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Manufacturer-retailer relationships are often cited as an important determinant in product distribution. By coordinating the channel and aligning incentives, relationships can significantly affect both manufacturers’ and retailers’ profits and contribute to market concentration. However, empirical evidence is scarce because relationships are usually trade secrets. I study how beer manufacturers leverage their relationships with retailers to promote new products in the U.S. hard cider market. I present novel empirical evidence of mutual preferential treatments between manufacturers and retailers in assortment choices and wholesale pricing. I interpret the finding as pair-specific relationships sustained through repeated interactions, and use industry regulations on trade and wholesale pricing to address alternative mechanisms, including non-linear contracts. I estimate a structural model of consumer demand, retail and wholesale pricing, and assortment that incorporates the relationships. The results show that the relationships increase Anheuser-Busch InBev’s and MillerCoors’ new cider availability by 17.7% and 7.2%, respectively, and present a double win to both the manufacturers and retailers.

This study aimed to investigate the protective effects and underlying mechanism of seaweed polysaccharide (SWP) on intestinal epithelial barrier dysfunction induced by E. coli in an IPEC-J2 model. A preliminary study was done to screen optimum SWP concentrations by cell viability, cytotoxicity, apoptosis and proliferation evaluation. The regular study was conducted to evaluate the protective effects of SWP against E. coli challenge via the analysis of transepithelial electrical resistance (TEER), tight junction proteins, NF-κB signalling pathway, proinflammatory cytokines and the E. coli adhesion and invasion. Our results show that 4 h E. coli challenge down-regulated tight junction proteins expression, decreased TEER, activated NF-κB signalling pathway and increased proinflammatory response, which indicates that the E. coli infection model was well-established. Pre-treatment with 240 μg/ml SWP for 24 h alleviated the 4 h E. coli -induced intestinal epithelial barrier dysfunction, as evidenced by the up-regulated expression of Occludin, Claudin-1 and ZO-1 at both mRNA and protein level and the increased TEER of IPEC-J2 cells. Pre-incubation with 240 μg/ml SWP for 24 h inhibited the activation of the NF-κB signalling pathway by 4 h E. coli challenge, including the decreased mRNA expression of TLR-4, MyD88, IκBα, p-65, as well as the reduced ratio of protein expression of p-p65/p65. Also, pre-treatment with 240 μg/ml SWP for 24 h decreased proinflammatory response (IL-6 and TNF-α) induced by 4 h E. coli challenge and decreased the E. coli adhesion and invasion. In conclusion, SWP mitigated intestinal barrier dysfunction caused by E. coli through NF-κB pathway in IPEC-J2 cells and 240 μg/ml SWP exhibited better effect. Our results also provide a fundamental basis for SWP in reducing post-weaning diarrhoea of weaned piglets, especially under E. coli -infected or in-feed antibiotic-free conditions.

Background: Long noncoding RNAs (lncRNAs) play important roles in essential biological processes. However, our understanding of lncRNAs as competing endogenous RNAs (ceRNAs) and their responses to nitrogen stress is still limited.Results: Here, we surveyed the lncRNAs and miRNAs in maize inbred line P178 leaves and roots at the seedling stage under high-nitrogen and low-nitrogen conditions using lncRNA-Seq and small RNA-Seq. A total of 894 differentially expressed lncRNAs and 38 different miRNAs were identified. Co-expression analysis found two lncRNAs and four lncRNA-targets could competitively combine with ZmmiR159 and ZmmiR164, respectively. To dissect the genetic regulatory by which lncRNAs might enable adaptation to limited nitrogen availability. An association mapping panel containing a high-density single–nucleotide polymorphism (SNP) array (56,110 SNPs) combined with variable LN resistance-related phenotypes obtained from hydroponics was used for a genome-wide association study (GWAS). By combining GWAS and RNA-Seq, 170 differently expressed lncRNAs within the range of significant markers were screened. Moreover, 40 consistently LN-responsive genes including those involved in glutamine biosynthesis and nitrogen acquisition in root were identified. Transient expression assays in Nicotiana benthamiana demonstrated LNC_002923 could inhabit ZmmiR159-guided cleavage of Zm00001d015521. Conclusions: These lncRNAs containing trait-associated significant SNPs could consider to be related to root development and nutrient utilization. Taken together, the results of our study can provide new insights into the potential regulatory roles of lncRNAs in response to LN stress, and give valuable information for further screening of candidates as well as the improvement of maize regarding LN-responsive resistance.

