Asymmetric Expansion Research Articles

Impact of Asymmetric Stent Expansion on Neointimal Hyperplasia Following Sirolimus-Eluting Stent Implantation

To assess whether asymmetric stent expansion affects suppression of neointimal hyperplasia after sirolimus-eluting stent implantation, 64 patients in the SIRolImUS-coated Bx Velocity stent trial who underwent single 18-mm stent implantation and 3-dimensional intravascular ultrasonography at 8-month follow-up were enrolled. To assess the longitudinal stent asymmetric expansion, 2 cross sections with a maximal/minimal stent area were chosen in each patient. To assess for tomographic stent asymmetric expansion, stent eccentricity was determined by dividing the minimum stent diameter by the maximum stent diameter. At the 2 cross sections with a maximal/minimal stent area, a sirolimus-eluting stent reduced neointimal hyperplasia significantly with no interaction between the treatment and stent areas. A sirolimus-eluting stent also significantly reduced neointimal hyperplasia in the concentric and eccentric stent groups.

PH-responsive swelling behavior of poly(vinyl alcohol)/poly(acrylic acid) bi-component fibrous hydrogel membranes

The pH-responsive dimensional expansion and mass uptake of bi-component hydrogels in the form of fibrous membranes and films were reported. Fibrous membranes and monolithic films were prepared from aqueous mixture of poly(vinyl alcohol) and poly(acrylic acid) at 3.5 COOH/OH molar composition via electrospinning and solution cast, respectively, then cross-linked by heat-induced esterification. Both forms of hydrogels exhibited increasing swelling with increasing pH. For hydrogel fibrous membranes, planar expansion was immediate without the time lag observed on the films, and equilibrium thickness expansion and mass uptake took far longer than planar expansion. The dimensional expansion in the thickness direction was much higher than that in the planar directions for the fibrous membranes, while they were comparable for monolithic films. The peculiar asymmetric dimensional expansion of fibrous membrane is explicable with the asymmetric distribution of the fibers on the planar and thickness directions, which is formed during layer-by-layer collection process of electrospinning. The fibrous membranes distinguished themselves as being far stronger and faster in re-absorption in the swollen state than the cast-films.

Examination of membrane fusion by dissipative particle dynamics simulation and comparison with continuum elastic models

A dissipative particle dynamics model is applied to probe the lipidic membrane fusion. This model is verified by reproducing the lipid phase behavior. The classical stalk model has been visited and modified. The tilt deformation of the lipids and the noncircular shape of the stalk are supported. The stalk is shown to undergo asymmetric expansion to form the trans-monolayers contact (TMC). Unlike previous models, an energy barrier between the stalk and the TMC has been identified, implying that the TMC should be a metastable formation. This shows good agreement with the fusion experiments. Two typical elastic continuum models are compared with our result and possible modifications to the two elastic models are suggested. The effect of spontaneous curvature of lipid on selection of fusion pathway is also examined. It is observed that a bent stalk with pore or an inverted micellar intermediate will have more chance to occur than traditional stalk when the spontaneous curvature of the lipid becomes more negative.

Measurement of kinetic energy dissipation with gelatine fissure formation with special reference to gelatine validation

Various methods for calculating the amount of kinetic energy dissipated by a bullet into ballistic gelatine have been suggested in literature. These methods were compared using the results of thirteen 9 mm × 19 mm pistol and five 7.62 mm × 39 mm rifle bullets shot into 10% ballistic gelatine. The Wound Profile Method gave the highest correlation, 0.89, with the measured amounts of dissipated kinetic energy. The Fissure surface area and total crack length method gained 0.51 and 0.52, respectively. The experimental results were also compared with those from pig tests with the same bullet types. Using the z-test at 95% level of confidence no difference between impact velocity normalized bullet decelerations could be determined for the 9 mm bullet used. The same test showed significant difference for 7.62 mm bullets. That, however, can be considered to be the result of the bullet's tendency to tumble in non-homogenous living tissue causing significant dispersion of observed deceleration values. The results add further evidence supporting the validity of 10% gelatine at +4 °C as wound ballistic tissue simulant. The study also introduces the use of an elastic “shroud” to hold the gelatine in place, to some extent reduce the effects of asymmetric expansion of the gelatine and to simulate the expansion suppression effect of surrounding tissues.

