Chemical structure matching using correlation matrix memories

This paper describes the application of the Relaxation By Elimination (RBE) method to matching the 3D structure of molecules in chemical databases within the frame work of binary correlation matrix memories. The paper illustrates that, when combined with distributed representations, the method maps well onto these networks, allowing high performance implementation in parallel systems. It outlines the motivation, the neural architecture, the RBE method and presents some results of matching small molecules against a database of 100,000 models

Dependence of Inflationary Reconstruction upon Cosmological Parameters

The inflationary potential and its derivatives determine the spectrum of scalar and tensor metric perturbations that arise from quantum fluctuations during inflation. The CBR anisotropy offers a promising means of determining the spectra of metric perturbations and thereby a means of constraining the inflationary potential. The relation between the metric perturbations and CBR anisotropy depends upon cosmological parameters -- most notably the possibility of a cosmological constant. Motivated by some observational evidence for a cosmological constant (large-scale structure, cluster-baryon fraction, measurements of the Hubble constant and age of the Universe) we derive the reconstruction equations and consistency relation to second order in the presence of a cosmological constant. We also clarify previous notation and discuss alternative schemes for reconstruction.Comment: 15 pages, LaTeX, 3 postscript figures (included with epsf), submitted to Phys. Rev.

QSO's from Galaxy Collisions with Naked Black Holes

In the now well established conventional view (see Rees [1] and references therein), quasi-stellar objects (QSOs) and related active galactic nuclei (AGN) phenomena are explained as the result of accretion of plasma onto giant black holes which are postulated to form via gravitational collapse of the high density regions in the centers of massive host galaxies. This model is supported by a wide variety of indirect evidence and seems quite likely to apply at least to some observed AGN phenomena. However, one surprising set of new Hubble Space Telescope (HST) observations [2-4] directly challenges the conventional model, and the well known evolution of the QSO population raises some additional, though not widely recognized, difficulties. We propose here an alternative possibility: the Universe contains a substantial independent population of super-massive black holes, and QSO's are a phenomenon that occurs due to their collisions with galaxies or gas clouds in the intergalactic medium (IGM). This hypothesis would naturally explain why the QSO population declines very rapidly towards low redshift, as well as the new HST data.Comment: plain TeX file, no figures, submitted to Natur

Rhodococcus aetherivorans BCP1 as cell factory for the production of intracellular tellurium nanorods under aerobic conditions

Background: Tellurite (TeO32-) is recognized as a toxic oxyanion to living organisms. However, mainly anaerobic or facultative-anaerobic microorganisms are able to tolerate and convert TeO32- into the less toxic and available form of elemental Tellurium (Te0), producing Te-deposits or Te-nanostructures. The use of TeO32--reducing bacteria can lead to the decontamination of polluted environments and the development of "green-synthesis" methods for the production of nanomaterials. In this study, the tolerance and the consumption of TeO32- have been investigated, along with the production and characterization of Te-nanorods by Rhodococcus aetherivorans BCP1 grown under aerobic conditions. Results: Aerobically grown BCP1 cells showed high tolerance towards TeO32- with a minimal inhibitory concentration (MIC) of 2800μg/mL (11.2mM). TeO32- consumption has been evaluated exposing the BCP1 strain to either 100 or 500μg/mL of K2TeO3 (unconditioned growth) or after re-inoculation in fresh medium with new addition of K2TeO3 (conditioned growth). A complete consumption of TeO32- at 100μg/mL was observed under both growth conditions, although conditioned cells showed higher consumption rate. Unconditioned and conditioned BCP1 cells partially consumed TeO32- at 500μg/mL. However, a greater TeO32- consumption was observed with conditioned cells. The production of intracellular, not aggregated and rod-shaped Te-nanostructures (TeNRs) was observed as a consequence of TeO32- reduction. Extracted TeNRs appear to be embedded in an organic surrounding material, as suggested by the chemical-physical characterization. Moreover, we observed longer TeNRs depending on either the concentration of precursor (100 or 500μg/mL of K2TeO3) or the growth conditions (unconditioned or conditioned grown cells). Conclusions:Rhodococcus aetherivorans BCP1 is able to tolerate high concentrations of TeO32- during its growth under aerobic conditions. Moreover, compared to unconditioned BCP1 cells, TeO32- conditioned cells showed a higher oxyanion consumption rate (for 100μg/mL of K2TeO3) or to consume greater amount of TeO32- (for 500μg/mL of K2TeO3). TeO32- consumption by BCP1 cells led to the production of intracellular and not aggregated TeNRs embedded in an organic surrounding material. The high resistance of BCP1 to TeO32- along with its ability to produce Te-nanostructures supports the application of this microorganism as a possible eco-friendly nanofactory

Assembly, growth and conductive properties of tellurium nanorods produced by Rhodococcus aetherivorans BCP1

Tellurite (TeO32-) is a hazardous and toxic oxyanion for living organisms. However, several microorganisms can bioconvert TeO32- into the less toxic form of elemental tellurium (Te0). Here, Rhodococcus aetherivorans BCP1 resting (non-growing) cells showed the proficiency to produce tellurium-based nanoparticles (NPs) and nanorods (NRs) through the bioconversion of TeO32-, depending on the oxyanion initial concentration and time of cellular incubation. Te-nanostructures initially appeared in the cytoplasm of BCP1 cells as spherical NPs, which, as the exposure time increased, were converted into NRs. This observation suggested the existence of an intracellular mechanism of TeNRs assembly and growth that resembled the chemical surfactant-assisted process for NRs synthesis. The TeNRs produced by the BCP1 strain showed an average length (>700 nm) almost doubled compared to those observed in other studies. Further, the biogenic TeNRs displayed a regular single-crystalline structure typically obtained for those chemically synthesized. The chemical-physical characterization of the biogenic TeNRs reflected their thermodynamic stability that is likely derived from amphiphilic biomolecules present in the organic layer surrounding the NRs. Finally, the biogenic TeNRs extract showed good electrical conductivity. Thus, these findings support the suitability of this strain as eco-friendly biocatalyst to produce high quality tellurium-based nanomaterials exploitable for technological purposes

Decorrelating the Power Spectrum of Galaxies

It is shown how to decorrelate the (prewhitened) power spectrum measured from a galaxy survey into a set of high resolution uncorrelated band-powers. The treatment includes nonlinearity, but not redshift distortions. Amongst the infinitely many possible decorrelation matrices, the square root of the Fisher matrix, or a scaled version thereof, offers a particularly good choice, in the sense that the band-power windows are narrow, approximately symmetric, and well-behaved in the presence of noise. We use this method to compute band-power windows for, and the information content of, the Sloan Digital Sky Survey, the Las Campanas Redshift Survey, and the IRAS 1.2 Jy Survey.Comment: 11 pages, including 8 embedded PostScript figures. Minor changes to agree with published versio