Phosphorus deficiency is one of the major factors limiting plant growth and grain yield. Improving plant tolerance to Pi deficiency through genetic mechanism is an important source to increase grain yield. In this study, bioinformatics analysis, expression, and natural variation in ZmNAC134 gene with low Pi tolerant traits were analyzed under low Pi conditions. A total of 177 diverse heterotic groups of maize inbreds were used to identify the nucleotide diversity and alleles of ZmNAC134, which plays a vital role in the regulation of root architecture in response to Pi deficiency evolutionary results showed that ZmNAC134 has 3 homologous genes and these genes have one exon and conserved domain. The phenotypic traits showed significant difference for each of the 22 traits under deficient and sufficient Pi conditions. A total of 27 SNPs were identified in the coding region of ZmNAC134 and no InDels among 177 inbred lines. Among 27 SNPs, a total of 8 sites were highly significantly associated with multiple traits of low Pi tolerant trait index at − log10 P = 3.43. Although, 7 sites under Pi normal and 9 sites under Pi deficient conditions, of which four synonymous sites (position S24, S82, S164, and S1037) were associated with diverse number of traits in low Pi and normal Pi conditions and LD was not tight among these sites. Furthermore, the expression pattern was compared between Pi tolerant 178 and Pi sensitive 9782 inbred lines. ZmNAC134 was highly up-regulated in the roots and leaves of Pi tolerant 178 inbred line at 3 days, 7 days, and 9 days in roots and 7 days and 12 days in leaves while down-regulated in roots and leaves of Pi sensitive 9782 inbred line. In addition, protein encoded by ZmNAC134 was located in both nucleus and cytoplasm. Our findings provide the new insight of ZmNAC134 gene involved in low Pi stress and responsible against low Pi condition and the significant association of polymorphic loci with traits could be helpful to find out the molecular marker for genetic resources for further molecular maize breeding program.

In this paper, a high-gain, low radar cross-section (RCS) and dual-frequency microstrip antenna is designed. The radome with a symmetrical two-layer frequency selective surface (FSS) is adopted to achieve the RCS reduction in a wide range of frequencies while maintaining the radiation characteristics. The FSS structure used in this work is a 5 × 5 array, composed of two layers of metal patches printed on both sides of the F4B substrate (e r = 2.65 and the thickness is 1.0mm). The associated simulation results show that the S parameter is less affected by the new antenna after loading the radome. The gain of the antenna is increased by 5.1 dB, which improves the radiation pattern of the antenna. At the same time, in the range of 2.0–18.0 GHz, the in-band and out-of-band RCS reduction of the antenna is more than 2.0 dB and the maximum reduction attains 15.0 dB.

Aluminum (Al) toxicity is one of the primary factors limiting crop production in acid soils worldwide. The cell wall is the major target of Al toxicity owing to the presence of many Al binding sites. Previous studies have found that XTH, encoding xyloglucan endohydrolase (XEH) and xyloglucan endotransglucosylase (XET), could participate in cell wall extension and affect the binding ability of the cell wall to Al by impeding the activities of these two enzymes. In this study, we found that ZmXTH, an XTH gene in maize, was involved in Al detoxification. The Al-induced up-regulation of ZmXTH occurred in the roots, prominently in the root tips. Additionally, the expression of ZmXTH was specifically induced by Al3+ but no other divalent or trivalent cations. Compared with the wild-type Arabidopsis, ZmXTH overexpressing plants grew more healthy and had decreased Al content in their root and root cell wall after Al stress. Overall, the results suggest that ZmXTH could confer the Al tolerance of transgenic Arabidopsis plants by reducing the Al accumulation in their roots and cell walls.