A possibility of parallel and anti-parallel diffraction measurements on neutron diffractometer employing bent perfect crystal monochromator at the monochromatic focusing condition

In a conventional diffractometer having single monochromator, only one position, parallel position, is used for the diffraction experiment (i.e. detection) because the resolution property of the other one, anti-parallel position, is very poor. However, a bent perfect crystal (BPC) monochromator at monochromatic focusing condition can provide a quite flat and equal resolution property at both parallel and anti-parallel positions and thus one can have a chance to use both sides for the diffraction experiment. From the data of the FWHM and the Δd/d measured on three diffraction geometries (symmetric, asymmetric compression and asymmetric expansion), we can conclude that the simultaneous diffraction measurement in both parallel and anti-parallel positions can be achieved.

Mediastinal and chest wall limitations to asymmetry of lung inflation.

The extent to which inflation of one lung increases pleural pressure around the contralateral lung could affect ventilatory function, e.g., after pneumonectomy or lung transplantation. The rise in contralateral pleural pressure is limited by mediastinal stiffness and other chest wall properties. To estimate these properties, we determined an elastance of asymmetric expansion (E(Asym)) in 20 supine adults undergoing thoracic surgery requiring endobronchial intubation. Esophageal pressure, measured with a balloon catheter, was used as an estimate of pleural pressure for determining chest wall elastance during symmetric inflation. Pressures measured in the left and right lung airways during sequential asymmetric inflations with known volumes were used to calculate E(Asym) and elastances of left and right lungs by using a four-element mathematical model. Elastances (means +/- SD) were 13.0 +/- 8.7 (E(Asym)), 14.0 +/- 7.0 (left lung), 12.2 +/- 6.1 (right lung), and 6.7 +/- 2.1 cmH(2)O/l (chest wall). E(Asym) was high in three patients with prior cardiac surgery or mediastinal radiation therapy, suggesting that mediastinal stiffening due to scarring and fibrosis reduced pressure transmission between hemithoraxes. Simulations with a previously published model showed that changes in E(Asym) in the range of values observed could substantially affect lung ventilation after single-lung transplantation for emphysema.

Asymmetric maxillary expansion (AMEX) appliance for treatment of true unilateral posterior crossbite

The aim of this study was to evaluate the effects of an asymmetrical maxillary expansion (AMEX) appliance. Patients with true unilateral posterior crossbites were included in the study. The treatment group consisted of 18 patients who had a mean age of 14 ± 2.3 years. Treatment effects were evaluated on posteroanterior radiographs, dental casts, and photographs of the dental casts. All unilateral posterior crossbites were corrected in a mean expansion treatment time of 3.3 ± 0.48 months. As a result of expansion, maxillary interfirst molar, interfirst and second premolar, and intercanine arch widths increased significantly. Comparison of the 2 sides showed that the teeth on the crossbite side moved and tipped more buccally than the teeth on the noncrossbite side. Of the total expansion gained, 75.8% to 91.7% was due to the buccal movements of the teeth on the noncrossbite side. The AMEX appliance was found to be effective in correcting true unilateral posterior crossbites, and therefore it can be recommended for clinical use. (Am J Orthod Dentofacial Orthop 2002;122:164-73)

A distorted radio shell in the young supernova SN 1986J

We report here on 5 GHz global very-long-baseline interferometry (VLBI) observations of SN1986J, 16 yr after its explosion. We obtained a high-resolution image of the supernova, which shows a distorted shell of radio emission, indicative of a deformation of the shock front. The angular size of the shell is � 4.7mas, corresponding to a linear size of � 6.8 × 10 17 cm for a distance of 9.6 Mpc to NGC 891. The average speed of the shell has decreased from �7400 km s −1 in 1988.74 down to about 6300kms −1 in 1999.14, indicative of a mild deceleration in the expansion of SN1986J. Assuming a standard density profile for the progenitor wind (�cs / r −s ,s = 2), the swept-up mass by the shock front is �2.2M⊙. This large swept-up mass, coupled with the mild deceleration suffered by the supernova, suggests that the mass of the hydrogen-rich envelope ejected at explosion was > 12 M⊙. Thus, the supernova progenitor must have kept intact most of its hydrogen-rich envelope by the time of explosion, which favours a single, massive star progenitor scenario. We find a flux density for SN1986J of �7.2 mJy at the observing frequency of 5 GHz, which results in a radio luminosity of � 1.4 × 10 37 ergs −1 for the frequency range 10 7 –10 10 Hz (� = 0.69;S� / � � ). We detect four bright knots that delineate the shell structure, and an absolute minimum of emission, which we tentatively identify with the centre of the supernova explosion. If this is the case, SN1986J has then suffered an asymmetric expansion. We suggest that this asymmetry is due to the collision of the supernova ejecta with an anisotropic, clumpy (or filamentary) medium.

