Dall'a(ltro) all'altro. Attorno al Seminario Ancora di Jacques Lacan

L'articolo ricostruisce - a partire dal Seminario XX, Ancora, di Jacques Lacan - la posizione dell'oggetto a, come obiezione al rapporto con l'altro. Nella ricostruzione della problematica, riassunta dall'espressione lacaniana "non c'\ue8 rapporto sessuale", un posto importante viene riconosciuto alle riflessioni di S. Freud sull'innamoramento e la melanconia. Un momento esplicativo della problematica dell'oggetto a, viene individuato nel ciclo di opere dedicato alle Ninfee, di Claude Monet, soggetto costantemente ritratto negli ultimi vent'anni di vita del pittore francese. La direzione intravista per il passaggio dall' (a)-ltro all'altro \ue8 affidata ad un lavoro (di imputazione) utile a far cadere l'oggetto: cedere l'oggetto come riabilitazione del desiderio. Cedere l'oggetto a (castrazione) equivale a "non cedere sul proprio desiderio" (Seminario VII sull'etica di J. Lacan) ovvero al pensiero dell'imputabilit\ue0, come riapertura del rapporto con l'altro

Staff-led interventions for improving oral hygiene in patients following stroke

Background For people with limitations due to neurological conditions such as stroke, the routine practice of oral care may become a challenge. Evidence-based supported oral care intervention is essential for this patient group. Objectives To compare the effectiveness of staff-led oral care interventions with standard care for ensuring oral hygiene for individuals after a stroke. Search strategy We searched the trials registers of the Cochrane Stroke Group and Oral Health Group (August 2005), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2006), MEDLINE (1966 to February 2006), CINAHL (1982 to February 2006), Research Findings Electronic Register (February 2006), National Research Register (Issue 1, 2006), ISI Science and Technology Proceedings (August 2005), Dissertation Abstracts and Conference Papers Index (August 2005). We scanned reference lists from relevant papers and contacted authors and researchers in the field. Selection criteria We identified randomised controlled trials that evaluated one or more interventions designed to improve oral hygiene. Trials based on a mixed population were included, provided it was possible to extract the data specific to the individuals post stroke. Data collection and analysis Two review authors independently classified identified trials according to the inclusion and exclusion criteria, assessed the trial quality and extracted data. Clarification was sought from study authors when required. Main results Eight eligible randomised controlled trials were identified but only one provided stroke-specific information. It compared an oral health care education training programme (OHCE) delivered to nursing home care assistants to delayed training intervention in the control group. Comparisons were made at one and six months after the intervention, using the primary outcome measures dental plaque and denture plaque, and three secondary outcomes. The data available for the 67 individuals with a stroke (obtained from the larger cluster randomised controlled trial) showed that denture plaque scores were significantly reduced up to six months (P &lt; 0.00001) after the intervention. Staff knowledge (P = 0.0008) and attitudes (P = 0.0001) towards oral care also improved significantly. Authors' conclusions Based on one study with a small number of stroke survivors, providing oral care training for carers in a nursing home setting improves their knowledge of and attitudes towards the provision of oral care. In turn, residents' dentures were cleaner, though other oral hygiene measures did not change. Further evidence relating to oral care interventions is severely lacking, in particular with reference to care in hospital for those following stroke. This review is published as a Cochrane Review in the Cochrane Database of Systematic Reviews 2011, Issue 7. Cochrane Reviews are regularly updated as new evidence emerges and in response to comments and criticisms, and the Cochrane Database of Systematic Reviews should be consulted for the most recent version of the Review.</p

Mapping the Cosmic Web with Ly-alpha Emission

We use a high-resolution cosmological simulation to predict the distribution of HI Ly-alpha emission from the low-redshift (z<0.5) intergalactic medium (IGM). Our simulation can be used to reliably compute the emission from optically thin regions of the IGM but not that of self-shielded gas. We therefore consider several models that bracket the expected emission from self-shielded regions. Most galaxies are surrounded by extended (>10^2 kpc) ``coronae'' of optically thin gas with Ly-alpha surface brightness close to the expected background. Most of these regions contain smaller cores of dense, cool gas. Unless self-shielded gas is able to cool to T<10^4.1 K, these cores are much brighter than the background. The Ly-alpha coronae represent ``cooling flows'' of IGM gas accreting onto galaxies. We also estimate the number of Ly-alpha photons produced through the reprocessing of stellar ionizing radiation in the interstellar medium of galaxies; while this mechanism is responsible for the brightest Ly-alpha emission, it occurs on small physical scales and can be separated using high-resolution observations. In all cases, we find that Ly-alpha emitters are numerous (with a space density ~0.1 h^3 Mpc^-3) and closely trace the filamentary structure of the IGM, providing a new way to map gas inside the cosmic web.Comment: 4 pages, 3 figures, accepted by ApJ

