Corrosion behavior of pulse electrodeposited nanostructure Ni-SiC composite coatings

Ni-SiC nano-composite coatings with various contents of SiC were prepared by pulse electrodeposition from a modified Watts bath containing SiC nano-particles. The effect of SiC concentration, current density, duty cycle and pulse frequency on the corrosion behavior of the coatings was investigated by means of potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) methods. It has been found that the Ni-SiC composite coatings show better corrosion resistance in a 3.5% NaCI solution than pure nickel. The corrosion resistance of the coatings increases by increasing the amount of embedded SiC particles. This improvement can be attributed to the morphology and the crystallographic texture of the coatings.

Load transfer by fine threading the implant neck--a FEM study

Osseointegration of dental implants up-to-date is a well-confirmed phenomenon, however the long-term stability and integrity of the bone and soft tissue collar is under discussion. A homogenous distribution of the bone loading is a prerequisite for bone modelling and preservation in the neck area while overload must be avoided. Based on the finite element method (FEM) models of implants without and with a fine thread (implant types Tiolox and tioLogic) with surrounding bone were generated and analysed using the FE program system MSC.Marc/Mentat. The alveolar bone was considered to be an idealized segment with a cortical bone thickness of 2 or 3 mm, respectively with an enclosed spongy bone. The implants were loaded with forces up to 300 N in two different directions, in the first case with a purely vertical force and in other case with an additional lateral force component with a angle of 45 degrees with respect to the occlusal plane. The deflections of the implants ranged from 0.004 to 0.017 mm in the load direction, depending on the implant diameter and the cortical bone thickness. When considering a physiological vertical load of a maximum of 100 N, the highest strains were about 2100 micro strain in the spongy bone. Within the fine thread in the neck area of the implant, the maximum stresses were increased in the cortical bone by 3%. The improvement of implant anchorage in the cortical bone reduced the strains in the spongious bone, at the same time there were no additional stress peaks visible at the fine thread region.

Efficacy of Pharmacotherapy and Cognitive Therapy, alone and in Combination in Major Depressive Disorder

Objective:

To assess the efficacy of pharmacotherapy (citalopram) and cognitive therapy, alone or in combination for the treatment of major depressive disorder.

Methods:

This study was a randomised controlled clinical trial. We randomly assigned 120 adults with a major depressive disorder to 8-week treatment with either citalopram, cognitive therapy, or both. Major depressive disorder was diagnosed using DSM-IV criteria. Patients were assessed with the Beck Depression Inventory before and after treatment.

Results:

Statistical analysis showed that cognitive therapy, pharmacotherapy, and combined therapy were effective in the treatment of depression. There was no significant difference between medication and cognitive therapy. Treatment with the cognitive therapy intervention and citalopram combined yielded better responses than treatment with citalopram or cognitive therapy alone.

Rubella serology in pregnant women attending health centres of Tehran University of Medical Sciences

This study was performed in 2003-05 to determine the serological status of a sample of pregnant women as a preliminary study for the rubella vaccination programme. Out of 965 pregnant women attending health centres affiliated to Tehran University of Medical Sciences for prenatal care, the estimated rubella immunity rate was 91.1% (95% CI: 89.3%-92.9%) and the nonimmunity rate was 8.9% (95% CI: 7.1%-10.7%). The rubella immunity rate differed in different areas of Tehran but not significantly so. However, there was a significant difference in the level of rubella immunity by the number of persons per household and by age, but no significant relationship with economic status, occupation or level of education.

Computer-aided analysis of the biomechanics of tooth movements

Orthodontic biomechanics started in the early 1960s with the work of Burstone and later Nikolai. Experimental and theoretical studies using finite element methods (FEM) focused on the determination of the position of the center of resistance of single and multi-rooted teeth. Due to the complex structure of the system tooth/periodontal ligament/alveolar bone and because of the limited power of computers, the first numerical models were quite simple. Improved FE software, sophisticated programs for model generation and the explosion of computer power in the last decade resulted in more complex tooth-periodontium models and model assumptions. This paper describes the application of finite element methods in orthodontic biomechanics with the help of several typical examples. The examples cover aspects from basic orthodontic biomechanics to possible future applications in treatment planning using bone remodelling theories: determination of the mechanical properties of the periodontal ligament in a combined numerical and experimental study, calculation of the centers of resistance of different teeth, and simulation of orthodontic tooth movements. The examples show that nowadays finite element methods are a useful and easy-to-handle tool for the solution of a larger number of structure-mechanical and biomechanical problems. Nevertheless, in spite of the enormous technical progress in the last decade, many problems in orthodontic biomechanics remain to be solved.

Early and Long-term Results of Replacement of the Descending Aorta

OBJECTIVES

The aim of this analysis was to evaluate our results of open surgery on the descending thoracic aorta as benchmark to define indications for endovascular treatment.

METHODS

Between January 1981 and December 2000, 115 patients underwent replacement of the descending or thoraco-abdominal aorta. Follow-up to 20 years was complete in 98%.

RESULTS

Early mortality was 19% and paraplegia rate was 7%. Surgery before 1990 and coronary artery disease were independent predictors for early mortality. Thoraco-abdominal repair and normothermia were independent predictors for paraplegia. Ten years survival rate was 63%.

CONCLUSIONS

Our results confirm that replacement of the descending aorta can be performed today with acceptable low mortality and morbidity and with consistent exclusion of the aneurysm or dissection. Long-term results of endovascular stent-grafts in the descending aorta are unclear. In our opinion endovascular stent-grafts should be reserved for high risk patients, acute dissection or acute aortic rupture.