Turbulence forecasting

In order to forecast turbulence, one needs to have an understanding of the cause of turbulence. Therefore, an attempt is made to show the atmospheric structure that often results when aircraft encounter moderate or greater turbulence. The analysis is based on thousands of hours of observations of flights over the past 39 years of aviation meteorology

Airline meteorological requirements

A brief review of airline meteorological/flight planning is presented. The effects of variations in meteorological parameters upon flight and operational costs are reviewed. Flight path planning through the use of meteorological information is briefly discussed

Fluctuation-dissipation ratios in the dynamics of self-assembly

We consider two seemingly very different self-assembly processes: formation of viral capsids, and crystallization of sticky discs. At low temperatures, assembly is ineffective, since there are many metastable disordered states, which are a source of kinetic frustration. We use fluctuation-dissipation ratios to extract information about the degree of this frustration. We show that our analysis is a useful indicator of the long term fate of the system, based on the early stages of assembly.Comment: 8 pages, 6 figure

The stochastic dynamics of nanoscale mechanical oscillators immersed in a viscous fluid

The stochastic response of nanoscale oscillators of arbitrary geometry immersed in a viscous fluid is studied. Using the fluctuation-dissipation theorem it is shown that deterministic calculations of the governing fluid and solid equations can be used in a straightforward manner to directly calculate the stochastic response that would be measured in experiment. We use this approach to investigate the fluid coupled motion of single and multiple cantilevers with experimentally motivated geometries.Comment: 5 pages, 5 figure

Unveiling Sources of Heating in the Vicinity of the Orion BN/KL Hot Core as Traced by Highly Excited Inversion Transitions of Ammonia

Using the Expanded Very Large Array, we have mapped the vicinity of the Orion BN/KL Hot Core with sub-arcsecond angular resolution in seven metastable inversion transitions of ammonia: (J,K)=(6,6) to (12,12). This emission comes from levels up to 1500 K above the ground state, enabling identification of source(s) responsible for heating the region. We used this multi-transition dataset to produce images of the rotational/kinetic temperature and the column density of ammonia for ortho and para species separately and on a position-by-position basis. We find rotational temperature and column density in the range 160-490 K and (1-4)x10^17 cm^-2, respectively. Our spatially-resolved images show that the highest (column) density and hottest gas is found in a northeast-southwest elongated ridge to the southeast of Source I. We have also measured the ortho-para ratio of ammonia, estimated to vary in the range 0.9-1.6. Enhancement of ortho with respect to para and the offset of hot ammonia emission peaks from known (proto)stellar sources provide evidence that the ammonia molecules have been released from dust grains into the gas-phase through the passage of shocks and not by stellar radiation. We propose that the combined effect of Source I's proper motion and its low-velocity outflow impinging on a pre-existing dense medium is responsible for the excitation of ammonia and the Orion Hot Core. Finally, we found for the first time evidence of a slow (5 km/s) and compact (1000 AU) outflow towards IRc7.Comment: To appear in Astrophysical Journal Letters Special Issue on the EVLA. 8 pages, 4 figure

Two-stage coarsening mechanism in a kinetically constrained model of an attractive colloid

We study an attractive version of the East model using the real-space renormalization group (RG) introduced by Stella et al. The former is a kinetically constrained model with an Ising-like interaction between excitations, and shows striking agreement with the phenomonology of attractive colloidal systems. We find that the RG predicts two nonuniversal dynamic exponents, which suggests that in the out-of-equilibrium regime the model coarsens via a two-stage mechanism. We explain this mechanism physically, and verify this prediction numerically. In addition, we find that the characteristic relaxation time of the model is a non-monotonic function of attraction strength, again in agreement with numerical results.Comment: 10 page

Finite-temperature critical point of a glass transition

We generalize the simplest kinetically constrained model of a glass-forming liquid by softening kinetic constraints, allowing them to be violated with a small finite rate. We demonstrate that this model supports a first-order dynamical (space-time) phase transition, similar to those observed with hard constraints. In addition, we find that the first-order phase boundary in this softened model ends in a finite-temperature dynamical critical point, which we expect to be present in natural systems. We discuss links between this critical point and quantum phase transitions, showing that dynamical phase transitions in $d$ dimensions map to quantum transitions in the same dimension, and hence to classical thermodynamic phase transitions in $d+1$ dimensions. We make these links explicit through exact mappings between master operators, transfer matrices, and Hamiltonians for quantum spin chains.Comment: 10 pages, 5 figure

Ecological Effects of Forest Canopy Disturbance on the Understory Plant, American Ginseng (Panax quinquefolius L.)

