Electrically Tunable Reflective Metasurfaces with Continuous and Full-Phase Modulation for High-Efficiency Wavefront Control at Visible Frequencies.

All-dielectric optical metasurfaces can locally control the amplitude and phase of light at the nanoscale, enabling arbitrary wavefront shaping. However, lack of postfabrication tunability has limited the true potential of metasurfaces for many applications. Here, we utilize a thin liquid crystal (LC) layer as a tunable medium surrounding the metasurface to achieve a phase-only spatial light modulator (SLM) with high reflection in the visible frequency, exhibiting active and continuous resonance tuning with associated 2π phase control and uncoupled amplitude. Dynamic wavefront shaping is demonstrated by programming 96 individually addressable electrodes with a small pixel pitch of ∼1 µm. The small pixel size is facilitated by the reduced LC thickness, strongly suppressing cross-talk among pixels. This device is used to demonstrate dynamic beam steering with a wide field-of-view and high absolute diffraction efficiencies. We believe that our demonstration may help realize next-generation, high-resolution SLMs, with wide applications in dynamic holography, tunable optics, and light detection and ranging (LiDAR), to mention a few.

High resolution multispectral spatial light modulators based on tunable Fabry-Perot nanocavities.

Spatial light modulators (SLMs) are the most relevant technology for dynamic wavefront manipulation. They find diverse applications ranging from novel displays to optical and quantum communications. Among commercial SLMs for phase modulation, Liquid Crystal on Silicon (LCoS) offers the smallest pixel size and, thus, the most precise phase mapping and largest field of view (FOV). Further pixel miniaturization, however, is not possible in these devices due to inter-pixel cross-talks, which follow from the high driving voltages needed to modulate the thick liquid crystal (LC) cells that are necessary for full phase control. Newly introduced metasurface-based SLMs provide means for pixel miniaturization by modulating the phase via resonance tuning. These devices, however, are intrinsically monochromatic, limiting their use in applications requiring multi-wavelength operation. Here, we introduce a novel design allowing small pixel and multi-spectral operation. Based on LC-tunable Fabry-Perot nanocavities engineered to support multiple resonances across the visible range (including red, green and blue wavelengths), our design provides continuous 2π phase modulation with high reflectance at each of the operating wavelengths. Experimentally, we realize a device with 96 pixels (~1 µm pitch) that can be individually addressed by electrical biases. Using it, we first demonstrate multi-spectral programmable beam steering with FOV~18° and absolute efficiencies exceeding 40%. Then, we reprogram the device to achieve multi-spectral lensing with tunable focal distance and efficiencies ~27%. Our design paves the way towards a new class of SLM for future applications in displays, optical computing and beyond.

Near unity transmission and full phase control with asymmetric Huygens' dielectric metasurfaces for holographic projections.

Huygens' metasurfaces are transparent arrays of nanostructures that enable phase-front manipulation. This is achieved by simultaneous excitation of electric dipole (ED) and magnetic dipole (MD) resonances with equal amplitudes and phases in the constituent meta-atoms. In usual designs, the size changes of the meta-atoms, necessary to map the phase front, can detune the overlapping of ED and MD resonances, decreasing the transmission and limiting the operating bandwidth. In this report, we demonstrate that ED and MD resonances can be almost perfectly tuned together over a large wavelength range, keeping their spectral overlap, in a silicon metasurface by using anisotropic meta-atoms. In particular, we show near-unity transmission (>95% in simulations) and 2π phase control in a wavelength range from 760 to 815 nm using cuboidal nanoantennas. Using this concept, we also experimentally demonstrate clear reconstruction from holograms of a single metasurface spanning the near infrared and the whole visible spectral range.

Efficient visible light modulation based on electrically tunable all dielectric metasurfaces embedded in thin-layer nematic liquid crystals.

