Simulation Of Blood Flow Through Mechanical Heart Valve Using Ansys Fluid Structure Interaction

A successful mechanical prosthetic heart valve design is the bileaflet valve, which has been implanted for the first time more than 20 years ago. A key feature of bileaflet valves is the geometry of the two leaflets, which can be very important in determining the flow field. The aim of this research is to observe the flow pattern of the blood through the heart valve with different leaflets curvatures. In addition, the structural analysis of the leaflets was investigated. The simulation is carried out using ANSYS Fluid Structural Interaction(FSI). Particle image velocimetry experiment will also be conducted to validate the simulation results. Finally, the results such as velocity contour and vorticity are compared, revealing great similarity in leaflet motion and flow fields between the numerical simulation and the experimental test. Also, in this study, the leaflets which curved inwards with greater degrees are found to be the best configuration as it allows the greatest blood flow dynamic. Moreover, the maximum von mises stress is found to be at the hinge region. These results will serve as a basis for valve design to improve the hemodynamic of the heart

Clinical Characteristics and Risk Factors for Mortality in Patients with Meningitis Caused by Staphylococcus aureus and Vancomycin Minimal Inhibitory Concentrations Against These Isolates

Background/PurposeBacterial meningitis caused by Staphylococcus aureus is uncommon but has a high mortality rate. The aims of this study were to better understand the clinical manifestations of S. aureus meningitis, to identify the risk factors for mortality in the affected patients, and to determine the levels of vancomycin minimal inhibitory concentrations (MICs) against these pathogens.MethodsA retrospective study of patients with S. aureus meningitis hospitalized between December 2000 and December 2008 was made, and vancomycin MICs against S. aureus isolates was determined using Etest.ResultsAmong 37 patients with S. aureus meningitis, fever was most commonly observed. Twenty-six patients (70.3%) had received prior neurosurgery, and 24 (64.9%) patients were suffering from methicillin-resistant S. aureus (MRSA) infections. The vancomycin MIC of 2 μg/mL was found in 23 (74.2%) of 31 S. aureus isolates available for testing. Excluding three patients who did not receive antibiotics for their S. aureus meningitis the mortality rate was 35.3% in the 34 remaining patients, with concurrent infective endocarditis an independent risk factor for mortality (odds ratio = 21.00; 95% confidence interval, 1.834-240.515; p = 0.01).ConclusionPatients with S. aureus meningitis and concurrent infective endocarditis were at a higher risk of mortality. A vancomycin MIC of 2 μg/mL against a substantial number of S. aureus isolates that grew from the cerebrospinal fluid suggests the importance of obtaining trough vancomycin concentrations of 15-20 μg/mL for the treatment of MRSA meningitis

Structural and Thermodynamic Factors of Suppressed Interdiffusion Kinetics in Multi-component High-entropy Materials

We report multi-component high-entropy materials as extraordinarily robust diffusion barriers and clarify the highly suppressed interdiffusion kinetics in the multi-component materials from structural and thermodynamic perspectives. The failures of six alloy barriers with different numbers of elements, from unitary Ti to senary TiTaCrZrAlRu, against the interdiffusion of Cu and Si were characterized, and experimental results indicated that, with more elements incorporated, the failure temperature of the barriers increased from 550 to 900°C. The activation energy of Cu diffusion through the alloy barriers was determined to increase from 110 to 163 kJ/mole. Mechanistic analyses suggest that, structurally, severe lattice distortion strains and a high packing density caused by different atom sizes, and, thermodynamically, a strengthened cohesion provide a total increase of 55 kJ/mole in the activation energy of substitutional Cu diffusion, and are believed to be the dominant factors of suppressed interdiffusion kinetics through the multi-component barrier materials

Acute myocarditis in dengue hemorrhagic fever: a case report and review of cardiac complications in dengue-affected patients

SummaryWe report a case of dengue hemorrhagic fever (DHF) complicated by acute myocarditis and review the literature. A 65-year-old woman experienced DHF due to dengue virus serotype 3, complicated with acute myocarditis and acute pulmonary edema. Clinically this masqueraded as acute myocardial infarction, with an electrocardiographically depressed ST segment in precordial leads and elevated serum cardiac-specific troponin I level. Under supportive management, the patient recovered 3 days later. A total of 18 pertinent articles involving 339 dengue-affected patients with cardiac complications were found by PubMed search. Clinical manifestations of cardiac complications varied considerably, from self-limiting tachy–brady arrhythmia to severe myocardial damage, leading to hypotension and pulmonary edema. Although rare, a fatal outcome was reported in some cases of dengue with cardiac complications. To avoid otherwise preventable morbidity and mortality, physicians should have a high index of suspicion for cardiac complications in patients with dengue illness and should manage this accordingly

High entropy alloys:Key issues under passionate debate

The present Viewpoint set aims at providing a summary of the recent advancements in the fundamental understanding of high entropy alloys (HEAs) as well as igniting new ideas and activities in this rapidly evolving field of use-inspired basic research. The universality of the core effects in HEAs, ranging from configurational entropy contributions to cocktailing effects are still under a passionate debate and in particular the peer-reviewed articles are meant to provide original perspectives. The various contributions are strongly opinion-based in a variety of areas including diffusion, phase transformations, deformation behavior, corrosion, metastability, structural as well as functional properties. In addition, the impact of the original metallic HEAs onto the field of oxides and ceramics has been illustrated and the role of entropy in high-entropy oxides is critically discussed

