682 research outputs found
The Global Health System: Strengthening National Health Systems as the Next Step for Global Progress
In the second in a series of articles on the changing nature of global health institutions, Julio Frenk offers a framework to better understand national health systems and their role in global health
Magnetic Phase Transition of the Perovskite-type Ti Oxides
Properties and mechanism of the magnetic phase transition of the
perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle
distortion, are studied theoretically by using the effective spin and
pseudo-spin Hamiltonian with strong Coulomb repulsion. It is shown that the
A-type antiferromagnetic(AFM(A)) to ferromagnetic(FM) phase transition occurs
as the Ti-O-Ti bond angle is decreased. Through this phase transition, the
orbital state is hardly changed so that the spin-exchange coupling along the
c-axis changes nearly continuously from positive to negative and takes
approximately zero at the phase boundary. The resultant strong
two-dimensionality in the spin coupling causes a rapid suppression of the
critical temperature as is observed experimentally.Comment: 9 pages, 5 figure
Magnetic and Orbital States and Their Phase Transition of the Perovskite-Type Ti Oxides: Strong Coupling Approach
The properties and mechanism of the magnetic phase transition of the
perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle
distortion, are studied theoretically by using the effective spin and
pseudospin Hamiltonian with strong Coulomb repulsion. It is shown that the
A-type antiferromagnetic (AFM(A)) to ferromagnetic (FM) phase transition occurs
as the Ti-O-Ti bond angle is decreased. Through this phase transition, the
orbital state changes only little whereas the spin-exchange coupling along the
c-axis is expected to change from positive to negative nearly continuously and
approaches zero at the phase boundary. The resultant strong two-dimensionality
in the spin coupling causes rapid suppression of the critical temperature, as
observed experimentally. It may induce large quantum fluctuations in this
region.Comment: 13 pages, 15 figure
Various series expansions for a Heisenberg antiferromagnet model for SrCu(BO)
We use a variety of series expansion methods at both zero and finite
temperature to study an antiferromagnetic Heisenberg spin model proposed
recently by Miyahara and Ueda for the quasi two-dimensional material
SrCu(BO). We confirm that this model exhibits a first-order quantum
phase transition at T=0 between a gapped dimer phase and a gapless N\'eel phase
when the ratio of nearest and next-nearest neighbour interactions is
varied, and locate the transition at . Using longer series we are
able to give more accurate estimates of the model parameters by fitting to the
high temperature susceptibility data.Comment: RevTeX, 13 figure
Field dependent thermodynamics and Quantum Critical Phenomena in the dimerized spin system Cu2(C5H12N2)2Cl4
Experimental data for the uniform susceptibility, magnetization and specific
heat for the material Cu2(C5H12N2)2Cl4 (abbreviated CuHpCl) as a function of
temperature and external field are compared with those of three different
dimerized spin models: alternating spin-chains, spin-ladders and the bilayer
Heisenberg model. It is shown that because this material consists of weakly
coupled spin-dimers, much of the data is insensitive to how the dimers are
coupled together and what the effective dimensionality of the system is. When
such a system is tuned to the quantum critical point by application of a field,
the dimensionality shows up in the power-law dependences of thermodynamic
quantities on temperature. We discuss the temperature window for such a quantum
critical behavior in CuHpCl.Comment: Revtex, 5 pages, 4 figures (postscript
Success Rate of Embolization for Type II Endoleaks at a Major Tertiary Referral Center
Objective: The rise of endovascular aneurysm repair (EVAR) as the preferred treatment for abdominal aortic aneurysm (AAA) has introduced endoleaks as a major complication following AAA repair. The objective of this study is to assess the outcomes associated with endovascular embolization of type II endoleaks after EVAR. Methods: The institutional Radiology database at our tertiary referral hospital was queried for type II endoleak during the period 2006-2018. A retrospective chart review was then carried out. Only patients who underwent intervention for isolated type 2 endoleaks were analyzed. The primary outcome was success of the endoleak repair as determined by cessation of growth (i.e., ≤5mm change in diameter over follow-up period) of the native aneurysm sac. Patient outcomes for each failure of the above criterion were also collected. Other data pertaining to the location of endoleak, type of occlusion performed, type of embolic agent used, type of endograft used for EVAR, and incidence of aneurysm rupture were collected as secondary outcomes.Results:During this period 41 patients were treated for type II endoleaks. Demographics are shown in table 1. Cessation of growth was achieved in 28/41 (68.3%) of the patients after one embolization procedure. In 13/41 (31.7%) of patients, growth of the native aneurysm sac continued. Of the patients whose aneurysms continued to grow, 61.5% (8/13) did not undergo a second embolization. The remaining 38.5% (5/13) underwent a second embolization.Patient outcomes for both of these groups are presented in table II. None of the patients were found to have ruptured their aneurysm sac during follow-up after embolization. None of gender, race, the embolization site, or method of embolization were associated with embolization failure. Conclusions: Embolization of type II endoleaks is associated with a cessation of growth in the majority of cases and seems to be protective regarding the risk of aneurysm sac rupture. Future studies and additional follow-up will be important to elucidate the most significant risk factors for expansion and/or rupture of the endovascularly repaired abdominal aneurysm.Table I: Demographics for patients with type II endoleaks who underwent endovascular embolizationVariableValue Age (years +/- sd)75.66 +/- yearsAverage follow-up (months)62.65 monthsSex (%)71.7% male28.3% femaleRace (%)77.7% white17.8% black4.4% otherInflow vessel (%)43.2% lumbar only36.4% IMA only20.5% mixEmbolization site (%)40.5% vessel only14.3% cavity only20.5% mixEmbolization type (%)66.7% coil9.5% glue23.8% mixTable II: Outcomes for patients with continued growth after embolizationThose that did no undergo further embolizationThose that underwent a second embolization 3 were found to have type III endoleak and were successfully repaired with lining of the graft.2 whose aneurysm sac ceased growing. 