Search

An adaptive wheel-legged shape reconfigurable mobile robot, based on a scissor-like mechanism, is proposed for an obstacle detecting and surmounting robot, moving on complex terrain. The robot can dynamically adjust its own shape, according to the environment, realizing a transformation of wheel shape into leg shape and vice versa. Each wheel-legged mechanism has one degree of freedom, which means that only the relative motion of the inner and outer discs is needed to achieve the transformation of the shape into a wheel or a leg. First, the force analysis of the conversion process of the wheel-legged mechanism is carried out, while the relationship between the driving torque and the friction factor in the non-conversion trigger stage and in the conversion trigger stage is obtained. The results showed that the shape conversion can be better realized by increasing the friction factor of the trigger point. Next, the kinematics analysis of the robot, including climbing the obstacles, stairs and gully, is carried out. The motion of the spokes tip is obtained, in order to derive the folding ratio and the surmountable obstacle height of the wheel-legged mechanism. The parameters of the wheel-legged structure are optimized, to obtain better stability and obstacle climbing ability. Finally, a dynamic simulation model is established by ADAMS, to verify the obstacle climbing performance and gait rationality of the robot, in addition to a prototype experiment. The results showed that the surmountable obstacle height of the robot is about 3.05 times the spoke radius. The robot has the stability of a traditional wheel mechanism and the obstacle surmount performance of a leg mechanism, making it more suitable for field reconnaissance and exploration missions. [ABSTRACT FROM AUTHOR]

In recent years, metal-organic frameworks (MOFs) have been attracting ever more Interest owing to their fascinating structures and widespread applications. Among the optoelectronic materials, luminescent MOFs (LMOFs) have become one of the most attractive candidates in the fields of optics and photonics thanks to the unique characteristics of their frameworks. Luminescence from MOFs can originate from either the frameworks, mainly including organic linkers and metal ions, or the encapsulated guests, such as dyes, perovskites, and carbon dots. Here, we systematically review the recent progress in LMOFs, with an emphasis on the relationships between their structures and emission behaviour. On this basis, we comprehensively discuss the research progress and applications of multicolour emission from homogeneous and heterogeneous structures, host-guest hybrid lasers, and pure MOF lasers based on optically excited LMOFs in the field of micro/nanophotonics. We also highlight recent developments in other types of luminescence, such as electroluminescence and chemiluminescence, from LMOFs. Future perspectives and challenges for LMOFs are provided to give an outlook of this emerging field. We anticipate that this article will promote the development of MOF-based functional materials with desired performance towards robust optoelectronic applications. [ABSTRACT FROM AUTHOR]

Batch laboratory-scale experimentswere conducted to investigate the effects of hardness ions (Mg and Ca) onCr(VI) reduction with organic reducing substances in the form of sugarcane molasses at different conditions. Results illustrated that the reaction could be described as pseudo-first-order with respect to the Cr(VI) concentration. Reaction rate constants ofCr(VI) reductionwith sugarcanemolasseswere in the decreasing order of no hardness ions >Ca(II) >Mg(II). The possible mechanismwas that the complex formation between organic reducing substances and hardness ions (Mg or Ca) hampered the electron transfer rate of the organic reducing substances, and further led to a decrease in the reaction rate. For Mg(II), the initial reaction rates at different pH values (2.0, 2.5, 3.0, and 3.5) decreased by 0.0316, 0.0246, 0.0095, and 0.0023/h in the presence of Mg(II) compared with those in the absence of Mg(II). The inhibitory effect of Mg(II) on the reduction of Cr(VI) was present at different temperatures. The activation energy (Ea) was estimated at 57.4 and 65.6 kJ/mol in the presence and absence of Mg(II), respectively. This would be significant in promoting understanding influence mechanism of hardness ions on Cr(VI) reduction with sugarcane molasses. [ABSTRACT FROM AUTHOR]

