760 research outputs found
From chemical neuroanatomy to an understanding of the olfactory system
The olfactory system of mammals is the appropriate model for studying several aspects of neuronal physiology spanning from the developmental stage to neural network remodelling in the adult brain. Both the morphological and physiological understanding of this system were strongly supported by classical histochemistry. It is emblematic the case of the Olfactory Marker Protein (OMP) staining, the first, powerful marker for fully differentiated olfactory receptor neurons and a key tool to investigate the dynamic relations between peripheral sensory epithelia and central relay regions given its presence within olfactory fibers reaching the olfactory bulb (OB). Similarly, the use of thymidine analogues was able to show neurogenesis in an adult mammalian brain far before modern virus labelling and lipophilic tracers based methods. Nowadays, a wealth of new histochemical techniques combining cell and molecular biology approaches is available, giving stance to move from the analysis of the chemically identified circuitries to functional research. The study of adult neurogenesis is indeed one of the best explanatory examples of this statement. After defining the cell types involved and the basic physiology of this phenomenon in the OB plasticity, we can now analyze the role of neurogenesis in well testable behaviours related to socio-chemical communication in rodents
Characterizing precursors to stellar clusters with Herschel
Context. Despite their profound effect on the universe, the formation of massive stars and stellar clusters remains elusive. Recent advances in observing facilities and computing power have brought us closer to understanding this formation process. In the past decade, compelling evidence has emerged that suggests infrared dark clouds (IRDCs) may be precursors to stellar clusters. However, the usual method for identifying IRDCs is biased by the requirement that they are seen in absorption against background mid-IR emission, whereas dust continuum observations allow cold, dense pre-stellar-clusters to be identified anywhere. Aims: We aim to understand what dust temperatures and column densities characterize and distinguish IRDCs, to explore the population of dust continuum sources that are not IRDCs, and to roughly characterize the level of star formation activity in these dust continuum sources. Methods: We use Hi-GAL 70 to 500 m bright sources at the warmest. Finally, we identify five candidate IRDC-like sources on the far-side of the Galaxy. These are cold (20 K), high column density (N(H) gt 10 cm) clouds identified with Hi-GAL which, despite bright surrounding mid-IR emission, show little to no absorption at 8 $m. These are the first inner Galaxy far-side candidate IRDCs of which the authors are aware. Herschel in an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation by NASA.The FITS files discussed in the paper would be released publicly WITH the Hi-GAL data (on the Hi-GAL website) when the Hi-GAL data is released publicly.Peer reviewe
Probing the formation of intermediate- to high-mass stars in protoclusters II. Comparison between millimeter interferometric observations of NGC 2264-C and SPH simulations of a collapsing clump
The earliest phases of massive star formation in clusters are still poorly
understood. Here, we test the hypothesis for high-mass star formation proposed
in our earlier paper (Peretto et al. 2006). In order to confirm the physical
validity of this hypothesis, we carried out IRAM Plateau de Bure interferometer
observations of NGC 2264-C and performed SPH numerical simulations of the
collapse of a Jeans-unstable, prolate dense clump. Our Plateau de Bure
observations reveal the presence of a new compact source (C-MM13) located only
\~ 10000 AU away, but separated by ~ 1.1 km/s in (projected) velocity, from the
most massive Class 0 object (C-MM3) lying at the very center of NGC 2264-C.
Detailed comparison with our numerical SPH simulations supports the view that
NGC 2264-C is an elongated cluster-forming clump in the process of collapsing
and fragmenting along its long axis, leading to a strong dynamical interaction
and possible protostar merger in the central region of the clump. The present
study also sets several quantitative constraints on the initial conditions of
large-scale collapse in NGC 2264-C. Our hydrodynamic simulations indicate that
the observed velocity pattern characterizes an early phase of protocluster
collapse which survives for an only short period of time (i.e., < 10^5 yr). To
provide a good match to the observations the simulations require an initial
ratio of turbulent to gravitational energy of only ~ 5 %, which strongly
suggests that the NGC 2264-C clump is structured primarily by gravity rather
than turbulence. The required "cold'' initial conditions may result from rapid
compression by an external trigger.Comment: 15 pages, 8 figures, accepted for publication in A&
Modeling Stray Capacitances of High-Voltage Capacitive Dividers for Conventional Measurement Setups
Stray capacitances (SCs) are a serious issue in high-voltage (HV) applications. Their presence can alter the circuit or the operation of a device, resulting in wrong or even disastrous consequences. To this purpose, in this work, we describe the modeling of SCs in HV capacitive dividers. Such modeling does not rely on finite element analysis or complicated geometries; instead, it starts from an equivalent circuit of a conventional measurement setup described by the standard IEC 61869-11. Once the equivalent model including the SCs is found, closed expressions of the SCs are derived starting from the ratio error definition. Afterwards, they are validated in a simulation environment by implementing various circuit configurations. The results demonstrate the expressions applicability and effectiveness; hence, thanks to their simplicity, they can be implemented by system operators, researchers, and manufacturers avoiding the use of complicated methods and technologies
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