Vertical organic electrochemical transistors for complementary circuits.

Organic electrochemical transistors (OECTs) and OECT-based circuitry offer great potential in bioelectronics, wearable electronics and artificial neuromorphic electronics because of their exceptionally low driving voltages (<1 V), low power consumption (<1 µW), high transconductances (>10 mS) and biocompatibility1-5. However, the successful realization of critical complementary logic OECTs is currently limited by temporal and/or operational instability, slow redox processes and/or switching, incompatibility with high-density monolithic integration and inferior n-type OECT performance6-8. Here we demonstrate p- and n-type vertical OECTs with balanced and ultra-high performance by blending redox-active semiconducting polymers with a redox-inactive photocurable and/or photopatternable polymer to form an ion-permeable semiconducting channel, implemented in a simple, scalable vertical architecture that has a dense, impermeable top contact. Footprint current densities exceeding 1 kA cm-2 at less than ±0.7 V, transconductances of 0.2-0.4 S, short transient times of less than 1 ms and ultra-stable switching (>50,000 cycles) are achieved in, to our knowledge, the first vertically stacked complementary vertical OECT logic circuits. This architecture opens many possibilities for fundamental studies of organic semiconductor redox chemistry and physics in nanoscopically confined spaces, without macroscopic electrolyte contact, as well as wearable and implantable device applications.

General room-temperature Suzuki-Miyaura polymerization for organic electronics.

π-Conjugated polymers (CPs) have broad applications in high-performance optoelectronics, energy storage, sensors and biomedicine. However, developing green and efficient methods to precisely synthesize alternating CP structures on a large scale remains challenging and critical for their industrialization. Here a room-temperature, scalable and homogeneous Suzuki-Miyaura-type polymerization reaction is developed with broad generality validated for 24 CPs including donor-donor, donor-acceptor and acceptor-acceptor connectivities, yielding device-quality polymers with high molecular masses. Furthermore, the polymerization protocol significantly reduces homocoupling structural defects, yielding more structurally regular and higher-performance electronic materials and optoelectronic devices than conventional thermally activated polymerizations. Experimental and theoretical studies reveal that a borate transmetalation process plays a key role in suppressing protodeboronation, which is critical for large-scale structural regularity. Thus, these results provide a general polymerization tool for the scalable production of device-quality CPs with alternating structural regularity.

Temperature responses of leaf respiration in light and darkness are similar and modulated by leaf development.

Our ability to predict temperature responses of leaf respiration in light and darkness (RL and RDk ) is essential to models of global carbon dynamics. While many models rely on constant thermal sensitivity (characterized by Q10 ), uncertainty remains as to whether Q10 of RL and RDk are actually similar. We measured short-term temperature responses of RL and RDk in immature and mature leaves of two evergreen tree species, Castanopsis carlesii and Ormosia henry in an open field. RL was estimated by the Kok method, the Yin method and a newly developed Kok-iterCc method. When estimated by the Yin and Kok-iterCc methods, RL and RDk had similar Q10 (c. 2.5). The Kok method overestimated both Q10 and the light inhibition of respiration. RL /RDk was not affected by leaf temperature. Acclimation of respiration in summer was associated with a decline in basal respiration but not in Q10 in both species, which was related to changes in leaf nitrogen content between seasons. Q10 of RL and RDk in mature leaves were 40% higher than in immature leaves. Our results suggest similar Q10 values can be used to model RL and RDk while leaf development-associated changes in Q10 require special consideration in future respiration models.

Oxidative-Reductive Near-Infrared Electrochromic Switching Enabled by Porous Vertically Stacked Multilayer Devices.

