Efficient removal of sulfamethoxazole by resin-supported zero-valent iron composites with tunable structure: Performance, mechanisms, and degradation pathways.

Nanoscale zero-valent iron loaded polymer-based composites (D201-nZVI) are effective materials for the removal of inorganic contaminants from water. However, the removal efficiency of organic contaminants and the role of the distribution of nZVI in the performance of the composites still remains unclear. Herein, four resin-supported nZVI composites with different nZVI distributions (D1, D2, D3, and D4) were prepared and used for sulfamethoxazole (SMX) degradation. The four composites, D1-D4, demonstrated a high efficiency of SMX removal (99.02%, 94.61%, 89.00%, and 86.28%, respectively, at pH 5.0). In addition, the performance of D201-nZVI only dropped by approximately 10% after five cycles, indicating its strong potential for practical application. On the basis of kinetic and electron spin resonance (ESR) spectral analyses, this study showed that the formation of hydroxyl radicals (⋅OH) and superoxide radicals (⋅O2-) is the main mechanism of SMX degradation. Finally, based on six major degradation intermediates of SMX, five possible degradation pathways were proposed, including the coupling of N-centered radicals, demethylation, the isomerization of isoxazole rings, the oxidation of amino groups, and the S-N bond cleavage in the D201-nZVI system. These results are not only important for better understanding the role of Fe distribution in the removal of SMX but are also crucial for the potential application of D201-nZVI composites with a different Fe distribution in many other scenarios.

High-efficiency microwave photonic harmonic down-conversion with tunable and reconfigurable filtering.

A new optical-frequency comb-based microwave photonic harmonic down-convertor with tunable and reconfigurable filtering is proposed and experimentally demonstrated. The coherent evenly spaced optical carriers offer harmonic down-conversion for ultrahigh radio frequency signals with low-frequency local oscillator, and construct a tunable and reconfigurable bandpass filter for the intermediate-frequency (IF) signal combined with dispersion. This implementation features high conversion efficiency. Experimental results show the filtered output IF signal has a clean spectrum with high quality. Measured conversion loss is 8.3 dB without extra electrical amplification.

A time-domain photonic arbitrary waveform generator.

A time domain photonic arbitrary waveform generator (PAWG) scheme based on multi-wavelength optical differential quadrature phase shift keying modulation in combination with differential detection is proposed and experimentally demonstrated. The time domain method shows advantages of large time-bandwidth product, good flexibility, fast waveform refreshing rate, and high waveform quality over the frequency domain method. In contrast with other proposed time domain PAWGs or photonic digital-to-analog converters, our PAWG proposal shows a greater dynamic range and a larger noise margin due to its bipolar output, and possesses good scalabilities both in resolution and sampling rate. Assisted with the integration technology, this PAWG presents a good prospect for broad range practical applications in future.

Novel 2N bit bipolar photonic digital-to-analog converter based on optical DQPSK modulation coupled with differential detection.

A novel 2N bit bipolar photonic digital-to-analog converter (PDAC) scenario based on the optical differential quadrature phase shift keying (ODQPSK) modulation coupled with differential detection is proposed. Compared with other proposed schemes, this bipolar PDAC has a greater dynamic range and a larger noise margin with good scalabilities both in speed and resolution. We demonstrate a 4 bit PDAC in a proof-of-principle experiment at a sampling rate of 2.5 GS/s.

Reaction of endogenous progenitor cells in a rat model of posttraumatic syringomyelia.

