Dependence of chaotic behavior on optical properties and electrostatic effects in double beam torsional Casimir actuation

We investigate the influence of Casimir and electrostatic torques on double beam torsional microelectromechanical systems with materials covering a broad range of conductivities of more than three orders of magnitude. For the frictionless autonomous systems, bifurcation and phase space analysis shows that there is a significant difference between stable and unstable operating regimes for equal and unequal applied voltages on both sides of the double torsional system giving rise to heteroclinic and homoclinic orbits, respectively. For equal applied voltages, only the position of a symmetric unstable saddle equilibrium point is dependent on the material optical properties and electrostatic effects, while in any other case there are stable and unstable equilibrium points are dependent on both factors. For the periodically driven system, a Melnikov function approach is used to show the presence of chaotic motion rendering predictions of whether stiction or stable actuation will take place over long times impossible. Chaotic behavior introduces significant risk for stiction, and it is more prominent to occur for the more conductive systems that experience stronger Casimir forces and torques. Indeed, when unequal voltages are applied, the sensitive dependence of chaotic motion on electrostatics is more pronounced for the highest conductivity systems.Comment: 24 pages, 11 figure

Sensitivity of actuation dynamics on normal and lateral Casimir forces:Interaction of phase change and topological insulator materials

We investigated here the influence of the lateral and normal Casimir force on the actuation dynamics between sinusoidal corrugated surfaces undergoing both normal and lateral displacements. The calculations were performed for topological insulators and phase change materials that are of high interest for device applications. The results show that the lateral Casimir force becomes stronger by increasing the material conductivity and the corrugations toward similar sizes producing wider normal separation changes during lateral motion. In a conservative system, bifurcation and Poincaré portrait analysis shows that larger but similar in size corrugations and/or higher material conductivity favor stable motion along the lateral direction. However, in the normal direction, the system shows higher sensitivity on the optical properties for similar in size corrugations leading to reduced stable operation for higher material conductivity. Furthermore, in non-conservative systems, the Melnikov function with the Poincaré portrait analysis was combined to probe the possible occurrence of chaotic motion. During lateral actuation, systems with more conductive materials and/or the same but high corrugations exhibit lower possibility for chaotic motion. By contrast, during normal motion, chaotic behavior leading to stiction of the moving components is more likely to occur for systems with more conductive materials and similar in magnitude corrugations

Dynamical Casimir actuation under non-equilibrium conditions:The influence of optical properties from different interacting bodies

In this work we investigated the dynamical actuation of microsystems with non-identical material components in the presence of non-equilibrium Casimir forces between Au and highly doped SiC that show significant difference in conductivity. For autonomous systems, the bifurcation and phase space analysis revealed that when the less conductive material operates at higher temperature, then at short separations the non-equilibrium force causes instability. Furthermore, for periodically driven systems the Melnikov function and Poincare portrait analysis showed that the devices are more robust against chaotic motion when the less conductive component is at low temperature at short separations. At larger separations chaotic behavior is more likely to occur for systems with the more conductive component at higher temperature.</p

Comparing the effects of alcoholic extract of ginseng with itraconazole against Candida albicans and Candida krusei

Background: Candidiasis is a prevalent disease which is caused by different species of Candida. Herbal drugs (e.g. ginseng) were traditionally administrated for the treatment of different diseases. This study was carried out to compare the effect of alcoholic extract of ginseng with Itraconazole against Candida albicans (C. albicans) and Candida krusei (C. krusei). Material and Methods: This cross-sectional study was crried out on 22 and 8 species of C.albicans and 8 C.krusei, respectively which were isolated from vagina, urine and sputum of the patients. Using the CLSI M27 and disk diffusion methods the susceptibility test was done by Itraconazole (10 &micro;g) and ginseng extract (1, 2, 4, 8, 16, 32, 64 and 128 mg.ml-1). The standard species of C. albicans (PTCC 5027) and C. Krusei (PTCC 5295) were used for the quality control purposes. Results: The lowest and highest minimum inhibitory concentration (MIC) for C. albicans and C. Kruzei was 0.0625 and 0.5 &mu;g.ml-1, respectively for Itraconazole using the microdilution method. However, the lowest MIC and minimum fungal concentration (MFC) for alcoholic extract was 64 mg.ml-1 .The highest inhibition zone for C. albicans was 14 and 14-32 mm for alcoholic extract and Foritraconazole, respectively. Using the two methods no significant difference was seen between the alcoholic extract of ginseng (64 and 128 mg.ml-1) and the drug. (P&lt;0.05) Conclusion: Considering the MICs and disk diffusion results, the ginseng extract (64,128 mg.ml-1) shows considerable antifungal effects compared to Itraconazole

