Non-Hermitian chiral degeneracy of gated graphene metasurfaces.

Non-Hermitian degeneracies, also known as exceptional points (EPs), have been the focus of much attention due to their singular eigenvalue surface structure. Nevertheless, as pertaining to a non-Hermitian metasurface platform, the reduction of an eigenspace dimensionality at the EP has been investigated mostly in a passive repetitive manner. Here, we propose an electrical and spectral way of resolving chiral EPs and clarifying the consequences of chiral mode collapsing of a non-Hermitian gated graphene metasurface. More specifically, the measured non-Hermitian Jones matrix in parameter space enables the quantification of nonorthogonality of polarisation eigenstates and half-integer topological charges associated with a chiral EP. Interestingly, the output polarisation state can be made orthogonal to the coalesced polarisation eigenstate of the metasurface, revealing the missing dimension at the chiral EP. In addition, the maximal nonorthogonality at the chiral EP leads to a blocking of one of the cross-polarised transmission pathways and, consequently, the observation of enhanced asymmetric polarisation conversion. We anticipate that electrically controllable non-Hermitian metasurface platforms can serve as an interesting framework for the investigation of rich non-Hermitian polarisation dynamics around chiral EPs.

Metamaterials for Enhanced Optical Responses and their Application to Active Control of Terahertz Waves.

Metamaterials, artificially constructed structures that mimic lattices in natural materials, have made numerous contributions to the development of unconventional optical devices. With an increasing demand for more diverse functionalities, terahertz (THz) metamaterials are also expanding their domain, from the realm of mere passive devices to the broader area where functionalized active THz devices are particularly required. A brief review on THz metamaterials is given with a focus on research conducted in the authors' group. The first part is centered on enhanced THz optical responses from tightly coupled meta-atom structures, such as high refractive index, enhanced optical activity, anomalous wavelength scaling, large phase retardation, and nondispersive polarization rotation. Next, electrically gated graphene metamaterials are reviewed with an emphasis on the functionalization of enhanced THz optical responses. Finally, the linear frequency conversion of THz waves in a rapidly time-variant THz metamaterial is briefly discussed in the more general context of spatiotemporal control of light.

Prognostic Role of Serum Levels of Uric Acid in Amyotrophic Lateral Sclerosis.

BACKGROUND AND PURPOSE: It has been suggested that oxidative stress is one of the pathomechanisms underlying amyotrophic lateral sclerosis (ALS), and thus antioxidants such as uric acid (UA) that could reduce oxidative stress might be beneficial in the prevention or treatment of this disease. The objective of this study was to prospectively investigate serum UA levels in Korean ALS patients and to relate them to disease progression. METHODS: ALS patients and healthy controls who were individually well-matched for sex, age, and body mass index (BMI) underwent blood testing for serum UA levels, and analyzed whether UA levels were correlated with the disease status of the patients, as defined by the ALS Functional Rating Scale-Revised (ALSFRS-R). RESULTS: The study included 136 ALS patients and 136 matched controls. The UA level was lower in the ALS patients (4.50±1.17 mg/dL, mean±SD) than in the controls (5.51±1.22 mg/dL; p<0.001). Among the ALS patients, the level of UA acid was inversely correlated with the rate of disease progression (decrease in ALSFRS-R score). Kaplan-Meier analysis revealed that a better survival rate was more strongly correlated with top-tertile levels of serum UA than with bottom-tertile levels (log-rank test: p=0.035). CONCLUSIONS: ALS patients had lower serum UA levels than did healthy individuals. UA levels in ALS were negatively correlated with the rate of disease progression and positively associated with survival, suggesting that UA levels contribute to the progression of ALS. UA levels could be considered a biomarker of disease progression in the early phase in ALS patients.

Recombinant human erythropoietin reduces aggregation of mutant Cu/Zn-binding superoxide dismutase (SOD1) in NSC-34 cells.

Human erythropoietin (hEPO) has multiple actions in non-hematopoietic tissues, including neurotrophic, anti-oxidant, anti-apoptotic, and anti-inflammatory effects. To examine the effect of EPO in an vitro model of amyotrophic lateral sclerosis (ALS), we stably overexpressed wild SOD1 and a mutant form, SOD1/G93A, in NSC-34 motoneuron-like cells. Transformants harboring the wild and mutant forms of SOD1 were selected by G418 selection and immunoblot analysis. RT-PCR analysis showed that cox-2 expression was increased in the NSC-34/mSOD1s, and MTT assays and BrdU-ELISAs revealed reduced cell growth and proliferation in the NSC-34/mSOD1 cell line. Incubation with 5 or 10IU/mL rhEPO increased the viability and decreased the cox-2 expression in the dNSC-34/mSOD1s cells. Immunocytochemical staining with anti-SOD1 antibody revealed the presence of aggregates of mSOD1 protein in dNSC-34/mSOD1 cells. Incubation with10IU/mL rhEPO reduced the proportion of cells containing such aggregates. Our findings suggest that the anti-oxidant and anti-inflammatory effects of EPO increase the survival of NSC-34/mSOD1 cells and reduce aggregation of the mutant SOD1 protein.