Enhanced thermodynamic stability of tetragonal-phase field in epitaxial Pb(Zr,Ti)O-3 thin films under a two-dimensional compressive stress

A two-dimensional thermodynamic model was developed to account for the observed difficulty in the fabrication of epitaxial Pb(Zr,Ti)O-3 (PZT) thin films in which tetragonal and rhombohedral phases coexist. The thermodynamic formalism based on the Landau-Devonshire's phenomenological theory predicts the enhanced thermodynamic stability of the tetragonal-phase field under a two-dimensional compressive stress. We have experimentally proved this prediction by fabricating an epitaxially oriented tetragonal PZT thin film on MgO substrate with the target composition corresponding to the bulk morphotropic phase boundary (MPB). (C) 1998 American Institute of Physics.open1160sciescopu

Thermodynamic theory of stress distribution in epitaxial Pb(Zr, Ti)O-3 thin films

A phenomenological thermodynamic model has been developed to account for the effects of the film thickness on various properties of ferroelectric thin films. To this end, we have suitably incorporated a position-dependent stress distribution function into the elastic Gibbs function. Various physical properties can be predicted as a function of the film thickness using this modified thermodynamic formalism. A comparison of the theoretical predictions with experimental values of the average strain and the para-ferro transition temperature indicates that the tensile stress caused by the cubic-tetragonal displacive phase transition dominates over the compressive thermal stress in the epitaxially oriented tetragonal Pb(Zr, Ti)O-3 thin films. (C) 1999 American Institute of Physics. [S0003-6951(99)05546-1].open1158sciescopu

Injection scheme with deflecting cavity for a fourth-generation storage ring

We suggest a new on-axis injection scheme that uses a transverse deflecting rf cavity to kick the incoming beam into an already populated bucket but with a timing offset from the synchronous phase. In a new on-axis injection scheme, two deflecting rf cavities are required: one upstream of the injection point that crabs the stored beam and the other downstream of the injection point that both uncrabs the stored beam and kicks the incoming beam onto the axis of the orbital plane. We present a theoretical analysis and numerical simulations of the stored beam and injected beam with the new injection scheme.11Ysciescopu

Percutaneous Full Endoscopic Ligamentum Flavum Splitting Interlaminar Approach for Removal of Dorsally Migrated Lumbar Disc Herniation: A case Report with Technical Note

Treatment of dorsally migrated lumbar disc described so far commonly in present literature is removal by open technique through hemi or complete laminectomy or by use of microsurgical technique or by partial use of endoscope without use of irrigation system. We present a case of dorsally migrated disc herniation treated safely with good outcome by Percutaneous Full Endoscopic Ligamentum Flavum Splitting Interlaminar Approach. A 60 years old man presented with subacute onset of back pain and right leg radiating pain with weakness of right great toe dorsiflexion and diagnosed as a case of dorsally migrated L4-5 disc herniation was treated with this technique. He had also subtle instability at that level.His pain resolved immediately after surgery. Weakness of right great toe also resolved gradually in 2 months. Postoperative X-ray showed no further instability. Postoperative MRI revealed complete removal of disc with resolution of cauda equina compression. No complication was noted related to this technique. This new technique ultimately preserves motion segment while simultaneously addressing symptomatic pathology of dorsally migrated HNP with added benefits of minimally invasive spine surgery

Knuckling Down on Predictive Factors for Early Relapse after Posterolateral Percutaneous Endoscopic Lumbar Discectomy

Objective Percutaneous endoscopic lumbar discectomy (PELD) has several advantages, but it is not used routinely due to early relapse and steep learning curve. We have studied the factors associated with early relapse in patients who underwent posterolateral PELD at or above the L4-5 level. Methods In this retrospective study, we have enrolled 200 cases and divided them into 4 groups (A, B, C, and D) with 50 patients in each group, that had undergone PELD by 2 different techniques (inside-out and outside-in with or without anti-adhesive agent) and operated by 2 different surgeons between May 2009 and November 2010. The factors studied were - Age, gender, disc (degeneration grade, location, level), associated adjacent level herniated nucleus pulposus (HNP), episode (first or recurrent), anti-adhesive agent, annulus preservation, approach, disc height and segmental dynamic motion (discrepancy in flexion and extension). Statistical analysis was done by Pearson’s chi-square test and p value (significance). The clinical results were evaluated by visual analogue scale (VAS). Results The mean age and mean follow-up period was comparable in all four groups. The overall recurrence rate was 9.5% (19/200). Average early relapse time was 3.26 months. Factors like Age of the patient, multilevel HNP and degeneration grade showed significant correlation with relapse rate. The change in VAS pre-operatively to post-operatively was significant across all groups (p<0.001). Conclusion Based on the results of this study, high grade disc degeneration, multilevel disc herniation, and early postoperative activity are significantly associated with early relapse after PELD