Here, we demonstrate for the first time the ability of a porous π-conjugated semiconducting polymer film to enable facile electrolyte penetration through vertically stacked redox-active polymer layers, thereby enabling electrochromic switching between p-type and/or n-type polymers. The polymers P1 and P2, with structures diketopyrrolopyrrole (DPP)-πbridge-3,4,-ethylenedioxythiophene (EDOT)-πbridge [πbridge = 2,5-thienyl for P1 and πbridge = 2,5-thiazolyl for P2] are selected as the p-type polymers and N2200 (a known naphthalenediimide-dithiophene semiconductor) as the n-type polymer. Single-layer porous and dense (control) polymer films are fabricated and extensively characterized using optical microscopy, atomic force microscopy, scanning electron microscopy, and grazing incidence wide-angle X-ray scattering. The semiconducting films are then incorporated into single and multilayer electrochromic devices (ECDs). It is found that when a p-type (P2) porous top layer is used in a multilayer ECD, it enables electrolyte penetration to the bottom layer, enabling oxidative electrochromic switching of the P1 bottom layer at low potentials (+0.4 V versus +1.2 V with dense P2). Importantly, when using a porous P1 as the top layer with an n-type N2200 bottom layer, dynamic oxidative-reductive electrochromic switching is also realized. These results offer a proof of concept for development of new types of multilayer electrochromic devices where precise control of the semiconductor film morphology and polymer electronic structure is essential.

Highly stretchable organic electrochemical transistors with strain-resistant performance.

Realizing fully stretchable electronic materials is central to advancing new types of mechanically agile and skin-integrable optoelectronic device technologies. Here we demonstrate a materials design concept combining an organic semiconductor film with a honeycomb porous structure with biaxially prestretched platform that enables high-performance organic electrochemical transistors with a charge transport stability over 30-140% tensional strain, limited only by metal contact fatigue. The prestretched honeycomb semiconductor channel of donor-acceptor polymer poly(2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)-2,5-diketo-pyrrolopyrrole-alt-2,5-bis(3-triethyleneglycoloxy-thiophen-2-yl) exhibits high ion uptake and completely stable electrochemical and mechanical properties over 1,500 redox cycles with 104 stretching cycles under 30% strain. Invariant electrocardiogram recording cycles and synapse responses under varying strains, along with mechanical finite element analysis, underscore that the present stretchable organic electrochemical transistor design strategy is suitable for diverse applications requiring stable signal output under deformation with low power dissipation and mechanical robustness.

Enhancing the osmotic energy conversion of a nanoporous membrane: influence of pore density, pH, and temperature.

Salinity gradient power, which converts Gibbs free energy of mixing to electric energy through an ion-selective pore, has great potential. Towards practical use, developing membrane-scaled nanoporous materials is desirable and necessary. Unfortunately, the presence of a significant ion concentration polarization (ICP) lowers appreciably the power harvested, especially at a high pore density. To alleviate this problem, we suggest applying an extra pressure difference ΔP across a membrane containing multiple nanopores, taking account of the associated power consumption. The results gathered reveal that the application of a negative pressure difference can improve the power harvested due to the enhanced selectivity. In addition, if the pore density of a membrane is high, raising its pore length is necessary to make the energy harvested economic. For example, if the pore length is 2000 nm and the pore density is 2.5 × 109 pores per cm2, an increment in the power density of 213 mW m-2 can be obtained by applying ΔP = -1 bar at pH 11 and 323 K, where a net positive power density can be retrieved. The performance of the system considered under various conditions is examined in detail, along with associated mechanisms.

Mixed-flow design for microfluidic printing of two-component polymer semiconductor systems.

The rational creation of two-component conjugated polymer systems with high levels of phase purity in each component is challenging but crucial for realizing printed soft-matter electronics. Here, we report a mixed-flow microfluidic printing (MFMP) approach for two-component π-polymer systems that significantly elevates phase purity in bulk-heterojunction solar cells and thin-film transistors. MFMP integrates laminar and extensional flows using a specially microstructured shear blade, designed with fluid flow simulation tools to tune the flow patterns and induce shear, stretch, and pushout effects. This optimizes polymer conformation and semiconducting blend order as assessed by atomic force microscopy (AFM), transmission electron microscopy (TEM), grazing incidence wide-angle X-ray scattering (GIWAXS), resonant soft X-ray scattering (R-SoXS), photovoltaic response, and field effect mobility. For printed all-polymer (poly[(5,6-difluoro-2-octyl-2H-benzotriazole-4,7-diyl)-2,5-thiophenediyl[4,8-bis[5-(2-hexyldecyl)-2-thienyl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl]) [J51]:(poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}) [N2200]) solar cells, this approach enhances short-circuit currents and fill factors, with power conversion efficiency increasing from 5.20% for conventional blade coating to 7.80% for MFMP. Moreover, the performance of mixed polymer ambipolar [poly(3-hexylthiophene-2,5-diyl) (P3HT):N2200] and semiconducting:insulating polymer unipolar (N2200:polystyrene) transistors is similarly enhanced, underscoring versatility for two-component π-polymer systems. Mixed-flow designs offer modalities for achieving high-performance organic optoelectronics via innovative printing methodologies.

