A tunable diode laser diagnostic based on spectrally resolved laser absorption has been developed to detect water vapor. The system uses a distributed feedback InGaAsP diode laser, emitting at ~ 1.38 µm. The diode laser is tuned in wavelength by modulation of the current, resulting in 1-cm(-1) tuning at 80-Hz repetition rate. The directly measured absorption spectra yield values for water-vapor concentration and temperature, as well as a collision-broadening line shape. To our knowledge, we accurately determined required data for H(2)O line strengths and self-broadening coefficients for several spectral lines in a static cell filled with pure water vapor. The temperature and concentration of the water vapor present in laboratory room air and in the postflame gases above a methane-air flat flame burner have also been measured. These results agree well with calculated values and independent measurements.

to Ala, either singly or as a double mutant, yielded PCNA mutant proteins that had reduced capacity in enhancing the processivity of DNA polymerase ␦ but showed no deficiency in stimulation of the ATPase activity of replication factor C. S. pombe ⌬pcna strains sustained by these two mutant-pcna alleles had moderate defects in growth and displayed elongated phenotypes. These cells, however, were not sensitive to UV irradiation. Together, these in vitro and in vivo studies suggest that the side chains of Leu 2 and Arg 64 in one face of the PCNA trimer ring structure are two of the several sites involved in tethering DNA polymerase ␦ for processive DNA synthesis during DNA replication. Proliferating cell nuclear antigen (PCNA)1 is a multifunctional protein in the cell. It was originally identified as the auxiliary protein for DNA polymerase ␦ during DNA replication (1, 2). In vitro, it is able to enhance the DNA synthetic processivity of both DNA polymerases ␦ and ⑀ (3, 4) and is essential for synthesizing full-length SV40 DNA replication products (5-11). PCNA has also been found to be required for DNA excision repair and to be an essential component of the in vitro reconstituted DNA repair system (12-14). Furthermore, PCNA has been shown to associate with D-type cyclins and to interact with the cyclin kinase inhibitor p21. The interaction between PCNA and p21 leads to inhibition of DNA replication in vitro (15)(16)(17)(18), and this interaction has been shown to specifically inhibit the repair of DNA damage caused by either alkylating agents or by ultraviolet radiation (19). PCNA has also recently been found to physically bind flap endonuclease I, which is a 5Ј-flap DNA endonuclease and a nick-specific 5Ј-exonuclease (20), and to stimulate flap endonuclease I activity. This interaction is thought to be important for lagging strand synthesis and is implicated in a broad range of DNA metabolisms in which the flap endonuclease I nuclease family is involved (21).The ␤-subunit of Escherichia coli DNA pol III holoenzyme is a functional homologue of PCNA (2, 22, 23). Budding yeast PCNA and the ␤-subunit of E. coli DNA pol III holoenzyme are structurally similar, one exception being that the ␤-subunit is composed of three globular domains forming a dimeric closed ring, whereas PCNA is composed of only two domains, thus forming a trimeric six-domain ring with a central cavity large enough to encircle DNA (24,25). Structural data have suggested that PCNA forms a homotrimer torus that encircles DNA and interacts with DNA polymerase ␦, tethering it for processive DNA synthesis. These structural data also suggest that the protein loops between the six domains are important for interacting with other proteins for various DNA metabolic processes (24,25).There is substantial conservation in the primary sequences of PCNA proteins from human, mouse, rice, Drosophila, and budding and fission yeast (reviewed in Ref. 26). Double alanine scan mutagenesis of charged amino acid residues and random mutagenesis of budding yeast PCNA (POL30...

A distributed-feedback InGaAsP diode laser, emitting near 1.38 µm, was used to acquire spectrally resolved absorption profiles of H(2)O lines in the ν(1) + ν(3) band at a repetition rate of 10 kHz. The profiles were used for simultaneous measurements of flow parameters in high-speed, one-dimensional (1-D) transient flows generated in a shock tube. Velocity was determined from the Doppler shift, which was measured with a pair of profiles simultaneously acquired at different angles with respect to the flow direction. Temperature was determined from the intensity ratio of two adjacent lines. Pressure and density were found from the fractional absorption. From these primary gasdynamic variables, the mass and momentum fluxes were determined. Experiments were conducted with three different gas mixtures in the shock tube: pure H(2)O at initial pressures lower than 3 Torr, up to 6% of H(2)O in O(2) at initial pressures below 120 Torr, and up to 8% of H(2)O in O(2) at initial pressures below 35 Torr. In the third case, pyrolysis of H(2) /O(2) behind incident shocks produced known yields of H(2)O. With all three mixtures, results compare well with 1-D shock calculations. This H(2)O diagnostic strategy shows promise for applications in both ground and flight testing.