Nonlinear optical response of the alpha-T-3 model due to the nontrivial topology of the band dispersion

We study the electronic contribution to the nonlinear optical response of the α-T3 model. This model is an interpolation between a graphene (α = 0) and dice (α = 1) lattice. Using a second-quantized formalism, we calculate the first- and third-order responses for a range of α and chemical potential values as well as considering a band gap in the first-order case. Conductivity quantization is observed for the first-order, while higher-order harmonic generation is observed in the third-order response with the chemical potential determining which applied field frequencies both quantization and harmonic generation occur at. We observe a range of experimentally accessible critical fields between 102-106 V/m with dynamics depending on α, μ, and the applied field frequency. Our results suggest an α-T3-like lattice could be an ideal candidate for use in terahertz devices

Etanercept treatment for extended oligoarticular juvenile idiopathic arthritis, enthesitis-related arthritis, or psoriatic arthritis

To describe the 6-year safety and efficacy of etanercept (ETN) in children with extended oligoarticular juvenile idiopathic arthritis (eoJIA), enthesitis-related arthritis (ERA), and psoriatic arthritis (PsA) METHODS: Patients who completed the 2-year, open-label, phase III CLinical Study In Pediatric Patients of Etanercept for Treatment of ERA, PsA, and Extended Oligoarthritis (CLIPPER) were allowed to enroll in its 8-year long-term extension (CLIPPER2). Children received ETN at a once-weekly dose of 0.8 mg/kg, up to a maximum dose of 50 mg/week. Efficacy assessments included the JIA core set of outcomes, the JIA American College of Rheumatology response criteria (JIA-ACR), and the Juvenile Arthritis Disease Activity Score (JADAS). Efficacy data are reported as responder analyses using a hybrid method for missing data imputation and as observed cases. Safety assessments included treatment-emergent adverse events (TEAEs).Out of 127 patients originally enrolled in CLIPPER, 109 (86%) entered CLIPPER2. After 6 years of trial participation (2 years in CLIPPER and 4 years in CLIPPER2), 41 (32%) patients were still taking ETN, 13 (11%) entered the treatment withdrawal phase after achieving low/inactive disease (of whom 7 had to restart ETN), 36 (28%) discontinued treatment for other reasons but are still being observed, and 37 (29%) discontinued treatment permanently. According to the hybrid imputation analysis, proportions of patients achieving JIA ACR90, JIA ACR100, and JADAS inactive disease after the initial 2 years of treatment were 58%, 48%, and 32%, respectively. After the additional 4 years, those proportions in patients who remained in the trial were 46%, 35%, and 24%. Most frequently reported TEAEs [n (%), events per 100 patient-years] were headache [28 (22%), 5.3], arthralgia [24 (19%), 4.6], and pyrexia [20 (16%), 3.8]. Number and frequency of TEAEs, excluding infections and injection site reactions, decreased over the 6-year period from 193 and 173.8, respectively, during year 1 to 37 and 61.3 during year 6. A single case of malignancy (Hodgkin's lymphoma) and no cases of active tuberculosis, demyelinating disorders, or deaths were reported.Open-label etanercept treatment for up to 6 years was safe, well tolerated, and effective in patients with eoJIA, ERA, and PsA.ClinicalTrials.gov: CLIPPER, NCT00962741 , registered 20 August, 2009, CLIPPER2, NCT01421069 , registered 22 August, 2011

Proinsulin Atypical Maturation and Disposal Induces Extensive Defects in Mouse Ins2+/Akita β-Cells

Because of its low relative folding rate and plentiful manufacture in β-cells, proinsulin maintains a homeostatic balance of natively and plentiful non-natively folded states (i.e., proinsulin homeostasis, PIHO) through the integration of maturation and disposal processes. PIHO is susceptible to genetic and environmental influences, and its disorder has been critically linked to defects in β-cells in diabetes. To explore this hypothesis, we performed polymerase chain reaction (PCR), metabolic-labeling, immunoblotting, and histological studies to clarify what defects result from primary disorder of PIHO in model Ins2+/Akita β-cells. We used T antigen-transformed Ins2+/Akita and control Ins2+/+ β-cells established from Akita and wild-type littermate mice. In Ins2+/Akita β-cells, we found no apparent defect at the transcriptional and translational levels to contribute to reduced cellular content of insulin and its precursor and secreted insulin. Glucose response remained normal in proinsulin biosynthesis but was impaired for insulin secretion. The size and number of mature insulin granules were reduced, but the size/number of endoplasmic reticulum, Golgi, mitochondrion, and lysosome organelles and vacuoles were expanded/increased. Moreover, cell death increased, and severe oxidative stress, which manifested as increased reactive oxygen species, thioredoxin-interacting protein, and protein tyrosine nitration, occurred in Ins2+/Akita β-cells and/or islets. These data show the first clear evidence that primary PIHO imbalance induces severe oxidative stress and impairs glucose-stimulated insulin release and β-cell survival as well as producing other toxic consequences. The defects disclosed/clarified in model Ins2+/Akita β-cells further support a role of the genetic and stress-susceptible PIHO disorder in β-cell failure and diabetes

