1,769 research outputs found
Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin films
The composition dependence of the structural, magnetic, and transport
properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal
structure was observed to change from tetragonal to cubic as the Co content was
increased. In terms of the dependence of saturation magnetization on the Co
content, relatively small value was obtained for the
MnCoGa film at a large {\it K} value of 9.2
Merg/cm. Electrical resistivity of Mn-Co-Ga films was larger than that of
pure Mn-Ga film. The maximum value of the resistivity was 490 cm for
MnCoGa film. The high resistivity of Mn-Co-Ga might be
due to the presence of localized electron states in the films due to chemical
disordering caused by the Co substitution.Comment: 3 pages, 5 figures. The article has been submitted to the Journal of
Applied Physics as a Proceedings for the 12th Joint MMM/INTERMAG conferenc
Observations of [C II] 158 micron Line and Far-infrared Continuum Emission toward the High-latitude Molecular Clouds in Ursa Major
We report the results of a rocket-borne observation of [C II] 158\micron line
and far-infrared continuum emission at 152.5\micron toward the high latitude
molecular clouds in Ursa Major. We also present the results of a follow-up
observation of the millimeter ^{12}CO J=1-0 line over a selected region
observed by the rocket-borne experiment. We have discovered three small CO
cloudlets from the follow-up ^{12}CO observations. We show that these molecular
cloudlets, as well as the MBM clouds(MBM 27/28/29/30), are not gravitationally
bound. Magnetic pressure and turbulent pressure dominate the dynamic balance of
the clouds. After removing the HI-correlated and background contributions, we
find that the [C II] emission peak is displaced from the 152.5\micron and CO
peaks, while the 152.5\micron continuum emission is spatially correlated with
the CO emission. We interpret this behavior by attributing the origin of [C II]
emission to the photodissociation regions around the molecular clouds
illuminated by the local UV radiation field. We also find that the ratio of the
molecular hydrogen column density to velocity-integrated CO intensity is
1.19+-0.29x10^{20} cm^{-2} (K kms^{-1})^{-1} from the FIR continuum and the CO
data. The average [C II] /FIR intensity ratio over the MBM clouds is 0.0071,
which is close to the all sky average of 0.0082 reported by the FIRAS on the
COBE satellite. The average [C II]/CO ratio over the same regions is 420, which
is significantly lower than that of molecular clouds in the Galactic plane.Comment: 15 pages, LaTeX (aaspp4.sty) + 2 tables(apjpt4.sty) + 6 postscript
figures; accepted for publication in the Astrophysical Journal; Astrophys. J.
in press (Vol. 490, December 1, 1997 issue
Studies in binary nucleation: The dibutylphthalate/dioctylphthalate system
A continuous-flow mixing apparatus has been developed for the study of binary nucleation. This apparatus has been used to investigate the nucleation of mixed dibutylphthalate/dioctylphthalate vapors, and the interaction of the two vapors in particle formation has been demonstrated. A model that considers competition between nucleation and condensation processes during particle formation is applied in the analysis of the experimental results, allowing comparison of the magnitudes of the theoretical and actual nucleation rates in both the single-component and mixed vapor systems
High and low molecular weight crossovers in the longest relaxation time dependence of linear cis-1,4 polyisoprene by dielectric relaxations
The dielectric relaxation of cis-1,4 Polyisoprene [PI] is sensitive not only to the local and segmental dynamics but also to the larger scale chain (end-to-end) fluctuations. We have performed a careful dielectric investigation on linear PI with various molecular weights in the range of 1 to 320 kg/mol. The broadband dielectric spectra of all samples were measured isothermally at the same temperature to avoid utilizing shift factors. For the low and medium molecular weight range, the comparisons were performed at 250 K to access both the segmental relaxation and normal mode peaks inside the available frequency window (1 mHzâ10 MHz). In this way, we were able to observe simultaneously the effect of molecular mass on the segmental dynamicsârelated with the glass transition processâand on the end-to-end relaxation time of PI and thus