375 research outputs found
Electronic and magnetic properties of the monolayer RuCl: A first-principles and Monte Carlo study
Recent experiments revealed that monolayer -RuCl can be obtain by
chemical exfoliation method and exfoliation or restacking of nanosheets can
manipulate the magnetic properties of the materials. In this present paper, the
electronic and magnetic properties of -RuCl monolayer are
investigated by combining first-principles calculations and Monte Carlo
simulations. From first-principles calculations, we found that the spin
configuration FM corresponds to the ground state for -RuCl,
however, the other excited zigzag oriented spin configuration has energy of 5
meV/atom higher than the ground state. Energy band gap has been obtained as
meV using PBE functionals. When spin-orbit coupling effect is taken into
account, corresponding energy gap is determined to be as meV. We also
investigate the effect of Hubbard U energy terms on the electronic band
structure of -RuCl monolayer and revealed band gap increases
approximately linear with increasing U value. Moreover, spin-spin coupling
terms (, , ) have been obtained using first principles
calculations. By benefiting from these terms, Monte Carlo simulations with
single site update Metropolis algorithm have been implemented to elucidate
magnetic properties of the considered system. Thermal variations of
magnetization, susceptibility and also specific heat curves indicate that
monolayer -RuCl exhibits a phase transition between ordered and
disordered phases at the Curie temperature K. We believe that this
study can be utilized to improve two-dimensional magnet materials
Effects of intrathecal bupivacaine and bupivacaine plus sufentanil in elderly patients undergoing transurethral resection
Introduction: The present study compared the effect of bupivacaine and bupivacaine + sufentanil on hemodynamic parameters and characteristics of spinal anesthesia in elderly patients undergoing transurethral resection of the prostate (TURP) under spinal anesthesia.Technical Considerations: The study included 40 American Society of Anesthesiologists (ASA) I‑III patients scheduled to undergo TURP. Patients were blindly and randomly divided into two groups. Group B (n = 20) received 10 mg of intrathecal bupivacaine and group BS (n = 20) received 7.5 mg of bupivacaine + 5 μg of sufentanil. Sensory and motor block characteristics, hemodynamic changes, side effects, and time to first analgesic requirement were recorded. No differences in mean arterial pressure or heart rate, time for sensory blockade to reach the T10 level, and maximum sensory level were observed between the two groups. The time to first analgesic request was longer in group BS (P < 0.05). Motor block was significantly higher in group B (P < 0.05). In terms of side effects, no statistically significant differences occurred between the groups.Conclusions: Similar hemodynamic stability and sufficient level of sensory blockade were provided by bupivacaine and bupivacaine + sufentanil used for spinal anesthesia in patients undergoing TUR. Due to the fact that less motor block was observed and the time to first analgesic request was longer, the combination of bupivacaine + sufentanil might be appropriate for patients undergoing TUR.Key words: Bupivacaine, intrathecal, opioid, spinal, sufentani
Dynamic phase transition properties and hysteretic behavior of a ferrimagnetic core-shell nanoparticle in the presence of a time dependent magnetic field
We have presented dynamic phase transition features and stationary-state
behavior of a ferrimagnetic small nanoparticle system with a core-shell
structure. By means of detailed Monte Carlo simulations, a complete picture of
the phase diagrams and magnetization profiles have been presented and the
conditions for the occurrence of a compensation point in the system
have been investigated. According to N\'{e}el nomenclature, the magnetization
curves of the particle have been found to obey P-type, N-type and Q-type
classification schemes under certain conditions. Much effort has been devoted
to investigation of hysteretic response of the particle and we observed the
existence of triple hysteresis loop behavior which originates from the
existence of a weak ferromagnetic core coupling , as well as a
strong antiferromagnetic interface exchange interaction . Most
of the calculations have been performed for a particle in the presence of
oscillating fields of very high frequencies and high amplitudes in comparison
with exchange interactions which resembles a magnetic system under the
influence of ultrafast switching fields. Particular attention has also been
paid on the influence of the particle size on the thermal and magnetic
properties, as well as magnetic features such as coercivity, remanence and
compensation temperature of the particle. We have found that in the presence of
ultrafast switching fields, the particle may exhibit a dynamic phase transition
from paramagnetic to a dynamically ordered phase with increasing ferromagnetic
shell thickness.Comment: 12 pages, 12 figure
Stationary State Solutions of a Bond Diluted Kinetic Ising Model: An Effective-Field Theory Analysis
We have examined the stationary state solutions of a bond diluted kinetic
Ising model under a time dependent oscillating magnetic field within the
effective-field theory (EFT) for a honeycomb lattice . Time evolution of
the system has been modeled with a formalism of master equation. The effects of
the bond dilution, as well as the frequency and amplitude of
the external field on the dynamic phase diagrams have been discussed in detail.
