Analysis of the atomic force microscopy vibration behavior using the Timoshenko theory by multi-scale method in the air environment.

This article deals with the modeling and simulation of the vibration behavior of piezoelectric micro-cantilever (MC) based on the Timoshenko theory and using multi-scale (MTS) method in the air environment. In this regard, the results are compared with the previous literature, such as the finite element method and the MTS method. The analysis of the piezoelectric MC vibrating behavior is investigated in a dynamical mode including non-contact and tapping modes. The dynamics of this system is affected by interferential forces between probe tip and sample surface, such as van der Waals, capillary, and contact forces. According to the results, the forces applied to the probe tip reduce the amplitude and the resonance frequency. The simulation of surface topography in non-contact mode and tapping for rectangular and wedge-shaped roughness in the air environment are presented. Various experiments have been conducted in Ara research Company using the atomic force microscopy device in the amplitude mode. In the NSC15 Cantilever, the first natural frequency is derived from the results of the MC simulation based on Timoshenko beam theory, the practical results are 295.85 and 296.12 kHz, and the error rate is 0.09; at higher natural frequencies, the error rate has been increased. The γ f coefficient is a measure of the nonlinear effects on the system; the effect of the piezoelectric length and width on γ f coefficient is also investigated.

Neural network sliding mode controller of atomic force microscope-based manipulation with different cantilever probes.

Development of nanotechnology has given rise to various applications, including the nano-manipulation process within small-size environments. The implementation of such processes requires the use of tools and proper equipment and understanding of various factors influencing it. One such tool is the atomic force microscope (AFM) and its probe, used for imaging surfaces and manipulation tools. The AFM probe is the most important element of the AFM with a key role in system function. The dynamic analysis and control of AFM are necessary to increase efficiency. In this paper, a model of AFM is reviewed and rewritten by considering various cantilever probes, including rectangular, V-shaped, and dagger. The AFM actuator was modeled and analyzed on uncertain conditions. The position of the stage was controlled to the desired position through the desired motion profiles. To overcome the problem of model nonlinearity, a neural network (NN) sliding mode controller was used to optimize the controller parameter and provide the desired output. The simulation of system was performed by the effective parameters, its control was implemented, and the results were analyzed. The simulation revealed that the modified sliding mode controller with learnable NN improved controller performance by decreasing the rise time and eliminating the overshot.

Endoscopic implantation and patency evaluation of lumboperitoneal shunt: an innovative technique.

BACKGROUND: The placement of the lumboperitoneal (LP) shunt tube used in the management of idiopathic intracranial hypertension (IIH) and the evaluation of its patency necessitate an abdominal surgical incision. This procedure can now be done using a laparoscopic-assisted technique. This study was designed to evaluate the usefulness of this technique in treating patients with IIH in whom visual loss was progressive in spite of aggressive medical management, as well as for the evaluation of the function of the shunt tube after its placement. METHODS: Seventeen patients aged between 21 and 45 years (mean, 31) were included in the study. They were divided into two groups. Laparoscopy was used in the first group of 11 patients for primary placement of the peritoneal portion of shunt catheter in the right subphrenic recess. It was used in the second group, which consisted of six patients who had recurrence of symptoms after surgical LP shunt placement, for the evaluation of shunt patency and position inside the peritoneal cavity and for the repositioning of the displaced shunt, as needed. RESULTS: In the first group (n = 11), visual symptomatology was improved in 10 of 11 patients and became stable in the remaining one. In the second group (n = 6), two of six patients had a patent tube in a proper position; three had complete intraperitoneal migration of the shunt tubes, which were repositioned using a laparoscopic-assisted technique; and the last patient had occlusion of the peritoneal side of the shunt by omental adhesions that had been liberated by the laparoscopy. No complications related to laparoscopy were recorded in this series. CONCLUSION: This procedure was associated with better functional results, less postoperative pain and discomfort, a shorter hospital stay, an earlier return to normal activities, and cosmetic acceptability .

Magnetic resonance imaging of tuberculous spondylitis.

STUDY DESIGN: This retrospective study analyzed the magnetic resonance imaging characteristics of tuberculous spondylitis. OBJECTIVE: To describe the magnetic resonance imaging characteristics of tuberculous spondylitis and compare the diagnostic yield of magnetic resonance imaging versus other modalities. SUMMARY OF BACKGROUND DATA: Tuberculous spondylitis is not an uncommon occurrence with extrapulmonary disease. It requires prompt diagnosis and management. In the pre-magnetic resonance imaging era, computed tomography was used to delineate the associated radiologic changes. Data are limited that describe the magnetic resonance imaging pattern of tuberculous spondylitis and the effect of post-contrast enhancement. METHODS: The magnetic resonance imaging characteristics of 28 vertebrae in 12 patients with tuberculous spondylitis were studied. RESULTS: The thoracic spine was the most commonly involved region, with involvement occurring in the thoracic spine alone in 12 vertebrae (43%) and with other areas of the spine in an additional five (18%). Partial involvement was detected in the majority of the vertebral lesions (24; 86%). Magnetic resonance imaging evidence of disc space involvement was apparent in only 46% of the lesions. Paraspinal abscess and epidural extension were documented by magnetic resonance imaging in 71% and 61% of lesions, respectively. Decreased signal intensity on T1-weighted images was demonstrated in 13 vertebrae (46%), with increased signal intensity on T2-weighted images seen only in five (18%). CONCLUSION: Magnetic resonance imaging is a useful diagnostic modality for patients with suspected tuberculous spondylitis. Partial vertebral involvement and paraspinal and epidural extension were delineated. Study of the signal intensity on T1- and T2-weighted images revealed a pattern that may be dissimilar to that commonly reported. Post-contrast enhancement adds more certainty to the diagnosis of tuberculous spondylitis.

Synthesis of some new 3,5-pyrazolidinedione derivatives of expected biological activity.

4-Arylidene-1,2-diphenyl-3,5-pyrazolidinedione were synthetized. The alkyl and nitrile derivatives were also obtained. The structure of the synthesized compounds was elucidated by chemical and physical routes.