Helical Defects Research Articles

The lobular transposition flap: A useful adjunct to reconstruct helical defects

We detail our adjunct to Antia and Buch's chondrocutaneous advancement flap for helical reconstruction. It is simple, reliable and negates the need for transfer of the defect to the lobule and/or V-Y advancement of the helical crus.

Effect of die geometry on helical defect during extrusion of PDMS across a radial flow upstream the contraction

The present work aims at analyzing the influence of both die geometry and entry flow on the appearance and the evolution of the helical defect. The experiments have been performed with linear polydimethylsiloxane (PDMS) via a capillary rheometer in which a convergent radial flow was created upstream the contraction. For a small gap width of radial flow, it was demonstrated that the decrease of the die length-to-die diameter ratio allows the reduction of the helical defect. Moreover, with a short die, when the gap width-to-die diameter ratio is reduced, the helical defect is lessened. In fact, compared to the average diameter of extrudate, the helix pitch and the distortion amplitude are reduced when the die is of a small length and a large diameter as well as the radial flow is of a small gap width.

Successful Reconstruction of a Large Helical Rim Defect Using Retroauricular Artery Perforator-Based Island Flap

The retroauricular flap has many applications, providing coverage for various portions of the face as a pedicled flap or a free flap. The retroauricular skin, having similar attributes to the facial skin, is an ideal donor site for facial reconstruction. Also, the donor site can be primarily closed without morbidity, which is also an advantage. In this article, a large helical defect resulting from a traumatic amputation was reconstructed using the contralateral conchal cartilage graft and a retroauricular perforator-based island flap. Using the "perforator pedicled propeller flap" concept, no meticulous dissection around the perforator was done, and the flap was elevated only until sufficient rotation arc was achieved. There was some degree of venous congestion on the flap for 3 days postoperatively, but the flap survived completely. By using the conchal cartilage from the contralateral side, the final contour of the ear was maintained aesthetically. The flap had some bulkiness on the posterior side of the auricle where it was transposed, but it was inconspicuous on frontal or lateral view because the conchoscaphal angle had not changed. The patient was satisfied with the aesthetic results. The retroauricular flap is useful for resurfacing any portion of the ear, and by using the propeller flap method, significant reduction in operative time can be achieved without compromising the final results.

Helical defects in smectic-Aand smectic-A∗phases

There are two categories of helical line defects in Sm-A phases: screw dislocations of small Burgers vectors and double helices (DHs), whose macroscopic configuration constitutes a mode of splitting of screw dislocations of giant Burgers vectors. Their counterparts in Sm-A∗'s (Sm-A's with chiral molecules) show a number of differences with the former and are investigated theoretically on the basis of recent observations [C. Meyer, Liq. Cryst. 37, 1047 (2010)]. The first part of the paper is a short review of the main features of helical defects in Sm-A's proper. In Sm-A∗'s, small Burgers vector screw dislocations with the same chirality as the high-temperature N∗ phase are favored over the opposite ones, a result that is related to the defect core singularity. This is also true for the macroscopic DH∗ s for a more subtle reason; we advance that the DH∗ nucleation at the N∗→Sm-A∗ transition stems from a peculiar texture of the cybotactic groups, akin in the ideal case to a set of two twisted χ disclinations in the N∗ phase, linked by a stacking fault of continuous disclinations. This stacking fault vanishes in the Sm-A∗ phase, and one recovers a DH∗ much similar to a DH but with the appropriate chirality. Cases that differ from ideality are described: they involve small Burgers vector screw dislocations and can be evoked to explain the numerous observed distorted double helices (the Darboux condition is not obeyed) and twisted ribbons. The case when the N∗→Sm-A∗ transition is type II (presence of a twist grain boundary phase in between) is briefly discussed.