Historical accounts suggest that American ginseng was once far more abundant than it is today, and extensive changes in forest canopy structure and ginseng habitat caused by clearcut timber harvest occurred coincidentally to the precipitous decline in abundance. The presence of natural American ginseng populations after widespread clearcuts suggests that ginseng can survive under sparse canopies, and the presence of ginseng in the second growth forests common today suggest that ginseng can survive under dense canopies. However, performance may not be optimal at either end of the disturbance spectrum, and the net effect of direct and indirect anthropogenic canopy disturbances on ginseng has been unknown. The present suite of studies addresses the question how does American ginseng respond to changes in forest dynamics that result from changes in canopy disturbance regimes caused by humans? I first determined how different types of disturbances affected canopy openness on the scale of a small herbaceous plant. In Chapter 2, I found that canopy openness after timber harvest was greatest at the most intensely harvested site, and that subsequent understory canopy closure differed from that occurring in higher strata. Relative canopy closure was greatest in areas with high densities of shade-intolerant weedy and invasive species. The purpose of Chapter 3 was to determine if canopy disturbances via patch cut timber harvest were physiological stressors to American ginseng, or whether increases in light following timber harvest benefited carbon assimilation and growth. I found that ginseng is a \u27slow opportunist;\u27 photosynthesis and growth increased following canopy disturbance, but stimulation lagged behind changes in canopy structure. Although ginseng benefited from a patch cut timber harvest, it was unclear whether varying intensities of timber harvest deferentially affected the survival, growth, and reproduction of ginseng. In Chapter 4, I found that survival generally decreased following timber harvest, and was lowest at the most intensely harvested site. However, growth and seed production increased in individuals that survived. In order to provide an integrated assessment of survival, growth, and fertility following canopy disturbance, I quantified the demographic response of five populations of American ginseng to natural disturbances whose regimes are being altered by climate change. In Chapter 5, I found that population growth rate increased after natural canopy disturbances, and did so even at the current frequency of disturbance within American ginseng populations. Additionally, canopy disturbances produced sustained increases in population size via influxes of seeds to the seed bank. These studies provide clear evidence that American ginseng is surprisingly resilient in the face of rapid environmental shifts. Further, American ginseng, and perhaps similar herbs, benefit from moderate intensity, anthropogenic canopy disturbances whose frequencies and spatial extents are predicted to increase

A Proposed Program for Organization and Administration of Guidance Services in a Small Elementary School

The incidence of small schools that do not have organized programs and services that are found in the larger schools is fairly frequent (25). If administrators of some of these schools believe that such programs of service are not needed, this is a false assumption (17). Other administrators may believe that they cannot offer these services because of the lack of special personnel to head or direct these services (17). In such cases, it is possible to prove that classroom teachers can and would perform most of these duties within an organized program. But, because of the lack of organization, the teachers in schools without such programs are deprived of activities and services needed. These children are not receiving the education that should be guaranteed them—an education they should have, and the teachers of these children are unable to be as effective as they otherwise could be. This is not to say that small schools should mimic the larger schools, rather, they should try to be more effective with what they have. Thus, the purpose of establishing this program was, (1) to point out the need of an organized guidance service program in small elementary schools, (2) to identify specific services and activities, and (3) to show that these services, and even others, may be offered by small schools without access to specially trained personnel. It is not the purpose here to disparage the need for personnel with special guidance training, but rather to indicate that which can be accomplished without such personnel