The growing use of nanoscale zero-valent iron (NZVI) in the remediation of contaminated groundwater raises concerns regarding its transport in aquifers. Laboratory-scale sand-packed column experiments were conducted with bare and sucrose-modified NZVI (SM-NZVI) to improve our understanding of the transport of the nanoparticles in saturated porous media, as well as the role of media size, suspension injection rate and concentration on the nanoparticle behavior. As the main indicative parameters, the normalized effluent concentration was measured and the deposition rate coefficient (k) was calculated for different simulated conditions. Overall, compared to the high retention of bare NZVI in the saturated silica column, SM-NZVI suspension could travel through the coarse sand column easily. However, the transport of SM-NZVI particles was not very satisfactory in a smaller size granular matrix especially in fine silica sand. Furthermore, the value of k regularly decreased with the increasing injection rate of suspension but increased with suspension concentration, which could reflect the role of these factors in the SM-NZVI travel process. The calculation of k-value at the tests condition adequately described the experimental results from the point of deposition dynamics, which meant the assumption of first-order deposition kinetics for the transport of NZVI particles was reasonable and feasible. [ABSTRACT FROM AUTHOR]

Nanophotonics, which is mainly the study of the behavior of light-matter interaction at the wavelength scale, has developed into one of the most important branches in optics-related disciplines. Utilizing organic functional molecules as the building blocks of nanophotonic materials and devices has great potential due to the multiple advantages, including the molecular designability, good processability, tailorable properties, and so on. Small molecules exhibit a strong tendency to aggregate into lowdimensional structures through an assembly process. The morphologies of the formed products, which are tightly related to the stacking modes of the molecules, can be precisely controlled through the modulation of various intermolecular interactions. The optical properties of organic complex structures, assembled from one or more types of small molecules, show heavy dependence on the composition, distribution, as well as the topological structures, manifesting a strategy to acquire desired photonic properties via rational structural design and/or componential modulation. This tutorial review focuses on the relationship among various molecules, diverse structures and photonic properties, with emphasis on the controllable assembly processes to fabricate low-dimensional structures and assembly strategies to achieve requisite optofunctional properties. [ABSTRACT FROM AUTHOR]

This paper presents the results of a laboratory investigation of the influence zone (IZ) of air sparging (AS) in different media at different surface tension. Different kinds of media were used in two-dimensional tank experiments, designed to determine (1) the effect of surface tension reduction on the airflow pattern during AS in different air travelling modes (channels and bubbles) in homogeneous aquifer and (2) the airflow distribution and migration characteristics in heterogeneous aquifer at different surface tension during AS. The results demonstrated that in homogeneous gravel aquifer, the IZ was almost identical with or without surfactant addition into groundwater, the air saturation, however, was increased with decreasing surface tension. In homogeneous coarse sand tank saturated with 500 mg/L sodium dodecyl benzene sulphonate (SDBS) solution, the IZ was approximately 1.3 times larger than that in the same medium saturated with distilled water. In addition, the density of airflow channels was much larger in medium saturated with SDBS solution. In heterogeneous subsurface saturated with distilled water, when the permeability ratio between two adjoining layers was 8:1, air would bypass low-permeable soils. In contrast, the air would infiltrate into low-permeable soils when SDBS concentration in groundwater was 1000 mg/L. The results indicate that surfactant-enhanced air sparging can effectively improve the volatile organic compounds removal both in homogeneous and heterogeneous media. [ABSTRACT FROM PUBLISHER]

