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  • Electronic Resource  (7)
  • 1995-1999  (7)
  • 1970-1974
  • 1998  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of Er:YAG laser treatment on the root canal walls of human teeth: an SEM study (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Dental traumatology 14 (1998), S. 0 
    Details
    ISSN: 1600-0595
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The purposes of the study were to observe the morphological changes on root canal walls after instrumentation and irrigation, and assess the efficacy of conventional cleansing procedures and the effectiveness of Er:YAG laser in removing debris and smear layer from the root canal walls. Thirty-six endodontically treated human mandibular incisor teeth with single root canals were bisected longitudinally and divided into three groups of 12 teeth. Group 1 (Gl) was left unlased as a control. The teeth of group 2 (G2) and group 3 (G3) were irradiated by Er:YAG laser (laser parameters were set at 1 W, 100 mJ/pulse and 10 Hz) for 3 s and 5 s. The teeth were prepared for scanning electron microscope study. Control specimens showed debris and heavy smear layer obscuring the dentinal tubules at all levels in the canals. The root canal walls irradiated by Er:YAG laser were free of debris, with an evaporated smear layer and open dentinal tubules. These results suggested that Er:YAG laser irradiation had an efficient cleaning effect on the prepared root canal walls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-9657.1998.tb00851.x
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  • 2
    Electronic Resource
    Electronic Resource
    Solvation state selective excitation in resonance Raman spectroscopy. II. Theoretical calculation (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9084-9095 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have reported in the previous paper [J. Chem. Phys. 109, 9075 (1998)] that the Raman Stokes shifts of the C(Double Bond)O and the C(Double Bond)N stretching modes in the resonance Raman spectra of a solvatochromic dye, phenol blue (PB), appear to depend on the excitation photon energy in polar or protic solvents. The reason was ascribed to the solvation state selective excitation due to the inhomogeneous distribution of the solvation environment. In this paper we have made a theoretical model calculation to demonstrate that the solvation state selective excitation indeed brings about the excitation energy dependence of the resonance Raman Stokes shift in solution. In our model, both the electronic and the vibrational transitions are linearly coupled to the same harmonic bath, to embody the coupling between the fluctuations of the electronic and the vibrational transition energies. The absorption and the resonance Raman cross sections are formulated for this model on the basis of the time dependent path integral method. In the formulation, the finite relaxation time of the bath mode and the vibrational progressions in the absorption spectra are also taken into account. We have calculated the resonance Raman spectra at various excitation photon energies for the model system probable for PB in methanol. The parameters for the calculation are estimated from the analysis of the absorption and the resonance Raman spectra. It is demonstrated that the Raman Stokes shift indeed depends on the excitation energy for this model. It is noted that the vibrational dephasing due to the coupling with the solvent bath mode should be faster than the relaxation time of the bath mode for the excitation energy dependence of the Raman Stokes shift to be observed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477464
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  • 3
    Electronic Resource
    Electronic Resource
    Solvation state selective excitation in resonance Raman spectroscopy. I. Experimental study on the C(Double Bond)N and the C(Double Bond)O stretching modes of phenol blue (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9075-9083 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have measured the excitation photon energy dependence of the resonance Raman spectra of a solvatochromic dye, phenol blue (PB) in various solvents from nonpolar to dipolar ones, including supercritical fluids of trifluoromethane and carbon dioxide. We have found that the band peak positions of the C(Double Bond)N stretching mode of PB appear to change with the excitation laser frequency in polar solvents. On the other hand, no dependence of the band peak positions on the excitation frequency is found in nonpolar solvents. The peak positions of the C(Double Bond)O stretching mode also show small excitation energy dependence in chloroform and in methanol. The extent of the excitation energy dependence is correlated with the amount of the fluctuation of the local field on PB molecule exerted by the solvent, which had been estimated from the bandwidths of the absorption and the Raman spectra of PB in solution. The IR absorption spectra of PB are measured in chloroform and carbon tetrachloride, and compared with the Raman spectra in the same solvents. The excitation energy dependence is explained by the solvation state selective excitation in the resonance Raman spectroscopy, that is, the inhomogeneity that appears in the absorption spectra of PB also appears in the resonance Raman process. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477463
