In contrast to many diblock copolymer assemblies, the semiconducting backbone runs parallel, not perpendicular, to the long axis of the cylindrical micelle. Solution-phase micelle formation is observed by X-ray and visible light scattering. The micelles can be cast as thin films, and the cylindrical morphology is preserved in the solid state. The effects of self-assembly are also observed through spectral shifts in optical absorption and photoluminescence. Solutions of higher-molecular-weight PFT micelles form gel networks at sufficiently high aqueous concentrations. Rheological characterization of the PFT gels reveals solid-like behavior and strain hardening below the yield point, properties similar to those found in entangled gels formed from surfactant-based micelles. Finally, electrical measurements on diode test structures indicate that, despite a complete lack of crystallinity in these self-assembled polymers, they effectively conduct electricity.
Collapse
|
60
|
|
61
|
Fryd MM, Mason TG. Nanoinclusions in cryogenically quenched nanoemulsions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:12015-12021. [PMID: 22881456 DOI: 10.1021/la301834x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Nanodroplets containing mixtures of silicone oil and squalene are dispersed in a simple aqueous surfactant solution, quenched in liquid ethane, and examined using cryogenic transmission electron microscopy (CTEM). Depending on the phase of ice that forms around the nanodroplets and on the composition of the oil mixture, nanoinclusions can be observed inside oil nanodroplets, independent of surfactant type. Our observations suggest that these nanoinclusions arise from nucleation of vapor cavities as the water freezes and expands while the oil remains liquid during the quench.
Collapse
|
62
|
|
63
|
Zhao K, Bruinsma R, Mason TG. Local chiral symmetry breaking in triatic liquid crystals. Nat Commun 2012; 3:801. [DOI: 10.1038/ncomms1803] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 03/26/2012] [Indexed: 11/09/2022] Open
|
64
|
Zhu X, Fryd MM, Huang JR, Mason TG. Optically probing nanoemulsion compositions. Phys Chem Chem Phys 2012; 14:2455-61. [DOI: 10.1039/c2cp23007k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
65
|
Mayoral K, Kennair TP, Zhu X, Milazzo J, Ngo K, Fryd MM, Mason TG. Rotational Fourier tracking of diffusing polygons. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:051405. [PMID: 22181415 DOI: 10.1103/physreve.84.051405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Indexed: 05/31/2023]
Abstract
We use optical microscopy to measure the rotational Brownian motion of polygonal platelets that are dispersed in a liquid and confined by depletion attractions near a wall. The depletion attraction inhibits out-of-plane translational and rotational Brownian fluctuations, thereby facilitating in-plane imaging and video analysis. By taking fast Fourier transforms (FFTs) of the images and analyzing the angular position of rays in the FFTs, we determine an isolated particle's rotational trajectory, independent of its position. The measured in-plane rotational diffusion coefficients are significantly smaller than estimates for the bulk; this difference is likely due to the close proximity of the particles to the wall arising from the depletion attraction.
Collapse
|
66
|
Datta SS, Gerrard DD, Rhodes TS, Mason TG, Weitz DA. Rheology of attractive emulsions. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:041404. [PMID: 22181143 DOI: 10.1103/physreve.84.041404] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Indexed: 05/31/2023]
Abstract
We show how attractive interactions dramatically influence emulsion rheology. Unlike the repulsive case, attractive emulsions below random close packing, φ(RCP), can form soft gel-like elastic solids. However, above φ(RCP), attractive and repulsive emulsions have similar elasticities. Such compressed attractive emulsions undergo an additional shear-driven relaxation process during yielding. Our results suggest that attractive emulsions begin to yield at weak points through the breakage of bonds, and, above φ(RCP), also undergo droplet configurational rearrangements.
Collapse
|
67
|
Lapointe CP, Mason TG, Smalyukh II. Towards total photonic control of complex-shaped colloids by vortex beams. OPTICS EXPRESS 2011; 19:18182-18189. [PMID: 21935184 DOI: 10.1364/oe.19.018182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We demonstrate optical trapping and orientational control over colloidal particles having complex shapes in an anisotropic host fluid using a dynamic holographic optical tweezers system. Interactions between a colloidal particle and the toroidal intensity distributions of focused Laguerre-Gaussian beams allow for stable optical tweezing and provide a tunable tilt of the particle out of the focal plane. Use of an aligned nematic liquid crystal as the host fluid suppresses rotations about the optical axis arising from angular momentum transfer from the beam and effectively defines a rotational axis for the colloid within the trap.
