25,931 research outputs found

    Monte Carlo Co-Ordinate Ascent Variational Inference

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    In Variational Inference (VI), coordinate-ascent and gradient-based approaches are two major types of algorithms for approximating difficult-to-compute probability densities. In real-world implementations of complex models, Monte Carlo methods are widely used to estimate expectations in coordinate-ascent approaches and gradients in derivative-driven ones. We discuss a Monte Carlo Co-ordinate Ascent VI (MC-CAVI) algorithm that makes use of Markov chain Monte Carlo (MCMC) methods in the calculation of expectations required within Co-ordinate Ascent VI (CAVI). We show that, under regularity conditions, an MC-CAVI recursion will get arbitrarily close to a maximiser of the evidence lower bound (ELBO) with any given high probability. In numerical examples, the performance of MC-CAVI algorithm is compared with that of MCMC and -- as a representative of derivative-based VI methods -- of Black Box VI (BBVI). We discuss and demonstrate MC-CAVI's suitability for models with hard constraints in simulated and real examples. We compare MC-CAVI's performance with that of MCMC in an important complex model used in Nuclear Magnetic Resonance (NMR) spectroscopy data analysis -- BBVI is nearly impossible to be employed in this setting due to the hard constraints involved in the model

    Arterial stiffness index beta and cardio-ankle vascular index inherently depend on blood pressure but can be readily corrected

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    Objectives: Arterial stiffness index beta and cardio-ankle vascular index (CAVI) are widely accepted to quantify the intrinsic exponent (beta(0)) of the blood pressure (BP)-diameter relationship. CAVI and b assume an exponential relationship between pressure (P) and diameter (d). We aim to demonstrate that, under this assumption, beta and CAVI as currently implemented are inherently BP-dependent and to provide corrected, BP-independent forms of CAVI and beta.Methods and results: In P = P(ref)e(beta 0[(d/dref)-1)], usually reference pressure (P-ref) and reference diameter (d(ref)) are substituted with DBP and diastolic diameter to accommodate measurements. Consequently, the resulting exponent is not equal to the pressure-independent beta(0). CAVI does not only suffer from this 'reference pressure' effect, but also from the linear approximation of (dP=dd). For example, assuming beta(0) = 7, an increase of SBP/DBP from 110/70 to 170/120mmHg increased beta by 8.1% and CAVI by 14.3%. We derived corrected forms of b and of CAVI (CAVI(0)) that indeed did not change with BP and represent the pressure-independent beta(0). To substantiate the BP effect on CAVI in a typical follow-up study, we realistically simulated patients (n = 161) before and following BP-lowering 'treatment' (assuming no follow-up change in intrinsic beta(0) and therefore in actual P-d relationship). Lowering BP from 160 +/- 14/111 +/- 11 to 120 +/- 15/79 +/- 11 mmHg (p &lt;0.001) resulted in a significant CAVI decrease (from 8.1 +/- 2.0 to 7.7 +/- 2.1, p = 0.008); CAVI(0) did not change (9.8 +/- 2.4 and 9.9 +/- 2.6, p = 0.499).Conclusion: beta and CAVI as currently implemented are inherently BP-dependent, potentially leading to erroneous conclusions in arterial stiffness trials. BP-independent forms are presented to readily overcome this problem.</p

    Pediatric reference values for arterial stiffness parameters cardio-ankle vascular index and CAVI0

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    The process of arteriosclerosis begins early in life, and cardiovascular risk factors identified in childhood tend to persist into adulthood. Cardio-ankle vascular index (CAVI), a recent parameter of arterial stiffness, is considered an independent predictor of cardiovascular risk. However, there are no studies reporting sex- and age-specific physiological values of CAVI in childhood. We aimed to establish reference values for CAVI and its blood pressure-corrected variant (CAVI0) in 500 healthy children and adolescents aged 7 to 19 years and to study potential relationships with anthropometric indices. Sex- and age-specific distributions of CAVI and CAVI0 values in healthy children and adolescents are presented. Boys aged 15-19 years had lower CAVI than girls, which could result from CAVI's slight blood pressure dependence. CAVI0 did not show such sex difference. Body roundness index-a novel parameter to quantify abdominal fat-was a strong anthropometric predictor of both CAVI and CAVI0. This is the first study providing pediatric age- and sex-specific reference values for arterial stiffness parameters CAVI and CAVI0. The presented data can contribute to the understanding of the evolution of these indices during childhood and adolescence. Under specific conditions, CAVI0 may offer more robust information about arterial stiffness than standard CAVI

    New Iconographic Sources for Velázquez’s Equestrian Royal Portraits in the Salón de los Reinos at the Buen Retiro (1628-1634/35)

