The opportunistic pathogen Pseudomonas aeruginosa, which causes serious nosocomial infections, is a gamma-proteobacterium that can live in many different environments. Interestingly P. aeruginosa encodes three ribonucleotide reductases (RNRs) that all differ from other well known RNRs. The RNR enzymes are central for de novo synthesis of deoxyribonucleotides and essential to all living cells. T...

Opsins, like many other G-protein-coupled receptors, sustain constitutive activity in the absence of ligand. In partially bleached rods and cones, opsin's activity closes cGMP-gated channels and produces a state of "pigment adaptation" with reduced sensitivity to light and accelerated flash response kinetics. The truncated retinal analogue, beta-ionone, further desensitizes partially bleached g...

Behavioral experiments in humans with a rare genetic mutation that compromises the function of !-transducin (G! the !-subunit of the G-protein in the primary cone phototransduction cascade) reveal a residual cone response only viable at high light levels and at low temporal frequencies. It has three characteristic properties. First, it limits temporal frequency sensitivity to the equivalent of ...

This study was performed to investigate the iterative reconstruction of a segment of a long object using cone-beam projections acquired with a practical-size detector. This reconstruction problem is commonly called the cone-beam long object problem. The cone-beam focal-point trajectories studied were either helical or helical with planar arcs. We assume that the long object is confined in a tal...

Furthermore, we can see that the outline in Fig. 6 does not have a second plane of symmetry at right angles to that shown. This means that, even if we were to determine the lines of flow for the truncated cone, the condition of detailed balance of the rays (Sec. III) at a mirror along the flow lines could not be fulfilled. Thus, the flow at other regions would be perturbed, and the concentrator...