ALBERT

Description: Highlights • Empirical approach was used to study effects of seabird guano on marine phytoplankton. • Seabird guano enhances phytoplankton productivity in different water masses. • Nutrient run-off from seabird colonies is a significant nutrient source. Abstract Six incubation experiments were carried out to investigate the phytoplankton biomass response to seabird guano-enrichment under different nutrient regimes. Study locations included Antarctic waters of the Ross Sea and sub-Antarctic waters offshore of the Otago Peninsula, both being characterized by iron limitation of phytoplankton productivity in summer, the Sub-Tropical Frontal Zone offshore of the Snares Islands, which is generally micronutrient-replete, and the island wake waters of the Snares Islands, which have a high nutrient supply from land. In all of the experiments the increase of phytoplankton biomass was higher in the treatments with guano addition compared to the controls. Guano additions were compared to Fe and macronutrients treatments (both added in quantities similar to those in the guano treatment) to shed light on which constituent(s) of guano are responsible for the observed increases in phytoplankton biomass. Macronutrients increased the phytoplankton biomass in the Sub-Tropical Frontal Zone, however, the response was less prominent than in the Guano treatment, suggesting synergetic effects of nutrients in seabird guano on phytoplankton production. It was also found that the pattern of response varied between the water masses with 6–10 days lag phase in the Sub-Antarctic water mass and no lag phase in Sub-Tropical Frontal Zone. The calculations presented here suggest that micro- and macronutrients delivered from seabird colonies on some of the sub-Antarctic islands may provide a significant amount of limiting nutrients to the nutrient budget of the surrounding coastal waters, potentially sufficient to sustain a local phytoplankton bloom. Findings of the present study indicate that biological recycling of nutrients by seabirds likely supports marine primary production and enhances productivity of associated food webs in the vicinity of islands.

Description: The rapid loss of skeletal-muscle protein during starvation and after denervation occurs primarily through increased rates of protein breakdown and activation of a non-lysosomal ATP-dependent proteolytic process. To investigate whether protein flux through the ubiquitin (Ub)-proteasome pathway is enhanced, as was suggested by related studies, we measured, using specific polyclonal antibodies, the levels of Ub-conjugated proteins in normal and atrophying muscles. The content of these critical intermediates had increased 50-250% after food deprivation in the extensor digitorum longus and soleus muscles 2 days after denervation. Like rates of proteolysis, the amount of Ub-protein conjugates and the fraction of Ub conjugated to proteins increased progressively during food deprivation and returned to normal within 1 day of refeeding. During starvation, muscles of adrenalectomized rats failed to increase protein breakdown, and they showed 50% lower levels of Ub-protein conjugates than those of starved control animals. The changes in the pools of Ub-conjugated proteins (the substrates for the 26S proteasome) thus coincided with and can account for the alterations in overall proteolysis. In this pathway, large multiubiquitinated proteins are preferentially degraded, and the Ub-protein conjugates that accumulated in atrophying muscles were of high molecular mass (〉 100 kDa). When innervated and denervated gastrocnemius muscles were fractionated, a significant increase in ubiquitinated proteins was found in the myofibrillar fraction, the proteins of which are preferentially degraded on denervation, but not in the soluble fraction. Thus activation of this proteolytic pathway in atrophying muscles probably occurs initially by increasing Ub conjugation to cell proteins. The resulting accumulation of Ub-protein conjugates suggests that their degradation by the 26S proteasome complex subsequently becomes rate-limiting in these catabolic states.

Description: The objective of this program is to identify, develop, and demonstrate an optimum wire insulation system capable of continuous operation at 300 C which possesses a combination of superior electrical (AC or DC), mechanical, and physical properties over Kapton derived insulations described in MIL-W-81381 and those hybrid materials commonly known as TKT constructions.

Description: Existing observations of the Galactic Center at infrared and radio wavelengths challenge our understanding of the detailed morphology and energy balance of the inner few parsec, including the Galactic Center and the infrared torus. The distribution and nature of the sources heating this region are still not well understood; existing determinations of dust temperature and ionization do not provide us with consistent pictures of the relative important of the central source and the embedded stars in this dusty region. The composite IR emission of the Galactic Center can be crudely divided into three categories: (1) hot dust heated directly by an incident UV field along the inner region of the Galactic Center torus; (2) warm dust heated by te non-ionizing radiation of the embedded stars and re-radiated NIR dust emission; (3) cooler absorbing dust located along the galactic line of sight. The apparent inconsistencies between the observations and theoretical expectations may stem from the interplay of various physical process and source-cloud geometries. Observations with increased spatial and spectral resolution are clearly needed to provide the information necessary to address the various problems. Therefore, we made 15-45 micron spectrophotometric observations of the inner 80 min (3 pc) regions surrounding the Galactic Center with the 20 min aperture of Goddard Cryogenic Grating Spectrometer No. 2 in May 1994 from the KAO. We measured nine points, including the 50 and 90 micron peaks of Davidson et al. and points between them and SgrA,. The wavelength coverage of our instrument ensures sensitivity to the hot dust component, silicate emission and/or absorption features, and cooler dust at longer wavelengths. Our observations will be used to set limits on the luminosity of any central sources, or give an independent estimate of central luminosity, and to set limits on the range of acceptable dust parameters for this region.

