DNA-controlled excitonic switches

Fluorescence resonance energy transfer (FRET) is a promising means of enabling information processing in nanoscale devices, but dynamic control over exciton pathways is required. Here, we demonstrate the operation of two complementary switches consisting of diffusive FRET transmission lines in which exciton flow is controlled by DNA. Repeatable switching is accomplished by the removal or addition of fluorophores through toehold-mediated strand invasion. In principle, these switches can be networked to implement any Boolean function.     

Effect of protein concentrations of bovine serum albumin and γ-globulin on the frictional response of a cobalt-chromium femoral head

The study aims to identify the concentration-dependent role of bovine serum albumin (BSA) and γ-globulin in the lubricating ability of a cobalt-chromium femoral head. The frictional coefficients of the cobalt-chromium femoral head decreased with increasing BSA concentrations from 10 to 40 mg/ml and showed statistical differences between any of the BSA concentration groups, except between the 30 and 40 mg/ml concentration groups. In γ-globulin, the frictional coefficients significantly decreased at concentrations of 2.5 and 5.0 mg/ml as compared with the PBS control group, but significant increases were observed at 7.5 and 12.5 mg/ml. These results suggest that the friction of the cobalt-chromium femoral head is dependent on the concentration of both BSA and γ-globulin. However, there is a maximum concentration for BSA to act as an effective boundary lubricant, while the lubricating ability of γ-globulin is most effective in the physiological concentration range within human synovial fluid.     

A hybrid water flow algorithm for multi-objective flexible flow shop scheduling problems

In this article, the multi-objective flexible flow shop scheduling problem with limited intermediate buffers is addressed. The objectives considered in this problem consist of minimizing the completion time of jobs and minimizing the total tardiness time of jobs. A hybrid water flow algorithm for solving this problem is proposed. Landscape analysis is performed to determine the weights of objective functions, which guide the exploration of feasible regions and movement towards the optimal Pareto solution set. Local and global neighbourhood structures are integrated in the erosion process of the algorithm, while evaporation and precipitation processes are included to enhance the solution exploitation capability of the algorithm in unexplored neighbouring regions. An improvement process is used to reinforce the final Pareto solution set obtained. The performance of the proposed algorithm is tested with benchmark and randomly generated instances. The computational results and comparisons demonstrate the effectiveness and efficiency of the proposed algorithm.     

Effect of biogas technology on nutrient flows for small- and medium-scale pig farms in Vietnam

Increased demand for meat products has led to increased livestock production in Vietnam, which now risks environmental pollution from inappropriate animal manure management on livestock farms. Biogas technology is generally considered an efficient solution for such farms to produce renewable biofuel for use in the household and to reduce the pollution impact from animal waste. However, with biogas technology, farmers may reduce their use of manure for fertilising crops. This field survey investigated nutrient flows on small- and medium-scale livestock farms with and without biogas in Northern Vietnam, in order to identify existing problems and possibilities for sustainable livestock production. A field survey was conducted on 12 pig farms with biogas and 12 pig farms without biogas in Quoc Oai district, Hanoi city. In general, the non-biogas pig farms used on average 3.8 ton compost and 3.1 ton fresh solid manure ha^?1?crop^?1 for each of three crops typically grown per year on their arable land. They discharged on average 16?% of the total manure produced into the environment in liquid form through the public sewage system. On biogas pig farms, the use of fresh solid manure for crops and discharge of liquid manure was lower, as manure was used to produce biogas. However, excessive use of washing water on several of these farms resulted in very dilute slurry (solid manure:water ratio 1:11) entering the biogas digester. This lowered the retention time in the digester (below the optimum range of 35?C55?days), leading to low biogas production rates and possible accumulation of sediment. The digestate was also highly diluted and hence difficult and costly to transport and apply to crops, so it was largely (60?%) discharged to the environment. The input volume of washing water should therefore be reduced to a ratio of 1:5. For better sustainability, appropriate technologies are needed to absorb nutrients from the digestate before discharge and to recycle these nutrients to crops.     

Multiwall carbon nanotubes grown by thermocatalytic carbonization of polyacrylonitrile

A method is reported for the growth of multiwall carbon nanotubes (MWCNTs) using polyacrylonitrile as a solid carbon source and nanosized SiO₂ particles as catalyst. The nanotubes were grown either on a Si substrate or as a freestanding film at temperatures as low as 800 °C. The smallest measured inner diameter of the resultant MWCNTs is about 0.6 nm and therefore this method provides a new direction to prepare MWCNTs with very small inner diameter from solid carbon source.     

