Search

This paper presents a numerical investigation of microscopic lubricant flows from the cavities to the plateaus of the surface roughness of metal sheets during forming processes. This phenomenon, called micro-plasto-hydrodynamic lubrication, was observed experimentally in various situations such as compression sliding tests, strip drawing and cold rolling. It leads to local friction drop and wear reduction. It is therefore critical to achieve a good understanding of this phenomenon. As to move towards that goal, a multiscale fluid-structure interaction model is developed to model lubricant flows at the microscopic scale. These simulations are made possible through the use of the Arbitrary Lagrangian Eulerian (ALE) formalism. In this paper, this methodology is used to study plane strip drawing. The numerical model is able to predict the onset of lubricant escape and the amount of lubricant flowing on the plateaus. Numerical results exhibit good agreement with experimental measurements. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

During Intensive Observation Period 15a (20 October 2012) of the first Special Observation Period of the Hydrological cycle in the Mediterranean Experiment, northeastern Spain experienced heavy precipitation (130 mm in 24 h) associated with a retrograde regeneration mesoscale convective system (MCS) developing in the exit region of the Ebro River Valley (ERV). The life cycle of the MCS that brought intense hourly rainfall (34 mm) from the foothills of the Iberian Plateau to the central Pyrenees, as well as the detailed structure of the moist marine flow upstream, were analysed using a combination of ground-based, airborne and space-borne observations as well as model analyses. Over the Balearic Sea, the southwesterlies along the northeastern flank of a surface low converged with southeasterlies from North Africa, creating a near-surface moisture tongue in the region of the Balearic Islands, and a southeast-northwest oriented convergence line within a cloud cluster advecting from northern Africa. Airborne lidar measurements, acquired upstream of the ERV, evidenced water vapour mixing ratios in excess of 15 g kg−1 in the marine atmospheric boundary layer. In the mid-level (700 hPa), the presence of an elevated moisture plume from tropical Africa contributed about one third to the large moisture content present over the western Mediterranean Sea. In this moist environment, the MCS was initiated over the orography of the northeastern tip of the Iberian plateau, due to the combined influence of the approaching convergence line ahead of the surface low and the convergence resulting from weak northwesterlies channelled in the ERV and the easterlies impinging on the coastal range. After the initiation phase, the MCS further developed over the foothills of the Iberian Plateau and moved into the ERV and along the southern flank of the Pyrenees, thanks to the penetration of the warm and moist maritime southeasterly flow through the narrow gap between the northeastern part of the Iberian Plateau and the Catalan coastal range. [ABSTRACT FROM AUTHOR]

ABSTRACT This study presents an analysis of a 14-year data set of 30-min averaged experimental UVI values derived from ground-based broadband irradiance measurements, satellite-derived total ozone observations and total solar radiation recorded in Barcelona ( NE Spain). Most maximum daily UVI values do occur at noon (82% of cases between 11:30 and 13:00 UTC). Considering all seasons, the maximum daily UVI presents a bimodal, approximately symmetrical, frequency distribution with a maximum around UVI class 2 (22%) and UVI 7 and 8 classes (23%) while June median presents a value of 8.2. According to attenuation criteria there is a preponderance of Clear sky days (77%) compared to Broken (22%) and Overcast (8%) conditions, which concentrate mostly in October, November and December (reaching 20% of days). An additional classification in terms of World Health Organisation UVI intensity categories indicates that 40% of days exceeded the Lower threshold of UVI category Moderate ( UVI values above 5.5), from them 21% of days had UVI values considered Very High (above 9.5) and one single case was classified as Extreme ( UVI above 10.5). UVI values above 7.5 were found under Broken sky conditions in June, July and August. Additionally UVI diurnal daily cycles have also been analyzed in terms of selected percentile values and maximum levels. Under all sky conditions UVI median values exceed the lower threshold of category High (5.5) from April to late August around noon (in June from 10:00 to 14:30 UTC). These results provide an exhaustive quantitative description of average and extreme values of experimental UVI values observed in the region and can be of interest for a wide range of applications, including ground-based UV modelling through the use of radiative transfer models, trend analysis or verification of UVI forecasts. [ABSTRACT FROM AUTHOR]

