2,104 research outputs found
Influence of corruption on economic growth rate and foreign investments
In order to investigate whether government regulations against corruption can
affect the economic growth of a country, we analyze the dependence between
Gross Domestic Product (GDP) per capita growth rates and changes in the
Corruption Perceptions Index (CPI). For the period 1999-2004 on average for all
countries in the world, we find that an increase of CPI by one unit leads to an
increase of the annual GDP per capita by 1.7 %. By regressing only European
transition countries, we find that CPI = 1 generates increase of the
annual GDP per capita by 2.4 %. We also analyze the relation between foreign
direct investments received by different countries and CPI, and we find a
statistically significant power-law functional dependence between foreign
direct investment per capita and the country corruption level measured by the
CPI. We introduce a new measure to quantify the relative corruption between
countries based on their respective wealth as measured by GDP per capita.Comment: 8 pages, 3 figures, elsart styl
Statistics of the dissipated energy in driven single-electron transitions
We analyze the distribution of heat generated in driven single-electron
transitions and discuss the related non-equilibrium work theorems. In the
adiabatic limit, the heat distribution is shown to become Gaussian, with the
heat noise that, in spite of thermal fluctuations, vanishes together with the
average dissipated energy. We show that the transitions satisfy Jarzynski
equality for arbitrary drive and calculate the probability of the negative heat
values. We also derive a general condition on the heat distribution that
generalizes the Bochkov-Kuzovlev equality and connects it to the Jarzynski
equality.Comment: 5 pages, 2 figure
Discrete Symmetries and Generalized Fields of Dyons
We have studied the different symmetric properties of the generalized
Maxwell's - Dirac equation along with their quantum properties. Applying the
parity (\mathcal{P}), time reversal (\mathcal{T}), charge conjugation
(\mathcal{C}) and their combined effect like parity time reversal
(\mathcal{PT}), charge conjugation and parity (\mathcal{CP}) and \mathcal{CP}T
transformations to varius equations of generalized fields of dyons, it is shown
that the corresponding dynamical quantities and equations of dyons are
invariant under these discrete symmetries.
Abstract Key words- parity, time reversal, charge-conjugation, dyons
Abstract PACS No.- 14.80 Hv
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
Identifying Abnormal Connectivity in Patients Using Dynamic Causal Modeling of fMRI Responses
Functional imaging studies of brain damaged patients offer a unique opportunity to understand how sensorimotor and cognitive tasks can be carried out when parts of the neural system that support normal performance are no longer available. In addition to knowing which regions a patient activates, we also need to know how these regions interact with one another, and how these inter-regional interactions deviate from normal. Dynamic causal modeling (DCM) offers the opportunity to assess task-dependent interactions within a set of regions. Here we review its use in patients when the question of interest concerns the characterization of abnormal connectivity for a given pathology. We describe the currently available implementations of DCM for fMRI responses, varying from the deterministic bilinear models with one-state equation to the stochastic non-linear models with two-state equations. We also highlight the importance of the new Bayesian model selection and averaging tools that allow different plausible models to be compared at the single subject and group level. These procedures allow inferences to be made at different levels of model selection, from features (model families) to connectivity parameters. Following a critical review of previous DCM studies that investigated abnormal connectivity we propose a systematic procedure that will ensure more flexibility and efficiency when using DCM in patients. Finally, some practical and methodological issues crucial for interpreting or generalizing DCM findings in patients are discussed
Sand as Maxwell's demon
We consider a dilute gas of granular material inside a box, kept in a
stationary state by shaking. A wall separates the box into two identical
compartments, save for a small hole at some finite height . As the gas is
cooled, a second order phase transition occurs, in which the particles
preferentially occupy one side of the box. We develop a quantitative theory of
this clustering phenomenon and find good agreement with numerical simulations
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.
How does iReadMore therapy change the reading network of patients with central alexia?
Central alexia (CA) is an acquired reading disorder co-occurring with a generalised language deficit (aphasia). The roles of perilesional and ipsilesional tissue in recovery from post-stroke aphasia are unclear. We investigated the impact of reading training (using iReadMore, a therapy app) on the connections within and between the right and left hemisphere of the reading network of patients with CA. In patients with pure alexia, iReadMore increased feedback from left inferior frontal region (IFG) to the left occipital (OCC) region. We aimed to identify if iReadMore therapy was effective through a similar mechanism in CA patients.Participants with chronic post-stroke CA (n=23) completed 35 hours of iReadMore training over four weeks. Reading accuracy for trained and untrained words was assessed before and after therapy. The neural response to reading trained and untrained words in the left and right OCC, ventral occipitotemporal (vOT) and IFG was examined using event-related magnetoencephalography.The training-related modulation in effective connectivity between regions was modelled at the group level with Dynamic Causal Modelling.iReadMore training improved participants' reading accuracy by an average of 8.4% (range: -2.77 to 31.66) while accuracy for untrained words was stable. Training increased regional sensitivity in bilateral frontal and occipital regions, and strengthened feedforward connections within the left hemisphere. Our data suggests that iReadMore training in these patients modulates lower-order visual representations, as opposed to higher-order, more abstract ones, in order to improve word reading accuracy.SIGNIFICANCE STATEMENTThis is the first study to conduct a network-level analyses of therapy effects in participants with post-stroke central alexia. When patients trained with iReadMore (a multimodal, behavioural, mass practice, computer-based therapy), reading accuracy improved by an average 8.4% on trained items. A network analysis of the magnetoencephalography data associated with this improvement revealed an increase in regional sensitivity in bilateral frontal and occipital regions and strengthening of feedforward connections within the left hemisphere. This indicates that in CA patients iReadMore engages lower-order, intact resources within the left hemisphere (posterior to their lesion locations) to improve word reading. This provides a foundation for future research to investigate reading network modulation in different CA subtypes, or for sentence level therapy
Heat Transfer Operators Associated with Quantum Operations
Any quantum operation applied on a physical system is performed as a unitary
transformation on a larger extended system. If the extension used is a heat
bath in thermal equilibrium, the concomitant change in the state of the bath
necessarily implies a heat exchange with it. The dependence of the average heat
transferred to the bath on the initial state of the system can then be found
from the expectation value of a hermitian operator, which is named as the heat
transfer operator (HTO). The purpose of this article is the investigation of
the relation between the HTOs and the associated quantum operations. Since, any
given quantum operation on a system can be realized by different baths and
unitaries, many different HTOs are possible for each quantum operation. On the
other hand, there are also strong restrictions on the HTOs which arise from the
unitarity of the transformations. The most important of these is the Landauer
erasure principle. This article is concerned with the question of finding a
complete set of restrictions on the HTOs that are associated with a given
quantum operation. An answer to this question has been found only for a subset
of quantum operations. For erasure operations, these characterizations are
equivalent to the generalized Landauer erasure principle. For the case of
generic quantum operations however, it appears that the HTOs obey further
restrictions which cannot be obtained from the entropic restrictions of the
generalized Landauer erasure principle.Comment: A significant revision is made; 33 pages with 2 figure
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