Description: The 16-48 micron spectra of five carbon-rich post-asymptotic giant branch (post-AGB) objects known to have an unidentified 21 micron feature in their IRAS low resolution spectrometer (LRS) spectra have been obtained using the Kuiper Airborne Observatory. A broad emission band extending from 24 to approximately 45 microns is present in the spectra of these objects. The strength of this band is variable from source to source and is not correlated with the strength of the 21 micron band. The possible identifications for the emitting material of both the 21 and 30 micron emission bands is discussed.

Description: An aerodynamic and acoustic investigation was performed on two small-scale supersonic inlets to determine which inlet would be more suitable for a High Speed Civil Transport (HSCT) aircraft during approach and takeoff flight conditions. The comparison was made between an axisymmetric supersonic P inlet and a bifurcated two-dimensional supersonic inlet. The 1/14 scale model supersonic inlets were used in conjunction with a 4.1 in (10.4 cm) turbofan engine simulator. A bellmouth was utilized on each inlet to eliminate lip separation commonly associated with airplane engine inlets that are tested under static conditions. Steady state measurements of the aerodynamic flowfield and acoustic farfield were made in order to evaluate the aeroacoustic performance of the inlets. The aerodynamic results show the total pressure recovery of the two inlets to be nearly identical, 99% at the approach condition and 98% at the takeoff condition. At the approach fan speed (60% design speed), there was no appreciable difference in the acoustic performance of either inlet over the entire 0 deg to 110 deg farfield measurement sector. The inlet flow field results at the takeoff fan speed (88% design speed), show the average inlet throat Mach number for the P inlet (Mach 0.52) to be approximately 2 times that of the 2D inlet (Mach 0.26). The difference in the throat Mach number is a result of the smaller throughflow area of the P inlet. This reduced area resulted in a 'soft choking' of the P inlet which lowered the tone and overall sound pressure levels of the simulator in the forward sector by an average of 9 dB and 3 dB, respectively, when compared to the 2D inlet.

Description: The thrust efficiency and vectoring performance of a convergent-divergent nozzle were investigated at static conditions in the model preparation area of the Langley 16-Foot Transonic Tunnel. The diamond-shaped nozzle was capable of varying the internal contour of each quadrant individually by using cam mechanisms and retractable drawers to produce pitch and yaw thrust vectoring. Pitch thrust vectoring was achieved by either retracting the lower drawers to incline the throat or varying the internal flow-path contours to incline the throat. Yaw thrust vectoring was achieved by reducing flow area left of the nozzle centerline and increasing flow area right of the nozzle centerline; a skewed throat deflected the flow in the lateral direction.

Description: Results are presented of an experimental program that investigated the use of a secondary air stream to control the amount of flow through a convergent-divergent nozzle. These static tests utilized high pressure, ambient temperature air that was injected at the throat of the nozzle through an annular slot. Multiple injection slot sizes and injection angles were tested. The introduction of secondary flow was made in an opposing direction to the primary flow and the resulting flow field caused the primary stream to react as though the physical throat size had been reduced. The percentage reduction in primary flow rate was generally about twice the injected flow rate. The most effective throttling was achieved by injecting through the smallest slot in an orientation most nearly opposed to the approaching primary flow. Thrust edliciency, as measured by changes in nozzle thrust coefficient, was highest at high nozzle pressure ratios, NPR. The static test results agreed with predictions obtained prior from PABSD, a fully viscous computational fluid dynamics program. Since use of such an injection system on gas turbine engine exhaust nozzles would be primarily at high NPRs, it was concluded that fluidic control holds promise for reducing nozzle weight and complexity on future systems.

Description: The static internal performance of a multiaxis-thrust-vectoring, spherical convergent flap (SCF) nozzle with a non-rectangular divergent duct was obtained in the model preparation area of the Langley 16-Foot Transonic Tunnel. Duct cross sections of hexagonal and bowtie shapes were tested. Additional geometric parameters included throat area (power setting), pitch flap deflection angle, and yaw gimbal angle. Nozzle pressure ratio was varied from 2 to 12 for dry power configurations and from 2 to 6 for afterburning power configurations. Approximately a 1-percent loss in thrust efficiency from SCF nozzles with a rectangular divergent duct was incurred as a result of internal oblique shocks in the flow field. The internal oblique shocks were the result of cross flow generated by the vee-shaped geometric throat. The hexagonal and bowtie nozzles had mirror-imaged flow fields and therefore similar thrust performance. Thrust vectoring was not hampered by the three-dimensional internal geometry of the nozzles. Flow visualization indicates pitch thrust-vector angles larger than 10' may be achievable with minimal adverse effect on or a possible gain in resultant thrust efficiency as compared with the performance at a pitch thrust-vector angle of 10 deg.

Description: Distributions of static pressure coefficient over the afterbody and axisymmetric nozzles of a generic, twin-tail twin-engine fighter were obtained in the Langley 16-Foot Transonic Tunnel. The longitudinal positions of the vertical and horizontal tails were varied for a total of six aft-end configurations. Static pressure coefficients were obtained at Mach numbers between 0.6 and 1.2, angles of attack between 0 deg and 8 deg, and nozzle pressure ratios ranging from jet-off to 8. The results of this investigation indicate that the influence of the vertical and horizontal tails extends beyond the vicinity of the tail-afterbody juncture. The pressure distribution affecting the aft-end drag is influenced more by the position of the vertical tails than by the position of the horizontal tails. Transonic tail-interference effects are seen at lower free-stream Mach numbers at positive angles of attack than at an angle of attack of 0 deg.