Reid and Condillac on Sensation and Perception: A Thought Experiment on Sensory Deprivation

In order to illustrate the difference between sensation and perception, Reid imagines a blind man that by ‘some strange distemper’ has lost all his notions of external objects, but has retained the power of sensation and reasoning. Reid argues that since sensations do not resemble external objects, the blind man could not possibly infer from them any notion of primary qualities. Condillac proposed a similar thought experiment in the Treatise on Sensations. I argue that Condillac can reach a conclusion opposite to that of Reid only by assuming that some particular collections of sensations do indeed resemble the qualities of external objects. Reid had considered a similar case in a manuscript, but he again notices that such complex collections sensations do not resemble the qualities of external objects

Competing Glauber and Kawasaki Dynamics

Using a quantum formulation of the master equation we study a kinetic Ising model with competing stochastic processes: the Glauber dynamics with probability $p$ and the Kawasaki dynamics with probability $1 - p$. Introducing explicitely the coupling to a heat bath and the mutual static interaction of the spins the model can be traced back exactly to a Ginzburg Landau functional when the interaction is of long range order. The dependence of the correlation length on the temperature and on the probability $p$ is calculated. In case that the spins are subject to flip processes the correlation length disappears for each finite temperature. In the exchange dominated case the system is strongly correlated for each temperature.Comment: 9 pages, Revte

The Chandra view of the 3C/FRI sample of low luminosity radio-galaxies

We present results from Chandra observations of the 3C/FRI sample of low luminosity radio-galaxies. We detected a power-law nuclear component in 12 objects out of the 18 with available data. In 4 galaxies we detected nuclear X-ray absorption at a level of about N_H= (0.2-6)e22 cm-2. X-ray absorbed sources are associated with the presence of highly inclined dusty disks (or dust filaments projected onto the nuclei) seen in the HST images. This suggests the existence of a flattened X-ray absorber, but of much lower optical depth than in classical obscuring tori. We thus have an un-obstructed view toward most FR~I nuclei while absorption plays only a marginal role in the remaining objects. Three pieces of evidence support an interpretation for a jet origin for the X-ray cores: i) the presence of strong correlations between the nuclear luminosities in the radio, optical and X-ray bands, extending over 4 orders of magnitude and with a much smaller dispersion (about 0.3 dex) when compared to similar trends found for other classes of AGNs, pointing to a common origin for the emission in the three bands; ii) the close similarity of the broad-band spectral indices with the sub-class of BL Lac objects sharing the same range of extended radio-luminosity, in accord with the FRI/BL Lacs unified model; iii) the presence of a common luminosity evolution of spectral indices in both FRI and BL Lacs. The low luminosities of the X-ray nuclei, regardless of their origin, strengthens the interpretation of low efficiency accretion in low luminosity radio-galaxies.Comment: Accepted in A&

Phenomenological Renormalization Group Methods

Some renormalization group approaches have been proposed during the last few years which are close in spirit to the Nightingale phenomenological procedure. In essence, by exploiting the finite size scaling hypothesis, the approximate critical behavior of the model on infinite lattice is obtained through the exact computation of some thermal quantities of the model on finite clusters. In this work some of these methods are reviewed, namely the mean field renormalization group, the effective field renormalization group and the finite size scaling renormalization group procedures. Although special emphasis is given to the mean field renormalization group (since it has been, up to now, much more applied an extended to study a wide variety of different systems) a discussion of their potentialities and interrelations to other methods is also addressed.Comment: Review Articl

Positional changes of pericentromeric heterochromatin and nucleoli in postmitotic Purkinje cells during murine cerebellum development

