Search

Wind and wave loads subject the tower structures of wind turbines to bending stress. The resulting initial linear strain gradients in the tower cross-section cause fatigue-induced degradation of the concrete at the outer edge of the structures. As the number of load cycles increases, stresses are gradually redistributed to the inner cross-section of the structure consequently. Most of the test results documented in the literature were obtained from small-scale concrete specimens or small-scale components. In those cases, the stiffness and stress redistributions occurring in the real component can only be insufficiently derived, and possible scale effects cannot be taken into account. Besides, available test results for individual component tests are mostly only for load cycles up to 2⋅106. However, significantly lower load levels and thus higher number of load cycles are expected to occur in wind turbines compared to usual fatigue tests. To deal with this issue, extensive fatigue tests on small cylindrical specimens as well as large-scale beams in the very-high-cycle fatigue range are carried out in this work. The test results of both cylindrical and beam specimens show the typical three-phase stiffness curves known from the literature. These curves exhibit a disproportionate decrease at the beginning of the loading, followed by a constant decrease in stiffness, and finally, a greater decrease in stiffness shortly before failure. Moreover, the stiffness curves from the tests on both specimen types show good agreement. It can be concluded that the results from small cylindrical specimen tests can be transferred to large-scale structural components. • Fatigue tests on large-scale concrete beams were carried out in a unique resonance-based testing facility. • Stiffness development of concrete cylinders and beam specimens was compared. • Good agreement between the stiffness behavior of both specimen types was found. • The stiffness behavior of cylindrical specimens can be transferred to large structures. [ABSTRACT FROM AUTHOR]

Copyright of Revista Española de Cardiología (18855857) is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Non-destructive testing techniques, such as ultrasonic testing and acoustic emission analysis, commonly employ piezoelectric sensors for monitoring and detecting defects in structures. The quality of data acquired using these sensors is highly dependent on the coupling layer between the transducer and the structure's surface. In this context, this study compares the signal response of four different couplant materials, namely acrylic adhesive pads, honey, vaseline, and hot glue, applied to a steel surface. For this purpose, experiments were conducted using a laser Doppler vibrometer and acoustic emission analysis to investigate the signal transmission of the couplant materials and their impact on the signal response of a coupled piezoelectric sensor VS30-V. The repeatability of the experiments was statistically analyzed. The findings indicate that acoustic emission measurements with acrylic adhesive pads exhibited the lowest relative standard deviation of 11.4%, followed by honey (13.2%), hot glue (21.9%), and vaseline (32.1%). The investigated couplant materials exhibited different effects on the signal response of the piezoelectric sensor. Specifically, acrylic adhesive pads and hot glue demonstrated more reliable signal transmission in the frequency range of 50 kHz to 65 kHz. In contrast, honey and vaseline had better performance within the frequency range of 65 kHz and 80 kHz. Considering the frequency-dependent characteristics of signal transmission and the ease of application, acrylic adhesive pads and honey are considered the preferred couplant materials for the frequency ranges of 50 kHz to 65 kHz and 65 kHz to 80 kHz, respectively. • Analysis of frequency-dependent signal transmission of couplant materials. • Measurements involved laser Doppler vibrometer and acoustic emission techniques. • Relative standard deviation for statistical analysis of measurement repeatability. • Computation of transfer functions for couplant materials. [ABSTRACT FROM AUTHOR]

The last version of Web’s hypertext standard has been developed from 2004 to 2014. During this era, HTML5 has experienced different crossroads due to the variety of motivations and needs that the main stakeholders interested in its development had. On October 2014, the standard got official by the W3C and closed a period of uncertainty around the future of the Web but at the same time, this agreement also introduced a major change in the own conception of the hypertext’s standard. In this paper we review the current status of digital commons on the Web and the development of HTML5. We also confront this analysis with several semi-structured interviews carried out with different experts in web development that represent at the same time different players of Web’s value chain. We argue that the development of HTML5 represents a new digital commons that prevented the proliferation of proprietary software that took place during the “Web 2.0” period. We claim that the World Wide Web promotes the development of new digital commons due to its own basis as a non-proprietary socio-technological platform. We also conclude that the development of standards and non-proprietary digital technologies is of outmost importance for the future of web business models that are fueled by major digital players. [ABSTRACT FROM AUTHOR]

