Study on stable equilibrium of levitated impeller in rotary pump with passive magnetic bearings

It is widely acknowledged that the permanent maglev cannot achieve stable equilibrium; the authors have developed, however, a stable permanent maglev centrifugal blood pump. Permanent maglev needs no position detection and feedback control of the rotor, nevertheless the eccentric distance (ED) and vibration amplitude (VA) of the levitator have been measured to demonstrate the levitation and to investigate the factors affecting levitation. Permanent maglev centrifugal impeller pump has a rotor and a stator. The rotor is driven by stator coil and levitated by two passive magnetic bearings. The rotor position is measured by four Hall sensors, which are distributed evenly and peripherally on the end of the stator against the magnetic ring of the bearing on the rotor. The voltage differences of the sensors due to different distances between the sensors and the magnetic ring are converted into ED. The results verify that the rotor can be disaffiliated from the stator if the rotating speed and the flow rate of the pump are large enough, that is, the maximal ED will reduce to about half of the gap between the rotor and the stator. In addition, the gap between rotor and stator and the viscosity of the fluid to be pumped also affect levitation. The former has an optimal value of ≈ 2% of the radius of the rotor. For the latter, levitation stability is better with higher viscosity, meaning smaller ED and VA. The pressure to be pumped has no effect on levitation.     

Measurement of rotary pump flow and pressure by computation of driving motor power and speed

Measurement of pump flow and pressure by ventricular assist is an important process, but difficult to achieve. On one hand, the pump flow and pressure are indicators of pump performance and the physiologic status of the receptor, meanwhile providing a control basis of the blood pump itself. On the other hand, the direct measurement forces the receptor to connect with a flow meter and a manometer, and the sensors of these meters may cause haematological problems and increase the danger of infection. A novel method for measuring flow rate and pressure of rotary pump has been developed recently. First the pump performs at several rotating speeds, and at each speed the flow rate, pump head and the motor power (voltage x current) are recorded and shown in diagrams, thus obtaining P (motor power) - Q (pump volume) curves as well as P - H (pump head) curves. Secondly, the P, n (rotating speed) values are loaded into the input layer of a 3-layer BP (back propagation) neural network and the Q and H values into the output layer, to convert P-Q and P-H relations into Q=f (P,n) and H=g (P, n) functions. Thirdly, these functions are stored by computer to establish a database as an archive of this pump. Finally, the pump flow and pressure can be computed from motor power and speed during animal experiments or clinical trials. This new method was used in the authors' impeller pump. The results demonstrated that the error for pump head was less than 2% and that for pump flow was under 5%, so its accuracy is better than that of non-invasive measuring methods.     

Axial reciprocation of rotating impeller: a new concept of antithrombogenecity in centrifugal pump

For long-term application, rotary pumps have to solve the problems of bearing wear and thrombosis along the bearing. Most investigators choose the magnetic bearing to realize zerofriction and no contact between the rotor and stator; the former avoids the mechanical wear and the latter eliminates the possibility of thrombus formation. The authors have tried and found, however, that it is difficult to apply a magnetic bearing to the rotary pump without disturbing its simplicity, reliability and implantability, and have therefore developed a much simpler and much more creative approach to achieve the same results. Instead of using a sliding bearing, a rolling bearing has been devised for the pump, and its friction is about 1/15 of the sliding bearing. Furthermore, a wear-proof material of ultra-high-molecular weight polythene has been adopted to make the rollers, and its anti-wear property is 8 times better than metal. Thereby, the service life of the bearing has been prolonged to ten years according to the documents provided by the producer. In order to prevent the thrombus formation along the bearing, the impeller reciprocates axially as the impeller changes its rotating speed periodically to produce a pulsatile flow. The reciprocation is the result of the effects of a magnetic force between the motor rotor and stator, and a hydraulic force between the blood flow and the impeller. Similar to a piston pump, the oscillating impeller can make the blood flow in and out of the bearing, resulting in wash-out once a circle. This obviously helps to prevent thrombosis along the bearing and in the pump. The endurance tests with saline of this novel pump demonstrated the durability of the device. It promises to be able to assist the circulation of patients permanently, and to be able to replace heart transplantation in the future.     

