Multi-heterojunctioned plastics with high thermoelectric figure of merit.

Conjugated polymers promise inherently flexible and low-cost thermoelectrics for powering the Internet of Things from waste heat1,2. Their valuable applications, however, have been hitherto hindered by the low dimensionless figure of merit (ZT)3-6. Here we report high-ZT thermoelectric plastics, which were achieved by creating a polymeric multi-heterojunction with periodic dual-heterojunction features, where each period is composed of two polymers with a sub-ten-nanometre layered heterojunction structure and an interpenetrating bulk-heterojunction interface. This geometry produces significantly enhanced interfacial phonon-like scattering while maintaining efficient charge transport. We observed a significant suppression of thermal conductivity by over 60 per cent and an enhanced power factor when compared with individual polymers, resulting in a ZT of up to 1.28 at 368 kelvin. This polymeric thermoelectric performance surpasses that of commercial thermoelectric materials and existing flexible thermoelectric candidates. Importantly, we demonstrated the compatibility of the polymeric multi-heterojunction structure with solution coating techniques for satisfying the demand for large-area plastic thermoelectrics, which paves the way for polymeric multi-heterojunctions towards cost-effective wearable thermoelectric technologies.

A drug-mediated organic electrochemical transistor for robustly reusable biosensors.

Reusable point-of-care biosensors offer a cost-effective solution for serial biomarker monitoring, addressing the critical demand for tumour treatments and recurrence diagnosis. However, their realization has been limited by the contradictory requirements of robust reusability and high sensing capability to multiple interactions among transducer surface, sensing probes and target analytes. Here we propose a drug-mediated organic electrochemical transistor as a robust, reusable epidermal growth factor receptor sensor with striking sensitivity and selectivity. By electrostatically adsorbing protonated gefitinib onto poly(3,4-ethylenedioxythiophene):polystyrene sulfonate and leveraging its strong binding to the epidermal growth factor receptor target, the device operates with a unique refresh-in-sensing mechanism. It not only yields an ultralow limit-of-detection concentration down to 5.74 fg ml-1 for epidermal growth factor receptor but, more importantly, also produces an unprecedented regeneration cycle exceeding 200. We further validate the potential of our devices for easy-to-use biomedical applications by creating an 8 × 12 diagnostic drug-mediated organic electrochemical transistor array with excellent uniformity to clinical blood samples.

Boosting the Thermoelectric Performance of the Doped DPP-EDOT Conjugated Polymer by Incorporating an Ionic Additive.

The thermoelectric (TE) performance of organic materials is limited by the coupling of Seebeck coefficient and electrical conductivity. Herein a new strategy is reported to boost the Seebeck coefficient of conjugated polymer without significantly reducing the electrical conductivity by incorporation of an ionic additive DPPNMe3 Br. The doped polymer PDPP-EDOT thin film exhibits high electrical conductivity up to 1377 ± 109 S cm-1 but low Seebeck coefficient below 30 µV K-1 and a maximum power factor of 59 ± 10 µW m-1 K-2 . Interestingly, incorporation of small amount (at a molar ratio of 1:30) of DPPNMe3 Br into PDPP-EDOT results in the significant enhancement of Seebeck coefficient along with the slight decrease of electrical conductivity after doping. Consequently, the power factor (PF) is boosted to 571 ± 38 µW m-1 K-2 and ZT reaches 0.28 ± 0.02 at 130 °C, which is among the highest for the reported organic TE materials. Based on the theoretical calculation, it is assumed that the enhancement of TE performance for the doped PDPP-EDOT by DPPNMe3 Br is mainly attributed to the increase of energetic disorder for PDPP-EDOT.

Robust functional principal component analysis via a functional pairwise spatial sign operator.

