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1.
Artigo em Inglês | MEDLINE | ID: mdl-31940167

RESUMO

In this research, a series of polymer materials composed of trans-polyisoprene (TPI) and paraffin were prepared by melting blending and compression molding, then the TPI was crosslinked by vulcanization. As a result of the large difference of melting temperature and crystallization temperature between TPI and paraffin, the obtained polymer materials exhibit a triple shape memory behavior. According to the analysis of crystal behavior, microscopic morphology, and mechanical properties of the materials with different paraffin content and TPI crosslinking density by DSC, XRD, SEM, and DMTA, the shape memory behavior of the obtained materials was tunable by the crosslinking density of TPI and the crystallization degree of TPI or paraffin. Compared with the traditional triple shape memory material, our samples are prepared in a more facile way and can recover at human body temperature (37 °C). Moreover, our TPI/paraffin (TPI/P) material can realize more flexible multi-directionally recovery, as well as be reprogrammed and used for multiple times. To the best of our knowledge, there are few polymer materials reported can realize multi-directionally recovery. These unique multi-directional and reprogrammable properties will enable the application of this polymer material, especially in the medical fixing materials.

2.
Artif Cells Nanomed Biotechnol ; 48(1): 362-376, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31899965

RESUMO

Microvascular disturbance, excessive inflammation and gliosis are key pathophysiologic changes in relation to functional status following the traumatic spinal cord injury (SCI). Continuous release of vascular endothelial growth factor (VEGF) to the lesion site was proved be able to promote the vascular remodelling, whereas the effects on reduction of inflammation and gliosis remain unclear. Currently, aiming at exploring the synergistic roles of VEGF and neurotrophin-3 (NT-3) on angiogenesis, anti-inflammation and neural repair, we developed a technique to co-deliver VEGF165 and NT-3 locally with a homotopic graft of tissue-engineered acellular spinal cord scaffold (ASCS) in a hemisected (3 mm in length) SCI model. As the potential in secretion of growth factors (GFs), bone mesenchymal stem cells (BMSCs) were introduced with the aim to enhance the VEGF/NT-3 release. Our data demonstrate that sustained VEGF/NT-3 release from ASCS significantly increases the local levels of VEGF/NT-3 and angiogenesis, regardless of whether it is in combination with BMSCs transplantation that exhibits positive effects on anti-inflammation, axonal outgrowth and locomotor recovery. This study verifies that co-delivery of VEGF/NT-3 reduces inflammation and gliosis in the hemisected spinal cord, promotes axonal outgrowth and results in better locomotor recovery, while the BMSCs transplantation facilitates these functions limitedly.

3.
Soft Matter ; 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31909411

RESUMO

It is well-known that a fine dispersed rubber phase in thermoplastic vulcanizates (TPVs) is a key to obtain good mechanical properties and high elasticity of TPV products. Previous studies reported that the rubber nanodroplets formed during shearing blending can transform into rubber nanoparticles by in situ rapid crosslinking and these rubber nanoparticles spontaneously form agglomerates dispersed in a plastic matrix during dynamic vulcanization (DV). However, important influencing factors on the formation of rubber nanoparticles and their agglomeration during DV have not been reported yet. In this study, the coupling effect of the molecular weight (MW) of polypropylene (PP) and crosslinking kinetics including the crosslinking rate (CR) and crosslinking degree (CD) on the size of ethylene propylene diene monomer (EPDM) rubber nanoparticles and their agglomerates in EPDM/PP TPVs was systematically studied for the first time. The minimum diameter of EPDM nanodroplets was theoretically calculated by using the critical break-up law of viscoelastic melts for the blend with high MW PP or the critical capillary equation for the blend with low MW PP, and the real size of the EPDM nanoparticles was experimentally verified. Interestingly, the results show that the lower MW of the PP phase, lower CD and higher CR contribute to the formation of smaller rubber nanoparticles, whereas the higher MW of the PP phase and higher CD of the rubber phase contribute to the formation of smaller rubber nanoparticle agglomerates. This study provides guidance to optimize the microstructure of EPDM/PP TPVs for the preparation of high-performance TPV products.

