A third member of the photolyase/blue-light photoreceptor family in Drosophila: a putative circadian photoreceptor

Two photolyases, specific for cyclobutane pyrimidine dimers and (6-4) photoproducts, have been reported in Drosophila. These enzymes share extensive sequence homologies with the plant blue-light photoreceptor. We have now identified a third gene in Drosophila melanogaster with extensive sequence homology to the photolyase gene. The newly identified gene, which we named dCRY, was expressed as a recombinant protein and tested for photolyase activity. The recombinant protein exhibited photochemical properties similar to those of Drosophila pyrimidine dimer and (6-4) photolyases but lacked photolyase activity. In light of recent evidence that blue-light photoreceptors regulate the circadian clock in mammals, we propose that dCRY is the circadian photoreceptor in this organism.     

Investigation of surface plasma resonances in small sodium clusters

Photoabsorption cross sections of small neutral sodium clusters are measured at wavelengths from 452 to 604 nm. We find that surface plasma oscillations of the valence electrons dominate the photoabsorption spectra. The experimental results are consistent with predictions based on an extended Clemenger-Nilsson model, general sum rules, and the experimental static electric polarizabilities. For Na₈ a single broad resonance is observed, the peak wavelength is in excellent agreement with the model. The data for Na₉ and Na₁₀ support the prediction of double resonances.     

COMPARISON OF UV ACTION SPECTRA FOR LETHALITY AND MUTATION IN Salmonella typhimurium USING A BROAD BAND SOURCE AND MONOCHROMATIC RADIATIONS

Abstract— The UV-B region (280–320 nm) is thought to be primarily responsible for the mutagenic, lethal, and carcinogenic effects of solar radiation. We have conducted UV-B action spectroscopy for mutagenesis and survival of Ames' Salmonella typhimurium strain TA98 ( uvrB , pKM101) using both monochromatic radiation from a dye laser and broader bandwidth radiation emitted from FS-20 sunlamps. A series of optical filters having different transmission cut-offs together with the sunlamp source provided bandwidths having successively less short wavelength components from which a "broad band" action spectrum was deduced. The two sets of action spectra differed both qualitatively and quantitatively: in comparison to the monochromatic action spectra, the "broad band" spectra showed up to a 200-fold reduced efficiency for both mutation induction and lethality by UV-B wavelengths. These results suggest a large protective effect of the background UV-A and/or visible radiations which were present during the broad spectrum irradiations and which are also present in solar radiation. Additional experiments show that to the extent tested this protective effect is not due to photo-reactivation or irradiance (dose rate) effects     

Stability and convergence of the spectral Lagrange-Galerkin method for mixed periodic/non-periodic convection-dominated diffusion problems

We present a convergence analysis of the spectral Lagrange-Galerkinmethod for mixed periodic/non-periodic convection-diffusionproblems. The scheme is unconditionally stable, independentof the diffusion coefficient, even in the case when numericalquadrature is used. The theoretical predictions are illustratedby a series of numerical experiments. For the periodic case,our results present a significant improvement on those givenby Süli & Ware (1991) SIAM J. Numer.Anal.28, 423-445).     

Effects of Testosterone Replacement on a Male Professional Singer

Testosterone has been known to play an important role in the development of the postpubertal male voice for many centuries. In fact, the prevention of pubertal development of the voice by castrating young male singers was a well-known practice, especially in Italy beginning in the sixteenth century. The “castrati” were well known for their clear, high-pitched voices. Because of the resulting small larynx and vocal folds, castrati apparently produced a distinctive resonance as well as the high pitch, which cannot be matched even by the counter tenors of today. Busy voice labs occasionally see males with sex hormone deficiencies secondary to chromosomal or gonadal problems. This is a presentation of an unusual patient who was a trained tenor singer and was found to have hypogonadism on a premarital health examination. Administration of replacement testosterone resulted in significant vocal register and voice quality changes.     

Single-step synthesis of D3h-symmetric bicyclooxacalixarenes

Bicyclooxacalixarenes are obtained in up to 95% yield by condensation of phloroglucinol with electron-poor meta-dihalogenated benzenes or pyridines. Single-crystal X-ray analysis reveals that these compounds adopt highly symmetrical, all-1,3-alternate cage-like structures. [structure: see text]     

Oracles and Query Lower Bounds in Generalised Probabilistic Theories

We investigate the connection between interference and computational power within the operationally defined framework of generalised probabilistic theories. To compare the computational abilities of different theories within this framework we show that any theory satisfying four natural physical principles possess a well-defined oracle model. Indeed, we prove a subroutine theorem for oracles in such theories which is a necessary condition for the oracle model to be well-defined. The four principles are: causality (roughly, no signalling from the future), purification (each mixed state arises as the marginal of a pure state of a larger system), strong symmetry (existence of a rich set of nontrivial reversible transformations), and informationally consistent composition (roughly: the information capacity of a composite system is the sum of the capacities of its constituent subsystems). Sorkin has defined a hierarchy of conceivable interference behaviours, where the order in the hierarchy corresponds to the number of paths that have an irreducible interaction in a multi-slit experiment. Given our oracle model, we show that if a classical computer requires at least n queries to solve a learning problem, because fewer queries provide no information about the solution, then the corresponding “no-information” lower bound in theories lying at the kth level of Sorkin’s hierarchy is \(\lceil {n/k}\rceil \). This lower bound leaves open the possibility that quantum oracles are less powerful than general probabilistic oracles, although it is not known whether the lower bound is achievable in general. Hence searches for higher-order interference are not only foundationally motivated, but constitute a search for a computational resource that might have power beyond that offered by quantum computation.     

Control of low-speed turbulent separated flow using jet vortex generators

A parametric study has been performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulent flow over a two-dimensional rearward-facing ramp. Results indicate that flow-separation control can be accomplished, with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction), and jet location (distance from the separation region in the free-stream direction). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).Nomenclature C _p pressure coefficient, 2(P-P_)/V ² - C _Q total flow coefficient, Q/ v - D ₀ jet orifice diameter - Q total volumetric flow rate - R Reynolds number based on momentum thickness - u fluctuating velocity component in the free-stream (x) direction - V free-stream flow speed - VR ratio of jet speed to free-stream flow speed - x coordinate along the wall in the free-stream direction - jet inclination angle (angle between the jet axis and the wall) - jet azimuthal angle (angle between the jet axis and the free-stream direction in a horizontal plane) - boundary-layer thickness - momentum thickness - lateral distance between jet orifices A version of this paper was presented at the 12th Symposium on Turbulence, University of Missouri-Rolla, 24–26 Sept. 1990     

Unusual Hydrogen-bonding Networks Consisting of π-Extended 4,4′-Bipyridines and Chloranilic Acid

Hydrogen-bonding networks of π-extended 4,4′-bipyridines, 2,5-di(4-pyridyl)thiophene (1), 2,5-di(4-pyridyl)furan (2) and 1,4-di(4-pyridyl)benzene (3) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid, CA) have been investigated. The dipyridyl compounds afforded complexes 4 [(dication of 1)·(monoanion of CA)²], 5 [(dication of 2)·(dianion of CA)·(MeOH)] and 6 [(3)·(dication of 3)·(dianion of CA)·(H²O)⁶] with CA. X-ray structure analyses revealed the formation of unusual molecular tape and sheet structures involving N–H ?O, O–H ?O, C–H ?O and N–H ?N hydrogen bonds, where the aromatic spacer groups play an important role in constructing the unique crystal structures.