Broad-band and extremely flat super-continuum generation via optical parametric gain extended spectrally by fourth-order dispersion in anomalous-dispersion-flattened fibers

Broad-band and extremely flat super-continuum (SC) generation phenomenon was found out in propagation of sub-100 fs and pJ optical pulse along very short anomalous-dispersion-flattened fibers (0.6/spl sim/3.4 m). In contrast to the usual SC cases, fiber-optic anomalous-dispersion characteristics are essential. Results of numerical and experimental analyzes suggest that its origin stays in the broad-band optical parametric gain generation whose spectrum is extended by fourth-order dispersion characteristics. The remarkable features of SC spectra are (1) excellent static flatness of /spl plusmn/1 dB over 150 nm (or /spl plusmn/0.5 dB over 100 nm) and (2) asymmetric spectral expansion toward the shorter wavelength side overwhelming S-band.

The ECB and Euro-Area Enlargement

The likely enlargement of euro-area membership will radically change the environment under which monetary policy will be made in the euro area. Within less than a decade, the number of member countries in the euro area could more than double, with the vast majority of accession countries being relatively small in economic terms, compared with current members. Absent reforms, such a significant but asymmetric expansion could impede the effectiveness of the institutional policymaking process of the European Central Bank (ECB) and be seen by some as resulting in the overrepresentation of small member countries in the ECB Council. The paper illustrates these issues, describes the principles on which reforms of the ECB statute could build, and discusses four specific institutional reform scenarios. The analysis coincides with the ECB Council being scheduled to present suggestions for reform by late 2002.

A Semianalytical Model for the Motion of the Trojan Asteroids: Proper Elements and Families

In this paper we develop a semianalytical model to describe the long-term motion of Trojan asteroids located in tadpole orbits around the L 4 and L 5 jovian Lagrangian points. The dynamical model is based on the spatial elliptic three-body problem, including the main secular variations of Jupiter's orbit and the direct perturbations of the remaining outer planets. Based on ideas introduced by A. H. Jupp (1969, Astron. J. 74, 35–43), we develop a canonical transformation which allows the transformation of the tadpole librating orbits into circulating orbits. The disturbing function is then explicitly expanded around each libration point by means of a Taylor–Fourier asymmetric expansion. Making use of the property in which the different degrees of freedom in the Trojan problem are well separated with regard to their periods of oscillation, we are able to find approximate action-angle variables combining Hori's method with the theory of adiabatic invariants. This procedure is applied to estimate proper elements for the sample of 533 Trojans with well determined orbits at December 2000. The errors of our semianalytical estimates are about 2–3 times larger than those previously obtained with numerical approaches by other authors. Finally, we use these results to search for asteroidal families among the Trojan swarms. We are able to identify and confirm the existence of most of the families previously detected by Milani (1993, Celest. Mech. Dynam. Astron. 57, 59–94). The families of Menelaus and Epeios, both around L 4, are the most robust candidates to be the by-product of catastrophic disruption of larger asteroids. On the other hand, no significant family is detected around L 5.

Applications of Planar‐Chiral Heterocycles in Enantioselective Catalysis: Cu(I)/Bisazaferrocene‐Catalyzed Asymmetric Ring Expansion of Oxetanes to Tetrahydrofurans.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Optical Survey of Outlying Ejecta in Cassiopeia A: Evidence for a Turbulent, Asymmetric Explosion

