Fast algorithms for min independent dominating set

We first devise a branching algorithm that computes a minimum independent dominating set on any graph with running time O*(2^0.424n) and polynomial space. This improves the O*(2^0.441n) result by (S. Gaspers and M. Liedloff, A branch-and-reduce algorithm for finding a minimum independent dominating set in graphs, Proc. WG'06). We then show that, for every r>3, it is possible to compute an r-((r-1)/r)log_2(r)-approximate solution for min independent dominating set within time O*(2^(nlog_2(r)/r))

Highly efficient synthesis of the tricyclic core of Taxol by cascade metathesis

An efficient enantioselective synthesis of the ABC tricyclic core of the anticancer drug Taxol is reported. The key step of this synthesis is a cascade metathesis reaction, which leads in one operation to the required tricycle if appropriate fine-tuning of the dienyne precursor is performed

Cell Cycle-Dependent Binding of Yeast Heat Shock Factor to Nucleosomes

In the nucleus, transcription factors must contend with the presence of chromatin in order to gain access to their cognate regulatory sequences. As most nuclear DNA is assembled into nucleosomes, activators must either invade a stable, preassembled nucleosome or preempt the formation of nucleosomes on newly replicated DNA, which is transiently free of histones. We have investigated the mechanism by which heat shock factor (HSF) binds to target nucleosomal heat shock elements (HSEs), using as our model a dinucleosomal heat shock promoter (hsp82-ΔHSE1). We find that activated HSF cannot bind a stable, sequence-positioned nucleosome in G1-arrested cells. It can do so readily, however, following release from G1 arrest or after the imposition of either an early S- or late G2-phase arrest. Surprisingly, despite the S-phase requirement, HSF nucleosomal binding activity is restored in the absence of hsp82 replication. These results contrast with the prevailing paradigm for activator-nucleosome interactions and implicate a nonreplicative, S-phase-specific event as a prerequisite for HSF binding to nucleosomal sites in vivo

On Field Induced Diaelastic Effect in a Small Josephson Contact

An analog of the diaelastic effect is predicted to occur in a small Josephson contact with Josephson vortices manifesting itself as magnetic field induced softening of the contact shear modulus C(T,H). In addition to Fraunhofer type field oscillations, C(T,H) is found to exhibit pronounced flux driven temperature oscillations near T_C

Controlling the Frequency-Temperature Sensitivity of a Cryogenic Sapphire Maser Frequency Standard by Manipulating Fe3+ Spins in the Sapphire Lattice

To create a stable signal from a cryogenic sapphire maser frequency standard, the frequency-temperature dependence of the supporting Whispering Gallery mode must be annulled. We report the ability to control this dependence by manipulating the paramagnetic susceptibility of Fe3+ ions in the sapphire lattice. We show that the maser signal depends on other Whispering Gallery modes tuned to the pump signal near 31 GHz, and the annulment point can be controlled to exist between 5 to 10 K depending on the Fe3+ ion concentration and the frequency of the pump. This level of control has not been achieved previously, and will allow improvements in the stability of such devices.Comment: 17 pages, 10 figure

Response of maize inbred lines to two European corn borer (Ostrinia nubilalis) strains in Canada

Six lignées de maïs-grain (CM47, A619, F2, CM107, CM7 et A654) ont été évaluées en 1986 et 1987 dans quatre localités de l'Ontario et du Québec pour leur résistance à des infestations artificielles de la pyrale du maïs, Ostrinia nubilalis, de la race univoltine et de la première génération de la race bivoltine. Trois critères ont été utilisés: la criblure du feuillage, les dégâts totaux des plantes à la récolte, et le rapport longueur des galeries creusées par les chenilles dans les tiges sur la hauteur des plantes. Des interactions importantes ont été observées pour les critères utilisés entre les années et localités, mais la réaction des lignées de maïs a été plutôt constante. Pour tous les critères, la race univoltine a souvent causé, d'une façon significative, plus de dégâts aux plantes que la race bivoltine. En général, la lignée A619 a démontré le plus de résistance-tolérance tout en conservant une bonne tenue des tiges jusqu'à la récolte. On aurait avantage à utiliser la race univoltine dans les programmes d'amélioration génétique du maïs pour sa résistance à la pyrale.In 1986 and 1987, six maize inbred lines (CM47, A619, F2, CM107, CM7, and A654) were evaluated at four locations across Ontario and Quebec for their resistance to artificially infested univoltine and lst generation bivoltine strains of the European corn borer, Ostrinia nubilalis. Three criteria were used: leaf feeding, total plant damage at harvest and length of tunnels/plant height ratio. Substantial interactions in borer damage measurements were observed between locations and years, but inbred reaction was relatively consistent. For all criteria, the univoltine strain often caused significantly more damage than the bivoltine borer. In general, A619 had the greatest resistance-tolerance with good standability until harvest. Wherever possible, evaluation of genetic resistance in maize germplasm should be conducted using the univoltine borer strain

Creating traveling waves from standing waves from the gyrotropic paramagnetic properties of Fe3+^{3+} ions in a high-Q whispering gallery mode sapphire resonator

We report observations of the gyrotropic change in magnetic susceptibility of the Fe$^{3+}$ electron paramagnetic resonance at 12.037GHz (between spin states $|1/2>$ and $|3/2>$) in sapphire with respect to applied magnetic field. Measurements were made by observing the response of the high-Q Whispering Gallery doublet (WGH$_{\pm17,0,0}$) in a Hemex sapphire resonator cooled to 5 K. The doublets initially existed as standing waves at zero field and were transformed to traveling waves due to the gyrotropic response.Comment: Accepted for publication in Phys. Rev.