Mach 4 and Mach 8 axisymmetric nozzles for a shock tunnel

The performance of two axisymmetric nozzles which were designed to produce uniform, parallel flow with nominal Mach numbers of 4 and 8 is examined. A free-piston-driven shock tube was used to supply the nozzle with high-temperature, high-pressure test gas. The inviscid design procedure treated the nozzle expansion in two stages. Close to the nozzle throat, the nozzle wall was specified as conical and the gas flow was treated as a quasi-one-dimensional chemically-reacting flow. At the end of the conical expansion, the gas was assumed to be calorically perfect, and a contoured wall was designed (using method of characteristics) to convert the source flow into a uniform and parallel flow at the end of the nozzle. Performance was assessed by measuring Pitot pressures across the exit plane of the nozzles and, over the range of operating conditions examined, the nozzles produced satisfactory test flows. However, there were flow disturbances in the Mach 8 nozzle flow that persisted for significant times after flow initiation

Shock tunnel studies of scramjet phenomena

Commissioning of the new T4 shock tunnel at the University of Queensland implied that it was no longer necessary to focus the work of the research group about an annual test series conducted in the T3 shock tunnel in Canberra. Therefore, it has been possible to organize a group for work to proceed along lines such that particular personnel are associated with particular project areas. The format of this report consists of a series of reports on specific project areas, with a brief general introduction commenting on each report. The introduction is structured by project areas, with the title of the relevant report stated under the project area heading. The reports themselves follow in the order of the project area headings

Shock tunnel studies of scramjet phenomena, supplement 5

A series of reports are presented on SCRAMjet studies, shock tunnel studies, and expansion tube studies. The SCRAMjet studies include: (1) Investigation of a Supersonic Combustion Layer; (2) Wall Injected SCRAMjet Experiments; (3) Supersonic Combustion with Transvers, Circular, Wall Jets; (4) Dissociated Test Gas Effects on SCRAMjet Combustors; (5) Use of Silane as a Fuel Additive for Hypersonic Thrust Production, (6) Pressure-length Correlations in Supersonic Combustion; (7) Hot Hydrogen Injection Technique for Shock Tunnels; (8) Heat Release - Wave Interaction Phenomena in Hypersonic Flows; (9) A Study of the Wave Drag in Hypersonic SCRAMjets; (10) Parametric Study of Thrust Production in the Two Dimensional SCRAMjet; (11) The Design of a Mass Spectrometer for use in Hypersonic Impulse Facilities; and (12) Development of a Skin Friction Gauge for use in an Impulse Facility. The shock tunnel studies include: (1) Hypervelocity flow in Axisymmetric Nozzles; (2) Shock Tunnel Development; and (3) Real Gas Efects in Hypervelocity Flows over an Inclined Cone. The expansion tube studies include: (1) Investigation of Flow Characteristics in TQ Expansion Tube; and (2) Disturbances in the Driver Gas of a Shock Tube

Scramjets and Shock Tunnels: The Queensland Experience

This article reports on the use of a shock tunnel to study the operation of scramjet powered configurations at sub-orbital velocities above 2 km/s. Thrust, as given by a net thrust equation, is used as a figure of merit throughout the study. After a short description of the shock tunnel used and its operating characteristics, experiments on the combustion release of heat in a constant area duct with hydrogen fuel are reviewed. The interaction between heat release in the combustion wake and the walls of the duct produced pressure distributions which followed a binary scaling law, and indicated that the theoretically expected heat release could be realized in practice, albeit with high pressure or long combustion ducts. This heat release, combined with attainable thrust nozzle characteristics and a modest level of configuration drag, indicated that positive thrust levels could be obtained well into the sub-orbital range of velocities. Development of a stress wave force balance for use in shock tunnels allowed the net thrust generated to be measured for integrated scramjet configurations and, although the combination of model size and shock tunnel operating pressure prevented complete combustion of hydrogen, the cruise condition of zero net thrust was achieved at 2.5 km/s with one configuration, while net thrust was produced with another configuration using an ignition promoter in hydrogen fuel. Nevertheless, the combination of boundary layer separation induced inlet choking and limited operating pressure levels prevented realization of the thrust potential of the fuel. This problem may be alleviated by recent increases in the shock tunnel operating pressures, and by promising research involving inlet injection of the fuel. Research on the drag component of the net thrust equation resulted from the development of a fast response skin friction gauge. It was found that existing theories of turbulent boundary skin friction predicted the skin friction when combustion of hydrogen occurred outside the boundary layer, but combustion within the boundary layer dramatically reduced the skin friction. Finally, for the first time in the world, supersonic combustion was produced in a free flight experiment. This experiment validated shock tunnel results at stagnation enthalpies near 3 MJ/k

Speciation, Cytogenetics, and Utilization of Arachis Species

Utilization of wild species for improvement of cultivated forms has been investigated since Faircloth made the first interspecific hybrids in 1717. Many wild species have been of value in crop improvement for a large number of traits (Harlan, 1976; Hawkes, 1977; Stalker, 1980a; Hadley and Openshaw, 1980). However, in leguminous oilseeds, utilization of species germplasm has proven difficult, in large part because of barriers to interspecific hybridization between species (Smartt, 1979). Further, sterility often restricts introgression from wild to cultivated accessions even when initial hybridization is possible. Interspecific hybridization is also difficult among the peanut species in the genus Arachis, but breeding populations derived from crossing A . hypogaea L. with related species are currently being evaluated for farmer use (Moss, 1985b). Four species of Arachis have been cultivated, including two diploids (2n = 2x = 20: A . villosulicarpa Hoehne and A . repens Handro) and two tetraploids (2n = 4x = 40: A . glabrata Benth. and A . hypogaea). Arachis villosulicarpa has only been cultivated by Indians in the northwestern part of the Brazilian state of Mato Grosso (Gregory et al., 1973). Arachis repens and A . glabrata have been grown in different parts of South America as forages or as ground covers in urban areas. Arachis glabrata has also been selected for forage qualities in Florida, where recent cultivar releases have been made (Prine et al., 1981). However, A . hypogaea is the only species which is cultivated extensively for commercial production of seeds and oil

