Dirac point plays a crucial role in regulating electronic properties of topological semimetals. In two dimensions, the manipulation of Dirac points can spur a transition from Dirac semimetal through ...semi-Dirac phase to a gapped phase. Across such a so-called Lifshitz transition, we find that the quantum interference corrections to the conductivity δσxx and δσyy are always negative, giving rise to a weak localization behavior. The ratio δσxx/δσyy undergoes a transition from linear to parabolic dependence on the merging parameter across the Lifshitz transition, which leads to a crossover of the temperature dependence of the inverse inelastic scattering time 1/τɛ from ∼ T to ∼ T ln (T0/T). This fingerprint behavior can be readily tested experimentally through merging Dirac points in two-dimensional lattices. This work presents an alternative perspective to understand weak localization through Lifshitz transition.
Our previous studies showed that neutrophil infiltration and activation plays an important role in the pathogenesis of abdominal aortic aneurysms (AAA). However, there is a lack of noninvasive, ...inflammatory cell-specific molecular imaging methods to provide early diagnosis of AAA formation. Formyl peptide receptor 1 (FPR1) is rapidly upregulated on neutrophils during inflammation. Therefore, it is hypothesized that the use of cinnamoyl-F-(D)L-F-(D)L-F-K (cFLFLF), a PEGylated peptide ligand that binds FPR1 on activated neutrophils, would permit accurate and noninvasive diagnosis of AAA via single-photon emission computed tomography (SPECT) imaging.
Male C57BL/6 (wild-type) mice were treated with topical elastase (0.4 U/mL type 1 porcine pancreatic elastase) or heat-inactivated elastase (control), and aortic diameter was measured by video micrometry. Comparative histology was performed on Day 14 to assess neutrophil infiltration in aortic tissue. We performed near-infrared fluorescence imaging using c-FLFLF-Cy7 probe on Days 7 and 14 postelastase treatment and measured fluorescence intensity ex vivo in excised aortic tissue. A separate group of animals were injected with 99mTc-c-FLFLF 2 h before SPECT imaging on Day 14 using a SPECT/computed tomography/positron emission tomography trimodal scanner. Coexpression of neutrophils with c-FLFLF was also performed on aortic tissue by immunostaining on Day 14.
Aortic diameter was significantly increased in the elastase group compared with controls on Days 7 and 14. Simultaneously, a marked increase in neutrophil infiltration and elastin degradation as well as decrease in smooth muscle integrity were observed in aortic tissue after elastase treatment compared with controls. Moreover, a significant increase in fluorescence intensity of c-FLFLF-Cy7 imaging probe was also observed in elastase-treated mice on Day 7 (approximately twofold increase) and Day 14 (approximately 2.5-fold increase) compared with respective controls. SPECT imaging demonstrated a multifold increase in signal intensity for 99mTc-cFLFLF radiolabel probe in mice with AAA compared with controls on Day 14. Immunostaining of aortic tissue with c-FLFLF-Cy5 demonstrated a marked increase in coexpression with neutrophils in AAA compared with controls.
cFLFLF, a novel FPR1 ligand, enables quantifiable, noninvasive diagnosis and progression of AAAs. Clinical application of this inflammatory, cell-specific molecular probe using SPECT imaging may permit early diagnosis of AAA formation, enabling targeted therapeutic interventions and preventing impending aortic rupture.
Three different tensor network (TN) optimization algorithms are employed to accurately determine the ground state and thermodynamic properties of the spin-3/2 kagome Heisenberg antiferromagnet. We ...found that the sqrt3×sqrt3 state (i.e., the state with 120^{∘} spin configuration within a unit cell containing 9 sites) is the ground state of this system, and such an ordered state is melted at any finite temperature, thereby clarifying the existing experimental controversies. Three magnetization plateaus (m/m_{s}=1/3,23/27, and 25/27) were obtained, where the 1/3-magnetization plateau has been observed experimentally. The absence of a zero-magnetization plateau indicates a gapless spin excitation that is further supported by the thermodynamic asymptotic behaviors of the susceptibility and specific heat. At low temperatures, the specific heat is shown to exhibit a T^{2} behavior, and the susceptibility approaches a finite constant as T→0. Our TN results of thermodynamic properties are compared with those from high-temperature series expansion. In addition, we disclose a quantum phase transition between q=0 state (i.e., the state with 120^{∘} spin configuration within a unit cell containing three sites) and sqrt3×sqrt3 state in a spin-3/2 kagome XXZ model at the critical point Δ_{c}=0.54. This study provides reliable and useful information for further explorations on high-spin kagome physics.
