Oriented growth of ZnO nanostructures on different substrates via a hydrothermal method

Well-oriented ZnO nanorod arrays are successfully fabricated on different substrates. They are formed on different substrates at low temperature via a hydrothermal method, without adding any catalysts or templates. This approach is convenient and inexpensive. The morphologies of ZnO crystals could be controlled and transformed to other morphologies successfully by using different substrates. The effects of the substrates on the ZnO nanorod arrays have been systematically studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterizations of XRD and scanning electron microscopy (SEM) reveal that these products are pure single-crystal and the structure is uniform. The photoluminescence property has been detected by photoluminescence (PL) spectrum and Raman spectrum. Photoluminescence measurements show that each spectrum consists of the ultraviolet (UV) band and a relative broad visible light emission peak. But substrates play roles in the intensity of ultraviolet and visible light emission peak. The green emission in Raman measurement may be related to the surface states.     

Biomass accumulation in rapidly growing loblolly pine and sweetgum

Loblolly pine (Pinus taeda) and sweetgum (Liquidambar styraciflua) trees, growing in International Paper Company's study of intensive management on marginal agricultural land near Bainbridge GA, were destructively sampled at the end of the sixth growing season. All trees were single family blocks of genetically superior trees planted 2.5 m apart on sub-soiled rows 3.6 m apart and grown with complete competition control. Management treatments were: control, irrigation, irrigation plus fertilization, and irrigation plus fertilization plus pest control. Tree measures were basal diameter, DBH, height of live crown, diameter at base of live crown, and total height. Twenty trees of each species were destructively sampled. Stems were sectioned at 1 m intervals, stem diameter determined at each end and sections were weighed green. Branches were removed and height, basal diameter, and length were measured on each branch. Branches were separated into foliated and unfoliated segments and weighed green. A stem disk and branch from each meter were returned to the lab to determine dry weight: green weight ratio. Foliated limb: foliage ratios were also determined from sub-sampled branches. Intensive culture resulted in larger growth differences for sweetgum (most intensive treatment 9.5 m tall, 13.1 cm DBH; control trees 5.0 m tall, 6.3 cm DBH) than in pine (most intensive treatment 10.3 m tall, 17.7 cm DBH; control, 7.6 m tall, 13.4 cm DBH). The pipe model of tree development explained dimensions of the upper 5 m of crown with leaf biomass highly correlated to branch basal area (r² from 0.697 to 0.947). There was a constant ratio of leaf biomass to branch basal area (50 gm/cm² for pine, 30 gm/cm² for sweetgum). We also found a constant ratio of bole basal area to cumulative branch basal area throughout the crowns. Rapidly growing pines produced about 49 Mg ha⁻¹ of stem biomass, 11 Mg ha⁻¹ of dead branch biomass, and 17 Mg ha⁻¹ of unfoliated branch biomass at the end of six years.     

Biomechanics of oral mucosa

The prevalence of prosthodontic treatment has been well recognized, and the need is continuously increasing with the ageing population. While the oral mucosa plays a critical role in the treatment outcome, the associated biomechanics is not yet fully understood. Using the literature available, this paper provides a critical review on four aspects of mucosal biomechanics, including static, dynamic, volumetric and interactive responses, which are interpreted by its elasticity, viscosity/permeability, apparent Poisson''s ratio and friction coefficient, respectively. Both empirical studies and numerical models are analysed and compared to gain anatomical and physiological insights. Furthermore, the clinical applications of such biomechanical knowledge on the mucosa are explored to address some critical concerns, including stimuli for tissue remodelling (interstitial hydrostatic pressure), pressure–pain thresholds, tissue displaceability and residual bone resorption. Through this review, the state of the art in mucosal biomechanics and their clinical implications are discussed for future research interests, including clinical applications, computational modelling, design optimization and prosthetic fabrication.     

Trace sulfur promoted Fe,N-codoped carbon black as electrocatalyst for oxygen reduction reaction

Doping carbon materials with Fe and N attracts great attention due to its promising application in preparing ORR electrode with high performance and low cost. Previously, Fe, N-codoped catalyst (Fe/N/C) had been synthesized via a simple one-pot method using carbon materials, dopamine and FeCl₃ by our group. However, the unstable activity and low selectivity (electron transfer number of ∼3.5) are key problems that should be solved. Herein, trace sulfur has been introduced into Fe, N-codoped carbon black by using 2-mercaptoethanol as an adhesive sulfur precursor. By the doping of trace S atoms (∼0.25 at%) into Fe, N-codoped carbon frameworks, the ORR performance has been obviously improved simply without any re-treatment process, such as acid-etching or nitrogen supplement. The mechanism of this process has been systematically investigated by changing the amount of initial sulfur precursor. A moderate amount of trace sulfur can effectively enhance the ORR performance of Fe, N-codoped carbon black due to suitable interactions among Fe, N, S and C elements. Both the content and the state of Fe and N species on the surface of carbon black can be changed and controlled by trace sulfur. The as-synthesized 1.0 SFe/N/C catalyst exhibits a good ORR activity (E_1/2 = 0.749 V, J_k = 54.56 mA cm⁻²) and a total 4-electron selectivity. 1.0 SFe/N/C also shows better catalytic stability and methanol tolerance than 20 wt% Pt/C.     

