Design and experimental realization of triple-band electromagnetically induced transparency terahertz metamaterials employing two big-bright modes for sensing applications.

Multi-band electromagnetically induced transparency (EIT) effects have attracted widespread attention due to their great application prospects. However, their realization is mainly based on the coupling of multiple sub-resonators that typically exceed the number of transparency peaks, resulting in complex structural designs and cumbersome preparation procedures. This paper reports a simple design of a terahertz metamaterial that can produce the triple-band EIT effect using two "big-bright" mode coupling of two sub-resonators. The design adopts the classical two-layer structure. A U-shaped split-ring resonator and a fork-shaped resonator form a periodic array on the surface of the flexible organic polymer material. Three transparency peaks around 0.59 THz, 1.07 THz, and 1.34 THz are experimentally realized, and their formation mechanisms are explored. Furthermore, the triple-band EIT metamaterial was prepared by the photolithography technology and characterized by terahertz time-domain spectroscopy. Theoretical simulation results agree well with experimental results. Sensing characteristics and slow light effects of the terahertz metamaterial are further discussed experimentally. The proposed triple-band EIT metamaterial having excellent properties, including thin size, good flexibility, simple and compact structure, and high sensing sensitivity, could provide guidance for the subsequent design and implementation of multifunctional multi-band EIT metamaterials.

Tunable dielectric metasurfaces by structuring the phase-change material.

Metasurfaces have made great progress in the last decade for generating miniature and integrated optical devices. The optical properties of metasurfaces can be tuned dynamically by integrating with phase-change materials. However, the efficiency of tunable metasurfaces remains a bit low, which is a disadvantage for the realistic applications of metasurfaces. Here, we demonstrate the tunable dielectric metasurfaces by structuring the phase-change material Ge2Sb2Te5. The unit cell of metasurface is composed of several Ge2Sb2Te5 nanopillars with different geometric parameters, and the incident light interacts with different nanopillars at diverse phases of Ge2Sb2Te5, leading to various functions. By elaborately arranging the Ge2Sb2Te5 nanopillars, various tunable optical devices have been realized, including tunable beam steering, reconfigurable metalens and switchable wave plate. The refractive direction, focal length and polarization state can be tuned through the phase transition of Ge2Sb2Te5. The phase-change metasurfaces based on Ge2Sb2Te5 nanostructures could be used in cameras, optical microscopy and adaptive optics.

Switchable transmissive and reflective metadevices based on the phase transition of vanadium dioxide.

Metasurfaces have made great progress in the past decade in generating various planar optical devices. However, most metasurfaces exhibit their functions in either reflection mode or transmission mode, with the other mode unutilized. In this work, we demonstrate switchable transmissive and reflective metadevices by combining metasurfaces with vanadium dioxide. The composite metasurface can work as a transmissive metadevice, with one function for vanadium dioxide in the insulating phase, and is changed to a reflective metadevice with another function for vanadium dioxide in the metallic phase. By carefully designing the structures, the metasurface can be switched from a transmissive metalens to a reflective vortex generator, or between a transmissive beam steering and a reflective quarter-wave plate through the phase transition of vanadium dioxide. The switchable transmissive and reflective metadevices have potential applications in imaging, communication, and information processing.

Tunable wave plates based on phase-change metasurfaces.

Wave plates based on metasurfaces have attracted intensive attention over the past decade owing to their compactness and design flexibility. Although various wave plates have been designed, their working wavelengths are fixed once they are made. Here we present a study on tunable wave plates based on phase-change metasurfaces made of Ge2Sb2Te5 nanopillar structures. The Ge2Sb2Te5 nanopillars can work as a high-efficiency transmissive half- or quarter-wave plate depending on their structural parameters. The working wavelength of wave plate can be tuned via the phase transition of Ge2Sb2Te5. Moreover, the polarization state of the transmitted light at a fixed wavelength can be modified by changing the crystallinity of Ge2Sb2Te5. The features suggest that tunable wave plates may have applications in optical modulators, molecular detection, and polarimetric imaging.

Predictive value of microRNA-143 in evaluating the prognosis of patients with hepatocellular carcinoma.

