Vibrations and stresses in layered anisotropic cylinders

An equation describing the radial displacement in a k layered anisotropic cylinder was obtained. The cylinders are initially unstressed but are subjected to either a time dependent normal stress or a displacement at the external boundaries of the laminate. The solution is obtained by utilizing the Vodicka orthogonalization technique. Numerical examples are given to illustrate the procedure

Study of airborne science experiment management concepts for application to space shuttle. Volume 3: Appendixes

Detailed information is presented concerning specific airborne missions in support of the ASSESS program. These missions are the AIDJEX expeditions, meteor shower expeditions, CAT and atmospheric sampling missions, ocean color expeditions, and the Lear Jet missions. For Vol. 2, see N73-31729

JPL development ephemeris no. 69

Improved lunar and planetary ephemeri

Midwinter suppression of baroclinic storm activity on Mars: observations and models

Baroclinic instability and intense traveling wave activity on Mars is well known to occur in “storm zones” (Hollingsworth et al. 1996) close to the edge of the advancing or retreating polar ice cap. Such activity usually sets in during Martian fall and continues until the onset of the summer season when large-scale instability mostly ceases as the atmosphere is no longer baroclinically unstable. The stormy season is typically characterized by large-scale, zonally-propagating waves with zonal wavenumbers m = 1-3, the lower wavenumber modes typically penetrating to considerable altitude though may also be surface-intensified. As we show below, however, some observations suggest that this eddy activity does not persist uniformly throughout the autumn, winter and spring seasons, but appears to die down quite consistently within 10 sols or so either side of the winter solstice. This midwinter ‘solsticial pause’ appears to be a sufficiently consistent feature of each winter season in both hemispheres to be regarded as a significant feature of Martian climatology, and could affect a variety of aspects of Martian meteorology including global heat and momentum transport, occurrence of dust storms etc. A somewhat similar phenomenon has also been documented for the Earth (e.g. Nakamura 1992; Penny et al. 2010), especially in relation to seasonal variations in the north Pacific storm tracks. The cause of this phenomenon is still not well established, though suggested mechanisms include the effects of enhanced barotropic shear (the so-called ‘barotropic governor’ (James & Gray 1986) and interactions with topography over central Asia. In this presentation we examine evidence for this phenomenon in the assimilated record of Martian climate from the Thermal Emission Spectrometer on board the Mars Global Surveyor mission (MGSTES), in conjunction with the UK version of the LMD-Oxford-OU-IAA Mars GCM (Forget et al. 1999; Montabone et al. 2006; Lewis et al. 2007). This is further corroborated in other evidence from seasonal variations in the incidence of local and regional dust storms that owe their origin to circumpolar baroclinic storms. We also discuss the extent to which this ‘solsticial pause’ phenomenon is reproduced in stand-alone atmospheric models and present results of some simulations to test a number of hypotheses for its dynamical origin on Mars

Critical Point Field Mixing in an Asymmetric Lattice Gas Model

The field mixing that manifests broken particle-hole symmetry is studied for a 2-D asymmetric lattice gas model having tunable field mixing properties. Monte Carlo simulations within the grand canonical ensemble are used to obtain the critical density distribution for different degrees of particle-hole asymmetry. Except in the special case when this asymmetry vanishes, the density distributions exhibit an antisymmetric correction to the limiting scale-invariant form. The presence of this correction reflects the mixing of the critical energy density into the ordering operator. Its functional form is found to be in excellent agreement with that predicted by the mixed-field finite-size-scaling theory of Bruce and Wilding. A computational procedure for measuring the significant field mixing parameter is also described, and its accuracy gauged by comparing the results with exact values obtained analytically.Comment: 10 Pages, LaTeX + 8 figures available from author on request, To appear in Z. Phys.

Dynamic modeling of nitrogen losses in river networks unravels the coupled effects of hydrological and biogeochemical processes

The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction of nitrogen in streamflow is removed to the atmosphere via denitrification with the remainder exported in streamflow as nitrogen loads. At the watershed scale, there is a keen interest in understanding the factors that control the fate of nitrogen throughout the stream channel network, with particular attention to the processes that deliver large nitrogen loads to sensitive coastal ecosystems. We use a dynamic stream transport model to assess biogeochemical (nitrate loadings, concentration, temperature) and hydrological (discharge, depth, velocity) effects on reach-scale denitrification and nitrate removal in the river networks of two watersheds having widely differing levels of nitrate enrichment but nearly identical discharges. Stream denitrification is estimated by regression as a nonlinear function of nitrate concentration, streamflow, and temperature, using more than 300 published measurements from a variety of US streams. These relations are used in the stream transport model to characterize nitrate dynamics related to denitrification at a monthly time scale in the stream reaches of the two watersheds. Results indicate that the nitrate removal efficiency of streams, as measured by the percentage of the stream nitrate flux removed via denitrification per unit length of channel, is appreciably reduced during months with high discharge and nitrate flux and increases during months of low-discharge and flux. Biogeochemical factors, including land use, nitrate inputs, and stream concentrations, are a major control on reach-scale denitrification, evidenced by the disproportionately lower nitrate removal efficiency in streams of the highly nitrate-enriched watershed as compared with that in similarly sized streams in the less nitrate-enriched watershed. Sensitivity analyses reveal that these important biogeochemical factors and physical hydrological factors contribute nearly equally to seasonal and stream-size related variations in the percentage of the stream nitrate flux removed in each watershed

