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At least 145 records · Page 8Linked to original sources
PubMed1965

INVESTIGATION OF AN OPERATOR METHOD IN THE ANALYSIS OF BIOLOGICAL TRACER DATA.

Some factors affecting the usefulness of a linear operator in the analysis of tracer data were evaluated. Application of the operator to a sum of two exponential components resulted in the separation of the rate constants with an accuracy of 10 to 15 per cent if they differed by a factor of at least 2 and the error in the data was about 2 per cent. A factor of 4 was necessary if the error in the data was 6 per cent, and of 6 if the error was 10 per cent. The ratio of amplitudes varied from near unity to equality with the ratio of rate constants. However, if the ratio of amplitudes was greater than the ratio of rate constants the method would not resolve the rate constants. Application of the operator to a sum of three exponential components was also considered.

Computers↗
PubMed2000

Fast reconstruction with uniform noise properties in halfscan computed tomography.

The hybrid algorithms developed recently for the reconstruction of fan-beam images possess computational and noise properties superior to those of the fan-beam filtered backprojection (FFBP) algorithm. However, the hybrid algorithms cannot be applied directly to a halfscan fan-beam sinogram because they require knowledge of a fullscan fan-beam sinogram. In this work, we developed halfscan-hybrid algorithms for image reconstruction in halfscan computed tomography (CT). Numerical evaluation indicates that the proposed halfscan-hybrid algorithms are computationally more efficient than are the widely used halfscan-FFBP algorithms. Also, the results of quantitative studies demonstrated clearly that the noise levels in images reconstructed by use of the halfscan-hybrid algorithm are generally lower and spatially more uniform than are those in images reconstructed by use of the halfscan-FFBP algorithm. Such reduced and uniform image noise levels may be translated into improvement of the accuracy and precision of lesion detection and parameter estimation in noisy CT images without increasing the radiation dose to the patient. Therefore, the halfscan-hybrid algorithms may have significant implication for image reconstruction in conventional and helical CT.

Algorithms↗
PubMed1965

NERVOUS SYSTEM RESEARCH WITH COMPUTERS.

The experimental system described above has been in full-scale operation now for about one year. It has been possible in this short period only to begin the exploration of the potentialities of the system for aiding nervous system research. The most intensively developed programs have been those on the insect (3) and on human vision and eye movements (5). In both of these programs the facility has permitted new research techniques which have provided answers to important questions, answers which would have been unobtainable without such a data-processing and control system.

Animals↗
PubMed2006

Synthesis of 2'-O-methyl-RNAs incorporating a 3-deazaguanine, and UV melting and computational studies on its hybridization properties.

2'-O-methyl-RNAs incorporating 3-deazaguanine (c3G) were synthesized by use of N,N-diphenylcarbamoyl and N,N-dimethylaminomethylene as its base protecting groups to suppress sheared-type 5'-GA-3'/5'-GA-3' tandem mismatched base pairing which requires the N3 atom. These modified RNAs hybridized more weakly with the complementary and single mismatch-containing RNAs than the unmodified RNAs. The T(m) experiments were performed to clarify the effects of replacement of the fifth G with c(3)G on stabilization of 2'-O-methyl-(5'-CGGCGAGGAG-3')/5'-CUCCGAGCCG-3' and 2'-O-methyl-(5'-CGGGGACGAG-3')/5'-CUCGGACCCG-3'duplexes, which form sheared-type and face-to-face type 5'-GA-3'/5'-GA-3' tandem mismatched base pairs, respectively. Consequently, this replacement led to more pronounced destabilization of the former duplex that needs the N3 atom for the sheared-type base pair than the latter that does not need it for the face-to-face type base pair. A similar tendency was observed for 2'-O-methyl-RNA/DNA duplexes. These results suggest that the N3 atom of G plays an important role in stabilization of the canonical G/C base pair as well as the base discrimination and its loss suppressed formation of the undesired sheared-type mismatched base pair. Computational studies based on ab initio calculations suggest that the weaker hydrogen bonding ability and larger dipole moment of c3G can be the origin of the lower T(m).

Base Pairing↗