Ventricular remodeling in growing rats with experimental diabetes: The impact of swimming training

Diabetic cardiomyopathy is associated with cardiac muscle remodeling, resulting in myocardial dysfunction, whereas exercise training (ET) is a useful nonpharmacological strategy for the therapy of cardiac diseases. This study tested the effects of low-intensity swimming-training on the structural remodeling of the left ventricle (LV) in growing rats with unmanaged experimental diabetes. Thirty-day-old male Wistar rats were divided into four groups (n = 5/group): sedentary-control (SC), exercised-control (EC), sedentary-diabetic (SD), and exercised-diabetic (ED). Swimming-training rats exercised 5 days/week, 90 min/day, with a load of 5% BW during 8 weeks. Sections of LV were stained with Periodic acid-Schiff, Sirius Red, and Gomori's reticulin. Seven days and 8 weeks after streptozotocin (STZ) induction (60 mg kg⁻¹ BW), blood glucose (BG) in the diabetic groups (SD = 581.40 ± 40.48; ED = 558.00 ± 48.89) was greater (p < 0.05) than in their controls (SC = 88.80 ± 21.70; EC = 85.60 ± 11.55). Swimming-training reduced BG by 23 mg/dL in the diabetics (p > 0.05). The LV of diabetic rats had increased interstitial collagen and reticular fibers on the extracellular matrix and presented glycogen accumulation. More importantly, all these adverse tissue changes induced by STZ were attenuated by ET. Together, these findings support the idea of a beneficial role of exercise in the LV remodeling in rats with unmanaged type-1 diabetes mellitus.     

The value of asphericity derived from T1-weighted MR in differentiating intraparenchymal ring-enhancing lesions–comparison of glioblastomas and brain abscesses

Neurological Sciences - Both brain abscess(BA)and glioblastoma (GBM) are common causative pathologies of intraparenchymal ring-enhancing lesions. Advanced MR sequences such as diffusion weighted...     

Sustained and differential antibody responses to virulence proteins of Brucella melitensis during acute and chronic infections in human brucellosis

Brucellosis is an important zoonotic disease caused primarily by the bacterial pathogens Brucella melitensis and B. abortus. The pathogens cause debilitating febrile illness that can progress into a long-lasting disease with severe complications in humans. Understanding the mechanisms by which the host immune system responds to the infection will provide important information on the pathogenesis and development of differential diagnostic assays. In this study, a protein microarray was used to evaluate the antibody responses of brucellosis patients at different infection stages. A total of 107 outer membrane proteins, surface-exposed or secreted proteins, and known or putative virulence-associated proteins of B. melitensis were successfully expressed in Escherichia coli and used to fabricate the protein microarray. Then, 99 serum samples from acute, chronic, primary infection, or relapse brucellosis patients were probed with the protein microarray. Antibodies to 66 of the proteins were detected at least in one serum sample. Among the antigens, the combination of BMEII0318, BMEII0513, BMEI0748, and BMEII1116 could be used as serodiagnostic antigens for brucellosis. Patients at different infection stages show distinct antibody profiles. The numbers of antibodies in the relapse patients were superior to those in the primary infection patients, and the response magnitude of antibodies in the chronic infection patients was higher than those in the acute brucellosis patients. The sustained and differential antibody profiles of patients at different infection stages have implications for the development of new serological methods for the accurate diagnosis of human brucellosis, and contribute to a more detailed understanding of the pathogenesis of chronic brucellosis.     

Application of modern neuroimaging technology in the diagnosis and study of Alzheimer's disease

Neurological abnormalities identified via neuroimaging are common in patients with Alzheimer's disease. However, it is not yet possible to easily detect these abnormalities using head computed tomography in the early stages of the disease. In this review, we evaluated the ways in which modern imaging techniques such as positron emission computed tomography, single photon emission tomography, magnetic resonance spectrum imaging, structural magnetic resonance imaging, magnetic resonance diffusion tensor imaging, magnetic resonance perfusion weighted imaging, magnetic resonance sensitive weighted imaging, and functional magnetic resonance imaging have revealed specific changes not only in brain structure, but also in brain function in Alzheimer's disease patients. The reviewed literature indicated that decreased fluorodeoxyglucose metabolism in the temporal and parietal lobes of Alzheimer's disease patients is frequently observed via positron emission computed tomography. Furthermore, patients with Alzheimer's disease often show a decreased N-acetylaspartic acid/creatine ratio and an increased myoinositol/creatine ratio revealed via magnetic resonance imaging. Atrophy of the entorhinal cortex, hippocampus, and posterior cingulate gyrus can be detected early using structural magnetic resonance imaging. Magnetic resonance sensitive weighted imaging can show small bleeds and abnormal iron metabolism. Task-related functional magnetic resonance imaging can display brain function activity through cerebral blood oxygenation. Resting functional magnetic resonance imaging can display the functional connection between brain neural networks. These are helpful for the differential diagnosis and experimental study of Alzheimer's disease, and are valuable for exploring the pathogenesis of Alzheimer's disease.     

Application of metagenomic next-generation sequencing in the diagnosis and treatment guidance of Pneumocystis jirovecii pneumonia in renal transplant recipients

European Journal of Clinical Microbiology & Infectious Diseases - Pneumocystis jirovecii&nbsp;pneumonia (PJP) is difficult to be diagnosed, so this study explored if PJP could be diagnosed...