Auricular reconstruction with the use of a modified rhomboid flap

Sir, We describe a simple, safe one-stage procedure for reconstruction of marginal helical defects. Auricular reconstruction after trauma, burn or local excision of tumours has been a common challenge in plastic surgery. Apart from functional importance, the ear also has great aesthetic value, because it frames the face and provides symmetry. A common defect on the ear is partial loss of the helical margin with or without a cartilage defect. Keeping general principles in mind, one can consider various surgical options, based on a reconstructive triangle approach. One effective solution is the use of the rhomboid flap [1]. The skin defect over the superior part of the ear can be covered by a superiorly based random pattern post-auricular flap designed on the non-hair bearing area, this has the advantage of having the same skin colour as the original auricular skin (Figs. 1, 2, 3 and 4). Although the dimensions and shape of both defect and flap are precise, they are variables in planning, namely which of four potential flaps should be used, and the axis around which the excisional rhomboid is be drawn. It is possible to manipulate these variables in such a way that closure of the secondary defect makes use of the laxity of the skin present (use of Dufourmental instead of Limberg flap). A further advantage of this flap is that the donor site scarring comes to lie behind the ear and is, therefore, inconspicuous. The anterior edge of the flap can be cut along the retroauricular sulcus. The greater skin mobility on the post-auricular surface, coupled with the fact that ear tolerates being set back closer to the head, increases the role of this flap considerably. There is some loss of the curve of the helical margin, but patients tend to be in an older age group and thus the result can be acceptable. For small defects, a simple transposition flap that is designed as a formal rhomboid flap is a useful option (Figs. 5, 6). In this situation, Fortier-Riberdy et al. gave some useful tips [2]:

Double helical defects in smectic A and smectic A* phases

Double helical (DH and DH*) domains, defects of the smectic A (SmA) phase, have for the first time been studied in the smectic A* (SmA*) phase, composed of chiral molecules. Both left- and right-handed DH*s are found in SmA*s, but not in equal numbers. The majority of the DH*s in the two left-handed cholesterics studied are left-handed, whereas in the SmA phase of non-chiral molecules the DHs are left- and right-handed in equal numbers. DHs and DH*s, which are topologically screw dislocations of giant Burgers vectors, appear to be significantly distorted with respect to a geometrically ideal model. It has been shown that imperfections in the DH*s and DHs are covered by a combination of three types of elementary distortions. The relation between the pitch in DH* and DH and temperature is discussed.

Caudal Antia–Buch reconstruction for helical defect reconstruction: Burow’s triangle always in the lobule

Different reconstructive techniques regarding helical ear defect reconstruction exist. The best cosmetic results are achieved using the modified Antia–Buch chondrocutaneous advancement flaps. In addition to this flap when it is caudally based, we always place Burow’s triangle in the earlobe. This technique provides the most normal cosmetic appearance of the ear without the need for a cranial-based flap in most cases.

The visor ear flap: a new method for reconstruction of upper helical defects

Helical defects in the upper pole of the ear have been traditionally reconstructed by a variety of techniques. However, some of these techniques decrease the length of the ear while others produce a bulky helix. This paper describes a new technique in which a visor flap is raised from the medial aspect of the ear to form the soft tissue cover of the helical rim. A rotation flap is subsequently raised to cover the donor defect of the visor flap and a conchal cartilage graft taken from underneath the rotation flap is used to construct the helical cartilage. This method has the advantage of being a single-staged procedure, avoids reduction in the length of the ear and provides acceptable cosmetic result. The visor ear flap should be a valuable tool in the armamentarium of reconstructive procedures for upper helical defects.

Effect of Chain Topology on the Self-Organization and Dynamics of Block Copolypeptides: From Diblock Copolymers to Stars

The effect of chain topology on (i) the peptide secondary structure, (ii) the nanophase self-assembly, and (iii) the local segmental and global peptide relaxations has been studied in a series of model diblock and 3-arm star copolypeptides of poly(epsilon-carbobenzyloxy-L-lysine) (PZLL) and poly(gamma-benzyl-L-glutamate) (PBLG) with PZLL forming the core. Diblock copolypeptides are nanophase separated with PBLG and PZLL domains comprising alpha-helices packed in a hexagonal lattice. Star copolypeptides are only weakly phase separated, comprising PBLG and PZLL alpha-helices in a pseudohexagonal lattice. Phase mixing has profound consequences on the local and global dynamics. The relaxation of the peptide secondary structure speeds up, and the helix persistence length is further reduced in the stars, signifying an increased concentration of helical defects.