4.
J Cell Biochem ; 121(1): 661-671, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31385362

RESUMO

Glioblastoma multiforme (GBM) is a refractory tumor with poor prognosis and requires more effective treatment regimens. It has been confirmed that long noncoding RNAs (lncRNAs) substantially regulate various human disease including GBM. However, the biological roles and its underlying molecular mechanisms still need to be further investigated. In this study, the biological function and potential molecular mechanism of lncHAS2-AS1 in GBM were explored. It was discovered that HAS2-AS1 was elevated in glioma tissues and correlated with the prognosis of patients with glioma. Reduction of HAS2-AS1 suppressed the migration and invasion in vitro and in vivo. The transcription factor STAT1 could raise HAS2-AS1 by binding to its promoter region. Besides, HAS2-AS1 could adjust PRPS1 via sponging miR-608 in a direct manner. On the whole, the results of this study evidence that HAS2-AS1 is an oncogene and a potential therapeutic target for GBM.

5.
Langmuir ; 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31820992

RESUMO

Through coarse-grained molecular-dynamic simulation of polymer-grafted nanoparticles in a lamellar forming diblock copolymer (BCP), we systematically study the effects of the grafting density (Ng), the compatibility between the grafted chains and the A-block of BCPs (εgA), and the NPs number (N) on the distance (D) of the NPs from the interface by proposing a novel characterization parameters of the orientation and distribution of the grafted chains. The nanoparticle gradually migrates away from the interface and into the A-block region with the increase of εgA for all studied Ng, while slightly returns towards the interface at high εgA and great Ng, which is the first observation of non-monotonic migration at the molecular level. We ascribe the reason of this to the behavior of the grafted chains that are near the interface. Furthermore, we classify the grafted chains into three types along the normal direction of the interface and the migration process is illustrated by the distribution and orientation of the different types of grafted chains, together with the radial distribution function between the NP and the A-block chains. We observe the formation of the NPs layers parallel to the interface for N<20, and a similar non-monotonic migration of the layers is as well observed. The D is the largest for a small N because of the excluded volume effects between the nanoparticles. Increasing Ng and N pushes the neighboring NPs layers towards the interface due to the mutual repulsion. Generally, this study may shed some light on how to better understand and design high performance polymer nanocomposites with tunable location of NPs.

6.
Microbiol Res ; 233: 126391, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-31865097

RESUMO

Pseudomonas fluorescens 2P24 is a plant-beneficial rhizobacteria that controls many root diseases caused by soil-borne pathogens, and the production of the antibiotic compound 2,4-diacetylphloroglucinol (2,4-DAPG) is essential for its biocontrol ability. In the present study, we investigated the regulatory mechanism acting on the production of 2,4-DAPG by the GacA-dependent small non-coding RNAs (sRNAs) and RsmA/E proteins in strain 2P24. Our results showed that the GacS-GacA system regulates the expression of the phlACBD locus, which is responsible for 2,4-DAPG production, by inducing the expression of rsmX, rsmX1, rsmY, and rsmZ. A novel GacA-regulated sRNA, RgsA, was found to negatively regulate 2,4-DAPG production. Activation of the phlACBD locus by the GacS-GacA system is mediated through RsmA and RsmE proteins (but not RsmI), which inhibit phlACBD translation by binding to the putative RsmA/E recognition element in the phlACBD leader. Taken together, our results suggested that in P. fluorescens 2P24, the GacS-GacA system controls the cellular 2,4-DAPG levels in the cell by fine-tuning the function of sRNAs in P. fluorescens.

7.
Commun Biol ; 2: 402, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31701030

RESUMO

Human ß-defensins (hBD) play central roles in antimicrobial activities against various microorganisms and in immune-regulation. These peptides perturb phospholipid membranes for function, but it is not well understood how defensins approach, insert and finally disrupt membranes on the molecular level. Here we show that hBD-3 analogs interact with lipid bilayers through a conserved surface that is formed by two adjacent loops in the solution structure. By integrating a collection of 13C, 1H and 31P solid-state NMR methods with long-term molecular dynamic simulations, we reveal that membrane-binding rigidifies the peptide, enhances structural polymorphism, and promotes ß-strand conformation. The peptide colocalizes with negatively charged lipids, confines the headgroup motion, and deforms membrane into smaller, ellipsoidal vesicles. This study designates the residue-specific, membrane-bound topology of hBD-3 analogs, serves as the basis for further elucidating the function-relevant structure and dynamics of other defensins, and facilitates the development of defensin-mimetic antibiotics, antifungals, and anti-inflammatories.