Energy is the backbone of a country's economy and development. The potential contribution of renewable energy technology to energy stability, climate change mitigation and economic growth is immense. Biogas, is a renewable energy resource and enriched with methane, produced through the breakdown of organic matters (anaerobically). The large quantity of livestock has significant contributions in Pakistan's economy, and also having a high potential for production of biogas. Therefore, this study was conducted in 6 southern districts of Khyber Pakhtunkhwa province of Pakistan, to identify the expected willingness of households for adopting any biogas system. A sum of 360 households (livestock-farmers) was selected for data collection by the procedure of equal allocation. The identification of the influencing factors on the household's willingness to adopt any biogas system was determined through probit analysis. It has been validated from the research outcomes of probit analysis that the selected household's qualification, electricity shortfall on daily basis and its impact on children's education and female work, awareness of the selected household's about the biogas utilization and its benefits as well as the availability of space have demonstrated their significance and relationship with the household's willingness to adopt biogas system. The overall model is statistically significant at 1% significance level and confirmed the impact of socioeconomic features as the prominent factors for the household's decision to adopt a biogas system. This study suggests the public awareness, which has more significant impact on identifying the household's adoption behavior. Similarly, adequate investments both at the private and public level, should be encouraged for promoting biogas technology. At the same time, the government's fiscal policy should be subsidized which will encourage the lower-income populations' participation in adopting and installing biogas plants.

An effective binary catalyst by using tungstic acid (H2WO4) and Ru/C was employed for the hydrodeoxygenation (HDO) of phenolic compounds and raw lignin-oil. H2WO4 was presented as solid at ambient temperature, but it dissolved at high temperature above 100 °C and therefore functioned as an active homogeneous catalyst. This phenomenon resulted in a temperature-controlled phase-transfer behavior in the HDO of phenolic compounds. An efficient HDO performance and an exceptional reusability for guaiacol HDO were presented by this bifunctional catalyst, which can be reused more than 10 times with guaiacol conversion and cyclohexane selectivity over 90%. The comparison of traditional liquid organic and mineral acids, as well as solid acids, with H2WO4 confirmed the outstanding catalytic performance of H2WO4 and highlighted the advantages of H2WO4 as a homogeneous catalyst. Besides guaiacol, other phenolic compounds including various monomers and dimers all exhibited good HDO results, with 100% conversion and cycloalkanes selectivity. Moreover, the raw lignin-oil can be efficiently deoxygenated under the catalysis of this bifunctional catalyst. 99.3% content of hydrocarbons was obtained in the upgraded lignin-oil, which was promising to be used as fuel directly. This catalytic system has great potential for the industrial application of lignin-oil upgrade.

At present, urban computing and intelligence has become an important topic in the research field of artificial intelligence. On the other hand, computer vision as a crucial bridge between urban world and artificial intelligence is playing a key role in urban computing and intelligence. Conventional particle filter is derived from Karman filter, which theoretically based on Monte Carlo method. Sequential importance resampling (SIR) is implemented in conventional particle filter to avoid the degeneracy problem. In order to overcome the shortcomings of the resampling algorithm in the traditional particle filter, we proposed an optimized particle filter using the maximum variance weight segmentation resampling algorithm in this paper, which improved the performance of particle filter. Compared with the traditional particle filter algorithm, the experimental results show that the proposed scheme outperforms in terms of computational consumption and the accuracy of particle tracking. The final experimental results proved that the quality of the maximum variance weight segmentation method increased the accuracy and stability in motion trajectory tracking tasks.