All-dielectric metasurfaces have attracted attention for highly efficient visible light manipulation. So far, however, they are mostly passive devices, while those allowing dynamic control remain a challenge. A highly efficient tuning mechanism is immersing the metasurface in a birefringent liquid crystal (LC), whose refractive index can be electrically controlled. Here, an all-dielectric tunable metasurface is demonstrated based on this concept, operating at visible frequencies and based on TiO2 nanodisks embedded in a thin LC layer. Small driving voltages from 3~5 V are sufficient to tune the metasurface resonances, with an associated transmission modulation of more than 65%. The metasurface optical responses, including the observed electric and magnetic dipole resonance shifts as well as the interfacial anchoring effect of the LC induced by the presence of the nanostructures, are systematically discussed. The dynamic tuning observed in the transmission spectra can pave the way to dynamically tunable metasurface devices for efficient visible light modulation applications.

Phase-only transmissive spatial light modulator based on tunable dielectric metasurface.

Rapidly developing augmented reality, solid-state light detection and ranging (LIDAR), and holographic display technologies require spatial light modulators (SLMs) with high resolution and viewing angle to satisfy increasing customer demands. Performance of currently available SLMs is limited by their large pixel sizes on the order of several micrometers. Here, we propose a concept of tunable dielectric metasurfaces modulated by liquid crystal, which can provide abrupt phase change, thus enabling pixel-size miniaturization. We present a metasurface-based transmissive SLM, configured to generate active beam steering with >35% efficiency and a large beam deflection angle of 11°. The high resolution and steering angle obtained provide opportunities to develop the next generation of LIDAR and display technologies.

Transgenic increase in the ß-endorphin concentration in cerebrospinal fluid alleviates morphine-primed relapse behavior through the µ opioid receptor in rats.

BACKGROUND: Opioid-primed relapse is a global burden. Although current strategies have improved, optimal therapy is urgently needed. METHODS: A recombinant adenovirus (Ad-NEP) expressing ß-endorphin (ß-EP) was designed and injected intracerebroventricularly (icv) into the right lateral ventricle in rats. Spatial and temporal ß-EP expression in the lateral ventricle wall, subventricular zone and adjacent choroid plexus and the ß-EP concentration in the cerebrospinal fluid (CSF) were observed during a 21-day period. A morphine priming-induced conditioned place preference (CPP) rat model was established. The ß-EP-ir neuron counts, CSF ß-EP concentration, and CPP score, which were used to evaluate morphine-primed reinstatement following extinction, were recorded 7 days after the icv injection. Additionally, the rats were pretreated with the irreversible µ opioid receptor antagonist ß-funaltrexamine (ß-FNA) and the selective κ opioid receptor antagonist nor-binaltorphimine (nor-BNI) to identify the receptor-dependent mechanism. RESULTS: Both peak ß-EP expression in target neurons and the peak CSF ß-EP concentration occurred 7 to 8 days after Ad-NEP icv injection. The sustainable increase in the CSF ß-EP concentration was correlated with a decrease in the CPP score 7 days after the Ad-NEP icv injection. Furthermore, reinstatement was almost reversed by ß-FNA pretreatment 24 hours before the behavioral test, but nor-BNI had little effect. CONCLUSION: The increasing cerebrospinal fluid ß-endorphin concentrations showed that the therapeutic effect on opioid relapse occurred predominantly through a µ opioid receptor-dependent mechanism. The Ad-NEP adenovirus can be considered an alternative therapy for opioid relapse.

Efficacy and Safety of Opioids for the Prevention of Etomidate-Induced Myoclonus: A Meta-Analysis.