Prediction of the mechanisms of action of Qutan Huoxue decoction in non-alcoholic steatohepatitis (NASH): a network pharmacology study and experimental validation.

CONTEXT: Qutan Huoxue decoction (QTHX) is used to treat non-alcoholic steatohepatitis (NASH) with good efficacy in the clinic. However, the mechanism is not clear yet. OBJECTIVE: This study investigates the mechanism of QTHX in the treatment of NASH. MATERIALS AND METHODS: Potential pathways of QTHX were predicted by network pharmacology. Fourty Sprague Dawley (SD) rats (half normal diet, half high-fat diet) were fed six to eight weeks, primary hepatocytes and Kupffer cells were extracted and co-cultured by the 0.4-micron trans well culture system. Then, the normal co-cultured cells were treated by normal serum, the NASH co-cultured cells were treated with various concentrations of QTHX-containing serum (0, 5, 7.5 or 10 µg/mL) for 24 h. The expression of targets were measured with Activity Fluorometric Assay, Western blot and PCR assay. RESULTS: Network pharmacology indicated that liver-protective effect of QTHX was associated with its anti-inflammation response, oxidative stress, and lipid receptor signalling. 10 µg/mL QTHX significantly reduced the inflammation response and lipid levels in primary hepatocytes (ALT: 46.43 ± 2.76 U/L, AST: 13.96 ± 1.08 U/L, TG: 0.25 ± 0.01 mmol/L, TC: 0.14 ± 0.05 mmol/L), comparing with 0 µg/mL NASH group (ALT: 148 ± 9.22 U/L, AST: 53.02 ± 2.30 U/L, TG: 0.74 ± 0.07 mmol/L, TC: 0.91 ± 0.07 mmol/L) (p < 0.01). Meanwhile, QTHX increased expression of SOCS1 and decreased expression of TLR4, Myd88, NF-κB. CONCLUSIONS: The study suggested that QTHX treats NASH in rats by activating the SCOS1/NF-κB/TLR4 pathway, suggesting QTHX could be further developed as a potential liver-protecting agent.

Tunable Broad Light Emission from 3D "Hollow" Bromide Perovskites through Defect Engineering.

Hybrid halide perovskites consisting of corner-sharing metal halide octahedra and small cuboctahedral cages filled with counter cations have proven to be prominent candidates for many high-performance optoelectronic devices. The stability limits of their three-dimensional perovskite framework are defined by the size range of the cations present in the cages of the structure. In some cases, the stability of the perovskite-type structure can be extended even when the counterions violate the size and shape requirements, as is the case in the so-called "hollow" perovskites. In this work, we engineered a new family of 3D highly defective yet crystalline "hollow" bromide perovskites with general formula (FA)1-x(en)x(Pb)1-0.7x(Br)3-0.4x (FA = formamidinium (FA+), en = ethylenediammonium (en2+), x = 0-0.44). Pair distribution function analysis shed light on the local structural coherence, revealing a wide distribution of Pb-Pb distances in the crystal structure as a consequence of the Pb/Br-deficient nature and en inclusion in the lattice. By manipulating the number of Pb/Br vacancies, we finely tune the optical properties of the pristine FAPbBr3 by blue shifting the band gap from 2.20 to 2.60 eV for the x = 0.42 en sample. A most unexpected outcome was that at x> 0.33 en incorporation, the material exhibits strong broad light emission (1% photoluminescence quantum yield (PLQY)) that is maintained after exposure to air for more than a year. This is the first example of strong broad light emission from a 3D hybrid halide perovskite, demonstrating that meticulous defect engineering is an excellent tool for customizing the optical properties of these semiconductors.

Piezoelectric potential enhanced photocatalytic performance based on ZnO with different nanostructures.

