The equations of an inviscid blade force component for modeling the flow turning through real blade rows are analytically combined with Euler equations in the meanline annulus of a complete ...compressor. This combination gives rise to a modified set of unsteady 2D flow equations with specific convective flux and source terms that explicitly depend on the geometry of the blade camberline. At the leading and trailing edges of each bladed region, the new set of equations is coupled to standard Euler equations in unbladed regions by means of boundary conditions that allow modeling of a leading edge shock. The numerical flux difference splitting scheme for time integration of the governing equations includes a consistent, upwind formulation of the delay model for correction of empirical input on loss and deviation at each (either stalled or unstalled) circumferential grid station. The steady 1D solution of the new equations provides the numerical compressor map in normal operation. Several stall configurations can then be obtained by artificially perturbing a near-stall solution assumed as unstable with respect to some well-known stall criteria. The method predicts experimental stalled performance of a transonic rotor with accuracy higher than 4%. The predicted stall inception transients and stall propagation speed are also in line with previous experience.
Cigarette smoking and hypertension Virdis, A; Giannarelli, C; Neves, M Fritsch ...
Current pharmaceutical design,
08/2010, Letnik:
16, Številka:
23
Journal Article
Recenzirano
Cigarette smoking is a powerful cardiovascular risk factor and smoking cessation is the single most effective lifestyle measure for the prevention of a large number of cardiovascular diseases. ...Impairment of endothelial function, arterial stiffness, inflammation, lipid modification as well as an alteration of antithrombotic and prothrombotic factors are smoking-related major determinants of initiation, and acceleration of the atherothrombotic process, leading to cardiovascular events. Cigarette smoking acutely exerts an hypertensive effect, mainly through the stimulation of the sympathetic nervous system. As concern the impact of chronic smoking on blood pressure, available data do not put clearly in evidence a direct causal relationship between these two cardiovascular risk factors, a concept supported by the evidence that no lower blood pressure values have been observed after chronic smoking cessation. Nevertheless, smoking, affecting arterial stiffness and wave reflection might have greater detrimental effect on central blood pressure, which is more closely related to target organ damage than brachial blood pressure. Hypertensive smokers are more likely to develop severe forms of hypertension, including malignant and renovascular hypertension, an effect likely due to an accelerated atherosclerosis.
The properties of the wake generated by a porous body fully immersed in a turbulent boundary layer are experimentally assessed. The body consists of an array of cylinders, with diameter
$d$
, ...covering a circular patch of diameter
$D$
. For fixed
$d$
and
$D$
, by increasing the number of cylinders,
$N_{c}$
, within the patch, the wake properties are systematically tested under different levels of density (
$\unicodeSTIX{x1D719}$
$=$
covered planar area per total surface) and compared to the flow past a solid body of equivalent diameter and height (
$H$
). Some insights on the complex flow developing in the wake are captured:
$\unicodeSTIX{x1D719}$
varying in the range 2 %–24 % results in the flow meandering among the cylinders and bleeding from the top, the sides and the trailing edge of the patch. The interplay between trailing edge and top bleeding prevents wake entrainment, locking the wake longitudinal extent to 5–7 patch diameters, regardless of the density level. Due to the finite body vertical extent, a third shear layer develops from the top of the patch. The interaction between the top shear layer and the lateral ones leads to a mutual alteration, namely a nonlinear growth not captured by the classical mixing layer theory. Nevertheless, on the horizontal plane at the patch mid-height, the mean flow recovers, exhibiting a self-similar decay. Surprisingly, the recovery is well described by the classical planar wake theory and the characteristic scales, namely the maximum velocity deficit and the wake half-width, evolve linearly as proposed by Wygnanski
et al.
(
J. Fluid Mech.
, vol. 168, 1986, pp. 31–71).
Blood pressure through aging and menopause Taddei, S.
