ALBERT

Description: The murine Ly6-E gene is transcriptionally induced by interferon-α/β (IFN-α/β) and IFN-γ in a variety of distinct cell types. The mechanism of IFN inducibility in B-cell lines was investigated by deletion analysis of the promoter and by identifying DNA binding proteins in mobility shift assays. A region located in the distal part of the promoter at −2.3 kb contributed to inducibility by both types of IFNs. This region contains a novel element in addition to the previously well-characterized IFN-stimulated response element (ISRE). The probes containing ISRE detected IFN-inducible complexes in mobility shift assays and the signal transducer and activator of transcripition–1 was found to be in these complexes from cells treated with either type of IFN. An additional element present in the proximal part of the promoter at position −109 is also required for IFN-α/β–mediated induction. These data suggested a cooperative interaction between these physically disparate regulatory regions. A crucial role for HMGI(Y) protein in this cooperative multiprotein complex is supported by the evidence that inhibition of HMGI(Y) expression via antisense RNA results in the loss of IFN-α/β–mediated induction of the Ly6-E gene. These results show the complexity involved in achieving cell-type specificity in IFN-mediated gene regulation.

Description: The murine Ly6-E gene is transcriptionally induced by interferon-α/β (IFN-α/β) and IFN-γ in a variety of distinct cell types. The mechanism of IFN inducibility in B-cell lines was investigated by deletion analysis of the promoter and by identifying DNA binding proteins in mobility shift assays. A region located in the distal part of the promoter at −2.3 kb contributed to inducibility by both types of IFNs. This region contains a novel element in addition to the previously well-characterized IFN-stimulated response element (ISRE). The probes containing ISRE detected IFN-inducible complexes in mobility shift assays and the signal transducer and activator of transcripition–1 was found to be in these complexes from cells treated with either type of IFN. An additional element present in the proximal part of the promoter at position −109 is also required for IFN-α/β–mediated induction. These data suggested a cooperative interaction between these physically disparate regulatory regions. A crucial role for HMGI(Y) protein in this cooperative multiprotein complex is supported by the evidence that inhibition of HMGI(Y) expression via antisense RNA results in the loss of IFN-α/β–mediated induction of the Ly6-E gene. These results show the complexity involved in achieving cell-type specificity in IFN-mediated gene regulation.

Description: The effect of a simulated glaze ice accretion on the aerodynamic performance of a three-dimensional wing is studied experimentally. Results are reviewed from earlier two-dimensional tests which show the character of the large leading-edge separation bubbles caused by the simulated ice accretion. The 2-D bubbles are found to closely resemble well known airfoil laminar separation bubbles. For the 3-D experiments a semispan wing of effective aspect ratio five was mounted from the sidewall of the UIUC subsonic wind tunnel. The model uses a NACA 0012 airfoil section on a rectangular planform with interchangeable tip and root sections to allow for 0- and 30-degree sweep. A three-component sidewall balance was used to measure lift, drag and pitching moment on the clean and iced model. Fluorescent oil flow visualization has been performed on the iced model and reveals extensive spanwise and vortical flow in the separation bubble aft of the upper surface horn. Sidewall interaction and spanwise nonuniformity are also seen on the unswept model. Comparisons to the computed flow fields are shown. Results are also shown for roughness effects on the straight wing. Sand grain roughness on the ice shape is seen to have a different effect than isolated 3-D roughness elements.

Description: Wind tunnel experiments were conducted in order to study the effect of a simulated glaze ice accretion on the flowfield of a semispan, reflection-plane, rectangular wing at Re = 1.5 million and M = 0.12. A laser Doppler velocimeter was used to map the flowfield on the upper surface of the model in both the clean and iced configurations at alpha = 0, 4, and 8 degrees angle of attack. At low angles of attack, the massive separation bubble aft of the leading edge ice horn was found to behave in a manner similar to laminar separation bubbles. At alpha = 0 and 4 degrees, the locations of transition and reattachment, as deduced from momentum thickness distributions, were found to be in good agreement with transition and reattachment locations in laminar separation bubbles. These values at y/b = 0.470, the centerline measurement location, matched well with data obtained on a similar but two dimensional model. The measured velocity profiles on the iced wing compared reasonably with the predicted profiles from Navier-Stokes computations. The iced-induced separation bubble was also found to have features similar to the recirculating region aft of rearward-facing steps. At alpha = 0 degrees and 4 degrees, reverse flow magnitudes and turbulence intensity levels were typical of those found in the recirculating region aft of rearward-facing steps. The calculated separation streamline aft of the ice horn at alpha = 4 degrees, y/b = 0.470 coincided with the locus of the maximum Reynolds normal stress. The maximum Reynolds normal stress peaked at two locations along the separation streamline. The location of the first peak-value coincided with the transition location, as deduced from the momentum thickness distributions. The location of the second peak was just upstream of reattachment, in good agreement with measurements of flows over similar obstacles. The intermittency factor in the vicinity of reattachment at alpha = 4 degrees, y/b = 0.470, revealed the time-dependent nature of the reattachment process. The size and extent of the separation bubble were found to be a function of angle of attack and the spanwise location. Three dimensional effects were found to be strongest at alpha = 8 degrees. The calculated separation and stagnation streamlines were found to vary little with spanwise location at alpha = 0 degrees. The calculated separation streamlines at alpha = 4 degrees revealed that the bubble was largest near the centerline measurement plane, whereas the tip-induced vortex flow and the model root-tunnel wall boundary-layer interaction reduced the size of the bubble. These effects were found to be most dramatic at alpha = 8 degrees.

Description: The effect of a simulated glaze-ice accretion on the flowfield of a 3D wing is studied experimentally. The model used for these tests was a semispan wing of effective aspect ratio five, mounted from the sidewall of a subsonic wind tunnel. The model has a NACA 0012 airfoil section on a rectangular untwisted planform with interchangeable leading edges to allow for testing both the baseline and the iced-wing geometry. A four-beam two-color fiberoptic laser Doppler velocimeter (LDV) was used to map the flowfield along three spanwise cuts on the model. Measurements on the centerline of the clean model compared favorably with theory and centerline measurements on the iced model compared well with measurements on a similar 2D model. The flow has the largest separation bubble at the model midspan with the smallest separation bubble occurring near the root and the wing tip.

Description: The effect of a simulated glaze ice accretion on the aerodynamic performance of a three-dimensional wing is studied experimentally. The model used for these tests was a semi-span wing of effective aspect ratio five, mounted from the sidewall of the UIUC subsonic wind tunnel. The model has an NACA 0012 airfoil section on a rectangular, untwisted planform with interchangeable leading edges to allow for testing both the baseline and the iced wing geometry. A three-component sidewall balance was used to measure lift, drag and pitching moment on the clean and iced model. A four-beam two-color fiberoptic laser Doppler velocimeter (LDV) was used to map the flowfield along several spanwise cuts on the model. Preliminary results from LDV scans, which will be the bulk of this paper, are presented following the force balance measurement results. Initial comparison of LDV surveys compare favorably with inviscid theory results and 2D split hot-film measurements near the model surface.