Sharif Digital Repository

Diatoms are unicellular microalga found in soil and almost every aquatic environment (marine and fresh water). Biogenic silica and diatoms are attractive for biotechnological and industrial applications, especially in the field of biomedicine, industrial/synthetic manufacturing processes, and biomedical/pharmaceutical sciences. Deposition of silica by diatoms allows them to create micro- or nanoscale structures which may be utilized in nanomedicine and especially in drug/gene delivery. Diatoms with their unique architectures, good thermal stability, suitable surface area, simple chemical functionalization/modification procedures, ease of genetic manipulations, optical/photonic... 

The application of quantum dots (QDs) for detecting and treating various types of coronaviruses is very promising, as their low toxicity and high surface performance make them superior among other nanomaterials; in conjugation with fluorescent probes they are promising semiconductor nanomaterials for the detection of various cellular processes and viral infections. In view of the successful results for inhibiting SARS-CoV-2, functional QDs could serve eminent role in the growth of safe nanotherapy for the cure of viral infections in the near future; their large surface areas help bind numerous molecules post-synthetically. Functionalized QDs with high functionality, targeted selectivity,... 

Lung cancer (LC) is the leading cause of cancer mortality so, the analysis of exhaled human breath has great significance for early non-invasive diagnosis. Poor selectivity and strong humidity are two bottlenecks for the application of gas sensors to exhaled breath analysis. The development of novel extractive phases for the analysis of exhaled breath by chromatography is therefore a lucrative object. Polyhedral oligomeric silsesquioxanes (POSS) are among the 3D porous materials whose unique properties make them promising coatings for solid-phase microextraction (SPME). Selective enrichment of polar or nonpolar targets depends on the pore size and functional groups on the POSSs. Herein, we... 

Rapid and selective detection of biomarkers at trace levels is a highly coveted objective in the early diagnosis of cancer. Herein, we disclose the design and synthesis of a polyhedral oligomeric silsesquioxane (POSS) substituted perylene diimide. This compound is fully characterized in solution by multi nuclear NMR, as well as in gas state by ESI-MS. Surprisingly, solid-state characterization revealed an unusual cubic morphology with particle dimensions of 80–160 nm. Fluorescence studies indicate that the bulky POSS units effectively prevent perylene's aggregation caused quenching, yielding quantum yields as high as 92%. Exposing the sensor droplet-cast on quartz to anline and o-toluidine,... 

Recently, electrode-based Dielectrophoresis (eDEP) has been used for particle manipulation by means of triangular electrodes. In this theoretical and numerical study, a microchannel with quarter-of-ellipse electrodes is presented and a detailed comparison with triangular electrodes is provided. Electric field, resultant DEP force, and particle trajectories for each microchannel are evaluated by means of COMSOL Multiphysics 4.4. Afterwards, focusing and separation efficiencies of the systems are assessed and compared. Finally, separation efficiency of our proposed model for live and dead cells is compared with that of our previous model published in the literature [1]. It is demonstrated that... 

In this research work, graphene/cobalt nanocomposites are functionalized with polyethylene glycol (PEG) to be a platform for theranostics application and antibacterial activity. The non-covalent functionalization of PEG on the surfaces of nanocomposites improved their stability and diminished their cytotoxicity. The PEGylated nanocomposites are demonstrated to allow simultaneous administration of two cancer therapy methods such as magnetic fluids hyperthermia (MFH) which is carried out by converting magnetic energy into heat through ferromagnetic cobalt nanoparticles and heat generation through near-infrared optical absorption by the reduced graphene oxide. A concise simulation is carried... 

Therapeutic drug monitoring (TDM) of methotrexate (MTX), an anticancer drug, is critical since MTX therapy can lead to severe adverse effects if not monitored to ensure clearance. Discriminating and quantifying MTX among its metabolites is challenging, time consuming, and not universally available. Therefore, we propose a surface-enhanced Raman scattering (SERS) based method as a rapid and easy-to-use alternative to complex standard methods. We implemented a solid phase extraction (SPE) process in a syringe filter holder (μ-SPE-SFH), suitable for the extraction of MTX and compatible with nanopillar assisted separation (NPAS) and SERS-based detection. All of the parameters related to the... 

Metal-organic framework (MOF) based graphene oxide (GO) recently merits of attention because of the relative correspondence of GO with metal ions and organic binding linkers. Furthermore, introducing the GO to the Co-MOF to make a new nanoporous hybrid have are improved the selectivity and stability of the Co-MOF. Here the graphene oxide/cobalt metal organic framework (GO/Co-MOF) was synthesized by a solvothermal process using cobalt salt and terephthalic acid and used for biocidal activity, against the growth of the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy were confirmed... 

Inclusion of nano-clays into hydrogels is an efficient approach to produce nanocomposite hydrogels. The introduction of nano-clay into hydrogels causes an increase in water absorbency. In the present work, Nanocomposite hydro-gels based on kappa-carrageenan were synthesized using sodium montmorillonite as nano-clay. Acrylamide and meth-ylenebisacrylamide were used as monomer and crosslinker, respectively. The structure of nanocomposite hydrogels was investigated by XRD and SEM techniques. Swelling behavior of nanocomposite hydrogels was studied by varying clay and carrageenan contents as well as methylenebisacrylamide concentration. An optimum swelling capacity was achieved at 12% of sodium... 