Functional principal component analysis (FPCA) has been widely used to capture major modes of variation and reduce dimensions in functional data analysis. However, standard FPCA based on the sample covariance estimator does not work well if the data exhibits heavy-tailedness or outliers. To address this challenge, a new robust FPCA approach based on a functional pairwise spatial sign (PASS) operator, termed PASS FPCA, is introduced. We propose robust estimation procedures for eigenfunctions and eigenvalues. Theoretical properties of the PASS operator are established, showing that it adopts the same eigenfunctions as the standard covariance operator and also allows recovering ratios between eigenvalues. We also extend the proposed procedure to handle functional data measured with noise. Compared to existing robust FPCA approaches, the proposed PASS FPCA requires weaker distributional assumptions to conserve the eigenspace of the covariance function. Specifically, existing work are often built upon a class of functional elliptical distributions, which requires inherently symmetry. In contrast, we introduce a class of distributions called the weakly functional coordinate symmetry (weakly FCS), which allows for severe asymmetry and is much more flexible than the functional elliptical distribution family. The robustness of the PASS FPCA is demonstrated via extensive simulation studies, especially its advantages in scenarios with nonelliptical distributions. The proposed method was motivated by and applied to analysis of accelerometry data from the Objective Physical Activity and Cardiovascular Health Study, a large-scale epidemiological study to investigate the relationship between objectively measured physical activity and cardiovascular health among older women.

Constant Force-Tracking Control Based on Deep Reinforcement Learning in Dynamic Auscultation Environment.

Intelligent medical robots can effectively help doctors carry out a series of medical diagnoses and auxiliary treatments and alleviate the current shortage of social personnel. Therefore, this paper investigates how to use deep reinforcement learning to solve dynamic medical auscultation tasks. We propose a constant force-tracking control method for dynamic environments and a modeling method that satisfies physical characteristics to simulate the dynamic breathing process and design an optimal reward function for the task of achieving efficient learning of the control strategy. We have carried out a large number of simulation experiments, and the error between the tracking of normal force and expected force is basically within ±0.5 N. The control strategy is tested in a real environment. The preliminary results show that the control strategy performs well in the constant force-tracking of medical auscultation tasks. The contact force is always within a safe and stable range, and the average contact force is about 5.2 N.

Chemical doping of organic semiconductors for thermoelectric applications.

Doping is essential to manipulate the electrical performance of both thermoelectric (TE) materials and organic semiconductors (OSCs). Although organic thermoelectric (OTE) materials have experienced a rapid development over the past decade, the chemical doping of OSCs for TE applications lags behind, which has limited further breakthroughs in this cutting-edge field. Recently, increasing efforts have been devoted to the development of energetically matched host and dopant molecules, exploring novel doping methods and revealing the doping mechanisms. This tutorial review covers the basic mechanisms, fundamental requirements, recent advances and remaining challenges of chemical doping in OSCs for TE applications. We first present the basic knowledge of the trade-off relationship in TE materials and its critical requirements for doped OSCs, followed by a brief introduction of recent advances in the molecular design of OSCs and dopants. Moreover, we provide an overview of the existing categories of doping mechanisms and methods, and more importantly, emphasize the summarized doping strategies for the state-of-the-art OTE materials. Finally, challenges and perspectives on the chemical doping of OSCs are proposed to highlight the research directions that deserve attention towards a bright future of OTE materials.

Enabling Multifunctional Organic Transistors with Fine-Tuned Charge Transport.

