Finite element solution of low bond number sloshing

The dynamics of liquid propellant in a low Bond number environment which are critical to the design of spacecraft systems with respect to orbital propellant transfer and attitude control system were investigated. Digital computer programs were developed for the determination of liquid free surface equilibrium shape, lateral slosh natural vibration mode shapes, and frequencies for a liquid in a container of arbitrary axisymmetric shape with surface tension forces the same order of magnitude as acceleration forces. A finite volume element representation of the liquid was used for the vibration analysis. The liquid free surface equilibrium shapes were computed for several tanks at various contact angles and ullage volumes. A configuration was selected for vibration analysis and lateral slosh mode shapes and natural frequencies were obtained. Results are documented

Smectic-C tilt under shear in Smectic-A elastomers

Stenull and Lubensky [Phys. Rev. E {\bf 76}, 011706 (2007)] have argued that shear strain and tilt of the director relative to the layer normal are coupled in smectic elastomers and that the imposition of one necessarily leads to the development of the other. This means, in particular, that a Smectic-A elastomer subjected to a simple shear will develop Smectic-C-like tilt of the director. Recently, Kramer and Finkelmann [arXiv:0708.2024, Phys. Rev. E {\bf 78}, 021704 (2008)] performed shear experiments on Smectic-A elastomers using two different shear geometries. One of the experiments, which implements simple shear, produces clear evidence for the development of Smectic-C-like tilt. Here, we generalize a model for smectic elastomers introduced by Adams and Warner [Phys. Rev. E {\bf 71}, 021708 (2005)] and use it to study the magnitude of Smectic-C-like tilt under shear for the two geometries investigated by Kramer and Finkelmann. Using reasonable estimates of model parameters, we estimate the tilt angle for both geometries, and we compare our estimates to the experimental results. The other shear geometry is problematic since it introduces additional in-plane compressions in a sheet-like sample, thus inducing instabilities that we discuss.Comment: 8 pages, 5 figure

Fuel conservative guidance concept for shipboard landing of powered-life aircraft

A simulation study was undertaken to investigate the application of energy conservative guidance (ECG) software, developed at NASA Ames Research Center, to improve the time and fuel efficiency of powered lift airplanes operating from aircraft carriers at sea. When a flightpath is indicated by a set of initial conditions for the aircraft and a set of positional waypoints with associated airspeeds, the ECG software synthesizes the necessary guidance commands to optimize fuel and time along the specified path. A major feature of the ECG system is the ability to synthesize a trajectory that will allow the aircraft to capture the specified path at any waypoint with the desired heading and airspeed from an arbitrary set of initial conditions. Five paths were identified and studied. These paths demonstrate the ECG system's ability to save flight time and fuel by more efficiently managing the aircraft's capabilities. Results of this simulation study show that when restrictions on the approach flightpath imposed for manual operation are removed completely, fuel consumption during the approach was reduced by as much as 49% (610 lb fuel) and the time required to fly the flightpath was reduced by as much as 41% (5 min). Savings due to ECG were produced by: (1) shortening the total flight time; (2) keeping the airspeed high as long as possible to minimize time spent flying in a regime in which more engine thrust is required for lift to aid the aerodynamic lift; (3) minimizing time spent flying at constant altitude at slow airspeeds; and (4) synthesizing a path from any location for a direct approach to landing without entering a holding pattern or other fixed approach path

Radio and near-infrared observations of the steep spectrum Galactic plane radio source WKB 0314+57.8

Radio and near-infared observations towards the steep spectrum Galactic plane radio source WKB 0314+57.8 are presented, in order to clarify the nature of this source. The radio observations include archival and survey data, together with new Giant Metrewave Radio Telescope observations at 617 MHz. The near-infrared observations are in the J and K bands, from the Gemini instrument on the Shane 3-m telescope. The radio observations show that WKB 0314+57.8 is extended, with an very steep spectrum (with flux density proportional to frequency to -2.5 power between 40 MHz and 1.5 GHz). The colour--magnitude diagram constructed from near-infrared observations of the field suggests the presence of a z approx 0.08 galaxy cluster behind the Galactic plane, reddened by about 6 magnitudes of visual extinction. Although the steep spectrum source has no obvious identification, two other radio sources in the field covered by the near-infrared observations have tentative identifications with galaxies. These observations indicate that WKB 0314+57.8 is a relic source in a cluster of galaxies, not a pulsar.Comment: 6 pages, to appear in MNRAS, typos correcte

Analysis of combustion instability in liquid propellant engines with or without acoustic cavities

Analytical studies have been made of the relative combustion stability of various propellant combinations when used with hardware configurations representative of current design practices and with or without acoustic cavities. Two combustion instability models, a Priem-type model and a modification of the Northern Research and Engineering (NREC) instability model, were used to predict the variation in engine stability with changes in operating conditions, hardware characteristics or propellant combination, exclusive of acoustic cavity effects. The NREC model was developed for turbojet engines but is applicable to liquid propellant engines. A steady-state combustion model was used to predict the needed input for the instability models. In addition, preliminary development was completed on a new model to predict the influence of an acoustic cavity with specific allowance for the effects the nozzle, steady flow and combustion

Determination of surface resistance and magnetic penetration depth of superconducting YBa2Cu3O(7-delta) thin films by microwave power transmission measurements

A novel waveguide power transmission measurement technique was developed to extract the complex conductivity of superconducting thin films at microwave frequencies. The microwave conductivity was taken of two laser ablated YBa2Cu3O(7-delta) thin films on LaAlO3 with transition temperatures of approx. 86.3 and 82 K, respectively, in the temperature range 25 to 300 K. From the conductivity values, the penetration depth was found to be approx. 0.54 and 0.43 micron, and the surface resistance (R sub s) to be approx. 24 and 36 micro-Ohms at 36 GHz and 76 K for the two films under consideration. The R sub s values were compared with those obtained from the change in the Q-factor of a 36 GHz Te sub 011-mode (OFHC) copper cavity by replacing one of its end walls with the superconducting sample. This technique allows noninvasive characterization of high transition temperature superconducting thin films at microwave frequencies

Natural cytotoxicity of haemopoietic cell populations against murine lymphoid tumours.