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of the solvent density and species on the back-electron transfer rate in the hexamethylbenzene/tetracyanoethylene charge-transfer complex (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 1485-1498 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The back-electron transfer (b-ET) process in the hexamethylbenzene/tetracyanoethylene charge-transfer complex was studied by the transient absorption spectroscopy in several fluids (ethane, nitrous oxide, carbon dioxide, and trifluoromethane) from the critical density to twice that of it at 323.2 K. The b-ET rate was determined by the decay rate of the excited state absorption. The b-ET rate increased with the increase of solvent density in carbon dioxide and nitrous oxide. The b-ET rate also increased in the order of ethane, nitrous oxide, carbon dioxide, and trifluoromethane, compared at the similar reduced density divided by the solvent critical density. Based on the formulation by Marcus and Jortner, the reaction free energy and the solvent reorganization energy were estimated from the change of the absorption spectrum relative to the gaseous phase spectrum, simply by assuming that the intramolecular reorganization energy does not depend on the solvent density and the species. The reaction free energy and the solvent reorganization energy in fluids obtained in this way were almost linearly correlated, and the density dependence was larger in the lower density region. The b-ET rates in various conditions showed a good correlation with the reaction free energy estimated from the spectral simulation. The b-ET rate showed a significant isotope effect by perdeuteriation of hexamethylbenzene as is predicted by the fluorescence quantum yield [K. Kulinowski et al., J. Phys. Chem. 99, 17715 (1995)], which could not be reproduced by this model. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475520
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of argon laser irradiation on instrumented root canal wall (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Dental traumatology 14 (1998), S. 0 
    Details
    ISSN: 1600-0595
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The objective of the study was to examine whether argon laser has a property to remove debris and smear layer from root canal walls. Twelve endodontically treated human maxillary molar teeth with three root canals were divided into two groups of six teeth. The first group was left unlased as a control; in the second group the root canals were irradiated by argon laser (laser parameters were set at 1 W and pulse duration and pulse frequency fixed at 0.05 s and 5 Hz). After the usual root canal preparation and lasing had been camed out, the teeth were decoronated, bisected longitudinally, observed with a scanning electron microscope and evaluated as to how clean the surfaces of root canal walls were. In most cases control teeth presented surfaces with debris covering the root canals, obscuring the dentinal tubules. Only 1 of 18 specimens was free of debris. In the lased group, root canal surfaces free of debris and vaporized pulpal tissue remnants were observed in 13 of 18 specimens. The results showed sigmficant statistical differences between the control group and the lased groups (P〈0.001). These results suggested that argon laser irradiation has an efficient cleaning effect on instrumented root canal surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-9657.1998.tb00805.x
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  • 6
    Electronic Resource
    Electronic Resource
    Myelodysplastic syndrome with translocation (8; 21): a distinct myelodysplastic syndrome entity or M2-acute myeloid leukemia with extensive myeloid maturation? (1998)
    Springer
    Annals of hematology 76 (1998), S. 279-282 
    Details
    ISSN: 1432-0584
    Keywords: Key words Translocation (8; 21) ; Myelodysplastic syndromes ; Acute myeloid leukemia ; Fluorescence in situ hybridization ; Myeloid maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report a case of refractory anemia with excess of blasts in transformation with the translocation (8; 21), which is frequent in acute myeloid leukemia (AML) but not in myelodysplastic syndromes (MDS). Bone marrow blasts were 1.6% and an extensive myeloid differentiation was noted. Fluorescence in situ hybridization analysis revealed the presence of 21q22 translocations in mature neutrophils, indicating that clonogenic blast progenitors could actively undergo terminal differentiation to mature end cells in vivo. We consider that t(8; 21)+ MDS may represent a rare clinical manifestation of M2-AML, in which blast progenitors have an extensive differentiation potential to mature neutrophils without maturation arrests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002770050402
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  • 7
    Electronic Resource
    Electronic Resource
    Propionyl-CoA carboxylase of Myxococcus xanthus: catalytic properties and function in developing cells (1998)
    Springer
    Archives of microbiology 170 (1998), S. 179-184 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsMyxococcus xanthus ; Propionyl-CoA ; carboxylase ; Acetyl-CoA carboxylase ; Kinetic constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An acyl-coenzyme A carboxylase that carboxylates acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA was purified from Myxococcus xanthus. Since the enzyme showed maximal rates of carboxylation with propionyl-CoA, the enzyme is thought to be propionyl-CoA carboxylase. The apparent K m values for acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA were found to be 0.2, 0.2, 0.03, and 1.0 mM, respectively. The native enzyme has a molecular mass of 605–615 kDa and is composed of nonidentical subunits (α and β) with molecular masses of 53 and 56 kDa, respectively. The enzyme showed maximal activity at pH 7.0–7.5 and at 25–30°C, and was affected by variation in concentrations of ATP and Mg2+. During development of M. xanthus, the propionyl-CoA carboxylase activity increased gradually, with maximum activity observed during the sporulation stage. Previous work has shown that a propionyl-CoA-carboxylase-deficient mutant of M. xanthus reduces levels of long-chain fatty acids. These results suggest that the propionyl-CoA carboxylase is also responsible for the carboxylation of acetyl-CoA to malonyl-CoA used for the synthesis of long-chain fatty acids during development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050631
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