Phosphorus (P) is required for numerous developmental processes, such as flowering and reproduction, in maize (Zea mays L.). It is also an essential nutrient in fertilizers to sustain high yields in farmlands with insufficient available phosphate, particularly in acid soils in China. Flowering time is a key factor influencing the adaptation of maize to the local environment and is associated with high yields. However, few studies have focused on the genetic characteristics of flowering time under low phosphate conditions. In this study, a recombinant inbred line (RIL) population derived from a cross between X178 and 9782 was evaluated for three flowering time traits under two phosphates (Pi) levels at four locations. We found that low phosphate significantly delayed the flowering stage of maize and proposed the hypothesis of “Phosphorus Accumulation Effect”. Mixed-model-based composite interval mapping was used to dissect the genetic basis of the flowering time traits. A total of 41 quantitative trait loci (QTL) was identified for the three flowering time traits through four procedures. Among these 41 QTL, 38 focused on four hot regions, including bin 2.02, bin 2.03, bin 5.04, and bin 6.01. These regions and linked markers should be the targets for fine mapping, map-based cloning, and marker-assisted selection of flowering time and phosphate utilization efficiency.

We study the effects of positive and negative advertising in presidential elections. We develop a model to disentangle these effects on voter turnout and candidate choice. The central empirical challenges are highly correlated and endogenous advertising quantities that are measured with error. To address these challenges, we construct a large set of potential instruments, including interactions with incumbency that we demonstrate provide the critical identifying variation, and apply machine-learning causal inference methods. Using data from the 2000 and 2004 U.S. presidential elections, we find that positive and negative ads play fundamentally different roles. Negative ads are more effective at driving relative candidate shares, whereas positive ads stimulate turnout. These results indicate that a candidate geographically targeting tone trades off local relative share gains and local increases in turnout for localities with a strong base. Counterfactual simulations, where the candidates adjust the quantity of positive and negative advertising while budgets remain fixed, indicate that ad tone alone can impact the outcome of close elections. Our analysis also provides potential explanations as to why past studies have produced mixed findings on both ad-tone and turnout effects. This paper was accepted by Matthew Shum, marketing. Supplemental Material: The data and online appendix are available at https://doi.org/10.1287/mnsc.2022.4347 .

Metal particle size and metal dispersion significantly influence the catalyst activity, and an efficient catalytic upgrade of bio-oil to high-quality liquid fuel is always difficult. Herein, a high dispersed Ru/SiO2-ZrO2 catalyst was prepared by polyol reduction method, which exhibited a high catalytic activity on hydrodeoxygenation (HDO) of the phenolic compounds and pyrolysis lignin-oil. As a model compound, guaiacol had a conversion of 99.9% and a cyclohexane selectivity of 96.7% at the temperature of 240 °C. This polyol Ru/SiO2-ZrO2 catalyst had a good recyclability in the guaiacol HDO. No significant decrease on the catalytic activity was presented after continuous 5 runs, and the conversion kept close to 100% and the selectivity of cyclohexane kept above 88%. Several common phenolic compounds also enabled to be turned into corresponding cycloalkanes efficiently. The high Ru dispersion and the large amount of strong acid sites in the polyol Ru/SiO2-ZrO2 are the main reasons for the good catalytic performances. The synergetic effects between high dispersed metal site and strong acid site lead to a promoted efficiency in the HDO process to form the cycloalkanes. This active catalyst was also applicable to the upgrade of pyrolysis lignin-oil. After reaction, the content of hydrocarbons in the lignin-oil increased from 16.2% to 86.1%, and guaiacols and other oxygenated compounds were almost disappeared. The upgraded lignin-oil has potential to be used as high-quality fuels directly.

Nitrogen (N) is the most important macronutrient for plant growth and development. Hence, understanding genetic architectures and functional genes involved in the response to N deficiency can greatly facilitate the development of low-N-tolerant cultivars. In this study, we collected 212 quantitative trait loci (QTL) of agronomically important traits under low-N stress conditions in maize. We then identified 21 consensus QTL (cQTL) strongly induced for low-N tolerance after excluding overlapping cQTL containing QTL simultaneously identified in meta-analyses of studies performed under other environmental conditions. Among the 21 cQTL, 30 candidate maize genes were identified from maize large-scale differential expression data derived from analyses of low-N stress, and the 12 most important maize orthologs were identified using homologous BLAST analyses of genes with known functions in N use efficiency in model plants. Furthermore, maize orthologs associated with low-N tolerance and metabolism were also predicted using large-scale expression data from other model plants. The present genetic loci and candidate genes indicate the molecular mechanisms of low-N tolerance in maize and may provide information for QTL fine mapping and molecular marker-assisted selection.

