789,582 research outputs found
Nonlinear and spin-glass susceptibilities of three site-diluted systems
The nonlinear magnetic and spin-glass susceptibilities
in zero applied field are obtained, from tempered Monte Carlo simulations, for
three different spin glasses (SGs) of Ising spins with quenched site disorder.
We find that the relation ( is the temperature),
which holds for Edwards-Anderson SGs, is approximately fulfilled in
canonical-like SGs. For nearest neighbor antiferromagnetic interactions, on a
0.4 fraction of all sites in fcc lattices, as well as for spatially disordered
Ising dipolar (DID) systems, and appear to diverge in
the same manner at the critical temperature . However, is
smaller than by over two orders of magnitude in the diluted fcc
system. In DID systems, is very sensitive to the systems
aspect ratio. Whereas near , varies by approximately a
factor of 2 as system shape varies from cubic to long-thin-needle shapes,
sweeps over some four decades.Comment: 7 pages, 7 figure
Random Magnetic Interactions and Spin Glass Order Competing with Superconductivity: Interference of the Quantum Parisi Phase
We analyse the competition between spin glass (SG) order and local pairing
superconductivity (SC) in the fermionic Ising spin glass with frustrated
fermionic spin interaction and nonrandom attractive interaction. The phase
diagram is presented for all temperatures T and chemical potentials \mu. SC-SG
transitions are derived for the relevant ratios between attractive and
frustrated-magnetic interaction. Characteristic features of pairbreaking caused
by random magnetic interaction and/or by spin glass proximity are found. The
existence of low-energy excitations, arising from replica permutation symmetry
breaking (RPSB) in the Quantum Parisi Phase, is shown to be relevant for the
SC-SG phase boundary. Complete 1-step RPSB-calculations for the SG-phase are
presented together with a few results for infinity-step breaking. Suppression
of reentrant SG - SC - SG transitions due to RPSB is found and discussed in
context of ferromagnet - SG boundaries. The relative positioning of the SC and
SG phases presents a theoretical landmark for comparison with experiments in
heavy fermion systems and high T_c superconductors. We find a crossover line
traversing the SG-phase with (\mu=0,T=0) as its quantum critical (end)point in
complete RPSB, and scaling is proposed for its vicinity. We argue that this
line indicates a random field instability and suggest Dotsenko-Mezard vector
replica symmetry breaking to occur at low temperatures beyond.Comment: 24 pages, 14 figures replaced by published versio
Three Dimensional Heisenberg Spin Glass Models with and without Random Anisotropy
We reexamine the spin glass (SG) phase transition of the Heisenberg
models with and without the random anisotropy in three dimensions ()
using complementary two methods, i.e., (i) the defect energy method and (ii)
the Monte Carlo method. We reveal that the conventional defect energy method is
not convincing and propose a new method which considers the stiffness of the
lattice itself. Using the method, we show that the stiffness exponent
has a positive value () even when . Considering the
stiffness at finite temperatures, we obtain the SG phase transition temperature
of for . On the other hand, a large scale MC
simulation shows that, in contrary to the previous results, a scaling plot of
the SG susceptibility for is obtained using almost the
same transiton temperature of . Hence we believe that
the SG phase transition occurs in the Heisenberg SG model in .Comment: 15 pages, 9 figures, to be published in J. Phys.
Critical behavior at edge singularities in one dimensional spin models
In ferromagnetic spin models above the critical temperature ()
the partition function zeros accumulate at complex values of the magnetic field
() with a universal behavior for the density of zeros \rho (H) \sim | H -
H_E |^{\sg}. The critical exponent \sg is believed to be universal at each
space dimension and it is related to the magnetic scaling exponent via
\sg = (d-y_h)/y_h. In two dimensions we have y_h=12/5 (\sg = -1/6) while
y_h=2 (\sg=-1/2) in . For the one dimensional Blume-Capel and
Blume-Emery-Griffiths models we show here, for different temperatures, that a
new value y_h=3 (\sg =-2/3) can emerge if we have a triple degeneracy of the
transfer matrix eigenvalues.Comment: to appear in Phys. Rev. E, 16 pages, 3 figure
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Outcomes of ab interno trabeculectomy with the trabectome by degree of angle opening.
AimTo analyse ab interno trabeculectomy (AIT) with the trabectome and combined phacoemulsification with AIT (phaco-AIT) by Shaffer angle grade (SG).MethodsProspective study of AIT and phaco-AIT with narrow angles of SGâ€2 versus open angles â„3. Outcomes included intraocular pressure (IOP), medications, complications, secondary surgery and success (IOP <21â
mmâ
Hg and >20% reduction without further surgery). Exclusion criteria were missing preoperative data and <1â
year follow-up.ResultsOf 671 included cases, at 1â
year AIT SGâ€2 (n=43) had an IOP reduction of 42% from 27.3±7.4 to 15.7±3.0â
mmâ
Hg (p<0.01) versus AIT SGâ„3 (n=271) with an IOP reduction of 37% from 26.1±7.8 to 16.4±3.9â
mmâ
Hg (p<0.01). In phaco-AIT with SGâ€2 (n=48), IOP was reduced 24% from 20.7±7.0 to 15.7±3.6â
mmâ
Hg (p<0.01) versus phaco-AIT with SGâ„3 (n=309) with an IOP reduction of 25% from 22.6±6.4 to 17.0±3.4â
mmâ
Hg (p<0.01). There was no difference between SGâ€2 and SGâ„3 in reduction of IOP or medications, complications, secondary surgery and success rates (p>0.05).ConclusionsSGâ€2 is not associated with worse outcomes in AIT or phaco-AIT
Impact of use of optical surface imaging on initial patient setup for stereotactic body radiotherapy treatments
Purpose
To evaluate the effectiveness of surface image guidance (SG) for preâimaging setup of stereotactic body radiotherapy (SBRT) patients, and to investigate the impact of SG reference surface selection on this process.
Methods and materials
284 SBRT fractions (SGâSBRT = 113, nonâSGâSBRT = 171) were retrospectively evaluated. Differences between initial (preâimaging) and treatment couch positions were extracted from the recordâandâverify system and compared for the two groups. Rotational setup discrepancies were also computed. The utility of orthogonal kVs in reducing CBCT shifts in the SGâSBRT/nonâSGâSBRT groups was also calculated. Additionally, the number of CBCTs acquired for setup was recorded and the average for each cohort was compared. These data served to evaluate the effectiveness of surface imaging in preâimaging patient positioning and its potential impact on the necessity of including orthogonal kVs for setup. Since reference surface selection can affect SG setup, daily surface reproducibility was estimated by comparing cameraâacquired surface references (VRT surface) at each fraction to the external surface of the planning CT (DICOM surface) and to the VRT surface from the previous fraction.
Results
The reduction in all initialâtoâtreatment translation/rotation differences when using SGâSBRT was statistically significant (RankâSum test, α = 0.05). Orthogonal kV imaging kept CBCT shifts below reimaging thresholds in 19%/51% of fractions for SGâSBRT/nonâSGâSBRT cohorts. Differences in average number of CBCTs acquired were not statistically significant. The reference surface study found no statistically significant differences between the use of DICOM or VRT surfaces.
Conclusions
SGâSBRT improved preâimaging treatment setup compared to inâroom laser localization alone. It decreased the necessity of orthogonal kV imaging prior to CBCT but did not affect the average number of CBCTs acquired for setup. The selection of reference surface did not have a significant impact on initial patient positioning
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