8.
Artigo em Inglês | MEDLINE | ID: mdl-31755684

RESUMO

A highly stretchable conductor was fabricated through dip-coating a new liquid metal (LM) electric ink on a polydopamine (PDA)-modified three-dimensional (3D) polyurethane sponge (PUS) followed by mechanical sintering. The LM was first sonicated to nanodroplets to reduce the consumption of LM and then modified by 3-mercaptopropionic acid (LMNPS-MPA) to improve the interfacial adhesion between LM and PUS. The denser and even distribution of LMNPS-MPA self-assembling on PDA-treated PUS (PUS-PDA) was successfully prepared via hydrogen bonding interactions. Mechanical sintering of 3D PUS-PDA coated by a two-dimensional (2D) LM layer was then conducted to obtain a continuous conductive network. Comparing with those of the reported 3D conductors, the resulting PUS-PDA-LM composite conductor shows both high electrical conductivity (478 S cm-1) under a low LM consumption of 10 vol% and excellent conductivity stability with the relative resistance change, ΔR/R0, of 2% at 50% strain under stretching deformation. The as-prepared PUS-PDA-LM composites were then successfully applied as flexible and stretchable light-emitting diode (LED) arrays with excellent conductivity and conductivity stability at different deformations. We believe that the 3D stretchable PUS-PDA-LM conductor has many potential applications in flexible sensors, flexible circuits, rollable displays, etc.

9.
Artigo em Inglês | MEDLINE | ID: mdl-31755694

RESUMO

Wearable epidermal sensors are attracting growing interests in human activity monitoring and flexible touch display, but they are still limited by the poor self-healing property and the difficult dissolvable feature. Herein, we report polyvinyl alcohol (PVA)-stabilized liquid metal particles (LMPs) (PVA-LMPs) hydrogels with excellent self-healing performance and the dissolvable feature for wearable epidermal sensors, constructed by dispersing LMPs of eutectic gallium and indium into the borate-modified PVA polymer networks. Interestingly, the PVA-LMPs hydrogels exhibited excellent electrically and mechanically self-healing ability. Moreover, the PVA-LMPs hydrogel can be fabricated as epidermal sensors, which can accurately monitor the human activities. Additionally, the epidermal sensors are dissolvable, showing an attractive feature for on demand transient electronics. It is demonstrated that the hydroxyl groups of PVA can stabilize LMPs via hydrogen-bonding interactions. Furthermore, the dynamic cross-linking bonds between hydrogels and LMPs can rupture and coalesce reversibly in the hydrogel network, which endow the hydrogels with both electrically and mechanically self-healing ability. This work shows the potential of constructing next-generation multifunctional hydrogel-based epidermal sensors for human activity monitoring, wearable healthcare diagnosis, portable electronics, and robot tactile systems.

10.
Soft Matter ; 15(45): 9195-9204, 2019 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-31693047

RESUMO

It is very important to understand the molecular mechanism of the fracture behavior of chemically cross-linked polymer nanocomposites (PNCs). Thus, in this work, by employing a coarse-grained molecular dynamics simulation we investigated the effect of the cross-link density and the cross-link distribution on it by calculating the void formation and the chemical bond scission. Considering the fracture energy, the optimal fracture properties of PNCs are realized at the moderate cross-link density which results from the competition between the chain slippage induced voids and the bond scission induced voids. Meanwhile, more bond scission occurs on the chain backbone while a high broken percentage of the cross-link bonds appears between chains because of the higher average stress borne by one cross-linked bead than by one other bead. In addition, the number of voids is quantified which first increases and then decreases with the strain at low cross-link density. However, the number of newly formed voids increases again at high cross-link density. Finally, it decreases because of the low rate of bond scission. Furthermore, the chemical bonds are broken at a similar strain for the uniform cross-link distribution while they are broken at any strain for the nonuniform cross-link distribution. The low number of broken bonds induces the disappearance of the second peak of the number of voids with the strain for the nonuniform cross-link distribution. In summary, this work could provide a clear understanding of the fracture mechanism of the chemically cross-linked PNCs on the molecular level.