Background context The most common adverse event after a lumbar puncture (LP) is a headache: In anaesthesiology, well studied is the protective effect of atraumatic spinal needles, and they are routinely used. However, this is less well known in diagnostic LP, and neurologists use atraumatic needles in less than 2% of times. Purpose The purpose of this study was to define the impact of needle type, atraumatic (Sprotte [S]) versus traumatic (Quincke [Q]) on postdural puncture headache (PDPH) incidence. Study design The study is based on a prospective, randomized, and simple-blinded clinical trial. Patient Sample Patients older than 14 years were scheduled for a diagnostic or therapeutic LP. Outcome Measures The outcome measure included the development of PDPH according to the International Headache Association criteria. Methods Patients fulfilling eligibility criteria were randomly allocated to one of two kinds of spinal needle: atraumatic or S-type or traumatic or Q-type. They were interviewed on days 2 and 7 about the development of PDPH. Results The incidence of PDPH was 22.43% with Q-type needle and 8.51% with S-type needle, p=.04. The duration of PDPH in patients in the S-type was 1 day or less, compared with a median of 4.14 days in the Q-type (p=.00). In the logistic regression model, the S-type needle together with the age of the patient were the only two statistically significant factors in the development of postlumbar puncture headache (PLPH), both of them being protective. Conclusions We found a lower incidence of PDPH with atraumatic needles, and it was statistically significant compared with the traumatic needles. Our study confirms the effectiveness of the atraumatic needles to prevent PDPH. [ABSTRACT FROM AUTHOR]

Abstract: The main objective was to study the effects, on sperm function, of the addition of two superoxide dismutase (SOD) analogues (Tempo and Tempol) to alpaca semen extender for cryopreservation. Twelve alpaca semen samples were collected using an artificial vagina and then diluted at a 1:3 ratio in an extender based on skim milk, egg yolk, and fructose. Each semen sample was divided into three equal parts to form the following groups: control, Tempo (1 mM), and Tempol (1 mM). Groups were cooled to 5 °C in 90 minutes (−1 °C in 3 minutes); when samples reached approximately 10 °C, SOD analogues were added to the respective groups. At 5 °C, ethylene glycol (final concentration, 0.1 M) was added to each group. After 30 minutes at 5 °C, samples were loaded in 0.25 mL plastic straws, placed in liquid nitrogen vapor for 15 minutes, and then plunged. Percentages of sperm motility, functional sperm membrane integrity, and viable sperm with intact acrosomes were evaluated before and after freeze-thaw using visual analysis, the hypoosmotic swelling test, and the double-stain trypan blue/giemsa technique, respectively. The Terminal deoxymucleotidyl transferase dUTP Nick End Labeling assay was performed for evaluation of sperm DNA fragmentation of frozen-thawed sperm. Sperm motility was higher (P < 0.05) in the Tempol and Tempo groups than in the control group (mean, 22.1%, 19.7%, and 11.2%, respectively), with similar results for functional sperm membrane integrity. Additionally, DNA fragmentation was lower (P < 0.05) in the Tempol group (16.7%) than in the control group (38.8%). Viable sperm with intact acrosomes were not affected by the use of SOD analogues. There was a negative correlation (r = −0.58) between DNA fragmentation of alpaca sperm and sperm motility after freeze-thawing, but DNA damage was neither related to functional membrane integrity nor viable sperm with intact acrosomes. We concluded that DNA fragmentation and loss of motility during cryopreservation of alpaca sperm could be partially prevented by supplementation of the semen extender with 1 mM Tempo or Tempol. [Copyright &y& Elsevier]