1,231 research outputs found
Mechanism for current saturation and energy dissipation in graphene transistors
From a combination of careful and detailed theoretical and experimental
studies, we demonstrate that the Boltzmann theory including all scattering
mechanisms gives an excellent account, with no adjustable parameters, of high
electric field transport in single as well as double-oxide graphene
transistors. We further show unambiguously that scattering from the substrate
and superstrate surface optical (SO) phonons governs the high field transport
and heat dissipation over a wide range of experimentally relevant parameters.
Models that neglect SO phonons altogether or treat them in a simple
phenomenological manner are inadequate. We outline possible strategies for
achieving higher current and complete saturation in graphene devices.Comment: revtex, 5 pages, 3 figures, to appear in Phys. Rev. Lett
A quantitative model of the initiation of DNA replication in Saccharomyces cerevisiae predicts the effects of system perturbations.
BackgroundEukaryotic cell proliferation involves DNA replication, a tightly regulated process mediated by a multitude of protein factors. In budding yeast, the initiation of replication is facilitated by the heterohexameric origin recognition complex (ORC). ORC binds to specific origins of replication and then serves as a scaffold for the recruitment of other factors such as Cdt1, Cdc6, the Mcm2-7 complex, Cdc45 and the Dbf4-Cdc7 kinase complex. While many of the mechanisms controlling these associations are well documented, mathematical models are needed to explore the network's dynamic behaviour. We have developed an ordinary differential equation-based model of the protein-protein interaction network describing replication initiation.ResultsThe model was validated against quantified levels of protein factors over a range of cell cycle timepoints. Using chromatin extracts from synchronized Saccharomyces cerevisiae cell cultures, we were able to monitor the in vivo fluctuations of several of the aforementioned proteins, with additional data obtained from the literature. The model behaviour conforms to perturbation trials previously reported in the literature, and accurately predicts the results of our own knockdown experiments. Furthermore, we successfully incorporated our replication initiation model into an established model of the entire yeast cell cycle, thus providing a comprehensive description of these processes.ConclusionsThis study establishes a robust model of the processes driving DNA replication initiation. The model was validated against observed cell concentrations of the driving factors, and characterizes the interactions between factors implicated in eukaryotic DNA replication. Finally, this model can serve as a guide in efforts to generate a comprehensive model of the mammalian cell cycle in order to explore cancer-related phenotypes
Mandate-driven networking eco-system : a paradigm shift in end-to-end communications
The wireless industry is driven by key stakeholders that follow a holistic approach of "one-system-fits-all" that leads to moving network functionality of meeting stringent End-to-End (E2E) communication requirements towards the core and cloud infrastructures. This trend is limiting smaller and new players for bringing in new and novel solutions. For meeting these E2E requirements, tenants and end-users need to be active players for bringing their needs and innovations. Driving E2E communication not only in terms of quality of service (QoS) but also overall carbon footprint and spectrum efficiency from one specific community may lead to undesirable simplifications and a higher level of abstraction of other network segments may lead to sub-optimal operations. Based on this, the paper presents a paradigm shift that will enlarge the role of wireless innovation at academia, Small and Medium-sized Enterprises (SME)'s, industries and start-ups while taking into account decentralized mandate-driven intelligence in E2E communications
Biological warfare, bioterrorism, biodefence and the biological and toxin weapons convention
Biological warfare is the intentional use of micro-organisms, and
toxins, generally of microbial, plant or animal origin to produce
disease and death in humans, livestock and crops. The attraction of
bioweapons in war, and for use in terroristic attacks is attributed to
easy access to a wide range of disease-producing biological agents, to
their low production costs, to their non-detection by routine security
systems, and to their easy transportation from one place to another. In
addition, novel and accessible technologies give rise to proliferation
of such weapons that have implications for regional and global
security. In counteraction of such threats, and in securing the culture
and defence of peace, the need for leadership and example in devising
preventive and protective strategies has been emphasised through
international consultation and co-operation. Adherence to the
Biological and Toxin Weapons Convention reinforced by
confidence-building measures sustained by use of monitoring and
verification protocols, is indeed, an important and necessary step in
reducing and eliminating the threats of biological warfare and
bioterrorism
Formation energy and interaction of point defects in two-dimensional colloidal crystals
The manipulation of individual colloidal particles using optical tweezers has
allowed vacancies to be created in two-dimensional (2d) colloidal crystals,
with unprecedented possibility of real-time monitoring the dynamics of such
defects (Nature {\bf 413}, 147 (2001)). In this Letter, we employ molecular
dynamics (MD) simulations to calculate the formation energy of single defects
and the binding energy between pairs of defects in a 2d colloidal crystal. In
the light of our results, experimental observations of vacancies could be
explained and then compared to simulation results for the interstitial defects.
We see a remarkable similarity between our results for a 2d colloidal crystal
and the 2d Wigner crystal (Phys. Rev. Lett. {\bf 86}, 492 (2001)). The results
show that the formation energy to create a single interstitial is
lower than that of the vacancy. Because the pair binding energies of the
defects are strongly attractive for short distances, the ground state should
correspond to bound pairs with the interstitial bound pairs being the most
probable.Comment: 5 pages, 2 figure
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