Nonlinear actuation of micromechanical Casimir oscillators with topological insulator materials toward chaotic motion:Sensitivity on magnetization and dielectric properties

We have investigated the dynamical actuation of micro-electromechanical systems under the influence of attractive and repulsive Casimir forces between topological insulator plates as a function of their dielectric function and coating magnetization. The analysis of the Casimir force in the limit of strong and weak magnetization shows that the attractive force, which is produced for plate magnetizations in the same direction, is greater than the repulsive force that is produced for opposite magnetizations. However, both forces remain comparable for intermediate magnetizations. Moreover, for weak magnetization, the attractive force becomes stronger for an increasing dielectric function, while the opposite occurs for the repulsive force. On the other hand, increasing magnetization decreases the influence of the dielectric function on both the repulsive and attractive forces. Furthermore, for conservative systems, bifurcation and phase portrait analysis revealed that increasing magnetization decreases the regime of stable operation for devices with attractive forces, while their operation remains always stable under the presence of repulsive forces. Finally, for non-conservative periodically driven systems, the Melnikov function and Poincaré portrait analysis show that for magnetizations in the same direction leading to strong attractive Casimir forces, chaotic motion toward stiction is highly likely to occur preventing the long-term prediction of actuating dynamics. A remedy for this situation is obtained by the application of any magnetization in opposite directions between the interacting surfaces since the repulsive force makes it possible to prevent stiction

Non-surgical removal of some stones from a red tailed catfish (Phractocephalus hemioliopterus) stomach as gastric foreign bodies

A red-tailed catfish (Phractocephalus hemioliopterus) referred to Aquatic Animal Health Department, Faculty of Veterinary Medicine, University of Tehran for showing lethargy, bottom sitting, extension of abdomen and severe abdominal injuries. Its abdomen was swollen and the bulk of the foreign bodies were easily palpated. The heaviness of foreign bodies had made swimming and buoyancy difficult for fish. Several radiographic images were taken after anaesthetizing the catfish with 10% carvacrol, 2 drops in 1 liter of water. Radiographs revealed some stones with their size, number and location. Stones were removed non-surgically through the large oral cavity using suitable forceps. Totally 16 stones and 2 shells were removed from the stomach of the fish. The catfish was then returned to the water where normal swimming and buoyancy was restored

Sensitivity of nonequilibrium Casimir forces on low frequency optical properties toward chaotic motion of microsystems:Drude vs plasma model

Here, we investigate the sensitivity of nonequilibrium Casimir forces to optical properties at low frequencies via the Drude and plasma models and the associated effects on the actuation of microelectromechanical systems. The stability and chaotic motion for both autonomous conservative and nonconservative driven systems were explored assuming good, e.g., Au, and poor, e.g., doped SiC, interacting conductors having large static conductivity differences. For both material systems, we used the Drude and plasma methods to model the optical properties at low frequencies, where measurements are not feasible. In fact, for the conservative actuating system, bifurcation and phase space analysis show that the system motion is strongly influenced by the thermal nonequilibrium effects depending on the modeling of the optical properties at low frequencies, where also the presence of residual electrostatic forces can also drastically alter the actuating state of the system, depending strongly on the material conductivity. For nonconservative systems, the Melnikov function approach is used to explore the presence of chaotic motion rendering predictions of stable actuation or malfunction due to stiction on a long-term time scale rather impossible. In fact, the thermal effects produce the opposite effect for the emerging chaotic behavior for the Au-Au and SiC-SiC systems if the Drude model is used to model the low optical frequencies. However, using the plasma model, only for the poor conducting SiC-SiC system, the chance of chaotic motion is enhanced, while for the good conducting Au-Au system, the chaotic behavior will remain unaffected at relatively short separations (<2 μm)