Organic field-effect transistors (OFETs) are promising candidates for many electronic applications not only because of the intrinsic features of organic semiconductors in mechanical flexibility and solution processability but also owing to their multifunctionalities promised by combined signal switching and transduction properties. In contrast to rapid developments of high performance devices, the construction of multifunctional OFETs remains challenging. A key issue is fine-tuning the charge transport by modulating electric fields that are coupled with various external stimuli. Given that the charge transport is determined by complicated factors involving material and device engineering, the development of effective strategies to manipulate charge transport is highly desired toward state-of-the-art multifunctional OFETs. In this Account, we present our recent progress on device-engineered OFETs for sensing applications and thermoelectric studies of organic semiconductors. The interactions between organic semiconductors and the target analyte determine the performance of chemical sensors based on OFETs. We introduced gas receptors and in situ tailored molecular antenna on the surface of ultrathin active layers. The engineered interfaces enable direct and specific semiconductor-analyte interactions, as demonstrated in developed chemical sensors and biosensors with prominent sensitivity and good selectivity. In comparison with chemical stimuli, many physical stimuli such as pressure typically possess a limit effect on the charge transport properties of organic semiconductors. By utilizing the suspended-gate geometry, the carrier concentration in a conductive channel can be controlled quantitatively by the pressure dominated changes in the capacitance of an air dielectric layer, allowing for ultrasensitive pressure detection in a unique manner. More importantly, the transduced current can be further processed by a synaptic OFET, in which the proton/electron coupling interfaces contribute to the dynamic modulation of carrier concentration, thus mimicking biological synapses. The integrated pressure sensor and synaptic OFETs, namely, the dual-organic-transistor-based tactile-perception element, has exhibited promising applications in artificial intelligence elements. Aiming at revealing thermoelectric (TE) properties of organic semiconductors, we also investigated field-modulated TE performance of several high-mobility semiconductors by varying the driving electric field to the temperature gradient. This has been confirmed to offer a strategy to accelerate the search for promising TE materials from well-developed organic semiconductors. By tuning the charge transport process in the device, the functional modulation of OFETs has experienced significant progress in the preceding years. The exploration of new ways to create OFETs with more fascinating functionalities is still full of opportunities to obtain greater benefit from organic transistors.

A Conjugated Polymer Containing Arylazopyrazole Units in the Side Chains for Field-Effect Transistors Optically Tunable by Near Infra-Red Light.

Optically tunable field-effect transistors (FETs) with near infra-red (NIR) light show promising applications in various areas. Now, arylazopyrazole groups are incorporated in the side chains of a semiconducting donor-acceptor (D-A) polymer. The cis-trans interconversion of the arylazopyrazole can be controlled by 980 nm and 808 nm NIR light irradiation, by utilizing NaYF4 :Yb,Tm upconversion nanoparticles and the photothermal effect of conjugated D-A polymers, respectively. This reversible transformation affects the interchain packing of the polymer thin film, which in turn reversibly tunes the semiconducting properties of the FETs by the successive 980 nm and 808 nm light irradiation. The resultant FETs display fast response to NIR light, good resistance to photofatigue, and stability in storage for up to 120 days. These unique features will be useful in future memory and bioelectronic wearable devices.

2D Semiconducting Metal-Organic Framework Thin Films for Organic Spin Valves.

2D conductive metal-organic frameworks (2D c-MOFs) feature promising applications as chemiresistive sensors, electrode materials, electrocatalysts, and electronic devices. However, exploration of the spin-polarized transport in this emerging materials and development of the relevant spintronics have not yet been implemented. In this work, layer-by-layer assembly was applied to fabricate highly crystalline and oriented thin films of a 2D c-MOF, Cu3 (HHTP)2 , (HHTP: 2,3,6,7,10,11-hexahydroxytriphenylene), with tunable thicknesses on the La0.67 Sr0.33 MnO3 (LSMO) ferromagnetic electrode. The magnetoresistance (MR) of the LSMO/Cu3 (HHTP)2 /Co organic spin valves (OSVs) reaches up to 25 % at 10 K. The MR can be retained with good film thickness adaptability varied from 30 to 100 nm and also at high temperatures (up to 200 K). This work demonstrates the first potential applications of 2D c-MOFs in spintronics.

Selenium-Substituted Diketopyrrolopyrrole Polymer for High-Performance p-Type Organic Thermoelectric Materials.

Development of high-performance organic thermoelectric (TE) materials is of vital importance for flexible power generation and solid-cooling applications. Demonstrated here is the significant enhancement in TE performance of selenium-substituted diketopyrrolopyrrole (DPP) derivatives. Along with strong intermolecular interactions and high Hall mobilities of 1.0-2.3 cm2 V-1 s-1 in doping-states for polymers, PDPPSe-12 exhibits a maximum power factor and ZT of up to 364 µW m-1 K-2 and 0.25, respectively. The performance is more than twice that of the sulfur-based DPP derivative and represents the highest value for p-type organic thermoelectric materials based on high-mobility polymers. These results reveal that selenium substitution can serve as a powerful strategy towards rationally designed thermoelectric polymers with state-of-the-art performances.