To develop genetic markers associated with tolerance to low phosphorus, we identified candidate phosphate starvation responsive (PSR) genes and developed their intron length polymorphism (ILP) markers in maize on a genome-wide scale. Based on the known plant PSR genes, 161 candidate PSR genes were identified. Of these genes, 138 genes contained at least one intron and were then used to develop 606 PSR-ILP markers by designing PCR primers to the intron-flanking exonic regions. PCR evaluation was performed on 43 randomly selected PSR-ILP markers in 30 maize inbred lines. Of the primers, 88.4% amplified stable and pure products in all maize inbred lines, and 53.5% of the markers showed ILP, with PIC values ranging from 0.06 to 0.80. The result of clustering analysis of the 30 maize inbred lines, based on the polymorphism of 23 ILP markers, suggests that the ILP markers developed in this study are not only efficient for genetic diversity analysis but also potentially useful for marker assisted selection for tolerance to low phosphorus.

In the present study, Pd nanoparticles supported on either holey graphene sheets incorporating boron oxides (Pd/BG) or unmodified holey graphene sheets (Pd/G) are prepared through a heat treatment and impregnation method. The synthesized Pd/BG and Pd/G are characterized by Raman, XRD, TEM, XPS and tested as electrocatalysts for formic acid electrooxidation. Pd/G shows sluggish activity towards HCOOH oxidation while Pd/BG shows obviously enhanced catalytic activity and stability. We propose that the smaller Pd particle size and electron transfer caused by incorporation of boron oxides BxOy in the graphene sheets contributes to the improved electrocatalytic performance. Keywords: HCOOH electrooxidation, BxOy, Graphene sheets, Electron transfer

A novel approach to generating ultra-wideband (UWB) impulses based on a Mach–Zehnder modulator (MZM) and a Fabry–Perot semiconductor optical amplifier (FP-SOA) is proposed and demonstrated. Both the carrier dynamic behavior of SOA and the feedback of FP cavity are exploited to generate a pair of polarity-reversed doublet-like impulses. Simulations and experiments are carried out to verify the UWB generation. In the experiment, the fractional bandwidths of the negative-doublet-like and the positive-doublet-like impulses are 100% and 108%, respectively. The bit error rate (BER) performance of the UWB before and after a span of 19-km standard single mode fiber (SSMF) transmission is also investigated and error-free performance can be achieved for each condition. Finally the UWB wireless transmission over a span of 10 cm is investigated.

We propose and experimentally demonstrate a microwave photonic filter based on an electro-optic phase modulator (EOPM) and a Fabry–Perot semiconductor optical amplifier (FP-SOA). A microwave photonic filter with a single passband between 0 and 40 GHz is obtained. The center frequency, the −3 dB bandwidth and the −30 dB bandwidth of the microwave photonic filter are 18.3, 3.184 and 4.005 GHz respectively. Correspondingly, the shape factor, which is defined as the ratio of the −30 dB bandwidth to the −3 dB bandwidth, is 1.26, and the Q factor, which is defined as the ratio of center frequency to the −3 dB bandwidth of the microwave passband, is 5.75. The achieved microwave passband can be fitted by an 8th order super-Gaussian shape.

