1,611 research outputs found
A Constraint on the Organization of the Galactic Center Magnetic Field Using Faraday Rotation
We present new 6 and 20 cm Very Large Array (VLA) observations of polarized
continuum emission of roughly 0.5 square degrees of the Galactic center (GC)
region. The 6 cm observations detect diffuse linearly-polarized emission
throughout the region with a brightness of roughly 1 mJy per 15"x10" beam. The
Faraday rotation measure (RM) toward this polarized emission has structure on
degree size scales and ranges from roughly +330 rad/m2 east of the dynamical
center (Sgr A) to -880 rad/m2 west of the dynamical center. This RM structure
is also seen toward several nonthermal radio filaments, which implies that they
have a similar magnetic field orientation and constrains models for their
origin. Modeling shows that the RM and its change with Galactic longitude are
best explained by the high electron density and strong magnetic field of the GC
region. Considering the emissivity of the GC plasma shows that while the
absolute RM values are indirect measures of the GC magnetic field, the RM
longitude structure directly traces the magnetic field in the central
kiloparsec of the Galaxy. Combining this result with previous work reveals a
larger RM structure covering the central ~2 degrees of the Galaxy. This RM
structure is similar to that proposed by Novak and coworkers, but is shifted
roughly 50 pc west of the dynamical center of the Galaxy. If this RM structure
originates in the GC region, it shows that the GC magnetic field is organized
on ~300 pc size scales. The pattern is consistent with a predominantly poloidal
field geometry, pointing from south to north, that is perturbed by the motion
of gas in the Galactic disk.Comment: Accepted to ApJ. emulateapj style, 14 pages, 15 figure
The magnetic environment in the central region of nearby galaxies
The central regions of galaxies harbor some of the most extreme physical
phenomena, including dense stellar clusters, non-circular motions of molecular
clouds and strong and pervasive magnetic field structures. In particular, radio
observations have shown that the central few hundred parsecs of our Galaxy has
a striking magnetic field configuration. It is not yet clear whether these
magnetic structures are unique to our Milky Way or a common feature of all
similar galaxies. Therefore, we report on (a) a new radio polarimetric survey
of the central 200 pc of the Galaxy to better characterize the magnetic field
structure and (b) a search for large-scale and organized magnetized structure
in the nuclear regions of nearby galaxies using data from the Very Large Array
(VLA) archive. The high angular resolution of the VLA allows us to study the
central 1 kpc of the nearest galaxies to search for magnetized nuclear features
similar to what is detected in our own Galactic center. Such magnetic features
play a important role in the nuclear regions of galaxies in terms of gas
transport and the physical conditions of the interstellar medium in this
unusual region of galaxies.Comment: 8 pages; Proceedings for "The Universe under the Microscope" (AHAR
2008), held in Bad Honnef (Germany) in April 2008, to be published in Journal
of Physics: Conference Series by Institute of Physics Publishing, R.
Schoedel, A. Eckart, S. Pfalzner, and E. Ros (eds.
Last tesserae of a fading mosaic: floristic census and forest vegetation survey at Parche di Bilello (south-western Sicily, Italy), a site needing urgent protection measures.