Embryo Rescue in Wide Crosses in Arachis. 3. In vitro Culture of Peg Tips of A. hypogaea Selfs and Interspecific Hybrids

Embryo rescue in wide crosses in Arachis has only been achieved from culturing ovules excised from well developed pods, or from immature pods derived from flowers treated with gibberellic acid (GA) and which had embryos large enough to dissect without injury. The objective of this study was to determine whether reproductive tissues could grow in vitro without the need to dissect them from the peg tip and to determine the effects of GA application on flowers at the time of pollination, age of peg when cultured, and the presence of the peg meristem on reproductive growth, callus production, and peg elongation in vitro. Pegs elongated in culture only when the peg meristem was not removed. Ovules enlarged and grew out of the surrounding peg tissue in 3.8 to 32.8% of the cultures. Significantly more ovules grew when the peg meristem was removed (p < 0.01) and when 10- and 20- day-old pegs were cultured (p < 0.05). Overall, the most successful treatment for growth of ovules was treating flowers with GA at pollination and culturing without the peg meristem 10 days after pollination when 25.0 and 32.8% of all hybrid and selfed ovules, respectively, grew. Embryo growth was observed in an average of 8.4 and 17.6% of embryo sacs in hybrid and self peg tips, respectively, with several embryos reaching the globular stage after 21 days in vitro. This illustrates the potential for culturing young reproductive tissues of Arachis to recover interspecific hybrid

Do advisors perceive climate change as an agricultural risk? An in-depth examination of Midwestern U.S. Ag advisors’ views on drought, climate change, and risk management

Through the lens of the Health Belief Model and Protection Motivation Theory, we analyzed interviews of 36 agricultural advisors in Indiana and Nebraska to understand their appraisals of climate change risk, related decision making processes and subsequent risk management advice to producers. Most advisors interviewed accept that weather events are a risk for US Midwestern agriculture; however, they are more concerned about tangible threats such as crop prices. There is not much concern about climate change among agricultural advisors. Management practices that could help producers adapt to climate change were more likely to be recommended by conservation and Extension advisors, while financial and crop advisors focused more upon season-to-season decision making (e.g., hybrid seeds and crop insurance). We contend that the agricultural community should integrate long-term thinking as part of farm decision making processes and that agricultural advisors are in a prime position to influence producers. In the face of increasing extreme weather events, climatologists and advisors should work more closely to reach a shared understanding of the risks posed to agriculture by climate change

GRK6 regulates the hemostatic response to injury through its rate-limiting effects on GPCR signaling in platelets.

G protein-coupled receptors (GPCRs) mediate the majority of platelet activation in response to agonists. However, questions remain regarding the mechanisms that provide negative feedback toward activated GPCRs to limit platelet activation and thrombus formation. Here we provide the first evidence that GPCR kinase 6 (GRK6) serves this role in platelets, using GRK6-/- mice generated by CRISPR-Cas9 genome editing to examine the consequences of GRK6 knockout on GPCR-dependent signaling. Hemostatic thrombi formed in GRK6-/- mice are larger than in wild-type (WT) controls during the early stages of thrombus formation, with a rapid increase in platelet accumulation at the site of injury. GRK6-/- platelets have increased platelet activation, but in an agonist-selective manner. Responses to PAR4 agonist or adenosine 5\u27-diphosphate stimulation in GRK6-/- platelets are increased compared with WT littermates, whereas the response to thromboxane A2 (TxA2) is normal. Underlying these changes in GRK6-/- platelets is an increase in Ca2+ mobilization, Akt activation, and granule secretion. Furthermore, deletion of GRK6 in human MEG-01 cells causes an increase in Ca2+ response and PAR1 surface expression in response to thrombin. Finally, we show that human platelet activation in response to thrombin causes an increase in binding of GRK6 to PAR1, as well as an increase in the phosphorylation of PAR1. Deletion of GRK6 in MEG-01 cells causes a decrease in PAR1 phosphorylation. Taken together, these data show that GRK6 regulates the hemostatic response to injury through PAR- and P2Y12-mediated effects, helping to limit the rate of platelet activation during thrombus growth and prevent inappropriate platelet activation

Bounds on the mass-to-radius ratio for non-compact field configurations

It is well known that a spherically symmetric compact star whose energy density decreases monotonically possesses an upper bound on its mass-to-radius ratio, $2M/R\leq 8/9$. However, field configurations typically will not be compact. Here we investigate non-compact static configurations whose matter fields have a slow global spatial decay, bounded by a power law behavior. These matter distributions have no sharp boundaries. We derive an upper bound on the fundamental ratio max_r{2m(r)/r} which is valid throughout the bulk. In its simplest form, the bound implies that in any region of spacetime in which the radial pressure increases, or alternatively decreases not faster than some power law $r^{-(c+4)}$, one has $2m(r)/r \leq (2+2c)/(3+2c)$. [For $c \leq 0$ the bound degenerates to $2m(r)/r \leq 2/3$.] In its general version, the bound is expressed in terms of two physical parameters: the spatial decaying rate of the matter fields, and the highest occurring ratio of the trace of the pressure tensor to the local energy density.Comment: 4 page