Dependence of non-equilibrium Casimir forces on material optical properties toward chaotic motion during device actuation

The sensitivity of nonequilibrium Casimir forces on material optical properties can have strong impact on the actuation of devices. For this purpose, we considered nonequilibrium Casimir interactions between good and poor conductors, for example, gold (Au) and highly doped silicon carbide (SiC), respectively. Indeed, for autonomous conservative systems, the bifurcation and phase portrait analysis have shown that the nonequilibrium Casimir forces can have significant impact on the stable and unstable operating regimes depending on the material optical properties. At a few micrometer separations, for systems with high conductivity materials, an increasing temperature difference between the actuating components can enhance the stable operation range due to the reduction of the Casimir force, while for the poor conductive materials, the opposite takes place. For periodically driven dissipative systems, the Melnikov function and Poincare portrait analysis have shown that for poor conductive systems, the nonequilibrium Casimir forces lead to an increased possibility for chaotic behavior and stiction with an increasing temperature difference between the actuating components. However, for good conducting systems, the thermal contribution to Casimir forces reduces the possibility for chaotic behavior with increasing temperature, as comparison with systems without thermal fluctuations shows. Nevertheless, the positive benefit of good conductors toward increased actuation stability and reduced the chaotic behavior under nonequilibrium conditions can be easily compromised by any voltage application. Therefore, thermal, nonequilibrium Casimir forces can influence the actuation of devices toward unstable and chaotic behavior in strong correlation with their optical properties, and associated conduction state, as well as applied electrostatic potentials

Public Health Outcomes as a Measure of Efficacy of Syringe Exchange Programs

Introduction. A syringe exchange is a public health intervention that offers nonjudgmental services to intravenous drug users (IVDU), providing clean syringes in exchange for used syringes. While prior studies demonstrated that syringe exchanges can reduce transmission of HIV, hepatitis C, and other blood-borne pathogens, other measures of health improvements have been less studied. Methods. 91 members of Vermont CARES syringe exchange program were surveyed on their healthcare practices. New members were defined asprogram. Results. Long-term members tended to have a primary care provider (PCP). Lack of insurance and fear of judgment were commonly cited reasons for not having a PCP. Long-term members were significantly less likely (p=0.04) to use costly emergency department (ED) services and less likely to reuse their own or another person\u27s needles. Long-term members were more likely to be in addiction treatment and reported a greater desire to abstain from drug use. New members were more likely to obtain hepatitis C and HIV testing in the past year. Discussion. Subjects responded positively to the possibility of accessing PCP services through VT CARES, offering a continuation of the nonjudgmental healthcare environment. Decreased ED visits significantly correlated with longer membership, reflecting the positive impact of the syringe exchange education services on reducing healthcare costs. Decreased testing among long-term members may reflect prior knowledge of their status. Long-term members were less likely to reuse their own needles or ones used by another person, suggesting the distribution of clean syringes encourages safer injection practices.https://scholarworks.uvm.edu/comphp_gallery/1247/thumbnail.jp

Diagnosis of lipomatous hypertrophy of the atrial septum by two-dimensional echocardiography

Originally described in 1964, lipomatous hypertrophy of the atrial septum currently remains a diagnosis established primarily at autopsy. Clinical interest in this disorder has centered on the reported association with supraventricular arrhythmias and sudden death. Because two-dimensional echocardiography allows detailed assessment of atrial septal configuration, we reviewed two-dimensional echocardiographic reports obtained over a 1 year period and identified 17 patients who had features consistent with lipomatous hypertrophy of the atrial septum. Nine were men and the average age was 70 years. Autopsy confirmation of the echographic findings was possible in one patient. In nine patients, ideal body weight was exceeded by 10% or more. The atrial septum viewed from the subcostal transducer position showed a distinctive echo-dense globular thickening sparing the valve of the fossa ovalis. The resultant tomographic image of the atrial septum had a characteristic dumbbell appearance. The mean thickness of the atrial septum was 21 mm (range 15 to 29). Seven patients had supraventricular arrhythmias, and eight had P wave abnormalities.The two-dimensional echocardiographic features described are distinctive and suggest that this technique is the procedure of choice not only for establishing the diagnosis of lipomatous hypertrophy of the atrial septum but also for providing a means for prospective follow-up of patients with this little known entity