7,808 research outputs found
Monodromy Substitutions and Rational Blowdowns
We introduce several new families of relations in the mapping class groups of
planar surfaces, each equating two products of right-handed Dehn twists. The
interest of these relations lies in their geometric interpretation in terms of
rational blowdowns of 4-manifolds, specifically via monodromy substitution in
Lefschetz fibrations. The simplest example is the lantern relation, already
shown by the first author and Gurtas to correspond to rational blowdown along a
-4 sphere; here we give relations that extend that result to realize the
"generalized" rational blowdowns of Fintushel-Stern and Park by monodromy
subsitution, as well as several of the families of rational blowdowns
discovered by Stipsicz-Szab\'o-Wahl.Comment: 28 pages, many figures. v2: minor edits; this version accepted for
publication in Journal of Topolog
Effect of Oscillating Landau Bandwidth on the Integer Quantum Hall Effect in a Unidirectional Lateral Superlattice
We have measured activation gaps for odd-integer quantum Hall states in a
unidirectional lateral superlattice (ULSL) -- a two-dimensional electron gas
(2DEG) subjected to a unidirectional periodic modulation of the electrostatic
potential. By comparing the activation gaps with those simultaneously measured
in the adjacent section of the same 2DEG sample without modulation, we find
that the gaps are reduced in the ULSL by an amount corresponding to the width
acquired by the Landau levels through the introduction of the modulation. The
decrement of the activation gap varies with the magnetic field following the
variation of the Landau bandwidth due to the commensurability effect. Notably,
the decrement vanishes at the flat band conditions.Comment: 7 pages, 6 figures, minor revisio
Pemantauan Dan Evaluasi Garam Beryodium Sebagai Salah Satu Upaya Untuk Meningkatkan Cakupan Dan Kualitas Program Penanggulangan Gaky Di Kabupaten Banyumas
Background:Although the prevalence of iodine deficiency disorders in Banyumas as measured by total goitre rate, fro 27% (1980) to 3,5 % (1996) the prevalence at IDD sti high in some subdistrict. Therefore, there is a need to monitor iodine content in salt distributed in the area. Objectives: To determine iodine content in salt consumed by households of elementary school children. Methods: A total of samples 1260 pack of ionized salt were randomly selected from 60 elementary school in Banyumas Regency. The data collection was done in 2003th. The quality of iodized was done by titration test and iodine test. Results: In general, the contain of iodium in iodized salt is good enough that is 75,6%, most of the type of iodized salt (98,4%) have trade mark, most of the type of iodized salt (82,9%) is granulated salt and most of iodized salt (74,2%) in the market has number of the trade mark. Conclosions: The quality of iodized salt is good. [Penel Gizi Makan 2005,28(1): 16-22
Semimetalic antiferromagnetism in the half-Heusler compound CuMnSb
The half-Heusler compound CuMnSb, the first antiferromagnet (AFM) in the
Mn-based class of Heuslers and half-Heuslers that contains several conventional
and half metallic ferromagnets, shows a peculiar stability of its magnetic
order in high magnetic fields. Density functional based studies reveal an
unusual nature of its unstable (and therefore unseen) paramagnetic state, which
for one electron less (CuMnSn, for example) would be a zero gap semiconductor
(accidentally so) between two sets of very narrow, topologically separate bands
of Mn 3d character. The extremely flat Mn 3d bands result from the environment:
Mn has four tetrahedrally coordinated Cu atoms whose 3d states lie well below
the Fermi level, and the other four tetrahedrally coordinated sites are empty,
leaving chemically isolated Mn 3d states. The AFM phase can be pictured
heuristically as a self-doped CuMnSb compensated semimetal
with heavy mass electrons and light mass holes, with magnetic coupling
proceeding through Kondo and/or antiKondo coupling separately through the two
carrier types. The ratio of the linear specific heat coefficient and the
calculated Fermi level density of states indicates a large mass enhancement
, or larger if a correlated band structure is taken as the
reference
Modulation Induced Phase Transition from Fractional Quantum Hall to Stripe State at nu=5/3
We have investigated the effect of unidirectional periodic potential
modulation on the fractional quantum Hall (FQH) state at filling factors nu=5/3
and 4/3. For large enough modulation amplitude, we find that the resistivity
minimum at nu=5/3 gives way to a peak that grows with decreasing temperature.
