2,773 research outputs found
Interactions between the neuromodulatory systems and the amygdala: exploratory survey using the Allen Mouse Brain Atlas.
Neuromodulatory systems originate in nuclei localized in the subcortical region of the brain and control fundamental behaviors by interacting with many areas of the central nervous system. An exploratory survey of the cholinergic, dopaminergic, noradrenergic, and serotonergic receptor expression energy in the amygdala, and in the neuromodulatory areas themselves was undertaken using the Allen Mouse Brain Atlas. The amygdala was chosen because of its importance in cognitive behavior and its bidirectional interaction with the neuromodulatory systems. The gene expression data of 38 neuromodulatory receptor subtypes were examined across 13 brain regions. The substantia innominata of the basal forebrain and regions of the amygdala had the highest amount of receptor expression energy for all four neuromodulatory systems examined. The ventral tegmental area also displayed high receptor expression of all four neuromodulators. In contrast, the locus coeruleus displayed low receptor expression energy overall. In general, cholinergic receptor expression was an order of magnitude greater than other neuromodulatory receptors. Since the nuclei of these neuromodulatory systems are thought to be the source of specific neurotransmitters, the projections from these nuclei to target regions may be inferred by receptor expression energy. The comprehensive analysis revealed many connectivity relations and receptor localization that had not been previously reported. The methodology presented here may be applied to other neural systems with similar characteristics, and to other animal models as these brain atlases become available
Aromatic nitrations by mixed acid. Slow liquid-liquid reaction regime
Aromatic nitrations by mixed acid have been selected as a specific case of a heterogeneous liquid-liquid reaction. An extensive experimental programme has been followed using adiabatic and heat-flow calorimetry and pilot reactor experiments, supported by chemical analysis. A series of nitration experiments has been carried out to study the influences of different initial and operating conditions such as temperature, stirring speed and sulphuric acid concentration. In parallel, a mathematical model to predict the overall conversion rate has been developed. In this paper the mathematical modelling and the implementation and experimental validation for benzene, toluene and chlorobenzene mononitration in the kinetic control regime (slow liquid-liquid reaction) are presented and discussed
The Flavour Portal to Dark Matter
We present a class of models in which dark matter (DM) is a fermionic singlet
under the Standard Model (SM) gauge group but is charged under a symmetry of
flavour that acts as well on the SM fermions. Interactions between DM and SM
particles are mediated by the scalar fields that spontaneously break the
flavour symmetry, the so-called flavons. In the case of gauged flavour
symmetries, the interactions are also mediated by the flavour gauge bosons. We
first discuss the construction and the generic features of this class of
models. Then a concrete example with an abelian flavour symmetry is considered.
We compute the complementary constraints from the relic abundance, direct
detection experiments and flavour observables, showing that wide portions of
the parameter space are still viable. Other possibilities like non-abelian
flavour symmetries can be analysed within the same framework.Comment: 7 pages, 2 figures, more detailed presentation of flavour
constraints, version accepted for publication in PR
Thermal and non-thermal production of dark matter via Z'-portal(s)
We study the genesis of dark matter in the primordial Universe for
representative classes of Z'-portals models. For weak-scale Z' mediators we
compute the range of values of the kinetic mixing allowed by WMAP/PLANCK
experiments corresponding to a FIMP regime. We show that very small values of
the kinetic coupling (1.e-12 < delta < 1.e-11) are sufficient to produce the
right amount of dark matter. We also analyse the case of very massive gauge
mediators, whose mass is larger than the reheating temperature, "T_RH", with a
weak-scale coupling to ordinary matter. Relic abundance constraints then impose
a direct correlation between T_RH and the effective scale "Lambda" of the
interactions: Lambda ~ 1.e3--1.e5 * T_RH. Finally we describe in some detail
the process of dark thermalisation and study its consequences on the
computation of the relic abundance.Comment: version accepted for publication in JCA
Freeze-in through portals
The popular freeze-out paradigm for Dark Matter (DM) production, relies on
DM-baryon couplings of the order of the weak interactions. However, different
search strategies for DM have failed to provide a conclusive evidence of such
(non-gravitational) interactions, while greatly reducing the parameter space of
many representative models. This motivates the study of alternative mechanisms
for DM genesis. In the freeze-in framework, the DM is slowly populated from the
thermal bath while never reaching equilibrium. In this work, we analyse in
detail the possibility of producing a frozen-in DM via a mediator particle
which acts as a portal. We give analytical estimates of different freeze-in
regimes and support them with full numerical analyses, taking into account the
proper distribution functions of bath particles. Finally, we constrain the
parameter space of generic models by requiring agreement with DM relic
abundance observations.Comment: 18 pages, 6 figure
- …