The Shapes of Flux Domains in the Intermediate State of Type-I Superconductors

In the intermediate state of a thin type-I superconductor magnetic flux penetrates in a disordered set of highly branched and fingered macroscopic domains. To understand these shapes, we study in detail a recently proposed "current-loop" (CL) model that models the intermediate state as a collection of tense current ribbons flowing along the superconducting-normal interfaces and subject to the constraint of global flux conservation. The validity of this model is tested through a detailed reanalysis of Landau's original conformal mapping treatment of the laminar state, in which the superconductor-normal interfaces are flared within the slab, and of a closely-related straight-lamina model. A simplified dynamical model is described that elucidates the nature of possible shape instabilities of flux stripes and stripe arrays, and numerical studies of the highly nonlinear regime of those instabilities demonstrate patterns like those seen experimentally. Of particular interest is the buckling instability commonly seen in the intermediate state. The free-boundary approach further allows for a calculation of the elastic properties of the laminar state, which closely resembles that of smectic liquid crystals. We suggest several new experiments to explore of flux domain shape instabilities, including an Eckhaus instability induced by changing the out-of-plane magnetic field, and an analog of the Helfrich-Hurault instability of smectics induced by an in-plane field.Comment: 23 pages, 22 bitmapped postscript figures, RevTex 3.0, submitted to Phys. Rev. B. Higher resolution figures may be obtained by contacting the author

Anatomical and Physiological Changes Following Primary Palatoplasty Using the Buccal Flap Approach

Individuals born with cleft palate typically undergo primary palatoplasty between 6-12 months of age to repair their palate. Traditional primary palatoplasty surgical techniques include the V-Y pushback, the intravelar veloplasty, the von Langenbeck approach, and the Furlow Z-plasty. However, approximately 5-20% of patients present with velopharyngeal dysfunction post-surgery and require a secondary surgery for speech. The buccal flap approach, another surgical technique, has been used at the time of primary palatoplasty, during secondary surgery for velopharyngeal dysfunction (VPD) and for fistula repair. Study outcomes related to the buccal flap approach have failed to fully document the resulting anatomic changes in the velopharyngeal (VP) anatomy but have reported promising perceptual speech outcomes. The study was designed to use magnetic resonance imaging (MRI) to evaluate how the use of the buccal flap approach, used during primary palatoplasty, alters VP anatomy and physiology. Specifically, VP anatomy was evaluated for anatomical differences and function in comparison to non-cleft individuals to determine if the use of a buccal flap creates a more normal VP system for adequate VP closure. Significant differences for effective velar length, effective VP ratio, sella-nasion-subspinale (SNA) angle, sella-nasion-supramentale (SNB) angle, and velar stretch were noted between the two groups. There were no significant differences for velar thickness, velar length, VP portal depth, nasion-sella-basion (NSBa) angle or subspinale-nasion-supramentale (ANB) angle. This study defined anatomic changes resulting from primary palate repair using the buccal flap approach. Results from the study add valuable information to the literature on VP and craniofacial changes following the use of this specific surgical technique. As a secondary contribution, this study highlights the utility of using MRI to quantify the changes that occur to the VP anatomy following the buccal flap surgical approach and may help improve diagnostic and treatment approaches for individuals with cleft palate

Anatomical and Physiological Changes Following Primary Palatoplasty Using the Buccal Flap Approach

Individuals born with cleft palate typically undergo primary palatoplasty between 6-12 months of age to repair their palate. Traditional primary palatoplasty surgical techniques include the V-Y pushback, the intravelar veloplasty, the von Langenbeck approach, and the Furlow Z-plasty. However, approximately 5-20% of patients present with velopharyngeal dysfunction post-surgery and require a secondary surgery for speech. The buccal flap approach, another surgical technique, has been used at the time of primary palatoplasty, during secondary surgery for velopharyngeal dysfunction (VPD) and for fistula repair. Study outcomes related to the buccal flap approach have failed to fully document the resulting anatomic changes in the velopharyngeal (VP) anatomy but have reported promising perceptual speech outcomes.\r\n\r\nThe study was designed to use magnetic resonance imaging (MRI) to evaluate how the use of the buccal flap approach, used during primary palatoplasty, alters VP anatomy and physiology. Specifically, VP anatomy was evaluated for anatomical differences and function in comparison to non-cleft individuals to determine if the use of a buccal flap creates a more normal VP system for adequate VP closure. Significant differences for effective velar length, effective VP ratio, sella-nasion-subspinale (SNA) angle, sella-nasion-supramentale (SNB) angle, and velar stretch were noted between the two groups. There were no significant differences for velar thickness, velar length, VP portal depth, nasion-sella-basion (NSBa) angle or subspinale-nasion-supramentale (ANB) angle. \r\n\r\nThis study defined anatomic changes resulting from primary palate repair using the buccal flap approach. Results from the study add valuable information to the literature on VP and craniofacial changes following the use of this specific surgical technique. As a secondary contribution, this study highlights the utility of using MRI to quantify the changes that occur to the VP anatomy following the buccal flap surgical approach and may help improve diagnostic and treatment approaches for individuals with cleft palate