Etomidate is a widely used hypnotic drug for induction of general anesthesia and sedation, especially in elderly patients and hemodynamically unstable patients. Myoclonus, however, is the most prominent problem during induction of anesthesia with etomidate. Many agents have been used to prevent it and opioid is one of them. This meta-analysis was to evaluate effects of opioids pretreatment for preventing etomidate-induced myoclonus. We searched the PubMed, EMBASE, and the Cochrane Library databases and published studies in English updated to September 2015. Randomized controlled trials of opioids versus placebo/control in patients were included. We evaluated the prophylactic effect of opioids on etomidate-induced myoclonus. All statistical analysis was performed using RevMan 5.2 software. Nine randomized controlled trials involving 604 participants were included. The results indicated that compared with placebo/control, opioids allow more patients to experience no myoclonic movements after etomidate injection [risk ratio (RR) 2.76, 95% confidence interval (CI) 1.75-4.37, P < 0.0001]. The numbers of patients with mild myoclonus [(RR) 0.53, 95% (CI) 0.36-0.78, P = 0.001], moderate myoclonus [(RR) 0.36, 95% (CI) 0.23-0.55, P < 0.00001], and severe myoclonus [(RR) 0.20, 95% (CI) 0.08-0.52, P = 0.0009] after etomidate injection were significantly decreased with the pretreatment of opioids. This meta-analysis suggests that pretreatment with opioids before injecting etomidate was effective for preventing etomidate-induced myoclonus and can reduce the intensity of myoclonus without any adverse effects.

Fast distributed large-pixel-count hologram computation using a GPU cluster.

Large-pixel-count holograms are one essential part for big size holographic three-dimensional (3D) display, but the generation of such holograms is computationally demanding. In order to address this issue, we have built a graphics processing unit (GPU) cluster with 32.5 Tflop/s computing power and implemented distributed hologram computation on it with speed improvement techniques, such as shared memory on GPU, GPU level adaptive load balancing, and node level load distribution. Using these speed improvement techniques on the GPU cluster, we have achieved 71.4 times computation speed increase for 186M-pixel holograms. Furthermore, we have used the approaches of diffraction limits and subdivision of holograms to overcome the GPU memory limit in computing large-pixel-count holograms. 745M-pixel and 1.80G-pixel holograms were computed in 343 and 3326 s, respectively, for more than 2 million object points with RGB colors. Color 3D objects with 1.02M points were successfully reconstructed from 186M-pixel hologram computed in 8.82 s with all the above three speed improvement techniques. It is shown that distributed hologram computation using a GPU cluster is a promising approach to increase the computation speed of large-pixel-count holograms for large size holographic display.

Effect of recombinant adenovirus coding for endomorphin-2 on neuropathic pain in rats.

OBJECTIVE: To construct a transgene expressing human endomorphin-2 by linking the signal peptide of mouse nerve growth factor (PN) to a human endomorphin-2 DNA sequence containing a short linker recognized by the protease FURIN and test the analgesic effect of endomorphin-2 on neuropathic pain. METHODS: The transgene was inserted into the cosmid pAxCAwt to generate PN-EM-2-pAxCAwt. The recombinant adenovirus Ad-PNEM2 was packaged and propagated in HEK293 cells. After the Ad-PNEM2-infected NIH3T3 cells had been cultured, protein expression was examined by immunofluorescence and ELISA. A CCI rat model was constructed and the Ad-PNEM2 was administered intrathecally. The rats' pain thresholds (PWL) were measured and the presence of endomorphin-2 in the cerebrospinal fluid was confirmed through ELISA. RESULTS: The Ad-PNEM2 expressed endomorphin-2 smoothly and abundantly in NIH3T3 cells at a significantly higher rate than the viral control (P<0.01) or blank control (P<0.01). The expressed endomorphin-2 was mainly observed in the cytoplasm. The concentration of endomorphin-2 in the cerebrospinal fluid increased 1 day after injection and peaked between 7 and 14 days after injection. After injection, PWL approached normal levels in the operated study group. No significant change was observed in the control groups. There was a significant correlation between PWL and endomorphin-2 level (r = 0.944, P<0.001). CONCLUSION: The constructed human endomorphin-2 transgene was expressed effectively, and endomorphin-2 expressed by the recombinant adenovirus altered the threshold to thermal stimulus and showed good analgesic effect.

Suppression of acute morphine withdrawal syndrome by adenovirus-mediated ß-endorphin in rats.

