62 research outputs found
Lo spirito del male
In questo volume Nathalie Zaltzman -membro fondatore del IV Gruppo e co-redattrice della Rivista Topique- esplora il rapporto tra il Kulturarbeit e la dimensione del male, presentandoci il progredire di una riflessione da lungo tempo praticata sulle questioni della civilizzazione e delle sue oscurità.
Avvalendosi di appassionanti incursioni nella letteratura, con un procedere dialettico dell’argomentazione in cui le domande sono veri strumenti di pensiero e con una prosa dialogica e a tratti spumeggiante, Zaltzman ci mostra i punti di vulnerabilità del Kulturarbeit, alla ricerca di una leva in grado di scardinare quella resilienza della dimensione del male refrattaria ad ogni progresso di civiltà. Il movimento è circolare: dopo aver isolato le due direzioni di analisi freudiana -civilizzazione e Kulturarbeit- che vanno a tessere la trama del saggio, si entra nel vivo della questione sullo spirito del male che dopo un lungo détour esplorativo -sul rapporto tra le rappresentazioni dell’umano, il progresso dell’opera di civiltà rivelato dalla nascita della nozione di crimine contro l’umanità e la dimensione del male-, viene ripresa ed arricchita dalla proposta di una topica del male. La problematica in gioco, la cui complessità apre più questioni di quante ne possa risolvere -come segnalato dalla scelta di titolare i due ultimi capitoli: Perplessità-, sembra trovare una sortita nel mantenimento del focus sul legame tra ontogenetico e filogenetico, tra individuale e collettivo
Electro-osmotic Instability of Concentration Enrichment in Curved Geometries for an Aqueous Electrolyte
We report that an electro-osmotic instability of concentration enrichment in
curved geometries for an aqueous electrolyte, as opposed to the well-known one,
is initiated exclusively at the enriched interface (anode), rather than at the
depleted one (cathode). For this instability, the limitation of unrealistically
high material Peclet number in planar geometry is eliminated by the strong
electric field arising from the line charge singularity. In a model setup of
concentric circular electrodes, we show by stability analysis, numerical
simulation, and experimental visualization that instability occurs at the inner
anode, below a critical radius of curvature. The stability criterion is also
formulated in terms of a critical electric field and extended to arbitrary (2d)
geometries by conformal mapping. This discovery suggests that transport may be
enhanced in processes limited by salt enrichment, such as reverse osmosis, by
triggering this instability with needle-like electrodes.Comment: 5 pages, 4 figure
Enhanced complement susceptibility of avidin-biotin-treated human erythrocytes is a consequence of neutralization of the complement regulators CD59 and decay accelerating factor
Controlling domain patterns far from equilibrium
A high degree of control over the structure and dynamics of domain patterns
in nonequilibrium systems can be achieved by applying nonuniform external
fields near parity breaking front bifurcations. An external field with a linear
spatial profile stabilizes a propagating front at a fixed position or induces
oscillations with frequency that scales like the square root of the field
gradient. Nonmonotonic profiles produce a variety of patterns with controllable
wavelengths, domain sizes, and frequencies and phases of oscillations.Comment: Published version, 4 pages, RevTeX. More at
http://t7.lanl.gov/People/Aric
Electrostatic and electrokinetic contributions to the elastic moduli of a driven membrane
We discuss the electrostatic contribution to the elastic moduli of a cell or
artificial membrane placed in an electrolyte and driven by a DC electric field.
The field drives ion currents across the membrane, through specific channels,
pumps or natural pores. In steady state, charges accumulate in the Debye layers
close to the membrane, modifying the membrane elastic moduli. We first study a
model of a membrane of zero thickness, later generalizing this treatment to
allow for a finite thickness and finite dielectric constant. Our results
clarify and extend the results presented in [D. Lacoste, M. Cosentino
Lagomarsino, and J. F. Joanny, Europhys. Lett., {\bf 77}, 18006 (2007)], by
providing a physical explanation for a destabilizing term proportional to
\kps^3 in the fluctuation spectrum, which we relate to a nonlinear ()
electro-kinetic effect called induced-charge electro-osmosis (ICEO). Recent
studies of ICEO have focused on electrodes and polarizable particles, where an
applied bulk field is perturbed by capacitive charging of the double layer and
drives flow along the field axis toward surface protrusions; in contrast, we
predict "reverse" ICEO flows around driven membranes, due to curvature-induced
tangential fields within a non-equilibrium double layer, which hydrodynamically
enhance protrusions. We also consider the effect of incorporating the dynamics
of a spatially dependent concentration field for the ion channels.Comment: 22 pages, 10 figures. Under review for EPJ
Order Parameter Equations for Front Transitions: Planar and Circular Fronts
Near a parity breaking front bifurcation, small perturbations may reverse the
propagation direction of fronts. Often this results in nonsteady asymptotic
motion such as breathing and domain breakup. Exploiting the time scale
differences of an activator-inhibitor model and the proximity to the front
bifurcation, we derive equations of motion for planar and circular fronts. The
equations involve a translational degree of freedom and an order parameter
describing transitions between left and right propagating fronts.
Perturbations, such as a space dependent advective field or uniform curvature
(axisymmetric spots), couple these two degrees of freedom. In both cases this
leads to a transition from stationary to oscillating fronts as the parity
breaking bifurcation is approached. For axisymmetric spots, two additional
dynamic behaviors are found: rebound and collapse.Comment: 9 pages. Aric Hagberg: http://t7.lanl.gov/People/Aric/; Ehud Meron:
http://www.bgu.ac.il/BIDR/research/staff/meron.htm
Stabilization of Ion Concentration Polarization Using a Heterogeneous Nanoporous Junction
We demonstrate a recycled ion-flux through heterogeneous nanoporous junctions, which induce stable ion concentration polarization with an electric field. The nanoporous junctions are based on integration of ionic hydrogels whose surfaces are negatively or positively charged for cationic or anionic selectivity, respectively. Such heterogeneous junctions can be matched up in a way to achieve continuous ion-flux operation for stable concentration gradient or ionic conductance. Furthermore, the combined junctions can be used to accumulate ions on a specific region of the device.Korea Research Foundation (Grant MOEHRD: KRF-2007-331-D00040)Korean Science and Engineering Foundation (Grant MOST: R01-2007-000-20675-0)Korea Research Foundation (Grant MOEHRD: KRF-J03000)National Research Foundation of Korea (Grant NRF-2009- 352-D00034)National Institutes of Health (U.S.) (EB005743)National Science Foundation (U.S.). (CBET-0347348
Multi-messenger observations of a binary neutron star merger
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta
Synergistic effect of mycophenolate mofetil and angiotensin-converting enzyme inhibitor in patients with chronic allograft nephropathy
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