In the present study, the out-of-phase thermomechanical fatigue (OP-TMF) behavior of a cast aluminum-silicon-magnesium alloy, the A356.0 alloy which has been widely used in diesel engine cylinder heads, is compared to room-temperature and high-temperature low cycle fatigue (RT-, HT-LCF) behaviors. For this purpose, strain/temperature-controlled isothermal and non-isothermal fatigue tests were performed based on realistic loading conditions in cylinder heads. Fatigue tests results showed that the plastic strain increased during cycles under constant mechanical strain amplitude, while the specimen failed. Under LCF loadings, the cyclic hardening occurred at low temperatures for the A356.0... 

Machine learning (ML) is generating new opportunities for innovative research in energy economics and finance. We critically review the burgeoning literature dedicated to Energy Economics/Finance applications of ML. Our review identifies applications in areas such as predicting energy prices (e.g. crude oil, natural gas, and power), demand forecasting, risk management, trading strategies, data processing, and analyzing macro/energy trends. We critically review the content (methods and findings) of more than 130 articles published between 2005 and 2018. Our analysis suggests that Support Vector Machine (SVM), Artificial Neural Network (ANN), and Genetic Algorithms (GAs) are among the most... 

The general approach to fault tolerance in uniprocessor systems is to maintain enough time redundancy in the schedule so that any task instance can be re-executed in presence of faults during the execution. In this paper a scheme is presented to add enough and efficient time redundancy to the Earliest-Deadline-First (EDF) scheduling policy for periodic real-time tasks. This scheme can be used to tolerate transient faults during the execution of tasks. We describe a recovery scheme which can be used to re-execute tasks in the event of transient faults and discuss conditions that must be met by any such recovery scheme. For performance evaluation of this idea a tool is developed. © 2007 IEEE  

The reliable transfer in Network on Chips (NoCs) can be threatened by crosstalk fault occurring in wires. Crossstalk fault is due to inter-wire coupling capacitance that based on the patterns of transitions appearing on the wires, significantly limits the reliability of NoCs. Among these transitions, 101 and 010 bit patterns impose the worst crosstalk effects to wires. This work intends to increase the reliability of NoCs against crosstalk faults by applying an improved Fibonacci-based numeral system, called Doubled-Penultimate Fibonacci (DP-Fibo). In the DP-Fibo coding algorithm, code words without ‘101’ and ‘010’ bit patterns are produced to reduce crosstalk faults. Experimental results... 

In the present work, specimens were cut out from St-37 plates with 19 mm thickness. The thickness of plates was reduced to 12.5 mm by milling and grinding operations. Then a standard V-shaped fillet was made on one edge of the plates. Two plates were butt-welded by standard metal arc gas (MAG) welding process. Residual stresses induced by welding were measured on 20 specimens by centre hole drilling. Load controlled axial fatigue tests were carried out to determine the fatigue life of specimens. Crack growth rates were obtained from experiment. Fractography of specimens was performed. Genetic Algorithm (GA) was employed for prediction of residual stress value in weldments using the crack... 

In this work, we implement some analytical techniques such as the Exp-function, Tanh, and extended Tanh methods for solving nonlinear partial differential equation, which contains sine terms, its name Double Sine-Gordon equation. These methods obtain exact solutions of different types of differential equations in engineering mathematics  

The qualitative effects of residual stress parameters on fatigue crack growth are investigated using Monte Carlo probabilistic analysis technique. These parameters include the maximum residual stress,σ0, half-width of the tensile residual stress region, b, and the redistribution of residual stress parameter, β. A normal distribution is assumed for all parameters considered in the investigation and fatigue life is determined using Forman equation. The results indicate that: (i) fatigue life decreases nonlinearly if the mean of random maximum residual stress and the half-width of tensile residual stress region increases; (ii) fatigue life increases nonlinearly if the rate of residual stress... 

In this paper residual stresses induced by butt metal arc gas welding (MAGW), in accordance with ASTM E837, are determined by hole drilling. The results are analyzed by probabilistic methods. Also, the effect of fatigue life on relaxation of welding residual stress is investigated. The specimens are tested to measure fatigue life and crack growth rates in accordance with ASTM E466 for force controlled amplitude axial fatigue testing. © 2008 Verlag Stahleisen GmbH, Düsseldorf  

The effect of contact geometry on fretting fatigue life was investigated by experiments and numerical simulation. The experiments were conducted for flat and cylindrical pads under the same contact normal force. The post-test examinations including crack growth measurements and fractography were carried out using optical and scanning electron microscopy (SEM). Numerical simulations of pad-specimen assembly with and without crack were performed using a finite element (FE) analysis. The experimental study revealed that the rate of crack growth was higher at the early stages of fretting fatigue for cylindrical pads. This stage corresponds to a higher KII for cylindrical contact model. After...