BACKGROUND: Endogenous ß-endorphin (ß-EP) in the central nervous system (CNS) is decreased upon opioid addiction. The current study examined whether exogenous ß-EP, delivered using an adenoviral vector into the CNS could attenuate morphine withdrawal syndrome in rats. METHODS: The model of opioid-dependent rats was set up by receiving subcutaneous injection of morphine using an escalating regimen for 6days (5, 10, 20, 40, 50, 60mg/kg, three times/day). The adenovirus mediated ß-EP gene was constructed based on our previous work. The ilea of opioid-dependent rats were isolated and treated with the supernatant of Ad-NEP. The basic and naloxone-induced (4µm/l) contractions of dependent ilea were recorded. The Ad-NEP was injected into the left lateral ventricle of the addition rats. The expression of the ß-EP gene was verified by radioimmunoassay of the cerebrospinal fluid (CSF) and immunocytochemistry for ß-EP. Withdrawal syndrome was evaluated after intraperitoneal injection of naloxone. RESULTS: The contractions of dependent ilea were attenuated with supernatant containing ß-EP expressed by Ad-NEP. Injection of the Ad-NEP resulted in significant increases in ß-EP level in the CSF and ß-EP-positive neurons. Rats receiving adenovirus carrying the ß-EP gene had significantly less severe withdrawal symptoms upon naloxone challenge. CONCLUSIONS: Exogenous ß-EP mediated by adenovirus could attenuate withdrawal syndrome in morphine-dependent rats.

Intrathecal siRNA against Toll-like receptor 4 reduces nociception in a rat model of neuropathic pain.

BACKGROUND: Neuropathic pain is characterized by hyperalgesia, allodynia and spontaneous pain. It often occurs as a result of injury to peripheral nerves, dorsal root ganglions (DRG), spinal cord, or brain. Recent studies have suggested that Toll-like receptor 4 (TLR4) might play a role in neuropathic pain. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we investigated the role of TLR4 in a rat chronic constriction injury (CCI) model and explored the feasibility of treating neuropathic pain by inhibiting TLR4. Our results demonstrated that intrathecal siRNA-mediated suppression of TLR4 attenuated CCI-induced mechanical allodynia and thermal hyperalgesia through inhibiting the activation of NF-kappaB p65 and production of proinflammatory cytokines (e.g., TNF-alpha and IL-1 beta). CONCLUSIONS/SIGNIFICANCE: These findings suggest that suppression of TLR4 mediated by intrathecally administered siRNA may be a new strategy for the treatment of neuropathic pain.

Regular effective hologram regions for computer generated holography.

An effective hologram region (EHR) based approach is presented to speed up the computation of computer generated holograms (CGHs). The object space is predivided into subspaces, and an EHR for each subspace is predefined according to the maximum spatial frequency of interference fringes, light diffraction efficiency, and CGH binarization effect. To compute the hologram of an object, the object points are first categorized according to which subspace they are located in, and then their holograms are calculated using the corresponding EHRs. As each EHR usually takes up only a portion of the hologram plate, the CGH computational load is thus reduced. This new approach is highly suitable for large hologram display systems. In addition, when compared to the reconstructed image using the conventional approach, our experimental results show that more noise can be blocked off and the reconstructed image appears sharper without noticeable brightness reduction.

Baroreflex sensitivity is impaired in patients with obstructive jaundice.

BACKGROUND: Obstructive jaundice is associated with enhanced susceptibility to hypotensive shock, renal failure, and toxic effects of endotoxin, which results in high perioperative morbidity and mortality. Since the normal arterial baroreflex function is necessary for hemodynamic homeostasis and improving survival in sepsis, this study aimed to determine whether baroreflex sensitivity was impaired in jaundiced patients. METHODS: Thirty-five patients with obstructive jaundice scheduled for surgery were included, and 30 nonjaundiced patients served as controls. A modified Oxford pharmacologic technique was used for evaluating baroreflex sensitivity immediately before the surgery. Potential factors that may affect baroreflex sensitivity in jaundice, such as liver biochemistry, plasma concentrations of methionine-enkephalin, atrial natriuretic peptide and nitrate, were also measured. RESULTS: Patients with obstructive jaundice had decreased sensitivity in both the sympathetic and vagal components of the baroreflex, as compared with the controls (P < 0.01). There was a significant inverse correlation between plasma atrial natriuretic peptide concentration and decreased sympathetic baroreflex sensitivity in the jaundiced group (r = -0.44, P = 0.008). CONCLUSIONS: Baroreflex sensitivity is impaired in patients with obstructive jaundice, which may contribute to their enhanced susceptibility to the well-known perioperative complications. The underlying mechanisms for such a change may be associated with an increased level of plasma atrial natriuretic peptide.

