Stretching dependence of the vibration modes of a single-molecule Pt-H2-Pt bridge

A conducting bridge of a single hydrogen molecule between Pt electrodes is formed in a break junction experiment. It has a conductance near the quantum unit, G0=2e2∕h, carried by a single channel. Using point-contact spectroscopy three vibration modes are observed and their variation upon isotope substitution is obtained. The stretching dependence for each of the modes allows uniquely classifying them as longitudinal or transversal modes. The interpretation of the experiment in terms of a Pt-H2-Pt bridge is verified by density-functional theory calculations for the stability, vibrational modes, and conductance of the structure.

Analysis of a metallic pedestrian bridge under dynamic human loads in pre and post reinforcement phases

The purpose of this work is to study the dynamic behavior of a pedestrian bridge in Alicante, Spain. It is a very slender footbridge with vertical and horizontal vibration problems during the passage of pedestrians. Accelerations have been recorded by accelerometers installed at various locations of the bridge. Two scenarios, in free vibration (after the passage of a certain number of pedestrians on the bridge) and forced vibration produced by a fixed number of pedestrians walking on the bridge at a certain speed and frequency. In each test, the effect on the comfort of the pedestrians, the natural frequencies of vibration, the mode shapes and damping factors have been estimated. It has been found that the acceleration levels are much higher than the allowable by the Spanish standards and this should be considered in the restoration of the footbridge.

A public-professional web-bridge for vaccines and vaccination: User concerns about vaccine safety

Vacunas.org (http://www.vacunas.org), a website founded by the Spanish Association of Vaccinology offers a personalized service called Ask the Expert, which answers any questions posed by the public or health professionals about vaccines and vaccination. The aim of this study was to analyze the factors associated with questions on vaccination safety and determine the characteristics of questioners and the type of question asked during the period 2008–2010. A total of 1341 questions were finally included in the analysis. Of those, 30% were related to vaccine safety. Questions about pregnant women had 5.01 higher odds of asking about safety (95% CI 2.82–8.93) than people not belonging to any risk group. Older questioners (>50 years) were less likely to ask about vaccine safety compared to younger questioners (OR: 0.44, 95% CI 0.25–0.76). Questions made after vaccination or related to influenza (including H1N1) or travel vaccines were also associated with a higher likelihood of asking about vaccine safety. These results identify risk groups (pregnant women), population groups (older people) and some vaccines (travel and influenza vaccines, including H1N1) where greater efforts to provide improved, more-tailored vaccine information in general and on the Internet are required.

Steel Pedestrian Bridge to Protect a Unique Tree

This paper describes the “Variation Guggenheim 3: Mirador de la palmera” project, situated in Daya Vieja (Alicante-Spain). This structure is inspired by the Guggenheim museum of New York and is designed to protect a land-mark palm-tree from wind loads. This six – trunk palm tree was declared monument by the Valencian government in 2012. The structure that now protect it appears to fly around de palm tree creating a helicoidally skywalk made of steel, while retrofitting the lateral trunks of the tree to protect them from collapse. An 18 m. long straight beam starts on the top of this helix, and stretches towards a lookout point that offers a view of the whole village and its surroundings. The reduction of the visual impact of the structure on the tree was a major aim for the project design. The structural elements are as slender as possible to avoid the visual obstruction of tree. They are painted white, while the walkway steel corrugated plate is painted green in order to highlight its neat shape among the blur created by the apparent mess of bars of the supporting structure. The two main piles of this pedestrian bridge were designed in steel and geometrically resemble trees. A Ground Penetrating Radar analysis was performed to detect the palm root location and to decide the best foundation system. Slender cast in-situ steel-concrete micropiles along with a concrete pile-cap, raised some centimeters above the ground level, were used to reduce the damage to the roots. The projected pile-cap is a slender, continuous, circular ring; which geometry resembles a concrete bench. This structure has been a finalist in the Architecture Awards for the 2010-2014 best construction projects, held by the Diputación de Alicante.

A Unique Prestressed Concrete Pedestrian Bridge in Spain

This paper describes the so-called Kiss Bridge. This structure resembles a kiss, a subtle touch of structures. The beams have been structurally designed to adapt the Japanese art of paper folding called "origami." The material used for constructing the floating beams is white reinforced concrete in the form of folded shells. The two geometrically different parts have distinct structural behaviors. The length of the main pathway of both structures is over 60 m. The pedestrian bridge crosses an artificial rainwater channel with a skew of 45° with respect to the referred channel. The joint between the cantilever structure and the Y-shaped one is located over the middle of the channel. Each stretch has different transversal sections. The pedestrian bridge is made with prestressed self-compacting reinforced concrete of 60 MPa. The foundation is shallow, comprising footings and footing beams made of 25 MPa conventional concrete. The cantilever structure with its foundations is designed as a semi-integral bridge whereas the Y-shaped one is an integral structure. The dynamic behavior of the structure was carefully studied to ensure that the dynamic loads generated by pedestrians do not cause excessive vibrations, especially to the cantilever structure, which could present dynamic interactions with the pedestrians walking. The bridge was recognized, in the 2014 edition of the fib Awards for Outstanding Concrete Structures, for having made a valuable contribution to the image and promotion of concrete structures.