The number of measurements of a surface’s topography and the expected variation in adhesion to the surface

Variations in roughness on a surface spawn variations in adhesion force between the surface and any particles that contact the surface. To fully characterize the adhesion that will be exhibited when a particle contacts any location on the surface, it is desirable to map the surface with nanoscale detail. Since it is impractical to make nanoscale roughness measurements over the entirety of a surface with a characteristic dimension on the order of centimeters, a relationship between the number of surface measurements and the likely variation in the expected adhesion force is similarly desirable. In this work, the predicted van der Waals force was used to describe the particle adhesion force. The bootstrap statistical method was employed to estimate the error associated with the predicted mean adhesion force between a smooth spherical particle and a rough surface as a function of the number of locations on the surface where the roughness was measured. Specifically, 40 atomic force microscope (AFM) topographical scans (5 × 5 μm) were taken of three different surfaces and used as model surface inputs to an existing van der Waals adhesion force simulator. The simulator described the expected adhesion force resulting from 1200 contacts between the smooth, spherical particle (10 μm diameter) and random locations on each scanned area. After analyzing the results using the bootstrap method, it was determined that the adhesion between the particle and 10–15 scanned areas (out of 40) optimizes the accuracy of the predicted adhesion with respect to the researcher’s labor.     

Studies on solvent extraction of La(III) using [A336][NO3–] and modeling by statistical analysis and neural network

Solvent extraction of La(III) from acidic nitrate medium has been studied with [A336][NO₃^–] in kerosene. The factors affecting the extraction of La(III) like equilibration time, nitrate ion, extractant and La(III) concentrations, aqueous acidity, O/A ratio variation, nature of diluent, and temperature have been investigated. McCabe-Thiele diagram has been plotted to find out the actual number of theoretical stages needed for complete extraction of lanthanum. The solvent has been successfully regenerated for further use after stripping of the metal. IR studies of [A336][NO₃^–] and La(III) loaded [A336][NO₃^–] have been carried out. Modeling of extraction data has been done using Multiple linear regression analysis and Artificial Neural Network, and the performances have been compared. Error in each case was evaluated in terms of R² and Root mean squared error (RMSE). Maximum extraction of La(III) was 82% when 0.6 M [A336][NO₃^–] was used for extraction. About 98% of the metal has been recovered using 0.2 M HNO₃ as stripping agent. Extractive separation of La(III) and Sm(III) was maximum (β = 65.2) using 0.1 M [A336][NO₃^–]. IR studies revealed formation of lanthanum complex in the extraction process. Artificial Neural Network proved to be better over Multiple linear regression in data prediction.     

Prediction of 3D elastic moduli and Poisson’s ratios of pillared graphene nanostructures

A computational finite element analysis based on a structural molecular mechanics approach was conducted to predict effective mechanical stiffness properties of a novel 3D carbon structure, pillared graphene structure (PGS), which is constituted with several graphene sheets and single-walled carbon nanotubes. Four sets of representative unitcell models were developed atomistically for predicting the mechanical properties of PGSs having different values of pillar length and inter-pillar distance. We introduced proper selections of the periodic geometry and boundary conditions which enabled our unitcell model to yield consistent results on the property prediction without any size or edge effects. The parametric study shows that the pillar length and inter-pillar distance significantly affect the effective in-plane and through-thickness properties. PGSs with shorter pillars in height yield higher planar Young’s and shear moduli, while those with smaller inter-pillar distance yield higher through-thickness moduli. Negative in-plane Poisson’s ratios are observed for all sets of PGSs and are associated with the curvature at the junction.     