The structural and magnetic properties of SmFeO3 with B site substitution of non-magnetic atom Al are investigated. The x-ray diffraction patterns show that SmFe(1−x)AlxO3 remains an orthorhombic structure within the whole doping range, and the unit-cell volume decreases monotonically with the increase of doped Al concentration. Besides, the octahedral tilting distortions of FeO6 are found to be alleviated while the tolerance factor increases. However, the relationship between the lattice parameters and Al concentration is observed to deviate from Vegard's rule, and this may be caused by magnetostriction effects. For the doping content values in a range 0 ≤ x ≤ 0.6, the ferromagnetism, antiferromagnetism, and paramagnetism are observed to occur continuously. Moreover, the magnetization and the spin reorientation temperature (Tk) decrease monotonically as Al content value increases. With the doping content values being x = 0.8 and 1.0, these compounds only show paramagnetic behavior. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) nanostructures, including nanorods, nanowires, nanotubes, etc., exhibit the quantum confinement effects in the other two dimensions. Nanomaterials with 1D coherence are more suitable for the construction of active nanodevices and interconnects rather than zero-dimensional (0D) amorphous nanoparticles. Inorganic 1D nanomaterials have been widely investigated and widely used as building blocks in many kinds of optoelectronic integrations, and it is very reasonable to assume that their organic counterparts can also play an important role in this field. During the past ten years, organic 1D nanomaterials constructed from small functional molecules have obtained more and more attention due to their unique optical and electronic properties as well as their potential applications in nanoscale devices. Their high structural tunability, reaction activity and processability provide great opportunities to miniaturized optoelectronic chips based on organic 1D nanostructures, since they are usually assembled from molecular units with weak intermolecular interactions, such as hydrogen bonds, π–π stacking and van der Waals force. These weak interactions allow for more facile and mild conditions in the fabrication of high quality organic 1D nanostructures rather than those in the construction of their inorganic counterparts. More importantly, very recent studies reveal that the diversity of energy/electron transfer processes in organic semiconductors brings new hopes to break the performance limitations of traditional photonic and electronic devices, thus allowing higher luminescence intensity, more efficient photon confinement, stronger exciton–photon coupling, and so on. Indeed, organic 1D nanomaterials have already emerged to play increasingly an important role in many optoelectronic applications, such as nanolasers, optical waveguides, light-emitting devices, solar cells and sensors. In the past two decades, people have not only witnessed but also taken for granted the rapid development of nanomaterial science, and here we would like to promote awareness of the significance of organic 1D nanomaterials in the field of nanotechnology and optoelectronic nanodevices. This report presents a comprehensive review about recent research in the preparation and applications of 1D nanomaterials from functional low-molecular-weight organic compounds, whose optical and electronic properties are fundamentally different from those of their inorganic counterparts. Here we try to summarize the important breakthroughs from the fabrication of organic nanorods, nanowires and nanotubes, to the application of these nanostructures in integrated photonic elements and optoelectronic nanodevices. We begin with a general summary of the construction strategies (liquid-phase assembly, vapor deposition and template methods) for achieving 1D nanostructures from small organic functional molecules, then provide an overview of the unique optoelectronic properties induced by molecular aggregation in the nanostructures. Special emphasis is put on the luminescent properties of low dimensional sizes that are different from those of the corresponding bulk materials. This offers the materials better photon confinement ability or charge carrier transport property, and hence better optoelectronic performances such as optical waveguiding, multicolor emission, low-threshold nanolasers, light-emitting devices, photon-detecting devices, etc., which are presented one by one in the following section. In the last part of this report, we conclude with our personal viewpoints of the future development of organic 1D nanomaterials and also their great potentials in highly integrated photonic and electronic devices and chips. [ABSTRACT FROM AUTHOR]

In the presence of trifluoroacetic acid and methanesulfonic acid (MSA), a series of monohydric and polyhydric phenols readily undergo a domino Pechmann-dehydration reaction with various 4-hydroxy-6-oxocyclohexane-1,3-dicarboxylates to give 7,8-dihydro-6H-dibenzo[b,d]pyran-6-ones. Subsequent dehydrogenation of the 7,8-dihydro-6H-dibenzo[b,d]pyran-6-ones was performed expediently with DBU/BrCCl3 to give various 6Hdibenzo[ b,d]pyran-6-one derivatives. This strategy has the advantages of inexpensive and easily available raw materials, metal-free procedure, mild reaction conditions, good compatibility with various functional groups, and satisfactory yields. [ABSTRACT FROM AUTHOR]