Homozygous nude and normal mice of 3 strains, BALB/c, CBA and C57BL, were used as sources of nucleated haemopoietic "natural killer" (NK) cells. These killer cells could lyse a wide range of syngeneic and allogeneic lymphoid tumour cell lines in vitro, and it was found that cell suspensions from nude mice were always significantly more active than those from normal mice, and that the most active effector population was a polymorph-enriched peritoneal-exudate cell suspension. Eosinophils did not appear to be involved in the phenomenon, and mononuclear peritoneal-exudate cell suspensions were actually highly inhibitory. Three non-lymphoid tumours, a carcinoma, a fibrosarcoma and a mastocytoma, were totally resistant to in vitro lysis. Although all susceptible tumour cell lines were C-type virus-associated, not all of these tumours were killed by all strain sources of spleen cells, indicating a specificity of killing

Preventing Violence in Low-Income Communities: Facilitating Residents\u27 Ability to Intervene in Neighborhood Problems

The violence found in low-income communities, including areas of concentrated poverty, is often extensive and can involve illegal drugs, juvenile delinquency, and even homicide. A large body of research has emerged which points to the positive effects of informal social control and social capital in preventing violence in lowincome communities, including neighbors taking leadership roles by intervening themselves. This article contains a description of an exploratory study ofa pilot training program the authors developed to facilitate residents\u27 ability to intervene in neighborhood problems in a low-income community in Atlanta, Georgia. The training incorporated concepts from restorative justice, peacemaking criminology, and macro social work, particularly consensus organizing. The results demonstrated that after their participation in the training, residents were more likely to intervene in a variety of neighborhood problems and were more likely to use direct, non-violent and peaceful intervention strategies. Participants also improved their attitudes about intervening,feeling it was appropriate to intervene and their neighborhood was safer if residents intervened in problem behaviors. This article provides an important step in exploring the development of informal social control and social capital in low-income neighborhoods. Moreover, the strategies used in the training program can be used by social workers to design programs to prevent violence

SURFACE IMMUNOGLOBULINS ON THYMUS AND THYMUS-DERIVED LYMPHOID CELLS

Lymphoid cells from thymus, thoracic duct lymph (TDL), and thoracic duct lymph in irradiated animals reconstituted with allogeneic thymus cells (TTDL) were labeled with radioiodinated anti-immunoglobulins using radioautographic techniques. Thymus and TTDL were labeled (14.4 and 37.0%, respectively) with anti-light chain protein after prolonged exposures (30–60 days). No labeling was observed on thymus and TTDL with anti-polyheavy chain globulin. In contrast 18.5–19.0% of TDL labeled on short exposure (6 days) with anti-polyheavy chain and anti-light chain materials. It is proposed that the difference between the labeling observed on short exposures versus long exposures can be related to the difference in surface density of immunoglobulins between nonthymus-derived (B) and thymus-derived (T) cells. The distribution of labeled cells in the thymus was preferentially among the larger cells (greater than 10 µ diameter). The TTDL population was mostly composed of a larger, blast-like population and the distribution of label was independent of size. As the thymus and TTDL preparations contain almost exclusively T cells, this represents a direct demonstration of surface immunoglobulin light chains on T lymphoid cells

V2051 Ophiuchi after superoutburst : out-of-plane material and the superhump light source

Aims. We performed a detailed spectroscopic analysis of the dwarf nova V2051 Oph at the end of its 1999 superoutburst. We studied and interpreted the simultaneous behaviour of various emission lines. Methods. We obtained high-resolution echelle spectroscopic data at ESO’s NTT with EMMI, covering the spectral range of 4000–7500 Å. The analysis was performed using standard IRAF tools. The indirect imaging technique of Doppler tomography was applied, in order to map the accretion disc and distinguish between the different emission sources. Results. The spectra are characterised by strong Balmer emission, together with lines of He i and the iron triplet Fe ii 42. All lines are double-peaked, but the blue-to-red peak strength and central absorption depth vary. The primary’s velocity was found to be 84.9 kms−1. The spectrograms of the emission lines reveal the prograde rotation of a disc-like emitting region and, for the Balmer and He i lines, an enhancement of the red-wing during eclipse indicates a bright spot origin. The modulation of the double-peak separation shows a highly asymmetric disc with non-uniform emissivity. This is confirmed by the Doppler maps, which apart from the disc and bright spot emission also indicate an additional region of enhanced emission in the 4th quadrant (+Vx, −Vy), which we associate with the superhump light source. Given the behaviour of the iron triplet and its distinct differences from the rest of the lines, we attribute its existence to an extended gas region above the disc. Its origin can be explained through the fluorescence mechanism