A unified powerful set-based test for sequencing data analysis of GxE interactions.

The development of next-generation sequencing technologies has allowed researchers to study comprehensively the contribution of genetic variation particularly rare variants to complex diseases. To date many sequencing analyses of rare variants have focused on marginal genetic effects and have not explored the potential role environmental factors play in modifying genetic risk. Analysis of gene-environment interaction (GxE) for rare variants poses considerable challenges because of variant rarity and paucity of subjects who carry the variants while being exposed. To tackle this challenge, we propose a hierarchical model to jointly assess the GxE effects of a set of rare variants for example, in a gene or regulatory region, leveraging the information across the variants. Under this model, GxE is modeled by two components. The first component incorporates variant functional information as weights to calculate the weighted burden of variant alleles across variants, and then assess their GxE interaction with the environmental factor. Since this information is a priori known, this component is fixed effects in the model. The second component involves residual GxE effects that have not been accounted for by the fixed effects. In this component, the residual GxE effects are postulated to follow an unspecified distribution with mean 0 and variance [Formula: see text] We develop a novel testing procedure by deriving two independent score statistics for the fixed effects and the variance component separately. We propose two data-adaptive combination approaches for combining these two score statistics and establish the asymptotic distributions. An extensive simulation study shows that the proposed approaches maintain the correct type I error and the power is comparable to or better than existing methods under a wide range of scenarios. Finally we illustrate the proposed methods by a exome-wide GxE analysis with NSAIDs use in colorectal cancer.

Genotyping and Quantifying Lyme Pathogen Strains by Deep Sequencing of the Outer Surface Protein C (ospC) Locus.

A mixed infection of a single tick or host by Lyme disease spirochetes is common and a unique challenge for the diagnosis, treatment, and surveillance of Lyme disease. Here, we describe a novel protocol for differentiating Lyme strains on the basis of deep sequencing of the hypervariable outer surface protein C locus (ospC). Improving upon the traditional DNA-DNA hybridization method, the next-generation sequencing-based protocol is high throughput, quantitative, and able to detect new pathogen strains. We applied the method to more than one hundred infected Ixodes scapularis ticks collected from New York State, USA, in 2015 and 2016. An analysis of strain distributions within individual ticks suggests an overabundance of multiple infections by five or more strains, inhibitory interactions among coinfecting strains, and the presence of a new strain closely related to Borreliella bissettiae A supporting bioinformatics pipeline has been developed. The newly designed pair of universal ospC primers target intergenic sequences conserved among all known Lyme pathogens. The protocol could be used for culture-free identification and quantification of Lyme pathogens in wildlife and potentially in clinical specimens.

Dynamic changes and clinical significance of serum S100B protein and glial fibrillary acidic protein in patients with delayed encephalopathy after acute carbon monoxide poisoning.

OBJECTIVE: To study the dynamic changes and clinical significance of serum S100B protein and glial fibrillary acidic protein (GFAP) in patients with delayed encephalopathy after acute carbon monoxide poisoning (DEACMP). METHODS: This study was conducted among DEACMP patients who were hospitalized from November 2014 to February 2016. Serum levels of S100B and GFAP in 66 DEACMP patients were measured by ELISA. Changes in patient states were examined dynamically using activities of daily living (ADL) scale, information-memory-concentration test (IMCT) and Hasegawa's dementia scale (HDS), and compared with those of 64 patients without DE after ACMP. RESULTS: Serum S100B [(0.59 ± 0.11) ng/ml] and GFAP [(227.67 ± 12.43) ng/ml] levels of DEACMP group in acute phase were significantly higher than those of ACMP group [(0.48 ± 0.10) ng/ml and (178.91 ± 11.47) ng/ml] and DEACMP group in recovery phase [(0.49 ± 0.12) ng/ml and (179.54 ± 12.32) ng/ml] (all P<0.05). Serum S100B and GFAP levels of DEACMP group were significantly correlated in both acute and recovery phases (r=0.432 in acute phase, P=0.007; r=0.378 in recovery phase, P=0.034). ADL, HDS and IMCT scores of DEACMP group in acute phase were (45.12 ± 3.12), (7.98 ± 1.02) and (9.61 ± 1.41) points respectively, which were significantly different from those of recovery phase [(33.25 ± 3.09), (16.13 ± 1.17) and (19.54 ± 1.43) points respectively] (P<0.05). CONCLUSIONS: DEACMP was accompanied by secondary brain injury, for which glial activation may be important. Serum S100B and GFAP levels may be related to prognosis.