Taguchi analysis of bonded composite single-lap joints using a combined interface–adhesive damage model

The mechanical behaviour of bonded composite joints depends on several factors, such as the strength of the composite–adhesive interface, the strength of the adhesive and the strength of the composite itself. In this regard, a finite element model was developed using a combined interface–adhesive damage approach. A cohesive zone model is used to represent the composite–adhesive interface and a continuum damage model for the adhesive bondline. The influence of the composite–adhesive interfacial adhesion and the strength of the adhesive on the performance of a bonded composite single-lap joint was investigated numerically. A Taguchi analysis was conducted to rank the influence of material parameters on the static behaviour of the joint. It was found that the composite–adhesive interfacial fracture energy and the mechanical properties of the adhesive predominantly govern the static performance of the joints. A parametric study was performed by varying the most important material parameters, and a response surface equation is proposed to predict the joint strength. It is shown that the influence of experimental parameter variations, e.g. variation in adhesive curing and surface preparation conditions, can be numerically accommodated to investigate the static behaviour of bonded composite joints by combining finite element and statistical techniques. The methods presented could be used by practicing engineers to describe the failure envelope of adhesively bonded composite joints.     

Efficient and solvent-free microwave-accelerated synthesis of isothiocyanates using Lawesson’s reagent

A new and practical procedure for the synthesis of isothiocyanates is described. A series of iso-thiocyanates (ITC) was readily obtained from the corresponding isocyanates (IC) using Lawesson’s Reagent (LR) under microwave irradiation and solvent-free conditions.     

Prediction of ring crack initiation in ceramics and glasses using a stress–energy fracture criterion

Crack initiation in brittle materials upon spherical indentation is associated with the tensile radial stresses during loading. However, location of crack onset often differs (offset) from the site of maximal stress. In addition, experiments reveal a strong dependency of crack initiation forces on geometrical parameters as well as the surface condition of the sample. In this work, a coupled stress–energy fracture criterion is introduced to describe the initiation of ring cracks in brittle materials, which takes into account the geometry of the contact and the inherent strength and fracture toughness of the material. Several experiments reported in literature are evaluated and compared. The criterion can explain the location offset of the ring crack upon loading, as observed in various ceramics and glasses. It also predicts the ring crack initiation force upon contact loading, provided that surface compressive stresses, introduced during grinding or polishing processes, are taken into account. Furthermore, the stress–energy criterion may be employed to estimate the surface residual stress of ceramic parts, based on simple contact damage experiments.     

Electrical breakdown of an acrylic dielectric elastomer: effects of hemispherical probing electrode’s size and force

Dielectric elastomers are widely investigated as soft electromechanically active polymers (EAPs) for actuators, stretch/force sensors, and mechanical energy harvesters to generate electricity. Although the performance of such devices is limited by the dielectric strength of the constitutive material, the electrical breakdown of soft elastomers for electromechanical transduction is still scarcely studied. Here, we describe a custom-made setup to measure electrical breakdown of soft EAPs, and we present data for a widely studied acrylic elastomer (VHB 4905 from 3M). The elastomer was electrically stimulated via a planar and a hemispherical metal electrode. The breakdown was characterized under different conditions to investigate the effects of the radius of curvature and applied force of the hemispherical electrode. With a given radius of curvature, the breakdown field increased by about 50% for a nearly 10-fold increase of the applied mechanical stress, while with a given mechanical stress the breakdown field increased by about 20% for an approximately twofold increase of the radius of curvature. These results indicate that the breakdown field is highly dependent on the boundary conditions, suggesting the need for reporting breakdown data always in close association with the measurement conditions. These findings might help future investigations in elucidating the ultimate breakdown mechanism/s of soft elastomers.     

The aerobic and peroxide-induced coupling of aqueous thiols—II. Reaction mechanisms,model analysis,and a comparison of the model and experimental results

Kinetic results of the preceeding paper are used to formulate the most probable reaction mechanisms for the peroxide-induced and aerobic coupling of aqueous thiols. Parameters in the proposed mechanisms are evaluated for n-propylthiol using the results of independent measurements. A remarkably good agreement is achieved between the model and experimental results.The peroxide reaction, which is not affected by either copper ion or radical scavengers, is shown to be a nucleophilic substitution (S_N 2) reaction which proceeds by a two-step mechanism as follows: RS⁻ + H₂O₂

