Evaluation of kinetic friction between regular and colored titanium molybdenum alloy archwires.

AIM: The aim of this study was to evaluate the kinetic frictional properties of colored titanium molybdenum alloy (TMA) archwires (purple-coated TMA and honey dew-coated TMA) and the regular TMA archwires. MATERIALS AND METHODS: The experiment comprised of three groups, Group I - Regular TMA archwires, Group II - Purple-coated TMA archwires, Group III - Honey dew-coated TMA wires involving 21 samples each that were evaluated for their frictional properties using Instron Universal Testing Machine. RESULTS: The results were subjected to statistical analysis using analysis of variance wherein Group I Regular TMA wires revealed mean kinetic frictional value of 8.236 N and a standard deviation of 0.4038 N, while Group II (purple-coated TMA wires) showed a mean value of 5.297 N, standard deviation of 0.3128 N and Group III (honey dew-coated TMA wires) showed a mean value of 4.206 N and a standard deviation of 0.5353 N. CONCLUSION: The kinetic frictional values are higher for regular TMA wire exhibiting superior characteristic of color-coated TMA. Wires exhibiting superior characteristics are color-coated TMA wires, especially honey dew-coated TMA wires over the regular and purple-coated TMA wires. These superior properties of newly introduced wires can be considered for its application in both details friction and frictionless mechanics in retraction phase of fixed orthodontic treatment.

Salvageability of kidney in Grade IV renal trauma by minimally invasive treatment methods.

CONTEXT: Renal trauma is increasingly being managed conservatively. Grade I-III injuries are managed conservatively whereas Grade V injuries may end in surgery. Managing Grade IV renal trauma is individualized and managed accordingly. AIMS: To evaluate retrospectively all Grade IV renal injuries managed in our institute over five years and to review the available literature. SETTINGS AND DESIGN: Reviewing the records of patients who sustained renal trauma and study all Grade IV renal injuries. MATERIALS AND METHODS: We retrospectively analyzed all Grade IV renal injuries (16) managed at our institute between July 2008-August 2013. All patients were treated conservatively initially by hemodynamic stabilization, strict bed rest, if required endoscopic procedures. These patients were followed up with CECT. STATISTICAL ANALYSIS: Descriptive statistics was performed using Microsoft excel spreadsheet 2007. Continuous data were described as mean and range. Categorical data was described as percentages. RESULTS: Sixteen patients with Grade IV renal injury were included in the study. All patients had gross hematuria and 15 had urinary extravasation. D-J Stenting was done in 7 patients; perinephric tube drainage with D-J stentingwas done in 2 patients. One required selective upper pole arterial embolisation. Nephrectomy was not required in any of the patients. In the follow-up period, no patient had delayed complications. CONCLUSIONS: Successful conservative management of Grade IV renal trauma requires constant monitoring both clinically and radiologically, and if properly managed, kidneys can be salvaged in all stable patients as reinforced by our study.

Centralized PI controllers for interacting multivariable processes by synthesis method.

In this article, two methods of designing a centralized control system for multi-input, multi-output (MIMO) processes are presented. Centralized proportional-integral (PI) controllers are designed based on a direct synthesis method. The inverse of the process transfer function matrix in the direct synthesis method is approximated based on the relative gain array concept. The method is further improved by using a relative normalized gain array, and an equivalent transfer function for each element in the process transfer function matrix is derived for the closed-loop control system. The transpose of the effective transfer function is used to approximate the inverse of the process transfer function matrix. The simulation studies demonstrate the effectiveness of this method. The proposed centralized controllers reduce the interactions better than recently reported decentralized controllers do. A centralized controller designed based on a relative normalized gain array (RNGA) gives a better performance than a centralized controller designed based on a relative gain array (RGA).