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    Senza entrare nel tema all’autografi a integrale o parziale dei dipinti di Velázquez, per la quale si attendono nuovi studi tecnici dal Prado di prossima pubblicazione, questo articolo offre una sintetica rassegna degli studi sui dipinti del Salón de los Reinos al Buen Retiro a Madrid (1628-1634/35), proponendo due nuove fonti iconografi che per i ritratti equestri degli Asburgo di Spagna. Da un lato si sottolinea l’importanza dell’esperienza visiva delle entrate regie durante il regno di Filippo III e Margherita d’Asburgo a partire dal 1599, vere e proprie performances urbane che offrirono un importante spazio per elaborazione di un’iconografi a uffi ciale e di coppia dei regnanti Asburgo a cavallo. Dall’altro si segnala l’importanza della circolazione di incisioni fi amminghe quali la serie dei cavalli en corvette di Johannes Stradanus (Ioannes van der Straet, 1523-1605) stampate nel 1580 e 1585 e i numerosi ritratti equestri di vari regnanti nordici di Cornelis Anthonisz (c. 1499-1553). Ritrattista «popolare» di Carlo V, Anthonisz sviluppò in particolare il motivo della regina amazzone e proprio in ambito borgognone. In definitiva il saggio suggerisce una linea di ricerca «nordica» e «asburgica» per la nascita del ritratto equestre in Spagna, altrimenti tradizionalmente spiegato con la ripresa e traduzione di modelli scultorei romani e italiani (Marco Aurelio, Tacca), e con l’opera pittorica di Tiziano e di Rubens.This essay examines the painting cycle realized for the Salón de los Reinos at the Buen Retiro in Madrid (1628-1634/35), without broaching the question of the full or partial autography of Velázquez, a theme which awaits the result of technical analysis currently undergoing at the Prado. Rather, it proposes two new iconographic sources for the equestrian portraits of the Spanish Habsburgs. The study focuses initially on the visual impact of royal entries during the kingdom of Philip III and Margaret of Habsburg, from 1599 onwards. In fact, these urban performances offered an important experimental space for the elaboration of a public iconography of the Habsburg couple, presented together and both on horseback. In addition, it points to the common circulation of northern prints such as the series of horses en corvette by Johannes Stradanus (Ioannes van der Straet, 1523-1605) printed in 1580 and 1585, and a number of engraved portraits by Cornelis Anthonisz (c. 1499-1553), where northern rulers and aristocrats are represented horseriding and in corvette. The latter in particular was known as a popular portraitist of Charles V, and for his portraits of female Burgundian rulers on a horseback. Overall, this essay suggests a northern line of research, pointing to Burgundy and to the Habsburg legacy, for the birth of the Spanish Habsburg portrait, otherwise commonly related to the tradition of sculptural Italian models (Marco Aurelio, Tacca), or to the painting activity of Titian and Rubens

    Establishing baseline criteria of cardio-ankle vascular index as a new indicator of arteriosclerosis: a cross-sectional study

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    <p>Abstract</p> <p>Background</p> <p>A cardio-ankle vascular index (CAVI) has been developed to represent the extent of arteriosclerosis throughout the aorta, femoral artery and tibial artery independent of blood pressure. To practically use CAVI as a diagnostic tool for determining the extent of arteriosclerosis, our study objectives were (1) to establish the baseline CAVI scores by age and gender among cardiovascular disease (CVD) risk-free persons, (2) to compare CAVI scores between genders to test the hypothesis that the extent of arteriosclerosis in men is greater than in women, and (3) to compare CAVI scores between the CVD risk-free group and the CVD high-risk group in order to test the hypothesis that the extent of arteriosclerosis in the CVD high-risk group is greater than in the CVD risk-free group.</p> <p>Methods</p> <p>Study subjects were 32,627 urban residents 20-74 years of age who participated in CVD screening in Japan during 2004-2006. A new device (model VaSera VS-1000) was used to measure CAVI scores. At the time of screening, CVD high-risk persons were defined as those having any clinical abnormalities of CVD, and CVD risk-free persons were defined as those without any clinical abnormalities of CVD. Age-specific average CAVI scores were compared between genders and between the CVD risk-free group and the CVD high-risk group. Student's t-test using two independent samples was applied to a comparison of means between two groups.</p> <p>Results</p> <p>Average age-specific baseline scores of CAVI in the CVD risk-free group linearly increased in both genders as their age increased. Average age-specific baseline scores of CAVI in the CVD risk-free group were significantly greater among men than among women. Average age-specific baseline scores of CAVI in the CVD risk-free group were significantly smaller than those in the CVD high-risk group in both genders after 40 years of age.</p> <p>Conclusions</p> <p>The baseline CAVI scores from the CVD risk-free group are useful for future studies as control values. The CAVI method is a useful tool to screen persons with moderate to advanced levels of arteriosclerosis.</p

    Effects of metabolic syndrome on arterial function in different age groups: the Advanced Approach to Arterial Stiffness study