2 who declined further treatment. 2 whose aneurysm sac continued to grow with persistent evidence of endoleak.1 who died from non-vascular complications. 1 who was lost to follow-up. 1 who is scheduled future surgical repair. 1 who was lost to follow-up.https://scholarlycommons.henryford.com/merf2019clinres/1026/thumbnail.jp
Role of a Lateral Orbital Frontal Cortex-Basolateral Amygdala Circuit in Cue-Induced Cocaine-Seeking Behavior
Cocaine addiction is a disease characterized by chronic relapse despite long periods of abstinence. The lateral orbitofrontal cortex (lOFC) and basolateral amygdala (BLA) promote cocaine-seeking behavior in response to drug-associated conditioned stimuli (CS) and share dense reciprocal connections. Hence, we hypothesized that monosynaptic projections between these brain regions mediate CS-induced cocaine-seeking behavior. Male Sprague-Dawley rats received bilateral infusions of a Cre-dependent adeno-associated viral (AAV) vector expressing enhanced halorhodopsin 3.0 fused with a reporter protein (NpHR-mCherry) or a control AAV (mCherry) plus optic fiber implants into the lOFC (Experiment 1) or BLA (Experiment 2). The same rats also received bilateral infusions of a retrogradely transported AAV vector expressing Cre recombinase (Retro-Cre-GFP) into the BLA (Experiment 1) or lOFC (Experiment 2). Thus, NpHR-mCherry or mCherry expression was targeted to lOFC neurons that project to the BLA or to BLA neurons that project to the lOFC in different groups. Rats were trained to lever press for cocaine infusions paired with 5-s CS presentations. Responding was then extinguished. At test, response-contingent CS presentation was discretely coupled with optogenetic inhibition (5-s laser activation) or no optogenetic inhibition while lever responding was assessed without cocaine/food reinforcement. Optogenetic inhibition of lOFC to BLA, but not BLA to lOFC, projections in the NpHR-mCherry groups disrupted CS-induced reinstatement of cocaine-seeking behavior relative to (i) no optogenetic inhibition or (ii) manipulations in mCherry control or (iii) NpHR-mCherry food control groups. These findings suggest that the lOFC sends requisite input to the BLA, via monosynaptic connections, to promote CS-induced cocaine-seeking behavior
Anharmonic double-phonon excitations in the interacting boson model
Double- vibrations in deformed nuclei are analyzed in the context of
the interacting boson model. A simple extension of the original version of the
model towards higher-order interactions is required to explain the observed
anharmonicities of nuclear vibrations. The influence of three- and four-body
interactions on the moments of inertia of ground- and -bands, and on
the relative position of single- and double- bands is studied
in detail. As an example of a realistic calculation, spectra and transitions of
the highly -anharmonic nuclei Dy, Er, and Er
are interpreted in this approach.Comment: 38 pages, TeX (ReVTeX). 15 ps figures. Submitted to Phys. Rev.
Epidemic space
The aim of this article is to highlight the importance of 'spatiality' in understanding the materialization of risk society and cultivation of risk sensibilities. More specifically it provides a cultural analysis of pathogen virulence (as a social phenomenon) by means of tracing and mapping the spatial flows that operate in the uncharted zones between the microphysics of infection and the macrophysics of epidemics. It will be argued that epidemic space consists of three types of forces: the vector, the index and the vortex. It will draw on Latour's Actor Network Theory to argue that epidemic space is geared towards instability when the vortex (of expanding associations and concerns) displaces the index (of finding a single cause)
The Effect of the Pairing Interaction on the Energies of Isobar Analog Resonances in Sb and Isospin Admixture in Sn Isotopes
In the present study, the effect of the pairing interaction and the isovector
correlation between nucleons on the properties of the isobar analog resonances
(IAR) in Sb isotopes and the isospin admixture in Sn
isotopes is investigated within the framework of the quasiparticle random phase
approximation (QRPA). The form of the interaction strength parameter is related
to the shell model potential by restoring the isotopic invariance of the
nuclear part of the total Hamiltonian. In this respect, the isospin admixtures
in the Sn isotopes are calculated, and the dependence of the
differential cross section and the volume integral for the
Sn(He,t)Sb reactions at E(He) MeV occurring by the excitation
of IAR on mass number A is examined. Our results show that the calculated value
for the isospin mixing in the Sn isotope is in good agreement with Colo
et al.'s estimates , and the obtained values for the volume integral
change within the error range of the value reported by Fujiwara et al.
(535 MeV fm). Moreover, it is concluded that although the
differential cross section of the isobar analog resonance for the (He,t)
reactions is not sensitive to pairing correlations between nucleons, a
considerable effect on the isospin admixtures in isotopes can be
seen with the presence of these correlations.Comment: 16 pages, 5 EPS figures and 2 tables, Late
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