Sharif Digital Repository

Production of glucoamylase (GA) by using various agro-wastes as carbon sources has been widely carried out as an environmentally friendly approach with a competent value-added result. Similar to other value-added products generated by a bioconversion process, the characteristics of produced enzymes highly depend on the selected medium and microbial strain. Oilseeds such as canola, safflower, soybean, and sunflower are among those agricultural products in the country with a rising rate of production. Therefore, optimal use of their meals will lead to economic and environmental profitability. Thus, in the present study, dry potato peel and waste, soybean, canola, sunflower and safflower meals... 

Laser nanomanipulation by metallic nanoparticles, which are smaller than the diffraction limit, has become a great interest, especially in the manipulation of unstained biological samples. However, they are hard to image in bright-field microscopy, because of the diffraction limit. Thus, incorporation of a dark-field microscopy technique with optical tweezers would be an inevitable choice, enforcing the use of the backward scattering detection scheme. Here in this paper, we have taken into account the reflected light from the coverslip along with backscattered light from the trapped particle to validate and reveal some precautions of using this detection scheme, based on Mie-Debye... 

Nanocrystalline Al-5vol%Al2O3 nanocomposite was synthesised by mechanical milling of a mixture containing nanometric alumina with an average particle size of 35 nm. Morphology of as-synthesised powder was investigated by SEM while crystallite size of Al matrix was determined by XRD analysis. The results confirmed formation of nanocrystalline Al matrix induced by severe plastic deformation during mechanical milling. Nanocomposite bars were produced by hot powder extrusion route. TEM investigation of as-extruded nanocomposite revealed formation of elongated grains along the extrusion direction decorated by alumina nanoparticles. Tensile and compressive properties of as-extruded nanocomposite... 

In this study, the authors optimise the outage probability of amplify and forward incremental relaying (IR) scheme using two different power allocation methods in the presence of channel estimation errors. The authors find the outage probability of IR scheme and minimise it subject to traditional power (TP) constraint in which the sum of nodes' powers is fixed and outage-dependent power (ODP) constraint which is compatible with the physical concept of IR and takes into account the quality of the direct path in the optimisation problem. The authors provide closed-form expressions to allocate power to pilot and data symbols of both the source and the relay. Although, their analysis uses high... 

This paper studies the statistical properties of the signal-to-noise ratio (SNR) of the dual-hop relaying link in a cooperative wireless communication system in the presence of channel estimation errors for fixed-gain (FG) and variable-gain (VG) relays. The SNR expression is derived and three different analytical approaches with different simplifying assumptions are proposed to obtain the probability distribution function of the SNR and the outage probability in each mode. All but one approach result in closed-form expressions for the outage probability. The simplest approach in each mode has been used to find an optimum power allocation scheme for pilot and data symbols transmission at the... 

6061 aluminum matrix composites containing 30vol% SiC with mean mass particle size of 16 and 22 μm as the reinforcing phase were synthesized by squeeze casting route. The process consisted of fabricating of SiC preform followed by squeeze casting of 6061 aluminum alloy. The SiC preform was made by blending SiC particles with silica as a coal and sintering. The microstructural features, aging behavior, mechanical properties and wear characteristics of the composites were investigated. The results indicated that a homogenous distribution of SiC particles in the aluminum matrix, which is almost free of pores, can be obtained by squeeze casting method. Higher strength and lower wear rates were... 

Purpose - Digital Delta Sigma Modulator (DDSM) is used widely in electronic circuits including Radars, class-D power amplifiers and fractional frequency synthesizers. The purpose of this paper is to propose an implementation for MASH DDSMs named as Multi Modulus Reduced Complexity (MMRC) architecture. Design/methodology/approach - This architecture will use a very simple pseudorandom Linear Feedback Shift Register (LFSR) dither signal with period N-d to randomize the digital MMRC modulator used for fractional frequency synthesizers. Using error masking methodology, the MMRC modulator can decrease the hardware consumption and increase accuracy of the fractional frequency synthesizer. Rules... 

Tissue engineering (TE), a fast-growing field of regenerative medicine, has been designed to replace diseased or damaged tissues. As cellular factories, microbes produce a wide range of intracellular and extracellular biopolymers using energy resources. Bacterial biopolymers play an essential role in the competition of microorganisms with competitors. With the detailed knowledge of these bacterial metabolites, extensive applications have been provided in the medicine, food, and drug industry. Bacterial biopolymers, including polysaccharides, polyamides, polyphosphates, polyesters, and enzymes, with vast diversity and desirable properties, are the most frequently used products in TE. Herein... 

A Gaussian laser beam tightly focused through a high-numerical-aperture objective lens, so-called optical tweezers, is widely used for piconewton-range force spectroscopy. Utilizing a proper value for parameters such as bead size, numerical aperture of the objective, and power of the laser is always a challenge. Here, we show which set of values for the parameters can maximize lateral trapping efficiency. Our results show that for a high-numerical-aperture force spectroscopy, a bead with a diameter of 4–5 µm is suitable, and that for manipulation using large beads, utilizing a proper value for laser power and numerical aperture of the objective is crucial. We present a practical method for... 

A Gaussian laser beam tightly focused through a high-numerical-aperture objective lens, so-called optical tweezers, is widely used for piconewton-range force spectroscopy. Utilizing a proper value for parameters such as bead size, numerical aperture of the objective, and power of the laser is always a challenge. Here, we show which set of values for the parameters can maximize lateral trapping efficiency. Our results show that for a high-numerical-aperture force spectroscopy, a bead with a diameter of 4–5 µm is suitable, and that for manipulation using large beads, utilizing a proper value for laser power and numerical aperture of the objective is crucial. We present a practical method for... 

