42,616 research outputs found
THE DYNAMIC EFFECTS OF AGRICULTURAL SUBSIDY PROGRAMS IN THE UNITED STATES
This paper analyzes the dynamic effects of the acreage restrictions and land diversion requirements that are characteristic of the farm subsidy programs in the United States. The subsidy payments a farmer receives are based upon historical base acreage, and it 1s sometimes optimal for a farmer not to participate in a pr9gr~m in order to increase base acreage in anticipation of higher future subsidies. This paper determines the farmer's optimal policy as the solution to a deterministic dynamic program. It shows that farmers with low base acreage typically opt out of these programs, whereas those with high base acreage participate in them. The paper concludes with an examination of aggregate data from the programs involving barley, corn, cotton, oats, rice, sorghum, and wheat during 1987. It shows that these programs actually increase the aggregate output of each of these crops and that they represent an annual deadweight loss of more than $3 billion.Crop Production/Industries, Land Economics/Use,
THE DYNAMIC EFFECTS OF AGRICULTURAL SUBSIDIES IN THE UNITED STATES
This article analyzes the dynamics effects of the farm subsidies in the United States. The subsidies a farmer receives are based upon historical plantings, also called based acreage. It is sometimes optimal for a farmer temporarily not to participate in a program in order to increase future subsidies. The farmerÂ’'s optimal policy is the solution to a deterministic dynamic program. Farmers with low base acreage opt out of these programs, whereas those with high base acreage participate in them. The article examines aggregate data involving corn, cotton, rice, and wheat during 1987. It shows that these programs increase the output of each of these crops and represent an annual deadweight loss of more than $2 billion.Agricultural and Food Policy,
A Simple Kinetic Model Describes the Processivity of Myosin-V
Myosin-V is a motor protein responsible for organelle and vesicle transport
in cells. Recent single-molecule experiments have shown that it is an efficient
processive motor that walks along actin filaments taking steps of mean size
close to 36 nm. A theoretical study of myosin-V motility is presented following
an approach used successfully to analyze the dynamics of conventional kinesin
but also taking some account of step-size variations. Much of the present
experimental data for myosin-V can be well described by a two-state chemical
kinetic model with three load-dependent rates. In addition, the analysis
predicts the variation of the mean velocity and of the randomness -- a
quantitative measure of the stochastic deviations from uniform, constant-speed
motion -- with ATP concentration under both resisting and assisting loads, and
indicates a {\it sub}step of size 13-14 nm (from the ATP-binding
site) that appears to accord with independent observations.Comment: 20 pages, 7 figures, to be published in Biophys. J. in 200
Liquid-gas phase transition in finite nuclei
In a finite temperature Thomas-Fermi framework, we calculate density
distributions of hot nuclei enclosed in a freeze-out volume of few times the
normal nuclear volume and then construct the caloric curve, with and without
inclusion of radial collective flow. In both cases, the calculated specific
heats show a peaked structure signalling a liquid-gas phase transition.
Without flow, the caloric curve indicates a continuous phase transition whereas
with inclusion of flow, the transition is very sharp. In the latter case, the
nucleus undergoes a shape change to a bubble from a diffuse sphere at the
transition temperature.Comment: Proc. of 6th Int. Conf. on N-N Collisions (Gatlinburg); Nuclear
Physics A (in press
A coverage independent method to analyze large scale anisotropies
The arrival time distribution of cosmic ray events is well suited to extract
information regarding sky anisotropies. For an experiment with nearly constant
exposure, the frequency resolution one can achieve is given by the inverse of
the time during which the data was recorded. For larger than one
calendar year the resolution becomes sufficient to resolve the sidereal and
diurnal frequencies. Using a Fourier expansion on a modified time parameter, we
show in this note that one can accurately extract sidereal modulations without
knowledge of the experimental coverage. This procedure also gives the full
frequency pattern of the event sample under studies which contains important
information about possible systematics entering in the sidereal analysis. We
also show how this method allows to correct for those systematics. Finally, we
show that a two dimensional analysis, in the form of the spherical harmonic
() decomposition, can be performed under the same conditions for all
.Comment: 8 pages, 6 figure
The reward value of infant facial cuteness tracks within-subject changes in women’s salivary testosterone
“Baby schema” refers to infant characteristics, such as facial cues, that
positively influence cuteness perceptions and trigger caregiving and protective
behaviors in adults. Current models of hormonal regulation of parenting
behaviors address how hormones may modulate protective behaviors and
nurturance, but not how hormones may modulate responses to infant
cuteness. To explore this issue, we investigated possible relationships
between the reward value of infant facial cuteness and within-woman changes
in testosterone, estradiol, and progesterone levels. Multilevel modeling of
these data showed that infant cuteness was more rewarding when women’s
salivary testosterone levels were high. Moreover, this within-woman effect of
testosterone was independent of the possible effects of estradiol and
progesterone and was not simply a consequence of changes in women’s
cuteness perceptions. These results suggest that testosterone may modulate
differential responses to infant facial cuteness, potentially revealing a new
route through which testosterone shapes selective allocation of parental
resources
Sliding Objects with Random Friction
We study the motion of elastic networks driven over a random substrate. Our
model which includes local friction forces leads to complex dynamical behavior.
We find a transition to a sliding state which belongs to a new universality
class. The phase diagram comprises of a pinned state, a stick-slip motion
phase, and a free motion phase.Comment: proceedings of Conference "Percolation and Disordered Systems:
*Theory and Applications*", Giessen (Germany) 1998, see
http://ory.ph.biu.ac.il/PERCOLATION98/ , 12 pages, 5 figures, in press, will
be published in Physica
Tempering simulations in the four dimensional +-J Ising spin glass in a magnetic field
We study the four dimensional (4D) Ising spin glass in a magnetic
field by using the simulated tempering method recently introduced by Marinari
and Parisi. We compute numerically the first four moments of the order
parameter probability distribution . We find a finite cusp in the
spin-glass susceptibility and strong tendency to paramagnetic ordering at low
temperatures. Assuming a well defined transition we are able to bound its
critical temperature.Comment: 6 Pages including 5 figures, Revte
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