1,177 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 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
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
Manajemen Rantai Distribusi Bahan Baku Berbasis Web Studi Kasus Syahfira Bakery and Cake
The process of distributing raw materials is of concern to the company, because it is very influential on the smooth production process. Especially on products that use raw materials have an expiration time limit. So that the application of good management and supported by the application of information technology, will support the process of distributing raw materials running smoothly and not disrupt the production process.Syahfira bakery and cake is a company that produces a variety of cakes for marketing in the city of Medan. Syahfira bakery and cake strives to maintain the quality of production by selling processed cakes / bread on the same day. For this reason, it is necessary to have good and accurate management of the distribution of raw materials. Research conducted at the Syahfira Bakery and Cake shop, can be seen through direct observation and interviews that there is no information technology based management process distribution.This research uses the SCM approach to simplify the process of distributing raw materials. SCM helps to see how the flow of ordering raw materials to the process of shipping raw materials. The results of this study conclude that the SCM approach is very helpful for business owners, shop admins, suppliers and existing branch shops, in monitoring the distribution of raw material shipments and ordering raw materials through webbased applications
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.
Specific immunotherapy for allergic rhinitis in Italy: The patients' points of view
Specific immunotherapy (SIT) is the unique causal treatment for allergy, but its use is quite limited. A perspective, cross-sectional telephone interview survey was carried out in Italy to evaluate the characteristics of 500 patients with allergic rhinitis (250 of whom treated with SIT). Relevant differences were found concerning therapeutic management of allergic rhinitis, mainly regarding the use of drugs and co-morbidities. The allergist is the most important consultant who prescribes SIT. This study therefore provides evidence that the course of allergic rhinitis may depend on the therapy prescribed by and the level of allergy awareness of the physician
Evidence for a Weak Galactic Center Magnetic Field from Diffuse Low Frequency Nonthermal Radio Emission
New low-frequency 74 and 330 MHz observations of the Galactic center (GC)
region reveal the presence of a large-scale (6\arcdeg\times 2\arcdeg) diffuse
source of nonthermal synchrotron emission. A minimum energy analysis of this
emission yields a total energy of ergs
and a magnetic field strength of \muG (where is
the proton to electron energy ratio and is the filling factor of the
synchrotron emitting gas). The equipartition particle energy density is
\evcm, a value consistent with cosmic-ray data. However,
the derived magnetic field is several orders of magnitude below the 1 mG field
commonly invoked for the GC. With this field the source can be maintained with
the SN rate inferred from the GC star formation. Furthermore, a strong magnetic
field implies an abnormally low GC cosmic-ray energy density. We conclude that
the mean magnetic field in the GC region must be weak, of order 10 \muG (at
least on size scales \ga 125\arcsec).Comment: 12 pages, 1 JPEG figure, uses aastex.sty; Accepted for publication,
ApJL (2005, published
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