Climacteric : the journal of the International Menopause Society,
01/2009, Letnik:
12, Številka:
s1
Journal Article
Recenzirano
Together with the aging process, hypertension is the main risk factor contributing to the increase in cardiovascular morbidity and mortality in postmenopausal women, with a prevalence of around 60% ...in women older than 65 years. Considering that hypertension is a modifiable risk factor, the understanding of its epidemiology and pathophysiology and the development of appropriate therapeutic strategies are conceivably crucial in reducing cardiovascular risk. The high prevalence of hypertension in older women is largely due to the progressive stiffening of the arterial structure which accompanies the aging process in both sexes. However, the abrupt fall in circulating estrogen levels might independently contribute to the rise in blood pressure, through partly unknown mechanisms, such as a direct effect on the arterial wall, the activation of the renin-angiotensin system and of the sympathetic nervous system. Postmenopausal hypertension fosters the development of left ventricular hypertrophy and is the main factor contributing to coronary artery disease, chronic heart failure and stroke in older women. Recent analysis demonstrates that men and women receive a similar benefit from antihypertensive therapy in terms of reduction of cardiovascular morbidity and mortality and, considering that generally the response to different drugs is not different between the sexes, currently there is no need to use specific antihypertensive drug classes after menopause. Finally, although observational studies have shown that hormone replacement therapy is associated with lower cardiovascular risk and lower blood pressure values, randomized clinical trials have conversely denied this benefit and demonstrated rather that this therapeutical approach increases the risk of cardiovascular events.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The wakes and the drag forces of canopy patches with different densities, immersed in turbulent boundary layers, are investigated experimentally. The patches are circular (with outer diameter
$D$
) ...and are made of several identical circular cylinders (height,
$H$
, and diameter,
$d$
). The bulk aspect ratio of all of the patches (
$AR=H/D$
) was fixed at 1 and the patch density (
${\it\phi}=N_{c}d^{2}/D^{2}$
, also referred to as the solidity) is altered by varying the number of cylinders (
$N_{c}$
) in the patch. Drag measurements show that the patch drag coefficient increases with increasing density. However, the drag coefficient of the highest investigated density (
${\it\phi}\approx 0.25$
) is greater than the drag coefficient of a solid patch (i.e.
${\it\phi}=1$
, which is a solid cylinder with
$AR=1$
). Particle image velocimetry (PIV) measurements were carried out along the streamwise–wall-normal (
$x$
–
$y$
) plane along the centreline of patch and in the streamwise–spanwise (
$x$
–
$z$
) plane at its mid height (i.e.
$y=H/2$
). Mean velocity fields show that the porosity of the patch promotes bleeding along all directions. It was observed that bleeding along the vertical/horizontal direction increases/decreases with increasing
${\it\phi}$
. Furthermore, it was also observed that bleeding along the lateral direction dictates the point of flow separation along the sides of the patch and makes it independent of
${\it\phi}$
. All of these aspects make wakes for porous patches markedly different from their solid counterpart and provide a rational basis to explain the observed trends in the drag coefficient.
Abstract 5-Lipoxygenase (5-LO) metabolites are important pro-inflammatory lipid mediators. However, much still remains to be understood about the role of such mediators in bone remodeling. This study ...aimed to investigate the effect of 5-LO metabolites, LTB4 and CysLTs, in a model of mechanical loading-induced bone remodeling. Strain-induced tooth movement and consequently alveolar bone resorption/apposition was achieved by using a coil spring placed on molar and attached to incisors of C57BL6 (wild-type-WT), 5-LO deficient mice (5-LO−/− ) and mice treated with 5-LO inhibitor (zileuton—ZN) or with antagonist of CysLTs receptor (montelukast—MT). The amount of bone resorption and the number of osteoclasts were determined morphometrically. The expression of inflammatory and bone remodeling markers in periodontium was analyzed by qPCR. Osteoclast differentiation and TNF-α production were evaluated in vitro using RAW 264.7 cells treated with LTB4 or LTD4 . Bone resorption, TRAP+ cells and expression of Tnfa , Il10 and Runx2 were significantly diminished in 5-LO−/− , ZN- and MT-treated mice. The expression of Rank was also reduced in 5-LO−/− and MT-treated mice. Accordingly, LTB4 and LTD4 in association with RANKL promoted osteoclast differentiation and increased TNF-α release in vitro. These data demonstrate that the absence of 5-LO metabolites, LTB4 and CysLTs reduces osteoclast recruitment and differentiation, consequently diminishing bone resorption induced by mechanical loading. Thus, 5-LO might be a potential target for controlling bone resorption in physiological and pathological conditions.
•Roux-en-Y Gastric Bypass significantly reduced and sustained glycated haemoglobin (HbA1c) levels compared to medical therapy at ten-year follow-up.•The short duration of diabetes is of fundamental ...importance to achieve long-term remission of diabetes after bariatric surgery.•Weight loss impacts the short-term remission of type 2 diabetes, but has a marginal role in long-term relapse.