We have found that the system exhibits the first order phase transition with a
dynamic tricritical point (DTCP) at low temperature and high amplitude regions,
in contrast to the previously published results for the pure case \cite{Ling}.
Bond dilution process on the kinetic Ising model gives rise to a number of
interesting and unusual phenomena such as reentrant phenomena and has a
tendency to destruct the first-order transitions and the DTCP. Moreover, we
have investigated the variation of the bond percolation threshold as functions
of the amplitude and frequency of the oscillating field.Comment: 8 pages, 4 figure
Neutrino Spectrum from SN 1987A and from Cosmic Supernovae
The detection of neutrinos from SN 1987A by the Kamiokande-II and
Irvine-Michigan-Brookhaven detectors provided the first glimpse of core
collapse in a supernova, complementing the optical observations and confirming
our basic understanding of the mechanism behind the explosion. One
long-standing puzzle is that, when fitted with thermal spectra, the two
independent detections do not seem to agree with either each other or typical
theoretical expectations. We assess the compatibility of the two data sets in a
model-independent way and show that they can be reconciled if one avoids any
bias on the neutrino spectrum stemming from theoretical conjecture. We
reconstruct the neutrino spectrum from SN 1987A directly from the data through
non-parametric inferential statistical methods and present predictions for the
Diffuse Supernova Neutrino Background based on SN 1987A data. We show that this
prediction cannot be too small (especially in the 10-18 MeV range), since the
majority of the detected events from SN 1987 were above 18 MeV (including 6
events above 35 MeV), suggesting an imminent detection in operational and
planned detectors.Comment: 9 pages, 4 figures; Matches version published in Phys. Rev.
A Case Report of Sandhoff Disease
Sandhoff disease is a rare and severe lysosomal storage disorder representing 7% of GM2 gangliosidoses. Bilateral thalamic involvement has been suggested as a diagnostic marker of Sandhoff disease. A case of an 18-month-old infant admitted for psychomotor regression and drug resistant myoclonic epilepsy is presented. Cerebral CT scan showed bilateral and symmetrical thalamic hyperdensity. MRI revealed that the thalamus was hyperintense on T1-weighted images and hypointense on T2-weighted images with a hypersignal T2 of the white matter. Enzymatic assays objectified a deficiency of both hexosaminidases A and B confirming the diagnosis of Sandhoff disease
Turner syndrome and associated problems in turkish children: A multicenter study
Objective: Turner syndrome (TS) is a chromosomal disorder caused by complete or partial X chromosome monosomy that manifests various clinical features depending on the karyotype and on the genetic background of affected girls. This study aimed to systematically investigate the key clinical features of TS in relationship to karyotype in a large pediatric Turkish patient population. Methods: Our retrospective study included 842 karyotype-proven TS patients aged 0-18 years who were evaluated in 35 different centers in Turkey in the years 2013-2014. Results: The most common karyotype was 45,X (50.7%), followed by 45,X/46,XX (10.8%), 46,X,i(Xq) (10.1%) and 45,X/46,X,i(Xq) (9.5%). Mean age at diagnosis was 10.2±4.4 years. The most common presenting complaints were short stature and delayed puberty. Among patients diagnosed before age one year, the ratio of karyotype 45,X was significantly higher than that of other karyotype groups. Cardiac defects (bicuspid aortic valve, coarctation of the aorta and aortic stenosi) were the most common congenital anomalies, occurring in 25% of the TS cases. This was followed by urinary system anomalies (horseshoe kidney, double collector duct system and renal rotation) detected in 16.3%. Hashimoto’s thyroiditis was found in 11.1% of patients, gastrointestinal abnormalities in 8.9%, ear nose and throat problems in 22.6%, dermatologic problems in 21.8% and osteoporosis in 15.3%. Learning difficulties and/or psychosocial problems were encountered in 39.1%. Insulin resistance and impaired fasting glucose were detected in 3.4% and 2.2%, respectively. Dyslipidemia prevalence was 11.4%. Conclusion: This comprehensive study systematically evaluated the largest group of karyotype-proven TS girls to date. The karyotype distribution, congenital anomaly and comorbidity profile closely parallel that from other countries and support the need for close medical surveillance of these complex patients throughout their lifespan. © Journal of Clinical Research in Pediatric Endocrinology
Neutrino Mixing and Nucleosynthesis in Core-Collapse Supernovae
A simple description of core-collapse supernovae is given. Properties of the
neutrino-driven wind, neutrino fluxes and luminosities, reaction rates, and the
equilibrium electron fraction in supernova environments are discussed. Neutrino
mixing and neutrino interactions that are relevant to core-collapse supernovae
are briefly reviewed. The values of electron fraction under several evolution
scenarios that may impact rapid neutron capture process (r-process)
nucleosynthesis are calculated.Comment: 17 pages, 4 figure
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