The set union problem with dynamic weighted backtracking

We consider an extension of the set union problem, in which dynamic weighted backtracking over sequences of unions is permitted. We present a new data structure which can support each operation inO(logn) time in the worst case. We prove that this bound is tight for pointer based algorithms. Furthermore, we design a different data structure to achieve better amortized bounds. The space complexity of both our data structures isO(n). Motivations for studying this problem arise in logic programming memory management.Work partially supported by NSF Grant CCR-88-14977, by the ESPRIT II Basic Research Actions Program of the EC under contract No. 3075 (Project ALCOM), and by the Italian MURST Project Algoritmi e Strutture di Calcolo.Partially supported by an IBM Graduate Fellowship.     

Proton and α sequential emission in the 16O + 58Ni deep inelastic reaction: A semi-classical approach

The 132 MeV ¹⁶O + ⁵⁸Ni reaction has been experimentally investigated by using coincident charged particle techniques. A closed-form theoretical approach, describing in a simple picture the non-equilibrium component and the evaporative one of the angular correlation between light particles and reaction residues emitted in a peripheral heavy-ion collision, is applied — in the hypotesis of a sequential process — to the (C,N,O)-α and (C,N,O)-p differential multiplicities for the ¹⁶O + ⁵⁸Ni at 8.25 MeV/A deep inelastic collision. From this analysis some reaction mechanism information is deduced.     

Reversible binding of metal ions onto bacterial layers revealed by protonation-induced ATR-FTIR difference spectroscopy

The ability of microorganisms to adhere to abiotic surfaces and the potentialities of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy have been exploited to study protonation and heavy metal binding events onto bacterial surfaces. This work represents the first attempt to apply on bacteria the recently developed method known as perfusion-induced ATR-FTIR difference spectroscopy. Such a technique allows measurement of even slight changes in the infrared spectrum of the sample, deposited as a thin layer on an ATR crystal, while an aqueous solution is perfused over its surface. Solutions at different pH have been used for inducing protonation/deprotonation of functional groups lying on the surface of Rhodobacter sphaeroides cells, chosen as a model system. The interaction of Ni(2+) with surface protonable groups of this microorganism has been investigated with a double-difference approach exploiting competition between nickel cations and protons. Protonation-induced difference spectra of simple model compounds have been acquired to guide band assignment in bacterial spectra, thus allowing identification of major components involved in proton uptake and metal binding. The data collected reveal that carboxylate moieties on the bacterial surface of R. sphaeroides play a role in extracellular biosorption of Ni(2+), establishing with this ion relatively weak coordinative bonds.     

Identification of a set of genes showing regionally enriched expression in the mouse brain

Background

We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.

Results

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.

Conclusion

Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.     

Spectroscopic parameters of theJ π=1+,T=0 excited6Li level

An analysis of thed- coincidence spectra of the⁷Li(³He, d)⁴He reaction at incident energy of 5.0 MeV and at various detector angles has been carried out. The values of the spectroscopic parameters of theJ =1⁺,T=0⁶Li state at excitation energy of 5.65 MeV have been deduced. The results, considering the experimental errors, do not appear to be dependent on the geometry and are in line with the ones adopted in literature.