: To assess the impact of bariatric surgery on remission and relapse of type 2 diabetes mellitus (T2DM) at 10 years of follow-up and analyze predictive factors.
: Eighty-eight obese subjects undergoing Roux-en-Y gastric bypass (RYGB) and 25 subjects assigned to medical therapy (MT) were evaluated every year for 10 years. T2DM remission was defined by the American Diabetes Association criteria.
: Body mass index (BMI), fasting glucose, and haemoglobin A1c (HbA1c) improved more markedly in RYGB than MT patients throughout the 10-year period. Post-surgery remission rates were 74% and 53% at 1 and 10 years, respectively, while remission did not occur in MT patients. One-year post-surgery, BMI decreased more in subjects with remission than in those without, but no further decrease was observed thereafter. By partial-least-squares analysis, T2DM duration, baseline HbA1c, and ensuing insulin therapy were the strongest predictors of remission. Remission was achieved at one year in 91% of patients with T2DM duration < 4 years, and 79% of them remained in remission at 10 years. On the contrary only 42% of patients with T2DM duration ≥ 4 years achieved remission, which was maintained only in 6% at the end of 10 years. By survival analysis, patients with T2DM duration < 4 years had higher remission rates than those with duration ≥ 4 years (hazards ratio (HR) 3.1 95%CI 1.8–5.7). Relapse did not occur before two years post-surgery and was much less frequent in patients with < 4- vs ≥ 4-year duration (HR 11.8 4.9–29.4).
: Short T2DM duration and good glycemic control before RYGB surgery were the best requisites for a long-lasting T2DM remission, whereas weight loss had no impact on the long-term relapse of T2DM.
Cardiovascular trials have revealed the positive impact of GLP-1 receptor agonists (GLP-1 RAs) on cardiovascular outcomes in type 2 diabetes (T2D). However, the specific effects of endogenous GLP-1 ...on arterial stiffness and renal function remain understudied. This study aimed to explore the influence of endogenous GLP-1 response post-bariatric surgery on arterial stiffness and renal haemodynamic.
Thirty individuals with morbid obesity and without T2D, scheduled for Roux-en-Y Gastric Bypass (RYGB), were included. Clinical parameters, 3-hour oral glucose tolerance test (OGTT) with serial sampling for glycaemia, GLP-1 and insulin, carotid-femoral pulse wave velocity (cf-PWV), carotid distensibility coefficient (carotid-DC) and renal resistive index (RRI) measurements were conducted pre-surgery and 1-year post-surgery. Participants were categorized into high-response and low-response groups based on their post-surgery increase in GLP-1 (median increase of 104% and 1%, respectively, pre- vs. post-surgery).
Post-surgery, high-response group demonstrated a greater reduction in cf-PWV (p = .033) and a greater increase (p = .043) in carotid DC compared to low-response group. These enhancements were observed independently of weight loss or blood pressure changes. High-response group exhibited a reduction in RRI (p = .034), although this association was influenced by improvement in pulse pressure. Finally, a multivariate stepwise regression analysis indicated that the percentage increase of GLP1, Δ-GLP1
%, was the best predictor of percentage decrease in cf-PWV (p = .014).
Elevated endogenous GLP-1 response following RYGB was associated with improved arterial stiffness and renal resistances, suggesting potential cardio-renal benefits. The findings underscore the potential role of endogenous GLP-1 in influencing vascular and renal haemodynamics independent of traditional weight loss.
Abstract The endothelium plays a pivotal role in maintaining vascular homeostasis, mainly by the production of the relaxing factor nitric oxide, which protects the vessel wall from the development of ...atherosclerosis. Aging is a powerful cardiovascular risk factor, associated with endothelial dysfunction both in normotensive subjects and in hypertensive patients. Premenopausal normotensive women are protected against the deleterious effect of aging on endothelial function, and age-related impairment of endothelial function is attenuated in premenopausal hypertensive women. This protective effect on endothelium seems to be mediated by endogenous estrogen, which preserves nitric oxide availability by activating the l -arginine-NO pathway in normotensive women and by inhibiting reactive oxygen species generation. Whether endogenous androgen may modulate endothelial function and the mechanisms involved are still unsolved issues, since data concerning the effect of testosterone on endothelium are scanty and contradictory.
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