19 research outputs found
Chaotic behavior of gas bubble in non-Newtonian fluid: A numerical study
In the present paper, the nonlinear behavior of bubble growth under the excitation of an acoustic pressure pulse in non-Newtonian fluid domain has been investigated. Due to the importance of the bubble in the medical applications such as drug, protein or gene delivery, blood is assumed to be the reference fluid. Effects of viscoelasticity term, Deborah number, amplitude and frequency of the acoustic pulse are studied. We have studied the dynamic behavior of the radial response of bubble using Lyapunov exponent spectra, bifurcation diagrams, time series and phase diagram. A period-doubling bifurcation structure is predicted to occur for certain values of the effects of parameters. The results show that by increasing the elasticity of the fluid, the growth phenomenon will be unstable. On the other hand, when the frequency of the external pulse increases the bubble growth experiences more stable condition. It is shown that the results are in good agreement with the previous studies. © 2013 Springer Science+Business Media Dordrecht
Effect of magnetic field on the radial pulsations of a gas bubble in a non-Newtonian fluid
Dynamics of acoustically driven bubbles' radial oscillations in viscoelastic fluids are known as complex and uncontrollable phenomenon indicative of highly active nonlinear as well as chaotic behavior. In the present paper, the effect of magnetic fields on the non-linear behavior of bubble growth under the excitation of an acoustic pressure pulse in non-Newtonian fluid domain has been investigated. The constitutive equation [Upper-Convective Maxwell (UCM)] was used for modeling the rheological behaviors of the fluid. Due to the importance of the bubble in the medical applications such as drug, protein or gene delivery, blood is assumed to be the reference fluid. It was found that the magnetic field parameter (B) can be used for controlling the nonlinear radial oscillations of a spherical, acoustically forced gas bubble in nonlinear viscoelastic media. The relevance and importance of this control method to biomedical ultrasound applications were highlighted. We have studied the dynamic behavior of the radial response of the bubble before and after applying the magnetic field using Lyapunov exponent spectra, bifurcation diagrams and time series. A period-doubling bifurcation structure was predicted to occur for certain values of the parameters effects. Results indicated its strong impact on reducing the chaotic radial oscillations to regular ones. © 2015 Elsevier Ltd. All rights reserved
Detection of Mycobacterium avium subsp. paratuberculosis in Cow Milk Using Culture and PCR methods
Mycobacterium avium subspecies paratuberculosis (MAP) is the cause of John’s disease also calledparatuberculosis. This is economically one of the important infectious diseases in cattle and ruminanthusbandry. This disease is manifested as granulomatosis entrocolitis, lymphadenitis and inflammation locallymphatic vessels. The typical sign of this disease is progressive loss of weight. Considering the importanceof detection of this disease in this study, two methods, culture and PCR, were used for the identification ofthis microorganism. In this study 100 milk samples from apparently healthy cows and 100 milk samplesfrom cows that have been suspicious of John’s disease were taken from in Sarab, East Azarbaijan, Iran.Direct microscope observation after ziehl-neelsen staining was done. Then, bacterial culture on specificmedium was carried out, and finally, identification of Mycobacterium avium subsp. paratuberculosis wasexamined using PCR and specific primers. Using direct observation, culture and PCR analyses showed thatfrom 100 healthy cow milk samples, 8, 9 and 12 samples were positive MAP for each method respectively.The results of direct observation, culture and PCR analysis on affected cows were 15, 40 and 44, respectively. The results of this study showed that culture and PCR analyses methods are important in the identification of the causes of this disease. Therefore, considering the frequency of the disease in the studied region, either of those methods can be used in the microorganism identification
Mesoscale Computational Techniques in Interfacial Science: Smoothed Particle Hydrodynamics Method
Identification and determination of the prevalence of Toxoplasma gondii in patients with chronic renal failure by ELISA and PCR
Objective: To detect Toxoplasma gondii (T. gondii) among end-stage renal disease (ESRD) patients. Methods: This case-control study was conducted on 180 blood samples. In compliance with all ethical principles, 90 blood samples were taken from hemodialysis patients with ESRD and 90 samples from healthy volunteers. T. gondii screening was done using ELISA to search for immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies and by PCR for amplification of the T. gondii genome using specific primers. Results: The results were analyzed using SPSS software. Out of 90 patients on hemodialysis, 54 (60.0) were positive for anti-toxoplasma IgG antibody, 3 (3.3) for anti-toxoplasma IgM antibody and 5 patients (6) were positive by PCR. From 90 healthy volunteers, 34 (37.8) were positive for anti-toxoplasma IgG antibody. All the healthy volunteers were negative for anti-toxoplasma IgM antibody and in PCR. Compared with the gold standard method of ELISA, PCR had 100 sensitivity and 98.9 specificity in detection of T. gondii. Conclusions: PCR alongside serologic methods can be valuable for T. gondii screening. Given the high prevalence of T. gondii among hemodialysis patients with ESRD, T. gondii screening together with sanitary control of biological agents was recommended in dialysis units. © 2016 Asian Pacific Tropical Medicine Press
Lethal Pneumocystis jiroveci pneumonia 24 Years After Kidney Transplantation
INTRODUCTION: Pneumocystis jiroveci is an opportunistic infectious fungus in immunosuppressed patients, particularly in ones with acquired immunodeficiency syndrome (AIDS). The use of immunosuppressive drugs especially corticosteroids predisposes the transplanted patients to a variety of infectious diseases including Pneumocystis infection. In many developed countries, the incidence of Pneumocystis jiroveci pneumonia (PJP) is dwindling in transplant patients receiving appropriate prophylaxis. In this study, definitive diagnosis of Pneumocystis infection in a patient receiving kidney transplant was presented. CASE PRESENTATION: The patient was a 45-year-old man with a history of kidney transplantation 24 years ago, admitted to a specialized hospital in Tehran because of fever and respiratory distress. Upon admission, the patient showed symptoms of unconsciousness and shortness of breath. Paraclinical tests and complementary examinations such as microscopic observation and molecular analysis confirmed the definitive diagnosis of Pneumocystis infection. Specific treatment with trimethoprim/sulfamethoxazole was carried out alongside other therapeutic measures; but unfortunately the patient did not respond to the specific treatment and died in the course of a progressive disease. DISCUSSION: The disease progress in these patients can still be fast and deadly. Applying rapid molecular diagnostic techniques to start appropriate and timely treatment is essential. Utilization of such diagnostic methods is recommended in our country