Plant Diversity Patterns Along Altitudinal Gradient in Understory Communities of Darkesh Region, Bojnord, Iran

The ecotone region of Darkesh with an area of 22,500 hectares is located in the Irano-Turanian xeric-continental bioclimatic zone of Khorassan-Kopet Dagh. To investigate the plant diversity patterns of understory communities along three elevation classes of 1100-1600, 1600-2100, and 2100-2600 m, 187 plots were sampled randomly and abundance and cover of species were recorded using 4-m2 plots. Beta diversity and Hill indices were calculated by using R and PAST software. A total of 252 species were recorded including 31 perennial grasses. The most abundant grasses were Poa nemoralis, Poa bulbosa, Bromus sterilis, Brachypodium sylvaticum, and Dactylis glomerata subsp. glomerata. Poa nemoralis was an important dominant grass under Quercus community. From the standpoint of species richness, Hill indices were highest under woods stories along the elevation of 1100-1600 m. Understories of oak forest and alpine communities had almost the same indices and were in the second rank compared to woods communities. Based on the β diversity index, the wood understory had the highest indices followed by Quercus and alpine communities. By increasing the elevations, the diversity of understory communities also decreased

Drying of foam under microgravity conditions

Foams have recently been characterised as ideal products for pharmaceutical and topical use applications for the delivery of topical active agents. Foams are usually produced in a wet form but in a number of applications moderately dry foams are required. Drying of foam under terrestrial conditions proceeds under the action of gravity, which is impossible under microgravity condition. Below a new method of drying foams under microgravity condition is suggested. According to this method foam should be placed on a porous support, which will absorb the liquid from foam based on capillary forces only. The final liquid content inside the foam can be achieved by a proper selection of the porous support. The suggested method allows drying foams under microgravity conditions. Interaction of foams with porous support under terrestrial conditions was developed only recently and theoretically investigated (Arjmandi-Tash, O.; Kovalchuk, N.; Trybala, A.; Starov, V. Foam Drainage Placed on a Porous Substrate. Soft Matter2015, 11 (18), 3643–3652) followed by a theory of foam drainage on thin porous substrates (Koursari, N.; Arjmandi-Tash, O.; Johnson, P.; Trybala, A.; Starov, M. V. Foam Drainage Placed on Thin Porous Substrate. Soft Matter, 2019, (submitted)), where rate of drainage, radius of the wetted area inside the porous layer and other characteristics of the process were predicted. The latter model is modified below to investigate foam drying under microgravity conditions. Model predictions are compared with experimental observations for foam created using Triton X-100 at concentrations above CMC. Wetted radius inside the porous substrate was measured and results were compered to model predictions. Experimental observations for spreading area versus time show reasonable agreement with theoretical predictions for all investigated systems

Kinetics of Wetting and Spreading of Droplets over Various Substrates

There has been a substantial increase in the number of publications in the field of wetting and spreading since 2010. This increase in the rate of publications can be attributed to the broader application of wetting phenomena in new areas. It is impossible to review such a huge number of publications; that is, some topics in the field of wetting and spreading are selected to be discussed below. These topics are as follows: (i) Contact angle hysteresis on smooth homogeneous solid surfaces via disjoining/conjoining pressure. It is shown that the hysteresis contact angles can be calculated via disjoining/conjoining pressure. The theory indicates that the equilibrium contact angle is closer to a static receding contact angle than to a static advancing contact angle. (ii) The wetting of deformable substrates, which is caused by surface forces action in the vicinity of the apparent three-phase contact line, leading to a deformation on the substrate. (iii) The kinetics of wetting and spreading of non-Newtonian liquid (blood) over porous substrates. We showed that in spite of the enormous complexity of blood, the spreading over porous substrate can be described using a relatively simple model: a power low-shear-thinning non-Newtonian liquid. (iv) The kinetics of spreading of surfactant solutions. In this part, new results related to various surfactant solution mixtures (synergy and crystallization) are discussed, which shows some possible direction for the future revealing of superspreading phenomena. (v) The kinetics of spreading of surfactant solutions over hair. Fundamental problems to be solved are identified

