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The opportunity cost and endowment effects of resources and capabilities on stages of entrepreneurship
In this paper, the start-up process is split conceptually into four entrepreneurial stages considering entrepreneurship, intending to start a new business in the next three years, nascent entrepreneurship and newly established business. We investigate the determinants of the start-up process using a multinomial logit model which allows the effects of resources and capabilities to vary across the different entrepreneurial stages. We employ a pooled Global Entrepreneurship Monitor database for the years 2006 to 2009, containing 8,269 usable observations of the East Midlands region in the United Kingdom, controlling for the local environmental effects. Our results show that the combinative role of human capital, experience and local context varies along the different stages of the entrepreneurial process. In the early stages the (negative) opportunity cost effect of resources dominates tends to reverse in advanced stages, where the (positive) endowment effect becomes stronger
Resource endowment and opportunity cost effects along the stages of entrepreneurship
In this paper, the start-up process is split conceptually into four stages: considering entrepreneurship, intending to start a new business in the next three years, nascent entrepreneurship, and owning-managing a newly established business. We investigate the determinants of all of these jointly, using a multinomial logit model; it allows for the effects of resources and capabilities to vary across these stages. We employ the Global Entrepreneurship Monitor database for the years 2006 to 2009, containing 8,269 usable observations from respondents drawn from the Lower Layer Super Output Areas in the East Midlands (UK) so that individual observations are linked to space. Our results show that the role of education, experience, and availability of 'entrepreneurial capital' in the local neighbourhood varies along the different stages of the entrepreneurial process. In the early stages the negative (opportunity cost) effect of resources endowment dominates, yet it tends to reverse in the advanced stages, where the positive effect of resources becomes stronger
Lyapunov exponents as a dynamical indicator of a phase transition
We study analytically the behavior of the largest Lyapunov exponent
for a one-dimensional chain of coupled nonlinear oscillators, by
combining the transfer integral method and a Riemannian geometry approach. We
apply the results to a simple model, proposed for the DNA denaturation, which
emphasizes a first order-like or second order phase transition depending on the
ratio of two length scales: this is an excellent model to characterize
as a dynamical indicator close to a phase transition.Comment: 8 Pages, 3 Figure
Bubbles, clusters and denaturation in genomic DNA: modeling, parametrization, efficient computation
The paper uses mesoscopic, non-linear lattice dynamics based
(Peyrard-Bishop-Dauxois, PBD) modeling to describe thermal properties of DNA
below and near the denaturation temperature. Computationally efficient notation
is introduced for the relevant statistical mechanics. Computed melting profiles
of long and short heterogeneous sequences are presented, using a recently
introduced reparametrization of the PBD model, and critically discussed. The
statistics of extended open bubbles and bound clusters is formulated and
results are presented for selected examples.Comment: to appear in a special issue of the Journal of Nonlinear Mathematical
Physics (ed. G. Gaeta
Effect of defects on thermal denaturation of DNA Oligomers
The effect of defects on the melting profile of short heterogeneous DNA
chains are calculated using the Peyrard-Bishop Hamiltonian. The on-site
potential on a defect site is represented by a potential which has only the
short-range repulsion and the flat part without well of the Morse potential.
The stacking energy between the two neigbouring pairs involving a defect site
is also modified. The results are found to be in good agreement with the
experiments.Comment: 11 pages including 5 postscript figure; To be appear in Phys. Rev.
Thermodynamic instabilities in one dimensional particle lattices: a finite-size scaling approach
One-dimensional thermodynamic instabilities are phase transitions not
prohibited by Landau's argument, because the energy of the domain wall (DW)
which separates the two phases is infinite. Whether they actually occur in a
given system of particles must be demonstrated on a case-by-case basis by
examining the (non-) analyticity properties of the corresponding transfer
integral (TI) equation. The present note deals with the generic Peyrard-Bishop
model of DNA denaturation. In the absence of exact statements about the
spectrum of the singular TI equation, I use Gauss-Hermite quadratures to
achieve a single-parameter-controlled approach to rounding effects; this allows
me to employ finite-size scaling concepts in order to demonstrate that a phase
transition occurs and to derive the critical exponents.Comment: 5 pages, 6 figures, subm. to Phys. Rev.
Experimental and theoretical studies of sequence effects on the fluctuation and melting of short DNA molecules
Understanding the melting of short DNA sequences probes DNA at the scale of
the genetic code and raises questions which are very different from those posed
by very long sequences, which have been extensively studied. We investigate
this problem by combining experiments and theory. A new experimental method
allows us to make a mapping of the opening of the guanines along the sequence
as a function of temperature. The results indicate that non-local effects may
be important in DNA because an AT-rich region is able to influence the opening
of a base pair which is about 10 base pairs away. An earlier mesoscopic model
of DNA is modified to correctly describe the time scales associated to the
opening of individual base pairs well below melting, and to properly take into
account the sequence. Using this model to analyze some characteristic sequences
for which detailed experimental data on the melting is available [Montrichok et
al. 2003 Europhys. Lett. {\bf 62} 452], we show that we have to introduce
non-local effects of AT-rich regions to get acceptable results. This brings a
second indication that the influence of these highly fluctuating regions of DNA
on their neighborhood can extend to some distance.Comment: To be published in J. Phys. Condensed Matte
Roles of stiffness and excluded volume in DNA denaturation
The nature and the universal properties of DNA thermal denaturation are
investigated by Monte Carlo simulations. For suitable lattice models we
determine the exponent c describing the decay of the probability distribution
of denaturated loops of length l, . If excluded volume effects
are fully taken into account, c= 2.10(4) is consistent with a first order
transition. The stiffness of the double stranded chain has the effect of
sharpening the transition, if it is continuous, but not of changing its order
and the value of the exponent c, which is also robust with respect to inclusion
of specific base-pair sequence heterogeneities.Comment: RevTeX 4 Pages and 4 PostScript figures included. Final version as
publishe
Controlling the energy flow in nonlinear lattices: a model for a thermal rectifier
We address the problem of heat conduction in 1-D nonlinear chains; we show
that, acting on the parameter which controls the strength of the on site
potential inside a segment of the chain, we induce a transition from conducting
to insulating behavior in the whole system. Quite remarkably, the same
transition can be observed by increasing the temperatures of the thermal baths
at both ends of the chain by the same amount. The control of heat conduction by
nonlinearity opens the possibility to propose new devices such as a thermal
rectifier.Comment: 4 pages with figures included. Phys. Rev. Lett., to be published
(Ref. [10] corrected
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