Historical biogeography of Melastomataceae

Melastomataceae and Memecylaceae are pantropically distributed sister groups for which an ndhF gene phylogeny for 91 species in 59 genera is here linked with Eurasian and North American fossils in a molecular clock approach to biogeographical reconstruction. Nine species from the eight next-closest families are used to root phylogenetic trees obtained under maximum likelihood criteria. Melastomataceae comprise ∼3000 species in the neotropics, ∼1000 in tropical Asia, 240 in Africa, and 225 in Madagascar in 150-166 genera, and the taxa sampled come from throughout this geographic range. Based on fossils, ranges of closest relatives, tree topology, and calibrated molecular divergences, Melastomataceae initially diversified in Paloecene/Eocene times in tropical forest north of the Tethys. Their earliest (Eocene) fossils are from northeastern North America, and during the Oligocene and Miocene melastomes occurred in North America as well as throughout Eurasia. They also entered South America, with earliest (Oligocene) South American fossils representing Merianieae. One clade (Melastomeae) reached Africa from the neotropics 14-12 million years ago and from there spread to Madagascar, India, and Indochina. Basalmost Melastomataceae (Kibessieae, Astronieae) are species-poor lineages restricted to Southeast Asia. However, a more derived Asian clade (Sonerileae/Dissochaeteae) repeatedly reached Madagascar and Africa during the Miocene and Pliocene. Contradicting earlier hypotheses, the current distribution of Melastomataceae is thus best explained by Neogene long-distance dispersal, not Gondwana fragmentation

An information-theoretic security proof for QKD protocols

We present a new technique for proving the security of quantum key distribution (QKD) protocols. It is based on direct information-theoretic arguments and thus also applies if no equivalent entanglement purification scheme can be found. Using this technique, we investigate a general class of QKD protocols with one-way classical post-processing. We show that, in order to analyze the full security of these protocols, it suffices to consider collective attacks. Indeed, we give new lower and upper bounds on the secret-key rate which only involve entropies of two-qubit density operators and which are thus easy to compute. As an illustration of our results, we analyze the BB84, the six-state, and the B92 protocol with one-way error correction and privacy amplification. Surprisingly, the performance of these protocols is increased if one of the parties adds noise to the measurement data before the error correction. In particular, this additional noise makes the protocols more robust against noise in the quantum channel.Comment: 18 pages, 3 figure

A Survey Tool, Retrenchment Blues and a Career Alternatives Program

Two-thirds of the faculty of Canadian universities will reach the traditional retirement age of 65 between the years 2000 to 2010. As a result there will be little academic or financial flexibility for at least another decade. A questionnaire is presented as a tool for measuring the personal and professional characteristics of this age group with respect to three considerations: (1) their level of career satisfaction, (2) their interest in a career alternatives program, and (3) their plans to retire either before or by the age of 65 or to continue to work after 65 if mandatory retirement is abolished. A significant proportion of academic faculty are no longer finding satisfaction in their academic work and would consider an alternative career if that were feasible. Those who are not interested in leaving academic life early tend to be happy and productive. A career alternatives program could be an effective way to begin the renewal process within higher education now, not after the year 2000.Les deux tiers des professeurs d'université canadiens atteindront 65 ans, l'âge de la retraite prévu par la loi, entre les années 2000 et 2010. Ceci veut dire qu'il y aura toujours aussi peu de flexibilité, tant dans les cours que dans /'organisation financière, pendant les dix prochaines années au moins. On a tenté, à partir d'un questionnaire, de mesurer certaines caractéristiques personnelles et professionnelles de ce groupe d'âge dans les trois domaines suivants: 1) leur niveau de satisfaction vis-à-vis leur carrière, 2) l'intérêt qu'ils pourraient avoir pour une formation en vue d'une autre carrière, et 3) leur désir de prendre leur retraite avant 65 ans, à 65 ans ou plus tard si la retraite obligatoire à 65 ans était abolie. Un grand nombre de professeurs d'université n'éprouvent plus de satisfaction à exercer leur métier et aimeraient entreprendre une nouvelle carrière si cela était possible. Quant à ceux qui ne souhaitent pas arrêter de travailler tôt, ce sont, dans l'ensemble, les plus productifs et les plus heureux. La conclusion que l'on peut tirer de cette étude, c'est qu'un programme d'intégration à d'autres milieux professionnels pourrait être un bon moyen de rajeunir l'enseignement supérieur dès maintenant, et de ne pas attendre l'an 2000 pour s'en préoccuper

Size Matters: Notes on Green Design Process and Goals

Richard Renner presents architectural design principles that should be employed to minimize buildings’ “loads,” i.e., demands for resources and energy, and to maximize efficiency

Security of quantum key distribution protocols using two-way classical communication or weak coherent pulses

We apply the techniques introduced in [Kraus et. al., Phys. Rev. Lett. 95, 080501, 2005] to prove security of quantum key distribution (QKD) schemes using two-way classical post-processing as well as QKD schemes based on weak coherent pulses instead of single-photon pulses. As a result, we obtain improved bounds on the secret-key rate of these schemes

Linear and field-independent relation between vortex core state energy and gap in Bi2Sr2CaCu2O8+d

We present a scanning tunneling spectroscopy study on quasiparticle states in vortex cores in Bi2Sr2CaCu2O8+δ. The energy of the observed vortex core states shows an approximately linear scaling with the superconducting gap in the region just outside the core. This clearly distinguishes them from conventional localized core states and is a signature of the mechanism responsible for their discrete appearance in high-temperature superconductors. The energy scaling of the vortex core states also suggests a common nature of vortex cores in Bi2Sr2CaCu2O8+δ and YBa2Cu3O7-δ. Finally, these states do not show any dependence on the applied magnetic field between 1 and 6 T

Helicity Dependent and Independent Generalized Parton Distributions of the Nucleon in Lattice QCD

A complete description of the nucleon structure in terms of generalized parton distributions (GPDs) at twist 2 level requires the measurement/computation of the eight functions H, E, \tilde H, \tilde E, H_T, E_T, \tilde H_T and \tilde E_T, all depending on the three variables x, \xi and t. In this talk, we present and discuss our first steps in the framework of lattice QCD towards this enormous task. Dynamical lattice QCD results for the lowest three Mellin moments of the helicity dependent and independent GPDs are shown in terms of their corresponding generalized form factors. Implications for the transverse coordinate space structure of the nucleon as well as the orbital angular momentum (OAM) contribution of quarks to the nucleon spin are discussed in some detail.Comment: 5 pages, 5 figures, Talk presented by Ph.H. at Electron-Nucleus Scattering VIII, Elba, Italy, June 21-25, 2004; typos corrected, minor change in wording on p.4&

Quantum circuit for security proof of quantum key distribution without encryption of error syndrome and noisy processing

One of the simplest security proofs of quantum key distribution is based on the so-called complementarity scenario, which involves the complementarity control of an actual protocol and a virtual protocol [M. Koashi, e-print arXiv:0704.3661 (2007)]. The existing virtual protocol has a limitation in classical postprocessing, i.e., the syndrome for the error-correction step has to be encrypted. In this paper, we remove this limitation by constructing a quantum circuit for the virtual protocol. Moreover, our circuit with a shield system gives an intuitive proof of why adding noise to the sifted key increases the bit error rate threshold in the general case in which one of the parties does not possess a qubit. Thus, our circuit bridges the simple proof and the use of wider classes of classical postprocessing.Comment: 8 pages, 2 figures. Typo correcte