A new test method to determine the compressive properties of composite materials under both static and fatigue loading was developed. The novel fixture is based on the concept of transmitting the load by a fixed ratio of end-to-shear loading. The end-to-shear load ratio is kept fixed during the test through a mechanical mechanism, which automatically maintains the gripping pressure. The combined loading method has proven very efficient in static loading and is used in the new fixture which is specially designed for fatigue testing. Optimum gripping (shear loading) and alignment of the test coupon are achieved throughout the fatigue life. The fatigue strength obtained is more reliable because bending of the specimen due to poor gripping and alignment is minimised. The application of the new fixture to static and fatigue compression is demonstrated by using unidirectional carbon/epoxy and glass/polyester composite systems. Repeatable results and acceptable failure modes are obtained under both static and fatigue loading. [ABSTRACT FROM AUTHOR]

Statins improve cardiovascular survival in both nondia-betic and diabetic patients, but diabetic patients benefit more, in both primary and secondary prevention. Statins seem to have multiple effects beyond cholesterol lowering, that is, pleiotropic effects that may include changes in renal function. This study tests the hypothesis that acute treatment with atorvastatin may change glomerular filtration rate, tubular function, vasoactive hormones, blood pressure, and pulse rate in patients with type 2 diabetes. In an acute, randomized, placebo-controlled, double-blinded, crossover trial, the effects of atorvastatin on renal function, vasoactive hormones, blood pressure, and pulse rate are measured in 21 patients with type 2 diabetes. Patients are randomized to either 2 doses of atorvastatin 80 mg or placebo before 2 different study days. Treatment with atorvastatin induces a significant reduction in fractional sodium excretion compared with placebo, and sodium clearance tends to be reduced. No significant differences in glomerular filtration rate, albumin/creatinine ratio, vasoactive hormones, and blood pressure by acute treatment with atorvastatin are found in diabetic patients. Acute treatment with atorvastatin reduces renal fractional sodium excretion in patients with type 2 diabetes. No changes are measured in glomerular filtration rate, albumin/creatinine ratio, vasoactive hormones, and blood pressure. [ABSTRACT FROM AUTHOR]

The present study examined the cardiac effects of football training and running for inactive pre-menopausal women by standard echocardiography and tissue Doppler imaging. Thirty-seven subjects were randomized to two training groups (football: FG; n=19; running; RG; n=18) training 1 h with equal average heart rates twice a week for 16 weeks and compared with a matched inactive control group (CG; n=10). During the training period, left ventricular end-diastolic volume increased by 13% in FG and 11% in RG ( P<0.05). Left ventricular posterior wall thickness increased in FG from 8.5±1.4 to 9.0±1.3 mm ( P<0.05). Right ventricle diameter increased by 12% in FG and 10% in RG ( P<0.05). Tissue Doppler imaging demonstrated increased left ventricular systolic and diastolic performances in both training groups. Peak systolic velocity increased by 26% in FG and 17% in RG ( P<0.05) and left ventricular longitudinal displacement increased in both groups by 13% ( P<0.05). Isovolumetric relaxation time decreased significantly more in FG than in RG (26% vs 14%, respectively P<0.05). In conclusion, 16 weeks of football and running exercise training induced significant changes of cardiac dimensions and had favorable effects on both left ventricular systolic and diastolic function. These training-induced cardiac adaptations appeared to be more consistent after football training compared with running. [ABSTRACT FROM AUTHOR]

