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81.
Mehdi Kiani M. Sharif Bakhtiar Mojtaba Atarodi 《Analog Integrated Circuits and Signal Processing》2010,62(3):319-325
This paper presents a low voltage low noise open loop automatic amplitude control method for voltage-controlled oscillators
(VCO’s). In this method a feedback mechanism keeps the VCO at its optimum amplitude over temperature and process variations
and then the loop is broken to avoid noise injection form the control circuitry to the VCO. The loop does not add extra noise
to the VCO. Based on the proposed method, a low voltage low noise LC-VCO was designed for a low phase noise application in
TSMC 0.18 micron RFCMOS technology. Simulations show considerable improvement in the phase noise with the application of the
proposed method. 相似文献
82.
The composition of essential oils from aerial parts of Heracleum persicum, a widely used medicinal plant, and three other Heracleum species growing wild in Iran were analysed by GC and GC–MS. Myristicin (53.6%), (E)-anethole (25.0%), hexyl butanoate (29.7%) and elemicin (41.1%) were the major compounds of Heracleum pastinacifolium, H. persicum, Heracleum rechingeri and Heracleum transcaucasicum, respectively. Cytotoxic activity assessed on three human cancer cell lines (HeLa, LS180 and Raji), showed that essential oils from H. transcaucasicum (IC50 values; 0.362–0.594 mg/ml) followed by H. pastinacifolium (0.497–1.398 mg/ml) had moderate antitumoral activities. In the DPPH radical scavenging assay, H. pastinacifolium and H. persicum oils showed the highest activities with IC50 values of 7.3 and 7.4 mg/ml, respectively. Antioxidant activity correlated well with the total phenolic content of the oils. None of the essential oils showed significant antimicrobial activities. 相似文献
83.
Amphiphilic block copolymers are macromolecular compounds of great importance from both fundamental scientific and many technological
point of views for a large variety of applications. Amphiphilic diblock copolymer containing segments of monomethoxypoly(ethylene
glycol) and polystyrene (MPEG-b-PS) was synthesised by a convenient method for preparation of macroinitiator MPEG-TEMPO for
‘living’ free radical polymerization (NMRP technique). Initially, derivative of MPEG with chlorine function has been prepared
in an one-step reaction with thionyl chloride. 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-OH) obtained by reduction of
2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) with sodium ascorbate was coupled with chlorinated MPEG to yield the macroinitiator
MPEG terminated with a TEMPO unit (MPEG-TEMPO), which was further used to prepare the diblock copolymer MPEG-b-PS of styrene.
The product was purified and identified by 1H NMR, GPC and, FT-IR. 相似文献
84.
Mohammad Ali Faramarzi Nadia Zolfaghary Mojtaba Tabatabaei Yazdi Sina Adrangi Hossein Rastegar Mohsen Amini Mohsen Badiee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(7):1021-1025
BACKGROUND: A large number of bacterial, fungal and microalgal species are able to bio‐transform steroid compounds. Among them, fungi from the Mucor genus have been shown to mediate hydroxylation, oxidation, and desaturation by the double bond formation and epoxidation of various steroid substances. Mucor racemocus has not been studied for its ability to modify androst‐1,4‐dien‐3,17‐dione, a pharmaceutically important steroid precursor. RESULTS: The filamentous fungus M. racemosus was applied for bioconversion of androst‐1,4‐dien‐3,17‐dione (ADD, I ) in a 5‐day fermentation. Microbial metabolites were purified chromatographically and identified on the basis of their spectral data as 17β‐hydroxyandrost‐1,4‐dien‐3‐one ( II ), 14α‐hydroxyandrost‐1,4‐dien‐3,17‐dione ( III ), 15α‐hydroxyandrost‐1,4‐dien‐3,17‐dione ( IV ), 15α,17β‐dihydroxyandrost‐1,4‐dien‐3‐one ( V ), 14α,17β‐dihydroxyandrost‐1,4‐dien‐3‐one ( VI ), and 6β,17β‐dihydroxyandrost‐1,4‐dien‐3‐one ( VII ). CONCLUSION: Observed modifications included hydroxylation at C‐6β, C‐14α, C‐15α positions and 17‐carbonyl reduction. The best fermentation conditions for production of hydroxysteroid‐1,4‐dien‐3‐one derivatives were found to be 25 °C at 150 rpm for 5 days with a substrate concentration of 0.5 g L?1. Copyright © 2009 Society of Chemical Industry 相似文献
85.
