Comprehensive Investigation of the Temperature-Dependent Electromechanical Behaviors of Carbon Nanotube/Polymer Composites.

The performances of flexible piezoresistive sensors based on polymer nanocomposites are significantly affected by the environmental temperature; therefore, comprehensively investigating the temperature-dependent electromechanical response behaviors of conductive polymer nanocomposites is crucial for developing high-precision flexible piezoresistive sensors in a wide-temperature range. Herein, carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composites widely used for flexible piezoresistive sensors were prepared, and then the temperature-dependent electrical, mechanical, and electromechanical properties of the optimized CNT/PDMS composite in the temperature range from -150 to 150 °C were systematically investigated. At a low temperature of -150 °C, the CNT/PDMS composite becomes brittle with a compressive modulus of ∼1.2 MPa and loses its elasticity and reversible sensing capability. At a high temperature (above 90 °C), the CNT/PDMS composite softens, shows a fluid-like mechanical property, and loses its reversible sensing capability. In the temperature range from -60 to 90 °C, the CNT/PDMS composite exhibits good elasticity and reversible sensing behaviors and its modulus, resistivity, and sensing sensitivity decrease with an increasing temperature. At room temperature (30 °C), the CNT/PDMS composite exhibits better mechanical and piezoresistive stability than those at low and high temperatures. Given that environmental temperature changes have significant effects on the sensing performances of conductive polymer composites, the effect of ambient temperature changes must be considered when flexible piezoresistive sensors are designed and fabricated.

Melatonin rescues impaired penetration ability of human spermatozoa induced by mitochondrial dysfunction.

Fertilization failure often occurs during in vitro fertilization (IVF) cycles despite apparently normal sperm and oocytes. Accumulating evidence suggests that mitochondria play crucial roles in the regulation of sperm function and male fertility. 3-Nitrophthalic acid (3-NPA) can induce oxidative stress in mitochondria, and melatonin, as an antioxidant, can improve mitochondrial function by reducing mitochondrial oxidative stress. The role of sperm mitochondrial dysfunction in fertilization failure during IVF is unclear. The present study revealed that spermatozoa with low, or poor, fertilization rates had swollen mitochondria, increased mitochondria-derived ROS, and attenuated mitochondrial respiratory capacity. 3-NPA treatment enhanced mitochondrial dysfunction in sperm. Spermatozoa with poor fertilization rates, and spermatozoa treated with 3-NPA, had reduced penetration ability. The concentration of melatonin was decreased in semen samples with low and poor fertilization rates. Melatonin, not only decreased excessive mitochondria-derived ROS, but also 'rescued' the reduced penetration capacity of spermatozoa treated with 3-NPA. Taken together, the study suggested that mitochondria-derived ROS and mitochondrial respiratory capacity are independent bio-markers for sperm dysfunction, and melatonin may be useful in improving sperm quality and overall male fertility.

Flexible Pressure Sensor with an Excellent Linear Response in a Broad Detection Range for Human Motion Monitoring.

Pressure sensing is highly demanding in wearable devices, robotics, and artificial intelligence, whereas it is still a big challenge to develop a pressure sensor with an excellent linear response in a broad detection range. Herein, a flexible and porous carbon nanotube (CNT)/carbon black (CB)/carbonyl iron powder (CIP)/silicone composite is proposed by a simple strategy of mixing, curing, and washing. Due to the porous structure induced by the sacrifice of sugar particles, an excellent linear response (R2 = 0.999) is achieved for the composite sensor by manipulating the contributions of contact resistance and tunnel resistance to the sensing performance via the alternation of CB and CNT contents. Moreover, the porous structure donates the composite sensor a low compressive modulus at a low pressure level, while the CIPs introduced lead to a high compressive modulus at a high pressure level with the assistance of an external magnetic field. As a result, the sensor produced has a wide linear response range of 80 Pa to 220 kPa, much wider than most of the linear response pressure sensors reported previously. The wide detection range is demonstrated by cyclic pressure tests in the frequency range of 0.1-5 Hz, durability tests, and monitoring human or robot motions including breathing, walking, lifting, and boxing, etc. Taking the advantages of low cost, high sensitivity, and excellent linear response in a wide pressure range, the current composite sensor is promising for precise monitoring of human motions and delicate controlling of robots.

Multiresponsive Ti3C2Tx MXene-Based Actuators Enabled by Dual-Mechanism Synergism for Soft Robotics.