11.
Polymers (Basel) ; 11(11)2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31698688

RESUMO

Ester-functionalized styrene-butadiene rubber (dibutyl itaconate-styrene-butadiene rubber) (D-ESBR) was synthesized by low-temperature emulsion polymerization using dibutyl itaconate (DBI) as a modified monomer containing ester groups. Nonpetroleum-based silica with hydroxy groups was used as a filler to enhance the D-ESBR, which can provide excellent mechanical properties, low rolling resistance, and high wet skid resistance. During the preparation of the silica/D-ESBR nanocomposites, a hydrogen-bonding interface was formed between the hydroxy groups on the surface of silica and the ester groups in the D-ESBR macromolecules. As the content of ester groups in the D-ESBR increases, the dispersion of silica in the nanocomposites is gradually improved, which was verified by rubber process analyzer (RPA) and scanning electron microscopy (SEM). Overall mechanical properties of the silica/D-ESBR modified with 5 wt % DBI were improved and became superior to that of the non-modified nanocomposite. Compared with the non-modified silica/D-ESBR, the DBI modified silica/D-ESBR exhibited a lower tan δ value at 60 °C and comparable tan δ value at 0 °C, indicating that the DBI modified silica/D-ESBR had lower rolling resistance without sacrificing wet skid resistance.

12.
Polymers (Basel) ; 11(11)2019 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-31744215

RESUMO

A novel elastomer poly(diethyl itaconate-co-butyl acrylate-co-ethyl acrylate-co-glycidyl methacrylate) (PDEBEG) was designed and synthesized by redox emulsion polymerization based on bio-based diethyl itaconate, butyl acrylate, ethyl acrylate, and glycidyl methacrylate. The PDEBEG has a number average molecular weight of more than 200,000 and the yield is up to 96%. It is easy to control the glass transition temperature of the PDEBEG, which is ranged from -25.2 to -0.8 °C, by adjusting the monomer ratio. We prepared PDEBEG/CB composites by mixing PDEBEG with carbon black N330 and studied the oil resistance of the composites. The results show that the tensile strength and the elongation at break of the composites with 10 wt% diethyl itaconate can reach up to 14.5 MPa and 305%, respectively. The mechanical properties and high-temperature oil resistance of the composites are superior to that of the commercially available acrylate rubber AR72LS.

13.
Appl Environ Microbiol ; 85(24)2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31604771

RESUMO

Many Gram-negative bacteria employ N-acylhomoserine lactones (AHLs) as quorum-sensing (QS) signal molecules to regulate virulence expression in a density-dependent manner. Quorum quenching (QQ) via enzymatic inactivation of AHLs is a promising strategy to reduce bacterial infections and drug resistance. Herein, a thermostable AHL lactonase (AidB), which could degrade different AHLs, with or without a substitution of carbonyl or hydroxyl at the C-3 position, was identified from the soil bacterium Bosea sp. strain F3-2. Ultrahigh-performance liquid chromatography analysis demonstrated that AidB is an AHL lactonase that hydrolyzes the ester bond of the homoserine lactone (HSL) ring. AidB was thermostable in the range 30 to 80°C and showed maximum activity after preincubation at 60°C for 30 min. The optimum temperature of AidB was 60°C, and the enzyme could be stably stored in double-distilled water (ddH2O) at 4°C or room temperature. AidB homologs were found only in Rhizobiales and Rhodospirillales of the Alphaproteobacteria AidB from Agrobacterium tumefaciens and AidB from Rhizobium multihospitium (with amino acid identities of 50.6% and 52.8% to AidB, respectively) also showed thermostable AHL degradation activity. When introduced into bacteria, plasmid-expressed AidB attenuated pyocyanin production by Pseudomonas aeruginosa PAO1 and the pathogenicity of Pectobacterium carotovorum subsp. carotovorum Z3-3, suggesting that AidB is a potential therapeutic agent by degrading AHLs.IMPORTANCE A quorum-sensing system using AHLs as the signal in many bacterial pathogens is a critical virulence regulator and an attractive target for anti-infective drugs. In this work, we identified a novel AHL lactonase, AidB, from a soil bacterial strain, Bosea sp. F3-2. The expression of aidB reduced the production of AHL signals and QS-dependent virulence factors in Pseudomonas aeruginosa and Pectobacterium carotovorum The homologs of AidB with AHL-degrading activities were found only in several genera belonging to the Alphaproteobacteria Remarkably, AidB is a thermostable enzyme that retained its catalytic activity after treatment at 80°C for 30 min and exhibits reliable storage stability at both 4°C and room temperature. These properties might make it more suitable for practical application.

