Various Approaches In Literature Research Articles

Infraorbital approach for retrobulbar orbital neurofibroma: a case report

<p class="abstract">Retrobulbar orbital tumours are rare and treatment is challenging. These tumors include cavernous hemangioma, neurofibroma, A-V malformations, glioma etc. A variety of approaches have been used in resection of these tumours. The various approaches in literature include endoscopic transethmoidal and sphenoidal, lateral orbitotomy, transmaxillary infraorbital, and cranial and sub cranial approaches. Such tumours located inferior to the optic nerve can be reached through infraorbital approach avoiding traction on optic nerve or pressure on globe. We are reporting a retrobulbar orbital neurofibroma in a middle aged lady who presented with unilateral loss of vision, episodic giddiness, severe left sided headache, left orbital pain and epiphora on exposure to sunlight. MRI showed well defined 1.8×1.8×1.7 cm enhancing lobulated solid left intraorbital mass extending along the substance of inferior aspect of left optic nerve with mass effect. With transmaxillary infraorbital endoscope assisted approach, the retrobulbar tumor was exposed and enucleated. Floor of orbit was reconstructed with tensor fascia lata and nasal septal cartilage graft. The patient had uneventful recovery and immediate post operative visual acuity was perception of light and likely to improve further. Histopathology revealed neurofibroma. This case report highlights the advantages of infraorbital approach as it is a simple approach along the suture lines through the orbital floor with the help of endoscopic guidance. It has the advantages of avoiding traction on optic nerve or optic chiasma, no retraction of brain, no communication with cranial cavity, no pressure on globe and easy reconstruction of orbital floor.</p>

Strain gradient elasticity with geometric nonlinearities and its computational evaluation

Abstract Background The theory of linear elasticity is insufficient at small length scales, e.g., when dealing with micro-devices. In particular, it cannot predict the “size effect” observed at the micro- and nanometer scales. In order to design at such small scales an improvement of the theory of elasticity is necessary, which is referred to as strain gradient elasticity. Methods There are various approaches in literature, especially for small deformations. In order to include geometric nonlinearities we start by discussing the necessary balance equations. Then we present a generic approach for obtaining adequate constitutive equations. By combining balance equations and constitutive relations nonlinear field equations result. We apply a variational formulation to the nonlinear field equations in order to find a weak form, which can be solved numerically by using open-source codes. Results By using balances of linear and angular momentum we obtain the so-called stress and couple stress as tensors of rank two and three, respectively. Since dealing with tensors an adequate representation theorem can be applied. We propose for an isotropic material a stress with two and a couple stress with three material parameters. For understanding their impact during deformation the numerical solution procedure is performed. By successfully simulating the size effect known from experiments, we verify the proposed theory and its numerical implementation. Conclusion Based on representation theorems a self consistent strain gradient theory is presented, discussed, and implemented into a computational reality.