Single-crystal ZnS1−xSexnanoribbons with various compositions were synthesized through an Au-catalyzed vapor transport method. Under two-photon pumping with an 800 nm femtosecond pulsed laser, the spontaneous emission peak of the ternary nanoribbons undergoes a gradual red-shift from 422 to 464 nm with the increase of Se content. When the pump energy densities are increased above the thresholds, the nanoribbons exhibit a tunable upconverted laser emission accompanied by a dramatic decrease in spectral linewidth as a set of sharp peaks on the corresponding wavelengths of each sample, featuring the occurrence of stimulated emission. Two components appear in the fluorescence lifetimes, which indicate that the ZnS1−xSexnanoribbons have two different recombination centers. Both lifetime components decrease with the increase of pump energy, further confirming the occurrence of stimulated emission. The two-photon pumped lasing behavior was also observed from single nanoribbons, in which the photoluminescence (PL) spectra are composed of multimode of lasing. The distinct modes show gain competition and pronounced shifts as a function of excitation density. [ABSTRACT FROM AUTHOR]

AIM: To investigate the sphingosine 1-phosphate (S1P) receptor expression profile in human esophageal cancer cells and the effects of S1P5 on proliferation and migration of human esophageal cancer cells. METHODS: S1P receptor expression profile in human esophageal squamous cell carcinoma cell line Eca109 was detected by semi-quantitative reverse transcription polymerase chain reaction. Eca109 cells were stably transfected with S1P5-EGFP or control-EGFP constructs. The relation between the responses of cell proliferation and migration to S1P and S1P5 expression was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and migration assay, respectively. RESULTS: Both normal human esophageal mucosal epithelium and Eca109 cells expressed S1P1, S1P2, S1P3 and S1P5, respectively. Esophageal mucosal epithelium expressed S1P5 at a higher level than Eca109 cell line. S1P5 over-expressing Eca109 cells displayed spindle cell morphology with elongated and extended filopodia-like projections. The proliferation response of S1P5-transfected Eca109 cells was lower than that of control vectortransfected cells with or without S1P stimulation (P < 0.05 or 0.01). S1P significantly inhibited the migration of S1P5- transfected Eca109 cells (P < 0.001). However, without S1P in transwell lower chamber, the number of migrated S1P5-transfected Eca109 cells was greater than that of control vector-transfected Eca109 cells (P < 0.001). CONCLUSION: S1P binding to S1P5 inhibits the proliferation and migration of S1P5-transfected Eca109 cells. Esophageal cancer cells may down-regulate the expression of S1P5 to escape the inhibitory effect. [ABSTRACT FROM AUTHOR]

Fluorescence resonance energy transfer in conjugated polymer composite materials was exploited for the detection of γ ray dosage with high sensitivity and response linearity. [ABSTRACT FROM AUTHOR]

Endemic fluorosis was investigated and studied in the west region of the Songnen plain, Northeast China in 2001–2002. The results showed that the fluorine distribution in aquatic environment was that the fluorine concentrations in the lake water and unconfined ground water were higher than that in the river water and confined ground water. The lake water (Alkali lake) is connected with unconfined ground water. In unconfined ground water, from the east and southeast areas to the west and the northwest areas of the plain, fluorine concentration fluctuated with high and low alternatively. The fluorine in the water comes from the weathering of rocks and minerals in the mountains and hills around the Songnen Plain. The main influence factors of the fluorine distribution in aquatic environment are discussed. Unconfined ground water containing high fluorine is used as drinking water. In this region, the fluorine concentration in drinking water is evidently correlated to the morbidity of dental and skeletal fluorosis. High fluorine concentration in drinking water has endangered human health. [ABSTRACT FROM AUTHOR]

Two classes of bulk high-Zpolymer composites were prepared, which exhibit scintillation properties for γ-radiation detection. [ABSTRACT FROM AUTHOR]

The high-pressure behaviors of SmFeO3 are investigated by angle-dispersive synchrotron X-ray powder diffraction under a pressure of up to 40.3 GPa at room temperature. The crystal structure of SmFeO3 remains stable at up to the highest pressure. The different pressure coefficients of the normalized axial compressibility are obtained to be βa = 0.60 × 10−3 GPa−1, βb = 0.79 × 10m3 GPa−1, βc = 1.28 × 10−3 GPa−1, and the bulk modulus (B0) is determined to be 293(3) GPa by fitting the pressure-volume data using the Birch—Murnaghan equation of state. Furthermore, the larger compressibility of the FeO6 octahedra suggests the evolution of the orthorhombic structure towards higher symmetry configuration at high pressures. [ABSTRACT FROM AUTHOR]