Foams built up by non-Newtonian polymeric solutions: Free drainage

A mathematical model of free drainage of foam built up by a power-law non-Newtonian liquid is developed. The theory predictions are compared with the experimental data on the drainage of foams formed using commercially available Aculyn™22 and Aculyn™33 polymeric solutions. The rheological parameters of the polymeric solutions were independently measured and used in the calculations. The deduced dimensionless equations were solved using finite element method with appropriate boundary conditions. The numerical simulations show that the decrease in the foam height and liquid content is very fast in the very beginning of the drainage; however, it reaches a steady state at longer time. The predicted values of the time evolution of the foam height and liquid content are in good agreement with the measured experimental data

Mechanical and oxygen barrier properties of LDPE/MMT/MAPE and LDPE/MMT/EVA nanocomposite films: A comparison study

Enhanced mechanical and barrier properties are of special interest in food packaging industries, in which uniform dispersion of nanoparticles in polymers confers considerable improvement in these properties. In this study, maleic anhydride grafted polyethylene (MAPE) and ethylene vinyl acetate (EVA) compatibilised low density polyethylene/montmorillonite (LDPE/MMT) nanocomposite films were prepared with different concentrations of the compatibilisers by melt mixing technique. The delamination of MMT layers was evidenced from X-ray diffraction results that suggested an increase in the interlayer distance with the addition of compatibilisers, where MAPE is the better compatibiliser in delaminating MMT platelets in LDPE/MMT nanocomposites compared to EVA. The mechanical and barrier properties of compatibilised LDPE/MMT nanocomposites were better than uncompatibilised nanocomposites. The best improvement in tensile strength, tear strength and oxygen barrier were observed for LDPE/MMT/MAPE nanocomposites. However, the best improvements in elongation at break were seen for the LDPE/MMT nanocomposites compatibilised with EVA. Conclusively, MAPE compatibiliser is more effective in delaminating MMT platelets in LDPE/MMT nanocomposites, enhancing the mechanical and barrier properties of the nanocomposites. Results revealed that the optimum content of MAPE in terms of mechanical and barrier properties is 3 phc. The enhanced tensile and barrier properties of LDPE/MMT films with the incorporation of MAPE suggest a great potential of these nanocomposite films in food packaging

Impact of a Single Spoiler on Scouring Depth Status Beneath a River Crossing Inclined Pipeline

Deep river crossing pipelines utilized to carry fluids are often placed upon the sand bed. Placement of pipe on the non-smooth bed would result in the production of some local gaps beneath the pipe. Asymmetric scouring is one of the main reasons for pipe underwater failures which are significant in pipeline management. So, in designing pipelines, knowing the interaction between pipelines and bed, and predicting the scour depth with respect to the pipe distance from the bed is significant to ensure that the pipe will finally deposit on the bed. Numerical models have been developed for predicting the balance depth of scouring beneath the pipelines. In this paper, the impact of pipe orientation on maximum scour depth beneath the pipelines is investigated. To do this, a pipe is modeled with various angles with the flow. To manage the local scouring, some spoilers are placed and modeled upon some pipes too. Also, in order to know the effects of placement of a pipe at various distances from the bed, the impact of placement of each pipe at a distance of 0.2D, 0.4D and 0.6D is investigated as well. To model the pipe with and without a spoiler, the finite element model Flow-3D is utilized and the results show good accordance with previous experimental studies and proof the current model’s precision in predicting the scour depth. Results show that in the placement of the pipe in angles not investigated before and also with the installing of a spoiler, the scour process has a reverse ratio with the distance which would result in full deposition of the pipe on the bed. The least scour depth belongs to the condition in which the pipe has a 130° angle with the side wall

Foam drainage: experimental study and numerical simulations

Foam drainage: experimental study and numerical simulation