This paper illustrates the botanic heritage of Parche di Bilello, a site located in the municipality of Castelvetrano. The study area hosts several woodland fragments dominated by Olea europaea var. sylvestris, Quercus suber and Quercus ilex, respectively. According to historical data, these nuclei represent the last remnants of an open forestland which covered a much wider coastal area between Mazara del Vallo and Sciacca until the end of Middle Age. Phytosociological relevés were focused on these forest nuclei, probably the most representative of south-western Sicily, which correspond to three habitats included in the 92/43 EEC Directive (9320, 9330 and
9340, respectively) and represent the final stage of three different edaphic series. Wild olive forests probably dominated on sandy calcareous soils, holm oaks prevailed on steep calcareous and N-exposed slopes. In contrast, cork oaks mostly occurred on sandy subacid soils issuing from pedogenetic processes on palaeodunes. Moreover, field surveys allowed to list 331 vascular plant taxa. Among them, Linaria multicaulis subsp. humilis, Orobanche balsensis and Serapias orientalis subsp. siciliensis are new to Trapani Province. Detailed information on the current distribution and the synecology of several plant taxa of high biogeographic and conservation interest is also provided. The study site also hosts one habitat of priority interest (6220, i.e. xerophilous Mediterranean perennial grasslands and annual swards) and two species protected by international laws, i.e. the orchid Ophrys lunulata and the lichen Teloschistes chrysophthalmus. Considering the high value of its natural heritage, this territory deserves the adoption of more effective protection measures. For this reason the authors recommend its inclusion as a new Site of Community Interest within the Sicilian Natura 2000 network
Respon GA3 Terhadap Induksi Tunas Mikro Tanaman Karet (Hevea Brasiliensis (Muell). Arg)
The aim of the research was to know effect of GA3 to rubber plant in micro shoot formation. The research was conducted at the rubber plant microcutting labortory PT Perkebunan Nusantara III Kebun Gunung Pamela, Tebing Tinggi, North Sumatera, Indonesia from April 2015 to Juli 2015. The Completely randomize design was used with two factors,i.e.:the addition of GA3 (GA3 0 mg/l; GA3 0.5 mg/l; GA3 1 mg/l; GA3 1.5 mg/l) and the immersion of nodes (GA3 0 mg/l; GA3 5 mg/l; GA3 10 mg/l; GA3 15 mg/l) with seven replications. The result showed that addition of 0.5 mg/l GA3 of significantly affected the percent of shoot emergence but no significantly different age of shoot emergence and immersion of nodes of 0 mg/l significantly affected the percent of shoot emergence but no significantly different age of shoot emergence and the interraction that addition of 0.5 mg/l GA3 and immersion of nodes significant affected the percent of shoot emergence on age of shoot emergence but no significantly different.Keywords : rubber, micro shoot, addition of GA3, immersion of nodesThe aim of the research was to know effect of GA3 to rubber plant in micro shoot formation. The research was conducted at the rubber plant microcutting labortory PT Perkebunan Nusantara III Kebun Gunung Pamela, Tebing Tinggi, North Sumatera, Indonesia from April 2015 to Juli 2015. The Completely randomize design was used with two factors,i.e.:the addition of GA3 (GA3 0 mg/l; GA3 0.5 mg/l; GA3 1 mg/l; GA3 1.5 mg/l) and the immersion of nodes (GA3 0 mg/l; GA3 5 mg/l; GA3 10 mg/l; GA3 15 mg/l) with seven replications. The result showed that addition of 0.5 mg/l GA3 of significantly affected the percent of shoot emergence but no significantly different age of shoot emergence and immersion of nodes of 0 mg/l significantly affected the percent of shoot emergence but no significantly different age of shoot emergence and the interraction that addition of 0.5 mg/l GA3 and immersion of nodes significant affected the percent of shoot emergence on age of shoot emergence but no significantly different
Frame-dragging effects on magnetic fields near a rotating black hole
We discuss the role of general relativity frame dragging acting on magnetic
field lines near a rotating (Kerr) black hole. Near ergosphere the magnetic
structure becomes strongly influenced and magnetic null points can develop. We
consider aligned magnetic fields as well as fields inclined with respect to the
rotation axis, and the two cases are shown to behave in profoundly different
ways. Further, we construct surfaces of equal values of local electric and
magnetic intensities, which have not yet been discussed in the full generality
of a boosted rotating black hole.Comment: to appear in the proceedings of "The Central Kiloparsec in Galactic
Nuclei (AHAR 2011)", Journal of Physics: Conference Series (JPCS), IOP
Publishin
The Sound Emission Board of the KM3NeT Acoustic Positioning System
We describe the sound emission board proposed for installation in the
acoustic positioning system of the future KM3NeT underwater neutrino telescope.
The KM3NeT European consortium aims to build a multi-cubic kilometre underwater
neutrino telescope in the deep Mediterranean Sea. In this kind of telescope the
mechanical structures holding the optical sensors, which detect the Cherenkov
radiation produced by muons emanating from neutrino interactions, are not
completely rigid and can move up to dozens of meters in undersea currents.
Knowledge of the position of the optical sensors to an accuracy of about 10 cm
is needed for adequate muon track reconstruction. A positioning system based on
the acoustic triangulation of sound transit time differences between fixed
seabed emitters and receiving hydrophones attached to the kilometre-scale
vertical flexible structures carrying the optical sensors is being developed.
In this paper, we describe the sound emission board developed in the framework
of KM3NeT project, which is totally adapted to the chosen FFR SX30 ultrasonic
transducer and fulfils the requirements imposed by the collaboration in terms
of cost, high reliability, low power consumption, high acoustic emission power
for short signals, low intrinsic noise and capacity to use arbitrary signals in
emission mode.Comment: 9 pages, 4 figure
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