1,433 research outputs found
The International Linear Collider beam dumps
The ILC beam dumps are a key part of the accelerator design. At Snowmass
2005, the current status of the beam dump designs were reviewed, and the
options for the overall dump layout considered. This paper describes the
available dump options for the baseline and the alternatives and considers
issues for the dumps that require resolution.Comment: Prepared for 2005 International Linear Collider Physics and Detector
Workshop and 2nd ILC Accelerator Workshop, Snowmass, Colorado, 14-27 Aug 200
Structure and magnetism of self-organized Ge(1-x)Mn(x) nano-columns
We report on the structural and magnetic properties of thin Ge(1-x)Mn(x)films
grown by molecular beam epitaxy (MBE) on Ge(001) substrates at temperatures
(Tg) ranging from 80deg C to 200deg C, with average Mn contents between 1 % and
11 %. Their crystalline structure, morphology and composition have been
investigated by transmission electron microscopy (TEM), electron energy loss
spectroscopy and x-ray diffraction. In the whole range of growth temperatures
and Mn concentrations, we observed the formation of manganese rich
nanostructures embedded in a nearly pure germanium matrix. Growth temperature
mostly determines the structural properties of Mn-rich nanostructures. For low
growth temperatures (below 120deg C), we evidenced a two-dimensional spinodal
decomposition resulting in the formation of vertical one-dimensional
nanostructures (nanocolumns). Moreover we show in this paper the influence of
growth parameters (Tg and Mn content) on this decomposition i.e. on nanocolumns
size and density. For temperatures higher than 180deg C, we observed the
formation of Ge3Mn5 clusters. For intermediate growth temperatures nanocolumns
and nanoclusters coexist. Combining high resolution TEM and superconducting
quantum interference device magnetometry, we could evidence at least four
different magnetic phases in Ge(1-x)Mn(x) films: (i) paramagnetic diluted Mn
atoms in the germanium matrix, (ii) superparamagnetic and ferromagnetic low-Tc
nanocolumns (120 K 400 K) and
(iv) Ge3Mn5 clusters.Comment: 10 pages 2 colonnes revTex formatte
Spin-glass-like behavior of Ge:Mn
We present a detailed study of the magnetic properties of
low-temperature-molecular-beam-epitaxy grown Ge:Mn dilute magnetic
semiconductor films. We find strong indications for a frozen state of
Ge_{1-x}Mn_{x}, with freezing temperatures of T_f=12K and T_f=15K for samples
with x=0.04 and x=0.2, respectively, determined from the difference between
field-cooled and zero-field-cooled magnetization. For Ge_{0.96}Mn_{0.04}, ac
susceptibility measurements show a peak around T_f, with the peak position T'_f
shifting as a function of the driving frequency f by Delta T_f' / [T_f' Delta
log f] ~ 0.06, whereas for sample Ge_{0.8}Mn_{0.2} a more complicated behavior
is observed. Furthermore, both samples exhibit relaxation effects of the
magnetization after switching the magnitude of the external magnetic field
below T_f which are in qualitative agreement with the field- and
zero-field-cooled magnetization measurements. These findings consistently show
that Ge:Mn exhibits a frozen magnetic state at low temperatures and that it is
not a conventional ferromagnet.Comment: Revised version contains extended interpretation of experimental dat
High Temperature Ferromagnetism in GaAs-based Heterostructures with Mn Delta Doping
We show that suitably-designed magnetic semiconductor heterostructures
consisting of Mn delta-doped GaAs and p-type AlGaAs layers, in which the
locally high concentration of magnetic moments of Mn atoms are controllably
overlapped with the 2-dimensional hole gas wavefunction, realized remarkably
high ferromagnetic transition temperatures (TC). Significant reduction of
compensative Mn interstitials by varying the growth sequence of the structures
followed by low temperature annealing led to high TC up to 250 K. The
heterostructure with high TC exhibited peculiar anomalous Hall effect behavior,
whose sign depends on temperature.Comment: 18 pages, 4 figure
Food Product Traceability by Using Automated Identification Technologies
Part 7: Perceptional SystemsInternational audienceFood product traceability from harvesting, through food processing to the final food product and through the retailer to the end consumer is a significant process that has to ensure food quality and safety. The traceability enables the end consumer to get information from all previous stages of the food product, leading back to the food origin. In this way, the consumer can get more information on the specific product, and thus make a decision on buying the product that suits his needs best. In each stage of the food product transformation, important data are generated for the subsequent chain participants. Every participant should have access to certain data of interest to them. This can be achieved by using automated identification technologies, like RFID (Radio Frequency IDentification) and two-dimensional barcode, which allow faster data acquisition, recording and reading processes than the traditional means, and provide up-to-date information in each product stage. Furthermore, these technologies allow the possibility to record large amounts of data for each specific product, and interconnect all the data in a database. This paper discusses the process of providing traceability of food products, recording, transmitting and reading of significant data in specific stages of food product chain, with the application of automated identification technologies, including the possibility of obtaining additional data from a database, according to appropriate access level of each participant in the chain. Advantages and disadvantages of automated identification technologies are discussed, with the proposition for using specific technologies in certain food product stages
Structure of the Isovector Dipole Resonance in Neutron-Rich Nucleus and Direct Decay from Pygmy Resonance
The structure of the isovector dipole resonance in neutron-rich calcium
isotope, , has been investigated by implementing a careful treatment
of the differences of neutron and proton radii in the continuum random phase
approximation (). The calculations have taken into account the current
estimates of the neutron skin. The estimates of the escape widths for direct
neutron decay from the pygmy dipole resonance () were shown rather wide,
implicating a strong coupling to the continuum. The width of the giant dipole
resonance () was evaluated, bringing on a detailed discussion about its
microscopic structure.Comment: 13 pages, 2 figures, RevTex
ARSENIC REMOVAL FROM GROUNDWATER USING INDIGENOUS IRON AND MANGANESE OXDIZING BACTERIA
Joint Research on Environmental Science and Technology for the Eart
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