Hot deformation behaviour of as-extruded Al-5vol% Al 2O 3 nanocomposite was investigated at temperatures range 350 to 450°C and initial strain rates of 5.5 × 10 -4 to 10 -1 s -1 and compared with those of monolithic (unreinforced) aluminium. Both extruded materials exhibited work-softening during hot deformation. The results showed that with the addition of 5 vol% alumina nanoparticles with an average particle size of 35 nm, a significant increase in compressive strength of aluminium was obtained. For instance, at 350°C an abrupt rise of ∼340% in hot strength of the nanocomposite relative to monolithic aluminium was achieved. TEM investigation of microstructure of the nanocomposite after hot... 

Syndapin 1 FBAR, a member of the Bin-amphiphysin-Rvs (BAR) domain protein family, is known to induce membrane curvature and is an essential component in biological processes like endocytosis and formation and growth of neurites. We quantify the curvature sensing of FBAR on reconstituted porcine brain lipid vesicles and show that it senses membrane curvature at low density whereas it induces and reinforces tube stiffness at higher density. FBAR strongly up-concentrates on the high curvature tubes pulled out of Giant Unilamellar lipid Vesicles (GUVs), this sorting behavior is strongly amplified at low protein densities. Interestingly, FBAR from syndapin 1 has a large affinity for tubular... 

Optical tweezers are indispensable force spectroscopes. The trap stiffness and the linear force range of the instrument determine the working force range of the instrument. Here we show both theoretically and experimentallythat utilizing a circular obstruction at the back focal plane of the objective can significantly increase the maximumlinear force. For instance, utilizing a disk with an obstruction ratio of 0.773 could increase the maximum linearforce by a factor of ∼39 when a 3.4 μm polystyrene bead is trapped. We also show that this simple beam shapingmethod can significantly improve the maximum applicable force per unit power of the laser entering the objectivelens. © 2018 Optical... 

Gold nanoparticles (GNPs) are very often used as handles for nanotechnological micromanipulation. In this regard, optical trapping of GNPs is of great importance, in which locating the trapped GNP within the focal spot with nanometer precision is crucial. Very recently, we have introduced a new position detection system for optical tweezers based on moiré deflectometry (MD). Here we show, both theoretically and experimentally, that an MD detection system could provide significantly larger detection sensitivity for a trapped GNP compared to that provided by conventional back focal plane (BFP) detection systems. For instance, for a trapped 200 nm GNP, the detection sensitivity provided by the... 

In this work, the production and properties of Al 6061/SiC composites, made using a squeeze casting method, were investigated. SiC preforms were manufactured by mixing SiC powder, having a 16 and 22 pm particle size, with colloidal silica as a binder. 6061 Al melt was squeeze cast into the pores of the SiC preform to manufacture a DRA composite containing 30v/o reinforcement. The aging behavior, tensile properties and fracture mechanism of the cast material were studied. The results show that higher hardness, yield strength, tensile strength and Young's modulus can be obtained by the addition of SiC particles to 6061 Al alloy, whereas tensile elongation decreases. This is mainly caused by a... 

Optical tweezers are proven and indispensable micro-manipulation tools. It is very common to use an immersion-assisted high NA objective for optical trapping of micrometer-sized beads. However, such objectives suffer from low working depth range. Here we show, both by theory and experiment, that a dry objective can be utilized for optimal trapping of even sub-micrometer objects. For the first time, to the best of our knowledge, we were able to stably trap polystyrene beads with radii of 270 and 175 nm in 3D using an objective with numerical aperture of 0.9. © 2022 Optica Publishing Group  

Controlling the safe distances between vehicles on freeways can be used to prevent many accidents. In this research, image-processing techniques have been used to develop an online system that calculates the longitudinal distances between vehicles. This system facilitates controlling safe distances between vehicles without the need for high technology devices. Our approach is real-time and simple, but efficient operations have been used to reduce the image occlusion problem. The main concept of this system is using simple, quick, and effective algorithms for calculating the position of each vehicle in each image. In this way, traffic parameters like speed and distances between vehicles can... 

Developing drug delivery systems with both antibacterial and anti-cancer effects is of importance in the treatment process of infection-associated cancers, especially prostate cancer. In this study, Span 60, Tween 60, and cholesterol were used to formulate doxycycline-loaded niosomes as a promising drug carrier system as either antibacterial or anticancer formulation. The formulation process was optimized by multi-objective response surface methodology (RSM), and then characterized. The developed niosomal formulation showed great storage stability for up to 2 weeks. In addition, they showed remarkable drug release in acidic solution (pH = 3) compared with physiological pH (7.4). The in-vitro... 

In the present work, ultrafine-grained Al-5vol.% Al2O3 nanocomposite was synthesized through mechanical milling followed by direct powder extrusion method. The characteristics of the processed nanocomposite were examined by electron microscopy (SEM and TEM), Xray diffraction (XRD), tensile test and Vickers hardness measurement. It was shown that the addition of the reinforcement nanoparticles accelerates the milling process of the aluminum matrix and enhances the grain refinement of the aluminum matrix. An improved mechanical strength as compared with Al-Al2O3 microcompoiste was obtained. A dimple-type fracture mode was observed, which is a clear evidence of micro-deformation. In addition,... 

Multiple-beam optical traps facilitate advanced trapping geometries and exciting discoveries. However, the increased manipulation capabilities come at the price of more challenging position and force detection. Due to unrivaled bandwidth and resolution, photodiode based detection is preferred over camera based detection in most single/dual-beam optical traps assays. However, it has not been trivial to implement photodiode based detection for multiple-beam optical traps. Here, we present a simple and efficient method based on spatial filtering for parallel photodiode detection of multiple traps. The technique enables fast and accurate 3D force and distance detection of multiple objects...