A deep optical survey of the Cassiopeia A supernova remnant has revealed dozens of new emission-line ejecta knots out beyond the remnant's bright nebular shell. Most of the newly detected knots exhibit a 4500-7500 A spectrum dominated by [N II] λλ6548,6583 line emissions. After accounting for possible decelerations, the estimated space velocities for about four dozen of these [N II] knots suggest a nearly isotropic 10,000 km s-1 ejection velocity. However, a small group along the southwestern limb show significantly higher velocities of up to 12,000 km s-1. Over 20 outlying O + S emission knots were also discovered, mostly along the remnant's western limb. These knots have optical spectral properties like those seen in the main shell's metal-rich fast-moving knots but with much higher estimated space velocities of between 7600 and 12,600 km s-1. Discovery of these knots means that the remnant's highest-velocity, O + S debris are not confined to just the remnant's northeast jet. [S II] λλ6716,6731 emissions dominate the spectra of these knots above an expansion velocity of 11,000 km s-1. A few mixed emission knots, which show both strong nitrogen and sulfur line emissions, were also detected along the remnant's western rim. The properties of these outlying debris knots suggest a turbulent supernova expansion in which the innermost S-rich layers were ejected up through overlying material in certain regions, attaining final outward velocities greater than the star's N and He-rich surface layers. The detection of such high-velocity, sulfur-rich ejecta only along the remnant's northeast and southwest limbs further suggests an asymmetric expansion, possibly bipolar. A turbulent expansion may help explain the creation of the observed mixed emission knots. It is unclear, however, if mixed knots represent truly microscopically mixed debris or are simply small, comoving clusters of chemically distinct ejecta.

A bonded functional ramp to aid in asymmetric expansion of unilateral posterior crossbites

Unilateral posterior crossbite is a common finding in patients seeking orthodontic treatment. When treating this condition with a rapid maxillary expander, clinicians occasionally observe no resolution of the crossbite and document an unnecessary overexpansion of the contralateral dentition. This article describes a method for treating unilateral posterior crossbite and, specifically, the lack of crossbite correction after expansion with a rapid maxillary expander. A composite ramp is bonded to the mesial buccal cusp of the maxillary first molar in crossbite. The necessary materials and instruments are typically found in an orthodontic office. This adjunctive procedure requires no more than 5 extra minutes during an examination, and no additional appointments are necessary. (Am J Orthod Dentofacial Orthop 2001;119:320-2)

Relaxation of polymer thin films in isothermal temperature‐jump measurements

The dynamic behavior of thin polymer films is of interest in the fabrication of microelectronics and optoelectronics and in the coatings industry. It is known that polymer relaxation is affected by film thickness and the particular substrate/polymer pair. We previously used a spectroscopic ellipsometer to investigate the glass transition in thin films. In addition to information on the modification of thermal transitions such as the glass-transition temperature, the speed of data acquisition in an automated, spectroscopic ellipsometer, operated at a single wavelength of 780 nm, allows for the direct observation of the isothermal dimensions of a thin polymer film as a function of time after a rapid temperature change. In this article, we discuss recent results from the observation of the time dependence of film-normal thickness and normalized, in-plane, lateral dimension as well as simple fits to this relaxation behavior in terms of a normalized viscosity and relaxation time. The results support a highly asymmetric initial thermal expansion normal to the film followed by close to isotropic relaxation and anisotropic “flow” (the flow in response to the vanishingly small shears of thermal expansion). These features may clarify issues involving the observation of chain confinement in thin polymer films in terms of potential differences between equilibrium and dynamic measurements. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2929–2936, 2000

Cortical development in roots of the aquatic plant Pontederia cordata (Pontederiaceae)

Adventitious roots of marsh-grown Pontederia cordata were examined to determine cortical development and structure. The innermost layer of the ground meristem forms the endodermis and aerenchymatous cortex. The outermost layer of the early ground meristem undergoes a precise pattern of oblique and periclinal cell divisions to produce a single or double layer of prohypodermis with an anchor cell for each radial file of aerenchyma cells. At maturity, endodermal cell walls are modified only by narrow Casparian bands. The central regions of the ground meristem become proaerenchyma and exhibit asymmetric cell division and expansion. They produce an aerenchymatous zone with barrel-shaped large cells and irregularly shaped small cells traversing the aerenchyma horizontally along radii; some crystalliferous cells with raphides are present in the aerenchyma. The walls of the hypodermis are modified early by polyphenols. The outermost layer of the hypodermis later matures into an exodermis with Casparian bands that are impermeable to berberine, an apoplastic tracer dye. The nonexodermal layer(s) of the hypodermis has suberin-modified walls. Radial files of aerenchyma are usually connected by narrow protuberances near their midpoints, the aerenchyma lacunae having been produced by expansion of cells along walls lining intercellular spaces. We are terming this type of aerenchyma development, which is neither schizogenous nor lysigenous, "differential expansion."

