Thermally actuated pumping of a single-phase fluid using surface asymmetry

An experimental study of thermally actuated pumping of a single-phase, single-component fluid is presented in the context of thermal management of a heat source. The prominent feature of this pumping method is that the very heat that is to be removed from the heat source causes a net fluid motion. Therefore, such a thermal management system tends to be passive and noiseless. The dominant driving force for convection in this study is surface tension. An asymmetry in this force is created by the use of a surface with repeated asymmetric triangular structures. Silicone oil was used as the working fluid. Independent parameters consisted of the channel surface-to-ambient temperature difference and the fluid thickness. A dye-tracking imaging method was developed to determine the fluid interfacial velocity. The flow results were corroborated with interfacial temperature measurements obtained using infrared thermography. Dye tracking experiments indicate that the direction of net fluid motion is from the less-steep side of the ratchet towards its steeper side, resulting in a clockwise flow direction in the closed loop channel for all three liquid depths of 0.5 mm, 1.0 mm and 2.7 mm. The range of the net flow velocities varies from 0.18 mm/min to 0.86 mm/min. A fluid height of 1 mm results in a maximum net fluid velocity at both surface-to-ambient temperatures studied. Interfacial temperature contour maps indicate the presence of thermal structures that are indicative of convection cells, and that an optimum thickness exists for maximum heat transfer coefficient. Difference in streamwise gradients of temperature (and hence surface tension) on either side of the thermal structures causes a net streamwise surface tension gradient in the direction of net fluid motion. An optimal fluid thickness for heat transfer as well as net interfacial fluid velocity is suggested by the results

Sheathless Size-Based Acoustic Particle Separation

Particle separation is of great interest in many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In this paper, we present a microfluidic platform for sheathless particle separation using standing surface acoustic waves. In this platform, particles are first lined up at the center of the channel without introducing any external sheath flow. The particles are then entered into the second stage where particles are driven towards the off-center pressure nodes for size based separation. The larger particles are exposed to more lateral displacement in the channel due to the acoustic force differences. Consequently, different-size particles are separated into multiple collection outlets. The prominent feature of the present microfluidic platform is that the device does not require the use of the sheath flow for positioning and aligning of particles. Instead, the sheathless flow focusing and separation are integrated within a single microfluidic device and accomplished simultaneously. In this paper, we demonstrated two different particle size-resolution separations; (1) 3 µm and 10 µm and (2) 3 µm and 5 µm. Also, the effects of the input power, the flow rate, and particle concentration on the separation efficiency were investigated. These technologies have potential to impact broadly various areas including the essential microfluidic components for lab-on-a-chip system and integrated biological and biomedical applications.Bankhead-Coley Florida Cancer Research Program (Grant # 1BN04-34183)National Science Foundation (U.S.) (Grant 0968736)National Science Foundation (U.S.) (Grant 1135419)National Science Foundation (U.S.) (Grant 1056475

Concomitant renal insufficiency and diabetes mellitus as prognostic factors for acute myocardial infarction

<p>Abstract</p> <p>Background</p> <p>Diabetes mellitus and renal dysfunction are prognostic factors after acute myocardial infarction (AMI). However, few studies have assessed the effects of renal insufficiency in association with diabetes in the context of AMI. Here, we investigated the clinical outcomes according to the concomitance of renal dysfunction and diabetes mellitus in patients with AMI.</p> <p>Methods</p> <p>From November 2005 to August 2008, 9905 patients (63 ± 13 years; 70% men) with AMI were enrolled in a nationwide prospective Korea Acute Myocardial Infarction Registry (KAMIR) and were categorized into 4 groups: Group I (n = 5700) had neither diabetes nor renal insufficiency (glomerular filtration rate [GFR] ≥ 60 ml/min/1.73 m²), Group II (n = 1730) had diabetes but no renal insufficiency, Group III (n = 1431) had no diabetes but renal insufficiency, and Group IV (n = 1044) had both diabetes and renal insufficiency. The primary endpoints were major adverse cardiac events (MACE), including a composite of all cause-of-death, myocardial infarction, target lesion revascularization, and coronary artery bypass graft after 1-year clinical follow-up.</p> <p>Results</p> <p>Primary endpoints occurred in 1804 (18.2%) patients. There were significant differences in composite MACE among the 4 groups (Group I, 12.5%; Group II, 15.7%; Group III, 30.5%; Group IV, 36.5%; <it>p </it>< 0.001). In a Cox proportional hazards model, after adjusting for multiple covariates, the 1-year mortality increased stepwise from Group III to IV as compared with Group I (hazard ratio [HR], 1.96; 95% confidence interval [CI], 1.34-2.86; <it>p </it>= 0.001; and HR, 2.42; 95% CI, 1.62-3.62; <it>p </it>< 0.001, respectively). However, Kaplan-Meier analysis showed no significant difference in probability of death at 1 year between Group III and IV (p = 0.288).</p> <p>Conclusions</p> <p>Renal insufficiency, especially in association with diabetes, is associated with the occurrence of composite MACE and indicates poor prognosis in patients with AMI. Categorization of patients with diabetes and/or renal insufficiency provides valuable information for early-risk stratification of AMI patients.</p

Does gender influence the impact of impaired renal function on prognosis after ST-segment elevated myocardial infarction?