Multiresponsive and high-performance flexible actuators with a simple configuration, high mechanical strength, and low-power consumption are highly desirable for soft robotics. Here, a novel mechanically robust and multiresponsive Ti3C2Tx MXene-based actuator with high actuation performance via dual-mechanism synergistic effect driven by the hygroexpansion of bacterial cellulose (BC) layer and the thermal expansion of biaxially oriented polypropylene (BOPP) layer is developed. The actuator is flexible and shows an ultrahigh tensile strength of 195 MPa. Unlike the conventional bimorph-structured actuators based on a single-mechanism, the actuator developed provides a favorable architecture for dual-mechanism synergism, resulting in exceptionally reversible actuation performance under electricity and near-infrared (NIR) light stimuli. Typically, the developed actuator can produce the largest bending angle (∼400°) at the lowest voltage (≤4 V) compared with that reported previously for single mechanism soft actuators. Furthermore, the actuator also can be driven by a NIR light at a 2 m distance, displaying an excellent long-distance photoresponsive property. Finally, various intriguing applications are demonstrated to show the great potential of the actuator for soft robotics.

One-Step Synthesis of Microdome Patterns for Microstructured Pressure Sensors with Ultra-High Sensing Performance.

Pressure sensors usually suffer from a trade-off between sensitivity and the linear sensing range, which may be improved by manipulating the geometric microstructure of active sensing materials via the molding strategy, standard photolithography technique, and so on. However, these conventional microengineering techniques require specialized equipment, which are extremely complicated, high-cost, and time-consuming to manufacture. Herein, a mold-free, scalable, low-cost, and environment-friendly one-step thermofoaming strategy is proposed to fabricate surface morphology-tunable microdome-patterned composites (MPCs). The microstructured pressure sensor is then prepared by coating the MPCs with highly conductive graphene. Remarkably, the as-prepared pressure sensor presents a better overall sensing performance compared to the previous pressure sensors prepared using complicated microengineering methods. Moreover, an electromechanical response model and finite-element analysis are used to clarify the sensing mechanisms of the present microstructured pressure sensor. Furthermore, several successful application demonstrations are conducted under various pressure levels. Considering the advantages of the one-step fabrication strategy over conventional surface microengineering techniques and the high performance of the microstructured pressure sensor, the present pressure sensor has promising potential applications in health monitoring, tactile sensation, wearable devices, etc.

Excellent Bipolar Resistive Switching Characteristics of Bi4Ti3O12 Thin Films Prepared via Sol-Gel Process.

Herein, Bi4Ti3O12 (BIT) ferroelectric thin films were fabricated into Au/BIT/LaNiO3/Si structures to demonstrate their memristor properties. Repeatable and stable bipolar resistive switching (RS) characteristics of the device are first reported in this work. The switching ratio of the device annealed in air reached approximately 102 at 0.1 and -0.1 V. The RS performance was not significantly degraded after 100 consecutive cycles of testing. We also explored the factors affecting the RS behavior of the device. By investigating the RS characteristics of the devices annealed in O2, and in combination with XPS analysis, we found that the RS properties were closely related to the presence of oxygen vacancies. The devices annealed in air exhibited a markedly improved RS effect over those annealed in O2. According to the slope fitting, the conduction mechanism of the device was the ohmic conduction and space charge limited current (SCLC). This study is the first to successfully apply BIT ferroelectric films to the RS layers of memristors. Additionally, a theory of conductive filaments is proposed to adequately explain the relationship between RS behavior and oxygen vacancies, providing meaningful inspiration for designing high-quality resistive random access memory devices.

Excellent Bidirectional Adjustable Multistage Resistive Switching Memory in Bi2FeCrO6 Thin Film.

As an important method to further improve the storage density of resistive memory, multistage resistive switching devices have become an important research direction. However, no stable and controllable multistage resistive switching device has been prepared, and the working mechanism is still unclear. Here, a sandwich-structured device is simply prepared by spin coating, with the work layer is the Bi2FeCrO6 thin film. The device can realize bidirectional controllable multistage resistive switching behavior, the biggest on/off ratio is 104, and it can maintain stability without attenuation at 100 times slow loop and 104 times pulse cycle. The analyzes showed that the charged ions formed by defects in the device migrated under the action of an external electric field lead to the Schottky barrier height reversible changed. Which is the key to cause multistage resistive switching behavior. This work is the first report about the voltage control of bidirectional adjustable multistage resistive switching behavior in the Bi2FeCrO6 thin film. The principle of generation is analyzed, and important ideas and insights are provided for the preparation and treatment of related multistage resistive problems.

