Search

The ground-state phase transition of the quantum double-well model is studied by virtue of Dirac's time-dependent variational principle together with a Hartree-type many-body trial wave function for the particles. The single-particle state is taken to be a Jackiw–Kerman wave function. We derive an effective classical Hamiltonian for the system, and coupled equations of particle's expectation values and quantum fluctuations for the ground state. It is shown clearly that the ground state transits from broken symmetric phase to restored symmetric phase as the quantum fluctuations renormalize the substrate potential from effective double-well potential to effective single-well potential. We obtain quantitatively the phase diagram, the quantum fluctuations and the energy of the ground state, respectively.

Bioinformatics is a dynamic research area in which a large number of algorithms and programs have been developed rapidly and independently without much consideration so far of the need for standardization. The lack of such common standards combined with unfriendly interfaces make it difficult for biologists to learn how to use these tools and to translate the data formats from one to another. Consequently, the construction of an integrative bioinformatics platform to facilitate biologists’ research is an urgent and challenging task. KDE Bioscience is a java-based software platform that collects a variety of bioinformatics tools and provides a workflow mechanism to integrate them. Nucleotide and protein sequences from local flat files, web sites, and relational databases can be entered, annotated, and aligned. Several home-made or 3rd-party viewers are built-in to provide visualization of annotations or alignments. KDE Bioscience can also be deployed in client-server mode where simultaneous execution of the same workflow is supported for multiple users. Moreover, workflows can be published as web pages that can be executed from a web browser. The power of KDE Bioscience comes from the integrated algorithms and data sources. With its generic workflow mechanism other novel calculations and simulations can be integrated to augment the current sequence analysis functions. Because of this flexible and extensible architecture, KDE Bioscience makes an ideal integrated informatics environment for future bioinformatics or systems biology research.

Prolonged illumination of the isolated Photosystem II reaction centre under aerobic conditions causes a selective photodestruction of chlorophyll which absorbs maximally at 680 nm. Concomitant with this effect is a loss of photochemical activity. When oxygen is absent, the reaction centre is no longer damaged by illumination. Protection of the 680 nm absorbing chlorophyll against photodamage and maintenance of photochemical activity can also be achieved if silicomolybdate (SiMo) is present as an electron acceptor, although in this case there is an irreversible bleaching at 670 nm, whether oxygen is present or not. We therefore suggest that there are two chlorophyll species in the reaction centre absorbing at 670 nm and 680 nm, respectively. The latter we attribute to the primary donor P680 and the former to an accessory chlorophyll. It seems highly likely that in the absence of SiMo but under aerobic conditions, the photodestruction of P680 involves singlet oxygen generated from the P680 triplet. When SiMo is present the yield of the triplet is significantly reduced (Nugent, J.H.A., Telfer, A., Demetriou, C. and Barber, J. (1989) FEBS Lett. 255, 53–58) due to electron transfer to the acceptor and thus this mode of photodegradation is reduced. However, the accumulation of P680+ when SiMo is present facilitates the oxidation of the accessory 670 nm chlorophyll which seems to result in its photodestruction by a mechanism not involving oxygen.