OBJECTIVE: The study aims to evaluate the predictive value of microRNA-143 (miR-143) for the prognosis of patients with hepatocellular carcinoma (HCC). METHODS: Between October 2010 and October 2012, 131 HCC patients were selected as a case group; meanwhile, 122 healthy controls were enrolled as a control group. The miR-143 expression in serum was detected by quantitative real-time polymerase chain reaction (qRT-PCR). These HCC patients were divided into the high miR-143 expression group and the low miR-143 expression group based on the threshold of receiver operating characteristic (ROC) curve. Kaplan-Meier method was applied to analyze the prognosis of HCC patients. RESULTS: MiR-143 exhibited decreased expression in the case group significantly compared to the control group. The areas under the ROC curve (AUC), sensitivity value and specificity value of the miR-143 expression for the diagnosis of HCC were 0.831, 80.30% and 82.40%, respectively. The miR-143 expression was negatively correlated with vascular invasion, TNM staging, tumor recurrence, metastasis and survival of HCC patients. CONCLUSIONS: Our study provides evidence that miR-143 may be negatively correlated with the prognosis of HCC and provides a promising strategy for HCC treatment and prognosis improvement.

Nerve injury-induced tactile allodynia is present in the absence of FOS labeling in retrogradely labeled post-synaptic dorsal column neurons.

The dorsal column pathway consists of direct projections from primary afferents and of ascending fibers of the post-synaptic dorsal column (PSDC) cells. This pathway mediates touch but may also mediate allodynia after nerve injury. The role of PSDC neurons in nerve injury-induced mechanical allodynia is unknown. Repetitive gentle, tactile stimulus or noxious pinch was applied to the ipsilateral hindpaw of rats with spinal nerve ligation (SNL) or sham surgery that had previously received tetramethylrhodamine dextran in the ipsilateral n. gracilis. Both touch and noxious stimuli produced marked increases in FOS expression in other cells throughout all laminae of the ipsilateral dorsal horn after nerve injury. However, virtually none of the identified PSDC cells expressed FOS immunofluorescence in response to repetitive touch or pinch in either the nerve-injured or sham groups. In contrast, labeled PSDC cells expressed FOS in response to ureter ligation and labeled spinothalamic tract (STT) cells expressed FOS in response to noxious pinch. Identified PSDC neurons from either sham-operated or SNL rats did not express immunoreactivity to substance P, CGRP, NPY, PKCY, MOR, the NK1 and the NPY-Y1 receptor. Retrogradely labeled DRG cells of nerve injured rats were large diameter neurons, which expressed NPY, but no detectable CGRP or substance P. Spinal nerve injury sensitizes neurons in the spinal dorsal horn to repetitive light touch but PSDC neurons apparently do not participate in touch-evoked allodynia. Sensitization of these non-PSDC neurons may result in activation of projections integral to the spinal/supraspinal processing of enhanced pain states and of descending facilitation, thus priming the central nervous system to interpret tactile stimuli as being aversive.

An efficient intrathecal delivery of small interfering RNA to the spinal cord and peripheral neurons.

We have developed a highly effective method for in vivo gene silencing in the spinal cord and dorsal root ganglia (DRG) by a cationic lipid facilitated delivery of synthetic, small interfering RNA (siRNA). A siRNA to the delta opioid receptor (DOR), or a mismatch RNA, was mixed with the transfection reagent, i-Fect (vehicle), and delivered as repeated daily bolus doses (0.5 microg to 4 microg) via implanted intrathecal catheter to the lumbar spinal cord of rats. Twenty-four hours after the last injection, rats were tested for antinociception by the DOR selective agonist, [D-Ala(2), Glu(4)]deltorphin II (DELT), or the mu opioid receptor (MOR) selective agonist, [D-Ala(2), N-Me-Phe(4), Gly-ol(5)]enkephalin (DAMGO). Pretreatment with the siRNA, but not the mismatch RNA or vehicle alone, blocked DELT antinociception dose-dependently. The latter was concomitant with a reduction in the spinal immunoreactivity and receptor density of DOR, and in DOR transcripts in the lumbar DRG and spinal dorsal horn. Neither siRNA nor mismatch RNA pretreatment altered spinal immunoreactivity of MOR or antinociception by spinal DAMGO, and had no effect on the baseline thermal nociceptive threshold. The inhibition of function and expression of DOR by siRNA was reversed by 72 hr after the last RNA injection. The uptake of fluorescence-tagged siRNA was detected in both DRG and spinal cord. The low effective dose of siRNA/i-Fect complex reflects an efficient delivery of the siRNA to peripheral and spinal neurons, produced no behavioral signs of toxicity. This delivery method may be optimized for other gene targets.