Accretional Heating of Asymmetric Supernova Cores

The role of accretion in heating a stalled bounce shock in a core-collapse supernova is investigated. We show that eUective accretional heating causes an asymmetric expansion of the shock, sufficient to impart a net impulse of D300¨400 km s~1 to the neutron core. To simplify the analysis, we consider a failed accretion shock. Below such a shock, inward advection is faster than neutrino heating and the usual gain criterion does not suffice to determine a successful explosion. A mechanism that enhances buoyancy and inhibits mixing between hot and cold postshock —uid elements is required to revive the shock. We focus on the response of a magnetic —eld to the accretion —ow. Ram heating and shearing of a low-density, magnetized —uid phase (ii M-—uid ˇˇ) is shown to be faster than neutrino cooling. The long duration of the accretion —ow compared with the dynamical time allows for a large ampli—cation of the magnetic energy. We calculate the stability of a spherical shock in the presence of a low-density hydro- static atmosphere below it and show that below a critical atmospheric density the shock is unstable to a global Rayleigh-Taylor mode. We then calculate the equilibrium structure of this Rayleigh-Taylor plume as it accumulates energy and the critical size beyond which quasi-static expansion is no longer possible and its outer boundary converts to a running shock. Accretion continues while the shock expands, and an energy of D1051 ergs is a direct consequence of the efficiency of ram heating close to the neutron core. The linear momentum imparted to the core is directly related to the mass pro—le of the precollapse core and explains the proper motions of (most) radio pulsars. We also estimate the net circulation imparted to the last 0.1¨0.2 of collapsing material, which appears sufficient to torque the core down M _ to a spin period of 1¨100 ms. The eUect of photodissociation on the shock jump conditions is calculated, and the implications for nucleosynthesis of iron peak elements are considered. Finally, the residual mag- netic —eld advected out into the eventual supernova remnant is compared with the —eld generated by a rapidly spinning neutron star. Subject headings: accretion, accretion disksshock wavesstars: magnetic —elds ¨ stars: neutronsupernovae: general

Relaxation of polymer thin films in isothermal temperature-jump measurements

The dynamic behavior of thin polymer films is of interest in the fabrication of microelectronics and optoelectronics and in the coatings industry. It is known that polymer relaxation is affected by film thickness and the particular substrate/polymer pair. We previously used a spectroscopic ellipsometer to investigate the glass transition in thin films. In addition to information on the modification of thermal transitions such as the glass-transition temperature, the speed of data acquisition in an automated, spectroscopic ellipsometer, operated at a single wavelength of 780 nm, allows for the direct observation of the isothermal dimensions of a thin polymer film as a function of time after a rapid temperature change. In this article, we discuss recent results from the observation of the time dependence of film-normal thickness and normalized, in-plane, lateral dimension as well as simple fits to this relaxation behavior in terms of a normalized viscosity and relaxation time. The results support a highly asymmetric initial thermal expansion normal to the film followed by close to isotropic relaxation and anisotropic “flow” (the flow in response to the vanishingly small shears of thermal expansion). These features may clarify issues involving the observation of chain confinement in thin polymer films in terms of potential differences between equilibrium and dynamic measurements. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2929–2936, 2000

Nasotemporal asymmetry during teleost retinal growth: preserving an area of specialization.

Teleost fish retinas grow throughout adult life through both cell addition and stretching. Cell division occurs at the periphery of the retina, resulting in annular addition of all cell types except rod photoreceptors, which are added in the central retina. Since many teleosts have a region of high cellular density at the temporal pole of the eye, we analyzed whether and how this specialized region of high visual acuity maintained its relative topographical position through asymmetric circumferential growth. To do this, we measured the pattern of long-term retinal growth in the African cichlid Haplochromis burtoni. We found that the retina expands asymmetrically along the nasotemporal axis, with the nasal retina growing at a higher rate than the temporal, dorsal, or ventral retinae, whose growth rates are equal. This nasotemporal asymmetry is produced via significantly greater expansion of retinal tissue at the nasal pole rather than through differential cell proliferation. The mechanisms responsible for this differential retinal enlargement are unknown; however, such asymmetric expansion very likely minimizes disruption in vision during rapid growth.

1,7-Asymmetric induction in a nitrogen ring expansion process facilitated by in situ tethering.

[formula: see text] There are only a few methods for the asymmetric ring expansion of prochiral ketones. Symmetrically substituted cyclohexanones can be converted to the corresponding ring-expanded caprolactam with excellent 1,7-diastereoselectivity (> or = 93% ds) and yields (> or = 86%), using a chiral hydroxy azide-mediated Schmidt reaction.