RSOH + OH⁻ rate-determining RS⁻ + RSOH → RSSR + OH⁻ In the reaction the thiolate anion acts as the nucleophile while hydrogen peroxide and the transient sulfenic acid, RSOH, function as electrophiles.The most plausible mechanism for the copper-catalyzed, aerobic coupling reaction is as follows: Cu⁺ (RSSR)₂⁺ + RS⁻

(RSSR)Cu⁺ (RS⁻) + RSSR (RSSR)Cu⁺ (RS⁻) + RS⁻

(RSSR)Cu⁺ (RS⁻)₂⁻ (RSSR)Cu⁺ (RS⁻)₂⁻ + O₂

Cu⁺(RSSR)₂⁺ + HO₂⁻ rate-determining RS⁻ + H₂O₂

RSOH + OH⁻ rate-determining RS⁻ + RSOH → RSSR + OH⁻ For the n-propylthiol substrate, the pertinent parameters in the mechanism are 1n (K₁) = −11,000 K/T + 33.6, where K₁ is dimensionless, 1n (K₂) = 4270 K/T −10.5, where K₂ is in 1/mol, 1n (k₂) = 30.0 − 5260 K/T, and 1n (k₂) = 26.8 − 6190 K/T, where k₁ and k₂ are in 1/(mol min).     

A model of energy-dependent agglomeration of hydrocarbon aerosol particles and implication to titan’s aerosols

A simple model of coagulation with subsequent coalescence of two colliding polymer aerosol particles allows for the estimation of some indices of the process, depending on the physio-chemical properties of the primary particles and the medium. The model can describe well our experimental results and, hence, could be valid also for the analysis of Titan’s hydrocarbon aerosols.     

Modeling of paper mill sewage sludge drying using artificial neural networks: Reduction of the training database through Taguchi’s method

Drying of sewage sludge is typically modeled as simultaneous heat and mass transfer phenomena. The capability of conventional models to take into account crust formation, cracks, and shrinking is limited. Artificial neural networks (ANNs) are suitable tools for dynamic representation of drying processes; however, obtaining a suitable database is a resource consuming task. Based on the Taguchi method, nine experiments were defined to set up a training database and to develop an ANN model. A high Pearson correlation coefficient was verified when comparing the drying kinetic curve generated by the ANN model with the one obtained during the validation experiments.     

Computational analysis of airflow and nanoparticle deposition in a combined nasal–oral–tracheobronchial airway model

In light of the exponentially increasing industrial production and consumer use of ultrafine particles, deposition in the human lung is of great environmental and biomedical concern, especially for children, asthmatics and the elderly. Considering spherical nanoparticles in the 1–100 nm mean-diameter range and different breathing routes with Q_total=30 and 60 L/min, local deposition fractions and global surface concentrations were predicted employing an experimentally validated computer simulation model. It was found that the change in breathing route (from nasal to oral breathing) not only significantly influences nanoparticle deposition in the regions of nasal and oral cavities, nasopharynx and oropharynx, but also measurably affects depositions from pharynx to bronchial airways for tiny nanoparticles (≤5 nm). The effect of breathing routes on deposition of larger nanoparticles (>5 nm) after the pharynx tends to be minor. The impact of different outlet flow-rate ratios generated by downstream resistances, e.g., caused by airway inflammation or tumors, is discussed in this study as well. Specifically, different outlet pressures primarily influence the velocity profiles and nanoparticle deposition fractions at that particular branch and adjacent bifurcations. In addition, the impact of change in outlet flow rate ratio on total deposition is confined to all same-level bifurcations and direct upstream-level bifurcations. The mass transfer coefficients of depositing nanoparticles (in terms of Sherwood number) can be well correlated as a function of Reynolds number and Schmidt number. The influence of downstream resistance on the Sherwood number in bronchial airways is smaller than intra-subject effects, i.e., variations of bifurcation levels and geometric parameters.     

A fast and easy approach to the synthesis of Zeise’s salt using microwave heating

A fast and easy approach to the synthesis of Zeise’s salt, KPtCl₃(C₂H₄), is reported using microwave heating. The reaction is complete after 15 min at 130 °C using K₂PtCl₄ as starting material, a 1:1:1 ratio of water:ethanol:concentrated HCl as solvent, and a loading of 50 psi of ethene.     

