Different Sets Of Initial Conditions Research Articles

Case Study of a Population Bottleneck: Lions of the Ngorongoro Crater

Abstract: Lions in the Ngorongoro Crater, Tanzania, form a small and naturally isolated population. In 1962, the Crater lions suffered an epizootic that reduced the population to nine females and one male. An additional seven males apparently immigrated into the Crater in 1964–1965, but there has been no further immigration into the Crater in the past 25 years. By 1975, the population had recovered to its current level of 75‐125 animals. All members of the current Crater population are descended from only 15 founders, and over the years there has been considerable variance in the reproductive success of both sexes. The Crater was probably colonized by lions from the nearby Serengeti ecosystem and the contemporary Crater lion population shows a significant lack of genetic diversity compared to the much larger Serengeti population. The detailed reproductive history of the Crater population was incorporated into a series of stochastic computer simulations that generated distributions of expected allele frequencies under different sets of initial conditions. The simulations suggest that the Crater population may have passed through previous bottlenecks before 1962 but that the level of heterozygosity in the breeding population has been declining since the mid‐1970s, regardless of the population's genetic composition in the 1960s. High levels of inbreeding are correlated with increased levels of sperm abnormality in lions and there is evidence that the reproductive performance of the Crater lions has decreased as a result of decreasing heterozygosity.

New ion-optical devices utilizing oscillatory electric fields. II. Stability of ion motion in a two-dimensional hexapole field

Trajectories and stability diagrams have been calculated for oscillatory motions of charged particles in a two-dimensional hexapole electric field by numerical integration of the appropriate equations of motion. A charged particle in its dynamically stable state can execute a wide variety of non-linear periodic and non-periodic forced oscillations. Numerical computations of trajectories for charged particle motion were applied to determine a whole series of stability diagrams associated with different sets of initial conditions. The trajectories remain stable for an unexpectedly wide range of vlaues for the parameters, a 3 and q 3, which are equivalent to the parameters a and q, respectively, for the quadrupole geometry. However, the shape and size of the stability diagram depend on the initial conditions. The boundary of the stable and unstable regions in the ( a 3, q 3) plane is diffuse. Possible explanations for this anomalous effect are also given. This phenomenon is likely to occur in multipoles of any order, except for the quadrupole geometry. Hexapoles are suitable for confining and transporting low-energy ion beams for the purpose of ion spectroscopy and ion chemistry experiments. However, their mass resolution is probably too low for purpose of mass analysis.

An experiment on the initial conditions for a mesoscale forecast

AbstractA 6–h forecast starting at midday on a good sea breeze day has been repeated for seven different sets of initial conditions. The initial values for each field could either be given by an 8–h mesoscale forecast valid at 1200GMT or interpolated from a synoptic scale forecast valid at the same time. It was found that changing the initial temperature field had an important effect on the subsequent forecast, but the impact of changing the initial wind field was relatively small. Changing the initial surface pressures had no visible effect on any aspect of the subsequent forecast other than the forecast of surface pressure itself.

Perceptions of crowding and resource quality by early and more recent visitors

Abstract Previous literature suggests that a recreationist's current evaluations of a natural setting are influenced by the conditions that existed during the individual's initial exposure to the environment. Given the rapid growth in backcountry use and the ecological impairments associated with this use, it follows that each new generation of visitors will experience a different set of initial conditions. This paper explores the relationship between the year boaters made their first trip to the Apostle Islands National Lakeshore and their current evaluations of the resource. Results indicate that those who made their first trip prior to the area's national designation, when use levels were lower, perceived significantly greater levels of environmental damage to the islands and evaluated perceived increases in visitor numbers more negatively than the more recent boaters. The implications of these findings for managing the recreational experience are discussed.

On the Conditions Required for the r-PROCESS

The astrophysical site for the production of the r-process nuclei is not presently known. Part of the reason for this lack of knowledge is that the range of conditions which enable the production of these nuclei has not been accurately determined. Dynamic r-process nucleosynthesis calculations provide a means by which limits can be placed on the range of initial conditions that can produce r-process nuclei. Such calculations have several important time scales inherent to them. By requiring the time scales for neutron captures, ..beta..-decays, hydrodynamic expansion, and seed-nucleus production to be mutually compatible, it has been found that constraints can be placed on the initial temperatures, densities, neutron/proton ratios, and chemical compositions that can produce the r-process nuclei. The allowed ranges of these parameters are presented along with the results of r-process calculations performed for several different sets of initial conditions.

Quadrupolar relaxation parameters for a spin7/2system

Using pulsed nuclear magnetic resonance methods the central component magnetisation recovery curves have been measured for 59Co in a single crystal of K3Co(CN)6 at 295K. By using two different sets of initial conditions it has been possible to measure the parameters W1 and W2 which are related to the transition rates for Delta m=+or-1 and Delta m=+or-2 transitions. Previous relaxation measurements have suggested that an optical mode of the Co(CN)6 octahedron is responsible for spin-lattice relaxation in the temperature interval 100-300K. The present value of 0.2+or-0.06 obtained for the ratio W2/W1, together with theoretical calculations, suggests that a band of several overlapping modes, of wavenumber approximately 412 cm-1, is involved in relaxation.