14.
ACS Appl Mater Interfaces ; 11(44): 41701-41709, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31625378

RESUMO

Flexible wearable soft epidermal sensors assembled from conductive hydrogels have recently attracted tremendous research attention because of their extensive and significant applications in body-attachable healthcare monitoring, ultrasensitive electronic skins, and personal healthcare diagnosis. However, traditional conductive hydrogels inevitably face the challenge of long-term usage under room temperature and cold conditions, due to the lost water, elasticity, and conductivity at room temperature, and freezing at the water icing temperatures. It severely limits the applications in flexible electronics at room temperature or cold environment. Herein, we report a flexible, wearable, antifreezing, and healable epidermal sensor assembled from an antifreezing, long-lasting moist, and conductive organohydrogel. The nanocomposite organohydrogel is prepared from the conformal coating of functionalized reduced graphene oxide network by the hydrogel polymer networks consisting of poly(vinyl alcohol), phenylboronic acid grafted alginate, and polyacrylamide in the binary ethylene glycol (EG)/H2O solvent system. The obtained organohydrogel exhibits excellent temperature tolerance (-40 °C), long-lasting moisture (20 days), reliable self-healing ability, and can be assembled as wearable sensor for an accurate detection of both large and tiny human activities under extreme environment. Thus, it paves the way for the design of highly sensitive wearable epidermal sensors with reliable long-lasting moisture and excellent temperature tolerance for potential versatile applications in electronic skins, wearable healthcare monitoring, and human-machine interaction.

15.
Materials (Basel) ; 12(20)2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31640209

RESUMO

In the field of engineering, the annual economic loss caused by material fatigue failure reaches 4% of the total economic output. The deep understanding of rubber fatigue failure can help develop and prepare rubber composites with high durability. The crack precursor sizes within the rubber composites are vital for the material mechanical and fatigue properties. In this study, we adopted three different characterization methods to analyze crack precursor sizes and their distribution. First, based on the theoretical formula of fracture mechanics, the size of the crack precursor was deduced from 180 µm to 500 µm by the uniaxial tensile experiment combined with tear test (nicked angle tear, planar tear and trouser tear). Second, by combining the uniaxial fatigue test of dumbbell specimen with the fatigue crack growth rate test, the average size of the crack precursor was calculated as 3.3 µm based on the Thomas fatigue crack growth model. Third, the average size of the crack precursor was 3.6 µm obtained by scanning electron microscope. Through theoretical calculations and experimental tests, the size and distribution of the crack precursors of rubber composites were systematically presented. This work can provide theoretical guidance for the improvement of fatigue performance of rubber composites.

16.
Immunology ; 158(4): 362-374, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31559637

RESUMO

The neuroinflammation following traumatic spinal cord injury (SCI) is a critical process that impacts both the injury and the recovery of spinal cord parenchyma. Infiltrating regulatory T (Treg) cells are potent anti-inflammatory cells that restrain post-SCI neuroinflammation. To understand the molecular mechanisms underlying the activity of infiltrating Treg cells, we used a mouse spinal cord compression injury model to analyze the role of Sirtuins (SIRTs) in the modulation of infiltrating Treg cell functions. We found that the expressions of SIRT4 and SIRT6 were up-regulated in infiltrating Treg cells. Using lentivirus-mediated gene expression or RNA interference, we revealed that SIRT4 substantially inhibited the expression of Foxp3, interleukin-10, and transforming growth factor-ß in Treg cells, whereas SIRT6 had little effect on Treg cells. Consistently, SIRT4 overexpression weakened the suppressive effect of Treg cells on lipopolysaccharide-stimulated spinal cord CD11b+ myeloid cells. Knock-down of SIRT4 enhanced the anti-inflammatory activity of infiltrating Treg cells in the parenchyma of injured spinal cords. Additionally, SIRT4 overexpression blocked in vitro Treg cell generation from conventional T cells. Furthermore, SIRT4 down-regulated 5' AMP-activated protein kinase (AMPK) signaling in Treg cells, whereas the AMPK agonist AICAR restored the expression of Foxp3 and interleukin-10 in SIRT4-overexpressing Treg cells. In conclusion, our research unveils a new mechanism by which the post-SCI neuroinflammation is regulated.

