Sn-adopted fullerene $$(\hbox {C}_{60})$$ nanocage as acceptable catalyst for silicon monoxide oxidation

In recent years, the discovery of metal catalysts for the oxidation of silicon monoxide (SiO) has become extremely important. In first step, the Sn adoption of fullerene (\(\hbox {C}_{60})\) was investigated and then activation of surface of \(\hbox {Sn-C}_{60}\) via \(\hbox {O}_{2}\) molecule was examined. In second step, the SiO oxidation on surface of \(\hbox {Sn-C}_{60}\) via Langmuir Hinshelwood (LH) and Eley Rideal (ER) mechanisms was investigated. Results show that \(\hbox {O}_{2}\hbox {-Sn-C}_{60}\) can oxidize the SiO molecule via \(\hbox {Sn-C}_{60}\hbox {-O-O}^{*} + \hbox {SiO}\rightarrow \hbox {Sn-C}_{60}\hbox {-O-O}^{*}\hbox {-SiO} \rightarrow \hbox {Sn-C}_{60}\hbox {-O}^{*} + \hbox {SiO}_{2}\) and \(\hbox {Sn-C}_{60}\hbox {-O}^{*} + \hbox {SiO}\rightarrow \hbox {Sn-C}_{60} + \hbox {SiO}_{2}\) reactions. Results show that SiO oxidation via the LH mechanism has lower energy barrier than ER mechanism. Finally, \(\hbox {Sn-C}_{60}\) is an acceptable catalyst with high performance for SiO oxidation in normal temperature.     

Improving Impact Strength in FSW of Polymeric Nanocomposites Using Stepwise Tool Design

In recent years, many studies have been conducted on process parameters of polymers friction stir welding, while material parameters are still facing serious problems especially in polymeric nanocomposites. In the present study, the impact behavior of friction stir–welded polycarbonate (PC) nanocomposites under different material and process conditions has been investigated using Taguchi approach. A stepwise tool design procedure has been carried out to enhance the welding process. The samples containing various weight percentages of alumina nanoparticles have been welded under different welding process parameters. The analysis of variance results illustrated that nanoalumina content is the most effective parameter on impact strength followed by rotational and transverse speeds. Impact strength of welded samples was conspicuously improved up to 15% by adding 2?wt% of nanoalumina compared with pure PC samples. Also increasing rotational speed and decreasing transverse speed leads to increase of impact strength. In order to optimize the process, signal-to-noise ratio analysis was performed. The results indicated that the optimum levels of input parameters that give the maximum impact strength are as following: 2?wt% of nanoalumina, 2500?rpm of rotational speed, and 8?mm/min of transverse speed which causes 26.14% improvement in impact strength of samples.     

Electrical Stimulation of Medial Prefrontal Cortex Reduces Conditioned Fear in a Temporally Specific Manner.

The authors recently showed that extinction of auditory fear conditioning leads to potentiation of tone-evoked activity of neurons in the infralimbic (IL) subregion of the medial prefrontal cortex, suggesting that IL inhibits fear after extinction (M. R. Milad, & G. J. Quirk, 2002). In support of this finding, pairing conditioned tones with brief (300-ms) electrical stimulation of IL reduces conditioned freezing. The present study showed that IL stimulation inhibits freezing if given 0.1 s after tone onset (the latency of tone-evoked responses) but has no effect if given either 1 s before or 1 s after tone onset. This suggests that IL gates the response of downstream structures such as the amygdala to fear stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rheology of fluids measured by correlation force spectroscopy

We describe a method, correlation force spectrometry (CFS), which characterizes fluids through measurement of the correlations between the thermally stimulated vibrations of two closely spaced micrometer-scale cantilevers in fluid. We discuss a major application: measurement of the rheological properties of fluids at high frequency and high spatial resolution. Use of CFS as a rheometer is validated by comparison between experimental data and finite element modeling of the deterministic ring-down of cantilevers using the known viscosity of fluids. The data can also be accurately fitted using a harmonic oscillator model, which can be used for rapid rheometric measurements after calibration. The method is non-invasive, uses a very small amount of fluid, and has no actively moving parts. It can also be used to analyze the rheology of complex fluids. We use CFS to show that (non-Newtonian) aqueous polyethylene oxide solution can be modeled approximately by incorporating an elastic spring between the cantilevers.     

