Chest pulse-wave velocity: a novel approach to assess arterial stiffness.

Pulse-wave velocity (PWV) is considered as the gold-standard method to assess arterial stiffness, an independent predictor of cardiovascular morbidity and mortality. Current available devices that measure PWV need to be operated by skilled medical staff, thus, reducing the potential use of PWV in the ambulatory setting. In this paper, we present a new technique allowing continuous, unsupervised measurements of pulse transit times (PTT) in central arteries by means of a chest sensor. This technique relies on measuring the propagation time of pressure pulses from their genesis in the left ventricle to their later arrival at the cutaneous vasculature on the sternum. Combined thoracic impedance cardiography and phonocardiography are used to detect the opening of the aortic valve, from which a pre-ejection period (PEP) value is estimated. Multichannel reflective photoplethysmography at the sternum is used to detect the distal pulse-arrival time (PAT). A PTT value is then calculated as PTT = PAT - PEP. After optimizing the parameters of the chest PTT calculation algorithm on a nine-subject cohort, a prospective validation study involving 31 normo- and hypertensive subjects was performed. 1/chest PTT correlated very well with the COMPLIOR carotid to femoral PWV (r = 0.88, p < 10 (-9)). Finally, an empirical method to map chest PTT values onto chest PWV values is explored.

The Macrocirculation and Microcirculation of Hypertension.

Changes in vascular structure that accompany hypertension may contribute to hypertensive end-organ damage. Both the macrovascular and microvascular levels should be considered, as interactions between them are believed to be critically important. Regarding the macrocirculation, the article first reviews basic concepts of vascular biomechanics, such as arterial compliance, arterial distensibility, and stress-strain relationships of arterial wall material, and then reviews how hypertension affects the properties of conduit arteries, particularly examining evidence that it accelerates the progressive stiffening that normally occurs with advancing age. High arterial stiffness may increase central systolic and pulse pressure by two different mechanisms: 1) Abnormally high pulse wave velocity may cause pressure waves reflected in the periphery to reach the central aorta in systole, thus augmenting systolic pressure; 2) In the elderly, the interaction of the forward pressure wave with high arterial stiffness is mostly responsible for abnormally high pulse pressure. At the microvascular level, hypertensive disease is characterized by inward eutrophic or hypertrophic arteriolar remodeling and capillary rarefaction. These abnormalities may depend in part on the abnormal transmission of highly pulsatile blood pressure into microvascular networks, especially in highly perfused organs with low vascular resistance, such as the kidney, heart, and brain, where it contributes to hypertensive end-organ damage.

Urocortins improve dystrophic skeletal muscle structure and function through both PKA- and Epac-dependent pathways.

In Duchenne muscular dystrophy, the absence of dystrophin causes progressive muscle wasting and premature death. Excessive calcium influx is thought to initiate the pathogenic cascade, resulting in muscle cell death. Urocortins (Ucns) have protected muscle in several experimental paradigms. Herein, we demonstrate that daily s.c. injections of either Ucn 1 or Ucn 2 to 3-week-old dystrophic mdx(5Cv) mice for 2 weeks increased skeletal muscle mass and normalized plasma creatine kinase activity. Histological examination showed that Ucns remarkably reduced necrosis in the diaphragm and slow- and fast-twitch muscles. Ucns improved muscle resistance to mechanical stress provoked by repetitive tetanizations. Ucn 2 treatment resulted in faster kinetics of contraction and relaxation and a rightward shift of the force-frequency curve, suggesting improved calcium homeostasis. Ucn 2 decreased calcium influx into freshly isolated dystrophic muscles. Pharmacological manipulation demonstrated that the mechanism involved the corticotropin-releasing factor type 2 receptor, cAMP elevation, and activation of both protein kinase A and the cAMP-binding protein Epac. Moreover, both STIM1, the calcium sensor that initiates the assembly of store-operated channels, and the calcium-independent phospholipase A(2) that activates these channels were reduced in dystrophic muscle by Ucn 2. Altogether, our results demonstrate the high potency of Ucns for improving dystrophic muscle structure and function, suggesting that these peptides may be considered for treatment of Duchenne muscular dystrophy.

Front-crawl instantaneous velocity estimation using a wearable inertial measurement unit.

Monitoring the performance is a crucial task for elite sports during both training and competition. Velocity is the key parameter of performance in swimming, but swimming performance evaluation remains immature due to the complexities of measurements in water. The purpose of this study is to use a single inertial measurement unit (IMU) to estimate front crawl velocity. Thirty swimmers, equipped with an IMU on the sacrum, each performed four different velocity trials of 25 m in ascending order. A tethered speedometer was used as the velocity measurement reference. Deployment of biomechanical constraints of front crawl locomotion and change detection framework on acceleration signal paved the way for a drift-free integration of forward acceleration using IMU to estimate the swimmers velocity. A difference of 0.6 ± 5.4 cm · s(-1) on mean cycle velocity and an RMS difference of 11.3 cm · s(-1) in instantaneous velocity estimation were observed between IMU and the reference. The most important contribution of the study is a new practical tool for objective evaluation of swimming performance. A single body-worn IMU provides timely feedback for coaches and sport scientists without any complicated setup or restraining the swimmer's natural technique.