Aims To investigate the acute effects of prostacyclin (Flolan® ) on renal haemodynamics, renal tubular function, plasma concentration of angiotensin II (Ang II), aldosterone (Aldo), atrial natriuretic peptide (ANP), arginine vasopressin (AVP), mean arterial blood pressure (MBP), and heart rate (HR). Methods Thirteen healthy control subjects were investigated on two separate occasions in a placebo controlled, randomized, dose-response study of the effect of intravenous infusion of prostacyclin (PGI2, Flolan®, 2, 4 and 8 ng kg−1min−1 ). Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured by the use of constant infusion of []> 51Cr]-EDTA and [125I]-hippurane. Urinary output, urinary sodium excretion, fractional sodium excretion, fractional lithium excretion were measured and hormones were measured using radioimmunoassay. Results During prostacyclin (PGI2 ) infusion we observed a significant increase in RPF (PGI2: 4.8%; 6.1% and 5.2%vs Plac: −1.5%; −1.9% and −5.8% for 2,4 and 8 ng kg−1min−1 respectively; P≤0.05 for 4 and 8 ng kg−1min−1 ) in Ang II (PGI2: 20.0%; 42.9% and 88.9%vs Plac: 0.1%; 8.0% and 0.0%, P≤0.01 for 4 and 8 ng kg−1 min−1 ) in ANP (PGI2: 13.6%; 12.7% and 37.5%vs Plac: −10.2%; −6.6% and −2.4%, P≤0.05 for 2 ng kg−1min−1 and P≤0.01 for 4 and 8 ng kg−1min−1 ), and in HR (PGI2: 8.8%; 17.6% and 32.7%vs Plac: 0.8%; 4.1% and 3.5%, P≤0.05 for 2 and P≤0.01 for 4 and 8 ng kg−1min−1.). A significant decrease was observed in MBP (MBP:PGI2: −1.7%; −1.9% and −5.6%vs Plac: −0.4%; −1.6% and +2.1%, P≤0.01 for 8 ng kg−1min−1 ). No significant changes were seen in the other effect variables. Conclusions Infusion of prostacyclin in healthy control subjects increases renal plasma flow, angiotensin II, atrial natriuretic peptide, and heart rate and decreases mean blood pressure. Furthermore prostacyclin infusion does not change net sodium excretion in healthy controls. [ABSTRACT FROM AUTHOR]

Purpose: Layer-specific global longitudinal strain (GLS) may provide important insights in patients with suspected coronary artery disease (CAD). We aimed to investigate the association between layer-specific GLS and coronary artery calcium score (CACS) in patients suspected of CAD., Methods: We performed a retrospective study of patients suspected of CAD who underwent both an echocardiogram and cardiac computed tomography (median 42 days between). Layer-specific (endocardial-, whole-layer-, and epicardial-) GLS was measured using speckle tracking echocardiography. We assessed the continuous association between layer-specific GLS and CACS by negative binomial regression, and the association with high CACS (≥400) using logistic regression., Results: Of the 496 patients included (mean age 59 years, 56% male), 64 (13%) had a high CACS. Those with high CACS had reduced GLS in all layers compared to those with CACS < 400 (endocardial GLS: -20.5 vs. -22.7%, whole-layer GLS: -17.7 vs. -19.4%, epicardial GLS: -15.3 vs. -16.9%, p < .001 for all). Negative binomial regression revealed a significant continuous association showing increasing CACS with worsening GLS in all layers, which remained significant after multivariable adjustment including SCORE chart risk factors. All layers of GLS were associated with high CACS in univariable analyses, which was consistent after multivariable adjustment (endocardial GLS: OR = 1.11 (1.03-1.20); whole-layer GLS: OR = 1.14 (1.04-1.24); epicardial GLS: OR = 1.16 (1.05-1.29), per 1% absolute decrease)., Conclusion: In this study population with patients suspected of CAD and normal systolic function, impaired layer-specific GLS was continuously associated with increasing CACS, and decreasing GLS in all layers were associated with presence of high CACS., (© 2024 Wiley Periodicals LLC.)

Background: Studies suggest cardiac time intervals to be associated with cardiac ischemia. A novel method to assess cardiac time intervals by tissue Doppler echocardiography has been proposed. Cardiac time intervals can assess the myocardial performance index (MPI), which quantifies the proportion of time spent contributing effective myocardial work. We hypothesized that MPI associates with coronary artery lesions detected by cardiac computed tomography (CT) in patients suspected of coronary artery disease (CAD)., Methods: We investigated patients referred for cardiac CT under suspicion of CAD who had an echocardiogram performed. Curved m-mode tissue Doppler imaging was used to measure cardiac time intervals and MPI. The outcome was coronary artery lesions, defined as a calcium score > 400 and/or coronary artery stenosis (>70% luminal narrowing). Logistic regression was applied with multivariable models including: (a) SCORE chart risk factors and (b) SCORE chart risk factors, body mass index, dyslipidemia, familial history of CAD, diabetes mellitus, LVEF, and left ventricular mass index., Results: Of 404 patients, 41 (10%) had a coronary artery lesion. Overall, 42% were male, mean age was 58 years, and LVEF was 58%. Patients with coronary artery lesions exhibited higher MPI than those without (0.52 vs. 0.44, P < .001). MPI associated with coronary artery lesions in unadjusted analyses (OR = 1.69 [1.30-2.19], per 0.1 increase), and this association persisted when adjusted for SCORE chart risk factors (OR = 1.55 [1.16-2.07], P = .003, per 0.1 increase), and additional risk factors (OR = 1.64 [1.11-2.41], P = .013, per 0.1 increase)., Conclusion: Curved m-mode-derived MPI is associated with coronary artery lesions detected by cardiac CT in suspected CAD patients., (© 2020 Wiley Periodicals LLC.)