decouple the direct effect of molecular weight on the normal mode from that due to the effect on the monomeric friction coefficient. The latter effect is significant for low molecular weight (M wâ<â33 kg/mol), i.e., in the range where the crossover from Rouse dynamics to entanglement limited flow occurs. Despite the conductivity contribution at low frequency, careful experiments allowed us to access to the normal mode signal for molecular weights as high as M wâ=â320 kg/mol, i.e., into the range of high molecular weights where the pure reptation behavior could be valid, at least for the description of the slowest chain modes. The comparison between the dielectric relaxations of PI samples with medium and high molecular weight was performed at 320 K. We found two crossovers in the molecular weight dependence of the longest relaxation time, the first around a molecular weight of 6.5 ± 0.5 kg/mol corresponding to the end of the Rouse regime and the second around 75 ± 10 kg/mol. Above this latter value, we find a power law compatible with exponent 3 as predicted by the De Gennes theory
Optimized unconventional superconductivity in a molecular Jahn-Teller metal
Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above Tc is a major challenge for all unconventional superconductors. The molecular A3C60 fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C603â electronic structure controls the geometry and spin state of the structural building unit via the on-molecule Jahn-Teller effect. We identify the Jahn-Teller metal as a fluctuating microscopically heterogeneous coexistence of both localized Jahn-Tellerâactive and itinerant electrons that connects the insulating and superconducting states of fullerides. The balance between these molecular and extended lattice features of the electrons at the Fermi level gives a dome-shaped variation of Tc with interfulleride separation, demonstrating molecular electronic structure control of superconductivity
Modulation of mucus production by interleukin-13 receptor alpha(2) in the human airway epithelium
The definitive version is available at www.blackwell-synergy.comArticleCLINICAL AND EXPERIMENTAL ALLERGY. 38(1): 122-134 (2008)journal articl
Magnetic Phase Diagrams with Possible Field-induced Antiferroquadrupolar Order in TbBC
Magnetic phase diagrams of a tetragonal antiferromagnet TbBC were
clarified by temperature and field dependence of magnetization. It is
noticeable that the N{\'e}el temperature in TbBC is anomalously
enhanced with magnetic fields, in particular the enhancement reaches 13.5 K for
the direction at 10 T. The magnetization processes as well as the
phase diagrams are well interpreted assuming that there appear field-induced
antiferroquadrupolar ordered phases in TbBC. The phase diagrams of the
AFQ compounds in RBC are systematically understood in terms of the
competition with AFQ and AFM interactions.Comment: 4 pages, 4 figures, RevTeX
PRELIMINARY STUDY OF MICROSTRUCTURE DEPENDENCE OF MAGNETORESISTANCE BEHAVIOR ON Sm.-xLaxMo2Ge2 COMPOUND WITH X=O,l-o,3
AbstractPRELIMINARY STUDY OF MICROSTRUCTURE DEPENDENCE OF MAGNETORESISTANCE BEHAVIORON SmI. ' La , Mn 2G e 2 COMPOUND WITH x=O.l--O.3. We present the microstructure dependence of magnetoresistancebehavior in Sml.,La,Mn2Ge2 compound with x=0.1~0.3. We found that in bulk samples after milling and cold pressingP=10 tonlcm2 the magnetoresistance properties have improved from 0.6% to almost 7% with the adding of La concentration10%,20% and 30%. The bulk samples were prepared by tri arc melting, melted 4-5 times with the Ti addition for oxygen getter.After that, the samples were annealed for 96 hours at 900 °C at the vaccum furnace to make a good homogeneity. X -ray diffractionmeasurement was done using Cu target then the data was refined by Rietan software. Scanning electron micrograph data a pelletsamp.lesw ere taken by SEM 515 from Phillips company with two thousands magnification and operation power 20keV. Fromthe micrograph results, it was shown that the granular diameter increases with the Lanthanum content. In this preliminary studywe can conclude the magnetoresistance behavior is related to the density of samples and also to the fraction of primary phase ofSm La Mn Ge Analysis on this magnetoresistance behavior with magnetic granular solid model can help understanding this I- x x 2 2phenomenon.ABSTRAKSTurn PENDAHULUAN HUBUNGAN ANTARA MIKROSTRUKTUR DENGAN SIFAT MAGNETO