STUDIES ON PLANT BILE PIGMENTS-6. PHOTOCHEMICALLY ASSISTED REACTION OF A-DIHYDROBILINDIONE WITH NUCLEOPHILES AS A MODEL FOR PHYTOCHROME INTERCONVERSION

From the A-dihydrobilindione 3. the pyridinium derivatives 6a,b and analogues thereof have been obtained by a formal nucleophilic substitution. The reaction is rationalized as a photochemically assisted oxidation of 3 with a subsequent regioselective addition of pyridine at C-5. By thermolysis. 6a.b yields back the parent bilin 3, together with an oxidation product. The significance of the reaction with respect to the phytochrome interconversion is discussed

Polymer Dissolution Model: An Energy Adaptation Of The Critical Ionization Theory

The current scale of features size in the microelectronics industry has reached the point where molecular level interactions affect process fidelity and produce excursions from the continuum world like line edge roughness (LER). Here we present a 3D molecular level model based on the adaptation of the critical ionization (CI) theory using a fundamental interaction energy approach. The model asserts that it is the favorable interaction between the ionized part of the polymer and the developer solution which renders the polymer soluble. Dynamic Monte Carlo methods were used in the current model to study the polymer dissolution phenomenon. The surface ionization was captured by employing an electric double layer at the interface, and polymer motion was simulated using the Metropolis algorithm. The approximated interaction parameters, for different species in the system, were obtained experimentally and used to calibrate the simulated dissolution rate response to polymer molecular weight and developer concentration. The predicted response is in good agreement with experimental dissolution rate data. The simulation results support the premise of the CI theory and provide an insight into the CI model from a new prospective. This model may provide a means to study the contribution of development to LER and other related defects based on molecular level interactions between distinct components in the polymer and the developer.Chemical Engineerin

Conduction Channels of One-Atom Zinc Contacts

We have determined the transmission coefficients of atomic-sized Zn contacts using a new type of breakjunction which contains a whisker as a central bridge. We find that in the last conductance plateau the transport is unexpectedly dominated by a well-transmitting single conduction channel. We explain the experimental findings with the help of a tight-binding model which shows that in an one-atom Zn contact the current proceeds through the 4s and 4p orbitals of the central atom.Comment: revtex4, 5 pages, 5 figure

Chemical Bonding and Charge Distribution at Metallic Nanocontacts

We present results of electronic structure calculations for aluminium contacts of atomic size, based on density functional theory and the local density approximation. Addressing the atomic orbitals at the neck of the nanocontact, we find that the local band structure deviates strongly from bulk fcc aluminium. In particular, hybridization between Al 3s and 3p states is fully suppressed due to directed bonds at the contact. Moreover, a charge transfer of 0.6 electrons off the contact aluminium site is found. Both the suppressed hybridization and the violated charge neutrality are characteristic features of metallic nanocontacts. This fact has serious consequences for models aiming at a microscopic description of transport properties.Comment: 6 pages, 3 figures, accepted by Chemical Physics Letter

Report on the Stony Corals from the Maldive Archipelago

The Maldive Archipelago, situated at the southwest of India, consists of 22 atolls, extending over a length of nearly 470km in a north-south direction. The northern limit is Ihavandiffulu Atoll (7"'05'N, 72' 55'E), while Addu, one of the scientifically well known atolls, is located at the southern tip (0' 40'5, 73'1 O'E). The largest among the Maldivian atolls is located in the northern half of the chain and is known by twO names, a nonhern smaller part called Tiladummati, and the southern part Miladummadulu. At the middle pan of the Archipelago the atolls are arranged in two almost parallel rows, incorporating a great number of Faros with their small lagoon-like water bodies, termed Velu. The type locality of Atolls and Faros are the Maldives, the names originating from the Maldivian language. Nearly 2000 small islands enter into the geography of the Maldives, of which circa 200 are inhabited with a population of nearly 120000

Report on the Stony Corals from the Red Sea

The first to mention corals of the Red Sea was Thomas SHAW, who travelled through Tunisis , Algeria, Egypt, Syria and the Sinai Peninsula, and who in his "Travels or observations re lati ng to several parts of Barbary and the Levant" described 24 corals of Et Tur (1738, German edition 1765). From these one can recognize P1atygyra, Favia, Goniastrea, Acropora, Stylophora and Tubipora, but his Latin descriptions are not sufficient for an identification at a species level

PHYCOBILISOMES AND ISOLATED PHYCOBILIPROTEINS. EFFECT OF GLUTARDIALDEHYDE AND BENZOQUINONE ON FLUORESCENCE

The fluorescence of the biliproteins C-phycocyanin from Spirulina platensis, B-phycoerythrin from Porphyridium cruentum and of isolated whole P. cruentum phycobilisomes is quenched in the presence of glutardialdehyde (GA) or benzoquinone (BQ). The kinetics of fluorescence decrease thus induced is biphasic. If GA is used as a quencher, the fluorescence can be recovered at 77 K. Contrary to the GA-effect, only a minor recovery takes place with BQ at 77K, thus demonstrating a different mechanism of action of GA and BQ on biliprotein