Radon and its progeny, lung carcinogens recognized by International Agency for Research on Cancer (IARC) and World Health Organization(WHO), are often obtained to high concentrations in underground space. Based on its decay law, radon and its progeny with bound and unbound state will cause serious damage on health. At present, several common mitigation methods had been taken to eliminate Rn in the indoor air. However, the environment of underground space often limits the effect of these facilities. Both electrostatic field and filtration are mature technologies in the field of atmosphere purification. Combined with these two different technologies, the electrostatic-filtration radon progeny eliminator is an effective equipment which can eliminate radon and its progeny indirectly. The method is an effective complement to the construction anti-radon technology and ventilation radon elimination technology, and also it is an essential way to solve the problem of radon damage in the underground space.

We propose and experimentally demonstrate two simple solutions for power-efficient ultra-wideband (UWB) radio frequency (RF) system assisted by an electrical bandpass filter (EBPF). In the first solution, any optical Gaussian pulse with enough bandwidth is transmitted over optical fiber link, and then converted to a power-efficient UWB pulse by an EBPF with a passband of 3.1–10.6 GHz. The transmission and modulation of UWB signal is processed in optical domain, whereas the generation of UWB is processed in electrical domain. Both UWB modulations of on-off keying (OOK) and binary phase shift keying (BPSK) are experimentally demonstrated. In the second solution, the EBPF is used to convert any electrical waveform to a power-efficient UWB pulse. Then the electrical UWB pulse is converted to an optical UWB pulse with a Mach-Zehnder modulator (MZM), and then distributed over long haul fiber link. These two solutions embody the advantages of both low-loss longhaul transmission of optical fiber and mature electrical circuits. And the millimeter-wave UWB signal is also demonstrated.

Multifunctional microwave photonic filters (MWPFs) have potential applications in flexible and various microwave signal processing. The authors propose and demonstrate a MWPF, including all-pass filter, band-pass filter and notch filter based on a single fibre Bragg grating. A high Q band-pass filter with a Q factor of 235 and a rejection ration exceeding 30 dB, and a notch filter with a flat top and a rejection ratio exceeding 25 dB are experimentally achieved.

We theoretically and experimentally demonstrate a novel scheme of bandwidth-variable ultra-wideband (UWB) monocycle generation, using a semiconductor-optical-amplifier (SOA)-based nonlinear optical loop mirror (NOLM). In our scheme, the probe light is split into two parts by the NOLM, and both of them are phase modulated by the pump light due to the cross-phase modulation in the SOA. An extra phase difference between these two parts is also introduced by tuning the polarization controller within the loop. When both parts interfere at the NOLM output port, the phase modulation is converted to the intensity modulation with a UWB monocycle waveform. In addition, the bandwidth of the UWB spectrum is variable by tuning the optical delay line within the loop.

We theoretically and experimentally demonstrate a scheme to implement bipolar millimeter-wave (MMW) ultrawideband (UWB) monocycles using a nonlinear optical loop mirror (NOLM). A 20-GHz optical clock as the probe light and a Gaussian pulse as the pump light are launched into the NOLM for cross-phase modulation (XPM). At the reflection and transmission ports of the NOLM, a pair of polarity-reversed MMW-Gaussian pulses is generated due to constructive and destructive interferences. They are then mixed with proper time delay and orthogonal polarization states. Thus, a photonic MMW-UWB monocycle is obtained. By adjusting the time delay between the reflection and transmission ports of the NOLM, bipolar MMW-UWB pulses are generated.

We experimentally demonstrate an arbitrary-order bandwidth-tunable differentiator using a programmable optical pulse shaper, which is based on spatial diffraction and liquid crystal modulation. The impact of bandwidth of optical pulse shaper on output power and pulsewidth of differentiation is theoretically analyzed. In the experiment, all first-order, second-order, and third-order differentiators with bandwidths of 80, 160, and 320 GHz are obtained with average deviations of less than 4.2%. The differentiation of pseudorandom nonreturn-to-zero (NRZ) signals at 10 and 20 Gbit/s is also discussed.

The finite element static analysis software Algor is used to simulate and analyze the engine connecting rod, and the distribution diagram of the change of stress and displacement is obtained. Theoretically, the force analysis of engine connecting rod is carried out, which provides a necessary theoretical basis for further structural design and optimization of engine connecting rod.