Control,data acquisition and analysis of catalytic gas—liquid mini slurry reactors using a personal computer

An automated gas-consumption measuring system is designed which can be used to keep constant or time-variable pressure and record continuously the consumption or production of gases in a batch-type microreactor. Process control, data acquisition and analysis is carried out using a personal computer (IBM) and a Lab-master (Tecmar Inc.) interface device. Hardware and software was designed and developed for the system. A direct digital feedback control loop is employed to keep constant or time-variable pressure in the batch-type slurry reactor. In order to investigate the dynamic behavior of the system, mathematical analysis for a continuous and a sampled system is presented. The application of the system is illustrated for a kinetic run involving the catalytic hydrogenation of an acrylonitrile-butadiene copolymer in the liquid phase.Scope—There are numerous types of chemical reactions which involve gas consumption or production. Batch-type reactors are commonly employed in kinetic studies of such reactions. Presently, manual techniques are used where the operator adjusts the pressure in the reactor at specific time intervals and measures the gas supplied. Alternatively, sampling techniques are used where samples are withdrawn from the gaseous or liquid phase and subsequently analyzed. The major disadvantages with these manual techniques however are the relatively large sampling period and/or difficulty in data collection which makes the study tedious and often subject to considerable error. The computer-controlled system presented in this paper, besides providing for facile reaction control, enables the aquisition of reliable kinetic data and its immediate analysis with a high degree of precision.Conclusions and Significance—Hardware, software and system analysis of a newly-designed computer-controlled batch-type reactor has been developed. From the excellent reproducibility obtained with the system for the hydrogenation of several substrates, it can be concluded that the system can be successfully and conveniently employed for kinetic studies of a variety of gas-producing/gas-consuming reactions, with constant or operator-specified variable pressure. Results of a system analysis, carried out in this investigation, indicate that the system is inherently stable when an analog controller is used, as shown by equation (19) (reactor pressure response for a step input in the reaction rate). However, the stability of the system depends on sampling period when a digital controller is employed, as shown by equation (20) (reactor pressure response for a step input in the reaction rate).     

Prediction of Protein S-Nitrosylation Sites Based on Adapted Normal Distribution Bi-Profile Bayes and Chou’s Pseudo Amino Acid Composition

Protein S-nitrosylation is a reversible post-translational modification by covalent modification on the thiol group of cysteine residues by nitric oxide. Growing evidence shows that protein S-nitrosylation plays an important role in normal cellular function as well as in various pathophysiologic conditions. Because of the inherent chemical instability of the S-NO bond and the low abundance of endogenous S-nitrosylated proteins, the unambiguous identification of S-nitrosylation sites by commonly used proteomic approaches remains challenging. Therefore, computational prediction of S-nitrosylation sites has been considered as a powerful auxiliary tool. In this work, we mainly adopted an adapted normal distribution bi-profile Bayes (ANBPB) feature extraction model to characterize the distinction of position-specific amino acids in 784 S-nitrosylated and 1568 non-S-nitrosylated peptide sequences. We developed a support vector machine prediction model, iSNO-ANBPB, by incorporating ANBPB with the Chou’s pseudo amino acid composition. In jackknife cross-validation experiments, iSNO-ANBPB yielded an accuracy of 65.39% and a Matthew’s correlation coefficient (MCC) of 0.3014. When tested on an independent dataset, iSNO-ANBPB achieved an accuracy of 63.41% and a MCC of 0.2984, which are much higher than the values achieved by the existing predictors SNOSite, iSNO-PseAAC, the Li et al. algorithm, and iSNO-AAPair. On another training dataset, iSNO-ANBPB also outperformed GPS-SNO and iSNO-PseAAC in the 10-fold crossvalidation test.     