Previous studies revealed changes of pericentromeric heterochromatin arrangements in postmitotic Purkinje cells (PCs) during postnatal development in the mouse cerebellum (Manuelidis, 1985; Martou and De Boni, 2000). Here, we performed vibratome sections of mouse cerebellum (vermis) at P0 (day of birth), at various stages of the postnatal development (P2-P21), as well as in very young (P28) and 17-months-old adults. FISH was carried out on these sections with major mouse satellite DNA in combination with immunostaining of the nucleolar protein B23 (nucleophosmin). Laser confocal microscopy, 3D reconstructions and quantitative image analysis were employed to describe changes in the number and topology of chromocenters and nucleoli. At all stages of postnatal PC development heterochromatin clusters were typically associated either with nucleoli or with the nuclear periphery, while non-associated clusters were rare (<1% at P0 to P21 and about 3% in adult stages). At P0, about 2-4 nucleoli and 7-8 pericentromeric heterochromatin clusters were variably located within PC nuclei. The relative volume of heterochromatin clusters associated with the nucleoli (about 50%) was roughly equal to the volume of clusters associated with the nuclear periphery. Positional changes of both nucleoli and centromeres towards the nuclear center occurred between P0 and P6. At P6 the average number of chromocenters per PC nucleus had decreased to about five. In agreement with previous studies, one or occasionally two nucleoli were noted at the nuclear center surrounded by major perinucleolar heterochromatin clusters. The relative volume of these perinucleolar clusters increased to about 84%, while the volume of clusters in the nuclear periphery decreased to about 15%. At subsequent postnatal stages, the arrangement of most pericentromeric heterochromatin around a central nucleolus was maintained. In adult animals, however, we observed a partial redistribution of heterochromatin towards the nuclear periphery. The average total number of pericentromeric heterochromatin signals increased again to about ten. The volume of heterochromatin associated with the nuclear periphery roughly doubled (30%), while the volume of the perinucleolar heterochromatin decreased correspondingly. Copyright (C) 2004 S. Karger AG, Basel

Hume and Reid on Political Economy

While Hume had a favorable opinion of the new commercial society, Reid envisioned a utopian system that would eliminate private property and substitute the profit incentive with a system of state-conferred honors. Reid’s predilection for a centralized command economy cannot be explained by his alleged discovery of market failures, and has to be considered in the context of his moral psychology. Hume tried to explain how the desire for gain that motivates the merchant leads to industry and frugality. These, in their turn, benefit all society. Reid still saw the desire for money as a degenerate form of the desire for power. The contrast between Hume and Reid, however, has not to be taken too far. On some particular matters of economic policy, such as paper credit, Hume and Reid eventually came to similar views

One-dimensional Ising model built on small-world networks: competing dynamics

In this paper, we offer a competing dynamic analysis of the one-dimensional Ising model built on the small-world network (SWN). Adding-type SWNs are investigated in detail using a simplified Hamiltonian of mean-field nature, and the result of rewiring-type is given because of the similarities of these two typical networks. We study the dynamical processes with competing Glauber mechanism and Kawasaki mechanism. The Glauber-type single-spin transition mechanism with probability p simulates the contact of the system with a heat bath and the Kawasaki-type dynamics with probability 1-p simulates an external energy flux. By studying the phase diagram obtained in the present work, we can realize some dynamical properties influenced by the small-world effect.Comment: 5 pages, one figure, accepted for publication in Physical Review

Integration of SARS-CoV-2 RNA in infected human cells by retrotransposons: an unlikely hypothesis and old viral relationships

Zhang et al. (Proc Natl Acad Sci 118:e2105968118, 2021) recently reported that SARS-CoV-2 RNA can be retrotranscribed and integrated into the DNA of human cells by the L1 retrotransposon machinery. This phenomenon could cause persistence of viral sequences in patients and may explain the prolonged PCR-positivity of SARS-CoV-2 infected patients, even long after the phase of active virus replication has ended. This commentary does critically review the available data on this topic and discusses them in the context of findings made for other exogenous viruses and ancestral endogenous retroviral elements

Analytical evaluation of output current ripple amplitude in three-phase three-level inverters

Nowadays, three-phase multilevel inverters are widely employed in medium and high-power applications, increasing the power ratings, improving the output voltage quality and reducing the conducted electromagnetic interferences. Despite of numerous pulse-width modulation (PWM) techniques have been developed for multilevel inverters, a detailed analysis of the output current ripple amplitude has not been reported yet. In this study, the peak-to-peak current ripple distribution over a fundamental period is analysed in details specifically for three-level three-phase voltage source inverters for both motor-load and grid-connected applications. In particular, the peak-to-peak amplitude of the current ripple is determined analytically as a function of the modulation index. The centred PWM strategy is considered in all the developments, implemented either by carrier-based or space vector (SV) PWM methods. With this modulation, the dc bus utilisation is maximised in a simple and effective way, and a nearly-optimal behaviour is obtained to minimise the current ripple rms. The results obtained in different cases and sub-cases identified in the proposed analytical approach are verified by experimental tests with reference to three-phase three-level neutral-point clamped configuration