Advances in nano-/microfabrication allow the fabrication of biomimetic substrates for various biomedical applications. In particular, it would be beneficial to control the distribution of cells and relevant biomolecules on an extracellular matrix (ECM)-like substrate with arbitrary micropatterns. In this regard, the possibilities of patterning biomolecules and cells on nanofibrous matrices are explored here by combining inkjet printing and electrospinning. Upon investigation of key parameters for patterning accuracy and reproducibility, three independent studies are performed to demonstrate the potential of this platform for: i) transforming growth factor (TGF)-β1-induced spatial differentiation of fibroblasts, ii) spatiotemporal interactions between breast cancer cells and stromal cells, and iii) cancer-regulated angiogenesis. The results show that TGF-β1 induces local fibroblast-to-myofibroblast differentiation in a dose-dependent fashion, and breast cancer clusters recruit activated stromal cells and guide the sprouting of endothelial cells in a spatially resolved manner. The established platform not only provides strategies to fabricate ECM-like interfaces for medical devices, but also offers the capability of spatially controlling cell organization for fundamental studies, and for high-throughput screening of various biomolecules for stem cell differentiation and cancer therapeutics.

To deal with the short burst signals' combining problem at low Signal-to-Noise Ratio (SNR) in an antenna array, this paper presents a novel combining weights estimate algorithm, called CM-WE, which based on the information mining of the array signals' correlation matrix. Then, it compares CM-WE's performance with SUMPLE algorithm which is commonly used in the Deep Space Network (DSN). Simulation shows that, the CM-WE algorithm has the equal combining SNR gain but a faster convergence speed compared with SUMPLE algorithm, and has advantage over it on the computational complexity.

We propose and demonstrate a scheme to implement photonic multi-shape ultra-wideband (UWB) signal generation using a semiconductor optical amplifier (SOA) based nonlinear optical loop mirror (NOLM). By employing the cross phase modulation (XPM) effect, cross gain modulation (XGM), or both, multi-shape UWB waveforms are generated including monocycle, doublet, triplet, and quadruplet pulses. Both the shapes and polarities of the generated pulses are flexible to adjust, which may be very useful in UWB pulse shape modulation and pulse polarity modulation.

We propose and demonstrate a novel scheme of ultra-wideband (UWB) doublet pulse generation using a semiconductor optical amplifier (SOA) based polarization-diversified loop (PDL) without any assistant light. In our scheme, the incoming gaussian pulse is split into two parts by the PDL, and each of them is intensity modulated by the other due to cross-gain modulation (XGM) in the SOA. Then, both parts are recombined with incoherent summation to form a UWB doublet pulse. Bi-polar UWB doublet pulse generation is demonstrated using an inverted gaussian pulse injection. Moreover, pulse amplitude modulation of UWB doublet is also experimentally demonstrated. Our scheme shows some advantages, such as simple implementation without assistant light and single optical carrier operation with good fiber dispersion tolerance.

We theoretically design a power-efficient ultra-wideband pulse generator by combining three monocycle pulses with different weights. We also experimentally demonstrate a feasible scheme to generate such power-efficient ultra-wideband waveforms using cross-phase modulation in a single semiconductor optical amplifier. The designed ultra-wideband pulse fully satisfies the requirements for the spectral mask specified by the Federal Communications Commission with high power efficiency. In the experiment, a power-efficient ultra-wideband waveform with a pulse duration of 310 ps is achieved, and the power efficiency is greatly improved compared with that of a single monocycle pulse or a mixture of two monocycles.

We experimentally demonstrate an all-optical temporal differentiator using a high resolution optical arbitrary waveform shaper, which is based on liquid crystal on silicon switching elements, and both amplitude and phase of the spectrum are programmable. By designing specific transfer functions with the optical waveform shaper, we obtain first-, second-, and third-order differentiators for periodic pulses with small average errors. We also theoretically analyze the bandwidth limitation of optical waveform shaper on the differentiator.