Shewanella soft tissue infection: case report and literature review

SummaryObjectiveTo better understand the clinical characteristics of soft tissue infections caused by Shewanella in humans.MethodsWe report a case of Shewanella soft tissue infection and review the English literature from a search of PubMed.ResultsA total of 27 adults (mean age 61.1±16.0 years) with soft tissue infections caused by Shewanella were included for analysis. Limb involvement was found in 22 (81.5%) patients, while scalp, face, perineum, lacrimal sac, and abdominal wall involvement were each found in one patient. Chronic ulcer over the leg (14 cases (51.9%)), steroid use (four cases (14.8%)), and liver cirrhosis (three cases (11.1%)) were the major underlying conditions. Shewanella bacteremia was found in 14 out of 22 patients with soft tissue infections involving the limbs. Two patients died of septicemia, giving a mortality rate of 7.4%.ConclusionsShewanella soft tissue infections usually develop in immunocompromised patients with a preexisting cutaneous ulcer (particularly over the legs) after marine environment or seawater exposure. In view of the possible catastrophic consequences, education on the prevention of Shewanella soft tissue infections in at-risk people (e.g., the immunocompromised or elderly with a cutaneous ulcer) relating the need to avoid exposure to the marine environment or seawater may be of importance

Structural study in Highly Compressed BiFeO3 Epitaxial Thin Films on YAlO3

We report a study on the thermodynamic stability and structure analysis of the epitaxial BiFeO3 (BFO) thin films grown on YAlO3 (YAO) substrate. First we observe a phase transition of MC-MA-T occurs in thin sample (<60 nm) with an utter tetragonal-like phase (denoted as MII here) with a large c/a ratio (~1.23). Specifically, MII phase transition process refers to the structural evolution from a monoclinic MC structure at room temperature to a monoclinic MA at higher temperature (150oC) and eventually to a presence of nearly tetragonal structure above 275oC. This phase transition is further confirmed by the piezoforce microscopy measurement, which shows the rotation of polarization axis during the phase transition. A systematic study on structural evolution with thickness to elucidate the impact of strain state is performed. We note that the YAO substrate can serve as a felicitous base for growing T-like BFO because this phase stably exists in very thick film. Thick BFO films grown on YAO substrate exhibit a typical "morphotropic-phase-boundary"-like feature with coexisting multiple phases (MII, MI, and R) and a periodic stripe-like topography. A discrepancy of arrayed stripe morphology in different direction on YAO substrate due to the anisotropic strain suggests a possibility to tune the MPB-like region. Our study provides more insights to understand the strain mediated phase co-existence in multiferroic BFO system.Comment: 18 pages, 6 figures, submitted to Journal of Applied Physic

Evaluation of applying retaining shield rotor for high-speed interior permanent magnet motors

This paper proposes a novel rotor structure for high-speed interior permanent magnet motors to overcome huge centrifugal forces under high-speed operation. Instead of the conventional axial stacking of silicon-steel laminations, the retaining shield rotor is inter-stacked by high-strength stainless-steel plates to enhance the rotor strength against the huge centrifugal force. Both mechanical characteristics and electromagnetic behaviors of the retaining shield rotor are analyzed using finite-element method in this paper. Prototypes and experimental results are demonstrated to evaluate the performance. The analysis and test results show that the proposed retaining shield rotor could effectively enhance the rotor strength without a significant impact on the electromagnetic performance, while some design constraints should be compromised

Effects of implementation of an online comprehensive antimicrobial-stewardship program in ICUs: A longitudinal study

AbstractBackground/purposeThe long-term effects of antimicrobial-stewardship programs in the intensive care units (ICUs) have not been adequately examined. We evaluated the impact of an online comprehensive antimicrobial stewardship program (OCASP) on the outcomes of patients in 200-bed medical/surgical ICUs over the course of 11 years.MethodsWe analyzed the records of adult patients admitted to ICUs during the 5 years before (n = 27,499) and the 6 years after (n = 33,834) implementation of an OCASP. Antimicrobial consumption, expenditures, duration of treatment, incidence of healthcare-associated infections (HAIs), prevalence of HAIs caused by antimicrobial-resistant strains, and crude or sepsis-related mortality of patients were analyzed. Segmented regression analyses of interrupted time series were used to assess the significance of changes in antimicrobial use.ResultsCompared to the patients in the pre-OCASP period, the patients in the post-OCASP period were older, had greater disease severity, longer ICU stays, and were more likely to receive antimicrobials, but had lower antimicrobial expenditures and crude and sepsis-related mortality. The trend of overall antimicrobial use [slope of defined daily dose/1000 patient-days vs. time) increased significantly before OCASP implementation (p < 0.001), but decreased significantly after implementation (p < 0.01). The administration duration of all classes of antibiotics were significantly shorter (p < 0.001) and the incidences of HAIs were significantly lower (p < 0.001) after implementation. However, there was an increase in the proportion of HAIs caused by carbapenem-resistant Acinetobacter baumannii relative to all A. baumannii infections.ConclusionImplementation of an OCASP in the ICUs reduced antimicrobial consumption and expenditures, but did not compromise healthcare quality