Mn-PBP is discovered to be the first ferromagnetic 2D MOF with the Shastry-Sutherland lattice and the predicted Curie temperature is 105 K.
Inspired by the successful synthesis of ...Fe/Cu-5,5′-bis(4-pyridyl)(2,2′-bipirimidine) (PBP), a family of two-dimensional (2D) metal–organic frameworks (MOFs) with the Shastry-Sutherland lattice,
i.e.
, transition metal (TM)-PBP (TM = Cr, Mn, Fe, Co, Ni, Cu, Zn) has been systematically investigated by means of first-principles density functional theory calculations and Monte Carlo simulations. Mn-PBP is discovered to be the first ferromagnetic 2D MOF with the Shastry-Sutherland lattice and the Curie temperature is predicted to be about 105 K, while Fe-PBP, TM-PBP (TM = Cr, Co, Ni) and TM-PBP (TM = Cu, Zn) are found to be stripe-order antiferromagnetic, magnetic-dimerized and nonmagnetic, respectively. The electronic structure calculations reveal that TM-PBP MOFs are semiconductors with band gaps ranging from 0.12 eV to 0.85 eV, which could be easily modulated by various methods. Particularly, Mn-PBP would exhibit half-metallic behavior under compressive strain or appropriate electron/hole doping and a Mn-PBP based spintronic device has been proposed. This study not only improves the understanding of the geometric, electronic and magnetic properties of the 2D TM-PBP MOF family, but also provides a novel spin lattice playground for the research of 2D magnetic systems, which has diverse modulating possibilities and rich potential applications.
Few large-animal models exist for the study of aortic aneurysms. β-Aminopropionitrile (BAPN) is a compound known to cause aortic aneurysms by inhibiting lysyl oxidase, a collagen cross-linking ...enzyme. It is hypothesized that BAPN plus aneurysm induction surgery would result in significant aneurysm formation in swine with biologic properties similar to human disease.
Initial experiments were performed in uncastrated male swine not treated with BAPN (surgery alone). Subsequently, uncastrated male swine were fed BAPN (0.15 g/kg) for 7 days before undergoing surgery; the infrarenal aorta was circumferentially dissected and measured, balloon dilated, and perfused with elastase (500 units) and type I collagenase (8000 units), with extraluminal elastase application. In the BAPN groups, daily BAPN feedings continued until swine harvest at postoperative days 7, 14, and 28.
Swine undergoing surgery alone (n = 12) had significantly less dilation at 28 days compared with BAPN + surgery swine (51.9% ± 29.2% 0%-100% vs 113.5% ± 30.2% 52.9%-146.2%; P < .0003). Mean aortic dilation in animals undergoing treatment with surgery and BAPN was 86.9% ± 47.4% (range, 55.6%-157.1%), 105.4% ± 58.1% (50%-133.3%), and 113.5% ± 30.2% (52.9%-146.2%) at 7, 14, and 28 days, respectively. In the BAPN + surgery group, significant elastolysis was present at all time points, whereas aortic wall collagen content was not significantly different. Smooth muscle cells were significantly depleted at 14 and 28 days, and M1 macrophages were increased at 14 and 28 days (P < .05, all). Matrix metalloproteinase 2 was elevated at 7 days (P < .05). Multiple proinflammatory cytokines were elevated within the aortic wall of BAPN + surgery swine.
BAPN plus surgery resulted in significantly larger aortic aneurysms than surgery alone and was critical to aneurysm formation in this novel swine model. Hallmarks of human disease, such as elastin fragmentation, smooth muscle cell depletion, macrophage infiltration, matrix metalloproteinase activation, and proinflammatory cytokine expression, were observed in BAPN-treated swine. This model better parallels many of the characteristics of human AAAs and may be suitable for prehuman drug trials.
Translation of abdominal aortic aneurysm (AAA) models from small animals to large animals is critical for device development and further elucidation of AAA pathogenesis mechanisms. We have developed a reproducible large-animal model of AAA disease with >100% dilation in swine. The swine AAA have a histology and inflammatory milieu similar to human, and it is hoped that further work using this model will expand our understanding of this disease.
