2,065 research outputs found
An Initial Examination of Girls’ Cognitions of Their Relationally Aggressive Peers as a Function of Their Own Social Standing
The primary aim of the present study was to examine girls’ cognitions of their relationally aggressive peers as a function of their own relationally aggressive and sociometric status. Participants were 151 4th- and 5th-grade girls attending four public elementary schools. Findings suggest that relationally aggressive girls tend to display a relatively cautious and wary social cognitive style in relationally provocative social situations. For example, they view relationally aggressive behaviors as being relatively stable and unchanging, and they exhibit little trust for peers who exhibit a similar behavioral style. Results suggest that rejected girls may exhibit markedly different social processing styles depending upon whether they are also relationally aggressive themselves. For instance, rejected-relational aggressors appear to interpret others’ negative behaviors as being quite intentional. In contrast, rejected-nonrelational aggressors demonstrate relatively high levels of trust for peers who treat them poorly while also interpreting these peers’ behaviors as being relatively unintentional. Implications for designing multilevel interventions to combat relational aggressive problems are discussed
Energy Requirement of Control: Comments on Szilard's Engine and Maxwell's Demon
In mathematical physical analyses of Szilard's engine and Maxwell's demon, a
general assumption (explicit or implicit) is that one can neglect the energy
needed for relocating the piston in Szilard's engine and for driving the trap
door in Maxwell's demon. If this basic assumption is wrong, then the
conclusions of a vast literature on the implications of the Second Law of
Thermodynamics and of Landauer's erasure theorem are incorrect too. Our
analyses of the fundamental information physical aspects of various type of
control within Szilard's engine and Maxwell's demon indicate that the entropy
production due to the necessary generation of information yield much greater
energy dissipation than the energy Szilard's engine is able to produce even if
all sources of dissipation in the rest of these demons (due to measurement,
decision, memory, etc) are neglected.Comment: New, simpler and more fundamental approach utilizing the physical
meaning of control-information and the related entropy production. Criticism
of recent experiments adde
Correlation functions of eigenvalues of multi-matrix models, and the limit of a time dependent matrix
We consider the correlation functions of eigenvalues of a unidimensional
chain of large random hermitian matrices. An asymptotic expression of the
orthogonal polynomials allows to find new results for the correlations of
eigenvalues of different matrices of the chain. Eventually, we consider the
limit of the infinite chain of matrices, which can be interpreted as a time
dependent one-matrix model, and give the correlation functions of eigenvalues
at different times.Comment: Tex-Harvmac, 27 pages, submitted to Journ. Phys.
Arbitrarily slow, non-quasistatic, isothermal transformations
For an overdamped colloidal particle diffusing in a fluid in a controllable,
virtual potential, we show that arbitrarily slow transformations, produced by
smooth deformations of a double-well potential, need not be reversible. The
arbitrarily slow transformations do need to be fast compared to the barrier
crossing time, but that time can be extremely long. We consider two types of
cyclic, isothermal transformations of a double-well potential. Both start and
end in the same equilibrium state, and both use the same basic operations---but
in different order. By measuring the work for finite cycle times and
extrapolating to infinite times, we found that one transformation required no
work, while the other required a finite amount of work, no matter how slowly it
was carried out. The difference traces back to the observation that when time
is reversed, the two protocols have different outcomes, when carried out
arbitrarily slowly. A recently derived formula relating work production to the
relative entropy of forward and backward path probabilities predicts the
observed work average.Comment: 6 pages, 6 figure
The thermodynamic meaning of negative entropy
Landauer's erasure principle exposes an intrinsic relation between
thermodynamics and information theory: the erasure of information stored in a
system, S, requires an amount of work proportional to the entropy of that
system. This entropy, H(S|O), depends on the information that a given observer,
O, has about S, and the work necessary to erase a system may therefore vary for
different observers. Here, we consider a general setting where the information
held by the observer may be quantum-mechanical, and show that an amount of work
proportional to H(S|O) is still sufficient to erase S. Since the entropy H(S|O)
can now become negative, erasing a system can result in a net gain of work (and
a corresponding cooling of the environment).Comment: Added clarification on non-cyclic erasure and reversible computation
(Appendix E). For a new version of all technical proofs see the Supplementary
Information of the journal version (free access
Correspondence between geometrical and differential definitions of the sine and cosine functions and connection with kinematics
In classical physics, the familiar sine and cosine functions appear in two
forms: (1) geometrical, in the treatment of vectors such as forces and
velocities, and (2) differential, as solutions of oscillation and wave
equations. These two forms correspond to two different definitions of
trigonometric functions, one geometrical using right triangles and unit
circles, and the other employing differential equations. Although the two
definitions must be equivalent, this equivalence is not demonstrated in
textbooks. In this manuscript, the equivalence between the geometrical and the
differential definition is presented assuming no a priori knowledge of the
properties of sine and cosine functions. We start with the usual length
projections on the unit circle and use elementary geometry and elementary
calculus to arrive to harmonic differential equations. This more general and
abstract treatment not only reveals the equivalence of the two definitions but
also provides an instructive perspective on circular and harmonic motion as
studied in kinematics. This exercise can help develop an appreciation of
abstract thinking in physics.Comment: 6 pages including 1 figur
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