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    Objective: The aim of the Advanced Approach to Arterial Stiffness study was to compare arterial stiffness measured simultaneously with two different methods in different age groups of middle-aged and older adults with or without metabolic syndrome (MetS). The specific effects of the different MetS components on arterial stiffness were also studied. Methods: This prospective, multicentre, international study included 2224 patients aged 40 years and older, 1664 with and 560 without MetS. Patients were enrolled in 32 centres from 18 European countries affiliated to the International Society of Vascular Health & Aging. Arterial stiffness was evaluated using the cardio-ankle vascular index (CAVI) and the carotid-femoral pulse wave velocity (CF-PWV) in four prespecified age groups: 40-49, 50-59, 60-74, 75-90 years. In this report, we present the baseline data of this study. Results: Both CF-PWV and CAVI increased with age, with a higher correlation coefficient for CAVI (comparison of coefficients P < 0.001). Age-adjusted and sex-adjusted values of CF-PWV and CAVI were weakly intercorrelated (r 2 = 0.06, P < 0.001). Age-adjusted and sex-adjusted values for CF-PWV but not CAVI were higher in presence of MetS (CF-PWV: 9.57 ± 0.06 vs. 8.65 ± 0.10, P < 0.001; CAVI: 8.34 ± 0.03 vs. 8.29 ± 0.04, P = 0.40; mean ± SEM; MetS vs. no MetS). The absence of an overall effect of MetS on CAVI was related to the heterogeneous effects of the components of MetS on this parameter: CAVI was positively associated with the high glycaemia and high blood pressure components, whereas lacked significant associations with the HDL and triglycerides components while exhibiting a negative association with the overweight component. In contrast, all five MetS components showed positive associations with CF-PWV. Conclusion: This large European multicentre study reveals a differential impact of MetS and age on CAVI and CF-PWV and suggests that age may have a more pronounced effect on CAVI, whereas MetS increases CF-PWV but not CAVI. This important finding may be due to heterogeneous effects of MetS components on CAVI. The clinical significance of these original results will be assessed during the longitudinal phase of the study

    cardio ankle vascular index is associated with diabetic retinopathy in younger than 70 years patients with type 2 diabetes mellitus

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    Abstract Aims This study aimed to investigate the relationship between cardio-ankle vascular index (CAVI) and diabetic retinopathy (DR) in Caucasian patients with type 2 Diabetes Mellitus (T2DM). Methods This was a cross-sectional study of 299 T2DM patients admitted to Endocrine Unit of Foggia. DR was diagnosed using the International Clinical Disease Severity Scale of American Academy of Ophthalmology. The VaSera VS-1500N was used to measure CAVI. Because age is the most powerful determinant of arterial stiffness and affects the progression of DR, we divided the whole sample into two subgroups: above (older) and below (younger) 70 years. Results The mean age of patients was 60.4 ± 12.6 years and the mean CAVI value was 8.6 ± 1.7. In the whole population DR was diagnosed in 74 (24.7%) patients. CAVI value was clearly higher in patients with DR (9.5 ± 1.6) than in those without (8.7 ± 1.7) ( P =0.001) although this difference was not any more significant when adjusted by age and gender (P=0.067). In the multivariate model taking into account several possible confounders, the correlation between DR and CAVI remained significant only in younger subjects. In the same subgroup we found a significant association between the stages of DR and CAVI (p=0.019 adjusted by age and gender). Conclusions This study shows that CAVI is significantly higher in younger patients with DR than in those without, with a relationship between the stages of DR and CAVI in the same subgroup. Physicians should pay attention to sub-clinical macroangiopathy in younger T2DM patients who have DR

    Correlation Between Smoking and Il-1 Level and Arterial Stiffness as Measured By Cavi in the Young Adult Population Without other Cardiovascular Risk Factors.

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    Background: Recent studies have shown that arterial stiffness is a strong predictor of cardiovascular events and all-cause mortality, with CAVI (Cardio-Ankle Vascular Index) as a non-invasive arterial stiffness testing method indaily practice.Objective: This study was conducted to examine the relationship between smoking -as a risk factor for arterial stiffness- and CAVI values, as well as levels of IL-1β (Interleukin 1β) as a cytokine that plays a role in the pathophysiology of arterial stiffness.Methods: Eighty-four participants, including smokers and non-smokers without other cardiovascular risk factors, were included in the study. Demographic data, medical history, and smoking behavior were taken using a questionnaire, then IL-1β and CAVI levels were examinedResults: The mean level of IL-1β in smoking subjects was significantly higher (15.09 ± 0.48) than in non-smoking subjects (5.53 ± 0.79; p=0.001). CAVI values in smoking subjects were also significantly higher (8.0 ± 0.06) than in non-smoking subjects (6.9 ± 0.02; p=0.001). Further analysis showed a strong positive correlation between smoking and IL-1β levels (r=+0.776; p=0.001) and CAVI values (r=+0.759; p=0.001).Conclusion: This study shows that smoking significantly correlates with IL-1β levels and CAVI values. The greater number of cigarettes used per day and the longer duration of smoking, there was a positive correlation between IL-1β levels and arterial stiffness as measured by CAVI
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