Nuclear and Cytoplasmic Soluble Proteins Extraction from a Small Quantity of Drosophila’s Whole Larvae and Tissues

The identification and study of protein’s function in several model organisms is carried out using both nuclear and cytoplasmic extracts. For a long time, Drosophila’s embryos have represented the main source for protein extractions, although in the last year, the importance of collecting proteins extracts also from larval tissues has also been understood. Here we report a very simple protocol, improved by a previously developed method, to produce in a single extraction both highly stable nuclear and cytoplasmic protein extracts from a small quantity of whole Drosophila’s larvae or tissues, suitable for biochemical analyses like co-immunoprecipitation.     

Isolation and Enhancement of a Homogenous in Vitro Human Hertwig’s Epithelial Root Sheath Cell Population

Hertwig’s epithelial root sheath (HERS) cells play a pivotal role during root formation of the tooth and are able to form cementum-like tissue. The aim of the present study was to establish a HERS cell line for molecular and biochemical studies using a selective digestion method. Selective digestion was performed by the application of trypsin-EDTA for 2 min, which led to the detachment of fibroblast-like-cells, with the rounded cells attached to the culture plate. The HERS cells displayed a typical cuboidal/squamous-shaped appearance. Characterization of the HERS cells using immunofluorescence staining and flow cytometry analysis showed that these cells expressed pan-cytokeratin, E-cadherin, and p63 as epithelial markers. Moreover, RT-PCR confirmed that these cells expressed epithelial-related genes, such as cytokeratin 14, E-cadherin, and ΔNp63. Additionally, HERS cells showed low expression of CD44 and CD105 with absence of CD34 and amelogenin expressions. In conclusion, HERS cells have been successfully isolated using a selective digestion method, thus enabling future studies on the roles of these cells in the formation of cementum-like tissue in vitro.     

Toxicity and Metabolism of Layered Double Hydroxide Intercalated with Levodopa in a Parkinson’s Disease Model

Layered hydroxide nanoparticles are generally biocompatible, and less toxic than most inorganic nanoparticles, making them an acceptable alternative drug delivery system. Due to growing concern over animal welfare and the expense of in vivo experiments both the public and the government are interested to find alternatives to animal testing. The toxicity potential of zinc aluminum layered hydroxide (ZAL) nanocomposite containing anti-Parkinsonian agent may be determined using a PC 12 cell model. ZAL nanocomposite demonstrated a decreased cytotoxic effect when compared to levodopa on PC12 cells with more than 80% cell viability at 100 μg/mL compared to less than 20% cell viability in a direct levodopa exposure. Neither levodopa-loaded nanocomposite nor the un-intercalated nanocomposite disturbed the cytoskeletal structure of the neurogenic cells at their IC₅₀ concentration. Levodopa metabolite (HVA) released from the nanocomposite demonstrated the slow sustained and controlled release character of layered hydroxide nanoparticles unlike the burst uptake and release system shown with pure levodopa treatment.     

Comparative in Vivo Assessment of Some Adverse Bioeffects of Equidimensional Gold and Silver Nanoparticles and the Attenuation of Nanosilver’s Effects with a Complex of Innocuous Bioprotectors

Stable suspensions of nanogold (NG) and nanosilver (NS) with mean particle diameter 50 and 49 nm, respectively, were prepared by laser ablation of metals in water. To assess rat’s pulmonary phagocytosis response to a single intratracheal instillation of these suspensions, we used optical, transmission electron, and semi-contact atomic force microscopy. NG and NS were also repeatedly injected intraperitoneally into rats at a dose of 10 mg/kg (0.5 mg per mL of deionized water) three times a week, up to 20 injections. A group of rats was thus injected with NS after oral administration of a “bioprotective complex” (BPC) comprised of pectin, multivitamins, some amino acids, calcium, selenium, and omega-3 PUFA. After the termination of the injections, many functional and biochemical indices and histopathological features of the spleen, kidneys and liver were evaluated for signs of toxicity, and accumulation of NG or NS in these organs was measured. From the same rats, we obtained cell suspensions of different tissues for performing the RAPD test. It was demonstrated that, although both nanometals were adversely bioactive in all respects considered in this study, NS was more noxious as compared with NG, and that the BPC tested by us attenuated both the toxicity and genotoxicity of NS.