Background: A limited number of studies have investigated the impact of gender on renal function and clinical outcomes after ST-segment elevated myocardial infarction (STEMI), and these studies have provided discrepant results.Methods and Results: This study was based on a retrospective cohort, the Korean Acute Myocardial Infarction Registry (KAMIR). Patients (n = 7,679) with a discharge diagnosis of STEMI were analyzed to investigate association of gender with renal function and clinical outcomes. Compared to men, women were older and exhibited more comorbidity, including impaired renal function. Women showed higher mortality compared to men (1-month mortality,5.6% in men vs. 12.6% in women, p &lt; 0.001; 1-year mortality, 6.8% in men vs. 14.4% in women, p &lt; 0.001). The risk of death proportionally increased as estimated glomerular filtration rate (eGFR) decreased in both genders. After adjusting for potential confounders, hazard ratios for women did not significantly differ from those for men at each eGFR level.The interaction test showed no significant interaction between gender and eGFR in 1-month mortality and 1-year mortality.Conclusions: Impaired renal function was an independent prognostic factor after STEMI in both genders, and the impact of impaired renal function on prognosis after STEMI did not significantly differ between genders

Characteristics, Outcomes and Predictors of Long-Term Mortality for Patients Hospitalized for Acute Heart Failure: A Report From the Korean Heart Failure Registry

BACKGROUND AND OBJECTIVES: Acute heart failure (AHF) is associated with a poor prognosis and it requires repeated hospitalizations. However, there are few studies on the characteristics, treatment and prognostic factors of AHF. The aims of this study were to describe the clinical characteristics, management and outcomes of the patients hospitalized for AHF in Korea. SUBJECTS AND METHODS: We analyzed the clinical data of 3,200 hospitalization episodes that were recorded between June 2004 and April 2009 from the Korean Heart Failure (KorHF) Registry database. The mean age was 67.6±14.3 years and 50% of the patients were female. RESULTS: Twenty-nine point six percent (29.6%) of the patients had a history of previous HF and 52.3% of the patients had ischemic heart disease. Left ventricular ejection fraction (LVEF) was reported for 89% of the patients. The mean LVEF was 38.5±15.7% and 26.1% of the patients had preserved systolic function (LVEF ≥50%), which was more prevalent in the females (34.0% vs. 18.4%, respectively, p<0.001). At discharge, 58.6% of the patients received beta-blockers (BB), 53.7% received either angiotensin converting enzyme-inhibitors or angiotensin receptor blockers (ACEi/ARB), and 58.4% received both BB and ACEi/ARB. The 1-, 2-, 3- and 4-year mortality rates were 15%, 21%, 26% and 30%, respectively. Multivariate analysis revealed that advanced age {hazard ratio: 1.023 (95% confidence interval: 1.004-1.042); p=0.020}, a previous history of heart failure {1.735 (1.150-2.618); p=0.009}, anemia {1.973 (1.271-3.063); p=0.002}, hyponatremia {1.861 (1.184-2.926); p=0.007}, a high level of serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) {3.152 (1.450-6.849); p=0.004} and the use of BB at discharge {0.599 (0.360-0.997); p=0.490} were significantly associated with total death. CONCLUSION: We present here the characteristics and prognosis of an unselected population of AHF patients in Korea. The long-term mortality rate was comparable to that reported in other countries. The independent clinical risk factors included age, a previous history of heart failure, anemia, hyponatremia, a high NT-proBNP level and taking BB at discharge.ope

A Novel Risk Stratification Model for Patients with Non-ST Elevation Myocardial Infarction in the Korea Acute Myocardial Infarction Registry (KAMIR): Limitation of the TIMI Risk Scoring System