Conjugated-Backbone Effect of Organic Small Molecules for n-Type Thermoelectric Materials with ZT over 0.2.

Conjugated backbones play a fundamental role in determining the electronic properties of organic semiconductors. On the basis of two solution-processable dihydropyrrolo[3,4-c]pyrrole-1,4-diylidenebis(thieno[3,2-b]thiophene) derivatives with aromatic and quinoid structures, we have carried out a systematic study of the relationship between the conjugated-backbone structure and the thermoelectric properties. In particular, a combination of UV-vis-NIR spectra, photoemission spectroscopy, and doping optimization are utilized to probe the interplay between energy levels, chemical doping, and thermoelectric performance. We found that a moderate change in the conjugated backbone leads to varied doping mechanisms and contributes to dramatic changes in the thermoelectric performance. Notably, the chemically doped A-DCV-DPPTT, a small molecule with aromatic structure, exhibits an electrical conductivity of 5.3 S cm-1 and a high power factor (PF373 K) up to 236 µW m-1 K-2, which is 50 times higher than that of Q-DCM-DPPTT with a quinoid structure. More importantly, the low thermal conductivity enables A-DCV-DPPTT to possess a figure of merit (ZT) of 0.23 ± 0.03, which is the highest value reported to date for thermoelectric materials based on organic small molecules. These results demonstrate that the modulation of the conjugated backbone represents a powerful strategy for tuning the electronic structure and mobility of organic semiconductors toward a maximum thermoelectric performance.

Hypothesis testing in functional linear models.

Functional data arise frequently in biomedical studies, where it is often of interest to investigate the association between functional predictors and a scalar response variable. While functional linear models (FLM) are widely used to address these questions, hypothesis testing for the functional association in the FLM framework remains challenging. A popular approach to testing the functional effects is through dimension reduction by functional principal component (PC) analysis. However, its power performance depends on the choice of the number of PCs, and is not systematically studied. In this article, we first investigate the power performance of the Wald-type test with varying thresholds in selecting the number of PCs for the functional covariates, and show that the power is sensitive to the choice of thresholds. To circumvent the issue, we propose a new method of ordering and selecting principal components to construct test statistics. The proposed method takes into account both the association with the response and the variation along each eigenfunction. We establish its theoretical properties and assess the finite sample properties through simulations. Our simulation results show that the proposed test is more robust against the choice of threshold while being as powerful as, and often more powerful than, the existing method. We then apply the proposed method to the cerebral white matter tracts data obtained from a diffusion tensor imaging tractography study.

Effects of transforming growth factor-ß inhibitor on the proliferation of glioma stem/progenitor cell.

Transforming growth factor-ß (TGF-ß) signaling pathways play an important role in inhibition and promotion of cell proliferation in neural stem cells (NSCs) and glioma stem/progenitor cells (GSPCs), respectively. However, the mechanisms underlying these processes remain unknown. We presumed that there may be functional inhibition at the receptor downstream of TGF-ß signaling pathway leading to the activation of non- TGF-ß/Smad signaling pathway, which stimulates the proliferation of GSPCs. In this study, GSPCs, from glioma cell lines SHG44, were cultivated with TGF-ß receptor inhibitors (LY2157299 and LY2109761), and then the proliferative capability of GSPCs was measured; as well, the synthesis of TGF-ß ligands, and the mRNA expression level of TGF-ß and some key molecules of non-Smad signaling pathways were also detected. Our results showed that inhibitors against TGF-ß receptors could promote the proliferation of GSPCs, and the synthesis of TGF-ß ligands was enhanced. Furthermore, the inhibition of TGF-ß receptor may lead to the activation of non-Smad signaling pathways (mTOR and NF-κB). In conclusion, the down-regulation of TGF-ß receptor capability by TGF-ß receptor inhibitors can increase TGF-ß ligands synthesis and secretion, which then promote GSPCs proliferation by activating non-Smad signaling pathways.