OBJECT: Endogenous stem cells theoretically could replace lost tissue and repair deficits caused by syringes. In this study the authors quantitatively examined 1) whether neural progenitor cells exist in an adult rat model of posttraumatic syringomyelia (PTS); 2) and if so, how long an active population of progenitor cells can persist; 3) whether the cell population's location is associated with the syrinx; 4) the degree of differentiation of the progenitor cells; and 5) the phenotypic fate of the progenitor cells. METHODS: Wistar rats were divided into intact, sham-operated, and experimental syrinx groups. Animals in each group were equally subdivided according to 4 time points: 7, 14, 28, and 56 days post-syrinx induction. Rats in the experimental syrinx group underwent a C-7 and T-1 laminectomy and then received 0.5 µl of a 24-mg/ml quisqualic acid spinal cord injection at the C-8 level to mimic an excitotoxic injury with an initial cyst, and 10 µl of a 250-mg/ml kaolin injection into the subarachnoid space at the C-8 level to create arachnoiditis. The proliferation, distribution, and differentiation of endogenous progenitor cells were identified immunocytochemically. RESULTS: The authors observed a 20-fold increase in progenitor cells excluding inflammatory cells in the 1st 2 weeks post-syrinx induction. The cells persisted for at least 56 days, and 80% of them were located in the gray matter along the border of cysts. They included neural multipotential progenitor cells, oligodendroglial progenitor cells, and astrocytes. CONCLUSIONS: Data in this study provide evidence for proliferation, distribution, and differentiation of endogenous progenitor cells in a model of PTS in adult rats. These progenitor cells proliferate rapidly, extend for long periods, and are mainly located in the gray matter along the border of syringes. Neural multipotential progenitor cells are expected to be associated with reparative and regenerative mechanisms of PTS. Glial cells are involved in the formation of a glial scar barrier that surrounds the syrinx and may prevent cyst enlargement. The authors' findings suggest that neural progenitor cells play a protective role in PTS.

Simultaneous clock recovery and dispersion, OSNR monitoring for 112-Gbit/s NRZ-DQPSK using frequency down-conversion electro-optical phase-locked loop.

A cost effective clock recovery scheme simultaneously providing signal performance monitoring is proposed for high speed electrical time domain multiplexing (ETDM) transmission systems to release the bandwidth requirement on the involved electrical devices. In the scheme, we first convert the clock frequency down in the optical domain using electroptic modulation, and then extract the clock with a phase locked loop (PLL) after photo-detection. All the devices involved are operated at frequencies lower than half of the symbol rate. Furthermore, we use a quadrature phase detector in the PLL to create a monitor signal which characterizes the transmitted signal performance in terms of optical-to-noise ratio (OSNR) and accumulated chromatic dispersion (ACD). This scheme is applied to a 112-Gbit/s none-return-to-zero (NRZ) differential quadrature phase shift keying (DQPSK) system. Experimental results show that the clock can be recovered in a dispersion range of -40 to 40 ps/nm, and the evaluated OSNR, over a range of 18~36 dB, has a deviation smaller than 1 dB compared to the measured one based on the optical spectrum method. The bit error ratio remains below 10(-9) for 12 hours in the back-to-back case and 2 hours after transmission over 100-km standard single mode fiber (SSMF).

Differentiation of endogenous progenitors in an animal model of post-traumatic syringomyelia.

STUDY DESIGN: An in vivo study to examine the differentiation of endogenous neural progenitor cells in an adult rat model of post-traumatic syringomyelia. OBJECTIVE: To quantitatively evaluate the phenotypic fate of endogenous neural progenitor cells in post-traumatic syringomyelia. SUMMARY OF BACKGROUND DATA: Although neural progenitors have been identified in the central nervous system, their differentiation in experimental post-traumatic syringomyelia and possible role in the pathophysiology of this condition have not been investigated. METHODS: Bromodeoxyuridine was used to label proliferating cells in a time-dependent rat model of post-traumatic syringomyelia. Eight neural markers were quantitatively analyzed to phenotype the cellular fate of these cells by double labeling immunohistochemistry. RESULTS: Following syrinx induction, cell proliferation rate increased to 25-115 times that of cells in the intact and sham-operated controls with a peak at day 14 post-injury. In the earliest time points post-syrinx induction, ED1-expressing inflammatory cells formed a significant proportion of the proliferating population. Proliferating neural progenitor cells predominantly differentiated into NG2-expressing immature oligodendrocytes at all stages post-syrinx induction, except the final time point of 56 days. At this time, there was a peak in the number of newly generated astrocytes identified to have developed from labeled proliferating precursor cells. CONCLUSIONS: Endogenous neural progenitors proliferate markedly following induction of post-traumatic syringomyelia which consists of two stages, initial cyst formation and progressive cyst enlargement. During the former stage, macrophages proliferate in situ and contribute to the inflammatory process. The predominant cell type formed from progeny of the induced neural progenitors was characterized to be immature oligodendrocytes. However, during the latter stage of cyst development, there was an increase in astrocytic progeny which may represent an environment more conductive to glial scar formation acting to limit further cyst enlargement.