RESISTANSIPADA Sml-lLa.Mn"Ge] UNTUKx = O,1-{},3. Pada makalah ini disampaikan basil penelitian awal tentang ketergantungansifat magnetoresistance bahan terhadap strukturmikro pada paduan in Sm1-.La.Mn2Ge2d engan x = 0,1-{),3. Hasil pengukuranpada cuplikan pelet pada tekanan P=10 ton/cm2 memperlihatkan kenaikan sifat magnetoresistance bahandari 0,6 % menjadi 7 %dengan penggantian unsur Sm oleh unsur La pada konsentrasi 10 %, 20 % clan 30 %. Pembuatan cuplikan dilakukan denganmetoda tri arc melting, yang dilakukan sebanyak 4 sampai 5 dengan Ii yang dilebur ter~ebih dahulu sebagai penyerap oksigen.Setelah itu cuplikan dianil selam 96 jam pada suhu 900 °C dalamfumace vakum. Kemudian dilakukan pengukuran difraksi sinar-X clan hasilnya dihaluskan dengan software RIEIAN. Studi strukturmikro dilakukan dengan memakai alat SEM 515 buatanPHll..IPS pada perbesaran 2000 kali clan tegangan 20 keV. Hasil pengamatan tadi memperlihatkan bahwa terjadi perbesarandiameter granular sesuai dengan penambahan kadar unsur La. Pada awal studi ini dapat disimpulkan bahwa sifatmagnetoresistancebahan tergantung pada kerapatan bahan, ukuran granular clan fraksi rasa utama Sml-xLaxM~Ge, Analisis sifat magnetoresistancedengan model magnetic granular solid dapat menjelaskan fenomena proses hamburan yang terkait dengan sifat resistansibahan
Relations Between Molecular Cloud Structure Sizes and Line Widths in the Large Magellanic Cloud
We present a comparative study of the size-line width relation for
substructures within six molecular clouds in the Large Magellanic Cloud (LMC)
mapped with the Atacama Large Millimeter/submillimeter Array (ALMA). Our sample
extends our previous study, which compared a Planck detected cold cloud in the
outskirts of the LMC with the 30 Doradus molecular cloud and found the typical
line width for 1 pc radius structures to be 5 times larger in 30 Doradus. By
observing clouds with intermediate levels of star formation activity, we find
evidence that line width at a given size increases with increasing local and
cloud-scale 8m intensity. At the same time, line width at a given size
appears to independently correlate with measures of mass surface density. Our
results suggest that both virial-like motions due to gravity and local energy
injection by star formation feedback play important roles in determining
intracloud dynamics.Comment: 20 pages, to appear in ApJ. Data presented in this paper can be found
at https://mmwave.astro.illinois.edu/almalmc
Spitzer View of Massive Star Formation in the Tidally Stripped Magellanic Bridge
The Magellanic Bridge is the nearest low-metallicity, tidally stripped
environment, offering a unique high-resolution view of physical conditions in
merging and forming galaxies. In this paper we present analysis of candidate
massive young stellar objects (YSOs), i.e., {\it in situ, current} massive star
formation (MSF) in the Bridge using {\it Spitzer} mid-IR and complementary
optical and near-IR photometry. While we definitely find YSOs in the Bridge,
the most massive are , found in the Large
Magellanic Cloud (LMC). The intensity of MSF in the Bridge also appears
decreasing, as the most massive YSOs are less massive than those formed in the
past. To investigate environmental effects on MSF, we have compared properties
of massive YSOs in the Bridge to those in the LMC. First, YSOs in the Bridge
are apparently less embedded than in the LMC: 81% of Bridge YSOs show optical
counterparts, compared to only 56% of LMC sources with the same range of mass,
circumstellar dust mass, and line-of-sight extinction. Circumstellar envelopes
are evidently more porous or clumpy in the Bridge's low-metallicity
environment. Second, we have used whole samples of YSOs in the LMC and the
Bridge to estimate the probability of finding YSOs at a given \hi\ column
density, N(HI). We found that the LMC has higher probability than
the Bridge for N(HI) cm, but the trend reverses at
lower N(HI). Investigating whether this lower efficiency relative to HI is due
to less efficient molecular cloud formation, or less efficient cloud collapse,
or both, will require sensitive molecular gas observations.Comment: 41 pages, 20 figures, 6 tables; accepted for publication in ApJ;
several figures are in low resolution due to the size limit here and a high
resolution version can be downloaded via
http://www.astro.virginia.edu/~cc5ye/ms_bridge20140215.pd
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