131,214 research outputs found
Non-commutative (D)-instantons
Full text linkWe study systems of D3 and D(-1) branes in a NS-NS magnetic background and show that, when the brane configuration is stable, the physical degrees of freedom of the open strings with at least one end-point on the D-instantons describe the ADHM moduli of instantons for non-commutative gauge theories. We also prove that disk diagrams with mixed boundary conditions are the sources for the classical profile of the non-commutative gauge instantons in the singular gauge. We finally compare the string theory description in a large distance expansion with the non-commutative ADHM construction in the singular gauge and find complete agreement at perturbative level in the non-commutativity parameter
Dysfunctions in Dopamine Systems and ADHD: Evidence From Animals and Modeling
No full textAnimal models are useful for characterizing
neural substrates of neuropsychiatric disorders.
Several models have been proposed for the
study of Attention Deficit Hyperactivity Disorder
(ADHD). The models can be divided into various
groups: (i) genetically derived hyperactivity/
inattention, (ii) animal models showing symptoms
after pharmacological intervention, and (iii)
those based on spontaneous variations in a
random population. Spontaneously hypertensive
(SHR) and Naples High Excitability (NHE) rats
show behavioral traits featuring the main
aspects of ADHD in humans but show different
changes in dopamine (DA) systems. In fact, the
enzyme tyrosine hydroxylase is hyperexpressed
in NHE rats and hypoexpressed in SHR. The DA
transporter is hyperexpressed in both lines,
although in the SHR, DAT activity is low
(reduced DA uptake). The DA levels in the
striatum and prefrontal cortex are increased in
the juvenile SHR, but are decreased in handled
young and non-handled older animals. The
mRNA of the D1 DA receptor is upregulated
in the prefrontal cortex of SHR and downregulated
in NHE. The D2 DA receptors are
likely to be hypofunctioning in SHR, although
the experimental evidence is not univocal,
whereas their mRNA is hyperexpressed in
NHE. Thus, in SHR both the mesocortical and
mesolimbic DA pathways appear to be
involved, whereas in NHE only the mesocortical
system. To understand the effects of
methylphenidate, the elective ADHD drug
treatment in humans, in a dysfunctioning DA
system, we realized a simple mathematical
model of DA regulation based on experimental
data from electrophysiological, cyclic
voltammetry, and microdialysis studies. This
model allows the estimation of a higher firing
frequency of DA neurons in SHR rats and
suggests that methylphenidate increases
attentive processes by regulating the firing rate
of DA neurons
Compact integrated interferometer with semiconductor optical amplifiers
No full textThe semiconductor optical amplifiers (SOA) are becoming key elements of modern communication systems, particularly in view of optical signal processing. The carrier dynamics in the gain medium can be exploited to implement all-optical wavelength conversion, demultiplexing, clock recovery and signal regeneration. It can be integrated with waveguides to form compact and polarization-insensitive functional devices. A very compact Michelson interferometer, obtained by monolithic integration of two SOA with a passive waveguide section, incorporating turning mirrors is presented. Basing on the cross-phase modulation effect, taking place in the SOA under optical pumping, a device developed and used to obtain wavelength conversion
Large-scale optical interferometry in general spacetimes
No full textWe introduce a convenient formalism to evaluate the phase of a light signal propagating on a general curved background. It allows us to obtain a transparent relation between the frequency-shift and the phase difference in large-scale optical interferometry for a general relativistic setting, as well as to derive compact expressions generalizing the Doppler effect in one-way and two-way schemes. Our recipe is easily applicable to stationary spacetimes, and in particular to the near-Earth experiments where the geometry is described in the parametrized post-Newtonian approximation. As an example, we use it to evaluate the phase difference arising in the optical version of the Colella-Overhauser-Werner experiment
The fish circadian timing system: The illuminating case of light-responsive peripheral clocks [*Pagano C. first author]
No full textTommaso Briganti di fronte alla feudalità
No full textLa figura di Tommaso Briganti rivela una complessa trama d'influssi culturali, in particolare la presenza del neoumanesimo come fondo delle aperture preilluministiche, che non scalfisce il riconoscimento dell'ordine feudale come parte della costituzione d' Antico Regime
Un inedito del Mazzzini al Brunetti ed altri scritti suoi per l'insurrezione polacca del 1863
No full text- …