The Thrombolysis in Myocardial Infarction (TIMI) risk score (TRS) has proven value in predicting prognosis in unstable angina/non ST-elevation myocardial infarction (NSTEMI) as well as in ST-elevation myocardial infarction. The TRS system has little implication, however, in the extent of myocardial damage in high-risk patients with NSTEMI. A total of 1621 patients (63.6±12.2 years; 1043 males) with NSTEMI were enrolled in the Korea Acute Myocardial Infarction Registry (KAMIR). We analyzed the risk for major adverse cardiac events (MACE) during a 6-month follow-up period. The TRS system showed good correlation with MACE for patients in the low and intermediate groups but had poor correlation when the high-risk group was included (p=0.128). The MACE rate was 3.8% for TRS 1, 9.4% for TRS 2, 10.7% for TRS 3, and 12.3% for TRS 4 (HR=1.29, p=0.026). Among the biomarkers and clinical risk factors, elevated N-terminal pro-brain natriuretic peptide (NT-proBNP) (HR=2.61, p=0.001) and Killip class above III showed good correlation with MACE (HR=0.302, p<0.001). Therefore, we revised an alternative clinical scoring system by including these two variables that reflect left ventricular dysfunction: age > 65 years, history of ischemic heart disease, Killip class above III, and elevated pro-BNP levels above the 75th percentile. This modified scoring system, when tested for validity, showed good predictive value for MACE (HR=1.64, p<0.001). Compared with the traditional TRS, the novel alternative scoring system based on age, history of ischemic heart disease, Killip class, and NT-proBNP showed a better predictive value for 6-month MACE in high-risk patients with NSTEMI

HIGH-DOSE CLOPIDOGREL LOADING IS SAFE AND EFFECTIVE IN PATIENTS WITH ST-ELEVATION MYOCARDIAL INFARCTION UNDERGOING PRIMARY PERCUTANEOUS CORONARY INTERVENTION

OBJECTIVE: The two- to fourfold higher risk of cardiovascular disease in diabetes mellitus is more strongly predicted by the postprandial than by the fasting blood glucose and lipids. We aimed to investigate the impact of postprandial changes in serum lipoprotein fractions on lipid peroxidation in type I diabetes mellitus (T1DM). DESIGN: This was a prospective observational study. SETTING: The study was performed at Antwerp University Hospital, Belgium.Subjects:Twenty-three well-controlled T1DM patients were included. INTERVENTION: Patients received a standard breakfast and lunch (&gt;50% energy as fat). Blood was sampled at fasting (F), after the post-breakfast hyperglycemic peak (BP), just before lunch (B), after the post-lunch hyperglycemic peak (LP), after the post-lunch dale (LD) and 5 h after lunch (L) for the measurement of serum lipids, lipoprotein subfraction composition, alpha-tocopherol and lipid peroxidation in vivo and in vitro. RESULTS: Serum triacylglycerols (Tgs) increased (from 1.03+/-0.40 at F to 1.60+/-0.87 mmol/l at LP, P=0.001), but cholesterol decreased by 12% in parallel with alpha-tocopherol (from 4.43+/-0.76 at F to 4.12+/-0.82 micromol/mmol total lipid at B, P=0.006). Although plasma malondialdehyde increased from 1.02+/-0.36 at F to 1.14+/-0.40 micromol/L at LP, P=0.03, copper-induced in vitro peroxidation decreased in the low-density lipoprotein and high-density lipoprotein fractions. CONCLUSIONS: In well-controlled T1DM patients moderate postprandial increases in serum Tgs are accompanied by a relative deficiency in alpha-tocopherol. Lipid peroxidation in vivo increases but cannot be ascribed to changes in the susceptibility of lipoproteins to copper-induced in vitro peroxidation</p

Impact of the Metabolic Syndrome on the Clinical Outcome of Patients with Acute ST-Elevation Myocardial Infarction

We sought to determine the prevalence of metabolic syndrome (MS) in patients with acute myocardial infarction and its effect on clinical outcomes. Employing data from the Korea Acute Myocardial Infarction Registry, a total of 1,990 patients suffered from acute ST-elevation myocardial infarction (STEMI) between November 2005 and December 2006 were categorized according to the National Cholesterol Education Program-Adult Treatment Panel III criteria of MS. Primary study outcomes included major adverse cardiac events (MACE) during one-year follow-up. Patients were grouped based on existence of MS: group I: MS (n=1,182, 777 men, 62.8±12.3 yr); group II: Non-MS (n=808, 675 men, 64.2±13.1 yr). Group I showed lower left ventricular ejection fraction (LVEF) (P=0.005). There were no differences between two groups in the coronary angiographic findings except for multivessel involvement (P=0.01). The incidence of in-hospital death was higher in group I than in group II (P=0.047), but the rates of composite MACE during one-year clinical follow-up showed no significant differences. Multivariate analysis showed that low LVEF, old age, MS, low high density lipoprotein cholesterol and multivessel involvement were associated with high in-hospital death rate. In conclusion, MS is an important predictor for in-hospital death in patients with STEMI