QUANTUM TRANSPORT IN TOPOLOGICAL MATERIALS

In this thesis, we examine five main transport properties: nonlinear optical conductivity, self-focusing, thermionic conductivity, photogalvanic conductivity and magneto-optical conductivity across a number of topological materials. In the case of Weyl, Dirac and gapped semimetals as well as the α-T3 model, minimal coupling Hamiltonia are able to capture multiple topological phases through the same equation. This allows us to survey nonlinear optical conductivity, self-focusing and thermionic conductivity for the nodal semimetals whilst only nonlinear conductivity is studied for the α-T3 lattice. Shift current generation and circularly polarised photogalvanic conductivity are uncovered for a symmetry broken nodal ring material whilst twisted bilayer graphene is the system in which we study both nonlinear and magneto-optical conductivity

Superconducting pair-breaking under intense sub-gap terahertz radiation

We study the effect of a strong and low frequency (ω \u3c Δ, the superconducting gap) electrical field on a superconducting state. It is found that the superconducting gap decreases with the field intensity and wavelength. The physical mechanism for this dependence is the multiphoton absorption by a superconducting electron. By constructing the state of a superconducting electron dressed by photons, we determined the dependence of the superconducting gap on E / ω and temperature. We show that the critical temperature is determined by the parameter E / ω which is distinct from that induced by the heating effect. The result is consistent with experimental findings. This result can be applied to study terahertz nonlinear superconducting metamaterials

Anisotropic thermionic response of Weyl semimetals with application in thermionic cooling

© 2020 Author(s). We demonstrate that Weyl semimetals can exhibit intriguing thermionic properties. The emission current varies significantly in systems with different Weyl point separation, the key topological parameter of such materials. The emission is highly anisotropic along directions parallel and perpendicular to the Weyl point separation. For large separations, emission is higher along the perpendicular direction. However, for smaller separations, there exists a changeover temperature at which the dominant emission direction changes from parallel to perpendicular when increasing temperature. The optimal cooling efficiency of a single barrier device can approach 80% of the theoretical limit in the perpendicular direction, 5% greater than a conventional parabolic material. Our results suggest that this class of material has potential applications in thermionic cooling and power generation

Strong tunable photomixing in semi-Dirac materials in the terahertz regime

We demonstrate a strong and anisotropic photomixing effect in an electronic system whose energy–momentum dispersion is parabolic in the direction and linear in the direction, such as a TiO2/VO2 multilayered structure. The third-order photoresponses along the linear and parabolic directions have been analyzed and determined quantitatively. We have found a remarkable tunability of the mixing efficiency along the parabolic direction by a small electric field in the linear direction, up to two orders of magnitude. In the terahertz (THz) regime, the third-order response is comparable to the linear response under an applied field of 103–104  V/cm. Additionally, the nonlinear response persists at room temperature. The results may have applications where different current responses are required along different directions in the THz regime. We demonstrate a strong and anisotropic photomixing effect in an electronic system whose energy–momentum dispersion is parabolic in the direction and linear in the direction, such as a TiO2/VO2 multilayered structure. The third-order photoresponses along the linear and parabolic directions have been analyzed and determined quantitatively. We have found a remarkable tunability of the mixing efficiency along the parabolic direction by a small electric field in the linear direction, up to two orders of magnitude. In the terahertz (THz) regime, the third-order response is comparable to the linear response under an applied field of 103–104  V/cm. Additionally, the nonlinear response persists at room temperature. The results may have applications where different current responses are required along different directions in the THz regime

Tunable strong photo-mixing in Weyl semimetals

We study both the temperature and band-gap dependence of the first-and third-order intraband conductivities of a Weyl semimetal (WSM) as well as the resultant critical field. By a semiclassical model we further explore how different chemical potentials, cone separations, field geometries, and finite relaxation times affect photoresponse. We determine that the band-gap variation is characterized by the Weyl cone separation and observe significant thermal enhancement of the nonlinear response. Universal behaviors of both the linear and nonlinear response have also been observed under certain conditions. Coupled with experimentally accessible critical field values of 104-105 V m-1, our results give strong impetus for the use of WSMs as tunable photo-mixers