Hubble Diagram of Gamma-Rays Bursts calibrated with Gurzadyan-Xue Cosmology

Gamma-ray bursts (GRBs) being the most luminous among known cosmic objects carry an essential potential for cosmological studies if properly used as standard candles. In this paper we test with GRBs the cosmological predictions of the Gurzadyan-Xue (GX) model of dark energy, a novel theory that predicts, without any free parameters, the current vacuum fluctuation energy density close to the value inferred from the SNIa observations. We also compare the GX results with those predicted by the concordance scenario $\Lambda$-CDM. According to the statistical approach by Schaefer (2007), the use of several empirical relations obtained from GRBs observables, after a consistent calibration for a specific model, enables one to probe current cosmological models. Based on this recently introduced method, we use the 69 GRBs sample collected by Schaefer (2007); and the most recently released SWIFT satellite data (Sakamoto et al. 2007) together with the 41 GRBs sample collected by Rizzuto et al. (2007), which has the more firmly determined redshifts. Both data samples span a distance scale up to redshift about 7. We show that the GX models are compatible with the Hubble diagram of the Schaefer (2007) 69 GRBs sample. Such adjustment is almost identical to the one for the concordance $\Lambda$-CDM.Comment: 9 pages, 17 figures, 11 tables; Astr. & Astrophys. (in press

Constraining the Collisional Nature of the Dark Matter Through Observations of Gravitational Wakes

We propose to use gravitational wakes as a direct observational probe of the collisional nature of the dark matter. We calculate analytically the structure of a wake generated by the motion of a galaxy in the core of an X-ray cluster for dark matter in the highly-collisional and collisionless limits. We show that the difference between these limits can be recovered from detailed X-ray or weak lensing observations. We also discuss the sizes of sub-halos in these limits. Preliminary X-ray data on the motion of NGC 1404 through the Fornax group disfavors fluid-like dark matter but does not exclude scenarios in which the dark matter is weakly collisional.Comment: 29 pages, 3 figures, submitted to Ap

Radio Recombination Lines at Decametre Wavelengths: Prospects for the Future

This paper considers the suitability of a number of emerging and future instruments for the study of radio recombination lines (RRLs) at frequencies below 200 MHz. These lines arise only in low-density regions of the ionized interstellar medium, and they may represent a frequency-dependent foreground for next-generation experiments trying to detect H I signals from the Epoch of Reionization and Dark Ages ("21-cm cosmology"). We summarize existing decametre-wavelength observations of RRLs, which have detected only carbon RRLs. We then show that, for an interferometric array, the primary instrumental factor limiting detection and study of the RRLs is the areal filling factor of the array. We consider the Long Wavelength Array (LWA-1), the LOw Frequency ARray (LOFAR), the low-frequency component of the Square Kilometre Array (SKA-lo), and a future Lunar Radio Array (LRA), all of which will operate at decametre wavelengths. These arrays offer digital signal processing, which should produce more stable and better defined spectral bandpasses; larger frequency tuning ranges; and better angular resolution than that of the previous generation of instruments that have been used in the past for RRL observations. Detecting Galactic carbon RRLs, with optical depths at the level of 10^-3, appears feasible for all of these arrays, with integration times of no more than 100 hr. The SKA-lo and LRA, and the LWA-1 and LOFAR at the lowest frequencies, should have a high enough filling factor to detect lines with much lower optical depths, of order 10^-4 in a few hundred hours. The amount of RRL-hosting gas present in the Galaxy at the high Galactic latitudes likely to be targeted in 21-cm cosmology studies is currently unknown. If present, however, the spectral fluctuations from RRLs could be comparable to or exceed the anticipated H I signals.Comment: 9 pages; Astron. & Astrophys., in pres