The Modified Chondrocutaneous Advancement Flap for the Reconstruction of Helical Defects of the Ear

The Modified Chondrocutaneous Advancement Flap for the Reconstruction of Helical Defects of the Ear

Investigation of LDPE converging flows using fieldwise measurements techniques

This study is devoted to the analysis of the secondary flow of a low-density polyethylene melt occurring in the entrance region of extrusion dies. From a processing point of view, the appearance of secondary flows can lead to flow instabilities (as observed for helical defect in circular channels) and polymer degradation (due to long residence times). The flow is investigated in the entrance region of a flow channel by means of both Laser Doppler Velocimetry (LDV) and Flow Induced Birefringence (FIB) using a transparent slit die with a planar contraction of 14:1. We focus on the influence of temperature T and flow rate Q on the vortex size of the secondary flow, which strongly depends on balance between shear and extensional rheological properties of the material, as previously observed by means of LDV. The same dependence with T and Q is also observed on FIB patterns, in which one can identify a boundary line which exhibits a strong contrast in the birefringence pattern. This contrast could be related to the fact that molecular conformations (and consequently the birefringence pattern) change locally due to a different thermomechanical history, which indeed would occur close to the vortex boundary.

The Modified Chondrocutaneous Advancement Flap for the Reconstruction of Helical Defects of the Ear

*Consultant, University of Geneva Vevey, Switzerland Address correspondence and reprint requests to: Andreas M. Skaria, MD, Mohs Surgeon, Rue de Lausanne 15, 1800 Vevey, Switzerland, or e-mail: [email protected] Andreas M. Skaria, MD, has indicated no significant interest with commercial supporters.

Thermodynamic Confinement and α-Helix Persistence Length in Poly(γ-benzyl-l-glutamate)-b-poly(dimethyl siloxane)-b-poly(γ-benzyl-l-glutamate) Triblock Copolymers

The structure and the associated dynamics of a series of poly(gamma-benzyl-L-glutamate)-b-poly(dimethyl siloxane)-b-poly(gamma-benzyl-L-glutamate) (PBLG-b-PDMS-b-PBLG) triblock copolymers were investigated using small- and wide-angle X-ray scattering, NMR, transmission electron microscopy, and dielectric spectroscopy, respectively. The structural analysis revealed phase separation in the case of the longer blocks with defected alpha-helical segments embedded within the block copolymer nanodomains. The alpha-helical persistence length was found to depend on the degree of segregation; thermodynamic confinement and chain stretching results in the partial annihilation of helical defects.

Tubed flap interpolation in reconstruction of helical and ear lobe defects.

A useful reconstructive tool, as a delayed method, for marginal defects of the ear of more than 2.5 cm wide with no deficit of the cartilaginous frame and low scapha involvement, consists of tubed flaps raised from neighboring areas. The patients treated with this technique sustained a dog bite in three cases, a human bite in one case, a motorcycle accident in one case, and finally, a burn trauma in two cases. Three different cases of acquired marginal defects, namely ascending superior helix, descending helix, and cauda elicis with lobule involvement, are shown. In the helix reconstruction, the tube width has not to be more than 15 mm, and the tube length has to be 1 cm longer than the defect. There was no conditioning of the flaps. No pedicle bridge was interposed along the major tube. The interval between two divisions was on average approximately 5 weeks. Seven patients were treated with this technique: In all cases, we had no infections or skin necrosis. To avoid a shrinkage of the tube, a correct ratio between flap dimensions and helical defect has to be estimated. Although it is considered an old technique and it is a multistage reconstructive sequence, this procedure could be the first preference in cases of marginal defects more than 2.5 cm wide. This is because it restores naturally the anatomy of the helix.

