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Production of Alkaline Protease by Entrapped Bacillus Licheniformis Cells in Repeated Batch Process
( Mashhadi Karim ),( Mohammad ),( Mehrdad Azin* ),( Seyyed Latif Mousavi Gargari ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.12
In this study, Bacillus licheniformis cells were immobilized by entrapment in calcium alginate beads and were used for production of alkaline protease by repeated batch process. In order to increase the stability of the beads, the immobilization procedure was optimized by statistical full factorial method, by which three factors including alginate type, calcium chloride concentration, and agitation speed were studied. Optimization of the enzyme production medium, by the Taguchi method, was also studied. The obtained results showed that optimization of the cell immobilization procedure and medium constituents significantly enhanced the production of alkaline protease. In comparison with the free-cell culture in pre-optimized medium, about 7.3-fold higher productivity was resulted after optimization of the overall procedure. Repeated batch mode of operation, using optimized conditions, resulted in continuous production of the alkaline protease for 13 batches in 19 days.
Analysis of Warrant Attacks on Some Threshold Proxy Signature Schemes
Mashhadi, Samaneh Korea Information Processing Society 2016 Journal of information processing systems Vol.12 No.2
In 2004, Yang et al. proposed a threshold proxy signature scheme that efficiently reduced the computational complexity of previous schemes. In 2009, Hu and Zhang presented some security leakages of Yang's scheme and proposed an improvement to eliminate the security leakages that had been pointed out. In this paper, we will point out that both Yang and Hu's schemes still have some security weaknesses, which cannot resist warrant attacks where an adversary can forge valid proxy signatures by changing the warrant $m_w$. We also propose two secure improvements for these schemes.
Efficient Photothermoelectric Conversion in Lateral Topological Insulator Heterojunctions
Mashhadi, Soudabeh,Duong, Dinh Loc,Burghard, Marko,Kern, Klaus American Chemical Society 2017 Nano letters Vol.17 No.1
<P>Tuning the electron and phonon transport properties of thermoelectric materials by nanostructuring has enabled improving their thermopower figure of merit. Three-dimensional topological insulators, including many bismuth chalcogenides, attract increasing attention for this purpose, as their topologically protected surface states are promising to further enhance the thermoelectric performance. While individual bismuth chalcogenide nanostructures have been studied with respect to their photothermoelectric properties, nanostructured p-n junctions of these compounds have not yet been explored. Here, we experimentally investigate the room temperature thermoelectric conversion capability of lateral heterostructures consisting of two different three-dimensional topological insulators, namely, the n-type doped Bi2Te2Se and the p-type doped Sb2Te3. Scanning photocurrent microscopy of the nanoplatelets reveals efficient thermoelectric conversion at the p-n heterojunction, exploiting hot carriers of opposite sign in the two materials. From the photocurrent data, a Seebeck coefficient difference of Delta S = 200 mu V/K was extracted, in accordance with the best values reported for the corresponding bulk materials. Furthermore, it is in very good agreement with the value of Delta S = 185 mu V/K obtained by DFT calculation taking into account the specific doping levels of the two nanostructured components.</P>
Analysis of Warrant Attacks on Some Threshold Proxy Signature Schemes
( Samaneh Mashhadi ) 한국정보처리학회 2016 Journal of information processing systems Vol.12 No.2
In 2004, Yang et al. proposed a threshold proxy signature scheme that efficiently reduced the computational complexity of previous schemes. In 2009, Hu and Zhang presented some security leakages of Yang’s scheme and proposed an improvement to eliminate the security leakages that had been pointed out. In this paper, we will point out that both Yang and Hu’s schemes still have some security weaknesses, which cannot resist warrant attacks where an adversary can forge valid proxy signatures by changing the warrant m_{w}. We also propose two secure improvements for these schemes.
Fatemeh Mashhadi Abolghasem,Sun Young Park,Jaecheol Kim,Keum Taek Hwang 한국식품영양과학회 2021 한국식품영양과학회 학술대회발표집 Vol.2021 No.10
Black seed (BS; Nigella sativa) has considerable amounts of bioactive compounds. Among them, thymoquinone (TQ), which has been known to have antioxidant and anti-inflammatory effects, exists in essential oil of BS oil. This study aims to investigate the effect of enzymatic hydrolysis (EH) on oil yield, TQ content of the oil, and antioxidant properties of defatted seed meal (DSM). After incubating BS at 37°C with cellulase and protease (0:6, 1:5, 2:4, 3:3, 4:2, 5:1, or 6:0 enzyme to buffer ratio), oil was extracted with hexane using Soxhlet method. TQ content of the oil was measured by HPLC. Total phenolic content (TPC), total flavonoid content (TFC), and DPPH and ABTS radical scavenging activities of DSM were determined. Both oil yield and TQ content increased significantly through EH (p<0.05). Using cellulase resulted in higher oil yield than protease. There were no significant differences between the two enzymes in TQ content. TPC, TFC, DPPH, and ABTS significantly increased through EH compared to the control (p<0.05). EH with cellulase resulted in higher oil yield, TQ content, TPC, TFC, and antioxidant properties than with protease.
Dynamic Increase factor based on residual strength to assess progressive collapse
Javad Mashhadi,Hamed Saffari 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.5
In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity (Mu) and moment demand (Md) to plastic moment capacity (Mp) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member. In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity (Mu) and moment demand (Md) to plastic moment capacity (Mp) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member.
Ferrite‐based wideband circularly polarized microstrip antenna design
Mostafa Mashhadi,Nader Komjani,Behzad Rejaei,Javad Ghalibafan 한국전자통신연구원 2019 ETRI Journal Vol.41 No.3
In this paper, a wideband, circularly polarized patch antenna is proposed that leverages the unidirectional resonant modes of a circular patch mounted on top of a grounded dielectric‐ferrite substrate. The proposed antenna is fed via the proximity coupling method and several parasitically coupled patches are placed on a dielectric superstrate to enhance the impedance bandwidth of the antenna. The resonant modes of the structure rotate only in the clockwise or counter clockwise directions. In the frequency range where the effective permeability of the ferrite layer is negative, the resonance frequencies of these modes differ significantly, which produces a large axial ratio (AR) bandwidth. For the proposed antenna, the numerical results show the 10 dB impedance bandwidth to be around 44% and the 3 dB axial ratio bandwidth to be higher than 64%.
Faraji, Ghader,Mashhadi, Mahmoud Mosavi,Kim, Hyoung Seop The Japan Institute of Metals 2012 MATERIALS TRANSACTIONS Vol.53 No.1
<P>In this paper, two different (triangular and semicircular) channel types were investigated in tubular channel angular pressing (TCAP) suitable for deforming cylindrical tubes to large strains without changing the tube dimensions. To examine the effects of the channel geometry on the strain distribution and deformation behavior during the TCAP process, finite element method (FEM) simulations and an analytical model were employed. The FEM results demonstrate that equivalent plastic strains of 2.15–2.9 and 2.35–2.6 were developed after applying one pass TCAP in the triangular and semicircular channels, respectively. The mean values of the equivalent plastic strains were almost identical for both cases, but the strain through the thickness with semicircular channel was more homogeneous than that in the triangular channel. Tube thinning in the early stages of the process was observed as a result of tensile circumferential strains, but this can be compensated by the back pressure effect resulting from the next shear zones and also compressive circumferential strain resulting from the decreasing tube diameter. While the strain values for both channel types were similar, the required load for the semicircular channel was lower than that of the triangular channel.</P>