The low-lying excitations of polydiacetylene

The Pariser-Parr-Pople Hamiltonian is used to calculate and identify the nature of the low-lying vertical transition energies of polydiacetylene. The model is solved using the density matrix renormalisation group method for a fixed acetylenic geometry for chains of up to 102 atoms. The non-linear optical properties of polydiacetylene are considered, which are determined by the third-order susceptibility. The experimental 1Bu data of Giesa and Schultz are used as the geometric model for the calculation. For short chains, the calculated E(1Bu) agrees with the experimental value, within solvation effects (ca. 0.3 eV). The charge gap is used to characterise bound and unbound states. The nBu is above the charge gap and hence a continuum state; the 1Bu, 2Ag and mAg are not and hence are bound excitons. For large chain lengths, the nBu tends towards the charge gap as expected, strongly suggesting that the nBu is the conduction band edge. The conduction band edge for PDA is agreed in the literature to be ca. 3.0 eV. Accounting for the strong polarisation effects of the medium and polaron formation gives our calculated E(nBu) ca. 3.6 eV, with an exciton binding energy of ca. 1.0 eV. The 2Ag state is found to be above the 1Bu, which does not agree with relaxed transition experimental data. However, this could be resolved by including explicit lattice relaxation in the Pariser- Parr-Pople-Peierls model. Particle-hole separation data further suggest that the 1Bu, 2Ag and mAg are bound excitons, and that the nBu is an unbound exciton.Comment: LaTeX, 23 pages, 4 postscript tables and 8 postscript figure

Application of Smartphone Technology in the Management and Treatment of Mental Illnesses

Abstract: Background: Mental illness continues to be a significant Public Health problem and the innovative use of technology to improve the treatment of mental illnesses holds great public health relevance. Over the past decade telecommunications technology has been used to increase access to and improve the quality of mental health care. There is current evidence that the use of landline and cellular telephones, computer-assisted therapy, and videoconferencing can be effective in improving treatment outcomes. Smartphones, as the newest development in communications technology, offer a new opportunity to improve mental health care through their versatile nature to perform a variety of functions. Methods: A critical literature review was performed to examine the potential of smartphones to increase access to mental health care, reduce barriers to care, and improve patient treatment outcomes. The review was performed by searching several electronic databases using a combination of keywords related to smartphones and mental health interventions using mobile devices. Literature concerning the use of cell phones, handheld computers, and smartphones to improve access to mental health care and improve treatment outcomes was identified.Results: The majority of studies identified were feasibility and pilot studies on patients with a variety of diagnosed mental illnesses using cell phones and PDAs. Authors report that most study participants, with some exceptions, were capable of using a mobile device and found them acceptable to use. Few studies extensively measured treatment outcomes and instead reported preliminary results and presented case illustrations. Studies which used smartphones successfully used them collect data on patients and deliver multimedia interventions. Discussion: The current literature offers encouraging evidence for the use of smartphones to improve mental health care but also reflects the lack of research conducted using smartphones. Studies which examine care provider use of smartphones to improve care is encouraging but has limited generalizability to mental health care. The feasibility of patient use of smartphones is also encouraging, but questions remain about feasibility in some sub-populations, particularly schizophrenia patients. Pilot testing of mobile devices and applications can greatly increase the feasibility of using smartphones in mental health care. Patients who are unfamiliar with smartphones will likely need initial training and support in their use. Conclusion: The literature identified several ways in which smartphones can increase access to care, reduce barriers, and improve treatment outcomes. Study results were encouraging but scientifically weak. Future studies are needed replicating results of studies using cell phones and PDAs on smartphones. Larger and higher quality studies are needed to examine the feasibility, efficacy, and cost-effectiveness of smartphones to deliver multiple component interventions that improve access to mental health care and improve treatment outcomes

Beyond Language Equivalence on Visibly Pushdown Automata

We study (bi)simulation-like preorder/equivalence checking on the class of visibly pushdown automata and its natural subclasses visibly BPA (Basic Process Algebra) and visibly one-counter automata. We describe generic methods for proving complexity upper and lower bounds for a number of studied preorders and equivalences like simulation, completed simulation, ready simulation, 2-nested simulation preorders/equivalences and bisimulation equivalence. Our main results are that all the mentioned equivalences and preorders are EXPTIME-complete on visibly pushdown automata, PSPACE-complete on visibly one-counter automata and P-complete on visibly BPA. Our PSPACE lower bound for visibly one-counter automata improves also the previously known DP-hardness results for ordinary one-counter automata and one-counter nets. Finally, we study regularity checking problems for visibly pushdown automata and show that they can be decided in polynomial time.Comment: Final version of paper, accepted by LMC

Photocurrent in conjugated polymers

Nonlinear photocurrent carriers in conjugated polymers, such as polarons, bipolarons and solitons, are considered at low photon energies where a tunnelling process is necessary. We show that polarons usually dominate the photocurrent I due to a novel electric field assisted tunnelling for which ln(I) ~ -E^{-2/3}. For near degenerate polymers an electric field E which exceeds the confinement potential and frequencies above twice the soliton energy, soliton tunnelling is favored. Photocurrent data can then be used to identify the remarkable phenomenon of soliton conduction.Comment: 4 pages, 2 eps figures, Revte

Path computation in multi-layer networks: Complexity and algorithms

Carrier-grade networks comprise several layers where different protocols coexist. Nowadays, most of these networks have different control planes to manage routing on different layers, leading to a suboptimal use of the network resources and additional operational costs. However, some routers are able to encapsulate, decapsulate and convert protocols and act as a liaison between these layers. A unified control plane would be useful to optimize the use of the network resources and automate the routing configurations. Software-Defined Networking (SDN) based architectures, such as OpenFlow, offer a chance to design such a control plane. One of the most important problems to deal with in this design is the path computation process. Classical path computation algorithms cannot resolve the problem as they do not take into account encapsulations and conversions of protocols. In this paper, we propose algorithms to solve this problem and study several cases: Path computation without bandwidth constraint, under bandwidth constraint and under other Quality of Service constraints. We study the complexity and the scalability of our algorithms and evaluate their performances on real topologies. The results show that they outperform the previous ones proposed in the literature.Comment: IEEE INFOCOM 2016, Apr 2016, San Francisco, United States. To be published in IEEE INFOCOM 2016, \<http://infocom2016.ieee-infocom.org/\&g