Measuring driver responses at railway level crossings

Railway level crossings are amongst the most complex of road safety control systems, due to the conflicts between road vehicles and rail infrastructure, trains and train operations. Driver behaviour at railway crossings is the major collision factor. The main objective of the present paper was to evaluate the existing conventional warning devices in relation to driver behaviour. The common conventional warning devices in Australia are a stop sign (passive), flashing lights and a half boom-barrier with flashing lights (active). The data were collected using two approaches, namely: field video recordings at selected sites and a driving simulator in a laboratory. This paper describes and compares the driver response results from both the field survey and the driving simulator. The conclusion drawn is that different types of warning systems resulted in varying driver responses at crossings. The results showed that on average driver responses to passive crossings were poor when compared to active ones. The field results were consistent with the simulator results for the existing conventional warning devices and hence they may be used to calibrate the simulator for further evaluation of alternative warning systems.     

Studies on the structure and properties of thermoplastic starch/luffa fiber composites

Thermoplastic starch (TPS)/luffa fiber composites were prepared using compression molding. The luffa fiber contents ranged from 0 wt.% to 20 wt.%. The tensile strength of the TPS/luffa fiber composite with 10 wt.% of luffa fiber had a twofold increase compared to TPS. The temperature values of maximum weight loss of the TPS/luffa fiber composites were higher than for TPS. The water absorption of the TPS/luffa fiber composites decreased significantly when the luffa fiber contents increased. The strength of adhesion between the luffa fiber and the TPS matrix was clearly demonstrated by their compatibility presumably due to their similar chemical structures as shown by scanning electron microscope (SEM) micrographs and Fourier transform infrared (FTIR) spectra.     

Test of shear transfer enhancement in symmetric cold-formed steel-concrete composite beams

An experimental programme was conducted to study the strength and behaviour of a bent-up tab shear transfer enhancement. Sixty eight push-out test specimens of cold-formed steel lipped channel sections (CFS) embedded in concrete planks which make use of the new proposed shear transfer enhancement called bent-up triangular tab shear transfer (BTTST) were tested in this programme. This paper summarises the results of the experimental study and develops an expression in order to predict the innovative shear transfer enhancement mechanism, BTTST in a new type of precast composite beam comprising CFS embedded in a precast concrete plank. The results show that specimens employed with shear transfer enhancements increase the shear capacities of the specimens as compared to those relying only on a natural bond between cold-formed steel and concrete. In this investigation, BTTST provided better performance in terms of strength. Furthermore the effects of different angles and sizes for BTTST, different thickness for CFS and different strengths for concrete are also discussed. It is concluded that the proposed shear transfer enhancement has sufficient strength and is also feasible.     

Surface structural alteration of multi-walled carbon nanotubes decorated by nickel nanoparticles based on laser ablation/chemical reduction methods to enhance hydrogen storage properties

The catalytic effect of nickel is addressed to decorate the multi-walled carbon nanotubes for the purpose of hydrogen storage. The hydrogen sorption/desorption are investigated using the volumetric technique. Nickel nanoparticles are distributed on the surface of nanotubes using the laser ablation/chemical reduction treatments. The hydrogen uptake is elevated at higher nickel population up to a certain value and then experiences a significant drop for larger nickel content. The laser treatment is accompanied by the induced pores around nanotubes. This gives rise to the creation of the larger pores at higher laser doses leading to decrease the hydrogen trapping. Despite the pore size distribution strongly alters during both synthesis methods, however the abundance of small pore size in laser treatments is relatively higher than the that of the other technique. In comparison, the laser ablation demonstrates a relatively smaller desorption temperature against chemical one, mainly owing to the formation of larger pore size/volume. Generally, the hydrogen trapping efficiently takes place in the laser treated samples against chemical reduction method. The highest value of hydrogen storage ∼1% (0.6% weight) is corresponding to 12.3% (13% weight) of nickel loading via the laser ablation (chemical reduction).     

Effects of micronization on viability and thermotolerance of probiotic freeze-dried cultures

Three strains of probiotic freeze-dried bacteria, Bifidobacterium breve R070 (BB R070), Bifidobacterium longum R023 (BL R023), and Lactobacillus acidophilus R335 (LA R335), were micronized using a spiral jet mill as grinding system, in order to decrease the powder particle size for incorporation in multiphase low-diameter microcapsules produced by emulsification and spray-drying. The effects of grind air pressure (1, 2, 4 or 5.5 bar) and product feed rate (150 or 300 g h⁻¹) on powder particle-size distribution and bacterial viability were evaluated. The D(ν, 0.9) of the micronized powder was found to be only affected by grind air pressure (P<0.05). Survival of the micro-organisms to the particle-size reduction process was essentially related to the final powder particle size. A grind air pressure of 4 bar with a product feed rate of 300 g h⁻¹ was selected as the least destructive treatment (survival rate of 25.5±5.2%) to produce powders of probiotic freeze-dried cultures with particle-size distribution suitable for the microencapsulation technology (D(ν, 0.9)<25 μm). Heat susceptibility of the two micronized bifidobacteria strains prepared using these operating conditions was compared with that of the unprocessed cultures by means of various thermotolerance parameters (E_a, D_45°C, D_65°C, D_80°C). Results indicated that BL R023 displayed intrinsic low heat resistance whereas particle-size reduction dramatically increased the thermosensitivity of BB R070. Micronization is an effective way of reducing powder particle size of freeze-dried bacterial cultures for subsequent use in cell immobilization applications with low heat treatment.