Mohammad Mojtaba Sadeghi Mohamed F. Salama Yusuf A. Hannun 《International journal of molecular sciences》2021,22(11)
Driver-directed therapeutics have revolutionized cancer treatment, presenting similar or better efficacy compared to traditional chemotherapy and substantially improving quality of life. Despite significant advances, targeted therapy is greatly limited by resistance acquisition, which emerges in nearly all patients receiving treatment. As a result, identifying the molecular modulators of resistance is of great interest. Recent work has implicated protein kinase C (PKC) isozymes as mediators of drug resistance in non-small cell lung cancer (NSCLC). Importantly, previous findings on PKC have implicated this family of enzymes in both tumor-promotive and tumor-suppressive biology in various tissues. Here, we review the biological role of PKC isozymes in NSCLC through extensive analysis of cell-line-based studies to better understand the rationale for PKC inhibition. PKC isoforms α, ε, η, ι, ζ upregulation has been reported in lung cancer, and overexpression correlates with worse prognosis in NSCLC patients. Most importantly, PKC isozymes have been established as mediators of resistance to tyrosine kinase inhibitors in NSCLC. Unfortunately, however, PKC-directed therapeutics have yielded unsatisfactory results, likely due to a lack of specific evaluation for PKC. To achieve satisfactory results in clinical trials, predictive biomarkers of PKC activity must be established and screened for prior to patient enrollment. Furthermore, tandem inhibition of PKC and molecular drivers may be a potential therapeutic strategy to prevent the emergence of resistance in NSCLC. 相似文献
86.
Serati Mehdi Bahaaddini Mojtaba Roshan Hamid Zhang Tian Tian Bryant Nicholas 《Bulletin of Engineering Geology and the Environment》2021,80(7):5867-5879
Bulletin of Engineering Geology and the Environment - This work aims to identify fracture pattern and crack growth mode in brittle rocks and solids under induced tensile stresses, and further... 相似文献
87.
88.
Saharnaz Ahmadi Maryam Farokhi Parisa Padidar Mojtaba Falahati 《International journal of molecular sciences》2015,16(8):17289-17302
In this study the effect of surface modification of mesoporous silica nanoparticles (MSNs) on its adsorption capacities and protein stability after immobilization of beta-lactoglobulin B (BLG-B) was investigated. For this purpose, non-functionalized (KIT-6) and aminopropyl-functionalized cubic Ia3d mesoporous silica ([n-PrNH2-KIT-6]) nanoparticles were used as nanoporous supports. Aminopropyl-functionalized mesoporous nanoparticles exhibited more potential candidates for BLG-B adsorption and minimum BLG leaching than non-functionalized nanoparticles. It was observed that the amount of adsorbed BLG is dependent on the initial BLG concentration for both KIT-6 and [n-PrNH2-KIT-6] mesoporous nanoparticles. Also larger amounts of BLG-B on KIT-6 was immobilized upon raising the temperature of the medium from 4 to 55 °C while such increase was undetectable in the case of immobilization of BLG-B on the [n-PrNH2-KIT-6]. At temperatures above 55 °C the amounts of adsorbed BLG on both studied nanomaterials decreased significantly. By Differential scanning calorimetry or DSC analysis the heterogeneity of the protein solution and increase in Tm may indicate that immobilization of BLG-B onto the modified KIT-6 results in higher thermal stability compared to unmodified one. The obtained results provide several crucial factors in determining the mechanism(s) of protein adsorption and stability on the nanostructured solid supports and the development of engineered nano-biomaterials for controlled drug-delivery systems and biomimetic interfaces for the immobilization of living cells. 相似文献
89.
Gholamreza Moradi Fereydoon Yaripour Hossein Abbasian Mostefa Rahmanzadeh 《Korean Journal of Chemical Engineering》2010,27(5):1435-1440
The kinetic behavior of a commercial γ-Al2O3 catalyst for the methanol to dimethyl ether (DME) dehydration reaction has been investigated using a differential fixed bed
reactor at the pressure range 1–16 barg within a temperature range of 260–380 °C. The experimental runs were performed in
a wide range of feed to water ratios. The experiments were designed by general full factorial design (GEFD) and a novel rate
equation has been developed which exhibited the best fitting with our experimental data. Based on the analysis of variance
(ANOVA), the following order of importance for operating conditions was obtained when the objective function is the yield
of DME: Temperature >Water % in feed >Pressure. In addition, the optimum operating conditions for the maximum yield of DME,
were found at T= 380°C, P=16 barg and zero wt% of water in the feed. 相似文献
90.
Nowadays, solvent‐free, one‐part cyanoacrylate adhesive is widely used in medicine and dentistry. According to a literature survey done by the authors, there are few papers concentrated on the role of nano‐sized particles on the thermal behavior of cyanoacrylate glue. Thus the main goal of the current research focused on clarifying the role of nano‐sized SiO2 on the thermal behavior of cyanoacrylate. Thermal behavior of all materials including cyanoacrylate and its nanocomposites was studied by using Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods. The results of DSC analysis showed that an increase in the amount of nano‐sized SiO2 results in decreases in the duration of cyanoacrylate curing, energy release during polymerization, and incubation time of polymerization. Furthermore, the results of TGA tests illustrated that the weight loss of cyanoacrylate strongly depends on the contents of both caffeine and SiO2. In fact, an increase in nano‐sized SiO2 content increases the degradation temperature of cyanoacrylate. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers 相似文献