An eco-friendly and efficient route of lignin extraction from black liquor and a lignin-based copolyester synthesis

Traditional method for extraction of lignin from black liquor in chemical pulping processes requires a huge amount of toxic inorganic acids like sulfuric acid which are potentially harmful to our environment and life. Furthermore, the traditional method always contains multiple steps, and thus it is time-consuming process. With a purpose to eliminate all these above disadvantages, in this study, we successfully developed an efficient process for the extraction of lignin from black liquor using a non-toxic aluminum potassium sulfate dodecahydrate (AlK(SO₄)₂·12H₂O). The developed process is simple, efficient, and short-time, which obviously have more advantages over the traditional extraction method. Furthermore, the lignin extracted in this study was used to synthesize a copolyester through polyesterification between lignin and sebacoyl chloride. The copolymer possesses a molecular weight of 31,800, corresponding to four to five repeating units of lignin macromonomers. Notably, it showed a good thermal stability up to 200 °C in TGA analysis. It was also possible to shape the copolymer using solvent casting. We believe that this newly developed method of lignin extraction may exploit new applications for eco-friendly sustainable materials in various fields.     

Synthesis of single-crystal SnO2 nanowires for NOx gas sensors application

Single-crystal SnO₂ nanowires (NWs) were successfully synthesized and characterized as sensing materials for long-term NO_x stability detection in environmental monitoring. Reproducible and selective growths of the SnO₂ NWs on a patterned, 5 nm-thick gold catalyst coated on a SiO₂/Si wafer as substrate were conducted by evaporating SnO powder source at 960 °C in a mixture of argon/oxygen ambient gas (Ar: 50 sccm/O₂: 0.5 sccm). The as-obtained products were characterized by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman scattering, and photoluminescence (PL). The SEM and HRTEM images revealed that the products are single-crystal SnO₂ NWs with diameter and length ranges of 70 nm–150 nm and 10 μm–100 μm, respectively. The three observed Raman peaks at 476, 633, and 774 cm⁻¹ indicated the typical rutile phase, which is in agreement with the XRD results. The NWs showed stable PL with an emission peak centered at around 620 nm at room-temperature, indicating the existence of oxygen vacancies in the NW samples. The electrical properties of synthesized SnO₂ NWs sensor were also investigated and it exhibited a negative temperature coefficient of resistance in the measured range (300–525 K). The calculated activation energy E_c of SnO₂ NWs was 0.186 eV. Moreover, the SnO₂ NW sensors exhibited good response to NO_x gas. The response of the sensors to 5 ppm NO_x reached 105% at an operating temperature of 200 °C.     

Estimating mechanical properties of clear wood from ten‐year‐old Melia azedarach trees using the stress wave method

The objective of this study was to examine the potential of stress wave velocity (SWV) as a rapid and non-destructive method to estimate the mechanical properties of Melia azedarach wood. The SWV, dynamic modulus of elasticity (MOE_d), modulus of elasticity (MOE), modulus of rupture (MOR, bending strength) and density were determined on ninety 20 ? 20 ? 320 mm clear wood specimens, obtained from stems of three ten-year-old M. azedarach trees, and tested at environmental equilibrium in 20°C, 60?% relative humidity (a moisture content of approximately 12?%). There was a statistically significant (0.1?% level) but weak correlation (R²?=?0.23) between the SWV and MOE, but no statistically significant correlation was found between the SWV and MOR. Much better results for prediction of static properties of M. azedarach wood were obtained when SWV and wood density (WD) were used together through calculation of MOE_d in the air-dry condition (MOE: R²?=?0.76, MOR: R²?=?0.47), although in the case of MOR a model based on WD alone is slightly better (R²?=?0.58), and WD is also almost as good as MOE_d for predicting MOE. It is concluded that SWV coupled with WD can be employed as a predicting parameter to evaluate the mechanical properties of M. azedarach wood during the manufacturing process, although WD alone is also effective. The SWV alone would not be useful due to MOE being almost directly proportional to WD at this moisture content.

     

Design of characteristic parameters for controlling tungsten tip profile during electrochemical etching

Micro/nano-scale tungsten tips fabricated by electrochemical etching have many diverse industrial applications. The characteristic parameters of the tungsten tip profile include apex radius, taper angle, and aspect ratio. These parameters are governed by many factors including applied voltage, concentration of the electrolyte (potassium hydroxide) solution, and diameter of the inner gold ring. However, a systematic investigation with the aim of determining the best conditions for fabricating micro/nano-scale tips with desired profiles has not been carried out yet. This study is aimed at obtaining controllable tungsten tip profiles—particularly with respect to the radius of curvature and aspect ratio of tips (taper angle)—by altering the experimental conditions. A series of experiments were executed and the results were aggregated and analyzed using response surface methodology in order to identify the relationships between the tungsten tip characteristics and input parameters. The method proposed herein would prove to be suitable for a variety of applications in industries that require tungsten tips with a specific profile.