3,194 research outputs found
G-quartet biomolecular nanowires
We present a first-principle investigation of quadruple helix nanowires,
consisting of stacked planar hydrogen-bonded guanine tetramers. Our results
show that long wires form and are stable in potassium-rich conditions. We
present their electronic bandstructure and discuss the interpretation in terms
of effective wide-bandgap semiconductors. The microscopic structural and
electronic properties of the guanine quadruple helices make them suitable
candidates for molecular nanoelectronics.Comment: 7 pages, 3 figures, to be published in Applied Physics Letters (2002
A TDDFT study of the excited states of DNA bases and their assemblies
We present a detailed study of the optical absorption spectra of DNA bases
and base pairs, carried out by means of time dependent density functional
theory. The spectra for the isolated bases are compared to available
theoretical and experimental data and used to assess the accuracy of the method
and the quality of the exchange-correlation functional: Our approach turns out
to be a reliable tool to describe the response of the nucleobases. Furthermore,
we analyze in detail the impact of hydrogen bonding and -stacking in the
calculated spectra for both Watson-Crick base pairs and Watson-Crick stacked
assemblies. We show that the reduction of the UV absorption intensity
(hypochromicity) for light polarized along the base-pair plane depends strongly
on the type of interaction. For light polarized perpendicular to the basal
plane, the hypochromicity effect is reduced, but another characteristic is
found, namely a blue shift of the optical spectrum of the base-assembly
compared to that of the isolated bases. The use of optical tools as
fingerprints for the characterization of the structure (and type of
interaction) is extensively discussed.Comment: 31 pages, 8 figure
First principle theory of correlated transport through nano-junctions
We report the inclusion of electron-electron correlation in the calculation
of transport properties within an ab initio scheme. A key step is the
reformulation of Landauer's approach in terms of an effective transmittance for
the interacting electron system. We apply this framework to analyze the effect
of short range interactions on Pt atomic wires and discuss the coherent and
incoherent correction to the mean-field approach.Comment: 5 pages, 3 figure
What is a Gene? A Two Sided View
The need to account for all currently available experimental observations
concerning the gene nature, has reshaped the concept of gene turning it from the
essentially mechanistic unit, predominant during the '70s, into a quite abstract
open and generalized entity, whose contour appears less defined as compared to the
past. Here we propose the essence of the gene to be considered double faced. In
this respect genotypic and phenotypic entities of a gene would coexist and mix
reciprocally. This harmonizes present knowledge with current definitions and
predisposes for remodelling of our thinking as a consequence of future discoveries.
A two sided view of the gene also allows to combine the genetic and epigenetic
aspects in a unique solution, being structural and functional at the same time and
simultaneously able to include the different levels in an overlapping unicum
Bluetooth Mesh Technology for the Joint Monitoring of Indoor Environments and Mobile Device Localization: A Performance Study
Bluetooth Mesh is a recent SIG standard enabling the deployment of multi-hop Wireless Sensor Networks (WSNs) over Bluetooth Low Energy (BLE) communication links. The standard introduces many novel and interesting features in the Internet of Things (IoT) domain, such as the seamless integration among sensors and mobile and wearable devices, and the support for a wide range of different IoT application profiles. At the same time, fine-grained assessments of the performance are still needed to understand the potential of the technology. In this paper, we investigate the usage of Bluetooth Mesh solutions for the joint monitoring of indoor spaces and humans. Through the deployment of a test-bed, we evaluate the performance of Bluetooth Mesh WSNs under varying traffic loads and network sizes. In addition, by exploiting the short-range, multi-hop communications, we propose a procedure for the indoor localization of mobile devices and evaluate its accuracy. The results demonstrate that the technology supports reasonable delivery ratio under high traffic loads, however the network and localization performance sharply decreases when increasing the number of hops between the source and destination nodes
E-learning success determinants: Brazilian empirical study
E-learning is a web-based learning ecosystem for the dissemination of information, communication, and knowledge for education and training. Understanding the impact of e-learning on society, as well as its benefits, is important to link e-learning systems to their success drivers. The aim of this study is to find the determinants of user perceived satisfaction, use, and individual impact of e-learning. This study proposes a theoretical model integrating theories of information systems' satisfaction and success in the e-learning systems. The model was empirically validated in higher education institutions and university centers in Brazil through a quantitative method of structural equation modeling. Collaboration quality, information quality, and user perceived satisfaction explain e-learning use. The drivers of user perceived satisfaction are information quality, system quality, instructor attitude toward e-learning, diversity in assessment, and learner perceived interaction with others. System quality, use, and user perceived satisfaction explain individual impact.info:eu-repo/semantics/acceptedVersio
Effect of Exercise on Fatty Acid Metabolism and Adipokine Secretion in Adipose Tissue
Increased physical activity is an optimal way to maintain a good health. During exercise,
triacylglycerols, an energy reservoir in adipose tissue, are hydrolyzed to free fatty
acids (FAs) which are then released to the circulation, providing a fuel for working
muscles. Thus, regular physical activity leads to a reduction of adipose tissue mass
and improves metabolism. However, the reduction of lipid reservoir is also associated
with many other interesting changes in adipose tissue FA metabolism. For example, a
prolonged exercise contributes to a decrease in lipoprotein lipase activity and resultant
reduction of FA uptake. This results in the improvement of mitochondrial function and
upregulation of enzymes involved in the metabolism of polyunsaturated fatty acids. The
exercise-induced changes in adipocyte metabolism are associated with modifications
of FA composition. The modifications are adipose tissue depot-specific and follow
different patterns in visceral and subcutaneous adipose tissue. Moreover, exercise
affects adipokine release from adipose tissue, and thus, may mitigate inflammation and
improve insulin sensitivity. Another consequence of exercise is the recently described
phenomenon of adipose tissue “beiging,” i.e., a switch from energy-storing white
adipocyte phenotype to thermogenic FA oxidizing beige adipocytes. This process is
regulated by myokines released during the exercise. In this review, we summarize
published evidence for the exercise-related changes in FA metabolism and adipokine
release in adipose tissue, and their potential contribution to beneficial cardiovascular
and metabolic effects of physical activit
WoTwins: Automatic Digital Twin Generator for the Web of Things
Digital Twins are crucial in Industry 4.0 IoT scenarios, as they replicate physical assets and enable important tasks such as predictive analytics, what-if scenarios and real time monitoring. The heterogeneity of IoT use cases usually makes the development of digital twins extremely application-specific as well as prone to interoperability issues. To overcome these two challenges, we propose WoTwins, a framework that, on one side, leverages the W3C Web of Things (WoT) standard to model data and entities, and, on the other side, generates automatically Digital Twins of existing Web Things by modeling their state space through a Markov Decision Process (MDP) graph and by predicting its behavior though Machine Learning techniques. We conduct experiments on a simulated use cases related to IoT robotics to evaluate our proposa
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