Trichalcogenasumanene ortho-Quinones: Synthesis, Properties, and Transformation into Various Heteropolycycles.

The regioselective transformation of heterobuckybowl trichalcogenasumanenes 1 a,b at peripheral butoxy groups afforded trichalcogenasumanene ortho-quinones 2 a,b. Compounds 2 a,b are distinct from 1 a,b in terms of their molecular geometry and electronic state; that is, they have a shallower bowl depth and show absorbance in the NIR region. The reaction of 2 a,b with diamines resulted in a variety of heteropolycycles, including molecular spoon 3 a-6 a, planar π-systems 3 b-6 b, and highly twisted [7-6-6]-fused systems 7 a,b. These new heteropolycycles had different optical/electrical properties: 4 a,b showed hole mobility of approximately 0.002 cm2 V-1 s-1 , 6 a displayed red emission in both solution and the solid state, and 7 a,b formed tight stacks of the curved π-surface.

Dithienoindophenines: p-Type Semiconductors Designed by Quinoid Stabilization for Solar-Cell Applications.

Compared with the dominant aromatic conjugated materials, photovoltaic applications of their quinoidal counterparts featuring rigid and planar molecular structures have long been unexplored despite their narrow optical bandgaps, large absorption coefficients, and excellent charge-transport properties. The design and synthesis of dithienoindophenine derivatives (DTIPs) by stabilizing the quinoidal resonance of the parent indophenine framework is reported here. Compared with the ambipolar indophenine derivatives, DTIPs with the fixed molecular configuration are found to be p-type semiconductors exhibiting excellent unipolar hole mobilities up to 0.22 cm2 V-1 s-1 , which is one order of magnitude higher than that of the parent IP-O and is even comparable to that of QQT(CN)4-based single-crystal field-effect transistors (FET). DTIPs exhibit better photovoltaic performance than their aromatic bithieno[3,4-b]thiophene (BTT) counterparts with an optimal power-conversion efficiency (PCE) of 4.07 %.

Bismuth Interfacial Doping of Organic Small Molecules for High Performance n-type Thermoelectric Materials.

Development of chemically doped high performance n-type organic thermoelectric (TE) materials is of vital importance for flexible power generating applications. For the first time, bismuth (Bi) n-type chemical doping of organic semiconductors is described, enabling high performance TE materials. The Bi interfacial doping of thiophene-diketopyrrolopyrrole-based quinoidal (TDPPQ) molecules endows the film with a balanced electrical conductivity of 3.3 S cm(-1) and a Seebeck coefficient of 585 µV K(-1) . The newly developed TE material possesses a maximum power factor of 113 µW m(-1) K(-2) , which is at the forefront for organic small molecule-based n-type TE materials. These studies reveal that fine-tuning of the heavy metal doping of organic semiconductors opens up a new strategy for exploring high performance organic TE materials.

Toward High Performance n-Type Thermoelectric Materials by Rational Modification of BDPPV Backbones.

Three n-type polymers BDPPV, ClBDPPV, and FBDPPV which exhibit outstanding electrical conductivities when mixed with an n-type dopant, N-DMBI ((4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine), in solution. High electron mobility and an efficient doping process endow FBDPPV with the highest electrical conductivities of 14 S cm(-1) and power factors up to 28 µW m(-1) K(-2), which is the highest thermoelectric (TE) power factor that has been reported for solution processable n-type conjugated polymers. Our investigations reveal that introduction of halogen atoms to the polymer backbones has a dramatic influence on not only the electron mobilities but also the doping levels, both of which are critical to the electrical conductivities. This work suggests the significance of rational modification of polymer structures and opens the gate for applying the rapidly developed organic semiconductors with high carrier mobilities to thermoelectric field.