Resistive Switching Characteristics of HfO2 Thin Films on Mica Substrates Prepared by Sol-Gel Process.

The resistive switching (RS) characteristics of flexible films deposited on mica substrates have rarely been reported upon, especially flexible HfO2 films. A novel flexible Au/HfO2/Pt/mica resistive random access memory device was prepared by a sol-gel process, and a Au/HfO2/Pt/Ti/SiO2/Si (100) device was also prepared for comparison. The HfO2 thin films were grown into the monoclinic phase by the proper annealing process at 700 °C, demonstrated by grazing-incidence X-ray diffraction patterns. The ratio of high/low resistance (off/on) reached 1000 and 50 for the two devices, respectively, being relatively stable for the former but not for the latter. The great difference in ratios for the two devices may have been caused by different concentrations of the oxygen defect obtained by the X-ray photoelectron spectroscopy spectra indicating composition and chemical state of the HfO2 thin films. The conduction mechanism was dominated by Ohm's law in the low resistance state, while in high resistance state, Ohmic conduction, space charge limited conduction (SCLC), and trap-filled SCLC conducted together.

E6/E7 proteins are potential markers for the screening and diagnosis of cervical pre-cancerous lesions and cervical cancer in a Chinese population.

The present prospective study aimed to evaluate the effects of E6/E7 protein detection by western blotting on cervical cancer (CC) early screening compared with detection by Hybrid Capture 2 (HC2) test and ThinPrep cytological test (TCT) in a Chinese population. A total of 450 cases of cervical intraepithelial neoplasia (CIN) suspected samples (positive in ≥1 indicator of TCT and HC2 test) were recruited from women who were treated at the International Peace Maternity and Child Health Hospital (Shanghai, China) from March 2014 to February 2015. Each sample was analyzed by cytological test. In addition, human papillomavirus (HPV) DNA examination by Hybrid Capture Tube test and E6/E7 protein expression detection by western blotting were performed in all samples, as well as histologic diagnosis to determine the stage of CIN. The results revealed that, for the diagnosis of CIN2+, although the sensitivity of E6/E7 protein detection was lower than that of HC2 test (71.3 vs. 96.6%, respectively), the specificity was markedly improved (67.6 vs. 5.9%, respectively). Compared with that of TCT, the sensitivity of E6/E7 protein detection was much higher (36.2 vs. 71.3%, respectively), but the specificity was lower (88.2 vs. 67.6%, respectively). In the present study, HPV E6/E7 protein expression was evaluated as a potential new biomarker for CC, with satisfactory diagnostic values for HPV types 16 and 18. The relative diagnostic value may be further improved by combination of E6/E7 messenger RNA detection.

Effect of a mixture of iprobenfos and malathion on the development of malathion resistance in the mosquito Culex pipiens pallens Coq.

A malathion-resistant (RM) strain of Culex pipiens pallens Coq was obtained by successively selecting a field population with malathion in the laboratory. The synergistic effect of iprobenfos on malathion toxicity and alpha-naphthyl acetate (alpha-NA) esterase assay revealed that malathion resistance in the RM strain was associated with increased alpha-NA esterase activity and the synergism was mainly due to the inhibition by iprobenfos of this activity. There was no difference in alpha-NA esterase activity between the larvae and female adults in the susceptible (S) strain, but the activity in the adults was 13-fold higher than in the larvae of the RM strain. To understand the effect of the application of a mixture of iprobenfos and malathion on the evolution of malathion resistance, an artificial strain (Syn) was generated by mixing the RM and S strains with 0.1 frequency of the malathion-resistant individuals. The offspring of the Syn strain were divided into two sub-strains, Rm and Rm+ibp, which were successively treated with, respectively, malathion alone and malathion + iprobenfos (1:2) at LC70. In the mixture, the fungicide iprobenfos acted as a synergist of malathion. After treatment for 10 generations, the resistance level to malathion was 317.4-fold for the Rm sub-strain, whereas for the Rm+ibp sub-strain it was only 38.9-fold, compared with the Syn strain. Similar results were obtained by measurement of alpha-NA esterase activity from both larvae and female adults. The alpha-NA esterase activities in larvae and female adults at F10 generation were 2.6- and 10.9-fold from the Rm+ibp sub-strain and 5.7- and 98.5-fold from the Rm sub-strain, respectively, compared with the Syn strain. The above results suggested that iprobenfos, although it cannot completely stop or prevent the onset of malathion resistance, could dramatically delay its evolution.

