DIFFERENT EFFECTS OF RAD GENES OF SACCHAROMYCES CEREVISIAE ON INCISIONS OF INTERSTRAND CROSSLINKS AND MONOADDUCTS IN DNA INDUCED BY PSORALEN PLUS NEAR UV LIGHT TREATMENT

Abstract— The RAD1, RAD2, RAD3 and RAD4 genes of Saccharomyces cerevisiae are required for incising DNA containing UV induced pyrimidine dimers or psoralen plus 360 nm light induced interstrand crosslinks. We have now determined if these genes are also required for incising DNA at psoralen plus 360 nm light induced monoadducts. For distinguishing between incision breaks occurring at crosslinks and at monoadducts. we have used the cdc9-2 mutant, defective in DNA ligase activity at the restrictive temperature, and the radl-2 cdc9-2, rad2-5 cdc9-2 , rad3-2 cdc9-2 and rad4-4 cdc9-2 double mutant combinations. We conclude that the radl, rad2 , and rad4 mutants are defective in incising DNA both at crosslinks and monoadducts, whereas the rad3 mutant is proficient in incising DNA at monoadducts but not at crosslinks.     

SOLVENT INFLUENCES ON THE SINGLET QUENCHING OF CHLOROPHYLL a BY 2, 5-DIMETHYL-p-BENZOQUINONE

Abstract— The quenching of chlorophyll a excited singlet states by 2.5-dimethyl- p -benzoquinone has been investigated in solvents of varying viscosity and polarity. The observed singlet lifetimes showed little variation in several hydrocarbon solvents. Stern-Volmer constant K depends on the viscosity of the solvent, although cyclic and straight-chain hydrocarbons behave somewhat differently. The decrease of the K values with increase of viscosity suggests that the quenching mechanism is at least partly dynamic, although there is evidence for static quenching as well. The influence of solvent polarity on the K values was found to be insignificant, which is consistent with a very short-lived ion pair intermediate formed by electron-transfer quenching.     

Algebraic study of chiral anomalies?

The algebraic structure of chiral anomalies ismade globally valid on non-trivial bundles by the introduction of a fixed background connection. Some of the techniques used in the study of the anomaly are improved or generalized, including a systematic way of generating towers of ??descent equations??.     

Evaluation of a new maintenance concept for the preservation of highways

Asphalt roads gradually deteriorate over time and need mendingto remain in a good state. Inspections are performed to obtaininformation about the current state of the road; when the levelof damage reaches the established standards, the road is repairedthrough a maintenance action that is considered most cost-effective.Because of economies of scale, it is to a certain extent economicalto limit the number of maintenance services by integrating neighbouringsegments into a homogeneous section which is completely repaired.In this report we consider the question of whether it is economicallyjustified to adopt a maintenance concept in which the road isoccasionally regenerated from junction to junction with a distanceof several kilometers. The big advantage of junction-to-junctionmaintenance is that it can be done within special road barrierconstructions which reduce the road capacity only slightly,so that the road can be maintained 24 hours a day.     

Toeplitz Preconditioners for Toeplitz Systems with Nonnegative Generating Functions

The preconditioned conjugate gradient method is employed tosolve Toeplitz systems T_nx = b where the generating functionsof the n-by-n Toeplitz matrices T_n are continuous nonnegativeperiodic functions defined in [–,]. The preconditionedC_n are band Toeplitz matrices with band-widths independent ofn. We prove that the spectra of C_n^-1T_n are uniformly boundedby constants independent of n. In particular, we show that thesolutions of T_nx = b can be obtained in O(nlogn) operations.