An Initial State Perturbation Experiment with the GISS Model

Monthly mean global forecasts for January 1975 have been computed with the Goddard Institute for Space Studies model from four slightly different sets of initial conditions - a 'control' state and three random perturbations thereof - to simulate the effects of initial state uncertainty on forecast quality. Differences among the forecasts are examined in terms of energetics, synoptic patterns and forecast statistics. The 'noise level' of the model predictions is depicted on global maps of standard deviations of sea level pressures, 500 mb heights and 850 mb temperatures for the set of four forecasts. Initial small-scale random errors do not appear to result in any major degradation of the large-scale monthly mean forecast beyond that generated by the model itself, nor do they appear to represent the major source of large-scale forecast error.

Existence and uniqueness of solutions to uni-axial elastic-plastic wave interactions

This paper treats the propagation of stress waves through an elastic-plastic medium on the assumption of uni-axial displacement. With the further simplification to a piecewise linear stress-strain curve in terms of engineering stress and strain, wave equations are obtained for the longitudinal stress in both elastic and plastic regions, each with a distinct constant Lagrangian wave speed. The stress distribution in any region is then simply expressed in terms of two wave functions. In a general motion the medium will be divided into a sequence of alternating elastic and plastic regions separated by moving interfaces. A detailed analysis is presented for a single-interface wave interaction under general initial conditions, namely, continuous initial waves in the two directions in both elastic and plastic regions with a non-uniform yield stress in the elastic region. For different sets of initial conditions six distinct types of solution are shown to exist, and these are classified according to the direction and speed of the interface. In particular, two types involve interface speeds in excess of the elastic wave speed, not, to the authors’ knowledge, demonstrated in previous plastic wave treatments, noting the absence of possible shock formation for the present linearized stress-strain laws. Further, it is shown that stress discontinuities cannot form at the interface (or elsewhere) from initially continuous stress profiles. Associated with the different types of solution are four distinct sets of interface conditions so that there is no common form for the interaction solution. Each of the six types of solution is shown to be consistent with the elastic-plastic model only under a restricted set of initial conditions, and these sets are found to be mutually exclusive for the six types, thus deciding a unique choice for the type of single-interface solution. The six sets, however, are not inclusive of all possible initial conditions, indicating a need for multi-interface solutions in the exceptional situations. Multi-interface solutions may be possible even in the non-exceptional situations, but this possibility is felt to be unlikely. Finally, it can be noted that the analysis dealing with validity of solution is, for most cases, only local in that it applies in some small neighbourhood of the current point on the interface path, being based on expansions about this point. The results of such local analysis will therefore extend to the case of non-uniform wave speeds arising from non-linear stress-strain laws, provided that no shock is formed in the neighbourhood, but a global solution can no longer be expressed simply in terms of wave functions.

低緯度偏東風擾乱の発達•減衰に関する数値実験

A numerical experiment has been performed on a tropical disturbance embedded in easterlies to test the dependency of the vertical coupling on the value of Richardson number in tropics. By a 2-layer primitive equation model in sigma system of coordinates integrations have been performed for a period of 24 hours with two different sets of initial conditions in which the three dimensional structure of the initial easterly pattern is specified through pre-specified wind shear and different values of the Richardson number. The order of magnitude of vertical velocities, the time rate of change of kinetic energy and the phase speed of the disturbances is discussed for both the cases. The preliminary results indicate that, even the tropical motions have appreciable degree of vertical coupling and baroclinic nature in the cases of low Richardson number. The results seem to be of special interest in context of the fact that even the mean monthly values of static stability during summer are found to be very small and even negative in the middle and lower troposphere in the tropics.

The evaporation of raindrops

AbstractThe evaporation of a single drop of water as it falls through an atmosphere in which the lapse rate is 6·5°C/km and the surface temperature either 15°C or 41°C is examined. By making certain justified assumptions, it is shown that the change in surface area of a large drop (i.e., with radius exceeding 0·15 mm) as it falls from height z1 to z2 is proportional to (1 — f)1·13 exp (— lz) where 100 f is the relative humidity and l is a constant. Values are given for the constant of proportionality and for l. If the drop has a radius less than 0·15 mm the change in volume of the drop is proportional to (1 — f)1·062 exp (— lz).These results are then used to assess the effect of evaporation on the size and size distribution of raindrops falling through a constant atmosphere. It is shown that if the size distribution of raindrops at some initial height is given by 1 — F = exp [ — (2a/b)n] where F is the fraction of liquid water comprised by drops with radius less than a, and b and n are constants, then evaporation will lead to a change in the values of b and n but will not affect the general validity of the formula. As the rain falls through the non‐saturated air the distributive index n tends to a value between 3·5 and 4·0 whether it was greater or less than such a value initially. If the initial value of n is less than 3·0 the scale diameter b increases as a result of evaporation. If the initial value of n exceeds about 3·5 the scale diameter decreases. The effect of evaporation upon the radar response from falling rain is also examined.In the last part of the paper the effect of the evaporation of rain into air which is initially unsaturated is considered. It is shown that the air temperature tends to a steady value and the relative humidity to 100 per cent. The excess of temperature above the steady‐state value and the deficit of relative humidity below 100 per cent decrease exponentially to zero with time. The depression of the steady‐state temperature below the initial temperature is a function only of the initial temperature and relative humidity and a table is given showing the value of the steady‐state temperature for nine different sets of initial conditions. The rate at which the final state is approached depends however only upon the rate of rainfall and a formula is derived for this dependence.