Human signal peptide had advantage over mouse in secretory expression.

The signal peptide is a critical component in the secretory expression of protein in eukaryotic cells. It has been verified that the signal peptide of mouse nerve growth factor could mediate the secretory expression of beta-endorphin in cultured non-neuronal cells. Although there is a counterpart of nerve growth factor in human genome, no research about the signal sequence from human genome has been reported. The function of mediating secretory expression is affected by many factors. We assumed that the counterpart from human genome could function as the signal peptide from mouse nerve growth factor does and these two signal sequences had different efficiency in mediating secretory expression of beta-endorphin, but we could not figure out which one had a better function. To validate our hypothesis and give an answer to the question, we constructed two eukaryotic vectors, pcDNA3.1-hEP and pcDNA3.1-mEP, containing human and mouse signal sequences in fusion genes, respectively. RT-PCR showed that the constructed fusion genes were expressed in NIH3T3 cells. We also found that the detected beta-endorphin by the immunofluorescent technique was mainly in the cytoplasm of NIH3T3 cells. The concentration of beta-endorphin in the culture medium by RIA is 280.33 +/- 24.16 (pg/ml) and 191.04 +/- 7.96 (pg/ml) from pcDNA3.1-hEP and pcDNA3.1-mEP, respectively, and there was a significant statistical difference between them (P < 0.05). A difference existed between them and that from blank vector individually (P < 0.01). These findings suggest that our constructed fusion gene containing the signal sequence of human nerve growth factor can be secretorily expressed and the efficiency of the signal peptide from human nerve growth factor is higher than that of mouse signal peptide.

Fast CGH computation using S-LUT on GPU.

In computation of full-parallax computer-generated hologram (CGH), balance between speed and memory usage is always the core of algorithm development. To solve the speed problem of coherent ray trace (CRT) algorithm and memory problem of look-up table (LUT) algorithm without sacrificing reconstructed object quality, we develop a novel algorithm with split look-up tables (S-LUT) and implement it on graphics processing unit (GPU). Our results show that S-LUT on GPU has the fastest speed among all the algorithms investigated in this paper, while it still maintaining low memory usage. We also demonstrate high quality objects reconstructed from CGHs computed with S-LUT on GPU. The GPU implementation of our new algorithm may enable real-time and interactive holographic 3D display in the future.

[Experimental study of compatibility between chondrocytes and allogenic cartilage microparticle acellular tissue matris in vitro].

OBJECTIVE: To construct tissue engineered cartilage using cartilage microparticle acellular tissue matrix (CMACTM) as scaffold. METHODS: To determine the content of hydroxyproline, glycosaminoglycan and DNA of CMACTM prepared from sheep's articular cartilage with multistep enzymic method, and to analyze CMACTM with gross observation, histology and scanning electron microscopy. Allogenic chondrocytes were mixed with CMACTM and cultured in vitro from 0 to 35 days. Observations through inverted microscope, scanning and transmission electron microscope, quantifications of hydroxyproline, glycosaminoglycan and DNA in the composite, cells adhesion rate were applied to analyze the results. RESULTS: The diameter of CMACTM was 0.100-0.154 mm, which contain extracellular matrix only. Hydroxyproline, glycosaminoglycan and DNA quantifications in CMACTM were 204.374 +/- 3.120 microg/mg, 18.302 +/- 2.037 microg/mg and 0.042 +/- 0.013 microg/mg respectively. Allogenic chondrocytes enclosed CMACTM tightly, hydroxyproline, glycosaminoglycan and DNA quantifications in the composite of the two formers increased with difference on 7th day compared with that on 0 day, reached to the peaks on 14th day (hydroxyproline, DNA) and on 21st day (glycosaminoglycan), and retained at a high level on the following days. Cells adhesion rate was 92%. CONCLUSION: Allogenic CMACTM possessed satisfactory biocompatibility for chondrocytes and provided a new scaffold for cartilage tissue engineering.