17.
Front Plant Sci ; 10: 1059, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31543889

RESUMO

The type III secretion system (T3SS) in many Gram-negative bacterial pathogens is regarded as the most critical virulence determinant and an attractive target for novel anti-virulence drugs. In this study, we constructed a T3SS secretion reporter containing the ß-lactamase gene fused with a signal peptide sequence of the T3SS effector gene, and established a high-throughput screening system for T3SS inhibitors in the plant pathogenic bacterium Acidovorax citrulli. From a library of 12,000 chemical compounds, we identified a series of benzyloxy carbonimidoyl dicyanide (BCD) derivatives that effectively blocked T3SS-dependent ß-lactamase secretion. Substitution of halogens or nitro groups at the para-position on the benzene ring contributed to an increased inhibitory activity. One representative compound, BCD03 (3,4-dichloro-benzyloxy carbonimidoyl dicyanide), dramatically reduced pathogenicity of A. citrulli on melon seedlings, and attenuated hypersensitive responses in the non-host Nicotiana tabacum caused by pathogenic bacteria A. citrulli, Xanthomonas oryzae pv. oryzae and Pseudomonas syringae pv. tomato at sub-MIC concentrations. Western blotting assay further confirmed that BCD03 inhibited effector secretion from the above bacteria via T3SS in the liquid medium. Taken together, our data suggest that BCD derivatives act as novel inhibitors of T3SS in multiple plant bacterial pathogens.

18.
Free Radic Res ; 53(8): 910-921, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31401895

RESUMO

Heart failure (HF) has become a global public health problem due to its unclear pathogenesis. Our previous studies have found that RNA oxidation is associated with the occurrence and development of a variety of chronic diseases in the elderly, but whether RNA oxidation is related to the pathogenesis of HF remains unclear. Male Dahl salt-sensitive rats (DSSR) were divided into 8% NaCl groups and 0.3% NaCl groups. The blood pressure of DSSR, HE staining of cardiac tissue, cardiac function index of colour Doppler echocardiography and plasma N-terminal probrain Natriuretic Peptide (NT-ProBNP) were used to evaluate the model making. The levels of 8-hydroxyguanosine (8-oxoGsn) and 8-hydroxydeoxyguanosine (8-oxodGsn) in myocardium and urine of DSSR were determined by high-performance liquid chromatography-mass spectrometry (LC-MS/MS). The expression of ERK-MAPK pathway and MTH1 was detected by Western blot (WB). Rats in the 8% NaCl group developed heart failure symptoms such as increased blood pressure, myocardial hypertrophy, decreased diastolic function, and increased plasma NT-ProBNP. The content of 8-oxoGsn in urine and heart tissue also increased, which was positively correlated with the related indicators of heart failure. This process is also accompanied by the sequential activation of ERK-MAPK pathway molecules and the increase of MTH1. The mechanism of RNA oxidation and inhibition is related to the occurrence and development of HF, which may be involved through ERK-MAPK pathway.

19.
Artigo em Inglês | MEDLINE | ID: mdl-31425016

RESUMO

OBJECTIVE: This study aimed to decode shoulder, elbow and wrist dynamic movements continuously and simultaneously based on multi-channel surface electromyography signals, useful for electromyography controlled exoskeleton robots for upper-limb rehabilitation. METHODS: Ten able-bodied subjects and ten stroke subjects were instructed to voluntarily move the shoulder, elbow and wrist joints back and forth in a horizontal plane with an exoskeleton robot. The shoulder, elbow and wrist movements and surface electromyography signals from six muscles crossing the joints were recorded. A set of three parallel linear-nonlinear cascade decoders was developed to continuously estimate the selected shoulder, elbow and wrist movements based on a generalized linear model using the anterior deltoid, posterior deltoid, biceps brachii, long head triceps brachii, flexor carpi radialis, and extensor carpi radialis muscle electromyography signals as the model inputs. RESULTS: The decoder performed well for both healthy and stroke populations. As movement smoothness decreased, decoding performance decreased for the stroke population. CONCLUSION: The proposed method is capable of simultaneously and continuously estimating multi-joint movements of the human arm in real-time by characterizing the nonlinear mappings between muscle activity and kinematic signals based on linear regression. SIGNIFICANCE: This may prove useful in developing myoelectric controlled exoskeletons for motor rehabilitation of neurological disorders.

20.
Nanoscale Res Lett ; 14(1): 280, 2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31420760

RESUMO

A new method to grow Indium quantum dots (In QDs) on the surface of an epitaxial InGaN layer by MOCVD is proposed. Uniform-sized In quantum dots have been found to form on the surface of an InGaN layer when a two-step cooling process is taken. Through analyzing, we found that the formation of In QDs on the surface is due to the reaction between the surface In-rich layer and the carrier gas H2 at the lower temperature period in the two-step cooling process. At the same time, as the density of In QDs is closely dependent on the surface In-rich layer, this provides us a way to study the surface property of the InGaN layer directly.

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