1,720,971 research outputs found
Defying chemical equilibrium with light
Full text linkChemical systems capable of exploiting an energy source to function away from thermodynamic equilibrium are a hallmark of the biological world. The design and operation of artificial versions of such systems constitute a stimulating and highly challenging scientific goal with considerable expectations for application in synthetic chemistry, catalysis, materials science, energy conversion, and medical therapy. In this context, supplying energy in the form of photons has several elements of conceptual interest and practical advantage. Here we present the progress of research over the past 5 years on artificial molecular-based systems that can use light energy to operate away from equilibrium – an emerging field that has just begun to express its innovative potential
Photoactivated Artificial Molecular Motors
Full text linkAccurate control of long-range motion at the molecular scale holds great potential for the development of ground-breaking applications in energy storage and bionanotechnology. The past decade has seen tremendous development in this area, with a focus on the directional operation away from thermal equilibrium, giving rise to tailored man-made molecular motors. As light is a highly tunable, controllable, clean, and renewable source of energy, photochemical processes are appealing to activate molecular motors. Nonetheless, the successful operation of molecular motors fueled by light is a highly challenging task, which requires a judicious coupling of thermal and photoinduced reactions. In this paper, we focus on the key aspects of light-driven artificial molecular motors with the aid of recent examples. A critical assessment of the criteria for the design, operation, and technological potential of such systems is provided, along with a perspective view on future advances in this exciting research area
Severe and polytraumatic injuries among recreational skiers and snowboarders: incidence, demographics and injury patterns in South Tyrol
No full textBackground Alpine skiing and snowboarding are popular winter sports. The practice of these sports is related to traumatic injuries, some of which are severe and/or life threatening. Objectives To identify the incidence, injury patterns and associated risk factors of severe and polytraumatic injuries in South Tyrol. Materials and methods During four consecutive winter seasons (2001-2005), data of every patient referred to our emergency department (Bolzano-Bozen) after a skiing or snowboarding accident were collected. One hundred and five patients with an Injury Severity Score of 16 or higher were identified (90 skiers, 15 snowboarders). Statistical descriptive analyses were carried out by producing frequency tables. Chi-square test was performed to verify possible association between injury severity and type of sport. Risk factors for severe injuries were evaluated using logistic regression with robust variance estimators. Results Traumatic brain injury was the most common injury observed (51 cases), followed by vertebral injury (45 cases); 63% of the patients reported two or more associated injuries. We observed significant associations between severe spine injuries and the following risk factors: snowboarders who reported more severe injuries than skiers [odds ratio = 5.89, 95% confidence interval (CI) = 1.31, 26.44], age classes of 40-50 years and over 60 years showed an OR of 8.10 (95% CI = 1.87, 35.06) and 5.16 (95% CI = 1.27, 21.01), respectively, with respect to age class (20-40 years). Conclusion Severe traumatic injuries occur among skiers and snowboarders, and preventive measures such as the use of helmets and educational programs, are necessar
Light‐Responsive (Supra)Molecular Architectures: Recent Advances
Full text linkThe development and investigation of (supra)molecular-based architectures characterized by light-activated functionalities is a highly relevant topic of chemical research. The interest on photo-controlled systems arises not only from their potential applications in different fields of technology but also from their scientific significance related to the understanding of light–matter interactions at the nanoscale. Indeed, light is a peculiar and unique tool as it can be conveniently applied to supply the energy required to affect and operate a system and, at the same time, to probe its state and investigate its transformations. Some basic aspects of light-induced processes in (supra) molecular architectures are discussed here in the frame of their use to implement novel functionalities in nanostructured systems and materials. In this perspective, a few recent examples from our own work will be illustrated which are meant to provide an overview of the current directions in this highly cross-disciplinary field of research
Photoactivated Artificial Molecular Machines that Can Perform Tasks