Acetylcholinesterase alterations reveal the fitness cost of mutations conferring insecticide resistance.

BACKGROUND: Insecticide resistance is now common in insects due to the frequent use of chemicals to control them, which provides a useful tool to study the adaptation of eukaryotic genome to new environments. Although numerous potential mutations may provide high level of resistance, only few alleles are found in insect natural populations. Then, we hypothesized that only alleles linked to the highest fitness in the absence of insecticide are selected. RESULTS: To obtain information on the origin of the fitness of resistant alleles, we studied Drosophila melanogaster acetylcholinesterase, the target of organophosphate and carbamate insecticides. We produced in vitro 15 possible proteins resulting from the combination of the four most frequent mutations and we tested their catalytic activity and enzymatic stability. Mutations affected deacetylation of the enzyme, decreasing or increasing its catalytic efficiency and all mutations diminished the stability of the enzyme. Combination of mutations result to an additive alteration. CONCLUSION: Our findings suggest that the alteration of activity and stability of acetylcholinesterase are at the origin of the fitness cost associated with mutations providing resistance. Magnitude of the alterations was related to the allelic frequency in Drosophila populations suggesting that the fitness cost is the main driving force for the maintenance of resistant alleles in insecticide free conditions.

Mutations of acetylcholinesterase which confer insecticide resistance in Drosophila melanogaster populations.

BACKGROUND: Organophosphate and carbamate insecticides irreversibly inhibit acetylcholinesterase causing death of insects. Resistance-modified acetylcholinesterases(AChEs) have been described in many insect species and sequencing of their genes allowed several point mutations to be described. However, their relative frequency and their cartography had not yet been addressed. RESULTS: To analyze the most frequent mutations providing insecticide resistance in Drosophila melanogaster acetylcholinesterase, the Ace gene was cloned and sequenced in several strains harvested from different parts of the world. Sequence comparison revealed four widespread mutations, I161V, G265A, F330Y and G368A. We confirm here that mutations are found either isolated or in combination in the same protein and we show that most natural populations are heterogeneous, composed of a mixture of different alleles. In vitro expression of mutated proteins showed that combining mutations in the same protein has two consequences: it increases resistance level and provides a wide spectrum of resistance. CONCLUSION: The presence of several alleles in natural populations, offering various resistance to carbamate and organophosphate compounds will complicate the establishment of resistance management programs.

Stratification analysis and case-control study of relationships between interleukin-6 gene polymorphisms and cervical cancer risk in a Chinese population.

Interleukin-6 (IL-6), a central proinflammatory cytokine, maintains immune homeostasis and also plays important roles in cervical cancer. Therefore, we aimed to evaluate any associations of IL-6 gene polymorphisms at positions -174 and -572 with predisposition to cervical cancer in a Chinese population. The present hospital- based case-control study comprised 518 patients with cervical cancer and 518 healthy controls. Polymorphisms of the IL-6 gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Patients with cervical cancer had a significantly higher frequency of the IL-6 -174 CC genotype [odds ratio (OR) =1.52, 95% confidence interval (CI) = 1.06-2.19; p=0.02], IL-6 -572 CC genotype (OR =1.91, 95% CI = 1.16-3.13; p=0.01) and IL-6 -174 C allele (OR =1.21, 95% CI = 1.02-1.44; p=0.03) compared to healthy controls. When stratifying by the FIGO stage, patients with III-IV cervical cancer had a significantly higher frequency of IL-6 -174 CC genotype (OR =1.64, 95% CI =1.04-2.61; p=0.04). The CC genotypes of the IL-6 gene polymorphisms at positions -174 and -572 may confer a high risk of cervical cancer. Additional studies with detailed human papillomavirus (HPV) infection data are warranted to validate our findings.

[Comparative study on impacted high tibial osteotomy and conventional high tibial osteotomy for the treatment of flexional medial knee osteoarthritis in aged patients].