Influence of solvent and nanoparticles on the morphology and gas separation properties of copolyimide membranes

In this study, the effect of solvent type and nanoparticles of silica and zeolite 4A on the gas separation properties of polyimide (PI) membranes were investigated. Gas separation of the membranes based on pure solvents of dimethylformamide (DMF), n-methyl-2-pirrolidone (NMP), dimethylacetamide (DMAc), and dimethylsulfoxide (DMSO) were studied. The prepared PI membranes using DMAc and DMSO showed the highest selectivity and permeability, respectively. In this regard, the influence of their mixing on transport properties of the PI was evaluated. The prepared membrane using the mixture of DMSO/DMAc with the volume ratio of 1:3 showed the best gas separation performance in comparison to the Robeson's upper bound. Incorporation of 20 wt% of silica and zeolite 4A nanoparticles into the PI membrane indicated that the selectivity of CO₂/CH₄ increased from 39.4 to 57.6 and 68.5, respectively. Besides, gas transport properties of the PI-based mixed matrix membranes were satisfactory predicted by modified Maxwell model. Furthermore, characteristic parameters of the encapsulated particles by interfacial layer were determined.     

Zur Tragfähigkeitsbewertung bestehender Bauwerke

On the appraisal of existing structures. Starting out from the target of a minimum‐cost management for existing structures national and international standardization activities in the field of the structural health monitoring and assessment are introduced. An ongoing project at Federal Institute for Materials Research and Testing (BAM) which deals with a concept for the assessment of existing structures and the implementation of it is described.     

Numerical investigation of the energy separation effect and flow mechanism inside convergent,straight, and divergent double‐sleeve RHVT

This study provides analysis of a cooled Ranque–Hilsch vortex tube (RHVT) with various specifications. It shows how cooling influences energy conversion inside the RHVT and improves performance of the device in separation of hot gas from the cold stream within the fluid by presenting the temperature detachment (the temperature diminution of cold air (ΔT_c = T_i ? T_c), isentropic efficiency (η_is), and coefficient of performance (COP) of divergent, convergent, and straight VTs. Two key parameters including hot tube length and number of nozzles for cooling and insulated cases are investigated to find out how the performance of the VT is affected by different geometry configurations under cooling conditions. These influences were researched for straight, convergent, and divergent VT separators under different flow characteristics. The optimum geometrical conditions for the cooling cases were identified. Results are indicative of positive influence of cooling for energy separation inside a VT. The quantities of ΔT_c, η_is, and COP for the cooled RHVT are greater than uncooled RHVT for various types of VTs. Cooling the VTs leads to an increase of 12.5% in ΔT_c, 14.4% in η_is, and 15.1% in COP when the base case was an uncooled VT.     

A study of capillary flow from a pendant droplet

Surface tension driven capillary flow from a pendant droplet into a horizontal glass capillary is investigated in this paper. Effect of the droplet surface on dynamic behavior of such capillary flow is examined and compared with surface tension driven capillary flow from an infinite reservoir. In the experiment, capillaries of 300–700 μm in diameter were used with glycerol–DI water mixture solutions having viscosities ranging from 80 to 934 mPa s. It is observed that compared to the capillary flow from an infinite reservoir, the capillary flow from a droplet exhibits higher rates of meniscus displacement. This is due to an additional driving force resulted from change in droplet surface area (or curvature). The two main parameters influencing the flow are the dimensionless droplet geometry parameter (k) and the dynamic contact angle (θ _D). The molecular kinetics theory of Blake and De Coninck’s model [Adv Colloid Interface Sci 96(1–3):21–36, 2002] is used to interpret the dynamic contact angle. This theory considers a molecular friction coefficient (ζ) at the liquid front flowing over a solid surface. Moreover, three models are proposed to describe the shape of the pendant droplet during capillary action. It is found that the egg-shaped model provides a more realistic model to compute the shape of the pendant droplet deformed during the capillary action. Thus the predictions by the egg-shaped model are in good agreement with the experimental data.     

Recent advances in plant-based compounds for mitigation of mycotoxin contamination in food products: current status,challenges and perspectives

There are numerous strategies to control the growth of mycotoxigenic fungi and reduce mycotoxins in food, including physical, chemical and biological treatments. However, consumers prefer organic food and natural inhibitors because they are biodegradable and safe for human and animal health. This review summarises the current advances in plant-based compounds to mitigate contamination of food products by mycotoxigenic fungi and their toxins. In addition, a clear understanding of the roles of plant-based extracts in food products, their mechanisms of action and challenges and perspectives in mycotoxin degradation are presented. Essential oils and plant-based extracts are complex mixtures of major and minor chemical compounds with antimicrobial and antioxidant properties. In general, the mechanisms of antifungal activity of plant-based compounds are attributed to the reduction of the ergosterol content, disruption of cell membrane integrity, enhancing of membrane ion leakage and permeability, disruption to the organisation of mitochondrial structure, interference in enzymatic reactions of cell wall synthesis, disturbance of oxidative balance, inhibition of carbohydrate metabolism, suppression of mycotoxin biosynthetic genes and alterations in the molecular structure of mycotoxins.