In this paper, two novel nanostructures with ZnO nanowire and nanosheet arrays vertically growing on the FTO and Al foil have been synthesized by a hydrothermal method, which exhibit both the piezoelectric and photocatalytic properties. These nanostructures have typical wurtzite structures based on the XRD results. From the SEM results, the average diameter and length of nanowire have been measured to be about 150 nm and 4.5 µm, the thickness of ZnO nanosheet is about 50 nm and the width is about 5 µm. In the photocatalytic test, the photodegradation of RhB under 365 nm illumination for nanowire and nanosheet is about 25% and 37% in 80 min reaction. With stirring, the degradation rate is increased to 61% and 85%. Finally, the photocurrent test and finite element method were used to analyze the piezo-photodegradation mechanism.

[Evaluation of genetic diversity and population structure of genus Tripterygium based on SSR markers].

The genus Tripterygium is an immune suppressor in the Chinese traditional medicines. Due to the habitat destruction and anthropogenic over-exploitation, the wild genus Tripterygium plants have decreased dramatically in recent years or even been endangered. It is critical to evaluate and protect genus Tripterygium wild resource. In this research, simple sequence repeat (SSR) molecular markers were applied to the investigation of the genetic diversity and genetic structure of 28 populations for genus Tripterygium (396 samples from 9 provinces in China). We found a high level of genetic diversity (percentage of polymorphic loci PPL = 77.29%, Shannon's information index I = 0.639 4; Nei's expected heterozygosity H = 0.359 9) and high genetic differentiation among the populations (gene flow N_m = 0.228 7). Based on Nei's genetic distance, the phylogenic tree of populations was constructed and 28 populations were divided into 6 clusters according to STRUCTURE clustering analysis. T. hypoglaucumwas was mainly divided into 3 clusters, including Sichuan, Yunnan and Guizhou- Chongqing. T. regelii was separated to cluster 4, while T. wilfordii was divided into two clusters: the transition type LQ and NY were divided into cluster 5, and the others were in cluster 6. These results provide a theory basis for the conservation of wild resource, research of genetic polymorphism and molecular marker for assisted breeding of genus Tripterygium.

[Effects of Different Shading Treatment and Planting Patterns on Several Main Characters and Yield of Elephantopus scaber].

OBJECTIVE: To study the growth and yield of Elephantopus scaber under different light conditions. METHODS: Several main characters and yield performances were studied under six shading treatment as well as two planting patterns. RESULTS: The plant height, leaf number, root length and root-shoot ratio were increased under moderate shading. With the increase of shading ratio, the process of Elephantopus scaber vegetative growth to reproductive growth were shortened, seed yield, dry biomass and root yield decreased as well. Among different shading treatments, dry seed-yield showed 8. 46 ~31. 10 kg/667 m2 dry biomass showed 327. 28 ~ 800. 95 kg/ 667 m2 and dry root yield showed 30. 65 ~ 70. 72 kg/667 m2. CONCLUSION: Elephantopus scaber is a light-demanding but shade-tolerant plant. The patterns of hole seeding were suggested in planting, and not more than 60% shade density may be good under plantations.

A Deep Neural Network for Predicting Synergistic Drug Combinations on Cancer.

The exploration of drug combinations presents an opportunity to amplify therapeutic effectiveness while alleviating undesirable side effects. Nevertheless, the extensive array of potential combinations poses challenges in terms of cost and time constraints for experimental screening. Thus, it is crucial to narrow down the search space. Deep learning approaches have gained widespread popularity in predicting synergistic drug combinations tailored for specific cell lines in vitro settings. In the present study, we introduce a novel method termed GTextSyn, which utilizes the integration of gene expression data and chemical structure information for the prediction of synergistic effects in drug combinations. GTextSyn employs a sentence classification model within the domain of Natural Language Processing (NLP), wherein drugs and cell lines are regarded as entities possessing biochemical relevance. Meanwhile, combinations of drug pairs and cell lines are construed as sentences with biochemical relational significance. To assess the efficacy of GTextSyn, we conduct a comparative analysis with alternative deep learning approaches using a standard benchmark dataset. The results from a five-fold cross-validation demonstrate a 49.5% reduction in Mean Square Error (MSE) achieved by GTextSyn, surpassing the performance of the next best method in the regression task. Furthermore, we conduct a comprehensive literature survey on the predicted novel drug combinations and find substantial support from prior experimental studies for many of the combinations identified by GTextSyn.