Lamellar-to-nematic phase transition in a lipid-surfactant mixture

A lyotropic system, consisting of a lecithin (DMPC) and a non-ionic surfactant (C12E5) in water was studied. The system exhibits a lamellar-to-nematic phase transition. The nematic phase appears as the temperature is decreased and only exists in a very limited temperature and concentration range, for specific lipid-to-surfactant ratios. While a lamellar phase is found at higher temperatures in both mixed and pure C12E5 systems, the transition to the nematic phase at lower temperatures coincides with a micellar phase in the pure C12E5 system. The transition appears to be driven by the strong temperature dependence of the surfactant film spontaneous curvature. The structural properties of the lamellar phase close to the lamellar-to-nematic boundary have been studied by polarised light microscopy and small-angle neutron and X-ray scattering experiments. The signature of a helical defect with Burgers vector of magnitude 2 is apparent in our data, close to the lamellar-to-nematic phase transition. The proliferation of screw dislocations in the lamellar phase might be a plausible mechanism for driving this transition.

Fluoropolymer force fields derived from semiempirical molecular orbital calculations

Abstract The van der Waals parameters for Lennard-Jones (6–12) and 6–9 potentials and equilibrium geometries for use in molecular mechanics and dynamics calculations on perfluoroalkanes and polytetrafluoroethylene (PTFE) have been derived from MOPAC AM1 (Austin model 1) semiempirical calculations on the model molecule perfluorohexadecane (PFHD). Parameters derived from MOPAC AM1 energies scaled to yield higher barriers to torsional motion, as suggested by ab initio results, provide a large trans barrier and stronger intermolecular attractions, which will probably be important for dynamics investigations into the nature of the solid-state phase transitions and helical defects. Reasonable intramolecular geometries and intermolecular packing arrangements are obtained with all parameter sets reported.

Self-assembled microstructures from 1,2-ethanediol suspensions of pure and binary mixtures of neutral and acidic biological galactosylceramides

Optical and electron microscopy were employed to characterize microstructures formed by thermal-mechanical treatment of glycol suspensions of various pure and binary mixtures of the brain-derived galactosphingolipids hydroxy fatty acid cerebroside (HFA-Cer), non-hydroxy fatty acid cerebroside (NFA-Cer) and sulfatide (S-Cer). Negative staining indicated some new features of the neutral cerebroside suspensions in glycol. HFA-Cer formed a small fraction of both unilamellar cylinders (ULCs) (lumina ca. 27 nm) and giant multilamellar cochleates in addition to the typical nonhelical multilamellar cylinders (MLCs) (lumina ca. 10–30 nm). NFA-Cer formed a gel composed of a significant fraction of very long ULCs (lumina ca. 17 nm) without helical substructure, in addition to multilamellar helical structures such as ribbons and cylinders (lumina ca. 70 nm). Anisotropic lamellar micelle-shards of NFA-Cer were also detected by negative staining. S-Cer formed short ULCs (lumina ca. 44 nm) with no obvious helical substructure. Complex mixture data are thought to result from thermodynamic and kinetic factors. HFA-Cer is highly insoluble and promotes a network of rigid intralamellar hydrogen bonding that tends to exclude other lipids. NFA-Cer stabilizes helical defects in the lamellae, and S-Cer enhances disorder or micellization. The processes of microstructure nucleation and lipid phase separation were affected by mixtures such that metastable microstructures were trapped or the length of lamellar cylinders was altered.

耳介軟骨皮膚弁を用いた耳介部分欠損再建術

A 73-year-old man was treated surgically for a 20×18mm granulomatous hemorrhagic squamous cell carcinoma on the posterior aspect of the middle third of the helix. Tumor excision with a 7-8mm margin including subjacent cartilage left a rectangular skin defect on the anterior surface and a wedge shaped skin defect on the posterior. The width of the helical defect was 3.5mm.A chondrocutaneous advancement flap, as described by Antia, was modified conform to the arterial supply to the ear. The auricular segmental defect was repaired successfully with a wider chondrocutaneous helical flap than that described by Antia. The reconstructed ear was reduced by 9mm longitudinally and 2mm transversely, with the lobulus 6mm shorter than its original size.No signs of recurrence were visible seven month after surgery.