Gaussian process framework for pervasive estimation of swimming velocity with body-worn IMU

Presented is an accurate swimming velocity estimation method using an inertial measurement unit (IMU) by employing a simple biomechanical constraint of motion along with Gaussian process regression to deal with sensor inherent errors. Experimental validation shows a velocity RMS error of 9.0 cm/s and high linear correlation when compared with a commercial tethered reference system. The results confirm the practicality of the presented method to estimate swimming velocity using a single low-cost, body-worn IMU.

The mycorrhizal contribution to plant productivity, plant nutrition and soil structure in experimental grassland.

Previous studies have shown that arbuscular mycorrhizal fungi (AMF) can influence plant diversity and ecosystem productivity. However, little is known about the effects of AMF and different AMF taxa on other important community properties such as nutrient acquisition, plant survival and soil structure. We established experimental grassland microcosms and tested the impact of AMF and of different AMF taxa on a number of grassland characteristics. We also tested whether plant species benefited from the same or different AMF taxa in subsequent growing seasons. AMF enhanced phosphorus acquisition, soil aggregation and survival of several plant species, but AMF did not increase total plant productivity. Moreover, AMF increased nitrogen acquisition by some plant species, but AMF had no effect on total N uptake by the plant community. Plant growth responses to AMF were temporally variable and some plant species obtained the highest biomass with different AMF in different years. Hence the results indicate that it may be beneficial for a plant to be colonized by different AMF taxa in different seasons. This study shows that AMF play a key role in grassland by improving plant nutrition and soil structure, and by regulating the make-up of the plant community.

Towards a theory of the credit-risk balance sheet (II). The evolution of its structure

This article has an immediate predecessor, upon which it is based and with which readers must necessarily be familiar: Towards a Theory of the Credit-Risk Balance Sheet (Vallverdú, Somoza and Moya, 2006). The Balance Sheet is conceptualised on the basis of the duality of a credit-based transaction; it deals with its theoretical foundations, providing evidence of a causal credit-risk duality, that is, a true causal relationship; its characteristics, properties and its static and dynamic characteristics are analyzed. This article, which provides a logical continuation to the previous one, studies the evolution of the structure of the Credit-Risk Balance Sheet as a consequence of a business¿s dynamics in the credit area. Given the Credit-Risk Balance Sheet of a company at any given time, it attempts to estimate, by means of sequential analysis, its structural evolution, showing its usefulness in the management and control of credit and risk. To do this, it bases itself, with the necessary adaptations, on the by-now classic works of Palomba and Cutolo. The establishment of the corresponding transformation matrices allows one to move from an initial balance sheet structure to a final, future one, to understand its credit-risk situation trends, as well as to make possible its monitoring and control, basic elements in providing support for risk management.

Dynamic properties of human brain structure: learning-related changes in cortical areas and associated fiber connections.

Recent findings in neuroscience suggest that adult brain structure changes in response to environmental alterations and skill learning. Whereas much is known about structural changes after intensive practice for several months, little is known about the effects of single practice sessions on macroscopic brain structure and about progressive (dynamic) morphological alterations relative to improved task proficiency during learning for several weeks. Using T1-weighted and diffusion tensor imaging in humans, we demonstrate significant gray matter volume increases in frontal and parietal brain areas following only two sessions of practice in a complex whole-body balancing task. Gray matter volume increase in the prefrontal cortex correlated positively with subject's performance improvements during a 6 week learning period. Furthermore, we found that microstructural changes of fractional anisotropy in corresponding white matter regions followed the same temporal dynamic in relation to task performance. The results make clear how marginal alterations in our ever changing environment affect adult brain structure and elucidate the interrelated reorganization in cortical areas and associated fiber connections in correlation with improvements in task performance.

Regional structure of wages and external economies in Spain

Regional data on wages for the Spanish economy show that workers who live in developed regions earn more than workers in other regions.Literature on external economies provides a possible explanation of why firms do not move from these regions to others where wages are lower. Previous studies for the Spanish case use aggregated sectoral data to explain in terms of external economies why average wages are different across regions. The originalcontribution of this paper consists of using individual data to detect the existenceand nature of external economies as an explanatory cause of territorial wagedifferences. With this aim, we have used individual data from the EPF 1990-91(INE). This information permits us to control the influence of individual and jobcharacteristics on wages to, first, detect the existence of external economies and,second, to test alternative explanations of their presence. The empirical evidenceobtained confirms the relevance of territorial external economies and their influence on wages, as a result of improvements in the productive efficiency of the firm. In concrete terms, the more relevant external economies are associatedwith the regional human capital stock and geographical productive specialisation

Ownership structure and innovation: Is there a real link?

This work focuses on the study of the relationship between ownership and control structure of the company and its innovative activity. Its aim consists of analysing the role that may be played by determinants within the company related to ownership structure when the decision to incur research and development activities is taken as well as on the output of this innovate process. Among these determinants we may think of issues such as who owns the firm and how the control of decision-making is distributed, the nature of this control and the level of concentration of ownership, among others. The study is carried out for the year 2001 using a representative sample of Spanish manufacturing industries.

Induced aggregation operators in decision making with the Dempster-Shafer belief structure

We study the induced aggregation operators. The analysis begins with a revision of some basic concepts such as the induced ordered weighted averaging (IOWA) operator and the induced ordered weighted geometric (IOWG) operator. We then analyze the problem of decision making with Dempster-Shafer theory of evidence. We suggest the use of induced aggregation operators in decision making with Dempster-Shafer theory. We focus on the aggregation step and examine some of its main properties, including the distinction between descending and ascending orders and different families of induced operators. Finally, we present an illustrative example in which the results obtained using different types of aggregation operators can be seen.