Highly deformable bi-continuous conducting polymer hydrogels for electrochemical energy storage.

Conducting polymer hydrogels with inherent flexibility, ionic conductivity and environment friendliness are promising materials in the fields of energy storage. However, a trade-off between mechanical and electrochemical properties has limited the development of flexible/stretchable conducting polymer hydrogel electrodes, owing to the intrinsic conflict among mechanical and electrical phases. Here, we report a reliable design to enable conducting polymer with both exceptional mechanical and electrical/electrochemical performance through the construction of bi-continuous conducting polymer crosslinked network. The resultant bi-continuous conducting polymer hydrogels (BCPH) demonstrate significantly improved mechanical and electrochemical properties compared to the conventional conducting polymer hydrogel (CPH) electrode. BCPH presents a high specific capacitance of 715 F g-1 at 0.5 A/g, a high mechanical strength (∼1 MPa) and a large stretchability (∼300%). Enabled by such intrinsically deformability and electrochemical properties, we further demonstrate its utility in flexible solid-state supercapacitor (FSSC), which exhibits an outstanding specific capacitance of 760 mF cm-2 at 2 mA cm-2, excellent electrochemical stability with 81% capacitance retention after 5000 charge/discharge cycles, and superior bending cycle stability. This simple and scalable strategy provides a platform for the fabrication of high-performance conducting hydrogel electrodes for various wearable electronic equipment.

Integration of single-cell and bulk RNA-sequencing to analyze the heterogeneity of hepatocellular carcinoma and establish a prognostic model.

BACKGROUND: The highly heterogeneous nature of hepatocellular carcinoma (HCC) results in different responses and prognoses to the same treatment in patients with similar clinical stages. AIMS: Thus, it is imperative to investigate the association between HCC tumor heterogeneity and treatment response and prognosis. METHODS AND RESULTS: At first, we downloaded scRNA-seq, bulk RNA-seq, and clinical data from TCGA and GEO databases. We conducted quality control, normalization using SCTransform, dimensionality reduction using PCA, batch effect removal using Harmony, dimensionality reduction using UMAP, and cell annotation-based marker genes on the scRNA-seq data. We recognized tumor cells, identified tumor-related genes (TRGs), and performed cell communication analysis. Next, we developed a prognostic model using univariable Cox, LASSO, and multivariate Cox analyses. The signature was evaluated using survival analysis, ROC curves, C-index, and nomogram. Last, we studied the predictability of the signature in terms of prognosis and immunotherapeutic response for HCC, assessed a variety of drugs for clinical treatment, and used the qRT-PCR analysis to validate the mRNA expression levels of prognostic TRGs. CONCLUSION: To conclude, this study expounded upon the influence of tumor cell heterogeneity on the prediction of treatment outcomes and prognosis in HCC. This, in turn, enhances the predictive ability of the TNM staging system and furnishes novel perspectives on the prognostic assessment and therapy of HCC.

Evaluate the clinical efficacy of traditional Chinese Medicine as the neoadjuvant treatment in reducing the incidence of hepatocellular carcinoma in patients with hepatitis B-related cirrhosis: A systematic review and meta-analysis.

Background: Traditional Chinese Medicine (TCM), has been used for hepatocellular carcinoma (HCC) at every therapeutic stage, even before tumor formation. However, the efficacy of TCM in reducing the incidence of HCC in patients with chronic hepatitis B-related cirrhosis remains unclear. This study aims to address this gap. Methods: Publications were collected from PubMed, EMBASE, Cochrane Library, Web of Science, CNKI, Sino Med, VIP, and Wan Fang Databases. Relative risk (RR) was calculated with a 95 % confidence interval (CI). Heterogeneity was assessed. The Cochrane Collaboration's tool was used to assess the risk of bias. Results: 10 studies with 2702 patients showed that the combination therapy significantly reduced the incidence of HCC in patients with post-hepatitis B cirrhosis at 1, 3, and 5 years. However, the preventive effects of TCM were in compensated cirrhosis, but not the decompensated cirrhosis. Furthermore, TCM correlated with improved liver function and enhanced virological response. Conclusion: Combination therapy with TCM demonstrated the certain potential in reducing the incidence of HCC in patients with hepatitis B cirrhosis. This is attrinuted to the improvement of liver function and enhancement of the viral response. However, the efficacy of TCM in the field still needs more high-quality RCTs to provide stronger evidence in the future.