Density matrix renormalization group calculation reveals that phase transition
from FQH state to unidirectional striped state having a period sim 4 l (with l
the magnetic length) takes place at nu=1/3 (equivalent to nu=5/3 by the
particle-hole symmetry) with the increase of the modulation amplitude,
suggesting that the observed peak is the manifestation of the stripe phase.Comment: 4 pages, 6 figures; minor revisio
A new method for monitoring global volcanic activity
The ERTS Data Collection System makes it feasible for the first time to monitor the level of activity at widely separated volcanoes and to relay these data rapidly to one central office for analysis. While prediction of specific eruptions is still an evasive goal, early warning of a reawakening of quiescent volcanoes is now a distinct possibility. A prototypical global volcano surveillance system was established under the ERTS program. Instruments were installed in cooperation with local scientists on 15 volcanoes in Alaska, Hawaii, Washington, California, Iceland, Guatemala, El Salvador and Nicaragua. The sensors include 19 seismic event counters that count four different sizes of earthquakes and six biaxial borehole tiltmeters that measure ground tilt with a resolution of 1 microradian. Only seismic and tilt data are collected because these have been shown in the past to indicate most reliably the level of volcano activity at many different volcanoes. Furthermore, these parameters can be measured relatively easily with new instrumentation
Triplet Production by Linearly Polarized Photons
The process of electron-positron pair production by linearly polarized
photons is used as a polarimeter to perform mobile measurement of linear photon
polarization. In the limit of high photon energies, omega, the distributions of
the recoil-electron momentum and azimuthal angle do not depend on the photon
energy in the laboratory frame. We calculate the power corrections of order
m/omega to the above distributions and estimate the deviation from the
asymptotic result for various values of omega.Comment: LaTeX2e, 13 pages, 5 figure files (eps), submitted to Phys. Rev.
Gangguan Akibat Kekurangan Yodium pada Wanita Usia Subur di Kecamatan Baturaden Kabupaten Banyumas, Jawa Tengah
Iodine Deficiency Disorder (IDD) is one of nutrient problems in Banyumas Regency. IDD is caused by chronic deficiency of dietary iodine intake, goitrogenic consumption, hormonal contraception use, genetic factor, and level of knowledge. Prevalence of goiter in Baturaden district of BanyumasRegency constantly increases up to 35,38% in 2007, so this location is categorized as high endemic IDD. To analyze risk factors of IDD in Baturaden district, a case-control explanatory study has been carried involving 30 reproductive age women (15-45 years old) suffering from IDD as case group and 30 reproductive age women with no IDD as control group. Both groups were residents of Kebumen, Karang Tengah, Kemutug Kidul, and Karang Salam villages. This study shows that two factors are simultaneously influenced the IDD i.e. consumption of iodine (p = 0,007) and goitrogen (p = 0,015). Of the two, iodine consumption is the dominant factor influencing the IDD cases
Anisotropic transport in unidirectional lateral superlattice around half-filling of the second Landau level
We have observed marked transport anisotropy in short period (a=92 nm)
unidirectional lateral superlattices around filling factors nu=5/2 and 7/2:
magnetoresistance shows a sharp peak for current along the modulation grating
while a dip appears for current across the grating. By altering the ratio a/l
(with l=sqrt{hbar/eB_perp} the magnetic length) via changing the electron
density n_e, it is shown that the nu=5/2 anisotropic features appear in the
range 6.6 alt a/l alt 7.2 varying their intensities, becoming most conspicuous
at a/l simeq 6.7. The peak/dip broadens with temperature roughly preserving its
height/depth up to 250 mK. Tilt experiments reveal that the structures are
slightly enhanced by an in-plane magnetic field B_| perpendicular to the
grating but are almost completely destroyed by B_| parallel to the grating. The
observations suggest the stabilization of a unidirectional charge-density-wave
or stripe phase by weak external periodic modulation at the second Landau
level.Comment: REVTeX, 5 pages, 3 figures, Some minor revisions, Added notes and
reference
Region of hadron-quark mixed phase in hybrid stars
Hadron--quark mixed phase is expected in a wide region of the inner structure
of hybrid stars. However, we show that the hadron--quark mixed phase should be
restricted to a narrower region to because of the charge screening effect. The
narrow region of the mixed phase seems to explain physical phenomena of neutron
stars such as the strong magnetic field and glitch phenomena, and it would give
a new cooling curve for the neutron star.Comment: to be published in Physical Review
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