Collapse
|
68
|
Wilking JN, Chang CB, Fryd MM, Porcar L, Mason TG. Shear-induced disruption of dense nanoemulsion gels. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:5204-5210. [PMID: 21469673 DOI: 10.1021/la200021r] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The structural evolution and rheology of dense nanoemulsion gels, which have been formed by creating strong attractions between slippery nanodroplets, are explored as a function of steady shear rate using rheological small-angle neutron scattering (rheo-SANS). For applied stresses above the yield stress of the gel, the network yields, fracturing into aggregates that break and reform as they tumble and interact in the shear flow. The average aggregate size decreases with increasing shear rate; meanwhile, droplet rearrangements within the clusters, allowed by the slippery nature of the attractive interaction, increase the local density within the aggregates. At the highest shear rates, all clusters disaggregate completely into individual droplets.
Collapse
|
69
|
Wilson SC, Turner C, Green KL, Mason TG, Thurston DE. An Investigation of the Michael Addition of Mesna to Clazamycins A and B. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1990.tb14440.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
70
|
Moseley BD, Burrus TM, Mason TG, Shin C. Neurological picture. Contralateral cutaneous and MRI findings in a patient with Parry-Romberg syndrome. J Neurol Neurosurg Psychiatry 2010; 81:1400-1. [PMID: 20802222 DOI: 10.1136/jnnp.2009.202044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
|
71
|
Lapointe CP, Hopkins S, Mason TG, Smalyukh II. Electrically driven multiaxis rotational dynamics of colloidal platelets in nematic liquid crystals. PHYSICAL REVIEW LETTERS 2010; 105:178301. [PMID: 21231084 DOI: 10.1103/physrevlett.105.178301] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2010] [Indexed: 05/30/2023]
Abstract
We describe field-induced multiaxis rotations of colloids in a nematic liquid crystal. Anchoring of the nematic director to the colloidal platelet's surface and interplay of dielectric and elastic energies enable robust control over colloid orientation that cannot be achieved in isotropic liquids. Because of the anisotropy of the fluid and the platelike shape of particles, the colloids can be forced to rotate about four different rotational axes even for a fixed direction of the applied field. The time scale of these unexpected voltage-dependent dynamics varies over four orders of magnitude (10⁻²-10² s) and promises a number of novel electro-optic, photonic, and display applications.
Collapse
|
72
|
Akkara Veetil BM, Yee AH, Warrington KJ, Aksamit AJ, Mason TG. Aseptic meningitis in adult onset Still’s disease. Rheumatol Int 2010; 32:4031-4. [DOI: 10.1007/s00296-010-1529-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 05/05/2010] [Indexed: 12/01/2022]
|
73
|
Lapointe CP, Mason TG, Smalyukh II. Shape-Controlled Colloidal Interactions in Nematic Liquid Crystals. Science 2009; 326:1083-6. [DOI: 10.1126/science.1176587] [Citation(s) in RCA: 258] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
74
|
Zhao K, Mason TG. Frustrated rotator crystals and glasses of Brownian pentagons. PHYSICAL REVIEW LETTERS 2009; 103:208302. [PMID: 20366016 DOI: 10.1103/physrevlett.103.208302] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Indexed: 05/29/2023]
Abstract
Two-dimensional Brownian dispersions of microscale pentagonal platelets exhibit rich structural and dynamical behavior as the particle area fraction, phi(A), is increased. As phi(A) is raised above 0.66, a rotator crystal forms, and while in an equilateral hexagonal lattice, pentagons still explore all angles as they rotationally diffuse. At larger phi(A), the interference of the tips of neighboring pentagons causes rotational dynamical heterogeneity; particle rotations become nonergodic, the hallmark of a frustrated rotator crystal. Upon further compression, the quenched-in rotational disorder and inability of pentagons to fully tile a flat plane creates spatial defects, precluding access to a dense striped crystalline packing.
Collapse
|
75
|
Abstract
Patients commonly present to primary care physicians with musculoskeletal symptoms. Clinicians certified in internal medicine must be knowledgeable about the diagnosis and management of musculoskeletal diseases, yet they often receive inadequate postgraduate training on this topic. The musculoskeletal problems most frequently encountered in our busy injection practice involve, in decreasing order, the knees, trochanteric bursae, and glenohumeral joints. This article reviews the clinical presentations of these problems. It also discusses musculoskeletal injections for these problems in terms of medications, indications, injection technique, and supporting evidence from the literature. Experience with joint injection and the pharmacological principles described in this article should allow primary care physicians to become comfortable and proficient with musculoskeletal injections.
Collapse
|