Background: Coronary microvascular dysfunction (CMD) may cause angina in the absence of obstructive coronary artery disease (CAD) and increases the risk of future adverse cardiovascular events. Transthoracic Doppler echocardiography (TTDE) with pharmacological stress can assess coronary flow velocity reserve (CFVR), a measure of coronary microvascular function. However, simpler methods would be preferable for diagnosing CMD. Therefore, we examined the relationship between CFVR and cardiac time intervals measured by TTDE in a cohort of women with angina and no obstructive CAD., Methods: In a prospective cohort study, we included 389 women with angina, left ventricular ejection fraction > 45%, and no obstructive CAD. CMD was defined as CFVR < 2.0. The study population was divided into three groups according to cutoff values of CFVR < 2, 2 ≤ CFVR ≤ 2.5, and CFVR > 2.5. Isovolumic contraction time (IVCT), ejection time (ET), and isovolumic relaxation time (IVRT) were measured by tissue Doppler M-mode, and the myocardial performance index (MPI = (IVCT + IVRT)/ET) was calculated., Results: Coronary microvascular dysfunction was associated with increasing age, hypertension, higher resting heart rate, and lower diastolic blood pressure. Moreover, CMD was associated with higher E/e' ratio (P = 0.002) and longer IVCT (P < 0.001), higher MPI (P < 0.001) and shorter ET (P = 0.002), but not with IVRT or conventional measures of left ventricular geometry, mass, and function. In multivariable analysis, longer IVCT (P < 0.001) and higher MPI (P = 0.002) remained associated with CMD., Conclusion: In women with angina and no obstructive CAD, CMD is associated with longer IVCT and higher MPI indicating a link between CMD and subtle alternations of systolic and combined measures of cardiac time intervals., (© 2019 Wiley Periodicals, Inc.)

Background: Coronary microvascular dysfunction (CMD) is a potential cause of myocardial ischemia and may affect myocardial function at rest and during stress. We investigated whether CMD was associated with left ventricular diastolic and systolic function at rest and during pharmacologically induced hyperemic stress., Methods: In a prospective cohort study, we included 963 women with angina, left ventricular ejection fraction (LVEF) >45%, and an invasive coronary angiogram without significant stenosis (<50%). Parameters of left ventricular diastolic function, LVEF, speckle tracking-derived global longitudinal strain (GLS), and coronary flow velocity reserve (CFVR) were assessed by transthoracic echocardiography at rest and during dipyridamole stress. The GLS and LVEF reserves were defined as the absolute increases in GLS and LVEF during stress., Results: Coronary flow velocity reserve (CFVR) was measured in 919 women of whom 26% had CMD (defined as CFVR < 2). Coronary microvascular dysfunction (CMD) was associated with higher age and a higher resting heart rate. Women with CMD had a reduced GLS reserve (P = .005), while we found no association between CFVR and LVEF at rest, GLS at rest, or the LVEF reserve, respectively. Global longitudinal strain (GLS) reserve remained associated with CFVR (P = .002) in a multivariable regression analysis adjusted for age, hemodynamic variables, and GLS at rest. In age-adjusted analysis, women with low CFVR had no signs of left ventricular diastolic dysfunction measured by echocardiography at rest., Conclusion: The GLS reserve was significantly lower in women with CMD. The mechanisms underlying the association between CMD and GLS reserve warrant further study., (© 2017, Wiley Periodicals, Inc.)