Full text linkResearch on artificial photoactivated molecular machines has moved in recent years from a basic scientific endeavor toward a more applicative effort. Nowadays, the prospect of reproducing the operation of natural nanomachines with artificial counterparts is no longer a dream but a concrete possibility. The progress toward the construction of molecular-machine-based devices and materials in which light irradiation results in the execution of a task as a result of nanoscale movements is illustrated here. After a brief description of a few basic types of photoactivated molecular machines, significant examples of their exploitation to perform predetermined functions are presented. These include switchable catalysts, nanoactuators that interact with cellular membranes, transporters of small molecular cargos, and active joints capable of mechanically coupling molecular-scale movements. Investigations aimed at harnessing the collective operation of a multitude of molecular machines organized in arrays to perform tasks at the microscale and macroscale in hard and soft materials are also reviewed. Surfaces, gels, liquid crystals, polymers, and self-assembled nanostructures are described wherein the nanoscale movement of embedded molecular machines is amplified, allowing the realization of muscle-like actuators, microfluidic devices, and polymeric materials for light energy transduction and storage
Stereodynamics of E/Z isomerization in rotaxanes through mechanical shuttling and covalent bond rotation
Full text linkWe report on a set of rotaxanes with symmetrical axles equipped with a central
amide group that installs E/Z stereoisomerism owing to the ring position along the
axle. Isomerization by concomitant rotation about the amide bond and ring
shuttling along the axle was thoroughly characterized in different solvents. The
results trigger a discussion on core concepts, such as microscopic reversibility and
transition state theory, and provide insights for designing molecules capable to
transform and transmit motion between subcomponents
Factors affecting injury severity among recreational skiers and snowboarders: an epidemiology study
No full textDifferent results have been reported for skiing and snowboarding injuries worldwide. Few studies consider the injury severity score (ISS) for the evaluation of differences among injured skiers-snowboarders. The aim of this study is to identify possible risk factors that affect the severity of skiing and snowboarding injuries in three winter seasons (2002-2005) in South Tyrol. For every injured skier or snowboarder referred to our emergency department in three consecutive seasons, the following data were collected: date of birth, gender, self-declared technical skills level, place of residence (local/non-local), as well as the date, time, and place of the accident. Type of injury and ISS were retrospectively assigned. Data concerning the snowfall in the last 24 h, average snow level, and outdoor air temperature values were obtained from four weather stations that were located inside the ski resorts. A multiple linear regression model was used to evaluate the association between ISS and potential determinants. In the analyzed seasons, 2,511 injured skiers and 843 injured snowboarders were evaluated at our emergency department. There was a significant change in the ISS value for subjects with different self-reported skills levels (P < 0.001). Men and non-local residents experienced more severe injuries than women and local residents, respectively (P < 0.013, P < 0.001). The ISS was higher for people aged over 60 (P < 0.001). Snowfalls brought about a decrease in accident severity (P = 0.009). The severity of the injuries increases with age. Prevention and information programs should be targeted to people who are at high risk of severe injury. A 24-h fresh snowfall seems to reduce the severity of injuries. Very little is known about snow conditions and winter sports injury. Further studies are needed to explore this field
Chemical On/Off Switching of Mechanically Planar Chirality and Chiral Anion Recognition in a [2]Rotaxane Molecular Shuttle
Full text linkWe exploit a reversible acid-base triggered molecular shuttling process to switch an appropriately designed rotaxane between prochiral and mechanically planar chiral forms. The mechanically planar enantiomers and their interconversion, arising from ring shuttling, have been characterized by NMR spectroscopy. We also show that the supramolecular interaction of the positively charged rotaxane with optically active anions causes an imbalance in the population of the two enantiomeric co-conformations. This result represents an unprecedented example of chiral molecular recognition and can disclose innovative approaches to enantioselective sensing and catalysis
Second-Generation Light-Fueled Supramolecular Pump
Full text linkWe describe the modular design of a pseudorotaxane-based supramolecular pump and its photochemically driven autonomous nonequilibrium operation in a dissipative regime. These properties derive from careful engineering of the energy maxima and minima along the threading coordinate and their light-triggered modulation. Unlike its precursor, this second-generation system is amenable to functionalization for integration into more complex devices
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