Cosmological Parameter Estimation Using 21 cm Radiation from the Epoch of Reionization

A number of radio interferometers are currently being planned or constructed to observe 21 cm emission from reionization. Not only will such measurements provide a detailed view of that epoch, but, since the 21 cm emission also traces the distribution of matter in the Universe, this signal can be used to constrain cosmological parameters at 6 < z < 20. The sensitivity of an interferometer to the cosmological information in the signal may depend on how precisely the angular dependence of the 21 cm 3-D power spectrum can be measured. Utilizing an analytic model for reionization, we quantify all the effects that break the spherical symmetry of the 3-D 21 cm power spectrum and produce physically motivated predictions for this power spectrum. We find that upcoming observatories will be sensitive to the 21 cm signal over a wide range of scales, from larger than 100 to as small as 1 comoving Mpc. We consider three methods to measure cosmological parameters from the signal: (1) direct fitting of the density power spectrum to the signal, (2) using only the velocity field fluctuations in the signal, (3) looking at the signal at large enough scales such that all fluctuations trace the density field. With the foremost method, the first generation of 21 cm observations should moderately improve existing constraints on cosmological parameters for certain low-redshift reionization scenarios, and a two year observation with the second generation interferometer MWA5000 can improve constraints on Omega_w, Omega_m h^2, Omega_b h^2, Omega_nu, n_s, and alpha_s. If the Universe is substantially ionized by z = 12 or if spin temperature fluctuations are important, we show that it will be difficult to place competitive constraints on cosmological parameters with any of the considered methods.Comment: 20 pages, 12 figures, accepted by Ap

Searching for the earliest galaxies in the 21 cm forest

We use a model developed by Xu et al. (2010) to compute the 21 cm line absorption signatures imprinted by star-forming dwarf galaxies (DGs) and starless minihalos (MHs). The method, based on a statistical comparison of the equivalent width (W_\nu) distribution and flux correlation function, allows us to derive a simple selection criteria for candidate DGs at very high (z >= 8) redshift. We find that ~ 18% of the total number of DGs along a line of sight to a target radio source (GRB or quasar) can be identified by the condition W_\nu < 0; these objects correspond to the high-mass tail of the DG distribution at high redshift, and are embedded in large HII regions. The criterion W_\nu > 0.37 kHz instead selects ~ 11% of MHs. Selected candidate DGs could later be re-observed in the near-IR by the JWST with high efficiency, thus providing a direct probe of the most likely reionization sources.Comment: 8 pages, 3 figures. Accepted for publication in Science in China Series

Optimization of the íon source cathodes of the CV-28 Cyclotron

This improvement intends to expand the useful life of the cathodes of the CV-28’s ion source. The original cathodes had an average life of 8 hours for proton, deuteron, alpha and helium-3 particle acceleration, making a weekly replacement necessary. With the beginning of the commercial production of the 123I radiopharmaceutical, the reliability of the CV-28 had to be increased, so the cyclotron was optimized for 24-MeV proton acceleration. Within this framework, there was the idea of optimizing the cathodes for the exclusive acceleration of protons. The developed version is in use presently and has an average useful life of 300 hours

Reionization History from Coupled CMB/21cm Line Data

We study CMB secondary anisotropies produced by inhomogeneous reionization by means of cosmological simulations coupled with the radiative transfer code CRASH. The reionization history is consistent with the WMAP Thomson optical depth determination. We find that the signal arising from this process dominates over the primary CMB component for l > 4000 and reaches a maximum amplitude of l(l+1)C_l/2\pi ~ 1.6 x 10^{-13} on arcmin scale, i.e. l as large as several thousands. We then cross-correlate secondary CMB anisotropy maps with neutral hydrogen 21cm line emission fluctuations obtained from the same simulations. The two signals are highly anti-correlated on angular scales corresponding to the typical size of HII regions (including overlapping) at the 21cm map redshift. We show how the CMB/21cm cross-correlation can be used to: (a) study the nature of the reionization sources, (b) reconstruct the cosmic reionization history, (c) infer the mean cosmic ionization level at any redshift. We discuss the feasibility of the proposed experiment with forthcoming facilities.Comment: 7 pages, 5 figures, MNRAS in pres