Deterministic beam fanning in Fe-doped stoichiometric lithium niobate crystals.

We investigated the beam-fanning effect in Fe-doped stoichiometric lithium niobate (Fe:SLN) crystals that were grown by the top-seeded solution growth method. Deterministic beam fanning (DBF) was measured in Z-cut Fe:SLN crystal for incident light propagating along the c+ and c- axes. The dependence of beam-fanning factors on incident power density was also studied. The experimental results of DBF in the Z-cut Fe:SLN crystal were in good agreement with a theoretical simulation based on a two-wave mixing model. The results compared with those for Fe-doped congruent lithium niobate crystals indicate that the beam-fanning process in Fe:SLN is deterministic because of its much-reduced intrinsic density of defects.

[Construction and analysis of in vitro expression of adenovirus/adeno-associated hybrid virus containing the fusion gene of human beta-endorphin].

The fusion gene of human beta-endorphin was cloned into the shuttle plasmid pDC312-AAVEE with the method of molecular bilology. The latter and genomic plasmids were cotransfected into HEK293 to package the Adenovirus/Adeno-associated hybrid virus containing fusion gene of human beta-endorphin. The hybrid virus was identified with the method of PCR. The titer of proliferated virus, after purified, was determined by TCID50. The expression of transgene was studied after the hybrid virus infected the cultured cells, through testing the concentration of expressed product in the culture liquid by ELISA. It was identified that the sequence of fusion gene of human beta-endorphin was correctly inserted into the genome of hybrid virus, and not contaminated by wild type virus. The titer of Ad/AAV-EE is 1.29 x 10(10) PFU/mL after purification. The ascending trend of transgene expression was observed from the 1st to the 14th day, and the protein concentration reached 3141 pg/mL at the 14th day.

[Transferring neurovascular rectus femoris muscle segment for treatment of facial paralysis].

OBJECTIVE: To investigate a new technique for functional treatment of chronic facial paralysis. METHODS: Based on anatomy of intramuscular neurovascular structure in the rectus femoris muscle, 7 consecutive patients with facial paralysis were treated by using a technique of microsurgically free-transferring neurovascular rectus femoris muscle segment to the face in one-stage. Follow-ups were 10 to 24 months. RESULTS: All of the 7 patients showed significantly improvement in the appearance of the oral commissure and oral competence. No complications occurred in the donor site. CONCLUSIONS: The above mentioned technique may have the advantages of preventing the intramuscular nerve and vessel from the surgical injury during splitting the muscle. It could also maintain the transferred muscular segment in a proper tension in the recipient site.

[The neurovascular anatomy and its clinical implication of the rectus femoris muscle].

OBJECTIVE: The objective of this anatomic study was to investigate the intramuscular neurovascular configuration and to evaluate whether the muscle could be split into two functional units in transplantation. METHODS: Ten fresh cadavers and ten preserved cadavers were used in the study. A mixture of lead oxide, gelatin and water was injected to the femoral artery of the fresh cadaver. The rectus femoris muscle with its neurovascular pedicles was dissected and radiographed. RESULTS: Three vascular patterns of the rectus femoris muscle were found in the 40 cadaver legs. The muscle received its blood supply through a single vascular pedicle (12.5%), or a dominant pedicle with 1-2 ramified (80%), or two dominant vascular pedicles (7.5%). CONCLUSIONS: The study provided a detailed description on the intramuscular neurovascular territories of the rectus femoris muscle. Based on the neurovascular supply of the muscle, it is possible to subdivide the muscle into two functional units for segmental muscle transfer.