An Overview of Traditional Chinese Medicine in the Treatment After Radical Resection of Hepatocellular Carcinoma.

According to the Barcelona Clinic Liver Cancer (BCLC) system, radical resection of early stage primary hepatocellular carcinoma (HCC) mainly includes liver transplantation, surgical resection, and radiofrequency ablation (RFA), which yield 5-year survival rates of about 70-79%, 41.3-69.5%, and 40-70%, respectively. The tumor-free 5-year rate for HCC patients undergoing radical resection only reach up to 13.7 months, so the prevention of recurrence after radical resection of HCC is very important for the prognosis of patients. The traditional Chinese medicine (TCM) takes the approach of multitarget and overall-regulation to treat tumors, it can also independently present the "component-target-pathway" related to a particular disease, and its systematic and holistic characteristics can provide a personalized therapy based on symptoms of the patient by treating the patient as a whole. TCM as postoperative adjuvant therapy after radical resection of HCC in Barcelona Clinic liver cancer A or B stages, and the numerous clinical trials confirmed that the efficacy of TCM in the field of HCC has a significant effect, not only improving the prognosis and quality of life but also enhancing patient survival rate. However, with the characteristics of multi-target, multi-component, and multi-pathway, the specific mechanism of Chinese medicine in the treatment of diseases is still unclear. Because of the positive pharmacological activities of TCM in combating anti-tumors, the mechanism studies of TCM have demonstrated beneficial effects on the regulation of immune function, chronic inflammation, the proliferation and metastasis of liver cancer cells, autophagy, and cell signaling pathways related to liver cancer. Therefore, this article reviews the mechanism of traditional Chinese medicine in reducing the recurrence rate of HCC after radical resection.

Identification of a novel ANK1 mutation in a Chinese family with hereditary spherocytosis: A case report.

The present study describes the clinical profile and ankyrin 1 (ANK1) mutation status of a Chinese family with hereditary spherocytosis (HS). A young male patient (proband) was diagnosed with HS after presenting with anaemia and jaundice. The Coombs test was negative and spherocytes were found in peripheral blood smears. Magnetic resonance imaging showed splenomegaly and splenic iron depositions. The red blood cell osmotic fragility test was positive. The eosin-5'-maleimide binding test showed reduced mean channel fluorescence. Whole-exome sequencing revealed a novel ANK1 mutation (c.4707G>A), resulting in a nonsense mutation (p.Trp1569*). The patient's father, paternal aunt and paternal grandmother exhibited comparable clinical symptoms and Sanger sequencing confirmed the same mutation in these family members. To the best of our knowledge, an HS pedigree with this novel ANK1 nonsense mutation has not been previously reported. At the same time, the unique clinical presentation of this pedigree helps our understanding of the heterogeneity of clinical manifestations of HS.

DFT-Based Study of the Structure, Stability, and Spectral and Optical Properties of Gas-Phase NbMgn (n = 2-12) Clusters.

Gas-phase NbMgn (n = 2-12) clusters were fully searched by CALYPSO software, and then the low-energy isomers were further optimized and calculated under DFT. It is shown that the three lowest energy isomers of NbMgn (n = 3-12) at each size are grown from two seed structures, i.e., tetrahedral and pentahedral structures, and the transition size occurs at the NbMg8 cluster. Interestingly, the relative stability calculations of the NbMg8 cluster ground-state isomer stand out under the examination of several parameters' calculations. The charge-transfer properties of the clusters of the ground-state isomers of various sizes had been comprehensively investigated. In order to be able to provide data guidance for future experimental probing of these ground-state clusters, this work also predicted infrared and Raman spectra at the same level of theoretical calculations. The results show that the multipeak nature of the IR and Raman spectra predicts that it is difficult to distinguish them directly. Finally, the optical properties of these clusters were investigated by calculating the static linear, second-order nonlinear, and third-order nonlinear coefficients. Importantly and interestingly, the NbMg8 cluster was shown to have superior nonlinear optical characteristics to all other clusters; thus, it is a powerful candidate for a potentially ultrasensitive nonlinear optical response device for some special purpose.