Due to the potential applications in low-power-consumption spintronic devices, the quantum anomalous Hall effect (QAHE) has attracted tremendous attention in past decades. However, up to now, the ...QAHE was only observed experimentally in topological insulators with Chern numbers C = 1 and 2 at very low temperatures. Here, we propose three two-dimensional stable kagome ferromagnets Co3 Pb3 S2 , Co3 Pb3 Se2 , and Co3 Sn3 Se2 that can realize the QAHE with high Chern number of | C | = 3 . Monolayers Co3 Pb3 S2 , Co3 Pb3 Se2 , and Co3 Sn3 Se2 possess the large band gap of 70, 77, and 63 meV with Curie temperature TC of 51, 42, and 46 K, respectively. By constructing a heterostructure Co3 Sn3 Se2/MoS2 , its TC is enhanced to 60 K and the band gap remains at about 60 meV due to the tensile strain of 2% at the interface. For the bilayer compound Co6 Sn5 Se4 , it becomes a half metal, with a relatively flat plateau in its anomalous Hall conductivity corresponding to | C | = 3 near the Fermi level. Our results provide topological nontrivial systems of kagome ferromagnetic monolayers and heterostructures possessing the QAHE with high Chern number | C | = 3 and large band gaps.
Ion transport processes in mixtures of 1-methyl-3-pentylimidazolium tetrafluoroborate (MPIBF4) and lithium tetrafluoroborate (LiBF4) are characterized using conductivity and pulsed field gradient NMR ...measurements at various temperatures. The viscosity, ionic conductivity, molar conductivity, and self diffusion coefficient in neat MPIBF4 and LiBF4-doped MPIBF4 change with temperature following the Vogel-Tamman-Fulcher equation, and the density shows a linear decrease. The ionic conductivity and the self-diffusion coefficient of each ionic specie decrease with increasing concentration of LiBF4 in LiBF4-doped MPIBF4. The correlation between ionic conductivity and viscosity is based on the classical Walden rule, the α□ values of neat MPIBF4 and LiBF4-doped MPIBF4 calculated from the slopes of the Walden plots are compared to those calculated from the ratio of activation energies for viscosity and molar conductivity (Ea,Λ/Ea,η). The comparison of activation energies of the reciprocal of viscosity, the ionic conductivity, and individual ion diffusion against the LiBF4 concentration is also studied.
In this work we propose to simulate many-body thermodynamics of infinite-size quantum lattice models in one, two, and three dimensions, in terms of few-body models of only O(10) sites, which we coin ...as quantum entanglement simulators (QES's). The QES is described by a temperature-independent Hamiltonian, with the boundary interactions optimized by the tensor network methods to mimic the entanglement between the bulk and environment in a finite-size canonical ensemble. The reduced density matrix of the physical bulk then gives that of the infinite-size canonical ensemble under interest. We show that the QES can, for instance, accurately simulate varieties of many-body phenomena, including finite-temperature crossover and algebraic excitations of the one-dimensional spin liquid, the phase transitions and low-temperature physics of the two- and three-dimensional antiferromagnets, and the crossovers of the two-dimensional topological system. Our work provides an efficient way to explore the thermodynamics of intractable quantum many-body systems with easily accessible systems.
To evaluate the PR to RR interval ratio (PR/RR, heart rate-adjusted PR) as a prognostic marker for long-term ventricular arrhythmias and cardiac death in patients with implantable cardioverter ...defibrillator (ICDs) and cardiac resynchronization therapy with defibrillators (CRT-D).
We retrospectively analyzed data from 428 patients who had an ICD/CRT-D equipped with home monitoring. Baseline PR and RR interval data prior to ICD/CRT-D implantation were collected from standard 12-lead electrocardiograph, and the PR/RR was calculated. The primary endpoint was appropriate ICD/CRT-D treatment of ventricular arrhythmias (VAs), and the secondary endpoint was cardiac death.
During a mean follow-up period of 38.8 ± 10.6 months, 197 patients (46%) experienced VAs, and 47 patients (11%) experienced cardiac death. The overall PR interval was 160 ± 40 ms, and the RR interval was 866 ± 124 ms. Based on the receiver operating characteristic curve, a cut-off value of 18.5% for the PR/RR was identified to predict VAs. A PR/RR ≥ 18.5% was associated with an increased risk of VAs hazard ratio (HR) = 2.243, 95% confidence interval (CI) = 1.665-3.022,
< 0.001) and cardiac death (HR = 2.358, 95%CI = 1.240-4.483,
= 0.009) in an unadjusted analysis. After adjustment in a multivariate Cox model, the relationship remained significant among PR/RR ≥ 18.5%, VAs (HR = 2.230, 95%CI = 1.555-2.825,
< 0.001) and cardiac death (HR = 2.105, 95%CI = 1.101-4.025,
= 0.024.
A PR/RR ≥ 18.5% at baseline can serve as a predictor of future VAs and cardiac death in ICD/CRT-D recipients.
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