Study of airborne science experiment management concepts for application to space shuttle. Volume 1: Executive summary

The management concepts and operating procedures are documented as they apply to the planning of shuttle spacelab operations. Areas discussed include: airborne missions; formulation of missions; management procedures; experimenter involvement; experiment development and performance; data handling; safety procedures; and applications to shuttle spacelab planning. Characteristics of the airborne science experience are listed, and references and figures are included

Compact laser system for a laser-cooled ytterbium ion microwave frequency standard

The development of a transportable microwave frequency standard based on the ground-state transition of $^{171}\mathrm{Yb^{+}}$ at ~12.6 GHz requires a compact laser system for cooling the ions, clearing out of long-lived states and also for photoionisation. In this paper, we describe the development of a suitable compact laser system based on a 6U height rack-mounted arrangement with overall dimensions $260 \times 194 \times 335$ mm. Laser outputs at 369 nm (for cooling), 399 nm (photoionisation), 935 nm (repumping) and 760 nm (state clearout) are combined in a fiber arrangement for delivery to our linear ion trap and we demonstrate this system by cooling of $^{171}\mathrm{Yb^{+}}$ ions. Additionally, we demonstrate that the lasers at 935 nm and 760 nm are close in frequency to water vapor and oxygen absorption lines respectively; specifically, at 760 nm, we show that one $^{171}\mathrm{Yb^{+}}$ transition is within the pressure broadened profile of an oxygen line. These molecular transitions form convenient wavelength references for the stabilization of lasers for a $^{171}\mathrm{Yb^{+}}$ frequency standard.Comment: 12 pages, 7 figures. (Fig 3 added since previous submission - now published

A novel method of supplying nutrients permits predictable shoot growth and root: shoot ratios of pre-transplant bedding plants

BACKGROUND AND AIMS: Growth of bedding plants, in small peat plugs, relies on nutrients in the irrigation solution. The object of the study was to find a way of modifying the nutrient supply so that good-quality seedlings can be grown rapidly and yet have the high root : shoot ratios essential for efficient transplanting. METHODS: A new procedure was devised in which the concentrations of nutrients in the irrigation solution were modified during growth according to changing plant demand, instead of maintaining the same concentrations throughout growth. The new procedure depends on published algorithms for the dependence of growth rate and optimal plant nutrient concentrations on shoot dry weight Ws (g m–2), and on measuring evapotranspiration rates and shoot dry weights at weekly intervals. Pansy, Viola tricola ‘Universal plus yellow’ and petunia, Petunia hybrida ‘Multiflora light salmon vein’ were grown in four independent experiments with the expected optimum nutrient concentration and fractions of the optimum. Root and shoot weights were measured during growth. KEY RESULTS: For each level of nutrient supply Ws increased with time (t) in days, according to the equation {Delta}Ws/{Delta}t=K2Ws/(100+Ws) in which the growth rate coefficient (K2) remained approximately constant throughout growth. The value of K2 for the optimum treatment was defined by incoming radiation and temperature. The value of K2 for each sub-optimum treatment relative to that for the optimum treatment was logarithmically related to the sub-optimal nutrient supply. Provided the aerial environment was optimal, Rsb/Ro{approx}Wo/Wsb where R is the root : shoot ratio, W is the shoot dry weight, and sb and o indicate sub-optimum and optimum nutrient supplies, respectively. Sub-optimal nutrient concentrations also depressed shoot growth without appreciably affecting root growth when the aerial environment was non-limiting. CONCLUSION: The new procedure can predict the effects of nutrient supply, incoming radiation and temperature on the time course of shoot growth and the root : shoot ratio for a range of growing conditions

Preliminary estimates of mass-loss rates, changes in stable isotope composition, and invertebrate colonisation of evergreen and deciduous leaves in a Waikato, New Zealand, stream.

Rates of mass loss are important in the choice of tree species used in riparian rehabilitation because leaves that break down fast should contribute to stream food-webs more rapidly than leaves that break down more slowly. To examine comparative mass-loss rates of some native evergreen and introduced deciduous trees in a New Zealand stream, fallen leaves were incubated in bags with 2 x 3 mm mesh openings. The native trees were mahoe (Melicytus ramiflorus), kahikatea (Dacrycarpus dacrydioides), silver beech (Nothofagus menziesii), rewarewa (Knightia excelsa), tawa (Beilschmiedia tawa), and the introduced trees were silver birch (Betula pendula) and alder (Alnus glutinosa). The leaf bags were left in the Mangaotama Stream for 28 days from mid April to mid May 1995 when mean water temperature was 14.5deg.C, giving a total of 406 degree days. Rates of mass loss followed the sequence: mahoe > silver birch > alder > kahikatea > silver beech > rewarewa > tawa. Mean mass-loss rate for mahoe, assuming a negative exponential model, was 0.0507 k day-1 (0.00350 k (degree day)-1), and for tawa was 0.0036 k day-1 (0.00025 k (degree day)-1). C:N ratio decreased on average from 45:1 to 35:1, and d15N increased between 0.7 and 3.0[[perthousand]] (1.8 +/- 0.41[[perthousand]], mean +/-1 standard error), excluding kahikatea. Changes in d13C were smaller and not consistent in direction. Biomass of invertebrates was greatest in bags that had lost 25-45% of their initial leaf biomass