OBJECTIVE: To compare the therapeutic effect of impacted high tibial osteotomy and conventional high tibial osteotomy for the treatment of flexional medial osteoarthritis of knee joint in aged patients. METHODS: From July 2003 to July 2006, 30 patients with flexional medial knee osteoarthritis were treated with impacted high tibial osteotomy or conventional high tibial osteotomy randomly. All patients,aged from 60 to 82 years,were suffered from 7 degrees to 19 degrees knee flexion deformities and 3 to 20 years medical histories. The bone healing periods, the recover of flexion and inversion deformities, and the recover of the knee joint function were observed postoperatively. The patients were followed up at 4, 6, 8, 9, 10, 12 and 16 weeks, and 5, 7, 9 and 12 months postoperatively. The bone healing periods and the recover of flexional and inversion deformities were evaluated and compared. Twelve months postoperatively,the knee joint function were assessed with the Lysholm scoring criteria, and the therapeutic effects were compared between the two groups. RESULTS: There was a significant difference in the average bone healing period between the impacted high tibial osteotomy group (9.26 +/- 2.23) weeks and the conventional high tibial osteotomy group (11.53 +/- 3.15) weeks. The knee joint function were evaluated according to the Lysholm clinical rating scales. One year postoperatively,the average Lysholm score were (88.5 +/- 4.4) points in the impacted high tibial osteotomy group,and the results showed excellent in 14 cases, good in 1. The average Lysholm score were (78.1 +/- 5.7) points in the conventional high tibial osteotomy group. The results showed 8 cases excellent, 5 good, 2 fair, accordingly. Postoperatively, the flexion deformities of the knee in the impacted high tibial osteotomy group were -1.1 degrees to 0 degrees and was corrected averagely (130 +/- 3.30) after surgery, and that in conventional high tibial osteotomy group (140 +/- 3.30) (the same as preoperation). The average postoperative femorotibial angle (FTA) were 170.2 degrees (ranged from 169.1 degrees to 172.3 degrees) and was corrected 12.3 degrees to 12.5 degrees after surgery in both groups. CONCLUSION: Compared with conventional high tibial osteotomy, impacted high tibial osteotomy can significantly shorten the bone healing period, improve the knee flexion, varus deformity, and the knee function.

Molecular characterization of a sodium channel gene from the Silkworm Bombyx mori.

The voltage-gated sodium channel mediates the rapid rising phase of action potentials in almost all excitable cells and is a molecular target of a variety of neurotoxins including pyrethroid insecticides. Most studies have focused on the expression of sodium channel genes in the adult stage, information on other developmental stages, however, is limited. In this study, we characterized the para sodium channel orthologous gene (BmNa(v)) of the silkworm Bombyx mori, a model insect of Lepidopteran species. The BmNa(v) gene covers a 31 kb genome region and contains 36 exons. The longest ORF contained 6258 bp and encoded 2085 amino acid residues, which shares 74%, and 77% overall amino acid sequence identities with the sodium channel proteins from Drosophila melanogaster and Blattella germanica, respectively. Using high-throughput Solexa sequence technology we conducted sequence analysis of BmNa(v) cDNAs from embryos, larvae, pupae and adults of the silkworm, identified alternative splicing sites and determined the frequencies of these splicing events in four developmental stages. Three optional exons, two sets of mutually exclusive exons, and one internal spliced exon were identified. One optional exon is unique to BmNa(v), while the others are conserved in other insect sodium channel genes. Interestingly, the expression of the mutually exclusive exons is developmentally regulated.

Expression and regulation of phospholipase A2 in venom gland of the chinese honeybee, Apis cerana cerana.

Phospholipase A(2) (PLA(2)) is one of the components of bee venom with a wide range of pharmacological functions. It operates as a major allergen working with other venom components to defend the colony from intruder. In the present study, the cDNA sequence of the Ac-pla(2) gene from cDNA library of the venom gland of Apis cerana was compared with the amplified corresponding region of genomic DNA. The result showed that the Ac-pla(2) gene consisted of four exons and three introns. Southern blot showed that the Ac-pla(2) gene was a single copy per haploid genome. The most active transcription period was during the first 8 days of adults, which correspondingly was the period of sharp increase of PLA(2) protein. ELISA analysis revealed that the PLA(2) was undetectable in pupal stage and the newly eclosed adult, but increased sharply to a maximum of 10-12 mug per honeybee by 8-10 days of adult life, followed by a gradual decrease to 8 mug for the rest of adult life. Transcriptional or post transcriptional regulation is the key step for Ac-pla(2) expression. The early secreted Ac-PLA(2) showed a low degree of post-translational modification; with increasing age, glycosylation was detected by Western blot and glycoprotein staining analysis. Different post-translational modifications were found among different individuals in A. cerana when compared to A. mellifera.